ScalingIntelligence/swe-bench-verified-codebase-content

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7dc3f64ff52293a7ebb9c91d48b9f2ba54c63fe24eb7a9cb754054e7c085c94f	import sys sys._running_pytest = True # type: ignore from distutils.version import LooseVersion as V import pytest from sympy.core.cache import clear_cache import re sp = re.compile(r'([0-9]+)/([1-9][0-9])') def process_split(config, items): split = config.getoption("--split") if not split: return m = sp.match(split) if not m: raise ValueError("split must be a string of the form a/b " "where a and b are ints.") i, t = map(int, m.groups()) start, end = (i-1)len(items)//t, ilen(items)//t if i < t: # remove elements from end of list first del items[end:] del items[:start] def pytest_report_header(config): from sympy.utilities.misc import ARCH s = "architecture: %s\n" % ARCH from sympy.core.cache import USE_CACHE s += "cache: %s\n" % USE_CACHE from sympy.core.compatibility import GROUND_TYPES, HAS_GMPY version = '' if GROUND_TYPES =='gmpy': if HAS_GMPY == 1: import gmpy elif HAS_GMPY == 2: import gmpy2 as gmpy version = gmpy.version() s += "ground types: %s %s\n" % (GROUND_TYPES, version) return s def pytest_terminal_summary(terminalreporter): if (terminalreporter.stats.get('error', None) or terminalreporter.stats.get('failed', None)): terminalreporter.write_sep( ' ', 'DO NOT* COMMIT!', red=True, bold=True) def pytest_addoption(parser): parser.addoption("--split", action="store", default="", help="split tests") def pytest_collection_modifyitems(config, items): """ pytest hook. """ # handle splits process_split(config, items) @pytest.fixture(autouse=True, scope='module') def file_clear_cache(): clear_cache() @pytest.fixture(autouse=True, scope='module') def check_disabled(request): if getattr(request.module, 'disabled', False): pytest.skip("test requirements not met.") elif getattr(request.module, 'ipython', False): # need to check version and options for ipython tests if (V(pytest.__version__) < '2.6.3' and pytest.config.getvalue('-s') != 'no'): pytest.skip("run py.test with -s or upgrade to newer version.")
3861d7ed5195f05f9d07f5161360ab694893a1a257001f9ef7325324f49c060f	__version__ = "1.8.dev"
c41b6ec7cd8316a22cefcbd855c0f976935539297e72afdaebb464ed84ee2d1a	""" This module exports all latin and greek letters as Symbols, so you can conveniently do >>> from sympy.abc import x, y instead of the slightly more clunky-looking >>> from sympy import symbols >>> x, y = symbols('x y') Caveats ======= 1. As of the time of writing this, the names ``C``, ``O``, ``S``, ``I``, ``N``, ``E``, and ``Q`` are colliding with names defined in SymPy. If you import them from both ``sympy.abc`` and ``sympy``, the second import will "win". This is an issue only for * imports, which should only be used for short-lived code such as interactive sessions and throwaway scripts that do not survive until the next SymPy upgrade, where ``sympy`` may contain a different set of names. 2. This module does not define symbol names on demand, i.e. ``from sympy.abc import foo`` will be reported as an error because ``sympy.abc`` does not contain the name ``foo``. To get a symbol named ``foo``, you still need to use ``Symbol('foo')`` or ``symbols('foo')``. You can freely mix usage of ``sympy.abc`` and ``Symbol``/``symbols``, though sticking with one and only one way to get the symbols does tend to make the code more readable. The module also defines some special names to help detect which names clash with the default SymPy namespace. ``_clash1`` defines all the single letter variables that clash with SymPy objects; ``_clash2`` defines the multi-letter clashing symbols; and ``_clash`` is the union of both. These can be passed for ``locals`` during sympification if one desires Symbols rather than the non-Symbol objects for those names. Examples ======== >>> from sympy import S >>> from sympy.abc import _clash1, _clash2, _clash >>> S("Q & C", locals=_clash1) C & Q >>> S('pi(x)', locals=_clash2) pi(x) >>> S('pi(C, Q)', locals=_clash) pi(C, Q) """ from typing import Any, Dict import string from .core import Symbol, symbols from .core.alphabets import greeks from .core.compatibility import exec_ ##### Symbol definitions ##### # Implementation note: The easiest way to avoid typos in the symbols() # parameter is to copy it from the left-hand side of the assignment. a, b, c, d, e, f, g, h, i, j = symbols('a, b, c, d, e, f, g, h, i, j') k, l, m, n, o, p, q, r, s, t = symbols('k, l, m, n, o, p, q, r, s, t') u, v, w, x, y, z = symbols('u, v, w, x, y, z') A, B, C, D, E, F, G, H, I, J = symbols('A, B, C, D, E, F, G, H, I, J') K, L, M, N, O, P, Q, R, S, T = symbols('K, L, M, N, O, P, Q, R, S, T') U, V, W, X, Y, Z = symbols('U, V, W, X, Y, Z') alpha, beta, gamma, delta = symbols('alpha, beta, gamma, delta') epsilon, zeta, eta, theta = symbols('epsilon, zeta, eta, theta') iota, kappa, lamda, mu = symbols('iota, kappa, lamda, mu') nu, xi, omicron, pi = symbols('nu, xi, omicron, pi') rho, sigma, tau, upsilon = symbols('rho, sigma, tau, upsilon') phi, chi, psi, omega = symbols('phi, chi, psi, omega') ##### Clashing-symbols diagnostics ##### # We want to know which names in SymPy collide with those in here. # This is mostly for diagnosing SymPy's namespace during SymPy development. _latin = list(string.ascii_letters) # OSINEQ should not be imported as they clash; gamma, pi and zeta clash, too _greek = list(greeks) # make a copy, so we can mutate it # Note: We import lamda since lambda is a reserved keyword in Python _greek.remove("lambda") _greek.append("lamda") ns = {} # type: Dict[str, Any] exec_('from sympy import *', ns) _clash1 = {} _clash2 = {} while ns: _k, _ = ns.popitem() if _k in _greek: _clash2[_k] = Symbol(_k) _greek.remove(_k) elif _k in _latin: _clash1[_k] = Symbol(_k) _latin.remove(_k) _clash = {} _clash.update(_clash1) _clash.update(_clash2) del _latin, _greek, Symbol, _k
cd11e92bdc44b45374069b191a3ce010b0c0cd7bb98d9836b8900c8138101ecc	""" Continuous Random Variables - Prebuilt variables Contains ======== Arcsin Benini Beta BetaNoncentral BetaPrime BoundedPareto Cauchy Chi ChiNoncentral ChiSquared Dagum Erlang ExGaussian Exponential ExponentialPower FDistribution FisherZ Frechet Gamma GammaInverse Gumbel Gompertz Kumaraswamy Laplace Levy Logistic LogLogistic LogNormal Lomax Maxwell Moyal Nakagami Normal Pareto PowerFunction QuadraticU RaisedCosine Rayleigh Reciprocal ShiftedGompertz StudentT Trapezoidal Triangular Uniform UniformSum VonMises Wald Weibull WignerSemicircle """ from sympy import beta as beta_fn from sympy import cos, sin, tan, atan, exp, besseli, besselj, besselk from sympy import (log, sqrt, pi, S, Dummy, Interval, sympify, gamma, sign, Piecewise, And, Eq, binomial, factorial, Sum, floor, Abs, Lambda, Basic, lowergamma, erf, erfc, erfi, erfinv, I, asin, hyper, uppergamma, sinh, Ne, expint, Rational, integrate) from sympy.matrices import MatrixBase, MatrixExpr from sympy.stats.crv import SingleContinuousPSpace, SingleContinuousDistribution from sympy.stats.rv import _value_check, is_random oo = S.Infinity __all__ = ['ContinuousRV', 'Arcsin', 'Benini', 'Beta', 'BetaNoncentral', 'BetaPrime', 'BoundedPareto', 'Cauchy', 'Chi', 'ChiNoncentral', 'ChiSquared', 'Dagum', 'Erlang', 'ExGaussian', 'Exponential', 'ExponentialPower', 'FDistribution', 'FisherZ', 'Frechet', 'Gamma', 'GammaInverse', 'Gompertz', 'Gumbel', 'Kumaraswamy', 'Laplace', 'Levy', 'Logistic', 'LogLogistic', 'LogNormal', 'Lomax', 'Maxwell', 'Moyal', 'Nakagami', 'Normal', 'GaussianInverse', 'Pareto', 'PowerFunction', 'QuadraticU', 'RaisedCosine', 'Rayleigh', 'Reciprocal', 'StudentT', 'ShiftedGompertz', 'Trapezoidal', 'Triangular', 'Uniform', 'UniformSum', 'VonMises', 'Wald', 'Weibull', 'WignerSemicircle', ] @is_random.register(MatrixBase) def _(x): return any([is_random(i) for i in x]) def rv(symbol, cls, args, *kwargs): args = list(map(sympify, args)) dist = cls(args) if kwargs.pop('check', True): dist.check(args) pspace = SingleContinuousPSpace(symbol, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(symbol, CompoundDistribution(dist)) return pspace.value class ContinuousDistributionHandmade(SingleContinuousDistribution): _argnames = ('pdf',) def __new__(cls, pdf, set=Interval(-oo, oo)): return Basic.__new__(cls, pdf, set) @property def set(self): return self.args[1] @staticmethod def check(pdf, set): x = Dummy('x') val = integrate(pdf(x), (x, set)) _value_check(Eq(val, 1) != S.false, "The pdf on the given set is incorrect.") def ContinuousRV(symbol, density, set=Interval(-oo, oo), kwargs): """ Create a Continuous Random Variable given the following: Parameters ========== symbol : Symbol Represents name of the random variable. density : Expression containing symbol Represents probability density function. set : set/Interval Represents the region where the pdf is valid, by default is real line. check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Returns ======= RandomSymbol Many common continuous random variable types are already implemented. This function should be necessary only very rarely. Examples ======== >>> from sympy import Symbol, sqrt, exp, pi >>> from sympy.stats import ContinuousRV, P, E >>> x = Symbol("x") >>> pdf = sqrt(2)exp(-x*2/2)/(2sqrt(pi)) # Normal distribution >>> X = ContinuousRV(x, pdf) >>> E(X) 0 >>> P(X>0) 1/2 """ pdf = Piecewise((density, set.as_relational(symbol)), (0, True)) pdf = Lambda(symbol, pdf) # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(symbol.name, ContinuousDistributionHandmade, (pdf, set), *kwargs) ######################################## # Continuous Probability Distributions # ######################################## #------------------------------------------------------------------------------- # Arcsin distribution ---------------------------------------------------------- class ArcsinDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) def pdf(self, x): a, b = self.a, self.b return 1/(pisqrt((x - a)(b - x))) def _cdf(self, x): a, b = self.a, self.b return Piecewise( (S.Zero, x < a), (2asin(sqrt((x - a)/(b - a)))/pi, x <= b), (S.One, True)) def Arcsin(name, a=0, b=1): r""" Create a Continuous Random Variable with an arcsin distribution. The density of the arcsin distribution is given by .. math:: f(x) := \frac{1}{\pi\sqrt{(x-a)(b-x)}} with :math:`x \in (a,b)`. It must hold that :math:`-\infty < a < b < \infty`. Parameters ========== a : Real number, the left interval boundary b : Real number, the right interval boundary Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Arcsin, density, cdf >>> from sympy import Symbol >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = Arcsin("x", a, b) >>> density(X)(z) 1/(pisqrt((-a + z)(b - z))) >>> cdf(X)(z) Piecewise((0, a > z), (2asin(sqrt((-a + z)/(-a + b)))/pi, b >= z), (1, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Arcsine_distribution """ return rv(name, ArcsinDistribution, (a, b)) #------------------------------------------------------------------------------- # Benini distribution ---------------------------------------------------------- class BeniniDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta', 'sigma') @staticmethod def check(alpha, beta, sigma): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") _value_check(sigma > 0, "Scale parameter Sigma must be positive.") @property def set(self): return Interval(self.sigma, oo) def pdf(self, x): alpha, beta, sigma = self.alpha, self.beta, self.sigma return (exp(-alphalog(x/sigma) - betalog(x/sigma)2) (alpha/x + 2betalog(x/sigma)/x)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function of the ' 'Benini distribution does not exist.') def Benini(name, alpha, beta, sigma): r""" Create a Continuous Random Variable with a Benini distribution. The density of the Benini distribution is given by .. math:: f(x) := e^{-\alpha\log{\frac{x}{\sigma}} -\beta\log^2\left[{\frac{x}{\sigma}}\right]} \left(\frac{\alpha}{x}+\frac{2\beta\log{\frac{x}{\sigma}}}{x}\right) This is a heavy-tailed distribution and is also known as the log-Rayleigh distribution. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape sigma : Real number, `\sigma > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Benini, density, cdf >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = Benini("x", alpha, beta, sigma) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / / z \\ / z \ 2/ z \ \| 2betalog\|-----\|\| - alphalog\|-----\| - betalog \|-----\| \|alpha \sigma/\| \sigma/ \sigma/ \|----- + -----------------\|e \ z z / >>> cdf(X)(z) Piecewise((1 - exp(-alphalog(z/sigma) - betalog(z/sigma)2), sigma <= z), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Benini_distribution .. [2] http://reference.wolfram.com/legacy/v8/ref/BeniniDistribution.html """ return rv(name, BeniniDistribution, (alpha, beta, sigma)) #------------------------------------------------------------------------------- # Beta distribution ------------------------------------------------------------ class BetaDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, 1) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") def pdf(self, x): alpha, beta = self.alpha, self.beta return x(alpha - 1) (1 - x)*(beta - 1) / beta_fn(alpha, beta) def _characteristic_function(self, t): return hyper((self.alpha,), (self.alpha + self.beta,), It) def _moment_generating_function(self, t): return hyper((self.alpha,), (self.alpha + self.beta,), t) def Beta(name, alpha, beta): r""" Create a Continuous Random Variable with a Beta distribution. The density of the Beta distribution is given by .. math:: f(x) := \frac{x^{\alpha-1}(1-x)^{\beta-1}} {\mathrm{B}(\alpha,\beta)} with :math:`x \in [0,1]`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Beta, density, E, variance >>> from sympy import Symbol, simplify, pprint, factor >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = Beta("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) alpha - 1 beta - 1 z (1 - z) -------------------------- B(alpha, beta) >>> simplify(E(X)) alpha/(alpha + beta) >>> factor(simplify(variance(X))) alphabeta/((alpha + beta)*2(alpha + beta + 1)) References ========== .. [1] https://en.wikipedia.org/wiki/Beta_distribution .. [2] http://mathworld.wolfram.com/BetaDistribution.html """ return rv(name, BetaDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Noncentral Beta distribution ------------------------------------------------------------ class BetaNoncentralDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta', 'lamda') set = Interval(0, 1) @staticmethod def check(alpha, beta, lamda): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") _value_check(lamda >= 0, "Noncentrality parameter Lambda must be positive") def pdf(self, x): alpha, beta, lamda = self.alpha, self.beta, self.lamda k = Dummy("k") return Sum(exp(-lamda / 2) * (lamda / 2)*k x*(alpha + k - 1) ( 1 - x)*(beta - 1) / (factorial(k) beta_fn(alpha + k, beta)), (k, 0, oo)) def BetaNoncentral(name, alpha, beta, lamda): r""" Create a Continuous Random Variable with a Type I Noncentral Beta distribution. The density of the Noncentral Beta distribution is given by .. math:: f(x) := \sum_{k=0}^\infty e^{-\lambda/2}\frac{(\lambda/2)^k}{k!} \frac{x^{\alpha+k-1}(1-x)^{\beta-1}}{\mathrm{B}(\alpha+k,\beta)} with :math:`x \in [0,1]`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape lamda: Real number, `\lambda >= 0`, noncentrality parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import BetaNoncentral, density, cdf >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> lamda = Symbol("lamda", nonnegative=True) >>> z = Symbol("z") >>> X = BetaNoncentral("x", alpha, beta, lamda) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) oo _____ \ ` \ -lamda \ k ------- \ k + alpha - 1 /lamda\ beta - 1 2 ) z \|-----\| (1 - z) e / \ 2 / / ------------------------------------------------ / B(k + alpha, beta)k! /____, k = 0 Compute cdf with specific 'x', 'alpha', 'beta' and 'lamda' values as follows : >>> cdf(BetaNoncentral("x", 1, 1, 1), evaluate=False)(2).doit() 2exp(1/2) The argument evaluate=False prevents an attempt at evaluation of the sum for general x, before the argument 2 is passed. References ========== .. [1] https://en.wikipedia.org/wiki/Noncentral_beta_distribution .. [2] https://reference.wolfram.com/language/ref/NoncentralBetaDistribution.html """ return rv(name, BetaNoncentralDistribution, (alpha, beta, lamda)) #------------------------------------------------------------------------------- # Beta prime distribution ------------------------------------------------------ class BetaPrimeDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") set = Interval(0, oo) def pdf(self, x): alpha, beta = self.alpha, self.beta return x(alpha - 1)(1 + x)*(-alpha - beta)/beta_fn(alpha, beta) def BetaPrime(name, alpha, beta): r""" Create a continuous random variable with a Beta prime distribution. The density of the Beta prime distribution is given by .. math:: f(x) := \frac{x^{\alpha-1} (1+x)^{-\alpha -\beta}}{B(\alpha,\beta)} with :math:`x > 0`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import BetaPrime, density >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = BetaPrime("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) alpha - 1 -alpha - beta z (z + 1) ------------------------------- B(alpha, beta) References ========== .. [1] https://en.wikipedia.org/wiki/Beta_prime_distribution .. [2] http://mathworld.wolfram.com/BetaPrimeDistribution.html """ return rv(name, BetaPrimeDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Bounded Pareto Distribution -------------------------------------------------- class BoundedParetoDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'left', 'right') @property def set(self): return Interval(self.left , self.right) @staticmethod def check(alpha, left, right): _value_check (alpha.is_positive, "Shape must be positive.") _value_check (left.is_positive, "Left value should be positive.") _value_check (right > left, "Right should be greater than left.") def pdf(self, x): alpha, left, right = self.alpha, self.left, self.right num = alpha * (left*alpha) x(- alpha -1) den = 1 - (left/right)alpha return num/den def BoundedPareto(name, alpha, left, right): r""" Create a continuous random variable with a Bounded Pareto distribution. The density of the Bounded Pareto distribution is given by .. math:: f(x) := \frac{\alpha L^{\alpha}x^{-\alpha-1}}{1-(\frac{L}{H})^{\alpha}} Parameters ========== alpha : Real Number, `alpha > 0` Shape parameter left : Real Number, `left > 0` Location parameter right : Real Number, `right > left` Location parameter Examples ======== >>> from sympy.stats import BoundedPareto, density, cdf, E >>> from sympy import symbols >>> L, H = symbols('L, H', positive=True) >>> X = BoundedPareto('X', 2, L, H) >>> x = symbols('x') >>> density(X)(x) 2L2/(x3(1 - L2/H2)) >>> cdf(X)(x) Piecewise((-H*2L2/(x2(H2 - L2)) + H2/(H2 - L2), L <= x), (0, True)) >>> E(X).simplify() 2HL/(H + L) Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Pareto_distribution#Bounded_Pareto_distribution """ return rv (name, BoundedParetoDistribution, (alpha, left, right)) # ------------------------------------------------------------------------------ # Cauchy distribution ---------------------------------------------------------- class CauchyDistribution(SingleContinuousDistribution): _argnames = ('x0', 'gamma') @staticmethod def check(x0, gamma): _value_check(gamma > 0, "Scale parameter Gamma must be positive.") _value_check(x0.is_real, "Location parameter must be real.") def pdf(self, x): return 1/(piself.gamma(1 + ((x - self.x0)/self.gamma)2)) def _cdf(self, x): x0, gamma = self.x0, self.gamma return (1/pi)atan((x - x0)/gamma) + S.Half def _characteristic_function(self, t): return exp(self.x0 * I * t - self.gamma * Abs(t)) def _moment_generating_function(self, t): raise NotImplementedError("The moment generating function for the " "Cauchy distribution does not exist.") def _quantile(self, p): return self.x0 + self.gammatan(pi(p - S.Half)) def Cauchy(name, x0, gamma): r""" Create a continuous random variable with a Cauchy distribution. The density of the Cauchy distribution is given by .. math:: f(x) := \frac{1}{\pi \gamma [1 + {(\frac{x-x_0}{\gamma})}^2]} Parameters ========== x0 : Real number, the location gamma : Real number, `\gamma > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Cauchy, density >>> from sympy import Symbol >>> x0 = Symbol("x0") >>> gamma = Symbol("gamma", positive=True) >>> z = Symbol("z") >>> X = Cauchy("x", x0, gamma) >>> density(X)(z) 1/(pigamma(1 + (-x0 + z)2/gamma2)) References ========== .. [1] https://en.wikipedia.org/wiki/Cauchy_distribution .. [2] http://mathworld.wolfram.com/CauchyDistribution.html """ return rv(name, CauchyDistribution, (x0, gamma)) #------------------------------------------------------------------------------- # Chi distribution ------------------------------------------------------------- class ChiDistribution(SingleContinuousDistribution): _argnames = ('k',) @staticmethod def check(k): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") set = Interval(0, oo) def pdf(self, x): return 2*(1 - self.k/2)x*(self.k - 1)exp(-x2/2)/gamma(self.k/2) def _characteristic_function(self, t): k = self.k part_1 = hyper((k/2,), (S.Half,), -t2/2) part_2 = Itsqrt(2)gamma((k+1)/2)/gamma(k/2) part_3 = hyper(((k+1)/2,), (Rational(3, 2),), -t2/2) return part_1 + part_2part_3 def _moment_generating_function(self, t): k = self.k part_1 = hyper((k / 2,), (S.Half,), t ** 2 / 2) part_2 = t * sqrt(2) * gamma((k + 1) / 2) / gamma(k / 2) part_3 = hyper(((k + 1) / 2,), (S(3) / 2,), t ** 2 / 2) return part_1 + part_2 * part_3 def Chi(name, k): r""" Create a continuous random variable with a Chi distribution. The density of the Chi distribution is given by .. math:: f(x) := \frac{2^{1-k/2}x^{k-1}e^{-x^2/2}}{\Gamma(k/2)} with :math:`x \geq 0`. Parameters ========== k : Positive integer, The number of degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Chi, density, E >>> from sympy import Symbol, simplify >>> k = Symbol("k", integer=True) >>> z = Symbol("z") >>> X = Chi("x", k) >>> density(X)(z) 2*(1 - k/2)z*(k - 1)exp(-z*2/2)/gamma(k/2) >>> simplify(E(X)) sqrt(2)gamma(k/2 + 1/2)/gamma(k/2) References ========== .. [1] https://en.wikipedia.org/wiki/Chi_distribution .. [2] http://mathworld.wolfram.com/ChiDistribution.html """ return rv(name, ChiDistribution, (k,)) #------------------------------------------------------------------------------- # Non-central Chi distribution ------------------------------------------------- class ChiNoncentralDistribution(SingleContinuousDistribution): _argnames = ('k', 'l') @staticmethod def check(k, l): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") _value_check(l > 0, "Shift parameter Lambda must be positive.") set = Interval(0, oo) def pdf(self, x): k, l = self.k, self.l return exp(-(x2+l2)/2)xkl / (lx)(k/2) besseli(k/2-1, lx) def ChiNoncentral(name, k, l): r""" Create a continuous random variable with a non-central Chi distribution. The density of the non-central Chi distribution is given by .. math:: f(x) := \frac{e^{-(x^2+\lambda^2)/2} x^k\lambda} {(\lambda x)^{k/2}} I_{k/2-1}(\lambda x) with `x \geq 0`. Here, `I_\nu (x)` is the :ref:`modified Bessel function of the first kind <besseli>`. Parameters ========== k : A positive Integer, `k > 0`, the number of degrees of freedom lambda : Real number, `\lambda > 0`, Shift parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ChiNoncentral, density >>> from sympy import Symbol >>> k = Symbol("k", integer=True) >>> l = Symbol("l") >>> z = Symbol("z") >>> X = ChiNoncentral("x", k, l) >>> density(X)(z) lz*k(lz)(-k/2)exp(-l2/2 - z2/2)besseli(k/2 - 1, lz) References ========== .. [1] https://en.wikipedia.org/wiki/Noncentral_chi_distribution """ return rv(name, ChiNoncentralDistribution, (k, l)) #------------------------------------------------------------------------------- # Chi squared distribution ----------------------------------------------------- class ChiSquaredDistribution(SingleContinuousDistribution): _argnames = ('k',) @staticmethod def check(k): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") set = Interval(0, oo) def pdf(self, x): k = self.k return 1/(2*(k/2)gamma(k/2))x(k/2 - 1)exp(-x/2) def _cdf(self, x): k = self.k return Piecewise( (S.One/gamma(k/2)lowergamma(k/2, x/2), x >= 0), (0, True) ) def _characteristic_function(self, t): return (1 - 2It)(-self.k/2) def _moment_generating_function(self, t): return (1 - 2t)(-self.k/2) def ChiSquared(name, k): r""" Create a continuous random variable with a Chi-squared distribution. The density of the Chi-squared distribution is given by .. math:: f(x) := \frac{1}{2^{\frac{k}{2}}\Gamma\left(\frac{k}{2}\right)} x^{\frac{k}{2}-1} e^{-\frac{x}{2}} with :math:`x \geq 0`. Parameters ========== k : Positive integer, The number of degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ChiSquared, density, E, variance, moment >>> from sympy import Symbol >>> k = Symbol("k", integer=True, positive=True) >>> z = Symbol("z") >>> X = ChiSquared("x", k) >>> density(X)(z) 2(-k/2)z(k/2 - 1)exp(-z/2)/gamma(k/2) >>> E(X) k >>> variance(X) 2k >>> moment(X, 3) k3 + 6k*2 + 8k References ========== .. [1] https://en.wikipedia.org/wiki/Chi_squared_distribution .. [2] http://mathworld.wolfram.com/Chi-SquaredDistribution.html """ return rv(name, ChiSquaredDistribution, (k, )) #------------------------------------------------------------------------------- # Dagum distribution ----------------------------------------------------------- class DagumDistribution(SingleContinuousDistribution): _argnames = ('p', 'a', 'b') set = Interval(0, oo) @staticmethod def check(p, a, b): _value_check(p > 0, "Shape parameter p must be positive.") _value_check(a > 0, "Shape parameter a must be positive.") _value_check(b > 0, "Scale parameter b must be positive.") def pdf(self, x): p, a, b = self.p, self.a, self.b return ap/x((x/b)*(ap)/(((x/b)a + 1)(p + 1))) def _cdf(self, x): p, a, b = self.p, self.a, self.b return Piecewise(((S.One + (S(x)/b)-a)-p, x>=0), (S.Zero, True)) def Dagum(name, p, a, b): r""" Create a continuous random variable with a Dagum distribution. The density of the Dagum distribution is given by .. math:: f(x) := \frac{a p}{x} \left( \frac{\left(\tfrac{x}{b}\right)^{a p}} {\left(\left(\tfrac{x}{b}\right)^a + 1 \right)^{p+1}} \right) with :math:`x > 0`. Parameters ========== p : Real number, `p > 0`, a shape a : Real number, `a > 0`, a shape b : Real number, `b > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Dagum, density, cdf >>> from sympy import Symbol >>> p = Symbol("p", positive=True) >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Dagum("x", p, a, b) >>> density(X)(z) ap(z/b)*(ap)((z/b)a + 1)(-p - 1)/z >>> cdf(X)(z) Piecewise(((1 + (z/b)(-a))(-p), z >= 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Dagum_distribution """ return rv(name, DagumDistribution, (p, a, b)) #------------------------------------------------------------------------------- # Erlang distribution ---------------------------------------------------------- def Erlang(name, k, l): r""" Create a continuous random variable with an Erlang distribution. The density of the Erlang distribution is given by .. math:: f(x) := \frac{\lambda^k x^{k-1} e^{-\lambda x}}{(k-1)!} with :math:`x \in [0,\infty]`. Parameters ========== k : Positive integer l : Real number, `\lambda > 0`, the rate Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Erlang, density, cdf, E, variance >>> from sympy import Symbol, simplify, pprint >>> k = Symbol("k", integer=True, positive=True) >>> l = Symbol("l", positive=True) >>> z = Symbol("z") >>> X = Erlang("x", k, l) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) k k - 1 -lz l z e --------------- Gamma(k) >>> C = cdf(X)(z) >>> pprint(C, use_unicode=False) /lowergamma(k, lz) \|------------------ for z > 0 < Gamma(k) \| \ 0 otherwise >>> E(X) k/l >>> simplify(variance(X)) k/l2 References ========== .. [1] https://en.wikipedia.org/wiki/Erlang_distribution .. [2] http://mathworld.wolfram.com/ErlangDistribution.html """ return rv(name, GammaDistribution, (k, S.One/l)) # ------------------------------------------------------------------------------- # ExGaussian distribution ----------------------------------------------------- class ExGaussianDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std', 'rate') set = Interval(-oo, oo) @staticmethod def check(mean, std, rate): _value_check( std > 0, "Standard deviation of ExGaussian must be positive.") _value_check(rate > 0, "Rate of ExGaussian must be positive.") def pdf(self, x): mean, std, rate = self.mean, self.std, self.rate term1 = rate/2 term2 = exp(rate (2 * mean + rate * std*2 - 2x)/2) term3 = erfc((mean + ratestd2 - x)/(sqrt(2)std)) return term1term2term3 def _cdf(self, x): from sympy.stats import cdf mean, std, rate = self.mean, self.std, self.rate u = rate(x - mean) v = ratestd GaussianCDF1 = cdf(Normal('x', 0, v))(u) GaussianCDF2 = cdf(Normal('x', v2, v))(u) return GaussianCDF1 - exp(-u + (v2/2) + log(GaussianCDF2)) def _characteristic_function(self, t): mean, std, rate = self.mean, self.std, self.rate term1 = (1 - It/rate)(-1) term2 = exp(Imeant - std2t*2/2) return term1 term2 def _moment_generating_function(self, t): mean, std, rate = self.mean, self.std, self.rate term1 = (1 - t/rate)*(-1) term2 = exp(meant + std*2t*2/2) return term1term2 def ExGaussian(name, mean, std, rate): r""" Create a continuous random variable with an Exponentially modified Gaussian (EMG) distribution. The density of the exponentially modified Gaussian distribution is given by .. math:: f(x) := \frac{\lambda}{2}e^{\frac{\lambda}{2}(2\mu+\lambda\sigma^2-2x)} \text{erfc}(\frac{\mu + \lambda\sigma^2 - x}{\sqrt{2}\sigma}) with `x > 0`. Note that the expected value is `1/\lambda`. Parameters ========== mu : A Real number, the mean of Gaussian component std: A positive Real number, :math: `\sigma^2 > 0` the variance of Gaussian component lambda: A positive Real number, :math: `\lambda > 0` the rate of Exponential component Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ExGaussian, density, cdf, E >>> from sympy.stats import variance, skewness >>> from sympy import Symbol, pprint, simplify >>> mean = Symbol("mu") >>> std = Symbol("sigma", positive=True) >>> rate = Symbol("lamda", positive=True) >>> z = Symbol("z") >>> X = ExGaussian("x", mean, std, rate) >>> pprint(density(X)(z), use_unicode=False) / 2 \ lamda\lamdasigma + 2mu - 2z/ --------------------------------- / ___ / 2 \\ 2 \|\/ 2 \lamdasigma + mu - z/\| lamdae erfc\|-----------------------------\| \ 2sigma / ---------------------------------------------------------------------------- 2 >>> cdf(X)(z) -(erf(sqrt(2)(-lamda*2sigma*2 + lamda(-mu + z))/(2lamdasigma))/2 + 1/2)exp(lamda2sigma*2/2 - lamda(-mu + z)) + erf(sqrt(2)(-mu + z)/(2sigma))/2 + 1/2 >>> E(X) (lamdamu + 1)/lamda >>> simplify(variance(X)) sigma2 + lamda(-2) >>> simplify(skewness(X)) 2/(lamda2sigma2 + 1)(3/2) References ========== .. [1] https://en.wikipedia.org/wiki/Exponentially_modified_Gaussian_distribution """ return rv(name, ExGaussianDistribution, (mean, std, rate)) #------------------------------------------------------------------------------- # Exponential distribution ----------------------------------------------------- class ExponentialDistribution(SingleContinuousDistribution): _argnames = ('rate',) set = Interval(0, oo) @staticmethod def check(rate): _value_check(rate > 0, "Rate must be positive.") def pdf(self, x): return self.rate * exp(-self.ratex) def _cdf(self, x): return Piecewise( (S.One - exp(-self.ratex), x >= 0), (0, True), ) def _characteristic_function(self, t): rate = self.rate return rate / (rate - It) def _moment_generating_function(self, t): rate = self.rate return rate / (rate - t) def _quantile(self, p): return -log(1-p)/self.rate def Exponential(name, rate): r""" Create a continuous random variable with an Exponential distribution. The density of the exponential distribution is given by .. math:: f(x) := \lambda \exp(-\lambda x) with `x > 0`. Note that the expected value is `1/\lambda`. Parameters ========== rate : A positive Real number, `\lambda > 0`, the rate (or inverse scale/inverse mean) Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Exponential, density, cdf, E >>> from sympy.stats import variance, std, skewness, quantile >>> from sympy import Symbol >>> l = Symbol("lambda", positive=True) >>> z = Symbol("z") >>> p = Symbol("p") >>> X = Exponential("x", l) >>> density(X)(z) lambdaexp(-lambdaz) >>> cdf(X)(z) Piecewise((1 - exp(-lambdaz), z >= 0), (0, True)) >>> quantile(X)(p) -log(1 - p)/lambda >>> E(X) 1/lambda >>> variance(X) lambda*(-2) >>> skewness(X) 2 >>> X = Exponential('x', 10) >>> density(X)(z) 10exp(-10z) >>> E(X) 1/10 >>> std(X) 1/10 References ========== .. [1] https://en.wikipedia.org/wiki/Exponential_distribution .. [2] http://mathworld.wolfram.com/ExponentialDistribution.html """ return rv(name, ExponentialDistribution, (rate, )) # ------------------------------------------------------------------------------- # Exponential Power distribution ----------------------------------------------------- class ExponentialPowerDistribution(SingleContinuousDistribution): _argnames = ('mu', 'alpha', 'beta') set = Interval(-oo, oo) @staticmethod def check(mu, alpha, beta): _value_check(alpha > 0, "Scale parameter alpha must be positive.") _value_check(beta > 0, "Shape parameter beta must be positive.") def pdf(self, x): mu, alpha, beta = self.mu, self.alpha, self.beta num = betaexp(-(Abs(x - mu)/alpha)*beta) den = 2alphagamma(1/beta) return num/den def _cdf(self, x): mu, alpha, beta = self.mu, self.alpha, self.beta num = lowergamma(1/beta, (Abs(x - mu) / alpha)beta) den = 2gamma(1/beta) return sign(x - mu)num/den + S.Half def ExponentialPower(name, mu, alpha, beta): r""" Create a Continuous Random Variable with Exponential Power distribution. This distribution is known also as Generalized Normal distribution version 1 The density of the Exponential Power distribution is given by .. math:: f(x) := \frac{\beta}{2\alpha\Gamma(\frac{1}{\beta})} e^{{-(\frac{\|x - \mu\|}{\alpha})^{\beta}}} with :math:`x \in [ - \infty, \infty ]`. Parameters ========== mu : Real number, 'mu' is a location alpha : Real number, 'alpha > 0' is a scale beta : Real number, 'beta > 0' is a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ExponentialPower, density, cdf >>> from sympy import Symbol, pprint >>> z = Symbol("z") >>> mu = Symbol("mu") >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> X = ExponentialPower("x", mu, alpha, beta) >>> pprint(density(X)(z), use_unicode=False) beta /\|mu - z\|\ -\|--------\| \ alpha / betae --------------------- / 1 \ 2alphaGamma\|----\| \beta/ >>> cdf(X)(z) 1/2 + lowergamma(1/beta, (Abs(mu - z)/alpha)*beta)sign(-mu + z)/(2gamma(1/beta)) References ========== .. [1] https://reference.wolfram.com/language/ref/ExponentialPowerDistribution.html .. [2] https://en.wikipedia.org/wiki/Generalized_normal_distribution#Version_1 """ return rv(name, ExponentialPowerDistribution, (mu, alpha, beta)) #------------------------------------------------------------------------------- # F distribution --------------------------------------------------------------- class FDistributionDistribution(SingleContinuousDistribution): _argnames = ('d1', 'd2') set = Interval(0, oo) @staticmethod def check(d1, d2): _value_check((d1 > 0, d1.is_integer), "Degrees of freedom d1 must be positive integer.") _value_check((d2 > 0, d2.is_integer), "Degrees of freedom d2 must be positive integer.") def pdf(self, x): d1, d2 = self.d1, self.d2 return (sqrt((d1x)*d1d2*d2 / (d1x+d2)*(d1+d2)) / (x beta_fn(d1/2, d2/2))) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the ' 'F-distribution does not exist.') def FDistribution(name, d1, d2): r""" Create a continuous random variable with a F distribution. The density of the F distribution is given by .. math:: f(x) := \frac{\sqrt{\frac{(d_1 x)^{d_1} d_2^{d_2}} {(d_1 x + d_2)^{d_1 + d_2}}}} {x \mathrm{B} \left(\frac{d_1}{2}, \frac{d_2}{2}\right)} with :math:`x > 0`. Parameters ========== d1 : `d_1 > 0`, where d_1 is the degrees of freedom (n_1 - 1) d2 : `d_2 > 0`, where d_2 is the degrees of freedom (n_2 - 1) Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import FDistribution, density >>> from sympy import Symbol, pprint >>> d1 = Symbol("d1", positive=True) >>> d2 = Symbol("d2", positive=True) >>> z = Symbol("z") >>> X = FDistribution("x", d1, d2) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) d2 -- ______________________________ 2 / d1 -d1 - d2 d2 \/ (d1z) (d1z + d2) -------------------------------------- /d1 d2\ zB\|--, --\| \2 2 / References ========== .. [1] https://en.wikipedia.org/wiki/F-distribution .. [2] http://mathworld.wolfram.com/F-Distribution.html """ return rv(name, FDistributionDistribution, (d1, d2)) #------------------------------------------------------------------------------- # Fisher Z distribution -------------------------------------------------------- class FisherZDistribution(SingleContinuousDistribution): _argnames = ('d1', 'd2') set = Interval(-oo, oo) @staticmethod def check(d1, d2): _value_check(d1 > 0, "Degree of freedom d1 must be positive.") _value_check(d2 > 0, "Degree of freedom d2 must be positive.") def pdf(self, x): d1, d2 = self.d1, self.d2 return (2d1*(d1/2)d2*(d2/2) / beta_fn(d1/2, d2/2) exp(d1x) / (d1exp(2x)+d2)((d1+d2)/2)) def FisherZ(name, d1, d2): r""" Create a Continuous Random Variable with an Fisher's Z distribution. The density of the Fisher's Z distribution is given by .. math:: f(x) := \frac{2d_1^{d_1/2} d_2^{d_2/2}} {\mathrm{B}(d_1/2, d_2/2)} \frac{e^{d_1z}}{\left(d_1e^{2z}+d_2\right)^{\left(d_1+d_2\right)/2}} .. TODO - What is the difference between these degrees of freedom? Parameters ========== d1 : `d_1 > 0`, degree of freedom d2 : `d_2 > 0`, degree of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import FisherZ, density >>> from sympy import Symbol, pprint >>> d1 = Symbol("d1", positive=True) >>> d2 = Symbol("d2", positive=True) >>> z = Symbol("z") >>> X = FisherZ("x", d1, d2) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) d1 d2 d1 d2 - -- - -- -- -- 2 2 2 2 / 2z \ d1z 2d1 d2 \d1e + d2/ e ----------------------------------------- /d1 d2\ B\|--, --\| \2 2 / References ========== .. [1] https://en.wikipedia.org/wiki/Fisher%27s_z-distribution .. [2] http://mathworld.wolfram.com/Fishersz-Distribution.html """ return rv(name, FisherZDistribution, (d1, d2)) #------------------------------------------------------------------------------- # Frechet distribution --------------------------------------------------------- class FrechetDistribution(SingleContinuousDistribution): _argnames = ('a', 's', 'm') set = Interval(0, oo) @staticmethod def check(a, s, m): _value_check(a > 0, "Shape parameter alpha must be positive.") _value_check(s > 0, "Scale parameter s must be positive.") def __new__(cls, a, s=1, m=0): a, s, m = list(map(sympify, (a, s, m))) return Basic.__new__(cls, a, s, m) def pdf(self, x): a, s, m = self.a, self.s, self.m return a/s * ((x-m)/s)*(-1-a) exp(-((x-m)/s)(-a)) def _cdf(self, x): a, s, m = self.a, self.s, self.m return Piecewise((exp(-((x-m)/s)(-a)), x >= m), (S.Zero, True)) def Frechet(name, a, s=1, m=0): r""" Create a continuous random variable with a Frechet distribution. The density of the Frechet distribution is given by .. math:: f(x) := \frac{\alpha}{s} \left(\frac{x-m}{s}\right)^{-1-\alpha} e^{-(\frac{x-m}{s})^{-\alpha}} with :math:`x \geq m`. Parameters ========== a : Real number, :math:`a \in \left(0, \infty\right)` the shape s : Real number, :math:`s \in \left(0, \infty\right)` the scale m : Real number, :math:`m \in \left(-\infty, \infty\right)` the minimum Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Frechet, density, cdf >>> from sympy import Symbol >>> a = Symbol("a", positive=True) >>> s = Symbol("s", positive=True) >>> m = Symbol("m", real=True) >>> z = Symbol("z") >>> X = Frechet("x", a, s, m) >>> density(X)(z) a((-m + z)/s)(-a - 1)exp(-((-m + z)/s)(-a))/s >>> cdf(X)(z) Piecewise((exp(-((-m + z)/s)(-a)), m <= z), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Fr%C3%A9chet_distribution """ return rv(name, FrechetDistribution, (a, s, m)) #------------------------------------------------------------------------------- # Gamma distribution ----------------------------------------------------------- class GammaDistribution(SingleContinuousDistribution): _argnames = ('k', 'theta') set = Interval(0, oo) @staticmethod def check(k, theta): _value_check(k > 0, "k must be positive") _value_check(theta > 0, "Theta must be positive") def pdf(self, x): k, theta = self.k, self.theta return x*(k - 1) exp(-x/theta) / (gamma(k)thetak) def _cdf(self, x): k, theta = self.k, self.theta return Piecewise( (lowergamma(k, S(x)/theta)/gamma(k), x > 0), (S.Zero, True)) def _characteristic_function(self, t): return (1 - self.thetaIt)(-self.k) def _moment_generating_function(self, t): return (1- self.thetat)*(-self.k) def Gamma(name, k, theta): r""" Create a continuous random variable with a Gamma distribution. The density of the Gamma distribution is given by .. math:: f(x) := \frac{1}{\Gamma(k) \theta^k} x^{k - 1} e^{-\frac{x}{\theta}} with :math:`x \in [0,1]`. Parameters ========== k : Real number, `k > 0`, a shape theta : Real number, `\theta > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gamma, density, cdf, E, variance >>> from sympy import Symbol, pprint, simplify >>> k = Symbol("k", positive=True) >>> theta = Symbol("theta", positive=True) >>> z = Symbol("z") >>> X = Gamma("x", k, theta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) -z ----- -k k - 1 theta theta z e --------------------- Gamma(k) >>> C = cdf(X, meijerg=True)(z) >>> pprint(C, use_unicode=False) / / z \ \|klowergamma\|k, -----\| \| \ theta/ <---------------------- for z >= 0 \| Gamma(k + 1) \| \ 0 otherwise >>> E(X) ktheta >>> V = simplify(variance(X)) >>> pprint(V, use_unicode=False) 2 ktheta References ========== .. [1] https://en.wikipedia.org/wiki/Gamma_distribution .. [2] http://mathworld.wolfram.com/GammaDistribution.html """ return rv(name, GammaDistribution, (k, theta)) #------------------------------------------------------------------------------- # Inverse Gamma distribution --------------------------------------------------- class GammaInverseDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') set = Interval(0, oo) @staticmethod def check(a, b): _value_check(a > 0, "alpha must be positive") _value_check(b > 0, "beta must be positive") def pdf(self, x): a, b = self.a, self.b return b*a/gamma(a) x*(-a-1) exp(-b/x) def _cdf(self, x): a, b = self.a, self.b return Piecewise((uppergamma(a,b/x)/gamma(a), x > 0), (S.Zero, True)) def _characteristic_function(self, t): a, b = self.a, self.b return 2 * (-Ibt)*(a/2) besselk(a, sqrt(-4Ibt)) / gamma(a) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the ' 'gamma inverse distribution does not exist.') def GammaInverse(name, a, b): r""" Create a continuous random variable with an inverse Gamma distribution. The density of the inverse Gamma distribution is given by .. math:: f(x) := \frac{\beta^\alpha}{\Gamma(\alpha)} x^{-\alpha - 1} \exp\left(\frac{-\beta}{x}\right) with :math:`x > 0`. Parameters ========== a : Real number, `a > 0` a shape b : Real number, `b > 0` a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import GammaInverse, density, cdf >>> from sympy import Symbol, pprint >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = GammaInverse("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) -b --- a -a - 1 z b z e --------------- Gamma(a) >>> cdf(X)(z) Piecewise((uppergamma(a, b/z)/gamma(a), z > 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Inverse-gamma_distribution """ return rv(name, GammaInverseDistribution, (a, b)) #------------------------------------------------------------------------------- # Gumbel distribution (Maximum and Minimum) -------------------------------------------------------- class GumbelDistribution(SingleContinuousDistribution): _argnames = ('beta', 'mu', 'minimum') set = Interval(-oo, oo) @staticmethod def check(beta, mu, minimum): _value_check(beta > 0, "Scale parameter beta must be positive.") def pdf(self, x): beta, mu = self.beta, self.mu z = (x - mu)/beta f_max = (1/beta)exp(-z - exp(-z)) f_min = (1/beta)exp(z - exp(z)) return Piecewise((f_min, self.minimum), (f_max, not self.minimum)) def _cdf(self, x): beta, mu = self.beta, self.mu z = (x - mu)/beta F_max = exp(-exp(-z)) F_min = 1 - exp(-exp(z)) return Piecewise((F_min, self.minimum), (F_max, not self.minimum)) def _characteristic_function(self, t): cf_max = gamma(1 - Iself.betat) exp(Iself.mut) cf_min = gamma(1 + Iself.betat) * exp(Iself.mut) return Piecewise((cf_min, self.minimum), (cf_max, not self.minimum)) def _moment_generating_function(self, t): mgf_max = gamma(1 - self.betat) exp(self.mut) mgf_min = gamma(1 + self.betat) * exp(self.mut) return Piecewise((mgf_min, self.minimum), (mgf_max, not self.minimum)) def Gumbel(name, beta, mu, minimum=False): r""" Create a Continuous Random Variable with Gumbel distribution. The density of the Gumbel distribution is given by For Maximum .. math:: f(x) := \dfrac{1}{\beta} \exp \left( -\dfrac{x-\mu}{\beta} - \exp \left( -\dfrac{x - \mu}{\beta} \right) \right) with :math:`x \in [ - \infty, \infty ]`. For Minimum .. math:: f(x) := \frac{e^{- e^{\frac{- \mu + x}{\beta}} + \frac{- \mu + x}{\beta}}}{\beta} with :math:`x \in [ - \infty, \infty ]`. Parameters ========== mu : Real number, 'mu' is a location beta : Real number, 'beta > 0' is a scale minimum : Boolean, by default, False, set to True for enabling minimum distribution Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gumbel, density, cdf >>> from sympy import Symbol >>> x = Symbol("x") >>> mu = Symbol("mu") >>> beta = Symbol("beta", positive=True) >>> X = Gumbel("x", beta, mu) >>> density(X)(x) exp(-exp(-(-mu + x)/beta) - (-mu + x)/beta)/beta >>> cdf(X)(x) exp(-exp(-(-mu + x)/beta)) References ========== .. [1] http://mathworld.wolfram.com/GumbelDistribution.html .. [2] https://en.wikipedia.org/wiki/Gumbel_distribution .. [3] http://www.mathwave.com/help/easyfit/html/analyses/distributions/gumbel_max.html .. [4] http://www.mathwave.com/help/easyfit/html/analyses/distributions/gumbel_min.html """ return rv(name, GumbelDistribution, (beta, mu, minimum)) #------------------------------------------------------------------------------- # Gompertz distribution -------------------------------------------------------- class GompertzDistribution(SingleContinuousDistribution): _argnames = ('b', 'eta') set = Interval(0, oo) @staticmethod def check(b, eta): _value_check(b > 0, "b must be positive") _value_check(eta > 0, "eta must be positive") def pdf(self, x): eta, b = self.eta, self.b return betaexp(bx)exp(eta)exp(-etaexp(bx)) def _cdf(self, x): eta, b = self.eta, self.b return 1 - exp(eta)exp(-etaexp(bx)) def _moment_generating_function(self, t): eta, b = self.eta, self.b return eta exp(eta) * expint(t/b, eta) def Gompertz(name, b, eta): r""" Create a Continuous Random Variable with Gompertz distribution. The density of the Gompertz distribution is given by .. math:: f(x) := b \eta e^{b x} e^{\eta} \exp \left(-\eta e^{bx} \right) with :math: 'x \in [0, \inf)'. Parameters ========== b: Real number, 'b > 0' a scale eta: Real number, 'eta > 0' a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gompertz, density >>> from sympy import Symbol >>> b = Symbol("b", positive=True) >>> eta = Symbol("eta", positive=True) >>> z = Symbol("z") >>> X = Gompertz("x", b, eta) >>> density(X)(z) betaexp(eta)exp(bz)exp(-etaexp(bz)) References ========== .. [1] https://en.wikipedia.org/wiki/Gompertz_distribution """ return rv(name, GompertzDistribution, (b, eta)) #------------------------------------------------------------------------------- # Kumaraswamy distribution ----------------------------------------------------- class KumaraswamyDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') set = Interval(0, oo) @staticmethod def check(a, b): _value_check(a > 0, "a must be positive") _value_check(b > 0, "b must be positive") def pdf(self, x): a, b = self.a, self.b return a b * x*(a-1) (1-xa)(b-1) def _cdf(self, x): a, b = self.a, self.b return Piecewise( (S.Zero, x < S.Zero), (1 - (1 - xa)b, x <= S.One), (S.One, True)) def Kumaraswamy(name, a, b): r""" Create a Continuous Random Variable with a Kumaraswamy distribution. The density of the Kumaraswamy distribution is given by .. math:: f(x) := a b x^{a-1} (1-x^a)^{b-1} with :math:`x \in [0,1]`. Parameters ========== a : Real number, `a > 0` a shape b : Real number, `b > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Kumaraswamy, density, cdf >>> from sympy import Symbol, pprint >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Kumaraswamy("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) b - 1 a - 1 / a\ abz \1 - z / >>> cdf(X)(z) Piecewise((0, z < 0), (1 - (1 - za)b, z <= 1), (1, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Kumaraswamy_distribution """ return rv(name, KumaraswamyDistribution, (a, b)) #------------------------------------------------------------------------------- # Laplace distribution --------------------------------------------------------- class LaplaceDistribution(SingleContinuousDistribution): _argnames = ('mu', 'b') set = Interval(-oo, oo) @staticmethod def check(mu, b): _value_check(b > 0, "Scale parameter b must be positive.") _value_check(mu.is_real, "Location parameter mu should be real") def pdf(self, x): mu, b = self.mu, self.b return 1/(2b)exp(-Abs(x - mu)/b) def _cdf(self, x): mu, b = self.mu, self.b return Piecewise( (S.Halfexp((x - mu)/b), x < mu), (S.One - S.Halfexp(-(x - mu)/b), x >= mu) ) def _characteristic_function(self, t): return exp(self.muIt) / (1 + self.b2t*2) def _moment_generating_function(self, t): return exp(self.mut) / (1 - self.b*2t*2) def Laplace(name, mu, b): r""" Create a continuous random variable with a Laplace distribution. The density of the Laplace distribution is given by .. math:: f(x) := \frac{1}{2 b} \exp \left(-\frac{\|x-\mu\|}b \right) Parameters ========== mu : Real number or a list/matrix, the location (mean) or the location vector b : Real number or a positive definite matrix, representing a scale or the covariance matrix. Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Laplace, density, cdf >>> from sympy import Symbol, pprint >>> mu = Symbol("mu") >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Laplace("x", mu, b) >>> density(X)(z) exp(-Abs(mu - z)/b)/(2b) >>> cdf(X)(z) Piecewise((exp((-mu + z)/b)/2, mu > z), (1 - exp((mu - z)/b)/2, True)) >>> L = Laplace('L', [1, 2], [[1, 0], [0, 1]]) >>> pprint(density(L)(1, 2), use_unicode=False) 5 / ____\ e besselk\0, \/ 35 / --------------------- pi References ========== .. [1] https://en.wikipedia.org/wiki/Laplace_distribution .. [2] http://mathworld.wolfram.com/LaplaceDistribution.html """ if isinstance(mu, (list, MatrixBase)) and\ isinstance(b, (list, MatrixBase)): from sympy.stats.joint_rv_types import MultivariateLaplace return MultivariateLaplace(name, mu, b) return rv(name, LaplaceDistribution, (mu, b)) #------------------------------------------------------------------------------- # Levy distribution --------------------------------------------------------- class LevyDistribution(SingleContinuousDistribution): _argnames = ('mu', 'c') @property def set(self): return Interval(self.mu, oo) @staticmethod def check(mu, c): _value_check(c > 0, "c (scale parameter) must be positive") _value_check(mu.is_real, "mu (location paramater) must be real") def pdf(self, x): mu, c = self.mu, self.c return sqrt(c/(2pi))exp(-c/(2(x - mu)))/((x - mu)*(S.One + S.Half)) def _cdf(self, x): mu, c = self.mu, self.c return erfc(sqrt(c/(2(x - mu)))) def _characteristic_function(self, t): mu, c = self.mu, self.c return exp(I * mu * t - sqrt(-2 * I * c * t)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function of Levy distribution does not exist.') def Levy(name, mu, c): r""" Create a continuous random variable with a Levy distribution. The density of the Levy distribution is given by .. math:: f(x) := \sqrt(\frac{c}{2 \pi}) \frac{\exp -\frac{c}{2 (x - \mu)}}{(x - \mu)^{3/2}} Parameters ========== mu : Real number, the location parameter c : Real number, `c > 0`, a scale parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Levy, density, cdf >>> from sympy import Symbol >>> mu = Symbol("mu", real=True) >>> c = Symbol("c", positive=True) >>> z = Symbol("z") >>> X = Levy("x", mu, c) >>> density(X)(z) sqrt(2)sqrt(c)exp(-c/(-2mu + 2z))/(2sqrt(pi)(-mu + z)*(3/2)) >>> cdf(X)(z) erfc(sqrt(c)sqrt(1/(-2mu + 2z))) References ========== .. [1] https://en.wikipedia.org/wiki/L%C3%A9vy_distribution .. [2] http://mathworld.wolfram.com/LevyDistribution.html """ return rv(name, LevyDistribution, (mu, c)) #------------------------------------------------------------------------------- # Logistic distribution -------------------------------------------------------- class LogisticDistribution(SingleContinuousDistribution): _argnames = ('mu', 's') set = Interval(-oo, oo) @staticmethod def check(mu, s): _value_check(s > 0, "Scale parameter s must be positive.") def pdf(self, x): mu, s = self.mu, self.s return exp(-(x - mu)/s)/(s(1 + exp(-(x - mu)/s))2) def _cdf(self, x): mu, s = self.mu, self.s return S.One/(1 + exp(-(x - mu)/s)) def _characteristic_function(self, t): return Piecewise((exp(Itself.mu) piself.st / sinh(piself.st), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): return exp(self.mut) beta_fn(1 - self.st, 1 + self.st) def _quantile(self, p): return self.mu - self.slog(-S.One + S.One/p) def Logistic(name, mu, s): r""" Create a continuous random variable with a logistic distribution. The density of the logistic distribution is given by .. math:: f(x) := \frac{e^{-(x-\mu)/s}} {s\left(1+e^{-(x-\mu)/s}\right)^2} Parameters ========== mu : Real number, the location (mean) s : Real number, `s > 0` a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Logistic, density, cdf >>> from sympy import Symbol >>> mu = Symbol("mu", real=True) >>> s = Symbol("s", positive=True) >>> z = Symbol("z") >>> X = Logistic("x", mu, s) >>> density(X)(z) exp((mu - z)/s)/(s(exp((mu - z)/s) + 1)*2) >>> cdf(X)(z) 1/(exp((mu - z)/s) + 1) References ========== .. [1] https://en.wikipedia.org/wiki/Logistic_distribution .. [2] http://mathworld.wolfram.com/LogisticDistribution.html """ return rv(name, LogisticDistribution, (mu, s)) #------------------------------------------------------------------------------- # Log-logistic distribution -------------------------------------------------------- class LogLogisticDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, oo) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Scale parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") def pdf(self, x): a, b = self.alpha, self.beta return ((b/a)(x/a)(b - 1))/(1 + (x/a)b)2 def _cdf(self, x): a, b = self.alpha, self.beta return 1/(1 + (x/a)(-b)) def _quantile(self, p): a, b = self.alpha, self.beta return a((p/(1 - p))(1/b)) def expectation(self, expr, var, kwargs): a, b = self.args return Piecewise((S.NaN, b <= 1), (pia/(bsin(pi/b)), True)) def LogLogistic(name, alpha, beta): r""" Create a continuous random variable with a log-logistic distribution. The distribution is unimodal when `beta > 1`. The density of the log-logistic distribution is given by .. math:: f(x) := \frac{(\frac{\beta}{\alpha})(\frac{x}{\alpha})^{\beta - 1}} {(1 + (\frac{x}{\alpha})^{\beta})^2} Parameters ========== alpha : Real number, `\alpha > 0`, scale parameter and median of distribution beta : Real number, `\beta > 0` a shape parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import LogLogistic, density, cdf, quantile >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", real=True, positive=True) >>> beta = Symbol("beta", real=True, positive=True) >>> p = Symbol("p") >>> z = Symbol("z", positive=True) >>> X = LogLogistic("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) beta - 1 / z \ beta\|-----\| \alpha/ ------------------------ 2 / beta \ \|/ z \ \| alpha\|\|-----\| + 1\| \\alpha/ / >>> cdf(X)(z) 1/(1 + (z/alpha)(-beta)) >>> quantile(X)(p) alpha(p/(1 - p))(1/beta) References ========== .. [1] https://en.wikipedia.org/wiki/Log-logistic_distribution """ return rv(name, LogLogisticDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Log Normal distribution ------------------------------------------------------ class LogNormalDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std') set = Interval(0, oo) @staticmethod def check(mean, std): _value_check(std > 0, "Parameter std must be positive.") def pdf(self, x): mean, std = self.mean, self.std return exp(-(log(x) - mean)2 / (2std2)) / (xsqrt(2pi)std) def _cdf(self, x): mean, std = self.mean, self.std return Piecewise( (S.Half + S.Halferf((log(x) - mean)/sqrt(2)/std), x > 0), (S.Zero, True) ) def _moment_generating_function(self, t): raise NotImplementedError('Moment generating function of the log-normal distribution is not defined.') def LogNormal(name, mean, std): r""" Create a continuous random variable with a log-normal distribution. The density of the log-normal distribution is given by .. math:: f(x) := \frac{1}{x\sqrt{2\pi\sigma^2}} e^{-\frac{\left(\ln x-\mu\right)^2}{2\sigma^2}} with :math:`x \geq 0`. Parameters ========== mu : Real number, the log-scale sigma : Real number, :math:`\sigma^2 > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import LogNormal, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", real=True) >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = LogNormal("x", mu, sigma) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -(-mu + log(z)) ----------------- 2 ___ 2sigma \/ 2 e ------------------------ ____ 2\/ pi sigmaz >>> X = LogNormal('x', 0, 1) # Mean 0, standard deviation 1 >>> density(X)(z) sqrt(2)exp(-log(z)2/2)/(2sqrt(pi)z) References ========== .. [1] https://en.wikipedia.org/wiki/Lognormal .. [2] http://mathworld.wolfram.com/LogNormalDistribution.html """ return rv(name, LogNormalDistribution, (mean, std)) #------------------------------------------------------------------------------- # Lomax Distribution ----------------------------------------------------------- class LomaxDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'lamda',) set = Interval(0, oo) @staticmethod def check(alpha, lamda): _value_check(alpha.is_real, "Shape parameter should be real.") _value_check(lamda.is_real, "Scale parameter should be real.") _value_check(alpha.is_positive, "Shape parameter should be positive.") _value_check(lamda.is_positive, "Scale parameter should be positive.") def pdf(self, x): lamba, alpha = self.lamda, self.alpha return (alpha/lamba) (S.One + x/lamba)*(-alpha-1) def Lomax(name, alpha, lamda): r""" Create a continuous random variable with a Lomax distribution. The density of the Lomax distribution is given by .. math:: f(x) := \frac{\alpha}{\lambda}\left[1+\frac{x}{\lambda}\right]^{-(\alpha+1)} Parameters ========== alpha : Real Number, `alpha > 0` Shape parameter lamda : Real Number, `lamda > 0` Scale parameter Examples ======== >>> from sympy.stats import Lomax, density, cdf, E >>> from sympy import symbols >>> a, l = symbols('a, l', positive=True) >>> X = Lomax('X', a, l) >>> x = symbols('x') >>> density(X)(x) a(1 + x/l)(-a - 1)/l >>> cdf(X)(x) Piecewise((1 - (1 + x/l)(-a), x >= 0), (0, True)) >>> a = 2 >>> X = Lomax('X', a, l) >>> E(X) l Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Lomax_distribution """ return rv(name, LomaxDistribution, (alpha, lamda)) #------------------------------------------------------------------------------- # Maxwell distribution --------------------------------------------------------- class MaxwellDistribution(SingleContinuousDistribution): _argnames = ('a',) set = Interval(0, oo) @staticmethod def check(a): _value_check(a > 0, "Parameter a must be positive.") def pdf(self, x): a = self.a return sqrt(2/pi)x2exp(-x*2/(2a2))/a3 def _cdf(self, x): a = self.a return erf(sqrt(2)x/(2a)) - sqrt(2)xexp(-x*2/(2a*2))/(sqrt(pi)a) def Maxwell(name, a): r""" Create a continuous random variable with a Maxwell distribution. The density of the Maxwell distribution is given by .. math:: f(x) := \sqrt{\frac{2}{\pi}} \frac{x^2 e^{-x^2/(2a^2)}}{a^3} with :math:`x \geq 0`. .. TODO - what does the parameter mean? Parameters ========== a : Real number, `a > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Maxwell, density, E, variance >>> from sympy import Symbol, simplify >>> a = Symbol("a", positive=True) >>> z = Symbol("z") >>> X = Maxwell("x", a) >>> density(X)(z) sqrt(2)z2exp(-z*2/(2a*2))/(sqrt(pi)a*3) >>> E(X) 2sqrt(2)a/sqrt(pi) >>> simplify(variance(X)) a2(-8 + 3pi)/pi References ========== .. [1] https://en.wikipedia.org/wiki/Maxwell_distribution .. [2] http://mathworld.wolfram.com/MaxwellDistribution.html """ return rv(name, MaxwellDistribution, (a, )) #------------------------------------------------------------------------------- # Moyal Distribution ----------------------------------------------------------- class MoyalDistribution(SingleContinuousDistribution): _argnames = ('mu', 'sigma') @staticmethod def check(mu, sigma): _value_check(mu.is_real, "Location parameter must be real.") _value_check(sigma.is_real and sigma > 0, "Scale parameter must be real\ and positive.") def pdf(self, x): mu, sigma = self.mu, self.sigma num = exp(-(exp(-(x - mu)/sigma) + (x - mu)/(sigma))/2) den = (sqrt(2pi) * sigma) return num/den def _characteristic_function(self, t): mu, sigma = self.mu, self.sigma term1 = exp(Itmu) term2 = (2*(-Isigmat) gamma(Rational(1, 2) - Itsigma)) return (term1 * term2)/sqrt(pi) def _moment_generating_function(self, t): mu, sigma = self.mu, self.sigma term1 = exp(tmu) term2 = (2(-1sigmat) gamma(Rational(1, 2) - tsigma)) return (term1 term2)/sqrt(pi) def Moyal(name, mu, sigma): r""" Create a continuous random variable with a Moyal distribution. The density of the Moyal distribution is given by .. math:: f(x) := \frac{\exp-\frac{1}{2}\exp-\frac{x-\mu}{\sigma}-\frac{x-\mu}{2\sigma}}{\sqrt{2\pi}\sigma} with :math:`x \in \mathbb{R}`. Parameters ========== mu : Real number Location parameter sigma : Real positive number Scale parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Moyal, density, cdf >>> from sympy import Symbol, simplify >>> mu = Symbol("mu", real=True) >>> sigma = Symbol("sigma", positive=True, real=True) >>> z = Symbol("z") >>> X = Moyal("x", mu, sigma) >>> density(X)(z) sqrt(2)exp(-exp((mu - z)/sigma)/2 - (-mu + z)/(2sigma))/(2sqrt(pi)sigma) >>> simplify(cdf(X)(z)) 1 - erf(sqrt(2)exp((mu - z)/(2sigma))/2) References ========== .. [1] https://reference.wolfram.com/language/ref/MoyalDistribution.html .. [2] http://www.stat.rice.edu/~dobelman/textfiles/DistributionsHandbook.pdf """ return rv(name, MoyalDistribution, (mu, sigma)) #------------------------------------------------------------------------------- # Nakagami distribution -------------------------------------------------------- class NakagamiDistribution(SingleContinuousDistribution): _argnames = ('mu', 'omega') set = Interval(0, oo) @staticmethod def check(mu, omega): _value_check(mu >= S.Half, "Shape parameter mu must be greater than equal to 1/2.") _value_check(omega > 0, "Spread parameter omega must be positive.") def pdf(self, x): mu, omega = self.mu, self.omega return 2mumu/(gamma(mu)omega*mu)x*(2mu - 1)exp(-mu/omegax*2) def _cdf(self, x): mu, omega = self.mu, self.omega return Piecewise( (lowergamma(mu, (mu/omega)x*2)/gamma(mu), x > 0), (S.Zero, True)) def Nakagami(name, mu, omega): r""" Create a continuous random variable with a Nakagami distribution. The density of the Nakagami distribution is given by .. math:: f(x) := \frac{2\mu^\mu}{\Gamma(\mu)\omega^\mu} x^{2\mu-1} \exp\left(-\frac{\mu}{\omega}x^2 \right) with :math:`x > 0`. Parameters ========== mu : Real number, `\mu \geq \frac{1}{2}` a shape omega : Real number, `\omega > 0`, the spread Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Nakagami, density, E, variance, cdf >>> from sympy import Symbol, simplify, pprint >>> mu = Symbol("mu", positive=True) >>> omega = Symbol("omega", positive=True) >>> z = Symbol("z") >>> X = Nakagami("x", mu, omega) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -muz ------- mu -mu 2mu - 1 omega 2mu omega z e ---------------------------------- Gamma(mu) >>> simplify(E(X)) sqrt(mu)sqrt(omega)gamma(mu + 1/2)/gamma(mu + 1) >>> V = simplify(variance(X)) >>> pprint(V, use_unicode=False) 2 omegaGamma (mu + 1/2) omega - ----------------------- Gamma(mu)Gamma(mu + 1) >>> cdf(X)(z) Piecewise((lowergamma(mu, muz2/omega)/gamma(mu), z > 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Nakagami_distribution """ return rv(name, NakagamiDistribution, (mu, omega)) #------------------------------------------------------------------------------- # Normal distribution ---------------------------------------------------------- class NormalDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std') @staticmethod def check(mean, std): _value_check(std > 0, "Standard deviation must be positive") def pdf(self, x): return exp(-(x - self.mean)2 / (2self.std2)) / (sqrt(2pi)self.std) def _cdf(self, x): mean, std = self.mean, self.std return erf(sqrt(2)(-mean + x)/(2std))/2 + S.Half def _characteristic_function(self, t): mean, std = self.mean, self.std return exp(Imeant - std2t*2/2) def _moment_generating_function(self, t): mean, std = self.mean, self.std return exp(meant + std*2t*2/2) def _quantile(self, p): mean, std = self.mean, self.std return mean + stdsqrt(2)erfinv(2p - 1) def Normal(name, mean, std): r""" Create a continuous random variable with a Normal distribution. The density of the Normal distribution is given by .. math:: f(x) := \frac{1}{\sigma\sqrt{2\pi}} e^{ -\frac{(x-\mu)^2}{2\sigma^2} } Parameters ========== mu : Real number or a list representing the mean or the mean vector sigma : Real number or a positive definite square matrix, :math:`\sigma^2 > 0` the variance Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Normal, density, E, std, cdf, skewness, quantile, marginal_distribution >>> from sympy import Symbol, simplify, pprint >>> mu = Symbol("mu") >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> y = Symbol("y") >>> p = Symbol("p") >>> X = Normal("x", mu, sigma) >>> density(X)(z) sqrt(2)exp(-(-mu + z)2/(2sigma*2))/(2sqrt(pi)sigma) >>> C = simplify(cdf(X))(z) # it needs a little more help... >>> pprint(C, use_unicode=False) / ___ \ \|\/ 2 (-mu + z)\| erf\|---------------\| \ 2sigma / 1 -------------------- + - 2 2 >>> quantile(X)(p) mu + sqrt(2)sigmaerfinv(2p - 1) >>> simplify(skewness(X)) 0 >>> X = Normal("x", 0, 1) # Mean 0, standard deviation 1 >>> density(X)(z) sqrt(2)exp(-z2/2)/(2sqrt(pi)) >>> E(2X + 1) 1 >>> simplify(std(2X + 1)) 2 >>> m = Normal('X', [1, 2], [[2, 1], [1, 2]]) >>> pprint(density(m)(y, z), use_unicode=False) /1 y\ /2y z\ / z\ / y 2z \ \|- - -\|\|--- - -\| + \|1 - -\|\|- - + --- - 1\| ___ \2 2/ \ 3 3/ \ 2/ \ 3 3 / \/ 3 e -------------------------------------------------- 6pi >>> marginal_distribution(m, m[0])(1) 1/(2sqrt(pi)) References ========== .. [1] https://en.wikipedia.org/wiki/Normal_distribution .. [2] http://mathworld.wolfram.com/NormalDistributionFunction.html """ if isinstance(mean, (list, MatrixBase, MatrixExpr)) and\ isinstance(std, (list, MatrixBase, MatrixExpr)): from sympy.stats.joint_rv_types import MultivariateNormal return MultivariateNormal(name, mean, std) return rv(name, NormalDistribution, (mean, std)) #------------------------------------------------------------------------------- # Inverse Gaussian distribution ---------------------------------------------------------- class GaussianInverseDistribution(SingleContinuousDistribution): _argnames = ('mean', 'shape') @property def set(self): return Interval(0, oo) @staticmethod def check(mean, shape): _value_check(shape > 0, "Shape parameter must be positive") _value_check(mean > 0, "Mean must be positive") def pdf(self, x): mu, s = self.mean, self.shape return exp(-s(x - mu)*2 / (2xmu2)) sqrt(s/(2pix*3)) def _cdf(self, x): from sympy.stats import cdf mu, s = self.mean, self.shape stdNormalcdf = cdf(Normal('x', 0, 1)) first_term = stdNormalcdf(sqrt(s/x) ((x/mu) - S.One)) second_term = exp(2s/mu) stdNormalcdf(-sqrt(s/x)(x/mu + S.One)) return first_term + second_term def _characteristic_function(self, t): mu, s = self.mean, self.shape return exp((s/mu)(1 - sqrt(1 - (2mu2It)/s))) def _moment_generating_function(self, t): mu, s = self.mean, self.shape return exp((s/mu)(1 - sqrt(1 - (2mu2t)/s))) def GaussianInverse(name, mean, shape): r""" Create a continuous random variable with an Inverse Gaussian distribution. Inverse Gaussian distribution is also known as Wald distribution. The density of the Inverse Gaussian distribution is given by .. math:: f(x) := \sqrt{\frac{\lambda}{2\pi x^3}} e^{-\frac{\lambda(x-\mu)^2}{2x\mu^2}} Parameters ========== mu : Positive number representing the mean lambda : Positive number representing the shape parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import GaussianInverse, density, E, std, skewness >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", positive=True) >>> lamda = Symbol("lambda", positive=True) >>> z = Symbol("z", positive=True) >>> X = GaussianInverse("x", mu, lamda) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -lambda(-mu + z) ------------------- 2 ___ ________ 2mu z \/ 2 \/ lambda e ------------------------------------- ____ 3/2 2\/ pi z >>> E(X) mu >>> std(X).expand() mu(3/2)/sqrt(lambda) >>> skewness(X).expand() 3sqrt(mu)/sqrt(lambda) References ========== .. [1] https://en.wikipedia.org/wiki/Inverse_Gaussian_distribution .. [2] http://mathworld.wolfram.com/InverseGaussianDistribution.html """ return rv(name, GaussianInverseDistribution, (mean, shape)) Wald = GaussianInverse #------------------------------------------------------------------------------- # Pareto distribution ---------------------------------------------------------- class ParetoDistribution(SingleContinuousDistribution): _argnames = ('xm', 'alpha') @property def set(self): return Interval(self.xm, oo) @staticmethod def check(xm, alpha): _value_check(xm > 0, "Xm must be positive") _value_check(alpha > 0, "Alpha must be positive") def pdf(self, x): xm, alpha = self.xm, self.alpha return alpha * xmalpha / x(alpha + 1) def _cdf(self, x): xm, alpha = self.xm, self.alpha return Piecewise( (S.One - xmalpha/xalpha, x>=xm), (0, True), ) def _moment_generating_function(self, t): xm, alpha = self.xm, self.alpha return alpha * (-xmt)alpha uppergamma(-alpha, -xmt) def _characteristic_function(self, t): xm, alpha = self.xm, self.alpha return alpha (-I * xm * t) ** alpha * uppergamma(-alpha, -I * xm * t) def Pareto(name, xm, alpha): r""" Create a continuous random variable with the Pareto distribution. The density of the Pareto distribution is given by .. math:: f(x) := \frac{\alpha\,x_m^\alpha}{x^{\alpha+1}} with :math:`x \in [x_m,\infty]`. Parameters ========== xm : Real number, `x_m > 0`, a scale alpha : Real number, `\alpha > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Pareto, density >>> from sympy import Symbol >>> xm = Symbol("xm", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = Pareto("x", xm, beta) >>> density(X)(z) betaxmbetaz*(-beta - 1) References ========== .. [1] https://en.wikipedia.org/wiki/Pareto_distribution .. [2] http://mathworld.wolfram.com/ParetoDistribution.html """ return rv(name, ParetoDistribution, (xm, alpha)) #------------------------------------------------------------------------------- # PowerFunction distribution --------------------------------------------------- class PowerFunctionDistribution(SingleContinuousDistribution): _argnames=('alpha','a','b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(alpha, a, b): _value_check(a.is_real, "Continuous Boundary parameter should be real.") _value_check(b.is_real, "Continuous Boundary parameter should be real.") _value_check(a < b, " 'a' the left Boundary must be smaller than 'b' the right Boundary." ) _value_check(alpha.is_positive, "Continuous Shape parameter should be positive.") def pdf(self, x): alpha, a, b = self.alpha, self.a, self.b num = alpha(x - a)(alpha - 1) den = (b - a)alpha return num/den def PowerFunction(name, alpha, a, b): r""" Creates a continuous random variable with a Power Function Distribution The density of PowerFunction distribution is given by .. math:: f(x) := \frac{{\alpha}(x - a)^{\alpha - 1}}{(b - a)^{\alpha}} with :math:`x \in [a,b]`. Parameters ========== alpha: Positive number, `0 < alpha` the shape paramater a : Real number, :math:`-\infty < a` the left boundary b : Real number, :math:`a < b < \infty` the right boundary Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import PowerFunction, density, cdf, E, variance >>> from sympy import Symbol >>> alpha = Symbol("alpha", positive=True) >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = PowerFunction("X", 2, a, b) >>> density(X)(z) (-2a + 2z)/(-a + b)2 >>> cdf(X)(z) Piecewise((a2/(a*2 - 2ab + b2) - 2az/(a2 - 2ab + b2) + z2/(a2 - 2ab + b2), a <= z), (0, True)) >>> alpha = 2 >>> a = 0 >>> b = 1 >>> Y = PowerFunction("Y", alpha, a, b) >>> E(Y) 2/3 >>> variance(Y) 1/18 References ========== .. [1] http://www.mathwave.com/help/easyfit/html/analyses/distributions/power_func.html """ return rv(name, PowerFunctionDistribution, (alpha, a, b)) #------------------------------------------------------------------------------- # QuadraticU distribution ------------------------------------------------------ class QuadraticUDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b): _value_check(b > a, "Parameter b must be in range (%s, oo)."%(a)) def pdf(self, x): a, b = self.a, self.b alpha = 12 / (b-a)3 beta = (a+b) / 2 return Piecewise( (alpha (x-beta)*2, And(a<=x, x<=b)), (S.Zero, True)) def _moment_generating_function(self, t): a, b = self.a, self.b return -3 (exp(at) (4 + (a*2 + 2a(-2 + b) + b2) t) \ - exp(bt) (4 + (-4b + (a + b)2) t)) / ((a-b)*3 t*2) def _characteristic_function(self, t): a, b = self.a, self.b return -3I(exp(Iatexp(Ibt)) * (4I - (-4b + (a+b)*2)t)) \ / ((a-b)*3 t*2) def QuadraticU(name, a, b): r""" Create a Continuous Random Variable with a U-quadratic distribution. The density of the U-quadratic distribution is given by .. math:: f(x) := \alpha (x-\beta)^2 with :math:`x \in [a,b]`. Parameters ========== a : Real number b : Real number, :math:`a < b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import QuadraticU, density >>> from sympy import Symbol, pprint >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = QuadraticU("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / 2 \| / a b \ \|12\|- - - - + z\| \| \ 2 2 / <----------------- for And(b >= z, a <= z) \| 3 \| (-a + b) \| \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/U-quadratic_distribution """ return rv(name, QuadraticUDistribution, (a, b)) #------------------------------------------------------------------------------- # RaisedCosine distribution ---------------------------------------------------- class RaisedCosineDistribution(SingleContinuousDistribution): _argnames = ('mu', 's') @property def set(self): return Interval(self.mu - self.s, self.mu + self.s) @staticmethod def check(mu, s): _value_check(s > 0, "s must be positive") def pdf(self, x): mu, s = self.mu, self.s return Piecewise( ((1+cos(pi(x-mu)/s)) / (2s), And(mu-s<=x, x<=mu+s)), (S.Zero, True)) def _characteristic_function(self, t): mu, s = self.mu, self.s return Piecewise((exp(-Ipimu/s)/2, Eq(t, -pi/s)), (exp(Ipimu/s)/2, Eq(t, pi/s)), (pi*2sin(st)exp(Imut) / (st(pi2 - s2t2)), True)) def _moment_generating_function(self, t): mu, s = self.mu, self.s return pi2 sinh(st) exp(mut) / (st(pi2 + s2t*2)) def RaisedCosine(name, mu, s): r""" Create a Continuous Random Variable with a raised cosine distribution. The density of the raised cosine distribution is given by .. math:: f(x) := \frac{1}{2s}\left(1+\cos\left(\frac{x-\mu}{s}\pi\right)\right) with :math:`x \in [\mu-s,\mu+s]`. Parameters ========== mu : Real number s : Real number, `s > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import RaisedCosine, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", real=True) >>> s = Symbol("s", positive=True) >>> z = Symbol("z") >>> X = RaisedCosine("x", mu, s) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / /pi(-mu + z)\ \|cos\|------------\| + 1 \| \ s / <--------------------- for And(z >= mu - s, z <= mu + s) \| 2s \| \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Raised_cosine_distribution """ return rv(name, RaisedCosineDistribution, (mu, s)) #------------------------------------------------------------------------------- # Rayleigh distribution -------------------------------------------------------- class RayleighDistribution(SingleContinuousDistribution): _argnames = ('sigma',) set = Interval(0, oo) @staticmethod def check(sigma): _value_check(sigma > 0, "Scale parameter sigma must be positive.") def pdf(self, x): sigma = self.sigma return x/sigma2exp(-x*2/(2sigma2)) def _cdf(self, x): sigma = self.sigma return 1 - exp(-(x2/(2sigma2))) def _characteristic_function(self, t): sigma = self.sigma return 1 - sigmatexp(-sigma2t*2/2) sqrt(pi/2) * (erfi(sigmat/sqrt(2)) - I) def _moment_generating_function(self, t): sigma = self.sigma return 1 + sigmatexp(sigma2t*2/2) sqrt(pi/2) * (erf(sigmat/sqrt(2)) + 1) def Rayleigh(name, sigma): r""" Create a continuous random variable with a Rayleigh distribution. The density of the Rayleigh distribution is given by .. math :: f(x) := \frac{x}{\sigma^2} e^{-x^2/2\sigma^2} with :math:`x > 0`. Parameters ========== sigma : Real number, `\sigma > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Rayleigh, density, E, variance >>> from sympy import Symbol >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = Rayleigh("x", sigma) >>> density(X)(z) zexp(-z*2/(2sigma2))/sigma2 >>> E(X) sqrt(2)sqrt(pi)sigma/2 >>> variance(X) -pisigma2/2 + 2sigma*2 References ========== .. [1] https://en.wikipedia.org/wiki/Rayleigh_distribution .. [2] http://mathworld.wolfram.com/RayleighDistribution.html """ return rv(name, RayleighDistribution, (sigma, )) #------------------------------------------------------------------------------- # Reciprocal distribution -------------------------------------------------------- class ReciprocalDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b): _value_check(a > 0, "Parameter > 0. a = %s"%a) _value_check((a < b), "Parameter b must be in range (%s, +oo]. b = %s"%(a, b)) def pdf(self, x): a, b = self.a, self.b return 1/(x(log(b) - log(a))) def Reciprocal(name, a, b): r"""Creates a continuous random variable with a reciprocal distribution. Parameters ========== a : Real number, :math:`0 < a` b : Real number, :math:`a < b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Reciprocal, density, cdf >>> from sympy import symbols >>> a, b, x = symbols('a, b, x', positive=True) >>> R = Reciprocal('R', a, b) >>> density(R)(x) 1/(x(-log(a) + log(b))) >>> cdf(R)(x) Piecewise((log(a)/(log(a) - log(b)) - log(x)/(log(a) - log(b)), a <= x), (0, True)) Reference ========= .. [1] https://en.wikipedia.org/wiki/Reciprocal_distribution """ return rv(name, ReciprocalDistribution, (a, b)) #------------------------------------------------------------------------------- # Shifted Gompertz distribution ------------------------------------------------ class ShiftedGompertzDistribution(SingleContinuousDistribution): _argnames = ('b', 'eta') set = Interval(0, oo) @staticmethod def check(b, eta): _value_check(b > 0, "b must be positive") _value_check(eta > 0, "eta must be positive") def pdf(self, x): b, eta = self.b, self.eta return bexp(-bx)exp(-etaexp(-bx))(1+eta(1-exp(-bx))) def ShiftedGompertz(name, b, eta): r""" Create a continuous random variable with a Shifted Gompertz distribution. The density of the Shifted Gompertz distribution is given by .. math:: f(x) := b e^{-b x} e^{-\eta \exp(-b x)} \left[1 + \eta(1 - e^(-bx)) \right] with :math: 'x \in [0, \inf)'. Parameters ========== b: Real number, 'b > 0' a scale eta: Real number, 'eta > 0' a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ShiftedGompertz, density >>> from sympy import Symbol >>> b = Symbol("b", positive=True) >>> eta = Symbol("eta", positive=True) >>> x = Symbol("x") >>> X = ShiftedGompertz("x", b, eta) >>> density(X)(x) b(eta(1 - exp(-bx)) + 1)exp(-bx)exp(-etaexp(-bx)) References ========== .. [1] https://en.wikipedia.org/wiki/Shifted_Gompertz_distribution """ return rv(name, ShiftedGompertzDistribution, (b, eta)) #------------------------------------------------------------------------------- # StudentT distribution -------------------------------------------------------- class StudentTDistribution(SingleContinuousDistribution): _argnames = ('nu',) set = Interval(-oo, oo) @staticmethod def check(nu): _value_check(nu > 0, "Degrees of freedom nu must be positive.") def pdf(self, x): nu = self.nu return 1/(sqrt(nu)beta_fn(S.Half, nu/2))(1 + x2/nu)(-(nu + 1)/2) def _cdf(self, x): nu = self.nu return S.Half + xgamma((nu+1)/2)hyper((S.Half, (nu+1)/2), (Rational(3, 2),), -x2/nu)/(sqrt(pinu)gamma(nu/2)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the Student-T distribution is undefined.') def StudentT(name, nu): r""" Create a continuous random variable with a student's t distribution. The density of the student's t distribution is given by .. math:: f(x) := \frac{\Gamma \left(\frac{\nu+1}{2} \right)} {\sqrt{\nu\pi}\Gamma \left(\frac{\nu}{2} \right)} \left(1+\frac{x^2}{\nu} \right)^{-\frac{\nu+1}{2}} Parameters ========== nu : Real number, `\nu > 0`, the degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import StudentT, density, cdf >>> from sympy import Symbol, pprint >>> nu = Symbol("nu", positive=True) >>> z = Symbol("z") >>> X = StudentT("x", nu) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) nu 1 - -- - - 2 2 / 2\ \| z \| \|1 + --\| \ nu/ ----------------- ____ / nu\ \/ nu B\|1/2, --\| \ 2 / >>> cdf(X)(z) 1/2 + zgamma(nu/2 + 1/2)hyper((1/2, nu/2 + 1/2), (3/2,), -z*2/nu)/(sqrt(pi)sqrt(nu)gamma(nu/2)) References ========== .. [1] https://en.wikipedia.org/wiki/Student_t-distribution .. [2] http://mathworld.wolfram.com/Studentst-Distribution.html """ return rv(name, StudentTDistribution, (nu, )) #------------------------------------------------------------------------------- # Trapezoidal distribution ------------------------------------------------------ class TrapezoidalDistribution(SingleContinuousDistribution): _argnames = ('a', 'b', 'c', 'd') @property def set(self): return Interval(self.a, self.d) @staticmethod def check(a, b, c, d): _value_check(a < d, "Lower bound parameter a < %s. a = %s"%(d, a)) _value_check((a <= b, b < c), "Level start parameter b must be in range [%s, %s). b = %s"%(a, c, b)) _value_check((b < c, c <= d), "Level end parameter c must be in range (%s, %s]. c = %s"%(b, d, c)) _value_check(d >= c, "Upper bound parameter d > %s. d = %s"%(c, d)) def pdf(self, x): a, b, c, d = self.a, self.b, self.c, self.d return Piecewise( (2(x-a) / ((b-a)(d+c-a-b)), And(a <= x, x < b)), (2 / (d+c-a-b), And(b <= x, x < c)), (2(d-x) / ((d-c)(d+c-a-b)), And(c <= x, x <= d)), (S.Zero, True)) def Trapezoidal(name, a, b, c, d): r""" Create a continuous random variable with a trapezoidal distribution. The density of the trapezoidal distribution is given by .. math:: f(x) := \begin{cases} 0 & \mathrm{for\ } x < a, \\ \frac{2(x-a)}{(b-a)(d+c-a-b)} & \mathrm{for\ } a \le x < b, \\ \frac{2}{d+c-a-b} & \mathrm{for\ } b \le x < c, \\ \frac{2(d-x)}{(d-c)(d+c-a-b)} & \mathrm{for\ } c \le x < d, \\ 0 & \mathrm{for\ } d < x. \end{cases} Parameters ========== a : Real number, :math:`a < d` b : Real number, :math:`a <= b < c` c : Real number, :math:`b < c <= d` d : Real number Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Trapezoidal, density >>> from sympy import Symbol, pprint >>> a = Symbol("a") >>> b = Symbol("b") >>> c = Symbol("c") >>> d = Symbol("d") >>> z = Symbol("z") >>> X = Trapezoidal("x", a,b,c,d) >>> pprint(density(X)(z), use_unicode=False) / -2a + 2z \|------------------------- for And(a <= z, b > z) \|(-a + b)(-a - b + c + d) \| \| 2 \| -------------- for And(b <= z, c > z) < -a - b + c + d \| \| 2d - 2z \|------------------------- for And(d >= z, c <= z) \|(-c + d)(-a - b + c + d) \| \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Trapezoidal_distribution """ return rv(name, TrapezoidalDistribution, (a, b, c, d)) #------------------------------------------------------------------------------- # Triangular distribution ------------------------------------------------------ class TriangularDistribution(SingleContinuousDistribution): _argnames = ('a', 'b', 'c') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b, c): _value_check(b > a, "Parameter b > %s. b = %s"%(a, b)) _value_check((a <= c, c <= b), "Parameter c must be in range [%s, %s]. c = %s"%(a, b, c)) def pdf(self, x): a, b, c = self.a, self.b, self.c return Piecewise( (2(x - a)/((b - a)(c - a)), And(a <= x, x < c)), (2/(b - a), Eq(x, c)), (2(b - x)/((b - a)(b - c)), And(c < x, x <= b)), (S.Zero, True)) def _characteristic_function(self, t): a, b, c = self.a, self.b, self.c return -2 ((b-c) * exp(Iat) - (b-a) * exp(Ict) + (c-a) * exp(Ibt)) / ((b-a)(c-a)(b-c)t2) def _moment_generating_function(self, t): a, b, c = self.a, self.b, self.c return 2 ((b - c) * exp(a * t) - (b - a) * exp(c * t) + (c - a) * exp(b * t)) / ( (b - a) * (c - a) * (b - c) * t ** 2) def Triangular(name, a, b, c): r""" Create a continuous random variable with a triangular distribution. The density of the triangular distribution is given by .. math:: f(x) := \begin{cases} 0 & \mathrm{for\ } x < a, \\ \frac{2(x-a)}{(b-a)(c-a)} & \mathrm{for\ } a \le x < c, \\ \frac{2}{b-a} & \mathrm{for\ } x = c, \\ \frac{2(b-x)}{(b-a)(b-c)} & \mathrm{for\ } c < x \le b, \\ 0 & \mathrm{for\ } b < x. \end{cases} Parameters ========== a : Real number, :math:`a \in \left(-\infty, \infty\right)` b : Real number, :math:`a < b` c : Real number, :math:`a \leq c \leq b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Triangular, density >>> from sympy import Symbol, pprint >>> a = Symbol("a") >>> b = Symbol("b") >>> c = Symbol("c") >>> z = Symbol("z") >>> X = Triangular("x", a,b,c) >>> pprint(density(X)(z), use_unicode=False) / -2a + 2z \|----------------- for And(a <= z, c > z) \|(-a + b)(-a + c) \| \| 2 \| ------ for c = z < -a + b \| \| 2b - 2z \|---------------- for And(b >= z, c < z) \|(-a + b)(b - c) \| \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Triangular_distribution .. [2] http://mathworld.wolfram.com/TriangularDistribution.html """ return rv(name, TriangularDistribution, (a, b, c)) #------------------------------------------------------------------------------- # Uniform distribution --------------------------------------------------------- class UniformDistribution(SingleContinuousDistribution): _argnames = ('left', 'right') @property def set(self): return Interval(self.left, self.right) @staticmethod def check(left, right): _value_check(left < right, "Lower limit should be less than Upper limit.") def pdf(self, x): left, right = self.left, self.right return Piecewise( (S.One/(right - left), And(left <= x, x <= right)), (S.Zero, True) ) def _cdf(self, x): left, right = self.left, self.right return Piecewise( (S.Zero, x < left), ((x - left)/(right - left), x <= right), (S.One, True) ) def _characteristic_function(self, t): left, right = self.left, self.right return Piecewise(((exp(Itright) - exp(Itleft)) / (It(right - left)), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): left, right = self.left, self.right return Piecewise(((exp(tright) - exp(tleft)) / (t * (right - left)), Ne(t, 0)), (S.One, True)) def expectation(self, expr, var, kwargs): from sympy import Max, Min kwargs['evaluate'] = True result = SingleContinuousDistribution.expectation(self, expr, var, kwargs) result = result.subs({Max(self.left, self.right): self.right, Min(self.left, self.right): self.left}) return result def Uniform(name, left, right): r""" Create a continuous random variable with a uniform distribution. The density of the uniform distribution is given by .. math:: f(x) := \begin{cases} \frac{1}{b - a} & \text{for } x \in [a,b] \\ 0 & \text{otherwise} \end{cases} with :math:`x \in [a,b]`. Parameters ========== a : Real number, :math:`-\infty < a` the left boundary b : Real number, :math:`a < b < \infty` the right boundary Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Uniform, density, cdf, E, variance >>> from sympy import Symbol, simplify >>> a = Symbol("a", negative=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Uniform("x", a, b) >>> density(X)(z) Piecewise((1/(-a + b), (b >= z) & (a <= z)), (0, True)) >>> cdf(X)(z) Piecewise((0, a > z), ((-a + z)/(-a + b), b >= z), (1, True)) >>> E(X) a/2 + b/2 >>> simplify(variance(X)) a*2/12 - ab/6 + b*2/12 References ========== .. [1] https://en.wikipedia.org/wiki/Uniform_distribution_%28continuous%29 .. [2] http://mathworld.wolfram.com/UniformDistribution.html """ return rv(name, UniformDistribution, (left, right)) #------------------------------------------------------------------------------- # UniformSum distribution ------------------------------------------------------ class UniformSumDistribution(SingleContinuousDistribution): _argnames = ('n',) @property def set(self): return Interval(0, self.n) @staticmethod def check(n): _value_check((n > 0, n.is_integer), "Parameter n must be positive integer.") def pdf(self, x): n = self.n k = Dummy("k") return 1/factorial( n - 1)Sum((-1)*kbinomial(n, k)(x - k)(n - 1), (k, 0, floor(x))) def _cdf(self, x): n = self.n k = Dummy("k") return Piecewise((S.Zero, x < 0), (1/factorial(n)Sum((-1)*kbinomial(n, k)(x - k)(n), (k, 0, floor(x))), x <= n), (S.One, True)) def _characteristic_function(self, t): return ((exp(It) - 1) / (It))self.n def _moment_generating_function(self, t): return ((exp(t) - 1) / t)self.n def UniformSum(name, n): r""" Create a continuous random variable with an Irwin-Hall distribution. The probability distribution function depends on a single parameter `n` which is an integer. The density of the Irwin-Hall distribution is given by .. math :: f(x) := \frac{1}{(n-1)!}\sum_{k=0}^{\left\lfloor x\right\rfloor}(-1)^k \binom{n}{k}(x-k)^{n-1} Parameters ========== n : A positive Integer, `n > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import UniformSum, density, cdf >>> from sympy import Symbol, pprint >>> n = Symbol("n", integer=True) >>> z = Symbol("z") >>> X = UniformSum("x", n) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) floor(z) ___ \ ` \ k n - 1 /n\ ) (-1) (-k + z) \| \| / \k/ /__, k = 0 -------------------------------- (n - 1)! >>> cdf(X)(z) Piecewise((0, z < 0), (Sum((-1)_k(-_k + z)*nbinomial(n, _k), (_k, 0, floor(z)))/factorial(n), n >= z), (1, True)) Compute cdf with specific 'x' and 'n' values as follows : >>> cdf(UniformSum("x", 5), evaluate=False)(2).doit() 9/40 The argument evaluate=False prevents an attempt at evaluation of the sum for general n, before the argument 2 is passed. References ========== .. [1] https://en.wikipedia.org/wiki/Uniform_sum_distribution .. [2] http://mathworld.wolfram.com/UniformSumDistribution.html """ return rv(name, UniformSumDistribution, (n, )) #------------------------------------------------------------------------------- # VonMises distribution -------------------------------------------------------- class VonMisesDistribution(SingleContinuousDistribution): _argnames = ('mu', 'k') set = Interval(0, 2pi) @staticmethod def check(mu, k): _value_check(k > 0, "k must be positive") def pdf(self, x): mu, k = self.mu, self.k return exp(kcos(x-mu)) / (2pibesseli(0, k)) def VonMises(name, mu, k): r""" Create a Continuous Random Variable with a von Mises distribution. The density of the von Mises distribution is given by .. math:: f(x) := \frac{e^{\kappa\cos(x-\mu)}}{2\pi I_0(\kappa)} with :math:`x \in [0,2\pi]`. Parameters ========== mu : Real number, measure of location k : Real number, measure of concentration Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import VonMises, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu") >>> k = Symbol("k", positive=True) >>> z = Symbol("z") >>> X = VonMises("x", mu, k) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) kcos(mu - z) e ------------------ 2pibesseli(0, k) References ========== .. [1] https://en.wikipedia.org/wiki/Von_Mises_distribution .. [2] http://mathworld.wolfram.com/vonMisesDistribution.html """ return rv(name, VonMisesDistribution, (mu, k)) #------------------------------------------------------------------------------- # Weibull distribution --------------------------------------------------------- class WeibullDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, oo) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Alpha must be positive") _value_check(beta > 0, "Beta must be positive") def pdf(self, x): alpha, beta = self.alpha, self.beta return beta (x/alpha)*(beta - 1) exp(-(x/alpha)*beta) / alpha def Weibull(name, alpha, beta): r""" Create a continuous random variable with a Weibull distribution. The density of the Weibull distribution is given by .. math:: f(x) := \begin{cases} \frac{k}{\lambda}\left(\frac{x}{\lambda}\right)^{k-1} e^{-(x/\lambda)^{k}} & x\geq0\\ 0 & x<0 \end{cases} Parameters ========== lambda : Real number, :math:`\lambda > 0` a scale k : Real number, `k > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Weibull, density, E, variance >>> from sympy import Symbol, simplify >>> l = Symbol("lambda", positive=True) >>> k = Symbol("k", positive=True) >>> z = Symbol("z") >>> X = Weibull("x", l, k) >>> density(X)(z) k(z/lambda)*(k - 1)exp(-(z/lambda)*k)/lambda >>> simplify(E(X)) lambdagamma(1 + 1/k) >>> simplify(variance(X)) lambda*2(-gamma(1 + 1/k)*2 + gamma(1 + 2/k)) References ========== .. [1] https://en.wikipedia.org/wiki/Weibull_distribution .. [2] http://mathworld.wolfram.com/WeibullDistribution.html """ return rv(name, WeibullDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Wigner semicircle distribution ----------------------------------------------- class WignerSemicircleDistribution(SingleContinuousDistribution): _argnames = ('R',) @property def set(self): return Interval(-self.R, self.R) @staticmethod def check(R): _value_check(R > 0, "Radius R must be positive.") def pdf(self, x): R = self.R return 2/(piR*2)sqrt(R2 - x2) def _characteristic_function(self, t): return Piecewise((2 * besselj(1, self.Rt) / (self.Rt), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): return Piecewise((2 * besseli(1, self.Rt) / (self.Rt), Ne(t, 0)), (S.One, True)) def WignerSemicircle(name, R): r""" Create a continuous random variable with a Wigner semicircle distribution. The density of the Wigner semicircle distribution is given by .. math:: f(x) := \frac2{\pi R^2}\,\sqrt{R^2-x^2} with :math:`x \in [-R,R]`. Parameters ========== R : Real number, `R > 0`, the radius Returns ======= A `RandomSymbol`. Examples ======== >>> from sympy.stats import WignerSemicircle, density, E >>> from sympy import Symbol >>> R = Symbol("R", positive=True) >>> z = Symbol("z") >>> X = WignerSemicircle("x", R) >>> density(X)(z) 2sqrt(R2 - z2)/(piR**2) >>> E(X) 0 References ========== .. [1] https://en.wikipedia.org/wiki/Wigner_semicircle_distribution .. [2] http://mathworld.wolfram.com/WignersSemicircleLaw.html """ return rv(name, WignerSemicircleDistribution, (R,))
65c15591aa99adb2cd607d96465393711b882d1b40925d999cc025233f0a9e92	""" Finite Discrete Random Variables - Prebuilt variable types Contains ======== FiniteRV DiscreteUniform Die Bernoulli Coin Binomial BetaBinomial Hypergeometric Rademacher """ from sympy import (S, sympify, Rational, binomial, cacheit, Integer, Dummy, Eq, Intersection, Interval, Symbol, Lambda, Piecewise, Or, Gt, Lt, Ge, Le, Contains) from sympy import beta as beta_fn from sympy.stats.frv import (SingleFiniteDistribution, SingleFinitePSpace) from sympy.stats.rv import _value_check, Density, is_random __all__ = ['FiniteRV', 'DiscreteUniform', 'Die', 'Bernoulli', 'Coin', 'Binomial', 'BetaBinomial', 'Hypergeometric', 'Rademacher' ] def rv(name, cls, args, kwargs): args = list(map(sympify, args)) dist = cls(args) if kwargs.pop('check', True): dist.check(args) pspace = SingleFinitePSpace(name, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(name, CompoundDistribution(dist)) return pspace.value class FiniteDistributionHandmade(SingleFiniteDistribution): @property def dict(self): return self.args[0] def pmf(self, x): x = Symbol('x') return Lambda(x, Piecewise(( [(v, Eq(k, x)) for k, v in self.dict.items()] + [(S.Zero, True)]))) @property def set(self): return set(self.dict.keys()) @staticmethod def check(density): for p in density.values(): _value_check((p >= 0, p <= 1), "Probability at a point must be between 0 and 1.") val = sum(density.values()) _value_check(Eq(val, 1) != S.false, "Total Probability must be 1.") def FiniteRV(name, density, kwargs): r""" Create a Finite Random Variable given a dict representing the density. Parameters ========== name : Symbol Represents name of the random variable. density: A dict Dictionary conatining the pdf of finite distribution check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Examples ======== >>> from sympy.stats import FiniteRV, P, E >>> density = {0: .1, 1: .2, 2: .3, 3: .4} >>> X = FiniteRV('X', density) >>> E(X) 2.00000000000000 >>> P(X >= 2) 0.700000000000000 Returns ======= RandomSymbol """ # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(name, FiniteDistributionHandmade, density, kwargs) class DiscreteUniformDistribution(SingleFiniteDistribution): @staticmethod def check(args): # not using _value_check since there is a # suggestion for the user if len(set(args)) != len(args): from sympy.utilities.iterables import multiset from sympy.utilities.misc import filldedent weights = multiset(args) n = Integer(len(args)) for k in weights: weights[k] /= n raise ValueError(filldedent(""" Repeated args detected but set expected. For a distribution having different weights for each item use the following:""") + ( '\nS("FiniteRV(%s, %s)")' % ("'X'", weights))) @property def p(self): return Rational(1, len(self.args)) @property # type: ignore @cacheit def dict(self): return {k: self.p for k in self.set} @property def set(self): return set(self.args) def pmf(self, x): if x in self.args: return self.p else: return S.Zero def DiscreteUniform(name, items): r""" Create a Finite Random Variable representing a uniform distribution over the input set. Parameters ========== items: list/tuple Items over which Uniform distribution is to be made Examples ======== >>> from sympy.stats import DiscreteUniform, density >>> from sympy import symbols >>> X = DiscreteUniform('X', symbols('a b c')) # equally likely over a, b, c >>> density(X).dict {a: 1/3, b: 1/3, c: 1/3} >>> Y = DiscreteUniform('Y', list(range(5))) # distribution over a range >>> density(Y).dict {0: 1/5, 1: 1/5, 2: 1/5, 3: 1/5, 4: 1/5} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Discrete_uniform_distribution .. [2] http://mathworld.wolfram.com/DiscreteUniformDistribution.html """ return rv(name, DiscreteUniformDistribution, items) class DieDistribution(SingleFiniteDistribution): _argnames = ('sides',) @staticmethod def check(sides): _value_check((sides.is_positive, sides.is_integer), "number of sides must be a positive integer.") @property def is_symbolic(self): return not self.sides.is_number @property def high(self): return self.sides @property def low(self): return S.One @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.sides)) return set(map(Integer, list(range(1, self.sides + 1)))) def pmf(self, x): x = sympify(x) if not (x.is_number or x.is_Symbol or is_random(x)): raise ValueError("'x' expected as an argument of type 'number' or 'Symbol' or , " "'RandomSymbol' not %s" % (type(x))) cond = Ge(x, 1) & Le(x, self.sides) & Contains(x, S.Integers) return Piecewise((S.One/self.sides, cond), (S.Zero, True)) def Die(name, sides=6): r""" Create a Finite Random Variable representing a fair die. Parameters ========== sides: Integer Represents the number of sides of the Die, by default is 6 Examples ======== >>> from sympy.stats import Die, density >>> from sympy import Symbol >>> D6 = Die('D6', 6) # Six sided Die >>> density(D6).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> D4 = Die('D4', 4) # Four sided Die >>> density(D4).dict {1: 1/4, 2: 1/4, 3: 1/4, 4: 1/4} >>> n = Symbol('n', positive=True, integer=True) >>> Dn = Die('Dn', n) # n sided Die >>> density(Dn).dict Density(DieDistribution(n)) >>> density(Dn).dict.subs(n, 4).doit() {1: 1/4, 2: 1/4, 3: 1/4, 4: 1/4} Returns ======= RandomSymbol """ return rv(name, DieDistribution, sides) class BernoulliDistribution(SingleFiniteDistribution): _argnames = ('p', 'succ', 'fail') @staticmethod def check(p, succ, fail): _value_check((p >= 0, p <= 1), "p should be in range [0, 1].") @property def set(self): return {self.succ, self.fail} def pmf(self, x): if isinstance(self.succ, Symbol) and isinstance(self.fail, Symbol): return Piecewise((self.p, x == self.succ), (1 - self.p, x == self.fail), (S.Zero, True)) return Piecewise((self.p, Eq(x, self.succ)), (1 - self.p, Eq(x, self.fail)), (S.Zero, True)) def Bernoulli(name, p, succ=1, fail=0): r""" Create a Finite Random Variable representing a Bernoulli process. Parameters ========== p : Rational number between 0 and 1 Represents probability of success succ : Integer/symbol/string Represents event of success fail : Integer/symbol/string Represents event of failure Examples ======== >>> from sympy.stats import Bernoulli, density >>> from sympy import S >>> X = Bernoulli('X', S(3)/4) # 1-0 Bernoulli variable, probability = 3/4 >>> density(X).dict {0: 1/4, 1: 3/4} >>> X = Bernoulli('X', S.Half, 'Heads', 'Tails') # A fair coin toss >>> density(X).dict {Heads: 1/2, Tails: 1/2} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Bernoulli_distribution .. [2] http://mathworld.wolfram.com/BernoulliDistribution.html """ return rv(name, BernoulliDistribution, p, succ, fail) def Coin(name, p=S.Half): r""" Create a Finite Random Variable representing a Coin toss. Parameters ========== p : Rational Numeber between 0 and 1 Represents probability of getting "Heads", by default is Half Examples ======== >>> from sympy.stats import Coin, density >>> from sympy import Rational >>> C = Coin('C') # A fair coin toss >>> density(C).dict {H: 1/2, T: 1/2} >>> C2 = Coin('C2', Rational(3, 5)) # An unfair coin >>> density(C2).dict {H: 3/5, T: 2/5} Returns ======= RandomSymbol See Also ======== sympy.stats.Binomial References ========== .. [1] https://en.wikipedia.org/wiki/Coin_flipping """ return rv(name, BernoulliDistribution, p, 'H', 'T') class BinomialDistribution(SingleFiniteDistribution): _argnames = ('n', 'p', 'succ', 'fail') @staticmethod def check(n, p, succ, fail): _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer.") _value_check((p <= 1, p >= 0), "p should be in range [0, 1].") @property def high(self): return self.n @property def low(self): return S.Zero @property def is_symbolic(self): return not self.n.is_number @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.n)) return set(self.dict.keys()) def pmf(self, x): n, p = self.n, self.p x = sympify(x) if not (x.is_number or x.is_Symbol or is_random(x)): raise ValueError("'x' expected as an argument of type 'number' or 'Symbol' or , " "'RandomSymbol' not %s" % (type(x))) cond = Ge(x, 0) & Le(x, n) & Contains(x, S.Integers) return Piecewise((binomial(n, x) * p*x (1 - p)*(n - x), cond), (S.Zero, True)) @property # type: ignore @cacheit def dict(self): if self.is_symbolic: return Density(self) return {kself.succ + (self.n-k)self.fail: self.pmf(k) for k in range(0, self.n + 1)} def Binomial(name, n, p, succ=1, fail=0): r""" Create a Finite Random Variable representing a binomial distribution. Parameters ========== n : Positive Integer Represents number of trials p : Rational Number between 0 and 1 Represents probability of success succ : Integer/symbol/string Represents event of success, by default is 1 fail : Integer/symbol/string Represents event of failure, by default is 0 Examples ======== >>> from sympy.stats import Binomial, density >>> from sympy import S, Symbol >>> X = Binomial('X', 4, S.Half) # Four "coin flips" >>> density(X).dict {0: 1/16, 1: 1/4, 2: 3/8, 3: 1/4, 4: 1/16} >>> n = Symbol('n', positive=True, integer=True) >>> p = Symbol('p', positive=True) >>> X = Binomial('X', n, S.Half) # n "coin flips" >>> density(X).dict Density(BinomialDistribution(n, 1/2, 1, 0)) >>> density(X).dict.subs(n, 4).doit() {0: 1/16, 1: 1/4, 2: 3/8, 3: 1/4, 4: 1/16} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Binomial_distribution .. [2] http://mathworld.wolfram.com/BinomialDistribution.html """ return rv(name, BinomialDistribution, n, p, succ, fail) #------------------------------------------------------------------------------- # Beta-binomial distribution ---------------------------------------------------------- class BetaBinomialDistribution(SingleFiniteDistribution): _argnames = ('n', 'alpha', 'beta') @staticmethod def check(n, alpha, beta): _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer. n = %s." % str(n)) _value_check((alpha > 0), "'alpha' must be: alpha > 0 . alpha = %s" % str(alpha)) _value_check((beta > 0), "'beta' must be: beta > 0 . beta = %s" % str(beta)) @property def high(self): return self.n @property def low(self): return S.Zero @property def is_symbolic(self): return not self.n.is_number @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.n)) return set(map(Integer, list(range(0, self.n + 1)))) def pmf(self, k): n, a, b = self.n, self.alpha, self.beta return binomial(n, k) beta_fn(k + a, n - k + b) / beta_fn(a, b) def BetaBinomial(name, n, alpha, beta): r""" Create a Finite Random Variable representing a Beta-binomial distribution. Parameters ========== n : Positive Integer Represents number of trials alpha : Real positive number beta : Real positive number Examples ======== >>> from sympy.stats import BetaBinomial, density >>> X = BetaBinomial('X', 2, 1, 1) >>> density(X).dict {0: 1/3, 1: 2beta(2, 2), 2: 1/3} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Beta-binomial_distribution .. [2] http://mathworld.wolfram.com/BetaBinomialDistribution.html """ return rv(name, BetaBinomialDistribution, n, alpha, beta) class HypergeometricDistribution(SingleFiniteDistribution): _argnames = ('N', 'm', 'n') @staticmethod def check(n, N, m): _value_check((N.is_integer, N.is_nonnegative), "'N' must be nonnegative integer. N = %s." % str(n)) _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer. n = %s." % str(n)) _value_check((m.is_integer, m.is_nonnegative), "'m' must be nonnegative integer. m = %s." % str(n)) @property def is_symbolic(self): return any(not x.is_number for x in (self.N, self.m, self.n)) @property def high(self): return Piecewise((self.n, Lt(self.n, self.m) != False), (self.m, True)) @property def low(self): return Piecewise((0, Gt(0, self.n + self.m - self.N) != False), (self.n + self.m - self.N, True)) @property def set(self): N, m, n = self.N, self.m, self.n if self.is_symbolic: return Intersection(S.Naturals0, Interval(self.low, self.high)) return {i for i in range(max(0, n + m - N), min(n, m) + 1)} def pmf(self, k): N, m, n = self.N, self.m, self.n return S(binomial(m, k) binomial(N - m, n - k))/binomial(N, n) def Hypergeometric(name, N, m, n): r""" Create a Finite Random Variable representing a hypergeometric distribution. Parameters ========== N : Positive Integer Represents finite population of size N. m : Positive Integer Represents number of trials with required feature. n : Positive Integer Represents numbers of draws. Examples ======== >>> from sympy.stats import Hypergeometric, density >>> X = Hypergeometric('X', 10, 5, 3) # 10 marbles, 5 white (success), 3 draws >>> density(X).dict {0: 1/12, 1: 5/12, 2: 5/12, 3: 1/12} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Hypergeometric_distribution .. [2] http://mathworld.wolfram.com/HypergeometricDistribution.html """ return rv(name, HypergeometricDistribution, N, m, n) class RademacherDistribution(SingleFiniteDistribution): @property def set(self): return {-1, 1} @property def pmf(self): k = Dummy('k') return Lambda(k, Piecewise((S.Half, Or(Eq(k, -1), Eq(k, 1))), (S.Zero, True))) def Rademacher(name): r""" Create a Finite Random Variable representing a Rademacher distribution. Examples ======== >>> from sympy.stats import Rademacher, density >>> X = Rademacher('X') >>> density(X).dict {-1: 1/2, 1: 1/2} Returns ======= RandomSymbol See Also ======== sympy.stats.Bernoulli References ========== .. [1] https://en.wikipedia.org/wiki/Rademacher_distribution """ return rv(name, RademacherDistribution)
0b964834b4ced5429f410f052ba38d6c628f7a05b5bda2bfde7d0edf169b50a1	import random import itertools from typing import Sequence as tSequence, Union as tUnion, List as tList, Tuple as tTuple from sympy import (Matrix, MatrixSymbol, S, Indexed, Basic, Tuple, Range, Set, And, Eq, FiniteSet, ImmutableMatrix, Integer, igcd, Lambda, Mul, Dummy, IndexedBase, Add, Interval, oo, linsolve, eye, Or, Not, Intersection, factorial, Contains, Union, Expr, Function, exp, cacheit, sqrt, pi, gamma, Ge, Piecewise, Symbol, NonSquareMatrixError, EmptySet, ceiling, MatrixBase, ConditionSet, ones, zeros, Identity, Rational, Lt, Gt, Ne, BlockMatrix) from sympy.core.relational import Relational from sympy.logic.boolalg import Boolean from sympy.utilities.exceptions import SymPyDeprecationWarning from sympy.utilities.iterables import strongly_connected_components from sympy.stats.joint_rv import JointDistribution from sympy.stats.joint_rv_types import JointDistributionHandmade from sympy.stats.rv import (RandomIndexedSymbol, random_symbols, RandomSymbol, _symbol_converter, _value_check, pspace, given, dependent, is_random, sample_iter) from sympy.stats.stochastic_process import StochasticPSpace from sympy.stats.symbolic_probability import Probability, Expectation from sympy.stats.frv_types import Bernoulli, BernoulliDistribution, FiniteRV from sympy.stats.drv_types import Poisson, PoissonDistribution from sympy.stats.crv_types import Normal, NormalDistribution, Gamma, GammaDistribution from sympy.core.sympify import _sympify, sympify __all__ = [ 'StochasticProcess', 'DiscreteTimeStochasticProcess', 'DiscreteMarkovChain', 'TransitionMatrixOf', 'StochasticStateSpaceOf', 'GeneratorMatrixOf', 'ContinuousMarkovChain', 'BernoulliProcess', 'PoissonProcess', 'WienerProcess', 'GammaProcess' ] @is_random.register(Indexed) def _(x): return is_random(x.base) @is_random.register(RandomIndexedSymbol) # type: ignore def _(x): return True def _set_converter(itr): """ Helper function for converting list/tuple/set to Set. If parameter is not an instance of list/tuple/set then no operation is performed. Returns ======= Set The argument converted to Set. Raises ====== TypeError If the argument is not an instance of list/tuple/set. """ if isinstance(itr, (list, tuple, set)): itr = FiniteSet(itr) if not isinstance(itr, Set): raise TypeError("%s is not an instance of list/tuple/set."%(itr)) return itr def _state_converter(itr: tSequence) -> tUnion[Tuple, Range]: """ Helper function for converting list/tuple/set/Range/Tuple/FiniteSet to tuple/Range. """ if isinstance(itr, (Tuple, set, FiniteSet)): itr = Tuple((sympify(i) if isinstance(i, str) else i for i in itr)) elif isinstance(itr, (list, tuple)): # check if states are unique if len(set(itr)) != len(itr): raise ValueError('The state space must have unique elements.') itr = Tuple((sympify(i) if isinstance(i, str) else i for i in itr)) elif isinstance(itr, Range): # the only ordered set in sympy I know of # try to convert to tuple try: itr = Tuple((sympify(i) if isinstance(i, str) else i for i in itr)) except ValueError: pass else: raise TypeError("%s is not an instance of list/tuple/set/Range/Tuple/FiniteSet." % (itr)) return itr def _sym_sympify(arg): """ Converts an arbitrary expression to a type that can be used inside SymPy. As generally strings are unwise to use in the expressions, it returns the Symbol of argument if the string type argument is passed. Parameters ========= arg: The parameter to be converted to be used in Sympy. Returns ======= The converted parameter. """ if isinstance(arg, str): return Symbol(arg) else: return _sympify(arg) def _matrix_checks(matrix): if not isinstance(matrix, (Matrix, MatrixSymbol, ImmutableMatrix)): raise TypeError("Transition probabilities either should " "be a Matrix or a MatrixSymbol.") if matrix.shape[0] != matrix.shape[1]: raise NonSquareMatrixError("%s is not a square matrix"%(matrix)) if isinstance(matrix, Matrix): matrix = ImmutableMatrix(matrix.tolist()) return matrix class StochasticProcess(Basic): """ Base class for all the stochastic processes whether discrete or continuous. Parameters ========== sym: Symbol or str state_space: Set The state space of the stochastic process, by default S.Reals. For discrete sets it is zero indexed. See Also ======== DiscreteTimeStochasticProcess """ index_set = S.Reals def __new__(cls, sym, state_space=S.Reals, *kwargs): sym = _symbol_converter(sym) state_space = _set_converter(state_space) return Basic.__new__(cls, sym, state_space) @property def symbol(self): return self.args[0] @property def state_space(self) -> tUnion[FiniteSet, Range]: if not isinstance(self.args[1], (FiniteSet, Range)): return FiniteSet(self.args[1]) return self.args[1] @property def distribution(self): return None def __call__(self, time): """ Overridden in ContinuousTimeStochasticProcess. """ raise NotImplementedError("Use [] for indexing discrete time stochastic process.") def __getitem__(self, time): """ Overridden in DiscreteTimeStochasticProcess. """ raise NotImplementedError("Use () for indexing continuous time stochastic process.") def probability(self, condition): raise NotImplementedError() def joint_distribution(self, args): """ Computes the joint distribution of the random indexed variables. Parameters ========== args: iterable The finite list of random indexed variables/the key of a stochastic process whose joint distribution has to be computed. Returns ======= JointDistribution The joint distribution of the list of random indexed variables. An unevaluated object is returned if it is not possible to compute the joint distribution. Raises ====== ValueError: When the arguments passed are not of type RandomIndexSymbol or Number. """ args = list(args) for i, arg in enumerate(args): if S(arg).is_Number: if self.index_set.is_subset(S.Integers): args[i] = self.__getitem__(arg) else: args[i] = self.__call__(arg) elif not isinstance(arg, RandomIndexedSymbol): raise ValueError("Expected a RandomIndexedSymbol or " "key not %s"%(type(arg))) if args[0].pspace.distribution == None: # checks if there is any distribution available return JointDistribution(args) pdf = Lambda(tuple(args), expr=Mul.fromiter(arg.pspace.process.density(arg) for arg in args)) return JointDistributionHandmade(pdf) def expectation(self, condition, given_condition): raise NotImplementedError("Abstract method for expectation queries.") def sample(self): raise NotImplementedError("Abstract method for sampling queries.") class DiscreteTimeStochasticProcess(StochasticProcess): """ Base class for all discrete stochastic processes. """ def __getitem__(self, time): """ For indexing discrete time stochastic processes. Returns ======= RandomIndexedSymbol """ if time not in self.index_set: raise IndexError("%s is not in the index set of %s"%(time, self.symbol)) idx_obj = Indexed(self.symbol, time) pspace_obj = StochasticPSpace(self.symbol, self, self.distribution) return RandomIndexedSymbol(idx_obj, pspace_obj) class ContinuousTimeStochasticProcess(StochasticProcess): """ Base class for all continuous time stochastic process. """ def __call__(self, time): """ For indexing continuous time stochastic processes. Returns ======= RandomIndexedSymbol """ if time not in self.index_set: raise IndexError("%s is not in the index set of %s"%(time, self.symbol)) func_obj = Function(self.symbol)(time) pspace_obj = StochasticPSpace(self.symbol, self, self.distribution) return RandomIndexedSymbol(func_obj, pspace_obj) class TransitionMatrixOf(Boolean): """ Assumes that the matrix is the transition matrix of the process. """ def __new__(cls, process, matrix): if not isinstance(process, DiscreteMarkovChain): raise ValueError("Currently only DiscreteMarkovChain " "support TransitionMatrixOf.") matrix = _matrix_checks(matrix) return Basic.__new__(cls, process, matrix) process = property(lambda self: self.args[0]) matrix = property(lambda self: self.args[1]) class GeneratorMatrixOf(TransitionMatrixOf): """ Assumes that the matrix is the generator matrix of the process. """ def __new__(cls, process, matrix): if not isinstance(process, ContinuousMarkovChain): raise ValueError("Currently only ContinuousMarkovChain " "support GeneratorMatrixOf.") matrix = _matrix_checks(matrix) return Basic.__new__(cls, process, matrix) class StochasticStateSpaceOf(Boolean): def __new__(cls, process, state_space): if not isinstance(process, (DiscreteMarkovChain, ContinuousMarkovChain)): raise ValueError("Currently only DiscreteMarkovChain and ContinuousMarkovChain " "support StochasticStateSpaceOf.") state_space = _state_converter(state_space) if isinstance(state_space, Range): ss_size = ceiling((state_space.stop - state_space.start) / state_space.step) else: ss_size = len(state_space) state_index = Range(ss_size) return Basic.__new__(cls, process, state_index) process = property(lambda self: self.args[0]) state_index = property(lambda self: self.args[1]) class MarkovProcess(StochasticProcess): """ Contains methods that handle queries common to Markov processes. """ @property def number_of_states(self) -> tUnion[Integer, Symbol]: """ The number of states in the Markov Chain. """ return _sympify(self.args[2].shape[0]) @property def _state_index(self) -> Range: """ Returns state index as Range. """ return self.args[1] @classmethod def _sanity_checks(cls, state_space, trans_probs): # Try to never have None as state_space or trans_probs. # This helps a lot if we get it done at the start. if (state_space is None) and (trans_probs is None): _n = Dummy('n', integer=True, nonnegative=True) state_space = _state_converter(Range(_n)) trans_probs = _matrix_checks(MatrixSymbol('_T', _n, _n)) elif state_space is None: trans_probs = _matrix_checks(trans_probs) state_space = _state_converter(Range(trans_probs.shape[0])) elif trans_probs is None: state_space = _state_converter(state_space) if isinstance(state_space, Range): _n = ceiling((state_space.stop - state_space.start) / state_space.step) else: _n = len(state_space) trans_probs = MatrixSymbol('_T', _n, _n) else: state_space = _state_converter(state_space) trans_probs = _matrix_checks(trans_probs) # Range object doesn't want to give a symbolic size # so we do it ourselves. if isinstance(state_space, Range): ss_size = ceiling((state_space.stop - state_space.start) / state_space.step) else: ss_size = len(state_space) if ss_size != trans_probs.shape[0]: raise ValueError('The size of the state space and the number of ' 'rows of the transition matrix must be the same.') return state_space, trans_probs def _extract_information(self, given_condition): """ Helper function to extract information, like, transition matrix/generator matrix, state space, etc. """ if isinstance(self, DiscreteMarkovChain): trans_probs = self.transition_probabilities state_index = self._state_index elif isinstance(self, ContinuousMarkovChain): trans_probs = self.generator_matrix state_index = self._state_index if isinstance(given_condition, And): gcs = given_condition.args given_condition = S.true for gc in gcs: if isinstance(gc, TransitionMatrixOf): trans_probs = gc.matrix if isinstance(gc, StochasticStateSpaceOf): state_index = gc.state_index if isinstance(gc, Relational): given_condition = given_condition & gc if isinstance(given_condition, TransitionMatrixOf): trans_probs = given_condition.matrix given_condition = S.true if isinstance(given_condition, StochasticStateSpaceOf): state_index = given_condition.state_index given_condition = S.true return trans_probs, state_index, given_condition def _check_trans_probs(self, trans_probs, row_sum=1): """ Helper function for checking the validity of transition probabilities. """ if not isinstance(trans_probs, MatrixSymbol): rows = trans_probs.tolist() for row in rows: if (sum(row) - row_sum) != 0: raise ValueError("Values in a row must sum to %s. " "If you are using Float or floats then please use Rational."%(row_sum)) def _work_out_state_index(self, state_index, given_condition, trans_probs): """ Helper function to extract state space if there is a random symbol in the given condition. """ # if given condition is None, then there is no need to work out # state_space from random variables if given_condition != None: rand_var = list(given_condition.atoms(RandomSymbol) - given_condition.atoms(RandomIndexedSymbol)) if len(rand_var) == 1: state_index = rand_var[0].pspace.set # `not None` is `True`. So the old test fails for symbolic sizes. # Need to build the statement differently. sym_cond = not isinstance(self.number_of_states, (int, Integer)) cond1 = not sym_cond and len(state_index) != trans_probs.shape[0] if cond1: raise ValueError("state space is not compatible with the transition probabilities.") if not isinstance(trans_probs.shape[0], Symbol): state_index = FiniteSet([i for i in range(trans_probs.shape[0])]) return state_index @cacheit def _preprocess(self, given_condition, evaluate): """ Helper function for pre-processing the information. """ is_insufficient = False if not evaluate: # avoid pre-processing if the result is not to be evaluated return (True, None, None, None) # extracting transition matrix and state space trans_probs, state_index, given_condition = self._extract_information(given_condition) # given_condition does not have sufficient information # for computations if trans_probs == None or \ given_condition == None: is_insufficient = True else: # checking transition probabilities if isinstance(self, DiscreteMarkovChain): self._check_trans_probs(trans_probs, row_sum=1) elif isinstance(self, ContinuousMarkovChain): self._check_trans_probs(trans_probs, row_sum=0) # working out state space state_index = self._work_out_state_index(state_index, given_condition, trans_probs) return is_insufficient, trans_probs, state_index, given_condition def replace_with_index(self, condition): if isinstance(condition, Relational): lhs, rhs = condition.lhs, condition.rhs if not isinstance(lhs, RandomIndexedSymbol): lhs, rhs = rhs, lhs condition = type(condition)(self.index_of.get(lhs, lhs), self.index_of.get(rhs, rhs)) return condition def probability(self, condition, given_condition=None, evaluate=True, kwargs): """ Handles probability queries for Markov process. Parameters ========== condition: Relational given_condition: Relational/And Returns ======= Probability If the information is not sufficient. Expr In all other cases. Note ==== Any information passed at the time of query overrides any information passed at the time of object creation like transition probabilities, state space. Pass the transition matrix using TransitionMatrixOf, generator matrix using GeneratorMatrixOf and state space using StochasticStateSpaceOf in given_condition using & or And. """ check, mat, state_index, new_given_condition = \ self._preprocess(given_condition, evaluate) if check: return Probability(condition, new_given_condition) if isinstance(self, ContinuousMarkovChain): trans_probs = self.transition_probabilities(mat) elif isinstance(self, DiscreteMarkovChain): trans_probs = mat condition = self.replace_with_index(condition) given_condition = self.replace_with_index(given_condition) new_given_condition = self.replace_with_index(new_given_condition) if isinstance(condition, Relational): if isinstance(new_given_condition, And): gcs = new_given_condition.args else: gcs = (new_given_condition, ) min_key_rv = list(new_given_condition.atoms(RandomIndexedSymbol)) rv = list(condition.atoms(RandomIndexedSymbol)) if len(min_key_rv): min_key_rv = min_key_rv[0] for r in rv: if min_key_rv.key > r.key: return Probability(condition) else: min_key_rv = None return Probability(condition) if len(rv) > 1: rv = rv[:2] if rv[0].key < rv[1].key: rv[0], rv[1] = rv[1], rv[0] s = Rational(0, 1) n = len(self.state_space) if isinstance(condition, Eq) or isinstance(condition, Ne): for i in range(0, n): s += self.probability(Eq(rv[0], i), Eq(rv[1], i)) self.probability(Eq(rv[1], i), new_given_condition) return s if isinstance(condition, Eq) else 1 - s else: upper = 0 greater = False if isinstance(condition, Ge) or isinstance(condition, Lt): upper = 1 if isinstance(condition, Gt) or isinstance(condition, Ge): greater = True for i in range(0, n): if i <= n//2: for j in range(0, i + upper): s += self.probability(Eq(rv[0], i), Eq(rv[1], j)) * self.probability(Eq(rv[1], j), new_given_condition) else: s += self.probability(Eq(rv[0], i), new_given_condition) for j in range(i + upper, n): s -= self.probability(Eq(rv[0], i), Eq(rv[1], j)) * self.probability(Eq(rv[1], j), new_given_condition) return s if greater else 1 - s rv = rv[0] states = condition.as_set() prob, gstate = dict(), None for gc in gcs: if gc.has(min_key_rv): if gc.has(Probability): p, gp = (gc.rhs, gc.lhs) if isinstance(gc.lhs, Probability) \ else (gc.lhs, gc.rhs) gr = gp.args[0] gset = Intersection(gr.as_set(), state_index) gstate = list(gset)[0] prob[gset] = p else: _, gstate = (gc.lhs.key, gc.rhs) if isinstance(gc.lhs, RandomIndexedSymbol) \ else (gc.rhs.key, gc.lhs) if any((k not in self.index_set) for k in (rv.key, min_key_rv.key)): raise IndexError("The timestamps of the process are not in it's index set.") states = Intersection(states, state_index) if not isinstance(self.number_of_states, Symbol) else states for state in Union(states, FiniteSet(gstate)): if not isinstance(state, (int, Integer)) or Ge(state, mat.shape[0]) is True: raise IndexError("No information is available for (%s, %s) in " "transition probabilities of shape, (%s, %s). " "State space is zero indexed." %(gstate, state, mat.shape[0], mat.shape[1])) if prob: gstates = Union(prob.keys()) if len(gstates) == 1: gstate = list(gstates)[0] gprob = list(prob.values())[0] prob[gstates] = gprob elif len(gstates) == len(state_index) - 1: gstate = list(state_index - gstates)[0] gprob = S.One - sum(prob.values()) prob[state_index - gstates] = gprob else: raise ValueError("Conflicting information.") else: gprob = S.One if min_key_rv == rv: return sum([prob[FiniteSet(state)] for state in states]) if isinstance(self, ContinuousMarkovChain): return gprob sum([trans_probs(rv.key - min_key_rv.key).__getitem__((gstate, state)) for state in states]) if isinstance(self, DiscreteMarkovChain): return gprob * sum([(trans_probs(rv.key - min_key_rv.key)).__getitem__((gstate, state)) for state in states]) if isinstance(condition, Not): expr = condition.args[0] return S.One - self.probability(expr, given_condition, evaluate, kwargs) if isinstance(condition, And): compute_later, state2cond, conds = [], dict(), condition.args for expr in conds: if isinstance(expr, Relational): ris = list(expr.atoms(RandomIndexedSymbol))[0] if state2cond.get(ris, None) is None: state2cond[ris] = S.true state2cond[ris] &= expr else: compute_later.append(expr) ris = [] for ri in state2cond: ris.append(ri) cset = Intersection(state2cond[ri].as_set(), state_index) if len(cset) == 0: return S.Zero state2cond[ri] = cset.as_relational(ri) sorted_ris = sorted(ris, key=lambda ri: ri.key) prod = self.probability(state2cond[sorted_ris[0]], given_condition, evaluate, *kwargs) for i in range(1, len(sorted_ris)): ri, prev_ri = sorted_ris[i], sorted_ris[i-1] if not isinstance(state2cond[ri], Eq): raise ValueError("The process is in multiple states at %s, unable to determine the probability."%(ri)) mat_of = TransitionMatrixOf(self, mat) if isinstance(self, DiscreteMarkovChain) else GeneratorMatrixOf(self, mat) prod = self.probability(state2cond[ri], state2cond[prev_ri] & mat_of & StochasticStateSpaceOf(self, state_index), evaluate, *kwargs) for expr in compute_later: prod = self.probability(expr, given_condition, evaluate, kwargs) return prod if isinstance(condition, Or): return sum([self.probability(expr, given_condition, evaluate, kwargs) for expr in condition.args]) raise NotImplementedError("Mechanism for handling (%s, %s) queries hasn't been " "implemented yet."%(condition, given_condition)) def expectation(self, expr, condition=None, evaluate=True, *kwargs): """ Handles expectation queries for markov process. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation Unevaluated object if computations cannot be done due to insufficient information. Expr In all other cases when the computations are successful. Note ==== Any information passed at the time of query overrides any information passed at the time of object creation like transition probabilities, state space. Pass the transition matrix using TransitionMatrixOf, generator matrix using GeneratorMatrixOf and state space using StochasticStateSpaceOf in given_condition using & or And. """ check, mat, state_index, condition = \ self._preprocess(condition, evaluate) if check: return Expectation(expr, condition) rvs = random_symbols(expr) if isinstance(expr, Expr) and isinstance(condition, Eq) \ and len(rvs) == 1: # handle queries similar to E(f(X[i]), Eq(X[i-m], <some-state>)) condition=self.replace_with_index(condition) state_index=self.replace_with_index(state_index) rv = list(rvs)[0] lhsg, rhsg = condition.lhs, condition.rhs if not isinstance(lhsg, RandomIndexedSymbol): lhsg, rhsg = (rhsg, lhsg) if rhsg not in state_index: raise ValueError("%s state is not in the state space."%(rhsg)) if rv.key < lhsg.key: raise ValueError("Incorrect given condition is given, expectation " "time %s < time %s"%(rv.key, rv.key)) mat_of = TransitionMatrixOf(self, mat) if isinstance(self, DiscreteMarkovChain) else GeneratorMatrixOf(self, mat) cond = condition & mat_of & \ StochasticStateSpaceOf(self, state_index) func = lambda s: self.probability(Eq(rv, s), cond) expr.subs(rv, self._state_index[s]) return sum([func(s) for s in state_index]) raise NotImplementedError("Mechanism for handling (%s, %s) queries hasn't been " "implemented yet."%(expr, condition)) class DiscreteMarkovChain(DiscreteTimeStochasticProcess, MarkovProcess): """ Represents a finite discrete time-homogeneous Markov chain. This type of Markov Chain can be uniquely characterised by its (ordered) state space and its one-step transition probability matrix. Parameters ========== sym: The name given to the Markov Chain state_space: Optional, by default, Range(n) trans_probs: Optional, by default, MatrixSymbol('_T', n, n) Examples ======== >>> from sympy.stats import DiscreteMarkovChain, TransitionMatrixOf, P, E >>> from sympy import Matrix, MatrixSymbol, Eq, symbols >>> T = Matrix([[0.5, 0.2, 0.3],[0.2, 0.5, 0.3],[0.2, 0.3, 0.5]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> YS = DiscreteMarkovChain("Y") >>> Y.state_space FiniteSet(0, 1, 2) >>> Y.transition_probabilities Matrix([ [0.5, 0.2, 0.3], [0.2, 0.5, 0.3], [0.2, 0.3, 0.5]]) >>> TS = MatrixSymbol('T', 3, 3) >>> P(Eq(YS[3], 2), Eq(YS[1], 1) & TransitionMatrixOf(YS, TS)) T[0, 2]T[1, 0] + T[1, 1]T[1, 2] + T[1, 2]T[2, 2] >>> P(Eq(Y[3], 2), Eq(Y[1], 1)).round(2) 0.36 Probabilities will be calculated based on indexes rather than state names. For example, with the Sunny-Cloudy-Rainy model with string state names: >>> from sympy.core.symbol import Str >>> Y = DiscreteMarkovChain("Y", [Str('Sunny'), Str('Cloudy'), Str('Rainy')], T) >>> P(Eq(Y[3], 2), Eq(Y[1], 1)).round(2) 0.36 This gives the same answer as the ``[0, 1, 2]`` state space. Currently, there is no support for state names within probability and expectation statements. Here is a work-around using ``Str``: >>> P(Eq(Str('Rainy'), Y[3]), Eq(Y[1], Str('Cloudy'))).round(2) 0.36 Symbol state names can also be used: >>> sunny, cloudy, rainy = symbols('Sunny, Cloudy, Rainy') >>> Y = DiscreteMarkovChain("Y", [sunny, cloudy, rainy], T) >>> P(Eq(Y[3], rainy), Eq(Y[1], cloudy)).round(2) 0.36 Expectations will be calculated as follows: >>> E(Y[3], Eq(Y[1], cloudy)) 0.38Cloudy + 0.36Rainy + 0.26Sunny Probability of expressions with multiple RandomIndexedSymbols can also be calculated provided there is only 1 RandomIndexedSymbol in the given condition. It is always better to use Rational instead of floating point numbers for the probabilities in the transition matrix to avoid errors. >>> from sympy import Gt, Le, Rational >>> T = Matrix([[Rational(5, 10), Rational(3, 10), Rational(2, 10)], [Rational(2, 10), Rational(7, 10), Rational(1, 10)], [Rational(3, 10), Rational(3, 10), Rational(4, 10)]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> P(Eq(Y[3], Y[1]), Eq(Y[0], 0)).round(3) 0.409 >>> P(Gt(Y[3], Y[1]), Eq(Y[0], 0)).round(2) 0.36 >>> P(Le(Y[15], Y[10]), Eq(Y[8], 2)).round(7) 0.6963328 There is limited support for arbitrarily sized states: >>> n = symbols('n', nonnegative=True, integer=True) >>> T = MatrixSymbol('T', n, n) >>> Y = DiscreteMarkovChain("Y", trans_probs=T) >>> Y.state_space Range(0, n, 1) References ========== .. [1] https://en.wikipedia.org/wiki/Markov_chain#Discrete-time_Markov_chain .. [2] https://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/Chapter11.pdf """ index_set = S.Naturals0 def __new__(cls, sym, state_space=None, trans_probs=None): # type: (Basic, tUnion[str, Symbol], tSequence, tUnion[MatrixBase, MatrixSymbol]) -> DiscreteMarkovChain sym = _symbol_converter(sym) state_space, trans_probs = MarkovProcess._sanity_checks(state_space, trans_probs) obj = Basic.__new__(cls, sym, state_space, trans_probs) indices = dict() if isinstance(obj.number_of_states, Integer): for index, state in enumerate(obj._state_index): indices[state] = index obj.index_of = indices return obj @property def transition_probabilities(self) -> tUnion[MatrixBase, MatrixSymbol]: """ Transition probabilities of discrete Markov chain, either an instance of Matrix or MatrixSymbol. """ return self.args[2] def _transient2transient(self): """ Computes the one step probabilities of transient states to transient states. Used in finding fundamental matrix, absorbing probabilities. """ trans_probs = self.transition_probabilities if not isinstance(trans_probs, ImmutableMatrix): return None m = trans_probs.shape[0] trans_states = [i for i in range(m) if trans_probs[i, i] != 1] t2t = [[trans_probs[si, sj] for sj in trans_states] for si in trans_states] return ImmutableMatrix(t2t) def _transient2absorbing(self): """ Computes the one step probabilities of transient states to absorbing states. Used in finding fundamental matrix, absorbing probabilities. """ trans_probs = self.transition_probabilities if not isinstance(trans_probs, ImmutableMatrix): return None m, trans_states, absorb_states = \ trans_probs.shape[0], [], [] for i in range(m): if trans_probs[i, i] == 1: absorb_states.append(i) else: trans_states.append(i) if not absorb_states or not trans_states: return None t2a = [[trans_probs[si, sj] for sj in absorb_states] for si in trans_states] return ImmutableMatrix(t2a) def communication_classes(self) -> tList[tTuple[tList[Basic], Boolean, Integer]]: """ Returns the list of communication classes that partition the states of the markov chain. A communication class is defined to be a set of states such that every state in that set is reachable from every other state in that set. Due to its properties this forms a class in the mathematical sense. Communication classes are also known as recurrence classes. Returns ======= classes The ``classes`` are a list of tuples. Each tuple represents a single communication class with its properties. The first element in the tuple is the list of states in the class, the second element is whether the class is recurrent and the third element is the period of the communication class. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix >>> T = Matrix([[0, 1, 0], ... [1, 0, 0], ... [1, 0, 0]]) >>> X = DiscreteMarkovChain('X', [1, 2, 3], T) >>> classes = X.communication_classes() >>> for states, is_recurrent, period in classes: ... states, is_recurrent, period ([1, 2], True, 2) ([3], False, 1) From this we can see that states ``1`` and ``2`` communicate, are recurrent and have a period of 2. We can also see state ``3`` is transient with a period of 1. Notes ===== The algorithm used is of order ``O(n*2)`` where ``n`` is the number of states in the markov chain. It uses Tarjan's algorithm to find the classes themselves and then it uses a breadth-first search algorithm to find each class's periodicity. Most of the algorithm's components approach ``O(n)`` as the matrix becomes more and more sparse. References ========== .. [1] http://www.columbia.edu/~ww2040/4701Sum07/4701-06-Notes-MCII.pdf .. [2] http://cecas.clemson.edu/~shierd/Shier/markov.pdf .. [3] https://ujcontent.uj.ac.za/vital/access/services/Download/uj:7506/CONTENT1 .. [4] https://www.mathworks.com/help/econ/dtmc.classify.html """ n = self.number_of_states T = self.transition_probabilities if isinstance(T, MatrixSymbol): raise NotImplementedError("Cannot perform the operation with a symbolic matrix.") # begin Tarjan's algorithm V = Range(n) # don't use state names. Rather use state # indexes since we use them for matrix # indexing here and later onward E = [(i, j) for i in V for j in V if T[i, j] != 0] classes = strongly_connected_components((V, E)) # end Tarjan's algorithm recurrence = [] periods = [] for class_ in classes: # begin recurrent check (similar to self._check_trans_probs()) submatrix = T[class_, class_] # get the submatrix with those states is_recurrent = S.true rows = submatrix.tolist() for row in rows: if (sum(row) - 1) != 0: is_recurrent = S.false break recurrence.append(is_recurrent) # end recurrent check # begin breadth-first search non_tree_edge_values = set() visited = {class_[0]} newly_visited = {class_[0]} level = {class_[0]: 0} current_level = 0 done = False # imitate a do-while loop while not done: # runs at most len(class_) times done = len(visited) == len(class_) current_level += 1 # this loop and the while loop above run a combined len(class_) number of times. # so this triple nested loop runs through each of the n states once. for i in newly_visited: # the loop below runs len(class_) number of times # complexity is around about O(n avg(len(class_))) newly_visited = {j for j in class_ if T[i, j] != 0} new_tree_edges = newly_visited.difference(visited) for j in new_tree_edges: level[j] = current_level new_non_tree_edges = newly_visited.intersection(visited) new_non_tree_edge_values = {level[i]-level[j]+1 for j in new_non_tree_edges} non_tree_edge_values = non_tree_edge_values.union(new_non_tree_edge_values) visited = visited.union(new_tree_edges) # igcd needs at least 2 arguments positive_ntev = {val_e for val_e in non_tree_edge_values if val_e > 0} if len(positive_ntev) == 0: periods.append(len(class_)) elif len(positive_ntev) == 1: periods.append(positive_ntev.pop()) else: periods.append(igcd(positive_ntev)) # end breadth-first search # convert back to the user's state names classes = [[self._state_index[i] for i in class_] for class_ in classes] return sympify(list(zip(classes, recurrence, periods))) def fundamental_matrix(self): Q = self._transient2transient() if Q == None: return None I = eye(Q.shape[0]) if (I - Q).det() == 0: raise ValueError("Fundamental matrix doesn't exists.") return ImmutableMatrix((I - Q).inv().tolist()) def absorbing_probabilities(self): """ Computes the absorbing probabilities, i.e., the ij-th entry of the matrix denotes the probability of Markov chain being absorbed in state j starting from state i. """ R = self._transient2absorbing() N = self.fundamental_matrix() if R == None or N == None: return None return NR def absorbing_probabilites(self): SymPyDeprecationWarning( feature="absorbing_probabilites", useinstead="absorbing_probabilities", issue=20042, deprecated_since_version="1.7" ).warn() return self.absorbing_probabilities() def is_regular(self): tuples = self.communication_classes() if len(tuples) == 0: return S.false # not defined for a 0x0 matrix classes, _, periods = list(zip(tuples)) return And(len(classes) == 1, periods[0] == 1) def is_ergodic(self): tuples = self.communication_classes() if len(tuples) == 0: return S.false # not defined for a 0x0 matrix classes, _, _ = list(zip(tuples)) return S(len(classes) == 1) def is_absorbing_state(self, state): trans_probs = self.transition_probabilities if isinstance(trans_probs, ImmutableMatrix) and \ state < trans_probs.shape[0]: return S(trans_probs[state, state]) is S.One def is_absorbing_chain(self): states, A, B, C = self.decompose() r = A.shape[0] return And(r > 0, A == Identity(r).as_explicit()) def stationary_distribution(self, condition_set=False) -> tUnion[ImmutableMatrix, ConditionSet, Lambda]: """ The stationary distribution is any row vector, p, that solves p = pP, is row stochastic and each element in p must be nonnegative. That means in matrix form: :math:`(P-I)^T p^T = 0` and :math:`(1, ..., 1) p = 1` where ``P`` is the one-step transition matrix. All time-homogeneous Markov Chains with a finite state space have at least one stationary distribution. In addition, if a finite time-homogeneous Markov Chain is irreducible, the stationary distribution is unique. Parameters ========== condition_set : bool If the chain has a symbolic size or transition matrix, it will return a ``Lambda`` if ``False`` and return a ``ConditionSet`` if ``True``. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S An irreducible Markov Chain >>> T = Matrix([[S(1)/2, S(1)/2, 0], ... [S(4)/5, S(1)/5, 0], ... [1, 0, 0]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> X.stationary_distribution() Matrix([[8/13, 5/13, 0]]) A reducible Markov Chain >>> T = Matrix([[S(1)/2, S(1)/2, 0], ... [S(4)/5, S(1)/5, 0], ... [0, 0, 1]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> X.stationary_distribution() Matrix([[8/13 - 8tau0/13, 5/13 - 5tau0/13, tau0]]) >>> Y = DiscreteMarkovChain('Y') >>> Y.stationary_distribution() Lambda((wm, _T), Eq(wm_T, wm)) >>> Y.stationary_distribution(condition_set=True) ConditionSet(wm, Eq(wm_T, wm)) References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_2_6_stationary_and_limiting_distributions.php .. [2] https://galton.uchicago.edu/~yibi/teaching/stat317/2014/Lectures/Lecture4_6up.pdf See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.limiting_distribution """ trans_probs = self.transition_probabilities n = self.number_of_states if n == 0: return ImmutableMatrix(Matrix([[]])) # symbolic matrix version if isinstance(trans_probs, MatrixSymbol): wm = MatrixSymbol('wm', 1, n) if condition_set: return ConditionSet(wm, Eq(wm * trans_probs, wm)) else: return Lambda((wm, trans_probs), Eq(wm * trans_probs, wm)) # numeric matrix version a = Matrix(trans_probs - Identity(n)).T a[0, 0:n] = ones(1, n) b = zeros(n, 1) b[0, 0] = 1 soln = list(linsolve((a, b)))[0] return ImmutableMatrix([[sol for sol in soln]]) def fixed_row_vector(self): """ A wrapper for ``stationary_distribution()``. """ return self.stationary_distribution() @property def limiting_distribution(self): """ The fixed row vector is the limiting distribution of a discrete Markov chain. """ return self.fixed_row_vector() def decompose(self) -> tTuple[tList[Basic], ImmutableMatrix, ImmutableMatrix, ImmutableMatrix]: """ Decomposes the transition matrix into submatrices with special properties. The transition matrix can be decomposed into 4 submatrices: - A - the submatrix from recurrent states to recurrent states. - B - the submatrix from transient to recurrent states. - C - the submatrix from transient to transient states. - O - the submatrix of zeros for recurrent to transient states. Returns ======= states, A, B, C ``states`` - a list of state names with the first being the recurrent states and the last being the transient states in the order of the row names of A and then the row names of C. ``A`` - the submatrix from recurrent states to recurrent states. ``B`` - the submatrix from transient to recurrent states. ``C`` - the submatrix from transient to transient states. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S One can decompose this chain for example: >>> T = Matrix([[S(1)/2, S(1)/2, 0, 0, 0], ... [S(2)/5, S(1)/5, S(2)/5, 0, 0], ... [0, 0, 1, 0, 0], ... [0, 0, S(1)/2, S(1)/2, 0], ... [S(1)/2, 0, 0, 0, S(1)/2]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> states, A, B, C = X.decompose() >>> states [2, 0, 1, 3, 4] >>> A # recurrent to recurrent Matrix([[1]]) >>> B # transient to recurrent Matrix([ [ 0], [2/5], [1/2], [ 0]]) >>> C # transient to transient Matrix([ [1/2, 1/2, 0, 0], [2/5, 1/5, 0, 0], [ 0, 0, 1/2, 0], [1/2, 0, 0, 1/2]]) This means that state 2 is the only absorbing state (since A is a 1x1 matrix). B is a 4x1 matrix since the 4 remaining transient states all merge into reccurent state 2. And C is the 4x4 matrix that shows how the transient states 0, 1, 3, 4 all interact. See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.communication_classes sympy.stats.stochastic_process_types.DiscreteMarkovChain.canonical_form References ========== .. [1] https://en.wikipedia.org/wiki/Absorbing_Markov_chain .. [2] http://people.brandeis.edu/~igusa/Math56aS08/Math56a_S08_notes015.pdf """ trans_probs = self.transition_probabilities classes = self.communication_classes() r_states = [] t_states = [] for states, recurrent, period in classes: if recurrent: r_states += states else: t_states += states states = r_states + t_states indexes = [self.index_of[state] for state in states] A = Matrix(len(r_states), len(r_states), lambda i, j: trans_probs[indexes[i], indexes[j]]) B = Matrix(len(t_states), len(r_states), lambda i, j: trans_probs[indexes[len(r_states) + i], indexes[j]]) C = Matrix(len(t_states), len(t_states), lambda i, j: trans_probs[indexes[len(r_states) + i], indexes[len(r_states) + j]]) return states, A.as_immutable(), B.as_immutable(), C.as_immutable() def canonical_form(self) -> tTuple[tList[Basic], ImmutableMatrix]: """ Reorders the one-step transition matrix so that recurrent states appear first and transient states appear last. Other representations include inserting transient states first and recurrent states last. Returns ======= states, P_new ``states`` is the list that describes the order of the new states in the matrix so that the ith element in ``states`` is the state of the ith row of A. ``P_new`` is the new transition matrix in canonical form. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S You can convert your chain into canonical form: >>> T = Matrix([[S(1)/2, S(1)/2, 0, 0, 0], ... [S(2)/5, S(1)/5, S(2)/5, 0, 0], ... [0, 0, 1, 0, 0], ... [0, 0, S(1)/2, S(1)/2, 0], ... [S(1)/2, 0, 0, 0, S(1)/2]]) >>> X = DiscreteMarkovChain('X', list(range(1, 6)), trans_probs=T) >>> states, new_matrix = X.canonical_form() >>> states [3, 1, 2, 4, 5] >>> new_matrix Matrix([ [ 1, 0, 0, 0, 0], [ 0, 1/2, 1/2, 0, 0], [2/5, 2/5, 1/5, 0, 0], [1/2, 0, 0, 1/2, 0], [ 0, 1/2, 0, 0, 1/2]]) The new states are [3, 1, 2, 4, 5] and you can create a new chain with this and its canonical form will remain the same (since it is already in canonical form). >>> X = DiscreteMarkovChain('X', states, new_matrix) >>> states, new_matrix = X.canonical_form() >>> states [3, 1, 2, 4, 5] >>> new_matrix Matrix([ [ 1, 0, 0, 0, 0], [ 0, 1/2, 1/2, 0, 0], [2/5, 2/5, 1/5, 0, 0], [1/2, 0, 0, 1/2, 0], [ 0, 1/2, 0, 0, 1/2]]) This is not limited to absorbing chains: >>> T = Matrix([[0, 5, 5, 0, 0], ... [0, 0, 0, 10, 0], ... [5, 0, 5, 0, 0], ... [0, 10, 0, 0, 0], ... [0, 3, 0, 3, 4]])/10 >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> states, new_matrix = X.canonical_form() >>> states [1, 3, 0, 2, 4] >>> new_matrix Matrix([ [ 0, 1, 0, 0, 0], [ 1, 0, 0, 0, 0], [ 1/2, 0, 0, 1/2, 0], [ 0, 0, 1/2, 1/2, 0], [3/10, 3/10, 0, 0, 2/5]]) See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.communication_classes sympy.stats.stochastic_process_types.DiscreteMarkovChain.decompose References ========== .. [1] https://onlinelibrary.wiley.com/doi/pdf/10.1002/9780470316887.app1 .. [2] http://www.columbia.edu/~ww2040/6711F12/lect1023big.pdf """ states, A, B, C = self.decompose() O = zeros(A.shape[0], C.shape[1]) return states, BlockMatrix([[A, O], [B, C]]).as_explicit() def sample(self): """ Returns ======= sample: iterator object iterator object containing the sample """ if not isinstance(self.transition_probabilities, (Matrix, ImmutableMatrix)): raise ValueError("Transition Matrix must be provided for sampling") Tlist = self.transition_probabilities.tolist() samps = [random.choice(list(self.state_space))] yield samps[0] time = 1 densities = {} for state in self.state_space: states = list(self.state_space) densities[state] = {states[i]: Tlist[state][i] for i in range(len(states))} while time < S.Infinity: samps.append(next(sample_iter(FiniteRV("_", densities[samps[time - 1]])))) yield samps[time] time += 1 class ContinuousMarkovChain(ContinuousTimeStochasticProcess, MarkovProcess): """ Represents continuous time Markov chain. Parameters ========== sym: Symbol/str state_space: Set Optional, by default, S.Reals gen_mat: Matrix/ImmutableMatrix/MatrixSymbol Optional, by default, None Examples ======== >>> from sympy.stats import ContinuousMarkovChain >>> from sympy import Matrix, S >>> G = Matrix([[-S(1), S(1)], [S(1), -S(1)]]) >>> C = ContinuousMarkovChain('C', state_space=[0, 1], gen_mat=G) >>> C.limiting_distribution() Matrix([[1/2, 1/2]]) References ========== .. [1] https://en.wikipedia.org/wiki/Markov_chain#Continuous-time_Markov_chain .. [2] http://u.math.biu.ac.il/~amirgi/CTMCnotes.pdf """ index_set = S.Reals def __new__(cls, sym, state_space=None, gen_mat=None): sym = _symbol_converter(sym) state_space, gen_mat = MarkovProcess._sanity_checks(state_space, gen_mat) obj = Basic.__new__(cls, sym, state_space, gen_mat) indices = dict() if isinstance(obj.number_of_states, Integer): for index, state in enumerate(obj.state_space): indices[state] = index obj.index_of = indices return obj @property def generator_matrix(self): return self.args[2] @cacheit def transition_probabilities(self, gen_mat=None): t = Dummy('t') if isinstance(gen_mat, (Matrix, ImmutableMatrix)) and \ gen_mat.is_diagonalizable(): # for faster computation use diagonalized generator matrix Q, D = gen_mat.diagonalize() return Lambda(t, Qexp(tD)Q.inv()) if gen_mat != None: return Lambda(t, exp(tgen_mat)) def limiting_distribution(self): gen_mat = self.generator_matrix if gen_mat == None: return None if isinstance(gen_mat, MatrixSymbol): wm = MatrixSymbol('wm', 1, gen_mat.shape[0]) return Lambda((wm, gen_mat), Eq(wmgen_mat, wm)) w = IndexedBase('w') wi = [w[i] for i in range(gen_mat.shape[0])] wm = Matrix([wi]) eqs = (wmgen_mat).tolist()[0] eqs.append(sum(wi) - 1) soln = list(linsolve(eqs, wi))[0] return ImmutableMatrix([[sol for sol in soln]]) class BernoulliProcess(DiscreteTimeStochasticProcess): """ The Bernoulli process consists of repeated independent Bernoulli process trials with the same parameter `p`. It's assumed that the probability `p` applies to every trial and that the outcomes of each trial are independent of all the rest. Therefore Bernoulli Processs is Discrete State and Discrete Time Stochastic Process. Parameters ========== sym: Symbol/str success: Integer/str The event which is considered to be success, by default is 1. failure: Integer/str The event which is considered to be failure, by default is 0. p: Real Number between 0 and 1 Represents the probability of getting success. Examples ======== >>> from sympy.stats import BernoulliProcess, P, E >>> from sympy import Eq, Gt >>> B = BernoulliProcess("B", p=0.7, success=1, failure=0) >>> B.state_space FiniteSet(0, 1) >>> (B.p).round(2) 0.70 >>> B.success 1 >>> B.failure 0 >>> X = B[1] + B[2] + B[3] >>> P(Eq(X, 0)).round(2) 0.03 >>> P(Eq(X, 2)).round(2) 0.44 >>> P(Eq(X, 4)).round(2) 0 >>> P(Gt(X, 1)).round(2) 0.78 >>> P(Eq(B[1], 0) & Eq(B[2], 1) & Eq(B[3], 0) & Eq(B[4], 1)).round(2) 0.04 >>> B.joint_distribution(B[1], B[2]) JointDistributionHandmade(Lambda((B[1], B[2]), Piecewise((0.7, Eq(B[1], 1)), (0.3, Eq(B[1], 0)), (0, True))Piecewise((0.7, Eq(B[2], 1)), (0.3, Eq(B[2], 0)), (0, True)))) >>> E(2B[1] + B[2]).round(2) 2.10 >>> P(B[1] < 1).round(2) 0.30 References ========== .. [1] https://en.wikipedia.org/wiki/Bernoulli_process .. [2] https://mathcs.clarku.edu/~djoyce/ma217/bernoulli.pdf """ index_set = S.Naturals0 def __new__(cls, sym, p, success=1, failure=0): _value_check(p >= 0 and p <= 1, 'Value of p must be between 0 and 1.') sym = _symbol_converter(sym) p = _sympify(p) success = _sym_sympify(success) failure = _sym_sympify(failure) return Basic.__new__(cls, sym, p, success, failure) @property def symbol(self): return self.args[0] @property def p(self): return self.args[1] @property def success(self): return self.args[2] @property def failure(self): return self.args[3] @property def state_space(self): return _set_converter([self.success, self.failure]) @property def distribution(self): return BernoulliDistribution(self.p) def simple_rv(self, rv): return Bernoulli(rv.name, p=self.p, succ=self.success, fail=self.failure) def expectation(self, expr, condition=None, evaluate=True, kwargs): """ Computes expectation. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation of the RandomIndexedSymbol. """ return _SubstituteRV._expectation(expr, condition, evaluate, kwargs) def probability(self, condition, given_condition=None, evaluate=True, kwargs): """ Computes probability. Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational/And The given conditions under which computations should be done. Returns ======= Probability of the condition. """ return _SubstituteRV._probability(condition, given_condition, evaluate, kwargs) def density(self, x): return Piecewise((self.p, Eq(x, self.success)), (1 - self.p, Eq(x, self.failure)), (S.Zero, True)) class _SubstituteRV: """ Internal class to handle the queries of expectation and probability by substitution. """ @staticmethod def _rvindexed_subs(expr, condition=None): """ Substitutes the RandomIndexedSymbol with the RandomSymbol with same name, distribution and probability as RandomIndexedSymbol. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. """ rvs_expr = random_symbols(expr) if len(rvs_expr) != 0: swapdict_expr = {} for rv in rvs_expr: if isinstance(rv, RandomIndexedSymbol): newrv = rv.pspace.process.simple_rv(rv) # substitute with equivalent simple rv swapdict_expr[rv] = newrv expr = expr.subs(swapdict_expr) rvs_cond = random_symbols(condition) if len(rvs_cond)!=0: swapdict_cond = {} for rv in rvs_cond: if isinstance(rv, RandomIndexedSymbol): newrv = rv.pspace.process.simple_rv(rv) swapdict_cond[rv] = newrv condition = condition.subs(swapdict_cond) return expr, condition @classmethod def _expectation(self, expr, condition=None, evaluate=True, *kwargs): """ Internal method for computing expectation of indexed RV. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation of the RandomIndexedSymbol. """ new_expr, new_condition = self._rvindexed_subs(expr, condition) if not is_random(new_expr): return new_expr new_pspace = pspace(new_expr) if new_condition is not None: new_expr = given(new_expr, new_condition) if new_expr.is_Add: # As E is Linear return Add([new_pspace.compute_expectation( expr=arg, evaluate=evaluate, kwargs) for arg in new_expr.args]) return new_pspace.compute_expectation( new_expr, evaluate=evaluate, kwargs) @classmethod def _probability(self, condition, given_condition=None, evaluate=True, kwargs): """ Internal method for computing probability of indexed RV Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational/And The given conditions under which computations should be done. Returns ======= Probability of the condition. """ new_condition, new_givencondition = self._rvindexed_subs(condition, given_condition) if isinstance(new_givencondition, RandomSymbol): condrv = random_symbols(new_condition) if len(condrv) == 1 and condrv[0] == new_givencondition: return BernoulliDistribution(self._probability(new_condition), 0, 1) if any([dependent(rv, new_givencondition) for rv in condrv]): return Probability(new_condition, new_givencondition) else: return self._probability(new_condition) if new_givencondition is not None and \ not isinstance(new_givencondition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (new_givencondition)) if new_givencondition == False or new_condition == False: return S.Zero if new_condition == True: return S.One if not isinstance(new_condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (new_condition)) if new_givencondition is not None: # If there is a condition # Recompute on new conditional expr return self._probability(given(new_condition, new_givencondition, kwargs), kwargs) result = pspace(new_condition).probability(new_condition, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def get_timerv_swaps(expr, condition): """ Finds the appropriate interval for each time stamp in expr by parsing the given condition and returns intervals for each timestamp and dictionary that maps variable time-stamped Random Indexed Symbol to its corresponding Random Indexed variable with fixed time stamp. Parameters ========== expr: Sympy Expression Expression containing Random Indexed Symbols with variable time stamps condition: Relational/Boolean Expression Expression containing time bounds of variable time stamps in expr Examples ======== >>> from sympy.stats.stochastic_process_types import get_timerv_swaps, PoissonProcess >>> from sympy import symbols, Contains, Interval >>> x, t, d = symbols('x t d', positive=True) >>> X = PoissonProcess("X", 3) >>> get_timerv_swaps(xX(t), Contains(t, Interval.Lopen(0, 1))) ([Interval.Lopen(0, 1)], {X(t): X(1)}) >>> get_timerv_swaps((X(t)2 + X(d)2), Contains(t, Interval.Lopen(0, 1)) ... & Contains(d, Interval.Ropen(1, 4))) # doctest: +SKIP ([Interval.Ropen(1, 4), Interval.Lopen(0, 1)], {X(d): X(3), X(t): X(1)}) Returns ======= intervals: list List of Intervals/FiniteSet on which each time stamp is defined rv_swap: dict Dictionary mapping variable time Random Indexed Symbol to constant time Random Indexed Variable """ if not isinstance(condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (condition)) expr_syms = list(expr.atoms(RandomIndexedSymbol)) if isinstance(condition, (And, Or)): given_cond_args = condition.args else: # single condition given_cond_args = (condition, ) rv_swap = {} intervals = [] for expr_sym in expr_syms: for arg in given_cond_args: if arg.has(expr_sym.key) and isinstance(expr_sym.key, Symbol): intv = _set_converter(arg.args[1]) diff_key = intv._sup - intv._inf if diff_key == oo: raise ValueError("%s should have finite bounds" % str(expr_sym.name)) elif diff_key == S.Zero: # has singleton set diff_key = intv._sup rv_swap[expr_sym] = expr_sym.subs({expr_sym.key: diff_key}) intervals.append(intv) return intervals, rv_swap class CountingProcess(ContinuousTimeStochasticProcess): """ This class handles the common methods of the Counting Processes such as Poisson, Wiener and Gamma Processes """ index_set = _set_converter(Interval(0, oo)) @property def symbol(self): return self.args[0] def expectation(self, expr, condition=None, evaluate=True, kwargs): """ Computes expectation Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Boolean The given conditions under which computations should be done, i.e, the intervals on which each variable time stamp in expr is defined Returns ======= Expectation of the given expr """ if condition is not None: intervals, rv_swap = get_timerv_swaps(expr, condition) # they are independent when they have non-overlapping intervals if len(intervals) == 1 or all(Intersection(intv_comb) == EmptySet for intv_comb in itertools.combinations(intervals, 2)): if expr.is_Add: return Add.fromiter(self.expectation(arg, condition) for arg in expr.args) expr = expr.subs(rv_swap) else: return Expectation(expr, condition) return _SubstituteRV._expectation(expr, evaluate=evaluate, *kwargs) def _solve_argwith_tworvs(self, arg): if arg.args[0].key >= arg.args[1].key or isinstance(arg, Eq): diff_key = abs(arg.args[0].key - arg.args[1].key) rv = arg.args[0] arg = arg.__class__(rv.pspace.process(diff_key), 0) else: diff_key = arg.args[1].key - arg.args[0].key rv = arg.args[1] arg = arg.__class__(rv.pspace.process(diff_key), 0) return arg def _solve_numerical(self, condition, given_condition=None): if isinstance(condition, And): args_list = list(condition.args) else: args_list = [condition] if given_condition is not None: if isinstance(given_condition, And): args_list.extend(list(given_condition.args)) else: args_list.extend([given_condition]) # sort the args based on timestamp to get the independent increments in # each segment using all the condition args as well as given_condition args args_list = sorted(args_list, key=lambda x: x.args[0].key) result = [] cond_args = list(condition.args) if isinstance(condition, And) else [condition] if args_list[0] in cond_args and not (is_random(args_list[0].args[0]) and is_random(args_list[0].args[1])): result.append(_SubstituteRV._probability(args_list[0])) if is_random(args_list[0].args[0]) and is_random(args_list[0].args[1]): arg = self._solve_argwith_tworvs(args_list[0]) result.append(_SubstituteRV._probability(arg)) for i in range(len(args_list) - 1): curr, nex = args_list[i], args_list[i + 1] diff_key = nex.args[0].key - curr.args[0].key working_set = curr.args[0].pspace.process.state_space if curr.args[1] > nex.args[1]: #impossible condition so return 0 result.append(0) break if isinstance(curr, Eq): working_set = Intersection(working_set, Interval.Lopen(curr.args[1], oo)) else: working_set = Intersection(working_set, curr.as_set()) if isinstance(nex, Eq): working_set = Intersection(working_set, Interval(-oo, nex.args[1])) else: working_set = Intersection(working_set, nex.as_set()) if working_set == EmptySet: rv = Eq(curr.args[0].pspace.process(diff_key), 0) result.append(_SubstituteRV._probability(rv)) else: if working_set.is_finite_set: if isinstance(curr, Eq) and isinstance(nex, Eq): rv = Eq(curr.args[0].pspace.process(diff_key), len(working_set)) result.append(_SubstituteRV._probability(rv)) elif isinstance(curr, Eq) ^ isinstance(nex, Eq): result.append(Add.fromiter(_SubstituteRV._probability(Eq( curr.args[0].pspace.process(diff_key), x)) for x in range(len(working_set)))) else: n = len(working_set) result.append(Add.fromiter((n - x)_SubstituteRV._probability(Eq( curr.args[0].pspace.process(diff_key), x)) for x in range(n))) else: result.append(_SubstituteRV._probability( curr.args[0].pspace.process(diff_key) <= working_set._sup - working_set._inf)) return Mul.fromiter(result) def probability(self, condition, given_condition=None, evaluate=True, *kwargs): """ Computes probability Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational, Boolean The given conditions under which computations should be done, i.e, the intervals on which each variable time stamp in expr is defined Returns ======= Probability of the condition """ check_numeric = True if isinstance(condition, (And, Or)): cond_args = condition.args else: cond_args = (condition, ) # check that condition args are numeric or not if not all(arg.args[0].key.is_number for arg in cond_args): check_numeric = False if given_condition is not None: check_given_numeric = True if isinstance(given_condition, (And, Or)): given_cond_args = given_condition.args else: given_cond_args = (given_condition, ) # check that given condition args are numeric or not if given_condition.has(Contains): check_given_numeric = False # Handle numerical queries if check_numeric and check_given_numeric: res = [] if isinstance(condition, Or): res.append(Add.fromiter(self._solve_numerical(arg, given_condition) for arg in condition.args)) if isinstance(given_condition, Or): res.append(Add.fromiter(self._solve_numerical(condition, arg) for arg in given_condition.args)) if res: return Add.fromiter(res) return self._solve_numerical(condition, given_condition) # No numeric queries, go by Contains?... then check that all the # given condition are in form of `Contains` if not all(arg.has(Contains) for arg in given_cond_args): raise ValueError("If given condition is passed with `Contains`, then " "please pass the evaluated condition with its corresponding information " "in terms of intervals of each time stamp to be passed in given condition.") intervals, rv_swap = get_timerv_swaps(condition, given_condition) # they are independent when they have non-overlapping intervals if len(intervals) == 1 or all(Intersection(intv_comb) == EmptySet for intv_comb in itertools.combinations(intervals, 2)): if isinstance(condition, And): return Mul.fromiter(self.probability(arg, given_condition) for arg in condition.args) elif isinstance(condition, Or): return Add.fromiter(self.probability(arg, given_condition) for arg in condition.args) condition = condition.subs(rv_swap) else: return Probability(condition, given_condition) if check_numeric: return self._solve_numerical(condition) return _SubstituteRV._probability(condition, evaluate=evaluate, *kwargs) class PoissonProcess(CountingProcess): """ The Poisson process is a counting process. It is usually used in scenarios where we are counting the occurrences of certain events that appear to happen at a certain rate, but completely at random. Parameters ========== sym: Symbol/str lamda: Positive number Rate of the process, ``lamda > 0`` Examples ======== >>> from sympy.stats import PoissonProcess, P, E >>> from sympy import symbols, Eq, Ne, Contains, Interval >>> X = PoissonProcess("X", lamda=3) >>> X.state_space Naturals0 >>> X.lamda 3 >>> t1, t2 = symbols('t1 t2', positive=True) >>> P(X(t1) < 4) (9t1*3/2 + 9t1*2/2 + 3t1 + 1)exp(-3t1) >>> P(Eq(X(t1), 2) \| Ne(X(t1), 4), Contains(t1, Interval.Ropen(2, 4))) 1 - 36exp(-6) >>> P(Eq(X(t1), 2) & Eq(X(t2), 3), Contains(t1, Interval.Lopen(0, 2)) ... & Contains(t2, Interval.Lopen(2, 4))) 648exp(-12) >>> E(X(t1)) 3t1 >>> E(X(t1)2 + 2X(t2), Contains(t1, Interval.Lopen(0, 1)) ... & Contains(t2, Interval.Lopen(1, 2))) 18 >>> P(X(3) < 1, Eq(X(1), 0)) exp(-6) >>> P(Eq(X(4), 3), Eq(X(2), 3)) exp(-6) >>> P(X(2) <= 3, X(1) > 1) 5exp(-3) Merging two Poisson Processes >>> Y = PoissonProcess("Y", lamda=4) >>> Z = X + Y >>> Z.lamda 7 Splitting a Poisson Process into two independent Poisson Processes >>> N, M = Z.split(l1=2, l2=5) >>> N.lamda, M.lamda (2, 5) References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_0_0_intro.php .. [2] https://en.wikipedia.org/wiki/Poisson_point_process """ def __new__(cls, sym, lamda): _value_check(lamda > 0, 'lamda should be a positive number.') sym = _symbol_converter(sym) lamda = _sympify(lamda) return Basic.__new__(cls, sym, lamda) @property def lamda(self): return self.args[1] @property def state_space(self): return S.Naturals0 def distribution(self, rv): return PoissonDistribution(self.lamdarv.key) def density(self, x): return (self.lamdax.key)x / factorial(x) exp(-(self.lamdax.key)) def simple_rv(self, rv): return Poisson(rv.name, lamda=self.lamdarv.key) def __add__(self, other): if not isinstance(other, PoissonProcess): raise ValueError("Only instances of Poisson Process can be merged") return PoissonProcess(Dummy(self.symbol.name + other.symbol.name), self.lamda + other.lamda) def split(self, l1, l2): if _sympify(l1 + l2) != self.lamda: raise ValueError("Sum of l1 and l2 should be %s" % str(self.lamda)) return PoissonProcess(Dummy("l1"), l1), PoissonProcess(Dummy("l2"), l2) class WienerProcess(CountingProcess): """ The Wiener process is a real valued continuous-time stochastic process. In physics it is used to study Brownian motion and therefore also known as Brownian Motion. Parameters ========== sym: Symbol/str Examples ======== >>> from sympy.stats import WienerProcess, P, E >>> from sympy import symbols, Contains, Interval >>> X = WienerProcess("X") >>> X.state_space Reals >>> t1, t2 = symbols('t1 t2', positive=True) >>> P(X(t1) < 7).simplify() erf(7sqrt(2)/(2sqrt(t1)))/2 + 1/2 >>> P((X(t1) > 2) \| (X(t1) < 4), Contains(t1, Interval.Ropen(2, 4))).simplify() -erf(1)/2 + erf(2)/2 + 1 >>> E(X(t1)) 0 >>> E(X(t1) + 2X(t2), Contains(t1, Interval.Lopen(0, 1)) ... & Contains(t2, Interval.Lopen(1, 2))) 0 References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_4_0_brownian_motion_wiener_process.php .. [2] https://en.wikipedia.org/wiki/Wiener_process """ def __new__(cls, sym): sym = _symbol_converter(sym) return Basic.__new__(cls, sym) @property def state_space(self): return S.Reals def distribution(self, rv): return NormalDistribution(0, sqrt(rv.key)) def density(self, x): return exp(-x2/(2x.key)) / (sqrt(2pi)sqrt(x.key)) def simple_rv(self, rv): return Normal(rv.name, 0, sqrt(rv.key)) class GammaProcess(CountingProcess): """ A Gamma process is a random process with independent gamma distributed increments. It is a pure-jump increasing Levy process. Parameters ========== sym: Symbol/str lamda: Positive number Jump size of the process, ``lamda > 0`` gamma: Positive number Rate of jump arrivals, ``gamma > 0`` Examples ======== >>> from sympy.stats import GammaProcess, E, P, variance >>> from sympy import symbols, Contains, Interval, Not >>> t, d, x, l, g = symbols('t d x l g', positive=True) >>> X = GammaProcess("X", l, g) >>> E(X(t)) gt/l >>> variance(X(t)).simplify() gt/l*2 >>> X = GammaProcess('X', 1, 2) >>> P(X(t) < 1).simplify() lowergamma(2t, 1)/gamma(2t) >>> P(Not((X(t) < 5) & (X(d) > 3)), Contains(t, Interval.Ropen(2, 4)) & ... Contains(d, Interval.Lopen(7, 8))).simplify() -4exp(-3) + 472exp(-8)/3 + 1 >>> E(X(2) + xE(X(5))) 10x + 4 References ========== .. [1] https://en.wikipedia.org/wiki/Gamma_process """ def __new__(cls, sym, lamda, gamma): _value_check(lamda > 0, 'lamda should be a positive number') _value_check(gamma > 0, 'gamma should be a positive number') sym = _symbol_converter(sym) gamma = _sympify(gamma) lamda = _sympify(lamda) return Basic.__new__(cls, sym, lamda, gamma) @property def lamda(self): return self.args[1] @property def gamma(self): return self.args[2] @property def state_space(self): return _set_converter(Interval(0, oo)) def distribution(self, rv): return GammaDistribution(self.gammarv.key, 1/self.lamda) def density(self, x): k = self.gammax.key theta = 1/self.lamda return x(k - 1) exp(-x/theta) / (gamma(k)thetak) def simple_rv(self, rv): return Gamma(rv.name, self.gammarv.key, 1/self.lamda)
11006d95d054685811a86705e3bedec66da29b1dd21a490cd39c1962ce6d08bf	from sympy import Basic from sympy.stats.rv import PSpace, _symbol_converter, RandomMatrixSymbol class RandomMatrixPSpace(PSpace): """ Represents probability space for random matrices. It contains the mechanics for handling the API calls for random matrices. """ def __new__(cls, sym, model=None): sym = _symbol_converter(sym) return Basic.__new__(cls, sym, model) model = property(lambda self: self.args[1]) def compute_density(self, expr, *args): rms = expr.atoms(RandomMatrixSymbol) if len(rms) > 2 or (not isinstance(expr, RandomMatrixSymbol)): raise NotImplementedError("Currently, no algorithm has been " "implemented to handle general expressions containing " "multiple random matrices.") return self.model.density(expr)
a75326df053687003ca2dad0e6d5a64c94ffd90f58329f227a4b8a82bf185057	"""Tools for arithmetic error propagation.""" from itertools import repeat, combinations from sympy import S, Symbol, Add, Mul, simplify, Pow, exp from sympy.stats.symbolic_probability import RandomSymbol, Variance, Covariance from sympy.stats.rv import is_random _arg0_or_var = lambda var: var.args[0] if len(var.args) > 0 else var def variance_prop(expr, consts=(), include_covar=False): r"""Symbolically propagates variance (`\sigma^2`) for expressions. This is computed as as seen in [1]_. Parameters ========== expr : Expr A sympy expression to compute the variance for. consts : sequence of Symbols, optional Represents symbols that are known constants in the expr, and thus have zero variance. All symbols not in consts are assumed to be variant. include_covar : bool, optional Flag for whether or not to include covariances, default=False. Returns ======= var_expr : Expr An expression for the total variance of the expr. The variance for the original symbols (e.g. x) are represented via instance of the Variance symbol (e.g. Variance(x)). Examples ======== >>> from sympy import symbols, exp >>> from sympy.stats.error_prop import variance_prop >>> x, y = symbols('x y') >>> variance_prop(x + y) Variance(x) + Variance(y) >>> variance_prop(x * y) x*2Variance(y) + y*2Variance(x) >>> variance_prop(exp(2x)) 4exp(4x)Variance(x) References ========== .. [1] https://en.wikipedia.org/wiki/Propagation_of_uncertainty """ args = expr.args if len(args) == 0: if expr in consts: return S.Zero elif is_random(expr): return Variance(expr).doit() elif isinstance(expr, Symbol): return Variance(RandomSymbol(expr)).doit() else: return S.Zero nargs = len(args) var_args = list(map(variance_prop, args, repeat(consts, nargs), repeat(include_covar, nargs))) if isinstance(expr, Add): var_expr = Add(var_args) if include_covar: terms = [2 Covariance(_arg0_or_var(x), _arg0_or_var(y)).expand() \ for x, y in combinations(var_args, 2)] var_expr += Add(terms) elif isinstance(expr, Mul): terms = [v/a2 for a, v in zip(args, var_args)] var_expr = simplify(expr2 Add(terms)) if include_covar: terms = [2Covariance(_arg0_or_var(x), _arg0_or_var(y)).expand()/(ab) \ for (a, b), (x, y) in zip(combinations(args, 2), combinations(var_args, 2))] var_expr += Add(terms) elif isinstance(expr, Pow): b = args[1] v = var_args[0] * (expr * b / args[0])*2 var_expr = simplify(v) elif isinstance(expr, exp): var_expr = simplify(var_args[0] expr**2) else: # unknown how to proceed, return variance of whole expr. var_expr = Variance(expr) return var_expr
c2a7db439ebd009d6dcf09cedeb15172aad81627f4f11279bb73b229188d4eb0	""" Contains ======== Geometric Hermite Logarithmic NegativeBinomial Poisson Skellam YuleSimon Zeta """ from sympy import (Basic, factorial, exp, S, sympify, I, zeta, polylog, log, beta, hyper, binomial, Piecewise, floor, besseli, sqrt, Sum, Dummy, Lambda, Eq) from sympy.stats.drv import SingleDiscreteDistribution, SingleDiscretePSpace from sympy.stats.rv import _value_check, is_random __all__ = ['Geometric', 'Hermite', 'Logarithmic', 'NegativeBinomial', 'Poisson', 'Skellam', 'YuleSimon', 'Zeta' ] def rv(symbol, cls, args, kwargs): args = list(map(sympify, args)) dist = cls(args) if kwargs.pop('check', True): dist.check(args) pspace = SingleDiscretePSpace(symbol, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(symbol, CompoundDistribution(dist)) return pspace.value class DiscreteDistributionHandmade(SingleDiscreteDistribution): _argnames = ('pdf',) def __new__(cls, pdf, set=S.Integers): return Basic.__new__(cls, pdf, set) @property def set(self): return self.args[1] @staticmethod def check(pdf, set): x = Dummy('x') val = Sum(pdf(x), (x, set._inf, set._sup)).doit() _value_check(Eq(val, 1) != S.false, "The pdf is incorrect on the given set.") def DiscreteRV(symbol, density, set=S.Integers, kwargs): """ Create a Discrete Random Variable given the following: Parameters ========== symbol : Symbol Represents name of the random variable. density : Expression containing symbol Represents probability density function. set : set Represents the region where the pdf is valid, by default is real line. check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Examples ======== >>> from sympy.stats import DiscreteRV, P, E >>> from sympy import Rational, Symbol >>> x = Symbol('x') >>> n = 10 >>> density = Rational(1, 10) >>> X = DiscreteRV(x, density, set=set(range(n))) >>> E(X) 9/2 >>> P(X>3) 3/5 Returns ======= RandomSymbol """ set = sympify(set) pdf = Piecewise((density, set.as_relational(symbol)), (0, True)) pdf = Lambda(symbol, pdf) # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(symbol.name, DiscreteDistributionHandmade, pdf, set, kwargs) #------------------------------------------------------------------------------- # Geometric distribution ------------------------------------------------------------ class GeometricDistribution(SingleDiscreteDistribution): _argnames = ('p',) set = S.Naturals @staticmethod def check(p): _value_check((0 < p, p <= 1), "p must be between 0 and 1") def pdf(self, k): return (1 - self.p)(k - 1) self.p def _characteristic_function(self, t): p = self.p return p * exp(It) / (1 - (1 - p)exp(It)) def _moment_generating_function(self, t): p = self.p return p exp(t) / (1 - (1 - p) * exp(t)) def Geometric(name, p): r""" Create a discrete random variable with a Geometric distribution. The density of the Geometric distribution is given by .. math:: f(k) := p (1 - p)^{k - 1} Parameters ========== p: A probability between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Geometric, density, E, variance >>> from sympy import Symbol, S >>> p = S.One / 5 >>> z = Symbol("z") >>> X = Geometric("x", p) >>> density(X)(z) (4/5)(z - 1)/5 >>> E(X) 5 >>> variance(X) 20 References ========== .. [1] https://en.wikipedia.org/wiki/Geometric_distribution .. [2] http://mathworld.wolfram.com/GeometricDistribution.html """ return rv(name, GeometricDistribution, p) #------------------------------------------------------------------------------- # Hermite distribution --------------------------------------------------------- class HermiteDistribution(SingleDiscreteDistribution): _argnames = ('a1', 'a2') set = S.Naturals0 @staticmethod def check(a1, a2): _value_check(a1.is_nonnegative, 'Parameter a1 must be >= 0.') _value_check(a2.is_nonnegative, 'Parameter a2 must be >= 0.') def pdf(self, k): a1, a2 = self.a1, self.a2 term1 = exp(-(a1 + a2)) j = Dummy("j", integer=True) num = a1(k - 2j) a2*j den = factorial(k - 2j) * factorial(j) return term1 * Sum(num/den, (j, 0, k//2)).doit() def _moment_generating_function(self, t): a1, a2 = self.a1, self.a2 term1 = a1 * (exp(t) - 1) term2 = a2 * (exp(2t) - 1) return exp(term1 + term2) def _characteristic_function(self, t): a1, a2 = self.a1, self.a2 term1 = a1 (exp(It) - 1) term2 = a2 (exp(2It) - 1) return exp(term1 + term2) def Hermite(name, a1, a2): r""" Create a discrete random variable with a Hermite distribution. The density of the Hermite distribution is given by .. math:: f(x):= e^{-a_1 -a_2}\sum_{j=0}^{\left \lfloor x/2 \right \rfloor} \frac{a_{1}^{x-2j}a_{2}^{j}}{(x-2j)!j!} Parameters ========== a1: A Positive number greater than equal to 0. a2: A Positive number greater than equal to 0. Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Hermite, density, E, variance >>> from sympy import Symbol >>> a1 = Symbol("a1", positive=True) >>> a2 = Symbol("a2", positive=True) >>> x = Symbol("x") >>> H = Hermite("H", a1=5, a2=4) >>> density(H)(2) 33exp(-9)/2 >>> E(H) 13 >>> variance(H) 21 References ========== .. [1] https://en.wikipedia.org/wiki/Hermite_distribution """ return rv(name, HermiteDistribution, a1, a2) #------------------------------------------------------------------------------- # Logarithmic distribution ------------------------------------------------------------ class LogarithmicDistribution(SingleDiscreteDistribution): _argnames = ('p',) set = S.Naturals @staticmethod def check(p): _value_check((p > 0, p < 1), "p should be between 0 and 1") def pdf(self, k): p = self.p return (-1) p*k / (k log(1 - p)) def _characteristic_function(self, t): p = self.p return log(1 - p * exp(It)) / log(1 - p) def _moment_generating_function(self, t): p = self.p return log(1 - p exp(t)) / log(1 - p) def Logarithmic(name, p): r""" Create a discrete random variable with a Logarithmic distribution. The density of the Logarithmic distribution is given by .. math:: f(k) := \frac{-p^k}{k \ln{(1 - p)}} Parameters ========== p: A value between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Logarithmic, density, E, variance >>> from sympy import Symbol, S >>> p = S.One / 5 >>> z = Symbol("z") >>> X = Logarithmic("x", p) >>> density(X)(z) -5*(-z)/(zlog(4/5)) >>> E(X) -1/(-4log(5) + 8log(2)) >>> variance(X) -1/((-4log(5) + 8log(2))(-2log(5) + 4log(2))) + 1/(-64log(2)log(5) + 64log(2)*2 + 16log(5)*2) - 10/(-32log(5) + 64log(2)) References ========== .. [1] https://en.wikipedia.org/wiki/Logarithmic_distribution .. [2] http://mathworld.wolfram.com/LogarithmicDistribution.html """ return rv(name, LogarithmicDistribution, p) #------------------------------------------------------------------------------- # Negative binomial distribution ------------------------------------------------------------ class NegativeBinomialDistribution(SingleDiscreteDistribution): _argnames = ('r', 'p') set = S.Naturals0 @staticmethod def check(r, p): _value_check(r > 0, 'r should be positive') _value_check((p > 0, p < 1), 'p should be between 0 and 1') def pdf(self, k): r = self.r p = self.p return binomial(k + r - 1, k) (1 - p)*r p*k def _characteristic_function(self, t): r = self.r p = self.p return ((1 - p) / (1 - p exp(It)))r def _moment_generating_function(self, t): r = self.r p = self.p return ((1 - p) / (1 - p exp(t)))*r def NegativeBinomial(name, r, p): r""" Create a discrete random variable with a Negative Binomial distribution. The density of the Negative Binomial distribution is given by .. math:: f(k) := \binom{k + r - 1}{k} (1 - p)^r p^k Parameters ========== r: A positive value p: A value between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import NegativeBinomial, density, E, variance >>> from sympy import Symbol, S >>> r = 5 >>> p = S.One / 5 >>> z = Symbol("z") >>> X = NegativeBinomial("x", r, p) >>> density(X)(z) 10245*(-z)binomial(z + 4, z)/3125 >>> E(X) 5/4 >>> variance(X) 25/16 References ========== .. [1] https://en.wikipedia.org/wiki/Negative_binomial_distribution .. [2] http://mathworld.wolfram.com/NegativeBinomialDistribution.html """ return rv(name, NegativeBinomialDistribution, r, p) #------------------------------------------------------------------------------- # Poisson distribution ------------------------------------------------------------ class PoissonDistribution(SingleDiscreteDistribution): _argnames = ('lamda',) set = S.Naturals0 @staticmethod def check(lamda): _value_check(lamda > 0, "Lambda must be positive") def pdf(self, k): return self.lamda*k / factorial(k) exp(-self.lamda) def _characteristic_function(self, t): return exp(self.lamda * (exp(It) - 1)) def _moment_generating_function(self, t): return exp(self.lamda (exp(t) - 1)) def Poisson(name, lamda): r""" Create a discrete random variable with a Poisson distribution. The density of the Poisson distribution is given by .. math:: f(k) := \frac{\lambda^{k} e^{- \lambda}}{k!} Parameters ========== lamda: Positive number, a rate Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Poisson, density, E, variance >>> from sympy import Symbol, simplify >>> rate = Symbol("lambda", positive=True) >>> z = Symbol("z") >>> X = Poisson("x", rate) >>> density(X)(z) lambda*zexp(-lambda)/factorial(z) >>> E(X) lambda >>> simplify(variance(X)) lambda References ========== .. [1] https://en.wikipedia.org/wiki/Poisson_distribution .. [2] http://mathworld.wolfram.com/PoissonDistribution.html """ return rv(name, PoissonDistribution, lamda) # ----------------------------------------------------------------------------- # Skellam distribution -------------------------------------------------------- class SkellamDistribution(SingleDiscreteDistribution): _argnames = ('mu1', 'mu2') set = S.Integers @staticmethod def check(mu1, mu2): _value_check(mu1 >= 0, 'Parameter mu1 must be >= 0') _value_check(mu2 >= 0, 'Parameter mu2 must be >= 0') def pdf(self, k): (mu1, mu2) = (self.mu1, self.mu2) term1 = exp(-(mu1 + mu2)) * (mu1 / mu2) ** (k / 2) term2 = besseli(k, 2 * sqrt(mu1 * mu2)) return term1 * term2 def _cdf(self, x): raise NotImplementedError( "Skellam doesn't have closed form for the CDF.") def _characteristic_function(self, t): (mu1, mu2) = (self.mu1, self.mu2) return exp(-(mu1 + mu2) + mu1 * exp(I * t) + mu2 * exp(-I * t)) def _moment_generating_function(self, t): (mu1, mu2) = (self.mu1, self.mu2) return exp(-(mu1 + mu2) + mu1 * exp(t) + mu2 * exp(-t)) def Skellam(name, mu1, mu2): r""" Create a discrete random variable with a Skellam distribution. The Skellam is the distribution of the difference N1 - N2 of two statistically independent random variables N1 and N2 each Poisson-distributed with respective expected values mu1 and mu2. The density of the Skellam distribution is given by .. math:: f(k) := e^{-(\mu_1+\mu_2)}(\frac{\mu_1}{\mu_2})^{k/2}I_k(2\sqrt{\mu_1\mu_2}) Parameters ========== mu1: A non-negative value mu2: A non-negative value Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Skellam, density, E, variance >>> from sympy import Symbol, pprint >>> z = Symbol("z", integer=True) >>> mu1 = Symbol("mu1", positive=True) >>> mu2 = Symbol("mu2", positive=True) >>> X = Skellam("x", mu1, mu2) >>> pprint(density(X)(z), use_unicode=False) z - 2 /mu1\ -mu1 - mu2 / _____ _____\ \|---\| e besseli\z, 2\/ mu1 \/ mu2 / \mu2/ >>> E(X) mu1 - mu2 >>> variance(X).expand() mu1 + mu2 References ========== .. [1] https://en.wikipedia.org/wiki/Skellam_distribution """ return rv(name, SkellamDistribution, mu1, mu2) #------------------------------------------------------------------------------- # Yule-Simon distribution ------------------------------------------------------------ class YuleSimonDistribution(SingleDiscreteDistribution): _argnames = ('rho',) set = S.Naturals @staticmethod def check(rho): _value_check(rho > 0, 'rho should be positive') def pdf(self, k): rho = self.rho return rho * beta(k, rho + 1) def _cdf(self, x): return Piecewise((1 - floor(x) * beta(floor(x), self.rho + 1), x >= 1), (0, True)) def _characteristic_function(self, t): rho = self.rho return rho * hyper((1, 1), (rho + 2,), exp(It)) exp(It) / (rho + 1) def _moment_generating_function(self, t): rho = self.rho return rho hyper((1, 1), (rho + 2,), exp(t)) * exp(t) / (rho + 1) def YuleSimon(name, rho): r""" Create a discrete random variable with a Yule-Simon distribution. The density of the Yule-Simon distribution is given by .. math:: f(k) := \rho B(k, \rho + 1) Parameters ========== rho: A positive value Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import YuleSimon, density, E, variance >>> from sympy import Symbol, simplify >>> p = 5 >>> z = Symbol("z") >>> X = YuleSimon("x", p) >>> density(X)(z) 5beta(z, 6) >>> simplify(E(X)) 5/4 >>> simplify(variance(X)) 25/48 References ========== .. [1] https://en.wikipedia.org/wiki/Yule%E2%80%93Simon_distribution """ return rv(name, YuleSimonDistribution, rho) #------------------------------------------------------------------------------- # Zeta distribution ------------------------------------------------------------ class ZetaDistribution(SingleDiscreteDistribution): _argnames = ('s',) set = S.Naturals @staticmethod def check(s): _value_check(s > 1, 's should be greater than 1') def pdf(self, k): s = self.s return 1 / (ks zeta(s)) def _characteristic_function(self, t): return polylog(self.s, exp(It)) / zeta(self.s) def _moment_generating_function(self, t): return polylog(self.s, exp(t)) / zeta(self.s) def Zeta(name, s): r""" Create a discrete random variable with a Zeta distribution. The density of the Zeta distribution is given by .. math:: f(k) := \frac{1}{k^s \zeta{(s)}} Parameters ========== s: A value greater than 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Zeta, density, E, variance >>> from sympy import Symbol >>> s = 5 >>> z = Symbol("z") >>> X = Zeta("x", s) >>> density(X)(z) 1/(z5zeta(5)) >>> E(X) pi*4/(90zeta(5)) >>> variance(X) -pi*8/(8100zeta(5)**2) + zeta(3)/zeta(5) References ========== .. [1] https://en.wikipedia.org/wiki/Zeta_distribution """ return rv(name, ZetaDistribution, s)
853eeaa953001805a1b43ff9e77c108e4bb4a60cb7c1158a239a22286ae74e09	from sympy.sets import FiniteSet from sympy import (sqrt, log, exp, FallingFactorial, Rational, Eq, Dummy, piecewise_fold, solveset, Integral) from .rv import (probability, expectation, density, where, given, pspace, cdf, PSpace, characteristic_function, sample, sample_iter, random_symbols, independent, dependent, sampling_density, moment_generating_function, quantile, is_random, sample_stochastic_process) __all__ = ['P', 'E', 'H', 'density', 'where', 'given', 'sample', 'cdf', 'characteristic_function', 'pspace', 'sample_iter', 'variance', 'std', 'skewness', 'kurtosis', 'covariance', 'dependent', 'entropy', 'median', 'independent', 'random_symbols', 'correlation', 'factorial_moment', 'moment', 'cmoment', 'sampling_density', 'moment_generating_function', 'smoment', 'quantile', 'sample_stochastic_process'] def moment(X, n, c=0, condition=None, , evaluate=True, kwargs): """ Return the nth moment of a random expression about c. .. math:: moment(X, c, n) = E((X-c)^{n}) Default value of c is 0. Examples ======== >>> from sympy.stats import Die, moment, E >>> X = Die('X', 6) >>> moment(X, 1, 6) -5/2 >>> moment(X, 2) 91/6 >>> moment(X, 1) == E(X) True """ from sympy.stats.symbolic_probability import Moment if evaluate: return Moment(X, n, c, condition).doit() return Moment(X, n, c, condition).rewrite(Integral) def variance(X, condition=None, kwargs): """ Variance of a random expression .. math:: variance(X) = E((X-E(X))^{2}) Examples ======== >>> from sympy.stats import Die, Bernoulli, variance >>> from sympy import simplify, Symbol >>> X = Die('X', 6) >>> p = Symbol('p') >>> B = Bernoulli('B', p, 1, 0) >>> variance(2X) 35/3 >>> simplify(variance(B)) p(1 - p) """ if is_random(X) and pspace(X) == PSpace(): from sympy.stats.symbolic_probability import Variance return Variance(X, condition) return cmoment(X, 2, condition, kwargs) def standard_deviation(X, condition=None, kwargs): r""" Standard Deviation of a random expression .. math:: std(X) = \sqrt(E((X-E(X))^{2})) Examples ======== >>> from sympy.stats import Bernoulli, std >>> from sympy import Symbol, simplify >>> p = Symbol('p') >>> B = Bernoulli('B', p, 1, 0) >>> simplify(std(B)) sqrt(p(1 - p)) """ return sqrt(variance(X, condition, kwargs)) std = standard_deviation def entropy(expr, condition=None, kwargs): """ Calculuates entropy of a probability distribution Parameters ========== expression : the random expression whose entropy is to be calculated condition : optional, to specify conditions on random expression b: base of the logarithm, optional By default, it is taken as Euler's number Returns ======= result : Entropy of the expression, a constant Examples ======== >>> from sympy.stats import Normal, Die, entropy >>> X = Normal('X', 0, 1) >>> entropy(X) log(2)/2 + 1/2 + log(pi)/2 >>> D = Die('D', 4) >>> entropy(D) log(4) References ========== .. [1] https://en.wikipedia.org/wiki/Entropy_(information_theory) .. [2] https://www.crmarsh.com/static/pdf/Charles_Marsh_Continuous_Entropy.pdf .. [3] http://www.math.uconn.edu/~kconrad/blurbs/analysis/entropypost.pdf """ pdf = density(expr, condition, *kwargs) base = kwargs.get('b', exp(1)) if hasattr(pdf, 'dict'): return sum([-problog(prob, base) for prob in pdf.dict.values()]) return expectation(-log(pdf(expr), base)) def covariance(X, Y, condition=None, kwargs): """ Covariance of two random expressions The expectation that the two variables will rise and fall together .. math:: covariance(X,Y) = E((X-E(X)) (Y-E(Y))) Examples ======== >>> from sympy.stats import Exponential, covariance >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> X = Exponential('X', rate) >>> Y = Exponential('Y', rate) >>> covariance(X, X) lambda(-2) >>> covariance(X, Y) 0 >>> covariance(X, Y + rateX) 1/lambda """ if (is_random(X) and pspace(X) == PSpace()) or (is_random(Y) and pspace(Y) == PSpace()): from sympy.stats.symbolic_probability import Covariance return Covariance(X, Y, condition) return expectation( (X - expectation(X, condition, kwargs)) (Y - expectation(Y, condition, kwargs)), condition, kwargs) def correlation(X, Y, condition=None, *kwargs): r""" Correlation of two random expressions, also known as correlation coefficient or Pearson's correlation The normalized expectation that the two variables will rise and fall together .. math:: correlation(X,Y) = E((X-E(X))(Y-E(Y)) / (\sigma_x \sigma_y)) Examples ======== >>> from sympy.stats import Exponential, correlation >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> X = Exponential('X', rate) >>> Y = Exponential('Y', rate) >>> correlation(X, X) 1 >>> correlation(X, Y) 0 >>> correlation(X, Y + rateX) 1/sqrt(1 + lambda(-2)) """ return covariance(X, Y, condition, kwargs)/(std(X, condition, *kwargs) std(Y, condition, *kwargs)) def cmoment(X, n, condition=None, , evaluate=True, kwargs): """ Return the nth central moment of a random expression about its mean. .. math:: cmoment(X, n) = E((X - E(X))^{n}) Examples ======== >>> from sympy.stats import Die, cmoment, variance >>> X = Die('X', 6) >>> cmoment(X, 3) 0 >>> cmoment(X, 2) 35/12 >>> cmoment(X, 2) == variance(X) True """ from sympy.stats.symbolic_probability import CentralMoment if evaluate: return CentralMoment(X, n, condition).doit() return CentralMoment(X, n, condition).rewrite(Integral) def smoment(X, n, condition=None, kwargs): r""" Return the nth Standardized moment of a random expression. .. math:: smoment(X, n) = E(((X - \mu)/\sigma_X)^{n}) Examples ======== >>> from sympy.stats import skewness, Exponential, smoment >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> smoment(Y, 4) 9 >>> smoment(Y, 4) == smoment(3Y, 4) True >>> smoment(Y, 3) == skewness(Y) True """ sigma = std(X, condition, kwargs) return (1/sigma)ncmoment(X, n, condition, kwargs) def skewness(X, condition=None, kwargs): r""" Measure of the asymmetry of the probability distribution. Positive skew indicates that most of the values lie to the right of the mean. .. math:: skewness(X) = E(((X - E(X))/\sigma_X)^{3}) Parameters ========== condition : Expr containing RandomSymbols A conditional expression. skewness(X, X>0) is skewness of X given X > 0 Examples ======== >>> from sympy.stats import skewness, Exponential, Normal >>> from sympy import Symbol >>> X = Normal('X', 0, 1) >>> skewness(X) 0 >>> skewness(X, X > 0) # find skewness given X > 0 (-sqrt(2)/sqrt(pi) + 4sqrt(2)/pi(3/2))/(1 - 2/pi)(3/2) >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> skewness(Y) 2 """ return smoment(X, 3, condition=condition, kwargs) def kurtosis(X, condition=None, kwargs): r""" Characterizes the tails/outliers of a probability distribution. Kurtosis of any univariate normal distribution is 3. Kurtosis less than 3 means that the distribution produces fewer and less extreme outliers than the normal distribution. .. math:: kurtosis(X) = E(((X - E(X))/\sigma_X)^{4}) Parameters ========== condition : Expr containing RandomSymbols A conditional expression. kurtosis(X, X>0) is kurtosis of X given X > 0 Examples ======== >>> from sympy.stats import kurtosis, Exponential, Normal >>> from sympy import Symbol >>> X = Normal('X', 0, 1) >>> kurtosis(X) 3 >>> kurtosis(X, X > 0) # find kurtosis given X > 0 (-4/pi - 12/pi2 + 3)/(1 - 2/pi)2 >>> rate = Symbol('lamda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> kurtosis(Y) 9 References ========== .. [1] https://en.wikipedia.org/wiki/Kurtosis .. [2] http://mathworld.wolfram.com/Kurtosis.html """ return smoment(X, 4, condition=condition, kwargs) def factorial_moment(X, n, condition=None, kwargs): """ The factorial moment is a mathematical quantity defined as the expectation or average of the falling factorial of a random variable. .. math:: factorial-moment(X, n) = E(X(X - 1)(X - 2)...(X - n + 1)) Parameters ========== n: A natural number, n-th factorial moment. condition : Expr containing RandomSymbols A conditional expression. Examples ======== >>> from sympy.stats import factorial_moment, Poisson, Binomial >>> from sympy import Symbol, S >>> lamda = Symbol('lamda') >>> X = Poisson('X', lamda) >>> factorial_moment(X, 2) lamda2 >>> Y = Binomial('Y', 2, S.Half) >>> factorial_moment(Y, 2) 1/2 >>> factorial_moment(Y, 2, Y > 1) # find factorial moment for Y > 1 2 References ========== .. [1] https://en.wikipedia.org/wiki/Factorial_moment .. [2] http://mathworld.wolfram.com/FactorialMoment.html """ return expectation(FallingFactorial(X, n), condition=condition, kwargs) def median(X, evaluate=True, kwargs): r""" Calculuates the median of the probability distribution. Mathematically, median of Probability distribution is defined as all those values of `m` for which the following condition is satisfied .. math:: P(X\leq m) \geq \frac{1}{2} \text{ and} \text{ } P(X\geq m)\geq \frac{1}{2} Parameters ========== X: The random expression whose median is to be calculated. Returns ======= The FiniteSet or an Interval which contains the median of the random expression. Examples ======== >>> from sympy.stats import Normal, Die, median >>> N = Normal('N', 3, 1) >>> median(N) FiniteSet(3) >>> D = Die('D') >>> median(D) FiniteSet(3, 4) References ========== .. [1] https://en.wikipedia.org/wiki/Median#Probability_distributions """ from sympy.stats.crv import ContinuousPSpace from sympy.stats.drv import DiscretePSpace from sympy.stats.frv import FinitePSpace if isinstance(pspace(X), FinitePSpace): cdf = pspace(X).compute_cdf(X) result = [] for key, value in cdf.items(): if value>= Rational(1, 2) and (1 - value) + \ pspace(X).probability(Eq(X, key)) >= Rational(1, 2): result.append(key) return FiniteSet(result) if isinstance(pspace(X), ContinuousPSpace) or isinstance(pspace(X), DiscretePSpace): cdf = pspace(X).compute_cdf(X) x = Dummy('x') result = solveset(piecewise_fold(cdf(x) - Rational(1, 2)), x, pspace(X).set) return result raise NotImplementedError("The median of %s is not implemeted."%str(pspace(X))) def coskewness(X, Y, Z, condition=None, *kwargs): r""" Calculates the co-skewness of three random variables. Mathematically Coskewness is defined as .. math:: coskewness(X,Y,Z)=\frac{E[(X-E[X]) (Y-E[Y]) * (Z-E[Z])]} {\sigma_{X}\sigma_{Y}\sigma_{Z}} Parameters ========== X : RandomSymbol Random Variable used to calculate coskewness Y : RandomSymbol Random Variable used to calculate coskewness Z : RandomSymbol Random Variable used to calculate coskewness condition : Expr containing RandomSymbols A conditional expression Examples ======== >>> from sympy.stats import coskewness, Exponential, skewness >>> from sympy import symbols >>> p = symbols('p', positive=True) >>> X = Exponential('X', p) >>> Y = Exponential('Y', 2p) >>> coskewness(X, Y, Y) 0 >>> coskewness(X, Y + X, Y + 2X) 16sqrt(85)/85 >>> coskewness(X + 2Y, Y + X, Y + 2X, X > 3) 9sqrt(170)/85 >>> coskewness(Y, Y, Y) == skewness(Y) True >>> coskewness(X, Y + pX, Y + 2pX) 4/(sqrt(1 + 1/(4p*2))sqrt(4 + 1/(4p2))) Returns ======= coskewness : The coskewness of the three random variables References ========== .. [1] https://en.wikipedia.org/wiki/Coskewness """ num = expectation((X - expectation(X, condition, kwargs)) \ (Y - expectation(Y, condition, *kwargs)) \ (Z - expectation(Z, condition, kwargs)), condition, kwargs) den = std(X, condition, *kwargs) std(Y, condition, *kwargs) \ std(Z, condition, **kwargs) return num/den P = probability E = expectation H = entropy
0b11e6a3403228ec07bd8d08ede68446f5662cc9868519ae065f4ea404df35ad	""" Main Random Variables Module Defines abstract random variable type. Contains interfaces for probability space object (PSpace) as well as standard operators, P, E, sample, density, where, quantile See Also ======== sympy.stats.crv sympy.stats.frv sympy.stats.rv_interface """ from functools import singledispatch from typing import Tuple as tTuple from sympy import (Basic, S, Expr, Symbol, Tuple, And, Add, Eq, lambdify, Or, Equality, Lambda, sympify, Dummy, Ne, KroneckerDelta, DiracDelta, Mul, Indexed, MatrixSymbol, Function) from sympy.core.relational import Relational from sympy.core.sympify import _sympify from sympy.sets.sets import FiniteSet, ProductSet, Intersection from sympy.solvers.solveset import solveset from sympy.external import import_module from sympy.utilities.misc import filldedent import warnings x = Symbol('x') @singledispatch def is_random(x): return False @is_random.register(Basic) def _(x): atoms = x.free_symbols return any([is_random(i) for i in atoms]) class RandomDomain(Basic): """ Represents a set of variables and the values which they can take See Also ======== sympy.stats.crv.ContinuousDomain sympy.stats.frv.FiniteDomain """ is_ProductDomain = False is_Finite = False is_Continuous = False is_Discrete = False def __new__(cls, symbols, args): symbols = FiniteSet(symbols) return Basic.__new__(cls, symbols, args) @property def symbols(self): return self.args[0] @property def set(self): return self.args[1] def __contains__(self, other): raise NotImplementedError() def compute_expectation(self, expr): raise NotImplementedError() class SingleDomain(RandomDomain): """ A single variable and its domain See Also ======== sympy.stats.crv.SingleContinuousDomain sympy.stats.frv.SingleFiniteDomain """ def __new__(cls, symbol, set): assert symbol.is_Symbol return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) def __contains__(self, other): if len(other) != 1: return False sym, val = tuple(other)[0] return self.symbol == sym and val in self.set class MatrixDomain(RandomDomain): """ A Random Matrix variable and its domain """ def __new__(cls, symbol, set): symbol, set = _symbol_converter(symbol), _sympify(set) return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) class ConditionalDomain(RandomDomain): """ A RandomDomain with an attached condition See Also ======== sympy.stats.crv.ConditionalContinuousDomain sympy.stats.frv.ConditionalFiniteDomain """ def __new__(cls, fulldomain, condition): condition = condition.xreplace({rs: rs.symbol for rs in random_symbols(condition)}) return Basic.__new__(cls, fulldomain, condition) @property def symbols(self): return self.fulldomain.symbols @property def fulldomain(self): return self.args[0] @property def condition(self): return self.args[1] @property def set(self): raise NotImplementedError("Set of Conditional Domain not Implemented") def as_boolean(self): return And(self.fulldomain.as_boolean(), self.condition) class PSpace(Basic): """ A Probability Space Probability Spaces encode processes that equal different values probabilistically. These underly Random Symbols which occur in SymPy expressions and contain the mechanics to evaluate statistical statements. See Also ======== sympy.stats.crv.ContinuousPSpace sympy.stats.frv.FinitePSpace """ is_Finite = None # type: bool is_Continuous = None # type: bool is_Discrete = None # type: bool is_real = None # type: bool @property def domain(self): return self.args[0] @property def density(self): return self.args[1] @property def values(self): return frozenset(RandomSymbol(sym, self) for sym in self.symbols) @property def symbols(self): return self.domain.symbols def where(self, condition): raise NotImplementedError() def compute_density(self, expr): raise NotImplementedError() def sample(self): raise NotImplementedError() def probability(self, condition): raise NotImplementedError() def compute_expectation(self, expr): raise NotImplementedError() class SinglePSpace(PSpace): """ Represents the probabilities of a set of random events that can be attributed to a single variable/symbol. """ def __new__(cls, s, distribution): s = _symbol_converter(s) return Basic.__new__(cls, s, distribution) @property def value(self): return RandomSymbol(self.symbol, self) @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[1] @property def pdf(self): return self.distribution.pdf(self.symbol) class RandomSymbol(Expr): """ Random Symbols represent ProbabilitySpaces in SymPy Expressions In principle they can take on any value that their symbol can take on within the associated PSpace with probability determined by the PSpace Density. Random Symbols contain pspace and symbol properties. The pspace property points to the represented Probability Space The symbol is a standard SymPy Symbol that is used in that probability space for example in defining a density. You can form normal SymPy expressions using RandomSymbols and operate on those expressions with the Functions E - Expectation of a random expression P - Probability of a condition density - Probability Density of an expression given - A new random expression (with new random symbols) given a condition An object of the RandomSymbol type should almost never be created by the user. They tend to be created instead by the PSpace class's value method. Traditionally a user doesn't even do this but instead calls one of the convenience functions Normal, Exponential, Coin, Die, FiniteRV, etc.... """ def __new__(cls, symbol, pspace=None): from sympy.stats.joint_rv import JointRandomSymbol if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() symbol = _symbol_converter(symbol) if not isinstance(pspace, PSpace): raise TypeError("pspace variable should be of type PSpace") if cls == JointRandomSymbol and isinstance(pspace, SinglePSpace): cls = RandomSymbol return Basic.__new__(cls, symbol, pspace) is_finite = True is_symbol = True is_Atom = True _diff_wrt = True pspace = property(lambda self: self.args[1]) symbol = property(lambda self: self.args[0]) name = property(lambda self: self.symbol.name) def _eval_is_positive(self): return self.symbol.is_positive def _eval_is_integer(self): return self.symbol.is_integer def _eval_is_real(self): return self.symbol.is_real or self.pspace.is_real @property def is_commutative(self): return self.symbol.is_commutative @property def free_symbols(self): return {self} class RandomIndexedSymbol(RandomSymbol): def __new__(cls, idx_obj, pspace=None): if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() if not isinstance(idx_obj, (Indexed, Function)): raise TypeError("An Function or Indexed object is expected not %s"%(idx_obj)) return Basic.__new__(cls, idx_obj, pspace) symbol = property(lambda self: self.args[0]) name = property(lambda self: str(self.args[0])) @property def key(self): if isinstance(self.symbol, Indexed): return self.symbol.args[1] elif isinstance(self.symbol, Function): return self.symbol.args[0] @property def free_symbols(self): if self.key.free_symbols: free_syms = self.key.free_symbols free_syms.add(self) return free_syms return {self} class RandomMatrixSymbol(RandomSymbol, MatrixSymbol): # type: ignore def __new__(cls, symbol, n, m, pspace=None): n, m = _sympify(n), _sympify(m) symbol = _symbol_converter(symbol) if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() return Basic.__new__(cls, symbol, n, m, pspace) symbol = property(lambda self: self.args[0]) pspace = property(lambda self: self.args[3]) class ProductPSpace(PSpace): """ Abstract class for representing probability spaces with multiple random variables. See Also ======== sympy.stats.rv.IndependentProductPSpace sympy.stats.joint_rv.JointPSpace """ pass class IndependentProductPSpace(ProductPSpace): """ A probability space resulting from the merger of two independent probability spaces. Often created using the function, pspace """ def __new__(cls, spaces): rs_space_dict = {} for space in spaces: for value in space.values: rs_space_dict[value] = space symbols = FiniteSet([val.symbol for val in rs_space_dict.keys()]) # Overlapping symbols from sympy.stats.joint_rv import MarginalDistribution from sympy.stats.compound_rv import CompoundDistribution if len(symbols) < sum(len(space.symbols) for space in spaces if not isinstance(space.distribution, ( CompoundDistribution, MarginalDistribution))): raise ValueError("Overlapping Random Variables") if all(space.is_Finite for space in spaces): from sympy.stats.frv import ProductFinitePSpace cls = ProductFinitePSpace obj = Basic.__new__(cls, FiniteSet(spaces)) return obj @property def pdf(self): p = Mul([space.pdf for space in self.spaces]) return p.subs({rv: rv.symbol for rv in self.values}) @property def rs_space_dict(self): d = {} for space in self.spaces: for value in space.values: d[value] = space return d @property def symbols(self): return FiniteSet([val.symbol for val in self.rs_space_dict.keys()]) @property def spaces(self): return FiniteSet(self.args) @property def values(self): return sumsets(space.values for space in self.spaces) def compute_expectation(self, expr, rvs=None, evaluate=False, kwargs): rvs = rvs or self.values rvs = frozenset(rvs) for space in self.spaces: expr = space.compute_expectation(expr, rvs & space.values, evaluate=False, kwargs) if evaluate and hasattr(expr, 'doit'): return expr.doit(*kwargs) return expr @property def domain(self): return ProductDomain([space.domain for space in self.spaces]) @property def density(self): raise NotImplementedError("Density not available for ProductSpaces") def sample(self, size=(), library='scipy'): return {k: v for space in self.spaces for k, v in space.sample(size=size, library=library).items()} def probability(self, condition, *kwargs): cond_inv = False if isinstance(condition, Ne): condition = Eq(condition.args[0], condition.args[1]) cond_inv = True elif isinstance(condition, And): # they are independent return Mul([self.probability(arg) for arg in condition.args]) elif isinstance(condition, Or): # they are independent return Add([self.probability(arg) for arg in condition.args]) expr = condition.lhs - condition.rhs rvs = random_symbols(expr) dens = self.compute_density(expr) if any([pspace(rv).is_Continuous for rv in rvs]): from sympy.stats.crv import SingleContinuousPSpace from sympy.stats.crv_types import ContinuousDistributionHandmade if expr in self.values: # Marginalize all other random symbols out of the density randomsymbols = tuple(set(self.values) - frozenset([expr])) symbols = tuple(rs.symbol for rs in randomsymbols) pdf = self.domain.integrate(self.pdf, symbols, kwargs) return Lambda(expr.symbol, pdf) dens = ContinuousDistributionHandmade(dens) z = Dummy('z', real=True) space = SingleContinuousPSpace(z, dens) result = space.probability(condition.__class__(space.value, 0)) else: from sympy.stats.drv import SingleDiscretePSpace from sympy.stats.drv_types import DiscreteDistributionHandmade dens = DiscreteDistributionHandmade(dens) z = Dummy('z', integer=True) space = SingleDiscretePSpace(z, dens) result = space.probability(condition.__class__(space.value, 0)) return result if not cond_inv else S.One - result def compute_density(self, expr, kwargs): rvs = random_symbols(expr) if any(pspace(rv).is_Continuous for rv in rvs): z = Dummy('z', real=True) expr = self.compute_expectation(DiracDelta(expr - z), kwargs) else: z = Dummy('z', integer=True) expr = self.compute_expectation(KroneckerDelta(expr, z), kwargs) return Lambda(z, expr) def compute_cdf(self, expr, kwargs): raise ValueError("CDF not well defined on multivariate expressions") def conditional_space(self, condition, normalize=True, kwargs): rvs = random_symbols(condition) condition = condition.xreplace({rv: rv.symbol for rv in self.values}) if any([pspace(rv).is_Continuous for rv in rvs]): from sympy.stats.crv import (ConditionalContinuousDomain, ContinuousPSpace) space = ContinuousPSpace domain = ConditionalContinuousDomain(self.domain, condition) elif any([pspace(rv).is_Discrete for rv in rvs]): from sympy.stats.drv import (ConditionalDiscreteDomain, DiscretePSpace) space = DiscretePSpace domain = ConditionalDiscreteDomain(self.domain, condition) elif all([pspace(rv).is_Finite for rv in rvs]): from sympy.stats.frv import FinitePSpace return FinitePSpace.conditional_space(self, condition) if normalize: replacement = {rv: Dummy(str(rv)) for rv in self.symbols} norm = domain.compute_expectation(self.pdf, kwargs) pdf = self.pdf / norm.xreplace(replacement) # XXX: Converting symbols from set to tuple. The order matters to # Lambda though so we shouldn't be starting with a set here... density = Lambda(tuple(domain.symbols), pdf) return space(domain, density) class ProductDomain(RandomDomain): """ A domain resulting from the merger of two independent domains See Also ======== sympy.stats.crv.ProductContinuousDomain sympy.stats.frv.ProductFiniteDomain """ is_ProductDomain = True def __new__(cls, domains): # Flatten any product of products domains2 = [] for domain in domains: if not domain.is_ProductDomain: domains2.append(domain) else: domains2.extend(domain.domains) domains2 = FiniteSet(domains2) if all(domain.is_Finite for domain in domains2): from sympy.stats.frv import ProductFiniteDomain cls = ProductFiniteDomain if all(domain.is_Continuous for domain in domains2): from sympy.stats.crv import ProductContinuousDomain cls = ProductContinuousDomain if all(domain.is_Discrete for domain in domains2): from sympy.stats.drv import ProductDiscreteDomain cls = ProductDiscreteDomain return Basic.__new__(cls, domains2) @property def sym_domain_dict(self): return {symbol: domain for domain in self.domains for symbol in domain.symbols} @property def symbols(self): return FiniteSet([sym for domain in self.domains for sym in domain.symbols]) @property def domains(self): return self.args @property def set(self): return ProductSet((domain.set for domain in self.domains)) def __contains__(self, other): # Split event into each subdomain for domain in self.domains: # Collect the parts of this event which associate to this domain elem = frozenset([item for item in other if sympify(domain.symbols.contains(item[0])) is S.true]) # Test this sub-event if elem not in domain: return False # All subevents passed return True def as_boolean(self): return And([domain.as_boolean() for domain in self.domains]) def random_symbols(expr): """ Returns all RandomSymbols within a SymPy Expression. """ atoms = getattr(expr, 'atoms', None) if atoms is not None: comp = lambda rv: rv.symbol.name l = list(atoms(RandomSymbol)) return sorted(l, key=comp) else: return [] def pspace(expr): """ Returns the underlying Probability Space of a random expression. For internal use. Examples ======== >>> from sympy.stats import pspace, Normal >>> X = Normal('X', 0, 1) >>> pspace(2X + 1) == X.pspace True """ expr = sympify(expr) if isinstance(expr, RandomSymbol) and expr.pspace is not None: return expr.pspace if expr.has(RandomMatrixSymbol): rm = list(expr.atoms(RandomMatrixSymbol))[0] return rm.pspace rvs = random_symbols(expr) if not rvs: raise ValueError("Expression containing Random Variable expected, not %s" % (expr)) # If only one space present if all(rv.pspace == rvs[0].pspace for rv in rvs): return rvs[0].pspace from sympy.stats.compound_rv import CompoundPSpace for rv in rvs: if isinstance(rv.pspace, CompoundPSpace): return rv.pspace # Otherwise make a product space return IndependentProductPSpace([rv.pspace for rv in rvs]) def sumsets(sets): """ Union of sets """ return frozenset().union(sets) def rs_swap(a, b): """ Build a dictionary to swap RandomSymbols based on their underlying symbol. i.e. if ``X = ('x', pspace1)`` and ``Y = ('x', pspace2)`` then ``X`` and ``Y`` match and the key, value pair ``{X:Y}`` will appear in the result Inputs: collections a and b of random variables which share common symbols Output: dict mapping RVs in a to RVs in b """ d = {} for rsa in a: d[rsa] = [rsb for rsb in b if rsa.symbol == rsb.symbol][0] return d def given(expr, condition=None, *kwargs): r""" Conditional Random Expression From a random expression and a condition on that expression creates a new probability space from the condition and returns the same expression on that conditional probability space. Examples ======== >>> from sympy.stats import given, density, Die >>> X = Die('X', 6) >>> Y = given(X, X > 3) >>> density(Y).dict {4: 1/3, 5: 1/3, 6: 1/3} Following convention, if the condition is a random symbol then that symbol is considered fixed. >>> from sympy.stats import Normal >>> from sympy import pprint >>> from sympy.abc import z >>> X = Normal('X', 0, 1) >>> Y = Normal('Y', 0, 1) >>> pprint(density(X + Y, Y)(z), use_unicode=False) 2 -(-Y + z) ----------- ___ 2 \/ 2 e ------------------ ____ 2\/ pi """ if not is_random(condition) or pspace_independent(expr, condition): return expr if isinstance(condition, RandomSymbol): condition = Eq(condition, condition.symbol) condsymbols = random_symbols(condition) if (isinstance(condition, Equality) and len(condsymbols) == 1 and not isinstance(pspace(expr).domain, ConditionalDomain)): rv = tuple(condsymbols)[0] results = solveset(condition, rv) if isinstance(results, Intersection) and S.Reals in results.args: results = list(results.args[1]) sums = 0 for res in results: temp = expr.subs(rv, res) if temp == True: return True if temp != False: # XXX: This seems nonsensical but preserves existing behaviour # after the change that Relational is no longer a subclass of # Expr. Here expr is sometimes Relational and sometimes Expr # but we are trying to add them with +=. This needs to be # fixed somehow. if sums == 0 and isinstance(expr, Relational): sums = expr.subs(rv, res) else: sums += expr.subs(rv, res) if sums == 0: return False return sums # Get full probability space of both the expression and the condition fullspace = pspace(Tuple(expr, condition)) # Build new space given the condition space = fullspace.conditional_space(condition, kwargs) # Dictionary to swap out RandomSymbols in expr with new RandomSymbols # That point to the new conditional space swapdict = rs_swap(fullspace.values, space.values) # Swap random variables in the expression expr = expr.xreplace(swapdict) return expr def expectation(expr, condition=None, numsamples=None, evaluate=True, kwargs): """ Returns the expected value of a random expression Parameters ========== expr : Expr containing RandomSymbols The expression of which you want to compute the expectation value given : Expr containing RandomSymbols A conditional expression. E(X, X>0) is expectation of X given X > 0 numsamples : int Enables sampling and approximates the expectation with this many samples evalf : Bool (defaults to True) If sampling return a number rather than a complex expression evaluate : Bool (defaults to True) In case of continuous systems return unevaluated integral Examples ======== >>> from sympy.stats import E, Die >>> X = Die('X', 6) >>> E(X) 7/2 >>> E(2X + 1) 8 >>> E(X, X > 3) # Expectation of X given that it is above 3 5 """ if not is_random(expr): # expr isn't random? return expr kwargs['numsamples'] = numsamples from sympy.stats.symbolic_probability import Expectation if evaluate: return Expectation(expr, condition).doit(kwargs) ### TODO: Remove the user warnings in the future releases message = ("Since version 1.7, using `evaluate=False` returns `Expectation` " "object. If you want unevaluated Integral/Sum use " "`E(expr, condition, evaluate=False).rewrite(Integral)`") warnings.warn(filldedent(message)) return Expectation(expr, condition) def probability(condition, given_condition=None, numsamples=None, evaluate=True, kwargs): """ Probability that a condition is true, optionally given a second condition Parameters ========== condition : Combination of Relationals containing RandomSymbols The condition of which you want to compute the probability given_condition : Combination of Relationals containing RandomSymbols A conditional expression. P(X > 1, X > 0) is expectation of X > 1 given X > 0 numsamples : int Enables sampling and approximates the probability with this many samples evaluate : Bool (defaults to True) In case of continuous systems return unevaluated integral Examples ======== >>> from sympy.stats import P, Die >>> from sympy import Eq >>> X, Y = Die('X', 6), Die('Y', 6) >>> P(X > 3) 1/2 >>> P(Eq(X, 5), X > 2) # Probability that X == 5 given that X > 2 1/4 >>> P(X > Y) 5/12 """ kwargs['numsamples'] = numsamples from sympy.stats.symbolic_probability import Probability if evaluate: return Probability(condition, given_condition).doit(kwargs) ### TODO: Remove the user warnings in the future releases message = ("Since version 1.7, using `evaluate=False` returns `Probability` " "object. If you want unevaluated Integral/Sum use " "`P(condition, given_condition, evaluate=False).rewrite(Integral)`") warnings.warn(filldedent(message)) return Probability(condition, given_condition) class Density(Basic): expr = property(lambda self: self.args[0]) @property def condition(self): if len(self.args) > 1: return self.args[1] else: return None def doit(self, evaluate=True, kwargs): from sympy.stats.random_matrix import RandomMatrixPSpace from sympy.stats.joint_rv import JointPSpace from sympy.stats.matrix_distributions import MatrixPSpace from sympy.stats.compound_rv import CompoundPSpace from sympy.stats.frv import SingleFiniteDistribution expr, condition = self.expr, self.condition if isinstance(expr, SingleFiniteDistribution): return expr.dict if condition is not None: # Recompute on new conditional expr expr = given(expr, condition, kwargs) if not random_symbols(expr): return Lambda(x, DiracDelta(x - expr)) if isinstance(expr, RandomSymbol): if isinstance(expr.pspace, (SinglePSpace, JointPSpace, MatrixPSpace)) and \ hasattr(expr.pspace, 'distribution'): return expr.pspace.distribution elif isinstance(expr.pspace, RandomMatrixPSpace): return expr.pspace.model if isinstance(pspace(expr), CompoundPSpace): kwargs['compound_evaluate'] = evaluate result = pspace(expr).compute_density(expr, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def density(expr, condition=None, evaluate=True, numsamples=None, *kwargs): """ Probability density of a random expression, optionally given a second condition. This density will take on different forms for different types of probability spaces. Discrete variables produce Dicts. Continuous variables produce Lambdas. Parameters ========== expr : Expr containing RandomSymbols The expression of which you want to compute the density value condition : Relational containing RandomSymbols A conditional expression. density(X > 1, X > 0) is density of X > 1 given X > 0 numsamples : int Enables sampling and approximates the density with this many samples Examples ======== >>> from sympy.stats import density, Die, Normal >>> from sympy import Symbol >>> x = Symbol('x') >>> D = Die('D', 6) >>> X = Normal(x, 0, 1) >>> density(D).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> density(2D).dict {2: 1/6, 4: 1/6, 6: 1/6, 8: 1/6, 10: 1/6, 12: 1/6} >>> density(X)(x) sqrt(2)exp(-x2/2)/(2sqrt(pi)) """ if numsamples: return sampling_density(expr, condition, numsamples=numsamples, kwargs) return Density(expr, condition).doit(evaluate=evaluate, kwargs) def cdf(expr, condition=None, evaluate=True, *kwargs): """ Cumulative Distribution Function of a random expression. optionally given a second condition This density will take on different forms for different types of probability spaces. Discrete variables produce Dicts. Continuous variables produce Lambdas. Examples ======== >>> from sympy.stats import density, Die, Normal, cdf >>> D = Die('D', 6) >>> X = Normal('X', 0, 1) >>> density(D).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> cdf(D) {1: 1/6, 2: 1/3, 3: 1/2, 4: 2/3, 5: 5/6, 6: 1} >>> cdf(3D, D > 2) {9: 1/4, 12: 1/2, 15: 3/4, 18: 1} >>> cdf(X) Lambda(_z, erf(sqrt(2)_z/2)/2 + 1/2) """ if condition is not None: # If there is a condition # Recompute on new conditional expr return cdf(given(expr, condition, kwargs), kwargs) # Otherwise pass work off to the ProbabilitySpace result = pspace(expr).compute_cdf(expr, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def characteristic_function(expr, condition=None, evaluate=True, kwargs): """ Characteristic function of a random expression, optionally given a second condition Returns a Lambda Examples ======== >>> from sympy.stats import Normal, DiscreteUniform, Poisson, characteristic_function >>> X = Normal('X', 0, 1) >>> characteristic_function(X) Lambda(_t, exp(-_t2/2)) >>> Y = DiscreteUniform('Y', [1, 2, 7]) >>> characteristic_function(Y) Lambda(_t, exp(7_tI)/3 + exp(2_tI)/3 + exp(_tI)/3) >>> Z = Poisson('Z', 2) >>> characteristic_function(Z) Lambda(_t, exp(2exp(_tI) - 2)) """ if condition is not None: return characteristic_function(given(expr, condition, kwargs), kwargs) result = pspace(expr).compute_characteristic_function(expr, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def moment_generating_function(expr, condition=None, evaluate=True, kwargs): if condition is not None: return moment_generating_function(given(expr, condition, kwargs), kwargs) result = pspace(expr).compute_moment_generating_function(expr, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def where(condition, given_condition=None, kwargs): """ Returns the domain where a condition is True. Examples ======== >>> from sympy.stats import where, Die, Normal >>> from sympy import And >>> D1, D2 = Die('a', 6), Die('b', 6) >>> a, b = D1.symbol, D2.symbol >>> X = Normal('x', 0, 1) >>> where(X2<1) Domain: (-1 < x) & (x < 1) >>> where(X2<1).set Interval.open(-1, 1) >>> where(And(D1<=D2 , D2<3)) Domain: (Eq(a, 1) & Eq(b, 1)) \| (Eq(a, 1) & Eq(b, 2)) \| (Eq(a, 2) & Eq(b, 2)) """ if given_condition is not None: # If there is a condition # Recompute on new conditional expr return where(given(condition, given_condition, kwargs), kwargs) # Otherwise pass work off to the ProbabilitySpace return pspace(condition).where(condition, kwargs) def sample(expr, condition=None, size=(), library='scipy', numsamples=1, kwargs): """ A realization of the random expression Parameters ========== expr : Expression of random variables Expression from which sample is extracted condition : Expr containing RandomSymbols A conditional expression size : int, tuple Represents size of each sample in numsamples library : str - 'scipy' : Sample using scipy - 'numpy' : Sample using numpy - 'pymc3' : Sample using PyMC3 Choose any of the available options to sample from as string, by default is 'scipy' numsamples : int Number of samples, each with size as ``size`` Examples ======== >>> from sympy.stats import Die, sample, Normal, Geometric >>> X, Y, Z = Die('X', 6), Die('Y', 6), Die('Z', 6) # Finite Random Variable >>> die_roll = sample(X + Y + Z) # doctest: +SKIP >>> next(die_roll) # doctest: +SKIP 6 >>> N = Normal('N', 3, 4) # Continuous Random Variable >>> samp = next(sample(N)) # doctest: +SKIP >>> samp in N.pspace.domain.set # doctest: +SKIP True >>> samp = next(sample(N, N>0)) # doctest: +SKIP >>> samp > 0 # doctest: +SKIP True >>> samp_list = next(sample(N, size=4)) # doctest: +SKIP >>> [sam in N.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True, True] >>> G = Geometric('G', 0.5) # Discrete Random Variable >>> samp_list = next(sample(G, size=3)) # doctest: +SKIP >>> samp_list # doctest: +SKIP array([10, 4, 1]) >>> [sam in G.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True] >>> MN = Normal("MN", [3, 4], [[2, 1], [1, 2]]) # Joint Random Variable >>> samp_list = next(sample(MN, size=4)) # doctest: +SKIP >>> samp_list # doctest: +SKIP array([[4.22564264, 3.23364418], [3.41002011, 4.60090908], [3.76151866, 4.77617143], [4.71440865, 2.65714157]]) >>> [tuple(sam) in MN.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True, True] Returns ======= sample: iterator object iterator object containing the sample/samples of given expr """ ### TODO: Remove the user warnings in the future releases message = ("The return type of sample has been changed to return an " "iterator object since version 1.7. For more information see " "https://github.com/sympy/sympy/issues/19061") warnings.warn(filldedent(message)) return sample_iter(expr, condition, size=size, library=library, numsamples=numsamples) def quantile(expr, evaluate=True, kwargs): r""" Return the :math:`p^{th}` order quantile of a probability distribution. Quantile is defined as the value at which the probability of the random variable is less than or equal to the given probability. ..math:: Q(p) = inf{x \in (-\infty, \infty) such that p <= F(x)} Examples ======== >>> from sympy.stats import quantile, Die, Exponential >>> from sympy import Symbol, pprint >>> p = Symbol("p") >>> l = Symbol("lambda", positive=True) >>> X = Exponential("x", l) >>> quantile(X)(p) -log(1 - p)/lambda >>> D = Die("d", 6) >>> pprint(quantile(D)(p), use_unicode=False) /nan for Or(p > 1, p < 0) \| \| 1 for p <= 1/6 \| \| 2 for p <= 1/3 \| < 3 for p <= 1/2 \| \| 4 for p <= 2/3 \| \| 5 for p <= 5/6 \| \ 6 for p <= 1 """ result = pspace(expr).compute_quantile(expr, kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def sample_iter(expr, condition=None, size=(), library='scipy', numsamples=S.Infinity, *kwargs): """ Returns an iterator of realizations from the expression given a condition Parameters ========== expr: Expr Random expression to be realized condition: Expr, optional A conditional expression size : int, tuple Represents size of each sample in numsamples numsamples: integer, optional Length of the iterator (defaults to infinity) Examples ======== >>> from sympy.stats import Normal, sample_iter >>> X = Normal('X', 0, 1) >>> expr = XX + 3 >>> iterator = sample_iter(expr, numsamples=3) # doctest: +SKIP >>> list(iterator) # doctest: +SKIP [12, 4, 7] Returns ======= sample_iter: iterator object iterator object containing the sample/samples of given expr See Also ======== sample sampling_P sampling_E """ from sympy.stats.joint_rv import JointRandomSymbol if not import_module(library): raise ValueError("Failed to import %s" % library) if condition is not None: ps = pspace(Tuple(expr, condition)) else: ps = pspace(expr) rvs = list(ps.values) if isinstance(expr, JointRandomSymbol): expr = expr.subs({expr: RandomSymbol(expr.symbol, expr.pspace)}) else: sub = {} for arg in expr.args: if isinstance(arg, JointRandomSymbol): sub[arg] = RandomSymbol(arg.symbol, arg.pspace) expr = expr.subs(sub) if library == 'pymc3': # Currently unable to lambdify in pymc3 # TODO : Remove 'pymc3' when lambdify accepts 'pymc3' as module fn = lambdify(rvs, expr, kwargs) else: fn = lambdify(rvs, expr, modules=library, kwargs) if condition is not None: given_fn = lambdify(rvs, condition, *kwargs) def return_generator(): count = 0 while count < numsamples: d = ps.sample(size=size, library=library) # a dictionary that maps RVs to values args = [d[rv] for rv in rvs] if condition is not None: # Check that these values satisfy the condition gd = given_fn(args) if gd != True and gd != False: raise ValueError( "Conditions must not contain free symbols") if not gd: # If the values don't satisfy then try again continue yield fn(args) count += 1 return return_generator() def sample_iter_lambdify(expr, condition=None, size=(), numsamples=S.Infinity, kwargs): return sample_iter(expr, condition=condition, size=size, numsamples=numsamples, kwargs) def sample_iter_subs(expr, condition=None, size=(), numsamples=S.Infinity, kwargs): return sample_iter(expr, condition=condition, size=size, numsamples=numsamples, kwargs) def sampling_P(condition, given_condition=None, library='scipy', numsamples=1, evalf=True, kwargs): """ Sampling version of P See Also ======== P sampling_E sampling_density """ count_true = 0 count_false = 0 samples = sample_iter(condition, given_condition, library=library, numsamples=numsamples, kwargs) for sample in samples: if sample: count_true += 1 else: count_false += 1 result = S(count_true) / numsamples if evalf: return result.evalf() else: return result def sampling_E(expr, given_condition=None, library='scipy', numsamples=1, evalf=True, kwargs): """ Sampling version of E See Also ======== P sampling_P sampling_density """ samples = list(sample_iter(expr, given_condition, library=library, numsamples=numsamples, kwargs)) result = Add([samp for samp in samples]) / numsamples if evalf: return result.evalf() else: return result def sampling_density(expr, given_condition=None, library='scipy', numsamples=1, kwargs): """ Sampling version of density See Also ======== density sampling_P sampling_E """ results = {} for result in sample_iter(expr, given_condition, library=library, numsamples=numsamples, kwargs): results[result] = results.get(result, 0) + 1 return results def dependent(a, b): """ Dependence of two random expressions Two expressions are independent if knowledge of one does not change computations on the other. Examples ======== >>> from sympy.stats import Normal, dependent, given >>> from sympy import Tuple, Eq >>> X, Y = Normal('X', 0, 1), Normal('Y', 0, 1) >>> dependent(X, Y) False >>> dependent(2X + Y, -Y) True >>> X, Y = given(Tuple(X, Y), Eq(X + Y, 3)) >>> dependent(X, Y) True See Also ======== independent """ if pspace_independent(a, b): return False z = Symbol('z', real=True) # Dependent if density is unchanged when one is given information about # the other return (density(a, Eq(b, z)) != density(a) or density(b, Eq(a, z)) != density(b)) def independent(a, b): """ Independence of two random expressions Two expressions are independent if knowledge of one does not change computations on the other. Examples ======== >>> from sympy.stats import Normal, independent, given >>> from sympy import Tuple, Eq >>> X, Y = Normal('X', 0, 1), Normal('Y', 0, 1) >>> independent(X, Y) True >>> independent(2X + Y, -Y) False >>> X, Y = given(Tuple(X, Y), Eq(X + Y, 3)) >>> independent(X, Y) False See Also ======== dependent """ return not dependent(a, b) def pspace_independent(a, b): """ Tests for independence between a and b by checking if their PSpaces have overlapping symbols. This is a sufficient but not necessary condition for independence and is intended to be used internally. Notes ===== pspace_independent(a, b) implies independent(a, b) independent(a, b) does not imply pspace_independent(a, b) """ a_symbols = set(pspace(b).symbols) b_symbols = set(pspace(a).symbols) if len(set(random_symbols(a)).intersection(random_symbols(b))) != 0: return False if len(a_symbols.intersection(b_symbols)) == 0: return True return None def rv_subs(expr, symbols=None): """ Given a random expression replace all random variables with their symbols. If symbols keyword is given restrict the swap to only the symbols listed. """ if symbols is None: symbols = random_symbols(expr) if not symbols: return expr swapdict = {rv: rv.symbol for rv in symbols} return expr.subs(swapdict) class NamedArgsMixin: _argnames = () # type: tTuple[str, ...] def __getattr__(self, attr): try: return self.args[self._argnames.index(attr)] except ValueError: raise AttributeError("'%s' object has no attribute '%s'" % ( type(self).__name__, attr)) def _value_check(condition, message): """ Raise a ValueError with message if condition is False, else return True if all conditions were True, else False. Examples ======== >>> from sympy.stats.rv import _value_check >>> from sympy.abc import a, b, c >>> from sympy import And, Dummy >>> _value_check(2 < 3, '') True Here, the condition is not False, but it doesn't evaluate to True so False is returned (but no error is raised). So checking if the return value is True or False will tell you if all conditions were evaluated. >>> _value_check(a < b, '') False In this case the condition is False so an error is raised: >>> r = Dummy(real=True) >>> _value_check(r < r - 1, 'condition is not true') Traceback (most recent call last): ... ValueError: condition is not true If no condition of many conditions must be False, they can be checked by passing them as an iterable: >>> _value_check((a < 0, b < 0, c < 0), '') False The iterable can be a generator, too: >>> _value_check((i < 0 for i in (a, b, c)), '') False The following are equivalent to the above but do not pass an iterable: >>> all(_value_check(i < 0, '') for i in (a, b, c)) False >>> _value_check(And(a < 0, b < 0, c < 0), '') False """ from sympy.core.compatibility import iterable from sympy.core.logic import fuzzy_and if not iterable(condition): condition = [condition] truth = fuzzy_and(condition) if truth == False: raise ValueError(message) return truth == True def _symbol_converter(sym): """ Casts the parameter to Symbol if it is 'str' otherwise no operation is performed on it. Parameters ========== sym The parameter to be converted. Returns ======= Symbol the parameter converted to Symbol. Raises ====== TypeError If the parameter is not an instance of both str and Symbol. Examples ======== >>> from sympy import Symbol >>> from sympy.stats.rv import _symbol_converter >>> s = _symbol_converter('s') >>> isinstance(s, Symbol) True >>> _symbol_converter(1) Traceback (most recent call last): ... TypeError: 1 is neither a Symbol nor a string >>> r = Symbol('r') >>> isinstance(r, Symbol) True """ if isinstance(sym, str): sym = Symbol(sym) if not isinstance(sym, Symbol): raise TypeError("%s is neither a Symbol nor a string"%(sym)) return sym def sample_stochastic_process(process): """ This function is used to sample from stochastic process. Parameters ========== process: StochasticProcess Process used to extract the samples. It must be an instance of StochasticProcess Examples ======== >>> from sympy.stats import sample_stochastic_process, DiscreteMarkovChain >>> from sympy import Matrix >>> T = Matrix([[0.5, 0.2, 0.3],[0.2, 0.5, 0.3],[0.2, 0.3, 0.5]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> next(sample_stochastic_process(Y)) in Y.state_space # doctest: +SKIP True >>> next(sample_stochastic_process(Y)) # doctest: +SKIP 0 >>> next(sample_stochastic_process(Y)) # doctest: +SKIP 2 Returns ======= sample: iterator object iterator object containing the sample of given process """ from sympy.stats.stochastic_process_types import StochasticProcess if not isinstance(process, StochasticProcess): raise ValueError("Process must be an instance of Stochastic Process") return process.sample()
3ec3b41e784781b8dc39b74b7e6ed3ca520d02083b7690e4e9c699edeafd04ea	""" Joint Random Variables Module See Also ======== sympy.stats.rv sympy.stats.frv sympy.stats.crv sympy.stats.drv """ from sympy import (Basic, Lambda, sympify, Indexed, Symbol, ProductSet, S, Dummy) from sympy.concrete.products import Product from sympy.concrete.summations import Sum, summation from sympy.core.compatibility import iterable from sympy.core.containers import Tuple from sympy.integrals.integrals import Integral, integrate from sympy.matrices import ImmutableMatrix, matrix2numpy, list2numpy from sympy.stats.crv import SingleContinuousDistribution, SingleContinuousPSpace from sympy.stats.drv import SingleDiscreteDistribution, SingleDiscretePSpace from sympy.stats.rv import (ProductPSpace, NamedArgsMixin, ProductDomain, RandomSymbol, random_symbols, SingleDomain, _symbol_converter) from sympy.utilities.misc import filldedent from sympy.external import import_module # __all__ = ['marginal_distribution'] class JointPSpace(ProductPSpace): """ Represents a joint probability space. Represented using symbols for each component and a distribution. """ def __new__(cls, sym, dist): if isinstance(dist, SingleContinuousDistribution): return SingleContinuousPSpace(sym, dist) if isinstance(dist, SingleDiscreteDistribution): return SingleDiscretePSpace(sym, dist) sym = _symbol_converter(sym) return Basic.__new__(cls, sym, dist) @property def set(self): return self.domain.set @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[1] @property def value(self): return JointRandomSymbol(self.symbol, self) @property def component_count(self): _set = self.distribution.set if isinstance(_set, ProductSet): return S(len(_set.args)) elif isinstance(_set, Product): return _set.limits[0][-1] return S.One @property def pdf(self): sym = [Indexed(self.symbol, i) for i in range(self.component_count)] return self.distribution(sym) @property def domain(self): rvs = random_symbols(self.distribution) if not rvs: return SingleDomain(self.symbol, self.distribution.set) return ProductDomain([rv.pspace.domain for rv in rvs]) def component_domain(self, index): return self.set.args[index] def marginal_distribution(self, indices): count = self.component_count if count.atoms(Symbol): raise ValueError("Marginal distributions cannot be computed " "for symbolic dimensions. It is a work under progress.") orig = [Indexed(self.symbol, i) for i in range(count)] all_syms = [Symbol(str(i)) for i in orig] replace_dict = dict(zip(all_syms, orig)) sym = tuple(Symbol(str(Indexed(self.symbol, i))) for i in indices) limits = list([i,] for i in all_syms if i not in sym) index = 0 for i in range(count): if i not in indices: limits[index].append(self.distribution.set.args[i]) limits[index] = tuple(limits[index]) index += 1 if self.distribution.is_Continuous: f = Lambda(sym, integrate(self.distribution(all_syms), limits)) elif self.distribution.is_Discrete: f = Lambda(sym, summation(self.distribution(all_syms), limits)) return f.xreplace(replace_dict) def compute_expectation(self, expr, rvs=None, evaluate=False, kwargs): syms = tuple(self.value[i] for i in range(self.component_count)) rvs = rvs or syms if not any([i in rvs for i in syms]): return expr expr = exprself.pdf for rv in rvs: if isinstance(rv, Indexed): expr = expr.xreplace({rv: Indexed(str(rv.base), rv.args[1])}) elif isinstance(rv, RandomSymbol): expr = expr.xreplace({rv: rv.symbol}) if self.value in random_symbols(expr): raise NotImplementedError(filldedent(''' Expectations of expression with unindexed joint random symbols cannot be calculated yet.''')) limits = tuple((Indexed(str(rv.base),rv.args[1]), self.distribution.set.args[rv.args[1]]) for rv in syms) return Integral(expr, limits) def where(self, condition): raise NotImplementedError() def compute_density(self, expr): raise NotImplementedError() def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {RandomSymbol(self.symbol, self): self.distribution.sample(size, library=library)} def probability(self, condition): raise NotImplementedError() class SampleJointScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" from scipy import stats as scipy_stats scipy_rv_map = { 'MultivariateNormalDistribution': lambda dist, size: scipy_stats.multivariate_normal.rvs( mean=matrix2numpy(dist.mu).flatten(), cov=matrix2numpy(dist.sigma), size=size), 'MultivariateBetaDistribution': lambda dist, size: scipy_stats.dirichlet.rvs( alpha=list2numpy(dist.alpha, float).flatten(), size=size), 'MultinomialDistribution': lambda dist, size: scipy_stats.multinomial.rvs( n=int(dist.n), p=list2numpy(dist.p, float).flatten(), size=size) } dist_list = scipy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return scipy_rv_map[dist.__class__.__name__](dist, size) class SampleJointNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'MultivariateNormalDistribution': lambda dist, size: numpy.random.multivariate_normal( mean=matrix2numpy(dist.mu, float).flatten(), cov=matrix2numpy(dist.sigma, float), size=size), 'MultivariateBetaDistribution': lambda dist, size: numpy.random.dirichlet( alpha=list2numpy(dist.alpha, float).flatten(), size=size), 'MultinomialDistribution': lambda dist, size: numpy.random.multinomial( n=int(dist.n), pvals=list2numpy(dist.p, float).flatten(), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleJointPymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'MultivariateNormalDistribution': lambda dist: pymc3.MvNormal('X', mu=matrix2numpy(dist.mu, float).flatten(), cov=matrix2numpy(dist.sigma, float), shape=(1, dist.mu.shape[0])), 'MultivariateBetaDistribution': lambda dist: pymc3.Dirichlet('X', a=list2numpy(dist.alpha, float).flatten()), 'MultinomialDistribution': lambda dist: pymc3.Multinomial('X', n=int(dist.n), p=list2numpy(dist.p, float).flatten(), shape=(1, len(dist.p))) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_jrv = { 'scipy': SampleJointScipy, 'pymc3': SampleJointPymc, 'numpy': SampleJointNumpy } class JointDistribution(Basic, NamedArgsMixin): """ Represented by the random variables part of the joint distribution. Contains methods for PDF, CDF, sampling, marginal densities, etc. """ _argnames = ('pdf', ) def __new__(cls, args): args = list(map(sympify, args)) for i in range(len(args)): if isinstance(args[i], list): args[i] = ImmutableMatrix(args[i]) return Basic.__new__(cls, args) @property def domain(self): return ProductDomain(self.symbols) @property def pdf(self): return self.density.args[1] def cdf(self, other): if not isinstance(other, dict): raise ValueError("%s should be of type dict, got %s"%(other, type(other))) rvs = other.keys() _set = self.domain.set.sets expr = self.pdf(tuple(i.args[0] for i in self.symbols)) for i in range(len(other)): if rvs[i].is_Continuous: density = Integral(expr, (rvs[i], _set[i].inf, other[rvs[i]])) elif rvs[i].is_Discrete: density = Sum(expr, (rvs[i], _set[i].inf, other[rvs[i]])) return density def sample(self, size=(), library='scipy'): """ A random realization from the distribution """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_jrv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) def __call__(self, args): return self.pdf(args) class JointRandomSymbol(RandomSymbol): """ Representation of random symbols with joint probability distributions to allow indexing." """ def __getitem__(self, key): if isinstance(self.pspace, JointPSpace): if (self.pspace.component_count <= key) == True: raise ValueError("Index keys for %s can only up to %s." % (self.name, self.pspace.component_count - 1)) return Indexed(self, key) class MarginalDistribution(Basic): """ Represents the marginal distribution of a joint probability space. Initialised using a probability distribution and random variables(or their indexed components) which should be a part of the resultant distribution. """ def __new__(cls, dist, rvs): if len(rvs) == 1 and iterable(rvs[0]): rvs = tuple(rvs[0]) if not all([isinstance(rv, (Indexed, RandomSymbol))] for rv in rvs): raise ValueError(filldedent('''Marginal distribution can be intitialised only in terms of random variables or indexed random variables''')) rvs = Tuple.fromiter(rv for rv in rvs) if not isinstance(dist, JointDistribution) and len(random_symbols(dist)) == 0: return dist return Basic.__new__(cls, dist, rvs) def check(self): pass @property def set(self): rvs = [i for i in self.args[1] if isinstance(i, RandomSymbol)] return ProductSet([rv.pspace.set for rv in rvs]) @property def symbols(self): rvs = self.args[1] return {rv.pspace.symbol for rv in rvs} def pdf(self, x): expr, rvs = self.args[0], self.args[1] marginalise_out = [i for i in random_symbols(expr) if i not in rvs] if isinstance(expr, JointDistribution): count = len(expr.domain.args) x = Dummy('x', real=True, finite=True) syms = tuple(Indexed(x, i) for i in count) expr = expr.pdf(syms) else: syms = tuple(rv.pspace.symbol if isinstance(rv, RandomSymbol) else rv.args[0] for rv in rvs) return Lambda(syms, self.compute_pdf(expr, marginalise_out))(x) def compute_pdf(self, expr, rvs): for rv in rvs: lpdf = 1 if isinstance(rv, RandomSymbol): lpdf = rv.pspace.pdf expr = self.marginalise_out(exprlpdf, rv) return expr def marginalise_out(self, expr, rv): from sympy.concrete.summations import Sum if isinstance(rv, RandomSymbol): dom = rv.pspace.set elif isinstance(rv, Indexed): dom = rv.base.component_domain( rv.pspace.component_domain(rv.args[1])) expr = expr.xreplace({rv: rv.pspace.symbol}) if rv.pspace.is_Continuous: #TODO: Modify to support integration #for all kinds of sets. expr = Integral(expr, (rv.pspace.symbol, dom)) elif rv.pspace.is_Discrete: #incorporate this into `Sum`/`summation` if dom in (S.Integers, S.Naturals, S.Naturals0): dom = (dom.inf, dom.sup) expr = Sum(expr, (rv.pspace.symbol, dom)) return expr def __call__(self, args): return self.pdf(args)
c30e893f2554adef2f886678a8a85be79908b7c7b9b726943074544f290d8935	from sympy import (Basic, sympify, symbols, Dummy, Lambda, summation, Piecewise, S, cacheit, Sum, exp, I, Ne, Eq, poly, series, factorial, And, lambdify) from sympy.polys.polyerrors import PolynomialError from sympy.stats.crv import reduce_rational_inequalities_wrap from sympy.stats.rv import (NamedArgsMixin, SinglePSpace, SingleDomain, random_symbols, PSpace, ConditionalDomain, RandomDomain, ProductDomain) from sympy.stats.symbolic_probability import Probability from sympy.sets.fancysets import Range, FiniteSet from sympy.sets.sets import Union from sympy.sets.contains import Contains from sympy.utilities import filldedent from sympy.core.sympify import _sympify from sympy.external import import_module class DiscreteDistribution(Basic): def __call__(self, args): return self.pdf(args) class SampleDiscreteScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" from scipy import stats as scipy_stats scipy_rv_map = { 'GeometricDistribution': lambda dist, size: scipy_stats.geom.rvs(p=float(dist.p), size=size), 'LogarithmicDistribution': lambda dist, size: scipy_stats.logser.rvs(p=float(dist.p), size=size), 'NegativeBinomialDistribution': lambda dist, size: scipy_stats.nbinom.rvs(n=float(dist.r), p=float(dist.p), size=size), 'PoissonDistribution': lambda dist, size: scipy_stats.poisson.rvs(mu=float(dist.lamda), size=size), 'SkellamDistribution': lambda dist, size: scipy_stats.skellam.rvs(mu1=float(dist.mu1), mu2=float(dist.mu2), size=size), 'YuleSimonDistribution': lambda dist, size: scipy_stats.yulesimon.rvs(alpha=float(dist.rho), size=size), 'ZetaDistribution': lambda dist, size: scipy_stats.zipf.rvs(a=float(dist.s), size=size) } dist_list = scipy_rv_map.keys() if dist.__class__.__name__ == 'DiscreteDistributionHandmade': from scipy.stats import rv_discrete z = Dummy('z') handmade_pmf = lambdify(z, dist.pdf(z), ['numpy', 'scipy']) class scipy_pmf(rv_discrete): def _pmf(self, x): return handmade_pmf(x) scipy_rv = scipy_pmf(a=float(dist.set._inf), b=float(dist.set._sup), name='scipy_pmf') return scipy_rv.rvs(size=size) if dist.__class__.__name__ not in dist_list: return None return scipy_rv_map[dist.__class__.__name__](dist, size) class SampleDiscreteNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'GeometricDistribution': lambda dist, size: numpy.random.geometric(p=float(dist.p), size=size), 'PoissonDistribution': lambda dist, size: numpy.random.poisson(lam=float(dist.lamda), size=size), 'ZetaDistribution': lambda dist, size: numpy.random.zipf(a=float(dist.s), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleDiscretePymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'GeometricDistribution': lambda dist: pymc3.Geometric('X', p=float(dist.p)), 'PoissonDistribution': lambda dist: pymc3.Poisson('X', mu=float(dist.lamda)), 'NegativeBinomialDistribution': lambda dist: pymc3.NegativeBinomial('X', mu=float((dist.pdist.r)/(1-dist.p)), alpha=float(dist.r)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_drv = { 'scipy': SampleDiscreteScipy, 'pymc3': SampleDiscretePymc, 'numpy': SampleDiscreteNumpy } class SingleDiscreteDistribution(DiscreteDistribution, NamedArgsMixin): """ Discrete distribution of a single variable Serves as superclass for PoissonDistribution etc.... Provides methods for pdf, cdf, and sampling See Also: sympy.stats.crv_types. """ set = S.Integers def __new__(cls, args): args = list(map(sympify, args)) return Basic.__new__(cls, args) @staticmethod def check(args): pass def sample(self, size=(), library='scipy'): """ A random realization from the distribution""" libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_drv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) @cacheit def compute_cdf(self, kwargs): """ Compute the CDF from the PDF Returns a Lambda """ x, z = symbols('x, z', integer=True, cls=Dummy) left_bound = self.set.inf # CDF is integral of PDF from left bound to z pdf = self.pdf(x) cdf = summation(pdf, (x, left_bound, z), kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) def _cdf(self, x): return None def cdf(self, x, kwargs): """ Cumulative density function """ if not kwargs: cdf = self._cdf(x) if cdf is not None: return cdf return self.compute_cdf(kwargs)(x) @cacheit def compute_characteristic_function(self, kwargs): """ Compute the characteristic function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) cf = summation(exp(Itx)pdf, (x, self.set.inf, self.set.sup)) return Lambda(t, cf) def _characteristic_function(self, t): return None def characteristic_function(self, t, kwargs): """ Characteristic function """ if not kwargs: cf = self._characteristic_function(t) if cf is not None: return cf return self.compute_characteristic_function(kwargs)(t) @cacheit def compute_moment_generating_function(self, *kwargs): t = Dummy('t', real=True) x = Dummy('x', integer=True) pdf = self.pdf(x) mgf = summation(exp(tx)pdf, (x, self.set.inf, self.set.sup)) return Lambda(t, mgf) def _moment_generating_function(self, t): return None def moment_generating_function(self, t, kwargs): if not kwargs: mgf = self._moment_generating_function(t) if mgf is not None: return mgf return self.compute_moment_generating_function(kwargs)(t) @cacheit def compute_quantile(self, kwargs): """ Compute the Quantile from the PDF Returns a Lambda """ x = Dummy('x', integer=True) p = Dummy('p', real=True) left_bound = self.set.inf pdf = self.pdf(x) cdf = summation(pdf, (x, left_bound, x), kwargs) set = ((x, p <= cdf), ) return Lambda(p, Piecewise(set)) def _quantile(self, x): return None def quantile(self, x, kwargs): """ Cumulative density function """ if not kwargs: quantile = self._quantile(x) if quantile is not None: return quantile return self.compute_quantile(kwargs)(x) def expectation(self, expr, var, evaluate=True, kwargs): """ Expectation of expression over distribution """ # TODO: support discrete sets with non integer stepsizes if evaluate: try: p = poly(expr, var) t = Dummy('t', real=True) mgf = self.moment_generating_function(t) deg = p.degree() taylor = poly(series(mgf, t, 0, deg + 1).removeO(), t) result = 0 for k in range(deg+1): result += p.coeff_monomial(var k) * taylor.coeff_monomial(t ** k) * factorial(k) return result except PolynomialError: return summation(expr * self.pdf(var), (var, self.set.inf, self.set.sup), *kwargs) else: return Sum(expr self.pdf(var), (var, self.set.inf, self.set.sup), *kwargs) def __call__(self, args): return self.pdf(args) class DiscreteDomain(RandomDomain): """ A domain with discrete support with step size one. Represented using symbols and Range. """ is_Discrete = True class SingleDiscreteDomain(DiscreteDomain, SingleDomain): def as_boolean(self): return Contains(self.symbol, self.set) class ConditionalDiscreteDomain(DiscreteDomain, ConditionalDomain): """ Domain with discrete support of step size one, that is restricted by some condition. """ @property def set(self): rv = self.symbols if len(self.symbols) > 1: raise NotImplementedError(filldedent(''' Multivariate conditional domains are not yet implemented.''')) rv = list(rv)[0] return reduce_rational_inequalities_wrap(self.condition, rv).intersect(self.fulldomain.set) class DiscretePSpace(PSpace): is_real = True is_Discrete = True @property def pdf(self): return self.density(self.symbols) def where(self, condition): rvs = random_symbols(condition) assert all(r.symbol in self.symbols for r in rvs) if len(rvs) > 1: raise NotImplementedError(filldedent('''Multivariate discrete random variables are not yet supported.''')) conditional_domain = reduce_rational_inequalities_wrap(condition, rvs[0]) conditional_domain = conditional_domain.intersect(self.domain.set) return SingleDiscreteDomain(rvs[0].symbol, conditional_domain) def probability(self, condition): complement = isinstance(condition, Ne) if complement: condition = Eq(condition.args[0], condition.args[1]) try: _domain = self.where(condition).set if condition == False or _domain is S.EmptySet: return S.Zero if condition == True or _domain == self.domain.set: return S.One prob = self.eval_prob(_domain) except NotImplementedError: from sympy.stats.rv import density expr = condition.lhs - condition.rhs dens = density(expr) if not isinstance(dens, DiscreteDistribution): from sympy.stats.drv_types import DiscreteDistributionHandmade dens = DiscreteDistributionHandmade(dens) z = Dummy('z', real=True) space = SingleDiscretePSpace(z, dens) prob = space.probability(condition.__class__(space.value, 0)) if prob is None: prob = Probability(condition) return prob if not complement else S.One - prob def eval_prob(self, _domain): sym = list(self.symbols)[0] if isinstance(_domain, Range): n = symbols('n', integer=True) inf, sup, step = (r for r in _domain.args) summand = ((self.pdf).replace( sym, nstep)) rv = summation(summand, (n, inf/step, (sup)/step - 1)).doit() return rv elif isinstance(_domain, FiniteSet): pdf = Lambda(sym, self.pdf) rv = sum(pdf(x) for x in _domain) return rv elif isinstance(_domain, Union): rv = sum(self.eval_prob(x) for x in _domain.args) return rv def conditional_space(self, condition): # XXX: Converting from set to tuple. The order matters to Lambda # though so we should be starting with a set... density = Lambda(tuple(self.symbols), self.pdf/self.probability(condition)) condition = condition.xreplace({rv: rv.symbol for rv in self.values}) domain = ConditionalDiscreteDomain(self.domain, condition) return DiscretePSpace(domain, density) class ProductDiscreteDomain(ProductDomain, DiscreteDomain): def as_boolean(self): return And([domain.as_boolean for domain in self.domains]) class SingleDiscretePSpace(DiscretePSpace, SinglePSpace): """ Discrete probability space over a single univariate variable """ is_real = True @property def set(self): return self.distribution.set @property def domain(self): return SingleDiscreteDomain(self.symbol, self.set) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {self.value: self.distribution.sample(size, library=library)} def compute_expectation(self, expr, rvs=None, evaluate=True, kwargs): rvs = rvs or (self.value,) if self.value not in rvs: return expr expr = _sympify(expr) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) x = self.value.symbol try: return self.distribution.expectation(expr, x, evaluate=evaluate, kwargs) except NotImplementedError: return Sum(expr * self.pdf, (x, self.set.inf, self.set.sup), kwargs) def compute_cdf(self, expr, kwargs): if expr == self.value: x = Dummy("x", real=True) return Lambda(x, self.distribution.cdf(x, kwargs)) else: raise NotImplementedError() def compute_density(self, expr, kwargs): if expr == self.value: return self.distribution raise NotImplementedError() def compute_characteristic_function(self, expr, kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.characteristic_function(t, kwargs)) else: raise NotImplementedError() def compute_moment_generating_function(self, expr, kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.moment_generating_function(t, kwargs)) else: raise NotImplementedError() def compute_quantile(self, expr, kwargs): if expr == self.value: p = Dummy("p", real=True) return Lambda(p, self.distribution.quantile(p, kwargs)) else: raise NotImplementedError()
c833bb8dafda6367b4f45cddf8245fd73073893589964a5f17201d8342174243	""" Continuous Random Variables Module See Also ======== sympy.stats.crv_types sympy.stats.rv sympy.stats.frv """ from sympy import (Interval, Intersection, symbols, sympify, Dummy, nan, Integral, And, Or, Piecewise, cacheit, integrate, oo, Lambda, Basic, S, exp, I, FiniteSet, Ne, Eq, Union, poly, series, factorial, lambdify) from sympy.core.function import PoleError from sympy.functions.special.delta_functions import DiracDelta from sympy.polys.polyerrors import PolynomialError from sympy.solvers.solveset import solveset from sympy.solvers.inequalities import reduce_rational_inequalities from sympy.core.sympify import _sympify from sympy.external import import_module from sympy.stats.rv import (RandomDomain, SingleDomain, ConditionalDomain, is_random, ProductDomain, PSpace, SinglePSpace, random_symbols, NamedArgsMixin) class ContinuousDomain(RandomDomain): """ A domain with continuous support Represented using symbols and Intervals. """ is_Continuous = True def as_boolean(self): raise NotImplementedError("Not Implemented for generic Domains") class SingleContinuousDomain(ContinuousDomain, SingleDomain): """ A univariate domain with continuous support Represented using a single symbol and interval. """ def compute_expectation(self, expr, variables=None, kwargs): if variables is None: variables = self.symbols if not variables: return expr if frozenset(variables) != frozenset(self.symbols): raise ValueError("Values should be equal") # assumes only intervals return Integral(expr, (self.symbol, self.set), kwargs) def as_boolean(self): return self.set.as_relational(self.symbol) class ProductContinuousDomain(ProductDomain, ContinuousDomain): """ A collection of independent domains with continuous support """ def compute_expectation(self, expr, variables=None, kwargs): if variables is None: variables = self.symbols for domain in self.domains: domain_vars = frozenset(variables) & frozenset(domain.symbols) if domain_vars: expr = domain.compute_expectation(expr, domain_vars, kwargs) return expr def as_boolean(self): return And([domain.as_boolean() for domain in self.domains]) class ConditionalContinuousDomain(ContinuousDomain, ConditionalDomain): """ A domain with continuous support that has been further restricted by a condition such as x > 3 """ def compute_expectation(self, expr, variables=None, kwargs): if variables is None: variables = self.symbols if not variables: return expr # Extract the full integral fullintgrl = self.fulldomain.compute_expectation(expr, variables) # separate into integrand and limits integrand, limits = fullintgrl.function, list(fullintgrl.limits) conditions = [self.condition] while conditions: cond = conditions.pop() if cond.is_Boolean: if isinstance(cond, And): conditions.extend(cond.args) elif isinstance(cond, Or): raise NotImplementedError("Or not implemented here") elif cond.is_Relational: if cond.is_Equality: # Add the appropriate Delta to the integrand integrand = DiracDelta(cond.lhs - cond.rhs) else: symbols = cond.free_symbols & set(self.symbols) if len(symbols) != 1: # Can't handle x > y raise NotImplementedError( "Multivariate Inequalities not yet implemented") # Can handle x > 0 symbol = symbols.pop() # Find the limit with x, such as (x, -oo, oo) for i, limit in enumerate(limits): if limit[0] == symbol: # Make condition into an Interval like [0, oo] cintvl = reduce_rational_inequalities_wrap( cond, symbol) # Make limit into an Interval like [-oo, oo] lintvl = Interval(limit[1], limit[2]) # Intersect them to get [0, oo] intvl = cintvl.intersect(lintvl) # Put back into limits list limits[i] = (symbol, intvl.left, intvl.right) else: raise TypeError( "Condition %s is not a relational or Boolean" % cond) return Integral(integrand, limits, kwargs) def as_boolean(self): return And(self.fulldomain.as_boolean(), self.condition) @property def set(self): if len(self.symbols) == 1: return (self.fulldomain.set & reduce_rational_inequalities_wrap( self.condition, tuple(self.symbols)[0])) else: raise NotImplementedError( "Set of Conditional Domain not Implemented") class ContinuousDistribution(Basic): def __call__(self, args): return self.pdf(args) class SampleContinuousScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" # scipy does not require map as it can handle using custom distributions from scipy.stats import rv_continuous z = Dummy('z') handmade_pdf = lambdify(z, dist.pdf(z), ['numpy', 'scipy']) class scipy_pdf(rv_continuous): def _pdf(self, x): return handmade_pdf(x) scipy_rv = scipy_pdf(a=float(dist.set._inf), b=float(dist.set._sup), name='scipy_pdf') return scipy_rv.rvs(size=size) class SampleContinuousNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'BetaDistribution': lambda dist, size: numpy.random.beta(a=float(dist.alpha), b=float(dist.beta), size=size), 'ChiSquaredDistribution': lambda dist, size: numpy.random.chisquare( df=float(dist.k), size=size), 'ExponentialDistribution': lambda dist, size: numpy.random.exponential( 1/float(dist.rate), size=size), 'GammaDistribution': lambda dist, size: numpy.random.gamma(float(dist.k), float(dist.theta), size=size), 'LogNormalDistribution': lambda dist, size: numpy.random.lognormal( float(dist.mean), float(dist.std), size=size), 'NormalDistribution': lambda dist, size: numpy.random.normal( float(dist.mean), float(dist.std), size=size), 'ParetoDistribution': lambda dist, size: (numpy.random.pareto( a=float(dist.alpha), size=size) + 1) float(dist.xm), 'UniformDistribution': lambda dist, size: numpy.random.uniform( low=float(dist.left), high=float(dist.right), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleContinuousPymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'BetaDistribution': lambda dist: pymc3.Beta('X', alpha=float(dist.alpha), beta=float(dist.beta)), 'CauchyDistribution': lambda dist: pymc3.Cauchy('X', alpha=float(dist.x0), beta=float(dist.gamma)), 'ChiSquaredDistribution': lambda dist: pymc3.ChiSquared('X', nu=float(dist.k)), 'ExponentialDistribution': lambda dist: pymc3.Exponential('X', lam=float(dist.rate)), 'GammaDistribution': lambda dist: pymc3.Gamma('X', alpha=float(dist.k), beta=1/float(dist.theta)), 'LogNormalDistribution': lambda dist: pymc3.Lognormal('X', mu=float(dist.mean), sigma=float(dist.std)), 'NormalDistribution': lambda dist: pymc3.Normal('X', float(dist.mean), float(dist.std)), 'GaussianInverseDistribution': lambda dist: pymc3.Wald('X', mu=float(dist.mean), lam=float(dist.shape)), 'ParetoDistribution': lambda dist: pymc3.Pareto('X', alpha=float(dist.alpha), m=float(dist.xm)), 'UniformDistribution': lambda dist: pymc3.Uniform('X', lower=float(dist.left), upper=float(dist.right)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_crv = { 'scipy': SampleContinuousScipy, 'pymc3': SampleContinuousPymc, 'numpy': SampleContinuousNumpy } class SingleContinuousDistribution(ContinuousDistribution, NamedArgsMixin): """ Continuous distribution of a single variable Serves as superclass for Normal/Exponential/UniformDistribution etc.... Represented by parameters for each of the specific classes. E.g NormalDistribution is represented by a mean and standard deviation. Provides methods for pdf, cdf, and sampling See Also ======== sympy.stats.crv_types.* """ set = Interval(-oo, oo) def __new__(cls, args): args = list(map(sympify, args)) return Basic.__new__(cls, args) @staticmethod def check(args): pass def sample(self, size=(), library='scipy'): """ A random realization from the distribution """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_crv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) @cacheit def compute_cdf(self, kwargs): """ Compute the CDF from the PDF Returns a Lambda """ x, z = symbols('x, z', real=True, cls=Dummy) left_bound = self.set.start # CDF is integral of PDF from left bound to z pdf = self.pdf(x) cdf = integrate(pdf.doit(), (x, left_bound, z), kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) def _cdf(self, x): return None def cdf(self, x, kwargs): """ Cumulative density function """ if len(kwargs) == 0: cdf = self._cdf(x) if cdf is not None: return cdf return self.compute_cdf(kwargs)(x) @cacheit def compute_characteristic_function(self, kwargs): """ Compute the characteristic function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) cf = integrate(exp(Itx)pdf, (x, self.set)) return Lambda(t, cf) def _characteristic_function(self, t): return None def characteristic_function(self, t, kwargs): """ Characteristic function """ if len(kwargs) == 0: cf = self._characteristic_function(t) if cf is not None: return cf return self.compute_characteristic_function(kwargs)(t) @cacheit def compute_moment_generating_function(self, *kwargs): """ Compute the moment generating function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) mgf = integrate(exp(t x) * pdf, (x, self.set)) return Lambda(t, mgf) def _moment_generating_function(self, t): return None def moment_generating_function(self, t, kwargs): """ Moment generating function """ if not kwargs: mgf = self._moment_generating_function(t) if mgf is not None: return mgf return self.compute_moment_generating_function(kwargs)(t) def expectation(self, expr, var, evaluate=True, *kwargs): """ Expectation of expression over distribution """ if evaluate: try: p = poly(expr, var) t = Dummy('t', real=True) mgf = self._moment_generating_function(t) if mgf is None: return integrate(expr self.pdf(var), (var, self.set), kwargs) deg = p.degree() taylor = poly(series(mgf, t, 0, deg + 1).removeO(), t) result = 0 for k in range(deg+1): result += p.coeff_monomial(var k) * taylor.coeff_monomial(t ** k) * factorial(k) return result except PolynomialError: return integrate(expr * self.pdf(var), (var, self.set), *kwargs) else: return Integral(expr self.pdf(var), (var, self.set), kwargs) @cacheit def compute_quantile(self, kwargs): """ Compute the Quantile from the PDF Returns a Lambda """ x, p = symbols('x, p', real=True, cls=Dummy) left_bound = self.set.start pdf = self.pdf(x) cdf = integrate(pdf, (x, left_bound, x), kwargs) quantile = solveset(cdf - p, x, self.set) return Lambda(p, Piecewise((quantile, (p >= 0) & (p <= 1) ), (nan, True))) def _quantile(self, x): return None def quantile(self, x, kwargs): """ Cumulative density function """ if len(kwargs) == 0: quantile = self._quantile(x) if quantile is not None: return quantile return self.compute_quantile(*kwargs)(x) class ContinuousPSpace(PSpace): """ Continuous Probability Space Represents the likelihood of an event space defined over a continuum. Represented with a ContinuousDomain and a PDF (Lambda-Like) """ is_Continuous = True is_real = True @property def pdf(self): return self.density(self.domain.symbols) def compute_expectation(self, expr, rvs=None, evaluate=False, *kwargs): if rvs is None: rvs = self.values else: rvs = frozenset(rvs) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) domain_symbols = frozenset(rv.symbol for rv in rvs) return self.domain.compute_expectation(self.pdf expr, domain_symbols, kwargs) def compute_density(self, expr, kwargs): # Common case Density(X) where X in self.values if expr in self.values: # Marginalize all other random symbols out of the density randomsymbols = tuple(set(self.values) - frozenset([expr])) symbols = tuple(rs.symbol for rs in randomsymbols) pdf = self.domain.compute_expectation(self.pdf, symbols, kwargs) return Lambda(expr.symbol, pdf) z = Dummy('z', real=True) return Lambda(z, self.compute_expectation(DiracDelta(expr - z), kwargs)) @cacheit def compute_cdf(self, expr, kwargs): if not self.domain.set.is_Interval: raise ValueError( "CDF not well defined on multivariate expressions") d = self.compute_density(expr, kwargs) x, z = symbols('x, z', real=True, cls=Dummy) left_bound = self.domain.set.start # CDF is integral of PDF from left bound to z cdf = integrate(d(x), (x, left_bound, z), kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) @cacheit def compute_characteristic_function(self, expr, kwargs): if not self.domain.set.is_Interval: raise NotImplementedError("Characteristic function of multivariate expressions not implemented") d = self.compute_density(expr, *kwargs) x, t = symbols('x, t', real=True, cls=Dummy) cf = integrate(exp(Itx)d(x), (x, -oo, oo), kwargs) return Lambda(t, cf) @cacheit def compute_moment_generating_function(self, expr, kwargs): if not self.domain.set.is_Interval: raise NotImplementedError("Moment generating function of multivariate expressions not implemented") d = self.compute_density(expr, *kwargs) x, t = symbols('x, t', real=True, cls=Dummy) mgf = integrate(exp(t x) * d(x), (x, -oo, oo), kwargs) return Lambda(t, mgf) @cacheit def compute_quantile(self, expr, kwargs): if not self.domain.set.is_Interval: raise ValueError( "Quantile not well defined on multivariate expressions") d = self.compute_cdf(expr, kwargs) x = Dummy('x', real=True) p = Dummy('p', positive=True) quantile = solveset(d(x) - p, x, self.set) return Lambda(p, quantile) def probability(self, condition, kwargs): z = Dummy('z', real=True) cond_inv = False if isinstance(condition, Ne): condition = Eq(condition.args[0], condition.args[1]) cond_inv = True # Univariate case can be handled by where try: domain = self.where(condition) rv = [rv for rv in self.values if rv.symbol == domain.symbol][0] # Integrate out all other random variables pdf = self.compute_density(rv, kwargs) # return S.Zero if `domain` is empty set if domain.set is S.EmptySet or isinstance(domain.set, FiniteSet): return S.Zero if not cond_inv else S.One if isinstance(domain.set, Union): return sum( Integral(pdf(z), (z, subset), kwargs) for subset in domain.set.args if isinstance(subset, Interval)) # Integrate out the last variable over the special domain return Integral(pdf(z), (z, domain.set), kwargs) # Other cases can be turned into univariate case # by computing a density handled by density computation except NotImplementedError: from sympy.stats.rv import density expr = condition.lhs - condition.rhs if not is_random(expr): dens = self.density comp = condition.rhs else: dens = density(expr, kwargs) comp = 0 if not isinstance(dens, ContinuousDistribution): from sympy.stats.crv_types import ContinuousDistributionHandmade dens = ContinuousDistributionHandmade(dens, set=self.domain.set) # Turn problem into univariate case space = SingleContinuousPSpace(z, dens) result = space.probability(condition.__class__(space.value, comp)) return result if not cond_inv else S.One - result def where(self, condition): rvs = frozenset(random_symbols(condition)) if not (len(rvs) == 1 and rvs.issubset(self.values)): raise NotImplementedError( "Multiple continuous random variables not supported") rv = tuple(rvs)[0] interval = reduce_rational_inequalities_wrap(condition, rv) interval = interval.intersect(self.domain.set) return SingleContinuousDomain(rv.symbol, interval) def conditional_space(self, condition, normalize=True, kwargs): condition = condition.xreplace({rv: rv.symbol for rv in self.values}) domain = ConditionalContinuousDomain(self.domain, condition) if normalize: # create a clone of the variable to # make sure that variables in nested integrals are different # from the variables outside the integral # this makes sure that they are evaluated separately # and in the correct order replacement = {rv: Dummy(str(rv)) for rv in self.symbols} norm = domain.compute_expectation(self.pdf, kwargs) pdf = self.pdf / norm.xreplace(replacement) # XXX: Converting set to tuple. The order matters to Lambda though # so we shouldn't be starting with a set here... density = Lambda(tuple(domain.symbols), pdf) return ContinuousPSpace(domain, density) class SingleContinuousPSpace(ContinuousPSpace, SinglePSpace): """ A continuous probability space over a single univariate variable These consist of a Symbol and a SingleContinuousDistribution This class is normally accessed through the various random variable functions, Normal, Exponential, Uniform, etc.... """ @property def set(self): return self.distribution.set @property def domain(self): return SingleContinuousDomain(sympify(self.symbol), self.set) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {self.value: self.distribution.sample(size, library=library)} def compute_expectation(self, expr, rvs=None, evaluate=False, kwargs): rvs = rvs or (self.value,) if self.value not in rvs: return expr expr = _sympify(expr) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) x = self.value.symbol try: return self.distribution.expectation(expr, x, evaluate=evaluate, kwargs) except PoleError: return Integral(expr * self.pdf, (x, self.set), kwargs) def compute_cdf(self, expr, kwargs): if expr == self.value: z = Dummy("z", real=True) return Lambda(z, self.distribution.cdf(z, kwargs)) else: return ContinuousPSpace.compute_cdf(self, expr, kwargs) def compute_characteristic_function(self, expr, kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.characteristic_function(t, kwargs)) else: return ContinuousPSpace.compute_characteristic_function(self, expr, kwargs) def compute_moment_generating_function(self, expr, kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.moment_generating_function(t, kwargs)) else: return ContinuousPSpace.compute_moment_generating_function(self, expr, kwargs) def compute_density(self, expr, *kwargs): # https://en.wikipedia.org/wiki/Random_variable#Functions_of_random_variables if expr == self.value: return self.density y = Dummy('y', real=True) gs = solveset(expr - y, self.value, S.Reals) if isinstance(gs, Intersection) and S.Reals in gs.args: gs = list(gs.args[1]) if not gs: raise ValueError("Can not solve %s for %s"%(expr, self.value)) fx = self.compute_density(self.value) fy = sum(fx(g) abs(g.diff(y)) for g in gs) return Lambda(y, fy) def compute_quantile(self, expr, kwargs): if expr == self.value: p = Dummy("p", real=True) return Lambda(p, self.distribution.quantile(p, kwargs)) else: return ContinuousPSpace.compute_quantile(self, expr, kwargs) def _reduce_inequalities(conditions, var, kwargs): try: return reduce_rational_inequalities(conditions, var, *kwargs) except PolynomialError: raise ValueError("Reduction of condition failed %s\n" % conditions[0]) def reduce_rational_inequalities_wrap(condition, var): if condition.is_Relational: return _reduce_inequalities([[condition]], var, relational=False) if isinstance(condition, Or): return Union([_reduce_inequalities([[arg]], var, relational=False) for arg in condition.args]) if isinstance(condition, And): intervals = [_reduce_inequalities([[arg]], var, relational=False) for arg in condition.args] I = intervals[0] for i in intervals: I = I.intersect(i) return I
83472ee206ac646412cae109c880a39296e5fb4293fea8195be98dfdbbb14919	from sympy import Basic, Sum, Dummy, Lambda, Integral from sympy.stats.rv import (NamedArgsMixin, random_symbols, _symbol_converter, PSpace, RandomSymbol, is_random) from sympy.stats.crv import ContinuousDistribution, SingleContinuousPSpace from sympy.stats.drv import DiscreteDistribution, SingleDiscretePSpace from sympy.stats.frv import SingleFiniteDistribution, SingleFinitePSpace from sympy.stats.crv_types import ContinuousDistributionHandmade from sympy.stats.drv_types import DiscreteDistributionHandmade from sympy.stats.frv_types import FiniteDistributionHandmade class CompoundPSpace(PSpace): """ A temporary Probability Space for the Compound Distribution. After Marginalization, this returns the corresponding Probability Space of the parent distribution. """ def __new__(cls, s, distribution): s = _symbol_converter(s) if isinstance(distribution, ContinuousDistribution): return SingleContinuousPSpace(s, distribution) if isinstance(distribution, DiscreteDistribution): return SingleDiscretePSpace(s, distribution) if isinstance(distribution, SingleFiniteDistribution): return SingleFinitePSpace(s, distribution) if not isinstance(distribution, CompoundDistribution): raise ValueError("%s should be an isinstance of " "CompoundDistribution"%(distribution)) return Basic.__new__(cls, s, distribution) @property def value(self): return RandomSymbol(self.symbol, self) @property def symbol(self): return self.args[0] @property def is_Continuous(self): return self.distribution.is_Continuous @property def is_Finite(self): return self.distribution.is_Finite @property def is_Discrete(self): return self.distribution.is_Discrete @property def distribution(self): return self.args[1] @property def pdf(self): return self.distribution.pdf(self.symbol) @property def set(self): return self.distribution.set @property def domain(self): return self._get_newpspace().domain def _get_newpspace(self, evaluate=False): x = Dummy('x') parent_dist = self.distribution.args[0] func = Lambda(x, self.distribution.pdf(x, evaluate)) new_pspace = self._transform_pspace(self.symbol, parent_dist, func) if new_pspace is not None: return new_pspace message = ("Compound Distribution for %s is not implemeted yet" % str(parent_dist)) raise NotImplementedError(message) def _transform_pspace(self, sym, dist, pdf): """ This function returns the new pspace of the distribution using handmade Distributions and their corresponding pspace. """ pdf = Lambda(sym, pdf(sym)) _set = dist.set if isinstance(dist, ContinuousDistribution): return SingleContinuousPSpace(sym, ContinuousDistributionHandmade(pdf, _set)) elif isinstance(dist, DiscreteDistribution): return SingleDiscretePSpace(sym, DiscreteDistributionHandmade(pdf, _set)) elif isinstance(dist, SingleFiniteDistribution): dens = {k: pdf(k) for k in _set} return SingleFinitePSpace(sym, FiniteDistributionHandmade(dens)) def compute_density(self, expr, , compound_evaluate=True, kwargs): new_pspace = self._get_newpspace(compound_evaluate) expr = expr.subs({self.value: new_pspace.value}) return new_pspace.compute_density(expr, kwargs) def compute_cdf(self, expr, , compound_evaluate=True, kwargs): new_pspace = self._get_newpspace(compound_evaluate) expr = expr.subs({self.value: new_pspace.value}) return new_pspace.compute_cdf(expr, kwargs) def compute_expectation(self, expr, rvs=None, evaluate=False, kwargs): new_pspace = self._get_newpspace(evaluate) expr = expr.subs({self.value: new_pspace.value}) if rvs: rvs = rvs.subs({self.value: new_pspace.value}) if isinstance(new_pspace, SingleFinitePSpace): return new_pspace.compute_expectation(expr, rvs, kwargs) return new_pspace.compute_expectation(expr, rvs, evaluate, *kwargs) def probability(self, condition, , compound_evaluate=True, *kwargs): new_pspace = self._get_newpspace(compound_evaluate) condition = condition.subs({self.value: new_pspace.value}) return new_pspace.probability(condition) def conditional_space(self, condition, , compound_evaluate=True, kwargs): new_pspace = self._get_newpspace(compound_evaluate) condition = condition.subs({self.value: new_pspace.value}) return new_pspace.conditional_space(condition) class CompoundDistribution(Basic, NamedArgsMixin): """ Class for Compound Distributions. Parameters ========== dist : Distribution Distribution must contain a random parameter Examples ======== >>> from sympy.stats.compound_rv import CompoundDistribution >>> from sympy.stats.crv_types import NormalDistribution >>> from sympy.stats import Normal >>> from sympy.abc import x >>> X = Normal('X', 2, 4) >>> N = NormalDistribution(X, 4) >>> C = CompoundDistribution(N) >>> C.set Interval(-oo, oo) >>> C.pdf(x, evaluate=True).simplify() exp(-x2/64 + x/16 - 1/16)/(8sqrt(pi)) References ========== .. [1] https://en.wikipedia.org/wiki/Compound_probability_distribution """ def __new__(cls, dist): if not isinstance(dist, (ContinuousDistribution, SingleFiniteDistribution, DiscreteDistribution)): message = "Compound Distribution for %s is not implemeted yet" % str(dist) raise NotImplementedError(message) if not cls._compound_check(dist): return dist return Basic.__new__(cls, dist) @property def set(self): return self.args[0].set @property def is_Continuous(self): return isinstance(self.args[0], ContinuousDistribution) @property def is_Finite(self): return isinstance(self.args[0], SingleFiniteDistribution) @property def is_Discrete(self): return isinstance(self.args[0], DiscreteDistribution) def pdf(self, x, evaluate=False): dist = self.args[0] randoms = [rv for rv in dist.args if is_random(rv)] if isinstance(dist, SingleFiniteDistribution): y = Dummy('y', integer=True, negative=False) expr = dist.pmf(y) else: y = Dummy('y') expr = dist.pdf(y) for rv in randoms: expr = self._marginalise(expr, rv, evaluate) return Lambda(y, expr)(x) def _marginalise(self, expr, rv, evaluate): if isinstance(rv.pspace.distribution, SingleFiniteDistribution): rv_dens = rv.pspace.distribution.pmf(rv) else: rv_dens = rv.pspace.distribution.pdf(rv) rv_dom = rv.pspace.domain.set if rv.pspace.is_Discrete or rv.pspace.is_Finite: expr = Sum(exprrv_dens, (rv, rv_dom._inf, rv_dom._sup)) else: expr = Integral(expr*rv_dens, (rv, rv_dom._inf, rv_dom._sup)) if evaluate: return expr.doit() return expr @classmethod def _compound_check(self, dist): """ Checks if the given distribution contains random parameters. """ randoms = [] for arg in dist.args: randoms.extend(random_symbols(arg)) if len(randoms) == 0: return False return True
8c20011283a91f32ae0eedbc864de362e825d8582d0fe6667c951b9bcb9ef67c	import itertools from sympy import (Expr, Add, Mul, S, Integral, Eq, Sum, Symbol, expand as _expand, Not) from sympy.core.compatibility import default_sort_key from sympy.core.parameters import global_parameters from sympy.core.sympify import _sympify from sympy.core.relational import Relational from sympy.logic.boolalg import Boolean from sympy.stats import variance, covariance from sympy.stats.rv import (RandomSymbol, pspace, dependent, given, sampling_E, RandomIndexedSymbol, is_random, PSpace, sampling_P, random_symbols) __all__ = ['Probability', 'Expectation', 'Variance', 'Covariance'] @is_random.register(Expr) def _(x): atoms = x.free_symbols if len(atoms) == 1 and next(iter(atoms)) == x: return False return any([is_random(i) for i in atoms]) @is_random.register(RandomSymbol) # type: ignore def _(x): return True class Probability(Expr): """ Symbolic expression for the probability. Examples ======== >>> from sympy.stats import Probability, Normal >>> from sympy import Integral >>> X = Normal("X", 0, 1) >>> prob = Probability(X > 1) >>> prob Probability(X > 1) Integral representation: >>> prob.rewrite(Integral) Integral(sqrt(2)exp(-_z2/2)/(2sqrt(pi)), (_z, 1, oo)) Evaluation of the integral: >>> prob.evaluate_integral() sqrt(2)(-sqrt(2)sqrt(pi)erf(sqrt(2)/2) + sqrt(2)sqrt(pi))/(4sqrt(pi)) """ def __new__(cls, prob, condition=None, kwargs): prob = _sympify(prob) if condition is None: obj = Expr.__new__(cls, prob) else: condition = _sympify(condition) obj = Expr.__new__(cls, prob, condition) obj._condition = condition return obj def doit(self, hints): condition = self.args[0] given_condition = self._condition numsamples = hints.get('numsamples', False) for_rewrite = not hints.get('for_rewrite', False) if isinstance(condition, Not): return S.One - self.func(condition.args[0], given_condition, evaluate=for_rewrite).doit(hints) if condition.has(RandomIndexedSymbol): return pspace(condition).probability(condition, given_condition, evaluate=for_rewrite) if isinstance(given_condition, RandomSymbol): condrv = random_symbols(condition) if len(condrv) == 1 and condrv[0] == given_condition: from sympy.stats.frv_types import BernoulliDistribution return BernoulliDistribution(self.func(condition).doit(hints), 0, 1) if any([dependent(rv, given_condition) for rv in condrv]): return Probability(condition, given_condition) else: return Probability(condition).doit() if given_condition is not None and \ not isinstance(given_condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (given_condition)) if given_condition == False or condition is S.false: return S.Zero if not isinstance(condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (condition)) if condition is S.true: return S.One if numsamples: return sampling_P(condition, given_condition, numsamples=numsamples) if given_condition is not None: # If there is a condition # Recompute on new conditional expr return Probability(given(condition, given_condition)).doit() # Otherwise pass work off to the ProbabilitySpace if pspace(condition) == PSpace(): return Probability(condition, given_condition) result = pspace(condition).probability(condition) if hasattr(result, 'doit') and for_rewrite: return result.doit() else: return result def _eval_rewrite_as_Integral(self, arg, condition=None, kwargs): return self.func(arg, condition=condition).doit(for_rewrite=True) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Expectation(Expr): """ Symbolic expression for the expectation. Examples ======== >>> from sympy.stats import Expectation, Normal, Probability, Poisson >>> from sympy import symbols, Integral, Sum >>> mu = symbols("mu") >>> sigma = symbols("sigma", positive=True) >>> X = Normal("X", mu, sigma) >>> Expectation(X) Expectation(X) >>> Expectation(X).evaluate_integral().simplify() mu To get the integral expression of the expectation: >>> Expectation(X).rewrite(Integral) Integral(sqrt(2)Xexp(-(X - mu)2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)) The same integral expression, in more abstract terms: >>> Expectation(X).rewrite(Probability) Integral(xProbability(Eq(X, x)), (x, -oo, oo)) To get the Summation expression of the expectation for discrete random variables: >>> lamda = symbols('lamda', positive=True) >>> Z = Poisson('Z', lamda) >>> Expectation(Z).rewrite(Sum) Sum(ZlamdaZexp(-lamda)/factorial(Z), (Z, 0, oo)) This class is aware of some properties of the expectation: >>> from sympy.abc import a >>> Expectation(aX) Expectation(aX) >>> Y = Normal("Y", 1, 2) >>> Expectation(X + Y) Expectation(X + Y) To expand the ``Expectation`` into its expression, use ``expand()``: >>> Expectation(X + Y).expand() Expectation(X) + Expectation(Y) >>> Expectation(aX + Y).expand() aExpectation(X) + Expectation(Y) >>> Expectation(aX + Y) Expectation(aX + Y) >>> Expectation((X + Y)(X - Y)).expand() Expectation(X2) - Expectation(Y2) To evaluate the ``Expectation``, use ``doit()``: >>> Expectation(X + Y).doit() mu + 1 >>> Expectation(X + Expectation(Y + Expectation(2X))).doit() 3mu + 1 To prevent evaluating nested ``Expectation``, use ``doit(deep=False)`` >>> Expectation(X + Expectation(Y)).doit(deep=False) mu + Expectation(Expectation(Y)) >>> Expectation(X + Expectation(Y + Expectation(2X))).doit(deep=False) mu + Expectation(Expectation(Y + Expectation(2X))) """ def __new__(cls, expr, condition=None, kwargs): expr = _sympify(expr) if expr.is_Matrix: from sympy.stats.symbolic_multivariate_probability import ExpectationMatrix return ExpectationMatrix(expr, condition) if condition is None: if not is_random(expr): return expr obj = Expr.__new__(cls, expr) else: condition = _sympify(condition) obj = Expr.__new__(cls, expr, condition) obj._condition = condition return obj def expand(self, hints): expr = self.args[0] condition = self._condition if not is_random(expr): return expr if isinstance(expr, Add): return Add.fromiter(Expectation(a, condition=condition).expand() for a in expr.args) expand_expr = _expand(expr) if isinstance(expand_expr, Add): return Add.fromiter(Expectation(a, condition=condition).expand() for a in expand_expr.args) elif isinstance(expr, Mul): rv = [] nonrv = [] for a in expr.args: if is_random(a): rv.append(a) else: nonrv.append(a) return Mul.fromiter(nonrv)Expectation(Mul.fromiter(rv), condition=condition) return self def doit(self, hints): deep = hints.get('deep', True) condition = self._condition expr = self.args[0] numsamples = hints.get('numsamples', False) for_rewrite = not hints.get('for_rewrite', False) if deep: expr = expr.doit(hints) if not is_random(expr) or isinstance(expr, Expectation): # expr isn't random? return expr if numsamples: # Computing by monte carlo sampling? evalf = hints.get('evalf', True) return sampling_E(expr, condition, numsamples=numsamples, evalf=evalf) if expr.has(RandomIndexedSymbol): return pspace(expr).compute_expectation(expr, condition) # Create new expr and recompute E if condition is not None: # If there is a condition return self.func(given(expr, condition)).doit(*hints) # A few known statements for efficiency if expr.is_Add: # We know that E is Linear return Add([self.func(arg, condition).doit(hints) if not isinstance(arg, Expectation) else self.func(arg, condition) for arg in expr.args]) if expr.is_Mul: if expr.atoms(Expectation): return expr if pspace(expr) == PSpace(): return self.func(expr) # Otherwise case is simple, pass work off to the ProbabilitySpace result = pspace(expr).compute_expectation(expr, evaluate=for_rewrite) if hasattr(result, 'doit') and for_rewrite: return result.doit(hints) else: return result def _eval_rewrite_as_Probability(self, arg, condition=None, *kwargs): rvs = arg.atoms(RandomSymbol) if len(rvs) > 1: raise NotImplementedError() if len(rvs) == 0: return arg rv = rvs.pop() if rv.pspace is None: raise ValueError("Probability space not known") symbol = rv.symbol if symbol.name[0].isupper(): symbol = Symbol(symbol.name.lower()) else : symbol = Symbol(symbol.name + "_1") if rv.pspace.is_Continuous: return Integral(arg.replace(rv, symbol)Probability(Eq(rv, symbol), condition), (symbol, rv.pspace.domain.set.inf, rv.pspace.domain.set.sup)) else: if rv.pspace.is_Finite: raise NotImplementedError else: return Sum(arg.replace(rv, symbol)Probability(Eq(rv, symbol), condition), (symbol, rv.pspace.domain.set.inf, rv.pspace.set.sup)) def _eval_rewrite_as_Integral(self, arg, condition=None, kwargs): return self.func(arg, condition=condition).doit(deep=False, for_rewrite=True) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral # For discrete this will be Sum def evaluate_integral(self): return self.rewrite(Integral).doit() evaluate_sum = evaluate_integral class Variance(Expr): """ Symbolic expression for the variance. Examples ======== >>> from sympy import symbols, Integral >>> from sympy.stats import Normal, Expectation, Variance, Probability >>> mu = symbols("mu", positive=True) >>> sigma = symbols("sigma", positive=True) >>> X = Normal("X", mu, sigma) >>> Variance(X) Variance(X) >>> Variance(X).evaluate_integral() sigma2 Integral representation of the underlying calculations: >>> Variance(X).rewrite(Integral) Integral(sqrt(2)(X - Integral(sqrt(2)Xexp(-(X - mu)*2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)))2exp(-(X - mu)*2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)) Integral representation, without expanding the PDF: >>> Variance(X).rewrite(Probability) -Integral(xProbability(Eq(X, x)), (x, -oo, oo))2 + Integral(x2Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the variance in terms of the expectation >>> Variance(X).rewrite(Expectation) -Expectation(X)2 + Expectation(X2) Some transformations based on the properties of the variance may happen: >>> from sympy.abc import a >>> Y = Normal("Y", 0, 1) >>> Variance(aX) Variance(aX) To expand the variance in its expression, use ``expand()``: >>> Variance(aX).expand() a*2Variance(X) >>> Variance(X + Y) Variance(X + Y) >>> Variance(X + Y).expand() 2Covariance(X, Y) + Variance(X) + Variance(Y) """ def __new__(cls, arg, condition=None, kwargs): arg = _sympify(arg) if arg.is_Matrix: from sympy.stats.symbolic_multivariate_probability import VarianceMatrix return VarianceMatrix(arg, condition) if condition is None: obj = Expr.__new__(cls, arg) else: condition = _sympify(condition) obj = Expr.__new__(cls, arg, condition) obj._condition = condition return obj def expand(self, hints): arg = self.args[0] condition = self._condition if not is_random(arg): return S.Zero if isinstance(arg, RandomSymbol): return self elif isinstance(arg, Add): rv = [] for a in arg.args: if is_random(a): rv.append(a) variances = Add(map(lambda xv: Variance(xv, condition).expand(), rv)) map_to_covar = lambda x: 2Covariance(x, condition=condition).expand() covariances = Add(map(map_to_covar, itertools.combinations(rv, 2))) return variances + covariances elif isinstance(arg, Mul): nonrv = [] rv = [] for a in arg.args: if is_random(a): rv.append(a) else: nonrv.append(a2) if len(rv) == 0: return S.Zero return Mul.fromiter(nonrv)Variance(Mul.fromiter(rv), condition) # this expression contains a RandomSymbol somehow: return self def _eval_rewrite_as_Expectation(self, arg, condition=None, kwargs): e1 = Expectation(arg2, condition) e2 = Expectation(arg, condition)2 return e1 - e2 def _eval_rewrite_as_Probability(self, arg, condition=None, kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, arg, condition=None, *kwargs): return variance(self.args[0], self._condition, evaluate=False) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Covariance(Expr): """ Symbolic expression for the covariance. Examples ======== >>> from sympy.stats import Covariance >>> from sympy.stats import Normal >>> X = Normal("X", 3, 2) >>> Y = Normal("Y", 0, 1) >>> Z = Normal("Z", 0, 1) >>> W = Normal("W", 0, 1) >>> cexpr = Covariance(X, Y) >>> cexpr Covariance(X, Y) Evaluate the covariance, `X` and `Y` are independent, therefore zero is the result: >>> cexpr.evaluate_integral() 0 Rewrite the covariance expression in terms of expectations: >>> from sympy.stats import Expectation >>> cexpr.rewrite(Expectation) Expectation(XY) - Expectation(X)Expectation(Y) In order to expand the argument, use ``expand()``: >>> from sympy.abc import a, b, c, d >>> Covariance(aX + bY, cZ + dW) Covariance(aX + bY, cZ + dW) >>> Covariance(aX + bY, cZ + dW).expand() acCovariance(X, Z) + adCovariance(W, X) + bcCovariance(Y, Z) + bdCovariance(W, Y) This class is aware of some properties of the covariance: >>> Covariance(X, X).expand() Variance(X) >>> Covariance(aX, bY).expand() abCovariance(X, Y) """ def __new__(cls, arg1, arg2, condition=None, kwargs): arg1 = _sympify(arg1) arg2 = _sympify(arg2) if arg1.is_Matrix or arg2.is_Matrix: from sympy.stats.symbolic_multivariate_probability import CrossCovarianceMatrix return CrossCovarianceMatrix(arg1, arg2, condition) if kwargs.pop('evaluate', global_parameters.evaluate): arg1, arg2 = sorted([arg1, arg2], key=default_sort_key) if condition is None: obj = Expr.__new__(cls, arg1, arg2) else: condition = _sympify(condition) obj = Expr.__new__(cls, arg1, arg2, condition) obj._condition = condition return obj def expand(self, hints): arg1 = self.args[0] arg2 = self.args[1] condition = self._condition if arg1 == arg2: return Variance(arg1, condition).expand() if not is_random(arg1): return S.Zero if not is_random(arg2): return S.Zero arg1, arg2 = sorted([arg1, arg2], key=default_sort_key) if isinstance(arg1, RandomSymbol) and isinstance(arg2, RandomSymbol): return Covariance(arg1, arg2, condition) coeff_rv_list1 = self._expand_single_argument(arg1.expand()) coeff_rv_list2 = self._expand_single_argument(arg2.expand()) addends = [abCovariance(sorted([r1, r2], key=default_sort_key), condition=condition) for (a, r1) in coeff_rv_list1 for (b, r2) in coeff_rv_list2] return Add.fromiter(addends) @classmethod def _expand_single_argument(cls, expr): # return (coefficient, random_symbol) pairs: if isinstance(expr, RandomSymbol): return [(S.One, expr)] elif isinstance(expr, Add): outval = [] for a in expr.args: if isinstance(a, Mul): outval.append(cls._get_mul_nonrv_rv_tuple(a)) elif is_random(a): outval.append((S.One, a)) return outval elif isinstance(expr, Mul): return [cls._get_mul_nonrv_rv_tuple(expr)] elif is_random(expr): return [(S.One, expr)] @classmethod def _get_mul_nonrv_rv_tuple(cls, m): rv = [] nonrv = [] for a in m.args: if is_random(a): rv.append(a) else: nonrv.append(a) return (Mul.fromiter(nonrv), Mul.fromiter(rv)) def _eval_rewrite_as_Expectation(self, arg1, arg2, condition=None, *kwargs): e1 = Expectation(arg1arg2, condition) e2 = Expectation(arg1, condition)Expectation(arg2, condition) return e1 - e2 def _eval_rewrite_as_Probability(self, arg1, arg2, condition=None, kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, arg1, arg2, condition=None, kwargs): return covariance(self.args[0], self.args[1], self._condition, evaluate=False) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Moment(Expr): """ Symbolic class for Moment Examples ======== >>> from sympy import Symbol, Integral >>> from sympy.stats import Normal, Expectation, Probability, Moment >>> mu = Symbol('mu', real=True) >>> sigma = Symbol('sigma', real=True, positive=True) >>> X = Normal('X', mu, sigma) >>> M = Moment(X, 3, 1) To evaluate the result of Moment use `doit`: >>> M.doit() mu3 - 3mu*2 + 3musigma2 + 3mu - 3sigma2 - 1 Rewrite the Moment expression in terms of Expectation: >>> M.rewrite(Expectation) Expectation((X - 1)3) Rewrite the Moment expression in terms of Probability: >>> M.rewrite(Probability) Integral((x - 1)3Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the Moment expression in terms of Integral: >>> M.rewrite(Integral) Integral(sqrt(2)(X - 1)3exp(-(X - mu)*2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)) """ def __new__(cls, X, n, c=0, condition=None, kwargs): X = _sympify(X) n = _sympify(n) c = _sympify(c) if condition is not None: condition = _sympify(condition) return Expr.__new__(cls, X, n, c, condition) def doit(self, hints): if not is_random(self.args[0]): return self.args[0] return self.rewrite(Expectation).doit(hints) def _eval_rewrite_as_Expectation(self, X, n, c=0, condition=None, kwargs): return Expectation((X - c)n, condition) def _eval_rewrite_as_Probability(self, X, n, c=0, condition=None, kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, X, n, c=0, condition=None, kwargs): return self.rewrite(Expectation).rewrite(Integral) class CentralMoment(Expr): """ Symbolic class Central Moment Examples ======== >>> from sympy import Symbol, Integral >>> from sympy.stats import Normal, Expectation, Probability, CentralMoment >>> mu = Symbol('mu', real=True) >>> sigma = Symbol('sigma', real=True, positive=True) >>> X = Normal('X', mu, sigma) >>> CM = CentralMoment(X, 4) To evaluate the result of CentralMoment use `doit`: >>> CM.doit().simplify() 3sigma4 Rewrite the CentralMoment expression in terms of Expectation: >>> CM.rewrite(Expectation) Expectation((X - Expectation(X))4) Rewrite the CentralMoment expression in terms of Probability: >>> CM.rewrite(Probability) Integral((x - Integral(xProbability(True), (x, -oo, oo)))4Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the CentralMoment expression in terms of Integral: >>> CM.rewrite(Integral) Integral(sqrt(2)(X - Integral(sqrt(2)Xexp(-(X - mu)2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)))4exp(-(X - mu)*2/(2sigma*2))/(2sqrt(pi)sigma), (X, -oo, oo)) """ def __new__(cls, X, n, condition=None, kwargs): X = _sympify(X) n = _sympify(n) if condition is not None: condition = _sympify(condition) return Expr.__new__(cls, X, n, condition) def doit(self, hints): if not is_random(self.args[0]): return self.args[0] return self.rewrite(Expectation).doit(hints) def _eval_rewrite_as_Expectation(self, X, n, condition=None, kwargs): mu = Expectation(X, condition, kwargs) return Moment(X, n, mu, condition, kwargs).rewrite(Expectation) def _eval_rewrite_as_Probability(self, X, n, condition=None, kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, X, n, condition=None, *kwargs): return self.rewrite(Expectation).rewrite(Integral)
c9e18e2774e69ca828c9df209d651ec4aff2aaabb0eafbc599719921fd59f224	from sympy import (Basic, exp, pi, Lambda, Trace, S, MatrixSymbol, Integral, gamma, Product, Dummy, Sum, Abs, IndexedBase, I) from sympy.core.sympify import _sympify from sympy.stats.rv import _symbol_converter, Density, RandomMatrixSymbol, is_random from sympy.stats.joint_rv_types import JointDistributionHandmade from sympy.stats.random_matrix import RandomMatrixPSpace from sympy.tensor.array import ArrayComprehension __all__ = [ 'CircularEnsemble', 'CircularUnitaryEnsemble', 'CircularOrthogonalEnsemble', 'CircularSymplecticEnsemble', 'GaussianEnsemble', 'GaussianUnitaryEnsemble', 'GaussianOrthogonalEnsemble', 'GaussianSymplecticEnsemble', 'joint_eigen_distribution', 'JointEigenDistribution', 'level_spacing_distribution' ] @is_random.register(RandomMatrixSymbol) def _(x): return True class RandomMatrixEnsembleModel(Basic): """ Base class for random matrix ensembles. It acts as an umbrella and contains the methods common to all the ensembles defined in sympy.stats.random_matrix_models. """ def __new__(cls, sym, dim=None): sym, dim = _symbol_converter(sym), _sympify(dim) if dim.is_integer == False: raise ValueError("Dimension of the random matrices must be " "integers, received %s instead."%(dim)) return Basic.__new__(cls, sym, dim) symbol = property(lambda self: self.args[0]) dimension = property(lambda self: self.args[1]) def density(self, expr): return Density(expr) def __call__(self, expr): return self.density(expr) class GaussianEnsembleModel(RandomMatrixEnsembleModel): """ Abstract class for Gaussian ensembles. Contains the properties common to all the gaussian ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Random_matrix#Gaussian_ensembles .. [2] https://arxiv.org/pdf/1712.07903.pdf """ def _compute_normalization_constant(self, beta, n): """ Helper function for computing normalization constant for joint probability density of eigen values of Gaussian ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Selberg_integral#Mehta's_integral """ n = S(n) prod_term = lambda j: gamma(1 + betaS(j)/2)/gamma(S.One + beta/S(2)) j = Dummy('j', integer=True, positive=True) term1 = Product(prod_term(j), (j, 1, n)).doit() term2 = (2/(betan))*(betan(n - 1)/4 + n/2) term3 = (2pi)*(n/2) return term1 term2 * term3 def _compute_joint_eigen_distribution(self, beta): """ Helper function for computing the joint probability distribution of eigen values of the random matrix. """ n = self.dimension Zbn = self._compute_normalization_constant(beta, n) l = IndexedBase('l') i = Dummy('i', integer=True, positive=True) j = Dummy('j', integer=True, positive=True) k = Dummy('k', integer=True, positive=True) term1 = exp((-S(n)/2) * Sum(l[k]2, (k, 1, n)).doit()) sub_term = Lambda(i, Product(Abs(l[j] - l[i])beta, (j, i + 1, n))) term2 = Product(sub_term(i).doit(), (i, 1, n - 1)).doit() syms = ArrayComprehension(l[k], (k, 1, n)).doit() return Lambda(tuple(syms), (term1 * term2)/Zbn) class GaussianUnitaryEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension return 2*(S(n)/2) pi(S(n2)/2) def density(self, expr): n, ZGUE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n)/2 * Trace(H2))/ZGUE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(2)) def level_spacing_distribution(self): s = Dummy('s') f = (32/pi2)(s2)exp((-4/pi)s2) return Lambda(s, f) class GaussianOrthogonalEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension _H = MatrixSymbol('_H', n, n) return Integral(exp(-S(n)/4 Trace(_H*2))) def density(self, expr): n, ZGOE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n)/4 Trace(H*2))/ZGOE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S.One) def level_spacing_distribution(self): s = Dummy('s') f = (pi/2)sexp((-pi/4)s*2) return Lambda(s, f) class GaussianSymplecticEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension _H = MatrixSymbol('_H', n, n) return Integral(exp(-S(n) Trace(_H*2))) def density(self, expr): n, ZGSE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n) Trace(H2))/ZGSE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(4)) def level_spacing_distribution(self): s = Dummy('s') f = ((S(2)18)/((S(3)*6)(pi*3)))(s*4)exp((-64/(9pi))s2) return Lambda(s, f) def GaussianEnsemble(sym, dim): sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianUnitaryEnsemble(sym, dim): """ Represents Gaussian Unitary Ensembles. Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE, density >>> from sympy import MatrixSymbol >>> G = GUE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-Trace(X2))/(2pi2) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianUnitaryEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianOrthogonalEnsemble(sym, dim): """ Represents Gaussian Orthogonal Ensembles. Examples ======== >>> from sympy.stats import GaussianOrthogonalEnsemble as GOE, density >>> from sympy import MatrixSymbol >>> G = GOE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-Trace(X2)/2)/Integral(exp(-Trace(_H2)/2), _H) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianOrthogonalEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianSymplecticEnsemble(sym, dim): """ Represents Gaussian Symplectic Ensembles. Examples ======== >>> from sympy.stats import GaussianSymplecticEnsemble as GSE, density >>> from sympy import MatrixSymbol >>> G = GSE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-2Trace(X*2))/Integral(exp(-2Trace(_H*2)), _H) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianSymplecticEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) class CircularEnsembleModel(RandomMatrixEnsembleModel): """ Abstract class for Circular ensembles. Contains the properties and methods common to all the circular ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Circular_ensemble """ def density(self, expr): # TODO : Add support for Lie groups(as extensions of sympy.diffgeom) # and define measures on them raise NotImplementedError("Support for Haar measure hasn't been " "implemented yet, therefore the density of " "%s cannot be computed."%(self)) def _compute_joint_eigen_distribution(self, beta): """ Helper function to compute the joint distribution of phases of the complex eigen values of matrices belonging to any circular ensembles. """ n = self.dimension Zbn = ((2pi)*n)(gamma(betan/2 + 1)/S(gamma(beta/2 + 1))n) t = IndexedBase('t') i, j, k = (Dummy('i', integer=True), Dummy('j', integer=True), Dummy('k', integer=True)) syms = ArrayComprehension(t[i], (i, 1, n)).doit() f = Product(Product(Abs(exp(It[k]) - exp(It[j]))beta, (j, k + 1, n)).doit(), (k, 1, n - 1)).doit() return Lambda(tuple(syms), f/Zbn) class CircularUnitaryEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(2)) class CircularOrthogonalEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S.One) class CircularSymplecticEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(4)) def CircularEnsemble(sym, dim): sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularUnitaryEnsemble(sym, dim): """ Represents Cicular Unitary Ensembles. Examples ======== >>> from sympy.stats import CircularUnitaryEnsemble as CUE >>> from sympy.stats import joint_eigen_distribution >>> C = CUE('U', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(It[_j]) - exp(It[_k]))2, (_j, _k + 1, 1), (_k, 1, 0))/(2pi)) Note ==== As can be seen above in the example, density of CiruclarUnitaryEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularUnitaryEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularOrthogonalEnsemble(sym, dim): """ Represents Cicular Orthogonal Ensembles. Examples ======== >>> from sympy.stats import CircularOrthogonalEnsemble as COE >>> from sympy.stats import joint_eigen_distribution >>> C = COE('O', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(It[_j]) - exp(It[_k])), (_j, _k + 1, 1), (_k, 1, 0))/(2pi)) Note ==== As can be seen above in the example, density of CiruclarOrthogonalEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularOrthogonalEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularSymplecticEnsemble(sym, dim): """ Represents Cicular Symplectic Ensembles. Examples ======== >>> from sympy.stats import CircularSymplecticEnsemble as CSE >>> from sympy.stats import joint_eigen_distribution >>> C = CSE('S', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(It[_j]) - exp(It[_k]))4, (_j, _k + 1, 1), (_k, 1, 0))/(2pi)) Note ==== As can be seen above in the example, density of CiruclarSymplecticEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularSymplecticEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def joint_eigen_distribution(mat): """ For obtaining joint probability distribution of eigen values of random matrix. Parameters ========== mat: RandomMatrixSymbol The matrix symbol whose eigen values are to be considered. Returns ======= Lambda Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE >>> from sympy.stats import joint_eigen_distribution >>> U = GUE('U', 2) >>> joint_eigen_distribution(U) Lambda((l[1], l[2]), exp(-l[1]2 - l[2]2)Product(Abs(l[_i] - l[_j])2, (_j, _i + 1, 2), (_i, 1, 1))/pi) """ if not isinstance(mat, RandomMatrixSymbol): raise ValueError("%s is not of type, RandomMatrixSymbol."%(mat)) return mat.pspace.model.joint_eigen_distribution() def JointEigenDistribution(mat): """ Creates joint distribution of eigen values of matrices with random expressions. Parameters ========== mat: Matrix The matrix under consideration Returns ======= JointDistributionHandmade Examples ======== >>> from sympy.stats import Normal, JointEigenDistribution >>> from sympy import Matrix >>> A = [[Normal('A00', 0, 1), Normal('A01', 0, 1)], ... [Normal('A10', 0, 1), Normal('A11', 0, 1)]] >>> JointEigenDistribution(Matrix(A)) JointDistributionHandmade(-sqrt(A002 - 2A00A11 + 4A01A10 + A112)/2 + A00/2 + A11/2, sqrt(A002 - 2A00A11 + 4A01A10 + A112)/2 + A00/2 + A11/2) """ eigenvals = mat.eigenvals(multiple=True) if any(not is_random(eigenval) for eigenval in set(eigenvals)): raise ValueError("Eigen values don't have any random expression, " "joint distribution cannot be generated.") return JointDistributionHandmade(eigenvals) def level_spacing_distribution(mat): """ For obtaining distribution of level spacings. Parameters ========== mat: RandomMatrixSymbol The random matrix symbol whose eigen values are to be considered for finding the level spacings. Returns ======= Lambda Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE >>> from sympy.stats import level_spacing_distribution >>> U = GUE('U', 2) >>> level_spacing_distribution(U) Lambda(_s, 32_s2exp(-4_s2/pi)/pi*2) References ========== .. [1] https://en.wikipedia.org/wiki/Random_matrix#Distribution_of_level_spacings """ return mat.pspace.model.level_spacing_distribution()
06c176ccf7c83f0d5dfc72b2be45b9b18c5cb1de057e1229f9cd948b4792175a	""" Finite Discrete Random Variables Module See Also ======== sympy.stats.frv_types sympy.stats.rv sympy.stats.crv """ from itertools import product from sympy import (Basic, Symbol, cacheit, sympify, Mul, And, Or, Piecewise, Eq, Lambda, exp, I, Dummy, nan, Sum, Intersection, S) from sympy.core.containers import Dict from sympy.core.logic import Logic from sympy.core.relational import Relational from sympy.core.sympify import _sympify from sympy.sets.sets import FiniteSet from sympy.stats.rv import (RandomDomain, ProductDomain, ConditionalDomain, PSpace, IndependentProductPSpace, SinglePSpace, random_symbols, sumsets, rv_subs, NamedArgsMixin, Density) from sympy.external import import_module class FiniteDensity(dict): """ A domain with Finite Density. """ def __call__(self, item): """ Make instance of a class callable. If item belongs to current instance of a class, return it. Otherwise, return 0. """ item = sympify(item) if item in self: return self[item] else: return 0 @property def dict(self): """ Return item as dictionary. """ return dict(self) class FiniteDomain(RandomDomain): """ A domain with discrete finite support Represented using a FiniteSet. """ is_Finite = True @property def symbols(self): return FiniteSet(sym for sym, val in self.elements) @property def elements(self): return self.args[0] @property def dict(self): return FiniteSet([Dict(dict(el)) for el in self.elements]) def __contains__(self, other): return other in self.elements def __iter__(self): return self.elements.__iter__() def as_boolean(self): return Or([And([Eq(sym, val) for sym, val in item]) for item in self]) class SingleFiniteDomain(FiniteDomain): """ A FiniteDomain over a single symbol/set Example: The possibilities of a single* die roll. """ def __new__(cls, symbol, set): if not isinstance(set, FiniteSet) and \ not isinstance(set, Intersection): set = FiniteSet(set) return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) @property def set(self): return self.args[1] @property def elements(self): return FiniteSet([frozenset(((self.symbol, elem), )) for elem in self.set]) def __iter__(self): return (frozenset(((self.symbol, elem),)) for elem in self.set) def __contains__(self, other): sym, val = tuple(other)[0] return sym == self.symbol and val in self.set class ProductFiniteDomain(ProductDomain, FiniteDomain): """ A Finite domain consisting of several other FiniteDomains Example: The possibilities of the rolls of three independent dice """ def __iter__(self): proditer = product(self.domains) return (sumsets(items) for items in proditer) @property def elements(self): return FiniteSet(self) class ConditionalFiniteDomain(ConditionalDomain, ProductFiniteDomain): """ A FiniteDomain that has been restricted by a condition Example: The possibilities of a die roll under the condition that the roll is even. """ def __new__(cls, domain, condition): """ Create a new instance of ConditionalFiniteDomain class """ if condition is True: return domain cond = rv_subs(condition) return Basic.__new__(cls, domain, cond) def _test(self, elem): """ Test the value. If value is boolean, return it. If value is equality relational (two objects are equal), return it with left-hand side being equal to right-hand side. Otherwise, raise ValueError exception. """ val = self.condition.xreplace(dict(elem)) if val in [True, False]: return val elif val.is_Equality: return val.lhs == val.rhs raise ValueError("Undecidable if %s" % str(val)) def __contains__(self, other): return other in self.fulldomain and self._test(other) def __iter__(self): return (elem for elem in self.fulldomain if self._test(elem)) @property def set(self): if isinstance(self.fulldomain, SingleFiniteDomain): return FiniteSet([elem for elem in self.fulldomain.set if frozenset(((self.fulldomain.symbol, elem),)) in self]) else: raise NotImplementedError( "Not implemented on multi-dimensional conditional domain") def as_boolean(self): return FiniteDomain.as_boolean(self) class SingleFiniteDistribution(Basic, NamedArgsMixin): def __new__(cls, args): args = list(map(sympify, args)) return Basic.__new__(cls, args) @staticmethod def check(args): pass @property # type: ignore @cacheit def dict(self): if self.is_symbolic: return Density(self) return {k: self.pmf(k) for k in self.set} def pmf(self, args): # to be overridden by specific distribution raise NotImplementedError() @property def set(self): # to be overridden by specific distribution raise NotImplementedError() values = property(lambda self: self.dict.values) items = property(lambda self: self.dict.items) is_symbolic = property(lambda self: False) __iter__ = property(lambda self: self.dict.__iter__) __getitem__ = property(lambda self: self.dict.__getitem__) def __call__(self, args): return self.pmf(args) def __contains__(self, other): return other in self.set #============================================= #========= Probability Space =============== #============================================= class FinitePSpace(PSpace): """ A Finite Probability Space Represents the probabilities of a finite number of events. """ is_Finite = True def __new__(cls, domain, density): density = {sympify(key): sympify(val) for key, val in density.items()} public_density = Dict(density) obj = PSpace.__new__(cls, domain, public_density) obj._density = density return obj def prob_of(self, elem): elem = sympify(elem) density = self._density if isinstance(list(density.keys())[0], FiniteSet): return density.get(elem, S.Zero) return density.get(tuple(elem)[0][1], S.Zero) def where(self, condition): assert all(r.symbol in self.symbols for r in random_symbols(condition)) return ConditionalFiniteDomain(self.domain, condition) def compute_density(self, expr): expr = rv_subs(expr, self.values) d = FiniteDensity() for elem in self.domain: val = expr.xreplace(dict(elem)) prob = self.prob_of(elem) d[val] = d.get(val, S.Zero) + prob return d @cacheit def compute_cdf(self, expr): d = self.compute_density(expr) cum_prob = S.Zero cdf = [] for key in sorted(d): prob = d[key] cum_prob += prob cdf.append((key, cum_prob)) return dict(cdf) @cacheit def sorted_cdf(self, expr, python_float=False): cdf = self.compute_cdf(expr) items = list(cdf.items()) sorted_items = sorted(items, key=lambda val_cumprob: val_cumprob[1]) if python_float: sorted_items = [(v, float(cum_prob)) for v, cum_prob in sorted_items] return sorted_items @cacheit def compute_characteristic_function(self, expr): d = self.compute_density(expr) t = Dummy('t', real=True) return Lambda(t, sum(exp(Ikt)v for k,v in d.items())) @cacheit def compute_moment_generating_function(self, expr): d = self.compute_density(expr) t = Dummy('t', real=True) return Lambda(t, sum(exp(kt)v for k,v in d.items())) def compute_expectation(self, expr, rvs=None, *kwargs): rvs = rvs or self.values expr = rv_subs(expr, rvs) probs = [self.prob_of(elem) for elem in self.domain] if isinstance(expr, (Logic, Relational)): parse_domain = [tuple(elem)[0][1] for elem in self.domain] bools = [expr.xreplace(dict(elem)) for elem in self.domain] else: parse_domain = [expr.xreplace(dict(elem)) for elem in self.domain] bools = [True for elem in self.domain] return sum([Piecewise((prob elem, blv), (S.Zero, True)) for prob, elem, blv in zip(probs, parse_domain, bools)]) def compute_quantile(self, expr): cdf = self.compute_cdf(expr) p = Dummy('p', real=True) set = ((nan, (p < 0) \| (p > 1)),) for key, value in cdf.items(): set = set + ((key, p <= value), ) return Lambda(p, Piecewise(set)) def probability(self, condition): cond_symbols = frozenset(rs.symbol for rs in random_symbols(condition)) cond = rv_subs(condition) if not cond_symbols.issubset(self.symbols): raise ValueError("Cannot compare foreign random symbols, %s" %(str(cond_symbols - self.symbols))) if isinstance(condition, Relational) and \ (not cond.free_symbols.issubset(self.domain.free_symbols)): rv = condition.lhs if isinstance(condition.rhs, Symbol) else condition.rhs return sum(Piecewise( (self.prob_of(elem), condition.subs(rv, list(elem)[0][1])), (S.Zero, True)) for elem in self.domain) return sympify(sum(self.prob_of(elem) for elem in self.where(condition))) def conditional_space(self, condition): domain = self.where(condition) prob = self.probability(condition) density = {key: val / prob for key, val in self._density.items() if domain._test(key)} return FinitePSpace(domain, density) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_frv[library](self.distribution, size) if samps is not None: return {self.value: samps} raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) class SampleFiniteScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" # scipy can handle with custom distributions from scipy.stats import rv_discrete density_ = dist.dict x, y = [], [] for k, v in density_.items(): x.append(int(k)) y.append(float(v)) scipy_rv = rv_discrete(name='scipy_rv', values=(x, y)) return scipy_rv.rvs(size=size) class SampleFiniteNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'BinomialDistribution': lambda dist, size: numpy.random.binomial(n=int(dist.n), p=float(dist.p), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleFinitePymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'BernoulliDistribution': lambda dist: pymc3.Bernoulli('X', p=float(dist.p)), 'BinomialDistribution': lambda dist: pymc3.Binomial('X', n=int(dist.n), p=float(dist.p)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_frv = { 'scipy': SampleFiniteScipy, 'pymc3': SampleFinitePymc, 'numpy': SampleFiniteNumpy } class SingleFinitePSpace(SinglePSpace, FinitePSpace): """ A single finite probability space Represents the probabilities of a set of random events that can be attributed to a single variable/symbol. This class is implemented by many of the standard FiniteRV types such as Die, Bernoulli, Coin, etc.... """ @property def domain(self): return SingleFiniteDomain(self.symbol, self.distribution.set) @property def _is_symbolic(self): """ Helper property to check if the distribution of the random variable is having symbolic dimension. """ return self.distribution.is_symbolic @property def distribution(self): return self.args[1] def pmf(self, expr): return self.distribution.pmf(expr) @property # type: ignore @cacheit def _density(self): return {FiniteSet((self.symbol, val)): prob for val, prob in self.distribution.dict.items()} @cacheit def compute_characteristic_function(self, expr): if self._is_symbolic: d = self.compute_density(expr) t = Dummy('t', real=True) ki = Dummy('ki') return Lambda(t, Sum(d(ki)exp(Ikit), (ki, self.args[1].low, self.args[1].high))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_characteristic_function(expr) @cacheit def compute_moment_generating_function(self, expr): if self._is_symbolic: d = self.compute_density(expr) t = Dummy('t', real=True) ki = Dummy('ki') return Lambda(t, Sum(d(ki)exp(kit), (ki, self.args[1].low, self.args[1].high))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_moment_generating_function(expr) def compute_quantile(self, expr): if self._is_symbolic: raise NotImplementedError("Computing quantile for random variables " "with symbolic dimension because the bounds of searching the required " "value is undetermined.") expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_quantile(expr) def compute_density(self, expr): if self._is_symbolic: rv = list(random_symbols(expr))[0] k = Dummy('k', integer=True) cond = True if not isinstance(expr, (Relational, Logic)) \ else expr.subs(rv, k) return Lambda(k, Piecewise((self.pmf(k), And(k >= self.args[1].low, k <= self.args[1].high, cond)), (S.Zero, True))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_density(expr) def compute_cdf(self, expr): if self._is_symbolic: d = self.compute_density(expr) k = Dummy('k') ki = Dummy('ki') return Lambda(k, Sum(d(ki), (ki, self.args[1].low, k))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_cdf(expr) def compute_expectation(self, expr, rvs=None, *kwargs): if self._is_symbolic: rv = random_symbols(expr)[0] k = Dummy('k', integer=True) expr = expr.subs(rv, k) cond = True if not isinstance(expr, (Relational, Logic)) \ else expr func = self.pmf(k) k if cond != True else self.pmf(k) * expr return Sum(Piecewise((func, cond), (S.Zero, True)), (k, self.distribution.low, self.distribution.high)).doit() expr = _sympify(expr) expr = rv_subs(expr, rvs) return FinitePSpace(self.domain, self.distribution).compute_expectation(expr, rvs, *kwargs) def probability(self, condition): if self._is_symbolic: #TODO: Implement the mechanism for handling queries for symbolic sized distributions. raise NotImplementedError("Currently, probability queries are not " "supported for random variables with symbolic sized distributions.") condition = rv_subs(condition) return FinitePSpace(self.domain, self.distribution).probability(condition) def conditional_space(self, condition): """ This method is used for transferring the computation to probability method because conditional space of random variables with symbolic dimensions is currently not possible. """ if self._is_symbolic: self domain = self.where(condition) prob = self.probability(condition) density = {key: val / prob for key, val in self._density.items() if domain._test(key)} return FinitePSpace(domain, density) class ProductFinitePSpace(IndependentProductPSpace, FinitePSpace): """ A collection of several independent finite probability spaces """ @property def domain(self): return ProductFiniteDomain([space.domain for space in self.spaces]) @property # type: ignore @cacheit def _density(self): proditer = product([iter(space._density.items()) for space in self.spaces]) d = {} for items in proditer: elems, probs = list(zip(items)) elem = sumsets(elems) prob = Mul(*probs) d[elem] = d.get(elem, S.Zero) + prob return Dict(d) @property # type: ignore @cacheit def density(self): return Dict(self._density) def probability(self, condition): return FinitePSpace.probability(self, condition) def compute_density(self, expr): return FinitePSpace.compute_density(self, expr)
7e6a197e0deb9c9f325e29a7ee46107dcff7a3760a051d0aec207cdba04111fa	from sympy import Basic from sympy.stats.joint_rv import ProductPSpace from sympy.stats.rv import ProductDomain, _symbol_converter class StochasticPSpace(ProductPSpace): """ Represents probability space of stochastic processes and their random variables. Contains mechanics to do computations for queries of stochastic processes. Initialized by symbol, the specific process and distribution(optional) if the random indexed symbols of the process follows any specific distribution, like, in Bernoulli Process, each random indexed symbol follows Bernoulli distribution. For processes with memory, this parameter should not be passed. """ def __new__(cls, sym, process, distribution=None): sym = _symbol_converter(sym) from sympy.stats.stochastic_process_types import StochasticProcess if not isinstance(process, StochasticProcess): raise TypeError("`process` must be an instance of StochasticProcess.") return Basic.__new__(cls, sym, process, distribution) @property def process(self): """ The associated stochastic process. """ return self.args[1] @property def domain(self): return ProductDomain(self.process.index_set, self.process.state_space) @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[2] def probability(self, condition, given_condition=None, evaluate=True, kwargs): """ Transfers the task of handling queries to the specific stochastic process because every process has their own logic of handling such queries. """ return self.process.probability(condition, given_condition, evaluate, kwargs) def compute_expectation(self, expr, condition=None, evaluate=True, kwargs): """ Transfers the task of handling queries to the specific stochastic process because every process has their own logic of handling such queries. """ return self.process.expectation(expr, condition, evaluate, kwargs)
f06411db8a8e5e375294eaaa3908318a126056525e5a0881a1245a7e56f61d8a	from sympy.combinatorics import Permutation from sympy.combinatorics.util import _distribute_gens_by_base rmul = Permutation.rmul def _cmp_perm_lists(first, second): """ Compare two lists of permutations as sets. Explanation =========== This is used for testing purposes. Since the array form of a permutation is currently a list, Permutation is not hashable and cannot be put into a set. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.testutil import _cmp_perm_lists >>> a = Permutation([0, 2, 3, 4, 1]) >>> b = Permutation([1, 2, 0, 4, 3]) >>> c = Permutation([3, 4, 0, 1, 2]) >>> ls1 = [a, b, c] >>> ls2 = [b, c, a] >>> _cmp_perm_lists(ls1, ls2) True """ return {tuple(a) for a in first} == \ {tuple(a) for a in second} def _naive_list_centralizer(self, other, af=False): from sympy.combinatorics.perm_groups import PermutationGroup """ Return a list of elements for the centralizer of a subgroup/set/element. Explanation =========== This is a brute force implementation that goes over all elements of the group and checks for membership in the centralizer. It is used to test ``.centralizer()`` from ``sympy.combinatorics.perm_groups``. Examples ======== >>> from sympy.combinatorics.testutil import _naive_list_centralizer >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> _naive_list_centralizer(D, D) [Permutation([0, 1, 2, 3]), Permutation([2, 3, 0, 1])] See Also ======== sympy.combinatorics.perm_groups.centralizer """ from sympy.combinatorics.permutations import _af_commutes_with if hasattr(other, 'generators'): elements = list(self.generate_dimino(af=True)) gens = [x._array_form for x in other.generators] commutes_with_gens = lambda x: all(_af_commutes_with(x, gen) for gen in gens) centralizer_list = [] if not af: for element in elements: if commutes_with_gens(element): centralizer_list.append(Permutation._af_new(element)) else: for element in elements: if commutes_with_gens(element): centralizer_list.append(element) return centralizer_list elif hasattr(other, 'getitem'): return _naive_list_centralizer(self, PermutationGroup(other), af) elif hasattr(other, 'array_form'): return _naive_list_centralizer(self, PermutationGroup([other]), af) def _verify_bsgs(group, base, gens): """ Verify the correctness of a base and strong generating set. Explanation =========== This is a naive implementation using the definition of a base and a strong generating set relative to it. There are other procedures for verifying a base and strong generating set, but this one will serve for more robust testing. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> A = AlternatingGroup(4) >>> A.schreier_sims() >>> _verify_bsgs(A, A.base, A.strong_gens) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims """ from sympy.combinatorics.perm_groups import PermutationGroup strong_gens_distr = _distribute_gens_by_base(base, gens) current_stabilizer = group for i in range(len(base)): candidate = PermutationGroup(strong_gens_distr[i]) if current_stabilizer.order() != candidate.order(): return False current_stabilizer = current_stabilizer.stabilizer(base[i]) if current_stabilizer.order() != 1: return False return True def _verify_centralizer(group, arg, centr=None): """ Verify the centralizer of a group/set/element inside another group. This is used for testing ``.centralizer()`` from ``sympy.combinatorics.perm_groups`` Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.testutil import _verify_centralizer >>> S = SymmetricGroup(5) >>> A = AlternatingGroup(5) >>> centr = PermutationGroup([Permutation([0, 1, 2, 3, 4])]) >>> _verify_centralizer(S, A, centr) True See Also ======== _naive_list_centralizer, sympy.combinatorics.perm_groups.PermutationGroup.centralizer, _cmp_perm_lists """ if centr is None: centr = group.centralizer(arg) centr_list = list(centr.generate_dimino(af=True)) centr_list_naive = _naive_list_centralizer(group, arg, af=True) return _cmp_perm_lists(centr_list, centr_list_naive) def _verify_normal_closure(group, arg, closure=None): from sympy.combinatorics.perm_groups import PermutationGroup """ Verify the normal closure of a subgroup/subset/element in a group. This is used to test sympy.combinatorics.perm_groups.PermutationGroup.normal_closure Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.testutil import _verify_normal_closure >>> S = SymmetricGroup(3) >>> A = AlternatingGroup(3) >>> _verify_normal_closure(S, A, closure=A) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.normal_closure """ if closure is None: closure = group.normal_closure(arg) conjugates = set() if hasattr(arg, 'generators'): subgr_gens = arg.generators elif hasattr(arg, '__getitem__'): subgr_gens = arg elif hasattr(arg, 'array_form'): subgr_gens = [arg] for el in group.generate_dimino(): for gen in subgr_gens: conjugates.add(gen ^ el) naive_closure = PermutationGroup(list(conjugates)) return closure.is_subgroup(naive_closure) def canonicalize_naive(g, dummies, sym, v): """ Canonicalize tensor formed by tensors of the different types. Explanation =========== sym_i symmetry under exchange of two component tensors of type `i` None no symmetry 0 commuting 1 anticommuting Parameters ========== g : Permutation representing the tensor. dummies : List of dummy indices. msym : Symmetry of the metric. v : A list of (base_i, gens_i, n_i, sym_i) for tensors of type `i`. base_i, gens_i BSGS for tensors of this type n_i number ot tensors of type `i` Returns ======= Returns 0 if the tensor is zero, else returns the array form of the permutation representing the canonical form of the tensor. Examples ======== >>> from sympy.combinatorics.testutil import canonicalize_naive >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs >>> from sympy.combinatorics import Permutation >>> g = Permutation([1, 3, 2, 0, 4, 5]) >>> base2, gens2 = get_symmetric_group_sgs(2) >>> canonicalize_naive(g, [2, 3], 0, (base2, gens2, 2, 0)) [0, 2, 1, 3, 4, 5] """ from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.tensor_can import gens_products, dummy_sgs from sympy.combinatorics.permutations import Permutation, _af_rmul v1 = [] for i in range(len(v)): base_i, gens_i, n_i, sym_i = v[i] v1.append((base_i, gens_i, [[]]n_i, sym_i)) size, sbase, sgens = gens_products(v1) dgens = dummy_sgs(dummies, sym, size-2) if isinstance(sym, int): num_types = 1 dummies = [dummies] sym = [sym] else: num_types = len(sym) dgens = [] for i in range(num_types): dgens.extend(dummy_sgs(dummies[i], sym[i], size - 2)) S = PermutationGroup(sgens) D = PermutationGroup([Permutation(x) for x in dgens]) dlist = list(D.generate(af=True)) g = g.array_form st = set() for s in S.generate(af=True): h = _af_rmul(g, s) for d in dlist: q = tuple(_af_rmul(d, h)) st.add(q) a = list(st) a.sort() prev = (0,)size for h in a: if h[:-2] == prev[:-2]: if h[-1] != prev[-1]: return 0 prev = h return list(a[0]) def graph_certificate(gr): """ Return a certificate for the graph Parameters ========== gr : adjacency list Explanation =========== The graph is assumed to be unoriented and without external lines. Associate to each vertex of the graph a symmetric tensor with number of indices equal to the degree of the vertex; indices are contracted when they correspond to the same line of the graph. The canonical form of the tensor gives a certificate for the graph. This is not an efficient algorithm to get the certificate of a graph. Examples ======== >>> from sympy.combinatorics.testutil import graph_certificate >>> gr1 = {0:[1, 2, 3, 5], 1:[0, 2, 4], 2:[0, 1, 3, 4], 3:[0, 2, 4], 4:[1, 2, 3, 5], 5:[0, 4]} >>> gr2 = {0:[1, 5], 1:[0, 2, 3, 4], 2:[1, 3, 5], 3:[1, 2, 4, 5], 4:[1, 3, 5], 5:[0, 2, 3, 4]} >>> c1 = graph_certificate(gr1) >>> c2 = graph_certificate(gr2) >>> c1 [0, 2, 4, 6, 1, 8, 10, 12, 3, 14, 16, 18, 5, 9, 15, 7, 11, 17, 13, 19, 20, 21] >>> c1 == c2 True """ from sympy.combinatorics.permutations import _af_invert from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, canonicalize items = list(gr.items()) items.sort(key=lambda x: len(x[1]), reverse=True) pvert = [x[0] for x in items] pvert = _af_invert(pvert) # the indices of the tensor are twice the number of lines of the graph num_indices = 0 for v, neigh in items: num_indices += len(neigh) # associate to each vertex its indices; for each line # between two vertices assign the # even index to the vertex which comes first in items, # the odd index to the other vertex vertices = [[] for i in items] i = 0 for v, neigh in items: for v2 in neigh: if pvert[v] < pvert[v2]: vertices[pvert[v]].append(i) vertices[pvert[v2]].append(i+1) i += 2 g = [] for v in vertices: g.extend(v) assert len(g) == num_indices g += [num_indices, num_indices + 1] size = num_indices + 2 assert sorted(g) == list(range(size)) g = Permutation(g) vlen = [0](len(vertices[0])+1) for neigh in vertices: vlen[len(neigh)] += 1 v = [] for i in range(len(vlen)): n = vlen[i] if n: base, gens = get_symmetric_group_sgs(i) v.append((base, gens, n, 0)) v.reverse() dummies = list(range(num_indices)) can = canonicalize(g, dummies, 0, v) return can
3d1a58d440d65b2b096de9751356033803b160020f51a13da8e5b54795a73acb	from random import randrange, choice from math import log from sympy.ntheory import primefactors from sympy import multiplicity, factorint, Symbol from sympy.combinatorics import Permutation from sympy.combinatorics.permutations import (_af_commutes_with, _af_invert, _af_rmul, _af_rmuln, _af_pow, Cycle) from sympy.combinatorics.util import (_check_cycles_alt_sym, _distribute_gens_by_base, _orbits_transversals_from_bsgs, _handle_precomputed_bsgs, _base_ordering, _strong_gens_from_distr, _strip, _strip_af) from sympy.core import Basic from sympy.functions.combinatorial.factorials import factorial from sympy.ntheory import sieve from sympy.utilities.iterables import has_variety, is_sequence, uniq from sympy.testing.randtest import _randrange from itertools import islice from sympy.core.sympify import _sympify rmul = Permutation.rmul_with_af _af_new = Permutation._af_new class PermutationGroup(Basic): """The class defining a Permutation group. Explanation =========== PermutationGroup([p1, p2, ..., pn]) returns the permutation group generated by the list of permutations. This group can be supplied to Polyhedron if one desires to decorate the elements to which the indices of the permutation refer. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.polyhedron import Polyhedron >>> from sympy.combinatorics.perm_groups import PermutationGroup The permutations corresponding to motion of the front, right and bottom face of a 2x2 Rubik's cube are defined: >>> F = Permutation(2, 19, 21, 8)(3, 17, 20, 10)(4, 6, 7, 5) >>> R = Permutation(1, 5, 21, 14)(3, 7, 23, 12)(8, 10, 11, 9) >>> D = Permutation(6, 18, 14, 10)(7, 19, 15, 11)(20, 22, 23, 21) These are passed as permutations to PermutationGroup: >>> G = PermutationGroup(F, R, D) >>> G.order() 3674160 The group can be supplied to a Polyhedron in order to track the objects being moved. An example involving the 2x2 Rubik's cube is given there, but here is a simple demonstration: >>> a = Permutation(2, 1) >>> b = Permutation(1, 0) >>> G = PermutationGroup(a, b) >>> P = Polyhedron(list('ABC'), pgroup=G) >>> P.corners (A, B, C) >>> P.rotate(0) # apply permutation 0 >>> P.corners (A, C, B) >>> P.reset() >>> P.corners (A, B, C) Or one can make a permutation as a product of selected permutations and apply them to an iterable directly: >>> P10 = G.make_perm([0, 1]) >>> P10('ABC') ['C', 'A', 'B'] See Also ======== sympy.combinatorics.polyhedron.Polyhedron, sympy.combinatorics.permutations.Permutation References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" .. [2] Seress, A. "Permutation Group Algorithms" .. [3] https://en.wikipedia.org/wiki/Schreier_vector .. [4] https://en.wikipedia.org/wiki/Nielsen_transformation#Product_replacement_algorithm .. [5] Frank Celler, Charles R.Leedham-Green, Scott H.Murray, Alice C.Niemeyer, and E.A.O'Brien. "Generating Random Elements of a Finite Group" .. [6] https://en.wikipedia.org/wiki/Block_%28permutation_group_theory%29 .. [7] http://www.algorithmist.com/index.php/Union_Find .. [8] https://en.wikipedia.org/wiki/Multiply_transitive_group#Multiply_transitive_groups .. [9] https://en.wikipedia.org/wiki/Center_%28group_theory%29 .. [10] https://en.wikipedia.org/wiki/Centralizer_and_normalizer .. [11] http://groupprops.subwiki.org/wiki/Derived_subgroup .. [12] https://en.wikipedia.org/wiki/Nilpotent_group .. [13] http://www.math.colostate.edu/~hulpke/CGT/cgtnotes.pdf .. [14] https://www.gap-system.org/Manuals/doc/ref/manual.pdf """ is_group = True def __new__(cls, args, dups=True, kwargs): """The default constructor. Accepts Cycle and Permutation forms. Removes duplicates unless ``dups`` keyword is ``False``. """ if not args: args = [Permutation()] else: args = list(args[0] if is_sequence(args[0]) else args) if not args: args = [Permutation()] if any(isinstance(a, Cycle) for a in args): args = [Permutation(a) for a in args] if has_variety(a.size for a in args): degree = kwargs.pop('degree', None) if degree is None: degree = max(a.size for a in args) for i in range(len(args)): if args[i].size != degree: args[i] = Permutation(args[i], size=degree) if dups: args = list(uniq([_af_new(list(a)) for a in args])) if len(args) > 1: args = [g for g in args if not g.is_identity] obj = Basic.__new__(cls, args, *kwargs) obj._generators = args obj._order = None obj._center = [] obj._is_abelian = None obj._is_transitive = None obj._is_sym = None obj._is_alt = None obj._is_primitive = None obj._is_nilpotent = None obj._is_solvable = None obj._is_trivial = None obj._transitivity_degree = None obj._max_div = None obj._is_perfect = None obj._is_cyclic = None obj._r = len(obj._generators) obj._degree = obj._generators[0].size # these attributes are assigned after running schreier_sims obj._base = [] obj._strong_gens = [] obj._strong_gens_slp = [] obj._basic_orbits = [] obj._transversals = [] obj._transversal_slp = [] # these attributes are assigned after running _random_pr_init obj._random_gens = [] # finite presentation of the group as an instance of `FpGroup` obj._fp_presentation = None return obj def __getitem__(self, i): return self._generators[i] def __contains__(self, i): """Return ``True`` if i* is contained in PermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = Permutation(1, 2, 3) >>> Permutation(3) in PermutationGroup(p) True """ if not isinstance(i, Permutation): raise TypeError("A PermutationGroup contains only Permutations as " "elements, not elements of type %s" % type(i)) return self.contains(i) def __len__(self): return len(self._generators) def __eq__(self, other): """Return ``True`` if PermutationGroup generated by elements in the group are same i.e they represent the same PermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> p = Permutation(0, 1, 2, 3, 4, 5) >>> G = PermutationGroup([p, p2]) >>> H = PermutationGroup([p2, p]) >>> G.generators == H.generators False >>> G == H True """ if not isinstance(other, PermutationGroup): return False set_self_gens = set(self.generators) set_other_gens = set(other.generators) # before reaching the general case there are also certain # optimisation and obvious cases requiring less or no actual # computation. if set_self_gens == set_other_gens: return True # in the most general case it will check that each generator of # one group belongs to the other PermutationGroup and vice-versa for gen1 in set_self_gens: if not other.contains(gen1): return False for gen2 in set_other_gens: if not self.contains(gen2): return False return True def __hash__(self): return super().__hash__() def __mul__(self, other): """ Return the direct product of two permutation groups as a permutation group. Explanation =========== This implementation realizes the direct product by shifting the index set for the generators of the second group: so if we have ``G`` acting on ``n1`` points and ``H`` acting on ``n2`` points, ``GH`` acts on ``n1 + n2`` points. Examples ======== >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(5) >>> H = GG >>> H PermutationGroup([ (9)(0 1 2 3 4), (5 6 7 8 9)]) >>> H.order() 25 """ if isinstance(other, Permutation): return Coset(other, self, dir='+') gens1 = [perm._array_form for perm in self.generators] gens2 = [perm._array_form for perm in other.generators] n1 = self._degree n2 = other._degree start = list(range(n1)) end = list(range(n1, n1 + n2)) for i in range(len(gens2)): gens2[i] = [x + n1 for x in gens2[i]] gens2 = [start + gen for gen in gens2] gens1 = [gen + end for gen in gens1] together = gens1 + gens2 gens = [_af_new(x) for x in together] return PermutationGroup(gens) def _random_pr_init(self, r, n, _random_prec_n=None): r"""Initialize random generators for the product replacement algorithm. Explanation =========== The implementation uses a modification of the original product replacement algorithm due to Leedham-Green, as described in [1], pp. 69-71; also, see [2], pp. 27-29 for a detailed theoretical analysis of the original product replacement algorithm, and [4]. The product replacement algorithm is used for producing random, uniformly distributed elements of a group `G` with a set of generators `S`. For the initialization ``_random_pr_init``, a list ``R`` of `\max\{r, \|S\|\}` group generators is created as the attribute ``G._random_gens``, repeating elements of `S` if necessary, and the identity element of `G` is appended to ``R`` - we shall refer to this last element as the accumulator. Then the function ``random_pr()`` is called ``n`` times, randomizing the list ``R`` while preserving the generation of `G` by ``R``. The function ``random_pr()`` itself takes two random elements ``g, h`` among all elements of ``R`` but the accumulator and replaces ``g`` with a randomly chosen element from `\{gh, g(~h), hg, (~h)g\}`. Then the accumulator is multiplied by whatever ``g`` was replaced by. The new value of the accumulator is then returned by ``random_pr()``. The elements returned will eventually (for ``n`` large enough) become uniformly distributed across `G` ([5]). For practical purposes however, the values ``n = 50, r = 11`` are suggested in [1]. Notes ===== THIS FUNCTION HAS SIDE EFFECTS: it changes the attribute self._random_gens See Also ======== random_pr """ deg = self.degree random_gens = [x._array_form for x in self.generators] k = len(random_gens) if k < r: for i in range(k, r): random_gens.append(random_gens[i - k]) acc = list(range(deg)) random_gens.append(acc) self._random_gens = random_gens # handle randomized input for testing purposes if _random_prec_n is None: for i in range(n): self.random_pr() else: for i in range(n): self.random_pr(_random_prec=_random_prec_n[i]) def _union_find_merge(self, first, second, ranks, parents, not_rep): """Merges two classes in a union-find data structure. Explanation =========== Used in the implementation of Atkinson's algorithm as suggested in [1], pp. 83-87. The class merging process uses union by rank as an optimization. ([7]) Notes ===== THIS FUNCTION HAS SIDE EFFECTS: the list of class representatives, ``parents``, the list of class sizes, ``ranks``, and the list of elements that are not representatives, ``not_rep``, are changed due to class merging. See Also ======== minimal_block, _union_find_rep References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" .. [7] http://www.algorithmist.com/index.php/Union_Find """ rep_first = self._union_find_rep(first, parents) rep_second = self._union_find_rep(second, parents) if rep_first != rep_second: # union by rank if ranks[rep_first] >= ranks[rep_second]: new_1, new_2 = rep_first, rep_second else: new_1, new_2 = rep_second, rep_first total_rank = ranks[new_1] + ranks[new_2] if total_rank > self.max_div: return -1 parents[new_2] = new_1 ranks[new_1] = total_rank not_rep.append(new_2) return 1 return 0 def _union_find_rep(self, num, parents): """Find representative of a class in a union-find data structure. Explanation =========== Used in the implementation of Atkinson's algorithm as suggested in [1], pp. 83-87. After the representative of the class to which ``num`` belongs is found, path compression is performed as an optimization ([7]). Notes ===== THIS FUNCTION HAS SIDE EFFECTS: the list of class representatives, ``parents``, is altered due to path compression. See Also ======== minimal_block, _union_find_merge References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" .. [7] http://www.algorithmist.com/index.php/Union_Find """ rep, parent = num, parents[num] while parent != rep: rep = parent parent = parents[rep] # path compression temp, parent = num, parents[num] while parent != rep: parents[temp] = rep temp = parent parent = parents[temp] return rep @property def base(self): """Return a base from the Schreier-Sims algorithm. Explanation =========== For a permutation group `G`, a base is a sequence of points `B = (b_1, b_2, ..., b_k)` such that no element of `G` apart from the identity fixes all the points in `B`. The concepts of a base and strong generating set and their applications are discussed in depth in [1], pp. 87-89 and [2], pp. 55-57. An alternative way to think of `B` is that it gives the indices of the stabilizer cosets that contain more than the identity permutation. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> G = PermutationGroup([Permutation(0, 1, 3)(2, 4)]) >>> G.base [0, 2] See Also ======== strong_gens, basic_transversals, basic_orbits, basic_stabilizers """ if self._base == []: self.schreier_sims() return self._base def baseswap(self, base, strong_gens, pos, randomized=False, transversals=None, basic_orbits=None, strong_gens_distr=None): r"""Swap two consecutive base points in base and strong generating set. Explanation =========== If a base for a group `G` is given by `(b_1, b_2, ..., b_k)`, this function returns a base `(b_1, b_2, ..., b_{i+1}, b_i, ..., b_k)`, where `i` is given by ``pos``, and a strong generating set relative to that base. The original base and strong generating set are not modified. The randomized version (default) is of Las Vegas type. Parameters ========== base, strong_gens The base and strong generating set. pos The position at which swapping is performed. randomized A switch between randomized and deterministic version. transversals The transversals for the basic orbits, if known. basic_orbits The basic orbits, if known. strong_gens_distr The strong generators distributed by basic stabilizers, if known. Returns ======= (base, strong_gens) ``base`` is the new base, and ``strong_gens`` is a generating set relative to it. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> S = SymmetricGroup(4) >>> S.schreier_sims() >>> S.base [0, 1, 2] >>> base, gens = S.baseswap(S.base, S.strong_gens, 1, randomized=False) >>> base, gens ([0, 2, 1], [(0 1 2 3), (3)(0 1), (1 3 2), (2 3), (1 3)]) check that base, gens is a BSGS >>> S1 = PermutationGroup(gens) >>> _verify_bsgs(S1, base, gens) True See Also ======== schreier_sims Notes ===== The deterministic version of the algorithm is discussed in [1], pp. 102-103; the randomized version is discussed in [1], p.103, and [2], p.98. It is of Las Vegas type. Notice that [1] contains a mistake in the pseudocode and discussion of BASESWAP: on line 3 of the pseudocode, `\|\beta_{i+1}^{\left\langle T\right\rangle}\|` should be replaced by `\|\beta_{i}^{\left\langle T\right\rangle}\|`, and the same for the discussion of the algorithm. """ # construct the basic orbits, generators for the stabilizer chain # and transversal elements from whatever was provided transversals, basic_orbits, strong_gens_distr = \ _handle_precomputed_bsgs(base, strong_gens, transversals, basic_orbits, strong_gens_distr) base_len = len(base) degree = self.degree # size of orbit of base[pos] under the stabilizer we seek to insert # in the stabilizer chain at position pos + 1 size = len(basic_orbits[pos])len(basic_orbits[pos + 1]) \ //len(_orbit(degree, strong_gens_distr[pos], base[pos + 1])) # initialize the wanted stabilizer by a subgroup if pos + 2 > base_len - 1: T = [] else: T = strong_gens_distr[pos + 2][:] # randomized version if randomized is True: stab_pos = PermutationGroup(strong_gens_distr[pos]) schreier_vector = stab_pos.schreier_vector(base[pos + 1]) # add random elements of the stabilizer until they generate it while len(_orbit(degree, T, base[pos])) != size: new = stab_pos.random_stab(base[pos + 1], schreier_vector=schreier_vector) T.append(new) # deterministic version else: Gamma = set(basic_orbits[pos]) Gamma.remove(base[pos]) if base[pos + 1] in Gamma: Gamma.remove(base[pos + 1]) # add elements of the stabilizer until they generate it by # ruling out member of the basic orbit of base[pos] along the way while len(_orbit(degree, T, base[pos])) != size: gamma = next(iter(Gamma)) x = transversals[pos][gamma] temp = x._array_form.index(base[pos + 1]) # (~x)(base[pos + 1]) if temp not in basic_orbits[pos + 1]: Gamma = Gamma - _orbit(degree, T, gamma) else: y = transversals[pos + 1][temp] el = rmul(x, y) if el(base[pos]) not in _orbit(degree, T, base[pos]): T.append(el) Gamma = Gamma - _orbit(degree, T, base[pos]) # build the new base and strong generating set strong_gens_new_distr = strong_gens_distr[:] strong_gens_new_distr[pos + 1] = T base_new = base[:] base_new[pos], base_new[pos + 1] = base_new[pos + 1], base_new[pos] strong_gens_new = _strong_gens_from_distr(strong_gens_new_distr) for gen in T: if gen not in strong_gens_new: strong_gens_new.append(gen) return base_new, strong_gens_new @property def basic_orbits(self): """ Return the basic orbits relative to a base and strong generating set. Explanation =========== If `(b_1, b_2, ..., b_k)` is a base for a group `G`, and `G^{(i)} = G_{b_1, b_2, ..., b_{i-1}}` is the ``i``-th basic stabilizer (so that `G^{(1)} = G`), the ``i``-th basic orbit relative to this base is the orbit of `b_i` under `G^{(i)}`. See [1], pp. 87-89 for more information. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(4) >>> S.basic_orbits [[0, 1, 2, 3], [1, 2, 3], [2, 3]] See Also ======== base, strong_gens, basic_transversals, basic_stabilizers """ if self._basic_orbits == []: self.schreier_sims() return self._basic_orbits @property def basic_stabilizers(self): """ Return a chain of stabilizers relative to a base and strong generating set. Explanation =========== The ``i``-th basic stabilizer `G^{(i)}` relative to a base `(b_1, b_2, ..., b_k)` is `G_{b_1, b_2, ..., b_{i-1}}`. For more information, see [1], pp. 87-89. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> A = AlternatingGroup(4) >>> A.schreier_sims() >>> A.base [0, 1] >>> for g in A.basic_stabilizers: ... print(g) ... PermutationGroup([ (3)(0 1 2), (1 2 3)]) PermutationGroup([ (1 2 3)]) See Also ======== base, strong_gens, basic_orbits, basic_transversals """ if self._transversals == []: self.schreier_sims() strong_gens = self._strong_gens base = self._base if not base: # e.g. if self is trivial return [] strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_stabilizers = [] for gens in strong_gens_distr: basic_stabilizers.append(PermutationGroup(gens)) return basic_stabilizers @property def basic_transversals(self): """ Return basic transversals relative to a base and strong generating set. Explanation =========== The basic transversals are transversals of the basic orbits. They are provided as a list of dictionaries, each dictionary having keys - the elements of one of the basic orbits, and values - the corresponding transversal elements. See [1], pp. 87-89 for more information. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> A = AlternatingGroup(4) >>> A.basic_transversals [{0: (3), 1: (3)(0 1 2), 2: (3)(0 2 1), 3: (0 3 1)}, {1: (3), 2: (1 2 3), 3: (1 3 2)}] See Also ======== strong_gens, base, basic_orbits, basic_stabilizers """ if self._transversals == []: self.schreier_sims() return self._transversals def composition_series(self): r""" Return the composition series for a group as a list of permutation groups. Explanation =========== The composition series for a group `G` is defined as a subnormal series `G = H_0 > H_1 > H_2 \ldots` A composition series is a subnormal series such that each factor group `H(i+1) / H(i)` is simple. A subnormal series is a composition series only if it is of maximum length. The algorithm works as follows: Starting with the derived series the idea is to fill the gap between `G = der[i]` and `H = der[i+1]` for each `i` independently. Since, all subgroups of the abelian group `G/H` are normal so, first step is to take the generators `g` of `G` and add them to generators of `H` one by one. The factor groups formed are not simple in general. Each group is obtained from the previous one by adding one generator `g`, if the previous group is denoted by `H` then the next group `K` is generated by `g` and `H`. The factor group `K/H` is cyclic and it's order is `K.order()//G.order()`. The series is then extended between `K` and `H` by groups generated by powers of `g` and `H`. The series formed is then prepended to the already existing series. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.named_groups import CyclicGroup >>> S = SymmetricGroup(12) >>> G = S.sylow_subgroup(2) >>> C = G.composition_series() >>> [H.order() for H in C] [1024, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1] >>> G = S.sylow_subgroup(3) >>> C = G.composition_series() >>> [H.order() for H in C] [243, 81, 27, 9, 3, 1] >>> G = CyclicGroup(12) >>> C = G.composition_series() >>> [H.order() for H in C] [12, 6, 3, 1] """ der = self.derived_series() if not (all(g.is_identity for g in der[-1].generators)): raise NotImplementedError('Group should be solvable') series = [] for i in range(len(der)-1): H = der[i+1] up_seg = [] for g in der[i].generators: K = PermutationGroup([g] + H.generators) order = K.order() // H.order() down_seg = [] for p, e in factorint(order).items(): for j in range(e): down_seg.append(PermutationGroup([g] + H.generators)) g = gp up_seg = down_seg + up_seg H = K up_seg[0] = der[i] series.extend(up_seg) series.append(der[-1]) return series def coset_transversal(self, H): """Return a transversal of the right cosets of self by its subgroup H using the second method described in [1], Subsection 4.6.7 """ if not H.is_subgroup(self): raise ValueError("The argument must be a subgroup") if H.order() == 1: return self._elements self._schreier_sims(base=H.base) # make G.base an extension of H.base base = self.base base_ordering = _base_ordering(base, self.degree) identity = Permutation(self.degree - 1) transversals = self.basic_transversals[:] # transversals is a list of dictionaries. Get rid of the keys # so that it is a list of lists and sort each list in # the increasing order of base[l]^x for l, t in enumerate(transversals): transversals[l] = sorted(t.values(), key = lambda x: base_ordering[base[l]^x]) orbits = H.basic_orbits h_stabs = H.basic_stabilizers g_stabs = self.basic_stabilizers indices = [x.order()//y.order() for x, y in zip(g_stabs, h_stabs)] # T^(l) should be a right transversal of H^(l) in G^(l) for # 1<=l<=len(base). While H^(l) is the trivial group, T^(l) # contains all the elements of G^(l) so we might just as well # start with l = len(h_stabs)-1 if len(g_stabs) > len(h_stabs): T = g_stabs[len(h_stabs)]._elements else: T = [identity] l = len(h_stabs)-1 t_len = len(T) while l > -1: T_next = [] for u in transversals[l]: if u == identity: continue b = base_ordering[base[l]^u] for t in T: p = tu if all([base_ordering[h^p] >= b for h in orbits[l]]): T_next.append(p) if t_len + len(T_next) == indices[l]: break if t_len + len(T_next) == indices[l]: break T += T_next t_len += len(T_next) l -= 1 T.remove(identity) T = [identity] + T return T def _coset_representative(self, g, H): """Return the representative of Hg from the transversal that would be computed by ``self.coset_transversal(H)``. """ if H.order() == 1: return g # The base of self must be an extension of H.base. if not(self.base[:len(H.base)] == H.base): self._schreier_sims(base=H.base) orbits = H.basic_orbits[:] h_transversals = [list(_.values()) for _ in H.basic_transversals] transversals = [list(_.values()) for _ in self.basic_transversals] base = self.base base_ordering = _base_ordering(base, self.degree) def step(l, x): gamma = sorted(orbits[l], key = lambda y: base_ordering[y^x])[0] i = [base[l]^h for h in h_transversals[l]].index(gamma) x = h_transversals[l][i]x if l < len(orbits)-1: for u in transversals[l]: if base[l]^u == base[l]^x: break x = step(l+1, xu*-1)u return x return step(0, g) def coset_table(self, H): """Return the standardised (right) coset table of self in H as a list of lists. """ # Maybe this should be made to return an instance of CosetTable # from fp_groups.py but the class would need to be changed first # to be compatible with PermutationGroups from itertools import chain, product if not H.is_subgroup(self): raise ValueError("The argument must be a subgroup") T = self.coset_transversal(H) n = len(T) A = list(chain.from_iterable((gen, gen*-1) for gen in self.generators)) table = [] for i in range(n): row = [self._coset_representative(T[i]x, H) for x in A] row = [T.index(r) for r in row] table.append(row) # standardize (this is the same as the algorithm used in coset_table) # If CosetTable is made compatible with PermutationGroups, this # should be replaced by table.standardize() A = range(len(A)) gamma = 1 for alpha, a in product(range(n), A): beta = table[alpha][a] if beta >= gamma: if beta > gamma: for x in A: z = table[gamma][x] table[gamma][x] = table[beta][x] table[beta][x] = z for i in range(n): if table[i][x] == beta: table[i][x] = gamma elif table[i][x] == gamma: table[i][x] = beta gamma += 1 if gamma >= n-1: return table def center(self): r""" Return the center of a permutation group. Explanation =========== The center for a group `G` is defined as `Z(G) = \{z\in G \| \forall g\in G, zg = gz \}`, the set of elements of `G` that commute with all elements of `G`. It is equal to the centralizer of `G` inside `G`, and is naturally a subgroup of `G` ([9]). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> G = D.center() >>> G.order() 2 See Also ======== centralizer Notes ===== This is a naive implementation that is a straightforward application of ``.centralizer()`` """ return self.centralizer(self) def centralizer(self, other): r""" Return the centralizer of a group/set/element. Explanation =========== The centralizer of a set of permutations ``S`` inside a group ``G`` is the set of elements of ``G`` that commute with all elements of ``S``:: `C_G(S) = \{ g \in G \| gs = sg \forall s \in S\}` ([10]) Usually, ``S`` is a subset of ``G``, but if ``G`` is a proper subgroup of the full symmetric group, we allow for ``S`` to have elements outside ``G``. It is naturally a subgroup of ``G``; the centralizer of a permutation group is equal to the centralizer of any set of generators for that group, since any element commuting with the generators commutes with any product of the generators. Parameters ========== other a permutation group/list of permutations/single permutation Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) >>> S = SymmetricGroup(6) >>> C = CyclicGroup(6) >>> H = S.centralizer(C) >>> H.is_subgroup(C) True See Also ======== subgroup_search Notes ===== The implementation is an application of ``.subgroup_search()`` with tests using a specific base for the group ``G``. """ if hasattr(other, 'generators'): if other.is_trivial or self.is_trivial: return self degree = self.degree identity = _af_new(list(range(degree))) orbits = other.orbits() num_orbits = len(orbits) orbits.sort(key=lambda x: -len(x)) long_base = [] orbit_reps = [None]num_orbits orbit_reps_indices = [None]num_orbits orbit_descr = [None]degree for i in range(num_orbits): orbit = list(orbits[i]) orbit_reps[i] = orbit[0] orbit_reps_indices[i] = len(long_base) for point in orbit: orbit_descr[point] = i long_base = long_base + orbit base, strong_gens = self.schreier_sims_incremental(base=long_base) strong_gens_distr = _distribute_gens_by_base(base, strong_gens) i = 0 for i in range(len(base)): if strong_gens_distr[i] == [identity]: break base = base[:i] base_len = i for j in range(num_orbits): if base[base_len - 1] in orbits[j]: break rel_orbits = orbits[: j + 1] num_rel_orbits = len(rel_orbits) transversals = [None]num_rel_orbits for j in range(num_rel_orbits): rep = orbit_reps[j] transversals[j] = dict( other.orbit_transversal(rep, pairs=True)) trivial_test = lambda x: True tests = [None]base_len for l in range(base_len): if base[l] in orbit_reps: tests[l] = trivial_test else: def test(computed_words, l=l): g = computed_words[l] rep_orb_index = orbit_descr[base[l]] rep = orbit_reps[rep_orb_index] im = g._array_form[base[l]] im_rep = g._array_form[rep] tr_el = transversals[rep_orb_index][base[l]] # using the definition of transversal, # base[l]^g = rep^(tr_elg); # if g belongs to the centralizer, then # base[l]^g = (rep^g)^tr_el return im == tr_el._array_form[im_rep] tests[l] = test def prop(g): return [rmul(g, gen) for gen in other.generators] == \ [rmul(gen, g) for gen in other.generators] return self.subgroup_search(prop, base=base, strong_gens=strong_gens, tests=tests) elif hasattr(other, '__getitem__'): gens = list(other) return self.centralizer(PermutationGroup(gens)) elif hasattr(other, 'array_form'): return self.centralizer(PermutationGroup([other])) def commutator(self, G, H): """ Return the commutator of two subgroups. Explanation =========== For a permutation group ``K`` and subgroups ``G``, ``H``, the commutator of ``G`` and ``H`` is defined as the group generated by all the commutators `[g, h] = hgh^{-1}g^{-1}` for ``g`` in ``G`` and ``h`` in ``H``. It is naturally a subgroup of ``K`` ([1], p.27). Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> S = SymmetricGroup(5) >>> A = AlternatingGroup(5) >>> G = S.commutator(S, A) >>> G.is_subgroup(A) True See Also ======== derived_subgroup Notes ===== The commutator of two subgroups `H, G` is equal to the normal closure of the commutators of all the generators, i.e. `hgh^{-1}g^{-1}` for `h` a generator of `H` and `g` a generator of `G` ([1], p.28) """ ggens = G.generators hgens = H.generators commutators = [] for ggen in ggens: for hgen in hgens: commutator = rmul(hgen, ggen, ~hgen, ~ggen) if commutator not in commutators: commutators.append(commutator) res = self.normal_closure(commutators) return res def coset_factor(self, g, factor_index=False): """Return ``G``'s (self's) coset factorization of ``g`` Explanation =========== If ``g`` is an element of ``G`` then it can be written as the product of permutations drawn from the Schreier-Sims coset decomposition, The permutations returned in ``f`` are those for which the product gives ``g``: ``g = f[n]...f[1]f[0]`` where ``n = len(B)`` and ``B = G.base``. f[i] is one of the permutations in ``self._basic_orbits[i]``. If factor_index==True, returns a tuple ``[b[0],..,b[n]]``, where ``b[i]`` belongs to ``self._basic_orbits[i]`` Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> a = Permutation(0, 1, 3, 7, 6, 4)(2, 5) >>> b = Permutation(0, 1, 3, 2)(4, 5, 7, 6) >>> G = PermutationGroup([a, b]) Define g: >>> g = Permutation(7)(1, 2, 4)(3, 6, 5) Confirm that it is an element of G: >>> G.contains(g) True Thus, it can be written as a product of factors (up to 3) drawn from u. See below that a factor from u1 and u2 and the Identity permutation have been used: >>> f = G.coset_factor(g) >>> f[2]f[1]f[0] == g True >>> f1 = G.coset_factor(g, True); f1 [0, 4, 4] >>> tr = G.basic_transversals >>> f[0] == tr[0][f1[0]] True If g is not an element of G then [] is returned: >>> c = Permutation(5, 6, 7) >>> G.coset_factor(c) [] See Also ======== sympy.combinatorics.util._strip """ if isinstance(g, (Cycle, Permutation)): g = g.list() if len(g) != self._degree: # this could either adjust the size or return [] immediately # but we don't choose between the two and just signal a possible # error raise ValueError('g should be the same size as permutations of G') I = list(range(self._degree)) basic_orbits = self.basic_orbits transversals = self._transversals factors = [] base = self.base h = g for i in range(len(base)): beta = h[base[i]] if beta == base[i]: factors.append(beta) continue if beta not in basic_orbits[i]: return [] u = transversals[i][beta]._array_form h = _af_rmul(_af_invert(u), h) factors.append(beta) if h != I: return [] if factor_index: return factors tr = self.basic_transversals factors = [tr[i][factors[i]] for i in range(len(base))] return factors def generator_product(self, g, original=False): ''' Return a list of strong generators `[s1, ..., sn]` s.t `g = sn...s1`. If `original=True`, make the list contain only the original group generators ''' product = [] if g.is_identity: return [] if g in self.strong_gens: if not original or g in self.generators: return [g] else: slp = self._strong_gens_slp[g] for s in slp: product.extend(self.generator_product(s, original=True)) return product elif g-1 in self.strong_gens: g = g-1 if not original or g in self.generators: return [g-1] else: slp = self._strong_gens_slp[g] for s in slp: product.extend(self.generator_product(s, original=True)) l = len(product) product = [product[l-i-1]-1 for i in range(l)] return product f = self.coset_factor(g, True) for i, j in enumerate(f): slp = self._transversal_slp[i][j] for s in slp: if not original: product.append(self.strong_gens[s]) else: s = self.strong_gens[s] product.extend(self.generator_product(s, original=True)) return product def coset_rank(self, g): """rank using Schreier-Sims representation. Explanation =========== The coset rank of ``g`` is the ordering number in which it appears in the lexicographic listing according to the coset decomposition The ordering is the same as in G.generate(method='coset'). If ``g`` does not belong to the group it returns None. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(0, 1, 3, 7, 6, 4)(2, 5) >>> b = Permutation(0, 1, 3, 2)(4, 5, 7, 6) >>> G = PermutationGroup([a, b]) >>> c = Permutation(7)(2, 4)(3, 5) >>> G.coset_rank(c) 16 >>> G.coset_unrank(16) (7)(2 4)(3 5) See Also ======== coset_factor """ factors = self.coset_factor(g, True) if not factors: return None rank = 0 b = 1 transversals = self._transversals base = self._base basic_orbits = self._basic_orbits for i in range(len(base)): k = factors[i] j = basic_orbits[i].index(k) rank += bj b = blen(transversals[i]) return rank def coset_unrank(self, rank, af=False): """unrank using Schreier-Sims representation coset_unrank is the inverse operation of coset_rank if 0 <= rank < order; otherwise it returns None. """ if rank < 0 or rank >= self.order(): return None base = self.base transversals = self.basic_transversals basic_orbits = self.basic_orbits m = len(base) v = [0]m for i in range(m): rank, c = divmod(rank, len(transversals[i])) v[i] = basic_orbits[i][c] a = [transversals[i][v[i]]._array_form for i in range(m)] h = _af_rmuln(a) if af: return h else: return _af_new(h) @property def degree(self): """Returns the size of the permutations in the group. Explanation =========== The number of permutations comprising the group is given by ``len(group)``; the number of permutations that can be generated by the group is given by ``group.order()``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2]) >>> G = PermutationGroup([a]) >>> G.degree 3 >>> len(G) 1 >>> G.order() 2 >>> list(G.generate()) [(2), (2)(0 1)] See Also ======== order """ return self._degree @property def identity(self): ''' Return the identity element of the permutation group. ''' return _af_new(list(range(self.degree))) @property def elements(self): """Returns all the elements of the permutation group as a set Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = PermutationGroup(Permutation(1, 3), Permutation(1, 2)) >>> p.elements {(1 2 3), (1 3 2), (1 3), (2 3), (3), (3)(1 2)} """ return set(self._elements) @property def _elements(self): """Returns all the elements of the permutation group as a list Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = PermutationGroup(Permutation(1, 3), Permutation(1, 2)) >>> p._elements [(3), (3)(1 2), (1 3), (2 3), (1 2 3), (1 3 2)] """ return list(islice(self.generate(), None)) def derived_series(self): r"""Return the derived series for the group. Explanation =========== The derived series for a group `G` is defined as `G = G_0 > G_1 > G_2 > \ldots` where `G_i = [G_{i-1}, G_{i-1}]`, i.e. `G_i` is the derived subgroup of `G_{i-1}`, for `i\in\mathbb{N}`. When we have `G_k = G_{k-1}` for some `k\in\mathbb{N}`, the series terminates. Returns ======= A list of permutation groups containing the members of the derived series in the order `G = G_0, G_1, G_2, \ldots`. Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup, DihedralGroup) >>> A = AlternatingGroup(5) >>> len(A.derived_series()) 1 >>> S = SymmetricGroup(4) >>> len(S.derived_series()) 4 >>> S.derived_series()[1].is_subgroup(AlternatingGroup(4)) True >>> S.derived_series()[2].is_subgroup(DihedralGroup(2)) True See Also ======== derived_subgroup """ res = [self] current = self next = self.derived_subgroup() while not current.is_subgroup(next): res.append(next) current = next next = next.derived_subgroup() return res def derived_subgroup(self): r"""Compute the derived subgroup. Explanation =========== The derived subgroup, or commutator subgroup is the subgroup generated by all commutators `[g, h] = hgh^{-1}g^{-1}` for `g, h\in G` ; it is equal to the normal closure of the set of commutators of the generators ([1], p.28, [11]). Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2, 4, 3]) >>> b = Permutation([0, 1, 3, 2, 4]) >>> G = PermutationGroup([a, b]) >>> C = G.derived_subgroup() >>> list(C.generate(af=True)) [[0, 1, 2, 3, 4], [0, 1, 3, 4, 2], [0, 1, 4, 2, 3]] See Also ======== derived_series """ r = self._r gens = [p._array_form for p in self.generators] set_commutators = set() degree = self._degree rng = list(range(degree)) for i in range(r): for j in range(r): p1 = gens[i] p2 = gens[j] c = list(range(degree)) for k in rng: c[p2[p1[k]]] = p1[p2[k]] ct = tuple(c) if not ct in set_commutators: set_commutators.add(ct) cms = [_af_new(p) for p in set_commutators] G2 = self.normal_closure(cms) return G2 def generate(self, method="coset", af=False): """Return iterator to generate the elements of the group. Explanation =========== Iteration is done with one of these methods:: method='coset' using the Schreier-Sims coset representation method='dimino' using the Dimino method If ``af = True`` it yields the array form of the permutations Examples ======== >>> from sympy.combinatorics import PermutationGroup >>> from sympy.combinatorics.polyhedron import tetrahedron The permutation group given in the tetrahedron object is also true groups: >>> G = tetrahedron.pgroup >>> G.is_group True Also the group generated by the permutations in the tetrahedron pgroup -- even the first two -- is a proper group: >>> H = PermutationGroup(G[0], G[1]) >>> J = PermutationGroup(list(H.generate())); J PermutationGroup([ (0 1)(2 3), (1 2 3), (1 3 2), (0 3 1), (0 2 3), (0 3)(1 2), (0 1 3), (3)(0 2 1), (0 3 2), (3)(0 1 2), (0 2)(1 3)]) >>> _.is_group True """ if method == "coset": return self.generate_schreier_sims(af) elif method == "dimino": return self.generate_dimino(af) else: raise NotImplementedError('No generation defined for %s' % method) def generate_dimino(self, af=False): """Yield group elements using Dimino's algorithm. If ``af == True`` it yields the array form of the permutations. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([0, 2, 3, 1]) >>> g = PermutationGroup([a, b]) >>> list(g.generate_dimino(af=True)) [[0, 1, 2, 3], [0, 2, 1, 3], [0, 2, 3, 1], [0, 1, 3, 2], [0, 3, 2, 1], [0, 3, 1, 2]] References ========== .. [1] The Implementation of Various Algorithms for Permutation Groups in the Computer Algebra System: AXIOM, N.J. Doye, M.Sc. Thesis """ idn = list(range(self.degree)) order = 0 element_list = [idn] set_element_list = {tuple(idn)} if af: yield idn else: yield _af_new(idn) gens = [p._array_form for p in self.generators] for i in range(len(gens)): # D elements of the subgroup G_i generated by gens[:i] D = element_list[:] N = [idn] while N: A = N N = [] for a in A: for g in gens[:i + 1]: ag = _af_rmul(a, g) if tuple(ag) not in set_element_list: # produce G_ig for d in D: order += 1 ap = _af_rmul(d, ag) if af: yield ap else: p = _af_new(ap) yield p element_list.append(ap) set_element_list.add(tuple(ap)) N.append(ap) self._order = len(element_list) def generate_schreier_sims(self, af=False): """Yield group elements using the Schreier-Sims representation in coset_rank order If ``af = True`` it yields the array form of the permutations Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([0, 2, 3, 1]) >>> g = PermutationGroup([a, b]) >>> list(g.generate_schreier_sims(af=True)) [[0, 1, 2, 3], [0, 2, 1, 3], [0, 3, 2, 1], [0, 1, 3, 2], [0, 2, 3, 1], [0, 3, 1, 2]] """ n = self._degree u = self.basic_transversals basic_orbits = self._basic_orbits if len(u) == 0: for x in self.generators: if af: yield x._array_form else: yield x return if len(u) == 1: for i in basic_orbits[0]: if af: yield u[0][i]._array_form else: yield u[0][i] return u = list(reversed(u)) basic_orbits = basic_orbits[::-1] # stg stack of group elements stg = [list(range(n))] posmax = [len(x) for x in u] n1 = len(posmax) - 1 pos = [0]n1 h = 0 while 1: # backtrack when finished iterating over coset if pos[h] >= posmax[h]: if h == 0: return pos[h] = 0 h -= 1 stg.pop() continue p = _af_rmul(u[h][basic_orbits[h][pos[h]]]._array_form, stg[-1]) pos[h] += 1 stg.append(p) h += 1 if h == n1: if af: for i in basic_orbits[-1]: p = _af_rmul(u[-1][i]._array_form, stg[-1]) yield p else: for i in basic_orbits[-1]: p = _af_rmul(u[-1][i]._array_form, stg[-1]) p1 = _af_new(p) yield p1 stg.pop() h -= 1 @property def generators(self): """Returns the generators of the group. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.generators [(1 2), (2)(0 1)] """ return self._generators def contains(self, g, strict=True): """Test if permutation ``g`` belong to self, ``G``. Explanation =========== If ``g`` is an element of ``G`` it can be written as a product of factors drawn from the cosets of ``G``'s stabilizers. To see if ``g`` is one of the actual generators defining the group use ``G.has(g)``. If ``strict`` is not ``True``, ``g`` will be resized, if necessary, to match the size of permutations in ``self``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1, 2) >>> b = Permutation(2, 3, 1) >>> G = PermutationGroup(a, b, degree=5) >>> G.contains(G[0]) # trivial check True >>> elem = Permutation([[2, 3]], size=5) >>> G.contains(elem) True >>> G.contains(Permutation(4)(0, 1, 2, 3)) False If strict is False, a permutation will be resized, if necessary: >>> H = PermutationGroup(Permutation(5)) >>> H.contains(Permutation(3)) False >>> H.contains(Permutation(3), strict=False) True To test if a given permutation is present in the group: >>> elem in G.generators False >>> G.has(elem) False See Also ======== coset_factor, sympy.core.basic.Basic.has, __contains__ """ if not isinstance(g, Permutation): return False if g.size != self.degree: if strict: return False g = Permutation(g, size=self.degree) if g in self.generators: return True return bool(self.coset_factor(g.array_form, True)) @property def is_perfect(self): """Return ``True`` if the group is perfect. A group is perfect if it equals to its derived subgroup. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1,2,3)(4,5) >>> b = Permutation(1,2,3,4,5) >>> G = PermutationGroup([a, b]) >>> G.is_perfect False """ if self._is_perfect is None: self._is_perfect = self == self.derived_subgroup() return self._is_perfect @property def is_abelian(self): """Test if the group is Abelian. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.is_abelian False >>> a = Permutation([0, 2, 1]) >>> G = PermutationGroup([a]) >>> G.is_abelian True """ if self._is_abelian is not None: return self._is_abelian self._is_abelian = True gens = [p._array_form for p in self.generators] for x in gens: for y in gens: if y <= x: continue if not _af_commutes_with(x, y): self._is_abelian = False return False return True def abelian_invariants(self): """ Returns the abelian invariants for the given group. Let ``G`` be a nontrivial finite abelian group. Then G is isomorphic to the direct product of finitely many nontrivial cyclic groups of prime-power order. Explanation =========== The prime-powers that occur as the orders of the factors are uniquely determined by G. More precisely, the primes that occur in the orders of the factors in any such decomposition of ``G`` are exactly the primes that divide ``\|G\|`` and for any such prime ``p``, if the orders of the factors that are p-groups in one such decomposition of ``G`` are ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``, then the orders of the factors that are p-groups in any such decomposition of ``G`` are ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``. The uniquely determined integers ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``, taken for all primes that divide ``\|G\|`` are called the invariants of the nontrivial group ``G`` as suggested in ([14], p. 542). Notes ===== We adopt the convention that the invariants of a trivial group are []. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.abelian_invariants() [2] >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(7) >>> G.abelian_invariants() [7] """ if self.is_trivial: return [] gns = self.generators inv = [] G = self H = G.derived_subgroup() Hgens = H.generators for p in primefactors(G.order()): ranks = [] while True: pows = [] for g in gns: elm = g*p if not H.contains(elm): pows.append(elm) K = PermutationGroup(Hgens + pows) if pows else H r = G.order()//K.order() G = K gns = pows if r == 1: break; ranks.append(multiplicity(p, r)) if ranks: pows = [1]ranks[0] for i in ranks: for j in range(0, i): pows[j] = pows[j]p inv.extend(pows) inv.sort() return inv def is_elementary(self, p): """Return ``True`` if the group is elementary abelian. An elementary abelian group is a finite abelian group, where every nontrivial element has order `p`, where `p` is a prime. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> G = PermutationGroup([a]) >>> G.is_elementary(2) True >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([3, 1, 2, 0]) >>> G = PermutationGroup([a, b]) >>> G.is_elementary(2) True >>> G.is_elementary(3) False """ return self.is_abelian and all(g.order() == p for g in self.generators) def _eval_is_alt_sym_naive(self, only_sym=False, only_alt=False): """A naive test using the group order.""" if only_sym and only_alt: raise ValueError( "Both {} and {} cannot be set to True" .format(only_sym, only_alt)) n = self.degree sym_order = 1 for i in range(2, n+1): sym_order = i order = self.order() if order == sym_order: self._is_sym = True self._is_alt = False if only_alt: return False return True elif 2order == sym_order: self._is_sym = False self._is_alt = True if only_sym: return False return True return False def _eval_is_alt_sym_monte_carlo(self, eps=0.05, perms=None): """A test using monte-carlo algorithm. Parameters ========== eps : float, optional The criterion for the incorrect ``False`` return. perms : list[Permutation], optional If explicitly given, it tests over the given candidats for testing. If ``None``, it randomly computes ``N_eps`` and chooses ``N_eps`` sample of the permutation from the group. See Also ======== _check_cycles_alt_sym """ if perms is None: n = self.degree if n < 17: c_n = 0.34 else: c_n = 0.57 d_n = (c_nlog(2))/log(n) N_eps = int(-log(eps)/d_n) perms = (self.random_pr() for i in range(N_eps)) return self._eval_is_alt_sym_monte_carlo(perms=perms) for perm in perms: if _check_cycles_alt_sym(perm): return True return False def is_alt_sym(self, eps=0.05, _random_prec=None): r"""Monte Carlo test for the symmetric/alternating group for degrees >= 8. Explanation =========== More specifically, it is one-sided Monte Carlo with the answer True (i.e., G is symmetric/alternating) guaranteed to be correct, and the answer False being incorrect with probability eps. For degree < 8, the order of the group is checked so the test is deterministic. Notes ===== The algorithm itself uses some nontrivial results from group theory and number theory: 1) If a transitive group ``G`` of degree ``n`` contains an element with a cycle of length ``n/2 < p < n-2`` for ``p`` a prime, ``G`` is the symmetric or alternating group ([1], pp. 81-82) 2) The proportion of elements in the symmetric/alternating group having the property described in 1) is approximately `\log(2)/\log(n)` ([1], p.82; [2], pp. 226-227). The helper function ``_check_cycles_alt_sym`` is used to go over the cycles in a permutation and look for ones satisfying 1). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.is_alt_sym() False See Also ======== _check_cycles_alt_sym """ if _random_prec is not None: N_eps = _random_prec['N_eps'] perms= (_random_prec[i] for i in range(N_eps)) return self._eval_is_alt_sym_monte_carlo(perms=perms) if self._is_sym or self._is_alt: return True if self._is_sym is False and self._is_alt is False: return False n = self.degree if n < 8: return self._eval_is_alt_sym_naive() elif self.is_transitive(): return self._eval_is_alt_sym_monte_carlo(eps=eps) self._is_sym, self._is_alt = False, False return False @property def is_nilpotent(self): """Test if the group is nilpotent. Explanation =========== A group `G` is nilpotent if it has a central series of finite length. Alternatively, `G` is nilpotent if its lower central series terminates with the trivial group. Every nilpotent group is also solvable ([1], p.29, [12]). Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) >>> C = CyclicGroup(6) >>> C.is_nilpotent True >>> S = SymmetricGroup(5) >>> S.is_nilpotent False See Also ======== lower_central_series, is_solvable """ if self._is_nilpotent is None: lcs = self.lower_central_series() terminator = lcs[len(lcs) - 1] gens = terminator.generators degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in gens): self._is_solvable = True self._is_nilpotent = True return True else: self._is_nilpotent = False return False else: return self._is_nilpotent def is_normal(self, gr, strict=True): """Test if ``G=self`` is a normal subgroup of ``gr``. Explanation =========== G is normal in gr if for each g2 in G, g1 in gr, ``g = g1g2g1*-1`` belongs to G It is sufficient to check this for each g1 in gr.generators and g2 in G.generators. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 2, 0]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G1 = PermutationGroup([a, Permutation([2, 0, 1])]) >>> G1.is_normal(G) True """ if not self.is_subgroup(gr, strict=strict): return False d_self = self.degree d_gr = gr.degree if self.is_trivial and (d_self == d_gr or not strict): return True if self._is_abelian: return True new_self = self.copy() if not strict and d_self != d_gr: if d_self < d_gr: new_self = PermGroup(new_self.generators + [Permutation(d_gr - 1)]) else: gr = PermGroup(gr.generators + [Permutation(d_self - 1)]) gens2 = [p._array_form for p in new_self.generators] gens1 = [p._array_form for p in gr.generators] for g1 in gens1: for g2 in gens2: p = _af_rmuln(g1, g2, _af_invert(g1)) if not new_self.coset_factor(p, True): return False return True def is_primitive(self, randomized=True): r"""Test if a group is primitive. Explanation =========== A permutation group ``G`` acting on a set ``S`` is called primitive if ``S`` contains no nontrivial block under the action of ``G`` (a block is nontrivial if its cardinality is more than ``1``). Notes ===== The algorithm is described in [1], p.83, and uses the function minimal_block to search for blocks of the form `\{0, k\}` for ``k`` ranging over representatives for the orbits of `G_0`, the stabilizer of ``0``. This algorithm has complexity `O(n^2)` where ``n`` is the degree of the group, and will perform badly if `G_0` is small. There are two implementations offered: one finds `G_0` deterministically using the function ``stabilizer``, and the other (default) produces random elements of `G_0` using ``random_stab``, hoping that they generate a subgroup of `G_0` with not too many more orbits than `G_0` (this is suggested in [1], p.83). Behavior is changed by the ``randomized`` flag. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.is_primitive() False See Also ======== minimal_block, random_stab """ if self._is_primitive is not None: return self._is_primitive if self.is_transitive() is False: return False if randomized: random_stab_gens = [] v = self.schreier_vector(0) for i in range(len(self)): random_stab_gens.append(self.random_stab(0, v)) stab = PermutationGroup(random_stab_gens) else: stab = self.stabilizer(0) orbits = stab.orbits() for orb in orbits: x = orb.pop() if x != 0 and any(e != 0 for e in self.minimal_block([0, x])): self._is_primitive = False return False self._is_primitive = True return True def minimal_blocks(self, randomized=True): ''' For a transitive group, return the list of all minimal block systems. If a group is intransitive, return `False`. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.named_groups import DihedralGroup >>> DihedralGroup(6).minimal_blocks() [[0, 1, 0, 1, 0, 1], [0, 1, 2, 0, 1, 2]] >>> G = PermutationGroup(Permutation(1,2,5)) >>> G.minimal_blocks() False See Also ======== minimal_block, is_transitive, is_primitive ''' def _number_blocks(blocks): # number the blocks of a block system # in order and return the number of # blocks and the tuple with the # reordering n = len(blocks) appeared = {} m = 0 b = [None]n for i in range(n): if blocks[i] not in appeared: appeared[blocks[i]] = m b[i] = m m += 1 else: b[i] = appeared[blocks[i]] return tuple(b), m if not self.is_transitive(): return False blocks = [] num_blocks = [] rep_blocks = [] if randomized: random_stab_gens = [] v = self.schreier_vector(0) for i in range(len(self)): random_stab_gens.append(self.random_stab(0, v)) stab = PermutationGroup(random_stab_gens) else: stab = self.stabilizer(0) orbits = stab.orbits() for orb in orbits: x = orb.pop() if x != 0: block = self.minimal_block([0, x]) num_block, m = _number_blocks(block) # a representative block (containing 0) rep = {j for j in range(self.degree) if num_block[j] == 0} # check if the system is minimal with # respect to the already discovere ones minimal = True blocks_remove_mask = [False] * len(blocks) for i, r in enumerate(rep_blocks): if len(r) > len(rep) and rep.issubset(r): # i-th block system is not minimal blocks_remove_mask[i] = True elif len(r) < len(rep) and r.issubset(rep): # the system being checked is not minimal minimal = False break # remove non-minimal representative blocks blocks = [b for i, b in enumerate(blocks) if not blocks_remove_mask[i]] num_blocks = [n for i, n in enumerate(num_blocks) if not blocks_remove_mask[i]] rep_blocks = [r for i, r in enumerate(rep_blocks) if not blocks_remove_mask[i]] if minimal and num_block not in num_blocks: blocks.append(block) num_blocks.append(num_block) rep_blocks.append(rep) return blocks @property def is_solvable(self): """Test if the group is solvable. ``G`` is solvable if its derived series terminates with the trivial group ([1], p.29). Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(3) >>> S.is_solvable True See Also ======== is_nilpotent, derived_series """ if self._is_solvable is None: if self.order() % 2 != 0: return True ds = self.derived_series() terminator = ds[len(ds) - 1] gens = terminator.generators degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in gens): self._is_solvable = True return True else: self._is_solvable = False return False else: return self._is_solvable def is_subgroup(self, G, strict=True): """Return ``True`` if all elements of ``self`` belong to ``G``. If ``strict`` is ``False`` then if ``self``'s degree is smaller than ``G``'s, the elements will be resized to have the same degree. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) Testing is strict by default: the degree of each group must be the same: >>> p = Permutation(0, 1, 2, 3, 4, 5) >>> G1 = PermutationGroup([Permutation(0, 1, 2), Permutation(0, 1)]) >>> G2 = PermutationGroup([Permutation(0, 2), Permutation(0, 1, 2)]) >>> G3 = PermutationGroup([p, p*2]) >>> assert G1.order() == G2.order() == G3.order() == 6 >>> G1.is_subgroup(G2) True >>> G1.is_subgroup(G3) False >>> G3.is_subgroup(PermutationGroup(G3[1])) False >>> G3.is_subgroup(PermutationGroup(G3[0])) True To ignore the size, set ``strict`` to ``False``: >>> S3 = SymmetricGroup(3) >>> S5 = SymmetricGroup(5) >>> S3.is_subgroup(S5, strict=False) True >>> C7 = CyclicGroup(7) >>> G = S5C7 >>> S5.is_subgroup(G, False) True >>> C7.is_subgroup(G, 0) False """ if isinstance(G, SymmetricPermutationGroup): if self.degree != G.degree: return False return True if not isinstance(G, PermutationGroup): return False if self == G or self.generators[0]==Permutation(): return True if G.order() % self.order() != 0: return False if self.degree == G.degree or \ (self.degree < G.degree and not strict): gens = self.generators else: return False return all(G.contains(g, strict=strict) for g in gens) @property def is_polycyclic(self): """Return ``True`` if a group is polycyclic. A group is polycyclic if it has a subnormal series with cyclic factors. For finite groups, this is the same as if the group is solvable. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([2, 0, 1, 3]) >>> G = PermutationGroup([a, b]) >>> G.is_polycyclic True """ return self.is_solvable def is_transitive(self, strict=True): """Test if the group is transitive. Explanation =========== A group is transitive if it has a single orbit. If ``strict`` is ``False`` the group is transitive if it has a single orbit of length different from 1. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([2, 0, 1, 3]) >>> G1 = PermutationGroup([a, b]) >>> G1.is_transitive() False >>> G1.is_transitive(strict=False) True >>> c = Permutation([2, 3, 0, 1]) >>> G2 = PermutationGroup([a, c]) >>> G2.is_transitive() True >>> d = Permutation([1, 0, 2, 3]) >>> e = Permutation([0, 1, 3, 2]) >>> G3 = PermutationGroup([d, e]) >>> G3.is_transitive() or G3.is_transitive(strict=False) False """ if self._is_transitive: # strict or not, if True then True return self._is_transitive if strict: if self._is_transitive is not None: # we only store strict=True return self._is_transitive ans = len(self.orbit(0)) == self.degree self._is_transitive = ans return ans got_orb = False for x in self.orbits(): if len(x) > 1: if got_orb: return False got_orb = True return got_orb @property def is_trivial(self): """Test if the group is the trivial group. This is true if the group contains only the identity permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> G = PermutationGroup([Permutation([0, 1, 2])]) >>> G.is_trivial True """ if self._is_trivial is None: self._is_trivial = len(self) == 1 and self[0].is_Identity return self._is_trivial def lower_central_series(self): r"""Return the lower central series for the group. The lower central series for a group `G` is the series `G = G_0 > G_1 > G_2 > \ldots` where `G_k = [G, G_{k-1}]`, i.e. every term after the first is equal to the commutator of `G` and the previous term in `G1` ([1], p.29). Returns ======= A list of permutation groups in the order `G = G_0, G_1, G_2, \ldots` Examples ======== >>> from sympy.combinatorics.named_groups import (AlternatingGroup, ... DihedralGroup) >>> A = AlternatingGroup(4) >>> len(A.lower_central_series()) 2 >>> A.lower_central_series()[1].is_subgroup(DihedralGroup(2)) True See Also ======== commutator, derived_series """ res = [self] current = self next = self.commutator(self, current) while not current.is_subgroup(next): res.append(next) current = next next = self.commutator(self, current) return res @property def max_div(self): """Maximum proper divisor of the degree of a permutation group. Explanation =========== Obviously, this is the degree divided by its minimal proper divisor (larger than ``1``, if one exists). As it is guaranteed to be prime, the ``sieve`` from ``sympy.ntheory`` is used. This function is also used as an optimization tool for the functions ``minimal_block`` and ``_union_find_merge``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> G = PermutationGroup([Permutation([0, 2, 1, 3])]) >>> G.max_div 2 See Also ======== minimal_block, _union_find_merge """ if self._max_div is not None: return self._max_div n = self.degree if n == 1: return 1 for x in sieve: if n % x == 0: d = n//x self._max_div = d return d def minimal_block(self, points): r"""For a transitive group, finds the block system generated by ``points``. Explanation =========== If a group ``G`` acts on a set ``S``, a nonempty subset ``B`` of ``S`` is called a block under the action of ``G`` if for all ``g`` in ``G`` we have ``gB = B`` (``g`` fixes ``B``) or ``gB`` and ``B`` have no common points (``g`` moves ``B`` entirely). ([1], p.23; [6]). The distinct translates ``gB`` of a block ``B`` for ``g`` in ``G`` partition the set ``S`` and this set of translates is known as a block system. Moreover, we obviously have that all blocks in the partition have the same size, hence the block size divides ``\|S\|`` ([1], p.23). A ``G``-congruence is an equivalence relation ``~`` on the set ``S`` such that ``a ~ b`` implies ``g(a) ~ g(b)`` for all ``g`` in ``G``. For a transitive group, the equivalence classes of a ``G``-congruence and the blocks of a block system are the same thing ([1], p.23). The algorithm below checks the group for transitivity, and then finds the ``G``-congruence generated by the pairs ``(p_0, p_1), (p_0, p_2), ..., (p_0,p_{k-1})`` which is the same as finding the maximal block system (i.e., the one with minimum block size) such that ``p_0, ..., p_{k-1}`` are in the same block ([1], p.83). It is an implementation of Atkinson's algorithm, as suggested in [1], and manipulates an equivalence relation on the set ``S`` using a union-find data structure. The running time is just above `O(\|points\|\|S\|)`. ([1], pp. 83-87; [7]). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.minimal_block([0, 5]) [0, 1, 2, 3, 4, 0, 1, 2, 3, 4] >>> D.minimal_block([0, 1]) [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] See Also ======== _union_find_rep, _union_find_merge, is_transitive, is_primitive """ if not self.is_transitive(): return False n = self.degree gens = self.generators # initialize the list of equivalence class representatives parents = list(range(n)) ranks = [1]n not_rep = [] k = len(points) # the block size must divide the degree of the group if k > self.max_div: return [0]n for i in range(k - 1): parents[points[i + 1]] = points[0] not_rep.append(points[i + 1]) ranks[points[0]] = k i = 0 len_not_rep = k - 1 while i < len_not_rep: gamma = not_rep[i] i += 1 for gen in gens: # find has side effects: performs path compression on the list # of representatives delta = self._union_find_rep(gamma, parents) # union has side effects: performs union by rank on the list # of representatives temp = self._union_find_merge(gen(gamma), gen(delta), ranks, parents, not_rep) if temp == -1: return [0]n len_not_rep += temp for i in range(n): # force path compression to get the final state of the equivalence # relation self._union_find_rep(i, parents) # rewrite result so that block representatives are minimal new_reps = {} return [new_reps.setdefault(r, i) for i, r in enumerate(parents)] def conjugacy_class(self, x): r"""Return the conjugacy class of an element in the group. Explanation =========== The conjugacy class of an element ``g`` in a group ``G`` is the set of elements ``x`` in ``G`` that are conjugate with ``g``, i.e. for which ``g = xax^{-1}`` for some ``a`` in ``G``. Note that conjugacy is an equivalence relation, and therefore that conjugacy classes are partitions of ``G``. For a list of all the conjugacy classes of the group, use the conjugacy_classes() method. In a permutation group, each conjugacy class corresponds to a particular `cycle structure': for example, in ``S_3``, the conjugacy classes are: the identity class, ``{()}`` * all transpositions, ``{(1 2), (1 3), (2 3)}`` * all 3-cycles, ``{(1 2 3), (1 3 2)}`` Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S3 = SymmetricGroup(3) >>> S3.conjugacy_class(Permutation(0, 1, 2)) {(0 1 2), (0 2 1)} Notes ===== This procedure computes the conjugacy class directly by finding the orbit of the element under conjugation in G. This algorithm is only feasible for permutation groups of relatively small order, but is like the orbit() function itself in that respect. """ # Ref: "Computing the conjugacy classes of finite groups"; Butler, G. # Groups '93 Galway/St Andrews; edited by Campbell, C. M. new_class = {x} last_iteration = new_class while len(last_iteration) > 0: this_iteration = set() for y in last_iteration: for s in self.generators: conjugated = s * y * (~s) if conjugated not in new_class: this_iteration.add(conjugated) new_class.update(last_iteration) last_iteration = this_iteration return new_class def conjugacy_classes(self): r"""Return the conjugacy classes of the group. Explanation =========== As described in the documentation for the .conjugacy_class() function, conjugacy is an equivalence relation on a group G which partitions the set of elements. This method returns a list of all these conjugacy classes of G. Examples ======== >>> from sympy.combinatorics import SymmetricGroup >>> SymmetricGroup(3).conjugacy_classes() [{(2)}, {(0 1 2), (0 2 1)}, {(0 2), (1 2), (2)(0 1)}] """ identity = _af_new(list(range(self.degree))) known_elements = {identity} classes = [known_elements.copy()] for x in self.generate(): if x not in known_elements: new_class = self.conjugacy_class(x) classes.append(new_class) known_elements.update(new_class) return classes def normal_closure(self, other, k=10): r"""Return the normal closure of a subgroup/set of permutations. Explanation =========== If ``S`` is a subset of a group ``G``, the normal closure of ``A`` in ``G`` is defined as the intersection of all normal subgroups of ``G`` that contain ``A`` ([1], p.14). Alternatively, it is the group generated by the conjugates ``x^{-1}yx`` for ``x`` a generator of ``G`` and ``y`` a generator of the subgroup ``\left\langle S\right\rangle`` generated by ``S`` (for some chosen generating set for ``\left\langle S\right\rangle``) ([1], p.73). Parameters ========== other a subgroup/list of permutations/single permutation k an implementation-specific parameter that determines the number of conjugates that are adjoined to ``other`` at once Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup, AlternatingGroup) >>> S = SymmetricGroup(5) >>> C = CyclicGroup(5) >>> G = S.normal_closure(C) >>> G.order() 60 >>> G.is_subgroup(AlternatingGroup(5)) True See Also ======== commutator, derived_subgroup, random_pr Notes ===== The algorithm is described in [1], pp. 73-74; it makes use of the generation of random elements for permutation groups by the product replacement algorithm. """ if hasattr(other, 'generators'): degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in other.generators): return other Z = PermutationGroup(other.generators[:]) base, strong_gens = Z.schreier_sims_incremental() strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, basic_transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) self._random_pr_init(r=10, n=20) _loop = True while _loop: Z._random_pr_init(r=10, n=10) for i in range(k): g = self.random_pr() h = Z.random_pr() conj = h^g res = _strip(conj, base, basic_orbits, basic_transversals) if res[0] != identity or res[1] != len(base) + 1: gens = Z.generators gens.append(conj) Z = PermutationGroup(gens) strong_gens.append(conj) temp_base, temp_strong_gens = \ Z.schreier_sims_incremental(base, strong_gens) base, strong_gens = temp_base, temp_strong_gens strong_gens_distr = \ _distribute_gens_by_base(base, strong_gens) basic_orbits, basic_transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) _loop = False for g in self.generators: for h in Z.generators: conj = h^g res = _strip(conj, base, basic_orbits, basic_transversals) if res[0] != identity or res[1] != len(base) + 1: _loop = True break if _loop: break return Z elif hasattr(other, '__getitem__'): return self.normal_closure(PermutationGroup(other)) elif hasattr(other, 'array_form'): return self.normal_closure(PermutationGroup([other])) def orbit(self, alpha, action='tuples'): r"""Compute the orbit of alpha `\{g(\alpha) \| g \in G\}` as a set. Explanation =========== The time complexity of the algorithm used here is `O(\|Orb\|r)` where `\|Orb\|` is the size of the orbit and ``r`` is the number of generators of the group. For a more detailed analysis, see [1], p.78, [2], pp. 19-21. Here alpha can be a single point, or a list of points. If alpha is a single point, the ordinary orbit is computed. if alpha is a list of points, there are three available options: 'union' - computes the union of the orbits of the points in the list 'tuples' - computes the orbit of the list interpreted as an ordered tuple under the group action ( i.e., g((1,2,3)) = (g(1), g(2), g(3)) ) 'sets' - computes the orbit of the list interpreted as a sets Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 2, 0, 4, 5, 6, 3]) >>> G = PermutationGroup([a]) >>> G.orbit(0) {0, 1, 2} >>> G.orbit([0, 4], 'union') {0, 1, 2, 3, 4, 5, 6} See Also ======== orbit_transversal """ return _orbit(self.degree, self.generators, alpha, action) def orbit_rep(self, alpha, beta, schreier_vector=None): """Return a group element which sends ``alpha`` to ``beta``. Explanation =========== If ``beta`` is not in the orbit of ``alpha``, the function returns ``False``. This implementation makes use of the schreier vector. For a proof of correctness, see [1], p.80 Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> G = AlternatingGroup(5) >>> G.orbit_rep(0, 4) (0 4 1 2 3) See Also ======== schreier_vector """ if schreier_vector is None: schreier_vector = self.schreier_vector(alpha) if schreier_vector[beta] is None: return False k = schreier_vector[beta] gens = [x._array_form for x in self.generators] a = [] while k != -1: a.append(gens[k]) beta = gens[k].index(beta) # beta = (~gens[k])(beta) k = schreier_vector[beta] if a: return _af_new(_af_rmuln(a)) else: return _af_new(list(range(self._degree))) def orbit_transversal(self, alpha, pairs=False): r"""Computes a transversal for the orbit of ``alpha`` as a set. Explanation =========== For a permutation group `G`, a transversal for the orbit `Orb = \{g(\alpha) \| g \in G\}` is a set `\{g_\beta \| g_\beta(\alpha) = \beta\}` for `\beta \in Orb`. Note that there may be more than one possible transversal. If ``pairs`` is set to ``True``, it returns the list of pairs `(\beta, g_\beta)`. For a proof of correctness, see [1], p.79 Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> G.orbit_transversal(0) [(5), (0 1 2 3 4 5), (0 5)(1 4)(2 3), (0 2 4)(1 3 5), (5)(0 4)(1 3), (0 3)(1 4)(2 5)] See Also ======== orbit """ return _orbit_transversal(self._degree, self.generators, alpha, pairs) def orbits(self, rep=False): """Return the orbits of ``self``, ordered according to lowest element in each orbit. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1, 5)(2, 3)(4, 0, 6) >>> b = Permutation(1, 5)(3, 4)(2, 6, 0) >>> G = PermutationGroup([a, b]) >>> G.orbits() [{0, 2, 3, 4, 6}, {1, 5}] """ return _orbits(self._degree, self._generators) def order(self): """Return the order of the group: the number of permutations that can be generated from elements of the group. The number of permutations comprising the group is given by ``len(group)``; the length of each permutation in the group is given by ``group.size``. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2]) >>> G = PermutationGroup([a]) >>> G.degree 3 >>> len(G) 1 >>> G.order() 2 >>> list(G.generate()) [(2), (2)(0 1)] >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.order() 6 See Also ======== degree """ if self._order is not None: return self._order if self._is_sym: n = self._degree self._order = factorial(n) return self._order if self._is_alt: n = self._degree self._order = factorial(n)/2 return self._order basic_transversals = self.basic_transversals m = 1 for x in basic_transversals: m = len(x) self._order = m return m def index(self, H): """ Returns the index of a permutation group. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1,2,3) >>> b =Permutation(3) >>> G = PermutationGroup([a]) >>> H = PermutationGroup([b]) >>> G.index(H) 3 """ if H.is_subgroup(self): return self.order()//H.order() @property def is_symmetric(self): """Return ``True`` if the group is symmetric. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> g = SymmetricGroup(5) >>> g.is_symmetric True >>> from sympy.combinatorics import Permutation, PermutationGroup >>> g = PermutationGroup( ... Permutation(0, 1, 2, 3, 4), ... Permutation(2, 3)) >>> g.is_symmetric True Notes ===== This uses a naive test involving the computation of the full group order. If you need more quicker taxonomy for large groups, you can use :meth:`PermutationGroup.is_alt_sym`. However, :meth:`PermutationGroup.is_alt_sym` may not be accurate and is not able to distinguish between an alternating group and a symmetric group. See Also ======== is_alt_sym """ _is_sym = self._is_sym if _is_sym is not None: return _is_sym n = self.degree if n >= 8: if self.is_transitive(): _is_alt_sym = self._eval_is_alt_sym_monte_carlo() if _is_alt_sym: if any(g.is_odd for g in self.generators): self._is_sym, self._is_alt = True, False return True self._is_sym, self._is_alt = False, True return False return self._eval_is_alt_sym_naive(only_sym=True) self._is_sym, self._is_alt = False, False return False return self._eval_is_alt_sym_naive(only_sym=True) @property def is_alternating(self): """Return ``True`` if the group is alternating. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> g = AlternatingGroup(5) >>> g.is_alternating True >>> from sympy.combinatorics import Permutation, PermutationGroup >>> g = PermutationGroup( ... Permutation(0, 1, 2, 3, 4), ... Permutation(2, 3, 4)) >>> g.is_alternating True Notes ===== This uses a naive test involving the computation of the full group order. If you need more quicker taxonomy for large groups, you can use :meth:`PermutationGroup.is_alt_sym`. However, :meth:`PermutationGroup.is_alt_sym` may not be accurate and is not able to distinguish between an alternating group and a symmetric group. See Also ======== is_alt_sym """ _is_alt = self._is_alt if _is_alt is not None: return _is_alt n = self.degree if n >= 8: if self.is_transitive(): _is_alt_sym = self._eval_is_alt_sym_monte_carlo() if _is_alt_sym: if all(g.is_even for g in self.generators): self._is_sym, self._is_alt = False, True return True self._is_sym, self._is_alt = True, False return False return self._eval_is_alt_sym_naive(only_alt=True) self._is_sym, self._is_alt = False, False return False return self._eval_is_alt_sym_naive(only_alt=True) @classmethod def _distinct_primes_lemma(cls, primes): """Subroutine to test if there is only one cyclic group for the order.""" primes = sorted(primes) l = len(primes) for i in range(l): for j in range(i+1, l): if primes[j] % primes[i] == 1: return None return True @property def is_cyclic(self): r""" Return ``True`` if the group is Cyclic. Examples ======== >>> from sympy.combinatorics.named_groups import AbelianGroup >>> G = AbelianGroup(3, 4) >>> G.is_cyclic True >>> G = AbelianGroup(4, 4) >>> G.is_cyclic False Notes ===== If the order of a group $n$ can be factored into the distinct primes $p_1, p_2, ... , p_s$ and if .. math:: \forall i, j \in \{1, 2, \ldots, s \}: p_i \not \equiv 1 \pmod {p_j} holds true, there is only one group of the order $n$ which is a cyclic group. [1]_ This is a generalization of the lemma that the group of order $15, 35, ...$ are cyclic. And also, these additional lemmas can be used to test if a group is cyclic if the order of the group is already found. - If the group is abelian and the order of the group is square-free, the group is cyclic. - If the order of the group is less than $6$ and is not $4$, the group is cyclic. - If the order of the group is prime, the group is cyclic. References ========== .. [1] 1978: John S. Rose: A Course on Group Theory, Introduction to Finite Group Theory: 1.4 """ if self._is_cyclic is not None: return self._is_cyclic if len(self.generators) == 1: self._is_cyclic = True self._is_abelian = True return True if self._is_abelian is False: self._is_cyclic = False return False order = self.order() if order < 6: self._is_abelian == True if order != 4: self._is_cyclic == True return True factors = factorint(order) if all(v == 1 for v in factors.values()): if self._is_abelian: self._is_cyclic = True return True primes = list(factors.keys()) if PermutationGroup._distinct_primes_lemma(primes) is True: self._is_cyclic = True self._is_abelian = True return True for p in factors: pgens = [] for g in self.generators: pgens.append(gp) if self.index(self.subgroup(pgens)) != p: self._is_cyclic = False return False self._is_cyclic = True self._is_abelian = True return True def pointwise_stabilizer(self, points, incremental=True): r"""Return the pointwise stabilizer for a set of points. Explanation =========== For a permutation group `G` and a set of points `\{p_1, p_2,\ldots, p_k\}`, the pointwise stabilizer of `p_1, p_2, \ldots, p_k` is defined as `G_{p_1,\ldots, p_k} = \{g\in G \| g(p_i) = p_i \forall i\in\{1, 2,\ldots,k\}\}` ([1],p20). It is a subgroup of `G`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(7) >>> Stab = S.pointwise_stabilizer([2, 3, 5]) >>> Stab.is_subgroup(S.stabilizer(2).stabilizer(3).stabilizer(5)) True See Also ======== stabilizer, schreier_sims_incremental Notes ===== When incremental == True, rather than the obvious implementation using successive calls to ``.stabilizer()``, this uses the incremental Schreier-Sims algorithm to obtain a base with starting segment - the given points. """ if incremental: base, strong_gens = self.schreier_sims_incremental(base=points) stab_gens = [] degree = self.degree for gen in strong_gens: if [gen(point) for point in points] == points: stab_gens.append(gen) if not stab_gens: stab_gens = _af_new(list(range(degree))) return PermutationGroup(stab_gens) else: gens = self._generators degree = self.degree for x in points: gens = _stabilizer(degree, gens, x) return PermutationGroup(gens) def make_perm(self, n, seed=None): """ Multiply ``n`` randomly selected permutations from pgroup together, starting with the identity permutation. If ``n`` is a list of integers, those integers will be used to select the permutations and they will be applied in L to R order: make_perm((A, B, C)) will give CBA(I) where I is the identity permutation. ``seed`` is used to set the seed for the random selection of permutations from pgroup. If this is a list of integers, the corresponding permutations from pgroup will be selected in the order give. This is mainly used for testing purposes. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a, b = [Permutation([1, 0, 3, 2]), Permutation([1, 3, 0, 2])] >>> G = PermutationGroup([a, b]) >>> G.make_perm(1, [0]) (0 1)(2 3) >>> G.make_perm(3, [0, 1, 0]) (0 2 3 1) >>> G.make_perm([0, 1, 0]) (0 2 3 1) See Also ======== random """ if is_sequence(n): if seed is not None: raise ValueError('If n is a sequence, seed should be None') n, seed = len(n), n else: try: n = int(n) except TypeError: raise ValueError('n must be an integer or a sequence.') randrange = _randrange(seed) # start with the identity permutation result = Permutation(list(range(self.degree))) m = len(self) for i in range(n): p = self[randrange(m)] result = rmul(result, p) return result def random(self, af=False): """Return a random group element """ rank = randrange(self.order()) return self.coset_unrank(rank, af) def random_pr(self, gen_count=11, iterations=50, _random_prec=None): """Return a random group element using product replacement. Explanation =========== For the details of the product replacement algorithm, see ``_random_pr_init`` In ``random_pr`` the actual 'product replacement' is performed. Notice that if the attribute ``_random_gens`` is empty, it needs to be initialized by ``_random_pr_init``. See Also ======== _random_pr_init """ if self._random_gens == []: self._random_pr_init(gen_count, iterations) random_gens = self._random_gens r = len(random_gens) - 1 # handle randomized input for testing purposes if _random_prec is None: s = randrange(r) t = randrange(r - 1) if t == s: t = r - 1 x = choice([1, 2]) e = choice([-1, 1]) else: s = _random_prec['s'] t = _random_prec['t'] if t == s: t = r - 1 x = _random_prec['x'] e = _random_prec['e'] if x == 1: random_gens[s] = _af_rmul(random_gens[s], _af_pow(random_gens[t], e)) random_gens[r] = _af_rmul(random_gens[r], random_gens[s]) else: random_gens[s] = _af_rmul(_af_pow(random_gens[t], e), random_gens[s]) random_gens[r] = _af_rmul(random_gens[s], random_gens[r]) return _af_new(random_gens[r]) def random_stab(self, alpha, schreier_vector=None, _random_prec=None): """Random element from the stabilizer of ``alpha``. The schreier vector for ``alpha`` is an optional argument used for speeding up repeated calls. The algorithm is described in [1], p.81 See Also ======== random_pr, orbit_rep """ if schreier_vector is None: schreier_vector = self.schreier_vector(alpha) if _random_prec is None: rand = self.random_pr() else: rand = _random_prec['rand'] beta = rand(alpha) h = self.orbit_rep(alpha, beta, schreier_vector) return rmul(~h, rand) def schreier_sims(self): """Schreier-Sims algorithm. Explanation =========== It computes the generators of the chain of stabilizers `G > G_{b_1} > .. > G_{b1,..,b_r} > 1` in which `G_{b_1,..,b_i}` stabilizes `b_1,..,b_i`, and the corresponding ``s`` cosets. An element of the group can be written as the product `h_1..h_s`. We use the incremental Schreier-Sims algorithm. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.schreier_sims() >>> G.basic_transversals [{0: (2)(0 1), 1: (2), 2: (1 2)}, {0: (2), 2: (0 2)}] """ if self._transversals: return self._schreier_sims() return def _schreier_sims(self, base=None): schreier = self.schreier_sims_incremental(base=base, slp_dict=True) base, strong_gens = schreier[:2] self._base = base self._strong_gens = strong_gens self._strong_gens_slp = schreier[2] if not base: self._transversals = [] self._basic_orbits = [] return strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, transversals, slps = _orbits_transversals_from_bsgs(base,\ strong_gens_distr, slp=True) # rewrite the indices stored in slps in terms of strong_gens for i, slp in enumerate(slps): gens = strong_gens_distr[i] for k in slp: slp[k] = [strong_gens.index(gens[s]) for s in slp[k]] self._transversals = transversals self._basic_orbits = [sorted(x) for x in basic_orbits] self._transversal_slp = slps def schreier_sims_incremental(self, base=None, gens=None, slp_dict=False): """Extend a sequence of points and generating set to a base and strong generating set. Parameters ========== base The sequence of points to be extended to a base. Optional parameter with default value ``[]``. gens The generating set to be extended to a strong generating set relative to the base obtained. Optional parameter with default value ``self.generators``. slp_dict If `True`, return a dictionary `{g: gens}` for each strong generator `g` where `gens` is a list of strong generators coming before `g` in `strong_gens`, such that the product of the elements of `gens` is equal to `g`. Returns ======= (base, strong_gens) ``base`` is the base obtained, and ``strong_gens`` is the strong generating set relative to it. The original parameters ``base``, ``gens`` remain unchanged. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> A = AlternatingGroup(7) >>> base = [2, 3] >>> seq = [2, 3] >>> base, strong_gens = A.schreier_sims_incremental(base=seq) >>> _verify_bsgs(A, base, strong_gens) True >>> base[:2] [2, 3] Notes ===== This version of the Schreier-Sims algorithm runs in polynomial time. There are certain assumptions in the implementation - if the trivial group is provided, ``base`` and ``gens`` are returned immediately, as any sequence of points is a base for the trivial group. If the identity is present in the generators ``gens``, it is removed as it is a redundant generator. The implementation is described in [1], pp. 90-93. See Also ======== schreier_sims, schreier_sims_random """ if base is None: base = [] if gens is None: gens = self.generators[:] degree = self.degree id_af = list(range(degree)) # handle the trivial group if len(gens) == 1 and gens[0].is_Identity: if slp_dict: return base, gens, {gens[0]: [gens[0]]} return base, gens # prevent side effects _base, _gens = base[:], gens[:] # remove the identity as a generator _gens = [x for x in _gens if not x.is_Identity] # make sure no generator fixes all base points for gen in _gens: if all(x == gen._array_form[x] for x in _base): for new in id_af: if gen._array_form[new] != new: break else: assert None # can this ever happen? _base.append(new) # distribute generators according to basic stabilizers strong_gens_distr = _distribute_gens_by_base(_base, _gens) strong_gens_slp = [] # initialize the basic stabilizers, basic orbits and basic transversals orbs = {} transversals = {} slps = {} base_len = len(_base) for i in range(base_len): transversals[i], slps[i] = _orbit_transversal(degree, strong_gens_distr[i], _base[i], pairs=True, af=True, slp=True) transversals[i] = dict(transversals[i]) orbs[i] = list(transversals[i].keys()) # main loop: amend the stabilizer chain until we have generators # for all stabilizers i = base_len - 1 while i >= 0: # this flag is used to continue with the main loop from inside # a nested loop continue_i = False # test the generators for being a strong generating set db = {} for beta, u_beta in list(transversals[i].items()): for j, gen in enumerate(strong_gens_distr[i]): gb = gen._array_form[beta] u1 = transversals[i][gb] g1 = _af_rmul(gen._array_form, u_beta) slp = [(i, g) for g in slps[i][beta]] slp = [(i, j)] + slp if g1 != u1: # test if the schreier generator is in the i+1-th # would-be basic stabilizer y = True try: u1_inv = db[gb] except KeyError: u1_inv = db[gb] = _af_invert(u1) schreier_gen = _af_rmul(u1_inv, g1) u1_inv_slp = slps[i][gb][:] u1_inv_slp.reverse() u1_inv_slp = [(i, (g,)) for g in u1_inv_slp] slp = u1_inv_slp + slp h, j, slp = _strip_af(schreier_gen, _base, orbs, transversals, i, slp=slp, slps=slps) if j <= base_len: # new strong generator h at level j y = False elif h: # h fixes all base points y = False moved = 0 while h[moved] == moved: moved += 1 _base.append(moved) base_len += 1 strong_gens_distr.append([]) if y is False: # if a new strong generator is found, update the # data structures and start over h = _af_new(h) strong_gens_slp.append((h, slp)) for l in range(i + 1, j): strong_gens_distr[l].append(h) transversals[l], slps[l] =\ _orbit_transversal(degree, strong_gens_distr[l], _base[l], pairs=True, af=True, slp=True) transversals[l] = dict(transversals[l]) orbs[l] = list(transversals[l].keys()) i = j - 1 # continue main loop using the flag continue_i = True if continue_i is True: break if continue_i is True: break if continue_i is True: continue i -= 1 strong_gens = _gens[:] if slp_dict: # create the list of the strong generators strong_gens and # rewrite the indices of strong_gens_slp in terms of the # elements of strong_gens for k, slp in strong_gens_slp: strong_gens.append(k) for i in range(len(slp)): s = slp[i] if isinstance(s[1], tuple): slp[i] = strong_gens_distr[s[0]][s[1][0]]-1 else: slp[i] = strong_gens_distr[s[0]][s[1]] strong_gens_slp = dict(strong_gens_slp) # add the original generators for g in _gens: strong_gens_slp[g] = [g] return (_base, strong_gens, strong_gens_slp) strong_gens.extend([k for k, _ in strong_gens_slp]) return _base, strong_gens def schreier_sims_random(self, base=None, gens=None, consec_succ=10, _random_prec=None): r"""Randomized Schreier-Sims algorithm. Explanation =========== The randomized Schreier-Sims algorithm takes the sequence ``base`` and the generating set ``gens``, and extends ``base`` to a base, and ``gens`` to a strong generating set relative to that base with probability of a wrong answer at most `2^{-consec\_succ}`, provided the random generators are sufficiently random. Parameters ========== base The sequence to be extended to a base. gens The generating set to be extended to a strong generating set. consec_succ The parameter defining the probability of a wrong answer. _random_prec An internal parameter used for testing purposes. Returns ======= (base, strong_gens) ``base`` is the base and ``strong_gens`` is the strong generating set relative to it. Examples ======== >>> from sympy.combinatorics.testutil import _verify_bsgs >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(5) >>> base, strong_gens = S.schreier_sims_random(consec_succ=5) >>> _verify_bsgs(S, base, strong_gens) #doctest: +SKIP True Notes ===== The algorithm is described in detail in [1], pp. 97-98. It extends the orbits ``orbs`` and the permutation groups ``stabs`` to basic orbits and basic stabilizers for the base and strong generating set produced in the end. The idea of the extension process is to "sift" random group elements through the stabilizer chain and amend the stabilizers/orbits along the way when a sift is not successful. The helper function ``_strip`` is used to attempt to decompose a random group element according to the current state of the stabilizer chain and report whether the element was fully decomposed (successful sift) or not (unsuccessful sift). In the latter case, the level at which the sift failed is reported and used to amend ``stabs``, ``base``, ``gens`` and ``orbs`` accordingly. The halting condition is for ``consec_succ`` consecutive successful sifts to pass. This makes sure that the current ``base`` and ``gens`` form a BSGS with probability at least `1 - 1/\text{consec\_succ}`. See Also ======== schreier_sims """ if base is None: base = [] if gens is None: gens = self.generators base_len = len(base) n = self.degree # make sure no generator fixes all base points for gen in gens: if all(gen(x) == x for x in base): new = 0 while gen._array_form[new] == new: new += 1 base.append(new) base_len += 1 # distribute generators according to basic stabilizers strong_gens_distr = _distribute_gens_by_base(base, gens) # initialize the basic stabilizers, basic transversals and basic orbits transversals = {} orbs = {} for i in range(base_len): transversals[i] = dict(_orbit_transversal(n, strong_gens_distr[i], base[i], pairs=True)) orbs[i] = list(transversals[i].keys()) # initialize the number of consecutive elements sifted c = 0 # start sifting random elements while the number of consecutive sifts # is less than consec_succ while c < consec_succ: if _random_prec is None: g = self.random_pr() else: g = _random_prec['g'].pop() h, j = _strip(g, base, orbs, transversals) y = True # determine whether a new base point is needed if j <= base_len: y = False elif not h.is_Identity: y = False moved = 0 while h(moved) == moved: moved += 1 base.append(moved) base_len += 1 strong_gens_distr.append([]) # if the element doesn't sift, amend the strong generators and # associated stabilizers and orbits if y is False: for l in range(1, j): strong_gens_distr[l].append(h) transversals[l] = dict(_orbit_transversal(n, strong_gens_distr[l], base[l], pairs=True)) orbs[l] = list(transversals[l].keys()) c = 0 else: c += 1 # build the strong generating set strong_gens = strong_gens_distr[0][:] for gen in strong_gens_distr[1]: if gen not in strong_gens: strong_gens.append(gen) return base, strong_gens def schreier_vector(self, alpha): """Computes the schreier vector for ``alpha``. Explanation =========== The Schreier vector efficiently stores information about the orbit of ``alpha``. It can later be used to quickly obtain elements of the group that send ``alpha`` to a particular element in the orbit. Notice that the Schreier vector depends on the order in which the group generators are listed. For a definition, see [3]. Since list indices start from zero, we adopt the convention to use "None" instead of 0 to signify that an element doesn't belong to the orbit. For the algorithm and its correctness, see [2], pp.78-80. Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([2, 4, 6, 3, 1, 5, 0]) >>> b = Permutation([0, 1, 3, 5, 4, 6, 2]) >>> G = PermutationGroup([a, b]) >>> G.schreier_vector(0) [-1, None, 0, 1, None, 1, 0] See Also ======== orbit """ n = self.degree v = [None]n v[alpha] = -1 orb = [alpha] used = [False]n used[alpha] = True gens = self.generators r = len(gens) for b in orb: for i in range(r): temp = gens[i]._array_form[b] if used[temp] is False: orb.append(temp) used[temp] = True v[temp] = i return v def stabilizer(self, alpha): r"""Return the stabilizer subgroup of ``alpha``. Explanation =========== The stabilizer of `\alpha` is the group `G_\alpha = \{g \in G \| g(\alpha) = \alpha\}`. For a proof of correctness, see [1], p.79. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> G.stabilizer(5) PermutationGroup([ (5)(0 4)(1 3)]) See Also ======== orbit """ return PermGroup(_stabilizer(self._degree, self._generators, alpha)) @property def strong_gens(self): r"""Return a strong generating set from the Schreier-Sims algorithm. Explanation =========== A generating set `S = \{g_1, g_2, ..., g_t\}` for a permutation group `G` is a strong generating set relative to the sequence of points (referred to as a "base") `(b_1, b_2, ..., b_k)` if, for `1 \leq i \leq k` we have that the intersection of the pointwise stabilizer `G^{(i+1)} := G_{b_1, b_2, ..., b_i}` with `S` generates the pointwise stabilizer `G^{(i+1)}`. The concepts of a base and strong generating set and their applications are discussed in depth in [1], pp. 87-89 and [2], pp. 55-57. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> D.strong_gens [(0 1 2 3), (0 3)(1 2), (1 3)] >>> D.base [0, 1] See Also ======== base, basic_transversals, basic_orbits, basic_stabilizers """ if self._strong_gens == []: self.schreier_sims() return self._strong_gens def subgroup(self, gens): """ Return the subgroup generated by `gens` which is a list of elements of the group """ if not all([g in self for g in gens]): raise ValueError("The group doesn't contain the supplied generators") G = PermutationGroup(gens) return G def subgroup_search(self, prop, base=None, strong_gens=None, tests=None, init_subgroup=None): """Find the subgroup of all elements satisfying the property ``prop``. Explanation =========== This is done by a depth-first search with respect to base images that uses several tests to prune the search tree. Parameters ========== prop The property to be used. Has to be callable on group elements and always return ``True`` or ``False``. It is assumed that all group elements satisfying ``prop`` indeed form a subgroup. base A base for the supergroup. strong_gens A strong generating set for the supergroup. tests A list of callables of length equal to the length of ``base``. These are used to rule out group elements by partial base images, so that ``tests[l](g)`` returns False if the element ``g`` is known not to satisfy prop base on where g sends the first ``l + 1`` base points. init_subgroup if a subgroup of the sought group is known in advance, it can be passed to the function as this parameter. Returns ======= res The subgroup of all elements satisfying ``prop``. The generating set for this group is guaranteed to be a strong generating set relative to the base ``base``. Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.testutil import _verify_bsgs >>> S = SymmetricGroup(7) >>> prop_even = lambda x: x.is_even >>> base, strong_gens = S.schreier_sims_incremental() >>> G = S.subgroup_search(prop_even, base=base, strong_gens=strong_gens) >>> G.is_subgroup(AlternatingGroup(7)) True >>> _verify_bsgs(G, base, G.generators) True Notes ===== This function is extremely lengthy and complicated and will require some careful attention. The implementation is described in [1], pp. 114-117, and the comments for the code here follow the lines of the pseudocode in the book for clarity. The complexity is exponential in general, since the search process by itself visits all members of the supergroup. However, there are a lot of tests which are used to prune the search tree, and users can define their own tests via the ``tests`` parameter, so in practice, and for some computations, it's not terrible. A crucial part in the procedure is the frequent base change performed (this is line 11 in the pseudocode) in order to obtain a new basic stabilizer. The book mentiones that this can be done by using ``.baseswap(...)``, however the current implementation uses a more straightforward way to find the next basic stabilizer - calling the function ``.stabilizer(...)`` on the previous basic stabilizer. """ # initialize BSGS and basic group properties def get_reps(orbits): # get the minimal element in the base ordering return [min(orbit, key = lambda x: base_ordering[x]) \ for orbit in orbits] def update_nu(l): temp_index = len(basic_orbits[l]) + 1 -\ len(res_basic_orbits_init_base[l]) # this corresponds to the element larger than all points if temp_index >= len(sorted_orbits[l]): nu[l] = base_ordering[degree] else: nu[l] = sorted_orbits[l][temp_index] if base is None: base, strong_gens = self.schreier_sims_incremental() base_len = len(base) degree = self.degree identity = _af_new(list(range(degree))) base_ordering = _base_ordering(base, degree) # add an element larger than all points base_ordering.append(degree) # add an element smaller than all points base_ordering.append(-1) # compute BSGS-related structures strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, transversals = _orbits_transversals_from_bsgs(base, strong_gens_distr) # handle subgroup initialization and tests if init_subgroup is None: init_subgroup = PermutationGroup([identity]) if tests is None: trivial_test = lambda x: True tests = [] for i in range(base_len): tests.append(trivial_test) # line 1: more initializations. res = init_subgroup f = base_len - 1 l = base_len - 1 # line 2: set the base for K to the base for G res_base = base[:] # line 3: compute BSGS and related structures for K res_base, res_strong_gens = res.schreier_sims_incremental( base=res_base) res_strong_gens_distr = _distribute_gens_by_base(res_base, res_strong_gens) res_generators = res.generators res_basic_orbits_init_base = \ [_orbit(degree, res_strong_gens_distr[i], res_base[i])\ for i in range(base_len)] # initialize orbit representatives orbit_reps = [None]base_len # line 4: orbit representatives for f-th basic stabilizer of K orbits = _orbits(degree, res_strong_gens_distr[f]) orbit_reps[f] = get_reps(orbits) # line 5: remove the base point from the representatives to avoid # getting the identity element as a generator for K orbit_reps[f].remove(base[f]) # line 6: more initializations c = [0]base_len u = [identity]base_len sorted_orbits = [None]base_len for i in range(base_len): sorted_orbits[i] = basic_orbits[i][:] sorted_orbits[i].sort(key=lambda point: base_ordering[point]) # line 7: initializations mu = [None]base_len nu = [None]base_len # this corresponds to the element smaller than all points mu[l] = degree + 1 update_nu(l) # initialize computed words computed_words = [identity]base_len # line 8: main loop while True: # apply all the tests while l < base_len - 1 and \ computed_words[l](base[l]) in orbit_reps[l] and \ base_ordering[mu[l]] < \ base_ordering[computed_words[l](base[l])] < \ base_ordering[nu[l]] and \ tests[l](computed_words): # line 11: change the (partial) base of K new_point = computed_words[l](base[l]) res_base[l] = new_point new_stab_gens = _stabilizer(degree, res_strong_gens_distr[l], new_point) res_strong_gens_distr[l + 1] = new_stab_gens # line 12: calculate minimal orbit representatives for the # l+1-th basic stabilizer orbits = _orbits(degree, new_stab_gens) orbit_reps[l + 1] = get_reps(orbits) # line 13: amend sorted orbits l += 1 temp_orbit = [computed_words[l - 1](point) for point in basic_orbits[l]] temp_orbit.sort(key=lambda point: base_ordering[point]) sorted_orbits[l] = temp_orbit # lines 14 and 15: update variables used minimality tests new_mu = degree + 1 for i in range(l): if base[l] in res_basic_orbits_init_base[i]: candidate = computed_words[i](base[i]) if base_ordering[candidate] > base_ordering[new_mu]: new_mu = candidate mu[l] = new_mu update_nu(l) # line 16: determine the new transversal element c[l] = 0 temp_point = sorted_orbits[l][c[l]] gamma = computed_words[l - 1]._array_form.index(temp_point) u[l] = transversals[l][gamma] # update computed words computed_words[l] = rmul(computed_words[l - 1], u[l]) # lines 17 & 18: apply the tests to the group element found g = computed_words[l] temp_point = g(base[l]) if l == base_len - 1 and \ base_ordering[mu[l]] < \ base_ordering[temp_point] < base_ordering[nu[l]] and \ temp_point in orbit_reps[l] and \ tests[l](computed_words) and \ prop(g): # line 19: reset the base of K res_generators.append(g) res_base = base[:] # line 20: recalculate basic orbits (and transversals) res_strong_gens.append(g) res_strong_gens_distr = _distribute_gens_by_base(res_base, res_strong_gens) res_basic_orbits_init_base = \ [_orbit(degree, res_strong_gens_distr[i], res_base[i]) \ for i in range(base_len)] # line 21: recalculate orbit representatives # line 22: reset the search depth orbit_reps[f] = get_reps(orbits) l = f # line 23: go up the tree until in the first branch not fully # searched while l >= 0 and c[l] == len(basic_orbits[l]) - 1: l = l - 1 # line 24: if the entire tree is traversed, return K if l == -1: return PermutationGroup(res_generators) # lines 25-27: update orbit representatives if l < f: # line 26 f = l c[l] = 0 # line 27 temp_orbits = _orbits(degree, res_strong_gens_distr[f]) orbit_reps[f] = get_reps(temp_orbits) # line 28: update variables used for minimality testing mu[l] = degree + 1 temp_index = len(basic_orbits[l]) + 1 - \ len(res_basic_orbits_init_base[l]) if temp_index >= len(sorted_orbits[l]): nu[l] = base_ordering[degree] else: nu[l] = sorted_orbits[l][temp_index] # line 29: set the next element from the current branch and update # accordingly c[l] += 1 if l == 0: gamma = sorted_orbits[l][c[l]] else: gamma = computed_words[l - 1]._array_form.index(sorted_orbits[l][c[l]]) u[l] = transversals[l][gamma] if l == 0: computed_words[l] = u[l] else: computed_words[l] = rmul(computed_words[l - 1], u[l]) @property def transitivity_degree(self): r"""Compute the degree of transitivity of the group. Explanation =========== A permutation group `G` acting on `\Omega = \{0, 1, ..., n-1\}` is ``k``-fold transitive, if, for any k points `(a_1, a_2, ..., a_k)\in\Omega` and any k points `(b_1, b_2, ..., b_k)\in\Omega` there exists `g\in G` such that `g(a_1)=b_1, g(a_2)=b_2, ..., g(a_k)=b_k` The degree of transitivity of `G` is the maximum ``k`` such that `G` is ``k``-fold transitive. ([8]) Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([1, 2, 0]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.transitivity_degree 3 See Also ======== is_transitive, orbit """ if self._transitivity_degree is None: n = self.degree G = self # if G is k-transitive, a tuple (a_0,..,a_k) # can be brought to (b_0,...,b_(k-1), b_k) # where b_0,...,b_(k-1) are fixed points; # consider the group G_k which stabilizes b_0,...,b_(k-1) # if G_k is transitive on the subset excluding b_0,...,b_(k-1) # then G is (k+1)-transitive for i in range(n): orb = G.orbit(i) if len(orb) != n - i: self._transitivity_degree = i return i G = G.stabilizer(i) self._transitivity_degree = n return n else: return self._transitivity_degree def _p_elements_group(G, p): ''' For an abelian p-group G return the subgroup consisting of all elements of order p (and the identity) ''' gens = G.generators[:] gens = sorted(gens, key=lambda x: x.order(), reverse=True) gens_p = [g(g.order()/p) for g in gens] gens_r = [] for i in range(len(gens)): x = gens[i] x_order = x.order() # x_p has order p x_p = x(x_order/p) if i > 0: P = PermutationGroup(gens_p[:i]) else: P = PermutationGroup(G.identity) if x(x_order/p) not in P: gens_r.append(x(x_order/p)) else: # replace x by an element of order (x.order()/p) # so that gens still generates G g = P.generator_product(x_p, original=True) for s in g: x = xs-1 x_order = x_order/p # insert x to gens so that the sorting is preserved del gens[i] del gens_p[i] j = i - 1 while j < len(gens) and gens[j].order() >= x_order: j += 1 gens = gens[:j] + [x] + gens[j:] gens_p = gens_p[:j] + [x] + gens_p[j:] return PermutationGroup(gens_r) def _sylow_alt_sym(self, p): ''' Return a p-Sylow subgroup of a symmetric or an alternating group. Explanation =========== The algorithm for this is hinted at in [1], Chapter 4, Exercise 4. For Sym(n) with n = p^i, the idea is as follows. Partition the interval [0..n-1] into p equal parts, each of length p^(i-1): [0..p^(i-1)-1], [p^(i-1)..2p^(i-1)-1]...[(p-1)p^(i-1)..p^i-1]. Find a p-Sylow subgroup of Sym(p^(i-1)) (treated as a subgroup of ``self``) acting on each of the parts. Call the subgroups P_1, P_2...P_p. The generators for the subgroups P_2...P_p can be obtained from those of P_1 by applying a "shifting" permutation to them, that is, a permutation mapping [0..p^(i-1)-1] to the second part (the other parts are obtained by using the shift multiple times). The union of this permutation and the generators of P_1 is a p-Sylow subgroup of ``self``. For n not equal to a power of p, partition [0..n-1] in accordance with how n would be written in base p. E.g. for p=2 and n=11, 11 = 2^3 + 2^2 + 1 so the partition is [[0..7], [8..9], {10}]. To generate a p-Sylow subgroup, take the union of the generators for each of the parts. For the above example, {(0 1), (0 2)(1 3), (0 4), (1 5)(2 7)} from the first part, {(8 9)} from the second part and nothing from the third. This gives 4 generators in total, and the subgroup they generate is p-Sylow. Alternating groups are treated the same except when p=2. In this case, (0 1)(s s+1) should be added for an appropriate s (the start of a part) for each part in the partitions. See Also ======== sylow_subgroup, is_alt_sym ''' n = self.degree gens = [] identity = Permutation(n-1) # the case of 2-sylow subgroups of alternating groups # needs special treatment alt = p == 2 and all(g.is_even for g in self.generators) # find the presentation of n in base p coeffs = [] m = n while m > 0: coeffs.append(m % p) m = m // p power = len(coeffs)-1 # for a symmetric group, gens[:i] is the generating # set for a p-Sylow subgroup on [0..p(i-1)-1]. For # alternating groups, the same is given by gens[:2(i-1)] for i in range(1, power+1): if i == 1 and alt: # (0 1) shouldn't be added for alternating groups continue gen = Permutation([(j + p(i-1)) % pi for j in range(p*i)]) gens.append(identitygen) if alt: gen = Permutation(0, 1)genPermutation(0, 1)gen gens.append(gen) # the first point in the current part (see the algorithm # description in the docstring) start = 0 while power > 0: a = coeffs[power] # make the permutation shifting the start of the first # part ([0..p^i-1] for some i) to the current one for s in range(a): shift = Permutation() if start > 0: for i in range(ppower): shift = shift(i, start + i) if alt: gen = Permutation(0, 1)shiftPermutation(0, 1)shift gens.append(gen) j = 2(power - 1) else: j = power for i, gen in enumerate(gens[:j]): if alt and i % 2 == 1: continue # shift the generator to the start of the # partition part gen = shiftgenshift gens.append(gen) start += ppower power = power-1 return gens def sylow_subgroup(self, p): ''' Return a p-Sylow subgroup of the group. The algorithm is described in [1], Chapter 4, Section 7 Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> D = DihedralGroup(6) >>> S = D.sylow_subgroup(2) >>> S.order() 4 >>> G = SymmetricGroup(6) >>> S = G.sylow_subgroup(5) >>> S.order() 5 >>> G1 = AlternatingGroup(3) >>> G2 = AlternatingGroup(5) >>> G3 = AlternatingGroup(9) >>> S1 = G1.sylow_subgroup(3) >>> S2 = G2.sylow_subgroup(3) >>> S3 = G3.sylow_subgroup(3) >>> len1 = len(S1.lower_central_series()) >>> len2 = len(S2.lower_central_series()) >>> len3 = len(S3.lower_central_series()) >>> len1 == len2 True >>> len1 < len3 True ''' from sympy.combinatorics.homomorphisms import ( orbit_homomorphism, block_homomorphism) from sympy.ntheory.primetest import isprime if not isprime(p): raise ValueError("p must be a prime") def is_p_group(G): # check if the order of G is a power of p # and return the power m = G.order() n = 0 while m % p == 0: m = m/p n += 1 if m == 1: return True, n return False, n def _sylow_reduce(mu, nu): # reduction based on two homomorphisms # mu and nu with trivially intersecting # kernels Q = mu.image().sylow_subgroup(p) Q = mu.invert_subgroup(Q) nu = nu.restrict_to(Q) R = nu.image().sylow_subgroup(p) return nu.invert_subgroup(R) order = self.order() if order % p != 0: return PermutationGroup([self.identity]) p_group, n = is_p_group(self) if p_group: return self if self.is_alt_sym(): return PermutationGroup(self._sylow_alt_sym(p)) # if there is a non-trivial orbit with size not divisible # by p, the sylow subgroup is contained in its stabilizer # (by orbit-stabilizer theorem) orbits = self.orbits() non_p_orbits = [o for o in orbits if len(o) % p != 0 and len(o) != 1] if non_p_orbits: G = self.stabilizer(list(non_p_orbits[0]).pop()) return G.sylow_subgroup(p) if not self.is_transitive(): # apply _sylow_reduce to orbit actions orbits = sorted(orbits, key = lambda x: len(x)) omega1 = orbits.pop() omega2 = orbits[0].union(orbits) mu = orbit_homomorphism(self, omega1) nu = orbit_homomorphism(self, omega2) return _sylow_reduce(mu, nu) blocks = self.minimal_blocks() if len(blocks) > 1: # apply _sylow_reduce to block system actions mu = block_homomorphism(self, blocks[0]) nu = block_homomorphism(self, blocks[1]) return _sylow_reduce(mu, nu) elif len(blocks) == 1: block = list(blocks)[0] if any(e != 0 for e in block): # self is imprimitive mu = block_homomorphism(self, block) if not is_p_group(mu.image())[0]: S = mu.image().sylow_subgroup(p) return mu.invert_subgroup(S).sylow_subgroup(p) # find an element of order p g = self.random() g_order = g.order() while g_order % p != 0 or g_order == 0: g = self.random() g_order = g.order() g = g(g_order // p) if order % p2 != 0: return PermutationGroup(g) C = self.centralizer(g) while C.order() % p*n != 0: S = C.sylow_subgroup(p) s_order = S.order() Z = S.center() P = Z._p_elements_group(p) h = P.random() C_h = self.centralizer(h) while C_h.order() % ps_order != 0: h = P.random() C_h = self.centralizer(h) C = C_h return C.sylow_subgroup(p) def _block_verify(H, L, alpha): delta = sorted(list(H.orbit(alpha))) H_gens = H.generators # p[i] will be the number of the block # delta[i] belongs to p = [-1]len(delta) blocks = [-1]len(delta) B = [[]] # future list of blocks u = [0]len(delta) # u[i] in L s.t. alpha^u[i] = B[0][i] t = L.orbit_transversal(alpha, pairs=True) for a, beta in t: B[0].append(a) i_a = delta.index(a) p[i_a] = 0 blocks[i_a] = alpha u[i_a] = beta rho = 0 m = 0 # number of blocks - 1 while rho <= m: beta = B[rho][0] for g in H_gens: d = beta^g i_d = delta.index(d) sigma = p[i_d] if sigma < 0: # define a new block m += 1 sigma = m u[i_d] = u[delta.index(beta)]g p[i_d] = sigma rep = d blocks[i_d] = rep newb = [rep] for gamma in B[rho][1:]: i_gamma = delta.index(gamma) d = gamma^g i_d = delta.index(d) if p[i_d] < 0: u[i_d] = u[i_gamma]g p[i_d] = sigma blocks[i_d] = rep newb.append(d) else: # B[rho] is not a block s = u[i_gamma]gu[i_d](-1) return False, s B.append(newb) else: for h in B[rho][1:]: if not h^g in B[sigma]: # B[rho] is not a block s = u[delta.index(beta)]gu[i_d](-1) return False, s rho += 1 return True, blocks def _verify(H, K, phi, z, alpha): ''' Return a list of relators ``rels`` in generators ``gens`_h` that are mapped to ``H.generators`` by ``phi`` so that given a finite presentation <gens_k \| rels_k> of ``K`` on a subset of ``gens_h`` <gens_h \| rels_k + rels> is a finite presentation of ``H``. Explanation =========== ``H`` should be generated by the union of ``K.generators`` and ``z`` (a single generator), and ``H.stabilizer(alpha) == K``; ``phi`` is a canonical injection from a free group into a permutation group containing ``H``. The algorithm is described in [1], Chapter 6. Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.homomorphisms import homomorphism >>> from sympy.combinatorics.free_groups import free_group >>> from sympy.combinatorics.fp_groups import FpGroup >>> H = PermutationGroup(Permutation(0, 2), Permutation (1, 5)) >>> K = PermutationGroup(Permutation(5)(0, 2)) >>> F = free_group("x_0 x_1")[0] >>> gens = F.generators >>> phi = homomorphism(F, H, F.generators, H.generators) >>> rels_k = [gens[0]2] # relators for presentation of K >>> z= Permutation(1, 5) >>> check, rels_h = H._verify(K, phi, z, 1) >>> check True >>> rels = rels_k + rels_h >>> G = FpGroup(F, rels) # presentation of H >>> G.order() == H.order() True See also ======== strong_presentation, presentation, stabilizer ''' orbit = H.orbit(alpha) beta = alpha^(z-1) K_beta = K.stabilizer(beta) # orbit representatives of K_beta gammas = [alpha, beta] orbits = list({tuple(K_beta.orbit(o)) for o in orbit}) orbit_reps = [orb[0] for orb in orbits] for rep in orbit_reps: if rep not in gammas: gammas.append(rep) # orbit transversal of K betas = [alpha, beta] transversal = {alpha: phi.invert(H.identity), beta: phi.invert(z-1)} for s, g in K.orbit_transversal(beta, pairs=True): if not s in transversal: transversal[s] = transversal[beta]phi.invert(g) union = K.orbit(alpha).union(K.orbit(beta)) while (len(union) < len(orbit)): for gamma in gammas: if gamma in union: r = gamma^z if r not in union: betas.append(r) transversal[r] = transversal[gamma]phi.invert(z) for s, g in K.orbit_transversal(r, pairs=True): if not s in transversal: transversal[s] = transversal[r]phi.invert(g) union = union.union(K.orbit(r)) break # compute relators rels = [] for b in betas: k_gens = K.stabilizer(b).generators for y in k_gens: new_rel = transversal[b] gens = K.generator_product(y, original=True) for g in gens[::-1]: new_rel = new_relphi.invert(g) new_rel = new_reltransversal[b]*-1 perm = phi(new_rel) try: gens = K.generator_product(perm, original=True) except ValueError: return False, perm for g in gens: new_rel = new_relphi.invert(g)*-1 if new_rel not in rels: rels.append(new_rel) for gamma in gammas: new_rel = transversal[gamma]phi.invert(z)transversal[gamma^z]-1 perm = phi(new_rel) try: gens = K.generator_product(perm, original=True) except ValueError: return False, perm for g in gens: new_rel = new_relphi.invert(g)-1 if new_rel not in rels: rels.append(new_rel) return True, rels def strong_presentation(G): ''' Return a strong finite presentation of `G`. The generators of the returned group are in the same order as the strong generators of `G`. The algorithm is based on Sims' Verify algorithm described in [1], Chapter 6. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> P = DihedralGroup(4) >>> G = P.strong_presentation() >>> P.order() == G.order() True See Also ======== presentation, _verify ''' from sympy.combinatorics.fp_groups import (FpGroup, simplify_presentation) from sympy.combinatorics.free_groups import free_group from sympy.combinatorics.homomorphisms import (block_homomorphism, homomorphism, GroupHomomorphism) strong_gens = G.strong_gens[:] stabs = G.basic_stabilizers[:] base = G.base[:] # injection from a free group on len(strong_gens) # generators into G gen_syms = [('x_%d'%i) for i in range(len(strong_gens))] F = free_group(', '.join(gen_syms))[0] phi = homomorphism(F, G, F.generators, strong_gens) H = PermutationGroup(G.identity) while stabs: alpha = base.pop() K = H H = stabs.pop() new_gens = [g for g in H.generators if g not in K] if K.order() == 1: z = new_gens.pop() rels = [F.generators[-1]z.order()] intermediate_gens = [z] K = PermutationGroup(intermediate_gens) # add generators one at a time building up from K to H while new_gens: z = new_gens.pop() intermediate_gens = [z] + intermediate_gens K_s = PermutationGroup(intermediate_gens) orbit = K_s.orbit(alpha) orbit_k = K.orbit(alpha) # split into cases based on the orbit of K_s if orbit_k == orbit: if z in K: rel = phi.invert(z) perm = z else: t = K.orbit_rep(alpha, alpha^z) rel = phi.invert(z)phi.invert(t)-1 perm = zt*-1 for g in K.generator_product(perm, original=True): rel = relphi.invert(g)*-1 new_rels = [rel] elif len(orbit_k) == 1: # `success` is always true because `strong_gens` # and `base` are already a verified BSGS. Later # this could be changed to start with a randomly # generated (potential) BSGS, and then new elements # would have to be appended to it when `success` # is false. success, new_rels = K_s._verify(K, phi, z, alpha) else: # K.orbit(alpha) should be a block # under the action of K_s on K_s.orbit(alpha) check, block = K_s._block_verify(K, alpha) if check: # apply _verify to the action of K_s # on the block system; for convenience, # add the blocks as additional points # that K_s should act on t = block_homomorphism(K_s, block) m = t.codomain.degree # number of blocks d = K_s.degree # conjugating with p will shift # permutations in t.image() to # higher numbers, e.g. # p(0 1)p = (m m+1) p = Permutation() for i in range(m): p = Permutation(i, i+d) t_img = t.images # combine generators of K_s with their # action on the block system images = {g: gpt_img[g]p for g in t_img} for g in G.strong_gens[:-len(K_s.generators)]: images[g] = g K_s_act = PermutationGroup(list(images.values())) f = GroupHomomorphism(G, K_s_act, images) K_act = PermutationGroup([f(g) for g in K.generators]) success, new_rels = K_s_act._verify(K_act, f.compose(phi), f(z), d) for n in new_rels: if not n in rels: rels.append(n) K = K_s group = FpGroup(F, rels) return simplify_presentation(group) def presentation(G, eliminate_gens=True): ''' Return an `FpGroup` presentation of the group. The algorithm is described in [1], Chapter 6.1. ''' from sympy.combinatorics.fp_groups import (FpGroup, simplify_presentation) from sympy.combinatorics.coset_table import CosetTable from sympy.combinatorics.free_groups import free_group from sympy.combinatorics.homomorphisms import homomorphism from itertools import product if G._fp_presentation: return G._fp_presentation if G._fp_presentation: return G._fp_presentation def _factor_group_by_rels(G, rels): if isinstance(G, FpGroup): rels.extend(G.relators) return FpGroup(G.free_group, list(set(rels))) return FpGroup(G, rels) gens = G.generators len_g = len(gens) if len_g == 1: order = gens[0].order() # handle the trivial group if order == 1: return free_group([])[0] F, x = free_group('x') return FpGroup(F, [xorder]) if G.order() > 20: half_gens = G.generators[0:(len_g+1)//2] else: half_gens = [] H = PermutationGroup(half_gens) H_p = H.presentation() len_h = len(H_p.generators) C = G.coset_table(H) n = len(C) # subgroup index gen_syms = [('x_%d'%i) for i in range(len(gens))] F = free_group(', '.join(gen_syms))[0] # mapping generators of H_p to those of F images = [F.generators[i] for i in range(len_h)] R = homomorphism(H_p, F, H_p.generators, images, check=False) # rewrite relators rels = R(H_p.relators) G_p = FpGroup(F, rels) # injective homomorphism from G_p into G T = homomorphism(G_p, G, G_p.generators, gens) C_p = CosetTable(G_p, []) C_p.table = [[None](2len_g) for i in range(n)] # initiate the coset transversal transversal = [None]n transversal[0] = G_p.identity # fill in the coset table as much as possible for i in range(2len_h): C_p.table[0][i] = 0 gamma = 1 for alpha, x in product(range(0, n), range(2len_g)): beta = C[alpha][x] if beta == gamma: gen = G_p.generators[x//2]((-1)(x % 2)) transversal[beta] = transversal[alpha]gen C_p.table[alpha][x] = beta C_p.table[beta][x + (-1)(x % 2)] = alpha gamma += 1 if gamma == n: break C_p.p = list(range(n)) beta = x = 0 while not C_p.is_complete(): # find the first undefined entry while C_p.table[beta][x] == C[beta][x]: x = (x + 1) % (2len_g) if x == 0: beta = (beta + 1) % n # define a new relator gen = G_p.generators[x//2]((-1)(x % 2)) new_rel = transversal[beta]gentransversal[C[beta][x]]*-1 perm = T(new_rel) next = G_p.identity for s in H.generator_product(perm, original=True): next = nextT.invert(s)*-1 new_rel = new_relnext # continue coset enumeration G_p = _factor_group_by_rels(G_p, [new_rel]) C_p.scan_and_fill(0, new_rel) C_p = G_p.coset_enumeration([], strategy="coset_table", draft=C_p, max_cosets=n, incomplete=True) G._fp_presentation = simplify_presentation(G_p) return G._fp_presentation def polycyclic_group(self): """ Return the PolycyclicGroup instance with below parameters: Explanation =========== * ``pc_sequence`` : Polycyclic sequence is formed by collecting all the missing generators between the adjacent groups in the derived series of given permutation group. * ``pc_series`` : Polycyclic series is formed by adding all the missing generators of ``der[i+1]`` in ``der[i]``, where ``der`` represents the derived series. * ``relative_order`` : A list, computed by the ratio of adjacent groups in pc_series. """ from sympy.combinatorics.pc_groups import PolycyclicGroup if not self.is_polycyclic: raise ValueError("The group must be solvable") der = self.derived_series() pc_series = [] pc_sequence = [] relative_order = [] pc_series.append(der[-1]) der.reverse() for i in range(len(der)-1): H = der[i] for g in der[i+1].generators: if g not in H: H = PermutationGroup([g] + H.generators) pc_series.insert(0, H) pc_sequence.insert(0, g) G1 = pc_series[0].order() G2 = pc_series[1].order() relative_order.insert(0, G1 // G2) return PolycyclicGroup(pc_sequence, pc_series, relative_order, collector=None) def _orbit(degree, generators, alpha, action='tuples'): r"""Compute the orbit of alpha `\{g(\alpha) \| g \in G\}` as a set. Explanation =========== The time complexity of the algorithm used here is `O(\|Orb\|r)` where `\|Orb\|` is the size of the orbit and ``r`` is the number of generators of the group. For a more detailed analysis, see [1], p.78, [2], pp. 19-21. Here alpha can be a single point, or a list of points. If alpha is a single point, the ordinary orbit is computed. if alpha is a list of points, there are three available options: 'union' - computes the union of the orbits of the points in the list 'tuples' - computes the orbit of the list interpreted as an ordered tuple under the group action ( i.e., g((1, 2, 3)) = (g(1), g(2), g(3)) ) 'sets' - computes the orbit of the list interpreted as a sets Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup, _orbit >>> a = Permutation([1, 2, 0, 4, 5, 6, 3]) >>> G = PermutationGroup([a]) >>> _orbit(G.degree, G.generators, 0) {0, 1, 2} >>> _orbit(G.degree, G.generators, [0, 4], 'union') {0, 1, 2, 3, 4, 5, 6} See Also ======== orbit, orbit_transversal """ if not hasattr(alpha, '__getitem__'): alpha = [alpha] gens = [x._array_form for x in generators] if len(alpha) == 1 or action == 'union': orb = alpha used = [False]degree for el in alpha: used[el] = True for b in orb: for gen in gens: temp = gen[b] if used[temp] == False: orb.append(temp) used[temp] = True return set(orb) elif action == 'tuples': alpha = tuple(alpha) orb = [alpha] used = {alpha} for b in orb: for gen in gens: temp = tuple([gen[x] for x in b]) if temp not in used: orb.append(temp) used.add(temp) return set(orb) elif action == 'sets': alpha = frozenset(alpha) orb = [alpha] used = {alpha} for b in orb: for gen in gens: temp = frozenset([gen[x] for x in b]) if temp not in used: orb.append(temp) used.add(temp) return {tuple(x) for x in orb} def _orbits(degree, generators): """Compute the orbits of G. If ``rep=False`` it returns a list of sets else it returns a list of representatives of the orbits Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import _orbits >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> _orbits(a.size, [a, b]) [{0, 1, 2}] """ orbs = [] sorted_I = list(range(degree)) I = set(sorted_I) while I: i = sorted_I[0] orb = _orbit(degree, generators, i) orbs.append(orb) # remove all indices that are in this orbit I -= orb sorted_I = [i for i in sorted_I if i not in orb] return orbs def _orbit_transversal(degree, generators, alpha, pairs, af=False, slp=False): r"""Computes a transversal for the orbit of ``alpha`` as a set. Explanation =========== generators generators of the group ``G`` For a permutation group ``G``, a transversal for the orbit `Orb = \{g(\alpha) \| g \in G\}` is a set `\{g_\beta \| g_\beta(\alpha) = \beta\}` for `\beta \in Orb`. Note that there may be more than one possible transversal. If ``pairs`` is set to ``True``, it returns the list of pairs `(\beta, g_\beta)`. For a proof of correctness, see [1], p.79 if ``af`` is ``True``, the transversal elements are given in array form. If `slp` is `True`, a dictionary `{beta: slp_beta}` is returned for `\beta \in Orb` where `slp_beta` is a list of indices of the generators in `generators` s.t. if `slp_beta = [i_1 ... i_n]` `g_\beta = generators[i_n]...generators[i_1]`. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.perm_groups import _orbit_transversal >>> G = DihedralGroup(6) >>> _orbit_transversal(G.degree, G.generators, 0, False) [(5), (0 1 2 3 4 5), (0 5)(1 4)(2 3), (0 2 4)(1 3 5), (5)(0 4)(1 3), (0 3)(1 4)(2 5)] """ tr = [(alpha, list(range(degree)))] slp_dict = {alpha: []} used = [False]degree used[alpha] = True gens = [x._array_form for x in generators] for x, px in tr: px_slp = slp_dict[x] for gen in gens: temp = gen[x] if used[temp] == False: slp_dict[temp] = [gens.index(gen)] + px_slp tr.append((temp, _af_rmul(gen, px))) used[temp] = True if pairs: if not af: tr = [(x, _af_new(y)) for x, y in tr] if not slp: return tr return tr, slp_dict if af: tr = [y for _, y in tr] if not slp: return tr return tr, slp_dict tr = [_af_new(y) for _, y in tr] if not slp: return tr return tr, slp_dict def _stabilizer(degree, generators, alpha): r"""Return the stabilizer subgroup of ``alpha``. Explanation =========== The stabilizer of `\alpha` is the group `G_\alpha = \{g \in G \| g(\alpha) = \alpha\}`. For a proof of correctness, see [1], p.79. degree : degree of G generators : generators of G Examples ======== >>> from sympy.combinatorics.perm_groups import _stabilizer >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> _stabilizer(G.degree, G.generators, 5) [(5)(0 4)(1 3), (5)] See Also ======== orbit """ orb = [alpha] table = {alpha: list(range(degree))} table_inv = {alpha: list(range(degree))} used = [False]degree used[alpha] = True gens = [x._array_form for x in generators] stab_gens = [] for b in orb: for gen in gens: temp = gen[b] if used[temp] is False: gen_temp = _af_rmul(gen, table[b]) orb.append(temp) table[temp] = gen_temp table_inv[temp] = _af_invert(gen_temp) used[temp] = True else: schreier_gen = _af_rmuln(table_inv[temp], gen, table[b]) if schreier_gen not in stab_gens: stab_gens.append(schreier_gen) return [_af_new(x) for x in stab_gens] PermGroup = PermutationGroup class SymmetricPermutationGroup(Basic): """ The class defining the lazy form of SymmetricGroup. deg : int """ def __new__(cls, deg): deg = _sympify(deg) obj = Basic.__new__(cls, deg) obj._deg = deg obj._order = None return obj def __contains__(self, i): """Return ``True`` if i is contained in SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation, SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> Permutation(1, 2, 3) in G True """ if not isinstance(i, Permutation): raise TypeError("A SymmetricPermutationGroup contains only Permutations as " "elements, not elements of type %s" % type(i)) return i.size == self.degree def order(self): """ Return the order of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.order() 24 """ if self._order is not None: return self._order n = self._deg self._order = factorial(n) return self._order @property def degree(self): """ Return the degree of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.degree 4 """ return self._deg @property def identity(self): ''' Return the identity element of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.identity() (3) ''' return _af_new(list(range(self._deg))) class Coset(Basic): """A left coset of a permutation group with respect to an element. Parameters ========== g : Permutation H : PermutationGroup dir : "+" or "-", If not specified by default it will be "+" here ``dir`` specified the type of coset "+" represent the right coset and "-" represent the left coset. G : PermutationGroup, optional The group which contains H as its subgroup and g as its element. If not specified, it would automatically become a symmetric group ``SymmetricPermutationGroup(g.size)`` and ``SymmetricPermutationGroup(H.degree)`` if ``g.size`` and ``H.degree`` are matching.``SymmetricPermutationGroup`` is a lazy form of SymmetricGroup used for representation purpose. """ def __new__(cls, g, H, G=None, dir="+"): g = _sympify(g) if not isinstance(g, Permutation): raise NotImplementedError H = _sympify(H) if not isinstance(H, PermutationGroup): raise NotImplementedError if G is not None: G = _sympify(G) if not isinstance(G, PermutationGroup) and not isinstance(G, SymmetricPermutationGroup): raise NotImplementedError if not H.is_subgroup(G): raise ValueError("{} must be a subgroup of {}.".format(H, G)) if g not in G: raise ValueError("{} must be an element of {}.".format(g, G)) else: g_size = g.size h_degree = H.degree if g_size != h_degree: raise ValueError( "The size of the permutation {} and the degree of " "the permutation group {} should be matching " .format(g, H)) G = SymmetricPermutationGroup(g.size) if isinstance(dir, str): dir = Symbol(dir) elif not isinstance(dir, Symbol): raise TypeError("dir must be of type basestring or " "Symbol, not %s" % type(dir)) if str(dir) not in ('+', '-'): raise ValueError("dir must be one of '+' or '-' not %s" % dir) obj = Basic.__new__(cls, g, H, G, dir) obj._dir = dir return obj @property def is_left_coset(self): """ Check if the coset is left coset that is ``gH``. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup, Coset >>> a = Permutation(1, 2) >>> b = Permutation(0, 1) >>> G = PermutationGroup([a, b]) >>> cst = Coset(a, G, dir="-") >>> cst.is_left_coset True """ return str(self._dir) == '-' @property def is_right_coset(self): """ Check if the coset is right coset that is ``Hg``. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup, Coset >>> a = Permutation(1, 2) >>> b = Permutation(0, 1) >>> G = PermutationGroup([a, b]) >>> cst = Coset(a, G, dir="+") >>> cst.is_right_coset True """ return str(self._dir) == '+' def as_list(self): """ Return all the elements of coset in the form of list. """ g = self.args[0] H = self.args[1] cst = [] if str(self._dir) == '+': for h in H.elements: cst.append(hg) else: for h in H.elements: cst.append(gh) return cst
63ed4e6adc5ac1d4a921424f2c62fef8853e61b9caab3fc64142548895f0d48d	import random from collections import defaultdict from sympy.core.parameters import global_parameters from sympy.core.basic import Atom from sympy.core.expr import Expr from sympy.core.compatibility import \ is_sequence, reduce, as_int, Iterable from sympy.core.numbers import Integer from sympy.core.sympify import _sympify from sympy.matrices import zeros from sympy.polys.polytools import lcm from sympy.utilities.iterables import (flatten, has_variety, minlex, has_dups, runs) from mpmath.libmp.libintmath import ifac from sympy.multipledispatch import dispatch def _af_rmul(a, b): """ Return the product ba; input and output are array forms. The ith value is a[b[i]]. Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> _af_rmul(a, b) [1, 2, 0] >>> [a[b[i]] for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ```` operator: >>> a = Permutation(a) >>> b = Permutation(b) >>> list(ab) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] See Also ======== rmul, _af_rmuln """ return [a[i] for i in b] def _af_rmuln(abc): """ Given [a, b, c, ...] return the product of ...cba using array forms. The ith value is a[b[c[i]]]. Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> _af_rmul(a, b) [1, 2, 0] >>> [a[b[i]] for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ```` operator: >>> a = Permutation(a); b = Permutation(b) >>> list(ab) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] See Also ======== rmul, _af_rmul """ a = abc m = len(a) if m == 3: p0, p1, p2 = a return [p0[p1[i]] for i in p2] if m == 4: p0, p1, p2, p3 = a return [p0[p1[p2[i]]] for i in p3] if m == 5: p0, p1, p2, p3, p4 = a return [p0[p1[p2[p3[i]]]] for i in p4] if m == 6: p0, p1, p2, p3, p4, p5 = a return [p0[p1[p2[p3[p4[i]]]]] for i in p5] if m == 7: p0, p1, p2, p3, p4, p5, p6 = a return [p0[p1[p2[p3[p4[p5[i]]]]]] for i in p6] if m == 8: p0, p1, p2, p3, p4, p5, p6, p7 = a return [p0[p1[p2[p3[p4[p5[p6[i]]]]]]] for i in p7] if m == 1: return a[0][:] if m == 2: a, b = a return [a[i] for i in b] if m == 0: raise ValueError("String must not be empty") p0 = _af_rmuln(a[:m//2]) p1 = _af_rmuln(a[m//2:]) return [p0[i] for i in p1] def _af_parity(pi): """ Computes the parity of a permutation in array form. Explanation =========== The parity of a permutation reflects the parity of the number of inversions in the permutation, i.e., the number of pairs of x and y such that x > y but p[x] < p[y]. Examples ======== >>> from sympy.combinatorics.permutations import _af_parity >>> _af_parity([0, 1, 2, 3]) 0 >>> _af_parity([3, 2, 0, 1]) 1 See Also ======== Permutation """ n = len(pi) a = [0] n c = 0 for j in range(n): if a[j] == 0: c += 1 a[j] = 1 i = j while pi[i] != j: i = pi[i] a[i] = 1 return (n - c) % 2 def _af_invert(a): """ Finds the inverse, ~A, of a permutation, A, given in array form. Examples ======== >>> from sympy.combinatorics.permutations import _af_invert, _af_rmul >>> A = [1, 2, 0, 3] >>> _af_invert(A) [2, 0, 1, 3] >>> _af_rmul(_, A) [0, 1, 2, 3] See Also ======== Permutation, __invert__ """ inv_form = [0] * len(a) for i, ai in enumerate(a): inv_form[ai] = i return inv_form def _af_pow(a, n): """ Routine for finding powers of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation, _af_pow >>> p = Permutation([2, 0, 3, 1]) >>> p.order() 4 >>> _af_pow(p._array_form, 4) [0, 1, 2, 3] """ if n == 0: return list(range(len(a))) if n < 0: return _af_pow(_af_invert(a), -n) if n == 1: return a[:] elif n == 2: b = [a[i] for i in a] elif n == 3: b = [a[a[i]] for i in a] elif n == 4: b = [a[a[a[i]]] for i in a] else: # use binary multiplication b = list(range(len(a))) while 1: if n & 1: b = [b[i] for i in a] n -= 1 if not n: break if n % 4 == 0: a = [a[a[a[i]]] for i in a] n = n // 4 elif n % 2 == 0: a = [a[i] for i in a] n = n // 2 return b def _af_commutes_with(a, b): """ Checks if the two permutations with array forms given by ``a`` and ``b`` commute. Examples ======== >>> from sympy.combinatorics.permutations import _af_commutes_with >>> _af_commutes_with([1, 2, 0], [0, 2, 1]) False See Also ======== Permutation, commutes_with """ return not any(a[b[i]] != b[a[i]] for i in range(len(a) - 1)) class Cycle(dict): """ Wrapper around dict which provides the functionality of a disjoint cycle. Explanation =========== A cycle shows the rule to use to move subsets of elements to obtain a permutation. The Cycle class is more flexible than Permutation in that 1) all elements need not be present in order to investigate how multiple cycles act in sequence and 2) it can contain singletons: >>> from sympy.combinatorics.permutations import Perm, Cycle A Cycle will automatically parse a cycle given as a tuple on the rhs: >>> Cycle(1, 2)(2, 3) (1 3 2) The identity cycle, Cycle(), can be used to start a product: >>> Cycle()(1, 2)(2, 3) (1 3 2) The array form of a Cycle can be obtained by calling the list method (or passing it to the list function) and all elements from 0 will be shown: >>> a = Cycle(1, 2) >>> a.list() [0, 2, 1] >>> list(a) [0, 2, 1] If a larger (or smaller) range is desired use the list method and provide the desired size -- but the Cycle cannot be truncated to a size smaller than the largest element that is out of place: >>> b = Cycle(2, 4)(1, 2)(3, 1, 4)(1, 3) >>> b.list() [0, 2, 1, 3, 4] >>> b.list(b.size + 1) [0, 2, 1, 3, 4, 5] >>> b.list(-1) [0, 2, 1] Singletons are not shown when printing with one exception: the largest element is always shown -- as a singleton if necessary: >>> Cycle(1, 4, 10)(4, 5) (1 5 4 10) >>> Cycle(1, 2)(4)(5)(10) (1 2)(10) The array form can be used to instantiate a Permutation so other properties of the permutation can be investigated: >>> Perm(Cycle(1, 2)(3, 4).list()).transpositions() [(1, 2), (3, 4)] Notes ===== The underlying structure of the Cycle is a dictionary and although the __iter__ method has been redefined to give the array form of the cycle, the underlying dictionary items are still available with the such methods as items(): >>> list(Cycle(1, 2).items()) [(1, 2), (2, 1)] See Also ======== Permutation """ def __missing__(self, arg): """Enter arg into dictionary and return arg.""" return as_int(arg) def __iter__(self): yield from self.list() def __call__(self, other): """Return product of cycles processed from R to L. Examples ======== >>> from sympy.combinatorics.permutations import Cycle as C >>> C(1, 2)(2, 3) (1 3 2) An instance of a Cycle will automatically parse list-like objects and Permutations that are on the right. It is more flexible than the Permutation in that all elements need not be present: >>> a = C(1, 2) >>> a(2, 3) (1 3 2) >>> a(2, 3)(4, 5) (1 3 2)(4 5) """ rv = Cycle(other) for k, v in zip(list(self.keys()), [rv[self[k]] for k in self.keys()]): rv[k] = v return rv def list(self, size=None): """Return the cycles as an explicit list starting from 0 up to the greater of the largest value in the cycles and size. Truncation of trailing unmoved items will occur when size is less than the maximum element in the cycle; if this is desired, setting ``size=-1`` will guarantee such trimming. Examples ======== >>> from sympy.combinatorics.permutations import Cycle >>> p = Cycle(2, 3)(4, 5) >>> p.list() [0, 1, 3, 2, 5, 4] >>> p.list(10) [0, 1, 3, 2, 5, 4, 6, 7, 8, 9] Passing a length too small will trim trailing, unchanged elements in the permutation: >>> Cycle(2, 4)(1, 2, 4).list(-1) [0, 2, 1] """ if not self and size is None: raise ValueError('must give size for empty Cycle') if size is not None: big = max([i for i in self.keys() if self[i] != i] + [0]) size = max(size, big + 1) else: size = self.size return [self[i] for i in range(size)] def __repr__(self): """We want it to print as a Cycle, not as a dict. Examples ======== >>> from sympy.combinatorics import Cycle >>> Cycle(1, 2) (1 2) >>> print(_) (1 2) >>> list(Cycle(1, 2).items()) [(1, 2), (2, 1)] """ if not self: return 'Cycle()' cycles = Permutation(self).cyclic_form s = ''.join(str(tuple(c)) for c in cycles) big = self.size - 1 if not any(i == big for c in cycles for i in c): s += '(%s)' % big return 'Cycle%s' % s def __str__(self): """We want it to be printed in a Cycle notation with no comma in-between. Examples ======== >>> from sympy.combinatorics import Cycle >>> Cycle(1, 2) (1 2) >>> Cycle(1, 2, 4)(5, 6) (1 2 4)(5 6) """ if not self: return '()' cycles = Permutation(self).cyclic_form s = ''.join(str(tuple(c)) for c in cycles) big = self.size - 1 if not any(i == big for c in cycles for i in c): s += '(%s)' % big s = s.replace(',', '') return s def __init__(self, args): """Load up a Cycle instance with the values for the cycle. Examples ======== >>> from sympy.combinatorics.permutations import Cycle >>> Cycle(1, 2, 6) (1 2 6) """ if not args: return if len(args) == 1: if isinstance(args[0], Permutation): for c in args[0].cyclic_form: self.update(self(c)) return elif isinstance(args[0], Cycle): for k, v in args[0].items(): self[k] = v return args = [as_int(a) for a in args] if any(i < 0 for i in args): raise ValueError('negative integers are not allowed in a cycle.') if has_dups(args): raise ValueError('All elements must be unique in a cycle.') for i in range(-len(args), 0): self[args[i]] = args[i + 1] @property def size(self): if not self: return 0 return max(self.keys()) + 1 def copy(self): return Cycle(self) class Permutation(Atom): """ A permutation, alternatively known as an 'arrangement number' or 'ordering' is an arrangement of the elements of an ordered list into a one-to-one mapping with itself. The permutation of a given arrangement is given by indicating the positions of the elements after re-arrangement [2]_. For example, if one started with elements [x, y, a, b] (in that order) and they were reordered as [x, y, b, a] then the permutation would be [0, 1, 3, 2]. Notice that (in SymPy) the first element is always referred to as 0 and the permutation uses the indices of the elements in the original ordering, not the elements (a, b, etc...) themselves. >>> from sympy.combinatorics import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) Permutations Notation ===================== Permutations are commonly represented in disjoint cycle or array forms. Array Notation and 2-line Form ------------------------------------ In the 2-line form, the elements and their final positions are shown as a matrix with 2 rows: [0 1 2 ... n-1] [p(0) p(1) p(2) ... p(n-1)] Since the first line is always range(n), where n is the size of p, it is sufficient to represent the permutation by the second line, referred to as the "array form" of the permutation. This is entered in brackets as the argument to the Permutation class: >>> p = Permutation([0, 2, 1]); p Permutation([0, 2, 1]) Given i in range(p.size), the permutation maps i to i^p >>> [i^p for i in range(p.size)] [0, 2, 1] The composite of two permutations pq means first apply p, then q, so i^(pq) = (i^p)^q which is i^p^q according to Python precedence rules: >>> q = Permutation([2, 1, 0]) >>> [i^p^q for i in range(3)] [2, 0, 1] >>> [i^(pq) for i in range(3)] [2, 0, 1] One can use also the notation p(i) = i^p, but then the composition rule is (pq)(i) = q(p(i)), not p(q(i)): >>> [(pq)(i) for i in range(p.size)] [2, 0, 1] >>> [q(p(i)) for i in range(p.size)] [2, 0, 1] >>> [p(q(i)) for i in range(p.size)] [1, 2, 0] Disjoint Cycle Notation ----------------------- In disjoint cycle notation, only the elements that have shifted are indicated. In the above case, the 2 and 1 switched places. This can be entered in two ways: >>> Permutation(1, 2) == Permutation([[1, 2]]) == p True Only the relative ordering of elements in a cycle matter: >>> Permutation(1,2,3) == Permutation(2,3,1) == Permutation(3,1,2) True The disjoint cycle notation is convenient when representing permutations that have several cycles in them: >>> Permutation(1, 2)(3, 5) == Permutation([[1, 2], [3, 5]]) True It also provides some economy in entry when computing products of permutations that are written in disjoint cycle notation: >>> Permutation(1, 2)(1, 3)(2, 3) Permutation([0, 3, 2, 1]) >>> _ == Permutation([[1, 2]])Permutation([[1, 3]])Permutation([[2, 3]]) True Caution: when the cycles have common elements between them then the order in which the permutations are applied matters. The convention is that the permutations are applied from right to left. In the following, the transposition of elements 2 and 3 is followed by the transposition of elements 1 and 2: >>> Permutation(1, 2)(2, 3) == Permutation([(1, 2), (2, 3)]) True >>> Permutation(1, 2)(2, 3).list() [0, 3, 1, 2] If the first and second elements had been swapped first, followed by the swapping of the second and third, the result would have been [0, 2, 3, 1]. If, for some reason, you want to apply the cycles in the order they are entered, you can simply reverse the order of cycles: >>> Permutation([(1, 2), (2, 3)][::-1]).list() [0, 2, 3, 1] Entering a singleton in a permutation is a way to indicate the size of the permutation. The ``size`` keyword can also be used. Array-form entry: >>> Permutation([[1, 2], [9]]) Permutation([0, 2, 1], size=10) >>> Permutation([[1, 2]], size=10) Permutation([0, 2, 1], size=10) Cyclic-form entry: >>> Permutation(1, 2, size=10) Permutation([0, 2, 1], size=10) >>> Permutation(9)(1, 2) Permutation([0, 2, 1], size=10) Caution: no singleton containing an element larger than the largest in any previous cycle can be entered. This is an important difference in how Permutation and Cycle handle the __call__ syntax. A singleton argument at the start of a Permutation performs instantiation of the Permutation and is permitted: >>> Permutation(5) Permutation([], size=6) A singleton entered after instantiation is a call to the permutation -- a function call -- and if the argument is out of range it will trigger an error. For this reason, it is better to start the cycle with the singleton: The following fails because there is no element 3: >>> Permutation(1, 2)(3) Traceback (most recent call last): ... IndexError: list index out of range This is ok: only the call to an out of range singleton is prohibited; otherwise the permutation autosizes: >>> Permutation(3)(1, 2) Permutation([0, 2, 1, 3]) >>> Permutation(1, 2)(3, 4) == Permutation(3, 4)(1, 2) True Equality testing ---------------- The array forms must be the same in order for permutations to be equal: >>> Permutation([1, 0, 2, 3]) == Permutation([1, 0]) False Identity Permutation -------------------- The identity permutation is a permutation in which no element is out of place. It can be entered in a variety of ways. All the following create an identity permutation of size 4: >>> I = Permutation([0, 1, 2, 3]) >>> all(p == I for p in [ ... Permutation(3), ... Permutation(range(4)), ... Permutation([], size=4), ... Permutation(size=4)]) True Watch out for entering the range inside* a set of brackets (which is cycle notation): >>> I == Permutation([range(4)]) False Permutation Printing ==================== There are a few things to note about how Permutations are printed. 1) If you prefer one form (array or cycle) over another, you can set ``init_printing`` with the ``perm_cyclic`` flag. >>> from sympy import init_printing >>> p = Permutation(1, 2)(4, 5)(3, 4) >>> p Permutation([0, 2, 1, 4, 5, 3]) >>> init_printing(perm_cyclic=True, pretty_print=False) >>> p (1 2)(3 4 5) 2) Regardless of the setting, a list of elements in the array for cyclic form can be obtained and either of those can be copied and supplied as the argument to Permutation: >>> p.array_form [0, 2, 1, 4, 5, 3] >>> p.cyclic_form [[1, 2], [3, 4, 5]] >>> Permutation(_) == p True 3) Printing is economical in that as little as possible is printed while retaining all information about the size of the permutation: >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation([1, 0, 2, 3]) Permutation([1, 0, 2, 3]) >>> Permutation([1, 0, 2, 3], size=20) Permutation([1, 0], size=20) >>> Permutation([1, 0, 2, 4, 3, 5, 6], size=20) Permutation([1, 0, 2, 4, 3], size=20) >>> p = Permutation([1, 0, 2, 3]) >>> init_printing(perm_cyclic=True, pretty_print=False) >>> p (3)(0 1) >>> init_printing(perm_cyclic=False, pretty_print=False) The 2 was not printed but it is still there as can be seen with the array_form and size methods: >>> p.array_form [1, 0, 2, 3] >>> p.size 4 Short introduction to other methods =================================== The permutation can act as a bijective function, telling what element is located at a given position >>> q = Permutation([5, 2, 3, 4, 1, 0]) >>> q.array_form[1] # the hard way 2 >>> q(1) # the easy way 2 >>> {i: q(i) for i in range(q.size)} # showing the bijection {0: 5, 1: 2, 2: 3, 3: 4, 4: 1, 5: 0} The full cyclic form (including singletons) can be obtained: >>> p.full_cyclic_form [[0, 1], [2], [3]] Any permutation can be factored into transpositions of pairs of elements: >>> Permutation([[1, 2], [3, 4, 5]]).transpositions() [(1, 2), (3, 5), (3, 4)] >>> Permutation.rmul([Permutation([ti], size=6) for ti in _]).cyclic_form [[1, 2], [3, 4, 5]] The number of permutations on a set of n elements is given by n! and is called the cardinality. >>> p.size 4 >>> p.cardinality 24 A given permutation has a rank among all the possible permutations of the same elements, but what that rank is depends on how the permutations are enumerated. (There are a number of different methods of doing so.) The lexicographic rank is given by the rank method and this rank is used to increment a permutation with addition/subtraction: >>> p.rank() 6 >>> p + 1 Permutation([1, 0, 3, 2]) >>> p.next_lex() Permutation([1, 0, 3, 2]) >>> _.rank() 7 >>> p.unrank_lex(p.size, rank=7) Permutation([1, 0, 3, 2]) The product of two permutations p and q is defined as their composition as functions, (pq)(i) = q(p(i)) [6]_. >>> p = Permutation([1, 0, 2, 3]) >>> q = Permutation([2, 3, 1, 0]) >>> list(qp) [2, 3, 0, 1] >>> list(pq) [3, 2, 1, 0] >>> [q(p(i)) for i in range(p.size)] [3, 2, 1, 0] The permutation can be 'applied' to any list-like object, not only Permutations: >>> p(['zero', 'one', 'four', 'two']) ['one', 'zero', 'four', 'two'] >>> p('zo42') ['o', 'z', '4', '2'] If you have a list of arbitrary elements, the corresponding permutation can be found with the from_sequence method: >>> Permutation.from_sequence('SymPy') Permutation([1, 3, 2, 0, 4]) See Also ======== Cycle References ========== .. [1] Skiena, S. 'Permutations.' 1.1 in Implementing Discrete Mathematics Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, pp. 3-16, 1990. .. [2] Knuth, D. E. The Art of Computer Programming, Vol. 4: Combinatorial Algorithms, 1st ed. Reading, MA: Addison-Wesley, 2011. .. [3] Wendy Myrvold and Frank Ruskey. 2001. Ranking and unranking permutations in linear time. Inf. Process. Lett. 79, 6 (September 2001), 281-284. DOI=10.1016/S0020-0190(01)00141-7 .. [4] D. L. Kreher, D. R. Stinson 'Combinatorial Algorithms' CRC Press, 1999 .. [5] Graham, R. L.; Knuth, D. E.; and Patashnik, O. Concrete Mathematics: A Foundation for Computer Science, 2nd ed. Reading, MA: Addison-Wesley, 1994. .. [6] https://en.wikipedia.org/wiki/Permutation#Product_and_inverse .. [7] https://en.wikipedia.org/wiki/Lehmer_code """ is_Permutation = True _array_form = None _cyclic_form = None _cycle_structure = None _size = None _rank = None def __new__(cls, args, size=None, kwargs): """ Constructor for the Permutation object from a list or a list of lists in which all elements of the permutation may appear only once. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) Permutations entered in array-form are left unaltered: >>> Permutation([0, 2, 1]) Permutation([0, 2, 1]) Permutations entered in cyclic form are converted to array form; singletons need not be entered, but can be entered to indicate the largest element: >>> Permutation([[4, 5, 6], [0, 1]]) Permutation([1, 0, 2, 3, 5, 6, 4]) >>> Permutation([[4, 5, 6], [0, 1], [19]]) Permutation([1, 0, 2, 3, 5, 6, 4], size=20) All manipulation of permutations assumes that the smallest element is 0 (in keeping with 0-based indexing in Python) so if the 0 is missing when entering a permutation in array form, an error will be raised: >>> Permutation([2, 1]) Traceback (most recent call last): ... ValueError: Integers 0 through 2 must be present. If a permutation is entered in cyclic form, it can be entered without singletons and the ``size`` specified so those values can be filled in, otherwise the array form will only extend to the maximum value in the cycles: >>> Permutation([[1, 4], [3, 5, 2]], size=10) Permutation([0, 4, 3, 5, 1, 2], size=10) >>> _.array_form [0, 4, 3, 5, 1, 2, 6, 7, 8, 9] """ if size is not None: size = int(size) #a) () #b) (1) = identity #c) (1, 2) = cycle #d) ([1, 2, 3]) = array form #e) ([[1, 2]]) = cyclic form #f) (Cycle) = conversion to permutation #g) (Permutation) = adjust size or return copy ok = True if not args: # a return cls._af_new(list(range(size or 0))) elif len(args) > 1: # c return cls._af_new(Cycle(args).list(size)) if len(args) == 1: a = args[0] if isinstance(a, cls): # g if size is None or size == a.size: return a return cls(a.array_form, size=size) if isinstance(a, Cycle): # f return cls._af_new(a.list(size)) if not is_sequence(a): # b if size is not None and a + 1 > size: raise ValueError('size is too small when max is %s' % a) return cls._af_new(list(range(a + 1))) if has_variety(is_sequence(ai) for ai in a): ok = False else: ok = False if not ok: raise ValueError("Permutation argument must be a list of ints, " "a list of lists, Permutation or Cycle.") # safe to assume args are valid; this also makes a copy # of the args args = list(args[0]) is_cycle = args and is_sequence(args[0]) if is_cycle: # e args = [[int(i) for i in c] for c in args] else: # d args = [int(i) for i in args] # if there are n elements present, 0, 1, ..., n-1 should be present # unless a cycle notation has been provided. A 0 will be added # for convenience in case one wants to enter permutations where # counting starts from 1. temp = flatten(args) if has_dups(temp) and not is_cycle: raise ValueError('there were repeated elements.') temp = set(temp) if not is_cycle: if any(i not in temp for i in range(len(temp))): raise ValueError('Integers 0 through %s must be present.' % max(temp)) if size is not None and temp and max(temp) + 1 > size: raise ValueError('max element should not exceed %s' % (size - 1)) if is_cycle: # it's not necessarily canonical so we won't store # it -- use the array form instead c = Cycle() for ci in args: c = c(ci) aform = c.list() else: aform = list(args) if size and size > len(aform): # don't allow for truncation of permutation which # might split a cycle and lead to an invalid aform # but do allow the permutation size to be increased aform.extend(list(range(len(aform), size))) return cls._af_new(aform) @classmethod def _af_new(cls, perm): """A method to produce a Permutation object from a list; the list is bound to the _array_form attribute, so it must not be modified; this method is meant for internal use only; the list ``a`` is supposed to be generated as a temporary value in a method, so p = Perm._af_new(a) is the only object to hold a reference to ``a``:: Examples ======== >>> from sympy.combinatorics.permutations import Perm >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> a = [2, 1, 3, 0] >>> p = Perm._af_new(a) >>> p Permutation([2, 1, 3, 0]) """ p = super().__new__(cls) p._array_form = perm p._size = len(perm) return p def _hashable_content(self): # the array_form (a list) is the Permutation arg, so we need to # return a tuple, instead return tuple(self.array_form) @property def array_form(self): """ Return a copy of the attribute _array_form Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[2, 0], [3, 1]]) >>> p.array_form [2, 3, 0, 1] >>> Permutation([[2, 0, 3, 1]]).array_form [3, 2, 0, 1] >>> Permutation([2, 0, 3, 1]).array_form [2, 0, 3, 1] >>> Permutation([[1, 2], [4, 5]]).array_form [0, 2, 1, 3, 5, 4] """ return self._array_form[:] def list(self, size=None): """Return the permutation as an explicit list, possibly trimming unmoved elements if size is less than the maximum element in the permutation; if this is desired, setting ``size=-1`` will guarantee such trimming. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation(2, 3)(4, 5) >>> p.list() [0, 1, 3, 2, 5, 4] >>> p.list(10) [0, 1, 3, 2, 5, 4, 6, 7, 8, 9] Passing a length too small will trim trailing, unchanged elements in the permutation: >>> Permutation(2, 4)(1, 2, 4).list(-1) [0, 2, 1] >>> Permutation(3).list(-1) [] """ if not self and size is None: raise ValueError('must give size for empty Cycle') rv = self.array_form if size is not None: if size > self.size: rv.extend(list(range(self.size, size))) else: # find first value from rhs where rv[i] != i i = self.size - 1 while rv: if rv[-1] != i: break rv.pop() i -= 1 return rv @property def cyclic_form(self): """ This is used to convert to the cyclic notation from the canonical notation. Singletons are omitted. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2]) >>> p.cyclic_form [[1, 3, 2]] >>> Permutation([1, 0, 2, 4, 3, 5]).cyclic_form [[0, 1], [3, 4]] See Also ======== array_form, full_cyclic_form """ if self._cyclic_form is not None: return list(self._cyclic_form) array_form = self.array_form unchecked = [True] len(array_form) cyclic_form = [] for i in range(len(array_form)): if unchecked[i]: cycle = [] cycle.append(i) unchecked[i] = False j = i while unchecked[array_form[j]]: j = array_form[j] cycle.append(j) unchecked[j] = False if len(cycle) > 1: cyclic_form.append(cycle) assert cycle == list(minlex(cycle, is_set=True)) cyclic_form.sort() self._cyclic_form = cyclic_form[:] return cyclic_form @property def full_cyclic_form(self): """Return permutation in cyclic form including singletons. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> Permutation([0, 2, 1]).full_cyclic_form [[0], [1, 2]] """ need = set(range(self.size)) - set(flatten(self.cyclic_form)) rv = self.cyclic_form rv.extend([[i] for i in need]) rv.sort() return rv @property def size(self): """ Returns the number of elements in the permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([[3, 2], [0, 1]]).size 4 See Also ======== cardinality, length, order, rank """ return self._size def support(self): """Return the elements in permutation, P, for which P[i] != i. Examples ======== >>> from sympy.combinatorics import Permutation >>> p = Permutation([[3, 2], [0, 1], [4]]) >>> p.array_form [1, 0, 3, 2, 4] >>> p.support() [0, 1, 2, 3] """ a = self.array_form return [i for i, e in enumerate(a) if a[i] != i] def __add__(self, other): """Return permutation that is other higher in rank than self. The rank is the lexicographical rank, with the identity permutation having rank of 0. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> I = Permutation([0, 1, 2, 3]) >>> a = Permutation([2, 1, 3, 0]) >>> I + a.rank() == a True See Also ======== __sub__, inversion_vector """ rank = (self.rank() + other) % self.cardinality rv = self.unrank_lex(self.size, rank) rv._rank = rank return rv def __sub__(self, other): """Return the permutation that is other lower in rank than self. See Also ======== __add__ """ return self.__add__(-other) @staticmethod def rmul(args): """ Return product of Permutations [a, b, c, ...] as the Permutation whose ith value is a(b(c(i))). a, b, c, ... can be Permutation objects or tuples. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> a = Permutation(a); b = Permutation(b) >>> list(Permutation.rmul(a, b)) [1, 2, 0] >>> [a(b(i)) for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ```` operator: >>> a = Permutation(a); b = Permutation(b) >>> list(ab) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] Notes ===== All items in the sequence will be parsed by Permutation as necessary as long as the first item is a Permutation: >>> Permutation.rmul(a, [0, 2, 1]) == Permutation.rmul(a, b) True The reverse order of arguments will raise a TypeError. """ rv = args[0] for i in range(1, len(args)): rv = args[i]rv return rv @classmethod def rmul_with_af(cls, args): """ same as rmul, but the elements of args are Permutation objects which have _array_form """ a = [x._array_form for x in args] rv = cls._af_new(_af_rmuln(a)) return rv def mul_inv(self, other): """ other~self, self and other have _array_form """ a = _af_invert(self._array_form) b = other._array_form return self._af_new(_af_rmul(a, b)) def __rmul__(self, other): """This is needed to coerce other to Permutation in rmul.""" cls = type(self) return cls(other)self def __mul__(self, other): """ Return the product ab as a Permutation; the ith value is b(a(i)). Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> a = Permutation(a); b = Permutation(b) >>> list(ab) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] This handles operands in reverse order compared to _af_rmul and rmul: >>> al = list(a); bl = list(b) >>> _af_rmul(al, bl) [1, 2, 0] >>> [al[bl[i]] for i in range(3)] [1, 2, 0] It is acceptable for the arrays to have different lengths; the shorter one will be padded to match the longer one: >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> bPermutation([1, 0]) Permutation([1, 2, 0]) >>> Permutation([1, 0])b Permutation([2, 0, 1]) It is also acceptable to allow coercion to handle conversion of a single list to the left of a Permutation: >>> [0, 1]a # no change: 2-element identity Permutation([1, 0, 2]) >>> [[0, 1]]a # exchange first two elements Permutation([0, 1, 2]) You cannot use more than 1 cycle notation in a product of cycles since coercion can only handle one argument to the left. To handle multiple cycles it is convenient to use Cycle instead of Permutation: >>> [[1, 2]][[2, 3]]Permutation([]) # doctest: +SKIP >>> from sympy.combinatorics.permutations import Cycle >>> Cycle(1, 2)(2, 3) (1 3 2) """ from sympy.combinatorics.perm_groups import PermutationGroup, Coset if isinstance(other, PermutationGroup): return Coset(self, other, dir='-') a = self.array_form # __rmul__ makes sure the other is a Permutation b = other.array_form if not b: perm = a else: b.extend(list(range(len(b), len(a)))) perm = [b[i] for i in a] + b[len(a):] return self._af_new(perm) def commutes_with(self, other): """ Checks if the elements are commuting. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([1, 4, 3, 0, 2, 5]) >>> b = Permutation([0, 1, 2, 3, 4, 5]) >>> a.commutes_with(b) True >>> b = Permutation([2, 3, 5, 4, 1, 0]) >>> a.commutes_with(b) False """ a = self.array_form b = other.array_form return _af_commutes_with(a, b) def __pow__(self, n): """ Routine for finding powers of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([2, 0, 3, 1]) >>> p.order() 4 >>> p4 Permutation([0, 1, 2, 3]) """ if isinstance(n, Permutation): raise NotImplementedError( 'pp is not defined; do you mean p^p (conjugate)?') n = int(n) return self._af_new(_af_pow(self.array_form, n)) def __rxor__(self, i): """Return self(i) when ``i`` is an int. Examples ======== >>> from sympy.combinatorics import Permutation >>> p = Permutation(1, 2, 9) >>> 2^p == p(2) == 9 True """ if int(i) == i: return self(i) else: raise NotImplementedError( "i^p = p(i) when i is an integer, not %s." % i) def __xor__(self, h): """Return the conjugate permutation ``~hselfh` `. Explanation =========== If ``a`` and ``b`` are conjugates, ``a = hb~h`` and ``b = ~hah`` and both have the same cycle structure. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation(1, 2, 9) >>> q = Permutation(6, 9, 8) >>> pq != qp True Calculate and check properties of the conjugate: >>> c = p^q >>> c == ~qpq and p == qc~q True The expression q^p^r is equivalent to q^(pr): >>> r = Permutation(9)(4, 6, 8) >>> q^p^r == q^(pr) True If the term to the left of the conjugate operator, i, is an integer then this is interpreted as selecting the ith element from the permutation to the right: >>> all(i^p == p(i) for i in range(p.size)) True Note that the * operator as higher precedence than the ^ operator: >>> q^rp^r == q^(rp)^r == Permutation(9)(1, 6, 4) True Notes ===== In Python the precedence rule is p^q^r = (p^q)^r which differs in general from p^(q^r) >>> q^p^r (9)(1 4 8) >>> q^(p^r) (9)(1 8 6) For a given r and p, both of the following are conjugates of p: ~rpr and rp~r. But these are not necessarily the same: >>> ~rpr == rp~r True >>> p = Permutation(1, 2, 9)(5, 6) >>> ~rpr == rp~r False The conjugate ~rpr was chosen so that ``p^q^r`` would be equivalent to ``p^(qr)`` rather than ``p^(rq)``. To obtain rp~r, pass ~r to this method: >>> p^~r == rp~r True """ if self.size != h.size: raise ValueError("The permutations must be of equal size.") a = [None]self.size h = h._array_form p = self._array_form for i in range(self.size): a[h[i]] = h[p[i]] return self._af_new(a) def transpositions(self): """ Return the permutation decomposed into a list of transpositions. Explanation =========== It is always possible to express a permutation as the product of transpositions, see [1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[1, 2, 3], [0, 4, 5, 6, 7]]) >>> t = p.transpositions() >>> t [(0, 7), (0, 6), (0, 5), (0, 4), (1, 3), (1, 2)] >>> print(''.join(str(c) for c in t)) (0, 7)(0, 6)(0, 5)(0, 4)(1, 3)(1, 2) >>> Permutation.rmul([Permutation([ti], size=p.size) for ti in t]) == p True References ========== .. [1] https://en.wikipedia.org/wiki/Transposition_%28mathematics%29#Properties """ a = self.cyclic_form res = [] for x in a: nx = len(x) if nx == 2: res.append(tuple(x)) elif nx > 2: first = x[0] for y in x[nx - 1:0:-1]: res.append((first, y)) return res @classmethod def from_sequence(self, i, key=None): """Return the permutation needed to obtain ``i`` from the sorted elements of ``i``. If custom sorting is desired, a key can be given. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation.from_sequence('SymPy') (4)(0 1 3) >>> _(sorted("SymPy")) ['S', 'y', 'm', 'P', 'y'] >>> Permutation.from_sequence('SymPy', key=lambda x: x.lower()) (4)(0 2)(1 3) """ ic = list(zip(i, list(range(len(i))))) if key: ic.sort(key=lambda x: key(x[0])) else: ic.sort() return ~Permutation([i[1] for i in ic]) def __invert__(self): """ Return the inverse of the permutation. A permutation multiplied by its inverse is the identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([[2, 0], [3, 1]]) >>> ~p Permutation([2, 3, 0, 1]) >>> _ == p*-1 True >>> p~p == ~pp == Permutation([0, 1, 2, 3]) True """ return self._af_new(_af_invert(self._array_form)) def __iter__(self): """Yield elements from array form. Examples ======== >>> from sympy.combinatorics import Permutation >>> list(Permutation(range(3))) [0, 1, 2] """ yield from self.array_form def __repr__(self): from sympy.printing.repr import srepr return srepr(self) def __call__(self, i): """ Allows applying a permutation instance as a bijective function. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[2, 0], [3, 1]]) >>> p.array_form [2, 3, 0, 1] >>> [p(i) for i in range(4)] [2, 3, 0, 1] If an array is given then the permutation selects the items from the array (i.e. the permutation is applied to the array): >>> from sympy.abc import x >>> p([x, 1, 0, x2]) [0, x2, x, 1] """ # list indices can be Integer or int; leave this # as it is (don't test or convert it) because this # gets called a lot and should be fast if len(i) == 1: i = i[0] if not isinstance(i, Iterable): i = as_int(i) if i < 0 or i > self.size: raise TypeError( "{} should be an integer between 0 and {}" .format(i, self.size-1)) return self._array_form[i] # P([a, b, c]) if len(i) != self.size: raise TypeError( "{} should have the length {}.".format(i, self.size)) return [i[j] for j in self._array_form] # P(1, 2, 3) return selfPermutation(Cycle(i), size=self.size) def atoms(self): """ Returns all the elements of a permutation Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 1, 2, 3, 4, 5]).atoms() {0, 1, 2, 3, 4, 5} >>> Permutation([[0, 1], [2, 3], [4, 5]]).atoms() {0, 1, 2, 3, 4, 5} """ return set(self.array_form) def apply(self, i): r"""Apply the permutation to an expression. Parameters ========== i : Expr It should be an integer between $0$ and $n-1$ where $n$ is the size of the permutation. If it is a symbol or a symbolic expression that can have integer values, an ``AppliedPermutation`` object will be returned which can represent an unevaluated function. Notes ===== Any permutation can be defined as a bijective function $\sigma : \{ 0, 1, ..., n-1 \} \rightarrow \{ 0, 1, ..., n-1 \}$ where $n$ denotes the size of the permutation. The definition may even be extended for any set with distinctive elements, such that the permutation can even be applied for real numbers or such, however, it is not implemented for now for computational reasons and the integrity with the group theory module. This function is similar to the ``__call__`` magic, however, ``__call__`` magic already has some other applications like permuting an array or attatching new cycles, which would not always be mathematically consistent. This also guarantees that the return type is a SymPy integer, which guarantees the safety to use assumptions. """ i = _sympify(i) if i.is_integer is False: raise NotImplementedError("{} should be an integer.".format(i)) n = self.size if (i < 0) == True or (i >= n) == True: raise NotImplementedError( "{} should be an integer between 0 and {}".format(i, n-1)) if i.is_Integer: return Integer(self._array_form[i]) return AppliedPermutation(self, i) def next_lex(self): """ Returns the next permutation in lexicographical order. If self is the last permutation in lexicographical order it returns None. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 3, 1, 0]) >>> p = Permutation([2, 3, 1, 0]); p.rank() 17 >>> p = p.next_lex(); p.rank() 18 See Also ======== rank, unrank_lex """ perm = self.array_form[:] n = len(perm) i = n - 2 while perm[i + 1] < perm[i]: i -= 1 if i == -1: return None else: j = n - 1 while perm[j] < perm[i]: j -= 1 perm[j], perm[i] = perm[i], perm[j] i += 1 j = n - 1 while i < j: perm[j], perm[i] = perm[i], perm[j] i += 1 j -= 1 return self._af_new(perm) @classmethod def unrank_nonlex(self, n, r): """ This is a linear time unranking algorithm that does not respect lexicographic order [3]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.unrank_nonlex(4, 5) Permutation([2, 0, 3, 1]) >>> Permutation.unrank_nonlex(4, -1) Permutation([0, 1, 2, 3]) See Also ======== next_nonlex, rank_nonlex """ def _unrank1(n, r, a): if n > 0: a[n - 1], a[r % n] = a[r % n], a[n - 1] _unrank1(n - 1, r//n, a) id_perm = list(range(n)) n = int(n) r = r % ifac(n) _unrank1(n, r, id_perm) return self._af_new(id_perm) def rank_nonlex(self, inv_perm=None): """ This is a linear time ranking algorithm that does not enforce lexicographic order [3]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank_nonlex() 23 See Also ======== next_nonlex, unrank_nonlex """ def _rank1(n, perm, inv_perm): if n == 1: return 0 s = perm[n - 1] t = inv_perm[n - 1] perm[n - 1], perm[t] = perm[t], s inv_perm[n - 1], inv_perm[s] = inv_perm[s], t return s + n_rank1(n - 1, perm, inv_perm) if inv_perm is None: inv_perm = (~self).array_form if not inv_perm: return 0 perm = self.array_form[:] r = _rank1(len(perm), perm, inv_perm) return r def next_nonlex(self): """ Returns the next permutation in nonlex order [3]. If self is the last permutation in this order it returns None. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([2, 0, 3, 1]); p.rank_nonlex() 5 >>> p = p.next_nonlex(); p Permutation([3, 0, 1, 2]) >>> p.rank_nonlex() 6 See Also ======== rank_nonlex, unrank_nonlex """ r = self.rank_nonlex() if r == ifac(self.size) - 1: return None return self.unrank_nonlex(self.size, r + 1) def rank(self): """ Returns the lexicographic rank of the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank() 0 >>> p = Permutation([3, 2, 1, 0]) >>> p.rank() 23 See Also ======== next_lex, unrank_lex, cardinality, length, order, size """ if not self._rank is None: return self._rank rank = 0 rho = self.array_form[:] n = self.size - 1 size = n + 1 psize = int(ifac(n)) for j in range(size - 1): rank += rho[j]psize for i in range(j + 1, size): if rho[i] > rho[j]: rho[i] -= 1 psize //= n n -= 1 self._rank = rank return rank @property def cardinality(self): """ Returns the number of all possible permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.cardinality 24 See Also ======== length, order, rank, size """ return int(ifac(self.size)) def parity(self): """ Computes the parity of a permutation. Explanation =========== The parity of a permutation reflects the parity of the number of inversions in the permutation, i.e., the number of pairs of x and y such that ``x > y`` but ``p[x] < p[y]``. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.parity() 0 >>> p = Permutation([3, 2, 0, 1]) >>> p.parity() 1 See Also ======== _af_parity """ if self._cyclic_form is not None: return (self.size - self.cycles) % 2 return _af_parity(self.array_form) @property def is_even(self): """ Checks if a permutation is even. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.is_even True >>> p = Permutation([3, 2, 1, 0]) >>> p.is_even True See Also ======== is_odd """ return not self.is_odd @property def is_odd(self): """ Checks if a permutation is odd. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.is_odd False >>> p = Permutation([3, 2, 0, 1]) >>> p.is_odd True See Also ======== is_even """ return bool(self.parity() % 2) @property def is_Singleton(self): """ Checks to see if the permutation contains only one number and is thus the only possible permutation of this set of numbers Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0]).is_Singleton True >>> Permutation([0, 1]).is_Singleton False See Also ======== is_Empty """ return self.size == 1 @property def is_Empty(self): """ Checks to see if the permutation is a set with zero elements Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([]).is_Empty True >>> Permutation([0]).is_Empty False See Also ======== is_Singleton """ return self.size == 0 @property def is_identity(self): return self.is_Identity @property def is_Identity(self): """ Returns True if the Permutation is an identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([]) >>> p.is_Identity True >>> p = Permutation([[0], [1], [2]]) >>> p.is_Identity True >>> p = Permutation([0, 1, 2]) >>> p.is_Identity True >>> p = Permutation([0, 2, 1]) >>> p.is_Identity False See Also ======== order """ af = self.array_form return not af or all(i == af[i] for i in range(self.size)) def ascents(self): """ Returns the positions of ascents in a permutation, ie, the location where p[i] < p[i+1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 0, 1, 3, 2]) >>> p.ascents() [1, 2] See Also ======== descents, inversions, min, max """ a = self.array_form pos = [i for i in range(len(a) - 1) if a[i] < a[i + 1]] return pos def descents(self): """ Returns the positions of descents in a permutation, ie, the location where p[i] > p[i+1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 0, 1, 3, 2]) >>> p.descents() [0, 3] See Also ======== ascents, inversions, min, max """ a = self.array_form pos = [i for i in range(len(a) - 1) if a[i] > a[i + 1]] return pos def max(self): """ The maximum element moved by the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([1, 0, 2, 3, 4]) >>> p.max() 1 See Also ======== min, descents, ascents, inversions """ max = 0 a = self.array_form for i in range(len(a)): if a[i] != i and a[i] > max: max = a[i] return max def min(self): """ The minimum element moved by the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 4, 3, 2]) >>> p.min() 2 See Also ======== max, descents, ascents, inversions """ a = self.array_form min = len(a) for i in range(len(a)): if a[i] != i and a[i] < min: min = a[i] return min def inversions(self): """ Computes the number of inversions of a permutation. Explanation =========== An inversion is where i > j but p[i] < p[j]. For small length of p, it iterates over all i and j values and calculates the number of inversions. For large length of p, it uses a variation of merge sort to calculate the number of inversions. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3, 4, 5]) >>> p.inversions() 0 >>> Permutation([3, 2, 1, 0]).inversions() 6 See Also ======== descents, ascents, min, max References ========== .. [1] http://www.cp.eng.chula.ac.th/~piak/teaching/algo/algo2008/count-inv.htm """ inversions = 0 a = self.array_form n = len(a) if n < 130: for i in range(n - 1): b = a[i] for c in a[i + 1:]: if b > c: inversions += 1 else: k = 1 right = 0 arr = a[:] temp = a[:] while k < n: i = 0 while i + k < n: right = i + k * 2 - 1 if right >= n: right = n - 1 inversions += _merge(arr, temp, i, i + k, right) i = i + k * 2 k = k * 2 return inversions def commutator(self, x): """Return the commutator of ``self`` and ``x``: ``~x~selfxself`` If f and g are part of a group, G, then the commutator of f and g is the group identity iff f and g commute, i.e. fg == gf. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([0, 2, 3, 1]) >>> x = Permutation([2, 0, 3, 1]) >>> c = p.commutator(x); c Permutation([2, 1, 3, 0]) >>> c == ~x~pxp True >>> I = Permutation(3) >>> p = [I + i for i in range(6)] >>> for i in range(len(p)): ... for j in range(len(p)): ... c = p[i].commutator(p[j]) ... if p[i]p[j] == p[j]p[i]: ... assert c == I ... else: ... assert c != I ... References ========== https://en.wikipedia.org/wiki/Commutator """ a = self.array_form b = x.array_form n = len(a) if len(b) != n: raise ValueError("The permutations must be of equal size.") inva = [None]n for i in range(n): inva[a[i]] = i invb = [None]n for i in range(n): invb[b[i]] = i return self._af_new([a[b[inva[i]]] for i in invb]) def signature(self): """ Gives the signature of the permutation needed to place the elements of the permutation in canonical order. The signature is calculated as (-1)^<number of inversions> Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2]) >>> p.inversions() 0 >>> p.signature() 1 >>> q = Permutation([0,2,1]) >>> q.inversions() 1 >>> q.signature() -1 See Also ======== inversions """ if self.is_even: return 1 return -1 def order(self): """ Computes the order of a permutation. When the permutation is raised to the power of its order it equals the identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([3, 1, 5, 2, 4, 0]) >>> p.order() 4 >>> (p*(p.order())) Permutation([], size=6) See Also ======== identity, cardinality, length, rank, size """ return reduce(lcm, [len(cycle) for cycle in self.cyclic_form], 1) def length(self): """ Returns the number of integers moved by a permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 3, 2, 1]).length() 2 >>> Permutation([[0, 1], [2, 3]]).length() 4 See Also ======== min, max, support, cardinality, order, rank, size """ return len(self.support()) @property def cycle_structure(self): """Return the cycle structure of the permutation as a dictionary indicating the multiplicity of each cycle length. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation(3).cycle_structure {1: 4} >>> Permutation(0, 4, 3)(1, 2)(5, 6).cycle_structure {2: 2, 3: 1} """ if self._cycle_structure: rv = self._cycle_structure else: rv = defaultdict(int) singletons = self.size for c in self.cyclic_form: rv[len(c)] += 1 singletons -= len(c) if singletons: rv[1] = singletons self._cycle_structure = rv return dict(rv) # make a copy @property def cycles(self): """ Returns the number of cycles contained in the permutation (including singletons). Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 1, 2]).cycles 3 >>> Permutation([0, 1, 2]).full_cyclic_form [[0], [1], [2]] >>> Permutation(0, 1)(2, 3).cycles 2 See Also ======== sympy.functions.combinatorial.numbers.stirling """ return len(self.full_cyclic_form) def index(self): """ Returns the index of a permutation. The index of a permutation is the sum of all subscripts j such that p[j] is greater than p[j+1]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([3, 0, 2, 1, 4]) >>> p.index() 2 """ a = self.array_form return sum([j for j in range(len(a) - 1) if a[j] > a[j + 1]]) def runs(self): """ Returns the runs of a permutation. An ascending sequence in a permutation is called a run [5]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 5, 7, 3, 6, 0, 1, 4, 8]) >>> p.runs() [[2, 5, 7], [3, 6], [0, 1, 4, 8]] >>> q = Permutation([1,3,2,0]) >>> q.runs() [[1, 3], [2], [0]] """ return runs(self.array_form) def inversion_vector(self): """Return the inversion vector of the permutation. The inversion vector consists of elements whose value indicates the number of elements in the permutation that are lesser than it and lie on its right hand side. The inversion vector is the same as the Lehmer encoding of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 8, 0, 7, 1, 5, 3, 6, 2]) >>> p.inversion_vector() [4, 7, 0, 5, 0, 2, 1, 1] >>> p = Permutation([3, 2, 1, 0]) >>> p.inversion_vector() [3, 2, 1] The inversion vector increases lexicographically with the rank of the permutation, the -ith element cycling through 0..i. >>> p = Permutation(2) >>> while p: ... print('%s %s %s' % (p, p.inversion_vector(), p.rank())) ... p = p.next_lex() (2) [0, 0] 0 (1 2) [0, 1] 1 (2)(0 1) [1, 0] 2 (0 1 2) [1, 1] 3 (0 2 1) [2, 0] 4 (0 2) [2, 1] 5 See Also ======== from_inversion_vector """ self_array_form = self.array_form n = len(self_array_form) inversion_vector = [0] (n - 1) for i in range(n - 1): val = 0 for j in range(i + 1, n): if self_array_form[j] < self_array_form[i]: val += 1 inversion_vector[i] = val return inversion_vector def rank_trotterjohnson(self): """ Returns the Trotter Johnson rank, which we get from the minimal change algorithm. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank_trotterjohnson() 0 >>> p = Permutation([0, 2, 1, 3]) >>> p.rank_trotterjohnson() 7 See Also ======== unrank_trotterjohnson, next_trotterjohnson """ if self.array_form == [] or self.is_Identity: return 0 if self.array_form == [1, 0]: return 1 perm = self.array_form n = self.size rank = 0 for j in range(1, n): k = 1 i = 0 while perm[i] != j: if perm[i] < j: k += 1 i += 1 j1 = j + 1 if rank % 2 == 0: rank = j1rank + j1 - k else: rank = j1rank + k - 1 return rank @classmethod def unrank_trotterjohnson(cls, size, rank): """ Trotter Johnson permutation unranking. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.unrank_trotterjohnson(5, 10) Permutation([0, 3, 1, 2, 4]) See Also ======== rank_trotterjohnson, next_trotterjohnson """ perm = [0]size r2 = 0 n = ifac(size) pj = 1 for j in range(2, size + 1): pj = j r1 = (rank * pj) // n k = r1 - jr2 if r2 % 2 == 0: for i in range(j - 1, j - k - 1, -1): perm[i] = perm[i - 1] perm[j - k - 1] = j - 1 else: for i in range(j - 1, k, -1): perm[i] = perm[i - 1] perm[k] = j - 1 r2 = r1 return cls._af_new(perm) def next_trotterjohnson(self): """ Returns the next permutation in Trotter-Johnson order. If self is the last permutation it returns None. See [4] section 2.4. If it is desired to generate all such permutations, they can be generated in order more quickly with the ``generate_bell`` function. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([3, 0, 2, 1]) >>> p.rank_trotterjohnson() 4 >>> p = p.next_trotterjohnson(); p Permutation([0, 3, 2, 1]) >>> p.rank_trotterjohnson() 5 See Also ======== rank_trotterjohnson, unrank_trotterjohnson, sympy.utilities.iterables.generate_bell """ pi = self.array_form[:] n = len(pi) st = 0 rho = pi[:] done = False m = n-1 while m > 0 and not done: d = rho.index(m) for i in range(d, m): rho[i] = rho[i + 1] par = _af_parity(rho[:m]) if par == 1: if d == m: m -= 1 else: pi[st + d], pi[st + d + 1] = pi[st + d + 1], pi[st + d] done = True else: if d == 0: m -= 1 st += 1 else: pi[st + d], pi[st + d - 1] = pi[st + d - 1], pi[st + d] done = True if m == 0: return None return self._af_new(pi) def get_precedence_matrix(self): """ Gets the precedence matrix. This is used for computing the distance between two permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation.josephus(3, 6, 1) >>> p Permutation([2, 5, 3, 1, 4, 0]) >>> p.get_precedence_matrix() Matrix([ [0, 0, 0, 0, 0, 0], [1, 0, 0, 0, 1, 0], [1, 1, 0, 1, 1, 1], [1, 1, 0, 0, 1, 0], [1, 0, 0, 0, 0, 0], [1, 1, 0, 1, 1, 0]]) See Also ======== get_precedence_distance, get_adjacency_matrix, get_adjacency_distance """ m = zeros(self.size) perm = self.array_form for i in range(m.rows): for j in range(i + 1, m.cols): m[perm[i], perm[j]] = 1 return m def get_precedence_distance(self, other): """ Computes the precedence distance between two permutations. Explanation =========== Suppose p and p' represent n jobs. The precedence metric counts the number of times a job j is preceded by job i in both p and p'. This metric is commutative. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 0, 4, 3, 1]) >>> q = Permutation([3, 1, 2, 4, 0]) >>> p.get_precedence_distance(q) 7 >>> q.get_precedence_distance(p) 7 See Also ======== get_precedence_matrix, get_adjacency_matrix, get_adjacency_distance """ if self.size != other.size: raise ValueError("The permutations must be of equal size.") self_prec_mat = self.get_precedence_matrix() other_prec_mat = other.get_precedence_matrix() n_prec = 0 for i in range(self.size): for j in range(self.size): if i == j: continue if self_prec_mat[i, j] other_prec_mat[i, j] == 1: n_prec += 1 d = self.size * (self.size - 1)//2 - n_prec return d def get_adjacency_matrix(self): """ Computes the adjacency matrix of a permutation. Explanation =========== If job i is adjacent to job j in a permutation p then we set m[i, j] = 1 where m is the adjacency matrix of p. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation.josephus(3, 6, 1) >>> p.get_adjacency_matrix() Matrix([ [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 1, 0], [0, 0, 0, 0, 0, 1], [0, 1, 0, 0, 0, 0], [1, 0, 0, 0, 0, 0], [0, 0, 0, 1, 0, 0]]) >>> q = Permutation([0, 1, 2, 3]) >>> q.get_adjacency_matrix() Matrix([ [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1], [0, 0, 0, 0]]) See Also ======== get_precedence_matrix, get_precedence_distance, get_adjacency_distance """ m = zeros(self.size) perm = self.array_form for i in range(self.size - 1): m[perm[i], perm[i + 1]] = 1 return m def get_adjacency_distance(self, other): """ Computes the adjacency distance between two permutations. Explanation =========== This metric counts the number of times a pair i,j of jobs is adjacent in both p and p'. If n_adj is this quantity then the adjacency distance is n - n_adj - 1 [1] [1] Reeves, Colin R. Landscapes, Operators and Heuristic search, Annals of Operational Research, 86, pp 473-490. (1999) Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2, 4]) >>> q = Permutation.josephus(4, 5, 2) >>> p.get_adjacency_distance(q) 3 >>> r = Permutation([0, 2, 1, 4, 3]) >>> p.get_adjacency_distance(r) 4 See Also ======== get_precedence_matrix, get_precedence_distance, get_adjacency_matrix """ if self.size != other.size: raise ValueError("The permutations must be of the same size.") self_adj_mat = self.get_adjacency_matrix() other_adj_mat = other.get_adjacency_matrix() n_adj = 0 for i in range(self.size): for j in range(self.size): if i == j: continue if self_adj_mat[i, j] * other_adj_mat[i, j] == 1: n_adj += 1 d = self.size - n_adj - 1 return d def get_positional_distance(self, other): """ Computes the positional distance between two permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2, 4]) >>> q = Permutation.josephus(4, 5, 2) >>> r = Permutation([3, 1, 4, 0, 2]) >>> p.get_positional_distance(q) 12 >>> p.get_positional_distance(r) 12 See Also ======== get_precedence_distance, get_adjacency_distance """ a = self.array_form b = other.array_form if len(a) != len(b): raise ValueError("The permutations must be of the same size.") return sum([abs(a[i] - b[i]) for i in range(len(a))]) @classmethod def josephus(cls, m, n, s=1): """Return as a permutation the shuffling of range(n) using the Josephus scheme in which every m-th item is selected until all have been chosen. The returned permutation has elements listed by the order in which they were selected. The parameter ``s`` stops the selection process when there are ``s`` items remaining and these are selected by continuing the selection, counting by 1 rather than by ``m``. Consider selecting every 3rd item from 6 until only 2 remain:: choices chosen ======== ====== 012345 01 345 2 01 34 25 01 4 253 0 4 2531 0 25314 253140 Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation.josephus(3, 6, 2).array_form [2, 5, 3, 1, 4, 0] References ========== .. [1] https://en.wikipedia.org/wiki/Flavius_Josephus .. [2] https://en.wikipedia.org/wiki/Josephus_problem .. [3] http://www.wou.edu/~burtonl/josephus.html """ from collections import deque m -= 1 Q = deque(list(range(n))) perm = [] while len(Q) > max(s, 1): for dp in range(m): Q.append(Q.popleft()) perm.append(Q.popleft()) perm.extend(list(Q)) return cls(perm) @classmethod def from_inversion_vector(cls, inversion): """ Calculates the permutation from the inversion vector. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.from_inversion_vector([3, 2, 1, 0, 0]) Permutation([3, 2, 1, 0, 4, 5]) """ size = len(inversion) N = list(range(size + 1)) perm = [] try: for k in range(size): val = N[inversion[k]] perm.append(val) N.remove(val) except IndexError: raise ValueError("The inversion vector is not valid.") perm.extend(N) return cls._af_new(perm) @classmethod def random(cls, n): """ Generates a random permutation of length ``n``. Uses the underlying Python pseudo-random number generator. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> Permutation.random(2) in (Permutation([1, 0]), Permutation([0, 1])) True """ perm_array = list(range(n)) random.shuffle(perm_array) return cls._af_new(perm_array) @classmethod def unrank_lex(cls, size, rank): """ Lexicographic permutation unranking. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> a = Permutation.unrank_lex(5, 10) >>> a.rank() 10 >>> a Permutation([0, 2, 4, 1, 3]) See Also ======== rank, next_lex """ perm_array = [0] * size psize = 1 for i in range(size): new_psize = psize(i + 1) d = (rank % new_psize) // psize rank -= dpsize perm_array[size - i - 1] = d for j in range(size - i, size): if perm_array[j] > d - 1: perm_array[j] += 1 psize = new_psize return cls._af_new(perm_array) def resize(self, n): """Resize the permutation to the new size ``n``. Parameters ========== n : int The new size of the permutation. Raises ====== ValueError If the permutation cannot be resized to the given size. This may only happen when resized to a smaller size than the original. Examples ======== >>> from sympy.combinatorics.permutations import Permutation Increasing the size of a permutation: >>> p = Permutation(0, 1, 2) >>> p = p.resize(5) >>> p (4)(0 1 2) Decreasing the size of the permutation: >>> p = p.resize(4) >>> p (3)(0 1 2) If resizing to the specific size breaks the cycles: >>> p.resize(2) Traceback (most recent call last): ... ValueError: The permutation can not be resized to 2 because the cycle (0, 1, 2) may break. """ aform = self.array_form l = len(aform) if n > l: aform += list(range(l, n)) return Permutation._af_new(aform) elif n < l: cyclic_form = self.full_cyclic_form new_cyclic_form = [] for cycle in cyclic_form: cycle_min = min(cycle) cycle_max = max(cycle) if cycle_min <= n-1: if cycle_max > n-1: raise ValueError( "The permutation can not be resized to {} " "because the cycle {} may break." .format(n, tuple(cycle))) new_cyclic_form.append(cycle) return Permutation(new_cyclic_form) return self # XXX Deprecated flag print_cyclic = None def _merge(arr, temp, left, mid, right): """ Merges two sorted arrays and calculates the inversion count. Helper function for calculating inversions. This method is for internal use only. """ i = k = left j = mid inv_count = 0 while i < mid and j <= right: if arr[i] < arr[j]: temp[k] = arr[i] k += 1 i += 1 else: temp[k] = arr[j] k += 1 j += 1 inv_count += (mid -i) while i < mid: temp[k] = arr[i] k += 1 i += 1 if j <= right: k += right - j + 1 j += right - j + 1 arr[left:k + 1] = temp[left:k + 1] else: arr[left:right + 1] = temp[left:right + 1] return inv_count Perm = Permutation _af_new = Perm._af_new class AppliedPermutation(Expr): """A permutation applied to a symbolic variable. Parameters ========== perm : Permutation x : Expr Examples ======== >>> from sympy import Symbol >>> from sympy.combinatorics import Permutation Creating a symbolic permutation function application: >>> x = Symbol('x') >>> p = Permutation(0, 1, 2) >>> p.apply(x) AppliedPermutation((0 1 2), x) >>> _.subs(x, 1) 2 """ def __new__(cls, perm, x, evaluate=None): if evaluate is None: evaluate = global_parameters.evaluate perm = _sympify(perm) x = _sympify(x) if not isinstance(perm, Permutation): raise ValueError("{} must be a Permutation instance." .format(perm)) if evaluate: if x.is_Integer: return perm.apply(x) obj = super().__new__(cls, perm, x) return obj @dispatch(Permutation, Permutation) def _eval_is_eq(lhs, rhs): if lhs._size != rhs._size: return None return lhs._array_form == rhs._array_form
dcbff30c138b49b2ba5c8435bedee7ec8b793900e080202fb10db1224d56aa56	from itertools import combinations from sympy.combinatorics.graycode import GrayCode from sympy.core import Basic class Subset(Basic): """ Represents a basic subset object. Explanation =========== We generate subsets using essentially two techniques, binary enumeration and lexicographic enumeration. The Subset class takes two arguments, the first one describes the initial subset to consider and the second describes the superset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset ['b'] >>> a.prev_binary().subset ['c'] """ _rank_binary = None _rank_lex = None _rank_graycode = None _subset = None _superset = None def __new__(cls, subset, superset): """ Default constructor. It takes the ``subset`` and its ``superset`` as its parameters. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.subset ['c', 'd'] >>> a.superset ['a', 'b', 'c', 'd'] >>> a.size 2 """ if len(subset) > len(superset): raise ValueError('Invalid arguments have been provided. The ' 'superset must be larger than the subset.') for elem in subset: if elem not in superset: raise ValueError('The superset provided is invalid as it does ' 'not contain the element {}'.format(elem)) obj = Basic.__new__(cls) obj._subset = subset obj._superset = superset return obj def iterate_binary(self, k): """ This is a helper function. It iterates over the binary subsets by ``k`` steps. This variable can be both positive or negative. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.iterate_binary(-2).subset ['d'] >>> a = Subset(['a', 'b', 'c'], ['a', 'b', 'c', 'd']) >>> a.iterate_binary(2).subset [] See Also ======== next_binary, prev_binary """ bin_list = Subset.bitlist_from_subset(self.subset, self.superset) n = (int(''.join(bin_list), 2) + k) % 2self.superset_size bits = bin(n)[2:].rjust(self.superset_size, '0') return Subset.subset_from_bitlist(self.superset, bits) def next_binary(self): """ Generates the next binary ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset ['b'] >>> a = Subset(['a', 'b', 'c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset [] See Also ======== prev_binary, iterate_binary """ return self.iterate_binary(1) def prev_binary(self): """ Generates the previous binary ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a', 'b', 'c', 'd']) >>> a.prev_binary().subset ['a', 'b', 'c', 'd'] >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.prev_binary().subset ['c'] See Also ======== next_binary, iterate_binary """ return self.iterate_binary(-1) def next_lexicographic(self): """ Generates the next lexicographically ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_lexicographic().subset ['d'] >>> a = Subset(['d'], ['a', 'b', 'c', 'd']) >>> a.next_lexicographic().subset [] See Also ======== prev_lexicographic """ i = self.superset_size - 1 indices = Subset.subset_indices(self.subset, self.superset) if i in indices: if i - 1 in indices: indices.remove(i - 1) else: indices.remove(i) i = i - 1 while not i in indices and i >= 0: i = i - 1 if i >= 0: indices.remove(i) indices.append(i+1) else: while i not in indices and i >= 0: i = i - 1 indices.append(i + 1) ret_set = [] super_set = self.superset for i in indices: ret_set.append(super_set[i]) return Subset(ret_set, super_set) def prev_lexicographic(self): """ Generates the previous lexicographically ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a', 'b', 'c', 'd']) >>> a.prev_lexicographic().subset ['d'] >>> a = Subset(['c','d'], ['a', 'b', 'c', 'd']) >>> a.prev_lexicographic().subset ['c'] See Also ======== next_lexicographic """ i = self.superset_size - 1 indices = Subset.subset_indices(self.subset, self.superset) while i not in indices and i >= 0: i = i - 1 if i - 1 in indices or i == 0: indices.remove(i) else: if i >= 0: indices.remove(i) indices.append(i - 1) indices.append(self.superset_size - 1) ret_set = [] super_set = self.superset for i in indices: ret_set.append(super_set[i]) return Subset(ret_set, super_set) def iterate_graycode(self, k): """ Helper function used for prev_gray and next_gray. It performs ``k`` step overs to get the respective Gray codes. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([1, 2, 3], [1, 2, 3, 4]) >>> a.iterate_graycode(3).subset [1, 4] >>> a.iterate_graycode(-2).subset [1, 2, 4] See Also ======== next_gray, prev_gray """ unranked_code = GrayCode.unrank(self.superset_size, (self.rank_gray + k) % self.cardinality) return Subset.subset_from_bitlist(self.superset, unranked_code) def next_gray(self): """ Generates the next Gray code ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([1, 2, 3], [1, 2, 3, 4]) >>> a.next_gray().subset [1, 3] See Also ======== iterate_graycode, prev_gray """ return self.iterate_graycode(1) def prev_gray(self): """ Generates the previous Gray code ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([2, 3, 4], [1, 2, 3, 4, 5]) >>> a.prev_gray().subset [2, 3, 4, 5] See Also ======== iterate_graycode, next_gray """ return self.iterate_graycode(-1) @property def rank_binary(self): """ Computes the binary ordered rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a','b','c','d']) >>> a.rank_binary 0 >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.rank_binary 3 See Also ======== iterate_binary, unrank_binary """ if self._rank_binary is None: self._rank_binary = int("".join( Subset.bitlist_from_subset(self.subset, self.superset)), 2) return self._rank_binary @property def rank_lexicographic(self): """ Computes the lexicographic ranking of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.rank_lexicographic 14 >>> a = Subset([2, 4, 5], [1, 2, 3, 4, 5, 6]) >>> a.rank_lexicographic 43 """ if self._rank_lex is None: def _ranklex(self, subset_index, i, n): if subset_index == [] or i > n: return 0 if i in subset_index: subset_index.remove(i) return 1 + _ranklex(self, subset_index, i + 1, n) return 2(n - i - 1) + _ranklex(self, subset_index, i + 1, n) indices = Subset.subset_indices(self.subset, self.superset) self._rank_lex = _ranklex(self, indices, 0, self.superset_size) return self._rank_lex @property def rank_gray(self): """ Computes the Gray code ranking of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c','d'], ['a','b','c','d']) >>> a.rank_gray 2 >>> a = Subset([2, 4, 5], [1, 2, 3, 4, 5, 6]) >>> a.rank_gray 27 See Also ======== iterate_graycode, unrank_gray """ if self._rank_graycode is None: bits = Subset.bitlist_from_subset(self.subset, self.superset) self._rank_graycode = GrayCode(len(bits), start=bits).rank return self._rank_graycode @property def subset(self): """ Gets the subset represented by the current instance. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.subset ['c', 'd'] See Also ======== superset, size, superset_size, cardinality """ return self._subset @property def size(self): """ Gets the size of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.size 2 See Also ======== subset, superset, superset_size, cardinality """ return len(self.subset) @property def superset(self): """ Gets the superset of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.superset ['a', 'b', 'c', 'd'] See Also ======== subset, size, superset_size, cardinality """ return self._superset @property def superset_size(self): """ Returns the size of the superset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.superset_size 4 See Also ======== subset, superset, size, cardinality """ return len(self.superset) @property def cardinality(self): """ Returns the number of all possible subsets. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.cardinality 16 See Also ======== subset, superset, size, superset_size """ return 2*(self.superset_size) @classmethod def subset_from_bitlist(self, super_set, bitlist): """ Gets the subset defined by the bitlist. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.subset_from_bitlist(['a', 'b', 'c', 'd'], '0011').subset ['c', 'd'] See Also ======== bitlist_from_subset """ if len(super_set) != len(bitlist): raise ValueError("The sizes of the lists are not equal") ret_set = [] for i in range(len(bitlist)): if bitlist[i] == '1': ret_set.append(super_set[i]) return Subset(ret_set, super_set) @classmethod def bitlist_from_subset(self, subset, superset): """ Gets the bitlist corresponding to a subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.bitlist_from_subset(['c', 'd'], ['a', 'b', 'c', 'd']) '0011' See Also ======== subset_from_bitlist """ bitlist = ['0'] len(superset) if type(subset) is Subset: subset = subset.subset for i in Subset.subset_indices(subset, superset): bitlist[i] = '1' return ''.join(bitlist) @classmethod def unrank_binary(self, rank, superset): """ Gets the binary ordered subset of the specified rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.unrank_binary(4, ['a', 'b', 'c', 'd']).subset ['b'] See Also ======== iterate_binary, rank_binary """ bits = bin(rank)[2:].rjust(len(superset), '0') return Subset.subset_from_bitlist(superset, bits) @classmethod def unrank_gray(self, rank, superset): """ Gets the Gray code ordered subset of the specified rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.unrank_gray(4, ['a', 'b', 'c']).subset ['a', 'b'] >>> Subset.unrank_gray(0, ['a', 'b', 'c']).subset [] See Also ======== iterate_graycode, rank_gray """ graycode_bitlist = GrayCode.unrank(len(superset), rank) return Subset.subset_from_bitlist(superset, graycode_bitlist) @classmethod def subset_indices(self, subset, superset): """Return indices of subset in superset in a list; the list is empty if all elements of ``subset`` are not in ``superset``. Examples ======== >>> from sympy.combinatorics import Subset >>> superset = [1, 3, 2, 5, 4] >>> Subset.subset_indices([3, 2, 1], superset) [1, 2, 0] >>> Subset.subset_indices([1, 6], superset) [] >>> Subset.subset_indices([], superset) [] """ a, b = superset, subset sb = set(b) d = {} for i, ai in enumerate(a): if ai in sb: d[ai] = i sb.remove(ai) if not sb: break else: return list() return [d[bi] for bi in b] def ksubsets(superset, k): """ Finds the subsets of size ``k`` in lexicographic order. This uses the itertools generator. Examples ======== >>> from sympy.combinatorics.subsets import ksubsets >>> list(ksubsets([1, 2, 3], 2)) [(1, 2), (1, 3), (2, 3)] >>> list(ksubsets([1, 2, 3, 4, 5], 2)) [(1, 2), (1, 3), (1, 4), (1, 5), (2, 3), (2, 4), \ (2, 5), (3, 4), (3, 5), (4, 5)] See Also ======== Subset """ return combinations(superset, k)
20ac75dbfc9626a110ee0fa806e0167795512db08e5b22f42c6e0f42ee37052f	from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.permutations import Permutation from sympy.utilities.iterables import uniq _af_new = Permutation._af_new def DirectProduct(groups): """ Returns the direct product of several groups as a permutation group. Explanation =========== This is implemented much like the __mul__ procedure for taking the direct product of two permutation groups, but the idea of shifting the generators is realized in the case of an arbitrary number of groups. A call to DirectProduct(G1, G2, ..., Gn) is generally expected to be faster than a call to G1G2...Gn (and thus the need for this algorithm). Examples ======== >>> from sympy.combinatorics.group_constructs import DirectProduct >>> from sympy.combinatorics.named_groups import CyclicGroup >>> C = CyclicGroup(4) >>> G = DirectProduct(C, C, C) >>> G.order() 64 See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.__mul__ """ degrees = [] gens_count = [] total_degree = 0 total_gens = 0 for group in groups: current_deg = group.degree current_num_gens = len(group.generators) degrees.append(current_deg) total_degree += current_deg gens_count.append(current_num_gens) total_gens += current_num_gens array_gens = [] for i in range(total_gens): array_gens.append(list(range(total_degree))) current_gen = 0 current_deg = 0 for i in range(len(gens_count)): for j in range(current_gen, current_gen + gens_count[i]): gen = ((groups[i].generators)[j - current_gen]).array_form array_gens[j][current_deg:current_deg + degrees[i]] = \ [x + current_deg for x in gen] current_gen += gens_count[i] current_deg += degrees[i] perm_gens = list(uniq([_af_new(list(a)) for a in array_gens])) return PermutationGroup(perm_gens, dups=False)
e606bdf433557bb0e9363559f9b0d58af0c56dde60895b16bda3bfe1546a88ff	from sympy.combinatorics.permutations import Permutation, _af_rmul, \ _af_invert, _af_new from sympy.combinatorics.perm_groups import PermutationGroup, _orbit, \ _orbit_transversal from sympy.combinatorics.util import _distribute_gens_by_base, \ _orbits_transversals_from_bsgs """ References for tensor canonicalization: [1] R. Portugal "Algorithmic simplification of tensor expressions", J. Phys. A 32 (1999) 7779-7789 [2] R. Portugal, B.F. Svaiter "Group-theoretic Approach for Symbolic Tensor Manipulation: I. Free Indices" arXiv:math-ph/0107031v1 [3] L.R.U. Manssur, R. Portugal "Group-theoretic Approach for Symbolic Tensor Manipulation: II. Dummy Indices" arXiv:math-ph/0107032v1 [4] xperm.c part of XPerm written by J. M. Martin-Garcia http://www.xact.es/index.html """ def dummy_sgs(dummies, sym, n): """ Return the strong generators for dummy indices. Parameters ========== dummies : List of dummy indices. `dummies[2k], dummies[2k+1]` are paired indices. In base form, the dummy indices are always in consecutive positions. sym : symmetry under interchange of contracted dummies:: * None no symmetry * 0 commuting * 1 anticommuting n : number of indices Examples ======== >>> from sympy.combinatorics.tensor_can import dummy_sgs >>> dummy_sgs(list(range(2, 8)), 0, 8) [[0, 1, 3, 2, 4, 5, 6, 7, 8, 9], [0, 1, 2, 3, 5, 4, 6, 7, 8, 9], [0, 1, 2, 3, 4, 5, 7, 6, 8, 9], [0, 1, 4, 5, 2, 3, 6, 7, 8, 9], [0, 1, 2, 3, 6, 7, 4, 5, 8, 9]] """ if len(dummies) > n: raise ValueError("List too large") res = [] # exchange of contravariant and covariant indices if sym is not None: for j in dummies[::2]: a = list(range(n + 2)) if sym == 1: a[n] = n + 1 a[n + 1] = n a[j], a[j + 1] = a[j + 1], a[j] res.append(a) # rename dummy indices for j in dummies[:-3:2]: a = list(range(n + 2)) a[j:j + 4] = a[j + 2], a[j + 3], a[j], a[j + 1] res.append(a) return res def _min_dummies(dummies, sym, indices): """ Return list of minima of the orbits of indices in group of dummies. See ``double_coset_can_rep`` for the description of ``dummies`` and ``sym``. ``indices`` is the initial list of dummy indices. Examples ======== >>> from sympy.combinatorics.tensor_can import _min_dummies >>> _min_dummies([list(range(2, 8))], [0], list(range(10))) [0, 1, 2, 2, 2, 2, 2, 2, 8, 9] """ num_types = len(sym) m = [] for dx in dummies: if dx: m.append(min(dx)) else: m.append(None) res = indices[:] for i in range(num_types): for c, i in enumerate(indices): for j in range(num_types): if i in dummies[j]: res[c] = m[j] break return res def _trace_S(s, j, b, S_cosets): """ Return the representative h satisfying s[h[b]] == j If there is not such a representative return None """ for h in S_cosets[b]: if s[h[b]] == j: return h return None def _trace_D(gj, p_i, Dxtrav): """ Return the representative h satisfying h[gj] == p_i If there is not such a representative return None """ for h in Dxtrav: if h[gj] == p_i: return h return None def _dumx_remove(dumx, dumx_flat, p0): """ remove p0 from dumx """ res = [] for dx in dumx: if p0 not in dx: res.append(dx) continue k = dx.index(p0) if k % 2 == 0: p0_paired = dx[k + 1] else: p0_paired = dx[k - 1] dx.remove(p0) dx.remove(p0_paired) dumx_flat.remove(p0) dumx_flat.remove(p0_paired) res.append(dx) def transversal2coset(size, base, transversal): a = [] j = 0 for i in range(size): if i in base: a.append(sorted(transversal[j].values())) j += 1 else: a.append([list(range(size))]) j = len(a) - 1 while a[j] == [list(range(size))]: j -= 1 return a[:j + 1] def double_coset_can_rep(dummies, sym, b_S, sgens, S_transversals, g): """ Butler-Portugal algorithm for tensor canonicalization with dummy indices. Parameters ========== dummies list of lists of dummy indices, one list for each type of index; the dummy indices are put in order contravariant, covariant [d0, -d0, d1, -d1, ...]. sym list of the symmetries of the index metric for each type. possible symmetries of the metrics * 0 symmetric * 1 antisymmetric * None no symmetry b_S base of a minimal slot symmetry BSGS. sgens generators of the slot symmetry BSGS. S_transversals transversals for the slot BSGS. g permutation representing the tensor. Returns ======= Return 0 if the tensor is zero, else return the array form of the permutation representing the canonical form of the tensor. Notes ===== A tensor with dummy indices can be represented in a number of equivalent ways which typically grows exponentially with the number of indices. To be able to establish if two tensors with many indices are equal becomes computationally very slow in absence of an efficient algorithm. The Butler-Portugal algorithm [3] is an efficient algorithm to put tensors in canonical form, solving the above problem. Portugal observed that a tensor can be represented by a permutation, and that the class of tensors equivalent to it under slot and dummy symmetries is equivalent to the double coset `DgS` (Note: in this documentation we use the conventions for multiplication of permutations p, q with (pq)(i) = p[q[i]] which is opposite to the one used in the Permutation class) Using the algorithm by Butler to find a representative of the double coset one can find a canonical form for the tensor. To see this correspondence, let `g` be a permutation in array form; a tensor with indices `ind` (the indices including both the contravariant and the covariant ones) can be written as `t = T(ind[g[0]],..., ind[g[n-1]])`, where `n= len(ind)`; `g` has size `n + 2`, the last two indices for the sign of the tensor (trick introduced in [4]). A slot symmetry transformation `s` is a permutation acting on the slots `t -> T(ind[(gs)[0]],..., ind[(gs)[n-1]])` A dummy symmetry transformation acts on `ind` `t -> T(ind[(dg)[0]],..., ind[(dg)[n-1]])` Being interested only in the transformations of the tensor under these symmetries, one can represent the tensor by `g`, which transforms as `g -> dgs`, so it belongs to the coset `DgS`, or in other words to the set of all permutations allowed by the slot and dummy symmetries. Let us explain the conventions by an example. Given a tensor `T^{d3 d2 d1}{}_{d1 d2 d3}` with the slot symmetries `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}` `T^{a0 a1 a2 a3 a4 a5} = -T^{a4 a1 a2 a3 a0 a5}` and symmetric metric, find the tensor equivalent to it which is the lowest under the ordering of indices: lexicographic ordering `d1, d2, d3` and then contravariant before covariant index; that is the canonical form of the tensor. The canonical form is `-T^{d1 d2 d3}{}_{d1 d2 d3}` obtained using `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}`. To convert this problem in the input for this function, use the following ordering of the index names (- for covariant for short) `d1, -d1, d2, -d2, d3, -d3` `T^{d3 d2 d1}{}_{d1 d2 d3}` corresponds to `g = [4, 2, 0, 1, 3, 5, 6, 7]` where the last two indices are for the sign `sgens = [Permutation(0, 2)(6, 7), Permutation(0, 4)(6, 7)]` sgens[0] is the slot symmetry `-(0, 2)` `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}` sgens[1] is the slot symmetry `-(0, 4)` `T^{a0 a1 a2 a3 a4 a5} = -T^{a4 a1 a2 a3 a0 a5}` The dummy symmetry group D is generated by the strong base generators `[(0, 1), (2, 3), (4, 5), (0, 2)(1, 3), (0, 4)(1, 5)]` where the first three interchange covariant and contravariant positions of the same index (d1 <-> -d1) and the last two interchange the dummy indices themselves (d1 <-> d2). The dummy symmetry acts from the left `d = [1, 0, 2, 3, 4, 5, 6, 7]` exchange `d1 <-> -d1` `T^{d3 d2 d1}{}_{d1 d2 d3} == T^{d3 d2}{}_{d1}{}^{d1}{}_{d2 d3}` `g=[4, 2, 0, 1, 3, 5, 6, 7] -> [4, 2, 1, 0, 3, 5, 6, 7] = _af_rmul(d, g)` which differs from `_af_rmul(g, d)`. The slot symmetry acts from the right `s = [2, 1, 0, 3, 4, 5, 7, 6]` exchanges slots 0 and 2 and changes sign `T^{d3 d2 d1}{}_{d1 d2 d3} == -T^{d1 d2 d3}{}_{d1 d2 d3}` `g=[4,2,0,1,3,5,6,7] -> [0, 2, 4, 1, 3, 5, 7, 6] = _af_rmul(g, s)` Example in which the tensor is zero, same slot symmetries as above: `T^{d2}{}_{d1 d3}{}^{d1 d3}{}_{d2}` `= -T^{d3}{}_{d1 d3}{}^{d1 d2}{}_{d2}` under slot symmetry `-(0,4)`; `= T_{d3 d1}{}^{d3}{}^{d1 d2}{}_{d2}` under slot symmetry `-(0,2)`; `= T^{d3}{}_{d1 d3}{}^{d1 d2}{}_{d2}` symmetric metric; `= 0` since two of these lines have tensors differ only for the sign. The double coset DgS consists of permutations `h = dgs` corresponding to equivalent tensors; if there are two `h` which are the same apart from the sign, return zero; otherwise choose as representative the tensor with indices ordered lexicographically according to `[d1, -d1, d2, -d2, d3, -d3]` that is `rep = min(DgS) = min([dgs for d in D for s in S])` The indices are fixed one by one; first choose the lowest index for slot 0, then the lowest remaining index for slot 1, etc. Doing this one obtains a chain of stabilizers `S -> S_{b0} -> S_{b0,b1} -> ...` and `D -> D_{p0} -> D_{p0,p1} -> ...` where `[b0, b1, ...] = range(b)` is a base of the symmetric group; the strong base `b_S` of S is an ordered sublist of it; therefore it is sufficient to compute once the strong base generators of S using the Schreier-Sims algorithm; the stabilizers of the strong base generators are the strong base generators of the stabilizer subgroup. `dbase = [p0, p1, ...]` is not in general in lexicographic order, so that one must recompute the strong base generators each time; however this is trivial, there is no need to use the Schreier-Sims algorithm for D. The algorithm keeps a TAB of elements `(s_i, d_i, h_i)` where `h_i = d_igs_i` satisfying `h_i[j] = p_j` for `0 <= j < i` starting from `s_0 = id, d_0 = id, h_0 = g`. The equations `h_0[0] = p_0, h_1[1] = p_1,...` are solved in this order, choosing each time the lowest possible value of p_i For `j < i` `d_igs_iS_{b_0,...,b_{i-1}}b_j = D_{p_0,...,p_{i-1}}p_j` so that for dx in `D_{p_0,...,p_{i-1}}` and sx in `S_{base[0],...,base[i-1]}` one has `dxd_igs_isxb_j = p_j` Search for dx, sx such that this equation holds for `j = i`; it can be written as `s_isxb_j = J, dxd_igJ = p_j` `sxb_j = s_i-1J; sx = trace(s_i-1, S_{b_0,...,b_{i-1}})` `dx-1p_j = d_igJ; dx = trace(d_igJ, D_{p_0,...,p_{i-1}})` `s_{i+1} = s_itrace(s_i*-1J, S_{b_0,...,b_{i-1}})` `d_{i+1} = trace(d_igJ, D_{p_0,...,p_{i-1}})*-1d_i` `h_{i+1}b_i = d_{i+1}gs_{i+1}b_i = p_i` `h_nb_j = p_j` for all j, so that `h_n` is the solution. Add the found `(s, d, h)` to TAB1. At the end of the iteration sort TAB1 with respect to the `h`; if there are two consecutive `h` in TAB1 which differ only for the sign, the tensor is zero, so return 0; if there are two consecutive `h` which are equal, keep only one. Then stabilize the slot generators under `i` and the dummy generators under `p_i`. Assign `TAB = TAB1` at the end of the iteration step. At the end `TAB` contains a unique `(s, d, h)`, since all the slots of the tensor `h` have been fixed to have the minimum value according to the symmetries. The algorithm returns `h`. It is important that the slot BSGS has lexicographic minimal base, otherwise there is an `i` which does not belong to the slot base for which `p_i` is fixed by the dummy symmetry only, while `i` is not invariant from the slot stabilizer, so `p_i` is not in general the minimal value. This algorithm differs slightly from the original algorithm [3]: the canonical form is minimal lexicographically, and the BSGS has minimal base under lexicographic order. Equal tensors `h` are eliminated from TAB. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.tensor_can import double_coset_can_rep, get_transversals >>> gens = [Permutation(x) for x in [[2, 1, 0, 3, 4, 5, 7, 6], [4, 1, 2, 3, 0, 5, 7, 6]]] >>> base = [0, 2] >>> g = Permutation([4, 2, 0, 1, 3, 5, 6, 7]) >>> transversals = get_transversals(base, gens) >>> double_coset_can_rep([list(range(6))], [0], base, gens, transversals, g) [0, 1, 2, 3, 4, 5, 7, 6] >>> g = Permutation([4, 1, 3, 0, 5, 2, 6, 7]) >>> double_coset_can_rep([list(range(6))], [0], base, gens, transversals, g) 0 """ size = g.size g = g.array_form num_dummies = size - 2 indices = list(range(num_dummies)) all_metrics_with_sym = all([_ is not None for _ in sym]) num_types = len(sym) dumx = dummies[:] dumx_flat = [] for dx in dumx: dumx_flat.extend(dx) b_S = b_S[:] sgensx = [h._array_form for h in sgens] if b_S: S_transversals = transversal2coset(size, b_S, S_transversals) # strong generating set for D dsgsx = [] for i in range(num_types): dsgsx.extend(dummy_sgs(dumx[i], sym[i], num_dummies)) idn = list(range(size)) # TAB = list of entries (s, d, h) where h = _af_rmuln(d,g,s) # for short, in the following dgs means _af_rmuln(d,g,s) TAB = [(idn, idn, g)] for i in range(size - 2): b = i testb = b in b_S and sgensx if testb: sgensx1 = [_af_new(_) for _ in sgensx] deltab = _orbit(size, sgensx1, b) else: deltab = {b} # p1 = min(IMAGES) = min(Union D_phdeltab for h in TAB) if all_metrics_with_sym: md = _min_dummies(dumx, sym, indices) else: md = [min(_orbit(size, [_af_new( ddx) for ddx in dsgsx], ii)) for ii in range(size - 2)] p_i = min([min([md[h[x]] for x in deltab]) for s, d, h in TAB]) dsgsx1 = [_af_new(_) for _ in dsgsx] Dxtrav = _orbit_transversal(size, dsgsx1, p_i, False, af=True) \ if dsgsx else None if Dxtrav: Dxtrav = [_af_invert(x) for x in Dxtrav] # compute the orbit of p_i for ii in range(num_types): if p_i in dumx[ii]: # the orbit is made by all the indices in dum[ii] if sym[ii] is not None: deltap = dumx[ii] else: # the orbit is made by all the even indices if p_i # is even, by all the odd indices if p_i is odd p_i_index = dumx[ii].index(p_i) % 2 deltap = dumx[ii][p_i_index::2] break else: deltap = [p_i] TAB1 = [] while TAB: s, d, h = TAB.pop() if min([md[h[x]] for x in deltab]) != p_i: continue deltab1 = [x for x in deltab if md[h[x]] == p_i] # NEXT = sdeltab1 intersection (dg)-1deltap dg = _af_rmul(d, g) dginv = _af_invert(dg) sdeltab = [s[x] for x in deltab1] gdeltap = [dginv[x] for x in deltap] NEXT = [x for x in sdeltab if x in gdeltap] # d, s satisfy # dgsbase[i-1] = p_{i-1}; using the stabilizers # dgsS_{base[0],...,base[i-1]}base[i-1] = # D_{p_0,...,p_{i-1}}p_{i-1} # so that to find d1, s1 satisfying d1gs1b = p_i # one can look for dx in D_{p_0,...,p_{i-1}} and # sx in S_{base[0],...,base[i-1]} # d1 = dxd; s1 = ssx # d1gs1b = dxdgssxb = p_i for j in NEXT: if testb: # solve s1b = j with s1 = ssx for some element sx # of the stabilizer of ..., base[i-1] # sxb = s*-1j; sx = _trace_S(s, j,...) # s1 = strace_S(s-1j,...) s1 = _trace_S(s, j, b, S_transversals) if not s1: continue else: s1 = [s[ix] for ix in s1] else: s1 = s # assert s1[b] == j # invariant # solve d1gj = p_i with d1 = dxd for some element dg # of the stabilizer of ..., p_{i-1} # dx-1p_i = dgj; dx*-1 = trace_D(dgj,...) # d1 = trace_D(dgj,...)-1d # to save an inversion in the inner loop; notice we did # Dxtrav = [perm_af_invert(x) for x in Dxtrav] out of the loop if Dxtrav: d1 = _trace_D(dg[j], p_i, Dxtrav) if not d1: continue else: if p_i != dg[j]: continue d1 = idn assert d1[dg[j]] == p_i # invariant d1 = [d1[ix] for ix in d] h1 = [d1[g[ix]] for ix in s1] # assert h1[b] == p_i # invariant TAB1.append((s1, d1, h1)) # if TAB contains equal permutations, keep only one of them; # if TAB contains equal permutations up to the sign, return 0 TAB1.sort(key=lambda x: x[-1]) prev = [0] * size while TAB1: s, d, h = TAB1.pop() if h[:-2] == prev[:-2]: if h[-1] != prev[-1]: return 0 else: TAB.append((s, d, h)) prev = h # stabilize the SGS sgensx = [h for h in sgensx if h[b] == b] if b in b_S: b_S.remove(b) _dumx_remove(dumx, dumx_flat, p_i) dsgsx = [] for i in range(num_types): dsgsx.extend(dummy_sgs(dumx[i], sym[i], num_dummies)) return TAB[0][-1] def canonical_free(base, gens, g, num_free): """ Canonicalization of a tensor with respect to free indices choosing the minimum with respect to lexicographical ordering in the free indices. Explanation =========== ``base``, ``gens`` BSGS for slot permutation group ``g`` permutation representing the tensor ``num_free`` number of free indices The indices must be ordered with first the free indices See explanation in double_coset_can_rep The algorithm is a variation of the one given in [2]. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import canonical_free >>> gens = [[1, 0, 2, 3, 5, 4], [2, 3, 0, 1, 4, 5],[0, 1, 3, 2, 5, 4]] >>> gens = [Permutation(h) for h in gens] >>> base = [0, 2] >>> g = Permutation([2, 1, 0, 3, 4, 5]) >>> canonical_free(base, gens, g, 4) [0, 3, 1, 2, 5, 4] Consider the product of Riemann tensors ``T = R^{a}_{d0}^{d1,d2}R_{d2,d1}^{d0,b}`` The order of the indices is ``[a, b, d0, -d0, d1, -d1, d2, -d2]`` The permutation corresponding to the tensor is ``g = [0, 3, 4, 6, 7, 5, 2, 1, 8, 9]`` In particular ``a`` is position ``0``, ``b`` is in position ``9``. Use the slot symmetries to get `T` is a form which is the minimal in lexicographic order in the free indices ``a`` and ``b``, e.g. ``-R^{a}_{d0}^{d1,d2}R^{b,d0}_{d2,d1}`` corresponding to ``[0, 3, 4, 6, 1, 2, 7, 5, 9, 8]`` >>> from sympy.combinatorics.tensor_can import riemann_bsgs, tensor_gens >>> base, gens = riemann_bsgs >>> size, sbase, sgens = tensor_gens(base, gens, [[], []], 0) >>> g = Permutation([0, 3, 4, 6, 7, 5, 2, 1, 8, 9]) >>> canonical_free(sbase, [Permutation(h) for h in sgens], g, 2) [0, 3, 4, 6, 1, 2, 7, 5, 9, 8] """ g = g.array_form size = len(g) if not base: return g[:] transversals = get_transversals(base, gens) for x in sorted(g[:-2]): if x not in base: base.append(x) h = g for i, transv in enumerate(transversals): h_i = [size]num_free # find the element s in transversals[i] such that # _af_rmul(h, s) has its free elements with the lowest position in h s = None for sk in transv.values(): h1 = _af_rmul(h, sk) hi = [h1.index(ix) for ix in range(num_free)] if hi < h_i: h_i = hi s = sk if s: h = _af_rmul(h, s) return h def _get_map_slots(size, fixed_slots): res = list(range(size)) pos = 0 for i in range(size): if i in fixed_slots: continue res[i] = pos pos += 1 return res def _lift_sgens(size, fixed_slots, free, s): a = [] j = k = 0 fd = list(zip(fixed_slots, free)) fd = [y for x, y in sorted(fd)] num_free = len(free) for i in range(size): if i in fixed_slots: a.append(fd[k]) k += 1 else: a.append(s[j] + num_free) j += 1 return a def canonicalize(g, dummies, msym, v): """ canonicalize tensor formed by tensors Parameters ========== g : permutation representing the tensor dummies : list representing the dummy indices it can be a list of dummy indices of the same type or a list of lists of dummy indices, one list for each type of index; the dummy indices must come after the free indices, and put in order contravariant, covariant [d0, -d0, d1,-d1,...] msym : symmetry of the metric(s) it can be an integer or a list; in the first case it is the symmetry of the dummy index metric; in the second case it is the list of the symmetries of the index metric for each type v : list, (base_i, gens_i, n_i, sym_i) for tensors of type `i` base_i, gens_i : BSGS for tensors of this type. The BSGS should have minimal base under lexicographic ordering; if not, an attempt is made do get the minimal BSGS; in case of failure, canonicalize_naive is used, which is much slower. n_i : number of tensors of type `i`. sym_i : symmetry under exchange of component tensors of type `i`. Both for msym and sym_i the cases are * None no symmetry * 0 commuting * 1 anticommuting Returns ======= 0 if the tensor is zero, else return the array form of the permutation representing the canonical form of the tensor. Algorithm ========= First one uses canonical_free to get the minimum tensor under lexicographic order, using only the slot symmetries. If the component tensors have not minimal BSGS, it is attempted to find it; if the attempt fails canonicalize_naive is used instead. Compute the residual slot symmetry keeping fixed the free indices using tensor_gens(base, gens, list_free_indices, sym). Reduce the problem eliminating the free indices. Then use double_coset_can_rep and lift back the result reintroducing the free indices. Examples ======== one type of index with commuting metric; `A_{a b}` and `B_{a b}` antisymmetric and commuting `T = A_{d0 d1} * B^{d0}{}_{d2} * B^{d2 d1}` `ord = [d0,-d0,d1,-d1,d2,-d2]` order of the indices g = [1, 3, 0, 5, 4, 2, 6, 7] `T_c = 0` >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, canonicalize, bsgs_direct_product >>> from sympy.combinatorics import Permutation >>> base2a, gens2a = get_symmetric_group_sgs(2, 1) >>> t0 = (base2a, gens2a, 1, 0) >>> t1 = (base2a, gens2a, 2, 0) >>> g = Permutation([1, 3, 0, 5, 4, 2, 6, 7]) >>> canonicalize(g, range(6), 0, t0, t1) 0 same as above, but with `B_{a b}` anticommuting `T_c = -A^{d0 d1} * B_{d0}{}^{d2} * B_{d1 d2}` can = [0,2,1,4,3,5,7,6] >>> t1 = (base2a, gens2a, 2, 1) >>> canonicalize(g, range(6), 0, t0, t1) [0, 2, 1, 4, 3, 5, 7, 6] two types of indices `[a,b,c,d,e,f]` and `[m,n]`, in this order, both with commuting metric `f^{a b c}` antisymmetric, commuting `A_{m a}` no symmetry, commuting `T = f^c{}_{d a} * f^f{}_{e b} * A_m{}^d * A^{m b} * A_n{}^a * A^{n e}` ord = [c,f,a,-a,b,-b,d,-d,e,-e,m,-m,n,-n] g = [0,7,3, 1,9,5, 11,6, 10,4, 13,2, 12,8, 14,15] The canonical tensor is `T_c = -f^{c a b} * f^{f d e} * A^m{}_a * A_{m d} * A^n{}_b * A_{n e}` can = [0,2,4, 1,6,8, 10,3, 11,7, 12,5, 13,9, 15,14] >>> base_f, gens_f = get_symmetric_group_sgs(3, 1) >>> base1, gens1 = get_symmetric_group_sgs(1) >>> base_A, gens_A = bsgs_direct_product(base1, gens1, base1, gens1) >>> t0 = (base_f, gens_f, 2, 0) >>> t1 = (base_A, gens_A, 4, 0) >>> dummies = [range(2, 10), range(10, 14)] >>> g = Permutation([0, 7, 3, 1, 9, 5, 11, 6, 10, 4, 13, 2, 12, 8, 14, 15]) >>> canonicalize(g, dummies, [0, 0], t0, t1) [0, 2, 4, 1, 6, 8, 10, 3, 11, 7, 12, 5, 13, 9, 15, 14] """ from sympy.combinatorics.testutil import canonicalize_naive if not isinstance(msym, list): if not msym in [0, 1, None]: raise ValueError('msym must be 0, 1 or None') num_types = 1 else: num_types = len(msym) if not all(msymx in [0, 1, None] for msymx in msym): raise ValueError('msym entries must be 0, 1 or None') if len(dummies) != num_types: raise ValueError( 'dummies and msym must have the same number of elements') size = g.size num_tensors = 0 v1 = [] for i in range(len(v)): base_i, gens_i, n_i, sym_i = v[i] # check that the BSGS is minimal; # this property is used in double_coset_can_rep; # if it is not minimal use canonicalize_naive if not _is_minimal_bsgs(base_i, gens_i): mbsgs = get_minimal_bsgs(base_i, gens_i) if not mbsgs: can = canonicalize_naive(g, dummies, msym, v) return can base_i, gens_i = mbsgs v1.append((base_i, gens_i, [[]] n_i, sym_i)) num_tensors += n_i if num_types == 1 and not isinstance(msym, list): dummies = [dummies] msym = [msym] flat_dummies = [] for dumx in dummies: flat_dummies.extend(dumx) if flat_dummies and flat_dummies != list(range(flat_dummies[0], flat_dummies[-1] + 1)): raise ValueError('dummies is not valid') # slot symmetry of the tensor size1, sbase, sgens = gens_products(v1) if size != size1: raise ValueError( 'g has size %d, generators have size %d' % (size, size1)) free = [i for i in range(size - 2) if i not in flat_dummies] num_free = len(free) # g1 minimal tensor under slot symmetry g1 = canonical_free(sbase, sgens, g, num_free) if not flat_dummies: return g1 # save the sign of g1 sign = 0 if g1[-1] == size - 1 else 1 # the free indices are kept fixed. # Determine free_i, the list of slots of tensors which are fixed # since they are occupied by free indices, which are fixed. start = 0 for i in range(len(v)): free_i = [] base_i, gens_i, n_i, sym_i = v[i] len_tens = gens_i[0].size - 2 # for each component tensor get a list od fixed islots for j in range(n_i): # get the elements corresponding to the component tensor h = g1[start:(start + len_tens)] fr = [] # get the positions of the fixed elements in h for k in free: if k in h: fr.append(h.index(k)) free_i.append(fr) start += len_tens v1[i] = (base_i, gens_i, free_i, sym_i) # BSGS of the tensor with fixed free indices # if tensor_gens fails in gens_product, use canonicalize_naive size, sbase, sgens = gens_products(v1) # reduce the permutations getting rid of the free indices pos_free = [g1.index(x) for x in range(num_free)] size_red = size - num_free g1_red = [x - num_free for x in g1 if x in flat_dummies] if sign: g1_red.extend([size_red - 1, size_red - 2]) else: g1_red.extend([size_red - 2, size_red - 1]) map_slots = _get_map_slots(size, pos_free) sbase_red = [map_slots[i] for i in sbase if i not in pos_free] sgens_red = [_af_new([map_slots[i] for i in y._array_form if i not in pos_free]) for y in sgens] dummies_red = [[x - num_free for x in y] for y in dummies] transv_red = get_transversals(sbase_red, sgens_red) g1_red = _af_new(g1_red) g2 = double_coset_can_rep( dummies_red, msym, sbase_red, sgens_red, transv_red, g1_red) if g2 == 0: return 0 # lift to the case with the free indices g3 = _lift_sgens(size, pos_free, free, g2) return g3 def perm_af_direct_product(gens1, gens2, signed=True): """ Direct products of the generators gens1 and gens2. Examples ======== >>> from sympy.combinatorics.tensor_can import perm_af_direct_product >>> gens1 = [[1, 0, 2, 3], [0, 1, 3, 2]] >>> gens2 = [[1, 0]] >>> perm_af_direct_product(gens1, gens2, False) [[1, 0, 2, 3, 4, 5], [0, 1, 3, 2, 4, 5], [0, 1, 2, 3, 5, 4]] >>> gens1 = [[1, 0, 2, 3, 5, 4], [0, 1, 3, 2, 4, 5]] >>> gens2 = [[1, 0, 2, 3]] >>> perm_af_direct_product(gens1, gens2, True) [[1, 0, 2, 3, 4, 5, 7, 6], [0, 1, 3, 2, 4, 5, 6, 7], [0, 1, 2, 3, 5, 4, 6, 7]] """ gens1 = [list(x) for x in gens1] gens2 = [list(x) for x in gens2] s = 2 if signed else 0 n1 = len(gens1[0]) - s n2 = len(gens2[0]) - s start = list(range(n1)) end = list(range(n1, n1 + n2)) if signed: gens1 = [gen[:-2] + end + [gen[-2] + n2, gen[-1] + n2] for gen in gens1] gens2 = [start + [x + n1 for x in gen] for gen in gens2] else: gens1 = [gen + end for gen in gens1] gens2 = [start + [x + n1 for x in gen] for gen in gens2] res = gens1 + gens2 return res def bsgs_direct_product(base1, gens1, base2, gens2, signed=True): """ Direct product of two BSGS. Parameters ========== base1 : base of the first BSGS. gens1 : strong generating sequence of the first BSGS. base2, gens2 : similarly for the second BSGS. signed : flag for signed permutations. Examples ======== >>> from sympy.combinatorics.tensor_can import (get_symmetric_group_sgs, bsgs_direct_product) >>> base1, gens1 = get_symmetric_group_sgs(1) >>> base2, gens2 = get_symmetric_group_sgs(2) >>> bsgs_direct_product(base1, gens1, base2, gens2) ([1], [(4)(1 2)]) """ s = 2 if signed else 0 n1 = gens1[0].size - s base = list(base1) base += [x + n1 for x in base2] gens1 = [h._array_form for h in gens1] gens2 = [h._array_form for h in gens2] gens = perm_af_direct_product(gens1, gens2, signed) size = len(gens[0]) id_af = list(range(size)) gens = [h for h in gens if h != id_af] if not gens: gens = [id_af] return base, [_af_new(h) for h in gens] def get_symmetric_group_sgs(n, antisym=False): """ Return base, gens of the minimal BSGS for (anti)symmetric tensor Parameters ========== ``n``: rank of the tensor ``antisym`` : bool ``antisym = False`` symmetric tensor ``antisym = True`` antisymmetric tensor Examples ======== >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs >>> get_symmetric_group_sgs(3) ([0, 1], [(4)(0 1), (4)(1 2)]) """ if n == 1: return [], [_af_new(list(range(3)))] gens = [Permutation(n - 1)(i, i + 1)._array_form for i in range(n - 1)] if antisym == 0: gens = [x + [n, n + 1] for x in gens] else: gens = [x + [n + 1, n] for x in gens] base = list(range(n - 1)) return base, [_af_new(h) for h in gens] riemann_bsgs = [0, 2], [Permutation(0, 1)(4, 5), Permutation(2, 3)(4, 5), Permutation(5)(0, 2)(1, 3)] def get_transversals(base, gens): """ Return transversals for the group with BSGS base, gens """ if not base: return [] stabs = _distribute_gens_by_base(base, gens) orbits, transversals = _orbits_transversals_from_bsgs(base, stabs) transversals = [{x: h._array_form for x, h in y.items()} for y in transversals] return transversals def _is_minimal_bsgs(base, gens): """ Check if the BSGS has minimal base under lexigographic order. base, gens BSGS Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import riemann_bsgs, _is_minimal_bsgs >>> _is_minimal_bsgs(riemann_bsgs) True >>> riemann_bsgs1 = ([2, 0], ([Permutation(5)(0, 1)(4, 5), Permutation(5)(0, 2)(1, 3)])) >>> _is_minimal_bsgs(riemann_bsgs1) False """ base1 = [] sgs1 = gens[:] size = gens[0].size for i in range(size): if not all(h._array_form[i] == i for h in sgs1): base1.append(i) sgs1 = [h for h in sgs1 if h._array_form[i] == i] return base1 == base def get_minimal_bsgs(base, gens): """ Compute a minimal GSGS base, gens BSGS If base, gens is a minimal BSGS return it; else return a minimal BSGS if it fails in finding one, it returns None TODO: use baseswap in the case in which if it fails in finding a minimal BSGS Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import get_minimal_bsgs >>> riemann_bsgs1 = ([2, 0], ([Permutation(5)(0, 1)(4, 5), Permutation(5)(0, 2)(1, 3)])) >>> get_minimal_bsgs(riemann_bsgs1) ([0, 2], [(0 1)(4 5), (5)(0 2)(1 3), (2 3)(4 5)]) """ G = PermutationGroup(gens) base, gens = G.schreier_sims_incremental() if not _is_minimal_bsgs(base, gens): return None return base, gens def tensor_gens(base, gens, list_free_indices, sym=0): """ Returns size, res_base, res_gens BSGS for n tensors of the same type. Explanation =========== base, gens BSGS for tensors of this type list_free_indices list of the slots occupied by fixed indices for each of the tensors sym symmetry under commutation of two tensors sym None no symmetry sym 0 commuting sym 1 anticommuting Examples ======== >>> from sympy.combinatorics.tensor_can import tensor_gens, get_symmetric_group_sgs two symmetric tensors with 3 indices without free indices >>> base, gens = get_symmetric_group_sgs(3) >>> tensor_gens(base, gens, [[], []]) (8, [0, 1, 3, 4], [(7)(0 1), (7)(1 2), (7)(3 4), (7)(4 5), (7)(0 3)(1 4)(2 5)]) two symmetric tensors with 3 indices with free indices in slot 1 and 0 >>> tensor_gens(base, gens, [[1], [0]]) (8, [0, 4], [(7)(0 2), (7)(4 5)]) four symmetric tensors with 3 indices, two of which with free indices """ def _get_bsgs(G, base, gens, free_indices): """ return the BSGS for G.pointwise_stabilizer(free_indices) """ if not free_indices: return base[:], gens[:] else: H = G.pointwise_stabilizer(free_indices) base, sgs = H.schreier_sims_incremental() return base, sgs # if not base there is no slot symmetry for the component tensors # if list_free_indices.count([]) < 2 there is no commutation symmetry # so there is no resulting slot symmetry if not base and list_free_indices.count([]) < 2: n = len(list_free_indices) size = gens[0].size size = n (gens[0].size - 2) + 2 return size, [], [_af_new(list(range(size)))] # if any(list_free_indices) one needs to compute the pointwise # stabilizer, so G is needed if any(list_free_indices): G = PermutationGroup(gens) else: G = None # no_free list of lists of indices for component tensors without fixed # indices no_free = [] size = gens[0].size id_af = list(range(size)) num_indices = size - 2 if not list_free_indices[0]: no_free.append(list(range(num_indices))) res_base, res_gens = _get_bsgs(G, base, gens, list_free_indices[0]) for i in range(1, len(list_free_indices)): base1, gens1 = _get_bsgs(G, base, gens, list_free_indices[i]) res_base, res_gens = bsgs_direct_product(res_base, res_gens, base1, gens1, 1) if not list_free_indices[i]: no_free.append(list(range(size - 2, size - 2 + num_indices))) size += num_indices nr = size - 2 res_gens = [h for h in res_gens if h._array_form != id_af] # if sym there are no commuting tensors stop here if sym is None or not no_free: if not res_gens: res_gens = [_af_new(id_af)] return size, res_base, res_gens # if the component tensors have moinimal BSGS, so is their direct # product P; the slot symmetry group is S = PC, where C is the group # to (anti)commute the component tensors with no free indices # a stabilizer has the property S_i = P_iC_i; # the BSGS of PC has SGS_P + SGS_C and the base is # the ordered union of the bases of P and C. # If P has minimal BSGS, so has S with this base. base_comm = [] for i in range(len(no_free) - 1): ind1 = no_free[i] ind2 = no_free[i + 1] a = list(range(ind1[0])) a.extend(ind2) a.extend(ind1) base_comm.append(ind1[0]) a.extend(list(range(ind2[-1] + 1, nr))) if sym == 0: a.extend([nr, nr + 1]) else: a.extend([nr + 1, nr]) res_gens.append(_af_new(a)) res_base = list(res_base) # each base is ordered; order the union of the two bases for i in base_comm: if i not in res_base: res_base.append(i) res_base.sort() if not res_gens: res_gens = [_af_new(id_af)] return size, res_base, res_gens def gens_products(v): """ Returns size, res_base, res_gens BSGS for n tensors of different types. Explanation =========== v is a sequence of (base_i, gens_i, free_i, sym_i) where base_i, gens_i BSGS of tensor of type `i` free_i list of the fixed slots for each of the tensors of type `i`; if there are `n_i` tensors of type `i` and none of them have fixed slots, `free = [[]]n_i` sym 0 (1) if the tensors of type `i` (anti)commute among themselves Examples ======== >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, gens_products >>> base, gens = get_symmetric_group_sgs(2) >>> gens_products((base, gens, [[], []], 0)) (6, [0, 2], [(5)(0 1), (5)(2 3), (5)(0 2)(1 3)]) >>> gens_products((base, gens, [[1], []], 0)) (6, [2], [(5)(2 3)]) """ res_size, res_base, res_gens = tensor_gens(v[0]) for i in range(1, len(v)): size, base, gens = tensor_gens(*v[i]) res_base, res_gens = bsgs_direct_product(res_base, res_gens, base, gens, 1) res_size = res_gens[0].size id_af = list(range(res_size)) res_gens = [h for h in res_gens if h != id_af] if not res_gens: res_gens = [id_af] return res_size, res_base, res_gens
7980f821d4c2d10739349db72691d4e9292c8317bb12a550f1a34a0466e180f3	from sympy import isprime from sympy.combinatorics.perm_groups import PermutationGroup from sympy.printing.defaults import DefaultPrinting from sympy.combinatorics.free_groups import free_group class PolycyclicGroup(DefaultPrinting): is_group = True is_solvable = True def __init__(self, pc_sequence, pc_series, relative_order, collector=None): """ Parameters ========== pc_sequence : list A sequence of elements whose classes generate the cyclic factor groups of pc_series. pc_series : list A subnormal sequence of subgroups where each factor group is cyclic. relative_order : list The orders of factor groups of pc_series. collector : Collector By default, it is None. Collector class provides the polycyclic presentation with various other functionalities. """ self.pcgs = pc_sequence self.pc_series = pc_series self.relative_order = relative_order self.collector = Collector(self.pcgs, pc_series, relative_order) if not collector else collector def is_prime_order(self): return all(isprime(order) for order in self.relative_order) def length(self): return len(self.pcgs) class Collector(DefaultPrinting): """ References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.3 """ def __init__(self, pcgs, pc_series, relative_order, free_group_=None, pc_presentation=None): """ Most of the parameters for the Collector class are the same as for PolycyclicGroup. Others are described below. Parameters ========== free_group_ : tuple free_group_ provides the mapping of polycyclic generating sequence with the free group elements. pc_presentation : dict Provides the presentation of polycyclic groups with the help of power and conjugate relators. See Also ======== PolycyclicGroup """ self.pcgs = pcgs self.pc_series = pc_series self.relative_order = relative_order self.free_group = free_group('x:{}'.format(len(pcgs)))[0] if not free_group_ else free_group_ self.index = {s: i for i, s in enumerate(self.free_group.symbols)} self.pc_presentation = self.pc_relators() def minimal_uncollected_subword(self, word): r""" Returns the minimal uncollected subwords. Explanation =========== A word ``v`` defined on generators in ``X`` is a minimal uncollected subword of the word ``w`` if ``v`` is a subword of ``w`` and it has one of the following form * `v = {x_{i+1}}^{a_j}x_i` * `v = {x_{i+1}}^{a_j}{x_i}^{-1}` * `v = {x_i}^{a_j}` for `a_j` not in `\{1, \ldots, s-1\}`. Where, ``s`` is the power exponent of the corresponding generator. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x1, x2 = free_group("x1, x2") >>> word = x2*2x17 >>> collector.minimal_uncollected_subword(word) ((x2, 2),) """ # To handle the case word = <identity> if not word: return None array = word.array_form re = self.relative_order index = self.index for i in range(len(array)): s1, e1 = array[i] if re[index[s1]] and (e1 < 0 or e1 > re[index[s1]]-1): return ((s1, e1), ) for i in range(len(array)-1): s1, e1 = array[i] s2, e2 = array[i+1] if index[s1] > index[s2]: e = 1 if e2 > 0 else -1 return ((s1, e1), (s2, e)) return None def relations(self): """ Separates the given relators of pc presentation in power and conjugate relations. Returns ======= (power_rel, conj_rel) Separates pc presentation into power and conjugate relations. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> power_rel, conj_rel = collector.relations() >>> power_rel {x02: (), x13: ()} >>> conj_rel {x0-1x1x0: x12} See Also ======== pc_relators """ power_relators = {} conjugate_relators = {} for key, value in self.pc_presentation.items(): if len(key.array_form) == 1: power_relators[key] = value else: conjugate_relators[key] = value return power_relators, conjugate_relators def subword_index(self, word, w): """ Returns the start and ending index of a given subword in a word. Parameters ========== word : FreeGroupElement word defined on free group elements for a polycyclic group. w : FreeGroupElement subword of a given word, whose starting and ending index to be computed. Returns ======= (i, j) A tuple containing starting and ending index of ``w`` in the given word. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x1, x2 = free_group("x1, x2") >>> word = x22x17 >>> w = x22x1 >>> collector.subword_index(word, w) (0, 3) >>> w = x1*7 >>> collector.subword_index(word, w) (2, 9) """ low = -1 high = -1 for i in range(len(word)-len(w)+1): if word.subword(i, i+len(w)) == w: low = i high = i+len(w) break if low == high == -1: return -1, -1 return low, high def map_relation(self, w): """ Return a conjugate relation. Explanation =========== Given a word formed by two free group elements, the corresponding conjugate relation with those free group elements is formed and mapped with the collected word in the polycyclic presentation. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x0, x1 = free_group("x0, x1") >>> w = x1x0 >>> collector.map_relation(w) x1*2 See Also ======== pc_presentation """ array = w.array_form s1 = array[0][0] s2 = array[1][0] key = ((s2, -1), (s1, 1), (s2, 1)) key = self.free_group.dtype(key) return self.pc_presentation[key] def collected_word(self, word): r""" Return the collected form of a word. Explanation =========== A word ``w`` is called collected, if `w = {x_{i_1}}^{a_1} \ldots * {x_{i_r}}^{a_r}` with `i_1 < i_2< \ldots < i_r` and `a_j` is in `\{1, \ldots, {s_j}-1\}`. Otherwise w is uncollected. Parameters ========== word : FreeGroupElement An uncollected word. Returns ======= word A collected word of form `w = {x_{i_1}}^{a_1}, \ldots, {x_{i_r}}^{a_r}` with `i_1, i_2, \ldots, i_r` and `a_j \in \{1, \ldots, {s_j}-1\}`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x0, x1, x2, x3 = free_group("x0, x1, x2, x3") >>> word = x3x2x1x0 >>> collected_word = collector.collected_word(word) >>> free_to_perm = {} >>> free_group = collector.free_group >>> for sym, gen in zip(free_group.symbols, collector.pcgs): ... free_to_perm[sym] = gen >>> G1 = PermutationGroup() >>> for w in word: ... sym = w[0] ... perm = free_to_perm[sym] ... G1 = PermutationGroup([perm] + G1.generators) >>> G2 = PermutationGroup() >>> for w in collected_word: ... sym = w[0] ... perm = free_to_perm[sym] ... G2 = PermutationGroup([perm] + G2.generators) >>> G1 == G2 True See Also ======== minimal_uncollected_subword """ free_group = self.free_group while True: w = self.minimal_uncollected_subword(word) if not w: break low, high = self.subword_index(word, free_group.dtype(w)) if low == -1: continue s1, e1 = w[0] if len(w) == 1: re = self.relative_order[self.index[s1]] q = e1 // re r = e1-qre key = ((w[0][0], re), ) key = free_group.dtype(key) if self.pc_presentation[key]: presentation = self.pc_presentation[key].array_form sym, exp = presentation[0] word_ = ((w[0][0], r), (sym, qexp)) word_ = free_group.dtype(word_) else: if r != 0: word_ = ((w[0][0], r), ) word_ = free_group.dtype(word_) else: word_ = None word = word.eliminate_word(free_group.dtype(w), word_) if len(w) == 2 and w[1][1] > 0: s2, e2 = w[1] s2 = ((s2, 1), ) s2 = free_group.dtype(s2) word_ = self.map_relation(free_group.dtype(w)) word_ = s2word_e1 word_ = free_group.dtype(word_) word = word.substituted_word(low, high, word_) elif len(w) == 2 and w[1][1] < 0: s2, e2 = w[1] s2 = ((s2, 1), ) s2 = free_group.dtype(s2) word_ = self.map_relation(free_group.dtype(w)) word_ = s2-1word_e1 word_ = free_group.dtype(word_) word = word.substituted_word(low, high, word_) return word def pc_relators(self): r""" Return the polycyclic presentation. Explanation =========== There are two types of relations used in polycyclic presentation. ``Power relations`` : Power relators are of the form `x_i^{re_i}`, where `i \in \{0, \ldots, \mathrm{len(pcgs)}\}`, ``x`` represents polycyclic generator and ``re`` is the corresponding relative order. * ``Conjugate relations`` : Conjugate relators are of the form `x_j^-1x_ix_j`, where `j < i \in \{0, \ldots, \mathrm{len(pcgs)}\}`. Returns ======= A dictionary with power and conjugate relations as key and their collected form as corresponding values. Notes ===== Identity Permutation is mapped with empty ``()``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> S = SymmetricGroup(49).sylow_subgroup(7) >>> der = S.derived_series() >>> G = der[len(der)-2] >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> pcgs = PcGroup.pcgs >>> len(pcgs) 6 >>> free_group = collector.free_group >>> pc_resentation = collector.pc_presentation >>> free_to_perm = {} >>> for s, g in zip(free_group.symbols, pcgs): ... free_to_perm[s] = g >>> for k, v in pc_resentation.items(): ... k_array = k.array_form ... if v != (): ... v_array = v.array_form ... lhs = Permutation() ... for gen in k_array: ... s = gen[0] ... e = gen[1] ... lhs = lhsfree_to_perm[s]e ... if v == (): ... assert lhs.is_identity ... continue ... rhs = Permutation() ... for gen in v_array: ... s = gen[0] ... e = gen[1] ... rhs = rhsfree_to_perm[s]e ... assert lhs == rhs """ free_group = self.free_group rel_order = self.relative_order pc_relators = {} perm_to_free = {} pcgs = self.pcgs for gen, s in zip(pcgs, free_group.generators): perm_to_free[gen-1] = s-1 perm_to_free[gen] = s pcgs = pcgs[::-1] series = self.pc_series[::-1] rel_order = rel_order[::-1] collected_gens = [] for i, gen in enumerate(pcgs): re = rel_order[i] relation = perm_to_free[gen]re G = series[i] l = G.generator_product(gen*re, original = True) l.reverse() word = free_group.identity for g in l: word = wordperm_to_free[g] word = self.collected_word(word) pc_relators[relation] = word if word else () self.pc_presentation = pc_relators collected_gens.append(gen) if len(collected_gens) > 1: conj = collected_gens[len(collected_gens)-1] conjugator = perm_to_free[conj] for j in range(len(collected_gens)-1): conjugated = perm_to_free[collected_gens[j]] relation = conjugator*-1conjugatedconjugator gens = conj-1collected_gens[j]conj l = G.generator_product(gens, original = True) l.reverse() word = free_group.identity for g in l: word = wordperm_to_free[g] word = self.collected_word(word) pc_relators[relation] = word if word else () self.pc_presentation = pc_relators return pc_relators def exponent_vector(self, element): r""" Return the exponent vector of length equal to the length of polycyclic generating sequence. Explanation =========== For a given generator/element ``g`` of the polycyclic group, it can be represented as `g = {x_1}^{e_1}, \ldots, {x_n}^{e_n}`, where `x_i` represents polycyclic generators and ``n`` is the number of generators in the free_group equal to the length of pcgs. Parameters ========== element : Permutation Generator of a polycyclic group. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> pcgs = PcGroup.pcgs >>> collector.exponent_vector(G[0]) [1, 0, 0, 0] >>> exp = collector.exponent_vector(G[1]) >>> g = Permutation() >>> for i in range(len(exp)): ... g = gpcgs[i]exp[i] if exp[i] else g >>> assert g == G[1] References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.1, Definition 8.4 """ free_group = self.free_group G = PermutationGroup() for g in self.pcgs: G = PermutationGroup([g] + G.generators) gens = G.generator_product(element, original = True) gens.reverse() perm_to_free = {} for sym, g in zip(free_group.generators, self.pcgs): perm_to_free[g-1] = sym-1 perm_to_free[g] = sym w = free_group.identity for g in gens: w = wperm_to_free[g] word = self.collected_word(w) index = self.index exp_vector = [0]len(free_group) word = word.array_form for t in word: exp_vector[index[t[0]]] = t[1] return exp_vector def depth(self, element): r""" Return the depth of a given element. Explanation =========== The depth of a given element ``g`` is defined by `\mathrm{dep}[g] = i` if `e_1 = e_2 = \ldots = e_{i-1} = 0` and `e_i != 0`, where ``e`` represents the exponent-vector. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> collector.depth(G[0]) 2 >>> collector.depth(G[1]) 1 References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.1, Definition 8.5 """ exp_vector = self.exponent_vector(element) return next((i+1 for i, x in enumerate(exp_vector) if x), len(self.pcgs)+1) def leading_exponent(self, element): r""" Return the leading non-zero exponent. Explanation =========== The leading exponent for a given element `g` is defined by `\mathrm{leading\_exponent}[g]` `= e_i`, if `\mathrm{depth}[g] = i`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> collector.leading_exponent(G[1]) 1 """ exp_vector = self.exponent_vector(element) depth = self.depth(element) if depth != len(self.pcgs)+1: return exp_vector[depth-1] return None def _sift(self, z, g): h = g d = self.depth(h) while d < len(self.pcgs) and z[d-1] != 1: k = z[d-1] e = self.leading_exponent(h)(self.leading_exponent(k))-1 e = e % self.relative_order[d-1] h = k-eh d = self.depth(h) return h def induced_pcgs(self, gens): """ Parameters ========== gens : list A list of generators on which polycyclic subgroup is to be defined. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(8) >>> G = S.sylow_subgroup(2) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> gens = [G[0], G[1]] >>> ipcgs = collector.induced_pcgs(gens) >>> [gen.order() for gen in ipcgs] [2, 2, 2] >>> G = S.sylow_subgroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> gens = [G[0], G[1]] >>> ipcgs = collector.induced_pcgs(gens) >>> [gen.order() for gen in ipcgs] [3] """ z = [1]len(self.pcgs) G = gens while G: g = G.pop(0) h = self._sift(z, g) d = self.depth(h) if d < len(self.pcgs): for gen in z: if gen != 1: G.append(h*-1gen*-1hgen) z[d-1] = h; z = [gen for gen in z if gen != 1] return z def constructive_membership_test(self, ipcgs, g): """ Return the exponent vector for induced pcgs. """ e = [0]len(ipcgs) h = g d = self.depth(h) for i, gen in enumerate(ipcgs): while self.depth(gen) == d: f = self.leading_exponent(h)self.leading_exponent(gen) f = f % self.relative_order[d-1] h = gen(-f)h e[i] = f d = self.depth(h) if h == 1: return e return False
b356a6b760fffb62e9f4a9615d26e6716ea5c1c47add792a123d95aba509a5d6	from sympy.combinatorics import Permutation as Perm from sympy.combinatorics.perm_groups import PermutationGroup from sympy.core import Basic, Tuple from sympy.core.compatibility import as_int from sympy.sets import FiniteSet from sympy.utilities.iterables import (minlex, unflatten, flatten) rmul = Perm.rmul class Polyhedron(Basic): """ Represents the polyhedral symmetry group (PSG). Explanation =========== The PSG is one of the symmetry groups of the Platonic solids. There are three polyhedral groups: the tetrahedral group of order 12, the octahedral group of order 24, and the icosahedral group of order 60. All doctests have been given in the docstring of the constructor of the object. References ========== .. [1] http://mathworld.wolfram.com/PolyhedralGroup.html """ _edges = None def __new__(cls, corners, faces=[], pgroup=[]): """ The constructor of the Polyhedron group object. Explanation =========== It takes up to three parameters: the corners, faces, and allowed transformations. The corners/vertices are entered as a list of arbitrary expressions that are used to identify each vertex. The faces are entered as a list of tuples of indices; a tuple of indices identifies the vertices which define the face. They should be entered in a cw or ccw order; they will be standardized by reversal and rotation to be give the lowest lexical ordering. If no faces are given then no edges will be computed. >>> from sympy.combinatorics.polyhedron import Polyhedron >>> Polyhedron(list('abc'), [(1, 2, 0)]).faces FiniteSet((0, 1, 2)) >>> Polyhedron(list('abc'), [(1, 0, 2)]).faces FiniteSet((0, 1, 2)) The allowed transformations are entered as allowable permutations of the vertices for the polyhedron. Instance of Permutations (as with faces) should refer to the supplied vertices by index. These permutation are stored as a PermutationGroup. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> from sympy.abc import w, x, y, z >>> init_printing(pretty_print=False, perm_cyclic=False) Here we construct the Polyhedron object for a tetrahedron. >>> corners = [w, x, y, z] >>> faces = [(0, 1, 2), (0, 2, 3), (0, 3, 1), (1, 2, 3)] Next, allowed transformations of the polyhedron must be given. This is given as permutations of vertices. Although the vertices of a tetrahedron can be numbered in 24 (4!) different ways, there are only 12 different orientations for a physical tetrahedron. The following permutations, applied once or twice, will generate all 12 of the orientations. (The identity permutation, Permutation(range(4)), is not included since it does not change the orientation of the vertices.) >>> pgroup = [Permutation([[0, 1, 2], [3]]), \ Permutation([[0, 1, 3], [2]]), \ Permutation([[0, 2, 3], [1]]), \ Permutation([[1, 2, 3], [0]]), \ Permutation([[0, 1], [2, 3]]), \ Permutation([[0, 2], [1, 3]]), \ Permutation([[0, 3], [1, 2]])] The Polyhedron is now constructed and demonstrated: >>> tetra = Polyhedron(corners, faces, pgroup) >>> tetra.size 4 >>> tetra.edges FiniteSet((0, 1), (0, 2), (0, 3), (1, 2), (1, 3), (2, 3)) >>> tetra.corners (w, x, y, z) It can be rotated with an arbitrary permutation of vertices, e.g. the following permutation is not in the pgroup: >>> tetra.rotate(Permutation([0, 1, 3, 2])) >>> tetra.corners (w, x, z, y) An allowed permutation of the vertices can be constructed by repeatedly applying permutations from the pgroup to the vertices. Here is a demonstration that applying p and p2 for every p in pgroup generates all the orientations of a tetrahedron and no others: >>> all = ( (w, x, y, z), \ (x, y, w, z), \ (y, w, x, z), \ (w, z, x, y), \ (z, w, y, x), \ (w, y, z, x), \ (y, z, w, x), \ (x, z, y, w), \ (z, y, x, w), \ (y, x, z, w), \ (x, w, z, y), \ (z, x, w, y) ) >>> got = [] >>> for p in (pgroup + [p2 for p in pgroup]): ... h = Polyhedron(corners) ... h.rotate(p) ... got.append(h.corners) ... >>> set(got) == set(all) True The make_perm method of a PermutationGroup will randomly pick permutations, multiply them together, and return the permutation that can be applied to the polyhedron to give the orientation produced by those individual permutations. Here, 3 permutations are used: >>> tetra.pgroup.make_perm(3) # doctest: +SKIP Permutation([0, 3, 1, 2]) To select the permutations that should be used, supply a list of indices to the permutations in pgroup in the order they should be applied: >>> use = [0, 0, 2] >>> p002 = tetra.pgroup.make_perm(3, use) >>> p002 Permutation([1, 0, 3, 2]) Apply them one at a time: >>> tetra.reset() >>> for i in use: ... tetra.rotate(pgroup[i]) ... >>> tetra.vertices (x, w, z, y) >>> sequentially = tetra.vertices Apply the composite permutation: >>> tetra.reset() >>> tetra.rotate(p002) >>> tetra.corners (x, w, z, y) >>> tetra.corners in all and tetra.corners == sequentially True Notes ===== Defining permutation groups --------------------------- It is not necessary to enter any permutations, nor is necessary to enter a complete set of transformations. In fact, for a polyhedron, all configurations can be constructed from just two permutations. For example, the orientations of a tetrahedron can be generated from an axis passing through a vertex and face and another axis passing through a different vertex or from an axis passing through the midpoints of two edges opposite of each other. For simplicity of presentation, consider a square -- not a cube -- with vertices 1, 2, 3, and 4: 1-----2 We could think of axes of rotation being: \| \| 1) through the face \| \| 2) from midpoint 1-2 to 3-4 or 1-3 to 2-4 3-----4 3) lines 1-4 or 2-3 To determine how to write the permutations, imagine 4 cameras, one at each corner, labeled A-D: A B A B 1-----2 1-----3 vertex index: \| \| \| \| 1 0 \| \| \| \| 2 1 3-----4 2-----4 3 2 C D C D 4 3 original after rotation along 1-4 A diagonal and a face axis will be chosen for the "permutation group" from which any orientation can be constructed. >>> pgroup = [] Imagine a clockwise rotation when viewing 1-4 from camera A. The new orientation is (in camera-order): 1, 3, 2, 4 so the permutation is given using the indices of the vertices as: >>> pgroup.append(Permutation((0, 2, 1, 3))) Now imagine rotating clockwise when looking down an axis entering the center of the square as viewed. The new camera-order would be 3, 1, 4, 2 so the permutation is (using indices): >>> pgroup.append(Permutation((2, 0, 3, 1))) The square can now be constructed: use real-world labels for the vertices, entering them in camera order for the faces we use zero-based indices of the vertices in edge-order as the face is traversed; neither the direction nor the starting point matter -- the faces are only used to define edges (if so desired). >>> square = Polyhedron((1, 2, 3, 4), [(0, 1, 3, 2)], pgroup) To rotate the square with a single permutation we can do: >>> square.rotate(square.pgroup[0]) >>> square.corners (1, 3, 2, 4) To use more than one permutation (or to use one permutation more than once) it is more convenient to use the make_perm method: >>> p011 = square.pgroup.make_perm([0, 1, 1]) # diag flip + 2 rotations >>> square.reset() # return to initial orientation >>> square.rotate(p011) >>> square.corners (4, 2, 3, 1) Thinking outside the box ------------------------ Although the Polyhedron object has a direct physical meaning, it actually has broader application. In the most general sense it is just a decorated PermutationGroup, allowing one to connect the permutations to something physical. For example, a Rubik's cube is not a proper polyhedron, but the Polyhedron class can be used to represent it in a way that helps to visualize the Rubik's cube. >>> from sympy.utilities.iterables import flatten, unflatten >>> from sympy import symbols >>> from sympy.combinatorics import RubikGroup >>> facelets = flatten([symbols(s+'1:5') for s in 'UFRBLD']) >>> def show(): ... pairs = unflatten(r2.corners, 2) ... print(pairs[::2]) ... print(pairs[1::2]) ... >>> r2 = Polyhedron(facelets, pgroup=RubikGroup(2)) >>> show() [(U1, U2), (F1, F2), (R1, R2), (B1, B2), (L1, L2), (D1, D2)] [(U3, U4), (F3, F4), (R3, R4), (B3, B4), (L3, L4), (D3, D4)] >>> r2.rotate(0) # cw rotation of F >>> show() [(U1, U2), (F3, F1), (U3, R2), (B1, B2), (L1, D1), (R3, R1)] [(L4, L2), (F4, F2), (U4, R4), (B3, B4), (L3, D2), (D3, D4)] Predefined Polyhedra ==================== For convenience, the vertices and faces are defined for the following standard solids along with a permutation group for transformations. When the polyhedron is oriented as indicated below, the vertices in a given horizontal plane are numbered in ccw direction, starting from the vertex that will give the lowest indices in a given face. (In the net of the vertices, indices preceded by "-" indicate replication of the lhs index in the net.) tetrahedron, tetrahedron_faces ------------------------------ 4 vertices (vertex up) net: 0 0-0 1 2 3-1 4 faces: (0, 1, 2) (0, 2, 3) (0, 3, 1) (1, 2, 3) cube, cube_faces ---------------- 8 vertices (face up) net: 0 1 2 3-0 4 5 6 7-4 6 faces: (0, 1, 2, 3) (0, 1, 5, 4) (1, 2, 6, 5) (2, 3, 7, 6) (0, 3, 7, 4) (4, 5, 6, 7) octahedron, octahedron_faces ---------------------------- 6 vertices (vertex up) net: 0 0 0-0 1 2 3 4-1 5 5 5-5 8 faces: (0, 1, 2) (0, 2, 3) (0, 3, 4) (0, 1, 4) (1, 2, 5) (2, 3, 5) (3, 4, 5) (1, 4, 5) dodecahedron, dodecahedron_faces -------------------------------- 20 vertices (vertex up) net: 0 1 2 3 4 -0 5 6 7 8 9 -5 14 10 11 12 13-14 15 16 17 18 19-15 12 faces: (0, 1, 2, 3, 4) (0, 1, 6, 10, 5) (1, 2, 7, 11, 6) (2, 3, 8, 12, 7) (3, 4, 9, 13, 8) (0, 4, 9, 14, 5) (5, 10, 16, 15, 14) (6, 10, 16, 17, 11) (7, 11, 17, 18, 12) (8, 12, 18, 19, 13) (9, 13, 19, 15, 14)(15, 16, 17, 18, 19) icosahedron, icosahedron_faces ------------------------------ 12 vertices (face up) net: 0 0 0 0 -0 1 2 3 4 5 -1 6 7 8 9 10 -6 11 11 11 11 -11 20 faces: (0, 1, 2) (0, 2, 3) (0, 3, 4) (0, 4, 5) (0, 1, 5) (1, 2, 6) (2, 3, 7) (3, 4, 8) (4, 5, 9) (1, 5, 10) (2, 6, 7) (3, 7, 8) (4, 8, 9) (5, 9, 10) (1, 6, 10) (6, 7, 11) (7, 8, 11) (8, 9, 11) (9, 10, 11) (6, 10, 11) >>> from sympy.combinatorics.polyhedron import cube >>> cube.edges FiniteSet((0, 1), (0, 3), (0, 4), (1, 2), (1, 5), (2, 3), (2, 6), (3, 7), (4, 5), (4, 7), (5, 6), (6, 7)) If you want to use letters or other names for the corners you can still use the pre-calculated faces: >>> corners = list('abcdefgh') >>> Polyhedron(corners, cube.faces).corners (a, b, c, d, e, f, g, h) References ========== .. [1] www.ocf.berkeley.edu/~wwu/articles/platonicsolids.pdf """ faces = [minlex(f, directed=False, is_set=True) for f in faces] corners, faces, pgroup = args = \ [Tuple(a) for a in (corners, faces, pgroup)] obj = Basic.__new__(cls, args) obj._corners = tuple(corners) # in order given obj._faces = FiniteSet(faces) if pgroup and pgroup[0].size != len(corners): raise ValueError("Permutation size unequal to number of corners.") # use the identity permutation if none are given obj._pgroup = PermutationGroup( pgroup or [Perm(range(len(corners)))] ) return obj @property def corners(self): """ Get the corners of the Polyhedron. The method ``vertices`` is an alias for ``corners``. Examples ======== >>> from sympy.combinatorics import Polyhedron >>> from sympy.abc import a, b, c, d >>> p = Polyhedron(list('abcd')) >>> p.corners == p.vertices == (a, b, c, d) True See Also ======== array_form, cyclic_form """ return self._corners vertices = corners @property def array_form(self): """Return the indices of the corners. The indices are given relative to the original position of corners. Examples ======== >>> from sympy.combinatorics.polyhedron import tetrahedron >>> tetrahedron = tetrahedron.copy() >>> tetrahedron.array_form [0, 1, 2, 3] >>> tetrahedron.rotate(0) >>> tetrahedron.array_form [0, 2, 3, 1] >>> tetrahedron.pgroup[0].array_form [0, 2, 3, 1] See Also ======== corners, cyclic_form """ corners = list(self.args[0]) return [corners.index(c) for c in self.corners] @property def cyclic_form(self): """Return the indices of the corners in cyclic notation. The indices are given relative to the original position of corners. See Also ======== corners, array_form """ return Perm._af_new(self.array_form).cyclic_form @property def size(self): """ Get the number of corners of the Polyhedron. """ return len(self._corners) @property def faces(self): """ Get the faces of the Polyhedron. """ return self._faces @property def pgroup(self): """ Get the permutations of the Polyhedron. """ return self._pgroup @property def edges(self): """ Given the faces of the polyhedra we can get the edges. Examples ======== >>> from sympy.combinatorics import Polyhedron >>> from sympy.abc import a, b, c >>> corners = (a, b, c) >>> faces = [(0, 1, 2)] >>> Polyhedron(corners, faces).edges FiniteSet((0, 1), (0, 2), (1, 2)) """ if self._edges is None: output = set() for face in self.faces: for i in range(len(face)): edge = tuple(sorted([face[i], face[i - 1]])) output.add(edge) self._edges = FiniteSet(output) return self._edges def rotate(self, perm): """ Apply a permutation to the polyhedron in place. The permutation may be given as a Permutation instance or an integer indicating which permutation from pgroup of the Polyhedron should be applied. This is an operation that is analogous to rotation about an axis by a fixed increment. Notes ===== When a Permutation is applied, no check is done to see if that is a valid permutation for the Polyhedron. For example, a cube could be given a permutation which effectively swaps only 2 vertices. A valid permutation (that rotates the object in a physical way) will be obtained if one only uses permutations from the ``pgroup`` of the Polyhedron. On the other hand, allowing arbitrary rotations (applications of permutations) gives a way to follow named elements rather than indices since Polyhedron allows vertices to be named while Permutation works only with indices. Examples ======== >>> from sympy.combinatorics import Polyhedron, Permutation >>> from sympy.combinatorics.polyhedron import cube >>> cube = cube.copy() >>> cube.corners (0, 1, 2, 3, 4, 5, 6, 7) >>> cube.rotate(0) >>> cube.corners (1, 2, 3, 0, 5, 6, 7, 4) A non-physical "rotation" that is not prohibited by this method: >>> cube.reset() >>> cube.rotate(Permutation([[1, 2]], size=8)) >>> cube.corners (0, 2, 1, 3, 4, 5, 6, 7) Polyhedron can be used to follow elements of set that are identified by letters instead of integers: >>> shadow = h5 = Polyhedron(list('abcde')) >>> p = Permutation([3, 0, 1, 2, 4]) >>> h5.rotate(p) >>> h5.corners (d, a, b, c, e) >>> _ == shadow.corners True >>> copy = h5.copy() >>> h5.rotate(p) >>> h5.corners == copy.corners False """ if not isinstance(perm, Perm): perm = self.pgroup[perm] # and we know it's valid else: if perm.size != self.size: raise ValueError('Polyhedron and Permutation sizes differ.') a = perm.array_form corners = [self.corners[a[i]] for i in range(len(self.corners))] self._corners = tuple(corners) def reset(self): """Return corners to their original positions. Examples ======== >>> from sympy.combinatorics.polyhedron import tetrahedron as T >>> T = T.copy() >>> T.corners (0, 1, 2, 3) >>> T.rotate(0) >>> T.corners (0, 2, 3, 1) >>> T.reset() >>> T.corners (0, 1, 2, 3) """ self._corners = self.args[0] def _pgroup_calcs(): """Return the permutation groups for each of the polyhedra and the face definitions: tetrahedron, cube, octahedron, dodecahedron, icosahedron, tetrahedron_faces, cube_faces, octahedron_faces, dodecahedron_faces, icosahedron_faces Explanation =========== (This author didn't find and didn't know of a better way to do it though there likely is such a way.) Although only 2 permutations are needed for a polyhedron in order to generate all the possible orientations, a group of permutations is provided instead. A set of permutations is called a "group" if:: ab = c (for any pair of permutations in the group, a and b, their product, c, is in the group) a(bc) = (ab)c (for any 3 permutations in the group associativity holds) there is an identity permutation, I, such that Ia = aI for all elements in the group ab = I (the inverse of each permutation is also in the group) None of the polyhedron groups defined follow these definitions of a group. Instead, they are selected to contain those permutations whose powers alone will construct all orientations of the polyhedron, i.e. for permutations ``a``, ``b``, etc... in the group, ``a, a2, ..., ao_a``, ``b, b2, ..., bo_b``, etc... (where ``o_i`` is the order of permutation ``i``) generate all permutations of the polyhedron instead of mixed products like ``ab``, ``ab2``, etc.... Note that for a polyhedron with n vertices, the valid permutations of the vertices exclude those that do not maintain its faces. e.g. the permutation BCDE of a square's four corners, ABCD, is a valid permutation while CBDE is not (because this would twist the square). Examples ======== The is_group checks for: closure, the presence of the Identity permutation, and the presence of the inverse for each of the elements in the group. This confirms that none of the polyhedra are true groups: >>> from sympy.combinatorics.polyhedron import ( ... tetrahedron, cube, octahedron, dodecahedron, icosahedron) ... >>> polyhedra = (tetrahedron, cube, octahedron, dodecahedron, icosahedron) >>> [h.pgroup.is_group for h in polyhedra] ... [True, True, True, True, True] Although tests in polyhedron's test suite check that powers of the permutations in the groups generate all permutations of the vertices of the polyhedron, here we also demonstrate the powers of the given permutations create a complete group for the tetrahedron: >>> from sympy.combinatorics import Permutation, PermutationGroup >>> for h in polyhedra[:1]: ... G = h.pgroup ... perms = set() ... for g in G: ... for e in range(g.order()): ... p = tuple((ge).array_form) ... perms.add(p) ... ... perms = [Permutation(p) for p in perms] ... assert PermutationGroup(perms).is_group In addition to doing the above, the tests in the suite confirm that the faces are all present after the application of each permutation. References ========== .. [1] http://dogschool.tripod.com/trianglegroup.html """ def _pgroup_of_double(polyh, ordered_faces, pgroup): n = len(ordered_faces[0]) # the vertices of the double which sits inside a give polyhedron # can be found by tracking the faces of the outer polyhedron. # A map between face and the vertex of the double is made so that # after rotation the position of the vertices can be located fmap = dict(zip(ordered_faces, range(len(ordered_faces)))) flat_faces = flatten(ordered_faces) new_pgroup = [] for i, p in enumerate(pgroup): h = polyh.copy() h.rotate(p) c = h.corners # reorder corners in the order they should appear when # enumerating the faces reorder = unflatten([c[j] for j in flat_faces], n) # make them canonical reorder = [tuple(map(as_int, minlex(f, directed=False, is_set=True))) for f in reorder] # map face to vertex: the resulting list of vertices are the # permutation that we seek for the double new_pgroup.append(Perm([fmap[f] for f in reorder])) return new_pgroup tetrahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 1), # upper 3 (1, 2, 3), # bottom ] # cw from top # _t_pgroup = [ Perm([[1, 2, 3], [0]]), # cw from top Perm([[0, 1, 2], [3]]), # cw from front face Perm([[0, 3, 2], [1]]), # cw from back right face Perm([[0, 3, 1], [2]]), # cw from back left face Perm([[0, 1], [2, 3]]), # through front left edge Perm([[0, 2], [1, 3]]), # through front right edge Perm([[0, 3], [1, 2]]), # through back edge ] tetrahedron = Polyhedron( range(4), tetrahedron_faces, _t_pgroup) cube_faces = [ (0, 1, 2, 3), # upper (0, 1, 5, 4), (1, 2, 6, 5), (2, 3, 7, 6), (0, 3, 7, 4), # middle 4 (4, 5, 6, 7), # lower ] # U, D, F, B, L, R = up, down, front, back, left, right _c_pgroup = [Perm(p) for p in [ [1, 2, 3, 0, 5, 6, 7, 4], # cw from top, U [4, 0, 3, 7, 5, 1, 2, 6], # cw from F face [4, 5, 1, 0, 7, 6, 2, 3], # cw from R face [1, 0, 4, 5, 2, 3, 7, 6], # cw through UF edge [6, 2, 1, 5, 7, 3, 0, 4], # cw through UR edge [6, 7, 3, 2, 5, 4, 0, 1], # cw through UB edge [3, 7, 4, 0, 2, 6, 5, 1], # cw through UL edge [4, 7, 6, 5, 0, 3, 2, 1], # cw through FL edge [6, 5, 4, 7, 2, 1, 0, 3], # cw through FR edge [0, 3, 7, 4, 1, 2, 6, 5], # cw through UFL vertex [5, 1, 0, 4, 6, 2, 3, 7], # cw through UFR vertex [5, 6, 2, 1, 4, 7, 3, 0], # cw through UBR vertex [7, 4, 0, 3, 6, 5, 1, 2], # cw through UBL ]] cube = Polyhedron( range(8), cube_faces, _c_pgroup) octahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 4), (0, 1, 4), # top 4 (1, 2, 5), (2, 3, 5), (3, 4, 5), (1, 4, 5), # bottom 4 ] octahedron = Polyhedron( range(6), octahedron_faces, _pgroup_of_double(cube, cube_faces, _c_pgroup)) dodecahedron_faces = [ (0, 1, 2, 3, 4), # top (0, 1, 6, 10, 5), (1, 2, 7, 11, 6), (2, 3, 8, 12, 7), # upper 5 (3, 4, 9, 13, 8), (0, 4, 9, 14, 5), (5, 10, 16, 15, 14), (6, 10, 16, 17, 11), (7, 11, 17, 18, 12), # lower 5 (8, 12, 18, 19, 13), (9, 13, 19, 15, 14), (15, 16, 17, 18, 19) # bottom ] def _string_to_perm(s): rv = [Perm(range(20))] p = None for si in s: if si not in '01': count = int(si) - 1 else: count = 1 if si == '0': p = _f0 elif si == '1': p = _f1 rv.extend([p]count) return Perm.rmul(rv) # top face cw _f0 = Perm([ 1, 2, 3, 4, 0, 6, 7, 8, 9, 5, 11, 12, 13, 14, 10, 16, 17, 18, 19, 15]) # front face cw _f1 = Perm([ 5, 0, 4, 9, 14, 10, 1, 3, 13, 15, 6, 2, 8, 19, 16, 17, 11, 7, 12, 18]) # the strings below, like 0104 are shorthand for F0F1F0**4 and are # the remaining 4 face rotations, 15 edge permutations, and the # 10 vertex rotations. _dodeca_pgroup = [_f0, _f1] + [_string_to_perm(s) for s in ''' 0104 140 014 0410 010 1403 03104 04103 102 120 1304 01303 021302 03130 0412041 041204103 04120410 041204104 041204102 10 01 1402 0140 04102 0412 1204 1302 0130 03120'''.strip().split()] dodecahedron = Polyhedron( range(20), dodecahedron_faces, _dodeca_pgroup) icosahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 4), (0, 4, 5), (0, 1, 5), (1, 6, 7), (1, 2, 7), (2, 7, 8), (2, 3, 8), (3, 8, 9), (3, 4, 9), (4, 9, 10), (4, 5, 10), (5, 6, 10), (1, 5, 6), (6, 7, 11), (7, 8, 11), (8, 9, 11), (9, 10, 11), (6, 10, 11)] icosahedron = Polyhedron( range(12), icosahedron_faces, _pgroup_of_double( dodecahedron, dodecahedron_faces, _dodeca_pgroup)) return (tetrahedron, cube, octahedron, dodecahedron, icosahedron, tetrahedron_faces, cube_faces, octahedron_faces, dodecahedron_faces, icosahedron_faces) # ----------------------------------------------------------------------- # Standard Polyhedron groups # # These are generated using _pgroup_calcs() above. However to save # import time we encode them explicitly here. # ----------------------------------------------------------------------- tetrahedron = Polyhedron( Tuple(0, 1, 2, 3), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 1, 3), Tuple(1, 2, 3)), Tuple( Perm(1, 2, 3), Perm(3)(0, 1, 2), Perm(0, 3, 2), Perm(0, 3, 1), Perm(0, 1)(2, 3), Perm(0, 2)(1, 3), Perm(0, 3)(1, 2) )) cube = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7), Tuple( Tuple(0, 1, 2, 3), Tuple(0, 1, 5, 4), Tuple(1, 2, 6, 5), Tuple(2, 3, 7, 6), Tuple(0, 3, 7, 4), Tuple(4, 5, 6, 7)), Tuple( Perm(0, 1, 2, 3)(4, 5, 6, 7), Perm(0, 4, 5, 1)(2, 3, 7, 6), Perm(0, 4, 7, 3)(1, 5, 6, 2), Perm(0, 1)(2, 4)(3, 5)(6, 7), Perm(0, 6)(1, 2)(3, 5)(4, 7), Perm(0, 6)(1, 7)(2, 3)(4, 5), Perm(0, 3)(1, 7)(2, 4)(5, 6), Perm(0, 4)(1, 7)(2, 6)(3, 5), Perm(0, 6)(1, 5)(2, 4)(3, 7), Perm(1, 3, 4)(2, 7, 5), Perm(7)(0, 5, 2)(3, 4, 6), Perm(0, 5, 7)(1, 6, 3), Perm(0, 7, 2)(1, 4, 6))) octahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 3, 4), Tuple(0, 1, 4), Tuple(1, 2, 5), Tuple(2, 3, 5), Tuple(3, 4, 5), Tuple(1, 4, 5)), Tuple( Perm(5)(1, 2, 3, 4), Perm(0, 4, 5, 2), Perm(0, 1, 5, 3), Perm(0, 1)(2, 4)(3, 5), Perm(0, 2)(1, 3)(4, 5), Perm(0, 3)(1, 5)(2, 4), Perm(0, 4)(1, 3)(2, 5), Perm(0, 5)(1, 4)(2, 3), Perm(0, 5)(1, 2)(3, 4), Perm(0, 4, 1)(2, 3, 5), Perm(0, 1, 2)(3, 4, 5), Perm(0, 2, 3)(1, 5, 4), Perm(0, 4, 3)(1, 5, 2))) dodecahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19), Tuple( Tuple(0, 1, 2, 3, 4), Tuple(0, 1, 6, 10, 5), Tuple(1, 2, 7, 11, 6), Tuple(2, 3, 8, 12, 7), Tuple(3, 4, 9, 13, 8), Tuple(0, 4, 9, 14, 5), Tuple(5, 10, 16, 15, 14), Tuple(6, 10, 16, 17, 11), Tuple(7, 11, 17, 18, 12), Tuple(8, 12, 18, 19, 13), Tuple(9, 13, 19, 15, 14), Tuple(15, 16, 17, 18, 19)), Tuple( Perm(0, 1, 2, 3, 4)(5, 6, 7, 8, 9)(10, 11, 12, 13, 14)(15, 16, 17, 18, 19), Perm(0, 5, 10, 6, 1)(2, 4, 14, 16, 11)(3, 9, 15, 17, 7)(8, 13, 19, 18, 12), Perm(0, 10, 17, 12, 3)(1, 6, 11, 7, 2)(4, 5, 16, 18, 8)(9, 14, 15, 19, 13), Perm(0, 6, 17, 19, 9)(1, 11, 18, 13, 4)(2, 7, 12, 8, 3)(5, 10, 16, 15, 14), Perm(0, 2, 12, 19, 14)(1, 7, 18, 15, 5)(3, 8, 13, 9, 4)(6, 11, 17, 16, 10), Perm(0, 4, 9, 14, 5)(1, 3, 13, 15, 10)(2, 8, 19, 16, 6)(7, 12, 18, 17, 11), Perm(0, 1)(2, 5)(3, 10)(4, 6)(7, 14)(8, 16)(9, 11)(12, 15)(13, 17)(18, 19), Perm(0, 7)(1, 2)(3, 6)(4, 11)(5, 12)(8, 10)(9, 17)(13, 16)(14, 18)(15, 19), Perm(0, 12)(1, 8)(2, 3)(4, 7)(5, 18)(6, 13)(9, 11)(10, 19)(14, 17)(15, 16), Perm(0, 8)(1, 13)(2, 9)(3, 4)(5, 12)(6, 19)(7, 14)(10, 18)(11, 15)(16, 17), Perm(0, 4)(1, 9)(2, 14)(3, 5)(6, 13)(7, 15)(8, 10)(11, 19)(12, 16)(17, 18), Perm(0, 5)(1, 14)(2, 15)(3, 16)(4, 10)(6, 9)(7, 19)(8, 17)(11, 13)(12, 18), Perm(0, 11)(1, 6)(2, 10)(3, 16)(4, 17)(5, 7)(8, 15)(9, 18)(12, 14)(13, 19), Perm(0, 18)(1, 12)(2, 7)(3, 11)(4, 17)(5, 19)(6, 8)(9, 16)(10, 13)(14, 15), Perm(0, 18)(1, 19)(2, 13)(3, 8)(4, 12)(5, 17)(6, 15)(7, 9)(10, 16)(11, 14), Perm(0, 13)(1, 19)(2, 15)(3, 14)(4, 9)(5, 8)(6, 18)(7, 16)(10, 12)(11, 17), Perm(0, 16)(1, 15)(2, 19)(3, 18)(4, 17)(5, 10)(6, 14)(7, 13)(8, 12)(9, 11), Perm(0, 18)(1, 17)(2, 16)(3, 15)(4, 19)(5, 12)(6, 11)(7, 10)(8, 14)(9, 13), Perm(0, 15)(1, 19)(2, 18)(3, 17)(4, 16)(5, 14)(6, 13)(7, 12)(8, 11)(9, 10), Perm(0, 17)(1, 16)(2, 15)(3, 19)(4, 18)(5, 11)(6, 10)(7, 14)(8, 13)(9, 12), Perm(0, 19)(1, 18)(2, 17)(3, 16)(4, 15)(5, 13)(6, 12)(7, 11)(8, 10)(9, 14), Perm(1, 4, 5)(2, 9, 10)(3, 14, 6)(7, 13, 16)(8, 15, 11)(12, 19, 17), Perm(19)(0, 6, 2)(3, 5, 11)(4, 10, 7)(8, 14, 17)(9, 16, 12)(13, 15, 18), Perm(0, 11, 8)(1, 7, 3)(4, 6, 12)(5, 17, 13)(9, 10, 18)(14, 16, 19), Perm(0, 7, 13)(1, 12, 9)(2, 8, 4)(5, 11, 19)(6, 18, 14)(10, 17, 15), Perm(0, 3, 9)(1, 8, 14)(2, 13, 5)(6, 12, 15)(7, 19, 10)(11, 18, 16), Perm(0, 14, 10)(1, 9, 16)(2, 13, 17)(3, 19, 11)(4, 15, 6)(7, 8, 18), Perm(0, 16, 7)(1, 10, 11)(2, 5, 17)(3, 14, 18)(4, 15, 12)(8, 9, 19), Perm(0, 16, 13)(1, 17, 8)(2, 11, 12)(3, 6, 18)(4, 10, 19)(5, 15, 9), Perm(0, 11, 15)(1, 17, 14)(2, 18, 9)(3, 12, 13)(4, 7, 19)(5, 6, 16), Perm(0, 8, 15)(1, 12, 16)(2, 18, 10)(3, 19, 5)(4, 13, 14)(6, 7, 17))) icosahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 3, 4), Tuple(0, 4, 5), Tuple(0, 1, 5), Tuple(1, 6, 7), Tuple(1, 2, 7), Tuple(2, 7, 8), Tuple(2, 3, 8), Tuple(3, 8, 9), Tuple(3, 4, 9), Tuple(4, 9, 10), Tuple(4, 5, 10), Tuple(5, 6, 10), Tuple(1, 5, 6), Tuple(6, 7, 11), Tuple(7, 8, 11), Tuple(8, 9, 11), Tuple(9, 10, 11), Tuple(6, 10, 11)), Tuple( Perm(11)(1, 2, 3, 4, 5)(6, 7, 8, 9, 10), Perm(0, 5, 6, 7, 2)(3, 4, 10, 11, 8), Perm(0, 1, 7, 8, 3)(4, 5, 6, 11, 9), Perm(0, 2, 8, 9, 4)(1, 7, 11, 10, 5), Perm(0, 3, 9, 10, 5)(1, 2, 8, 11, 6), Perm(0, 4, 10, 6, 1)(2, 3, 9, 11, 7), Perm(0, 1)(2, 5)(3, 6)(4, 7)(8, 10)(9, 11), Perm(0, 2)(1, 3)(4, 7)(5, 8)(6, 9)(10, 11), Perm(0, 3)(1, 9)(2, 4)(5, 8)(6, 11)(7, 10), Perm(0, 4)(1, 9)(2, 10)(3, 5)(6, 8)(7, 11), Perm(0, 5)(1, 4)(2, 10)(3, 6)(7, 9)(8, 11), Perm(0, 6)(1, 5)(2, 10)(3, 11)(4, 7)(8, 9), Perm(0, 7)(1, 2)(3, 6)(4, 11)(5, 8)(9, 10), Perm(0, 8)(1, 9)(2, 3)(4, 7)(5, 11)(6, 10), Perm(0, 9)(1, 11)(2, 10)(3, 4)(5, 8)(6, 7), Perm(0, 10)(1, 9)(2, 11)(3, 6)(4, 5)(7, 8), Perm(0, 11)(1, 6)(2, 10)(3, 9)(4, 8)(5, 7), Perm(0, 11)(1, 8)(2, 7)(3, 6)(4, 10)(5, 9), Perm(0, 11)(1, 10)(2, 9)(3, 8)(4, 7)(5, 6), Perm(0, 11)(1, 7)(2, 6)(3, 10)(4, 9)(5, 8), Perm(0, 11)(1, 9)(2, 8)(3, 7)(4, 6)(5, 10), Perm(0, 5, 1)(2, 4, 6)(3, 10, 7)(8, 9, 11), Perm(0, 1, 2)(3, 5, 7)(4, 6, 8)(9, 10, 11), Perm(0, 2, 3)(1, 8, 4)(5, 7, 9)(6, 11, 10), Perm(0, 3, 4)(1, 8, 10)(2, 9, 5)(6, 7, 11), Perm(0, 4, 5)(1, 3, 10)(2, 9, 6)(7, 8, 11), Perm(0, 10, 7)(1, 5, 6)(2, 4, 11)(3, 9, 8), Perm(0, 6, 8)(1, 7, 2)(3, 5, 11)(4, 10, 9), Perm(0, 7, 9)(1, 11, 4)(2, 8, 3)(5, 6, 10), Perm(0, 8, 10)(1, 7, 6)(2, 11, 5)(3, 9, 4), Perm(0, 9, 6)(1, 3, 11)(2, 8, 7)(4, 10, 5))) tetrahedron_faces = list(tuple(arg) for arg in tetrahedron.faces) cube_faces = list(tuple(arg) for arg in cube.faces) octahedron_faces = list(tuple(arg) for arg in octahedron.faces) dodecahedron_faces = list(tuple(arg) for arg in dodecahedron.faces) icosahedron_faces = list(tuple(arg) for arg in icosahedron.faces)
154b1e85fb2ec21248a0d65c1c0bc33949f23361183bf4e26e83094c9d58e7cf	import itertools from sympy.combinatorics.fp_groups import FpGroup, FpSubgroup, simplify_presentation from sympy.combinatorics.free_groups import FreeGroup from sympy.combinatorics.perm_groups import PermutationGroup from sympy.core.numbers import igcd from sympy.ntheory.factor_ import totient from sympy import S class GroupHomomorphism: ''' A class representing group homomorphisms. Instantiate using `homomorphism()`. References ========== .. [1] Holt, D., Eick, B. and O'Brien, E. (2005). Handbook of computational group theory. ''' def __init__(self, domain, codomain, images): self.domain = domain self.codomain = codomain self.images = images self._inverses = None self._kernel = None self._image = None def _invs(self): ''' Return a dictionary with `{gen: inverse}` where `gen` is a rewriting generator of `codomain` (e.g. strong generator for permutation groups) and `inverse` is an element of its preimage ''' image = self.image() inverses = {} for k in list(self.images.keys()): v = self.images[k] if not (v in inverses or v.is_identity): inverses[v] = k if isinstance(self.codomain, PermutationGroup): gens = image.strong_gens else: gens = image.generators for g in gens: if g in inverses or g.is_identity: continue w = self.domain.identity if isinstance(self.codomain, PermutationGroup): parts = image._strong_gens_slp[g][::-1] else: parts = g for s in parts: if s in inverses: w = winverses[s] else: w = winverses[s-1]-1 inverses[g] = w return inverses def invert(self, g): ''' Return an element of the preimage of ``g`` or of each element of ``g`` if ``g`` is a list. Explanation =========== If the codomain is an FpGroup, the inverse for equal elements might not always be the same unless the FpGroup's rewriting system is confluent. However, making a system confluent can be time-consuming. If it's important, try `self.codomain.make_confluent()` first. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.free_groups import FreeGroupElement if isinstance(g, (Permutation, FreeGroupElement)): if isinstance(self.codomain, FpGroup): g = self.codomain.reduce(g) if self._inverses is None: self._inverses = self._invs() image = self.image() w = self.domain.identity if isinstance(self.codomain, PermutationGroup): gens = image.generator_product(g)[::-1] else: gens = g # the following can't be "for s in gens:" # because that would be equivalent to # "for s in gens.array_form:" when g is # a FreeGroupElement. On the other hand, # when you call gens by index, the generator # (or inverse) at position i is returned. for i in range(len(gens)): s = gens[i] if s.is_identity: continue if s in self._inverses: w = wself._inverses[s] else: w = wself._inverses[s-1]-1 return w elif isinstance(g, list): return [self.invert(e) for e in g] def kernel(self): ''' Compute the kernel of `self`. ''' if self._kernel is None: self._kernel = self._compute_kernel() return self._kernel def _compute_kernel(self): from sympy import S G = self.domain G_order = G.order() if G_order is S.Infinity: raise NotImplementedError( "Kernel computation is not implemented for infinite groups") gens = [] if isinstance(G, PermutationGroup): K = PermutationGroup(G.identity) else: K = FpSubgroup(G, gens, normal=True) i = self.image().order() while K.order()i != G_order: r = G.random() k = rself.invert(self(r))*-1 if not k in K: gens.append(k) if isinstance(G, PermutationGroup): K = PermutationGroup(gens) else: K = FpSubgroup(G, gens, normal=True) return K def image(self): ''' Compute the image of `self`. ''' if self._image is None: values = list(set(self.images.values())) if isinstance(self.codomain, PermutationGroup): self._image = self.codomain.subgroup(values) else: self._image = FpSubgroup(self.codomain, values) return self._image def _apply(self, elem): ''' Apply `self` to `elem`. ''' if not elem in self.domain: if isinstance(elem, (list, tuple)): return [self._apply(e) for e in elem] raise ValueError("The supplied element doesn't belong to the domain") if elem.is_identity: return self.codomain.identity else: images = self.images value = self.codomain.identity if isinstance(self.domain, PermutationGroup): gens = self.domain.generator_product(elem, original=True) for g in gens: if g in self.images: value = images[g]value else: value = images[g-1]-1value else: i = 0 for _, p in elem.array_form: if p < 0: g = elem[i]-1 else: g = elem[i] value = valueimages[g]*p i += abs(p) return value def __call__(self, elem): return self._apply(elem) def is_injective(self): ''' Check if the homomorphism is injective ''' return self.kernel().order() == 1 def is_surjective(self): ''' Check if the homomorphism is surjective ''' from sympy import S im = self.image().order() oth = self.codomain.order() if im is S.Infinity and oth is S.Infinity: return None else: return im == oth def is_isomorphism(self): ''' Check if `self` is an isomorphism. ''' return self.is_injective() and self.is_surjective() def is_trivial(self): ''' Check is `self` is a trivial homomorphism, i.e. all elements are mapped to the identity. ''' return self.image().order() == 1 def compose(self, other): ''' Return the composition of `self` and `other`, i.e. the homomorphism phi such that for all g in the domain of `other`, phi(g) = self(other(g)) ''' if not other.image().is_subgroup(self.domain): raise ValueError("The image of `other` must be a subgroup of " "the domain of `self`") images = {g: self(other(g)) for g in other.images} return GroupHomomorphism(other.domain, self.codomain, images) def restrict_to(self, H): ''' Return the restriction of the homomorphism to the subgroup `H` of the domain. ''' if not isinstance(H, PermutationGroup) or not H.is_subgroup(self.domain): raise ValueError("Given H is not a subgroup of the domain") domain = H images = {g: self(g) for g in H.generators} return GroupHomomorphism(domain, self.codomain, images) def invert_subgroup(self, H): ''' Return the subgroup of the domain that is the inverse image of the subgroup ``H`` of the homomorphism image ''' if not H.is_subgroup(self.image()): raise ValueError("Given H is not a subgroup of the image") gens = [] P = PermutationGroup(self.image().identity) for h in H.generators: h_i = self.invert(h) if h_i not in P: gens.append(h_i) P = PermutationGroup(gens) for k in self.kernel().generators: if kh_i not in P: gens.append(kh_i) P = PermutationGroup(gens) return P def homomorphism(domain, codomain, gens, images=[], check=True): ''' Create (if possible) a group homomorphism from the group ``domain`` to the group ``codomain`` defined by the images of the domain's generators ``gens``. ``gens`` and ``images`` can be either lists or tuples of equal sizes. If ``gens`` is a proper subset of the group's generators, the unspecified generators will be mapped to the identity. If the images are not specified, a trivial homomorphism will be created. If the given images of the generators do not define a homomorphism, an exception is raised. If ``check`` is ``False``, don't check whether the given images actually define a homomorphism. ''' if not isinstance(domain, (PermutationGroup, FpGroup, FreeGroup)): raise TypeError("The domain must be a group") if not isinstance(codomain, (PermutationGroup, FpGroup, FreeGroup)): raise TypeError("The codomain must be a group") generators = domain.generators if any([g not in generators for g in gens]): raise ValueError("The supplied generators must be a subset of the domain's generators") if any([g not in codomain for g in images]): raise ValueError("The images must be elements of the codomain") if images and len(images) != len(gens): raise ValueError("The number of images must be equal to the number of generators") gens = list(gens) images = list(images) images.extend([codomain.identity](len(generators)-len(images))) gens.extend([g for g in generators if g not in gens]) images = dict(zip(gens,images)) if check and not _check_homomorphism(domain, codomain, images): raise ValueError("The given images do not define a homomorphism") return GroupHomomorphism(domain, codomain, images) def _check_homomorphism(domain, codomain, images): if hasattr(domain, 'relators'): rels = domain.relators else: gens = domain.presentation().generators rels = domain.presentation().relators identity = codomain.identity def _image(r): if r.is_identity: return identity else: w = identity r_arr = r.array_form i = 0 j = 0 # i is the index for r and j is for # r_arr. r_arr[j] is the tuple (sym, p) # where sym is the generator symbol # and p is the power to which it is # raised while r[i] is a generator # (not just its symbol) or the inverse of # a generator - hence the need for # both indices while i < len(r): power = r_arr[j][1] if isinstance(domain, PermutationGroup) and r[i] in gens: s = domain.generators[gens.index(r[i])] else: s = r[i] if s in images: w = wimages[s]power elif s-1 in images: w = wimages[s-1]power i += abs(power) j += 1 return w for r in rels: if isinstance(codomain, FpGroup): s = codomain.equals(_image(r), identity) if s is None: # only try to make the rewriting system # confluent when it can't determine the # truth of equality otherwise success = codomain.make_confluent() s = codomain.equals(_image(r), identity) if s is None and not success: raise RuntimeError("Can't determine if the images " "define a homomorphism. Try increasing " "the maximum number of rewriting rules " "(group._rewriting_system.set_max(new_value); " "the current value is stored in group._rewriting" "_system.maxeqns)") else: s = _image(r).is_identity if not s: return False return True def orbit_homomorphism(group, omega): ''' Return the homomorphism induced by the action of the permutation group ``group`` on the set ``omega`` that is closed under the action. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.named_groups import SymmetricGroup codomain = SymmetricGroup(len(omega)) identity = codomain.identity omega = list(omega) images = {g: identityPermutation([omega.index(o^g) for o in omega]) for g in group.generators} group._schreier_sims(base=omega) H = GroupHomomorphism(group, codomain, images) if len(group.basic_stabilizers) > len(omega): H._kernel = group.basic_stabilizers[len(omega)] else: H._kernel = PermutationGroup([group.identity]) return H def block_homomorphism(group, blocks): ''' Return the homomorphism induced by the action of the permutation group ``group`` on the block system ``blocks``. The latter should be of the same form as returned by the ``minimal_block`` method for permutation groups, namely a list of length ``group.degree`` where the i-th entry is a representative of the block i belongs to. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.named_groups import SymmetricGroup n = len(blocks) # number the blocks; m is the total number, # b is such that b[i] is the number of the block i belongs to, # p is the list of length m such that p[i] is the representative # of the i-th block m = 0 p = [] b = [None]n for i in range(n): if blocks[i] == i: p.append(i) b[i] = m m += 1 for i in range(n): b[i] = b[blocks[i]] codomain = SymmetricGroup(m) # the list corresponding to the identity permutation in codomain identity = range(m) images = {g: Permutation([b[p[i]^g] for i in identity]) for g in group.generators} H = GroupHomomorphism(group, codomain, images) return H def group_isomorphism(G, H, isomorphism=True): ''' Compute an isomorphism between 2 given groups. Parameters ========== G : A finite ``FpGroup`` or a ``PermutationGroup``. First group. H : A finite ``FpGroup`` or a ``PermutationGroup`` Second group. isomorphism : bool This is used to avoid the computation of homomorphism when the user only wants to check if there exists an isomorphism between the groups. Returns ======= If isomorphism = False -- Returns a boolean. If isomorphism = True -- Returns a boolean and an isomorphism between `G` and `H`. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.free_groups import free_group >>> from sympy.combinatorics.fp_groups import FpGroup >>> from sympy.combinatorics.homomorphisms import group_isomorphism >>> from sympy.combinatorics.named_groups import DihedralGroup, AlternatingGroup >>> D = DihedralGroup(8) >>> p = Permutation(0, 1, 2, 3, 4, 5, 6, 7) >>> P = PermutationGroup(p) >>> group_isomorphism(D, P) (False, None) >>> F, a, b = free_group("a, b") >>> G = FpGroup(F, [a3, b3, (ab)2]) >>> H = AlternatingGroup(4) >>> (check, T) = group_isomorphism(G, H) >>> check True >>> T(bab-1a*-1b*-1) (0 2 3) Notes ===== Uses the approach suggested by Robert Tarjan to compute the isomorphism between two groups. First, the generators of ``G`` are mapped to the elements of ``H`` and we check if the mapping induces an isomorphism. ''' if not isinstance(G, (PermutationGroup, FpGroup)): raise TypeError("The group must be a PermutationGroup or an FpGroup") if not isinstance(H, (PermutationGroup, FpGroup)): raise TypeError("The group must be a PermutationGroup or an FpGroup") if isinstance(G, FpGroup) and isinstance(H, FpGroup): G = simplify_presentation(G) H = simplify_presentation(H) # Two infinite FpGroups with the same generators are isomorphic # when the relators are same but are ordered differently. if G.generators == H.generators and (G.relators).sort() == (H.relators).sort(): if not isomorphism: return True return (True, homomorphism(G, H, G.generators, H.generators)) # `_H` is the permutation group isomorphic to `H`. _H = H g_order = G.order() h_order = H.order() if g_order is S.Infinity: raise NotImplementedError("Isomorphism methods are not implemented for infinite groups.") if isinstance(H, FpGroup): if h_order is S.Infinity: raise NotImplementedError("Isomorphism methods are not implemented for infinite groups.") _H, h_isomorphism = H._to_perm_group() if (g_order != h_order) or (G.is_abelian != H.is_abelian): if not isomorphism: return False return (False, None) if not isomorphism: # Two groups of the same cyclic numbered order # are isomorphic to each other. n = g_order if (igcd(n, totient(n))) == 1: return True # Match the generators of `G` with subsets of `_H` gens = list(G.generators) for subset in itertools.permutations(_H, len(gens)): images = list(subset) images.extend([_H.identity](len(G.generators)-len(images))) _images = dict(zip(gens,images)) if _check_homomorphism(G, _H, _images): if isinstance(H, FpGroup): images = h_isomorphism.invert(images) T = homomorphism(G, H, G.generators, images, check=False) if T.is_isomorphism(): # It is a valid isomorphism if not isomorphism: return True return (True, T) if not isomorphism: return False return (False, None) def is_isomorphic(G, H): ''' Check if the groups are isomorphic to each other Parameters ========== G : A finite ``FpGroup`` or a ``PermutationGroup`` First group. H : A finite ``FpGroup`` or a ``PermutationGroup`` Second group. Returns ======= boolean ''' return group_isomorphism(G, H, isomorphism=False)
9565b5f31f6b52a1711728114843fecc9843c6179d18e729c9945f8cee9e4b02	from sympy.core import Basic, Dict, sympify from sympy.core.compatibility import as_int, default_sort_key from sympy.core.sympify import _sympify from sympy.functions.combinatorial.numbers import bell from sympy.matrices import zeros from sympy.sets.sets import FiniteSet, Union from sympy.utilities.iterables import flatten, group from collections import defaultdict class Partition(FiniteSet): """ This class represents an abstract partition. A partition is a set of disjoint sets whose union equals a given set. See Also ======== sympy.utilities.iterables.partitions, sympy.utilities.iterables.multiset_partitions """ _rank = None _partition = None def __new__(cls, partition): """ Generates a new partition object. This method also verifies if the arguments passed are valid and raises a ValueError if they are not. Examples ======== Creating Partition from Python lists: >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a Partition(FiniteSet(1, 2), FiniteSet(3)) >>> a.partition [[1, 2], [3]] >>> len(a) 2 >>> a.members (1, 2, 3) Creating Partition from Python sets: >>> Partition({1, 2, 3}, {4, 5}) Partition(FiniteSet(1, 2, 3), FiniteSet(4, 5)) Creating Partition from SymPy finite sets: >>> from sympy.sets.sets import FiniteSet >>> a = FiniteSet(1, 2, 3) >>> b = FiniteSet(4, 5) >>> Partition(a, b) Partition(FiniteSet(1, 2, 3), FiniteSet(4, 5)) """ args = [] dups = False for arg in partition: if isinstance(arg, list): as_set = set(arg) if len(as_set) < len(arg): dups = True break # error below arg = as_set args.append(_sympify(arg)) if not all(isinstance(part, FiniteSet) for part in args): raise ValueError( "Each argument to Partition should be " \ "a list, set, or a FiniteSet") # sort so we have a canonical reference for RGS U = Union(args) if dups or len(U) < sum(len(arg) for arg in args): raise ValueError("Partition contained duplicate elements.") obj = FiniteSet.__new__(cls, args) obj.members = tuple(U) obj.size = len(U) return obj def sort_key(self, order=None): """Return a canonical key that can be used for sorting. Ordering is based on the size and sorted elements of the partition and ties are broken with the rank. Examples ======== >>> from sympy.utilities.iterables import default_sort_key >>> from sympy.combinatorics.partitions import Partition >>> from sympy.abc import x >>> a = Partition([1, 2]) >>> b = Partition([3, 4]) >>> c = Partition([1, x]) >>> d = Partition(list(range(4))) >>> l = [d, b, a + 1, a, c] >>> l.sort(key=default_sort_key); l [Partition(FiniteSet(1, 2)), Partition(FiniteSet(1), FiniteSet(2)), Partition(FiniteSet(1, x)), Partition(FiniteSet(3, 4)), Partition(FiniteSet(0, 1, 2, 3))] """ if order is None: members = self.members else: members = tuple(sorted(self.members, key=lambda w: default_sort_key(w, order))) return tuple(map(default_sort_key, (self.size, members, self.rank))) @property def partition(self): """Return partition as a sorted list of lists. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> Partition([1], [2, 3]).partition [[1], [2, 3]] """ if self._partition is None: self._partition = sorted([sorted(p, key=default_sort_key) for p in self.args]) return self._partition def __add__(self, other): """ Return permutation whose rank is ``other`` greater than current rank, (mod the maximum rank for the set). Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a.rank 1 >>> (a + 1).rank 2 >>> (a + 100).rank 1 """ other = as_int(other) offset = self.rank + other result = RGS_unrank((offset) % RGS_enum(self.size), self.size) return Partition.from_rgs(result, self.members) def __sub__(self, other): """ Return permutation whose rank is ``other`` less than current rank, (mod the maximum rank for the set). Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a.rank 1 >>> (a - 1).rank 0 >>> (a - 100).rank 1 """ return self.__add__(-other) def __le__(self, other): """ Checks if a partition is less than or equal to the other based on rank. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3, 4, 5]) >>> b = Partition([1], [2, 3], [4], [5]) >>> a.rank, b.rank (9, 34) >>> a <= a True >>> a <= b True """ return self.sort_key() <= sympify(other).sort_key() def __lt__(self, other): """ Checks if a partition is less than the other. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3, 4, 5]) >>> b = Partition([1], [2, 3], [4], [5]) >>> a.rank, b.rank (9, 34) >>> a < b True """ return self.sort_key() < sympify(other).sort_key() @property def rank(self): """ Gets the rank of a partition. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3], [4, 5]) >>> a.rank 13 """ if self._rank is not None: return self._rank self._rank = RGS_rank(self.RGS) return self._rank @property def RGS(self): """ Returns the "restricted growth string" of the partition. Explanation =========== The RGS is returned as a list of indices, L, where L[i] indicates the block in which element i appears. For example, in a partition of 3 elements (a, b, c) into 2 blocks ([c], [a, b]) the RGS is [1, 1, 0]: "a" is in block 1, "b" is in block 1 and "c" is in block 0. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3], [4, 5]) >>> a.members (1, 2, 3, 4, 5) >>> a.RGS (0, 0, 1, 2, 2) >>> a + 1 Partition(FiniteSet(1, 2), FiniteSet(3), FiniteSet(4), FiniteSet(5)) >>> _.RGS (0, 0, 1, 2, 3) """ rgs = {} partition = self.partition for i, part in enumerate(partition): for j in part: rgs[j] = i return tuple([rgs[i] for i in sorted( [i for p in partition for i in p], key=default_sort_key)]) @classmethod def from_rgs(self, rgs, elements): """ Creates a set partition from a restricted growth string. Explanation =========== The indices given in rgs are assumed to be the index of the element as given in elements as provided* (the elements are not sorted by this routine). Block numbering starts from 0. If any block was not referenced in ``rgs`` an error will be raised. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> Partition.from_rgs([0, 1, 2, 0, 1], list('abcde')) Partition(FiniteSet(c), FiniteSet(a, d), FiniteSet(b, e)) >>> Partition.from_rgs([0, 1, 2, 0, 1], list('cbead')) Partition(FiniteSet(e), FiniteSet(a, c), FiniteSet(b, d)) >>> a = Partition([1, 4], [2], [3, 5]) >>> Partition.from_rgs(a.RGS, a.members) Partition(FiniteSet(1, 4), FiniteSet(2), FiniteSet(3, 5)) """ if len(rgs) != len(elements): raise ValueError('mismatch in rgs and element lengths') max_elem = max(rgs) + 1 partition = [[] for i in range(max_elem)] j = 0 for i in rgs: partition[i].append(elements[j]) j += 1 if not all(p for p in partition): raise ValueError('some blocks of the partition were empty.') return Partition(partition) class IntegerPartition(Basic): """ This class represents an integer partition. Explanation =========== In number theory and combinatorics, a partition of a positive integer, ``n``, also called an integer partition, is a way of writing ``n`` as a list of positive integers that sum to n. Two partitions that differ only in the order of summands are considered to be the same partition; if order matters then the partitions are referred to as compositions. For example, 4 has five partitions: [4], [3, 1], [2, 2], [2, 1, 1], and [1, 1, 1, 1]; the compositions [1, 2, 1] and [1, 1, 2] are the same as partition [2, 1, 1]. See Also ======== sympy.utilities.iterables.partitions, sympy.utilities.iterables.multiset_partitions References ========== https://en.wikipedia.org/wiki/Partition_%28number_theory%29 """ _dict = None _keys = None def __new__(cls, partition, integer=None): """ Generates a new IntegerPartition object from a list or dictionary. Explantion ========== The partition can be given as a list of positive integers or a dictionary of (integer, multiplicity) items. If the partition is preceded by an integer an error will be raised if the partition does not sum to that given integer. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([5, 4, 3, 1, 1]) >>> a IntegerPartition(14, (5, 4, 3, 1, 1)) >>> print(a) [5, 4, 3, 1, 1] >>> IntegerPartition({1:3, 2:1}) IntegerPartition(5, (2, 1, 1, 1)) If the value that the partition should sum to is given first, a check will be made to see n error will be raised if there is a discrepancy: >>> IntegerPartition(10, [5, 4, 3, 1]) Traceback (most recent call last): ... ValueError: The partition is not valid """ if integer is not None: integer, partition = partition, integer if isinstance(partition, (dict, Dict)): _ = [] for k, v in sorted(list(partition.items()), reverse=True): if not v: continue k, v = as_int(k), as_int(v) _.extend([k]v) partition = tuple(_) else: partition = tuple(sorted(map(as_int, partition), reverse=True)) sum_ok = False if integer is None: integer = sum(partition) sum_ok = True else: integer = as_int(integer) if not sum_ok and sum(partition) != integer: raise ValueError("Partition did not add to %s" % integer) if any(i < 1 for i in partition): raise ValueError("The summands must all be positive.") obj = Basic.__new__(cls, integer, partition) obj.partition = list(partition) obj.integer = integer return obj def prev_lex(self): """Return the previous partition of the integer, n, in lexical order, wrapping around to [1, ..., 1] if the partition is [n]. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> p = IntegerPartition([4]) >>> print(p.prev_lex()) [3, 1] >>> p.partition > p.prev_lex().partition True """ d = defaultdict(int) d.update(self.as_dict()) keys = self._keys if keys == [1]: return IntegerPartition({self.integer: 1}) if keys[-1] != 1: d[keys[-1]] -= 1 if keys[-1] == 2: d[1] = 2 else: d[keys[-1] - 1] = d[1] = 1 else: d[keys[-2]] -= 1 left = d[1] + keys[-2] new = keys[-2] d[1] = 0 while left: new -= 1 if left - new >= 0: d[new] += left//new left -= d[new]new return IntegerPartition(self.integer, d) def next_lex(self): """Return the next partition of the integer, n, in lexical order, wrapping around to [n] if the partition is [1, ..., 1]. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> p = IntegerPartition([3, 1]) >>> print(p.next_lex()) [4] >>> p.partition < p.next_lex().partition True """ d = defaultdict(int) d.update(self.as_dict()) key = self._keys a = key[-1] if a == self.integer: d.clear() d[1] = self.integer elif a == 1: if d[a] > 1: d[a + 1] += 1 d[a] -= 2 else: b = key[-2] d[b + 1] += 1 d[1] = (d[b] - 1)b d[b] = 0 else: if d[a] > 1: if len(key) == 1: d.clear() d[a + 1] = 1 d[1] = self.integer - a - 1 else: a1 = a + 1 d[a1] += 1 d[1] = d[a]a - a1 d[a] = 0 else: b = key[-2] b1 = b + 1 d[b1] += 1 need = d[b]b + d[a]a - b1 d[a] = d[b] = 0 d[1] = need return IntegerPartition(self.integer, d) def as_dict(self): """Return the partition as a dictionary whose keys are the partition integers and the values are the multiplicity of that integer. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> IntegerPartition([1]3 + [2] + [3]4).as_dict() {1: 3, 2: 1, 3: 4} """ if self._dict is None: groups = group(self.partition, multiple=False) self._keys = [g[0] for g in groups] self._dict = dict(groups) return self._dict @property def conjugate(self): """ Computes the conjugate partition of itself. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([6, 3, 3, 2, 1]) >>> a.conjugate [5, 4, 3, 1, 1, 1] """ j = 1 temp_arr = list(self.partition) + [0] k = temp_arr[0] b = [0]k while k > 0: while k > temp_arr[j]: b[k - 1] = j k -= 1 j += 1 return b def __lt__(self, other): """Return True if self is less than other when the partition is listed from smallest to biggest. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([3, 1]) >>> a < a False >>> b = a.next_lex() >>> a < b True >>> a == b False """ return list(reversed(self.partition)) < list(reversed(other.partition)) def __le__(self, other): """Return True if self is less than other when the partition is listed from smallest to biggest. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([4]) >>> a <= a True """ return list(reversed(self.partition)) <= list(reversed(other.partition)) def as_ferrers(self, char='#'): """ Prints the ferrer diagram of a partition. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> print(IntegerPartition([1, 1, 5]).as_ferrers()) ##### # # """ return "\n".join([chari for i in self.partition]) def __str__(self): return str(list(self.partition)) def random_integer_partition(n, seed=None): """ Generates a random integer partition summing to ``n`` as a list of reverse-sorted integers. Examples ======== >>> from sympy.combinatorics.partitions import random_integer_partition For the following, a seed is given so a known value can be shown; in practice, the seed would not be given. >>> random_integer_partition(100, seed=[1, 1, 12, 1, 2, 1, 85, 1]) [85, 12, 2, 1] >>> random_integer_partition(10, seed=[1, 2, 3, 1, 5, 1]) [5, 3, 1, 1] >>> random_integer_partition(1) [1] """ from sympy.testing.randtest import _randint n = as_int(n) if n < 1: raise ValueError('n must be a positive integer') randint = _randint(seed) partition = [] while (n > 0): k = randint(1, n) mult = randint(1, n//k) partition.append((k, mult)) n -= kmult partition.sort(reverse=True) partition = flatten([[k]m for k, m in partition]) return partition def RGS_generalized(m): """ Computes the m + 1 generalized unrestricted growth strings and returns them as rows in matrix. Examples ======== >>> from sympy.combinatorics.partitions import RGS_generalized >>> RGS_generalized(6) Matrix([ [ 1, 1, 1, 1, 1, 1, 1], [ 1, 2, 3, 4, 5, 6, 0], [ 2, 5, 10, 17, 26, 0, 0], [ 5, 15, 37, 77, 0, 0, 0], [ 15, 52, 151, 0, 0, 0, 0], [ 52, 203, 0, 0, 0, 0, 0], [203, 0, 0, 0, 0, 0, 0]]) """ d = zeros(m + 1) for i in range(0, m + 1): d[0, i] = 1 for i in range(1, m + 1): for j in range(m): if j <= m - i: d[i, j] = j d[i - 1, j] + d[i - 1, j + 1] else: d[i, j] = 0 return d def RGS_enum(m): """ RGS_enum computes the total number of restricted growth strings possible for a superset of size m. Examples ======== >>> from sympy.combinatorics.partitions import RGS_enum >>> from sympy.combinatorics.partitions import Partition >>> RGS_enum(4) 15 >>> RGS_enum(5) 52 >>> RGS_enum(6) 203 We can check that the enumeration is correct by actually generating the partitions. Here, the 15 partitions of 4 items are generated: >>> a = Partition(list(range(4))) >>> s = set() >>> for i in range(20): ... s.add(a) ... a += 1 ... >>> assert len(s) == 15 """ if (m < 1): return 0 elif (m == 1): return 1 else: return bell(m) def RGS_unrank(rank, m): """ Gives the unranked restricted growth string for a given superset size. Examples ======== >>> from sympy.combinatorics.partitions import RGS_unrank >>> RGS_unrank(14, 4) [0, 1, 2, 3] >>> RGS_unrank(0, 4) [0, 0, 0, 0] """ if m < 1: raise ValueError("The superset size must be >= 1") if rank < 0 or RGS_enum(m) <= rank: raise ValueError("Invalid arguments") L = [1] * (m + 1) j = 1 D = RGS_generalized(m) for i in range(2, m + 1): v = D[m - i, j] cr = jv if cr <= rank: L[i] = j + 1 rank -= cr j += 1 else: L[i] = int(rank / v + 1) rank %= v return [x - 1 for x in L[1:]] def RGS_rank(rgs): """ Computes the rank of a restricted growth string. Examples ======== >>> from sympy.combinatorics.partitions import RGS_rank, RGS_unrank >>> RGS_rank([0, 1, 2, 1, 3]) 42 >>> RGS_rank(RGS_unrank(4, 7)) 4 """ rgs_size = len(rgs) rank = 0 D = RGS_generalized(rgs_size) for i in range(1, rgs_size): n = len(rgs[(i + 1):]) m = max(rgs[0:i]) rank += D[n, m + 1] rgs[i] return rank
8623821dff0c0e6e9e487fee93f54fbf2677ac5735901ac5dd6cc51e85fff678	from sympy.combinatorics.permutations import Permutation, _af_invert, _af_rmul from sympy.ntheory import isprime rmul = Permutation.rmul _af_new = Permutation._af_new ############################################ # # Utilities for computational group theory # ############################################ def _base_ordering(base, degree): r""" Order `\{0, 1, ..., n-1\}` so that base points come first and in order. Parameters ========== ``base`` : the base ``degree`` : the degree of the associated permutation group Returns ======= A list ``base_ordering`` such that ``base_ordering[point]`` is the number of ``point`` in the ordering. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _base_ordering >>> S = SymmetricGroup(4) >>> S.schreier_sims() >>> _base_ordering(S.base, S.degree) [0, 1, 2, 3] Notes ===== This is used in backtrack searches, when we define a relation `<<` on the underlying set for a permutation group of degree `n`, `\{0, 1, ..., n-1\}`, so that if `(b_1, b_2, ..., b_k)` is a base we have `b_i << b_j` whenever `i<j` and `b_i << a` for all `i\in\{1,2, ..., k\}` and `a` is not in the base. The idea is developed and applied to backtracking algorithms in [1], pp.108-132. The points that are not in the base are taken in increasing order. References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" """ base_len = len(base) ordering = [0]degree for i in range(base_len): ordering[base[i]] = i current = base_len for i in range(degree): if i not in base: ordering[i] = current current += 1 return ordering def _check_cycles_alt_sym(perm): """ Checks for cycles of prime length p with n/2 < p < n-2. Explanation =========== Here `n` is the degree of the permutation. This is a helper function for the function is_alt_sym from sympy.combinatorics.perm_groups. Examples ======== >>> from sympy.combinatorics.util import _check_cycles_alt_sym >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [11, 12]]) >>> _check_cycles_alt_sym(a) False >>> b = Permutation([[0, 1, 2, 3, 4, 5, 6], [7, 8, 9, 10]]) >>> _check_cycles_alt_sym(b) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.is_alt_sym """ n = perm.size af = perm.array_form current_len = 0 total_len = 0 used = set() for i in range(n//2): if not i in used and i < n//2 - total_len: current_len = 1 used.add(i) j = i while af[j] != i: current_len += 1 j = af[j] used.add(j) total_len += current_len if current_len > n//2 and current_len < n - 2 and isprime(current_len): return True return False def _distribute_gens_by_base(base, gens): r""" Distribute the group elements ``gens`` by membership in basic stabilizers. Explanation =========== Notice that for a base `(b_1, b_2, ..., b_k)`, the basic stabilizers are defined as `G^{(i)} = G_{b_1, ..., b_{i-1}}` for `i \in\{1, 2, ..., k\}`. Parameters ========== ``base`` : a sequence of points in `\{0, 1, ..., n-1\}` ``gens`` : a list of elements of a permutation group of degree `n`. Returns ======= List of length `k`, where `k` is the length of ``base``. The `i`-th entry contains those elements in ``gens`` which fix the first `i` elements of ``base`` (so that the `0`-th entry is equal to ``gens`` itself). If no element fixes the first `i` elements of ``base``, the `i`-th element is set to a list containing the identity element. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.util import _distribute_gens_by_base >>> D = DihedralGroup(3) >>> D.schreier_sims() >>> D.strong_gens [(0 1 2), (0 2), (1 2)] >>> D.base [0, 1] >>> _distribute_gens_by_base(D.base, D.strong_gens) [[(0 1 2), (0 2), (1 2)], [(1 2)]] See Also ======== _strong_gens_from_distr, _orbits_transversals_from_bsgs, _handle_precomputed_bsgs """ base_len = len(base) degree = gens[0].size stabs = [[] for _ in range(base_len)] max_stab_index = 0 for gen in gens: j = 0 while j < base_len - 1 and gen._array_form[base[j]] == base[j]: j += 1 if j > max_stab_index: max_stab_index = j for k in range(j + 1): stabs[k].append(gen) for i in range(max_stab_index + 1, base_len): stabs[i].append(_af_new(list(range(degree)))) return stabs def _handle_precomputed_bsgs(base, strong_gens, transversals=None, basic_orbits=None, strong_gens_distr=None): """ Calculate BSGS-related structures from those present. Explanation =========== The base and strong generating set must be provided; if any of the transversals, basic orbits or distributed strong generators are not provided, they will be calculated from the base and strong generating set. Parameters ========== ``base`` - the base ``strong_gens`` - the strong generators ``transversals`` - basic transversals ``basic_orbits`` - basic orbits ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Returns ======= ``(transversals, basic_orbits, strong_gens_distr)`` where ``transversals`` are the basic transversals, ``basic_orbits`` are the basic orbits, and ``strong_gens_distr`` are the strong generators distributed by membership in basic stabilizers. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.util import _handle_precomputed_bsgs >>> D = DihedralGroup(3) >>> D.schreier_sims() >>> _handle_precomputed_bsgs(D.base, D.strong_gens, ... basic_orbits=D.basic_orbits) ([{0: (2), 1: (0 1 2), 2: (0 2)}, {1: (2), 2: (1 2)}], [[0, 1, 2], [1, 2]], [[(0 1 2), (0 2), (1 2)], [(1 2)]]) See Also ======== _orbits_transversals_from_bsgs, _distribute_gens_by_base """ if strong_gens_distr is None: strong_gens_distr = _distribute_gens_by_base(base, strong_gens) if transversals is None: if basic_orbits is None: basic_orbits, transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) else: transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr, transversals_only=True) else: if basic_orbits is None: base_len = len(base) basic_orbits = [None]base_len for i in range(base_len): basic_orbits[i] = list(transversals[i].keys()) return transversals, basic_orbits, strong_gens_distr def _orbits_transversals_from_bsgs(base, strong_gens_distr, transversals_only=False, slp=False): """ Compute basic orbits and transversals from a base and strong generating set. Explanation =========== The generators are provided as distributed across the basic stabilizers. If the optional argument ``transversals_only`` is set to True, only the transversals are returned. Parameters ========== ``base`` - The base. ``strong_gens_distr`` - Strong generators distributed by membership in basic stabilizers. ``transversals_only`` - bool A flag switching between returning only the transversals and both orbits and transversals. ``slp`` - If ``True``, return a list of dictionaries containing the generator presentations of the elements of the transversals, i.e. the list of indices of generators from ``strong_gens_distr[i]`` such that their product is the relevant transversal element. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _distribute_gens_by_base >>> S = SymmetricGroup(3) >>> S.schreier_sims() >>> strong_gens_distr = _distribute_gens_by_base(S.base, S.strong_gens) >>> (S.base, strong_gens_distr) ([0, 1], [[(0 1 2), (2)(0 1), (1 2)], [(1 2)]]) See Also ======== _distribute_gens_by_base, _handle_precomputed_bsgs """ from sympy.combinatorics.perm_groups import _orbit_transversal base_len = len(base) degree = strong_gens_distr[0][0].size transversals = [None]base_len slps = [None]base_len if transversals_only is False: basic_orbits = [None]*base_len for i in range(base_len): transversals[i], slps[i] = _orbit_transversal(degree, strong_gens_distr[i], base[i], pairs=True, slp=True) transversals[i] = dict(transversals[i]) if transversals_only is False: basic_orbits[i] = list(transversals[i].keys()) if transversals_only: return transversals else: if not slp: return basic_orbits, transversals return basic_orbits, transversals, slps def _remove_gens(base, strong_gens, basic_orbits=None, strong_gens_distr=None): """ Remove redundant generators from a strong generating set. Parameters ========== ``base`` - a base ``strong_gens`` - a strong generating set relative to ``base`` ``basic_orbits`` - basic orbits ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Returns ======= A strong generating set with respect to ``base`` which is a subset of ``strong_gens``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _remove_gens >>> from sympy.combinatorics.testutil import _verify_bsgs >>> S = SymmetricGroup(15) >>> base, strong_gens = S.schreier_sims_incremental() >>> new_gens = _remove_gens(base, strong_gens) >>> len(new_gens) 14 >>> _verify_bsgs(S, base, new_gens) True Notes ===== This procedure is outlined in [1],p.95. References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" """ from sympy.combinatorics.perm_groups import _orbit base_len = len(base) degree = strong_gens[0].size if strong_gens_distr is None: strong_gens_distr = _distribute_gens_by_base(base, strong_gens) if basic_orbits is None: basic_orbits = [] for i in range(base_len): basic_orbit = _orbit(degree, strong_gens_distr[i], base[i]) basic_orbits.append(basic_orbit) strong_gens_distr.append([]) res = strong_gens[:] for i in range(base_len - 1, -1, -1): gens_copy = strong_gens_distr[i][:] for gen in strong_gens_distr[i]: if gen not in strong_gens_distr[i + 1]: temp_gens = gens_copy[:] temp_gens.remove(gen) if temp_gens == []: continue temp_orbit = _orbit(degree, temp_gens, base[i]) if temp_orbit == basic_orbits[i]: gens_copy.remove(gen) res.remove(gen) return res def _strip(g, base, orbits, transversals): """ Attempt to decompose a permutation using a (possibly partial) BSGS structure. Explanation =========== This is done by treating the sequence ``base`` as an actual base, and the orbits ``orbits`` and transversals ``transversals`` as basic orbits and transversals relative to it. This process is called "sifting". A sift is unsuccessful when a certain orbit element is not found or when after the sift the decomposition doesn't end with the identity element. The argument ``transversals`` is a list of dictionaries that provides transversal elements for the orbits ``orbits``. Parameters ========== ``g`` - permutation to be decomposed ``base`` - sequence of points ``orbits`` - a list in which the ``i``-th entry is an orbit of ``base[i]`` under some subgroup of the pointwise stabilizer of ` `base[0], base[1], ..., base[i - 1]``. The groups themselves are implicit in this function since the only information we need is encoded in the orbits and transversals ``transversals`` - a list of orbit transversals associated with the orbits ``orbits``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.util import _strip >>> S = SymmetricGroup(5) >>> S.schreier_sims() >>> g = Permutation([0, 2, 3, 1, 4]) >>> _strip(g, S.base, S.basic_orbits, S.basic_transversals) ((4), 5) Notes ===== The algorithm is described in [1],pp.89-90. The reason for returning both the current state of the element being decomposed and the level at which the sifting ends is that they provide important information for the randomized version of the Schreier-Sims algorithm. References ========== .. [1] Holt, D., Eick, B., O'Brien, E."Handbook of computational group theory" See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims_random """ h = g._array_form base_len = len(base) for i in range(base_len): beta = h[base[i]] if beta == base[i]: continue if beta not in orbits[i]: return _af_new(h), i + 1 u = transversals[i][beta]._array_form h = _af_rmul(_af_invert(u), h) return _af_new(h), base_len + 1 def _strip_af(h, base, orbits, transversals, j, slp=[], slps={}): """ optimized _strip, with h, transversals and result in array form if the stripped elements is the identity, it returns False, base_len + 1 j h[base[i]] == base[i] for i <= j """ base_len = len(base) for i in range(j+1, base_len): beta = h[base[i]] if beta == base[i]: continue if beta not in orbits[i]: if not slp: return h, i + 1 return h, i + 1, slp u = transversals[i][beta] if h == u: if not slp: return False, base_len + 1 return False, base_len + 1, slp h = _af_rmul(_af_invert(u), h) if slp: u_slp = slps[i][beta][:] u_slp.reverse() u_slp = [(i, (g,)) for g in u_slp] slp = u_slp + slp if not slp: return h, base_len + 1 return h, base_len + 1, slp def _strong_gens_from_distr(strong_gens_distr): """ Retrieve strong generating set from generators of basic stabilizers. This is just the union of the generators of the first and second basic stabilizers. Parameters ========== ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import (_strong_gens_from_distr, ... _distribute_gens_by_base) >>> S = SymmetricGroup(3) >>> S.schreier_sims() >>> S.strong_gens [(0 1 2), (2)(0 1), (1 2)] >>> strong_gens_distr = _distribute_gens_by_base(S.base, S.strong_gens) >>> _strong_gens_from_distr(strong_gens_distr) [(0 1 2), (2)(0 1), (1 2)] See Also ======== _distribute_gens_by_base """ if len(strong_gens_distr) == 1: return strong_gens_distr[0][:] else: result = strong_gens_distr[0] for gen in strong_gens_distr[1]: if gen not in result: result.append(gen) return result
8026745e91aed7a9e06c1461e66801e858648459e3b3010d6f91f590b762c781	from sympy.combinatorics.group_constructs import DirectProduct from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.permutations import Permutation _af_new = Permutation._af_new def AbelianGroup(cyclic_orders): """ Returns the direct product of cyclic groups with the given orders. Explanation =========== According to the structure theorem for finite abelian groups ([1]), every finite abelian group can be written as the direct product of finitely many cyclic groups. Examples ======== >>> from sympy.combinatorics.named_groups import AbelianGroup >>> AbelianGroup(3, 4) PermutationGroup([ (6)(0 1 2), (3 4 5 6)]) >>> _.is_group True See Also ======== DirectProduct References ========== .. [1] http://groupprops.subwiki.org/wiki/Structure_theorem_for_finitely_generated_abelian_groups """ groups = [] degree = 0 order = 1 for size in cyclic_orders: degree += size order = size groups.append(CyclicGroup(size)) G = DirectProduct(groups) G._is_abelian = True G._degree = degree G._order = order return G def AlternatingGroup(n): """ Generates the alternating group on ``n`` elements as a permutation group. Explanation =========== For ``n > 2``, the generators taken are ``(0 1 2), (0 1 2 ... n-1)`` for ``n`` odd and ``(0 1 2), (1 2 ... n-1)`` for ``n`` even (See [1], p.31, ex.6.9.). After the group is generated, some of its basic properties are set. The cases ``n = 1, 2`` are handled separately. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> G = AlternatingGroup(4) >>> G.is_group True >>> a = list(G.generate_dimino()) >>> len(a) 12 >>> all(perm.is_even for perm in a) True See Also ======== SymmetricGroup, CyclicGroup, DihedralGroup References ========== .. [1] Armstrong, M. "Groups and Symmetry" """ # small cases are special if n in (1, 2): return PermutationGroup([Permutation([0])]) a = list(range(n)) a[0], a[1], a[2] = a[1], a[2], a[0] gen1 = a if n % 2: a = list(range(1, n)) a.append(0) gen2 = a else: a = list(range(2, n)) a.append(1) a.insert(0, 0) gen2 = a gens = [gen1, gen2] if gen1 == gen2: gens = gens[:1] G = PermutationGroup([_af_new(a) for a in gens], dups=False) if n < 4: G._is_abelian = True G._is_nilpotent = True else: G._is_abelian = False G._is_nilpotent = False if n < 5: G._is_solvable = True else: G._is_solvable = False G._degree = n G._is_transitive = True G._is_alt = True return G def CyclicGroup(n): """ Generates the cyclic group of order ``n`` as a permutation group. Explanation =========== The generator taken is the ``n``-cycle ``(0 1 2 ... n-1)`` (in cycle notation). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(6) >>> G.is_group True >>> G.order() 6 >>> list(G.generate_schreier_sims(af=True)) [[0, 1, 2, 3, 4, 5], [1, 2, 3, 4, 5, 0], [2, 3, 4, 5, 0, 1], [3, 4, 5, 0, 1, 2], [4, 5, 0, 1, 2, 3], [5, 0, 1, 2, 3, 4]] See Also ======== SymmetricGroup, DihedralGroup, AlternatingGroup """ a = list(range(1, n)) a.append(0) gen = _af_new(a) G = PermutationGroup([gen]) G._is_abelian = True G._is_nilpotent = True G._is_solvable = True G._degree = n G._is_transitive = True G._order = n return G def DihedralGroup(n): r""" Generates the dihedral group `D_n` as a permutation group. Explanation =========== The dihedral group `D_n` is the group of symmetries of the regular ``n``-gon. The generators taken are the ``n``-cycle ``a = (0 1 2 ... n-1)`` (a rotation of the ``n``-gon) and ``b = (0 n-1)(1 n-2)...`` (a reflection of the ``n``-gon) in cycle rotation. It is easy to see that these satisfy ``an = b2 = 1`` and ``bab = ~a`` so they indeed generate `D_n` (See [1]). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(5) >>> G.is_group True >>> a = list(G.generate_dimino()) >>> [perm.cyclic_form for perm in a] [[], [[0, 1, 2, 3, 4]], [[0, 2, 4, 1, 3]], [[0, 3, 1, 4, 2]], [[0, 4, 3, 2, 1]], [[0, 4], [1, 3]], [[1, 4], [2, 3]], [[0, 1], [2, 4]], [[0, 2], [3, 4]], [[0, 3], [1, 2]]] See Also ======== SymmetricGroup, CyclicGroup, AlternatingGroup References ========== .. [1] https://en.wikipedia.org/wiki/Dihedral_group """ # small cases are special if n == 1: return PermutationGroup([Permutation([1, 0])]) if n == 2: return PermutationGroup([Permutation([1, 0, 3, 2]), Permutation([2, 3, 0, 1]), Permutation([3, 2, 1, 0])]) a = list(range(1, n)) a.append(0) gen1 = _af_new(a) a = list(range(n)) a.reverse() gen2 = _af_new(a) G = PermutationGroup([gen1, gen2]) # if n is a power of 2, group is nilpotent if n & (n-1) == 0: G._is_nilpotent = True else: G._is_nilpotent = False G._is_abelian = False G._is_solvable = True G._degree = n G._is_transitive = True G._order = 2n return G def SymmetricGroup(n): """ Generates the symmetric group on ``n`` elements as a permutation group. Explanation =========== The generators taken are the ``n``-cycle ``(0 1 2 ... n-1)`` and the transposition ``(0 1)`` (in cycle notation). (See [1]). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(4) >>> G.is_group True >>> G.order() 24 >>> list(G.generate_schreier_sims(af=True)) [[0, 1, 2, 3], [1, 2, 3, 0], [2, 3, 0, 1], [3, 1, 2, 0], [0, 2, 3, 1], [1, 3, 0, 2], [2, 0, 1, 3], [3, 2, 0, 1], [0, 3, 1, 2], [1, 0, 2, 3], [2, 1, 3, 0], [3, 0, 1, 2], [0, 1, 3, 2], [1, 2, 0, 3], [2, 3, 1, 0], [3, 1, 0, 2], [0, 2, 1, 3], [1, 3, 2, 0], [2, 0, 3, 1], [3, 2, 1, 0], [0, 3, 2, 1], [1, 0, 3, 2], [2, 1, 0, 3], [3, 0, 2, 1]] See Also ======== CyclicGroup, DihedralGroup, AlternatingGroup References ========== .. [1] https://en.wikipedia.org/wiki/Symmetric_group#Generators_and_relations """ if n == 1: G = PermutationGroup([Permutation([0])]) elif n == 2: G = PermutationGroup([Permutation([1, 0])]) else: a = list(range(1, n)) a.append(0) gen1 = _af_new(a) a = list(range(n)) a[0], a[1] = a[1], a[0] gen2 = _af_new(a) G = PermutationGroup([gen1, gen2]) if n < 3: G._is_abelian = True G._is_nilpotent = True else: G._is_abelian = False G._is_nilpotent = False if n < 5: G._is_solvable = True else: G._is_solvable = False G._degree = n G._is_transitive = True G._is_sym = True return G def RubikGroup(n): """Return a group of Rubik's cube generators >>> from sympy.combinatorics.named_groups import RubikGroup >>> RubikGroup(2).is_group True """ from sympy.combinatorics.generators import rubik if n <= 1: raise ValueError("Invalid cube. n has to be greater than 1") return PermutationGroup(rubik(n))
b469c409285f40e99271b4fd2d8158e2101659962af8d7ff68794a281de4705b	from sympy import Integer from sympy.core import Symbol from sympy.utilities import public @public def approximants(l, X=Symbol('x'), simplify=False): """ Return a generator for consecutive Pade approximants for a series. It can also be used for computing the rational generating function of a series when possible, since the last approximant returned by the generator will be the generating function (if any). The input list can contain more complex expressions than integer or rational numbers; symbols may also be involved in the computation. An example below show how to compute the generating function of the whole Pascal triangle. The generator can be asked to apply the sympy.simplify function on each generated term, which will make the computation slower; however it may be useful when symbols are involved in the expressions. Examples ======== >>> from sympy.series import approximants >>> from sympy import lucas, fibonacci, symbols, binomial >>> g = [lucas(k) for k in range(16)] >>> [e for e in approximants(g)] [2, -4/(x - 2), (5x - 2)/(3x - 1), (x - 2)/(x2 + x - 1)] >>> h = [fibonacci(k) for k in range(16)] >>> [e for e in approximants(h)] [x, -x/(x - 1), (x2 - x)/(2x - 1), -x/(x2 + x - 1)] >>> x, t = symbols("x,t") >>> p=[sum(binomial(k,i)x*i for i in range(k+1)) for k in range(16)] >>> y = approximants(p, t) >>> for k in range(3): print(next(y)) 1 (x + 1)/((-x - 1)(t(x + 1) + (x + 1)/(-x - 1))) nan >>> y = approximants(p, t, simplify=True) >>> for k in range(3): print(next(y)) 1 -1/(t(x + 1) - 1) nan See Also ======== See function sympy.concrete.guess.guess_generating_function_rational and function mpmath.pade """ p1, q1 = [Integer(1)], [Integer(0)] p2, q2 = [Integer(0)], [Integer(1)] while len(l): b = 0 while l[b]==0: b += 1 if b == len(l): return m = [Integer(1)/l[b]] for k in range(b+1, len(l)): s = 0 for j in range(b, k): s -= l[j+1] * m[b-j-1] m.append(s/l[b]) l = m a, l[0] = l[0], 0 p = [0] * max(len(p2), b+len(p1)) q = [0] * max(len(q2), b+len(q1)) for k in range(len(p2)): p[k] = ap2[k] for k in range(b, b+len(p1)): p[k] += p1[k-b] for k in range(len(q2)): q[k] = aq2[k] for k in range(b, b+len(q1)): q[k] += q1[k-b] while p[-1]==0: p.pop() while q[-1]==0: q.pop() p1, p2 = p2, p q1, q2 = q2, q # yield result from sympy import denom, lcm, simplify as simp c = 1 for x in p: c = lcm(c, denom(x)) for x in q: c = lcm(c, denom(x)) out = ( sum(ceX*k for k, e in enumerate(p)) / sum(ceX*k for k, e in enumerate(q)) ) if simplify: yield(simp(out)) else: yield out return
d37dcd27945ef004b87aaf9c8667dcb77f8bcf6bc1a9d16a5ed9eb6f1b304f1d	""" Contains the base class for series Made using sequences in mind """ from sympy.core.expr import Expr from sympy.core.singleton import S from sympy.core.cache import cacheit class SeriesBase(Expr): """Base Class for series""" @property def interval(self): """The interval on which the series is defined""" raise NotImplementedError("(%s).interval" % self) @property def start(self): """The starting point of the series. This point is included""" raise NotImplementedError("(%s).start" % self) @property def stop(self): """The ending point of the series. This point is included""" raise NotImplementedError("(%s).stop" % self) @property def length(self): """Length of the series expansion""" raise NotImplementedError("(%s).length" % self) @property def variables(self): """Returns a tuple of variables that are bounded""" return () @property def free_symbols(self): """ This method returns the symbols in the object, excluding those that take on a specific value (i.e. the dummy symbols). """ return ({j for i in self.args for j in i.free_symbols} .difference(self.variables)) @cacheit def term(self, pt): """Term at point pt of a series""" if pt < self.start or pt > self.stop: raise IndexError("Index %s out of bounds %s" % (pt, self.interval)) return self._eval_term(pt) def _eval_term(self, pt): raise NotImplementedError("The _eval_term method should be added to" "%s to return series term so it is available" "when 'term' calls it." % self.func) def _ith_point(self, i): """ Returns the i'th point of a series If start point is negative infinity, point is returned from the end. Assumes the first point to be indexed zero. Examples ======== TODO """ if self.start is S.NegativeInfinity: initial = self.stop step = -1 else: initial = self.start step = 1 return initial + i*step def __iter__(self): i = 0 while i < self.length: pt = self._ith_point(i) yield self.term(pt) i += 1 def __getitem__(self, index): if isinstance(index, int): index = self._ith_point(index) return self.term(index) elif isinstance(index, slice): start, stop = index.start, index.stop if start is None: start = 0 if stop is None: stop = self.length return [self.term(self._ith_point(i)) for i in range(start, stop, index.step or 1)]
72b4a440ad7003a15000a2358ac946eaba40cef5a5cf581964fc76030a78dd08	from sympy.core.sympify import sympify def series(expr, x=None, x0=0, n=6, dir="+"): """Series expansion of expr around point `x = x0`. Parameters ========== expr : Expression The expression whose series is to be expanded. x : Symbol It is the variable of the expression to be calculated. x0 : Value The value around which ``x`` is calculated. Can be any value from ``-oo`` to ``oo``. n : Value The number of terms upto which the series is to be expanded. dir : String, optional The series-expansion can be bi-directional. If ``dir="+"``, then (x->x0+). If ``dir="-", then (x->x0-). For infinite ``x0`` (``oo`` or ``-oo``), the ``dir`` argument is determined from the direction of the infinity (i.e., ``dir="-"`` for ``oo``). Examples ======== >>> from sympy import series, tan, oo >>> from sympy.abc import x >>> f = tan(x) >>> series(f, x, 2, 6, "+") tan(2) + (1 + tan(2)*2)(x - 2) + (x - 2)*2(tan(2)3 + tan(2)) + (x - 2)3(1/3 + 4tan(2)2/3 + tan(2)4) + (x - 2)*4(tan(2)*5 + 5tan(2)*3/3 + 2tan(2)/3) + (x - 2)*5(2/15 + 17tan(2)2/15 + 2tan(2)4 + tan(2)6) + O((x - 2)*6, (x, 2)) >>> series(f, x, 2, 3, "-") tan(2) + (2 - x)(-tan(2)2 - 1) + (2 - x)2(tan(2)3 + tan(2)) + O((x - 2)*3, (x, 2)) >>> series(f, x, 2, oo, "+") Traceback (most recent call last): ... TypeError: 'Infinity' object cannot be interpreted as an integer Returns ======= Expr Series expansion of the expression about x0 See Also ======== sympy.core.expr.Expr.series: See the docstring of Expr.series() for complete details of this wrapper. """ expr = sympify(expr) return expr.series(x, x0, n, dir)
7075464506b36b86b2a88ea38ba38736475010c57b064a387f8bee8366ee1106	from sympy.core.sympify import sympify def aseries(expr, x=None, n=6, bound=0, hir=False): """ See the docstring of Expr.aseries() for complete details of this wrapper. """ expr = sympify(expr) return expr.aseries(x, n, bound, hir)
ecbf10de75ef3b36145a643cbaec3bd045061e5f9afb83f83953214eb1a9337d	""" Convergence acceleration / extrapolation methods for series and sequences. References: Carl M. Bender & Steven A. Orszag, "Advanced Mathematical Methods for Scientists and Engineers: Asymptotic Methods and Perturbation Theory", Springer 1999. (Shanks transformation: pp. 368-375, Richardson extrapolation: pp. 375-377.) """ from sympy import factorial, Integer, S def richardson(A, k, n, N): """ Calculate an approximation for lim k->oo A(k) using Richardson extrapolation with the terms A(n), A(n+1), ..., A(n+N+1). Choosing N ~= 2n often gives good results. A simple example is to calculate exp(1) using the limit definition. This limit converges slowly; n = 100 only produces two accurate digits: >>> from sympy.abc import n >>> e = (1 + 1/n)n >>> print(round(e.subs(n, 100).evalf(), 10)) 2.7048138294 Richardson extrapolation with 11 appropriately chosen terms gives a value that is accurate to the indicated precision: >>> from sympy import E >>> from sympy.series.acceleration import richardson >>> print(round(richardson(e, n, 10, 20).evalf(), 10)) 2.7182818285 >>> print(round(E.evalf(), 10)) 2.7182818285 Another useful application is to speed up convergence of series. Computing 100 terms of the zeta(2) series 1/k2 yields only two accurate digits: >>> from sympy.abc import k, n >>> from sympy import Sum >>> A = Sum(k-2, (k, 1, n)) >>> print(round(A.subs(n, 100).evalf(), 10)) 1.6349839002 Richardson extrapolation performs much better: >>> from sympy import pi >>> print(round(richardson(A, n, 10, 20).evalf(), 10)) 1.6449340668 >>> print(round(((pi2)/6).evalf(), 10)) # Exact value 1.6449340668 """ s = S.Zero for j in range(0, N + 1): s += A.subs(k, Integer(n + j)).doit() (n + j)*N (-1)*(j + N) / \ (factorial(j) factorial(N - j)) return s def shanks(A, k, n, m=1): """ Calculate an approximation for lim k->oo A(k) using the n-term Shanks transformation S(A)(n). With m > 1, calculate the m-fold recursive Shanks transformation S(S(...S(A)...))(n). The Shanks transformation is useful for summing Taylor series that converge slowly near a pole or singularity, e.g. for log(2): >>> from sympy.abc import k, n >>> from sympy import Sum, Integer >>> from sympy.series.acceleration import shanks >>> A = Sum(Integer(-1)*(k+1) / k, (k, 1, n)) >>> print(round(A.subs(n, 100).doit().evalf(), 10)) 0.6881721793 >>> print(round(shanks(A, n, 25).evalf(), 10)) 0.6931396564 >>> print(round(shanks(A, n, 25, 5).evalf(), 10)) 0.6931471806 The correct value is 0.6931471805599453094172321215. """ table = [A.subs(k, Integer(j)).doit() for j in range(n + m + 2)] table2 = table[:] for i in range(1, m + 1): for j in range(i, n + m + 1): x, y, z = table[j - 1], table[j], table[j + 1] table2[j] = (zx - y*2) / (z + x - 2y) table = table2[:] return table[n]
7e6503609ee98d51720d7e261f57f930c5a147cf7bbcad96b064446db53698d3	""" Limits ====== Implemented according to the PhD thesis http://www.cybertester.com/data/gruntz.pdf, which contains very thorough descriptions of the algorithm including many examples. We summarize here the gist of it. All functions are sorted according to how rapidly varying they are at infinity using the following rules. Any two functions f and g can be compared using the properties of L: L=lim log\|f(x)\| / log\|g(x)\| (for x -> oo) We define >, < ~ according to:: 1. f > g .... L=+-oo we say that: - f is greater than any power of g - f is more rapidly varying than g - f goes to infinity/zero faster than g 2. f < g .... L=0 we say that: - f is lower than any power of g 3. f ~ g .... L!=0, +-oo we say that: - both f and g are bounded from above and below by suitable integral powers of the other Examples ======== :: 2 < x < exp(x) < exp(x2) < exp(exp(x)) 2 ~ 3 ~ -5 x ~ x2 ~ x3 ~ 1/x ~ xm ~ -x exp(x) ~ exp(-x) ~ exp(2x) ~ exp(x)*2 ~ exp(x+exp(-x)) f ~ 1/f So we can divide all the functions into comparability classes (x and x^2 belong to one class, exp(x) and exp(-x) belong to some other class). In principle, we could compare any two functions, but in our algorithm, we don't compare anything below the class 2~3~-5 (for example log(x) is below this), so we set 2~3~-5 as the lowest comparability class. Given the function f, we find the list of most rapidly varying (mrv set) subexpressions of it. This list belongs to the same comparability class. Let's say it is {exp(x), exp(2x)}. Using the rule f ~ 1/f we find an element "w" (either from the list or a new one) from the same comparability class which goes to zero at infinity. In our example we set w=exp(-x) (but we could also set w=exp(-2x) or w=exp(-3x) ...). We rewrite the mrv set using w, in our case {1/w, 1/w^2}, and substitute it into f. Then we expand f into a series in w:: f = c0w^e0 + c1w^e1 + ... + O(w^en), where e0<e1<...<en, c0!=0 but for x->oo, lim f = lim c0w^e0, because all the other terms go to zero, because w goes to zero faster than the ci and ei. So:: for e0>0, lim f = 0 for e0<0, lim f = +-oo (the sign depends on the sign of c0) for e0=0, lim f = lim c0 We need to recursively compute limits at several places of the algorithm, but as is shown in the PhD thesis, it always finishes. Important functions from the implementation: compare(a, b, x) compares "a" and "b" by computing the limit L. mrv(e, x) returns list of most rapidly varying (mrv) subexpressions of "e" rewrite(e, Omega, x, wsym) rewrites "e" in terms of w leadterm(f, x) returns the lowest power term in the series of f mrv_leadterm(e, x) returns the lead term (c0, e0) for e limitinf(e, x) computes lim e (for x->oo) limit(e, z, z0) computes any limit by converting it to the case x->oo All the functions are really simple and straightforward except rewrite(), which is the most difficult/complex part of the algorithm. When the algorithm fails, the bugs are usually in the series expansion (i.e. in SymPy) or in rewrite. This code is almost exact rewrite of the Maple code inside the Gruntz thesis. Debugging --------- Because the gruntz algorithm is highly recursive, it's difficult to figure out what went wrong inside a debugger. Instead, turn on nice debug prints by defining the environment variable SYMPY_DEBUG. For example: [user@localhost]: SYMPY_DEBUG=True ./bin/isympy In [1]: limit(sin(x)/x, x, 0) limitinf(_xsin(1/_x), _x) = 1 +-mrv_leadterm(_xsin(1/_x), _x) = (1, 0) \| +-mrv(_xsin(1/_x), _x) = set([_x]) \| \| +-mrv(_x, _x) = set([_x]) \| \| +-mrv(sin(1/_x), _x) = set([_x]) \| \| +-mrv(1/_x, _x) = set([_x]) \| \| +-mrv(_x, _x) = set([_x]) \| +-mrv_leadterm(exp(_x)sin(exp(-_x)), _x, set([exp(_x)])) = (1, 0) \| +-rewrite(exp(_x)sin(exp(-_x)), set([exp(_x)]), _x, _w) = (1/_wsin(_w), -_x) \| +-sign(_x, _x) = 1 \| +-mrv_leadterm(1, _x) = (1, 0) +-sign(0, _x) = 0 +-limitinf(1, _x) = 1 And check manually which line is wrong. Then go to the source code and debug this function to figure out the exact problem. """ from sympy import cacheit from sympy.core import Basic, S, oo, I, Dummy, Wild, Mul from sympy.core.compatibility import reduce from sympy.functions import log, exp from sympy.series.order import Order from sympy.simplify.powsimp import powsimp, powdenest from sympy.utilities.misc import debug_decorator as debug from sympy.utilities.timeutils import timethis timeit = timethis('gruntz') def compare(a, b, x): """Returns "<" if a<b, "=" for a == b, ">" for a>b""" # log(exp(...)) must always be simplified here for termination la, lb = log(a), log(b) if isinstance(a, Basic) and isinstance(a, exp): la = a.args[0] if isinstance(b, Basic) and isinstance(b, exp): lb = b.args[0] c = limitinf(la/lb, x) if c == 0: return "<" elif c.is_infinite: return ">" else: return "=" class SubsSet(dict): """ Stores (expr, dummy) pairs, and how to rewrite expr-s. The gruntz algorithm needs to rewrite certain expressions in term of a new variable w. We cannot use subs, because it is just too smart for us. For example:: > Omega=[exp(exp(_p - exp(-_p))/(1 - 1/_p)), exp(exp(_p))] > O2=[exp(-exp(_p) + exp(-exp(-_p))exp(_p)/(1 - 1/_p))/_w, 1/_w] > e = exp(exp(_p - exp(-_p))/(1 - 1/_p)) - exp(exp(_p)) > e.subs(Omega[0],O2[0]).subs(Omega[1],O2[1]) -1/w + exp(exp(p)exp(-exp(-p))/(1 - 1/p)) is really not what we want! So we do it the hard way and keep track of all the things we potentially want to substitute by dummy variables. Consider the expression:: exp(x - exp(-x)) + exp(x) + x. The mrv set is {exp(x), exp(-x), exp(x - exp(-x))}. We introduce corresponding dummy variables d1, d2, d3 and rewrite:: d3 + d1 + x. This class first of all keeps track of the mapping expr->variable, i.e. will at this stage be a dictionary:: {exp(x): d1, exp(-x): d2, exp(x - exp(-x)): d3}. [It turns out to be more convenient this way round.] But sometimes expressions in the mrv set have other expressions from the mrv set as subexpressions, and we need to keep track of that as well. In this case, d3 is really exp(x - d2), so rewrites at this stage is:: {d3: exp(x-d2)}. The function rewrite uses all this information to correctly rewrite our expression in terms of w. In this case w can be chosen to be exp(-x), i.e. d2. The correct rewriting then is:: exp(-w)/w + 1/w + x. """ def __init__(self): self.rewrites = {} def __repr__(self): return super().__repr__() + ', ' + self.rewrites.__repr__() def __getitem__(self, key): if not key in self: self[key] = Dummy() return dict.__getitem__(self, key) def do_subs(self, e): """Substitute the variables with expressions""" for expr, var in self.items(): e = e.xreplace({var: expr}) return e def meets(self, s2): """Tell whether or not self and s2 have non-empty intersection""" return set(self.keys()).intersection(list(s2.keys())) != set() def union(self, s2, exps=None): """Compute the union of self and s2, adjusting exps""" res = self.copy() tr = {} for expr, var in s2.items(): if expr in self: if exps: exps = exps.xreplace({var: res[expr]}) tr[var] = res[expr] else: res[expr] = var for var, rewr in s2.rewrites.items(): res.rewrites[var] = rewr.xreplace(tr) return res, exps def copy(self): """Create a shallow copy of SubsSet""" r = SubsSet() r.rewrites = self.rewrites.copy() for expr, var in self.items(): r[expr] = var return r @debug def mrv(e, x): """Returns a SubsSet of most rapidly varying (mrv) subexpressions of 'e', and e rewritten in terms of these""" e = powsimp(e, deep=True, combine='exp') if not isinstance(e, Basic): raise TypeError("e should be an instance of Basic") if not e.has(x): return SubsSet(), e elif e == x: s = SubsSet() return s, s[x] elif e.is_Mul or e.is_Add: i, d = e.as_independent(x) # throw away x-independent terms if d.func != e.func: s, expr = mrv(d, x) return s, e.func(i, expr) a, b = d.as_two_terms() s1, e1 = mrv(a, x) s2, e2 = mrv(b, x) return mrv_max1(s1, s2, e.func(i, e1, e2), x) elif e.is_Pow: e1 = S.One while e.is_Pow: b1 = e.base e1 = e.exp e = b1 if b1 == 1: return SubsSet(), b1 if e1.has(x): base_lim = limitinf(b1, x) if base_lim is S.One: return mrv(exp(e1 (b1 - 1)), x) return mrv(exp(e1 * log(b1)), x) else: s, expr = mrv(b1, x) return s, expr*e1 elif isinstance(e, log): s, expr = mrv(e.args[0], x) return s, log(expr) elif isinstance(e, exp): # We know from the theory of this algorithm that exp(log(...)) may always # be simplified here, and doing so is vital for termination. if isinstance(e.args[0], log): return mrv(e.args[0].args[0], x) # if a product has an infinite factor the result will be # infinite if there is no zero, otherwise NaN; here, we # consider the result infinite if any factor is infinite li = limitinf(e.args[0], x) if any(_.is_infinite for _ in Mul.make_args(li)): s1 = SubsSet() e1 = s1[e] s2, e2 = mrv(e.args[0], x) su = s1.union(s2)[0] su.rewrites[e1] = exp(e2) return mrv_max3(s1, e1, s2, exp(e2), su, e1, x) else: s, expr = mrv(e.args[0], x) return s, exp(expr) elif e.is_Function: l = [mrv(a, x) for a in e.args] l2 = [s for (s, _) in l if s != SubsSet()] if len(l2) != 1: # e.g. something like BesselJ(x, x) raise NotImplementedError("MRV set computation for functions in" " several variables not implemented.") s, ss = l2[0], SubsSet() args = [ss.do_subs(x[1]) for x in l] return s, e.func(args) elif e.is_Derivative: raise NotImplementedError("MRV set computation for derviatives" " not implemented yet.") return mrv(e.args[0], x) raise NotImplementedError( "Don't know how to calculate the mrv of '%s'" % e) def mrv_max3(f, expsf, g, expsg, union, expsboth, x): """Computes the maximum of two sets of expressions f and g, which are in the same comparability class, i.e. max() compares (two elements of) f and g and returns either (f, expsf) [if f is larger], (g, expsg) [if g is larger] or (union, expsboth) [if f, g are of the same class]. """ if not isinstance(f, SubsSet): raise TypeError("f should be an instance of SubsSet") if not isinstance(g, SubsSet): raise TypeError("g should be an instance of SubsSet") if f == SubsSet(): return g, expsg elif g == SubsSet(): return f, expsf elif f.meets(g): return union, expsboth c = compare(list(f.keys())[0], list(g.keys())[0], x) if c == ">": return f, expsf elif c == "<": return g, expsg else: if c != "=": raise ValueError("c should be =") return union, expsboth def mrv_max1(f, g, exps, x): """Computes the maximum of two sets of expressions f and g, which are in the same comparability class, i.e. mrv_max1() compares (two elements of) f and g and returns the set, which is in the higher comparability class of the union of both, if they have the same order of variation. Also returns exps, with the appropriate substitutions made. """ u, b = f.union(g, exps) return mrv_max3(f, g.do_subs(exps), g, f.do_subs(exps), u, b, x) @debug @cacheit @timeit def sign(e, x): """ Returns a sign of an expression e(x) for x->oo. :: e > 0 for x sufficiently large ... 1 e == 0 for x sufficiently large ... 0 e < 0 for x sufficiently large ... -1 The result of this function is currently undefined if e changes sign arbitrarily often for arbitrarily large x (e.g. sin(x)). Note that this returns zero only if e is constantly zero for x sufficiently large. [If e is constant, of course, this is just the same thing as the sign of e.] """ from sympy import sign as _sign if not isinstance(e, Basic): raise TypeError("e should be an instance of Basic") if e.is_positive: return 1 elif e.is_negative: return -1 elif e.is_zero: return 0 elif not e.has(x): return _sign(e) elif e == x: return 1 elif e.is_Mul: a, b = e.as_two_terms() sa = sign(a, x) if not sa: return 0 return sa * sign(b, x) elif isinstance(e, exp): return 1 elif e.is_Pow: s = sign(e.base, x) if s == 1: return 1 if e.exp.is_Integer: return s*e.exp elif isinstance(e, log): return sign(e.args[0] - 1, x) # if all else fails, do it the hard way c0, e0 = mrv_leadterm(e, x) return sign(c0, x) @debug @timeit @cacheit def limitinf(e, x, leadsimp=False): """Limit e(x) for x-> oo. If ``leadsimp`` is True, an attempt is made to simplify the leading term of the series expansion of ``e``. That may succeed even if ``e`` cannot be simplified. """ # rewrite e in terms of tractable functions only if not e.has(x): return e # e is a constant if e.has(Order): e = e.expand().removeO() if not x.is_positive or x.is_integer: # We make sure that x.is_positive is True and x.is_integer is None # so we get all the correct mathematical behavior from the expression. # We need a fresh variable. p = Dummy('p', positive=True) e = e.subs(x, p) x = p e = e.rewrite('tractable', deep=True, limitvar=x) e = powdenest(e) c0, e0 = mrv_leadterm(e, x) sig = sign(e0, x) if sig == 1: return S.Zero # e0>0: lim f = 0 elif sig == -1: # e0<0: lim f = +-oo (the sign depends on the sign of c0) if c0.match(IWild("a", exclude=[I])): return c0oo s = sign(c0, x) # the leading term shouldn't be 0: if s == 0: raise ValueError("Leading term should not be 0") return soo elif sig == 0: if leadsimp: c0 = c0.simplify() return limitinf(c0, x, leadsimp) # e0=0: lim f = lim c0 else: raise ValueError("{} could not be evaluated".format(sig)) def moveup2(s, x): r = SubsSet() for expr, var in s.items(): r[expr.xreplace({x: exp(x)})] = var for var, expr in s.rewrites.items(): r.rewrites[var] = s.rewrites[var].xreplace({x: exp(x)}) return r def moveup(l, x): return [e.xreplace({x: exp(x)}) for e in l] @debug @timeit def calculate_series(e, x, logx=None): """ Calculates at least one term of the series of "e" in "x". This is a place that fails most often, so it is in its own function. """ from sympy.polys import cancel for t in e.lseries(x, logx=logx): t = cancel(t) if t.has(exp) and t.has(log): t = powdenest(t) if t.simplify(): break return t @debug @timeit @cacheit def mrv_leadterm(e, x): """Returns (c0, e0) for e.""" Omega = SubsSet() if not e.has(x): return (e, S.Zero) if Omega == SubsSet(): Omega, exps = mrv(e, x) if not Omega: # e really does not depend on x after simplification return exps, S.Zero if x in Omega: # move the whole omega up (exponentiate each term): Omega_up = moveup2(Omega, x) e_up = moveup([e], x)[0] exps_up = moveup([exps], x)[0] # NOTE: there is no need to move this down! e = e_up Omega = Omega_up exps = exps_up # # The positive dummy, w, is used here so log(w2) etc. will expand; # a unique dummy is needed in this algorithm # # For limits of complex functions, the algorithm would have to be # improved, or just find limits of Re and Im components separately. # w = Dummy("w", real=True, positive=True) f, logw = rewrite(exps, Omega, x, w) series = calculate_series(f, w, logx=logw) return series.leadterm(w) def build_expression_tree(Omega, rewrites): r""" Helper function for rewrite. We need to sort Omega (mrv set) so that we replace an expression before we replace any expression in terms of which it has to be rewritten:: e1 ---> e2 ---> e3 \ -> e4 Here we can do e1, e2, e3, e4 or e1, e2, e4, e3. To do this we assemble the nodes into a tree, and sort them by height. This function builds the tree, rewrites then sorts the nodes. """ class Node: def ht(self): return reduce(lambda x, y: x + y, [x.ht() for x in self.before], 1) nodes = {} for expr, v in Omega: n = Node() n.before = [] n.var = v n.expr = expr nodes[v] = n for _, v in Omega: if v in rewrites: n = nodes[v] r = rewrites[v] for _, v2 in Omega: if r.has(v2): n.before.append(nodes[v2]) return nodes @debug @timeit def rewrite(e, Omega, x, wsym): """e(x) ... the function Omega ... the mrv set wsym ... the symbol which is going to be used for w Returns the rewritten e in terms of w and log(w). See test_rewrite1() for examples and correct results. """ from sympy import ilcm if not isinstance(Omega, SubsSet): raise TypeError("Omega should be an instance of SubsSet") if len(Omega) == 0: raise ValueError("Length can not be 0") # all items in Omega must be exponentials for t in Omega.keys(): if not isinstance(t, exp): raise ValueError("Value should be exp") rewrites = Omega.rewrites Omega = list(Omega.items()) nodes = build_expression_tree(Omega, rewrites) Omega.sort(key=lambda x: nodes[x[1]].ht(), reverse=True) # make sure we know the sign of each exp() term; after the loop, # g is going to be the "w" - the simplest one in the mrv set for g, _ in Omega: sig = sign(g.args[0], x) if sig != 1 and sig != -1: raise NotImplementedError('Result depends on the sign of %s' % sig) if sig == 1: wsym = 1/wsym # if g goes to oo, substitute 1/w # O2 is a list, which results by rewriting each item in Omega using "w" O2 = [] denominators = [] for f, var in Omega: c = limitinf(f.args[0]/g.args[0], x) if c.is_Rational: denominators.append(c.q) arg = f.args[0] if var in rewrites: if not isinstance(rewrites[var], exp): raise ValueError("Value should be exp") arg = rewrites[var].args[0] O2.append((var, exp((arg - cg.args[0]).expand())wsymc)) # Remember that Omega contains subexpressions of "e". So now we find # them in "e" and substitute them for our rewriting, stored in O2 # the following powsimp is necessary to automatically combine exponentials, # so that the .xreplace() below succeeds: # TODO this should not be necessary f = powsimp(e, deep=True, combine='exp') for a, b in O2: f = f.xreplace({a: b}) for _, var in Omega: assert not f.has(var) # finally compute the logarithm of w (logw). logw = g.args[0] if sig == 1: logw = -logw # log(w)->log(1/w)=-log(w) # Some parts of sympy have difficulty computing series expansions with # non-integral exponents. The following heuristic improves the situation: exponent = reduce(ilcm, denominators, 1) f = f.subs({wsym: wsym*exponent}) logw /= exponent return f, logw def gruntz(e, z, z0, dir="+"): """ Compute the limit of e(z) at the point z0 using the Gruntz algorithm. z0 can be any expression, including oo and -oo. For dir="+" (default) it calculates the limit from the right (z->z0+) and for dir="-" the limit from the left (z->z0-). For infinite z0 (oo or -oo), the dir argument doesn't matter. This algorithm is fully described in the module docstring in the gruntz.py file. It relies heavily on the series expansion. Most frequently, gruntz() is only used if the faster limit() function (which uses heuristics) fails. """ if not z.is_symbol: raise NotImplementedError("Second argument must be a Symbol") # convert all limits to the limit z->oo; sign of z is handled in limitinf r = None if z0 == oo: e0 = e elif z0 == -oo: e0 = e.subs(z, -z) else: if str(dir) == "-": e0 = e.subs(z, z0 - 1/z) elif str(dir) == "+": e0 = e.subs(z, z0 + 1/z) else: raise NotImplementedError("dir must be '+' or '-'") try: r = limitinf(e0, z) except ValueError: r = limitinf(e0, z, leadsimp=True) # This is a bit of a heuristic for nice results... we always rewrite # tractable functions in terms of familiar intractable ones. # It might be nicer to rewrite the exactly to what they were initially, # but that would take some work to implement. return r.rewrite('intractable', deep=True)
7fb8f5541de050478d729516884b9bac61c2cf5e21939ec52bb18a2b00bd036e	from sympy.core.basic import Basic from sympy.core.cache import cacheit from sympy.core.compatibility import is_sequence, iterable, ordered from sympy.core.containers import Tuple from sympy.core.decorators import call_highest_priority from sympy.core.parameters import global_parameters from sympy.core.function import AppliedUndef from sympy.core.mul import Mul from sympy.core.numbers import Integer from sympy.core.relational import Eq from sympy.core.singleton import S, Singleton from sympy.core.symbol import Dummy, Symbol, Wild from sympy.core.sympify import sympify from sympy.polys import lcm, factor from sympy.sets.sets import Interval, Intersection from sympy.simplify import simplify from sympy.tensor.indexed import Idx from sympy.utilities.iterables import flatten from sympy import expand ############################################################################### # SEQUENCES # ############################################################################### class SeqBase(Basic): """Base class for sequences""" is_commutative = True _op_priority = 15 @staticmethod def _start_key(expr): """Return start (if possible) else S.Infinity. adapted from Set._infimum_key """ try: start = expr.start except (NotImplementedError, AttributeError, ValueError): start = S.Infinity return start def _intersect_interval(self, other): """Returns start and stop. Takes intersection over the two intervals. """ interval = Intersection(self.interval, other.interval) return interval.inf, interval.sup @property def gen(self): """Returns the generator for the sequence""" raise NotImplementedError("(%s).gen" % self) @property def interval(self): """The interval on which the sequence is defined""" raise NotImplementedError("(%s).interval" % self) @property def start(self): """The starting point of the sequence. This point is included""" raise NotImplementedError("(%s).start" % self) @property def stop(self): """The ending point of the sequence. This point is included""" raise NotImplementedError("(%s).stop" % self) @property def length(self): """Length of the sequence""" raise NotImplementedError("(%s).length" % self) @property def variables(self): """Returns a tuple of variables that are bounded""" return () @property def free_symbols(self): """ This method returns the symbols in the object, excluding those that take on a specific value (i.e. the dummy symbols). Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n, m >>> SeqFormula(mn2, (n, 0, 5)).free_symbols {m} """ return ({j for i in self.args for j in i.free_symbols .difference(self.variables)}) @cacheit def coeff(self, pt): """Returns the coefficient at point pt""" if pt < self.start or pt > self.stop: raise IndexError("Index %s out of bounds %s" % (pt, self.interval)) return self._eval_coeff(pt) def _eval_coeff(self, pt): raise NotImplementedError("The _eval_coeff method should be added to" "%s to return coefficient so it is available" "when coeff calls it." % self.func) def _ith_point(self, i): """Returns the i'th point of a sequence. If start point is negative infinity, point is returned from the end. Assumes the first point to be indexed zero. Examples ========= >>> from sympy import oo >>> from sympy.series.sequences import SeqPer bounded >>> SeqPer((1, 2, 3), (-10, 10))._ith_point(0) -10 >>> SeqPer((1, 2, 3), (-10, 10))._ith_point(5) -5 End is at infinity >>> SeqPer((1, 2, 3), (0, oo))._ith_point(5) 5 Starts at negative infinity >>> SeqPer((1, 2, 3), (-oo, 0))._ith_point(5) -5 """ if self.start is S.NegativeInfinity: initial = self.stop else: initial = self.start if self.start is S.NegativeInfinity: step = -1 else: step = 1 return initial + istep def _add(self, other): """ Should only be used internally. self._add(other) returns a new, term-wise added sequence if self knows how to add with other, otherwise it returns ``None``. ``other`` should only be a sequence object. Used within :class:`SeqAdd` class. """ return None def _mul(self, other): """ Should only be used internally. self._mul(other) returns a new, term-wise multiplied sequence if self knows how to multiply with other, otherwise it returns ``None``. ``other`` should only be a sequence object. Used within :class:`SeqMul` class. """ return None def coeff_mul(self, other): """ Should be used when ``other`` is not a sequence. Should be defined to define custom behaviour. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n*2).coeff_mul(2) SeqFormula(2n*2, (n, 0, oo)) Notes ===== '' defines multiplication of sequences with sequences only. """ return Mul(self, other) def __add__(self, other): """Returns the term-wise addition of 'self' and 'other'. ``other`` should be a sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n2) + SeqFormula(n3) SeqFormula(n3 + n2, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot add sequence and %s' % type(other)) return SeqAdd(self, other) @call_highest_priority('__add__') def __radd__(self, other): return self + other def __sub__(self, other): """Returns the term-wise subtraction of 'self' and 'other'. ``other`` should be a sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n2) - (SeqFormula(n)) SeqFormula(n2 - n, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot subtract sequence and %s' % type(other)) return SeqAdd(self, -other) @call_highest_priority('__sub__') def __rsub__(self, other): return (-self) + other def __neg__(self): """Negates the sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> -SeqFormula(n2) SeqFormula(-n2, (n, 0, oo)) """ return self.coeff_mul(-1) def __mul__(self, other): """Returns the term-wise multiplication of 'self' and 'other'. ``other`` should be a sequence. For ``other`` not being a sequence see :func:`coeff_mul` method. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n*2) (SeqFormula(n)) SeqFormula(n*3, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot multiply sequence and %s' % type(other)) return SeqMul(self, other) @call_highest_priority('__mul__') def __rmul__(self, other): return self other def __iter__(self): for i in range(self.length): pt = self._ith_point(i) yield self.coeff(pt) def __getitem__(self, index): if isinstance(index, int): index = self._ith_point(index) return self.coeff(index) elif isinstance(index, slice): start, stop = index.start, index.stop if start is None: start = 0 if stop is None: stop = self.length return [self.coeff(self._ith_point(i)) for i in range(start, stop, index.step or 1)] def find_linear_recurrence(self,n,d=None,gfvar=None): r""" Finds the shortest linear recurrence that satisfies the first n terms of sequence of order `\leq` n/2 if possible. If d is specified, find shortest linear recurrence of order `\leq` min(d, n/2) if possible. Returns list of coefficients ``[b(1), b(2), ...]`` corresponding to the recurrence relation ``x(n) = b(1)x(n-1) + b(2)x(n-2) + ...`` Returns ``[]`` if no recurrence is found. If gfvar is specified, also returns ordinary generating function as a function of gfvar. Examples ======== >>> from sympy import sequence, sqrt, oo, lucas >>> from sympy.abc import n, x, y >>> sequence(n2).find_linear_recurrence(10, 2) [] >>> sequence(n2).find_linear_recurrence(10) [3, -3, 1] >>> sequence(2*n).find_linear_recurrence(10) [2] >>> sequence(23n*4+91n*2).find_linear_recurrence(10) [5, -10, 10, -5, 1] >>> sequence(sqrt(5)(((1 + sqrt(5))/2)n - (-(1 + sqrt(5))/2)(-n))/5).find_linear_recurrence(10) [1, 1] >>> sequence(x+y(-2)(-n), (n, 0, oo)).find_linear_recurrence(30) [1/2, 1/2] >>> sequence(35*n + 12).find_linear_recurrence(20,gfvar=x) ([6, -5], 3(5 - 21x)/((x - 1)(5x - 1))) >>> sequence(lucas(n)).find_linear_recurrence(15,gfvar=x) ([1, 1], (x - 2)/(x2 + x - 1)) """ from sympy.matrices import Matrix x = [simplify(expand(t)) for t in self[:n]] lx = len(x) if d is None: r = lx//2 else: r = min(d,lx//2) coeffs = [] for l in range(1, r+1): l2 = 2l mlist = [] for k in range(l): mlist.append(x[k:k+l]) m = Matrix(mlist) if m.det() != 0: y = simplify(m.LUsolve(Matrix(x[l:l2]))) if lx == l2: coeffs = flatten(y[::-1]) break mlist = [] for k in range(l,lx-l): mlist.append(x[k:k+l]) m = Matrix(mlist) if my == Matrix(x[l2:]): coeffs = flatten(y[::-1]) break if gfvar is None: return coeffs else: l = len(coeffs) if l == 0: return [], None else: n, d = x[l-1]gfvar*(l-1), 1 - coeffs[l-1]gfvar*l for i in range(l-1): n += x[i]gfvar*i for j in range(l-i-1): n -= coeffs[i]x[j]gfvar(i+j+1) d -= coeffs[i]gfvar*(i+1) return coeffs, simplify(factor(n)/factor(d)) class EmptySequence(SeqBase, metaclass=Singleton): """Represents an empty sequence. The empty sequence is also available as a singleton as ``S.EmptySequence``. Examples ======== >>> from sympy import EmptySequence, SeqPer >>> from sympy.abc import x >>> EmptySequence EmptySequence >>> SeqPer((1, 2), (x, 0, 10)) + EmptySequence SeqPer((1, 2), (x, 0, 10)) >>> SeqPer((1, 2)) EmptySequence EmptySequence >>> EmptySequence.coeff_mul(-1) EmptySequence """ @property def interval(self): return S.EmptySet @property def length(self): return S.Zero def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" return self def __iter__(self): return iter([]) class SeqExpr(SeqBase): """Sequence expression class. Various sequences should inherit from this class. Examples ======== >>> from sympy.series.sequences import SeqExpr >>> from sympy.abc import x >>> s = SeqExpr((1, 2, 3), (x, 0, 10)) >>> s.gen (1, 2, 3) >>> s.interval Interval(0, 10) >>> s.length 11 See Also ======== sympy.series.sequences.SeqPer sympy.series.sequences.SeqFormula """ @property def gen(self): return self.args[0] @property def interval(self): return Interval(self.args[1][1], self.args[1][2]) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return self.stop - self.start + 1 @property def variables(self): return (self.args[1][0],) class SeqPer(SeqExpr): """Represents a periodic sequence. The elements are repeated after a given period. Examples ======== >>> from sympy import SeqPer, oo >>> from sympy.abc import k >>> s = SeqPer((1, 2, 3), (0, 5)) >>> s.periodical (1, 2, 3) >>> s.period 3 For value at a particular point >>> s.coeff(3) 1 supports slicing >>> s[:] [1, 2, 3, 1, 2, 3] iterable >>> list(s) [1, 2, 3, 1, 2, 3] sequence starts from negative infinity >>> SeqPer((1, 2, 3), (-oo, 0))[0:6] [1, 2, 3, 1, 2, 3] Periodic formulas >>> SeqPer((k, k2, k3), (k, 0, oo))[0:6] [0, 1, 8, 3, 16, 125] See Also ======== sympy.series.sequences.SeqFormula """ def __new__(cls, periodical, limits=None): periodical = sympify(periodical) def _find_x(periodical): free = periodical.free_symbols if len(periodical.free_symbols) == 1: return free.pop() else: return Dummy('k') x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(periodical), 0, S.Infinity if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(periodical) start, stop = limits if not isinstance(x, (Symbol, Idx)) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) if start is S.NegativeInfinity and stop is S.Infinity: raise ValueError("Both the start and end value" "cannot be unbounded") limits = sympify((x, start, stop)) if is_sequence(periodical, Tuple): periodical = sympify(tuple(flatten(periodical))) else: raise ValueError("invalid period %s should be something " "like e.g (1, 2) " % periodical) if Interval(limits[1], limits[2]) is S.EmptySet: return S.EmptySequence return Basic.__new__(cls, periodical, limits) @property def period(self): return len(self.gen) @property def periodical(self): return self.gen def _eval_coeff(self, pt): if self.start is S.NegativeInfinity: idx = (self.stop - pt) % self.period else: idx = (pt - self.start) % self.period return self.periodical[idx].subs(self.variables[0], pt) def _add(self, other): """See docstring of SeqBase._add""" if isinstance(other, SeqPer): per1, lper1 = self.periodical, self.period per2, lper2 = other.periodical, other.period per_length = lcm(lper1, lper2) new_per = [] for x in range(per_length): ele1 = per1[x % lper1] ele2 = per2[x % lper2] new_per.append(ele1 + ele2) start, stop = self._intersect_interval(other) return SeqPer(new_per, (self.variables[0], start, stop)) def _mul(self, other): """See docstring of SeqBase._mul""" if isinstance(other, SeqPer): per1, lper1 = self.periodical, self.period per2, lper2 = other.periodical, other.period per_length = lcm(lper1, lper2) new_per = [] for x in range(per_length): ele1 = per1[x % lper1] ele2 = per2[x % lper2] new_per.append(ele1 * ele2) start, stop = self._intersect_interval(other) return SeqPer(new_per, (self.variables[0], start, stop)) def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" coeff = sympify(coeff) per = [x * coeff for x in self.periodical] return SeqPer(per, self.args[1]) class SeqFormula(SeqExpr): """Represents sequence based on a formula. Elements are generated using a formula. Examples ======== >>> from sympy import SeqFormula, oo, Symbol >>> n = Symbol('n') >>> s = SeqFormula(n2, (n, 0, 5)) >>> s.formula n2 For value at a particular point >>> s.coeff(3) 9 supports slicing >>> s[:] [0, 1, 4, 9, 16, 25] iterable >>> list(s) [0, 1, 4, 9, 16, 25] sequence starts from negative infinity >>> SeqFormula(n*2, (-oo, 0))[0:6] [0, 1, 4, 9, 16, 25] See Also ======== sympy.series.sequences.SeqPer """ def __new__(cls, formula, limits=None): formula = sympify(formula) def _find_x(formula): free = formula.free_symbols if len(free) == 1: return free.pop() elif not free: return Dummy('k') else: raise ValueError( " specify dummy variables for %s. If the formula contains" " more than one free symbol, a dummy variable should be" " supplied explicitly e.g., SeqFormula(mn*2, (n, 0, 5))" % formula) x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(formula), 0, S.Infinity if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(formula) start, stop = limits if not isinstance(x, (Symbol, Idx)) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) if start is S.NegativeInfinity and stop is S.Infinity: raise ValueError("Both the start and end value " "cannot be unbounded") limits = sympify((x, start, stop)) if Interval(limits[1], limits[2]) is S.EmptySet: return S.EmptySequence return Basic.__new__(cls, formula, limits) @property def formula(self): return self.gen def _eval_coeff(self, pt): d = self.variables[0] return self.formula.subs(d, pt) def _add(self, other): """See docstring of SeqBase._add""" if isinstance(other, SeqFormula): form1, v1 = self.formula, self.variables[0] form2, v2 = other.formula, other.variables[0] formula = form1 + form2.subs(v2, v1) start, stop = self._intersect_interval(other) return SeqFormula(formula, (v1, start, stop)) def _mul(self, other): """See docstring of SeqBase._mul""" if isinstance(other, SeqFormula): form1, v1 = self.formula, self.variables[0] form2, v2 = other.formula, other.variables[0] formula = form1 form2.subs(v2, v1) start, stop = self._intersect_interval(other) return SeqFormula(formula, (v1, start, stop)) def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" coeff = sympify(coeff) formula = self.formula * coeff return SeqFormula(formula, self.args[1]) def expand(self, args, kwargs): return SeqFormula(expand(self.formula, args, *kwargs), self.args[1]) class RecursiveSeq(SeqBase): """A finite degree recursive sequence. That is, a sequence a(n) that depends on a fixed, finite number of its previous values. The general form is a(n) = f(a(n - 1), a(n - 2), ..., a(n - d)) for some fixed, positive integer d, where f is some function defined by a SymPy expression. Parameters ========== recurrence : SymPy expression defining recurrence This is not* an equality, only the expression that the nth term is equal to. For example, if :code:`a(n) = f(a(n - 1), ..., a(n - d))`, then the expression should be :code:`f(a(n - 1), ..., a(n - d))`. yn : applied undefined function Represents the nth term of the sequence as e.g. :code:`y(n)` where :code:`y` is an undefined function and `n` is the sequence index. n : symbolic argument The name of the variable that the recurrence is in, e.g., :code:`n` if the recurrence function is :code:`y(n)`. initial : iterable with length equal to the degree of the recurrence The initial values of the recurrence. start : start value of sequence (inclusive) Examples ======== >>> from sympy import Function, symbols >>> from sympy.series.sequences import RecursiveSeq >>> y = Function("y") >>> n = symbols("n") >>> fib = RecursiveSeq(y(n - 1) + y(n - 2), y(n), n, [0, 1]) >>> fib.coeff(3) # Value at a particular point 2 >>> fib[:6] # supports slicing [0, 1, 1, 2, 3, 5] >>> fib.recurrence # inspect recurrence Eq(y(n), y(n - 2) + y(n - 1)) >>> fib.degree # automatically determine degree 2 >>> for x in zip(range(10), fib): # supports iteration ... print(x) (0, 0) (1, 1) (2, 1) (3, 2) (4, 3) (5, 5) (6, 8) (7, 13) (8, 21) (9, 34) See Also ======== sympy.series.sequences.SeqFormula """ def __new__(cls, recurrence, yn, n, initial=None, start=0): if not isinstance(yn, AppliedUndef): raise TypeError("recurrence sequence must be an applied undefined function" ", found `{}`".format(yn)) if not isinstance(n, Basic) or not n.is_symbol: raise TypeError("recurrence variable must be a symbol" ", found `{}`".format(n)) if yn.args != (n,): raise TypeError("recurrence sequence does not match symbol") y = yn.func k = Wild("k", exclude=(n,)) degree = 0 # Find all applications of y in the recurrence and check that: # 1. The function y is only being used with a single argument; and # 2. All arguments are n + k for constant negative integers k. prev_ys = recurrence.find(y) for prev_y in prev_ys: if len(prev_y.args) != 1: raise TypeError("Recurrence should be in a single variable") shift = prev_y.args[0].match(n + k)[k] if not (shift.is_constant() and shift.is_integer and shift < 0): raise TypeError("Recurrence should have constant," " negative, integer shifts" " (found {})".format(prev_y)) if -shift > degree: degree = -shift if not initial: initial = [Dummy("c_{}".format(k)) for k in range(degree)] if len(initial) != degree: raise ValueError("Number of initial terms must equal degree") degree = Integer(degree) start = sympify(start) initial = Tuple((sympify(x) for x in initial)) seq = Basic.__new__(cls, recurrence, yn, n, initial, start) seq.cache = {y(start + k): init for k, init in enumerate(initial)} seq.degree = degree return seq @property def _recurrence(self): """Equation defining recurrence.""" return self.args[0] @property def recurrence(self): """Equation defining recurrence.""" return Eq(self.yn, self.args[0]) @property def yn(self): """Applied function representing the nth term""" return self.args[1] @property def y(self): """Undefined function for the nth term of the sequence""" return self.yn.func @property def n(self): """Sequence index symbol""" return self.args[2] @property def initial(self): """The initial values of the sequence""" return self.args[3] @property def start(self): """The starting point of the sequence. This point is included""" return self.args[4] @property def stop(self): """The ending point of the sequence. (oo)""" return S.Infinity @property def interval(self): """Interval on which sequence is defined.""" return (self.start, S.Infinity) def _eval_coeff(self, index): if index - self.start < len(self.cache): return self.cache[self.y(index)] for current in range(len(self.cache), index + 1): # Use xreplace over subs for performance. # See issue #10697. seq_index = self.start + current current_recurrence = self._recurrence.xreplace({self.n: seq_index}) new_term = current_recurrence.xreplace(self.cache) self.cache[self.y(seq_index)] = new_term return self.cache[self.y(self.start + current)] def __iter__(self): index = self.start while True: yield self._eval_coeff(index) index += 1 def sequence(seq, limits=None): """Returns appropriate sequence object. If ``seq`` is a sympy sequence, returns :class:`SeqPer` object otherwise returns :class:`SeqFormula` object. Examples ======== >>> from sympy import sequence >>> from sympy.abc import n >>> sequence(n2, (n, 0, 5)) SeqFormula(n2, (n, 0, 5)) >>> sequence((1, 2, 3), (n, 0, 5)) SeqPer((1, 2, 3), (n, 0, 5)) See Also ======== sympy.series.sequences.SeqPer sympy.series.sequences.SeqFormula """ seq = sympify(seq) if is_sequence(seq, Tuple): return SeqPer(seq, limits) else: return SeqFormula(seq, limits) ############################################################################### # OPERATIONS # ############################################################################### class SeqExprOp(SeqBase): """Base class for operations on sequences. Examples ======== >>> from sympy.series.sequences import SeqExprOp, sequence >>> from sympy.abc import n >>> s1 = sequence(n2, (n, 0, 10)) >>> s2 = sequence((1, 2, 3), (n, 5, 10)) >>> s = SeqExprOp(s1, s2) >>> s.gen (n2, (1, 2, 3)) >>> s.interval Interval(5, 10) >>> s.length 6 See Also ======== sympy.series.sequences.SeqAdd sympy.series.sequences.SeqMul """ @property def gen(self): """Generator for the sequence. returns a tuple of generators of all the argument sequences. """ return tuple(a.gen for a in self.args) @property def interval(self): """Sequence is defined on the intersection of all the intervals of respective sequences """ return Intersection((a.interval for a in self.args)) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def variables(self): """Cumulative of all the bound variables""" return tuple(flatten([a.variables for a in self.args])) @property def length(self): return self.stop - self.start + 1 class SeqAdd(SeqExprOp): """Represents term-wise addition of sequences. Rules: * The interval on which sequence is defined is the intersection of respective intervals of sequences. * Anything + :class:`EmptySequence` remains unchanged. * Other rules are defined in ``_add`` methods of sequence classes. Examples ======== >>> from sympy import EmptySequence, oo, SeqAdd, SeqPer, SeqFormula >>> from sympy.abc import n >>> SeqAdd(SeqPer((1, 2), (n, 0, oo)), EmptySequence) SeqPer((1, 2), (n, 0, oo)) >>> SeqAdd(SeqPer((1, 2), (n, 0, 5)), SeqPer((1, 2), (n, 6, 10))) EmptySequence >>> SeqAdd(SeqPer((1, 2), (n, 0, oo)), SeqFormula(n2, (n, 0, oo))) SeqAdd(SeqFormula(n2, (n, 0, oo)), SeqPer((1, 2), (n, 0, oo))) >>> SeqAdd(SeqFormula(n3), SeqFormula(n2)) SeqFormula(n3 + n2, (n, 0, oo)) See Also ======== sympy.series.sequences.SeqMul """ def __new__(cls, args, kwargs): evaluate = kwargs.get('evaluate', global_parameters.evaluate) # flatten inputs args = list(args) # adapted from sympy.sets.sets.Union def _flatten(arg): if isinstance(arg, SeqBase): if isinstance(arg, SeqAdd): return sum(map(_flatten, arg.args), []) else: return [arg] if iterable(arg): return sum(map(_flatten, arg), []) raise TypeError("Input must be Sequences or " " iterables of Sequences") args = _flatten(args) args = [a for a in args if a is not S.EmptySequence] # Addition of no sequences is EmptySequence if not args: return S.EmptySequence if Intersection((a.interval for a in args)) is S.EmptySet: return S.EmptySequence # reduce using known rules if evaluate: return SeqAdd.reduce(args) args = list(ordered(args, SeqBase._start_key)) return Basic.__new__(cls, args) @staticmethod def reduce(args): """Simplify :class:`SeqAdd` using known rules. Iterates through all pairs and ask the constituent sequences if they can simplify themselves with any other constituent. Notes ===== adapted from ``Union.reduce`` """ new_args = True while new_args: for id1, s in enumerate(args): new_args = False for id2, t in enumerate(args): if id1 == id2: continue new_seq = s._add(t) # This returns None if s does not know how to add # with t. Returns the newly added sequence otherwise if new_seq is not None: new_args = [a for a in args if a not in (s, t)] new_args.append(new_seq) break if new_args: args = new_args break if len(args) == 1: return args.pop() else: return SeqAdd(args, evaluate=False) def _eval_coeff(self, pt): """adds up the coefficients of all the sequences at point pt""" return sum(a.coeff(pt) for a in self.args) class SeqMul(SeqExprOp): r"""Represents term-wise multiplication of sequences. Handles multiplication of sequences only. For multiplication with other objects see :func:`SeqBase.coeff_mul`. Rules: The interval on which sequence is defined is the intersection of respective intervals of sequences. * Anything \* :class:`EmptySequence` returns :class:`EmptySequence`. * Other rules are defined in ``_mul`` methods of sequence classes. Examples ======== >>> from sympy import EmptySequence, oo, SeqMul, SeqPer, SeqFormula >>> from sympy.abc import n >>> SeqMul(SeqPer((1, 2), (n, 0, oo)), EmptySequence) EmptySequence >>> SeqMul(SeqPer((1, 2), (n, 0, 5)), SeqPer((1, 2), (n, 6, 10))) EmptySequence >>> SeqMul(SeqPer((1, 2), (n, 0, oo)), SeqFormula(n2)) SeqMul(SeqFormula(n2, (n, 0, oo)), SeqPer((1, 2), (n, 0, oo))) >>> SeqMul(SeqFormula(n3), SeqFormula(n2)) SeqFormula(n*5, (n, 0, oo)) See Also ======== sympy.series.sequences.SeqAdd """ def __new__(cls, args, *kwargs): evaluate = kwargs.get('evaluate', global_parameters.evaluate) # flatten inputs args = list(args) # adapted from sympy.sets.sets.Union def _flatten(arg): if isinstance(arg, SeqBase): if isinstance(arg, SeqMul): return sum(map(_flatten, arg.args), []) else: return [arg] elif iterable(arg): return sum(map(_flatten, arg), []) raise TypeError("Input must be Sequences or " " iterables of Sequences") args = _flatten(args) # Multiplication of no sequences is EmptySequence if not args: return S.EmptySequence if Intersection((a.interval for a in args)) is S.EmptySet: return S.EmptySequence # reduce using known rules if evaluate: return SeqMul.reduce(args) args = list(ordered(args, SeqBase._start_key)) return Basic.__new__(cls, args) @staticmethod def reduce(args): """Simplify a :class:`SeqMul` using known rules. Iterates through all pairs and ask the constituent sequences if they can simplify themselves with any other constituent. Notes ===== adapted from ``Union.reduce`` """ new_args = True while new_args: for id1, s in enumerate(args): new_args = False for id2, t in enumerate(args): if id1 == id2: continue new_seq = s._mul(t) # This returns None if s does not know how to multiply # with t. Returns the newly multiplied sequence otherwise if new_seq is not None: new_args = [a for a in args if a not in (s, t)] new_args.append(new_seq) break if new_args: args = new_args break if len(args) == 1: return args.pop() else: return SeqMul(args, evaluate=False) def _eval_coeff(self, pt): """multiplies the coefficients of all the sequences at point pt""" val = 1 for a in self.args: val = a.coeff(pt) return val
53ec675f12ed86d53c3ce4201d982e01f27e6b10e33a0ad9d3df5319bcd926b3	from sympy.core import S, Symbol, Add, sympify, Expr, PoleError, Mul from sympy.core.exprtools import factor_terms from sympy.core.symbol import Dummy from sympy.functions.combinatorial.factorials import factorial from sympy.functions.special.gamma_functions import gamma from sympy.polys import PolynomialError, factor from sympy.series.order import Order from sympy.simplify.ratsimp import ratsimp from sympy.simplify.simplify import together from .gruntz import gruntz def limit(e, z, z0, dir="+"): """Computes the limit of ``e(z)`` at the point ``z0``. Parameters ========== e : expression, the limit of which is to be taken z : symbol representing the variable in the limit. Other symbols are treated as constants. Multivariate limits are not supported. z0 : the value toward which ``z`` tends. Can be any expression, including ``oo`` and ``-oo``. dir : string, optional (default: "+") The limit is bi-directional if ``dir="+-"``, from the right (z->z0+) if ``dir="+"``, and from the left (z->z0-) if ``dir="-"``. For infinite ``z0`` (``oo`` or ``-oo``), the ``dir`` argument is determined from the direction of the infinity (i.e., ``dir="-"`` for ``oo``). Examples ======== >>> from sympy import limit, sin, oo >>> from sympy.abc import x >>> limit(sin(x)/x, x, 0) 1 >>> limit(1/x, x, 0) # default dir='+' oo >>> limit(1/x, x, 0, dir="-") -oo >>> limit(1/x, x, 0, dir='+-') zoo >>> limit(1/x, x, oo) 0 Notes ===== First we try some heuristics for easy and frequent cases like "x", "1/x", "x*2" and similar, so that it's fast. For all other cases, we use the Gruntz algorithm (see the gruntz() function). See Also ======== limit_seq : returns the limit of a sequence. """ return Limit(e, z, z0, dir).doit(deep=False) def heuristics(e, z, z0, dir): """Computes the limit of an expression term-wise. Parameters are the same as for the ``limit`` function. Works with the arguments of expression ``e`` one by one, computing the limit of each and then combining the results. This approach works only for simple limits, but it is fast. """ from sympy.calculus.util import AccumBounds rv = None if abs(z0) is S.Infinity: rv = limit(e.subs(z, 1/z), z, S.Zero, "+" if z0 is S.Infinity else "-") if isinstance(rv, Limit): return elif e.is_Mul or e.is_Add or e.is_Pow or e.is_Function: r = [] for a in e.args: l = limit(a, z, z0, dir) if l.has(S.Infinity) and l.is_finite is None: if isinstance(e, Add): m = factor_terms(e) if not isinstance(m, Mul): # try together m = together(m) if not isinstance(m, Mul): # try factor if the previous methods failed m = factor(e) if isinstance(m, Mul): return heuristics(m, z, z0, dir) return return elif isinstance(l, Limit): return elif l is S.NaN: return else: r.append(l) if r: rv = e.func(r) if rv is S.NaN and e.is_Mul and any(isinstance(rr, AccumBounds) for rr in r): r2 = [] e2 = [] for ii in range(len(r)): if isinstance(r[ii], AccumBounds): r2.append(r[ii]) else: e2.append(e.args[ii]) if len(e2) > 0: e3 = Mul(e2).simplify() l = limit(e3, z, z0, dir) rv = l Mul(r2) if rv is S.NaN: try: rat_e = ratsimp(e) except PolynomialError: return if rat_e is S.NaN or rat_e == e: return return limit(rat_e, z, z0, dir) return rv class Limit(Expr): """Represents an unevaluated limit. Examples ======== >>> from sympy import Limit, sin >>> from sympy.abc import x >>> Limit(sin(x)/x, x, 0) Limit(sin(x)/x, x, 0) >>> Limit(1/x, x, 0, dir="-") Limit(1/x, x, 0, dir='-') """ def __new__(cls, e, z, z0, dir="+"): e = sympify(e) z = sympify(z) z0 = sympify(z0) if z0 is S.Infinity: dir = "-" elif z0 is S.NegativeInfinity: dir = "+" if isinstance(dir, str): dir = Symbol(dir) elif not isinstance(dir, Symbol): raise TypeError("direction must be of type basestring or " "Symbol, not %s" % type(dir)) if str(dir) not in ('+', '-', '+-'): raise ValueError("direction must be one of '+', '-' " "or '+-', not %s" % dir) obj = Expr.__new__(cls) obj._args = (e, z, z0, dir) return obj @property def free_symbols(self): e = self.args[0] isyms = e.free_symbols isyms.difference_update(self.args[1].free_symbols) isyms.update(self.args[2].free_symbols) return isyms def doit(self, hints): """Evaluates the limit. Parameters ========== deep : bool, optional (default: True) Invoke the ``doit`` method of the expressions involved before taking the limit. hints : optional keyword arguments To be passed to ``doit`` methods; only used if deep is True. """ from sympy import Abs, exp, log, sign from sympy.calculus.util import AccumBounds e, z, z0, dir = self.args if z0 is S.ComplexInfinity: raise NotImplementedError("Limits at complex " "infinity are not implemented") if hints.get('deep', True): e = e.doit(hints) z = z.doit(hints) z0 = z0.doit(hints) if e == z: return z0 if not e.has(z): return e cdir = 0 if str(dir) == "+": cdir = 1 elif str(dir) == "-": cdir = -1 def remove_abs(expr): if not expr.args: return expr newargs = tuple(remove_abs(arg) for arg in expr.args) if newargs != expr.args: expr = expr.func(newargs) if isinstance(expr, Abs): sig = limit(expr.args[0], z, z0, dir) if sig.is_zero: sig = limit(1/expr.args[0], z, z0, dir) if sig.is_extended_real: if (sig < 0) == True: return -expr.args[0] elif (sig > 0) == True: return expr.args[0] return expr e = remove_abs(e) if e.is_meromorphic(z, z0): if abs(z0) is S.Infinity: newe = e.subs(z, -1/z) else: newe = e.subs(z, z + z0) try: coeff, ex = newe.leadterm(z, cdir) except (ValueError, NotImplementedError): pass else: if ex > 0: return S.Zero elif ex == 0: return coeff if str(dir) == "+" or not(int(ex) & 1): return S.Infinitysign(coeff) elif str(dir) == "-": return S.NegativeInfinitysign(coeff) else: return S.ComplexInfinity # gruntz fails on factorials but works with the gamma function # If no factorial term is present, e should remain unchanged. # factorial is defined to be zero for negative inputs (which # differs from gamma) so only rewrite for positive z0. if z0.is_extended_positive: e = e.rewrite(factorial, gamma) if e.is_Mul and abs(z0) is S.Infinity: e = factor_terms(e) u = Dummy('u', positive=True) if z0 is S.NegativeInfinity: inve = e.subs(z, -1/u) else: inve = e.subs(z, 1/u) try: f = inve.as_leading_term(u).gammasimp() if f.is_meromorphic(u, S.Zero): r = limit(f, u, S.Zero, "+") if isinstance(r, Limit): return self else: return r except (ValueError, NotImplementedError, PoleError): pass if e.is_Order: return Order(limit(e.expr, z, z0), e.args[1:]) if e.is_Pow: if e.has(S.Infinity, S.NegativeInfinity, S.ComplexInfinity, S.NaN): return self b1, e1 = e.base, e.exp f1 = e1log(b1) if f1.is_meromorphic(z, z0): res = limit(f1, z, z0) return exp(res) ex_lim = limit(e1, z, z0) base_lim = limit(b1, z, z0) if base_lim is S.One: if ex_lim in (S.Infinity, S.NegativeInfinity): res = limit(e1(b1 - 1), z, z0) return exp(res) elif ex_lim.is_real: return S.One if base_lim in (S.Zero, S.Infinity, S.NegativeInfinity) and ex_lim is S.Zero: res = limit(f1, z, z0) return exp(res) if base_lim is S.NegativeInfinity: if ex_lim is S.NegativeInfinity: return S.Zero if ex_lim is S.Infinity: return S.ComplexInfinity if not isinstance(base_lim, AccumBounds) and not isinstance(ex_lim, AccumBounds): res = base_lim*ex_lim if res is not S.ComplexInfinity and not res.is_Pow: return res l = None try: if str(dir) == '+-': r = gruntz(e, z, z0, '+') l = gruntz(e, z, z0, '-') if l != r: raise ValueError("The limit does not exist since " "left hand limit = %s and right hand limit = %s" % (l, r)) else: r = gruntz(e, z, z0, dir) if r is S.NaN or l is S.NaN: raise PoleError() except (PoleError, ValueError): if l is not None: raise r = heuristics(e, z, z0, dir) if r is None: return self return r
468436b1499e66d2ade09cff6a77a7eff94c065ce9cb7f3db10be053d58dfb09	"""Limits of sequences""" from sympy.core.add import Add from sympy.core.function import PoleError from sympy.core.power import Pow from sympy.core.singleton import S from sympy.core.symbol import Dummy from sympy.core.sympify import sympify from sympy.functions.combinatorial.numbers import fibonacci from sympy.functions.combinatorial.factorials import factorial, subfactorial from sympy.functions.special.gamma_functions import gamma from sympy.functions.elementary.complexes import Abs from sympy.functions.elementary.miscellaneous import Max, Min from sympy.functions.elementary.trigonometric import cos, sin from sympy.series.limits import Limit def difference_delta(expr, n=None, step=1): """Difference Operator. Discrete analog of differential operator. Given a sequence x[n], returns the sequence x[n + step] - x[n]. Examples ======== >>> from sympy import difference_delta as dd >>> from sympy.abc import n >>> dd(n(n + 1), n) 2n + 2 >>> dd(n(n + 1), n, 2) 4n + 6 References ========== .. [1] https://reference.wolfram.com/language/ref/DifferenceDelta.html """ expr = sympify(expr) if n is None: f = expr.free_symbols if len(f) == 1: n = f.pop() elif len(f) == 0: return S.Zero else: raise ValueError("Since there is more than one variable in the" " expression, a variable must be supplied to" " take the difference of %s" % expr) step = sympify(step) if step.is_number is False or step.is_finite is False: raise ValueError("Step should be a finite number.") if hasattr(expr, '_eval_difference_delta'): result = expr._eval_difference_delta(n, step) if result: return result return expr.subs(n, n + step) - expr def dominant(expr, n): """Finds the dominant term in a sum, that is a term that dominates every other term. If limit(a/b, n, oo) is oo then a dominates b. If limit(a/b, n, oo) is 0 then b dominates a. Otherwise, a and b are comparable. If there is no unique dominant term, then returns ``None``. Examples ======== >>> from sympy import Sum >>> from sympy.series.limitseq import dominant >>> from sympy.abc import n, k >>> dominant(5n3 + 4n*2 + n + 1, n) 5n3 >>> dominant(2n + Sum(k, (k, 0, n)), n) 2*n See Also ======== sympy.series.limitseq.dominant """ terms = Add.make_args(expr.expand(func=True)) term0 = terms[-1] comp = [term0] # comparable terms for t in terms[:-1]: e = (term0 / t).gammasimp() l = limit_seq(e, n) if l is None: return None elif l.is_zero: term0 = t comp = [term0] elif l not in [S.Infinity, S.NegativeInfinity]: comp.append(t) if len(comp) > 1: return None return term0 def _limit_inf(expr, n): try: return Limit(expr, n, S.Infinity).doit(deep=False) except (NotImplementedError, PoleError): return None def _limit_seq(expr, n, trials): from sympy.concrete.summations import Sum for i in range(trials): if not expr.has(Sum): result = _limit_inf(expr, n) if result is not None: return result num, den = expr.as_numer_denom() if not den.has(n) or not num.has(n): result = _limit_inf(expr.doit(), n) if result is not None: return result return None num, den = (difference_delta(t.expand(), n) for t in [num, den]) expr = (num / den).gammasimp() if not expr.has(Sum): result = _limit_inf(expr, n) if result is not None: return result num, den = expr.as_numer_denom() num = dominant(num, n) if num is None: return None den = dominant(den, n) if den is None: return None expr = (num / den).gammasimp() def limit_seq(expr, n=None, trials=5): """Finds the limit of a sequence as index n tends to infinity. Parameters ========== expr : Expr SymPy expression for the n-th term of the sequence n : Symbol, optional The index of the sequence, an integer that tends to positive infinity. If None, inferred from the expression unless it has multiple symbols. trials: int, optional The algorithm is highly recursive. ``trials`` is a safeguard from infinite recursion in case the limit is not easily computed by the algorithm. Try increasing ``trials`` if the algorithm returns ``None``. Admissible Terms ================ The algorithm is designed for sequences built from rational functions, indefinite sums, and indefinite products over an indeterminate n. Terms of alternating sign are also allowed, but more complex oscillatory behavior is not supported. Examples ======== >>> from sympy import limit_seq, Sum, binomial >>> from sympy.abc import n, k, m >>> limit_seq((5n*3 + 3n*2 + 4) / (3n*3 + 4n - 5), n) 5/3 >>> limit_seq(binomial(2n, n) / Sum(binomial(2k, k), (k, 1, n)), n) 3/4 >>> limit_seq(Sum(k*2 Sum(2m/m, (m, 1, k)), (k, 1, n)) / (2nn), n) 4 See Also ======== sympy.series.limitseq.dominant References ========== .. [1] Computing Limits of Sequences - Manuel Kauers """ from sympy.concrete.summations import Sum from sympy.calculus.util import AccumulationBounds if n is None: free = expr.free_symbols if len(free) == 1: n = free.pop() elif not free: return expr else: raise ValueError("Expression has more than one variable. " "Please specify a variable.") elif n not in expr.free_symbols: return expr expr = expr.rewrite(fibonacci, S.GoldenRatio) expr = expr.rewrite(factorial, subfactorial, gamma) n_ = Dummy("n", integer=True, positive=True) n1 = Dummy("n", odd=True, positive=True) n2 = Dummy("n", even=True, positive=True) # If there is a negative term raised to a power involving n, or a # trigonometric function, then consider even and odd n separately. powers = (p.as_base_exp() for p in expr.atoms(Pow)) if (any(b.is_negative and e.has(n) for b, e in powers) or expr.has(cos, sin)): L1 = _limit_seq(expr.xreplace({n: n1}), n1, trials) if L1 is not None: L2 = _limit_seq(expr.xreplace({n: n2}), n2, trials) if L1 != L2: if L1.is_comparable and L2.is_comparable: return AccumulationBounds(Min(L1, L2), Max(L1, L2)) else: return None else: L1 = _limit_seq(expr.xreplace({n: n_}), n_, trials) if L1 is not None: return L1 else: if expr.is_Add: limits = [limit_seq(term, n, trials) for term in expr.args] if any(result is None for result in limits): return None else: return Add(limits) # Maybe the absolute value is easier to deal with (though not if # it has a Sum). If it tends to 0, the limit is 0. elif not expr.has(Sum): lim = _limit_seq(Abs(expr.xreplace({n: n_})), n_, trials) if lim is not None and lim.is_zero: return S.Zero
8844cdb1f5e648976b6fbc504dc3502f1267e18e232d1f199091c7d0f3366078	"""Fourier Series""" from sympy import pi, oo, Wild from sympy.core.expr import Expr from sympy.core.add import Add from sympy.core.compatibility import is_sequence from sympy.core.containers import Tuple from sympy.core.singleton import S from sympy.core.symbol import Dummy, Symbol from sympy.core.sympify import sympify from sympy.functions.elementary.trigonometric import sin, cos, sinc from sympy.series.series_class import SeriesBase from sympy.series.sequences import SeqFormula from sympy.sets.sets import Interval from sympy.simplify.fu import TR2, TR1, TR10, sincos_to_sum def fourier_cos_seq(func, limits, n): """Returns the cos sequence in a Fourier series""" from sympy.integrals import integrate x, L = limits[0], limits[2] - limits[1] cos_term = cos(2npix / L) formula = 2 cos_term * integrate(func * cos_term, limits) / L a0 = formula.subs(n, S.Zero) / 2 return a0, SeqFormula(2 * cos_term * integrate(func * cos_term, limits) / L, (n, 1, oo)) def fourier_sin_seq(func, limits, n): """Returns the sin sequence in a Fourier series""" from sympy.integrals import integrate x, L = limits[0], limits[2] - limits[1] sin_term = sin(2npix / L) return SeqFormula(2 sin_term * integrate(func * sin_term, limits) / L, (n, 1, oo)) def _process_limits(func, limits): """ Limits should be of the form (x, start, stop). x should be a symbol. Both start and stop should be bounded. * If x is not given, x is determined from func. * If limits is None. Limit of the form (x, -pi, pi) is returned. Examples ======== >>> from sympy.series.fourier import _process_limits as pari >>> from sympy.abc import x >>> pari(x2, (x, -2, 2)) (x, -2, 2) >>> pari(x2, (-2, 2)) (x, -2, 2) >>> pari(x*2, None) (x, -pi, pi) """ def _find_x(func): free = func.free_symbols if len(free) == 1: return free.pop() elif not free: return Dummy('k') else: raise ValueError( " specify dummy variables for %s. If the function contains" " more than one free symbol, a dummy variable should be" " supplied explicitly e.g. FourierSeries(mn*2, (n, -pi, pi))" % func) x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(func), -pi, pi if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(func) start, stop = limits if not isinstance(x, Symbol) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) unbounded = [S.NegativeInfinity, S.Infinity] if start in unbounded or stop in unbounded: raise ValueError("Both the start and end value should be bounded") return sympify((x, start, stop)) def finite_check(f, x, L): def check_fx(exprs, x): return x not in exprs.free_symbols def check_sincos(_expr, x, L): if isinstance(_expr, (sin, cos)): sincos_args = _expr.args[0] if sincos_args.match(a(pi/L)x + b) is not None: return True else: return False _expr = sincos_to_sum(TR2(TR1(f))) add_coeff = _expr.as_coeff_add() a = Wild('a', properties=[lambda k: k.is_Integer, lambda k: k != S.Zero, ]) b = Wild('b', properties=[lambda k: x not in k.free_symbols, ]) for s in add_coeff[1]: mul_coeffs = s.as_coeff_mul()[1] for t in mul_coeffs: if not (check_fx(t, x) or check_sincos(t, x, L)): return False, f return True, _expr class FourierSeries(SeriesBase): r"""Represents Fourier sine/cosine series. This class only represents a fourier series. No computation is performed. For how to compute Fourier series, see the :func:`fourier_series` docstring. See Also ======== sympy.series.fourier.fourier_series """ def __new__(cls, args): args = map(sympify, args) return Expr.__new__(cls, args) @property def function(self): return self.args[0] @property def x(self): return self.args[1][0] @property def period(self): return (self.args[1][1], self.args[1][2]) @property def a0(self): return self.args[2][0] @property def an(self): return self.args[2][1] @property def bn(self): return self.args[2][2] @property def interval(self): return Interval(0, oo) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return oo @property def L(self): return abs(self.period[1] - self.period[0]) / 2 def _eval_subs(self, old, new): x = self.x if old.has(x): return self def truncate(self, n=3): """ Return the first n nonzero terms of the series. If n is None return an iterator. Parameters ========== n : int or None Amount of non-zero terms in approximation or None. Returns ======= Expr or iterator Approximation of function expanded into Fourier series. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x, (x, -pi, pi)) >>> s.truncate(4) 2sin(x) - sin(2x) + 2sin(3x)/3 - sin(4x)/2 See Also ======== sympy.series.fourier.FourierSeries.sigma_approximation """ if n is None: return iter(self) terms = [] for t in self: if len(terms) == n: break if t is not S.Zero: terms.append(t) return Add(terms) def sigma_approximation(self, n=3): r""" Return :math:`\sigma`-approximation of Fourier series with respect to order n. Sigma approximation adjusts a Fourier summation to eliminate the Gibbs phenomenon which would otherwise occur at discontinuities. A sigma-approximated summation for a Fourier series of a T-periodical function can be written as .. math:: s(\theta) = \frac{1}{2} a_0 + \sum _{k=1}^{m-1} \operatorname{sinc} \Bigl( \frac{k}{m} \Bigr) \cdot \left[ a_k \cos \Bigl( \frac{2\pi k}{T} \theta \Bigr) + b_k \sin \Bigl( \frac{2\pi k}{T} \theta \Bigr) \right], where :math:`a_0, a_k, b_k, k=1,\ldots,{m-1}` are standard Fourier series coefficients and :math:`\operatorname{sinc} \Bigl( \frac{k}{m} \Bigr)` is a Lanczos :math:`\sigma` factor (expressed in terms of normalized :math:`\operatorname{sinc}` function). Parameters ========== n : int Highest order of the terms taken into account in approximation. Returns ======= Expr Sigma approximation of function expanded into Fourier series. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x, (x, -pi, pi)) >>> s.sigma_approximation(4) 2sin(x)sinc(pi/4) - 2sin(2x)/pi + 2sin(3x)sinc(3pi/4)/3 See Also ======== sympy.series.fourier.FourierSeries.truncate Notes ===== The behaviour of :meth:`~sympy.series.fourier.FourierSeries.sigma_approximation` is different from :meth:`~sympy.series.fourier.FourierSeries.truncate` - it takes all nonzero terms of degree smaller than n, rather than first n nonzero ones. References ========== .. [1] https://en.wikipedia.org/wiki/Gibbs_phenomenon .. [2] https://en.wikipedia.org/wiki/Sigma_approximation """ terms = [sinc(pi i / n) * t for i, t in enumerate(self[:n]) if t is not S.Zero] return Add(terms) def shift(self, s): """Shift the function by a term independent of x. f(x) -> f(x) + s This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x2, (x, -pi, pi)) >>> s.shift(1).truncate() -4cos(x) + cos(2x) + 1 + pi2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) a0 = self.a0 + s sfunc = self.function + s return self.func(sfunc, self.args[1], (a0, self.an, self.bn)) def shiftx(self, s): """Shift x by a term independent of x. f(x) -> f(x + s) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x2, (x, -pi, pi)) >>> s.shiftx(1).truncate() -4cos(x + 1) + cos(2x + 2) + pi2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.subs(x, x + s) bn = self.bn.subs(x, x + s) sfunc = self.function.subs(x, x + s) return self.func(sfunc, self.args[1], (self.a0, an, bn)) def scale(self, s): """Scale the function by a term independent of x. f(x) -> s f(x) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x*2, (x, -pi, pi)) >>> s.scale(2).truncate() -8cos(x) + 2cos(2x) + 2pi2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.coeff_mul(s) bn = self.bn.coeff_mul(s) a0 = self.a0 s sfunc = self.args[0] * s return self.func(sfunc, self.args[1], (a0, an, bn)) def scalex(self, s): """Scale x by a term independent of x. f(x) -> f(sx) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x2, (x, -pi, pi)) >>> s.scalex(2).truncate() -4cos(2x) + cos(4x) + pi*2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.subs(x, x s) bn = self.bn.subs(x, x * s) sfunc = self.function.subs(x, x * s) return self.func(sfunc, self.args[1], (self.a0, an, bn)) def _eval_as_leading_term(self, x, cdir=0): for t in self: if t is not S.Zero: return t def _eval_term(self, pt): if pt == 0: return self.a0 return self.an.coeff(pt) + self.bn.coeff(pt) def __neg__(self): return self.scale(-1) def __add__(self, other): if isinstance(other, FourierSeries): if self.period != other.period: raise ValueError("Both the series should have same periods") x, y = self.x, other.x function = self.function + other.function.subs(y, x) if self.x not in function.free_symbols: return function an = self.an + other.an bn = self.bn + other.bn a0 = self.a0 + other.a0 return self.func(function, self.args[1], (a0, an, bn)) return Add(self, other) def __sub__(self, other): return self.__add__(-other) class FiniteFourierSeries(FourierSeries): r"""Represents Finite Fourier sine/cosine series. For how to compute Fourier series, see the :func:`fourier_series` docstring. Parameters ========== f : Expr Expression for finding fourier_series limits : ( x, start, stop) x is the independent variable for the expression f (start, stop) is the period of the fourier series exprs: (a0, an, bn) or Expr a0 is the constant term a0 of the fourier series an is a dictionary of coefficients of cos terms an[k] = coefficient of cos(pi(k/L)x) bn is a dictionary of coefficients of sin terms bn[k] = coefficient of sin(pi(k/L)x) or exprs can be an expression to be converted to fourier form Methods ======= This class is an extension of FourierSeries class. Please refer to sympy.series.fourier.FourierSeries for further information. See Also ======== sympy.series.fourier.FourierSeries sympy.series.fourier.fourier_series """ def __new__(cls, f, limits, exprs): f = sympify(f) limits = sympify(limits) exprs = sympify(exprs) if not (type(exprs) == Tuple and len(exprs) == 3): # exprs is not of form (a0, an, bn) # Converts the expression to fourier form c, e = exprs.as_coeff_add() rexpr = c + Add([TR10(i) for i in e]) a0, exp_ls = rexpr.expand(trig=False, power_base=False, power_exp=False, log=False).as_coeff_add() x = limits[0] L = abs(limits[2] - limits[1]) / 2 a = Wild('a', properties=[lambda k: k.is_Integer, lambda k: k is not S.Zero, ]) b = Wild('b', properties=[lambda k: x not in k.free_symbols, ]) an = dict() bn = dict() # separates the coefficients of sin and cos terms in dictionaries an, and bn for p in exp_ls: t = p.match(b cos(a * (pi / L) * x)) q = p.match(b * sin(a * (pi / L) * x)) if t: an[t[a]] = t[b] + an.get(t[a], S.Zero) elif q: bn[q[a]] = q[b] + bn.get(q[a], S.Zero) else: a0 += p exprs = Tuple(a0, an, bn) return Expr.__new__(cls, f, limits, exprs) @property def interval(self): _length = 1 if self.a0 else 0 _length += max(set(self.an.keys()).union(set(self.bn.keys()))) + 1 return Interval(0, _length) @property def length(self): return self.stop - self.start def shiftx(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate().subs(x, x + s) sfunc = self.function.subs(x, x + s) return self.func(sfunc, self.args[1], _expr) def scale(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate() * s sfunc = self.function * s return self.func(sfunc, self.args[1], _expr) def scalex(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate().subs(x, x * s) sfunc = self.function.subs(x, x * s) return self.func(sfunc, self.args[1], _expr) def _eval_term(self, pt): if pt == 0: return self.a0 _term = self.an.get(pt, S.Zero) * cos(pt * (pi / self.L) * self.x) \ + self.bn.get(pt, S.Zero) * sin(pt * (pi / self.L) * self.x) return _term def __add__(self, other): if isinstance(other, FourierSeries): return other.__add__(fourier_series(self.function, self.args[1],\ finite=False)) elif isinstance(other, FiniteFourierSeries): if self.period != other.period: raise ValueError("Both the series should have same periods") x, y = self.x, other.x function = self.function + other.function.subs(y, x) if self.x not in function.free_symbols: return function return fourier_series(function, limits=self.args[1]) def fourier_series(f, limits=None, finite=True): r"""Computes the Fourier trigonometric series expansion. Explanation =========== Fourier trigonometric series of $f(x)$ over the interval $(a, b)$ is defined as: .. math:: \frac{a_0}{2} + \sum_{n=1}^{\infty} (a_n \cos(\frac{2n \pi x}{L}) + b_n \sin(\frac{2n \pi x}{L})) where the coefficients are: .. math:: L = b - a .. math:: a_0 = \frac{2}{L} \int_{a}^{b}{f(x) dx} .. math:: a_n = \frac{2}{L} \int_{a}^{b}{f(x) \cos(\frac{2n \pi x}{L}) dx} .. math:: b_n = \frac{2}{L} \int_{a}^{b}{f(x) \sin(\frac{2n \pi x}{L}) dx} The condition whether the function $f(x)$ given should be periodic or not is more than necessary, because it is sufficient to consider the series to be converging to $f(x)$ only in the given interval, not throughout the whole real line. This also brings a lot of ease for the computation because you don't have to make $f(x)$ artificially periodic by wrapping it with piecewise, modulo operations, but you can shape the function to look like the desired periodic function only in the interval $(a, b)$, and the computed series will automatically become the series of the periodic version of $f(x)$. This property is illustrated in the examples section below. Parameters ========== limits : (sym, start, end), optional sym denotes the symbol the series is computed with respect to. start and end denotes the start and the end of the interval where the fourier series converges to the given function. Default range is specified as $-\pi$ and $\pi$. Returns ======= FourierSeries A symbolic object representing the Fourier trigonometric series. Examples ======== Computing the Fourier series of $f(x) = x^2$: >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> f = x*2 >>> s = fourier_series(f, (x, -pi, pi)) >>> s1 = s.truncate(n=3) >>> s1 -4cos(x) + cos(2x) + pi2/3 Shifting of the Fourier series: >>> s.shift(1).truncate() -4cos(x) + cos(2x) + 1 + pi2/3 >>> s.shiftx(1).truncate() -4cos(x + 1) + cos(2x + 2) + pi2/3 Scaling of the Fourier series: >>> s.scale(2).truncate() -8cos(x) + 2cos(2x) + 2pi2/3 >>> s.scalex(2).truncate() -4cos(2x) + cos(4x) + pi2/3 Computing the Fourier series of $f(x) = x$: This illustrates how truncating to the higher order gives better convergence. .. plot:: :context: reset :format: doctest :include-source: True >>> from sympy import fourier_series, pi, plot >>> from sympy.abc import x >>> f = x >>> s = fourier_series(f, (x, -pi, pi)) >>> s1 = s.truncate(n = 3) >>> s2 = s.truncate(n = 5) >>> s3 = s.truncate(n = 7) >>> p = plot(f, s1, s2, s3, (x, -pi, pi), show=False, legend=True) >>> p[0].line_color = (0, 0, 0) >>> p[0].label = 'x' >>> p[1].line_color = (0.7, 0.7, 0.7) >>> p[1].label = 'n=3' >>> p[2].line_color = (0.5, 0.5, 0.5) >>> p[2].label = 'n=5' >>> p[3].line_color = (0.3, 0.3, 0.3) >>> p[3].label = 'n=7' >>> p.show() This illustrates how the series converges to different sawtooth waves if the different ranges are specified. .. plot:: :context: close-figs :format: doctest :include-source: True >>> s1 = fourier_series(x, (x, -1, 1)).truncate(10) >>> s2 = fourier_series(x, (x, -pi, pi)).truncate(10) >>> s3 = fourier_series(x, (x, 0, 1)).truncate(10) >>> p = plot(x, s1, s2, s3, (x, -5, 5), show=False, legend=True) >>> p[0].line_color = (0, 0, 0) >>> p[0].label = 'x' >>> p[1].line_color = (0.7, 0.7, 0.7) >>> p[1].label = '[-1, 1]' >>> p[2].line_color = (0.5, 0.5, 0.5) >>> p[2].label = '[-pi, pi]' >>> p[3].line_color = (0.3, 0.3, 0.3) >>> p[3].label = '[0, 1]' >>> p.show() Notes ===== Computing Fourier series can be slow due to the integration required in computing an, bn. It is faster to compute Fourier series of a function by using shifting and scaling on an already computed Fourier series rather than computing again. e.g. If the Fourier series of ``x2`` is known the Fourier series of ``x**2 - 1`` can be found by shifting by ``-1``. See Also ======== sympy.series.fourier.FourierSeries References ========== .. [1] https://mathworld.wolfram.com/FourierSeries.html """ f = sympify(f) limits = _process_limits(f, limits) x = limits[0] if x not in f.free_symbols: return f if finite: L = abs(limits[2] - limits[1]) / 2 is_finite, res_f = finite_check(f, x, L) if is_finite: return FiniteFourierSeries(f, limits, res_f) n = Dummy('n') center = (limits[1] + limits[2]) / 2 if center.is_zero: neg_f = f.subs(x, -x) if f == neg_f: a0, an = fourier_cos_seq(f, limits, n) bn = SeqFormula(0, (1, oo)) return FourierSeries(f, limits, (a0, an, bn)) elif f == -neg_f: a0 = S.Zero an = SeqFormula(0, (1, oo)) bn = fourier_sin_seq(f, limits, n) return FourierSeries(f, limits, (a0, an, bn)) a0, an = fourier_cos_seq(f, limits, n) bn = fourier_sin_seq(f, limits, n) return FourierSeries(f, limits, (a0, an, bn))
5844a3acac836e1030ec18ed03e3b63e1ca71213790653f69a4f9c62cfffe584	""" This module implements the Residue function and related tools for working with residues. """ from sympy import sympify from sympy.utilities.timeutils import timethis @timethis('residue') def residue(expr, x, x0): """ Finds the residue of ``expr`` at the point x=x0. The residue is defined as the coefficient of 1/(x-x0) in the power series expansion about x=x0. Examples ======== >>> from sympy import Symbol, residue, sin >>> x = Symbol("x") >>> residue(1/x, x, 0) 1 >>> residue(1/x*2, x, 0) 0 >>> residue(2/sin(x), x, 0) 2 This function is essential for the Residue Theorem [1]. References ========== .. [1] https://en.wikipedia.org/wiki/Residue_theorem """ # The current implementation uses series expansion to # calculate it. A more general implementation is explained in # the section 5.6 of the Bronstein's book {M. Bronstein: # Symbolic Integration I, Springer Verlag (2005)}. For purely # rational functions, the algorithm is much easier. See # sections 2.4, 2.5, and 2.7 (this section actually gives an # algorithm for computing any Laurent series coefficient for # a rational function). The theory in section 2.4 will help to # understand why the resultant works in the general algorithm. # For the definition of a resultant, see section 1.4 (and any # previous sections for more review). from sympy import collect, Mul, Order, S expr = sympify(expr) if x0 != 0: expr = expr.subs(x, x + x0) for n in [0, 1, 2, 4, 8, 16, 32]: s = expr.nseries(x, n=n) if not s.has(Order) or s.getn() >= 0: break s = collect(s.removeO(), x) if s.is_Add: args = s.args else: args = [s] res = S.Zero for arg in args: c, m = arg.as_coeff_mul(x) m = Mul(m) if not (m == 1 or m == x or (m.is_Pow and m.exp.is_Integer)): raise NotImplementedError('term of unexpected form: %s' % m) if m == 1/x: res += c return res
2f39430a9d0224e848a62b0f493977273a4cc94f377d5a4fd9d626f0172e0b5a	"""Formal Power Series""" from collections import defaultdict from sympy import oo, zoo, nan from sympy.core.add import Add from sympy.core.compatibility import iterable from sympy.core.expr import Expr from sympy.core.function import Derivative, Function, expand from sympy.core.mul import Mul from sympy.core.numbers import Rational from sympy.core.relational import Eq from sympy.sets.sets import Interval from sympy.core.singleton import S from sympy.core.symbol import Wild, Dummy, symbols, Symbol from sympy.core.sympify import sympify from sympy.discrete.convolutions import convolution from sympy.functions.combinatorial.factorials import binomial, factorial, rf from sympy.functions.combinatorial.numbers import bell from sympy.functions.elementary.integers import floor, frac, ceiling from sympy.functions.elementary.miscellaneous import Min, Max from sympy.functions.elementary.piecewise import Piecewise from sympy.series.limits import Limit from sympy.series.order import Order from sympy.simplify.powsimp import powsimp from sympy.series.sequences import sequence from sympy.series.series_class import SeriesBase def rational_algorithm(f, x, k, order=4, full=False): """ Rational algorithm for computing formula of coefficients of Formal Power Series of a function. Applicable when f(x) or some derivative of f(x) is a rational function in x. :func:`rational_algorithm` uses :func:`~.apart` function for partial fraction decomposition. :func:`~.apart` by default uses 'undetermined coefficients method'. By setting ``full=True``, 'Bronstein's algorithm' can be used instead. Looks for derivative of a function up to 4'th order (by default). This can be overridden using order option. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import log, atan >>> from sympy.series.formal import rational_algorithm as ra >>> from sympy.abc import x, k >>> ra(1 / (1 - x), x, k) (1, 0, 0) >>> ra(log(1 + x), x, k) (-(-1)*(-k)/k, 0, 1) >>> ra(atan(x), x, k, full=True) ((-I(-I)*(-k)/2 + II*(-k)/2)/k, 0, 1) Notes ===== By setting ``full=True``, range of admissible functions to be solved using ``rational_algorithm`` can be increased. This option should be used carefully as it can significantly slow down the computation as ``doit`` is performed on the :class:`~.RootSum` object returned by the :func:`~.apart` function. Use ``full=False`` whenever possible. See Also ======== sympy.polys.partfrac.apart References ========== .. [1] Formal Power Series - Dominik Gruntz, Wolfram Koepf .. [2] Power Series in Computer Algebra - Wolfram Koepf """ from sympy.polys import RootSum, apart from sympy.integrals import integrate diff = f ds = [] # list of diff for i in range(order + 1): if i: diff = diff.diff(x) if diff.is_rational_function(x): coeff, sep = S.Zero, S.Zero terms = apart(diff, x, full=full) if terms.has(RootSum): terms = terms.doit() for t in Add.make_args(terms): num, den = t.as_numer_denom() if not den.has(x): sep += t else: if isinstance(den, Mul): # m(nx - a)j -> (nx - a)*j ind = den.as_independent(x) den = ind[1] num /= ind[0] # (nx - a)j -> (x - b) den, j = den.as_base_exp() a, xterm = den.as_coeff_add(x) # term -> m/xn if not a: sep += t continue xc = xterm[0].coeff(x) a /= -xc num /= xcj ak = ((-1)j * num * binomial(j + k - 1, k).rewrite(factorial) / a(j + k)) coeff += ak # Hacky, better way? if coeff.is_zero: return None if (coeff.has(x) or coeff.has(zoo) or coeff.has(oo) or coeff.has(nan)): return None for j in range(i): coeff = (coeff / (k + j + 1)) sep = integrate(sep, x) sep += (ds.pop() - sep).limit(x, 0) # constant of integration return (coeff.subs(k, k - i), sep, i) else: ds.append(diff) return None def rational_independent(terms, x): """Returns a list of all the rationally independent terms. Examples ======== >>> from sympy import sin, cos >>> from sympy.series.formal import rational_independent >>> from sympy.abc import x >>> rational_independent([cos(x), sin(x)], x) [cos(x), sin(x)] >>> rational_independent([x2, sin(x), xsin(x), x3], x) [x3 + x2, xsin(x) + sin(x)] """ if not terms: return [] ind = terms[0:1] for t in terms[1:]: n = t.as_independent(x)[1] for i, term in enumerate(ind): d = term.as_independent(x)[1] q = (n / d).cancel() if q.is_rational_function(x): ind[i] += t break else: ind.append(t) return ind def simpleDE(f, x, g, order=4): r"""Generates simple DE. DE is of the form .. math:: f^k(x) + \sum\limits_{j=0}^{k-1} A_j f^j(x) = 0 where :math:`A_j` should be rational function in x. Generates DE's upto order 4 (default). DE's can also have free parameters. By increasing order, higher order DE's can be found. Yields a tuple of (DE, order). """ from sympy.solvers.solveset import linsolve a = symbols('a:%d' % (order)) def _makeDE(k): eq = f.diff(x, k) + Add([a[i]f.diff(x, i) for i in range(0, k)]) DE = g(x).diff(x, k) + Add([a[i]g(x).diff(x, i) for i in range(0, k)]) return eq, DE found = False for k in range(1, order + 1): eq, DE = _makeDE(k) eq = eq.expand() terms = eq.as_ordered_terms() ind = rational_independent(terms, x) if found or len(ind) == k: sol = dict(zip(a, (i for s in linsolve(ind, a[:k]) for i in s))) if sol: found = True DE = DE.subs(sol) DE = DE.as_numer_denom()[0] DE = DE.factor().as_coeff_mul(Derivative)[1][0] yield DE.collect(Derivative(g(x))), k def exp_re(DE, r, k): """Converts a DE with constant coefficients (explike) into a RE. Performs the substitution: .. math:: f^j(x) \\to r(k + j) Normalises the terms so that lowest order of a term is always r(k). Examples ======== >>> from sympy import Function, Derivative >>> from sympy.series.formal import exp_re >>> from sympy.abc import x, k >>> f, r = Function('f'), Function('r') >>> exp_re(-f(x) + Derivative(f(x)), r, k) -r(k) + r(k + 1) >>> exp_re(Derivative(f(x), x) + Derivative(f(x), (x, 2)), r, k) r(k) + r(k + 1) See Also ======== sympy.series.formal.hyper_re """ RE = S.Zero g = DE.atoms(Function).pop() mini = None for t in Add.make_args(DE): coeff, d = t.as_independent(g) if isinstance(d, Derivative): j = d.derivative_count else: j = 0 if mini is None or j < mini: mini = j RE += coeff * r(k + j) if mini: RE = RE.subs(k, k - mini) return RE def hyper_re(DE, r, k): """Converts a DE into a RE. Performs the substitution: .. math:: x^l f^j(x) \\to (k + 1 - l)_j . a_{k + j - l} Normalises the terms so that lowest order of a term is always r(k). Examples ======== >>> from sympy import Function, Derivative >>> from sympy.series.formal import hyper_re >>> from sympy.abc import x, k >>> f, r = Function('f'), Function('r') >>> hyper_re(-f(x) + Derivative(f(x)), r, k) (k + 1)r(k + 1) - r(k) >>> hyper_re(-xf(x) + Derivative(f(x), (x, 2)), r, k) (k + 2)(k + 3)r(k + 3) - r(k) See Also ======== sympy.series.formal.exp_re """ RE = S.Zero g = DE.atoms(Function).pop() x = g.atoms(Symbol).pop() mini = None for t in Add.make_args(DE.expand()): coeff, d = t.as_independent(g) c, v = coeff.as_independent(x) l = v.as_coeff_exponent(x)[1] if isinstance(d, Derivative): j = d.derivative_count else: j = 0 RE += c * rf(k + 1 - l, j) * r(k + j - l) if mini is None or j - l < mini: mini = j - l RE = RE.subs(k, k - mini) m = Wild('m') return RE.collect(r(k + m)) def _transformation_a(f, x, P, Q, k, m, shift): f = x(-shift) P = P.subs(k, k + shift) Q = Q.subs(k, k + shift) return f, P, Q, m def _transformation_c(f, x, P, Q, k, m, scale): f = f.subs(x, xscale) P = P.subs(k, k / scale) Q = Q.subs(k, k / scale) m = scale return f, P, Q, m def _transformation_e(f, x, P, Q, k, m): f = f.diff(x) P = P.subs(k, k + 1) * (k + m + 1) Q = Q.subs(k, k + 1) * (k + 1) return f, P, Q, m def _apply_shift(sol, shift): return [(res, cond + shift) for res, cond in sol] def _apply_scale(sol, scale): return [(res, cond / scale) for res, cond in sol] def _apply_integrate(sol, x, k): return [(res / ((cond + 1)(cond.as_coeff_Add()[1].coeff(k))), cond + 1) for res, cond in sol] def _compute_formula(f, x, P, Q, k, m, k_max): """Computes the formula for f.""" from sympy.polys import roots sol = [] for i in range(k_max + 1, k_max + m + 1): if (i < 0) == True: continue r = f.diff(x, i).limit(x, 0) / factorial(i) if r.is_zero: continue kterm = mk + i res = r p = P.subs(k, kterm) q = Q.subs(k, kterm) c1 = p.subs(k, 1/k).leadterm(k)[0] c2 = q.subs(k, 1/k).leadterm(k)[0] res = (-c1 / c2)k for r, mul in roots(p, k).items(): res = rf(-r, k)mul for r, mul in roots(q, k).items(): res /= rf(-r, k)mul sol.append((res, kterm)) return sol def _rsolve_hypergeometric(f, x, P, Q, k, m): """Recursive wrapper to rsolve_hypergeometric. Returns a Tuple of (formula, series independent terms, maximum power of x in independent terms) if successful otherwise ``None``. See :func:`rsolve_hypergeometric` for details. """ from sympy.polys import lcm, roots from sympy.integrals import integrate # transformation - c proots, qroots = roots(P, k), roots(Q, k) all_roots = dict(proots) all_roots.update(qroots) scale = lcm([r.as_numer_denom()[1] for r, t in all_roots.items() if r.is_rational]) f, P, Q, m = _transformation_c(f, x, P, Q, k, m, scale) # transformation - a qroots = roots(Q, k) if qroots: k_min = Min(qroots.keys()) else: k_min = S.Zero shift = k_min + m f, P, Q, m = _transformation_a(f, x, P, Q, k, m, shift) l = (xf).limit(x, 0) if not isinstance(l, Limit) and l != 0: # Ideally should only be l != 0 return None qroots = roots(Q, k) if qroots: k_max = Max(qroots.keys()) else: k_max = S.Zero ind, mp = S.Zero, -oo for i in range(k_max + m + 1): r = f.diff(x, i).limit(x, 0) / factorial(i) if r.is_finite is False: old_f = f f, P, Q, m = _transformation_a(f, x, P, Q, k, m, i) f, P, Q, m = _transformation_e(f, x, P, Q, k, m) sol, ind, mp = _rsolve_hypergeometric(f, x, P, Q, k, m) sol = _apply_integrate(sol, x, k) sol = _apply_shift(sol, i) ind = integrate(ind, x) ind += (old_f - ind).limit(x, 0) # constant of integration mp += 1 return sol, ind, mp elif r: ind += rx(i + shift) pow_x = Rational((i + shift), scale) if pow_x > mp: mp = pow_x # maximum power of x ind = ind.subs(x, x(1/scale)) sol = _compute_formula(f, x, P, Q, k, m, k_max) sol = _apply_shift(sol, shift) sol = _apply_scale(sol, scale) return sol, ind, mp def rsolve_hypergeometric(f, x, P, Q, k, m): """Solves RE of hypergeometric type. Attempts to solve RE of the form Q(k)a(k + m) - P(k)a(k) Transformations that preserve Hypergeometric type: a. x*nf(x): b(k + m) = R(k - n)b(k) b. f(Ax): b(k + m) = A*mR(k)b(k) c. f(xn): b(k + nm) = R(k/n)b(k) d. f(x(1/m)): b(k + 1) = R(km)b(k) e. f'(x): b(k + m) = ((k + m + 1)/(k + 1))R(k + 1)b(k) Some of these transformations have been used to solve the RE. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import exp, ln, S >>> from sympy.series.formal import rsolve_hypergeometric as rh >>> from sympy.abc import x, k >>> rh(exp(x), x, -S.One, (k + 1), k, 1) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> rh(ln(1 + x), x, k2, k(k + 1), k, 1) (Piecewise(((-1)*(k - 1)factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) References ========== .. [1] Formal Power Series - Dominik Gruntz, Wolfram Koepf .. [2] Power Series in Computer Algebra - Wolfram Koepf """ result = _rsolve_hypergeometric(f, x, P, Q, k, m) if result is None: return None sol_list, ind, mp = result sol_dict = defaultdict(lambda: S.Zero) for res, cond in sol_list: j, mk = cond.as_coeff_Add() c = mk.coeff(k) if j.is_integer is False: res = xfrac(j) j = floor(j) res = res.subs(k, (k - j) / c) cond = Eq(k % c, j % c) sol_dict[cond] += res # Group together formula for same conditions sol = [] for cond, res in sol_dict.items(): sol.append((res, cond)) sol.append((S.Zero, True)) sol = Piecewise(sol) if mp is -oo: s = S.Zero elif mp.is_integer is False: s = ceiling(mp) else: s = mp + 1 # save all the terms of # form 1/x*k in ind if s < 0: ind += sum(sequence(sol x*k, (k, s, -1))) s = S.Zero return (sol, ind, s) def _solve_hyper_RE(f, x, RE, g, k): """See docstring of :func:`rsolve_hypergeometric` for details.""" terms = Add.make_args(RE) if len(terms) == 2: gs = list(RE.atoms(Function)) P, Q = map(RE.coeff, gs) m = gs[1].args[0] - gs[0].args[0] if m < 0: P, Q = Q, P m = abs(m) return rsolve_hypergeometric(f, x, P, Q, k, m) def _solve_explike_DE(f, x, DE, g, k): """Solves DE with constant coefficients.""" from sympy.solvers import rsolve for t in Add.make_args(DE): coeff, d = t.as_independent(g) if coeff.free_symbols: return RE = exp_re(DE, g, k) init = {} for i in range(len(Add.make_args(RE))): if i: f = f.diff(x) init[g(k).subs(k, i)] = f.limit(x, 0) sol = rsolve(RE, g(k), init) if sol: return (sol / factorial(k), S.Zero, S.Zero) def _solve_simple(f, x, DE, g, k): """Converts DE into RE and solves using :func:`rsolve`.""" from sympy.solvers import rsolve RE = hyper_re(DE, g, k) init = {} for i in range(len(Add.make_args(RE))): if i: f = f.diff(x) init[g(k).subs(k, i)] = f.limit(x, 0) / factorial(i) sol = rsolve(RE, g(k), init) if sol: return (sol, S.Zero, S.Zero) def _transform_explike_DE(DE, g, x, order, syms): """Converts DE with free parameters into DE with constant coefficients.""" from sympy.solvers.solveset import linsolve eq = [] highest_coeff = DE.coeff(Derivative(g(x), x, order)) for i in range(order): coeff = DE.coeff(Derivative(g(x), x, i)) coeff = (coeff / highest_coeff).expand().collect(x) for t in Add.make_args(coeff): eq.append(t) temp = [] for e in eq: if e.has(x): break elif e.has(Symbol): temp.append(e) else: eq = temp if eq: sol = dict(zip(syms, (i for s in linsolve(eq, list(syms)) for i in s))) if sol: DE = DE.subs(sol) DE = DE.factor().as_coeff_mul(Derivative)[1][0] DE = DE.collect(Derivative(g(x))) return DE def _transform_DE_RE(DE, g, k, order, syms): """Converts DE with free parameters into RE of hypergeometric type.""" from sympy.solvers.solveset import linsolve RE = hyper_re(DE, g, k) eq = [] for i in range(1, order): coeff = RE.coeff(g(k + i)) eq.append(coeff) sol = dict(zip(syms, (i for s in linsolve(eq, list(syms)) for i in s))) if sol: m = Wild('m') RE = RE.subs(sol) RE = RE.factor().as_numer_denom()[0].collect(g(k + m)) RE = RE.as_coeff_mul(g)[1][0] for i in range(order): # smallest order should be g(k) if RE.coeff(g(k + i)) and i: RE = RE.subs(k, k - i) break return RE def solve_de(f, x, DE, order, g, k): """Solves the DE. Tries to solve DE by either converting into a RE containing two terms or converting into a DE having constant coefficients. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import Derivative as D, Function >>> from sympy import exp, ln >>> from sympy.series.formal import solve_de >>> from sympy.abc import x, k >>> f = Function('f') >>> solve_de(exp(x), x, D(f(x), x) - f(x), 1, f, k) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> solve_de(ln(1 + x), x, (x + 1)D(f(x), x, 2) + D(f(x)), 2, f, k) (Piecewise(((-1)*(k - 1)factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) """ sol = None syms = DE.free_symbols.difference({g, x}) if syms: RE = _transform_DE_RE(DE, g, k, order, syms) else: RE = hyper_re(DE, g, k) if not RE.free_symbols.difference({k}): sol = _solve_hyper_RE(f, x, RE, g, k) if sol: return sol if syms: DE = _transform_explike_DE(DE, g, x, order, syms) if not DE.free_symbols.difference({x}): sol = _solve_explike_DE(f, x, DE, g, k) if sol: return sol def hyper_algorithm(f, x, k, order=4): """Hypergeometric algorithm for computing Formal Power Series. Steps: * Generates DE * Convert the DE into RE * Solves the RE Examples ======== >>> from sympy import exp, ln >>> from sympy.series.formal import hyper_algorithm >>> from sympy.abc import x, k >>> hyper_algorithm(exp(x), x, k) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> hyper_algorithm(ln(1 + x), x, k) (Piecewise(((-1)*(k - 1)factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) See Also ======== sympy.series.formal.simpleDE sympy.series.formal.solve_de """ g = Function('g') des = [] # list of DE's sol = None for DE, i in simpleDE(f, x, g, order): if DE is not None: sol = solve_de(f, x, DE, i, g, k) if sol: return sol if not DE.free_symbols.difference({x}): des.append(DE) # If nothing works # Try plain rsolve for DE in des: sol = _solve_simple(f, x, DE, g, k) if sol: return sol def _compute_fps(f, x, x0, dir, hyper, order, rational, full): """Recursive wrapper to compute fps. See :func:`compute_fps` for details. """ if x0 in [S.Infinity, S.NegativeInfinity]: dir = S.One if x0 is S.Infinity else -S.One temp = f.subs(x, 1/x) result = _compute_fps(temp, x, 0, dir, hyper, order, rational, full) if result is None: return None return (result[0], result[1].subs(x, 1/x), result[2].subs(x, 1/x)) elif x0 or dir == -S.One: if dir == -S.One: rep = -x + x0 rep2 = -x rep2b = x0 else: rep = x + x0 rep2 = x rep2b = -x0 temp = f.subs(x, rep) result = _compute_fps(temp, x, 0, S.One, hyper, order, rational, full) if result is None: return None return (result[0], result[1].subs(x, rep2 + rep2b), result[2].subs(x, rep2 + rep2b)) if f.is_polynomial(x): k = Dummy('k') ak = sequence(Coeff(f, x, k), (k, 1, oo)) xk = sequence(x*k, (k, 0, oo)) ind = f.coeff(x, 0) return ak, xk, ind # Break instances of Add # this allows application of different # algorithms on different terms increasing the # range of admissible functions. if isinstance(f, Add): result = False ak = sequence(S.Zero, (0, oo)) ind, xk = S.Zero, None for t in Add.make_args(f): res = _compute_fps(t, x, 0, S.One, hyper, order, rational, full) if res: if not result: result = True xk = res[1] if res[0].start > ak.start: seq = ak s, f = ak.start, res[0].start else: seq = res[0] s, f = res[0].start, ak.start save = Add([z[0]z[1] for z in zip(seq[0:(f - s)], xk[s:f])]) ak += res[0] ind += res[2] + save else: ind += t if result: return ak, xk, ind return None # The symbolic term - symb, if present, is being separated from the function # Otherwise symb is being set to S.One syms = f.free_symbols.difference({x}) (f, symb) = expand(f).as_independent(syms) if symb.is_zero: symb = S.One symb = powsimp(symb) result = None # from here on it's x0=0 and dir=1 handling k = Dummy('k') if rational: result = rational_algorithm(f, x, k, order, full) if result is None and hyper: result = hyper_algorithm(f, x, k, order) if result is None: return None ak = sequence(result[0], (k, result[2], oo)) xk_formula = powsimp(x*k symb) xk = sequence(xk_formula, (k, 0, oo)) ind = powsimp(result[1] * symb) return ak, xk, ind def compute_fps(f, x, x0=0, dir=1, hyper=True, order=4, rational=True, full=False): """Computes the formula for Formal Power Series of a function. Tries to compute the formula by applying the following techniques (in order): * rational_algorithm * Hypergeometric algorithm Parameters ========== x : Symbol x0 : number, optional Point to perform series expansion about. Default is 0. dir : {1, -1, '+', '-'}, optional If dir is 1 or '+' the series is calculated from the right and for -1 or '-' the series is calculated from the left. For smooth functions this flag will not alter the results. Default is 1. hyper : {True, False}, optional Set hyper to False to skip the hypergeometric algorithm. By default it is set to False. order : int, optional Order of the derivative of ``f``, Default is 4. rational : {True, False}, optional Set rational to False to skip rational algorithm. By default it is set to True. full : {True, False}, optional Set full to True to increase the range of rational algorithm. See :func:`rational_algorithm` for details. By default it is set to False. Returns ======= ak : sequence Sequence of coefficients. xk : sequence Sequence of powers of x. ind : Expr Independent terms. mul : Pow Common terms. See Also ======== sympy.series.formal.rational_algorithm sympy.series.formal.hyper_algorithm """ f = sympify(f) x = sympify(x) if not f.has(x): return None x0 = sympify(x0) if dir == '+': dir = S.One elif dir == '-': dir = -S.One elif dir not in [S.One, -S.One]: raise ValueError("Dir must be '+' or '-'") else: dir = sympify(dir) return _compute_fps(f, x, x0, dir, hyper, order, rational, full) class Coeff(Function): """ Coeff(p, x, n) represents the nth coefficient of the polynomial p in x """ @classmethod def eval(cls, p, x, n): if p.is_polynomial(x) and n.is_integer: return p.coeff(x, n) class FormalPowerSeries(SeriesBase): """Represents Formal Power Series of a function. No computation is performed. This class should only to be used to represent a series. No checks are performed. For computing a series use :func:`fps`. See Also ======== sympy.series.formal.fps """ def __new__(cls, args): args = map(sympify, args) return Expr.__new__(cls, args) def __init__(self, args): ak = args[4][0] k = ak.variables[0] self.ak_seq = sequence(ak.formula, (k, 1, oo)) self.fact_seq = sequence(factorial(k), (k, 1, oo)) self.bell_coeff_seq = self.ak_seq self.fact_seq self.sign_seq = sequence((-1, 1), (k, 1, oo)) @property def function(self): return self.args[0] @property def x(self): return self.args[1] @property def x0(self): return self.args[2] @property def dir(self): return self.args[3] @property def ak(self): return self.args[4][0] @property def xk(self): return self.args[4][1] @property def ind(self): return self.args[4][2] @property def interval(self): return Interval(0, oo) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return oo @property def infinite(self): """Returns an infinite representation of the series""" from sympy.concrete import Sum ak, xk = self.ak, self.xk k = ak.variables[0] inf_sum = Sum(ak.formula * xk.formula, (k, ak.start, ak.stop)) return self.ind + inf_sum def _get_pow_x(self, term): """Returns the power of x in a term.""" xterm, pow_x = term.as_independent(self.x)[1].as_base_exp() if not xterm.has(self.x): return S.Zero return pow_x def polynomial(self, n=6): """Truncated series as polynomial. Returns series expansion of ``f`` upto order ``O(x*n)`` as a polynomial(without ``O`` term). """ terms = [] sym = self.free_symbols for i, t in enumerate(self): xp = self._get_pow_x(t) if xp.has(sym): xp = xp.as_coeff_add(sym)[0] if xp >= n: break elif xp.is_integer is True and i == n + 1: break elif t is not S.Zero: terms.append(t) return Add(terms) def truncate(self, n=6): """Truncated series. Returns truncated series expansion of f upto order ``O(x*n)``. If n is ``None``, returns an infinite iterator. """ if n is None: return iter(self) x, x0 = self.x, self.x0 pt_xk = self.xk.coeff(n) if x0 is S.NegativeInfinity: x0 = S.Infinity return self.polynomial(n) + Order(pt_xk, (x, x0)) def zero_coeff(self): return self._eval_term(0) def _eval_term(self, pt): try: pt_xk = self.xk.coeff(pt) pt_ak = self.ak.coeff(pt).simplify() # Simplify the coefficients except IndexError: term = S.Zero else: term = (pt_ak pt_xk) if self.ind: ind = S.Zero sym = self.free_symbols for t in Add.make_args(self.ind): pow_x = self._get_pow_x(t) if pow_x.has(sym): pow_x = pow_x.as_coeff_add(sym)[0] if pt == 0 and pow_x < 1: ind += t elif pow_x >= pt and pow_x < pt + 1: ind += t term += ind return term.collect(self.x) def _eval_subs(self, old, new): x = self.x if old.has(x): return self def _eval_as_leading_term(self, x, cdir=0): for t in self: if t is not S.Zero: return t def _eval_derivative(self, x): f = self.function.diff(x) ind = self.ind.diff(x) pow_xk = self._get_pow_x(self.xk.formula) ak = self.ak k = ak.variables[0] if ak.formula.has(x): form = [] for e, c in ak.formula.args: temp = S.Zero for t in Add.make_args(e): pow_x = self._get_pow_x(t) temp += t * (pow_xk + pow_x) form.append((temp, c)) form = Piecewise(form) ak = sequence(form.subs(k, k + 1), (k, ak.start - 1, ak.stop)) else: ak = sequence((ak.formula pow_xk).subs(k, k + 1), (k, ak.start - 1, ak.stop)) return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def integrate(self, x=None, kwargs): """Integrate Formal Power Series. Examples ======== >>> from sympy import fps, sin, integrate >>> from sympy.abc import x >>> f = fps(sin(x)) >>> f.integrate(x).truncate() -1 + x2/2 - x4/24 + O(x6) >>> integrate(f, (x, 0, 1)) 1 - cos(1) """ from sympy.integrals import integrate if x is None: x = self.x elif iterable(x): return integrate(self.function, x) f = integrate(self.function, x) ind = integrate(self.ind, x) ind += (f - ind).limit(x, 0) # constant of integration pow_xk = self._get_pow_x(self.xk.formula) ak = self.ak k = ak.variables[0] if ak.formula.has(x): form = [] for e, c in ak.formula.args: temp = S.Zero for t in Add.make_args(e): pow_x = self._get_pow_x(t) temp += t / (pow_xk + pow_x + 1) form.append((temp, c)) form = Piecewise(form) ak = sequence(form.subs(k, k - 1), (k, ak.start + 1, ak.stop)) else: ak = sequence((ak.formula / (pow_xk + 1)).subs(k, k - 1), (k, ak.start + 1, ak.stop)) return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def product(self, other, x=None, n=6): """Multiplies two Formal Power Series, using discrete convolution and return the truncated terms upto specified order. Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(sin(x)) >>> f2 = fps(exp(x)) >>> f1.product(f2, x).truncate(4) x + x2 + x3/3 + O(x4) See Also ======== sympy.discrete.convolutions sympy.series.formal.FormalPowerSeriesProduct """ if x is None: x = self.x if n is None: return iter(self) other = sympify(other) if not isinstance(other, FormalPowerSeries): raise ValueError("Both series should be an instance of FormalPowerSeries" " class.") if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") elif self.x != other.x: raise ValueError("Both series should have the same symbol.") return FormalPowerSeriesProduct(self, other) def coeff_bell(self, n): r""" self.coeff_bell(n) returns a sequence of Bell polynomials of the second kind. Note that ``n`` should be a integer. The second kind of Bell polynomials (are sometimes called "partial" Bell polynomials or incomplete Bell polynomials) are defined as .. math:: B_{n,k}(x_1, x_2,\dotsc x_{n-k+1}) = \sum_{j_1+j_2+j_2+\dotsb=k \atop j_1+2j_2+3j_2+\dotsb=n} \frac{n!}{j_1!j_2!\dotsb j_{n-k+1}!} \left(\frac{x_1}{1!} \right)^{j_1} \left(\frac{x_2}{2!} \right)^{j_2} \dotsb \left(\frac{x_{n-k+1}}{(n-k+1)!} \right) ^{j_{n-k+1}}. ``bell(n, k, (x1, x2, ...))`` gives Bell polynomials of the second kind, `B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1})`. See Also ======== sympy.functions.combinatorial.numbers.bell """ inner_coeffs = [bell(n, j, tuple(self.bell_coeff_seq[:n-j+1])) for j in range(1, n+1)] k = Dummy('k') return sequence(tuple(inner_coeffs), (k, 1, oo)) def compose(self, other, x=None, n=6): r""" Returns the truncated terms of the formal power series of the composed function, up to specified `n`. If `f` and `g` are two formal power series of two different functions, then the coefficient sequence ``ak`` of the composed formal power series `fp` will be as follows. .. math:: \sum\limits_{k=0}^{n} b_k B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1}) Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(sin(x)) >>> f1.compose(f2, x).truncate() 1 + x + x2/2 - x4/8 - x5/15 + O(x6) >>> f1.compose(f2, x).truncate(8) 1 + x + x2/2 - x4/8 - x5/15 - x6/240 + x7/90 + O(x8) See Also ======== sympy.functions.combinatorial.numbers.bell sympy.series.formal.FormalPowerSeriesCompose References ========== .. [1] Comtet, Louis: Advanced combinatorics; the art of finite and infinite expansions. Reidel, 1974. """ if x is None: x = self.x if n is None: return iter(self) other = sympify(other) if not isinstance(other, FormalPowerSeries): raise ValueError("Both series should be an instance of FormalPowerSeries" " class.") if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") elif self.x != other.x: raise ValueError("Both series should have the same symbol.") if other._eval_term(0).as_coeff_mul(other.x)[0] is not S.Zero: raise ValueError("The formal power series of the inner function should not have any " "constant coefficient term.") return FormalPowerSeriesCompose(self, other) def inverse(self, x=None, n=6): r""" Returns the truncated terms of the inverse of the formal power series, up to specified `n`. If `f` and `g` are two formal power series of two different functions, then the coefficient sequence ``ak`` of the composed formal power series `fp` will be as follows. .. math:: \sum\limits_{k=0}^{n} (-1)^{k} x_0^{-k-1} B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1}) Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, exp, cos >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(cos(x)) >>> f1.inverse(x).truncate() 1 - x + x2/2 - x3/6 + x4/24 - x5/120 + O(x6) >>> f2.inverse(x).truncate(8) 1 + x2/2 + 5x4/24 + 61x6/720 + O(x8) See Also ======== sympy.functions.combinatorial.numbers.bell sympy.series.formal.FormalPowerSeriesInverse References ========== .. [1] Comtet, Louis: Advanced combinatorics; the art of finite and infinite expansions. Reidel, 1974. """ if x is None: x = self.x if n is None: return iter(self) if self._eval_term(0).is_zero: raise ValueError("Constant coefficient should exist for an inverse of a formal" " power series to exist.") return FormalPowerSeriesInverse(self) def __add__(self, other): other = sympify(other) if isinstance(other, FormalPowerSeries): if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") x, y = self.x, other.x f = self.function + other.function.subs(y, x) if self.x not in f.free_symbols: return f ak = self.ak + other.ak if self.ak.start > other.ak.start: seq = other.ak s, e = other.ak.start, self.ak.start else: seq = self.ak s, e = self.ak.start, other.ak.start save = Add([z[0]z[1] for z in zip(seq[0:(e - s)], self.xk[s:e])]) ind = self.ind + other.ind + save return self.func(f, x, self.x0, self.dir, (ak, self.xk, ind)) elif not other.has(self.x): f = self.function + other ind = self.ind + other return self.func(f, self.x, self.x0, self.dir, (self.ak, self.xk, ind)) return Add(self, other) def __radd__(self, other): return self.__add__(other) def __neg__(self): return self.func(-self.function, self.x, self.x0, self.dir, (-self.ak, self.xk, -self.ind)) def __sub__(self, other): return self.__add__(-other) def __rsub__(self, other): return (-self).__add__(other) def __mul__(self, other): other = sympify(other) if other.has(self.x): return Mul(self, other) f = self.function * other ak = self.ak.coeff_mul(other) ind = self.ind * other return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def __rmul__(self, other): return self.__mul__(other) class FiniteFormalPowerSeries(FormalPowerSeries): """Base Class for Product, Compose and Inverse classes""" def __init__(self, args): pass @property def ffps(self): return self.args[0] @property def gfps(self): return self.args[1] @property def f(self): return self.ffps.function @property def g(self): return self.gfps.function @property def infinite(self): raise NotImplementedError("No infinite version for an object of" " FiniteFormalPowerSeries class.") def _eval_terms(self, n): raise NotImplementedError("(%s)._eval_terms()" % self) def _eval_term(self, pt): raise NotImplementedError("By the current logic, one can get terms" "upto a certain order, instead of getting term by term.") def polynomial(self, n): return self._eval_terms(n) def truncate(self, n=6): ffps = self.ffps pt_xk = ffps.xk.coeff(n) x, x0 = ffps.x, ffps.x0 return self.polynomial(n) + Order(pt_xk, (x, x0)) def _eval_derivative(self, x): raise NotImplementedError def integrate(self, x): raise NotImplementedError class FormalPowerSeriesProduct(FiniteFormalPowerSeries): """Represents the product of two formal power series of two functions. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There are two differences between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesProduct` object. The first argument contains the two functions involved in the product. Also, the coefficient sequence contains both the coefficient sequence of the formal power series of the involved functions. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ def __init__(self, args): ffps, gfps = self.ffps, self.gfps k = ffps.ak.variables[0] self.coeff1 = sequence(ffps.ak.formula, (k, 0, oo)) k = gfps.ak.variables[0] self.coeff2 = sequence(gfps.ak.formula, (k, 0, oo)) @property def function(self): """Function of the product of two formal power series.""" return self.f * self.g def _eval_terms(self, n): """ Returns the first `n` terms of the product formal power series. Term by term logic is implemented here. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(sin(x)) >>> f2 = fps(exp(x)) >>> fprod = f1.product(f2, x) >>> fprod._eval_terms(4) x3/3 + x2 + x See Also ======== sympy.series.formal.FormalPowerSeries.product """ coeff1, coeff2 = self.coeff1, self.coeff2 aks = convolution(coeff1[:n], coeff2[:n]) terms = [] for i in range(0, n): terms.append(aks[i] * self.ffps.xk.coeff(i)) return Add(terms) class FormalPowerSeriesCompose(FiniteFormalPowerSeries): """Represents the composed formal power series of two functions. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There are two differences between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesCompose` object. The first argument contains the outer function and the inner function involved in the omposition. Also, the coefficient sequence contains the generic sequence which is to be multiplied by a custom ``bell_seq`` finite sequence. The finite terms will then be added up to get the final terms. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ @property def function(self): """Function for the composed formal power series.""" f, g, x = self.f, self.g, self.ffps.x return f.subs(x, g) def _eval_terms(self, n): """ Returns the first `n` terms of the composed formal power series. Term by term logic is implemented here. The coefficient sequence of the :obj:`FormalPowerSeriesCompose` object is the generic sequence. It is multiplied by ``bell_seq`` to get a sequence, whose terms are added up to get the final terms for the polynomial. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(sin(x)) >>> fcomp = f1.compose(f2, x) >>> fcomp._eval_terms(6) -x5/15 - x4/8 + x2/2 + x + 1 >>> fcomp._eval_terms(8) x7/90 - x6/240 - x5/15 - x4/8 + x2/2 + x + 1 See Also ======== sympy.series.formal.FormalPowerSeries.compose sympy.series.formal.FormalPowerSeries.coeff_bell """ ffps, gfps = self.ffps, self.gfps terms = [ffps.zero_coeff()] for i in range(1, n): bell_seq = gfps.coeff_bell(i) seq = (ffps.bell_coeff_seq bell_seq) terms.append(Add((seq[:i])) / ffps.fact_seq[i-1] ffps.xk.coeff(i)) return Add(terms) class FormalPowerSeriesInverse(FiniteFormalPowerSeries): """Represents the Inverse of a formal power series. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There is a single difference between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesInverse` object. The coefficient sequence contains the generic sequence which is to be multiplied by a custom ``bell_seq`` finite sequence. The finite terms will then be added up to get the final terms. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ def __init__(self, args): ffps = self.ffps k = ffps.xk.variables[0] inv = ffps.zero_coeff() inv_seq = sequence(inv ** (-(k + 1)), (k, 1, oo)) self.aux_seq = ffps.sign_seq * ffps.fact_seq * inv_seq @property def function(self): """Function for the inverse of a formal power series.""" f = self.f return 1 / f @property def g(self): raise ValueError("Only one function is considered while performing" "inverse of a formal power series.") @property def gfps(self): raise ValueError("Only one function is considered while performing" "inverse of a formal power series.") def _eval_terms(self, n): """ Returns the first `n` terms of the composed formal power series. Term by term logic is implemented here. The coefficient sequence of the `FormalPowerSeriesInverse` object is the generic sequence. It is multiplied by ``bell_seq`` to get a sequence, whose terms are added up to get the final terms for the polynomial. Examples ======== >>> from sympy import fps, exp, cos >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(cos(x)) >>> finv1, finv2 = f1.inverse(), f2.inverse() >>> finv1._eval_terms(6) -x5/120 + x4/24 - x3/6 + x2/2 - x + 1 >>> finv2._eval_terms(8) 61x6/720 + 5x4/24 + x2/2 + 1 See Also ======== sympy.series.formal.FormalPowerSeries.inverse sympy.series.formal.FormalPowerSeries.coeff_bell """ ffps = self.ffps terms = [ffps.zero_coeff()] for i in range(1, n): bell_seq = ffps.coeff_bell(i) seq = (self.aux_seq * bell_seq) terms.append(Add((seq[:i])) / ffps.fact_seq[i-1] ffps.xk.coeff(i)) return Add(terms) def fps(f, x=None, x0=0, dir=1, hyper=True, order=4, rational=True, full=False): """Generates Formal Power Series of f. Returns the formal series expansion of ``f`` around ``x = x0`` with respect to ``x`` in the form of a ``FormalPowerSeries`` object. Formal Power Series is represented using an explicit formula computed using different algorithms. See :func:`compute_fps` for the more details regarding the computation of formula. Parameters ========== x : Symbol, optional If x is None and ``f`` is univariate, the univariate symbols will be supplied, otherwise an error will be raised. x0 : number, optional Point to perform series expansion about. Default is 0. dir : {1, -1, '+', '-'}, optional If dir is 1 or '+' the series is calculated from the right and for -1 or '-' the series is calculated from the left. For smooth functions this flag will not alter the results. Default is 1. hyper : {True, False}, optional Set hyper to False to skip the hypergeometric algorithm. By default it is set to False. order : int, optional Order of the derivative of ``f``, Default is 4. rational : {True, False}, optional Set rational to False to skip rational algorithm. By default it is set to True. full : {True, False}, optional Set full to True to increase the range of rational algorithm. See :func:`rational_algorithm` for details. By default it is set to False. Examples ======== >>> from sympy import fps, ln, atan, sin >>> from sympy.abc import x, n Rational Functions >>> fps(ln(1 + x)).truncate() x - x2/2 + x3/3 - x4/4 + x5/5 + O(x6) >>> fps(atan(x), full=True).truncate() x - x3/3 + x5/5 + O(x6) Symbolic Functions >>> fps(xnsin(x2), x).truncate(8) -x(n + 6)/6 + x(n + 2) + O(x(n + 8)) See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.compute_fps """ f = sympify(f) if x is None: free = f.free_symbols if len(free) == 1: x = free.pop() elif not free: return f else: raise NotImplementedError("multivariate formal power series") result = compute_fps(f, x, x0, dir, hyper, order, rational, full) if result is None: return f return FormalPowerSeries(f, x, x0, dir, result)
ea177139aa1de3f6c399e78491604b67c106794bccb7b6a951acdfb9df5812c5	from sympy.core import S, sympify, Expr, Rational, Dummy from sympy.core import Add, Mul, expand_power_base, expand_log from sympy.core.cache import cacheit from sympy.core.compatibility import default_sort_key, is_sequence from sympy.core.containers import Tuple from sympy.sets.sets import Complement from sympy.utilities.iterables import uniq class Order(Expr): r""" Represents the limiting behavior of some function The order of a function characterizes the function based on the limiting behavior of the function as it goes to some limit. Only taking the limit point to be a number is currently supported. This is expressed in big O notation [1]_. The formal definition for the order of a function `g(x)` about a point `a` is such that `g(x) = O(f(x))` as `x \rightarrow a` if and only if for any `\delta > 0` there exists a `M > 0` such that `\|g(x)\| \leq M\|f(x)\|` for `\|x-a\| < \delta`. This is equivalent to `\lim_{x \rightarrow a} \sup \|g(x)/f(x)\| < \infty`. Let's illustrate it on the following example by taking the expansion of `\sin(x)` about 0: .. math :: \sin(x) = x - x^3/3! + O(x^5) where in this case `O(x^5) = x^5/5! - x^7/7! + \cdots`. By the definition of `O`, for any `\delta > 0` there is an `M` such that: .. math :: \|x^5/5! - x^7/7! + ....\| <= M\|x^5\| \text{ for } \|x\| < \delta or by the alternate definition: .. math :: \lim_{x \rightarrow 0} \| (x^5/5! - x^7/7! + ....) / x^5\| < \infty which surely is true, because .. math :: \lim_{x \rightarrow 0} \| (x^5/5! - x^7/7! + ....) / x^5\| = 1/5! As it is usually used, the order of a function can be intuitively thought of representing all terms of powers greater than the one specified. For example, `O(x^3)` corresponds to any terms proportional to `x^3, x^4,\ldots` and any higher power. For a polynomial, this leaves terms proportional to `x^2`, `x` and constants. Examples ======== >>> from sympy import O, oo, cos, pi >>> from sympy.abc import x, y >>> O(x + x2) O(x) >>> O(x + x2, (x, 0)) O(x) >>> O(x + x2, (x, oo)) O(x2, (x, oo)) >>> O(1 + xy) O(1, x, y) >>> O(1 + xy, (x, 0), (y, 0)) O(1, x, y) >>> O(1 + xy, (x, oo), (y, oo)) O(xy, (x, oo), (y, oo)) >>> O(1) in O(1, x) True >>> O(1, x) in O(1) False >>> O(x) in O(1, x) True >>> O(x*2) in O(x) True >>> O(x)x O(x*2) >>> O(x) - O(x) O(x) >>> O(cos(x)) O(1) >>> O(cos(x), (x, pi/2)) O(x - pi/2, (x, pi/2)) References ========== .. [1] `Big O notation <https://en.wikipedia.org/wiki/Big_O_notation>`_ Notes ===== In ``O(f(x), x)`` the expression ``f(x)`` is assumed to have a leading term. ``O(f(x), x)`` is automatically transformed to ``O(f(x).as_leading_term(x),x)``. ``O(exprf(x), x)`` is ``O(f(x), x)`` ``O(expr, x)`` is ``O(1)`` ``O(0, x)`` is 0. Multivariate O is also supported: ``O(f(x, y), x, y)`` is transformed to ``O(f(x, y).as_leading_term(x,y).as_leading_term(y), x, y)`` In the multivariate case, it is assumed the limits w.r.t. the various symbols commute. If no symbols are passed then all symbols in the expression are used and the limit point is assumed to be zero. """ is_Order = True __slots__ = () @cacheit def __new__(cls, expr, args, kwargs): expr = sympify(expr) if not args: if expr.is_Order: variables = expr.variables point = expr.point else: variables = list(expr.free_symbols) point = [S.Zero]len(variables) else: args = list(args if is_sequence(args) else [args]) variables, point = [], [] if is_sequence(args[0]): for a in args: v, p = list(map(sympify, a)) variables.append(v) point.append(p) else: variables = list(map(sympify, args)) point = [S.Zero]len(variables) if not all(v.is_symbol for v in variables): raise TypeError('Variables are not symbols, got %s' % variables) if len(list(uniq(variables))) != len(variables): raise ValueError('Variables are supposed to be unique symbols, got %s' % variables) if expr.is_Order: expr_vp = dict(expr.args[1:]) new_vp = dict(expr_vp) vp = dict(zip(variables, point)) for v, p in vp.items(): if v in new_vp.keys(): if p != new_vp[v]: raise NotImplementedError( "Mixing Order at different points is not supported.") else: new_vp[v] = p if set(expr_vp.keys()) == set(new_vp.keys()): return expr else: variables = list(new_vp.keys()) point = [new_vp[v] for v in variables] if expr is S.NaN: return S.NaN if any(x in p.free_symbols for x in variables for p in point): raise ValueError('Got %s as a point.' % point) if variables: if any(p != point[0] for p in point): raise NotImplementedError( "Multivariable orders at different points are not supported.") if point[0] is S.Infinity: s = {k: 1/Dummy() for k in variables} rs = {1/v: 1/k for k, v in s.items()} elif point[0] is S.NegativeInfinity: s = {k: -1/Dummy() for k in variables} rs = {-1/v: -1/k for k, v in s.items()} elif point[0] is not S.Zero: s = {k: Dummy() + point[0] for k in variables} rs = {v - point[0]: k - point[0] for k, v in s.items()} else: s = () rs = () expr = expr.subs(s) if expr.is_Add: expr = expr.factor() if s: args = tuple([r[0] for r in rs.items()]) else: args = tuple(variables) if len(variables) > 1: # XXX: better way? We need this expand() to # workaround e.g: expr = x(x + y). # (x(x + y)).as_leading_term(x, y) currently returns # xy (wrong order term!). That's why we want to deal with # expand()'ed expr (handled in "if expr.is_Add" branch below). expr = expr.expand() old_expr = None while old_expr != expr: old_expr = expr if expr.is_Add: lst = expr.extract_leading_order(args) expr = Add([f.expr for (e, f) in lst]) elif expr: expr = expr.as_leading_term(args) expr = expr.as_independent(args, as_Add=False)[1] expr = expand_power_base(expr) expr = expand_log(expr) if len(args) == 1: # The definition of O(f(x)) symbol explicitly stated that # the argument of f(x) is irrelevant. That's why we can # combine some power exponents (only "on top" of the # expression tree for f(x)), e.g.: # xp (-x)q -> x(p+q) for real p, q. x = args[0] margs = list(Mul.make_args( expr.as_independent(x, as_Add=False)[1])) for i, t in enumerate(margs): if t.is_Pow: b, q = t.args if b in (x, -x) and q.is_real and not q.has(x): margs[i] = xq elif b.is_Pow and not b.exp.has(x): b, r = b.args if b in (x, -x) and r.is_real: margs[i] = x(rq) elif b.is_Mul and b.args[0] is S.NegativeOne: b = -b if b.is_Pow and not b.exp.has(x): b, r = b.args if b in (x, -x) and r.is_real: margs[i] = x(rq) expr = Mul(margs) expr = expr.subs(rs) if expr.is_Order: expr = expr.expr if not expr.has(variables) and not expr.is_zero: expr = S.One # create Order instance: vp = dict(zip(variables, point)) variables.sort(key=default_sort_key) point = [vp[v] for v in variables] args = (expr,) + Tuple(zip(variables, point)) obj = Expr.__new__(cls, args) return obj def _eval_nseries(self, x, n, logx, cdir=0): return self @property def expr(self): return self.args[0] @property def variables(self): if self.args[1:]: return tuple(x[0] for x in self.args[1:]) else: return () @property def point(self): if self.args[1:]: return tuple(x[1] for x in self.args[1:]) else: return () @property def free_symbols(self): return self.expr.free_symbols \| set(self.variables) def _eval_power(b, e): if e.is_Number and e.is_nonnegative: return b.func(b.expr ** e, b.args[1:]) if e == O(1): return b return def as_expr_variables(self, order_symbols): if order_symbols is None: order_symbols = self.args[1:] else: if (not all(o[1] == order_symbols[0][1] for o in order_symbols) and not all(p == self.point[0] for p in self.point)): # pragma: no cover raise NotImplementedError('Order at points other than 0 ' 'or oo not supported, got %s as a point.' % self.point) if order_symbols and order_symbols[0][1] != self.point[0]: raise NotImplementedError( "Multiplying Order at different points is not supported.") order_symbols = dict(order_symbols) for s, p in dict(self.args[1:]).items(): if s not in order_symbols.keys(): order_symbols[s] = p order_symbols = sorted(order_symbols.items(), key=lambda x: default_sort_key(x[0])) return self.expr, tuple(order_symbols) def removeO(self): return S.Zero def getO(self): return self @cacheit def contains(self, expr): r""" Return True if expr belongs to Order(self.expr, \self.variables). Return False if self belongs to expr. Return None if the inclusion relation cannot be determined (e.g. when self and expr have different symbols). """ from sympy import powsimp if expr.is_zero: return True if expr is S.NaN: return False point = self.point[0] if self.point else S.Zero if expr.is_Order: if (any(p != point for p in expr.point) or any(p != point for p in self.point)): return None if expr.expr == self.expr: # O(1) + O(1), O(1) + O(1, x), etc. return all([x in self.args[1:] for x in expr.args[1:]]) if expr.expr.is_Add: return all([self.contains(x) for x in expr.expr.args]) if self.expr.is_Add and point.is_zero: return any([self.func(x, self.args[1:]).contains(expr) for x in self.expr.args]) if self.variables and expr.variables: common_symbols = tuple( [s for s in self.variables if s in expr.variables]) elif self.variables: common_symbols = self.variables else: common_symbols = expr.variables if not common_symbols: return None if (self.expr.is_Pow and len(self.variables) == 1 and self.variables == expr.variables): symbol = self.variables[0] other = expr.expr.as_independent(symbol, as_Add=False)[1] if (other.is_Pow and other.base == symbol and self.expr.base == symbol): if point.is_zero: rv = (self.expr.exp - other.exp).is_nonpositive if point.is_infinite: rv = (self.expr.exp - other.exp).is_nonnegative if rv is not None: return rv r = None ratio = self.expr/expr.expr ratio = powsimp(ratio, deep=True, combine='exp') for s in common_symbols: from sympy.series.limits import Limit l = Limit(ratio, s, point).doit(heuristics=False) if not isinstance(l, Limit): l = l != 0 else: l = None if r is None: r = l else: if r != l: return return r if self.expr.is_Pow and len(self.variables) == 1: symbol = self.variables[0] other = expr.as_independent(symbol, as_Add=False)[1] if (other.is_Pow and other.base == symbol and self.expr.base == symbol): if point.is_zero: rv = (self.expr.exp - other.exp).is_nonpositive if point.is_infinite: rv = (self.expr.exp - other.exp).is_nonnegative if rv is not None: return rv obj = self.func(expr, self.args[1:]) return self.contains(obj) def __contains__(self, other): result = self.contains(other) if result is None: raise TypeError('contains did not evaluate to a bool') return result def _eval_subs(self, old, new): if old in self.variables: newexpr = self.expr.subs(old, new) i = self.variables.index(old) newvars = list(self.variables) newpt = list(self.point) if new.is_symbol: newvars[i] = new else: syms = new.free_symbols if len(syms) == 1 or old in syms: if old in syms: var = self.variables[i] else: var = syms.pop() # First, try to substitute self.point in the "new" # expr to see if this is a fixed point. # E.g. O(y).subs(y, sin(x)) point = new.subs(var, self.point[i]) if point != self.point[i]: from sympy.solvers.solveset import solveset d = Dummy() sol = solveset(old - new.subs(var, d), d) if isinstance(sol, Complement): e1 = sol.args[0] e2 = sol.args[1] sol = set(e1) - set(e2) res = [dict(zip((d, ), sol))] point = d.subs(res[0]).limit(old, self.point[i]) newvars[i] = var newpt[i] = point elif old not in syms: del newvars[i], newpt[i] if not syms and new == self.point[i]: newvars.extend(syms) newpt.extend([S.Zero]len(syms)) else: return return Order(newexpr, zip(newvars, newpt)) def _eval_conjugate(self): expr = self.expr._eval_conjugate() if expr is not None: return self.func(expr, self.args[1:]) def _eval_derivative(self, x): return self.func(self.expr.diff(x), self.args[1:]) or self def _eval_transpose(self): expr = self.expr._eval_transpose() if expr is not None: return self.func(expr, *self.args[1:]) def _sage_(self): #XXX: SAGE doesn't have Order yet. Let's return 0 instead. return Rational(0)._sage_() def __neg__(self): return self O = Order
3f30f43004cc3632e33e2f465b919018be94a9cd944feb8fc27ce18bb4e4247f	def finite_diff(expression, variable, increment=1): """ Takes as input a polynomial expression and the variable used to construct it and returns the difference between function's value when the input is incremented to 1 and the original function value. If you want an increment other than one supply it as a third argument. Examples ======== >>> from sympy.abc import x, y, z >>> from sympy.series.kauers import finite_diff >>> finite_diff(x*2, x) 2x + 1 >>> finite_diff(y*3 + 2y*2 + 3y + 4, y) 3y2 + 7y + 6 >>> finite_diff(x*2 + 3x + 8, x, 2) 4x + 10 >>> finite_diff(z3 + 8z, z, 3) 9z2 + 27z + 51 """ expression = expression.expand() expression2 = expression.subs(variable, variable + increment) expression2 = expression2.expand() return expression2 - expression def finite_diff_kauers(sum): """ Takes as input a Sum instance and returns the difference between the sum with the upper index incremented by 1 and the original sum. For example, if S(n) is a sum, then finite_diff_kauers will return S(n + 1) - S(n). Examples ======== >>> from sympy.series.kauers import finite_diff_kauers >>> from sympy import Sum >>> from sympy.abc import x, y, m, n, k >>> finite_diff_kauers(Sum(k, (k, 1, n))) n + 1 >>> finite_diff_kauers(Sum(1/k, (k, 1, n))) 1/(n + 1) >>> finite_diff_kauers(Sum((xy2), (x, 1, n), (y, 1, m))) (m + 1)2(n + 1) >>> finite_diff_kauers(Sum((xy), (x, 1, m), (y, 1, n))) (m + 1)(n + 1) """ function = sum.function for l in sum.limits: function = function.subs(l[0], l[- 1] + 1) return function
0607859c45509e32175013678990c98684543b1f679756914d2de9fad97e066a	""" Expand Hypergeometric (and Meijer G) functions into named special functions. The algorithm for doing this uses a collection of lookup tables of hypergeometric functions, and various of their properties, to expand many hypergeometric functions in terms of special functions. It is based on the following paper: Kelly B. Roach. Meijer G Function Representations. In: Proceedings of the 1997 International Symposium on Symbolic and Algebraic Computation, pages 205-211, New York, 1997. ACM. It is described in great(er) detail in the Sphinx documentation. """ # SUMMARY OF EXTENSIONS FOR MEIJER G FUNCTIONS # # o z*rho G(ap, bq; z) = G(ap + rho, bq + rho; z) # # o denote zd/dz by D # # o It is helpful to keep in mind that ap and bq play essentially symmetric # roles: G(1/z) has slightly altered parameters, with ap and bq interchanged. # # o There are four shift operators: # A_J = b_J - D, J = 1, ..., n # B_J = 1 - a_j + D, J = 1, ..., m # C_J = -b_J + D, J = m+1, ..., q # D_J = a_J - 1 - D, J = n+1, ..., p # # A_J, C_J increment b_J # B_J, D_J decrement a_J # # o The corresponding four inverse-shift operators are defined if there # is no cancellation. Thus e.g. an index a_J (upper or lower) can be # incremented if a_J != b_i for i = 1, ..., q. # # o Order reduction: if b_j - a_i is a non-negative integer, where # j <= m and i > n, the corresponding quotient of gamma functions reduces # to a polynomial. Hence the G function can be expressed using a G-function # of lower order. # Similarly if j > m and i <= n. # # Secondly, there are paired index theorems [Adamchik, The evaluation of # integrals of Bessel functions via G-function identities]. Suppose there # are three parameters a, b, c, where a is an a_i, i <= n, b is a b_j, # j <= m and c is a denominator parameter (i.e. a_i, i > n or b_j, j > m). # Suppose further all three differ by integers. # Then the order can be reduced. # TODO work this out in detail. # # o An index quadruple is called suitable if its order cannot be reduced. # If there exists a sequence of shift operators transforming one index # quadruple into another, we say one is reachable from the other. # # o Deciding if one index quadruple is reachable from another is tricky. For # this reason, we use hand-built routines to match and instantiate formulas. # from collections import defaultdict from itertools import product from sympy import SYMPY_DEBUG from sympy.core import (S, Dummy, symbols, sympify, Tuple, expand, I, pi, Mul, EulerGamma, oo, zoo, expand_func, Add, nan, Expr, Rational) from sympy.core.compatibility import default_sort_key, reduce from sympy.core.mod import Mod from sympy.functions import (exp, sqrt, root, log, lowergamma, cos, besseli, gamma, uppergamma, expint, erf, sin, besselj, Ei, Ci, Si, Shi, sinh, cosh, Chi, fresnels, fresnelc, polar_lift, exp_polar, floor, ceiling, rf, factorial, lerchphi, Piecewise, re, elliptic_k, elliptic_e) from sympy.functions.elementary.complexes import polarify, unpolarify from sympy.functions.special.hyper import (hyper, HyperRep_atanh, HyperRep_power1, HyperRep_power2, HyperRep_log1, HyperRep_asin1, HyperRep_asin2, HyperRep_sqrts1, HyperRep_sqrts2, HyperRep_log2, HyperRep_cosasin, HyperRep_sinasin, meijerg) from sympy.polys import poly, Poly from sympy.series import residue from sympy.simplify import simplify # type: ignore from sympy.simplify.powsimp import powdenest from sympy.utilities.iterables import sift # function to define "buckets" def _mod1(x): # TODO see if this can work as Mod(x, 1); this will require # different handling of the "buckets" since these need to # be sorted and that fails when there is a mixture of # integers and expressions with parameters. With the current # Mod behavior, Mod(k, 1) == Mod(1, 1) == 0 if k is an integer. # Although the sorting can be done with Basic.compare, this may # still require different handling of the sorted buckets. if x.is_Number: return Mod(x, 1) c, x = x.as_coeff_Add() return Mod(c, 1) + x # leave add formulae at the top for easy reference def add_formulae(formulae): """ Create our knowledge base. """ from sympy.matrices import Matrix a, b, c, z = symbols('a b c, z', cls=Dummy) def add(ap, bq, res): func = Hyper_Function(ap, bq) formulae.append(Formula(func, z, res, (a, b, c))) def addb(ap, bq, B, C, M): func = Hyper_Function(ap, bq) formulae.append(Formula(func, z, None, (a, b, c), B, C, M)) # Luke, Y. L. (1969), The Special Functions and Their Approximations, # Volume 1, section 6.2 # 0F0 add((), (), exp(z)) # 1F0 add((a, ), (), HyperRep_power1(-a, z)) # 2F1 addb((a, a - S.Half), (2a, ), Matrix([HyperRep_power2(a, z), HyperRep_power2(a + S.Half, z)/2]), Matrix([[1, 0]]), Matrix([[(a - S.Half)z/(1 - z), (S.Half - a)z/(1 - z)], [a/(1 - z), a(z - 2)/(1 - z)]])) addb((1, 1), (2, ), Matrix([HyperRep_log1(z), 1]), Matrix([[-1/z, 0]]), Matrix([[0, z/(z - 1)], [0, 0]])) addb((S.Half, 1), (S('3/2'), ), Matrix([HyperRep_atanh(z), 1]), Matrix([[1, 0]]), Matrix([[Rational(-1, 2), 1/(1 - z)/2], [0, 0]])) addb((S.Half, S.Half), (S('3/2'), ), Matrix([HyperRep_asin1(z), HyperRep_power1(Rational(-1, 2), z)]), Matrix([[1, 0]]), Matrix([[Rational(-1, 2), S.Half], [0, z/(1 - z)/2]])) addb((a, S.Half + a), (S.Half, ), Matrix([HyperRep_sqrts1(-a, z), -HyperRep_sqrts2(-a - S.Half, z)]), Matrix([[1, 0]]), Matrix([[0, -a], [z(-2a - 1)/2/(1 - z), S.Half - z(-2a - 1)/(1 - z)]])) # A. P. Prudnikov, Yu. A. Brychkov and O. I. Marichev (1990). # Integrals and Series: More Special Functions, Vol. 3,. # Gordon and Breach Science Publisher addb([a, -a], [S.Half], Matrix([HyperRep_cosasin(a, z), HyperRep_sinasin(a, z)]), Matrix([[1, 0]]), Matrix([[0, -a], [az/(1 - z), 1/(1 - z)/2]])) addb([1, 1], [3S.Half], Matrix([HyperRep_asin2(z), 1]), Matrix([[1, 0]]), Matrix([[(z - S.Half)/(1 - z), 1/(1 - z)/2], [0, 0]])) # Complete elliptic integrals K(z) and E(z), both a 2F1 function addb([S.Half, S.Half], [S.One], Matrix([elliptic_k(z), elliptic_e(z)]), Matrix([[2/pi, 0]]), Matrix([[Rational(-1, 2), -1/(2z-2)], [Rational(-1, 2), S.Half]])) addb([Rational(-1, 2), S.Half], [S.One], Matrix([elliptic_k(z), elliptic_e(z)]), Matrix([[0, 2/pi]]), Matrix([[Rational(-1, 2), -1/(2z-2)], [Rational(-1, 2), S.Half]])) # 3F2 addb([Rational(-1, 2), 1, 1], [S.Half, 2], Matrix([zHyperRep_atanh(z), HyperRep_log1(z), 1]), Matrix([[Rational(-2, 3), -S.One/(3z), Rational(2, 3)]]), Matrix([[S.Half, 0, z/(1 - z)/2], [0, 0, z/(z - 1)], [0, 0, 0]])) # actually the formula for 3/2 is much nicer ... addb([Rational(-1, 2), 1, 1], [2, 2], Matrix([HyperRep_power1(S.Half, z), HyperRep_log2(z), 1]), Matrix([[Rational(4, 9) - 16/(9z), 4/(3z), 16/(9z)]]), Matrix([[z/2/(z - 1), 0, 0], [1/(2(z - 1)), 0, S.Half], [0, 0, 0]])) # 1F1 addb([1], [b], Matrix([z*(1 - b) exp(z) * lowergamma(b - 1, z), 1]), Matrix([[b - 1, 0]]), Matrix([[1 - b + z, 1], [0, 0]])) addb([a], [2a], Matrix([z(S.Half - a)exp(z/2)besseli(a - S.Half, z/2) gamma(a + S.Half)/4(S.Half - a), z(S.Half - a)exp(z/2)besseli(a + S.Half, z/2) * gamma(a + S.Half)/4*(S.Half - a)]), Matrix([[1, 0]]), Matrix([[z/2, z/2], [z/2, (z/2 - 2a)]])) mz = polar_lift(-1)z addb([a], [a + 1], Matrix([mz(-a)alowergamma(a, mz), aexp(z)]), Matrix([[1, 0]]), Matrix([[-a, 1], [0, z]])) # This one is redundant. add([Rational(-1, 2)], [S.Half], exp(z) - sqrt(piz)(-I)erf(Isqrt(z))) # Added to get nice results for Laplace transform of Fresnel functions # http://functions.wolfram.com/07.22.03.6437.01 # Basic rule #add([1], [Rational(3, 4), Rational(5, 4)], # sqrt(pi) * (cos(2sqrt(polar_lift(-1)z))fresnelc(2root(polar_lift(-1)z,4)/sqrt(pi)) + # sin(2sqrt(polar_lift(-1)z))fresnels(2root(polar_lift(-1)z,4)/sqrt(pi))) # / (2root(polar_lift(-1)z,4))) # Manually tuned rule addb([1], [Rational(3, 4), Rational(5, 4)], Matrix([ sqrt(pi)(Isinh(2sqrt(z))fresnels(2root(z, 4)exp(Ipi/4)/sqrt(pi)) + cosh(2sqrt(z))fresnelc(2root(z, 4)exp(Ipi/4)/sqrt(pi))) * exp(-Ipi/4)/(2root(z, 4)), sqrt(pi)root(z, 4)(sinh(2sqrt(z))fresnelc(2root(z, 4)exp(Ipi/4)/sqrt(pi)) + Icosh(2sqrt(z))fresnels(2root(z, 4)exp(Ipi/4)/sqrt(pi))) exp(-Ipi/4)/2, 1 ]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 4), 1, Rational(1, 4)], [ z, Rational(1, 4), 0], [ 0, 0, 0]])) # 2F2 addb([S.Half, a], [Rational(3, 2), a + 1], Matrix([a/(2a - 1)(-I)sqrt(pi/z)erf(Isqrt(z)), a/(2a - 1)(polar_lift(-1)z)(-a) lowergamma(a, polar_lift(-1)z), a/(2a - 1)exp(z)]), Matrix([[1, -1, 0]]), Matrix([[Rational(-1, 2), 0, 1], [0, -a, 1], [0, 0, z]])) # We make a "basis" of four functions instead of three, and give EulerGamma # an extra slot (it could just be a coefficient to 1). The advantage is # that this way Polys will not see multivariate polynomials (it treats # EulerGamma as an indeterminate), which is way* faster. addb([1, 1], [2, 2], Matrix([Ei(z) - log(z), exp(z), 1, EulerGamma]), Matrix([[1/z, 0, 0, -1/z]]), Matrix([[0, 1, -1, 0], [0, z, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]])) # 0F1 add((), (S.Half, ), cosh(2sqrt(z))) addb([], [b], Matrix([gamma(b)z*((1 - b)/2)besseli(b - 1, 2sqrt(z)), gamma(b)z*(1 - b/2)besseli(b, 2sqrt(z))]), Matrix([[1, 0]]), Matrix([[0, 1], [z, (1 - b)]])) # 0F3 x = 4z*Rational(1, 4) def fp(a, z): return besseli(a, x) + besselj(a, x) def fm(a, z): return besseli(a, x) - besselj(a, x) # TODO branching addb([], [S.Half, a, a + S.Half], Matrix([fp(2a - 1, z), fm(2a, z)z*Rational(1, 4), fm(2a - 1, z)sqrt(z), fp(2a, z)zRational(3, 4)]) 2*(-2a)gamma(2a)z((1 - 2a)/4), Matrix([[1, 0, 0, 0]]), Matrix([[0, 1, 0, 0], [0, S.Half - a, 1, 0], [0, 0, S.Half, 1], [z, 0, 0, 1 - a]])) x = 2(4z)*Rational(1, 4)exp_polar(Ipi/4) addb([], [a, a + S.Half, 2a], (2sqrt(polar_lift(-1)z))*(1 - 2a)gamma(2a)*2 Matrix([besselj(2a - 1, x)besseli(2a - 1, x), x(besseli(2a, x)besselj(2a - 1, x) - besseli(2a - 1, x)besselj(2a, x)), x*2besseli(2a, x)besselj(2a, x), x3(besseli(2a, x)besselj(2a - 1, x) + besseli(2a - 1, x)besselj(2a, x))]), Matrix([[1, 0, 0, 0]]), Matrix([[0, Rational(1, 4), 0, 0], [0, (1 - 2a)/2, Rational(-1, 2), 0], [0, 0, 1 - 2a, Rational(1, 4)], [-32z, 0, 0, 1 - a]])) # 1F2 addb([a], [a - S.Half, 2a], Matrix([z*(S.Half - a)besseli(a - S.Half, sqrt(z))2, z(1 - a)besseli(a - S.Half, sqrt(z)) besseli(a - Rational(3, 2), sqrt(z)), z*(Rational(3, 2) - a)besseli(a - Rational(3, 2), sqrt(z))2]), Matrix([[-gamma(a + S.Half)2/4*(S.Half - a), 2gamma(a - S.Half)gamma(a + S.Half)/4(1 - a), 0]]), Matrix([[1 - 2a, 1, 0], [z/2, S.Half - a, S.Half], [0, z, 0]])) addb([S.Half], [b, 2 - b], pi(1 - b)/sin(pib)* Matrix([besseli(1 - b, sqrt(z))besseli(b - 1, sqrt(z)), sqrt(z)(besseli(-b, sqrt(z))besseli(b - 1, sqrt(z)) + besseli(1 - b, sqrt(z))besseli(b, sqrt(z))), besseli(-b, sqrt(z))besseli(b, sqrt(z))]), Matrix([[1, 0, 0]]), Matrix([[b - 1, S.Half, 0], [z, 0, z], [0, S.Half, -b]])) addb([S.Half], [Rational(3, 2), Rational(3, 2)], Matrix([Shi(2sqrt(z))/2/sqrt(z), sinh(2sqrt(z))/2/sqrt(z), cosh(2sqrt(z))]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 2), S.Half, 0], [0, Rational(-1, 2), S.Half], [0, 2z, 0]])) # FresnelS # Basic rule #add([Rational(3, 4)], [Rational(3, 2),Rational(7, 4)], 6fresnels( exp(piI/4)root(z,4)2/sqrt(pi) ) / ( pi (exp(piI/4)root(z,4)2/sqrt(pi))3 ) ) # Manually tuned rule addb([Rational(3, 4)], [Rational(3, 2), Rational(7, 4)], Matrix( [ fresnels( exp( piI/4)root( z, 4)2/sqrt( pi) ) / ( pi * (exp(piI/4)root(z, 4)2/sqrt(pi))3 ), sinh(2sqrt(z))/sqrt(z), cosh(2sqrt(z)) ]), Matrix([[6, 0, 0]]), Matrix([[Rational(-3, 4), Rational(1, 16), 0], [ 0, Rational(-1, 2), 1], [ 0, z, 0]])) # FresnelC # Basic rule #add([Rational(1, 4)], [S.Half,Rational(5, 4)], fresnelc( exp(piI/4)root(z,4)2/sqrt(pi) ) / ( exp(piI/4)root(z,4)2/sqrt(pi) ) ) # Manually tuned rule addb([Rational(1, 4)], [S.Half, Rational(5, 4)], Matrix( [ sqrt( pi)exp( -Ipi/4)fresnelc( 2root(z, 4)exp(Ipi/4)/sqrt(pi))/(2root(z, 4)), cosh(2sqrt(z)), sinh(2sqrt(z))sqrt(z) ]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 4), Rational(1, 4), 0 ], [ 0, 0, 1 ], [ 0, z, S.Half]])) # 2F3 # XXX with this five-parameter formula is pretty slow with the current # Formula.find_instantiations (creates 2!3!3(2+3) ~ 3000 # instantiations ... But it's not too bad. addb([a, a + S.Half], [2a, b, 2a - b + 1], gamma(b)gamma(2a - b + 1) (sqrt(z)/2)*(1 - 2a) * Matrix([besseli(b - 1, sqrt(z))besseli(2a - b, sqrt(z)), sqrt(z)besseli(b, sqrt(z))besseli(2a - b, sqrt(z)), sqrt(z)besseli(b - 1, sqrt(z))besseli(2a - b + 1, sqrt(z)), besseli(b, sqrt(z))besseli(2a - b + 1, sqrt(z))]), Matrix([[1, 0, 0, 0]]), Matrix([[0, S.Half, S.Half, 0], [z/2, 1 - b, 0, z/2], [z/2, 0, b - 2a, z/2], [0, S.Half, S.Half, -2a]])) # (C/f above comment about eulergamma in the basis). addb([1, 1], [2, 2, Rational(3, 2)], Matrix([Chi(2sqrt(z)) - log(2sqrt(z)), cosh(2sqrt(z)), sqrt(z)sinh(2sqrt(z)), 1, EulerGamma]), Matrix([[1/z, 0, 0, 0, -1/z]]), Matrix([[0, S.Half, 0, Rational(-1, 2), 0], [0, 0, 1, 0, 0], [0, z, S.Half, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]])) # 3F3 # This is rule: http://functions.wolfram.com/07.31.03.0134.01 # Initial reason to add it was a nice solution for # integrate(erf(az)/z*2, z) and same for erfc and erfi. # Basic rule # add([1, 1, a], [2, 2, a+1], (a/(z(a-1)*2)) # (1 - (-z)*(1-a) (gamma(a) - uppergamma(a,-z)) # - (a-1) * (EulerGamma + uppergamma(0,-z) + log(-z)) # - exp(z))) # Manually tuned rule addb([1, 1, a], [2, 2, a+1], Matrix([a(log(-z) + expint(1, -z) + EulerGamma)/(z(a*2 - 2a + 1)), a(-z)(-a)(gamma(a) - uppergamma(a, -z))/(a - 1)*2, aexp(z)/(a*2 - 2a + 1), a/(z(a2 - 2a + 1))]), Matrix([[1-a, 1, -1/z, 1]]), Matrix([[-1,0,-1/z,1], [0,-a,1,0], [0,0,z,0], [0,0,0,-1]])) def add_meijerg_formulae(formulae): from sympy.matrices import Matrix a, b, c, z = list(map(Dummy, 'abcz')) rho = Dummy('rho') def add(an, ap, bm, bq, B, C, M, matcher): formulae.append(MeijerFormula(an, ap, bm, bq, z, [a, b, c, rho], B, C, M, matcher)) def detect_uppergamma(func): x = func.an[0] y, z = func.bm swapped = False if not _mod1((x - y).simplify()): swapped = True (y, z) = (z, y) if _mod1((x - z).simplify()) or x - z > 0: return None l = [y, x] if swapped: l = [x, y] return {rho: y, a: x - y}, G_Function([x], [], l, []) add([a + rho], [], [rho, a + rho], [], Matrix([gamma(1 - a)zrhoexp(z)uppergamma(a, z), gamma(1 - a)z*(a + rho)]), Matrix([[1, 0]]), Matrix([[rho + z, -1], [0, a + rho]]), detect_uppergamma) def detect_3113(func): """http://functions.wolfram.com/07.34.03.0984.01""" x = func.an[0] u, v, w = func.bm if _mod1((u - v).simplify()) == 0: if _mod1((v - w).simplify()) == 0: return sig = (S.Half, S.Half, S.Zero) x1, x2, y = u, v, w else: if _mod1((x - u).simplify()) == 0: sig = (S.Half, S.Zero, S.Half) x1, y, x2 = u, v, w else: sig = (S.Zero, S.Half, S.Half) y, x1, x2 = u, v, w if (_mod1((x - x1).simplify()) != 0 or _mod1((x - x2).simplify()) != 0 or _mod1((x - y).simplify()) != S.Half or x - x1 > 0 or x - x2 > 0): return return {a: x}, G_Function([x], [], [x - S.Half + t for t in sig], []) s = sin(2sqrt(z)) c_ = cos(2sqrt(z)) S_ = Si(2sqrt(z)) - pi/2 C = Ci(2sqrt(z)) add([a], [], [a, a, a - S.Half], [], Matrix([sqrt(pi)z*(a - S.Half)(c_S_ - sC), sqrt(pi)za(sS_ + c_C), sqrt(pi)za]), Matrix([[-2, 0, 0]]), Matrix([[a - S.Half, -1, 0], [z, a, S.Half], [0, 0, a]]), detect_3113) def make_simp(z): """ Create a function that simplifies rational functions in ``z``. """ def simp(expr): """ Efficiently simplify the rational function ``expr``. """ numer, denom = expr.as_numer_denom() numer = numer.expand() # denom = denom.expand() # is this needed? c, numer, denom = poly(numer, z).cancel(poly(denom, z)) return c numer.as_expr() / denom.as_expr() return simp def debug(args): if SYMPY_DEBUG: for a in args: print(a, end="") print() class Hyper_Function(Expr): """ A generalized hypergeometric function. """ def __new__(cls, ap, bq): obj = super().__new__(cls) obj.ap = Tuple(list(map(expand, ap))) obj.bq = Tuple(list(map(expand, bq))) return obj @property def args(self): return (self.ap, self.bq) @property def sizes(self): return (len(self.ap), len(self.bq)) @property def gamma(self): """ Number of upper parameters that are negative integers This is a transformation invariant. """ return sum(bool(x.is_integer and x.is_negative) for x in self.ap) def _hashable_content(self): return super()._hashable_content() + (self.ap, self.bq) def __call__(self, arg): return hyper(self.ap, self.bq, arg) def build_invariants(self): """ Compute the invariant vector. Explanation =========== The invariant vector is: (gamma, ((s1, n1), ..., (sk, nk)), ((t1, m1), ..., (tr, mr))) where gamma is the number of integer a < 0, s1 < ... < sk nl is the number of parameters a_i congruent to sl mod 1 t1 < ... < tr ml is the number of parameters b_i congruent to tl mod 1 If the index pair contains parameters, then this is not truly an invariant, since the parameters cannot be sorted uniquely mod1. Examples ======== >>> from sympy.simplify.hyperexpand import Hyper_Function >>> from sympy import S >>> ap = (S.Half, S.One/3, S(-1)/2, -2) >>> bq = (1, 2) Here gamma = 1, k = 3, s1 = 0, s2 = 1/3, s3 = 1/2 n1 = 1, n2 = 1, n2 = 2 r = 1, t1 = 0 m1 = 2: >>> Hyper_Function(ap, bq).build_invariants() (1, ((0, 1), (1/3, 1), (1/2, 2)), ((0, 2),)) """ abuckets, bbuckets = sift(self.ap, _mod1), sift(self.bq, _mod1) def tr(bucket): bucket = list(bucket.items()) if not any(isinstance(x[0], Mod) for x in bucket): bucket.sort(key=lambda x: default_sort_key(x[0])) bucket = tuple([(mod, len(values)) for mod, values in bucket if values]) return bucket return (self.gamma, tr(abuckets), tr(bbuckets)) def difficulty(self, func): """ Estimate how many steps it takes to reach ``func`` from self. Return -1 if impossible. """ if self.gamma != func.gamma: return -1 oabuckets, obbuckets, abuckets, bbuckets = [sift(params, _mod1) for params in (self.ap, self.bq, func.ap, func.bq)] diff = 0 for bucket, obucket in [(abuckets, oabuckets), (bbuckets, obbuckets)]: for mod in set(list(bucket.keys()) + list(obucket.keys())): if (not mod in bucket) or (not mod in obucket) \ or len(bucket[mod]) != len(obucket[mod]): return -1 l1 = list(bucket[mod]) l2 = list(obucket[mod]) l1.sort() l2.sort() for i, j in zip(l1, l2): diff += abs(i - j) return diff def _is_suitable_origin(self): """ Decide if ``self`` is a suitable origin. Explanation =========== A function is a suitable origin iff: none of the ai equals bj + n, with n a non-negative integer * none of the ai is zero * none of the bj is a non-positive integer Note that this gives meaningful results only when none of the indices are symbolic. """ for a in self.ap: for b in self.bq: if (a - b).is_integer and (a - b).is_negative is False: return False for a in self.ap: if a == 0: return False for b in self.bq: if b.is_integer and b.is_nonpositive: return False return True class G_Function(Expr): """ A Meijer G-function. """ def __new__(cls, an, ap, bm, bq): obj = super().__new__(cls) obj.an = Tuple(list(map(expand, an))) obj.ap = Tuple(list(map(expand, ap))) obj.bm = Tuple(list(map(expand, bm))) obj.bq = Tuple(list(map(expand, bq))) return obj @property def args(self): return (self.an, self.ap, self.bm, self.bq) def _hashable_content(self): return super()._hashable_content() + self.args def __call__(self, z): return meijerg(self.an, self.ap, self.bm, self.bq, z) def compute_buckets(self): """ Compute buckets for the fours sets of parameters. Explanation =========== We guarantee that any two equal Mod objects returned are actually the same, and that the buckets are sorted by real part (an and bq descendending, bm and ap ascending). Examples ======== >>> from sympy.simplify.hyperexpand import G_Function >>> from sympy.abc import y >>> from sympy import S >>> a, b = [1, 3, 2, S(3)/2], [1 + y, y, 2, y + 3] >>> G_Function(a, b, [2], [y]).compute_buckets() ({0: [3, 2, 1], 1/2: [3/2]}, {0: [2], y: [y, y + 1, y + 3]}, {0: [2]}, {y: [y]}) """ dicts = pan, pap, pbm, pbq = [defaultdict(list) for i in range(4)] for dic, lis in zip(dicts, (self.an, self.ap, self.bm, self.bq)): for x in lis: dic[_mod1(x)].append(x) for dic, flip in zip(dicts, (True, False, False, True)): for m, items in dic.items(): x0 = items[0] items.sort(key=lambda x: x - x0, reverse=flip) dic[m] = items return tuple([dict(w) for w in dicts]) @property def signature(self): return (len(self.an), len(self.ap), len(self.bm), len(self.bq)) # Dummy variable. _x = Dummy('x') class Formula: """ This class represents hypergeometric formulae. Explanation =========== Its data members are: - z, the argument - closed_form, the closed form expression - symbols, the free symbols (parameters) in the formula - func, the function - B, C, M (see _compute_basis) Examples ======== >>> from sympy.abc import a, b, z >>> from sympy.simplify.hyperexpand import Formula, Hyper_Function >>> func = Hyper_Function((a/2, a/3 + b, (1+a)/2), (a, b, (a+b)/7)) >>> f = Formula(func, z, None, [a, b]) """ def _compute_basis(self, closed_form): """ Compute a set of functions B=(f1, ..., fn), a nxn matrix M and a 1xn matrix C such that: closed_form = C B z d/dz B = M B. """ from sympy.matrices import Matrix, eye, zeros afactors = [_x + a for a in self.func.ap] bfactors = [_x + b - 1 for b in self.func.bq] expr = _xMul(bfactors) - self.zMul(afactors) poly = Poly(expr, _x) n = poly.degree() - 1 b = [closed_form] for _ in range(n): b.append(self.zb[-1].diff(self.z)) self.B = Matrix(b) self.C = Matrix([[1] + [0]n]) m = eye(n) m = m.col_insert(0, zeros(n, 1)) l = poly.all_coeffs()[1:] l.reverse() self.M = m.row_insert(n, -Matrix([l])/poly.all_coeffs()[0]) def __init__(self, func, z, res, symbols, B=None, C=None, M=None): z = sympify(z) res = sympify(res) symbols = [x for x in sympify(symbols) if func.has(x)] self.z = z self.symbols = symbols self.B = B self.C = C self.M = M self.func = func # TODO with symbolic parameters, it could be advantageous # (for prettier answers) to compute a basis only after # instantiation if res is not None: self._compute_basis(res) @property def closed_form(self): return reduce(lambda s,m: s+m[0]m[1], zip(self.C, self.B), S.Zero) def find_instantiations(self, func): """ Find substitutions of the free symbols that match ``func``. Return the substitution dictionaries as a list. Note that the returned instantiations need not actually match, or be valid! """ from sympy.solvers import solve ap = func.ap bq = func.bq if len(ap) != len(self.func.ap) or len(bq) != len(self.func.bq): raise TypeError('Cannot instantiate other number of parameters') symbol_values = [] for a in self.symbols: if a in self.func.ap.args: symbol_values.append(ap) elif a in self.func.bq.args: symbol_values.append(bq) else: raise ValueError("At least one of the parameters of the " "formula must be equal to %s" % (a,)) base_repl = [dict(list(zip(self.symbols, values))) for values in product(symbol_values)] abuckets, bbuckets = [sift(params, _mod1) for params in [ap, bq]] a_inv, b_inv = [{a: len(vals) for a, vals in bucket.items()} for bucket in [abuckets, bbuckets]] critical_values = [[0] for _ in self.symbols] result = [] _n = Dummy() for repl in base_repl: symb_a, symb_b = [sift(params, lambda x: _mod1(x.xreplace(repl))) for params in [self.func.ap, self.func.bq]] for bucket, obucket in [(abuckets, symb_a), (bbuckets, symb_b)]: for mod in set(list(bucket.keys()) + list(obucket.keys())): if (not mod in bucket) or (not mod in obucket) \ or len(bucket[mod]) != len(obucket[mod]): break for a, vals in zip(self.symbols, critical_values): if repl[a].free_symbols: continue exprs = [expr for expr in obucket[mod] if expr.has(a)] repl0 = repl.copy() repl0[a] += _n for expr in exprs: for target in bucket[mod]: n0, = solve(expr.xreplace(repl0) - target, _n) if n0.free_symbols: raise ValueError("Value should not be true") vals.append(n0) else: values = [] for a, vals in zip(self.symbols, critical_values): a0 = repl[a] min_ = floor(min(vals)) max_ = ceiling(max(vals)) values.append([a0 + n for n in range(min_, max_ + 1)]) result.extend(dict(list(zip(self.symbols, l))) for l in product(values)) return result class FormulaCollection: """ A collection of formulae to use as origins. """ def __init__(self): """ Doing this globally at module init time is a pain ... """ self.symbolic_formulae = {} self.concrete_formulae = {} self.formulae = [] add_formulae(self.formulae) # Now process the formulae into a helpful form. # These dicts are indexed by (p, q). for f in self.formulae: sizes = f.func.sizes if len(f.symbols) > 0: self.symbolic_formulae.setdefault(sizes, []).append(f) else: inv = f.func.build_invariants() self.concrete_formulae.setdefault(sizes, {})[inv] = f def lookup_origin(self, func): """ Given the suitable target ``func``, try to find an origin in our knowledge base. Examples ======== >>> from sympy.simplify.hyperexpand import (FormulaCollection, ... Hyper_Function) >>> f = FormulaCollection() >>> f.lookup_origin(Hyper_Function((), ())).closed_form exp(_z) >>> f.lookup_origin(Hyper_Function([1], ())).closed_form HyperRep_power1(-1, _z) >>> from sympy import S >>> i = Hyper_Function([S('1/4'), S('3/4 + 4')], [S.Half]) >>> f.lookup_origin(i).closed_form HyperRep_sqrts1(-1/4, _z) """ inv = func.build_invariants() sizes = func.sizes if sizes in self.concrete_formulae and \ inv in self.concrete_formulae[sizes]: return self.concrete_formulae[sizes][inv] # We don't have a concrete formula. Try to instantiate. if not sizes in self.symbolic_formulae: return None # Too bad... possible = [] for f in self.symbolic_formulae[sizes]: repls = f.find_instantiations(func) for repl in repls: func2 = f.func.xreplace(repl) if not func2._is_suitable_origin(): continue diff = func2.difficulty(func) if diff == -1: continue possible.append((diff, repl, f, func2)) # find the nearest origin possible.sort(key=lambda x: x[0]) for _, repl, f, func2 in possible: f2 = Formula(func2, f.z, None, [], f.B.subs(repl), f.C.subs(repl), f.M.subs(repl)) if not any(e.has(S.NaN, oo, -oo, zoo) for e in [f2.B, f2.M, f2.C]): return f2 return None class MeijerFormula: """ This class represents a Meijer G-function formula. Its data members are: - z, the argument - symbols, the free symbols (parameters) in the formula - func, the function - B, C, M (c/f ordinary Formula) """ def __init__(self, an, ap, bm, bq, z, symbols, B, C, M, matcher): an, ap, bm, bq = [Tuple(list(map(expand, w))) for w in [an, ap, bm, bq]] self.func = G_Function(an, ap, bm, bq) self.z = z self.symbols = symbols self._matcher = matcher self.B = B self.C = C self.M = M @property def closed_form(self): return reduce(lambda s,m: s+m[0]m[1], zip(self.C, self.B), S.Zero) def try_instantiate(self, func): """ Try to instantiate the current formula to (almost) match func. This uses the _matcher passed on init. """ if func.signature != self.func.signature: return None res = self._matcher(func) if res is not None: subs, newfunc = res return MeijerFormula(newfunc.an, newfunc.ap, newfunc.bm, newfunc.bq, self.z, [], self.B.subs(subs), self.C.subs(subs), self.M.subs(subs), None) class MeijerFormulaCollection: """ This class holds a collection of meijer g formulae. """ def __init__(self): formulae = [] add_meijerg_formulae(formulae) self.formulae = defaultdict(list) for formula in formulae: self.formulae[formula.func.signature].append(formula) self.formulae = dict(self.formulae) def lookup_origin(self, func): """ Try to find a formula that matches func. """ if not func.signature in self.formulae: return None for formula in self.formulae[func.signature]: res = formula.try_instantiate(func) if res is not None: return res class Operator: """ Base class for operators to be applied to our functions. Explanation =========== These operators are differential operators. They are by convention expressed in the variable D = zd/dz (although this base class does not actually care). Note that when the operator is applied to an object, we typically do not blindly differentiate but instead use a different representation of the zd/dz operator (see make_derivative_operator). To subclass from this, define a __init__ method that initializes a self._poly variable. This variable stores a polynomial. By convention the generator is zd/dz, and acts to the right of all coefficients. Thus this poly x*2 + 2zx + 1 represents the differential operator (zd/dz)*2 + 2z*2d/dz. This class is used only in the implementation of the hypergeometric function expansion algorithm. """ def apply(self, obj, op): """ Apply ``self`` to the object ``obj``, where the generator is ``op``. Examples ======== >>> from sympy.simplify.hyperexpand import Operator >>> from sympy.polys.polytools import Poly >>> from sympy.abc import x, y, z >>> op = Operator() >>> op._poly = Poly(x*2 + zx + y, x) >>> op.apply(z*7, lambda f: f.diff(z)) yz*7 + 7z*7 + 42z*5 """ coeffs = self._poly.all_coeffs() coeffs.reverse() diffs = [obj] for c in coeffs[1:]: diffs.append(op(diffs[-1])) r = coeffs[0]diffs[0] for c, d in zip(coeffs[1:], diffs[1:]): r += cd return r class MultOperator(Operator): """ Simply multiply by a "constant" """ def __init__(self, p): self._poly = Poly(p, _x) class ShiftA(Operator): """ Increment an upper index. """ def __init__(self, ai): ai = sympify(ai) if ai == 0: raise ValueError('Cannot increment zero upper index.') self._poly = Poly(_x/ai + 1, _x) def __str__(self): return '<Increment upper %s.>' % (1/self._poly.all_coeffs()[0]) class ShiftB(Operator): """ Decrement a lower index. """ def __init__(self, bi): bi = sympify(bi) if bi == 1: raise ValueError('Cannot decrement unit lower index.') self._poly = Poly(_x/(bi - 1) + 1, _x) def __str__(self): return '<Decrement lower %s.>' % (1/self._poly.all_coeffs()[0] + 1) class UnShiftA(Operator): """ Decrement an upper index. """ def __init__(self, ap, bq, i, z): """ Note: i counts from zero! """ ap, bq, i = list(map(sympify, [ap, bq, i])) self._ap = ap self._bq = bq self._i = i ap = list(ap) bq = list(bq) ai = ap.pop(i) - 1 if ai == 0: raise ValueError('Cannot decrement unit upper index.') m = Poly(zai, _x) for a in ap: m = Poly(_x + a, _x) A = Dummy('A') n = D = Poly(aiA - ai, A) for b in bq: n = D + (b - 1).as_poly(A) b0 = -n.nth(0) if b0 == 0: raise ValueError('Cannot decrement upper index: ' 'cancels with lower') n = Poly(Poly(n.all_coeffs()[:-1], A).as_expr().subs(A, _x/ai + 1), _x) self._poly = Poly((n - m)/b0, _x) def __str__(self): return '<Decrement upper index #%s of %s, %s.>' % (self._i, self._ap, self._bq) class UnShiftB(Operator): """ Increment a lower index. """ def __init__(self, ap, bq, i, z): """ Note: i counts from zero! """ ap, bq, i = list(map(sympify, [ap, bq, i])) self._ap = ap self._bq = bq self._i = i ap = list(ap) bq = list(bq) bi = bq.pop(i) + 1 if bi == 0: raise ValueError('Cannot increment -1 lower index.') m = Poly(_x(bi - 1), _x) for b in bq: m = Poly(_x + b - 1, _x) B = Dummy('B') D = Poly((bi - 1)B - bi + 1, B) n = Poly(z, B) for a in ap: n = (D + a.as_poly(B)) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment index: cancels with upper') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, _x/(bi - 1) + 1), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment lower index #%s of %s, %s.>' % (self._i, self._ap, self._bq) class MeijerShiftA(Operator): """ Increment an upper b index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(bi - _x, _x) def __str__(self): return '<Increment upper b=%s.>' % (self._poly.all_coeffs()[1]) class MeijerShiftB(Operator): """ Decrement an upper a index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(1 - bi + _x, _x) def __str__(self): return '<Decrement upper a=%s.>' % (1 - self._poly.all_coeffs()[1]) class MeijerShiftC(Operator): """ Increment a lower b index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(-bi + _x, _x) def __str__(self): return '<Increment lower b=%s.>' % (-self._poly.all_coeffs()[1]) class MeijerShiftD(Operator): """ Decrement a lower a index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(bi - 1 - _x, _x) def __str__(self): return '<Decrement lower a=%s.>' % (self._poly.all_coeffs()[1] + 1) class MeijerUnShiftA(Operator): """ Decrement an upper b index. """ def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) bi = bm.pop(i) - 1 m = Poly(1, _x) for b in bm: m = Poly(b - _x, _x) for b in bq: m = Poly(_x - b, _x) A = Dummy('A') D = Poly(bi - A, A) n = Poly(z, A) for a in an: n = (D + 1 - a) for a in ap: n = (-D + a - 1) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot decrement upper b index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], A).as_expr().subs(A, bi - _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Decrement upper b index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftB(Operator): """ Increment an upper a index. """ def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) ai = an.pop(i) + 1 m = Poly(z, _x) for a in an: m = Poly(1 - a + _x, _x) for a in ap: m = Poly(a - 1 - _x, _x) B = Dummy('B') D = Poly(B + ai - 1, B) n = Poly(1, B) for b in bm: n = (-D + b) for b in bq: n = (D - b) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment upper a index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, 1 - ai + _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment upper a index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftC(Operator): """ Decrement a lower b index. """ # XXX this is "essentially" the same as MeijerUnShiftA. This "essentially" # can be made rigorous using the functional equation G(1/z) = G'(z), # where G' denotes a G function of slightly altered parameters. # However, sorting out the details seems harder than just coding it # again. def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) bi = bq.pop(i) - 1 m = Poly(1, _x) for b in bm: m = Poly(b - _x, _x) for b in bq: m = Poly(_x - b, _x) C = Dummy('C') D = Poly(bi + C, C) n = Poly(z, C) for a in an: n = (D + 1 - a) for a in ap: n = (-D + a - 1) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot decrement lower b index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], C).as_expr().subs(C, _x - bi), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Decrement lower b index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftD(Operator): """ Increment a lower a index. """ # XXX This is essentially the same as MeijerUnShiftA. # See comment at MeijerUnShiftC. def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) ai = ap.pop(i) + 1 m = Poly(z, _x) for a in an: m = Poly(1 - a + _x, _x) for a in ap: m = Poly(a - 1 - _x, _x) B = Dummy('B') # - this is the shift operator `D_I` D = Poly(ai - 1 - B, B) n = Poly(1, B) for b in bm: n = (-D + b) for b in bq: n = (D - b) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment lower a index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, ai - 1 - _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment lower a index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class ReduceOrder(Operator): """ Reduce Order by cancelling an upper and a lower index. """ def __new__(cls, ai, bj): """ For convenience if reduction is not possible, return None. """ ai = sympify(ai) bj = sympify(bj) n = ai - bj if not n.is_Integer or n < 0: return None if bj.is_integer and bj.is_nonpositive: return None expr = Operator.__new__(cls) p = S.One for k in range(n): p = (_x + bj + k)/(bj + k) expr._poly = Poly(p, _x) expr._a = ai expr._b = bj return expr @classmethod def _meijer(cls, b, a, sign): """ Cancel b + signs and a + signs This is for meijer G functions. """ b = sympify(b) a = sympify(a) n = b - a if n.is_negative or not n.is_Integer: return None expr = Operator.__new__(cls) p = S.One for k in range(n): p = (sign_x + a + k) expr._poly = Poly(p, _x) if sign == -1: expr._a = b expr._b = a else: expr._b = Add(1, a - 1, evaluate=False) expr._a = Add(1, b - 1, evaluate=False) return expr @classmethod def meijer_minus(cls, b, a): return cls._meijer(b, a, -1) @classmethod def meijer_plus(cls, a, b): return cls._meijer(1 - a, 1 - b, 1) def __str__(self): return '<Reduce order by cancelling upper %s with lower %s.>' % \ (self._a, self._b) def _reduce_order(ap, bq, gen, key): """ Order reduction algorithm used in Hypergeometric and Meijer G """ ap = list(ap) bq = list(bq) ap.sort(key=key) bq.sort(key=key) nap = [] # we will edit bq in place operators = [] for a in ap: op = None for i in range(len(bq)): op = gen(a, bq[i]) if op is not None: bq.pop(i) break if op is None: nap.append(a) else: operators.append(op) return nap, bq, operators def reduce_order(func): """ Given the hypergeometric function ``func``, find a sequence of operators to reduces order as much as possible. Explanation =========== Return (newfunc, [operators]), where applying the operators to the hypergeometric function newfunc yields func. Examples ======== >>> from sympy.simplify.hyperexpand import reduce_order, Hyper_Function >>> reduce_order(Hyper_Function((1, 2), (3, 4))) (Hyper_Function((1, 2), (3, 4)), []) >>> reduce_order(Hyper_Function((1,), (1,))) (Hyper_Function((), ()), [<Reduce order by cancelling upper 1 with lower 1.>]) >>> reduce_order(Hyper_Function((2, 4), (3, 3))) (Hyper_Function((2,), (3,)), [<Reduce order by cancelling upper 4 with lower 3.>]) """ nap, nbq, operators = _reduce_order(func.ap, func.bq, ReduceOrder, default_sort_key) return Hyper_Function(Tuple(nap), Tuple(nbq)), operators def reduce_order_meijer(func): """ Given the Meijer G function parameters, ``func``, find a sequence of operators that reduces order as much as possible. Return newfunc, [operators]. Examples ======== >>> from sympy.simplify.hyperexpand import (reduce_order_meijer, ... G_Function) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [3, 4], [1, 2]))[0] G_Function((4, 3), (5, 6), (3, 4), (2, 1)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [3, 4], [1, 8]))[0] G_Function((3,), (5, 6), (3, 4), (1,)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [7, 5], [1, 5]))[0] G_Function((3,), (), (), (1,)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [7, 5], [5, 3]))[0] G_Function((), (), (), ()) """ nan, nbq, ops1 = _reduce_order(func.an, func.bq, ReduceOrder.meijer_plus, lambda x: default_sort_key(-x)) nbm, nap, ops2 = _reduce_order(func.bm, func.ap, ReduceOrder.meijer_minus, default_sort_key) return G_Function(nan, nap, nbm, nbq), ops1 + ops2 def make_derivative_operator(M, z): """ Create a derivative operator, to be passed to Operator.apply. """ def doit(C): r = zC.diff(z) + CM r = r.applyfunc(make_simp(z)) return r return doit def apply_operators(obj, ops, op): """ Apply the list of operators ``ops`` to object ``obj``, substituting ``op`` for the generator. """ res = obj for o in reversed(ops): res = o.apply(res, op) return res def devise_plan(target, origin, z): """ Devise a plan (consisting of shift and un-shift operators) to be applied to the hypergeometric function ``target`` to yield ``origin``. Returns a list of operators. Examples ======== >>> from sympy.simplify.hyperexpand import devise_plan, Hyper_Function >>> from sympy.abc import z Nothing to do: >>> devise_plan(Hyper_Function((1, 2), ()), Hyper_Function((1, 2), ()), z) [] >>> devise_plan(Hyper_Function((), (1, 2)), Hyper_Function((), (1, 2)), z) [] Very simple plans: >>> devise_plan(Hyper_Function((2,), ()), Hyper_Function((1,), ()), z) [<Increment upper 1.>] >>> devise_plan(Hyper_Function((), (2,)), Hyper_Function((), (1,)), z) [<Increment lower index #0 of [], [1].>] Several buckets: >>> from sympy import S >>> devise_plan(Hyper_Function((1, S.Half), ()), ... Hyper_Function((2, S('3/2')), ()), z) #doctest: +NORMALIZE_WHITESPACE [<Decrement upper index #0 of [3/2, 1], [].>, <Decrement upper index #0 of [2, 3/2], [].>] A slightly more complicated plan: >>> devise_plan(Hyper_Function((1, 3), ()), Hyper_Function((2, 2), ()), z) [<Increment upper 2.>, <Decrement upper index #0 of [2, 2], [].>] Another more complicated plan: (note that the ap have to be shifted first!) >>> devise_plan(Hyper_Function((1, -1), (2,)), Hyper_Function((3, -2), (4,)), z) [<Decrement lower 3.>, <Decrement lower 4.>, <Decrement upper index #1 of [-1, 2], [4].>, <Decrement upper index #1 of [-1, 3], [4].>, <Increment upper -2.>] """ abuckets, bbuckets, nabuckets, nbbuckets = [sift(params, _mod1) for params in (target.ap, target.bq, origin.ap, origin.bq)] if len(list(abuckets.keys())) != len(list(nabuckets.keys())) or \ len(list(bbuckets.keys())) != len(list(nbbuckets.keys())): raise ValueError('%s not reachable from %s' % (target, origin)) ops = [] def do_shifts(fro, to, inc, dec): ops = [] for i in range(len(fro)): if to[i] - fro[i] > 0: sh = inc ch = 1 else: sh = dec ch = -1 while to[i] != fro[i]: ops += [sh(fro, i)] fro[i] += ch return ops def do_shifts_a(nal, nbk, al, aother, bother): """ Shift us from (nal, nbk) to (al, nbk). """ return do_shifts(nal, al, lambda p, i: ShiftA(p[i]), lambda p, i: UnShiftA(p + aother, nbk + bother, i, z)) def do_shifts_b(nal, nbk, bk, aother, bother): """ Shift us from (nal, nbk) to (nal, bk). """ return do_shifts(nbk, bk, lambda p, i: UnShiftB(nal + aother, p + bother, i, z), lambda p, i: ShiftB(p[i])) for r in sorted(list(abuckets.keys()) + list(bbuckets.keys()), key=default_sort_key): al = () nal = () bk = () nbk = () if r in abuckets: al = abuckets[r] nal = nabuckets[r] if r in bbuckets: bk = bbuckets[r] nbk = nbbuckets[r] if len(al) != len(nal) or len(bk) != len(nbk): raise ValueError('%s not reachable from %s' % (target, origin)) al, nal, bk, nbk = [sorted(list(w), key=default_sort_key) for w in [al, nal, bk, nbk]] def others(dic, key): l = [] for k, value in dic.items(): if k != key: l += list(dic[k]) return l aother = others(nabuckets, r) bother = others(nbbuckets, r) if len(al) == 0: # there can be no complications, just shift the bs as we please ops += do_shifts_b([], nbk, bk, aother, bother) elif len(bk) == 0: # there can be no complications, just shift the as as we please ops += do_shifts_a(nal, [], al, aother, bother) else: namax = nal[-1] amax = al[-1] if nbk[0] - namax <= 0 or bk[0] - amax <= 0: raise ValueError('Non-suitable parameters.') if namax - amax > 0: # we are going to shift down - first do the as, then the bs ops += do_shifts_a(nal, nbk, al, aother, bother) ops += do_shifts_b(al, nbk, bk, aother, bother) else: # we are going to shift up - first do the bs, then the as ops += do_shifts_b(nal, nbk, bk, aother, bother) ops += do_shifts_a(nal, bk, al, aother, bother) nabuckets[r] = al nbbuckets[r] = bk ops.reverse() return ops def try_shifted_sum(func, z): """ Try to recognise a hypergeometric sum that starts from k > 0. """ abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) if len(abuckets[S.Zero]) != 1: return None r = abuckets[S.Zero][0] if r <= 0: return None if not S.Zero in bbuckets: return None l = list(bbuckets[S.Zero]) l.sort() k = l[0] if k <= 0: return None nap = list(func.ap) nap.remove(r) nbq = list(func.bq) nbq.remove(k) k -= 1 nap = [x - k for x in nap] nbq = [x - k for x in nbq] ops = [] for n in range(r - 1): ops.append(ShiftA(n + 1)) ops.reverse() fac = factorial(k)/z*k for a in nap: fac /= rf(a, k) for b in nbq: fac = rf(b, k) ops += [MultOperator(fac)] p = 0 for n in range(k): m = z*n/factorial(n) for a in nap: m = rf(a, n) for b in nbq: m /= rf(b, n) p += m return Hyper_Function(nap, nbq), ops, -p def try_polynomial(func, z): """ Recognise polynomial cases. Returns None if not such a case. Requires order to be fully reduced. """ abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) a0 = abuckets[S.Zero] b0 = bbuckets[S.Zero] a0.sort() b0.sort() al0 = [x for x in a0 if x <= 0] bl0 = [x for x in b0 if x <= 0] if bl0 and all(a < bl0[-1] for a in al0): return oo if not al0: return None a = al0[-1] fac = 1 res = S.One for n in Tuple(list(range(-a))): fac = z fac /= n + 1 for a in func.ap: fac = a + n for b in func.bq: fac /= b + n res += fac return res def try_lerchphi(func): """ Try to find an expression for Hyper_Function ``func`` in terms of Lerch Transcendents. Return None if no such expression can be found. """ # This is actually quite simple, and is described in Roach's paper, # section 18. # We don't need to implement the reduction to polylog here, this # is handled by expand_func. from sympy.matrices import Matrix, zeros from sympy.polys import apart # First we need to figure out if the summation coefficient is a rational # function of the summation index, and construct that rational function. abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) paired = {} for key, value in abuckets.items(): if key != 0 and not key in bbuckets: return None bvalue = bbuckets[key] paired[key] = (list(value), list(bvalue)) bbuckets.pop(key, None) if bbuckets != {}: return None if not S.Zero in abuckets: return None aints, bints = paired[S.Zero] # Account for the additional n! in denominator paired[S.Zero] = (aints, bints + [1]) t = Dummy('t') numer = S.One denom = S.One for key, (avalue, bvalue) in paired.items(): if len(avalue) != len(bvalue): return None # Note that since order has been reduced fully, all the b are # bigger than all the a they differ from by an integer. In particular # if there are any negative b left, this function is not well-defined. for a, b in zip(avalue, bvalue): if (a - b).is_positive: k = a - b numer = rf(b + t, k) denom = rf(b, k) else: k = b - a numer = rf(a, k) denom = rf(a + t, k) # Now do a partial fraction decomposition. # We assemble two structures: a list monomials of pairs (a, b) representing # atb (b a non-negative integer), and a dict terms, where # terms[a] = [(b, c)] means that there is a term b/(t-a)c. part = apart(numer/denom, t) args = Add.make_args(part) monomials = [] terms = {} for arg in args: numer, denom = arg.as_numer_denom() if not denom.has(t): p = Poly(numer, t) if not p.is_monomial: raise TypeError("p should be monomial") ((b, ), a) = p.LT() monomials += [(a/denom, b)] continue if numer.has(t): raise NotImplementedError('Need partial fraction decomposition' ' with linear denominators') indep, [dep] = denom.as_coeff_mul(t) n = 1 if dep.is_Pow: n = dep.exp dep = dep.base if dep == t: a == 0 elif dep.is_Add: a, tmp = dep.as_independent(t) b = 1 if tmp != t: b, _ = tmp.as_independent(t) if dep != bt + a: raise NotImplementedError('unrecognised form %s' % dep) a /= b indep = b*n else: raise NotImplementedError('unrecognised form of partial fraction') terms.setdefault(a, []).append((numer/indep, n)) # Now that we have this information, assemble our formula. All the # monomials yield rational functions and go into one basis element. # The terms[a] are related by differentiation. If the largest exponent is # n, we need lerchphi(z, k, a) for k = 1, 2, ..., n. # deriv maps a basis to its derivative, expressed as a C(z)-linear # combination of other basis elements. deriv = {} coeffs = {} z = Dummy('z') monomials.sort(key=lambda x: x[1]) mon = {0: 1/(1 - z)} if monomials: for k in range(monomials[-1][1]): mon[k + 1] = zmon[k].diff(z) for a, n in monomials: coeffs.setdefault(S.One, []).append(amon[n]) for a, l in terms.items(): for c, k in l: coeffs.setdefault(lerchphi(z, k, a), []).append(c) l.sort(key=lambda x: x[1]) for k in range(2, l[-1][1] + 1): deriv[lerchphi(z, k, a)] = [(-a, lerchphi(z, k, a)), (1, lerchphi(z, k - 1, a))] deriv[lerchphi(z, 1, a)] = [(-a, lerchphi(z, 1, a)), (1/(1 - z), S.One)] trans = {} for n, b in enumerate([S.One] + list(deriv.keys())): trans[b] = n basis = [expand_func(b) for (b, _) in sorted(list(trans.items()), key=lambda x:x[1])] B = Matrix(basis) C = Matrix([[0]len(B)]) for b, c in coeffs.items(): C[trans[b]] = Add(c) M = zeros(len(B)) for b, l in deriv.items(): for c, b2 in l: M[trans[b], trans[b2]] = c return Formula(func, z, None, [], B, C, M) def build_hypergeometric_formula(func): """ Create a formula object representing the hypergeometric function ``func``. """ # We know that no `ap` are negative integers, otherwise "detect poly" # would have kicked in. However, `ap` could be empty. In this case we can # use a different basis. # I'm not aware of a basis that works in all cases. from sympy import zeros, Matrix, eye z = Dummy('z') if func.ap: afactors = [_x + a for a in func.ap] bfactors = [_x + b - 1 for b in func.bq] expr = _xMul(bfactors) - zMul(afactors) poly = Poly(expr, _x) n = poly.degree() basis = [] M = zeros(n) for k in range(n): a = func.ap[0] + k basis += [hyper([a] + list(func.ap[1:]), func.bq, z)] if k < n - 1: M[k, k] = -a M[k, k + 1] = a B = Matrix(basis) C = Matrix([[1] + [0](n - 1)]) derivs = [eye(n)] for k in range(n): derivs.append(Mderivs[k]) l = poly.all_coeffs() l.reverse() res = [0]n for k, c in enumerate(l): for r, d in enumerate(Cderivs[k]): res[r] += cd for k, c in enumerate(res): M[n - 1, k] = -c/derivs[n - 1][0, n - 1]/poly.all_coeffs()[0] return Formula(func, z, None, [], B, C, M) else: # Since there are no `ap`, none of the `bq` can be non-positive # integers. basis = [] bq = list(func.bq[:]) for i in range(len(bq)): basis += [hyper([], bq, z)] bq[i] += 1 basis += [hyper([], bq, z)] B = Matrix(basis) n = len(B) C = Matrix([[1] + [0](n - 1)]) M = zeros(n) M[0, n - 1] = z/Mul(func.bq) for k in range(1, n): M[k, k - 1] = func.bq[k - 1] M[k, k] = -func.bq[k - 1] return Formula(func, z, None, [], B, C, M) def hyperexpand_special(ap, bq, z): """ Try to find a closed-form expression for hyper(ap, bq, z), where ``z`` is supposed to be a "special" value, e.g. 1. This function tries various of the classical summation formulae (Gauss, Saalschuetz, etc). """ # This code is very ad-hoc. There are many clever algorithms # (notably Zeilberger's) related to this problem. # For now we just want a few simple cases to work. p, q = len(ap), len(bq) z_ = z z = unpolarify(z) if z == 0: return S.One if p == 2 and q == 1: # 2F1 a, b, c = ap + bq if z == 1: # Gauss return gamma(c - a - b)gamma(c)/gamma(c - a)/gamma(c - b) if z == -1 and simplify(b - a + c) == 1: b, a = a, b if z == -1 and simplify(a - b + c) == 1: # Kummer if b.is_integer and b.is_negative: return 2cos(pib/2)gamma(-b)gamma(b - a + 1) \ /gamma(-b/2)/gamma(b/2 - a + 1) else: return gamma(b/2 + 1)gamma(b - a + 1) \ /gamma(b + 1)/gamma(b/2 - a + 1) # TODO tons of more formulae # investigate what algorithms exist return hyper(ap, bq, z_) _collection = None def _hyperexpand(func, z, ops0=[], z0=Dummy('z0'), premult=1, prem=0, rewrite='default'): """ Try to find an expression for the hypergeometric function ``func``. Explanation =========== The result is expressed in terms of a dummy variable ``z0``. Then it is multiplied by ``premult``. Then ``ops0`` is applied. ``premult`` must be azprem for some a independent of ``z``. """ if z.is_zero: return S.One z = polarify(z, subs=False) if rewrite == 'default': rewrite = 'nonrepsmall' def carryout_plan(f, ops): C = apply_operators(f.C.subs(f.z, z0), ops, make_derivative_operator(f.M.subs(f.z, z0), z0)) from sympy import eye C = apply_operators(C, ops0, make_derivative_operator(f.M.subs(f.z, z0) + premeye(f.M.shape[0]), z0)) if premult == 1: C = C.applyfunc(make_simp(z0)) r = reduce(lambda s,m: s+m[0]m[1], zip(C, f.B.subs(f.z, z0)), S.Zero)premult res = r.subs(z0, z) if rewrite: res = res.rewrite(rewrite) return res # TODO # The following would be possible: # ) PFD Duplication (see Kelly Roach's paper) # ) In a similar spirit, try_lerchphi() can be generalised considerably. global _collection if _collection is None: _collection = FormulaCollection() debug('Trying to expand hypergeometric function ', func) # First reduce order as much as possible. func, ops = reduce_order(func) if ops: debug(' Reduced order to ', func) else: debug(' Could not reduce order.') # Now try polynomial cases res = try_polynomial(func, z0) if res is not None: debug(' Recognised polynomial.') p = apply_operators(res, ops, lambda f: z0f.diff(z0)) p = apply_operators(ppremult, ops0, lambda f: z0f.diff(z0)) return unpolarify(simplify(p).subs(z0, z)) # Try to recognise a shifted sum. p = S.Zero res = try_shifted_sum(func, z0) if res is not None: func, nops, p = res debug(' Recognised shifted sum, reduced order to ', func) ops += nops # apply the plan for poly p = apply_operators(p, ops, lambda f: z0f.diff(z0)) p = apply_operators(ppremult, ops0, lambda f: z0f.diff(z0)) p = simplify(p).subs(z0, z) # Try special expansions early. if unpolarify(z) in [1, -1] and (len(func.ap), len(func.bq)) == (2, 1): f = build_hypergeometric_formula(func) r = carryout_plan(f, ops).replace(hyper, hyperexpand_special) if not r.has(hyper): return r + p # Try to find a formula in our collection formula = _collection.lookup_origin(func) # Now try a lerch phi formula if formula is None: formula = try_lerchphi(func) if formula is None: debug(' Could not find an origin. ', 'Will return answer in terms of ' 'simpler hypergeometric functions.') formula = build_hypergeometric_formula(func) debug(' Found an origin: ', formula.closed_form, ' ', formula.func) # We need to find the operators that convert formula into func. ops += devise_plan(func, formula.func, z0) # Now carry out the plan. r = carryout_plan(formula, ops) + p return powdenest(r, polar=True).replace(hyper, hyperexpand_special) def devise_plan_meijer(fro, to, z): """ Find operators to convert G-function ``fro`` into G-function ``to``. Explanation =========== It is assumed that ``fro`` and ``to`` have the same signatures, and that in fact any corresponding pair of parameters differs by integers, and a direct path is possible. I.e. if there are parameters a1 b1 c1 and a2 b2 c2 it is assumed that a1 can be shifted to a2, etc. The only thing this routine determines is the order of shifts to apply, nothing clever will be tried. It is also assumed that ``fro`` is suitable. Examples ======== >>> from sympy.simplify.hyperexpand import (devise_plan_meijer, ... G_Function) >>> from sympy.abc import z Empty plan: >>> devise_plan_meijer(G_Function([1], [2], [3], [4]), ... G_Function([1], [2], [3], [4]), z) [] Very simple plans: >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([1], [], [], []), z) [<Increment upper a index #0 of [0], [], [], [].>] >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([-1], [], [], []), z) [<Decrement upper a=0.>] >>> devise_plan_meijer(G_Function([], [1], [], []), ... G_Function([], [2], [], []), z) [<Increment lower a index #0 of [], [1], [], [].>] Slightly more complicated plans: >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([2], [], [], []), z) [<Increment upper a index #0 of [1], [], [], [].>, <Increment upper a index #0 of [0], [], [], [].>] >>> devise_plan_meijer(G_Function([0], [], [0], []), ... G_Function([-1], [], [1], []), z) [<Increment upper b=0.>, <Decrement upper a=0.>] Order matters: >>> devise_plan_meijer(G_Function([0], [], [0], []), ... G_Function([1], [], [1], []), z) [<Increment upper a index #0 of [0], [], [1], [].>, <Increment upper b=0.>] """ # TODO for now, we use the following simple heuristic: inverse-shift # when possible, shift otherwise. Give up if we cannot make progress. def try_shift(f, t, shifter, diff, counter): """ Try to apply ``shifter`` in order to bring some element in ``f`` nearer to its counterpart in ``to``. ``diff`` is +/- 1 and determines the effect of ``shifter``. Counter is a list of elements blocking the shift. Return an operator if change was possible, else None. """ for idx, (a, b) in enumerate(zip(f, t)): if ( (a - b).is_integer and (b - a)/diff > 0 and all(a != x for x in counter)): sh = shifter(idx) f[idx] += diff return sh fan = list(fro.an) fap = list(fro.ap) fbm = list(fro.bm) fbq = list(fro.bq) ops = [] change = True while change: change = False op = try_shift(fan, to.an, lambda i: MeijerUnShiftB(fan, fap, fbm, fbq, i, z), 1, fbm + fbq) if op is not None: ops += [op] change = True continue op = try_shift(fap, to.ap, lambda i: MeijerUnShiftD(fan, fap, fbm, fbq, i, z), 1, fbm + fbq) if op is not None: ops += [op] change = True continue op = try_shift(fbm, to.bm, lambda i: MeijerUnShiftA(fan, fap, fbm, fbq, i, z), -1, fan + fap) if op is not None: ops += [op] change = True continue op = try_shift(fbq, to.bq, lambda i: MeijerUnShiftC(fan, fap, fbm, fbq, i, z), -1, fan + fap) if op is not None: ops += [op] change = True continue op = try_shift(fan, to.an, lambda i: MeijerShiftB(fan[i]), -1, []) if op is not None: ops += [op] change = True continue op = try_shift(fap, to.ap, lambda i: MeijerShiftD(fap[i]), -1, []) if op is not None: ops += [op] change = True continue op = try_shift(fbm, to.bm, lambda i: MeijerShiftA(fbm[i]), 1, []) if op is not None: ops += [op] change = True continue op = try_shift(fbq, to.bq, lambda i: MeijerShiftC(fbq[i]), 1, []) if op is not None: ops += [op] change = True continue if fan != list(to.an) or fap != list(to.ap) or fbm != list(to.bm) or \ fbq != list(to.bq): raise NotImplementedError('Could not devise plan.') ops.reverse() return ops _meijercollection = None def _meijergexpand(func, z0, allow_hyper=False, rewrite='default', place=None): """ Try to find an expression for the Meijer G function specified by the G_Function ``func``. If ``allow_hyper`` is True, then returning an expression in terms of hypergeometric functions is allowed. Currently this just does Slater's theorem. If expansions exist both at zero and at infinity, ``place`` can be set to ``0`` or ``zoo`` for the preferred choice. """ global _meijercollection if _meijercollection is None: _meijercollection = MeijerFormulaCollection() if rewrite == 'default': rewrite = None func0 = func debug('Try to expand Meijer G function corresponding to ', func) # We will play games with analytic continuation - rather use a fresh symbol z = Dummy('z') func, ops = reduce_order_meijer(func) if ops: debug(' Reduced order to ', func) else: debug(' Could not reduce order.') # Try to find a direct formula f = _meijercollection.lookup_origin(func) if f is not None: debug(' Found a Meijer G formula: ', f.func) ops += devise_plan_meijer(f.func, func, z) # Now carry out the plan. C = apply_operators(f.C.subs(f.z, z), ops, make_derivative_operator(f.M.subs(f.z, z), z)) C = C.applyfunc(make_simp(z)) r = Cf.B.subs(f.z, z) r = r[0].subs(z, z0) return powdenest(r, polar=True) debug(" Could not find a direct formula. Trying Slater's theorem.") # TODO the following would be possible: # ) Paired Index Theorems # ) PFD Duplication # (See Kelly Roach's paper for details on either.) # # TODO Also, we tend to create combinations of gamma functions that can be # simplified. def can_do(pbm, pap): """ Test if slater applies. """ for i in pbm: if len(pbm[i]) > 1: l = 0 if i in pap: l = len(pap[i]) if l + 1 < len(pbm[i]): return False return True def do_slater(an, bm, ap, bq, z, zfinal): # zfinal is the value that will eventually be substituted for z. # We pass it to _hyperexpand to improve performance. func = G_Function(an, bm, ap, bq) _, pbm, pap, _ = func.compute_buckets() if not can_do(pbm, pap): return S.Zero, False cond = len(an) + len(ap) < len(bm) + len(bq) if len(an) + len(ap) == len(bm) + len(bq): cond = abs(z) < 1 if cond is False: return S.Zero, False res = S.Zero for m in pbm: if len(pbm[m]) == 1: bh = pbm[m][0] fac = 1 bo = list(bm) bo.remove(bh) for bj in bo: fac = gamma(bj - bh) for aj in an: fac = gamma(1 + bh - aj) for bj in bq: fac /= gamma(1 + bh - bj) for aj in ap: fac /= gamma(aj - bh) nap = [1 + bh - a for a in list(an) + list(ap)] nbq = [1 + bh - b for b in list(bo) + list(bq)] k = polar_lift(S.NegativeOne(len(ap) - len(bm))) harg = kzfinal # NOTE even though k "is" +-1, this has to be t/k instead of # tk ... we are using polar numbers for consistency! premult = (t/k)bh hyp = _hyperexpand(Hyper_Function(nap, nbq), harg, ops, t, premult, bh, rewrite=None) res += fac hyp else: b_ = pbm[m][0] ki = [bi - b_ for bi in pbm[m][1:]] u = len(ki) li = [ai - b_ for ai in pap[m][:u + 1]] bo = list(bm) for b in pbm[m]: bo.remove(b) ao = list(ap) for a in pap[m][:u]: ao.remove(a) lu = li[-1] di = [l - k for (l, k) in zip(li, ki)] # We first work out the integrand: s = Dummy('s') integrand = z*s for b in bm: if not Mod(b, 1) and b.is_Number: b = int(round(b)) integrand = gamma(b - s) for a in an: integrand = gamma(1 - a + s) for b in bq: integrand /= gamma(1 - b + s) for a in ap: integrand /= gamma(a - s) # Now sum the finitely many residues: # XXX This speeds up some cases - is it a good idea? integrand = expand_func(integrand) for r in range(int(round(lu))): resid = residue(integrand, s, b_ + r) resid = apply_operators(resid, ops, lambda f: zf.diff(z)) res -= resid # Now the hypergeometric term. au = b_ + lu k = polar_lift(S.NegativeOne*(len(ao) + len(bo) + 1)) harg = kzfinal premult = (t/k)au nap = [1 + au - a for a in list(an) + list(ap)] + [1] nbq = [1 + au - b for b in list(bm) + list(bq)] hyp = _hyperexpand(Hyper_Function(nap, nbq), harg, ops, t, premult, au, rewrite=None) C = S.NegativeOne(lu)/factorial(lu) for i in range(u): C = S.NegativeOnedi[i]/rf(lu - li[i] + 1, di[i]) for a in an: C = gamma(1 - a + au) for b in bo: C = gamma(b - au) for a in ao: C /= gamma(a - au) for b in bq: C /= gamma(1 - b + au) res += Chyp return res, cond t = Dummy('t') slater1, cond1 = do_slater(func.an, func.bm, func.ap, func.bq, z, z0) def tr(l): return [1 - x for x in l] for op in ops: op._poly = Poly(op._poly.subs({z: 1/t, _x: -_x}), _x) slater2, cond2 = do_slater(tr(func.bm), tr(func.an), tr(func.bq), tr(func.ap), t, 1/z0) slater1 = powdenest(slater1.subs(z, z0), polar=True) slater2 = powdenest(slater2.subs(t, 1/z0), polar=True) if not isinstance(cond2, bool): cond2 = cond2.subs(t, 1/z) m = func(z) if m.delta > 0 or \ (m.delta == 0 and len(m.ap) == len(m.bq) and (re(m.nu) < -1) is not False and polar_lift(z0) == polar_lift(1)): # The condition delta > 0 means that the convergence region is # connected. Any expression we find can be continued analytically # to the entire convergence region. # The conditions delta==0, p==q, re(nu) < -1 imply that G is continuous # on the positive reals, so the values at z=1 agree. if cond1 is not False: cond1 = True if cond2 is not False: cond2 = True if cond1 is True: slater1 = slater1.rewrite(rewrite or 'nonrep') else: slater1 = slater1.rewrite(rewrite or 'nonrepsmall') if cond2 is True: slater2 = slater2.rewrite(rewrite or 'nonrep') else: slater2 = slater2.rewrite(rewrite or 'nonrepsmall') if cond1 is not False and cond2 is not False: # If one condition is False, there is no choice. if place == 0: cond2 = False if place == zoo: cond1 = False if not isinstance(cond1, bool): cond1 = cond1.subs(z, z0) if not isinstance(cond2, bool): cond2 = cond2.subs(z, z0) def weight(expr, cond): if cond is True: c0 = 0 elif cond is False: c0 = 1 else: c0 = 2 if expr.has(oo, zoo, -oo, nan): # XXX this actually should not happen, but consider # S('meijerg(((0, -1/2, 0, -1/2, 1/2), ()), ((0,), # (-1/2, -1/2, -1/2, -1)), exp_polar(I*pi))/4') c0 = 3 return (c0, expr.count(hyper), expr.count_ops()) w1 = weight(slater1, cond1) w2 = weight(slater2, cond2) if min(w1, w2) <= (0, 1, oo): if w1 < w2: return slater1 else: return slater2 if max(w1[0], w2[0]) <= 1 and max(w1[1], w2[1]) <= 1: return Piecewise((slater1, cond1), (slater2, cond2), (func0(z0), True)) # We couldn't find an expression without hypergeometric functions. # TODO it would be helpful to give conditions under which the integral # is known to diverge. r = Piecewise((slater1, cond1), (slater2, cond2), (func0(z0), True)) if r.has(hyper) and not allow_hyper: debug(' Could express using hypergeometric functions, ' 'but not allowed.') if not r.has(hyper) or allow_hyper: return r return func0(z0) def hyperexpand(f, allow_hyper=False, rewrite='default', place=None): """ Expand hypergeometric functions. If allow_hyper is True, allow partial simplification (that is a result different from input, but still containing hypergeometric functions). If a G-function has expansions both at zero and at infinity, ``place`` can be set to ``0`` or ``zoo`` to indicate the preferred choice. Examples ======== >>> from sympy.simplify.hyperexpand import hyperexpand >>> from sympy.functions import hyper >>> from sympy.abc import z >>> hyperexpand(hyper([], [], z)) exp(z) Non-hyperegeometric parts of the expression and hypergeometric expressions that are not recognised are left unchanged: >>> hyperexpand(1 + hyper([1, 1, 1], [], z)) hyper((1, 1, 1), (), z) + 1 """ f = sympify(f) def do_replace(ap, bq, z): r = _hyperexpand(Hyper_Function(ap, bq), z, rewrite=rewrite) if r is None: return hyper(ap, bq, z) else: return r def do_meijer(ap, bq, z): r = _meijergexpand(G_Function(ap[0], ap[1], bq[0], bq[1]), z, allow_hyper, rewrite=rewrite, place=place) if not r.has(nan, zoo, oo, -oo): return r return f.replace(hyper, do_replace).replace(meijerg, do_meijer)
9757d440686b51570176973fdb0aaf5b5fcbc34bd1bdc319c324164204422a18	""" Optimizations of the expression tree representation for better CSE opportunities. """ from sympy.core import Add, Basic, Mul from sympy.core.basic import preorder_traversal from sympy.core.singleton import S from sympy.utilities.iterables import default_sort_key def sub_pre(e): """ Replace y - x with -(x - y) if -1 can be extracted from y - x. """ # replacing Add, A, from which -1 can be extracted with -1-A adds = [a for a in e.atoms(Add) if a.could_extract_minus_sign()] reps = {} ignore = set() for a in adds: na = -a if na.is_Mul: # e.g. MatExpr ignore.add(a) continue reps[a] = Mul._from_args([S.NegativeOne, na]) e = e.xreplace(reps) # repeat again for persisting Adds but mark these with a leading 1, -1 # e.g. y - x -> 1-1(x - y) if isinstance(e, Basic): negs = {} for a in sorted(e.atoms(Add), key=default_sort_key): if a in ignore: continue if a in reps: negs[a] = reps[a] elif a.could_extract_minus_sign(): negs[a] = Mul._from_args([S.One, S.NegativeOne, -a]) e = e.xreplace(negs) return e def sub_post(e): """ Replace 1-1*x with -x. """ replacements = [] for node in preorder_traversal(e): if isinstance(node, Mul) and \ node.args[0] is S.One and node.args[1] is S.NegativeOne: replacements.append((node, -Mul._from_args(node.args[2:]))) for node, replacement in replacements: e = e.xreplace({node: replacement}) return e
ea1de60622e3707d7965d962f692b4e2346663147cb860dce0bb5f00c6b9e52d	from collections import defaultdict from sympy.core import (Basic, S, Add, Mul, Pow, Symbol, sympify, expand_func, Function, Dummy, Expr, factor_terms, expand_power_exp, Eq) from sympy.core.compatibility import iterable, ordered, as_int from sympy.core.parameters import global_parameters from sympy.core.function import (expand_log, count_ops, _mexpand, _coeff_isneg, nfloat, expand_mul) from sympy.core.numbers import Float, I, pi, Rational, Integer from sympy.core.relational import Relational from sympy.core.rules import Transform from sympy.core.sympify import _sympify from sympy.functions import gamma, exp, sqrt, log, exp_polar, re from sympy.functions.combinatorial.factorials import CombinatorialFunction from sympy.functions.elementary.complexes import unpolarify, Abs from sympy.functions.elementary.exponential import ExpBase from sympy.functions.elementary.hyperbolic import HyperbolicFunction from sympy.functions.elementary.integers import ceiling from sympy.functions.elementary.piecewise import Piecewise, piecewise_fold from sympy.functions.elementary.trigonometric import TrigonometricFunction from sympy.functions.special.bessel import besselj, besseli, besselk, jn, bessely from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.polys import together, cancel, factor from sympy.simplify.combsimp import combsimp from sympy.simplify.cse_opts import sub_pre, sub_post from sympy.simplify.powsimp import powsimp from sympy.simplify.radsimp import radsimp, fraction, collect_abs from sympy.simplify.sqrtdenest import sqrtdenest from sympy.simplify.trigsimp import trigsimp, exptrigsimp from sympy.utilities.iterables import has_variety, sift import mpmath def separatevars(expr, symbols=[], dict=False, force=False): """ Separates variables in an expression, if possible. By default, it separates with respect to all symbols in an expression and collects constant coefficients that are independent of symbols. Explanation =========== If ``dict=True`` then the separated terms will be returned in a dictionary keyed to their corresponding symbols. By default, all symbols in the expression will appear as keys; if symbols are provided, then all those symbols will be used as keys, and any terms in the expression containing other symbols or non-symbols will be returned keyed to the string 'coeff'. (Passing None for symbols will return the expression in a dictionary keyed to 'coeff'.) If ``force=True``, then bases of powers will be separated regardless of assumptions on the symbols involved. Notes ===== The order of the factors is determined by Mul, so that the separated expressions may not necessarily be grouped together. Although factoring is necessary to separate variables in some expressions, it is not necessary in all cases, so one should not count on the returned factors being factored. Examples ======== >>> from sympy.abc import x, y, z, alpha >>> from sympy import separatevars, sin >>> separatevars((xy)y) (xy)*y >>> separatevars((xy)y, force=True) xyyy >>> e = 2x*2zsin(y)+2zx2 >>> separatevars(e) 2x*2z(sin(y) + 1) >>> separatevars(e, symbols=(x, y), dict=True) {'coeff': 2z, x: x*2, y: sin(y) + 1} >>> separatevars(e, [x, y, alpha], dict=True) {'coeff': 2z, alpha: 1, x: x*2, y: sin(y) + 1} If the expression is not really separable, or is only partially separable, separatevars will do the best it can to separate it by using factoring. >>> separatevars(x + xy - 3x2) -x(3x - y - 1) If the expression is not separable then expr is returned unchanged or (if dict=True) then None is returned. >>> eq = 2x + ysin(x) >>> separatevars(eq) == eq True >>> separatevars(2x + ysin(x), symbols=(x, y), dict=True) is None True """ expr = sympify(expr) if dict: return _separatevars_dict(_separatevars(expr, force), symbols) else: return _separatevars(expr, force) def _separatevars(expr, force): if isinstance(expr, Abs): arg = expr.args[0] if arg.is_Mul and not arg.is_number: s = separatevars(arg, dict=True, force=force) if s is not None: return Mul(map(expr.func, s.values())) else: return expr if len(expr.free_symbols) < 2: return expr # don't destroy a Mul since much of the work may already be done if expr.is_Mul: args = list(expr.args) changed = False for i, a in enumerate(args): args[i] = separatevars(a, force) changed = changed or args[i] != a if changed: expr = expr.func(args) return expr # get a Pow ready for expansion if expr.is_Pow: expr = Pow(separatevars(expr.base, force=force), expr.exp) # First try other expansion methods expr = expr.expand(mul=False, multinomial=False, force=force) _expr, reps = posify(expr) if force else (expr, {}) expr = factor(_expr).subs(reps) if not expr.is_Add: return expr # Find any common coefficients to pull out args = list(expr.args) commonc = args[0].args_cnc(cset=True, warn=False)[0] for i in args[1:]: commonc &= i.args_cnc(cset=True, warn=False)[0] commonc = Mul(commonc) commonc = commonc.as_coeff_Mul()[1] # ignore constants commonc_set = commonc.args_cnc(cset=True, warn=False)[0] # remove them for i, a in enumerate(args): c, nc = a.args_cnc(cset=True, warn=False) c = c - commonc_set args[i] = Mul(c)Mul(nc) nonsepar = Add(args) if len(nonsepar.free_symbols) > 1: _expr = nonsepar _expr, reps = posify(_expr) if force else (_expr, {}) _expr = (factor(_expr)).subs(reps) if not _expr.is_Add: nonsepar = _expr return commoncnonsepar def _separatevars_dict(expr, symbols): if symbols: if not all(t.is_Atom for t in symbols): raise ValueError("symbols must be Atoms.") symbols = list(symbols) elif symbols is None: return {'coeff': expr} else: symbols = list(expr.free_symbols) if not symbols: return None ret = {i: [] for i in symbols + ['coeff']} for i in Mul.make_args(expr): expsym = i.free_symbols intersection = set(symbols).intersection(expsym) if len(intersection) > 1: return None if len(intersection) == 0: # There are no symbols, so it is part of the coefficient ret['coeff'].append(i) else: ret[intersection.pop()].append(i) # rebuild for k, v in ret.items(): ret[k] = Mul(v) return ret def _is_sum_surds(p): args = p.args if p.is_Add else [p] for y in args: if not ((y2).is_Rational and y.is_extended_real): return False return True def posify(eq): """Return ``eq`` (with generic symbols made positive) and a dictionary containing the mapping between the old and new symbols. Explanation =========== Any symbol that has positive=None will be replaced with a positive dummy symbol having the same name. This replacement will allow more symbolic processing of expressions, especially those involving powers and logarithms. A dictionary that can be sent to subs to restore ``eq`` to its original symbols is also returned. >>> from sympy import posify, Symbol, log, solve >>> from sympy.abc import x >>> posify(x + Symbol('p', positive=True) + Symbol('n', negative=True)) (_x + n + p, {_x: x}) >>> eq = 1/x >>> log(eq).expand() log(1/x) >>> log(posify(eq)[0]).expand() -log(_x) >>> p, rep = posify(eq) >>> log(p).expand().subs(rep) -log(x) It is possible to apply the same transformations to an iterable of expressions: >>> eq = x2 - 4 >>> solve(eq, x) [-2, 2] >>> eq_x, reps = posify([eq, x]); eq_x [_x*2 - 4, _x] >>> solve(eq_x) [2] """ eq = sympify(eq) if iterable(eq): f = type(eq) eq = list(eq) syms = set() for e in eq: syms = syms.union(e.atoms(Symbol)) reps = {} for s in syms: reps.update({v: k for k, v in posify(s)[1].items()}) for i, e in enumerate(eq): eq[i] = e.subs(reps) return f(eq), {r: s for s, r in reps.items()} reps = {s: Dummy(s.name, positive=True, s.assumptions0) for s in eq.free_symbols if s.is_positive is None} eq = eq.subs(reps) return eq, {r: s for s, r in reps.items()} def hypersimp(f, k): """Given combinatorial term f(k) simplify its consecutive term ratio i.e. f(k+1)/f(k). The input term can be composed of functions and integer sequences which have equivalent representation in terms of gamma special function. Explanation =========== The algorithm performs three basic steps: 1. Rewrite all functions in terms of gamma, if possible. 2. Rewrite all occurrences of gamma in terms of products of gamma and rising factorial with integer, absolute constant exponent. 3. Perform simplification of nested fractions, powers and if the resulting expression is a quotient of polynomials, reduce their total degree. If f(k) is hypergeometric then as result we arrive with a quotient of polynomials of minimal degree. Otherwise None is returned. For more information on the implemented algorithm refer to: 1. W. Koepf, Algorithms for m-fold Hypergeometric Summation, Journal of Symbolic Computation (1995) 20, 399-417 """ f = sympify(f) g = f.subs(k, k + 1) / f g = g.rewrite(gamma) if g.has(Piecewise): g = piecewise_fold(g) g = g.args[-1][0] g = expand_func(g) g = powsimp(g, deep=True, combine='exp') if g.is_rational_function(k): return simplify(g, ratio=S.Infinity) else: return None def hypersimilar(f, g, k): """ Returns True if ``f`` and ``g`` are hyper-similar. Explanation =========== Similarity in hypergeometric sense means that a quotient of f(k) and g(k) is a rational function in ``k``. This procedure is useful in solving recurrence relations. For more information see hypersimp(). """ f, g = list(map(sympify, (f, g))) h = (f/g).rewrite(gamma) h = h.expand(func=True, basic=False) return h.is_rational_function(k) def signsimp(expr, evaluate=None): """Make all Add sub-expressions canonical wrt sign. Explanation =========== If an Add subexpression, ``a``, can have a sign extracted, as determined by could_extract_minus_sign, it is replaced with Mul(-1, a, evaluate=False). This allows signs to be extracted from powers and products. Examples ======== >>> from sympy import signsimp, exp, symbols >>> from sympy.abc import x, y >>> i = symbols('i', odd=True) >>> n = -1 + 1/x >>> n/x/(-n)2 - 1/n/x (-1 + 1/x)/(x(1 - 1/x)2) - 1/(x(-1 + 1/x)) >>> signsimp(_) 0 >>> xn + x-n x(-1 + 1/x) + x(1 - 1/x) >>> signsimp(_) 0 Since powers automatically handle leading signs >>> (-2)i -2i signsimp can be used to put the base of a power with an integer exponent into canonical form: >>> ni (-1 + 1/x)i By default, signsimp doesn't leave behind any hollow simplification: if making an Add canonical wrt sign didn't change the expression, the original Add is restored. If this is not desired then the keyword ``evaluate`` can be set to False: >>> e = exp(y - x) >>> signsimp(e) == e True >>> signsimp(e, evaluate=False) exp(-(x - y)) """ if evaluate is None: evaluate = global_parameters.evaluate expr = sympify(expr) if not isinstance(expr, (Expr, Relational)) or expr.is_Atom: return expr e = sub_post(sub_pre(expr)) if not isinstance(e, (Expr, Relational)) or e.is_Atom: return e if e.is_Add: return e.func([signsimp(a, evaluate) for a in e.args]) if evaluate: e = e.xreplace({m: -(-m) for m in e.atoms(Mul) if -(-m) != m}) return e def simplify(expr, ratio=1.7, measure=count_ops, rational=False, inverse=False, doit=True, kwargs): """Simplifies the given expression. Explanation =========== Simplification is not a well defined term and the exact strategies this function tries can change in the future versions of SymPy. If your algorithm relies on "simplification" (whatever it is), try to determine what you need exactly - is it powsimp()?, radsimp()?, together()?, logcombine()?, or something else? And use this particular function directly, because those are well defined and thus your algorithm will be robust. Nonetheless, especially for interactive use, or when you don't know anything about the structure of the expression, simplify() tries to apply intelligent heuristics to make the input expression "simpler". For example: >>> from sympy import simplify, cos, sin >>> from sympy.abc import x, y >>> a = (x + x2)/(xsin(y)*2 + xcos(y)2) >>> a (x2 + x)/(xsin(y)2 + xcos(y)2) >>> simplify(a) x + 1 Note that we could have obtained the same result by using specific simplification functions: >>> from sympy import trigsimp, cancel >>> trigsimp(a) (x2 + x)/x >>> cancel(_) x + 1 In some cases, applying :func:`simplify` may actually result in some more complicated expression. The default ``ratio=1.7`` prevents more extreme cases: if (result length)/(input length) > ratio, then input is returned unmodified. The ``measure`` parameter lets you specify the function used to determine how complex an expression is. The function should take a single argument as an expression and return a number such that if expression ``a`` is more complex than expression ``b``, then ``measure(a) > measure(b)``. The default measure function is :func:`~.count_ops`, which returns the total number of operations in the expression. For example, if ``ratio=1``, ``simplify`` output can't be longer than input. :: >>> from sympy import sqrt, simplify, count_ops, oo >>> root = 1/(sqrt(2)+3) Since ``simplify(root)`` would result in a slightly longer expression, root is returned unchanged instead:: >>> simplify(root, ratio=1) == root True If ``ratio=oo``, simplify will be applied anyway:: >>> count_ops(simplify(root, ratio=oo)) > count_ops(root) True Note that the shortest expression is not necessary the simplest, so setting ``ratio`` to 1 may not be a good idea. Heuristically, the default value ``ratio=1.7`` seems like a reasonable choice. You can easily define your own measure function based on what you feel should represent the "size" or "complexity" of the input expression. Note that some choices, such as ``lambda expr: len(str(expr))`` may appear to be good metrics, but have other problems (in this case, the measure function may slow down simplify too much for very large expressions). If you don't know what a good metric would be, the default, ``count_ops``, is a good one. For example: >>> from sympy import symbols, log >>> a, b = symbols('a b', positive=True) >>> g = log(a) + log(b) + log(a)log(1/b) >>> h = simplify(g) >>> h log(ab(1 - log(a))) >>> count_ops(g) 8 >>> count_ops(h) 5 So you can see that ``h`` is simpler than ``g`` using the count_ops metric. However, we may not like how ``simplify`` (in this case, using ``logcombine``) has created the ``b(log(1/a) + 1)`` term. A simple way to reduce this would be to give more weight to powers as operations in ``count_ops``. We can do this by using the ``visual=True`` option: >>> print(count_ops(g, visual=True)) 2ADD + DIV + 4LOG + MUL >>> print(count_ops(h, visual=True)) 2LOG + MUL + POW + SUB >>> from sympy import Symbol, S >>> def my_measure(expr): ... POW = Symbol('POW') ... # Discourage powers by giving POW a weight of 10 ... count = count_ops(expr, visual=True).subs(POW, 10) ... # Every other operation gets a weight of 1 (the default) ... count = count.replace(Symbol, type(S.One)) ... return count >>> my_measure(g) 8 >>> my_measure(h) 14 >>> 15./8 > 1.7 # 1.7 is the default ratio True >>> simplify(g, measure=my_measure) -log(a)log(b) + log(a) + log(b) Note that because ``simplify()`` internally tries many different simplification strategies and then compares them using the measure function, we get a completely different result that is still different from the input expression by doing this. If ``rational=True``, Floats will be recast as Rationals before simplification. If ``rational=None``, Floats will be recast as Rationals but the result will be recast as Floats. If rational=False(default) then nothing will be done to the Floats. If ``inverse=True``, it will be assumed that a composition of inverse functions, such as sin and asin, can be cancelled in any order. For example, ``asin(sin(x))`` will yield ``x`` without checking whether x belongs to the set where this relation is true. The default is False. Note that ``simplify()`` automatically calls ``doit()`` on the final expression. You can avoid this behavior by passing ``doit=False`` as an argument. """ def shorter(choices): """ Return the choice that has the fewest ops. In case of a tie, the expression listed first is selected. """ if not has_variety(choices): return choices[0] return min(choices, key=measure) def done(e): rv = e.doit() if doit else e return shorter(rv, collect_abs(rv)) expr = sympify(expr) kwargs = dict( ratio=kwargs.get('ratio', ratio), measure=kwargs.get('measure', measure), rational=kwargs.get('rational', rational), inverse=kwargs.get('inverse', inverse), doit=kwargs.get('doit', doit)) # no routine for Expr needs to check for is_zero if isinstance(expr, Expr) and expr.is_zero: return S.Zero _eval_simplify = getattr(expr, '_eval_simplify', None) if _eval_simplify is not None: return _eval_simplify(kwargs) original_expr = expr = collect_abs(signsimp(expr)) if not isinstance(expr, Basic) or not expr.args: # XXX: temporary hack return expr if inverse and expr.has(Function): expr = inversecombine(expr) if not expr.args: # simplified to atomic return expr # do deep simplification handled = Add, Mul, Pow, ExpBase expr = expr.replace( # here, checking for x.args is not enough because Basic has # args but Basic does not always play well with replace, e.g. # when simultaneous is True found expressions will be masked # off with a Dummy but not all Basic objects in an expression # can be replaced with a Dummy lambda x: isinstance(x, Expr) and x.args and not isinstance( x, handled), lambda x: x.func([simplify(i, *kwargs) for i in x.args]), simultaneous=False) if not isinstance(expr, handled): return done(expr) if not expr.is_commutative: expr = nc_simplify(expr) # TODO: Apply different strategies, considering expression pattern: # is it a purely rational function? Is there any trigonometric function?... # See also https://github.com/sympy/sympy/pull/185. # rationalize Floats floats = False if rational is not False and expr.has(Float): floats = True expr = nsimplify(expr, rational=True) expr = bottom_up(expr, lambda w: getattr(w, 'normal', lambda: w)()) expr = Mul(powsimp(expr).as_content_primitive()) _e = cancel(expr) expr1 = shorter(_e, _mexpand(_e).cancel()) # issue 6829 expr2 = shorter(together(expr, deep=True), together(expr1, deep=True)) if ratio is S.Infinity: expr = expr2 else: expr = shorter(expr2, expr1, expr) if not isinstance(expr, Basic): # XXX: temporary hack return expr expr = factor_terms(expr, sign=False) from sympy.simplify.hyperexpand import hyperexpand from sympy.functions.special.bessel import BesselBase from sympy import Sum, Product, Integral from sympy.functions.elementary.complexes import sign # must come before `Piecewise` since this introduces more `Piecewise` terms if expr.has(sign): expr = expr.rewrite(Abs) # Deal with Piecewise separately to avoid recursive growth of expressions if expr.has(Piecewise): # Fold into a single Piecewise expr = piecewise_fold(expr) # Apply doit, if doit=True expr = done(expr) # Still a Piecewise? if expr.has(Piecewise): # Fold into a single Piecewise, in case doit lead to some # expressions being Piecewise expr = piecewise_fold(expr) # kroneckersimp also affects Piecewise if expr.has(KroneckerDelta): expr = kroneckersimp(expr) # Still a Piecewise? if expr.has(Piecewise): from sympy.functions.elementary.piecewise import piecewise_simplify # Do not apply doit on the segments as it has already # been done above, but simplify expr = piecewise_simplify(expr, deep=True, doit=False) # Still a Piecewise? if expr.has(Piecewise): # Try factor common terms expr = shorter(expr, factor_terms(expr)) # As all expressions have been simplified above with the # complete simplify, nothing more needs to be done here return expr # hyperexpand automatically only works on hypergeometric terms # Do this after the Piecewise part to avoid recursive expansion expr = hyperexpand(expr) if expr.has(KroneckerDelta): expr = kroneckersimp(expr) if expr.has(BesselBase): expr = besselsimp(expr) if expr.has(TrigonometricFunction, HyperbolicFunction): expr = trigsimp(expr, deep=True) if expr.has(log): expr = shorter(expand_log(expr, deep=True), logcombine(expr)) if expr.has(CombinatorialFunction, gamma): # expression with gamma functions or non-integer arguments is # automatically passed to gammasimp expr = combsimp(expr) if expr.has(Sum): expr = sum_simplify(expr, *kwargs) if expr.has(Integral): expr = expr.xreplace({ i: factor_terms(i) for i in expr.atoms(Integral)}) if expr.has(Product): expr = product_simplify(expr) from sympy.physics.units import Quantity from sympy.physics.units.util import quantity_simplify if expr.has(Quantity): expr = quantity_simplify(expr) short = shorter(powsimp(expr, combine='exp', deep=True), powsimp(expr), expr) short = shorter(short, cancel(short)) short = shorter(short, factor_terms(short), expand_power_exp(expand_mul(short))) if short.has(TrigonometricFunction, HyperbolicFunction, ExpBase): short = exptrigsimp(short) # get rid of hollow 2-arg Mul factorization hollow_mul = Transform( lambda x: Mul(x.args), lambda x: x.is_Mul and len(x.args) == 2 and x.args[0].is_Number and x.args[1].is_Add and x.is_commutative) expr = short.xreplace(hollow_mul) numer, denom = expr.as_numer_denom() if denom.is_Add: n, d = fraction(radsimp(1/denom, symbolic=False, max_terms=1)) if n is not S.One: expr = (numern).expand()/d if expr.could_extract_minus_sign(): n, d = fraction(expr) if d != 0: expr = signsimp(-n/(-d)) if measure(expr) > ratiomeasure(original_expr): expr = original_expr # restore floats if floats and rational is None: expr = nfloat(expr, exponent=False) return done(expr) def sum_simplify(s, kwargs): """Main function for Sum simplification""" from sympy.concrete.summations import Sum from sympy.core.function import expand if not isinstance(s, Add): s = s.xreplace({a: sum_simplify(a, kwargs) for a in s.atoms(Add) if a.has(Sum)}) s = expand(s) if not isinstance(s, Add): return s terms = s.args s_t = [] # Sum Terms o_t = [] # Other Terms for term in terms: sum_terms, other = sift(Mul.make_args(term), lambda i: isinstance(i, Sum), binary=True) if not sum_terms: o_t.append(term) continue other = [Mul(other)] s_t.append(Mul((other + [s._eval_simplify(*kwargs) for s in sum_terms]))) result = Add(sum_combine(s_t), o_t) return result def sum_combine(s_t): """Helper function for Sum simplification Attempts to simplify a list of sums, by combining limits / sum function's returns the simplified sum """ from sympy.concrete.summations import Sum used = [False] * len(s_t) for method in range(2): for i, s_term1 in enumerate(s_t): if not used[i]: for j, s_term2 in enumerate(s_t): if not used[j] and i != j: temp = sum_add(s_term1, s_term2, method) if isinstance(temp, Sum) or isinstance(temp, Mul): s_t[i] = temp s_term1 = s_t[i] used[j] = True result = S.Zero for i, s_term in enumerate(s_t): if not used[i]: result = Add(result, s_term) return result def factor_sum(self, limits=None, radical=False, clear=False, fraction=False, sign=True): """Return Sum with constant factors extracted. If ``limits`` is specified then ``self`` is the summand; the other keywords are passed to ``factor_terms``. Examples ======== >>> from sympy import Sum >>> from sympy.abc import x, y >>> from sympy.simplify.simplify import factor_sum >>> s = Sum(xy, (x, 1, 3)) >>> factor_sum(s) ySum(x, (x, 1, 3)) >>> factor_sum(s.function, s.limits) ySum(x, (x, 1, 3)) """ # XXX deprecate in favor of direct call to factor_terms from sympy.concrete.summations import Sum kwargs = dict(radical=radical, clear=clear, fraction=fraction, sign=sign) expr = Sum(self, limits) if limits else self return factor_terms(expr, *kwargs) def sum_add(self, other, method=0): """Helper function for Sum simplification""" from sympy.concrete.summations import Sum from sympy import Mul #we know this is something in terms of a constant a sum #so we temporarily put the constants inside for simplification #then simplify the result def __refactor(val): args = Mul.make_args(val) sumv = next(x for x in args if isinstance(x, Sum)) constant = Mul([x for x in args if x != sumv]) return Sum(constant sumv.function, sumv.limits) if isinstance(self, Mul): rself = __refactor(self) else: rself = self if isinstance(other, Mul): rother = __refactor(other) else: rother = other if type(rself) == type(rother): if method == 0: if rself.limits == rother.limits: return factor_sum(Sum(rself.function + rother.function, rself.limits)) elif method == 1: if simplify(rself.function - rother.function) == 0: if len(rself.limits) == len(rother.limits) == 1: i = rself.limits[0][0] x1 = rself.limits[0][1] y1 = rself.limits[0][2] j = rother.limits[0][0] x2 = rother.limits[0][1] y2 = rother.limits[0][2] if i == j: if x2 == y1 + 1: return factor_sum(Sum(rself.function, (i, x1, y2))) elif x1 == y2 + 1: return factor_sum(Sum(rself.function, (i, x2, y1))) return Add(self, other) def product_simplify(s): """Main function for Product simplification""" from sympy.concrete.products import Product terms = Mul.make_args(s) p_t = [] # Product Terms o_t = [] # Other Terms for term in terms: if isinstance(term, Product): p_t.append(term) else: o_t.append(term) used = [False] * len(p_t) for method in range(2): for i, p_term1 in enumerate(p_t): if not used[i]: for j, p_term2 in enumerate(p_t): if not used[j] and i != j: if isinstance(product_mul(p_term1, p_term2, method), Product): p_t[i] = product_mul(p_term1, p_term2, method) used[j] = True result = Mul(o_t) for i, p_term in enumerate(p_t): if not used[i]: result = Mul(result, p_term) return result def product_mul(self, other, method=0): """Helper function for Product simplification""" from sympy.concrete.products import Product if type(self) == type(other): if method == 0: if self.limits == other.limits: return Product(self.function other.function, self.limits) elif method == 1: if simplify(self.function - other.function) == 0: if len(self.limits) == len(other.limits) == 1: i = self.limits[0][0] x1 = self.limits[0][1] y1 = self.limits[0][2] j = other.limits[0][0] x2 = other.limits[0][1] y2 = other.limits[0][2] if i == j: if x2 == y1 + 1: return Product(self.function, (i, x1, y2)) elif x1 == y2 + 1: return Product(self.function, (i, x2, y1)) return Mul(self, other) def _nthroot_solve(p, n, prec): """ helper function for ``nthroot`` It denests ``pRational(1, n)`` using its minimal polynomial """ from sympy.polys.numberfields import _minimal_polynomial_sq from sympy.solvers import solve while n % 2 == 0: p = sqrtdenest(sqrt(p)) n = n // 2 if n == 1: return p pn = pRational(1, n) x = Symbol('x') f = _minimal_polynomial_sq(p, n, x) if f is None: return None sols = solve(f, x) for sol in sols: if abs(sol - pn).n() < 1./10prec: sol = sqrtdenest(sol) if _mexpand(soln) == p: return sol def logcombine(expr, force=False): """ Takes logarithms and combines them using the following rules: - log(x) + log(y) == log(xy) if both are positive - alog(x) == log(xa) if x is positive and a is real If ``force`` is ``True`` then the assumptions above will be assumed to hold if there is no assumption already in place on a quantity. For example, if ``a`` is imaginary or the argument negative, force will not perform a combination but if ``a`` is a symbol with no assumptions the change will take place. Examples ======== >>> from sympy import Symbol, symbols, log, logcombine, I >>> from sympy.abc import a, x, y, z >>> logcombine(alog(x) + log(y) - log(z)) alog(x) + log(y) - log(z) >>> logcombine(alog(x) + log(y) - log(z), force=True) log(x*ay/z) >>> x,y,z = symbols('x,y,z', positive=True) >>> a = Symbol('a', real=True) >>> logcombine(alog(x) + log(y) - log(z)) log(xay/z) The transformation is limited to factors and/or terms that contain logs, so the result depends on the initial state of expansion: >>> eq = (2 + 3I)log(x) >>> logcombine(eq, force=True) == eq True >>> logcombine(eq.expand(), force=True) log(x*2) + Ilog(x*3) See Also ======== posify: replace all symbols with symbols having positive assumptions sympy.core.function.expand_log: expand the logarithms of products and powers; the opposite of logcombine """ def f(rv): if not (rv.is_Add or rv.is_Mul): return rv def gooda(a): # bool to tell whether the leading ``a`` in ``alog(x)`` # could appear as log(x*a) return (a is not S.NegativeOne and # -1 could* go, but we disallow (a.is_extended_real or force and a.is_extended_real is not False)) def goodlog(l): # bool to tell whether log ``l``'s argument can combine with others a = l.args[0] return a.is_positive or force and a.is_nonpositive is not False other = [] logs = [] log1 = defaultdict(list) for a in Add.make_args(rv): if isinstance(a, log) and goodlog(a): log1[()].append(([], a)) elif not a.is_Mul: other.append(a) else: ot = [] co = [] lo = [] for ai in a.args: if ai.is_Rational and ai < 0: ot.append(S.NegativeOne) co.append(-ai) elif isinstance(ai, log) and goodlog(ai): lo.append(ai) elif gooda(ai): co.append(ai) else: ot.append(ai) if len(lo) > 1: logs.append((ot, co, lo)) elif lo: log1[tuple(ot)].append((co, lo[0])) else: other.append(a) # if there is only one log in other, put it with the # good logs if len(other) == 1 and isinstance(other[0], log): log1[()].append(([], other.pop())) # if there is only one log at each coefficient and none have # an exponent to place inside the log then there is nothing to do if not logs and all(len(log1[k]) == 1 and log1[k][0] == [] for k in log1): return rv # collapse multi-logs as far as possible in a canonical way # TODO: see if xlog(a)+xlog(a)log(b) -> xlog(a)(1+log(b))? # -- in this case, it's unambiguous, but if it were were a log(c) in # each term then it's arbitrary whether they are grouped by log(a) or # by log(c). So for now, just leave this alone; it's probably better to # let the user decide for o, e, l in logs: l = list(ordered(l)) e = log(l.pop(0).args[0]Mul(e)) while l: li = l.pop(0) e = log(li.args[0]*e) c, l = Mul(o), e if isinstance(l, log): # it should be, but check to be sure log1[(c,)].append(([], l)) else: other.append(cl) # logs that have the same coefficient can multiply for k in list(log1.keys()): log1[Mul(k)] = log(logcombine(Mul([ l.args[0]Mul(c) for c, l in log1.pop(k)]), force=force), evaluate=False) # logs that have oppositely signed coefficients can divide for k in ordered(list(log1.keys())): if not k in log1: # already popped as -k continue if -k in log1: # figure out which has the minus sign; the one with # more op counts should be the one num, den = k, -k if num.count_ops() > den.count_ops(): num, den = den, num other.append( numlog(log1.pop(num).args[0]/log1.pop(den).args[0], evaluate=False)) else: other.append(klog1.pop(k)) return Add(other) return bottom_up(expr, f) def inversecombine(expr): """Simplify the composition of a function and its inverse. Explanation =========== No attention is paid to whether the inverse is a left inverse or a right inverse; thus, the result will in general not be equivalent to the original expression. Examples ======== >>> from sympy.simplify.simplify import inversecombine >>> from sympy import asin, sin, log, exp >>> from sympy.abc import x >>> inversecombine(asin(sin(x))) x >>> inversecombine(2log(exp(3x))) 6x """ def f(rv): if rv.is_Function and hasattr(rv, "inverse"): if (len(rv.args) == 1 and len(rv.args[0].args) == 1 and isinstance(rv.args[0], rv.inverse(argindex=1))): rv = rv.args[0].args[0] return rv return bottom_up(expr, f) def walk(e, target): """Iterate through the args that are the given types (target) and return a list of the args that were traversed; arguments that are not of the specified types are not traversed. Examples ======== >>> from sympy.simplify.simplify import walk >>> from sympy import Min, Max >>> from sympy.abc import x, y, z >>> list(walk(Min(x, Max(y, Min(1, z))), Min)) [Min(x, Max(y, Min(1, z)))] >>> list(walk(Min(x, Max(y, Min(1, z))), Min, Max)) [Min(x, Max(y, Min(1, z))), Max(y, Min(1, z)), Min(1, z)] See Also ======== bottom_up """ if isinstance(e, target): yield e for i in e.args: yield from walk(i, target) def bottom_up(rv, F, atoms=False, nonbasic=False): """Apply ``F`` to all expressions in an expression tree from the bottom up. If ``atoms`` is True, apply ``F`` even if there are no args; if ``nonbasic`` is True, try to apply ``F`` to non-Basic objects. """ args = getattr(rv, 'args', None) if args is not None: if args: args = tuple([bottom_up(a, F, atoms, nonbasic) for a in args]) if args != rv.args: rv = rv.func(args) rv = F(rv) elif atoms: rv = F(rv) else: if nonbasic: try: rv = F(rv) except TypeError: pass return rv def kroneckersimp(expr): """ Simplify expressions with KroneckerDelta. The only simplification currently attempted is to identify multiplicative cancellation: Examples ======== >>> from sympy import KroneckerDelta, kroneckersimp >>> from sympy.abc import i >>> kroneckersimp(1 + KroneckerDelta(0, i) KroneckerDelta(1, i)) 1 """ def args_cancel(args1, args2): for i1 in range(2): for i2 in range(2): a1 = args1[i1] a2 = args2[i2] a3 = args1[(i1 + 1) % 2] a4 = args2[(i2 + 1) % 2] if Eq(a1, a2) is S.true and Eq(a3, a4) is S.false: return True return False def cancel_kronecker_mul(m): from sympy.utilities.iterables import subsets args = m.args deltas = [a for a in args if isinstance(a, KroneckerDelta)] for delta1, delta2 in subsets(deltas, 2): args1 = delta1.args args2 = delta2.args if args_cancel(args1, args2): return 0m return m if not expr.has(KroneckerDelta): return expr if expr.has(Piecewise): expr = expr.rewrite(KroneckerDelta) newexpr = expr expr = None while newexpr != expr: expr = newexpr newexpr = expr.replace(lambda e: isinstance(e, Mul), cancel_kronecker_mul) return expr def besselsimp(expr): """ Simplify bessel-type functions. Explanation =========== This routine tries to simplify bessel-type functions. Currently it only works on the Bessel J and I functions, however. It works by looking at all such functions in turn, and eliminating factors of "I" and "-1" (actually their polar equivalents) in front of the argument. Then, functions of half-integer order are rewritten using strigonometric functions and functions of integer order (> 1) are rewritten using functions of low order. Finally, if the expression was changed, compute factorization of the result with factor(). >>> from sympy import besselj, besseli, besselsimp, polar_lift, I, S >>> from sympy.abc import z, nu >>> besselsimp(besselj(nu, zpolar_lift(-1))) exp(Ipinu)besselj(nu, z) >>> besselsimp(besseli(nu, zpolar_lift(-I))) exp(-Ipinu/2)besselj(nu, z) >>> besselsimp(besseli(S(-1)/2, z)) sqrt(2)cosh(z)/(sqrt(pi)sqrt(z)) >>> besselsimp(zbesseli(0, z) + z(besseli(2, z))/2 + besseli(1, z)) 3zbesseli(0, z)/2 """ # TODO # - better algorithm? # - simplify (cos(pib)besselj(b,z) - besselj(-b,z))/sin(pib) ... # - use contiguity relations? def replacer(fro, to, factors): factors = set(factors) def repl(nu, z): if factors.intersection(Mul.make_args(z)): return to(nu, z) return fro(nu, z) return repl def torewrite(fro, to): def tofunc(nu, z): return fro(nu, z).rewrite(to) return tofunc def tominus(fro): def tofunc(nu, z): return exp(Ipinu)fro(nu, exp_polar(-Ipi)z) return tofunc orig_expr = expr ifactors = [I, exp_polar(Ipi/2), exp_polar(-Ipi/2)] expr = expr.replace( besselj, replacer(besselj, torewrite(besselj, besseli), ifactors)) expr = expr.replace( besseli, replacer(besseli, torewrite(besseli, besselj), ifactors)) minusfactors = [-1, exp_polar(Ipi)] expr = expr.replace( besselj, replacer(besselj, tominus(besselj), minusfactors)) expr = expr.replace( besseli, replacer(besseli, tominus(besseli), minusfactors)) z0 = Dummy('z') def expander(fro): def repl(nu, z): if (nu % 1) == S.Half: return simplify(trigsimp(unpolarify( fro(nu, z0).rewrite(besselj).rewrite(jn).expand( func=True)).subs(z0, z))) elif nu.is_Integer and nu > 1: return fro(nu, z).expand(func=True) return fro(nu, z) return repl expr = expr.replace(besselj, expander(besselj)) expr = expr.replace(bessely, expander(bessely)) expr = expr.replace(besseli, expander(besseli)) expr = expr.replace(besselk, expander(besselk)) def _bessel_simp_recursion(expr): def _use_recursion(bessel, expr): while True: bessels = expr.find(lambda x: isinstance(x, bessel)) try: for ba in sorted(bessels, key=lambda x: re(x.args[0])): a, x = ba.args bap1 = bessel(a+1, x) bap2 = bessel(a+2, x) if expr.has(bap1) and expr.has(bap2): expr = expr.subs(ba, 2(a+1)/xbap1 - bap2) break else: return expr except (ValueError, TypeError): return expr if expr.has(besselj): expr = _use_recursion(besselj, expr) if expr.has(bessely): expr = _use_recursion(bessely, expr) return expr expr = _bessel_simp_recursion(expr) if expr != orig_expr: expr = expr.factor() return expr def nthroot(expr, n, max_len=4, prec=15): """ Compute a real nth-root of a sum of surds. Parameters ========== expr : sum of surds n : integer max_len : maximum number of surds passed as constants to ``nsimplify`` Algorithm ========= First ``nsimplify`` is used to get a candidate root; if it is not a root the minimal polynomial is computed; the answer is one of its roots. Examples ======== >>> from sympy.simplify.simplify import nthroot >>> from sympy import sqrt >>> nthroot(90 + 34sqrt(7), 3) sqrt(7) + 3 """ expr = sympify(expr) n = sympify(n) p = exprRational(1, n) if not n.is_integer: return p if not _is_sum_surds(expr): return p surds = [] coeff_muls = [x.as_coeff_Mul() for x in expr.args] for x, y in coeff_muls: if not x.is_rational: return p if y is S.One: continue if not (y.is_Pow and y.exp == S.Half and y.base.is_integer): return p surds.append(y) surds.sort() surds = surds[:max_len] if expr < 0 and n % 2 == 1: p = (-expr)Rational(1, n) a = nsimplify(p, constants=surds) res = a if _mexpand(an) == _mexpand(-expr) else p return -res a = nsimplify(p, constants=surds) if _mexpand(a) is not _mexpand(p) and _mexpand(an) == _mexpand(expr): return _mexpand(a) expr = _nthroot_solve(expr, n, prec) if expr is None: return p return expr def nsimplify(expr, constants=(), tolerance=None, full=False, rational=None, rational_conversion='base10'): """ Find a simple representation for a number or, if there are free symbols or if ``rational=True``, then replace Floats with their Rational equivalents. If no change is made and rational is not False then Floats will at least be converted to Rationals. Explanation =========== For numerical expressions, a simple formula that numerically matches the given numerical expression is sought (and the input should be possible to evalf to a precision of at least 30 digits). Optionally, a list of (rationally independent) constants to include in the formula may be given. A lower tolerance may be set to find less exact matches. If no tolerance is given then the least precise value will set the tolerance (e.g. Floats default to 15 digits of precision, so would be tolerance=10-15). With ``full=True``, a more extensive search is performed (this is useful to find simpler numbers when the tolerance is set low). When converting to rational, if rational_conversion='base10' (the default), then convert floats to rationals using their base-10 (string) representation. When rational_conversion='exact' it uses the exact, base-2 representation. Examples ======== >>> from sympy import nsimplify, sqrt, GoldenRatio, exp, I, pi >>> nsimplify(4/(1+sqrt(5)), [GoldenRatio]) -2 + 2GoldenRatio >>> nsimplify((1/(exp(3piI/5)+1))) 1/2 - Isqrt(sqrt(5)/10 + 1/4) >>> nsimplify(II, [pi]) exp(-pi/2) >>> nsimplify(pi, tolerance=0.01) 22/7 >>> nsimplify(0.333333333333333, rational=True, rational_conversion='exact') 6004799503160655/18014398509481984 >>> nsimplify(0.333333333333333, rational=True) 1/3 See Also ======== sympy.core.function.nfloat """ try: return sympify(as_int(expr)) except (TypeError, ValueError): pass expr = sympify(expr).xreplace({ Float('inf'): S.Infinity, Float('-inf'): S.NegativeInfinity, }) if expr is S.Infinity or expr is S.NegativeInfinity: return expr if rational or expr.free_symbols: return _real_to_rational(expr, tolerance, rational_conversion) # SymPy's default tolerance for Rationals is 15; other numbers may have # lower tolerances set, so use them to pick the largest tolerance if None # was given if tolerance is None: tolerance = 10-min([15] + [mpmath.libmp.libmpf.prec_to_dps(n._prec) for n in expr.atoms(Float)]) # XXX should prec be set independent of tolerance or should it be computed # from tolerance? prec = 30 bprec = int(prec3.33) constants_dict = {} for constant in constants: constant = sympify(constant) v = constant.evalf(prec) if not v.is_Float: raise ValueError("constants must be real-valued") constants_dict[str(constant)] = v._to_mpmath(bprec) exprval = expr.evalf(prec, chop=True) re, im = exprval.as_real_imag() # safety check to make sure that this evaluated to a number if not (re.is_Number and im.is_Number): return expr def nsimplify_real(x): orig = mpmath.mp.dps xv = x._to_mpmath(bprec) try: # We'll be happy with low precision if a simple fraction if not (tolerance or full): mpmath.mp.dps = 15 rat = mpmath.pslq([xv, 1]) if rat is not None: return Rational(-int(rat[1]), int(rat[0])) mpmath.mp.dps = prec newexpr = mpmath.identify(xv, constants=constants_dict, tol=tolerance, full=full) if not newexpr: raise ValueError if full: newexpr = newexpr[0] expr = sympify(newexpr) if x and not expr: # don't let x become 0 raise ValueError if expr.is_finite is False and not xv in [mpmath.inf, mpmath.ninf]: raise ValueError return expr finally: # even though there are returns above, this is executed # before leaving mpmath.mp.dps = orig try: if re: re = nsimplify_real(re) if im: im = nsimplify_real(im) except ValueError: if rational is None: return _real_to_rational(expr, rational_conversion=rational_conversion) return expr rv = re + imS.ImaginaryUnit # if there was a change or rational is explicitly not wanted # return the value, else return the Rational representation if rv != expr or rational is False: return rv return _real_to_rational(expr, rational_conversion=rational_conversion) def _real_to_rational(expr, tolerance=None, rational_conversion='base10'): """ Replace all reals in expr with rationals. Examples ======== >>> from sympy.simplify.simplify import _real_to_rational >>> from sympy.abc import x >>> _real_to_rational(.76 + .1x*.5) sqrt(x)/10 + 19/25 If rational_conversion='base10', this uses the base-10 string. If rational_conversion='exact', the exact, base-2 representation is used. >>> _real_to_rational(0.333333333333333, rational_conversion='exact') 6004799503160655/18014398509481984 >>> _real_to_rational(0.333333333333333) 1/3 """ expr = _sympify(expr) inf = Float('inf') p = expr reps = {} reduce_num = None if tolerance is not None and tolerance < 1: reduce_num = ceiling(1/tolerance) for fl in p.atoms(Float): key = fl if reduce_num is not None: r = Rational(fl).limit_denominator(reduce_num) elif (tolerance is not None and tolerance >= 1 and fl.is_Integer is False): r = Rational(toleranceround(fl/tolerance) ).limit_denominator(int(tolerance)) else: if rational_conversion == 'exact': r = Rational(fl) reps[key] = r continue elif rational_conversion != 'base10': raise ValueError("rational_conversion must be 'base10' or 'exact'") r = nsimplify(fl, rational=False) # e.g. log(3).n() -> log(3) instead of a Rational if fl and not r: r = Rational(fl) elif not r.is_Rational: if fl == inf or fl == -inf: r = S.ComplexInfinity elif fl < 0: fl = -fl d = Pow(10, int(mpmath.log(fl)/mpmath.log(10))) r = -Rational(str(fl/d))d elif fl > 0: d = Pow(10, int(mpmath.log(fl)/mpmath.log(10))) r = Rational(str(fl/d))d else: r = Integer(0) reps[key] = r return p.subs(reps, simultaneous=True) def clear_coefficients(expr, rhs=S.Zero): """Return `p, r` where `p` is the expression obtained when Rational additive and multiplicative coefficients of `expr` have been stripped away in a naive fashion (i.e. without simplification). The operations needed to remove the coefficients will be applied to `rhs` and returned as `r`. Examples ======== >>> from sympy.simplify.simplify import clear_coefficients >>> from sympy.abc import x, y >>> from sympy import Dummy >>> expr = 4y(6x + 3) >>> clear_coefficients(expr - 2) (y(2x + 1), 1/6) When solving 2 or more expressions like `expr = a`, `expr = b`, etc..., it is advantageous to provide a Dummy symbol for `rhs` and simply replace it with `a`, `b`, etc... in `r`. >>> rhs = Dummy('rhs') >>> clear_coefficients(expr, rhs) (y(2x + 1), _rhs/12) >>> _[1].subs(rhs, 2) 1/6 """ was = None free = expr.free_symbols if expr.is_Rational: return (S.Zero, rhs - expr) while expr and was != expr: was = expr m, expr = ( expr.as_content_primitive() if free else factor_terms(expr).as_coeff_Mul(rational=True)) rhs /= m c, expr = expr.as_coeff_Add(rational=True) rhs -= c expr = signsimp(expr, evaluate = False) if _coeff_isneg(expr): expr = -expr rhs = -rhs return expr, rhs def nc_simplify(expr, deep=True): ''' Simplify a non-commutative expression composed of multiplication and raising to a power by grouping repeated subterms into one power. Priority is given to simplifications that give the fewest number of arguments in the end (for example, in ababcabc simplifying to (ab)2cabc gives 5 arguments while ab(abc)2 has 3). If ``expr`` is a sum of such terms, the sum of the simplified terms is returned. Keyword argument ``deep`` controls whether or not subexpressions nested deeper inside the main expression are simplified. See examples below. Setting `deep` to `False` can save time on nested expressions that don't need simplifying on all levels. Examples ======== >>> from sympy import symbols >>> from sympy.simplify.simplify import nc_simplify >>> a, b, c = symbols("a b c", commutative=False) >>> nc_simplify(ababcabc) ab(abc)2 >>> expr = a2ba*4ba4 >>> nc_simplify(expr) a2(ba4)2 >>> nc_simplify(ababc2(ab)2c*2) ((ab)*2c2)2 >>> nc_simplify(abab + 2aca*2ca2ca) (ab)*2 + 2(aca)3 >>> nc_simplify(b-1a-1(ab)2) ab >>> nc_simplify(a*-1b*-1ca) (ba)*(-1)ca >>> expr = (abab)*2acac >>> nc_simplify(expr) (ab)*4(ac)2 >>> nc_simplify(expr, deep=False) (abab)*2(ac)2 ''' from sympy.matrices.expressions import (MatrixExpr, MatAdd, MatMul, MatPow, MatrixSymbol) from sympy.core.exprtools import factor_nc if isinstance(expr, MatrixExpr): expr = expr.doit(inv_expand=False) _Add, _Mul, _Pow, _Symbol = MatAdd, MatMul, MatPow, MatrixSymbol else: _Add, _Mul, _Pow, _Symbol = Add, Mul, Pow, Symbol # =========== Auxiliary functions ======================== def _overlaps(args): # Calculate a list of lists m such that m[i][j] contains the lengths # of all possible overlaps between args[:i+1] and args[i+1+j:]. # An overlap is a suffix of the prefix that matches a prefix # of the suffix. # For example, let expr=cabababab. Then m[3][0] contains # the lengths of overlaps of cabab with abab. The overlaps # are abab, ab and the empty word so that m[3][0]=[4,2,0]. # All overlaps rather than only the longest one are recorded # because this information helps calculate other overlap lengths. m = [[([1, 0] if a == args[0] else [0]) for a in args[1:]]] for i in range(1, len(args)): overlaps = [] j = 0 for j in range(len(args) - i - 1): overlap = [] for v in m[i-1][j+1]: if j + i + 1 + v < len(args) and args[i] == args[j+i+1+v]: overlap.append(v + 1) overlap += [0] overlaps.append(overlap) m.append(overlaps) return m def _reduce_inverses(_args): # replace consecutive negative powers by an inverse # of a product of positive powers, e.g. a*-1b*-1c # will simplify to (ab)-1c; # return that new args list and the number of negative # powers in it (inv_tot) inv_tot = 0 # total number of inverses inverses = [] args = [] for arg in _args: if isinstance(arg, _Pow) and arg.args[1] < 0: inverses = [arg-1] + inverses inv_tot += 1 else: if len(inverses) == 1: args.append(inverses[0]-1) elif len(inverses) > 1: args.append(_Pow(_Mul(inverses), -1)) inv_tot -= len(inverses) - 1 inverses = [] args.append(arg) if inverses: args.append(_Pow(_Mul(inverses), -1)) inv_tot -= len(inverses) - 1 return inv_tot, tuple(args) def get_score(s): # compute the number of arguments of s # (including in nested expressions) overall # but ignore exponents if isinstance(s, _Pow): return get_score(s.args[0]) elif isinstance(s, (_Add, _Mul)): return sum([get_score(a) for a in s.args]) return 1 def compare(s, alt_s): # compare two possible simplifications and return a # "better" one if s != alt_s and get_score(alt_s) < get_score(s): return alt_s return s # ======================================================== if not isinstance(expr, (_Add, _Mul, _Pow)) or expr.is_commutative: return expr args = expr.args[:] if isinstance(expr, _Pow): if deep: return _Pow(nc_simplify(args[0]), args[1]).doit() else: return expr elif isinstance(expr, _Add): return _Add([nc_simplify(a, deep=deep) for a in args]).doit() else: # get the non-commutative part c_args, args = expr.args_cnc() com_coeff = Mul(c_args) if com_coeff != 1: return com_coeffnc_simplify(expr/com_coeff, deep=deep) inv_tot, args = _reduce_inverses(args) # if most arguments are negative, work with the inverse # of the expression, e.g. a-1ba-1c*-1 will become # (cab-1a)*-1 at the end so can work with cab-1a invert = False if inv_tot > len(args)/2: invert = True args = [a*-1 for a in args[::-1]] if deep: args = tuple(nc_simplify(a) for a in args) m = _overlaps(args) # simps will be {subterm: end} where `end` is the ending # index of a sequence of repetitions of subterm; # this is for not wasting time with subterms that are part # of longer, already considered sequences simps = {} post = 1 pre = 1 # the simplification coefficient is the number of # arguments by which contracting a given sequence # would reduce the word; e.g. in ababcabc, # contracting abab to (ab)*2 removes 3 arguments # while abcabc to (abc)*2 removes 6. It's # better to contract the latter so simplification # with a maximum simplification coefficient will be chosen max_simp_coeff = 0 simp = None # information about future simplification for i in range(1, len(args)): simp_coeff = 0 l = 0 # length of a subterm p = 0 # the power of a subterm if i < len(args) - 1: rep = m[i][0] start = i # starting index of the repeated sequence end = i+1 # ending index of the repeated sequence if i == len(args)-1 or rep == [0]: # no subterm is repeated at this stage, at least as # far as the arguments are concerned - there may be # a repetition if powers are taken into account if (isinstance(args[i], _Pow) and not isinstance(args[i].args[0], _Symbol)): subterm = args[i].args[0].args l = len(subterm) if args[i-l:i] == subterm: # e.g. ab in ab(ab)2 is not repeated # in args (= [a, b, (ab)*2]) but it # can be matched here p += 1 start -= l if args[i+1:i+1+l] == subterm: # e.g. ab in (ab)2ab p += 1 end += l if p: p += args[i].args[1] else: continue else: l = rep[0] # length of the longest repeated subterm at this point start -= l - 1 subterm = args[start:end] p = 2 end += l if subterm in simps and simps[subterm] >= start: # the subterm is part of a sequence that # has already been considered continue # count how many times it's repeated while end < len(args): if l in m[end-1][0]: p += 1 end += l elif isinstance(args[end], _Pow) and args[end].args[0].args == subterm: # for cases like abab(ab)*2ab p += args[end].args[1] end += 1 else: break # see if another match can be made, e.g. # for ba*2 in ba*2ba3 or ab in # a*2bab pre_exp = 0 pre_arg = 1 if start - l >= 0 and args[start-l+1:start] == subterm[1:]: if isinstance(subterm[0], _Pow): pre_arg = subterm[0].args[0] exp = subterm[0].args[1] else: pre_arg = subterm[0] exp = 1 if isinstance(args[start-l], _Pow) and args[start-l].args[0] == pre_arg: pre_exp = args[start-l].args[1] - exp start -= l p += 1 elif args[start-l] == pre_arg: pre_exp = 1 - exp start -= l p += 1 post_exp = 0 post_arg = 1 if end + l - 1 < len(args) and args[end:end+l-1] == subterm[:-1]: if isinstance(subterm[-1], _Pow): post_arg = subterm[-1].args[0] exp = subterm[-1].args[1] else: post_arg = subterm[-1] exp = 1 if isinstance(args[end+l-1], _Pow) and args[end+l-1].args[0] == post_arg: post_exp = args[end+l-1].args[1] - exp end += l p += 1 elif args[end+l-1] == post_arg: post_exp = 1 - exp end += l p += 1 # Consider aba*2ba2ba: # ba*2 is explicitly repeated, but note # that in this case aba is also repeated # so there are two possible simplifications: # a(ba2)3a*-1 or (aba)3 # The latter is obviously simpler. # But in aba2b*2a*2 the simplifications are # a(ba2)2 and (aba)3a in which case # it's better to stick with the shorter subterm if post_exp and exp % 2 == 0 and start > 0: exp = exp/2 _pre_exp = 1 _post_exp = 1 if isinstance(args[start-1], _Pow) and args[start-1].args[0] == post_arg: _post_exp = post_exp + exp _pre_exp = args[start-1].args[1] - exp elif args[start-1] == post_arg: _post_exp = post_exp + exp _pre_exp = 1 - exp if _pre_exp == 0 or _post_exp == 0: if not pre_exp: start -= 1 post_exp = _post_exp pre_exp = _pre_exp pre_arg = post_arg subterm = (post_argexp,) + subterm[:-1] + (post_argexp,) simp_coeff += end-start if post_exp: simp_coeff -= 1 if pre_exp: simp_coeff -= 1 simps[subterm] = end if simp_coeff > max_simp_coeff: max_simp_coeff = simp_coeff simp = (start, _Mul(subterm), p, end, l) pre = pre_argpre_exp post = post_argpost_exp if simp: subterm = _Pow(nc_simplify(simp[1], deep=deep), simp[2]) pre = nc_simplify(_Mul(args[:simp[0]])pre, deep=deep) post = postnc_simplify(_Mul(args[simp[3]:]), deep=deep) simp = presubtermpost if pre != 1 or post != 1: # new simplifications may be possible but no need # to recurse over arguments simp = nc_simplify(simp, deep=False) else: simp = _Mul(args) if invert: simp = _Pow(simp, -1) # see if factor_nc(expr) is simplified better if not isinstance(expr, MatrixExpr): f_expr = factor_nc(expr) if f_expr != expr: alt_simp = nc_simplify(f_expr, deep=deep) simp = compare(simp, alt_simp) else: simp = simp.doit(inv_expand=False) return simp def dotprodsimp(expr, withsimp=False): """Simplification for a sum of products targeted at the kind of blowup that occurs during summation of products. Intended to reduce expression blowup during matrix multiplication or other similar operations. Only works with algebraic expressions and does not recurse into non. Parameters ========== withsimp : bool, optional Specifies whether a flag should be returned along with the expression to indicate roughly whether simplification was successful. It is used in ``MatrixArithmetic._eval_pow_by_recursion`` to avoid attempting to simplify an expression repetitively which does not simplify. """ def count_ops_alg(expr): """Optimized count algebraic operations with no recursion into non-algebraic args that ``core.function.count_ops`` does. Also returns whether rational functions may be present according to negative exponents of powers or non-number fractions. Returns ======= ops, ratfunc : int, bool ``ops`` is the number of algebraic operations starting at the top level expression (not recursing into non-alg children). ``ratfunc`` specifies whether the expression MAY contain rational functions which ``cancel`` MIGHT optimize. """ ops = 0 args = [expr] ratfunc = False while args: a = args.pop() if not isinstance(a, Basic): continue if a.is_Rational: if a is not S.One: # -1/3 = NEG + DIV ops += bool (a.p < 0) + bool (a.q != 1) elif a.is_Mul: if _coeff_isneg(a): ops += 1 if a.args[0] is S.NegativeOne: a = a.as_two_terms()[1] else: a = -a n, d = fraction(a) if n.is_Integer: ops += 1 + bool (n < 0) args.append(d) # won't be -Mul but could be Add elif d is not S.One: if not d.is_Integer: args.append(d) ratfunc=True ops += 1 args.append(n) # could be -Mul else: ops += len(a.args) - 1 args.extend(a.args) elif a.is_Add: laargs = len(a.args) negs = 0 for ai in a.args: if _coeff_isneg(ai): negs += 1 ai = -ai args.append(ai) ops += laargs - (negs != laargs) # -x - y = NEG + SUB elif a.is_Pow: ops += 1 args.append(a.base) if not ratfunc: ratfunc = a.exp.is_negative is not False return ops, ratfunc def nonalg_subs_dummies(expr, dummies): """Substitute dummy variables for non-algebraic expressions to avoid evaluation of non-algebraic terms that ``polys.polytools.cancel`` does. """ if not expr.args: return expr if expr.is_Add or expr.is_Mul or expr.is_Pow: args = None for i, a in enumerate(expr.args): c = nonalg_subs_dummies(a, dummies) if c is a: continue if args is None: args = list(expr.args) args[i] = c if args is None: return expr return expr.func(*args) return dummies.setdefault(expr, Dummy()) simplified = False # doesn't really mean simplified, rather "can simplify again" if isinstance(expr, Basic) and (expr.is_Add or expr.is_Mul or expr.is_Pow): expr2 = expr.expand(deep=True, modulus=None, power_base=False, power_exp=False, mul=True, log=False, multinomial=True, basic=False) if expr2 != expr: expr = expr2 simplified = True exprops, ratfunc = count_ops_alg(expr) if exprops >= 6: # empirically tested cutoff for expensive simplification if ratfunc: dummies = {} expr2 = nonalg_subs_dummies(expr, dummies) if expr2 is expr or count_ops_alg(expr2)[0] >= 6: # check again after substitution expr3 = cancel(expr2) if expr3 != expr2: expr = expr3.subs([(d, e) for e, d in dummies.items()]) simplified = True # very special case: x/(x-1) - 1/(x-1) -> 1 elif (exprops == 5 and expr.is_Add and expr.args [0].is_Mul and expr.args [1].is_Mul and expr.args [0].args [-1].is_Pow and expr.args [1].args [-1].is_Pow and expr.args [0].args [-1].exp is S.NegativeOne and expr.args [1].args [-1].exp is S.NegativeOne): expr2 = together (expr) expr2ops = count_ops_alg(expr2)[0] if expr2ops < exprops: expr = expr2 simplified = True else: simplified = True return (expr, simplified) if withsimp else expr
87332005ca78b461da90cbc74b0568b8a67818df30d6e7ffdb97e41f6294405f	"""Tools for applying functions to specified parts of expressions. """ from sympy.core import sympify def use(expr, func, level=0, args=(), kwargs={}): """ Use ``func`` to transform ``expr`` at the given level. Examples ======== >>> from sympy import use, expand >>> from sympy.abc import x, y >>> f = (x + y)*2x + 1 >>> use(f, expand, level=2) x(x2 + 2xy + y2) + 1 >>> expand(f) x3 + 2x*2y + xy2 + 1 """ def _use(expr, level): if not level: return func(expr, args, *kwargs) else: if expr.is_Atom: return expr else: level -= 1 _args = [] for arg in expr.args: _args.append(_use(arg, level)) return expr.__class__(_args) return _use(sympify(expr), level)
6c1b4a8bf7bd8ff6aa680c23c9ba36060aaba78928c502ea4ac98624b79c1988	from collections import defaultdict from sympy import SYMPY_DEBUG from sympy.core import expand_power_base, sympify, Add, S, Mul, Derivative, Pow, symbols, expand_mul from sympy.core.add import _unevaluated_Add from sympy.core.compatibility import iterable, ordered, default_sort_key from sympy.core.parameters import global_parameters from sympy.core.exprtools import Factors, gcd_terms from sympy.core.function import _mexpand from sympy.core.mul import _keep_coeff, _unevaluated_Mul from sympy.core.numbers import Rational from sympy.functions import exp, sqrt, log from sympy.functions.elementary.complexes import Abs from sympy.polys import gcd from sympy.simplify.sqrtdenest import sqrtdenest def collect(expr, syms, func=None, evaluate=None, exact=False, distribute_order_term=True): """ Collect additive terms of an expression. Explanation =========== This function collects additive terms of an expression with respect to a list of expression up to powers with rational exponents. By the term symbol here are meant arbitrary expressions, which can contain powers, products, sums etc. In other words symbol is a pattern which will be searched for in the expression's terms. The input expression is not expanded by :func:`collect`, so user is expected to provide an expression is an appropriate form. This makes :func:`collect` more predictable as there is no magic happening behind the scenes. However, it is important to note, that powers of products are converted to products of powers using the :func:`~.expand_power_base` function. There are two possible types of output. First, if ``evaluate`` flag is set, this function will return an expression with collected terms or else it will return a dictionary with expressions up to rational powers as keys and collected coefficients as values. Examples ======== >>> from sympy import S, collect, expand, factor, Wild >>> from sympy.abc import a, b, c, x, y This function can collect symbolic coefficients in polynomials or rational expressions. It will manage to find all integer or rational powers of collection variable:: >>> collect(ax2 + bx*2 + ax - bx + c, x) c + x2(a + b) + x(a - b) The same result can be achieved in dictionary form:: >>> d = collect(ax*2 + bx*2 + ax - bx + c, x, evaluate=False) >>> d[x2] a + b >>> d[x] a - b >>> d[S.One] c You can also work with multivariate polynomials. However, remember that this function is greedy so it will care only about a single symbol at time, in specification order:: >>> collect(x2 + yx*2 + xy + y + ay, [x, y]) x2(y + 1) + xy + y(a + 1) Also more complicated expressions can be used as patterns:: >>> from sympy import sin, log >>> collect(asin(2x) + bsin(2x), sin(2x)) (a + b)sin(2x) >>> collect(axlog(x) + b(xlog(x)), xlog(x)) x(a + b)log(x) You can use wildcards in the pattern:: >>> w = Wild('w1') >>> collect(axy - bxy, wy) x*y(a - b) It is also possible to work with symbolic powers, although it has more complicated behavior, because in this case power's base and symbolic part of the exponent are treated as a single symbol:: >>> collect(axc + bx*c, x) ax*c + bx*c >>> collect(ax*c + bxc, xc) x*c(a + b) However if you incorporate rationals to the exponents, then you will get well known behavior:: >>> collect(ax(2c) + bx(2c), xc) x(2c)(a + b) Note also that all previously stated facts about :func:`collect` function apply to the exponential function, so you can get:: >>> from sympy import exp >>> collect(aexp(2x) + bexp(2x), exp(x)) (a + b)exp(2x) If you are interested only in collecting specific powers of some symbols then set ``exact`` flag in arguments:: >>> collect(ax7 + bx*7, x, exact=True) ax*7 + bx*7 >>> collect(ax*7 + bx7, x7, exact=True) x*7(a + b) You can also apply this function to differential equations, where derivatives of arbitrary order can be collected. Note that if you collect with respect to a function or a derivative of a function, all derivatives of that function will also be collected. Use ``exact=True`` to prevent this from happening:: >>> from sympy import Derivative as D, collect, Function >>> f = Function('f') (x) >>> collect(aD(f,x) + bD(f,x), D(f,x)) (a + b)Derivative(f(x), x) >>> collect(aD(D(f,x),x) + bD(D(f,x),x), f) (a + b)Derivative(f(x), (x, 2)) >>> collect(aD(D(f,x),x) + bD(D(f,x),x), D(f,x), exact=True) aDerivative(f(x), (x, 2)) + bDerivative(f(x), (x, 2)) >>> collect(aD(f,x) + bD(f,x) + af + bf, f) (a + b)f(x) + (a + b)Derivative(f(x), x) Or you can even match both derivative order and exponent at the same time:: >>> collect(aD(D(f,x),x)2 + bD(D(f,x),x)*2, D(f,x)) (a + b)Derivative(f(x), (x, 2))2 Finally, you can apply a function to each of the collected coefficients. For example you can factorize symbolic coefficients of polynomial:: >>> f = expand((x + a + 1)3) >>> collect(f, x, factor) x*3 + 3x*2(a + 1) + 3x(a + 1)2 + (a + 1)3 .. note:: Arguments are expected to be in expanded form, so you might have to call :func:`~.expand` prior to calling this function. See Also ======== collect_const, collect_sqrt, rcollect """ from sympy.core.assumptions import assumptions from sympy.utilities.iterables import sift from sympy.core.symbol import Dummy, Wild expr = sympify(expr) syms = [sympify(i) for i in (syms if iterable(syms) else [syms])] # replace syms[i] if it is not x, -x or has Wild symbols cond = lambda x: x.is_Symbol or (-x).is_Symbol or bool( x.atoms(Wild)) _, nonsyms = sift(syms, cond, binary=True) if nonsyms: reps = dict(zip(nonsyms, [Dummy(*assumptions(i)) for i in nonsyms])) syms = [reps.get(s, s) for s in syms] rv = collect(expr.subs(reps), syms, func=func, evaluate=evaluate, exact=exact, distribute_order_term=distribute_order_term) urep = {v: k for k, v in reps.items()} if not isinstance(rv, dict): return rv.xreplace(urep) else: return {urep.get(k, k).xreplace(urep): v.xreplace(urep) for k, v in rv.items()} if evaluate is None: evaluate = global_parameters.evaluate def make_expression(terms): product = [] for term, rat, sym, deriv in terms: if deriv is not None: var, order = deriv while order > 0: term, order = Derivative(term, var), order - 1 if sym is None: if rat is S.One: product.append(term) else: product.append(Pow(term, rat)) else: product.append(Pow(term, ratsym)) return Mul(product) def parse_derivative(deriv): # scan derivatives tower in the input expression and return # underlying function and maximal differentiation order expr, sym, order = deriv.expr, deriv.variables[0], 1 for s in deriv.variables[1:]: if s == sym: order += 1 else: raise NotImplementedError( 'Improve MV Derivative support in collect') while isinstance(expr, Derivative): s0 = expr.variables[0] for s in expr.variables: if s != s0: raise NotImplementedError( 'Improve MV Derivative support in collect') if s0 == sym: expr, order = expr.expr, order + len(expr.variables) else: break return expr, (sym, Rational(order)) def parse_term(expr): """Parses expression expr and outputs tuple (sexpr, rat_expo, sym_expo, deriv) where: - sexpr is the base expression - rat_expo is the rational exponent that sexpr is raised to - sym_expo is the symbolic exponent that sexpr is raised to - deriv contains the derivatives the the expression For example, the output of x would be (x, 1, None, None) the output of 2x would be (2, 1, x, None). """ rat_expo, sym_expo = S.One, None sexpr, deriv = expr, None if expr.is_Pow: if isinstance(expr.base, Derivative): sexpr, deriv = parse_derivative(expr.base) else: sexpr = expr.base if expr.exp.is_Number: rat_expo = expr.exp else: coeff, tail = expr.exp.as_coeff_Mul() if coeff.is_Number: rat_expo, sym_expo = coeff, tail else: sym_expo = expr.exp elif isinstance(expr, exp): arg = expr.args[0] if arg.is_Rational: sexpr, rat_expo = S.Exp1, arg elif arg.is_Mul: coeff, tail = arg.as_coeff_Mul(rational=True) sexpr, rat_expo = exp(tail), coeff elif isinstance(expr, Derivative): sexpr, deriv = parse_derivative(expr) return sexpr, rat_expo, sym_expo, deriv def parse_expression(terms, pattern): """Parse terms searching for a pattern. Terms is a list of tuples as returned by parse_terms; Pattern is an expression treated as a product of factors. """ pattern = Mul.make_args(pattern) if len(terms) < len(pattern): # pattern is longer than matched product # so no chance for positive parsing result return None else: pattern = [parse_term(elem) for elem in pattern] terms = terms[:] # need a copy elems, common_expo, has_deriv = [], None, False for elem, e_rat, e_sym, e_ord in pattern: if elem.is_Number and e_rat == 1 and e_sym is None: # a constant is a match for everything continue for j in range(len(terms)): if terms[j] is None: continue term, t_rat, t_sym, t_ord = terms[j] # keeping track of whether one of the terms had # a derivative or not as this will require rebuilding # the expression later if t_ord is not None: has_deriv = True if (term.match(elem) is not None and (t_sym == e_sym or t_sym is not None and e_sym is not None and t_sym.match(e_sym) is not None)): if exact is False: # we don't have to be exact so find common exponent # for both expression's term and pattern's element expo = t_rat / e_rat if common_expo is None: # first time common_expo = expo else: # common exponent was negotiated before so # there is no chance for a pattern match unless # common and current exponents are equal if common_expo != expo: common_expo = 1 else: # we ought to be exact so all fields of # interest must match in every details if e_rat != t_rat or e_ord != t_ord: continue # found common term so remove it from the expression # and try to match next element in the pattern elems.append(terms[j]) terms[j] = None break else: # pattern element not found return None return [_f for _f in terms if _f], elems, common_expo, has_deriv if evaluate: if expr.is_Add: o = expr.getO() or 0 expr = expr.func([ collect(a, syms, func, True, exact, distribute_order_term) for a in expr.args if a != o]) + o elif expr.is_Mul: return expr.func([ collect(term, syms, func, True, exact, distribute_order_term) for term in expr.args]) elif expr.is_Pow: b = collect( expr.base, syms, func, True, exact, distribute_order_term) return Pow(b, expr.exp) syms = [expand_power_base(i, deep=False) for i in syms] order_term = None if distribute_order_term: order_term = expr.getO() if order_term is not None: if order_term.has(syms): order_term = None else: expr = expr.removeO() summa = [expand_power_base(i, deep=False) for i in Add.make_args(expr)] collected, disliked = defaultdict(list), S.Zero for product in summa: c, nc = product.args_cnc(split_1=False) args = list(ordered(c)) + nc terms = [parse_term(i) for i in args] small_first = True for symbol in syms: if SYMPY_DEBUG: print("DEBUG: parsing of expression %s with symbol %s " % ( str(terms), str(symbol)) ) if isinstance(symbol, Derivative) and small_first: terms = list(reversed(terms)) small_first = not small_first result = parse_expression(terms, symbol) if SYMPY_DEBUG: print("DEBUG: returned %s" % str(result)) if result is not None: if not symbol.is_commutative: raise AttributeError("Can not collect noncommutative symbol") terms, elems, common_expo, has_deriv = result # when there was derivative in current pattern we # will need to rebuild its expression from scratch if not has_deriv: margs = [] for elem in elems: if elem[2] is None: e = elem[1] else: e = elem[1]elem[2] margs.append(Pow(elem[0], e)) index = Mul(margs) else: index = make_expression(elems) terms = expand_power_base(make_expression(terms), deep=False) index = expand_power_base(index, deep=False) collected[index].append(terms) break else: # none of the patterns matched disliked += product # add terms now for each key collected = {k: Add(v) for k, v in collected.items()} if disliked is not S.Zero: collected[S.One] = disliked if order_term is not None: for key, val in collected.items(): collected[key] = val + order_term if func is not None: collected = { key: func(val) for key, val in collected.items()} if evaluate: return Add([keyval for key, val in collected.items()]) else: return collected def rcollect(expr, vars): """ Recursively collect sums in an expression. Examples ======== >>> from sympy.simplify import rcollect >>> from sympy.abc import x, y >>> expr = (x*2y + xy + x + y)/(x + y) >>> rcollect(expr, y) (x + y(x*2 + x + 1))/(x + y) See Also ======== collect, collect_const, collect_sqrt """ if expr.is_Atom or not expr.has(vars): return expr else: expr = expr.__class__([rcollect(arg, vars) for arg in expr.args]) if expr.is_Add: return collect(expr, vars) else: return expr def collect_sqrt(expr, evaluate=None): """Return expr with terms having common square roots collected together. If ``evaluate`` is False a count indicating the number of sqrt-containing terms will be returned and, if non-zero, the terms of the Add will be returned, else the expression itself will be returned as a single term. If ``evaluate`` is True, the expression with any collected terms will be returned. Note: since I = sqrt(-1), it is collected, too. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import collect_sqrt >>> from sympy.abc import a, b >>> r2, r3, r5 = [sqrt(i) for i in [2, 3, 5]] >>> collect_sqrt(ar2 + br2) sqrt(2)(a + b) >>> collect_sqrt(ar2 + br2 + ar3 + br3) sqrt(2)(a + b) + sqrt(3)(a + b) >>> collect_sqrt(ar2 + br2 + ar3 + br5) sqrt(3)a + sqrt(5)b + sqrt(2)(a + b) If evaluate is False then the arguments will be sorted and returned as a list and a count of the number of sqrt-containing terms will be returned: >>> collect_sqrt(ar2 + br2 + ar3 + br5, evaluate=False) ((sqrt(3)a, sqrt(5)b, sqrt(2)(a + b)), 3) >>> collect_sqrt(asqrt(2) + b, evaluate=False) ((b, sqrt(2)a), 1) >>> collect_sqrt(a + b, evaluate=False) ((a + b,), 0) See Also ======== collect, collect_const, rcollect """ if evaluate is None: evaluate = global_parameters.evaluate # this step will help to standardize any complex arguments # of sqrts coeff, expr = expr.as_content_primitive() vars = set() for a in Add.make_args(expr): for m in a.args_cnc()[0]: if m.is_number and ( m.is_Pow and m.exp.is_Rational and m.exp.q == 2 or m is S.ImaginaryUnit): vars.add(m) # we only want radicals, so exclude Number handling; in this case # d will be evaluated d = collect_const(expr, vars, Numbers=False) hit = expr != d if not evaluate: nrad = 0 # make the evaluated args canonical args = list(ordered(Add.make_args(d))) for i, m in enumerate(args): c, nc = m.args_cnc() for ci in c: # XXX should this be restricted to ci.is_number as above? if ci.is_Pow and ci.exp.is_Rational and ci.exp.q == 2 or \ ci is S.ImaginaryUnit: nrad += 1 break args[i] = coeff if not (hit or nrad): args = [Add(args)] return tuple(args), nrad return coeffd def collect_abs(expr): """Return ``expr`` with arguments of multiple Abs in a term collected under a single instance. Examples ======== >>> from sympy.simplify.radsimp import collect_abs >>> from sympy.abc import x >>> collect_abs(abs(x + 1)/abs(x2 - 1)) Abs((x + 1)/(x2 - 1)) >>> collect_abs(abs(1/x)) Abs(1/x) """ def _abs(mul): from sympy.core.mul import _mulsort c, nc = mul.args_cnc() a = [] o = [] for i in c: if isinstance(i, Abs): a.append(i.args[0]) elif isinstance(i, Pow) and isinstance(i.base, Abs) and i.exp.is_real: a.append(i.base.args[0]i.exp) else: o.append(i) if len(a) < 2 and not any(i.exp.is_negative for i in a if isinstance(i, Pow)): return mul absarg = Mul(a) A = Abs(absarg) args = [A] args.extend(o) if not A.has(Abs): args.extend(nc) return Mul(args) if not isinstance(A, Abs): # reevaluate and make it unevaluated A = Abs(absarg, evaluate=False) args[0] = A _mulsort(args) args.extend(nc) # nc always go last return Mul._from_args(args, is_commutative=not nc) return expr.replace( lambda x: isinstance(x, Mul), lambda x: _abs(x)).replace( lambda x: isinstance(x, Pow), lambda x: _abs(x)) def collect_const(expr, vars, Numbers=True): """A non-greedy collection of terms with similar number coefficients in an Add expr. If ``vars`` is given then only those constants will be targeted. Although any Number can also be targeted, if this is not desired set ``Numbers=False`` and no Float or Rational will be collected. Parameters ========== expr : sympy expression This parameter defines the expression the expression from which terms with similar coefficients are to be collected. A non-Add expression is returned as it is. vars : variable length collection of Numbers, optional Specifies the constants to target for collection. Can be multiple in number. Numbers : bool Specifies to target all instance of :class:`sympy.core.numbers.Number` class. If ``Numbers=False``, then no Float or Rational will be collected. Returns ======= expr : Expr Returns an expression with similar coefficient terms collected. Examples ======== >>> from sympy import sqrt >>> from sympy.abc import s, x, y, z >>> from sympy.simplify.radsimp import collect_const >>> collect_const(sqrt(3) + sqrt(3)(1 + sqrt(2))) sqrt(3)(sqrt(2) + 2) >>> collect_const(sqrt(3)s + sqrt(7)s + sqrt(3) + sqrt(7)) (sqrt(3) + sqrt(7))(s + 1) >>> s = sqrt(2) + 2 >>> collect_const(sqrt(3)s + sqrt(3) + sqrt(7)s + sqrt(7)) (sqrt(2) + 3)(sqrt(3) + sqrt(7)) >>> collect_const(sqrt(3)s + sqrt(3) + sqrt(7)s + sqrt(7), sqrt(3)) sqrt(7) + sqrt(3)(sqrt(2) + 3) + sqrt(7)(sqrt(2) + 2) The collection is sign-sensitive, giving higher precedence to the unsigned values: >>> collect_const(x - y - z) x - (y + z) >>> collect_const(-y - z) -(y + z) >>> collect_const(2x - 2y - 2z, 2) 2(x - y - z) >>> collect_const(2x - 2y - 2z, -2) 2x - 2(y + z) See Also ======== collect, collect_sqrt, rcollect """ if not expr.is_Add: return expr recurse = False if not vars: recurse = True vars = set() for a in expr.args: for m in Mul.make_args(a): if m.is_number: vars.add(m) else: vars = sympify(vars) if not Numbers: vars = [v for v in vars if not v.is_Number] vars = list(ordered(vars)) for v in vars: terms = defaultdict(list) Fv = Factors(v) for m in Add.make_args(expr): f = Factors(m) q, r = f.div(Fv) if r.is_one: # only accept this as a true factor if # it didn't change an exponent from an Integer # to a non-Integer, e.g. 2/sqrt(2) -> sqrt(2) # -- we aren't looking for this sort of change fwas = f.factors.copy() fnow = q.factors if not any(k in fwas and fwas[k].is_Integer and not fnow[k].is_Integer for k in fnow): terms[v].append(q.as_expr()) continue terms[S.One].append(m) args = [] hit = False uneval = False for k in ordered(terms): v = terms[k] if k is S.One: args.extend(v) continue if len(v) > 1: v = Add(v) hit = True if recurse and v != expr: vars.append(v) else: v = v[0] # be careful not to let uneval become True unless # it must be because it's going to be more expensive # to rebuild the expression as an unevaluated one if Numbers and k.is_Number and v.is_Add: args.append(_keep_coeff(k, v, sign=True)) uneval = True else: args.append(kv) if hit: if uneval: expr = _unevaluated_Add(args) else: expr = Add(args) if not expr.is_Add: break return expr def radsimp(expr, symbolic=True, max_terms=4): r""" Rationalize the denominator by removing square roots. Explanation =========== The expression returned from radsimp must be used with caution since if the denominator contains symbols, it will be possible to make substitutions that violate the assumptions of the simplification process: that for a denominator matching a + bsqrt(c), a != +/-bsqrt(c). (If there are no symbols, this assumptions is made valid by collecting terms of sqrt(c) so the match variable ``a`` does not contain ``sqrt(c)``.) If you do not want the simplification to occur for symbolic denominators, set ``symbolic`` to False. If there are more than ``max_terms`` radical terms then the expression is returned unchanged. Examples ======== >>> from sympy import radsimp, sqrt, Symbol, pprint >>> from sympy import factor_terms, fraction, signsimp >>> from sympy.simplify.radsimp import collect_sqrt >>> from sympy.abc import a, b, c >>> radsimp(1/(2 + sqrt(2))) (2 - sqrt(2))/2 >>> x,y = map(Symbol, 'xy') >>> e = ((2 + 2sqrt(2))x + (2 + sqrt(8))y)/(2 + sqrt(2)) >>> radsimp(e) sqrt(2)(x + y) No simplification beyond removal of the gcd is done. One might want to polish the result a little, however, by collecting square root terms: >>> r2 = sqrt(2) >>> r5 = sqrt(5) >>> ans = radsimp(1/(yr2 + xr2 + ar5 + br5)); pprint(ans) ___ ___ ___ ___ \/ 5 a + \/ 5 b - \/ 2 x - \/ 2 y ------------------------------------------ 2 2 2 2 5a + 10ab + 5b - 2x - 4xy - 2y >>> n, d = fraction(ans) >>> pprint(factor_terms(signsimp(collect_sqrt(n))/d, radical=True)) ___ ___ \/ 5 (a + b) - \/ 2 (x + y) ------------------------------------------ 2 2 2 2 5a + 10ab + 5b - 2x - 4xy - 2y If radicals in the denominator cannot be removed or there is no denominator, the original expression will be returned. >>> radsimp(sqrt(2)x + sqrt(2)) sqrt(2)x + sqrt(2) Results with symbols will not always be valid for all substitutions: >>> eq = 1/(a + bsqrt(c)) >>> eq.subs(a, bsqrt(c)) 1/(2bsqrt(c)) >>> radsimp(eq).subs(a, bsqrt(c)) nan If ``symbolic=False``, symbolic denominators will not be transformed (but numeric denominators will still be processed): >>> radsimp(eq, symbolic=False) 1/(a + bsqrt(c)) """ from sympy.simplify.simplify import signsimp syms = symbols("a:d A:D") def _num(rterms): # return the multiplier that will simplify the expression described # by rterms [(sqrt arg, coeff), ... ] a, b, c, d, A, B, C, D = syms if len(rterms) == 2: reps = dict(list(zip([A, a, B, b], [j for i in rterms for j in i]))) return ( sqrt(A)a - sqrt(B)b).xreplace(reps) if len(rterms) == 3: reps = dict(list(zip([A, a, B, b, C, c], [j for i in rterms for j in i]))) return ( (sqrt(A)a + sqrt(B)b - sqrt(C)c)(2sqrt(A)sqrt(B)ab - Aa*2 - Bb*2 + Cc*2)).xreplace(reps) elif len(rterms) == 4: reps = dict(list(zip([A, a, B, b, C, c, D, d], [j for i in rterms for j in i]))) return ((sqrt(A)a + sqrt(B)b - sqrt(C)c - sqrt(D)d)(2sqrt(A)sqrt(B)ab - Aa2 - Bb*2 - 2sqrt(C)sqrt(D)cd + Cc*2 + Dd*2)(-8sqrt(A)sqrt(B)sqrt(C)sqrt(D)abcd + A*2a*4 - 2ABa*2b*2 - 2ACa*2c*2 - 2ADa*2d2 + B2b4 - 2BCb*2c*2 - 2BDb*2d2 + C2c4 - 2CDc*2d2 + D2d4)).xreplace(reps) elif len(rterms) == 1: return sqrt(rterms[0][0]) else: raise NotImplementedError def ispow2(d, log2=False): if not d.is_Pow: return False e = d.exp if e.is_Rational and e.q == 2 or symbolic and denom(e) == 2: return True if log2: q = 1 if e.is_Rational: q = e.q elif symbolic: d = denom(e) if d.is_Integer: q = d if q != 1 and log(q, 2).is_Integer: return True return False def handle(expr): # Handle first reduces to the case # expr = 1/d, where d is an add, or d is basep/2. # We do this by recursively calling handle on each piece. from sympy.simplify.simplify import nsimplify n, d = fraction(expr) if expr.is_Atom or (d.is_Atom and n.is_Atom): return expr elif not n.is_Atom: n = n.func([handle(a) for a in n.args]) return _unevaluated_Mul(n, handle(1/d)) elif n is not S.One: return _unevaluated_Mul(n, handle(1/d)) elif d.is_Mul: return _unevaluated_Mul([handle(1/d) for d in d.args]) # By this step, expr is 1/d, and d is not a mul. if not symbolic and d.free_symbols: return expr if ispow2(d): d2 = sqrtdenest(sqrt(d.base))numer(d.exp) if d2 != d: return handle(1/d2) elif d.is_Pow and (d.exp.is_integer or d.base.is_positive): # (1/di) = (1/d)i return handle(1/d.base)d.exp if not (d.is_Add or ispow2(d)): return 1/d.func([handle(a) for a in d.args]) # handle 1/d treating d as an Add (though it may not be) keep = True # keep changes that are made # flatten it and collect radicals after checking for special # conditions d = _mexpand(d) # did it change? if d.is_Atom: return 1/d # is it a number that might be handled easily? if d.is_number: _d = nsimplify(d) if _d.is_Number and _d.equals(d): return 1/_d while True: # collect similar terms collected = defaultdict(list) for m in Add.make_args(d): # d might have become non-Add p2 = [] other = [] for i in Mul.make_args(m): if ispow2(i, log2=True): p2.append(i.base if i.exp is S.Half else i.base*(2i.exp)) elif i is S.ImaginaryUnit: p2.append(S.NegativeOne) else: other.append(i) collected[tuple(ordered(p2))].append(Mul(other)) rterms = list(ordered(list(collected.items()))) rterms = [(Mul(i), Add(j)) for i, j in rterms] nrad = len(rterms) - (1 if rterms[0][0] is S.One else 0) if nrad < 1: break elif nrad > max_terms: # there may have been invalid operations leading to this point # so don't keep changes, e.g. this expression is troublesome # in collecting terms so as not to raise the issue of 2834: # r = sqrt(sqrt(5) + 5) # eq = 1/(sqrt(5)r + 2sqrt(5)sqrt(-sqrt(5) + 5) + 5r) keep = False break if len(rterms) > 4: # in general, only 4 terms can be removed with repeated squaring # but other considerations can guide selection of radical terms # so that radicals are removed if all([x.is_Integer and (y2).is_Rational for x, y in rterms]): nd, d = rad_rationalize(S.One, Add._from_args( [sqrt(x)y for x, y in rterms])) n = nd else: # is there anything else that might be attempted? keep = False break from sympy.simplify.powsimp import powsimp, powdenest num = powsimp(_num(rterms)) n = num d = num d = powdenest(_mexpand(d), force=symbolic) if d.is_Atom: break if not keep: return expr return _unevaluated_Mul(n, 1/d) coeff, expr = expr.as_coeff_Add() expr = expr.normal() old = fraction(expr) n, d = fraction(handle(expr)) if old != (n, d): if not d.is_Atom: was = (n, d) n = signsimp(n, evaluate=False) d = signsimp(d, evaluate=False) u = Factors(_unevaluated_Mul(n, 1/d)) u = _unevaluated_Mul([k*v for k, v in u.factors.items()]) n, d = fraction(u) if old == (n, d): n, d = was n = expand_mul(n) if d.is_Number or d.is_Add: n2, d2 = fraction(gcd_terms(_unevaluated_Mul(n, 1/d))) if d2.is_Number or (d2.count_ops() <= d.count_ops()): n, d = [signsimp(i) for i in (n2, d2)] if n.is_Mul and n.args[0].is_Number: n = n.func(n.args) return coeff + _unevaluated_Mul(n, 1/d) def rad_rationalize(num, den): """ Rationalize ``num/den`` by removing square roots in the denominator; num and den are sum of terms whose squares are positive rationals. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import rad_rationalize >>> rad_rationalize(sqrt(3), 1 + sqrt(2)/3) (-sqrt(3) + sqrt(6)/3, -7/9) """ if not den.is_Add: return num, den g, a, b = split_surds(den) a = asqrt(g) num = _mexpand((a - b)num) den = _mexpand(a2 - b2) return rad_rationalize(num, den) def fraction(expr, exact=False): """Returns a pair with expression's numerator and denominator. If the given expression is not a fraction then this function will return the tuple (expr, 1). This function will not make any attempt to simplify nested fractions or to do any term rewriting at all. If only one of the numerator/denominator pair is needed then use numer(expr) or denom(expr) functions respectively. >>> from sympy import fraction, Rational, Symbol >>> from sympy.abc import x, y >>> fraction(x/y) (x, y) >>> fraction(x) (x, 1) >>> fraction(1/y2) (1, y2) >>> fraction(xy/2) (xy, 2) >>> fraction(Rational(1, 2)) (1, 2) This function will also work fine with assumptions: >>> k = Symbol('k', negative=True) >>> fraction(x * yk) (x, y(-k)) If we know nothing about sign of some exponent and ``exact`` flag is unset, then structure this exponent's structure will be analyzed and pretty fraction will be returned: >>> from sympy import exp, Mul >>> fraction(2x(-y)) (2, xy) >>> fraction(exp(-x)) (1, exp(x)) >>> fraction(exp(-x), exact=True) (exp(-x), 1) The ``exact`` flag will also keep any unevaluated Muls from being evaluated: >>> u = Mul(2, x + 1, evaluate=False) >>> fraction(u) (2x + 2, 1) >>> fraction(u, exact=True) (2(x + 1), 1) """ expr = sympify(expr) numer, denom = [], [] for term in Mul.make_args(expr): if term.is_commutative and (term.is_Pow or isinstance(term, exp)): b, ex = term.as_base_exp() if ex.is_negative: if ex is S.NegativeOne: denom.append(b) elif exact: if ex.is_constant(): denom.append(Pow(b, -ex)) else: numer.append(term) else: denom.append(Pow(b, -ex)) elif ex.is_positive: numer.append(term) elif not exact and ex.is_Mul: n, d = term.as_numer_denom() if n != 1: numer.append(n) denom.append(d) else: numer.append(term) elif term.is_Rational and not term.is_Integer: if term.p != 1: numer.append(term.p) denom.append(term.q) else: numer.append(term) return Mul(numer, evaluate=not exact), Mul(denom, evaluate=not exact) def numer(expr): return fraction(expr)[0] def denom(expr): return fraction(expr)[1] def fraction_expand(expr, hints): return expr.expand(frac=True, hints) def numer_expand(expr, hints): a, b = fraction(expr) return a.expand(numer=True, hints) / b def denom_expand(expr, hints): a, b = fraction(expr) return a / b.expand(denom=True, hints) expand_numer = numer_expand expand_denom = denom_expand expand_fraction = fraction_expand def split_surds(expr): """ Split an expression with terms whose squares are positive rationals into a sum of terms whose surds squared have gcd equal to g and a sum of terms with surds squared prime with g. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import split_surds >>> split_surds(3sqrt(3) + sqrt(5)/7 + sqrt(6) + sqrt(10) + sqrt(15)) (3, sqrt(2) + sqrt(5) + 3, sqrt(5)/7 + sqrt(10)) """ args = sorted(expr.args, key=default_sort_key) coeff_muls = [x.as_coeff_Mul() for x in args] surds = [x[1]*2 for x in coeff_muls if x[1].is_Pow] surds.sort(key=default_sort_key) g, b1, b2 = _split_gcd(surds) g2 = g if not b2 and len(b1) >= 2: b1n = [x/g for x in b1] b1n = [x for x in b1n if x != 1] # only a common factor has been factored; split again g1, b1n, b2 = _split_gcd(b1n) g2 = gg1 a1v, a2v = [], [] for c, s in coeff_muls: if s.is_Pow and s.exp == S.Half: s1 = s.base if s1 in b1: a1v.append(csqrt(s1/g2)) else: a2v.append(cs) else: a2v.append(cs) a = Add(a1v) b = Add(a2v) return g2, a, b def _split_gcd(a): """ Split the list of integers ``a`` into a list of integers, ``a1`` having ``g = gcd(a1)``, and a list ``a2`` whose elements are not divisible by ``g``. Returns ``g, a1, a2``. Examples ======== >>> from sympy.simplify.radsimp import _split_gcd >>> _split_gcd(55, 35, 22, 14, 77, 10) (5, [55, 35, 10], [22, 14, 77]) """ g = a[0] b1 = [g] b2 = [] for x in a[1:]: g1 = gcd(g, x) if g1 == 1: b2.append(x) else: g = g1 b1.append(x) return g, b1, b2
35102055e5581845da44d59a64f8df8ca3602e598978cfa2698213b7e62a5d2b	"""Tools for manipulation of expressions using paths. """ from sympy.core import Basic class EPath: r""" Manipulate expressions using paths. EPath grammar in EBNF notation:: literal ::= /[A-Za-z_][A-Za-z_0-9]/ number ::= /-?\d+/ type ::= literal attribute ::= literal "?" all ::= "" slice ::= "[" number? (":" number? (":" number?)?)? "]" range ::= all \| slice query ::= (type \| attribute) ("\|" (type \| attribute))* selector ::= range \| query range? path ::= "/" selector ("/" selector)* See the docstring of the epath() function. """ __slots__ = ("_path", "_epath") def __new__(cls, path): """Construct new EPath. """ if isinstance(path, EPath): return path if not path: raise ValueError("empty EPath") _path = path if path[0] == '/': path = path[1:] else: raise NotImplementedError("non-root EPath") epath = [] for selector in path.split('/'): selector = selector.strip() if not selector: raise ValueError("empty selector") index = 0 for c in selector: if c.isalnum() or c == '_' or c == '\|' or c == '?': index += 1 else: break attrs = [] types = [] if index: elements = selector[:index] selector = selector[index:] for element in elements.split('\|'): element = element.strip() if not element: raise ValueError("empty element") if element.endswith('?'): attrs.append(element[:-1]) else: types.append(element) span = None if selector == '': pass else: if selector.startswith('['): try: i = selector.index(']') except ValueError: raise ValueError("expected ']', got EOL") _span, span = selector[1:i], [] if ':' not in _span: span = int(_span) else: for elt in _span.split(':', 3): if not elt: span.append(None) else: span.append(int(elt)) span = slice(span) selector = selector[i + 1:] if selector: raise ValueError("trailing characters in selector") epath.append((attrs, types, span)) obj = object.__new__(cls) obj._path = _path obj._epath = epath return obj def __repr__(self): return "%s(%r)" % (self.__class__.__name__, self._path) def _get_ordered_args(self, expr): """Sort ``expr.args`` using printing order. """ if expr.is_Add: return expr.as_ordered_terms() elif expr.is_Mul: return expr.as_ordered_factors() else: return expr.args def _hasattrs(self, expr, attrs): """Check if ``expr`` has any of ``attrs``. """ for attr in attrs: if not hasattr(expr, attr): return False return True def _hastypes(self, expr, types): """Check if ``expr`` is any of ``types``. """ _types = [ cls.__name__ for cls in expr.__class__.mro() ] return bool(set(_types).intersection(types)) def _has(self, expr, attrs, types): """Apply ``_hasattrs`` and ``_hastypes`` to ``expr``. """ if not (attrs or types): return True if attrs and self._hasattrs(expr, attrs): return True if types and self._hastypes(expr, types): return True return False def apply(self, expr, func, args=None, kwargs=None): """ Modify parts of an expression selected by a path. Examples ======== >>> from sympy.simplify.epathtools import EPath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = EPath("//[0]/Symbol") >>> expr = [((x, 1), 2), ((3, y), z)] >>> path.apply(expr, lambda expr: expr2) [((x2, 1), 2), ((3, y2), z)] >>> path = EPath("///Symbol") >>> expr = t + sin(x + 1) + cos(x + y + E) >>> path.apply(expr, lambda expr: 2expr) t + sin(2x + 1) + cos(2x + 2y + E) """ def _apply(path, expr, func): if not path: return func(expr) else: selector, path = path[0], path[1:] attrs, types, span = selector if isinstance(expr, Basic): if not expr.is_Atom: args, basic = self._get_ordered_args(expr), True else: return expr elif hasattr(expr, '__iter__'): args, basic = expr, False else: return expr args = list(args) if span is not None: if type(span) == slice: indices = range(span.indices(len(args))) else: indices = [span] else: indices = range(len(args)) for i in indices: try: arg = args[i] except IndexError: continue if self._has(arg, attrs, types): args[i] = _apply(path, arg, func) if basic: return expr.func(args) else: return expr.__class__(args) _args, _kwargs = args or (), kwargs or {} _func = lambda expr: func(expr, _args, *_kwargs) return _apply(self._epath, expr, _func) def select(self, expr): """ Retrieve parts of an expression selected by a path. Examples ======== >>> from sympy.simplify.epathtools import EPath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = EPath("//[0]/Symbol") >>> expr = [((x, 1), 2), ((3, y), z)] >>> path.select(expr) [x, y] >>> path = EPath("///Symbol") >>> expr = t + sin(x + 1) + cos(x + y + E) >>> path.select(expr) [x, x, y] """ result = [] def _select(path, expr): if not path: result.append(expr) else: selector, path = path[0], path[1:] attrs, types, span = selector if isinstance(expr, Basic): args = self._get_ordered_args(expr) elif hasattr(expr, '__iter__'): args = expr else: return if span is not None: if type(span) == slice: args = args[span] else: try: args = [args[span]] except IndexError: return for arg in args: if self._has(arg, attrs, types): _select(path, arg) _select(self._epath, expr) return result def epath(path, expr=None, func=None, args=None, kwargs=None): r""" Manipulate parts of an expression selected by a path. Explanation =========== This function allows to manipulate large nested expressions in single line of code, utilizing techniques to those applied in XML processing standards (e.g. XPath). If ``func`` is ``None``, :func:`epath` retrieves elements selected by the ``path``. Otherwise it applies ``func`` to each matching element. Note that it is more efficient to create an EPath object and use the select and apply methods of that object, since this will compile the path string only once. This function should only be used as a convenient shortcut for interactive use. This is the supported syntax: * select all: ``/`` Equivalent of ``for arg in args:``. select slice: ``/[0]`` or ``/[1:5]`` or ``/[1:5:2]`` Supports standard Python's slice syntax. * select by type: ``/list`` or ``/list\|tuple`` Emulates ``isinstance()``. * select by attribute: ``/__iter__?`` Emulates ``hasattr()``. Parameters ========== path : str \| EPath A path as a string or a compiled EPath. expr : Basic \| iterable An expression or a container of expressions. func : callable (optional) A callable that will be applied to matching parts. args : tuple (optional) Additional positional arguments to ``func``. kwargs : dict (optional) Additional keyword arguments to ``func``. Examples ======== >>> from sympy.simplify.epathtools import epath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = "//[0]/Symbol" >>> expr = [((x, 1), 2), ((3, y), z)] >>> epath(path, expr) [x, y] >>> epath(path, expr, lambda expr: expr2) [((x2, 1), 2), ((3, y2), z)] >>> path = "///Symbol" >>> expr = t + sin(x + 1) + cos(x + y + E) >>> epath(path, expr) [x, x, y] >>> epath(path, expr, lambda expr: 2expr) t + sin(2x + 1) + cos(2x + 2*y + E) """ _epath = EPath(path) if expr is None: return _epath if func is None: return _epath.select(expr) else: return _epath.apply(expr, func, args, kwargs)
a8029e2ba01f3f74c6531cab6bd69f7a122ed75d8ecd345234e2d91eddb775f4	from sympy.core import Mul from sympy.core.basic import preorder_traversal from sympy.core.function import count_ops from sympy.functions.combinatorial.factorials import binomial, factorial from sympy.functions import gamma from sympy.simplify.gammasimp import gammasimp, _gammasimp from sympy.utilities.timeutils import timethis @timethis('combsimp') def combsimp(expr): r""" Simplify combinatorial expressions. Explanation =========== This function takes as input an expression containing factorials, binomials, Pochhammer symbol and other "combinatorial" functions, and tries to minimize the number of those functions and reduce the size of their arguments. The algorithm works by rewriting all combinatorial functions as gamma functions and applying gammasimp() except simplification steps that may make an integer argument non-integer. See docstring of gammasimp for more information. Then it rewrites expression in terms of factorials and binomials by rewriting gammas as factorials and converting (a+b)!/a!b! into binomials. If expression has gamma functions or combinatorial functions with non-integer argument, it is automatically passed to gammasimp. Examples ======== >>> from sympy.simplify import combsimp >>> from sympy import factorial, binomial, symbols >>> n, k = symbols('n k', integer = True) >>> combsimp(factorial(n)/factorial(n - 3)) n(n - 2)(n - 1) >>> combsimp(binomial(n+1, k+1)/binomial(n, k)) (n + 1)/(k + 1) """ expr = expr.rewrite(gamma, piecewise=False) if any(isinstance(node, gamma) and not node.args[0].is_integer for node in preorder_traversal(expr)): return gammasimp(expr); expr = _gammasimp(expr, as_comb = True) expr = _gamma_as_comb(expr) return expr def _gamma_as_comb(expr): """ Helper function for combsimp. Rewrites expression in terms of factorials and binomials """ expr = expr.rewrite(factorial) from .simplify import bottom_up def f(rv): if not rv.is_Mul: return rv rvd = rv.as_powers_dict() nd_fact_args = [[], []] # numerator, denominator for k in rvd: if isinstance(k, factorial) and rvd[k].is_Integer: if rvd[k].is_positive: nd_fact_args[0].extend([k.args[0]]rvd[k]) else: nd_fact_args[1].extend([k.args[0]]-rvd[k]) rvd[k] = 0 if not nd_fact_args[0] or not nd_fact_args[1]: return rv hit = False for m in range(2): i = 0 while i < len(nd_fact_args[m]): ai = nd_fact_args[m][i] for j in range(i + 1, len(nd_fact_args[m])): aj = nd_fact_args[m][j] sum = ai + aj if sum in nd_fact_args[1 - m]: hit = True nd_fact_args[1 - m].remove(sum) del nd_fact_args[m][j] del nd_fact_args[m][i] rvd[binomial(sum, ai if count_ops(ai) < count_ops(aj) else aj)] += ( -1 if m == 0 else 1) break else: i += 1 if hit: return Mul(([krvd[k] for k in rvd] + [factorial(k) for k in nd_fact_args[0]]))/Mul([factorial(k) for k in nd_fact_args[1]]) return rv return bottom_up(expr, f)
7e51bf655cdc6a8bbe60c10138c6204747ba3d7f28108a3ec75bdab3c055b72c	from sympy.core import Add, Expr, Mul, S, sympify from sympy.core.function import _mexpand, count_ops, expand_mul from sympy.core.symbol import Dummy from sympy.functions import root, sign, sqrt from sympy.polys import Poly, PolynomialError from sympy.utilities import default_sort_key def is_sqrt(expr): """Return True if expr is a sqrt, otherwise False.""" return expr.is_Pow and expr.exp.is_Rational and abs(expr.exp) is S.Half def sqrt_depth(p): """Return the maximum depth of any square root argument of p. >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import sqrt_depth Neither of these square roots contains any other square roots so the depth is 1: >>> sqrt_depth(1 + sqrt(2)(1 + sqrt(3))) 1 The sqrt(3) is contained within a square root so the depth is 2: >>> sqrt_depth(1 + sqrt(2)sqrt(1 + sqrt(3))) 2 """ if p is S.ImaginaryUnit: return 1 if p.is_Atom: return 0 elif p.is_Add or p.is_Mul: return max([sqrt_depth(x) for x in p.args], key=default_sort_key) elif is_sqrt(p): return sqrt_depth(p.base) + 1 else: return 0 def is_algebraic(p): """Return True if p is comprised of only Rationals or square roots of Rationals and algebraic operations. Examples ======== >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import is_algebraic >>> from sympy import cos >>> is_algebraic(sqrt(2)(3/(sqrt(7) + sqrt(5)sqrt(2)))) True >>> is_algebraic(sqrt(2)(3/(sqrt(7) + sqrt(5)cos(2)))) False """ if p.is_Rational: return True elif p.is_Atom: return False elif is_sqrt(p) or p.is_Pow and p.exp.is_Integer: return is_algebraic(p.base) elif p.is_Add or p.is_Mul: return all(is_algebraic(x) for x in p.args) else: return False def _subsets(n): """ Returns all possible subsets of the set (0, 1, ..., n-1) except the empty set, listed in reversed lexicographical order according to binary representation, so that the case of the fourth root is treated last. Examples ======== >>> from sympy.simplify.sqrtdenest import _subsets >>> _subsets(2) [[1, 0], [0, 1], [1, 1]] """ if n == 1: a = [[1]] elif n == 2: a = [[1, 0], [0, 1], [1, 1]] elif n == 3: a = [[1, 0, 0], [0, 1, 0], [1, 1, 0], [0, 0, 1], [1, 0, 1], [0, 1, 1], [1, 1, 1]] else: b = _subsets(n - 1) a0 = [x + [0] for x in b] a1 = [x + [1] for x in b] a = a0 + [[0](n - 1) + [1]] + a1 return a def sqrtdenest(expr, max_iter=3): """Denests sqrts in an expression that contain other square roots if possible, otherwise returns the expr unchanged. This is based on the algorithms of [1]. Examples ======== >>> from sympy.simplify.sqrtdenest import sqrtdenest >>> from sympy import sqrt >>> sqrtdenest(sqrt(5 + 2 sqrt(6))) sqrt(2) + sqrt(3) See Also ======== sympy.solvers.solvers.unrad References ========== .. [1] http://researcher.watson.ibm.com/researcher/files/us-fagin/symb85.pdf .. [2] D. J. Jeffrey and A. D. Rich, 'Symplifying Square Roots of Square Roots by Denesting' (available at http://www.cybertester.com/data/denest.pdf) """ expr = expand_mul(sympify(expr)) for i in range(max_iter): z = _sqrtdenest0(expr) if expr == z: return expr expr = z return expr def _sqrt_match(p): """Return [a, b, r] for p.match(a + bsqrt(r)) where, in addition to matching, sqrt(r) also has then maximal sqrt_depth among addends of p. Examples ======== >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import _sqrt_match >>> _sqrt_match(1 + sqrt(2) + sqrt(2)sqrt(3) + 2sqrt(1+sqrt(5))) [1 + sqrt(2) + sqrt(6), 2, 1 + sqrt(5)] """ from sympy.simplify.radsimp import split_surds p = _mexpand(p) if p.is_Number: res = (p, S.Zero, S.Zero) elif p.is_Add: pargs = sorted(p.args, key=default_sort_key) sqargs = [x2 for x in pargs] if all(sq.is_Rational and sq.is_positive for sq in sqargs): r, b, a = split_surds(p) res = a, b, r return list(res) # to make the process canonical, the argument is included in the tuple # so when the max is selected, it will be the largest arg having a # given depth v = [(sqrt_depth(x), x, i) for i, x in enumerate(pargs)] nmax = max(v, key=default_sort_key) if nmax[0] == 0: res = [] else: # select r depth, _, i = nmax r = pargs.pop(i) v.pop(i) b = S.One if r.is_Mul: bv = [] rv = [] for x in r.args: if sqrt_depth(x) < depth: bv.append(x) else: rv.append(x) b = Mul._from_args(bv) r = Mul._from_args(rv) # collect terms comtaining r a1 = [] b1 = [b] for x in v: if x[0] < depth: a1.append(x[1]) else: x1 = x[1] if x1 == r: b1.append(1) else: if x1.is_Mul: x1args = list(x1.args) if r in x1args: x1args.remove(r) b1.append(Mul(x1args)) else: a1.append(x[1]) else: a1.append(x[1]) a = Add(a1) b = Add(b1) res = (a, b, r2) else: b, r = p.as_coeff_Mul() if is_sqrt(r): res = (S.Zero, b, r2) else: res = [] return list(res) class SqrtdenestStopIteration(StopIteration): pass def _sqrtdenest0(expr): """Returns expr after denesting its arguments.""" if is_sqrt(expr): n, d = expr.as_numer_denom() if d is S.One: # n is a square root if n.base.is_Add: args = sorted(n.base.args, key=default_sort_key) if len(args) > 2 and all((x*2).is_Integer for x in args): try: return _sqrtdenest_rec(n) except SqrtdenestStopIteration: pass expr = sqrt(_mexpand(Add([_sqrtdenest0(x) for x in args]))) return _sqrtdenest1(expr) else: n, d = [_sqrtdenest0(i) for i in (n, d)] return n/d if isinstance(expr, Add): cs = [] args = [] for arg in expr.args: c, a = arg.as_coeff_Mul() cs.append(c) args.append(a) if all(c.is_Rational for c in cs) and all(is_sqrt(arg) for arg in args): return _sqrt_ratcomb(cs, args) if isinstance(expr, Expr): args = expr.args if args: return expr.func([_sqrtdenest0(a) for a in args]) return expr def _sqrtdenest_rec(expr): """Helper that denests the square root of three or more surds. Explanation =========== It returns the denested expression; if it cannot be denested it throws SqrtdenestStopIteration Algorithm: expr.base is in the extension Q_m = Q(sqrt(r_1),..,sqrt(r_k)); split expr.base = a + bsqrt(r_k), where `a` and `b` are on Q_(m-1) = Q(sqrt(r_1),..,sqrt(r_(k-1))); then a2 - b2r_k is on Q_(m-1); denest sqrt(a2 - b2r_k) and so on. See [1], section 6. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import _sqrtdenest_rec >>> _sqrtdenest_rec(sqrt(-72sqrt(2) + 158sqrt(5) + 498)) -sqrt(10) + sqrt(2) + 9 + 9sqrt(5) >>> w=-6sqrt(55)-6sqrt(35)-2sqrt(22)-2sqrt(14)+2sqrt(77)+6sqrt(10)+65 >>> _sqrtdenest_rec(sqrt(w)) -sqrt(11) - sqrt(7) + sqrt(2) + 3sqrt(5) """ from sympy.simplify.radsimp import radsimp, rad_rationalize, split_surds if not expr.is_Pow: return sqrtdenest(expr) if expr.base < 0: return sqrt(-1)_sqrtdenest_rec(sqrt(-expr.base)) g, a, b = split_surds(expr.base) a = asqrt(g) if a < b: a, b = b, a c2 = _mexpand(a2 - b2) if len(c2.args) > 2: g, a1, b1 = split_surds(c2) a1 = a1sqrt(g) if a1 < b1: a1, b1 = b1, a1 c2_1 = _mexpand(a12 - b12) c_1 = _sqrtdenest_rec(sqrt(c2_1)) d_1 = _sqrtdenest_rec(sqrt(a1 + c_1)) num, den = rad_rationalize(b1, d_1) c = _mexpand(d_1/sqrt(2) + num/(densqrt(2))) else: c = _sqrtdenest1(sqrt(c2)) if sqrt_depth(c) > 1: raise SqrtdenestStopIteration ac = a + c if len(ac.args) >= len(expr.args): if count_ops(ac) >= count_ops(expr.base): raise SqrtdenestStopIteration d = sqrtdenest(sqrt(ac)) if sqrt_depth(d) > 1: raise SqrtdenestStopIteration num, den = rad_rationalize(b, d) r = d/sqrt(2) + num/(densqrt(2)) r = radsimp(r) return _mexpand(r) def _sqrtdenest1(expr, denester=True): """Return denested expr after denesting with simpler methods or, that failing, using the denester.""" from sympy.simplify.simplify import radsimp if not is_sqrt(expr): return expr a = expr.base if a.is_Atom: return expr val = _sqrt_match(a) if not val: return expr a, b, r = val # try a quick numeric denesting d2 = _mexpand(a2 - b2r) if d2.is_Rational: if d2.is_positive: z = _sqrt_numeric_denest(a, b, r, d2) if z is not None: return z else: # fourth root case # sqrtdenest(sqrt(3 + 2sqrt(3))) = # sqrt(2)3*(1/4)/2 + sqrt(2)3*(3/4)/2 dr2 = _mexpand(-d2r) dr = sqrt(dr2) if dr.is_Rational: z = _sqrt_numeric_denest(_mexpand(br), a, r, dr2) if z is not None: return z/root(r, 4) else: z = _sqrt_symbolic_denest(a, b, r) if z is not None: return z if not denester or not is_algebraic(expr): return expr res = sqrt_biquadratic_denest(expr, a, b, r, d2) if res: return res # now call to the denester av0 = [a, b, r, d2] z = _denester([radsimp(expr2)], av0, 0, sqrt_depth(expr))[0] if av0[1] is None: return expr if z is not None: if sqrt_depth(z) == sqrt_depth(expr) and count_ops(z) > count_ops(expr): return expr return z return expr def _sqrt_symbolic_denest(a, b, r): """Given an expression, sqrt(a + bsqrt(b)), return the denested expression or None. Explanation =========== If r = ra + rbsqrt(rr), try replacing sqrt(rr) in ``a`` with (y2 - ra)/rb, and if the result is a quadratic, cay*2 + cby + cc, and (cb + b)*2 - 4cacc is 0, then sqrt(a + bsqrt(r)) can be rewritten as sqrt(ca(sqrt(r) + (cb + b)/(2ca))*2). Examples ======== >>> from sympy.simplify.sqrtdenest import _sqrt_symbolic_denest, sqrtdenest >>> from sympy import sqrt, Symbol >>> from sympy.abc import x >>> a, b, r = 16 - 2sqrt(29), 2, -10sqrt(29) + 55 >>> _sqrt_symbolic_denest(a, b, r) sqrt(11 - 2sqrt(29)) + sqrt(5) If the expression is numeric, it will be simplified: >>> w = sqrt(sqrt(sqrt(3) + 1) + 1) + 1 + sqrt(2) >>> sqrtdenest(sqrt((w2).expand())) 1 + sqrt(2) + sqrt(1 + sqrt(1 + sqrt(3))) Otherwise, it will only be simplified if assumptions allow: >>> w = w.subs(sqrt(3), sqrt(x + 3)) >>> sqrtdenest(sqrt((w2).expand())) sqrt((sqrt(sqrt(sqrt(x + 3) + 1) + 1) + 1 + sqrt(2))2) Notice that the argument of the sqrt is a square. If x is made positive then the sqrt of the square is resolved: >>> _.subs(x, Symbol('x', positive=True)) sqrt(sqrt(sqrt(x + 3) + 1) + 1) + 1 + sqrt(2) """ a, b, r = map(sympify, (a, b, r)) rval = _sqrt_match(r) if not rval: return None ra, rb, rr = rval if rb: y = Dummy('y', positive=True) try: newa = Poly(a.subs(sqrt(rr), (y2 - ra)/rb), y) except PolynomialError: return None if newa.degree() == 2: ca, cb, cc = newa.all_coeffs() cb += b if _mexpand(cb*2 - 4cacc).equals(0): z = sqrt(ca(sqrt(r) + cb/(2ca))2) if z.is_number: z = _mexpand(Mul._from_args(z.as_content_primitive())) return z def _sqrt_numeric_denest(a, b, r, d2): r"""Helper that denest $\sqrt{a + b \sqrt{r}}, d^2 = a^2 - b^2 r > 0$ If it cannot be denested, it returns ``None``. """ d = sqrt(d2) s = a + d # sqrt_depth(res) <= sqrt_depth(s) + 1 # sqrt_depth(expr) = sqrt_depth(r) + 2 # there is denesting if sqrt_depth(s) + 1 < sqrt_depth(r) + 2 # if s2 is Number there is a fourth root if sqrt_depth(s) < sqrt_depth(r) + 1 or (s2).is_Rational: s1, s2 = sign(s), sign(b) if s1 == s2 == -1: s1 = s2 = 1 res = (s1 sqrt(a + d) + s2 * sqrt(a - d)) * sqrt(2) / 2 return res.expand() def sqrt_biquadratic_denest(expr, a, b, r, d2): """denest expr = sqrt(a + bsqrt(r)) where a, b, r are linear combinations of square roots of positive rationals on the rationals (SQRR) and r > 0, b != 0, d2 = a2 - b2r > 0 If it cannot denest it returns None. Explanation =========== Search for a solution A of type SQRR of the biquadratic equation 4A4 - 4aA2 + b2r = 0 (1) sqd = sqrt(a2 - b2r) Choosing the sqrt to be positive, the possible solutions are A = sqrt(a/2 +/- sqd/2) Since a, b, r are SQRR, then a2 - b2r is a SQRR, so if sqd can be denested, it is done by _sqrtdenest_rec, and the result is a SQRR. Similarly for A. Examples of solutions (in both cases a and sqd are positive): Example of expr with solution sqrt(a/2 + sqd/2) but not solution sqrt(a/2 - sqd/2): expr = sqrt(-sqrt(15) - sqrt(2)sqrt(-sqrt(5) + 5) - sqrt(3) + 8) a = -sqrt(15) - sqrt(3) + 8; sqd = -2sqrt(5) - 2 + 4sqrt(3) Example of expr with solution sqrt(a/2 - sqd/2) but not solution sqrt(a/2 + sqd/2): w = 2 + r2 + r3 + (1 + r3)sqrt(2 + r2 + 5r3) expr = sqrt((w2).expand()) a = 4sqrt(6) + 8sqrt(2) + 47 + 28sqrt(3) sqd = 29 + 20sqrt(3) Define B = b/2A; eq.(1) implies a = A2 + B2r; then expr2 = a + bsqrt(r) = (A + Bsqrt(r))2 Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import _sqrt_match, sqrt_biquadratic_denest >>> z = sqrt((2sqrt(2) + 4)sqrt(2 + sqrt(2)) + 5sqrt(2) + 8) >>> a, b, r = _sqrt_match(z2) >>> d2 = a2 - b*2r >>> sqrt_biquadratic_denest(z, a, b, r, d2) sqrt(2) + sqrt(sqrt(2) + 2) + 2 """ from sympy.simplify.radsimp import radsimp, rad_rationalize if r <= 0 or d2 < 0 or not b or sqrt_depth(expr.base) < 2: return None for x in (a, b, r): for y in x.args: y2 = y*2 if not y2.is_Integer or not y2.is_positive: return None sqd = _mexpand(sqrtdenest(sqrt(radsimp(d2)))) if sqrt_depth(sqd) > 1: return None x1, x2 = [a/2 + sqd/2, a/2 - sqd/2] # look for a solution A with depth 1 for x in (x1, x2): A = sqrtdenest(sqrt(x)) if sqrt_depth(A) > 1: continue Bn, Bd = rad_rationalize(b, _mexpand(2A)) B = Bn/Bd z = A + Bsqrt(r) if z < 0: z = -z return _mexpand(z) return None def _denester(nested, av0, h, max_depth_level): """Denests a list of expressions that contain nested square roots. Explanation =========== Algorithm based on <http://www.almaden.ibm.com/cs/people/fagin/symb85.pdf>. It is assumed that all of the elements of 'nested' share the same bottom-level radicand. (This is stated in the paper, on page 177, in the paragraph immediately preceding the algorithm.) When evaluating all of the arguments in parallel, the bottom-level radicand only needs to be denested once. This means that calling _denester with x arguments results in a recursive invocation with x+1 arguments; hence _denester has polynomial complexity. However, if the arguments were evaluated separately, each call would result in two recursive invocations, and the algorithm would have exponential complexity. This is discussed in the paper in the middle paragraph of page 179. """ from sympy.simplify.simplify import radsimp if h > max_depth_level: return None, None if av0[1] is None: return None, None if (av0[0] is None and all(n.is_Number for n in nested)): # no arguments are nested for f in _subsets(len(nested)): # test subset 'f' of nested p = _mexpand(Mul([nested[i] for i in range(len(f)) if f[i]])) if f.count(1) > 1 and f[-1]: p = -p sqp = sqrt(p) if sqp.is_Rational: return sqp, f # got a perfect square so return its square root. # Otherwise, return the radicand from the previous invocation. return sqrt(nested[-1]), [0]len(nested) else: R = None if av0[0] is not None: values = [av0[:2]] R = av0[2] nested2 = [av0[3], R] av0[0] = None else: values = list(filter(None, [_sqrt_match(expr) for expr in nested])) for v in values: if v[2]: # Since if b=0, r is not defined if R is not None: if R != v[2]: av0[1] = None return None, None else: R = v[2] if R is None: # return the radicand from the previous invocation return sqrt(nested[-1]), [0]len(nested) nested2 = [_mexpand(v[0]*2) - _mexpand(Rv[1]*2) for v in values] + [R] d, f = _denester(nested2, av0, h + 1, max_depth_level) if not f: return None, None if not any(f[i] for i in range(len(nested))): v = values[-1] return sqrt(v[0] + _mexpand(v[1]d)), f else: p = Mul([nested[i] for i in range(len(nested)) if f[i]]) v = _sqrt_match(p) if 1 in f and f.index(1) < len(nested) - 1 and f[len(nested) - 1]: v[0] = -v[0] v[1] = -v[1] if not f[len(nested)]: # Solution denests with square roots vad = _mexpand(v[0] + d) if vad <= 0: # return the radicand from the previous invocation. return sqrt(nested[-1]), [0]len(nested) if not(sqrt_depth(vad) <= sqrt_depth(R) + 1 or (vad*2).is_Number): av0[1] = None return None, None sqvad = _sqrtdenest1(sqrt(vad), denester=False) if not (sqrt_depth(sqvad) <= sqrt_depth(R) + 1): av0[1] = None return None, None sqvad1 = radsimp(1/sqvad) res = _mexpand(sqvad/sqrt(2) + (v[1]sqrt(R)sqvad1/sqrt(2))) return res, f # sign(v[1])sqrt(_mexpand(v[1]*2Rvad1/2))), f else: # Solution requires a fourth root s2 = _mexpand(v[1]R) + d if s2 <= 0: return sqrt(nested[-1]), [0]len(nested) FR, s = root(_mexpand(R), 4), sqrt(s2) return _mexpand(s/(sqrt(2)FR) + v[0]FR/(sqrt(2)s)), f def _sqrt_ratcomb(cs, args): """Denest rational combinations of radicals. Based on section 5 of [1]. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import sqrtdenest >>> z = sqrt(1+sqrt(3)) + sqrt(3+3sqrt(3)) - sqrt(10+6sqrt(3)) >>> sqrtdenest(z) 0 """ from sympy.simplify.radsimp import radsimp # check if there exists a pair of sqrt that can be denested def find(a): n = len(a) for i in range(n - 1): for j in range(i + 1, n): s1 = a[i].base s2 = a[j].base p = _mexpand(s1 * s2) s = sqrtdenest(sqrt(p)) if s != sqrt(p): return s, i, j indices = find(args) if indices is None: return Add([c arg for c, arg in zip(cs, args)]) s, i1, i2 = indices c2 = cs.pop(i2) args.pop(i2) a1 = args[i1] # replace a2 by s/a1 cs[i1] += radsimp(c2 * s / a1.base) return _sqrt_ratcomb(cs, args)
dedea045629a9e7426b27000dd5ed4e0484979f8f2fe6e670f98a1a6aff17940	from collections import defaultdict from sympy.core.function import expand_log, count_ops from sympy.core import sympify, Basic, Dummy, S, Add, Mul, Pow, expand_mul, factor_terms from sympy.core.compatibility import ordered, default_sort_key, reduce from sympy.core.numbers import Integer, Rational from sympy.core.mul import prod, _keep_coeff from sympy.core.rules import Transform from sympy.functions import exp_polar, exp, log, root, polarify, unpolarify from sympy.polys import lcm, gcd from sympy.ntheory.factor_ import multiplicity def powsimp(expr, deep=False, combine='all', force=False, measure=count_ops): """ reduces expression by combining powers with similar bases and exponents. Explanation =========== If ``deep`` is ``True`` then powsimp() will also simplify arguments of functions. By default ``deep`` is set to ``False``. If ``force`` is ``True`` then bases will be combined without checking for assumptions, e.g. sqrt(x)sqrt(y) -> sqrt(xy) which is not true if x and y are both negative. You can make powsimp() only combine bases or only combine exponents by changing combine='base' or combine='exp'. By default, combine='all', which does both. combine='base' will only combine:: a a a 2x x x * y => (xy) as well as things like 2 => 4 and combine='exp' will only combine :: a b (a + b) x x => x combine='exp' will strictly only combine exponents in the way that used to be automatic. Also use deep=True if you need the old behavior. When combine='all', 'exp' is evaluated first. Consider the first example below for when there could be an ambiguity relating to this. This is done so things like the second example can be completely combined. If you want 'base' combined first, do something like powsimp(powsimp(expr, combine='base'), combine='exp'). Examples ======== >>> from sympy import powsimp, exp, log, symbols >>> from sympy.abc import x, y, z, n >>> powsimp(x*yx*zyz, combine='all') x(y + z)yz >>> powsimp(xyx*zyz, combine='exp') x(y + z)yz >>> powsimp(xyx*zyz, combine='base', force=True) xy(xy)z >>> powsimp(xzxyn*zn*y, combine='all', force=True) (nx)(y + z) >>> powsimp(xzxyn*zny, combine='exp') n(y + z)x(y + z) >>> powsimp(xzx*yn*zn*y, combine='base', force=True) (nx)*y(nx)z >>> x, y = symbols('x y', positive=True) >>> powsimp(log(exp(x)exp(y))) log(exp(x)exp(y)) >>> powsimp(log(exp(x)exp(y)), deep=True) x + y Radicals with Mul bases will be combined if combine='exp' >>> from sympy import sqrt >>> x, y = symbols('x y') Two radicals are automatically joined through Mul: >>> a=sqrt(xsqrt(y)) >>> aa3 == a4 True But if an integer power of that radical has been autoexpanded then Mul does not join the resulting factors: >>> a4 # auto expands to a Mul, no longer a Pow x2y >>> _a # so Mul doesn't combine them x*2ysqrt(xsqrt(y)) >>> powsimp(_) # but powsimp will (xsqrt(y))(5/2) >>> powsimp(xya) # but won't when doing so would violate assumptions xysqrt(xsqrt(y)) """ from sympy.matrices.expressions.matexpr import MatrixSymbol def recurse(arg, *kwargs): _deep = kwargs.get('deep', deep) _combine = kwargs.get('combine', combine) _force = kwargs.get('force', force) _measure = kwargs.get('measure', measure) return powsimp(arg, _deep, _combine, _force, _measure) expr = sympify(expr) if (not isinstance(expr, Basic) or isinstance(expr, MatrixSymbol) or ( expr.is_Atom or expr in (exp_polar(0), exp_polar(1)))): return expr if deep or expr.is_Add or expr.is_Mul and _y not in expr.args: expr = expr.func([recurse(w) for w in expr.args]) if expr.is_Pow: return recurse(expr_y, deep=False)/_y if not expr.is_Mul: return expr # handle the Mul if combine in ('exp', 'all'): # Collect base/exp data, while maintaining order in the # non-commutative parts of the product c_powers = defaultdict(list) nc_part = [] newexpr = [] coeff = S.One for term in expr.args: if term.is_Rational: coeff = term continue if term.is_Pow: term = _denest_pow(term) if term.is_commutative: b, e = term.as_base_exp() if deep: b, e = [recurse(i) for i in [b, e]] if b.is_Pow or isinstance(b, exp): # don't let smthg like sqrt(xa) split into xa, 1/2 # or else it will be joined as x(a/2) later b, e = be, S.One c_powers[b].append(e) else: # This is the logic that combines exponents for equal, # but non-commutative bases: A*xAy == A(x+y). if nc_part: b1, e1 = nc_part[-1].as_base_exp() b2, e2 = term.as_base_exp() if (b1 == b2 and e1.is_commutative and e2.is_commutative): nc_part[-1] = Pow(b1, Add(e1, e2)) continue nc_part.append(term) # add up exponents of common bases for b, e in ordered(iter(c_powers.items())): # allow 2x/4 -> 2(x - 2); don't do this when b and e are # Numbers since autoevaluation will undo it, e.g. # 2(1/3)/4 -> 2(1/3 - 2) -> 2(1/3)/4 if (b and b.is_Rational and not all(ei.is_Number for ei in e) and \ coeff is not S.One and b not in (S.One, S.NegativeOne)): m = multiplicity(abs(b), abs(coeff)) if m: e.append(m) coeff /= bm c_powers[b] = Add(e) if coeff is not S.One: if coeff in c_powers: c_powers[coeff] += S.One else: c_powers[coeff] = S.One # convert to plain dictionary c_powers = dict(c_powers) # check for base and inverted base pairs be = list(c_powers.items()) skip = set() # skip if we already saw them for b, e in be: if b in skip: continue bpos = b.is_positive or b.is_polar if bpos: binv = 1/b if b != binv and binv in c_powers: if b.as_numer_denom()[0] is S.One: c_powers.pop(b) c_powers[binv] -= e else: skip.add(binv) e = c_powers.pop(binv) c_powers[b] -= e # check for base and negated base pairs be = list(c_powers.items()) _n = S.NegativeOne for b, e in be: if (b.is_Symbol or b.is_Add) and -b in c_powers and b in c_powers: if (b.is_positive is not None or e.is_integer): if e.is_integer or b.is_negative: c_powers[-b] += c_powers.pop(b) else: # (-b).is_positive so use its e e = c_powers.pop(-b) c_powers[b] += e if _n in c_powers: c_powers[_n] += e else: c_powers[_n] = e # filter c_powers and convert to a list c_powers = [(b, e) for b, e in c_powers.items() if e] # ============================================================== # check for Mul bases of Rational powers that can be combined with # separated bases, e.g. xsqrt(xy)sqrt(xsqrt(xy)) -> # (xsqrt(xy))(3/2) # ---------------- helper functions def ratq(x): '''Return Rational part of x's exponent as it appears in the bkey. ''' return bkey(x)[0][1] def bkey(b, e=None): '''Return (bs, c.q), c.p where e -> cs. If e is not given then it will be taken by using as_base_exp() on the input b. e.g. x3/2 -> (x, 2), 3 xy -> (xy, 1), 1 x(2y/3) -> (x*y, 3), 2 exp(x/2) -> (exp(a), 2), 1 ''' if e is not None: # coming from c_powers or from below if e.is_Integer: return (b, S.One), e elif e.is_Rational: return (b, Integer(e.q)), Integer(e.p) else: c, m = e.as_coeff_Mul(rational=True) if c is not S.One: if m.is_integer: return (b, Integer(c.q)), mInteger(c.p) return (bm, Integer(c.q)), Integer(c.p) else: return (be, S.One), S.One else: return bkey(b.as_base_exp()) def update(b): '''Decide what to do with base, b. If its exponent is now an integer multiple of the Rational denominator, then remove it and put the factors of its base in the common_b dictionary or update the existing bases if necessary. If it has been zeroed out, simply remove the base. ''' newe, r = divmod(common_b[b], b[1]) if not r: common_b.pop(b) if newe: for m in Mul.make_args(b[0]newe): b, e = bkey(m) if b not in common_b: common_b[b] = 0 common_b[b] += e if b[1] != 1: bases.append(b) # ---------------- end of helper functions # assemble a dictionary of the factors having a Rational power common_b = {} done = [] bases = [] for b, e in c_powers: b, e = bkey(b, e) if b in common_b: common_b[b] = common_b[b] + e else: common_b[b] = e if b[1] != 1 and b[0].is_Mul: bases.append(b) bases.sort(key=default_sort_key) # this makes tie-breaking canonical bases.sort(key=measure, reverse=True) # handle longest first for base in bases: if base not in common_b: # it may have been removed already continue b, exponent = base last = False # True when no factor of base is a radical qlcm = 1 # the lcm of the radical denominators while True: bstart = b qstart = qlcm bb = [] # list of factors ee = [] # (factor's expo. and it's current value in common_b) for bi in Mul.make_args(b): bib, bie = bkey(bi) if bib not in common_b or common_b[bib] < bie: ee = bb = [] # failed break ee.append([bie, common_b[bib]]) bb.append(bib) if ee: # find the number of integral extractions possible # e.g. [(1, 2), (2, 2)] -> min(2/1, 2/2) -> 1 min1 = ee[0][1]//ee[0][0] for i in range(1, len(ee)): rat = ee[i][1]//ee[i][0] if rat < 1: break min1 = min(min1, rat) else: # update base factor counts # e.g. if ee = [(2, 5), (3, 6)] then min1 = 2 # and the new base counts will be 5-22 and 6-23 for i in range(len(bb)): common_b[bb[i]] -= min1ee[i][0] update(bb[i]) # update the count of the base # e.g. x*2ysqrt(xsqrt(y)) the count of xsqrt(y) # will increase by 4 to give bkey (xsqrt(y), 2, 5) common_b[base] += min1qstartexponent if (last # no more radicals in base or len(common_b) == 1 # nothing left to join with or all(k[1] == 1 for k in common_b) # no rad's in common_b ): break # see what we can exponentiate base by to remove any radicals # so we know what to search for # e.g. if base were x*(1/2)y(1/3) then we should # exponentiate by 6 and look for powers of x and y in the ratio # of 2 to 3 qlcm = lcm([ratq(bi) for bi in Mul.make_args(bstart)]) if qlcm == 1: break # we are done b = bstartqlcm qlcm = qstart if all(ratq(bi) == 1 for bi in Mul.make_args(b)): last = True # we are going to be done after this next pass # this base no longer can find anything to join with and # since it was longer than any other we are done with it b, q = base done.append((b, common_b.pop(base)Rational(1, q))) # update c_powers and get ready to continue with powsimp c_powers = done # there may be terms still in common_b that were bases that were # identified as needing processing, so remove those, too for (b, q), e in common_b.items(): if (b.is_Pow or isinstance(b, exp)) and \ q is not S.One and not b.exp.is_Rational: b, be = b.as_base_exp() b = b*(be/q) else: b = root(b, q) c_powers.append((b, e)) check = len(c_powers) c_powers = dict(c_powers) assert len(c_powers) == check # there should have been no duplicates # ============================================================== # rebuild the expression newexpr = expr.func((newexpr + [Pow(b, e) for b, e in c_powers.items()])) if combine == 'exp': return expr.func(newexpr, expr.func(nc_part)) else: return recurse(expr.func(nc_part), combine='base') * \ recurse(newexpr, combine='base') elif combine == 'base': # Build c_powers and nc_part. These must both be lists not # dicts because exp's are not combined. c_powers = [] nc_part = [] for term in expr.args: if term.is_commutative: c_powers.append(list(term.as_base_exp())) else: nc_part.append(term) # Pull out numerical coefficients from exponent if assumptions allow # e.g., 2*(2x) => 4*x for i in range(len(c_powers)): b, e = c_powers[i] if not (all(x.is_nonnegative for x in b.as_numer_denom()) or e.is_integer or force or b.is_polar): continue exp_c, exp_t = e.as_coeff_Mul(rational=True) if exp_c is not S.One and exp_t is not S.One: c_powers[i] = [Pow(b, exp_c), exp_t] # Combine bases whenever they have the same exponent and # assumptions allow # first gather the potential bases under the common exponent c_exp = defaultdict(list) for b, e in c_powers: if deep: e = recurse(e) c_exp[e].append(b) del c_powers # Merge back in the results of the above to form a new product c_powers = defaultdict(list) for e in c_exp: bases = c_exp[e] # calculate the new base for e if len(bases) == 1: new_base = bases[0] elif e.is_integer or force: new_base = expr.func(bases) else: # see which ones can be joined unk = [] nonneg = [] neg = [] for bi in bases: if bi.is_negative: neg.append(bi) elif bi.is_nonnegative: nonneg.append(bi) elif bi.is_polar: nonneg.append( bi) # polar can be treated like non-negative else: unk.append(bi) if len(unk) == 1 and not neg or len(neg) == 1 and not unk: # a single neg or a single unk can join the rest nonneg.extend(unk + neg) unk = neg = [] elif neg: # their negative signs cancel in groups of 2q if we know # that e = p/q else we have to treat them as unknown israt = False if e.is_Rational: israt = True else: p, d = e.as_numer_denom() if p.is_integer and d.is_integer: israt = True if israt: neg = [-w for w in neg] unk.extend([S.NegativeOne]len(neg)) else: unk.extend(neg) neg = [] del israt # these shouldn't be joined for b in unk: c_powers[b].append(e) # here is a new joined base new_base = expr.func((nonneg + neg)) # if there are positive parts they will just get separated # again unless some change is made def _terms(e): # return the number of terms of this expression # when multiplied out -- assuming no joining of terms if e.is_Add: return sum([_terms(ai) for ai in e.args]) if e.is_Mul: return prod([_terms(mi) for mi in e.args]) return 1 xnew_base = expand_mul(new_base, deep=False) if len(Add.make_args(xnew_base)) < _terms(new_base): new_base = factor_terms(xnew_base) c_powers[new_base].append(e) # break out the powers from c_powers now c_part = [Pow(b, ei) for b, e in c_powers.items() for ei in e] # we're done return expr.func((c_part + nc_part)) else: raise ValueError("combine must be one of ('all', 'exp', 'base').") def powdenest(eq, force=False, polar=False): r""" Collect exponents on powers as assumptions allow. Explanation =========== Given ``(bbbe)e``, this can be simplified as follows: * if ``bb`` is positive, or * ``e`` is an integer, or * ``\|be\| < 1`` then this simplifies to ``bb*(bee)`` Given a product of powers raised to a power, ``(bb1*be1 bb2be2...)e``, simplification can be done as follows: - if e is positive, the gcd of all bei can be joined with e; - all non-negative bb can be separated from those that are negative and their gcd can be joined with e; autosimplification already handles this separation. - integer factors from powers that have integers in the denominator of the exponent can be removed from any term and the gcd of such integers can be joined with e Setting ``force`` to ``True`` will make symbols that are not explicitly negative behave as though they are positive, resulting in more denesting. Setting ``polar`` to ``True`` will do simplifications on the Riemann surface of the logarithm, also resulting in more denestings. When there are sums of logs in exp() then a product of powers may be obtained e.g. ``exp(3(log(a) + 2log(b)))`` - > ``a*3b6``. Examples ======== >>> from sympy.abc import a, b, x, y, z >>> from sympy import Symbol, exp, log, sqrt, symbols, powdenest >>> powdenest((x(2a/3))(3x)) (x*(2a/3))*(3x) >>> powdenest(exp(3xlog(2))) 2*(3x) Assumptions may prevent expansion: >>> powdenest(sqrt(x2)) sqrt(x2) >>> p = symbols('p', positive=True) >>> powdenest(sqrt(p2)) p No other expansion is done. >>> i, j = symbols('i,j', integer=True) >>> powdenest((xx)(i + j)) # -X-> (xx)*i(xx)j x*(x(i + j)) But exp() will be denested by moving all non-log terms outside of the function; this may result in the collapsing of the exp to a power with a different base: >>> powdenest(exp(3ylog(x))) x*(3y) >>> powdenest(exp(y(log(a) + log(b)))) (ab)*y >>> powdenest(exp(3(log(a) + log(b)))) a*3b3 If assumptions allow, symbols can also be moved to the outermost exponent: >>> i = Symbol('i', integer=True) >>> powdenest(((x(2i))(3y))x) ((x(2i))(3y))x >>> powdenest(((x(2i))(3y))x, force=True) x(6ixy) >>> powdenest(((x(2a/3))*(3y/i))x) ((x(2a/3))(3y/i))x >>> powdenest((x(2i)y*(4i))*z, force=True) (xy2)(2iz) >>> n = Symbol('n', negative=True) >>> powdenest((xi)y, force=True) x*(iy) >>> powdenest((ni)x, force=True) (ni)x """ from sympy.simplify.simplify import posify if force: eq, rep = posify(eq) return powdenest(eq, force=False).xreplace(rep) if polar: eq, rep = polarify(eq) return unpolarify(powdenest(unpolarify(eq, exponents_only=True)), rep) new = powsimp(sympify(eq)) return new.xreplace(Transform( _denest_pow, filter=lambda m: m.is_Pow or isinstance(m, exp))) _y = Dummy('y') def _denest_pow(eq): """ Denest powers. This is a helper function for powdenest that performs the actual transformation. """ from sympy.simplify.simplify import logcombine b, e = eq.as_base_exp() if b.is_Pow or isinstance(b.func, exp) and e != 1: new = b._eval_power(e) if new is not None: eq = new b, e = new.as_base_exp() # denest exp with log terms in exponent if b is S.Exp1 and e.is_Mul: logs = [] other = [] for ei in e.args: if any(isinstance(ai, log) for ai in Add.make_args(ei)): logs.append(ei) else: other.append(ei) logs = logcombine(Mul(logs)) return Pow(exp(logs), Mul(other)) _, be = b.as_base_exp() if be is S.One and not (b.is_Mul or b.is_Rational and b.q != 1 or b.is_positive): return eq # denest eq which is either pose or Powe or Mule or # Mul(b1e1, b2*e2) # handle polar numbers specially polars, nonpolars = [], [] for bb in Mul.make_args(b): if bb.is_polar: polars.append(bb.as_base_exp()) else: nonpolars.append(bb) if len(polars) == 1 and not polars[0][0].is_Mul: return Pow(polars[0][0], polars[0][1]e)powdenest(Mul(nonpolars)*e) elif polars: return Mul([powdenest(bb*(eee)) for (bb, ee) in polars]) \ powdenest(Mul(nonpolars)*e) if b.is_Integer: # use log to see if there is a power here logb = expand_log(log(b)) if logb.is_Mul: c, logb = logb.args e = c base = logb.args[0] return Pow(base, e) # if b is not a Mul or any factor is an atom then there is nothing to do if not b.is_Mul or any(s.is_Atom for s in Mul.make_args(b)): return eq # let log handle the case of the base of the argument being a Mul, e.g. # sqrt(x*(2i)y(6i)) -> x*iy(3i) if x and y are positive; we # will take the log, expand it, and then factor out the common powers that # now appear as coefficient. We do this manually since terms_gcd pulls out # fractions, terms_gcd(x+xy/2) -> x(y + 2)/2 and we don't want the 1/2; # gcd won't pull out numerators from a fraction: gcd(3x, 9x/2) -> x but # we want 3x. Neither work with noncommutatives. def nc_gcd(aa, bb): a, b = [i.as_coeff_Mul() for i in [aa, bb]] c = gcd(a[0], b[0]).as_numer_denom()[0] g = Mul((a[1].args_cnc(cset=True)[0] & b[1].args_cnc(cset=True)[0])) return _keep_coeff(c, g) glogb = expand_log(log(b)) if glogb.is_Add: args = glogb.args g = reduce(nc_gcd, args) if g != 1: cg, rg = g.as_coeff_Mul() glogb = _keep_coeff(cg, rgAdd([a/g for a in args])) # now put the log back together again if isinstance(glogb, log) or not glogb.is_Mul: if glogb.args[0].is_Pow or isinstance(glogb.args[0], exp): glogb = _denest_pow(glogb.args[0]) if (abs(glogb.exp) < 1) == True: return Pow(glogb.base, glogb.expe) return eq # the log(b) was a Mul so join any adds with logcombine add = [] other = [] for a in glogb.args: if a.is_Add: add.append(a) else: other.append(a) return Pow(exp(logcombine(Mul(add))), eMul(other))
0bf150af2b5a340b38eeeac388b9b62ce263c692768c3b697e04659a984923ce	from sympy.core import Function, S, Mul, Pow, Add from sympy.core.compatibility import ordered, default_sort_key from sympy.core.function import count_ops, expand_func from sympy.functions.combinatorial.factorials import binomial from sympy.functions import gamma, sqrt, sin from sympy.polys import factor, cancel from sympy.utilities.iterables import sift, uniq def gammasimp(expr): r""" Simplify expressions with gamma functions. Explanation =========== This function takes as input an expression containing gamma functions or functions that can be rewritten in terms of gamma functions and tries to minimize the number of those functions and reduce the size of their arguments. The algorithm works by rewriting all gamma functions as expressions involving rising factorials (Pochhammer symbols) and applies recurrence relations and other transformations applicable to rising factorials, to reduce their arguments, possibly letting the resulting rising factorial to cancel. Rising factorials with the second argument being an integer are expanded into polynomial forms and finally all other rising factorial are rewritten in terms of gamma functions. Then the following two steps are performed. 1. Reduce the number of gammas by applying the reflection theorem gamma(x)gamma(1-x) == pi/sin(pix). 2. Reduce the number of gammas by applying the multiplication theorem gamma(x)gamma(x+1/n)...gamma(x+(n-1)/n) == Cgamma(nx). It then reduces the number of prefactors by absorbing them into gammas where possible and expands gammas with rational argument. All transformation rules can be found (or was derived from) here: .. [1] http://functions.wolfram.com/GammaBetaErf/Pochhammer/17/01/02/ .. [2] http://functions.wolfram.com/GammaBetaErf/Pochhammer/27/01/0005/ Examples ======== >>> from sympy.simplify import gammasimp >>> from sympy import gamma, Symbol >>> from sympy.abc import x >>> n = Symbol('n', integer = True) >>> gammasimp(gamma(x)/gamma(x - 3)) (x - 3)(x - 2)(x - 1) >>> gammasimp(gamma(n + 3)) gamma(n + 3) """ expr = expr.rewrite(gamma) return _gammasimp(expr, as_comb = False) def _gammasimp(expr, as_comb): """ Helper function for gammasimp and combsimp. Explanation =========== Simplifies expressions written in terms of gamma function. If as_comb is True, it tries to preserve integer arguments. See docstring of gammasimp for more information. This was part of combsimp() in combsimp.py. """ expr = expr.replace(gamma, lambda n: _rf(1, (n - 1).expand())) if as_comb: expr = expr.replace(_rf, lambda a, b: gamma(b + 1)) else: expr = expr.replace(_rf, lambda a, b: gamma(a + b)/gamma(a)) def rule(n, k): coeff, rewrite = S.One, False cn, _n = n.as_coeff_Add() if _n and cn.is_Integer and cn: coeff = _rf(_n + 1, cn)/_rf(_n - k + 1, cn) rewrite = True n = _n # this sort of binomial has already been removed by # rising factorials but is left here in case the order # of rule application is changed if k.is_Add: ck, _k = k.as_coeff_Add() if _k and ck.is_Integer and ck: coeff = _rf(n - ck - _k + 1, ck)/_rf(_k + 1, ck) rewrite = True k = _k if count_ops(k) > count_ops(n - k): rewrite = True k = n - k if rewrite: return coeffbinomial(n, k) expr = expr.replace(binomial, rule) def rule_gamma(expr, level=0): """ Simplify products of gamma functions further. """ if expr.is_Atom: return expr def gamma_rat(x): # helper to simplify ratios of gammas was = x.count(gamma) xx = x.replace(gamma, lambda n: _rf(1, (n - 1).expand() ).replace(_rf, lambda a, b: gamma(a + b)/gamma(a))) if xx.count(gamma) < was: x = xx return x def gamma_factor(x): # return True if there is a gamma factor in shallow args if isinstance(x, gamma): return True if x.is_Add or x.is_Mul: return any(gamma_factor(xi) for xi in x.args) if x.is_Pow and (x.exp.is_integer or x.base.is_positive): return gamma_factor(x.base) return False # recursion step if level == 0: expr = expr.func([rule_gamma(x, level + 1) for x in expr.args]) level += 1 if not expr.is_Mul: return expr # non-commutative step if level == 1: args, nc = expr.args_cnc() if not args: return expr if nc: return rule_gamma(Mul._from_args(args), level + 1)Mul._from_args(nc) level += 1 # pure gamma handling, not factor absorption if level == 2: T, F = sift(expr.args, gamma_factor, binary=True) gamma_ind = Mul(F) d = Mul(T) nd, dd = d.as_numer_denom() for ipass in range(2): args = list(ordered(Mul.make_args(nd))) for i, ni in enumerate(args): if ni.is_Add: ni, dd = Add([ rule_gamma(gamma_rat(a/dd), level + 1) for a in ni.args] ).as_numer_denom() args[i] = ni if not dd.has(gamma): break nd = Mul(args) if ipass == 0 and not gamma_factor(nd): break nd, dd = dd, nd # now process in reversed order expr = gamma_indnd/dd if not (expr.is_Mul and (gamma_factor(dd) or gamma_factor(nd))): return expr level += 1 # iteration until constant if level == 3: while True: was = expr expr = rule_gamma(expr, 4) if expr == was: return expr numer_gammas = [] denom_gammas = [] numer_others = [] denom_others = [] def explicate(p): if p is S.One: return None, [] b, e = p.as_base_exp() if e.is_Integer: if isinstance(b, gamma): return True, [b.args[0]]e else: return False, [b]e else: return False, [p] newargs = list(ordered(expr.args)) while newargs: n, d = newargs.pop().as_numer_denom() isg, l = explicate(n) if isg: numer_gammas.extend(l) elif isg is False: numer_others.extend(l) isg, l = explicate(d) if isg: denom_gammas.extend(l) elif isg is False: denom_others.extend(l) # =========== level 2 work: pure gamma manipulation ========= if not as_comb: # Try to reduce the number of gamma factors by applying the # reflection formula gamma(x)gamma(1-x) = pi/sin(pix) for gammas, numer, denom in [( numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: new = [] while gammas: g1 = gammas.pop() if g1.is_integer: new.append(g1) continue for i, g2 in enumerate(gammas): n = g1 + g2 - 1 if not n.is_Integer: continue numer.append(S.Pi) denom.append(sin(S.Pig1)) gammas.pop(i) if n > 0: for k in range(n): numer.append(1 - g1 + k) elif n < 0: for k in range(-n): denom.append(-g1 - k) break else: new.append(g1) # /!\ updating IN PLACE gammas[:] = new # Try to reduce the number of gammas by using the duplication # theorem to cancel an upper and lower: gamma(2s)/gamma(s) = # 2(2s + 1)/(4sqrt(pi))gamma(s + 1/2). Although this could # be done with higher argument ratios like gamma(3x)/gamma(x), # this would not reduce the number of gammas as in this case. for ng, dg, no, do in [(numer_gammas, denom_gammas, numer_others, denom_others), (denom_gammas, numer_gammas, denom_others, numer_others)]: while True: for x in ng: for y in dg: n = x - 2y if n.is_Integer: break else: continue break else: break ng.remove(x) dg.remove(y) if n > 0: for k in range(n): no.append(2y + k) elif n < 0: for k in range(-n): do.append(2y - 1 - k) ng.append(y + S.Half) no.append(2*(2y - 1)) do.append(sqrt(S.Pi)) # Try to reduce the number of gamma factors by applying the # multiplication theorem (used when n gammas with args differing # by 1/n mod 1 are encountered). # # run of 2 with args differing by 1/2 # # >>> gammasimp(gamma(x)gamma(x+S.Half)) # 2sqrt(2)2(-2x - 1/2)sqrt(pi)gamma(2x) # # run of 3 args differing by 1/3 (mod 1) # # >>> gammasimp(gamma(x)gamma(x+S(1)/3)gamma(x+S(2)/3)) # 63*(-3x - 1/2)pigamma(3x) # >>> gammasimp(gamma(x)gamma(x+S(1)/3)gamma(x+S(5)/3)) # 23*(-3x - 1/2)pi(3x + 2)gamma(3x) # def _run(coeffs): # find runs in coeffs such that the difference in terms (mod 1) # of t1, t2, ..., tn is 1/n u = list(uniq(coeffs)) for i in range(len(u)): dj = ([((u[j] - u[i]) % 1, j) for j in range(i + 1, len(u))]) for one, j in dj: if one.p == 1 and one.q != 1: n = one.q got = [i] get = list(range(1, n)) for d, j in dj: m = nd if m.is_Integer and m in get: get.remove(m) got.append(j) if not get: break else: continue for i, j in enumerate(got): c = u[j] coeffs.remove(c) got[i] = c return one.q, got[0], got[1:] def _mult_thm(gammas, numer, denom): # pull off and analyze the leading coefficient from each gamma arg # looking for runs in those Rationals # expr -> coeff + resid -> rats[resid] = coeff rats = {} for g in gammas: c, resid = g.as_coeff_Add() rats.setdefault(resid, []).append(c) # look for runs in Rationals for each resid keys = sorted(rats, key=default_sort_key) for resid in keys: coeffs = list(sorted(rats[resid])) new = [] while True: run = _run(coeffs) if run is None: break # process the sequence that was found: # 1) convert all the gamma functions to have the right # argument (could be off by an integer) # 2) append the factors corresponding to the theorem # 3) append the new gamma function n, ui, other = run # (1) for u in other: con = resid + u - 1 for k in range(int(u - ui)): numer.append(con - k) con = n(resid + ui) # for (2) and (3) # (2) numer.append((2S.Pi)*(S(n - 1)/2) n*(S.Half - con)) # (3) new.append(con) # restore resid to coeffs rats[resid] = [resid + c for c in coeffs] + new # rebuild the gamma arguments g = [] for resid in keys: g += rats[resid] # /!\ updating IN PLACE gammas[:] = g for l, numer, denom in [(numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: _mult_thm(l, numer, denom) # =========== level >= 2 work: factor absorption ========= if level >= 2: # Try to absorb factors into the gammas: xgamma(x) -> gamma(x + 1) # and gamma(x)/(x - 1) -> gamma(x - 1) # This code (in particular repeated calls to find_fuzzy) can be very # slow. def find_fuzzy(l, x): if not l: return S1, T1 = compute_ST(x) for y in l: S2, T2 = inv[y] if T1 != T2 or (not S1.intersection(S2) and (S1 != set() or S2 != set())): continue # XXX we want some simplification (e.g. cancel or # simplify) but no matter what it's slow. a = len(cancel(x/y).free_symbols) b = len(x.free_symbols) c = len(y.free_symbols) # TODO is there a better heuristic? if a == 0 and (b > 0 or c > 0): return y # We thus try to avoid expensive calls by building the following # "invariants": For every factor or gamma function argument # - the set of free symbols S # - the set of functional components T # We will only try to absorb if T1==T2 and (S1 intersect S2 != emptyset # or S1 == S2 == emptyset) inv = {} def compute_ST(expr): if expr in inv: return inv[expr] return (expr.free_symbols, expr.atoms(Function).union( {e.exp for e in expr.atoms(Pow)})) def update_ST(expr): inv[expr] = compute_ST(expr) for expr in numer_gammas + denom_gammas + numer_others + denom_others: update_ST(expr) for gammas, numer, denom in [( numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: new = [] while gammas: g = gammas.pop() cont = True while cont: cont = False y = find_fuzzy(numer, g) if y is not None: numer.remove(y) if y != g: numer.append(y/g) update_ST(y/g) g += 1 cont = True y = find_fuzzy(denom, g - 1) if y is not None: denom.remove(y) if y != g - 1: numer.append((g - 1)/y) update_ST((g - 1)/y) g -= 1 cont = True new.append(g) # /!\ updating IN PLACE gammas[:] = new # =========== rebuild expr ================================== return Mul([gamma(g) for g in numer_gammas]) \ / Mul([gamma(g) for g in denom_gammas]) \ * Mul(numer_others) / Mul(denom_others) # (for some reason we cannot use Basic.replace in this case) was = factor(expr) expr = rule_gamma(was) if expr != was: expr = factor(expr) expr = expr.replace(gamma, lambda n: expand_func(gamma(n)) if n.is_Rational else gamma(n)) return expr class _rf(Function): @classmethod def eval(cls, a, b): if b.is_Integer: if not b: return S.One n, result = int(b), S.One if n > 0: for i in range(n): result = a + i return result elif n < 0: for i in range(1, -n + 1): result = a - i return 1/result else: if b.is_Add: c, _b = b.as_coeff_Add() if c.is_Integer: if c > 0: return _rf(a, _b)_rf(a + _b, c) elif c < 0: return _rf(a, _b)/_rf(a + _b + c, -c) if a.is_Add: c, _a = a.as_coeff_Add() if c.is_Integer: if c > 0: return _rf(_a, b)_rf(_a + b, c)/_rf(_a, c) elif c < 0: return _rf(_a, b)*_rf(_a + c, -c)/_rf(_a + b + c, -c)
e381b806646ed3ea8fd1280303b457cfb59c29dfc4986c44aaab050d544235dd	from collections import defaultdict from sympy.core import (sympify, Basic, S, Expr, expand_mul, factor_terms, Mul, Dummy, igcd, FunctionClass, Add, symbols, Wild, expand) from sympy.core.cache import cacheit from sympy.core.compatibility import reduce, iterable, SYMPY_INTS from sympy.core.function import count_ops, _mexpand from sympy.core.numbers import I, Integer from sympy.functions import sin, cos, exp, cosh, tanh, sinh, tan, cot, coth from sympy.functions.elementary.hyperbolic import HyperbolicFunction from sympy.functions.elementary.trigonometric import TrigonometricFunction from sympy.polys import Poly, factor, cancel, parallel_poly_from_expr from sympy.polys.domains import ZZ from sympy.polys.polyerrors import PolificationFailed from sympy.polys.polytools import groebner from sympy.simplify.cse_main import cse from sympy.strategies.core import identity from sympy.strategies.tree import greedy from sympy.utilities.misc import debug def trigsimp_groebner(expr, hints=[], quick=False, order="grlex", polynomial=False): """ Simplify trigonometric expressions using a groebner basis algorithm. Explanation =========== This routine takes a fraction involving trigonometric or hyperbolic expressions, and tries to simplify it. The primary metric is the total degree. Some attempts are made to choose the simplest possible expression of the minimal degree, but this is non-rigorous, and also very slow (see the ``quick=True`` option). If ``polynomial`` is set to True, instead of simplifying numerator and denominator together, this function just brings numerator and denominator into a canonical form. This is much faster, but has potentially worse results. However, if the input is a polynomial, then the result is guaranteed to be an equivalent polynomial of minimal degree. The most important option is hints. Its entries can be any of the following: - a natural number - a function - an iterable of the form (func, var1, var2, ...) - anything else, interpreted as a generator A number is used to indicate that the search space should be increased. A function is used to indicate that said function is likely to occur in a simplified expression. An iterable is used indicate that func(var1 + var2 + ...) is likely to occur in a simplified . An additional generator also indicates that it is likely to occur. (See examples below). This routine carries out various computationally intensive algorithms. The option ``quick=True`` can be used to suppress one particularly slow step (at the expense of potentially more complicated results, but never at the expense of increased total degree). Examples ======== >>> from sympy.abc import x, y >>> from sympy import sin, tan, cos, sinh, cosh, tanh >>> from sympy.simplify.trigsimp import trigsimp_groebner Suppose you want to simplify ``sin(x)cos(x)``. Naively, nothing happens: >>> ex = sin(x)cos(x) >>> trigsimp_groebner(ex) sin(x)cos(x) This is because ``trigsimp_groebner`` only looks for a simplification involving just ``sin(x)`` and ``cos(x)``. You can tell it to also try ``2x`` by passing ``hints=[2]``: >>> trigsimp_groebner(ex, hints=[2]) sin(2x)/2 >>> trigsimp_groebner(sin(x)2 - cos(x)2, hints=[2]) -cos(2x) Increasing the search space this way can quickly become expensive. A much faster way is to give a specific expression that is likely to occur: >>> trigsimp_groebner(ex, hints=[sin(2x)]) sin(2x)/2 Hyperbolic expressions are similarly supported: >>> trigsimp_groebner(sinh(2x)/sinh(x)) 2cosh(x) Note how no hints had to be passed, since the expression already involved ``2x``. The tangent function is also supported. You can either pass ``tan`` in the hints, to indicate that tan should be tried whenever cosine or sine are, or you can pass a specific generator: >>> trigsimp_groebner(sin(x)/cos(x), hints=[tan]) tan(x) >>> trigsimp_groebner(sinh(x)/cosh(x), hints=[tanh(x)]) tanh(x) Finally, you can use the iterable form to suggest that angle sum formulae should be tried: >>> ex = (tan(x) + tan(y))/(1 - tan(x)tan(y)) >>> trigsimp_groebner(ex, hints=[(tan, x, y)]) tan(x + y) """ # TODO # - preprocess by replacing everything by funcs we can handle # - optionally use cot instead of tan # - more intelligent hinting. # For example, if the ideal is small, and we have sin(x), sin(y), # add sin(x + y) automatically... ? # - algebraic numbers ... # - expressions of lowest degree are not distinguished properly # e.g. 1 - sin(x)*2 # - we could try to order the generators intelligently, so as to influence # which monomials appear in the quotient basis # THEORY # ------ # Ratsimpmodprime above can be used to "simplify" a rational function # modulo a prime ideal. "Simplify" mainly means finding an equivalent # expression of lower total degree. # # We intend to use this to simplify trigonometric functions. To do that, # we need to decide (a) which ring to use, and (b) modulo which ideal to # simplify. In practice, (a) means settling on a list of "generators" # a, b, c, ..., such that the fraction we want to simplify is a rational # function in a, b, c, ..., with coefficients in ZZ (integers). # (2) means that we have to decide what relations to impose on the # generators. There are two practical problems: # (1) The ideal has to be prime* (a technical term). # (2) The relations have to be polynomials in the generators. # # We typically have two kinds of generators: # - trigonometric expressions, like sin(x), cos(5x), etc # - "everything else", like gamma(x), pi, etc. # # Since this function is trigsimp, we will concentrate on what to do with # trigonometric expressions. We can also simplify hyperbolic expressions, # but the extensions should be clear. # # One crucial point is that all other* generators really should behave # like indeterminates. In particular if (say) "I" is one of them, then # in fact I2 + 1 = 0 and we may and will compute non-sensical # expressions. However, we can work with a dummy and add the relation # I2 + 1 = 0 to our ideal, then substitute back in the end. # # Now regarding trigonometric generators. We split them into groups, # according to the argument of the trigonometric functions. We want to # organise this in such a way that most trigonometric identities apply in # the same group. For example, given sin(x), cos(2x) and cos(y), we would # group as [sin(x), cos(2x)] and [cos(y)]. # # Our prime ideal will be built in three steps: # (1) For each group, compute a "geometrically prime" ideal of relations. # Geometrically prime means that it generates a prime ideal in # CC[gens], not just ZZ[gens]. # (2) Take the union of all the generators of the ideals for all groups. # By the geometric primality condition, this is still prime. # (3) Add further inter-group relations which preserve primality. # # Step (1) works as follows. We will isolate common factors in the # argument, so that all our generators are of the form sin(nx), cos(nx) # or tan(nx), with n an integer. Suppose first there are no tan terms. # The ideal [sin(x)2 + cos(x)2 - 1] is geometrically prime, since # X2 + Y2 - 1 is irreducible over CC. # Now, if we have a generator sin(nx), than we can, using trig identities, # express sin(nx) as a polynomial in sin(x) and cos(x). We can add this # relation to the ideal, preserving geometric primality, since the quotient # ring is unchanged. # Thus we have treated all sin and cos terms. # For tan(nx), we add a relation tan(nx)cos(nx) - sin(nx) = 0. # (This requires of course that we already have relations for cos(nx) and # sin(nx).) It is not obvious, but it seems that this preserves geometric # primality. # XXX A real proof would be nice. HELP! # Sketch that <S2 + C2 - 1, CT - S> is a prime ideal of # CC[S, C, T]: # - it suffices to show that the projective closure in CP3 is # irreducible # - using the half-angle substitutions, we can express sin(x), tan(x), # cos(x) as rational functions in tan(x/2) # - from this, we get a rational map from CP1 to our curve # - this is a morphism, hence the curve is prime # # Step (2) is trivial. # # Step (3) works by adding selected relations of the form # sin(x + y) - sin(x)cos(y) - sin(y)cos(x), etc. Geometric primality is # preserved by the same argument as before. def parse_hints(hints): """Split hints into (n, funcs, iterables, gens).""" n = 1 funcs, iterables, gens = [], [], [] for e in hints: if isinstance(e, (SYMPY_INTS, Integer)): n = e elif isinstance(e, FunctionClass): funcs.append(e) elif iterable(e): iterables.append((e[0], e[1:])) # XXX sin(x+2y)? # Note: we go through polys so e.g. # sin(-x) -> -sin(x) -> sin(x) gens.extend(parallel_poly_from_expr( [e[0](x) for x in e[1:]] + [e[0](Add(e[1:]))])[1].gens) else: gens.append(e) return n, funcs, iterables, gens def build_ideal(x, terms): """ Build generators for our ideal. ``Terms`` is an iterable with elements of the form (fn, coeff), indicating that we have a generator fn(coeffx). If any of the terms is trigonometric, sin(x) and cos(x) are guaranteed to appear in terms. Similarly for hyperbolic functions. For tan(nx), sin(nx) and cos(nx) are guaranteed. """ I = [] y = Dummy('y') for fn, coeff in terms: for c, s, t, rel in ( [cos, sin, tan, cos(x)2 + sin(x)2 - 1], [cosh, sinh, tanh, cosh(x)2 - sinh(x)2 - 1]): if coeff == 1 and fn in [c, s]: I.append(rel) elif fn == t: I.append(t(coeffx)c(coeffx) - s(coeffx)) elif fn in [c, s]: cn = fn(coeffy).expand(trig=True).subs(y, x) I.append(fn(coeffx) - cn) return list(set(I)) def analyse_gens(gens, hints): """ Analyse the generators ``gens``, using the hints ``hints``. The meaning of ``hints`` is described in the main docstring. Return a new list of generators, and also the ideal we should work with. """ # First parse the hints n, funcs, iterables, extragens = parse_hints(hints) debug('n=%s' % n, 'funcs:', funcs, 'iterables:', iterables, 'extragens:', extragens) # We just add the extragens to gens and analyse them as before gens = list(gens) gens.extend(extragens) # remove duplicates funcs = list(set(funcs)) iterables = list(set(iterables)) gens = list(set(gens)) # all the functions we can do anything with allfuncs = {sin, cos, tan, sinh, cosh, tanh} # sin(3x) -> ((3, x), sin) trigterms = [(g.args[0].as_coeff_mul(), g.func) for g in gens if g.func in allfuncs] # Our list of new generators - start with anything that we cannot # work with (i.e. is not a trigonometric term) freegens = [g for g in gens if g.func not in allfuncs] newgens = [] trigdict = {} for (coeff, var), fn in trigterms: trigdict.setdefault(var, []).append((coeff, fn)) res = [] # the ideal for key, val in trigdict.items(): # We have now assembeled a dictionary. Its keys are common # arguments in trigonometric expressions, and values are lists of # pairs (fn, coeff). x0, (fn, coeff) in trigdict means that we # need to deal with fn(coeffx0). We take the rational gcd of the # coeffs, call it ``gcd``. We then use x = x0/gcd as "base symbol", # all other arguments are integral multiples thereof. # We will build an ideal which works with sin(x), cos(x). # If hint tan is provided, also work with tan(x). Moreover, if # n > 1, also work with sin(kx) for k <= n, and similarly for cos # (and tan if the hint is provided). Finally, any generators which # the ideal does not work with but we need to accommodate (either # because it was in expr or because it was provided as a hint) # we also build into the ideal. # This selection process is expressed in the list ``terms``. # build_ideal then generates the actual relations in our ideal, # from this list. fns = [x[1] for x in val] val = [x[0] for x in val] gcd = reduce(igcd, val) terms = [(fn, v/gcd) for (fn, v) in zip(fns, val)] fs = set(funcs + fns) for c, s, t in ([cos, sin, tan], [cosh, sinh, tanh]): if any(x in fs for x in (c, s, t)): fs.add(c) fs.add(s) for fn in fs: for k in range(1, n + 1): terms.append((fn, k)) extra = [] for fn, v in terms: if fn == tan: extra.append((sin, v)) extra.append((cos, v)) if fn in [sin, cos] and tan in fs: extra.append((tan, v)) if fn == tanh: extra.append((sinh, v)) extra.append((cosh, v)) if fn in [sinh, cosh] and tanh in fs: extra.append((tanh, v)) terms.extend(extra) x = gcdMul(key) r = build_ideal(x, terms) res.extend(r) newgens.extend({fn(vx) for fn, v in terms}) # Add generators for compound expressions from iterables for fn, args in iterables: if fn == tan: # Tan expressions are recovered from sin and cos. iterables.extend([(sin, args), (cos, args)]) elif fn == tanh: # Tanh expressions are recovered from sihn and cosh. iterables.extend([(sinh, args), (cosh, args)]) else: dummys = symbols('d:%i' % len(args), cls=Dummy) expr = fn( Add(dummys)).expand(trig=True).subs(list(zip(dummys, args))) res.append(fn(Add(args)) - expr) if myI in gens: res.append(myI*2 + 1) freegens.remove(myI) newgens.append(myI) return res, freegens, newgens myI = Dummy('I') expr = expr.subs(S.ImaginaryUnit, myI) subs = [(myI, S.ImaginaryUnit)] num, denom = cancel(expr).as_numer_denom() try: (pnum, pdenom), opt = parallel_poly_from_expr([num, denom]) except PolificationFailed: return expr debug('initial gens:', opt.gens) ideal, freegens, gens = analyse_gens(opt.gens, hints) debug('ideal:', ideal) debug('new gens:', gens, " -- len", len(gens)) debug('free gens:', freegens, " -- len", len(gens)) # NOTE we force the domain to be ZZ to stop polys from injecting generators # (which is usually a sign of a bug in the way we build the ideal) if not gens: return expr G = groebner(ideal, order=order, gens=gens, domain=ZZ) debug('groebner basis:', list(G), " -- len", len(G)) # If our fraction is a polynomial in the free generators, simplify all # coefficients separately: from sympy.simplify.ratsimp import ratsimpmodprime if freegens and pdenom.has_only_gens(set(gens).intersection(pdenom.gens)): num = Poly(num, gens=gens+freegens).eject(gens) res = [] for monom, coeff in num.terms(): ourgens = set(parallel_poly_from_expr([coeff, denom])[1].gens) # We compute the transitive closure of all generators that can # be reached from our generators through relations in the ideal. changed = True while changed: changed = False for p in ideal: p = Poly(p) if not ourgens.issuperset(p.gens) and \ not p.has_only_gens(set(p.gens).difference(ourgens)): changed = True ourgens.update(p.exclude().gens) # NOTE preserve order! realgens = [x for x in gens if x in ourgens] # The generators of the ideal have now been (implicitly) split # into two groups: those involving ourgens and those that don't. # Since we took the transitive closure above, these two groups # live in subgrings generated by a disjoint set of variables. # Any sensible groebner basis algorithm will preserve this disjoint # structure (i.e. the elements of the groebner basis can be split # similarly), and and the two subsets of the groebner basis then # form groebner bases by themselves. (For the smaller generating # sets, of course.) ourG = [g.as_expr() for g in G.polys if g.has_only_gens(ourgens.intersection(g.gens))] res.append(Mul([a*b for a, b in zip(freegens, monom)]) \ ratsimpmodprime(coeff/denom, ourG, order=order, gens=realgens, quick=quick, domain=ZZ, polynomial=polynomial).subs(subs)) return Add(res) # NOTE The following is simpler and has less assumptions on the # groebner basis algorithm. If the above turns out to be broken, # use this. return Add([Mul([ab for a, b in zip(freegens, monom)]) \ ratsimpmodprime(coeff/denom, list(G), order=order, gens=gens, quick=quick, domain=ZZ) for monom, coeff in num.terms()]) else: return ratsimpmodprime( expr, list(G), order=order, gens=freegens+gens, quick=quick, domain=ZZ, polynomial=polynomial).subs(subs) _trigs = (TrigonometricFunction, HyperbolicFunction) def trigsimp(expr, *opts): """ reduces expression by using known trig identities Explanation =========== method: - Determine the method to use. Valid choices are 'matching' (default), 'groebner', 'combined', and 'fu'. If 'matching', simplify the expression recursively by targeting common patterns. If 'groebner', apply an experimental groebner basis algorithm. In this case further options are forwarded to ``trigsimp_groebner``, please refer to its docstring. If 'combined', first run the groebner basis algorithm with small default parameters, then run the 'matching' algorithm. 'fu' runs the collection of trigonometric transformations described by Fu, et al. (see the `fu` docstring). Examples ======== >>> from sympy import trigsimp, sin, cos, log >>> from sympy.abc import x >>> e = 2sin(x)*2 + 2cos(x)*2 >>> trigsimp(e) 2 Simplification occurs wherever trigonometric functions are located. >>> trigsimp(log(e)) log(2) Using `method="groebner"` (or `"combined"`) might lead to greater simplification. The old trigsimp routine can be accessed as with method 'old'. >>> from sympy import coth, tanh >>> t = 3tanh(x)7 - 2/coth(x)7 >>> trigsimp(t, method='old') == t True >>> trigsimp(t) tanh(x)7 """ from sympy.simplify.fu import fu expr = sympify(expr) _eval_trigsimp = getattr(expr, '_eval_trigsimp', None) if _eval_trigsimp is not None: return _eval_trigsimp(opts) old = opts.pop('old', False) if not old: opts.pop('deep', None) opts.pop('recursive', None) method = opts.pop('method', 'matching') else: method = 'old' def groebnersimp(ex, opts): def traverse(e): if e.is_Atom: return e args = [traverse(x) for x in e.args] if e.is_Function or e.is_Pow: args = [trigsimp_groebner(x, opts) for x in args] return e.func(args) new = traverse(ex) if not isinstance(new, Expr): return new return trigsimp_groebner(new, opts) trigsimpfunc = { 'fu': (lambda x: fu(x, opts)), 'matching': (lambda x: futrig(x)), 'groebner': (lambda x: groebnersimp(x, opts)), 'combined': (lambda x: futrig(groebnersimp(x, polynomial=True, hints=[2, tan]))), 'old': lambda x: trigsimp_old(x, opts), }[method] return trigsimpfunc(expr) def exptrigsimp(expr): """ Simplifies exponential / trigonometric / hyperbolic functions. Examples ======== >>> from sympy import exptrigsimp, exp, cosh, sinh >>> from sympy.abc import z >>> exptrigsimp(exp(z) + exp(-z)) 2cosh(z) >>> exptrigsimp(cosh(z) - sinh(z)) exp(-z) """ from sympy.simplify.fu import hyper_as_trig, TR2i from sympy.simplify.simplify import bottom_up def exp_trig(e): # select the better of e, and e rewritten in terms of exp or trig # functions choices = [e] if e.has(_trigs): choices.append(e.rewrite(exp)) choices.append(e.rewrite(cos)) return min(choices, key=count_ops) newexpr = bottom_up(expr, exp_trig) def f(rv): if not rv.is_Mul: return rv commutative_part, noncommutative_part = rv.args_cnc() # Since as_powers_dict loses order information, # if there is more than one noncommutative factor, # it should only be used to simplify the commutative part. if (len(noncommutative_part) > 1): return f(Mul(commutative_part))Mul(noncommutative_part) rvd = rv.as_powers_dict() newd = rvd.copy() def signlog(expr, sign=1): if expr is S.Exp1: return sign, 1 elif isinstance(expr, exp): return sign, expr.args[0] elif sign == 1: return signlog(-expr, sign=-1) else: return None, None ee = rvd[S.Exp1] for k in rvd: if k.is_Add and len(k.args) == 2: # k == c(1 + signEx) c = k.args[0] sign, x = signlog(k.args[1]/c) if not x: continue m = rvd[k] newd[k] -= m if ee == -xm/2: # sinh and cosh newd[S.Exp1] -= ee ee = 0 if sign == 1: newd[2ccosh(x/2)] += m else: newd[-2csinh(x/2)] += m elif newd[1 - signS.Exp1x] == -m: # tanh del newd[1 - signS.Exp1*x] if sign == 1: newd[-c/tanh(x/2)] += m else: newd[-ctanh(x/2)] += m else: newd[1 + signS.Exp1x] += m newd[c] += m return Mul([k*newd[k] for k in newd]) newexpr = bottom_up(newexpr, f) # sin/cos and sinh/cosh ratios to tan and tanh, respectively if newexpr.has(HyperbolicFunction): e, f = hyper_as_trig(newexpr) newexpr = f(TR2i(e)) if newexpr.has(TrigonometricFunction): newexpr = TR2i(newexpr) # can we ever generate an I where there was none previously? if not (newexpr.has(I) and not expr.has(I)): expr = newexpr return expr #-------------------- the old trigsimp routines --------------------- def trigsimp_old(expr, , first=True, *opts): """ Reduces expression by using known trig identities. Notes ===== deep: - Apply trigsimp inside all objects with arguments recursive: - Use common subexpression elimination (cse()) and apply trigsimp recursively (this is quite expensive if the expression is large) method: - Determine the method to use. Valid choices are 'matching' (default), 'groebner', 'combined', 'fu' and 'futrig'. If 'matching', simplify the expression recursively by pattern matching. If 'groebner', apply an experimental groebner basis algorithm. In this case further options are forwarded to ``trigsimp_groebner``, please refer to its docstring. If 'combined', first run the groebner basis algorithm with small default parameters, then run the 'matching' algorithm. 'fu' runs the collection of trigonometric transformations described by Fu, et al. (see the `fu` docstring) while `futrig` runs a subset of Fu-transforms that mimic the behavior of `trigsimp`. compare: - show input and output from `trigsimp` and `futrig` when different, but returns the `trigsimp` value. Examples ======== >>> from sympy import trigsimp, sin, cos, log, cot >>> from sympy.abc import x >>> e = 2sin(x)*2 + 2cos(x)*2 >>> trigsimp(e, old=True) 2 >>> trigsimp(log(e), old=True) log(2sin(x)*2 + 2cos(x)2) >>> trigsimp(log(e), deep=True, old=True) log(2) Using `method="groebner"` (or `"combined"`) can sometimes lead to a lot more simplification: >>> e = (-sin(x) + 1)/cos(x) + cos(x)/(-sin(x) + 1) >>> trigsimp(e, old=True) (1 - sin(x))/cos(x) + cos(x)/(1 - sin(x)) >>> trigsimp(e, method="groebner", old=True) 2/cos(x) >>> trigsimp(1/cot(x)2, compare=True, old=True) futrig: tan(x)2 cot(x)(-2) """ old = expr if first: if not expr.has(_trigs): return expr trigsyms = set().union([t.free_symbols for t in expr.atoms(_trigs)]) if len(trigsyms) > 1: from sympy.simplify.simplify import separatevars d = separatevars(expr) if d.is_Mul: d = separatevars(d, dict=True) or d if isinstance(d, dict): expr = 1 for k, v in d.items(): # remove hollow factoring was = v v = expand_mul(v) opts['first'] = False vnew = trigsimp(v, opts) if vnew == v: vnew = was expr = vnew old = expr else: if d.is_Add: for s in trigsyms: r, e = expr.as_independent(s) if r: opts['first'] = False expr = r + trigsimp(e, opts) if not expr.is_Add: break old = expr recursive = opts.pop('recursive', False) deep = opts.pop('deep', False) method = opts.pop('method', 'matching') def groebnersimp(ex, deep, opts): def traverse(e): if e.is_Atom: return e args = [traverse(x) for x in e.args] if e.is_Function or e.is_Pow: args = [trigsimp_groebner(x, *opts) for x in args] return e.func(args) if deep: ex = traverse(ex) return trigsimp_groebner(ex, opts) trigsimpfunc = { 'matching': (lambda x, d: _trigsimp(x, d)), 'groebner': (lambda x, d: groebnersimp(x, d, opts)), 'combined': (lambda x, d: _trigsimp(groebnersimp(x, d, polynomial=True, hints=[2, tan]), d)) }[method] if recursive: w, g = cse(expr) g = trigsimpfunc(g[0], deep) for sub in reversed(w): g = g.subs(sub[0], sub[1]) g = trigsimpfunc(g, deep) result = g else: result = trigsimpfunc(expr, deep) if opts.get('compare', False): f = futrig(old) if f != result: print('\tfutrig:', f) return result def _dotrig(a, b): """Helper to tell whether ``a`` and ``b`` have the same sorts of symbols in them -- no need to test hyperbolic patterns against expressions that have no hyperbolics in them.""" return a.func == b.func and ( a.has(TrigonometricFunction) and b.has(TrigonometricFunction) or a.has(HyperbolicFunction) and b.has(HyperbolicFunction)) _trigpat = None def _trigpats(): global _trigpat a, b, c = symbols('a b c', cls=Wild) d = Wild('d', commutative=False) # for the simplifications like sinh/cosh -> tanh: # DO NOT REORDER THE FIRST 14 since these are assumed to be in this # order in _match_div_rewrite. matchers_division = ( (asin(b)c/cos(b)c, atan(b)*c, sin(b), cos(b)), (atan(b)*ccos(b)*c, asin(b)*c, sin(b), cos(b)), (acot(b)*csin(b)*c, acos(b)*c, sin(b), cos(b)), (atan(b)c/sin(b)c, a/cos(b)*c, sin(b), cos(b)), (acot(b)c/cos(b)c, a/sin(b)*c, sin(b), cos(b)), (acot(b)*ctan(b)*c, a, sin(b), cos(b)), (a(cos(b) + 1)*c(cos(b) - 1)*c, a(-sin(b)2)c, cos(b) + 1, cos(b) - 1), (a(sin(b) + 1)c(sin(b) - 1)*c, a(-cos(b)2)c, sin(b) + 1, sin(b) - 1), (asinh(b)c/cosh(b)c, atanh(b)*c, S.One, S.One), (atanh(b)*ccosh(b)*c, asinh(b)*c, S.One, S.One), (acoth(b)*csinh(b)*c, acosh(b)*c, S.One, S.One), (atanh(b)c/sinh(b)c, a/cosh(b)*c, S.One, S.One), (acoth(b)c/cosh(b)c, a/sinh(b)*c, S.One, S.One), (acoth(b)*ctanh(b)*c, a, S.One, S.One), (c(tanh(a) + tanh(b))/(1 + tanh(a)tanh(b)), tanh(a + b)c, S.One, S.One), ) matchers_add = ( (csin(a)cos(b) + ccos(a)sin(b) + d, sin(a + b)c + d), (ccos(a)cos(b) - csin(a)sin(b) + d, cos(a + b)c + d), (csin(a)cos(b) - ccos(a)sin(b) + d, sin(a - b)c + d), (ccos(a)cos(b) + csin(a)sin(b) + d, cos(a - b)c + d), (csinh(a)cosh(b) + csinh(b)cosh(a) + d, sinh(a + b)c + d), (ccosh(a)cosh(b) + csinh(a)sinh(b) + d, cosh(a + b)c + d), ) # for cos(x)2 + sin(x)2 -> 1 matchers_identity = ( (asin(b)2, a - acos(b)*2), (atan(b)*2, a(1/cos(b))*2 - a), (acot(b)*2, a(1/sin(b))*2 - a), (asin(b + c), a(sin(b)cos(c) + sin(c)cos(b))), (acos(b + c), a(cos(b)cos(c) - sin(b)sin(c))), (atan(b + c), a((tan(b) + tan(c))/(1 - tan(b)tan(c)))), (asinh(b)2, acosh(b)*2 - a), (atanh(b)*2, a - a(1/cosh(b))*2), (acoth(b)*2, a + a(1/sinh(b))*2), (asinh(b + c), a(sinh(b)cosh(c) + sinh(c)cosh(b))), (acosh(b + c), a(cosh(b)cosh(c) + sinh(b)sinh(c))), (atanh(b + c), a((tanh(b) + tanh(c))/(1 + tanh(b)tanh(c)))), ) # Reduce any lingering artifacts, such as sin(x)2 changing # to 1-cos(x)2 when sin(x)*2 was "simpler" artifacts = ( (a - acos(b)*2 + c, asin(b)*2 + c, cos), (a - a(1/cos(b))*2 + c, -atan(b)*2 + c, cos), (a - a(1/sin(b))*2 + c, -acot(b)*2 + c, sin), (a - acosh(b)*2 + c, -asinh(b)*2 + c, cosh), (a - a(1/cosh(b))*2 + c, atanh(b)*2 + c, cosh), (a + a(1/sinh(b))*2 + c, acoth(b)*2 + c, sinh), # same as above but with noncommutative prefactor (ad - adcos(b)*2 + c, adsin(b)2 + c, cos), (ad - ad(1/cos(b))*2 + c, -adtan(b)2 + c, cos), (ad - ad(1/sin(b))*2 + c, -adcot(b)2 + c, sin), (ad - adcosh(b)*2 + c, -adsinh(b)2 + c, cosh), (ad - ad(1/cosh(b))*2 + c, adtanh(b)2 + c, cosh), (ad + ad(1/sinh(b))*2 + c, adcoth(b)2 + c, sinh), ) _trigpat = (a, b, c, d, matchers_division, matchers_add, matchers_identity, artifacts) return _trigpat def _replace_mul_fpowxgpow(expr, f, g, rexp, h, rexph): """Helper for _match_div_rewrite. Replace f(b_)c_g(b_)(rexp(c_)) with h(b)rexph(c) if f(b_) and g(b_) are both positive or if c_ is an integer. """ # assert expr.is_Mul and expr.is_commutative and f != g fargs = defaultdict(int) gargs = defaultdict(int) args = [] for x in expr.args: if x.is_Pow or x.func in (f, g): b, e = x.as_base_exp() if b.is_positive or e.is_integer: if b.func == f: fargs[b.args[0]] += e continue elif b.func == g: gargs[b.args[0]] += e continue args.append(x) common = set(fargs) & set(gargs) hit = False while common: key = common.pop() fe = fargs.pop(key) ge = gargs.pop(key) if fe == rexp(ge): args.append(h(key)rexph(fe)) hit = True else: fargs[key] = fe gargs[key] = ge if not hit: return expr while fargs: key, e = fargs.popitem() args.append(f(key)e) while gargs: key, e = gargs.popitem() args.append(g(key)*e) return Mul(args) _idn = lambda x: x _midn = lambda x: -x _one = lambda x: S.One def _match_div_rewrite(expr, i): """helper for __trigsimp""" if i == 0: expr = _replace_mul_fpowxgpow(expr, sin, cos, _midn, tan, _idn) elif i == 1: expr = _replace_mul_fpowxgpow(expr, tan, cos, _idn, sin, _idn) elif i == 2: expr = _replace_mul_fpowxgpow(expr, cot, sin, _idn, cos, _idn) elif i == 3: expr = _replace_mul_fpowxgpow(expr, tan, sin, _midn, cos, _midn) elif i == 4: expr = _replace_mul_fpowxgpow(expr, cot, cos, _midn, sin, _midn) elif i == 5: expr = _replace_mul_fpowxgpow(expr, cot, tan, _idn, _one, _idn) # i in (6, 7) is skipped elif i == 8: expr = _replace_mul_fpowxgpow(expr, sinh, cosh, _midn, tanh, _idn) elif i == 9: expr = _replace_mul_fpowxgpow(expr, tanh, cosh, _idn, sinh, _idn) elif i == 10: expr = _replace_mul_fpowxgpow(expr, coth, sinh, _idn, cosh, _idn) elif i == 11: expr = _replace_mul_fpowxgpow(expr, tanh, sinh, _midn, cosh, _midn) elif i == 12: expr = _replace_mul_fpowxgpow(expr, coth, cosh, _midn, sinh, _midn) elif i == 13: expr = _replace_mul_fpowxgpow(expr, coth, tanh, _idn, _one, _idn) else: return None return expr def _trigsimp(expr, deep=False): # protect the cache from non-trig patterns; we only allow # trig patterns to enter the cache if expr.has(_trigs): return __trigsimp(expr, deep) return expr @cacheit def __trigsimp(expr, deep=False): """recursive helper for trigsimp""" from sympy.simplify.fu import TR10i if _trigpat is None: _trigpats() a, b, c, d, matchers_division, matchers_add, \ matchers_identity, artifacts = _trigpat if expr.is_Mul: # do some simplifications like sin/cos -> tan: if not expr.is_commutative: com, nc = expr.args_cnc() expr = _trigsimp(Mul._from_args(com), deep)Mul._from_args(nc) else: for i, (pattern, simp, ok1, ok2) in enumerate(matchers_division): if not _dotrig(expr, pattern): continue newexpr = _match_div_rewrite(expr, i) if newexpr is not None: if newexpr != expr: expr = newexpr break else: continue # use SymPy matching instead res = expr.match(pattern) if res and res.get(c, 0): if not res[c].is_integer: ok = ok1.subs(res) if not ok.is_positive: continue ok = ok2.subs(res) if not ok.is_positive: continue # if "a" contains any of trig or hyperbolic funcs with # argument "b" then skip the simplification if any(w.args[0] == res[b] for w in res[a].atoms( TrigonometricFunction, HyperbolicFunction)): continue # simplify and finish: expr = simp.subs(res) break # process below if expr.is_Add: args = [] for term in expr.args: if not term.is_commutative: com, nc = term.args_cnc() nc = Mul._from_args(nc) term = Mul._from_args(com) else: nc = S.One term = _trigsimp(term, deep) for pattern, result in matchers_identity: res = term.match(pattern) if res is not None: term = result.subs(res) break args.append(termnc) if args != expr.args: expr = Add(args) expr = min(expr, expand(expr), key=count_ops) if expr.is_Add: for pattern, result in matchers_add: if not _dotrig(expr, pattern): continue expr = TR10i(expr) if expr.has(HyperbolicFunction): res = expr.match(pattern) # if "d" contains any trig or hyperbolic funcs with # argument "a" or "b" then skip the simplification; # this isn't perfect -- see tests if res is None or not (a in res and b in res) or any( w.args[0] in (res[a], res[b]) for w in res[d].atoms( TrigonometricFunction, HyperbolicFunction)): continue expr = result.subs(res) break # Reduce any lingering artifacts, such as sin(x)2 changing # to 1 - cos(x)2 when sin(x)2 was "simpler" for pattern, result, ex in artifacts: if not _dotrig(expr, pattern): continue # Substitute a new wild that excludes some function(s) # to help influence a better match. This is because # sometimes, for example, 'a' would match sec(x)2 a_t = Wild('a', exclude=[ex]) pattern = pattern.subs(a, a_t) result = result.subs(a, a_t) m = expr.match(pattern) was = None while m and was != expr: was = expr if m[a_t] == 0 or \ -m[a_t] in m[c].args or m[a_t] + m[c] == 0: break if d in m and m[a_t]m[d] + m[c] == 0: break expr = result.subs(m) m = expr.match(pattern) m.setdefault(c, S.Zero) elif expr.is_Mul or expr.is_Pow or deep and expr.args: expr = expr.func([_trigsimp(a, deep) for a in expr.args]) try: if not expr.has(_trigs): raise TypeError e = expr.atoms(exp) new = expr.rewrite(exp, deep=deep) if new == e: raise TypeError fnew = factor(new) if fnew != new: new = sorted([new, factor(new)], key=count_ops)[0] # if all exp that were introduced disappeared then accept it if not (new.atoms(exp) - e): expr = new except TypeError: pass return expr #------------------- end of old trigsimp routines -------------------- def futrig(e, , hyper=True, kwargs): """Return simplified ``e`` using Fu-like transformations. This is not the "Fu" algorithm. This is called by default from ``trigsimp``. By default, hyperbolics subexpressions will be simplified, but this can be disabled by setting ``hyper=False``. Examples ======== >>> from sympy import trigsimp, tan, sinh, tanh >>> from sympy.simplify.trigsimp import futrig >>> from sympy.abc import x >>> trigsimp(1/tan(x)2) tan(x)*(-2) >>> futrig(sinh(x)/tanh(x)) cosh(x) """ from sympy.simplify.fu import hyper_as_trig from sympy.simplify.simplify import bottom_up e = sympify(e) if not isinstance(e, Basic): return e if not e.args: return e old = e e = bottom_up(e, _futrig) if hyper and e.has(HyperbolicFunction): e, f = hyper_as_trig(e) e = f(bottom_up(e, _futrig)) if e != old and e.is_Mul and e.args[0].is_Rational: # redistribute leading coeff on 2-arg Add e = Mul(e.as_coeff_Mul()) return e def _futrig(e): """Helper for futrig.""" from sympy.simplify.fu import ( TR1, TR2, TR3, TR2i, TR10, L, TR10i, TR8, TR6, TR15, TR16, TR111, TR5, TRmorrie, TR11, _TR11, TR14, TR22, TR12) from sympy.core.compatibility import _nodes if not e.has(TrigonometricFunction): return e if e.is_Mul: coeff, e = e.as_independent(TrigonometricFunction) else: coeff = None Lops = lambda x: (L(x), x.count_ops(), _nodes(x), len(x.args), x.is_Add) trigs = lambda x: x.has(TrigonometricFunction) tree = [identity, ( TR3, # canonical angles TR1, # sec-csc -> cos-sin TR12, # expand tan of sum lambda x: _eapply(factor, x, trigs), TR2, # tan-cot -> sin-cos [identity, lambda x: _eapply(_mexpand, x, trigs)], TR2i, # sin-cos ratio -> tan lambda x: _eapply(lambda i: factor(i.normal()), x, trigs), TR14, # factored identities TR5, # sin-pow -> cos_pow TR10, # sin-cos of sums -> sin-cos prod TR11, _TR11, TR6, # reduce double angles and rewrite cos pows lambda x: _eapply(factor, x, trigs), TR14, # factored powers of identities [identity, lambda x: _eapply(_mexpand, x, trigs)], TR10i, # sin-cos products > sin-cos of sums TRmorrie, [identity, TR8], # sin-cos products -> sin-cos of sums [identity, lambda x: TR2i(TR2(x))], # tan -> sin-cos -> tan [ lambda x: _eapply(expand_mul, TR5(x), trigs), lambda x: _eapply( expand_mul, TR15(x), trigs)], # pos/neg powers of sin [ lambda x: _eapply(expand_mul, TR6(x), trigs), lambda x: _eapply( expand_mul, TR16(x), trigs)], # pos/neg powers of cos TR111, # tan, sin, cos to neg power -> cot, csc, sec [identity, TR2i], # sin-cos ratio to tan [identity, lambda x: _eapply( expand_mul, TR22(x), trigs)], # tan-cot to sec-csc TR1, TR2, TR2i, [identity, lambda x: _eapply( factor_terms, TR12(x), trigs)], # expand tan of sum )] e = greedy(tree, objective=Lops)(e) if coeff is not None: e = coeff * e return e def _is_Expr(e): """_eapply helper to tell whether ``e`` and all its args are Exprs.""" from sympy import Derivative if isinstance(e, Derivative): return _is_Expr(e.expr) if not isinstance(e, Expr): return False return all(_is_Expr(i) for i in e.args) def _eapply(func, e, cond=None): """Apply ``func`` to ``e`` if all args are Exprs else only apply it to those args that are Exprs.""" if not isinstance(e, Expr): return e if _is_Expr(e) or not e.args: return func(e) return e.func(*[ _eapply(func, ei) if (cond is None or cond(ei)) else ei for ei in e.args])
99eb4868fae8df81d96636f8d8b7e2d8e496eb20494cb78c3e7f605caba04a7e	""" Tools for doing common subexpression elimination. """ from sympy.core import Basic, Mul, Add, Pow, sympify, Symbol from sympy.core.compatibility import iterable from sympy.core.containers import Tuple, OrderedSet from sympy.core.exprtools import factor_terms from sympy.core.function import _coeff_isneg from sympy.core.singleton import S from sympy.utilities.iterables import numbered_symbols, sift, \ topological_sort, ordered from . import cse_opts # (preprocessor, postprocessor) pairs which are commonly useful. They should # each take a sympy expression and return a possibly transformed expression. # When used in the function ``cse()``, the target expressions will be transformed # by each of the preprocessor functions in order. After the common # subexpressions are eliminated, each resulting expression will have the # postprocessor functions transform them in reverse order in order to undo the # transformation if necessary. This allows the algorithm to operate on # a representation of the expressions that allows for more optimization # opportunities. # ``None`` can be used to specify no transformation for either the preprocessor or # postprocessor. basic_optimizations = [(cse_opts.sub_pre, cse_opts.sub_post), (factor_terms, None)] # sometimes we want the output in a different format; non-trivial # transformations can be put here for users # =============================================================== def reps_toposort(r): """Sort replacements ``r`` so (k1, v1) appears before (k2, v2) if k2 is in v1's free symbols. This orders items in the way that cse returns its results (hence, in order to use the replacements in a substitution option it would make sense to reverse the order). Examples ======== >>> from sympy.simplify.cse_main import reps_toposort >>> from sympy.abc import x, y >>> from sympy import Eq >>> for l, r in reps_toposort([(x, y + 1), (y, 2)]): ... print(Eq(l, r)) ... Eq(y, 2) Eq(x, y + 1) """ r = sympify(r) E = [] for c1, (k1, v1) in enumerate(r): for c2, (k2, v2) in enumerate(r): if k1 in v2.free_symbols: E.append((c1, c2)) return [r[i] for i in topological_sort((range(len(r)), E))] def cse_separate(r, e): """Move expressions that are in the form (symbol, expr) out of the expressions and sort them into the replacements using the reps_toposort. Examples ======== >>> from sympy.simplify.cse_main import cse_separate >>> from sympy.abc import x, y, z >>> from sympy import cos, exp, cse, Eq, symbols >>> x0, x1 = symbols('x:2') >>> eq = (x + 1 + exp((x + 1)/(y + 1)) + cos(y + 1)) >>> cse([eq, Eq(x, z + 1), z - 2], postprocess=cse_separate) in [ ... [[(x0, y + 1), (x, z + 1), (x1, x + 1)], ... [x1 + exp(x1/x0) + cos(x0), z - 2]], ... [[(x1, y + 1), (x, z + 1), (x0, x + 1)], ... [x0 + exp(x0/x1) + cos(x1), z - 2]]] ... True """ d = sift(e, lambda w: w.is_Equality and w.lhs.is_Symbol) r = r + [w.args for w in d[True]] e = d[False] return [reps_toposort(r), e] # ====end of cse postprocess idioms=========================== def preprocess_for_cse(expr, optimizations): """ Preprocess an expression to optimize for common subexpression elimination. Parameters ========== expr : sympy expression The target expression to optimize. optimizations : list of (callable, callable) pairs The (preprocessor, postprocessor) pairs. Returns ======= expr : sympy expression The transformed expression. """ for pre, post in optimizations: if pre is not None: expr = pre(expr) return expr def postprocess_for_cse(expr, optimizations): """ Postprocess an expression after common subexpression elimination to return the expression to canonical sympy form. Parameters ========== expr : sympy expression The target expression to transform. optimizations : list of (callable, callable) pairs, optional The (preprocessor, postprocessor) pairs. The postprocessors will be applied in reversed order to undo the effects of the preprocessors correctly. Returns ======= expr : sympy expression The transformed expression. """ for pre, post in reversed(optimizations): if post is not None: expr = post(expr) return expr class FuncArgTracker: """ A class which manages a mapping from functions to arguments and an inverse mapping from arguments to functions. """ def __init__(self, funcs): # To minimize the number of symbolic comparisons, all function arguments # get assigned a value number. self.value_numbers = {} self.value_number_to_value = [] # Both of these maps use integer indices for arguments / functions. self.arg_to_funcset = [] self.func_to_argset = [] for func_i, func in enumerate(funcs): func_argset = OrderedSet() for func_arg in func.args: arg_number = self.get_or_add_value_number(func_arg) func_argset.add(arg_number) self.arg_to_funcset[arg_number].add(func_i) self.func_to_argset.append(func_argset) def get_args_in_value_order(self, argset): """ Return the list of arguments in sorted order according to their value numbers. """ return [self.value_number_to_value[argn] for argn in sorted(argset)] def get_or_add_value_number(self, value): """ Return the value number for the given argument. """ nvalues = len(self.value_numbers) value_number = self.value_numbers.setdefault(value, nvalues) if value_number == nvalues: self.value_number_to_value.append(value) self.arg_to_funcset.append(OrderedSet()) return value_number def stop_arg_tracking(self, func_i): """ Remove the function func_i from the argument to function mapping. """ for arg in self.func_to_argset[func_i]: self.arg_to_funcset[arg].remove(func_i) def get_common_arg_candidates(self, argset, min_func_i=0): """Return a dict whose keys are function numbers. The entries of the dict are the number of arguments said function has in common with ``argset``. Entries have at least 2 items in common. All keys have value at least ``min_func_i``. """ from collections import defaultdict count_map = defaultdict(lambda: 0) funcsets = [self.arg_to_funcset[arg] for arg in argset] # As an optimization below, we handle the largest funcset separately from # the others. largest_funcset = max(funcsets, key=len) for funcset in funcsets: if largest_funcset is funcset: continue for func_i in funcset: if func_i >= min_func_i: count_map[func_i] += 1 # We pick the smaller of the two containers (count_map, largest_funcset) # to iterate over to reduce the number of iterations needed. (smaller_funcs_container, larger_funcs_container) = sorted( [largest_funcset, count_map], key=len) for func_i in smaller_funcs_container: # Not already in count_map? It can't possibly be in the output, so # skip it. if count_map[func_i] < 1: continue if func_i in larger_funcs_container: count_map[func_i] += 1 return {k: v for k, v in count_map.items() if v >= 2} def get_subset_candidates(self, argset, restrict_to_funcset=None): """ Return a set of functions each of which whose argument list contains ``argset``, optionally filtered only to contain functions in ``restrict_to_funcset``. """ iarg = iter(argset) indices = OrderedSet( fi for fi in self.arg_to_funcset[next(iarg)]) if restrict_to_funcset is not None: indices &= restrict_to_funcset for arg in iarg: indices &= self.arg_to_funcset[arg] return indices def update_func_argset(self, func_i, new_argset): """ Update a function with a new set of arguments. """ new_args = OrderedSet(new_argset) old_args = self.func_to_argset[func_i] for deleted_arg in old_args - new_args: self.arg_to_funcset[deleted_arg].remove(func_i) for added_arg in new_args - old_args: self.arg_to_funcset[added_arg].add(func_i) self.func_to_argset[func_i].clear() self.func_to_argset[func_i].update(new_args) class Unevaluated: def __init__(self, func, args): self.func = func self.args = args def __str__(self): return "Uneval<{}>({})".format( self.func, ", ".join(str(a) for a in self.args)) def as_unevaluated_basic(self): return self.func(self.args, evaluate=False) @property def free_symbols(self): return set().union([a.free_symbols for a in self.args]) __repr__ = __str__ def match_common_args(func_class, funcs, opt_subs): """ Recognize and extract common subexpressions of function arguments within a set of function calls. For instance, for the following function calls:: x + z + y sin(x + y) this will extract a common subexpression of `x + y`:: w = x + y w + z sin(w) The function we work with is assumed to be associative and commutative. Parameters ========== func_class: class The function class (e.g. Add, Mul) funcs: list of functions A list of function calls. opt_subs: dict A dictionary of substitutions which this function may update. """ # Sort to ensure that whole-function subexpressions come before the items # that use them. funcs = sorted(funcs, key=lambda f: len(f.args)) arg_tracker = FuncArgTracker(funcs) changed = OrderedSet() for i in range(len(funcs)): common_arg_candidates_counts = arg_tracker.get_common_arg_candidates( arg_tracker.func_to_argset[i], min_func_i=i + 1) # Sort the candidates in order of match size. # This makes us try combining smaller matches first. common_arg_candidates = OrderedSet(sorted( common_arg_candidates_counts.keys(), key=lambda k: (common_arg_candidates_counts[k], k))) while common_arg_candidates: j = common_arg_candidates.pop(last=False) com_args = arg_tracker.func_to_argset[i].intersection( arg_tracker.func_to_argset[j]) if len(com_args) <= 1: # This may happen if a set of common arguments was already # combined in a previous iteration. continue # For all sets, replace the common symbols by the function # over them, to allow recursive matches. diff_i = arg_tracker.func_to_argset[i].difference(com_args) if diff_i: # com_func needs to be unevaluated to allow for recursive matches. com_func = Unevaluated( func_class, arg_tracker.get_args_in_value_order(com_args)) com_func_number = arg_tracker.get_or_add_value_number(com_func) arg_tracker.update_func_argset(i, diff_i \| OrderedSet([com_func_number])) changed.add(i) else: # Treat the whole expression as a CSE. # # The reason this needs to be done is somewhat subtle. Within # tree_cse(), to_eliminate only contains expressions that are # seen more than once. The problem is unevaluated expressions # do not compare equal to the evaluated equivalent. So # tree_cse() won't mark funcs[i] as a CSE if we use an # unevaluated version. com_func_number = arg_tracker.get_or_add_value_number(funcs[i]) diff_j = arg_tracker.func_to_argset[j].difference(com_args) arg_tracker.update_func_argset(j, diff_j \| OrderedSet([com_func_number])) changed.add(j) for k in arg_tracker.get_subset_candidates( com_args, common_arg_candidates): diff_k = arg_tracker.func_to_argset[k].difference(com_args) arg_tracker.update_func_argset(k, diff_k \| OrderedSet([com_func_number])) changed.add(k) if i in changed: opt_subs[funcs[i]] = Unevaluated(func_class, arg_tracker.get_args_in_value_order(arg_tracker.func_to_argset[i])) arg_tracker.stop_arg_tracking(i) def opt_cse(exprs, order='canonical'): """Find optimization opportunities in Adds, Muls, Pows and negative coefficient Muls. Parameters ========== exprs : list of sympy expressions The expressions to optimize. order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. For large expressions where speed is a concern, use the setting order='none'. Returns ======= opt_subs : dictionary of expression substitutions The expression substitutions which can be useful to optimize CSE. Examples ======== >>> from sympy.simplify.cse_main import opt_cse >>> from sympy.abc import x >>> opt_subs = opt_cse([x-2]) >>> k, v = list(opt_subs.keys())[0], list(opt_subs.values())[0] >>> print((k, v.as_unevaluated_basic())) (x(-2), 1/(x*2)) """ from sympy.matrices.expressions import MatAdd, MatMul, MatPow opt_subs = dict() adds = OrderedSet() muls = OrderedSet() seen_subexp = set() def _find_opts(expr): if not isinstance(expr, (Basic, Unevaluated)): return if expr.is_Atom or expr.is_Order: return if iterable(expr): list(map(_find_opts, expr)) return if expr in seen_subexp: return expr seen_subexp.add(expr) list(map(_find_opts, expr.args)) if _coeff_isneg(expr): neg_expr = -expr if not neg_expr.is_Atom: opt_subs[expr] = Unevaluated(Mul, (S.NegativeOne, neg_expr)) seen_subexp.add(neg_expr) expr = neg_expr if isinstance(expr, (Mul, MatMul)): muls.add(expr) elif isinstance(expr, (Add, MatAdd)): adds.add(expr) elif isinstance(expr, (Pow, MatPow)): base, exp = expr.base, expr.exp if _coeff_isneg(exp): opt_subs[expr] = Unevaluated(Pow, (Pow(base, -exp), -1)) for e in exprs: if isinstance(e, (Basic, Unevaluated)): _find_opts(e) # split muls into commutative commutative_muls = OrderedSet() for m in muls: c, nc = m.args_cnc(cset=False) if c: c_mul = m.func(c) if nc: if c_mul == 1: new_obj = m.func(nc) else: new_obj = m.func(c_mul, m.func(nc), evaluate=False) opt_subs[m] = new_obj if len(c) > 1: commutative_muls.add(c_mul) match_common_args(Add, adds, opt_subs) match_common_args(Mul, commutative_muls, opt_subs) return opt_subs def tree_cse(exprs, symbols, opt_subs=None, order='canonical', ignore=()): """Perform raw CSE on expression tree, taking opt_subs into account. Parameters ========== exprs : list of sympy expressions The expressions to reduce. symbols : infinite iterator yielding unique Symbols The symbols used to label the common subexpressions which are pulled out. opt_subs : dictionary of expression substitutions The expressions to be substituted before any CSE action is performed. order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. For large expressions where speed is a concern, use the setting order='none'. ignore : iterable of Symbols Substitutions containing any Symbol from ``ignore`` will be ignored. """ from sympy.matrices.expressions import MatrixExpr, MatrixSymbol, MatMul, MatAdd from sympy.polys.rootoftools import RootOf if opt_subs is None: opt_subs = dict() ## Find repeated sub-expressions to_eliminate = set() seen_subexp = set() excluded_symbols = set() def _find_repeated(expr): if not isinstance(expr, (Basic, Unevaluated)): return if isinstance(expr, RootOf): return if isinstance(expr, Basic) and (expr.is_Atom or expr.is_Order): if expr.is_Symbol: excluded_symbols.add(expr) return if iterable(expr): args = expr else: if expr in seen_subexp: for ign in ignore: if ign in expr.free_symbols: break else: to_eliminate.add(expr) return seen_subexp.add(expr) if expr in opt_subs: expr = opt_subs[expr] args = expr.args list(map(_find_repeated, args)) for e in exprs: if isinstance(e, Basic): _find_repeated(e) ## Rebuild tree # Remove symbols from the generator that conflict with names in the expressions. symbols = (symbol for symbol in symbols if symbol not in excluded_symbols) replacements = [] subs = dict() def _rebuild(expr): if not isinstance(expr, (Basic, Unevaluated)): return expr if not expr.args: return expr if iterable(expr): new_args = [_rebuild(arg) for arg in expr] return expr.func(new_args) if expr in subs: return subs[expr] orig_expr = expr if expr in opt_subs: expr = opt_subs[expr] # If enabled, parse Muls and Adds arguments by order to ensure # replacement order independent from hashes if order != 'none': if isinstance(expr, (Mul, MatMul)): c, nc = expr.args_cnc() if c == [1]: args = nc else: args = list(ordered(c)) + nc elif isinstance(expr, (Add, MatAdd)): args = list(ordered(expr.args)) else: args = expr.args else: args = expr.args new_args = list(map(_rebuild, args)) if isinstance(expr, Unevaluated) or new_args != args: new_expr = expr.func(new_args) else: new_expr = expr if orig_expr in to_eliminate: try: sym = next(symbols) except StopIteration: raise ValueError("Symbols iterator ran out of symbols.") if isinstance(orig_expr, MatrixExpr): sym = MatrixSymbol(sym.name, orig_expr.rows, orig_expr.cols) subs[orig_expr] = sym replacements.append((sym, new_expr)) return sym else: return new_expr reduced_exprs = [] for e in exprs: if isinstance(e, Basic): reduced_e = _rebuild(e) else: reduced_e = e reduced_exprs.append(reduced_e) return replacements, reduced_exprs def cse(exprs, symbols=None, optimizations=None, postprocess=None, order='canonical', ignore=()): """ Perform common subexpression elimination on an expression. Parameters ========== exprs : list of sympy expressions, or a single sympy expression The expressions to reduce. symbols : infinite iterator yielding unique Symbols The symbols used to label the common subexpressions which are pulled out. The ``numbered_symbols`` generator is useful. The default is a stream of symbols of the form "x0", "x1", etc. This must be an infinite iterator. optimizations : list of (callable, callable) pairs The (preprocessor, postprocessor) pairs of external optimization functions. Optionally 'basic' can be passed for a set of predefined basic optimizations. Such 'basic' optimizations were used by default in old implementation, however they can be really slow on larger expressions. Now, no pre or post optimizations are made by default. postprocess : a function which accepts the two return values of cse and returns the desired form of output from cse, e.g. if you want the replacements reversed the function might be the following lambda: lambda r, e: return reversed(r), e order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. If set to 'canonical', arguments will be canonically ordered. If set to 'none', ordering will be faster but dependent on expressions hashes, thus machine dependent and variable. For large expressions where speed is a concern, use the setting order='none'. ignore : iterable of Symbols Substitutions containing any Symbol from ``ignore`` will be ignored. Returns ======= replacements : list of (Symbol, expression) pairs All of the common subexpressions that were replaced. Subexpressions earlier in this list might show up in subexpressions later in this list. reduced_exprs : list of sympy expressions The reduced expressions with all of the replacements above. Examples ======== >>> from sympy import cse, SparseMatrix >>> from sympy.abc import x, y, z, w >>> cse(((w + x + y + z)(w + y + z))/(w + x)3) ([(x0, y + z), (x1, w + x)], [(w + x0)(x0 + x1)/x1*3]) Note that currently, y + z will not get substituted if -y - z is used. >>> cse(((w + x + y + z)(w - y - z))/(w + x)*3) ([(x0, w + x)], [(w - y - z)(x0 + y + z)/x03]) List of expressions with recursive substitutions: >>> m = SparseMatrix([x + y, x + y + z]) >>> cse([(x+y)2, x + y + z, y + z, x + z + y, m]) ([(x0, x + y), (x1, x0 + z)], [x02, x1, y + z, x1, Matrix([ [x0], [x1]])]) Note: the type and mutability of input matrices is retained. >>> isinstance(_[1][-1], SparseMatrix) True The user may disallow substitutions containing certain symbols: >>> cse([y2(x + 1), 3y*2(x + 1)], ignore=(y,)) ([(x0, x + 1)], [x0y2, 3x0y2]) """ from sympy.matrices import (MatrixBase, Matrix, ImmutableMatrix, SparseMatrix, ImmutableSparseMatrix) if isinstance(exprs, (int, float)): exprs = sympify(exprs) # Handle the case if just one expression was passed. if isinstance(exprs, (Basic, MatrixBase)): exprs = [exprs] copy = exprs temp = [] for e in exprs: if isinstance(e, (Matrix, ImmutableMatrix)): temp.append(Tuple(e._mat)) elif isinstance(e, (SparseMatrix, ImmutableSparseMatrix)): temp.append(Tuple(*e._smat.items())) else: temp.append(e) exprs = temp del temp if optimizations is None: optimizations = list() elif optimizations == 'basic': optimizations = basic_optimizations # Preprocess the expressions to give us better optimization opportunities. reduced_exprs = [preprocess_for_cse(e, optimizations) for e in exprs] if symbols is None: symbols = numbered_symbols(cls=Symbol) else: # In case we get passed an iterable with an __iter__ method instead of # an actual iterator. symbols = iter(symbols) # Find other optimization opportunities. opt_subs = opt_cse(reduced_exprs, order) # Main CSE algorithm. replacements, reduced_exprs = tree_cse(reduced_exprs, symbols, opt_subs, order, ignore) # Postprocess the expressions to return the expressions to canonical form. exprs = copy for i, (sym, subtree) in enumerate(replacements): subtree = postprocess_for_cse(subtree, optimizations) replacements[i] = (sym, subtree) reduced_exprs = [postprocess_for_cse(e, optimizations) for e in reduced_exprs] # Get the matrices back for i, e in enumerate(exprs): if isinstance(e, (Matrix, ImmutableMatrix)): reduced_exprs[i] = Matrix(e.rows, e.cols, reduced_exprs[i]) if isinstance(e, ImmutableMatrix): reduced_exprs[i] = reduced_exprs[i].as_immutable() elif isinstance(e, (SparseMatrix, ImmutableSparseMatrix)): m = SparseMatrix(e.rows, e.cols, {}) for k, v in reduced_exprs[i]: m[k] = v if isinstance(e, ImmutableSparseMatrix): m = m.as_immutable() reduced_exprs[i] = m if postprocess is None: return replacements, reduced_exprs return postprocess(replacements, reduced_exprs)
daa9e086514933f6bdcd1d99ff39fd392d2ebd56fbe575774ab4e0421f77ffbe	from collections import defaultdict from sympy.core.add import Add from sympy.core.basic import S from sympy.core.compatibility import ordered from sympy.core.expr import Expr from sympy.core.exprtools import Factors, gcd_terms, factor_terms from sympy.core.function import expand_mul from sympy.core.mul import Mul from sympy.core.numbers import pi, I from sympy.core.power import Pow from sympy.core.symbol import Dummy from sympy.core.sympify import sympify from sympy.functions.combinatorial.factorials import binomial from sympy.functions.elementary.hyperbolic import ( cosh, sinh, tanh, coth, sech, csch, HyperbolicFunction) from sympy.functions.elementary.trigonometric import ( cos, sin, tan, cot, sec, csc, sqrt, TrigonometricFunction) from sympy.ntheory.factor_ import perfect_power from sympy.polys.polytools import factor from sympy.simplify.simplify import bottom_up from sympy.strategies.tree import greedy from sympy.strategies.core import identity, debug from sympy import SYMPY_DEBUG # ================== Fu-like tools =========================== def TR0(rv): """Simplification of rational polynomials, trying to simplify the expression, e.g. combine things like 3x + 2x, etc.... """ # although it would be nice to use cancel, it doesn't work # with noncommutatives return rv.normal().factor().expand() def TR1(rv): """Replace sec, csc with 1/cos, 1/sin Examples ======== >>> from sympy.simplify.fu import TR1, sec, csc >>> from sympy.abc import x >>> TR1(2csc(x) + sec(x)) 1/cos(x) + 2/sin(x) """ def f(rv): if isinstance(rv, sec): a = rv.args[0] return S.One/cos(a) elif isinstance(rv, csc): a = rv.args[0] return S.One/sin(a) return rv return bottom_up(rv, f) def TR2(rv): """Replace tan and cot with sin/cos and cos/sin Examples ======== >>> from sympy.simplify.fu import TR2 >>> from sympy.abc import x >>> from sympy import tan, cot, sin, cos >>> TR2(tan(x)) sin(x)/cos(x) >>> TR2(cot(x)) cos(x)/sin(x) >>> TR2(tan(tan(x) - sin(x)/cos(x))) 0 """ def f(rv): if isinstance(rv, tan): a = rv.args[0] return sin(a)/cos(a) elif isinstance(rv, cot): a = rv.args[0] return cos(a)/sin(a) return rv return bottom_up(rv, f) def TR2i(rv, half=False): """Converts ratios involving sin and cos as follows:: sin(x)/cos(x) -> tan(x) sin(x)/(cos(x) + 1) -> tan(x/2) if half=True Examples ======== >>> from sympy.simplify.fu import TR2i >>> from sympy.abc import x, a >>> from sympy import sin, cos >>> TR2i(sin(x)/cos(x)) tan(x) Powers of the numerator and denominator are also recognized >>> TR2i(sin(x)2/(cos(x) + 1)2, half=True) tan(x/2)2 The transformation does not take place unless assumptions allow (i.e. the base must be positive or the exponent must be an integer for both numerator and denominator) >>> TR2i(sin(x)a/(cos(x) + 1)a) (cos(x) + 1)(-a)sin(x)*a """ def f(rv): if not rv.is_Mul: return rv n, d = rv.as_numer_denom() if n.is_Atom or d.is_Atom: return rv def ok(k, e): # initial filtering of factors return ( (e.is_integer or k.is_positive) and ( k.func in (sin, cos) or (half and k.is_Add and len(k.args) >= 2 and any(any(isinstance(ai, cos) or ai.is_Pow and ai.base is cos for ai in Mul.make_args(a)) for a in k.args)))) n = n.as_powers_dict() ndone = [(k, n.pop(k)) for k in list(n.keys()) if not ok(k, n[k])] if not n: return rv d = d.as_powers_dict() ddone = [(k, d.pop(k)) for k in list(d.keys()) if not ok(k, d[k])] if not d: return rv # factoring if necessary def factorize(d, ddone): newk = [] for k in d: if k.is_Add and len(k.args) > 1: knew = factor(k) if half else factor_terms(k) if knew != k: newk.append((k, knew)) if newk: for i, (k, knew) in enumerate(newk): del d[k] newk[i] = knew newk = Mul(newk).as_powers_dict() for k in newk: v = d[k] + newk[k] if ok(k, v): d[k] = v else: ddone.append((k, v)) del newk factorize(n, ndone) factorize(d, ddone) # joining t = [] for k in n: if isinstance(k, sin): a = cos(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])n[k]) n[k] = d[a] = None elif half: a1 = 1 + a if a1 in d and d[a1] == n[k]: t.append((tan(k.args[0]/2))n[k]) n[k] = d[a1] = None elif isinstance(k, cos): a = sin(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])-n[k]) n[k] = d[a] = None elif half and k.is_Add and k.args[0] is S.One and \ isinstance(k.args[1], cos): a = sin(k.args[1].args[0], evaluate=False) if a in d and d[a] == n[k] and (d[a].is_integer or \ a.is_positive): t.append(tan(a.args[0]/2)-n[k]) n[k] = d[a] = None if t: rv = Mul((t + [be for b, e in n.items() if e]))/\ Mul([b*e for b, e in d.items() if e]) rv = Mul([be for b, e in ndone])/Mul([b*e for b, e in ddone]) return rv return bottom_up(rv, f) def TR3(rv): """Induced formula: example sin(-a) = -sin(a) Examples ======== >>> from sympy.simplify.fu import TR3 >>> from sympy.abc import x, y >>> from sympy import pi >>> from sympy import cos >>> TR3(cos(y - x(y - x))) cos(x(x - y) + y) >>> cos(pi/2 + x) -sin(x) >>> cos(30pi/2 + x) -cos(x) """ from sympy.simplify.simplify import signsimp # Negative argument (already automatic for funcs like sin(-x) -> -sin(x) # but more complicated expressions can use it, too). Also, trig angles # between pi/4 and pi/2 are not reduced to an angle between 0 and pi/4. # The following are automatically handled: # Argument of type: pi/2 +/- angle # Argument of type: pi +/- angle # Argument of type : 2kpi +/- angle def f(rv): if not isinstance(rv, TrigonometricFunction): return rv rv = rv.func(signsimp(rv.args[0])) if not isinstance(rv, TrigonometricFunction): return rv if (rv.args[0] - S.Pi/4).is_positive is (S.Pi/2 - rv.args[0]).is_positive is True: fmap = {cos: sin, sin: cos, tan: cot, cot: tan, sec: csc, csc: sec} rv = fmap[rv.func](S.Pi/2 - rv.args[0]) return rv return bottom_up(rv, f) def TR4(rv): """Identify values of special angles. a= 0 pi/6 pi/4 pi/3 pi/2 ---------------------------------------------------- cos(a) 0 1/2 sqrt(2)/2 sqrt(3)/2 1 sin(a) 1 sqrt(3)/2 sqrt(2)/2 1/2 0 tan(a) 0 sqt(3)/3 1 sqrt(3) -- Examples ======== >>> from sympy import pi >>> from sympy import cos, sin, tan, cot >>> for s in (0, pi/6, pi/4, pi/3, pi/2): ... print('%s %s %s %s' % (cos(s), sin(s), tan(s), cot(s))) ... 1 0 0 zoo sqrt(3)/2 1/2 sqrt(3)/3 sqrt(3) sqrt(2)/2 sqrt(2)/2 1 1 1/2 sqrt(3)/2 sqrt(3) sqrt(3)/3 0 1 zoo 0 """ # special values at 0, pi/6, pi/4, pi/3, pi/2 already handled return rv def _TR56(rv, f, g, h, max, pow): """Helper for TR5 and TR6 to replace f2 with h(g2) Options ======= max : controls size of exponent that can appear on f e.g. if max=4 then f4 will be changed to h(g2)2. pow : controls whether the exponent must be a perfect power of 2 e.g. if pow=True (and max >= 6) then f6 will not be changed but f8 will be changed to h(g2)4 >>> from sympy.simplify.fu import _TR56 as T >>> from sympy.abc import x >>> from sympy import sin, cos >>> h = lambda x: 1 - x >>> T(sin(x)3, sin, cos, h, 4, False) sin(x)3 >>> T(sin(x)6, sin, cos, h, 6, False) (1 - cos(x)2)3 >>> T(sin(x)6, sin, cos, h, 6, True) sin(x)6 >>> T(sin(x)8, sin, cos, h, 10, True) (1 - cos(x)2)4 """ def _f(rv): # I'm not sure if this transformation should target all even powers # or only those expressible as powers of 2. Also, should it only # make the changes in powers that appear in sums -- making an isolated # change is not going to allow a simplification as far as I can tell. if not (rv.is_Pow and rv.base.func == f): return rv if not rv.exp.is_real: return rv if (rv.exp < 0) == True: return rv if (rv.exp > max) == True: return rv if rv.exp == 2: return h(g(rv.base.args[0])2) else: if rv.exp == 4: e = 2 elif not pow: if rv.exp % 2: return rv e = rv.exp//2 else: p = perfect_power(rv.exp) if not p: return rv e = rv.exp//2 return h(g(rv.base.args[0])2)e return bottom_up(rv, _f) def TR5(rv, max=4, pow=False): """Replacement of sin2 with 1 - cos(x)2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR5 >>> from sympy.abc import x >>> from sympy import sin >>> TR5(sin(x)2) 1 - cos(x)2 >>> TR5(sin(x)-2) # unchanged sin(x)(-2) >>> TR5(sin(x)4) (1 - cos(x)2)2 """ return _TR56(rv, sin, cos, lambda x: 1 - x, max=max, pow=pow) def TR6(rv, max=4, pow=False): """Replacement of cos2 with 1 - sin(x)2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR6 >>> from sympy.abc import x >>> from sympy import cos >>> TR6(cos(x)2) 1 - sin(x)2 >>> TR6(cos(x)-2) #unchanged cos(x)(-2) >>> TR6(cos(x)4) (1 - sin(x)2)2 """ return _TR56(rv, cos, sin, lambda x: 1 - x, max=max, pow=pow) def TR7(rv): """Lowering the degree of cos(x)2. Examples ======== >>> from sympy.simplify.fu import TR7 >>> from sympy.abc import x >>> from sympy import cos >>> TR7(cos(x)2) cos(2x)/2 + 1/2 >>> TR7(cos(x)*2 + 1) cos(2x)/2 + 3/2 """ def f(rv): if not (rv.is_Pow and rv.base.func == cos and rv.exp == 2): return rv return (1 + cos(2rv.base.args[0]))/2 return bottom_up(rv, f) def TR8(rv, first=True): """Converting products of ``cos`` and/or ``sin`` to a sum or difference of ``cos`` and or ``sin`` terms. Examples ======== >>> from sympy.simplify.fu import TR8 >>> from sympy import cos, sin >>> TR8(cos(2)cos(3)) cos(5)/2 + cos(1)/2 >>> TR8(cos(2)sin(3)) sin(5)/2 + sin(1)/2 >>> TR8(sin(2)sin(3)) -cos(5)/2 + cos(1)/2 """ def f(rv): if not ( rv.is_Mul or rv.is_Pow and rv.base.func in (cos, sin) and (rv.exp.is_integer or rv.base.is_positive)): return rv if first: n, d = [expand_mul(i) for i in rv.as_numer_denom()] newn = TR8(n, first=False) newd = TR8(d, first=False) if newn != n or newd != d: rv = gcd_terms(newn/newd) if rv.is_Mul and rv.args[0].is_Rational and \ len(rv.args) == 2 and rv.args[1].is_Add: rv = Mul(rv.as_coeff_Mul()) return rv args = {cos: [], sin: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (cos, sin): args[a.func].append(a.args[0]) elif (a.is_Pow and a.exp.is_Integer and a.exp > 0 and \ a.base.func in (cos, sin)): # XXX this is ok but pathological expression could be handled # more efficiently as in TRmorrie args[a.base.func].extend([a.base.args[0]]a.exp) else: args[None].append(a) c = args[cos] s = args[sin] if not (c and s or len(c) > 1 or len(s) > 1): return rv args = args[None] n = min(len(c), len(s)) for i in range(n): a1 = s.pop() a2 = c.pop() args.append((sin(a1 + a2) + sin(a1 - a2))/2) while len(c) > 1: a1 = c.pop() a2 = c.pop() args.append((cos(a1 + a2) + cos(a1 - a2))/2) if c: args.append(cos(c.pop())) while len(s) > 1: a1 = s.pop() a2 = s.pop() args.append((-cos(a1 + a2) + cos(a1 - a2))/2) if s: args.append(sin(s.pop())) return TR8(expand_mul(Mul(args))) return bottom_up(rv, f) def TR9(rv): """Sum of ``cos`` or ``sin`` terms as a product of ``cos`` or ``sin``. Examples ======== >>> from sympy.simplify.fu import TR9 >>> from sympy import cos, sin >>> TR9(cos(1) + cos(2)) 2cos(1/2)cos(3/2) >>> TR9(cos(1) + 2sin(1) + 2sin(2)) cos(1) + 4sin(3/2)cos(1/2) If no change is made by TR9, no re-arrangement of the expression will be made. For example, though factoring of common term is attempted, if the factored expression wasn't changed, the original expression will be returned: >>> TR9(cos(3) + cos(3)cos(2)) cos(3) + cos(2)cos(3) """ def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # cos(a)+/-cos(b) can be combined into a product of cosines and # sin(a)+/-sin(b) can be combined into a product of cosine and # sine. # # If there are more than two args, the pairs which "work" will # have a gcd extractable and the remaining two terms will have # the above structure -- all pairs must be checked to find the # ones that work. args that don't have a common set of symbols # are skipped since this doesn't lead to a simpler formula and # also has the arbitrariness of combining, for example, the x # and y term instead of the y and z term in something like # cos(x) + cos(y) + cos(z). if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add([_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(args) if not split: return rv gcd, n1, n2, a, b, iscos = split # application of rule if possible if iscos: if n1 == n2: return gcdn12cos((a + b)/2)cos((a - b)/2) if n1 < 0: a, b = b, a return -2gcdsin((a + b)/2)sin((a - b)/2) else: if n1 == n2: return gcdn12sin((a + b)/2)cos((a - b)/2) if n1 < 0: a, b = b, a return 2gcdcos((a + b)/2)sin((a - b)/2) return process_common_addends(rv, do) # DON'T sift by free symbols return bottom_up(rv, f) def TR10(rv, first=True): """Separate sums in ``cos`` and ``sin``. Examples ======== >>> from sympy.simplify.fu import TR10 >>> from sympy.abc import a, b, c >>> from sympy import cos, sin >>> TR10(cos(a + b)) -sin(a)sin(b) + cos(a)cos(b) >>> TR10(sin(a + b)) sin(a)cos(b) + sin(b)cos(a) >>> TR10(sin(a + b + c)) (-sin(a)sin(b) + cos(a)cos(b))sin(c) + \ (sin(a)cos(b) + sin(b)cos(a))cos(c) """ def f(rv): if not rv.func in (cos, sin): return rv f = rv.func arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: if f == sin: return sin(a)TR10(cos(b), first=False) + \ cos(a)TR10(sin(b), first=False) else: return cos(a)TR10(cos(b), first=False) - \ sin(a)TR10(sin(b), first=False) else: if f == sin: return sin(a)cos(b) + cos(a)sin(b) else: return cos(a)cos(b) - sin(a)sin(b) return rv return bottom_up(rv, f) def TR10i(rv): """Sum of products to function of sum. Examples ======== >>> from sympy.simplify.fu import TR10i >>> from sympy import cos, sin, sqrt >>> from sympy.abc import x >>> TR10i(cos(1)cos(3) + sin(1)sin(3)) cos(2) >>> TR10i(cos(1)sin(3) + sin(1)cos(3) + cos(3)) cos(3) + sin(4) >>> TR10i(sqrt(2)cos(x)x + sqrt(6)sin(x)x) 2sqrt(2)xsin(x + pi/6) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # args which can be expressed as A(cos(a)cos(b)+/-sin(a)sin(b)) # or B(cos(a)sin(b)+/-cos(b)sin(a)) can be combined into # Af(a+/-b) where f is either sin or cos. # # If there are more than two args, the pairs which "work" will have # a gcd extractable and the remaining two terms will have the above # structure -- all pairs must be checked to find the ones that # work. if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add([_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(args, two=True) if not split: return rv gcd, n1, n2, a, b, same = split # identify and get c1 to be cos then apply rule if possible if same: # coscos, sinsin gcd = n1gcd if n1 == n2: return gcdcos(a - b) return gcdcos(a + b) else: #cossin, cossin gcd = n1gcd if n1 == n2: return gcdsin(a + b) return gcdsin(b - a) rv = process_common_addends( rv, do, lambda x: tuple(ordered(x.free_symbols))) # need to check for inducible pairs in ratio of sqrt(3):1 that # appeared in different lists when sorting by coefficient while rv.is_Add: byrad = defaultdict(list) for a in rv.args: hit = 0 if a.is_Mul: for ai in a.args: if ai.is_Pow and ai.exp is S.Half and \ ai.base.is_Integer: byrad[ai].append(a) hit = 1 break if not hit: byrad[S.One].append(a) # no need to check all pairs -- just check for the onees # that have the right ratio args = [] for a in byrad: for b in [_ROOT3a, _invROOT3]: if b in byrad: for i in range(len(byrad[a])): if byrad[a][i] is None: continue for j in range(len(byrad[b])): if byrad[b][j] is None: continue was = Add(byrad[a][i] + byrad[b][j]) new = do(was) if new != was: args.append(new) byrad[a][i] = None byrad[b][j] = None break if args: rv = Add((args + [Add([_f for _f in v if _f]) for v in byrad.values()])) else: rv = do(rv) # final pass to resolve any new inducible pairs break return rv return bottom_up(rv, f) def TR11(rv, base=None): """Function of double angle to product. The ``base`` argument can be used to indicate what is the un-doubled argument, e.g. if 3pi/7 is the base then cosine and sine functions with argument 6pi/7 will be replaced. Examples ======== >>> from sympy.simplify.fu import TR11 >>> from sympy import cos, sin, pi >>> from sympy.abc import x >>> TR11(sin(2x)) 2sin(x)cos(x) >>> TR11(cos(2x)) -sin(x)2 + cos(x)2 >>> TR11(sin(4x)) 4(-sin(x)2 + cos(x)2)sin(x)cos(x) >>> TR11(sin(4x/3)) 4(-sin(x/3)2 + cos(x/3)2)sin(x/3)cos(x/3) If the arguments are simply integers, no change is made unless a base is provided: >>> TR11(cos(2)) cos(2) >>> TR11(cos(4), 2) -sin(2)2 + cos(2)2 There is a subtle issue here in that autosimplification will convert some higher angles to lower angles >>> cos(6pi/7) + cos(3pi/7) -cos(pi/7) + cos(3pi/7) The 6pi/7 angle is now pi/7 but can be targeted with TR11 by supplying the 3pi/7 base: >>> TR11(_, 3pi/7) -sin(3pi/7)2 + cos(3pi/7)*2 + cos(3pi/7) """ def f(rv): if not rv.func in (cos, sin): return rv if base: f = rv.func t = f(base2) co = S.One if t.is_Mul: co, t = t.as_coeff_Mul() if not t.func in (cos, sin): return rv if rv.args[0] == t.args[0]: c = cos(base) s = sin(base) if f is cos: return (c2 - s2)/co else: return 2cs/co return rv elif not rv.args[0].is_Number: # make a change if the leading coefficient's numerator is # divisible by 2 c, m = rv.args[0].as_coeff_Mul(rational=True) if c.p % 2 == 0: arg = c.p//2m/c.q c = TR11(cos(arg)) s = TR11(sin(arg)) if rv.func == sin: rv = 2sc else: rv = c2 - s2 return rv return bottom_up(rv, f) def _TR11(rv): """ Helper for TR11 to find half-arguments for sin in factors of num/den that appear in cos or sin factors in the den/num. Examples ======== >>> from sympy.simplify.fu import TR11, _TR11 >>> from sympy import cos, sin >>> from sympy.abc import x >>> TR11(sin(x/3)/(cos(x/6))) sin(x/3)/cos(x/6) >>> _TR11(sin(x/3)/(cos(x/6))) 2sin(x/6) >>> TR11(sin(x/6)/(sin(x/3))) sin(x/6)/sin(x/3) >>> _TR11(sin(x/6)/(sin(x/3))) 1/(2cos(x/6)) """ def f(rv): if not isinstance(rv, Expr): return rv def sincos_args(flat): # find arguments of sin and cos that # appears as bases in args of flat # and have Integer exponents args = defaultdict(set) for fi in Mul.make_args(flat): b, e = fi.as_base_exp() if e.is_Integer and e > 0: if b.func in (cos, sin): args[b.func].add(b.args[0]) return args num_args, den_args = map(sincos_args, rv.as_numer_denom()) def handle_match(rv, num_args, den_args): # for arg in sin args of num_args, look for arg/2 # in den_args and pass this half-angle to TR11 # for handling in rv for narg in num_args[sin]: half = narg/2 if half in den_args[cos]: func = cos elif half in den_args[sin]: func = sin else: continue rv = TR11(rv, half) den_args[func].remove(half) return rv # sin in num, sin or cos in den rv = handle_match(rv, num_args, den_args) # sin in den, sin or cos in num rv = handle_match(rv, den_args, num_args) return rv return bottom_up(rv, f) def TR12(rv, first=True): """Separate sums in ``tan``. Examples ======== >>> from sympy.abc import x, y >>> from sympy import tan >>> from sympy.simplify.fu import TR12 >>> TR12(tan(x + y)) (tan(x) + tan(y))/(-tan(x)tan(y) + 1) """ def f(rv): if not rv.func == tan: return rv arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: tb = TR12(tan(b), first=False) else: tb = tan(b) return (tan(a) + tb)/(1 - tan(a)tb) return rv return bottom_up(rv, f) def TR12i(rv): """Combine tan arguments as (tan(y) + tan(x))/(tan(x)tan(y) - 1) -> -tan(x + y). Examples ======== >>> from sympy.simplify.fu import TR12i >>> from sympy import tan >>> from sympy.abc import a, b, c >>> ta, tb, tc = [tan(i) for i in (a, b, c)] >>> TR12i((ta + tb)/(-tatb + 1)) tan(a + b) >>> TR12i((ta + tb)/(tatb - 1)) -tan(a + b) >>> TR12i((-ta - tb)/(tatb - 1)) tan(a + b) >>> eq = (ta + tb)/(-tatb + 1)2(-3ta - 3tc)/(2(tatc - 1)) >>> TR12i(eq.expand()) -3tan(a + b)tan(a + c)/(2(tan(a) + tan(b) - 1)) """ from sympy import factor def f(rv): if not (rv.is_Add or rv.is_Mul or rv.is_Pow): return rv n, d = rv.as_numer_denom() if not d.args or not n.args: return rv dok = {} def ok(di): m = as_f_sign_1(di) if m: g, f, s = m if s is S.NegativeOne and f.is_Mul and len(f.args) == 2 and \ all(isinstance(fi, tan) for fi in f.args): return g, f d_args = list(Mul.make_args(d)) for i, di in enumerate(d_args): m = ok(di) if m: g, t = m s = Add([_.args[0] for _ in t.args]) dok[s] = S.One d_args[i] = g continue if di.is_Add: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One elif di.is_Pow and (di.exp.is_integer or di.base.is_positive): m = ok(di.base) if m: g, t = m s = Add([_.args[0] for _ in t.args]) dok[s] = di.exp d_args[i] = gdi.exp else: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One if not dok: return rv def ok(ni): if ni.is_Add and len(ni.args) == 2: a, b = ni.args if isinstance(a, tan) and isinstance(b, tan): return a, b n_args = list(Mul.make_args(factor_terms(n))) hit = False for i, ni in enumerate(n_args): m = ok(ni) if not m: m = ok(-ni) if m: n_args[i] = S.NegativeOne else: if ni.is_Add: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue elif ni.is_Pow and ( ni.exp.is_integer or ni.base.is_positive): m = ok(ni.base) if m: n_args[i] = S.One else: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue else: continue else: n_args[i] = S.One hit = True s = Add([_.args[0] for _ in m]) ed = dok[s] newed = ed.extract_additively(S.One) if newed is not None: if newed: dok[s] = newed else: dok.pop(s) n_args[i] = -tan(s) if hit: rv = Mul(n_args)/Mul(d_args)/Mul([(Add([ tan(a) for a in i.args]) - 1)e for i, e in dok.items()]) return rv return bottom_up(rv, f) def TR13(rv): """Change products of ``tan`` or ``cot``. Examples ======== >>> from sympy.simplify.fu import TR13 >>> from sympy import tan, cot >>> TR13(tan(3)tan(2)) -tan(2)/tan(5) - tan(3)/tan(5) + 1 >>> TR13(cot(3)cot(2)) cot(2)cot(5) + 1 + cot(3)cot(5) """ def f(rv): if not rv.is_Mul: return rv # XXX handle products of powers? or let power-reducing handle it? args = {tan: [], cot: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (tan, cot): args[a.func].append(a.args[0]) else: args[None].append(a) t = args[tan] c = args[cot] if len(t) < 2 and len(c) < 2: return rv args = args[None] while len(t) > 1: t1 = t.pop() t2 = t.pop() args.append(1 - (tan(t1)/tan(t1 + t2) + tan(t2)/tan(t1 + t2))) if t: args.append(tan(t.pop())) while len(c) > 1: t1 = c.pop() t2 = c.pop() args.append(1 + cot(t1)cot(t1 + t2) + cot(t2)cot(t1 + t2)) if c: args.append(cot(c.pop())) return Mul(args) return bottom_up(rv, f) def TRmorrie(rv): """Returns cos(x)cos(2x)...cos(2*(k-1)x) -> sin(2*kx)/(2*ksin(x)) Examples ======== >>> from sympy.simplify.fu import TRmorrie, TR8, TR3 >>> from sympy.abc import x >>> from sympy import Mul, cos, pi >>> TRmorrie(cos(x)cos(2x)) sin(4x)/(4sin(x)) >>> TRmorrie(7Mul([cos(x) for x in range(10)])) 7sin(12)sin(16)cos(5)cos(7)cos(9)/(64sin(1)sin(3)) Sometimes autosimplification will cause a power to be not recognized. e.g. in the following, cos(4pi/7) automatically simplifies to -cos(3pi/7) so only 2 of the 3 terms are recognized: >>> TRmorrie(cos(pi/7)cos(2pi/7)cos(4pi/7)) -sin(3pi/7)cos(3pi/7)/(4sin(pi/7)) A touch by TR8 resolves the expression to a Rational >>> TR8(_) -1/8 In this case, if eq is unsimplified, the answer is obtained directly: >>> eq = cos(pi/9)cos(2pi/9)cos(3pi/9)cos(4pi/9) >>> TRmorrie(eq) 1/16 But if angles are made canonical with TR3 then the answer is not simplified without further work: >>> TR3(eq) sin(pi/18)cos(pi/9)cos(2pi/9)/2 >>> TRmorrie(_) sin(pi/18)sin(4pi/9)/(8sin(pi/9)) >>> TR8(_) cos(7pi/18)/(16sin(pi/9)) >>> TR3(_) 1/16 The original expression would have resolve to 1/16 directly with TR8, however: >>> TR8(eq) 1/16 References ========== .. [1] https://en.wikipedia.org/wiki/Morrie%27s_law """ def f(rv, first=True): if not rv.is_Mul: return rv if first: n, d = rv.as_numer_denom() return f(n, 0)/f(d, 0) args = defaultdict(list) coss = {} other = [] for c in rv.args: b, e = c.as_base_exp() if e.is_Integer and isinstance(b, cos): co, a = b.args[0].as_coeff_Mul() args[a].append(co) coss[b] = e else: other.append(c) new = [] for a in args: c = args[a] c.sort() no = [] while c: k = 0 cc = ci = c[0] while cc in c: k += 1 cc = 2 if k > 1: newarg = sin(2*kcia)/2k/sin(cia) # see how many times this can be taken take = None ccs = [] for i in range(k): cc /= 2 key = cos(acc, evaluate=False) ccs.append(cc) take = min(coss[key], take or coss[key]) # update exponent counts for i in range(k): cc = ccs.pop() key = cos(acc, evaluate=False) coss[key] -= take if not coss[key]: c.remove(cc) new.append(newarg*take) else: no.append(c.pop(0)) c[:] = no if new: rv = Mul((new + other + [ cos(ka, evaluate=False) for a in args for k in args[a]])) return rv return bottom_up(rv, f) def TR14(rv, first=True): """Convert factored powers of sin and cos identities into simpler expressions. Examples ======== >>> from sympy.simplify.fu import TR14 >>> from sympy.abc import x, y >>> from sympy import cos, sin >>> TR14((cos(x) - 1)(cos(x) + 1)) -sin(x)*2 >>> TR14((sin(x) - 1)(sin(x) + 1)) -cos(x)*2 >>> p1 = (cos(x) + 1)(cos(x) - 1) >>> p2 = (cos(y) - 1)2(cos(y) + 1) >>> p3 = (3(cos(y) - 1))(3(cos(y) + 1)) >>> TR14(p1p2p3(x - 1)) -18(x - 1)sin(x)*2sin(y)4 """ def f(rv): if not rv.is_Mul: return rv if first: # sort them by location in numerator and denominator # so the code below can just deal with positive exponents n, d = rv.as_numer_denom() if d is not S.One: newn = TR14(n, first=False) newd = TR14(d, first=False) if newn != n or newd != d: rv = newn/newd return rv other = [] process = [] for a in rv.args: if a.is_Pow: b, e = a.as_base_exp() if not (e.is_integer or b.is_positive): other.append(a) continue a = b else: e = S.One m = as_f_sign_1(a) if not m or m[1].func not in (cos, sin): if e is S.One: other.append(a) else: other.append(ae) continue g, f, si = m process.append((g, e.is_Number, e, f, si, a)) # sort them to get like terms next to each other process = list(ordered(process)) # keep track of whether there was any change nother = len(other) # access keys keys = (g, t, e, f, si, a) = list(range(6)) while process: A = process.pop(0) if process: B = process[0] if A[e].is_Number and B[e].is_Number: # both exponents are numbers if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = min(A[e], B[e]) # reinsert any remainder # the B will likely sort after A so check it first if B[e] != take: rem = [B[i] for i in keys] rem[e] -= take process.insert(0, rem) elif A[e] != take: rem = [A[i] for i in keys] rem[e] -= take process.insert(0, rem) if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]B[g]t(A[f].args[0])2)take) continue elif A[e] == B[e]: # both exponents are equal symbols if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = A[e] if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]B[g]t(A[f].args[0])2)take) continue # either we are done or neither condition above applied other.append(A[a]*A[e]) if len(other) != nother: rv = Mul(other) return rv return bottom_up(rv, f) def TR15(rv, max=4, pow=False): """Convert sin(x)-2 to 1 + cot(x)2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR15 >>> from sympy.abc import x >>> from sympy import sin >>> TR15(1 - 1/sin(x)2) -cot(x)2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, sin)): return rv ia = 1/rv a = _TR56(ia, sin, cot, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR16(rv, max=4, pow=False): """Convert cos(x)-2 to 1 + tan(x)2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR16 >>> from sympy.abc import x >>> from sympy import cos >>> TR16(1 - 1/cos(x)2) -tan(x)2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, cos)): return rv ia = 1/rv a = _TR56(ia, cos, tan, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR111(rv): """Convert f(x)-i to g(x)i where either ``i`` is an integer or the base is positive and f, g are: tan, cot; sin, csc; or cos, sec. Examples ======== >>> from sympy.simplify.fu import TR111 >>> from sympy.abc import x >>> from sympy import tan >>> TR111(1 - 1/tan(x)2) 1 - cot(x)2 """ def f(rv): if not ( isinstance(rv, Pow) and (rv.base.is_positive or rv.exp.is_integer and rv.exp.is_negative)): return rv if isinstance(rv.base, tan): return cot(rv.base.args[0])-rv.exp elif isinstance(rv.base, sin): return csc(rv.base.args[0])-rv.exp elif isinstance(rv.base, cos): return sec(rv.base.args[0])-rv.exp return rv return bottom_up(rv, f) def TR22(rv, max=4, pow=False): """Convert tan(x)2 to sec(x)2 - 1 and cot(x)2 to csc(x)2 - 1. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR22 >>> from sympy.abc import x >>> from sympy import tan, cot >>> TR22(1 + tan(x)2) sec(x)2 >>> TR22(1 + cot(x)2) csc(x)2 """ def f(rv): if not (isinstance(rv, Pow) and rv.base.func in (cot, tan)): return rv rv = _TR56(rv, tan, sec, lambda x: x - 1, max=max, pow=pow) rv = _TR56(rv, cot, csc, lambda x: x - 1, max=max, pow=pow) return rv return bottom_up(rv, f) def TRpower(rv): """Convert sin(x)n and cos(x)n with positive n to sums. Examples ======== >>> from sympy.simplify.fu import TRpower >>> from sympy.abc import x >>> from sympy import cos, sin >>> TRpower(sin(x)*6) -15cos(2x)/32 + 3cos(4x)/16 - cos(6x)/32 + 5/16 >>> TRpower(sin(x)*3cos(2x)4) (3sin(x)/4 - sin(3x)/4)(cos(4x)/2 + cos(8x)/8 + 3/8) References ========== .. [1] https://en.wikipedia.org/wiki/List_of_trigonometric_identities#Power-reduction_formulae """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, (sin, cos))): return rv b, n = rv.as_base_exp() x = b.args[0] if n.is_Integer and n.is_positive: if n.is_odd and isinstance(b, cos): rv = 2*(1-n)Add([binomial(n, k)cos((n - 2k)x) for k in range((n + 1)/2)]) elif n.is_odd and isinstance(b, sin): rv = 2*(1-n)(-1)*((n-1)/2)Add([binomial(n, k) (-1)*ksin((n - 2k)x) for k in range((n + 1)/2)]) elif n.is_even and isinstance(b, cos): rv = 2*(1-n)Add([binomial(n, k)cos((n - 2k)x) for k in range(n/2)]) elif n.is_even and isinstance(b, sin): rv = 2*(1-n)(-1)*(n/2)Add([binomial(n, k) (-1)*kcos((n - 2k)x) for k in range(n/2)]) if n.is_even: rv += 2*(-n)binomial(n, n/2) return rv return bottom_up(rv, f) def L(rv): """Return count of trigonometric functions in expression. Examples ======== >>> from sympy.simplify.fu import L >>> from sympy.abc import x >>> from sympy import cos, sin >>> L(cos(x)+sin(x)) 2 """ return S(rv.count(TrigonometricFunction)) # ============== end of basic Fu-like tools ===================== if SYMPY_DEBUG: (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22 )= list(map(debug, (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22))) # tuples are chains -- (f, g) -> lambda x: g(f(x)) # lists are choices -- [f, g] -> lambda x: min(f(x), g(x), key=objective) CTR1 = [(TR5, TR0), (TR6, TR0), identity] CTR2 = (TR11, [(TR5, TR0), (TR6, TR0), TR0]) CTR3 = [(TRmorrie, TR8, TR0), (TRmorrie, TR8, TR10i, TR0), identity] CTR4 = [(TR4, TR10i), identity] RL1 = (TR4, TR3, TR4, TR12, TR4, TR13, TR4, TR0) # XXX it's a little unclear how this one is to be implemented # see Fu paper of reference, page 7. What is the Union symbol referring to? # The diagram shows all these as one chain of transformations, but the # text refers to them being applied independently. Also, a break # if L starts to increase has not been implemented. RL2 = [ (TR4, TR3, TR10, TR4, TR3, TR11), (TR5, TR7, TR11, TR4), (CTR3, CTR1, TR9, CTR2, TR4, TR9, TR9, CTR4), identity, ] def fu(rv, measure=lambda x: (L(x), x.count_ops())): """Attempt to simplify expression by using transformation rules given in the algorithm by Fu et al. :func:`fu` will try to minimize the objective function ``measure``. By default this first minimizes the number of trig terms and then minimizes the number of total operations. Examples ======== >>> from sympy.simplify.fu import fu >>> from sympy import cos, sin, tan, pi, S, sqrt >>> from sympy.abc import x, y, a, b >>> fu(sin(50)2 + cos(50)2 + sin(pi/6)) 3/2 >>> fu(sqrt(6)cos(x) + sqrt(2)sin(x)) 2sqrt(2)sin(x + pi/3) CTR1 example >>> eq = sin(x)4 - cos(y)2 + sin(y)*2 + 2cos(x)2 >>> fu(eq) cos(x)4 - 2cos(y)2 + 2 CTR2 example >>> fu(S.Half - cos(2x)/2) sin(x)*2 CTR3 example >>> fu(sin(a)(cos(b) - sin(b)) + cos(a)(sin(b) + cos(b))) sqrt(2)sin(a + b + pi/4) CTR4 example >>> fu(sqrt(3)cos(x)/2 + sin(x)/2) sin(x + pi/3) Example 1 >>> fu(1-sin(2x)2/4-sin(y)2-cos(x)4) -cos(x)2 + cos(y)*2 Example 2 >>> fu(cos(4pi/9)) sin(pi/18) >>> fu(cos(pi/9)cos(2pi/9)cos(3pi/9)cos(4pi/9)) 1/16 Example 3 >>> fu(tan(7pi/18)+tan(5pi/18)-sqrt(3)tan(5pi/18)tan(7pi/18)) -sqrt(3) Objective function example >>> fu(sin(x)/cos(x)) # default objective function tan(x) >>> fu(sin(x)/cos(x), measure=lambda x: -x.count_ops()) # maximize op count sin(x)/cos(x) References ========== .. [1] https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.657.2478&rep=rep1&type=pdf """ fRL1 = greedy(RL1, measure) fRL2 = greedy(RL2, measure) was = rv rv = sympify(rv) if not isinstance(rv, Expr): return rv.func([fu(a, measure=measure) for a in rv.args]) rv = TR1(rv) if rv.has(tan, cot): rv1 = fRL1(rv) if (measure(rv1) < measure(rv)): rv = rv1 if rv.has(tan, cot): rv = TR2(rv) if rv.has(sin, cos): rv1 = fRL2(rv) rv2 = TR8(TRmorrie(rv1)) rv = min([was, rv, rv1, rv2], key=measure) return min(TR2i(rv), rv, key=measure) def process_common_addends(rv, do, key2=None, key1=True): """Apply ``do`` to addends of ``rv`` that (if ``key1=True``) share at least a common absolute value of their coefficient and the value of ``key2`` when applied to the argument. If ``key1`` is False ``key2`` must be supplied and will be the only key applied. """ # collect by absolute value of coefficient and key2 absc = defaultdict(list) if key1: for a in rv.args: c, a = a.as_coeff_Mul() if c < 0: c = -c a = -a # put the sign on `a` absc[(c, key2(a) if key2 else 1)].append(a) elif key2: for a in rv.args: absc[(S.One, key2(a))].append(a) else: raise ValueError('must have at least one key') args = [] hit = False for k in absc: v = absc[k] c, _ = k if len(v) > 1: e = Add(v, evaluate=False) new = do(e) if new != e: e = new hit = True args.append(ce) else: args.append(cv[0]) if hit: rv = Add(args) return rv fufuncs = ''' TR0 TR1 TR2 TR3 TR4 TR5 TR6 TR7 TR8 TR9 TR10 TR10i TR11 TR12 TR13 L TR2i TRmorrie TR12i TR14 TR15 TR16 TR111 TR22'''.split() FU = dict(list(zip(fufuncs, list(map(locals().get, fufuncs))))) def _roots(): global _ROOT2, _ROOT3, _invROOT3 _ROOT2, _ROOT3 = sqrt(2), sqrt(3) _invROOT3 = 1/_ROOT3 _ROOT2 = None def trig_split(a, b, two=False): """Return the gcd, s1, s2, a1, a2, bool where If two is False (default) then:: a + b = gcd(s1f(a1) + s2f(a2)) where f = cos if bool else sin else: if bool, a + b was +/- cos(a1)cos(a2) +/- sin(a1)sin(a2) and equals n1gcdcos(a - b) if n1 == n2 else n1gcdcos(a + b) else a + b was +/- cos(a1)sin(a2) +/- sin(a1)cos(a2) and equals n1gcdsin(a + b) if n1 = n2 else n1gcdsin(b - a) Examples ======== >>> from sympy.simplify.fu import trig_split >>> from sympy.abc import x, y, z >>> from sympy import cos, sin, sqrt >>> trig_split(cos(x), cos(y)) (1, 1, 1, x, y, True) >>> trig_split(2cos(x), -2cos(y)) (2, 1, -1, x, y, True) >>> trig_split(cos(x)sin(y), cos(y)sin(y)) (sin(y), 1, 1, x, y, True) >>> trig_split(cos(x), -sqrt(3)sin(x), two=True) (2, 1, -1, x, pi/6, False) >>> trig_split(cos(x), sin(x), two=True) (sqrt(2), 1, 1, x, pi/4, False) >>> trig_split(cos(x), -sin(x), two=True) (sqrt(2), 1, -1, x, pi/4, False) >>> trig_split(sqrt(2)cos(x), -sqrt(6)sin(x), two=True) (2sqrt(2), 1, -1, x, pi/6, False) >>> trig_split(-sqrt(6)cos(x), -sqrt(2)sin(x), two=True) (-2sqrt(2), 1, 1, x, pi/3, False) >>> trig_split(cos(x)/sqrt(6), sin(x)/sqrt(2), two=True) (sqrt(6)/3, 1, 1, x, pi/6, False) >>> trig_split(-sqrt(6)cos(x)sin(y), -sqrt(2)sin(x)sin(y), two=True) (-2sqrt(2)sin(y), 1, 1, x, pi/3, False) >>> trig_split(cos(x), sin(x)) >>> trig_split(cos(x), sin(z)) >>> trig_split(2cos(x), -sin(x)) >>> trig_split(cos(x), -sqrt(3)sin(x)) >>> trig_split(cos(x)cos(y), sin(x)sin(z)) >>> trig_split(cos(x)cos(y), sin(x)sin(y)) >>> trig_split(-sqrt(6)cos(x), sqrt(2)sin(x)sin(y), two=True) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() a, b = [Factors(i) for i in (a, b)] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() n1 = n2 = 1 if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -n1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n2 = -n2 a, b = [i.as_expr() for i in (ua, ub)] def pow_cos_sin(a, two): """Return ``a`` as a tuple (r, c, s) such that ``a = (r or 1)(c or 1)(s or 1)``. Three arguments are returned (radical, c-factor, s-factor) as long as the conditions set by ``two`` are met; otherwise None is returned. If ``two`` is True there will be one or two non-None values in the tuple: c and s or c and r or s and r or s or c with c being a cosine function (if possible) else a sine, and s being a sine function (if possible) else oosine. If ``two`` is False then there will only be a c or s term in the tuple. ``two`` also require that either two cos and/or sin be present (with the condition that if the functions are the same the arguments are different or vice versa) or that a single cosine or a single sine be present with an optional radical. If the above conditions dictated by ``two`` are not met then None is returned. """ c = s = None co = S.One if a.is_Mul: co, a = a.as_coeff_Mul() if len(a.args) > 2 or not two: return None if a.is_Mul: args = list(a.args) else: args = [a] a = args.pop(0) if isinstance(a, cos): c = a elif isinstance(a, sin): s = a elif a.is_Pow and a.exp is S.Half: # autoeval doesn't allow -1/2 co = a else: return None if args: b = args[0] if isinstance(b, cos): if c: s = b else: c = b elif isinstance(b, sin): if s: c = b else: s = b elif b.is_Pow and b.exp is S.Half: co = b else: return None return co if co is not S.One else None, c, s elif isinstance(a, cos): c = a elif isinstance(a, sin): s = a if c is None and s is None: return co = co if co is not S.One else None return co, c, s # get the parts m = pow_cos_sin(a, two) if m is None: return coa, ca, sa = m m = pow_cos_sin(b, two) if m is None: return cob, cb, sb = m # check them if (not ca) and cb or ca and isinstance(ca, sin): coa, ca, sa, cob, cb, sb = cob, cb, sb, coa, ca, sa n1, n2 = n2, n1 if not two: # need cos(x) and cos(y) or sin(x) and sin(y) c = ca or sa s = cb or sb if not isinstance(c, s.func): return None return gcd, n1, n2, c.args[0], s.args[0], isinstance(c, cos) else: if not coa and not cob: if (ca and cb and sa and sb): if isinstance(ca, sa.func) is not isinstance(cb, sb.func): return args = {j.args for j in (ca, sa)} if not all(i.args in args for i in (cb, sb)): return return gcd, n1, n2, ca.args[0], sa.args[0], isinstance(ca, sa.func) if ca and sa or cb and sb or \ two and (ca is None and sa is None or cb is None and sb is None): return c = ca or sa s = cb or sb if c.args != s.args: return if not coa: coa = S.One if not cob: cob = S.One if coa is cob: gcd = _ROOT2 return gcd, n1, n2, c.args[0], pi/4, False elif coa/cob == _ROOT3: gcd = 2cob return gcd, n1, n2, c.args[0], pi/3, False elif coa/cob == _invROOT3: gcd = 2coa return gcd, n1, n2, c.args[0], pi/6, False def as_f_sign_1(e): """If ``e`` is a sum that can be written as ``g(a + s)`` where ``s`` is ``+/-1``, return ``g``, ``a``, and ``s`` where ``a`` does not have a leading negative coefficient. Examples ======== >>> from sympy.simplify.fu import as_f_sign_1 >>> from sympy.abc import x >>> as_f_sign_1(x + 1) (1, x, 1) >>> as_f_sign_1(x - 1) (1, x, -1) >>> as_f_sign_1(-x + 1) (-1, x, -1) >>> as_f_sign_1(-x - 1) (-1, x, 1) >>> as_f_sign_1(2x + 2) (2, x, 1) """ if not e.is_Add or len(e.args) != 2: return # exact match a, b = e.args if a in (S.NegativeOne, S.One): g = S.One if b.is_Mul and b.args[0].is_Number and b.args[0] < 0: a, b = -a, -b g = -g return g, b, a # gcd match a, b = [Factors(i) for i in e.args] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -1 n2 = 1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n1 = 1 n2 = -1 else: n1 = n2 = 1 a, b = [i.as_expr() for i in (ua, ub)] if a is S.One: a, b = b, a n1, n2 = n2, n1 if n1 == -1: gcd = -gcd n2 = -n2 if b is S.One: return gcd, a, n2 def _osborne(e, d): """Replace all hyperbolic functions with trig functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, HyperbolicFunction): return rv a = rv.args[0] a = ad if not a.is_Add else Add._from_args([id for i in a.args]) if isinstance(rv, sinh): return Isin(a) elif isinstance(rv, cosh): return cos(a) elif isinstance(rv, tanh): return Itan(a) elif isinstance(rv, coth): return cot(a)/I elif isinstance(rv, sech): return sec(a) elif isinstance(rv, csch): return csc(a)/I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def _osbornei(e, d): """Replace all trig functions with hyperbolic functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, TrigonometricFunction): return rv const, x = rv.args[0].as_independent(d, as_Add=True) a = x.xreplace({d: S.One}) + constI if isinstance(rv, sin): return sinh(a)/I elif isinstance(rv, cos): return cosh(a) elif isinstance(rv, tan): return tanh(a)/I elif isinstance(rv, cot): return coth(a)I elif isinstance(rv, sec): return sech(a) elif isinstance(rv, csc): return csch(a)I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def hyper_as_trig(rv): """Return an expression containing hyperbolic functions in terms of trigonometric functions. Any trigonometric functions initially present are replaced with Dummy symbols and the function to undo the masking and the conversion back to hyperbolics is also returned. It should always be true that:: t, f = hyper_as_trig(expr) expr == f(t) Examples ======== >>> from sympy.simplify.fu import hyper_as_trig, fu >>> from sympy.abc import x >>> from sympy import cosh, sinh >>> eq = sinh(x)2 + cosh(x)2 >>> t, f = hyper_as_trig(eq) >>> f(fu(t)) cosh(2x) References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ from sympy.simplify.simplify import signsimp from sympy.simplify.radsimp import collect # mask off trig functions trigs = rv.atoms(TrigonometricFunction) reps = [(t, Dummy()) for t in trigs] masked = rv.xreplace(dict(reps)) # get inversion substitutions in place reps = [(v, k) for k, v in reps] d = Dummy() return _osborne(masked, d), lambda x: collect(signsimp( _osbornei(x, d).xreplace(dict(reps))), S.ImaginaryUnit) def sincos_to_sum(expr): """Convert products and powers of sin and cos to sums. Explanation =========== Applied power reduction TRpower first, then expands products, and converts products to sums with TR8. Examples ======== >>> from sympy.simplify.fu import sincos_to_sum >>> from sympy.abc import x >>> from sympy import cos, sin >>> sincos_to_sum(16sin(x)*3cos(2x)2) 7sin(x) - 5sin(3x) + 3sin(5x) - sin(7*x) """ if not expr.has(cos, sin): return expr else: return TR8(expand_mul(TRpower(expr)))
55e107182ad69fdd4bea9061664d2eaebfee9062558cb6462b580df38506facc	""" This module cooks up a docstring when imported. Its only purpose is to be displayed in the sphinx documentation. """ from sympy import latex, Eq, hyper from sympy.simplify.hyperexpand import FormulaCollection c = FormulaCollection() doc = "" for f in c.formulae: obj = Eq(hyper(f.func.ap, f.func.bq, f.z), f.closed_form.rewrite('nonrepsmall')) doc += ".. math::\n %s\n" % latex(obj) __doc__ = doc
1ab8af4bff62a9ce031d149a748a0b74ec49773e9eb9dcad3d90fc3c5830a346	from itertools import combinations_with_replacement from sympy.core import symbols, Add, Dummy from sympy.core.numbers import Rational from sympy.polys import cancel, ComputationFailed, parallel_poly_from_expr, reduced, Poly from sympy.polys.monomials import Monomial, monomial_div from sympy.polys.polyerrors import DomainError, PolificationFailed from sympy.utilities.misc import debug def ratsimp(expr): """ Put an expression over a common denominator, cancel and reduce. Examples ======== >>> from sympy import ratsimp >>> from sympy.abc import x, y >>> ratsimp(1/x + 1/y) (x + y)/(xy) """ f, g = cancel(expr).as_numer_denom() try: Q, r = reduced(f, [g], field=True, expand=False) except ComputationFailed: return f/g return Add(Q) + cancel(r/g) def ratsimpmodprime(expr, G, gens, quick=True, polynomial=False, args): """ Simplifies a rational expression ``expr`` modulo the prime ideal generated by ``G``. ``G`` should be a Groebner basis of the ideal. Examples ======== >>> from sympy.simplify.ratsimp import ratsimpmodprime >>> from sympy.abc import x, y >>> eq = (x + y5 + y)/(x - y) >>> ratsimpmodprime(eq, [xy5 - x - y], x, y, order='lex') (-x2 - xy - x - y)/(-x2 + xy) If ``polynomial`` is ``False``, the algorithm computes a rational simplification which minimizes the sum of the total degrees of the numerator and the denominator. If ``polynomial`` is ``True``, this function just brings numerator and denominator into a canonical form. This is much faster, but has potentially worse results. References ========== .. [1] M. Monagan, R. Pearce, Rational Simplification Modulo a Polynomial Ideal, http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.163.6984 (specifically, the second algorithm) """ from sympy import solve debug('ratsimpmodprime', expr) # usual preparation of polynomials: num, denom = cancel(expr).as_numer_denom() try: polys, opt = parallel_poly_from_expr([num, denom] + G, gens, args) except PolificationFailed: return expr domain = opt.domain if domain.has_assoc_Field: opt.domain = domain.get_field() else: raise DomainError( "can't compute rational simplification over %s" % domain) # compute only once leading_monomials = [g.LM(opt.order) for g in polys[2:]] tested = set() def staircase(n): """ Compute all monomials with degree less than ``n`` that are not divisible by any element of ``leading_monomials``. """ if n == 0: return [1] S = [] for mi in combinations_with_replacement(range(len(opt.gens)), n): m = [0]len(opt.gens) for i in mi: m[i] += 1 if all([monomial_div(m, lmg) is None for lmg in leading_monomials]): S.append(m) return [Monomial(s).as_expr(opt.gens) for s in S] + staircase(n - 1) def _ratsimpmodprime(a, b, allsol, N=0, D=0): r""" Computes a rational simplification of ``a/b`` which minimizes the sum of the total degrees of the numerator and the denominator. Explanation =========== The algorithm proceeds by looking at ``a d - b * c`` modulo the ideal generated by ``G`` for some ``c`` and ``d`` with degree less than ``a`` and ``b`` respectively. The coefficients of ``c`` and ``d`` are indeterminates and thus the coefficients of the normalform of ``a * d - b * c`` are linear polynomials in these indeterminates. If these linear polynomials, considered as system of equations, have a nontrivial solution, then `\frac{a}{b} \equiv \frac{c}{d}` modulo the ideal generated by ``G``. So, by construction, the degree of ``c`` and ``d`` is less than the degree of ``a`` and ``b``, so a simpler representation has been found. After a simpler representation has been found, the algorithm tries to reduce the degree of the numerator and denominator and returns the result afterwards. As an extension, if quick=False, we look at all possible degrees such that the total degree is less than or equal to the best current solution. We retain a list of all solutions of minimal degree, and try to find the best one at the end. """ c, d = a, b steps = 0 maxdeg = a.total_degree() + b.total_degree() if quick: bound = maxdeg - 1 else: bound = maxdeg while N + D <= bound: if (N, D) in tested: break tested.add((N, D)) M1 = staircase(N) M2 = staircase(D) debug('%s / %s: %s, %s' % (N, D, M1, M2)) Cs = symbols("c:%d" % len(M1), cls=Dummy) Ds = symbols("d:%d" % len(M2), cls=Dummy) ng = Cs + Ds c_hat = Poly( sum([Cs[i] * M1[i] for i in range(len(M1))]), opt.gens + ng) d_hat = Poly( sum([Ds[i] * M2[i] for i in range(len(M2))]), opt.gens + ng) r = reduced(a * d_hat - b * c_hat, G, opt.gens + ng, order=opt.order, polys=True)[1] S = Poly(r, gens=opt.gens).coeffs() sol = solve(S, Cs + Ds, particular=True, quick=True) if sol and not all([s == 0 for s in sol.values()]): c = c_hat.subs(sol) d = d_hat.subs(sol) # The "free" variables occurring before as parameters # might still be in the substituted c, d, so set them # to the value chosen before: c = c.subs(dict(list(zip(Cs + Ds, [1] * (len(Cs) + len(Ds)))))) d = d.subs(dict(list(zip(Cs + Ds, [1] * (len(Cs) + len(Ds)))))) c = Poly(c, opt.gens) d = Poly(d, opt.gens) if d == 0: raise ValueError('Ideal not prime?') allsol.append((c_hat, d_hat, S, Cs + Ds)) if N + D != maxdeg: allsol = [allsol[-1]] break steps += 1 N += 1 D += 1 if steps > 0: c, d, allsol = _ratsimpmodprime(c, d, allsol, N, D - steps) c, d, allsol = _ratsimpmodprime(c, d, allsol, N - steps, D) return c, d, allsol # preprocessing. this improves performance a bit when deg(num) # and deg(denom) are large: num = reduced(num, G, opt.gens, order=opt.order)[1] denom = reduced(denom, G, opt.gens, order=opt.order)[1] if polynomial: return (num/denom).cancel() c, d, allsol = _ratsimpmodprime( Poly(num, opt.gens, domain=opt.domain), Poly(denom, opt.gens, domain=opt.domain), []) if not quick and allsol: debug('Looking for best minimal solution. Got: %s' % len(allsol)) newsol = [] for c_hat, d_hat, S, ng in allsol: sol = solve(S, ng, particular=True, quick=False) newsol.append((c_hat.subs(sol), d_hat.subs(sol))) c, d = min(newsol, key=lambda x: len(x[0].terms()) + len(x[1].terms())) if not domain.is_Field: cn, c = c.clear_denoms(convert=True) dn, d = d.clear_denoms(convert=True) r = Rational(cn, dn) else: r = Rational(1) return (cr.q)/(dr.p)
cab556bc3f59419547746c326c3d37caedeaaa73a68a721e961ad6c1290d80bf	from typing import Any, Set from itertools import permutations from sympy.combinatorics import Permutation from sympy.core import ( Basic, Expr, Function, diff, Pow, Mul, Add, Atom, Lambda, S, Tuple, Dict ) from sympy.core.cache import cacheit from sympy.core.compatibility import reduce from sympy.core.symbol import Symbol, Dummy from sympy.core.symbol import Str from sympy.core.sympify import _sympify from sympy.functions import factorial from sympy.matrices import ImmutableDenseMatrix as Matrix from sympy.simplify import simplify from sympy.solvers import solve from sympy.utilities.exceptions import SymPyDeprecationWarning # TODO you are a bit excessive in the use of Dummies # TODO dummy point, literal field # TODO too often one needs to call doit or simplify on the output, check the # tests and find out why from sympy.tensor.array import ImmutableDenseNDimArray class Manifold(Atom): """A mathematical manifold. Explanation =========== A manifold is a topological space that locally resembles Euclidean space near each point [1]. This class does not provide any means to study the topological characteristics of the manifold that it represents, though. Parameters ========== name : str The name of the manifold. dim : int The dimension of the manifold. Examples ======== >>> from sympy.diffgeom import Manifold >>> m = Manifold('M', 2) >>> m M >>> m.dim 2 References ========== .. [1] https://en.wikipedia.org/wiki/Manifold """ def __new__(cls, name, dim, kwargs): if not isinstance(name, Str): name = Str(name) dim = _sympify(dim) obj = super().__new__(cls, name, dim) obj.patches = _deprecated_list( "Manifold.patches", "external container for registry", 19321, "1.7", [] ) return obj @property def name(self): return self.args[0] @property def dim(self): return self.args[1] class Patch(Atom): """A patch on a manifold. Explanation =========== Coordinate patch, or patch in short, is a simply-connected open set around a point in the manifold [1]. On a manifold one can have many patches that do not always include the whole manifold. On these patches coordinate charts can be defined that permit the parameterization of any point on the patch in terms of a tuple of real numbers (the coordinates). This class does not provide any means to study the topological characteristics of the patch that it represents. Parameters ========== name : str The name of the patch. manifold : Manifold The manifold on which the patch is defined. Examples ======== >>> from sympy.diffgeom import Manifold, Patch >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> p P >>> p.dim 2 References ========== .. [1] G. Sussman, J. Wisdom, W. Farr, Functional Differential Geometry (2013) """ def __new__(cls, name, manifold, kwargs): if not isinstance(name, Str): name = Str(name) obj = super().__new__(cls, name, manifold) obj.manifold.patches.append(obj) # deprecated obj.coord_systems = _deprecated_list( "Patch.coord_systems", "external container for registry", 19321, "1.7", [] ) return obj @property def name(self): return self.args[0] @property def manifold(self): return self.args[1] @property def dim(self): return self.manifold.dim class CoordSystem(Atom): """A coordinate system defined on the patch. Explanation =========== Coordinate system is a system that uses one or more coordinates to uniquely determine the position of the points or other geometric elements on a manifold [1]. By passing Symbols to symbols parameter, user can define the name and assumptions of coordinate symbols of the coordinate system. If not passed, these symbols are generated automatically and are assumed to be real valued. By passing relations parameter, user can define the tranform relations of coordinate systems. Inverse transformation and indirect transformation can be found automatically. If this parameter is not passed, coordinate transformation cannot be done. Parameters ========== name : str The name of the coordinate system. patch : Patch The patch where the coordinate system is defined. symbols : list of Symbols, optional Defines the names and assumptions of coordinate symbols. relations : dict, optional - key : tuple of two strings, who are the names of systems where the coordinates transform from and transform to. - value : Lambda returning the transformed coordinates. Examples ======== >>> from sympy import symbols, pi, Lambda, Matrix, sqrt, atan2, cos, sin >>> from sympy.diffgeom import Manifold, Patch, CoordSystem >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> x, y = symbols('x y', real=True) >>> r, theta = symbols('r theta', nonnegative=True) >>> relation_dict = { ... ('Car2D', 'Pol'): Lambda((x, y), Matrix([sqrt(x2 + y2), atan2(y, x)])), ... ('Pol', 'Car2D'): Lambda((r, theta), Matrix([rcos(theta), rsin(theta)])) ... } >>> Car2D = CoordSystem('Car2D', p, [x, y], relation_dict) >>> Pol = CoordSystem('Pol', p, [r, theta], relation_dict) >>> Car2D Car2D >>> Car2D.dim 2 >>> Car2D.symbols [x, y] >>> Car2D.transformation(Pol) Lambda((x, y), Matrix([ [sqrt(x2 + y2)], [ atan2(y, x)]])) >>> Car2D.transform(Pol) Matrix([ [sqrt(x2 + y2)], [ atan2(y, x)]]) >>> Car2D.transform(Pol, [1, 2]) Matrix([ [sqrt(5)], [atan(2)]]) >>> Pol.jacobian(Car2D) Matrix([ [cos(theta), -rsin(theta)], [sin(theta), rcos(theta)]]) >>> Pol.jacobian(Car2D, [1, pi/2]) Matrix([ [0, -1], [1, 0]]) References ========== .. [1] https://en.wikipedia.org/wiki/Coordinate_system """ def __new__(cls, name, patch, symbols=None, relations={}, *kwargs): if not isinstance(name, Str): name = Str(name) # canonicallize the symbols if symbols is None: names = kwargs.get('names', None) if names is None: symbols = Tuple( [Symbol('%s_%s' % (name.name, i), real=True) for i in range(patch.dim)] ) else: SymPyDeprecationWarning( feature="Class signature 'names' of CoordSystem", useinstead="class signature 'symbols'", issue=19321, deprecated_since_version="1.7" ).warn() symbols = Tuple( [Symbol(n, real=True) for n in names] ) else: syms = [] for s in symbols: if isinstance(s, Symbol): syms.append(Symbol(s.name, s._assumptions.generator)) elif isinstance(s, str): SymPyDeprecationWarning( feature="Passing str as coordinate symbol's name", useinstead="Symbol which contains the name and assumption for coordinate symbol", issue=19321, deprecated_since_version="1.7" ).warn() syms.append(Symbol(s, real=True)) symbols = Tuple(syms) # canonicallize the relations rel_temp = {} for k,v in relations.items(): s1, s2 = k if not isinstance(s1, Str): s1 = Str(s1) if not isinstance(s2, Str): s2 = Str(s2) key = Tuple(s1, s2) rel_temp[key] = v relations = Dict(rel_temp) # construct the object obj = super().__new__(cls, name, patch, symbols, relations) # Add deprecated attributes obj.transforms = _deprecated_dict( "Mutable CoordSystem.transforms", "'relations' parameter in class signature", 19321, "1.7", {} ) obj._names = [str(n) for n in symbols] obj.patch.coord_systems.append(obj) # deprecated obj._dummies = [Dummy(str(n)) for n in symbols] # deprecated obj._dummy = Dummy() return obj @property def name(self): return self.args[0] @property def patch(self): return self.args[1] @property def manifold(self): return self.patch.manifold @property def symbols(self): return [ CoordinateSymbol( self, i, *s._assumptions.generator ) for i,s in enumerate(self.args[2]) ] @property def relations(self): return self.args[3] @property def dim(self): return self.patch.dim ########################################################################## # Finding transformation relation ########################################################################## def transformation(self, sys): """ Return coordinate transform relation from self* to sys as Lambda. """ if self.relations != sys.relations: raise TypeError( "Two coordinate systems have different relations") key = Tuple(self.name, sys.name) if key in self.relations: return self.relations[key] elif key[::-1] in self.relations: return self._inverse_transformation(sys, self) else: return self._indirect_transformation(self, sys) @staticmethod def _inverse_transformation(sys1, sys2): # Find the transformation relation from sys2 to sys1 forward_transform = sys1.transform(sys2) forward_syms, forward_results = forward_transform.args inv_syms = [i.as_dummy() for i in forward_syms] inv_results = solve( [t[0] - t[1] for t in zip(inv_syms, forward_results)], list(forward_syms), dict=True)[0] inv_results = [inv_results[s] for s in forward_syms] signature = tuple(inv_syms) expr = Matrix(inv_results) return Lambda(signature, expr) @classmethod @cacheit def _indirect_transformation(cls, sys1, sys2): # Find the transformation relation between two indirectly connected coordinate systems path = cls._dijkstra(sys1, sys2) Lambdas = [] for i in range(len(path) - 1): s1, s2 = path[i], path[i + 1] Lambdas.append(s1.transformation(s2)) syms = Lambdas[-1].signature expr = syms for l in reversed(Lambdas): expr = l(expr) return Lambda(syms, expr) @staticmethod def _dijkstra(sys1, sys2): # Use Dijkstra algorithm to find the shortest path between two indirectly-connected # coordinate systems relations = sys1.relations graph = {} for s1, s2 in relations.keys(): if s1 not in graph: graph[s1] = {s2} else: graph[s1].add(s2) if s2 not in graph: graph[s2] = {s1} else: graph[s2].add(s1) path_dict = {sys:[0, [], 0] for sys in graph} # minimum distance, path, times of visited def visit(sys): path_dict[sys][2] = 1 for newsys in graph[sys]: distance = path_dict[sys][0] + 1 if path_dict[newsys][0] >= distance or not path_dict[newsys][1]: path_dict[newsys][0] = distance path_dict[newsys][1] = [i for i in path_dict[sys][1]] path_dict[newsys][1].append(sys) visit(sys1) while True: min_distance = max(path_dict.values(), key=lambda x:x[0])[0] newsys = None for sys, lst in path_dict.items(): if 0 < lst[0] <= min_distance and not lst[2]: min_distance = lst[0] newsys = sys if newsys is None: break visit(newsys) result = path_dict[sys2][1] result.append(sys2) if result == [sys2]: raise KeyError("Two coordinate systems are not connected.") return result def connect_to(self, to_sys, from_coords, to_exprs, inverse=True, fill_in_gaps=False): SymPyDeprecationWarning( feature="CoordSystem.connect_to", useinstead="new instance generated with new 'transforms' parameter", issue=19321, deprecated_since_version="1.7" ).warn() from_coords, to_exprs = dummyfy(from_coords, to_exprs) self.transforms[to_sys] = Matrix(from_coords), Matrix(to_exprs) if inverse: to_sys.transforms[self] = self._inv_transf(from_coords, to_exprs) if fill_in_gaps: self._fill_gaps_in_transformations() @staticmethod def _inv_transf(from_coords, to_exprs): # Will be removed when connect_to is removed inv_from = [i.as_dummy() for i in from_coords] inv_to = solve( [t[0] - t[1] for t in zip(inv_from, to_exprs)], list(from_coords), dict=True)[0] inv_to = [inv_to[fc] for fc in from_coords] return Matrix(inv_from), Matrix(inv_to) @staticmethod def _fill_gaps_in_transformations(): # Will be removed when connect_to is removed raise NotImplementedError ########################################################################## # Coordinate transformations ########################################################################## def transform(self, sys, coordinates=None): """ Return the result of coordinate transformation from self* to sys. If coordinates are not given, coordinate symbols of self are used. """ if coordinates is None: coordinates = Matrix(self.symbols) else: coordinates = Matrix(coordinates) if self != sys: transf = self.transformation(sys) coordinates = transf(coordinates) return coordinates def coord_tuple_transform_to(self, to_sys, coords): """Transform ``coords`` to coord system ``to_sys``.""" SymPyDeprecationWarning( feature="CoordSystem.coord_tuple_transform_to", useinstead="CoordSystem.transform", issue=19321, deprecated_since_version="1.7" ).warn() coords = Matrix(coords) if self != to_sys: transf = self.transforms[to_sys] coords = transf[1].subs(list(zip(transf[0], coords))) return coords def jacobian(self, sys, coordinates=None): """ Return the jacobian matrix of a transformation. """ result = self.transform(sys).jacobian(self.symbols) if coordinates is not None: result = result.subs(list(zip(self.symbols, coordinates))) return result jacobian_matrix = jacobian def jacobian_determinant(self, sys, coordinates=None): """Return the jacobian determinant of a transformation.""" return self.jacobian(sys, coordinates).det() ########################################################################## # Points ########################################################################## def point(self, coords): """Create a ``Point`` with coordinates given in this coord system.""" return Point(self, coords) def point_to_coords(self, point): """Calculate the coordinates of a point in this coord system.""" return point.coords(self) ########################################################################## # Base fields. ########################################################################## def base_scalar(self, coord_index): """Return ``BaseScalarField`` that takes a point and returns one of the coordinates.""" return BaseScalarField(self, coord_index) coord_function = base_scalar def base_scalars(self): """Returns a list of all coordinate functions. For more details see the ``base_scalar`` method of this class.""" return [self.base_scalar(i) for i in range(self.dim)] coord_functions = base_scalars def base_vector(self, coord_index): """Return a basis vector field. The basis vector field for this coordinate system. It is also an operator on scalar fields.""" return BaseVectorField(self, coord_index) def base_vectors(self): """Returns a list of all base vectors. For more details see the ``base_vector`` method of this class.""" return [self.base_vector(i) for i in range(self.dim)] def base_oneform(self, coord_index): """Return a basis 1-form field. The basis one-form field for this coordinate system. It is also an operator on vector fields.""" return Differential(self.coord_function(coord_index)) def base_oneforms(self): """Returns a list of all base oneforms. For more details see the ``base_oneform`` method of this class.""" return [self.base_oneform(i) for i in range(self.dim)] class CoordinateSymbol(Symbol): """A symbol which denotes an abstract value of i-th coordinate of the coordinate system with given context. Explanation =========== Each coordinates in coordinate system are represented by unique symbol, such as x, y, z in Cartesian coordinate system. You may not construct this class directly. Instead, use `symbols` method of CoordSystem. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import symbols >>> from sympy.diffgeom import Manifold, Patch, CoordSystem >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> _x, _y = symbols('x y', nonnegative=True) >>> C = CoordSystem('C', p, [_x, _y]) >>> x, y = C.symbols >>> x.name 'x' >>> x.coord_sys == C True >>> x.index 0 >>> x.is_nonnegative True """ def __new__(cls, coord_sys, index, assumptions): name = coord_sys.args[2][index].name obj = super().__new__(cls, name, assumptions) obj.coord_sys = coord_sys obj.index = index return obj def __getnewargs__(self): return (self.coord_sys, self.index) def _hashable_content(self): return ( self.coord_sys, self.index ) + tuple(sorted(self.assumptions0.items())) class Point(Basic): """Point defined in a coordinate system. Explanation =========== Mathematically, point is defined in the manifold and does not have any coordinates by itself. Coordinate system is what imbues the coordinates to the point by coordinate chart. However, due to the difficulty of realizing such logic, you must supply a coordinate system and coordinates to define a Point here. The usage of this object after its definition is independent of the coordinate system that was used in order to define it, however due to limitations in the simplification routines you can arrive at complicated expressions if you use inappropriate coordinate systems. Parameters ========== coord_sys : CoordSystem coords : list The coordinates of the point. Examples ======== >>> from sympy import pi >>> from sympy.diffgeom import Point >>> from sympy.diffgeom.rn import R2, R2_r, R2_p >>> rho, theta = R2_p.symbols >>> p = Point(R2_p, [rho, 3pi/4]) >>> p.manifold == R2 True >>> p.coords() Matrix([ [ rho], [3pi/4]]) >>> p.coords(R2_r) Matrix([ [-sqrt(2)rho/2], [ sqrt(2)rho/2]]) """ def __new__(cls, coord_sys, coords, kwargs): coords = Matrix(coords) obj = super().__new__(cls, coord_sys, coords) obj._coord_sys = coord_sys obj._coords = coords return obj @property def patch(self): return self._coord_sys.patch @property def manifold(self): return self._coord_sys.manifold @property def dim(self): return self.manifold.dim def coords(self, sys=None): """ Coordinates of the point in given coordinate system. If coordinate system is not passed, it returns the coordinates in the coordinate system in which the poin was defined. """ if sys is None: return self._coords else: return self._coord_sys.transform(sys, self._coords) @property def free_symbols(self): return self._coords.free_symbols class BaseScalarField(Expr): """Base scalar field over a manifold for a given coordinate system. Explanation =========== A scalar field takes a point as an argument and returns a scalar. A base scalar field of a coordinate system takes a point and returns one of the coordinates of that point in the coordinate system in question. To define a scalar field you need to choose the coordinate system and the index of the coordinate. The use of the scalar field after its definition is independent of the coordinate system in which it was defined, however due to limitations in the simplification routines you may arrive at more complicated expression if you use unappropriate coordinate systems. You can build complicated scalar fields by just building up SymPy expressions containing ``BaseScalarField`` instances. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import Function, pi >>> from sympy.diffgeom import BaseScalarField >>> from sympy.diffgeom.rn import R2_r, R2_p >>> rho, _ = R2_p.symbols >>> point = R2_p.point([rho, 0]) >>> fx, fy = R2_r.base_scalars() >>> ftheta = BaseScalarField(R2_r, 1) >>> fx(point) rho >>> fy(point) 0 >>> (fx2+fy2).rcall(point) rho2 >>> g = Function('g') >>> fg = g(ftheta-pi) >>> fg.rcall(point) g(-pi) """ is_commutative = True def __new__(cls, coord_sys, index, kwargs): index = _sympify(index) obj = super().__new__(cls, coord_sys, index) obj._coord_sys = coord_sys obj._index = index return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def patch(self): return self.coord_sys.patch @property def manifold(self): return self.coord_sys.manifold @property def dim(self): return self.manifold.dim def __call__(self, args): """Evaluating the field at a point or doing nothing. If the argument is a ``Point`` instance, the field is evaluated at that point. The field is returned itself if the argument is any other object. It is so in order to have working recursive calling mechanics for all fields (check the ``__call__`` method of ``Expr``). """ point = args[0] if len(args) != 1 or not isinstance(point, Point): return self coords = point.coords(self._coord_sys) # XXX Calling doit is necessary with all the Subs expressions # XXX Calling simplify is necessary with all the trig expressions return simplify(coords[self._index]).doit() # XXX Workaround for limitations on the content of args free_symbols = set() # type: Set[Any] def doit(self): return self class BaseVectorField(Expr): r"""Base vector field over a manifold for a given coordinate system. Explanation =========== A vector field is an operator taking a scalar field and returning a directional derivative (which is also a scalar field). A base vector field is the same type of operator, however the derivation is specifically done with respect to a chosen coordinate. To define a base vector field you need to choose the coordinate system and the index of the coordinate. The use of the vector field after its definition is independent of the coordinate system in which it was defined, however due to limitations in the simplification routines you may arrive at more complicated expression if you use unappropriate coordinate systems. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import Function >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import BaseVectorField >>> from sympy import pprint >>> x, y = R2_r.symbols >>> rho, theta = R2_p.symbols >>> fx, fy = R2_r.base_scalars() >>> point_p = R2_p.point([rho, theta]) >>> point_r = R2_r.point([x, y]) >>> g = Function('g') >>> s_field = g(fx, fy) >>> v = BaseVectorField(R2_r, 1) >>> pprint(v(s_field)) / d \\| \|---(g(x, xi))\|\| \dxi /\|xi=y >>> pprint(v(s_field).rcall(point_r).doit()) d --(g(x, y)) dy >>> pprint(v(s_field).rcall(point_p)) / d \\| \|---(g(rhocos(theta), xi))\|\| \dxi /\|xi=rhosin(theta) """ is_commutative = False def __new__(cls, coord_sys, index, kwargs): index = _sympify(index) obj = super().__new__(cls, coord_sys, index) obj._coord_sys = coord_sys obj._index = index return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def patch(self): return self.coord_sys.patch @property def manifold(self): return self.coord_sys.manifold @property def dim(self): return self.manifold.dim def __call__(self, scalar_field): """Apply on a scalar field. The action of a vector field on a scalar field is a directional differentiation. If the argument is not a scalar field an error is raised. """ if covariant_order(scalar_field) or contravariant_order(scalar_field): raise ValueError('Only scalar fields can be supplied as arguments to vector fields.') if scalar_field is None: return self base_scalars = list(scalar_field.atoms(BaseScalarField)) # First step: e_x(x+r2) -> e_x(x) + 2re_x(r) d_var = self._coord_sys._dummy # TODO: you need a real dummy function for the next line d_funcs = [Function('_#_%s' % i)(d_var) for i, b in enumerate(base_scalars)] d_result = scalar_field.subs(list(zip(base_scalars, d_funcs))) d_result = d_result.diff(d_var) # Second step: e_x(x) -> 1 and e_x(r) -> cos(atan2(x, y)) coords = self._coord_sys.symbols d_funcs_deriv = [f.diff(d_var) for f in d_funcs] d_funcs_deriv_sub = [] for b in base_scalars: jac = self._coord_sys.jacobian(b._coord_sys, coords) d_funcs_deriv_sub.append(jac[b._index, self._index]) d_result = d_result.subs(list(zip(d_funcs_deriv, d_funcs_deriv_sub))) # Remove the dummies result = d_result.subs(list(zip(d_funcs, base_scalars))) result = result.subs(list(zip(coords, self._coord_sys.coord_functions()))) return result.doit() def _find_coords(expr): # Finds CoordinateSystems existing in expr fields = expr.atoms(BaseScalarField, BaseVectorField) result = set() for f in fields: result.add(f._coord_sys) return result class Commutator(Expr): r"""Commutator of two vector fields. Explanation =========== The commutator of two vector fields `v_1` and `v_2` is defined as the vector field `[v_1, v_2]` that evaluated on each scalar field `f` is equal to `v_1(v_2(f)) - v_2(v_1(f))`. Examples ======== >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import Commutator >>> from sympy.simplify import simplify >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> e_r = R2_p.base_vector(0) >>> c_xy = Commutator(e_x, e_y) >>> c_xr = Commutator(e_x, e_r) >>> c_xy 0 Unfortunately, the current code is not able to compute everything: >>> c_xr Commutator(e_x, e_rho) >>> simplify(c_xr(fy*2)) -2cos(theta)y2/(x2 + y2) """ def __new__(cls, v1, v2): if (covariant_order(v1) or contravariant_order(v1) != 1 or covariant_order(v2) or contravariant_order(v2) != 1): raise ValueError( 'Only commutators of vector fields are supported.') if v1 == v2: return S.Zero coord_sys = set().union([_find_coords(v) for v in (v1, v2)]) if len(coord_sys) == 1: # Only one coordinate systems is used, hence it is easy enough to # actually evaluate the commutator. if all(isinstance(v, BaseVectorField) for v in (v1, v2)): return S.Zero bases_1, bases_2 = [list(v.atoms(BaseVectorField)) for v in (v1, v2)] coeffs_1 = [v1.expand().coeff(b) for b in bases_1] coeffs_2 = [v2.expand().coeff(b) for b in bases_2] res = 0 for c1, b1 in zip(coeffs_1, bases_1): for c2, b2 in zip(coeffs_2, bases_2): res += c1b1(c2)b2 - c2b2(c1)b1 return res else: obj = super().__new__(cls, v1, v2) obj._v1 = v1 # deprecated assignment obj._v2 = v2 # deprecated assignment return obj @property def v1(self): return self.args[0] @property def v2(self): return self.args[1] def __call__(self, scalar_field): """Apply on a scalar field. If the argument is not a scalar field an error is raised. """ return self.v1(self.v2(scalar_field)) - self.v2(self.v1(scalar_field)) class Differential(Expr): r"""Return the differential (exterior derivative) of a form field. Explanation =========== The differential of a form (i.e. the exterior derivative) has a complicated definition in the general case. The differential `df` of the 0-form `f` is defined for any vector field `v` as `df(v) = v(f)`. Examples ======== >>> from sympy import Function >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import Differential >>> from sympy import pprint >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> g = Function('g') >>> s_field = g(fx, fy) >>> dg = Differential(s_field) >>> dg d(g(x, y)) >>> pprint(dg(e_x)) / d \\| \|---(g(xi, y))\|\| \dxi /\|xi=x >>> pprint(dg(e_y)) / d \\| \|---(g(x, xi))\|\| \dxi /\|xi=y Applying the exterior derivative operator twice always results in: >>> Differential(dg) 0 """ is_commutative = False def __new__(cls, form_field): if contravariant_order(form_field): raise ValueError( 'A vector field was supplied as an argument to Differential.') if isinstance(form_field, Differential): return S.Zero else: obj = super().__new__(cls, form_field) obj._form_field = form_field # deprecated assignment return obj @property def form_field(self): return self.args[0] def __call__(self, vector_fields): """Apply on a list of vector_fields. Explanation =========== If the number of vector fields supplied is not equal to 1 + the order of the form field inside the differential the result is undefined. For 1-forms (i.e. differentials of scalar fields) the evaluation is done as `df(v)=v(f)`. However if `v` is ``None`` instead of a vector field, the differential is returned unchanged. This is done in order to permit partial contractions for higher forms. In the general case the evaluation is done by applying the form field inside the differential on a list with one less elements than the number of elements in the original list. Lowering the number of vector fields is achieved through replacing each pair of fields by their commutator. If the arguments are not vectors or ``None``s an error is raised. """ if any((contravariant_order(a) != 1 or covariant_order(a)) and a is not None for a in vector_fields): raise ValueError('The arguments supplied to Differential should be vector fields or Nones.') k = len(vector_fields) if k == 1: if vector_fields[0]: return vector_fields[0].rcall(self._form_field) return self else: # For higher form it is more complicated: # Invariant formula: # https://en.wikipedia.org/wiki/Exterior_derivative#Invariant_formula # df(v1, ... vn) = +/- vi(f(v1..no i..vn)) # +/- f([vi,vj],v1..no i, no j..vn) f = self._form_field v = vector_fields ret = 0 for i in range(k): t = v[i].rcall(f.rcall(v[:i] + v[i + 1:])) ret += (-1)*it for j in range(i + 1, k): c = Commutator(v[i], v[j]) if c: # TODO this is ugly - the Commutator can be Zero and # this causes the next line to fail t = f.rcall((c,) + v[:i] + v[i + 1:j] + v[j + 1:]) ret += (-1)(i + j)t return ret class TensorProduct(Expr): """Tensor product of forms. Explanation =========== The tensor product permits the creation of multilinear functionals (i.e. higher order tensors) out of lower order fields (e.g. 1-forms and vector fields). However, the higher tensors thus created lack the interesting features provided by the other type of product, the wedge product, namely they are not antisymmetric and hence are not form fields. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> TensorProduct(dx, dy)(e_x, e_y) 1 >>> TensorProduct(dx, dy)(e_y, e_x) 0 >>> TensorProduct(dx, fxdy)(fxe_x, e_y) x2 >>> TensorProduct(e_x, e_y)(fx2, fy*2) 4xy >>> TensorProduct(e_y, dx)(fy) dx You can nest tensor products. >>> tp1 = TensorProduct(dx, dy) >>> TensorProduct(tp1, dx)(e_x, e_y, e_x) 1 You can make partial contraction for instance when 'raising an index'. Putting ``None`` in the second argument of ``rcall`` means that the respective position in the tensor product is left as it is. >>> TP = TensorProduct >>> metric = TP(dx, dx) + 3TP(dy, dy) >>> metric.rcall(e_y, None) 3dy Or automatically pad the args with ``None`` without specifying them. >>> metric.rcall(e_y) 3dy """ def __new__(cls, args): scalar = Mul([m for m in args if covariant_order(m) + contravariant_order(m) == 0]) multifields = [m for m in args if covariant_order(m) + contravariant_order(m)] if multifields: if len(multifields) == 1: return scalarmultifields[0] return scalarsuper().__new__(cls, multifields) else: return scalar def __call__(self, fields): """Apply on a list of fields. If the number of input fields supplied is not equal to the order of the tensor product field, the list of arguments is padded with ``None``'s. The list of arguments is divided in sublists depending on the order of the forms inside the tensor product. The sublists are provided as arguments to these forms and the resulting expressions are given to the constructor of ``TensorProduct``. """ tot_order = covariant_order(self) + contravariant_order(self) tot_args = len(fields) if tot_args != tot_order: fields = list(fields) + [None](tot_order - tot_args) orders = [covariant_order(f) + contravariant_order(f) for f in self._args] indices = [sum(orders[:i + 1]) for i in range(len(orders) - 1)] fields = [fields[i:j] for i, j in zip([0] + indices, indices + [None])] multipliers = [t[0].rcall(t[1]) for t in zip(self._args, fields)] return TensorProduct(multipliers) class WedgeProduct(TensorProduct): """Wedge product of forms. Explanation =========== In the context of integration only completely antisymmetric forms make sense. The wedge product permits the creation of such forms. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import WedgeProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> WedgeProduct(dx, dy)(e_x, e_y) 1 >>> WedgeProduct(dx, dy)(e_y, e_x) -1 >>> WedgeProduct(dx, fxdy)(fxe_x, e_y) x2 >>> WedgeProduct(e_x, e_y)(fy, None) -e_x You can nest wedge products. >>> wp1 = WedgeProduct(dx, dy) >>> WedgeProduct(wp1, dx)(e_x, e_y, e_x) 0 """ # TODO the calculation of signatures is slow # TODO you do not need all these permutations (neither the prefactor) def __call__(self, fields): """Apply on a list of vector_fields. The expression is rewritten internally in terms of tensor products and evaluated.""" orders = (covariant_order(e) + contravariant_order(e) for e in self.args) mul = 1/Mul((factorial(o) for o in orders)) perms = permutations(fields) perms_par = (Permutation( p).signature() for p in permutations(list(range(len(fields))))) tensor_prod = TensorProduct(self.args) return mulAdd([tensor_prod(p[0])p[1] for p in zip(perms, perms_par)]) class LieDerivative(Expr): """Lie derivative with respect to a vector field. Explanation =========== The transport operator that defines the Lie derivative is the pushforward of the field to be derived along the integral curve of the field with respect to which one derives. Examples ======== >>> from sympy.diffgeom.rn import R2_r, R2_p >>> from sympy.diffgeom import (LieDerivative, TensorProduct) >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> e_rho, e_theta = R2_p.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> LieDerivative(e_x, fy) 0 >>> LieDerivative(e_x, fx) 1 >>> LieDerivative(e_x, e_x) 0 The Lie derivative of a tensor field by another tensor field is equal to their commutator: >>> LieDerivative(e_x, e_rho) Commutator(e_x, e_rho) >>> LieDerivative(e_x + e_y, fx) 1 >>> tp = TensorProduct(dx, dy) >>> LieDerivative(e_x, tp) LieDerivative(e_x, TensorProduct(dx, dy)) >>> LieDerivative(e_x, tp) LieDerivative(e_x, TensorProduct(dx, dy)) """ def __new__(cls, v_field, expr): expr_form_ord = covariant_order(expr) if contravariant_order(v_field) != 1 or covariant_order(v_field): raise ValueError('Lie derivatives are defined only with respect to' ' vector fields. The supplied argument was not a ' 'vector field.') if expr_form_ord > 0: obj = super().__new__(cls, v_field, expr) # deprecated assignments obj._v_field = v_field obj._expr = expr return obj if expr.atoms(BaseVectorField): return Commutator(v_field, expr) else: return v_field.rcall(expr) @property def v_field(self): return self.args[0] @property def expr(self): return self.args[1] def __call__(self, args): v = self.v_field expr = self.expr lead_term = v(expr(args)) rest = Add([Mul(args[:i] + (Commutator(v, args[i]),) + args[i + 1:]) for i in range(len(args))]) return lead_term - rest class BaseCovarDerivativeOp(Expr): """Covariant derivative operator with respect to a base vector. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import BaseCovarDerivativeOp >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> ch = metric_to_Christoffel_2nd(TP(dx, dx) + TP(dy, dy)) >>> ch [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> cvd = BaseCovarDerivativeOp(R2_r, 0, ch) >>> cvd(fx) 1 >>> cvd(fxe_x) e_x """ def __new__(cls, coord_sys, index, christoffel): index = _sympify(index) christoffel = ImmutableDenseNDimArray(christoffel) obj = super().__new__(cls, coord_sys, index, christoffel) # deprecated assignments obj._coord_sys = coord_sys obj._index = index obj._christoffel = christoffel return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def christoffel(self): return self.args[2] def __call__(self, field): """Apply on a scalar field. The action of a vector field on a scalar field is a directional differentiation. If the argument is not a scalar field the behaviour is undefined. """ if covariant_order(field) != 0: raise NotImplementedError() field = vectors_in_basis(field, self._coord_sys) wrt_vector = self._coord_sys.base_vector(self._index) wrt_scalar = self._coord_sys.coord_function(self._index) vectors = list(field.atoms(BaseVectorField)) # First step: replace all vectors with something susceptible to # derivation and do the derivation # TODO: you need a real dummy function for the next line d_funcs = [Function('_#_%s' % i)(wrt_scalar) for i, b in enumerate(vectors)] d_result = field.subs(list(zip(vectors, d_funcs))) d_result = wrt_vector(d_result) # Second step: backsubstitute the vectors in d_result = d_result.subs(list(zip(d_funcs, vectors))) # Third step: evaluate the derivatives of the vectors derivs = [] for v in vectors: d = Add([(self._christoffel[k, wrt_vector._index, v._index] v._coord_sys.base_vector(k)) for k in range(v._coord_sys.dim)]) derivs.append(d) to_subs = [wrt_vector(d) for d in d_funcs] # XXX: This substitution can fail when there are Dummy symbols and the # cache is disabled: https://github.com/sympy/sympy/issues/17794 result = d_result.subs(list(zip(to_subs, derivs))) # Remove the dummies result = result.subs(list(zip(d_funcs, vectors))) return result.doit() class CovarDerivativeOp(Expr): """Covariant derivative operator. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import CovarDerivativeOp >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> ch = metric_to_Christoffel_2nd(TP(dx, dx) + TP(dy, dy)) >>> ch [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> cvd = CovarDerivativeOp(fxe_x, ch) >>> cvd(fx) x >>> cvd(fxe_x) xe_x """ def __new__(cls, wrt, christoffel): if len({v._coord_sys for v in wrt.atoms(BaseVectorField)}) > 1: raise NotImplementedError() if contravariant_order(wrt) != 1 or covariant_order(wrt): raise ValueError('Covariant derivatives are defined only with ' 'respect to vector fields. The supplied argument ' 'was not a vector field.') obj = super().__new__(cls, wrt, christoffel) # deprecated assigments obj._wrt = wrt obj._christoffel = christoffel return obj @property def wrt(self): return self.args[0] @property def christoffel(self): return self.args[1] def __call__(self, field): vectors = list(self._wrt.atoms(BaseVectorField)) base_ops = [BaseCovarDerivativeOp(v._coord_sys, v._index, self._christoffel) for v in vectors] return self._wrt.subs(list(zip(vectors, base_ops))).rcall(field) ############################################################################### # Integral curves on vector fields ############################################################################### def intcurve_series(vector_field, param, start_point, n=6, coord_sys=None, coeffs=False): r"""Return the series expansion for an integral curve of the field. Explanation =========== Integral curve is a function `\gamma` taking a parameter in `R` to a point in the manifold. It verifies the equation: `V(f)\big(\gamma(t)\big) = \frac{d}{dt}f\big(\gamma(t)\big)` where the given ``vector_field`` is denoted as `V`. This holds for any value `t` for the parameter and any scalar field `f`. This equation can also be decomposed of a basis of coordinate functions `V(f_i)\big(\gamma(t)\big) = \frac{d}{dt}f_i\big(\gamma(t)\big) \quad \forall i` This function returns a series expansion of `\gamma(t)` in terms of the coordinate system ``coord_sys``. The equations and expansions are necessarily done in coordinate-system-dependent way as there is no other way to represent movement between points on the manifold (i.e. there is no such thing as a difference of points for a general manifold). Parameters ========== vector_field the vector field for which an integral curve will be given param the argument of the function `\gamma` from R to the curve start_point the point which corresponds to `\gamma(0)` n the order to which to expand coord_sys the coordinate system in which to expand coeffs (default False) - if True return a list of elements of the expansion Examples ======== Use the predefined R2 manifold: >>> from sympy.abc import t, x, y >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import intcurve_series Specify a starting point and a vector field: >>> start_point = R2_r.point([x, y]) >>> vector_field = R2_r.e_x Calculate the series: >>> intcurve_series(vector_field, t, start_point, n=3) Matrix([ [t + x], [ y]]) Or get the elements of the expansion in a list: >>> series = intcurve_series(vector_field, t, start_point, n=3, coeffs=True) >>> series[0] Matrix([ [x], [y]]) >>> series[1] Matrix([ [t], [0]]) >>> series[2] Matrix([ [0], [0]]) The series in the polar coordinate system: >>> series = intcurve_series(vector_field, t, start_point, ... n=3, coord_sys=R2_p, coeffs=True) >>> series[0] Matrix([ [sqrt(x2 + y2)], [ atan2(y, x)]]) >>> series[1] Matrix([ [tx/sqrt(x2 + y2)], [ -ty/(x2 + y2)]]) >>> series[2] Matrix([ [t*2(-x2/(x2 + y2)(3/2) + 1/sqrt(x2 + y2))/2], [ t*2xy/(x2 + y2)2]]) See Also ======== intcurve_diffequ """ if contravariant_order(vector_field) != 1 or covariant_order(vector_field): raise ValueError('The supplied field was not a vector field.') def iter_vfield(scalar_field, i): """Return ``vector_field`` called `i` times on ``scalar_field``.""" return reduce(lambda s, v: v.rcall(s), [vector_field, ]i, scalar_field) def taylor_terms_per_coord(coord_function): """Return the series for one of the coordinates.""" return [param*iiter_vfield(coord_function, i).rcall(start_point)/factorial(i) for i in range(n)] coord_sys = coord_sys if coord_sys else start_point._coord_sys coord_functions = coord_sys.coord_functions() taylor_terms = [taylor_terms_per_coord(f) for f in coord_functions] if coeffs: return [Matrix(t) for t in zip(taylor_terms)] else: return Matrix([sum(c) for c in taylor_terms]) def intcurve_diffequ(vector_field, param, start_point, coord_sys=None): r"""Return the differential equation for an integral curve of the field. Explanation =========== Integral curve is a function `\gamma` taking a parameter in `R` to a point in the manifold. It verifies the equation: `V(f)\big(\gamma(t)\big) = \frac{d}{dt}f\big(\gamma(t)\big)` where the given ``vector_field`` is denoted as `V`. This holds for any value `t` for the parameter and any scalar field `f`. This function returns the differential equation of `\gamma(t)` in terms of the coordinate system ``coord_sys``. The equations and expansions are necessarily done in coordinate-system-dependent way as there is no other way to represent movement between points on the manifold (i.e. there is no such thing as a difference of points for a general manifold). Parameters ========== vector_field the vector field for which an integral curve will be given param the argument of the function `\gamma` from R to the curve start_point the point which corresponds to `\gamma(0)` coord_sys the coordinate system in which to give the equations Returns ======= a tuple of (equations, initial conditions) Examples ======== Use the predefined R2 manifold: >>> from sympy.abc import t >>> from sympy.diffgeom.rn import R2, R2_p, R2_r >>> from sympy.diffgeom import intcurve_diffequ Specify a starting point and a vector field: >>> start_point = R2_r.point([0, 1]) >>> vector_field = -R2.yR2.e_x + R2.xR2.e_y Get the equation: >>> equations, init_cond = intcurve_diffequ(vector_field, t, start_point) >>> equations [f_1(t) + Derivative(f_0(t), t), -f_0(t) + Derivative(f_1(t), t)] >>> init_cond [f_0(0), f_1(0) - 1] The series in the polar coordinate system: >>> equations, init_cond = intcurve_diffequ(vector_field, t, start_point, R2_p) >>> equations [Derivative(f_0(t), t), Derivative(f_1(t), t) - 1] >>> init_cond [f_0(0) - 1, f_1(0) - pi/2] See Also ======== intcurve_series """ if contravariant_order(vector_field) != 1 or covariant_order(vector_field): raise ValueError('The supplied field was not a vector field.') coord_sys = coord_sys if coord_sys else start_point._coord_sys gammas = [Function('f_%d' % i)(param) for i in range( start_point._coord_sys.dim)] arbitrary_p = Point(coord_sys, gammas) coord_functions = coord_sys.coord_functions() equations = [simplify(diff(cf.rcall(arbitrary_p), param) - vector_field.rcall(cf).rcall(arbitrary_p)) for cf in coord_functions] init_cond = [simplify(cf.rcall(arbitrary_p).subs(param, 0) - cf.rcall(start_point)) for cf in coord_functions] return equations, init_cond ############################################################################### # Helpers ############################################################################### def dummyfy(args, exprs): # TODO Is this a good idea? d_args = Matrix([s.as_dummy() for s in args]) reps = dict(zip(args, d_args)) d_exprs = Matrix([_sympify(expr).subs(reps) for expr in exprs]) return d_args, d_exprs ############################################################################### # Helpers ############################################################################### def contravariant_order(expr, _strict=False): """Return the contravariant order of an expression. Examples ======== >>> from sympy.diffgeom import contravariant_order >>> from sympy.diffgeom.rn import R2 >>> from sympy.abc import a >>> contravariant_order(a) 0 >>> contravariant_order(aR2.x + 2) 0 >>> contravariant_order(aR2.xR2.e_y + R2.e_x) 1 """ # TODO move some of this to class methods. # TODO rewrite using the .as_blah_blah methods if isinstance(expr, Add): orders = [contravariant_order(e) for e in expr.args] if len(set(orders)) != 1: raise ValueError('Misformed expression containing contravariant fields of varying order.') return orders[0] elif isinstance(expr, Mul): orders = [contravariant_order(e) for e in expr.args] not_zero = [o for o in orders if o != 0] if len(not_zero) > 1: raise ValueError('Misformed expression containing multiplication between vectors.') return 0 if not not_zero else not_zero[0] elif isinstance(expr, Pow): if covariant_order(expr.base) or covariant_order(expr.exp): raise ValueError( 'Misformed expression containing a power of a vector.') return 0 elif isinstance(expr, BaseVectorField): return 1 elif isinstance(expr, TensorProduct): return sum(contravariant_order(a) for a in expr.args) elif not _strict or expr.atoms(BaseScalarField): return 0 else: # If it does not contain anything related to the diffgeom module and it is _strict return -1 def covariant_order(expr, _strict=False): """Return the covariant order of an expression. Examples ======== >>> from sympy.diffgeom import covariant_order >>> from sympy.diffgeom.rn import R2 >>> from sympy.abc import a >>> covariant_order(a) 0 >>> covariant_order(aR2.x + 2) 0 >>> covariant_order(aR2.xR2.dy + R2.dx) 1 """ # TODO move some of this to class methods. # TODO rewrite using the .as_blah_blah methods if isinstance(expr, Add): orders = [covariant_order(e) for e in expr.args] if len(set(orders)) != 1: raise ValueError('Misformed expression containing form fields of varying order.') return orders[0] elif isinstance(expr, Mul): orders = [covariant_order(e) for e in expr.args] not_zero = [o for o in orders if o != 0] if len(not_zero) > 1: raise ValueError('Misformed expression containing multiplication between forms.') return 0 if not not_zero else not_zero[0] elif isinstance(expr, Pow): if covariant_order(expr.base) or covariant_order(expr.exp): raise ValueError( 'Misformed expression containing a power of a form.') return 0 elif isinstance(expr, Differential): return covariant_order(expr.args) + 1 elif isinstance(expr, TensorProduct): return sum(covariant_order(a) for a in expr.args) elif not _strict or expr.atoms(BaseScalarField): return 0 else: # If it does not contain anything related to the diffgeom module and it is _strict return -1 ############################################################################### # Coordinate transformation functions ############################################################################### def vectors_in_basis(expr, to_sys): """Transform all base vectors in base vectors of a specified coord basis. While the new base vectors are in the new coordinate system basis, any coefficients are kept in the old system. Examples ======== >>> from sympy.diffgeom import vectors_in_basis >>> from sympy.diffgeom.rn import R2_r, R2_p >>> vectors_in_basis(R2_r.e_x, R2_p) -ye_theta/(x2 + y2) + xe_rho/sqrt(x2 + y2) >>> vectors_in_basis(R2_p.e_r, R2_r) sin(theta)e_y + cos(theta)e_x """ vectors = list(expr.atoms(BaseVectorField)) new_vectors = [] for v in vectors: cs = v._coord_sys jac = cs.jacobian(to_sys, cs.coord_functions()) new = (jac.TMatrix(to_sys.base_vectors()))[v._index] new_vectors.append(new) return expr.subs(list(zip(vectors, new_vectors))) ############################################################################### # Coordinate-dependent functions ############################################################################### def twoform_to_matrix(expr): """Return the matrix representing the twoform. For the twoform `w` return the matrix `M` such that `M[i,j]=w(e_i, e_j)`, where `e_i` is the i-th base vector field for the coordinate system in which the expression of `w` is given. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import twoform_to_matrix, TensorProduct >>> TP = TensorProduct >>> twoform_to_matrix(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) Matrix([ [1, 0], [0, 1]]) >>> twoform_to_matrix(R2.xTP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) Matrix([ [x, 0], [0, 1]]) >>> twoform_to_matrix(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy) - TP(R2.dx, R2.dy)/2) Matrix([ [ 1, 0], [-1/2, 1]]) """ if covariant_order(expr) != 2 or contravariant_order(expr): raise ValueError('The input expression is not a two-form.') coord_sys = _find_coords(expr) if len(coord_sys) != 1: raise ValueError('The input expression concerns more than one ' 'coordinate systems, hence there is no unambiguous ' 'way to choose a coordinate system for the matrix.') coord_sys = coord_sys.pop() vectors = coord_sys.base_vectors() expr = expr.expand() matrix_content = [[expr.rcall(v1, v2) for v1 in vectors] for v2 in vectors] return Matrix(matrix_content) def metric_to_Christoffel_1st(expr): """Return the nested list of Christoffel symbols for the given metric. This returns the Christoffel symbol of first kind that represents the Levi-Civita connection for the given metric. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Christoffel_1st, TensorProduct >>> TP = TensorProduct >>> metric_to_Christoffel_1st(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> metric_to_Christoffel_1st(R2.xTP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[1/2, 0], [0, 0]], [[0, 0], [0, 0]]] """ matrix = twoform_to_matrix(expr) if not matrix.is_symmetric(): raise ValueError( 'The two-form representing the metric is not symmetric.') coord_sys = _find_coords(expr).pop() deriv_matrices = [matrix.applyfunc(lambda a: d(a)) for d in coord_sys.base_vectors()] indices = list(range(coord_sys.dim)) christoffel = [[[(deriv_matrices[k][i, j] + deriv_matrices[j][i, k] - deriv_matrices[i][j, k])/2 for k in indices] for j in indices] for i in indices] return ImmutableDenseNDimArray(christoffel) def metric_to_Christoffel_2nd(expr): """Return the nested list of Christoffel symbols for the given metric. This returns the Christoffel symbol of second kind that represents the Levi-Civita connection for the given metric. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> metric_to_Christoffel_2nd(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> metric_to_Christoffel_2nd(R2.xTP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[1/(2x), 0], [0, 0]], [[0, 0], [0, 0]]] """ ch_1st = metric_to_Christoffel_1st(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) # XXX workaround, inverting a matrix does not work if it contains non # symbols #matrix = twoform_to_matrix(expr).inv() matrix = twoform_to_matrix(expr) s_fields = set() for e in matrix: s_fields.update(e.atoms(BaseScalarField)) s_fields = list(s_fields) dums = coord_sys.symbols matrix = matrix.subs(list(zip(s_fields, dums))).inv().subs(list(zip(dums, s_fields))) # XXX end of workaround christoffel = [[[Add([matrix[i, l]ch_1st[l, j, k] for l in indices]) for k in indices] for j in indices] for i in indices] return ImmutableDenseNDimArray(christoffel) def metric_to_Riemann_components(expr): """Return the components of the Riemann tensor expressed in a given basis. Given a metric it calculates the components of the Riemann tensor in the canonical basis of the coordinate system in which the metric expression is given. Examples ======== >>> from sympy import exp >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Riemann_components, TensorProduct >>> TP = TensorProduct >>> metric_to_Riemann_components(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[[0, 0], [0, 0]], [[0, 0], [0, 0]]], [[[0, 0], [0, 0]], [[0, 0], [0, 0]]]] >>> non_trivial_metric = exp(2R2.r)TP(R2.dr, R2.dr) + \ R2.r2TP(R2.dtheta, R2.dtheta) >>> non_trivial_metric exp(2rho)TensorProduct(drho, drho) + rho*2TensorProduct(dtheta, dtheta) >>> riemann = metric_to_Riemann_components(non_trivial_metric) >>> riemann[0, :, :, :] [[[0, 0], [0, 0]], [[0, exp(-2rho)rho], [-exp(-2rho)rho, 0]]] >>> riemann[1, :, :, :] [[[0, -1/rho], [1/rho, 0]], [[0, 0], [0, 0]]] """ ch_2nd = metric_to_Christoffel_2nd(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) deriv_ch = [[[[d(ch_2nd[i, j, k]) for d in coord_sys.base_vectors()] for k in indices] for j in indices] for i in indices] riemann_a = [[[[deriv_ch[rho][sig][nu][mu] - deriv_ch[rho][sig][mu][nu] for nu in indices] for mu in indices] for sig in indices] for rho in indices] riemann_b = [[[[Add([ch_2nd[rho, l, mu]ch_2nd[l, sig, nu] - ch_2nd[rho, l, nu]ch_2nd[l, sig, mu] for l in indices]) for nu in indices] for mu in indices] for sig in indices] for rho in indices] riemann = [[[[riemann_a[rho][sig][mu][nu] + riemann_b[rho][sig][mu][nu] for nu in indices] for mu in indices] for sig in indices] for rho in indices] return ImmutableDenseNDimArray(riemann) def metric_to_Ricci_components(expr): """Return the components of the Ricci tensor expressed in a given basis. Given a metric it calculates the components of the Ricci tensor in the canonical basis of the coordinate system in which the metric expression is given. Examples ======== >>> from sympy import exp >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Ricci_components, TensorProduct >>> TP = TensorProduct >>> metric_to_Ricci_components(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[0, 0], [0, 0]] >>> non_trivial_metric = exp(2R2.r)TP(R2.dr, R2.dr) + \ R2.r2TP(R2.dtheta, R2.dtheta) >>> non_trivial_metric exp(2rho)TensorProduct(drho, drho) + rho*2TensorProduct(dtheta, dtheta) >>> metric_to_Ricci_components(non_trivial_metric) [[1/rho, 0], [0, exp(-2rho)rho]] """ riemann = metric_to_Riemann_components(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) ricci = [[Add(*[riemann[k, i, k, j] for k in indices]) for j in indices] for i in indices] return ImmutableDenseNDimArray(ricci) ############################################################################### # Classes for deprecation ############################################################################### class _deprecated_container: # This class gives deprecation warning. # When deprecated features are completely deleted, this should be removed as well. # See https://github.com/sympy/sympy/pull/19368 def __init__(self, feature, useinstead, issue, version, data): super().__init__(data) self.feature = feature self.useinstead = useinstead self.issue = issue self.version = version def warn(self): SymPyDeprecationWarning( feature=self.feature, useinstead=self.useinstead, issue=self.issue, deprecated_since_version=self.version).warn() def __iter__(self): self.warn() return super().__iter__() def __getitem__(self, key): self.warn() return super().__getitem__(key) def __contains__(self, key): self.warn() return super().__contains__(key) class _deprecated_list(_deprecated_container, list): pass class _deprecated_dict(_deprecated_container, dict): pass
e41fcf0c8e414118cb92fc5bd29ab382457035653c415a29bdf5ac158d9c48c9	""" AST nodes specific to the C family of languages """ from sympy.codegen.ast import ( Attribute, Declaration, Node, String, Token, Type, none, FunctionCall, CodeBlock ) from sympy.core.basic import Basic from sympy.core.containers import Tuple from sympy.core.sympify import sympify void = Type('void') restrict = Attribute('restrict') # guarantees no pointer aliasing volatile = Attribute('volatile') static = Attribute('static') def alignof(arg): """ Generate of FunctionCall instance for calling 'alignof' """ return FunctionCall('alignof', [String(arg) if isinstance(arg, str) else arg]) def sizeof(arg): """ Generate of FunctionCall instance for calling 'sizeof' Examples ======== >>> from sympy.codegen.ast import real >>> from sympy.codegen.cnodes import sizeof >>> from sympy.printing import ccode >>> ccode(sizeof(real)) 'sizeof(double)' """ return FunctionCall('sizeof', [String(arg) if isinstance(arg, str) else arg]) class CommaOperator(Basic): """ Represents the comma operator in C """ def __new__(cls, args): return Basic.__new__(cls, [sympify(arg) for arg in args]) class Label(Node): """ Label for use with e.g. goto statement. Examples ======== >>> from sympy import Symbol >>> from sympy.codegen.cnodes import Label, PreIncrement >>> from sympy.printing import ccode >>> print(ccode(Label('foo'))) foo: >>> print(ccode(Label('bar', [PreIncrement(Symbol('a'))]))) bar: ++(a); """ __slots__ = ('name', 'body') defaults = {'body': none} _construct_name = String @classmethod def _construct_body(cls, itr): if isinstance(itr, CodeBlock): return itr else: return CodeBlock(itr) class goto(Token): """ Represents goto in C """ __slots__ = ('label',) _construct_label = Label class PreDecrement(Basic): """ Represents the pre-decrement operator Examples ======== >>> from sympy.abc import x >>> from sympy.codegen.cnodes import PreDecrement >>> from sympy.printing import ccode >>> ccode(PreDecrement(x)) '--(x)' """ nargs = 1 class PostDecrement(Basic): """ Represents the post-decrement operator """ nargs = 1 class PreIncrement(Basic): """ Represents the pre-increment operator """ nargs = 1 class PostIncrement(Basic): """ Represents the post-increment operator """ nargs = 1 class struct(Node): """ Represents a struct in C """ __slots__ = ('name', 'declarations') defaults = {'name': none} _construct_name = String @classmethod def _construct_declarations(cls, args): return Tuple([Declaration(arg) for arg in args]) class union(struct): """ Represents a union in C """
7ea671bab2fca64a2d592c8f137a7460a29848eb7c40afa0cb1c0176202f1380	import bisect import itertools from functools import reduce from collections import defaultdict from sympy import Indexed, IndexedBase, Tuple, Sum, Add, S, Integer, diagonalize_vector, DiagMatrix from sympy.combinatorics import Permutation from sympy.core.basic import Basic from sympy.core.compatibility import accumulate, default_sort_key from sympy.core.mul import Mul from sympy.core.sympify import _sympify from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.matrices.expressions import (MatAdd, MatMul, Trace, Transpose, MatrixSymbol) from sympy.matrices.expressions.matexpr import MatrixExpr, MatrixElement from sympy.tensor.array import NDimArray class _CodegenArrayAbstract(Basic): @property def subranks(self): """ Returns the ranks of the objects in the uppermost tensor product inside the current object. In case no tensor products are contained, return the atomic ranks. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayTensorProduct, CodegenArrayContraction >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> P = MatrixSymbol("P", 3, 3) Important: do not confuse the rank of the matrix with the rank of an array. >>> tp = CodegenArrayTensorProduct(M, N, P) >>> tp.subranks [2, 2, 2] >>> co = CodegenArrayContraction(tp, (1, 2), (3, 4)) >>> co.subranks [2, 2, 2] """ return self._subranks[:] def subrank(self): """ The sum of ``subranks``. """ return sum(self.subranks) @property def shape(self): return self._shape class CodegenArrayContraction(_CodegenArrayAbstract): r""" This class is meant to represent contractions of arrays in a form easily processable by the code printers. """ def __new__(cls, expr, contraction_indices, kwargs): contraction_indices = _sort_contraction_indices(contraction_indices) expr = _sympify(expr) if len(contraction_indices) == 0: return expr if isinstance(expr, CodegenArrayContraction): return cls._flatten(expr, contraction_indices) obj = Basic.__new__(cls, expr, contraction_indices) obj._subranks = _get_subranks(expr) obj._mapping = _get_mapping_from_subranks(obj._subranks) free_indices_to_position = {i: i for i in range(sum(obj._subranks)) if all([i not in cind for cind in contraction_indices])} obj._free_indices_to_position = free_indices_to_position shape = expr.shape cls._validate(expr, contraction_indices) if shape: shape = tuple(shp for i, shp in enumerate(shape) if not any(i in j for j in contraction_indices)) obj._shape = shape return obj def __mul__(self, other): if other == 1: return self else: raise NotImplementedError("Product of N-dim arrays is not uniquely defined. Use another method.") def __rmul__(self, other): if other == 1: return self else: raise NotImplementedError("Product of N-dim arrays is not uniquely defined. Use another method.") @staticmethod def _validate(expr, contraction_indices): shape = expr.shape if shape is None: return # Check that no contraction happens when the shape is mismatched: for i in contraction_indices: if len({shape[j] for j in i if shape[j] != -1}) != 1: raise ValueError("contracting indices of different dimensions") @classmethod def _push_indices_down(cls, contraction_indices, indices): flattened_contraction_indices = [j for i in contraction_indices for j in i] flattened_contraction_indices.sort() transform = _build_push_indices_down_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) @classmethod def _push_indices_up(cls, contraction_indices, indices): flattened_contraction_indices = [j for i in contraction_indices for j in i] flattened_contraction_indices.sort() transform = _build_push_indices_up_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) def split_multiple_contractions(self): """ Recognize multiple contractions and attempt at rewriting them as paired-contractions. """ from sympy import ask, Q contraction_indices = self.contraction_indices if isinstance(self.expr, CodegenArrayTensorProduct): args = list(self.expr.args) else: args = [self.expr] # TODO: unify API, best location in CodegenArrayTensorProduct subranks = [get_rank(i) for i in args] # TODO: unify API mapping = _get_mapping_from_subranks(subranks) reverse_mapping = {v:k for k, v in mapping.items()} new_contraction_indices = [] for indl, links in enumerate(contraction_indices): if len(links) <= 2: new_contraction_indices.append(links) continue # Check multiple contractions: # # Examples: # # `A_ij b_j0 C_jk` ===> `ADiagMatrix(b)C` # # Care for: # - matrix being diagonalized (i.e. `A_ii`) # - vectors being diagonalized (i.e. `a_i0`) # Also consider the case of diagonal matrices being contracted: current_dimension = self.expr.shape[links[0]] tuple_links = [mapping[i] for i in links] arg_indices, arg_positions = zip(tuple_links) args_updates = {} if len(arg_indices) != len(set(arg_indices)): # Maybe trace should be supported? raise NotImplementedError not_vectors = [] vectors = [] for arg_ind, arg_pos in tuple_links: mat = args[arg_ind] other_arg_pos = 1-arg_pos other_arg_abs = reverse_mapping[arg_ind, other_arg_pos] if (((1 not in mat.shape) and (not ask(Q.diagonal(mat)))) or ((current_dimension == 1) is True and mat.shape != (1, 1)) or any([other_arg_abs in l for li, l in enumerate(contraction_indices) if li != indl]) ): not_vectors.append((arg_ind, arg_pos)) continue args_updates[arg_ind] = diagonalize_vector(mat) vectors.append((arg_ind, arg_pos)) vectors.append((arg_ind, 1-arg_pos)) if len(not_vectors) > 2: new_contraction_indices.append(links) continue if len(not_vectors) == 0: new_sequence = vectors[:1] + vectors[2:] elif len(not_vectors) == 1: new_sequence = not_vectors[:1] + vectors[:-1] else: new_sequence = not_vectors[:1] + vectors + not_vectors[1:] for i in range(0, len(new_sequence) - 1, 2): arg1, pos1 = new_sequence[i] arg2, pos2 = new_sequence[i+1] if arg1 == arg2: raise NotImplementedError continue abspos1 = reverse_mapping[arg1, pos1] abspos2 = reverse_mapping[arg2, pos2] new_contraction_indices.append((abspos1, abspos2)) for ind, newarg in args_updates.items(): args[ind] = newarg return CodegenArrayContraction( CodegenArrayTensorProduct(args), new_contraction_indices ) def flatten_contraction_of_diagonal(self): if not isinstance(self.expr, CodegenArrayDiagonal): return self contraction_down = self.expr._push_indices_down(self.expr.diagonal_indices, self.contraction_indices) new_contraction_indices = [] diagonal_indices = self.expr.diagonal_indices[:] for i in contraction_down: contraction_group = list(i) for j in i: diagonal_with = [k for k in diagonal_indices if j in k] contraction_group.extend([l for k in diagonal_with for l in k]) diagonal_indices = [k for k in diagonal_indices if k not in diagonal_with] new_contraction_indices.append(sorted(set(contraction_group))) new_contraction_indices = CodegenArrayDiagonal._push_indices_up(diagonal_indices, new_contraction_indices) return CodegenArrayContraction( CodegenArrayDiagonal( self.expr.expr, diagonal_indices ), new_contraction_indices ) @staticmethod def _get_free_indices_to_position_map(free_indices, contraction_indices): free_indices_to_position = {} flattened_contraction_indices = [j for i in contraction_indices for j in i] counter = 0 for ind in free_indices: while counter in flattened_contraction_indices: counter += 1 free_indices_to_position[ind] = counter counter += 1 return free_indices_to_position @staticmethod def _get_index_shifts(expr): """ Get the mapping of indices at the positions before the contraction occurs. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(M, N), [1, 2]) >>> cg._get_index_shifts(cg) [0, 2] Indeed, ``cg`` after the contraction has two dimensions, 0 and 1. They need to be shifted by 0 and 2 to get the corresponding positions before the contraction (that is, 0 and 3). """ inner_contraction_indices = expr.contraction_indices all_inner = [j for i in inner_contraction_indices for j in i] all_inner.sort() # TODO: add API for total rank and cumulative rank: total_rank = _get_subrank(expr) inner_rank = len(all_inner) outer_rank = total_rank - inner_rank shifts = [0 for i in range(outer_rank)] counter = 0 pointer = 0 for i in range(outer_rank): while pointer < inner_rank and counter >= all_inner[pointer]: counter += 1 pointer += 1 shifts[i] += pointer counter += 1 return shifts @staticmethod def _convert_outer_indices_to_inner_indices(expr, outer_contraction_indices): shifts = CodegenArrayContraction._get_index_shifts(expr) outer_contraction_indices = tuple(tuple(shifts[j] + j for j in i) for i in outer_contraction_indices) return outer_contraction_indices @staticmethod def _flatten(expr, outer_contraction_indices): inner_contraction_indices = expr.contraction_indices outer_contraction_indices = CodegenArrayContraction._convert_outer_indices_to_inner_indices(expr, outer_contraction_indices) contraction_indices = inner_contraction_indices + outer_contraction_indices return CodegenArrayContraction(expr.expr, contraction_indices) def _get_contraction_tuples(self): r""" Return tuples containing the argument index and position within the argument of the index position. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(A, B), (1, 2)) >>> cg._get_contraction_tuples() [[(0, 1), (1, 0)]] Here the contraction pair `(1, 2)` meaning that the 2nd and 3rd indices of the tensor product `A\otimes B` are contracted, has been transformed into `(0, 1)` and `(1, 0)`, identifying the same indices in a different notation. `(0, 1)` is the second index (1) of the first argument (i.e. 0 or `A`). `(1, 0)` is the first index (i.e. 0) of the second argument (i.e. 1 or `B`). """ mapping = self._mapping return [[mapping[j] for j in i] for i in self.contraction_indices] @staticmethod def _contraction_tuples_to_contraction_indices(expr, contraction_tuples): # TODO: check that `expr` has `.subranks`: ranks = expr.subranks cumulative_ranks = [0] + list(accumulate(ranks)) return [tuple(cumulative_ranks[j]+k for j, k in i) for i in contraction_tuples] @property def free_indices(self): return self._free_indices[:] @property def free_indices_to_position(self): return dict(self._free_indices_to_position) @property def expr(self): return self.args[0] @property def contraction_indices(self): return self.args[1:] def _contraction_indices_to_components(self): expr = self.expr if not isinstance(expr, CodegenArrayTensorProduct): raise NotImplementedError("only for contractions of tensor products") ranks = expr.subranks mapping = {} counter = 0 for i, rank in enumerate(ranks): for j in range(rank): mapping[counter] = (i, j) counter += 1 return mapping def sort_args_by_name(self): """ Sort arguments in the tensor product so that their order is lexicographical. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) >>> cg = parse_matrix_expression(CDAB) >>> cg CodegenArrayContraction(CodegenArrayTensorProduct(C, D, A, B), (1, 2), (3, 4), (5, 6)) >>> cg.sort_args_by_name() CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (0, 7), (1, 2), (5, 6)) """ expr = self.expr if not isinstance(expr, CodegenArrayTensorProduct): return self args = expr.args sorted_data = sorted(enumerate(args), key=lambda x: default_sort_key(x[1])) pos_sorted, args_sorted = zip(sorted_data) reordering_map = {i: pos_sorted.index(i) for i, arg in enumerate(args)} contraction_tuples = self._get_contraction_tuples() contraction_tuples = [[(reordering_map[j], k) for j, k in i] for i in contraction_tuples] c_tp = CodegenArrayTensorProduct(args_sorted) new_contr_indices = self._contraction_tuples_to_contraction_indices( c_tp, contraction_tuples ) return CodegenArrayContraction(c_tp, new_contr_indices) def _get_contraction_links(self): r""" Returns a dictionary of links between arguments in the tensor product being contracted. See the example for an explanation of the values. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) Matrix multiplications are pairwise contractions between neighboring matrices: `A_{ij} B_{jk} C_{kl} D_{lm}` >>> cg = parse_matrix_expression(ABCD) >>> cg CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (1, 2), (3, 4), (5, 6)) >>> cg._get_contraction_links() {0: {1: (1, 0)}, 1: {0: (0, 1), 1: (2, 0)}, 2: {0: (1, 1), 1: (3, 0)}, 3: {0: (2, 1)}} This dictionary is interpreted as follows: argument in position 0 (i.e. matrix `A`) has its second index (i.e. 1) contracted to `(1, 0)`, that is argument in position 1 (matrix `B`) on the first index slot of `B`, this is the contraction provided by the index `j` from `A`. The argument in position 1 (that is, matrix `B`) has two contractions, the ones provided by the indices `j` and `k`, respectively the first and second indices (0 and 1 in the sub-dict). The link `(0, 1)` and `(2, 0)` respectively. `(0, 1)` is the index slot 1 (the 2nd) of argument in position 0 (that is, `A_{\ldot j}`), and so on. """ args, dlinks = _get_contraction_links([self], self.subranks, self.contraction_indices) return dlinks def get_shape(expr): if hasattr(expr, "shape"): return expr.shape return () class CodegenArrayTensorProduct(_CodegenArrayAbstract): r""" Class to represent the tensor product of array-like objects. """ def __new__(cls, args): args = [_sympify(arg) for arg in args] args = cls._flatten(args) ranks = [_get_subrank(arg) for arg in args] if len(args) == 1: return args[0] # If there are contraction objects inside, transform the whole # expression into `CodegenArrayContraction`: contractions = {i: arg for i, arg in enumerate(args) if isinstance(arg, CodegenArrayContraction)} if contractions: cumulative_ranks = list(accumulate([0] + ranks))[:-1] tp = cls([arg.expr if isinstance(arg, CodegenArrayContraction) else arg for arg in args]) contraction_indices = [tuple(cumulative_ranks[i] + k for k in j) for i, arg in contractions.items() for j in arg.contraction_indices] return CodegenArrayContraction(tp, contraction_indices) #newargs = [i for i in args if hasattr(i, "shape")] #coeff = reduce(lambda x, y: xy, [i for i in args if not hasattr(i, "shape")], S.One) #newargs[0] = coeff obj = Basic.__new__(cls, args) obj._subranks = ranks shapes = [get_shape(i) for i in args] if any(i is None for i in shapes): obj._shape = None else: obj._shape = tuple(j for i in shapes for j in i) return obj @classmethod def _flatten(cls, args): args = [i for arg in args for i in (arg.args if isinstance(arg, cls) else [arg])] return args class CodegenArrayElementwiseAdd(_CodegenArrayAbstract): r""" Class for elementwise array additions. """ def __new__(cls, args): args = [_sympify(arg) for arg in args] obj = Basic.__new__(cls, args) ranks = [get_rank(arg) for arg in args] ranks = list(set(ranks)) if len(ranks) != 1: raise ValueError("summing arrays of different ranks") obj._subranks = ranks shapes = [arg.shape for arg in args] if len({i for i in shapes if i is not None}) > 1: raise ValueError("mismatching shapes in addition") if any(i is None for i in shapes): obj._shape = None else: obj._shape = shapes[0] return obj class CodegenArrayPermuteDims(_CodegenArrayAbstract): r""" Class to represent permutation of axes of arrays. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayPermuteDims >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> cg = CodegenArrayPermuteDims(M, [1, 0]) The object ``cg`` represents the transposition of ``M``, as the permutation ``[1, 0]`` will act on its indices by switching them: `M_{ij} \Rightarrow M_{ji}` This is evident when transforming back to matrix form: >>> from sympy.codegen.array_utils import recognize_matrix_expression >>> recognize_matrix_expression(cg) M.T >>> N = MatrixSymbol("N", 3, 2) >>> cg = CodegenArrayPermuteDims(N, [1, 0]) >>> cg.shape (2, 3) """ def __new__(cls, expr, permutation): from sympy.combinatorics import Permutation expr = _sympify(expr) permutation = Permutation(permutation) plist = permutation.array_form if plist == sorted(plist): return expr obj = Basic.__new__(cls, expr, permutation) obj._subranks = [get_rank(expr)] shape = expr.shape if shape is None: obj._shape = None else: obj._shape = tuple(shape[permutation(i)] for i in range(len(shape))) return obj @property def expr(self): return self.args[0] @property def permutation(self): return self.args[1] def nest_permutation(self): r""" Nest the permutation down the expression tree. Examples ======== >>> from sympy.codegen.array_utils import (CodegenArrayPermuteDims, CodegenArrayTensorProduct, nest_permutation) >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> cg = CodegenArrayPermuteDims(CodegenArrayTensorProduct(M, N), [1, 0, 3, 2]) >>> cg CodegenArrayPermuteDims(CodegenArrayTensorProduct(M, N), (0 1)(2 3)) >>> nest_permutation(cg) CodegenArrayTensorProduct(CodegenArrayPermuteDims(M, (0 1)), CodegenArrayPermuteDims(N, (0 1))) In ``cg`` both ``M`` and ``N`` are transposed. The cyclic representation of the permutation after the tensor product is `(0 1)(2 3)`. After nesting it down the expression tree, the usual transposition permutation `(0 1)` appears. """ expr = self.expr if isinstance(expr, CodegenArrayTensorProduct): # Check if the permutation keeps the subranks separated: subranks = expr.subranks subrank = expr.subrank() l = list(range(subrank)) p = [self.permutation(i) for i in l] dargs = {} counter = 0 for i, arg in zip(subranks, expr.args): p0 = p[counter:counter+i] counter += i s0 = sorted(p0) if not all([s0[j+1]-s0[j] == 1 for j in range(len(s0)-1)]): # Cross-argument permutations, impossible to nest the object: return self subpermutation = [p0.index(j) for j in s0] dargs[s0[0]] = CodegenArrayPermuteDims(arg, subpermutation) # Read the arguments sorting the according to the keys of the dict: args = [dargs[i] for i in sorted(dargs)] return CodegenArrayTensorProduct(args) elif isinstance(expr, CodegenArrayContraction): # Invert tree hierarchy: put the contraction above. cycles = self.permutation.cyclic_form newcycles = CodegenArrayContraction._convert_outer_indices_to_inner_indices(expr, cycles) newpermutation = Permutation(newcycles) new_contr_indices = [tuple(newpermutation(j) for j in i) for i in expr.contraction_indices] return CodegenArrayContraction(CodegenArrayPermuteDims(expr.expr, newpermutation), new_contr_indices) elif isinstance(expr, CodegenArrayElementwiseAdd): return CodegenArrayElementwiseAdd([CodegenArrayPermuteDims(arg, self.permutation) for arg in expr.args]) return self def nest_permutation(expr): if isinstance(expr, CodegenArrayPermuteDims): return expr.nest_permutation() else: return expr class CodegenArrayDiagonal(_CodegenArrayAbstract): r""" Class to represent the diagonal operator. In a 2-dimensional array it returns the diagonal, this looks like the operation: `A_{ij} \rightarrow A_{ii}` The diagonal over axes 1 and 2 (the second and third) of the tensor product of two 2-dimensional arrays `A \otimes B` is `\Big[ A_{ab} B_{cd} \Big]_{abcd} \rightarrow \Big[ A_{ai} B_{id} \Big]_{adi}` In this last example the array expression has been reduced from 4-dimensional to 3-dimensional. Notice that no contraction has occurred, rather there is a new index `i` for the diagonal, contraction would have reduced the array to 2 dimensions. Notice that the diagonalized out dimensions are added as new dimensions at the end of the indices. """ def __new__(cls, expr, diagonal_indices): expr = _sympify(expr) diagonal_indices = [Tuple(sorted(i)) for i in diagonal_indices] if isinstance(expr, CodegenArrayDiagonal): return cls._flatten(expr, diagonal_indices) shape = expr.shape if shape is not None: diagonal_indices = [i for i in diagonal_indices if len(i) > 1] cls._validate(expr, diagonal_indices) #diagonal_indices = cls._remove_trivial_dimensions(shape, diagonal_indices) # Get new shape: shp1 = tuple(shp for i,shp in enumerate(shape) if not any(i in j for j in diagonal_indices)) shp2 = tuple(shape[i[0]] for i in diagonal_indices) shape = shp1 + shp2 if len(diagonal_indices) == 0: return expr obj = Basic.__new__(cls, expr, diagonal_indices) obj._subranks = _get_subranks(expr) obj._shape = shape return obj @staticmethod def _validate(expr, diagonal_indices): # Check that no diagonalization happens on indices with mismatched # dimensions: shape = expr.shape for i in diagonal_indices: if len({shape[j] for j in i}) != 1: raise ValueError("diagonalizing indices of different dimensions") @staticmethod def _remove_trivial_dimensions(shape, diagonal_indices): return [tuple(j for j in i) for i in diagonal_indices if shape[i[0]] != 1] @property def expr(self): return self.args[0] @property def diagonal_indices(self): return self.args[1:] @staticmethod def _flatten(expr, outer_diagonal_indices): inner_diagonal_indices = expr.diagonal_indices all_inner = [j for i in inner_diagonal_indices for j in i] all_inner.sort() # TODO: add API for total rank and cumulative rank: total_rank = _get_subrank(expr) inner_rank = len(all_inner) outer_rank = total_rank - inner_rank shifts = [0 for i in range(outer_rank)] counter = 0 pointer = 0 for i in range(outer_rank): while pointer < inner_rank and counter >= all_inner[pointer]: counter += 1 pointer += 1 shifts[i] += pointer counter += 1 outer_diagonal_indices = tuple(tuple(shifts[j] + j for j in i) for i in outer_diagonal_indices) diagonal_indices = inner_diagonal_indices + outer_diagonal_indices return CodegenArrayDiagonal(expr.expr, diagonal_indices) @classmethod def _push_indices_down(cls, diagonal_indices, indices): flattened_contraction_indices = [j for i in diagonal_indices for j in i[1:]] flattened_contraction_indices.sort() transform = _build_push_indices_down_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) @classmethod def _push_indices_up(cls, diagonal_indices, indices): flattened_contraction_indices = [j for i in diagonal_indices for j in i[1:]] flattened_contraction_indices.sort() transform = _build_push_indices_up_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) def transform_to_product(self): from sympy import ask, Q diagonal_indices = self.diagonal_indices if isinstance(self.expr, CodegenArrayContraction): # invert Diagonal and Contraction: diagonal_down = CodegenArrayContraction._push_indices_down( self.expr.contraction_indices, diagonal_indices ) newexpr = CodegenArrayDiagonal( self.expr.expr, diagonal_down ).transform_to_product() contraction_up = newexpr._push_indices_up( diagonal_down, self.expr.contraction_indices ) return CodegenArrayContraction( newexpr, contraction_up ) if not isinstance(self.expr, CodegenArrayTensorProduct): return self args = list(self.expr.args) # TODO: unify API subranks = [get_rank(i) for i in args] # TODO: unify API mapping = _get_mapping_from_subranks(subranks) new_contraction_indices = [] drop_diagonal_indices = [] for indl, links in enumerate(diagonal_indices): if len(links) > 2: continue # Also consider the case of diagonal matrices being contracted: current_dimension = self.expr.shape[links[0]] if current_dimension == 1: drop_diagonal_indices.append(indl) continue tuple_links = [mapping[i] for i in links] arg_indices, arg_positions = zip(tuple_links) if len(arg_indices) != len(set(arg_indices)): # Maybe trace should be supported? raise NotImplementedError args_updates = {} count_nondiagonal = 0 last = None expression_is_square = False # Check that all args are vectors: for arg_ind, arg_pos in tuple_links: mat = args[arg_ind] if 1 in mat.shape and mat.shape != (1, 1): args_updates[arg_ind] = DiagMatrix(mat) last = arg_ind else: expression_is_square = True if not ask(Q.diagonal(mat)): count_nondiagonal += 1 if count_nondiagonal > 1: break if count_nondiagonal > 1: continue # TODO: if count_nondiagonal == 0 then the sub-expression can be recognized as HadamardProduct. for arg_ind, newmat in args_updates.items(): if not expression_is_square and arg_ind == last: continue #pass args[arg_ind] = newmat drop_diagonal_indices.append(indl) new_contraction_indices.append(links) new_diagonal_indices = CodegenArrayContraction._push_indices_up( new_contraction_indices, [e for i, e in enumerate(diagonal_indices) if i not in drop_diagonal_indices] ) return CodegenArrayDiagonal( CodegenArrayContraction( CodegenArrayTensorProduct(args), new_contraction_indices ), new_diagonal_indices ) def get_rank(expr): if isinstance(expr, (MatrixExpr, MatrixElement)): return 2 if isinstance(expr, _CodegenArrayAbstract): return len(expr.shape) if isinstance(expr, NDimArray): return expr.rank() if isinstance(expr, Indexed): return expr.rank if isinstance(expr, IndexedBase): shape = expr.shape if shape is None: return -1 else: return len(shape) if isinstance(expr, _RecognizeMatOp): return expr.rank() if isinstance(expr, _RecognizeMatMulLines): return expr.rank() return 0 def _get_subrank(expr): if isinstance(expr, _CodegenArrayAbstract): return expr.subrank() return get_rank(expr) def _get_subranks(expr): if isinstance(expr, _CodegenArrayAbstract): return expr.subranks else: return [get_rank(expr)] def _get_mapping_from_subranks(subranks): mapping = {} counter = 0 for i, rank in enumerate(subranks): for j in range(rank): mapping[counter] = (i, j) counter += 1 return mapping def _get_contraction_links(args, subranks, contraction_indices): mapping = _get_mapping_from_subranks(subranks) contraction_tuples = [[mapping[j] for j in i] for i in contraction_indices] dlinks = defaultdict(dict) for links in contraction_tuples: if len(links) == 2: (arg1, pos1), (arg2, pos2) = links dlinks[arg1][pos1] = (arg2, pos2) dlinks[arg2][pos2] = (arg1, pos1) continue return args, dict(dlinks) def _sort_contraction_indices(pairing_indices): pairing_indices = [Tuple(sorted(i)) for i in pairing_indices] pairing_indices.sort(key=lambda x: min(x)) return pairing_indices def _get_diagonal_indices(flattened_indices): axes_contraction = defaultdict(list) for i, ind in enumerate(flattened_indices): if isinstance(ind, (int, Integer)): # If the indices is a number, there can be no diagonal operation: continue axes_contraction[ind].append(i) axes_contraction = {k: v for k, v in axes_contraction.items() if len(v) > 1} # Put the diagonalized indices at the end: ret_indices = [i for i in flattened_indices if i not in axes_contraction] diag_indices = list(axes_contraction) diag_indices.sort(key=lambda x: flattened_indices.index(x)) diagonal_indices = [tuple(axes_contraction[i]) for i in diag_indices] ret_indices += diag_indices ret_indices = tuple(ret_indices) return diagonal_indices, ret_indices def _get_argindex(subindices, ind): for i, sind in enumerate(subindices): if ind == sind: return i if isinstance(sind, (set, frozenset)) and ind in sind: return i raise IndexError("%s not found in %s" % (ind, subindices)) def _codegen_array_parse(expr): if isinstance(expr, Sum): function = expr.function summation_indices = expr.variables subexpr, subindices = _codegen_array_parse(function) # Check dimensional consistency: shape = subexpr.shape if shape: for ind, istart, iend in expr.limits: i = _get_argindex(subindices, ind) if istart != 0 or iend+1 != shape[i]: raise ValueError("summation index and array dimension mismatch: %s" % ind) contraction_indices = [] subindices = list(subindices) if isinstance(subexpr, CodegenArrayDiagonal): diagonal_indices = list(subexpr.diagonal_indices) dindices = subindices[-len(diagonal_indices):] subindices = subindices[:-len(diagonal_indices)] for index in summation_indices: if index in dindices: position = dindices.index(index) contraction_indices.append(diagonal_indices[position]) diagonal_indices[position] = None diagonal_indices = [i for i in diagonal_indices if i is not None] for i, ind in enumerate(subindices): if ind in summation_indices: pass if diagonal_indices: subexpr = CodegenArrayDiagonal(subexpr.expr, diagonal_indices) else: subexpr = subexpr.expr axes_contraction = defaultdict(list) for i, ind in enumerate(subindices): if ind in summation_indices: axes_contraction[ind].append(i) subindices[i] = None for k, v in axes_contraction.items(): contraction_indices.append(tuple(v)) free_indices = [i for i in subindices if i is not None] indices_ret = list(free_indices) indices_ret.sort(key=lambda x: free_indices.index(x)) return CodegenArrayContraction( subexpr, contraction_indices, free_indices=free_indices ), tuple(indices_ret) if isinstance(expr, Mul): args, indices = zip([_codegen_array_parse(arg) for arg in expr.args]) # Check if there are KroneckerDelta objects: kronecker_delta_repl = {} for arg in args: if not isinstance(arg, KroneckerDelta): continue # Diagonalize two indices: i, j = arg.indices kindices = set(arg.indices) if i in kronecker_delta_repl: kindices.update(kronecker_delta_repl[i]) if j in kronecker_delta_repl: kindices.update(kronecker_delta_repl[j]) kindices = frozenset(kindices) for index in kindices: kronecker_delta_repl[index] = kindices # Remove KroneckerDelta objects, their relations should be handled by # CodegenArrayDiagonal: newargs = [] newindices = [] for arg, loc_indices in zip(args, indices): if isinstance(arg, KroneckerDelta): continue newargs.append(arg) newindices.append(loc_indices) flattened_indices = [kronecker_delta_repl.get(j, j) for i in newindices for j in i] diagonal_indices, ret_indices = _get_diagonal_indices(flattened_indices) tp = CodegenArrayTensorProduct(newargs) if diagonal_indices: return (CodegenArrayDiagonal(tp, diagonal_indices), ret_indices) else: return tp, ret_indices if isinstance(expr, MatrixElement): indices = expr.args[1:] diagonal_indices, ret_indices = _get_diagonal_indices(indices) if diagonal_indices: return (CodegenArrayDiagonal(expr.args[0], diagonal_indices), ret_indices) else: return expr.args[0], ret_indices if isinstance(expr, Indexed): indices = expr.indices diagonal_indices, ret_indices = _get_diagonal_indices(indices) if diagonal_indices: return (CodegenArrayDiagonal(expr.base, diagonal_indices), ret_indices) else: return expr.args[0], ret_indices if isinstance(expr, IndexedBase): raise NotImplementedError if isinstance(expr, KroneckerDelta): return expr, expr.indices if isinstance(expr, Add): args, indices = zip([_codegen_array_parse(arg) for arg in expr.args]) args = list(args) # Check if all indices are compatible. Otherwise expand the dimensions: index0set = set(indices[0]) index0 = indices[0] for i in range(1, len(args)): if set(indices[i]) != index0set: raise NotImplementedError("indices must be the same") permutation = Permutation([index0.index(j) for j in indices[i]]) # Perform index permutations: args[i] = CodegenArrayPermuteDims(args[i], permutation) return CodegenArrayElementwiseAdd(args), index0 return expr, () def parse_matrix_expression(expr: MatrixExpr) -> Basic: if isinstance(expr, MatMul): args_nonmat = [] args = [] for arg in expr.args: if isinstance(arg, MatrixExpr): args.append(arg) else: args_nonmat.append(arg) contractions = [(2i+1, 2i+2) for i in range(len(args)-1)] scalar = Mul.fromiter(args_nonmat) if scalar == 1: tprod = CodegenArrayTensorProduct( [parse_matrix_expression(arg) for arg in args]) else: tprod = CodegenArrayTensorProduct( scalar, [parse_matrix_expression(arg) for arg in args]) return CodegenArrayContraction( tprod, contractions ) elif isinstance(expr, MatAdd): return CodegenArrayElementwiseAdd( [parse_matrix_expression(arg) for arg in expr.args] ) elif isinstance(expr, Transpose): return CodegenArrayPermuteDims( parse_matrix_expression(expr.args[0]), [1, 0] ) elif isinstance(expr, Trace): inner_expr = parse_matrix_expression(expr.arg) return CodegenArrayContraction(inner_expr, (0, len(inner_expr.shape) - 1)) else: return expr def parse_indexed_expression(expr, first_indices=None): r""" Parse indexed expression into a form useful for code generation. Examples ======== >>> from sympy.codegen.array_utils import parse_indexed_expression >>> from sympy import MatrixSymbol, Sum, symbols >>> i, j, k, d = symbols("i j k d") >>> M = MatrixSymbol("M", d, d) >>> N = MatrixSymbol("N", d, d) Recognize the trace in summation form: >>> expr = Sum(M[i, i], (i, 0, d-1)) >>> parse_indexed_expression(expr) CodegenArrayContraction(M, (0, 1)) Recognize the extraction of the diagonal by using the same index `i` on both axes of the matrix: >>> expr = M[i, i] >>> parse_indexed_expression(expr) CodegenArrayDiagonal(M, (0, 1)) This function can help perform the transformation expressed in two different mathematical notations as: `\sum_{j=0}^{N-1} A_{i,j} B_{j,k} \Longrightarrow \mathbf{A}\cdot \mathbf{B}` Recognize the matrix multiplication in summation form: >>> expr = Sum(M[i, j]N[j, k], (j, 0, d-1)) >>> parse_indexed_expression(expr) CodegenArrayContraction(CodegenArrayTensorProduct(M, N), (1, 2)) Specify that ``k`` has to be the starting index: >>> parse_indexed_expression(expr, first_indices=[k]) CodegenArrayPermuteDims(CodegenArrayContraction(CodegenArrayTensorProduct(M, N), (1, 2)), (0 1)) """ result, indices = _codegen_array_parse(expr) if not first_indices: return result for i in first_indices: if i not in indices: first_indices.remove(i) #raise ValueError("index %s not found or not a free index" % i) first_indices.extend([i for i in indices if i not in first_indices]) permutation = [first_indices.index(i) for i in indices] return CodegenArrayPermuteDims(result, permutation) def _has_multiple_lines(expr): if isinstance(expr, _RecognizeMatMulLines): return True if isinstance(expr, _RecognizeMatOp): return expr.multiple_lines return False class _RecognizeMatOp: """ Class to help parsing matrix multiplication lines. """ def __init__(self, operator, args): self.operator = operator self.args = args if any(_has_multiple_lines(arg) for arg in args): multiple_lines = True else: multiple_lines = False self.multiple_lines = multiple_lines def rank(self): if self.operator == Trace: return 0 # TODO: check return 2 def __repr__(self): op = self.operator if op == MatMul: s = "" elif op == MatAdd: s = "+" else: s = op.__name__ return "_RecognizeMatOp(%s, %s)" % (s, repr(self.args)) return "_RecognizeMatOp(%s)" % (s.join(repr(i) for i in self.args)) def __eq__(self, other): if not isinstance(other, type(self)): return False if self.operator != other.operator: return False if self.args != other.args: return False return True def __iter__(self): return iter(self.args) class _RecognizeMatMulLines(list): """ This class handles multiple parsed multiplication lines. """ def __new__(cls, args): if len(args) == 1: return args[0] return list.__new__(cls, args) def rank(self): return reduce(lambda x, y: xy, [get_rank(i) for i in self], S.One) def __repr__(self): return "_RecognizeMatMulLines(%s)" % super().__repr__() def _support_function_tp1_recognize(contraction_indices, args): if not isinstance(args, list): args = [args] subranks = [get_rank(i) for i in args] coeff = reduce(lambda x, y: xy, [arg for arg, srank in zip(args, subranks) if srank == 0], S.One) mapping = _get_mapping_from_subranks(subranks) reverse_mapping = {v:k for k, v in mapping.items()} args, dlinks = _get_contraction_links(args, subranks, contraction_indices) flatten_contractions = [j for i in contraction_indices for j in i] total_rank = sum(subranks) # TODO: turn `free_indices` into a list? free_indices = {i: i for i in range(total_rank) if i not in flatten_contractions} return_list = [] while dlinks: if free_indices: first_index, starting_argind = min(free_indices.items(), key=lambda x: x[1]) free_indices.pop(first_index) starting_argind, starting_pos = mapping[starting_argind] else: # Maybe a Trace first_index = None starting_argind = min(dlinks) starting_pos = 0 current_argind, current_pos = starting_argind, starting_pos matmul_args = [] last_index = None while True: elem = args[current_argind] if current_pos == 1: elem = _RecognizeMatOp(Transpose, [elem]) matmul_args.append(elem) other_pos = 1 - current_pos if current_argind not in dlinks: other_absolute = reverse_mapping[current_argind, other_pos] free_indices.pop(other_absolute, None) break link_dict = dlinks.pop(current_argind) if other_pos not in link_dict: if free_indices: last_index = [i for i, j in free_indices.items() if mapping[j] == (current_argind, other_pos)][0] else: last_index = None break if len(link_dict) > 2: raise NotImplementedError("not a matrix multiplication line") # Get the last element of `link_dict` as the next link. The last # element is the correct start for trace expressions: current_argind, current_pos = link_dict[other_pos] if current_argind == starting_argind: # This is a trace: if len(matmul_args) > 1: matmul_args = [_RecognizeMatOp(Trace, [_RecognizeMatOp(MatMul, matmul_args)])] elif args[current_argind].shape != (1, 1): matmul_args = [_RecognizeMatOp(Trace, matmul_args)] break dlinks.pop(starting_argind, None) free_indices.pop(last_index, None) return_list.append(_RecognizeMatOp(MatMul, matmul_args)) if coeff != 1: # Let's inject the coefficient: return_list[0].args.insert(0, coeff) return _RecognizeMatMulLines(return_list) def recognize_matrix_expression(expr): r""" Recognize matrix expressions in codegen objects. If more than one matrix multiplication line have been detected, return a list with the matrix expressions. Examples ======== >>> from sympy import MatrixSymbol, Sum >>> from sympy.abc import i, j, k, l, N >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> from sympy.codegen.array_utils import recognize_matrix_expression, parse_indexed_expression, parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) >>> expr = Sum(A[i, j]B[j, k], (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) AB >>> cg = parse_indexed_expression(expr, first_indices=[k]) >>> recognize_matrix_expression(cg) (AB).T Transposition is detected: >>> expr = Sum(A[j, i]B[j, k], (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) A.TB >>> cg = parse_indexed_expression(expr, first_indices=[k]) >>> recognize_matrix_expression(cg) (A.TB).T Detect the trace: >>> expr = Sum(A[i, i], (i, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) Trace(A) Recognize some more complex traces: >>> expr = Sum(A[i, j]B[j, i], (i, 0, N-1), (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) Trace(AB) More complicated expressions: >>> expr = Sum(A[i, j]B[k, j]A[l, k], (j, 0, N-1), (k, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) AB.TA.T Expressions constructed from matrix expressions do not contain literal indices, the positions of free indices are returned instead: >>> expr = AB >>> cg = parse_matrix_expression(expr) >>> recognize_matrix_expression(cg) AB If more than one line of matrix multiplications is detected, return separate matrix multiplication factors: >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (1, 2), (5, 6)) >>> recognize_matrix_expression(cg) [AB, CD] The two lines have free indices at axes 0, 3 and 4, 7, respectively. """ # TODO: expr has to be a CodegenArray... type rec = _recognize_matrix_expression(expr) return _unfold_recognized_expr(rec) def _recognize_matrix_expression(expr): if isinstance(expr, CodegenArrayContraction): # Apply some transformations: expr = expr.flatten_contraction_of_diagonal() expr = expr.split_multiple_contractions() args = _recognize_matrix_expression(expr.expr) contraction_indices = expr.contraction_indices if isinstance(args, _RecognizeMatOp) and args.operator == MatAdd: addends = [] for arg in args.args: addends.append(_support_function_tp1_recognize(contraction_indices, arg)) return _RecognizeMatOp(MatAdd, addends) elif isinstance(args, _RecognizeMatMulLines): return _support_function_tp1_recognize(contraction_indices, args) return _support_function_tp1_recognize(contraction_indices, [args]) elif isinstance(expr, CodegenArrayElementwiseAdd): add_args = [] for arg in expr.args: add_args.append(_recognize_matrix_expression(arg)) return _RecognizeMatOp(MatAdd, add_args) elif isinstance(expr, (MatrixSymbol, IndexedBase)): return expr elif isinstance(expr, CodegenArrayPermuteDims): if expr.permutation.array_form == [1, 0]: return _RecognizeMatOp(Transpose, [_recognize_matrix_expression(expr.expr)]) elif isinstance(expr.expr, CodegenArrayTensorProduct): ranks = expr.expr.subranks newrange = [expr.permutation(i) for i in range(sum(ranks))] newpos = [] counter = 0 for rank in ranks: newpos.append(newrange[counter:counter+rank]) counter += rank newargs = [] for pos, arg in zip(newpos, expr.expr.args): if pos == sorted(pos): newargs.append((_recognize_matrix_expression(arg), pos[0])) elif len(pos) == 2: newargs.append((_RecognizeMatOp(Transpose, [_recognize_matrix_expression(arg)]), pos[0])) else: raise NotImplementedError newargs.sort(key=lambda x: x[1]) newargs = [i[0] for i in newargs] return _RecognizeMatMulLines(newargs) else: raise NotImplementedError elif isinstance(expr, CodegenArrayTensorProduct): args = [_recognize_matrix_expression(arg) for arg in expr.args] multiple_lines = [_has_multiple_lines(arg) for arg in args] if any(multiple_lines): if any(a.operator != MatAdd for i, a in enumerate(args) if multiple_lines[i] and isinstance(a, _RecognizeMatOp)): raise NotImplementedError getargs = lambda x: x.args if isinstance(x, _RecognizeMatOp) else list(x) expand_args = [getargs(arg) if multiple_lines[i] else [arg] for i, arg in enumerate(args)] it = itertools.product(expand_args) ret = _RecognizeMatOp(MatAdd, [_RecognizeMatMulLines([k for j in i for k in (j if isinstance(j, _RecognizeMatMulLines) else [j])]) for i in it]) return ret return _RecognizeMatMulLines(args) elif isinstance(expr, CodegenArrayDiagonal): pexpr = expr.transform_to_product() if expr == pexpr: return expr return _recognize_matrix_expression(pexpr) elif isinstance(expr, Transpose): return expr elif isinstance(expr, MatrixExpr): return expr return expr def _suppress_trivial_dims_in_tensor_product(mat_list): # Recognize expressions like [x, y] with shape (k, 1, k, 1) as `xy.T`. # The matrix expression has to be equivalent to the tensor product of the matrices, with trivial dimensions (i.e. dim=1) dropped. # That is, add contractions over trivial dimensions: mat_11 = [] mat_k1 = [] for mat in mat_list: if mat.shape == (1, 1): mat_11.append(mat) elif 1 in mat.shape: if mat.shape[0] == 1: mat_k1.append(mat.T) else: mat_k1.append(mat) else: return mat_list if len(mat_k1) > 2: return mat_list a = MatMul.fromiter(mat_k1[:1]) b = MatMul.fromiter(mat_k1[1:]) x = MatMul.fromiter(mat_11) return axb.T def _unfold_recognized_expr(expr): if isinstance(expr, _RecognizeMatOp): return expr.operator([_unfold_recognized_expr(i) for i in expr.args]) elif isinstance(expr, _RecognizeMatMulLines): unfolded = [_unfold_recognized_expr(i) for i in expr] mat_list = [i for i in unfolded if isinstance(i, MatrixExpr)] scalar_list = [i for i in unfolded if i not in mat_list] scalar = Mul.fromiter(scalar_list) mat_list = [i.doit() for i in mat_list] mat_list = [i for i in mat_list if not (i.shape == (1, 1) and i.is_Identity)] if mat_list: mat_list[0] *= scalar if len(mat_list) == 1: return mat_list[0].doit() else: return _suppress_trivial_dims_in_tensor_product(mat_list) else: return scalar else: return expr def _apply_recursively_over_nested_lists(func, arr): if isinstance(arr, (tuple, list, Tuple)): return tuple(_apply_recursively_over_nested_lists(func, i) for i in arr) elif isinstance(arr, Tuple): return Tuple.fromiter(_apply_recursively_over_nested_lists(func, i) for i in arr) else: return func(arr) def _build_push_indices_up_func_transformation(flattened_contraction_indices): shifts = {0: 0} i = 0 cumulative = 0 while i < len(flattened_contraction_indices): j = 1 while i+j < len(flattened_contraction_indices): if flattened_contraction_indices[i] + j != flattened_contraction_indices[i+j]: break j += 1 cumulative += j shifts[flattened_contraction_indices[i]] = cumulative i += j shift_keys = sorted(shifts.keys()) def func(idx): return shifts[shift_keys[bisect.bisect_right(shift_keys, idx)-1]] def transform(j): if j in flattened_contraction_indices: return None else: return j - func(j) return transform def _build_push_indices_down_func_transformation(flattened_contraction_indices): N = flattened_contraction_indices[-1]+2 shifts = [i for i in range(N) if i not in flattened_contraction_indices] def transform(j): if j < len(shifts): return shifts[j] else: return j + shifts[-1] - len(shifts) + 1 return transform
9a00e866fba102613418c91f5e9295fef7da15cefed39ca180fb376eea1fb675	""" Additional AST nodes for operations on matrices. The nodes in this module are meant to represent optimization of matrix expressions within codegen's target languages that cannot be represented by SymPy expressions. As an example, we can use :meth:`sympy.codegen.rewriting.optimize` and the ``matin_opt`` optimization provided in :mod:`sympy.codegen.rewriting` to transform matrix multiplication under certain assumptions: >>> from sympy import symbols, MatrixSymbol >>> n = symbols('n', integer=True) >>> A = MatrixSymbol('A', n, n) >>> x = MatrixSymbol('x', n, 1) >>> expr = A*(-1) x >>> from sympy.assumptions import assuming, Q >>> from sympy.codegen.rewriting import matinv_opt, optimize >>> with assuming(Q.fullrank(A)): ... optimize(expr, [matinv_opt]) MatrixSolve(A, vector=x) """ from .ast import Token from sympy.matrices import MatrixExpr from sympy.core.sympify import sympify class MatrixSolve(Token, MatrixExpr): """Represents an operation to solve a linear matrix equation. Parameters ========== matrix : MatrixSymbol Matrix representing the coefficients of variables in the linear equation. This matrix must be square and full-rank (i.e. all columns must be linearly independent) for the solving operation to be valid. vector : MatrixSymbol One-column matrix representing the solutions to the equations represented in ``matrix``. Examples ======== >>> from sympy import symbols, MatrixSymbol >>> from sympy.codegen.matrix_nodes import MatrixSolve >>> n = symbols('n', integer=True) >>> A = MatrixSymbol('A', n, n) >>> x = MatrixSymbol('x', n, 1) >>> from sympy.printing.pycode import NumPyPrinter >>> NumPyPrinter().doprint(MatrixSolve(A, x)) 'numpy.linalg.solve(A, x)' >>> from sympy.printing import octave_code >>> octave_code(MatrixSolve(A, x)) 'A \\\\ x' """ __slots__ = ('matrix', 'vector') _construct_matrix = staticmethod(sympify) @property def shape(self): return self.vector.shape
af2a3731ef0028c090a6a0908bd2ba653a6c17a26cec5b11a4473d1ab5369c2b	""" This file contains some classical ciphers and routines implementing a linear-feedback shift register (LFSR) and the Diffie-Hellman key exchange. .. warning:: This module is intended for educational purposes only. Do not use the functions in this module for real cryptographic applications. If you wish to encrypt real data, we recommend using something like the `cryptography <https://cryptography.io/en/latest/>`_ module. """ from string import whitespace, ascii_uppercase as uppercase, printable from functools import reduce import warnings from itertools import cycle from sympy import nextprime from sympy.core import Rational, Symbol from sympy.core.numbers import igcdex, mod_inverse, igcd from sympy.core.compatibility import as_int from sympy.matrices import Matrix from sympy.ntheory import isprime, primitive_root, factorint from sympy.polys.domains import FF from sympy.polys.polytools import gcd, Poly from sympy.utilities.misc import filldedent, translate from sympy.utilities.iterables import uniq, multiset from sympy.testing.randtest import _randrange, _randint class NonInvertibleCipherWarning(RuntimeWarning): """A warning raised if the cipher is not invertible.""" def __init__(self, msg): self.fullMessage = msg def __str__(self): return '\n\t' + self.fullMessage def warn(self, stacklevel=2): warnings.warn(self, stacklevel=stacklevel) def AZ(s=None): """Return the letters of ``s`` in uppercase. In case more than one string is passed, each of them will be processed and a list of upper case strings will be returned. Examples ======== >>> from sympy.crypto.crypto import AZ >>> AZ('Hello, world!') 'HELLOWORLD' >>> AZ('Hello, world!'.split()) ['HELLO', 'WORLD'] See Also ======== check_and_join """ if not s: return uppercase t = type(s) is str if t: s = [s] rv = [check_and_join(i.upper().split(), uppercase, filter=True) for i in s] if t: return rv[0] return rv bifid5 = AZ().replace('J', '') bifid6 = AZ() + '0123456789' bifid10 = printable def padded_key(key, symbols): """Return a string of the distinct characters of ``symbols`` with those of ``key`` appearing first. A ValueError is raised if a) there are duplicate characters in ``symbols`` or b) there are characters in ``key`` that are not in ``symbols``. Examples ======== >>> from sympy.crypto.crypto import padded_key >>> padded_key('PUPPY', 'OPQRSTUVWXY') 'PUYOQRSTVWX' >>> padded_key('RSA', 'ARTIST') Traceback (most recent call last): ... ValueError: duplicate characters in symbols: T """ syms = list(uniq(symbols)) if len(syms) != len(symbols): extra = ''.join(sorted({ i for i in symbols if symbols.count(i) > 1})) raise ValueError('duplicate characters in symbols: %s' % extra) extra = set(key) - set(syms) if extra: raise ValueError( 'characters in key but not symbols: %s' % ''.join( sorted(extra))) key0 = ''.join(list(uniq(key))) # remove from syms characters in key0 return key0 + translate(''.join(syms), None, key0) def check_and_join(phrase, symbols=None, filter=None): """ Joins characters of ``phrase`` and if ``symbols`` is given, raises an error if any character in ``phrase`` is not in ``symbols``. Parameters ========== phrase String or list of strings to be returned as a string. symbols Iterable of characters allowed in ``phrase``. If ``symbols`` is ``None``, no checking is performed. Examples ======== >>> from sympy.crypto.crypto import check_and_join >>> check_and_join('a phrase') 'a phrase' >>> check_and_join('a phrase'.upper().split()) 'APHRASE' >>> check_and_join('a phrase!'.upper().split(), 'ARE', filter=True) 'ARAE' >>> check_and_join('a phrase!'.upper().split(), 'ARE') Traceback (most recent call last): ... ValueError: characters in phrase but not symbols: "!HPS" """ rv = ''.join(''.join(phrase)) if symbols is not None: symbols = check_and_join(symbols) missing = ''.join(list(sorted(set(rv) - set(symbols)))) if missing: if not filter: raise ValueError( 'characters in phrase but not symbols: "%s"' % missing) rv = translate(rv, None, missing) return rv def _prep(msg, key, alp, default=None): if not alp: if not default: alp = AZ() msg = AZ(msg) key = AZ(key) else: alp = default else: alp = ''.join(alp) key = check_and_join(key, alp, filter=True) msg = check_and_join(msg, alp, filter=True) return msg, key, alp def cycle_list(k, n): """ Returns the elements of the list ``range(n)`` shifted to the left by ``k`` (so the list starts with ``k`` (mod ``n``)). Examples ======== >>> from sympy.crypto.crypto import cycle_list >>> cycle_list(3, 10) [3, 4, 5, 6, 7, 8, 9, 0, 1, 2] """ k = k % n return list(range(k, n)) + list(range(k)) ######## shift cipher examples ############ def encipher_shift(msg, key, symbols=None): """ Performs shift cipher encryption on plaintext msg, and returns the ciphertext. Parameters ========== key : int The secret key. msg : str Plaintext of upper-case letters. Returns ======= str Ciphertext of upper-case letters. Examples ======== >>> from sympy.crypto.crypto import encipher_shift, decipher_shift >>> msg = "GONAVYBEATARMY" >>> ct = encipher_shift(msg, 1); ct 'HPOBWZCFBUBSNZ' To decipher the shifted text, change the sign of the key: >>> encipher_shift(ct, -1) 'GONAVYBEATARMY' There is also a convenience function that does this with the original key: >>> decipher_shift(ct, 1) 'GONAVYBEATARMY' Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L1`` of corresponding integers. 2. Compute from the list ``L1`` a new list ``L2``, given by adding ``(k mod 26)`` to each element in ``L1``. 3. Compute from the list ``L2`` a string ``ct`` of corresponding letters. The shift cipher is also called the Caesar cipher, after Julius Caesar, who, according to Suetonius, used it with a shift of three to protect messages of military significance. Caesar's nephew Augustus reportedly used a similar cipher, but with a right shift of 1. References ========== .. [1] https://en.wikipedia.org/wiki/Caesar_cipher .. [2] http://mathworld.wolfram.com/CaesarsMethod.html See Also ======== decipher_shift """ msg, _, A = _prep(msg, '', symbols) shift = len(A) - key % len(A) key = A[shift:] + A[:shift] return translate(msg, key, A) def decipher_shift(msg, key, symbols=None): """ Return the text by shifting the characters of ``msg`` to the left by the amount given by ``key``. Examples ======== >>> from sympy.crypto.crypto import encipher_shift, decipher_shift >>> msg = "GONAVYBEATARMY" >>> ct = encipher_shift(msg, 1); ct 'HPOBWZCFBUBSNZ' To decipher the shifted text, change the sign of the key: >>> encipher_shift(ct, -1) 'GONAVYBEATARMY' Or use this function with the original key: >>> decipher_shift(ct, 1) 'GONAVYBEATARMY' """ return encipher_shift(msg, -key, symbols) def encipher_rot13(msg, symbols=None): """ Performs the ROT13 encryption on a given plaintext ``msg``. Explanation =========== ROT13 is a substitution cipher which substitutes each letter in the plaintext message for the letter furthest away from it in the English alphabet. Equivalently, it is just a Caeser (shift) cipher with a shift key of 13 (midway point of the alphabet). References ========== .. [1] https://en.wikipedia.org/wiki/ROT13 See Also ======== decipher_rot13 encipher_shift """ return encipher_shift(msg, 13, symbols) def decipher_rot13(msg, symbols=None): """ Performs the ROT13 decryption on a given plaintext ``msg``. Explanation ============ ``decipher_rot13`` is equivalent to ``encipher_rot13`` as both ``decipher_shift`` with a key of 13 and ``encipher_shift`` key with a key of 13 will return the same results. Nonetheless, ``decipher_rot13`` has nonetheless been explicitly defined here for consistency. Examples ======== >>> from sympy.crypto.crypto import encipher_rot13, decipher_rot13 >>> msg = 'GONAVYBEATARMY' >>> ciphertext = encipher_rot13(msg);ciphertext 'TBANILORNGNEZL' >>> decipher_rot13(ciphertext) 'GONAVYBEATARMY' >>> encipher_rot13(msg) == decipher_rot13(msg) True >>> msg == decipher_rot13(ciphertext) True """ return decipher_shift(msg, 13, symbols) ######## affine cipher examples ############ def encipher_affine(msg, key, symbols=None, _inverse=False): r""" Performs the affine cipher encryption on plaintext ``msg``, and returns the ciphertext. Explanation =========== Encryption is based on the map `x \rightarrow ax+b` (mod `N`) where ``N`` is the number of characters in the alphabet. Decryption is based on the map `x \rightarrow cx+d` (mod `N`), where `c = a^{-1}` (mod `N`) and `d = -a^{-1}b` (mod `N`). In particular, for the map to be invertible, we need `\mathrm{gcd}(a, N) = 1` and an error will be raised if this is not true. Parameters ========== msg : str Characters that appear in ``symbols``. a, b : int, int A pair integers, with ``gcd(a, N) = 1`` (the secret key). symbols String of characters (default = uppercase letters). When no symbols are given, ``msg`` is converted to upper case letters and all other characters are ignored. Returns ======= ct String of characters (the ciphertext message) Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L1`` of corresponding integers. 2. Compute from the list ``L1`` a new list ``L2``, given by replacing ``x`` by ``ax + b (mod N)``, for each element ``x`` in ``L1``. 3. Compute from the list ``L2`` a string ``ct`` of corresponding letters. This is a straightforward generalization of the shift cipher with the added complexity of requiring 2 characters to be deciphered in order to recover the key. References ========== .. [1] https://en.wikipedia.org/wiki/Affine_cipher See Also ======== decipher_affine """ msg, _, A = _prep(msg, '', symbols) N = len(A) a, b = key assert gcd(a, N) == 1 if _inverse: c = mod_inverse(a, N) d = -bc a, b = c, d B = ''.join([A[(ai + b) % N] for i in range(N)]) return translate(msg, A, B) def decipher_affine(msg, key, symbols=None): r""" Return the deciphered text that was made from the mapping, `x \rightarrow ax+b` (mod `N`), where ``N`` is the number of characters in the alphabet. Deciphering is done by reciphering with a new key: `x \rightarrow cx+d` (mod `N`), where `c = a^{-1}` (mod `N`) and `d = -a^{-1}b` (mod `N`). Examples ======== >>> from sympy.crypto.crypto import encipher_affine, decipher_affine >>> msg = "GO NAVY BEAT ARMY" >>> key = (3, 1) >>> encipher_affine(msg, key) 'TROBMVENBGBALV' >>> decipher_affine(_, key) 'GONAVYBEATARMY' See Also ======== encipher_affine """ return encipher_affine(msg, key, symbols, _inverse=True) def encipher_atbash(msg, symbols=None): r""" Enciphers a given ``msg`` into its Atbash ciphertext and returns it. Explanation =========== Atbash is a substitution cipher originally used to encrypt the Hebrew alphabet. Atbash works on the principle of mapping each alphabet to its reverse / counterpart (i.e. a would map to z, b to y etc.) Atbash is functionally equivalent to the affine cipher with ``a = 25`` and ``b = 25`` See Also ======== decipher_atbash """ return encipher_affine(msg, (25, 25), symbols) def decipher_atbash(msg, symbols=None): r""" Deciphers a given ``msg`` using Atbash cipher and returns it. Explanation =========== ``decipher_atbash`` is functionally equivalent to ``encipher_atbash``. However, it has still been added as a separate function to maintain consistency. Examples ======== >>> from sympy.crypto.crypto import encipher_atbash, decipher_atbash >>> msg = 'GONAVYBEATARMY' >>> encipher_atbash(msg) 'TLMZEBYVZGZINB' >>> decipher_atbash(msg) 'TLMZEBYVZGZINB' >>> encipher_atbash(msg) == decipher_atbash(msg) True >>> msg == encipher_atbash(encipher_atbash(msg)) True References ========== .. [1] https://en.wikipedia.org/wiki/Atbash See Also ======== encipher_atbash """ return decipher_affine(msg, (25, 25), symbols) #################### substitution cipher ########################### def encipher_substitution(msg, old, new=None): r""" Returns the ciphertext obtained by replacing each character that appears in ``old`` with the corresponding character in ``new``. If ``old`` is a mapping, then new is ignored and the replacements defined by ``old`` are used. Explanation =========== This is a more general than the affine cipher in that the key can only be recovered by determining the mapping for each symbol. Though in practice, once a few symbols are recognized the mappings for other characters can be quickly guessed. Examples ======== >>> from sympy.crypto.crypto import encipher_substitution, AZ >>> old = 'OEYAG' >>> new = '034^6' >>> msg = AZ("go navy! beat army!") >>> ct = encipher_substitution(msg, old, new); ct '60N^V4B3^T^RM4' To decrypt a substitution, reverse the last two arguments: >>> encipher_substitution(ct, new, old) 'GONAVYBEATARMY' In the special case where ``old`` and ``new`` are a permutation of order 2 (representing a transposition of characters) their order is immaterial: >>> old = 'NAVY' >>> new = 'ANYV' >>> encipher = lambda x: encipher_substitution(x, old, new) >>> encipher('NAVY') 'ANYV' >>> encipher(_) 'NAVY' The substitution cipher, in general, is a method whereby "units" (not necessarily single characters) of plaintext are replaced with ciphertext according to a regular system. >>> ords = dict(zip('abc', ['\\%i' % ord(i) for i in 'abc'])) >>> print(encipher_substitution('abc', ords)) \97\98\99 References ========== .. [1] https://en.wikipedia.org/wiki/Substitution_cipher """ return translate(msg, old, new) ###################################################################### #################### Vigenere cipher examples ######################## ###################################################################### def encipher_vigenere(msg, key, symbols=None): """ Performs the Vigenere cipher encryption on plaintext ``msg``, and returns the ciphertext. Examples ======== >>> from sympy.crypto.crypto import encipher_vigenere, AZ >>> key = "encrypt" >>> msg = "meet me on monday" >>> encipher_vigenere(msg, key) 'QRGKKTHRZQEBPR' Section 1 of the Kryptos sculpture at the CIA headquarters uses this cipher and also changes the order of the the alphabet [2]_. Here is the first line of that section of the sculpture: >>> from sympy.crypto.crypto import decipher_vigenere, padded_key >>> alp = padded_key('KRYPTOS', AZ()) >>> key = 'PALIMPSEST' >>> msg = 'EMUFPHZLRFAXYUSDJKZLDKRNSHGNFIVJ' >>> decipher_vigenere(msg, key, alp) 'BETWEENSUBTLESHADINGANDTHEABSENC' Explanation =========== The Vigenere cipher is named after Blaise de Vigenere, a sixteenth century diplomat and cryptographer, by a historical accident. Vigenere actually invented a different and more complicated cipher. The so-called Vigenere cipher* was actually invented by Giovan Batista Belaso in 1553. This cipher was used in the 1800's, for example, during the American Civil War. The Confederacy used a brass cipher disk to implement the Vigenere cipher (now on display in the NSA Museum in Fort Meade) [1]_. The Vigenere cipher is a generalization of the shift cipher. Whereas the shift cipher shifts each letter by the same amount (that amount being the key of the shift cipher) the Vigenere cipher shifts a letter by an amount determined by the key (which is a word or phrase known only to the sender and receiver). For example, if the key was a single letter, such as "C", then the so-called Vigenere cipher is actually a shift cipher with a shift of `2` (since "C" is the 2nd letter of the alphabet, if you start counting at `0`). If the key was a word with two letters, such as "CA", then the so-called Vigenere cipher will shift letters in even positions by `2` and letters in odd positions are left alone (shifted by `0`, since "A" is the 0th letter, if you start counting at `0`). ALGORITHM: INPUT: ``msg``: string of characters that appear in ``symbols`` (the plaintext) ``key``: a string of characters that appear in ``symbols`` (the secret key) ``symbols``: a string of letters defining the alphabet OUTPUT: ``ct``: string of characters (the ciphertext message) STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``key`` a list ``L1`` of corresponding integers. Let ``n1 = len(L1)``. 2. Compute from the string ``msg`` a list ``L2`` of corresponding integers. Let ``n2 = len(L2)``. 3. Break ``L2`` up sequentially into sublists of size ``n1``; the last sublist may be smaller than ``n1`` 4. For each of these sublists ``L`` of ``L2``, compute a new list ``C`` given by ``C[i] = L[i] + L1[i] (mod N)`` to the ``i``-th element in the sublist, for each ``i``. 5. Assemble these lists ``C`` by concatenation into a new list of length ``n2``. 6. Compute from the new list a string ``ct`` of corresponding letters. Once it is known that the key is, say, `n` characters long, frequency analysis can be applied to every `n`-th letter of the ciphertext to determine the plaintext. This method is called Kasiski examination (although it was first discovered by Babbage). If they key is as long as the message and is comprised of randomly selected characters -- a one-time pad -- the message is theoretically unbreakable. The cipher Vigenere actually discovered is an "auto-key" cipher described as follows. ALGORITHM: INPUT: ``key``: a string of letters (the secret key) ``msg``: string of letters (the plaintext message) OUTPUT: ``ct``: string of upper-case letters (the ciphertext message) STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L2`` of corresponding integers. Let ``n2 = len(L2)``. 2. Let ``n1`` be the length of the key. Append to the string ``key`` the first ``n2 - n1`` characters of the plaintext message. Compute from this string (also of length ``n2``) a list ``L1`` of integers corresponding to the letter numbers in the first step. 3. Compute a new list ``C`` given by ``C[i] = L1[i] + L2[i] (mod N)``. 4. Compute from the new list a string ``ct`` of letters corresponding to the new integers. To decipher the auto-key ciphertext, the key is used to decipher the first ``n1`` characters and then those characters become the key to decipher the next ``n1`` characters, etc...: >>> m = AZ('go navy, beat army! yes you can'); m 'GONAVYBEATARMYYESYOUCAN' >>> key = AZ('gold bug'); n1 = len(key); n2 = len(m) >>> auto_key = key + m[:n2 - n1]; auto_key 'GOLDBUGGONAVYBEATARMYYE' >>> ct = encipher_vigenere(m, auto_key); ct 'MCYDWSHKOGAMKZCELYFGAYR' >>> n1 = len(key) >>> pt = [] >>> while ct: ... part, ct = ct[:n1], ct[n1:] ... pt.append(decipher_vigenere(part, key)) ... key = pt[-1] ... >>> ''.join(pt) == m True References ========== .. [1] https://en.wikipedia.org/wiki/Vigenere_cipher .. [2] http://web.archive.org/web/20071116100808/ .. [3] http://filebox.vt.edu/users/batman/kryptos.html (short URL: https://goo.gl/ijr22d) """ msg, key, A = _prep(msg, key, symbols) map = {c: i for i, c in enumerate(A)} key = [map[c] for c in key] N = len(map) k = len(key) rv = [] for i, m in enumerate(msg): rv.append(A[(map[m] + key[i % k]) % N]) rv = ''.join(rv) return rv def decipher_vigenere(msg, key, symbols=None): """ Decode using the Vigenere cipher. Examples ======== >>> from sympy.crypto.crypto import decipher_vigenere >>> key = "encrypt" >>> ct = "QRGK kt HRZQE BPR" >>> decipher_vigenere(ct, key) 'MEETMEONMONDAY' """ msg, key, A = _prep(msg, key, symbols) map = {c: i for i, c in enumerate(A)} N = len(A) # normally, 26 K = [map[c] for c in key] n = len(K) C = [map[c] for c in msg] rv = ''.join([A[(-K[i % n] + c) % N] for i, c in enumerate(C)]) return rv #################### Hill cipher ######################## def encipher_hill(msg, key, symbols=None, pad="Q"): r""" Return the Hill cipher encryption of ``msg``. Explanation =========== The Hill cipher [1]_, invented by Lester S. Hill in the 1920's [2]_, was the first polygraphic cipher in which it was practical (though barely) to operate on more than three symbols at once. The following discussion assumes an elementary knowledge of matrices. First, each letter is first encoded as a number starting with 0. Suppose your message `msg` consists of `n` capital letters, with no spaces. This may be regarded an `n`-tuple M of elements of `Z_{26}` (if the letters are those of the English alphabet). A key in the Hill cipher is a `k x k` matrix `K`, all of whose entries are in `Z_{26}`, such that the matrix `K` is invertible (i.e., the linear transformation `K: Z_{N}^k \rightarrow Z_{N}^k` is one-to-one). Parameters ========== msg Plaintext message of `n` upper-case letters. key A `k \times k` invertible matrix `K`, all of whose entries are in `Z_{26}` (or whatever number of symbols are being used). pad Character (default "Q") to use to make length of text be a multiple of ``k``. Returns ======= ct Ciphertext of upper-case letters. Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L`` of corresponding integers. Let ``n = len(L)``. 2. Break the list ``L`` up into ``t = ceiling(n/k)`` sublists ``L_1``, ..., ``L_t`` of size ``k`` (with the last list "padded" to ensure its size is ``k``). 3. Compute new list ``C_1``, ..., ``C_t`` given by ``C[i] = KL_i`` (arithmetic is done mod N), for each ``i``. 4. Concatenate these into a list ``C = C_1 + ... + C_t``. 5. Compute from ``C`` a string ``ct`` of corresponding letters. This has length ``kt``. References ========== .. [1] https://en.wikipedia.org/wiki/Hill_cipher .. [2] Lester S. Hill, Cryptography in an Algebraic Alphabet, The American Mathematical Monthly Vol.36, June-July 1929, pp.306-312. See Also ======== decipher_hill """ assert key.is_square assert len(pad) == 1 msg, pad, A = _prep(msg, pad, symbols) map = {c: i for i, c in enumerate(A)} P = [map[c] for c in msg] N = len(A) k = key.cols n = len(P) m, r = divmod(n, k) if r: P = P + [map[pad]](k - r) m += 1 rv = ''.join([A[c % N] for j in range(m) for c in list(keyMatrix(k, 1, [P[i] for i in range(kj, k(j + 1))]))]) return rv def decipher_hill(msg, key, symbols=None): """ Deciphering is the same as enciphering but using the inverse of the key matrix. Examples ======== >>> from sympy.crypto.crypto import encipher_hill, decipher_hill >>> from sympy import Matrix >>> key = Matrix([[1, 2], [3, 5]]) >>> encipher_hill("meet me on monday", key) 'UEQDUEODOCTCWQ' >>> decipher_hill(_, key) 'MEETMEONMONDAY' When the length of the plaintext (stripped of invalid characters) is not a multiple of the key dimension, extra characters will appear at the end of the enciphered and deciphered text. In order to decipher the text, those characters must be included in the text to be deciphered. In the following, the key has a dimension of 4 but the text is 2 short of being a multiple of 4 so two characters will be added. >>> key = Matrix([[1, 1, 1, 2], [0, 1, 1, 0], ... [2, 2, 3, 4], [1, 1, 0, 1]]) >>> msg = "ST" >>> encipher_hill(msg, key) 'HJEB' >>> decipher_hill(_, key) 'STQQ' >>> encipher_hill(msg, key, pad="Z") 'ISPK' >>> decipher_hill(_, key) 'STZZ' If the last two characters of the ciphertext were ignored in either case, the wrong plaintext would be recovered: >>> decipher_hill("HD", key) 'ORMV' >>> decipher_hill("IS", key) 'UIKY' See Also ======== encipher_hill """ assert key.is_square msg, _, A = _prep(msg, '', symbols) map = {c: i for i, c in enumerate(A)} C = [map[c] for c in msg] N = len(A) k = key.cols n = len(C) m, r = divmod(n, k) if r: C = C + [0](k - r) m += 1 key_inv = key.inv_mod(N) rv = ''.join([A[p % N] for j in range(m) for p in list(key_invMatrix( k, 1, [C[i] for i in range(kj, k(j + 1))]))]) return rv #################### Bifid cipher ######################## def encipher_bifid(msg, key, symbols=None): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. This is the version of the Bifid cipher that uses an `n \times n` Polybius square. Parameters ========== msg Plaintext string. key Short string for key. Duplicate characters are ignored and then it is padded with the characters in ``symbols`` that were not in the short key. symbols `n \times n` characters defining the alphabet. (default is string.printable) Returns ======= ciphertext Ciphertext using Bifid5 cipher without spaces. See Also ======== decipher_bifid, encipher_bifid5, encipher_bifid6 References ========== .. [1] https://en.wikipedia.org/wiki/Bifid_cipher """ msg, key, A = _prep(msg, key, symbols, bifid10) long_key = ''.join(uniq(key)) or A n = len(A).5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) N = int(n) if len(long_key) < N2: long_key = list(long_key) + [x for x in A if x not in long_key] # the fractionalization row_col = {ch: divmod(i, N) for i, ch in enumerate(long_key)} r, c = zip([row_col[x] for x in msg]) rc = r + c ch = {i: ch for ch, i in row_col.items()} rv = ''.join(ch[i] for i in zip(rc[::2], rc[1::2])) return rv def decipher_bifid(msg, key, symbols=None): r""" Performs the Bifid cipher decryption on ciphertext ``msg``, and returns the plaintext. This is the version of the Bifid cipher that uses the `n \times n` Polybius square. Parameters ========== msg Ciphertext string. key Short string for key. Duplicate characters are ignored and then it is padded with the characters in symbols that were not in the short key. symbols `n \times n` characters defining the alphabet. (default=string.printable, a `10 \times 10` matrix) Returns ======= deciphered Deciphered text. Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_bifid, decipher_bifid, AZ) Do an encryption using the bifid5 alphabet: >>> alp = AZ().replace('J', '') >>> ct = AZ("meet me on monday!") >>> key = AZ("gold bug") >>> encipher_bifid(ct, key, alp) 'IEILHHFSTSFQYE' When entering the text or ciphertext, spaces are ignored so it can be formatted as desired. Re-entering the ciphertext from the preceding, putting 4 characters per line and padding with an extra J, does not cause problems for the deciphering: >>> decipher_bifid(''' ... IEILH ... HFSTS ... FQYEJ''', key, alp) 'MEETMEONMONDAY' When no alphabet is given, all 100 printable characters will be used: >>> key = '' >>> encipher_bifid('hello world!', key) 'bmtwmg-bIow' >>> decipher_bifid(_, key) 'hello world!' If the key is changed, a different encryption is obtained: >>> key = 'gold bug' >>> encipher_bifid('hello world!', 'gold_bug') 'hg2sfuei7t}w' And if the key used to decrypt the message is not exact, the original text will not be perfectly obtained: >>> decipher_bifid(_, 'gold pug') 'heldo~wor6d!' """ msg, _, A = _prep(msg, '', symbols, bifid10) long_key = ''.join(uniq(key)) or A n = len(A).5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) N = int(n) if len(long_key) < N2: long_key = list(long_key) + [x for x in A if x not in long_key] # the reverse fractionalization row_col = { ch: divmod(i, N) for i, ch in enumerate(long_key)} rc = [i for c in msg for i in row_col[c]] n = len(msg) rc = zip((rc[:n], rc[n:])) ch = {i: ch for ch, i in row_col.items()} rv = ''.join(ch[i] for i in rc) return rv def bifid_square(key): """Return characters of ``key`` arranged in a square. Examples ======== >>> from sympy.crypto.crypto import ( ... bifid_square, AZ, padded_key, bifid5) >>> bifid_square(AZ().replace('J', '')) Matrix([ [A, B, C, D, E], [F, G, H, I, K], [L, M, N, O, P], [Q, R, S, T, U], [V, W, X, Y, Z]]) >>> bifid_square(padded_key(AZ('gold bug!'), bifid5)) Matrix([ [G, O, L, D, B], [U, A, C, E, F], [H, I, K, M, N], [P, Q, R, S, T], [V, W, X, Y, Z]]) See Also ======== padded_key """ A = ''.join(uniq(''.join(key))) n = len(A).5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) n = int(n) f = lambda i, j: Symbol(A[ni + j]) rv = Matrix(n, n, f) return rv def encipher_bifid5(msg, key): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. Explanation =========== This is the version of the Bifid cipher that uses the `5 \times 5` Polybius square. The letter "J" is ignored so it must be replaced with something else (traditionally an "I") before encryption. ALGORITHM: (5x5 case) STEPS: 0. Create the `5 \times 5` Polybius square ``S`` associated to ``key`` as follows: a) moving from left-to-right, top-to-bottom, place the letters of the key into a `5 \times 5` matrix, b) if the key has less than 25 letters, add the letters of the alphabet not in the key until the `5 \times 5` square is filled. 1. Create a list ``P`` of pairs of numbers which are the coordinates in the Polybius square of the letters in ``msg``. 2. Let ``L1`` be the list of all first coordinates of ``P`` (length of ``L1 = n``), let ``L2`` be the list of all second coordinates of ``P`` (so the length of ``L2`` is also ``n``). 3. Let ``L`` be the concatenation of ``L1`` and ``L2`` (length ``L = 2n``), except that consecutive numbers are paired ``(L[2i], L[2i + 1])``. You can regard ``L`` as a list of pairs of length ``n``. 4. Let ``C`` be the list of all letters which are of the form ``S[i, j]``, for all ``(i, j)`` in ``L``. As a string, this is the ciphertext of ``msg``. Parameters ========== msg : str Plaintext string. Converted to upper case and filtered of anything but all letters except J. key Short string for key; non-alphabetic letters, J and duplicated characters are ignored and then, if the length is less than 25 characters, it is padded with other letters of the alphabet (in alphabetical order). Returns ======= ct Ciphertext (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_bifid5, decipher_bifid5) "J" will be omitted unless it is replaced with something else: >>> round_trip = lambda m, k: \ ... decipher_bifid5(encipher_bifid5(m, k), k) >>> key = 'a' >>> msg = "JOSIE" >>> round_trip(msg, key) 'OSIE' >>> round_trip(msg.replace("J", "I"), key) 'IOSIE' >>> j = "QIQ" >>> round_trip(msg.replace("J", j), key).replace(j, "J") 'JOSIE' Notes ===== The Bifid cipher was invented around 1901 by Felix Delastelle. It is a fractional substitution* cipher, where letters are replaced by pairs of symbols from a smaller alphabet. The cipher uses a `5 \times 5` square filled with some ordering of the alphabet, except that "J" is replaced with "I" (this is a so-called Polybius square; there is a `6 \times 6` analog if you add back in "J" and also append onto the usual 26 letter alphabet, the digits 0, 1, ..., 9). According to Helen Gaines' book Cryptanalysis, this type of cipher was used in the field by the German Army during World War I. See Also ======== decipher_bifid5, encipher_bifid """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid5) key = padded_key(key, bifid5) return encipher_bifid(msg, '', key) def decipher_bifid5(msg, key): r""" Return the Bifid cipher decryption of ``msg``. Explanation =========== This is the version of the Bifid cipher that uses the `5 \times 5` Polybius square; the letter "J" is ignored unless a ``key`` of length 25 is used. Parameters ========== msg Ciphertext string. key Short string for key; duplicated characters are ignored and if the length is less then 25 characters, it will be padded with other letters from the alphabet omitting "J". Non-alphabetic characters are ignored. Returns ======= plaintext Plaintext from Bifid5 cipher (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import encipher_bifid5, decipher_bifid5 >>> key = "gold bug" >>> encipher_bifid5('meet me on friday', key) 'IEILEHFSTSFXEE' >>> encipher_bifid5('meet me on monday', key) 'IEILHHFSTSFQYE' >>> decipher_bifid5(_, key) 'MEETMEONMONDAY' """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid5) key = padded_key(key, bifid5) return decipher_bifid(msg, '', key) def bifid5_square(key=None): r""" 5x5 Polybius square. Produce the Polybius square for the `5 \times 5` Bifid cipher. Examples ======== >>> from sympy.crypto.crypto import bifid5_square >>> bifid5_square("gold bug") Matrix([ [G, O, L, D, B], [U, A, C, E, F], [H, I, K, M, N], [P, Q, R, S, T], [V, W, X, Y, Z]]) """ if not key: key = bifid5 else: _, key, _ = _prep('', key.upper(), None, bifid5) key = padded_key(key, bifid5) return bifid_square(key) def encipher_bifid6(msg, key): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. This is the version of the Bifid cipher that uses the `6 \times 6` Polybius square. Parameters ========== msg Plaintext string (digits okay). key Short string for key (digits okay). If ``key`` is less than 36 characters long, the square will be filled with letters A through Z and digits 0 through 9. Returns ======= ciphertext Ciphertext from Bifid cipher (all caps, no spaces). See Also ======== decipher_bifid6, encipher_bifid """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid6) key = padded_key(key, bifid6) return encipher_bifid(msg, '', key) def decipher_bifid6(msg, key): r""" Performs the Bifid cipher decryption on ciphertext ``msg``, and returns the plaintext. This is the version of the Bifid cipher that uses the `6 \times 6` Polybius square. Parameters ========== msg Ciphertext string (digits okay); converted to upper case key Short string for key (digits okay). If ``key`` is less than 36 characters long, the square will be filled with letters A through Z and digits 0 through 9. All letters are converted to uppercase. Returns ======= plaintext Plaintext from Bifid cipher (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import encipher_bifid6, decipher_bifid6 >>> key = "gold bug" >>> encipher_bifid6('meet me on monday at 8am', key) 'KFKLJJHF5MMMKTFRGPL' >>> decipher_bifid6(_, key) 'MEETMEONMONDAYAT8AM' """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid6) key = padded_key(key, bifid6) return decipher_bifid(msg, '', key) def bifid6_square(key=None): r""" 6x6 Polybius square. Produces the Polybius square for the `6 \times 6` Bifid cipher. Assumes alphabet of symbols is "A", ..., "Z", "0", ..., "9". Examples ======== >>> from sympy.crypto.crypto import bifid6_square >>> key = "gold bug" >>> bifid6_square(key) Matrix([ [G, O, L, D, B, U], [A, C, E, F, H, I], [J, K, M, N, P, Q], [R, S, T, V, W, X], [Y, Z, 0, 1, 2, 3], [4, 5, 6, 7, 8, 9]]) """ if not key: key = bifid6 else: _, key, _ = _prep('', key.upper(), None, bifid6) key = padded_key(key, bifid6) return bifid_square(key) #################### RSA ############################# def _decipher_rsa_crt(i, d, factors): """Decipher RSA using chinese remainder theorem from the information of the relatively-prime factors of the modulus. Parameters ========== i : integer Ciphertext d : integer The exponent component. factors : list of relatively-prime integers The integers given must be coprime and the product must equal the modulus component of the original RSA key. Examples ======== How to decrypt RSA with CRT: >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key >>> primes = [61, 53] >>> e = 17 >>> args = primes + [e] >>> puk = rsa_public_key(args) >>> prk = rsa_private_key(args) >>> from sympy.crypto.crypto import encipher_rsa, _decipher_rsa_crt >>> msg = 65 >>> crt_primes = primes >>> encrypted = encipher_rsa(msg, puk) >>> decrypted = _decipher_rsa_crt(encrypted, prk[1], primes) >>> decrypted 65 """ from sympy.ntheory.modular import crt moduluses = [pow(i, d, p) for p in factors] result = crt(factors, moduluses) if not result: raise ValueError("CRT failed") return result[0] def _rsa_key(args, public=True, private=True, totient='Euler', index=None, multipower=None): r"""A private subroutine to generate RSA key Parameters ========== public, private : bool, optional Flag to generate either a public key, a private key. totient : 'Euler' or 'Carmichael' Different notation used for totient. multipower : bool, optional Flag to bypass warning for multipower RSA. """ from sympy.ntheory import totient as _euler from sympy.ntheory import reduced_totient as _carmichael if len(args) < 2: return False if totient not in ('Euler', 'Carmichael'): raise ValueError( "The argument totient={} should either be " \ "'Euler', 'Carmichalel'." \ .format(totient)) if totient == 'Euler': _totient = _euler else: _totient = _carmichael if index is not None: index = as_int(index) if totient != 'Carmichael': raise ValueError( "Setting the 'index' keyword argument requires totient" "notation to be specified as 'Carmichael'.") primes, e = args[:-1], args[-1] if any(not isprime(p) for p in primes): new_primes = [] for i in primes: new_primes.extend(factorint(i, multiple=True)) primes = new_primes n = reduce(lambda i, j: ij, primes) tally = multiset(primes) if all(v == 1 for v in tally.values()): multiple = list(tally.keys()) phi = _totient._from_distinct_primes(multiple) else: if not multipower: NonInvertibleCipherWarning( 'Non-distinctive primes found in the factors {}. ' 'The cipher may not be decryptable for some numbers ' 'in the complete residue system Z[{}], but the cipher ' 'can still be valid if you restrict the domain to be ' 'the reduced residue system Z[{}]. You can pass ' 'the flag multipower=True if you want to suppress this ' 'warning.' .format(primes, n, n) ).warn() phi = _totient._from_factors(tally) if igcd(e, phi) == 1: if public and not private: if isinstance(index, int): e = e % phi e += index * phi return n, e if private and not public: d = mod_inverse(e, phi) if isinstance(index, int): d += index * phi return n, d return False def rsa_public_key(args, kwargs): r"""Return the RSA public key* pair, `(n, e)` Parameters ========== args : naturals If specified as `p, q, e` where `p` and `q` are distinct primes and `e` is a desired public exponent of the RSA, `n = p q` and `e` will be verified against the totient `\phi(n)` (Euler totient) or `\lambda(n)` (Carmichael totient) to be `\gcd(e, \phi(n)) = 1` or `\gcd(e, \lambda(n)) = 1`. If specified as `p_1, p_2, ..., p_n, e` where `p_1, p_2, ..., p_n` are specified as primes, and `e` is specified as a desired public exponent of the RSA, it will be able to form a multi-prime RSA, which is a more generalized form of the popular 2-prime RSA. It can also be possible to form a single-prime RSA by specifying the argument as `p, e`, which can be considered a trivial case of a multiprime RSA. Furthermore, it can be possible to form a multi-power RSA by specifying two or more pairs of the primes to be same. However, unlike the two-distinct prime RSA or multi-prime RSA, not every numbers in the complete residue system (`\mathbb{Z}_n`) will be decryptable since the mapping `\mathbb{Z}_{n} \rightarrow \mathbb{Z}_{n}` will not be bijective. (Only except for the trivial case when `e = 1` or more generally, .. math:: e \in \left \{ 1 + k \lambda(n) \mid k \in \mathbb{Z} \land k \geq 0 \right \} when RSA reduces to the identity.) However, the RSA can still be decryptable for the numbers in the reduced residue system (`\mathbb{Z}_n^{\times}`), since the mapping `\mathbb{Z}_{n}^{\times} \rightarrow \mathbb{Z}_{n}^{\times}` can still be bijective. If you pass a non-prime integer to the arguments `p_1, p_2, ..., p_n`, the particular number will be prime-factored and it will become either a multi-prime RSA or a multi-power RSA in its canonical form, depending on whether the product equals its radical or not. `p_1 p_2 ... p_n = \text{rad}(p_1 p_2 ... p_n)` totient : bool, optional If ``'Euler'``, it uses Euler's totient `\phi(n)` which is :meth:`sympy.ntheory.factor_.totient` in SymPy. If ``'Carmichael'``, it uses Carmichael's totient `\lambda(n)` which is :meth:`sympy.ntheory.factor_.reduced_totient` in SymPy. Unlike private key generation, this is a trivial keyword for public key generation because `\gcd(e, \phi(n)) = 1 \iff \gcd(e, \lambda(n)) = 1`. index : nonnegative integer, optional Returns an arbitrary solution of a RSA public key at the index specified at `0, 1, 2, ...`. This parameter needs to be specified along with ``totient='Carmichael'``. Similarly to the non-uniquenss of a RSA private key as described in the ``index`` parameter documentation in :meth:`rsa_private_key`, RSA public key is also not unique and there is an infinite number of RSA public exponents which can behave in the same manner. From any given RSA public exponent `e`, there are can be an another RSA public exponent `e + k \lambda(n)` where `k` is an integer, `\lambda` is a Carmichael's totient function. However, considering only the positive cases, there can be a principal solution of a RSA public exponent `e_0` in `0 < e_0 < \lambda(n)`, and all the other solutions can be canonicalzed in a form of `e_0 + k \lambda(n)`. ``index`` specifies the `k` notation to yield any possible value an RSA public key can have. An example of computing any arbitrary RSA public key: >>> from sympy.crypto.crypto import rsa_public_key >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=0) (3233, 17) >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=1) (3233, 797) >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=2) (3233, 1577) multipower : bool, optional Any pair of non-distinct primes found in the RSA specification will restrict the domain of the cryptosystem, as noted in the explaination of the parameter ``args``. SymPy RSA key generator may give a warning before dispatching it as a multi-power RSA, however, you can disable the warning if you pass ``True`` to this keyword. Returns ======= (n, e) : int, int `n` is a product of any arbitrary number of primes given as the argument. `e` is relatively prime (coprime) to the Euler totient `\phi(n)`. False Returned if less than two arguments are given, or `e` is not relatively prime to the modulus. Examples ======== >>> from sympy.crypto.crypto import rsa_public_key A public key of a two-prime RSA: >>> p, q, e = 3, 5, 7 >>> rsa_public_key(p, q, e) (15, 7) >>> rsa_public_key(p, q, 30) False A public key of a multiprime RSA: >>> primes = [2, 3, 5, 7, 11, 13] >>> e = 7 >>> args = primes + [e] >>> rsa_public_key(args) (30030, 7) Notes ===== Although the RSA can be generalized over any modulus `n`, using two large primes had became the most popular specification because a product of two large primes is usually the hardest to factor relatively to the digits of `n` can have. However, it may need further understanding of the time complexities of each prime-factoring algorithms to verify the claim. See Also ======== rsa_private_key encipher_rsa decipher_rsa References ========== .. [1] https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29 .. [2] http://cacr.uwaterloo.ca/techreports/2006/cacr2006-16.pdf .. [3] https://link.springer.com/content/pdf/10.1007%2FBFb0055738.pdf .. [4] http://www.itiis.org/digital-library/manuscript/1381 """ return _rsa_key(args, public=True, private=False, *kwargs) def rsa_private_key(args, *kwargs): r"""Return the RSA private key* pair, `(n, d)` Parameters ========== args : naturals The keyword is identical to the ``args`` in :meth:`rsa_public_key`. totient : bool, optional If ``'Euler'``, it uses Euler's totient convention `\phi(n)` which is :meth:`sympy.ntheory.factor_.totient` in SymPy. If ``'Carmichael'``, it uses Carmichael's totient convention `\lambda(n)` which is :meth:`sympy.ntheory.factor_.reduced_totient` in SymPy. There can be some output differences for private key generation as examples below. Example using Euler's totient: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Euler') (3233, 2753) Example using Carmichael's totient: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Carmichael') (3233, 413) index : nonnegative integer, optional Returns an arbitrary solution of a RSA private key at the index specified at `0, 1, 2, ...`. This parameter needs to be specified along with ``totient='Carmichael'``. RSA private exponent is a non-unique solution of `e d \mod \lambda(n) = 1` and it is possible in any form of `d + k \lambda(n)`, where `d` is an another already-computed private exponent, and `\lambda` is a Carmichael's totient function, and `k` is any integer. However, considering only the positive cases, there can be a principal solution of a RSA private exponent `d_0` in `0 < d_0 < \lambda(n)`, and all the other solutions can be canonicalzed in a form of `d_0 + k \lambda(n)`. ``index`` specifies the `k` notation to yield any possible value an RSA private key can have. An example of computing any arbitrary RSA private key: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=0) (3233, 413) >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=1) (3233, 1193) >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=2) (3233, 1973) multipower : bool, optional The keyword is identical to the ``multipower`` in :meth:`rsa_public_key`. Returns ======= (n, d) : int, int `n` is a product of any arbitrary number of primes given as the argument. `d` is the inverse of `e` (mod `\phi(n)`) where `e` is the exponent given, and `\phi` is a Euler totient. False Returned if less than two arguments are given, or `e` is not relatively prime to the totient of the modulus. Examples ======== >>> from sympy.crypto.crypto import rsa_private_key A private key of a two-prime RSA: >>> p, q, e = 3, 5, 7 >>> rsa_private_key(p, q, e) (15, 7) >>> rsa_private_key(p, q, 30) False A private key of a multiprime RSA: >>> primes = [2, 3, 5, 7, 11, 13] >>> e = 7 >>> args = primes + [e] >>> rsa_private_key(args) (30030, 823) See Also ======== rsa_public_key encipher_rsa decipher_rsa References ========== .. [1] https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29 .. [2] http://cacr.uwaterloo.ca/techreports/2006/cacr2006-16.pdf .. [3] https://link.springer.com/content/pdf/10.1007%2FBFb0055738.pdf .. [4] http://www.itiis.org/digital-library/manuscript/1381 """ return _rsa_key(args, public=False, private=True, *kwargs) def _encipher_decipher_rsa(i, key, factors=None): n, d = key if not factors: return pow(i, d, n) def _is_coprime_set(l): is_coprime_set = True for i in range(len(l)): for j in range(i+1, len(l)): if igcd(l[i], l[j]) != 1: is_coprime_set = False break return is_coprime_set prod = reduce(lambda i, j: ij, factors) if prod == n and _is_coprime_set(factors): return _decipher_rsa_crt(i, d, factors) return _encipher_decipher_rsa(i, key, factors=None) def encipher_rsa(i, key, factors=None): r"""Encrypt the plaintext with RSA. Parameters ========== i : integer The plaintext to be encrypted for. key : (n, e) where n, e are integers `n` is the modulus of the key and `e` is the exponent of the key. The encryption is computed by `i^e \bmod n`. The key can either be a public key or a private key, however, the message encrypted by a public key can only be decrypted by a private key, and vice versa, as RSA is an asymmetric cryptography system. factors : list of coprime integers This is identical to the keyword ``factors`` in :meth:`decipher_rsa`. Notes ===== Some specifications may make the RSA not cryptographically meaningful. For example, `0`, `1` will remain always same after taking any number of exponentiation, thus, should be avoided. Furthermore, if `i^e < n`, `i` may easily be figured out by taking `e` th root. And also, specifying the exponent as `1` or in more generalized form as `1 + k \lambda(n)` where `k` is an nonnegative integer, `\lambda` is a carmichael totient, the RSA becomes an identity mapping. Examples ======== >>> from sympy.crypto.crypto import encipher_rsa >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key Public Key Encryption: >>> p, q, e = 3, 5, 7 >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> encipher_rsa(msg, puk) 3 Private Key Encryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> msg = 12 >>> encipher_rsa(msg, prk) 3 Encryption using chinese remainder theorem: >>> encipher_rsa(msg, prk, factors=[p, q]) 3 """ return _encipher_decipher_rsa(i, key, factors=factors) def decipher_rsa(i, key, factors=None): r"""Decrypt the ciphertext with RSA. Parameters ========== i : integer The ciphertext to be decrypted for. key : (n, d) where n, d are integers `n` is the modulus of the key and `d` is the exponent of the key. The decryption is computed by `i^d \bmod n`. The key can either be a public key or a private key, however, the message encrypted by a public key can only be decrypted by a private key, and vice versa, as RSA is an asymmetric cryptography system. factors : list of coprime integers As the modulus `n` created from RSA key generation is composed of arbitrary prime factors `n = {p_1}^{k_1}{p_2}^{k_2}...{p_n}^{k_n}` where `p_1, p_2, ..., p_n` are distinct primes and `k_1, k_2, ..., k_n` are positive integers, chinese remainder theorem can be used to compute `i^d \bmod n` from the fragmented modulo operations like .. math:: i^d \bmod {p_1}^{k_1}, i^d \bmod {p_2}^{k_2}, ... , i^d \bmod {p_n}^{k_n} or like .. math:: i^d \bmod {p_1}^{k_1}{p_2}^{k_2}, i^d \bmod {p_3}^{k_3}, ... , i^d \bmod {p_n}^{k_n} as long as every moduli does not share any common divisor each other. The raw primes used in generating the RSA key pair can be a good option. Note that the speed advantage of using this is only viable for very large cases (Like 2048-bit RSA keys) since the overhead of using pure python implementation of :meth:`sympy.ntheory.modular.crt` may overcompensate the theoritical speed advantage. Notes ===== See the ``Notes`` section in the documentation of :meth:`encipher_rsa` Examples ======== >>> from sympy.crypto.crypto import decipher_rsa, encipher_rsa >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key Public Key Encryption and Decryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> new_msg = encipher_rsa(msg, prk) >>> new_msg 3 >>> decipher_rsa(new_msg, puk) 12 Private Key Encryption and Decryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> new_msg = encipher_rsa(msg, puk) >>> new_msg 3 >>> decipher_rsa(new_msg, prk) 12 Decryption using chinese remainder theorem: >>> decipher_rsa(new_msg, prk, factors=[p, q]) 12 See Also ======== encipher_rsa """ return _encipher_decipher_rsa(i, key, factors=factors) #################### kid krypto (kid RSA) ############################# def kid_rsa_public_key(a, b, A, B): r""" Kid RSA is a version of RSA useful to teach grade school children since it does not involve exponentiation. Explanation =========== Alice wants to talk to Bob. Bob generates keys as follows. Key generation: * Select positive integers `a, b, A, B` at random. * Compute `M = a b - 1`, `e = A M + a`, `d = B M + b`, `n = (e d - 1)//M`. * The public key is `(n, e)`. Bob sends these to Alice. * The private key is `(n, d)`, which Bob keeps secret. Encryption: If `p` is the plaintext message then the ciphertext is `c = p e \pmod n`. Decryption: If `c` is the ciphertext message then the plaintext is `p = c d \pmod n`. Examples ======== >>> from sympy.crypto.crypto import kid_rsa_public_key >>> a, b, A, B = 3, 4, 5, 6 >>> kid_rsa_public_key(a, b, A, B) (369, 58) """ M = ab - 1 e = AM + a d = BM + b n = (ed - 1)//M return n, e def kid_rsa_private_key(a, b, A, B): """ Compute `M = a b - 1`, `e = A M + a`, `d = B M + b`, `n = (e d - 1) / M`. The private key is `d`, which Bob keeps secret. Examples ======== >>> from sympy.crypto.crypto import kid_rsa_private_key >>> a, b, A, B = 3, 4, 5, 6 >>> kid_rsa_private_key(a, b, A, B) (369, 70) """ M = ab - 1 e = AM + a d = BM + b n = (ed - 1)//M return n, d def encipher_kid_rsa(msg, key): """ Here ``msg`` is the plaintext and ``key`` is the public key. Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_kid_rsa, kid_rsa_public_key) >>> msg = 200 >>> a, b, A, B = 3, 4, 5, 6 >>> key = kid_rsa_public_key(a, b, A, B) >>> encipher_kid_rsa(msg, key) 161 """ n, e = key return (msge) % n def decipher_kid_rsa(msg, key): """ Here ``msg`` is the plaintext and ``key`` is the private key. Examples ======== >>> from sympy.crypto.crypto import ( ... kid_rsa_public_key, kid_rsa_private_key, ... decipher_kid_rsa, encipher_kid_rsa) >>> a, b, A, B = 3, 4, 5, 6 >>> d = kid_rsa_private_key(a, b, A, B) >>> msg = 200 >>> pub = kid_rsa_public_key(a, b, A, B) >>> pri = kid_rsa_private_key(a, b, A, B) >>> ct = encipher_kid_rsa(msg, pub) >>> decipher_kid_rsa(ct, pri) 200 """ n, d = key return (msgd) % n #################### Morse Code ###################################### morse_char = { ".-": "A", "-...": "B", "-.-.": "C", "-..": "D", ".": "E", "..-.": "F", "--.": "G", "....": "H", "..": "I", ".---": "J", "-.-": "K", ".-..": "L", "--": "M", "-.": "N", "---": "O", ".--.": "P", "--.-": "Q", ".-.": "R", "...": "S", "-": "T", "..-": "U", "...-": "V", ".--": "W", "-..-": "X", "-.--": "Y", "--..": "Z", "-----": "0", ".----": "1", "..---": "2", "...--": "3", "....-": "4", ".....": "5", "-....": "6", "--...": "7", "---..": "8", "----.": "9", ".-.-.-": ".", "--..--": ",", "---...": ":", "-.-.-.": ";", "..--..": "?", "-....-": "-", "..--.-": "_", "-.--.": "(", "-.--.-": ")", ".----.": "'", "-...-": "=", ".-.-.": "+", "-..-.": "/", ".--.-.": "@", "...-..-": "$", "-.-.--": "!"} char_morse = {v: k for k, v in morse_char.items()} def encode_morse(msg, sep='\|', mapping=None): """ Encodes a plaintext into popular Morse Code with letters separated by ``sep`` and words by a double ``sep``. Examples ======== >>> from sympy.crypto.crypto import encode_morse >>> msg = 'ATTACK RIGHT FLANK' >>> encode_morse(msg) '.-\|-\|-\|.-\|-.-.\|-.-\|\|.-.\|..\|--.\|....\|-\|\|..-.\|.-..\|.-\|-.\|-.-' References ========== .. [1] https://en.wikipedia.org/wiki/Morse_code """ mapping = mapping or char_morse assert sep not in mapping word_sep = 2sep mapping[" "] = word_sep suffix = msg and msg[-1] in whitespace # normalize whitespace msg = (' ' if word_sep else '').join(msg.split()) # omit unmapped chars chars = set(''.join(msg.split())) ok = set(mapping.keys()) msg = translate(msg, None, ''.join(chars - ok)) morsestring = [] words = msg.split() for word in words: morseword = [] for letter in word: morseletter = mapping[letter] morseword.append(morseletter) word = sep.join(morseword) morsestring.append(word) return word_sep.join(morsestring) + (word_sep if suffix else '') def decode_morse(msg, sep='\|', mapping=None): """ Decodes a Morse Code with letters separated by ``sep`` (default is '\|') and words by `word_sep` (default is '\|\|) into plaintext. Examples ======== >>> from sympy.crypto.crypto import decode_morse >>> mc = '--\|---\|...-\|.\|\|.\|.-\|...\|-' >>> decode_morse(mc) 'MOVE EAST' References ========== .. [1] https://en.wikipedia.org/wiki/Morse_code """ mapping = mapping or morse_char word_sep = 2sep characterstring = [] words = msg.strip(word_sep).split(word_sep) for word in words: letters = word.split(sep) chars = [mapping[c] for c in letters] word = ''.join(chars) characterstring.append(word) rv = " ".join(characterstring) return rv #################### LFSRs ########################################## def lfsr_sequence(key, fill, n): r""" This function creates an LFSR sequence. Parameters ========== key : list A list of finite field elements, `[c_0, c_1, \ldots, c_k].` fill : list The list of the initial terms of the LFSR sequence, `[x_0, x_1, \ldots, x_k].` n Number of terms of the sequence that the function returns. Returns ======= L The LFSR sequence defined by `x_{n+1} = c_k x_n + \ldots + c_0 x_{n-k}`, for `n \leq k`. Notes ===== S. Golomb [G]_ gives a list of three statistical properties a sequence of numbers `a = \{a_n\}_{n=1}^\infty`, `a_n \in \{0,1\}`, should display to be considered "random". Define the autocorrelation of `a` to be .. math:: C(k) = C(k,a) = \lim_{N\rightarrow \infty} {1\over N}\sum_{n=1}^N (-1)^{a_n + a_{n+k}}. In the case where `a` is periodic with period `P` then this reduces to .. math:: C(k) = {1\over P}\sum_{n=1}^P (-1)^{a_n + a_{n+k}}. Assume `a` is periodic with period `P`. - balance: .. math:: \left\|\sum_{n=1}^P(-1)^{a_n}\right\| \leq 1. - low autocorrelation: .. math:: C(k) = \left\{ \begin{array}{cc} 1,& k = 0,\\ \epsilon, & k \ne 0. \end{array} \right. (For sequences satisfying these first two properties, it is known that `\epsilon = -1/P` must hold.) - proportional runs property: In each period, half the runs have length `1`, one-fourth have length `2`, etc. Moreover, there are as many runs of `1`'s as there are of `0`'s. Examples ======== >>> from sympy.crypto.crypto import lfsr_sequence >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> lfsr_sequence(key, fill, 10) [1 mod 2, 1 mod 2, 0 mod 2, 1 mod 2, 0 mod 2, 1 mod 2, 1 mod 2, 0 mod 2, 0 mod 2, 1 mod 2] References ========== .. [G] Solomon Golomb, Shift register sequences, Aegean Park Press, Laguna Hills, Ca, 1967 """ if not isinstance(key, list): raise TypeError("key must be a list") if not isinstance(fill, list): raise TypeError("fill must be a list") p = key[0].mod F = FF(p) s = fill k = len(fill) L = [] for i in range(n): s0 = s[:] L.append(s[0]) s = s[1:k] x = sum([int(key[i]s0[i]) for i in range(k)]) s.append(F(x)) return L # use [x.to_int() for x in L] for int version def lfsr_autocorrelation(L, P, k): """ This function computes the LFSR autocorrelation function. Parameters ========== L A periodic sequence of elements of `GF(2)`. L must have length larger than P. P The period of L. k : int An integer `k` (`0 < k < P`). Returns ======= autocorrelation The k-th value of the autocorrelation of the LFSR L. Examples ======== >>> from sympy.crypto.crypto import ( ... lfsr_sequence, lfsr_autocorrelation) >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_autocorrelation(s, 15, 7) -1/15 >>> lfsr_autocorrelation(s, 15, 0) 1 """ if not isinstance(L, list): raise TypeError("L (=%s) must be a list" % L) P = int(P) k = int(k) L0 = L[:P] # slices makes a copy L1 = L0 + L0[:k] L2 = [(-1)(L1[i].to_int() + L1[i + k].to_int()) for i in range(P)] tot = sum(L2) return Rational(tot, P) def lfsr_connection_polynomial(s): """ This function computes the LFSR connection polynomial. Parameters ========== s A sequence of elements of even length, with entries in a finite field. Returns ======= C(x) The connection polynomial of a minimal LFSR yielding s. This implements the algorithm in section 3 of J. L. Massey's article [M]_. Examples ======== >>> from sympy.crypto.crypto import ( ... lfsr_sequence, lfsr_connection_polynomial) >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x4 + x + 1 >>> fill = [F(1), F(0), F(0), F(1)] >>> key = [F(1), F(1), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x3 + 1 >>> fill = [F(1), F(0), F(1)] >>> key = [F(1), F(1), F(0)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x3 + x2 + 1 >>> fill = [F(1), F(0), F(1)] >>> key = [F(1), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x3 + x + 1 References ========== .. [M] James L. Massey, "Shift-Register Synthesis and BCH Decoding." IEEE Trans. on Information Theory, vol. 15(1), pp. 122-127, Jan 1969. """ # Initialization: p = s[0].mod x = Symbol("x") C = 1x*0 B = 1x*0 m = 1 b = 1x0 L = 0 N = 0 while N < len(s): if L > 0: dC = Poly(C).degree() r = min(L + 1, dC + 1) coeffsC = [C.subs(x, 0)] + [C.coeff(xi) for i in range(1, dC + 1)] d = (s[N].to_int() + sum([coeffsC[i]s[N - i].to_int() for i in range(1, r)])) % p if L == 0: d = s[N].to_int()x*0 if d == 0: m += 1 N += 1 if d > 0: if 2L > N: C = (C - d((b(p - 2)) % p)x*mB).expand() m += 1 N += 1 else: T = C C = (C - d((b(p - 2)) % p)x*mB).expand() L = N + 1 - L m = 1 b = d B = T N += 1 dC = Poly(C).degree() coeffsC = [C.subs(x, 0)] + [C.coeff(x*i) for i in range(1, dC + 1)] return sum([coeffsC[i] % pxi for i in range(dC + 1) if coeffsC[i] is not None]) #################### ElGamal ############################# def elgamal_private_key(digit=10, seed=None): r""" Return three number tuple as private key. Explanation =========== Elgamal encryption is based on the mathmatical problem called the Discrete Logarithm Problem (DLP). For example, `a^{b} \equiv c \pmod p` In general, if ``a`` and ``b`` are known, ``ct`` is easily calculated. If ``b`` is unknown, it is hard to use ``a`` and ``ct`` to get ``b``. Parameters ========== digit : int Minimum number of binary digits for key. Returns ======= tuple : (p, r, d) p = prime number. r = primitive root. d = random number. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import elgamal_private_key >>> from sympy.ntheory import is_primitive_root, isprime >>> a, b, _ = elgamal_private_key() >>> isprime(a) True >>> is_primitive_root(b, a) True """ randrange = _randrange(seed) p = nextprime(2digit) return p, primitive_root(p), randrange(2, p) def elgamal_public_key(key): r""" Return three number tuple as public key. Parameters ========== key : (p, r, e) Tuple generated by ``elgamal_private_key``. Returns ======= tuple : (p, r, e) `e = r*d \bmod p` `d` is a random number in private key. Examples ======== >>> from sympy.crypto.crypto import elgamal_public_key >>> elgamal_public_key((1031, 14, 636)) (1031, 14, 212) """ p, r, e = key return p, r, pow(r, e, p) def encipher_elgamal(i, key, seed=None): r""" Encrypt message with public key. Explanation =========== ``i`` is a plaintext message expressed as an integer. ``key`` is public key (p, r, e). In order to encrypt a message, a random number ``a`` in ``range(2, p)`` is generated and the encryped message is returned as `c_{1}` and `c_{2}` where: `c_{1} \equiv r^{a} \pmod p` `c_{2} \equiv m e^{a} \pmod p` Parameters ========== msg int of encoded message. key Public key. Returns ======= tuple : (c1, c2) Encipher into two number. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import encipher_elgamal, elgamal_private_key, elgamal_public_key >>> pri = elgamal_private_key(5, seed=[3]); pri (37, 2, 3) >>> pub = elgamal_public_key(pri); pub (37, 2, 8) >>> msg = 36 >>> encipher_elgamal(msg, pub, seed=[3]) (8, 6) """ p, r, e = key if i < 0 or i >= p: raise ValueError( 'Message (%s) should be in range(%s)' % (i, p)) randrange = _randrange(seed) a = randrange(2, p) return pow(r, a, p), ipow(e, a, p) % p def decipher_elgamal(msg, key): r""" Decrypt message with private key. `msg = (c_{1}, c_{2})` `key = (p, r, d)` According to extended Eucliden theorem, `u c_{1}^{d} + p n = 1` `u \equiv 1/{{c_{1}}^d} \pmod p` `u c_{2} \equiv \frac{1}{c_{1}^d} c_{2} \equiv \frac{1}{r^{ad}} c_{2} \pmod p` `\frac{1}{r^{ad}} m e^a \equiv \frac{1}{r^{ad}} m {r^{d a}} \equiv m \pmod p` Examples ======== >>> from sympy.crypto.crypto import decipher_elgamal >>> from sympy.crypto.crypto import encipher_elgamal >>> from sympy.crypto.crypto import elgamal_private_key >>> from sympy.crypto.crypto import elgamal_public_key >>> pri = elgamal_private_key(5, seed=[3]) >>> pub = elgamal_public_key(pri); pub (37, 2, 8) >>> msg = 17 >>> decipher_elgamal(encipher_elgamal(msg, pub), pri) == msg True """ p, _, d = key c1, c2 = msg u = igcdex(c1*d, p)[0] return u c2 % p ################ Diffie-Hellman Key Exchange ######################### def dh_private_key(digit=10, seed=None): r""" Return three integer tuple as private key. Explanation =========== Diffie-Hellman key exchange is based on the mathematical problem called the Discrete Logarithm Problem (see ElGamal). Diffie-Hellman key exchange is divided into the following steps: * Alice and Bob agree on a base that consist of a prime ``p`` and a primitive root of ``p`` called ``g`` * Alice choses a number ``a`` and Bob choses a number ``b`` where ``a`` and ``b`` are random numbers in range `[2, p)`. These are their private keys. * Alice then publicly sends Bob `g^{a} \pmod p` while Bob sends Alice `g^{b} \pmod p` * They both raise the received value to their secretly chosen number (``a`` or ``b``) and now have both as their shared key `g^{ab} \pmod p` Parameters ========== digit Minimum number of binary digits required in key. Returns ======= tuple : (p, g, a) p = prime number. g = primitive root of p. a = random number from 2 through p - 1. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import dh_private_key >>> from sympy.ntheory import isprime, is_primitive_root >>> p, g, _ = dh_private_key() >>> isprime(p) True >>> is_primitive_root(g, p) True >>> p, g, _ = dh_private_key(5) >>> isprime(p) True >>> is_primitive_root(g, p) True """ p = nextprime(2*digit) g = primitive_root(p) randrange = _randrange(seed) a = randrange(2, p) return p, g, a def dh_public_key(key): r""" Return three number tuple as public key. This is the tuple that Alice sends to Bob. Parameters ========== key : (p, g, a) A tuple generated by ``dh_private_key``. Returns ======= tuple : int, int, int A tuple of `(p, g, g^a \mod p)` with `p`, `g` and `a` given as parameters.s Examples ======== >>> from sympy.crypto.crypto import dh_private_key, dh_public_key >>> p, g, a = dh_private_key(); >>> _p, _g, x = dh_public_key((p, g, a)) >>> p == _p and g == _g True >>> x == pow(g, a, p) True """ p, g, a = key return p, g, pow(g, a, p) def dh_shared_key(key, b): """ Return an integer that is the shared key. This is what Bob and Alice can both calculate using the public keys they received from each other and their private keys. Parameters ========== key : (p, g, x) Tuple `(p, g, x)` generated by ``dh_public_key``. b Random number in the range of `2` to `p - 1` (Chosen by second key exchange member (Bob)). Returns ======= int A shared key. Examples ======== >>> from sympy.crypto.crypto import ( ... dh_private_key, dh_public_key, dh_shared_key) >>> prk = dh_private_key(); >>> p, g, x = dh_public_key(prk); >>> sk = dh_shared_key((p, g, x), 1000) >>> sk == pow(x, 1000, p) True """ p, _, x = key if 1 >= b or b >= p: raise ValueError(filldedent(''' Value of b should be greater 1 and less than prime %s.''' % p)) return pow(x, b, p) ################ Goldwasser-Micali Encryption ######################### def _legendre(a, p): """ Returns the legendre symbol of a and p assuming that p is a prime. i.e. 1 if a is a quadratic residue mod p -1 if a is not a quadratic residue mod p 0 if a is divisible by p Parameters ========== a : int The number to test. p : prime The prime to test ``a`` against. Returns ======= int Legendre symbol (a / p). """ sig = pow(a, (p - 1)//2, p) if sig == 1: return 1 elif sig == 0: return 0 else: return -1 def _random_coprime_stream(n, seed=None): randrange = _randrange(seed) while True: y = randrange(n) if gcd(y, n) == 1: yield y def gm_private_key(p, q, a=None): """ Check if ``p`` and ``q`` can be used as private keys for the Goldwasser-Micali encryption. The method works roughly as follows. Explanation =========== $\\cdot$ Pick two large primes $p$ and $q$. $\\cdot$ Call their product $N$. $\\cdot$ Given a message as an integer $i$, write $i$ in its bit representation $b_0$ , $\\dotsc$ , $b_n$ . $\\cdot$ For each $k$ , if $b_k$ = 0: let $a_k$ be a random square (quadratic residue) modulo $p q$ such that $jacobi \\_symbol(a, p q) = 1$ if $b_k$ = 1: let $a_k$ be a random non-square (non-quadratic residue) modulo $p q$ such that $jacobi \\_ symbol(a, p q) = 1$ returns [$a_1$ , $a_2$ , $\\dotsc$ ] $b_k$ can be recovered by checking whether or not $a_k$ is a residue. And from the $b_k$ 's, the message can be reconstructed. The idea is that, while $jacobi \\_ symbol(a, p q)$ can be easily computed (and when it is equal to $-1$ will tell you that $a$ is not a square mod $p q$ ), quadratic residuosity modulo a composite number is hard to compute without knowing its factorization. Moreover, approximately half the numbers coprime to $p q$ have $jacobi \\_ symbol$ equal to $1$ . And among those, approximately half are residues and approximately half are not. This maximizes the entropy of the code. Parameters ========== p, q, a Initialization variables. Returns ======= tuple : (p, q) The input value ``p`` and ``q``. Raises ====== ValueError If ``p`` and ``q`` are not distinct odd primes. """ if p == q: raise ValueError("expected distinct primes, " "got two copies of %i" % p) elif not isprime(p) or not isprime(q): raise ValueError("first two arguments must be prime, " "got %i of %i" % (p, q)) elif p == 2 or q == 2: raise ValueError("first two arguments must not be even, " "got %i of %i" % (p, q)) return p, q def gm_public_key(p, q, a=None, seed=None): """ Compute public keys for ``p`` and ``q``. Note that in Goldwasser-Micali Encryption, public keys are randomly selected. Parameters ========== p, q, a : int, int, int Initialization variables. Returns ======= tuple : (a, N) ``a`` is the input ``a`` if it is not ``None`` otherwise some random integer coprime to ``p`` and ``q``. ``N`` is the product of ``p`` and ``q``. """ p, q = gm_private_key(p, q) N = p q if a is None: randrange = _randrange(seed) while True: a = randrange(N) if _legendre(a, p) == _legendre(a, q) == -1: break else: if _legendre(a, p) != -1 or _legendre(a, q) != -1: return False return (a, N) def encipher_gm(i, key, seed=None): """ Encrypt integer 'i' using public_key 'key' Note that gm uses random encryption. Parameters ========== i : int The message to encrypt. key : (a, N) The public key. Returns ======= list : list of int The randomized encrypted message. """ if i < 0: raise ValueError( "message must be a non-negative " "integer: got %d instead" % i) a, N = key bits = [] while i > 0: bits.append(i % 2) i //= 2 gen = _random_coprime_stream(N, seed) rev = reversed(bits) encode = lambda b: next(gen)*2pow(a, b) % N return [ encode(b) for b in rev ] def decipher_gm(message, key): """ Decrypt message 'message' using public_key 'key'. Parameters ========== message : list of int The randomized encrypted message. key : (p, q) The private key. Returns ======= int The encrypted message. """ p, q = key res = lambda m, p: _legendre(m, p) > 0 bits = [res(m, p) * res(m, q) for m in message] m = 0 for b in bits: m <<= 1 m += not b return m ########### RailFence Cipher ############# def encipher_railfence(message,rails): """ Performs Railfence Encryption on plaintext and returns ciphertext Examples ======== >>> from sympy.crypto.crypto import encipher_railfence >>> message = "hello world" >>> encipher_railfence(message,3) 'horel ollwd' Parameters ========== message : string, the message to encrypt. rails : int, the number of rails. Returns ======= The Encrypted string message. References ========== .. [1] https://en.wikipedia.org/wiki/Rail_fence_cipher """ r = list(range(rails)) p = cycle(r + r[-2:0:-1]) return ''.join(sorted(message, key=lambda i: next(p))) def decipher_railfence(ciphertext,rails): """ Decrypt the message using the given rails Examples ======== >>> from sympy.crypto.crypto import decipher_railfence >>> decipher_railfence("horel ollwd",3) 'hello world' Parameters ========== message : string, the message to encrypt. rails : int, the number of rails. Returns ======= The Decrypted string message. """ r = list(range(rails)) p = cycle(r + r[-2:0:-1]) idx = sorted(range(len(ciphertext)), key=lambda i: next(p)) res = [''] * len(ciphertext) for i, c in zip(idx, ciphertext): res[i] = c return ''.join(res) ################ Blum-Goldwasser cryptosystem ######################### def bg_private_key(p, q): """ Check if p and q can be used as private keys for the Blum-Goldwasser cryptosystem. Explanation =========== The three necessary checks for p and q to pass so that they can be used as private keys: 1. p and q must both be prime 2. p and q must be distinct 3. p and q must be congruent to 3 mod 4 Parameters ========== p, q The keys to be checked. Returns ======= p, q Input values. Raises ====== ValueError If p and q do not pass the above conditions. """ if not isprime(p) or not isprime(q): raise ValueError("the two arguments must be prime, " "got %i and %i" %(p, q)) elif p == q: raise ValueError("the two arguments must be distinct, " "got two copies of %i. " %p) elif (p - 3) % 4 != 0 or (q - 3) % 4 != 0: raise ValueError("the two arguments must be congruent to 3 mod 4, " "got %i and %i" %(p, q)) return p, q def bg_public_key(p, q): """ Calculates public keys from private keys. Explanation =========== The function first checks the validity of private keys passed as arguments and then returns their product. Parameters ========== p, q The private keys. Returns ======= N The public key. """ p, q = bg_private_key(p, q) N = p * q return N def encipher_bg(i, key, seed=None): """ Encrypts the message using public key and seed. Explanation =========== ALGORITHM: 1. Encodes i as a string of L bits, m. 2. Select a random element r, where 1 < r < key, and computes x = r^2 mod key. 3. Use BBS pseudo-random number generator to generate L random bits, b, using the initial seed as x. 4. Encrypted message, c_i = m_i XOR b_i, 1 <= i <= L. 5. x_L = x^(2^L) mod key. 6. Return (c, x_L) Parameters ========== i Message, a non-negative integer key The public key Returns ======= Tuple (encrypted_message, x_L) Raises ====== ValueError If i is negative. """ if i < 0: raise ValueError( "message must be a non-negative " "integer: got %d instead" % i) enc_msg = [] while i > 0: enc_msg.append(i % 2) i //= 2 enc_msg.reverse() L = len(enc_msg) r = _randint(seed)(2, key - 1) x = r2 % key x_L = pow(int(x), int(2L), int(key)) rand_bits = [] for _ in range(L): rand_bits.append(x % 2) x = x*2 % key encrypt_msg = [m ^ b for (m, b) in zip(enc_msg, rand_bits)] return (encrypt_msg, x_L) def decipher_bg(message, key): """ Decrypts the message using private keys. Explanation =========== ALGORITHM: 1. Let, c be the encrypted message, y the second number received, and p and q be the private keys. 2. Compute, r_p = y^((p+1)/4 ^ L) mod p and r_q = y^((q+1)/4 ^ L) mod q. 3. Compute x_0 = (q(q^-1 mod p)r_p + p(p^-1 mod q)r_q) mod N. 4. From, recompute the bits using the BBS generator, as in the encryption algorithm. 5. Compute original message by XORing c and b. Parameters ========== message Tuple of encrypted message and a non-negative integer. key Tuple of private keys. Returns ======= orig_msg The original message """ p, q = key encrypt_msg, y = message public_key = p q L = len(encrypt_msg) p_t = ((p + 1)/4)L q_t = ((q + 1)/4)L r_p = pow(int(y), int(p_t), int(p)) r_q = pow(int(y), int(q_t), int(q)) x = (q * mod_inverse(q, p) * r_p + p * mod_inverse(p, q) * r_q) % public_key orig_bits = [] for _ in range(L): orig_bits.append(x % 2) x = x*2 % public_key orig_msg = 0 for (m, b) in zip(encrypt_msg, orig_bits): orig_msg = orig_msg 2 orig_msg += (m ^ b) return orig_msg
995dbc94b5fcf1e2a06ce72aa655d2eeb83c6caff96e7299dfaf4e7e8a024e22	from sympy.core.add import Add from sympy.core.compatibility import ordered from sympy.core.function import expand_log from sympy.core.power import Pow from sympy.core.singleton import S from sympy.core.symbol import Dummy from sympy.functions.elementary.exponential import (LambertW, exp, log) from sympy.functions.elementary.miscellaneous import root from sympy.polys.polyroots import roots from sympy.polys.polytools import Poly, factor from sympy.core.function import _mexpand from sympy.simplify.simplify import separatevars from sympy.simplify.radsimp import collect from sympy.simplify.simplify import powsimp from sympy.solvers.solvers import solve, _invert from sympy.utilities.iterables import uniq def _filtered_gens(poly, symbol): """process the generators of ``poly``, returning the set of generators that have ``symbol``. If there are two generators that are inverses of each other, prefer the one that has no denominator. Examples ======== >>> from sympy.solvers.bivariate import _filtered_gens >>> from sympy import Poly, exp >>> from sympy.abc import x >>> _filtered_gens(Poly(x + 1/x + exp(x)), x) {x, exp(x)} """ gens = {g for g in poly.gens if symbol in g.free_symbols} for g in list(gens): ag = 1/g if g in gens and ag in gens: if ag.as_numer_denom()[1] is not S.One: g = ag gens.remove(g) return gens def _mostfunc(lhs, func, X=None): """Returns the term in lhs which contains the most of the func-type things e.g. log(log(x)) wins over log(x) if both terms appear. ``func`` can be a function (exp, log, etc...) or any other SymPy object, like Pow. If ``X`` is not ``None``, then the function returns the term composed with the most ``func`` having the specified variable. Examples ======== >>> from sympy.solvers.bivariate import _mostfunc >>> from sympy.functions.elementary.exponential import exp >>> from sympy.abc import x, y >>> _mostfunc(exp(x) + exp(exp(x) + 2), exp) exp(exp(x) + 2) >>> _mostfunc(exp(x) + exp(exp(y) + 2), exp) exp(exp(y) + 2) >>> _mostfunc(exp(x) + exp(exp(y) + 2), exp, x) exp(x) >>> _mostfunc(x, exp, x) is None True >>> _mostfunc(exp(x) + exp(xy), exp, x) exp(x) """ fterms = [tmp for tmp in lhs.atoms(func) if (not X or X.is_Symbol and X in tmp.free_symbols or not X.is_Symbol and tmp.has(X))] if len(fterms) == 1: return fterms[0] elif fterms: return max(list(ordered(fterms)), key=lambda x: x.count(func)) return None def _linab(arg, symbol): """Return ``a, b, X`` assuming ``arg`` can be written as ``aX + b`` where ``X`` is a symbol-dependent factor and ``a`` and ``b`` are independent of ``symbol``. Examples ======== >>> from sympy.functions.elementary.exponential import exp >>> from sympy.solvers.bivariate import _linab >>> from sympy.abc import x, y >>> from sympy import S >>> _linab(S(2), x) (2, 0, 1) >>> _linab(2x, x) (2, 0, x) >>> _linab(y + yx + 2x, x) (y + 2, y, x) >>> _linab(3 + 2exp(x), x) (2, 3, exp(x)) """ from sympy.core.exprtools import factor_terms arg = factor_terms(arg.expand()) ind, dep = arg.as_independent(symbol) if arg.is_Mul and dep.is_Add: a, b, x = _linab(dep, symbol) return inda, indb, x if not arg.is_Add: b = 0 a, x = ind, dep else: b = ind a, x = separatevars(dep).as_independent(symbol, as_Add=False) if x.could_extract_minus_sign(): a = -a x = -x return a, b, x def _lambert(eq, x): """ Given an expression assumed to be in the form ``F(X, a..f) = alog(bX + c) + dX + f = 0`` where X = g(x) and x = g^-1(X), return the Lambert solution, ``x = g^-1(-c/b + (a/d)W(d/(ab)exp(cd/a/b)exp(-f/a)))``. """ eq = _mexpand(expand_log(eq)) mainlog = _mostfunc(eq, log, x) if not mainlog: return [] # violated assumptions other = eq.subs(mainlog, 0) if isinstance(-other, log): eq = (eq - other).subs(mainlog, mainlog.args[0]) mainlog = mainlog.args[0] if not isinstance(mainlog, log): return [] # violated assumptions other = -(-other).args[0] eq += other if not x in other.free_symbols: return [] # violated assumptions d, f, X2 = _linab(other, x) logterm = collect(eq - other, mainlog) a = logterm.as_coefficient(mainlog) if a is None or x in a.free_symbols: return [] # violated assumptions logarg = mainlog.args[0] b, c, X1 = _linab(logarg, x) if X1 != X2: return [] # violated assumptions # invert the generator X1 so we have x(u) u = Dummy('rhs') xusolns = solve(X1 - u, x) # There are infinitely many branches for LambertW # but only branches for k = -1 and 0 might be real. The k = 0 # branch is real and the k = -1 branch is real if the LambertW argumen # in in range [-1/e, 0]. Since `solve` does not return infinite # solutions we will only include the -1 branch if it tests as real. # Otherwise, inclusion of any LambertW in the solution indicates to # the user that there are imaginary solutions corresponding to # different k values. lambert_real_branches = [-1, 0] sol = [] # solution of the given Lambert equation is like # sol = -c/b + (a/d)LambertW(arg, k), # where arg = d/(ab)exp((cd-bf)/a/b) and k in lambert_real_branches. # Instead of considering the single arg, `d/(ab)exp((cd-bf)/a/b)`, # the individual `p` roots obtained when writing `exp((cd-bf)/a/b)` # as `exp(A/p) = exp(A)(1/p)`, where `p` is an Integer, are used. # calculating args for LambertW num, den = ((cd-bf)/a/b).as_numer_denom() p, den = den.as_coeff_Mul() e = exp(num/den) t = Dummy('t') args = [d/(ab)t for t in roots(tp - e, t).keys()] # calculating solutions from args for arg in args: for k in lambert_real_branches: w = LambertW(arg, k) if k and not w.is_real: continue rhs = -c/b + (a/d)w for xu in xusolns: sol.append(xu.subs(u, rhs)) return sol def _solve_lambert(f, symbol, gens): """Return solution to ``f`` if it is a Lambert-type expression else raise NotImplementedError. For ``f(X, a..f) = alog(bX + c) + dX - f = 0`` the solution for ``X`` is ``X = -c/b + (a/d)W(d/(ab)exp(cd/a/b)exp(f/a))``. There are a variety of forms for `f(X, a..f)` as enumerated below: 1a1) if B*B = R for R not in [0, 1] (since those cases would already be solved before getting here) then log of both sides gives log(B) + log(log(B)) = log(log(R)) and X = log(B), a = 1, b = 1, c = 0, d = 1, f = log(log(R)) 1a2) if B(blog(B) + c)a = R then log of both sides gives log(B) + alog(blog(B) + c) = log(R) and X = log(B), d=1, f=log(R) 1b) if alog(bB + c) + dB = R and X = B, f = R 2a) if (bB + c)exp(dB + g) = R then log of both sides gives log(bB + c) + dB + g = log(R) and X = B, a = 1, f = log(R) - g 2b) if gexp(dB + h) - bB = c then the log form is log(g) + dB + h - log(bB + c) = 0 and X = B, a = -1, f = -h - log(g) 3) if dp(aB + g) - bB = c then the log form is log(d) + (aB + g)log(p) - log(bB + c) = 0 and X = B, a = -1, d = alog(p), f = -log(d) - glog(p) """ def _solve_even_degree_expr(expr, t, symbol): """Return the unique solutions of equations derived from ``expr`` by replacing ``t`` with ``+/- symbol``. Parameters ========== expr : Expr The expression which includes a dummy variable t to be replaced with +symbol and -symbol. symbol : Symbol The symbol for which a solution is being sought. Returns ======= List of unique solution of the two equations generated by replacing ``t`` with positive and negative ``symbol``. Notes ===== If ``expr = 2log(t) + x/2` then solutions for ``2log(x) + x/2 = 0`` and ``2log(-x) + x/2 = 0`` are returned by this function. Though this may seem counter-intuitive, one must note that the ``expr`` being solved here has been derived from a different expression. For an expression like ``eq = x2g(x) = 1``, if we take the log of both sides we obtain ``log(x*2) + log(g(x)) = 0``. If x is positive then this simplifies to ``2log(x) + log(g(x)) = 0``; the Lambert-solving routines will return solutions for this, but we must also consider the solutions for ``2log(-x) + log(g(x))`` since those must also be a solution of ``eq`` which has the same value when the ``x`` in ``x2`` is negated. If `g(x)` does not have even powers of symbol then we don't want to replace the ``x`` there with ``-x``. So the role of the ``t`` in the expression received by this function is to mark where ``+/-x`` should be inserted before obtaining the Lambert solutions. """ nlhs, plhs = [ expr.xreplace({t: sgnsymbol}) for sgn in (-1, 1)] sols = _solve_lambert(nlhs, symbol, gens) if plhs != nlhs: sols.extend(_solve_lambert(plhs, symbol, gens)) # uniq is needed for a case like # 2log(t) - log(-z2) + log(z + log(x) + log(z)) # where subtituting t with +/-x gives all the same solution; # uniq, rather than list(set()), is used to maintain canonical # order return list(uniq(sols)) nrhs, lhs = f.as_independent(symbol, as_Add=True) rhs = -nrhs lamcheck = [tmp for tmp in gens if (tmp.func in [exp, log] or (tmp.is_Pow and symbol in tmp.exp.free_symbols))] if not lamcheck: raise NotImplementedError() if lhs.is_Add or lhs.is_Mul: # replacing all even_degrees of symbol with dummy variable t # since these will need special handling; non-Add/Mul do not # need this handling t = Dummy('t', symbol.assumptions0) lhs = lhs.replace( lambda i: # find symboleven i.is_Pow and i.base == symbol and i.exp.is_even, lambda i: # replace teven ti.exp) if lhs.is_Add and lhs.has(t): t_indep = lhs.subs(t, 0) t_term = lhs - t_indep _rhs = rhs - t_indep if not t_term.is_Add and _rhs and not ( t_term.has(S.ComplexInfinity, S.NaN)): eq = expand_log(log(t_term) - log(_rhs)) return _solve_even_degree_expr(eq, t, symbol) elif lhs.is_Mul and rhs: # this needs to happen whether t is present or not lhs = expand_log(log(lhs), force=True) rhs = log(rhs) if lhs.has(t) and lhs.is_Add: # it expanded from Mul to Add eq = lhs - rhs return _solve_even_degree_expr(eq, t, symbol) # restore symbol in lhs lhs = lhs.xreplace({t: symbol}) lhs = powsimp(factor(lhs, deep=True)) # make sure we have inverted as completely as possible r = Dummy() i, lhs = _invert(lhs - r, symbol) rhs = i.xreplace({r: rhs}) # For the first forms: # # 1a1) BB = R will arrive here as Blog(B) = log(R) # lhs is Mul so take log of both sides: # log(B) + log(log(B)) = log(log(R)) # 1a2) B(blog(B) + c)*a = R will arrive unchanged so # lhs is Mul, so take log of both sides: # log(B) + alog(blog(B) + c) = log(R) # 1b) dlog(aB + b) + cB = R will arrive unchanged so # lhs is Add, so isolate cB and expand log of both sides: # log(c) + log(B) = log(R - dlog(aB + b)) soln = [] if not soln: mainlog = _mostfunc(lhs, log, symbol) if mainlog: if lhs.is_Mul and rhs != 0: soln = _lambert(log(lhs) - log(rhs), symbol) elif lhs.is_Add: other = lhs.subs(mainlog, 0) if other and not other.is_Add and [ tmp for tmp in other.atoms(Pow) if symbol in tmp.free_symbols]: if not rhs: diff = log(other) - log(other - lhs) else: diff = log(lhs - other) - log(rhs - other) soln = _lambert(expand_log(diff), symbol) else: #it's ready to go soln = _lambert(lhs - rhs, symbol) # For the next forms, # # collect on main exp # 2a) (bB + c)exp(dB + g) = R # lhs is mul, so take log of both sides: # log(bB + c) + dB = log(R) - g # 2b) gexp(dB + h) - bB = R # lhs is add, so add bB to both sides, # take the log of both sides and rearrange to give # log(R + bB) - dB = log(g) + h if not soln: mainexp = _mostfunc(lhs, exp, symbol) if mainexp: lhs = collect(lhs, mainexp) if lhs.is_Mul and rhs != 0: soln = _lambert(expand_log(log(lhs) - log(rhs)), symbol) elif lhs.is_Add: # move all but mainexp-containing term to rhs other = lhs.subs(mainexp, 0) mainterm = lhs - other rhs = rhs - other if (mainterm.could_extract_minus_sign() and rhs.could_extract_minus_sign()): mainterm = -1 rhs = -1 diff = log(mainterm) - log(rhs) soln = _lambert(expand_log(diff), symbol) # For the last form: # # 3) dp(aB + g) - bB = c # collect on main pow, add bB to both sides, # take log of both sides and rearrange to give # aBlog(p) - log(bB + c) = -log(d) - glog(p) if not soln: mainpow = _mostfunc(lhs, Pow, symbol) if mainpow and symbol in mainpow.exp.free_symbols: lhs = collect(lhs, mainpow) if lhs.is_Mul and rhs != 0: # bB = 0 soln = _lambert(expand_log(log(lhs) - log(rhs)), symbol) elif lhs.is_Add: # move all but mainpow-containing term to rhs other = lhs.subs(mainpow, 0) mainterm = lhs - other rhs = rhs - other diff = log(mainterm) - log(rhs) soln = _lambert(expand_log(diff), symbol) if not soln: raise NotImplementedError('%s does not appear to have a solution in ' 'terms of LambertW' % f) return list(ordered(soln)) def bivariate_type(f, x, y, , first=True): """Given an expression, f, 3 tests will be done to see what type of composite bivariate it might be, options for u(x, y) are:: xy x+y xy+x xy+y If it matches one of these types, ``u(x, y)``, ``P(u)`` and dummy variable ``u`` will be returned. Solving ``P(u)`` for ``u`` and equating the solutions to ``u(x, y)`` and then solving for ``x`` or ``y`` is equivalent to solving the original expression for ``x`` or ``y``. If ``x`` and ``y`` represent two functions in the same variable, e.g. ``x = g(t)`` and ``y = h(t)``, then if ``u(x, y) - p`` can be solved for ``t`` then these represent the solutions to ``P(u) = 0`` when ``p`` are the solutions of ``P(u) = 0``. Only positive values of ``u`` are considered. Examples ======== >>> from sympy.solvers.solvers import solve >>> from sympy.solvers.bivariate import bivariate_type >>> from sympy.abc import x, y >>> eq = (x2 - 3).subs(x, x + y) >>> bivariate_type(eq, x, y) (x + y, _u2 - 3, _u) >>> uxy, pu, u = _ >>> usol = solve(pu, u); usol [sqrt(3)] >>> [solve(uxy - s) for s in solve(pu, u)] [[{x: -y + sqrt(3)}]] >>> all(eq.subs(s).equals(0) for sol in _ for s in sol) True """ u = Dummy('u', positive=True) if first: p = Poly(f, x, y) f = p.as_expr() _x = Dummy() _y = Dummy() rv = bivariate_type(Poly(f.subs({x: _x, y: _y}), _x, _y), _x, _y, first=False) if rv: reps = {_x: x, _y: y} return rv[0].xreplace(reps), rv[1].xreplace(reps), rv[2] return p = f f = p.as_expr() # f(xy) args = Add.make_args(p.as_expr()) new = [] for a in args: a = _mexpand(a.subs(x, u/y)) free = a.free_symbols if x in free or y in free: break new.append(a) else: return xy, Add(new), u def ok(f, v, c): new = _mexpand(f.subs(v, c)) free = new.free_symbols return None if (x in free or y in free) else new # f(ax + by) new = [] d = p.degree(x) if p.degree(y) == d: a = root(p.coeff_monomial(xd), d) b = root(p.coeff_monomial(yd), d) new = ok(f, x, (u - by)/a) if new is not None: return ax + by, new, u # f(axy + by) new = [] d = p.degree(x) if p.degree(y) == d: for itry in range(2): a = root(p.coeff_monomial(x*dyd), d) b = root(p.coeff_monomial(yd), d) new = ok(f, x, (u - by)/a/y) if new is not None: return axy + by, new, u x, y = y, x
6979c6ce6a257f2ae9f98793ac839436534e4ab9bddc03a0420acae110359871	r""" This module is intended for solving recurrences or, in other words, difference equations. Currently supported are linear, inhomogeneous equations with polynomial or rational coefficients. The solutions are obtained among polynomials, rational functions, hypergeometric terms, or combinations of hypergeometric term which are pairwise dissimilar. ``rsolve_X`` functions were meant as a low level interface for ``rsolve`` which would use Mathematica's syntax. Given a recurrence relation: .. math:: a_{k}(n) y(n+k) + a_{k-1}(n) y(n+k-1) + ... + a_{0}(n) y(n) = f(n) where `k > 0` and `a_{i}(n)` are polynomials in `n`. To use ``rsolve_X`` we need to put all coefficients in to a list ``L`` of `k+1` elements the following way: ``L = [a_{0}(n), ..., a_{k-1}(n), a_{k}(n)]`` where ``L[i]``, for `i=0, \ldots, k`, maps to `a_{i}(n) y(n+i)` (`y(n+i)` is implicit). For example if we would like to compute `m`-th Bernoulli polynomial up to a constant (example was taken from rsolve_poly docstring), then we would use `b(n+1) - b(n) = m n^{m-1}` recurrence, which has solution `b(n) = B_m + C`. Then ``L = [-1, 1]`` and `f(n) = m n^(m-1)` and finally for `m=4`: >>> from sympy import Symbol, bernoulli, rsolve_poly >>> n = Symbol('n', integer=True) >>> rsolve_poly([-1, 1], 4n3, n) C0 + n4 - 2n3 + n2 >>> bernoulli(4, n) n*4 - 2n3 + n2 - 1/30 For the sake of completeness, `f(n)` can be: [1] a polynomial -> rsolve_poly [2] a rational function -> rsolve_ratio [3] a hypergeometric function -> rsolve_hyper """ from collections import defaultdict from sympy.core.singleton import S from sympy.core.numbers import Rational, I from sympy.core.symbol import Symbol, Wild, Dummy from sympy.core.relational import Equality from sympy.core.add import Add from sympy.core.mul import Mul from sympy.core import sympify from sympy.simplify import simplify, hypersimp, hypersimilar # type: ignore from sympy.solvers import solve, solve_undetermined_coeffs from sympy.polys import Poly, quo, gcd, lcm, roots, resultant from sympy.functions import binomial, factorial, FallingFactorial, RisingFactorial from sympy.matrices import Matrix, casoratian from sympy.concrete import product from sympy.core.compatibility import default_sort_key from sympy.utilities.iterables import numbered_symbols def rsolve_poly(coeffs, f, n, *hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f`, where `f` is a polynomial, we seek for all polynomial solutions over field `K` of characteristic zero. The algorithm performs two basic steps: (1) Compute degree `N` of the general polynomial solution. (2) Find all polynomials of degree `N` or less of `\operatorname{L} y = f`. There are two methods for computing the polynomial solutions. If the degree bound is relatively small, i.e. it's smaller than or equal to the order of the recurrence, then naive method of undetermined coefficients is being used. This gives system of algebraic equations with `N+1` unknowns. In the other case, the algorithm performs transformation of the initial equation to an equivalent one, for which the system of algebraic equations has only `r` indeterminates. This method is quite sophisticated (in comparison with the naive one) and was invented together by Abramov, Bronstein and Petkovsek. It is possible to generalize the algorithm implemented here to the case of linear q-difference and differential equations. Lets say that we would like to compute `m`-th Bernoulli polynomial up to a constant. For this we can use `b(n+1) - b(n) = m n^{m-1}` recurrence, which has solution `b(n) = B_m + C`. For example: >>> from sympy import Symbol, rsolve_poly >>> n = Symbol('n', integer=True) >>> rsolve_poly([-1, 1], 4n3, n) C0 + n4 - 2n3 + n2 References ========== .. [1] S. A. Abramov, M. Bronstein and M. Petkovsek, On polynomial solutions of linear operator equations, in: T. Levelt, ed., Proc. ISSAC '95, ACM Press, New York, 1995, 290-296. .. [2] M. Petkovsek, Hypergeometric solutions of linear recurrences with polynomial coefficients, J. Symbolic Computation, 14 (1992), 243-264. .. [3] M. Petkovsek, H. S. Wilf, D. Zeilberger, A = B, 1996. """ f = sympify(f) if not f.is_polynomial(n): return None homogeneous = f.is_zero r = len(coeffs) - 1 coeffs = [Poly(coeff, n) for coeff in coeffs] polys = [Poly(0, n)](r + 1) terms = [(S.Zero, S.NegativeInfinity)](r + 1) for i in range(r + 1): for j in range(i, r + 1): polys[i] += coeffs[j](binomial(j, i).as_poly(n)) if not polys[i].is_zero: (exp,), coeff = polys[i].LT() terms[i] = (coeff, exp) d = b = terms[0][1] for i in range(1, r + 1): if terms[i][1] > d: d = terms[i][1] if terms[i][1] - i > b: b = terms[i][1] - i d, b = int(d), int(b) x = Dummy('x') degree_poly = S.Zero for i in range(r + 1): if terms[i][1] - i == b: degree_poly += terms[i][0]FallingFactorial(x, i) nni_roots = list(roots(degree_poly, x, filter='Z', predicate=lambda r: r >= 0).keys()) if nni_roots: N = [max(nni_roots)] else: N = [] if homogeneous: N += [-b - 1] else: N += [f.as_poly(n).degree() - b, -b - 1] N = int(max(N)) if N < 0: if homogeneous: if hints.get('symbols', False): return (S.Zero, []) else: return S.Zero else: return None if N <= r: C = [] y = E = S.Zero for i in range(N + 1): C.append(Symbol('C' + str(i))) y += C[i] n*i for i in range(r + 1): E += coeffs[i].as_expr()y.subs(n, n + i) solutions = solve_undetermined_coeffs(E - f, C, n) if solutions is not None: C = [c for c in C if (c not in solutions)] result = y.subs(solutions) else: return None # TBD else: A = r U = N + A + b + 1 nni_roots = list(roots(polys[r], filter='Z', predicate=lambda r: r >= 0).keys()) if nni_roots != []: a = max(nni_roots) + 1 else: a = S.Zero def _zero_vector(k): return [S.Zero] * k def _one_vector(k): return [S.One] * k def _delta(p, k): B = S.One D = p.subs(n, a + k) for i in range(1, k + 1): B = Rational(i - k - 1, i) D += B p.subs(n, a + k - i) return D alpha = {} for i in range(-A, d + 1): I = _one_vector(d + 1) for k in range(1, d + 1): I[k] = I[k - 1] * (x + i - k + 1)/k alpha[i] = S.Zero for j in range(A + 1): for k in range(d + 1): B = binomial(k, i + j) D = _delta(polys[j].as_expr(), k) alpha[i] += I[k]BD V = Matrix(U, A, lambda i, j: int(i == j)) if homogeneous: for i in range(A, U): v = _zero_vector(A) for k in range(1, A + b + 1): if i - k < 0: break B = alpha[k - A].subs(x, i - k) for j in range(A): v[j] += B * V[i - k, j] denom = alpha[-A].subs(x, i) for j in range(A): V[i, j] = -v[j] / denom else: G = _zero_vector(U) for i in range(A, U): v = _zero_vector(A) g = S.Zero for k in range(1, A + b + 1): if i - k < 0: break B = alpha[k - A].subs(x, i - k) for j in range(A): v[j] += B * V[i - k, j] g += B * G[i - k] denom = alpha[-A].subs(x, i) for j in range(A): V[i, j] = -v[j] / denom G[i] = (_delta(f, i - A) - g) / denom P, Q = _one_vector(U), _zero_vector(A) for i in range(1, U): P[i] = (P[i - 1] * (n - a - i + 1)/i).expand() for i in range(A): Q[i] = Add([(vp).expand() for v, p in zip(V[:, i], P)]) if not homogeneous: h = Add([(gp).expand() for g, p in zip(G, P)]) C = [Symbol('C' + str(i)) for i in range(A)] g = lambda i: Add([c_delta(q, i) for c, q in zip(C, Q)]) if homogeneous: E = [g(i) for i in range(N + 1, U)] else: E = [g(i) + _delta(h, i) for i in range(N + 1, U)] if E != []: solutions = solve(E, C) if not solutions: if homogeneous: if hints.get('symbols', False): return (S.Zero, []) else: return S.Zero else: return None else: solutions = {} if homogeneous: result = S.Zero else: result = h for c, q in list(zip(C, Q)): if c in solutions: s = solutions[c]q C.remove(c) else: s = cq result += s.expand() if hints.get('symbols', False): return (result, C) else: return result def rsolve_ratio(coeffs, f, n, hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f`, where `f` is a polynomial, we seek for all rational solutions over field `K` of characteristic zero. This procedure accepts only polynomials, however if you are interested in solving recurrence with rational coefficients then use ``rsolve`` which will pre-process the given equation and run this procedure with polynomial arguments. The algorithm performs two basic steps: (1) Compute polynomial `v(n)` which can be used as universal denominator of any rational solution of equation `\operatorname{L} y = f`. (2) Construct new linear difference equation by substitution `y(n) = u(n)/v(n)` and solve it for `u(n)` finding all its polynomial solutions. Return ``None`` if none were found. Algorithm implemented here is a revised version of the original Abramov's algorithm, developed in 1989. The new approach is much simpler to implement and has better overall efficiency. This method can be easily adapted to q-difference equations case. Besides finding rational solutions alone, this functions is an important part of Hyper algorithm were it is used to find particular solution of inhomogeneous part of a recurrence. Examples ======== >>> from sympy.abc import x >>> from sympy.solvers.recurr import rsolve_ratio >>> rsolve_ratio([-2x3 + x2 + 2x - 1, 2x3 + x2 - 6x, ... - 2x*3 - 11x*2 - 18x - 9, 2x3 + 13x*2 + 22x + 8], 0, x) C2(2x - 3)/(2(x2 - 1)) References ========== .. [1] S. A. Abramov, Rational solutions of linear difference and q-difference equations with polynomial coefficients, in: T. Levelt, ed., Proc. ISSAC '95, ACM Press, New York, 1995, 285-289 See Also ======== rsolve_hyper """ f = sympify(f) if not f.is_polynomial(n): return None coeffs = list(map(sympify, coeffs)) r = len(coeffs) - 1 A, B = coeffs[r], coeffs[0] A = A.subs(n, n - r).expand() h = Dummy('h') res = resultant(A, B.subs(n, n + h), n) if not res.is_polynomial(h): p, q = res.as_numer_denom() res = quo(p, q, h) nni_roots = list(roots(res, h, filter='Z', predicate=lambda r: r >= 0).keys()) if not nni_roots: return rsolve_poly(coeffs, f, n, hints) else: C, numers = S.One, [S.Zero](r + 1) for i in range(int(max(nni_roots)), -1, -1): d = gcd(A, B.subs(n, n + i), n) A = quo(A, d, n) B = quo(B, d.subs(n, n - i), n) C = Mul([d.subs(n, n - j) for j in range(i + 1)]) denoms = [C.subs(n, n + i) for i in range(r + 1)] for i in range(r + 1): g = gcd(coeffs[i], denoms[i], n) numers[i] = quo(coeffs[i], g, n) denoms[i] = quo(denoms[i], g, n) for i in range(r + 1): numers[i] = Mul((denoms[:i] + denoms[i + 1:])) result = rsolve_poly(numers, f * Mul(denoms), n, hints) if result is not None: if hints.get('symbols', False): return (simplify(result[0] / C), result[1]) else: return simplify(result / C) else: return None def rsolve_hyper(coeffs, f, n, hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f` we seek for all hypergeometric solutions over field `K` of characteristic zero. The inhomogeneous part can be either hypergeometric or a sum of a fixed number of pairwise dissimilar hypergeometric terms. The algorithm performs three basic steps: (1) Group together similar hypergeometric terms in the inhomogeneous part of `\operatorname{L} y = f`, and find particular solution using Abramov's algorithm. (2) Compute generating set of `\operatorname{L}` and find basis in it, so that all solutions are linearly independent. (3) Form final solution with the number of arbitrary constants equal to dimension of basis of `\operatorname{L}`. Term `a(n)` is hypergeometric if it is annihilated by first order linear difference equations with polynomial coefficients or, in simpler words, if consecutive term ratio is a rational function. The output of this procedure is a linear combination of fixed number of hypergeometric terms. However the underlying method can generate larger class of solutions - D'Alembertian terms. Note also that this method not only computes the kernel of the inhomogeneous equation, but also reduces in to a basis so that solutions generated by this procedure are linearly independent Examples ======== >>> from sympy.solvers import rsolve_hyper >>> from sympy.abc import x >>> rsolve_hyper([-1, -1, 1], 0, x) C0(1/2 - sqrt(5)/2)*x + C1(1/2 + sqrt(5)/2)*x >>> rsolve_hyper([-1, 1], 1 + x, x) C0 + x(x + 1)/2 References ========== .. [1] M. Petkovsek, Hypergeometric solutions of linear recurrences with polynomial coefficients, J. Symbolic Computation, 14 (1992), 243-264. .. [2] M. Petkovsek, H. S. Wilf, D. Zeilberger, A = B, 1996. """ coeffs = list(map(sympify, coeffs)) f = sympify(f) r, kernel, symbols = len(coeffs) - 1, [], set() if not f.is_zero: if f.is_Add: similar = {} for g in f.expand().args: if not g.is_hypergeometric(n): return None for h in similar.keys(): if hypersimilar(g, h, n): similar[h] += g break else: similar[g] = S.Zero inhomogeneous = [] for g, h in similar.items(): inhomogeneous.append(g + h) elif f.is_hypergeometric(n): inhomogeneous = [f] else: return None for i, g in enumerate(inhomogeneous): coeff, polys = S.One, coeffs[:] denoms = [S.One](r + 1) s = hypersimp(g, n) for j in range(1, r + 1): coeff = s.subs(n, n + j - 1) p, q = coeff.as_numer_denom() polys[j] = p denoms[j] = q for j in range(r + 1): polys[j] = Mul((denoms[:j] + denoms[j + 1:])) R = rsolve_poly(polys, Mul(denoms), n) if not (R is None or R is S.Zero): inhomogeneous[i] = R else: return None result = Add(inhomogeneous) else: result = S.Zero Z = Dummy('Z') p, q = coeffs[0], coeffs[r].subs(n, n - r + 1) p_factors = [z for z in roots(p, n).keys()] q_factors = [z for z in roots(q, n).keys()] factors = [(S.One, S.One)] for p in p_factors: for q in q_factors: if p.is_integer and q.is_integer and p <= q: continue else: factors += [(n - p, n - q)] p = [(n - p, S.One) for p in p_factors] q = [(S.One, n - q) for q in q_factors] factors = p + factors + q for A, B in factors: polys, degrees = [], [] D = AB.subs(n, n + r - 1) for i in range(r + 1): a = Mul([A.subs(n, n + j) for j in range(i)]) b = Mul([B.subs(n, n + j) for j in range(i, r)]) poly = quo(coeffs[i]ab, D, n) polys.append(poly.as_poly(n)) if not poly.is_zero: degrees.append(polys[i].degree()) if degrees: d, poly = max(degrees), S.Zero else: return None for i in range(r + 1): coeff = polys[i].nth(d) if coeff is not S.Zero: poly += coeff Z*i for z in roots(poly, Z).keys(): if z.is_zero: continue (C, s) = rsolve_poly([polys[i].as_expr()z*i for i in range(r + 1)], 0, n, symbols=True) if C is not None and C is not S.Zero: symbols \|= set(s) ratio = z A * C.subs(n, n + 1) / B / C ratio = simplify(ratio) # If there is a nonnegative root in the denominator of the ratio, # this indicates that the term y(n_root) is zero, and one should # start the product with the term y(n_root + 1). n0 = 0 for n_root in roots(ratio.as_numer_denom()[1], n).keys(): if n_root.has(I): return None elif (n0 < (n_root + 1)) == True: n0 = n_root + 1 K = product(ratio, (n, n0, n - 1)) if K.has(factorial, FallingFactorial, RisingFactorial): K = simplify(K) if casoratian(kernel + [K], n, zero=False) != 0: kernel.append(K) kernel.sort(key=default_sort_key) sk = list(zip(numbered_symbols('C'), kernel)) if sk: for C, ker in sk: result += C * ker else: return None if hints.get('symbols', False): # XXX: This returns the symbols in a non-deterministic order symbols \|= {s for s, k in sk} return (result, list(symbols)) else: return result def rsolve(f, y, init=None): r""" Solve univariate recurrence with rational coefficients. Given `k`-th order linear recurrence `\operatorname{L} y = f`, or equivalently: .. math:: a_{k}(n) y(n+k) + a_{k-1}(n) y(n+k-1) + \cdots + a_{0}(n) y(n) = f(n) where `a_{i}(n)`, for `i=0, \ldots, k`, are polynomials or rational functions in `n`, and `f` is a hypergeometric function or a sum of a fixed number of pairwise dissimilar hypergeometric terms in `n`, finds all solutions or returns ``None``, if none were found. Initial conditions can be given as a dictionary in two forms: (1) ``{ n_0 : v_0, n_1 : v_1, ..., n_m : v_m}`` (2) ``{y(n_0) : v_0, y(n_1) : v_1, ..., y(n_m) : v_m}`` or as a list ``L`` of values: ``L = [v_0, v_1, ..., v_m]`` where ``L[i] = v_i``, for `i=0, \ldots, m`, maps to `y(n_i)`. Examples ======== Lets consider the following recurrence: .. math:: (n - 1) y(n + 2) - (n^2 + 3 n - 2) y(n + 1) + 2 n (n + 1) y(n) = 0 >>> from sympy import Function, rsolve >>> from sympy.abc import n >>> y = Function('y') >>> f = (n - 1)y(n + 2) - (n2 + 3n - 2)y(n + 1) + 2n(n + 1)y(n) >>> rsolve(f, y(n)) 2*nC0 + C1factorial(n) >>> rsolve(f, y(n), {y(0):0, y(1):3}) 32*n - 3factorial(n) See Also ======== rsolve_poly, rsolve_ratio, rsolve_hyper """ if isinstance(f, Equality): f = f.lhs - f.rhs n = y.args[0] k = Wild('k', exclude=(n,)) # Preprocess user input to allow things like # y(n) + a(y(n + 1) + y(n - 1))/2 f = f.expand().collect(y.func(Wild('m', integer=True))) h_part = defaultdict(list) i_part = [] for g in Add.make_args(f): coeff, dep = g.as_coeff_mul(y.func) if not dep: i_part.append(coeff) continue for h in dep: if h.is_Function and h.func == y.func: result = h.args[0].match(n + k) if result is not None: h_part[int(result[k])].append(coeff) continue raise ValueError( "'%s(%s + k)' expected, got '%s'" % (y.func, n, h)) for k in h_part: h_part[k] = Add(h_part[k]) h_part.default_factory = lambda: 0 i_part = Add(i_part) for k, coeff in h_part.items(): h_part[k] = simplify(coeff) common = S.One if not i_part.is_zero and not i_part.is_hypergeometric(n) and \ not (i_part.is_Add and all(map(lambda x: x.is_hypergeometric(n), i_part.expand().args))): raise ValueError("The independent term should be a sum of hypergeometric functions, got '%s'" % i_part) for coeff in h_part.values(): if coeff.is_rational_function(n): if not coeff.is_polynomial(n): common = lcm(common, coeff.as_numer_denom()[1], n) else: raise ValueError( "Polynomial or rational function expected, got '%s'" % coeff) i_numer, i_denom = i_part.as_numer_denom() if i_denom.is_polynomial(n): common = lcm(common, i_denom, n) if common is not S.One: for k, coeff in h_part.items(): numer, denom = coeff.as_numer_denom() h_part[k] = numerquo(common, denom, n) i_part = i_numerquo(common, i_denom, n) K_min = min(h_part.keys()) if K_min < 0: K = abs(K_min) H_part = defaultdict(lambda: S.Zero) i_part = i_part.subs(n, n + K).expand() common = common.subs(n, n + K).expand() for k, coeff in h_part.items(): H_part[k + K] = coeff.subs(n, n + K).expand() else: H_part = h_part K_max = max(H_part.keys()) coeffs = [H_part[i] for i in range(K_max + 1)] result = rsolve_hyper(coeffs, -i_part, n, symbols=True) if result is None: return None solution, symbols = result if init == {} or init == []: init = None if symbols and init is not None: if isinstance(init, list): init = {i: init[i] for i in range(len(init))} equations = [] for k, v in init.items(): try: i = int(k) except TypeError: if k.is_Function and k.func == y.func: i = int(k.args[0]) else: raise ValueError("Integer or term expected, got '%s'" % k) eq = solution.subs(n, i) - v if eq.has(S.NaN): eq = solution.limit(n, i) - v equations.append(eq) result = solve(equations, symbols) if not result: return None else: solution = solution.subs(result) return solution
582902239582005a55a76cf702ba605404b6fb238f1258a08d9bd066c7e8a215	""" This module contains functions to: - solve a single equation for a single variable, in any domain either real or complex. - solve a single transcendental equation for a single variable in any domain either real or complex. (currently supports solving in real domain only) - solve a system of linear equations with N variables and M equations. - solve a system of Non Linear Equations with N variables and M equations """ from sympy.core.sympify import sympify from sympy.core import (S, Pow, Dummy, pi, Expr, Wild, Mul, Equality, Add) from sympy.core.containers import Tuple from sympy.core.numbers import I, Number, Rational, oo from sympy.core.function import (Lambda, expand_complex, AppliedUndef, expand_log) from sympy.core.mod import Mod from sympy.core.numbers import igcd from sympy.core.relational import Eq, Ne, Relational from sympy.core.symbol import Symbol, _uniquely_named_symbol from sympy.core.sympify import _sympify from sympy.simplify.simplify import simplify, fraction, trigsimp from sympy.simplify import powdenest, logcombine from sympy.functions import (log, Abs, tan, cot, sin, cos, sec, csc, exp, acos, asin, acsc, asec, arg, piecewise_fold, Piecewise) from sympy.functions.elementary.trigonometric import (TrigonometricFunction, HyperbolicFunction) from sympy.functions.elementary.miscellaneous import real_root from sympy.logic.boolalg import And from sympy.sets import (FiniteSet, EmptySet, imageset, Interval, Intersection, Union, ConditionSet, ImageSet, Complement, Contains) from sympy.sets.sets import Set, ProductSet from sympy.matrices import Matrix, MatrixBase from sympy.ntheory import totient from sympy.ntheory.factor_ import divisors from sympy.ntheory.residue_ntheory import discrete_log, nthroot_mod from sympy.polys import (roots, Poly, degree, together, PolynomialError, RootOf, factor, lcm, gcd) from sympy.polys.polyerrors import CoercionFailed from sympy.polys.polytools import invert from sympy.polys.solvers import (sympy_eqs_to_ring, solve_lin_sys, PolyNonlinearError) from sympy.solvers.solvers import (checksol, denoms, unrad, _simple_dens, recast_to_symbols) from sympy.solvers.polysys import solve_poly_system from sympy.solvers.inequalities import solve_univariate_inequality from sympy.utilities import filldedent from sympy.utilities.iterables import numbered_symbols, has_dups from sympy.calculus.util import periodicity, continuous_domain from sympy.core.compatibility import ordered, default_sort_key, is_sequence from types import GeneratorType from collections import defaultdict class NonlinearError(ValueError): """Raised when unexpectedly encountering nonlinear equations""" pass _rc = Dummy("R", real=True), Dummy("C", complex=True) def _masked(f, atoms): """Return ``f``, with all objects given by ``atoms`` replaced with Dummy symbols, ``d``, and the list of replacements, ``(d, e)``, where ``e`` is an object of type given by ``atoms`` in which any other instances of atoms have been recursively replaced with Dummy symbols, too. The tuples are ordered so that if they are applied in sequence, the origin ``f`` will be restored. Examples ======== >>> from sympy import cos >>> from sympy.abc import x >>> from sympy.solvers.solveset import _masked >>> f = cos(cos(x) + 1) >>> f, reps = _masked(cos(1 + cos(x)), cos) >>> f _a1 >>> reps [(_a1, cos(_a0 + 1)), (_a0, cos(x))] >>> for d, e in reps: ... f = f.xreplace({d: e}) >>> f cos(cos(x) + 1) """ sym = numbered_symbols('a', cls=Dummy, real=True) mask = [] for a in ordered(f.atoms(atoms)): for i in mask: a = a.replace(i) mask.append((a, next(sym))) for i, (o, n) in enumerate(mask): f = f.replace(o, n) mask[i] = (n, o) mask = list(reversed(mask)) return f, mask def _invert(f_x, y, x, domain=S.Complexes): r""" Reduce the complex valued equation ``f(x) = y`` to a set of equations ``{g(x) = h_1(y), g(x) = h_2(y), ..., g(x) = h_n(y) }`` where ``g(x)`` is a simpler function than ``f(x)``. The return value is a tuple ``(g(x), set_h)``, where ``g(x)`` is a function of ``x`` and ``set_h`` is the set of function ``{h_1(y), h_2(y), ..., h_n(y)}``. Here, ``y`` is not necessarily a symbol. The ``set_h`` contains the functions, along with the information about the domain in which they are valid, through set operations. For instance, if ``y = Abs(x) - n`` is inverted in the real domain, then ``set_h`` is not simply `{-n, n}` as the nature of `n` is unknown; rather, it is: `Intersection([0, oo) {n}) U Intersection((-oo, 0], {-n})` By default, the complex domain is used which means that inverting even seemingly simple functions like ``exp(x)`` will give very different results from those obtained in the real domain. (In the case of ``exp(x)``, the inversion via ``log`` is multi-valued in the complex domain, having infinitely many branches.) If you are working with real values only (or you are not sure which function to use) you should probably set the domain to ``S.Reals`` (or use `invert\_real` which does that automatically). Examples ======== >>> from sympy.solvers.solveset import invert_complex, invert_real >>> from sympy.abc import x, y >>> from sympy import exp When does exp(x) == y? >>> invert_complex(exp(x), y, x) (x, ImageSet(Lambda(_n, I(2_npi + arg(y)) + log(Abs(y))), Integers)) >>> invert_real(exp(x), y, x) (x, Intersection(FiniteSet(log(y)), Reals)) When does exp(x) == 1? >>> invert_complex(exp(x), 1, x) (x, ImageSet(Lambda(_n, 2_nIpi), Integers)) >>> invert_real(exp(x), 1, x) (x, FiniteSet(0)) See Also ======== invert_real, invert_complex """ x = sympify(x) if not x.is_Symbol: raise ValueError("x must be a symbol") f_x = sympify(f_x) if x not in f_x.free_symbols: raise ValueError("Inverse of constant function doesn't exist") y = sympify(y) if x in y.free_symbols: raise ValueError("y should be independent of x ") if domain.is_subset(S.Reals): x1, s = _invert_real(f_x, FiniteSet(y), x) else: x1, s = _invert_complex(f_x, FiniteSet(y), x) if not isinstance(s, FiniteSet) or x1 != x: return x1, s # Avoid adding gratuitous intersections with S.Complexes. Actual # conditions should be handled by the respective inverters. if domain is S.Complexes: return x1, s else: return x1, s.intersection(domain) invert_complex = _invert def invert_real(f_x, y, x, domain=S.Reals): """ Inverts a real-valued function. Same as _invert, but sets the domain to ``S.Reals`` before inverting. """ return _invert(f_x, y, x, domain) def _invert_real(f, g_ys, symbol): """Helper function for _invert.""" if f == symbol: return (f, g_ys) n = Dummy('n', real=True) if hasattr(f, 'inverse') and not isinstance(f, ( TrigonometricFunction, HyperbolicFunction, )): if len(f.args) > 1: raise ValueError("Only functions with one argument are supported.") return _invert_real(f.args[0], imageset(Lambda(n, f.inverse()(n)), g_ys), symbol) if isinstance(f, Abs): return _invert_abs(f.args[0], g_ys, symbol) if f.is_Add: # f = g + h g, h = f.as_independent(symbol) if g is not S.Zero: return _invert_real(h, imageset(Lambda(n, n - g), g_ys), symbol) if f.is_Mul: # f = gh g, h = f.as_independent(symbol) if g is not S.One: return _invert_real(h, imageset(Lambda(n, n/g), g_ys), symbol) if f.is_Pow: base, expo = f.args base_has_sym = base.has(symbol) expo_has_sym = expo.has(symbol) if not expo_has_sym: res = imageset(Lambda(n, real_root(n, expo)), g_ys) if expo.is_rational: numer, denom = expo.as_numer_denom() if denom % 2 == 0: base_positive = solveset(base >= 0, symbol, S.Reals) res = imageset(Lambda(n, real_root(n, expo) ), g_ys.intersect( Interval.Ropen(S.Zero, S.Infinity))) _inv, _set = _invert_real(base, res, symbol) return (_inv, _set.intersect(base_positive)) elif numer % 2 == 0: n = Dummy('n') neg_res = imageset(Lambda(n, -n), res) return _invert_real(base, res + neg_res, symbol) else: return _invert_real(base, res, symbol) else: if not base.is_positive: raise ValueError("xw where w is irrational is not " "defined for negative x") return _invert_real(base, res, symbol) if not base_has_sym: rhs = g_ys.args[0] if base.is_positive: return _invert_real(expo, imageset(Lambda(n, log(n, base, evaluate=False)), g_ys), symbol) elif base.is_negative: from sympy.core.power import integer_log s, b = integer_log(rhs, base) if b: return _invert_real(expo, FiniteSet(s), symbol) else: return _invert_real(expo, S.EmptySet, symbol) elif base.is_zero: one = Eq(rhs, 1) if one == S.true: # special case: 0x - 1 return _invert_real(expo, FiniteSet(0), symbol) elif one == S.false: return _invert_real(expo, S.EmptySet, symbol) if isinstance(f, TrigonometricFunction): if isinstance(g_ys, FiniteSet): def inv(trig): if isinstance(f, (sin, csc)): F = asin if isinstance(f, sin) else acsc return (lambda a: npi + (-1)nF(a),) if isinstance(f, (cos, sec)): F = acos if isinstance(f, cos) else asec return ( lambda a: 2npi + F(a), lambda a: 2npi - F(a),) if isinstance(f, (tan, cot)): return (lambda a: npi + f.inverse()(a),) n = Dummy('n', integer=True) invs = S.EmptySet for L in inv(f): invs += Union([imageset(Lambda(n, L(g)), S.Integers) for g in g_ys]) return _invert_real(f.args[0], invs, symbol) return (f, g_ys) def _invert_complex(f, g_ys, symbol): """Helper function for _invert.""" if f == symbol: return (f, g_ys) n = Dummy('n') if f.is_Add: # f = g + h g, h = f.as_independent(symbol) if g is not S.Zero: return _invert_complex(h, imageset(Lambda(n, n - g), g_ys), symbol) if f.is_Mul: # f = gh g, h = f.as_independent(symbol) if g is not S.One: if g in {S.NegativeInfinity, S.ComplexInfinity, S.Infinity}: return (h, S.EmptySet) return _invert_complex(h, imageset(Lambda(n, n/g), g_ys), symbol) if hasattr(f, 'inverse') and \ not isinstance(f, TrigonometricFunction) and \ not isinstance(f, HyperbolicFunction) and \ not isinstance(f, exp): if len(f.args) > 1: raise ValueError("Only functions with one argument are supported.") return _invert_complex(f.args[0], imageset(Lambda(n, f.inverse()(n)), g_ys), symbol) if isinstance(f, exp): if isinstance(g_ys, FiniteSet): exp_invs = Union([imageset(Lambda(n, I(2npi + arg(g_y)) + log(Abs(g_y))), S.Integers) for g_y in g_ys if g_y != 0]) return _invert_complex(f.args[0], exp_invs, symbol) return (f, g_ys) def _invert_abs(f, g_ys, symbol): """Helper function for inverting absolute value functions. Returns the complete result of inverting an absolute value function along with the conditions which must also be satisfied. If it is certain that all these conditions are met, a `FiniteSet` of all possible solutions is returned. If any condition cannot be satisfied, an `EmptySet` is returned. Otherwise, a `ConditionSet` of the solutions, with all the required conditions specified, is returned. """ if not g_ys.is_FiniteSet: # this could be used for FiniteSet, but the # results are more compact if they aren't, e.g. # ConditionSet(x, Contains(n, Interval(0, oo)), {-n, n}) vs # Union(Intersection(Interval(0, oo), {n}), Intersection(Interval(-oo, 0), {-n})) # for the solution of abs(x) - n pos = Intersection(g_ys, Interval(0, S.Infinity)) parg = _invert_real(f, pos, symbol) narg = _invert_real(-f, pos, symbol) if parg[0] != narg[0]: raise NotImplementedError return parg[0], Union(narg[1], parg[1]) # check conditions: all these must be true. If any are unknown # then return them as conditions which must be satisfied unknown = [] for a in g_ys.args: ok = a.is_nonnegative if a.is_Number else a.is_positive if ok is None: unknown.append(a) elif not ok: return symbol, S.EmptySet if unknown: conditions = And([Contains(i, Interval(0, oo)) for i in unknown]) else: conditions = True n = Dummy('n', real=True) # this is slightly different than above: instead of solving # +/-f on positive values, here we solve for f on +/- g_ys g_x, values = _invert_real(f, Union( imageset(Lambda(n, n), g_ys), imageset(Lambda(n, -n), g_ys)), symbol) return g_x, ConditionSet(g_x, conditions, values) def domain_check(f, symbol, p): """Returns False if point p is infinite or any subexpression of f is infinite or becomes so after replacing symbol with p. If none of these conditions is met then True will be returned. Examples ======== >>> from sympy import Mul, oo >>> from sympy.abc import x >>> from sympy.solvers.solveset import domain_check >>> g = 1/(1 + (1/(x + 1))2) >>> domain_check(g, x, -1) False >>> domain_check(x2, x, 0) True >>> domain_check(1/x, x, oo) False * The function relies on the assumption that the original form of the equation has not been changed by automatic simplification. >>> domain_check(x/x, x, 0) # x/x is automatically simplified to 1 True * To deal with automatic evaluations use evaluate=False: >>> domain_check(Mul(x, 1/x, evaluate=False), x, 0) False """ f, p = sympify(f), sympify(p) if p.is_infinite: return False return _domain_check(f, symbol, p) def _domain_check(f, symbol, p): # helper for domain check if f.is_Atom and f.is_finite: return True elif f.subs(symbol, p).is_infinite: return False else: return all([_domain_check(g, symbol, p) for g in f.args]) def _is_finite_with_finite_vars(f, domain=S.Complexes): """ Return True if the given expression is finite. For symbols that don't assign a value for `complex` and/or `real`, the domain will be used to assign a value; symbols that don't assign a value for `finite` will be made finite. All other assumptions are left unmodified. """ def assumptions(s): A = s.assumptions0 A.setdefault('finite', A.get('finite', True)) if domain.is_subset(S.Reals): # if this gets set it will make complex=True, too A.setdefault('real', True) else: # don't change 'real' because being complex implies # nothing about being real A.setdefault('complex', True) return A reps = {s: Dummy(assumptions(s)) for s in f.free_symbols} return f.xreplace(reps).is_finite def _is_function_class_equation(func_class, f, symbol): """ Tests whether the equation is an equation of the given function class. The given equation belongs to the given function class if it is comprised of functions of the function class which are multiplied by or added to expressions independent of the symbol. In addition, the arguments of all such functions must be linear in the symbol as well. Examples ======== >>> from sympy.solvers.solveset import _is_function_class_equation >>> from sympy import tan, sin, tanh, sinh, exp >>> from sympy.abc import x >>> from sympy.functions.elementary.trigonometric import (TrigonometricFunction, ... HyperbolicFunction) >>> _is_function_class_equation(TrigonometricFunction, exp(x) + tan(x), x) False >>> _is_function_class_equation(TrigonometricFunction, tan(x) + sin(x), x) True >>> _is_function_class_equation(TrigonometricFunction, tan(x2), x) False >>> _is_function_class_equation(TrigonometricFunction, tan(x + 2), x) True >>> _is_function_class_equation(HyperbolicFunction, tanh(x) + sinh(x), x) True """ if f.is_Mul or f.is_Add: return all(_is_function_class_equation(func_class, arg, symbol) for arg in f.args) if f.is_Pow: if not f.exp.has(symbol): return _is_function_class_equation(func_class, f.base, symbol) else: return False if not f.has(symbol): return True if isinstance(f, func_class): try: g = Poly(f.args[0], symbol) return g.degree() <= 1 except PolynomialError: return False else: return False def _solve_as_rational(f, symbol, domain): """ solve rational functions""" f = together(f, deep=True) g, h = fraction(f) if not h.has(symbol): try: return _solve_as_poly(g, symbol, domain) except NotImplementedError: # The polynomial formed from g could end up having # coefficients in a ring over which finding roots # isn't implemented yet, e.g. ZZ[a] for some symbol a return ConditionSet(symbol, Eq(f, 0), domain) except CoercionFailed: # contained oo, zoo or nan return S.EmptySet else: valid_solns = _solveset(g, symbol, domain) invalid_solns = _solveset(h, symbol, domain) return valid_solns - invalid_solns class _SolveTrig1Error(Exception): """Raised when _solve_trig1 heuristics do not apply""" def _solve_trig(f, symbol, domain): """Function to call other helpers to solve trigonometric equations """ sol = None try: sol = _solve_trig1(f, symbol, domain) except _SolveTrig1Error: try: sol = _solve_trig2(f, symbol, domain) except ValueError: raise NotImplementedError(filldedent(''' Solution to this kind of trigonometric equations is yet to be implemented''')) return sol def _solve_trig1(f, symbol, domain): """Primary solver for trigonometric and hyperbolic equations Returns either the solution set as a ConditionSet (auto-evaluated to a union of ImageSets if no variables besides 'symbol' are involved) or raises _SolveTrig1Error if f == 0 can't be solved. Notes ===== Algorithm: 1. Do a change of variable x -> mux in arguments to trigonometric and hyperbolic functions, in order to reduce them to small integers. (This step is crucial to keep the degrees of the polynomials of step 4 low.) 2. Rewrite trigonometric/hyperbolic functions as exponentials. 3. Proceed to a 2nd change of variable, replacing exp(Ix) or exp(x) by y. 4. Solve the resulting rational equation. 5. Use invert_complex or invert_real to return to the original variable. 6. If the coefficients of 'symbol' were symbolic in nature, add the necessary consistency conditions in a ConditionSet. """ # Prepare change of variable x = Dummy('x') if _is_function_class_equation(HyperbolicFunction, f, symbol): cov = exp(x) inverter = invert_real if domain.is_subset(S.Reals) else invert_complex else: cov = exp(Ix) inverter = invert_complex f = trigsimp(f) f_original = f trig_functions = f.atoms(TrigonometricFunction, HyperbolicFunction) trig_arguments = [e.args[0] for e in trig_functions] # trigsimp may have reduced the equation to an expression # that is independent of 'symbol' (e.g. cos2+sin2) if not any(a.has(symbol) for a in trig_arguments): return solveset(f_original, symbol, domain) denominators = [] numerators = [] for ar in trig_arguments: try: poly_ar = Poly(ar, symbol) except PolynomialError: raise _SolveTrig1Error("trig argument is not a polynomial") if poly_ar.degree() > 1: # degree >1 still bad raise _SolveTrig1Error("degree of variable must not exceed one") if poly_ar.degree() == 0: # degree 0, don't care continue c = poly_ar.all_coeffs()[0] # got the coefficient of 'symbol' numerators.append(fraction(c)[0]) denominators.append(fraction(c)[1]) mu = lcm(denominators)/gcd(numerators) f = f.subs(symbol, mux) f = f.rewrite(exp) f = together(f) g, h = fraction(f) y = Dummy('y') g, h = g.expand(), h.expand() g, h = g.subs(cov, y), h.subs(cov, y) if g.has(x) or h.has(x): raise _SolveTrig1Error("change of variable not possible") solns = solveset_complex(g, y) - solveset_complex(h, y) if isinstance(solns, ConditionSet): raise _SolveTrig1Error("polynomial has ConditionSet solution") if isinstance(solns, FiniteSet): if any(isinstance(s, RootOf) for s in solns): raise _SolveTrig1Error("polynomial results in RootOf object") # revert the change of variable cov = cov.subs(x, symbol/mu) result = Union([inverter(cov, s, symbol)[1] for s in solns]) # In case of symbolic coefficients, the solution set is only valid # if numerator and denominator of mu are non-zero. if mu.has(Symbol): syms = (mu).atoms(Symbol) munum, muden = fraction(mu) condnum = munum.as_independent(syms, as_Add=False)[1] condden = muden.as_independent(syms, as_Add=False)[1] cond = And(Ne(condnum, 0), Ne(condden, 0)) else: cond = True # Actual conditions are returned as part of the ConditionSet. Adding an # intersection with C would only complicate some solution sets due to # current limitations of intersection code. (e.g. #19154) if domain is S.Complexes: # This is a slight abuse of ConditionSet. Ideally this should # be some kind of "PiecewiseSet". (See #19507 discussion) return ConditionSet(symbol, cond, result) else: return ConditionSet(symbol, cond, Intersection(result, domain)) elif solns is S.EmptySet: return S.EmptySet else: raise _SolveTrig1Error("polynomial solutions must form FiniteSet") def _solve_trig2(f, symbol, domain): """Secondary helper to solve trigonometric equations, called when first helper fails """ from sympy import ilcm, expand_trig, degree f = trigsimp(f) f_original = f trig_functions = f.atoms(sin, cos, tan, sec, cot, csc) trig_arguments = [e.args[0] for e in trig_functions] denominators = [] numerators = [] # todo: This solver can be extended to hyperbolics if the # analogous change of variable to tanh (instead of tan) # is used. if not trig_functions: return ConditionSet(symbol, Eq(f_original, 0), domain) # todo: The pre-processing below (extraction of numerators, denominators, # gcd, lcm, mu, etc.) should be updated to the enhanced version in # _solve_trig1. (See #19507) for ar in trig_arguments: try: poly_ar = Poly(ar, symbol) except PolynomialError: raise ValueError("give up, we can't solve if this is not a polynomial in x") if poly_ar.degree() > 1: # degree >1 still bad raise ValueError("degree of variable inside polynomial should not exceed one") if poly_ar.degree() == 0: # degree 0, don't care continue c = poly_ar.all_coeffs()[0] # got the coefficient of 'symbol' try: numerators.append(Rational(c).p) denominators.append(Rational(c).q) except TypeError: return ConditionSet(symbol, Eq(f_original, 0), domain) x = Dummy('x') # ilcm() and igcd() require more than one argument if len(numerators) > 1: mu = Rational(2)ilcm(denominators)/igcd(numerators) else: assert len(numerators) == 1 mu = Rational(2)denominators[0]/numerators[0] f = f.subs(symbol, mux) f = f.rewrite(tan) f = expand_trig(f) f = together(f) g, h = fraction(f) y = Dummy('y') g, h = g.expand(), h.expand() g, h = g.subs(tan(x), y), h.subs(tan(x), y) if g.has(x) or h.has(x): return ConditionSet(symbol, Eq(f_original, 0), domain) solns = solveset(g, y, S.Reals) - solveset(h, y, S.Reals) if isinstance(solns, FiniteSet): result = Union([invert_real(tan(symbol/mu), s, symbol)[1] for s in solns]) dsol = invert_real(tan(symbol/mu), oo, symbol)[1] if degree(h) > degree(g): # If degree(denom)>degree(num) then there result = Union(result, dsol) # would be another sol at Lim(denom-->oo) return Intersection(result, domain) elif solns is S.EmptySet: return S.EmptySet else: return ConditionSet(symbol, Eq(f_original, 0), S.Reals) def _solve_as_poly(f, symbol, domain=S.Complexes): """ Solve the equation using polynomial techniques if it already is a polynomial equation or, with a change of variables, can be made so. """ result = None if f.is_polynomial(symbol): solns = roots(f, symbol, cubics=True, quartics=True, quintics=True, domain='EX') num_roots = sum(solns.values()) if degree(f, symbol) <= num_roots: result = FiniteSet(solns.keys()) else: poly = Poly(f, symbol) solns = poly.all_roots() if poly.degree() <= len(solns): result = FiniteSet(solns) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: poly = Poly(f) if poly is None: result = ConditionSet(symbol, Eq(f, 0), domain) gens = [g for g in poly.gens if g.has(symbol)] if len(gens) == 1: poly = Poly(poly, gens[0]) gen = poly.gen deg = poly.degree() poly = Poly(poly.as_expr(), poly.gen, composite=True) poly_solns = FiniteSet(roots(poly, cubics=True, quartics=True, quintics=True).keys()) if len(poly_solns) < deg: result = ConditionSet(symbol, Eq(f, 0), domain) if gen != symbol: y = Dummy('y') inverter = invert_real if domain.is_subset(S.Reals) else invert_complex lhs, rhs_s = inverter(gen, y, symbol) if lhs == symbol: result = Union([rhs_s.subs(y, s) for s in poly_solns]) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: result = ConditionSet(symbol, Eq(f, 0), domain) if result is not None: if isinstance(result, FiniteSet): # this is to simplify solutions like -sqrt(-I) to sqrt(2)/2 # - sqrt(2)I/2. We are not expanding for solution with symbols # or undefined functions because that makes the solution more complicated. # For example, expand_complex(a) returns re(a) + Iim(a) if all([s.atoms(Symbol, AppliedUndef) == set() and not isinstance(s, RootOf) for s in result]): s = Dummy('s') result = imageset(Lambda(s, expand_complex(s)), result) if isinstance(result, FiniteSet) and domain != S.Complexes: # Avoid adding gratuitous intersections with S.Complexes. Actual # conditions should be handled elsewhere. result = result.intersection(domain) return result else: return ConditionSet(symbol, Eq(f, 0), domain) def _has_rational_power(expr, symbol): """ Returns (bool, den) where bool is True if the term has a non-integer rational power and den is the denominator of the expression's exponent. Examples ======== >>> from sympy.solvers.solveset import _has_rational_power >>> from sympy import sqrt >>> from sympy.abc import x >>> _has_rational_power(sqrt(x), x) (True, 2) >>> _has_rational_power(x2, x) (False, 1) """ a, p, q = Wild('a'), Wild('p'), Wild('q') pattern_match = expr.match(ap*q) or {} if pattern_match.get(a, S.Zero).is_zero: return (False, S.One) elif p not in pattern_match.keys(): return (False, S.One) elif isinstance(pattern_match[q], Rational) \ and pattern_match[p].has(symbol): if not pattern_match[q].q == S.One: return (True, pattern_match[q].q) if not isinstance(pattern_match[a], Pow) \ or isinstance(pattern_match[a], Mul): return (False, S.One) else: return _has_rational_power(pattern_match[a], symbol) def _solve_radical(f, symbol, solveset_solver): """ Helper function to solve equations with radicals """ res = unrad(f) eq, cov = res if res else (f, []) if not cov: result = solveset_solver(eq, symbol) - \ Union([solveset_solver(g, symbol) for g in denoms(f, symbol)]) else: y, yeq = cov if not solveset_solver(y - I, y): yreal = Dummy('yreal', real=True) yeq = yeq.xreplace({y: yreal}) eq = eq.xreplace({y: yreal}) y = yreal g_y_s = solveset_solver(yeq, symbol) f_y_sols = solveset_solver(eq, y) result = Union([imageset(Lambda(y, g_y), f_y_sols) for g_y in g_y_s]) if isinstance(result, Complement) or isinstance(result,ConditionSet): solution_set = result else: f_set = [] # solutions for FiniteSet c_set = [] # solutions for ConditionSet for s in result: if checksol(f, symbol, s): f_set.append(s) else: c_set.append(s) solution_set = FiniteSet(f_set) + ConditionSet(symbol, Eq(f, 0), FiniteSet(c_set)) return solution_set def _solve_abs(f, symbol, domain): """ Helper function to solve equation involving absolute value function """ if not domain.is_subset(S.Reals): raise ValueError(filldedent(''' Absolute values cannot be inverted in the complex domain.''')) p, q, r = Wild('p'), Wild('q'), Wild('r') pattern_match = f.match(pAbs(q) + r) or {} f_p, f_q, f_r = [pattern_match.get(i, S.Zero) for i in (p, q, r)] if not (f_p.is_zero or f_q.is_zero): domain = continuous_domain(f_q, symbol, domain) q_pos_cond = solve_univariate_inequality(f_q >= 0, symbol, relational=False, domain=domain, continuous=True) q_neg_cond = q_pos_cond.complement(domain) sols_q_pos = solveset_real(f_pf_q + f_r, symbol).intersect(q_pos_cond) sols_q_neg = solveset_real(f_p(-f_q) + f_r, symbol).intersect(q_neg_cond) return Union(sols_q_pos, sols_q_neg) else: return ConditionSet(symbol, Eq(f, 0), domain) def solve_decomposition(f, symbol, domain): """ Function to solve equations via the principle of "Decomposition and Rewriting". Examples ======== >>> from sympy import exp, sin, Symbol, pprint, S >>> from sympy.solvers.solveset import solve_decomposition as sd >>> x = Symbol('x') >>> f1 = exp(2x) - 3exp(x) + 2 >>> sd(f1, x, S.Reals) FiniteSet(0, log(2)) >>> f2 = sin(x)*2 + 2sin(x) + 1 >>> pprint(sd(f2, x, S.Reals), use_unicode=False) 3pi {2npi + ---- \| n in Integers} 2 >>> f3 = sin(x + 2) >>> pprint(sd(f3, x, S.Reals), use_unicode=False) {2npi - 2 \| n in Integers} U {2npi - 2 + pi \| n in Integers} """ from sympy.solvers.decompogen import decompogen from sympy.calculus.util import function_range # decompose the given function g_s = decompogen(f, symbol) # `y_s` represents the set of values for which the function `g` is to be # solved. # `solutions` represent the solutions of the equations `g = y_s` or # `g = 0` depending on the type of `y_s`. # As we are interested in solving the equation: f = 0 y_s = FiniteSet(0) for g in g_s: frange = function_range(g, symbol, domain) y_s = Intersection(frange, y_s) result = S.EmptySet if isinstance(y_s, FiniteSet): for y in y_s: solutions = solveset(Eq(g, y), symbol, domain) if not isinstance(solutions, ConditionSet): result += solutions else: if isinstance(y_s, ImageSet): iter_iset = (y_s,) elif isinstance(y_s, Union): iter_iset = y_s.args elif y_s is EmptySet: # y_s is not in the range of g in g_s, so no solution exists #in the given domain return EmptySet for iset in iter_iset: new_solutions = solveset(Eq(iset.lamda.expr, g), symbol, domain) dummy_var = tuple(iset.lamda.expr.free_symbols)[0] (base_set,) = iset.base_sets if isinstance(new_solutions, FiniteSet): new_exprs = new_solutions elif isinstance(new_solutions, Intersection): if isinstance(new_solutions.args[1], FiniteSet): new_exprs = new_solutions.args[1] for new_expr in new_exprs: result += ImageSet(Lambda(dummy_var, new_expr), base_set) if result is S.EmptySet: return ConditionSet(symbol, Eq(f, 0), domain) y_s = result return y_s def _solveset(f, symbol, domain, _check=False): """Helper for solveset to return a result from an expression that has already been sympify'ed and is known to contain the given symbol.""" # _check controls whether the answer is checked or not from sympy.simplify.simplify import signsimp from sympy.logic.boolalg import BooleanTrue if isinstance(f, BooleanTrue): return domain orig_f = f if f.is_Mul: coeff, f = f.as_independent(symbol, as_Add=False) if coeff in {S.ComplexInfinity, S.NegativeInfinity, S.Infinity}: f = together(orig_f) elif f.is_Add: a, h = f.as_independent(symbol) m, h = h.as_independent(symbol, as_Add=False) if m not in {S.ComplexInfinity, S.Zero, S.Infinity, S.NegativeInfinity}: f = a/m + h # XXX condition `m != 0` should be added to soln # assign the solvers to use solver = lambda f, x, domain=domain: _solveset(f, x, domain) inverter = lambda f, rhs, symbol: _invert(f, rhs, symbol, domain) result = EmptySet if f.expand().is_zero: return domain elif not f.has(symbol): return EmptySet elif f.is_Mul and all(_is_finite_with_finite_vars(m, domain) for m in f.args): # if f(x) and g(x) are both finite we can say that the solution of # f(x)g(x) == 0 is same as Union(f(x) == 0, g(x) == 0) is not true in # general. g(x) can grow to infinitely large for the values where # f(x) == 0. To be sure that we are not silently allowing any # wrong solutions we are using this technique only if both f and g are # finite for a finite input. result = Union([solver(m, symbol) for m in f.args]) elif _is_function_class_equation(TrigonometricFunction, f, symbol) or \ _is_function_class_equation(HyperbolicFunction, f, symbol): result = _solve_trig(f, symbol, domain) elif isinstance(f, arg): a = f.args[0] result = solveset_real(a > 0, symbol) elif f.is_Piecewise: expr_set_pairs = f.as_expr_set_pairs(domain) for (expr, in_set) in expr_set_pairs: if in_set.is_Relational: in_set = in_set.as_set() solns = solver(expr, symbol, in_set) result += solns elif isinstance(f, Eq): result = solver(Add(f.lhs, - f.rhs, evaluate=False), symbol, domain) elif f.is_Relational: if not domain.is_subset(S.Reals): raise NotImplementedError(filldedent(''' Inequalities in the complex domain are not supported. Try the real domain by setting domain=S.Reals''')) try: result = solve_univariate_inequality( f, symbol, domain=domain, relational=False) except NotImplementedError: result = ConditionSet(symbol, f, domain) return result elif _is_modular(f, symbol): result = _solve_modular(f, symbol, domain) else: lhs, rhs_s = inverter(f, 0, symbol) if lhs == symbol: # do some very minimal simplification since # repeated inversion may have left the result # in a state that other solvers (e.g. poly) # would have simplified; this is done here # rather than in the inverter since here it # is only done once whereas there it would # be repeated for each step of the inversion if isinstance(rhs_s, FiniteSet): rhs_s = FiniteSet([Mul(* signsimp(i).as_content_primitive()) for i in rhs_s]) result = rhs_s elif isinstance(rhs_s, FiniteSet): for equation in [lhs - rhs for rhs in rhs_s]: if equation == f: if any(_has_rational_power(g, symbol)[0] for g in equation.args) or _has_rational_power( equation, symbol)[0]: result += _solve_radical(equation, symbol, solver) elif equation.has(Abs): result += _solve_abs(f, symbol, domain) else: result_rational = _solve_as_rational(equation, symbol, domain) if isinstance(result_rational, ConditionSet): # may be a transcendental type equation result += _transolve(equation, symbol, domain) else: result += result_rational else: result += solver(equation, symbol) elif rhs_s is not S.EmptySet: result = ConditionSet(symbol, Eq(f, 0), domain) if isinstance(result, ConditionSet): if isinstance(f, Expr): num, den = f.as_numer_denom() else: num, den = f, S.One if den.has(symbol): _result = _solveset(num, symbol, domain) if not isinstance(_result, ConditionSet): singularities = _solveset(den, symbol, domain) result = _result - singularities if _check: if isinstance(result, ConditionSet): # it wasn't solved or has enumerated all conditions # -- leave it alone return result # whittle away all but the symbol-containing core # to use this for testing if isinstance(orig_f, Expr): fx = orig_f.as_independent(symbol, as_Add=True)[1] fx = fx.as_independent(symbol, as_Add=False)[1] else: fx = orig_f if isinstance(result, FiniteSet): # check the result for invalid solutions result = FiniteSet([s for s in result if isinstance(s, RootOf) or domain_check(fx, symbol, s)]) return result def _is_modular(f, symbol): """ Helper function to check below mentioned types of modular equations. ``A - Mod(B, C) = 0`` A -> This can or cannot be a function of symbol. B -> This is surely a function of symbol. C -> It is an integer. Parameters ========== f : Expr The equation to be checked. symbol : Symbol The concerned variable for which the equation is to be checked. Examples ======== >>> from sympy import symbols, exp, Mod >>> from sympy.solvers.solveset import _is_modular as check >>> x, y = symbols('x y') >>> check(Mod(x, 3) - 1, x) True >>> check(Mod(x, 3) - 1, y) False >>> check(Mod(x, 3)2 - 5, x) False >>> check(Mod(x, 3)2 - y, x) False >>> check(exp(Mod(x, 3)) - 1, x) False >>> check(Mod(3, y) - 1, y) False """ if not f.has(Mod): return False # extract modterms from f. modterms = list(f.atoms(Mod)) return (len(modterms) == 1 and # only one Mod should be present modterms[0].args[0].has(symbol) and # B-> function of symbol modterms[0].args[1].is_integer and # C-> to be an integer. any(isinstance(term, Mod) for term in list(_term_factors(f))) # free from other funcs ) def _invert_modular(modterm, rhs, n, symbol): """ Helper function to invert modular equation. ``Mod(a, m) - rhs = 0`` Generally it is inverted as (a, ImageSet(Lambda(n, mn + rhs), S.Integers)). More simplified form will be returned if possible. If it is not invertible then (modterm, rhs) is returned. The following cases arise while inverting equation ``Mod(a, m) - rhs = 0``: 1. If a is symbol then mn + rhs is the required solution. 2. If a is an instance of ``Add`` then we try to find two symbol independent parts of a and the symbol independent part gets tranferred to the other side and again the ``_invert_modular`` is called on the symbol dependent part. 3. If a is an instance of ``Mul`` then same as we done in ``Add`` we separate out the symbol dependent and symbol independent parts and transfer the symbol independent part to the rhs with the help of invert and again the ``_invert_modular`` is called on the symbol dependent part. 4. If a is an instance of ``Pow`` then two cases arise as following: - If a is of type (symbol_indep)(symbol_dep) then the remainder is evaluated with the help of discrete_log function and then the least period is being found out with the help of totient function. periodn + remainder is the required solution in this case. For reference: (https://en.wikipedia.org/wiki/Euler's_theorem) - If a is of type (symbol_dep)*(symbol_indep) then we try to find all primitive solutions list with the help of nthroot_mod function. mn + rem is the general solution where rem belongs to solutions list from nthroot_mod function. Parameters ========== modterm, rhs : Expr The modular equation to be inverted, ``modterm - rhs = 0`` symbol : Symbol The variable in the equation to be inverted. n : Dummy Dummy variable for output g_n. Returns ======= A tuple (f_x, g_n) is being returned where f_x is modular independent function of symbol and g_n being set of values f_x can have. Examples ======== >>> from sympy import symbols, exp, Mod, Dummy, S >>> from sympy.solvers.solveset import _invert_modular as invert_modular >>> x, y = symbols('x y') >>> n = Dummy('n') >>> invert_modular(Mod(exp(x), 7), S(5), n, x) (Mod(exp(x), 7), 5) >>> invert_modular(Mod(x, 7), S(5), n, x) (x, ImageSet(Lambda(_n, 7_n + 5), Integers)) >>> invert_modular(Mod(3x + 8, 7), S(5), n, x) (x, ImageSet(Lambda(_n, 7_n + 6), Integers)) >>> invert_modular(Mod(x4, 7), S(5), n, x) (x, EmptySet) >>> invert_modular(Mod(2(x2 + x + 1), 7), S(2), n, x) (x2 + x + 1, ImageSet(Lambda(_n, 3_n + 1), Naturals0)) """ a, m = modterm.args if rhs.is_real is False or any(term.is_real is False for term in list(_term_factors(a))): # Check for complex arguments return modterm, rhs if abs(rhs) >= abs(m): # if rhs has value greater than value of m. return symbol, EmptySet if a == symbol: return symbol, ImageSet(Lambda(n, mn + rhs), S.Integers) if a.is_Add: # g + h = a g, h = a.as_independent(symbol) if g is not S.Zero: x_indep_term = rhs - Mod(g, m) return _invert_modular(Mod(h, m), Mod(x_indep_term, m), n, symbol) if a.is_Mul: # gh = a g, h = a.as_independent(symbol) if g is not S.One: x_indep_term = rhsinvert(g, m) return _invert_modular(Mod(h, m), Mod(x_indep_term, m), n, symbol) if a.is_Pow: # baseexpo = a base, expo = a.args if expo.has(symbol) and not base.has(symbol): # remainder -> solution independent of n of equation. # m, rhs are made coprime by dividing igcd(m, rhs) try: remainder = discrete_log(m / igcd(m, rhs), rhs, a.base) except ValueError: # log does not exist return modterm, rhs # period -> coefficient of n in the solution and also referred as # the least period of expo in which it is repeats itself. # (a(totient(m)) - 1) divides m. Here is link of theorem: # (https://en.wikipedia.org/wiki/Euler's_theorem) period = totient(m) for p in divisors(period): # there might a lesser period exist than totient(m). if pow(a.base, p, m / igcd(m, a.base)) == 1: period = p break # recursion is not applied here since _invert_modular is currently # not smart enough to handle infinite rhs as here expo has infinite # rhs = ImageSet(Lambda(n, periodn + remainder), S.Naturals0). return expo, ImageSet(Lambda(n, periodn + remainder), S.Naturals0) elif base.has(symbol) and not expo.has(symbol): try: remainder_list = nthroot_mod(rhs, expo, m, all_roots=True) if remainder_list == []: return symbol, EmptySet except (ValueError, NotImplementedError): return modterm, rhs g_n = EmptySet for rem in remainder_list: g_n += ImageSet(Lambda(n, mn + rem), S.Integers) return base, g_n return modterm, rhs def _solve_modular(f, symbol, domain): r""" Helper function for solving modular equations of type ``A - Mod(B, C) = 0``, where A can or cannot be a function of symbol, B is surely a function of symbol and C is an integer. Currently ``_solve_modular`` is only able to solve cases where A is not a function of symbol. Parameters ========== f : Expr The modular equation to be solved, ``f = 0`` symbol : Symbol The variable in the equation to be solved. domain : Set A set over which the equation is solved. It has to be a subset of Integers. Returns ======= A set of integer solutions satisfying the given modular equation. A ``ConditionSet`` if the equation is unsolvable. Examples ======== >>> from sympy.solvers.solveset import _solve_modular as solve_modulo >>> from sympy import S, Symbol, sin, Intersection, Interval >>> from sympy.core.mod import Mod >>> x = Symbol('x') >>> solve_modulo(Mod(5x - 8, 7) - 3, x, S.Integers) ImageSet(Lambda(_n, 7_n + 5), Integers) >>> solve_modulo(Mod(5x - 8, 7) - 3, x, S.Reals) # domain should be subset of integers. ConditionSet(x, Eq(Mod(5x + 6, 7) - 3, 0), Reals) >>> solve_modulo(-7 + Mod(x, 5), x, S.Integers) EmptySet >>> solve_modulo(Mod(12*x, 21) - 18, x, S.Integers) ImageSet(Lambda(_n, 6_n + 2), Naturals0) >>> solve_modulo(Mod(sin(x), 7) - 3, x, S.Integers) # not solvable ConditionSet(x, Eq(Mod(sin(x), 7) - 3, 0), Integers) >>> solve_modulo(3 - Mod(x, 5), x, Intersection(S.Integers, Interval(0, 100))) Intersection(ImageSet(Lambda(_n, 5_n + 3), Integers), Range(0, 101, 1)) """ # extract modterm and g_y from f unsolved_result = ConditionSet(symbol, Eq(f, 0), domain) modterm = list(f.atoms(Mod))[0] rhs = -S.One(f.subs(modterm, S.Zero)) if f.as_coefficients_dict()[modterm].is_negative: # checks if coefficient of modterm is negative in main equation. rhs = -S.One if not domain.is_subset(S.Integers): return unsolved_result if rhs.has(symbol): # TODO Case: A-> function of symbol, can be extended here # in future. return unsolved_result n = Dummy('n', integer=True) f_x, g_n = _invert_modular(modterm, rhs, n, symbol) if f_x == modterm and g_n == rhs: return unsolved_result if f_x == symbol: if domain is not S.Integers: return domain.intersect(g_n) return g_n if isinstance(g_n, ImageSet): lamda_expr = g_n.lamda.expr lamda_vars = g_n.lamda.variables base_sets = g_n.base_sets sol_set = _solveset(f_x - lamda_expr, symbol, S.Integers) if isinstance(sol_set, FiniteSet): tmp_sol = EmptySet for sol in sol_set: tmp_sol += ImageSet(Lambda(lamda_vars, sol), base_sets) sol_set = tmp_sol else: sol_set = ImageSet(Lambda(lamda_vars, sol_set), base_sets) return domain.intersect(sol_set) return unsolved_result def _term_factors(f): """ Iterator to get the factors of all terms present in the given equation. Parameters ========== f : Expr Equation that needs to be addressed Returns ======= Factors of all terms present in the equation. Examples ======== >>> from sympy import symbols >>> from sympy.solvers.solveset import _term_factors >>> x = symbols('x') >>> list(_term_factors(-2 - x2 + x(x + 1))) [-2, -1, x2, x, x + 1] """ for add_arg in Add.make_args(f): yield from Mul.make_args(add_arg) def _solve_exponential(lhs, rhs, symbol, domain): r""" Helper function for solving (supported) exponential equations. Exponential equations are the sum of (currently) at most two terms with one or both of them having a power with a symbol-dependent exponent. For example .. math:: 5^{2x + 3} - 5^{3x - 1} .. math:: 4^{5 - 9x} - e^{2 - x} Parameters ========== lhs, rhs : Expr The exponential equation to be solved, `lhs = rhs` symbol : Symbol The variable in which the equation is solved domain : Set A set over which the equation is solved. Returns ======= A set of solutions satisfying the given equation. A ``ConditionSet`` if the equation is unsolvable or if the assumptions are not properly defined, in that case a different style of ``ConditionSet`` is returned having the solution(s) of the equation with the desired assumptions. Examples ======== >>> from sympy.solvers.solveset import _solve_exponential as solve_expo >>> from sympy import symbols, S >>> x = symbols('x', real=True) >>> a, b = symbols('a b') >>> solve_expo(2x + 3x - 5x, 0, x, S.Reals) # not solvable ConditionSet(x, Eq(2x + 3x - 5x, 0), Reals) >>> solve_expo(ax - bx, 0, x, S.Reals) # solvable but incorrect assumptions ConditionSet(x, (a > 0) & (b > 0), FiniteSet(0)) >>> solve_expo(3(2x) - 2(x + 3), 0, x, S.Reals) FiniteSet(-3log(2)/(-2log(3) + log(2))) >>> solve_expo(2x - 4x, 0, x, S.Reals) FiniteSet(0) Proof of correctness of the method The logarithm function is the inverse of the exponential function. The defining relation between exponentiation and logarithm is: .. math:: {\log_b x} = y \enspace if \enspace b^y = x Therefore if we are given an equation with exponent terms, we can convert every term to its corresponding logarithmic form. This is achieved by taking logarithms and expanding the equation using logarithmic identities so that it can easily be handled by ``solveset``. For example: .. math:: 3^{2x} = 2^{x + 3} Taking log both sides will reduce the equation to .. math:: (2x)\log(3) = (x + 3)\log(2) This form can be easily handed by ``solveset``. """ unsolved_result = ConditionSet(symbol, Eq(lhs - rhs, 0), domain) newlhs = powdenest(lhs) if lhs != newlhs: # it may also be advantageous to factor the new expr return _solveset(factor(newlhs - rhs), symbol, domain) # try again with _solveset if not (isinstance(lhs, Add) and len(lhs.args) == 2): # solving for the sum of more than two powers is possible # but not yet implemented return unsolved_result if rhs != 0: return unsolved_result a, b = list(ordered(lhs.args)) a_term = a.as_independent(symbol)[1] b_term = b.as_independent(symbol)[1] a_base, a_exp = a_term.base, a_term.exp b_base, b_exp = b_term.base, b_term.exp from sympy.functions.elementary.complexes import im if domain.is_subset(S.Reals): conditions = And( a_base > 0, b_base > 0, Eq(im(a_exp), 0), Eq(im(b_exp), 0)) else: conditions = And( Ne(a_base, 0), Ne(b_base, 0)) L, R = map(lambda i: expand_log(log(i), force=True), (a, -b)) solutions = _solveset(L - R, symbol, domain) return ConditionSet(symbol, conditions, solutions) def _is_exponential(f, symbol): r""" Return ``True`` if one or more terms contain ``symbol`` only in exponents, else ``False``. Parameters ========== f : Expr The equation to be checked symbol : Symbol The variable in which the equation is checked Examples ======== >>> from sympy import symbols, cos, exp >>> from sympy.solvers.solveset import _is_exponential as check >>> x, y = symbols('x y') >>> check(y, y) False >>> check(xy - 1, y) True >>> check(xy2y - 1, y) True >>> check(exp(x + 3) + 3x, x) True >>> check(cos(2x), x) False Philosophy behind the helper The function extracts each term of the equation and checks if it is of exponential form w.r.t ``symbol``. """ rv = False for expr_arg in _term_factors(f): if symbol not in expr_arg.free_symbols: continue if (isinstance(expr_arg, Pow) and symbol not in expr_arg.base.free_symbols or isinstance(expr_arg, exp)): rv = True # symbol in exponent else: return False # dependent on symbol in non-exponential way return rv def _solve_logarithm(lhs, rhs, symbol, domain): r""" Helper to solve logarithmic equations which are reducible to a single instance of `\log`. Logarithmic equations are (currently) the equations that contains `\log` terms which can be reduced to a single `\log` term or a constant using various logarithmic identities. For example: .. math:: \log(x) + \log(x - 4) can be reduced to: .. math:: \log(x(x - 4)) Parameters ========== lhs, rhs : Expr The logarithmic equation to be solved, `lhs = rhs` symbol : Symbol The variable in which the equation is solved domain : Set A set over which the equation is solved. Returns ======= A set of solutions satisfying the given equation. A ``ConditionSet`` if the equation is unsolvable. Examples ======== >>> from sympy import symbols, log, S >>> from sympy.solvers.solveset import _solve_logarithm as solve_log >>> x = symbols('x') >>> f = log(x - 3) + log(x + 3) >>> solve_log(f, 0, x, S.Reals) FiniteSet(sqrt(10), -sqrt(10)) * Proof of correctness A logarithm is another way to write exponent and is defined by .. math:: {\log_b x} = y \enspace if \enspace b^y = x When one side of the equation contains a single logarithm, the equation can be solved by rewriting the equation as an equivalent exponential equation as defined above. But if one side contains more than one logarithm, we need to use the properties of logarithm to condense it into a single logarithm. Take for example .. math:: \log(2x) - 15 = 0 contains single logarithm, therefore we can directly rewrite it to exponential form as .. math:: x = \frac{e^{15}}{2} But if the equation has more than one logarithm as .. math:: \log(x - 3) + \log(x + 3) = 0 we use logarithmic identities to convert it into a reduced form Using, .. math:: \log(a) + \log(b) = \log(ab) the equation becomes, .. math:: \log((x - 3)(x + 3)) This equation contains one logarithm and can be solved by rewriting to exponents. """ new_lhs = logcombine(lhs, force=True) new_f = new_lhs - rhs return _solveset(new_f, symbol, domain) def _is_logarithmic(f, symbol): r""" Return ``True`` if the equation is in the form `a\log(f(x)) + b\log(g(x)) + ... + c` else ``False``. Parameters ========== f : Expr The equation to be checked symbol : Symbol The variable in which the equation is checked Returns ======= ``True`` if the equation is logarithmic otherwise ``False``. Examples ======== >>> from sympy import symbols, tan, log >>> from sympy.solvers.solveset import _is_logarithmic as check >>> x, y = symbols('x y') >>> check(log(x + 2) - log(x + 3), x) True >>> check(tan(log(2x)), x) False >>> check(xlog(x), x) False >>> check(x + log(x), x) False >>> check(y + log(x), x) True * Philosophy behind the helper The function extracts each term and checks whether it is logarithmic w.r.t ``symbol``. """ rv = False for term in Add.make_args(f): saw_log = False for term_arg in Mul.make_args(term): if symbol not in term_arg.free_symbols: continue if isinstance(term_arg, log): if saw_log: return False # more than one log in term saw_log = True else: return False # dependent on symbol in non-log way if saw_log: rv = True return rv def _transolve(f, symbol, domain): r""" Function to solve transcendental equations. It is a helper to ``solveset`` and should be used internally. ``_transolve`` currently supports the following class of equations: - Exponential equations - Logarithmic equations Parameters ========== f : Any transcendental equation that needs to be solved. This needs to be an expression, which is assumed to be equal to ``0``. symbol : The variable for which the equation is solved. This needs to be of class ``Symbol``. domain : A set over which the equation is solved. This needs to be of class ``Set``. Returns ======= Set A set of values for ``symbol`` for which ``f`` is equal to zero. An ``EmptySet`` is returned if ``f`` does not have solutions in respective domain. A ``ConditionSet`` is returned as unsolved object if algorithms to evaluate complete solution are not yet implemented. How to use ``_transolve`` ========================= ``_transolve`` should not be used as an independent function, because it assumes that the equation (``f``) and the ``symbol`` comes from ``solveset`` and might have undergone a few modification(s). To use ``_transolve`` as an independent function the equation (``f``) and the ``symbol`` should be passed as they would have been by ``solveset``. Examples ======== >>> from sympy.solvers.solveset import _transolve as transolve >>> from sympy.solvers.solvers import _tsolve as tsolve >>> from sympy import symbols, S, pprint >>> x = symbols('x', real=True) # assumption added >>> transolve(5(x - 3) - 3(2x + 1), x, S.Reals) FiniteSet(-(log(3) + 3log(5))/(-log(5) + 2log(3))) How ``_transolve`` works ======================== ``_transolve`` uses two types of helper functions to solve equations of a particular class: Identifying helpers: To determine whether a given equation belongs to a certain class of equation or not. Returns either ``True`` or ``False``. Solving helpers: Once an equation is identified, a corresponding helper either solves the equation or returns a form of the equation that ``solveset`` might better be able to handle. Philosophy behind the module The purpose of ``_transolve`` is to take equations which are not already polynomial in their generator(s) and to either recast them as such through a valid transformation or to solve them outright. A pair of helper functions for each class of supported transcendental functions are employed for this purpose. One identifies the transcendental form of an equation and the other either solves it or recasts it into a tractable form that can be solved by ``solveset``. For example, an equation in the form `ab^{f(x)} - cd^{g(x)} = 0` can be transformed to `\log(a) + f(x)\log(b) - \log(c) - g(x)\log(d) = 0` (under certain assumptions) and this can be solved with ``solveset`` if `f(x)` and `g(x)` are in polynomial form. How ``_transolve`` is better than ``_tsolve`` ============================================= 1) Better output ``_transolve`` provides expressions in a more simplified form. Consider a simple exponential equation >>> f = 3*(2x) - 2*(x + 3) >>> pprint(transolve(f, x, S.Reals), use_unicode=False) -3log(2) {------------------} -2log(3) + log(2) >>> pprint(tsolve(f, x), use_unicode=False) / 3 \ \| --------\| \| log(2/9)\| [-log\2 /] 2) Extensible The API of ``_transolve`` is designed such that it is easily extensible, i.e. the code that solves a given class of equations is encapsulated in a helper and not mixed in with the code of ``_transolve`` itself. 3) Modular ``_transolve`` is designed to be modular i.e, for every class of equation a separate helper for identification and solving is implemented. This makes it easy to change or modify any of the method implemented directly in the helpers without interfering with the actual structure of the API. 4) Faster Computation Solving equation via ``_transolve`` is much faster as compared to ``_tsolve``. In ``solve``, attempts are made computing every possibility to get the solutions. This series of attempts makes solving a bit slow. In ``_transolve``, computation begins only after a particular type of equation is identified. How to add new class of equations ================================= Adding a new class of equation solver is a three-step procedure: - Identify the type of the equations Determine the type of the class of equations to which they belong: it could be of ``Add``, ``Pow``, etc. types. Separate internal functions are used for each type. Write identification and solving helpers and use them from within the routine for the given type of equation (after adding it, if necessary). Something like: .. code-block:: python def add_type(lhs, rhs, x): .... if _is_exponential(lhs, x): new_eq = _solve_exponential(lhs, rhs, x) .... rhs, lhs = eq.as_independent(x) if lhs.is_Add: result = add_type(lhs, rhs, x) - Define the identification helper. - Define the solving helper. Apart from this, a few other things needs to be taken care while adding an equation solver: - Naming conventions: Name of the identification helper should be as ``_is_class`` where class will be the name or abbreviation of the class of equation. The solving helper will be named as ``_solve_class``. For example: for exponential equations it becomes ``_is_exponential`` and ``_solve_expo``. - The identifying helpers should take two input parameters, the equation to be checked and the variable for which a solution is being sought, while solving helpers would require an additional domain parameter. - Be sure to consider corner cases. - Add tests for each helper. - Add a docstring to your helper that describes the method implemented. The documentation of the helpers should identify: - the purpose of the helper, - the method used to identify and solve the equation, - a proof of correctness - the return values of the helpers """ def add_type(lhs, rhs, symbol, domain): """ Helper for ``_transolve`` to handle equations of ``Add`` type, i.e. equations taking the form as ``af(x) + bg(x) + .... = c``. For example: 4x + 8x = 0 """ result = ConditionSet(symbol, Eq(lhs - rhs, 0), domain) # check if it is exponential type equation if _is_exponential(lhs, symbol): result = _solve_exponential(lhs, rhs, symbol, domain) # check if it is logarithmic type equation elif _is_logarithmic(lhs, symbol): result = _solve_logarithm(lhs, rhs, symbol, domain) return result result = ConditionSet(symbol, Eq(f, 0), domain) # invert_complex handles the call to the desired inverter based # on the domain specified. lhs, rhs_s = invert_complex(f, 0, symbol, domain) if isinstance(rhs_s, FiniteSet): assert (len(rhs_s.args)) == 1 rhs = rhs_s.args[0] if lhs.is_Add: result = add_type(lhs, rhs, symbol, domain) else: result = rhs_s return result def solveset(f, symbol=None, domain=S.Complexes): r"""Solves a given inequality or equation with set as output Parameters ========== f : Expr or a relational. The target equation or inequality symbol : Symbol The variable for which the equation is solved domain : Set The domain over which the equation is solved Returns ======= Set A set of values for `symbol` for which `f` is True or is equal to zero. An `EmptySet` is returned if `f` is False or nonzero. A `ConditionSet` is returned as unsolved object if algorithms to evaluate complete solution are not yet implemented. `solveset` claims to be complete in the solution set that it returns. Raises ====== NotImplementedError The algorithms to solve inequalities in complex domain are not yet implemented. ValueError The input is not valid. RuntimeError It is a bug, please report to the github issue tracker. Notes ===== Python interprets 0 and 1 as False and True, respectively, but in this function they refer to solutions of an expression. So 0 and 1 return the Domain and EmptySet, respectively, while True and False return the opposite (as they are assumed to be solutions of relational expressions). See Also ======== solveset_real: solver for real domain solveset_complex: solver for complex domain Examples ======== >>> from sympy import exp, sin, Symbol, pprint, S, Eq >>> from sympy.solvers.solveset import solveset, solveset_real The default domain is complex. Not specifying a domain will lead to the solving of the equation in the complex domain (and this is not affected by the assumptions on the symbol): >>> x = Symbol('x') >>> pprint(solveset(exp(x) - 1, x), use_unicode=False) {2nIpi \| n in Integers} >>> x = Symbol('x', real=True) >>> pprint(solveset(exp(x) - 1, x), use_unicode=False) {2nIpi \| n in Integers} * If you want to use `solveset` to solve the equation in the real domain, provide a real domain. (Using ``solveset_real`` does this automatically.) >>> R = S.Reals >>> x = Symbol('x') >>> solveset(exp(x) - 1, x, R) FiniteSet(0) >>> solveset_real(exp(x) - 1, x) FiniteSet(0) The solution is unaffected by assumptions on the symbol: >>> p = Symbol('p', positive=True) >>> pprint(solveset(p2 - 4)) {-2, 2} When a conditionSet is returned, symbols with assumptions that would alter the set are replaced with more generic symbols: >>> i = Symbol('i', imaginary=True) >>> solveset(Eq(i2 + isin(i), 1), i, domain=S.Reals) ConditionSet(_R, Eq(_R2 + _Rsin(_R) - 1, 0), Reals) * Inequalities can be solved over the real domain only. Use of a complex domain leads to a NotImplementedError. >>> solveset(exp(x) > 1, x, R) Interval.open(0, oo) """ f = sympify(f) symbol = sympify(symbol) if f is S.true: return domain if f is S.false: return S.EmptySet if not isinstance(f, (Expr, Relational, Number)): raise ValueError("%s is not a valid SymPy expression" % f) if not isinstance(symbol, (Expr, Relational)) and symbol is not None: raise ValueError("%s is not a valid SymPy symbol" % symbol) if not isinstance(domain, Set): raise ValueError("%s is not a valid domain" %(domain)) free_symbols = f.free_symbols if symbol is None and not free_symbols: b = Eq(f, 0) if b is S.true: return domain elif b is S.false: return S.EmptySet else: raise NotImplementedError(filldedent(''' relationship between value and 0 is unknown: %s''' % b)) if symbol is None: if len(free_symbols) == 1: symbol = free_symbols.pop() elif free_symbols: raise ValueError(filldedent(''' The independent variable must be specified for a multivariate equation.''')) elif not isinstance(symbol, Symbol): f, s, swap = recast_to_symbols([f], [symbol]) # the xreplace will be needed if a ConditionSet is returned return solveset(f[0], s[0], domain).xreplace(swap) # solveset should ignore assumptions on symbols if symbol not in _rc: x = _rc[0] if domain.is_subset(S.Reals) else _rc[1] rv = solveset(f.xreplace({symbol: x}), x, domain) # try to use the original symbol if possible try: _rv = rv.xreplace({x: symbol}) except TypeError: _rv = rv if rv.dummy_eq(_rv): rv = _rv return rv # Abs has its own handling method which avoids the # rewriting property that the first piece of abs(x) # is for x >= 0 and the 2nd piece for x < 0 -- solutions # can look better if the 2nd condition is x <= 0. Since # the solution is a set, duplication of results is not # an issue, e.g. {y, -y} when y is 0 will be {0} f, mask = _masked(f, Abs) f = f.rewrite(Piecewise) # everything that's not an Abs for d, e in mask: # everything in an Abs e = e.func(e.args[0].rewrite(Piecewise)) f = f.xreplace({d: e}) f = piecewise_fold(f) return _solveset(f, symbol, domain, _check=True) def solveset_real(f, symbol): return solveset(f, symbol, S.Reals) def solveset_complex(f, symbol): return solveset(f, symbol, S.Complexes) def _solveset_multi(eqs, syms, domains): '''Basic implementation of a multivariate solveset. For internal use (not ready for public consumption)''' rep = {} for sym, dom in zip(syms, domains): if dom is S.Reals: rep[sym] = Symbol(sym.name, real=True) eqs = [eq.subs(rep) for eq in eqs] syms = [sym.subs(rep) for sym in syms] syms = tuple(syms) if len(eqs) == 0: return ProductSet(domains) if len(syms) == 1: sym = syms[0] domain = domains[0] solsets = [solveset(eq, sym, domain) for eq in eqs] solset = Intersection(solsets) return ImageSet(Lambda((sym,), (sym,)), solset).doit() eqs = sorted(eqs, key=lambda eq: len(eq.free_symbols & set(syms))) for n in range(len(eqs)): sols = [] all_handled = True for sym in syms: if sym not in eqs[n].free_symbols: continue sol = solveset(eqs[n], sym, domains[syms.index(sym)]) if isinstance(sol, FiniteSet): i = syms.index(sym) symsp = syms[:i] + syms[i+1:] domainsp = domains[:i] + domains[i+1:] eqsp = eqs[:n] + eqs[n+1:] for s in sol: eqsp_sub = [eq.subs(sym, s) for eq in eqsp] sol_others = _solveset_multi(eqsp_sub, symsp, domainsp) fun = Lambda((symsp,), symsp[:i] + (s,) + symsp[i:]) sols.append(ImageSet(fun, sol_others).doit()) else: all_handled = False if all_handled: return Union(sols) def solvify(f, symbol, domain): """Solves an equation using solveset and returns the solution in accordance with the `solve` output API. Returns ======= We classify the output based on the type of solution returned by `solveset`. Solution \| Output ---------------------------------------- FiniteSet \| list ImageSet, \| list (if `f` is periodic) Union \| EmptySet \| empty list Others \| None Raises ====== NotImplementedError A ConditionSet is the input. Examples ======== >>> from sympy.solvers.solveset import solvify >>> from sympy.abc import x >>> from sympy import S, tan, sin, exp >>> solvify(x2 - 9, x, S.Reals) [-3, 3] >>> solvify(sin(x) - 1, x, S.Reals) [pi/2] >>> solvify(tan(x), x, S.Reals) [0] >>> solvify(exp(x) - 1, x, S.Complexes) >>> solvify(exp(x) - 1, x, S.Reals) [0] """ solution_set = solveset(f, symbol, domain) result = None if solution_set is S.EmptySet: result = [] elif isinstance(solution_set, ConditionSet): raise NotImplementedError('solveset is unable to solve this equation.') elif isinstance(solution_set, FiniteSet): result = list(solution_set) else: period = periodicity(f, symbol) if period is not None: solutions = S.EmptySet iter_solutions = () if isinstance(solution_set, ImageSet): iter_solutions = (solution_set,) elif isinstance(solution_set, Union): if all(isinstance(i, ImageSet) for i in solution_set.args): iter_solutions = solution_set.args for solution in iter_solutions: solutions += solution.intersect(Interval(0, period, False, True)) if isinstance(solutions, FiniteSet): result = list(solutions) else: solution = solution_set.intersect(domain) if isinstance(solution, FiniteSet): result += solution return result ############################################################################### ################################ LINSOLVE ##################################### ############################################################################### def linear_coeffs(eq, syms, *_kw): """Return a list whose elements are the coefficients of the corresponding symbols in the sum of terms in ``eq``. The additive constant is returned as the last element of the list. Raises ====== NonlinearError The equation contains a nonlinear term Examples ======== >>> from sympy.solvers.solveset import linear_coeffs >>> from sympy.abc import x, y, z >>> linear_coeffs(3x + 2y - 1, x, y) [3, 2, -1] It is not necessary to expand the expression: >>> linear_coeffs(x + y(z(x3 + 2) + 3), x) [3yz + 1, y(2z + 3)] But if there are nonlinear or cross terms -- even if they would cancel after simplification -- an error is raised so the situation does not pass silently past the caller's attention: >>> eq = 1/x(x - 1) + 1/x >>> linear_coeffs(eq.expand(), x) [0, 1] >>> linear_coeffs(eq, x) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: 1/x >>> linear_coeffs(x(y + 1) - xy, x, y) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: x(y + 1) """ d = defaultdict(list) eq = _sympify(eq) symset = set(syms) has = eq.free_symbols & symset if not has: return [S.Zero]len(syms) + [eq] c, terms = eq.as_coeff_add(has) d[0].extend(Add.make_args(c)) for t in terms: m, f = t.as_coeff_mul(has) if len(f) != 1: break f = f[0] if f in symset: d[f].append(m) elif f.is_Add: d1 = linear_coeffs(f, has, *{'dict': True}) d[0].append(md1.pop(0)) for xf, vf in d1.items(): d[xf].append(mvf) else: break else: for k, v in d.items(): d[k] = Add(v) if not _kw: return [d.get(s, S.Zero) for s in syms] + [d[0]] return d # default is still list but this won't matter raise NonlinearError('nonlinear term encountered: %s' % t) def linear_eq_to_matrix(equations, symbols): r""" Converts a given System of Equations into Matrix form. Here `equations` must be a linear system of equations in `symbols`. Element M[i, j] corresponds to the coefficient of the jth symbol in the ith equation. The Matrix form corresponds to the augmented matrix form. For example: .. math:: 4x + 2y + 3z = 1 .. math:: 3x + y + z = -6 .. math:: 2x + 4y + 9z = 2 This system would return `A` & `b` as given below: :: [ 4 2 3 ] [ 1 ] A = [ 3 1 1 ] b = [-6 ] [ 2 4 9 ] [ 2 ] The only simplification performed is to convert `Eq(a, b) -> a - b`. Raises ====== NonlinearError The equations contain a nonlinear term. ValueError The symbols are not given or are not unique. Examples ======== >>> from sympy import linear_eq_to_matrix, symbols >>> c, x, y, z = symbols('c, x, y, z') The coefficients (numerical or symbolic) of the symbols will be returned as matrices: >>> eqns = [cx + z - 1 - c, y + z, x - y] >>> A, b = linear_eq_to_matrix(eqns, [x, y, z]) >>> A Matrix([ [c, 0, 1], [0, 1, 1], [1, -1, 0]]) >>> b Matrix([ [c + 1], [ 0], [ 0]]) This routine does not simplify expressions and will raise an error if nonlinearity is encountered: >>> eqns = [ ... (x*2 - 3x)/(x - 3) - 3, ... y*2 - 3y - y(y - 4) + x - 4] >>> linear_eq_to_matrix(eqns, [x, y]) Traceback (most recent call last): ... NonlinearError: The term (x2 - 3x)/(x - 3) is nonlinear in {x, y} Simplifying these equations will discard the removable singularity in the first, reveal the linear structure of the second: >>> [e.simplify() for e in eqns] [x - 3, x + y - 4] Any such simplification needed to eliminate nonlinear terms must be done before calling this routine. """ if not symbols: raise ValueError(filldedent(''' Symbols must be given, for which coefficients are to be found. ''')) if hasattr(symbols[0], '__iter__'): symbols = symbols[0] for i in symbols: if not isinstance(i, Symbol): raise ValueError(filldedent(''' Expecting a Symbol but got %s ''' % i)) if has_dups(symbols): raise ValueError('Symbols must be unique') equations = sympify(equations) if isinstance(equations, MatrixBase): equations = list(equations) elif isinstance(equations, (Expr, Eq)): equations = [equations] elif not is_sequence(equations): raise ValueError(filldedent(''' Equation(s) must be given as a sequence, Expr, Eq or Matrix. ''')) A, b = [], [] for i, f in enumerate(equations): if isinstance(f, Equality): f = f.rewrite(Add, evaluate=False) coeff_list = linear_coeffs(f, symbols) b.append(-coeff_list.pop()) A.append(coeff_list) A, b = map(Matrix, (A, b)) return A, b def linsolve(system, symbols): r""" Solve system of N linear equations with M variables; both underdetermined and overdetermined systems are supported. The possible number of solutions is zero, one or infinite. Zero solutions throws a ValueError, whereas infinite solutions are represented parametrically in terms of the given symbols. For unique solution a FiniteSet of ordered tuples is returned. All Standard input formats are supported: For the given set of Equations, the respective input types are given below: .. math:: 3x + 2y - z = 1 .. math:: 2x - 2y + 4z = -2 .. math:: 2x - y + 2z = 0 * Augmented Matrix Form, `system` given below: :: [3 2 -1 1] system = [2 -2 4 -2] [2 -1 2 0] * List Of Equations Form `system = [3x + 2y - z - 1, 2x - 2y + 4z + 2, 2x - y + 2z]` * Input A & b Matrix Form (from Ax = b) are given as below: :: [3 2 -1 ] [ 1 ] A = [2 -2 4 ] b = [ -2 ] [2 -1 2 ] [ 0 ] `system = (A, b)` Symbols can always be passed but are actually only needed when 1) a system of equations is being passed and 2) the system is passed as an underdetermined matrix and one wants to control the name of the free variables in the result. An error is raised if no symbols are used for case 1, but if no symbols are provided for case 2, internally generated symbols will be provided. When providing symbols for case 2, there should be at least as many symbols are there are columns in matrix A. The algorithm used here is Gauss-Jordan elimination, which results, after elimination, in a row echelon form matrix. Returns ======= A FiniteSet containing an ordered tuple of values for the unknowns for which the `system` has a solution. (Wrapping the tuple in FiniteSet is used to maintain a consistent output format throughout solveset.) Returns EmptySet, if the linear system is inconsistent. Raises ====== ValueError The input is not valid. The symbols are not given. Examples ======== >>> from sympy import Matrix, linsolve, symbols >>> x, y, z = symbols("x, y, z") >>> A = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 10]]) >>> b = Matrix([3, 6, 9]) >>> A Matrix([ [1, 2, 3], [4, 5, 6], [7, 8, 10]]) >>> b Matrix([ [3], [6], [9]]) >>> linsolve((A, b), [x, y, z]) FiniteSet((-1, 2, 0)) * Parametric Solution: In case the system is underdetermined, the function will return a parametric solution in terms of the given symbols. Those that are free will be returned unchanged. e.g. in the system below, `z` is returned as the solution for variable z; it can take on any value. >>> A = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) >>> b = Matrix([3, 6, 9]) >>> linsolve((A, b), x, y, z) FiniteSet((z - 1, 2 - 2z, z)) If no symbols are given, internally generated symbols will be used. The `tau0` in the 3rd position indicates (as before) that the 3rd variable -- whatever it's named -- can take on any value: >>> linsolve((A, b)) FiniteSet((tau0 - 1, 2 - 2tau0, tau0)) * List of Equations as input >>> Eqns = [3x + 2y - z - 1, 2x - 2y + 4z + 2, - x + y/2 - z] >>> linsolve(Eqns, x, y, z) FiniteSet((1, -2, -2)) Augmented Matrix as input >>> aug = Matrix([[2, 1, 3, 1], [2, 6, 8, 3], [6, 8, 18, 5]]) >>> aug Matrix([ [2, 1, 3, 1], [2, 6, 8, 3], [6, 8, 18, 5]]) >>> linsolve(aug, x, y, z) FiniteSet((3/10, 2/5, 0)) * Solve for symbolic coefficients >>> a, b, c, d, e, f = symbols('a, b, c, d, e, f') >>> eqns = [ax + by - c, dx + ey - f] >>> linsolve(eqns, x, y) FiniteSet(((-bf + ce)/(ae - bd), (af - cd)/(ae - bd))) * A degenerate system returns solution as set of given symbols. >>> system = Matrix(([0, 0, 0], [0, 0, 0], [0, 0, 0])) >>> linsolve(system, x, y) FiniteSet((x, y)) * For an empty system linsolve returns empty set >>> linsolve([], x) EmptySet * An error is raised if, after expansion, any nonlinearity is detected: >>> linsolve([x(1/x - 1), (y - 1)2 - y2 + 1], x, y) FiniteSet((1, 1)) >>> linsolve([x2 - 1], x) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: x2 """ if not system: return S.EmptySet # If second argument is an iterable if symbols and hasattr(symbols[0], '__iter__'): symbols = symbols[0] sym_gen = isinstance(symbols, GeneratorType) b = None # if we don't get b the input was bad syms_needed_msg = None # unpack system if hasattr(system, '__iter__'): # 1). (A, b) if len(system) == 2 and isinstance(system[0], MatrixBase): A, b = system # 2). (eq1, eq2, ...) if not isinstance(system[0], MatrixBase): if sym_gen or not symbols: raise ValueError(filldedent(''' When passing a system of equations, the explicit symbols for which a solution is being sought must be given as a sequence, too. ''')) eqs = system try: eqs, ring = sympy_eqs_to_ring(eqs, symbols) except PolynomialError as exc: # e.g. cos(x) contains an element of the set of generators raise NonlinearError(str(exc)) try: sol = solve_lin_sys(eqs, ring, _raw=False) except PolyNonlinearError as exc: raise NonlinearError(str(exc)) if sol is None: return S.EmptySet sol = FiniteSet(Tuple((sol.get(sym, sym) for sym in symbols))) return sol elif isinstance(system, MatrixBase) and not ( symbols and not isinstance(symbols, GeneratorType) and isinstance(symbols[0], MatrixBase)): # 3). A augmented with b A, b = system[:, :-1], system[:, -1:] if b is None: raise ValueError("Invalid arguments") syms_needed_msg = syms_needed_msg or 'columns of A' if sym_gen: symbols = [next(symbols) for i in range(A.cols)] if any(set(symbols) & (A.free_symbols \| b.free_symbols)): raise ValueError(filldedent(''' At least one of the symbols provided already appears in the system to be solved. One way to avoid this is to use Dummy symbols in the generator, e.g. numbered_symbols('%s', cls=Dummy) ''' % symbols[0].name.rstrip('1234567890'))) if not symbols: symbols = [Dummy() for _ in range(A.cols)] name = _uniquely_named_symbol('tau', (A, b), compare=lambda i: str(i).rstrip('1234567890')).name gen = numbered_symbols(name) else: gen = None # This is just a wrapper for solve_lin_sys eqs = [] rows = A.tolist() for rowi, bi in zip(rows, b): terms = [elem * sym for elem, sym in zip(rowi, symbols) if elem] terms.append(-bi) eqs.append(Add(terms)) eqs, ring = sympy_eqs_to_ring(eqs, symbols) sol = solve_lin_sys(eqs, ring, _raw=False) if sol is None: return S.EmptySet #sol = {sym:val for sym, val in sol.items() if sym != val} sol = FiniteSet(Tuple((sol.get(sym, sym) for sym in symbols))) if gen is not None: solsym = sol.free_symbols rep = {sym: next(gen) for sym in symbols if sym in solsym} sol = sol.subs(rep) return sol ############################################################################## # ------------------------------nonlinsolve ---------------------------------# ############################################################################## def _return_conditionset(eqs, symbols): # return conditionset eqs = (Eq(lhs, 0) for lhs in eqs) condition_set = ConditionSet( Tuple(symbols), And(eqs), S.Complexes*len(symbols)) return condition_set def substitution(system, symbols, result=[{}], known_symbols=[], exclude=[], all_symbols=None): r""" Solves the `system` using substitution method. It is used in `nonlinsolve`. This will be called from `nonlinsolve` when any equation(s) is non polynomial equation. Parameters ========== system : list of equations The target system of equations symbols : list of symbols to be solved. The variable(s) for which the system is solved known_symbols : list of solved symbols Values are known for these variable(s) result : An empty list or list of dict If No symbol values is known then empty list otherwise symbol as keys and corresponding value in dict. exclude : Set of expression. Mostly denominator expression(s) of the equations of the system. Final solution should not satisfy these expressions. all_symbols : known_symbols + symbols(unsolved). Returns ======= A FiniteSet of ordered tuple of values of `all_symbols` for which the `system` has solution. Order of values in the tuple is same as symbols present in the parameter `all_symbols`. If parameter `all_symbols` is None then same as symbols present in the parameter `symbols`. Please note that general FiniteSet is unordered, the solution returned here is not simply a FiniteSet of solutions, rather it is a FiniteSet of ordered tuple, i.e. the first & only argument to FiniteSet is a tuple of solutions, which is ordered, & hence the returned solution is ordered. Also note that solution could also have been returned as an ordered tuple, FiniteSet is just a wrapper `{}` around the tuple. It has no other significance except for the fact it is just used to maintain a consistent output format throughout the solveset. Raises ====== ValueError The input is not valid. The symbols are not given. AttributeError The input symbols are not `Symbol` type. Examples ======== >>> from sympy.core.symbol import symbols >>> x, y = symbols('x, y', real=True) >>> from sympy.solvers.solveset import substitution >>> substitution([x + y], [x], [{y: 1}], [y], set([]), [x, y]) FiniteSet((-1, 1)) when you want soln should not satisfy eq `x + 1 = 0` >>> substitution([x + y], [x], [{y: 1}], [y], set([x + 1]), [y, x]) EmptySet >>> substitution([x + y], [x], [{y: 1}], [y], set([x - 1]), [y, x]) FiniteSet((1, -1)) >>> substitution([x + y - 1, y - x*2 + 5], [x, y]) FiniteSet((-3, 4), (2, -1)) Returns both real and complex solution >>> x, y, z = symbols('x, y, z') >>> from sympy import exp, sin >>> substitution([exp(x) - sin(y), y*2 - 4], [x, y]) FiniteSet((ImageSet(Lambda(_n, 2_nIpi + log(sin(2))), Integers), 2), (ImageSet(Lambda(_n, I(2_npi + pi) + log(sin(2))), Integers), -2)) >>> eqs = [z2 + exp(2x) - sin(y), -3 + exp(-y)] >>> substitution(eqs, [y, z]) FiniteSet((-log(3), sqrt(-exp(2x) - sin(log(3)))), (-log(3), -sqrt(-exp(2x) - sin(log(3)))), (ImageSet(Lambda(_n, 2_nIpi - log(3)), Integers), ImageSet(Lambda(_n, sqrt(-exp(2x) + sin(2_nIpi - log(3)))), Integers)), (ImageSet(Lambda(_n, 2_nIpi - log(3)), Integers), ImageSet(Lambda(_n, -sqrt(-exp(2x) + sin(2_nIpi - log(3)))), Integers))) """ from sympy import Complement from sympy.core.compatibility import is_sequence if not system: return S.EmptySet if not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise ValueError(filldedent(msg)) if not is_sequence(symbols): msg = ('symbols should be given as a sequence, e.g. a list.' 'Not type %s: %s') raise TypeError(filldedent(msg % (type(symbols), symbols))) if not getattr(symbols[0], 'is_Symbol', False): msg = ('Iterable of symbols must be given as ' 'second argument, not type %s: %s') raise ValueError(filldedent(msg % (type(symbols[0]), symbols[0]))) # By default `all_symbols` will be same as `symbols` if all_symbols is None: all_symbols = symbols old_result = result # storing complements and intersection for particular symbol complements = {} intersections = {} # when total_solveset_call equals total_conditionset # it means that solveset failed to solve all eqs. total_conditionset = -1 total_solveset_call = -1 def _unsolved_syms(eq, sort=False): """Returns the unsolved symbol present in the equation `eq`. """ free = eq.free_symbols unsolved = (free - set(known_symbols)) & set(all_symbols) if sort: unsolved = list(unsolved) unsolved.sort(key=default_sort_key) return unsolved # end of _unsolved_syms() # sort such that equation with the fewest potential symbols is first. # means eq with less number of variable first in the list. eqs_in_better_order = list( ordered(system, lambda _: len(_unsolved_syms(_)))) def add_intersection_complement(result, intersection_dict, complement_dict): # If solveset has returned some intersection/complement # for any symbol, it will be added in the final solution. final_result = [] for res in result: res_copy = res for key_res, value_res in res.items(): intersect_set, complement_set = None, None for key_sym, value_sym in intersection_dict.items(): if key_sym == key_res: intersect_set = value_sym for key_sym, value_sym in complement_dict.items(): if key_sym == key_res: complement_set = value_sym if intersect_set or complement_set: new_value = FiniteSet(value_res) if intersect_set and intersect_set != S.Complexes: new_value = Intersection(new_value, intersect_set) if complement_set: new_value = Complement(new_value, complement_set) if new_value is S.EmptySet: res_copy = None break elif new_value.is_FiniteSet and len(new_value) == 1: res_copy[key_res] = set(new_value).pop() else: res_copy[key_res] = new_value if res_copy is not None: final_result.append(res_copy) return final_result # end of def add_intersection_complement() def _extract_main_soln(sym, sol, soln_imageset): """Separate the Complements, Intersections, ImageSet lambda expr and its base_set. """ # if there is union, then need to check # Complement, Intersection, Imageset. # Order should not be changed. if isinstance(sol, Complement): # extract solution and complement complements[sym] = sol.args[1] sol = sol.args[0] # complement will be added at the end # using `add_intersection_complement` method if isinstance(sol, Intersection): # Interval/Set will be at 0th index always if sol.args[0] not in (S.Reals, S.Complexes): # Sometimes solveset returns soln with intersection # S.Reals or S.Complexes. We don't consider that # intersection. intersections[sym] = sol.args[0] sol = sol.args[1] # after intersection and complement Imageset should # be checked. if isinstance(sol, ImageSet): soln_imagest = sol expr2 = sol.lamda.expr sol = FiniteSet(expr2) soln_imageset[expr2] = soln_imagest # if there is union of Imageset or other in soln. # no testcase is written for this if block if isinstance(sol, Union): sol_args = sol.args sol = S.EmptySet # We need in sequence so append finteset elements # and then imageset or other. for sol_arg2 in sol_args: if isinstance(sol_arg2, FiniteSet): sol += sol_arg2 else: # ImageSet, Intersection, complement then # append them directly sol += FiniteSet(sol_arg2) if not isinstance(sol, FiniteSet): sol = FiniteSet(sol) return sol, soln_imageset # end of def _extract_main_soln() # helper function for _append_new_soln def _check_exclude(rnew, imgset_yes): rnew_ = rnew if imgset_yes: # replace all dummy variables (Imageset lambda variables) # with zero before `checksol`. Considering fundamental soln # for `checksol`. rnew_copy = rnew.copy() dummy_n = imgset_yes[0] for key_res, value_res in rnew_copy.items(): rnew_copy[key_res] = value_res.subs(dummy_n, 0) rnew_ = rnew_copy # satisfy_exclude == true if it satisfies the expr of `exclude` list. try: # something like : `Mod(-log(3), 2Ipi)` can't be # simplified right now, so `checksol` returns `TypeError`. # when this issue is fixed this try block should be # removed. Mod(-log(3), 2Ipi) == -log(3) satisfy_exclude = any( checksol(d, rnew_) for d in exclude) except TypeError: satisfy_exclude = None return satisfy_exclude # end of def _check_exclude() # helper function for _append_new_soln def _restore_imgset(rnew, original_imageset, newresult): restore_sym = set(rnew.keys()) & \ set(original_imageset.keys()) for key_sym in restore_sym: img = original_imageset[key_sym] rnew[key_sym] = img if rnew not in newresult: newresult.append(rnew) # end of def _restore_imgset() def _append_eq(eq, result, res, delete_soln, n=None): u = Dummy('u') if n: eq = eq.subs(n, 0) satisfy = checksol(u, u, eq, minimal=True) if satisfy is False: delete_soln = True res = {} else: result.append(res) return result, res, delete_soln def _append_new_soln(rnew, sym, sol, imgset_yes, soln_imageset, original_imageset, newresult, eq=None): """If `rnew` (A dict <symbol: soln>) contains valid soln append it to `newresult` list. `imgset_yes` is (base, dummy_var) if there was imageset in previously calculated result(otherwise empty tuple). `original_imageset` is dict of imageset expr and imageset from this result. `soln_imageset` dict of imageset expr and imageset of new soln. """ satisfy_exclude = _check_exclude(rnew, imgset_yes) delete_soln = False # soln should not satisfy expr present in `exclude` list. if not satisfy_exclude: local_n = None # if it is imageset if imgset_yes: local_n = imgset_yes[0] base = imgset_yes[1] if sym and sol: # when `sym` and `sol` is `None` means no new # soln. In that case we will append rnew directly after # substituting original imagesets in rnew values if present # (second last line of this function using _restore_imgset) dummy_list = list(sol.atoms(Dummy)) # use one dummy `n` which is in # previous imageset local_n_list = [ local_n for i in range( 0, len(dummy_list))] dummy_zip = zip(dummy_list, local_n_list) lam = Lambda(local_n, sol.subs(dummy_zip)) rnew[sym] = ImageSet(lam, base) if eq is not None: newresult, rnew, delete_soln = _append_eq( eq, newresult, rnew, delete_soln, local_n) elif eq is not None: newresult, rnew, delete_soln = _append_eq( eq, newresult, rnew, delete_soln) elif soln_imageset: rnew[sym] = soln_imageset[sol] # restore original imageset _restore_imgset(rnew, original_imageset, newresult) else: newresult.append(rnew) elif satisfy_exclude: delete_soln = True rnew = {} _restore_imgset(rnew, original_imageset, newresult) return newresult, delete_soln # end of def _append_new_soln() def _new_order_result(result, eq): # separate first, second priority. `res` that makes `eq` value equals # to zero, should be used first then other result(second priority). # If it is not done then we may miss some soln. first_priority = [] second_priority = [] for res in result: if not any(isinstance(val, ImageSet) for val in res.values()): if eq.subs(res) == 0: first_priority.append(res) else: second_priority.append(res) if first_priority or second_priority: return first_priority + second_priority return result def _solve_using_known_values(result, solver): """Solves the system using already known solution (result contains the dict <symbol: value>). solver is `solveset_complex` or `solveset_real`. """ # stores imageset <expr: imageset(Lambda(n, expr), base)>. soln_imageset = {} total_solvest_call = 0 total_conditionst = 0 # sort such that equation with the fewest potential symbols is first. # means eq with less variable first for index, eq in enumerate(eqs_in_better_order): newresult = [] original_imageset = {} # if imageset expr is used to solve other symbol imgset_yes = False result = _new_order_result(result, eq) for res in result: got_symbol = set() # symbols solved in one iteration if soln_imageset: # find the imageset and use its expr. for key_res, value_res in res.items(): if isinstance(value_res, ImageSet): res[key_res] = value_res.lamda.expr original_imageset[key_res] = value_res dummy_n = value_res.lamda.expr.atoms(Dummy).pop() (base,) = value_res.base_sets imgset_yes = (dummy_n, base) # update eq with everything that is known so far eq2 = eq.subs(res).expand() unsolved_syms = _unsolved_syms(eq2, sort=True) if not unsolved_syms: if res: newresult, delete_res = _append_new_soln( res, None, None, imgset_yes, soln_imageset, original_imageset, newresult, eq2) if delete_res: # `delete_res` is true, means substituting `res` in # eq2 doesn't return `zero` or deleting the `res` # (a soln) since it staisfies expr of `exclude` # list. result.remove(res) continue # skip as it's independent of desired symbols depen1, depen2 = (eq2.rewrite(Add)).as_independent(unsolved_syms) if (depen1.has(Abs) or depen2.has(Abs)) and solver == solveset_complex: # Absolute values cannot be inverted in the # complex domain continue soln_imageset = {} for sym in unsolved_syms: not_solvable = False try: soln = solver(eq2, sym) total_solvest_call += 1 soln_new = S.EmptySet if isinstance(soln, Complement): # separate solution and complement complements[sym] = soln.args[1] soln = soln.args[0] # complement will be added at the end if isinstance(soln, Intersection): # Interval will be at 0th index always if soln.args[0] != Interval(-oo, oo): # sometimes solveset returns soln # with intersection S.Reals, to confirm that # soln is in domain=S.Reals intersections[sym] = soln.args[0] soln_new += soln.args[1] soln = soln_new if soln_new else soln if index > 0 and solver == solveset_real: # one symbol's real soln , another symbol may have # corresponding complex soln. if not isinstance(soln, (ImageSet, ConditionSet)): soln += solveset_complex(eq2, sym) except NotImplementedError: # If sovleset is not able to solve equation `eq2`. Next # time we may get soln using next equation `eq2` continue if isinstance(soln, ConditionSet): soln = S.EmptySet # don't do `continue` we may get soln # in terms of other symbol(s) not_solvable = True total_conditionst += 1 if soln is not S.EmptySet: soln, soln_imageset = _extract_main_soln( sym, soln, soln_imageset) for sol in soln: # sol is not a `Union` since we checked it # before this loop sol, soln_imageset = _extract_main_soln( sym, sol, soln_imageset) sol = set(sol).pop() free = sol.free_symbols if got_symbol and any([ ss in free for ss in got_symbol ]): # sol depends on previously solved symbols # then continue continue rnew = res.copy() # put each solution in res and append the new result # in the new result list (solution for symbol `s`) # along with old results. for k, v in res.items(): if isinstance(v, Expr): # if any unsolved symbol is present # Then subs known value rnew[k] = v.subs(sym, sol) # and add this new solution if soln_imageset: # replace all lambda variables with 0. imgst = soln_imageset[sol] rnew[sym] = imgst.lamda( [0 for i in range(0, len( imgst.lamda.variables))]) else: rnew[sym] = sol newresult, delete_res = _append_new_soln( rnew, sym, sol, imgset_yes, soln_imageset, original_imageset, newresult) if delete_res: # deleting the `res` (a soln) since it staisfies # eq of `exclude` list result.remove(res) # solution got for sym if not not_solvable: got_symbol.add(sym) # next time use this new soln if newresult: result = newresult return result, total_solvest_call, total_conditionst # end def _solve_using_know_values() new_result_real, solve_call1, cnd_call1 = _solve_using_known_values( old_result, solveset_real) new_result_complex, solve_call2, cnd_call2 = _solve_using_known_values( old_result, solveset_complex) # when `total_solveset_call` is equals to `total_conditionset` # means solvest fails to solve all the eq. # return conditionset in this case total_conditionset += (cnd_call1 + cnd_call2) total_solveset_call += (solve_call1 + solve_call2) if total_conditionset == total_solveset_call and total_solveset_call != -1: return _return_conditionset(eqs_in_better_order, all_symbols) # overall result result = new_result_real + new_result_complex result_all_variables = [] result_infinite = [] for res in result: if not res: # means {None : None} continue # If length < len(all_symbols) means infinite soln. # Some or all the soln is dependent on 1 symbol. # eg. {x: y+2} then final soln {x: y+2, y: y} if len(res) < len(all_symbols): solved_symbols = res.keys() unsolved = list(filter( lambda x: x not in solved_symbols, all_symbols)) for unsolved_sym in unsolved: res[unsolved_sym] = unsolved_sym result_infinite.append(res) if res not in result_all_variables: result_all_variables.append(res) if result_infinite: # we have general soln # eg : [{x: -1, y : 1}, {x : -y , y: y}] then # return [{x : -y, y : y}] result_all_variables = result_infinite if intersections or complements: result_all_variables = add_intersection_complement( result_all_variables, intersections, complements) # convert to ordered tuple result = S.EmptySet for r in result_all_variables: temp = [r[symb] for symb in all_symbols] result += FiniteSet(tuple(temp)) return result # end of def substitution() def _solveset_work(system, symbols): soln = solveset(system[0], symbols[0]) if isinstance(soln, FiniteSet): _soln = FiniteSet([tuple((s,)) for s in soln]) return _soln else: return FiniteSet(tuple(FiniteSet(soln))) def _handle_positive_dimensional(polys, symbols, denominators): from sympy.polys.polytools import groebner # substitution method where new system is groebner basis of the system _symbols = list(symbols) _symbols.sort(key=default_sort_key) basis = groebner(polys, _symbols, polys=True) new_system = [] for poly_eq in basis: new_system.append(poly_eq.as_expr()) result = [{}] result = substitution( new_system, symbols, result, [], denominators) return result # end of def _handle_positive_dimensional() def _handle_zero_dimensional(polys, symbols, system): # solve 0 dimensional poly system using `solve_poly_system` result = solve_poly_system(polys, symbols) # May be some extra soln is added because # we used `unrad` in `_separate_poly_nonpoly`, so # need to check and remove if it is not a soln. result_update = S.EmptySet for res in result: dict_sym_value = dict(list(zip(symbols, res))) if all(checksol(eq, dict_sym_value) for eq in system): result_update += FiniteSet(res) return result_update # end of def _handle_zero_dimensional() def _separate_poly_nonpoly(system, symbols): polys = [] polys_expr = [] nonpolys = [] denominators = set() poly = None for eq in system: # Store denom expression if it contains symbol denominators.update(_simple_dens(eq, symbols)) # try to remove sqrt and rational power without_radicals = unrad(simplify(eq)) if without_radicals: eq_unrad, cov = without_radicals if not cov: eq = eq_unrad if isinstance(eq, Expr): eq = eq.as_numer_denom()[0] poly = eq.as_poly(symbols, extension=True) elif simplify(eq).is_number: continue if poly is not None: polys.append(poly) polys_expr.append(poly.as_expr()) else: nonpolys.append(eq) return polys, polys_expr, nonpolys, denominators # end of def _separate_poly_nonpoly() def nonlinsolve(system, symbols): r""" Solve system of N nonlinear equations with M variables, which means both under and overdetermined systems are supported. Positive dimensional system is also supported (A system with infinitely many solutions is said to be positive-dimensional). In Positive dimensional system solution will be dependent on at least one symbol. Returns both real solution and complex solution(If system have). The possible number of solutions is zero, one or infinite. Parameters ========== system : list of equations The target system of equations symbols : list of Symbols symbols should be given as a sequence eg. list Returns ======= A FiniteSet of ordered tuple of values of `symbols` for which the `system` has solution. Order of values in the tuple is same as symbols present in the parameter `symbols`. Please note that general FiniteSet is unordered, the solution returned here is not simply a FiniteSet of solutions, rather it is a FiniteSet of ordered tuple, i.e. the first & only argument to FiniteSet is a tuple of solutions, which is ordered, & hence the returned solution is ordered. Also note that solution could also have been returned as an ordered tuple, FiniteSet is just a wrapper `{}` around the tuple. It has no other significance except for the fact it is just used to maintain a consistent output format throughout the solveset. For the given set of Equations, the respective input types are given below: .. math:: xy - 1 = 0 .. math:: 4x2 + y2 - 5 = 0 `system = [xy - 1, 4x2 + y2 - 5]` `symbols = [x, y]` Raises ====== ValueError The input is not valid. The symbols are not given. AttributeError The input symbols are not `Symbol` type. Examples ======== >>> from sympy.core.symbol import symbols >>> from sympy.solvers.solveset import nonlinsolve >>> x, y, z = symbols('x, y, z', real=True) >>> nonlinsolve([xy - 1, 4x2 + y2 - 5], [x, y]) FiniteSet((-1, -1), (-1/2, -2), (1/2, 2), (1, 1)) 1. Positive dimensional system and complements: >>> from sympy import pprint >>> from sympy.polys.polytools import is_zero_dimensional >>> a, b, c, d = symbols('a, b, c, d', extended_real=True) >>> eq1 = a + b + c + d >>> eq2 = ab + bc + cd + da >>> eq3 = abc + bcd + cda + dab >>> eq4 = abcd - 1 >>> system = [eq1, eq2, eq3, eq4] >>> is_zero_dimensional(system) False >>> pprint(nonlinsolve(system, [a, b, c, d]), use_unicode=False) -1 1 1 -1 {(---, -d, -, {d} \ {0}), (-, -d, ---, {d} \ {0})} d d d d >>> nonlinsolve([(x+y)2 - 4, x + y - 2], [x, y]) FiniteSet((2 - y, y)) 2. If some of the equations are non-polynomial then `nonlinsolve` will call the `substitution` function and return real and complex solutions, if present. >>> from sympy import exp, sin >>> nonlinsolve([exp(x) - sin(y), y2 - 4], [x, y]) FiniteSet((ImageSet(Lambda(_n, 2_nIpi + log(sin(2))), Integers), 2), (ImageSet(Lambda(_n, I(2_npi + pi) + log(sin(2))), Integers), -2)) 3. If system is non-linear polynomial and zero-dimensional then it returns both solution (real and complex solutions, if present) using `solve_poly_system`: >>> from sympy import sqrt >>> nonlinsolve([x2 - 2y*2 -2, xy - 2], [x, y]) FiniteSet((-2, -1), (2, 1), (-sqrt(2)I, sqrt(2)I), (sqrt(2)I, -sqrt(2)I)) 4. `nonlinsolve` can solve some linear (zero or positive dimensional) system (because it uses the `groebner` function to get the groebner basis and then uses the `substitution` function basis as the new `system`). But it is not recommended to solve linear system using `nonlinsolve`, because `linsolve` is better for general linear systems. >>> nonlinsolve([x + 2y -z - 3, x - y - 4z + 9 , y + z - 4], [x, y, z]) FiniteSet((3z - 5, 4 - z, z)) 5. System having polynomial equations and only real solution is solved using `solve_poly_system`: >>> e1 = sqrt(x2 + y2) - 10 >>> e2 = sqrt(y2 + (-x + 10)2) - 3 >>> nonlinsolve((e1, e2), (x, y)) FiniteSet((191/20, -3sqrt(391)/20), (191/20, 3sqrt(391)/20)) >>> nonlinsolve([x2 + 2/y - 2, x + y - 3], [x, y]) FiniteSet((1, 2), (1 - sqrt(5), 2 + sqrt(5)), (1 + sqrt(5), 2 - sqrt(5))) >>> nonlinsolve([x2 + 2/y - 2, x + y - 3], [y, x]) FiniteSet((2, 1), (2 - sqrt(5), 1 + sqrt(5)), (2 + sqrt(5), 1 - sqrt(5))) 6. It is better to use symbols instead of Trigonometric Function or Function (e.g. replace `sin(x)` with symbol, replace `f(x)` with symbol and so on. Get soln from `nonlinsolve` and then using `solveset` get the value of `x`) How nonlinsolve is better than old solver `_solve_system` : =========================================================== 1. A positive dimensional system solver : nonlinsolve can return solution for positive dimensional system. It finds the Groebner Basis of the positive dimensional system(calling it as basis) then we can start solving equation(having least number of variable first in the basis) using solveset and substituting that solved solutions into other equation(of basis) to get solution in terms of minimum variables. Here the important thing is how we are substituting the known values and in which equations. 2. Real and Complex both solutions : nonlinsolve returns both real and complex solution. If all the equations in the system are polynomial then using `solve_poly_system` both real and complex solution is returned. If all the equations in the system are not polynomial equation then goes to `substitution` method with this polynomial and non polynomial equation(s), to solve for unsolved variables. Here to solve for particular variable solveset_real and solveset_complex is used. For both real and complex solution function `_solve_using_know_values` is used inside `substitution` function.(`substitution` function will be called when there is any non polynomial equation(s) is present). When solution is valid then add its general solution in the final result. 3. Complement and Intersection will be added if any : nonlinsolve maintains dict for complements and Intersections. If solveset find complements or/and Intersection with any Interval or set during the execution of `substitution` function ,then complement or/and Intersection for that variable is added before returning final solution. """ from sympy.polys.polytools import is_zero_dimensional if not system: return S.EmptySet if not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise ValueError(filldedent(msg)) if hasattr(symbols[0], '__iter__'): symbols = symbols[0] if not is_sequence(symbols) or not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise IndexError(filldedent(msg)) system, symbols, swap = recast_to_symbols(system, symbols) if swap: soln = nonlinsolve(system, symbols) return FiniteSet([tuple(i.xreplace(swap) for i in s) for s in soln]) if len(system) == 1 and len(symbols) == 1: return _solveset_work(system, symbols) # main code of def nonlinsolve() starts from here polys, polys_expr, nonpolys, denominators = _separate_poly_nonpoly( system, symbols) if len(symbols) == len(polys): # If all the equations in the system are poly if is_zero_dimensional(polys, symbols): # finite number of soln (Zero dimensional system) try: return _handle_zero_dimensional(polys, symbols, system) except NotImplementedError: # Right now it doesn't fail for any polynomial system of # equation. If `solve_poly_system` fails then `substitution` # method will handle it. result = substitution( polys_expr, symbols, exclude=denominators) return result # positive dimensional system res = _handle_positive_dimensional(polys, symbols, denominators) if res is EmptySet and any(not p.domain.is_Exact for p in polys): raise NotImplementedError("Equation not in exact domain. Try converting to rational") else: return res else: # If all the equations are not polynomial. # Use `substitution` method for the system result = substitution( polys_expr + nonpolys, symbols, exclude=denominators) return result
e550a4452e5c95ebe56244e1588b39c16741db74e8a21a9287ce29fd39236fcb	""" This module contains pdsolve() and different helper functions that it uses. It is heavily inspired by the ode module and hence the basic infrastructure remains the same. Functions in this module These are the user functions in this module: - pdsolve() - Solves PDE's - classify_pde() - Classifies PDEs into possible hints for dsolve(). - pde_separate() - Separate variables in partial differential equation either by additive or multiplicative separation approach. These are the helper functions in this module: - pde_separate_add() - Helper function for searching additive separable solutions. - pde_separate_mul() - Helper function for searching multiplicative separable solutions. Currently implemented solver methods The following methods are implemented for solving partial differential equations. See the docstrings of the various pde_hint() functions for more information on each (run help(pde)): - 1st order linear homogeneous partial differential equations with constant coefficients. - 1st order linear general partial differential equations with constant coefficients. - 1st order linear partial differential equations with variable coefficients. """ from itertools import combinations_with_replacement from sympy.simplify import simplify # type: ignore from sympy.core import Add, S from sympy.core.compatibility import reduce, is_sequence from sympy.core.function import Function, expand, AppliedUndef, Subs from sympy.core.relational import Equality, Eq from sympy.core.symbol import Symbol, Wild, symbols from sympy.functions import exp from sympy.integrals.integrals import Integral from sympy.utilities.iterables import has_dups from sympy.utilities.misc import filldedent from sympy.solvers.deutils import _preprocess, ode_order, _desolve from sympy.solvers.solvers import solve from sympy.simplify.radsimp import collect import operator allhints = ( "1st_linear_constant_coeff_homogeneous", "1st_linear_constant_coeff", "1st_linear_constant_coeff_Integral", "1st_linear_variable_coeff" ) def pdsolve(eq, func=None, hint='default', dict=False, solvefun=None, kwargs): """ Solves any (supported) kind of partial differential equation. Usage pdsolve(eq, f(x,y), hint) -> Solve partial differential equation eq for function f(x,y), using method hint. Details ``eq`` can be any supported partial differential equation (see the pde docstring for supported methods). This can either be an Equality, or an expression, which is assumed to be equal to 0. ``f(x,y)`` is a function of two variables whose derivatives in that variable make up the partial differential equation. In many cases it is not necessary to provide this; it will be autodetected (and an error raised if it couldn't be detected). ``hint`` is the solving method that you want pdsolve to use. Use classify_pde(eq, f(x,y)) to get all of the possible hints for a PDE. The default hint, 'default', will use whatever hint is returned first by classify_pde(). See Hints below for more options that you can use for hint. ``solvefun`` is the convention used for arbitrary functions returned by the PDE solver. If not set by the user, it is set by default to be F. Hints Aside from the various solving methods, there are also some meta-hints that you can pass to pdsolve(): "default": This uses whatever hint is returned first by classify_pde(). This is the default argument to pdsolve(). "all": To make pdsolve apply all relevant classification hints, use pdsolve(PDE, func, hint="all"). This will return a dictionary of hint:solution terms. If a hint causes pdsolve to raise the NotImplementedError, value of that hint's key will be the exception object raised. The dictionary will also include some special keys: - order: The order of the PDE. See also ode_order() in deutils.py - default: The solution that would be returned by default. This is the one produced by the hint that appears first in the tuple returned by classify_pde(). "all_Integral": This is the same as "all", except if a hint also has a corresponding "_Integral" hint, it only returns the "_Integral" hint. This is useful if "all" causes pdsolve() to hang because of a difficult or impossible integral. This meta-hint will also be much faster than "all", because integrate() is an expensive routine. See also the classify_pde() docstring for more info on hints, and the pde docstring for a list of all supported hints. Tips** - You can declare the derivative of an unknown function this way: >>> from sympy import Function, Derivative >>> from sympy.abc import x, y # x and y are the independent variables >>> f = Function("f")(x, y) # f is a function of x and y >>> # fx will be the partial derivative of f with respect to x >>> fx = Derivative(f, x) >>> # fy will be the partial derivative of f with respect to y >>> fy = Derivative(f, y) - See test_pde.py for many tests, which serves also as a set of examples for how to use pdsolve(). - pdsolve always returns an Equality class (except for the case when the hint is "all" or "all_Integral"). Note that it is not possible to get an explicit solution for f(x, y) as in the case of ODE's - Do help(pde.pde_hintname) to get help more information on a specific hint Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, Eq >>> from sympy.abc import x, y >>> f = Function('f') >>> u = f(x, y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> eq = Eq(1 + (2(ux/u)) + (3(uy/u)), 0) >>> pdsolve(eq) Eq(f(x, y), F(3x - 2y)exp(-2x/13 - 3y/13)) """ if not solvefun: solvefun = Function('F') # See the docstring of _desolve for more details. hints = _desolve(eq, func=func, hint=hint, simplify=True, type='pde', kwargs) eq = hints.pop('eq', False) all_ = hints.pop('all', False) if all_: # TODO : 'best' hint should be implemented when adequate # number of hints are added. pdedict = {} failed_hints = {} gethints = classify_pde(eq, dict=True) pdedict.update({'order': gethints['order'], 'default': gethints['default']}) for hint in hints: try: rv = _helper_simplify(eq, hint, hints[hint]['func'], hints[hint]['order'], hints[hint][hint], solvefun) except NotImplementedError as detail: failed_hints[hint] = detail else: pdedict[hint] = rv pdedict.update(failed_hints) return pdedict else: return _helper_simplify(eq, hints['hint'], hints['func'], hints['order'], hints[hints['hint']], solvefun) def _helper_simplify(eq, hint, func, order, match, solvefun): """Helper function of pdsolve that calls the respective pde functions to solve for the partial differential equations. This minimizes the computation in calling _desolve multiple times. """ if hint.endswith("_Integral"): solvefunc = globals()[ "pde_" + hint[:-len("_Integral")]] else: solvefunc = globals()["pde_" + hint] return _handle_Integral(solvefunc(eq, func, order, match, solvefun), func, order, hint) def _handle_Integral(expr, func, order, hint): r""" Converts a solution with integrals in it into an actual solution. Simplifies the integral mainly using doit() """ if hint.endswith("_Integral"): return expr elif hint == "1st_linear_constant_coeff": return simplify(expr.doit()) else: return expr def classify_pde(eq, func=None, dict=False, , prep=True, *kwargs): """ Returns a tuple of possible pdsolve() classifications for a PDE. The tuple is ordered so that first item is the classification that pdsolve() uses to solve the PDE by default. In general, classifications near the beginning of the list will produce better solutions faster than those near the end, though there are always exceptions. To make pdsolve use a different classification, use pdsolve(PDE, func, hint=<classification>). See also the pdsolve() docstring for different meta-hints you can use. If ``dict`` is true, classify_pde() will return a dictionary of hint:match expression terms. This is intended for internal use by pdsolve(). Note that because dictionaries are ordered arbitrarily, this will most likely not be in the same order as the tuple. You can get help on different hints by doing help(pde.pde_hintname), where hintname is the name of the hint without "_Integral". See sympy.pde.allhints or the sympy.pde docstring for a list of all supported hints that can be returned from classify_pde. Examples ======== >>> from sympy.solvers.pde import classify_pde >>> from sympy import Function, Eq >>> from sympy.abc import x, y >>> f = Function('f') >>> u = f(x, y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> eq = Eq(1 + (2(ux/u)) + (3(uy/u)), 0) >>> classify_pde(eq) ('1st_linear_constant_coeff_homogeneous',) """ if func and len(func.args) != 2: raise NotImplementedError("Right now only partial " "differential equations of two variables are supported") if prep or func is None: prep, func_ = _preprocess(eq, func) if func is None: func = func_ if isinstance(eq, Equality): if eq.rhs != 0: return classify_pde(eq.lhs - eq.rhs, func) eq = eq.lhs f = func.func x = func.args[0] y = func.args[1] fx = f(x,y).diff(x) fy = f(x,y).diff(y) # TODO : For now pde.py uses support offered by the ode_order function # to find the order with respect to a multi-variable function. An # improvement could be to classify the order of the PDE on the basis of # individual variables. order = ode_order(eq, f(x,y)) # hint:matchdict or hint:(tuple of matchdicts) # Also will contain "default":<default hint> and "order":order items. matching_hints = {'order': order} if not order: if dict: matching_hints["default"] = None return matching_hints else: return () eq = expand(eq) a = Wild('a', exclude = [f(x,y)]) b = Wild('b', exclude = [f(x,y), fx, fy, x, y]) c = Wild('c', exclude = [f(x,y), fx, fy, x, y]) d = Wild('d', exclude = [f(x,y), fx, fy, x, y]) e = Wild('e', exclude = [f(x,y), fx, fy]) n = Wild('n', exclude = [x, y]) # Try removing the smallest power of f(x,y) # from the highest partial derivatives of f(x,y) reduced_eq = None if eq.is_Add: var = set(combinations_with_replacement((x,y), order)) dummyvar = var.copy() power = None for i in var: coeff = eq.coeff(f(x,y).diff(i)) if coeff != 1: match = coeff.match(af(x,y)n) if match and match[a]: power = match[n] dummyvar.remove(i) break dummyvar.remove(i) for i in dummyvar: coeff = eq.coeff(f(x,y).diff(i)) if coeff != 1: match = coeff.match(af(x,y)n) if match and match[a] and match[n] < power: power = match[n] if power: den = f(x,y)power reduced_eq = Add([arg/den for arg in eq.args]) if not reduced_eq: reduced_eq = eq if order == 1: reduced_eq = collect(reduced_eq, f(x, y)) r = reduced_eq.match(bfx + cfy + df(x,y) + e) if r: if not r[e]: ## Linear first-order homogeneous partial-differential ## equation with constant coefficients r.update({'b': b, 'c': c, 'd': d}) matching_hints["1st_linear_constant_coeff_homogeneous"] = r else: if r[b]2 + r[c]2 != 0: ## Linear first-order general partial-differential ## equation with constant coefficients r.update({'b': b, 'c': c, 'd': d, 'e': e}) matching_hints["1st_linear_constant_coeff"] = r matching_hints[ "1st_linear_constant_coeff_Integral"] = r else: b = Wild('b', exclude=[f(x, y), fx, fy]) c = Wild('c', exclude=[f(x, y), fx, fy]) d = Wild('d', exclude=[f(x, y), fx, fy]) r = reduced_eq.match(bfx + cfy + df(x,y) + e) if r: r.update({'b': b, 'c': c, 'd': d, 'e': e}) matching_hints["1st_linear_variable_coeff"] = r # Order keys based on allhints. retlist = [] for i in allhints: if i in matching_hints: retlist.append(i) if dict: # Dictionaries are ordered arbitrarily, so make note of which # hint would come first for pdsolve(). Use an ordered dict in Py 3. matching_hints["default"] = None matching_hints["ordered_hints"] = tuple(retlist) for i in allhints: if i in matching_hints: matching_hints["default"] = i break return matching_hints else: return tuple(retlist) def checkpdesol(pde, sol, func=None, solve_for_func=True): """ Checks if the given solution satisfies the partial differential equation. pde is the partial differential equation which can be given in the form of an equation or an expression. sol is the solution for which the pde is to be checked. This can also be given in an equation or an expression form. If the function is not provided, the helper function _preprocess from deutils is used to identify the function. If a sequence of solutions is passed, the same sort of container will be used to return the result for each solution. The following methods are currently being implemented to check if the solution satisfies the PDE: 1. Directly substitute the solution in the PDE and check. If the solution hasn't been solved for f, then it will solve for f provided solve_for_func hasn't been set to False. If the solution satisfies the PDE, then a tuple (True, 0) is returned. Otherwise a tuple (False, expr) where expr is the value obtained after substituting the solution in the PDE. However if a known solution returns False, it may be due to the inability of doit() to simplify it to zero. Examples ======== >>> from sympy import Function, symbols >>> from sympy.solvers.pde import checkpdesol, pdsolve >>> x, y = symbols('x y') >>> f = Function('f') >>> eq = 2f(x,y) + 3f(x,y).diff(x) + 4f(x,y).diff(y) >>> sol = pdsolve(eq) >>> assert checkpdesol(eq, sol)[0] >>> eq = xf(x,y) + f(x,y).diff(x) >>> checkpdesol(eq, sol) (False, (xF(4x - 3y) - 6F(4x - 3y)/25 + 4Subs(Derivative(F(_xi_1), _xi_1), _xi_1, 4x - 3y))exp(-6x/25 - 8y/25)) """ # Converting the pde into an equation if not isinstance(pde, Equality): pde = Eq(pde, 0) # If no function is given, try finding the function present. if func is None: try: _, func = _preprocess(pde.lhs) except ValueError: funcs = [s.atoms(AppliedUndef) for s in ( sol if is_sequence(sol, set) else [sol])] funcs = set().union(funcs) if len(funcs) != 1: raise ValueError( 'must pass func arg to checkpdesol for this case.') func = funcs.pop() # If the given solution is in the form of a list or a set # then return a list or set of tuples. if is_sequence(sol, set): return type(sol)([checkpdesol( pde, i, func=func, solve_for_func=solve_for_func) for i in sol]) # Convert solution into an equation if not isinstance(sol, Equality): sol = Eq(func, sol) elif sol.rhs == func: sol = sol.reversed # Try solving for the function solved = sol.lhs == func and not sol.rhs.has(func) if solve_for_func and not solved: solved = solve(sol, func) if solved: if len(solved) == 1: return checkpdesol(pde, Eq(func, solved[0]), func=func, solve_for_func=False) else: return checkpdesol(pde, [Eq(func, t) for t in solved], func=func, solve_for_func=False) # try direct substitution of the solution into the PDE and simplify if sol.lhs == func: pde = pde.lhs - pde.rhs s = simplify(pde.subs(func, sol.rhs).doit()) return s is S.Zero, s raise NotImplementedError(filldedent(''' Unable to test if %s is a solution to %s.''' % (sol, pde))) def pde_1st_linear_constant_coeff_homogeneous(eq, func, order, match, solvefun): r""" Solves a first order linear homogeneous partial differential equation with constant coefficients. The general form of this partial differential equation is .. math:: a \frac{\partial f(x,y)}{\partial x} + b \frac{\partial f(x,y)}{\partial y} + c f(x,y) = 0 where `a`, `b` and `c` are constants. The general solution is of the form: .. math:: f(x, y) = F(- a y + b x ) e^{- \frac{c (a x + b y)}{a^2 + b^2}} and can be found in SymPy with ``pdsolve``:: >>> from sympy.solvers import pdsolve >>> from sympy.abc import x, y, a, b, c >>> from sympy import Function, pprint >>> f = Function('f') >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = aux + buy + cu >>> pprint(genform) d d a--(f(x, y)) + b--(f(x, y)) + cf(x, y) dx dy >>> pprint(pdsolve(genform)) -c(ax + by) --------------- 2 2 a + b f(x, y) = F(-ay + bx)e Examples ======== >>> from sympy import pdsolve >>> from sympy import Function, pprint >>> from sympy.abc import x,y >>> f = Function('f') >>> pdsolve(f(x,y) + f(x,y).diff(x) + f(x,y).diff(y)) Eq(f(x, y), F(x - y)exp(-x/2 - y/2)) >>> pprint(pdsolve(f(x,y) + f(x,y).diff(x) + f(x,y).diff(y))) x y - - - - 2 2 f(x, y) = F(x - y)e References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ # TODO : For now homogeneous first order linear PDE's having # two variables are implemented. Once there is support for # solving systems of ODE's, this can be extended to n variables. f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] return Eq(f(x,y), exp(-S(d)/(b2 + c2)(bx + cy))solvefun(cx - by)) def pde_1st_linear_constant_coeff(eq, func, order, match, solvefun): r""" Solves a first order linear partial differential equation with constant coefficients. The general form of this partial differential equation is .. math:: a \frac{\partial f(x,y)}{\partial x} + b \frac{\partial f(x,y)}{\partial y} + c f(x,y) = G(x,y) where `a`, `b` and `c` are constants and `G(x, y)` can be an arbitrary function in `x` and `y`. The general solution of the PDE is: .. math:: f(x, y) = \left. \left[F(\eta) + \frac{1}{a^2 + b^2} \int\limits^{a x + b y} G\left(\frac{a \xi + b \eta}{a^2 + b^2}, \frac{- a \eta + b \xi}{a^2 + b^2} \right) e^{\frac{c \xi}{a^2 + b^2}}\, d\xi\right] e^{- \frac{c \xi}{a^2 + b^2}} \right\|_{\substack{\eta=- a y + b x\\ \xi=a x + b y }}\, , where `F(\eta)` is an arbitrary single-valued function. The solution can be found in SymPy with ``pdsolve``:: >>> from sympy.solvers import pdsolve >>> from sympy.abc import x, y, a, b, c >>> from sympy import Function, pprint >>> f = Function('f') >>> G = Function('G') >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = aux + buy + cu - G(x,y) >>> pprint(genform) d d a--(f(x, y)) + b--(f(x, y)) + cf(x, y) - G(x, y) dx dy >>> pprint(pdsolve(genform, hint='1st_linear_constant_coeff_Integral')) // ax + by \ \|\| / \| \|\| \| \| \|\| \| cxi \| \|\| \| ------- \| \|\| \| 2 2 \| \|\| \| /axi + beta -aeta + bxi\ a + b \| \|\| \| G\|------------, -------------\|e d(xi)\| \|\| \| \| 2 2 2 2 \| \| \|\| \| \ a + b a + b / \| \|\| \| \| \|\| / \| \|\| \| f(x, y) = \|\|F(eta) + -------------------------------------------------------\|* \|\| 2 2 \| \\ a + b / <BLANKLINE> \\| \|\| \|\| \|\| \|\| \|\| \|\| \|\| \|\| -cxi \|\| -------\|\| 2 2\|\| a + b \|\| e \|\| \|\| /\|eta=-ay + bx, xi=ax + by Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, pprint, exp >>> from sympy.abc import x,y >>> f = Function('f') >>> eq = -2f(x,y).diff(x) + 4f(x,y).diff(y) + 5f(x,y) - exp(x + 3y) >>> pdsolve(eq) Eq(f(x, y), (F(4x + 2y) + exp(x/2 + 4y)/15)exp(x/2 - y)) References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ # TODO : For now homogeneous first order linear PDE's having # two variables are implemented. Once there is support for # solving systems of ODE's, this can be extended to n variables. xi, eta = symbols("xi eta") f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] e = -match[match['e']] expterm = exp(-S(d)/(b2 + c2)xi) functerm = solvefun(eta) solvedict = solve((bx + cy - xi, cx - by - eta), x, y) # Integral should remain as it is in terms of xi, # doit() should be done in _handle_Integral. genterm = (1/S(b2 + c2))Integral( (1/expterme).subs(solvedict), (xi, bx + cy)) return Eq(f(x,y), Subs(expterm(functerm + genterm), (eta, xi), (cx - by, bx + cy))) def pde_1st_linear_variable_coeff(eq, func, order, match, solvefun): r""" Solves a first order linear partial differential equation with variable coefficients. The general form of this partial differential equation is .. math:: a(x, y) \frac{\partial f(x, y)}{\partial x} + b(x, y) \frac{\partial f(x, y)}{\partial y} + c(x, y) f(x, y) = G(x, y) where `a(x, y)`, `b(x, y)`, `c(x, y)` and `G(x, y)` are arbitrary functions in `x` and `y`. This PDE is converted into an ODE by making the following transformation: 1. `\xi` as `x` 2. `\eta` as the constant in the solution to the differential equation `\frac{dy}{dx} = -\frac{b}{a}` Making the previous substitutions reduces it to the linear ODE .. math:: a(\xi, \eta)\frac{du}{d\xi} + c(\xi, \eta)u - G(\xi, \eta) = 0 which can be solved using ``dsolve``. >>> from sympy.abc import x, y >>> from sympy import Function, pprint >>> a, b, c, G, f= [Function(i) for i in ['a', 'b', 'c', 'G', 'f']] >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = a(x, y)u + b(x, y)ux + c(x, y)uy - G(x,y) >>> pprint(genform) d d -G(x, y) + a(x, y)f(x, y) + b(x, y)--(f(x, y)) + c(x, y)--(f(x, y)) dx dy Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, pprint >>> from sympy.abc import x,y >>> f = Function('f') >>> eq = x(u.diff(x)) - y(u.diff(y)) + y2u - y*2 >>> pdsolve(eq) Eq(f(x, y), F(xy)exp(y2/2) + 1) References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ from sympy.integrals.integrals import integrate from sympy.solvers.ode import dsolve xi, eta = symbols("xi eta") f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] e = -match[match['e']] if not d: # To deal with cases like bux = e or cuy = e if not (b and c): if c: try: tsol = integrate(e/c, y) except NotImplementedError: raise NotImplementedError("Unable to find a solution" " due to inability of integrate") else: return Eq(f(x,y), solvefun(x) + tsol) if b: try: tsol = integrate(e/b, x) except NotImplementedError: raise NotImplementedError("Unable to find a solution" " due to inability of integrate") else: return Eq(f(x,y), solvefun(y) + tsol) if not c: # To deal with cases when c is 0, a simpler method is used. # The PDE reduces to b(u.diff(x)) + du = e, which is a linear ODE in x plode = f(x).diff(x)b + df(x) - e sol = dsolve(plode, f(x)) syms = sol.free_symbols - plode.free_symbols - {x, y} rhs = _simplify_variable_coeff(sol.rhs, syms, solvefun, y) return Eq(f(x, y), rhs) if not b: # To deal with cases when b is 0, a simpler method is used. # The PDE reduces to c(u.diff(y)) + du = e, which is a linear ODE in y plode = f(y).diff(y)c + df(y) - e sol = dsolve(plode, f(y)) syms = sol.free_symbols - plode.free_symbols - {x, y} rhs = _simplify_variable_coeff(sol.rhs, syms, solvefun, x) return Eq(f(x, y), rhs) dummy = Function('d') h = (c/b).subs(y, dummy(x)) sol = dsolve(dummy(x).diff(x) - h, dummy(x)) if isinstance(sol, list): sol = sol[0] solsym = sol.free_symbols - h.free_symbols - {x, y} if len(solsym) == 1: solsym = solsym.pop() etat = (solve(sol, solsym)[0]).subs(dummy(x), y) ysub = solve(eta - etat, y)[0] deq = (b(f(x).diff(x)) + df(x) - e).subs(y, ysub) final = (dsolve(deq, f(x), hint='1st_linear')).rhs if isinstance(final, list): final = final[0] finsyms = final.free_symbols - deq.free_symbols - {x, y} rhs = _simplify_variable_coeff(final, finsyms, solvefun, etat) return Eq(f(x, y), rhs) else: raise NotImplementedError("Cannot solve the partial differential equation due" " to inability of constantsimp") def _simplify_variable_coeff(sol, syms, func, funcarg): r""" Helper function to replace constants by functions in 1st_linear_variable_coeff """ eta = Symbol("eta") if len(syms) == 1: sym = syms.pop() final = sol.subs(sym, func(funcarg)) else: for key, sym in enumerate(syms): final = sol.subs(sym, func(funcarg)) return simplify(final.subs(eta, funcarg)) def pde_separate(eq, fun, sep, strategy='mul'): """Separate variables in partial differential equation either by additive or multiplicative separation approach. It tries to rewrite an equation so that one of the specified variables occurs on a different side of the equation than the others. :param eq: Partial differential equation :param fun: Original function F(x, y, z) :param sep: List of separated functions [X(x), u(y, z)] :param strategy: Separation strategy. You can choose between additive separation ('add') and multiplicative separation ('mul') which is default. Examples ======== >>> from sympy import E, Eq, Function, pde_separate, Derivative as D >>> from sympy.abc import x, t >>> u, X, T = map(Function, 'uXT') >>> eq = Eq(D(u(x, t), x), E(u(x, t))D(u(x, t), t)) >>> pde_separate(eq, u(x, t), [X(x), T(t)], strategy='add') [exp(-X(x))Derivative(X(x), x), exp(T(t))Derivative(T(t), t)] >>> eq = Eq(D(u(x, t), x, 2), D(u(x, t), t, 2)) >>> pde_separate(eq, u(x, t), [X(x), T(t)], strategy='mul') [Derivative(X(x), (x, 2))/X(x), Derivative(T(t), (t, 2))/T(t)] See Also ======== pde_separate_add, pde_separate_mul """ do_add = False if strategy == 'add': do_add = True elif strategy == 'mul': do_add = False else: raise ValueError('Unknown strategy: %s' % strategy) if isinstance(eq, Equality): if eq.rhs != 0: return pde_separate(Eq(eq.lhs - eq.rhs, 0), fun, sep, strategy) else: return pde_separate(Eq(eq, 0), fun, sep, strategy) if eq.rhs != 0: raise ValueError("Value should be 0") # Handle arguments orig_args = list(fun.args) subs_args = [] for s in sep: for j in range(0, len(s.args)): subs_args.append(s.args[j]) if do_add: functions = reduce(operator.add, sep) else: functions = reduce(operator.mul, sep) # Check whether variables match if len(subs_args) != len(orig_args): raise ValueError("Variable counts do not match") # Check for duplicate arguments like [X(x), u(x, y)] if has_dups(subs_args): raise ValueError("Duplicate substitution arguments detected") # Check whether the variables match if set(orig_args) != set(subs_args): raise ValueError("Arguments do not match") # Substitute original function with separated... result = eq.lhs.subs(fun, functions).doit() # Divide by terms when doing multiplicative separation if not do_add: eq = 0 for i in result.args: eq += i/functions result = eq svar = subs_args[0] dvar = subs_args[1:] return _separate(result, svar, dvar) def pde_separate_add(eq, fun, sep): """ Helper function for searching additive separable solutions. Consider an equation of two independent variables x, y and a dependent variable w, we look for the product of two functions depending on different arguments: `w(x, y, z) = X(x) + y(y, z)` Examples ======== >>> from sympy import E, Eq, Function, pde_separate_add, Derivative as D >>> from sympy.abc import x, t >>> u, X, T = map(Function, 'uXT') >>> eq = Eq(D(u(x, t), x), E*(u(x, t))D(u(x, t), t)) >>> pde_separate_add(eq, u(x, t), [X(x), T(t)]) [exp(-X(x))Derivative(X(x), x), exp(T(t))Derivative(T(t), t)] """ return pde_separate(eq, fun, sep, strategy='add') def pde_separate_mul(eq, fun, sep): """ Helper function for searching multiplicative separable solutions. Consider an equation of two independent variables x, y and a dependent variable w, we look for the product of two functions depending on different arguments: `w(x, y, z) = X(x)u(y, z)` Examples ======== >>> from sympy import Function, Eq, pde_separate_mul, Derivative as D >>> from sympy.abc import x, y >>> u, X, Y = map(Function, 'uXY') >>> eq = Eq(D(u(x, y), x, 2), D(u(x, y), y, 2)) >>> pde_separate_mul(eq, u(x, y), [X(x), Y(y)]) [Derivative(X(x), (x, 2))/X(x), Derivative(Y(y), (y, 2))/Y(y)] """ return pde_separate(eq, fun, sep, strategy='mul') def _separate(eq, dep, others): """Separate expression into two parts based on dependencies of variables.""" # FIRST PASS # Extract derivatives depending our separable variable... terms = set() for term in eq.args: if term.is_Mul: for i in term.args: if i.is_Derivative and not i.has(others): terms.add(term) continue elif term.is_Derivative and not term.has(others): terms.add(term) # Find the factor that we need to divide by div = set() for term in terms: ext, sep = term.expand().as_independent(dep) # Failed? if sep.has(others): return None div.add(ext) # FIXME: Find lcm() of all the divisors and divide with it, instead of # current hack :( # https://github.com/sympy/sympy/issues/4597 if len(div) > 0: final = 0 for term in eq.args: eqn = 0 for i in div: eqn += term / i final += simplify(eqn) eq = final # SECOND PASS - separate the derivatives div = set() lhs = rhs = 0 for term in eq.args: # Check, whether we have already term with independent variable... if not term.has(others): lhs += term continue # ...otherwise, try to separate temp, sep = term.expand().as_independent(dep) # Failed? if sep.has(others): return None # Extract the divisors div.add(sep) rhs -= term.expand() # Do the division fulldiv = reduce(operator.add, div) lhs = simplify(lhs/fulldiv).expand() rhs = simplify(rhs/fulldiv).expand() # ...and check whether we were successful :) if lhs.has(*others) or rhs.has(dep): return None return [lhs, rhs]
41628ff36fc8874595494c5e1678fcbb8aae32012e79e69320be404666a9dd9e	"""Utility functions for classifying and solving ordinary and partial differential equations. Contains ======== _preprocess ode_order _desolve """ from sympy.core import Pow from sympy.core.function import Derivative, AppliedUndef from sympy.core.relational import Equality from sympy.core.symbol import Wild def _preprocess(expr, func=None, hint='_Integral'): """Prepare expr for solving by making sure that differentiation is done so that only func remains in unevaluated derivatives and (if hint doesn't end with _Integral) that doit is applied to all other derivatives. If hint is None, don't do any differentiation. (Currently this may cause some simple differential equations to fail.) In case func is None, an attempt will be made to autodetect the function to be solved for. >>> from sympy.solvers.deutils import _preprocess >>> from sympy import Derivative, Function >>> from sympy.abc import x, y, z >>> f, g = map(Function, 'fg') If f(x)p == 0 and p>0 then we can solve for f(x)=0 >>> _preprocess((f(x).diff(x)-4)5, f(x)) (Derivative(f(x), x) - 4, f(x)) Apply doit to derivatives that contain more than the function of interest: >>> _preprocess(Derivative(f(x) + x, x)) (Derivative(f(x), x) + 1, f(x)) Do others if the differentiation variable(s) intersect with those of the function of interest or contain the function of interest: >>> _preprocess(Derivative(g(x), y, z), f(y)) (0, f(y)) >>> _preprocess(Derivative(f(y), z), f(y)) (0, f(y)) Do others if the hint doesn't end in '_Integral' (the default assumes that it does): >>> _preprocess(Derivative(g(x), y), f(x)) (Derivative(g(x), y), f(x)) >>> _preprocess(Derivative(f(x), y), f(x), hint='') (0, f(x)) Don't do any derivatives if hint is None: >>> eq = Derivative(f(x) + 1, x) + Derivative(f(x), y) >>> _preprocess(eq, f(x), hint=None) (Derivative(f(x) + 1, x) + Derivative(f(x), y), f(x)) If it's not clear what the function of interest is, it must be given: >>> eq = Derivative(f(x) + g(x), x) >>> _preprocess(eq, g(x)) (Derivative(f(x), x) + Derivative(g(x), x), g(x)) >>> try: _preprocess(eq) ... except ValueError: print("A ValueError was raised.") A ValueError was raised. """ if isinstance(expr, Pow): # if f(x)*p=0 then f(x)=0 (p>0) if (expr.exp).is_positive: expr = expr.base derivs = expr.atoms(Derivative) if not func: funcs = set().union([d.atoms(AppliedUndef) for d in derivs]) if len(funcs) != 1: raise ValueError('The function cannot be ' 'automatically detected for %s.' % expr) func = funcs.pop() fvars = set(func.args) if hint is None: return expr, func reps = [(d, d.doit()) for d in derivs if not hint.endswith('_Integral') or d.has(func) or set(d.variables) & fvars] eq = expr.subs(reps) return eq, func def ode_order(expr, func): """ Returns the order of a given differential equation with respect to func. This function is implemented recursively. Examples ======== >>> from sympy import Function >>> from sympy.solvers.deutils import ode_order >>> from sympy.abc import x >>> f, g = map(Function, ['f', 'g']) >>> ode_order(f(x).diff(x, 2) + f(x).diff(x)*2 + ... f(x).diff(x), f(x)) 2 >>> ode_order(f(x).diff(x, 2) + g(x).diff(x, 3), f(x)) 2 >>> ode_order(f(x).diff(x, 2) + g(x).diff(x, 3), g(x)) 3 """ a = Wild('a', exclude=[func]) if expr.match(a): return 0 if isinstance(expr, Derivative): if expr.args[0] == func: return len(expr.variables) else: order = 0 for arg in expr.args[0].args: order = max(order, ode_order(arg, func) + len(expr.variables)) return order else: order = 0 for arg in expr.args: order = max(order, ode_order(arg, func)) return order def _desolve(eq, func=None, hint="default", ics=None, simplify=True, , prep=True, **kwargs): """This is a helper function to dsolve and pdsolve in the ode and pde modules. If the hint provided to the function is "default", then a dict with the following keys are returned 'func' - It provides the function for which the differential equation has to be solved. This is useful when the expression has more than one function in it. 'default' - The default key as returned by classifier functions in ode and pde.py 'hint' - The hint given by the user for which the differential equation is to be solved. If the hint given by the user is 'default', then the value of 'hint' and 'default' is the same. 'order' - The order of the function as returned by ode_order 'match' - It returns the match as given by the classifier functions, for the default hint. If the hint provided to the function is not "default" and is not in ('all', 'all_Integral', 'best'), then a dict with the above mentioned keys is returned along with the keys which are returned when dict in classify_ode or classify_pde is set True If the hint given is in ('all', 'all_Integral', 'best'), then this function returns a nested dict, with the keys, being the set of classified hints returned by classifier functions, and the values being the dict of form as mentioned above. Key 'eq' is a common key to all the above mentioned hints which returns an expression if eq given by user is an Equality. See Also ======== classify_ode(ode.py) classify_pde(pde.py) """ if isinstance(eq, Equality): eq = eq.lhs - eq.rhs # preprocess the equation and find func if not given if prep or func is None: eq, func = _preprocess(eq, func) prep = False # type is an argument passed by the solve functions in ode and pde.py # that identifies whether the function caller is an ordinary # or partial differential equation. Accordingly corresponding # changes are made in the function. type = kwargs.get('type', None) xi = kwargs.get('xi') eta = kwargs.get('eta') x0 = kwargs.get('x0', 0) terms = kwargs.get('n') if type == 'ode': from sympy.solvers.ode import classify_ode, allhints classifier = classify_ode string = 'ODE ' dummy = '' elif type == 'pde': from sympy.solvers.pde import classify_pde, allhints classifier = classify_pde string = 'PDE ' dummy = 'p' # Magic that should only be used internally. Prevents classify_ode from # being called more than it needs to be by passing its results through # recursive calls. if kwargs.get('classify', True): hints = classifier(eq, func, dict=True, ics=ics, xi=xi, eta=eta, n=terms, x0=x0, prep=prep) else: # Here is what all this means: # # hint: The hint method given to _desolve() by the user. # hints: The dictionary of hints that match the DE, along with other # information (including the internal pass-through magic). # default: The default hint to return, the first hint from allhints # that matches the hint; obtained from classify_ode(). # match: Dictionary containing the match dictionary for each hint # (the parts of the DE for solving). When going through the # hints in "all", this holds the match string for the current # hint. # order: The order of the DE, as determined by ode_order(). hints = kwargs.get('hint', {'default': hint, hint: kwargs['match'], 'order': kwargs['order']}) if not hints['default']: # classify_ode will set hints['default'] to None if no hints match. if hint not in allhints and hint != 'default': raise ValueError("Hint not recognized: " + hint) elif hint not in hints['ordered_hints'] and hint != 'default': raise ValueError(string + str(eq) + " does not match hint " + hint) # If dsolve can't solve the purely algebraic equation then dsolve will raise # ValueError elif hints['order'] == 0: raise ValueError( str(eq) + " is not a solvable differential equation in " + str(func)) else: raise NotImplementedError(dummy + "solve" + ": Cannot solve " + str(eq)) if hint == 'default': return _desolve(eq, func, ics=ics, hint=hints['default'], simplify=simplify, prep=prep, x0=x0, classify=False, order=hints['order'], match=hints[hints['default']], xi=xi, eta=eta, n=terms, type=type) elif hint in ('all', 'all_Integral', 'best'): retdict = {} gethints = set(hints) - {'order', 'default', 'ordered_hints'} if hint == 'all_Integral': for i in hints: if i.endswith('_Integral'): gethints.remove(i[:-len('_Integral')]) # special cases for k in ["1st_homogeneous_coeff_best", "1st_power_series", "lie_group", "2nd_power_series_ordinary", "2nd_power_series_regular"]: if k in gethints: gethints.remove(k) for i in gethints: sol = _desolve(eq, func, ics=ics, hint=i, x0=x0, simplify=simplify, prep=prep, classify=False, n=terms, order=hints['order'], match=hints[i], type=type) retdict[i] = sol retdict['all'] = True retdict['eq'] = eq return retdict elif hint not in allhints: # and hint not in ('default', 'ordered_hints'): raise ValueError("Hint not recognized: " + hint) elif hint not in hints: raise ValueError(string + str(eq) + " does not match hint " + hint) else: # Key added to identify the hint needed to solve the equation hints['hint'] = hint hints.update({'func': func, 'eq': eq}) return hints
fa495579c64fa1f211572a6625d7654afad8c46be569e839f71d86bd4b7b5811	"""Solvers of systems of polynomial equations. """ from sympy.core import S from sympy.polys import Poly, groebner, roots from sympy.polys.polytools import parallel_poly_from_expr from sympy.polys.polyerrors import (ComputationFailed, PolificationFailed, CoercionFailed) from sympy.simplify import rcollect from sympy.utilities import default_sort_key, postfixes from sympy.utilities.misc import filldedent class SolveFailed(Exception): """Raised when solver's conditions weren't met. """ def solve_poly_system(seq, gens, args): """ Solve a system of polynomial equations. Parameters ========== seq: a list/tuple/set Listing all the equations that are needed to be solved gens: generators generators of the equations in seq for which we want the solutions args: Keyword arguments Special options for solving the equations Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq Examples ======== >>> from sympy import solve_poly_system >>> from sympy.abc import x, y >>> solve_poly_system([xy - 2y, 2y2 - x2], x, y) [(0, 0), (2, -sqrt(2)), (2, sqrt(2))] """ try: polys, opt = parallel_poly_from_expr(seq, gens, args) except PolificationFailed as exc: raise ComputationFailed('solve_poly_system', len(seq), exc) if len(polys) == len(opt.gens) == 2: f, g = polys if all(i <= 2 for i in f.degree_list() + g.degree_list()): try: return solve_biquadratic(f, g, opt) except SolveFailed: pass return solve_generic(polys, opt) def solve_biquadratic(f, g, opt): """Solve a system of two bivariate quadratic polynomial equations. Parameters ========== f: a single Expr or Poly First equation g: a single Expr or Poly Second Equation opt: an Options object For specifying keyword arguments and generators Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq. Examples ======== >>> from sympy.polys import Options, Poly >>> from sympy.abc import x, y >>> from sympy.solvers.polysys import solve_biquadratic >>> NewOption = Options((x, y), {'domain': 'ZZ'}) >>> a = Poly(y2 - 4 + x, y, x, domain='ZZ') >>> b = Poly(y2 + 3x - 7, y, x, domain='ZZ') >>> solve_biquadratic(a, b, NewOption) [(1/3, 3), (41/27, 11/9)] >>> a = Poly(y + x2 - 3, y, x, domain='ZZ') >>> b = Poly(-y + x - 4, y, x, domain='ZZ') >>> solve_biquadratic(a, b, NewOption) [(7/2 - sqrt(29)/2, -sqrt(29)/2 - 1/2), (sqrt(29)/2 + 7/2, -1/2 + \ sqrt(29)/2)] """ G = groebner([f, g]) if len(G) == 1 and G[0].is_ground: return None if len(G) != 2: raise SolveFailed x, y = opt.gens p, q = G if not p.gcd(q).is_ground: # not 0-dimensional raise SolveFailed p = Poly(p, x, expand=False) p_roots = [rcollect(expr, y) for expr in roots(p).keys()] q = q.ltrim(-1) q_roots = list(roots(q).keys()) solutions = [] for q_root in q_roots: for p_root in p_roots: solution = (p_root.subs(y, q_root), q_root) solutions.append(solution) return sorted(solutions, key=default_sort_key) def solve_generic(polys, opt): """ Solve a generic system of polynomial equations. Returns all possible solutions over C[x_1, x_2, ..., x_m] of a set F = { f_1, f_2, ..., f_n } of polynomial equations, using Groebner basis approach. For now only zero-dimensional systems are supported, which means F can have at most a finite number of solutions. The algorithm works by the fact that, supposing G is the basis of F with respect to an elimination order (here lexicographic order is used), G and F generate the same ideal, they have the same set of solutions. By the elimination property, if G is a reduced, zero-dimensional Groebner basis, then there exists an univariate polynomial in G (in its last variable). This can be solved by computing its roots. Substituting all computed roots for the last (eliminated) variable in other elements of G, new polynomial system is generated. Applying the above procedure recursively, a finite number of solutions can be found. The ability of finding all solutions by this procedure depends on the root finding algorithms. If no solutions were found, it means only that roots() failed, but the system is solvable. To overcome this difficulty use numerical algorithms instead. Parameters ========== polys: a list/tuple/set Listing all the polynomial equations that are needed to be solved opt: an Options object For specifying keyword arguments and generators Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq References ========== .. [Buchberger01] B. Buchberger, Groebner Bases: A Short Introduction for Systems Theorists, In: R. Moreno-Diaz, B. Buchberger, J.L. Freire, Proceedings of EUROCAST'01, February, 2001 .. [Cox97] D. Cox, J. Little, D. O'Shea, Ideals, Varieties and Algorithms, Springer, Second Edition, 1997, pp. 112 Examples ======== >>> from sympy.polys import Poly, Options >>> from sympy.solvers.polysys import solve_generic >>> from sympy.abc import x, y >>> NewOption = Options((x, y), {'domain': 'ZZ'}) >>> a = Poly(x - y + 5, x, y, domain='ZZ') >>> b = Poly(x + y - 3, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(-1, 4)] >>> a = Poly(x - 2y + 5, x, y, domain='ZZ') >>> b = Poly(2x - y - 3, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(11/3, 13/3)] >>> a = Poly(x2 + y, x, y, domain='ZZ') >>> b = Poly(x + y4, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(0, 0), (1/4, -1/16)] """ def _is_univariate(f): """Returns True if 'f' is univariate in its last variable. """ for monom in f.monoms(): if any(monom[:-1]): return False return True def _subs_root(f, gen, zero): """Replace generator with a root so that the result is nice. """ p = f.as_expr({gen: zero}) if f.degree(gen) >= 2: p = p.expand(deep=False) return p def _solve_reduced_system(system, gens, entry=False): """Recursively solves reduced polynomial systems. """ if len(system) == len(gens) == 1: zeros = list(roots(system[0], gens[-1]).keys()) return [(zero,) for zero in zeros] basis = groebner(system, gens, polys=True) if len(basis) == 1 and basis[0].is_ground: if not entry: return [] else: return None univariate = list(filter(_is_univariate, basis)) if len(univariate) == 1: f = univariate.pop() else: raise NotImplementedError(filldedent(''' only zero-dimensional systems supported (finite number of solutions) ''')) gens = f.gens gen = gens[-1] zeros = list(roots(f.ltrim(gen)).keys()) if not zeros: return [] if len(basis) == 1: return [(zero,) for zero in zeros] solutions = [] for zero in zeros: new_system = [] new_gens = gens[:-1] for b in basis[:-1]: eq = _subs_root(b, gen, zero) if eq is not S.Zero: new_system.append(eq) for solution in _solve_reduced_system(new_system, new_gens): solutions.append(solution + (zero,)) if solutions and len(solutions[0]) != len(gens): raise NotImplementedError(filldedent(''' only zero-dimensional systems supported (finite number of solutions) ''')) return solutions try: result = _solve_reduced_system(polys, opt.gens, entry=True) except CoercionFailed: raise NotImplementedError if result is not None: return sorted(result, key=default_sort_key) else: return None def solve_triangulated(polys, gens, args): """ Solve a polynomial system using Gianni-Kalkbrenner algorithm. The algorithm proceeds by computing one Groebner basis in the ground domain and then by iteratively computing polynomial factorizations in appropriately constructed algebraic extensions of the ground domain. Parameters ========== polys: a list/tuple/set Listing all the equations that are needed to be solved gens: generators generators of the equations in polys for which we want the solutions args: Keyword arguments Special options for solving the equations Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in polys Examples ======== >>> from sympy.solvers.polysys import solve_triangulated >>> from sympy.abc import x, y, z >>> F = [x2 + y + z - 1, x + y2 + z - 1, x + y + z2 - 1] >>> solve_triangulated(F, x, y, z) [(0, 0, 1), (0, 1, 0), (1, 0, 0)] References ========== 1. Patrizia Gianni, Teo Mora, Algebraic Solution of System of Polynomial Equations using Groebner Bases, AAECC-5 on Applied Algebra, Algebraic Algorithms and Error-Correcting Codes, LNCS 356 247--257, 1989 """ G = groebner(polys, gens, polys=True) G = list(reversed(G)) domain = args.get('domain') if domain is not None: for i, g in enumerate(G): G[i] = g.set_domain(domain) f, G = G[0].ltrim(-1), G[1:] dom = f.get_domain() zeros = f.ground_roots() solutions = set() for zero in zeros: solutions.add(((zero,), dom)) var_seq = reversed(gens[:-1]) vars_seq = postfixes(gens[1:]) for var, vars in zip(var_seq, vars_seq): _solutions = set() for values, dom in solutions: H, mapping = [], list(zip(vars, values)) for g in G: _vars = (var,) + vars if g.has_only_gens(_vars) and g.degree(var) != 0: h = g.ltrim(var).eval(dict(mapping)) if g.degree(var) == h.degree(): H.append(h) p = min(H, key=lambda h: h.degree()) zeros = p.ground_roots() for zero in zeros: if not zero.is_Rational: dom_zero = dom.algebraic_field(zero) else: dom_zero = dom _solutions.add(((zero,) + values, dom_zero)) solutions = _solutions solutions = list(solutions) for i, (solution, _) in enumerate(solutions): solutions[i] = solution return sorted(solutions, key=default_sort_key)
2e1fd921dca5bc48d487b2c42feb036a6b6763ddafd9cc48952cb3e3e966f952	"""Tools for solving inequalities and systems of inequalities. """ from sympy.core import Symbol, Dummy, sympify from sympy.core.compatibility import iterable from sympy.core.exprtools import factor_terms from sympy.core.relational import Relational, Eq, Ge, Lt from sympy.sets import Interval from sympy.sets.sets import FiniteSet, Union, EmptySet, Intersection from sympy.core.singleton import S from sympy.core.function import expand_mul from sympy.functions import Abs from sympy.logic import And from sympy.polys import Poly, PolynomialError, parallel_poly_from_expr from sympy.polys.polyutils import _nsort from sympy.utilities.iterables import sift from sympy.utilities.misc import filldedent def solve_poly_inequality(poly, rel): """Solve a polynomial inequality with rational coefficients. Examples ======== >>> from sympy import Poly >>> from sympy.abc import x >>> from sympy.solvers.inequalities import solve_poly_inequality >>> solve_poly_inequality(Poly(x, x, domain='ZZ'), '==') [FiniteSet(0)] >>> solve_poly_inequality(Poly(x2 - 1, x, domain='ZZ'), '!=') [Interval.open(-oo, -1), Interval.open(-1, 1), Interval.open(1, oo)] >>> solve_poly_inequality(Poly(x2 - 1, x, domain='ZZ'), '==') [FiniteSet(-1), FiniteSet(1)] See Also ======== solve_poly_inequalities """ if not isinstance(poly, Poly): raise ValueError( 'For efficiency reasons, `poly` should be a Poly instance') if poly.as_expr().is_number: t = Relational(poly.as_expr(), 0, rel) if t is S.true: return [S.Reals] elif t is S.false: return [S.EmptySet] else: raise NotImplementedError( "could not determine truth value of %s" % t) reals, intervals = poly.real_roots(multiple=False), [] if rel == '==': for root, _ in reals: interval = Interval(root, root) intervals.append(interval) elif rel == '!=': left = S.NegativeInfinity for right, _ in reals + [(S.Infinity, 1)]: interval = Interval(left, right, True, True) intervals.append(interval) left = right else: if poly.LC() > 0: sign = +1 else: sign = -1 eq_sign, equal = None, False if rel == '>': eq_sign = +1 elif rel == '<': eq_sign = -1 elif rel == '>=': eq_sign, equal = +1, True elif rel == '<=': eq_sign, equal = -1, True else: raise ValueError("'%s' is not a valid relation" % rel) right, right_open = S.Infinity, True for left, multiplicity in reversed(reals): if multiplicity % 2: if sign == eq_sign: intervals.insert( 0, Interval(left, right, not equal, right_open)) sign, right, right_open = -sign, left, not equal else: if sign == eq_sign and not equal: intervals.insert( 0, Interval(left, right, True, right_open)) right, right_open = left, True elif sign != eq_sign and equal: intervals.insert(0, Interval(left, left)) if sign == eq_sign: intervals.insert( 0, Interval(S.NegativeInfinity, right, True, right_open)) return intervals def solve_poly_inequalities(polys): """Solve polynomial inequalities with rational coefficients. Examples ======== >>> from sympy.solvers.inequalities import solve_poly_inequalities >>> from sympy.polys import Poly >>> from sympy.abc import x >>> solve_poly_inequalities((( ... Poly(x2 - 3), ">"), ( ... Poly(-x2 + 1), ">"))) Union(Interval.open(-oo, -sqrt(3)), Interval.open(-1, 1), Interval.open(sqrt(3), oo)) """ from sympy import Union return Union([s for p in polys for s in solve_poly_inequality(p)]) def solve_rational_inequalities(eqs): """Solve a system of rational inequalities with rational coefficients. Examples ======== >>> from sympy.abc import x >>> from sympy import Poly >>> from sympy.solvers.inequalities import solve_rational_inequalities >>> solve_rational_inequalities([[ ... ((Poly(-x + 1), Poly(1, x)), '>='), ... ((Poly(-x + 1), Poly(1, x)), '<=')]]) FiniteSet(1) >>> solve_rational_inequalities([[ ... ((Poly(x), Poly(1, x)), '!='), ... ((Poly(-x + 1), Poly(1, x)), '>=')]]) Union(Interval.open(-oo, 0), Interval.Lopen(0, 1)) See Also ======== solve_poly_inequality """ result = S.EmptySet for _eqs in eqs: if not _eqs: continue global_intervals = [Interval(S.NegativeInfinity, S.Infinity)] for (numer, denom), rel in _eqs: numer_intervals = solve_poly_inequality(numerdenom, rel) denom_intervals = solve_poly_inequality(denom, '==') intervals = [] for numer_interval in numer_intervals: for global_interval in global_intervals: interval = numer_interval.intersect(global_interval) if interval is not S.EmptySet: intervals.append(interval) global_intervals = intervals intervals = [] for global_interval in global_intervals: for denom_interval in denom_intervals: global_interval -= denom_interval if global_interval is not S.EmptySet: intervals.append(global_interval) global_intervals = intervals if not global_intervals: break for interval in global_intervals: result = result.union(interval) return result def reduce_rational_inequalities(exprs, gen, relational=True): """Reduce a system of rational inequalities with rational coefficients. Examples ======== >>> from sympy import Symbol >>> from sympy.solvers.inequalities import reduce_rational_inequalities >>> x = Symbol('x', real=True) >>> reduce_rational_inequalities([[x2 <= 0]], x) Eq(x, 0) >>> reduce_rational_inequalities([[x + 2 > 0]], x) -2 < x >>> reduce_rational_inequalities([[(x + 2, ">")]], x) -2 < x >>> reduce_rational_inequalities([[x + 2]], x) Eq(x, -2) This function find the non-infinite solution set so if the unknown symbol is declared as extended real rather than real then the result may include finiteness conditions: >>> y = Symbol('y', extended_real=True) >>> reduce_rational_inequalities([[y + 2 > 0]], y) (-2 < y) & (y < oo) """ exact = True eqs = [] solution = S.Reals if exprs else S.EmptySet for _exprs in exprs: _eqs = [] for expr in _exprs: if isinstance(expr, tuple): expr, rel = expr else: if expr.is_Relational: expr, rel = expr.lhs - expr.rhs, expr.rel_op else: expr, rel = expr, '==' if expr is S.true: numer, denom, rel = S.Zero, S.One, '==' elif expr is S.false: numer, denom, rel = S.One, S.One, '==' else: numer, denom = expr.together().as_numer_denom() try: (numer, denom), opt = parallel_poly_from_expr( (numer, denom), gen) except PolynomialError: raise PolynomialError(filldedent(''' only polynomials and rational functions are supported in this context. ''')) if not opt.domain.is_Exact: numer, denom, exact = numer.to_exact(), denom.to_exact(), False domain = opt.domain.get_exact() if not (domain.is_ZZ or domain.is_QQ): expr = numer/denom expr = Relational(expr, 0, rel) solution &= solve_univariate_inequality(expr, gen, relational=False) else: _eqs.append(((numer, denom), rel)) if _eqs: eqs.append(_eqs) if eqs: solution &= solve_rational_inequalities(eqs) exclude = solve_rational_inequalities([[((d, d.one), '==') for i in eqs for ((n, d), _) in i if d.has(gen)]]) solution -= exclude if not exact and solution: solution = solution.evalf() if relational: solution = solution.as_relational(gen) return solution def reduce_abs_inequality(expr, rel, gen): """Reduce an inequality with nested absolute values. Examples ======== >>> from sympy import Abs, Symbol >>> from sympy.solvers.inequalities import reduce_abs_inequality >>> x = Symbol('x', real=True) >>> reduce_abs_inequality(Abs(x - 5) - 3, '<', x) (2 < x) & (x < 8) >>> reduce_abs_inequality(Abs(x + 2)3 - 13, '<', x) (-19/3 < x) & (x < 7/3) See Also ======== reduce_abs_inequalities """ if gen.is_extended_real is False: raise TypeError(filldedent(''' can't solve inequalities with absolute values containing non-real variables. ''')) def _bottom_up_scan(expr): exprs = [] if expr.is_Add or expr.is_Mul: op = expr.func for arg in expr.args: _exprs = _bottom_up_scan(arg) if not exprs: exprs = _exprs else: args = [] for expr, conds in exprs: for _expr, _conds in _exprs: args.append((op(expr, _expr), conds + _conds)) exprs = args elif expr.is_Pow: n = expr.exp if not n.is_Integer: raise ValueError("Only Integer Powers are allowed on Abs.") _exprs = _bottom_up_scan(expr.base) for expr, conds in _exprs: exprs.append((expr*n, conds)) elif isinstance(expr, Abs): _exprs = _bottom_up_scan(expr.args[0]) for expr, conds in _exprs: exprs.append(( expr, conds + [Ge(expr, 0)])) exprs.append((-expr, conds + [Lt(expr, 0)])) else: exprs = [(expr, [])] return exprs exprs = _bottom_up_scan(expr) mapping = {'<': '>', '<=': '>='} inequalities = [] for expr, conds in exprs: if rel not in mapping.keys(): expr = Relational( expr, 0, rel) else: expr = Relational(-expr, 0, mapping[rel]) inequalities.append([expr] + conds) return reduce_rational_inequalities(inequalities, gen) def reduce_abs_inequalities(exprs, gen): """Reduce a system of inequalities with nested absolute values. Examples ======== >>> from sympy import Abs, Symbol >>> from sympy.solvers.inequalities import reduce_abs_inequalities >>> x = Symbol('x', extended_real=True) >>> reduce_abs_inequalities([(Abs(3x - 5) - 7, '<'), ... (Abs(x + 25) - 13, '>')], x) (-2/3 < x) & (x < 4) & (((-oo < x) & (x < -38)) \| ((-12 < x) & (x < oo))) >>> reduce_abs_inequalities([(Abs(x - 4) + Abs(3x - 5) - 7, '<')], x) (1/2 < x) & (x < 4) See Also ======== reduce_abs_inequality """ return And([ reduce_abs_inequality(expr, rel, gen) for expr, rel in exprs ]) def solve_univariate_inequality(expr, gen, relational=True, domain=S.Reals, continuous=False): """Solves a real univariate inequality. Parameters ========== expr : Relational The target inequality gen : Symbol The variable for which the inequality is solved relational : bool A Relational type output is expected or not domain : Set The domain over which the equation is solved continuous: bool True if expr is known to be continuous over the given domain (and so continuous_domain() doesn't need to be called on it) Raises ====== NotImplementedError The solution of the inequality cannot be determined due to limitation in :func:`sympy.solvers.solveset.solvify`. Notes ===== Currently, we cannot solve all the inequalities due to limitations in :func:`sympy.solvers.solveset.solvify`. Also, the solution returned for trigonometric inequalities are restricted in its periodic interval. See Also ======== sympy.solvers.solveset.solvify: solver returning solveset solutions with solve's output API Examples ======== >>> from sympy.solvers.inequalities import solve_univariate_inequality >>> from sympy import Symbol, sin, Interval, S >>> x = Symbol('x') >>> solve_univariate_inequality(x2 >= 4, x) ((2 <= x) & (x < oo)) \| ((x <= -2) & (-oo < x)) >>> solve_univariate_inequality(x2 >= 4, x, relational=False) Union(Interval(-oo, -2), Interval(2, oo)) >>> domain = Interval(0, S.Infinity) >>> solve_univariate_inequality(x*2 >= 4, x, False, domain) Interval(2, oo) >>> solve_univariate_inequality(sin(x) > 0, x, relational=False) Interval.open(0, pi) """ from sympy import im from sympy.calculus.util import (continuous_domain, periodicity, function_range) from sympy.solvers.solvers import denoms from sympy.solvers.solveset import solvify, solveset # This keeps the function independent of the assumptions about `gen`. # `solveset` makes sure this function is called only when the domain is # real. _gen = gen _domain = domain if gen.is_extended_real is False: rv = S.EmptySet return rv if not relational else rv.as_relational(_gen) elif gen.is_extended_real is None: gen = Dummy('gen', extended_real=True) try: expr = expr.xreplace({_gen: gen}) except TypeError: raise TypeError(filldedent(''' When gen is real, the relational has a complex part which leads to an invalid comparison like I < 0. ''')) rv = None if expr is S.true: rv = domain elif expr is S.false: rv = S.EmptySet else: e = expr.lhs - expr.rhs period = periodicity(e, gen) if period == S.Zero: e = expand_mul(e) const = expr.func(e, 0) if const is S.true: rv = domain elif const is S.false: rv = S.EmptySet elif period is not None: frange = function_range(e, gen, domain) rel = expr.rel_op if rel == '<' or rel == '<=': if expr.func(frange.sup, 0): rv = domain elif not expr.func(frange.inf, 0): rv = S.EmptySet elif rel == '>' or rel == '>=': if expr.func(frange.inf, 0): rv = domain elif not expr.func(frange.sup, 0): rv = S.EmptySet inf, sup = domain.inf, domain.sup if sup - inf is S.Infinity: domain = Interval(0, period, False, True).intersect(_domain) _domain = domain if rv is None: n, d = e.as_numer_denom() try: if gen not in n.free_symbols and len(e.free_symbols) > 1: raise ValueError # this might raise ValueError on its own # or it might give None... solns = solvify(e, gen, domain) if solns is None: # in which case we raise ValueError raise ValueError except (ValueError, NotImplementedError): # replace gen with generic x since it's # univariate anyway raise NotImplementedError(filldedent(''' The inequality, %s, cannot be solved using solve_univariate_inequality. ''' % expr.subs(gen, Symbol('x')))) expanded_e = expand_mul(e) def valid(x): # this is used to see if gen=x satisfies the # relational by substituting it into the # expanded form and testing against 0, e.g. # if expr = x(x + 1) < 2 then e = x(x + 1) - 2 # and expanded_e = x2 + x - 2; the test is # whether a given value of x satisfies # x2 + x - 2 < 0 # # expanded_e, expr and gen used from enclosing scope v = expanded_e.subs(gen, expand_mul(x)) try: r = expr.func(v, 0) except TypeError: r = S.false if r in (S.true, S.false): return r if v.is_extended_real is False: return S.false else: v = v.n(2) if v.is_comparable: return expr.func(v, 0) # not comparable or couldn't be evaluated raise NotImplementedError( 'relationship did not evaluate: %s' % r) singularities = [] for d in denoms(expr, gen): singularities.extend(solvify(d, gen, domain)) if not continuous: domain = continuous_domain(expanded_e, gen, domain) include_x = '=' in expr.rel_op and expr.rel_op != '!=' try: discontinuities = set(domain.boundary - FiniteSet(domain.inf, domain.sup)) # remove points that are not between inf and sup of domain critical_points = FiniteSet((solns + singularities + list( discontinuities))).intersection( Interval(domain.inf, domain.sup, domain.inf not in domain, domain.sup not in domain)) if all(r.is_number for r in critical_points): reals = _nsort(critical_points, separated=True)[0] else: sifted = sift(critical_points, lambda x: x.is_extended_real) if sifted[None]: # there were some roots that weren't known # to be real raise NotImplementedError try: reals = sifted[True] if len(reals) > 1: reals = list(sorted(reals)) except TypeError: raise NotImplementedError except NotImplementedError: raise NotImplementedError('sorting of these roots is not supported') # If expr contains imaginary coefficients, only take real # values of x for which the imaginary part is 0 make_real = S.Reals if im(expanded_e) != S.Zero: check = True im_sol = FiniteSet() try: a = solveset(im(expanded_e), gen, domain) if not isinstance(a, Interval): for z in a: if z not in singularities and valid(z) and z.is_extended_real: im_sol += FiniteSet(z) else: start, end = a.inf, a.sup for z in _nsort(critical_points + FiniteSet(end)): valid_start = valid(start) if start != end: valid_z = valid(z) pt = _pt(start, z) if pt not in singularities and pt.is_extended_real and valid(pt): if valid_start and valid_z: im_sol += Interval(start, z) elif valid_start: im_sol += Interval.Ropen(start, z) elif valid_z: im_sol += Interval.Lopen(start, z) else: im_sol += Interval.open(start, z) start = z for s in singularities: im_sol -= FiniteSet(s) except (TypeError): im_sol = S.Reals check = False if isinstance(im_sol, EmptySet): raise ValueError(filldedent(''' %s contains imaginary parts which cannot be made 0 for any value of %s satisfying the inequality, leading to relations like I < 0. ''' % (expr.subs(gen, _gen), _gen))) make_real = make_real.intersect(im_sol) sol_sets = [S.EmptySet] start = domain.inf if start in domain and valid(start) and start.is_finite: sol_sets.append(FiniteSet(start)) for x in reals: end = x if valid(_pt(start, end)): sol_sets.append(Interval(start, end, True, True)) if x in singularities: singularities.remove(x) else: if x in discontinuities: discontinuities.remove(x) _valid = valid(x) else: # it's a solution _valid = include_x if _valid: sol_sets.append(FiniteSet(x)) start = end end = domain.sup if end in domain and valid(end) and end.is_finite: sol_sets.append(FiniteSet(end)) if valid(_pt(start, end)): sol_sets.append(Interval.open(start, end)) if im(expanded_e) != S.Zero and check: rv = (make_real).intersect(_domain) else: rv = Intersection( (Union(sol_sets)), make_real, _domain).subs(gen, _gen) return rv if not relational else rv.as_relational(_gen) def _pt(start, end): """Return a point between start and end""" if not start.is_infinite and not end.is_infinite: pt = (start + end)/2 elif start.is_infinite and end.is_infinite: pt = S.Zero else: if (start.is_infinite and start.is_extended_positive is None or end.is_infinite and end.is_extended_positive is None): raise ValueError('cannot proceed with unsigned infinite values') if (end.is_infinite and end.is_extended_negative or start.is_infinite and start.is_extended_positive): start, end = end, start # if possible, use a multiple of self which has # better behavior when checking assumptions than # an expression obtained by adding or subtracting 1 if end.is_infinite: if start.is_extended_positive: pt = start2 elif start.is_extended_negative: pt = startS.Half else: pt = start + 1 elif start.is_infinite: if end.is_extended_positive: pt = endS.Half elif end.is_extended_negative: pt = end2 else: pt = end - 1 return pt def _solve_inequality(ie, s, linear=False): """Return the inequality with s isolated on the left, if possible. If the relationship is non-linear, a solution involving And or Or may be returned. False or True are returned if the relationship is never True or always True, respectively. If `linear` is True (default is False) an `s`-dependent expression will be isolated on the left, if possible but it will not be solved for `s` unless the expression is linear in `s`. Furthermore, only "safe" operations which don't change the sense of the relationship are applied: no division by an unsigned value is attempted unless the relationship involves Eq or Ne and no division by a value not known to be nonzero is ever attempted. Examples ======== >>> from sympy import Eq, Symbol >>> from sympy.solvers.inequalities import _solve_inequality as f >>> from sympy.abc import x, y For linear expressions, the symbol can be isolated: >>> f(x - 2 < 0, x) x < 2 >>> f(-x - 6 < x, x) x > -3 Sometimes nonlinear relationships will be False >>> f(x2 + 4 < 0, x) False Or they may involve more than one region of values: >>> f(x2 - 4 < 0, x) (-2 < x) & (x < 2) To restrict the solution to a relational, set linear=True and only the x-dependent portion will be isolated on the left: >>> f(x2 - 4 < 0, x, linear=True) x2 < 4 Division of only nonzero quantities is allowed, so x cannot be isolated by dividing by y: >>> y.is_nonzero is None # it is unknown whether it is 0 or not True >>> f(xy < 1, x) xy < 1 And while an equality (or inequality) still holds after dividing by a non-zero quantity >>> nz = Symbol('nz', nonzero=True) >>> f(Eq(xnz, 1), x) Eq(x, 1/nz) the sign must be known for other inequalities involving > or <: >>> f(xnz <= 1, x) nzx <= 1 >>> p = Symbol('p', positive=True) >>> f(xp <= 1, x) x <= 1/p When there are denominators in the original expression that are removed by expansion, conditions for them will be returned as part of the result: >>> f(x < x(2/x - 1), x) (x < 1) & Ne(x, 0) """ from sympy.solvers.solvers import denoms if s not in ie.free_symbols: return ie if ie.rhs == s: ie = ie.reversed if ie.lhs == s and s not in ie.rhs.free_symbols: return ie def classify(ie, s, i): # return True or False if ie evaluates when substituting s with # i else None (if unevaluated) or NaN (when there is an error # in evaluating) try: v = ie.subs(s, i) if v is S.NaN: return v elif v not in (True, False): return return v except TypeError: return S.NaN rv = None oo = S.Infinity expr = ie.lhs - ie.rhs try: p = Poly(expr, s) if p.degree() == 0: rv = ie.func(p.as_expr(), 0) elif not linear and p.degree() > 1: # handle in except clause raise NotImplementedError except (PolynomialError, NotImplementedError): if not linear: try: rv = reduce_rational_inequalities([[ie]], s) except PolynomialError: rv = solve_univariate_inequality(ie, s) # remove restrictions wrt +/-oo that may have been # applied when using sets to simplify the relationship okoo = classify(ie, s, oo) if okoo is S.true and classify(rv, s, oo) is S.false: rv = rv.subs(s < oo, True) oknoo = classify(ie, s, -oo) if (oknoo is S.true and classify(rv, s, -oo) is S.false): rv = rv.subs(-oo < s, True) rv = rv.subs(s > -oo, True) if rv is S.true: rv = (s <= oo) if okoo is S.true else (s < oo) if oknoo is not S.true: rv = And(-oo < s, rv) else: p = Poly(expr) conds = [] if rv is None: e = p.as_expr() # this is in expanded form # Do a safe inversion of e, moving non-s terms # to the rhs and dividing by a nonzero factor if # the relational is Eq/Ne; for other relationals # the sign must also be positive or negative rhs = 0 b, ax = e.as_independent(s, as_Add=True) e -= b rhs -= b ef = factor_terms(e) a, e = ef.as_independent(s, as_Add=False) if (a.is_zero != False or # don't divide by potential 0 a.is_negative == a.is_positive is None and # if sign is not known then ie.rel_op not in ('!=', '==')): # reject if not Eq/Ne e = ef a = S.One rhs /= a if a.is_positive: rv = ie.func(e, rhs) else: rv = ie.reversed.func(e, rhs) # return conditions under which the value is # valid, too. beginning_denoms = denoms(ie.lhs) \| denoms(ie.rhs) current_denoms = denoms(rv) for d in beginning_denoms - current_denoms: c = _solve_inequality(Eq(d, 0), s, linear=linear) if isinstance(c, Eq) and c.lhs == s: if classify(rv, s, c.rhs) is S.true: # rv is permitting this value but it shouldn't conds.append(~c) for i in (-oo, oo): if (classify(rv, s, i) is S.true and classify(ie, s, i) is not S.true): conds.append(s < i if i is oo else i < s) conds.append(rv) return And(conds) def _reduce_inequalities(inequalities, symbols): # helper for reduce_inequalities poly_part, abs_part = {}, {} other = [] for inequality in inequalities: expr, rel = inequality.lhs, inequality.rel_op # rhs is 0 # check for gens using atoms which is more strict than free_symbols to # guard against EX domain which won't be handled by # reduce_rational_inequalities gens = expr.atoms(Symbol) if len(gens) == 1: gen = gens.pop() else: common = expr.free_symbols & symbols if len(common) == 1: gen = common.pop() other.append(_solve_inequality(Relational(expr, 0, rel), gen)) continue else: raise NotImplementedError(filldedent(''' inequality has more than one symbol of interest. ''')) if expr.is_polynomial(gen): poly_part.setdefault(gen, []).append((expr, rel)) else: components = expr.find(lambda u: u.has(gen) and ( u.is_Function or u.is_Pow and not u.exp.is_Integer)) if components and all(isinstance(i, Abs) for i in components): abs_part.setdefault(gen, []).append((expr, rel)) else: other.append(_solve_inequality(Relational(expr, 0, rel), gen)) poly_reduced = [] abs_reduced = [] for gen, exprs in poly_part.items(): poly_reduced.append(reduce_rational_inequalities([exprs], gen)) for gen, exprs in abs_part.items(): abs_reduced.append(reduce_abs_inequalities(exprs, gen)) return And((poly_reduced + abs_reduced + other)) def reduce_inequalities(inequalities, symbols=[]): """Reduce a system of inequalities with rational coefficients. Examples ======== >>> from sympy.abc import x, y >>> from sympy.solvers.inequalities import reduce_inequalities >>> reduce_inequalities(0 <= x + 3, []) (-3 <= x) & (x < oo) >>> reduce_inequalities(0 <= x + y2 - 1, [x]) (x < oo) & (x >= 1 - 2y) """ if not iterable(inequalities): inequalities = [inequalities] inequalities = [sympify(i) for i in inequalities] gens = set().union(*[i.free_symbols for i in inequalities]) if not iterable(symbols): symbols = [symbols] symbols = (set(symbols) or gens) & gens if any(i.is_extended_real is False for i in symbols): raise TypeError(filldedent(''' inequalities cannot contain symbols that are not real. ''')) # make vanilla symbol real recast = {i: Dummy(i.name, extended_real=True) for i in gens if i.is_extended_real is None} inequalities = [i.xreplace(recast) for i in inequalities] symbols = {i.xreplace(recast) for i in symbols} # prefilter keep = [] for i in inequalities: if isinstance(i, Relational): i = i.func(i.lhs.as_expr() - i.rhs.as_expr(), 0) elif i not in (True, False): i = Eq(i, 0) if i == True: continue elif i == False: return S.false if i.lhs.is_number: raise NotImplementedError( "could not determine truth value of %s" % i) keep.append(i) inequalities = keep del keep # solve system rv = _reduce_inequalities(inequalities, symbols) # restore original symbols and return return rv.xreplace({v: k for k, v in recast.items()})
27d45b731ee4f7e2f96b62eaaf80d520e37cfd204dc9a7fec1446d6a2e0455ef	""" This module contain solvers for all kinds of equations: - algebraic or transcendental, use solve() - recurrence, use rsolve() - differential, use dsolve() - nonlinear (numerically), use nsolve() (you will need a good starting point) """ from sympy import divisors, binomial, expand_func from sympy.core.assumptions import check_assumptions from sympy.core.compatibility import (iterable, is_sequence, ordered, default_sort_key) from sympy.core.sympify import sympify from sympy.core import (S, Add, Symbol, Equality, Dummy, Expr, Mul, Pow, Unequality, Wild) from sympy.core.exprtools import factor_terms from sympy.core.function import (expand_mul, expand_log, Derivative, AppliedUndef, UndefinedFunction, nfloat, Function, expand_power_exp, _mexpand, expand) from sympy.integrals.integrals import Integral from sympy.core.numbers import ilcm, Float, Rational from sympy.core.relational import Relational from sympy.core.logic import fuzzy_not from sympy.core.power import integer_log from sympy.logic.boolalg import And, Or, BooleanAtom from sympy.core.basic import preorder_traversal from sympy.functions import (log, exp, LambertW, cos, sin, tan, acos, asin, atan, Abs, re, im, arg, sqrt, atan2) from sympy.functions.elementary.trigonometric import (TrigonometricFunction, HyperbolicFunction) from sympy.simplify import (simplify, collect, powsimp, posify, # type: ignore powdenest, nsimplify, denom, logcombine, sqrtdenest, fraction, separatevars) from sympy.simplify.sqrtdenest import sqrt_depth from sympy.simplify.fu import TR1, TR2i from sympy.matrices.common import NonInvertibleMatrixError from sympy.matrices import Matrix, zeros from sympy.polys import roots, cancel, factor, Poly, degree from sympy.polys.polyerrors import GeneratorsNeeded, PolynomialError from sympy.polys.solvers import sympy_eqs_to_ring, solve_lin_sys from sympy.functions.elementary.piecewise import piecewise_fold, Piecewise from sympy.utilities.lambdify import lambdify from sympy.utilities.misc import filldedent from sympy.utilities.iterables import (cartes, connected_components, flatten, generate_bell, uniq, sift) from sympy.utilities.decorator import conserve_mpmath_dps from mpmath import findroot from sympy.solvers.polysys import solve_poly_system from sympy.solvers.inequalities import reduce_inequalities from types import GeneratorType from collections import defaultdict import warnings def recast_to_symbols(eqs, symbols): """ Return (e, s, d) where e and s are versions of eqs and symbols in which any non-Symbol objects in symbols have been replaced with generic Dummy symbols and d is a dictionary that can be used to restore the original expressions. Examples ======== >>> from sympy.solvers.solvers import recast_to_symbols >>> from sympy import symbols, Function >>> x, y = symbols('x y') >>> fx = Function('f')(x) >>> eqs, syms = [fx + 1, x, y], [fx, y] >>> e, s, d = recast_to_symbols(eqs, syms); (e, s, d) ([_X0 + 1, x, y], [_X0, y], {_X0: f(x)}) The original equations and symbols can be restored using d: >>> assert [i.xreplace(d) for i in eqs] == eqs >>> assert [d.get(i, i) for i in s] == syms """ if not iterable(eqs) and iterable(symbols): raise ValueError('Both eqs and symbols must be iterable') new_symbols = list(symbols) swap_sym = {} for i, s in enumerate(symbols): if not isinstance(s, Symbol) and s not in swap_sym: swap_sym[s] = Dummy('X%d' % i) new_symbols[i] = swap_sym[s] new_f = [] for i in eqs: isubs = getattr(i, 'subs', None) if isubs is not None: new_f.append(isubs(swap_sym)) else: new_f.append(i) swap_sym = {v: k for k, v in swap_sym.items()} return new_f, new_symbols, swap_sym def _ispow(e): """Return True if e is a Pow or is exp.""" return isinstance(e, Expr) and (e.is_Pow or isinstance(e, exp)) def _simple_dens(f, symbols): # when checking if a denominator is zero, we can just check the # base of powers with nonzero exponents since if the base is zero # the power will be zero, too. To keep it simple and fast, we # limit simplification to exponents that are Numbers dens = set() for d in denoms(f, symbols): if d.is_Pow and d.exp.is_Number: if d.exp.is_zero: continue # foo*0 is never 0 d = d.base dens.add(d) return dens def denoms(eq, symbols): """ Return (recursively) set of all denominators that appear in eq that contain any symbol in symbols; if symbols are not provided then all denominators will be returned. Examples ======== >>> from sympy.solvers.solvers import denoms >>> from sympy.abc import x, y, z >>> denoms(x/y) {y} >>> denoms(x/(yz)) {y, z} >>> denoms(3/x + y/z) {x, z} >>> denoms(x/2 + y/z) {2, z} If symbols* are provided then only denominators containing those symbols will be returned: >>> denoms(1/x + 1/y + 1/z, y, z) {y, z} """ pot = preorder_traversal(eq) dens = set() for p in pot: # Here p might be Tuple or Relational # Expr subtrees (e.g. lhs and rhs) will be traversed after by pot if not isinstance(p, Expr): continue den = denom(p) if den is S.One: continue for d in Mul.make_args(den): dens.add(d) if not symbols: return dens elif len(symbols) == 1: if iterable(symbols[0]): symbols = symbols[0] rv = [] for d in dens: free = d.free_symbols if any(s in free for s in symbols): rv.append(d) return set(rv) def checksol(f, symbol, sol=None, *flags): """ Checks whether sol is a solution of equation f == 0. Explanation =========== Input can be either a single symbol and corresponding value or a dictionary of symbols and values. When given as a dictionary and flag ``simplify=True``, the values in the dictionary will be simplified. f* can be a single equation or an iterable of equations. A solution must satisfy all equations in f to be considered valid; if a solution does not satisfy any equation, False is returned; if one or more checks are inconclusive (and none are False) then None is returned. Examples ======== >>> from sympy import symbols >>> from sympy.solvers import checksol >>> x, y = symbols('x,y') >>> checksol(x4 - 1, x, 1) True >>> checksol(x4 - 1, x, 0) False >>> checksol(x2 + y2 - 5*2, {x: 3, y: 4}) True To check if an expression is zero using ``checksol()``, pass it as f* and send an empty dictionary for symbol: >>> checksol(x*2 + x - x(x + 1), {}) True None is returned if ``checksol()`` could not conclude. flags: 'numerical=True (default)' do a fast numerical check if ``f`` has only one symbol. 'minimal=True (default is False)' a very fast, minimal testing. 'warn=True (default is False)' show a warning if checksol() could not conclude. 'simplify=True (default)' simplify solution before substituting into function and simplify the function before trying specific simplifications 'force=True (default is False)' make positive all symbols without assumptions regarding sign. """ from sympy.physics.units import Unit minimal = flags.get('minimal', False) if sol is not None: sol = {symbol: sol} elif isinstance(symbol, dict): sol = symbol else: msg = 'Expecting (sym, val) or ({sym: val}, None) but got (%s, %s)' raise ValueError(msg % (symbol, sol)) if iterable(f): if not f: raise ValueError('no functions to check') rv = True for fi in f: check = checksol(fi, sol, *flags) if check: continue if check is False: return False rv = None # don't return, wait to see if there's a False return rv if isinstance(f, Poly): f = f.as_expr() elif isinstance(f, (Equality, Unequality)): if f.rhs in (S.true, S.false): f = f.reversed B, E = f.args if isinstance(B, BooleanAtom): f = f.subs(sol) if not f.is_Boolean: return else: f = f.rewrite(Add, evaluate=False) if isinstance(f, BooleanAtom): return bool(f) elif not f.is_Relational and not f: return True if sol and not f.free_symbols & set(sol.keys()): # if f(y) == 0, x=3 does not set f(y) to zero...nor does it not return None illegal = {S.NaN, S.ComplexInfinity, S.Infinity, S.NegativeInfinity} if any(sympify(v).atoms() & illegal for k, v in sol.items()): return False was = f attempt = -1 numerical = flags.get('numerical', True) while 1: attempt += 1 if attempt == 0: val = f.subs(sol) if isinstance(val, Mul): val = val.as_independent(Unit)[0] if val.atoms() & illegal: return False elif attempt == 1: if not val.is_number: if not val.is_constant(list(sol.keys()), simplify=not minimal): return False # there are free symbols -- simple expansion might work _, val = val.as_content_primitive() val = _mexpand(val.as_numer_denom()[0], recursive=True) elif attempt == 2: if minimal: return if flags.get('simplify', True): for k in sol: sol[k] = simplify(sol[k]) # start over without the failed expanded form, possibly # with a simplified solution val = simplify(f.subs(sol)) if flags.get('force', True): val, reps = posify(val) # expansion may work now, so try again and check exval = _mexpand(val, recursive=True) if exval.is_number: # we can decide now val = exval else: # if there are no radicals and no functions then this can't be # zero anymore -- can it? pot = preorder_traversal(expand_mul(val)) seen = set() saw_pow_func = False for p in pot: if p in seen: continue seen.add(p) if p.is_Pow and not p.exp.is_Integer: saw_pow_func = True elif p.is_Function: saw_pow_func = True elif isinstance(p, UndefinedFunction): saw_pow_func = True if saw_pow_func: break if saw_pow_func is False: return False if flags.get('force', True): # don't do a zero check with the positive assumptions in place val = val.subs(reps) nz = fuzzy_not(val.is_zero) if nz is not None: # issue 5673: nz may be True even when False # so these are just hacks to keep a false positive # from being returned # HACK 1: LambertW (issue 5673) if val.is_number and val.has(LambertW): # don't eval this to verify solution since if we got here, # numerical must be False return None # add other HACKs here if necessary, otherwise we assume # the nz value is correct return not nz break if val == was: continue elif val.is_Rational: return val == 0 if numerical and val.is_number: return (abs(val.n(18).n(12, chop=True)) < 1e-9) is S.true was = val if flags.get('warn', False): warnings.warn("\n\tWarning: could not verify solution %s." % sol) # returns None if it can't conclude # TODO: improve solution testing def solve(f, symbols, flags): r""" Algebraically solves equations and systems of equations. Explanation =========== Currently supported: - polynomial - transcendental - piecewise combinations of the above - systems of linear and polynomial equations - systems containing relational expressions Examples ======== The output varies according to the input and can be seen by example: >>> from sympy import solve, Poly, Eq, Function, exp >>> from sympy.abc import x, y, z, a, b >>> f = Function('f') Boolean or univariate Relational: >>> solve(x < 3) (-oo < x) & (x < 3) To always get a list of solution mappings, use flag dict=True: >>> solve(x - 3, dict=True) [{x: 3}] >>> sol = solve([x - 3, y - 1], dict=True) >>> sol [{x: 3, y: 1}] >>> sol[0][x] 3 >>> sol[0][y] 1 To get a list of symbols* and set of solution(s) use flag set=True: >>> solve([x2 - 3, y - 1], set=True) ([x, y], {(-sqrt(3), 1), (sqrt(3), 1)}) Single expression and single symbol that is in the expression: >>> solve(x - y, x) [y] >>> solve(x - 3, x) [3] >>> solve(Eq(x, 3), x) [3] >>> solve(Poly(x - 3), x) [3] >>> solve(x2 - y2, x, set=True) ([x], {(-y,), (y,)}) >>> solve(x4 - 1, x, set=True) ([x], {(-1,), (1,), (-I,), (I,)}) Single expression with no symbol that is in the expression: >>> solve(3, x) [] >>> solve(x - 3, y) [] Single expression with no symbol given. In this case, all free symbols will be selected as potential symbols to solve for. If the equation is univariate then a list of solutions is returned; otherwise - as is the case when symbols are given as an iterable of length greater than 1 - a list of mappings will be returned: >>> solve(x - 3) [3] >>> solve(x2 - y2) [{x: -y}, {x: y}] >>> solve(z*2x2 - z2y2) [{x: -y}, {x: y}, {z: 0}] >>> solve(z2x - z*2y2) [{x: y2}, {z: 0}] When an object other than a Symbol is given as a symbol, it is isolated algebraically and an implicit solution may be obtained. This is mostly provided as a convenience to save you from replacing the object with a Symbol and solving for that Symbol. It will only work if the specified object can be replaced with a Symbol using the subs method: >>> solve(f(x) - x, f(x)) [x] >>> solve(f(x).diff(x) - f(x) - x, f(x).diff(x)) [x + f(x)] >>> solve(f(x).diff(x) - f(x) - x, f(x)) [-x + Derivative(f(x), x)] >>> solve(x + exp(x)*2, exp(x), set=True) ([exp(x)], {(-sqrt(-x),), (sqrt(-x),)}) >>> from sympy import Indexed, IndexedBase, Tuple, sqrt >>> A = IndexedBase('A') >>> eqs = Tuple(A[1] + A[2] - 3, A[1] - A[2] + 1) >>> solve(eqs, eqs.atoms(Indexed)) {A[1]: 1, A[2]: 2} To solve for a symbol implicitly, use implicit=True: >>> solve(x + exp(x), x) [-LambertW(1)] >>> solve(x + exp(x), x, implicit=True) [-exp(x)] * It is possible to solve for anything that can be targeted with subs: >>> solve(x + 2 + sqrt(3), x + 2) [-sqrt(3)] >>> solve((x + 2 + sqrt(3), x + 4 + y), y, x + 2) {y: -2 + sqrt(3), x + 2: -sqrt(3)} * Nothing heroic is done in this implicit solving so you may end up with a symbol still in the solution: >>> eqs = (xy + 3y + sqrt(3), x + 4 + y) >>> solve(eqs, y, x + 2) {y: -sqrt(3)/(x + 3), x + 2: -2x/(x + 3) - 6/(x + 3) + sqrt(3)/(x + 3)} >>> solve(eqs, yx, x) {x: -y - 4, xy: -3y - sqrt(3)} * If you attempt to solve for a number remember that the number you have obtained does not necessarily mean that the value is equivalent to the expression obtained: >>> solve(sqrt(2) - 1, 1) [sqrt(2)] >>> solve(x - y + 1, 1) # /!\ -1 is targeted, too [x/(y - 1)] >>> [_.subs(z, -1) for _ in solve((x - y + 1).subs(-1, z), 1)] [-x + y] * To solve for a function within a derivative, use ``dsolve``. Single expression and more than one symbol: * When there is a linear solution: >>> solve(x - y2, x, y) [(y2, y)] >>> solve(x2 - y, x, y) [(x, x2)] >>> solve(x2 - y, x, y, dict=True) [{y: x2}] * When undetermined coefficients are identified: * That are linear: >>> solve((a + b)x - b + 2, a, b) {a: -2, b: 2} That are nonlinear: >>> solve((a + b)x - b2 + 2, a, b, set=True) ([a, b], {(-sqrt(2), sqrt(2)), (sqrt(2), -sqrt(2))}) If there is no linear solution, then the first successful attempt for a nonlinear solution will be returned: >>> solve(x2 - y2, x, y, dict=True) [{x: -y}, {x: y}] >>> solve(x2 - y2/exp(x), x, y, dict=True) [{x: 2LambertW(-y/2)}, {x: 2LambertW(y/2)}] >>> solve(x2 - y2/exp(x), y, x) [(-xsqrt(exp(x)), x), (xsqrt(exp(x)), x)] Iterable of one or more of the above: * Involving relationals or bools: >>> solve([x < 3, x - 2]) Eq(x, 2) >>> solve([x > 3, x - 2]) False * When the system is linear: * With a solution: >>> solve([x - 3], x) {x: 3} >>> solve((x + 5y - 2, -3x + 6y - 15), x, y) {x: -3, y: 1} >>> solve((x + 5y - 2, -3x + 6y - 15), x, y, z) {x: -3, y: 1} >>> solve((x + 5y - 2, -3x + 6y - z), z, x, y) {x: 2 - 5y, z: 21y - 6} Without a solution: >>> solve([x + 3, x - 3]) [] * When the system is not linear: >>> solve([x2 + y -2, y2 - 4], x, y, set=True) ([x, y], {(-2, -2), (0, 2), (2, -2)}) * If no symbols are given, all free symbols will be selected and a list of mappings returned: >>> solve([x - 2, x2 + y]) [{x: 2, y: -4}] >>> solve([x - 2, x2 + f(x)], {f(x), x}) [{x: 2, f(x): -4}] * If any equation does not depend on the symbol(s) given, it will be eliminated from the equation set and an answer may be given implicitly in terms of variables that were not of interest: >>> solve([x - y, y - 3], x) {x: y} Additional Examples ``solve()`` with check=True (default) will run through the symbol tags to elimate unwanted solutions. If no assumptions are included, all possible solutions will be returned: >>> from sympy import Symbol, solve >>> x = Symbol("x") >>> solve(x2 - 1) [-1, 1] By using the positive tag, only one solution will be returned: >>> pos = Symbol("pos", positive=True) >>> solve(pos2 - 1) [1] Assumptions are not checked when ``solve()`` input involves relationals or bools. When the solutions are checked, those that make any denominator zero are automatically excluded. If you do not want to exclude such solutions, then use the check=False option: >>> from sympy import sin, limit >>> solve(sin(x)/x) # 0 is excluded [pi] If check=False, then a solution to the numerator being zero is found: x = 0. In this case, this is a spurious solution since $\sin(x)/x$ has the well known limit (without dicontinuity) of 1 at x = 0: >>> solve(sin(x)/x, check=False) [0, pi] In the following case, however, the limit exists and is equal to the value of x = 0 that is excluded when check=True: >>> eq = x*2(1/x - z2/x) >>> solve(eq, x) [] >>> solve(eq, x, check=False) [0] >>> limit(eq, x, 0, '-') 0 >>> limit(eq, x, 0, '+') 0 Disabling High-Order Explicit Solutions When solving polynomial expressions, you might not want explicit solutions (which can be quite long). If the expression is univariate, ``CRootOf`` instances will be returned instead: >>> solve(x3 - x + 1) [-1/((-1/2 - sqrt(3)I/2)(3sqrt(69)/2 + 27/2)(1/3)) - (-1/2 - sqrt(3)I/2)(3sqrt(69)/2 + 27/2)*(1/3)/3, -(-1/2 + sqrt(3)I/2)(3sqrt(69)/2 + 27/2)*(1/3)/3 - 1/((-1/2 + sqrt(3)I/2)(3sqrt(69)/2 + 27/2)*(1/3)), -(3sqrt(69)/2 + 27/2)*(1/3)/3 - 1/(3sqrt(69)/2 + 27/2)(1/3)] >>> solve(x3 - x + 1, cubics=False) [CRootOf(x3 - x + 1, 0), CRootOf(x3 - x + 1, 1), CRootOf(x3 - x + 1, 2)] If the expression is multivariate, no solution might be returned: >>> solve(x3 - x + a, x, cubics=False) [] Sometimes solutions will be obtained even when a flag is False because the expression could be factored. In the following example, the equation can be factored as the product of a linear and a quadratic factor so explicit solutions (which did not require solving a cubic expression) are obtained: >>> eq = x*3 + 3x2 + x - 1 >>> solve(eq, cubics=False) [-1, -1 + sqrt(2), -sqrt(2) - 1] Solving Equations Involving Radicals Because of SymPy's use of the principle root, some solutions to radical equations will be missed unless check=False: >>> from sympy import root >>> eq = root(x3 - 3x2, 3) + 1 - x >>> solve(eq) [] >>> solve(eq, check=False) [1/3] In the above example, there is only a single solution to the equation. Other expressions will yield spurious roots which must be checked manually; roots which give a negative argument to odd-powered radicals will also need special checking: >>> from sympy import real_root, S >>> eq = root(x, 3) - root(x, 5) + S(1)/7 >>> solve(eq) # this gives 2 solutions but misses a 3rd [CRootOf(7x*5 - 7x3 + 1, 1)15, CRootOf(7x5 - 7x3 + 1, 2)15] >>> sol = solve(eq, check=False) >>> [abs(eq.subs(x,i).n(2)) for i in sol] [0.48, 0.e-110, 0.e-110, 0.052, 0.052] The first solution is negative so ``real_root`` must be used to see that it satisfies the expression: >>> abs(real_root(eq.subs(x, sol[0])).n(2)) 0.e-110 If the roots of the equation are not real then more care will be necessary to find the roots, especially for higher order equations. Consider the following expression: >>> expr = root(x, 3) - root(x, 5) We will construct a known value for this expression at x = 3 by selecting the 1-th root for each radical: >>> expr1 = root(x, 3, 1) - root(x, 5, 1) >>> v = expr1.subs(x, -3) The ``solve`` function is unable to find any exact roots to this equation: >>> eq = Eq(expr, v); eq1 = Eq(expr1, v) >>> solve(eq, check=False), solve(eq1, check=False) ([], []) The function ``unrad``, however, can be used to get a form of the equation for which numerical roots can be found: >>> from sympy.solvers.solvers import unrad >>> from sympy import nroots >>> e, (p, cov) = unrad(eq) >>> pvals = nroots(e) >>> inversion = solve(cov, x)[0] >>> xvals = [inversion.subs(p, i) for i in pvals] Although ``eq`` or ``eq1`` could have been used to find ``xvals``, the solution can only be verified with ``expr1``: >>> z = expr - v >>> [xi.n(chop=1e-9) for xi in xvals if abs(z.subs(x, xi).n()) < 1e-9] [] >>> z1 = expr1 - v >>> [xi.n(chop=1e-9) for xi in xvals if abs(z1.subs(x, xi).n()) < 1e-9] [-3.0] Parameters ========== f : - a single Expr or Poly that must be zero - an Equality - a Relational expression - a Boolean - iterable of one or more of the above symbols : (object(s) to solve for) specified as - none given (other non-numeric objects will be used) - single symbol - denested list of symbols (e.g., ``solve(f, x, y)``) - ordered iterable of symbols (e.g., ``solve(f, [x, y])``) flags : dict=True (default is False) Return list (perhaps empty) of solution mappings. set=True (default is False) Return list of symbols and set of tuple(s) of solution(s). exclude=[] (default) Do not try to solve for any of the free symbols in exclude; if expressions are given, the free symbols in them will be extracted automatically. check=True (default) If False, do not do any testing of solutions. This can be useful if you want to include solutions that make any denominator zero. numerical=True (default) Do a fast numerical check if f has only one symbol. minimal=True (default is False) A very fast, minimal testing. warn=True (default is False) Show a warning if ``checksol()`` could not conclude. simplify=True (default) Simplify all but polynomials of order 3 or greater before returning them and (if check is not False) use the general simplify function on the solutions and the expression obtained when they are substituted into the function which should be zero. force=True (default is False) Make positive all symbols without assumptions regarding sign. rational=True (default) Recast Floats as Rational; if this option is not used, the system containing Floats may fail to solve because of issues with polys. If rational=None, Floats will be recast as rationals but the answer will be recast as Floats. If the flag is False then nothing will be done to the Floats. manual=True (default is False) Do not use the polys/matrix method to solve a system of equations, solve them one at a time as you might "manually." implicit=True (default is False) Allows ``solve`` to return a solution for a pattern in terms of other functions that contain that pattern; this is only needed if the pattern is inside of some invertible function like cos, exp, ect. particular=True (default is False) Instructs ``solve`` to try to find a particular solution to a linear system with as many zeros as possible; this is very expensive. quick=True (default is False) When using particular=True, use a fast heuristic to find a solution with many zeros (instead of using the very slow method guaranteed to find the largest number of zeros possible). cubics=True (default) Return explicit solutions when cubic expressions are encountered. quartics=True (default) Return explicit solutions when quartic expressions are encountered. quintics=True (default) Return explicit solutions (if possible) when quintic expressions are encountered. See Also ======== rsolve: For solving recurrence relationships dsolve: For solving differential equations """ # keeping track of how f was passed since if it is a list # a dictionary of results will be returned. ########################################################################### def _sympified_list(w): return list(map(sympify, w if iterable(w) else [w])) bare_f = not iterable(f) ordered_symbols = (symbols and symbols[0] and (isinstance(symbols[0], Symbol) or is_sequence(symbols[0], include=GeneratorType) ) ) f, symbols = (_sympified_list(w) for w in [f, symbols]) if isinstance(f, list): f = [s for s in f if s is not S.true and s is not True] implicit = flags.get('implicit', False) # preprocess symbol(s) ########################################################################### if not symbols: # get symbols from equations symbols = set().union([fi.free_symbols for fi in f]) if len(symbols) < len(f): for fi in f: pot = preorder_traversal(fi) for p in pot: if isinstance(p, AppliedUndef): flags['dict'] = True # better show symbols symbols.add(p) pot.skip() # don't go any deeper symbols = list(symbols) ordered_symbols = False elif len(symbols) == 1 and iterable(symbols[0]): symbols = symbols[0] # remove symbols the user is not interested in exclude = flags.pop('exclude', set()) if exclude: if isinstance(exclude, Expr): exclude = [exclude] exclude = set().union([e.free_symbols for e in sympify(exclude)]) symbols = [s for s in symbols if s not in exclude] # preprocess equation(s) ########################################################################### for i, fi in enumerate(f): if isinstance(fi, (Equality, Unequality)): if 'ImmutableDenseMatrix' in [type(a).__name__ for a in fi.args]: fi = fi.lhs - fi.rhs else: L, R = fi.args if isinstance(R, BooleanAtom): L, R = R, L if isinstance(L, BooleanAtom): if isinstance(fi, Unequality): L = ~L if R.is_Relational: fi = ~R if L is S.false else R elif R.is_Symbol: return L elif R.is_Boolean and (~R).is_Symbol: return ~L else: raise NotImplementedError(filldedent(''' Unanticipated argument of Eq when other arg is True or False. ''')) else: fi = fi.rewrite(Add, evaluate=False) f[i] = fi if fi.is_Relational: return reduce_inequalities(f, symbols=symbols) if isinstance(fi, Poly): f[i] = fi.as_expr() # rewrite hyperbolics in terms of exp f[i] = f[i].replace(lambda w: isinstance(w, HyperbolicFunction), lambda w: w.rewrite(exp)) # if we have a Matrix, we need to iterate over its elements again if f[i].is_Matrix: bare_f = False f.extend(list(f[i])) f[i] = S.Zero # if we can split it into real and imaginary parts then do so freei = f[i].free_symbols if freei and all(s.is_extended_real or s.is_imaginary for s in freei): fr, fi = f[i].as_real_imag() # accept as long as new re, im, arg or atan2 are not introduced had = f[i].atoms(re, im, arg, atan2) if fr and fi and fr != fi and not any( i.atoms(re, im, arg, atan2) - had for i in (fr, fi)): if bare_f: bare_f = False f[i: i + 1] = [fr, fi] # real/imag handling ----------------------------- if any(isinstance(fi, (bool, BooleanAtom)) for fi in f): if flags.get('set', False): return [], set() return [] for i, fi in enumerate(f): # Abs while True: was = fi fi = fi.replace(Abs, lambda arg: separatevars(Abs(arg)).rewrite(Piecewise) if arg.has(symbols) else Abs(arg)) if was == fi: break for e in fi.find(Abs): if e.has(symbols): raise NotImplementedError('solving %s when the argument ' 'is not real or imaginary.' % e) # arg fi = fi.replace(arg, lambda a: arg(a).rewrite(atan2).rewrite(atan)) # save changes f[i] = fi # see if re(s) or im(s) appear freim = [fi for fi in f if fi.has(re, im)] if freim: irf = [] for s in symbols: if s.is_real or s.is_imaginary: continue # neither re(x) nor im(x) will appear # if re(s) or im(s) appear, the auxiliary equation must be present if any(fi.has(re(s), im(s)) for fi in freim): irf.append((s, re(s) + S.ImaginaryUnitim(s))) if irf: for s, rhs in irf: for i, fi in enumerate(f): f[i] = fi.xreplace({s: rhs}) f.append(s - rhs) symbols.extend([re(s), im(s)]) if bare_f: bare_f = False flags['dict'] = True # end of real/imag handling ----------------------------- symbols = list(uniq(symbols)) if not ordered_symbols: # we do this to make the results returned canonical in case f # contains a system of nonlinear equations; all other cases should # be unambiguous symbols = sorted(symbols, key=default_sort_key) # we can solve for non-symbol entities by replacing them with Dummy symbols f, symbols, swap_sym = recast_to_symbols(f, symbols) # this is needed in the next two events symset = set(symbols) # get rid of equations that have no symbols of interest; we don't # try to solve them because the user didn't ask and they might be # hard to solve; this means that solutions may be given in terms # of the eliminated equations e.g. solve((x-y, y-3), x) -> {x: y} newf = [] for fi in f: # let the solver handle equations that.. # - have no symbols but are expressions # - have symbols of interest # - have no symbols of interest but are constant # but when an expression is not constant and has no symbols of # interest, it can't change what we obtain for a solution from # the remaining equations so we don't include it; and if it's # zero it can be removed and if it's not zero, there is no # solution for the equation set as a whole # # The reason for doing this filtering is to allow an answer # to be obtained to queries like solve((x - y, y), x); without # this mod the return value is [] ok = False if fi.free_symbols & symset: ok = True else: if fi.is_number: if fi.is_Number: if fi.is_zero: continue return [] ok = True else: if fi.is_constant(): ok = True if ok: newf.append(fi) if not newf: return [] f = newf del newf # mask off any Object that we aren't going to invert: Derivative, # Integral, etc... so that solving for anything that they contain will # give an implicit solution seen = set() non_inverts = set() for fi in f: pot = preorder_traversal(fi) for p in pot: if not isinstance(p, Expr) or isinstance(p, Piecewise): pass elif (isinstance(p, bool) or not p.args or p in symset or p.is_Add or p.is_Mul or p.is_Pow and not implicit or p.is_Function and not implicit) and p.func not in (re, im): continue elif not p in seen: seen.add(p) if p.free_symbols & symset: non_inverts.add(p) else: continue pot.skip() del seen non_inverts = dict(list(zip(non_inverts, [Dummy() for _ in non_inverts]))) f = [fi.subs(non_inverts) for fi in f] # Both xreplace and subs are needed below: xreplace to force substitution # inside Derivative, subs to handle non-straightforward substitutions non_inverts = [(v, k.xreplace(swap_sym).subs(swap_sym)) for k, v in non_inverts.items()] # rationalize Floats floats = False if flags.get('rational', True) is not False: for i, fi in enumerate(f): if fi.has(Float): floats = True f[i] = nsimplify(fi, rational=True) # capture any denominators before rewriting since # they may disappear after the rewrite, e.g. issue 14779 flags['_denominators'] = _simple_dens(f[0], symbols) # Any embedded piecewise functions need to be brought out to the # top level so that the appropriate strategy gets selected. # However, this is necessary only if one of the piecewise # functions depends on one of the symbols we are solving for. def _has_piecewise(e): if e.is_Piecewise: return e.has(symbols) return any([_has_piecewise(a) for a in e.args]) for i, fi in enumerate(f): if _has_piecewise(fi): f[i] = piecewise_fold(fi) # # try to get a solution ########################################################################### if bare_f: solution = _solve(f[0], symbols, flags) else: solution = _solve_system(f, symbols, flags) # # postprocessing ########################################################################### # Restore masked-off objects if non_inverts: def _do_dict(solution): return {k: v.subs(non_inverts) for k, v in solution.items()} for i in range(1): if isinstance(solution, dict): solution = _do_dict(solution) break elif solution and isinstance(solution, list): if isinstance(solution[0], dict): solution = [_do_dict(s) for s in solution] break elif isinstance(solution[0], tuple): solution = [tuple([v.subs(non_inverts) for v in s]) for s in solution] break else: solution = [v.subs(non_inverts) for v in solution] break elif not solution: break else: raise NotImplementedError(filldedent(''' no handling of %s was implemented''' % solution)) # Restore original "symbols" if a dictionary is returned. # This is not necessary for # - the single univariate equation case # since the symbol will have been removed from the solution; # - the nonlinear poly_system since that only supports zero-dimensional # systems and those results come back as a list # # * unless there were Derivatives with the symbols, but those were handled # above. if swap_sym: symbols = [swap_sym.get(k, k) for k in symbols] if isinstance(solution, dict): solution = {swap_sym.get(k, k): v.subs(swap_sym) for k, v in solution.items()} elif solution and isinstance(solution, list) and isinstance(solution[0], dict): for i, sol in enumerate(solution): solution[i] = {swap_sym.get(k, k): v.subs(swap_sym) for k, v in sol.items()} # undo the dictionary solutions returned when the system was only partially # solved with poly-system if all symbols are present if ( not flags.get('dict', False) and solution and ordered_symbols and not isinstance(solution, dict) and all(isinstance(sol, dict) for sol in solution) ): solution = [tuple([r.get(s, s) for s in symbols]) for r in solution] # Get assumptions about symbols, to filter solutions. # Note that if assumptions about a solution can't be verified, it is still # returned. check = flags.get('check', True) # restore floats if floats and solution and flags.get('rational', None) is None: solution = nfloat(solution, exponent=False) if check and solution: # assumption checking warn = flags.get('warn', False) got_None = [] # solutions for which one or more symbols gave None no_False = [] # solutions for which no symbols gave False if isinstance(solution, tuple): # this has already been checked and is in as_set form return solution elif isinstance(solution, list): if isinstance(solution[0], tuple): for sol in solution: for symb, val in zip(symbols, sol): test = check_assumptions(val, symb.assumptions0) if test is False: break if test is None: got_None.append(sol) else: no_False.append(sol) elif isinstance(solution[0], dict): for sol in solution: a_None = False for symb, val in sol.items(): test = check_assumptions(val, symb.assumptions0) if test: continue if test is False: break a_None = True else: no_False.append(sol) if a_None: got_None.append(sol) else: # list of expressions for sol in solution: test = check_assumptions(sol, symbols[0].assumptions0) if test is False: continue no_False.append(sol) if test is None: got_None.append(sol) elif isinstance(solution, dict): a_None = False for symb, val in solution.items(): test = check_assumptions(val, symb.assumptions0) if test: continue if test is False: no_False = None break a_None = True else: no_False = solution if a_None: got_None.append(solution) elif isinstance(solution, (Relational, And, Or)): if len(symbols) != 1: raise ValueError("Length should be 1") if warn and symbols[0].assumptions0: warnings.warn(filldedent(""" \tWarning: assumptions about variable '%s' are not handled currently.""" % symbols[0])) # TODO: check also variable assumptions for inequalities else: raise TypeError('Unrecognized solution') # improve the checker solution = no_False if warn and got_None: warnings.warn(filldedent(""" \tWarning: assumptions concerning following solution(s) can't be checked:""" + '\n\t' + ', '.join(str(s) for s in got_None))) # # done ########################################################################### as_dict = flags.get('dict', False) as_set = flags.get('set', False) if not as_set and isinstance(solution, list): # Make sure that a list of solutions is ordered in a canonical way. solution.sort(key=default_sort_key) if not as_dict and not as_set: return solution or [] # return a list of mappings or [] if not solution: solution = [] else: if isinstance(solution, dict): solution = [solution] elif iterable(solution[0]): solution = [dict(list(zip(symbols, s))) for s in solution] elif isinstance(solution[0], dict): pass else: if len(symbols) != 1: raise ValueError("Length should be 1") solution = [{symbols[0]: s} for s in solution] if as_dict: return solution assert as_set if not solution: return [], set() k = list(ordered(solution[0].keys())) return k, {tuple([s[ki] for ki in k]) for s in solution} def _solve(f, symbols, flags): """ Return a checked solution for f* in terms of one or more of the symbols. A list should be returned except for the case when a linear undetermined-coefficients equation is encountered (in which case a dictionary is returned). If no method is implemented to solve the equation, a NotImplementedError will be raised. In the case that conversion of an expression to a Poly gives None a ValueError will be raised. """ not_impl_msg = "No algorithms are implemented to solve equation %s" if len(symbols) != 1: soln = None free = f.free_symbols ex = free - set(symbols) if len(ex) != 1: ind, dep = f.as_independent(symbols) ex = ind.free_symbols & dep.free_symbols if len(ex) == 1: ex = ex.pop() try: # soln may come back as dict, list of dicts or tuples, or # tuple of symbol list and set of solution tuples soln = solve_undetermined_coeffs(f, symbols, ex, flags) except NotImplementedError: pass if soln: if flags.get('simplify', True): if isinstance(soln, dict): for k in soln: soln[k] = simplify(soln[k]) elif isinstance(soln, list): if isinstance(soln[0], dict): for d in soln: for k in d: d[k] = simplify(d[k]) elif isinstance(soln[0], tuple): soln = [tuple(simplify(i) for i in j) for j in soln] else: raise TypeError('unrecognized args in list') elif isinstance(soln, tuple): sym, sols = soln soln = sym, {tuple(simplify(i) for i in j) for j in sols} else: raise TypeError('unrecognized solution type') return soln # find first successful solution failed = [] got_s = set() result = [] for s in symbols: xi, v = solve_linear(f, symbols=[s]) if xi == s: # no need to check but we should simplify if desired if flags.get('simplify', True): v = simplify(v) vfree = v.free_symbols if got_s and any([ss in vfree for ss in got_s]): # sol depends on previously solved symbols: discard it continue got_s.add(xi) result.append({xi: v}) elif xi: # there might be a non-linear solution if xi is not 0 failed.append(s) if not failed: return result for s in failed: try: soln = _solve(f, s, flags) for sol in soln: if got_s and any([ss in sol.free_symbols for ss in got_s]): # sol depends on previously solved symbols: discard it continue got_s.add(s) result.append({s: sol}) except NotImplementedError: continue if got_s: return result else: raise NotImplementedError(not_impl_msg % f) symbol = symbols[0] #expand binomials only if it has the unknown symbol f = f.replace(lambda e: isinstance(e, binomial) and e.has(symbol), lambda e: expand_func(e)) # /!\ capture this flag then set it to False so that no checking in # recursive calls will be done; only the final answer is checked flags['check'] = checkdens = check = flags.pop('check', True) # build up solutions if f is a Mul if f.is_Mul: result = set() for m in f.args: if m in {S.NegativeInfinity, S.ComplexInfinity, S.Infinity}: result = set() break soln = _solve(m, symbol, flags) result.update(set(soln)) result = list(result) if check: # all solutions have been checked but now we must # check that the solutions do not set denominators # in any factor to zero dens = flags.get('_denominators', _simple_dens(f, symbols)) result = [s for s in result if all(not checksol(den, {symbol: s}, flags) for den in dens)] # set flags for quick exit at end; solutions for each # factor were already checked and simplified check = False flags['simplify'] = False elif f.is_Piecewise: result = set() for i, (expr, cond) in enumerate(f.args): if expr.is_zero: raise NotImplementedError( 'solve cannot represent interval solutions') candidates = _solve(expr, symbol, flags) # the explicit condition for this expr is the current cond # and none of the previous conditions args = [~c for _, c in f.args[:i]] + [cond] cond = And(args) for candidate in candidates: if candidate in result: # an unconditional value was already there continue try: v = cond.subs(symbol, candidate) _eval_simplify = getattr(v, '_eval_simplify', None) if _eval_simplify is not None: # unconditionally take the simpification of v v = _eval_simplify(ratio=2, measure=lambda x: 1) except TypeError: # incompatible type with condition(s) continue if v == False: continue if v == True: result.add(candidate) else: result.add(Piecewise( (candidate, v), (S.NaN, True))) # set flags for quick exit at end; solutions for each # piece were already checked and simplified check = False flags['simplify'] = False else: # first see if it really depends on symbol and whether there # is only a linear solution f_num, sol = solve_linear(f, symbols=symbols) if f_num.is_zero or sol is S.NaN: return [] elif f_num.is_Symbol: # no need to check but simplify if desired if flags.get('simplify', True): sol = simplify(sol) return [sol] poly = None # check for a single non-symbol generator dums = f_num.atoms(Dummy) D = f_num.replace( lambda i: isinstance(i, Add) and symbol in i.free_symbols, lambda i: Dummy()) if not D.is_Dummy: dgen = D.atoms(Dummy) - dums if len(dgen) == 1: d = dgen.pop() w = Wild('g') gen = f_num.match(D.xreplace({d: w}))[w] spart = gen.as_independent(symbol)[1].as_base_exp()[0] if spart == symbol: try: poly = Poly(f_num, spart) except PolynomialError: pass result = False # no solution was obtained msg = '' # there is no failure message # Poly is generally robust enough to convert anything to # a polynomial and tell us the different generators that it # contains, so we will inspect the generators identified by # polys to figure out what to do. # try to identify a single generator that will allow us to solve this # as a polynomial, followed (perhaps) by a change of variables if the # generator is not a symbol try: if poly is None: poly = Poly(f_num) if poly is None: raise ValueError('could not convert %s to Poly' % f_num) except GeneratorsNeeded: simplified_f = simplify(f_num) if simplified_f != f_num: return _solve(simplified_f, symbol, flags) raise ValueError('expression appears to be a constant') gens = [g for g in poly.gens if g.has(symbol)] def _as_base_q(x): """Return (be, q) for x = b*(pe/q) where p/q is the leading Rational of the exponent of x, e.g. exp(-2x/3) -> (exp(x), 3) """ b, e = x.as_base_exp() if e.is_Rational: return b, e.q if not e.is_Mul: return x, 1 c, ee = e.as_coeff_Mul() if c.is_Rational and c is not S.One: # c could be a Float return bee, c.q return x, 1 if len(gens) > 1: # If there is more than one generator, it could be that the # generators have the same base but different powers, e.g. # >>> Poly(exp(x) + 1/exp(x)) # Poly(exp(-x) + exp(x), exp(-x), exp(x), domain='ZZ') # # If unrad was not disabled then there should be no rational # exponents appearing as in # >>> Poly(sqrt(x) + sqrt(sqrt(x))) # Poly(sqrt(x) + x(1/4), sqrt(x), x(1/4), domain='ZZ') bases, qs = list(zip([_as_base_q(g) for g in gens])) bases = set(bases) if len(bases) > 1 or not all(q == 1 for q in qs): funcs = {b for b in bases if b.is_Function} trig = {_ for _ in funcs if isinstance(_, TrigonometricFunction)} other = funcs - trig if not other and len(funcs.intersection(trig)) > 1: newf = None if f_num.is_Add and len(f_num.args) == 2: # check for sin(x)p = cos(x)p _args = f_num.args t = a, b = [i.atoms(Function).intersection( trig) for i in _args] if all(len(i) == 1 for i in t): a, b = [i.pop() for i in t] if isinstance(a, cos): a, b = b, a _args = _args[::-1] if isinstance(a, sin) and isinstance(b, cos ) and a.args[0] == b.args[0]: # sin(x) + cos(x) = 0 -> tan(x) + 1 = 0 newf, _d = (TR2i(_args[0]/_args[1]) + 1 ).as_numer_denom() if not _d.is_Number: newf = None if newf is None: newf = TR1(f_num).rewrite(tan) if newf != f_num: # don't check the rewritten form --check # solutions in the un-rewritten form below flags['check'] = False result = _solve(newf, symbol, flags) flags['check'] = check # just a simple case - see if replacement of single function # clears all symbol-dependent functions, e.g. # log(x) - log(log(x) - 1) - 3 can be solved even though it has # two generators. if result is False and funcs: funcs = list(ordered(funcs)) # put shallowest function first f1 = funcs[0] t = Dummy('t') # perform the substitution ftry = f_num.subs(f1, t) # if no Functions left, we can proceed with usual solve if not ftry.has(symbol): cv_sols = _solve(ftry, t, flags) cv_inv = _solve(t - f1, symbol, flags)[0] sols = list() for sol in cv_sols: sols.append(cv_inv.subs(t, sol)) result = list(ordered(sols)) if result is False: msg = 'multiple generators %s' % gens else: # e.g. case where gens are exp(x), exp(-x) u = bases.pop() t = Dummy('t') inv = _solve(u - t, symbol, flags) if isinstance(u, (Pow, exp)): # this will be resolved by factor in _tsolve but we might # as well try a simple expansion here to get things in # order so something like the following will work now without # having to factor: # # >>> eq = (exp(I(-x-2))+exp(I(x+2))) # >>> eq.subs(exp(x),y) # fails # exp(I(-x - 2)) + exp(I(x + 2)) # >>> eq.expand().subs(exp(x),y) # works # y*Iexp(2I) + y(-I)exp(-2I) def _expand(p): b, e = p.as_base_exp() e = expand_mul(e) return expand_power_exp(be) ftry = f_num.replace( lambda w: w.is_Pow or isinstance(w, exp), _expand).subs(u, t) if not ftry.has(symbol): soln = _solve(ftry, t, flags) sols = list() for sol in soln: for i in inv: sols.append(i.subs(t, sol)) result = list(ordered(sols)) elif len(gens) == 1: # There is only one generator that we are interested in, but # there may have been more than one generator identified by # polys (e.g. for symbols other than the one we are interested # in) so recast the poly in terms of our generator of interest. # Also use composite=True with f_num since Poly won't update # poly as documented in issue 8810. poly = Poly(f_num, gens[0], composite=True) # if we aren't on the tsolve-pass, use roots if not flags.pop('tsolve', False): soln = None deg = poly.degree() flags['tsolve'] = True solvers = {k: flags.get(k, True) for k in ('cubics', 'quartics', 'quintics')} soln = roots(poly, solvers) if sum(soln.values()) < deg: # e.g. roots(32x*5 + 400x*4 + 2032x*3 + # 5000x*2 + 6250x + 3189) -> {} # so all_roots is used and RootOf instances are # returned unless the system is multivariate # or high-order EX domain. try: soln = poly.all_roots() except NotImplementedError: if not flags.get('incomplete', True): raise NotImplementedError( filldedent(''' Neither high-order multivariate polynomials nor sorting of EX-domain polynomials is supported. If you want to see any results, pass keyword incomplete=True to solve; to see numerical values of roots for univariate expressions, use nroots. ''')) else: pass else: soln = list(soln.keys()) if soln is not None: u = poly.gen if u != symbol: try: t = Dummy('t') iv = _solve(u - t, symbol, flags) soln = list(ordered({i.subs(t, s) for i in iv for s in soln})) except NotImplementedError: # perhaps _tsolve can handle f_num soln = None else: check = False # only dens need to be checked if soln is not None: if len(soln) > 2: # if the flag wasn't set then unset it since high-order # results are quite long. Perhaps one could base this # decision on a certain critical length of the # roots. In addition, wester test M2 has an expression # whose roots can be shown to be real with the # unsimplified form of the solution whereas only one of # the simplified forms appears to be real. flags['simplify'] = flags.get('simplify', False) result = soln # fallback if above fails # ----------------------- if result is False: # try unrad if flags.pop('_unrad', True): try: u = unrad(f_num, symbol) except (ValueError, NotImplementedError): u = False if u: eq, cov = u if cov: isym, ieq = cov inv = _solve(ieq, symbol, flags)[0] rv = {inv.subs(isym, xi) for xi in _solve(eq, isym, flags)} else: try: rv = set(_solve(eq, symbol, flags)) except NotImplementedError: rv = None if rv is not None: result = list(ordered(rv)) # if the flag wasn't set then unset it since unrad results # can be quite long or of very high order flags['simplify'] = flags.get('simplify', False) else: pass # for coverage # try _tsolve if result is False: flags.pop('tsolve', None) # allow tsolve to be used on next pass try: soln = _tsolve(f_num, symbol, flags) if soln is not None: result = soln except PolynomialError: pass # ----------- end of fallback ---------------------------- if result is False: raise NotImplementedError('\n'.join([msg, not_impl_msg % f])) if flags.get('simplify', True): result = list(map(simplify, result)) # we just simplified the solution so we now set the flag to # False so the simplification doesn't happen again in checksol() flags['simplify'] = False if checkdens: # reject any result that makes any denom. affirmatively 0; # if in doubt, keep it dens = _simple_dens(f, symbols) result = [s for s in result if all(not checksol(d, {symbol: s}, flags) for d in dens)] if check: # keep only results if the check is not False result = [r for r in result if checksol(f_num, {symbol: r}, flags) is not False] return result def _solve_system(exprs, symbols, flags): if not exprs: return [] if flags.pop('_split', True): # Split the system into connected components V = exprs symsset = set(symbols) exprsyms = {e: e.free_symbols & symsset for e in exprs} E = [] for n, e1 in enumerate(exprs): for e2 in exprs[:n]: # Equations are connected if they share a symbol if exprsyms[e1] & exprsyms[e2]: E.append((e1, e2)) G = V, E subexprs = connected_components(G) if len(subexprs) > 1: subsols = [] for subexpr in subexprs: subsyms = set() for e in subexpr: subsyms \|= exprsyms[e] subsyms = list(ordered(subsyms)) # use canonical subset to solve these equations # since there may be redundant equations in the set: # take the first equation of several that may have the # same sub-maximal free symbols of interest; the # other equations that weren't used should be checked # to see that they did not fail -- does the solver # take care of that? choices = sift(subexpr, lambda x: tuple(ordered(exprsyms[x]))) subexpr = choices.pop(tuple(ordered(subsyms)), []) for k in choices: subexpr.append(next(ordered(choices[k]))) flags['_split'] = False # skip split step subsol = _solve_system(subexpr, subsyms, *flags) if not isinstance(subsol, list): subsol = [subsol] subsols.append(subsol) # Full solution is cartesion product of subsystems sols = [] for soldicts in cartes(subsols): sols.append(dict(item for sd in soldicts for item in sd.items())) # Return a list with one dict as just the dict if len(sols) == 1: return sols[0] return sols polys = [] dens = set() failed = [] result = False linear = False manual = flags.get('manual', False) checkdens = check = flags.get('check', True) for j, g in enumerate(exprs): dens.update(_simple_dens(g, symbols)) i, d = _invert(g, symbols) g = d - i g = g.as_numer_denom()[0] if manual: failed.append(g) continue poly = g.as_poly(symbols, extension=True) if poly is not None: polys.append(poly) else: failed.append(g) if not polys: solved_syms = [] else: if all(p.is_linear for p in polys): n, m = len(polys), len(symbols) matrix = zeros(n, m + 1) for i, poly in enumerate(polys): for monom, coeff in poly.terms(): try: j = monom.index(1) matrix[i, j] = coeff except ValueError: matrix[i, m] = -coeff # returns a dictionary ({symbols: values}) or None if flags.pop('particular', False): result = minsolve_linear_system(matrix, symbols, flags) else: result = solve_linear_system(matrix, symbols, *flags) if failed: if result: solved_syms = list(result.keys()) else: solved_syms = [] else: linear = True else: if len(symbols) > len(polys): from sympy.utilities.iterables import subsets free = set().union([p.free_symbols for p in polys]) free = list(ordered(free.intersection(symbols))) got_s = set() result = [] for syms in subsets(free, len(polys)): try: # returns [] or list of tuples of solutions for syms res = solve_poly_system(polys, syms) if res: for r in res: skip = False for r1 in r: if got_s and any([ss in r1.free_symbols for ss in got_s]): # sol depends on previously # solved symbols: discard it skip = True if not skip: got_s.update(syms) result.extend([dict(list(zip(syms, r)))]) except NotImplementedError: pass if got_s: solved_syms = list(got_s) else: raise NotImplementedError('no valid subset found') else: try: result = solve_poly_system(polys, symbols) if result: solved_syms = symbols # we don't know here if the symbols provided # were given or not, so let solve resolve that. # A list of dictionaries is going to always be # returned from here. result = [dict(list(zip(solved_syms, r))) for r in result] except NotImplementedError: failed.extend([g.as_expr() for g in polys]) solved_syms = [] result = None if result: if isinstance(result, dict): result = [result] else: result = [{}] if failed: # For each failed equation, see if we can solve for one of the # remaining symbols from that equation. If so, we update the # solution set and continue with the next failed equation, # repeating until we are done or we get an equation that can't # be solved. def _ok_syms(e, sort=False): rv = (e.free_symbols - solved_syms) & legal if sort: rv = list(rv) rv.sort(key=default_sort_key) return rv solved_syms = set(solved_syms) # set of symbols we have solved for legal = set(symbols) # what we are interested in # sort so equation with the fewest potential symbols is first u = Dummy() # used in solution checking for eq in ordered(failed, lambda _: len(_ok_syms(_))): newresult = [] bad_results = [] got_s = set() hit = False for r in result: # update eq with everything that is known so far eq2 = eq.subs(r) # if check is True then we see if it satisfies this # equation, otherwise we just accept it if check and r: b = checksol(u, u, eq2, minimal=True) if b is not None: # this solution is sufficient to know whether # it is valid or not so we either accept or # reject it, then continue if b: newresult.append(r) else: bad_results.append(r) continue # search for a symbol amongst those available that # can be solved for ok_syms = _ok_syms(eq2, sort=True) if not ok_syms: if r: newresult.append(r) break # skip as it's independent of desired symbols for s in ok_syms: try: soln = _solve(eq2, s, flags) except NotImplementedError: continue # put each solution in r and append the now-expanded # result in the new result list; use copy since the # solution for s in being added in-place for sol in soln: if got_s and any([ss in sol.free_symbols for ss in got_s]): # sol depends on previously solved symbols: discard it continue rnew = r.copy() for k, v in r.items(): rnew[k] = v.subs(s, sol) # and add this new solution rnew[s] = sol newresult.append(rnew) hit = True got_s.add(s) if not hit: raise NotImplementedError('could not solve %s' % eq2) else: result = newresult for b in bad_results: if b in result: result.remove(b) default_simplify = bool(failed) # rely on system-solvers to simplify if flags.get('simplify', default_simplify): for r in result: for k in r: r[k] = simplify(r[k]) flags['simplify'] = False # don't need to do so in checksol now if checkdens: result = [r for r in result if not any(checksol(d, r, flags) for d in dens)] if check and not linear: result = [r for r in result if not any(checksol(e, r, *flags) is False for e in exprs)] result = [r for r in result if r] if linear and result: result = result[0] return result def solve_linear(lhs, rhs=0, symbols=[], exclude=[]): r""" Return a tuple derived from ``f = lhs - rhs`` that is one of the following: ``(0, 1)``, ``(0, 0)``, ``(symbol, solution)``, ``(n, d)``. Explanation =========== ``(0, 1)`` meaning that ``f`` is independent of the symbols in symbols* that are not in exclude. ``(0, 0)`` meaning that there is no solution to the equation amongst the symbols given. If the first element of the tuple is not zero, then the function is guaranteed to be dependent on a symbol in symbols. ``(symbol, solution)`` where symbol appears linearly in the numerator of ``f``, is in symbols (if given), and is not in exclude (if given). No simplification is done to ``f`` other than a ``mul=True`` expansion, so the solution will correspond strictly to a unique solution. ``(n, d)`` where ``n`` and ``d`` are the numerator and denominator of ``f`` when the numerator was not linear in any symbol of interest; ``n`` will never be a symbol unless a solution for that symbol was found (in which case the second element is the solution, not the denominator). Examples ======== >>> from sympy.core.power import Pow >>> from sympy.polys.polytools import cancel ``f`` is independent of the symbols in symbols that are not in exclude: >>> from sympy.solvers.solvers import solve_linear >>> from sympy.abc import x, y, z >>> from sympy import cos, sin >>> eq = ycos(x)2 + ysin(x)*2 - y # = y(1 - 1) = 0 >>> solve_linear(eq) (0, 1) >>> eq = cos(x)2 + sin(x)2 # = 1 >>> solve_linear(eq) (0, 1) >>> solve_linear(x, exclude=[x]) (0, 1) The variable ``x`` appears as a linear variable in each of the following: >>> solve_linear(x + y2) (x, -y2) >>> solve_linear(1/x - y2) (x, y(-2)) When not linear in ``x`` or ``y`` then the numerator and denominator are returned: >>> solve_linear(x2/y2 - 3) (x*2 - 3y2, y2) If the numerator of the expression is a symbol, then ``(0, 0)`` is returned if the solution for that symbol would have set any denominator to 0: >>> eq = 1/(1/x - 2) >>> eq.as_numer_denom() (x, 1 - 2x) >>> solve_linear(eq) (0, 0) But automatic rewriting may cause a symbol in the denominator to appear in the numerator so a solution will be returned: >>> (1/x)-1 x >>> solve_linear((1/x)-1) (x, 0) Use an unevaluated expression to avoid this: >>> solve_linear(Pow(1/x, -1, evaluate=False)) (0, 0) If ``x`` is allowed to cancel in the following expression, then it appears to be linear in ``x``, but this sort of cancellation is not done by ``solve_linear`` so the solution will always satisfy the original expression without causing a division by zero error. >>> eq = x2(1/x - z2/x) >>> solve_linear(cancel(eq)) (x, 0) >>> solve_linear(eq) (x2(1 - z2), x) A list of symbols for which a solution is desired may be given: >>> solve_linear(x + y + z, symbols=[y]) (y, -x - z) A list of symbols to ignore may also be given: >>> solve_linear(x + y + z, exclude=[x]) (y, -x - z) (A solution for ``y`` is obtained because it is the first variable from the canonically sorted list of symbols that had a linear solution.) """ if isinstance(lhs, Equality): if rhs: raise ValueError(filldedent(''' If lhs is an Equality, rhs must be 0 but was %s''' % rhs)) rhs = lhs.rhs lhs = lhs.lhs dens = None eq = lhs - rhs n, d = eq.as_numer_denom() if not n: return S.Zero, S.One free = n.free_symbols if not symbols: symbols = free else: bad = [s for s in symbols if not s.is_Symbol] if bad: if len(bad) == 1: bad = bad[0] if len(symbols) == 1: eg = 'solve(%s, %s)' % (eq, symbols[0]) else: eg = 'solve(%s, %s)' % (eq, list(symbols)) raise ValueError(filldedent(''' solve_linear only handles symbols, not %s. To isolate non-symbols use solve, e.g. >>> %s <<<. ''' % (bad, eg))) symbols = free.intersection(symbols) symbols = symbols.difference(exclude) if not symbols: return S.Zero, S.One # derivatives are easy to do but tricky to analyze to see if they # are going to disallow a linear solution, so for simplicity we # just evaluate the ones that have the symbols of interest derivs = defaultdict(list) for der in n.atoms(Derivative): csym = der.free_symbols & symbols for c in csym: derivs[c].append(der) all_zero = True for xi in sorted(symbols, key=default_sort_key): # canonical order # if there are derivatives in this var, calculate them now if isinstance(derivs[xi], list): derivs[xi] = {der: der.doit() for der in derivs[xi]} newn = n.subs(derivs[xi]) dnewn_dxi = newn.diff(xi) # dnewn_dxi can be nonzero if it survives differentation by any # of its free symbols free = dnewn_dxi.free_symbols if dnewn_dxi and (not free or any(dnewn_dxi.diff(s) for s in free)): all_zero = False if dnewn_dxi is S.NaN: break if xi not in dnewn_dxi.free_symbols: vi = -1/dnewn_dxi(newn.subs(xi, 0)) if dens is None: dens = _simple_dens(eq, symbols) if not any(checksol(di, {xi: vi}, minimal=True) is True for di in dens): # simplify any trivial integral irep = [(i, i.doit()) for i in vi.atoms(Integral) if i.function.is_number] # do a slight bit of simplification vi = expand_mul(vi.subs(irep)) return xi, vi if all_zero: return S.Zero, S.One if n.is_Symbol: # no solution for this symbol was found return S.Zero, S.Zero return n, d def minsolve_linear_system(system, symbols, *flags): r""" Find a particular solution to a linear system. Explanation =========== In particular, try to find a solution with the minimal possible number of non-zero variables using a naive algorithm with exponential complexity. If ``quick=True``, a heuristic is used. """ quick = flags.get('quick', False) # Check if there are any non-zero solutions at all s0 = solve_linear_system(system, symbols, *flags) if not s0 or all(v == 0 for v in s0.values()): return s0 if quick: # We just solve the system and try to heuristically find a nice # solution. s = solve_linear_system(system, symbols) def update(determined, solution): delete = [] for k, v in solution.items(): solution[k] = v.subs(determined) if not solution[k].free_symbols: delete.append(k) determined[k] = solution[k] for k in delete: del solution[k] determined = {} update(determined, s) while s: # NOTE sort by default_sort_key to get deterministic result k = max((k for k in s.values()), key=lambda x: (len(x.free_symbols), default_sort_key(x))) x = max(k.free_symbols, key=default_sort_key) if len(k.free_symbols) != 1: determined[x] = S.Zero else: val = solve(k)[0] if val == 0 and all(v.subs(x, val) == 0 for v in s.values()): determined[x] = S.One else: determined[x] = val update(determined, s) return determined else: # We try to select n variables which we want to be non-zero. # All others will be assumed zero. We try to solve the modified system. # If there is a non-trivial solution, just set the free variables to # one. If we do this for increasing n, trying all combinations of # variables, we will find an optimal solution. # We speed up slightly by starting at one less than the number of # variables the quick method manages. from itertools import combinations from sympy.utilities.misc import debug N = len(symbols) bestsol = minsolve_linear_system(system, symbols, quick=True) n0 = len([x for x in bestsol.values() if x != 0]) for n in range(n0 - 1, 1, -1): debug('minsolve: %s' % n) thissol = None for nonzeros in combinations(list(range(N)), n): subm = Matrix([system.col(i).T for i in nonzeros] + [system.col(-1).T]).T s = solve_linear_system(subm, [symbols[i] for i in nonzeros]) if s and not all(v == 0 for v in s.values()): subs = [(symbols[v], S.One) for v in nonzeros] for k, v in s.items(): s[k] = v.subs(subs) for sym in symbols: if sym not in s: if symbols.index(sym) in nonzeros: s[sym] = S.One else: s[sym] = S.Zero thissol = s break if thissol is None: break bestsol = thissol return bestsol def solve_linear_system(system, symbols, flags): r""" Solve system of $N$ linear equations with $M$ variables, which means both under- and overdetermined systems are supported. Explanation =========== The possible number of solutions is zero, one, or infinite. Respectively, this procedure will return None or a dictionary with solutions. In the case of underdetermined systems, all arbitrary parameters are skipped. This may cause a situation in which an empty dictionary is returned. In that case, all symbols can be assigned arbitrary values. Input to this function is a $N\times M + 1$ matrix, which means it has to be in augmented form. If you prefer to enter $N$ equations and $M$ unknowns then use ``solve(Neqs, Msymbols)`` instead. Note: a local copy of the matrix is made by this routine so the matrix that is passed will not be modified. The algorithm used here is fraction-free Gaussian elimination, which results, after elimination, in an upper-triangular matrix. Then solutions are found using back-substitution. This approach is more efficient and compact than the Gauss-Jordan method. Examples ======== >>> from sympy import Matrix, solve_linear_system >>> from sympy.abc import x, y Solve the following system:: x + 4 y == 2 -2 x + y == 14 >>> system = Matrix(( (1, 4, 2), (-2, 1, 14))) >>> solve_linear_system(system, x, y) {x: -6, y: 2} A degenerate system returns an empty dictionary: >>> system = Matrix(( (0,0,0), (0,0,0) )) >>> solve_linear_system(system, x, y) {} """ assert system.shape[1] == len(symbols) + 1 # This is just a wrapper for solve_lin_sys eqs = list(system * Matrix(symbols + (-1,))) eqs, ring = sympy_eqs_to_ring(eqs, symbols) sol = solve_lin_sys(eqs, ring, _raw=False) if sol is not None: sol = {sym:val for sym, val in sol.items() if sym != val} return sol def solve_undetermined_coeffs(equ, coeffs, sym, *flags): r""" Solve equation of a type $p(x; a_1, \ldots, a_k) = q(x)$ where both $p$ and $q$ are univariate polynomials that depend on $k$ parameters. Explanation =========== The result of this function is a dictionary with symbolic values of those parameters with respect to coefficients in $q$. This function accepts both equations class instances and ordinary SymPy expressions. Specification of parameters and variables is obligatory for efficiency and simplicity reasons. Examples ======== >>> from sympy import Eq >>> from sympy.abc import a, b, c, x >>> from sympy.solvers import solve_undetermined_coeffs >>> solve_undetermined_coeffs(Eq(2ax + a+b, x), [a, b], x) {a: 1/2, b: -1/2} >>> solve_undetermined_coeffs(Eq(acx + a+b, x), [a, b], x) {a: 1/c, b: -1/c} """ if isinstance(equ, Equality): # got equation, so move all the # terms to the left hand side equ = equ.lhs - equ.rhs equ = cancel(equ).as_numer_denom()[0] system = list(collect(equ.expand(), sym, evaluate=False).values()) if not any(equ.has(sym) for equ in system): # consecutive powers in the input expressions have # been successfully collected, so solve remaining # system using Gaussian elimination algorithm return solve(system, coeffs, *flags) else: return None # no solutions def solve_linear_system_LU(matrix, syms): """ Solves the augmented matrix system using ``LUsolve`` and returns a dictionary in which solutions are keyed to the symbols of syms* as ordered. Explanation =========== The matrix must be invertible. Examples ======== >>> from sympy import Matrix >>> from sympy.abc import x, y, z >>> from sympy.solvers.solvers import solve_linear_system_LU >>> solve_linear_system_LU(Matrix([ ... [1, 2, 0, 1], ... [3, 2, 2, 1], ... [2, 0, 0, 1]]), [x, y, z]) {x: 1/2, y: 1/4, z: -1/2} See Also ======== LUsolve """ if matrix.rows != matrix.cols - 1: raise ValueError("Rows should be equal to columns - 1") A = matrix[:matrix.rows, :matrix.rows] b = matrix[:, matrix.cols - 1:] soln = A.LUsolve(b) solutions = {} for i in range(soln.rows): solutions[syms[i]] = soln[i, 0] return solutions def det_perm(M): """ Return the determinant of M by using permutations to select factors. Explanation =========== For sizes larger than 8 the number of permutations becomes prohibitively large, or if there are no symbols in the matrix, it is better to use the standard determinant routines (e.g., ``M.det()``.) See Also ======== det_minor det_quick """ args = [] s = True n = M.rows list_ = getattr(M, '_mat', None) if list_ is None: list_ = flatten(M.tolist()) for perm in generate_bell(n): fac = [] idx = 0 for j in perm: fac.append(list_[idx + j]) idx += n term = Mul(fac) # disaster with unevaluated Mul -- takes forever for n=7 args.append(term if s else -term) s = not s return Add(args) def det_minor(M): """ Return the ``det(M)`` computed from minors without introducing new nesting in products. See Also ======== det_perm det_quick """ n = M.rows if n == 2: return M[0, 0]M[1, 1] - M[1, 0]M[0, 1] else: return sum([(1, -1)[i % 2]Add([M[0, i]d for d in Add.make_args(det_minor(M.minor_submatrix(0, i)))]) if M[0, i] else S.Zero for i in range(n)]) def det_quick(M, method=None): """ Return ``det(M)`` assuming that either there are lots of zeros or the size of the matrix is small. If this assumption is not met, then the normal Matrix.det function will be used with method = ``method``. See Also ======== det_minor det_perm """ if any(i.has(Symbol) for i in M): if M.rows < 8 and all(i.has(Symbol) for i in M): return det_perm(M) return det_minor(M) else: return M.det(method=method) if method else M.det() def inv_quick(M): """Return the inverse of ``M``, assuming that either there are lots of zeros or the size of the matrix is small. """ from sympy.matrices import zeros if not all(i.is_Number for i in M): if not any(i.is_Number for i in M): det = lambda _: det_perm(_) else: det = lambda _: det_minor(_) else: return M.inv() n = M.rows d = det(M) if d == S.Zero: raise NonInvertibleMatrixError("Matrix det == 0; not invertible") ret = zeros(n) s1 = -1 for i in range(n): s = s1 = -s1 for j in range(n): di = det(M.minor_submatrix(i, j)) ret[j, i] = sdi/d s = -s return ret # these are functions that have multiple inverse values per period multi_inverses = { sin: lambda x: (asin(x), S.Pi - asin(x)), cos: lambda x: (acos(x), 2S.Pi - acos(x)), } def _tsolve(eq, sym, flags): """ Helper for ``_solve`` that solves a transcendental equation with respect to the given symbol. Various equations containing powers and logarithms, can be solved. There is currently no guarantee that all solutions will be returned or that a real solution will be favored over a complex one. Either a list of potential solutions will be returned or None will be returned (in the case that no method was known to get a solution for the equation). All other errors (like the inability to cast an expression as a Poly) are unhandled. Examples ======== >>> from sympy import log >>> from sympy.solvers.solvers import _tsolve as tsolve >>> from sympy.abc import x >>> tsolve(3(2x + 5) - 4, x) [-5/2 + log(2)/log(3), (-5log(3)/2 + log(2) + Ipi)/log(3)] >>> tsolve(log(x) + 2x, x) [LambertW(2)/2] """ if 'tsolve_saw' not in flags: flags['tsolve_saw'] = [] if eq in flags['tsolve_saw']: return None else: flags['tsolve_saw'].append(eq) rhs, lhs = _invert(eq, sym) if lhs == sym: return [rhs] try: if lhs.is_Add: # it's time to try factoring; powdenest is used # to try get powers in standard form for better factoring f = factor(powdenest(lhs - rhs)) if f.is_Mul: return _solve(f, sym, flags) if rhs: f = logcombine(lhs, force=flags.get('force', True)) if f.count(log) != lhs.count(log): if isinstance(f, log): return _solve(f.args[0] - exp(rhs), sym, flags) return _tsolve(f - rhs, sym, flags) elif lhs.is_Pow: if lhs.exp.is_Integer: if lhs - rhs != eq: return _solve(lhs - rhs, sym, flags) if sym not in lhs.exp.free_symbols: return _solve(lhs.base - rhs(1/lhs.exp), sym, flags) # _tsolve calls this with Dummy before passing the actual number in. if any(t.is_Dummy for t in rhs.free_symbols): raise NotImplementedError # _tsolve will call here again... # a * g(x) == 0 if not rhs: # f(x)g(x) only has solutions where f(x) == 0 and g(x) != 0 at # the same place sol_base = _solve(lhs.base, sym, flags) return [s for s in sol_base if lhs.exp.subs(sym, s) != 0] # a g(x) == b if not lhs.base.has(sym): if lhs.base == 0: return _solve(lhs.exp, sym, flags) if rhs != 0 else [] # Gets most solutions... if lhs.base == rhs.as_base_exp()[0]: # handles case when bases are equal sol = _solve(lhs.exp - rhs.as_base_exp()[1], sym, *flags) else: # handles cases when bases are not equal and exp # may or may not be equal sol = _solve(exp(log(lhs.base)lhs.exp)-exp(log(rhs)), sym, flags) # Check for duplicate solutions def equal(expr1, expr2): _ = Dummy() eq = checksol(expr1 - _, _, expr2) if eq is None: if nsimplify(expr1) != nsimplify(expr2): return False # they might be coincidentally the same # so check more rigorously eq = expr1.equals(expr2) return eq # Guess a rational exponent e_rat = nsimplify(log(abs(rhs))/log(abs(lhs.base))) e_rat = simplify(posify(e_rat)[0]) n, d = fraction(e_rat) if expand(lhs.basen - rhsd) == 0: sol = [s for s in sol if not equal(lhs.exp.subs(sym, s), e_rat)] sol.extend(_solve(lhs.exp - e_rat, sym, flags)) return list(ordered(set(sol))) # f(x) ** g(x) == c else: sol = [] logform = lhs.explog(lhs.base) - log(rhs) if logform != lhs - rhs: try: sol.extend(_solve(logform, sym, flags)) except NotImplementedError: pass # Collect possible solutions and check with substitution later. check = [] if rhs == 1: # f(x) * g(x) = 1 -- g(x)=0 or f(x)=+-1 check.extend(_solve(lhs.exp, sym, flags)) check.extend(_solve(lhs.base - 1, sym, flags)) check.extend(_solve(lhs.base + 1, sym, flags)) elif rhs.is_Rational: for d in (i for i in divisors(abs(rhs.p)) if i != 1): e, t = integer_log(rhs.p, d) if not t: continue # rhs.p != db for s in divisors(abs(rhs.q)): if se== rhs.q: r = Rational(d, s) check.extend(_solve(lhs.base - r, sym, flags)) check.extend(_solve(lhs.base + r, sym, flags)) check.extend(_solve(lhs.exp - e, sym, flags)) elif rhs.is_irrational: b_l, e_l = lhs.base.as_base_exp() n, d = (e_llhs.exp).as_numer_denom() b, e = sqrtdenest(rhs).as_base_exp() check = [sqrtdenest(i) for i in (_solve(lhs.base - b, sym, flags))] check.extend([sqrtdenest(i) for i in (_solve(lhs.exp - e, sym, flags))]) if e_ld != 1: check.extend(_solve(b_ln - rhs(e_ld), sym, flags)) for s in check: ok = checksol(eq, sym, s) if ok is None: ok = eq.subs(sym, s).equals(0) if ok: sol.append(s) return list(ordered(set(sol))) elif lhs.is_Function and len(lhs.args) == 1: if lhs.func in multi_inverses: # sin(x) = 1/3 -> x - asin(1/3) & x - (pi - asin(1/3)) soln = [] for i in multi_inverses[lhs.func](rhs): soln.extend(_solve(lhs.args[0] - i, sym, flags)) return list(ordered(soln)) elif lhs.func == LambertW: return _solve(lhs.args[0] - rhsexp(rhs), sym, flags) rewrite = lhs.rewrite(exp) if rewrite != lhs: return _solve(rewrite - rhs, sym, flags) except NotImplementedError: pass # maybe it is a lambert pattern if flags.pop('bivariate', True): # lambert forms may need some help being recognized, e.g. changing # 2*(3x) + x*3log(2)*3 + 3x*2log(2)*2 + 3xlog(2) + 1 # to 2(3x) + (xlog(2) + 1)3 g = _filtered_gens(eq.as_poly(), sym) up_or_log = set() for gi in g: if isinstance(gi, exp) or isinstance(gi, log): up_or_log.add(gi) elif gi.is_Pow: gisimp = powdenest(expand_power_exp(gi)) if gisimp.is_Pow and sym in gisimp.exp.free_symbols: up_or_log.add(gi) eq_down = expand_log(expand_power_exp(eq)).subs( dict(list(zip(up_or_log, [0]len(up_or_log))))) eq = expand_power_exp(factor(eq_down, deep=True) + (eq - eq_down)) rhs, lhs = _invert(eq, sym) if lhs.has(sym): try: poly = lhs.as_poly() g = _filtered_gens(poly, sym) _eq = lhs - rhs sols = _solve_lambert(_eq, sym, g) # use a simplified form if it satisfies eq # and has fewer operations for n, s in enumerate(sols): ns = nsimplify(s) if ns != s and ns.count_ops() <= s.count_ops(): ok = checksol(_eq, sym, ns) if ok is None: ok = _eq.subs(sym, ns).equals(0) if ok: sols[n] = ns return sols except NotImplementedError: # maybe it's a convoluted function if len(g) == 2: try: gpu = bivariate_type(lhs - rhs, g) if gpu is None: raise NotImplementedError g, p, u = gpu flags['bivariate'] = False inversion = _tsolve(g - u, sym, flags) if inversion: sol = _solve(p, u, flags) return list(ordered({i.subs(u, s) for i in inversion for s in sol})) except NotImplementedError: pass else: pass if flags.pop('force', True): flags['force'] = False pos, reps = posify(lhs - rhs) if rhs == S.ComplexInfinity: return [] for u, s in reps.items(): if s == sym: break else: u = sym if pos.has(u): try: soln = _solve(pos, u, flags) return list(ordered([s.subs(reps) for s in soln])) except NotImplementedError: pass else: pass # here for coverage return # here for coverage # TODO: option for calculating J numerically @conserve_mpmath_dps def nsolve(args, dict=False, kwargs): r""" Solve a nonlinear equation system numerically: ``nsolve(f, [args,] x0, modules=['mpmath'], kwargs)``. Explanation =========== ``f`` is a vector function of symbolic expressions representing the system. args are the variables. If there is only one variable, this argument can be omitted. ``x0`` is a starting vector close to a solution. Use the modules keyword to specify which modules should be used to evaluate the function and the Jacobian matrix. Make sure to use a module that supports matrices. For more information on the syntax, please see the docstring of ``lambdify``. If the keyword arguments contain ``dict=True`` (default is False) ``nsolve`` will return a list (perhaps empty) of solution mappings. This might be especially useful if you want to use ``nsolve`` as a fallback to solve since using the dict argument for both methods produces return values of consistent type structure. Please note: to keep this consistent with ``solve``, the solution will be returned in a list even though ``nsolve`` (currently at least) only finds one solution at a time. Overdetermined systems are supported. Examples ======== >>> from sympy import Symbol, nsolve >>> import mpmath >>> mpmath.mp.dps = 15 >>> x1 = Symbol('x1') >>> x2 = Symbol('x2') >>> f1 = 3 * x1*2 - 2 x22 - 1 >>> f2 = x12 - 2 * x1 + x2*2 + 2 x2 - 8 >>> print(nsolve((f1, f2), (x1, x2), (-1, 1))) Matrix([[-1.19287309935246], [1.27844411169911]]) For one-dimensional functions the syntax is simplified: >>> from sympy import sin, nsolve >>> from sympy.abc import x >>> nsolve(sin(x), x, 2) 3.14159265358979 >>> nsolve(sin(x), 2) 3.14159265358979 To solve with higher precision than the default, use the prec argument: >>> from sympy import cos >>> nsolve(cos(x) - x, 1) 0.739085133215161 >>> nsolve(cos(x) - x, 1, prec=50) 0.73908513321516064165531208767387340401341175890076 >>> cos(_) 0.73908513321516064165531208767387340401341175890076 To solve for complex roots of real functions, a nonreal initial point must be specified: >>> from sympy import I >>> nsolve(x*2 + 2, I) 1.4142135623731I ``mpmath.findroot`` is used and you can find their more extensive documentation, especially concerning keyword parameters and available solvers. Note, however, that functions which are very steep near the root, the verification of the solution may fail. In this case you should use the flag ``verify=False`` and independently verify the solution. >>> from sympy import cos, cosh >>> f = cos(x)cosh(x) - 1 >>> nsolve(f, 3.14100) Traceback (most recent call last): ... ValueError: Could not find root within given tolerance. (1.39267e+230 > 2.1684e-19) >>> ans = nsolve(f, 3.14100, verify=False); ans 312.588469032184 >>> f.subs(x, ans).n(2) 2.1e+121 >>> (f/f.diff(x)).subs(x, ans).n(2) 7.4e-15 One might safely skip the verification if bounds of the root are known and a bisection method is used: >>> bounds = lambda i: (3.14i, 3.14(i + 1)) >>> nsolve(f, bounds(100), solver='bisect', verify=False) 315.730061685774 Alternatively, a function may be better behaved when the denominator is ignored. Since this is not always the case, however, the decision of what function to use is left to the discretion of the user. >>> eq = x2/(1 - x)/(1 - 2x)2 - 100 >>> nsolve(eq, 0.46) Traceback (most recent call last): ... ValueError: Could not find root within given tolerance. (10000 > 2.1684e-19) Try another starting point or tweak arguments. >>> nsolve(eq.as_numer_denom()[0], 0.46) 0.46792545969349058 """ # there are several other SymPy functions that use method= so # guard against that here if 'method' in kwargs: raise ValueError(filldedent(''' Keyword "method" should not be used in this context. When using some mpmath solvers directly, the keyword "method" is used, but when using nsolve (and findroot) the keyword to use is "solver".''')) if 'prec' in kwargs: prec = kwargs.pop('prec') import mpmath mpmath.mp.dps = prec else: prec = None # keyword argument to return result as a dictionary as_dict = dict from builtins import dict # to unhide the builtin # interpret arguments if len(args) == 3: f = args[0] fargs = args[1] x0 = args[2] if iterable(fargs) and iterable(x0): if len(x0) != len(fargs): raise TypeError('nsolve expected exactly %i guess vectors, got %i' % (len(fargs), len(x0))) elif len(args) == 2: f = args[0] fargs = None x0 = args[1] if iterable(f): raise TypeError('nsolve expected 3 arguments, got 2') elif len(args) < 2: raise TypeError('nsolve expected at least 2 arguments, got %i' % len(args)) else: raise TypeError('nsolve expected at most 3 arguments, got %i' % len(args)) modules = kwargs.get('modules', ['mpmath']) if iterable(f): f = list(f) for i, fi in enumerate(f): if isinstance(fi, Equality): f[i] = fi.lhs - fi.rhs f = Matrix(f).T if iterable(x0): x0 = list(x0) if not isinstance(f, Matrix): # assume it's a sympy expression if isinstance(f, Equality): f = f.lhs - f.rhs syms = f.free_symbols if fargs is None: fargs = syms.copy().pop() if not (len(syms) == 1 and (fargs in syms or fargs[0] in syms)): raise ValueError(filldedent(''' expected a one-dimensional and numerical function''')) # the function is much better behaved if there is no denominator # but sending the numerator is left to the user since sometimes # the function is better behaved when the denominator is present # e.g., issue 11768 f = lambdify(fargs, f, modules) x = sympify(findroot(f, x0, kwargs)) if as_dict: return [{fargs: x}] return x if len(fargs) > f.cols: raise NotImplementedError(filldedent(''' need at least as many equations as variables''')) verbose = kwargs.get('verbose', False) if verbose: print('f(x):') print(f) # derive Jacobian J = f.jacobian(fargs) if verbose: print('J(x):') print(J) # create functions f = lambdify(fargs, f.T, modules) J = lambdify(fargs, J, modules) # solve the system numerically x = findroot(f, x0, J=J, *kwargs) if as_dict: return [dict(zip(fargs, [sympify(xi) for xi in x]))] return Matrix(x) def _invert(eq, symbols, *kwargs): """ Return tuple (i, d) where ``i`` is independent of symbols* and ``d`` contains symbols. Explanation =========== ``i`` and ``d`` are obtained after recursively using algebraic inversion until an uninvertible ``d`` remains. If there are no free symbols then ``d`` will be zero. Some (but not necessarily all) solutions to the expression ``i - d`` will be related to the solutions of the original expression. Examples ======== >>> from sympy.solvers.solvers import _invert as invert >>> from sympy import sqrt, cos >>> from sympy.abc import x, y >>> invert(x - 3) (3, x) >>> invert(3) (3, 0) >>> invert(2cos(x) - 1) (1/2, cos(x)) >>> invert(sqrt(x) - 3) (3, sqrt(x)) >>> invert(sqrt(x) + y, x) (-y, sqrt(x)) >>> invert(sqrt(x) + y, y) (-sqrt(x), y) >>> invert(sqrt(x) + y, x, y) (0, sqrt(x) + y) If there is more than one symbol in a power's base and the exponent is not an Integer, then the principal root will be used for the inversion: >>> invert(sqrt(x + y) - 2) (4, x + y) >>> invert(sqrt(x + y) - 2) (4, x + y) If the exponent is an Integer, setting ``integer_power`` to True will force the principal root to be selected: >>> invert(x2 - 4, integer_power=True) (2, x) """ eq = sympify(eq) if eq.args: # make sure we are working with flat eq eq = eq.func(eq.args) free = eq.free_symbols if not symbols: symbols = free if not free & set(symbols): return eq, S.Zero dointpow = bool(kwargs.get('integer_power', False)) lhs = eq rhs = S.Zero while True: was = lhs while True: indep, dep = lhs.as_independent(symbols) # dep + indep == rhs if lhs.is_Add: # this indicates we have done it all if indep.is_zero: break lhs = dep rhs -= indep # dep indep == rhs else: # this indicates we have done it all if indep is S.One: break lhs = dep rhs /= indep # collect like-terms in symbols if lhs.is_Add: terms = {} for a in lhs.args: i, d = a.as_independent(symbols) terms.setdefault(d, []).append(i) if any(len(v) > 1 for v in terms.values()): args = [] for d, i in terms.items(): if len(i) > 1: args.append(Add(i)d) else: args.append(i[0]d) lhs = Add(args) # if it's a two-term Add with rhs = 0 and two powers we can get the # dependent terms together, e.g. 3f(x) + 2g(x) -> f(x)/g(x) = -2/3 if lhs.is_Add and not rhs and len(lhs.args) == 2 and \ not lhs.is_polynomial(symbols): a, b = ordered(lhs.args) ai, ad = a.as_independent(symbols) bi, bd = b.as_independent(symbols) if any(_ispow(i) for i in (ad, bd)): a_base, a_exp = ad.as_base_exp() b_base, b_exp = bd.as_base_exp() if a_base == b_base: # a = -b lhs = powsimp(powdenest(ad/bd)) rhs = -bi/ai else: rat = ad/bd _lhs = powsimp(ad/bd) if _lhs != rat: lhs = _lhs rhs = -bi/ai elif ai == -bi: if isinstance(ad, Function) and ad.func == bd.func: if len(ad.args) == len(bd.args) == 1: lhs = ad.args[0] - bd.args[0] elif len(ad.args) == len(bd.args): # should be able to solve # f(x, y) - f(2 - x, 0) == 0 -> x == 1 raise NotImplementedError( 'equal function with more than 1 argument') else: raise ValueError( 'function with different numbers of args') elif lhs.is_Mul and any(_ispow(a) for a in lhs.args): lhs = powsimp(powdenest(lhs)) if lhs.is_Function: if hasattr(lhs, 'inverse') and len(lhs.args) == 1: # -1 # f(x) = g -> x = f (g) # # /!\ inverse should not be defined if there are multiple values # for the function -- these are handled in _tsolve # rhs = lhs.inverse()(rhs) lhs = lhs.args[0] elif isinstance(lhs, atan2): y, x = lhs.args lhs = 2atan(y/(sqrt(x2 + y2) + x)) elif lhs.func == rhs.func: if len(lhs.args) == len(rhs.args) == 1: lhs = lhs.args[0] rhs = rhs.args[0] elif len(lhs.args) == len(rhs.args): # should be able to solve # f(x, y) == f(2, 3) -> x == 2 # f(x, x + y) == f(2, 3) -> x == 2 raise NotImplementedError( 'equal function with more than 1 argument') else: raise ValueError( 'function with different numbers of args') if rhs and lhs.is_Pow and lhs.exp.is_Integer and lhs.exp < 0: lhs = 1/lhs rhs = 1/rhs # basea = b -> base = b(1/a) if # a is an Integer and dointpow=True (this gives real branch of root) # a is not an Integer and the equation is multivariate and the # base has more than 1 symbol in it # The rationale for this is that right now the multi-system solvers # doesn't try to resolve generators to see, for example, if the whole # system is written in terms of sqrt(x + y) so it will just fail, so we # do that step here. if lhs.is_Pow and ( lhs.exp.is_Integer and dointpow or not lhs.exp.is_Integer and len(symbols) > 1 and len(lhs.base.free_symbols & set(symbols)) > 1): rhs = rhs(1/lhs.exp) lhs = lhs.base if lhs == was: break return rhs, lhs def unrad(eq, syms, *flags): """ Remove radicals with symbolic arguments and return (eq, cov), None, or raise an error. Explanation =========== None is returned if there are no radicals to remove. NotImplementedError is raised if there are radicals and they cannot be removed or if the relationship between the original symbols and the change of variable needed to rewrite the system as a polynomial cannot be solved. Otherwise the tuple, ``(eq, cov)``, is returned where: eq, ``cov`` eq* is an equation without radicals (in the symbol(s) of interest) whose solutions are a superset of the solutions to the original expression. eq might be rewritten in terms of a new variable; the relationship to the original variables is given by ``cov`` which is a list containing ``v`` and ``vp - b`` where ``p`` is the power needed to clear the radical and ``b`` is the radical now expressed as a polynomial in the symbols of interest. For example, for sqrt(2 - x) the tuple would be ``(c, c2 - 2 + x)``. The solutions of eq will contain solutions to the original equation (if there are any). syms An iterable of symbols which, if provided, will limit the focus of radical removal: only radicals with one or more of the symbols of interest will be cleared. All free symbols are used if syms is not set. flags are used internally for communication during recursive calls. Two options are also recognized: ``take``, when defined, is interpreted as a single-argument function that returns True if a given Pow should be handled. Radicals can be removed from an expression if: * All bases of the radicals are the same; a change of variables is done in this case. * If all radicals appear in one term of the expression. * There are only four terms with sqrt() factors or there are less than four terms having sqrt() factors. * There are only two terms with radicals. Examples ======== >>> from sympy.solvers.solvers import unrad >>> from sympy.abc import x >>> from sympy import sqrt, Rational, root >>> unrad(sqrt(x)xRational(1, 3) + 2) (x5 - 64, []) >>> unrad(sqrt(x) + root(x + 1, 3)) (x3 - x2 - 2x - 1, []) >>> eq = sqrt(x) + root(x, 3) - 2 >>> unrad(eq) (_p3 + _p2 - 2, [_p, _p6 - x]) """ uflags = dict(check=False, simplify=False) def _cov(p, e): if cov: # XXX - uncovered oldp, olde = cov if Poly(e, p).degree(p) in (1, 2): cov[:] = [p, olde.subs(oldp, _solve(e, p, uflags)[0])] else: raise NotImplementedError else: cov[:] = [p, e] def _canonical(eq, cov): if cov: # change symbol to vanilla so no solutions are eliminated p, e = cov rep = {p: Dummy(p.name)} eq = eq.xreplace(rep) cov = [p.xreplace(rep), e.xreplace(rep)] # remove constants and powers of factors since these don't change # the location of the root; XXX should factor or factor_terms be used? eq = factor_terms(_mexpand(eq.as_numer_denom()[0], recursive=True), clear=True) if eq.is_Mul: args = [] for f in eq.args: if f.is_number: continue if f.is_Pow and _take(f, True): args.append(f.base) else: args.append(f) eq = Mul(args) # leave as Mul for more efficient solving # make the sign canonical free = eq.free_symbols if len(free) == 1: if eq.coeff(free.pop()degree(eq)).could_extract_minus_sign(): eq = -eq elif eq.could_extract_minus_sign(): eq = -eq return eq, cov def _Q(pow): # return leading Rational of denominator of Pow's exponent c = pow.as_base_exp()[1].as_coeff_Mul()[0] if not c.is_Rational: return S.One return c.q # define the _take method that will determine whether a term is of interest def _take(d, take_int_pow): # return True if coefficient of any factor's exponent's den is not 1 for pow in Mul.make_args(d): if not (pow.is_Symbol or pow.is_Pow): continue b, e = pow.as_base_exp() if not b.has(syms): continue if not take_int_pow and _Q(pow) == 1: continue free = pow.free_symbols if free.intersection(syms): return True return False _take = flags.setdefault('_take', _take) cov, nwas, rpt = [flags.setdefault(k, v) for k, v in sorted(dict(cov=[], n=None, rpt=0).items())] # preconditioning eq = powdenest(factor_terms(eq, radical=True, clear=True)) if isinstance(eq, Relational): eq, d = eq, 1 else: eq, d = eq.as_numer_denom() eq = _mexpand(eq, recursive=True) if eq.is_number: return syms = set(syms) or eq.free_symbols poly = eq.as_poly() gens = [g for g in poly.gens if _take(g, True)] if not gens: return # check for trivial case # - already a polynomial in integer powers if all(_Q(g) == 1 for g in gens): if (len(gens) == len(poly.gens) and d!=1): return eq, [] else: return # - an exponent has a symbol of interest (don't handle) if any(g.as_base_exp()[1].has(syms) for g in gens): return def _rads_bases_lcm(poly): # if all the bases are the same or all the radicals are in one # term, `lcm` will be the lcm of the denominators of the # exponents of the radicals lcm = 1 rads = set() bases = set() for g in poly.gens: if not _take(g, False): continue q = _Q(g) if q != 1: rads.add(g) lcm = ilcm(lcm, q) bases.add(g.base) return rads, bases, lcm rads, bases, lcm = _rads_bases_lcm(poly) if not rads: return covsym = Dummy('p', nonnegative=True) # only keep in syms symbols that actually appear in radicals; # and update gens newsyms = set() for r in rads: newsyms.update(syms & r.free_symbols) if newsyms != syms: syms = newsyms gens = [g for g in gens if g.free_symbols & syms] # get terms together that have common generators drad = dict(list(zip(rads, list(range(len(rads)))))) rterms = {(): []} args = Add.make_args(poly.as_expr()) for t in args: if _take(t, False): common = set(t.as_poly().gens).intersection(rads) key = tuple(sorted([drad[i] for i in common])) else: key = () rterms.setdefault(key, []).append(t) others = Add(rterms.pop(())) rterms = [Add(rterms[k]) for k in rterms.keys()] # the output will depend on the order terms are processed, so # make it canonical quickly rterms = list(reversed(list(ordered(rterms)))) ok = False # we don't have a solution yet depth = sqrt_depth(eq) if len(rterms) == 1 and not (rterms[0].is_Add and lcm > 2): eq = rterms[0]lcm - ((-others)lcm) ok = True else: if len(rterms) == 1 and rterms[0].is_Add: rterms = list(rterms[0].args) if len(bases) == 1: b = bases.pop() if len(syms) > 1: free = b.free_symbols x = {g for g in gens if g.is_Symbol} & free if not x: x = free x = ordered(x) else: x = syms x = list(x)[0] try: inv = _solve(covsymlcm - b, x, uflags) if not inv: raise NotImplementedError eq = poly.as_expr().subs(b, covsymlcm).subs(x, inv[0]) _cov(covsym, covsymlcm - b) return _canonical(eq, cov) except NotImplementedError: pass else: # no longer consider integer powers as generators gens = [g for g in gens if _Q(g) != 1] if len(rterms) == 2: if not others: eq = rterms[0]lcm - (-rterms[1])lcm ok = True elif not log(lcm, 2).is_Integer: # the lcm-is-power-of-two case is handled below r0, r1 = rterms if flags.get('_reverse', False): r1, r0 = r0, r1 i0 = _rads0, _bases0, lcm0 = _rads_bases_lcm(r0.as_poly()) i1 = _rads1, _bases1, lcm1 = _rads_bases_lcm(r1.as_poly()) for reverse in range(2): if reverse: i0, i1 = i1, i0 r0, r1 = r1, r0 _rads1, _, lcm1 = i1 _rads1 = Mul(_rads1) t1 = _rads1lcm1 c = covsymlcm1 - t1 for x in syms: try: sol = _solve(c, x, *uflags) if not sol: raise NotImplementedError neweq = r0.subs(x, sol[0]) + covsymr1/_rads1 + \ others tmp = unrad(neweq, covsym) if tmp: eq, newcov = tmp if newcov: newp, newc = newcov _cov(newp, c.subs(covsym, _solve(newc, covsym, uflags)[0])) else: _cov(covsym, c) else: eq = neweq _cov(covsym, c) ok = True break except NotImplementedError: if reverse: raise NotImplementedError( 'no successful change of variable found') else: pass if ok: break elif len(rterms) == 3: # two cube roots and another with order less than 5 # (so an analytical solution can be found) or a base # that matches one of the cube root bases info = [_rads_bases_lcm(i.as_poly()) for i in rterms] RAD = 0 BASES = 1 LCM = 2 if info[0][LCM] != 3: info.append(info.pop(0)) rterms.append(rterms.pop(0)) elif info[1][LCM] != 3: info.append(info.pop(1)) rterms.append(rterms.pop(1)) if info[0][LCM] == info[1][LCM] == 3: if info[1][BASES] != info[2][BASES]: info[0], info[1] = info[1], info[0] rterms[0], rterms[1] = rterms[1], rterms[0] if info[1][BASES] == info[2][BASES]: eq = rterms[0]3 + (rterms[1] + rterms[2] + others)*3 ok = True elif info[2][LCM] < 5: # aroot(A, 3) + broot(B, 3) + others = c a, b, c, d, A, B = [Dummy(i) for i in 'abcdAB'] # zz represents the unraded expression into which the # specifics for this case are substituted zz = (c - d)(A*3a*9 + 3A*2Ba6b*3 - 3A*2a*6c*3 + 9A*2a*6c*2d - 9A2a*6cd2 + 3A*2a*6d*3 + 3AB2a*3b*6 + 21ABa*3b*3c*3 - 63ABa*3b*3c*2d + 63ABa3b*3cd2 - 21ABa*3b*3d*3 + 3Aa3c*6 - 18Aa3c*5d + 45Aa*3c*4d*2 - 60Aa3c*3d*3 + 45Aa3c*2d*4 - 18Aa3cd5 + 3Aa3d6 + B3b9 - 3B*2b*6c*3 + 9B*2b*6c*2d - 9B2b*6cd2 + 3B*2b*6d*3 + 3Bb3c*6 - 18Bb3c*5d + 45Bb*3c*4d*2 - 60Bb3c*3d*3 + 45Bb3c*2d*4 - 18Bb3cd5 + 3Bb3d6 - c9 + 9c8d - 36c7d*2 + 84c*6d*3 - 126c*5d*4 + 126c*4d*5 - 84c*3d*6 + 36c*2d*7 - 9cd8 + d9) def _t(i): b = Mul(info[i][RAD]) return cancel(rterms[i]/b), Mul(info[i][BASES]) aa, AA = _t(0) bb, BB = _t(1) cc = -rterms[2] dd = others eq = zz.xreplace(dict(zip( (a, A, b, B, c, d), (aa, AA, bb, BB, cc, dd)))) ok = True # handle power-of-2 cases if not ok: if log(lcm, 2).is_Integer and (not others and len(rterms) == 4 or len(rterms) < 4): def _norm2(a, b): return a2 + b2 + 2ab if len(rterms) == 4: # (r0+r1)2 - (r2+r3)2 r0, r1, r2, r3 = rterms eq = _norm2(r0, r1) - _norm2(r2, r3) ok = True elif len(rterms) == 3: # (r1+r2)2 - (r0+others)2 r0, r1, r2 = rterms eq = _norm2(r1, r2) - _norm2(r0, others) ok = True elif len(rterms) == 2: # r02 - (r1+others)2 r0, r1 = rterms eq = r02 - _norm2(r1, others) ok = True new_depth = sqrt_depth(eq) if ok else depth rpt += 1 # XXX how many repeats with others unchanging is enough? if not ok or ( nwas is not None and len(rterms) == nwas and new_depth is not None and new_depth == depth and rpt > 3): raise NotImplementedError('Cannot remove all radicals') flags.update(dict(cov=cov, n=len(rterms), rpt=rpt)) neq = unrad(eq, syms, **flags) if neq: eq, cov = neq eq, cov = _canonical(eq, cov) return eq, cov from sympy.solvers.bivariate import ( bivariate_type, _solve_lambert, _filtered_gens)
125b7cab1477fa0901681cd031d9cd8b30882465b3e85a56ba9585313f42c370	from sympy import Order, S, log, limit, lcm_list, im, re, Dummy from sympy.core import Add, Mul, Pow from sympy.core.basic import Basic from sympy.core.compatibility import iterable from sympy.core.expr import AtomicExpr, Expr from sympy.core.function import expand_mul from sympy.core.numbers import _sympifyit, oo from sympy.core.relational import is_le, is_lt, is_ge, is_gt from sympy.core.sympify import _sympify from sympy.functions.elementary.miscellaneous import Min, Max from sympy.logic.boolalg import And from sympy.sets.sets import (Interval, Intersection, FiniteSet, Union, Complement, EmptySet) from sympy.sets.fancysets import ImageSet from sympy.solvers.inequalities import solve_univariate_inequality from sympy.utilities import filldedent from sympy.multipledispatch import dispatch def continuous_domain(f, symbol, domain): """ Returns the intervals in the given domain for which the function is continuous. This method is limited by the ability to determine the various singularities and discontinuities of the given function. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the intervals are to be determined. domain : Interval The domain over which the continuity of the symbol has to be checked. Examples ======== >>> from sympy import Symbol, S, tan, log, pi, sqrt >>> from sympy.sets import Interval >>> from sympy.calculus.util import continuous_domain >>> x = Symbol('x') >>> continuous_domain(1/x, x, S.Reals) Union(Interval.open(-oo, 0), Interval.open(0, oo)) >>> continuous_domain(tan(x), x, Interval(0, pi)) Union(Interval.Ropen(0, pi/2), Interval.Lopen(pi/2, pi)) >>> continuous_domain(sqrt(x - 2), x, Interval(-5, 5)) Interval(2, 5) >>> continuous_domain(log(2x - 1), x, S.Reals) Interval.open(1/2, oo) Returns ======= Interval Union of all intervals where the function is continuous. Raises ====== NotImplementedError If the method to determine continuity of such a function has not yet been developed. """ from sympy.solvers.inequalities import solve_univariate_inequality from sympy.solvers.solveset import _has_rational_power from sympy.calculus.singularities import singularities if domain.is_subset(S.Reals): constrained_interval = domain for atom in f.atoms(Pow): predicate, denomin = _has_rational_power(atom, symbol) if predicate and denomin == 2: constraint = solve_univariate_inequality(atom.base >= 0, symbol).as_set() constrained_interval = Intersection(constraint, constrained_interval) for atom in f.atoms(log): constraint = solve_univariate_inequality(atom.args[0] > 0, symbol).as_set() constrained_interval = Intersection(constraint, constrained_interval) return constrained_interval - singularities(f, symbol, domain) def function_range(f, symbol, domain): """ Finds the range of a function in a given domain. This method is limited by the ability to determine the singularities and determine limits. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the range of function is to be determined. domain : Interval The domain under which the range of the function has to be found. Examples ======== >>> from sympy import Symbol, S, exp, log, pi, sqrt, sin, tan >>> from sympy.sets import Interval >>> from sympy.calculus.util import function_range >>> x = Symbol('x') >>> function_range(sin(x), x, Interval(0, 2pi)) Interval(-1, 1) >>> function_range(tan(x), x, Interval(-pi/2, pi/2)) Interval(-oo, oo) >>> function_range(1/x, x, S.Reals) Union(Interval.open(-oo, 0), Interval.open(0, oo)) >>> function_range(exp(x), x, S.Reals) Interval.open(0, oo) >>> function_range(log(x), x, S.Reals) Interval(-oo, oo) >>> function_range(sqrt(x), x , Interval(-5, 9)) Interval(0, 3) Returns ======= Interval Union of all ranges for all intervals under domain where function is continuous. Raises ====== NotImplementedError If any of the intervals, in the given domain, for which function is continuous are not finite or real, OR if the critical points of the function on the domain can't be found. """ from sympy.solvers.solveset import solveset if isinstance(domain, EmptySet): return S.EmptySet period = periodicity(f, symbol) if period == S.Zero: # the expression is constant wrt symbol return FiniteSet(f.expand()) if period is not None: if isinstance(domain, Interval): if (domain.inf - domain.sup).is_infinite: domain = Interval(0, period) elif isinstance(domain, Union): for sub_dom in domain.args: if isinstance(sub_dom, Interval) and \ ((sub_dom.inf - sub_dom.sup).is_infinite): domain = Interval(0, period) intervals = continuous_domain(f, symbol, domain) range_int = S.EmptySet if isinstance(intervals,(Interval, FiniteSet)): interval_iter = (intervals,) elif isinstance(intervals, Union): interval_iter = intervals.args else: raise NotImplementedError(filldedent(''' Unable to find range for the given domain. ''')) for interval in interval_iter: if isinstance(interval, FiniteSet): for singleton in interval: if singleton in domain: range_int += FiniteSet(f.subs(symbol, singleton)) elif isinstance(interval, Interval): vals = S.EmptySet critical_points = S.EmptySet critical_values = S.EmptySet bounds = ((interval.left_open, interval.inf, '+'), (interval.right_open, interval.sup, '-')) for is_open, limit_point, direction in bounds: if is_open: critical_values += FiniteSet(limit(f, symbol, limit_point, direction)) vals += critical_values else: vals += FiniteSet(f.subs(symbol, limit_point)) solution = solveset(f.diff(symbol), symbol, interval) if not iterable(solution): raise NotImplementedError( 'Unable to find critical points for {}'.format(f)) if isinstance(solution, ImageSet): raise NotImplementedError( 'Infinite number of critical points for {}'.format(f)) critical_points += solution for critical_point in critical_points: vals += FiniteSet(f.subs(symbol, critical_point)) left_open, right_open = False, False if critical_values is not S.EmptySet: if critical_values.inf == vals.inf: left_open = True if critical_values.sup == vals.sup: right_open = True range_int += Interval(vals.inf, vals.sup, left_open, right_open) else: raise NotImplementedError(filldedent(''' Unable to find range for the given domain. ''')) return range_int def not_empty_in(finset_intersection, syms): """ Finds the domain of the functions in `finite_set` in which the `finite_set` is not-empty Parameters ========== finset_intersection : The unevaluated intersection of FiniteSet containing real-valued functions with Union of Sets syms : Tuple of symbols Symbol for which domain is to be found Raises ====== NotImplementedError The algorithms to find the non-emptiness of the given FiniteSet are not yet implemented. ValueError The input is not valid. RuntimeError It is a bug, please report it to the github issue tracker (https://github.com/sympy/sympy/issues). Examples ======== >>> from sympy import FiniteSet, Interval, not_empty_in, oo >>> from sympy.abc import x >>> not_empty_in(FiniteSet(x/2).intersect(Interval(0, 1)), x) Interval(0, 2) >>> not_empty_in(FiniteSet(x, x2).intersect(Interval(1, 2)), x) Union(Interval(1, 2), Interval(-sqrt(2), -1)) >>> not_empty_in(FiniteSet(x2/(x + 2)).intersect(Interval(1, oo)), x) Union(Interval.Lopen(-2, -1), Interval(2, oo)) """ # TODO: handle piecewise defined functions # TODO: handle transcendental functions # TODO: handle multivariate functions if len(syms) == 0: raise ValueError("One or more symbols must be given in syms.") if finset_intersection is S.EmptySet: return S.EmptySet if isinstance(finset_intersection, Union): elm_in_sets = finset_intersection.args[0] return Union(not_empty_in(finset_intersection.args[1], syms), elm_in_sets) if isinstance(finset_intersection, FiniteSet): finite_set = finset_intersection _sets = S.Reals else: finite_set = finset_intersection.args[1] _sets = finset_intersection.args[0] if not isinstance(finite_set, FiniteSet): raise ValueError('A FiniteSet must be given, not %s: %s' % (type(finite_set), finite_set)) if len(syms) == 1: symb = syms[0] else: raise NotImplementedError('more than one variables %s not handled' % (syms,)) def elm_domain(expr, intrvl): """ Finds the domain of an expression in any given interval """ from sympy.solvers.solveset import solveset _start = intrvl.start _end = intrvl.end _singularities = solveset(expr.as_numer_denom()[1], symb, domain=S.Reals) if intrvl.right_open: if _end is S.Infinity: _domain1 = S.Reals else: _domain1 = solveset(expr < _end, symb, domain=S.Reals) else: _domain1 = solveset(expr <= _end, symb, domain=S.Reals) if intrvl.left_open: if _start is S.NegativeInfinity: _domain2 = S.Reals else: _domain2 = solveset(expr > _start, symb, domain=S.Reals) else: _domain2 = solveset(expr >= _start, symb, domain=S.Reals) # domain in the interval expr_with_sing = Intersection(_domain1, _domain2) expr_domain = Complement(expr_with_sing, _singularities) return expr_domain if isinstance(_sets, Interval): return Union([elm_domain(element, _sets) for element in finite_set]) if isinstance(_sets, Union): _domain = S.EmptySet for intrvl in _sets.args: _domain_element = Union([elm_domain(element, intrvl) for element in finite_set]) _domain = Union(_domain, _domain_element) return _domain def periodicity(f, symbol, check=False): """ Tests the given function for periodicity in the given symbol. Parameters ========== f : Expr. The concerned function. symbol : Symbol The variable for which the period is to be determined. check : Boolean, optional The flag to verify whether the value being returned is a period or not. Returns ======= period The period of the function is returned. `None` is returned when the function is aperiodic or has a complex period. The value of `0` is returned as the period of a constant function. Raises ====== NotImplementedError The value of the period computed cannot be verified. Notes ===== Currently, we do not support functions with a complex period. The period of functions having complex periodic values such as `exp`, `sinh` is evaluated to `None`. The value returned might not be the "fundamental" period of the given function i.e. it may not be the smallest periodic value of the function. The verification of the period through the `check` flag is not reliable due to internal simplification of the given expression. Hence, it is set to `False` by default. Examples ======== >>> from sympy import Symbol, sin, cos, tan, exp >>> from sympy.calculus.util import periodicity >>> x = Symbol('x') >>> f = sin(x) + sin(2x) + sin(3x) >>> periodicity(f, x) 2pi >>> periodicity(sin(x)cos(x), x) pi >>> periodicity(exp(tan(2x) - 1), x) pi/2 >>> periodicity(sin(4x)*cos(2x), x) pi >>> periodicity(exp(x), x) """ from sympy.core.mod import Mod from sympy.core.relational import Relational from sympy.functions.elementary.exponential import exp from sympy.functions.elementary.complexes import Abs from sympy.functions.elementary.trigonometric import ( TrigonometricFunction, sin, cos, csc, sec) from sympy.simplify.simplify import simplify from sympy.solvers.decompogen import decompogen from sympy.polys.polytools import degree temp = Dummy('x', real=True) f = f.subs(symbol, temp) symbol = temp def _check(orig_f, period): '''Return the checked period or raise an error.''' new_f = orig_f.subs(symbol, symbol + period) if new_f.equals(orig_f): return period else: raise NotImplementedError(filldedent(''' The period of the given function cannot be verified. When `%s` was replaced with `%s + %s` in `%s`, the result was `%s` which was not recognized as being the same as the original function. So either the period was wrong or the two forms were not recognized as being equal. Set check=False to obtain the value.''' % (symbol, symbol, period, orig_f, new_f))) orig_f = f period = None if isinstance(f, Relational): f = f.lhs - f.rhs f = simplify(f) if symbol not in f.free_symbols: return S.Zero if isinstance(f, TrigonometricFunction): try: period = f.period(symbol) except NotImplementedError: pass if isinstance(f, Abs): arg = f.args[0] if isinstance(arg, (sec, csc, cos)): # all but tan and cot might have a # a period that is half as large # so recast as sin arg = sin(arg.args[0]) period = periodicity(arg, symbol) if period is not None and isinstance(arg, sin): # the argument of Abs was a trigonometric other than # cot or tan; test to see if the half-period # is valid. Abs(arg) has behaviour equivalent to # orig_f, so use that for test: orig_f = Abs(arg) try: return _check(orig_f, period/2) except NotImplementedError as err: if check: raise NotImplementedError(err) # else let new orig_f and period be # checked below if isinstance(f, exp): f = f.func(expand_mul(f.args[0])) if im(f) != 0: period_real = periodicity(re(f), symbol) period_imag = periodicity(im(f), symbol) if period_real is not None and period_imag is not None: period = lcim([period_real, period_imag]) if f.is_Pow: base, expo = f.args base_has_sym = base.has(symbol) expo_has_sym = expo.has(symbol) if base_has_sym and not expo_has_sym: period = periodicity(base, symbol) elif expo_has_sym and not base_has_sym: period = periodicity(expo, symbol) else: period = _periodicity(f.args, symbol) elif f.is_Mul: coeff, g = f.as_independent(symbol, as_Add=False) if isinstance(g, TrigonometricFunction) or coeff is not S.One: period = periodicity(g, symbol) else: period = _periodicity(g.args, symbol) elif f.is_Add: k, g = f.as_independent(symbol) if k is not S.Zero: return periodicity(g, symbol) period = _periodicity(g.args, symbol) elif isinstance(f, Mod): a, n = f.args if a == symbol: period = n elif isinstance(a, TrigonometricFunction): period = periodicity(a, symbol) #check if 'f' is linear in 'symbol' elif (a.is_polynomial(symbol) and degree(a, symbol) == 1 and symbol not in n.free_symbols): period = Abs(n / a.diff(symbol)) elif period is None: from sympy.solvers.decompogen import compogen g_s = decompogen(f, symbol) num_of_gs = len(g_s) if num_of_gs > 1: for index, g in enumerate(reversed(g_s)): start_index = num_of_gs - 1 - index g = compogen(g_s[start_index:], symbol) if g != orig_f and g != f: # Fix for issue 12620 period = periodicity(g, symbol) if period is not None: break if period is not None: if check: return _check(orig_f, period) return period return None def _periodicity(args, symbol): """ Helper for `periodicity` to find the period of a list of simpler functions. It uses the `lcim` method to find the least common period of all the functions. Parameters ========== args : Tuple of Symbol All the symbols present in a function. symbol : Symbol The symbol over which the function is to be evaluated. Returns ======= period The least common period of the function for all the symbols of the function. None if for at least one of the symbols the function is aperiodic """ periods = [] for f in args: period = periodicity(f, symbol) if period is None: return None if period is not S.Zero: periods.append(period) if len(periods) > 1: return lcim(periods) if periods: return periods[0] def lcim(numbers): """Returns the least common integral multiple of a list of numbers. The numbers can be rational or irrational or a mixture of both. `None` is returned for incommensurable numbers. Parameters ========== numbers : list Numbers (rational and/or irrational) for which lcim is to be found. Returns ======= number lcim if it exists, otherwise `None` for incommensurable numbers. Examples ======== >>> from sympy import S, pi >>> from sympy.calculus.util import lcim >>> lcim([S(1)/2, S(3)/4, S(5)/6]) 15/2 >>> lcim([2pi, 3pi, pi, pi/2]) 6pi >>> lcim([S(1), 2pi]) """ result = None if all(num.is_irrational for num in numbers): factorized_nums = list(map(lambda num: num.factor(), numbers)) factors_num = list( map(lambda num: num.as_coeff_Mul(), factorized_nums)) term = factors_num[0][1] if all(factor == term for coeff, factor in factors_num): common_term = term coeffs = [coeff for coeff, factor in factors_num] result = lcm_list(coeffs) * common_term elif all(num.is_rational for num in numbers): result = lcm_list(numbers) else: pass return result def is_convex(f, syms, domain=S.Reals): """Determines the convexity of the function passed in the argument. Parameters ========== f : Expr The concerned function. syms : Tuple of symbols The variables with respect to which the convexity is to be determined. domain : Interval, optional The domain over which the convexity of the function has to be checked. If unspecified, S.Reals will be the default domain. Returns ======= Boolean The method returns `True` if the function is convex otherwise it returns `False`. Raises ====== NotImplementedError The check for the convexity of multivariate functions is not implemented yet. Notes ===== To determine concavity of a function pass `-f` as the concerned function. To determine logarithmic convexity of a function pass log(f) as concerned function. To determine logartihmic concavity of a function pass -log(f) as concerned function. Currently, convexity check of multivariate functions is not handled. Examples ======== >>> from sympy import symbols, exp, oo, Interval >>> from sympy.calculus.util import is_convex >>> x = symbols('x') >>> is_convex(exp(x), x) True >>> is_convex(x3, x, domain = Interval(-1, oo)) False References ========== .. [1] https://en.wikipedia.org/wiki/Convex_function .. [2] http://www.ifp.illinois.edu/~angelia/L3_convfunc.pdf .. [3] https://en.wikipedia.org/wiki/Logarithmically_convex_function .. [4] https://en.wikipedia.org/wiki/Logarithmically_concave_function .. [5] https://en.wikipedia.org/wiki/Concave_function """ if len(syms) > 1: raise NotImplementedError( "The check for the convexity of multivariate functions is not implemented yet.") f = _sympify(f) var = syms[0] condition = f.diff(var, 2) < 0 if solve_univariate_inequality(condition, var, False, domain): return False return True def stationary_points(f, symbol, domain=S.Reals): """ Returns the stationary points of a function (where derivative of the function is 0) in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the stationary points are to be determined. domain : Interval The domain over which the stationary points have to be checked. If unspecified, S.Reals will be the default domain. Returns ======= Set A set of stationary points for the function. If there are no stationary point, an EmptySet is returned. Examples ======== >>> from sympy import Symbol, S, sin, pi, pprint, stationary_points >>> from sympy.sets import Interval >>> x = Symbol('x') >>> stationary_points(1/x, x, S.Reals) EmptySet >>> pprint(stationary_points(sin(x), x), use_unicode=False) pi 3pi {2npi + -- \| n in Integers} U {2npi + ---- \| n in Integers} 2 2 >>> stationary_points(sin(x),x, Interval(0, 4pi)) FiniteSet(pi/2, 3pi/2, 5pi/2, 7pi/2) """ from sympy import solveset, diff if isinstance(domain, EmptySet): return S.EmptySet domain = continuous_domain(f, symbol, domain) set = solveset(diff(f, symbol), symbol, domain) return set def maximum(f, symbol, domain=S.Reals): """ Returns the maximum value of a function in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for maximum value needs to be determined. domain : Interval The domain over which the maximum have to be checked. If unspecified, then Global maximum is returned. Returns ======= number Maximum value of the function in given domain. Examples ======== >>> from sympy import Symbol, S, sin, cos, pi, maximum >>> from sympy.sets import Interval >>> x = Symbol('x') >>> f = -x*2 + 2x + 5 >>> maximum(f, x, S.Reals) 6 >>> maximum(sin(x), x, Interval(-pi, pi/4)) sqrt(2)/2 >>> maximum(sin(x)cos(x), x) 1/2 """ from sympy import Symbol if isinstance(symbol, Symbol): if isinstance(domain, EmptySet): raise ValueError("Maximum value not defined for empty domain.") return function_range(f, symbol, domain).sup else: raise ValueError("%s is not a valid symbol." % symbol) def minimum(f, symbol, domain=S.Reals): """ Returns the minimum value of a function in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for minimum value needs to be determined. domain : Interval The domain over which the minimum have to be checked. If unspecified, then Global minimum is returned. Returns ======= number Minimum value of the function in the given domain. Examples ======== >>> from sympy import Symbol, S, sin, cos, minimum >>> from sympy.sets import Interval >>> x = Symbol('x') >>> f = x2 + 2x + 5 >>> minimum(f, x, S.Reals) 4 >>> minimum(sin(x), x, Interval(2, 3)) sin(3) >>> minimum(sin(x)cos(x), x) -1/2 """ from sympy import Symbol if isinstance(symbol, Symbol): if isinstance(domain, EmptySet): raise ValueError("Minimum value not defined for empty domain.") return function_range(f, symbol, domain).inf else: raise ValueError("%s is not a valid symbol." % symbol) class AccumulationBounds(AtomicExpr): r""" # Note AccumulationBounds has an alias: AccumBounds AccumulationBounds represent an interval `[a, b]`, which is always closed at the ends. Here `a` and `b` can be any value from extended real numbers. The intended meaning of AccummulationBounds is to give an approximate location of the accumulation points of a real function at a limit point. Let `a` and `b` be reals such that a <= b. `\left\langle a, b\right\rangle = \{x \in \mathbb{R} \mid a \le x \le b\}` `\left\langle -\infty, b\right\rangle = \{x \in \mathbb{R} \mid x \le b\} \cup \{-\infty, \infty\}` `\left\langle a, \infty \right\rangle = \{x \in \mathbb{R} \mid a \le x\} \cup \{-\infty, \infty\}` `\left\langle -\infty, \infty \right\rangle = \mathbb{R} \cup \{-\infty, \infty\}` `oo` and `-oo` are added to the second and third definition respectively, since if either `-oo` or `oo` is an argument, then the other one should be included (though not as an end point). This is forced, since we have, for example, `1/AccumBounds(0, 1) = AccumBounds(1, oo)`, and the limit at `0` is not one-sided. As x tends to `0-`, then `1/x -> -oo`, so `-oo` should be interpreted as belonging to `AccumBounds(1, oo)` though it need not appear explicitly. In many cases it suffices to know that the limit set is bounded. However, in some other cases more exact information could be useful. For example, all accumulation values of cos(x) + 1 are non-negative. (AccumBounds(-1, 1) + 1 = AccumBounds(0, 2)) A AccumulationBounds object is defined to be real AccumulationBounds, if its end points are finite reals. Let `X`, `Y` be real AccumulationBounds, then their sum, difference, product are defined to be the following sets: `X + Y = \{ x+y \mid x \in X \cap y \in Y\}` `X - Y = \{ x-y \mid x \in X \cap y \in Y\}` `X Y = \{ xy \mid x \in X \cap y \in Y\}` There is, however, no consensus on Interval division. `X / Y = \{ z \mid \exists x \in X, y \in Y \mid y \neq 0, z = x/y\}` Note: According to this definition the quotient of two AccumulationBounds may not be a AccumulationBounds object but rather a union of AccumulationBounds. Note ==== The main focus in the interval arithmetic is on the simplest way to calculate upper and lower endpoints for the range of values of a function in one or more variables. These barriers are not necessarily the supremum or infimum, since the precise calculation of those values can be difficult or impossible. Examples ======== >>> from sympy import AccumBounds, sin, exp, log, pi, E, S, oo >>> from sympy.abc import x >>> AccumBounds(0, 1) + AccumBounds(1, 2) AccumBounds(1, 3) >>> AccumBounds(0, 1) - AccumBounds(0, 2) AccumBounds(-2, 1) >>> AccumBounds(-2, 3)AccumBounds(-1, 1) AccumBounds(-3, 3) >>> AccumBounds(1, 2)AccumBounds(3, 5) AccumBounds(3, 10) The exponentiation of AccumulationBounds is defined as follows: If 0 does not belong to `X` or `n > 0` then `X^n = \{ x^n \mid x \in X\}` otherwise `X^n = \{ x^n \mid x \neq 0, x \in X\} \cup \{-\infty, \infty\}` Here for fractional `n`, the part of `X` resulting in a complex AccumulationBounds object is neglected. >>> AccumBounds(-1, 4)(S(1)/2) AccumBounds(0, 2) >>> AccumBounds(1, 2)2 AccumBounds(1, 4) >>> AccumBounds(-1, oo)(-1) AccumBounds(-oo, oo) Note: `<a, b>^2` is not same as `<a, b><a, b>` >>> AccumBounds(-1, 1)2 AccumBounds(0, 1) >>> AccumBounds(1, 3) < 4 True >>> AccumBounds(1, 3) < -1 False Some elementary functions can also take AccumulationBounds as input. A function `f` evaluated for some real AccumulationBounds `<a, b>` is defined as `f(\left\langle a, b\right\rangle) = \{ f(x) \mid a \le x \le b \}` >>> sin(AccumBounds(pi/6, pi/3)) AccumBounds(1/2, sqrt(3)/2) >>> exp(AccumBounds(0, 1)) AccumBounds(1, E) >>> log(AccumBounds(1, E)) AccumBounds(0, 1) Some symbol in an expression can be substituted for a AccumulationBounds object. But it doesn't necessarily evaluate the AccumulationBounds for that expression. Same expression can be evaluated to different values depending upon the form it is used for substitution. For example: >>> (x2 + 2x + 1).subs(x, AccumBounds(-1, 1)) AccumBounds(-1, 4) >>> ((x + 1)2).subs(x, AccumBounds(-1, 1)) AccumBounds(0, 4) References ========== .. [1] https://en.wikipedia.org/wiki/Interval_arithmetic .. [2] http://fab.cba.mit.edu/classes/S62.12/docs/Hickey_interval.pdf Notes ===== Do not use ``AccumulationBounds`` for floating point interval arithmetic calculations, use ``mpmath.iv`` instead. """ is_extended_real = True def __new__(cls, min, max): min = _sympify(min) max = _sympify(max) # Only allow real intervals (use symbols with 'is_extended_real=True'). if not min.is_extended_real or not max.is_extended_real: raise ValueError("Only real AccumulationBounds are supported") # Make sure that the created AccumBounds object will be valid. if max.is_comparable and min.is_comparable: if max < min: raise ValueError( "Lower limit should be smaller than upper limit") if max == min: return max return Basic.__new__(cls, min, max) # setting the operation priority _op_priority = 11.0 def _eval_is_real(self): if self.min.is_real and self.max.is_real: return True @property def min(self): """ Returns the minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).min 1 """ return self.args[0] @property def max(self): """ Returns the maximum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).max 3 """ return self.args[1] @property def delta(self): """ Returns the difference of maximum possible value attained by AccumulationBounds object and minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).delta 2 """ return self.max - self.min @property def mid(self): """ Returns the mean of maximum possible value attained by AccumulationBounds object and minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).mid 2 """ return (self.min + self.max) / 2 @_sympifyit('other', NotImplemented) def _eval_power(self, other): return self.__pow__(other) @_sympifyit('other', NotImplemented) def __add__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds( Add(self.min, other.min), Add(self.max, other.max)) if other is S.Infinity and self.min is S.NegativeInfinity or \ other is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif other.is_extended_real: if self.min is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif self.min is S.NegativeInfinity: return AccumBounds(-oo, self.max + other) elif self.max is S.Infinity: return AccumBounds(self.min + other, oo) else: return AccumBounds(Add(self.min, other), Add(self.max, other)) return Add(self, other, evaluate=False) return NotImplemented __radd__ = __add__ def __neg__(self): return AccumBounds(-self.max, -self.min) @_sympifyit('other', NotImplemented) def __sub__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds( Add(self.min, -other.max), Add(self.max, -other.min)) if other is S.NegativeInfinity and self.min is S.NegativeInfinity or \ other is S.Infinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif other.is_extended_real: if self.min is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif self.min is S.NegativeInfinity: return AccumBounds(-oo, self.max - other) elif self.max is S.Infinity: return AccumBounds(self.min - other, oo) else: return AccumBounds( Add(self.min, -other), Add(self.max, -other)) return Add(self, -other, evaluate=False) return NotImplemented @_sympifyit('other', NotImplemented) def __rsub__(self, other): return self.__neg__() + other @_sympifyit('other', NotImplemented) def __mul__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds(Min(Mul(self.min, other.min), Mul(self.min, other.max), Mul(self.max, other.min), Mul(self.max, other.max)), Max(Mul(self.min, other.min), Mul(self.min, other.max), Mul(self.max, other.min), Mul(self.max, other.max))) if other is S.Infinity: if self.min.is_zero: return AccumBounds(0, oo) if self.max.is_zero: return AccumBounds(-oo, 0) if other is S.NegativeInfinity: if self.min.is_zero: return AccumBounds(-oo, 0) if self.max.is_zero: return AccumBounds(0, oo) if other.is_extended_real: if other.is_zero: if self == AccumBounds(-oo, oo): return AccumBounds(-oo, oo) if self.max is S.Infinity: return AccumBounds(0, oo) if self.min is S.NegativeInfinity: return AccumBounds(-oo, 0) return S.Zero if other.is_extended_positive: return AccumBounds( Mul(self.min, other), Mul(self.max, other)) elif other.is_extended_negative: return AccumBounds( Mul(self.max, other), Mul(self.min, other)) if isinstance(other, Order): return other return Mul(self, other, evaluate=False) return NotImplemented __rmul__ = __mul__ @_sympifyit('other', NotImplemented) def __truediv__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): if other.min.is_positive or other.max.is_negative: return self AccumBounds(1/other.max, 1/other.min) if (self.min.is_extended_nonpositive and self.max.is_extended_nonnegative and other.min.is_extended_nonpositive and other.max.is_extended_nonnegative): if self.min.is_zero and other.min.is_zero: return AccumBounds(0, oo) if self.max.is_zero and other.min.is_zero: return AccumBounds(-oo, 0) return AccumBounds(-oo, oo) if self.max.is_extended_negative: if other.min.is_extended_negative: if other.max.is_zero: return AccumBounds(self.max / other.min, oo) if other.max.is_extended_positive: # the actual answer is a Union of AccumBounds, # Union(AccumBounds(-oo, self.max/other.max), # AccumBounds(self.max/other.min, oo)) return AccumBounds(-oo, oo) if other.min.is_zero and other.max.is_extended_positive: return AccumBounds(-oo, self.max / other.max) if self.min.is_extended_positive: if other.min.is_extended_negative: if other.max.is_zero: return AccumBounds(-oo, self.min / other.min) if other.max.is_extended_positive: # the actual answer is a Union of AccumBounds, # Union(AccumBounds(-oo, self.min/other.min), # AccumBounds(self.min/other.max, oo)) return AccumBounds(-oo, oo) if other.min.is_zero and other.max.is_extended_positive: return AccumBounds(self.min / other.max, oo) elif other.is_extended_real: if other is S.Infinity or other is S.NegativeInfinity: if self == AccumBounds(-oo, oo): return AccumBounds(-oo, oo) if self.max is S.Infinity: return AccumBounds(Min(0, other), Max(0, other)) if self.min is S.NegativeInfinity: return AccumBounds(Min(0, -other), Max(0, -other)) if other.is_extended_positive: return AccumBounds(self.min / other, self.max / other) elif other.is_extended_negative: return AccumBounds(self.max / other, self.min / other) if (1 / other) is S.ComplexInfinity: return Mul(self, 1 / other, evaluate=False) else: return Mul(self, 1 / other) return NotImplemented @_sympifyit('other', NotImplemented) def __rtruediv__(self, other): if isinstance(other, Expr): if other.is_extended_real: if other.is_zero: return S.Zero if (self.min.is_extended_nonpositive and self.max.is_extended_nonnegative): if self.min.is_zero: if other.is_extended_positive: return AccumBounds(Mul(other, 1 / self.max), oo) if other.is_extended_negative: return AccumBounds(-oo, Mul(other, 1 / self.max)) if self.max.is_zero: if other.is_extended_positive: return AccumBounds(-oo, Mul(other, 1 / self.min)) if other.is_extended_negative: return AccumBounds(Mul(other, 1 / self.min), oo) return AccumBounds(-oo, oo) else: return AccumBounds(Min(other / self.min, other / self.max), Max(other / self.min, other / self.max)) return Mul(other, 1 / self, evaluate=False) else: return NotImplemented @_sympifyit('other', NotImplemented) def __pow__(self, other): from sympy.functions.elementary.miscellaneous import real_root if isinstance(other, Expr): if other is S.Infinity: if self.min.is_extended_nonnegative: if self.max < 1: return S.Zero if self.min > 1: return S.Infinity return AccumBounds(0, oo) elif self.max.is_extended_negative: if self.min > -1: return S.Zero if self.max < -1: return FiniteSet(-oo, oo) return AccumBounds(-oo, oo) else: if self.min > -1: if self.max < 1: return S.Zero return AccumBounds(0, oo) return AccumBounds(-oo, oo) if other is S.NegativeInfinity: return (1 / self)oo if other.is_extended_real and other.is_number: if other.is_zero: return S.One if other.is_Integer: if self.min.is_extended_positive: return AccumBounds( Min(self.min other, self.max other), Max(self.min other, self.max other)) elif self.max.is_extended_negative: return AccumBounds( Min(self.max other, self.min other), Max(self.max other, self.min other)) if other % 2 == 0: if other.is_extended_negative: if self.min.is_zero: return AccumBounds(self.maxother, oo) if self.max.is_zero: return AccumBounds(self.minother, oo) return AccumBounds(0, oo) return AccumBounds( S.Zero, Max(self.minother, self.maxother)) else: if other.is_extended_negative: if self.min.is_zero: return AccumBounds(self.maxother, oo) if self.max.is_zero: return AccumBounds(-oo, self.minother) return AccumBounds(-oo, oo) return AccumBounds(self.minother, self.maxother) num, den = other.as_numer_denom() if num == S.One: if den % 2 == 0: if S.Zero in self: if self.min.is_extended_negative: return AccumBounds(0, real_root(self.max, den)) return AccumBounds(real_root(self.min, den), real_root(self.max, den)) if den!=1: num_pow = selfnum return num_pow**(1 / den) return AccumBounds(-oo, oo) return NotImplemented def __abs__(self): if self.max.is_extended_negative: return self.__neg__() elif self.min.is_extended_negative: return AccumBounds(S.Zero, Max(abs(self.min), self.max)) else: return self def __contains__(self, other): """ Returns True if other is contained in self, where other belongs to extended real numbers, False if not contained, otherwise TypeError is raised. Examples ======== >>> from sympy import AccumBounds, oo >>> 1 in AccumBounds(-1, 3) True -oo and oo go together as limits (in AccumulationBounds). >>> -oo in AccumBounds(1, oo) True >>> oo in AccumBounds(-oo, 0) True """ other = _sympify(other) if other is S.Infinity or other is S.NegativeInfinity: if self.min is S.NegativeInfinity or self.max is S.Infinity: return True return False rv = And(self.min <= other, self.max >= other) if rv not in (True, False): raise TypeError("input failed to evaluate") return rv def intersection(self, other): """ Returns the intersection of 'self' and 'other'. Here other can be an instance of FiniteSet or AccumulationBounds. Parameters ========== other: AccumulationBounds Another AccumulationBounds object with which the intersection has to be computed. Returns ======= AccumulationBounds Intersection of 'self' and 'other'. Examples ======== >>> from sympy import AccumBounds, FiniteSet >>> AccumBounds(1, 3).intersection(AccumBounds(2, 4)) AccumBounds(2, 3) >>> AccumBounds(1, 3).intersection(AccumBounds(4, 6)) EmptySet >>> AccumBounds(1, 4).intersection(FiniteSet(1, 2, 5)) FiniteSet(1, 2) """ if not isinstance(other, (AccumBounds, FiniteSet)): raise TypeError( "Input must be AccumulationBounds or FiniteSet object") if isinstance(other, FiniteSet): fin_set = S.EmptySet for i in other: if i in self: fin_set = fin_set + FiniteSet(i) return fin_set if self.max < other.min or self.min > other.max: return S.EmptySet if self.min <= other.min: if self.max <= other.max: return AccumBounds(other.min, self.max) if self.max > other.max: return other if other.min <= self.min: if other.max < self.max: return AccumBounds(self.min, other.max) if other.max > self.max: return self def union(self, other): # TODO : Devise a better method for Union of AccumBounds # this method is not actually correct and # can be made better if not isinstance(other, AccumBounds): raise TypeError( "Input must be AccumulationBounds or FiniteSet object") if self.min <= other.min and self.max >= other.min: return AccumBounds(self.min, Max(self.max, other.max)) if other.min <= self.min and other.max >= self.min: return AccumBounds(other.min, Max(self.max, other.max)) @dispatch(AccumulationBounds, AccumulationBounds) # type: ignore # noqa:F811 def _eval_is_le(lhs, rhs): # noqa:F811 if is_le(lhs.max, rhs.min): return True if is_gt(lhs.min, rhs.max): return False @dispatch(AccumulationBounds, Basic) # type: ignore # noqa:F811 def _eval_is_le(lhs, rhs): # noqa: F811 """ Returns True if range of values attained by `self` AccumulationBounds object is greater than the range of values attained by `other`, where other may be any value of type AccumulationBounds object or extended real number value, False if `other` satisfies the same property, else an unevaluated Relational. Examples ======== >>> from sympy import AccumBounds, oo >>> AccumBounds(1, 3) > AccumBounds(4, oo) False >>> AccumBounds(1, 4) > AccumBounds(3, 4) AccumBounds(1, 4) > AccumBounds(3, 4) >>> AccumBounds(1, oo) > -1 True """ if not rhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(rhs), rhs)) elif rhs.is_comparable: if is_le(lhs.max, rhs): return True if is_gt(lhs.min, rhs): return False @dispatch(AccumulationBounds, AccumulationBounds) def _eval_is_ge(lhs, rhs): # noqa:F811 if is_ge(lhs.min, rhs.max): return True if is_lt(lhs.max, rhs.min): return False @dispatch(AccumulationBounds, Expr) # type:ignore def _eval_is_ge(lhs, rhs): # noqa: F811 """ Returns True if range of values attained by `lhs` AccumulationBounds object is less that the range of values attained by `rhs`, where other may be any value of type AccumulationBounds object or extended real number value, False if `rhs` satisfies the same property, else an unevaluated Relational. Examples ======== >>> from sympy import AccumBounds, oo >>> AccumBounds(1, 3) >= AccumBounds(4, oo) False >>> AccumBounds(1, 4) >= AccumBounds(3, 4) AccumBounds(1, 4) >= AccumBounds(3, 4) >>> AccumBounds(1, oo) >= 1 True """ if not rhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(rhs), rhs)) elif rhs.is_comparable: if is_ge(lhs.min, rhs): return True if is_lt(lhs.max, rhs): return False @dispatch(Expr, AccumulationBounds) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 if not lhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(lhs), lhs)) elif lhs.is_comparable: if is_le(rhs.max, lhs): return True if is_gt(rhs.min, lhs): return False @dispatch(AccumulationBounds, AccumulationBounds) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 if is_ge(lhs.min, rhs.max): return True if is_lt(lhs.max, rhs.min): return False # setting an alias for AccumulationBounds AccumBounds = AccumulationBounds
cb53b82ad984aa09934edfa2044d7e26a9f507a4ed59cb19979d31434af9427d	from sympy.tensor import Indexed from sympy import Integral, Dummy, sympify, Tuple class IndexedIntegral(Integral): """ Experimental class to test integration by indexed variables. Usage is analogue to ``Integral``, it simply adds awareness of integration over indices. Contraction of non-identical index symbols referring to the same ``IndexedBase`` is not yet supported. Examples ======== >>> from sympy.sandbox.indexed_integrals import IndexedIntegral >>> from sympy import IndexedBase, symbols >>> A = IndexedBase('A') >>> i, j = symbols('i j', integer=True) >>> ii = IndexedIntegral(A[i], A[i]) >>> ii Integral(_A[i], _A[i]) >>> ii.doit() A[i]*2/2 If the indices are different, indexed objects are considered to be different variables: >>> i2 = IndexedIntegral(A[j], A[i]) >>> i2 Integral(A[j], _A[i]) >>> i2.doit() A[i]A[j] """ def __new__(cls, function, limits, assumptions): repl, limits = IndexedIntegral._indexed_process_limits(limits) function = sympify(function) function = function.xreplace(repl) obj = Integral.__new__(cls, function, limits, **assumptions) obj._indexed_repl = repl obj._indexed_reverse_repl = {val: key for key, val in repl.items()} return obj def doit(self): res = super().doit() return res.xreplace(self._indexed_reverse_repl) @staticmethod def _indexed_process_limits(limits): repl = {} newlimits = [] for i in limits: if isinstance(i, (tuple, list, Tuple)): v = i[0] vrest = i[1:] else: v = i vrest = () if isinstance(v, Indexed): if v not in repl: r = Dummy(str(v)) repl[v] = r newlimits.append((r,)+vrest) else: newlimits.append(i) return repl, newlimits
d6b3a9921058d13b3a5171efaa34567e10ce2f0221951c83af4caf2e7414c18e	""" Generic SymPy-Independent Strategies """ from sympy.core.compatibility import get_function_name identity = lambda x: x def exhaust(rule): """ Apply a rule repeatedly until it has no effect """ def exhaustive_rl(expr): new, old = rule(expr), expr while new != old: new, old = rule(new), new return new return exhaustive_rl def memoize(rule): """ Memoized version of a rule """ cache = {} def memoized_rl(expr): if expr in cache: return cache[expr] else: result = rule(expr) cache[expr] = result return result return memoized_rl def condition(cond, rule): """ Only apply rule if condition is true """ def conditioned_rl(expr): if cond(expr): return rule(expr) else: return expr return conditioned_rl def chain(rules): """ Compose a sequence of rules so that they apply to the expr sequentially """ def chain_rl(expr): for rule in rules: expr = rule(expr) return expr return chain_rl def debug(rule, file=None): """ Print out before and after expressions each time rule is used """ if file is None: from sys import stdout file = stdout def debug_rl(args, *kwargs): expr = args[0] result = rule(args, *kwargs) if result != expr: file.write("Rule: %s\n" % get_function_name(rule)) file.write("In: %s\nOut: %s\n\n"%(expr, result)) return result return debug_rl def null_safe(rule): """ Return original expr if rule returns None """ def null_safe_rl(expr): result = rule(expr) if result is None: return expr else: return result return null_safe_rl def tryit(rule, exception): """ Return original expr if rule raises exception """ def try_rl(expr): try: return rule(expr) except exception: return expr return try_rl def do_one(rules): """ Try each of the rules until one works. Then stop. """ def do_one_rl(expr): for rl in rules: result = rl(expr) if result != expr: return result return expr return do_one_rl def switch(key, ruledict): """ Select a rule based on the result of key called on the function """ def switch_rl(expr): rl = ruledict.get(key(expr), identity) return rl(expr) return switch_rl def minimize(*rules, objective=identity): """ Select result of rules that minimizes objective >>> from sympy.strategies import minimize >>> inc = lambda x: x + 1 >>> dec = lambda x: x - 1 >>> rl = minimize(inc, dec) >>> rl(4) 3 >>> rl = minimize(inc, dec, objective=lambda x: -x) # maximize >>> rl(4) 5 """ def minrule(expr): return min([rule(expr) for rule in rules], key=objective) return minrule
1e1ed6be8c816053f910f8055fe5ed2e445fedf8ac067a1b31de13e8baecc02a	from functools import partial from sympy.strategies import chain, minimize import sympy.strategies.branch as branch from sympy.strategies.branch import yieldify identity = lambda x: x def treeapply(tree, join, leaf=identity): """ Apply functions onto recursive containers (tree) join - a dictionary mapping container types to functions e.g. ``{list: minimize, tuple: chain}`` Keys are containers/iterables. Values are functions [a] -> a. Examples ======== >>> from sympy.strategies.tree import treeapply >>> tree = [(3, 2), (4, 1)] >>> treeapply(tree, {list: max, tuple: min}) 2 >>> add = lambda args: sum(args) >>> def mul(args): ... total = 1 ... for arg in args: ... total = arg ... return total >>> treeapply(tree, {list: mul, tuple: add}) 25 """ for typ in join: if isinstance(tree, typ): return join[typ](map(partial(treeapply, join=join, leaf=leaf), tree)) return leaf(tree) def greedy(tree, objective=identity, *kwargs): """ Execute a strategic tree. Select alternatives greedily Trees ----- Nodes in a tree can be either function - a leaf list - a selection among operations tuple - a sequence of chained operations Textual examples ---------------- Text: Run f, then run g, e.g. ``lambda x: g(f(x))`` Code: ``(f, g)`` Text: Run either f or g, whichever minimizes the objective Code: ``[f, g]`` Textx: Run either f or g, whichever is better, then run h Code: ``([f, g], h)`` Text: Either expand then simplify or try factor then foosimp. Finally print Code: ``([(expand, simplify), (factor, foosimp)], print)`` Objective --------- "Better" is determined by the objective keyword. This function makes choices to minimize the objective. It defaults to the identity. Examples ======== >>> from sympy.strategies.tree import greedy >>> inc = lambda x: x + 1 >>> dec = lambda x: x - 1 >>> double = lambda x: 2x >>> tree = [inc, (dec, double)] # either inc or dec-then-double >>> fn = greedy(tree) >>> fn(4) # lowest value comes from the inc 5 >>> fn(1) # lowest value comes from dec then double 0 This function selects between options in a tuple. The result is chosen that minimizes the objective function. >>> fn = greedy(tree, objective=lambda x: -x) # maximize >>> fn(4) # highest value comes from the dec then double 6 >>> fn(1) # highest value comes from the inc 2 Greediness ---------- This is a greedy algorithm. In the example: ([a, b], c) # do either a or b, then do c the choice between running ``a`` or ``b`` is made without foresight to c """ optimize = partial(minimize, objective=objective) return treeapply(tree, {list: optimize, tuple: chain}, kwargs) def allresults(tree, leaf=yieldify): """ Execute a strategic tree. Return all possibilities. Returns a lazy iterator of all possible results Exhaustiveness -------------- This is an exhaustive algorithm. In the example ([a, b], [c, d]) All of the results from (a, c), (b, c), (a, d), (b, d) are returned. This can lead to combinatorial blowup. See sympy.strategies.greedy for details on input """ return treeapply(tree, {list: branch.multiplex, tuple: branch.chain}, leaf=leaf) def brute(tree, objective=identity, kwargs): return lambda expr: min(tuple(allresults(tree, **kwargs)(expr)), key=objective)
02d0ea37d52030f3e60fbd8e3a296de3f14ad6e43ffa1167feff7c68785636d3	from . import rl from .core import do_one, exhaust, switch from .traverse import top_down def subs(d, *kwargs): """ Full simultaneous exact substitution Examples ======== >>> from sympy.strategies.tools import subs >>> from sympy import Basic >>> mapping = {1: 4, 4: 1, Basic(5): Basic(6, 7)} >>> expr = Basic(1, Basic(2, 3), Basic(4, Basic(5))) >>> subs(mapping)(expr) Basic(4, Basic(2, 3), Basic(1, Basic(6, 7))) """ if d: return top_down(do_one(map(rl.subs, zip(d.items()))), *kwargs) else: return lambda x: x def canon(rules, *kwargs): """ Strategy for canonicalization Apply each rule in a bottom_up fashion through the tree. Do each one in turn. Keep doing this until there is no change. """ return exhaust(top_down(exhaust(do_one(rules)), **kwargs)) def typed(ruletypes): """ Apply rules based on the expression type inputs: ruletypes -- a dict mapping {Type: rule} >>> from sympy.strategies import rm_id, typed >>> from sympy import Add, Mul >>> rm_zeros = rm_id(lambda x: x==0) >>> rm_ones = rm_id(lambda x: x==1) >>> remove_idents = typed({Add: rm_zeros, Mul: rm_ones}) """ return switch(type, ruletypes)
3e1c3f1edbf42774ed9ae9bb9735f766a712de69cbc05db2e934161a7325ddc0	""" Generic Rules for SymPy This file assumes knowledge of Basic and little else. """ from sympy.utilities.iterables import sift from .util import new # Functions that create rules def rm_id(isid, new=new): """ Create a rule to remove identities isid - fn :: x -> Bool --- whether or not this element is an identity >>> from sympy.strategies import rm_id >>> from sympy import Basic >>> remove_zeros = rm_id(lambda x: x==0) >>> remove_zeros(Basic(1, 0, 2)) Basic(1, 2) >>> remove_zeros(Basic(0, 0)) # If only identites then we keep one Basic(0) See Also: unpack """ def ident_remove(expr): """ Remove identities """ ids = list(map(isid, expr.args)) if sum(ids) == 0: # No identities. Common case return expr elif sum(ids) != len(ids): # there is at least one non-identity return new(expr.__class__, [arg for arg, x in zip(expr.args, ids) if not x]) else: return new(expr.__class__, expr.args[0]) return ident_remove def glom(key, count, combine): """ Create a rule to conglomerate identical args >>> from sympy.strategies import glom >>> from sympy import Add >>> from sympy.abc import x >>> key = lambda x: x.as_coeff_Mul()[1] >>> count = lambda x: x.as_coeff_Mul()[0] >>> combine = lambda cnt, arg: cnt arg >>> rl = glom(key, count, combine) >>> rl(Add(x, -x, 3x, 2, 3, evaluate=False)) 3x + 5 Wait, how are key, count and combine supposed to work? >>> key(2x) x >>> count(2x) 2 >>> combine(2, x) 2x """ def conglomerate(expr): """ Conglomerate together identical args x + x -> 2x """ groups = sift(expr.args, key) counts = {k: sum(map(count, args)) for k, args in groups.items()} newargs = [combine(cnt, mat) for mat, cnt in counts.items()] if set(newargs) != set(expr.args): return new(type(expr), newargs) else: return expr return conglomerate def sort(key, new=new): """ Create a rule to sort by a key function >>> from sympy.strategies import sort >>> from sympy import Basic >>> sort_rl = sort(str) >>> sort_rl(Basic(3, 1, 2)) Basic(1, 2, 3) """ def sort_rl(expr): return new(expr.__class__, sorted(expr.args, key=key)) return sort_rl def distribute(A, B): """ Turns an A containing Bs into a B of As where A, B are container types >>> from sympy.strategies import distribute >>> from sympy import Add, Mul, symbols >>> x, y = symbols('x,y') >>> dist = distribute(Mul, Add) >>> expr = Mul(2, x+y, evaluate=False) >>> expr 2(x + y) >>> dist(expr) 2x + 2y """ def distribute_rl(expr): for i, arg in enumerate(expr.args): if isinstance(arg, B): first, b, tail = expr.args[:i], expr.args[i], expr.args[i+1:] return B([A((first + (arg,) + tail)) for arg in b.args]) return expr return distribute_rl def subs(a, b): """ Replace expressions exactly """ def subs_rl(expr): if expr == a: return b else: return expr return subs_rl # Functions that are rules def unpack(expr): """ Rule to unpack singleton args >>> from sympy.strategies import unpack >>> from sympy import Basic >>> unpack(Basic(2)) 2 """ if len(expr.args) == 1: return expr.args[0] else: return expr def flatten(expr, new=new): """ Flatten T(a, b, T(c, d), T2(e)) to T(a, b, c, d, T2(e)) """ cls = expr.__class__ args = [] for arg in expr.args: if arg.__class__ == cls: args.extend(arg.args) else: args.append(arg) return new(expr.__class__, args) def rebuild(expr): """ Rebuild a SymPy tree This function recursively calls constructors in the expression tree. This forces canonicalization and removes ugliness introduced by the use of Basic.__new__ """ if expr.is_Atom: return expr else: return expr.func(list(map(rebuild, expr.args)))
0e13e7049e51c3fc73846881b527224f257e1f6ce19718236158eb347fa02f29	"""Strategies to Traverse a Tree.""" from sympy.strategies.util import basic_fns from sympy.strategies.core import chain, do_one def top_down(rule, fns=basic_fns): """Apply a rule down a tree running it on the top nodes first.""" return chain(rule, lambda expr: sall(top_down(rule, fns), fns)(expr)) def bottom_up(rule, fns=basic_fns): """Apply a rule down a tree running it on the bottom nodes first.""" return chain(lambda expr: sall(bottom_up(rule, fns), fns)(expr), rule) def top_down_once(rule, fns=basic_fns): """Apply a rule down a tree - stop on success.""" return do_one(rule, lambda expr: sall(top_down(rule, fns), fns)(expr)) def bottom_up_once(rule, fns=basic_fns): """Apply a rule up a tree - stop on success.""" return do_one(lambda expr: sall(bottom_up(rule, fns), fns)(expr), rule) def sall(rule, fns=basic_fns): """Strategic all - apply rule to args.""" op, new, children, leaf = map(fns.get, ('op', 'new', 'children', 'leaf')) def all_rl(expr): if leaf(expr): return expr else: args = map(rule, children(expr)) return new(op(expr), *args) return all_rl
d0e6d9fa0d43122d60d3b005fabe93f35978a2f1b05bb1ea713ae39243aa8034	from sympy import Basic new = Basic.__new__ def assoc(d, k, v): d = d.copy() d[k] = v return d basic_fns = {'op': type, 'new': Basic.__new__, 'leaf': lambda x: not isinstance(x, Basic) or x.is_Atom, 'children': lambda x: x.args} expr_fns = assoc(basic_fns, 'new', lambda op, args: op(args))
81c2ee6523a14b167fb3fd56f704089ee5baacba2e8d5196cb103ae97eaf911c	""" This module provides convenient functions to transform sympy expressions to lambda functions which can be used to calculate numerical values very fast. """ from typing import Any, Dict, Iterable import inspect import keyword import textwrap import linecache from sympy.utilities.exceptions import SymPyDeprecationWarning from sympy.core.compatibility import (exec_, is_sequence, iterable, NotIterable, builtins) from sympy.utilities.misc import filldedent from sympy.utilities.decorator import doctest_depends_on __doctest_requires__ = {('lambdify',): ['numpy', 'tensorflow']} # Default namespaces, letting us define translations that can't be defined # by simple variable maps, like I => 1j MATH_DEFAULT = {} # type: Dict[str, Any] MPMATH_DEFAULT = {} # type: Dict[str, Any] NUMPY_DEFAULT = {"I": 1j} # type: Dict[str, Any] SCIPY_DEFAULT = {"I": 1j} # type: Dict[str, Any] TENSORFLOW_DEFAULT = {} # type: Dict[str, Any] SYMPY_DEFAULT = {} # type: Dict[str, Any] NUMEXPR_DEFAULT = {} # type: Dict[str, Any] # These are the namespaces the lambda functions will use. # These are separate from the names above because they are modified # throughout this file, whereas the defaults should remain unmodified. MATH = MATH_DEFAULT.copy() MPMATH = MPMATH_DEFAULT.copy() NUMPY = NUMPY_DEFAULT.copy() SCIPY = SCIPY_DEFAULT.copy() TENSORFLOW = TENSORFLOW_DEFAULT.copy() SYMPY = SYMPY_DEFAULT.copy() NUMEXPR = NUMEXPR_DEFAULT.copy() # Mappings between sympy and other modules function names. MATH_TRANSLATIONS = { "ceiling": "ceil", "E": "e", "ln": "log", } # NOTE: This dictionary is reused in Function._eval_evalf to allow subclasses # of Function to automatically evalf. MPMATH_TRANSLATIONS = { "Abs": "fabs", "elliptic_k": "ellipk", "elliptic_f": "ellipf", "elliptic_e": "ellipe", "elliptic_pi": "ellippi", "ceiling": "ceil", "chebyshevt": "chebyt", "chebyshevu": "chebyu", "E": "e", "I": "j", "ln": "log", #"lowergamma":"lower_gamma", "oo": "inf", #"uppergamma":"upper_gamma", "LambertW": "lambertw", "MutableDenseMatrix": "matrix", "ImmutableDenseMatrix": "matrix", "conjugate": "conj", "dirichlet_eta": "altzeta", "Ei": "ei", "Shi": "shi", "Chi": "chi", "Si": "si", "Ci": "ci", "RisingFactorial": "rf", "FallingFactorial": "ff", } NUMPY_TRANSLATIONS = {} # type: Dict[str, str] SCIPY_TRANSLATIONS = {} # type: Dict[str, str] TENSORFLOW_TRANSLATIONS = {} # type: Dict[str, str] NUMEXPR_TRANSLATIONS = {} # type: Dict[str, str] # Available modules: MODULES = { "math": (MATH, MATH_DEFAULT, MATH_TRANSLATIONS, ("from math import ",)), "mpmath": (MPMATH, MPMATH_DEFAULT, MPMATH_TRANSLATIONS, ("from mpmath import ",)), "numpy": (NUMPY, NUMPY_DEFAULT, NUMPY_TRANSLATIONS, ("import numpy; from numpy import ; from numpy.linalg import ",)), "scipy": (SCIPY, SCIPY_DEFAULT, SCIPY_TRANSLATIONS, ("import numpy; import scipy; from scipy import ; from scipy.special import ",)), "tensorflow": (TENSORFLOW, TENSORFLOW_DEFAULT, TENSORFLOW_TRANSLATIONS, ("import tensorflow",)), "sympy": (SYMPY, SYMPY_DEFAULT, {}, ( "from sympy.functions import ", "from sympy.matrices import ", "from sympy import Integral, pi, oo, nan, zoo, E, I",)), "numexpr" : (NUMEXPR, NUMEXPR_DEFAULT, NUMEXPR_TRANSLATIONS, ("import_module('numexpr')", )), } def _import(module, reload=False): """ Creates a global translation dictionary for module. The argument module has to be one of the following strings: "math", "mpmath", "numpy", "sympy", "tensorflow". These dictionaries map names of python functions to their equivalent in other modules. """ # Required despite static analysis claiming it is not used from sympy.external import import_module # noqa:F401 try: namespace, namespace_default, translations, import_commands = MODULES[ module] except KeyError: raise NameError( "'%s' module can't be used for lambdification" % module) # Clear namespace or exit if namespace != namespace_default: # The namespace was already generated, don't do it again if not forced. if reload: namespace.clear() namespace.update(namespace_default) else: return for import_command in import_commands: if import_command.startswith('import_module'): module = eval(import_command) if module is not None: namespace.update(module.__dict__) continue else: try: exec_(import_command, {}, namespace) continue except ImportError: pass raise ImportError( "can't import '%s' with '%s' command" % (module, import_command)) # Add translated names to namespace for sympyname, translation in translations.items(): namespace[sympyname] = namespace[translation] # For computing the modulus of a sympy expression we use the builtin abs # function, instead of the previously used fabs function for all # translation modules. This is because the fabs function in the math # module does not accept complex valued arguments. (see issue 9474). The # only exception, where we don't use the builtin abs function is the # mpmath translation module, because mpmath.fabs returns mpf objects in # contrast to abs(). if 'Abs' not in namespace: namespace['Abs'] = abs # Used for dynamically generated filenames that are inserted into the # linecache. _lambdify_generated_counter = 1 @doctest_depends_on(modules=('numpy', 'tensorflow', ), python_version=(3,)) def lambdify(args: Iterable, expr, modules=None, printer=None, use_imps=True, dummify=False): """Convert a SymPy expression into a function that allows for fast numeric evaluation. .. warning:: This function uses ``exec``, and thus shouldn't be used on unsanitized input. .. versionchanged:: 1.7.0 Passing a set for the args parameter is deprecated as sets are unordered. Use an ordered iterable such as a list or tuple. Explanation =========== For example, to convert the SymPy expression ``sin(x) + cos(x)`` to an equivalent NumPy function that numerically evaluates it: >>> from sympy import sin, cos, symbols, lambdify >>> import numpy as np >>> x = symbols('x') >>> expr = sin(x) + cos(x) >>> expr sin(x) + cos(x) >>> f = lambdify(x, expr, 'numpy') >>> a = np.array([1, 2]) >>> f(a) [1.38177329 0.49315059] The primary purpose of this function is to provide a bridge from SymPy expressions to numerical libraries such as NumPy, SciPy, NumExpr, mpmath, and tensorflow. In general, SymPy functions do not work with objects from other libraries, such as NumPy arrays, and functions from numeric libraries like NumPy or mpmath do not work on SymPy expressions. ``lambdify`` bridges the two by converting a SymPy expression to an equivalent numeric function. The basic workflow with ``lambdify`` is to first create a SymPy expression representing whatever mathematical function you wish to evaluate. This should be done using only SymPy functions and expressions. Then, use ``lambdify`` to convert this to an equivalent function for numerical evaluation. For instance, above we created ``expr`` using the SymPy symbol ``x`` and SymPy functions ``sin`` and ``cos``, then converted it to an equivalent NumPy function ``f``, and called it on a NumPy array ``a``. Parameters ========== args : List[Symbol] A variable or a list of variables whose nesting represents the nesting of the arguments that will be passed to the function. Variables can be symbols, undefined functions, or matrix symbols. >>> from sympy import Eq >>> from sympy.abc import x, y, z The list of variables should match the structure of how the arguments will be passed to the function. Simply enclose the parameters as they will be passed in a list. To call a function like ``f(x)`` then ``[x]`` should be the first argument to ``lambdify``; for this case a single ``x`` can also be used: >>> f = lambdify(x, x + 1) >>> f(1) 2 >>> f = lambdify([x], x + 1) >>> f(1) 2 To call a function like ``f(x, y)`` then ``[x, y]`` will be the first argument of the ``lambdify``: >>> f = lambdify([x, y], x + y) >>> f(1, 1) 2 To call a function with a single 3-element tuple like ``f((x, y, z))`` then ``[(x, y, z)]`` will be the first argument of the ``lambdify``: >>> f = lambdify([(x, y, z)], Eq(z2, x2 + y*2)) >>> f((3, 4, 5)) True If two args will be passed and the first is a scalar but the second is a tuple with two arguments then the items in the list should match that structure: >>> f = lambdify([x, (y, z)], x + y + z) >>> f(1, (2, 3)) 6 expr : Expr An expression, list of expressions, or matrix to be evaluated. Lists may be nested. If the expression is a list, the output will also be a list. >>> f = lambdify(x, [x, [x + 1, x + 2]]) >>> f(1) [1, [2, 3]] If it is a matrix, an array will be returned (for the NumPy module). >>> from sympy import Matrix >>> f = lambdify(x, Matrix([x, x + 1])) >>> f(1) [[1] [2]] Note that the argument order here (variables then expression) is used to emulate the Python ``lambda`` keyword. ``lambdify(x, expr)`` works (roughly) like ``lambda x: expr`` (see :ref:`lambdify-how-it-works` below). modules : str, optional Specifies the numeric library to use. If not specified, modules* defaults to: - ``["scipy", "numpy"]`` if SciPy is installed - ``["numpy"]`` if only NumPy is installed - ``["math", "mpmath", "sympy"]`` if neither is installed. That is, SymPy functions are replaced as far as possible by either ``scipy`` or ``numpy`` functions if available, and Python's standard library ``math``, or ``mpmath`` functions otherwise. modules can be one of the following types: - The strings ``"math"``, ``"mpmath"``, ``"numpy"``, ``"numexpr"``, ``"scipy"``, ``"sympy"``, or ``"tensorflow"``. This uses the corresponding printer and namespace mapping for that module. - A module (e.g., ``math``). This uses the global namespace of the module. If the module is one of the above known modules, it will also use the corresponding printer and namespace mapping (i.e., ``modules=numpy`` is equivalent to ``modules="numpy"``). - A dictionary that maps names of SymPy functions to arbitrary functions (e.g., ``{'sin': custom_sin}``). - A list that contains a mix of the arguments above, with higher priority given to entries appearing first (e.g., to use the NumPy module but override the ``sin`` function with a custom version, you can use ``[{'sin': custom_sin}, 'numpy']``). dummify : bool, optional Whether or not the variables in the provided expression that are not valid Python identifiers are substituted with dummy symbols. This allows for undefined functions like ``Function('f')(t)`` to be supplied as arguments. By default, the variables are only dummified if they are not valid Python identifiers. Set ``dummify=True`` to replace all arguments with dummy symbols (if ``args`` is not a string) - for example, to ensure that the arguments do not redefine any built-in names. Examples ======== >>> from sympy.utilities.lambdify import implemented_function >>> from sympy import sqrt, sin, Matrix >>> from sympy import Function >>> from sympy.abc import w, x, y, z >>> f = lambdify(x, x*2) >>> f(2) 4 >>> f = lambdify((x, y, z), [z, y, x]) >>> f(1,2,3) [3, 2, 1] >>> f = lambdify(x, sqrt(x)) >>> f(4) 2.0 >>> f = lambdify((x, y), sin(xy)*2) >>> f(0, 5) 0.0 >>> row = lambdify((x, y), Matrix((x, x + y)).T, modules='sympy') >>> row(1, 2) Matrix([[1, 3]]) ``lambdify`` can be used to translate SymPy expressions into mpmath functions. This may be preferable to using ``evalf`` (which uses mpmath on the backend) in some cases. >>> f = lambdify(x, sin(x), 'mpmath') >>> f(1) 0.8414709848078965 Tuple arguments are handled and the lambdified function should be called with the same type of arguments as were used to create the function: >>> f = lambdify((x, (y, z)), x + y) >>> f(1, (2, 4)) 3 The ``flatten`` function can be used to always work with flattened arguments: >>> from sympy.utilities.iterables import flatten >>> args = w, (x, (y, z)) >>> vals = 1, (2, (3, 4)) >>> f = lambdify(flatten(args), w + x + y + z) >>> f(flatten(vals)) 10 Functions present in ``expr`` can also carry their own numerical implementations, in a callable attached to the ``_imp_`` attribute. This can be used with undefined functions using the ``implemented_function`` factory: >>> f = implemented_function(Function('f'), lambda x: x+1) >>> func = lambdify(x, f(x)) >>> func(4) 5 ``lambdify`` always prefers ``_imp_`` implementations to implementations in other namespaces, unless the ``use_imps`` input parameter is False. Usage with Tensorflow: >>> import tensorflow as tf >>> from sympy import Max, sin, lambdify >>> from sympy.abc import x >>> f = Max(x, sin(x)) >>> func = lambdify(x, f, 'tensorflow') After tensorflow v2, eager execution is enabled by default. If you want to get the compatible result across tensorflow v1 and v2 as same as this tutorial, run this line. >>> tf.compat.v1.enable_eager_execution() If you have eager execution enabled, you can get the result out immediately as you can use numpy. If you pass tensorflow objects, you may get an ``EagerTensor`` object instead of value. >>> result = func(tf.constant(1.0)) >>> print(result) tf.Tensor(1.0, shape=(), dtype=float32) >>> print(result.__class__) <class 'tensorflow.python.framework.ops.EagerTensor'> You can use ``.numpy()`` to get the numpy value of the tensor. >>> result.numpy() 1.0 >>> var = tf.Variable(2.0) >>> result = func(var) # also works for tf.Variable and tf.Placeholder >>> result.numpy() 2.0 And it works with any shape array. >>> tensor = tf.constant([[1.0, 2.0], [3.0, 4.0]]) >>> result = func(tensor) >>> result.numpy() [[1. 2.] [3. 4.]] Notes ===== - For functions involving large array calculations, numexpr can provide a significant speedup over numpy. Please note that the available functions for numexpr are more limited than numpy but can be expanded with ``implemented_function`` and user defined subclasses of Function. If specified, numexpr may be the only option in modules. The official list of numexpr functions can be found at: https://numexpr.readthedocs.io/en/latest/user_guide.html#supported-functions - In previous versions of SymPy, ``lambdify`` replaced ``Matrix`` with ``numpy.matrix`` by default. As of SymPy 1.0 ``numpy.array`` is the default. To get the old default behavior you must pass in ``[{'ImmutableDenseMatrix': numpy.matrix}, 'numpy']`` to the ``modules`` kwarg. >>> from sympy import lambdify, Matrix >>> from sympy.abc import x, y >>> import numpy >>> array2mat = [{'ImmutableDenseMatrix': numpy.matrix}, 'numpy'] >>> f = lambdify((x, y), Matrix([x, y]), modules=array2mat) >>> f(1, 2) [[1] [2]] - In the above examples, the generated functions can accept scalar values or numpy arrays as arguments. However, in some cases the generated function relies on the input being a numpy array: >>> from sympy import Piecewise >>> from sympy.testing.pytest import ignore_warnings >>> f = lambdify(x, Piecewise((x, x <= 1), (1/x, x > 1)), "numpy") >>> with ignore_warnings(RuntimeWarning): ... f(numpy.array([-1, 0, 1, 2])) [-1. 0. 1. 0.5] >>> f(0) Traceback (most recent call last): ... ZeroDivisionError: division by zero In such cases, the input should be wrapped in a numpy array: >>> with ignore_warnings(RuntimeWarning): ... float(f(numpy.array([0]))) 0.0 Or if numpy functionality is not required another module can be used: >>> f = lambdify(x, Piecewise((x, x <= 1), (1/x, x > 1)), "math") >>> f(0) 0 .. _lambdify-how-it-works: How it works ============ When using this function, it helps a great deal to have an idea of what it is doing. At its core, lambdify is nothing more than a namespace translation, on top of a special printer that makes some corner cases work properly. To understand lambdify, first we must properly understand how Python namespaces work. Say we had two files. One called ``sin_cos_sympy.py``, with .. code:: python # sin_cos_sympy.py from sympy import sin, cos def sin_cos(x): return sin(x) + cos(x) and one called ``sin_cos_numpy.py`` with .. code:: python # sin_cos_numpy.py from numpy import sin, cos def sin_cos(x): return sin(x) + cos(x) The two files define an identical function ``sin_cos``. However, in the first file, ``sin`` and ``cos`` are defined as the SymPy ``sin`` and ``cos``. In the second, they are defined as the NumPy versions. If we were to import the first file and use the ``sin_cos`` function, we would get something like >>> from sin_cos_sympy import sin_cos # doctest: +SKIP >>> sin_cos(1) # doctest: +SKIP cos(1) + sin(1) On the other hand, if we imported ``sin_cos`` from the second file, we would get >>> from sin_cos_numpy import sin_cos # doctest: +SKIP >>> sin_cos(1) # doctest: +SKIP 1.38177329068 In the first case we got a symbolic output, because it used the symbolic ``sin`` and ``cos`` functions from SymPy. In the second, we got a numeric result, because ``sin_cos`` used the numeric ``sin`` and ``cos`` functions from NumPy. But notice that the versions of ``sin`` and ``cos`` that were used was not inherent to the ``sin_cos`` function definition. Both ``sin_cos`` definitions are exactly the same. Rather, it was based on the names defined at the module where the ``sin_cos`` function was defined. The key point here is that when function in Python references a name that is not defined in the function, that name is looked up in the "global" namespace of the module where that function is defined. Now, in Python, we can emulate this behavior without actually writing a file to disk using the ``exec`` function. ``exec`` takes a string containing a block of Python code, and a dictionary that should contain the global variables of the module. It then executes the code "in" that dictionary, as if it were the module globals. The following is equivalent to the ``sin_cos`` defined in ``sin_cos_sympy.py``: >>> import sympy >>> module_dictionary = {'sin': sympy.sin, 'cos': sympy.cos} >>> exec(''' ... def sin_cos(x): ... return sin(x) + cos(x) ... ''', module_dictionary) >>> sin_cos = module_dictionary['sin_cos'] >>> sin_cos(1) cos(1) + sin(1) and similarly with ``sin_cos_numpy``: >>> import numpy >>> module_dictionary = {'sin': numpy.sin, 'cos': numpy.cos} >>> exec(''' ... def sin_cos(x): ... return sin(x) + cos(x) ... ''', module_dictionary) >>> sin_cos = module_dictionary['sin_cos'] >>> sin_cos(1) 1.38177329068 So now we can get an idea of how ``lambdify`` works. The name "lambdify" comes from the fact that we can think of something like ``lambdify(x, sin(x) + cos(x), 'numpy')`` as ``lambda x: sin(x) + cos(x)``, where ``sin`` and ``cos`` come from the ``numpy`` namespace. This is also why the symbols argument is first in ``lambdify``, as opposed to most SymPy functions where it comes after the expression: to better mimic the ``lambda`` keyword. ``lambdify`` takes the input expression (like ``sin(x) + cos(x)``) and 1. Converts it to a string 2. Creates a module globals dictionary based on the modules that are passed in (by default, it uses the NumPy module) 3. Creates the string ``"def func({vars}): return {expr}"``, where ``{vars}`` is the list of variables separated by commas, and ``{expr}`` is the string created in step 1., then ``exec``s that string with the module globals namespace and returns ``func``. In fact, functions returned by ``lambdify`` support inspection. So you can see exactly how they are defined by using ``inspect.getsource``, or ``??`` if you are using IPython or the Jupyter notebook. >>> f = lambdify(x, sin(x) + cos(x)) >>> import inspect >>> print(inspect.getsource(f)) def _lambdifygenerated(x): return (sin(x) + cos(x)) This shows us the source code of the function, but not the namespace it was defined in. We can inspect that by looking at the ``__globals__`` attribute of ``f``: >>> f.__globals__['sin'] <ufunc 'sin'> >>> f.__globals__['cos'] <ufunc 'cos'> >>> f.__globals__['sin'] is numpy.sin True This shows us that ``sin`` and ``cos`` in the namespace of ``f`` will be ``numpy.sin`` and ``numpy.cos``. Note that there are some convenience layers in each of these steps, but at the core, this is how ``lambdify`` works. Step 1 is done using the ``LambdaPrinter`` printers defined in the printing module (see :mod:`sympy.printing.lambdarepr`). This allows different SymPy expressions to define how they should be converted to a string for different modules. You can change which printer ``lambdify`` uses by passing a custom printer in to the ``printer`` argument. Step 2 is augmented by certain translations. There are default translations for each module, but you can provide your own by passing a list to the ``modules`` argument. For instance, >>> def mysin(x): ... print('taking the sin of', x) ... return numpy.sin(x) ... >>> f = lambdify(x, sin(x), [{'sin': mysin}, 'numpy']) >>> f(1) taking the sin of 1 0.8414709848078965 The globals dictionary is generated from the list by merging the dictionary ``{'sin': mysin}`` and the module dictionary for NumPy. The merging is done so that earlier items take precedence, which is why ``mysin`` is used above instead of ``numpy.sin``. If you want to modify the way ``lambdify`` works for a given function, it is usually easiest to do so by modifying the globals dictionary as such. In more complicated cases, it may be necessary to create and pass in a custom printer. Finally, step 3 is augmented with certain convenience operations, such as the addition of a docstring. Understanding how ``lambdify`` works can make it easier to avoid certain gotchas when using it. For instance, a common mistake is to create a lambdified function for one module (say, NumPy), and pass it objects from another (say, a SymPy expression). For instance, say we create >>> from sympy.abc import x >>> f = lambdify(x, x + 1, 'numpy') Now if we pass in a NumPy array, we get that array plus 1 >>> import numpy >>> a = numpy.array([1, 2]) >>> f(a) [2 3] But what happens if you make the mistake of passing in a SymPy expression instead of a NumPy array: >>> f(x + 1) x + 2 This worked, but it was only by accident. Now take a different lambdified function: >>> from sympy import sin >>> g = lambdify(x, x + sin(x), 'numpy') This works as expected on NumPy arrays: >>> g(a) [1.84147098 2.90929743] But if we try to pass in a SymPy expression, it fails >>> try: ... g(x + 1) ... # NumPy release after 1.17 raises TypeError instead of ... # AttributeError ... except (AttributeError, TypeError): ... raise AttributeError() # doctest: +IGNORE_EXCEPTION_DETAIL Traceback (most recent call last): ... AttributeError: Now, let's look at what happened. The reason this fails is that ``g`` calls ``numpy.sin`` on the input expression, and ``numpy.sin`` does not know how to operate on a SymPy object. As a general rule, NumPy functions do not know how to operate on SymPy expressions, and SymPy functions do not know how to operate on NumPy arrays. This is why lambdify exists: to provide a bridge between SymPy and NumPy. However, why is it that ``f`` did work? That's because ``f`` doesn't call any functions, it only adds 1. So the resulting function that is created, ``def _lambdifygenerated(x): return x + 1`` does not depend on the globals namespace it is defined in. Thus it works, but only by accident. A future version of ``lambdify`` may remove this behavior. Be aware that certain implementation details described here may change in future versions of SymPy. The API of passing in custom modules and printers will not change, but the details of how a lambda function is created may change. However, the basic idea will remain the same, and understanding it will be helpful to understanding the behavior of lambdify. In general: you should create lambdified functions for one module (say, NumPy), and only pass it input types that are compatible with that module (say, NumPy arrays). Remember that by default, if the ``module`` argument is not provided, ``lambdify`` creates functions using the NumPy and SciPy namespaces. """ from sympy.core.symbol import Symbol # If the user hasn't specified any modules, use what is available. if modules is None: try: _import("scipy") except ImportError: try: _import("numpy") except ImportError: # Use either numpy (if available) or python.math where possible. # XXX: This leads to different behaviour on different systems and # might be the reason for irreproducible errors. modules = ["math", "mpmath", "sympy"] else: modules = ["numpy"] else: modules = ["numpy", "scipy"] # Get the needed namespaces. namespaces = [] # First find any function implementations if use_imps: namespaces.append(_imp_namespace(expr)) # Check for dict before iterating if isinstance(modules, (dict, str)) or not hasattr(modules, '__iter__'): namespaces.append(modules) else: # consistency check if _module_present('numexpr', modules) and len(modules) > 1: raise TypeError("numexpr must be the only item in 'modules'") namespaces += list(modules) # fill namespace with first having highest priority namespace = {} # type: Dict[str, Any] for m in namespaces[::-1]: buf = _get_namespace(m) namespace.update(buf) if hasattr(expr, "atoms"): #Try if you can extract symbols from the expression. #Move on if expr.atoms in not implemented. syms = expr.atoms(Symbol) for term in syms: namespace.update({str(term): term}) if printer is None: if _module_present('mpmath', namespaces): from sympy.printing.pycode import MpmathPrinter as Printer # type: ignore elif _module_present('scipy', namespaces): from sympy.printing.pycode import SciPyPrinter as Printer # type: ignore elif _module_present('numpy', namespaces): from sympy.printing.pycode import NumPyPrinter as Printer # type: ignore elif _module_present('numexpr', namespaces): from sympy.printing.lambdarepr import NumExprPrinter as Printer # type: ignore elif _module_present('tensorflow', namespaces): from sympy.printing.tensorflow import TensorflowPrinter as Printer # type: ignore elif _module_present('sympy', namespaces): from sympy.printing.pycode import SymPyPrinter as Printer # type: ignore else: from sympy.printing.pycode import PythonCodePrinter as Printer # type: ignore user_functions = {} for m in namespaces[::-1]: if isinstance(m, dict): for k in m: user_functions[k] = k printer = Printer({'fully_qualified_modules': False, 'inline': True, 'allow_unknown_functions': True, 'user_functions': user_functions}) if isinstance(args, set): SymPyDeprecationWarning( feature="The list of arguments is a `set`. This leads to unpredictable results", useinstead=": Convert set into list or tuple", issue=20013, deprecated_since_version="1.6.3" ).warn() # Get the names of the args, for creating a docstring if not iterable(args): args = (args,) names = [] # Grab the callers frame, for getting the names by inspection (if needed) callers_local_vars = inspect.currentframe().f_back.f_locals.items() # type: ignore for n, var in enumerate(args): if hasattr(var, 'name'): names.append(var.name) else: # It's an iterable. Try to get name by inspection of calling frame. name_list = [var_name for var_name, var_val in callers_local_vars if var_val is var] if len(name_list) == 1: names.append(name_list[0]) else: # Cannot infer name with certainty. arg_# will have to do. names.append('arg_' + str(n)) # Create the function definition code and execute it funcname = '_lambdifygenerated' if _module_present('tensorflow', namespaces): funcprinter = _TensorflowEvaluatorPrinter(printer, dummify) # type: _EvaluatorPrinter else: funcprinter = _EvaluatorPrinter(printer, dummify) funcstr = funcprinter.doprint(funcname, args, expr) # Collect the module imports from the code printers. imp_mod_lines = [] for mod, keys in (getattr(printer, 'module_imports', None) or {}).items(): for k in keys: if k not in namespace: ln = "from %s import %s" % (mod, k) try: exec_(ln, {}, namespace) except ImportError: # Tensorflow 2.0 has issues with importing a specific # function from its submodule. # https://github.com/tensorflow/tensorflow/issues/33022 ln = "%s = %s.%s" % (k, mod, k) exec_(ln, {}, namespace) imp_mod_lines.append(ln) # Provide lambda expression with builtins, and compatible implementation of range namespace.update({'builtins':builtins, 'range':range}) funclocals = {} # type: Dict[str, Any] global _lambdify_generated_counter filename = '<lambdifygenerated-%s>' % _lambdify_generated_counter _lambdify_generated_counter += 1 c = compile(funcstr, filename, 'exec') exec_(c, namespace, funclocals) # mtime has to be None or else linecache.checkcache will remove it linecache.cache[filename] = (len(funcstr), None, funcstr.splitlines(True), filename) # type: ignore func = funclocals[funcname] # Apply the docstring sig = "func({})".format(", ".join(str(i) for i in names)) sig = textwrap.fill(sig, subsequent_indent=' '8) expr_str = str(expr) if len(expr_str) > 78: expr_str = textwrap.wrap(expr_str, 75)[0] + '...' func.__doc__ = ( "Created with lambdify. Signature:\n\n" "{sig}\n\n" "Expression:\n\n" "{expr}\n\n" "Source code:\n\n" "{src}\n\n" "Imported modules:\n\n" "{imp_mods}" ).format(sig=sig, expr=expr_str, src=funcstr, imp_mods='\n'.join(imp_mod_lines)) return func def _module_present(modname, modlist): if modname in modlist: return True for m in modlist: if hasattr(m, '__name__') and m.__name__ == modname: return True return False def _get_namespace(m): """ This is used by _lambdify to parse its arguments. """ if isinstance(m, str): _import(m) return MODULES[m][0] elif isinstance(m, dict): return m elif hasattr(m, "__dict__"): return m.__dict__ else: raise TypeError("Argument must be either a string, dict or module but it is: %s" % m) def lambdastr(args, expr, printer=None, dummify=None): """ Returns a string that can be evaluated to a lambda function. Examples ======== >>> from sympy.abc import x, y, z >>> from sympy.utilities.lambdify import lambdastr >>> lambdastr(x, x2) 'lambda x: (x2)' >>> lambdastr((x,y,z), [z,y,x]) 'lambda x,y,z: ([z, y, x])' Although tuples may not appear as arguments to lambda in Python 3, lambdastr will create a lambda function that will unpack the original arguments so that nested arguments can be handled: >>> lambdastr((x, (y, z)), x + y) 'lambda _0,_1: (lambda x,y,z: (x + y))(_0,_1[0],_1[1])' """ # Transforming everything to strings. from sympy.matrices import DeferredVector from sympy import Dummy, sympify, Symbol, Function, flatten, Derivative, Basic if printer is not None: if inspect.isfunction(printer): lambdarepr = printer else: if inspect.isclass(printer): lambdarepr = lambda expr: printer().doprint(expr) else: lambdarepr = lambda expr: printer.doprint(expr) else: #XXX: This has to be done here because of circular imports from sympy.printing.lambdarepr import lambdarepr def sub_args(args, dummies_dict): if isinstance(args, str): return args elif isinstance(args, DeferredVector): return str(args) elif iterable(args): dummies = flatten([sub_args(a, dummies_dict) for a in args]) return ",".join(str(a) for a in dummies) else: # replace these with Dummy symbols if isinstance(args, (Function, Symbol, Derivative)): dummies = Dummy() dummies_dict.update({args : dummies}) return str(dummies) else: return str(args) def sub_expr(expr, dummies_dict): expr = sympify(expr) # dict/tuple are sympified to Basic if isinstance(expr, Basic): expr = expr.xreplace(dummies_dict) # list is not sympified to Basic elif isinstance(expr, list): expr = [sub_expr(a, dummies_dict) for a in expr] return expr # Transform args def isiter(l): return iterable(l, exclude=(str, DeferredVector, NotIterable)) def flat_indexes(iterable): n = 0 for el in iterable: if isiter(el): for ndeep in flat_indexes(el): yield (n,) + ndeep else: yield (n,) n += 1 if dummify is None: dummify = any(isinstance(a, Basic) and a.atoms(Function, Derivative) for a in ( args if isiter(args) else [args])) if isiter(args) and any(isiter(i) for i in args): dum_args = [str(Dummy(str(i))) for i in range(len(args))] indexed_args = ','.join([ dum_args[ind[0]] + ''.join(["[%s]" % k for k in ind[1:]]) for ind in flat_indexes(args)]) lstr = lambdastr(flatten(args), expr, printer=printer, dummify=dummify) return 'lambda %s: (%s)(%s)' % (','.join(dum_args), lstr, indexed_args) dummies_dict = {} if dummify: args = sub_args(args, dummies_dict) else: if isinstance(args, str): pass elif iterable(args, exclude=DeferredVector): args = ",".join(str(a) for a in args) # Transform expr if dummify: if isinstance(expr, str): pass else: expr = sub_expr(expr, dummies_dict) expr = lambdarepr(expr) return "lambda %s: (%s)" % (args, expr) class _EvaluatorPrinter: def __init__(self, printer=None, dummify=False): self._dummify = dummify #XXX: This has to be done here because of circular imports from sympy.printing.lambdarepr import LambdaPrinter if printer is None: printer = LambdaPrinter() if inspect.isfunction(printer): self._exprrepr = printer else: if inspect.isclass(printer): printer = printer() self._exprrepr = printer.doprint #if hasattr(printer, '_print_Symbol'): # symbolrepr = printer._print_Symbol #if hasattr(printer, '_print_Dummy'): # dummyrepr = printer._print_Dummy # Used to print the generated function arguments in a standard way self._argrepr = LambdaPrinter().doprint def doprint(self, funcname, args, expr): """Returns the function definition code as a string.""" from sympy import Dummy funcbody = [] if not iterable(args): args = [args] argstrs, expr = self._preprocess(args, expr) # Generate argument unpacking and final argument list funcargs = [] unpackings = [] for argstr in argstrs: if iterable(argstr): funcargs.append(self._argrepr(Dummy())) unpackings.extend(self._print_unpacking(argstr, funcargs[-1])) else: funcargs.append(argstr) funcsig = 'def {}({}):'.format(funcname, ', '.join(funcargs)) # Wrap input arguments before unpacking funcbody.extend(self._print_funcargwrapping(funcargs)) funcbody.extend(unpackings) funcbody.append('return ({})'.format(self._exprrepr(expr))) funclines = [funcsig] funclines.extend(' ' + line for line in funcbody) return '\n'.join(funclines) + '\n' @classmethod def _is_safe_ident(cls, ident): return isinstance(ident, str) and ident.isidentifier() \ and not keyword.iskeyword(ident) def _preprocess(self, args, expr): """Preprocess args, expr to replace arguments that do not map to valid Python identifiers. Returns string form of args, and updated expr. """ from sympy import Dummy, Function, flatten, Derivative, ordered, Basic from sympy.matrices import DeferredVector from sympy.core.symbol import uniquely_named_symbol from sympy.core.expr import Expr # Args of type Dummy can cause name collisions with args # of type Symbol. Force dummify of everything in this # situation. dummify = self._dummify or any( isinstance(arg, Dummy) for arg in flatten(args)) argstrs = [None]len(args) for arg, i in reversed(list(ordered(zip(args, range(len(args)))))): if iterable(arg): s, expr = self._preprocess(arg, expr) elif isinstance(arg, DeferredVector): s = str(arg) elif isinstance(arg, Basic) and arg.is_symbol: s = self._argrepr(arg) if dummify or not self._is_safe_ident(s): dummy = Dummy() if isinstance(expr, Expr): dummy = uniquely_named_symbol( dummy.name, expr, modify=lambda s: '_' + s) s = self._argrepr(dummy) expr = self._subexpr(expr, {arg: dummy}) elif dummify or isinstance(arg, (Function, Derivative)): dummy = Dummy() s = self._argrepr(dummy) expr = self._subexpr(expr, {arg: dummy}) else: s = str(arg) argstrs[i] = s return argstrs, expr def _subexpr(self, expr, dummies_dict): from sympy.matrices import DeferredVector from sympy import sympify expr = sympify(expr) xreplace = getattr(expr, 'xreplace', None) if xreplace is not None: expr = xreplace(dummies_dict) else: if isinstance(expr, DeferredVector): pass elif isinstance(expr, dict): k = [self._subexpr(sympify(a), dummies_dict) for a in expr.keys()] v = [self._subexpr(sympify(a), dummies_dict) for a in expr.values()] expr = dict(zip(k, v)) elif isinstance(expr, tuple): expr = tuple(self._subexpr(sympify(a), dummies_dict) for a in expr) elif isinstance(expr, list): expr = [self._subexpr(sympify(a), dummies_dict) for a in expr] return expr def _print_funcargwrapping(self, args): """Generate argument wrapping code. args is the argument list of the generated function (strings). Return value is a list of lines of code that will be inserted at the beginning of the function definition. """ return [] def _print_unpacking(self, unpackto, arg): """Generate argument unpacking code. arg is the function argument to be unpacked (a string), and unpackto is a list or nested lists of the variable names (strings) to unpack to. """ def unpack_lhs(lvalues): return '[{}]'.format(', '.join( unpack_lhs(val) if iterable(val) else val for val in lvalues)) return ['{} = {}'.format(unpack_lhs(unpackto), arg)] class _TensorflowEvaluatorPrinter(_EvaluatorPrinter): def _print_unpacking(self, lvalues, rvalue): """Generate argument unpacking code. This method is used when the input value is not interable, but can be indexed (see issue #14655). """ from sympy import flatten def flat_indexes(elems): n = 0 for el in elems: if iterable(el): for ndeep in flat_indexes(el): yield (n,) + ndeep else: yield (n,) n += 1 indexed = ', '.join('{}[{}]'.format(rvalue, ']['.join(map(str, ind))) for ind in flat_indexes(lvalues)) return ['[{}] = [{}]'.format(', '.join(flatten(lvalues)), indexed)] def _imp_namespace(expr, namespace=None): """ Return namespace dict with function implementations We need to search for functions in anything that can be thrown at us - that is - anything that could be passed as ``expr``. Examples include sympy expressions, as well as tuples, lists and dicts that may contain sympy expressions. Parameters ---------- expr : object Something passed to lambdify, that will generate valid code from ``str(expr)``. namespace : None or mapping Namespace to fill. None results in new empty dict Returns ------- namespace : dict dict with keys of implemented function names within ``expr`` and corresponding values being the numerical implementation of function Examples ======== >>> from sympy.abc import x >>> from sympy.utilities.lambdify import implemented_function, _imp_namespace >>> from sympy import Function >>> f = implemented_function(Function('f'), lambda x: x+1) >>> g = implemented_function(Function('g'), lambda x: x10) >>> namespace = _imp_namespace(f(g(x))) >>> sorted(namespace.keys()) ['f', 'g'] """ # Delayed import to avoid circular imports from sympy.core.function import FunctionClass if namespace is None: namespace = {} # tuples, lists, dicts are valid expressions if is_sequence(expr): for arg in expr: _imp_namespace(arg, namespace) return namespace elif isinstance(expr, dict): for key, val in expr.items(): # functions can be in dictionary keys _imp_namespace(key, namespace) _imp_namespace(val, namespace) return namespace # sympy expressions may be Functions themselves func = getattr(expr, 'func', None) if isinstance(func, FunctionClass): imp = getattr(func, '_imp_', None) if imp is not None: name = expr.func.__name__ if name in namespace and namespace[name] != imp: raise ValueError('We found more than one ' 'implementation with name ' '"%s"' % name) namespace[name] = imp # and / or they may take Functions as arguments if hasattr(expr, 'args'): for arg in expr.args: _imp_namespace(arg, namespace) return namespace def implemented_function(symfunc, implementation): """ Add numerical ``implementation`` to function ``symfunc``. ``symfunc`` can be an ``UndefinedFunction`` instance, or a name string. In the latter case we create an ``UndefinedFunction`` instance with that name. Be aware that this is a quick workaround, not a general method to create special symbolic functions. If you want to create a symbolic function to be used by all the machinery of SymPy you should subclass the ``Function`` class. Parameters ---------- symfunc : ``str`` or ``UndefinedFunction`` instance If ``str``, then create new ``UndefinedFunction`` with this as name. If ``symfunc`` is an Undefined function, create a new function with the same name and the implemented function attached. implementation : callable numerical implementation to be called by ``evalf()`` or ``lambdify`` Returns ------- afunc : sympy.FunctionClass instance function with attached implementation Examples ======== >>> from sympy.abc import x >>> from sympy.utilities.lambdify import lambdify, implemented_function >>> f = implemented_function('f', lambda x: x+1) >>> lam_f = lambdify(x, f(x)) >>> lam_f(4) 5 """ # Delayed import to avoid circular imports from sympy.core.function import UndefinedFunction # if name, create function to hold implementation kwargs = {} if isinstance(symfunc, UndefinedFunction): kwargs = symfunc._kwargs symfunc = symfunc.__name__ if isinstance(symfunc, str): # Keyword arguments to UndefinedFunction are added as attributes to # the created class. symfunc = UndefinedFunction( symfunc, _imp_=staticmethod(implementation), *kwargs) elif not isinstance(symfunc, UndefinedFunction): raise ValueError(filldedent(''' symfunc should be either a string or an UndefinedFunction instance.''')) return symfunc
a53ba351df1b9660ac721ffc99f61a04975b9ee024eb120a5f519c84e63cbaa9	from collections import defaultdict, OrderedDict from itertools import ( combinations, combinations_with_replacement, permutations, product, product as cartes ) import random from operator import gt from sympy.core import Basic # this is the logical location of these functions from sympy.core.compatibility import ( as_int, default_sort_key, is_sequence, iterable, ordered ) from sympy.utilities.enumerative import ( multiset_partitions_taocp, list_visitor, MultisetPartitionTraverser) def is_palindromic(s, i=0, j=None): """return True if the sequence is the same from left to right as it is from right to left in the whole sequence (default) or in the Python slice ``s[i: j]``; else False. Examples ======== >>> from sympy.utilities.iterables import is_palindromic >>> is_palindromic([1, 0, 1]) True >>> is_palindromic('abcbb') False >>> is_palindromic('abcbb', 1) False Normal Python slicing is performed in place so there is no need to create a slice of the sequence for testing: >>> is_palindromic('abcbb', 1, -1) True >>> is_palindromic('abcbb', -4, -1) True See Also ======== sympy.ntheory.digits.is_palindromic: tests integers """ i, j, _ = slice(i, j).indices(len(s)) m = (j - i)//2 # if length is odd, middle element will be ignored return all(s[i + k] == s[j - 1 - k] for k in range(m)) def flatten(iterable, levels=None, cls=None): """ Recursively denest iterable containers. >>> from sympy.utilities.iterables import flatten >>> flatten([1, 2, 3]) [1, 2, 3] >>> flatten([1, 2, [3]]) [1, 2, 3] >>> flatten([1, [2, 3], [4, 5]]) [1, 2, 3, 4, 5] >>> flatten([1.0, 2, (1, None)]) [1.0, 2, 1, None] If you want to denest only a specified number of levels of nested containers, then set ``levels`` flag to the desired number of levels:: >>> ls = [[(-2, -1), (1, 2)], [(0, 0)]] >>> flatten(ls, levels=1) [(-2, -1), (1, 2), (0, 0)] If cls argument is specified, it will only flatten instances of that class, for example: >>> from sympy.core import Basic >>> class MyOp(Basic): ... pass ... >>> flatten([MyOp(1, MyOp(2, 3))], cls=MyOp) [1, 2, 3] adapted from https://kogs-www.informatik.uni-hamburg.de/~meine/python_tricks """ from sympy.tensor.array import NDimArray if levels is not None: if not levels: return iterable elif levels > 0: levels -= 1 else: raise ValueError( "expected non-negative number of levels, got %s" % levels) if cls is None: reducible = lambda x: is_sequence(x, set) else: reducible = lambda x: isinstance(x, cls) result = [] for el in iterable: if reducible(el): if hasattr(el, 'args') and not isinstance(el, NDimArray): el = el.args result.extend(flatten(el, levels=levels, cls=cls)) else: result.append(el) return result def unflatten(iter, n=2): """Group ``iter`` into tuples of length ``n``. Raise an error if the length of ``iter`` is not a multiple of ``n``. """ if n < 1 or len(iter) % n: raise ValueError('iter length is not a multiple of %i' % n) return list(zip((iter[i::n] for i in range(n)))) def reshape(seq, how): """Reshape the sequence according to the template in ``how``. Examples ======== >>> from sympy.utilities import reshape >>> seq = list(range(1, 9)) >>> reshape(seq, [4]) # lists of 4 [[1, 2, 3, 4], [5, 6, 7, 8]] >>> reshape(seq, (4,)) # tuples of 4 [(1, 2, 3, 4), (5, 6, 7, 8)] >>> reshape(seq, (2, 2)) # tuples of 4 [(1, 2, 3, 4), (5, 6, 7, 8)] >>> reshape(seq, (2, [2])) # (i, i, [i, i]) [(1, 2, [3, 4]), (5, 6, [7, 8])] >>> reshape(seq, ((2,), [2])) # etc.... [((1, 2), [3, 4]), ((5, 6), [7, 8])] >>> reshape(seq, (1, [2], 1)) [(1, [2, 3], 4), (5, [6, 7], 8)] >>> reshape(tuple(seq), ([[1], 1, (2,)],)) (([[1], 2, (3, 4)],), ([[5], 6, (7, 8)],)) >>> reshape(tuple(seq), ([1], 1, (2,))) (([1], 2, (3, 4)), ([5], 6, (7, 8))) >>> reshape(list(range(12)), [2, [3], {2}, (1, (3,), 1)]) [[0, 1, [2, 3, 4], {5, 6}, (7, (8, 9, 10), 11)]] """ m = sum(flatten(how)) n, rem = divmod(len(seq), m) if m < 0 or rem: raise ValueError('template must sum to positive number ' 'that divides the length of the sequence') i = 0 container = type(how) rv = [None]n for k in range(len(rv)): rv[k] = [] for hi in how: if type(hi) is int: rv[k].extend(seq[i: i + hi]) i += hi else: n = sum(flatten(hi)) hi_type = type(hi) rv[k].append(hi_type(reshape(seq[i: i + n], hi)[0])) i += n rv[k] = container(rv[k]) return type(seq)(rv) def group(seq, multiple=True): """ Splits a sequence into a list of lists of equal, adjacent elements. Examples ======== >>> from sympy.utilities.iterables import group >>> group([1, 1, 1, 2, 2, 3]) [[1, 1, 1], [2, 2], [3]] >>> group([1, 1, 1, 2, 2, 3], multiple=False) [(1, 3), (2, 2), (3, 1)] >>> group([1, 1, 3, 2, 2, 1], multiple=False) [(1, 2), (3, 1), (2, 2), (1, 1)] See Also ======== multiset """ if not seq: return [] current, groups = [seq[0]], [] for elem in seq[1:]: if elem == current[-1]: current.append(elem) else: groups.append(current) current = [elem] groups.append(current) if multiple: return groups for i, current in enumerate(groups): groups[i] = (current[0], len(current)) return groups def _iproduct2(iterable1, iterable2): '''Cartesian product of two possibly infinite iterables''' it1 = iter(iterable1) it2 = iter(iterable2) elems1 = [] elems2 = [] sentinel = object() def append(it, elems): e = next(it, sentinel) if e is not sentinel: elems.append(e) n = 0 append(it1, elems1) append(it2, elems2) while n <= len(elems1) + len(elems2): for m in range(n-len(elems1)+1, len(elems2)): yield (elems1[n-m], elems2[m]) n += 1 append(it1, elems1) append(it2, elems2) def iproduct(iterables): ''' Cartesian product of iterables. Generator of the cartesian product of iterables. This is analogous to itertools.product except that it works with infinite iterables and will yield any item from the infinite product eventually. Examples ======== >>> from sympy.utilities.iterables import iproduct >>> sorted(iproduct([1,2], [3,4])) [(1, 3), (1, 4), (2, 3), (2, 4)] With an infinite iterator: >>> from sympy import S >>> (3,) in iproduct(S.Integers) True >>> (3, 4) in iproduct(S.Integers, S.Integers) True .. seealso:: `itertools.product <https://docs.python.org/3/library/itertools.html#itertools.product>`_ ''' if len(iterables) == 0: yield () return elif len(iterables) == 1: for e in iterables[0]: yield (e,) elif len(iterables) == 2: yield from _iproduct2(iterables) else: first, others = iterables[0], iterables[1:] for ef, eo in _iproduct2(first, iproduct(others)): yield (ef,) + eo def multiset(seq): """Return the hashable sequence in multiset form with values being the multiplicity of the item in the sequence. Examples ======== >>> from sympy.utilities.iterables import multiset >>> multiset('mississippi') {'i': 4, 'm': 1, 'p': 2, 's': 4} See Also ======== group """ rv = defaultdict(int) for s in seq: rv[s] += 1 return dict(rv) def postorder_traversal(node, keys=None): """ Do a postorder traversal of a tree. This generator recursively yields nodes that it has visited in a postorder fashion. That is, it descends through the tree depth-first to yield all of a node's children's postorder traversal before yielding the node itself. Parameters ========== node : sympy expression The expression to traverse. keys : (default None) sort key(s) The key(s) used to sort args of Basic objects. When None, args of Basic objects are processed in arbitrary order. If key is defined, it will be passed along to ordered() as the only key(s) to use to sort the arguments; if ``key`` is simply True then the default keys of ``ordered`` will be used (node count and default_sort_key). Yields ====== subtree : sympy expression All of the subtrees in the tree. Examples ======== >>> from sympy.utilities.iterables import postorder_traversal >>> from sympy.abc import w, x, y, z The nodes are returned in the order that they are encountered unless key is given; simply passing key=True will guarantee that the traversal is unique. >>> list(postorder_traversal(w + (x + y)z)) # doctest: +SKIP [z, y, x, x + y, z(x + y), w, w + z(x + y)] >>> list(postorder_traversal(w + (x + y)z, keys=True)) [w, z, x, y, x + y, z(x + y), w + z(x + y)] """ if isinstance(node, Basic): args = node.args if keys: if keys != True: args = ordered(args, keys, default=False) else: args = ordered(args) for arg in args: yield from postorder_traversal(arg, keys) elif iterable(node): for item in node: yield from postorder_traversal(item, keys) yield node def interactive_traversal(expr): """Traverse a tree asking a user which branch to choose. """ from sympy.printing import pprint RED, BRED = '\033[0;31m', '\033[1;31m' GREEN, BGREEN = '\033[0;32m', '\033[1;32m' YELLOW, BYELLOW = '\033[0;33m', '\033[1;33m' # noqa BLUE, BBLUE = '\033[0;34m', '\033[1;34m' # noqa MAGENTA, BMAGENTA = '\033[0;35m', '\033[1;35m'# noqa CYAN, BCYAN = '\033[0;36m', '\033[1;36m' # noqa END = '\033[0m' def cprint(args): print("".join(map(str, args)) + END) def _interactive_traversal(expr, stage): if stage > 0: print() cprint("Current expression (stage ", BYELLOW, stage, END, "):") print(BCYAN) pprint(expr) print(END) if isinstance(expr, Basic): if expr.is_Add: args = expr.as_ordered_terms() elif expr.is_Mul: args = expr.as_ordered_factors() else: args = expr.args elif hasattr(expr, "__iter__"): args = list(expr) else: return expr n_args = len(args) if not n_args: return expr for i, arg in enumerate(args): cprint(GREEN, "[", BGREEN, i, GREEN, "] ", BLUE, type(arg), END) pprint(arg) print() if n_args == 1: choices = '0' else: choices = '0-%d' % (n_args - 1) try: choice = input("Your choice [%s,f,l,r,d,?]: " % choices) except EOFError: result = expr print() else: if choice == '?': cprint(RED, "%s - select subexpression with the given index" % choices) cprint(RED, "f - select the first subexpression") cprint(RED, "l - select the last subexpression") cprint(RED, "r - select a random subexpression") cprint(RED, "d - done\n") result = _interactive_traversal(expr, stage) elif choice in ['d', '']: result = expr elif choice == 'f': result = _interactive_traversal(args[0], stage + 1) elif choice == 'l': result = _interactive_traversal(args[-1], stage + 1) elif choice == 'r': result = _interactive_traversal(random.choice(args), stage + 1) else: try: choice = int(choice) except ValueError: cprint(BRED, "Choice must be a number in %s range\n" % choices) result = _interactive_traversal(expr, stage) else: if choice < 0 or choice >= n_args: cprint(BRED, "Choice must be in %s range\n" % choices) result = _interactive_traversal(expr, stage) else: result = _interactive_traversal(args[choice], stage + 1) return result return _interactive_traversal(expr, 0) def ibin(n, bits=None, str=False): """Return a list of length ``bits`` corresponding to the binary value of ``n`` with small bits to the right (last). If bits is omitted, the length will be the number required to represent ``n``. If the bits are desired in reversed order, use the ``[::-1]`` slice of the returned list. If a sequence of all bits-length lists starting from ``[0, 0,..., 0]`` through ``[1, 1, ..., 1]`` are desired, pass a non-integer for bits, e.g. ``'all'``. If the bit string is desired pass ``str=True``. Examples ======== >>> from sympy.utilities.iterables import ibin >>> ibin(2) [1, 0] >>> ibin(2, 4) [0, 0, 1, 0] If all lists corresponding to 0 to 2n - 1, pass a non-integer for bits: >>> bits = 2 >>> for i in ibin(2, 'all'): ... print(i) (0, 0) (0, 1) (1, 0) (1, 1) If a bit string is desired of a given length, use str=True: >>> n = 123 >>> bits = 10 >>> ibin(n, bits, str=True) '0001111011' >>> ibin(n, bits, str=True)[::-1] # small bits left '1101111000' >>> list(ibin(3, 'all', str=True)) ['000', '001', '010', '011', '100', '101', '110', '111'] """ if n < 0: raise ValueError("negative numbers are not allowed") n = as_int(n) if bits is None: bits = 0 else: try: bits = as_int(bits) except ValueError: bits = -1 else: if n.bit_length() > bits: raise ValueError( "`bits` must be >= {}".format(n.bit_length())) if not str: if bits >= 0: return [1 if i == "1" else 0 for i in bin(n)[2:].rjust(bits, "0")] else: return variations(list(range(2)), n, repetition=True) else: if bits >= 0: return bin(n)[2:].rjust(bits, "0") else: return (bin(i)[2:].rjust(n, "0") for i in range(2n)) def variations(seq, n, repetition=False): r"""Returns a generator of the n-sized variations of ``seq`` (size N). ``repetition`` controls whether items in ``seq`` can appear more than once; Examples ======== ``variations(seq, n)`` will return `\frac{N!}{(N - n)!}` permutations without repetition of ``seq``'s elements: >>> from sympy.utilities.iterables import variations >>> list(variations([1, 2], 2)) [(1, 2), (2, 1)] ``variations(seq, n, True)`` will return the `N^n` permutations obtained by allowing repetition of elements: >>> list(variations([1, 2], 2, repetition=True)) [(1, 1), (1, 2), (2, 1), (2, 2)] If you ask for more items than are in the set you get the empty set unless you allow repetitions: >>> list(variations([0, 1], 3, repetition=False)) [] >>> list(variations([0, 1], 3, repetition=True))[:4] [(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1)] .. seealso:: `itertools.permutations <https://docs.python.org/3/library/itertools.html#itertools.permutations>`_, `itertools.product <https://docs.python.org/3/library/itertools.html#itertools.product>`_ """ if not repetition: seq = tuple(seq) if len(seq) < n: return yield from permutations(seq, n) else: if n == 0: yield () else: yield from product(seq, repeat=n) def subsets(seq, k=None, repetition=False): r"""Generates all `k`-subsets (combinations) from an `n`-element set, ``seq``. A `k`-subset of an `n`-element set is any subset of length exactly `k`. The number of `k`-subsets of an `n`-element set is given by ``binomial(n, k)``, whereas there are `2^n` subsets all together. If `k` is ``None`` then all `2^n` subsets will be returned from shortest to longest. Examples ======== >>> from sympy.utilities.iterables import subsets ``subsets(seq, k)`` will return the `\frac{n!}{k!(n - k)!}` `k`-subsets (combinations) without repetition, i.e. once an item has been removed, it can no longer be "taken": >>> list(subsets([1, 2], 2)) [(1, 2)] >>> list(subsets([1, 2])) [(), (1,), (2,), (1, 2)] >>> list(subsets([1, 2, 3], 2)) [(1, 2), (1, 3), (2, 3)] ``subsets(seq, k, repetition=True)`` will return the `\frac{(n - 1 + k)!}{k!(n - 1)!}` combinations with repetition: >>> list(subsets([1, 2], 2, repetition=True)) [(1, 1), (1, 2), (2, 2)] If you ask for more items than are in the set you get the empty set unless you allow repetitions: >>> list(subsets([0, 1], 3, repetition=False)) [] >>> list(subsets([0, 1], 3, repetition=True)) [(0, 0, 0), (0, 0, 1), (0, 1, 1), (1, 1, 1)] """ if k is None: for k in range(len(seq) + 1): yield from subsets(seq, k, repetition) else: if not repetition: yield from combinations(seq, k) else: yield from combinations_with_replacement(seq, k) def filter_symbols(iterator, exclude): """ Only yield elements from `iterator` that do not occur in `exclude`. Parameters ========== iterator : iterable iterator to take elements from exclude : iterable elements to exclude Returns ======= iterator : iterator filtered iterator """ exclude = set(exclude) for s in iterator: if s not in exclude: yield s def numbered_symbols(prefix='x', cls=None, start=0, exclude=[], args, assumptions): """ Generate an infinite stream of Symbols consisting of a prefix and increasing subscripts provided that they do not occur in ``exclude``. Parameters ========== prefix : str, optional The prefix to use. By default, this function will generate symbols of the form "x0", "x1", etc. cls : class, optional The class to use. By default, it uses ``Symbol``, but you can also use ``Wild`` or ``Dummy``. start : int, optional The start number. By default, it is 0. Returns ======= sym : Symbol The subscripted symbols. """ exclude = set(exclude or []) if cls is None: # We can't just make the default cls=Symbol because it isn't # imported yet. from sympy import Symbol cls = Symbol while True: name = '%s%s' % (prefix, start) s = cls(name, args, assumptions) if s not in exclude: yield s start += 1 def capture(func): """Return the printed output of func(). ``func`` should be a function without arguments that produces output with print statements. >>> from sympy.utilities.iterables import capture >>> from sympy import pprint >>> from sympy.abc import x >>> def foo(): ... print('hello world!') ... >>> 'hello' in capture(foo) # foo, not foo() True >>> capture(lambda: pprint(2/x)) '2\\n-\\nx\\n' """ from sympy.core.compatibility import StringIO import sys stdout = sys.stdout sys.stdout = file = StringIO() try: func() finally: sys.stdout = stdout return file.getvalue() def sift(seq, keyfunc, binary=False): """ Sift the sequence, ``seq`` according to ``keyfunc``. Returns ======= When ``binary`` is ``False`` (default), the output is a dictionary where elements of ``seq`` are stored in a list keyed to the value of keyfunc for that element. If ``binary`` is True then a tuple with lists ``T`` and ``F`` are returned where ``T`` is a list containing elements of seq for which ``keyfunc`` was ``True`` and ``F`` containing those elements for which ``keyfunc`` was ``False``; a ValueError is raised if the ``keyfunc`` is not binary. Examples ======== >>> from sympy.utilities import sift >>> from sympy.abc import x, y >>> from sympy import sqrt, exp, pi, Tuple >>> sift(range(5), lambda x: x % 2) {0: [0, 2, 4], 1: [1, 3]} sift() returns a defaultdict() object, so any key that has no matches will give []. >>> sift([x], lambda x: x.is_commutative) {True: [x]} >>> _[False] [] Sometimes you will not know how many keys you will get: >>> sift([sqrt(x), exp(x), (yx)2], ... lambda x: x.as_base_exp()[0]) {E: [exp(x)], x: [sqrt(x)], y: [y(2x)]} Sometimes you expect the results to be binary; the results can be unpacked by setting ``binary`` to True: >>> sift(range(4), lambda x: x % 2, binary=True) ([1, 3], [0, 2]) >>> sift(Tuple(1, pi), lambda x: x.is_rational, binary=True) ([1], [pi]) A ValueError is raised if the predicate was not actually binary (which is a good test for the logic where sifting is used and binary results were expected): >>> unknown = exp(1) - pi # the rationality of this is unknown >>> args = Tuple(1, pi, unknown) >>> sift(args, lambda x: x.is_rational, binary=True) Traceback (most recent call last): ... ValueError: keyfunc gave non-binary output The non-binary sifting shows that there were 3 keys generated: >>> set(sift(args, lambda x: x.is_rational).keys()) {None, False, True} If you need to sort the sifted items it might be better to use ``ordered`` which can economically apply multiple sort keys to a sequence while sorting. See Also ======== ordered """ if not binary: m = defaultdict(list) for i in seq: m[keyfunc(i)].append(i) return m sift = F, T = [], [] for i in seq: try: sift[keyfunc(i)].append(i) except (IndexError, TypeError): raise ValueError('keyfunc gave non-binary output') return T, F def take(iter, n): """Return ``n`` items from ``iter`` iterator. """ return [ value for _, value in zip(range(n), iter) ] def dict_merge(dicts): """Merge dictionaries into a single dictionary. """ merged = {} for dict in dicts: merged.update(dict) return merged def common_prefix(seqs): """Return the subsequence that is a common start of sequences in ``seqs``. >>> from sympy.utilities.iterables import common_prefix >>> common_prefix(list(range(3))) [0, 1, 2] >>> common_prefix(list(range(3)), list(range(4))) [0, 1, 2] >>> common_prefix([1, 2, 3], [1, 2, 5]) [1, 2] >>> common_prefix([1, 2, 3], [1, 3, 5]) [1] """ if any(not s for s in seqs): return [] elif len(seqs) == 1: return seqs[0] i = 0 for i in range(min(len(s) for s in seqs)): if not all(seqs[j][i] == seqs[0][i] for j in range(len(seqs))): break else: i += 1 return seqs[0][:i] def common_suffix(seqs): """Return the subsequence that is a common ending of sequences in ``seqs``. >>> from sympy.utilities.iterables import common_suffix >>> common_suffix(list(range(3))) [0, 1, 2] >>> common_suffix(list(range(3)), list(range(4))) [] >>> common_suffix([1, 2, 3], [9, 2, 3]) [2, 3] >>> common_suffix([1, 2, 3], [9, 7, 3]) [3] """ if any(not s for s in seqs): return [] elif len(seqs) == 1: return seqs[0] i = 0 for i in range(-1, -min(len(s) for s in seqs) - 1, -1): if not all(seqs[j][i] == seqs[0][i] for j in range(len(seqs))): break else: i -= 1 if i == -1: return [] else: return seqs[0][i + 1:] def prefixes(seq): """ Generate all prefixes of a sequence. Examples ======== >>> from sympy.utilities.iterables import prefixes >>> list(prefixes([1,2,3,4])) [[1], [1, 2], [1, 2, 3], [1, 2, 3, 4]] """ n = len(seq) for i in range(n): yield seq[:i + 1] def postfixes(seq): """ Generate all postfixes of a sequence. Examples ======== >>> from sympy.utilities.iterables import postfixes >>> list(postfixes([1,2,3,4])) [[4], [3, 4], [2, 3, 4], [1, 2, 3, 4]] """ n = len(seq) for i in range(n): yield seq[n - i - 1:] def topological_sort(graph, key=None): r""" Topological sort of graph's vertices. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph to be sorted topologically. key : callable[T] (optional) Ordering key for vertices on the same level. By default the natural (e.g. lexicographic) ordering is used (in this case the base type must implement ordering relations). Examples ======== Consider a graph:: +---+ +---+ +---+ \| 7 \|\ \| 5 \| \| 3 \| +---+ \ +---+ +---+ \| _\___/ ____ _/ \| \| / \___/ \ / \| V V V V \| +----+ +---+ \| \| 11 \| \| 8 \| \| +----+ +---+ \| \| \| \____ ___/ _ \| \| \ \ / / \ \| V \ V V / V V +---+ \ +---+ \| +----+ \| 2 \| \| \| 9 \| \| \| 10 \| +---+ \| +---+ \| +----+ \________/ where vertices are integers. This graph can be encoded using elementary Python's data structures as follows:: >>> V = [2, 3, 5, 7, 8, 9, 10, 11] >>> E = [(7, 11), (7, 8), (5, 11), (3, 8), (3, 10), ... (11, 2), (11, 9), (11, 10), (8, 9)] To compute a topological sort for graph ``(V, E)`` issue:: >>> from sympy.utilities.iterables import topological_sort >>> topological_sort((V, E)) [3, 5, 7, 8, 11, 2, 9, 10] If specific tie breaking approach is needed, use ``key`` parameter:: >>> topological_sort((V, E), key=lambda v: -v) [7, 5, 11, 3, 10, 8, 9, 2] Only acyclic graphs can be sorted. If the input graph has a cycle, then ``ValueError`` will be raised:: >>> topological_sort((V, E + [(10, 7)])) Traceback (most recent call last): ... ValueError: cycle detected References ========== .. [1] https://en.wikipedia.org/wiki/Topological_sorting """ V, E = graph L = [] S = set(V) E = list(E) for v, u in E: S.discard(u) if key is None: key = lambda value: value S = sorted(S, key=key, reverse=True) while S: node = S.pop() L.append(node) for u, v in list(E): if u == node: E.remove((u, v)) for _u, _v in E: if v == _v: break else: kv = key(v) for i, s in enumerate(S): ks = key(s) if kv > ks: S.insert(i, v) break else: S.append(v) if E: raise ValueError("cycle detected") else: return L def strongly_connected_components(G): r""" Strongly connected components of a directed graph in reverse topological order. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph whose strongly connected components are to be found. Examples ======== Consider a directed graph (in dot notation):: digraph { A -> B A -> C B -> C C -> B B -> D } where vertices are the letters A, B, C and D. This graph can be encoded using Python's elementary data structures as follows:: >>> V = ['A', 'B', 'C', 'D'] >>> E = [('A', 'B'), ('A', 'C'), ('B', 'C'), ('C', 'B'), ('B', 'D')] The strongly connected components of this graph can be computed as >>> from sympy.utilities.iterables import strongly_connected_components >>> strongly_connected_components((V, E)) [['D'], ['B', 'C'], ['A']] This also gives the components in reverse topological order. Since the subgraph containing B and C has a cycle they must be together in a strongly connected component. A and D are connected to the rest of the graph but not in a cyclic manner so they appear as their own strongly connected components. Notes ===== The vertices of the graph must be hashable for the data structures used. If the vertices are unhashable replace them with integer indices. This function uses Tarjan's algorithm to compute the strongly connected components in `O(\|V\|+\|E\|)` (linear) time. References ========== .. [1] https://en.wikipedia.org/wiki/Strongly_connected_component .. [2] https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm See Also ======== sympy.utilities.iterables.connected_components """ # Map from a vertex to its neighbours V, E = G Gmap = {vi: [] for vi in V} for v1, v2 in E: Gmap[v1].append(v2) # Non-recursive Tarjan's algorithm: lowlink = {} indices = {} stack = OrderedDict() callstack = [] components = [] nomore = object() def start(v): index = len(stack) indices[v] = lowlink[v] = index stack[v] = None callstack.append((v, iter(Gmap[v]))) def finish(v1): # Finished a component? if lowlink[v1] == indices[v1]: component = [stack.popitem()[0]] while component[-1] is not v1: component.append(stack.popitem()[0]) components.append(component[::-1]) v2, _ = callstack.pop() if callstack: v1, _ = callstack[-1] lowlink[v1] = min(lowlink[v1], lowlink[v2]) for v in V: if v in indices: continue start(v) while callstack: v1, it1 = callstack[-1] v2 = next(it1, nomore) # Finished children of v1? if v2 is nomore: finish(v1) # Recurse on v2 elif v2 not in indices: start(v2) elif v2 in stack: lowlink[v1] = min(lowlink[v1], indices[v2]) # Reverse topological sort order: return components def connected_components(G): r""" Connected components of an undirected graph or weakly connected components of a directed graph. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph whose connected components are to be found. Examples ======== Given an undirected graph:: graph { A -- B C -- D } We can find the connected components using this function if we include each edge in both directions:: >>> from sympy.utilities.iterables import connected_components >>> V = ['A', 'B', 'C', 'D'] >>> E = [('A', 'B'), ('B', 'A'), ('C', 'D'), ('D', 'C')] >>> connected_components((V, E)) [['A', 'B'], ['C', 'D']] The weakly connected components of a directed graph can found the same way. Notes ===== The vertices of the graph must be hashable for the data structures used. If the vertices are unhashable replace them with integer indices. This function uses Tarjan's algorithm to compute the connected components in `O(\|V\|+\|E\|)` (linear) time. References ========== .. [1] https://en.wikipedia.org/wiki/Connected_component_(graph_theory) .. [2] https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm See Also ======== sympy.utilities.iterables.strongly_connected_components """ # Duplicate edges both ways so that the graph is effectively undirected # and return the strongly connected components: V, E = G E_undirected = [] for v1, v2 in E: E_undirected.extend([(v1, v2), (v2, v1)]) return strongly_connected_components((V, E_undirected)) def rotate_left(x, y): """ Left rotates a list x by the number of steps specified in y. Examples ======== >>> from sympy.utilities.iterables import rotate_left >>> a = [0, 1, 2] >>> rotate_left(a, 1) [1, 2, 0] """ if len(x) == 0: return [] y = y % len(x) return x[y:] + x[:y] def rotate_right(x, y): """ Right rotates a list x by the number of steps specified in y. Examples ======== >>> from sympy.utilities.iterables import rotate_right >>> a = [0, 1, 2] >>> rotate_right(a, 1) [2, 0, 1] """ if len(x) == 0: return [] y = len(x) - y % len(x) return x[y:] + x[:y] def least_rotation(x): ''' Returns the number of steps of left rotation required to obtain lexicographically minimal string/list/tuple, etc. Examples ======== >>> from sympy.utilities.iterables import least_rotation, rotate_left >>> a = [3, 1, 5, 1, 2] >>> least_rotation(a) 3 >>> rotate_left(a, _) [1, 2, 3, 1, 5] References ========== .. [1] https://en.wikipedia.org/wiki/Lexicographically_minimal_string_rotation ''' S = x + x # Concatenate string to it self to avoid modular arithmetic f = [-1] * len(S) # Failure function k = 0 # Least rotation of string found so far for j in range(1,len(S)): sj = S[j] i = f[j-k-1] while i != -1 and sj != S[k+i+1]: if sj < S[k+i+1]: k = j-i-1 i = f[i] if sj != S[k+i+1]: if sj < S[k]: k = j f[j-k] = -1 else: f[j-k] = i+1 return k def multiset_combinations(m, n, g=None): """ Return the unique combinations of size ``n`` from multiset ``m``. Examples ======== >>> from sympy.utilities.iterables import multiset_combinations >>> from itertools import combinations >>> [''.join(i) for i in multiset_combinations('baby', 3)] ['abb', 'aby', 'bby'] >>> def count(f, s): return len(list(f(s, 3))) The number of combinations depends on the number of letters; the number of unique combinations depends on how the letters are repeated. >>> s1 = 'abracadabra' >>> s2 = 'banana tree' >>> count(combinations, s1), count(multiset_combinations, s1) (165, 23) >>> count(combinations, s2), count(multiset_combinations, s2) (165, 54) """ if g is None: if type(m) is dict: if n > sum(m.values()): return g = [[k, m[k]] for k in ordered(m)] else: m = list(m) if n > len(m): return try: m = multiset(m) g = [(k, m[k]) for k in ordered(m)] except TypeError: m = list(ordered(m)) g = [list(i) for i in group(m, multiple=False)] del m if sum(v for k, v in g) < n or not n: yield [] else: for i, (k, v) in enumerate(g): if v >= n: yield [k]n v = n - 1 for v in range(min(n, v), 0, -1): for j in multiset_combinations(None, n - v, g[i + 1:]): rv = [k]v + j if len(rv) == n: yield rv def multiset_permutations(m, size=None, g=None): """ Return the unique permutations of multiset ``m``. Examples ======== >>> from sympy.utilities.iterables import multiset_permutations >>> from sympy import factorial >>> [''.join(i) for i in multiset_permutations('aab')] ['aab', 'aba', 'baa'] >>> factorial(len('banana')) 720 >>> len(list(multiset_permutations('banana'))) 60 """ if g is None: if type(m) is dict: g = [[k, m[k]] for k in ordered(m)] else: m = list(ordered(m)) g = [list(i) for i in group(m, multiple=False)] del m do = [gi for gi in g if gi[1] > 0] SUM = sum([gi[1] for gi in do]) if not do or size is not None and (size > SUM or size < 1): if size < 1: yield [] return elif size == 1: for k, v in do: yield [k] elif len(do) == 1: k, v = do[0] v = v if size is None else (size if size <= v else 0) yield [k for i in range(v)] elif all(v == 1 for k, v in do): for p in permutations([k for k, v in do], size): yield list(p) else: size = size if size is not None else SUM for i, (k, v) in enumerate(do): do[i][1] -= 1 for j in multiset_permutations(None, size - 1, do): if j: yield [k] + j do[i][1] += 1 def _partition(seq, vector, m=None): """ Return the partition of seq as specified by the partition vector. Examples ======== >>> from sympy.utilities.iterables import _partition >>> _partition('abcde', [1, 0, 1, 2, 0]) [['b', 'e'], ['a', 'c'], ['d']] Specifying the number of bins in the partition is optional: >>> _partition('abcde', [1, 0, 1, 2, 0], 3) [['b', 'e'], ['a', 'c'], ['d']] The output of _set_partitions can be passed as follows: >>> output = (3, [1, 0, 1, 2, 0]) >>> _partition('abcde', output) [['b', 'e'], ['a', 'c'], ['d']] See Also ======== combinatorics.partitions.Partition.from_rgs """ if m is None: m = max(vector) + 1 elif type(vector) is int: # entered as m, vector vector, m = m, vector p = [[] for i in range(m)] for i, v in enumerate(vector): p[v].append(seq[i]) return p def _set_partitions(n): """Cycle through all partions of n elements, yielding the current number of partitions, ``m``, and a mutable list, ``q`` such that element[i] is in part q[i] of the partition. NOTE: ``q`` is modified in place and generally should not be changed between function calls. Examples ======== >>> from sympy.utilities.iterables import _set_partitions, _partition >>> for m, q in _set_partitions(3): ... print('%s %s %s' % (m, q, _partition('abc', q, m))) 1 [0, 0, 0] [['a', 'b', 'c']] 2 [0, 0, 1] [['a', 'b'], ['c']] 2 [0, 1, 0] [['a', 'c'], ['b']] 2 [0, 1, 1] [['a'], ['b', 'c']] 3 [0, 1, 2] [['a'], ['b'], ['c']] Notes ===== This algorithm is similar to, and solves the same problem as, Algorithm 7.2.1.5H, from volume 4A of Knuth's The Art of Computer Programming. Knuth uses the term "restricted growth string" where this code refers to a "partition vector". In each case, the meaning is the same: the value in the ith element of the vector specifies to which part the ith set element is to be assigned. At the lowest level, this code implements an n-digit big-endian counter (stored in the array q) which is incremented (with carries) to get the next partition in the sequence. A special twist is that a digit is constrained to be at most one greater than the maximum of all the digits to the left of it. The array p maintains this maximum, so that the code can efficiently decide when a digit can be incremented in place or whether it needs to be reset to 0 and trigger a carry to the next digit. The enumeration starts with all the digits 0 (which corresponds to all the set elements being assigned to the same 0th part), and ends with 0123...n, which corresponds to each set element being assigned to a different, singleton, part. This routine was rewritten to use 0-based lists while trying to preserve the beauty and efficiency of the original algorithm. References ========== .. [1] Nijenhuis, Albert and Wilf, Herbert. (1978) Combinatorial Algorithms, 2nd Ed, p 91, algorithm "nexequ". Available online from https://www.math.upenn.edu/~wilf/website/CombAlgDownld.html (viewed November 17, 2012). """ p = [0]n q = [0]n nc = 1 yield nc, q while nc != n: m = n while 1: m -= 1 i = q[m] if p[i] != 1: break q[m] = 0 i += 1 q[m] = i m += 1 nc += m - n p[0] += n - m if i == nc: p[nc] = 0 nc += 1 p[i - 1] -= 1 p[i] += 1 yield nc, q def multiset_partitions(multiset, m=None): """ Return unique partitions of the given multiset (in list form). If ``m`` is None, all multisets will be returned, otherwise only partitions with ``m`` parts will be returned. If ``multiset`` is an integer, a range [0, 1, ..., multiset - 1] will be supplied. Examples ======== >>> from sympy.utilities.iterables import multiset_partitions >>> list(multiset_partitions([1, 2, 3, 4], 2)) [[[1, 2, 3], [4]], [[1, 2, 4], [3]], [[1, 2], [3, 4]], [[1, 3, 4], [2]], [[1, 3], [2, 4]], [[1, 4], [2, 3]], [[1], [2, 3, 4]]] >>> list(multiset_partitions([1, 2, 3, 4], 1)) [[[1, 2, 3, 4]]] Only unique partitions are returned and these will be returned in a canonical order regardless of the order of the input: >>> a = [1, 2, 2, 1] >>> ans = list(multiset_partitions(a, 2)) >>> a.sort() >>> list(multiset_partitions(a, 2)) == ans True >>> a = range(3, 1, -1) >>> (list(multiset_partitions(a)) == ... list(multiset_partitions(sorted(a)))) True If m is omitted then all partitions will be returned: >>> list(multiset_partitions([1, 1, 2])) [[[1, 1, 2]], [[1, 1], [2]], [[1, 2], [1]], [[1], [1], [2]]] >>> list(multiset_partitions([1]3)) [[[1, 1, 1]], [[1], [1, 1]], [[1], [1], [1]]] Counting ======== The number of partitions of a set is given by the bell number: >>> from sympy import bell >>> len(list(multiset_partitions(5))) == bell(5) == 52 True The number of partitions of length k from a set of size n is given by the Stirling Number of the 2nd kind: >>> from sympy.functions.combinatorial.numbers import stirling >>> stirling(5, 2) == len(list(multiset_partitions(5, 2))) == 15 True These comments on counting apply to sets, not multisets. Notes ===== When all the elements are the same in the multiset, the order of the returned partitions is determined by the ``partitions`` routine. If one is counting partitions then it is better to use the ``nT`` function. See Also ======== partitions sympy.combinatorics.partitions.Partition sympy.combinatorics.partitions.IntegerPartition sympy.functions.combinatorial.numbers.nT """ # This function looks at the supplied input and dispatches to # several special-case routines as they apply. if type(multiset) is int: n = multiset if m and m > n: return multiset = list(range(n)) if m == 1: yield [multiset[:]] return # If m is not None, it can sometimes be faster to use # MultisetPartitionTraverser.enum_range() even for inputs # which are sets. Since the _set_partitions code is quite # fast, this is only advantageous when the overall set # partitions outnumber those with the desired number of parts # by a large factor. (At least 60.) Such a switch is not # currently implemented. for nc, q in _set_partitions(n): if m is None or nc == m: rv = [[] for i in range(nc)] for i in range(n): rv[q[i]].append(multiset[i]) yield rv return if len(multiset) == 1 and isinstance(multiset, str): multiset = [multiset] if not has_variety(multiset): # Only one component, repeated n times. The resulting # partitions correspond to partitions of integer n. n = len(multiset) if m and m > n: return if m == 1: yield [multiset[:]] return x = multiset[:1] for size, p in partitions(n, m, size=True): if m is None or size == m: rv = [] for k in sorted(p): rv.extend([xk]p[k]) yield rv else: multiset = list(ordered(multiset)) n = len(multiset) if m and m > n: return if m == 1: yield [multiset[:]] return # Split the information of the multiset into two lists - # one of the elements themselves, and one (of the same length) # giving the number of repeats for the corresponding element. elements, multiplicities = zip(group(multiset, False)) if len(elements) < len(multiset): # General case - multiset with more than one distinct element # and at least one element repeated more than once. if m: mpt = MultisetPartitionTraverser() for state in mpt.enum_range(multiplicities, m-1, m): yield list_visitor(state, elements) else: for state in multiset_partitions_taocp(multiplicities): yield list_visitor(state, elements) else: # Set partitions case - no repeated elements. Pretty much # same as int argument case above, with same possible, but # currently unimplemented optimization for some cases when # m is not None for nc, q in _set_partitions(n): if m is None or nc == m: rv = [[] for i in range(nc)] for i in range(n): rv[q[i]].append(i) yield [[multiset[j] for j in i] for i in rv] def partitions(n, m=None, k=None, size=False): """Generate all partitions of positive integer, n. Parameters ========== m : integer (default gives partitions of all sizes) limits number of parts in partition (mnemonic: m, maximum parts) k : integer (default gives partitions number from 1 through n) limits the numbers that are kept in the partition (mnemonic: k, keys) size : bool (default False, only partition is returned) when ``True`` then (M, P) is returned where M is the sum of the multiplicities and P is the generated partition. Each partition is represented as a dictionary, mapping an integer to the number of copies of that integer in the partition. For example, the first partition of 4 returned is {4: 1}, "4: one of them". Examples ======== >>> from sympy.utilities.iterables import partitions The numbers appearing in the partition (the key of the returned dict) are limited with k: >>> for p in partitions(6, k=2): # doctest: +SKIP ... print(p) {2: 3} {1: 2, 2: 2} {1: 4, 2: 1} {1: 6} The maximum number of parts in the partition (the sum of the values in the returned dict) are limited with m (default value, None, gives partitions from 1 through n): >>> for p in partitions(6, m=2): # doctest: +SKIP ... print(p) ... {6: 1} {1: 1, 5: 1} {2: 1, 4: 1} {3: 2} References ========== .. [1] modified from Tim Peter's version to allow for k and m values: http://code.activestate.com/recipes/218332-generator-for-integer-partitions/ See Also ======== sympy.combinatorics.partitions.Partition sympy.combinatorics.partitions.IntegerPartition """ if (n <= 0 or m is not None and m < 1 or k is not None and k < 1 or m and k and mk < n): # the empty set is the only way to handle these inputs # and returning {} to represent it is consistent with # the counting convention, e.g. nT(0) == 1. if size: yield 0, {} else: yield {} return if m is None: m = n else: m = min(m, n) if n == 0: if size: yield 1, {0: 1} else: yield {0: 1} return k = min(k or n, n) n, m, k = as_int(n), as_int(m), as_int(k) q, r = divmod(n, k) ms = {k: q} keys = [k] # ms.keys(), from largest to smallest if r: ms[r] = 1 keys.append(r) room = m - q - bool(r) if size: yield sum(ms.values()), ms.copy() else: yield ms.copy() while keys != [1]: # Reuse any 1's. if keys[-1] == 1: del keys[-1] reuse = ms.pop(1) room += reuse else: reuse = 0 while 1: # Let i be the smallest key larger than 1. Reuse one # instance of i. i = keys[-1] newcount = ms[i] = ms[i] - 1 reuse += i if newcount == 0: del keys[-1], ms[i] room += 1 # Break the remainder into pieces of size i-1. i -= 1 q, r = divmod(reuse, i) need = q + bool(r) if need > room: if not keys: return continue ms[i] = q keys.append(i) if r: ms[r] = 1 keys.append(r) break room -= need if size: yield sum(ms.values()), ms.copy() else: yield ms.copy() def ordered_partitions(n, m=None, sort=True): """Generates ordered partitions of integer ``n``. Parameters ========== m : integer (default None) The default value gives partitions of all sizes else only those with size m. In addition, if ``m`` is not None then partitions are generated in place (see examples). sort : bool (default True) Controls whether partitions are returned in sorted order when ``m`` is not None; when False, the partitions are returned as fast as possible with elements sorted, but when m\|n the partitions will not be in ascending lexicographical order. Examples ======== >>> from sympy.utilities.iterables import ordered_partitions All partitions of 5 in ascending lexicographical: >>> for p in ordered_partitions(5): ... print(p) [1, 1, 1, 1, 1] [1, 1, 1, 2] [1, 1, 3] [1, 2, 2] [1, 4] [2, 3] [5] Only partitions of 5 with two parts: >>> for p in ordered_partitions(5, 2): ... print(p) [1, 4] [2, 3] When ``m`` is given, a given list objects will be used more than once for speed reasons so you will not see the correct partitions unless you make a copy of each as it is generated: >>> [p for p in ordered_partitions(7, 3)] [[1, 1, 1], [1, 1, 1], [1, 1, 1], [2, 2, 2]] >>> [list(p) for p in ordered_partitions(7, 3)] [[1, 1, 5], [1, 2, 4], [1, 3, 3], [2, 2, 3]] When ``n`` is a multiple of ``m``, the elements are still sorted but the partitions themselves will be unordered if sort is False; the default is to return them in ascending lexicographical order. >>> for p in ordered_partitions(6, 2): ... print(p) [1, 5] [2, 4] [3, 3] But if speed is more important than ordering, sort can be set to False: >>> for p in ordered_partitions(6, 2, sort=False): ... print(p) [1, 5] [3, 3] [2, 4] References ========== .. [1] Generating Integer Partitions, [online], Available: https://jeromekelleher.net/generating-integer-partitions.html .. [2] Jerome Kelleher and Barry O'Sullivan, "Generating All Partitions: A Comparison Of Two Encodings", [online], Available: https://arxiv.org/pdf/0909.2331v2.pdf """ if n < 1 or m is not None and m < 1: # the empty set is the only way to handle these inputs # and returning {} to represent it is consistent with # the counting convention, e.g. nT(0) == 1. yield [] return if m is None: # The list `a`'s leading elements contain the partition in which # y is the biggest element and x is either the same as y or the # 2nd largest element; v and w are adjacent element indices # to which x and y are being assigned, respectively. a = [1]n y = -1 v = n while v > 0: v -= 1 x = a[v] + 1 while y >= 2 x: a[v] = x y -= x v += 1 w = v + 1 while x <= y: a[v] = x a[w] = y yield a[:w + 1] x += 1 y -= 1 a[v] = x + y y = a[v] - 1 yield a[:w] elif m == 1: yield [n] elif n == m: yield [1]n else: # recursively generate partitions of size m for b in range(1, n//m + 1): a = [b]m x = n - bm if not x: if sort: yield a elif not sort and x <= m: for ax in ordered_partitions(x, sort=False): mi = len(ax) a[-mi:] = [i + b for i in ax] yield a a[-mi:] = [b]mi else: for mi in range(1, m): for ax in ordered_partitions(x, mi, sort=True): a[-mi:] = [i + b for i in ax] yield a a[-mi:] = [b]mi def binary_partitions(n): """ Generates the binary partition of n. A binary partition consists only of numbers that are powers of two. Each step reduces a `2^{k+1}` to `2^k` and `2^k`. Thus 16 is converted to 8 and 8. Examples ======== >>> from sympy.utilities.iterables import binary_partitions >>> for i in binary_partitions(5): ... print(i) ... [4, 1] [2, 2, 1] [2, 1, 1, 1] [1, 1, 1, 1, 1] References ========== .. [1] TAOCP 4, section 7.2.1.5, problem 64 """ from math import ceil, log pow = int(2(ceil(log(n, 2)))) sum = 0 partition = [] while pow: if sum + pow <= n: partition.append(pow) sum += pow pow >>= 1 last_num = len(partition) - 1 - (n & 1) while last_num >= 0: yield partition if partition[last_num] == 2: partition[last_num] = 1 partition.append(1) last_num -= 1 continue partition.append(1) partition[last_num] >>= 1 x = partition[last_num + 1] = partition[last_num] last_num += 1 while x > 1: if x <= len(partition) - last_num - 1: del partition[-x + 1:] last_num += 1 partition[last_num] = x else: x >>= 1 yield [1]n def has_dups(seq): """Return True if there are any duplicate elements in ``seq``. Examples ======== >>> from sympy.utilities.iterables import has_dups >>> from sympy import Dict, Set >>> has_dups((1, 2, 1)) True >>> has_dups(range(3)) False >>> all(has_dups(c) is False for c in (set(), Set(), dict(), Dict())) True """ from sympy.core.containers import Dict from sympy.sets.sets import Set if isinstance(seq, (dict, set, Dict, Set)): return False uniq = set() return any(True for s in seq if s in uniq or uniq.add(s)) def has_variety(seq): """Return True if there are any different elements in ``seq``. Examples ======== >>> from sympy.utilities.iterables import has_variety >>> has_variety((1, 2, 1)) True >>> has_variety((1, 1, 1)) False """ for i, s in enumerate(seq): if i == 0: sentinel = s else: if s != sentinel: return True return False def uniq(seq, result=None): """ Yield unique elements from ``seq`` as an iterator. The second parameter ``result`` is used internally; it is not necessary to pass anything for this. Note: changing the sequence during iteration will raise a RuntimeError if the size of the sequence is known; if you pass an iterator and advance the iterator you will change the output of this routine but there will be no warning. Examples ======== >>> from sympy.utilities.iterables import uniq >>> dat = [1, 4, 1, 5, 4, 2, 1, 2] >>> type(uniq(dat)) in (list, tuple) False >>> list(uniq(dat)) [1, 4, 5, 2] >>> list(uniq(x for x in dat)) [1, 4, 5, 2] >>> list(uniq([[1], [2, 1], [1]])) [[1], [2, 1]] """ try: n = len(seq) except TypeError: n = None def check(): # check that size of seq did not change during iteration; # if n == None the object won't support size changing, e.g. # an iterator can't be changed if n is not None and len(seq) != n: raise RuntimeError('sequence changed size during iteration') try: seen = set() result = result or [] for i, s in enumerate(seq): if not (s in seen or seen.add(s)): yield s check() except TypeError: if s not in result: yield s check() result.append(s) if hasattr(seq, '__getitem__'): yield from uniq(seq[i + 1:], result) else: yield from uniq(seq, result) def generate_bell(n): """Return permutations of [0, 1, ..., n - 1] such that each permutation differs from the last by the exchange of a single pair of neighbors. The ``n!`` permutations are returned as an iterator. In order to obtain the next permutation from a random starting permutation, use the ``next_trotterjohnson`` method of the Permutation class (which generates the same sequence in a different manner). Examples ======== >>> from itertools import permutations >>> from sympy.utilities.iterables import generate_bell >>> from sympy import zeros, Matrix This is the sort of permutation used in the ringing of physical bells, and does not produce permutations in lexicographical order. Rather, the permutations differ from each other by exactly one inversion, and the position at which the swapping occurs varies periodically in a simple fashion. Consider the first few permutations of 4 elements generated by ``permutations`` and ``generate_bell``: >>> list(permutations(range(4)))[:5] [(0, 1, 2, 3), (0, 1, 3, 2), (0, 2, 1, 3), (0, 2, 3, 1), (0, 3, 1, 2)] >>> list(generate_bell(4))[:5] [(0, 1, 2, 3), (0, 1, 3, 2), (0, 3, 1, 2), (3, 0, 1, 2), (3, 0, 2, 1)] Notice how the 2nd and 3rd lexicographical permutations have 3 elements out of place whereas each "bell" permutation always has only two elements out of place relative to the previous permutation (and so the signature (+/-1) of a permutation is opposite of the signature of the previous permutation). How the position of inversion varies across the elements can be seen by tracing out where the largest number appears in the permutations: >>> m = zeros(4, 24) >>> for i, p in enumerate(generate_bell(4)): ... m[:, i] = Matrix([j - 3 for j in list(p)]) # make largest zero >>> m.print_nonzero('X') [XXX XXXXXX XXXXXX XXX] [XX XX XXXX XX XXXX XX XX] [X XXXX XX XXXX XX XXXX X] [ XXXXXX XXXXXX XXXXXX ] See Also ======== sympy.combinatorics.permutations.Permutation.next_trotterjohnson References ========== .. [1] https://en.wikipedia.org/wiki/Method_ringing .. [2] https://stackoverflow.com/questions/4856615/recursive-permutation/4857018 .. [3] http://programminggeeks.com/bell-algorithm-for-permutation/ .. [4] https://en.wikipedia.org/wiki/Steinhaus%E2%80%93Johnson%E2%80%93Trotter_algorithm .. [5] Generating involutions, derangements, and relatives by ECO Vincent Vajnovszki, DMTCS vol 1 issue 12, 2010 """ n = as_int(n) if n < 1: raise ValueError('n must be a positive integer') if n == 1: yield (0,) elif n == 2: yield (0, 1) yield (1, 0) elif n == 3: yield from [(0, 1, 2), (0, 2, 1), (2, 0, 1), (2, 1, 0), (1, 2, 0), (1, 0, 2)] else: m = n - 1 op = [0] + [-1]m l = list(range(n)) while True: yield tuple(l) # find biggest element with op big = None, -1 # idx, value for i in range(n): if op[i] and l[i] > big[1]: big = i, l[i] i, _ = big if i is None: break # there are no ops left # swap it with neighbor in the indicated direction j = i + op[i] l[i], l[j] = l[j], l[i] op[i], op[j] = op[j], op[i] # if it landed at the end or if the neighbor in the same # direction is bigger then turn off op if j == 0 or j == m or l[j + op[j]] > l[j]: op[j] = 0 # any element bigger to the left gets +1 op for i in range(j): if l[i] > l[j]: op[i] = 1 # any element bigger to the right gets -1 op for i in range(j + 1, n): if l[i] > l[j]: op[i] = -1 def generate_involutions(n): """ Generates involutions. An involution is a permutation that when multiplied by itself equals the identity permutation. In this implementation the involutions are generated using Fixed Points. Alternatively, an involution can be considered as a permutation that does not contain any cycles with a length that is greater than two. Examples ======== >>> from sympy.utilities.iterables import generate_involutions >>> list(generate_involutions(3)) [(0, 1, 2), (0, 2, 1), (1, 0, 2), (2, 1, 0)] >>> len(list(generate_involutions(4))) 10 References ========== .. [1] http://mathworld.wolfram.com/PermutationInvolution.html """ idx = list(range(n)) for p in permutations(idx): for i in idx: if p[p[i]] != i: break else: yield p def generate_derangements(perm): """ Routine to generate unique derangements. TODO: This will be rewritten to use the ECO operator approach once the permutations branch is in master. Examples ======== >>> from sympy.utilities.iterables import generate_derangements >>> list(generate_derangements([0, 1, 2])) [[1, 2, 0], [2, 0, 1]] >>> list(generate_derangements([0, 1, 2, 3])) [[1, 0, 3, 2], [1, 2, 3, 0], [1, 3, 0, 2], [2, 0, 3, 1], \ [2, 3, 0, 1], [2, 3, 1, 0], [3, 0, 1, 2], [3, 2, 0, 1], \ [3, 2, 1, 0]] >>> list(generate_derangements([0, 1, 1])) [] See Also ======== sympy.functions.combinatorial.factorials.subfactorial """ for p in multiset_permutations(perm): if not any(i == j for i, j in zip(perm, p)): yield p def necklaces(n, k, free=False): """ A routine to generate necklaces that may (free=True) or may not (free=False) be turned over to be viewed. The "necklaces" returned are comprised of ``n`` integers (beads) with ``k`` different values (colors). Only unique necklaces are returned. Examples ======== >>> from sympy.utilities.iterables import necklaces, bracelets >>> def show(s, i): ... return ''.join(s[j] for j in i) The "unrestricted necklace" is sometimes also referred to as a "bracelet" (an object that can be turned over, a sequence that can be reversed) and the term "necklace" is used to imply a sequence that cannot be reversed. So ACB == ABC for a bracelet (rotate and reverse) while the two are different for a necklace since rotation alone cannot make the two sequences the same. (mnemonic: Bracelets can be viewed Backwards, but Not Necklaces.) >>> B = [show('ABC', i) for i in bracelets(3, 3)] >>> N = [show('ABC', i) for i in necklaces(3, 3)] >>> set(N) - set(B) {'ACB'} >>> list(necklaces(4, 2)) [(0, 0, 0, 0), (0, 0, 0, 1), (0, 0, 1, 1), (0, 1, 0, 1), (0, 1, 1, 1), (1, 1, 1, 1)] >>> [show('.o', i) for i in bracelets(4, 2)] ['....', '...o', '..oo', '.o.o', '.ooo', 'oooo'] References ========== .. [1] http://mathworld.wolfram.com/Necklace.html """ return uniq(minlex(i, directed=not free) for i in variations(list(range(k)), n, repetition=True)) def bracelets(n, k): """Wrapper to necklaces to return a free (unrestricted) necklace.""" return necklaces(n, k, free=True) def generate_oriented_forest(n): """ This algorithm generates oriented forests. An oriented graph is a directed graph having no symmetric pair of directed edges. A forest is an acyclic graph, i.e., it has no cycles. A forest can also be described as a disjoint union of trees, which are graphs in which any two vertices are connected by exactly one simple path. Examples ======== >>> from sympy.utilities.iterables import generate_oriented_forest >>> list(generate_oriented_forest(4)) [[0, 1, 2, 3], [0, 1, 2, 2], [0, 1, 2, 1], [0, 1, 2, 0], \ [0, 1, 1, 1], [0, 1, 1, 0], [0, 1, 0, 1], [0, 1, 0, 0], [0, 0, 0, 0]] References ========== .. [1] T. Beyer and S.M. Hedetniemi: constant time generation of rooted trees, SIAM J. Computing Vol. 9, No. 4, November 1980 .. [2] https://stackoverflow.com/questions/1633833/oriented-forest-taocp-algorithm-in-python """ P = list(range(-1, n)) while True: yield P[1:] if P[n] > 0: P[n] = P[P[n]] else: for p in range(n - 1, 0, -1): if P[p] != 0: target = P[p] - 1 for q in range(p - 1, 0, -1): if P[q] == target: break offset = p - q for i in range(p, n + 1): P[i] = P[i - offset] break else: break def minlex(seq, directed=True, is_set=False, small=None): """ Return a tuple representing the rotation of the sequence in which the lexically smallest elements appear first, e.g. `cba ->acb`. If ``directed`` is False then the smaller of the sequence and the reversed sequence is returned, e.g. `cba -> abc`. For more efficient processing, ``is_set`` can be set to True if there are no duplicates in the sequence. If the smallest element is known at the time of calling, it can be passed as ``small`` and the calculation of the smallest element will be omitted. Examples ======== >>> from sympy.combinatorics.polyhedron import minlex >>> minlex((1, 2, 0)) (0, 1, 2) >>> minlex((1, 0, 2)) (0, 2, 1) >>> minlex((1, 0, 2), directed=False) (0, 1, 2) >>> minlex('11010011000', directed=True) '00011010011' >>> minlex('11010011000', directed=False) '00011001011' """ is_str = isinstance(seq, str) seq = list(seq) if small is None: small = min(seq, key=default_sort_key) if is_set: i = seq.index(small) if not directed: n = len(seq) p = (i + 1) % n m = (i - 1) % n if default_sort_key(seq[p]) > default_sort_key(seq[m]): seq = list(reversed(seq)) i = n - i - 1 if i: seq = rotate_left(seq, i) best = seq else: count = seq.count(small) if count == 1 and directed: best = rotate_left(seq, seq.index(small)) else: # if not directed, and not a set, we can't just # pass this off to minlex with is_set True since # peeking at the neighbor may not be sufficient to # make the decision so we continue... best = seq for i in range(count): seq = rotate_left(seq, seq.index(small, count != 1)) if seq < best: best = seq # it's cheaper to rotate now rather than search # again for these in reversed order so we test # the reverse now if not directed: seq = rotate_left(seq, 1) seq = list(reversed(seq)) if seq < best: best = seq seq = list(reversed(seq)) seq = rotate_right(seq, 1) # common return if is_str: return ''.join(best) return tuple(best) def runs(seq, op=gt): """Group the sequence into lists in which successive elements all compare the same with the comparison operator, ``op``: op(seq[i + 1], seq[i]) is True from all elements in a run. Examples ======== >>> from sympy.utilities.iterables import runs >>> from operator import ge >>> runs([0, 1, 2, 2, 1, 4, 3, 2, 2]) [[0, 1, 2], [2], [1, 4], [3], [2], [2]] >>> runs([0, 1, 2, 2, 1, 4, 3, 2, 2], op=ge) [[0, 1, 2, 2], [1, 4], [3], [2, 2]] """ cycles = [] seq = iter(seq) try: run = [next(seq)] except StopIteration: return [] while True: try: ei = next(seq) except StopIteration: break if op(ei, run[-1]): run.append(ei) continue else: cycles.append(run) run = [ei] if run: cycles.append(run) return cycles def kbins(l, k, ordered=None): """ Return sequence ``l`` partitioned into ``k`` bins. Examples ======== >>> from __future__ import print_function The default is to give the items in the same order, but grouped into k partitions without any reordering: >>> from sympy.utilities.iterables import kbins >>> for p in kbins(list(range(5)), 2): ... print(p) ... [[0], [1, 2, 3, 4]] [[0, 1], [2, 3, 4]] [[0, 1, 2], [3, 4]] [[0, 1, 2, 3], [4]] The ``ordered`` flag is either None (to give the simple partition of the elements) or is a 2 digit integer indicating whether the order of the bins and the order of the items in the bins matters. Given:: A = [[0], [1, 2]] B = [[1, 2], [0]] C = [[2, 1], [0]] D = [[0], [2, 1]] the following values for ``ordered`` have the shown meanings:: 00 means A == B == C == D 01 means A == B 10 means A == D 11 means A == A >>> for ordered_flag in [None, 0, 1, 10, 11]: ... print('ordered = %s' % ordered_flag) ... for p in kbins(list(range(3)), 2, ordered=ordered_flag): ... print(' %s' % p) ... ordered = None [[0], [1, 2]] [[0, 1], [2]] ordered = 0 [[0, 1], [2]] [[0, 2], [1]] [[0], [1, 2]] ordered = 1 [[0], [1, 2]] [[0], [2, 1]] [[1], [0, 2]] [[1], [2, 0]] [[2], [0, 1]] [[2], [1, 0]] ordered = 10 [[0, 1], [2]] [[2], [0, 1]] [[0, 2], [1]] [[1], [0, 2]] [[0], [1, 2]] [[1, 2], [0]] ordered = 11 [[0], [1, 2]] [[0, 1], [2]] [[0], [2, 1]] [[0, 2], [1]] [[1], [0, 2]] [[1, 0], [2]] [[1], [2, 0]] [[1, 2], [0]] [[2], [0, 1]] [[2, 0], [1]] [[2], [1, 0]] [[2, 1], [0]] See Also ======== partitions, multiset_partitions """ def partition(lista, bins): # EnricoGiampieri's partition generator from # https://stackoverflow.com/questions/13131491/ # partition-n-items-into-k-bins-in-python-lazily if len(lista) == 1 or bins == 1: yield [lista] elif len(lista) > 1 and bins > 1: for i in range(1, len(lista)): for part in partition(lista[i:], bins - 1): if len([lista[:i]] + part) == bins: yield [lista[:i]] + part if ordered is None: yield from partition(l, k) elif ordered == 11: for pl in multiset_permutations(l): pl = list(pl) yield from partition(pl, k) elif ordered == 00: yield from multiset_partitions(l, k) elif ordered == 10: for p in multiset_partitions(l, k): for perm in permutations(p): yield list(perm) elif ordered == 1: for kgot, p in partitions(len(l), k, size=True): if kgot != k: continue for li in multiset_permutations(l): rv = [] i = j = 0 li = list(li) for size, multiplicity in sorted(p.items()): for m in range(multiplicity): j = i + size rv.append(li[i: j]) i = j yield rv else: raise ValueError( 'ordered must be one of 00, 01, 10 or 11, not %s' % ordered) def permute_signs(t): """Return iterator in which the signs of non-zero elements of t are permuted. Examples ======== >>> from sympy.utilities.iterables import permute_signs >>> list(permute_signs((0, 1, 2))) [(0, 1, 2), (0, -1, 2), (0, 1, -2), (0, -1, -2)] """ for signs in cartes([(1, -1)](len(t) - t.count(0))): signs = list(signs) yield type(t)([isigns.pop() if i else i for i in t]) def signed_permutations(t): """Return iterator in which the signs of non-zero elements of t and the order of the elements are permuted. Examples ======== >>> from sympy.utilities.iterables import signed_permutations >>> list(signed_permutations((0, 1, 2))) [(0, 1, 2), (0, -1, 2), (0, 1, -2), (0, -1, -2), (0, 2, 1), (0, -2, 1), (0, 2, -1), (0, -2, -1), (1, 0, 2), (-1, 0, 2), (1, 0, -2), (-1, 0, -2), (1, 2, 0), (-1, 2, 0), (1, -2, 0), (-1, -2, 0), (2, 0, 1), (-2, 0, 1), (2, 0, -1), (-2, 0, -1), (2, 1, 0), (-2, 1, 0), (2, -1, 0), (-2, -1, 0)] """ return (type(t)(i) for j in permutations(t) for i in permute_signs(j)) def rotations(s, dir=1): """Return a generator giving the items in s as list where each subsequent list has the items rotated to the left (default) or right (dir=-1) relative to the previous list. Examples ======== >>> from sympy.utilities.iterables import rotations >>> list(rotations([1,2,3])) [[1, 2, 3], [2, 3, 1], [3, 1, 2]] >>> list(rotations([1,2,3], -1)) [[1, 2, 3], [3, 1, 2], [2, 3, 1]] """ seq = list(s) for i in range(len(seq)): yield seq seq = rotate_left(seq, dir) def roundrobin(*iterables): """roundrobin recipe taken from itertools documentation: https://docs.python.org/2/library/itertools.html#recipes roundrobin('ABC', 'D', 'EF') --> A D E B F C Recipe credited to George Sakkis """ import itertools nexts = itertools.cycle(iter(it).__next__ for it in iterables) pending = len(iterables) while pending: try: for next in nexts: yield next() except StopIteration: pending -= 1 nexts = itertools.cycle(itertools.islice(nexts, pending))
5359449d9fa55e2073811b9613b9650fed082e07901a1adcae6351f1c89be9c9	""" This is a shim file to provide backwards compatibility (cxxcode.py was renamed to cxx.py in SymPy 1.7). """ from sympy.utilities.exceptions import SymPyDeprecationWarning SymPyDeprecationWarning( feature="importing from sympy.printing.cxxcode", useinstead="Import from sympy.printing.cxx", issue=20256, deprecated_since_version="1.7").warn() from .cxx import (cxxcode, reserved, CXX98CodePrinter, # noqa:F401 CXX11CodePrinter, CXX17CodePrinter, cxx_code_printers)
4a4d988f93d7e42793ea8df31f1f99542d6425303b610333c17a632709547ae7	"""A module providing information about the necessity of brackets""" from sympy.core.function import _coeff_isneg # Default precedence values for some basic types PRECEDENCE = { "Lambda": 1, "Xor": 10, "Or": 20, "And": 30, "Relational": 35, "Add": 40, "Mul": 50, "Pow": 60, "Func": 70, "Not": 100, "Atom": 1000, "BitwiseOr": 36, "BitwiseXor": 37, "BitwiseAnd": 38 } # A dictionary assigning precedence values to certain classes. These values are # treated like they were inherited, so not every single class has to be named # here. # Do not use this with printers other than StrPrinter PRECEDENCE_VALUES = { "Equivalent": PRECEDENCE["Xor"], "Xor": PRECEDENCE["Xor"], "Implies": PRECEDENCE["Xor"], "Or": PRECEDENCE["Or"], "And": PRECEDENCE["And"], "Add": PRECEDENCE["Add"], "Pow": PRECEDENCE["Pow"], "Relational": PRECEDENCE["Relational"], "Sub": PRECEDENCE["Add"], "Not": PRECEDENCE["Not"], "Function" : PRECEDENCE["Func"], "NegativeInfinity": PRECEDENCE["Add"], "MatAdd": PRECEDENCE["Add"], "MatPow": PRECEDENCE["Pow"], "MatrixSolve": PRECEDENCE["Mul"], "TensAdd": PRECEDENCE["Add"], # As soon as `TensMul` is a subclass of `Mul`, remove this: "TensMul": PRECEDENCE["Mul"], "HadamardProduct": PRECEDENCE["Mul"], "HadamardPower": PRECEDENCE["Pow"], "KroneckerProduct": PRECEDENCE["Mul"], "Equality": PRECEDENCE["Mul"], "Unequality": PRECEDENCE["Mul"], } # Sometimes it's not enough to assign a fixed precedence value to a # class. Then a function can be inserted in this dictionary that takes # an instance of this class as argument and returns the appropriate # precedence value. # Precedence functions def precedence_Mul(item): if _coeff_isneg(item): return PRECEDENCE["Add"] return PRECEDENCE["Mul"] def precedence_Rational(item): if item.p < 0: return PRECEDENCE["Add"] return PRECEDENCE["Mul"] def precedence_Integer(item): if item.p < 0: return PRECEDENCE["Add"] return PRECEDENCE["Atom"] def precedence_Float(item): if item < 0: return PRECEDENCE["Add"] return PRECEDENCE["Atom"] def precedence_PolyElement(item): if item.is_generator: return PRECEDENCE["Atom"] elif item.is_ground: return precedence(item.coeff(1)) elif item.is_term: return PRECEDENCE["Mul"] else: return PRECEDENCE["Add"] def precedence_FracElement(item): if item.denom == 1: return precedence_PolyElement(item.numer) else: return PRECEDENCE["Mul"] def precedence_UnevaluatedExpr(item): return precedence(item.args[0]) PRECEDENCE_FUNCTIONS = { "Integer": precedence_Integer, "Mul": precedence_Mul, "Rational": precedence_Rational, "Float": precedence_Float, "PolyElement": precedence_PolyElement, "FracElement": precedence_FracElement, "UnevaluatedExpr": precedence_UnevaluatedExpr, } def precedence(item): """Returns the precedence of a given object. This is the precedence for StrPrinter. """ if hasattr(item, "precedence"): return item.precedence try: mro = item.__class__.__mro__ except AttributeError: return PRECEDENCE["Atom"] for i in mro: n = i.__name__ if n in PRECEDENCE_FUNCTIONS: return PRECEDENCE_FUNCTIONS[n](item) elif n in PRECEDENCE_VALUES: return PRECEDENCE_VALUES[n] return PRECEDENCE["Atom"] PRECEDENCE_TRADITIONAL = PRECEDENCE.copy() PRECEDENCE_TRADITIONAL['Integral'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Sum'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Product'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Limit'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Derivative'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['TensorProduct'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Transpose'] = PRECEDENCE["Pow"] PRECEDENCE_TRADITIONAL['Adjoint'] = PRECEDENCE["Pow"] PRECEDENCE_TRADITIONAL['Dot'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Cross'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Gradient'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Divergence'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Curl'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Laplacian'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Union'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['Intersection'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['Complement'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['SymmetricDifference'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['ProductSet'] = PRECEDENCE['Xor'] def precedence_traditional(item): """Returns the precedence of a given object according to the traditional rules of mathematics. This is the precedence for the LaTeX and pretty printer. """ # Integral, Sum, Product, Limit have the precedence of Mul in LaTeX, # the precedence of Atom for other printers: from sympy.core.expr import UnevaluatedExpr if isinstance(item, UnevaluatedExpr): return precedence_traditional(item.args[0]) n = item.__class__.__name__ if n in PRECEDENCE_TRADITIONAL: return PRECEDENCE_TRADITIONAL[n] return precedence(item)
a6d9f063126be68c772c6e130836d1220c6c0a291a56f1335816aa2292135177	from sympy.printing.mathml import mathml from sympy.utilities.mathml import c2p import tempfile import subprocess def print_gtk(x, start_viewer=True): """Print to Gtkmathview, a gtk widget capable of rendering MathML. Needs libgtkmathview-bin""" with tempfile.NamedTemporaryFile('w') as file: file.write(c2p(mathml(x), simple=True)) file.flush() if start_viewer: subprocess.check_call(('mathmlviewer', file.name))
5bc85f19902188d42d8dc16766e92de828c8b07056502212bde859aadb9effcc	""" Python code printers This module contains python code printers for plain python as well as NumPy & SciPy enabled code. """ from collections import defaultdict from itertools import chain from sympy.core import S from .precedence import precedence from .codeprinter import CodePrinter _kw_py2and3 = { 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield', 'None' # 'None' is actually not in Python 2's keyword.kwlist } _kw_only_py2 = {'exec', 'print'} _kw_only_py3 = {'False', 'nonlocal', 'True'} _known_functions = { 'Abs': 'abs', } _known_functions_math = { 'acos': 'acos', 'acosh': 'acosh', 'asin': 'asin', 'asinh': 'asinh', 'atan': 'atan', 'atan2': 'atan2', 'atanh': 'atanh', 'ceiling': 'ceil', 'cos': 'cos', 'cosh': 'cosh', 'erf': 'erf', 'erfc': 'erfc', 'exp': 'exp', 'expm1': 'expm1', 'factorial': 'factorial', 'floor': 'floor', 'gamma': 'gamma', 'hypot': 'hypot', 'loggamma': 'lgamma', 'log': 'log', 'ln': 'log', 'log10': 'log10', 'log1p': 'log1p', 'log2': 'log2', 'sin': 'sin', 'sinh': 'sinh', 'Sqrt': 'sqrt', 'tan': 'tan', 'tanh': 'tanh' } # Not used from ``math``: [copysign isclose isfinite isinf isnan ldexp frexp pow modf # radians trunc fmod fsum gcd degrees fabs] _known_constants_math = { 'Exp1': 'e', 'Pi': 'pi', 'E': 'e' # Only in python >= 3.5: # 'Infinity': 'inf', # 'NaN': 'nan' } def _print_known_func(self, expr): known = self.known_functions[expr.__class__.__name__] return '{name}({args})'.format(name=self._module_format(known), args=', '.join(map(lambda arg: self._print(arg), expr.args))) def _print_known_const(self, expr): known = self.known_constants[expr.__class__.__name__] return self._module_format(known) class AbstractPythonCodePrinter(CodePrinter): printmethod = "_pythoncode" language = "Python" reserved_words = _kw_py2and3.union(_kw_only_py3) modules = None # initialized to a set in __init__ tab = ' ' _kf = dict(chain( _known_functions.items(), [(k, 'math.' + v) for k, v in _known_functions_math.items()] )) _kc = {k: 'math.'+v for k, v in _known_constants_math.items()} _operators = {'and': 'and', 'or': 'or', 'not': 'not'} _default_settings = dict( CodePrinter._default_settings, user_functions={}, precision=17, inline=True, fully_qualified_modules=True, contract=False, standard='python3', ) def __init__(self, settings=None): super().__init__(settings) # Python standard handler std = self._settings['standard'] if std is None: import sys std = 'python{}'.format(sys.version_info.major) if std not in ('python2', 'python3'): raise ValueError('Unrecognized python standard : {}'.format(std)) self.standard = std self.module_imports = defaultdict(set) # Known functions and constants handler self.known_functions = dict(self._kf, (settings or {}).get( 'user_functions', {})) self.known_constants = dict(self._kc, (settings or {}).get( 'user_constants', {})) def _declare_number_const(self, name, value): return "%s = %s" % (name, value) def _module_format(self, fqn, register=True): parts = fqn.split('.') if register and len(parts) > 1: self.module_imports['.'.join(parts[:-1])].add(parts[-1]) if self._settings['fully_qualified_modules']: return fqn else: return fqn.split('(')[0].split('[')[0].split('.')[-1] def _format_code(self, lines): return lines def _get_statement(self, codestring): return "{}".format(codestring) def _get_comment(self, text): return " # {}".format(text) def _expand_fold_binary_op(self, op, args): """ This method expands a fold on binary operations. ``functools.reduce`` is an example of a folded operation. For example, the expression `A + B + C + D` is folded into `((A + B) + C) + D` """ if len(args) == 1: return self._print(args[0]) else: return "%s(%s, %s)" % ( self._module_format(op), self._expand_fold_binary_op(op, args[:-1]), self._print(args[-1]), ) def _expand_reduce_binary_op(self, op, args): """ This method expands a reductin on binary operations. Notice: this is NOT the same as ``functools.reduce``. For example, the expression `A + B + C + D` is reduced into: `(A + B) + (C + D)` """ if len(args) == 1: return self._print(args[0]) else: N = len(args) Nhalf = N // 2 return "%s(%s, %s)" % ( self._module_format(op), self._expand_reduce_binary_op(args[:Nhalf]), self._expand_reduce_binary_op(args[Nhalf:]), ) def _get_einsum_string(self, subranks, contraction_indices): letters = self._get_letter_generator_for_einsum() contraction_string = "" counter = 0 d = {j: min(i) for i in contraction_indices for j in i} indices = [] for rank_arg in subranks: lindices = [] for i in range(rank_arg): if counter in d: lindices.append(d[counter]) else: lindices.append(counter) counter += 1 indices.append(lindices) mapping = {} letters_free = [] letters_dum = [] for i in indices: for j in i: if j not in mapping: l = next(letters) mapping[j] = l else: l = mapping[j] contraction_string += l if j in d: if l not in letters_dum: letters_dum.append(l) else: letters_free.append(l) contraction_string += "," contraction_string = contraction_string[:-1] return contraction_string, letters_free, letters_dum def _print_NaN(self, expr): return "float('nan')" def _print_Infinity(self, expr): return "float('inf')" def _print_NegativeInfinity(self, expr): return "float('-inf')" def _print_ComplexInfinity(self, expr): return self._print_NaN(expr) def _print_Mod(self, expr): PREC = precedence(expr) return ('{} % {}'.format(map(lambda x: self.parenthesize(x, PREC), expr.args))) def _print_Piecewise(self, expr): result = [] i = 0 for arg in expr.args: e = arg.expr c = arg.cond if i == 0: result.append('(') result.append('(') result.append(self._print(e)) result.append(')') result.append(' if ') result.append(self._print(c)) result.append(' else ') i += 1 result = result[:-1] if result[-1] == 'True': result = result[:-2] result.append(')') else: result.append(' else None)') return ''.join(result) def _print_Relational(self, expr): "Relational printer for Equality and Unequality" op = { '==' :'equal', '!=' :'not_equal', '<' :'less', '<=' :'less_equal', '>' :'greater', '>=' :'greater_equal', } if expr.rel_op in op: lhs = self._print(expr.lhs) rhs = self._print(expr.rhs) return '({lhs} {op} {rhs})'.format(op=expr.rel_op, lhs=lhs, rhs=rhs) return super()._print_Relational(expr) def _print_ITE(self, expr): from sympy.functions.elementary.piecewise import Piecewise return self._print(expr.rewrite(Piecewise)) def _print_Sum(self, expr): loops = ( 'for {i} in range({a}, {b}+1)'.format( i=self._print(i), a=self._print(a), b=self._print(b)) for i, a, b in expr.limits) return '(builtins.sum({function} {loops}))'.format( function=self._print(expr.function), loops=' '.join(loops)) def _print_ImaginaryUnit(self, expr): return '1j' def _print_KroneckerDelta(self, expr): a, b = expr.args return '(1 if {a} == {b} else 0)'.format( a = self._print(a), b = self._print(b) ) def _print_MatrixBase(self, expr): name = expr.__class__.__name__ func = self.known_functions.get(name, name) return "%s(%s)" % (func, self._print(expr.tolist())) _print_SparseMatrix = \ _print_MutableSparseMatrix = \ _print_ImmutableSparseMatrix = \ _print_Matrix = \ _print_DenseMatrix = \ _print_MutableDenseMatrix = \ _print_ImmutableMatrix = \ _print_ImmutableDenseMatrix = \ lambda self, expr: self._print_MatrixBase(expr) def _indent_codestring(self, codestring): return '\n'.join([self.tab + line for line in codestring.split('\n')]) def _print_FunctionDefinition(self, fd): body = '\n'.join(map(lambda arg: self._print(arg), fd.body)) return "def {name}({parameters}):\n{body}".format( name=self._print(fd.name), parameters=', '.join([self._print(var.symbol) for var in fd.parameters]), body=self._indent_codestring(body) ) def _print_While(self, whl): body = '\n'.join(map(lambda arg: self._print(arg), whl.body)) return "while {cond}:\n{body}".format( cond=self._print(whl.condition), body=self._indent_codestring(body) ) def _print_Declaration(self, decl): return '%s = %s' % ( self._print(decl.variable.symbol), self._print(decl.variable.value) ) def _print_Return(self, ret): arg, = ret.args return 'return %s' % self._print(arg) def _print_Print(self, prnt): print_args = ', '.join(map(lambda arg: self._print(arg), prnt.print_args)) if prnt.format_string != None: # Must be '!= None', cannot be 'is not None' print_args = '{} % ({})'.format( self._print(prnt.format_string), print_args) if prnt.file != None: # Must be '!= None', cannot be 'is not None' print_args += ', file=%s' % self._print(prnt.file) if self.standard == 'python2': return 'print %s' % print_args return 'print(%s)' % print_args def _print_Stream(self, strm): if str(strm.name) == 'stdout': return self._module_format('sys.stdout') elif str(strm.name) == 'stderr': return self._module_format('sys.stderr') else: return self._print(strm.name) def _print_NoneToken(self, arg): return 'None' def _hprint_Pow(self, expr, rational=False, sqrt='math.sqrt'): """Printing helper function for ``Pow`` Notes ===== This only preprocesses the ``sqrt`` as math formatter Examples ======== >>> from sympy.functions import sqrt >>> from sympy.printing.pycode import PythonCodePrinter >>> from sympy.abc import x Python code printer automatically looks up ``math.sqrt``. >>> printer = PythonCodePrinter({'standard':'python3'}) >>> printer._hprint_Pow(sqrt(x), rational=True) 'x(1/2)' >>> printer._hprint_Pow(sqrt(x), rational=False) 'math.sqrt(x)' >>> printer._hprint_Pow(1/sqrt(x), rational=True) 'x(-1/2)' >>> printer._hprint_Pow(1/sqrt(x), rational=False) '1/math.sqrt(x)' Using sqrt from numpy or mpmath >>> printer._hprint_Pow(sqrt(x), sqrt='numpy.sqrt') 'numpy.sqrt(x)' >>> printer._hprint_Pow(sqrt(x), sqrt='mpmath.sqrt') 'mpmath.sqrt(x)' See Also ======== sympy.printing.str.StrPrinter._print_Pow """ PREC = precedence(expr) if expr.exp == S.Half and not rational: func = self._module_format(sqrt) arg = self._print(expr.base) return '{func}({arg})'.format(func=func, arg=arg) if expr.is_commutative: if -expr.exp is S.Half and not rational: func = self._module_format(sqrt) num = self._print(S.One) arg = self._print(expr.base) return "{num}/{func}({arg})".format( num=num, func=func, arg=arg) base_str = self.parenthesize(expr.base, PREC, strict=False) exp_str = self.parenthesize(expr.exp, PREC, strict=False) return "{}{}".format(base_str, exp_str) class PythonCodePrinter(AbstractPythonCodePrinter): def _print_sign(self, e): return '(0.0 if {e} == 0 else {f}(1, {e}))'.format( f=self._module_format('math.copysign'), e=self._print(e.args[0])) def _print_Not(self, expr): PREC = precedence(expr) return self._operators['not'] + self.parenthesize(expr.args[0], PREC) def _print_Indexed(self, expr): base = expr.args[0] index = expr.args[1:] return "{}[{}]".format(str(base), ", ".join([self._print(ind) for ind in index])) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational) def _print_Rational(self, expr): if self.standard == 'python2': return '{}./{}.'.format(expr.p, expr.q) return '{}/{}'.format(expr.p, expr.q) def _print_Half(self, expr): return self._print_Rational(expr) def _print_frac(self, expr): from sympy import Mod return self._print_Mod(Mod(expr.args[0], 1)) _print_lowergamma = CodePrinter._print_not_supported _print_uppergamma = CodePrinter._print_not_supported _print_fresnelc = CodePrinter._print_not_supported _print_fresnels = CodePrinter._print_not_supported for k in PythonCodePrinter._kf: setattr(PythonCodePrinter, '_print_%s' % k, _print_known_func) for k in _known_constants_math: setattr(PythonCodePrinter, '_print_%s' % k, _print_known_const) def pycode(expr, settings): """ Converts an expr to a string of Python code Parameters ========== expr : Expr A SymPy expression. fully_qualified_modules : bool Whether or not to write out full module names of functions (``math.sin`` vs. ``sin``). default: ``True``. standard : str or None, optional If 'python2', Python 2 sematics will be used. If 'python3', Python 3 sematics will be used. If None, the standard will be automatically detected. Default is 'python3'. And this parameter may be removed in the future. Examples ======== >>> from sympy import tan, Symbol >>> from sympy.printing.pycode import pycode >>> pycode(tan(Symbol('x')) + 1) 'math.tan(x) + 1' """ return PythonCodePrinter(settings).doprint(expr) _not_in_mpmath = 'log1p log2'.split() _in_mpmath = [(k, v) for k, v in _known_functions_math.items() if k not in _not_in_mpmath] _known_functions_mpmath = dict(_in_mpmath, { 'beta': 'beta', 'frac': 'frac', 'fresnelc': 'fresnelc', 'fresnels': 'fresnels', 'sign': 'sign', 'loggamma': 'loggamma', }) _known_constants_mpmath = { 'Exp1': 'e', 'Pi': 'pi', 'GoldenRatio': 'phi', 'EulerGamma': 'euler', 'Catalan': 'catalan', 'NaN': 'nan', 'Infinity': 'inf', 'NegativeInfinity': 'ninf' } def _unpack_integral_limits(integral_expr): """ helper function for _print_Integral that - accepts an Integral expression - returns a tuple of - a list variables of integration - a list of tuples of the upper and lower limits of integration """ integration_vars = [] limits = [] for integration_range in integral_expr.limits: if len(integration_range) == 3: integration_var, lower_limit, upper_limit = integration_range else: raise NotImplementedError("Only definite integrals are supported") integration_vars.append(integration_var) limits.append((lower_limit, upper_limit)) return integration_vars, limits class MpmathPrinter(PythonCodePrinter): """ Lambda printer for mpmath which maintains precision for floats """ printmethod = "_mpmathcode" language = "Python with mpmath" _kf = dict(chain( _known_functions.items(), [(k, 'mpmath.' + v) for k, v in _known_functions_mpmath.items()] )) _kc = {k: 'mpmath.'+v for k, v in _known_constants_mpmath.items()} def _print_Float(self, e): # XXX: This does not handle setting mpmath.mp.dps. It is assumed that # the caller of the lambdified function will have set it to sufficient # precision to match the Floats in the expression. # Remove 'mpz' if gmpy is installed. args = str(tuple(map(int, e._mpf_))) return '{func}({args})'.format(func=self._module_format('mpmath.mpf'), args=args) def _print_Rational(self, e): return "{func}({p})/{func}({q})".format( func=self._module_format('mpmath.mpf'), q=self._print(e.q), p=self._print(e.p) ) def _print_Half(self, e): return self._print_Rational(e) def _print_uppergamma(self, e): return "{}({}, {}, {})".format( self._module_format('mpmath.gammainc'), self._print(e.args[0]), self._print(e.args[1]), self._module_format('mpmath.inf')) def _print_lowergamma(self, e): return "{}({}, 0, {})".format( self._module_format('mpmath.gammainc'), self._print(e.args[0]), self._print(e.args[1])) def _print_log2(self, e): return '{0}({1})/{0}(2)'.format( self._module_format('mpmath.log'), self._print(e.args[0])) def _print_log1p(self, e): return '{}({}+1)'.format( self._module_format('mpmath.log'), self._print(e.args[0])) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational, sqrt='mpmath.sqrt') def _print_Integral(self, e): integration_vars, limits = _unpack_integral_limits(e) return "{}(lambda {}: {}, {})".format( self._module_format("mpmath.quad"), ", ".join(map(self._print, integration_vars)), self._print(e.args[0]), ", ".join("(%s, %s)" % tuple(map(self._print, l)) for l in limits)) for k in MpmathPrinter._kf: setattr(MpmathPrinter, '_print_%s' % k, _print_known_func) for k in _known_constants_mpmath: setattr(MpmathPrinter, '_print_%s' % k, _print_known_const) _not_in_numpy = 'erf erfc factorial gamma loggamma'.split() _in_numpy = [(k, v) for k, v in _known_functions_math.items() if k not in _not_in_numpy] _known_functions_numpy = dict(_in_numpy, { 'acos': 'arccos', 'acosh': 'arccosh', 'asin': 'arcsin', 'asinh': 'arcsinh', 'atan': 'arctan', 'atan2': 'arctan2', 'atanh': 'arctanh', 'exp2': 'exp2', 'sign': 'sign', 'logaddexp': 'logaddexp', 'logaddexp2': 'logaddexp2', }) _known_constants_numpy = { 'Exp1': 'e', 'Pi': 'pi', 'EulerGamma': 'euler_gamma', 'NaN': 'nan', 'Infinity': 'PINF', 'NegativeInfinity': 'NINF' } class NumPyPrinter(PythonCodePrinter): """ Numpy printer which handles vectorized piecewise functions, logical operators, etc. """ printmethod = "_numpycode" language = "Python with NumPy" _kf = dict(chain( PythonCodePrinter._kf.items(), [(k, 'numpy.' + v) for k, v in _known_functions_numpy.items()] )) _kc = {k: 'numpy.'+v for k, v in _known_constants_numpy.items()} def _print_seq(self, seq): "General sequence printer: converts to tuple" # Print tuples here instead of lists because numba supports # tuples in nopython mode. delimiter=', ' return '({},)'.format(delimiter.join(self._print(item) for item in seq)) def _print_MatMul(self, expr): "Matrix multiplication printer" if expr.as_coeff_matrices()[0] is not S.One: expr_list = expr.as_coeff_matrices()[1]+[(expr.as_coeff_matrices()[0])] return '({})'.format(').dot('.join(self._print(i) for i in expr_list)) return '({})'.format(').dot('.join(self._print(i) for i in expr.args)) def _print_MatPow(self, expr): "Matrix power printer" return '{}({}, {})'.format(self._module_format('numpy.linalg.matrix_power'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_Inverse(self, expr): "Matrix inverse printer" return '{}({})'.format(self._module_format('numpy.linalg.inv'), self._print(expr.args[0])) def _print_DotProduct(self, expr): # DotProduct allows any shape order, but numpy.dot does matrix # multiplication, so we have to make sure it gets 1 x n by n x 1. arg1, arg2 = expr.args if arg1.shape[0] != 1: arg1 = arg1.T if arg2.shape[1] != 1: arg2 = arg2.T return "%s(%s, %s)" % (self._module_format('numpy.dot'), self._print(arg1), self._print(arg2)) def _print_MatrixSolve(self, expr): return "%s(%s, %s)" % (self._module_format('numpy.linalg.solve'), self._print(expr.matrix), self._print(expr.vector)) def _print_ZeroMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.zeros'), self._print(expr.shape)) def _print_OneMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.ones'), self._print(expr.shape)) def _print_FunctionMatrix(self, expr): from sympy.core.function import Lambda from sympy.abc import i, j lamda = expr.lamda if not isinstance(lamda, Lambda): lamda = Lambda((i, j), lamda(i, j)) return '{}(lambda {}: {}, {})'.format(self._module_format('numpy.fromfunction'), ', '.join(self._print(arg) for arg in lamda.args[0]), self._print(lamda.args[1]), self._print(expr.shape)) def _print_HadamardProduct(self, expr): func = self._module_format('numpy.multiply') return ''.join('{}({}, '.format(func, self._print(arg)) \ for arg in expr.args[:-1]) + "{}{}".format(self._print(expr.args[-1]), ')' (len(expr.args) - 1)) def _print_KroneckerProduct(self, expr): func = self._module_format('numpy.kron') return ''.join('{}({}, '.format(func, self._print(arg)) \ for arg in expr.args[:-1]) + "{}{}".format(self._print(expr.args[-1]), ')' * (len(expr.args) - 1)) def _print_Adjoint(self, expr): return '{}({}({}))'.format( self._module_format('numpy.conjugate'), self._module_format('numpy.transpose'), self._print(expr.args[0])) def _print_DiagonalOf(self, expr): vect = '{}({})'.format( self._module_format('numpy.diag'), self._print(expr.arg)) return '{}({}, (-1, 1))'.format( self._module_format('numpy.reshape'), vect) def _print_DiagMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.diagflat'), self._print(expr.args[0])) def _print_DiagonalMatrix(self, expr): return '{}({}, {}({}, {}))'.format(self._module_format('numpy.multiply'), self._print(expr.arg), self._module_format('numpy.eye'), self._print(expr.shape[0]), self._print(expr.shape[1])) def _print_Piecewise(self, expr): "Piecewise function printer" exprs = '[{}]'.format(','.join(self._print(arg.expr) for arg in expr.args)) conds = '[{}]'.format(','.join(self._print(arg.cond) for arg in expr.args)) # If [default_value, True] is a (expr, cond) sequence in a Piecewise object # it will behave the same as passing the 'default' kwarg to select() # as long as it is the last element in expr.args. # If this is not the case, it may be triggered prematurely. return '{}({}, {}, default={})'.format( self._module_format('numpy.select'), conds, exprs, self._print(S.NaN)) def _print_Relational(self, expr): "Relational printer for Equality and Unequality" op = { '==' :'equal', '!=' :'not_equal', '<' :'less', '<=' :'less_equal', '>' :'greater', '>=' :'greater_equal', } if expr.rel_op in op: lhs = self._print(expr.lhs) rhs = self._print(expr.rhs) return '{op}({lhs}, {rhs})'.format(op=self._module_format('numpy.'+op[expr.rel_op]), lhs=lhs, rhs=rhs) return super()._print_Relational(expr) def _print_And(self, expr): "Logical And printer" # We have to override LambdaPrinter because it uses Python 'and' keyword. # If LambdaPrinter didn't define it, we could use StrPrinter's # version of the function and add 'logical_and' to NUMPY_TRANSLATIONS. return '{}.reduce(({}))'.format(self._module_format('numpy.logical_and'), ','.join(self._print(i) for i in expr.args)) def _print_Or(self, expr): "Logical Or printer" # We have to override LambdaPrinter because it uses Python 'or' keyword. # If LambdaPrinter didn't define it, we could use StrPrinter's # version of the function and add 'logical_or' to NUMPY_TRANSLATIONS. return '{}.reduce(({}))'.format(self._module_format('numpy.logical_or'), ','.join(self._print(i) for i in expr.args)) def _print_Not(self, expr): "Logical Not printer" # We have to override LambdaPrinter because it uses Python 'not' keyword. # If LambdaPrinter didn't define it, we would still have to define our # own because StrPrinter doesn't define it. return '{}({})'.format(self._module_format('numpy.logical_not'), ','.join(self._print(i) for i in expr.args)) def _print_Pow(self, expr, rational=False): # XXX Workaround for negative integer power error from sympy.core.power import Pow if expr.exp.is_integer and expr.exp.is_negative: expr = Pow(expr.base, expr.exp.evalf(), evaluate=False) return self._hprint_Pow(expr, rational=rational, sqrt='numpy.sqrt') def _print_Min(self, expr): return '{}(({}), axis=0)'.format(self._module_format('numpy.amin'), ','.join(self._print(i) for i in expr.args)) def _print_Max(self, expr): return '{}(({}), axis=0)'.format(self._module_format('numpy.amax'), ','.join(self._print(i) for i in expr.args)) def _print_arg(self, expr): return "%s(%s)" % (self._module_format('numpy.angle'), self._print(expr.args[0])) def _print_im(self, expr): return "%s(%s)" % (self._module_format('numpy.imag'), self._print(expr.args[0])) def _print_Mod(self, expr): return "%s(%s)" % (self._module_format('numpy.mod'), ', '.join( map(lambda arg: self._print(arg), expr.args))) def _print_re(self, expr): return "%s(%s)" % (self._module_format('numpy.real'), self._print(expr.args[0])) def _print_sinc(self, expr): return "%s(%s)" % (self._module_format('numpy.sinc'), self._print(expr.args[0]/S.Pi)) def _print_MatrixBase(self, expr): func = self.known_functions.get(expr.__class__.__name__, None) if func is None: func = self._module_format('numpy.array') return "%s(%s)" % (func, self._print(expr.tolist())) def _print_Identity(self, expr): shape = expr.shape if all([dim.is_Integer for dim in shape]): return "%s(%s)" % (self._module_format('numpy.eye'), self._print(expr.shape[0])) else: raise NotImplementedError("Symbolic matrix dimensions are not yet supported for identity matrices") def _print_BlockMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.block'), self._print(expr.args[0].tolist())) def _print_CodegenArrayTensorProduct(self, expr): array_list = [j for i, arg in enumerate(expr.args) for j in (self._print(arg), "[%i, %i]" % (2i, 2i+1))] return "%s(%s)" % (self._module_format('numpy.einsum'), ", ".join(array_list)) def _print_CodegenArrayContraction(self, expr): from sympy.codegen.array_utils import CodegenArrayTensorProduct base = expr.expr contraction_indices = expr.contraction_indices if not contraction_indices: return self._print(base) if isinstance(base, CodegenArrayTensorProduct): counter = 0 d = {j: min(i) for i in contraction_indices for j in i} indices = [] for rank_arg in base.subranks: lindices = [] for i in range(rank_arg): if counter in d: lindices.append(d[counter]) else: lindices.append(counter) counter += 1 indices.append(lindices) elems = ["%s, %s" % (self._print(arg), ind) for arg, ind in zip(base.args, indices)] return "%s(%s)" % ( self._module_format('numpy.einsum'), ", ".join(elems) ) raise NotImplementedError() def _print_CodegenArrayDiagonal(self, expr): diagonal_indices = list(expr.diagonal_indices) if len(diagonal_indices) > 1: # TODO: this should be handled in sympy.codegen.array_utils, # possibly by creating the possibility of unfolding the # CodegenArrayDiagonal object into nested ones. Same reasoning for # the array contraction. raise NotImplementedError if len(diagonal_indices[0]) != 2: raise NotImplementedError return "%s(%s, 0, axis1=%s, axis2=%s)" % ( self._module_format("numpy.diagonal"), self._print(expr.expr), diagonal_indices[0][0], diagonal_indices[0][1], ) def _print_CodegenArrayPermuteDims(self, expr): return "%s(%s, %s)" % ( self._module_format("numpy.transpose"), self._print(expr.expr), self._print(expr.permutation.array_form), ) def _print_CodegenArrayElementwiseAdd(self, expr): return self._expand_fold_binary_op('numpy.add', expr.args) _print_lowergamma = CodePrinter._print_not_supported _print_uppergamma = CodePrinter._print_not_supported _print_fresnelc = CodePrinter._print_not_supported _print_fresnels = CodePrinter._print_not_supported for k in NumPyPrinter._kf: setattr(NumPyPrinter, '_print_%s' % k, _print_known_func) for k in NumPyPrinter._kc: setattr(NumPyPrinter, '_print_%s' % k, _print_known_const) _known_functions_scipy_special = { 'erf': 'erf', 'erfc': 'erfc', 'besselj': 'jv', 'bessely': 'yv', 'besseli': 'iv', 'besselk': 'kv', 'cosm1': 'cosm1', 'factorial': 'factorial', 'gamma': 'gamma', 'loggamma': 'gammaln', 'digamma': 'psi', 'RisingFactorial': 'poch', 'jacobi': 'eval_jacobi', 'gegenbauer': 'eval_gegenbauer', 'chebyshevt': 'eval_chebyt', 'chebyshevu': 'eval_chebyu', 'legendre': 'eval_legendre', 'hermite': 'eval_hermite', 'laguerre': 'eval_laguerre', 'assoc_laguerre': 'eval_genlaguerre', 'beta': 'beta', 'LambertW' : 'lambertw', } _known_constants_scipy_constants = { 'GoldenRatio': 'golden_ratio', 'Pi': 'pi', } class SciPyPrinter(NumPyPrinter): language = "Python with SciPy" _kf = dict(chain( NumPyPrinter._kf.items(), [(k, 'scipy.special.' + v) for k, v in _known_functions_scipy_special.items()] )) _kc =dict(chain( NumPyPrinter._kc.items(), [(k, 'scipy.constants.' + v) for k, v in _known_constants_scipy_constants.items()] )) def _print_SparseMatrix(self, expr): i, j, data = [], [], [] for (r, c), v in expr._smat.items(): i.append(r) j.append(c) data.append(v) return "{name}(({data}, ({i}, {j})), shape={shape})".format( name=self._module_format('scipy.sparse.coo_matrix'), data=data, i=i, j=j, shape=expr.shape ) _print_ImmutableSparseMatrix = _print_SparseMatrix # SciPy's lpmv has a different order of arguments from assoc_legendre def _print_assoc_legendre(self, expr): return "{0}({2}, {1}, {3})".format( self._module_format('scipy.special.lpmv'), self._print(expr.args[0]), self._print(expr.args[1]), self._print(expr.args[2])) def _print_lowergamma(self, expr): return "{0}({2}){1}({2}, {3})".format( self._module_format('scipy.special.gamma'), self._module_format('scipy.special.gammainc'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_uppergamma(self, expr): return "{0}({2}){1}({2}, {3})".format( self._module_format('scipy.special.gamma'), self._module_format('scipy.special.gammaincc'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_fresnels(self, expr): return "{}({})[0]".format( self._module_format("scipy.special.fresnel"), self._print(expr.args[0])) def _print_fresnelc(self, expr): return "{}({})[1]".format( self._module_format("scipy.special.fresnel"), self._print(expr.args[0])) def _print_airyai(self, expr): return "{}({})[0]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airyaiprime(self, expr): return "{}({})[1]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airybi(self, expr): return "{}({})[2]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airybiprime(self, expr): return "{}({})[3]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_Integral(self, e): integration_vars, limits = _unpack_integral_limits(e) if len(limits) == 1: # nicer (but not necessary) to prefer quad over nquad for 1D case module_str = self._module_format("scipy.integrate.quad") limit_str = "%s, %s" % tuple(map(self._print, limits[0])) else: module_str = self._module_format("scipy.integrate.nquad") limit_str = "({})".format(", ".join( "(%s, %s)" % tuple(map(self._print, l)) for l in limits)) return "{}(lambda {}: {}, {})[0]".format( module_str, ", ".join(map(self._print, integration_vars)), self._print(e.args[0]), limit_str) for k in SciPyPrinter._kf: setattr(SciPyPrinter, '_print_%s' % k, _print_known_func) for k in SciPyPrinter._kc: setattr(SciPyPrinter, '_print_%s' % k, _print_known_const) class SymPyPrinter(AbstractPythonCodePrinter): language = "Python with SymPy" def _print_Function(self, expr): mod = expr.func.__module__ or '' return '%s(%s)' % (self._module_format(mod + ('.' if mod else '') + expr.func.__name__), ', '.join(map(lambda arg: self._print(arg), expr.args))) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational, sqrt='sympy.sqrt')
d5abad2058348a36008c41c78a7dd78c4addbbcb434c56bb31355fc6ceee9b5b	""" A Printer for generating readable representation of most sympy classes. """ from typing import Any, Dict from sympy.core import S, Rational, Pow, Basic, Mul, Number from sympy.core.mul import _keep_coeff from .printer import Printer, print_function from sympy.printing.precedence import precedence, PRECEDENCE from mpmath.libmp import prec_to_dps, to_str as mlib_to_str from sympy.utilities import default_sort_key class StrPrinter(Printer): printmethod = "_sympystr" _default_settings = { "order": None, "full_prec": "auto", "sympy_integers": False, "abbrev": False, "perm_cyclic": True, "min": None, "max": None, } # type: Dict[str, Any] _relationals = dict() # type: Dict[str, str] def parenthesize(self, item, level, strict=False): if (precedence(item) < level) or ((not strict) and precedence(item) <= level): return "(%s)" % self._print(item) else: return self._print(item) def stringify(self, args, sep, level=0): return sep.join([self.parenthesize(item, level) for item in args]) def emptyPrinter(self, expr): if isinstance(expr, str): return expr elif isinstance(expr, Basic): return repr(expr) else: return str(expr) def _print_Add(self, expr, order=None): terms = self._as_ordered_terms(expr, order=order) PREC = precedence(expr) l = [] for term in terms: t = self._print(term) if t.startswith('-'): sign = "-" t = t[1:] else: sign = "+" if precedence(term) < PREC: l.extend([sign, "(%s)" % t]) else: l.extend([sign, t]) sign = l.pop(0) if sign == '+': sign = "" return sign + ' '.join(l) def _print_BooleanTrue(self, expr): return "True" def _print_BooleanFalse(self, expr): return "False" def _print_Not(self, expr): return '~%s' %(self.parenthesize(expr.args[0],PRECEDENCE["Not"])) def _print_And(self, expr): return self.stringify(expr.args, " & ", PRECEDENCE["BitwiseAnd"]) def _print_Or(self, expr): return self.stringify(expr.args, " \| ", PRECEDENCE["BitwiseOr"]) def _print_Xor(self, expr): return self.stringify(expr.args, " ^ ", PRECEDENCE["BitwiseXor"]) def _print_AppliedPredicate(self, expr): return '%s(%s)' % (self._print(expr.func), self._print(expr.arg)) def _print_Basic(self, expr): l = [self._print(o) for o in expr.args] return expr.__class__.__name__ + "(%s)" % ", ".join(l) def _print_BlockMatrix(self, B): if B.blocks.shape == (1, 1): self._print(B.blocks[0, 0]) return self._print(B.blocks) def _print_Catalan(self, expr): return 'Catalan' def _print_ComplexInfinity(self, expr): return 'zoo' def _print_ConditionSet(self, s): args = tuple([self._print(i) for i in (s.sym, s.condition)]) if s.base_set is S.UniversalSet: return 'ConditionSet(%s, %s)' % args args += (self._print(s.base_set),) return 'ConditionSet(%s, %s, %s)' % args def _print_Derivative(self, expr): dexpr = expr.expr dvars = [i[0] if i[1] == 1 else i for i in expr.variable_count] return 'Derivative(%s)' % ", ".join(map(lambda arg: self._print(arg), [dexpr] + dvars)) def _print_dict(self, d): keys = sorted(d.keys(), key=default_sort_key) items = [] for key in keys: item = "%s: %s" % (self._print(key), self._print(d[key])) items.append(item) return "{%s}" % ", ".join(items) def _print_Dict(self, expr): return self._print_dict(expr) def _print_RandomDomain(self, d): if hasattr(d, 'as_boolean'): return 'Domain: ' + self._print(d.as_boolean()) elif hasattr(d, 'set'): return ('Domain: ' + self._print(d.symbols) + ' in ' + self._print(d.set)) else: return 'Domain on ' + self._print(d.symbols) def _print_Dummy(self, expr): return '_' + expr.name def _print_EulerGamma(self, expr): return 'EulerGamma' def _print_Exp1(self, expr): return 'E' def _print_ExprCondPair(self, expr): return '(%s, %s)' % (self._print(expr.expr), self._print(expr.cond)) def _print_Function(self, expr): return expr.func.__name__ + "(%s)" % self.stringify(expr.args, ", ") def _print_GoldenRatio(self, expr): return 'GoldenRatio' def _print_TribonacciConstant(self, expr): return 'TribonacciConstant' def _print_ImaginaryUnit(self, expr): return 'I' def _print_Infinity(self, expr): return 'oo' def _print_Integral(self, expr): def _xab_tostr(xab): if len(xab) == 1: return self._print(xab[0]) else: return self._print((xab[0],) + tuple(xab[1:])) L = ', '.join([_xab_tostr(l) for l in expr.limits]) return 'Integral(%s, %s)' % (self._print(expr.function), L) def _print_Interval(self, i): fin = 'Interval{m}({a}, {b})' a, b, l, r = i.args if a.is_infinite and b.is_infinite: m = '' elif a.is_infinite and not r: m = '' elif b.is_infinite and not l: m = '' elif not l and not r: m = '' elif l and r: m = '.open' elif l: m = '.Lopen' else: m = '.Ropen' return fin.format({'a': a, 'b': b, 'm': m}) def _print_AccumulationBounds(self, i): return "AccumBounds(%s, %s)" % (self._print(i.min), self._print(i.max)) def _print_Inverse(self, I): return "%s(-1)" % self.parenthesize(I.arg, PRECEDENCE["Pow"]) def _print_Lambda(self, obj): expr = obj.expr sig = obj.signature if len(sig) == 1 and sig[0].is_symbol: sig = sig[0] return "Lambda(%s, %s)" % (self._print(sig), self._print(expr)) def _print_LatticeOp(self, expr): args = sorted(expr.args, key=default_sort_key) return expr.func.__name__ + "(%s)" % ", ".join(self._print(arg) for arg in args) def _print_Limit(self, expr): e, z, z0, dir = expr.args if str(dir) == "+": return "Limit(%s, %s, %s)" % tuple(map(self._print, (e, z, z0))) else: return "Limit(%s, %s, %s, dir='%s')" % tuple(map(self._print, (e, z, z0, dir))) def _print_list(self, expr): return "[%s]" % self.stringify(expr, ", ") def _print_MatrixBase(self, expr): return expr._format_str(self) def _print_MatrixElement(self, expr): return self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) \ + '[%s, %s]' % (self._print(expr.i), self._print(expr.j)) def _print_MatrixSlice(self, expr): def strslice(x, dim): x = list(x) if x[2] == 1: del x[2] if x[0] == 0: x[0] = '' if x[1] == dim: x[1] = '' return ':'.join(map(lambda arg: self._print(arg), x)) return (self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) + '[' + strslice(expr.rowslice, expr.parent.rows) + ', ' + strslice(expr.colslice, expr.parent.cols) + ']') def _print_DeferredVector(self, expr): return expr.name def _print_Mul(self, expr): prec = precedence(expr) # Check for unevaluated Mul. In this case we need to make sure the # identities are visible, multiple Rational factors are not combined # etc so we display in a straight-forward form that fully preserves all # args and their order. args = expr.args if args[0] is S.One or any(isinstance(arg, Number) for arg in args[1:]): factors = [self.parenthesize(a, prec, strict=False) for a in args] return ''.join(factors) c, e = expr.as_coeff_Mul() if c < 0: expr = _keep_coeff(-c, e) sign = "-" else: sign = "" a = [] # items in the numerator b = [] # items that are in the denominator (if any) pow_paren = [] # Will collect all pow with more than one base element and exp = -1 if self.order not in ('old', 'none'): args = expr.as_ordered_factors() else: # use make_args in case expr was something like -x -> x args = Mul.make_args(expr) # Gather args for numerator/denominator for item in args: if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative: if item.exp != -1: b.append(Pow(item.base, -item.exp, evaluate=False)) else: if len(item.args[0].args) != 1 and isinstance(item.base, Mul): # To avoid situations like #14160 pow_paren.append(item) b.append(Pow(item.base, -item.exp)) elif item.is_Rational and item is not S.Infinity: if item.p != 1: a.append(Rational(item.p)) if item.q != 1: b.append(Rational(item.q)) else: a.append(item) a = a or [S.One] a_str = [self.parenthesize(x, prec, strict=False) for x in a] b_str = [self.parenthesize(x, prec, strict=False) for x in b] # To parenthesize Pow with exp = -1 and having more than one Symbol for item in pow_paren: if item.base in b: b_str[b.index(item.base)] = "(%s)" % b_str[b.index(item.base)] if not b: return sign + ''.join(a_str) elif len(b) == 1: return sign + ''.join(a_str) + "/" + b_str[0] else: return sign + ''.join(a_str) + "/(%s)" % ''.join(b_str) def _print_MatMul(self, expr): c, m = expr.as_coeff_mmul() sign = "" if c.is_number: re, im = c.as_real_imag() if im.is_zero and re.is_negative: expr = _keep_coeff(-c, m) sign = "-" elif re.is_zero and im.is_negative: expr = _keep_coeff(-c, m) sign = "-" return sign + ''.join( [self.parenthesize(arg, precedence(expr)) for arg in expr.args] ) def _print_ElementwiseApplyFunction(self, expr): return "{}.({})".format( expr.function, self._print(expr.expr), ) def _print_NaN(self, expr): return 'nan' def _print_NegativeInfinity(self, expr): return '-oo' def _print_Order(self, expr): if not expr.variables or all(p is S.Zero for p in expr.point): if len(expr.variables) <= 1: return 'O(%s)' % self._print(expr.expr) else: return 'O(%s)' % self.stringify((expr.expr,) + expr.variables, ', ', 0) else: return 'O(%s)' % self.stringify(expr.args, ', ', 0) def _print_Ordinal(self, expr): return expr.__str__() def _print_Cycle(self, expr): return expr.__str__() def _print_Permutation(self, expr): from sympy.combinatorics.permutations import Permutation, Cycle from sympy.utilities.exceptions import SymPyDeprecationWarning perm_cyclic = Permutation.print_cyclic if perm_cyclic is not None: SymPyDeprecationWarning( feature="Permutation.print_cyclic = {}".format(perm_cyclic), useinstead="init_printing(perm_cyclic={})" .format(perm_cyclic), issue=15201, deprecated_since_version="1.6").warn() else: perm_cyclic = self._settings.get("perm_cyclic", True) if perm_cyclic: if not expr.size: return '()' # before taking Cycle notation, see if the last element is # a singleton and move it to the head of the string s = Cycle(expr)(expr.size - 1).__repr__()[len('Cycle'):] last = s.rfind('(') if not last == 0 and ',' not in s[last:]: s = s[last:] + s[:last] s = s.replace(',', '') return s else: s = expr.support() if not s: if expr.size < 5: return 'Permutation(%s)' % self._print(expr.array_form) return 'Permutation([], size=%s)' % self._print(expr.size) trim = self._print(expr.array_form[:s[-1] + 1]) + ', size=%s' % self._print(expr.size) use = full = self._print(expr.array_form) if len(trim) < len(full): use = trim return 'Permutation(%s)' % use def _print_Subs(self, obj): expr, old, new = obj.args if len(obj.point) == 1: old = old[0] new = new[0] return "Subs(%s, %s, %s)" % ( self._print(expr), self._print(old), self._print(new)) def _print_TensorIndex(self, expr): return expr._print() def _print_TensorHead(self, expr): return expr._print() def _print_Tensor(self, expr): return expr._print() def _print_TensMul(self, expr): # prints expressions like "A(a)", "3A(a)", "(1+x)A(a)" sign, args = expr._get_args_for_traditional_printer() return sign + "".join( [self.parenthesize(arg, precedence(expr)) for arg in args] ) def _print_TensAdd(self, expr): return expr._print() def _print_PermutationGroup(self, expr): p = [' %s' % self._print(a) for a in expr.args] return 'PermutationGroup([\n%s])' % ',\n'.join(p) def _print_Pi(self, expr): return 'pi' def _print_PolyRing(self, ring): return "Polynomial ring in %s over %s with %s order" % \ (", ".join(map(lambda rs: self._print(rs), ring.symbols)), self._print(ring.domain), self._print(ring.order)) def _print_FracField(self, field): return "Rational function field in %s over %s with %s order" % \ (", ".join(map(lambda fs: self._print(fs), field.symbols)), self._print(field.domain), self._print(field.order)) def _print_FreeGroupElement(self, elm): return elm.__str__() def _print_GaussianElement(self, poly): return "(%s + %sI)" % (poly.x, poly.y) def _print_PolyElement(self, poly): return poly.str(self, PRECEDENCE, "%s*%s", "") def _print_FracElement(self, frac): if frac.denom == 1: return self._print(frac.numer) else: numer = self.parenthesize(frac.numer, PRECEDENCE["Mul"], strict=True) denom = self.parenthesize(frac.denom, PRECEDENCE["Atom"], strict=True) return numer + "/" + denom def _print_Poly(self, expr): ATOM_PREC = PRECEDENCE["Atom"] - 1 terms, gens = [], [ self.parenthesize(s, ATOM_PREC) for s in expr.gens ] for monom, coeff in expr.terms(): s_monom = [] for i, exp in enumerate(monom): if exp > 0: if exp == 1: s_monom.append(gens[i]) else: s_monom.append(gens[i] + "*%d" % exp) s_monom = "".join(s_monom) if coeff.is_Add: if s_monom: s_coeff = "(" + self._print(coeff) + ")" else: s_coeff = self._print(coeff) else: if s_monom: if coeff is S.One: terms.extend(['+', s_monom]) continue if coeff is S.NegativeOne: terms.extend(['-', s_monom]) continue s_coeff = self._print(coeff) if not s_monom: s_term = s_coeff else: s_term = s_coeff + "" + s_monom if s_term.startswith('-'): terms.extend(['-', s_term[1:]]) else: terms.extend(['+', s_term]) if terms[0] in ['-', '+']: modifier = terms.pop(0) if modifier == '-': terms[0] = '-' + terms[0] format = expr.__class__.__name__ + "(%s, %s" from sympy.polys.polyerrors import PolynomialError try: format += ", modulus=%s" % expr.get_modulus() except PolynomialError: format += ", domain='%s'" % expr.get_domain() format += ")" for index, item in enumerate(gens): if len(item) > 2 and (item[:1] == "(" and item[len(item) - 1:] == ")"): gens[index] = item[1:len(item) - 1] return format % (' '.join(terms), ', '.join(gens)) def _print_UniversalSet(self, p): return 'UniversalSet' def _print_AlgebraicNumber(self, expr): if expr.is_aliased: return self._print(expr.as_poly().as_expr()) else: return self._print(expr.as_expr()) def _print_Pow(self, expr, rational=False): """Printing helper function for ``Pow`` Parameters ========== rational : bool, optional If ``True``, it will not attempt printing ``sqrt(x)`` or ``xS.Half`` as ``sqrt``, and will use ``x(1/2)`` instead. See examples for additional details Examples ======== >>> from sympy.functions import sqrt >>> from sympy.printing.str import StrPrinter >>> from sympy.abc import x How ``rational`` keyword works with ``sqrt``: >>> printer = StrPrinter() >>> printer._print_Pow(sqrt(x), rational=True) 'x(1/2)' >>> printer._print_Pow(sqrt(x), rational=False) 'sqrt(x)' >>> printer._print_Pow(1/sqrt(x), rational=True) 'x(-1/2)' >>> printer._print_Pow(1/sqrt(x), rational=False) '1/sqrt(x)' Notes ===== ``sqrt(x)`` is canonicalized as ``Pow(x, S.Half)`` in SymPy, so there is no need of defining a separate printer for ``sqrt``. Instead, it should be handled here as well. """ PREC = precedence(expr) if expr.exp is S.Half and not rational: return "sqrt(%s)" % self._print(expr.base) if expr.is_commutative: if -expr.exp is S.Half and not rational: # Note: Don't test "expr.exp == -S.Half" here, because that will # match -0.5, which we don't want. return "%s/sqrt(%s)" % tuple(map(lambda arg: self._print(arg), (S.One, expr.base))) if expr.exp is -S.One: # Similarly to the S.Half case, don't test with "==" here. return '%s/%s' % (self._print(S.One), self.parenthesize(expr.base, PREC, strict=False)) e = self.parenthesize(expr.exp, PREC, strict=False) if self.printmethod == '_sympyrepr' and expr.exp.is_Rational and expr.exp.q != 1: # the parenthesized exp should be '(Rational(a, b))' so strip parens, # but just check to be sure. if e.startswith('(Rational'): return '%s%s' % (self.parenthesize(expr.base, PREC, strict=False), e[1:-1]) return '%s%s' % (self.parenthesize(expr.base, PREC, strict=False), e) def _print_UnevaluatedExpr(self, expr): return self._print(expr.args[0]) def _print_MatPow(self, expr): PREC = precedence(expr) return '%s%s' % (self.parenthesize(expr.base, PREC, strict=False), self.parenthesize(expr.exp, PREC, strict=False)) def _print_Integer(self, expr): if self._settings.get("sympy_integers", False): return "S(%s)" % (expr) return str(expr.p) def _print_Integers(self, expr): return 'Integers' def _print_Naturals(self, expr): return 'Naturals' def _print_Naturals0(self, expr): return 'Naturals0' def _print_Rationals(self, expr): return 'Rationals' def _print_Reals(self, expr): return 'Reals' def _print_Complexes(self, expr): return 'Complexes' def _print_EmptySet(self, expr): return 'EmptySet' def _print_EmptySequence(self, expr): return 'EmptySequence' def _print_int(self, expr): return str(expr) def _print_mpz(self, expr): return str(expr) def _print_Rational(self, expr): if expr.q == 1: return str(expr.p) else: if self._settings.get("sympy_integers", False): return "S(%s)/%s" % (expr.p, expr.q) return "%s/%s" % (expr.p, expr.q) def _print_PythonRational(self, expr): if expr.q == 1: return str(expr.p) else: return "%d/%d" % (expr.p, expr.q) def _print_Fraction(self, expr): if expr.denominator == 1: return str(expr.numerator) else: return "%s/%s" % (expr.numerator, expr.denominator) def _print_mpq(self, expr): if expr.denominator == 1: return str(expr.numerator) else: return "%s/%s" % (expr.numerator, expr.denominator) def _print_Float(self, expr): prec = expr._prec if prec < 5: dps = 0 else: dps = prec_to_dps(expr._prec) if self._settings["full_prec"] is True: strip = False elif self._settings["full_prec"] is False: strip = True elif self._settings["full_prec"] == "auto": strip = self._print_level > 1 low = self._settings["min"] if "min" in self._settings else None high = self._settings["max"] if "max" in self._settings else None rv = mlib_to_str(expr._mpf_, dps, strip_zeros=strip, min_fixed=low, max_fixed=high) if rv.startswith('-.0'): rv = '-0.' + rv[3:] elif rv.startswith('.0'): rv = '0.' + rv[2:] if rv.startswith('+'): # e.g., +inf -> inf rv = rv[1:] return rv def _print_Relational(self, expr): charmap = { "==": "Eq", "!=": "Ne", ":=": "Assignment", '+=': "AddAugmentedAssignment", "-=": "SubAugmentedAssignment", "=": "MulAugmentedAssignment", "/=": "DivAugmentedAssignment", "%=": "ModAugmentedAssignment", } if expr.rel_op in charmap: return '%s(%s, %s)' % (charmap[expr.rel_op], self._print(expr.lhs), self._print(expr.rhs)) return '%s %s %s' % (self.parenthesize(expr.lhs, precedence(expr)), self._relationals.get(expr.rel_op) or expr.rel_op, self.parenthesize(expr.rhs, precedence(expr))) def _print_ComplexRootOf(self, expr): return "CRootOf(%s, %d)" % (self._print_Add(expr.expr, order='lex'), expr.index) def _print_RootSum(self, expr): args = [self._print_Add(expr.expr, order='lex')] if expr.fun is not S.IdentityFunction: args.append(self._print(expr.fun)) return "RootSum(%s)" % ", ".join(args) def _print_GroebnerBasis(self, basis): cls = basis.__class__.__name__ exprs = [self._print_Add(arg, order=basis.order) for arg in basis.exprs] exprs = "[%s]" % ", ".join(exprs) gens = [ self._print(gen) for gen in basis.gens ] domain = "domain='%s'" % self._print(basis.domain) order = "order='%s'" % self._print(basis.order) args = [exprs] + gens + [domain, order] return "%s(%s)" % (cls, ", ".join(args)) def _print_set(self, s): items = sorted(s, key=default_sort_key) args = ', '.join(self._print(item) for item in items) if not args: return "set()" return '{%s}' % args def _print_frozenset(self, s): if not s: return "frozenset()" return "frozenset(%s)" % self._print_set(s) def _print_Sum(self, expr): def _xab_tostr(xab): if len(xab) == 1: return self._print(xab[0]) else: return self._print((xab[0],) + tuple(xab[1:])) L = ', '.join([_xab_tostr(l) for l in expr.limits]) return 'Sum(%s, %s)' % (self._print(expr.function), L) def _print_Symbol(self, expr): return expr.name _print_MatrixSymbol = _print_Symbol _print_RandomSymbol = _print_Symbol def _print_Identity(self, expr): return "I" def _print_ZeroMatrix(self, expr): return "0" def _print_OneMatrix(self, expr): return "1" def _print_Predicate(self, expr): return "Q.%s" % expr.name def _print_str(self, expr): return str(expr) def _print_tuple(self, expr): if len(expr) == 1: return "(%s,)" % self._print(expr[0]) else: return "(%s)" % self.stringify(expr, ", ") def _print_Tuple(self, expr): return self._print_tuple(expr) def _print_Transpose(self, T): return "%s.T" % self.parenthesize(T.arg, PRECEDENCE["Pow"]) def _print_Uniform(self, expr): return "Uniform(%s, %s)" % (self._print(expr.a), self._print(expr.b)) def _print_Quantity(self, expr): if self._settings.get("abbrev", False): return "%s" % expr.abbrev return "%s" % expr.name def _print_Quaternion(self, expr): s = [self.parenthesize(i, PRECEDENCE["Mul"], strict=True) for i in expr.args] a = [s[0]] + [i+""+j for i, j in zip(s[1:], "ijk")] return " + ".join(a) def _print_Dimension(self, expr): return str(expr) def _print_Wild(self, expr): return expr.name + '_' def _print_WildFunction(self, expr): return expr.name + '_' def _print_Zero(self, expr): if self._settings.get("sympy_integers", False): return "S(0)" return "0" def _print_DMP(self, p): from sympy.core.sympify import SympifyError try: if p.ring is not None: # TODO incorporate order return self._print(p.ring.to_sympy(p)) except SympifyError: pass cls = p.__class__.__name__ rep = self._print(p.rep) dom = self._print(p.dom) ring = self._print(p.ring) return "%s(%s, %s, %s)" % (cls, rep, dom, ring) def _print_DMF(self, expr): return self._print_DMP(expr) def _print_Object(self, obj): return 'Object("%s")' % obj.name def _print_IdentityMorphism(self, morphism): return 'IdentityMorphism(%s)' % morphism.domain def _print_NamedMorphism(self, morphism): return 'NamedMorphism(%s, %s, "%s")' % \ (morphism.domain, morphism.codomain, morphism.name) def _print_Category(self, category): return 'Category("%s")' % category.name def _print_Manifold(self, manifold): return manifold.name.name def _print_Patch(self, patch): return patch.name.name def _print_CoordSystem(self, coords): return coords.name.name def _print_BaseScalarField(self, field): return field._coord_sys.symbols[field._index].name def _print_BaseVectorField(self, field): return 'e_%s' % field._coord_sys.symbols[field._index].name def _print_Differential(self, diff): field = diff._form_field if hasattr(field, '_coord_sys'): return 'd%s' % field._coord_sys.symbols[field._index].name else: return 'd(%s)' % self._print(field) def _print_Tr(self, expr): #TODO : Handle indices return "%s(%s)" % ("Tr", self._print(expr.args[0])) def _print_Str(self, s): return self._print(s.name) @print_function(StrPrinter) def sstr(expr, settings): """Returns the expression as a string. For large expressions where speed is a concern, use the setting order='none'. If abbrev=True setting is used then units are printed in abbreviated form. Examples ======== >>> from sympy import symbols, Eq, sstr >>> a, b = symbols('a b') >>> sstr(Eq(a + b, 0)) 'Eq(a + b, 0)' """ p = StrPrinter(settings) s = p.doprint(expr) return s class StrReprPrinter(StrPrinter): """(internal) -- see sstrrepr""" def _print_str(self, s): return repr(s) def _print_Str(self, s): # Str does not to be printed same as str here return "%s(%s)" % (s.__class__.__name__, self._print(s.name)) @print_function(StrReprPrinter) def sstrrepr(expr, *settings): """return expr in mixed str/repr form i.e. strings are returned in repr form with quotes, and everything else is returned in str form. This function could be useful for hooking into sys.displayhook """ p = StrReprPrinter(settings) s = p.doprint(expr) return s
1b1105d5621f94f3528653ab65cf0065c87623a1b10e56e92261ea5fad7f3f9a	def pprint_nodes(subtrees): """ Prettyprints systems of nodes. Examples ======== >>> from sympy.printing.tree import pprint_nodes >>> print(pprint_nodes(["a", "b1\\nb2", "c"])) +-a +-b1 \| b2 +-c """ def indent(s, type=1): x = s.split("\n") r = "+-%s\n" % x[0] for a in x[1:]: if a == "": continue if type == 1: r += "\| %s\n" % a else: r += " %s\n" % a return r if not subtrees: return "" f = "" for a in subtrees[:-1]: f += indent(a) f += indent(subtrees[-1], 2) return f def print_node(node, assumptions=True): """ Returns information about the "node". This includes class name, string representation and assumptions. Parameters ========== assumptions : bool, optional See the ``assumptions`` keyword in ``tree`` """ s = "%s: %s\n" % (node.__class__.__name__, str(node)) if assumptions: d = node._assumptions else: d = None if d: for a in sorted(d): v = d[a] if v is None: continue s += "%s: %s\n" % (a, v) return s def tree(node, assumptions=True): """ Returns a tree representation of "node" as a string. It uses print_node() together with pprint_nodes() on node.args recursively. Parameters ========== asssumptions : bool, optional The flag to decide whether to print out all the assumption data (such as ``is_integer`, ``is_real``) associated with the expression or not. Enabling the flag makes the result verbose, and the printed result may not be determinisitic because of the randomness used in backtracing the assumptions. See Also ======== print_tree """ subtrees = [] for arg in node.args: subtrees.append(tree(arg, assumptions=assumptions)) s = print_node(node, assumptions=assumptions) + pprint_nodes(subtrees) return s def print_tree(node, assumptions=True): """ Prints a tree representation of "node". Parameters ========== asssumptions : bool, optional The flag to decide whether to print out all the assumption data (such as ``is_integer`, ``is_real``) associated with the expression or not. Enabling the flag makes the result verbose, and the printed result may not be determinisitic because of the randomness used in backtracing the assumptions. Examples ======== >>> from sympy.printing import print_tree >>> from sympy import Symbol >>> x = Symbol('x', odd=True) >>> y = Symbol('y', even=True) Printing with full assumptions information: >>> print_tree(yx) Pow: yx +-Symbol: y \| algebraic: True \| commutative: True \| complex: True \| even: True \| extended_real: True \| finite: True \| hermitian: True \| imaginary: False \| infinite: False \| integer: True \| irrational: False \| noninteger: False \| odd: False \| rational: True \| real: True \| transcendental: False +-Symbol: x algebraic: True commutative: True complex: True even: False extended_nonzero: True extended_real: True finite: True hermitian: True imaginary: False infinite: False integer: True irrational: False noninteger: False nonzero: True odd: True rational: True real: True transcendental: False zero: False Hiding the assumptions: >>> print_tree(yx, assumptions=False) Pow: yx +-Symbol: y +-Symbol: x See Also ======== tree """ print(tree(node, assumptions=assumptions))
7667356eadb26d9f12aa8ea8875ab411fa95b54016d741f82bf7a12e2827b5a0	""" Rust code printer The `RustCodePrinter` converts SymPy expressions into Rust expressions. A complete code generator, which uses `rust_code` extensively, can be found in `sympy.utilities.codegen`. The `codegen` module can be used to generate complete source code files. """ # Possible Improvement # # * make sure we follow Rust Style Guidelines_ # * make use of pattern matching # * better support for reference # * generate generic code and use trait to make sure they have specific methods # * use crates_ to get more math support # - num_ # + BigInt_, BigUint_ # + Complex_ # + Rational64_, Rational32_, BigRational_ # # .. _crates: https://crates.io/ # .. _Guidelines: https://github.com/rust-lang/rust/tree/master/src/doc/style # .. _num: http://rust-num.github.io/num/num/ # .. _BigInt: http://rust-num.github.io/num/num/bigint/struct.BigInt.html # .. _BigUint: http://rust-num.github.io/num/num/bigint/struct.BigUint.html # .. _Complex: http://rust-num.github.io/num/num/complex/struct.Complex.html # .. _Rational32: http://rust-num.github.io/num/num/rational/type.Rational32.html # .. _Rational64: http://rust-num.github.io/num/num/rational/type.Rational64.html # .. _BigRational: http://rust-num.github.io/num/num/rational/type.BigRational.html from typing import Any, Dict from sympy.core import S, Rational, Float, Lambda from sympy.printing.codeprinter import CodePrinter # Rust's methods for integer and float can be found at here : # # * `Rust - Primitive Type f64 <https://doc.rust-lang.org/std/primitive.f64.html>`_ # * `Rust - Primitive Type i64 <https://doc.rust-lang.org/std/primitive.i64.html>`_ # # Function Style : # # 1. args[0].func(args[1:]), method with arguments # 2. args[0].func(), method without arguments # 3. args[1].func(), method without arguments (e.g. (e, x) => x.exp()) # 4. func(args), function with arguments # dictionary mapping sympy function to (argument_conditions, Rust_function). # Used in RustCodePrinter._print_Function(self) # f64 method in Rust known_functions = { # "": "is_nan", # "": "is_infinite", # "": "is_finite", # "": "is_normal", # "": "classify", "floor": "floor", "ceiling": "ceil", # "": "round", # "": "trunc", # "": "fract", "Abs": "abs", "sign": "signum", # "": "is_sign_positive", # "": "is_sign_negative", # "": "mul_add", "Pow": [(lambda base, exp: exp == -S.One, "recip", 2), # 1.0/x (lambda base, exp: exp == S.Half, "sqrt", 2), # x 0.5 (lambda base, exp: exp == -S.Half, "sqrt().recip", 2), # 1/(x 0.5) (lambda base, exp: exp == Rational(1, 3), "cbrt", 2), # x ** (1/3) (lambda base, exp: base == S.One2, "exp2", 3), # 2 * x (lambda base, exp: exp.is_integer, "powi", 1), # x y, for i32 (lambda base, exp: not exp.is_integer, "powf", 1)], # x y, for f64 "exp": [(lambda exp: True, "exp", 2)], # e x "log": "ln", # "": "log", # number.log(base) # "": "log2", # "": "log10", # "": "to_degrees", # "": "to_radians", "Max": "max", "Min": "min", # "": "hypot", # (x2 + y2) 0.5 "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", # "": "sin_cos", # "": "exp_m1", # e ** x - 1 # "": "ln_1p", # ln(1 + x) "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "asinh": "asinh", "acosh": "acosh", "atanh": "atanh", } # i64 method in Rust # known_functions_i64 = { # "": "min_value", # "": "max_value", # "": "from_str_radix", # "": "count_ones", # "": "count_zeros", # "": "leading_zeros", # "": "trainling_zeros", # "": "rotate_left", # "": "rotate_right", # "": "swap_bytes", # "": "from_be", # "": "from_le", # "": "to_be", # to big endian # "": "to_le", # to little endian # "": "checked_add", # "": "checked_sub", # "": "checked_mul", # "": "checked_div", # "": "checked_rem", # "": "checked_neg", # "": "checked_shl", # "": "checked_shr", # "": "checked_abs", # "": "saturating_add", # "": "saturating_sub", # "": "saturating_mul", # "": "wrapping_add", # "": "wrapping_sub", # "": "wrapping_mul", # "": "wrapping_div", # "": "wrapping_rem", # "": "wrapping_neg", # "": "wrapping_shl", # "": "wrapping_shr", # "": "wrapping_abs", # "": "overflowing_add", # "": "overflowing_sub", # "": "overflowing_mul", # "": "overflowing_div", # "": "overflowing_rem", # "": "overflowing_neg", # "": "overflowing_shl", # "": "overflowing_shr", # "": "overflowing_abs", # "Pow": "pow", # "Abs": "abs", # "sign": "signum", # "": "is_positive", # "": "is_negnative", # } # These are the core reserved words in the Rust language. Taken from: # http://doc.rust-lang.org/grammar.html#keywords reserved_words = ['abstract', 'alignof', 'as', 'become', 'box', 'break', 'const', 'continue', 'crate', 'do', 'else', 'enum', 'extern', 'false', 'final', 'fn', 'for', 'if', 'impl', 'in', 'let', 'loop', 'macro', 'match', 'mod', 'move', 'mut', 'offsetof', 'override', 'priv', 'proc', 'pub', 'pure', 'ref', 'return', 'Self', 'self', 'sizeof', 'static', 'struct', 'super', 'trait', 'true', 'type', 'typeof', 'unsafe', 'unsized', 'use', 'virtual', 'where', 'while', 'yield'] class RustCodePrinter(CodePrinter): """A printer to convert python expressions to strings of Rust code""" printmethod = "_rust_code" language = "Rust" _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'contract': True, 'dereference': set(), 'error_on_reserved': False, 'reserved_word_suffix': '_', 'inline': False, } # type: Dict[str, Any] def __init__(self, settings={}): CodePrinter.__init__(self, settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}) self.known_functions.update(userfuncs) self._dereference = set(settings.get('dereference', [])) self.reserved_words = set(reserved_words) def _rate_index_position(self, p): return p5 def _get_statement(self, codestring): return "%s;" % codestring def _get_comment(self, text): return "// %s" % text def _declare_number_const(self, name, value): return "const %s: f64 = %s;" % (name, value) def _format_code(self, lines): return self.indent_code(lines) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for i in range(rows) for j in range(cols)) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] loopstart = "for %(var)s in %(start)s..%(end)s {" for i in indices: # Rust arrays start at 0 and end at dimension-1 open_lines.append(loopstart % { 'var': self._print(i), 'start': self._print(i.lower), 'end': self._print(i.upper + 1)}) close_lines.append("}") return open_lines, close_lines def _print_caller_var(self, expr): if len(expr.args) > 1: # for something like `sin(x + y + z)`, # make sure we can get '(x + y + z).sin()' # instead of 'x + y + z.sin()' return '(' + self._print(expr) + ')' elif expr.is_number: return self._print(expr, _type=True) else: return self._print(expr) def _print_Function(self, expr): """ basic function for printing `Function` Function Style : 1. args[0].func(args[1:]), method with arguments 2. args[0].func(), method without arguments 3. args[1].func(), method without arguments (e.g. (e, x) => x.exp()) 4. func(args), function with arguments """ if expr.func.__name__ in self.known_functions: cond_func = self.known_functions[expr.func.__name__] func = None style = 1 if isinstance(cond_func, str): func = cond_func else: for cond, func, style in cond_func: if cond(expr.args): break if func is not None: if style == 1: ret = "%(var)s.%(method)s(%(args)s)" % { 'var': self._print_caller_var(expr.args[0]), 'method': func, 'args': self.stringify(expr.args[1:], ", ") if len(expr.args) > 1 else '' } elif style == 2: ret = "%(var)s.%(method)s()" % { 'var': self._print_caller_var(expr.args[0]), 'method': func, } elif style == 3: ret = "%(var)s.%(method)s()" % { 'var': self._print_caller_var(expr.args[1]), 'method': func, } else: ret = "%(func)s(%(args)s)" % { 'func': func, 'args': self.stringify(expr.args, ", "), } return ret elif hasattr(expr, '_imp_') and isinstance(expr._imp_, Lambda): # inlined function return self._print(expr._imp_(expr.args)) else: return self._print_not_supported(expr) def _print_Pow(self, expr): if expr.base.is_integer and not expr.exp.is_integer: expr = type(expr)(Float(expr.base), expr.exp) return self._print(expr) return self._print_Function(expr) def _print_Float(self, expr, _type=False): ret = super()._print_Float(expr) if _type: return ret + '_f64' else: return ret def _print_Integer(self, expr, _type=False): ret = super()._print_Integer(expr) if _type: return ret + '_i32' else: return ret def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) return '%d_f64/%d.0' % (p, q) def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) def _print_Indexed(self, expr): # calculate index for 1d array dims = expr.shape elem = S.Zero offset = S.One for i in reversed(range(expr.rank)): elem += expr.indices[i]offset offset = dims[i] return "%s[%s]" % (self._print(expr.base.label), self._print(elem)) def _print_Idx(self, expr): return expr.label.name def _print_Dummy(self, expr): return expr.name def _print_Exp1(self, expr, _type=False): return "E" def _print_Pi(self, expr, _type=False): return 'PI' def _print_Infinity(self, expr, _type=False): return 'INFINITY' def _print_NegativeInfinity(self, expr, _type=False): return 'NEG_INFINITY' def _print_BooleanTrue(self, expr, _type=False): return "true" def _print_BooleanFalse(self, expr, _type=False): return "false" def _print_bool(self, expr, _type=False): return str(expr).lower() def _print_NaN(self, expr, _type=False): return "NAN" def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) {" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines[-1] += " else {" else: lines[-1] += " else if (%s) {" % self._print(c) code0 = self._print(e) lines.append(code0) lines.append("}") if self._settings['inline']: return " ".join(lines) else: return "\n".join(lines) def _print_ITE(self, expr): from sympy.functions import Piecewise _piecewise = Piecewise((expr.args[1], expr.args[0]), (expr.args[2], True)) return self._print(_piecewise) def _print_MatrixBase(self, A): if A.cols == 1: return "[%s]" % ", ".join(self._print(a) for a in A) else: raise ValueError("Full Matrix Support in Rust need Crates (https://crates.io/keywords/matrix).") def _print_SparseMatrix(self, mat): # do not allow sparse matrices to be made dense return self._print_not_supported(mat) def _print_MatrixElement(self, expr): return "%s[%s]" % (expr.parent, expr.j + expr.iexpr.parent.shape[1]) def _print_Symbol(self, expr): name = super()._print_Symbol(expr) if expr in self._dereference: return '(%s)' % name else: return name def _print_Assignment(self, expr): from sympy.tensor.indexed import IndexedBase lhs = expr.lhs rhs = expr.rhs if self._settings["contract"] and (lhs.has(IndexedBase) or rhs.has(IndexedBase)): # Here we check if there is looping to be done, and if so # print the required loops. return self._doprint_loops(rhs, lhs) else: lhs_code = self._print(lhs) rhs_code = self._print(rhs) return self._get_statement("%s = %s" % (lhs_code, rhs_code)) def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) tab = " " inc_token = ('{', '(', '{\n', '(\n') dec_token = ('}', ')') code = [ line.lstrip(' \t') for line in code ] increase = [ int(any(map(line.endswith, inc_token))) for line in code ] decrease = [ int(any(map(line.startswith, dec_token))) for line in code ] pretty = [] level = 0 for n, line in enumerate(code): if line == '' or line == '\n': pretty.append(line) continue level -= decrease[n] pretty.append("%s%s" % (tablevel, line)) level += increase[n] return pretty def rust_code(expr, assign_to=None, *settings): """Converts an expr to a string of Rust code Parameters ========== expr : Expr A sympy expression to be converted. assign_to : optional When given, the argument is used as the name of the variable to which the expression is assigned. Can be a string, ``Symbol``, ``MatrixSymbol``, or ``Indexed`` type. This is helpful in case of line-wrapping, or for expressions that generate multi-line statements. precision : integer, optional The precision for numbers such as pi [default=15]. user_functions : dict, optional A dictionary where the keys are string representations of either ``FunctionClass`` or ``UndefinedFunction`` instances and the values are their desired C string representations. Alternatively, the dictionary value can be a list of tuples i.e. [(argument_test, cfunction_string)]. See below for examples. dereference : iterable, optional An iterable of symbols that should be dereferenced in the printed code expression. These would be values passed by address to the function. For example, if ``dereference=[a]``, the resulting code would print ``(a)`` instead of ``a``. human : bool, optional If True, the result is a single string that may contain some constant declarations for the number symbols. If False, the same information is returned in a tuple of (symbols_to_declare, not_supported_functions, code_text). [default=True]. contract: bool, optional If True, ``Indexed`` instances are assumed to obey tensor contraction rules and the corresponding nested loops over indices are generated. Setting contract=False will not generate loops, instead the user is responsible to provide values for the indices in the code. [default=True]. Examples ======== >>> from sympy import rust_code, symbols, Rational, sin, ceiling, Abs, Function >>> x, tau = symbols("x, tau") >>> rust_code((2tau)Rational(7, 2)) '81.4142135623731tau.powf(7_f64/2.0)' >>> rust_code(sin(x), assign_to="s") 's = x.sin();' Simple custom printing can be defined for certain types by passing a dictionary of {"type" : "function"} to the ``user_functions`` kwarg. Alternatively, the dictionary value can be a list of tuples i.e. [(argument_test, cfunction_string)]. >>> custom_functions = { ... "ceiling": "CEIL", ... "Abs": [(lambda x: not x.is_integer, "fabs", 4), ... (lambda x: x.is_integer, "ABS", 4)], ... "func": "f" ... } >>> func = Function('func') >>> rust_code(func(Abs(x) + ceiling(x)), user_functions=custom_functions) '(fabs(x) + x.CEIL()).f()' ``Piecewise`` expressions are converted into conditionals. If an ``assign_to`` variable is provided an if statement is created, otherwise the ternary operator is used. Note that if the ``Piecewise`` lacks a default term, represented by ``(expr, True)`` then an error will be thrown. This is to prevent generating an expression that may not evaluate to anything. >>> from sympy import Piecewise >>> expr = Piecewise((x + 1, x > 0), (x, True)) >>> print(rust_code(expr, tau)) tau = if (x > 0) { x + 1 } else { x }; Support for loops is provided through ``Indexed`` types. With ``contract=True`` these expressions will be turned into loops, whereas ``contract=False`` will just print the assignment expression that should be looped over: >>> from sympy import Eq, IndexedBase, Idx >>> len_y = 5 >>> y = IndexedBase('y', shape=(len_y,)) >>> t = IndexedBase('t', shape=(len_y,)) >>> Dy = IndexedBase('Dy', shape=(len_y-1,)) >>> i = Idx('i', len_y-1) >>> e=Eq(Dy[i], (y[i+1]-y[i])/(t[i+1]-t[i])) >>> rust_code(e.rhs, assign_to=e.lhs, contract=False) 'Dy[i] = (y[i + 1] - y[i])/(t[i + 1] - t[i]);' Matrices are also supported, but a ``MatrixSymbol`` of the same dimensions must be provided to ``assign_to``. Note that any expression that can be generated normally can also exist inside a Matrix: >>> from sympy import Matrix, MatrixSymbol >>> mat = Matrix([x2, Piecewise((x + 1, x > 0), (x, True)), sin(x)]) >>> A = MatrixSymbol('A', 3, 1) >>> print(rust_code(mat, A)) A = [x.powi(2), if (x > 0) { x + 1 } else { x }, x.sin()]; """ return RustCodePrinter(settings).doprint(expr, assign_to) def print_rust_code(expr, settings): """Prints Rust representation of the given expression.""" print(rust_code(expr, *settings))
13ad35f79d34139f8dd984ed7c3b6fc764a631493817e041242011d9b230b4ed	""" C++ code printer """ from itertools import chain from sympy.codegen.ast import Type, none from .c import C89CodePrinter, C99CodePrinter # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import cxxcode # noqa:F401 # from http://en.cppreference.com/w/cpp/keyword reserved = { 'C++98': [ 'and', 'and_eq', 'asm', 'auto', 'bitand', 'bitor', 'bool', 'break', 'case', 'catch,', 'char', 'class', 'compl', 'const', 'const_cast', 'continue', 'default', 'delete', 'do', 'double', 'dynamic_cast', 'else', 'enum', 'explicit', 'export', 'extern', 'false', 'float', 'for', 'friend', 'goto', 'if', 'inline', 'int', 'long', 'mutable', 'namespace', 'new', 'not', 'not_eq', 'operator', 'or', 'or_eq', 'private', 'protected', 'public', 'register', 'reinterpret_cast', 'return', 'short', 'signed', 'sizeof', 'static', 'static_cast', 'struct', 'switch', 'template', 'this', 'throw', 'true', 'try', 'typedef', 'typeid', 'typename', 'union', 'unsigned', 'using', 'virtual', 'void', 'volatile', 'wchar_t', 'while', 'xor', 'xor_eq' ] } reserved['C++11'] = reserved['C++98'][:] + [ 'alignas', 'alignof', 'char16_t', 'char32_t', 'constexpr', 'decltype', 'noexcept', 'nullptr', 'static_assert', 'thread_local' ] reserved['C++17'] = reserved['C++11'][:] reserved['C++17'].remove('register') # TM TS: atomic_cancel, atomic_commit, atomic_noexcept, synchronized # concepts TS: concept, requires # module TS: import, module _math_functions = { 'C++98': { 'Mod': 'fmod', 'ceiling': 'ceil', }, 'C++11': { 'gamma': 'tgamma', }, 'C++17': { 'beta': 'beta', 'Ei': 'expint', 'zeta': 'riemann_zeta', } } # from http://en.cppreference.com/w/cpp/header/cmath for k in ('Abs', 'exp', 'log', 'log10', 'sqrt', 'sin', 'cos', 'tan', # 'Pow' 'asin', 'acos', 'atan', 'atan2', 'sinh', 'cosh', 'tanh', 'floor'): _math_functions['C++98'][k] = k.lower() for k in ('asinh', 'acosh', 'atanh', 'erf', 'erfc'): _math_functions['C++11'][k] = k.lower() def _attach_print_method(cls, sympy_name, func_name): meth_name = '_print_%s' % sympy_name if hasattr(cls, meth_name): raise ValueError("Edit method (or subclass) instead of overwriting.") def _print_method(self, expr): return '{}{}({})'.format(self._ns, func_name, ', '.join(map(self._print, expr.args))) _print_method.__doc__ = "Prints code for %s" % k setattr(cls, meth_name, _print_method) def _attach_print_methods(cls, cont): for sympy_name, cxx_name in cont[cls.standard].items(): _attach_print_method(cls, sympy_name, cxx_name) class _CXXCodePrinterBase: printmethod = "_cxxcode" language = 'C++' _ns = 'std::' # namespace def __init__(self, settings=None): super().__init__(settings or {}) def _print_Max(self, expr): from sympy import Max if len(expr.args) == 1: return self._print(expr.args[0]) return "%smax(%s, %s)" % (self._ns, expr.args[0], self._print(Max(expr.args[1:]))) def _print_Min(self, expr): from sympy import Min if len(expr.args) == 1: return self._print(expr.args[0]) return "%smin(%s, %s)" % (self._ns, expr.args[0], self._print(Min(expr.args[1:]))) def _print_using(self, expr): if expr.alias == none: return 'using %s' % expr.type else: raise ValueError("C++98 does not support type aliases") class CXX98CodePrinter(_CXXCodePrinterBase, C89CodePrinter): standard = 'C++98' reserved_words = set(reserved['C++98']) # _attach_print_methods(CXX98CodePrinter, _math_functions) class CXX11CodePrinter(_CXXCodePrinterBase, C99CodePrinter): standard = 'C++11' reserved_words = set(reserved['C++11']) type_mappings = dict(chain( CXX98CodePrinter.type_mappings.items(), { Type('int8'): ('int8_t', {'cstdint'}), Type('int16'): ('int16_t', {'cstdint'}), Type('int32'): ('int32_t', {'cstdint'}), Type('int64'): ('int64_t', {'cstdint'}), Type('uint8'): ('uint8_t', {'cstdint'}), Type('uint16'): ('uint16_t', {'cstdint'}), Type('uint32'): ('uint32_t', {'cstdint'}), Type('uint64'): ('uint64_t', {'cstdint'}), Type('complex64'): ('std::complex<float>', {'complex'}), Type('complex128'): ('std::complex<double>', {'complex'}), Type('bool'): ('bool', None), }.items() )) def _print_using(self, expr): if expr.alias == none: return super()._print_using(expr) else: return 'using %(alias)s = %(type)s' % expr.kwargs(apply=self._print) # _attach_print_methods(CXX11CodePrinter, _math_functions) class CXX17CodePrinter(_CXXCodePrinterBase, C99CodePrinter): standard = 'C++17' reserved_words = set(reserved['C++17']) _kf = dict(C99CodePrinter._kf, **_math_functions['C++17']) def _print_beta(self, expr): return self._print_math_func(expr) def _print_Ei(self, expr): return self._print_math_func(expr) def _print_zeta(self, expr): return self._print_math_func(expr) # _attach_print_methods(CXX17CodePrinter, _math_functions) cxx_code_printers = { 'c++98': CXX98CodePrinter, 'c++11': CXX11CodePrinter, 'c++17': CXX17CodePrinter }
87f685c022e66623460379d2592826df4c8b0fd146e255692247df5bc1dc0a6b	''' Use llvmlite to create executable functions from Sympy expressions This module requires llvmlite (https://github.com/numba/llvmlite). ''' import ctypes from sympy.external import import_module from sympy.printing.printer import Printer from sympy import S, IndexedBase from sympy.utilities.decorator import doctest_depends_on llvmlite = import_module('llvmlite') if llvmlite: ll = import_module('llvmlite.ir').ir llvm = import_module('llvmlite.binding').binding llvm.initialize() llvm.initialize_native_target() llvm.initialize_native_asmprinter() __doctest_requires__ = {('llvm_callable'): ['llvmlite']} class LLVMJitPrinter(Printer): '''Convert expressions to LLVM IR''' def __init__(self, module, builder, fn, args, kwargs): self.func_arg_map = kwargs.pop("func_arg_map", {}) if not llvmlite: raise ImportError("llvmlite is required for LLVMJITPrinter") super().__init__(args, *kwargs) self.fp_type = ll.DoubleType() self.module = module self.builder = builder self.fn = fn self.ext_fn = {} # keep track of wrappers to external functions self.tmp_var = {} def _add_tmp_var(self, name, value): self.tmp_var[name] = value def _print_Number(self, n): return ll.Constant(self.fp_type, float(n)) def _print_Integer(self, expr): return ll.Constant(self.fp_type, float(expr.p)) def _print_Symbol(self, s): val = self.tmp_var.get(s) if not val: # look up parameter with name s val = self.func_arg_map.get(s) if not val: raise LookupError("Symbol not found: %s" % s) return val def _print_Pow(self, expr): base0 = self._print(expr.base) if expr.exp == S.NegativeOne: return self.builder.fdiv(ll.Constant(self.fp_type, 1.0), base0) if expr.exp == S.Half: fn = self.ext_fn.get("sqrt") if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type]) fn = ll.Function(self.module, fn_type, "sqrt") self.ext_fn["sqrt"] = fn return self.builder.call(fn, [base0], "sqrt") if expr.exp == 2: return self.builder.fmul(base0, base0) exp0 = self._print(expr.exp) fn = self.ext_fn.get("pow") if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type, self.fp_type]) fn = ll.Function(self.module, fn_type, "pow") self.ext_fn["pow"] = fn return self.builder.call(fn, [base0, exp0], "pow") def _print_Mul(self, expr): nodes = [self._print(a) for a in expr.args] e = nodes[0] for node in nodes[1:]: e = self.builder.fmul(e, node) return e def _print_Add(self, expr): nodes = [self._print(a) for a in expr.args] e = nodes[0] for node in nodes[1:]: e = self.builder.fadd(e, node) return e # TODO - assumes all called functions take one double precision argument. # Should have a list of math library functions to validate this. def _print_Function(self, expr): name = expr.func.__name__ e0 = self._print(expr.args[0]) fn = self.ext_fn.get(name) if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type]) fn = ll.Function(self.module, fn_type, name) self.ext_fn[name] = fn return self.builder.call(fn, [e0], name) def emptyPrinter(self, expr): raise TypeError("Unsupported type for LLVM JIT conversion: %s" % type(expr)) # Used when parameters are passed by array. Often used in callbacks to # handle a variable number of parameters. class LLVMJitCallbackPrinter(LLVMJitPrinter): def __init__(self, args, *kwargs): super().__init__(args, *kwargs) def _print_Indexed(self, expr): array, idx = self.func_arg_map[expr.base] offset = int(expr.indices[0].evalf()) array_ptr = self.builder.gep(array, [ll.Constant(ll.IntType(32), offset)]) fp_array_ptr = self.builder.bitcast(array_ptr, ll.PointerType(self.fp_type)) value = self.builder.load(fp_array_ptr) return value def _print_Symbol(self, s): val = self.tmp_var.get(s) if val: return val array, idx = self.func_arg_map.get(s, [None, 0]) if not array: raise LookupError("Symbol not found: %s" % s) array_ptr = self.builder.gep(array, [ll.Constant(ll.IntType(32), idx)]) fp_array_ptr = self.builder.bitcast(array_ptr, ll.PointerType(self.fp_type)) value = self.builder.load(fp_array_ptr) return value # ensure lifetime of the execution engine persists (else call to compiled # function will seg fault) exe_engines = [] # ensure names for generated functions are unique link_names = set() current_link_suffix = 0 class LLVMJitCode: def __init__(self, signature): self.signature = signature self.fp_type = ll.DoubleType() self.module = ll.Module('mod1') self.fn = None self.llvm_arg_types = [] self.llvm_ret_type = self.fp_type self.param_dict = {} # map symbol name to LLVM function argument self.link_name = '' def _from_ctype(self, ctype): if ctype == ctypes.c_int: return ll.IntType(32) if ctype == ctypes.c_double: return self.fp_type if ctype == ctypes.POINTER(ctypes.c_double): return ll.PointerType(self.fp_type) if ctype == ctypes.c_void_p: return ll.PointerType(ll.IntType(32)) if ctype == ctypes.py_object: return ll.PointerType(ll.IntType(32)) print("Unhandled ctype = %s" % str(ctype)) def _create_args(self, func_args): """Create types for function arguments""" self.llvm_ret_type = self._from_ctype(self.signature.ret_type) self.llvm_arg_types = \ [self._from_ctype(a) for a in self.signature.arg_ctypes] def _create_function_base(self): """Create function with name and type signature""" global link_names, current_link_suffix default_link_name = 'jit_func' current_link_suffix += 1 self.link_name = default_link_name + str(current_link_suffix) link_names.add(self.link_name) fn_type = ll.FunctionType(self.llvm_ret_type, self.llvm_arg_types) self.fn = ll.Function(self.module, fn_type, name=self.link_name) def _create_param_dict(self, func_args): """Mapping of symbolic values to function arguments""" for i, a in enumerate(func_args): self.fn.args[i].name = str(a) self.param_dict[a] = self.fn.args[i] def _create_function(self, expr): """Create function body and return LLVM IR""" bb_entry = self.fn.append_basic_block('entry') builder = ll.IRBuilder(bb_entry) lj = LLVMJitPrinter(self.module, builder, self.fn, func_arg_map=self.param_dict) ret = self._convert_expr(lj, expr) lj.builder.ret(self._wrap_return(lj, ret)) strmod = str(self.module) return strmod def _wrap_return(self, lj, vals): # Return a single double if there is one return value, # else return a tuple of doubles. # Don't wrap return value in this case if self.signature.ret_type == ctypes.c_double: return vals[0] # Use this instead of a real PyObject void_ptr = ll.PointerType(ll.IntType(32)) # Create a wrapped double: PyObject* PyFloat_FromDouble(double v) wrap_type = ll.FunctionType(void_ptr, [self.fp_type]) wrap_fn = ll.Function(lj.module, wrap_type, "PyFloat_FromDouble") wrapped_vals = [lj.builder.call(wrap_fn, [v]) for v in vals] if len(vals) == 1: final_val = wrapped_vals[0] else: # Create a tuple: PyObject* PyTuple_Pack(Py_ssize_t n, ...) # This should be Py_ssize_t tuple_arg_types = [ll.IntType(32)] tuple_arg_types.extend([void_ptr]len(vals)) tuple_type = ll.FunctionType(void_ptr, tuple_arg_types) tuple_fn = ll.Function(lj.module, tuple_type, "PyTuple_Pack") tuple_args = [ll.Constant(ll.IntType(32), len(wrapped_vals))] tuple_args.extend(wrapped_vals) final_val = lj.builder.call(tuple_fn, tuple_args) return final_val def _convert_expr(self, lj, expr): try: # Match CSE return data structure. if len(expr) == 2: tmp_exprs = expr[0] final_exprs = expr[1] if len(final_exprs) != 1 and self.signature.ret_type == ctypes.c_double: raise NotImplementedError("Return of multiple expressions not supported for this callback") for name, e in tmp_exprs: val = lj._print(e) lj._add_tmp_var(name, val) except TypeError: final_exprs = [expr] vals = [lj._print(e) for e in final_exprs] return vals def _compile_function(self, strmod): global exe_engines llmod = llvm.parse_assembly(strmod) pmb = llvm.create_pass_manager_builder() pmb.opt_level = 2 pass_manager = llvm.create_module_pass_manager() pmb.populate(pass_manager) pass_manager.run(llmod) target_machine = \ llvm.Target.from_default_triple().create_target_machine() exe_eng = llvm.create_mcjit_compiler(llmod, target_machine) exe_eng.finalize_object() exe_engines.append(exe_eng) if False: print("Assembly") print(target_machine.emit_assembly(llmod)) fptr = exe_eng.get_function_address(self.link_name) return fptr class LLVMJitCodeCallback(LLVMJitCode): def __init__(self, signature): super().__init__(signature) def _create_param_dict(self, func_args): for i, a in enumerate(func_args): if isinstance(a, IndexedBase): self.param_dict[a] = (self.fn.args[i], i) self.fn.args[i].name = str(a) else: self.param_dict[a] = (self.fn.args[self.signature.input_arg], i) def _create_function(self, expr): """Create function body and return LLVM IR""" bb_entry = self.fn.append_basic_block('entry') builder = ll.IRBuilder(bb_entry) lj = LLVMJitCallbackPrinter(self.module, builder, self.fn, func_arg_map=self.param_dict) ret = self._convert_expr(lj, expr) if self.signature.ret_arg: output_fp_ptr = builder.bitcast(self.fn.args[self.signature.ret_arg], ll.PointerType(self.fp_type)) for i, val in enumerate(ret): index = ll.Constant(ll.IntType(32), i) output_array_ptr = builder.gep(output_fp_ptr, [index]) builder.store(val, output_array_ptr) builder.ret(ll.Constant(ll.IntType(32), 0)) # return success else: lj.builder.ret(self._wrap_return(lj, ret)) strmod = str(self.module) return strmod class CodeSignature: def __init__(self, ret_type): self.ret_type = ret_type self.arg_ctypes = [] # Input argument array element index self.input_arg = 0 # For the case output value is referenced through a parameter rather # than the return value self.ret_arg = None def _llvm_jit_code(args, expr, signature, callback_type): """Create a native code function from a Sympy expression""" if callback_type is None: jit = LLVMJitCode(signature) else: jit = LLVMJitCodeCallback(signature) jit._create_args(args) jit._create_function_base() jit._create_param_dict(args) strmod = jit._create_function(expr) if False: print("LLVM IR") print(strmod) fptr = jit._compile_function(strmod) return fptr @doctest_depends_on(modules=('llvmlite', 'scipy')) def llvm_callable(args, expr, callback_type=None): '''Compile function from a Sympy expression Expressions are evaluated using double precision arithmetic. Some single argument math functions (exp, sin, cos, etc.) are supported in expressions. Parameters ========== args : List of Symbol Arguments to the generated function. Usually the free symbols in the expression. Currently each one is assumed to convert to a double precision scalar. expr : Expr, or (Replacements, Expr) as returned from 'cse' Expression to compile. callback_type : string Create function with signature appropriate to use as a callback. Currently supported: 'scipy.integrate' 'scipy.integrate.test' 'cubature' Returns ======= Compiled function that can evaluate the expression. Examples ======== >>> import sympy.printing.llvmjitcode as jit >>> from sympy.abc import a >>> e = aa + a + 1 >>> e1 = jit.llvm_callable([a], e) >>> e.subs(a, 1.1) # Evaluate via substitution 3.31000000000000 >>> e1(1.1) # Evaluate using JIT-compiled code 3.3100000000000005 Callbacks for integration functions can be JIT compiled. >>> import sympy.printing.llvmjitcode as jit >>> from sympy.abc import a >>> from sympy import integrate >>> from scipy.integrate import quad >>> e = aa >>> e1 = jit.llvm_callable([a], e, callback_type='scipy.integrate') >>> integrate(e, (a, 0.0, 2.0)) 2.66666666666667 >>> quad(e1, 0.0, 2.0)[0] 2.66666666666667 The 'cubature' callback is for the Python wrapper around the cubature package ( https://github.com/saullocastro/cubature ) and ( http://ab-initio.mit.edu/wiki/index.php/Cubature ) There are two signatures for the SciPy integration callbacks. The first ('scipy.integrate') is the function to be passed to the integration routine, and will pass the signature checks. The second ('scipy.integrate.test') is only useful for directly calling the function using ctypes variables. It will not pass the signature checks for scipy.integrate. The return value from the cse module can also be compiled. This can improve the performance of the compiled function. If multiple expressions are given to cse, the compiled function returns a tuple. The 'cubature' callback handles multiple expressions (set `fdim` to match in the integration call.) >>> import sympy.printing.llvmjitcode as jit >>> from sympy import cse >>> from sympy.abc import x,y >>> e1 = xx + yy >>> e2 = 4(xx + yy) + 8.0 >>> after_cse = cse([e1,e2]) >>> after_cse ([(x0, x2), (x1, y2)], [x0 + x1, 4x0 + 4x1 + 8.0]) >>> j1 = jit.llvm_callable([x,y], after_cse) >>> j1(1.0, 2.0) (5.0, 28.0) ''' if not llvmlite: raise ImportError("llvmlite is required for llvmjitcode") signature = CodeSignature(ctypes.py_object) arg_ctypes = [] if callback_type is None: for _ in args: arg_ctype = ctypes.c_double arg_ctypes.append(arg_ctype) elif callback_type == 'scipy.integrate' or callback_type == 'scipy.integrate.test': signature.ret_type = ctypes.c_double arg_ctypes = [ctypes.c_int, ctypes.POINTER(ctypes.c_double)] arg_ctypes_formal = [ctypes.c_int, ctypes.c_double] signature.input_arg = 1 elif callback_type == 'cubature': arg_ctypes = [ctypes.c_int, ctypes.POINTER(ctypes.c_double), ctypes.c_void_p, ctypes.c_int, ctypes.POINTER(ctypes.c_double) ] signature.ret_type = ctypes.c_int signature.input_arg = 1 signature.ret_arg = 4 else: raise ValueError("Unknown callback type: %s" % callback_type) signature.arg_ctypes = arg_ctypes fptr = _llvm_jit_code(args, expr, signature, callback_type) if callback_type and callback_type == 'scipy.integrate': arg_ctypes = arg_ctypes_formal cfunc = ctypes.CFUNCTYPE(signature.ret_type, *arg_ctypes)(fptr) return cfunc
92660d821a3ff9220ca9bd043b0e90ca4630395cbf8e3760bab2bf272d3e71fd	""" A few practical conventions common to all printers. """ import re from sympy.core.compatibility import Iterable from sympy import Derivative _name_with_digits_p = re.compile(r'^([a-zA-Z]+)([0-9]+)$') def split_super_sub(text): """Split a symbol name into a name, superscripts and subscripts The first part of the symbol name is considered to be its actual 'name', followed by super- and subscripts. Each superscript is preceded with a "^" character or by "__". Each subscript is preceded by a "_" character. The three return values are the actual name, a list with superscripts and a list with subscripts. Examples ======== >>> from sympy.printing.conventions import split_super_sub >>> split_super_sub('a_x^1') ('a', ['1'], ['x']) >>> split_super_sub('var_sub1__sup_sub2') ('var', ['sup'], ['sub1', 'sub2']) """ if not text: return text, [], [] pos = 0 name = None supers = [] subs = [] while pos < len(text): start = pos + 1 if text[pos:pos + 2] == "__": start += 1 pos_hat = text.find("^", start) if pos_hat < 0: pos_hat = len(text) pos_usc = text.find("_", start) if pos_usc < 0: pos_usc = len(text) pos_next = min(pos_hat, pos_usc) part = text[pos:pos_next] pos = pos_next if name is None: name = part elif part.startswith("^"): supers.append(part[1:]) elif part.startswith("__"): supers.append(part[2:]) elif part.startswith("_"): subs.append(part[1:]) else: raise RuntimeError("This should never happen.") # make a little exception when a name ends with digits, i.e. treat them # as a subscript too. m = _name_with_digits_p.match(name) if m: name, sub = m.groups() subs.insert(0, sub) return name, supers, subs def requires_partial(expr): """Return whether a partial derivative symbol is required for printing This requires checking how many free variables there are, filtering out the ones that are integers. Some expressions don't have free variables. In that case, check its variable list explicitly to get the context of the expression. """ if isinstance(expr, Derivative): return requires_partial(expr.expr) if not isinstance(expr.free_symbols, Iterable): return len(set(expr.variables)) > 1 return sum(not s.is_integer for s in expr.free_symbols) > 1
8e7eb188f89152bd63e88a65e06d76d41e26b0b1e4e9df569746680fc178dbb9	""" A Printer which converts an expression into its LaTeX equivalent. """ from typing import Any, Dict import itertools from sympy.core import Add, Float, Mod, Mul, Number, S, Symbol from sympy.core.alphabets import greeks from sympy.core.containers import Tuple from sympy.core.function import _coeff_isneg, AppliedUndef, Derivative from sympy.core.operations import AssocOp from sympy.core.sympify import SympifyError from sympy.logic.boolalg import true # sympy.printing imports from sympy.printing.precedence import precedence_traditional from sympy.printing.printer import Printer, print_function from sympy.printing.conventions import split_super_sub, requires_partial from sympy.printing.precedence import precedence, PRECEDENCE import mpmath.libmp as mlib from mpmath.libmp import prec_to_dps from sympy.core.compatibility import default_sort_key from sympy.utilities.iterables import has_variety import re # Hand-picked functions which can be used directly in both LaTeX and MathJax # Complete list at # https://docs.mathjax.org/en/latest/tex.html#supported-latex-commands # This variable only contains those functions which sympy uses. accepted_latex_functions = ['arcsin', 'arccos', 'arctan', 'sin', 'cos', 'tan', 'sinh', 'cosh', 'tanh', 'sqrt', 'ln', 'log', 'sec', 'csc', 'cot', 'coth', 're', 'im', 'frac', 'root', 'arg', ] tex_greek_dictionary = { 'Alpha': 'A', 'Beta': 'B', 'Gamma': r'\Gamma', 'Delta': r'\Delta', 'Epsilon': 'E', 'Zeta': 'Z', 'Eta': 'H', 'Theta': r'\Theta', 'Iota': 'I', 'Kappa': 'K', 'Lambda': r'\Lambda', 'Mu': 'M', 'Nu': 'N', 'Xi': r'\Xi', 'omicron': 'o', 'Omicron': 'O', 'Pi': r'\Pi', 'Rho': 'P', 'Sigma': r'\Sigma', 'Tau': 'T', 'Upsilon': r'\Upsilon', 'Phi': r'\Phi', 'Chi': 'X', 'Psi': r'\Psi', 'Omega': r'\Omega', 'lamda': r'\lambda', 'Lamda': r'\Lambda', 'khi': r'\chi', 'Khi': r'X', 'varepsilon': r'\varepsilon', 'varkappa': r'\varkappa', 'varphi': r'\varphi', 'varpi': r'\varpi', 'varrho': r'\varrho', 'varsigma': r'\varsigma', 'vartheta': r'\vartheta', } other_symbols = {'aleph', 'beth', 'daleth', 'gimel', 'ell', 'eth', 'hbar', 'hslash', 'mho', 'wp'} # Variable name modifiers modifier_dict = { # Accents 'mathring': lambda s: r'\mathring{'+s+r'}', 'ddddot': lambda s: r'\ddddot{'+s+r'}', 'dddot': lambda s: r'\dddot{'+s+r'}', 'ddot': lambda s: r'\ddot{'+s+r'}', 'dot': lambda s: r'\dot{'+s+r'}', 'check': lambda s: r'\check{'+s+r'}', 'breve': lambda s: r'\breve{'+s+r'}', 'acute': lambda s: r'\acute{'+s+r'}', 'grave': lambda s: r'\grave{'+s+r'}', 'tilde': lambda s: r'\tilde{'+s+r'}', 'hat': lambda s: r'\hat{'+s+r'}', 'bar': lambda s: r'\bar{'+s+r'}', 'vec': lambda s: r'\vec{'+s+r'}', 'prime': lambda s: "{"+s+"}'", 'prm': lambda s: "{"+s+"}'", # Faces 'bold': lambda s: r'\boldsymbol{'+s+r'}', 'bm': lambda s: r'\boldsymbol{'+s+r'}', 'cal': lambda s: r'\mathcal{'+s+r'}', 'scr': lambda s: r'\mathscr{'+s+r'}', 'frak': lambda s: r'\mathfrak{'+s+r'}', # Brackets 'norm': lambda s: r'\left\\|{'+s+r'}\right\\|', 'avg': lambda s: r'\left\langle{'+s+r'}\right\rangle', 'abs': lambda s: r'\left\|{'+s+r'}\right\|', 'mag': lambda s: r'\left\|{'+s+r'}\right\|', } greek_letters_set = frozenset(greeks) _between_two_numbers_p = ( re.compile(r'[0-9][} ]$'), # search re.compile(r'[{ ][-+0-9]'), # match ) def latex_escape(s): """ Escape a string such that latex interprets it as plaintext. We can't use verbatim easily with mathjax, so escaping is easier. Rules from https://tex.stackexchange.com/a/34586/41112. """ s = s.replace('\\', r'\textbackslash') for c in '&%$#_{}': s = s.replace(c, '\\' + c) s = s.replace('~', r'\textasciitilde') s = s.replace('^', r'\textasciicircum') return s class LatexPrinter(Printer): printmethod = "_latex" _default_settings = { "full_prec": False, "fold_frac_powers": False, "fold_func_brackets": False, "fold_short_frac": None, "inv_trig_style": "abbreviated", "itex": False, "ln_notation": False, "long_frac_ratio": None, "mat_delim": "[", "mat_str": None, "mode": "plain", "mul_symbol": None, "order": None, "symbol_names": {}, "root_notation": True, "mat_symbol_style": "plain", "imaginary_unit": "i", "gothic_re_im": False, "decimal_separator": "period", "perm_cyclic": True, "parenthesize_super": True, "min": None, "max": None, } # type: Dict[str, Any] def __init__(self, settings=None): Printer.__init__(self, settings) if 'mode' in self._settings: valid_modes = ['inline', 'plain', 'equation', 'equation'] if self._settings['mode'] not in valid_modes: raise ValueError("'mode' must be one of 'inline', 'plain', " "'equation' or 'equation'") if self._settings['fold_short_frac'] is None and \ self._settings['mode'] == 'inline': self._settings['fold_short_frac'] = True mul_symbol_table = { None: r" ", "ldot": r" \,.\, ", "dot": r" \cdot ", "times": r" \times " } try: self._settings['mul_symbol_latex'] = \ mul_symbol_table[self._settings['mul_symbol']] except KeyError: self._settings['mul_symbol_latex'] = \ self._settings['mul_symbol'] try: self._settings['mul_symbol_latex_numbers'] = \ mul_symbol_table[self._settings['mul_symbol'] or 'dot'] except KeyError: if (self._settings['mul_symbol'].strip() in ['', ' ', '\\', '\\,', '\\:', '\\;', '\\quad']): self._settings['mul_symbol_latex_numbers'] = \ mul_symbol_table['dot'] else: self._settings['mul_symbol_latex_numbers'] = \ self._settings['mul_symbol'] self._delim_dict = {'(': ')', '[': ']'} imaginary_unit_table = { None: r"i", "i": r"i", "ri": r"\mathrm{i}", "ti": r"\text{i}", "j": r"j", "rj": r"\mathrm{j}", "tj": r"\text{j}", } try: self._settings['imaginary_unit_latex'] = \ imaginary_unit_table[self._settings['imaginary_unit']] except KeyError: self._settings['imaginary_unit_latex'] = \ self._settings['imaginary_unit'] def _add_parens(self, s): return r"\left({}\right)".format(s) # TODO: merge this with the above, which requires a lot of test changes def _add_parens_lspace(self, s): return r"\left( {}\right)".format(s) def parenthesize(self, item, level, is_neg=False, strict=False): prec_val = precedence_traditional(item) if is_neg and strict: return self._add_parens(self._print(item)) if (prec_val < level) or ((not strict) and prec_val <= level): return self._add_parens(self._print(item)) else: return self._print(item) def parenthesize_super(self, s): """ Protect superscripts in s If the parenthesize_super option is set, protect with parentheses, else wrap in braces. """ if "^" in s: if self._settings['parenthesize_super']: return self._add_parens(s) else: return "{{{}}}".format(s) return s def doprint(self, expr): tex = Printer.doprint(self, expr) if self._settings['mode'] == 'plain': return tex elif self._settings['mode'] == 'inline': return r"$%s$" % tex elif self._settings['itex']: return r"$$%s$$" % tex else: env_str = self._settings['mode'] return r"\begin{%s}%s\end{%s}" % (env_str, tex, env_str) def _needs_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when printed, False otherwise. For example: a + b => True; a => False; 10 => False; -10 => True. """ return not ((expr.is_Integer and expr.is_nonnegative) or (expr.is_Atom and (expr is not S.NegativeOne and expr.is_Rational is False))) def _needs_function_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when passed as an argument to a function, False otherwise. This is a more liberal version of _needs_brackets, in that many expressions which need to be wrapped in brackets when added/subtracted/raised to a power do not need them when passed to a function. Such an example is ab. """ if not self._needs_brackets(expr): return False else: # Muls of the form abc... can be folded if expr.is_Mul and not self._mul_is_clean(expr): return True # Pows which don't need brackets can be folded elif expr.is_Pow and not self._pow_is_clean(expr): return True # Add and Function always need brackets elif expr.is_Add or expr.is_Function: return True else: return False def _needs_mul_brackets(self, expr, first=False, last=False): """ Returns True if the expression needs to be wrapped in brackets when printed as part of a Mul, False otherwise. This is True for Add, but also for some container objects that would not need brackets when appearing last in a Mul, e.g. an Integral. ``last=True`` specifies that this expr is the last to appear in a Mul. ``first=True`` specifies that this expr is the first to appear in a Mul. """ from sympy import Integral, Product, Sum if expr.is_Mul: if not first and _coeff_isneg(expr): return True elif precedence_traditional(expr) < PRECEDENCE["Mul"]: return True elif expr.is_Relational: return True if expr.is_Piecewise: return True if any([expr.has(x) for x in (Mod,)]): return True if (not last and any([expr.has(x) for x in (Integral, Product, Sum)])): return True return False def _needs_add_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when printed as part of an Add, False otherwise. This is False for most things. """ if expr.is_Relational: return True if any([expr.has(x) for x in (Mod,)]): return True if expr.is_Add: return True return False def _mul_is_clean(self, expr): for arg in expr.args: if arg.is_Function: return False return True def _pow_is_clean(self, expr): return not self._needs_brackets(expr.base) def _do_exponent(self, expr, exp): if exp is not None: return r"\left(%s\right)^{%s}" % (expr, exp) else: return expr def _print_Basic(self, expr): ls = [self._print(o) for o in expr.args] return self._deal_with_super_sub(expr.__class__.__name__) + \ r"\left(%s\right)" % ", ".join(ls) def _print_bool(self, e): return r"\text{%s}" % e _print_BooleanTrue = _print_bool _print_BooleanFalse = _print_bool def _print_NoneType(self, e): return r"\text{%s}" % e def _print_Add(self, expr, order=None): terms = self._as_ordered_terms(expr, order=order) tex = "" for i, term in enumerate(terms): if i == 0: pass elif _coeff_isneg(term): tex += " - " term = -term else: tex += " + " term_tex = self._print(term) if self._needs_add_brackets(term): term_tex = r"\left(%s\right)" % term_tex tex += term_tex return tex def _print_Cycle(self, expr): from sympy.combinatorics.permutations import Permutation if expr.size == 0: return r"\left( \right)" expr = Permutation(expr) expr_perm = expr.cyclic_form siz = expr.size if expr.array_form[-1] == siz - 1: expr_perm = expr_perm + [[siz - 1]] term_tex = '' for i in expr_perm: term_tex += str(i).replace(',', r"\;") term_tex = term_tex.replace('[', r"\left( ") term_tex = term_tex.replace(']', r"\right)") return term_tex def _print_Permutation(self, expr): from sympy.combinatorics.permutations import Permutation from sympy.utilities.exceptions import SymPyDeprecationWarning perm_cyclic = Permutation.print_cyclic if perm_cyclic is not None: SymPyDeprecationWarning( feature="Permutation.print_cyclic = {}".format(perm_cyclic), useinstead="init_printing(perm_cyclic={})" .format(perm_cyclic), issue=15201, deprecated_since_version="1.6").warn() else: perm_cyclic = self._settings.get("perm_cyclic", True) if perm_cyclic: return self._print_Cycle(expr) if expr.size == 0: return r"\left( \right)" lower = [self._print(arg) for arg in expr.array_form] upper = [self._print(arg) for arg in range(len(lower))] row1 = " & ".join(upper) row2 = " & ".join(lower) mat = r" \\ ".join((row1, row2)) return r"\begin{pmatrix} %s \end{pmatrix}" % mat def _print_AppliedPermutation(self, expr): perm, var = expr.args return r"\sigma_{%s}(%s)" % (self._print(perm), self._print(var)) def _print_Float(self, expr): # Based off of that in StrPrinter dps = prec_to_dps(expr._prec) strip = False if self._settings['full_prec'] else True low = self._settings["min"] if "min" in self._settings else None high = self._settings["max"] if "max" in self._settings else None str_real = mlib.to_str(expr._mpf_, dps, strip_zeros=strip, min_fixed=low, max_fixed=high) # Must always have a mul symbol (as 2.5 10^{20} just looks odd) # thus we use the number separator separator = self._settings['mul_symbol_latex_numbers'] if 'e' in str_real: (mant, exp) = str_real.split('e') if exp[0] == '+': exp = exp[1:] if self._settings['decimal_separator'] == 'comma': mant = mant.replace('.','{,}') return r"%s%s10^{%s}" % (mant, separator, exp) elif str_real == "+inf": return r"\infty" elif str_real == "-inf": return r"- \infty" else: if self._settings['decimal_separator'] == 'comma': str_real = str_real.replace('.','{,}') return str_real def _print_Cross(self, expr): vec1 = expr._expr1 vec2 = expr._expr2 return r"%s \times %s" % (self.parenthesize(vec1, PRECEDENCE['Mul']), self.parenthesize(vec2, PRECEDENCE['Mul'])) def _print_Curl(self, expr): vec = expr._expr return r"\nabla\times %s" % self.parenthesize(vec, PRECEDENCE['Mul']) def _print_Divergence(self, expr): vec = expr._expr return r"\nabla\cdot %s" % self.parenthesize(vec, PRECEDENCE['Mul']) def _print_Dot(self, expr): vec1 = expr._expr1 vec2 = expr._expr2 return r"%s \cdot %s" % (self.parenthesize(vec1, PRECEDENCE['Mul']), self.parenthesize(vec2, PRECEDENCE['Mul'])) def _print_Gradient(self, expr): func = expr._expr return r"\nabla %s" % self.parenthesize(func, PRECEDENCE['Mul']) def _print_Laplacian(self, expr): func = expr._expr return r"\triangle %s" % self.parenthesize(func, PRECEDENCE['Mul']) def _print_Mul(self, expr): from sympy.core.power import Pow from sympy.physics.units import Quantity from sympy.simplify import fraction separator = self._settings['mul_symbol_latex'] numbersep = self._settings['mul_symbol_latex_numbers'] def convert(expr): if not expr.is_Mul: return str(self._print(expr)) else: if self.order not in ('old', 'none'): args = expr.as_ordered_factors() else: args = list(expr.args) # If quantities are present append them at the back args = sorted(args, key=lambda x: isinstance(x, Quantity) or (isinstance(x, Pow) and isinstance(x.base, Quantity))) return convert_args(args) def convert_args(args): _tex = last_term_tex = "" for i, term in enumerate(args): term_tex = self._print(term) if self._needs_mul_brackets(term, first=(i == 0), last=(i == len(args) - 1)): term_tex = r"\left(%s\right)" % term_tex if _between_two_numbers_p[0].search(last_term_tex) and \ _between_two_numbers_p[1].match(term_tex): # between two numbers _tex += numbersep elif _tex: _tex += separator _tex += term_tex last_term_tex = term_tex return _tex # Check for unevaluated Mul. In this case we need to make sure the # identities are visible, multiple Rational factors are not combined # etc so we display in a straight-forward form that fully preserves all # args and their order. # XXX: _print_Pow calls this routine with instances of Pow... if isinstance(expr, Mul): args = expr.args if args[0] is S.One or any(isinstance(arg, Number) for arg in args[1:]): return convert_args(args) include_parens = False if _coeff_isneg(expr): expr = -expr tex = "- " if expr.is_Add: tex += "(" include_parens = True else: tex = "" numer, denom = fraction(expr, exact=True) if denom is S.One and Pow(1, -1, evaluate=False) not in expr.args: # use the original expression here, since fraction() may have # altered it when producing numer and denom tex += convert(expr) else: snumer = convert(numer) sdenom = convert(denom) ldenom = len(sdenom.split()) ratio = self._settings['long_frac_ratio'] if self._settings['fold_short_frac'] and ldenom <= 2 and \ "^" not in sdenom: # handle short fractions if self._needs_mul_brackets(numer, last=False): tex += r"\left(%s\right) / %s" % (snumer, sdenom) else: tex += r"%s / %s" % (snumer, sdenom) elif ratio is not None and \ len(snumer.split()) > ratioldenom: # handle long fractions if self._needs_mul_brackets(numer, last=True): tex += r"\frac{1}{%s}%s\left(%s\right)" \ % (sdenom, separator, snumer) elif numer.is_Mul: # split a long numerator a = S.One b = S.One for x in numer.args: if self._needs_mul_brackets(x, last=False) or \ len(convert(ax).split()) > ratioldenom or \ (b.is_commutative is x.is_commutative is False): b = x else: a = x if self._needs_mul_brackets(b, last=True): tex += r"\frac{%s}{%s}%s\left(%s\right)" \ % (convert(a), sdenom, separator, convert(b)) else: tex += r"\frac{%s}{%s}%s%s" \ % (convert(a), sdenom, separator, convert(b)) else: tex += r"\frac{1}{%s}%s%s" % (sdenom, separator, snumer) else: tex += r"\frac{%s}{%s}" % (snumer, sdenom) if include_parens: tex += ")" return tex def _print_Pow(self, expr): # Treat x*Rational(1,n) as special case if expr.exp.is_Rational and abs(expr.exp.p) == 1 and expr.exp.q != 1 \ and self._settings['root_notation']: base = self._print(expr.base) expq = expr.exp.q if expq == 2: tex = r"\sqrt{%s}" % base elif self._settings['itex']: tex = r"\root{%d}{%s}" % (expq, base) else: tex = r"\sqrt[%d]{%s}" % (expq, base) if expr.exp.is_negative: return r"\frac{1}{%s}" % tex else: return tex elif self._settings['fold_frac_powers'] \ and expr.exp.is_Rational \ and expr.exp.q != 1: base = self.parenthesize(expr.base, PRECEDENCE['Pow']) p, q = expr.exp.p, expr.exp.q # issue #12886: add parentheses for superscripts raised to powers if expr.base.is_Symbol: base = self.parenthesize_super(base) if expr.base.is_Function: return self._print(expr.base, exp="%s/%s" % (p, q)) return r"%s^{%s/%s}" % (base, p, q) elif expr.exp.is_Rational and expr.exp.is_negative and \ expr.base.is_commutative: # special case for 1^(-x), issue 9216 if expr.base == 1: return r"%s^{%s}" % (expr.base, expr.exp) # things like 1/x return self._print_Mul(expr) else: if expr.base.is_Function: return self._print(expr.base, exp=self._print(expr.exp)) else: tex = r"%s^{%s}" return self._helper_print_standard_power(expr, tex) def _helper_print_standard_power(self, expr, template): exp = self._print(expr.exp) # issue #12886: add parentheses around superscripts raised # to powers base = self.parenthesize(expr.base, PRECEDENCE['Pow']) if expr.base.is_Symbol: base = self.parenthesize_super(base) elif (isinstance(expr.base, Derivative) and base.startswith(r'\left(') and re.match(r'\\left\(\\d?d?dot', base) and base.endswith(r'\right)')): # don't use parentheses around dotted derivative base = base[6: -7] # remove outermost added parens return template % (base, exp) def _print_UnevaluatedExpr(self, expr): return self._print(expr.args[0]) def _print_Sum(self, expr): if len(expr.limits) == 1: tex = r"\sum_{%s=%s}^{%s} " % \ tuple([self._print(i) for i in expr.limits[0]]) else: def _format_ineq(l): return r"%s \leq %s \leq %s" % \ tuple([self._print(s) for s in (l[1], l[0], l[2])]) tex = r"\sum_{\substack{%s}} " % \ str.join('\\\\', [_format_ineq(l) for l in expr.limits]) if isinstance(expr.function, Add): tex += r"\left(%s\right)" % self._print(expr.function) else: tex += self._print(expr.function) return tex def _print_Product(self, expr): if len(expr.limits) == 1: tex = r"\prod_{%s=%s}^{%s} " % \ tuple([self._print(i) for i in expr.limits[0]]) else: def _format_ineq(l): return r"%s \leq %s \leq %s" % \ tuple([self._print(s) for s in (l[1], l[0], l[2])]) tex = r"\prod_{\substack{%s}} " % \ str.join('\\\\', [_format_ineq(l) for l in expr.limits]) if isinstance(expr.function, Add): tex += r"\left(%s\right)" % self._print(expr.function) else: tex += self._print(expr.function) return tex def _print_BasisDependent(self, expr): from sympy.vector import Vector o1 = [] if expr == expr.zero: return expr.zero._latex_form if isinstance(expr, Vector): items = expr.separate().items() else: items = [(0, expr)] for system, vect in items: inneritems = list(vect.components.items()) inneritems.sort(key=lambda x: x[0].__str__()) for k, v in inneritems: if v == 1: o1.append(' + ' + k._latex_form) elif v == -1: o1.append(' - ' + k._latex_form) else: arg_str = '(' + self._print(v) + ')' o1.append(' + ' + arg_str + k._latex_form) outstr = (''.join(o1)) if outstr[1] != '-': outstr = outstr[3:] else: outstr = outstr[1:] return outstr def _print_Indexed(self, expr): tex_base = self._print(expr.base) tex = '{'+tex_base+'}'+'_{%s}' % ','.join( map(self._print, expr.indices)) return tex def _print_IndexedBase(self, expr): return self._print(expr.label) def _print_Derivative(self, expr): if requires_partial(expr.expr): diff_symbol = r'\partial' else: diff_symbol = r'd' tex = "" dim = 0 for x, num in reversed(expr.variable_count): dim += num if num == 1: tex += r"%s %s" % (diff_symbol, self._print(x)) else: tex += r"%s %s^{%s}" % (diff_symbol, self.parenthesize_super(self._print(x)), self._print(num)) if dim == 1: tex = r"\frac{%s}{%s}" % (diff_symbol, tex) else: tex = r"\frac{%s^{%s}}{%s}" % (diff_symbol, self._print(dim), tex) if any(_coeff_isneg(i) for i in expr.args): return r"%s %s" % (tex, self.parenthesize(expr.expr, PRECEDENCE["Mul"], is_neg=True, strict=True)) return r"%s %s" % (tex, self.parenthesize(expr.expr, PRECEDENCE["Mul"], is_neg=False, strict=True)) def _print_Subs(self, subs): expr, old, new = subs.args latex_expr = self._print(expr) latex_old = (self._print(e) for e in old) latex_new = (self._print(e) for e in new) latex_subs = r'\\ '.join( e[0] + '=' + e[1] for e in zip(latex_old, latex_new)) return r'\left. %s \right\|_{\substack{ %s }}' % (latex_expr, latex_subs) def _print_Integral(self, expr): tex, symbols = "", [] # Only up to \iiiint exists if len(expr.limits) <= 4 and all(len(lim) == 1 for lim in expr.limits): # Use len(expr.limits)-1 so that syntax highlighters don't think # \" is an escaped quote tex = r"\i" + "i"(len(expr.limits) - 1) + "nt" symbols = [r"\, d%s" % self._print(symbol[0]) for symbol in expr.limits] else: for lim in reversed(expr.limits): symbol = lim[0] tex += r"\int" if len(lim) > 1: if self._settings['mode'] != 'inline' \ and not self._settings['itex']: tex += r"\limits" if len(lim) == 3: tex += "_{%s}^{%s}" % (self._print(lim[1]), self._print(lim[2])) if len(lim) == 2: tex += "^{%s}" % (self._print(lim[1])) symbols.insert(0, r"\, d%s" % self._print(symbol)) return r"%s %s%s" % (tex, self.parenthesize(expr.function, PRECEDENCE["Mul"], is_neg=any(_coeff_isneg(i) for i in expr.args), strict=True), "".join(symbols)) def _print_Limit(self, expr): e, z, z0, dir = expr.args tex = r"\lim_{%s \to " % self._print(z) if str(dir) == '+-' or z0 in (S.Infinity, S.NegativeInfinity): tex += r"%s}" % self._print(z0) else: tex += r"%s^%s}" % (self._print(z0), self._print(dir)) if isinstance(e, AssocOp): return r"%s\left(%s\right)" % (tex, self._print(e)) else: return r"%s %s" % (tex, self._print(e)) def _hprint_Function(self, func): r''' Logic to decide how to render a function to latex - if it is a recognized latex name, use the appropriate latex command - if it is a single letter, just use that letter - if it is a longer name, then put \operatorname{} around it and be mindful of undercores in the name ''' func = self._deal_with_super_sub(func) if func in accepted_latex_functions: name = r"\%s" % func elif len(func) == 1 or func.startswith('\\'): name = func else: name = r"\operatorname{%s}" % func return name def _print_Function(self, expr, exp=None): r''' Render functions to LaTeX, handling functions that LaTeX knows about e.g., sin, cos, ... by using the proper LaTeX command (\sin, \cos, ...). For single-letter function names, render them as regular LaTeX math symbols. For multi-letter function names that LaTeX does not know about, (e.g., Li, sech) use \operatorname{} so that the function name is rendered in Roman font and LaTeX handles spacing properly. expr is the expression involving the function exp is an exponent ''' func = expr.func.__name__ if hasattr(self, '_print_' + func) and \ not isinstance(expr, AppliedUndef): return getattr(self, '_print_' + func)(expr, exp) else: args = [str(self._print(arg)) for arg in expr.args] # How inverse trig functions should be displayed, formats are: # abbreviated: asin, full: arcsin, power: sin^-1 inv_trig_style = self._settings['inv_trig_style'] # If we are dealing with a power-style inverse trig function inv_trig_power_case = False # If it is applicable to fold the argument brackets can_fold_brackets = self._settings['fold_func_brackets'] and \ len(args) == 1 and \ not self._needs_function_brackets(expr.args[0]) inv_trig_table = [ "asin", "acos", "atan", "acsc", "asec", "acot", "asinh", "acosh", "atanh", "acsch", "asech", "acoth", ] # If the function is an inverse trig function, handle the style if func in inv_trig_table: if inv_trig_style == "abbreviated": pass elif inv_trig_style == "full": func = "arc" + func[1:] elif inv_trig_style == "power": func = func[1:] inv_trig_power_case = True # Can never fold brackets if we're raised to a power if exp is not None: can_fold_brackets = False if inv_trig_power_case: if func in accepted_latex_functions: name = r"\%s^{-1}" % func else: name = r"\operatorname{%s}^{-1}" % func elif exp is not None: func_tex = self._hprint_Function(func) func_tex = self.parenthesize_super(func_tex) name = r'%s^{%s}' % (func_tex, exp) else: name = self._hprint_Function(func) if can_fold_brackets: if func in accepted_latex_functions: # Wrap argument safely to avoid parse-time conflicts # with the function name itself name += r" {%s}" else: name += r"%s" else: name += r"{\left(%s \right)}" if inv_trig_power_case and exp is not None: name += r"^{%s}" % exp return name % ",".join(args) def _print_UndefinedFunction(self, expr): return self._hprint_Function(str(expr)) def _print_ElementwiseApplyFunction(self, expr): return r"{%s}_{\circ}\left({%s}\right)" % ( self._print(expr.function), self._print(expr.expr), ) @property def _special_function_classes(self): from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.functions.special.gamma_functions import gamma, lowergamma from sympy.functions.special.beta_functions import beta from sympy.functions.special.delta_functions import DiracDelta from sympy.functions.special.error_functions import Chi return {KroneckerDelta: r'\delta', gamma: r'\Gamma', lowergamma: r'\gamma', beta: r'\operatorname{B}', DiracDelta: r'\delta', Chi: r'\operatorname{Chi}'} def _print_FunctionClass(self, expr): for cls in self._special_function_classes: if issubclass(expr, cls) and expr.__name__ == cls.__name__: return self._special_function_classes[cls] return self._hprint_Function(str(expr)) def _print_Lambda(self, expr): symbols, expr = expr.args if len(symbols) == 1: symbols = self._print(symbols[0]) else: symbols = self._print(tuple(symbols)) tex = r"\left( %s \mapsto %s \right)" % (symbols, self._print(expr)) return tex def _print_IdentityFunction(self, expr): return r"\left( x \mapsto x \right)" def _hprint_variadic_function(self, expr, exp=None): args = sorted(expr.args, key=default_sort_key) texargs = [r"%s" % self._print(symbol) for symbol in args] tex = r"\%s\left(%s\right)" % (str(expr.func).lower(), ", ".join(texargs)) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex _print_Min = _print_Max = _hprint_variadic_function def _print_floor(self, expr, exp=None): tex = r"\left\lfloor{%s}\right\rfloor" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_ceiling(self, expr, exp=None): tex = r"\left\lceil{%s}\right\rceil" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_log(self, expr, exp=None): if not self._settings["ln_notation"]: tex = r"\log{\left(%s \right)}" % self._print(expr.args[0]) else: tex = r"\ln{\left(%s \right)}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_Abs(self, expr, exp=None): tex = r"\left\|{%s}\right\|" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex _print_Determinant = _print_Abs def _print_re(self, expr, exp=None): if self._settings['gothic_re_im']: tex = r"\Re{%s}" % self.parenthesize(expr.args[0], PRECEDENCE['Atom']) else: tex = r"\operatorname{{re}}{{{}}}".format(self.parenthesize(expr.args[0], PRECEDENCE['Atom'])) return self._do_exponent(tex, exp) def _print_im(self, expr, exp=None): if self._settings['gothic_re_im']: tex = r"\Im{%s}" % self.parenthesize(expr.args[0], PRECEDENCE['Atom']) else: tex = r"\operatorname{{im}}{{{}}}".format(self.parenthesize(expr.args[0], PRECEDENCE['Atom'])) return self._do_exponent(tex, exp) def _print_Not(self, e): from sympy import Equivalent, Implies if isinstance(e.args[0], Equivalent): return self._print_Equivalent(e.args[0], r"\not\Leftrightarrow") if isinstance(e.args[0], Implies): return self._print_Implies(e.args[0], r"\not\Rightarrow") if (e.args[0].is_Boolean): return r"\neg \left(%s\right)" % self._print(e.args[0]) else: return r"\neg %s" % self._print(e.args[0]) def _print_LogOp(self, args, char): arg = args[0] if arg.is_Boolean and not arg.is_Not: tex = r"\left(%s\right)" % self._print(arg) else: tex = r"%s" % self._print(arg) for arg in args[1:]: if arg.is_Boolean and not arg.is_Not: tex += r" %s \left(%s\right)" % (char, self._print(arg)) else: tex += r" %s %s" % (char, self._print(arg)) return tex def _print_And(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\wedge") def _print_Or(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\vee") def _print_Xor(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\veebar") def _print_Implies(self, e, altchar=None): return self._print_LogOp(e.args, altchar or r"\Rightarrow") def _print_Equivalent(self, e, altchar=None): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, altchar or r"\Leftrightarrow") def _print_conjugate(self, expr, exp=None): tex = r"\overline{%s}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_polar_lift(self, expr, exp=None): func = r"\operatorname{polar\_lift}" arg = r"{\left(%s \right)}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (func, exp, arg) else: return r"%s%s" % (func, arg) def _print_ExpBase(self, expr, exp=None): # TODO should exp_polar be printed differently? # what about exp_polar(0), exp_polar(1)? tex = r"e^{%s}" % self._print(expr.args[0]) return self._do_exponent(tex, exp) def _print_elliptic_k(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"K^{%s}%s" % (exp, tex) else: return r"K%s" % tex def _print_elliptic_f(self, expr, exp=None): tex = r"\left(%s\middle\| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"F^{%s}%s" % (exp, tex) else: return r"F%s" % tex def _print_elliptic_e(self, expr, exp=None): if len(expr.args) == 2: tex = r"\left(%s\middle\| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"E^{%s}%s" % (exp, tex) else: return r"E%s" % tex def _print_elliptic_pi(self, expr, exp=None): if len(expr.args) == 3: tex = r"\left(%s; %s\middle\| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1]), self._print(expr.args[2])) else: tex = r"\left(%s\middle\| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\Pi^{%s}%s" % (exp, tex) else: return r"\Pi%s" % tex def _print_beta(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\operatorname{B}^{%s}%s" % (exp, tex) else: return r"\operatorname{B}%s" % tex def _print_uppergamma(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\Gamma^{%s}%s" % (exp, tex) else: return r"\Gamma%s" % tex def _print_lowergamma(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\gamma^{%s}%s" % (exp, tex) else: return r"\gamma%s" % tex def _hprint_one_arg_func(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (self._print(expr.func), exp, tex) else: return r"%s%s" % (self._print(expr.func), tex) _print_gamma = _hprint_one_arg_func def _print_Chi(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\operatorname{Chi}^{%s}%s" % (exp, tex) else: return r"\operatorname{Chi}%s" % tex def _print_expint(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[1]) nu = self._print(expr.args[0]) if exp is not None: return r"\operatorname{E}_{%s}^{%s}%s" % (nu, exp, tex) else: return r"\operatorname{E}_{%s}%s" % (nu, tex) def _print_fresnels(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"S^{%s}%s" % (exp, tex) else: return r"S%s" % tex def _print_fresnelc(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"C^{%s}%s" % (exp, tex) else: return r"C%s" % tex def _print_subfactorial(self, expr, exp=None): tex = r"!%s" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"\left(%s\right)^{%s}" % (tex, exp) else: return tex def _print_factorial(self, expr, exp=None): tex = r"%s!" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_factorial2(self, expr, exp=None): tex = r"%s!!" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_binomial(self, expr, exp=None): tex = r"{\binom{%s}{%s}}" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_RisingFactorial(self, expr, exp=None): n, k = expr.args base = r"%s" % self.parenthesize(n, PRECEDENCE['Func']) tex = r"{%s}^{\left(%s\right)}" % (base, self._print(k)) return self._do_exponent(tex, exp) def _print_FallingFactorial(self, expr, exp=None): n, k = expr.args sub = r"%s" % self.parenthesize(k, PRECEDENCE['Func']) tex = r"{\left(%s\right)}_{%s}" % (self._print(n), sub) return self._do_exponent(tex, exp) def _hprint_BesselBase(self, expr, exp, sym): tex = r"%s" % (sym) need_exp = False if exp is not None: if tex.find('^') == -1: tex = r"%s^{%s}" % (tex, exp) else: need_exp = True tex = r"%s_{%s}\left(%s\right)" % (tex, self._print(expr.order), self._print(expr.argument)) if need_exp: tex = self._do_exponent(tex, exp) return tex def _hprint_vec(self, vec): if not vec: return "" s = "" for i in vec[:-1]: s += "%s, " % self._print(i) s += self._print(vec[-1]) return s def _print_besselj(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'J') def _print_besseli(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'I') def _print_besselk(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'K') def _print_bessely(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'Y') def _print_yn(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'y') def _print_jn(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'j') def _print_hankel1(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'H^{(1)}') def _print_hankel2(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'H^{(2)}') def _print_hn1(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'h^{(1)}') def _print_hn2(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'h^{(2)}') def _hprint_airy(self, expr, exp=None, notation=""): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (notation, exp, tex) else: return r"%s%s" % (notation, tex) def _hprint_airy_prime(self, expr, exp=None, notation=""): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"{%s^\prime}^{%s}%s" % (notation, exp, tex) else: return r"%s^\prime%s" % (notation, tex) def _print_airyai(self, expr, exp=None): return self._hprint_airy(expr, exp, 'Ai') def _print_airybi(self, expr, exp=None): return self._hprint_airy(expr, exp, 'Bi') def _print_airyaiprime(self, expr, exp=None): return self._hprint_airy_prime(expr, exp, 'Ai') def _print_airybiprime(self, expr, exp=None): return self._hprint_airy_prime(expr, exp, 'Bi') def _print_hyper(self, expr, exp=None): tex = r"{{}_{%s}F_{%s}\left(\begin{matrix} %s \\ %s \end{matrix}" \ r"\middle\| {%s} \right)}" % \ (self._print(len(expr.ap)), self._print(len(expr.bq)), self._hprint_vec(expr.ap), self._hprint_vec(expr.bq), self._print(expr.argument)) if exp is not None: tex = r"{%s}^{%s}" % (tex, exp) return tex def _print_meijerg(self, expr, exp=None): tex = r"{G_{%s, %s}^{%s, %s}\left(\begin{matrix} %s & %s \\" \ r"%s & %s \end{matrix} \middle\| {%s} \right)}" % \ (self._print(len(expr.ap)), self._print(len(expr.bq)), self._print(len(expr.bm)), self._print(len(expr.an)), self._hprint_vec(expr.an), self._hprint_vec(expr.aother), self._hprint_vec(expr.bm), self._hprint_vec(expr.bother), self._print(expr.argument)) if exp is not None: tex = r"{%s}^{%s}" % (tex, exp) return tex def _print_dirichlet_eta(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\eta^{%s}%s" % (exp, tex) return r"\eta%s" % tex def _print_zeta(self, expr, exp=None): if len(expr.args) == 2: tex = r"\left(%s, %s\right)" % tuple(map(self._print, expr.args)) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\zeta^{%s}%s" % (exp, tex) return r"\zeta%s" % tex def _print_stieltjes(self, expr, exp=None): if len(expr.args) == 2: tex = r"_{%s}\left(%s\right)" % tuple(map(self._print, expr.args)) else: tex = r"_{%s}" % self._print(expr.args[0]) if exp is not None: return r"\gamma%s^{%s}" % (tex, exp) return r"\gamma%s" % tex def _print_lerchphi(self, expr, exp=None): tex = r"\left(%s, %s, %s\right)" % tuple(map(self._print, expr.args)) if exp is None: return r"\Phi%s" % tex return r"\Phi^{%s}%s" % (exp, tex) def _print_polylog(self, expr, exp=None): s, z = map(self._print, expr.args) tex = r"\left(%s\right)" % z if exp is None: return r"\operatorname{Li}_{%s}%s" % (s, tex) return r"\operatorname{Li}_{%s}^{%s}%s" % (s, exp, tex) def _print_jacobi(self, expr, exp=None): n, a, b, x = map(self._print, expr.args) tex = r"P_{%s}^{\left(%s,%s\right)}\left(%s\right)" % (n, a, b, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_gegenbauer(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"C_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_chebyshevt(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"T_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_chebyshevu(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"U_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_legendre(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"P_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_assoc_legendre(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"P_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_hermite(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"H_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_laguerre(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"L_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_assoc_laguerre(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"L_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_Ynm(self, expr, exp=None): n, m, theta, phi = map(self._print, expr.args) tex = r"Y_{%s}^{%s}\left(%s,%s\right)" % (n, m, theta, phi) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_Znm(self, expr, exp=None): n, m, theta, phi = map(self._print, expr.args) tex = r"Z_{%s}^{%s}\left(%s,%s\right)" % (n, m, theta, phi) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def __print_mathieu_functions(self, character, args, prime=False, exp=None): a, q, z = map(self._print, args) sup = r"^{\prime}" if prime else "" exp = "" if not exp else "^{%s}" % exp return r"%s%s\left(%s, %s, %s\right)%s" % (character, sup, a, q, z, exp) def _print_mathieuc(self, expr, exp=None): return self.__print_mathieu_functions("C", expr.args, exp=exp) def _print_mathieus(self, expr, exp=None): return self.__print_mathieu_functions("S", expr.args, exp=exp) def _print_mathieucprime(self, expr, exp=None): return self.__print_mathieu_functions("C", expr.args, prime=True, exp=exp) def _print_mathieusprime(self, expr, exp=None): return self.__print_mathieu_functions("S", expr.args, prime=True, exp=exp) def _print_Rational(self, expr): if expr.q != 1: sign = "" p = expr.p if expr.p < 0: sign = "- " p = -p if self._settings['fold_short_frac']: return r"%s%d / %d" % (sign, p, expr.q) return r"%s\frac{%d}{%d}" % (sign, p, expr.q) else: return self._print(expr.p) def _print_Order(self, expr): s = self._print(expr.expr) if expr.point and any(p != S.Zero for p in expr.point) or \ len(expr.variables) > 1: s += '; ' if len(expr.variables) > 1: s += self._print(expr.variables) elif expr.variables: s += self._print(expr.variables[0]) s += r'\rightarrow ' if len(expr.point) > 1: s += self._print(expr.point) else: s += self._print(expr.point[0]) return r"O\left(%s\right)" % s def _print_Symbol(self, expr, style='plain'): if expr in self._settings['symbol_names']: return self._settings['symbol_names'][expr] return self._deal_with_super_sub(expr.name, style=style) _print_RandomSymbol = _print_Symbol def _deal_with_super_sub(self, string, style='plain'): if '{' in string: name, supers, subs = string, [], [] else: name, supers, subs = split_super_sub(string) name = translate(name) supers = [translate(sup) for sup in supers] subs = [translate(sub) for sub in subs] # apply the style only to the name if style == 'bold': name = "\\mathbf{{{}}}".format(name) # glue all items together: if supers: name += "^{%s}" % " ".join(supers) if subs: name += "_{%s}" % " ".join(subs) return name def _print_Relational(self, expr): if self._settings['itex']: gt = r"\gt" lt = r"\lt" else: gt = ">" lt = "<" charmap = { "==": "=", ">": gt, "<": lt, ">=": r"\geq", "<=": r"\leq", "!=": r"\neq", } return "%s %s %s" % (self._print(expr.lhs), charmap[expr.rel_op], self._print(expr.rhs)) def _print_Piecewise(self, expr): ecpairs = [r"%s & \text{for}\: %s" % (self._print(e), self._print(c)) for e, c in expr.args[:-1]] if expr.args[-1].cond == true: ecpairs.append(r"%s & \text{otherwise}" % self._print(expr.args[-1].expr)) else: ecpairs.append(r"%s & \text{for}\: %s" % (self._print(expr.args[-1].expr), self._print(expr.args[-1].cond))) tex = r"\begin{cases} %s \end{cases}" return tex % r" \\".join(ecpairs) def _print_MatrixBase(self, expr): lines = [] for line in range(expr.rows): # horrible, should be 'rows' lines.append(" & ".join([self._print(i) for i in expr[line, :]])) mat_str = self._settings['mat_str'] if mat_str is None: if self._settings['mode'] == 'inline': mat_str = 'smallmatrix' else: if (expr.cols <= 10) is True: mat_str = 'matrix' else: mat_str = 'array' out_str = r'\begin{%MATSTR%}%s\end{%MATSTR%}' out_str = out_str.replace('%MATSTR%', mat_str) if mat_str == 'array': out_str = out_str.replace('%s', '{' + 'c'expr.cols + '}%s') if self._settings['mat_delim']: left_delim = self._settings['mat_delim'] right_delim = self._delim_dict[left_delim] out_str = r'\left' + left_delim + out_str + \ r'\right' + right_delim return out_str % r"\\".join(lines) def _print_MatrixElement(self, expr): return self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True)\ + '_{%s, %s}' % (self._print(expr.i), self._print(expr.j)) def _print_MatrixSlice(self, expr): def latexslice(x, dim): x = list(x) if x[2] == 1: del x[2] if x[0] == 0: x[0] = None if x[1] == dim: x[1] = None return ':'.join(self._print(xi) if xi is not None else '' for xi in x) return (self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) + r'\left[' + latexslice(expr.rowslice, expr.parent.rows) + ', ' + latexslice(expr.colslice, expr.parent.cols) + r'\right]') def _print_BlockMatrix(self, expr): return self._print(expr.blocks) def _print_Transpose(self, expr): mat = expr.arg from sympy.matrices import MatrixSymbol if not isinstance(mat, MatrixSymbol): return r"\left(%s\right)^{T}" % self._print(mat) else: return "%s^{T}" % self.parenthesize(mat, precedence_traditional(expr), True) def _print_Trace(self, expr): mat = expr.arg return r"\operatorname{tr}\left(%s \right)" % self._print(mat) def _print_Adjoint(self, expr): mat = expr.arg from sympy.matrices import MatrixSymbol if not isinstance(mat, MatrixSymbol): return r"\left(%s\right)^{\dagger}" % self._print(mat) else: return r"%s^{\dagger}" % self._print(mat) def _print_MatMul(self, expr): from sympy import MatMul, Mul parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) args = expr.args if isinstance(args[0], Mul): args = args[0].as_ordered_factors() + list(args[1:]) else: args = list(args) if isinstance(expr, MatMul) and _coeff_isneg(expr): if args[0] == -1: args = args[1:] else: args[0] = -args[0] return '- ' + ' '.join(map(parens, args)) else: return ' '.join(map(parens, args)) def _print_Mod(self, expr, exp=None): if exp is not None: return r'\left(%s\bmod{%s}\right)^{%s}' % \ (self.parenthesize(expr.args[0], PRECEDENCE['Mul'], strict=True), self._print(expr.args[1]), exp) return r'%s\bmod{%s}' % (self.parenthesize(expr.args[0], PRECEDENCE['Mul'], strict=True), self._print(expr.args[1])) def _print_HadamardProduct(self, expr): args = expr.args prec = PRECEDENCE['Pow'] parens = self.parenthesize return r' \circ '.join( map(lambda arg: parens(arg, prec, strict=True), args)) def _print_HadamardPower(self, expr): if precedence_traditional(expr.exp) < PRECEDENCE["Mul"]: template = r"%s^{\circ \left({%s}\right)}" else: template = r"%s^{\circ {%s}}" return self._helper_print_standard_power(expr, template) def _print_KroneckerProduct(self, expr): args = expr.args prec = PRECEDENCE['Pow'] parens = self.parenthesize return r' \otimes '.join( map(lambda arg: parens(arg, prec, strict=True), args)) def _print_MatPow(self, expr): base, exp = expr.base, expr.exp from sympy.matrices import MatrixSymbol if not isinstance(base, MatrixSymbol): return "\\left(%s\\right)^{%s}" % (self._print(base), self._print(exp)) else: return "%s^{%s}" % (self._print(base), self._print(exp)) def _print_MatrixSymbol(self, expr): return self._print_Symbol(expr, style=self._settings[ 'mat_symbol_style']) def _print_ZeroMatrix(self, Z): return r"\mathbb{0}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{0}" def _print_OneMatrix(self, O): return r"\mathbb{1}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{1}" def _print_Identity(self, I): return r"\mathbb{I}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{I}" def _print_PermutationMatrix(self, P): perm_str = self._print(P.args[0]) return "P_{%s}" % perm_str def _print_NDimArray(self, expr): if expr.rank() == 0: return self._print(expr[()]) mat_str = self._settings['mat_str'] if mat_str is None: if self._settings['mode'] == 'inline': mat_str = 'smallmatrix' else: if (expr.rank() == 0) or (expr.shape[-1] <= 10): mat_str = 'matrix' else: mat_str = 'array' block_str = r'\begin{%MATSTR%}%s\end{%MATSTR%}' block_str = block_str.replace('%MATSTR%', mat_str) if self._settings['mat_delim']: left_delim = self._settings['mat_delim'] right_delim = self._delim_dict[left_delim] block_str = r'\left' + left_delim + block_str + \ r'\right' + right_delim if expr.rank() == 0: return block_str % "" level_str = [[]] + [[] for i in range(expr.rank())] shape_ranges = [list(range(i)) for i in expr.shape] for outer_i in itertools.product(shape_ranges): level_str[-1].append(self._print(expr[outer_i])) even = True for back_outer_i in range(expr.rank()-1, -1, -1): if len(level_str[back_outer_i+1]) < expr.shape[back_outer_i]: break if even: level_str[back_outer_i].append( r" & ".join(level_str[back_outer_i+1])) else: level_str[back_outer_i].append( block_str % (r"\\".join(level_str[back_outer_i+1]))) if len(level_str[back_outer_i+1]) == 1: level_str[back_outer_i][-1] = r"\left[" + \ level_str[back_outer_i][-1] + r"\right]" even = not even level_str[back_outer_i+1] = [] out_str = level_str[0][0] if expr.rank() % 2 == 1: out_str = block_str % out_str return out_str def _printer_tensor_indices(self, name, indices, index_map={}): out_str = self._print(name) last_valence = None prev_map = None for index in indices: new_valence = index.is_up if ((index in index_map) or prev_map) and \ last_valence == new_valence: out_str += "," if last_valence != new_valence: if last_valence is not None: out_str += "}" if index.is_up: out_str += "{}^{" else: out_str += "{}_{" out_str += self._print(index.args[0]) if index in index_map: out_str += "=" out_str += self._print(index_map[index]) prev_map = True else: prev_map = False last_valence = new_valence if last_valence is not None: out_str += "}" return out_str def _print_Tensor(self, expr): name = expr.args[0].args[0] indices = expr.get_indices() return self._printer_tensor_indices(name, indices) def _print_TensorElement(self, expr): name = expr.expr.args[0].args[0] indices = expr.expr.get_indices() index_map = expr.index_map return self._printer_tensor_indices(name, indices, index_map) def _print_TensMul(self, expr): # prints expressions like "A(a)", "3A(a)", "(1+x)A(a)" sign, args = expr._get_args_for_traditional_printer() return sign + "".join( [self.parenthesize(arg, precedence(expr)) for arg in args] ) def _print_TensAdd(self, expr): a = [] args = expr.args for x in args: a.append(self.parenthesize(x, precedence(expr))) a.sort() s = ' + '.join(a) s = s.replace('+ -', '- ') return s def _print_TensorIndex(self, expr): return "{}%s{%s}" % ( "^" if expr.is_up else "_", self._print(expr.args[0]) ) def _print_PartialDerivative(self, expr): if len(expr.variables) == 1: return r"\frac{\partial}{\partial {%s}}{%s}" % ( self._print(expr.variables[0]), self.parenthesize(expr.expr, PRECEDENCE["Mul"], False) ) else: return r"\frac{\partial^{%s}}{%s}{%s}" % ( len(expr.variables), " ".join([r"\partial {%s}" % self._print(i) for i in expr.variables]), self.parenthesize(expr.expr, PRECEDENCE["Mul"], False) ) def _print_UniversalSet(self, expr): return r"\mathbb{U}" def _print_frac(self, expr, exp=None): if exp is None: return r"\operatorname{frac}{\left(%s\right)}" % self._print(expr.args[0]) else: return r"\operatorname{frac}{\left(%s\right)}^{%s}" % ( self._print(expr.args[0]), exp) def _print_tuple(self, expr): if self._settings['decimal_separator'] == 'comma': sep = ";" elif self._settings['decimal_separator'] == 'period': sep = "," else: raise ValueError('Unknown Decimal Separator') if len(expr) == 1: # 1-tuple needs a trailing separator return self._add_parens_lspace(self._print(expr[0]) + sep) else: return self._add_parens_lspace( (sep + r" \ ").join([self._print(i) for i in expr])) def _print_TensorProduct(self, expr): elements = [self._print(a) for a in expr.args] return r' \otimes '.join(elements) def _print_WedgeProduct(self, expr): elements = [self._print(a) for a in expr.args] return r' \wedge '.join(elements) def _print_Tuple(self, expr): return self._print_tuple(expr) def _print_list(self, expr): if self._settings['decimal_separator'] == 'comma': return r"\left[ %s\right]" % \ r"; \ ".join([self._print(i) for i in expr]) elif self._settings['decimal_separator'] == 'period': return r"\left[ %s\right]" % \ r", \ ".join([self._print(i) for i in expr]) else: raise ValueError('Unknown Decimal Separator') def _print_dict(self, d): keys = sorted(d.keys(), key=default_sort_key) items = [] for key in keys: val = d[key] items.append("%s : %s" % (self._print(key), self._print(val))) return r"\left\{ %s\right\}" % r", \ ".join(items) def _print_Dict(self, expr): return self._print_dict(expr) def _print_DiracDelta(self, expr, exp=None): if len(expr.args) == 1 or expr.args[1] == 0: tex = r"\delta\left(%s\right)" % self._print(expr.args[0]) else: tex = r"\delta^{\left( %s \right)}\left( %s \right)" % ( self._print(expr.args[1]), self._print(expr.args[0])) if exp: tex = r"\left(%s\right)^{%s}" % (tex, exp) return tex def _print_SingularityFunction(self, expr): shift = self._print(expr.args[0] - expr.args[1]) power = self._print(expr.args[2]) tex = r"{\left\langle %s \right\rangle}^{%s}" % (shift, power) return tex def _print_Heaviside(self, expr, exp=None): tex = r"\theta\left(%s\right)" % self._print(expr.args[0]) if exp: tex = r"\left(%s\right)^{%s}" % (tex, exp) return tex def _print_KroneckerDelta(self, expr, exp=None): i = self._print(expr.args[0]) j = self._print(expr.args[1]) if expr.args[0].is_Atom and expr.args[1].is_Atom: tex = r'\delta_{%s %s}' % (i, j) else: tex = r'\delta_{%s, %s}' % (i, j) if exp is not None: tex = r'\left(%s\right)^{%s}' % (tex, exp) return tex def _print_LeviCivita(self, expr, exp=None): indices = map(self._print, expr.args) if all(x.is_Atom for x in expr.args): tex = r'\varepsilon_{%s}' % " ".join(indices) else: tex = r'\varepsilon_{%s}' % ", ".join(indices) if exp: tex = r'\left(%s\right)^{%s}' % (tex, exp) return tex def _print_RandomDomain(self, d): if hasattr(d, 'as_boolean'): return '\\text{Domain: }' + self._print(d.as_boolean()) elif hasattr(d, 'set'): return ('\\text{Domain: }' + self._print(d.symbols) + '\\text{ in }' + self._print(d.set)) elif hasattr(d, 'symbols'): return '\\text{Domain on }' + self._print(d.symbols) else: return self._print(None) def _print_FiniteSet(self, s): items = sorted(s.args, key=default_sort_key) return self._print_set(items) def _print_set(self, s): items = sorted(s, key=default_sort_key) if self._settings['decimal_separator'] == 'comma': items = "; ".join(map(self._print, items)) elif self._settings['decimal_separator'] == 'period': items = ", ".join(map(self._print, items)) else: raise ValueError('Unknown Decimal Separator') return r"\left\{%s\right\}" % items _print_frozenset = _print_set def _print_Range(self, s): dots = object() if s.has(Symbol): return self._print_Basic(s) if s.start.is_infinite and s.stop.is_infinite: if s.step.is_positive: printset = dots, -1, 0, 1, dots else: printset = dots, 1, 0, -1, dots elif s.start.is_infinite: printset = dots, s[-1] - s.step, s[-1] elif s.stop.is_infinite: it = iter(s) printset = next(it), next(it), dots elif len(s) > 4: it = iter(s) printset = next(it), next(it), dots, s[-1] else: printset = tuple(s) return (r"\left\{" + r", ".join(self._print(el) if el is not dots else r'\ldots' for el in printset) + r"\right\}") def __print_number_polynomial(self, expr, letter, exp=None): if len(expr.args) == 2: if exp is not None: return r"%s_{%s}^{%s}\left(%s\right)" % (letter, self._print(expr.args[0]), exp, self._print(expr.args[1])) return r"%s_{%s}\left(%s\right)" % (letter, self._print(expr.args[0]), self._print(expr.args[1])) tex = r"%s_{%s}" % (letter, self._print(expr.args[0])) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_bernoulli(self, expr, exp=None): return self.__print_number_polynomial(expr, "B", exp) def _print_bell(self, expr, exp=None): if len(expr.args) == 3: tex1 = r"B_{%s, %s}" % (self._print(expr.args[0]), self._print(expr.args[1])) tex2 = r"\left(%s\right)" % r", ".join(self._print(el) for el in expr.args[2]) if exp is not None: tex = r"%s^{%s}%s" % (tex1, exp, tex2) else: tex = tex1 + tex2 return tex return self.__print_number_polynomial(expr, "B", exp) def _print_fibonacci(self, expr, exp=None): return self.__print_number_polynomial(expr, "F", exp) def _print_lucas(self, expr, exp=None): tex = r"L_{%s}" % self._print(expr.args[0]) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_tribonacci(self, expr, exp=None): return self.__print_number_polynomial(expr, "T", exp) def _print_SeqFormula(self, s): dots = object() if len(s.start.free_symbols) > 0 or len(s.stop.free_symbols) > 0: return r"\left\{%s\right\}_{%s=%s}^{%s}" % ( self._print(s.formula), self._print(s.variables[0]), self._print(s.start), self._print(s.stop) ) if s.start is S.NegativeInfinity: stop = s.stop printset = (dots, s.coeff(stop - 3), s.coeff(stop - 2), s.coeff(stop - 1), s.coeff(stop)) elif s.stop is S.Infinity or s.length > 4: printset = s[:4] printset.append(dots) else: printset = tuple(s) return (r"\left[" + r", ".join(self._print(el) if el is not dots else r'\ldots' for el in printset) + r"\right]") _print_SeqPer = _print_SeqFormula _print_SeqAdd = _print_SeqFormula _print_SeqMul = _print_SeqFormula def _print_Interval(self, i): if i.start == i.end: return r"\left\{%s\right\}" % self._print(i.start) else: if i.left_open: left = '(' else: left = '[' if i.right_open: right = ')' else: right = ']' return r"\left%s%s, %s\right%s" % \ (left, self._print(i.start), self._print(i.end), right) def _print_AccumulationBounds(self, i): return r"\left\langle %s, %s\right\rangle" % \ (self._print(i.min), self._print(i.max)) def _print_Union(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \cup ".join(args_str) def _print_Complement(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \setminus ".join(args_str) def _print_Intersection(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \cap ".join(args_str) def _print_SymmetricDifference(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \triangle ".join(args_str) def _print_ProductSet(self, p): prec = precedence_traditional(p) if len(p.sets) >= 1 and not has_variety(p.sets): return self.parenthesize(p.sets[0], prec) + "^{%d}" % len(p.sets) return r" \times ".join( self.parenthesize(set, prec) for set in p.sets) def _print_EmptySet(self, e): return r"\emptyset" def _print_Naturals(self, n): return r"\mathbb{N}" def _print_Naturals0(self, n): return r"\mathbb{N}_0" def _print_Integers(self, i): return r"\mathbb{Z}" def _print_Rationals(self, i): return r"\mathbb{Q}" def _print_Reals(self, i): return r"\mathbb{R}" def _print_Complexes(self, i): return r"\mathbb{C}" def _print_ImageSet(self, s): expr = s.lamda.expr sig = s.lamda.signature xys = ((self._print(x), self._print(y)) for x, y in zip(sig, s.base_sets)) xinys = r" , ".join(r"%s \in %s" % xy for xy in xys) return r"\left\{%s\; \|\; %s\right\}" % (self._print(expr), xinys) def _print_ConditionSet(self, s): vars_print = ', '.join([self._print(var) for var in Tuple(s.sym)]) if s.base_set is S.UniversalSet: return r"\left\{%s \mid %s \right\}" % \ (vars_print, self._print(s.condition)) return r"\left\{%s \mid %s \in %s \wedge %s \right\}" % ( vars_print, vars_print, self._print(s.base_set), self._print(s.condition)) def _print_ComplexRegion(self, s): vars_print = ', '.join([self._print(var) for var in s.variables]) return r"\left\{%s\; \|\; %s \in %s \right\}" % ( self._print(s.expr), vars_print, self._print(s.sets)) def _print_Contains(self, e): return r"%s \in %s" % tuple(self._print(a) for a in e.args) def _print_FourierSeries(self, s): return self._print_Add(s.truncate()) + r' + \ldots' def _print_FormalPowerSeries(self, s): return self._print_Add(s.infinite) def _print_FiniteField(self, expr): return r"\mathbb{F}_{%s}" % expr.mod def _print_IntegerRing(self, expr): return r"\mathbb{Z}" def _print_RationalField(self, expr): return r"\mathbb{Q}" def _print_RealField(self, expr): return r"\mathbb{R}" def _print_ComplexField(self, expr): return r"\mathbb{C}" def _print_PolynomialRing(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) return r"%s\left[%s\right]" % (domain, symbols) def _print_FractionField(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) return r"%s\left(%s\right)" % (domain, symbols) def _print_PolynomialRingBase(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) inv = "" if not expr.is_Poly: inv = r"S_<^{-1}" return r"%s%s\left[%s\right]" % (inv, domain, symbols) def _print_Poly(self, poly): cls = poly.__class__.__name__ terms = [] for monom, coeff in poly.terms(): s_monom = '' for i, exp in enumerate(monom): if exp > 0: if exp == 1: s_monom += self._print(poly.gens[i]) else: s_monom += self._print(pow(poly.gens[i], exp)) if coeff.is_Add: if s_monom: s_coeff = r"\left(%s\right)" % self._print(coeff) else: s_coeff = self._print(coeff) else: if s_monom: if coeff is S.One: terms.extend(['+', s_monom]) continue if coeff is S.NegativeOne: terms.extend(['-', s_monom]) continue s_coeff = self._print(coeff) if not s_monom: s_term = s_coeff else: s_term = s_coeff + " " + s_monom if s_term.startswith('-'): terms.extend(['-', s_term[1:]]) else: terms.extend(['+', s_term]) if terms[0] in ['-', '+']: modifier = terms.pop(0) if modifier == '-': terms[0] = '-' + terms[0] expr = ' '.join(terms) gens = list(map(self._print, poly.gens)) domain = "domain=%s" % self._print(poly.get_domain()) args = ", ".join([expr] + gens + [domain]) if cls in accepted_latex_functions: tex = r"\%s {\left(%s \right)}" % (cls, args) else: tex = r"\operatorname{%s}{\left( %s \right)}" % (cls, args) return tex def _print_ComplexRootOf(self, root): cls = root.__class__.__name__ if cls == "ComplexRootOf": cls = "CRootOf" expr = self._print(root.expr) index = root.index if cls in accepted_latex_functions: return r"\%s {\left(%s, %d\right)}" % (cls, expr, index) else: return r"\operatorname{%s} {\left(%s, %d\right)}" % (cls, expr, index) def _print_RootSum(self, expr): cls = expr.__class__.__name__ args = [self._print(expr.expr)] if expr.fun is not S.IdentityFunction: args.append(self._print(expr.fun)) if cls in accepted_latex_functions: return r"\%s {\left(%s\right)}" % (cls, ", ".join(args)) else: return r"\operatorname{%s} {\left(%s\right)}" % (cls, ", ".join(args)) def _print_PolyElement(self, poly): mul_symbol = self._settings['mul_symbol_latex'] return poly.str(self, PRECEDENCE, "{%s}^{%d}", mul_symbol) def _print_FracElement(self, frac): if frac.denom == 1: return self._print(frac.numer) else: numer = self._print(frac.numer) denom = self._print(frac.denom) return r"\frac{%s}{%s}" % (numer, denom) def _print_euler(self, expr, exp=None): m, x = (expr.args[0], None) if len(expr.args) == 1 else expr.args tex = r"E_{%s}" % self._print(m) if exp is not None: tex = r"%s^{%s}" % (tex, exp) if x is not None: tex = r"%s\left(%s\right)" % (tex, self._print(x)) return tex def _print_catalan(self, expr, exp=None): tex = r"C_{%s}" % self._print(expr.args[0]) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_UnifiedTransform(self, expr, s, inverse=False): return r"\mathcal{{{}}}{}_{{{}}}\left[{}\right]\left({}\right)".format(s, '^{-1}' if inverse else '', self._print(expr.args[1]), self._print(expr.args[0]), self._print(expr.args[2])) def _print_MellinTransform(self, expr): return self._print_UnifiedTransform(expr, 'M') def _print_InverseMellinTransform(self, expr): return self._print_UnifiedTransform(expr, 'M', True) def _print_LaplaceTransform(self, expr): return self._print_UnifiedTransform(expr, 'L') def _print_InverseLaplaceTransform(self, expr): return self._print_UnifiedTransform(expr, 'L', True) def _print_FourierTransform(self, expr): return self._print_UnifiedTransform(expr, 'F') def _print_InverseFourierTransform(self, expr): return self._print_UnifiedTransform(expr, 'F', True) def _print_SineTransform(self, expr): return self._print_UnifiedTransform(expr, 'SIN') def _print_InverseSineTransform(self, expr): return self._print_UnifiedTransform(expr, 'SIN', True) def _print_CosineTransform(self, expr): return self._print_UnifiedTransform(expr, 'COS') def _print_InverseCosineTransform(self, expr): return self._print_UnifiedTransform(expr, 'COS', True) def _print_DMP(self, p): try: if p.ring is not None: # TODO incorporate order return self._print(p.ring.to_sympy(p)) except SympifyError: pass return self._print(repr(p)) def _print_DMF(self, p): return self._print_DMP(p) def _print_Object(self, object): return self._print(Symbol(object.name)) def _print_LambertW(self, expr): if len(expr.args) == 1: return r"W\left(%s\right)" % self._print(expr.args[0]) return r"W_{%s}\left(%s\right)" % \ (self._print(expr.args[1]), self._print(expr.args[0])) def _print_Morphism(self, morphism): domain = self._print(morphism.domain) codomain = self._print(morphism.codomain) return "%s\\rightarrow %s" % (domain, codomain) def _print_TransferFunction(self, expr): from sympy.core import Mul, Pow num, den = expr.num, expr.den res = Mul(num, Pow(den, -1, evaluate=False), evaluate=False) return self._print_Mul(res) def _print_Series(self, expr): args = list(expr.args) parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) return ' '.join(map(parens, args)) def _print_Parallel(self, expr): args = list(expr.args) parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) return ' '.join(map(parens, args)) def _print_Feedback(self, expr): from sympy.physics.control import TransferFunction, Parallel, Series num, tf = expr.num, TransferFunction(1, 1, expr.num.var) num_arg_list = list(num.args) if isinstance(num, Series) else [num] den_arg_list = list(expr.den.args) if isinstance(expr.den, Series) else [expr.den] if isinstance(num, Series) and isinstance(expr.den, Series): den = Parallel(tf, Series(num_arg_list, den_arg_list)) elif isinstance(num, Series) and isinstance(expr.den, TransferFunction): if expr.den == tf: den = Parallel(tf, Series(num_arg_list)) else: den = Parallel(tf, Series(num_arg_list, expr.den)) elif isinstance(num, TransferFunction) and isinstance(expr.den, Series): if num == tf: den = Parallel(tf, Series(den_arg_list)) else: den = Parallel(tf, Series(num, den_arg_list)) else: if num == tf: den = Parallel(tf, den_arg_list) elif expr.den == tf: den = Parallel(tf, num_arg_list) else: den = Parallel(tf, Series(num_arg_list, den_arg_list)) numer = self._print(num) denom = self._print(den) return r"\frac{%s}{%s}" % (numer, denom) def _print_NamedMorphism(self, morphism): pretty_name = self._print(Symbol(morphism.name)) pretty_morphism = self._print_Morphism(morphism) return "%s:%s" % (pretty_name, pretty_morphism) def _print_IdentityMorphism(self, morphism): from sympy.categories import NamedMorphism return self._print_NamedMorphism(NamedMorphism( morphism.domain, morphism.codomain, "id")) def _print_CompositeMorphism(self, morphism): # All components of the morphism have names and it is thus # possible to build the name of the composite. component_names_list = [self._print(Symbol(component.name)) for component in morphism.components] component_names_list.reverse() component_names = "\\circ ".join(component_names_list) + ":" pretty_morphism = self._print_Morphism(morphism) return component_names + pretty_morphism def _print_Category(self, morphism): return r"\mathbf{{{}}}".format(self._print(Symbol(morphism.name))) def _print_Diagram(self, diagram): if not diagram.premises: # This is an empty diagram. return self._print(S.EmptySet) latex_result = self._print(diagram.premises) if diagram.conclusions: latex_result += "\\Longrightarrow %s" % \ self._print(diagram.conclusions) return latex_result def _print_DiagramGrid(self, grid): latex_result = "\\begin{array}{%s}\n" % ("c" * grid.width) for i in range(grid.height): for j in range(grid.width): if grid[i, j]: latex_result += latex(grid[i, j]) latex_result += " " if j != grid.width - 1: latex_result += "& " if i != grid.height - 1: latex_result += "\\\\" latex_result += "\n" latex_result += "\\end{array}\n" return latex_result def _print_FreeModule(self, M): return '{{{}}}^{{{}}}'.format(self._print(M.ring), self._print(M.rank)) def _print_FreeModuleElement(self, m): # Print as row vector for convenience, for now. return r"\left[ {} \right]".format(",".join( '{' + self._print(x) + '}' for x in m)) def _print_SubModule(self, m): return r"\left\langle {} \right\rangle".format(",".join( '{' + self._print(x) + '}' for x in m.gens)) def _print_ModuleImplementedIdeal(self, m): return r"\left\langle {} \right\rangle".format(",".join( '{' + self._print(x) + '}' for [x] in m._module.gens)) def _print_Quaternion(self, expr): # TODO: This expression is potentially confusing, # shall we print it as `Quaternion( ... )`? s = [self.parenthesize(i, PRECEDENCE["Mul"], strict=True) for i in expr.args] a = [s[0]] + [i+" "+j for i, j in zip(s[1:], "ijk")] return " + ".join(a) def _print_QuotientRing(self, R): # TODO nicer fractions for few generators... return r"\frac{{{}}}{{{}}}".format(self._print(R.ring), self._print(R.base_ideal)) def _print_QuotientRingElement(self, x): return r"{{{}}} + {{{}}}".format(self._print(x.data), self._print(x.ring.base_ideal)) def _print_QuotientModuleElement(self, m): return r"{{{}}} + {{{}}}".format(self._print(m.data), self._print(m.module.killed_module)) def _print_QuotientModule(self, M): # TODO nicer fractions for few generators... return r"\frac{{{}}}{{{}}}".format(self._print(M.base), self._print(M.killed_module)) def _print_MatrixHomomorphism(self, h): return r"{{{}}} : {{{}}} \to {{{}}}".format(self._print(h._sympy_matrix()), self._print(h.domain), self._print(h.codomain)) def _print_Manifold(self, manifold): string = manifold.name.name if '{' in string: name, supers, subs = string, [], [] else: name, supers, subs = split_super_sub(string) name = translate(name) supers = [translate(sup) for sup in supers] subs = [translate(sub) for sub in subs] name = r'\text{%s}' % name if supers: name += "^{%s}" % " ".join(supers) if subs: name += "_{%s}" % " ".join(subs) return name def _print_Patch(self, patch): return r'\text{%s}_{%s}' % (self._print(patch.name), self._print(patch.manifold)) def _print_CoordSystem(self, coordsys): return r'\text{%s}^{\text{%s}}_{%s}' % ( self._print(coordsys.name), self._print(coordsys.patch.name), self._print(coordsys.manifold) ) def _print_CovarDerivativeOp(self, cvd): return r'\mathbb{\nabla}_{%s}' % self._print(cvd._wrt) def _print_BaseScalarField(self, field): string = field._coord_sys.symbols[field._index].name return r'\mathbf{{{}}}'.format(self._print(Symbol(string))) def _print_BaseVectorField(self, field): string = field._coord_sys.symbols[field._index].name return r'\partial_{{{}}}'.format(self._print(Symbol(string))) def _print_Differential(self, diff): field = diff._form_field if hasattr(field, '_coord_sys'): string = field._coord_sys.symbols[field._index].name return r'\operatorname{{d}}{}'.format(self._print(Symbol(string))) else: string = self._print(field) return r'\operatorname{{d}}\left({}\right)'.format(string) def _print_Tr(self, p): # TODO: Handle indices contents = self._print(p.args[0]) return r'\operatorname{{tr}}\left({}\right)'.format(contents) def _print_totient(self, expr, exp=None): if exp is not None: return r'\left(\phi\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\phi\left(%s\right)' % self._print(expr.args[0]) def _print_reduced_totient(self, expr, exp=None): if exp is not None: return r'\left(\lambda\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\lambda\left(%s\right)' % self._print(expr.args[0]) def _print_divisor_sigma(self, expr, exp=None): if len(expr.args) == 2: tex = r"_%s\left(%s\right)" % tuple(map(self._print, (expr.args[1], expr.args[0]))) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\sigma^{%s}%s" % (exp, tex) return r"\sigma%s" % tex def _print_udivisor_sigma(self, expr, exp=None): if len(expr.args) == 2: tex = r"_%s\left(%s\right)" % tuple(map(self._print, (expr.args[1], expr.args[0]))) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\sigma^^{%s}%s" % (exp, tex) return r"\sigma^%s" % tex def _print_primenu(self, expr, exp=None): if exp is not None: return r'\left(\nu\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\nu\left(%s\right)' % self._print(expr.args[0]) def _print_primeomega(self, expr, exp=None): if exp is not None: return r'\left(\Omega\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\Omega\left(%s\right)' % self._print(expr.args[0]) def _print_Str(self, s): return str(s.name) def _print_float(self, expr): return self._print(Float(expr)) def _print_int(self, expr): return str(expr) def _print_mpz(self, expr): return str(expr) def _print_mpq(self, expr): return str(expr) def emptyPrinter(self, expr): # default to just printing as monospace, like would normally be shown s = super().emptyPrinter(expr) return r"\mathtt{\text{%s}}" % latex_escape(s) def translate(s): r''' Check for a modifier ending the string. If present, convert the modifier to latex and translate the rest recursively. Given a description of a Greek letter or other special character, return the appropriate latex. Let everything else pass as given. >>> from sympy.printing.latex import translate >>> translate('alphahatdotprime') "{\\dot{\\hat{\\alpha}}}'" ''' # Process the rest tex = tex_greek_dictionary.get(s) if tex: return tex elif s.lower() in greek_letters_set: return "\\" + s.lower() elif s in other_symbols: return "\\" + s else: # Process modifiers, if any, and recurse for key in sorted(modifier_dict.keys(), key=lambda k:len(k), reverse=True): if s.lower().endswith(key) and len(s) > len(key): return modifier_dict[key](translate(s[:-len(key)])) return s @print_function(LatexPrinter) def latex(expr, *settings): r"""Convert the given expression to LaTeX string representation. Parameters ========== full_prec: boolean, optional If set to True, a floating point number is printed with full precision. fold_frac_powers : boolean, optional Emit ``^{p/q}`` instead of ``^{\frac{p}{q}}`` for fractional powers. fold_func_brackets : boolean, optional Fold function brackets where applicable. fold_short_frac : boolean, optional Emit ``p / q`` instead of ``\frac{p}{q}`` when the denominator is simple enough (at most two terms and no powers). The default value is ``True`` for inline mode, ``False`` otherwise. inv_trig_style : string, optional How inverse trig functions should be displayed. Can be one of ``abbreviated``, ``full``, or ``power``. Defaults to ``abbreviated``. itex : boolean, optional Specifies if itex-specific syntax is used, including emitting ``$$...$$``. ln_notation : boolean, optional If set to ``True``, ``\ln`` is used instead of default ``\log``. long_frac_ratio : float or None, optional The allowed ratio of the width of the numerator to the width of the denominator before the printer breaks off long fractions. If ``None`` (the default value), long fractions are not broken up. mat_delim : string, optional The delimiter to wrap around matrices. Can be one of ``[``, ``(``, or the empty string. Defaults to ``[``. mat_str : string, optional Which matrix environment string to emit. ``smallmatrix``, ``matrix``, ``array``, etc. Defaults to ``smallmatrix`` for inline mode, ``matrix`` for matrices of no more than 10 columns, and ``array`` otherwise. mode: string, optional Specifies how the generated code will be delimited. ``mode`` can be one of ``plain``, ``inline``, ``equation`` or ``equation``. If ``mode`` is set to ``plain``, then the resulting code will not be delimited at all (this is the default). If ``mode`` is set to ``inline`` then inline LaTeX ``$...$`` will be used. If ``mode`` is set to ``equation`` or ``equation``, the resulting code will be enclosed in the ``equation`` or ``equation`` environment (remember to import ``amsmath`` for ``equation``), unless the ``itex`` option is set. In the latter case, the ``$$...$$`` syntax is used. mul_symbol : string or None, optional The symbol to use for multiplication. Can be one of ``None``, ``ldot``, ``dot``, or ``times``. order: string, optional Any of the supported monomial orderings (currently ``lex``, ``grlex``, or ``grevlex``), ``old``, and ``none``. This parameter does nothing for Mul objects. Setting order to ``old`` uses the compatibility ordering for Add defined in Printer. For very large expressions, set the ``order`` keyword to ``none`` if speed is a concern. symbol_names : dictionary of strings mapped to symbols, optional Dictionary of symbols and the custom strings they should be emitted as. root_notation : boolean, optional If set to ``False``, exponents of the form 1/n are printed in fractonal form. Default is ``True``, to print exponent in root form. mat_symbol_style : string, optional Can be either ``plain`` (default) or ``bold``. If set to ``bold``, a MatrixSymbol A will be printed as ``\mathbf{A}``, otherwise as ``A``. imaginary_unit : string, optional String to use for the imaginary unit. Defined options are "i" (default) and "j". Adding "r" or "t" in front gives ``\mathrm`` or ``\text``, so "ri" leads to ``\mathrm{i}`` which gives `\mathrm{i}`. gothic_re_im : boolean, optional If set to ``True``, `\Re` and `\Im` is used for ``re`` and ``im``, respectively. The default is ``False`` leading to `\operatorname{re}` and `\operatorname{im}`. decimal_separator : string, optional Specifies what separator to use to separate the whole and fractional parts of a floating point number as in `2.5` for the default, ``period`` or `2{,}5` when ``comma`` is specified. Lists, sets, and tuple are printed with semicolon separating the elements when ``comma`` is chosen. For example, [1; 2; 3] when ``comma`` is chosen and [1,2,3] for when ``period`` is chosen. parenthesize_super : boolean, optional If set to ``False``, superscripted expressions will not be parenthesized when powered. Default is ``True``, which parenthesizes the expression when powered. min: Integer or None, optional Sets the lower bound for the exponent to print floating point numbers in fixed-point format. max: Integer or None, optional Sets the upper bound for the exponent to print floating point numbers in fixed-point format. Notes ===== Not using a print statement for printing, results in double backslashes for latex commands since that's the way Python escapes backslashes in strings. >>> from sympy import latex, Rational >>> from sympy.abc import tau >>> latex((2tau)*Rational(7,2)) '8 \\sqrt{2} \\tau^{\\frac{7}{2}}' >>> print(latex((2tau)*Rational(7,2))) 8 \sqrt{2} \tau^{\frac{7}{2}} Examples ======== >>> from sympy import latex, pi, sin, asin, Integral, Matrix, Rational, log >>> from sympy.abc import x, y, mu, r, tau Basic usage: >>> print(latex((2tau)*Rational(7,2))) 8 \sqrt{2} \tau^{\frac{7}{2}} ``mode`` and ``itex`` options: >>> print(latex((2mu)*Rational(7,2), mode='plain')) 8 \sqrt{2} \mu^{\frac{7}{2}} >>> print(latex((2tau)*Rational(7,2), mode='inline')) $8 \sqrt{2} \tau^{7 / 2}$ >>> print(latex((2mu)*Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2mu)Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2mu)*Rational(7,2), mode='equation', itex=True)) $$8 \sqrt{2} \mu^{\frac{7}{2}}$$ >>> print(latex((2mu)*Rational(7,2), mode='plain')) 8 \sqrt{2} \mu^{\frac{7}{2}} >>> print(latex((2tau)*Rational(7,2), mode='inline')) $8 \sqrt{2} \tau^{7 / 2}$ >>> print(latex((2mu)*Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2mu)Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2mu)*Rational(7,2), mode='equation', itex=True)) $$8 \sqrt{2} \mu^{\frac{7}{2}}$$ Fraction options: >>> print(latex((2tau)*Rational(7,2), fold_frac_powers=True)) 8 \sqrt{2} \tau^{7/2} >>> print(latex((2tau)*sin(Rational(7,2)))) \left(2 \tau\right)^{\sin{\left(\frac{7}{2} \right)}} >>> print(latex((2tau)*sin(Rational(7,2)), fold_func_brackets=True)) \left(2 \tau\right)^{\sin {\frac{7}{2}}} >>> print(latex(3x*2/y)) \frac{3 x^{2}}{y} >>> print(latex(3x*2/y, fold_short_frac=True)) 3 x^{2} / y >>> print(latex(Integral(r, r)/2/pi, long_frac_ratio=2)) \frac{\int r\, dr}{2 \pi} >>> print(latex(Integral(r, r)/2/pi, long_frac_ratio=0)) \frac{1}{2 \pi} \int r\, dr Multiplication options: >>> print(latex((2tau)sin(Rational(7,2)), mul_symbol="times")) \left(2 \times \tau\right)^{\sin{\left(\frac{7}{2} \right)}} Trig options: >>> print(latex(asin(Rational(7,2)))) \operatorname{asin}{\left(\frac{7}{2} \right)} >>> print(latex(asin(Rational(7,2)), inv_trig_style="full")) \arcsin{\left(\frac{7}{2} \right)} >>> print(latex(asin(Rational(7,2)), inv_trig_style="power")) \sin^{-1}{\left(\frac{7}{2} \right)} Matrix options: >>> print(latex(Matrix(2, 1, [x, y]))) \left[\begin{matrix}x\\y\end{matrix}\right] >>> print(latex(Matrix(2, 1, [x, y]), mat_str = "array")) \left[\begin{array}{c}x\\y\end{array}\right] >>> print(latex(Matrix(2, 1, [x, y]), mat_delim="(")) \left(\begin{matrix}x\\y\end{matrix}\right) Custom printing of symbols: >>> print(latex(x2, symbol_names={x: 'x_i'})) x_i^{2} Logarithms: >>> print(latex(log(10))) \log{\left(10 \right)} >>> print(latex(log(10), ln_notation=True)) \ln{\left(10 \right)} ``latex()`` also supports the builtin container types :class:`list`, :class:`tuple`, and :class:`dict`: >>> print(latex([2/x, y], mode='inline')) $\left[ 2 / x, \ y\right]$ Unsupported types are rendered as monospaced plaintext: >>> print(latex(int)) \mathtt{\text{<class 'int'>}} >>> print(latex("plain % text")) \mathtt{\text{plain \% text}} See :ref:`printer_method_example` for an example of how to override this behavior for your own types by implementing ``_latex``. .. versionchanged:: 1.7.0 Unsupported types no longer have their ``str`` representation treated as valid latex. """ return LatexPrinter(settings).doprint(expr) def print_latex(expr, settings): """Prints LaTeX representation of the given expression. Takes the same settings as ``latex()``.""" print(latex(expr, settings)) def multiline_latex(lhs, rhs, terms_per_line=1, environment="align", use_dots=False, settings): r""" This function generates a LaTeX equation with a multiline right-hand side in an ``align``, ``eqnarray`` or ``IEEEeqnarray`` environment. Parameters ========== lhs : Expr Left-hand side of equation rhs : Expr Right-hand side of equation terms_per_line : integer, optional Number of terms per line to print. Default is 1. environment : "string", optional Which LaTeX wnvironment to use for the output. Options are "align" (default), "eqnarray", and "IEEEeqnarray". use_dots : boolean, optional If ``True``, ``\\dots`` is added to the end of each line. Default is ``False``. Examples ======== >>> from sympy import multiline_latex, symbols, sin, cos, exp, log, I >>> x, y, alpha = symbols('x y alpha') >>> expr = sin(alphay) + exp(Ialpha) - cos(log(y)) >>> print(multiline_latex(x, expr)) \begin{align} x = & e^{i \alpha} \\ & + \sin{\left(\alpha y \right)} \\ & - \cos{\left(\log{\left(y \right)} \right)} \end{align} Using at most two terms per line: >>> print(multiline_latex(x, expr, 2)) \begin{align} x = & e^{i \alpha} + \sin{\left(\alpha y \right)} \\ & - \cos{\left(\log{\left(y \right)} \right)} \end{align} Using ``eqnarray`` and dots: >>> print(multiline_latex(x, expr, terms_per_line=2, environment="eqnarray", use_dots=True)) \begin{eqnarray} x & = & e^{i \alpha} + \sin{\left(\alpha y \right)} \dots\nonumber\\ & & - \cos{\left(\log{\left(y \right)} \right)} \end{eqnarray} Using ``IEEEeqnarray``: >>> print(multiline_latex(x, expr, environment="IEEEeqnarray")) \begin{IEEEeqnarray}{rCl} x & = & e^{i \alpha} \nonumber\\ & & + \sin{\left(\alpha y \right)} \nonumber\\ & & - \cos{\left(\log{\left(y \right)} \right)} \end{IEEEeqnarray} Notes ===== All optional parameters from ``latex`` can also be used. """ # Based on code from https://github.com/sympy/sympy/issues/3001 l = LatexPrinter(settings) if environment == "eqnarray": result = r'\begin{eqnarray}' + '\n' first_term = '& = &' nonumber = r'\nonumber' end_term = '\n\\end{eqnarray}' doubleet = True elif environment == "IEEEeqnarray": result = r'\begin{IEEEeqnarray}{rCl}' + '\n' first_term = '& = &' nonumber = r'\nonumber' end_term = '\n\\end{IEEEeqnarray}' doubleet = True elif environment == "align": result = r'\begin{align}' + '\n' first_term = '= &' nonumber = '' end_term = '\n\\end{align}' doubleet = False else: raise ValueError("Unknown environment: {}".format(environment)) dots = '' if use_dots: dots=r'\dots' terms = rhs.as_ordered_terms() n_terms = len(terms) term_count = 1 for i in range(n_terms): term = terms[i] term_start = '' term_end = '' sign = '+' if term_count > terms_per_line: if doubleet: term_start = '& & ' else: term_start = '& ' term_count = 1 if term_count == terms_per_line: # End of line if i < n_terms-1: # There are terms remaining term_end = dots + nonumber + r'\\' + '\n' else: term_end = '' if term.as_ordered_factors()[0] == -1: term = -1*term sign = r'-' if i == 0: # beginning if sign == '+': sign = '' result += r'{:s} {:s}{:s} {:s} {:s}'.format(l.doprint(lhs), first_term, sign, l.doprint(term), term_end) else: result += r'{:s}{:s} {:s} {:s}'.format(term_start, sign, l.doprint(term), term_end) term_count += 1 result += end_term return result
0da82ef731f8bba722e818a5fd0144d60b4c3433b29b085cff3d9c256e38f143	"""Printing subsystem driver SymPy's printing system works the following way: Any expression can be passed to a designated Printer who then is responsible to return an adequate representation of that expression. The basic concept is the following: 1. Let the object print itself if it knows how. 2. Take the best fitting method defined in the printer. 3. As fall-back use the emptyPrinter method for the printer. Which Method is Responsible for Printing? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The whole printing process is started by calling ``.doprint(expr)`` on the printer which you want to use. This method looks for an appropriate method which can print the given expression in the given style that the printer defines. While looking for the method, it follows these steps: 1. Let the object print itself if it knows how. The printer looks for a specific method in every object. The name of that method depends on the specific printer and is defined under ``Printer.printmethod``. For example, StrPrinter calls ``_sympystr`` and LatexPrinter calls ``_latex``. Look at the documentation of the printer that you want to use. The name of the method is specified there. This was the original way of doing printing in sympy. Every class had its own latex, mathml, str and repr methods, but it turned out that it is hard to produce a high quality printer, if all the methods are spread out that far. Therefore all printing code was combined into the different printers, which works great for built-in sympy objects, but not that good for user defined classes where it is inconvenient to patch the printers. 2. Take the best fitting method defined in the printer. The printer loops through expr classes (class + its bases), and tries to dispatch the work to ``_print_<EXPR_CLASS>`` e.g., suppose we have the following class hierarchy:: Basic \| Atom \| Number \| Rational then, for ``expr=Rational(...)``, the Printer will try to call printer methods in the order as shown in the figure below:: p._print(expr) \| \|-- p._print_Rational(expr) \| \|-- p._print_Number(expr) \| \|-- p._print_Atom(expr) \| `-- p._print_Basic(expr) if ``._print_Rational`` method exists in the printer, then it is called, and the result is returned back. Otherwise, the printer tries to call ``._print_Number`` and so on. 3. As a fall-back use the emptyPrinter method for the printer. As fall-back ``self.emptyPrinter`` will be called with the expression. If not defined in the Printer subclass this will be the same as ``str(expr)``. .. _printer_example: Example of Custom Printer ^^^^^^^^^^^^^^^^^^^^^^^^^ In the example below, we have a printer which prints the derivative of a function in a shorter form. .. code-block:: python from sympy import Symbol from sympy.printing.latex import LatexPrinter, print_latex from sympy.core.function import UndefinedFunction, Function class MyLatexPrinter(LatexPrinter): \"\"\"Print derivative of a function of symbols in a shorter form. \"\"\" def _print_Derivative(self, expr): function, vars = expr.args if not isinstance(type(function), UndefinedFunction) or \\ not all(isinstance(i, Symbol) for i in vars): return super()._print_Derivative(expr) # If you want the printer to work correctly for nested # expressions then use self._print() instead of str() or latex(). # See the example of nested modulo below in the custom printing # method section. return "{}_{{{}}}".format( self._print(Symbol(function.func.__name__)), ''.join(self._print(i) for i in vars)) def print_my_latex(expr): \"\"\" Most of the printers define their own wrappers for print(). These wrappers usually take printer settings. Our printer does not have any settings. \"\"\" print(MyLatexPrinter().doprint(expr)) y = Symbol("y") x = Symbol("x") f = Function("f") expr = f(x, y).diff(x, y) # Print the expression using the normal latex printer and our custom # printer. print_latex(expr) print_my_latex(expr) The output of the code above is:: \\frac{\\partial^{2}}{\\partial x\\partial y} f{\\left(x,y \\right)} f_{xy} .. _printer_method_example: Example of Custom Printing Method ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In the example below, the latex printing of the modulo operator is modified. This is done by overriding the method ``_latex`` of ``Mod``. >>> from sympy import Symbol, Mod, Integer >>> from sympy.printing.latex import print_latex >>> # Always use printer._print() >>> class ModOp(Mod): ... def _latex(self, printer): ... a, b = [printer._print(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) Comparing the output of our custom operator to the builtin one: >>> x = Symbol('x') >>> m = Symbol('m') >>> print_latex(Mod(x, m)) x\\bmod{m} >>> print_latex(ModOp(x, m)) \\operatorname{Mod}{\\left( x,m \\right)} Common mistakes ~~~~~~~~~~~~~~~ It's important to always use ``self._print(obj)`` to print subcomponents of an expression when customizing a printer. Mistakes include: 1. Using ``self.doprint(obj)`` instead: >>> # This example does not work properly, as only the outermost call may use >>> # doprint. >>> class ModOpModeWrong(Mod): ... def _latex(self, printer): ... a, b = [printer.doprint(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This fails when the `mode` argument is passed to the printer: >>> print_latex(ModOp(x, m), mode='inline') # ok $\\operatorname{Mod}{\\left( x,m \\right)}$ >>> print_latex(ModOpModeWrong(x, m), mode='inline') # bad $\\operatorname{Mod}{\\left( $x$,$m$ \\right)}$ 2. Using ``str(obj)`` instead: >>> class ModOpNestedWrong(Mod): ... def _latex(self, printer): ... a, b = [str(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This fails on nested objects: >>> # Nested modulo. >>> print_latex(ModOp(ModOp(x, m), Integer(7))) # ok \\operatorname{Mod}{\\left( \\operatorname{Mod}{\\left( x,m \\right)},7 \\right)} >>> print_latex(ModOpNestedWrong(ModOpNestedWrong(x, m), Integer(7))) # bad \\operatorname{Mod}{\\left( ModOpNestedWrong(x, m),7 \\right)} 3. Using ``LatexPrinter()._print(obj)`` instead. >>> from sympy.printing.latex import LatexPrinter >>> class ModOpSettingsWrong(Mod): ... def _latex(self, printer): ... a, b = [LatexPrinter()._print(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This causes all the settings to be discarded in the subobjects. As an example, the ``full_prec`` setting which shows floats to full precision is ignored: >>> from sympy import Float >>> print_latex(ModOp(Float(1) x, m), full_prec=True) # ok \\operatorname{Mod}{\\left( 1.00000000000000 x,m \\right)} >>> print_latex(ModOpSettingsWrong(Float(1) * x, m), full_prec=True) # bad \\operatorname{Mod}{\\left( 1.0 x,m \\right)} """ from typing import Any, Dict, Type import inspect from contextlib import contextmanager from functools import cmp_to_key, update_wrapper from sympy import Basic, Add from sympy.core.core import BasicMeta from sympy.core.function import AppliedUndef, UndefinedFunction, Function @contextmanager def printer_context(printer, kwargs): original = printer._context.copy() try: printer._context.update(kwargs) yield finally: printer._context = original class Printer: """ Generic printer Its job is to provide infrastructure for implementing new printers easily. If you want to define your custom Printer or your custom printing method for your custom class then see the example above: printer_example_ . """ _global_settings = {} # type: Dict[str, Any] _default_settings = {} # type: Dict[str, Any] printmethod = None # type: str @classmethod def _get_initial_settings(cls): settings = cls._default_settings.copy() for key, val in cls._global_settings.items(): if key in cls._default_settings: settings[key] = val return settings def __init__(self, settings=None): self._str = str self._settings = self._get_initial_settings() self._context = dict() # mutable during printing if settings is not None: self._settings.update(settings) if len(self._settings) > len(self._default_settings): for key in self._settings: if key not in self._default_settings: raise TypeError("Unknown setting '%s'." % key) # _print_level is the number of times self._print() was recursively # called. See StrPrinter._print_Float() for an example of usage self._print_level = 0 @classmethod def set_global_settings(cls, settings): """Set system-wide printing settings. """ for key, val in settings.items(): if val is not None: cls._global_settings[key] = val @property def order(self): if 'order' in self._settings: return self._settings['order'] else: raise AttributeError("No order defined.") def doprint(self, expr): """Returns printer's representation for expr (as a string)""" return self._str(self._print(expr)) def _print(self, expr, kwargs): """Internal dispatcher Tries the following concepts to print an expression: 1. Let the object print itself if it knows how. 2. Take the best fitting method defined in the printer. 3. As fall-back use the emptyPrinter method for the printer. """ self._print_level += 1 try: # If the printer defines a name for a printing method # (Printer.printmethod) and the object knows for itself how it # should be printed, use that method. if (self.printmethod and hasattr(expr, self.printmethod) and not isinstance(expr, BasicMeta)): return getattr(expr, self.printmethod)(self, kwargs) # See if the class of expr is known, or if one of its super # classes is known, and use that print function # Exception: ignore the subclasses of Undefined, so that, e.g., # Function('gamma') does not get dispatched to _print_gamma classes = type(expr).__mro__ if AppliedUndef in classes: classes = classes[classes.index(AppliedUndef):] if UndefinedFunction in classes: classes = classes[classes.index(UndefinedFunction):] # Another exception: if someone subclasses a known function, e.g., # gamma, and changes the name, then ignore _print_gamma if Function in classes: i = classes.index(Function) classes = tuple(c for c in classes[:i] if \ c.__name__ == classes[0].__name__ or \ c.__name__.endswith("Base")) + classes[i:] for cls in classes: printmethod = '_print_' + cls.__name__ if hasattr(self, printmethod): return getattr(self, printmethod)(expr, kwargs) # Unknown object, fall back to the emptyPrinter. return self.emptyPrinter(expr) finally: self._print_level -= 1 def emptyPrinter(self, expr): return str(expr) def _as_ordered_terms(self, expr, order=None): """A compatibility function for ordering terms in Add. """ order = order or self.order if order == 'old': return sorted(Add.make_args(expr), key=cmp_to_key(Basic._compare_pretty)) elif order == 'none': return list(expr.args) else: return expr.as_ordered_terms(order=order) class _PrintFunction: """ Function wrapper to replace ``settings`` in the signature with printer defaults """ def __init__(self, f, print_cls: Type[Printer]): # find all the non-setting arguments params = list(inspect.signature(f).parameters.values()) assert params.pop(-1).kind == inspect.Parameter.VAR_KEYWORD self.__other_params = params self.__print_cls = print_cls update_wrapper(self, f) def __repr__(self) -> str: return repr(self.__wrapped__) # type:ignore def __call__(self, args, kwargs): return self.__wrapped__(args, **kwargs) @property def __signature__(self) -> inspect.Signature: settings = self.__print_cls._get_initial_settings() return inspect.Signature( parameters=self.__other_params + [ inspect.Parameter(k, inspect.Parameter.KEYWORD_ONLY, default=v) for k, v in settings.items() ], return_annotation=self.__wrapped__.__annotations__.get('return', inspect.Signature.empty) # type:ignore ) def print_function(print_cls): """ A decorator to replace kwargs with the printer settings in __signature__ """ def decorator(f): return _PrintFunction(f, print_cls) return decorator
27dc6e30be2b6370cd1eece613d2cc7aae83e2bbe428f8569882ba3cfb9b7f9a	from sympy.core.containers import Tuple from types import FunctionType class TableForm: r""" Create a nice table representation of data. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]]) >>> print(t) 5 7 4 2 10 3 You can use the SymPy's printing system to produce tables in any format (ascii, latex, html, ...). >>> print(t.as_latex()) \begin{tabular}{l l} $5$ & $7$ \\ $4$ & $2$ \\ $10$ & $3$ \\ \end{tabular} """ def __init__(self, data, *kwarg): """ Creates a TableForm. Parameters: data ... 2D data to be put into the table; data can be given as a Matrix headings ... gives the labels for rows and columns: Can be a single argument that applies to both dimensions: - None ... no labels - "automatic" ... labels are 1, 2, 3, ... Can be a list of labels for rows and columns: The labels for each dimension can be given as None, "automatic", or [l1, l2, ...] e.g. ["automatic", None] will number the rows [default: None] alignments ... alignment of the columns with: - "left" or "<" - "center" or "^" - "right" or ">" When given as a single value, the value is used for all columns. The row headings (if given) will be right justified unless an explicit alignment is given for it and all other columns. [default: "left"] formats ... a list of format strings or functions that accept 3 arguments (entry, row number, col number) and return a string for the table entry. (If a function returns None then the _print method will be used.) wipe_zeros ... Don't show zeros in the table. [default: True] pad ... the string to use to indicate a missing value (e.g. elements that are None or those that are missing from the end of a row (i.e. any row that is shorter than the rest is assumed to have missing values). When None, nothing will be shown for values that are missing from the end of a row; values that are None, however, will be shown. [default: None] Examples ======== >>> from sympy import TableForm, Symbol >>> TableForm([[5, 7], [4, 2], [10, 3]]) 5 7 4 2 10 3 >>> TableForm([list('.'i) for i in range(1, 4)], headings='automatic') \| 1 2 3 --------- 1 \| . 2 \| . . 3 \| . . . >>> TableForm([[Symbol('.'(j if not i%2 else 1)) for i in range(3)] ... for j in range(4)], alignments='rcl') . . . . .. . .. ... . ... """ from sympy import Symbol, S, Matrix from sympy.core.sympify import SympifyError # We only support 2D data. Check the consistency: if isinstance(data, Matrix): data = data.tolist() _h = len(data) # fill out any short lines pad = kwarg.get('pad', None) ok_None = False if pad is None: pad = " " ok_None = True pad = Symbol(pad) _w = max(len(line) for line in data) for i, line in enumerate(data): if len(line) != _w: line.extend([pad](_w - len(line))) for j, lj in enumerate(line): if lj is None: if not ok_None: lj = pad else: try: lj = S(lj) except SympifyError: lj = Symbol(str(lj)) line[j] = lj data[i] = line _lines = Tuple(data) headings = kwarg.get("headings", [None, None]) if headings == "automatic": _headings = [range(1, _h + 1), range(1, _w + 1)] else: h1, h2 = headings if h1 == "automatic": h1 = range(1, _h + 1) if h2 == "automatic": h2 = range(1, _w + 1) _headings = [h1, h2] allow = ('l', 'r', 'c') alignments = kwarg.get("alignments", "l") def _std_align(a): a = a.strip().lower() if len(a) > 1: return {'left': 'l', 'right': 'r', 'center': 'c'}.get(a, a) else: return {'<': 'l', '>': 'r', '^': 'c'}.get(a, a) std_align = _std_align(alignments) if std_align in allow: _alignments = [std_align]_w else: _alignments = [] for a in alignments: std_align = _std_align(a) _alignments.append(std_align) if std_align not in ('l', 'r', 'c'): raise ValueError('alignment "%s" unrecognized' % alignments) if _headings[0] and len(_alignments) == _w + 1: _head_align = _alignments[0] _alignments = _alignments[1:] else: _head_align = 'r' if len(_alignments) != _w: raise ValueError( 'wrong number of alignments: expected %s but got %s' % (_w, len(_alignments))) _column_formats = kwarg.get("formats", [None]_w) _wipe_zeros = kwarg.get("wipe_zeros", True) self._w = _w self._h = _h self._lines = _lines self._headings = _headings self._head_align = _head_align self._alignments = _alignments self._column_formats = _column_formats self._wipe_zeros = _wipe_zeros def __repr__(self): from .str import sstr return sstr(self, order=None) def __str__(self): from .str import sstr return sstr(self, order=None) def as_matrix(self): """Returns the data of the table in Matrix form. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]], headings='automatic') >>> t \| 1 2 -------- 1 \| 5 7 2 \| 4 2 3 \| 10 3 >>> t.as_matrix() Matrix([ [ 5, 7], [ 4, 2], [10, 3]]) """ from sympy import Matrix return Matrix(self._lines) def as_str(self): # XXX obsolete ? return str(self) def as_latex(self): from .latex import latex return latex(self) def _sympystr(self, p): """ Returns the string representation of 'self'. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]]) >>> s = t.as_str() """ column_widths = [0] self._w lines = [] for line in self._lines: new_line = [] for i in range(self._w): # Format the item somehow if needed: s = str(line[i]) if self._wipe_zeros and (s == "0"): s = " " w = len(s) if w > column_widths[i]: column_widths[i] = w new_line.append(s) lines.append(new_line) # Check heading: if self._headings[0]: self._headings[0] = [str(x) for x in self._headings[0]] _head_width = max([len(x) for x in self._headings[0]]) if self._headings[1]: new_line = [] for i in range(self._w): # Format the item somehow if needed: s = str(self._headings[1][i]) w = len(s) if w > column_widths[i]: column_widths[i] = w new_line.append(s) self._headings[1] = new_line format_str = [] def _align(align, w): return '%%%s%ss' % ( ("-" if align == "l" else ""), str(w)) format_str = [_align(align, w) for align, w in zip(self._alignments, column_widths)] if self._headings[0]: format_str.insert(0, _align(self._head_align, _head_width)) format_str.insert(1, '\|') format_str = ' '.join(format_str) + '\n' s = [] if self._headings[1]: d = self._headings[1] if self._headings[0]: d = [""] + d first_line = format_str % tuple(d) s.append(first_line) s.append("-" * (len(first_line) - 1) + "\n") for i, line in enumerate(lines): d = [l if self._alignments[j] != 'c' else l.center(column_widths[j]) for j, l in enumerate(line)] if self._headings[0]: l = self._headings[0][i] l = (l if self._head_align != 'c' else l.center(_head_width)) d = [l] + d s.append(format_str % tuple(d)) return ''.join(s)[:-1] # don't include trailing newline def _latex(self, printer): """ Returns the string representation of 'self'. """ # Check heading: if self._headings[1]: new_line = [] for i in range(self._w): # Format the item somehow if needed: new_line.append(str(self._headings[1][i])) self._headings[1] = new_line alignments = [] if self._headings[0]: self._headings[0] = [str(x) for x in self._headings[0]] alignments = [self._head_align] alignments.extend(self._alignments) s = r"\begin{tabular}{" + " ".join(alignments) + "}\n" if self._headings[1]: d = self._headings[1] if self._headings[0]: d = [""] + d first_line = " & ".join(d) + r" \\" + "\n" s += first_line s += r"\hline" + "\n" for i, line in enumerate(self._lines): d = [] for j, x in enumerate(line): if self._wipe_zeros and (x in (0, "0")): d.append(" ") continue f = self._column_formats[j] if f: if isinstance(f, FunctionType): v = f(x, i, j) if v is None: v = printer._print(x) else: v = f % x d.append(v) else: v = printer._print(x) d.append("$%s$" % v) if self._headings[0]: d = [self._headings[0][i]] + d s += " & ".join(d) + r" \\" + "\n" s += r"\end{tabular}" return s
b1d1f05f9d617f22ecc79254ccc8b7d1b06f6e1c1f8c62d34e38ebc1f6858667	""" C code printer The C89CodePrinter & C99CodePrinter converts single sympy expressions into single C expressions, using the functions defined in math.h where possible. A complete code generator, which uses ccode extensively, can be found in sympy.utilities.codegen. The codegen module can be used to generate complete source code files that are compilable without further modifications. """ from typing import Any, Dict, Tuple from functools import wraps from itertools import chain from sympy.core import S from sympy.codegen.ast import ( Assignment, Pointer, Variable, Declaration, Type, real, complex_, integer, bool_, float32, float64, float80, complex64, complex128, intc, value_const, pointer_const, int8, int16, int32, int64, uint8, uint16, uint32, uint64, untyped, none ) from sympy.printing.codeprinter import CodePrinter, requires from sympy.printing.precedence import precedence, PRECEDENCE from sympy.sets.fancysets import Range # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import ccode, print_ccode # noqa:F401 # dictionary mapping sympy function to (argument_conditions, C_function). # Used in C89CodePrinter._print_Function(self) known_functions_C89 = { "Abs": [(lambda x: not x.is_integer, "fabs"), (lambda x: x.is_integer, "abs")], "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", "exp": "exp", "log": "log", "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "floor": "floor", "ceiling": "ceil", } known_functions_C99 = dict(known_functions_C89, { 'exp2': 'exp2', 'expm1': 'expm1', 'log10': 'log10', 'log2': 'log2', 'log1p': 'log1p', 'Cbrt': 'cbrt', 'hypot': 'hypot', 'fma': 'fma', 'loggamma': 'lgamma', 'erfc': 'erfc', 'Max': 'fmax', 'Min': 'fmin', "asinh": "asinh", "acosh": "acosh", "atanh": "atanh", "erf": "erf", "gamma": "tgamma", }) # These are the core reserved words in the C language. Taken from: # http://en.cppreference.com/w/c/keyword reserved_words = [ 'auto', 'break', 'case', 'char', 'const', 'continue', 'default', 'do', 'double', 'else', 'enum', 'extern', 'float', 'for', 'goto', 'if', 'int', 'long', 'register', 'return', 'short', 'signed', 'sizeof', 'static', 'struct', 'entry', # never standardized, we'll leave it here anyway 'switch', 'typedef', 'union', 'unsigned', 'void', 'volatile', 'while' ] reserved_words_c99 = ['inline', 'restrict'] def get_math_macros(): """ Returns a dictionary with math-related macros from math.h/cmath Note that these macros are not strictly required by the C/C++-standard. For MSVC they are enabled by defining "_USE_MATH_DEFINES" (preferably via a compilation flag). Returns ======= Dictionary mapping sympy expressions to strings (macro names) """ from sympy.codegen.cfunctions import log2, Sqrt from sympy.functions.elementary.exponential import log from sympy.functions.elementary.miscellaneous import sqrt return { S.Exp1: 'M_E', log2(S.Exp1): 'M_LOG2E', 1/log(2): 'M_LOG2E', log(2): 'M_LN2', log(10): 'M_LN10', S.Pi: 'M_PI', S.Pi/2: 'M_PI_2', S.Pi/4: 'M_PI_4', 1/S.Pi: 'M_1_PI', 2/S.Pi: 'M_2_PI', 2/sqrt(S.Pi): 'M_2_SQRTPI', 2/Sqrt(S.Pi): 'M_2_SQRTPI', sqrt(2): 'M_SQRT2', Sqrt(2): 'M_SQRT2', 1/sqrt(2): 'M_SQRT1_2', 1/Sqrt(2): 'M_SQRT1_2' } def _as_macro_if_defined(meth): """ Decorator for printer methods When a Printer's method is decorated using this decorator the expressions printed will first be looked for in the attribute ``math_macros``, and if present it will print the macro name in ``math_macros`` followed by a type suffix for the type ``real``. e.g. printing ``sympy.pi`` would print ``M_PIl`` if real is mapped to float80. """ @wraps(meth) def _meth_wrapper(self, expr, kwargs): if expr in self.math_macros: return '%s%s' % (self.math_macros[expr], self._get_math_macro_suffix(real)) else: return meth(self, expr, kwargs) return _meth_wrapper class C89CodePrinter(CodePrinter): """A printer to convert python expressions to strings of c code""" printmethod = "_ccode" language = "C" standard = "C89" reserved_words = set(reserved_words) _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, 'contract': True, 'dereference': set(), 'error_on_reserved': False, 'reserved_word_suffix': '_', } # type: Dict[str, Any] type_aliases = { real: float64, complex_: complex128, integer: intc } type_mappings = { real: 'double', intc: 'int', float32: 'float', float64: 'double', integer: 'int', bool_: 'bool', int8: 'int8_t', int16: 'int16_t', int32: 'int32_t', int64: 'int64_t', uint8: 'int8_t', uint16: 'int16_t', uint32: 'int32_t', uint64: 'int64_t', } # type: Dict[Type, Any] type_headers = { bool_: {'stdbool.h'}, int8: {'stdint.h'}, int16: {'stdint.h'}, int32: {'stdint.h'}, int64: {'stdint.h'}, uint8: {'stdint.h'}, uint16: {'stdint.h'}, uint32: {'stdint.h'}, uint64: {'stdint.h'}, } # Macros needed to be defined when using a Type type_macros = {} # type: Dict[Type, Tuple[str, ...]] type_func_suffixes = { float32: 'f', float64: '', float80: 'l' } type_literal_suffixes = { float32: 'F', float64: '', float80: 'L' } type_math_macro_suffixes = { float80: 'l' } math_macros = None _ns = '' # namespace, C++ uses 'std::' # known_functions-dict to copy _kf = known_functions_C89 # type: Dict[str, Any] def __init__(self, settings=None): settings = settings or {} if self.math_macros is None: self.math_macros = settings.pop('math_macros', get_math_macros()) self.type_aliases = dict(chain(self.type_aliases.items(), settings.pop('type_aliases', {}).items())) self.type_mappings = dict(chain(self.type_mappings.items(), settings.pop('type_mappings', {}).items())) self.type_headers = dict(chain(self.type_headers.items(), settings.pop('type_headers', {}).items())) self.type_macros = dict(chain(self.type_macros.items(), settings.pop('type_macros', {}).items())) self.type_func_suffixes = dict(chain(self.type_func_suffixes.items(), settings.pop('type_func_suffixes', {}).items())) self.type_literal_suffixes = dict(chain(self.type_literal_suffixes.items(), settings.pop('type_literal_suffixes', {}).items())) self.type_math_macro_suffixes = dict(chain(self.type_math_macro_suffixes.items(), settings.pop('type_math_macro_suffixes', {}).items())) super().__init__(settings) self.known_functions = dict(self._kf, settings.get('user_functions', {})) self._dereference = set(settings.get('dereference', [])) self.headers = set() self.libraries = set() self.macros = set() def _rate_index_position(self, p): return p5 def _get_statement(self, codestring): """ Get code string as a statement - i.e. ending with a semicolon. """ return codestring if codestring.endswith(';') else codestring + ';' def _get_comment(self, text): return "// {}".format(text) def _declare_number_const(self, name, value): type_ = self.type_aliases[real] var = Variable(name, type=type_, value=value.evalf(type_.decimal_dig), attrs={value_const}) decl = Declaration(var) return self._get_statement(self._print(decl)) def _format_code(self, lines): return self.indent_code(lines) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for i in range(rows) for j in range(cols)) @_as_macro_if_defined def _print_Mul(self, expr, kwargs): return super()._print_Mul(expr, kwargs) @_as_macro_if_defined def _print_Pow(self, expr): if "Pow" in self.known_functions: return self._print_Function(expr) PREC = precedence(expr) suffix = self._get_func_suffix(real) if expr.exp == -1: literal_suffix = self._get_literal_suffix(real) return '1.0%s/%s' % (literal_suffix, self.parenthesize(expr.base, PREC)) elif expr.exp == 0.5: return '%ssqrt%s(%s)' % (self._ns, suffix, self._print(expr.base)) elif expr.exp == S.One/3 and self.standard != 'C89': return '%scbrt%s(%s)' % (self._ns, suffix, self._print(expr.base)) else: return '%spow%s(%s, %s)' % (self._ns, suffix, self._print(expr.base), self._print(expr.exp)) def _print_Mod(self, expr): num, den = expr.args if num.is_integer and den.is_integer: return "(({}) % ({}))".format(self._print(num), self._print(den)) else: return self._print_math_func(expr, known='fmod') def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) suffix = self._get_literal_suffix(real) return '%d.0%s/%d.0%s' % (p, suffix, q, suffix) def _print_Indexed(self, expr): # calculate index for 1d array offset = getattr(expr.base, 'offset', S.Zero) strides = getattr(expr.base, 'strides', None) indices = expr.indices if strides is None or isinstance(strides, str): dims = expr.shape shift = S.One temp = tuple() if strides == 'C' or strides is None: traversal = reversed(range(expr.rank)) indices = indices[::-1] elif strides == 'F': traversal = range(expr.rank) for i in traversal: temp += (shift,) shift = dims[i] strides = temp flat_index = sum([x[0]x[1] for x in zip(indices, strides)]) + offset return "%s[%s]" % (self._print(expr.base.label), self._print(flat_index)) def _print_Idx(self, expr): return self._print(expr.label) @_as_macro_if_defined def _print_NumberSymbol(self, expr): return super()._print_NumberSymbol(expr) def _print_Infinity(self, expr): return 'HUGE_VAL' def _print_NegativeInfinity(self, expr): return '-HUGE_VAL' def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] if expr.has(Assignment): for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) {" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines.append("else {") else: lines.append("else if (%s) {" % self._print(c)) code0 = self._print(e) lines.append(code0) lines.append("}") return "\n".join(lines) else: # The piecewise was used in an expression, need to do inline # operators. This has the downside that inline operators will # not work for statements that span multiple lines (Matrix or # Indexed expressions). ecpairs = ["((%s) ? (\n%s\n)\n" % (self._print(c), self._print(e)) for e, c in expr.args[:-1]] last_line = ": (\n%s\n)" % self._print(expr.args[-1].expr) return ": ".join(ecpairs) + last_line + " ".join([")"len(ecpairs)]) def _print_ITE(self, expr): from sympy.functions import Piecewise _piecewise = Piecewise((expr.args[1], expr.args[0]), (expr.args[2], True)) return self._print(_piecewise) def _print_MatrixElement(self, expr): return "{}[{}]".format(self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True), expr.j + expr.iexpr.parent.shape[1]) def _print_Symbol(self, expr): name = super()._print_Symbol(expr) if expr in self._settings['dereference']: return '({})'.format(name) else: return name def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) def _print_sinc(self, expr): from sympy.functions.elementary.trigonometric import sin from sympy.core.relational import Ne from sympy.functions import Piecewise _piecewise = Piecewise( (sin(expr.args[0]) / expr.args[0], Ne(expr.args[0], 0)), (1, True)) return self._print(_piecewise) def _print_For(self, expr): target = self._print(expr.target) if isinstance(expr.iterable, Range): start, stop, step = expr.iterable.args else: raise NotImplementedError("Only iterable currently supported is Range") body = self._print(expr.body) return ('for ({target} = {start}; {target} < {stop}; {target} += ' '{step}) {{\n{body}\n}}').format(target=target, start=start, stop=stop, step=step, body=body) def _print_sign(self, func): return '((({0}) > 0) - (({0}) < 0))'.format(self._print(func.args[0])) def _print_Max(self, expr): if "Max" in self.known_functions: return self._print_Function(expr) def inner_print_max(args): # The more natural abstraction of creating if len(args) == 1: # and printing smaller Max objects is slow return self._print(args[0]) # when there are many arguments. half = len(args) // 2 return "((%(a)s > %(b)s) ? %(a)s : %(b)s)" % { 'a': inner_print_max(args[:half]), 'b': inner_print_max(args[half:]) } return inner_print_max(expr.args) def _print_Min(self, expr): if "Min" in self.known_functions: return self._print_Function(expr) def inner_print_min(args): # The more natural abstraction of creating if len(args) == 1: # and printing smaller Min objects is slow return self._print(args[0]) # when there are many arguments. half = len(args) // 2 return "((%(a)s < %(b)s) ? %(a)s : %(b)s)" % { 'a': inner_print_min(args[:half]), 'b': inner_print_min(args[half:]) } return inner_print_min(expr.args) def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) tab = " " inc_token = ('{', '(', '{\n', '(\n') dec_token = ('}', ')') code = [line.lstrip(' \t') for line in code] increase = [int(any(map(line.endswith, inc_token))) for line in code] decrease = [int(any(map(line.startswith, dec_token))) for line in code] pretty = [] level = 0 for n, line in enumerate(code): if line == '' or line == '\n': pretty.append(line) continue level -= decrease[n] pretty.append("%s%s" % (tablevel, line)) level += increase[n] return pretty def _get_func_suffix(self, type_): return self.type_func_suffixes[self.type_aliases.get(type_, type_)] def _get_literal_suffix(self, type_): return self.type_literal_suffixes[self.type_aliases.get(type_, type_)] def _get_math_macro_suffix(self, type_): alias = self.type_aliases.get(type_, type_) dflt = self.type_math_macro_suffixes.get(alias, '') return self.type_math_macro_suffixes.get(type_, dflt) def _print_Type(self, type_): self.headers.update(self.type_headers.get(type_, set())) self.macros.update(self.type_macros.get(type_, set())) return self._print(self.type_mappings.get(type_, type_.name)) def _print_Declaration(self, decl): from sympy.codegen.cnodes import restrict var = decl.variable val = var.value if var.type == untyped: raise ValueError("C does not support untyped variables") if isinstance(var, Pointer): result = '{vc}{t} {pc} {r}{s}'.format( vc='const ' if value_const in var.attrs else '', t=self._print(var.type), pc=' const' if pointer_const in var.attrs else '', r='restrict ' if restrict in var.attrs else '', s=self._print(var.symbol) ) elif isinstance(var, Variable): result = '{vc}{t} {s}'.format( vc='const ' if value_const in var.attrs else '', t=self._print(var.type), s=self._print(var.symbol) ) else: raise NotImplementedError("Unknown type of var: %s" % type(var)) if val != None: # Must be "!= None", cannot be "is not None" result += ' = %s' % self._print(val) return result def _print_Float(self, flt): type_ = self.type_aliases.get(real, real) self.macros.update(self.type_macros.get(type_, set())) suffix = self._get_literal_suffix(type_) num = str(flt.evalf(type_.decimal_dig)) if 'e' not in num and '.' not in num: num += '.0' num_parts = num.split('e') num_parts[0] = num_parts[0].rstrip('0') if num_parts[0].endswith('.'): num_parts[0] += '0' return 'e'.join(num_parts) + suffix @requires(headers={'stdbool.h'}) def _print_BooleanTrue(self, expr): return 'true' @requires(headers={'stdbool.h'}) def _print_BooleanFalse(self, expr): return 'false' def _print_Element(self, elem): if elem.strides == None: # Must be "== None", cannot be "is None" if elem.offset != None: # Must be "!= None", cannot be "is not None" raise ValueError("Expected strides when offset is given") idxs = ']['.join(map(lambda arg: self._print(arg), elem.indices)) else: global_idx = sum([is for i, s in zip(elem.indices, elem.strides)]) if elem.offset != None: # Must be "!= None", cannot be "is not None" global_idx += elem.offset idxs = self._print(global_idx) return "{symb}[{idxs}]".format( symb=self._print(elem.symbol), idxs=idxs ) def _print_CodeBlock(self, expr): """ Elements of code blocks printed as statements. """ return '\n'.join([self._get_statement(self._print(i)) for i in expr.args]) def _print_While(self, expr): return 'while ({condition}) {{\n{body}\n}}'.format(expr.kwargs( apply=lambda arg: self._print(arg))) def _print_Scope(self, expr): return '{\n%s\n}' % self._print_CodeBlock(expr.body) @requires(headers={'stdio.h'}) def _print_Print(self, expr): return 'printf({fmt}, {pargs})'.format( fmt=self._print(expr.format_string), pargs=', '.join(map(lambda arg: self._print(arg), expr.print_args)) ) def _print_FunctionPrototype(self, expr): pars = ', '.join(map(lambda arg: self._print(Declaration(arg)), expr.parameters)) return "%s %s(%s)" % ( tuple(map(lambda arg: self._print(arg), (expr.return_type, expr.name))) + (pars,) ) def _print_FunctionDefinition(self, expr): return "%s%s" % (self._print_FunctionPrototype(expr), self._print_Scope(expr)) def _print_Return(self, expr): arg, = expr.args return 'return %s' % self._print(arg) def _print_CommaOperator(self, expr): return '(%s)' % ', '.join(map(lambda arg: self._print(arg), expr.args)) def _print_Label(self, expr): if expr.body == none: return '%s:' % str(expr.name) if len(expr.body.args) == 1: return '%s:\n%s' % (str(expr.name), self._print_CodeBlock(expr.body)) return '%s:\n{\n%s\n}' % (str(expr.name), self._print_CodeBlock(expr.body)) def _print_goto(self, expr): return 'goto %s' % expr.label.name def _print_PreIncrement(self, expr): arg, = expr.args return '++(%s)' % self._print(arg) def _print_PostIncrement(self, expr): arg, = expr.args return '(%s)++' % self._print(arg) def _print_PreDecrement(self, expr): arg, = expr.args return '--(%s)' % self._print(arg) def _print_PostDecrement(self, expr): arg, = expr.args return '(%s)--' % self._print(arg) def _print_struct(self, expr): return "%(keyword)s %(name)s {\n%(lines)s}" % dict( keyword=expr.__class__.__name__, name=expr.name, lines=';\n'.join( [self._print(decl) for decl in expr.declarations] + ['']) ) def _print_BreakToken(self, _): return 'break' def _print_ContinueToken(self, _): return 'continue' _print_union = _print_struct class C99CodePrinter(C89CodePrinter): standard = 'C99' reserved_words = set(reserved_words + reserved_words_c99) type_mappings=dict(chain(C89CodePrinter.type_mappings.items(), { complex64: 'float complex', complex128: 'double complex', }.items())) type_headers = dict(chain(C89CodePrinter.type_headers.items(), { complex64: {'complex.h'}, complex128: {'complex.h'} }.items())) # known_functions-dict to copy _kf = known_functions_C99 # type: Dict[str, Any] # functions with versions with 'f' and 'l' suffixes: _prec_funcs = ('fabs fmod remainder remquo fma fmax fmin fdim nan exp exp2' ' expm1 log log10 log2 log1p pow sqrt cbrt hypot sin cos tan' ' asin acos atan atan2 sinh cosh tanh asinh acosh atanh erf' ' erfc tgamma lgamma ceil floor trunc round nearbyint rint' ' frexp ldexp modf scalbn ilogb logb nextafter copysign').split() def _print_Infinity(self, expr): return 'INFINITY' def _print_NegativeInfinity(self, expr): return '-INFINITY' def _print_NaN(self, expr): return 'NAN' # tgamma was already covered by 'known_functions' dict @requires(headers={'math.h'}, libraries={'m'}) @_as_macro_if_defined def _print_math_func(self, expr, nest=False, known=None): if known is None: known = self.known_functions[expr.__class__.__name__] if not isinstance(known, str): for cb, name in known: if cb(expr.args): known = name break else: raise ValueError("No matching printer") try: return known(self, *expr.args) except TypeError: suffix = self._get_func_suffix(real) if self._ns + known in self._prec_funcs else '' if nest: args = self._print(expr.args[0]) if len(expr.args) > 1: paren_pile = '' for curr_arg in expr.args[1:-1]: paren_pile += ')' args += ', {ns}{name}{suffix}({next}'.format( ns=self._ns, name=known, suffix=suffix, next = self._print(curr_arg) ) args += ', %s%s' % ( self._print(expr.func(expr.args[-1])), paren_pile ) else: args = ', '.join(map(lambda arg: self._print(arg), expr.args)) return '{ns}{name}{suffix}({args})'.format( ns=self._ns, name=known, suffix=suffix, args=args ) def _print_Max(self, expr): return self._print_math_func(expr, nest=True) def _print_Min(self, expr): return self._print_math_func(expr, nest=True) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] loopstart = "for (int %(var)s=%(start)s; %(var)s<%(end)s; %(var)s++){" # C99 for i in indices: # C arrays start at 0 and end at dimension-1 open_lines.append(loopstart % { 'var': self._print(i.label), 'start': self._print(i.lower), 'end': self._print(i.upper + 1)}) close_lines.append("}") return open_lines, close_lines for k in ('Abs Sqrt exp exp2 expm1 log log10 log2 log1p Cbrt hypot fma' ' loggamma sin cos tan asin acos atan atan2 sinh cosh tanh asinh acosh ' 'atanh erf erfc loggamma gamma ceiling floor').split(): setattr(C99CodePrinter, '_print_%s' % k, C99CodePrinter._print_math_func) class C11CodePrinter(C99CodePrinter): @requires(headers={'stdalign.h'}) def _print_alignof(self, expr): arg, = expr.args return 'alignof(%s)' % self._print(arg) c_code_printers = { 'c89': C89CodePrinter, 'c99': C99CodePrinter, 'c11': C11CodePrinter }
7a26db2a5cd10577fbe4e1bb04202e46545654d23dcdd57393af4fff8a7d9a0d	from .pycode import ( PythonCodePrinter, MpmathPrinter, # MpmathPrinter is imported for backward compatibility NumPyPrinter # NumPyPrinter is imported for backward compatibility ) from sympy.utilities import default_sort_key __all__ = [ 'PythonCodePrinter', 'MpmathPrinter', 'NumPyPrinter', 'LambdaPrinter', 'NumPyPrinter', 'lambdarepr', ] class LambdaPrinter(PythonCodePrinter): """ This printer converts expressions into strings that can be used by lambdify. """ printmethod = "_lambdacode" def _print_And(self, expr): result = ['('] for arg in sorted(expr.args, key=default_sort_key): result.extend(['(', self._print(arg), ')']) result.append(' and ') result = result[:-1] result.append(')') return ''.join(result) def _print_Or(self, expr): result = ['('] for arg in sorted(expr.args, key=default_sort_key): result.extend(['(', self._print(arg), ')']) result.append(' or ') result = result[:-1] result.append(')') return ''.join(result) def _print_Not(self, expr): result = ['(', 'not (', self._print(expr.args[0]), '))'] return ''.join(result) def _print_BooleanTrue(self, expr): return "True" def _print_BooleanFalse(self, expr): return "False" def _print_ITE(self, expr): result = [ '((', self._print(expr.args[1]), ') if (', self._print(expr.args[0]), ') else (', self._print(expr.args[2]), '))' ] return ''.join(result) def _print_NumberSymbol(self, expr): return str(expr) def _print_Pow(self, expr, kwargs): # XXX Temporary workaround. Should python math printer be # isolated from PythonCodePrinter? return super(PythonCodePrinter, self)._print_Pow(expr, kwargs) # numexpr works by altering the string passed to numexpr.evaluate # rather than by populating a namespace. Thus a special printer... class NumExprPrinter(LambdaPrinter): # key, value pairs correspond to sympy name and numexpr name # functions not appearing in this dict will raise a TypeError printmethod = "_numexprcode" _numexpr_functions = { 'sin' : 'sin', 'cos' : 'cos', 'tan' : 'tan', 'asin': 'arcsin', 'acos': 'arccos', 'atan': 'arctan', 'atan2' : 'arctan2', 'sinh' : 'sinh', 'cosh' : 'cosh', 'tanh' : 'tanh', 'asinh': 'arcsinh', 'acosh': 'arccosh', 'atanh': 'arctanh', 'ln' : 'log', 'log': 'log', 'exp': 'exp', 'sqrt' : 'sqrt', 'Abs' : 'abs', 'conjugate' : 'conj', 'im' : 'imag', 're' : 'real', 'where' : 'where', 'complex' : 'complex', 'contains' : 'contains', } def _print_ImaginaryUnit(self, expr): return '1j' def _print_seq(self, seq, delimiter=', '): # simplified _print_seq taken from pretty.py s = [self._print(item) for item in seq] if s: return delimiter.join(s) else: return "" def _print_Function(self, e): func_name = e.func.__name__ nstr = self._numexpr_functions.get(func_name, None) if nstr is None: # check for implemented_function if hasattr(e, '_imp_'): return "(%s)" % self._print(e._imp_(e.args)) else: raise TypeError("numexpr does not support function '%s'" % func_name) return "%s(%s)" % (nstr, self._print_seq(e.args)) def _print_Piecewise(self, expr): "Piecewise function printer" exprs = [self._print(arg.expr) for arg in expr.args] conds = [self._print(arg.cond) for arg in expr.args] # If [default_value, True] is a (expr, cond) sequence in a Piecewise object # it will behave the same as passing the 'default' kwarg to select() # as long as* it is the last element in expr.args. # If this is not the case, it may be triggered prematurely. ans = [] parenthesis_count = 0 is_last_cond_True = False for cond, expr in zip(conds, exprs): if cond == 'True': ans.append(expr) is_last_cond_True = True break else: ans.append('where(%s, %s, ' % (cond, expr)) parenthesis_count += 1 if not is_last_cond_True: # simplest way to put a nan but raises # 'RuntimeWarning: invalid value encountered in log' ans.append('log(-1)') return ''.join(ans) + ')' * parenthesis_count def blacklisted(self, expr): raise TypeError("numexpr cannot be used with %s" % expr.__class__.__name__) # blacklist all Matrix printing _print_SparseMatrix = \ _print_MutableSparseMatrix = \ _print_ImmutableSparseMatrix = \ _print_Matrix = \ _print_DenseMatrix = \ _print_MutableDenseMatrix = \ _print_ImmutableMatrix = \ _print_ImmutableDenseMatrix = \ blacklisted # blacklist some python expressions _print_list = \ _print_tuple = \ _print_Tuple = \ _print_dict = \ _print_Dict = \ blacklisted def doprint(self, expr): lstr = super().doprint(expr) return "evaluate('%s', truediv=True)" % lstr for k in NumExprPrinter._numexpr_functions: setattr(NumExprPrinter, '_print_%s' % k, NumExprPrinter._print_Function) def lambdarepr(expr, **settings): """ Returns a string usable for lambdifying. """ return LambdaPrinter(settings).doprint(expr)
b446d20e585feb73df58019aa6d696abfc62d6fe5ab2a73a72dd820b2a82ccc8	""" Mathematica code printer """ from typing import Any, Dict, Set, Tuple from sympy.core import Basic, Expr, Float from sympy.printing.codeprinter import CodePrinter from sympy.printing.precedence import precedence # Used in MCodePrinter._print_Function(self) known_functions = { "exp": [(lambda x: True, "Exp")], "log": [(lambda x: True, "Log")], "sin": [(lambda x: True, "Sin")], "cos": [(lambda x: True, "Cos")], "tan": [(lambda x: True, "Tan")], "cot": [(lambda x: True, "Cot")], "sec": [(lambda x: True, "Sec")], "csc": [(lambda x: True, "Csc")], "asin": [(lambda x: True, "ArcSin")], "acos": [(lambda x: True, "ArcCos")], "atan": [(lambda x: True, "ArcTan")], "acot": [(lambda x: True, "ArcCot")], "asec": [(lambda x: True, "ArcSec")], "acsc": [(lambda x: True, "ArcCsc")], "atan2": [(lambda x: True, "ArcTan")], "sinh": [(lambda x: True, "Sinh")], "cosh": [(lambda x: True, "Cosh")], "tanh": [(lambda x: True, "Tanh")], "coth": [(lambda x: True, "Coth")], "sech": [(lambda x: True, "Sech")], "csch": [(lambda x: True, "Csch")], "asinh": [(lambda x: True, "ArcSinh")], "acosh": [(lambda x: True, "ArcCosh")], "atanh": [(lambda x: True, "ArcTanh")], "acoth": [(lambda x: True, "ArcCoth")], "asech": [(lambda x: True, "ArcSech")], "acsch": [(lambda x: True, "ArcCsch")], "conjugate": [(lambda x: True, "Conjugate")], "Max": [(lambda x: True, "Max")], "Min": [(lambda x: True, "Min")], "erf": [(lambda x: True, "Erf")], "erf2": [(lambda x: True, "Erf")], "erfc": [(lambda x: True, "Erfc")], "erfi": [(lambda x: True, "Erfi")], "erfinv": [(lambda x: True, "InverseErf")], "erfcinv": [(lambda x: True, "InverseErfc")], "erf2inv": [(lambda x: True, "InverseErf")], "expint": [(lambda x: True, "ExpIntegralE")], "Ei": [(lambda x: True, "ExpIntegralEi")], "fresnelc": [(lambda x: True, "FresnelC")], "fresnels": [(lambda x: True, "FresnelS")], "gamma": [(lambda x: True, "Gamma")], "uppergamma": [(lambda x: True, "Gamma")], "polygamma": [(lambda x: True, "PolyGamma")], "loggamma": [(lambda x: True, "LogGamma")], "beta": [(lambda x: True, "Beta")], "Ci": [(lambda x: True, "CosIntegral")], "Si": [(lambda x: True, "SinIntegral")], "Chi": [(lambda x: True, "CoshIntegral")], "Shi": [(lambda x: True, "SinhIntegral")], "li": [(lambda x: True, "LogIntegral")], "factorial": [(lambda x: True, "Factorial")], "factorial2": [(lambda x: True, "Factorial2")], "subfactorial": [(lambda x: True, "Subfactorial")], "catalan": [(lambda x: True, "CatalanNumber")], "harmonic": [(lambda x: True, "HarmonicNumber")], "RisingFactorial": [(lambda x: True, "Pochhammer")], "FallingFactorial": [(lambda x: True, "FactorialPower")], "laguerre": [(lambda x: True, "LaguerreL")], "assoc_laguerre": [(lambda x: True, "LaguerreL")], "hermite": [(lambda x: True, "HermiteH")], "jacobi": [(lambda x: True, "JacobiP")], "gegenbauer": [(lambda x: True, "GegenbauerC")], "chebyshevt": [(lambda x: True, "ChebyshevT")], "chebyshevu": [(lambda x: True, "ChebyshevU")], "legendre": [(lambda x: True, "LegendreP")], "assoc_legendre": [(lambda x: True, "LegendreP")], "mathieuc": [(lambda x: True, "MathieuC")], "mathieus": [(lambda x: True, "MathieuS")], "mathieucprime": [(lambda x: True, "MathieuCPrime")], "mathieusprime": [(lambda x: True, "MathieuSPrime")], "stieltjes": [(lambda x: True, "StieltjesGamma")], "elliptic_e": [(lambda x: True, "EllipticE")], "elliptic_f": [(lambda x: True, "EllipticE")], "elliptic_k": [(lambda x: True, "EllipticK")], "elliptic_pi": [(lambda x: True, "EllipticPi")], "zeta": [(lambda x: True, "Zeta")], "besseli": [(lambda x: True, "BesselI")], "besselj": [(lambda x: True, "BesselJ")], "besselk": [(lambda x: True, "BesselK")], "bessely": [(lambda x: True, "BesselY")], "hankel1": [(lambda x: True, "HankelH1")], "hankel2": [(lambda x: True, "HankelH2")], "airyai": [(lambda x: True, "AiryAi")], "airybi": [(lambda x: True, "AiryBi")], "airyaiprime": [(lambda x: True, "AiryAiPrime")], "airybiprime": [(lambda x: True, "AiryBiPrime")], "polylog": [(lambda x: True, "PolyLog")], "lerchphi": [(lambda x: True, "LerchPhi")], "gcd": [(lambda x: True, "GCD")], "lcm": [(lambda x: True, "LCM")], "jn": [(lambda x: True, "SphericalBesselJ")], "yn": [(lambda x: True, "SphericalBesselY")], "hyper": [(lambda x: True, "HypergeometricPFQ")], "meijerg": [(lambda x: True, "MeijerG")], "appellf1": [(lambda x: True, "AppellF1")], "DiracDelta": [(lambda x: True, "DiracDelta")], "Heaviside": [(lambda x: True, "HeavisideTheta")], "KroneckerDelta": [(lambda x: True, "KroneckerDelta")], } class MCodePrinter(CodePrinter): """A printer to convert python expressions to strings of the Wolfram's Mathematica code """ printmethod = "_mcode" language = "Wolfram Language" _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 15, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, } # type: Dict[str, Any] _number_symbols = set() # type: Set[Tuple[Expr, Float]] _not_supported = set() # type: Set[Basic] def __init__(self, settings={}): """Register function mappings supplied by user""" CodePrinter.__init__(self, settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}).copy() for k, v in userfuncs.items(): if not isinstance(v, list): userfuncs[k] = [(lambda x: True, v)] self.known_functions.update(userfuncs) def _format_code(self, lines): return lines def _print_Pow(self, expr): PREC = precedence(expr) return '%s^%s' % (self.parenthesize(expr.base, PREC), self.parenthesize(expr.exp, PREC)) def _print_Mul(self, expr): PREC = precedence(expr) c, nc = expr.args_cnc() res = super()._print_Mul(expr.func(c)) if nc: res += '' res += '*'.join(self.parenthesize(a, PREC) for a in nc) return res def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) # Primitive numbers def _print_Zero(self, expr): return '0' def _print_One(self, expr): return '1' def _print_NegativeOne(self, expr): return '-1' def _print_Half(self, expr): return '1/2' def _print_ImaginaryUnit(self, expr): return 'I' # Infinity and invalid numbers def _print_Infinity(self, expr): return 'Infinity' def _print_NegativeInfinity(self, expr): return '-Infinity' def _print_ComplexInfinity(self, expr): return 'ComplexInfinity' def _print_NaN(self, expr): return 'Indeterminate' # Mathematical constants def _print_Exp1(self, expr): return 'E' def _print_Pi(self, expr): return 'Pi' def _print_GoldenRatio(self, expr): return 'GoldenRatio' def _print_TribonacciConstant(self, expr): expanded = expr.expand(func=True) PREC = precedence(expr) return self.parenthesize(expanded, PREC) def _print_EulerGamma(self, expr): return 'EulerGamma' def _print_Catalan(self, expr): return 'Catalan' def _print_list(self, expr): return '{' + ', '.join(self.doprint(a) for a in expr) + '}' _print_tuple = _print_list _print_Tuple = _print_list def _print_ImmutableDenseMatrix(self, expr): return self.doprint(expr.tolist()) def _print_ImmutableSparseMatrix(self, expr): from sympy.core.compatibility import default_sort_key def print_rule(pos, val): return '{} -> {}'.format( self.doprint((pos[0]+1, pos[1]+1)), self.doprint(val)) def print_data(): items = sorted(expr._smat.items(), key=default_sort_key) return '{' + \ ', '.join(print_rule(k, v) for k, v in items) + \ '}' def print_dims(): return self.doprint(expr.shape) return 'SparseArray[{}, {}]'.format(print_data(), print_dims()) def _print_ImmutableDenseNDimArray(self, expr): return self.doprint(expr.tolist()) def _print_ImmutableSparseNDimArray(self, expr): def print_string_list(string_list): return '{' + ', '.join(a for a in string_list) + '}' def to_mathematica_index(args): """Helper function to change Python style indexing to Pathematica indexing. Python indexing (0, 1 ... n-1) -> Mathematica indexing (1, 2 ... n) """ return tuple(i + 1 for i in args) def print_rule(pos, val): """Helper function to print a rule of Mathematica""" return '{} -> {}'.format(self.doprint(pos), self.doprint(val)) def print_data(): """Helper function to print data part of Mathematica sparse array. It uses the fourth notation ``SparseArray[data,{d1,d2,...}]`` from https://reference.wolfram.com/language/ref/SparseArray.html ``data`` must be formatted with rule. """ return print_string_list( [print_rule( to_mathematica_index((expr._get_tuple_index(key))), value) for key, value in sorted(expr._sparse_array.items())] ) def print_dims(): """Helper function to print dimensions part of Mathematica sparse array. It uses the fourth notation ``SparseArray[data,{d1,d2,...}]`` from https://reference.wolfram.com/language/ref/SparseArray.html """ return self.doprint(expr.shape) return 'SparseArray[{}, {}]'.format(print_data(), print_dims()) def _print_Function(self, expr): if expr.func.__name__ in self.known_functions: cond_mfunc = self.known_functions[expr.func.__name__] for cond, mfunc in cond_mfunc: if cond(expr.args): return "%s[%s]" % (mfunc, self.stringify(expr.args, ", ")) elif (expr.func.__name__ in self._rewriteable_functions and self._rewriteable_functions[expr.func.__name__] in self.known_functions): # Simple rewrite to supported function possible return self._print(expr.rewrite(self._rewriteable_functions[expr.func.__name__])) return expr.func.__name__ + "[%s]" % self.stringify(expr.args, ", ") _print_MinMaxBase = _print_Function def _print_LambertW(self, expr): if len(expr.args) == 1: return "ProductLog[{}]".format(self._print(expr.args[0])) return "ProductLog[{}, {}]".format( self._print(expr.args[1]), self._print(expr.args[0])) def _print_Integral(self, expr): if len(expr.variables) == 1 and not expr.limits[0][1:]: args = [expr.args[0], expr.variables[0]] else: args = expr.args return "Hold[Integrate[" + ', '.join(self.doprint(a) for a in args) + "]]" def _print_Sum(self, expr): return "Hold[Sum[" + ', '.join(self.doprint(a) for a in expr.args) + "]]" def _print_Derivative(self, expr): dexpr = expr.expr dvars = [i[0] if i[1] == 1 else i for i in expr.variable_count] return "Hold[D[" + ', '.join(self.doprint(a) for a in [dexpr] + dvars) + "]]" def _get_comment(self, text): return "(* {} )".format(text) def mathematica_code(expr, settings): r"""Converts an expr to a string of the Wolfram Mathematica code Examples ======== >>> from sympy import mathematica_code as mcode, symbols, sin >>> x = symbols('x') >>> mcode(sin(x).series(x).removeO()) '(1/120)x^5 - 1/6*x^3 + x' """ return MCodePrinter(settings).doprint(expr)
4c4d60548399b611a0a8fafcf738e5d0db6fb629d78253cd25a227b2c8e67c28	""" Fortran code printer The FCodePrinter converts single sympy expressions into single Fortran expressions, using the functions defined in the Fortran 77 standard where possible. Some useful pointers to Fortran can be found on wikipedia: https://en.wikipedia.org/wiki/Fortran Most of the code below is based on the "Professional Programmer\'s Guide to Fortran77" by Clive G. Page: http://www.star.le.ac.uk/~cgp/prof77.html Fortran is a case-insensitive language. This might cause trouble because SymPy is case sensitive. So, fcode adds underscores to variable names when it is necessary to make them different for Fortran. """ from typing import Dict, Any from collections import defaultdict from itertools import chain import string from sympy.codegen.ast import ( Assignment, Declaration, Pointer, value_const, float32, float64, float80, complex64, complex128, int8, int16, int32, int64, intc, real, integer, bool_, complex_ ) from sympy.codegen.fnodes import ( allocatable, isign, dsign, cmplx, merge, literal_dp, elemental, pure, intent_in, intent_out, intent_inout ) from sympy.core import S, Add, N, Float, Symbol from sympy.core.function import Function from sympy.core.relational import Eq from sympy.sets import Range from sympy.printing.codeprinter import CodePrinter from sympy.printing.precedence import precedence, PRECEDENCE from sympy.printing.printer import printer_context # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import fcode, print_fcode # noqa:F401 known_functions = { "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "log": "log", "exp": "exp", "erf": "erf", "Abs": "abs", "conjugate": "conjg", "Max": "max", "Min": "min", } class FCodePrinter(CodePrinter): """A printer to convert sympy expressions to strings of Fortran code""" printmethod = "_fcode" language = "Fortran" type_aliases = { integer: int32, real: float64, complex_: complex128, } type_mappings = { intc: 'integer(c_int)', float32: 'real4', # real(kind(0.e0)) float64: 'real8', # real(kind(0.d0)) float80: 'real10', # real(kind(????)) complex64: 'complex8', complex128: 'complex16', int8: 'integer1', int16: 'integer2', int32: 'integer4', int64: 'integer8', bool_: 'logical' } type_modules = { intc: {'iso_c_binding': 'c_int'} } _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, 'source_format': 'fixed', 'contract': True, 'standard': 77, 'name_mangling' : True, } # type: Dict[str, Any] _operators = { 'and': '.and.', 'or': '.or.', 'xor': '.neqv.', 'equivalent': '.eqv.', 'not': '.not. ', } _relationals = { '!=': '/=', } def __init__(self, settings=None): if not settings: settings = {} self.mangled_symbols = {} # Dict showing mapping of all words self.used_name = [] self.type_aliases = dict(chain(self.type_aliases.items(), settings.pop('type_aliases', {}).items())) self.type_mappings = dict(chain(self.type_mappings.items(), settings.pop('type_mappings', {}).items())) super().__init__(settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}) self.known_functions.update(userfuncs) # leading columns depend on fixed or free format standards = {66, 77, 90, 95, 2003, 2008} if self._settings['standard'] not in standards: raise ValueError("Unknown Fortran standard: %s" % self._settings[ 'standard']) self.module_uses = defaultdict(set) # e.g.: use iso_c_binding, only: c_int @property def _lead(self): if self._settings['source_format'] == 'fixed': return {'code': " ", 'cont': " @ ", 'comment': "C "} elif self._settings['source_format'] == 'free': return {'code': "", 'cont': " ", 'comment': "! "} else: raise ValueError("Unknown source format: %s" % self._settings['source_format']) def _print_Symbol(self, expr): if self._settings['name_mangling'] == True: if expr not in self.mangled_symbols: name = expr.name while name.lower() in self.used_name: name += '_' self.used_name.append(name.lower()) if name == expr.name: self.mangled_symbols[expr] = expr else: self.mangled_symbols[expr] = Symbol(name) expr = expr.xreplace(self.mangled_symbols) name = super()._print_Symbol(expr) return name def _rate_index_position(self, p): return -p5 def _get_statement(self, codestring): return codestring def _get_comment(self, text): return "! {}".format(text) def _declare_number_const(self, name, value): return "parameter ({} = {})".format(name, self._print(value)) def _print_NumberSymbol(self, expr): # A Number symbol that is not implemented here or with _printmethod # is registered and evaluated self._number_symbols.add((expr, Float(expr.evalf(self._settings['precision'])))) return str(expr) def _format_code(self, lines): return self._wrap_fortran(self.indent_code(lines)) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for j in range(cols) for i in range(rows)) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] for i in indices: # fortran arrays start at 1 and end at dimension var, start, stop = map(self._print, [i.label, i.lower + 1, i.upper + 1]) open_lines.append("do %s = %s, %s" % (var, start, stop)) close_lines.append("end do") return open_lines, close_lines def _print_sign(self, expr): from sympy import Abs arg, = expr.args if arg.is_integer: new_expr = merge(0, isign(1, arg), Eq(arg, 0)) elif (arg.is_complex or arg.is_infinite): new_expr = merge(cmplx(literal_dp(0), literal_dp(0)), arg/Abs(arg), Eq(Abs(arg), literal_dp(0))) else: new_expr = merge(literal_dp(0), dsign(literal_dp(1), arg), Eq(arg, literal_dp(0))) return self._print(new_expr) def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] if expr.has(Assignment): for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) then" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines.append("else") else: lines.append("else if (%s) then" % self._print(c)) lines.append(self._print(e)) lines.append("end if") return "\n".join(lines) elif self._settings["standard"] >= 95: # Only supported in F95 and newer: # The piecewise was used in an expression, need to do inline # operators. This has the downside that inline operators will # not work for statements that span multiple lines (Matrix or # Indexed expressions). pattern = "merge({T}, {F}, {COND})" code = self._print(expr.args[-1].expr) terms = list(expr.args[:-1]) while terms: e, c = terms.pop() expr = self._print(e) cond = self._print(c) code = pattern.format(T=expr, F=code, COND=cond) return code else: # `merge` is not supported prior to F95 raise NotImplementedError("Using Piecewise as an expression using " "inline operators is not supported in " "standards earlier than Fortran95.") def _print_MatrixElement(self, expr): return "{}({}, {})".format(self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True), expr.i + 1, expr.j + 1) def _print_Add(self, expr): # purpose: print complex numbers nicely in Fortran. # collect the purely real and purely imaginary parts: pure_real = [] pure_imaginary = [] mixed = [] for arg in expr.args: if arg.is_number and arg.is_real: pure_real.append(arg) elif arg.is_number and arg.is_imaginary: pure_imaginary.append(arg) else: mixed.append(arg) if pure_imaginary: if mixed: PREC = precedence(expr) term = Add(mixed) t = self._print(term) if t.startswith('-'): sign = "-" t = t[1:] else: sign = "+" if precedence(term) < PREC: t = "(%s)" % t return "cmplx(%s,%s) %s %s" % ( self._print(Add(pure_real)), self._print(-S.ImaginaryUnitAdd(pure_imaginary)), sign, t, ) else: return "cmplx(%s,%s)" % ( self._print(Add(pure_real)), self._print(-S.ImaginaryUnitAdd(pure_imaginary)), ) else: return CodePrinter._print_Add(self, expr) def _print_Function(self, expr): # All constant function args are evaluated as floats prec = self._settings['precision'] args = [N(a, prec) for a in expr.args] eval_expr = expr.func(args) if not isinstance(eval_expr, Function): return self._print(eval_expr) else: return CodePrinter._print_Function(self, expr.func(args)) def _print_Mod(self, expr): # NOTE : Fortran has the functions mod() and modulo(). modulo() behaves # the same wrt to the sign of the arguments as Python and SymPy's # modulus computations (% and Mod()) but is not available in Fortran 66 # or Fortran 77, thus we raise an error. if self._settings['standard'] in [66, 77]: msg = ("Python % operator and SymPy's Mod() function are not " "supported by Fortran 66 or 77 standards.") raise NotImplementedError(msg) else: x, y = expr.args return " modulo({}, {})".format(self._print(x), self._print(y)) def _print_ImaginaryUnit(self, expr): # purpose: print complex numbers nicely in Fortran. return "cmplx(0,1)" def _print_int(self, expr): return str(expr) def _print_Mul(self, expr): # purpose: print complex numbers nicely in Fortran. if expr.is_number and expr.is_imaginary: return "cmplx(0,%s)" % ( self._print(-S.ImaginaryUnitexpr) ) else: return CodePrinter._print_Mul(self, expr) def _print_Pow(self, expr): PREC = precedence(expr) if expr.exp == -1: return '%s/%s' % ( self._print(literal_dp(1)), self.parenthesize(expr.base, PREC) ) elif expr.exp == 0.5: if expr.base.is_integer: # Fortran intrinsic sqrt() does not accept integer argument if expr.base.is_Number: return 'sqrt(%s.0d0)' % self._print(expr.base) else: return 'sqrt(dble(%s))' % self._print(expr.base) else: return 'sqrt(%s)' % self._print(expr.base) else: return CodePrinter._print_Pow(self, expr) def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) return "%d.0d0/%d.0d0" % (p, q) def _print_Float(self, expr): printed = CodePrinter._print_Float(self, expr) e = printed.find('e') if e > -1: return "%sd%s" % (printed[:e], printed[e + 1:]) return "%sd0" % printed def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op op = op if op not in self._relationals else self._relationals[op] return "{} {} {}".format(lhs_code, op, rhs_code) def _print_Indexed(self, expr): inds = [ self._print(i) for i in expr.indices ] return "%s(%s)" % (self._print(expr.base.label), ", ".join(inds)) def _print_Idx(self, expr): return self._print(expr.label) def _print_AugmentedAssignment(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) return self._get_statement("{0} = {0} {1} {2}".format( map(lambda arg: self._print(arg), [lhs_code, expr.binop, rhs_code]))) def _print_sum_(self, sm): params = self._print(sm.array) if sm.dim != None: # Must use '!= None', cannot use 'is not None' params += ', ' + self._print(sm.dim) if sm.mask != None: # Must use '!= None', cannot use 'is not None' params += ', mask=' + self._print(sm.mask) return '%s(%s)' % (sm.__class__.__name__.rstrip('_'), params) def _print_product_(self, prod): return self._print_sum_(prod) def _print_Do(self, do): excl = ['concurrent'] if do.step == 1: excl.append('step') step = '' else: step = ', {step}' return ( 'do {concurrent}{counter} = {first}, {last}'+step+'\n' '{body}\n' 'end do\n' ).format( concurrent='concurrent ' if do.concurrent else '', do.kwargs(apply=lambda arg: self._print(arg), exclude=excl) ) def _print_ImpliedDoLoop(self, idl): step = '' if idl.step == 1 else ', {step}' return ('({expr}, {counter} = {first}, {last}'+step+')').format( idl.kwargs(apply=lambda arg: self._print(arg)) ) def _print_For(self, expr): target = self._print(expr.target) if isinstance(expr.iterable, Range): start, stop, step = expr.iterable.args else: raise NotImplementedError("Only iterable currently supported is Range") body = self._print(expr.body) return ('do {target} = {start}, {stop}, {step}\n' '{body}\n' 'end do').format(target=target, start=start, stop=stop, step=step, body=body) def _print_Type(self, type_): type_ = self.type_aliases.get(type_, type_) type_str = self.type_mappings.get(type_, type_.name) module_uses = self.type_modules.get(type_) if module_uses: for k, v in module_uses: self.module_uses[k].add(v) return type_str def _print_Element(self, elem): return '{symbol}({idxs})'.format( symbol=self._print(elem.symbol), idxs=', '.join(map(lambda arg: self._print(arg), elem.indices)) ) def _print_Extent(self, ext): return str(ext) def _print_Declaration(self, expr): var = expr.variable val = var.value dim = var.attr_params('dimension') intents = [intent in var.attrs for intent in (intent_in, intent_out, intent_inout)] if intents.count(True) == 0: intent = '' elif intents.count(True) == 1: intent = ', intent(%s)' % ['in', 'out', 'inout'][intents.index(True)] else: raise ValueError("Multiple intents specified for %s" % self) if isinstance(var, Pointer): raise NotImplementedError("Pointers are not available by default in Fortran.") if self._settings["standard"] >= 90: result = '{t}{vc}{dim}{intent}{alloc} :: {s}'.format( t=self._print(var.type), vc=', parameter' if value_const in var.attrs else '', dim=', dimension(%s)' % ', '.join(map(lambda arg: self._print(arg), dim)) if dim else '', intent=intent, alloc=', allocatable' if allocatable in var.attrs else '', s=self._print(var.symbol) ) if val != None: # Must be "!= None", cannot be "is not None" result += ' = %s' % self._print(val) else: if value_const in var.attrs or val: raise NotImplementedError("F77 init./parameter statem. req. multiple lines.") result = ' '.join(map(lambda arg: self._print(arg), [var.type, var.symbol])) return result def _print_Infinity(self, expr): return '(huge(%s) + 1)' % self._print(literal_dp(0)) def _print_While(self, expr): return 'do while ({condition})\n{body}\nend do'.format(expr.kwargs( apply=lambda arg: self._print(arg))) def _print_BooleanTrue(self, expr): return '.true.' def _print_BooleanFalse(self, expr): return '.false.' def _pad_leading_columns(self, lines): result = [] for line in lines: if line.startswith('!'): result.append(self._lead['comment'] + line[1:].lstrip()) else: result.append(self._lead['code'] + line) return result def _wrap_fortran(self, lines): """Wrap long Fortran lines Argument: lines -- a list of lines (without \\n character) A comment line is split at white space. Code lines are split with a more complex rule to give nice results. """ # routine to find split point in a code line my_alnum = set("_+-." + string.digits + string.ascii_letters) my_white = set(" \t()") def split_pos_code(line, endpos): if len(line) <= endpos: return len(line) pos = endpos split = lambda pos: \ (line[pos] in my_alnum and line[pos - 1] not in my_alnum) or \ (line[pos] not in my_alnum and line[pos - 1] in my_alnum) or \ (line[pos] in my_white and line[pos - 1] not in my_white) or \ (line[pos] not in my_white and line[pos - 1] in my_white) while not split(pos): pos -= 1 if pos == 0: return endpos return pos # split line by line and add the split lines to result result = [] if self._settings['source_format'] == 'free': trailing = ' &' else: trailing = '' for line in lines: if line.startswith(self._lead['comment']): # comment line if len(line) > 72: pos = line.rfind(" ", 6, 72) if pos == -1: pos = 72 hunk = line[:pos] line = line[pos:].lstrip() result.append(hunk) while line: pos = line.rfind(" ", 0, 66) if pos == -1 or len(line) < 66: pos = 66 hunk = line[:pos] line = line[pos:].lstrip() result.append("%s%s" % (self._lead['comment'], hunk)) else: result.append(line) elif line.startswith(self._lead['code']): # code line pos = split_pos_code(line, 72) hunk = line[:pos].rstrip() line = line[pos:].lstrip() if line: hunk += trailing result.append(hunk) while line: pos = split_pos_code(line, 65) hunk = line[:pos].rstrip() line = line[pos:].lstrip() if line: hunk += trailing result.append("%s%s" % (self._lead['cont'], hunk)) else: result.append(line) return result def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) free = self._settings['source_format'] == 'free' code = [ line.lstrip(' \t') for line in code ] inc_keyword = ('do ', 'if(', 'if ', 'do\n', 'else', 'program', 'interface') dec_keyword = ('end do', 'enddo', 'end if', 'endif', 'else', 'end program', 'end interface') increase = [ int(any(map(line.startswith, inc_keyword))) for line in code ] decrease = [ int(any(map(line.startswith, dec_keyword))) for line in code ] continuation = [ int(any(map(line.endswith, ['&', '&\n']))) for line in code ] level = 0 cont_padding = 0 tabwidth = 3 new_code = [] for i, line in enumerate(code): if line == '' or line == '\n': new_code.append(line) continue level -= decrease[i] if free: padding = " "(leveltabwidth + cont_padding) else: padding = " "leveltabwidth line = "%s%s" % (padding, line) if not free: line = self._pad_leading_columns([line])[0] new_code.append(line) if continuation[i]: cont_padding = 2tabwidth else: cont_padding = 0 level += increase[i] if not free: return self._wrap_fortran(new_code) return new_code def _print_GoTo(self, goto): if goto.expr: # computed goto return "go to ({labels}), {expr}".format( labels=', '.join(map(lambda arg: self._print(arg), goto.labels)), expr=self._print(goto.expr) ) else: lbl, = goto.labels return "go to %s" % self._print(lbl) def _print_Program(self, prog): return ( "program {name}\n" "{body}\n" "end program\n" ).format(prog.kwargs(apply=lambda arg: self._print(arg))) def _print_Module(self, mod): return ( "module {name}\n" "{declarations}\n" "\ncontains\n\n" "{definitions}\n" "end module\n" ).format(mod.kwargs(apply=lambda arg: self._print(arg))) def _print_Stream(self, strm): if strm.name == 'stdout' and self._settings["standard"] >= 2003: self.module_uses['iso_c_binding'].add('stdint=>input_unit') return 'input_unit' elif strm.name == 'stderr' and self._settings["standard"] >= 2003: self.module_uses['iso_c_binding'].add('stdint=>error_unit') return 'error_unit' else: if strm.name == 'stdout': return '' else: return strm.name def _print_Print(self, ps): if ps.format_string != None: # Must be '!= None', cannot be 'is not None' fmt = self._print(ps.format_string) else: fmt = "" return "print {fmt}, {iolist}".format(fmt=fmt, iolist=', '.join( map(lambda arg: self._print(arg), ps.print_args))) def _print_Return(self, rs): arg, = rs.args return "{result_name} = {arg}".format( result_name=self._context.get('result_name', 'sympy_result'), arg=self._print(arg) ) def _print_FortranReturn(self, frs): arg, = frs.args if arg: return 'return %s' % self._print(arg) else: return 'return' def _head(self, entity, fp, **kwargs): bind_C_params = fp.attr_params('bind_C') if bind_C_params is None: bind = '' else: bind = ' bind(C, name="%s")' % bind_C_params[0] if bind_C_params else ' bind(C)' result_name = self._settings.get('result_name', None) return ( "{entity}{name}({arg_names}){result}{bind}\n" "{arg_declarations}" ).format( entity=entity, name=self._print(fp.name), arg_names=', '.join([self._print(arg.symbol) for arg in fp.parameters]), result=(' result(%s)' % result_name) if result_name else '', bind=bind, arg_declarations='\n'.join(map(lambda arg: self._print(Declaration(arg)), fp.parameters)) ) def _print_FunctionPrototype(self, fp): entity = "{} function ".format(self._print(fp.return_type)) return ( "interface\n" "{function_head}\n" "end function\n" "end interface" ).format(function_head=self._head(entity, fp)) def _print_FunctionDefinition(self, fd): if elemental in fd.attrs: prefix = 'elemental ' elif pure in fd.attrs: prefix = 'pure ' else: prefix = '' entity = "{} function ".format(self._print(fd.return_type)) with printer_context(self, result_name=fd.name): return ( "{prefix}{function_head}\n" "{body}\n" "end function\n" ).format( prefix=prefix, function_head=self._head(entity, fd), body=self._print(fd.body) ) def _print_Subroutine(self, sub): return ( '{subroutine_head}\n' '{body}\n' 'end subroutine\n' ).format( subroutine_head=self._head('subroutine ', sub), body=self._print(sub.body) ) def _print_SubroutineCall(self, scall): return 'call {name}({args})'.format( name=self._print(scall.name), args=', '.join(map(lambda arg: self._print(arg), scall.subroutine_args)) ) def _print_use_rename(self, rnm): return "%s => %s" % tuple(map(lambda arg: self._print(arg), rnm.args)) def _print_use(self, use): result = 'use %s' % self._print(use.namespace) if use.rename != None: # Must be '!= None', cannot be 'is not None' result += ', ' + ', '.join([self._print(rnm) for rnm in use.rename]) if use.only != None: # Must be '!= None', cannot be 'is not None' result += ', only: ' + ', '.join([self._print(nly) for nly in use.only]) return result def _print_BreakToken(self, _): return 'exit' def _print_ContinueToken(self, _): return 'cycle' def _print_ArrayConstructor(self, ac): fmtstr = "[%s]" if self._settings["standard"] >= 2003 else '(/%s/)' return fmtstr % ', '.join(map(lambda arg: self._print(arg), ac.elements))

7dc3f64ff52293a7ebb9c91d48b9f2ba54c63fe24eb7a9cb754054e7c085c94f

import sys sys._running_pytest = True # type: ignore from distutils.version import LooseVersion as V import pytest from sympy.core.cache import clear_cache import re sp = re.compile(r'([0-9]+)/([1-9][0-9]*)') def process_split(config, items): split = config.getoption("--split") if not split: return m = sp.match(split) if not m: raise ValueError("split must be a string of the form a/b " "where a and b are ints.") i, t = map(int, m.groups()) start, end = (i-1)*len(items)//t, i*len(items)//t if i < t: # remove elements from end of list first del items[end:] del items[:start] def pytest_report_header(config): from sympy.utilities.misc import ARCH s = "architecture: %s\n" % ARCH from sympy.core.cache import USE_CACHE s += "cache: %s\n" % USE_CACHE from sympy.core.compatibility import GROUND_TYPES, HAS_GMPY version = '' if GROUND_TYPES =='gmpy': if HAS_GMPY == 1: import gmpy elif HAS_GMPY == 2: import gmpy2 as gmpy version = gmpy.version() s += "ground types: %s %s\n" % (GROUND_TYPES, version) return s def pytest_terminal_summary(terminalreporter): if (terminalreporter.stats.get('error', None) or terminalreporter.stats.get('failed', None)): terminalreporter.write_sep( ' ', 'DO *NOT* COMMIT!', red=True, bold=True) def pytest_addoption(parser): parser.addoption("--split", action="store", default="", help="split tests") def pytest_collection_modifyitems(config, items): """ pytest hook. """ # handle splits process_split(config, items) @pytest.fixture(autouse=True, scope='module') def file_clear_cache(): clear_cache() @pytest.fixture(autouse=True, scope='module') def check_disabled(request): if getattr(request.module, 'disabled', False): pytest.skip("test requirements not met.") elif getattr(request.module, 'ipython', False): # need to check version and options for ipython tests if (V(pytest.__version__) < '2.6.3' and pytest.config.getvalue('-s') != 'no'): pytest.skip("run py.test with -s or upgrade to newer version.")

3861d7ed5195f05f9d07f5161360ab694893a1a257001f9ef7325324f49c060f

__version__ = "1.8.dev"

c41b6ec7cd8316a22cefcbd855c0f976935539297e72afdaebb464ed84ee2d1a

""" This module exports all latin and greek letters as Symbols, so you can conveniently do >>> from sympy.abc import x, y instead of the slightly more clunky-looking >>> from sympy import symbols >>> x, y = symbols('x y') Caveats ======= 1. As of the time of writing this, the names ``C``, ``O``, ``S``, ``I``, ``N``, ``E``, and ``Q`` are colliding with names defined in SymPy. If you import them from both ``sympy.abc`` and ``sympy``, the second import will "win". This is an issue only for * imports, which should only be used for short-lived code such as interactive sessions and throwaway scripts that do not survive until the next SymPy upgrade, where ``sympy`` may contain a different set of names. 2. This module does not define symbol names on demand, i.e. ``from sympy.abc import foo`` will be reported as an error because ``sympy.abc`` does not contain the name ``foo``. To get a symbol named ``foo``, you still need to use ``Symbol('foo')`` or ``symbols('foo')``. You can freely mix usage of ``sympy.abc`` and ``Symbol``/``symbols``, though sticking with one and only one way to get the symbols does tend to make the code more readable. The module also defines some special names to help detect which names clash with the default SymPy namespace. ``_clash1`` defines all the single letter variables that clash with SymPy objects; ``_clash2`` defines the multi-letter clashing symbols; and ``_clash`` is the union of both. These can be passed for ``locals`` during sympification if one desires Symbols rather than the non-Symbol objects for those names. Examples ======== >>> from sympy import S >>> from sympy.abc import _clash1, _clash2, _clash >>> S("Q & C", locals=_clash1) C & Q >>> S('pi(x)', locals=_clash2) pi(x) >>> S('pi(C, Q)', locals=_clash) pi(C, Q) """ from typing import Any, Dict import string from .core import Symbol, symbols from .core.alphabets import greeks from .core.compatibility import exec_ ##### Symbol definitions ##### # Implementation note: The easiest way to avoid typos in the symbols() # parameter is to copy it from the left-hand side of the assignment. a, b, c, d, e, f, g, h, i, j = symbols('a, b, c, d, e, f, g, h, i, j') k, l, m, n, o, p, q, r, s, t = symbols('k, l, m, n, o, p, q, r, s, t') u, v, w, x, y, z = symbols('u, v, w, x, y, z') A, B, C, D, E, F, G, H, I, J = symbols('A, B, C, D, E, F, G, H, I, J') K, L, M, N, O, P, Q, R, S, T = symbols('K, L, M, N, O, P, Q, R, S, T') U, V, W, X, Y, Z = symbols('U, V, W, X, Y, Z') alpha, beta, gamma, delta = symbols('alpha, beta, gamma, delta') epsilon, zeta, eta, theta = symbols('epsilon, zeta, eta, theta') iota, kappa, lamda, mu = symbols('iota, kappa, lamda, mu') nu, xi, omicron, pi = symbols('nu, xi, omicron, pi') rho, sigma, tau, upsilon = symbols('rho, sigma, tau, upsilon') phi, chi, psi, omega = symbols('phi, chi, psi, omega') ##### Clashing-symbols diagnostics ##### # We want to know which names in SymPy collide with those in here. # This is mostly for diagnosing SymPy's namespace during SymPy development. _latin = list(string.ascii_letters) # OSINEQ should not be imported as they clash; gamma, pi and zeta clash, too _greek = list(greeks) # make a copy, so we can mutate it # Note: We import lamda since lambda is a reserved keyword in Python _greek.remove("lambda") _greek.append("lamda") ns = {} # type: Dict[str, Any] exec_('from sympy import *', ns) _clash1 = {} _clash2 = {} while ns: _k, _ = ns.popitem() if _k in _greek: _clash2[_k] = Symbol(_k) _greek.remove(_k) elif _k in _latin: _clash1[_k] = Symbol(_k) _latin.remove(_k) _clash = {} _clash.update(_clash1) _clash.update(_clash2) del _latin, _greek, Symbol, _k

cd11e92bdc44b45374069b191a3ce010b0c0cd7bb98d9836b8900c8138101ecc

""" Continuous Random Variables - Prebuilt variables Contains ======== Arcsin Benini Beta BetaNoncentral BetaPrime BoundedPareto Cauchy Chi ChiNoncentral ChiSquared Dagum Erlang ExGaussian Exponential ExponentialPower FDistribution FisherZ Frechet Gamma GammaInverse Gumbel Gompertz Kumaraswamy Laplace Levy Logistic LogLogistic LogNormal Lomax Maxwell Moyal Nakagami Normal Pareto PowerFunction QuadraticU RaisedCosine Rayleigh Reciprocal ShiftedGompertz StudentT Trapezoidal Triangular Uniform UniformSum VonMises Wald Weibull WignerSemicircle """ from sympy import beta as beta_fn from sympy import cos, sin, tan, atan, exp, besseli, besselj, besselk from sympy import (log, sqrt, pi, S, Dummy, Interval, sympify, gamma, sign, Piecewise, And, Eq, binomial, factorial, Sum, floor, Abs, Lambda, Basic, lowergamma, erf, erfc, erfi, erfinv, I, asin, hyper, uppergamma, sinh, Ne, expint, Rational, integrate) from sympy.matrices import MatrixBase, MatrixExpr from sympy.stats.crv import SingleContinuousPSpace, SingleContinuousDistribution from sympy.stats.rv import _value_check, is_random oo = S.Infinity __all__ = ['ContinuousRV', 'Arcsin', 'Benini', 'Beta', 'BetaNoncentral', 'BetaPrime', 'BoundedPareto', 'Cauchy', 'Chi', 'ChiNoncentral', 'ChiSquared', 'Dagum', 'Erlang', 'ExGaussian', 'Exponential', 'ExponentialPower', 'FDistribution', 'FisherZ', 'Frechet', 'Gamma', 'GammaInverse', 'Gompertz', 'Gumbel', 'Kumaraswamy', 'Laplace', 'Levy', 'Logistic', 'LogLogistic', 'LogNormal', 'Lomax', 'Maxwell', 'Moyal', 'Nakagami', 'Normal', 'GaussianInverse', 'Pareto', 'PowerFunction', 'QuadraticU', 'RaisedCosine', 'Rayleigh', 'Reciprocal', 'StudentT', 'ShiftedGompertz', 'Trapezoidal', 'Triangular', 'Uniform', 'UniformSum', 'VonMises', 'Wald', 'Weibull', 'WignerSemicircle', ] @is_random.register(MatrixBase) def _(x): return any([is_random(i) for i in x]) def rv(symbol, cls, args, **kwargs): args = list(map(sympify, args)) dist = cls(*args) if kwargs.pop('check', True): dist.check(*args) pspace = SingleContinuousPSpace(symbol, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(symbol, CompoundDistribution(dist)) return pspace.value class ContinuousDistributionHandmade(SingleContinuousDistribution): _argnames = ('pdf',) def __new__(cls, pdf, set=Interval(-oo, oo)): return Basic.__new__(cls, pdf, set) @property def set(self): return self.args[1] @staticmethod def check(pdf, set): x = Dummy('x') val = integrate(pdf(x), (x, set)) _value_check(Eq(val, 1) != S.false, "The pdf on the given set is incorrect.") def ContinuousRV(symbol, density, set=Interval(-oo, oo), **kwargs): """ Create a Continuous Random Variable given the following: Parameters ========== symbol : Symbol Represents name of the random variable. density : Expression containing symbol Represents probability density function. set : set/Interval Represents the region where the pdf is valid, by default is real line. check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Returns ======= RandomSymbol Many common continuous random variable types are already implemented. This function should be necessary only very rarely. Examples ======== >>> from sympy import Symbol, sqrt, exp, pi >>> from sympy.stats import ContinuousRV, P, E >>> x = Symbol("x") >>> pdf = sqrt(2)*exp(-x**2/2)/(2*sqrt(pi)) # Normal distribution >>> X = ContinuousRV(x, pdf) >>> E(X) 0 >>> P(X>0) 1/2 """ pdf = Piecewise((density, set.as_relational(symbol)), (0, True)) pdf = Lambda(symbol, pdf) # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(symbol.name, ContinuousDistributionHandmade, (pdf, set), **kwargs) ######################################## # Continuous Probability Distributions # ######################################## #------------------------------------------------------------------------------- # Arcsin distribution ---------------------------------------------------------- class ArcsinDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) def pdf(self, x): a, b = self.a, self.b return 1/(pi*sqrt((x - a)*(b - x))) def _cdf(self, x): a, b = self.a, self.b return Piecewise( (S.Zero, x < a), (2*asin(sqrt((x - a)/(b - a)))/pi, x <= b), (S.One, True)) def Arcsin(name, a=0, b=1): r""" Create a Continuous Random Variable with an arcsin distribution. The density of the arcsin distribution is given by .. math:: f(x) := \frac{1}{\pi\sqrt{(x-a)(b-x)}} with :math:`x \in (a,b)`. It must hold that :math:`-\infty < a >> from sympy.stats import Arcsin, density, cdf >>> from sympy import Symbol >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = Arcsin("x", a, b) >>> density(X)(z) 1/(pi*sqrt((-a + z)*(b - z))) >>> cdf(X)(z) Piecewise((0, a > z), (2*asin(sqrt((-a + z)/(-a + b)))/pi, b >= z), (1, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Arcsine_distribution """ return rv(name, ArcsinDistribution, (a, b)) #------------------------------------------------------------------------------- # Benini distribution ---------------------------------------------------------- class BeniniDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta', 'sigma') @staticmethod def check(alpha, beta, sigma): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") _value_check(sigma > 0, "Scale parameter Sigma must be positive.") @property def set(self): return Interval(self.sigma, oo) def pdf(self, x): alpha, beta, sigma = self.alpha, self.beta, self.sigma return (exp(-alpha*log(x/sigma) - beta*log(x/sigma)**2) *(alpha/x + 2*beta*log(x/sigma)/x)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function of the ' 'Benini distribution does not exist.') def Benini(name, alpha, beta, sigma): r""" Create a Continuous Random Variable with a Benini distribution. The density of the Benini distribution is given by .. math:: f(x) := e^{-\alpha\log{\frac{x}{\sigma}} -\beta\log^2\left[{\frac{x}{\sigma}}\right]} \left(\frac{\alpha}{x}+\frac{2\beta\log{\frac{x}{\sigma}}}{x}\right) This is a heavy-tailed distribution and is also known as the log-Rayleigh distribution. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape sigma : Real number, `\sigma > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Benini, density, cdf >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = Benini("x", alpha, beta, sigma) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / / z \\ / z \ 2/ z \ | 2*beta*log|-----|| - alpha*log|-----| - beta*log |-----| |alpha \sigma/| \sigma/ \sigma/ |----- + -----------------|*e \ z z / >>> cdf(X)(z) Piecewise((1 - exp(-alpha*log(z/sigma) - beta*log(z/sigma)**2), sigma <= z), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Benini_distribution .. [2] http://reference.wolfram.com/legacy/v8/ref/BeniniDistribution.html """ return rv(name, BeniniDistribution, (alpha, beta, sigma)) #------------------------------------------------------------------------------- # Beta distribution ------------------------------------------------------------ class BetaDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, 1) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") def pdf(self, x): alpha, beta = self.alpha, self.beta return x**(alpha - 1) * (1 - x)**(beta - 1) / beta_fn(alpha, beta) def _characteristic_function(self, t): return hyper((self.alpha,), (self.alpha + self.beta,), I*t) def _moment_generating_function(self, t): return hyper((self.alpha,), (self.alpha + self.beta,), t) def Beta(name, alpha, beta): r""" Create a Continuous Random Variable with a Beta distribution. The density of the Beta distribution is given by .. math:: f(x) := \frac{x^{\alpha-1}(1-x)^{\beta-1}} {\mathrm{B}(\alpha,\beta)} with :math:`x \in [0,1]`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Beta, density, E, variance >>> from sympy import Symbol, simplify, pprint, factor >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = Beta("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) alpha - 1 beta - 1 z *(1 - z) -------------------------- B(alpha, beta) >>> simplify(E(X)) alpha/(alpha + beta) >>> factor(simplify(variance(X))) alpha*beta/((alpha + beta)**2*(alpha + beta + 1)) References ========== .. [1] https://en.wikipedia.org/wiki/Beta_distribution .. [2] http://mathworld.wolfram.com/BetaDistribution.html """ return rv(name, BetaDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Noncentral Beta distribution ------------------------------------------------------------ class BetaNoncentralDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta', 'lamda') set = Interval(0, 1) @staticmethod def check(alpha, beta, lamda): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") _value_check(lamda >= 0, "Noncentrality parameter Lambda must be positive") def pdf(self, x): alpha, beta, lamda = self.alpha, self.beta, self.lamda k = Dummy("k") return Sum(exp(-lamda / 2) * (lamda / 2)**k * x**(alpha + k - 1) *( 1 - x)**(beta - 1) / (factorial(k) * beta_fn(alpha + k, beta)), (k, 0, oo)) def BetaNoncentral(name, alpha, beta, lamda): r""" Create a Continuous Random Variable with a Type I Noncentral Beta distribution. The density of the Noncentral Beta distribution is given by .. math:: f(x) := \sum_{k=0}^\infty e^{-\lambda/2}\frac{(\lambda/2)^k}{k!} \frac{x^{\alpha+k-1}(1-x)^{\beta-1}}{\mathrm{B}(\alpha+k,\beta)} with :math:`x \in [0,1]`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape lamda: Real number, `\lambda >= 0`, noncentrality parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import BetaNoncentral, density, cdf >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> lamda = Symbol("lamda", nonnegative=True) >>> z = Symbol("z") >>> X = BetaNoncentral("x", alpha, beta, lamda) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) oo _____ \ ` \ -lamda \ k ------- \ k + alpha - 1 /lamda\ beta - 1 2 ) z *|-----| *(1 - z) *e / \ 2 / / ------------------------------------------------ / B(k + alpha, beta)*k! /____, k = 0 Compute cdf with specific 'x', 'alpha', 'beta' and 'lamda' values as follows : >>> cdf(BetaNoncentral("x", 1, 1, 1), evaluate=False)(2).doit() 2*exp(1/2) The argument evaluate=False prevents an attempt at evaluation of the sum for general x, before the argument 2 is passed. References ========== .. [1] https://en.wikipedia.org/wiki/Noncentral_beta_distribution .. [2] https://reference.wolfram.com/language/ref/NoncentralBetaDistribution.html """ return rv(name, BetaNoncentralDistribution, (alpha, beta, lamda)) #------------------------------------------------------------------------------- # Beta prime distribution ------------------------------------------------------ class BetaPrimeDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Shape parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") set = Interval(0, oo) def pdf(self, x): alpha, beta = self.alpha, self.beta return x**(alpha - 1)*(1 + x)**(-alpha - beta)/beta_fn(alpha, beta) def BetaPrime(name, alpha, beta): r""" Create a continuous random variable with a Beta prime distribution. The density of the Beta prime distribution is given by .. math:: f(x) := \frac{x^{\alpha-1} (1+x)^{-\alpha -\beta}}{B(\alpha,\beta)} with :math:`x > 0`. Parameters ========== alpha : Real number, `\alpha > 0`, a shape beta : Real number, `\beta > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import BetaPrime, density >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = BetaPrime("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) alpha - 1 -alpha - beta z *(z + 1) ------------------------------- B(alpha, beta) References ========== .. [1] https://en.wikipedia.org/wiki/Beta_prime_distribution .. [2] http://mathworld.wolfram.com/BetaPrimeDistribution.html """ return rv(name, BetaPrimeDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Bounded Pareto Distribution -------------------------------------------------- class BoundedParetoDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'left', 'right') @property def set(self): return Interval(self.left , self.right) @staticmethod def check(alpha, left, right): _value_check (alpha.is_positive, "Shape must be positive.") _value_check (left.is_positive, "Left value should be positive.") _value_check (right > left, "Right should be greater than left.") def pdf(self, x): alpha, left, right = self.alpha, self.left, self.right num = alpha * (left**alpha) * x**(- alpha -1) den = 1 - (left/right)**alpha return num/den def BoundedPareto(name, alpha, left, right): r""" Create a continuous random variable with a Bounded Pareto distribution. The density of the Bounded Pareto distribution is given by .. math:: f(x) := \frac{\alpha L^{\alpha}x^{-\alpha-1}}{1-(\frac{L}{H})^{\alpha}} Parameters ========== alpha : Real Number, `alpha > 0` Shape parameter left : Real Number, `left > 0` Location parameter right : Real Number, `right > left` Location parameter Examples ======== >>> from sympy.stats import BoundedPareto, density, cdf, E >>> from sympy import symbols >>> L, H = symbols('L, H', positive=True) >>> X = BoundedPareto('X', 2, L, H) >>> x = symbols('x') >>> density(X)(x) 2*L**2/(x**3*(1 - L**2/H**2)) >>> cdf(X)(x) Piecewise((-H**2*L**2/(x**2*(H**2 - L**2)) + H**2/(H**2 - L**2), L <= x), (0, True)) >>> E(X).simplify() 2*H*L/(H + L) Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Pareto_distribution#Bounded_Pareto_distribution """ return rv (name, BoundedParetoDistribution, (alpha, left, right)) # ------------------------------------------------------------------------------ # Cauchy distribution ---------------------------------------------------------- class CauchyDistribution(SingleContinuousDistribution): _argnames = ('x0', 'gamma') @staticmethod def check(x0, gamma): _value_check(gamma > 0, "Scale parameter Gamma must be positive.") _value_check(x0.is_real, "Location parameter must be real.") def pdf(self, x): return 1/(pi*self.gamma*(1 + ((x - self.x0)/self.gamma)**2)) def _cdf(self, x): x0, gamma = self.x0, self.gamma return (1/pi)*atan((x - x0)/gamma) + S.Half def _characteristic_function(self, t): return exp(self.x0 * I * t - self.gamma * Abs(t)) def _moment_generating_function(self, t): raise NotImplementedError("The moment generating function for the " "Cauchy distribution does not exist.") def _quantile(self, p): return self.x0 + self.gamma*tan(pi*(p - S.Half)) def Cauchy(name, x0, gamma): r""" Create a continuous random variable with a Cauchy distribution. The density of the Cauchy distribution is given by .. math:: f(x) := \frac{1}{\pi \gamma [1 + {(\frac{x-x_0}{\gamma})}^2]} Parameters ========== x0 : Real number, the location gamma : Real number, `\gamma > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Cauchy, density >>> from sympy import Symbol >>> x0 = Symbol("x0") >>> gamma = Symbol("gamma", positive=True) >>> z = Symbol("z") >>> X = Cauchy("x", x0, gamma) >>> density(X)(z) 1/(pi*gamma*(1 + (-x0 + z)**2/gamma**2)) References ========== .. [1] https://en.wikipedia.org/wiki/Cauchy_distribution .. [2] http://mathworld.wolfram.com/CauchyDistribution.html """ return rv(name, CauchyDistribution, (x0, gamma)) #------------------------------------------------------------------------------- # Chi distribution ------------------------------------------------------------- class ChiDistribution(SingleContinuousDistribution): _argnames = ('k',) @staticmethod def check(k): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") set = Interval(0, oo) def pdf(self, x): return 2**(1 - self.k/2)*x**(self.k - 1)*exp(-x**2/2)/gamma(self.k/2) def _characteristic_function(self, t): k = self.k part_1 = hyper((k/2,), (S.Half,), -t**2/2) part_2 = I*t*sqrt(2)*gamma((k+1)/2)/gamma(k/2) part_3 = hyper(((k+1)/2,), (Rational(3, 2),), -t**2/2) return part_1 + part_2*part_3 def _moment_generating_function(self, t): k = self.k part_1 = hyper((k / 2,), (S.Half,), t ** 2 / 2) part_2 = t * sqrt(2) * gamma((k + 1) / 2) / gamma(k / 2) part_3 = hyper(((k + 1) / 2,), (S(3) / 2,), t ** 2 / 2) return part_1 + part_2 * part_3 def Chi(name, k): r""" Create a continuous random variable with a Chi distribution. The density of the Chi distribution is given by .. math:: f(x) := \frac{2^{1-k/2}x^{k-1}e^{-x^2/2}}{\Gamma(k/2)} with :math:`x \geq 0`. Parameters ========== k : Positive integer, The number of degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Chi, density, E >>> from sympy import Symbol, simplify >>> k = Symbol("k", integer=True) >>> z = Symbol("z") >>> X = Chi("x", k) >>> density(X)(z) 2**(1 - k/2)*z**(k - 1)*exp(-z**2/2)/gamma(k/2) >>> simplify(E(X)) sqrt(2)*gamma(k/2 + 1/2)/gamma(k/2) References ========== .. [1] https://en.wikipedia.org/wiki/Chi_distribution .. [2] http://mathworld.wolfram.com/ChiDistribution.html """ return rv(name, ChiDistribution, (k,)) #------------------------------------------------------------------------------- # Non-central Chi distribution ------------------------------------------------- class ChiNoncentralDistribution(SingleContinuousDistribution): _argnames = ('k', 'l') @staticmethod def check(k, l): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") _value_check(l > 0, "Shift parameter Lambda must be positive.") set = Interval(0, oo) def pdf(self, x): k, l = self.k, self.l return exp(-(x**2+l**2)/2)*x**k*l / (l*x)**(k/2) * besseli(k/2-1, l*x) def ChiNoncentral(name, k, l): r""" Create a continuous random variable with a non-central Chi distribution. The density of the non-central Chi distribution is given by .. math:: f(x) := \frac{e^{-(x^2+\lambda^2)/2} x^k\lambda} {(\lambda x)^{k/2}} I_{k/2-1}(\lambda x) with `x \geq 0`. Here, `I_\nu (x)` is the :ref:`modified Bessel function of the first kind <besseli>`. Parameters ========== k : A positive Integer, `k > 0`, the number of degrees of freedom lambda : Real number, `\lambda > 0`, Shift parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ChiNoncentral, density >>> from sympy import Symbol >>> k = Symbol("k", integer=True) >>> l = Symbol("l") >>> z = Symbol("z") >>> X = ChiNoncentral("x", k, l) >>> density(X)(z) l*z**k*(l*z)**(-k/2)*exp(-l**2/2 - z**2/2)*besseli(k/2 - 1, l*z) References ========== .. [1] https://en.wikipedia.org/wiki/Noncentral_chi_distribution """ return rv(name, ChiNoncentralDistribution, (k, l)) #------------------------------------------------------------------------------- # Chi squared distribution ----------------------------------------------------- class ChiSquaredDistribution(SingleContinuousDistribution): _argnames = ('k',) @staticmethod def check(k): _value_check(k > 0, "Number of degrees of freedom (k) must be positive.") _value_check(k.is_integer, "Number of degrees of freedom (k) must be an integer.") set = Interval(0, oo) def pdf(self, x): k = self.k return 1/(2**(k/2)*gamma(k/2))*x**(k/2 - 1)*exp(-x/2) def _cdf(self, x): k = self.k return Piecewise( (S.One/gamma(k/2)*lowergamma(k/2, x/2), x >= 0), (0, True) ) def _characteristic_function(self, t): return (1 - 2*I*t)**(-self.k/2) def _moment_generating_function(self, t): return (1 - 2*t)**(-self.k/2) def ChiSquared(name, k): r""" Create a continuous random variable with a Chi-squared distribution. The density of the Chi-squared distribution is given by .. math:: f(x) := \frac{1}{2^{\frac{k}{2}}\Gamma\left(\frac{k}{2}\right)} x^{\frac{k}{2}-1} e^{-\frac{x}{2}} with :math:`x \geq 0`. Parameters ========== k : Positive integer, The number of degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ChiSquared, density, E, variance, moment >>> from sympy import Symbol >>> k = Symbol("k", integer=True, positive=True) >>> z = Symbol("z") >>> X = ChiSquared("x", k) >>> density(X)(z) 2**(-k/2)*z**(k/2 - 1)*exp(-z/2)/gamma(k/2) >>> E(X) k >>> variance(X) 2*k >>> moment(X, 3) k**3 + 6*k**2 + 8*k References ========== .. [1] https://en.wikipedia.org/wiki/Chi_squared_distribution .. [2] http://mathworld.wolfram.com/Chi-SquaredDistribution.html """ return rv(name, ChiSquaredDistribution, (k, )) #------------------------------------------------------------------------------- # Dagum distribution ----------------------------------------------------------- class DagumDistribution(SingleContinuousDistribution): _argnames = ('p', 'a', 'b') set = Interval(0, oo) @staticmethod def check(p, a, b): _value_check(p > 0, "Shape parameter p must be positive.") _value_check(a > 0, "Shape parameter a must be positive.") _value_check(b > 0, "Scale parameter b must be positive.") def pdf(self, x): p, a, b = self.p, self.a, self.b return a*p/x*((x/b)**(a*p)/(((x/b)**a + 1)**(p + 1))) def _cdf(self, x): p, a, b = self.p, self.a, self.b return Piecewise(((S.One + (S(x)/b)**-a)**-p, x>=0), (S.Zero, True)) def Dagum(name, p, a, b): r""" Create a continuous random variable with a Dagum distribution. The density of the Dagum distribution is given by .. math:: f(x) := \frac{a p}{x} \left( \frac{\left(\tfrac{x}{b}\right)^{a p}} {\left(\left(\tfrac{x}{b}\right)^a + 1 \right)^{p+1}} \right) with :math:`x > 0`. Parameters ========== p : Real number, `p > 0`, a shape a : Real number, `a > 0`, a shape b : Real number, `b > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Dagum, density, cdf >>> from sympy import Symbol >>> p = Symbol("p", positive=True) >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Dagum("x", p, a, b) >>> density(X)(z) a*p*(z/b)**(a*p)*((z/b)**a + 1)**(-p - 1)/z >>> cdf(X)(z) Piecewise(((1 + (z/b)**(-a))**(-p), z >= 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Dagum_distribution """ return rv(name, DagumDistribution, (p, a, b)) #------------------------------------------------------------------------------- # Erlang distribution ---------------------------------------------------------- def Erlang(name, k, l): r""" Create a continuous random variable with an Erlang distribution. The density of the Erlang distribution is given by .. math:: f(x) := \frac{\lambda^k x^{k-1} e^{-\lambda x}}{(k-1)!} with :math:`x \in [0,\infty]`. Parameters ========== k : Positive integer l : Real number, `\lambda > 0`, the rate Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Erlang, density, cdf, E, variance >>> from sympy import Symbol, simplify, pprint >>> k = Symbol("k", integer=True, positive=True) >>> l = Symbol("l", positive=True) >>> z = Symbol("z") >>> X = Erlang("x", k, l) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) k k - 1 -l*z l *z *e --------------- Gamma(k) >>> C = cdf(X)(z) >>> pprint(C, use_unicode=False) /lowergamma(k, l*z) |------------------ for z > 0 < Gamma(k) | \ 0 otherwise >>> E(X) k/l >>> simplify(variance(X)) k/l**2 References ========== .. [1] https://en.wikipedia.org/wiki/Erlang_distribution .. [2] http://mathworld.wolfram.com/ErlangDistribution.html """ return rv(name, GammaDistribution, (k, S.One/l)) # ------------------------------------------------------------------------------- # ExGaussian distribution ----------------------------------------------------- class ExGaussianDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std', 'rate') set = Interval(-oo, oo) @staticmethod def check(mean, std, rate): _value_check( std > 0, "Standard deviation of ExGaussian must be positive.") _value_check(rate > 0, "Rate of ExGaussian must be positive.") def pdf(self, x): mean, std, rate = self.mean, self.std, self.rate term1 = rate/2 term2 = exp(rate * (2 * mean + rate * std**2 - 2*x)/2) term3 = erfc((mean + rate*std**2 - x)/(sqrt(2)*std)) return term1*term2*term3 def _cdf(self, x): from sympy.stats import cdf mean, std, rate = self.mean, self.std, self.rate u = rate*(x - mean) v = rate*std GaussianCDF1 = cdf(Normal('x', 0, v))(u) GaussianCDF2 = cdf(Normal('x', v**2, v))(u) return GaussianCDF1 - exp(-u + (v**2/2) + log(GaussianCDF2)) def _characteristic_function(self, t): mean, std, rate = self.mean, self.std, self.rate term1 = (1 - I*t/rate)**(-1) term2 = exp(I*mean*t - std**2*t**2/2) return term1 * term2 def _moment_generating_function(self, t): mean, std, rate = self.mean, self.std, self.rate term1 = (1 - t/rate)**(-1) term2 = exp(mean*t + std**2*t**2/2) return term1*term2 def ExGaussian(name, mean, std, rate): r""" Create a continuous random variable with an Exponentially modified Gaussian (EMG) distribution. The density of the exponentially modified Gaussian distribution is given by .. math:: f(x) := \frac{\lambda}{2}e^{\frac{\lambda}{2}(2\mu+\lambda\sigma^2-2x)} \text{erfc}(\frac{\mu + \lambda\sigma^2 - x}{\sqrt{2}\sigma}) with `x > 0`. Note that the expected value is `1/\lambda`. Parameters ========== mu : A Real number, the mean of Gaussian component std: A positive Real number, :math: `\sigma^2 > 0` the variance of Gaussian component lambda: A positive Real number, :math: `\lambda > 0` the rate of Exponential component Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ExGaussian, density, cdf, E >>> from sympy.stats import variance, skewness >>> from sympy import Symbol, pprint, simplify >>> mean = Symbol("mu") >>> std = Symbol("sigma", positive=True) >>> rate = Symbol("lamda", positive=True) >>> z = Symbol("z") >>> X = ExGaussian("x", mean, std, rate) >>> pprint(density(X)(z), use_unicode=False) / 2 \ lamda*\lamda*sigma + 2*mu - 2*z/ --------------------------------- / ___ / 2 \\ 2 |\/ 2 *\lamda*sigma + mu - z/| lamda*e *erfc|-----------------------------| \ 2*sigma / ---------------------------------------------------------------------------- 2 >>> cdf(X)(z) -(erf(sqrt(2)*(-lamda**2*sigma**2 + lamda*(-mu + z))/(2*lamda*sigma))/2 + 1/2)*exp(lamda**2*sigma**2/2 - lamda*(-mu + z)) + erf(sqrt(2)*(-mu + z)/(2*sigma))/2 + 1/2 >>> E(X) (lamda*mu + 1)/lamda >>> simplify(variance(X)) sigma**2 + lamda**(-2) >>> simplify(skewness(X)) 2/(lamda**2*sigma**2 + 1)**(3/2) References ========== .. [1] https://en.wikipedia.org/wiki/Exponentially_modified_Gaussian_distribution """ return rv(name, ExGaussianDistribution, (mean, std, rate)) #------------------------------------------------------------------------------- # Exponential distribution ----------------------------------------------------- class ExponentialDistribution(SingleContinuousDistribution): _argnames = ('rate',) set = Interval(0, oo) @staticmethod def check(rate): _value_check(rate > 0, "Rate must be positive.") def pdf(self, x): return self.rate * exp(-self.rate*x) def _cdf(self, x): return Piecewise( (S.One - exp(-self.rate*x), x >= 0), (0, True), ) def _characteristic_function(self, t): rate = self.rate return rate / (rate - I*t) def _moment_generating_function(self, t): rate = self.rate return rate / (rate - t) def _quantile(self, p): return -log(1-p)/self.rate def Exponential(name, rate): r""" Create a continuous random variable with an Exponential distribution. The density of the exponential distribution is given by .. math:: f(x) := \lambda \exp(-\lambda x) with `x > 0`. Note that the expected value is `1/\lambda`. Parameters ========== rate : A positive Real number, `\lambda > 0`, the rate (or inverse scale/inverse mean) Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Exponential, density, cdf, E >>> from sympy.stats import variance, std, skewness, quantile >>> from sympy import Symbol >>> l = Symbol("lambda", positive=True) >>> z = Symbol("z") >>> p = Symbol("p") >>> X = Exponential("x", l) >>> density(X)(z) lambda*exp(-lambda*z) >>> cdf(X)(z) Piecewise((1 - exp(-lambda*z), z >= 0), (0, True)) >>> quantile(X)(p) -log(1 - p)/lambda >>> E(X) 1/lambda >>> variance(X) lambda**(-2) >>> skewness(X) 2 >>> X = Exponential('x', 10) >>> density(X)(z) 10*exp(-10*z) >>> E(X) 1/10 >>> std(X) 1/10 References ========== .. [1] https://en.wikipedia.org/wiki/Exponential_distribution .. [2] http://mathworld.wolfram.com/ExponentialDistribution.html """ return rv(name, ExponentialDistribution, (rate, )) # ------------------------------------------------------------------------------- # Exponential Power distribution ----------------------------------------------------- class ExponentialPowerDistribution(SingleContinuousDistribution): _argnames = ('mu', 'alpha', 'beta') set = Interval(-oo, oo) @staticmethod def check(mu, alpha, beta): _value_check(alpha > 0, "Scale parameter alpha must be positive.") _value_check(beta > 0, "Shape parameter beta must be positive.") def pdf(self, x): mu, alpha, beta = self.mu, self.alpha, self.beta num = beta*exp(-(Abs(x - mu)/alpha)**beta) den = 2*alpha*gamma(1/beta) return num/den def _cdf(self, x): mu, alpha, beta = self.mu, self.alpha, self.beta num = lowergamma(1/beta, (Abs(x - mu) / alpha)**beta) den = 2*gamma(1/beta) return sign(x - mu)*num/den + S.Half def ExponentialPower(name, mu, alpha, beta): r""" Create a Continuous Random Variable with Exponential Power distribution. This distribution is known also as Generalized Normal distribution version 1 The density of the Exponential Power distribution is given by .. math:: f(x) := \frac{\beta}{2\alpha\Gamma(\frac{1}{\beta})} e^{{-(\frac{|x - \mu|}{\alpha})^{\beta}}} with :math:`x \in [ - \infty, \infty ]`. Parameters ========== mu : Real number, 'mu' is a location alpha : Real number, 'alpha > 0' is a scale beta : Real number, 'beta > 0' is a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ExponentialPower, density, cdf >>> from sympy import Symbol, pprint >>> z = Symbol("z") >>> mu = Symbol("mu") >>> alpha = Symbol("alpha", positive=True) >>> beta = Symbol("beta", positive=True) >>> X = ExponentialPower("x", mu, alpha, beta) >>> pprint(density(X)(z), use_unicode=False) beta /|mu - z|\ -|--------| \ alpha / beta*e --------------------- / 1 \ 2*alpha*Gamma|----| \beta/ >>> cdf(X)(z) 1/2 + lowergamma(1/beta, (Abs(mu - z)/alpha)**beta)*sign(-mu + z)/(2*gamma(1/beta)) References ========== .. [1] https://reference.wolfram.com/language/ref/ExponentialPowerDistribution.html .. [2] https://en.wikipedia.org/wiki/Generalized_normal_distribution#Version_1 """ return rv(name, ExponentialPowerDistribution, (mu, alpha, beta)) #------------------------------------------------------------------------------- # F distribution --------------------------------------------------------------- class FDistributionDistribution(SingleContinuousDistribution): _argnames = ('d1', 'd2') set = Interval(0, oo) @staticmethod def check(d1, d2): _value_check((d1 > 0, d1.is_integer), "Degrees of freedom d1 must be positive integer.") _value_check((d2 > 0, d2.is_integer), "Degrees of freedom d2 must be positive integer.") def pdf(self, x): d1, d2 = self.d1, self.d2 return (sqrt((d1*x)**d1*d2**d2 / (d1*x+d2)**(d1+d2)) / (x * beta_fn(d1/2, d2/2))) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the ' 'F-distribution does not exist.') def FDistribution(name, d1, d2): r""" Create a continuous random variable with a F distribution. The density of the F distribution is given by .. math:: f(x) := \frac{\sqrt{\frac{(d_1 x)^{d_1} d_2^{d_2}} {(d_1 x + d_2)^{d_1 + d_2}}}} {x \mathrm{B} \left(\frac{d_1}{2}, \frac{d_2}{2}\right)} with :math:`x > 0`. Parameters ========== d1 : `d_1 > 0`, where d_1 is the degrees of freedom (n_1 - 1) d2 : `d_2 > 0`, where d_2 is the degrees of freedom (n_2 - 1) Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import FDistribution, density >>> from sympy import Symbol, pprint >>> d1 = Symbol("d1", positive=True) >>> d2 = Symbol("d2", positive=True) >>> z = Symbol("z") >>> X = FDistribution("x", d1, d2) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) d2 -- ______________________________ 2 / d1 -d1 - d2 d2 *\/ (d1*z) *(d1*z + d2) -------------------------------------- /d1 d2\ z*B|--, --| \2 2 / References ========== .. [1] https://en.wikipedia.org/wiki/F-distribution .. [2] http://mathworld.wolfram.com/F-Distribution.html """ return rv(name, FDistributionDistribution, (d1, d2)) #------------------------------------------------------------------------------- # Fisher Z distribution -------------------------------------------------------- class FisherZDistribution(SingleContinuousDistribution): _argnames = ('d1', 'd2') set = Interval(-oo, oo) @staticmethod def check(d1, d2): _value_check(d1 > 0, "Degree of freedom d1 must be positive.") _value_check(d2 > 0, "Degree of freedom d2 must be positive.") def pdf(self, x): d1, d2 = self.d1, self.d2 return (2*d1**(d1/2)*d2**(d2/2) / beta_fn(d1/2, d2/2) * exp(d1*x) / (d1*exp(2*x)+d2)**((d1+d2)/2)) def FisherZ(name, d1, d2): r""" Create a Continuous Random Variable with an Fisher's Z distribution. The density of the Fisher's Z distribution is given by .. math:: f(x) := \frac{2d_1^{d_1/2} d_2^{d_2/2}} {\mathrm{B}(d_1/2, d_2/2)} \frac{e^{d_1z}}{\left(d_1e^{2z}+d_2\right)^{\left(d_1+d_2\right)/2}} .. TODO - What is the difference between these degrees of freedom? Parameters ========== d1 : `d_1 > 0`, degree of freedom d2 : `d_2 > 0`, degree of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import FisherZ, density >>> from sympy import Symbol, pprint >>> d1 = Symbol("d1", positive=True) >>> d2 = Symbol("d2", positive=True) >>> z = Symbol("z") >>> X = FisherZ("x", d1, d2) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) d1 d2 d1 d2 - -- - -- -- -- 2 2 2 2 / 2*z \ d1*z 2*d1 *d2 *\d1*e + d2/ *e ----------------------------------------- /d1 d2\ B|--, --| \2 2 / References ========== .. [1] https://en.wikipedia.org/wiki/Fisher%27s_z-distribution .. [2] http://mathworld.wolfram.com/Fishersz-Distribution.html """ return rv(name, FisherZDistribution, (d1, d2)) #------------------------------------------------------------------------------- # Frechet distribution --------------------------------------------------------- class FrechetDistribution(SingleContinuousDistribution): _argnames = ('a', 's', 'm') set = Interval(0, oo) @staticmethod def check(a, s, m): _value_check(a > 0, "Shape parameter alpha must be positive.") _value_check(s > 0, "Scale parameter s must be positive.") def __new__(cls, a, s=1, m=0): a, s, m = list(map(sympify, (a, s, m))) return Basic.__new__(cls, a, s, m) def pdf(self, x): a, s, m = self.a, self.s, self.m return a/s * ((x-m)/s)**(-1-a) * exp(-((x-m)/s)**(-a)) def _cdf(self, x): a, s, m = self.a, self.s, self.m return Piecewise((exp(-((x-m)/s)**(-a)), x >= m), (S.Zero, True)) def Frechet(name, a, s=1, m=0): r""" Create a continuous random variable with a Frechet distribution. The density of the Frechet distribution is given by .. math:: f(x) := \frac{\alpha}{s} \left(\frac{x-m}{s}\right)^{-1-\alpha} e^{-(\frac{x-m}{s})^{-\alpha}} with :math:`x \geq m`. Parameters ========== a : Real number, :math:`a \in \left(0, \infty\right)` the shape s : Real number, :math:`s \in \left(0, \infty\right)` the scale m : Real number, :math:`m \in \left(-\infty, \infty\right)` the minimum Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Frechet, density, cdf >>> from sympy import Symbol >>> a = Symbol("a", positive=True) >>> s = Symbol("s", positive=True) >>> m = Symbol("m", real=True) >>> z = Symbol("z") >>> X = Frechet("x", a, s, m) >>> density(X)(z) a*((-m + z)/s)**(-a - 1)*exp(-((-m + z)/s)**(-a))/s >>> cdf(X)(z) Piecewise((exp(-((-m + z)/s)**(-a)), m <= z), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Fr%C3%A9chet_distribution """ return rv(name, FrechetDistribution, (a, s, m)) #------------------------------------------------------------------------------- # Gamma distribution ----------------------------------------------------------- class GammaDistribution(SingleContinuousDistribution): _argnames = ('k', 'theta') set = Interval(0, oo) @staticmethod def check(k, theta): _value_check(k > 0, "k must be positive") _value_check(theta > 0, "Theta must be positive") def pdf(self, x): k, theta = self.k, self.theta return x**(k - 1) * exp(-x/theta) / (gamma(k)*theta**k) def _cdf(self, x): k, theta = self.k, self.theta return Piecewise( (lowergamma(k, S(x)/theta)/gamma(k), x > 0), (S.Zero, True)) def _characteristic_function(self, t): return (1 - self.theta*I*t)**(-self.k) def _moment_generating_function(self, t): return (1- self.theta*t)**(-self.k) def Gamma(name, k, theta): r""" Create a continuous random variable with a Gamma distribution. The density of the Gamma distribution is given by .. math:: f(x) := \frac{1}{\Gamma(k) \theta^k} x^{k - 1} e^{-\frac{x}{\theta}} with :math:`x \in [0,1]`. Parameters ========== k : Real number, `k > 0`, a shape theta : Real number, `\theta > 0`, a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gamma, density, cdf, E, variance >>> from sympy import Symbol, pprint, simplify >>> k = Symbol("k", positive=True) >>> theta = Symbol("theta", positive=True) >>> z = Symbol("z") >>> X = Gamma("x", k, theta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) -z ----- -k k - 1 theta theta *z *e --------------------- Gamma(k) >>> C = cdf(X, meijerg=True)(z) >>> pprint(C, use_unicode=False) / / z \ |k*lowergamma|k, -----| | \ theta/ <---------------------- for z >= 0 | Gamma(k + 1) | \ 0 otherwise >>> E(X) k*theta >>> V = simplify(variance(X)) >>> pprint(V, use_unicode=False) 2 k*theta References ========== .. [1] https://en.wikipedia.org/wiki/Gamma_distribution .. [2] http://mathworld.wolfram.com/GammaDistribution.html """ return rv(name, GammaDistribution, (k, theta)) #------------------------------------------------------------------------------- # Inverse Gamma distribution --------------------------------------------------- class GammaInverseDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') set = Interval(0, oo) @staticmethod def check(a, b): _value_check(a > 0, "alpha must be positive") _value_check(b > 0, "beta must be positive") def pdf(self, x): a, b = self.a, self.b return b**a/gamma(a) * x**(-a-1) * exp(-b/x) def _cdf(self, x): a, b = self.a, self.b return Piecewise((uppergamma(a,b/x)/gamma(a), x > 0), (S.Zero, True)) def _characteristic_function(self, t): a, b = self.a, self.b return 2 * (-I*b*t)**(a/2) * besselk(a, sqrt(-4*I*b*t)) / gamma(a) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the ' 'gamma inverse distribution does not exist.') def GammaInverse(name, a, b): r""" Create a continuous random variable with an inverse Gamma distribution. The density of the inverse Gamma distribution is given by .. math:: f(x) := \frac{\beta^\alpha}{\Gamma(\alpha)} x^{-\alpha - 1} \exp\left(\frac{-\beta}{x}\right) with :math:`x > 0`. Parameters ========== a : Real number, `a > 0` a shape b : Real number, `b > 0` a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import GammaInverse, density, cdf >>> from sympy import Symbol, pprint >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = GammaInverse("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) -b --- a -a - 1 z b *z *e --------------- Gamma(a) >>> cdf(X)(z) Piecewise((uppergamma(a, b/z)/gamma(a), z > 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Inverse-gamma_distribution """ return rv(name, GammaInverseDistribution, (a, b)) #------------------------------------------------------------------------------- # Gumbel distribution (Maximum and Minimum) -------------------------------------------------------- class GumbelDistribution(SingleContinuousDistribution): _argnames = ('beta', 'mu', 'minimum') set = Interval(-oo, oo) @staticmethod def check(beta, mu, minimum): _value_check(beta > 0, "Scale parameter beta must be positive.") def pdf(self, x): beta, mu = self.beta, self.mu z = (x - mu)/beta f_max = (1/beta)*exp(-z - exp(-z)) f_min = (1/beta)*exp(z - exp(z)) return Piecewise((f_min, self.minimum), (f_max, not self.minimum)) def _cdf(self, x): beta, mu = self.beta, self.mu z = (x - mu)/beta F_max = exp(-exp(-z)) F_min = 1 - exp(-exp(z)) return Piecewise((F_min, self.minimum), (F_max, not self.minimum)) def _characteristic_function(self, t): cf_max = gamma(1 - I*self.beta*t) * exp(I*self.mu*t) cf_min = gamma(1 + I*self.beta*t) * exp(I*self.mu*t) return Piecewise((cf_min, self.minimum), (cf_max, not self.minimum)) def _moment_generating_function(self, t): mgf_max = gamma(1 - self.beta*t) * exp(self.mu*t) mgf_min = gamma(1 + self.beta*t) * exp(self.mu*t) return Piecewise((mgf_min, self.minimum), (mgf_max, not self.minimum)) def Gumbel(name, beta, mu, minimum=False): r""" Create a Continuous Random Variable with Gumbel distribution. The density of the Gumbel distribution is given by For Maximum .. math:: f(x) := \dfrac{1}{\beta} \exp \left( -\dfrac{x-\mu}{\beta} - \exp \left( -\dfrac{x - \mu}{\beta} \right) \right) with :math:`x \in [ - \infty, \infty ]`. For Minimum .. math:: f(x) := \frac{e^{- e^{\frac{- \mu + x}{\beta}} + \frac{- \mu + x}{\beta}}}{\beta} with :math:`x \in [ - \infty, \infty ]`. Parameters ========== mu : Real number, 'mu' is a location beta : Real number, 'beta > 0' is a scale minimum : Boolean, by default, False, set to True for enabling minimum distribution Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gumbel, density, cdf >>> from sympy import Symbol >>> x = Symbol("x") >>> mu = Symbol("mu") >>> beta = Symbol("beta", positive=True) >>> X = Gumbel("x", beta, mu) >>> density(X)(x) exp(-exp(-(-mu + x)/beta) - (-mu + x)/beta)/beta >>> cdf(X)(x) exp(-exp(-(-mu + x)/beta)) References ========== .. [1] http://mathworld.wolfram.com/GumbelDistribution.html .. [2] https://en.wikipedia.org/wiki/Gumbel_distribution .. [3] http://www.mathwave.com/help/easyfit/html/analyses/distributions/gumbel_max.html .. [4] http://www.mathwave.com/help/easyfit/html/analyses/distributions/gumbel_min.html """ return rv(name, GumbelDistribution, (beta, mu, minimum)) #------------------------------------------------------------------------------- # Gompertz distribution -------------------------------------------------------- class GompertzDistribution(SingleContinuousDistribution): _argnames = ('b', 'eta') set = Interval(0, oo) @staticmethod def check(b, eta): _value_check(b > 0, "b must be positive") _value_check(eta > 0, "eta must be positive") def pdf(self, x): eta, b = self.eta, self.b return b*eta*exp(b*x)*exp(eta)*exp(-eta*exp(b*x)) def _cdf(self, x): eta, b = self.eta, self.b return 1 - exp(eta)*exp(-eta*exp(b*x)) def _moment_generating_function(self, t): eta, b = self.eta, self.b return eta * exp(eta) * expint(t/b, eta) def Gompertz(name, b, eta): r""" Create a Continuous Random Variable with Gompertz distribution. The density of the Gompertz distribution is given by .. math:: f(x) := b \eta e^{b x} e^{\eta} \exp \left(-\eta e^{bx} \right) with :math: 'x \in [0, \inf)'. Parameters ========== b: Real number, 'b > 0' a scale eta: Real number, 'eta > 0' a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Gompertz, density >>> from sympy import Symbol >>> b = Symbol("b", positive=True) >>> eta = Symbol("eta", positive=True) >>> z = Symbol("z") >>> X = Gompertz("x", b, eta) >>> density(X)(z) b*eta*exp(eta)*exp(b*z)*exp(-eta*exp(b*z)) References ========== .. [1] https://en.wikipedia.org/wiki/Gompertz_distribution """ return rv(name, GompertzDistribution, (b, eta)) #------------------------------------------------------------------------------- # Kumaraswamy distribution ----------------------------------------------------- class KumaraswamyDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') set = Interval(0, oo) @staticmethod def check(a, b): _value_check(a > 0, "a must be positive") _value_check(b > 0, "b must be positive") def pdf(self, x): a, b = self.a, self.b return a * b * x**(a-1) * (1-x**a)**(b-1) def _cdf(self, x): a, b = self.a, self.b return Piecewise( (S.Zero, x < S.Zero), (1 - (1 - x**a)**b, x <= S.One), (S.One, True)) def Kumaraswamy(name, a, b): r""" Create a Continuous Random Variable with a Kumaraswamy distribution. The density of the Kumaraswamy distribution is given by .. math:: f(x) := a b x^{a-1} (1-x^a)^{b-1} with :math:`x \in [0,1]`. Parameters ========== a : Real number, `a > 0` a shape b : Real number, `b > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Kumaraswamy, density, cdf >>> from sympy import Symbol, pprint >>> a = Symbol("a", positive=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Kumaraswamy("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) b - 1 a - 1 / a\ a*b*z *\1 - z / >>> cdf(X)(z) Piecewise((0, z < 0), (1 - (1 - z**a)**b, z <= 1), (1, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Kumaraswamy_distribution """ return rv(name, KumaraswamyDistribution, (a, b)) #------------------------------------------------------------------------------- # Laplace distribution --------------------------------------------------------- class LaplaceDistribution(SingleContinuousDistribution): _argnames = ('mu', 'b') set = Interval(-oo, oo) @staticmethod def check(mu, b): _value_check(b > 0, "Scale parameter b must be positive.") _value_check(mu.is_real, "Location parameter mu should be real") def pdf(self, x): mu, b = self.mu, self.b return 1/(2*b)*exp(-Abs(x - mu)/b) def _cdf(self, x): mu, b = self.mu, self.b return Piecewise( (S.Half*exp((x - mu)/b), x < mu), (S.One - S.Half*exp(-(x - mu)/b), x >= mu) ) def _characteristic_function(self, t): return exp(self.mu*I*t) / (1 + self.b**2*t**2) def _moment_generating_function(self, t): return exp(self.mu*t) / (1 - self.b**2*t**2) def Laplace(name, mu, b): r""" Create a continuous random variable with a Laplace distribution. The density of the Laplace distribution is given by .. math:: f(x) := \frac{1}{2 b} \exp \left(-\frac{|x-\mu|}b \right) Parameters ========== mu : Real number or a list/matrix, the location (mean) or the location vector b : Real number or a positive definite matrix, representing a scale or the covariance matrix. Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Laplace, density, cdf >>> from sympy import Symbol, pprint >>> mu = Symbol("mu") >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Laplace("x", mu, b) >>> density(X)(z) exp(-Abs(mu - z)/b)/(2*b) >>> cdf(X)(z) Piecewise((exp((-mu + z)/b)/2, mu > z), (1 - exp((mu - z)/b)/2, True)) >>> L = Laplace('L', [1, 2], [[1, 0], [0, 1]]) >>> pprint(density(L)(1, 2), use_unicode=False) 5 / ____\ e *besselk\0, \/ 35 / --------------------- pi References ========== .. [1] https://en.wikipedia.org/wiki/Laplace_distribution .. [2] http://mathworld.wolfram.com/LaplaceDistribution.html """ if isinstance(mu, (list, MatrixBase)) and\ isinstance(b, (list, MatrixBase)): from sympy.stats.joint_rv_types import MultivariateLaplace return MultivariateLaplace(name, mu, b) return rv(name, LaplaceDistribution, (mu, b)) #------------------------------------------------------------------------------- # Levy distribution --------------------------------------------------------- class LevyDistribution(SingleContinuousDistribution): _argnames = ('mu', 'c') @property def set(self): return Interval(self.mu, oo) @staticmethod def check(mu, c): _value_check(c > 0, "c (scale parameter) must be positive") _value_check(mu.is_real, "mu (location paramater) must be real") def pdf(self, x): mu, c = self.mu, self.c return sqrt(c/(2*pi))*exp(-c/(2*(x - mu)))/((x - mu)**(S.One + S.Half)) def _cdf(self, x): mu, c = self.mu, self.c return erfc(sqrt(c/(2*(x - mu)))) def _characteristic_function(self, t): mu, c = self.mu, self.c return exp(I * mu * t - sqrt(-2 * I * c * t)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function of Levy distribution does not exist.') def Levy(name, mu, c): r""" Create a continuous random variable with a Levy distribution. The density of the Levy distribution is given by .. math:: f(x) := \sqrt(\frac{c}{2 \pi}) \frac{\exp -\frac{c}{2 (x - \mu)}}{(x - \mu)^{3/2}} Parameters ========== mu : Real number, the location parameter c : Real number, `c > 0`, a scale parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Levy, density, cdf >>> from sympy import Symbol >>> mu = Symbol("mu", real=True) >>> c = Symbol("c", positive=True) >>> z = Symbol("z") >>> X = Levy("x", mu, c) >>> density(X)(z) sqrt(2)*sqrt(c)*exp(-c/(-2*mu + 2*z))/(2*sqrt(pi)*(-mu + z)**(3/2)) >>> cdf(X)(z) erfc(sqrt(c)*sqrt(1/(-2*mu + 2*z))) References ========== .. [1] https://en.wikipedia.org/wiki/L%C3%A9vy_distribution .. [2] http://mathworld.wolfram.com/LevyDistribution.html """ return rv(name, LevyDistribution, (mu, c)) #------------------------------------------------------------------------------- # Logistic distribution -------------------------------------------------------- class LogisticDistribution(SingleContinuousDistribution): _argnames = ('mu', 's') set = Interval(-oo, oo) @staticmethod def check(mu, s): _value_check(s > 0, "Scale parameter s must be positive.") def pdf(self, x): mu, s = self.mu, self.s return exp(-(x - mu)/s)/(s*(1 + exp(-(x - mu)/s))**2) def _cdf(self, x): mu, s = self.mu, self.s return S.One/(1 + exp(-(x - mu)/s)) def _characteristic_function(self, t): return Piecewise((exp(I*t*self.mu) * pi*self.s*t / sinh(pi*self.s*t), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): return exp(self.mu*t) * beta_fn(1 - self.s*t, 1 + self.s*t) def _quantile(self, p): return self.mu - self.s*log(-S.One + S.One/p) def Logistic(name, mu, s): r""" Create a continuous random variable with a logistic distribution. The density of the logistic distribution is given by .. math:: f(x) := \frac{e^{-(x-\mu)/s}} {s\left(1+e^{-(x-\mu)/s}\right)^2} Parameters ========== mu : Real number, the location (mean) s : Real number, `s > 0` a scale Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Logistic, density, cdf >>> from sympy import Symbol >>> mu = Symbol("mu", real=True) >>> s = Symbol("s", positive=True) >>> z = Symbol("z") >>> X = Logistic("x", mu, s) >>> density(X)(z) exp((mu - z)/s)/(s*(exp((mu - z)/s) + 1)**2) >>> cdf(X)(z) 1/(exp((mu - z)/s) + 1) References ========== .. [1] https://en.wikipedia.org/wiki/Logistic_distribution .. [2] http://mathworld.wolfram.com/LogisticDistribution.html """ return rv(name, LogisticDistribution, (mu, s)) #------------------------------------------------------------------------------- # Log-logistic distribution -------------------------------------------------------- class LogLogisticDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, oo) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Scale parameter Alpha must be positive.") _value_check(beta > 0, "Shape parameter Beta must be positive.") def pdf(self, x): a, b = self.alpha, self.beta return ((b/a)*(x/a)**(b - 1))/(1 + (x/a)**b)**2 def _cdf(self, x): a, b = self.alpha, self.beta return 1/(1 + (x/a)**(-b)) def _quantile(self, p): a, b = self.alpha, self.beta return a*((p/(1 - p))**(1/b)) def expectation(self, expr, var, **kwargs): a, b = self.args return Piecewise((S.NaN, b <= 1), (pi*a/(b*sin(pi/b)), True)) def LogLogistic(name, alpha, beta): r""" Create a continuous random variable with a log-logistic distribution. The distribution is unimodal when `beta > 1`. The density of the log-logistic distribution is given by .. math:: f(x) := \frac{(\frac{\beta}{\alpha})(\frac{x}{\alpha})^{\beta - 1}} {(1 + (\frac{x}{\alpha})^{\beta})^2} Parameters ========== alpha : Real number, `\alpha > 0`, scale parameter and median of distribution beta : Real number, `\beta > 0` a shape parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import LogLogistic, density, cdf, quantile >>> from sympy import Symbol, pprint >>> alpha = Symbol("alpha", real=True, positive=True) >>> beta = Symbol("beta", real=True, positive=True) >>> p = Symbol("p") >>> z = Symbol("z", positive=True) >>> X = LogLogistic("x", alpha, beta) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) beta - 1 / z \ beta*|-----| \alpha/ ------------------------ 2 / beta \ |/ z \ | alpha*||-----| + 1| \\alpha/ / >>> cdf(X)(z) 1/(1 + (z/alpha)**(-beta)) >>> quantile(X)(p) alpha*(p/(1 - p))**(1/beta) References ========== .. [1] https://en.wikipedia.org/wiki/Log-logistic_distribution """ return rv(name, LogLogisticDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Log Normal distribution ------------------------------------------------------ class LogNormalDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std') set = Interval(0, oo) @staticmethod def check(mean, std): _value_check(std > 0, "Parameter std must be positive.") def pdf(self, x): mean, std = self.mean, self.std return exp(-(log(x) - mean)**2 / (2*std**2)) / (x*sqrt(2*pi)*std) def _cdf(self, x): mean, std = self.mean, self.std return Piecewise( (S.Half + S.Half*erf((log(x) - mean)/sqrt(2)/std), x > 0), (S.Zero, True) ) def _moment_generating_function(self, t): raise NotImplementedError('Moment generating function of the log-normal distribution is not defined.') def LogNormal(name, mean, std): r""" Create a continuous random variable with a log-normal distribution. The density of the log-normal distribution is given by .. math:: f(x) := \frac{1}{x\sqrt{2\pi\sigma^2}} e^{-\frac{\left(\ln x-\mu\right)^2}{2\sigma^2}} with :math:`x \geq 0`. Parameters ========== mu : Real number, the log-scale sigma : Real number, :math:`\sigma^2 > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import LogNormal, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", real=True) >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = LogNormal("x", mu, sigma) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -(-mu + log(z)) ----------------- 2 ___ 2*sigma \/ 2 *e ------------------------ ____ 2*\/ pi *sigma*z >>> X = LogNormal('x', 0, 1) # Mean 0, standard deviation 1 >>> density(X)(z) sqrt(2)*exp(-log(z)**2/2)/(2*sqrt(pi)*z) References ========== .. [1] https://en.wikipedia.org/wiki/Lognormal .. [2] http://mathworld.wolfram.com/LogNormalDistribution.html """ return rv(name, LogNormalDistribution, (mean, std)) #------------------------------------------------------------------------------- # Lomax Distribution ----------------------------------------------------------- class LomaxDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'lamda',) set = Interval(0, oo) @staticmethod def check(alpha, lamda): _value_check(alpha.is_real, "Shape parameter should be real.") _value_check(lamda.is_real, "Scale parameter should be real.") _value_check(alpha.is_positive, "Shape parameter should be positive.") _value_check(lamda.is_positive, "Scale parameter should be positive.") def pdf(self, x): lamba, alpha = self.lamda, self.alpha return (alpha/lamba) * (S.One + x/lamba)**(-alpha-1) def Lomax(name, alpha, lamda): r""" Create a continuous random variable with a Lomax distribution. The density of the Lomax distribution is given by .. math:: f(x) := \frac{\alpha}{\lambda}\left[1+\frac{x}{\lambda}\right]^{-(\alpha+1)} Parameters ========== alpha : Real Number, `alpha > 0` Shape parameter lamda : Real Number, `lamda > 0` Scale parameter Examples ======== >>> from sympy.stats import Lomax, density, cdf, E >>> from sympy import symbols >>> a, l = symbols('a, l', positive=True) >>> X = Lomax('X', a, l) >>> x = symbols('x') >>> density(X)(x) a*(1 + x/l)**(-a - 1)/l >>> cdf(X)(x) Piecewise((1 - (1 + x/l)**(-a), x >= 0), (0, True)) >>> a = 2 >>> X = Lomax('X', a, l) >>> E(X) l Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Lomax_distribution """ return rv(name, LomaxDistribution, (alpha, lamda)) #------------------------------------------------------------------------------- # Maxwell distribution --------------------------------------------------------- class MaxwellDistribution(SingleContinuousDistribution): _argnames = ('a',) set = Interval(0, oo) @staticmethod def check(a): _value_check(a > 0, "Parameter a must be positive.") def pdf(self, x): a = self.a return sqrt(2/pi)*x**2*exp(-x**2/(2*a**2))/a**3 def _cdf(self, x): a = self.a return erf(sqrt(2)*x/(2*a)) - sqrt(2)*x*exp(-x**2/(2*a**2))/(sqrt(pi)*a) def Maxwell(name, a): r""" Create a continuous random variable with a Maxwell distribution. The density of the Maxwell distribution is given by .. math:: f(x) := \sqrt{\frac{2}{\pi}} \frac{x^2 e^{-x^2/(2a^2)}}{a^3} with :math:`x \geq 0`. .. TODO - what does the parameter mean? Parameters ========== a : Real number, `a > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Maxwell, density, E, variance >>> from sympy import Symbol, simplify >>> a = Symbol("a", positive=True) >>> z = Symbol("z") >>> X = Maxwell("x", a) >>> density(X)(z) sqrt(2)*z**2*exp(-z**2/(2*a**2))/(sqrt(pi)*a**3) >>> E(X) 2*sqrt(2)*a/sqrt(pi) >>> simplify(variance(X)) a**2*(-8 + 3*pi)/pi References ========== .. [1] https://en.wikipedia.org/wiki/Maxwell_distribution .. [2] http://mathworld.wolfram.com/MaxwellDistribution.html """ return rv(name, MaxwellDistribution, (a, )) #------------------------------------------------------------------------------- # Moyal Distribution ----------------------------------------------------------- class MoyalDistribution(SingleContinuousDistribution): _argnames = ('mu', 'sigma') @staticmethod def check(mu, sigma): _value_check(mu.is_real, "Location parameter must be real.") _value_check(sigma.is_real and sigma > 0, "Scale parameter must be real\ and positive.") def pdf(self, x): mu, sigma = self.mu, self.sigma num = exp(-(exp(-(x - mu)/sigma) + (x - mu)/(sigma))/2) den = (sqrt(2*pi) * sigma) return num/den def _characteristic_function(self, t): mu, sigma = self.mu, self.sigma term1 = exp(I*t*mu) term2 = (2**(-I*sigma*t) * gamma(Rational(1, 2) - I*t*sigma)) return (term1 * term2)/sqrt(pi) def _moment_generating_function(self, t): mu, sigma = self.mu, self.sigma term1 = exp(t*mu) term2 = (2**(-1*sigma*t) * gamma(Rational(1, 2) - t*sigma)) return (term1 * term2)/sqrt(pi) def Moyal(name, mu, sigma): r""" Create a continuous random variable with a Moyal distribution. The density of the Moyal distribution is given by .. math:: f(x) := \frac{\exp-\frac{1}{2}\exp-\frac{x-\mu}{\sigma}-\frac{x-\mu}{2\sigma}}{\sqrt{2\pi}\sigma} with :math:`x \in \mathbb{R}`. Parameters ========== mu : Real number Location parameter sigma : Real positive number Scale parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Moyal, density, cdf >>> from sympy import Symbol, simplify >>> mu = Symbol("mu", real=True) >>> sigma = Symbol("sigma", positive=True, real=True) >>> z = Symbol("z") >>> X = Moyal("x", mu, sigma) >>> density(X)(z) sqrt(2)*exp(-exp((mu - z)/sigma)/2 - (-mu + z)/(2*sigma))/(2*sqrt(pi)*sigma) >>> simplify(cdf(X)(z)) 1 - erf(sqrt(2)*exp((mu - z)/(2*sigma))/2) References ========== .. [1] https://reference.wolfram.com/language/ref/MoyalDistribution.html .. [2] http://www.stat.rice.edu/~dobelman/textfiles/DistributionsHandbook.pdf """ return rv(name, MoyalDistribution, (mu, sigma)) #------------------------------------------------------------------------------- # Nakagami distribution -------------------------------------------------------- class NakagamiDistribution(SingleContinuousDistribution): _argnames = ('mu', 'omega') set = Interval(0, oo) @staticmethod def check(mu, omega): _value_check(mu >= S.Half, "Shape parameter mu must be greater than equal to 1/2.") _value_check(omega > 0, "Spread parameter omega must be positive.") def pdf(self, x): mu, omega = self.mu, self.omega return 2*mu**mu/(gamma(mu)*omega**mu)*x**(2*mu - 1)*exp(-mu/omega*x**2) def _cdf(self, x): mu, omega = self.mu, self.omega return Piecewise( (lowergamma(mu, (mu/omega)*x**2)/gamma(mu), x > 0), (S.Zero, True)) def Nakagami(name, mu, omega): r""" Create a continuous random variable with a Nakagami distribution. The density of the Nakagami distribution is given by .. math:: f(x) := \frac{2\mu^\mu}{\Gamma(\mu)\omega^\mu} x^{2\mu-1} \exp\left(-\frac{\mu}{\omega}x^2 \right) with :math:`x > 0`. Parameters ========== mu : Real number, `\mu \geq \frac{1}{2}` a shape omega : Real number, `\omega > 0`, the spread Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Nakagami, density, E, variance, cdf >>> from sympy import Symbol, simplify, pprint >>> mu = Symbol("mu", positive=True) >>> omega = Symbol("omega", positive=True) >>> z = Symbol("z") >>> X = Nakagami("x", mu, omega) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -mu*z ------- mu -mu 2*mu - 1 omega 2*mu *omega *z *e ---------------------------------- Gamma(mu) >>> simplify(E(X)) sqrt(mu)*sqrt(omega)*gamma(mu + 1/2)/gamma(mu + 1) >>> V = simplify(variance(X)) >>> pprint(V, use_unicode=False) 2 omega*Gamma (mu + 1/2) omega - ----------------------- Gamma(mu)*Gamma(mu + 1) >>> cdf(X)(z) Piecewise((lowergamma(mu, mu*z**2/omega)/gamma(mu), z > 0), (0, True)) References ========== .. [1] https://en.wikipedia.org/wiki/Nakagami_distribution """ return rv(name, NakagamiDistribution, (mu, omega)) #------------------------------------------------------------------------------- # Normal distribution ---------------------------------------------------------- class NormalDistribution(SingleContinuousDistribution): _argnames = ('mean', 'std') @staticmethod def check(mean, std): _value_check(std > 0, "Standard deviation must be positive") def pdf(self, x): return exp(-(x - self.mean)**2 / (2*self.std**2)) / (sqrt(2*pi)*self.std) def _cdf(self, x): mean, std = self.mean, self.std return erf(sqrt(2)*(-mean + x)/(2*std))/2 + S.Half def _characteristic_function(self, t): mean, std = self.mean, self.std return exp(I*mean*t - std**2*t**2/2) def _moment_generating_function(self, t): mean, std = self.mean, self.std return exp(mean*t + std**2*t**2/2) def _quantile(self, p): mean, std = self.mean, self.std return mean + std*sqrt(2)*erfinv(2*p - 1) def Normal(name, mean, std): r""" Create a continuous random variable with a Normal distribution. The density of the Normal distribution is given by .. math:: f(x) := \frac{1}{\sigma\sqrt{2\pi}} e^{ -\frac{(x-\mu)^2}{2\sigma^2} } Parameters ========== mu : Real number or a list representing the mean or the mean vector sigma : Real number or a positive definite square matrix, :math:`\sigma^2 > 0` the variance Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Normal, density, E, std, cdf, skewness, quantile, marginal_distribution >>> from sympy import Symbol, simplify, pprint >>> mu = Symbol("mu") >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> y = Symbol("y") >>> p = Symbol("p") >>> X = Normal("x", mu, sigma) >>> density(X)(z) sqrt(2)*exp(-(-mu + z)**2/(2*sigma**2))/(2*sqrt(pi)*sigma) >>> C = simplify(cdf(X))(z) # it needs a little more help... >>> pprint(C, use_unicode=False) / ___ \ |\/ 2 *(-mu + z)| erf|---------------| \ 2*sigma / 1 -------------------- + - 2 2 >>> quantile(X)(p) mu + sqrt(2)*sigma*erfinv(2*p - 1) >>> simplify(skewness(X)) 0 >>> X = Normal("x", 0, 1) # Mean 0, standard deviation 1 >>> density(X)(z) sqrt(2)*exp(-z**2/2)/(2*sqrt(pi)) >>> E(2*X + 1) 1 >>> simplify(std(2*X + 1)) 2 >>> m = Normal('X', [1, 2], [[2, 1], [1, 2]]) >>> pprint(density(m)(y, z), use_unicode=False) /1 y\ /2*y z\ / z\ / y 2*z \ |- - -|*|--- - -| + |1 - -|*|- - + --- - 1| ___ \2 2/ \ 3 3/ \ 2/ \ 3 3 / \/ 3 *e -------------------------------------------------- 6*pi >>> marginal_distribution(m, m[0])(1) 1/(2*sqrt(pi)) References ========== .. [1] https://en.wikipedia.org/wiki/Normal_distribution .. [2] http://mathworld.wolfram.com/NormalDistributionFunction.html """ if isinstance(mean, (list, MatrixBase, MatrixExpr)) and\ isinstance(std, (list, MatrixBase, MatrixExpr)): from sympy.stats.joint_rv_types import MultivariateNormal return MultivariateNormal(name, mean, std) return rv(name, NormalDistribution, (mean, std)) #------------------------------------------------------------------------------- # Inverse Gaussian distribution ---------------------------------------------------------- class GaussianInverseDistribution(SingleContinuousDistribution): _argnames = ('mean', 'shape') @property def set(self): return Interval(0, oo) @staticmethod def check(mean, shape): _value_check(shape > 0, "Shape parameter must be positive") _value_check(mean > 0, "Mean must be positive") def pdf(self, x): mu, s = self.mean, self.shape return exp(-s*(x - mu)**2 / (2*x*mu**2)) * sqrt(s/(2*pi*x**3)) def _cdf(self, x): from sympy.stats import cdf mu, s = self.mean, self.shape stdNormalcdf = cdf(Normal('x', 0, 1)) first_term = stdNormalcdf(sqrt(s/x) * ((x/mu) - S.One)) second_term = exp(2*s/mu) * stdNormalcdf(-sqrt(s/x)*(x/mu + S.One)) return first_term + second_term def _characteristic_function(self, t): mu, s = self.mean, self.shape return exp((s/mu)*(1 - sqrt(1 - (2*mu**2*I*t)/s))) def _moment_generating_function(self, t): mu, s = self.mean, self.shape return exp((s/mu)*(1 - sqrt(1 - (2*mu**2*t)/s))) def GaussianInverse(name, mean, shape): r""" Create a continuous random variable with an Inverse Gaussian distribution. Inverse Gaussian distribution is also known as Wald distribution. The density of the Inverse Gaussian distribution is given by .. math:: f(x) := \sqrt{\frac{\lambda}{2\pi x^3}} e^{-\frac{\lambda(x-\mu)^2}{2x\mu^2}} Parameters ========== mu : Positive number representing the mean lambda : Positive number representing the shape parameter Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import GaussianInverse, density, E, std, skewness >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", positive=True) >>> lamda = Symbol("lambda", positive=True) >>> z = Symbol("z", positive=True) >>> X = GaussianInverse("x", mu, lamda) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) 2 -lambda*(-mu + z) ------------------- 2 ___ ________ 2*mu *z \/ 2 *\/ lambda *e ------------------------------------- ____ 3/2 2*\/ pi *z >>> E(X) mu >>> std(X).expand() mu**(3/2)/sqrt(lambda) >>> skewness(X).expand() 3*sqrt(mu)/sqrt(lambda) References ========== .. [1] https://en.wikipedia.org/wiki/Inverse_Gaussian_distribution .. [2] http://mathworld.wolfram.com/InverseGaussianDistribution.html """ return rv(name, GaussianInverseDistribution, (mean, shape)) Wald = GaussianInverse #------------------------------------------------------------------------------- # Pareto distribution ---------------------------------------------------------- class ParetoDistribution(SingleContinuousDistribution): _argnames = ('xm', 'alpha') @property def set(self): return Interval(self.xm, oo) @staticmethod def check(xm, alpha): _value_check(xm > 0, "Xm must be positive") _value_check(alpha > 0, "Alpha must be positive") def pdf(self, x): xm, alpha = self.xm, self.alpha return alpha * xm**alpha / x**(alpha + 1) def _cdf(self, x): xm, alpha = self.xm, self.alpha return Piecewise( (S.One - xm**alpha/x**alpha, x>=xm), (0, True), ) def _moment_generating_function(self, t): xm, alpha = self.xm, self.alpha return alpha * (-xm*t)**alpha * uppergamma(-alpha, -xm*t) def _characteristic_function(self, t): xm, alpha = self.xm, self.alpha return alpha * (-I * xm * t) ** alpha * uppergamma(-alpha, -I * xm * t) def Pareto(name, xm, alpha): r""" Create a continuous random variable with the Pareto distribution. The density of the Pareto distribution is given by .. math:: f(x) := \frac{\alpha\,x_m^\alpha}{x^{\alpha+1}} with :math:`x \in [x_m,\infty]`. Parameters ========== xm : Real number, `x_m > 0`, a scale alpha : Real number, `\alpha > 0`, a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Pareto, density >>> from sympy import Symbol >>> xm = Symbol("xm", positive=True) >>> beta = Symbol("beta", positive=True) >>> z = Symbol("z") >>> X = Pareto("x", xm, beta) >>> density(X)(z) beta*xm**beta*z**(-beta - 1) References ========== .. [1] https://en.wikipedia.org/wiki/Pareto_distribution .. [2] http://mathworld.wolfram.com/ParetoDistribution.html """ return rv(name, ParetoDistribution, (xm, alpha)) #------------------------------------------------------------------------------- # PowerFunction distribution --------------------------------------------------- class PowerFunctionDistribution(SingleContinuousDistribution): _argnames=('alpha','a','b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(alpha, a, b): _value_check(a.is_real, "Continuous Boundary parameter should be real.") _value_check(b.is_real, "Continuous Boundary parameter should be real.") _value_check(a < b, " 'a' the left Boundary must be smaller than 'b' the right Boundary." ) _value_check(alpha.is_positive, "Continuous Shape parameter should be positive.") def pdf(self, x): alpha, a, b = self.alpha, self.a, self.b num = alpha*(x - a)**(alpha - 1) den = (b - a)**alpha return num/den def PowerFunction(name, alpha, a, b): r""" Creates a continuous random variable with a Power Function Distribution The density of PowerFunction distribution is given by .. math:: f(x) := \frac{{\alpha}(x - a)^{\alpha - 1}}{(b - a)^{\alpha}} with :math:`x \in [a,b]`. Parameters ========== alpha: Positive number, `0 < alpha` the shape paramater a : Real number, :math:`-\infty < a` the left boundary b : Real number, :math:`a >> from sympy.stats import PowerFunction, density, cdf, E, variance >>> from sympy import Symbol >>> alpha = Symbol("alpha", positive=True) >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = PowerFunction("X", 2, a, b) >>> density(X)(z) (-2*a + 2*z)/(-a + b)**2 >>> cdf(X)(z) Piecewise((a**2/(a**2 - 2*a*b + b**2) - 2*a*z/(a**2 - 2*a*b + b**2) + z**2/(a**2 - 2*a*b + b**2), a <= z), (0, True)) >>> alpha = 2 >>> a = 0 >>> b = 1 >>> Y = PowerFunction("Y", alpha, a, b) >>> E(Y) 2/3 >>> variance(Y) 1/18 References ========== .. [1] http://www.mathwave.com/help/easyfit/html/analyses/distributions/power_func.html """ return rv(name, PowerFunctionDistribution, (alpha, a, b)) #------------------------------------------------------------------------------- # QuadraticU distribution ------------------------------------------------------ class QuadraticUDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b): _value_check(b > a, "Parameter b must be in range (%s, oo)."%(a)) def pdf(self, x): a, b = self.a, self.b alpha = 12 / (b-a)**3 beta = (a+b) / 2 return Piecewise( (alpha * (x-beta)**2, And(a<=x, x<=b)), (S.Zero, True)) def _moment_generating_function(self, t): a, b = self.a, self.b return -3 * (exp(a*t) * (4 + (a**2 + 2*a*(-2 + b) + b**2) * t) \ - exp(b*t) * (4 + (-4*b + (a + b)**2) * t)) / ((a-b)**3 * t**2) def _characteristic_function(self, t): a, b = self.a, self.b return -3*I*(exp(I*a*t*exp(I*b*t)) * (4*I - (-4*b + (a+b)**2)*t)) \ / ((a-b)**3 * t**2) def QuadraticU(name, a, b): r""" Create a Continuous Random Variable with a U-quadratic distribution. The density of the U-quadratic distribution is given by .. math:: f(x) := \alpha (x-\beta)^2 with :math:`x \in [a,b]`. Parameters ========== a : Real number b : Real number, :math:`a < b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import QuadraticU, density >>> from sympy import Symbol, pprint >>> a = Symbol("a", real=True) >>> b = Symbol("b", real=True) >>> z = Symbol("z") >>> X = QuadraticU("x", a, b) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / 2 | / a b \ |12*|- - - - + z| | \ 2 2 / <----------------- for And(b >= z, a <= z) | 3 | (-a + b) | \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/U-quadratic_distribution """ return rv(name, QuadraticUDistribution, (a, b)) #------------------------------------------------------------------------------- # RaisedCosine distribution ---------------------------------------------------- class RaisedCosineDistribution(SingleContinuousDistribution): _argnames = ('mu', 's') @property def set(self): return Interval(self.mu - self.s, self.mu + self.s) @staticmethod def check(mu, s): _value_check(s > 0, "s must be positive") def pdf(self, x): mu, s = self.mu, self.s return Piecewise( ((1+cos(pi*(x-mu)/s)) / (2*s), And(mu-s<=x, x<=mu+s)), (S.Zero, True)) def _characteristic_function(self, t): mu, s = self.mu, self.s return Piecewise((exp(-I*pi*mu/s)/2, Eq(t, -pi/s)), (exp(I*pi*mu/s)/2, Eq(t, pi/s)), (pi**2*sin(s*t)*exp(I*mu*t) / (s*t*(pi**2 - s**2*t**2)), True)) def _moment_generating_function(self, t): mu, s = self.mu, self.s return pi**2 * sinh(s*t) * exp(mu*t) / (s*t*(pi**2 + s**2*t**2)) def RaisedCosine(name, mu, s): r""" Create a Continuous Random Variable with a raised cosine distribution. The density of the raised cosine distribution is given by .. math:: f(x) := \frac{1}{2s}\left(1+\cos\left(\frac{x-\mu}{s}\pi\right)\right) with :math:`x \in [\mu-s,\mu+s]`. Parameters ========== mu : Real number s : Real number, `s > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import RaisedCosine, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu", real=True) >>> s = Symbol("s", positive=True) >>> z = Symbol("z") >>> X = RaisedCosine("x", mu, s) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) / /pi*(-mu + z)\ |cos|------------| + 1 | \ s / <--------------------- for And(z >= mu - s, z <= mu + s) | 2*s | \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Raised_cosine_distribution """ return rv(name, RaisedCosineDistribution, (mu, s)) #------------------------------------------------------------------------------- # Rayleigh distribution -------------------------------------------------------- class RayleighDistribution(SingleContinuousDistribution): _argnames = ('sigma',) set = Interval(0, oo) @staticmethod def check(sigma): _value_check(sigma > 0, "Scale parameter sigma must be positive.") def pdf(self, x): sigma = self.sigma return x/sigma**2*exp(-x**2/(2*sigma**2)) def _cdf(self, x): sigma = self.sigma return 1 - exp(-(x**2/(2*sigma**2))) def _characteristic_function(self, t): sigma = self.sigma return 1 - sigma*t*exp(-sigma**2*t**2/2) * sqrt(pi/2) * (erfi(sigma*t/sqrt(2)) - I) def _moment_generating_function(self, t): sigma = self.sigma return 1 + sigma*t*exp(sigma**2*t**2/2) * sqrt(pi/2) * (erf(sigma*t/sqrt(2)) + 1) def Rayleigh(name, sigma): r""" Create a continuous random variable with a Rayleigh distribution. The density of the Rayleigh distribution is given by .. math :: f(x) := \frac{x}{\sigma^2} e^{-x^2/2\sigma^2} with :math:`x > 0`. Parameters ========== sigma : Real number, `\sigma > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Rayleigh, density, E, variance >>> from sympy import Symbol >>> sigma = Symbol("sigma", positive=True) >>> z = Symbol("z") >>> X = Rayleigh("x", sigma) >>> density(X)(z) z*exp(-z**2/(2*sigma**2))/sigma**2 >>> E(X) sqrt(2)*sqrt(pi)*sigma/2 >>> variance(X) -pi*sigma**2/2 + 2*sigma**2 References ========== .. [1] https://en.wikipedia.org/wiki/Rayleigh_distribution .. [2] http://mathworld.wolfram.com/RayleighDistribution.html """ return rv(name, RayleighDistribution, (sigma, )) #------------------------------------------------------------------------------- # Reciprocal distribution -------------------------------------------------------- class ReciprocalDistribution(SingleContinuousDistribution): _argnames = ('a', 'b') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b): _value_check(a > 0, "Parameter > 0. a = %s"%a) _value_check((a < b), "Parameter b must be in range (%s, +oo]. b = %s"%(a, b)) def pdf(self, x): a, b = self.a, self.b return 1/(x*(log(b) - log(a))) def Reciprocal(name, a, b): r"""Creates a continuous random variable with a reciprocal distribution. Parameters ========== a : Real number, :math:`0 < a` b : Real number, :math:`a < b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Reciprocal, density, cdf >>> from sympy import symbols >>> a, b, x = symbols('a, b, x', positive=True) >>> R = Reciprocal('R', a, b) >>> density(R)(x) 1/(x*(-log(a) + log(b))) >>> cdf(R)(x) Piecewise((log(a)/(log(a) - log(b)) - log(x)/(log(a) - log(b)), a <= x), (0, True)) Reference ========= .. [1] https://en.wikipedia.org/wiki/Reciprocal_distribution """ return rv(name, ReciprocalDistribution, (a, b)) #------------------------------------------------------------------------------- # Shifted Gompertz distribution ------------------------------------------------ class ShiftedGompertzDistribution(SingleContinuousDistribution): _argnames = ('b', 'eta') set = Interval(0, oo) @staticmethod def check(b, eta): _value_check(b > 0, "b must be positive") _value_check(eta > 0, "eta must be positive") def pdf(self, x): b, eta = self.b, self.eta return b*exp(-b*x)*exp(-eta*exp(-b*x))*(1+eta*(1-exp(-b*x))) def ShiftedGompertz(name, b, eta): r""" Create a continuous random variable with a Shifted Gompertz distribution. The density of the Shifted Gompertz distribution is given by .. math:: f(x) := b e^{-b x} e^{-\eta \exp(-b x)} \left[1 + \eta(1 - e^(-bx)) \right] with :math: 'x \in [0, \inf)'. Parameters ========== b: Real number, 'b > 0' a scale eta: Real number, 'eta > 0' a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import ShiftedGompertz, density >>> from sympy import Symbol >>> b = Symbol("b", positive=True) >>> eta = Symbol("eta", positive=True) >>> x = Symbol("x") >>> X = ShiftedGompertz("x", b, eta) >>> density(X)(x) b*(eta*(1 - exp(-b*x)) + 1)*exp(-b*x)*exp(-eta*exp(-b*x)) References ========== .. [1] https://en.wikipedia.org/wiki/Shifted_Gompertz_distribution """ return rv(name, ShiftedGompertzDistribution, (b, eta)) #------------------------------------------------------------------------------- # StudentT distribution -------------------------------------------------------- class StudentTDistribution(SingleContinuousDistribution): _argnames = ('nu',) set = Interval(-oo, oo) @staticmethod def check(nu): _value_check(nu > 0, "Degrees of freedom nu must be positive.") def pdf(self, x): nu = self.nu return 1/(sqrt(nu)*beta_fn(S.Half, nu/2))*(1 + x**2/nu)**(-(nu + 1)/2) def _cdf(self, x): nu = self.nu return S.Half + x*gamma((nu+1)/2)*hyper((S.Half, (nu+1)/2), (Rational(3, 2),), -x**2/nu)/(sqrt(pi*nu)*gamma(nu/2)) def _moment_generating_function(self, t): raise NotImplementedError('The moment generating function for the Student-T distribution is undefined.') def StudentT(name, nu): r""" Create a continuous random variable with a student's t distribution. The density of the student's t distribution is given by .. math:: f(x) := \frac{\Gamma \left(\frac{\nu+1}{2} \right)} {\sqrt{\nu\pi}\Gamma \left(\frac{\nu}{2} \right)} \left(1+\frac{x^2}{\nu} \right)^{-\frac{\nu+1}{2}} Parameters ========== nu : Real number, `\nu > 0`, the degrees of freedom Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import StudentT, density, cdf >>> from sympy import Symbol, pprint >>> nu = Symbol("nu", positive=True) >>> z = Symbol("z") >>> X = StudentT("x", nu) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) nu 1 - -- - - 2 2 / 2\ | z | |1 + --| \ nu/ ----------------- ____ / nu\ \/ nu *B|1/2, --| \ 2 / >>> cdf(X)(z) 1/2 + z*gamma(nu/2 + 1/2)*hyper((1/2, nu/2 + 1/2), (3/2,), -z**2/nu)/(sqrt(pi)*sqrt(nu)*gamma(nu/2)) References ========== .. [1] https://en.wikipedia.org/wiki/Student_t-distribution .. [2] http://mathworld.wolfram.com/Studentst-Distribution.html """ return rv(name, StudentTDistribution, (nu, )) #------------------------------------------------------------------------------- # Trapezoidal distribution ------------------------------------------------------ class TrapezoidalDistribution(SingleContinuousDistribution): _argnames = ('a', 'b', 'c', 'd') @property def set(self): return Interval(self.a, self.d) @staticmethod def check(a, b, c, d): _value_check(a < d, "Lower bound parameter a < %s. a = %s"%(d, a)) _value_check((a <= b, b < c), "Level start parameter b must be in range [%s, %s). b = %s"%(a, c, b)) _value_check((b < c, c <= d), "Level end parameter c must be in range (%s, %s]. c = %s"%(b, d, c)) _value_check(d >= c, "Upper bound parameter d > %s. d = %s"%(c, d)) def pdf(self, x): a, b, c, d = self.a, self.b, self.c, self.d return Piecewise( (2*(x-a) / ((b-a)*(d+c-a-b)), And(a <= x, x < b)), (2 / (d+c-a-b), And(b <= x, x < c)), (2*(d-x) / ((d-c)*(d+c-a-b)), And(c <= x, x <= d)), (S.Zero, True)) def Trapezoidal(name, a, b, c, d): r""" Create a continuous random variable with a trapezoidal distribution. The density of the trapezoidal distribution is given by .. math:: f(x) := \begin{cases} 0 & \mathrm{for\ } x < a, \\ \frac{2(x-a)}{(b-a)(d+c-a-b)} & \mathrm{for\ } a \le x < b, \\ \frac{2}{d+c-a-b} & \mathrm{for\ } b \le x < c, \\ \frac{2(d-x)}{(d-c)(d+c-a-b)} & \mathrm{for\ } c \le x < d, \\ 0 & \mathrm{for\ } d < x. \end{cases} Parameters ========== a : Real number, :math:`a < d` b : Real number, :math:`a <= b < c` c : Real number, :math:`b < c <= d` d : Real number Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Trapezoidal, density >>> from sympy import Symbol, pprint >>> a = Symbol("a") >>> b = Symbol("b") >>> c = Symbol("c") >>> d = Symbol("d") >>> z = Symbol("z") >>> X = Trapezoidal("x", a,b,c,d) >>> pprint(density(X)(z), use_unicode=False) / -2*a + 2*z |------------------------- for And(a <= z, b > z) |(-a + b)*(-a - b + c + d) | | 2 | -------------- for And(b <= z, c > z) < -a - b + c + d | | 2*d - 2*z |------------------------- for And(d >= z, c <= z) |(-c + d)*(-a - b + c + d) | \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Trapezoidal_distribution """ return rv(name, TrapezoidalDistribution, (a, b, c, d)) #------------------------------------------------------------------------------- # Triangular distribution ------------------------------------------------------ class TriangularDistribution(SingleContinuousDistribution): _argnames = ('a', 'b', 'c') @property def set(self): return Interval(self.a, self.b) @staticmethod def check(a, b, c): _value_check(b > a, "Parameter b > %s. b = %s"%(a, b)) _value_check((a <= c, c <= b), "Parameter c must be in range [%s, %s]. c = %s"%(a, b, c)) def pdf(self, x): a, b, c = self.a, self.b, self.c return Piecewise( (2*(x - a)/((b - a)*(c - a)), And(a <= x, x < c)), (2/(b - a), Eq(x, c)), (2*(b - x)/((b - a)*(b - c)), And(c < x, x <= b)), (S.Zero, True)) def _characteristic_function(self, t): a, b, c = self.a, self.b, self.c return -2 *((b-c) * exp(I*a*t) - (b-a) * exp(I*c*t) + (c-a) * exp(I*b*t)) / ((b-a)*(c-a)*(b-c)*t**2) def _moment_generating_function(self, t): a, b, c = self.a, self.b, self.c return 2 * ((b - c) * exp(a * t) - (b - a) * exp(c * t) + (c - a) * exp(b * t)) / ( (b - a) * (c - a) * (b - c) * t ** 2) def Triangular(name, a, b, c): r""" Create a continuous random variable with a triangular distribution. The density of the triangular distribution is given by .. math:: f(x) := \begin{cases} 0 & \mathrm{for\ } x < a, \\ \frac{2(x-a)}{(b-a)(c-a)} & \mathrm{for\ } a \le x < c, \\ \frac{2}{b-a} & \mathrm{for\ } x = c, \\ \frac{2(b-x)}{(b-a)(b-c)} & \mathrm{for\ } c < x \le b, \\ 0 & \mathrm{for\ } b < x. \end{cases} Parameters ========== a : Real number, :math:`a \in \left(-\infty, \infty\right)` b : Real number, :math:`a < b` c : Real number, :math:`a \leq c \leq b` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Triangular, density >>> from sympy import Symbol, pprint >>> a = Symbol("a") >>> b = Symbol("b") >>> c = Symbol("c") >>> z = Symbol("z") >>> X = Triangular("x", a,b,c) >>> pprint(density(X)(z), use_unicode=False) / -2*a + 2*z |----------------- for And(a <= z, c > z) |(-a + b)*(-a + c) | | 2 | ------ for c = z < -a + b | | 2*b - 2*z |---------------- for And(b >= z, c < z) |(-a + b)*(b - c) | \ 0 otherwise References ========== .. [1] https://en.wikipedia.org/wiki/Triangular_distribution .. [2] http://mathworld.wolfram.com/TriangularDistribution.html """ return rv(name, TriangularDistribution, (a, b, c)) #------------------------------------------------------------------------------- # Uniform distribution --------------------------------------------------------- class UniformDistribution(SingleContinuousDistribution): _argnames = ('left', 'right') @property def set(self): return Interval(self.left, self.right) @staticmethod def check(left, right): _value_check(left < right, "Lower limit should be less than Upper limit.") def pdf(self, x): left, right = self.left, self.right return Piecewise( (S.One/(right - left), And(left <= x, x <= right)), (S.Zero, True) ) def _cdf(self, x): left, right = self.left, self.right return Piecewise( (S.Zero, x < left), ((x - left)/(right - left), x <= right), (S.One, True) ) def _characteristic_function(self, t): left, right = self.left, self.right return Piecewise(((exp(I*t*right) - exp(I*t*left)) / (I*t*(right - left)), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): left, right = self.left, self.right return Piecewise(((exp(t*right) - exp(t*left)) / (t * (right - left)), Ne(t, 0)), (S.One, True)) def expectation(self, expr, var, **kwargs): from sympy import Max, Min kwargs['evaluate'] = True result = SingleContinuousDistribution.expectation(self, expr, var, **kwargs) result = result.subs({Max(self.left, self.right): self.right, Min(self.left, self.right): self.left}) return result def Uniform(name, left, right): r""" Create a continuous random variable with a uniform distribution. The density of the uniform distribution is given by .. math:: f(x) := \begin{cases} \frac{1}{b - a} & \text{for } x \in [a,b] \\ 0 & \text{otherwise} \end{cases} with :math:`x \in [a,b]`. Parameters ========== a : Real number, :math:`-\infty < a` the left boundary b : Real number, :math:`a >> from sympy.stats import Uniform, density, cdf, E, variance >>> from sympy import Symbol, simplify >>> a = Symbol("a", negative=True) >>> b = Symbol("b", positive=True) >>> z = Symbol("z") >>> X = Uniform("x", a, b) >>> density(X)(z) Piecewise((1/(-a + b), (b >= z) & (a <= z)), (0, True)) >>> cdf(X)(z) Piecewise((0, a > z), ((-a + z)/(-a + b), b >= z), (1, True)) >>> E(X) a/2 + b/2 >>> simplify(variance(X)) a**2/12 - a*b/6 + b**2/12 References ========== .. [1] https://en.wikipedia.org/wiki/Uniform_distribution_%28continuous%29 .. [2] http://mathworld.wolfram.com/UniformDistribution.html """ return rv(name, UniformDistribution, (left, right)) #------------------------------------------------------------------------------- # UniformSum distribution ------------------------------------------------------ class UniformSumDistribution(SingleContinuousDistribution): _argnames = ('n',) @property def set(self): return Interval(0, self.n) @staticmethod def check(n): _value_check((n > 0, n.is_integer), "Parameter n must be positive integer.") def pdf(self, x): n = self.n k = Dummy("k") return 1/factorial( n - 1)*Sum((-1)**k*binomial(n, k)*(x - k)**(n - 1), (k, 0, floor(x))) def _cdf(self, x): n = self.n k = Dummy("k") return Piecewise((S.Zero, x < 0), (1/factorial(n)*Sum((-1)**k*binomial(n, k)*(x - k)**(n), (k, 0, floor(x))), x <= n), (S.One, True)) def _characteristic_function(self, t): return ((exp(I*t) - 1) / (I*t))**self.n def _moment_generating_function(self, t): return ((exp(t) - 1) / t)**self.n def UniformSum(name, n): r""" Create a continuous random variable with an Irwin-Hall distribution. The probability distribution function depends on a single parameter `n` which is an integer. The density of the Irwin-Hall distribution is given by .. math :: f(x) := \frac{1}{(n-1)!}\sum_{k=0}^{\left\lfloor x\right\rfloor}(-1)^k \binom{n}{k}(x-k)^{n-1} Parameters ========== n : A positive Integer, `n > 0` Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import UniformSum, density, cdf >>> from sympy import Symbol, pprint >>> n = Symbol("n", integer=True) >>> z = Symbol("z") >>> X = UniformSum("x", n) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) floor(z) ___ \ ` \ k n - 1 /n\ ) (-1) *(-k + z) *| | / \k/ /__, k = 0 -------------------------------- (n - 1)! >>> cdf(X)(z) Piecewise((0, z < 0), (Sum((-1)**_k*(-_k + z)**n*binomial(n, _k), (_k, 0, floor(z)))/factorial(n), n >= z), (1, True)) Compute cdf with specific 'x' and 'n' values as follows : >>> cdf(UniformSum("x", 5), evaluate=False)(2).doit() 9/40 The argument evaluate=False prevents an attempt at evaluation of the sum for general n, before the argument 2 is passed. References ========== .. [1] https://en.wikipedia.org/wiki/Uniform_sum_distribution .. [2] http://mathworld.wolfram.com/UniformSumDistribution.html """ return rv(name, UniformSumDistribution, (n, )) #------------------------------------------------------------------------------- # VonMises distribution -------------------------------------------------------- class VonMisesDistribution(SingleContinuousDistribution): _argnames = ('mu', 'k') set = Interval(0, 2*pi) @staticmethod def check(mu, k): _value_check(k > 0, "k must be positive") def pdf(self, x): mu, k = self.mu, self.k return exp(k*cos(x-mu)) / (2*pi*besseli(0, k)) def VonMises(name, mu, k): r""" Create a Continuous Random Variable with a von Mises distribution. The density of the von Mises distribution is given by .. math:: f(x) := \frac{e^{\kappa\cos(x-\mu)}}{2\pi I_0(\kappa)} with :math:`x \in [0,2\pi]`. Parameters ========== mu : Real number, measure of location k : Real number, measure of concentration Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import VonMises, density >>> from sympy import Symbol, pprint >>> mu = Symbol("mu") >>> k = Symbol("k", positive=True) >>> z = Symbol("z") >>> X = VonMises("x", mu, k) >>> D = density(X)(z) >>> pprint(D, use_unicode=False) k*cos(mu - z) e ------------------ 2*pi*besseli(0, k) References ========== .. [1] https://en.wikipedia.org/wiki/Von_Mises_distribution .. [2] http://mathworld.wolfram.com/vonMisesDistribution.html """ return rv(name, VonMisesDistribution, (mu, k)) #------------------------------------------------------------------------------- # Weibull distribution --------------------------------------------------------- class WeibullDistribution(SingleContinuousDistribution): _argnames = ('alpha', 'beta') set = Interval(0, oo) @staticmethod def check(alpha, beta): _value_check(alpha > 0, "Alpha must be positive") _value_check(beta > 0, "Beta must be positive") def pdf(self, x): alpha, beta = self.alpha, self.beta return beta * (x/alpha)**(beta - 1) * exp(-(x/alpha)**beta) / alpha def Weibull(name, alpha, beta): r""" Create a continuous random variable with a Weibull distribution. The density of the Weibull distribution is given by .. math:: f(x) := \begin{cases} \frac{k}{\lambda}\left(\frac{x}{\lambda}\right)^{k-1} e^{-(x/\lambda)^{k}} & x\geq0\\ 0 & x<0 \end{cases} Parameters ========== lambda : Real number, :math:`\lambda > 0` a scale k : Real number, `k > 0` a shape Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Weibull, density, E, variance >>> from sympy import Symbol, simplify >>> l = Symbol("lambda", positive=True) >>> k = Symbol("k", positive=True) >>> z = Symbol("z") >>> X = Weibull("x", l, k) >>> density(X)(z) k*(z/lambda)**(k - 1)*exp(-(z/lambda)**k)/lambda >>> simplify(E(X)) lambda*gamma(1 + 1/k) >>> simplify(variance(X)) lambda**2*(-gamma(1 + 1/k)**2 + gamma(1 + 2/k)) References ========== .. [1] https://en.wikipedia.org/wiki/Weibull_distribution .. [2] http://mathworld.wolfram.com/WeibullDistribution.html """ return rv(name, WeibullDistribution, (alpha, beta)) #------------------------------------------------------------------------------- # Wigner semicircle distribution ----------------------------------------------- class WignerSemicircleDistribution(SingleContinuousDistribution): _argnames = ('R',) @property def set(self): return Interval(-self.R, self.R) @staticmethod def check(R): _value_check(R > 0, "Radius R must be positive.") def pdf(self, x): R = self.R return 2/(pi*R**2)*sqrt(R**2 - x**2) def _characteristic_function(self, t): return Piecewise((2 * besselj(1, self.R*t) / (self.R*t), Ne(t, 0)), (S.One, True)) def _moment_generating_function(self, t): return Piecewise((2 * besseli(1, self.R*t) / (self.R*t), Ne(t, 0)), (S.One, True)) def WignerSemicircle(name, R): r""" Create a continuous random variable with a Wigner semicircle distribution. The density of the Wigner semicircle distribution is given by .. math:: f(x) := \frac2{\pi R^2}\,\sqrt{R^2-x^2} with :math:`x \in [-R,R]`. Parameters ========== R : Real number, `R > 0`, the radius Returns ======= A `RandomSymbol`. Examples ======== >>> from sympy.stats import WignerSemicircle, density, E >>> from sympy import Symbol >>> R = Symbol("R", positive=True) >>> z = Symbol("z") >>> X = WignerSemicircle("x", R) >>> density(X)(z) 2*sqrt(R**2 - z**2)/(pi*R**2) >>> E(X) 0 References ========== .. [1] https://en.wikipedia.org/wiki/Wigner_semicircle_distribution .. [2] http://mathworld.wolfram.com/WignersSemicircleLaw.html """ return rv(name, WignerSemicircleDistribution, (R,))

65c15591aa99adb2cd607d96465393711b882d1b40925d999cc025233f0a9e92

""" Finite Discrete Random Variables - Prebuilt variable types Contains ======== FiniteRV DiscreteUniform Die Bernoulli Coin Binomial BetaBinomial Hypergeometric Rademacher """ from sympy import (S, sympify, Rational, binomial, cacheit, Integer, Dummy, Eq, Intersection, Interval, Symbol, Lambda, Piecewise, Or, Gt, Lt, Ge, Le, Contains) from sympy import beta as beta_fn from sympy.stats.frv import (SingleFiniteDistribution, SingleFinitePSpace) from sympy.stats.rv import _value_check, Density, is_random __all__ = ['FiniteRV', 'DiscreteUniform', 'Die', 'Bernoulli', 'Coin', 'Binomial', 'BetaBinomial', 'Hypergeometric', 'Rademacher' ] def rv(name, cls, *args, **kwargs): args = list(map(sympify, args)) dist = cls(*args) if kwargs.pop('check', True): dist.check(*args) pspace = SingleFinitePSpace(name, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(name, CompoundDistribution(dist)) return pspace.value class FiniteDistributionHandmade(SingleFiniteDistribution): @property def dict(self): return self.args[0] def pmf(self, x): x = Symbol('x') return Lambda(x, Piecewise(*( [(v, Eq(k, x)) for k, v in self.dict.items()] + [(S.Zero, True)]))) @property def set(self): return set(self.dict.keys()) @staticmethod def check(density): for p in density.values(): _value_check((p >= 0, p <= 1), "Probability at a point must be between 0 and 1.") val = sum(density.values()) _value_check(Eq(val, 1) != S.false, "Total Probability must be 1.") def FiniteRV(name, density, **kwargs): r""" Create a Finite Random Variable given a dict representing the density. Parameters ========== name : Symbol Represents name of the random variable. density: A dict Dictionary conatining the pdf of finite distribution check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Examples ======== >>> from sympy.stats import FiniteRV, P, E >>> density = {0: .1, 1: .2, 2: .3, 3: .4} >>> X = FiniteRV('X', density) >>> E(X) 2.00000000000000 >>> P(X >= 2) 0.700000000000000 Returns ======= RandomSymbol """ # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(name, FiniteDistributionHandmade, density, **kwargs) class DiscreteUniformDistribution(SingleFiniteDistribution): @staticmethod def check(*args): # not using _value_check since there is a # suggestion for the user if len(set(args)) != len(args): from sympy.utilities.iterables import multiset from sympy.utilities.misc import filldedent weights = multiset(args) n = Integer(len(args)) for k in weights: weights[k] /= n raise ValueError(filldedent(""" Repeated args detected but set expected. For a distribution having different weights for each item use the following:""") + ( '\nS("FiniteRV(%s, %s)")' % ("'X'", weights))) @property def p(self): return Rational(1, len(self.args)) @property # type: ignore @cacheit def dict(self): return {k: self.p for k in self.set} @property def set(self): return set(self.args) def pmf(self, x): if x in self.args: return self.p else: return S.Zero def DiscreteUniform(name, items): r""" Create a Finite Random Variable representing a uniform distribution over the input set. Parameters ========== items: list/tuple Items over which Uniform distribution is to be made Examples ======== >>> from sympy.stats import DiscreteUniform, density >>> from sympy import symbols >>> X = DiscreteUniform('X', symbols('a b c')) # equally likely over a, b, c >>> density(X).dict {a: 1/3, b: 1/3, c: 1/3} >>> Y = DiscreteUniform('Y', list(range(5))) # distribution over a range >>> density(Y).dict {0: 1/5, 1: 1/5, 2: 1/5, 3: 1/5, 4: 1/5} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Discrete_uniform_distribution .. [2] http://mathworld.wolfram.com/DiscreteUniformDistribution.html """ return rv(name, DiscreteUniformDistribution, *items) class DieDistribution(SingleFiniteDistribution): _argnames = ('sides',) @staticmethod def check(sides): _value_check((sides.is_positive, sides.is_integer), "number of sides must be a positive integer.") @property def is_symbolic(self): return not self.sides.is_number @property def high(self): return self.sides @property def low(self): return S.One @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.sides)) return set(map(Integer, list(range(1, self.sides + 1)))) def pmf(self, x): x = sympify(x) if not (x.is_number or x.is_Symbol or is_random(x)): raise ValueError("'x' expected as an argument of type 'number' or 'Symbol' or , " "'RandomSymbol' not %s" % (type(x))) cond = Ge(x, 1) & Le(x, self.sides) & Contains(x, S.Integers) return Piecewise((S.One/self.sides, cond), (S.Zero, True)) def Die(name, sides=6): r""" Create a Finite Random Variable representing a fair die. Parameters ========== sides: Integer Represents the number of sides of the Die, by default is 6 Examples ======== >>> from sympy.stats import Die, density >>> from sympy import Symbol >>> D6 = Die('D6', 6) # Six sided Die >>> density(D6).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> D4 = Die('D4', 4) # Four sided Die >>> density(D4).dict {1: 1/4, 2: 1/4, 3: 1/4, 4: 1/4} >>> n = Symbol('n', positive=True, integer=True) >>> Dn = Die('Dn', n) # n sided Die >>> density(Dn).dict Density(DieDistribution(n)) >>> density(Dn).dict.subs(n, 4).doit() {1: 1/4, 2: 1/4, 3: 1/4, 4: 1/4} Returns ======= RandomSymbol """ return rv(name, DieDistribution, sides) class BernoulliDistribution(SingleFiniteDistribution): _argnames = ('p', 'succ', 'fail') @staticmethod def check(p, succ, fail): _value_check((p >= 0, p <= 1), "p should be in range [0, 1].") @property def set(self): return {self.succ, self.fail} def pmf(self, x): if isinstance(self.succ, Symbol) and isinstance(self.fail, Symbol): return Piecewise((self.p, x == self.succ), (1 - self.p, x == self.fail), (S.Zero, True)) return Piecewise((self.p, Eq(x, self.succ)), (1 - self.p, Eq(x, self.fail)), (S.Zero, True)) def Bernoulli(name, p, succ=1, fail=0): r""" Create a Finite Random Variable representing a Bernoulli process. Parameters ========== p : Rational number between 0 and 1 Represents probability of success succ : Integer/symbol/string Represents event of success fail : Integer/symbol/string Represents event of failure Examples ======== >>> from sympy.stats import Bernoulli, density >>> from sympy import S >>> X = Bernoulli('X', S(3)/4) # 1-0 Bernoulli variable, probability = 3/4 >>> density(X).dict {0: 1/4, 1: 3/4} >>> X = Bernoulli('X', S.Half, 'Heads', 'Tails') # A fair coin toss >>> density(X).dict {Heads: 1/2, Tails: 1/2} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Bernoulli_distribution .. [2] http://mathworld.wolfram.com/BernoulliDistribution.html """ return rv(name, BernoulliDistribution, p, succ, fail) def Coin(name, p=S.Half): r""" Create a Finite Random Variable representing a Coin toss. Parameters ========== p : Rational Numeber between 0 and 1 Represents probability of getting "Heads", by default is Half Examples ======== >>> from sympy.stats import Coin, density >>> from sympy import Rational >>> C = Coin('C') # A fair coin toss >>> density(C).dict {H: 1/2, T: 1/2} >>> C2 = Coin('C2', Rational(3, 5)) # An unfair coin >>> density(C2).dict {H: 3/5, T: 2/5} Returns ======= RandomSymbol See Also ======== sympy.stats.Binomial References ========== .. [1] https://en.wikipedia.org/wiki/Coin_flipping """ return rv(name, BernoulliDistribution, p, 'H', 'T') class BinomialDistribution(SingleFiniteDistribution): _argnames = ('n', 'p', 'succ', 'fail') @staticmethod def check(n, p, succ, fail): _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer.") _value_check((p <= 1, p >= 0), "p should be in range [0, 1].") @property def high(self): return self.n @property def low(self): return S.Zero @property def is_symbolic(self): return not self.n.is_number @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.n)) return set(self.dict.keys()) def pmf(self, x): n, p = self.n, self.p x = sympify(x) if not (x.is_number or x.is_Symbol or is_random(x)): raise ValueError("'x' expected as an argument of type 'number' or 'Symbol' or , " "'RandomSymbol' not %s" % (type(x))) cond = Ge(x, 0) & Le(x, n) & Contains(x, S.Integers) return Piecewise((binomial(n, x) * p**x * (1 - p)**(n - x), cond), (S.Zero, True)) @property # type: ignore @cacheit def dict(self): if self.is_symbolic: return Density(self) return {k*self.succ + (self.n-k)*self.fail: self.pmf(k) for k in range(0, self.n + 1)} def Binomial(name, n, p, succ=1, fail=0): r""" Create a Finite Random Variable representing a binomial distribution. Parameters ========== n : Positive Integer Represents number of trials p : Rational Number between 0 and 1 Represents probability of success succ : Integer/symbol/string Represents event of success, by default is 1 fail : Integer/symbol/string Represents event of failure, by default is 0 Examples ======== >>> from sympy.stats import Binomial, density >>> from sympy import S, Symbol >>> X = Binomial('X', 4, S.Half) # Four "coin flips" >>> density(X).dict {0: 1/16, 1: 1/4, 2: 3/8, 3: 1/4, 4: 1/16} >>> n = Symbol('n', positive=True, integer=True) >>> p = Symbol('p', positive=True) >>> X = Binomial('X', n, S.Half) # n "coin flips" >>> density(X).dict Density(BinomialDistribution(n, 1/2, 1, 0)) >>> density(X).dict.subs(n, 4).doit() {0: 1/16, 1: 1/4, 2: 3/8, 3: 1/4, 4: 1/16} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Binomial_distribution .. [2] http://mathworld.wolfram.com/BinomialDistribution.html """ return rv(name, BinomialDistribution, n, p, succ, fail) #------------------------------------------------------------------------------- # Beta-binomial distribution ---------------------------------------------------------- class BetaBinomialDistribution(SingleFiniteDistribution): _argnames = ('n', 'alpha', 'beta') @staticmethod def check(n, alpha, beta): _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer. n = %s." % str(n)) _value_check((alpha > 0), "'alpha' must be: alpha > 0 . alpha = %s" % str(alpha)) _value_check((beta > 0), "'beta' must be: beta > 0 . beta = %s" % str(beta)) @property def high(self): return self.n @property def low(self): return S.Zero @property def is_symbolic(self): return not self.n.is_number @property def set(self): if self.is_symbolic: return Intersection(S.Naturals0, Interval(0, self.n)) return set(map(Integer, list(range(0, self.n + 1)))) def pmf(self, k): n, a, b = self.n, self.alpha, self.beta return binomial(n, k) * beta_fn(k + a, n - k + b) / beta_fn(a, b) def BetaBinomial(name, n, alpha, beta): r""" Create a Finite Random Variable representing a Beta-binomial distribution. Parameters ========== n : Positive Integer Represents number of trials alpha : Real positive number beta : Real positive number Examples ======== >>> from sympy.stats import BetaBinomial, density >>> X = BetaBinomial('X', 2, 1, 1) >>> density(X).dict {0: 1/3, 1: 2*beta(2, 2), 2: 1/3} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Beta-binomial_distribution .. [2] http://mathworld.wolfram.com/BetaBinomialDistribution.html """ return rv(name, BetaBinomialDistribution, n, alpha, beta) class HypergeometricDistribution(SingleFiniteDistribution): _argnames = ('N', 'm', 'n') @staticmethod def check(n, N, m): _value_check((N.is_integer, N.is_nonnegative), "'N' must be nonnegative integer. N = %s." % str(n)) _value_check((n.is_integer, n.is_nonnegative), "'n' must be nonnegative integer. n = %s." % str(n)) _value_check((m.is_integer, m.is_nonnegative), "'m' must be nonnegative integer. m = %s." % str(n)) @property def is_symbolic(self): return any(not x.is_number for x in (self.N, self.m, self.n)) @property def high(self): return Piecewise((self.n, Lt(self.n, self.m) != False), (self.m, True)) @property def low(self): return Piecewise((0, Gt(0, self.n + self.m - self.N) != False), (self.n + self.m - self.N, True)) @property def set(self): N, m, n = self.N, self.m, self.n if self.is_symbolic: return Intersection(S.Naturals0, Interval(self.low, self.high)) return {i for i in range(max(0, n + m - N), min(n, m) + 1)} def pmf(self, k): N, m, n = self.N, self.m, self.n return S(binomial(m, k) * binomial(N - m, n - k))/binomial(N, n) def Hypergeometric(name, N, m, n): r""" Create a Finite Random Variable representing a hypergeometric distribution. Parameters ========== N : Positive Integer Represents finite population of size N. m : Positive Integer Represents number of trials with required feature. n : Positive Integer Represents numbers of draws. Examples ======== >>> from sympy.stats import Hypergeometric, density >>> X = Hypergeometric('X', 10, 5, 3) # 10 marbles, 5 white (success), 3 draws >>> density(X).dict {0: 1/12, 1: 5/12, 2: 5/12, 3: 1/12} Returns ======= RandomSymbol References ========== .. [1] https://en.wikipedia.org/wiki/Hypergeometric_distribution .. [2] http://mathworld.wolfram.com/HypergeometricDistribution.html """ return rv(name, HypergeometricDistribution, N, m, n) class RademacherDistribution(SingleFiniteDistribution): @property def set(self): return {-1, 1} @property def pmf(self): k = Dummy('k') return Lambda(k, Piecewise((S.Half, Or(Eq(k, -1), Eq(k, 1))), (S.Zero, True))) def Rademacher(name): r""" Create a Finite Random Variable representing a Rademacher distribution. Examples ======== >>> from sympy.stats import Rademacher, density >>> X = Rademacher('X') >>> density(X).dict {-1: 1/2, 1: 1/2} Returns ======= RandomSymbol See Also ======== sympy.stats.Bernoulli References ========== .. [1] https://en.wikipedia.org/wiki/Rademacher_distribution """ return rv(name, RademacherDistribution)

0b964834b4ced5429f410f052ba38d6c628f7a05b5bda2bfde7d0edf169b50a1

import random import itertools from typing import Sequence as tSequence, Union as tUnion, List as tList, Tuple as tTuple from sympy import (Matrix, MatrixSymbol, S, Indexed, Basic, Tuple, Range, Set, And, Eq, FiniteSet, ImmutableMatrix, Integer, igcd, Lambda, Mul, Dummy, IndexedBase, Add, Interval, oo, linsolve, eye, Or, Not, Intersection, factorial, Contains, Union, Expr, Function, exp, cacheit, sqrt, pi, gamma, Ge, Piecewise, Symbol, NonSquareMatrixError, EmptySet, ceiling, MatrixBase, ConditionSet, ones, zeros, Identity, Rational, Lt, Gt, Ne, BlockMatrix) from sympy.core.relational import Relational from sympy.logic.boolalg import Boolean from sympy.utilities.exceptions import SymPyDeprecationWarning from sympy.utilities.iterables import strongly_connected_components from sympy.stats.joint_rv import JointDistribution from sympy.stats.joint_rv_types import JointDistributionHandmade from sympy.stats.rv import (RandomIndexedSymbol, random_symbols, RandomSymbol, _symbol_converter, _value_check, pspace, given, dependent, is_random, sample_iter) from sympy.stats.stochastic_process import StochasticPSpace from sympy.stats.symbolic_probability import Probability, Expectation from sympy.stats.frv_types import Bernoulli, BernoulliDistribution, FiniteRV from sympy.stats.drv_types import Poisson, PoissonDistribution from sympy.stats.crv_types import Normal, NormalDistribution, Gamma, GammaDistribution from sympy.core.sympify import _sympify, sympify __all__ = [ 'StochasticProcess', 'DiscreteTimeStochasticProcess', 'DiscreteMarkovChain', 'TransitionMatrixOf', 'StochasticStateSpaceOf', 'GeneratorMatrixOf', 'ContinuousMarkovChain', 'BernoulliProcess', 'PoissonProcess', 'WienerProcess', 'GammaProcess' ] @is_random.register(Indexed) def _(x): return is_random(x.base) @is_random.register(RandomIndexedSymbol) # type: ignore def _(x): return True def _set_converter(itr): """ Helper function for converting list/tuple/set to Set. If parameter is not an instance of list/tuple/set then no operation is performed. Returns ======= Set The argument converted to Set. Raises ====== TypeError If the argument is not an instance of list/tuple/set. """ if isinstance(itr, (list, tuple, set)): itr = FiniteSet(*itr) if not isinstance(itr, Set): raise TypeError("%s is not an instance of list/tuple/set."%(itr)) return itr def _state_converter(itr: tSequence) -> tUnion[Tuple, Range]: """ Helper function for converting list/tuple/set/Range/Tuple/FiniteSet to tuple/Range. """ if isinstance(itr, (Tuple, set, FiniteSet)): itr = Tuple(*(sympify(i) if isinstance(i, str) else i for i in itr)) elif isinstance(itr, (list, tuple)): # check if states are unique if len(set(itr)) != len(itr): raise ValueError('The state space must have unique elements.') itr = Tuple(*(sympify(i) if isinstance(i, str) else i for i in itr)) elif isinstance(itr, Range): # the only ordered set in sympy I know of # try to convert to tuple try: itr = Tuple(*(sympify(i) if isinstance(i, str) else i for i in itr)) except ValueError: pass else: raise TypeError("%s is not an instance of list/tuple/set/Range/Tuple/FiniteSet." % (itr)) return itr def _sym_sympify(arg): """ Converts an arbitrary expression to a type that can be used inside SymPy. As generally strings are unwise to use in the expressions, it returns the Symbol of argument if the string type argument is passed. Parameters ========= arg: The parameter to be converted to be used in Sympy. Returns ======= The converted parameter. """ if isinstance(arg, str): return Symbol(arg) else: return _sympify(arg) def _matrix_checks(matrix): if not isinstance(matrix, (Matrix, MatrixSymbol, ImmutableMatrix)): raise TypeError("Transition probabilities either should " "be a Matrix or a MatrixSymbol.") if matrix.shape[0] != matrix.shape[1]: raise NonSquareMatrixError("%s is not a square matrix"%(matrix)) if isinstance(matrix, Matrix): matrix = ImmutableMatrix(matrix.tolist()) return matrix class StochasticProcess(Basic): """ Base class for all the stochastic processes whether discrete or continuous. Parameters ========== sym: Symbol or str state_space: Set The state space of the stochastic process, by default S.Reals. For discrete sets it is zero indexed. See Also ======== DiscreteTimeStochasticProcess """ index_set = S.Reals def __new__(cls, sym, state_space=S.Reals, **kwargs): sym = _symbol_converter(sym) state_space = _set_converter(state_space) return Basic.__new__(cls, sym, state_space) @property def symbol(self): return self.args[0] @property def state_space(self) -> tUnion[FiniteSet, Range]: if not isinstance(self.args[1], (FiniteSet, Range)): return FiniteSet(*self.args[1]) return self.args[1] @property def distribution(self): return None def __call__(self, time): """ Overridden in ContinuousTimeStochasticProcess. """ raise NotImplementedError("Use [] for indexing discrete time stochastic process.") def __getitem__(self, time): """ Overridden in DiscreteTimeStochasticProcess. """ raise NotImplementedError("Use () for indexing continuous time stochastic process.") def probability(self, condition): raise NotImplementedError() def joint_distribution(self, *args): """ Computes the joint distribution of the random indexed variables. Parameters ========== args: iterable The finite list of random indexed variables/the key of a stochastic process whose joint distribution has to be computed. Returns ======= JointDistribution The joint distribution of the list of random indexed variables. An unevaluated object is returned if it is not possible to compute the joint distribution. Raises ====== ValueError: When the arguments passed are not of type RandomIndexSymbol or Number. """ args = list(args) for i, arg in enumerate(args): if S(arg).is_Number: if self.index_set.is_subset(S.Integers): args[i] = self.__getitem__(arg) else: args[i] = self.__call__(arg) elif not isinstance(arg, RandomIndexedSymbol): raise ValueError("Expected a RandomIndexedSymbol or " "key not %s"%(type(arg))) if args[0].pspace.distribution == None: # checks if there is any distribution available return JointDistribution(*args) pdf = Lambda(tuple(args), expr=Mul.fromiter(arg.pspace.process.density(arg) for arg in args)) return JointDistributionHandmade(pdf) def expectation(self, condition, given_condition): raise NotImplementedError("Abstract method for expectation queries.") def sample(self): raise NotImplementedError("Abstract method for sampling queries.") class DiscreteTimeStochasticProcess(StochasticProcess): """ Base class for all discrete stochastic processes. """ def __getitem__(self, time): """ For indexing discrete time stochastic processes. Returns ======= RandomIndexedSymbol """ if time not in self.index_set: raise IndexError("%s is not in the index set of %s"%(time, self.symbol)) idx_obj = Indexed(self.symbol, time) pspace_obj = StochasticPSpace(self.symbol, self, self.distribution) return RandomIndexedSymbol(idx_obj, pspace_obj) class ContinuousTimeStochasticProcess(StochasticProcess): """ Base class for all continuous time stochastic process. """ def __call__(self, time): """ For indexing continuous time stochastic processes. Returns ======= RandomIndexedSymbol """ if time not in self.index_set: raise IndexError("%s is not in the index set of %s"%(time, self.symbol)) func_obj = Function(self.symbol)(time) pspace_obj = StochasticPSpace(self.symbol, self, self.distribution) return RandomIndexedSymbol(func_obj, pspace_obj) class TransitionMatrixOf(Boolean): """ Assumes that the matrix is the transition matrix of the process. """ def __new__(cls, process, matrix): if not isinstance(process, DiscreteMarkovChain): raise ValueError("Currently only DiscreteMarkovChain " "support TransitionMatrixOf.") matrix = _matrix_checks(matrix) return Basic.__new__(cls, process, matrix) process = property(lambda self: self.args[0]) matrix = property(lambda self: self.args[1]) class GeneratorMatrixOf(TransitionMatrixOf): """ Assumes that the matrix is the generator matrix of the process. """ def __new__(cls, process, matrix): if not isinstance(process, ContinuousMarkovChain): raise ValueError("Currently only ContinuousMarkovChain " "support GeneratorMatrixOf.") matrix = _matrix_checks(matrix) return Basic.__new__(cls, process, matrix) class StochasticStateSpaceOf(Boolean): def __new__(cls, process, state_space): if not isinstance(process, (DiscreteMarkovChain, ContinuousMarkovChain)): raise ValueError("Currently only DiscreteMarkovChain and ContinuousMarkovChain " "support StochasticStateSpaceOf.") state_space = _state_converter(state_space) if isinstance(state_space, Range): ss_size = ceiling((state_space.stop - state_space.start) / state_space.step) else: ss_size = len(state_space) state_index = Range(ss_size) return Basic.__new__(cls, process, state_index) process = property(lambda self: self.args[0]) state_index = property(lambda self: self.args[1]) class MarkovProcess(StochasticProcess): """ Contains methods that handle queries common to Markov processes. """ @property def number_of_states(self) -> tUnion[Integer, Symbol]: """ The number of states in the Markov Chain. """ return _sympify(self.args[2].shape[0]) @property def _state_index(self) -> Range: """ Returns state index as Range. """ return self.args[1] @classmethod def _sanity_checks(cls, state_space, trans_probs): # Try to never have None as state_space or trans_probs. # This helps a lot if we get it done at the start. if (state_space is None) and (trans_probs is None): _n = Dummy('n', integer=True, nonnegative=True) state_space = _state_converter(Range(_n)) trans_probs = _matrix_checks(MatrixSymbol('_T', _n, _n)) elif state_space is None: trans_probs = _matrix_checks(trans_probs) state_space = _state_converter(Range(trans_probs.shape[0])) elif trans_probs is None: state_space = _state_converter(state_space) if isinstance(state_space, Range): _n = ceiling((state_space.stop - state_space.start) / state_space.step) else: _n = len(state_space) trans_probs = MatrixSymbol('_T', _n, _n) else: state_space = _state_converter(state_space) trans_probs = _matrix_checks(trans_probs) # Range object doesn't want to give a symbolic size # so we do it ourselves. if isinstance(state_space, Range): ss_size = ceiling((state_space.stop - state_space.start) / state_space.step) else: ss_size = len(state_space) if ss_size != trans_probs.shape[0]: raise ValueError('The size of the state space and the number of ' 'rows of the transition matrix must be the same.') return state_space, trans_probs def _extract_information(self, given_condition): """ Helper function to extract information, like, transition matrix/generator matrix, state space, etc. """ if isinstance(self, DiscreteMarkovChain): trans_probs = self.transition_probabilities state_index = self._state_index elif isinstance(self, ContinuousMarkovChain): trans_probs = self.generator_matrix state_index = self._state_index if isinstance(given_condition, And): gcs = given_condition.args given_condition = S.true for gc in gcs: if isinstance(gc, TransitionMatrixOf): trans_probs = gc.matrix if isinstance(gc, StochasticStateSpaceOf): state_index = gc.state_index if isinstance(gc, Relational): given_condition = given_condition & gc if isinstance(given_condition, TransitionMatrixOf): trans_probs = given_condition.matrix given_condition = S.true if isinstance(given_condition, StochasticStateSpaceOf): state_index = given_condition.state_index given_condition = S.true return trans_probs, state_index, given_condition def _check_trans_probs(self, trans_probs, row_sum=1): """ Helper function for checking the validity of transition probabilities. """ if not isinstance(trans_probs, MatrixSymbol): rows = trans_probs.tolist() for row in rows: if (sum(row) - row_sum) != 0: raise ValueError("Values in a row must sum to %s. " "If you are using Float or floats then please use Rational."%(row_sum)) def _work_out_state_index(self, state_index, given_condition, trans_probs): """ Helper function to extract state space if there is a random symbol in the given condition. """ # if given condition is None, then there is no need to work out # state_space from random variables if given_condition != None: rand_var = list(given_condition.atoms(RandomSymbol) - given_condition.atoms(RandomIndexedSymbol)) if len(rand_var) == 1: state_index = rand_var[0].pspace.set # `not None` is `True`. So the old test fails for symbolic sizes. # Need to build the statement differently. sym_cond = not isinstance(self.number_of_states, (int, Integer)) cond1 = not sym_cond and len(state_index) != trans_probs.shape[0] if cond1: raise ValueError("state space is not compatible with the transition probabilities.") if not isinstance(trans_probs.shape[0], Symbol): state_index = FiniteSet(*[i for i in range(trans_probs.shape[0])]) return state_index @cacheit def _preprocess(self, given_condition, evaluate): """ Helper function for pre-processing the information. """ is_insufficient = False if not evaluate: # avoid pre-processing if the result is not to be evaluated return (True, None, None, None) # extracting transition matrix and state space trans_probs, state_index, given_condition = self._extract_information(given_condition) # given_condition does not have sufficient information # for computations if trans_probs == None or \ given_condition == None: is_insufficient = True else: # checking transition probabilities if isinstance(self, DiscreteMarkovChain): self._check_trans_probs(trans_probs, row_sum=1) elif isinstance(self, ContinuousMarkovChain): self._check_trans_probs(trans_probs, row_sum=0) # working out state space state_index = self._work_out_state_index(state_index, given_condition, trans_probs) return is_insufficient, trans_probs, state_index, given_condition def replace_with_index(self, condition): if isinstance(condition, Relational): lhs, rhs = condition.lhs, condition.rhs if not isinstance(lhs, RandomIndexedSymbol): lhs, rhs = rhs, lhs condition = type(condition)(self.index_of.get(lhs, lhs), self.index_of.get(rhs, rhs)) return condition def probability(self, condition, given_condition=None, evaluate=True, **kwargs): """ Handles probability queries for Markov process. Parameters ========== condition: Relational given_condition: Relational/And Returns ======= Probability If the information is not sufficient. Expr In all other cases. Note ==== Any information passed at the time of query overrides any information passed at the time of object creation like transition probabilities, state space. Pass the transition matrix using TransitionMatrixOf, generator matrix using GeneratorMatrixOf and state space using StochasticStateSpaceOf in given_condition using & or And. """ check, mat, state_index, new_given_condition = \ self._preprocess(given_condition, evaluate) if check: return Probability(condition, new_given_condition) if isinstance(self, ContinuousMarkovChain): trans_probs = self.transition_probabilities(mat) elif isinstance(self, DiscreteMarkovChain): trans_probs = mat condition = self.replace_with_index(condition) given_condition = self.replace_with_index(given_condition) new_given_condition = self.replace_with_index(new_given_condition) if isinstance(condition, Relational): if isinstance(new_given_condition, And): gcs = new_given_condition.args else: gcs = (new_given_condition, ) min_key_rv = list(new_given_condition.atoms(RandomIndexedSymbol)) rv = list(condition.atoms(RandomIndexedSymbol)) if len(min_key_rv): min_key_rv = min_key_rv[0] for r in rv: if min_key_rv.key > r.key: return Probability(condition) else: min_key_rv = None return Probability(condition) if len(rv) > 1: rv = rv[:2] if rv[0].key < rv[1].key: rv[0], rv[1] = rv[1], rv[0] s = Rational(0, 1) n = len(self.state_space) if isinstance(condition, Eq) or isinstance(condition, Ne): for i in range(0, n): s += self.probability(Eq(rv[0], i), Eq(rv[1], i)) * self.probability(Eq(rv[1], i), new_given_condition) return s if isinstance(condition, Eq) else 1 - s else: upper = 0 greater = False if isinstance(condition, Ge) or isinstance(condition, Lt): upper = 1 if isinstance(condition, Gt) or isinstance(condition, Ge): greater = True for i in range(0, n): if i <= n//2: for j in range(0, i + upper): s += self.probability(Eq(rv[0], i), Eq(rv[1], j)) * self.probability(Eq(rv[1], j), new_given_condition) else: s += self.probability(Eq(rv[0], i), new_given_condition) for j in range(i + upper, n): s -= self.probability(Eq(rv[0], i), Eq(rv[1], j)) * self.probability(Eq(rv[1], j), new_given_condition) return s if greater else 1 - s rv = rv[0] states = condition.as_set() prob, gstate = dict(), None for gc in gcs: if gc.has(min_key_rv): if gc.has(Probability): p, gp = (gc.rhs, gc.lhs) if isinstance(gc.lhs, Probability) \ else (gc.lhs, gc.rhs) gr = gp.args[0] gset = Intersection(gr.as_set(), state_index) gstate = list(gset)[0] prob[gset] = p else: _, gstate = (gc.lhs.key, gc.rhs) if isinstance(gc.lhs, RandomIndexedSymbol) \ else (gc.rhs.key, gc.lhs) if any((k not in self.index_set) for k in (rv.key, min_key_rv.key)): raise IndexError("The timestamps of the process are not in it's index set.") states = Intersection(states, state_index) if not isinstance(self.number_of_states, Symbol) else states for state in Union(states, FiniteSet(gstate)): if not isinstance(state, (int, Integer)) or Ge(state, mat.shape[0]) is True: raise IndexError("No information is available for (%s, %s) in " "transition probabilities of shape, (%s, %s). " "State space is zero indexed." %(gstate, state, mat.shape[0], mat.shape[1])) if prob: gstates = Union(*prob.keys()) if len(gstates) == 1: gstate = list(gstates)[0] gprob = list(prob.values())[0] prob[gstates] = gprob elif len(gstates) == len(state_index) - 1: gstate = list(state_index - gstates)[0] gprob = S.One - sum(prob.values()) prob[state_index - gstates] = gprob else: raise ValueError("Conflicting information.") else: gprob = S.One if min_key_rv == rv: return sum([prob[FiniteSet(state)] for state in states]) if isinstance(self, ContinuousMarkovChain): return gprob * sum([trans_probs(rv.key - min_key_rv.key).__getitem__((gstate, state)) for state in states]) if isinstance(self, DiscreteMarkovChain): return gprob * sum([(trans_probs**(rv.key - min_key_rv.key)).__getitem__((gstate, state)) for state in states]) if isinstance(condition, Not): expr = condition.args[0] return S.One - self.probability(expr, given_condition, evaluate, **kwargs) if isinstance(condition, And): compute_later, state2cond, conds = [], dict(), condition.args for expr in conds: if isinstance(expr, Relational): ris = list(expr.atoms(RandomIndexedSymbol))[0] if state2cond.get(ris, None) is None: state2cond[ris] = S.true state2cond[ris] &= expr else: compute_later.append(expr) ris = [] for ri in state2cond: ris.append(ri) cset = Intersection(state2cond[ri].as_set(), state_index) if len(cset) == 0: return S.Zero state2cond[ri] = cset.as_relational(ri) sorted_ris = sorted(ris, key=lambda ri: ri.key) prod = self.probability(state2cond[sorted_ris[0]], given_condition, evaluate, **kwargs) for i in range(1, len(sorted_ris)): ri, prev_ri = sorted_ris[i], sorted_ris[i-1] if not isinstance(state2cond[ri], Eq): raise ValueError("The process is in multiple states at %s, unable to determine the probability."%(ri)) mat_of = TransitionMatrixOf(self, mat) if isinstance(self, DiscreteMarkovChain) else GeneratorMatrixOf(self, mat) prod *= self.probability(state2cond[ri], state2cond[prev_ri] & mat_of & StochasticStateSpaceOf(self, state_index), evaluate, **kwargs) for expr in compute_later: prod *= self.probability(expr, given_condition, evaluate, **kwargs) return prod if isinstance(condition, Or): return sum([self.probability(expr, given_condition, evaluate, **kwargs) for expr in condition.args]) raise NotImplementedError("Mechanism for handling (%s, %s) queries hasn't been " "implemented yet."%(condition, given_condition)) def expectation(self, expr, condition=None, evaluate=True, **kwargs): """ Handles expectation queries for markov process. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation Unevaluated object if computations cannot be done due to insufficient information. Expr In all other cases when the computations are successful. Note ==== Any information passed at the time of query overrides any information passed at the time of object creation like transition probabilities, state space. Pass the transition matrix using TransitionMatrixOf, generator matrix using GeneratorMatrixOf and state space using StochasticStateSpaceOf in given_condition using & or And. """ check, mat, state_index, condition = \ self._preprocess(condition, evaluate) if check: return Expectation(expr, condition) rvs = random_symbols(expr) if isinstance(expr, Expr) and isinstance(condition, Eq) \ and len(rvs) == 1: # handle queries similar to E(f(X[i]), Eq(X[i-m], <some-state>)) condition=self.replace_with_index(condition) state_index=self.replace_with_index(state_index) rv = list(rvs)[0] lhsg, rhsg = condition.lhs, condition.rhs if not isinstance(lhsg, RandomIndexedSymbol): lhsg, rhsg = (rhsg, lhsg) if rhsg not in state_index: raise ValueError("%s state is not in the state space."%(rhsg)) if rv.key < lhsg.key: raise ValueError("Incorrect given condition is given, expectation " "time %s < time %s"%(rv.key, rv.key)) mat_of = TransitionMatrixOf(self, mat) if isinstance(self, DiscreteMarkovChain) else GeneratorMatrixOf(self, mat) cond = condition & mat_of & \ StochasticStateSpaceOf(self, state_index) func = lambda s: self.probability(Eq(rv, s), cond) * expr.subs(rv, self._state_index[s]) return sum([func(s) for s in state_index]) raise NotImplementedError("Mechanism for handling (%s, %s) queries hasn't been " "implemented yet."%(expr, condition)) class DiscreteMarkovChain(DiscreteTimeStochasticProcess, MarkovProcess): """ Represents a finite discrete time-homogeneous Markov chain. This type of Markov Chain can be uniquely characterised by its (ordered) state space and its one-step transition probability matrix. Parameters ========== sym: The name given to the Markov Chain state_space: Optional, by default, Range(n) trans_probs: Optional, by default, MatrixSymbol('_T', n, n) Examples ======== >>> from sympy.stats import DiscreteMarkovChain, TransitionMatrixOf, P, E >>> from sympy import Matrix, MatrixSymbol, Eq, symbols >>> T = Matrix([[0.5, 0.2, 0.3],[0.2, 0.5, 0.3],[0.2, 0.3, 0.5]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> YS = DiscreteMarkovChain("Y") >>> Y.state_space FiniteSet(0, 1, 2) >>> Y.transition_probabilities Matrix([ [0.5, 0.2, 0.3], [0.2, 0.5, 0.3], [0.2, 0.3, 0.5]]) >>> TS = MatrixSymbol('T', 3, 3) >>> P(Eq(YS[3], 2), Eq(YS[1], 1) & TransitionMatrixOf(YS, TS)) T[0, 2]*T[1, 0] + T[1, 1]*T[1, 2] + T[1, 2]*T[2, 2] >>> P(Eq(Y[3], 2), Eq(Y[1], 1)).round(2) 0.36 Probabilities will be calculated based on indexes rather than state names. For example, with the Sunny-Cloudy-Rainy model with string state names: >>> from sympy.core.symbol import Str >>> Y = DiscreteMarkovChain("Y", [Str('Sunny'), Str('Cloudy'), Str('Rainy')], T) >>> P(Eq(Y[3], 2), Eq(Y[1], 1)).round(2) 0.36 This gives the same answer as the ``[0, 1, 2]`` state space. Currently, there is no support for state names within probability and expectation statements. Here is a work-around using ``Str``: >>> P(Eq(Str('Rainy'), Y[3]), Eq(Y[1], Str('Cloudy'))).round(2) 0.36 Symbol state names can also be used: >>> sunny, cloudy, rainy = symbols('Sunny, Cloudy, Rainy') >>> Y = DiscreteMarkovChain("Y", [sunny, cloudy, rainy], T) >>> P(Eq(Y[3], rainy), Eq(Y[1], cloudy)).round(2) 0.36 Expectations will be calculated as follows: >>> E(Y[3], Eq(Y[1], cloudy)) 0.38*Cloudy + 0.36*Rainy + 0.26*Sunny Probability of expressions with multiple RandomIndexedSymbols can also be calculated provided there is only 1 RandomIndexedSymbol in the given condition. It is always better to use Rational instead of floating point numbers for the probabilities in the transition matrix to avoid errors. >>> from sympy import Gt, Le, Rational >>> T = Matrix([[Rational(5, 10), Rational(3, 10), Rational(2, 10)], [Rational(2, 10), Rational(7, 10), Rational(1, 10)], [Rational(3, 10), Rational(3, 10), Rational(4, 10)]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> P(Eq(Y[3], Y[1]), Eq(Y[0], 0)).round(3) 0.409 >>> P(Gt(Y[3], Y[1]), Eq(Y[0], 0)).round(2) 0.36 >>> P(Le(Y[15], Y[10]), Eq(Y[8], 2)).round(7) 0.6963328 There is limited support for arbitrarily sized states: >>> n = symbols('n', nonnegative=True, integer=True) >>> T = MatrixSymbol('T', n, n) >>> Y = DiscreteMarkovChain("Y", trans_probs=T) >>> Y.state_space Range(0, n, 1) References ========== .. [1] https://en.wikipedia.org/wiki/Markov_chain#Discrete-time_Markov_chain .. [2] https://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/Chapter11.pdf """ index_set = S.Naturals0 def __new__(cls, sym, state_space=None, trans_probs=None): # type: (Basic, tUnion[str, Symbol], tSequence, tUnion[MatrixBase, MatrixSymbol]) -> DiscreteMarkovChain sym = _symbol_converter(sym) state_space, trans_probs = MarkovProcess._sanity_checks(state_space, trans_probs) obj = Basic.__new__(cls, sym, state_space, trans_probs) indices = dict() if isinstance(obj.number_of_states, Integer): for index, state in enumerate(obj._state_index): indices[state] = index obj.index_of = indices return obj @property def transition_probabilities(self) -> tUnion[MatrixBase, MatrixSymbol]: """ Transition probabilities of discrete Markov chain, either an instance of Matrix or MatrixSymbol. """ return self.args[2] def _transient2transient(self): """ Computes the one step probabilities of transient states to transient states. Used in finding fundamental matrix, absorbing probabilities. """ trans_probs = self.transition_probabilities if not isinstance(trans_probs, ImmutableMatrix): return None m = trans_probs.shape[0] trans_states = [i for i in range(m) if trans_probs[i, i] != 1] t2t = [[trans_probs[si, sj] for sj in trans_states] for si in trans_states] return ImmutableMatrix(t2t) def _transient2absorbing(self): """ Computes the one step probabilities of transient states to absorbing states. Used in finding fundamental matrix, absorbing probabilities. """ trans_probs = self.transition_probabilities if not isinstance(trans_probs, ImmutableMatrix): return None m, trans_states, absorb_states = \ trans_probs.shape[0], [], [] for i in range(m): if trans_probs[i, i] == 1: absorb_states.append(i) else: trans_states.append(i) if not absorb_states or not trans_states: return None t2a = [[trans_probs[si, sj] for sj in absorb_states] for si in trans_states] return ImmutableMatrix(t2a) def communication_classes(self) -> tList[tTuple[tList[Basic], Boolean, Integer]]: """ Returns the list of communication classes that partition the states of the markov chain. A communication class is defined to be a set of states such that every state in that set is reachable from every other state in that set. Due to its properties this forms a class in the mathematical sense. Communication classes are also known as recurrence classes. Returns ======= classes The ``classes`` are a list of tuples. Each tuple represents a single communication class with its properties. The first element in the tuple is the list of states in the class, the second element is whether the class is recurrent and the third element is the period of the communication class. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix >>> T = Matrix([[0, 1, 0], ... [1, 0, 0], ... [1, 0, 0]]) >>> X = DiscreteMarkovChain('X', [1, 2, 3], T) >>> classes = X.communication_classes() >>> for states, is_recurrent, period in classes: ... states, is_recurrent, period ([1, 2], True, 2) ([3], False, 1) From this we can see that states ``1`` and ``2`` communicate, are recurrent and have a period of 2. We can also see state ``3`` is transient with a period of 1. Notes ===== The algorithm used is of order ``O(n**2)`` where ``n`` is the number of states in the markov chain. It uses Tarjan's algorithm to find the classes themselves and then it uses a breadth-first search algorithm to find each class's periodicity. Most of the algorithm's components approach ``O(n)`` as the matrix becomes more and more sparse. References ========== .. [1] http://www.columbia.edu/~ww2040/4701Sum07/4701-06-Notes-MCII.pdf .. [2] http://cecas.clemson.edu/~shierd/Shier/markov.pdf .. [3] https://ujcontent.uj.ac.za/vital/access/services/Download/uj:7506/CONTENT1 .. [4] https://www.mathworks.com/help/econ/dtmc.classify.html """ n = self.number_of_states T = self.transition_probabilities if isinstance(T, MatrixSymbol): raise NotImplementedError("Cannot perform the operation with a symbolic matrix.") # begin Tarjan's algorithm V = Range(n) # don't use state names. Rather use state # indexes since we use them for matrix # indexing here and later onward E = [(i, j) for i in V for j in V if T[i, j] != 0] classes = strongly_connected_components((V, E)) # end Tarjan's algorithm recurrence = [] periods = [] for class_ in classes: # begin recurrent check (similar to self._check_trans_probs()) submatrix = T[class_, class_] # get the submatrix with those states is_recurrent = S.true rows = submatrix.tolist() for row in rows: if (sum(row) - 1) != 0: is_recurrent = S.false break recurrence.append(is_recurrent) # end recurrent check # begin breadth-first search non_tree_edge_values = set() visited = {class_[0]} newly_visited = {class_[0]} level = {class_[0]: 0} current_level = 0 done = False # imitate a do-while loop while not done: # runs at most len(class_) times done = len(visited) == len(class_) current_level += 1 # this loop and the while loop above run a combined len(class_) number of times. # so this triple nested loop runs through each of the n states once. for i in newly_visited: # the loop below runs len(class_) number of times # complexity is around about O(n * avg(len(class_))) newly_visited = {j for j in class_ if T[i, j] != 0} new_tree_edges = newly_visited.difference(visited) for j in new_tree_edges: level[j] = current_level new_non_tree_edges = newly_visited.intersection(visited) new_non_tree_edge_values = {level[i]-level[j]+1 for j in new_non_tree_edges} non_tree_edge_values = non_tree_edge_values.union(new_non_tree_edge_values) visited = visited.union(new_tree_edges) # igcd needs at least 2 arguments positive_ntev = {val_e for val_e in non_tree_edge_values if val_e > 0} if len(positive_ntev) == 0: periods.append(len(class_)) elif len(positive_ntev) == 1: periods.append(positive_ntev.pop()) else: periods.append(igcd(*positive_ntev)) # end breadth-first search # convert back to the user's state names classes = [[self._state_index[i] for i in class_] for class_ in classes] return sympify(list(zip(classes, recurrence, periods))) def fundamental_matrix(self): Q = self._transient2transient() if Q == None: return None I = eye(Q.shape[0]) if (I - Q).det() == 0: raise ValueError("Fundamental matrix doesn't exists.") return ImmutableMatrix((I - Q).inv().tolist()) def absorbing_probabilities(self): """ Computes the absorbing probabilities, i.e., the ij-th entry of the matrix denotes the probability of Markov chain being absorbed in state j starting from state i. """ R = self._transient2absorbing() N = self.fundamental_matrix() if R == None or N == None: return None return N*R def absorbing_probabilites(self): SymPyDeprecationWarning( feature="absorbing_probabilites", useinstead="absorbing_probabilities", issue=20042, deprecated_since_version="1.7" ).warn() return self.absorbing_probabilities() def is_regular(self): tuples = self.communication_classes() if len(tuples) == 0: return S.false # not defined for a 0x0 matrix classes, _, periods = list(zip(*tuples)) return And(len(classes) == 1, periods[0] == 1) def is_ergodic(self): tuples = self.communication_classes() if len(tuples) == 0: return S.false # not defined for a 0x0 matrix classes, _, _ = list(zip(*tuples)) return S(len(classes) == 1) def is_absorbing_state(self, state): trans_probs = self.transition_probabilities if isinstance(trans_probs, ImmutableMatrix) and \ state < trans_probs.shape[0]: return S(trans_probs[state, state]) is S.One def is_absorbing_chain(self): states, A, B, C = self.decompose() r = A.shape[0] return And(r > 0, A == Identity(r).as_explicit()) def stationary_distribution(self, condition_set=False) -> tUnion[ImmutableMatrix, ConditionSet, Lambda]: """ The stationary distribution is any row vector, p, that solves p = pP, is row stochastic and each element in p must be nonnegative. That means in matrix form: :math:`(P-I)^T p^T = 0` and :math:`(1, ..., 1) p = 1` where ``P`` is the one-step transition matrix. All time-homogeneous Markov Chains with a finite state space have at least one stationary distribution. In addition, if a finite time-homogeneous Markov Chain is irreducible, the stationary distribution is unique. Parameters ========== condition_set : bool If the chain has a symbolic size or transition matrix, it will return a ``Lambda`` if ``False`` and return a ``ConditionSet`` if ``True``. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S An irreducible Markov Chain >>> T = Matrix([[S(1)/2, S(1)/2, 0], ... [S(4)/5, S(1)/5, 0], ... [1, 0, 0]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> X.stationary_distribution() Matrix([[8/13, 5/13, 0]]) A reducible Markov Chain >>> T = Matrix([[S(1)/2, S(1)/2, 0], ... [S(4)/5, S(1)/5, 0], ... [0, 0, 1]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> X.stationary_distribution() Matrix([[8/13 - 8*tau0/13, 5/13 - 5*tau0/13, tau0]]) >>> Y = DiscreteMarkovChain('Y') >>> Y.stationary_distribution() Lambda((wm, _T), Eq(wm*_T, wm)) >>> Y.stationary_distribution(condition_set=True) ConditionSet(wm, Eq(wm*_T, wm)) References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_2_6_stationary_and_limiting_distributions.php .. [2] https://galton.uchicago.edu/~yibi/teaching/stat317/2014/Lectures/Lecture4_6up.pdf See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.limiting_distribution """ trans_probs = self.transition_probabilities n = self.number_of_states if n == 0: return ImmutableMatrix(Matrix([[]])) # symbolic matrix version if isinstance(trans_probs, MatrixSymbol): wm = MatrixSymbol('wm', 1, n) if condition_set: return ConditionSet(wm, Eq(wm * trans_probs, wm)) else: return Lambda((wm, trans_probs), Eq(wm * trans_probs, wm)) # numeric matrix version a = Matrix(trans_probs - Identity(n)).T a[0, 0:n] = ones(1, n) b = zeros(n, 1) b[0, 0] = 1 soln = list(linsolve((a, b)))[0] return ImmutableMatrix([[sol for sol in soln]]) def fixed_row_vector(self): """ A wrapper for ``stationary_distribution()``. """ return self.stationary_distribution() @property def limiting_distribution(self): """ The fixed row vector is the limiting distribution of a discrete Markov chain. """ return self.fixed_row_vector() def decompose(self) -> tTuple[tList[Basic], ImmutableMatrix, ImmutableMatrix, ImmutableMatrix]: """ Decomposes the transition matrix into submatrices with special properties. The transition matrix can be decomposed into 4 submatrices: - A - the submatrix from recurrent states to recurrent states. - B - the submatrix from transient to recurrent states. - C - the submatrix from transient to transient states. - O - the submatrix of zeros for recurrent to transient states. Returns ======= states, A, B, C ``states`` - a list of state names with the first being the recurrent states and the last being the transient states in the order of the row names of A and then the row names of C. ``A`` - the submatrix from recurrent states to recurrent states. ``B`` - the submatrix from transient to recurrent states. ``C`` - the submatrix from transient to transient states. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S One can decompose this chain for example: >>> T = Matrix([[S(1)/2, S(1)/2, 0, 0, 0], ... [S(2)/5, S(1)/5, S(2)/5, 0, 0], ... [0, 0, 1, 0, 0], ... [0, 0, S(1)/2, S(1)/2, 0], ... [S(1)/2, 0, 0, 0, S(1)/2]]) >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> states, A, B, C = X.decompose() >>> states [2, 0, 1, 3, 4] >>> A # recurrent to recurrent Matrix([[1]]) >>> B # transient to recurrent Matrix([ [ 0], [2/5], [1/2], [ 0]]) >>> C # transient to transient Matrix([ [1/2, 1/2, 0, 0], [2/5, 1/5, 0, 0], [ 0, 0, 1/2, 0], [1/2, 0, 0, 1/2]]) This means that state 2 is the only absorbing state (since A is a 1x1 matrix). B is a 4x1 matrix since the 4 remaining transient states all merge into reccurent state 2. And C is the 4x4 matrix that shows how the transient states 0, 1, 3, 4 all interact. See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.communication_classes sympy.stats.stochastic_process_types.DiscreteMarkovChain.canonical_form References ========== .. [1] https://en.wikipedia.org/wiki/Absorbing_Markov_chain .. [2] http://people.brandeis.edu/~igusa/Math56aS08/Math56a_S08_notes015.pdf """ trans_probs = self.transition_probabilities classes = self.communication_classes() r_states = [] t_states = [] for states, recurrent, period in classes: if recurrent: r_states += states else: t_states += states states = r_states + t_states indexes = [self.index_of[state] for state in states] A = Matrix(len(r_states), len(r_states), lambda i, j: trans_probs[indexes[i], indexes[j]]) B = Matrix(len(t_states), len(r_states), lambda i, j: trans_probs[indexes[len(r_states) + i], indexes[j]]) C = Matrix(len(t_states), len(t_states), lambda i, j: trans_probs[indexes[len(r_states) + i], indexes[len(r_states) + j]]) return states, A.as_immutable(), B.as_immutable(), C.as_immutable() def canonical_form(self) -> tTuple[tList[Basic], ImmutableMatrix]: """ Reorders the one-step transition matrix so that recurrent states appear first and transient states appear last. Other representations include inserting transient states first and recurrent states last. Returns ======= states, P_new ``states`` is the list that describes the order of the new states in the matrix so that the ith element in ``states`` is the state of the ith row of A. ``P_new`` is the new transition matrix in canonical form. Examples ======== >>> from sympy.stats import DiscreteMarkovChain >>> from sympy import Matrix, S You can convert your chain into canonical form: >>> T = Matrix([[S(1)/2, S(1)/2, 0, 0, 0], ... [S(2)/5, S(1)/5, S(2)/5, 0, 0], ... [0, 0, 1, 0, 0], ... [0, 0, S(1)/2, S(1)/2, 0], ... [S(1)/2, 0, 0, 0, S(1)/2]]) >>> X = DiscreteMarkovChain('X', list(range(1, 6)), trans_probs=T) >>> states, new_matrix = X.canonical_form() >>> states [3, 1, 2, 4, 5] >>> new_matrix Matrix([ [ 1, 0, 0, 0, 0], [ 0, 1/2, 1/2, 0, 0], [2/5, 2/5, 1/5, 0, 0], [1/2, 0, 0, 1/2, 0], [ 0, 1/2, 0, 0, 1/2]]) The new states are [3, 1, 2, 4, 5] and you can create a new chain with this and its canonical form will remain the same (since it is already in canonical form). >>> X = DiscreteMarkovChain('X', states, new_matrix) >>> states, new_matrix = X.canonical_form() >>> states [3, 1, 2, 4, 5] >>> new_matrix Matrix([ [ 1, 0, 0, 0, 0], [ 0, 1/2, 1/2, 0, 0], [2/5, 2/5, 1/5, 0, 0], [1/2, 0, 0, 1/2, 0], [ 0, 1/2, 0, 0, 1/2]]) This is not limited to absorbing chains: >>> T = Matrix([[0, 5, 5, 0, 0], ... [0, 0, 0, 10, 0], ... [5, 0, 5, 0, 0], ... [0, 10, 0, 0, 0], ... [0, 3, 0, 3, 4]])/10 >>> X = DiscreteMarkovChain('X', trans_probs=T) >>> states, new_matrix = X.canonical_form() >>> states [1, 3, 0, 2, 4] >>> new_matrix Matrix([ [ 0, 1, 0, 0, 0], [ 1, 0, 0, 0, 0], [ 1/2, 0, 0, 1/2, 0], [ 0, 0, 1/2, 1/2, 0], [3/10, 3/10, 0, 0, 2/5]]) See Also ======== sympy.stats.stochastic_process_types.DiscreteMarkovChain.communication_classes sympy.stats.stochastic_process_types.DiscreteMarkovChain.decompose References ========== .. [1] https://onlinelibrary.wiley.com/doi/pdf/10.1002/9780470316887.app1 .. [2] http://www.columbia.edu/~ww2040/6711F12/lect1023big.pdf """ states, A, B, C = self.decompose() O = zeros(A.shape[0], C.shape[1]) return states, BlockMatrix([[A, O], [B, C]]).as_explicit() def sample(self): """ Returns ======= sample: iterator object iterator object containing the sample """ if not isinstance(self.transition_probabilities, (Matrix, ImmutableMatrix)): raise ValueError("Transition Matrix must be provided for sampling") Tlist = self.transition_probabilities.tolist() samps = [random.choice(list(self.state_space))] yield samps[0] time = 1 densities = {} for state in self.state_space: states = list(self.state_space) densities[state] = {states[i]: Tlist[state][i] for i in range(len(states))} while time < S.Infinity: samps.append(next(sample_iter(FiniteRV("_", densities[samps[time - 1]])))) yield samps[time] time += 1 class ContinuousMarkovChain(ContinuousTimeStochasticProcess, MarkovProcess): """ Represents continuous time Markov chain. Parameters ========== sym: Symbol/str state_space: Set Optional, by default, S.Reals gen_mat: Matrix/ImmutableMatrix/MatrixSymbol Optional, by default, None Examples ======== >>> from sympy.stats import ContinuousMarkovChain >>> from sympy import Matrix, S >>> G = Matrix([[-S(1), S(1)], [S(1), -S(1)]]) >>> C = ContinuousMarkovChain('C', state_space=[0, 1], gen_mat=G) >>> C.limiting_distribution() Matrix([[1/2, 1/2]]) References ========== .. [1] https://en.wikipedia.org/wiki/Markov_chain#Continuous-time_Markov_chain .. [2] http://u.math.biu.ac.il/~amirgi/CTMCnotes.pdf """ index_set = S.Reals def __new__(cls, sym, state_space=None, gen_mat=None): sym = _symbol_converter(sym) state_space, gen_mat = MarkovProcess._sanity_checks(state_space, gen_mat) obj = Basic.__new__(cls, sym, state_space, gen_mat) indices = dict() if isinstance(obj.number_of_states, Integer): for index, state in enumerate(obj.state_space): indices[state] = index obj.index_of = indices return obj @property def generator_matrix(self): return self.args[2] @cacheit def transition_probabilities(self, gen_mat=None): t = Dummy('t') if isinstance(gen_mat, (Matrix, ImmutableMatrix)) and \ gen_mat.is_diagonalizable(): # for faster computation use diagonalized generator matrix Q, D = gen_mat.diagonalize() return Lambda(t, Q*exp(t*D)*Q.inv()) if gen_mat != None: return Lambda(t, exp(t*gen_mat)) def limiting_distribution(self): gen_mat = self.generator_matrix if gen_mat == None: return None if isinstance(gen_mat, MatrixSymbol): wm = MatrixSymbol('wm', 1, gen_mat.shape[0]) return Lambda((wm, gen_mat), Eq(wm*gen_mat, wm)) w = IndexedBase('w') wi = [w[i] for i in range(gen_mat.shape[0])] wm = Matrix([wi]) eqs = (wm*gen_mat).tolist()[0] eqs.append(sum(wi) - 1) soln = list(linsolve(eqs, wi))[0] return ImmutableMatrix([[sol for sol in soln]]) class BernoulliProcess(DiscreteTimeStochasticProcess): """ The Bernoulli process consists of repeated independent Bernoulli process trials with the same parameter `p`. It's assumed that the probability `p` applies to every trial and that the outcomes of each trial are independent of all the rest. Therefore Bernoulli Processs is Discrete State and Discrete Time Stochastic Process. Parameters ========== sym: Symbol/str success: Integer/str The event which is considered to be success, by default is 1. failure: Integer/str The event which is considered to be failure, by default is 0. p: Real Number between 0 and 1 Represents the probability of getting success. Examples ======== >>> from sympy.stats import BernoulliProcess, P, E >>> from sympy import Eq, Gt >>> B = BernoulliProcess("B", p=0.7, success=1, failure=0) >>> B.state_space FiniteSet(0, 1) >>> (B.p).round(2) 0.70 >>> B.success 1 >>> B.failure 0 >>> X = B[1] + B[2] + B[3] >>> P(Eq(X, 0)).round(2) 0.03 >>> P(Eq(X, 2)).round(2) 0.44 >>> P(Eq(X, 4)).round(2) 0 >>> P(Gt(X, 1)).round(2) 0.78 >>> P(Eq(B[1], 0) & Eq(B[2], 1) & Eq(B[3], 0) & Eq(B[4], 1)).round(2) 0.04 >>> B.joint_distribution(B[1], B[2]) JointDistributionHandmade(Lambda((B[1], B[2]), Piecewise((0.7, Eq(B[1], 1)), (0.3, Eq(B[1], 0)), (0, True))*Piecewise((0.7, Eq(B[2], 1)), (0.3, Eq(B[2], 0)), (0, True)))) >>> E(2*B[1] + B[2]).round(2) 2.10 >>> P(B[1] < 1).round(2) 0.30 References ========== .. [1] https://en.wikipedia.org/wiki/Bernoulli_process .. [2] https://mathcs.clarku.edu/~djoyce/ma217/bernoulli.pdf """ index_set = S.Naturals0 def __new__(cls, sym, p, success=1, failure=0): _value_check(p >= 0 and p <= 1, 'Value of p must be between 0 and 1.') sym = _symbol_converter(sym) p = _sympify(p) success = _sym_sympify(success) failure = _sym_sympify(failure) return Basic.__new__(cls, sym, p, success, failure) @property def symbol(self): return self.args[0] @property def p(self): return self.args[1] @property def success(self): return self.args[2] @property def failure(self): return self.args[3] @property def state_space(self): return _set_converter([self.success, self.failure]) @property def distribution(self): return BernoulliDistribution(self.p) def simple_rv(self, rv): return Bernoulli(rv.name, p=self.p, succ=self.success, fail=self.failure) def expectation(self, expr, condition=None, evaluate=True, **kwargs): """ Computes expectation. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation of the RandomIndexedSymbol. """ return _SubstituteRV._expectation(expr, condition, evaluate, **kwargs) def probability(self, condition, given_condition=None, evaluate=True, **kwargs): """ Computes probability. Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational/And The given conditions under which computations should be done. Returns ======= Probability of the condition. """ return _SubstituteRV._probability(condition, given_condition, evaluate, **kwargs) def density(self, x): return Piecewise((self.p, Eq(x, self.success)), (1 - self.p, Eq(x, self.failure)), (S.Zero, True)) class _SubstituteRV: """ Internal class to handle the queries of expectation and probability by substitution. """ @staticmethod def _rvindexed_subs(expr, condition=None): """ Substitutes the RandomIndexedSymbol with the RandomSymbol with same name, distribution and probability as RandomIndexedSymbol. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. """ rvs_expr = random_symbols(expr) if len(rvs_expr) != 0: swapdict_expr = {} for rv in rvs_expr: if isinstance(rv, RandomIndexedSymbol): newrv = rv.pspace.process.simple_rv(rv) # substitute with equivalent simple rv swapdict_expr[rv] = newrv expr = expr.subs(swapdict_expr) rvs_cond = random_symbols(condition) if len(rvs_cond)!=0: swapdict_cond = {} for rv in rvs_cond: if isinstance(rv, RandomIndexedSymbol): newrv = rv.pspace.process.simple_rv(rv) swapdict_cond[rv] = newrv condition = condition.subs(swapdict_cond) return expr, condition @classmethod def _expectation(self, expr, condition=None, evaluate=True, **kwargs): """ Internal method for computing expectation of indexed RV. Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Logic The given conditions under which computations should be done. Returns ======= Expectation of the RandomIndexedSymbol. """ new_expr, new_condition = self._rvindexed_subs(expr, condition) if not is_random(new_expr): return new_expr new_pspace = pspace(new_expr) if new_condition is not None: new_expr = given(new_expr, new_condition) if new_expr.is_Add: # As E is Linear return Add(*[new_pspace.compute_expectation( expr=arg, evaluate=evaluate, **kwargs) for arg in new_expr.args]) return new_pspace.compute_expectation( new_expr, evaluate=evaluate, **kwargs) @classmethod def _probability(self, condition, given_condition=None, evaluate=True, **kwargs): """ Internal method for computing probability of indexed RV Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational/And The given conditions under which computations should be done. Returns ======= Probability of the condition. """ new_condition, new_givencondition = self._rvindexed_subs(condition, given_condition) if isinstance(new_givencondition, RandomSymbol): condrv = random_symbols(new_condition) if len(condrv) == 1 and condrv[0] == new_givencondition: return BernoulliDistribution(self._probability(new_condition), 0, 1) if any([dependent(rv, new_givencondition) for rv in condrv]): return Probability(new_condition, new_givencondition) else: return self._probability(new_condition) if new_givencondition is not None and \ not isinstance(new_givencondition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (new_givencondition)) if new_givencondition == False or new_condition == False: return S.Zero if new_condition == True: return S.One if not isinstance(new_condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (new_condition)) if new_givencondition is not None: # If there is a condition # Recompute on new conditional expr return self._probability(given(new_condition, new_givencondition, **kwargs), **kwargs) result = pspace(new_condition).probability(new_condition, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def get_timerv_swaps(expr, condition): """ Finds the appropriate interval for each time stamp in expr by parsing the given condition and returns intervals for each timestamp and dictionary that maps variable time-stamped Random Indexed Symbol to its corresponding Random Indexed variable with fixed time stamp. Parameters ========== expr: Sympy Expression Expression containing Random Indexed Symbols with variable time stamps condition: Relational/Boolean Expression Expression containing time bounds of variable time stamps in expr Examples ======== >>> from sympy.stats.stochastic_process_types import get_timerv_swaps, PoissonProcess >>> from sympy import symbols, Contains, Interval >>> x, t, d = symbols('x t d', positive=True) >>> X = PoissonProcess("X", 3) >>> get_timerv_swaps(x*X(t), Contains(t, Interval.Lopen(0, 1))) ([Interval.Lopen(0, 1)], {X(t): X(1)}) >>> get_timerv_swaps((X(t)**2 + X(d)**2), Contains(t, Interval.Lopen(0, 1)) ... & Contains(d, Interval.Ropen(1, 4))) # doctest: +SKIP ([Interval.Ropen(1, 4), Interval.Lopen(0, 1)], {X(d): X(3), X(t): X(1)}) Returns ======= intervals: list List of Intervals/FiniteSet on which each time stamp is defined rv_swap: dict Dictionary mapping variable time Random Indexed Symbol to constant time Random Indexed Variable """ if not isinstance(condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (condition)) expr_syms = list(expr.atoms(RandomIndexedSymbol)) if isinstance(condition, (And, Or)): given_cond_args = condition.args else: # single condition given_cond_args = (condition, ) rv_swap = {} intervals = [] for expr_sym in expr_syms: for arg in given_cond_args: if arg.has(expr_sym.key) and isinstance(expr_sym.key, Symbol): intv = _set_converter(arg.args[1]) diff_key = intv._sup - intv._inf if diff_key == oo: raise ValueError("%s should have finite bounds" % str(expr_sym.name)) elif diff_key == S.Zero: # has singleton set diff_key = intv._sup rv_swap[expr_sym] = expr_sym.subs({expr_sym.key: diff_key}) intervals.append(intv) return intervals, rv_swap class CountingProcess(ContinuousTimeStochasticProcess): """ This class handles the common methods of the Counting Processes such as Poisson, Wiener and Gamma Processes """ index_set = _set_converter(Interval(0, oo)) @property def symbol(self): return self.args[0] def expectation(self, expr, condition=None, evaluate=True, **kwargs): """ Computes expectation Parameters ========== expr: RandomIndexedSymbol, Relational, Logic Condition for which expectation has to be computed. Must contain a RandomIndexedSymbol of the process. condition: Relational, Boolean The given conditions under which computations should be done, i.e, the intervals on which each variable time stamp in expr is defined Returns ======= Expectation of the given expr """ if condition is not None: intervals, rv_swap = get_timerv_swaps(expr, condition) # they are independent when they have non-overlapping intervals if len(intervals) == 1 or all(Intersection(*intv_comb) == EmptySet for intv_comb in itertools.combinations(intervals, 2)): if expr.is_Add: return Add.fromiter(self.expectation(arg, condition) for arg in expr.args) expr = expr.subs(rv_swap) else: return Expectation(expr, condition) return _SubstituteRV._expectation(expr, evaluate=evaluate, **kwargs) def _solve_argwith_tworvs(self, arg): if arg.args[0].key >= arg.args[1].key or isinstance(arg, Eq): diff_key = abs(arg.args[0].key - arg.args[1].key) rv = arg.args[0] arg = arg.__class__(rv.pspace.process(diff_key), 0) else: diff_key = arg.args[1].key - arg.args[0].key rv = arg.args[1] arg = arg.__class__(rv.pspace.process(diff_key), 0) return arg def _solve_numerical(self, condition, given_condition=None): if isinstance(condition, And): args_list = list(condition.args) else: args_list = [condition] if given_condition is not None: if isinstance(given_condition, And): args_list.extend(list(given_condition.args)) else: args_list.extend([given_condition]) # sort the args based on timestamp to get the independent increments in # each segment using all the condition args as well as given_condition args args_list = sorted(args_list, key=lambda x: x.args[0].key) result = [] cond_args = list(condition.args) if isinstance(condition, And) else [condition] if args_list[0] in cond_args and not (is_random(args_list[0].args[0]) and is_random(args_list[0].args[1])): result.append(_SubstituteRV._probability(args_list[0])) if is_random(args_list[0].args[0]) and is_random(args_list[0].args[1]): arg = self._solve_argwith_tworvs(args_list[0]) result.append(_SubstituteRV._probability(arg)) for i in range(len(args_list) - 1): curr, nex = args_list[i], args_list[i + 1] diff_key = nex.args[0].key - curr.args[0].key working_set = curr.args[0].pspace.process.state_space if curr.args[1] > nex.args[1]: #impossible condition so return 0 result.append(0) break if isinstance(curr, Eq): working_set = Intersection(working_set, Interval.Lopen(curr.args[1], oo)) else: working_set = Intersection(working_set, curr.as_set()) if isinstance(nex, Eq): working_set = Intersection(working_set, Interval(-oo, nex.args[1])) else: working_set = Intersection(working_set, nex.as_set()) if working_set == EmptySet: rv = Eq(curr.args[0].pspace.process(diff_key), 0) result.append(_SubstituteRV._probability(rv)) else: if working_set.is_finite_set: if isinstance(curr, Eq) and isinstance(nex, Eq): rv = Eq(curr.args[0].pspace.process(diff_key), len(working_set)) result.append(_SubstituteRV._probability(rv)) elif isinstance(curr, Eq) ^ isinstance(nex, Eq): result.append(Add.fromiter(_SubstituteRV._probability(Eq( curr.args[0].pspace.process(diff_key), x)) for x in range(len(working_set)))) else: n = len(working_set) result.append(Add.fromiter((n - x)*_SubstituteRV._probability(Eq( curr.args[0].pspace.process(diff_key), x)) for x in range(n))) else: result.append(_SubstituteRV._probability( curr.args[0].pspace.process(diff_key) <= working_set._sup - working_set._inf)) return Mul.fromiter(result) def probability(self, condition, given_condition=None, evaluate=True, **kwargs): """ Computes probability Parameters ========== condition: Relational Condition for which probability has to be computed. Must contain a RandomIndexedSymbol of the process. given_condition: Relational, Boolean The given conditions under which computations should be done, i.e, the intervals on which each variable time stamp in expr is defined Returns ======= Probability of the condition """ check_numeric = True if isinstance(condition, (And, Or)): cond_args = condition.args else: cond_args = (condition, ) # check that condition args are numeric or not if not all(arg.args[0].key.is_number for arg in cond_args): check_numeric = False if given_condition is not None: check_given_numeric = True if isinstance(given_condition, (And, Or)): given_cond_args = given_condition.args else: given_cond_args = (given_condition, ) # check that given condition args are numeric or not if given_condition.has(Contains): check_given_numeric = False # Handle numerical queries if check_numeric and check_given_numeric: res = [] if isinstance(condition, Or): res.append(Add.fromiter(self._solve_numerical(arg, given_condition) for arg in condition.args)) if isinstance(given_condition, Or): res.append(Add.fromiter(self._solve_numerical(condition, arg) for arg in given_condition.args)) if res: return Add.fromiter(res) return self._solve_numerical(condition, given_condition) # No numeric queries, go by Contains?... then check that all the # given condition are in form of `Contains` if not all(arg.has(Contains) for arg in given_cond_args): raise ValueError("If given condition is passed with `Contains`, then " "please pass the evaluated condition with its corresponding information " "in terms of intervals of each time stamp to be passed in given condition.") intervals, rv_swap = get_timerv_swaps(condition, given_condition) # they are independent when they have non-overlapping intervals if len(intervals) == 1 or all(Intersection(*intv_comb) == EmptySet for intv_comb in itertools.combinations(intervals, 2)): if isinstance(condition, And): return Mul.fromiter(self.probability(arg, given_condition) for arg in condition.args) elif isinstance(condition, Or): return Add.fromiter(self.probability(arg, given_condition) for arg in condition.args) condition = condition.subs(rv_swap) else: return Probability(condition, given_condition) if check_numeric: return self._solve_numerical(condition) return _SubstituteRV._probability(condition, evaluate=evaluate, **kwargs) class PoissonProcess(CountingProcess): """ The Poisson process is a counting process. It is usually used in scenarios where we are counting the occurrences of certain events that appear to happen at a certain rate, but completely at random. Parameters ========== sym: Symbol/str lamda: Positive number Rate of the process, ``lamda > 0`` Examples ======== >>> from sympy.stats import PoissonProcess, P, E >>> from sympy import symbols, Eq, Ne, Contains, Interval >>> X = PoissonProcess("X", lamda=3) >>> X.state_space Naturals0 >>> X.lamda 3 >>> t1, t2 = symbols('t1 t2', positive=True) >>> P(X(t1) < 4) (9*t1**3/2 + 9*t1**2/2 + 3*t1 + 1)*exp(-3*t1) >>> P(Eq(X(t1), 2) | Ne(X(t1), 4), Contains(t1, Interval.Ropen(2, 4))) 1 - 36*exp(-6) >>> P(Eq(X(t1), 2) & Eq(X(t2), 3), Contains(t1, Interval.Lopen(0, 2)) ... & Contains(t2, Interval.Lopen(2, 4))) 648*exp(-12) >>> E(X(t1)) 3*t1 >>> E(X(t1)**2 + 2*X(t2), Contains(t1, Interval.Lopen(0, 1)) ... & Contains(t2, Interval.Lopen(1, 2))) 18 >>> P(X(3) < 1, Eq(X(1), 0)) exp(-6) >>> P(Eq(X(4), 3), Eq(X(2), 3)) exp(-6) >>> P(X(2) <= 3, X(1) > 1) 5*exp(-3) Merging two Poisson Processes >>> Y = PoissonProcess("Y", lamda=4) >>> Z = X + Y >>> Z.lamda 7 Splitting a Poisson Process into two independent Poisson Processes >>> N, M = Z.split(l1=2, l2=5) >>> N.lamda, M.lamda (2, 5) References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_0_0_intro.php .. [2] https://en.wikipedia.org/wiki/Poisson_point_process """ def __new__(cls, sym, lamda): _value_check(lamda > 0, 'lamda should be a positive number.') sym = _symbol_converter(sym) lamda = _sympify(lamda) return Basic.__new__(cls, sym, lamda) @property def lamda(self): return self.args[1] @property def state_space(self): return S.Naturals0 def distribution(self, rv): return PoissonDistribution(self.lamda*rv.key) def density(self, x): return (self.lamda*x.key)**x / factorial(x) * exp(-(self.lamda*x.key)) def simple_rv(self, rv): return Poisson(rv.name, lamda=self.lamda*rv.key) def __add__(self, other): if not isinstance(other, PoissonProcess): raise ValueError("Only instances of Poisson Process can be merged") return PoissonProcess(Dummy(self.symbol.name + other.symbol.name), self.lamda + other.lamda) def split(self, l1, l2): if _sympify(l1 + l2) != self.lamda: raise ValueError("Sum of l1 and l2 should be %s" % str(self.lamda)) return PoissonProcess(Dummy("l1"), l1), PoissonProcess(Dummy("l2"), l2) class WienerProcess(CountingProcess): """ The Wiener process is a real valued continuous-time stochastic process. In physics it is used to study Brownian motion and therefore also known as Brownian Motion. Parameters ========== sym: Symbol/str Examples ======== >>> from sympy.stats import WienerProcess, P, E >>> from sympy import symbols, Contains, Interval >>> X = WienerProcess("X") >>> X.state_space Reals >>> t1, t2 = symbols('t1 t2', positive=True) >>> P(X(t1) < 7).simplify() erf(7*sqrt(2)/(2*sqrt(t1)))/2 + 1/2 >>> P((X(t1) > 2) | (X(t1) < 4), Contains(t1, Interval.Ropen(2, 4))).simplify() -erf(1)/2 + erf(2)/2 + 1 >>> E(X(t1)) 0 >>> E(X(t1) + 2*X(t2), Contains(t1, Interval.Lopen(0, 1)) ... & Contains(t2, Interval.Lopen(1, 2))) 0 References ========== .. [1] https://www.probabilitycourse.com/chapter11/11_4_0_brownian_motion_wiener_process.php .. [2] https://en.wikipedia.org/wiki/Wiener_process """ def __new__(cls, sym): sym = _symbol_converter(sym) return Basic.__new__(cls, sym) @property def state_space(self): return S.Reals def distribution(self, rv): return NormalDistribution(0, sqrt(rv.key)) def density(self, x): return exp(-x**2/(2*x.key)) / (sqrt(2*pi)*sqrt(x.key)) def simple_rv(self, rv): return Normal(rv.name, 0, sqrt(rv.key)) class GammaProcess(CountingProcess): """ A Gamma process is a random process with independent gamma distributed increments. It is a pure-jump increasing Levy process. Parameters ========== sym: Symbol/str lamda: Positive number Jump size of the process, ``lamda > 0`` gamma: Positive number Rate of jump arrivals, ``gamma > 0`` Examples ======== >>> from sympy.stats import GammaProcess, E, P, variance >>> from sympy import symbols, Contains, Interval, Not >>> t, d, x, l, g = symbols('t d x l g', positive=True) >>> X = GammaProcess("X", l, g) >>> E(X(t)) g*t/l >>> variance(X(t)).simplify() g*t/l**2 >>> X = GammaProcess('X', 1, 2) >>> P(X(t) < 1).simplify() lowergamma(2*t, 1)/gamma(2*t) >>> P(Not((X(t) < 5) & (X(d) > 3)), Contains(t, Interval.Ropen(2, 4)) & ... Contains(d, Interval.Lopen(7, 8))).simplify() -4*exp(-3) + 472*exp(-8)/3 + 1 >>> E(X(2) + x*E(X(5))) 10*x + 4 References ========== .. [1] https://en.wikipedia.org/wiki/Gamma_process """ def __new__(cls, sym, lamda, gamma): _value_check(lamda > 0, 'lamda should be a positive number') _value_check(gamma > 0, 'gamma should be a positive number') sym = _symbol_converter(sym) gamma = _sympify(gamma) lamda = _sympify(lamda) return Basic.__new__(cls, sym, lamda, gamma) @property def lamda(self): return self.args[1] @property def gamma(self): return self.args[2] @property def state_space(self): return _set_converter(Interval(0, oo)) def distribution(self, rv): return GammaDistribution(self.gamma*rv.key, 1/self.lamda) def density(self, x): k = self.gamma*x.key theta = 1/self.lamda return x**(k - 1) * exp(-x/theta) / (gamma(k)*theta**k) def simple_rv(self, rv): return Gamma(rv.name, self.gamma*rv.key, 1/self.lamda)

11006d95d054685811a86705e3bedec66da29b1dd21a490cd39c1962ce6d08bf

from sympy import Basic from sympy.stats.rv import PSpace, _symbol_converter, RandomMatrixSymbol class RandomMatrixPSpace(PSpace): """ Represents probability space for random matrices. It contains the mechanics for handling the API calls for random matrices. """ def __new__(cls, sym, model=None): sym = _symbol_converter(sym) return Basic.__new__(cls, sym, model) model = property(lambda self: self.args[1]) def compute_density(self, expr, *args): rms = expr.atoms(RandomMatrixSymbol) if len(rms) > 2 or (not isinstance(expr, RandomMatrixSymbol)): raise NotImplementedError("Currently, no algorithm has been " "implemented to handle general expressions containing " "multiple random matrices.") return self.model.density(expr)

a75326df053687003ca2dad0e6d5a64c94ffd90f58329f227a4b8a82bf185057

"""Tools for arithmetic error propagation.""" from itertools import repeat, combinations from sympy import S, Symbol, Add, Mul, simplify, Pow, exp from sympy.stats.symbolic_probability import RandomSymbol, Variance, Covariance from sympy.stats.rv import is_random _arg0_or_var = lambda var: var.args[0] if len(var.args) > 0 else var def variance_prop(expr, consts=(), include_covar=False): r"""Symbolically propagates variance (`\sigma^2`) for expressions. This is computed as as seen in [1]_. Parameters ========== expr : Expr A sympy expression to compute the variance for. consts : sequence of Symbols, optional Represents symbols that are known constants in the expr, and thus have zero variance. All symbols not in consts are assumed to be variant. include_covar : bool, optional Flag for whether or not to include covariances, default=False. Returns ======= var_expr : Expr An expression for the total variance of the expr. The variance for the original symbols (e.g. x) are represented via instance of the Variance symbol (e.g. Variance(x)). Examples ======== >>> from sympy import symbols, exp >>> from sympy.stats.error_prop import variance_prop >>> x, y = symbols('x y') >>> variance_prop(x + y) Variance(x) + Variance(y) >>> variance_prop(x * y) x**2*Variance(y) + y**2*Variance(x) >>> variance_prop(exp(2*x)) 4*exp(4*x)*Variance(x) References ========== .. [1] https://en.wikipedia.org/wiki/Propagation_of_uncertainty """ args = expr.args if len(args) == 0: if expr in consts: return S.Zero elif is_random(expr): return Variance(expr).doit() elif isinstance(expr, Symbol): return Variance(RandomSymbol(expr)).doit() else: return S.Zero nargs = len(args) var_args = list(map(variance_prop, args, repeat(consts, nargs), repeat(include_covar, nargs))) if isinstance(expr, Add): var_expr = Add(*var_args) if include_covar: terms = [2 * Covariance(_arg0_or_var(x), _arg0_or_var(y)).expand() \ for x, y in combinations(var_args, 2)] var_expr += Add(*terms) elif isinstance(expr, Mul): terms = [v/a**2 for a, v in zip(args, var_args)] var_expr = simplify(expr**2 * Add(*terms)) if include_covar: terms = [2*Covariance(_arg0_or_var(x), _arg0_or_var(y)).expand()/(a*b) \ for (a, b), (x, y) in zip(combinations(args, 2), combinations(var_args, 2))] var_expr += Add(*terms) elif isinstance(expr, Pow): b = args[1] v = var_args[0] * (expr * b / args[0])**2 var_expr = simplify(v) elif isinstance(expr, exp): var_expr = simplify(var_args[0] * expr**2) else: # unknown how to proceed, return variance of whole expr. var_expr = Variance(expr) return var_expr

c2a7db439ebd009d6dcf09cedeb15172aad81627f4f11279bb73b229188d4eb0

""" Contains ======== Geometric Hermite Logarithmic NegativeBinomial Poisson Skellam YuleSimon Zeta """ from sympy import (Basic, factorial, exp, S, sympify, I, zeta, polylog, log, beta, hyper, binomial, Piecewise, floor, besseli, sqrt, Sum, Dummy, Lambda, Eq) from sympy.stats.drv import SingleDiscreteDistribution, SingleDiscretePSpace from sympy.stats.rv import _value_check, is_random __all__ = ['Geometric', 'Hermite', 'Logarithmic', 'NegativeBinomial', 'Poisson', 'Skellam', 'YuleSimon', 'Zeta' ] def rv(symbol, cls, *args, **kwargs): args = list(map(sympify, args)) dist = cls(*args) if kwargs.pop('check', True): dist.check(*args) pspace = SingleDiscretePSpace(symbol, dist) if any(is_random(arg) for arg in args): from sympy.stats.compound_rv import CompoundPSpace, CompoundDistribution pspace = CompoundPSpace(symbol, CompoundDistribution(dist)) return pspace.value class DiscreteDistributionHandmade(SingleDiscreteDistribution): _argnames = ('pdf',) def __new__(cls, pdf, set=S.Integers): return Basic.__new__(cls, pdf, set) @property def set(self): return self.args[1] @staticmethod def check(pdf, set): x = Dummy('x') val = Sum(pdf(x), (x, set._inf, set._sup)).doit() _value_check(Eq(val, 1) != S.false, "The pdf is incorrect on the given set.") def DiscreteRV(symbol, density, set=S.Integers, **kwargs): """ Create a Discrete Random Variable given the following: Parameters ========== symbol : Symbol Represents name of the random variable. density : Expression containing symbol Represents probability density function. set : set Represents the region where the pdf is valid, by default is real line. check : bool If True, it will check whether the given density integrates to 1 over the given set. If False, it will not perform this check. Default is False. Examples ======== >>> from sympy.stats import DiscreteRV, P, E >>> from sympy import Rational, Symbol >>> x = Symbol('x') >>> n = 10 >>> density = Rational(1, 10) >>> X = DiscreteRV(x, density, set=set(range(n))) >>> E(X) 9/2 >>> P(X>3) 3/5 Returns ======= RandomSymbol """ set = sympify(set) pdf = Piecewise((density, set.as_relational(symbol)), (0, True)) pdf = Lambda(symbol, pdf) # have a default of False while `rv` should have a default of True kwargs['check'] = kwargs.pop('check', False) return rv(symbol.name, DiscreteDistributionHandmade, pdf, set, **kwargs) #------------------------------------------------------------------------------- # Geometric distribution ------------------------------------------------------------ class GeometricDistribution(SingleDiscreteDistribution): _argnames = ('p',) set = S.Naturals @staticmethod def check(p): _value_check((0 < p, p <= 1), "p must be between 0 and 1") def pdf(self, k): return (1 - self.p)**(k - 1) * self.p def _characteristic_function(self, t): p = self.p return p * exp(I*t) / (1 - (1 - p)*exp(I*t)) def _moment_generating_function(self, t): p = self.p return p * exp(t) / (1 - (1 - p) * exp(t)) def Geometric(name, p): r""" Create a discrete random variable with a Geometric distribution. The density of the Geometric distribution is given by .. math:: f(k) := p (1 - p)^{k - 1} Parameters ========== p: A probability between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Geometric, density, E, variance >>> from sympy import Symbol, S >>> p = S.One / 5 >>> z = Symbol("z") >>> X = Geometric("x", p) >>> density(X)(z) (4/5)**(z - 1)/5 >>> E(X) 5 >>> variance(X) 20 References ========== .. [1] https://en.wikipedia.org/wiki/Geometric_distribution .. [2] http://mathworld.wolfram.com/GeometricDistribution.html """ return rv(name, GeometricDistribution, p) #------------------------------------------------------------------------------- # Hermite distribution --------------------------------------------------------- class HermiteDistribution(SingleDiscreteDistribution): _argnames = ('a1', 'a2') set = S.Naturals0 @staticmethod def check(a1, a2): _value_check(a1.is_nonnegative, 'Parameter a1 must be >= 0.') _value_check(a2.is_nonnegative, 'Parameter a2 must be >= 0.') def pdf(self, k): a1, a2 = self.a1, self.a2 term1 = exp(-(a1 + a2)) j = Dummy("j", integer=True) num = a1**(k - 2*j) * a2**j den = factorial(k - 2*j) * factorial(j) return term1 * Sum(num/den, (j, 0, k//2)).doit() def _moment_generating_function(self, t): a1, a2 = self.a1, self.a2 term1 = a1 * (exp(t) - 1) term2 = a2 * (exp(2*t) - 1) return exp(term1 + term2) def _characteristic_function(self, t): a1, a2 = self.a1, self.a2 term1 = a1 * (exp(I*t) - 1) term2 = a2 * (exp(2*I*t) - 1) return exp(term1 + term2) def Hermite(name, a1, a2): r""" Create a discrete random variable with a Hermite distribution. The density of the Hermite distribution is given by .. math:: f(x):= e^{-a_1 -a_2}\sum_{j=0}^{\left \lfloor x/2 \right \rfloor} \frac{a_{1}^{x-2j}a_{2}^{j}}{(x-2j)!j!} Parameters ========== a1: A Positive number greater than equal to 0. a2: A Positive number greater than equal to 0. Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Hermite, density, E, variance >>> from sympy import Symbol >>> a1 = Symbol("a1", positive=True) >>> a2 = Symbol("a2", positive=True) >>> x = Symbol("x") >>> H = Hermite("H", a1=5, a2=4) >>> density(H)(2) 33*exp(-9)/2 >>> E(H) 13 >>> variance(H) 21 References ========== .. [1] https://en.wikipedia.org/wiki/Hermite_distribution """ return rv(name, HermiteDistribution, a1, a2) #------------------------------------------------------------------------------- # Logarithmic distribution ------------------------------------------------------------ class LogarithmicDistribution(SingleDiscreteDistribution): _argnames = ('p',) set = S.Naturals @staticmethod def check(p): _value_check((p > 0, p < 1), "p should be between 0 and 1") def pdf(self, k): p = self.p return (-1) * p**k / (k * log(1 - p)) def _characteristic_function(self, t): p = self.p return log(1 - p * exp(I*t)) / log(1 - p) def _moment_generating_function(self, t): p = self.p return log(1 - p * exp(t)) / log(1 - p) def Logarithmic(name, p): r""" Create a discrete random variable with a Logarithmic distribution. The density of the Logarithmic distribution is given by .. math:: f(k) := \frac{-p^k}{k \ln{(1 - p)}} Parameters ========== p: A value between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Logarithmic, density, E, variance >>> from sympy import Symbol, S >>> p = S.One / 5 >>> z = Symbol("z") >>> X = Logarithmic("x", p) >>> density(X)(z) -5**(-z)/(z*log(4/5)) >>> E(X) -1/(-4*log(5) + 8*log(2)) >>> variance(X) -1/((-4*log(5) + 8*log(2))*(-2*log(5) + 4*log(2))) + 1/(-64*log(2)*log(5) + 64*log(2)**2 + 16*log(5)**2) - 10/(-32*log(5) + 64*log(2)) References ========== .. [1] https://en.wikipedia.org/wiki/Logarithmic_distribution .. [2] http://mathworld.wolfram.com/LogarithmicDistribution.html """ return rv(name, LogarithmicDistribution, p) #------------------------------------------------------------------------------- # Negative binomial distribution ------------------------------------------------------------ class NegativeBinomialDistribution(SingleDiscreteDistribution): _argnames = ('r', 'p') set = S.Naturals0 @staticmethod def check(r, p): _value_check(r > 0, 'r should be positive') _value_check((p > 0, p < 1), 'p should be between 0 and 1') def pdf(self, k): r = self.r p = self.p return binomial(k + r - 1, k) * (1 - p)**r * p**k def _characteristic_function(self, t): r = self.r p = self.p return ((1 - p) / (1 - p * exp(I*t)))**r def _moment_generating_function(self, t): r = self.r p = self.p return ((1 - p) / (1 - p * exp(t)))**r def NegativeBinomial(name, r, p): r""" Create a discrete random variable with a Negative Binomial distribution. The density of the Negative Binomial distribution is given by .. math:: f(k) := \binom{k + r - 1}{k} (1 - p)^r p^k Parameters ========== r: A positive value p: A value between 0 and 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import NegativeBinomial, density, E, variance >>> from sympy import Symbol, S >>> r = 5 >>> p = S.One / 5 >>> z = Symbol("z") >>> X = NegativeBinomial("x", r, p) >>> density(X)(z) 1024*5**(-z)*binomial(z + 4, z)/3125 >>> E(X) 5/4 >>> variance(X) 25/16 References ========== .. [1] https://en.wikipedia.org/wiki/Negative_binomial_distribution .. [2] http://mathworld.wolfram.com/NegativeBinomialDistribution.html """ return rv(name, NegativeBinomialDistribution, r, p) #------------------------------------------------------------------------------- # Poisson distribution ------------------------------------------------------------ class PoissonDistribution(SingleDiscreteDistribution): _argnames = ('lamda',) set = S.Naturals0 @staticmethod def check(lamda): _value_check(lamda > 0, "Lambda must be positive") def pdf(self, k): return self.lamda**k / factorial(k) * exp(-self.lamda) def _characteristic_function(self, t): return exp(self.lamda * (exp(I*t) - 1)) def _moment_generating_function(self, t): return exp(self.lamda * (exp(t) - 1)) def Poisson(name, lamda): r""" Create a discrete random variable with a Poisson distribution. The density of the Poisson distribution is given by .. math:: f(k) := \frac{\lambda^{k} e^{- \lambda}}{k!} Parameters ========== lamda: Positive number, a rate Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Poisson, density, E, variance >>> from sympy import Symbol, simplify >>> rate = Symbol("lambda", positive=True) >>> z = Symbol("z") >>> X = Poisson("x", rate) >>> density(X)(z) lambda**z*exp(-lambda)/factorial(z) >>> E(X) lambda >>> simplify(variance(X)) lambda References ========== .. [1] https://en.wikipedia.org/wiki/Poisson_distribution .. [2] http://mathworld.wolfram.com/PoissonDistribution.html """ return rv(name, PoissonDistribution, lamda) # ----------------------------------------------------------------------------- # Skellam distribution -------------------------------------------------------- class SkellamDistribution(SingleDiscreteDistribution): _argnames = ('mu1', 'mu2') set = S.Integers @staticmethod def check(mu1, mu2): _value_check(mu1 >= 0, 'Parameter mu1 must be >= 0') _value_check(mu2 >= 0, 'Parameter mu2 must be >= 0') def pdf(self, k): (mu1, mu2) = (self.mu1, self.mu2) term1 = exp(-(mu1 + mu2)) * (mu1 / mu2) ** (k / 2) term2 = besseli(k, 2 * sqrt(mu1 * mu2)) return term1 * term2 def _cdf(self, x): raise NotImplementedError( "Skellam doesn't have closed form for the CDF.") def _characteristic_function(self, t): (mu1, mu2) = (self.mu1, self.mu2) return exp(-(mu1 + mu2) + mu1 * exp(I * t) + mu2 * exp(-I * t)) def _moment_generating_function(self, t): (mu1, mu2) = (self.mu1, self.mu2) return exp(-(mu1 + mu2) + mu1 * exp(t) + mu2 * exp(-t)) def Skellam(name, mu1, mu2): r""" Create a discrete random variable with a Skellam distribution. The Skellam is the distribution of the difference N1 - N2 of two statistically independent random variables N1 and N2 each Poisson-distributed with respective expected values mu1 and mu2. The density of the Skellam distribution is given by .. math:: f(k) := e^{-(\mu_1+\mu_2)}(\frac{\mu_1}{\mu_2})^{k/2}I_k(2\sqrt{\mu_1\mu_2}) Parameters ========== mu1: A non-negative value mu2: A non-negative value Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Skellam, density, E, variance >>> from sympy import Symbol, pprint >>> z = Symbol("z", integer=True) >>> mu1 = Symbol("mu1", positive=True) >>> mu2 = Symbol("mu2", positive=True) >>> X = Skellam("x", mu1, mu2) >>> pprint(density(X)(z), use_unicode=False) z - 2 /mu1\ -mu1 - mu2 / _____ _____\ |---| *e *besseli\z, 2*\/ mu1 *\/ mu2 / \mu2/ >>> E(X) mu1 - mu2 >>> variance(X).expand() mu1 + mu2 References ========== .. [1] https://en.wikipedia.org/wiki/Skellam_distribution """ return rv(name, SkellamDistribution, mu1, mu2) #------------------------------------------------------------------------------- # Yule-Simon distribution ------------------------------------------------------------ class YuleSimonDistribution(SingleDiscreteDistribution): _argnames = ('rho',) set = S.Naturals @staticmethod def check(rho): _value_check(rho > 0, 'rho should be positive') def pdf(self, k): rho = self.rho return rho * beta(k, rho + 1) def _cdf(self, x): return Piecewise((1 - floor(x) * beta(floor(x), self.rho + 1), x >= 1), (0, True)) def _characteristic_function(self, t): rho = self.rho return rho * hyper((1, 1), (rho + 2,), exp(I*t)) * exp(I*t) / (rho + 1) def _moment_generating_function(self, t): rho = self.rho return rho * hyper((1, 1), (rho + 2,), exp(t)) * exp(t) / (rho + 1) def YuleSimon(name, rho): r""" Create a discrete random variable with a Yule-Simon distribution. The density of the Yule-Simon distribution is given by .. math:: f(k) := \rho B(k, \rho + 1) Parameters ========== rho: A positive value Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import YuleSimon, density, E, variance >>> from sympy import Symbol, simplify >>> p = 5 >>> z = Symbol("z") >>> X = YuleSimon("x", p) >>> density(X)(z) 5*beta(z, 6) >>> simplify(E(X)) 5/4 >>> simplify(variance(X)) 25/48 References ========== .. [1] https://en.wikipedia.org/wiki/Yule%E2%80%93Simon_distribution """ return rv(name, YuleSimonDistribution, rho) #------------------------------------------------------------------------------- # Zeta distribution ------------------------------------------------------------ class ZetaDistribution(SingleDiscreteDistribution): _argnames = ('s',) set = S.Naturals @staticmethod def check(s): _value_check(s > 1, 's should be greater than 1') def pdf(self, k): s = self.s return 1 / (k**s * zeta(s)) def _characteristic_function(self, t): return polylog(self.s, exp(I*t)) / zeta(self.s) def _moment_generating_function(self, t): return polylog(self.s, exp(t)) / zeta(self.s) def Zeta(name, s): r""" Create a discrete random variable with a Zeta distribution. The density of the Zeta distribution is given by .. math:: f(k) := \frac{1}{k^s \zeta{(s)}} Parameters ========== s: A value greater than 1 Returns ======= RandomSymbol Examples ======== >>> from sympy.stats import Zeta, density, E, variance >>> from sympy import Symbol >>> s = 5 >>> z = Symbol("z") >>> X = Zeta("x", s) >>> density(X)(z) 1/(z**5*zeta(5)) >>> E(X) pi**4/(90*zeta(5)) >>> variance(X) -pi**8/(8100*zeta(5)**2) + zeta(3)/zeta(5) References ========== .. [1] https://en.wikipedia.org/wiki/Zeta_distribution """ return rv(name, ZetaDistribution, s)

853eeaa953001805a1b43ff9e77c108e4bb4a60cb7c1158a239a22286ae74e09

from sympy.sets import FiniteSet from sympy import (sqrt, log, exp, FallingFactorial, Rational, Eq, Dummy, piecewise_fold, solveset, Integral) from .rv import (probability, expectation, density, where, given, pspace, cdf, PSpace, characteristic_function, sample, sample_iter, random_symbols, independent, dependent, sampling_density, moment_generating_function, quantile, is_random, sample_stochastic_process) __all__ = ['P', 'E', 'H', 'density', 'where', 'given', 'sample', 'cdf', 'characteristic_function', 'pspace', 'sample_iter', 'variance', 'std', 'skewness', 'kurtosis', 'covariance', 'dependent', 'entropy', 'median', 'independent', 'random_symbols', 'correlation', 'factorial_moment', 'moment', 'cmoment', 'sampling_density', 'moment_generating_function', 'smoment', 'quantile', 'sample_stochastic_process'] def moment(X, n, c=0, condition=None, *, evaluate=True, **kwargs): """ Return the nth moment of a random expression about c. .. math:: moment(X, c, n) = E((X-c)^{n}) Default value of c is 0. Examples ======== >>> from sympy.stats import Die, moment, E >>> X = Die('X', 6) >>> moment(X, 1, 6) -5/2 >>> moment(X, 2) 91/6 >>> moment(X, 1) == E(X) True """ from sympy.stats.symbolic_probability import Moment if evaluate: return Moment(X, n, c, condition).doit() return Moment(X, n, c, condition).rewrite(Integral) def variance(X, condition=None, **kwargs): """ Variance of a random expression .. math:: variance(X) = E((X-E(X))^{2}) Examples ======== >>> from sympy.stats import Die, Bernoulli, variance >>> from sympy import simplify, Symbol >>> X = Die('X', 6) >>> p = Symbol('p') >>> B = Bernoulli('B', p, 1, 0) >>> variance(2*X) 35/3 >>> simplify(variance(B)) p*(1 - p) """ if is_random(X) and pspace(X) == PSpace(): from sympy.stats.symbolic_probability import Variance return Variance(X, condition) return cmoment(X, 2, condition, **kwargs) def standard_deviation(X, condition=None, **kwargs): r""" Standard Deviation of a random expression .. math:: std(X) = \sqrt(E((X-E(X))^{2})) Examples ======== >>> from sympy.stats import Bernoulli, std >>> from sympy import Symbol, simplify >>> p = Symbol('p') >>> B = Bernoulli('B', p, 1, 0) >>> simplify(std(B)) sqrt(p*(1 - p)) """ return sqrt(variance(X, condition, **kwargs)) std = standard_deviation def entropy(expr, condition=None, **kwargs): """ Calculuates entropy of a probability distribution Parameters ========== expression : the random expression whose entropy is to be calculated condition : optional, to specify conditions on random expression b: base of the logarithm, optional By default, it is taken as Euler's number Returns ======= result : Entropy of the expression, a constant Examples ======== >>> from sympy.stats import Normal, Die, entropy >>> X = Normal('X', 0, 1) >>> entropy(X) log(2)/2 + 1/2 + log(pi)/2 >>> D = Die('D', 4) >>> entropy(D) log(4) References ========== .. [1] https://en.wikipedia.org/wiki/Entropy_(information_theory) .. [2] https://www.crmarsh.com/static/pdf/Charles_Marsh_Continuous_Entropy.pdf .. [3] http://www.math.uconn.edu/~kconrad/blurbs/analysis/entropypost.pdf """ pdf = density(expr, condition, **kwargs) base = kwargs.get('b', exp(1)) if hasattr(pdf, 'dict'): return sum([-prob*log(prob, base) for prob in pdf.dict.values()]) return expectation(-log(pdf(expr), base)) def covariance(X, Y, condition=None, **kwargs): """ Covariance of two random expressions The expectation that the two variables will rise and fall together .. math:: covariance(X,Y) = E((X-E(X)) (Y-E(Y))) Examples ======== >>> from sympy.stats import Exponential, covariance >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> X = Exponential('X', rate) >>> Y = Exponential('Y', rate) >>> covariance(X, X) lambda**(-2) >>> covariance(X, Y) 0 >>> covariance(X, Y + rate*X) 1/lambda """ if (is_random(X) and pspace(X) == PSpace()) or (is_random(Y) and pspace(Y) == PSpace()): from sympy.stats.symbolic_probability import Covariance return Covariance(X, Y, condition) return expectation( (X - expectation(X, condition, **kwargs)) * (Y - expectation(Y, condition, **kwargs)), condition, **kwargs) def correlation(X, Y, condition=None, **kwargs): r""" Correlation of two random expressions, also known as correlation coefficient or Pearson's correlation The normalized expectation that the two variables will rise and fall together .. math:: correlation(X,Y) = E((X-E(X))(Y-E(Y)) / (\sigma_x \sigma_y)) Examples ======== >>> from sympy.stats import Exponential, correlation >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> X = Exponential('X', rate) >>> Y = Exponential('Y', rate) >>> correlation(X, X) 1 >>> correlation(X, Y) 0 >>> correlation(X, Y + rate*X) 1/sqrt(1 + lambda**(-2)) """ return covariance(X, Y, condition, **kwargs)/(std(X, condition, **kwargs) * std(Y, condition, **kwargs)) def cmoment(X, n, condition=None, *, evaluate=True, **kwargs): """ Return the nth central moment of a random expression about its mean. .. math:: cmoment(X, n) = E((X - E(X))^{n}) Examples ======== >>> from sympy.stats import Die, cmoment, variance >>> X = Die('X', 6) >>> cmoment(X, 3) 0 >>> cmoment(X, 2) 35/12 >>> cmoment(X, 2) == variance(X) True """ from sympy.stats.symbolic_probability import CentralMoment if evaluate: return CentralMoment(X, n, condition).doit() return CentralMoment(X, n, condition).rewrite(Integral) def smoment(X, n, condition=None, **kwargs): r""" Return the nth Standardized moment of a random expression. .. math:: smoment(X, n) = E(((X - \mu)/\sigma_X)^{n}) Examples ======== >>> from sympy.stats import skewness, Exponential, smoment >>> from sympy import Symbol >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> smoment(Y, 4) 9 >>> smoment(Y, 4) == smoment(3*Y, 4) True >>> smoment(Y, 3) == skewness(Y) True """ sigma = std(X, condition, **kwargs) return (1/sigma)**n*cmoment(X, n, condition, **kwargs) def skewness(X, condition=None, **kwargs): r""" Measure of the asymmetry of the probability distribution. Positive skew indicates that most of the values lie to the right of the mean. .. math:: skewness(X) = E(((X - E(X))/\sigma_X)^{3}) Parameters ========== condition : Expr containing RandomSymbols A conditional expression. skewness(X, X>0) is skewness of X given X > 0 Examples ======== >>> from sympy.stats import skewness, Exponential, Normal >>> from sympy import Symbol >>> X = Normal('X', 0, 1) >>> skewness(X) 0 >>> skewness(X, X > 0) # find skewness given X > 0 (-sqrt(2)/sqrt(pi) + 4*sqrt(2)/pi**(3/2))/(1 - 2/pi)**(3/2) >>> rate = Symbol('lambda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> skewness(Y) 2 """ return smoment(X, 3, condition=condition, **kwargs) def kurtosis(X, condition=None, **kwargs): r""" Characterizes the tails/outliers of a probability distribution. Kurtosis of any univariate normal distribution is 3. Kurtosis less than 3 means that the distribution produces fewer and less extreme outliers than the normal distribution. .. math:: kurtosis(X) = E(((X - E(X))/\sigma_X)^{4}) Parameters ========== condition : Expr containing RandomSymbols A conditional expression. kurtosis(X, X>0) is kurtosis of X given X > 0 Examples ======== >>> from sympy.stats import kurtosis, Exponential, Normal >>> from sympy import Symbol >>> X = Normal('X', 0, 1) >>> kurtosis(X) 3 >>> kurtosis(X, X > 0) # find kurtosis given X > 0 (-4/pi - 12/pi**2 + 3)/(1 - 2/pi)**2 >>> rate = Symbol('lamda', positive=True, real=True, finite=True) >>> Y = Exponential('Y', rate) >>> kurtosis(Y) 9 References ========== .. [1] https://en.wikipedia.org/wiki/Kurtosis .. [2] http://mathworld.wolfram.com/Kurtosis.html """ return smoment(X, 4, condition=condition, **kwargs) def factorial_moment(X, n, condition=None, **kwargs): """ The factorial moment is a mathematical quantity defined as the expectation or average of the falling factorial of a random variable. .. math:: factorial-moment(X, n) = E(X(X - 1)(X - 2)...(X - n + 1)) Parameters ========== n: A natural number, n-th factorial moment. condition : Expr containing RandomSymbols A conditional expression. Examples ======== >>> from sympy.stats import factorial_moment, Poisson, Binomial >>> from sympy import Symbol, S >>> lamda = Symbol('lamda') >>> X = Poisson('X', lamda) >>> factorial_moment(X, 2) lamda**2 >>> Y = Binomial('Y', 2, S.Half) >>> factorial_moment(Y, 2) 1/2 >>> factorial_moment(Y, 2, Y > 1) # find factorial moment for Y > 1 2 References ========== .. [1] https://en.wikipedia.org/wiki/Factorial_moment .. [2] http://mathworld.wolfram.com/FactorialMoment.html """ return expectation(FallingFactorial(X, n), condition=condition, **kwargs) def median(X, evaluate=True, **kwargs): r""" Calculuates the median of the probability distribution. Mathematically, median of Probability distribution is defined as all those values of `m` for which the following condition is satisfied .. math:: P(X\leq m) \geq \frac{1}{2} \text{ and} \text{ } P(X\geq m)\geq \frac{1}{2} Parameters ========== X: The random expression whose median is to be calculated. Returns ======= The FiniteSet or an Interval which contains the median of the random expression. Examples ======== >>> from sympy.stats import Normal, Die, median >>> N = Normal('N', 3, 1) >>> median(N) FiniteSet(3) >>> D = Die('D') >>> median(D) FiniteSet(3, 4) References ========== .. [1] https://en.wikipedia.org/wiki/Median#Probability_distributions """ from sympy.stats.crv import ContinuousPSpace from sympy.stats.drv import DiscretePSpace from sympy.stats.frv import FinitePSpace if isinstance(pspace(X), FinitePSpace): cdf = pspace(X).compute_cdf(X) result = [] for key, value in cdf.items(): if value>= Rational(1, 2) and (1 - value) + \ pspace(X).probability(Eq(X, key)) >= Rational(1, 2): result.append(key) return FiniteSet(*result) if isinstance(pspace(X), ContinuousPSpace) or isinstance(pspace(X), DiscretePSpace): cdf = pspace(X).compute_cdf(X) x = Dummy('x') result = solveset(piecewise_fold(cdf(x) - Rational(1, 2)), x, pspace(X).set) return result raise NotImplementedError("The median of %s is not implemeted."%str(pspace(X))) def coskewness(X, Y, Z, condition=None, **kwargs): r""" Calculates the co-skewness of three random variables. Mathematically Coskewness is defined as .. math:: coskewness(X,Y,Z)=\frac{E[(X-E[X]) * (Y-E[Y]) * (Z-E[Z])]} {\sigma_{X}\sigma_{Y}\sigma_{Z}} Parameters ========== X : RandomSymbol Random Variable used to calculate coskewness Y : RandomSymbol Random Variable used to calculate coskewness Z : RandomSymbol Random Variable used to calculate coskewness condition : Expr containing RandomSymbols A conditional expression Examples ======== >>> from sympy.stats import coskewness, Exponential, skewness >>> from sympy import symbols >>> p = symbols('p', positive=True) >>> X = Exponential('X', p) >>> Y = Exponential('Y', 2*p) >>> coskewness(X, Y, Y) 0 >>> coskewness(X, Y + X, Y + 2*X) 16*sqrt(85)/85 >>> coskewness(X + 2*Y, Y + X, Y + 2*X, X > 3) 9*sqrt(170)/85 >>> coskewness(Y, Y, Y) == skewness(Y) True >>> coskewness(X, Y + p*X, Y + 2*p*X) 4/(sqrt(1 + 1/(4*p**2))*sqrt(4 + 1/(4*p**2))) Returns ======= coskewness : The coskewness of the three random variables References ========== .. [1] https://en.wikipedia.org/wiki/Coskewness """ num = expectation((X - expectation(X, condition, **kwargs)) \ * (Y - expectation(Y, condition, **kwargs)) \ * (Z - expectation(Z, condition, **kwargs)), condition, **kwargs) den = std(X, condition, **kwargs) * std(Y, condition, **kwargs) \ * std(Z, condition, **kwargs) return num/den P = probability E = expectation H = entropy

0b11e6a3403228ec07bd8d08ede68446f5662cc9868519ae065f4ea404df35ad

""" Main Random Variables Module Defines abstract random variable type. Contains interfaces for probability space object (PSpace) as well as standard operators, P, E, sample, density, where, quantile See Also ======== sympy.stats.crv sympy.stats.frv sympy.stats.rv_interface """ from functools import singledispatch from typing import Tuple as tTuple from sympy import (Basic, S, Expr, Symbol, Tuple, And, Add, Eq, lambdify, Or, Equality, Lambda, sympify, Dummy, Ne, KroneckerDelta, DiracDelta, Mul, Indexed, MatrixSymbol, Function) from sympy.core.relational import Relational from sympy.core.sympify import _sympify from sympy.sets.sets import FiniteSet, ProductSet, Intersection from sympy.solvers.solveset import solveset from sympy.external import import_module from sympy.utilities.misc import filldedent import warnings x = Symbol('x') @singledispatch def is_random(x): return False @is_random.register(Basic) def _(x): atoms = x.free_symbols return any([is_random(i) for i in atoms]) class RandomDomain(Basic): """ Represents a set of variables and the values which they can take See Also ======== sympy.stats.crv.ContinuousDomain sympy.stats.frv.FiniteDomain """ is_ProductDomain = False is_Finite = False is_Continuous = False is_Discrete = False def __new__(cls, symbols, *args): symbols = FiniteSet(*symbols) return Basic.__new__(cls, symbols, *args) @property def symbols(self): return self.args[0] @property def set(self): return self.args[1] def __contains__(self, other): raise NotImplementedError() def compute_expectation(self, expr): raise NotImplementedError() class SingleDomain(RandomDomain): """ A single variable and its domain See Also ======== sympy.stats.crv.SingleContinuousDomain sympy.stats.frv.SingleFiniteDomain """ def __new__(cls, symbol, set): assert symbol.is_Symbol return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) def __contains__(self, other): if len(other) != 1: return False sym, val = tuple(other)[0] return self.symbol == sym and val in self.set class MatrixDomain(RandomDomain): """ A Random Matrix variable and its domain """ def __new__(cls, symbol, set): symbol, set = _symbol_converter(symbol), _sympify(set) return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) class ConditionalDomain(RandomDomain): """ A RandomDomain with an attached condition See Also ======== sympy.stats.crv.ConditionalContinuousDomain sympy.stats.frv.ConditionalFiniteDomain """ def __new__(cls, fulldomain, condition): condition = condition.xreplace({rs: rs.symbol for rs in random_symbols(condition)}) return Basic.__new__(cls, fulldomain, condition) @property def symbols(self): return self.fulldomain.symbols @property def fulldomain(self): return self.args[0] @property def condition(self): return self.args[1] @property def set(self): raise NotImplementedError("Set of Conditional Domain not Implemented") def as_boolean(self): return And(self.fulldomain.as_boolean(), self.condition) class PSpace(Basic): """ A Probability Space Probability Spaces encode processes that equal different values probabilistically. These underly Random Symbols which occur in SymPy expressions and contain the mechanics to evaluate statistical statements. See Also ======== sympy.stats.crv.ContinuousPSpace sympy.stats.frv.FinitePSpace """ is_Finite = None # type: bool is_Continuous = None # type: bool is_Discrete = None # type: bool is_real = None # type: bool @property def domain(self): return self.args[0] @property def density(self): return self.args[1] @property def values(self): return frozenset(RandomSymbol(sym, self) for sym in self.symbols) @property def symbols(self): return self.domain.symbols def where(self, condition): raise NotImplementedError() def compute_density(self, expr): raise NotImplementedError() def sample(self): raise NotImplementedError() def probability(self, condition): raise NotImplementedError() def compute_expectation(self, expr): raise NotImplementedError() class SinglePSpace(PSpace): """ Represents the probabilities of a set of random events that can be attributed to a single variable/symbol. """ def __new__(cls, s, distribution): s = _symbol_converter(s) return Basic.__new__(cls, s, distribution) @property def value(self): return RandomSymbol(self.symbol, self) @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[1] @property def pdf(self): return self.distribution.pdf(self.symbol) class RandomSymbol(Expr): """ Random Symbols represent ProbabilitySpaces in SymPy Expressions In principle they can take on any value that their symbol can take on within the associated PSpace with probability determined by the PSpace Density. Random Symbols contain pspace and symbol properties. The pspace property points to the represented Probability Space The symbol is a standard SymPy Symbol that is used in that probability space for example in defining a density. You can form normal SymPy expressions using RandomSymbols and operate on those expressions with the Functions E - Expectation of a random expression P - Probability of a condition density - Probability Density of an expression given - A new random expression (with new random symbols) given a condition An object of the RandomSymbol type should almost never be created by the user. They tend to be created instead by the PSpace class's value method. Traditionally a user doesn't even do this but instead calls one of the convenience functions Normal, Exponential, Coin, Die, FiniteRV, etc.... """ def __new__(cls, symbol, pspace=None): from sympy.stats.joint_rv import JointRandomSymbol if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() symbol = _symbol_converter(symbol) if not isinstance(pspace, PSpace): raise TypeError("pspace variable should be of type PSpace") if cls == JointRandomSymbol and isinstance(pspace, SinglePSpace): cls = RandomSymbol return Basic.__new__(cls, symbol, pspace) is_finite = True is_symbol = True is_Atom = True _diff_wrt = True pspace = property(lambda self: self.args[1]) symbol = property(lambda self: self.args[0]) name = property(lambda self: self.symbol.name) def _eval_is_positive(self): return self.symbol.is_positive def _eval_is_integer(self): return self.symbol.is_integer def _eval_is_real(self): return self.symbol.is_real or self.pspace.is_real @property def is_commutative(self): return self.symbol.is_commutative @property def free_symbols(self): return {self} class RandomIndexedSymbol(RandomSymbol): def __new__(cls, idx_obj, pspace=None): if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() if not isinstance(idx_obj, (Indexed, Function)): raise TypeError("An Function or Indexed object is expected not %s"%(idx_obj)) return Basic.__new__(cls, idx_obj, pspace) symbol = property(lambda self: self.args[0]) name = property(lambda self: str(self.args[0])) @property def key(self): if isinstance(self.symbol, Indexed): return self.symbol.args[1] elif isinstance(self.symbol, Function): return self.symbol.args[0] @property def free_symbols(self): if self.key.free_symbols: free_syms = self.key.free_symbols free_syms.add(self) return free_syms return {self} class RandomMatrixSymbol(RandomSymbol, MatrixSymbol): # type: ignore def __new__(cls, symbol, n, m, pspace=None): n, m = _sympify(n), _sympify(m) symbol = _symbol_converter(symbol) if pspace is None: # Allow single arg, representing pspace == PSpace() pspace = PSpace() return Basic.__new__(cls, symbol, n, m, pspace) symbol = property(lambda self: self.args[0]) pspace = property(lambda self: self.args[3]) class ProductPSpace(PSpace): """ Abstract class for representing probability spaces with multiple random variables. See Also ======== sympy.stats.rv.IndependentProductPSpace sympy.stats.joint_rv.JointPSpace """ pass class IndependentProductPSpace(ProductPSpace): """ A probability space resulting from the merger of two independent probability spaces. Often created using the function, pspace """ def __new__(cls, *spaces): rs_space_dict = {} for space in spaces: for value in space.values: rs_space_dict[value] = space symbols = FiniteSet(*[val.symbol for val in rs_space_dict.keys()]) # Overlapping symbols from sympy.stats.joint_rv import MarginalDistribution from sympy.stats.compound_rv import CompoundDistribution if len(symbols) < sum(len(space.symbols) for space in spaces if not isinstance(space.distribution, ( CompoundDistribution, MarginalDistribution))): raise ValueError("Overlapping Random Variables") if all(space.is_Finite for space in spaces): from sympy.stats.frv import ProductFinitePSpace cls = ProductFinitePSpace obj = Basic.__new__(cls, *FiniteSet(*spaces)) return obj @property def pdf(self): p = Mul(*[space.pdf for space in self.spaces]) return p.subs({rv: rv.symbol for rv in self.values}) @property def rs_space_dict(self): d = {} for space in self.spaces: for value in space.values: d[value] = space return d @property def symbols(self): return FiniteSet(*[val.symbol for val in self.rs_space_dict.keys()]) @property def spaces(self): return FiniteSet(*self.args) @property def values(self): return sumsets(space.values for space in self.spaces) def compute_expectation(self, expr, rvs=None, evaluate=False, **kwargs): rvs = rvs or self.values rvs = frozenset(rvs) for space in self.spaces: expr = space.compute_expectation(expr, rvs & space.values, evaluate=False, **kwargs) if evaluate and hasattr(expr, 'doit'): return expr.doit(**kwargs) return expr @property def domain(self): return ProductDomain(*[space.domain for space in self.spaces]) @property def density(self): raise NotImplementedError("Density not available for ProductSpaces") def sample(self, size=(), library='scipy'): return {k: v for space in self.spaces for k, v in space.sample(size=size, library=library).items()} def probability(self, condition, **kwargs): cond_inv = False if isinstance(condition, Ne): condition = Eq(condition.args[0], condition.args[1]) cond_inv = True elif isinstance(condition, And): # they are independent return Mul(*[self.probability(arg) for arg in condition.args]) elif isinstance(condition, Or): # they are independent return Add(*[self.probability(arg) for arg in condition.args]) expr = condition.lhs - condition.rhs rvs = random_symbols(expr) dens = self.compute_density(expr) if any([pspace(rv).is_Continuous for rv in rvs]): from sympy.stats.crv import SingleContinuousPSpace from sympy.stats.crv_types import ContinuousDistributionHandmade if expr in self.values: # Marginalize all other random symbols out of the density randomsymbols = tuple(set(self.values) - frozenset([expr])) symbols = tuple(rs.symbol for rs in randomsymbols) pdf = self.domain.integrate(self.pdf, symbols, **kwargs) return Lambda(expr.symbol, pdf) dens = ContinuousDistributionHandmade(dens) z = Dummy('z', real=True) space = SingleContinuousPSpace(z, dens) result = space.probability(condition.__class__(space.value, 0)) else: from sympy.stats.drv import SingleDiscretePSpace from sympy.stats.drv_types import DiscreteDistributionHandmade dens = DiscreteDistributionHandmade(dens) z = Dummy('z', integer=True) space = SingleDiscretePSpace(z, dens) result = space.probability(condition.__class__(space.value, 0)) return result if not cond_inv else S.One - result def compute_density(self, expr, **kwargs): rvs = random_symbols(expr) if any(pspace(rv).is_Continuous for rv in rvs): z = Dummy('z', real=True) expr = self.compute_expectation(DiracDelta(expr - z), **kwargs) else: z = Dummy('z', integer=True) expr = self.compute_expectation(KroneckerDelta(expr, z), **kwargs) return Lambda(z, expr) def compute_cdf(self, expr, **kwargs): raise ValueError("CDF not well defined on multivariate expressions") def conditional_space(self, condition, normalize=True, **kwargs): rvs = random_symbols(condition) condition = condition.xreplace({rv: rv.symbol for rv in self.values}) if any([pspace(rv).is_Continuous for rv in rvs]): from sympy.stats.crv import (ConditionalContinuousDomain, ContinuousPSpace) space = ContinuousPSpace domain = ConditionalContinuousDomain(self.domain, condition) elif any([pspace(rv).is_Discrete for rv in rvs]): from sympy.stats.drv import (ConditionalDiscreteDomain, DiscretePSpace) space = DiscretePSpace domain = ConditionalDiscreteDomain(self.domain, condition) elif all([pspace(rv).is_Finite for rv in rvs]): from sympy.stats.frv import FinitePSpace return FinitePSpace.conditional_space(self, condition) if normalize: replacement = {rv: Dummy(str(rv)) for rv in self.symbols} norm = domain.compute_expectation(self.pdf, **kwargs) pdf = self.pdf / norm.xreplace(replacement) # XXX: Converting symbols from set to tuple. The order matters to # Lambda though so we shouldn't be starting with a set here... density = Lambda(tuple(domain.symbols), pdf) return space(domain, density) class ProductDomain(RandomDomain): """ A domain resulting from the merger of two independent domains See Also ======== sympy.stats.crv.ProductContinuousDomain sympy.stats.frv.ProductFiniteDomain """ is_ProductDomain = True def __new__(cls, *domains): # Flatten any product of products domains2 = [] for domain in domains: if not domain.is_ProductDomain: domains2.append(domain) else: domains2.extend(domain.domains) domains2 = FiniteSet(*domains2) if all(domain.is_Finite for domain in domains2): from sympy.stats.frv import ProductFiniteDomain cls = ProductFiniteDomain if all(domain.is_Continuous for domain in domains2): from sympy.stats.crv import ProductContinuousDomain cls = ProductContinuousDomain if all(domain.is_Discrete for domain in domains2): from sympy.stats.drv import ProductDiscreteDomain cls = ProductDiscreteDomain return Basic.__new__(cls, *domains2) @property def sym_domain_dict(self): return {symbol: domain for domain in self.domains for symbol in domain.symbols} @property def symbols(self): return FiniteSet(*[sym for domain in self.domains for sym in domain.symbols]) @property def domains(self): return self.args @property def set(self): return ProductSet(*(domain.set for domain in self.domains)) def __contains__(self, other): # Split event into each subdomain for domain in self.domains: # Collect the parts of this event which associate to this domain elem = frozenset([item for item in other if sympify(domain.symbols.contains(item[0])) is S.true]) # Test this sub-event if elem not in domain: return False # All subevents passed return True def as_boolean(self): return And(*[domain.as_boolean() for domain in self.domains]) def random_symbols(expr): """ Returns all RandomSymbols within a SymPy Expression. """ atoms = getattr(expr, 'atoms', None) if atoms is not None: comp = lambda rv: rv.symbol.name l = list(atoms(RandomSymbol)) return sorted(l, key=comp) else: return [] def pspace(expr): """ Returns the underlying Probability Space of a random expression. For internal use. Examples ======== >>> from sympy.stats import pspace, Normal >>> X = Normal('X', 0, 1) >>> pspace(2*X + 1) == X.pspace True """ expr = sympify(expr) if isinstance(expr, RandomSymbol) and expr.pspace is not None: return expr.pspace if expr.has(RandomMatrixSymbol): rm = list(expr.atoms(RandomMatrixSymbol))[0] return rm.pspace rvs = random_symbols(expr) if not rvs: raise ValueError("Expression containing Random Variable expected, not %s" % (expr)) # If only one space present if all(rv.pspace == rvs[0].pspace for rv in rvs): return rvs[0].pspace from sympy.stats.compound_rv import CompoundPSpace for rv in rvs: if isinstance(rv.pspace, CompoundPSpace): return rv.pspace # Otherwise make a product space return IndependentProductPSpace(*[rv.pspace for rv in rvs]) def sumsets(sets): """ Union of sets """ return frozenset().union(*sets) def rs_swap(a, b): """ Build a dictionary to swap RandomSymbols based on their underlying symbol. i.e. if ``X = ('x', pspace1)`` and ``Y = ('x', pspace2)`` then ``X`` and ``Y`` match and the key, value pair ``{X:Y}`` will appear in the result Inputs: collections a and b of random variables which share common symbols Output: dict mapping RVs in a to RVs in b """ d = {} for rsa in a: d[rsa] = [rsb for rsb in b if rsa.symbol == rsb.symbol][0] return d def given(expr, condition=None, **kwargs): r""" Conditional Random Expression From a random expression and a condition on that expression creates a new probability space from the condition and returns the same expression on that conditional probability space. Examples ======== >>> from sympy.stats import given, density, Die >>> X = Die('X', 6) >>> Y = given(X, X > 3) >>> density(Y).dict {4: 1/3, 5: 1/3, 6: 1/3} Following convention, if the condition is a random symbol then that symbol is considered fixed. >>> from sympy.stats import Normal >>> from sympy import pprint >>> from sympy.abc import z >>> X = Normal('X', 0, 1) >>> Y = Normal('Y', 0, 1) >>> pprint(density(X + Y, Y)(z), use_unicode=False) 2 -(-Y + z) ----------- ___ 2 \/ 2 *e ------------------ ____ 2*\/ pi """ if not is_random(condition) or pspace_independent(expr, condition): return expr if isinstance(condition, RandomSymbol): condition = Eq(condition, condition.symbol) condsymbols = random_symbols(condition) if (isinstance(condition, Equality) and len(condsymbols) == 1 and not isinstance(pspace(expr).domain, ConditionalDomain)): rv = tuple(condsymbols)[0] results = solveset(condition, rv) if isinstance(results, Intersection) and S.Reals in results.args: results = list(results.args[1]) sums = 0 for res in results: temp = expr.subs(rv, res) if temp == True: return True if temp != False: # XXX: This seems nonsensical but preserves existing behaviour # after the change that Relational is no longer a subclass of # Expr. Here expr is sometimes Relational and sometimes Expr # but we are trying to add them with +=. This needs to be # fixed somehow. if sums == 0 and isinstance(expr, Relational): sums = expr.subs(rv, res) else: sums += expr.subs(rv, res) if sums == 0: return False return sums # Get full probability space of both the expression and the condition fullspace = pspace(Tuple(expr, condition)) # Build new space given the condition space = fullspace.conditional_space(condition, **kwargs) # Dictionary to swap out RandomSymbols in expr with new RandomSymbols # That point to the new conditional space swapdict = rs_swap(fullspace.values, space.values) # Swap random variables in the expression expr = expr.xreplace(swapdict) return expr def expectation(expr, condition=None, numsamples=None, evaluate=True, **kwargs): """ Returns the expected value of a random expression Parameters ========== expr : Expr containing RandomSymbols The expression of which you want to compute the expectation value given : Expr containing RandomSymbols A conditional expression. E(X, X>0) is expectation of X given X > 0 numsamples : int Enables sampling and approximates the expectation with this many samples evalf : Bool (defaults to True) If sampling return a number rather than a complex expression evaluate : Bool (defaults to True) In case of continuous systems return unevaluated integral Examples ======== >>> from sympy.stats import E, Die >>> X = Die('X', 6) >>> E(X) 7/2 >>> E(2*X + 1) 8 >>> E(X, X > 3) # Expectation of X given that it is above 3 5 """ if not is_random(expr): # expr isn't random? return expr kwargs['numsamples'] = numsamples from sympy.stats.symbolic_probability import Expectation if evaluate: return Expectation(expr, condition).doit(**kwargs) ### TODO: Remove the user warnings in the future releases message = ("Since version 1.7, using `evaluate=False` returns `Expectation` " "object. If you want unevaluated Integral/Sum use " "`E(expr, condition, evaluate=False).rewrite(Integral)`") warnings.warn(filldedent(message)) return Expectation(expr, condition) def probability(condition, given_condition=None, numsamples=None, evaluate=True, **kwargs): """ Probability that a condition is true, optionally given a second condition Parameters ========== condition : Combination of Relationals containing RandomSymbols The condition of which you want to compute the probability given_condition : Combination of Relationals containing RandomSymbols A conditional expression. P(X > 1, X > 0) is expectation of X > 1 given X > 0 numsamples : int Enables sampling and approximates the probability with this many samples evaluate : Bool (defaults to True) In case of continuous systems return unevaluated integral Examples ======== >>> from sympy.stats import P, Die >>> from sympy import Eq >>> X, Y = Die('X', 6), Die('Y', 6) >>> P(X > 3) 1/2 >>> P(Eq(X, 5), X > 2) # Probability that X == 5 given that X > 2 1/4 >>> P(X > Y) 5/12 """ kwargs['numsamples'] = numsamples from sympy.stats.symbolic_probability import Probability if evaluate: return Probability(condition, given_condition).doit(**kwargs) ### TODO: Remove the user warnings in the future releases message = ("Since version 1.7, using `evaluate=False` returns `Probability` " "object. If you want unevaluated Integral/Sum use " "`P(condition, given_condition, evaluate=False).rewrite(Integral)`") warnings.warn(filldedent(message)) return Probability(condition, given_condition) class Density(Basic): expr = property(lambda self: self.args[0]) @property def condition(self): if len(self.args) > 1: return self.args[1] else: return None def doit(self, evaluate=True, **kwargs): from sympy.stats.random_matrix import RandomMatrixPSpace from sympy.stats.joint_rv import JointPSpace from sympy.stats.matrix_distributions import MatrixPSpace from sympy.stats.compound_rv import CompoundPSpace from sympy.stats.frv import SingleFiniteDistribution expr, condition = self.expr, self.condition if isinstance(expr, SingleFiniteDistribution): return expr.dict if condition is not None: # Recompute on new conditional expr expr = given(expr, condition, **kwargs) if not random_symbols(expr): return Lambda(x, DiracDelta(x - expr)) if isinstance(expr, RandomSymbol): if isinstance(expr.pspace, (SinglePSpace, JointPSpace, MatrixPSpace)) and \ hasattr(expr.pspace, 'distribution'): return expr.pspace.distribution elif isinstance(expr.pspace, RandomMatrixPSpace): return expr.pspace.model if isinstance(pspace(expr), CompoundPSpace): kwargs['compound_evaluate'] = evaluate result = pspace(expr).compute_density(expr, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def density(expr, condition=None, evaluate=True, numsamples=None, **kwargs): """ Probability density of a random expression, optionally given a second condition. This density will take on different forms for different types of probability spaces. Discrete variables produce Dicts. Continuous variables produce Lambdas. Parameters ========== expr : Expr containing RandomSymbols The expression of which you want to compute the density value condition : Relational containing RandomSymbols A conditional expression. density(X > 1, X > 0) is density of X > 1 given X > 0 numsamples : int Enables sampling and approximates the density with this many samples Examples ======== >>> from sympy.stats import density, Die, Normal >>> from sympy import Symbol >>> x = Symbol('x') >>> D = Die('D', 6) >>> X = Normal(x, 0, 1) >>> density(D).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> density(2*D).dict {2: 1/6, 4: 1/6, 6: 1/6, 8: 1/6, 10: 1/6, 12: 1/6} >>> density(X)(x) sqrt(2)*exp(-x**2/2)/(2*sqrt(pi)) """ if numsamples: return sampling_density(expr, condition, numsamples=numsamples, **kwargs) return Density(expr, condition).doit(evaluate=evaluate, **kwargs) def cdf(expr, condition=None, evaluate=True, **kwargs): """ Cumulative Distribution Function of a random expression. optionally given a second condition This density will take on different forms for different types of probability spaces. Discrete variables produce Dicts. Continuous variables produce Lambdas. Examples ======== >>> from sympy.stats import density, Die, Normal, cdf >>> D = Die('D', 6) >>> X = Normal('X', 0, 1) >>> density(D).dict {1: 1/6, 2: 1/6, 3: 1/6, 4: 1/6, 5: 1/6, 6: 1/6} >>> cdf(D) {1: 1/6, 2: 1/3, 3: 1/2, 4: 2/3, 5: 5/6, 6: 1} >>> cdf(3*D, D > 2) {9: 1/4, 12: 1/2, 15: 3/4, 18: 1} >>> cdf(X) Lambda(_z, erf(sqrt(2)*_z/2)/2 + 1/2) """ if condition is not None: # If there is a condition # Recompute on new conditional expr return cdf(given(expr, condition, **kwargs), **kwargs) # Otherwise pass work off to the ProbabilitySpace result = pspace(expr).compute_cdf(expr, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def characteristic_function(expr, condition=None, evaluate=True, **kwargs): """ Characteristic function of a random expression, optionally given a second condition Returns a Lambda Examples ======== >>> from sympy.stats import Normal, DiscreteUniform, Poisson, characteristic_function >>> X = Normal('X', 0, 1) >>> characteristic_function(X) Lambda(_t, exp(-_t**2/2)) >>> Y = DiscreteUniform('Y', [1, 2, 7]) >>> characteristic_function(Y) Lambda(_t, exp(7*_t*I)/3 + exp(2*_t*I)/3 + exp(_t*I)/3) >>> Z = Poisson('Z', 2) >>> characteristic_function(Z) Lambda(_t, exp(2*exp(_t*I) - 2)) """ if condition is not None: return characteristic_function(given(expr, condition, **kwargs), **kwargs) result = pspace(expr).compute_characteristic_function(expr, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def moment_generating_function(expr, condition=None, evaluate=True, **kwargs): if condition is not None: return moment_generating_function(given(expr, condition, **kwargs), **kwargs) result = pspace(expr).compute_moment_generating_function(expr, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def where(condition, given_condition=None, **kwargs): """ Returns the domain where a condition is True. Examples ======== >>> from sympy.stats import where, Die, Normal >>> from sympy import And >>> D1, D2 = Die('a', 6), Die('b', 6) >>> a, b = D1.symbol, D2.symbol >>> X = Normal('x', 0, 1) >>> where(X**2<1) Domain: (-1 < x) & (x < 1) >>> where(X**2<1).set Interval.open(-1, 1) >>> where(And(D1<=D2 , D2<3)) Domain: (Eq(a, 1) & Eq(b, 1)) | (Eq(a, 1) & Eq(b, 2)) | (Eq(a, 2) & Eq(b, 2)) """ if given_condition is not None: # If there is a condition # Recompute on new conditional expr return where(given(condition, given_condition, **kwargs), **kwargs) # Otherwise pass work off to the ProbabilitySpace return pspace(condition).where(condition, **kwargs) def sample(expr, condition=None, size=(), library='scipy', numsamples=1, **kwargs): """ A realization of the random expression Parameters ========== expr : Expression of random variables Expression from which sample is extracted condition : Expr containing RandomSymbols A conditional expression size : int, tuple Represents size of each sample in numsamples library : str - 'scipy' : Sample using scipy - 'numpy' : Sample using numpy - 'pymc3' : Sample using PyMC3 Choose any of the available options to sample from as string, by default is 'scipy' numsamples : int Number of samples, each with size as ``size`` Examples ======== >>> from sympy.stats import Die, sample, Normal, Geometric >>> X, Y, Z = Die('X', 6), Die('Y', 6), Die('Z', 6) # Finite Random Variable >>> die_roll = sample(X + Y + Z) # doctest: +SKIP >>> next(die_roll) # doctest: +SKIP 6 >>> N = Normal('N', 3, 4) # Continuous Random Variable >>> samp = next(sample(N)) # doctest: +SKIP >>> samp in N.pspace.domain.set # doctest: +SKIP True >>> samp = next(sample(N, N>0)) # doctest: +SKIP >>> samp > 0 # doctest: +SKIP True >>> samp_list = next(sample(N, size=4)) # doctest: +SKIP >>> [sam in N.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True, True] >>> G = Geometric('G', 0.5) # Discrete Random Variable >>> samp_list = next(sample(G, size=3)) # doctest: +SKIP >>> samp_list # doctest: +SKIP array([10, 4, 1]) >>> [sam in G.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True] >>> MN = Normal("MN", [3, 4], [[2, 1], [1, 2]]) # Joint Random Variable >>> samp_list = next(sample(MN, size=4)) # doctest: +SKIP >>> samp_list # doctest: +SKIP array([[4.22564264, 3.23364418], [3.41002011, 4.60090908], [3.76151866, 4.77617143], [4.71440865, 2.65714157]]) >>> [tuple(sam) in MN.pspace.domain.set for sam in samp_list] # doctest: +SKIP [True, True, True, True] Returns ======= sample: iterator object iterator object containing the sample/samples of given expr """ ### TODO: Remove the user warnings in the future releases message = ("The return type of sample has been changed to return an " "iterator object since version 1.7. For more information see " "https://github.com/sympy/sympy/issues/19061") warnings.warn(filldedent(message)) return sample_iter(expr, condition, size=size, library=library, numsamples=numsamples) def quantile(expr, evaluate=True, **kwargs): r""" Return the :math:`p^{th}` order quantile of a probability distribution. Quantile is defined as the value at which the probability of the random variable is less than or equal to the given probability. ..math:: Q(p) = inf{x \in (-\infty, \infty) such that p <= F(x)} Examples ======== >>> from sympy.stats import quantile, Die, Exponential >>> from sympy import Symbol, pprint >>> p = Symbol("p") >>> l = Symbol("lambda", positive=True) >>> X = Exponential("x", l) >>> quantile(X)(p) -log(1 - p)/lambda >>> D = Die("d", 6) >>> pprint(quantile(D)(p), use_unicode=False) /nan for Or(p > 1, p < 0) | | 1 for p <= 1/6 | | 2 for p <= 1/3 | < 3 for p <= 1/2 | | 4 for p <= 2/3 | | 5 for p <= 5/6 | \ 6 for p <= 1 """ result = pspace(expr).compute_quantile(expr, **kwargs) if evaluate and hasattr(result, 'doit'): return result.doit() else: return result def sample_iter(expr, condition=None, size=(), library='scipy', numsamples=S.Infinity, **kwargs): """ Returns an iterator of realizations from the expression given a condition Parameters ========== expr: Expr Random expression to be realized condition: Expr, optional A conditional expression size : int, tuple Represents size of each sample in numsamples numsamples: integer, optional Length of the iterator (defaults to infinity) Examples ======== >>> from sympy.stats import Normal, sample_iter >>> X = Normal('X', 0, 1) >>> expr = X*X + 3 >>> iterator = sample_iter(expr, numsamples=3) # doctest: +SKIP >>> list(iterator) # doctest: +SKIP [12, 4, 7] Returns ======= sample_iter: iterator object iterator object containing the sample/samples of given expr See Also ======== sample sampling_P sampling_E """ from sympy.stats.joint_rv import JointRandomSymbol if not import_module(library): raise ValueError("Failed to import %s" % library) if condition is not None: ps = pspace(Tuple(expr, condition)) else: ps = pspace(expr) rvs = list(ps.values) if isinstance(expr, JointRandomSymbol): expr = expr.subs({expr: RandomSymbol(expr.symbol, expr.pspace)}) else: sub = {} for arg in expr.args: if isinstance(arg, JointRandomSymbol): sub[arg] = RandomSymbol(arg.symbol, arg.pspace) expr = expr.subs(sub) if library == 'pymc3': # Currently unable to lambdify in pymc3 # TODO : Remove 'pymc3' when lambdify accepts 'pymc3' as module fn = lambdify(rvs, expr, **kwargs) else: fn = lambdify(rvs, expr, modules=library, **kwargs) if condition is not None: given_fn = lambdify(rvs, condition, **kwargs) def return_generator(): count = 0 while count < numsamples: d = ps.sample(size=size, library=library) # a dictionary that maps RVs to values args = [d[rv] for rv in rvs] if condition is not None: # Check that these values satisfy the condition gd = given_fn(*args) if gd != True and gd != False: raise ValueError( "Conditions must not contain free symbols") if not gd: # If the values don't satisfy then try again continue yield fn(*args) count += 1 return return_generator() def sample_iter_lambdify(expr, condition=None, size=(), numsamples=S.Infinity, **kwargs): return sample_iter(expr, condition=condition, size=size, numsamples=numsamples, **kwargs) def sample_iter_subs(expr, condition=None, size=(), numsamples=S.Infinity, **kwargs): return sample_iter(expr, condition=condition, size=size, numsamples=numsamples, **kwargs) def sampling_P(condition, given_condition=None, library='scipy', numsamples=1, evalf=True, **kwargs): """ Sampling version of P See Also ======== P sampling_E sampling_density """ count_true = 0 count_false = 0 samples = sample_iter(condition, given_condition, library=library, numsamples=numsamples, **kwargs) for sample in samples: if sample: count_true += 1 else: count_false += 1 result = S(count_true) / numsamples if evalf: return result.evalf() else: return result def sampling_E(expr, given_condition=None, library='scipy', numsamples=1, evalf=True, **kwargs): """ Sampling version of E See Also ======== P sampling_P sampling_density """ samples = list(sample_iter(expr, given_condition, library=library, numsamples=numsamples, **kwargs)) result = Add(*[samp for samp in samples]) / numsamples if evalf: return result.evalf() else: return result def sampling_density(expr, given_condition=None, library='scipy', numsamples=1, **kwargs): """ Sampling version of density See Also ======== density sampling_P sampling_E """ results = {} for result in sample_iter(expr, given_condition, library=library, numsamples=numsamples, **kwargs): results[result] = results.get(result, 0) + 1 return results def dependent(a, b): """ Dependence of two random expressions Two expressions are independent if knowledge of one does not change computations on the other. Examples ======== >>> from sympy.stats import Normal, dependent, given >>> from sympy import Tuple, Eq >>> X, Y = Normal('X', 0, 1), Normal('Y', 0, 1) >>> dependent(X, Y) False >>> dependent(2*X + Y, -Y) True >>> X, Y = given(Tuple(X, Y), Eq(X + Y, 3)) >>> dependent(X, Y) True See Also ======== independent """ if pspace_independent(a, b): return False z = Symbol('z', real=True) # Dependent if density is unchanged when one is given information about # the other return (density(a, Eq(b, z)) != density(a) or density(b, Eq(a, z)) != density(b)) def independent(a, b): """ Independence of two random expressions Two expressions are independent if knowledge of one does not change computations on the other. Examples ======== >>> from sympy.stats import Normal, independent, given >>> from sympy import Tuple, Eq >>> X, Y = Normal('X', 0, 1), Normal('Y', 0, 1) >>> independent(X, Y) True >>> independent(2*X + Y, -Y) False >>> X, Y = given(Tuple(X, Y), Eq(X + Y, 3)) >>> independent(X, Y) False See Also ======== dependent """ return not dependent(a, b) def pspace_independent(a, b): """ Tests for independence between a and b by checking if their PSpaces have overlapping symbols. This is a sufficient but not necessary condition for independence and is intended to be used internally. Notes ===== pspace_independent(a, b) implies independent(a, b) independent(a, b) does not imply pspace_independent(a, b) """ a_symbols = set(pspace(b).symbols) b_symbols = set(pspace(a).symbols) if len(set(random_symbols(a)).intersection(random_symbols(b))) != 0: return False if len(a_symbols.intersection(b_symbols)) == 0: return True return None def rv_subs(expr, symbols=None): """ Given a random expression replace all random variables with their symbols. If symbols keyword is given restrict the swap to only the symbols listed. """ if symbols is None: symbols = random_symbols(expr) if not symbols: return expr swapdict = {rv: rv.symbol for rv in symbols} return expr.subs(swapdict) class NamedArgsMixin: _argnames = () # type: tTuple[str, ...] def __getattr__(self, attr): try: return self.args[self._argnames.index(attr)] except ValueError: raise AttributeError("'%s' object has no attribute '%s'" % ( type(self).__name__, attr)) def _value_check(condition, message): """ Raise a ValueError with message if condition is False, else return True if all conditions were True, else False. Examples ======== >>> from sympy.stats.rv import _value_check >>> from sympy.abc import a, b, c >>> from sympy import And, Dummy >>> _value_check(2 < 3, '') True Here, the condition is not False, but it doesn't evaluate to True so False is returned (but no error is raised). So checking if the return value is True or False will tell you if all conditions were evaluated. >>> _value_check(a < b, '') False In this case the condition is False so an error is raised: >>> r = Dummy(real=True) >>> _value_check(r < r - 1, 'condition is not true') Traceback (most recent call last): ... ValueError: condition is not true If no condition of many conditions must be False, they can be checked by passing them as an iterable: >>> _value_check((a < 0, b < 0, c < 0), '') False The iterable can be a generator, too: >>> _value_check((i < 0 for i in (a, b, c)), '') False The following are equivalent to the above but do not pass an iterable: >>> all(_value_check(i < 0, '') for i in (a, b, c)) False >>> _value_check(And(a < 0, b < 0, c < 0), '') False """ from sympy.core.compatibility import iterable from sympy.core.logic import fuzzy_and if not iterable(condition): condition = [condition] truth = fuzzy_and(condition) if truth == False: raise ValueError(message) return truth == True def _symbol_converter(sym): """ Casts the parameter to Symbol if it is 'str' otherwise no operation is performed on it. Parameters ========== sym The parameter to be converted. Returns ======= Symbol the parameter converted to Symbol. Raises ====== TypeError If the parameter is not an instance of both str and Symbol. Examples ======== >>> from sympy import Symbol >>> from sympy.stats.rv import _symbol_converter >>> s = _symbol_converter('s') >>> isinstance(s, Symbol) True >>> _symbol_converter(1) Traceback (most recent call last): ... TypeError: 1 is neither a Symbol nor a string >>> r = Symbol('r') >>> isinstance(r, Symbol) True """ if isinstance(sym, str): sym = Symbol(sym) if not isinstance(sym, Symbol): raise TypeError("%s is neither a Symbol nor a string"%(sym)) return sym def sample_stochastic_process(process): """ This function is used to sample from stochastic process. Parameters ========== process: StochasticProcess Process used to extract the samples. It must be an instance of StochasticProcess Examples ======== >>> from sympy.stats import sample_stochastic_process, DiscreteMarkovChain >>> from sympy import Matrix >>> T = Matrix([[0.5, 0.2, 0.3],[0.2, 0.5, 0.3],[0.2, 0.3, 0.5]]) >>> Y = DiscreteMarkovChain("Y", [0, 1, 2], T) >>> next(sample_stochastic_process(Y)) in Y.state_space # doctest: +SKIP True >>> next(sample_stochastic_process(Y)) # doctest: +SKIP 0 >>> next(sample_stochastic_process(Y)) # doctest: +SKIP 2 Returns ======= sample: iterator object iterator object containing the sample of given process """ from sympy.stats.stochastic_process_types import StochasticProcess if not isinstance(process, StochasticProcess): raise ValueError("Process must be an instance of Stochastic Process") return process.sample()

3ec3b41e784781b8dc39b74b7e6ed3ca520d02083b7690e4e9c699edeafd04ea

""" Joint Random Variables Module See Also ======== sympy.stats.rv sympy.stats.frv sympy.stats.crv sympy.stats.drv """ from sympy import (Basic, Lambda, sympify, Indexed, Symbol, ProductSet, S, Dummy) from sympy.concrete.products import Product from sympy.concrete.summations import Sum, summation from sympy.core.compatibility import iterable from sympy.core.containers import Tuple from sympy.integrals.integrals import Integral, integrate from sympy.matrices import ImmutableMatrix, matrix2numpy, list2numpy from sympy.stats.crv import SingleContinuousDistribution, SingleContinuousPSpace from sympy.stats.drv import SingleDiscreteDistribution, SingleDiscretePSpace from sympy.stats.rv import (ProductPSpace, NamedArgsMixin, ProductDomain, RandomSymbol, random_symbols, SingleDomain, _symbol_converter) from sympy.utilities.misc import filldedent from sympy.external import import_module # __all__ = ['marginal_distribution'] class JointPSpace(ProductPSpace): """ Represents a joint probability space. Represented using symbols for each component and a distribution. """ def __new__(cls, sym, dist): if isinstance(dist, SingleContinuousDistribution): return SingleContinuousPSpace(sym, dist) if isinstance(dist, SingleDiscreteDistribution): return SingleDiscretePSpace(sym, dist) sym = _symbol_converter(sym) return Basic.__new__(cls, sym, dist) @property def set(self): return self.domain.set @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[1] @property def value(self): return JointRandomSymbol(self.symbol, self) @property def component_count(self): _set = self.distribution.set if isinstance(_set, ProductSet): return S(len(_set.args)) elif isinstance(_set, Product): return _set.limits[0][-1] return S.One @property def pdf(self): sym = [Indexed(self.symbol, i) for i in range(self.component_count)] return self.distribution(*sym) @property def domain(self): rvs = random_symbols(self.distribution) if not rvs: return SingleDomain(self.symbol, self.distribution.set) return ProductDomain(*[rv.pspace.domain for rv in rvs]) def component_domain(self, index): return self.set.args[index] def marginal_distribution(self, *indices): count = self.component_count if count.atoms(Symbol): raise ValueError("Marginal distributions cannot be computed " "for symbolic dimensions. It is a work under progress.") orig = [Indexed(self.symbol, i) for i in range(count)] all_syms = [Symbol(str(i)) for i in orig] replace_dict = dict(zip(all_syms, orig)) sym = tuple(Symbol(str(Indexed(self.symbol, i))) for i in indices) limits = list([i,] for i in all_syms if i not in sym) index = 0 for i in range(count): if i not in indices: limits[index].append(self.distribution.set.args[i]) limits[index] = tuple(limits[index]) index += 1 if self.distribution.is_Continuous: f = Lambda(sym, integrate(self.distribution(*all_syms), *limits)) elif self.distribution.is_Discrete: f = Lambda(sym, summation(self.distribution(*all_syms), *limits)) return f.xreplace(replace_dict) def compute_expectation(self, expr, rvs=None, evaluate=False, **kwargs): syms = tuple(self.value[i] for i in range(self.component_count)) rvs = rvs or syms if not any([i in rvs for i in syms]): return expr expr = expr*self.pdf for rv in rvs: if isinstance(rv, Indexed): expr = expr.xreplace({rv: Indexed(str(rv.base), rv.args[1])}) elif isinstance(rv, RandomSymbol): expr = expr.xreplace({rv: rv.symbol}) if self.value in random_symbols(expr): raise NotImplementedError(filldedent(''' Expectations of expression with unindexed joint random symbols cannot be calculated yet.''')) limits = tuple((Indexed(str(rv.base),rv.args[1]), self.distribution.set.args[rv.args[1]]) for rv in syms) return Integral(expr, *limits) def where(self, condition): raise NotImplementedError() def compute_density(self, expr): raise NotImplementedError() def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {RandomSymbol(self.symbol, self): self.distribution.sample(size, library=library)} def probability(self, condition): raise NotImplementedError() class SampleJointScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" from scipy import stats as scipy_stats scipy_rv_map = { 'MultivariateNormalDistribution': lambda dist, size: scipy_stats.multivariate_normal.rvs( mean=matrix2numpy(dist.mu).flatten(), cov=matrix2numpy(dist.sigma), size=size), 'MultivariateBetaDistribution': lambda dist, size: scipy_stats.dirichlet.rvs( alpha=list2numpy(dist.alpha, float).flatten(), size=size), 'MultinomialDistribution': lambda dist, size: scipy_stats.multinomial.rvs( n=int(dist.n), p=list2numpy(dist.p, float).flatten(), size=size) } dist_list = scipy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return scipy_rv_map[dist.__class__.__name__](dist, size) class SampleJointNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'MultivariateNormalDistribution': lambda dist, size: numpy.random.multivariate_normal( mean=matrix2numpy(dist.mu, float).flatten(), cov=matrix2numpy(dist.sigma, float), size=size), 'MultivariateBetaDistribution': lambda dist, size: numpy.random.dirichlet( alpha=list2numpy(dist.alpha, float).flatten(), size=size), 'MultinomialDistribution': lambda dist, size: numpy.random.multinomial( n=int(dist.n), pvals=list2numpy(dist.p, float).flatten(), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleJointPymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'MultivariateNormalDistribution': lambda dist: pymc3.MvNormal('X', mu=matrix2numpy(dist.mu, float).flatten(), cov=matrix2numpy(dist.sigma, float), shape=(1, dist.mu.shape[0])), 'MultivariateBetaDistribution': lambda dist: pymc3.Dirichlet('X', a=list2numpy(dist.alpha, float).flatten()), 'MultinomialDistribution': lambda dist: pymc3.Multinomial('X', n=int(dist.n), p=list2numpy(dist.p, float).flatten(), shape=(1, len(dist.p))) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_jrv = { 'scipy': SampleJointScipy, 'pymc3': SampleJointPymc, 'numpy': SampleJointNumpy } class JointDistribution(Basic, NamedArgsMixin): """ Represented by the random variables part of the joint distribution. Contains methods for PDF, CDF, sampling, marginal densities, etc. """ _argnames = ('pdf', ) def __new__(cls, *args): args = list(map(sympify, args)) for i in range(len(args)): if isinstance(args[i], list): args[i] = ImmutableMatrix(args[i]) return Basic.__new__(cls, *args) @property def domain(self): return ProductDomain(self.symbols) @property def pdf(self): return self.density.args[1] def cdf(self, other): if not isinstance(other, dict): raise ValueError("%s should be of type dict, got %s"%(other, type(other))) rvs = other.keys() _set = self.domain.set.sets expr = self.pdf(tuple(i.args[0] for i in self.symbols)) for i in range(len(other)): if rvs[i].is_Continuous: density = Integral(expr, (rvs[i], _set[i].inf, other[rvs[i]])) elif rvs[i].is_Discrete: density = Sum(expr, (rvs[i], _set[i].inf, other[rvs[i]])) return density def sample(self, size=(), library='scipy'): """ A random realization from the distribution """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_jrv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) def __call__(self, *args): return self.pdf(*args) class JointRandomSymbol(RandomSymbol): """ Representation of random symbols with joint probability distributions to allow indexing." """ def __getitem__(self, key): if isinstance(self.pspace, JointPSpace): if (self.pspace.component_count <= key) == True: raise ValueError("Index keys for %s can only up to %s." % (self.name, self.pspace.component_count - 1)) return Indexed(self, key) class MarginalDistribution(Basic): """ Represents the marginal distribution of a joint probability space. Initialised using a probability distribution and random variables(or their indexed components) which should be a part of the resultant distribution. """ def __new__(cls, dist, *rvs): if len(rvs) == 1 and iterable(rvs[0]): rvs = tuple(rvs[0]) if not all([isinstance(rv, (Indexed, RandomSymbol))] for rv in rvs): raise ValueError(filldedent('''Marginal distribution can be intitialised only in terms of random variables or indexed random variables''')) rvs = Tuple.fromiter(rv for rv in rvs) if not isinstance(dist, JointDistribution) and len(random_symbols(dist)) == 0: return dist return Basic.__new__(cls, dist, rvs) def check(self): pass @property def set(self): rvs = [i for i in self.args[1] if isinstance(i, RandomSymbol)] return ProductSet(*[rv.pspace.set for rv in rvs]) @property def symbols(self): rvs = self.args[1] return {rv.pspace.symbol for rv in rvs} def pdf(self, *x): expr, rvs = self.args[0], self.args[1] marginalise_out = [i for i in random_symbols(expr) if i not in rvs] if isinstance(expr, JointDistribution): count = len(expr.domain.args) x = Dummy('x', real=True, finite=True) syms = tuple(Indexed(x, i) for i in count) expr = expr.pdf(syms) else: syms = tuple(rv.pspace.symbol if isinstance(rv, RandomSymbol) else rv.args[0] for rv in rvs) return Lambda(syms, self.compute_pdf(expr, marginalise_out))(*x) def compute_pdf(self, expr, rvs): for rv in rvs: lpdf = 1 if isinstance(rv, RandomSymbol): lpdf = rv.pspace.pdf expr = self.marginalise_out(expr*lpdf, rv) return expr def marginalise_out(self, expr, rv): from sympy.concrete.summations import Sum if isinstance(rv, RandomSymbol): dom = rv.pspace.set elif isinstance(rv, Indexed): dom = rv.base.component_domain( rv.pspace.component_domain(rv.args[1])) expr = expr.xreplace({rv: rv.pspace.symbol}) if rv.pspace.is_Continuous: #TODO: Modify to support integration #for all kinds of sets. expr = Integral(expr, (rv.pspace.symbol, dom)) elif rv.pspace.is_Discrete: #incorporate this into `Sum`/`summation` if dom in (S.Integers, S.Naturals, S.Naturals0): dom = (dom.inf, dom.sup) expr = Sum(expr, (rv.pspace.symbol, dom)) return expr def __call__(self, *args): return self.pdf(*args)

c30e893f2554adef2f886678a8a85be79908b7c7b9b726943074544f290d8935

from sympy import (Basic, sympify, symbols, Dummy, Lambda, summation, Piecewise, S, cacheit, Sum, exp, I, Ne, Eq, poly, series, factorial, And, lambdify) from sympy.polys.polyerrors import PolynomialError from sympy.stats.crv import reduce_rational_inequalities_wrap from sympy.stats.rv import (NamedArgsMixin, SinglePSpace, SingleDomain, random_symbols, PSpace, ConditionalDomain, RandomDomain, ProductDomain) from sympy.stats.symbolic_probability import Probability from sympy.sets.fancysets import Range, FiniteSet from sympy.sets.sets import Union from sympy.sets.contains import Contains from sympy.utilities import filldedent from sympy.core.sympify import _sympify from sympy.external import import_module class DiscreteDistribution(Basic): def __call__(self, *args): return self.pdf(*args) class SampleDiscreteScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" from scipy import stats as scipy_stats scipy_rv_map = { 'GeometricDistribution': lambda dist, size: scipy_stats.geom.rvs(p=float(dist.p), size=size), 'LogarithmicDistribution': lambda dist, size: scipy_stats.logser.rvs(p=float(dist.p), size=size), 'NegativeBinomialDistribution': lambda dist, size: scipy_stats.nbinom.rvs(n=float(dist.r), p=float(dist.p), size=size), 'PoissonDistribution': lambda dist, size: scipy_stats.poisson.rvs(mu=float(dist.lamda), size=size), 'SkellamDistribution': lambda dist, size: scipy_stats.skellam.rvs(mu1=float(dist.mu1), mu2=float(dist.mu2), size=size), 'YuleSimonDistribution': lambda dist, size: scipy_stats.yulesimon.rvs(alpha=float(dist.rho), size=size), 'ZetaDistribution': lambda dist, size: scipy_stats.zipf.rvs(a=float(dist.s), size=size) } dist_list = scipy_rv_map.keys() if dist.__class__.__name__ == 'DiscreteDistributionHandmade': from scipy.stats import rv_discrete z = Dummy('z') handmade_pmf = lambdify(z, dist.pdf(z), ['numpy', 'scipy']) class scipy_pmf(rv_discrete): def _pmf(self, x): return handmade_pmf(x) scipy_rv = scipy_pmf(a=float(dist.set._inf), b=float(dist.set._sup), name='scipy_pmf') return scipy_rv.rvs(size=size) if dist.__class__.__name__ not in dist_list: return None return scipy_rv_map[dist.__class__.__name__](dist, size) class SampleDiscreteNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'GeometricDistribution': lambda dist, size: numpy.random.geometric(p=float(dist.p), size=size), 'PoissonDistribution': lambda dist, size: numpy.random.poisson(lam=float(dist.lamda), size=size), 'ZetaDistribution': lambda dist, size: numpy.random.zipf(a=float(dist.s), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleDiscretePymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'GeometricDistribution': lambda dist: pymc3.Geometric('X', p=float(dist.p)), 'PoissonDistribution': lambda dist: pymc3.Poisson('X', mu=float(dist.lamda)), 'NegativeBinomialDistribution': lambda dist: pymc3.NegativeBinomial('X', mu=float((dist.p*dist.r)/(1-dist.p)), alpha=float(dist.r)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_drv = { 'scipy': SampleDiscreteScipy, 'pymc3': SampleDiscretePymc, 'numpy': SampleDiscreteNumpy } class SingleDiscreteDistribution(DiscreteDistribution, NamedArgsMixin): """ Discrete distribution of a single variable Serves as superclass for PoissonDistribution etc.... Provides methods for pdf, cdf, and sampling See Also: sympy.stats.crv_types.* """ set = S.Integers def __new__(cls, *args): args = list(map(sympify, args)) return Basic.__new__(cls, *args) @staticmethod def check(*args): pass def sample(self, size=(), library='scipy'): """ A random realization from the distribution""" libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_drv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) @cacheit def compute_cdf(self, **kwargs): """ Compute the CDF from the PDF Returns a Lambda """ x, z = symbols('x, z', integer=True, cls=Dummy) left_bound = self.set.inf # CDF is integral of PDF from left bound to z pdf = self.pdf(x) cdf = summation(pdf, (x, left_bound, z), **kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) def _cdf(self, x): return None def cdf(self, x, **kwargs): """ Cumulative density function """ if not kwargs: cdf = self._cdf(x) if cdf is not None: return cdf return self.compute_cdf(**kwargs)(x) @cacheit def compute_characteristic_function(self, **kwargs): """ Compute the characteristic function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) cf = summation(exp(I*t*x)*pdf, (x, self.set.inf, self.set.sup)) return Lambda(t, cf) def _characteristic_function(self, t): return None def characteristic_function(self, t, **kwargs): """ Characteristic function """ if not kwargs: cf = self._characteristic_function(t) if cf is not None: return cf return self.compute_characteristic_function(**kwargs)(t) @cacheit def compute_moment_generating_function(self, **kwargs): t = Dummy('t', real=True) x = Dummy('x', integer=True) pdf = self.pdf(x) mgf = summation(exp(t*x)*pdf, (x, self.set.inf, self.set.sup)) return Lambda(t, mgf) def _moment_generating_function(self, t): return None def moment_generating_function(self, t, **kwargs): if not kwargs: mgf = self._moment_generating_function(t) if mgf is not None: return mgf return self.compute_moment_generating_function(**kwargs)(t) @cacheit def compute_quantile(self, **kwargs): """ Compute the Quantile from the PDF Returns a Lambda """ x = Dummy('x', integer=True) p = Dummy('p', real=True) left_bound = self.set.inf pdf = self.pdf(x) cdf = summation(pdf, (x, left_bound, x), **kwargs) set = ((x, p <= cdf), ) return Lambda(p, Piecewise(*set)) def _quantile(self, x): return None def quantile(self, x, **kwargs): """ Cumulative density function """ if not kwargs: quantile = self._quantile(x) if quantile is not None: return quantile return self.compute_quantile(**kwargs)(x) def expectation(self, expr, var, evaluate=True, **kwargs): """ Expectation of expression over distribution """ # TODO: support discrete sets with non integer stepsizes if evaluate: try: p = poly(expr, var) t = Dummy('t', real=True) mgf = self.moment_generating_function(t) deg = p.degree() taylor = poly(series(mgf, t, 0, deg + 1).removeO(), t) result = 0 for k in range(deg+1): result += p.coeff_monomial(var ** k) * taylor.coeff_monomial(t ** k) * factorial(k) return result except PolynomialError: return summation(expr * self.pdf(var), (var, self.set.inf, self.set.sup), **kwargs) else: return Sum(expr * self.pdf(var), (var, self.set.inf, self.set.sup), **kwargs) def __call__(self, *args): return self.pdf(*args) class DiscreteDomain(RandomDomain): """ A domain with discrete support with step size one. Represented using symbols and Range. """ is_Discrete = True class SingleDiscreteDomain(DiscreteDomain, SingleDomain): def as_boolean(self): return Contains(self.symbol, self.set) class ConditionalDiscreteDomain(DiscreteDomain, ConditionalDomain): """ Domain with discrete support of step size one, that is restricted by some condition. """ @property def set(self): rv = self.symbols if len(self.symbols) > 1: raise NotImplementedError(filldedent(''' Multivariate conditional domains are not yet implemented.''')) rv = list(rv)[0] return reduce_rational_inequalities_wrap(self.condition, rv).intersect(self.fulldomain.set) class DiscretePSpace(PSpace): is_real = True is_Discrete = True @property def pdf(self): return self.density(*self.symbols) def where(self, condition): rvs = random_symbols(condition) assert all(r.symbol in self.symbols for r in rvs) if len(rvs) > 1: raise NotImplementedError(filldedent('''Multivariate discrete random variables are not yet supported.''')) conditional_domain = reduce_rational_inequalities_wrap(condition, rvs[0]) conditional_domain = conditional_domain.intersect(self.domain.set) return SingleDiscreteDomain(rvs[0].symbol, conditional_domain) def probability(self, condition): complement = isinstance(condition, Ne) if complement: condition = Eq(condition.args[0], condition.args[1]) try: _domain = self.where(condition).set if condition == False or _domain is S.EmptySet: return S.Zero if condition == True or _domain == self.domain.set: return S.One prob = self.eval_prob(_domain) except NotImplementedError: from sympy.stats.rv import density expr = condition.lhs - condition.rhs dens = density(expr) if not isinstance(dens, DiscreteDistribution): from sympy.stats.drv_types import DiscreteDistributionHandmade dens = DiscreteDistributionHandmade(dens) z = Dummy('z', real=True) space = SingleDiscretePSpace(z, dens) prob = space.probability(condition.__class__(space.value, 0)) if prob is None: prob = Probability(condition) return prob if not complement else S.One - prob def eval_prob(self, _domain): sym = list(self.symbols)[0] if isinstance(_domain, Range): n = symbols('n', integer=True) inf, sup, step = (r for r in _domain.args) summand = ((self.pdf).replace( sym, n*step)) rv = summation(summand, (n, inf/step, (sup)/step - 1)).doit() return rv elif isinstance(_domain, FiniteSet): pdf = Lambda(sym, self.pdf) rv = sum(pdf(x) for x in _domain) return rv elif isinstance(_domain, Union): rv = sum(self.eval_prob(x) for x in _domain.args) return rv def conditional_space(self, condition): # XXX: Converting from set to tuple. The order matters to Lambda # though so we should be starting with a set... density = Lambda(tuple(self.symbols), self.pdf/self.probability(condition)) condition = condition.xreplace({rv: rv.symbol for rv in self.values}) domain = ConditionalDiscreteDomain(self.domain, condition) return DiscretePSpace(domain, density) class ProductDiscreteDomain(ProductDomain, DiscreteDomain): def as_boolean(self): return And(*[domain.as_boolean for domain in self.domains]) class SingleDiscretePSpace(DiscretePSpace, SinglePSpace): """ Discrete probability space over a single univariate variable """ is_real = True @property def set(self): return self.distribution.set @property def domain(self): return SingleDiscreteDomain(self.symbol, self.set) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {self.value: self.distribution.sample(size, library=library)} def compute_expectation(self, expr, rvs=None, evaluate=True, **kwargs): rvs = rvs or (self.value,) if self.value not in rvs: return expr expr = _sympify(expr) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) x = self.value.symbol try: return self.distribution.expectation(expr, x, evaluate=evaluate, **kwargs) except NotImplementedError: return Sum(expr * self.pdf, (x, self.set.inf, self.set.sup), **kwargs) def compute_cdf(self, expr, **kwargs): if expr == self.value: x = Dummy("x", real=True) return Lambda(x, self.distribution.cdf(x, **kwargs)) else: raise NotImplementedError() def compute_density(self, expr, **kwargs): if expr == self.value: return self.distribution raise NotImplementedError() def compute_characteristic_function(self, expr, **kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.characteristic_function(t, **kwargs)) else: raise NotImplementedError() def compute_moment_generating_function(self, expr, **kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.moment_generating_function(t, **kwargs)) else: raise NotImplementedError() def compute_quantile(self, expr, **kwargs): if expr == self.value: p = Dummy("p", real=True) return Lambda(p, self.distribution.quantile(p, **kwargs)) else: raise NotImplementedError()

c833bb8dafda6367b4f45cddf8245fd73073893589964a5f17201d8342174243

""" Continuous Random Variables Module See Also ======== sympy.stats.crv_types sympy.stats.rv sympy.stats.frv """ from sympy import (Interval, Intersection, symbols, sympify, Dummy, nan, Integral, And, Or, Piecewise, cacheit, integrate, oo, Lambda, Basic, S, exp, I, FiniteSet, Ne, Eq, Union, poly, series, factorial, lambdify) from sympy.core.function import PoleError from sympy.functions.special.delta_functions import DiracDelta from sympy.polys.polyerrors import PolynomialError from sympy.solvers.solveset import solveset from sympy.solvers.inequalities import reduce_rational_inequalities from sympy.core.sympify import _sympify from sympy.external import import_module from sympy.stats.rv import (RandomDomain, SingleDomain, ConditionalDomain, is_random, ProductDomain, PSpace, SinglePSpace, random_symbols, NamedArgsMixin) class ContinuousDomain(RandomDomain): """ A domain with continuous support Represented using symbols and Intervals. """ is_Continuous = True def as_boolean(self): raise NotImplementedError("Not Implemented for generic Domains") class SingleContinuousDomain(ContinuousDomain, SingleDomain): """ A univariate domain with continuous support Represented using a single symbol and interval. """ def compute_expectation(self, expr, variables=None, **kwargs): if variables is None: variables = self.symbols if not variables: return expr if frozenset(variables) != frozenset(self.symbols): raise ValueError("Values should be equal") # assumes only intervals return Integral(expr, (self.symbol, self.set), **kwargs) def as_boolean(self): return self.set.as_relational(self.symbol) class ProductContinuousDomain(ProductDomain, ContinuousDomain): """ A collection of independent domains with continuous support """ def compute_expectation(self, expr, variables=None, **kwargs): if variables is None: variables = self.symbols for domain in self.domains: domain_vars = frozenset(variables) & frozenset(domain.symbols) if domain_vars: expr = domain.compute_expectation(expr, domain_vars, **kwargs) return expr def as_boolean(self): return And(*[domain.as_boolean() for domain in self.domains]) class ConditionalContinuousDomain(ContinuousDomain, ConditionalDomain): """ A domain with continuous support that has been further restricted by a condition such as x > 3 """ def compute_expectation(self, expr, variables=None, **kwargs): if variables is None: variables = self.symbols if not variables: return expr # Extract the full integral fullintgrl = self.fulldomain.compute_expectation(expr, variables) # separate into integrand and limits integrand, limits = fullintgrl.function, list(fullintgrl.limits) conditions = [self.condition] while conditions: cond = conditions.pop() if cond.is_Boolean: if isinstance(cond, And): conditions.extend(cond.args) elif isinstance(cond, Or): raise NotImplementedError("Or not implemented here") elif cond.is_Relational: if cond.is_Equality: # Add the appropriate Delta to the integrand integrand *= DiracDelta(cond.lhs - cond.rhs) else: symbols = cond.free_symbols & set(self.symbols) if len(symbols) != 1: # Can't handle x > y raise NotImplementedError( "Multivariate Inequalities not yet implemented") # Can handle x > 0 symbol = symbols.pop() # Find the limit with x, such as (x, -oo, oo) for i, limit in enumerate(limits): if limit[0] == symbol: # Make condition into an Interval like [0, oo] cintvl = reduce_rational_inequalities_wrap( cond, symbol) # Make limit into an Interval like [-oo, oo] lintvl = Interval(limit[1], limit[2]) # Intersect them to get [0, oo] intvl = cintvl.intersect(lintvl) # Put back into limits list limits[i] = (symbol, intvl.left, intvl.right) else: raise TypeError( "Condition %s is not a relational or Boolean" % cond) return Integral(integrand, *limits, **kwargs) def as_boolean(self): return And(self.fulldomain.as_boolean(), self.condition) @property def set(self): if len(self.symbols) == 1: return (self.fulldomain.set & reduce_rational_inequalities_wrap( self.condition, tuple(self.symbols)[0])) else: raise NotImplementedError( "Set of Conditional Domain not Implemented") class ContinuousDistribution(Basic): def __call__(self, *args): return self.pdf(*args) class SampleContinuousScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" # scipy does not require map as it can handle using custom distributions from scipy.stats import rv_continuous z = Dummy('z') handmade_pdf = lambdify(z, dist.pdf(z), ['numpy', 'scipy']) class scipy_pdf(rv_continuous): def _pdf(self, x): return handmade_pdf(x) scipy_rv = scipy_pdf(a=float(dist.set._inf), b=float(dist.set._sup), name='scipy_pdf') return scipy_rv.rvs(size=size) class SampleContinuousNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'BetaDistribution': lambda dist, size: numpy.random.beta(a=float(dist.alpha), b=float(dist.beta), size=size), 'ChiSquaredDistribution': lambda dist, size: numpy.random.chisquare( df=float(dist.k), size=size), 'ExponentialDistribution': lambda dist, size: numpy.random.exponential( 1/float(dist.rate), size=size), 'GammaDistribution': lambda dist, size: numpy.random.gamma(float(dist.k), float(dist.theta), size=size), 'LogNormalDistribution': lambda dist, size: numpy.random.lognormal( float(dist.mean), float(dist.std), size=size), 'NormalDistribution': lambda dist, size: numpy.random.normal( float(dist.mean), float(dist.std), size=size), 'ParetoDistribution': lambda dist, size: (numpy.random.pareto( a=float(dist.alpha), size=size) + 1) * float(dist.xm), 'UniformDistribution': lambda dist, size: numpy.random.uniform( low=float(dist.left), high=float(dist.right), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleContinuousPymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'BetaDistribution': lambda dist: pymc3.Beta('X', alpha=float(dist.alpha), beta=float(dist.beta)), 'CauchyDistribution': lambda dist: pymc3.Cauchy('X', alpha=float(dist.x0), beta=float(dist.gamma)), 'ChiSquaredDistribution': lambda dist: pymc3.ChiSquared('X', nu=float(dist.k)), 'ExponentialDistribution': lambda dist: pymc3.Exponential('X', lam=float(dist.rate)), 'GammaDistribution': lambda dist: pymc3.Gamma('X', alpha=float(dist.k), beta=1/float(dist.theta)), 'LogNormalDistribution': lambda dist: pymc3.Lognormal('X', mu=float(dist.mean), sigma=float(dist.std)), 'NormalDistribution': lambda dist: pymc3.Normal('X', float(dist.mean), float(dist.std)), 'GaussianInverseDistribution': lambda dist: pymc3.Wald('X', mu=float(dist.mean), lam=float(dist.shape)), 'ParetoDistribution': lambda dist: pymc3.Pareto('X', alpha=float(dist.alpha), m=float(dist.xm)), 'UniformDistribution': lambda dist: pymc3.Uniform('X', lower=float(dist.left), upper=float(dist.right)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_crv = { 'scipy': SampleContinuousScipy, 'pymc3': SampleContinuousPymc, 'numpy': SampleContinuousNumpy } class SingleContinuousDistribution(ContinuousDistribution, NamedArgsMixin): """ Continuous distribution of a single variable Serves as superclass for Normal/Exponential/UniformDistribution etc.... Represented by parameters for each of the specific classes. E.g NormalDistribution is represented by a mean and standard deviation. Provides methods for pdf, cdf, and sampling See Also ======== sympy.stats.crv_types.* """ set = Interval(-oo, oo) def __new__(cls, *args): args = list(map(sympify, args)) return Basic.__new__(cls, *args) @staticmethod def check(*args): pass def sample(self, size=(), library='scipy'): """ A random realization from the distribution """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_crv[library](self, size) if samps is not None: return samps raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) @cacheit def compute_cdf(self, **kwargs): """ Compute the CDF from the PDF Returns a Lambda """ x, z = symbols('x, z', real=True, cls=Dummy) left_bound = self.set.start # CDF is integral of PDF from left bound to z pdf = self.pdf(x) cdf = integrate(pdf.doit(), (x, left_bound, z), **kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) def _cdf(self, x): return None def cdf(self, x, **kwargs): """ Cumulative density function """ if len(kwargs) == 0: cdf = self._cdf(x) if cdf is not None: return cdf return self.compute_cdf(**kwargs)(x) @cacheit def compute_characteristic_function(self, **kwargs): """ Compute the characteristic function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) cf = integrate(exp(I*t*x)*pdf, (x, self.set)) return Lambda(t, cf) def _characteristic_function(self, t): return None def characteristic_function(self, t, **kwargs): """ Characteristic function """ if len(kwargs) == 0: cf = self._characteristic_function(t) if cf is not None: return cf return self.compute_characteristic_function(**kwargs)(t) @cacheit def compute_moment_generating_function(self, **kwargs): """ Compute the moment generating function from the PDF Returns a Lambda """ x, t = symbols('x, t', real=True, cls=Dummy) pdf = self.pdf(x) mgf = integrate(exp(t * x) * pdf, (x, self.set)) return Lambda(t, mgf) def _moment_generating_function(self, t): return None def moment_generating_function(self, t, **kwargs): """ Moment generating function """ if not kwargs: mgf = self._moment_generating_function(t) if mgf is not None: return mgf return self.compute_moment_generating_function(**kwargs)(t) def expectation(self, expr, var, evaluate=True, **kwargs): """ Expectation of expression over distribution """ if evaluate: try: p = poly(expr, var) t = Dummy('t', real=True) mgf = self._moment_generating_function(t) if mgf is None: return integrate(expr * self.pdf(var), (var, self.set), **kwargs) deg = p.degree() taylor = poly(series(mgf, t, 0, deg + 1).removeO(), t) result = 0 for k in range(deg+1): result += p.coeff_monomial(var ** k) * taylor.coeff_monomial(t ** k) * factorial(k) return result except PolynomialError: return integrate(expr * self.pdf(var), (var, self.set), **kwargs) else: return Integral(expr * self.pdf(var), (var, self.set), **kwargs) @cacheit def compute_quantile(self, **kwargs): """ Compute the Quantile from the PDF Returns a Lambda """ x, p = symbols('x, p', real=True, cls=Dummy) left_bound = self.set.start pdf = self.pdf(x) cdf = integrate(pdf, (x, left_bound, x), **kwargs) quantile = solveset(cdf - p, x, self.set) return Lambda(p, Piecewise((quantile, (p >= 0) & (p <= 1) ), (nan, True))) def _quantile(self, x): return None def quantile(self, x, **kwargs): """ Cumulative density function """ if len(kwargs) == 0: quantile = self._quantile(x) if quantile is not None: return quantile return self.compute_quantile(**kwargs)(x) class ContinuousPSpace(PSpace): """ Continuous Probability Space Represents the likelihood of an event space defined over a continuum. Represented with a ContinuousDomain and a PDF (Lambda-Like) """ is_Continuous = True is_real = True @property def pdf(self): return self.density(*self.domain.symbols) def compute_expectation(self, expr, rvs=None, evaluate=False, **kwargs): if rvs is None: rvs = self.values else: rvs = frozenset(rvs) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) domain_symbols = frozenset(rv.symbol for rv in rvs) return self.domain.compute_expectation(self.pdf * expr, domain_symbols, **kwargs) def compute_density(self, expr, **kwargs): # Common case Density(X) where X in self.values if expr in self.values: # Marginalize all other random symbols out of the density randomsymbols = tuple(set(self.values) - frozenset([expr])) symbols = tuple(rs.symbol for rs in randomsymbols) pdf = self.domain.compute_expectation(self.pdf, symbols, **kwargs) return Lambda(expr.symbol, pdf) z = Dummy('z', real=True) return Lambda(z, self.compute_expectation(DiracDelta(expr - z), **kwargs)) @cacheit def compute_cdf(self, expr, **kwargs): if not self.domain.set.is_Interval: raise ValueError( "CDF not well defined on multivariate expressions") d = self.compute_density(expr, **kwargs) x, z = symbols('x, z', real=True, cls=Dummy) left_bound = self.domain.set.start # CDF is integral of PDF from left bound to z cdf = integrate(d(x), (x, left_bound, z), **kwargs) # CDF Ensure that CDF left of left_bound is zero cdf = Piecewise((cdf, z >= left_bound), (0, True)) return Lambda(z, cdf) @cacheit def compute_characteristic_function(self, expr, **kwargs): if not self.domain.set.is_Interval: raise NotImplementedError("Characteristic function of multivariate expressions not implemented") d = self.compute_density(expr, **kwargs) x, t = symbols('x, t', real=True, cls=Dummy) cf = integrate(exp(I*t*x)*d(x), (x, -oo, oo), **kwargs) return Lambda(t, cf) @cacheit def compute_moment_generating_function(self, expr, **kwargs): if not self.domain.set.is_Interval: raise NotImplementedError("Moment generating function of multivariate expressions not implemented") d = self.compute_density(expr, **kwargs) x, t = symbols('x, t', real=True, cls=Dummy) mgf = integrate(exp(t * x) * d(x), (x, -oo, oo), **kwargs) return Lambda(t, mgf) @cacheit def compute_quantile(self, expr, **kwargs): if not self.domain.set.is_Interval: raise ValueError( "Quantile not well defined on multivariate expressions") d = self.compute_cdf(expr, **kwargs) x = Dummy('x', real=True) p = Dummy('p', positive=True) quantile = solveset(d(x) - p, x, self.set) return Lambda(p, quantile) def probability(self, condition, **kwargs): z = Dummy('z', real=True) cond_inv = False if isinstance(condition, Ne): condition = Eq(condition.args[0], condition.args[1]) cond_inv = True # Univariate case can be handled by where try: domain = self.where(condition) rv = [rv for rv in self.values if rv.symbol == domain.symbol][0] # Integrate out all other random variables pdf = self.compute_density(rv, **kwargs) # return S.Zero if `domain` is empty set if domain.set is S.EmptySet or isinstance(domain.set, FiniteSet): return S.Zero if not cond_inv else S.One if isinstance(domain.set, Union): return sum( Integral(pdf(z), (z, subset), **kwargs) for subset in domain.set.args if isinstance(subset, Interval)) # Integrate out the last variable over the special domain return Integral(pdf(z), (z, domain.set), **kwargs) # Other cases can be turned into univariate case # by computing a density handled by density computation except NotImplementedError: from sympy.stats.rv import density expr = condition.lhs - condition.rhs if not is_random(expr): dens = self.density comp = condition.rhs else: dens = density(expr, **kwargs) comp = 0 if not isinstance(dens, ContinuousDistribution): from sympy.stats.crv_types import ContinuousDistributionHandmade dens = ContinuousDistributionHandmade(dens, set=self.domain.set) # Turn problem into univariate case space = SingleContinuousPSpace(z, dens) result = space.probability(condition.__class__(space.value, comp)) return result if not cond_inv else S.One - result def where(self, condition): rvs = frozenset(random_symbols(condition)) if not (len(rvs) == 1 and rvs.issubset(self.values)): raise NotImplementedError( "Multiple continuous random variables not supported") rv = tuple(rvs)[0] interval = reduce_rational_inequalities_wrap(condition, rv) interval = interval.intersect(self.domain.set) return SingleContinuousDomain(rv.symbol, interval) def conditional_space(self, condition, normalize=True, **kwargs): condition = condition.xreplace({rv: rv.symbol for rv in self.values}) domain = ConditionalContinuousDomain(self.domain, condition) if normalize: # create a clone of the variable to # make sure that variables in nested integrals are different # from the variables outside the integral # this makes sure that they are evaluated separately # and in the correct order replacement = {rv: Dummy(str(rv)) for rv in self.symbols} norm = domain.compute_expectation(self.pdf, **kwargs) pdf = self.pdf / norm.xreplace(replacement) # XXX: Converting set to tuple. The order matters to Lambda though # so we shouldn't be starting with a set here... density = Lambda(tuple(domain.symbols), pdf) return ContinuousPSpace(domain, density) class SingleContinuousPSpace(ContinuousPSpace, SinglePSpace): """ A continuous probability space over a single univariate variable These consist of a Symbol and a SingleContinuousDistribution This class is normally accessed through the various random variable functions, Normal, Exponential, Uniform, etc.... """ @property def set(self): return self.distribution.set @property def domain(self): return SingleContinuousDomain(sympify(self.symbol), self.set) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ return {self.value: self.distribution.sample(size, library=library)} def compute_expectation(self, expr, rvs=None, evaluate=False, **kwargs): rvs = rvs or (self.value,) if self.value not in rvs: return expr expr = _sympify(expr) expr = expr.xreplace({rv: rv.symbol for rv in rvs}) x = self.value.symbol try: return self.distribution.expectation(expr, x, evaluate=evaluate, **kwargs) except PoleError: return Integral(expr * self.pdf, (x, self.set), **kwargs) def compute_cdf(self, expr, **kwargs): if expr == self.value: z = Dummy("z", real=True) return Lambda(z, self.distribution.cdf(z, **kwargs)) else: return ContinuousPSpace.compute_cdf(self, expr, **kwargs) def compute_characteristic_function(self, expr, **kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.characteristic_function(t, **kwargs)) else: return ContinuousPSpace.compute_characteristic_function(self, expr, **kwargs) def compute_moment_generating_function(self, expr, **kwargs): if expr == self.value: t = Dummy("t", real=True) return Lambda(t, self.distribution.moment_generating_function(t, **kwargs)) else: return ContinuousPSpace.compute_moment_generating_function(self, expr, **kwargs) def compute_density(self, expr, **kwargs): # https://en.wikipedia.org/wiki/Random_variable#Functions_of_random_variables if expr == self.value: return self.density y = Dummy('y', real=True) gs = solveset(expr - y, self.value, S.Reals) if isinstance(gs, Intersection) and S.Reals in gs.args: gs = list(gs.args[1]) if not gs: raise ValueError("Can not solve %s for %s"%(expr, self.value)) fx = self.compute_density(self.value) fy = sum(fx(g) * abs(g.diff(y)) for g in gs) return Lambda(y, fy) def compute_quantile(self, expr, **kwargs): if expr == self.value: p = Dummy("p", real=True) return Lambda(p, self.distribution.quantile(p, **kwargs)) else: return ContinuousPSpace.compute_quantile(self, expr, **kwargs) def _reduce_inequalities(conditions, var, **kwargs): try: return reduce_rational_inequalities(conditions, var, **kwargs) except PolynomialError: raise ValueError("Reduction of condition failed %s\n" % conditions[0]) def reduce_rational_inequalities_wrap(condition, var): if condition.is_Relational: return _reduce_inequalities([[condition]], var, relational=False) if isinstance(condition, Or): return Union(*[_reduce_inequalities([[arg]], var, relational=False) for arg in condition.args]) if isinstance(condition, And): intervals = [_reduce_inequalities([[arg]], var, relational=False) for arg in condition.args] I = intervals[0] for i in intervals: I = I.intersect(i) return I

83472ee206ac646412cae109c880a39296e5fb4293fea8195be98dfdbbb14919

from sympy import Basic, Sum, Dummy, Lambda, Integral from sympy.stats.rv import (NamedArgsMixin, random_symbols, _symbol_converter, PSpace, RandomSymbol, is_random) from sympy.stats.crv import ContinuousDistribution, SingleContinuousPSpace from sympy.stats.drv import DiscreteDistribution, SingleDiscretePSpace from sympy.stats.frv import SingleFiniteDistribution, SingleFinitePSpace from sympy.stats.crv_types import ContinuousDistributionHandmade from sympy.stats.drv_types import DiscreteDistributionHandmade from sympy.stats.frv_types import FiniteDistributionHandmade class CompoundPSpace(PSpace): """ A temporary Probability Space for the Compound Distribution. After Marginalization, this returns the corresponding Probability Space of the parent distribution. """ def __new__(cls, s, distribution): s = _symbol_converter(s) if isinstance(distribution, ContinuousDistribution): return SingleContinuousPSpace(s, distribution) if isinstance(distribution, DiscreteDistribution): return SingleDiscretePSpace(s, distribution) if isinstance(distribution, SingleFiniteDistribution): return SingleFinitePSpace(s, distribution) if not isinstance(distribution, CompoundDistribution): raise ValueError("%s should be an isinstance of " "CompoundDistribution"%(distribution)) return Basic.__new__(cls, s, distribution) @property def value(self): return RandomSymbol(self.symbol, self) @property def symbol(self): return self.args[0] @property def is_Continuous(self): return self.distribution.is_Continuous @property def is_Finite(self): return self.distribution.is_Finite @property def is_Discrete(self): return self.distribution.is_Discrete @property def distribution(self): return self.args[1] @property def pdf(self): return self.distribution.pdf(self.symbol) @property def set(self): return self.distribution.set @property def domain(self): return self._get_newpspace().domain def _get_newpspace(self, evaluate=False): x = Dummy('x') parent_dist = self.distribution.args[0] func = Lambda(x, self.distribution.pdf(x, evaluate)) new_pspace = self._transform_pspace(self.symbol, parent_dist, func) if new_pspace is not None: return new_pspace message = ("Compound Distribution for %s is not implemeted yet" % str(parent_dist)) raise NotImplementedError(message) def _transform_pspace(self, sym, dist, pdf): """ This function returns the new pspace of the distribution using handmade Distributions and their corresponding pspace. """ pdf = Lambda(sym, pdf(sym)) _set = dist.set if isinstance(dist, ContinuousDistribution): return SingleContinuousPSpace(sym, ContinuousDistributionHandmade(pdf, _set)) elif isinstance(dist, DiscreteDistribution): return SingleDiscretePSpace(sym, DiscreteDistributionHandmade(pdf, _set)) elif isinstance(dist, SingleFiniteDistribution): dens = {k: pdf(k) for k in _set} return SingleFinitePSpace(sym, FiniteDistributionHandmade(dens)) def compute_density(self, expr, *, compound_evaluate=True, **kwargs): new_pspace = self._get_newpspace(compound_evaluate) expr = expr.subs({self.value: new_pspace.value}) return new_pspace.compute_density(expr, **kwargs) def compute_cdf(self, expr, *, compound_evaluate=True, **kwargs): new_pspace = self._get_newpspace(compound_evaluate) expr = expr.subs({self.value: new_pspace.value}) return new_pspace.compute_cdf(expr, **kwargs) def compute_expectation(self, expr, rvs=None, evaluate=False, **kwargs): new_pspace = self._get_newpspace(evaluate) expr = expr.subs({self.value: new_pspace.value}) if rvs: rvs = rvs.subs({self.value: new_pspace.value}) if isinstance(new_pspace, SingleFinitePSpace): return new_pspace.compute_expectation(expr, rvs, **kwargs) return new_pspace.compute_expectation(expr, rvs, evaluate, **kwargs) def probability(self, condition, *, compound_evaluate=True, **kwargs): new_pspace = self._get_newpspace(compound_evaluate) condition = condition.subs({self.value: new_pspace.value}) return new_pspace.probability(condition) def conditional_space(self, condition, *, compound_evaluate=True, **kwargs): new_pspace = self._get_newpspace(compound_evaluate) condition = condition.subs({self.value: new_pspace.value}) return new_pspace.conditional_space(condition) class CompoundDistribution(Basic, NamedArgsMixin): """ Class for Compound Distributions. Parameters ========== dist : Distribution Distribution must contain a random parameter Examples ======== >>> from sympy.stats.compound_rv import CompoundDistribution >>> from sympy.stats.crv_types import NormalDistribution >>> from sympy.stats import Normal >>> from sympy.abc import x >>> X = Normal('X', 2, 4) >>> N = NormalDistribution(X, 4) >>> C = CompoundDistribution(N) >>> C.set Interval(-oo, oo) >>> C.pdf(x, evaluate=True).simplify() exp(-x**2/64 + x/16 - 1/16)/(8*sqrt(pi)) References ========== .. [1] https://en.wikipedia.org/wiki/Compound_probability_distribution """ def __new__(cls, dist): if not isinstance(dist, (ContinuousDistribution, SingleFiniteDistribution, DiscreteDistribution)): message = "Compound Distribution for %s is not implemeted yet" % str(dist) raise NotImplementedError(message) if not cls._compound_check(dist): return dist return Basic.__new__(cls, dist) @property def set(self): return self.args[0].set @property def is_Continuous(self): return isinstance(self.args[0], ContinuousDistribution) @property def is_Finite(self): return isinstance(self.args[0], SingleFiniteDistribution) @property def is_Discrete(self): return isinstance(self.args[0], DiscreteDistribution) def pdf(self, x, evaluate=False): dist = self.args[0] randoms = [rv for rv in dist.args if is_random(rv)] if isinstance(dist, SingleFiniteDistribution): y = Dummy('y', integer=True, negative=False) expr = dist.pmf(y) else: y = Dummy('y') expr = dist.pdf(y) for rv in randoms: expr = self._marginalise(expr, rv, evaluate) return Lambda(y, expr)(x) def _marginalise(self, expr, rv, evaluate): if isinstance(rv.pspace.distribution, SingleFiniteDistribution): rv_dens = rv.pspace.distribution.pmf(rv) else: rv_dens = rv.pspace.distribution.pdf(rv) rv_dom = rv.pspace.domain.set if rv.pspace.is_Discrete or rv.pspace.is_Finite: expr = Sum(expr*rv_dens, (rv, rv_dom._inf, rv_dom._sup)) else: expr = Integral(expr*rv_dens, (rv, rv_dom._inf, rv_dom._sup)) if evaluate: return expr.doit() return expr @classmethod def _compound_check(self, dist): """ Checks if the given distribution contains random parameters. """ randoms = [] for arg in dist.args: randoms.extend(random_symbols(arg)) if len(randoms) == 0: return False return True

8c20011283a91f32ae0eedbc864de362e825d8582d0fe6667c951b9bcb9ef67c

import itertools from sympy import (Expr, Add, Mul, S, Integral, Eq, Sum, Symbol, expand as _expand, Not) from sympy.core.compatibility import default_sort_key from sympy.core.parameters import global_parameters from sympy.core.sympify import _sympify from sympy.core.relational import Relational from sympy.logic.boolalg import Boolean from sympy.stats import variance, covariance from sympy.stats.rv import (RandomSymbol, pspace, dependent, given, sampling_E, RandomIndexedSymbol, is_random, PSpace, sampling_P, random_symbols) __all__ = ['Probability', 'Expectation', 'Variance', 'Covariance'] @is_random.register(Expr) def _(x): atoms = x.free_symbols if len(atoms) == 1 and next(iter(atoms)) == x: return False return any([is_random(i) for i in atoms]) @is_random.register(RandomSymbol) # type: ignore def _(x): return True class Probability(Expr): """ Symbolic expression for the probability. Examples ======== >>> from sympy.stats import Probability, Normal >>> from sympy import Integral >>> X = Normal("X", 0, 1) >>> prob = Probability(X > 1) >>> prob Probability(X > 1) Integral representation: >>> prob.rewrite(Integral) Integral(sqrt(2)*exp(-_z**2/2)/(2*sqrt(pi)), (_z, 1, oo)) Evaluation of the integral: >>> prob.evaluate_integral() sqrt(2)*(-sqrt(2)*sqrt(pi)*erf(sqrt(2)/2) + sqrt(2)*sqrt(pi))/(4*sqrt(pi)) """ def __new__(cls, prob, condition=None, **kwargs): prob = _sympify(prob) if condition is None: obj = Expr.__new__(cls, prob) else: condition = _sympify(condition) obj = Expr.__new__(cls, prob, condition) obj._condition = condition return obj def doit(self, **hints): condition = self.args[0] given_condition = self._condition numsamples = hints.get('numsamples', False) for_rewrite = not hints.get('for_rewrite', False) if isinstance(condition, Not): return S.One - self.func(condition.args[0], given_condition, evaluate=for_rewrite).doit(**hints) if condition.has(RandomIndexedSymbol): return pspace(condition).probability(condition, given_condition, evaluate=for_rewrite) if isinstance(given_condition, RandomSymbol): condrv = random_symbols(condition) if len(condrv) == 1 and condrv[0] == given_condition: from sympy.stats.frv_types import BernoulliDistribution return BernoulliDistribution(self.func(condition).doit(**hints), 0, 1) if any([dependent(rv, given_condition) for rv in condrv]): return Probability(condition, given_condition) else: return Probability(condition).doit() if given_condition is not None and \ not isinstance(given_condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (given_condition)) if given_condition == False or condition is S.false: return S.Zero if not isinstance(condition, (Relational, Boolean)): raise ValueError("%s is not a relational or combination of relationals" % (condition)) if condition is S.true: return S.One if numsamples: return sampling_P(condition, given_condition, numsamples=numsamples) if given_condition is not None: # If there is a condition # Recompute on new conditional expr return Probability(given(condition, given_condition)).doit() # Otherwise pass work off to the ProbabilitySpace if pspace(condition) == PSpace(): return Probability(condition, given_condition) result = pspace(condition).probability(condition) if hasattr(result, 'doit') and for_rewrite: return result.doit() else: return result def _eval_rewrite_as_Integral(self, arg, condition=None, **kwargs): return self.func(arg, condition=condition).doit(for_rewrite=True) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Expectation(Expr): """ Symbolic expression for the expectation. Examples ======== >>> from sympy.stats import Expectation, Normal, Probability, Poisson >>> from sympy import symbols, Integral, Sum >>> mu = symbols("mu") >>> sigma = symbols("sigma", positive=True) >>> X = Normal("X", mu, sigma) >>> Expectation(X) Expectation(X) >>> Expectation(X).evaluate_integral().simplify() mu To get the integral expression of the expectation: >>> Expectation(X).rewrite(Integral) Integral(sqrt(2)*X*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)) The same integral expression, in more abstract terms: >>> Expectation(X).rewrite(Probability) Integral(x*Probability(Eq(X, x)), (x, -oo, oo)) To get the Summation expression of the expectation for discrete random variables: >>> lamda = symbols('lamda', positive=True) >>> Z = Poisson('Z', lamda) >>> Expectation(Z).rewrite(Sum) Sum(Z*lamda**Z*exp(-lamda)/factorial(Z), (Z, 0, oo)) This class is aware of some properties of the expectation: >>> from sympy.abc import a >>> Expectation(a*X) Expectation(a*X) >>> Y = Normal("Y", 1, 2) >>> Expectation(X + Y) Expectation(X + Y) To expand the ``Expectation`` into its expression, use ``expand()``: >>> Expectation(X + Y).expand() Expectation(X) + Expectation(Y) >>> Expectation(a*X + Y).expand() a*Expectation(X) + Expectation(Y) >>> Expectation(a*X + Y) Expectation(a*X + Y) >>> Expectation((X + Y)*(X - Y)).expand() Expectation(X**2) - Expectation(Y**2) To evaluate the ``Expectation``, use ``doit()``: >>> Expectation(X + Y).doit() mu + 1 >>> Expectation(X + Expectation(Y + Expectation(2*X))).doit() 3*mu + 1 To prevent evaluating nested ``Expectation``, use ``doit(deep=False)`` >>> Expectation(X + Expectation(Y)).doit(deep=False) mu + Expectation(Expectation(Y)) >>> Expectation(X + Expectation(Y + Expectation(2*X))).doit(deep=False) mu + Expectation(Expectation(Y + Expectation(2*X))) """ def __new__(cls, expr, condition=None, **kwargs): expr = _sympify(expr) if expr.is_Matrix: from sympy.stats.symbolic_multivariate_probability import ExpectationMatrix return ExpectationMatrix(expr, condition) if condition is None: if not is_random(expr): return expr obj = Expr.__new__(cls, expr) else: condition = _sympify(condition) obj = Expr.__new__(cls, expr, condition) obj._condition = condition return obj def expand(self, **hints): expr = self.args[0] condition = self._condition if not is_random(expr): return expr if isinstance(expr, Add): return Add.fromiter(Expectation(a, condition=condition).expand() for a in expr.args) expand_expr = _expand(expr) if isinstance(expand_expr, Add): return Add.fromiter(Expectation(a, condition=condition).expand() for a in expand_expr.args) elif isinstance(expr, Mul): rv = [] nonrv = [] for a in expr.args: if is_random(a): rv.append(a) else: nonrv.append(a) return Mul.fromiter(nonrv)*Expectation(Mul.fromiter(rv), condition=condition) return self def doit(self, **hints): deep = hints.get('deep', True) condition = self._condition expr = self.args[0] numsamples = hints.get('numsamples', False) for_rewrite = not hints.get('for_rewrite', False) if deep: expr = expr.doit(**hints) if not is_random(expr) or isinstance(expr, Expectation): # expr isn't random? return expr if numsamples: # Computing by monte carlo sampling? evalf = hints.get('evalf', True) return sampling_E(expr, condition, numsamples=numsamples, evalf=evalf) if expr.has(RandomIndexedSymbol): return pspace(expr).compute_expectation(expr, condition) # Create new expr and recompute E if condition is not None: # If there is a condition return self.func(given(expr, condition)).doit(**hints) # A few known statements for efficiency if expr.is_Add: # We know that E is Linear return Add(*[self.func(arg, condition).doit(**hints) if not isinstance(arg, Expectation) else self.func(arg, condition) for arg in expr.args]) if expr.is_Mul: if expr.atoms(Expectation): return expr if pspace(expr) == PSpace(): return self.func(expr) # Otherwise case is simple, pass work off to the ProbabilitySpace result = pspace(expr).compute_expectation(expr, evaluate=for_rewrite) if hasattr(result, 'doit') and for_rewrite: return result.doit(**hints) else: return result def _eval_rewrite_as_Probability(self, arg, condition=None, **kwargs): rvs = arg.atoms(RandomSymbol) if len(rvs) > 1: raise NotImplementedError() if len(rvs) == 0: return arg rv = rvs.pop() if rv.pspace is None: raise ValueError("Probability space not known") symbol = rv.symbol if symbol.name[0].isupper(): symbol = Symbol(symbol.name.lower()) else : symbol = Symbol(symbol.name + "_1") if rv.pspace.is_Continuous: return Integral(arg.replace(rv, symbol)*Probability(Eq(rv, symbol), condition), (symbol, rv.pspace.domain.set.inf, rv.pspace.domain.set.sup)) else: if rv.pspace.is_Finite: raise NotImplementedError else: return Sum(arg.replace(rv, symbol)*Probability(Eq(rv, symbol), condition), (symbol, rv.pspace.domain.set.inf, rv.pspace.set.sup)) def _eval_rewrite_as_Integral(self, arg, condition=None, **kwargs): return self.func(arg, condition=condition).doit(deep=False, for_rewrite=True) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral # For discrete this will be Sum def evaluate_integral(self): return self.rewrite(Integral).doit() evaluate_sum = evaluate_integral class Variance(Expr): """ Symbolic expression for the variance. Examples ======== >>> from sympy import symbols, Integral >>> from sympy.stats import Normal, Expectation, Variance, Probability >>> mu = symbols("mu", positive=True) >>> sigma = symbols("sigma", positive=True) >>> X = Normal("X", mu, sigma) >>> Variance(X) Variance(X) >>> Variance(X).evaluate_integral() sigma**2 Integral representation of the underlying calculations: >>> Variance(X).rewrite(Integral) Integral(sqrt(2)*(X - Integral(sqrt(2)*X*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)))**2*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)) Integral representation, without expanding the PDF: >>> Variance(X).rewrite(Probability) -Integral(x*Probability(Eq(X, x)), (x, -oo, oo))**2 + Integral(x**2*Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the variance in terms of the expectation >>> Variance(X).rewrite(Expectation) -Expectation(X)**2 + Expectation(X**2) Some transformations based on the properties of the variance may happen: >>> from sympy.abc import a >>> Y = Normal("Y", 0, 1) >>> Variance(a*X) Variance(a*X) To expand the variance in its expression, use ``expand()``: >>> Variance(a*X).expand() a**2*Variance(X) >>> Variance(X + Y) Variance(X + Y) >>> Variance(X + Y).expand() 2*Covariance(X, Y) + Variance(X) + Variance(Y) """ def __new__(cls, arg, condition=None, **kwargs): arg = _sympify(arg) if arg.is_Matrix: from sympy.stats.symbolic_multivariate_probability import VarianceMatrix return VarianceMatrix(arg, condition) if condition is None: obj = Expr.__new__(cls, arg) else: condition = _sympify(condition) obj = Expr.__new__(cls, arg, condition) obj._condition = condition return obj def expand(self, **hints): arg = self.args[0] condition = self._condition if not is_random(arg): return S.Zero if isinstance(arg, RandomSymbol): return self elif isinstance(arg, Add): rv = [] for a in arg.args: if is_random(a): rv.append(a) variances = Add(*map(lambda xv: Variance(xv, condition).expand(), rv)) map_to_covar = lambda x: 2*Covariance(*x, condition=condition).expand() covariances = Add(*map(map_to_covar, itertools.combinations(rv, 2))) return variances + covariances elif isinstance(arg, Mul): nonrv = [] rv = [] for a in arg.args: if is_random(a): rv.append(a) else: nonrv.append(a**2) if len(rv) == 0: return S.Zero return Mul.fromiter(nonrv)*Variance(Mul.fromiter(rv), condition) # this expression contains a RandomSymbol somehow: return self def _eval_rewrite_as_Expectation(self, arg, condition=None, **kwargs): e1 = Expectation(arg**2, condition) e2 = Expectation(arg, condition)**2 return e1 - e2 def _eval_rewrite_as_Probability(self, arg, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, arg, condition=None, **kwargs): return variance(self.args[0], self._condition, evaluate=False) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Covariance(Expr): """ Symbolic expression for the covariance. Examples ======== >>> from sympy.stats import Covariance >>> from sympy.stats import Normal >>> X = Normal("X", 3, 2) >>> Y = Normal("Y", 0, 1) >>> Z = Normal("Z", 0, 1) >>> W = Normal("W", 0, 1) >>> cexpr = Covariance(X, Y) >>> cexpr Covariance(X, Y) Evaluate the covariance, `X` and `Y` are independent, therefore zero is the result: >>> cexpr.evaluate_integral() 0 Rewrite the covariance expression in terms of expectations: >>> from sympy.stats import Expectation >>> cexpr.rewrite(Expectation) Expectation(X*Y) - Expectation(X)*Expectation(Y) In order to expand the argument, use ``expand()``: >>> from sympy.abc import a, b, c, d >>> Covariance(a*X + b*Y, c*Z + d*W) Covariance(a*X + b*Y, c*Z + d*W) >>> Covariance(a*X + b*Y, c*Z + d*W).expand() a*c*Covariance(X, Z) + a*d*Covariance(W, X) + b*c*Covariance(Y, Z) + b*d*Covariance(W, Y) This class is aware of some properties of the covariance: >>> Covariance(X, X).expand() Variance(X) >>> Covariance(a*X, b*Y).expand() a*b*Covariance(X, Y) """ def __new__(cls, arg1, arg2, condition=None, **kwargs): arg1 = _sympify(arg1) arg2 = _sympify(arg2) if arg1.is_Matrix or arg2.is_Matrix: from sympy.stats.symbolic_multivariate_probability import CrossCovarianceMatrix return CrossCovarianceMatrix(arg1, arg2, condition) if kwargs.pop('evaluate', global_parameters.evaluate): arg1, arg2 = sorted([arg1, arg2], key=default_sort_key) if condition is None: obj = Expr.__new__(cls, arg1, arg2) else: condition = _sympify(condition) obj = Expr.__new__(cls, arg1, arg2, condition) obj._condition = condition return obj def expand(self, **hints): arg1 = self.args[0] arg2 = self.args[1] condition = self._condition if arg1 == arg2: return Variance(arg1, condition).expand() if not is_random(arg1): return S.Zero if not is_random(arg2): return S.Zero arg1, arg2 = sorted([arg1, arg2], key=default_sort_key) if isinstance(arg1, RandomSymbol) and isinstance(arg2, RandomSymbol): return Covariance(arg1, arg2, condition) coeff_rv_list1 = self._expand_single_argument(arg1.expand()) coeff_rv_list2 = self._expand_single_argument(arg2.expand()) addends = [a*b*Covariance(*sorted([r1, r2], key=default_sort_key), condition=condition) for (a, r1) in coeff_rv_list1 for (b, r2) in coeff_rv_list2] return Add.fromiter(addends) @classmethod def _expand_single_argument(cls, expr): # return (coefficient, random_symbol) pairs: if isinstance(expr, RandomSymbol): return [(S.One, expr)] elif isinstance(expr, Add): outval = [] for a in expr.args: if isinstance(a, Mul): outval.append(cls._get_mul_nonrv_rv_tuple(a)) elif is_random(a): outval.append((S.One, a)) return outval elif isinstance(expr, Mul): return [cls._get_mul_nonrv_rv_tuple(expr)] elif is_random(expr): return [(S.One, expr)] @classmethod def _get_mul_nonrv_rv_tuple(cls, m): rv = [] nonrv = [] for a in m.args: if is_random(a): rv.append(a) else: nonrv.append(a) return (Mul.fromiter(nonrv), Mul.fromiter(rv)) def _eval_rewrite_as_Expectation(self, arg1, arg2, condition=None, **kwargs): e1 = Expectation(arg1*arg2, condition) e2 = Expectation(arg1, condition)*Expectation(arg2, condition) return e1 - e2 def _eval_rewrite_as_Probability(self, arg1, arg2, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, arg1, arg2, condition=None, **kwargs): return covariance(self.args[0], self.args[1], self._condition, evaluate=False) _eval_rewrite_as_Sum = _eval_rewrite_as_Integral def evaluate_integral(self): return self.rewrite(Integral).doit() class Moment(Expr): """ Symbolic class for Moment Examples ======== >>> from sympy import Symbol, Integral >>> from sympy.stats import Normal, Expectation, Probability, Moment >>> mu = Symbol('mu', real=True) >>> sigma = Symbol('sigma', real=True, positive=True) >>> X = Normal('X', mu, sigma) >>> M = Moment(X, 3, 1) To evaluate the result of Moment use `doit`: >>> M.doit() mu**3 - 3*mu**2 + 3*mu*sigma**2 + 3*mu - 3*sigma**2 - 1 Rewrite the Moment expression in terms of Expectation: >>> M.rewrite(Expectation) Expectation((X - 1)**3) Rewrite the Moment expression in terms of Probability: >>> M.rewrite(Probability) Integral((x - 1)**3*Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the Moment expression in terms of Integral: >>> M.rewrite(Integral) Integral(sqrt(2)*(X - 1)**3*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)) """ def __new__(cls, X, n, c=0, condition=None, **kwargs): X = _sympify(X) n = _sympify(n) c = _sympify(c) if condition is not None: condition = _sympify(condition) return Expr.__new__(cls, X, n, c, condition) def doit(self, **hints): if not is_random(self.args[0]): return self.args[0] return self.rewrite(Expectation).doit(**hints) def _eval_rewrite_as_Expectation(self, X, n, c=0, condition=None, **kwargs): return Expectation((X - c)**n, condition) def _eval_rewrite_as_Probability(self, X, n, c=0, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, X, n, c=0, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Integral) class CentralMoment(Expr): """ Symbolic class Central Moment Examples ======== >>> from sympy import Symbol, Integral >>> from sympy.stats import Normal, Expectation, Probability, CentralMoment >>> mu = Symbol('mu', real=True) >>> sigma = Symbol('sigma', real=True, positive=True) >>> X = Normal('X', mu, sigma) >>> CM = CentralMoment(X, 4) To evaluate the result of CentralMoment use `doit`: >>> CM.doit().simplify() 3*sigma**4 Rewrite the CentralMoment expression in terms of Expectation: >>> CM.rewrite(Expectation) Expectation((X - Expectation(X))**4) Rewrite the CentralMoment expression in terms of Probability: >>> CM.rewrite(Probability) Integral((x - Integral(x*Probability(True), (x, -oo, oo)))**4*Probability(Eq(X, x)), (x, -oo, oo)) Rewrite the CentralMoment expression in terms of Integral: >>> CM.rewrite(Integral) Integral(sqrt(2)*(X - Integral(sqrt(2)*X*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)))**4*exp(-(X - mu)**2/(2*sigma**2))/(2*sqrt(pi)*sigma), (X, -oo, oo)) """ def __new__(cls, X, n, condition=None, **kwargs): X = _sympify(X) n = _sympify(n) if condition is not None: condition = _sympify(condition) return Expr.__new__(cls, X, n, condition) def doit(self, **hints): if not is_random(self.args[0]): return self.args[0] return self.rewrite(Expectation).doit(**hints) def _eval_rewrite_as_Expectation(self, X, n, condition=None, **kwargs): mu = Expectation(X, condition, **kwargs) return Moment(X, n, mu, condition, **kwargs).rewrite(Expectation) def _eval_rewrite_as_Probability(self, X, n, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Probability) def _eval_rewrite_as_Integral(self, X, n, condition=None, **kwargs): return self.rewrite(Expectation).rewrite(Integral)

c9e18e2774e69ca828c9df209d651ec4aff2aaabb0eafbc599719921fd59f224

from sympy import (Basic, exp, pi, Lambda, Trace, S, MatrixSymbol, Integral, gamma, Product, Dummy, Sum, Abs, IndexedBase, I) from sympy.core.sympify import _sympify from sympy.stats.rv import _symbol_converter, Density, RandomMatrixSymbol, is_random from sympy.stats.joint_rv_types import JointDistributionHandmade from sympy.stats.random_matrix import RandomMatrixPSpace from sympy.tensor.array import ArrayComprehension __all__ = [ 'CircularEnsemble', 'CircularUnitaryEnsemble', 'CircularOrthogonalEnsemble', 'CircularSymplecticEnsemble', 'GaussianEnsemble', 'GaussianUnitaryEnsemble', 'GaussianOrthogonalEnsemble', 'GaussianSymplecticEnsemble', 'joint_eigen_distribution', 'JointEigenDistribution', 'level_spacing_distribution' ] @is_random.register(RandomMatrixSymbol) def _(x): return True class RandomMatrixEnsembleModel(Basic): """ Base class for random matrix ensembles. It acts as an umbrella and contains the methods common to all the ensembles defined in sympy.stats.random_matrix_models. """ def __new__(cls, sym, dim=None): sym, dim = _symbol_converter(sym), _sympify(dim) if dim.is_integer == False: raise ValueError("Dimension of the random matrices must be " "integers, received %s instead."%(dim)) return Basic.__new__(cls, sym, dim) symbol = property(lambda self: self.args[0]) dimension = property(lambda self: self.args[1]) def density(self, expr): return Density(expr) def __call__(self, expr): return self.density(expr) class GaussianEnsembleModel(RandomMatrixEnsembleModel): """ Abstract class for Gaussian ensembles. Contains the properties common to all the gaussian ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Random_matrix#Gaussian_ensembles .. [2] https://arxiv.org/pdf/1712.07903.pdf """ def _compute_normalization_constant(self, beta, n): """ Helper function for computing normalization constant for joint probability density of eigen values of Gaussian ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Selberg_integral#Mehta's_integral """ n = S(n) prod_term = lambda j: gamma(1 + beta*S(j)/2)/gamma(S.One + beta/S(2)) j = Dummy('j', integer=True, positive=True) term1 = Product(prod_term(j), (j, 1, n)).doit() term2 = (2/(beta*n))**(beta*n*(n - 1)/4 + n/2) term3 = (2*pi)**(n/2) return term1 * term2 * term3 def _compute_joint_eigen_distribution(self, beta): """ Helper function for computing the joint probability distribution of eigen values of the random matrix. """ n = self.dimension Zbn = self._compute_normalization_constant(beta, n) l = IndexedBase('l') i = Dummy('i', integer=True, positive=True) j = Dummy('j', integer=True, positive=True) k = Dummy('k', integer=True, positive=True) term1 = exp((-S(n)/2) * Sum(l[k]**2, (k, 1, n)).doit()) sub_term = Lambda(i, Product(Abs(l[j] - l[i])**beta, (j, i + 1, n))) term2 = Product(sub_term(i).doit(), (i, 1, n - 1)).doit() syms = ArrayComprehension(l[k], (k, 1, n)).doit() return Lambda(tuple(syms), (term1 * term2)/Zbn) class GaussianUnitaryEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension return 2**(S(n)/2) * pi**(S(n**2)/2) def density(self, expr): n, ZGUE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n)/2 * Trace(H**2))/ZGUE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(2)) def level_spacing_distribution(self): s = Dummy('s') f = (32/pi**2)*(s**2)*exp((-4/pi)*s**2) return Lambda(s, f) class GaussianOrthogonalEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension _H = MatrixSymbol('_H', n, n) return Integral(exp(-S(n)/4 * Trace(_H**2))) def density(self, expr): n, ZGOE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n)/4 * Trace(H**2))/ZGOE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S.One) def level_spacing_distribution(self): s = Dummy('s') f = (pi/2)*s*exp((-pi/4)*s**2) return Lambda(s, f) class GaussianSymplecticEnsembleModel(GaussianEnsembleModel): @property def normalization_constant(self): n = self.dimension _H = MatrixSymbol('_H', n, n) return Integral(exp(-S(n) * Trace(_H**2))) def density(self, expr): n, ZGSE = self.dimension, self.normalization_constant h_pspace = RandomMatrixPSpace('P', model=self) H = RandomMatrixSymbol('H', n, n, pspace=h_pspace) return Lambda(H, exp(-S(n) * Trace(H**2))/ZGSE)(expr) def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(4)) def level_spacing_distribution(self): s = Dummy('s') f = ((S(2)**18)/((S(3)**6)*(pi**3)))*(s**4)*exp((-64/(9*pi))*s**2) return Lambda(s, f) def GaussianEnsemble(sym, dim): sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianUnitaryEnsemble(sym, dim): """ Represents Gaussian Unitary Ensembles. Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE, density >>> from sympy import MatrixSymbol >>> G = GUE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-Trace(X**2))/(2*pi**2) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianUnitaryEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianOrthogonalEnsemble(sym, dim): """ Represents Gaussian Orthogonal Ensembles. Examples ======== >>> from sympy.stats import GaussianOrthogonalEnsemble as GOE, density >>> from sympy import MatrixSymbol >>> G = GOE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-Trace(X**2)/2)/Integral(exp(-Trace(_H**2)/2), _H) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianOrthogonalEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def GaussianSymplecticEnsemble(sym, dim): """ Represents Gaussian Symplectic Ensembles. Examples ======== >>> from sympy.stats import GaussianSymplecticEnsemble as GSE, density >>> from sympy import MatrixSymbol >>> G = GSE('U', 2) >>> X = MatrixSymbol('X', 2, 2) >>> density(G)(X) exp(-2*Trace(X**2))/Integral(exp(-2*Trace(_H**2)), _H) """ sym, dim = _symbol_converter(sym), _sympify(dim) model = GaussianSymplecticEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) class CircularEnsembleModel(RandomMatrixEnsembleModel): """ Abstract class for Circular ensembles. Contains the properties and methods common to all the circular ensembles. References ========== .. [1] https://en.wikipedia.org/wiki/Circular_ensemble """ def density(self, expr): # TODO : Add support for Lie groups(as extensions of sympy.diffgeom) # and define measures on them raise NotImplementedError("Support for Haar measure hasn't been " "implemented yet, therefore the density of " "%s cannot be computed."%(self)) def _compute_joint_eigen_distribution(self, beta): """ Helper function to compute the joint distribution of phases of the complex eigen values of matrices belonging to any circular ensembles. """ n = self.dimension Zbn = ((2*pi)**n)*(gamma(beta*n/2 + 1)/S(gamma(beta/2 + 1))**n) t = IndexedBase('t') i, j, k = (Dummy('i', integer=True), Dummy('j', integer=True), Dummy('k', integer=True)) syms = ArrayComprehension(t[i], (i, 1, n)).doit() f = Product(Product(Abs(exp(I*t[k]) - exp(I*t[j]))**beta, (j, k + 1, n)).doit(), (k, 1, n - 1)).doit() return Lambda(tuple(syms), f/Zbn) class CircularUnitaryEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(2)) class CircularOrthogonalEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S.One) class CircularSymplecticEnsembleModel(CircularEnsembleModel): def joint_eigen_distribution(self): return self._compute_joint_eigen_distribution(S(4)) def CircularEnsemble(sym, dim): sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularUnitaryEnsemble(sym, dim): """ Represents Cicular Unitary Ensembles. Examples ======== >>> from sympy.stats import CircularUnitaryEnsemble as CUE >>> from sympy.stats import joint_eigen_distribution >>> C = CUE('U', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(I*t[_j]) - exp(I*t[_k]))**2, (_j, _k + 1, 1), (_k, 1, 0))/(2*pi)) Note ==== As can be seen above in the example, density of CiruclarUnitaryEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularUnitaryEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularOrthogonalEnsemble(sym, dim): """ Represents Cicular Orthogonal Ensembles. Examples ======== >>> from sympy.stats import CircularOrthogonalEnsemble as COE >>> from sympy.stats import joint_eigen_distribution >>> C = COE('O', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(I*t[_j]) - exp(I*t[_k])), (_j, _k + 1, 1), (_k, 1, 0))/(2*pi)) Note ==== As can be seen above in the example, density of CiruclarOrthogonalEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularOrthogonalEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def CircularSymplecticEnsemble(sym, dim): """ Represents Cicular Symplectic Ensembles. Examples ======== >>> from sympy.stats import CircularSymplecticEnsemble as CSE >>> from sympy.stats import joint_eigen_distribution >>> C = CSE('S', 1) >>> joint_eigen_distribution(C) Lambda(t[1], Product(Abs(exp(I*t[_j]) - exp(I*t[_k]))**4, (_j, _k + 1, 1), (_k, 1, 0))/(2*pi)) Note ==== As can be seen above in the example, density of CiruclarSymplecticEnsemble is not evaluated becuase the exact definition is based on haar measure of unitary group which is not unique. """ sym, dim = _symbol_converter(sym), _sympify(dim) model = CircularSymplecticEnsembleModel(sym, dim) rmp = RandomMatrixPSpace(sym, model=model) return RandomMatrixSymbol(sym, dim, dim, pspace=rmp) def joint_eigen_distribution(mat): """ For obtaining joint probability distribution of eigen values of random matrix. Parameters ========== mat: RandomMatrixSymbol The matrix symbol whose eigen values are to be considered. Returns ======= Lambda Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE >>> from sympy.stats import joint_eigen_distribution >>> U = GUE('U', 2) >>> joint_eigen_distribution(U) Lambda((l[1], l[2]), exp(-l[1]**2 - l[2]**2)*Product(Abs(l[_i] - l[_j])**2, (_j, _i + 1, 2), (_i, 1, 1))/pi) """ if not isinstance(mat, RandomMatrixSymbol): raise ValueError("%s is not of type, RandomMatrixSymbol."%(mat)) return mat.pspace.model.joint_eigen_distribution() def JointEigenDistribution(mat): """ Creates joint distribution of eigen values of matrices with random expressions. Parameters ========== mat: Matrix The matrix under consideration Returns ======= JointDistributionHandmade Examples ======== >>> from sympy.stats import Normal, JointEigenDistribution >>> from sympy import Matrix >>> A = [[Normal('A00', 0, 1), Normal('A01', 0, 1)], ... [Normal('A10', 0, 1), Normal('A11', 0, 1)]] >>> JointEigenDistribution(Matrix(A)) JointDistributionHandmade(-sqrt(A00**2 - 2*A00*A11 + 4*A01*A10 + A11**2)/2 + A00/2 + A11/2, sqrt(A00**2 - 2*A00*A11 + 4*A01*A10 + A11**2)/2 + A00/2 + A11/2) """ eigenvals = mat.eigenvals(multiple=True) if any(not is_random(eigenval) for eigenval in set(eigenvals)): raise ValueError("Eigen values don't have any random expression, " "joint distribution cannot be generated.") return JointDistributionHandmade(*eigenvals) def level_spacing_distribution(mat): """ For obtaining distribution of level spacings. Parameters ========== mat: RandomMatrixSymbol The random matrix symbol whose eigen values are to be considered for finding the level spacings. Returns ======= Lambda Examples ======== >>> from sympy.stats import GaussianUnitaryEnsemble as GUE >>> from sympy.stats import level_spacing_distribution >>> U = GUE('U', 2) >>> level_spacing_distribution(U) Lambda(_s, 32*_s**2*exp(-4*_s**2/pi)/pi**2) References ========== .. [1] https://en.wikipedia.org/wiki/Random_matrix#Distribution_of_level_spacings """ return mat.pspace.model.level_spacing_distribution()

06c176ccf7c83f0d5dfc72b2be45b9b18c5cb1de057e1229f9cd948b4792175a

""" Finite Discrete Random Variables Module See Also ======== sympy.stats.frv_types sympy.stats.rv sympy.stats.crv """ from itertools import product from sympy import (Basic, Symbol, cacheit, sympify, Mul, And, Or, Piecewise, Eq, Lambda, exp, I, Dummy, nan, Sum, Intersection, S) from sympy.core.containers import Dict from sympy.core.logic import Logic from sympy.core.relational import Relational from sympy.core.sympify import _sympify from sympy.sets.sets import FiniteSet from sympy.stats.rv import (RandomDomain, ProductDomain, ConditionalDomain, PSpace, IndependentProductPSpace, SinglePSpace, random_symbols, sumsets, rv_subs, NamedArgsMixin, Density) from sympy.external import import_module class FiniteDensity(dict): """ A domain with Finite Density. """ def __call__(self, item): """ Make instance of a class callable. If item belongs to current instance of a class, return it. Otherwise, return 0. """ item = sympify(item) if item in self: return self[item] else: return 0 @property def dict(self): """ Return item as dictionary. """ return dict(self) class FiniteDomain(RandomDomain): """ A domain with discrete finite support Represented using a FiniteSet. """ is_Finite = True @property def symbols(self): return FiniteSet(sym for sym, val in self.elements) @property def elements(self): return self.args[0] @property def dict(self): return FiniteSet(*[Dict(dict(el)) for el in self.elements]) def __contains__(self, other): return other in self.elements def __iter__(self): return self.elements.__iter__() def as_boolean(self): return Or(*[And(*[Eq(sym, val) for sym, val in item]) for item in self]) class SingleFiniteDomain(FiniteDomain): """ A FiniteDomain over a single symbol/set Example: The possibilities of a *single* die roll. """ def __new__(cls, symbol, set): if not isinstance(set, FiniteSet) and \ not isinstance(set, Intersection): set = FiniteSet(*set) return Basic.__new__(cls, symbol, set) @property def symbol(self): return self.args[0] @property def symbols(self): return FiniteSet(self.symbol) @property def set(self): return self.args[1] @property def elements(self): return FiniteSet(*[frozenset(((self.symbol, elem), )) for elem in self.set]) def __iter__(self): return (frozenset(((self.symbol, elem),)) for elem in self.set) def __contains__(self, other): sym, val = tuple(other)[0] return sym == self.symbol and val in self.set class ProductFiniteDomain(ProductDomain, FiniteDomain): """ A Finite domain consisting of several other FiniteDomains Example: The possibilities of the rolls of three independent dice """ def __iter__(self): proditer = product(*self.domains) return (sumsets(items) for items in proditer) @property def elements(self): return FiniteSet(*self) class ConditionalFiniteDomain(ConditionalDomain, ProductFiniteDomain): """ A FiniteDomain that has been restricted by a condition Example: The possibilities of a die roll under the condition that the roll is even. """ def __new__(cls, domain, condition): """ Create a new instance of ConditionalFiniteDomain class """ if condition is True: return domain cond = rv_subs(condition) return Basic.__new__(cls, domain, cond) def _test(self, elem): """ Test the value. If value is boolean, return it. If value is equality relational (two objects are equal), return it with left-hand side being equal to right-hand side. Otherwise, raise ValueError exception. """ val = self.condition.xreplace(dict(elem)) if val in [True, False]: return val elif val.is_Equality: return val.lhs == val.rhs raise ValueError("Undecidable if %s" % str(val)) def __contains__(self, other): return other in self.fulldomain and self._test(other) def __iter__(self): return (elem for elem in self.fulldomain if self._test(elem)) @property def set(self): if isinstance(self.fulldomain, SingleFiniteDomain): return FiniteSet(*[elem for elem in self.fulldomain.set if frozenset(((self.fulldomain.symbol, elem),)) in self]) else: raise NotImplementedError( "Not implemented on multi-dimensional conditional domain") def as_boolean(self): return FiniteDomain.as_boolean(self) class SingleFiniteDistribution(Basic, NamedArgsMixin): def __new__(cls, *args): args = list(map(sympify, args)) return Basic.__new__(cls, *args) @staticmethod def check(*args): pass @property # type: ignore @cacheit def dict(self): if self.is_symbolic: return Density(self) return {k: self.pmf(k) for k in self.set} def pmf(self, *args): # to be overridden by specific distribution raise NotImplementedError() @property def set(self): # to be overridden by specific distribution raise NotImplementedError() values = property(lambda self: self.dict.values) items = property(lambda self: self.dict.items) is_symbolic = property(lambda self: False) __iter__ = property(lambda self: self.dict.__iter__) __getitem__ = property(lambda self: self.dict.__getitem__) def __call__(self, *args): return self.pmf(*args) def __contains__(self, other): return other in self.set #============================================= #========= Probability Space =============== #============================================= class FinitePSpace(PSpace): """ A Finite Probability Space Represents the probabilities of a finite number of events. """ is_Finite = True def __new__(cls, domain, density): density = {sympify(key): sympify(val) for key, val in density.items()} public_density = Dict(density) obj = PSpace.__new__(cls, domain, public_density) obj._density = density return obj def prob_of(self, elem): elem = sympify(elem) density = self._density if isinstance(list(density.keys())[0], FiniteSet): return density.get(elem, S.Zero) return density.get(tuple(elem)[0][1], S.Zero) def where(self, condition): assert all(r.symbol in self.symbols for r in random_symbols(condition)) return ConditionalFiniteDomain(self.domain, condition) def compute_density(self, expr): expr = rv_subs(expr, self.values) d = FiniteDensity() for elem in self.domain: val = expr.xreplace(dict(elem)) prob = self.prob_of(elem) d[val] = d.get(val, S.Zero) + prob return d @cacheit def compute_cdf(self, expr): d = self.compute_density(expr) cum_prob = S.Zero cdf = [] for key in sorted(d): prob = d[key] cum_prob += prob cdf.append((key, cum_prob)) return dict(cdf) @cacheit def sorted_cdf(self, expr, python_float=False): cdf = self.compute_cdf(expr) items = list(cdf.items()) sorted_items = sorted(items, key=lambda val_cumprob: val_cumprob[1]) if python_float: sorted_items = [(v, float(cum_prob)) for v, cum_prob in sorted_items] return sorted_items @cacheit def compute_characteristic_function(self, expr): d = self.compute_density(expr) t = Dummy('t', real=True) return Lambda(t, sum(exp(I*k*t)*v for k,v in d.items())) @cacheit def compute_moment_generating_function(self, expr): d = self.compute_density(expr) t = Dummy('t', real=True) return Lambda(t, sum(exp(k*t)*v for k,v in d.items())) def compute_expectation(self, expr, rvs=None, **kwargs): rvs = rvs or self.values expr = rv_subs(expr, rvs) probs = [self.prob_of(elem) for elem in self.domain] if isinstance(expr, (Logic, Relational)): parse_domain = [tuple(elem)[0][1] for elem in self.domain] bools = [expr.xreplace(dict(elem)) for elem in self.domain] else: parse_domain = [expr.xreplace(dict(elem)) for elem in self.domain] bools = [True for elem in self.domain] return sum([Piecewise((prob * elem, blv), (S.Zero, True)) for prob, elem, blv in zip(probs, parse_domain, bools)]) def compute_quantile(self, expr): cdf = self.compute_cdf(expr) p = Dummy('p', real=True) set = ((nan, (p < 0) | (p > 1)),) for key, value in cdf.items(): set = set + ((key, p <= value), ) return Lambda(p, Piecewise(*set)) def probability(self, condition): cond_symbols = frozenset(rs.symbol for rs in random_symbols(condition)) cond = rv_subs(condition) if not cond_symbols.issubset(self.symbols): raise ValueError("Cannot compare foreign random symbols, %s" %(str(cond_symbols - self.symbols))) if isinstance(condition, Relational) and \ (not cond.free_symbols.issubset(self.domain.free_symbols)): rv = condition.lhs if isinstance(condition.rhs, Symbol) else condition.rhs return sum(Piecewise( (self.prob_of(elem), condition.subs(rv, list(elem)[0][1])), (S.Zero, True)) for elem in self.domain) return sympify(sum(self.prob_of(elem) for elem in self.where(condition))) def conditional_space(self, condition): domain = self.where(condition) prob = self.probability(condition) density = {key: val / prob for key, val in self._density.items() if domain._test(key)} return FinitePSpace(domain, density) def sample(self, size=(), library='scipy'): """ Internal sample method Returns dictionary mapping RandomSymbol to realization value. """ libraries = ['scipy', 'numpy', 'pymc3'] if library not in libraries: raise NotImplementedError("Sampling from %s is not supported yet." % str(library)) if not import_module(library): raise ValueError("Failed to import %s" % library) samps = _get_sample_class_frv[library](self.distribution, size) if samps is not None: return {self.value: samps} raise NotImplementedError( "Sampling for %s is not currently implemented from %s" % (self.__class__.__name__, library) ) class SampleFiniteScipy: """Returns the sample from scipy of the given distribution""" def __new__(cls, dist, size): return cls._sample_scipy(dist, size) @classmethod def _sample_scipy(cls, dist, size): """Sample from SciPy.""" # scipy can handle with custom distributions from scipy.stats import rv_discrete density_ = dist.dict x, y = [], [] for k, v in density_.items(): x.append(int(k)) y.append(float(v)) scipy_rv = rv_discrete(name='scipy_rv', values=(x, y)) return scipy_rv.rvs(size=size) class SampleFiniteNumpy: """Returns the sample from numpy of the given distribution""" def __new__(cls, dist, size): return cls._sample_numpy(dist, size) @classmethod def _sample_numpy(cls, dist, size): """Sample from NumPy.""" import numpy numpy_rv_map = { 'BinomialDistribution': lambda dist, size: numpy.random.binomial(n=int(dist.n), p=float(dist.p), size=size) } dist_list = numpy_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None return numpy_rv_map[dist.__class__.__name__](dist, size) class SampleFinitePymc: """Returns the sample from pymc3 of the given distribution""" def __new__(cls, dist, size): return cls._sample_pymc3(dist, size) @classmethod def _sample_pymc3(cls, dist, size): """Sample from PyMC3.""" import pymc3 pymc3_rv_map = { 'BernoulliDistribution': lambda dist: pymc3.Bernoulli('X', p=float(dist.p)), 'BinomialDistribution': lambda dist: pymc3.Binomial('X', n=int(dist.n), p=float(dist.p)) } dist_list = pymc3_rv_map.keys() if dist.__class__.__name__ not in dist_list: return None with pymc3.Model(): pymc3_rv_map[dist.__class__.__name__](dist) return pymc3.sample(size, chains=1, progressbar=False)[:]['X'] _get_sample_class_frv = { 'scipy': SampleFiniteScipy, 'pymc3': SampleFinitePymc, 'numpy': SampleFiniteNumpy } class SingleFinitePSpace(SinglePSpace, FinitePSpace): """ A single finite probability space Represents the probabilities of a set of random events that can be attributed to a single variable/symbol. This class is implemented by many of the standard FiniteRV types such as Die, Bernoulli, Coin, etc.... """ @property def domain(self): return SingleFiniteDomain(self.symbol, self.distribution.set) @property def _is_symbolic(self): """ Helper property to check if the distribution of the random variable is having symbolic dimension. """ return self.distribution.is_symbolic @property def distribution(self): return self.args[1] def pmf(self, expr): return self.distribution.pmf(expr) @property # type: ignore @cacheit def _density(self): return {FiniteSet((self.symbol, val)): prob for val, prob in self.distribution.dict.items()} @cacheit def compute_characteristic_function(self, expr): if self._is_symbolic: d = self.compute_density(expr) t = Dummy('t', real=True) ki = Dummy('ki') return Lambda(t, Sum(d(ki)*exp(I*ki*t), (ki, self.args[1].low, self.args[1].high))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_characteristic_function(expr) @cacheit def compute_moment_generating_function(self, expr): if self._is_symbolic: d = self.compute_density(expr) t = Dummy('t', real=True) ki = Dummy('ki') return Lambda(t, Sum(d(ki)*exp(ki*t), (ki, self.args[1].low, self.args[1].high))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_moment_generating_function(expr) def compute_quantile(self, expr): if self._is_symbolic: raise NotImplementedError("Computing quantile for random variables " "with symbolic dimension because the bounds of searching the required " "value is undetermined.") expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_quantile(expr) def compute_density(self, expr): if self._is_symbolic: rv = list(random_symbols(expr))[0] k = Dummy('k', integer=True) cond = True if not isinstance(expr, (Relational, Logic)) \ else expr.subs(rv, k) return Lambda(k, Piecewise((self.pmf(k), And(k >= self.args[1].low, k <= self.args[1].high, cond)), (S.Zero, True))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_density(expr) def compute_cdf(self, expr): if self._is_symbolic: d = self.compute_density(expr) k = Dummy('k') ki = Dummy('ki') return Lambda(k, Sum(d(ki), (ki, self.args[1].low, k))) expr = rv_subs(expr, self.values) return FinitePSpace(self.domain, self.distribution).compute_cdf(expr) def compute_expectation(self, expr, rvs=None, **kwargs): if self._is_symbolic: rv = random_symbols(expr)[0] k = Dummy('k', integer=True) expr = expr.subs(rv, k) cond = True if not isinstance(expr, (Relational, Logic)) \ else expr func = self.pmf(k) * k if cond != True else self.pmf(k) * expr return Sum(Piecewise((func, cond), (S.Zero, True)), (k, self.distribution.low, self.distribution.high)).doit() expr = _sympify(expr) expr = rv_subs(expr, rvs) return FinitePSpace(self.domain, self.distribution).compute_expectation(expr, rvs, **kwargs) def probability(self, condition): if self._is_symbolic: #TODO: Implement the mechanism for handling queries for symbolic sized distributions. raise NotImplementedError("Currently, probability queries are not " "supported for random variables with symbolic sized distributions.") condition = rv_subs(condition) return FinitePSpace(self.domain, self.distribution).probability(condition) def conditional_space(self, condition): """ This method is used for transferring the computation to probability method because conditional space of random variables with symbolic dimensions is currently not possible. """ if self._is_symbolic: self domain = self.where(condition) prob = self.probability(condition) density = {key: val / prob for key, val in self._density.items() if domain._test(key)} return FinitePSpace(domain, density) class ProductFinitePSpace(IndependentProductPSpace, FinitePSpace): """ A collection of several independent finite probability spaces """ @property def domain(self): return ProductFiniteDomain(*[space.domain for space in self.spaces]) @property # type: ignore @cacheit def _density(self): proditer = product(*[iter(space._density.items()) for space in self.spaces]) d = {} for items in proditer: elems, probs = list(zip(*items)) elem = sumsets(elems) prob = Mul(*probs) d[elem] = d.get(elem, S.Zero) + prob return Dict(d) @property # type: ignore @cacheit def density(self): return Dict(self._density) def probability(self, condition): return FinitePSpace.probability(self, condition) def compute_density(self, expr): return FinitePSpace.compute_density(self, expr)

7e6a197e0deb9c9f325e29a7ee46107dcff7a3760a051d0aec207cdba04111fa

from sympy import Basic from sympy.stats.joint_rv import ProductPSpace from sympy.stats.rv import ProductDomain, _symbol_converter class StochasticPSpace(ProductPSpace): """ Represents probability space of stochastic processes and their random variables. Contains mechanics to do computations for queries of stochastic processes. Initialized by symbol, the specific process and distribution(optional) if the random indexed symbols of the process follows any specific distribution, like, in Bernoulli Process, each random indexed symbol follows Bernoulli distribution. For processes with memory, this parameter should not be passed. """ def __new__(cls, sym, process, distribution=None): sym = _symbol_converter(sym) from sympy.stats.stochastic_process_types import StochasticProcess if not isinstance(process, StochasticProcess): raise TypeError("`process` must be an instance of StochasticProcess.") return Basic.__new__(cls, sym, process, distribution) @property def process(self): """ The associated stochastic process. """ return self.args[1] @property def domain(self): return ProductDomain(self.process.index_set, self.process.state_space) @property def symbol(self): return self.args[0] @property def distribution(self): return self.args[2] def probability(self, condition, given_condition=None, evaluate=True, **kwargs): """ Transfers the task of handling queries to the specific stochastic process because every process has their own logic of handling such queries. """ return self.process.probability(condition, given_condition, evaluate, **kwargs) def compute_expectation(self, expr, condition=None, evaluate=True, **kwargs): """ Transfers the task of handling queries to the specific stochastic process because every process has their own logic of handling such queries. """ return self.process.expectation(expr, condition, evaluate, **kwargs)

f06411db8a8e5e375294eaaa3908318a126056525e5a0881a1245a7e56f61d8a

from sympy.combinatorics import Permutation from sympy.combinatorics.util import _distribute_gens_by_base rmul = Permutation.rmul def _cmp_perm_lists(first, second): """ Compare two lists of permutations as sets. Explanation =========== This is used for testing purposes. Since the array form of a permutation is currently a list, Permutation is not hashable and cannot be put into a set. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.testutil import _cmp_perm_lists >>> a = Permutation([0, 2, 3, 4, 1]) >>> b = Permutation([1, 2, 0, 4, 3]) >>> c = Permutation([3, 4, 0, 1, 2]) >>> ls1 = [a, b, c] >>> ls2 = [b, c, a] >>> _cmp_perm_lists(ls1, ls2) True """ return {tuple(a) for a in first} == \ {tuple(a) for a in second} def _naive_list_centralizer(self, other, af=False): from sympy.combinatorics.perm_groups import PermutationGroup """ Return a list of elements for the centralizer of a subgroup/set/element. Explanation =========== This is a brute force implementation that goes over all elements of the group and checks for membership in the centralizer. It is used to test ``.centralizer()`` from ``sympy.combinatorics.perm_groups``. Examples ======== >>> from sympy.combinatorics.testutil import _naive_list_centralizer >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> _naive_list_centralizer(D, D) [Permutation([0, 1, 2, 3]), Permutation([2, 3, 0, 1])] See Also ======== sympy.combinatorics.perm_groups.centralizer """ from sympy.combinatorics.permutations import _af_commutes_with if hasattr(other, 'generators'): elements = list(self.generate_dimino(af=True)) gens = [x._array_form for x in other.generators] commutes_with_gens = lambda x: all(_af_commutes_with(x, gen) for gen in gens) centralizer_list = [] if not af: for element in elements: if commutes_with_gens(element): centralizer_list.append(Permutation._af_new(element)) else: for element in elements: if commutes_with_gens(element): centralizer_list.append(element) return centralizer_list elif hasattr(other, 'getitem'): return _naive_list_centralizer(self, PermutationGroup(other), af) elif hasattr(other, 'array_form'): return _naive_list_centralizer(self, PermutationGroup([other]), af) def _verify_bsgs(group, base, gens): """ Verify the correctness of a base and strong generating set. Explanation =========== This is a naive implementation using the definition of a base and a strong generating set relative to it. There are other procedures for verifying a base and strong generating set, but this one will serve for more robust testing. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> A = AlternatingGroup(4) >>> A.schreier_sims() >>> _verify_bsgs(A, A.base, A.strong_gens) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims """ from sympy.combinatorics.perm_groups import PermutationGroup strong_gens_distr = _distribute_gens_by_base(base, gens) current_stabilizer = group for i in range(len(base)): candidate = PermutationGroup(strong_gens_distr[i]) if current_stabilizer.order() != candidate.order(): return False current_stabilizer = current_stabilizer.stabilizer(base[i]) if current_stabilizer.order() != 1: return False return True def _verify_centralizer(group, arg, centr=None): """ Verify the centralizer of a group/set/element inside another group. This is used for testing ``.centralizer()`` from ``sympy.combinatorics.perm_groups`` Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.testutil import _verify_centralizer >>> S = SymmetricGroup(5) >>> A = AlternatingGroup(5) >>> centr = PermutationGroup([Permutation([0, 1, 2, 3, 4])]) >>> _verify_centralizer(S, A, centr) True See Also ======== _naive_list_centralizer, sympy.combinatorics.perm_groups.PermutationGroup.centralizer, _cmp_perm_lists """ if centr is None: centr = group.centralizer(arg) centr_list = list(centr.generate_dimino(af=True)) centr_list_naive = _naive_list_centralizer(group, arg, af=True) return _cmp_perm_lists(centr_list, centr_list_naive) def _verify_normal_closure(group, arg, closure=None): from sympy.combinatorics.perm_groups import PermutationGroup """ Verify the normal closure of a subgroup/subset/element in a group. This is used to test sympy.combinatorics.perm_groups.PermutationGroup.normal_closure Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.testutil import _verify_normal_closure >>> S = SymmetricGroup(3) >>> A = AlternatingGroup(3) >>> _verify_normal_closure(S, A, closure=A) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.normal_closure """ if closure is None: closure = group.normal_closure(arg) conjugates = set() if hasattr(arg, 'generators'): subgr_gens = arg.generators elif hasattr(arg, '__getitem__'): subgr_gens = arg elif hasattr(arg, 'array_form'): subgr_gens = [arg] for el in group.generate_dimino(): for gen in subgr_gens: conjugates.add(gen ^ el) naive_closure = PermutationGroup(list(conjugates)) return closure.is_subgroup(naive_closure) def canonicalize_naive(g, dummies, sym, *v): """ Canonicalize tensor formed by tensors of the different types. Explanation =========== sym_i symmetry under exchange of two component tensors of type `i` None no symmetry 0 commuting 1 anticommuting Parameters ========== g : Permutation representing the tensor. dummies : List of dummy indices. msym : Symmetry of the metric. v : A list of (base_i, gens_i, n_i, sym_i) for tensors of type `i`. base_i, gens_i BSGS for tensors of this type n_i number ot tensors of type `i` Returns ======= Returns 0 if the tensor is zero, else returns the array form of the permutation representing the canonical form of the tensor. Examples ======== >>> from sympy.combinatorics.testutil import canonicalize_naive >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs >>> from sympy.combinatorics import Permutation >>> g = Permutation([1, 3, 2, 0, 4, 5]) >>> base2, gens2 = get_symmetric_group_sgs(2) >>> canonicalize_naive(g, [2, 3], 0, (base2, gens2, 2, 0)) [0, 2, 1, 3, 4, 5] """ from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.tensor_can import gens_products, dummy_sgs from sympy.combinatorics.permutations import Permutation, _af_rmul v1 = [] for i in range(len(v)): base_i, gens_i, n_i, sym_i = v[i] v1.append((base_i, gens_i, [[]]*n_i, sym_i)) size, sbase, sgens = gens_products(*v1) dgens = dummy_sgs(dummies, sym, size-2) if isinstance(sym, int): num_types = 1 dummies = [dummies] sym = [sym] else: num_types = len(sym) dgens = [] for i in range(num_types): dgens.extend(dummy_sgs(dummies[i], sym[i], size - 2)) S = PermutationGroup(sgens) D = PermutationGroup([Permutation(x) for x in dgens]) dlist = list(D.generate(af=True)) g = g.array_form st = set() for s in S.generate(af=True): h = _af_rmul(g, s) for d in dlist: q = tuple(_af_rmul(d, h)) st.add(q) a = list(st) a.sort() prev = (0,)*size for h in a: if h[:-2] == prev[:-2]: if h[-1] != prev[-1]: return 0 prev = h return list(a[0]) def graph_certificate(gr): """ Return a certificate for the graph Parameters ========== gr : adjacency list Explanation =========== The graph is assumed to be unoriented and without external lines. Associate to each vertex of the graph a symmetric tensor with number of indices equal to the degree of the vertex; indices are contracted when they correspond to the same line of the graph. The canonical form of the tensor gives a certificate for the graph. This is not an efficient algorithm to get the certificate of a graph. Examples ======== >>> from sympy.combinatorics.testutil import graph_certificate >>> gr1 = {0:[1, 2, 3, 5], 1:[0, 2, 4], 2:[0, 1, 3, 4], 3:[0, 2, 4], 4:[1, 2, 3, 5], 5:[0, 4]} >>> gr2 = {0:[1, 5], 1:[0, 2, 3, 4], 2:[1, 3, 5], 3:[1, 2, 4, 5], 4:[1, 3, 5], 5:[0, 2, 3, 4]} >>> c1 = graph_certificate(gr1) >>> c2 = graph_certificate(gr2) >>> c1 [0, 2, 4, 6, 1, 8, 10, 12, 3, 14, 16, 18, 5, 9, 15, 7, 11, 17, 13, 19, 20, 21] >>> c1 == c2 True """ from sympy.combinatorics.permutations import _af_invert from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, canonicalize items = list(gr.items()) items.sort(key=lambda x: len(x[1]), reverse=True) pvert = [x[0] for x in items] pvert = _af_invert(pvert) # the indices of the tensor are twice the number of lines of the graph num_indices = 0 for v, neigh in items: num_indices += len(neigh) # associate to each vertex its indices; for each line # between two vertices assign the # even index to the vertex which comes first in items, # the odd index to the other vertex vertices = [[] for i in items] i = 0 for v, neigh in items: for v2 in neigh: if pvert[v] < pvert[v2]: vertices[pvert[v]].append(i) vertices[pvert[v2]].append(i+1) i += 2 g = [] for v in vertices: g.extend(v) assert len(g) == num_indices g += [num_indices, num_indices + 1] size = num_indices + 2 assert sorted(g) == list(range(size)) g = Permutation(g) vlen = [0]*(len(vertices[0])+1) for neigh in vertices: vlen[len(neigh)] += 1 v = [] for i in range(len(vlen)): n = vlen[i] if n: base, gens = get_symmetric_group_sgs(i) v.append((base, gens, n, 0)) v.reverse() dummies = list(range(num_indices)) can = canonicalize(g, dummies, 0, *v) return can

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from random import randrange, choice from math import log from sympy.ntheory import primefactors from sympy import multiplicity, factorint, Symbol from sympy.combinatorics import Permutation from sympy.combinatorics.permutations import (_af_commutes_with, _af_invert, _af_rmul, _af_rmuln, _af_pow, Cycle) from sympy.combinatorics.util import (_check_cycles_alt_sym, _distribute_gens_by_base, _orbits_transversals_from_bsgs, _handle_precomputed_bsgs, _base_ordering, _strong_gens_from_distr, _strip, _strip_af) from sympy.core import Basic from sympy.functions.combinatorial.factorials import factorial from sympy.ntheory import sieve from sympy.utilities.iterables import has_variety, is_sequence, uniq from sympy.testing.randtest import _randrange from itertools import islice from sympy.core.sympify import _sympify rmul = Permutation.rmul_with_af _af_new = Permutation._af_new class PermutationGroup(Basic): """The class defining a Permutation group. Explanation =========== PermutationGroup([p1, p2, ..., pn]) returns the permutation group generated by the list of permutations. This group can be supplied to Polyhedron if one desires to decorate the elements to which the indices of the permutation refer. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.polyhedron import Polyhedron >>> from sympy.combinatorics.perm_groups import PermutationGroup The permutations corresponding to motion of the front, right and bottom face of a 2x2 Rubik's cube are defined: >>> F = Permutation(2, 19, 21, 8)(3, 17, 20, 10)(4, 6, 7, 5) >>> R = Permutation(1, 5, 21, 14)(3, 7, 23, 12)(8, 10, 11, 9) >>> D = Permutation(6, 18, 14, 10)(7, 19, 15, 11)(20, 22, 23, 21) These are passed as permutations to PermutationGroup: >>> G = PermutationGroup(F, R, D) >>> G.order() 3674160 The group can be supplied to a Polyhedron in order to track the objects being moved. An example involving the 2x2 Rubik's cube is given there, but here is a simple demonstration: >>> a = Permutation(2, 1) >>> b = Permutation(1, 0) >>> G = PermutationGroup(a, b) >>> P = Polyhedron(list('ABC'), pgroup=G) >>> P.corners (A, B, C) >>> P.rotate(0) # apply permutation 0 >>> P.corners (A, C, B) >>> P.reset() >>> P.corners (A, B, C) Or one can make a permutation as a product of selected permutations and apply them to an iterable directly: >>> P10 = G.make_perm([0, 1]) >>> P10('ABC') ['C', 'A', 'B'] See Also ======== sympy.combinatorics.polyhedron.Polyhedron, sympy.combinatorics.permutations.Permutation References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" .. [2] Seress, A. "Permutation Group Algorithms" .. [3] https://en.wikipedia.org/wiki/Schreier_vector .. [4] https://en.wikipedia.org/wiki/Nielsen_transformation#Product_replacement_algorithm .. [5] Frank Celler, Charles R.Leedham-Green, Scott H.Murray, Alice C.Niemeyer, and E.A.O'Brien. "Generating Random Elements of a Finite Group" .. [6] https://en.wikipedia.org/wiki/Block_%28permutation_group_theory%29 .. [7] http://www.algorithmist.com/index.php/Union_Find .. [8] https://en.wikipedia.org/wiki/Multiply_transitive_group#Multiply_transitive_groups .. [9] https://en.wikipedia.org/wiki/Center_%28group_theory%29 .. [10] https://en.wikipedia.org/wiki/Centralizer_and_normalizer .. [11] http://groupprops.subwiki.org/wiki/Derived_subgroup .. [12] https://en.wikipedia.org/wiki/Nilpotent_group .. [13] http://www.math.colostate.edu/~hulpke/CGT/cgtnotes.pdf .. [14] https://www.gap-system.org/Manuals/doc/ref/manual.pdf """ is_group = True def __new__(cls, *args, dups=True, **kwargs): """The default constructor. Accepts Cycle and Permutation forms. Removes duplicates unless ``dups`` keyword is ``False``. """ if not args: args = [Permutation()] else: args = list(args[0] if is_sequence(args[0]) else args) if not args: args = [Permutation()] if any(isinstance(a, Cycle) for a in args): args = [Permutation(a) for a in args] if has_variety(a.size for a in args): degree = kwargs.pop('degree', None) if degree is None: degree = max(a.size for a in args) for i in range(len(args)): if args[i].size != degree: args[i] = Permutation(args[i], size=degree) if dups: args = list(uniq([_af_new(list(a)) for a in args])) if len(args) > 1: args = [g for g in args if not g.is_identity] obj = Basic.__new__(cls, *args, **kwargs) obj._generators = args obj._order = None obj._center = [] obj._is_abelian = None obj._is_transitive = None obj._is_sym = None obj._is_alt = None obj._is_primitive = None obj._is_nilpotent = None obj._is_solvable = None obj._is_trivial = None obj._transitivity_degree = None obj._max_div = None obj._is_perfect = None obj._is_cyclic = None obj._r = len(obj._generators) obj._degree = obj._generators[0].size # these attributes are assigned after running schreier_sims obj._base = [] obj._strong_gens = [] obj._strong_gens_slp = [] obj._basic_orbits = [] obj._transversals = [] obj._transversal_slp = [] # these attributes are assigned after running _random_pr_init obj._random_gens = [] # finite presentation of the group as an instance of `FpGroup` obj._fp_presentation = None return obj def __getitem__(self, i): return self._generators[i] def __contains__(self, i): """Return ``True`` if *i* is contained in PermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = Permutation(1, 2, 3) >>> Permutation(3) in PermutationGroup(p) True """ if not isinstance(i, Permutation): raise TypeError("A PermutationGroup contains only Permutations as " "elements, not elements of type %s" % type(i)) return self.contains(i) def __len__(self): return len(self._generators) def __eq__(self, other): """Return ``True`` if PermutationGroup generated by elements in the group are same i.e they represent the same PermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> p = Permutation(0, 1, 2, 3, 4, 5) >>> G = PermutationGroup([p, p**2]) >>> H = PermutationGroup([p**2, p]) >>> G.generators == H.generators False >>> G == H True """ if not isinstance(other, PermutationGroup): return False set_self_gens = set(self.generators) set_other_gens = set(other.generators) # before reaching the general case there are also certain # optimisation and obvious cases requiring less or no actual # computation. if set_self_gens == set_other_gens: return True # in the most general case it will check that each generator of # one group belongs to the other PermutationGroup and vice-versa for gen1 in set_self_gens: if not other.contains(gen1): return False for gen2 in set_other_gens: if not self.contains(gen2): return False return True def __hash__(self): return super().__hash__() def __mul__(self, other): """ Return the direct product of two permutation groups as a permutation group. Explanation =========== This implementation realizes the direct product by shifting the index set for the generators of the second group: so if we have ``G`` acting on ``n1`` points and ``H`` acting on ``n2`` points, ``G*H`` acts on ``n1 + n2`` points. Examples ======== >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(5) >>> H = G*G >>> H PermutationGroup([ (9)(0 1 2 3 4), (5 6 7 8 9)]) >>> H.order() 25 """ if isinstance(other, Permutation): return Coset(other, self, dir='+') gens1 = [perm._array_form for perm in self.generators] gens2 = [perm._array_form for perm in other.generators] n1 = self._degree n2 = other._degree start = list(range(n1)) end = list(range(n1, n1 + n2)) for i in range(len(gens2)): gens2[i] = [x + n1 for x in gens2[i]] gens2 = [start + gen for gen in gens2] gens1 = [gen + end for gen in gens1] together = gens1 + gens2 gens = [_af_new(x) for x in together] return PermutationGroup(gens) def _random_pr_init(self, r, n, _random_prec_n=None): r"""Initialize random generators for the product replacement algorithm. Explanation =========== The implementation uses a modification of the original product replacement algorithm due to Leedham-Green, as described in [1], pp. 69-71; also, see [2], pp. 27-29 for a detailed theoretical analysis of the original product replacement algorithm, and [4]. The product replacement algorithm is used for producing random, uniformly distributed elements of a group `G` with a set of generators `S`. For the initialization ``_random_pr_init``, a list ``R`` of `\max\{r, |S|\}` group generators is created as the attribute ``G._random_gens``, repeating elements of `S` if necessary, and the identity element of `G` is appended to ``R`` - we shall refer to this last element as the accumulator. Then the function ``random_pr()`` is called ``n`` times, randomizing the list ``R`` while preserving the generation of `G` by ``R``. The function ``random_pr()`` itself takes two random elements ``g, h`` among all elements of ``R`` but the accumulator and replaces ``g`` with a randomly chosen element from `\{gh, g(~h), hg, (~h)g\}`. Then the accumulator is multiplied by whatever ``g`` was replaced by. The new value of the accumulator is then returned by ``random_pr()``. The elements returned will eventually (for ``n`` large enough) become uniformly distributed across `G` ([5]). For practical purposes however, the values ``n = 50, r = 11`` are suggested in [1]. Notes ===== THIS FUNCTION HAS SIDE EFFECTS: it changes the attribute self._random_gens See Also ======== random_pr """ deg = self.degree random_gens = [x._array_form for x in self.generators] k = len(random_gens) if k < r: for i in range(k, r): random_gens.append(random_gens[i - k]) acc = list(range(deg)) random_gens.append(acc) self._random_gens = random_gens # handle randomized input for testing purposes if _random_prec_n is None: for i in range(n): self.random_pr() else: for i in range(n): self.random_pr(_random_prec=_random_prec_n[i]) def _union_find_merge(self, first, second, ranks, parents, not_rep): """Merges two classes in a union-find data structure. Explanation =========== Used in the implementation of Atkinson's algorithm as suggested in [1], pp. 83-87. The class merging process uses union by rank as an optimization. ([7]) Notes ===== THIS FUNCTION HAS SIDE EFFECTS: the list of class representatives, ``parents``, the list of class sizes, ``ranks``, and the list of elements that are not representatives, ``not_rep``, are changed due to class merging. See Also ======== minimal_block, _union_find_rep References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" .. [7] http://www.algorithmist.com/index.php/Union_Find """ rep_first = self._union_find_rep(first, parents) rep_second = self._union_find_rep(second, parents) if rep_first != rep_second: # union by rank if ranks[rep_first] >= ranks[rep_second]: new_1, new_2 = rep_first, rep_second else: new_1, new_2 = rep_second, rep_first total_rank = ranks[new_1] + ranks[new_2] if total_rank > self.max_div: return -1 parents[new_2] = new_1 ranks[new_1] = total_rank not_rep.append(new_2) return 1 return 0 def _union_find_rep(self, num, parents): """Find representative of a class in a union-find data structure. Explanation =========== Used in the implementation of Atkinson's algorithm as suggested in [1], pp. 83-87. After the representative of the class to which ``num`` belongs is found, path compression is performed as an optimization ([7]). Notes ===== THIS FUNCTION HAS SIDE EFFECTS: the list of class representatives, ``parents``, is altered due to path compression. See Also ======== minimal_block, _union_find_merge References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" .. [7] http://www.algorithmist.com/index.php/Union_Find """ rep, parent = num, parents[num] while parent != rep: rep = parent parent = parents[rep] # path compression temp, parent = num, parents[num] while parent != rep: parents[temp] = rep temp = parent parent = parents[temp] return rep @property def base(self): """Return a base from the Schreier-Sims algorithm. Explanation =========== For a permutation group `G`, a base is a sequence of points `B = (b_1, b_2, ..., b_k)` such that no element of `G` apart from the identity fixes all the points in `B`. The concepts of a base and strong generating set and their applications are discussed in depth in [1], pp. 87-89 and [2], pp. 55-57. An alternative way to think of `B` is that it gives the indices of the stabilizer cosets that contain more than the identity permutation. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> G = PermutationGroup([Permutation(0, 1, 3)(2, 4)]) >>> G.base [0, 2] See Also ======== strong_gens, basic_transversals, basic_orbits, basic_stabilizers """ if self._base == []: self.schreier_sims() return self._base def baseswap(self, base, strong_gens, pos, randomized=False, transversals=None, basic_orbits=None, strong_gens_distr=None): r"""Swap two consecutive base points in base and strong generating set. Explanation =========== If a base for a group `G` is given by `(b_1, b_2, ..., b_k)`, this function returns a base `(b_1, b_2, ..., b_{i+1}, b_i, ..., b_k)`, where `i` is given by ``pos``, and a strong generating set relative to that base. The original base and strong generating set are not modified. The randomized version (default) is of Las Vegas type. Parameters ========== base, strong_gens The base and strong generating set. pos The position at which swapping is performed. randomized A switch between randomized and deterministic version. transversals The transversals for the basic orbits, if known. basic_orbits The basic orbits, if known. strong_gens_distr The strong generators distributed by basic stabilizers, if known. Returns ======= (base, strong_gens) ``base`` is the new base, and ``strong_gens`` is a generating set relative to it. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> S = SymmetricGroup(4) >>> S.schreier_sims() >>> S.base [0, 1, 2] >>> base, gens = S.baseswap(S.base, S.strong_gens, 1, randomized=False) >>> base, gens ([0, 2, 1], [(0 1 2 3), (3)(0 1), (1 3 2), (2 3), (1 3)]) check that base, gens is a BSGS >>> S1 = PermutationGroup(gens) >>> _verify_bsgs(S1, base, gens) True See Also ======== schreier_sims Notes ===== The deterministic version of the algorithm is discussed in [1], pp. 102-103; the randomized version is discussed in [1], p.103, and [2], p.98. It is of Las Vegas type. Notice that [1] contains a mistake in the pseudocode and discussion of BASESWAP: on line 3 of the pseudocode, `|\beta_{i+1}^{\left\langle T\right\rangle}|` should be replaced by `|\beta_{i}^{\left\langle T\right\rangle}|`, and the same for the discussion of the algorithm. """ # construct the basic orbits, generators for the stabilizer chain # and transversal elements from whatever was provided transversals, basic_orbits, strong_gens_distr = \ _handle_precomputed_bsgs(base, strong_gens, transversals, basic_orbits, strong_gens_distr) base_len = len(base) degree = self.degree # size of orbit of base[pos] under the stabilizer we seek to insert # in the stabilizer chain at position pos + 1 size = len(basic_orbits[pos])*len(basic_orbits[pos + 1]) \ //len(_orbit(degree, strong_gens_distr[pos], base[pos + 1])) # initialize the wanted stabilizer by a subgroup if pos + 2 > base_len - 1: T = [] else: T = strong_gens_distr[pos + 2][:] # randomized version if randomized is True: stab_pos = PermutationGroup(strong_gens_distr[pos]) schreier_vector = stab_pos.schreier_vector(base[pos + 1]) # add random elements of the stabilizer until they generate it while len(_orbit(degree, T, base[pos])) != size: new = stab_pos.random_stab(base[pos + 1], schreier_vector=schreier_vector) T.append(new) # deterministic version else: Gamma = set(basic_orbits[pos]) Gamma.remove(base[pos]) if base[pos + 1] in Gamma: Gamma.remove(base[pos + 1]) # add elements of the stabilizer until they generate it by # ruling out member of the basic orbit of base[pos] along the way while len(_orbit(degree, T, base[pos])) != size: gamma = next(iter(Gamma)) x = transversals[pos][gamma] temp = x._array_form.index(base[pos + 1]) # (~x)(base[pos + 1]) if temp not in basic_orbits[pos + 1]: Gamma = Gamma - _orbit(degree, T, gamma) else: y = transversals[pos + 1][temp] el = rmul(x, y) if el(base[pos]) not in _orbit(degree, T, base[pos]): T.append(el) Gamma = Gamma - _orbit(degree, T, base[pos]) # build the new base and strong generating set strong_gens_new_distr = strong_gens_distr[:] strong_gens_new_distr[pos + 1] = T base_new = base[:] base_new[pos], base_new[pos + 1] = base_new[pos + 1], base_new[pos] strong_gens_new = _strong_gens_from_distr(strong_gens_new_distr) for gen in T: if gen not in strong_gens_new: strong_gens_new.append(gen) return base_new, strong_gens_new @property def basic_orbits(self): """ Return the basic orbits relative to a base and strong generating set. Explanation =========== If `(b_1, b_2, ..., b_k)` is a base for a group `G`, and `G^{(i)} = G_{b_1, b_2, ..., b_{i-1}}` is the ``i``-th basic stabilizer (so that `G^{(1)} = G`), the ``i``-th basic orbit relative to this base is the orbit of `b_i` under `G^{(i)}`. See [1], pp. 87-89 for more information. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(4) >>> S.basic_orbits [[0, 1, 2, 3], [1, 2, 3], [2, 3]] See Also ======== base, strong_gens, basic_transversals, basic_stabilizers """ if self._basic_orbits == []: self.schreier_sims() return self._basic_orbits @property def basic_stabilizers(self): """ Return a chain of stabilizers relative to a base and strong generating set. Explanation =========== The ``i``-th basic stabilizer `G^{(i)}` relative to a base `(b_1, b_2, ..., b_k)` is `G_{b_1, b_2, ..., b_{i-1}}`. For more information, see [1], pp. 87-89. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> A = AlternatingGroup(4) >>> A.schreier_sims() >>> A.base [0, 1] >>> for g in A.basic_stabilizers: ... print(g) ... PermutationGroup([ (3)(0 1 2), (1 2 3)]) PermutationGroup([ (1 2 3)]) See Also ======== base, strong_gens, basic_orbits, basic_transversals """ if self._transversals == []: self.schreier_sims() strong_gens = self._strong_gens base = self._base if not base: # e.g. if self is trivial return [] strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_stabilizers = [] for gens in strong_gens_distr: basic_stabilizers.append(PermutationGroup(gens)) return basic_stabilizers @property def basic_transversals(self): """ Return basic transversals relative to a base and strong generating set. Explanation =========== The basic transversals are transversals of the basic orbits. They are provided as a list of dictionaries, each dictionary having keys - the elements of one of the basic orbits, and values - the corresponding transversal elements. See [1], pp. 87-89 for more information. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> A = AlternatingGroup(4) >>> A.basic_transversals [{0: (3), 1: (3)(0 1 2), 2: (3)(0 2 1), 3: (0 3 1)}, {1: (3), 2: (1 2 3), 3: (1 3 2)}] See Also ======== strong_gens, base, basic_orbits, basic_stabilizers """ if self._transversals == []: self.schreier_sims() return self._transversals def composition_series(self): r""" Return the composition series for a group as a list of permutation groups. Explanation =========== The composition series for a group `G` is defined as a subnormal series `G = H_0 > H_1 > H_2 \ldots` A composition series is a subnormal series such that each factor group `H(i+1) / H(i)` is simple. A subnormal series is a composition series only if it is of maximum length. The algorithm works as follows: Starting with the derived series the idea is to fill the gap between `G = der[i]` and `H = der[i+1]` for each `i` independently. Since, all subgroups of the abelian group `G/H` are normal so, first step is to take the generators `g` of `G` and add them to generators of `H` one by one. The factor groups formed are not simple in general. Each group is obtained from the previous one by adding one generator `g`, if the previous group is denoted by `H` then the next group `K` is generated by `g` and `H`. The factor group `K/H` is cyclic and it's order is `K.order()//G.order()`. The series is then extended between `K` and `H` by groups generated by powers of `g` and `H`. The series formed is then prepended to the already existing series. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.named_groups import CyclicGroup >>> S = SymmetricGroup(12) >>> G = S.sylow_subgroup(2) >>> C = G.composition_series() >>> [H.order() for H in C] [1024, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1] >>> G = S.sylow_subgroup(3) >>> C = G.composition_series() >>> [H.order() for H in C] [243, 81, 27, 9, 3, 1] >>> G = CyclicGroup(12) >>> C = G.composition_series() >>> [H.order() for H in C] [12, 6, 3, 1] """ der = self.derived_series() if not (all(g.is_identity for g in der[-1].generators)): raise NotImplementedError('Group should be solvable') series = [] for i in range(len(der)-1): H = der[i+1] up_seg = [] for g in der[i].generators: K = PermutationGroup([g] + H.generators) order = K.order() // H.order() down_seg = [] for p, e in factorint(order).items(): for j in range(e): down_seg.append(PermutationGroup([g] + H.generators)) g = g**p up_seg = down_seg + up_seg H = K up_seg[0] = der[i] series.extend(up_seg) series.append(der[-1]) return series def coset_transversal(self, H): """Return a transversal of the right cosets of self by its subgroup H using the second method described in [1], Subsection 4.6.7 """ if not H.is_subgroup(self): raise ValueError("The argument must be a subgroup") if H.order() == 1: return self._elements self._schreier_sims(base=H.base) # make G.base an extension of H.base base = self.base base_ordering = _base_ordering(base, self.degree) identity = Permutation(self.degree - 1) transversals = self.basic_transversals[:] # transversals is a list of dictionaries. Get rid of the keys # so that it is a list of lists and sort each list in # the increasing order of base[l]^x for l, t in enumerate(transversals): transversals[l] = sorted(t.values(), key = lambda x: base_ordering[base[l]^x]) orbits = H.basic_orbits h_stabs = H.basic_stabilizers g_stabs = self.basic_stabilizers indices = [x.order()//y.order() for x, y in zip(g_stabs, h_stabs)] # T^(l) should be a right transversal of H^(l) in G^(l) for # 1<=l<=len(base). While H^(l) is the trivial group, T^(l) # contains all the elements of G^(l) so we might just as well # start with l = len(h_stabs)-1 if len(g_stabs) > len(h_stabs): T = g_stabs[len(h_stabs)]._elements else: T = [identity] l = len(h_stabs)-1 t_len = len(T) while l > -1: T_next = [] for u in transversals[l]: if u == identity: continue b = base_ordering[base[l]^u] for t in T: p = t*u if all([base_ordering[h^p] >= b for h in orbits[l]]): T_next.append(p) if t_len + len(T_next) == indices[l]: break if t_len + len(T_next) == indices[l]: break T += T_next t_len += len(T_next) l -= 1 T.remove(identity) T = [identity] + T return T def _coset_representative(self, g, H): """Return the representative of Hg from the transversal that would be computed by ``self.coset_transversal(H)``. """ if H.order() == 1: return g # The base of self must be an extension of H.base. if not(self.base[:len(H.base)] == H.base): self._schreier_sims(base=H.base) orbits = H.basic_orbits[:] h_transversals = [list(_.values()) for _ in H.basic_transversals] transversals = [list(_.values()) for _ in self.basic_transversals] base = self.base base_ordering = _base_ordering(base, self.degree) def step(l, x): gamma = sorted(orbits[l], key = lambda y: base_ordering[y^x])[0] i = [base[l]^h for h in h_transversals[l]].index(gamma) x = h_transversals[l][i]*x if l < len(orbits)-1: for u in transversals[l]: if base[l]^u == base[l]^x: break x = step(l+1, x*u**-1)*u return x return step(0, g) def coset_table(self, H): """Return the standardised (right) coset table of self in H as a list of lists. """ # Maybe this should be made to return an instance of CosetTable # from fp_groups.py but the class would need to be changed first # to be compatible with PermutationGroups from itertools import chain, product if not H.is_subgroup(self): raise ValueError("The argument must be a subgroup") T = self.coset_transversal(H) n = len(T) A = list(chain.from_iterable((gen, gen**-1) for gen in self.generators)) table = [] for i in range(n): row = [self._coset_representative(T[i]*x, H) for x in A] row = [T.index(r) for r in row] table.append(row) # standardize (this is the same as the algorithm used in coset_table) # If CosetTable is made compatible with PermutationGroups, this # should be replaced by table.standardize() A = range(len(A)) gamma = 1 for alpha, a in product(range(n), A): beta = table[alpha][a] if beta >= gamma: if beta > gamma: for x in A: z = table[gamma][x] table[gamma][x] = table[beta][x] table[beta][x] = z for i in range(n): if table[i][x] == beta: table[i][x] = gamma elif table[i][x] == gamma: table[i][x] = beta gamma += 1 if gamma >= n-1: return table def center(self): r""" Return the center of a permutation group. Explanation =========== The center for a group `G` is defined as `Z(G) = \{z\in G | \forall g\in G, zg = gz \}`, the set of elements of `G` that commute with all elements of `G`. It is equal to the centralizer of `G` inside `G`, and is naturally a subgroup of `G` ([9]). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> G = D.center() >>> G.order() 2 See Also ======== centralizer Notes ===== This is a naive implementation that is a straightforward application of ``.centralizer()`` """ return self.centralizer(self) def centralizer(self, other): r""" Return the centralizer of a group/set/element. Explanation =========== The centralizer of a set of permutations ``S`` inside a group ``G`` is the set of elements of ``G`` that commute with all elements of ``S``:: `C_G(S) = \{ g \in G | gs = sg \forall s \in S\}` ([10]) Usually, ``S`` is a subset of ``G``, but if ``G`` is a proper subgroup of the full symmetric group, we allow for ``S`` to have elements outside ``G``. It is naturally a subgroup of ``G``; the centralizer of a permutation group is equal to the centralizer of any set of generators for that group, since any element commuting with the generators commutes with any product of the generators. Parameters ========== other a permutation group/list of permutations/single permutation Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) >>> S = SymmetricGroup(6) >>> C = CyclicGroup(6) >>> H = S.centralizer(C) >>> H.is_subgroup(C) True See Also ======== subgroup_search Notes ===== The implementation is an application of ``.subgroup_search()`` with tests using a specific base for the group ``G``. """ if hasattr(other, 'generators'): if other.is_trivial or self.is_trivial: return self degree = self.degree identity = _af_new(list(range(degree))) orbits = other.orbits() num_orbits = len(orbits) orbits.sort(key=lambda x: -len(x)) long_base = [] orbit_reps = [None]*num_orbits orbit_reps_indices = [None]*num_orbits orbit_descr = [None]*degree for i in range(num_orbits): orbit = list(orbits[i]) orbit_reps[i] = orbit[0] orbit_reps_indices[i] = len(long_base) for point in orbit: orbit_descr[point] = i long_base = long_base + orbit base, strong_gens = self.schreier_sims_incremental(base=long_base) strong_gens_distr = _distribute_gens_by_base(base, strong_gens) i = 0 for i in range(len(base)): if strong_gens_distr[i] == [identity]: break base = base[:i] base_len = i for j in range(num_orbits): if base[base_len - 1] in orbits[j]: break rel_orbits = orbits[: j + 1] num_rel_orbits = len(rel_orbits) transversals = [None]*num_rel_orbits for j in range(num_rel_orbits): rep = orbit_reps[j] transversals[j] = dict( other.orbit_transversal(rep, pairs=True)) trivial_test = lambda x: True tests = [None]*base_len for l in range(base_len): if base[l] in orbit_reps: tests[l] = trivial_test else: def test(computed_words, l=l): g = computed_words[l] rep_orb_index = orbit_descr[base[l]] rep = orbit_reps[rep_orb_index] im = g._array_form[base[l]] im_rep = g._array_form[rep] tr_el = transversals[rep_orb_index][base[l]] # using the definition of transversal, # base[l]^g = rep^(tr_el*g); # if g belongs to the centralizer, then # base[l]^g = (rep^g)^tr_el return im == tr_el._array_form[im_rep] tests[l] = test def prop(g): return [rmul(g, gen) for gen in other.generators] == \ [rmul(gen, g) for gen in other.generators] return self.subgroup_search(prop, base=base, strong_gens=strong_gens, tests=tests) elif hasattr(other, '__getitem__'): gens = list(other) return self.centralizer(PermutationGroup(gens)) elif hasattr(other, 'array_form'): return self.centralizer(PermutationGroup([other])) def commutator(self, G, H): """ Return the commutator of two subgroups. Explanation =========== For a permutation group ``K`` and subgroups ``G``, ``H``, the commutator of ``G`` and ``H`` is defined as the group generated by all the commutators `[g, h] = hgh^{-1}g^{-1}` for ``g`` in ``G`` and ``h`` in ``H``. It is naturally a subgroup of ``K`` ([1], p.27). Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> S = SymmetricGroup(5) >>> A = AlternatingGroup(5) >>> G = S.commutator(S, A) >>> G.is_subgroup(A) True See Also ======== derived_subgroup Notes ===== The commutator of two subgroups `H, G` is equal to the normal closure of the commutators of all the generators, i.e. `hgh^{-1}g^{-1}` for `h` a generator of `H` and `g` a generator of `G` ([1], p.28) """ ggens = G.generators hgens = H.generators commutators = [] for ggen in ggens: for hgen in hgens: commutator = rmul(hgen, ggen, ~hgen, ~ggen) if commutator not in commutators: commutators.append(commutator) res = self.normal_closure(commutators) return res def coset_factor(self, g, factor_index=False): """Return ``G``'s (self's) coset factorization of ``g`` Explanation =========== If ``g`` is an element of ``G`` then it can be written as the product of permutations drawn from the Schreier-Sims coset decomposition, The permutations returned in ``f`` are those for which the product gives ``g``: ``g = f[n]*...f[1]*f[0]`` where ``n = len(B)`` and ``B = G.base``. f[i] is one of the permutations in ``self._basic_orbits[i]``. If factor_index==True, returns a tuple ``[b[0],..,b[n]]``, where ``b[i]`` belongs to ``self._basic_orbits[i]`` Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> a = Permutation(0, 1, 3, 7, 6, 4)(2, 5) >>> b = Permutation(0, 1, 3, 2)(4, 5, 7, 6) >>> G = PermutationGroup([a, b]) Define g: >>> g = Permutation(7)(1, 2, 4)(3, 6, 5) Confirm that it is an element of G: >>> G.contains(g) True Thus, it can be written as a product of factors (up to 3) drawn from u. See below that a factor from u1 and u2 and the Identity permutation have been used: >>> f = G.coset_factor(g) >>> f[2]*f[1]*f[0] == g True >>> f1 = G.coset_factor(g, True); f1 [0, 4, 4] >>> tr = G.basic_transversals >>> f[0] == tr[0][f1[0]] True If g is not an element of G then [] is returned: >>> c = Permutation(5, 6, 7) >>> G.coset_factor(c) [] See Also ======== sympy.combinatorics.util._strip """ if isinstance(g, (Cycle, Permutation)): g = g.list() if len(g) != self._degree: # this could either adjust the size or return [] immediately # but we don't choose between the two and just signal a possible # error raise ValueError('g should be the same size as permutations of G') I = list(range(self._degree)) basic_orbits = self.basic_orbits transversals = self._transversals factors = [] base = self.base h = g for i in range(len(base)): beta = h[base[i]] if beta == base[i]: factors.append(beta) continue if beta not in basic_orbits[i]: return [] u = transversals[i][beta]._array_form h = _af_rmul(_af_invert(u), h) factors.append(beta) if h != I: return [] if factor_index: return factors tr = self.basic_transversals factors = [tr[i][factors[i]] for i in range(len(base))] return factors def generator_product(self, g, original=False): ''' Return a list of strong generators `[s1, ..., sn]` s.t `g = sn*...*s1`. If `original=True`, make the list contain only the original group generators ''' product = [] if g.is_identity: return [] if g in self.strong_gens: if not original or g in self.generators: return [g] else: slp = self._strong_gens_slp[g] for s in slp: product.extend(self.generator_product(s, original=True)) return product elif g**-1 in self.strong_gens: g = g**-1 if not original or g in self.generators: return [g**-1] else: slp = self._strong_gens_slp[g] for s in slp: product.extend(self.generator_product(s, original=True)) l = len(product) product = [product[l-i-1]**-1 for i in range(l)] return product f = self.coset_factor(g, True) for i, j in enumerate(f): slp = self._transversal_slp[i][j] for s in slp: if not original: product.append(self.strong_gens[s]) else: s = self.strong_gens[s] product.extend(self.generator_product(s, original=True)) return product def coset_rank(self, g): """rank using Schreier-Sims representation. Explanation =========== The coset rank of ``g`` is the ordering number in which it appears in the lexicographic listing according to the coset decomposition The ordering is the same as in G.generate(method='coset'). If ``g`` does not belong to the group it returns None. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(0, 1, 3, 7, 6, 4)(2, 5) >>> b = Permutation(0, 1, 3, 2)(4, 5, 7, 6) >>> G = PermutationGroup([a, b]) >>> c = Permutation(7)(2, 4)(3, 5) >>> G.coset_rank(c) 16 >>> G.coset_unrank(16) (7)(2 4)(3 5) See Also ======== coset_factor """ factors = self.coset_factor(g, True) if not factors: return None rank = 0 b = 1 transversals = self._transversals base = self._base basic_orbits = self._basic_orbits for i in range(len(base)): k = factors[i] j = basic_orbits[i].index(k) rank += b*j b = b*len(transversals[i]) return rank def coset_unrank(self, rank, af=False): """unrank using Schreier-Sims representation coset_unrank is the inverse operation of coset_rank if 0 <= rank < order; otherwise it returns None. """ if rank < 0 or rank >= self.order(): return None base = self.base transversals = self.basic_transversals basic_orbits = self.basic_orbits m = len(base) v = [0]*m for i in range(m): rank, c = divmod(rank, len(transversals[i])) v[i] = basic_orbits[i][c] a = [transversals[i][v[i]]._array_form for i in range(m)] h = _af_rmuln(*a) if af: return h else: return _af_new(h) @property def degree(self): """Returns the size of the permutations in the group. Explanation =========== The number of permutations comprising the group is given by ``len(group)``; the number of permutations that can be generated by the group is given by ``group.order()``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2]) >>> G = PermutationGroup([a]) >>> G.degree 3 >>> len(G) 1 >>> G.order() 2 >>> list(G.generate()) [(2), (2)(0 1)] See Also ======== order """ return self._degree @property def identity(self): ''' Return the identity element of the permutation group. ''' return _af_new(list(range(self.degree))) @property def elements(self): """Returns all the elements of the permutation group as a set Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = PermutationGroup(Permutation(1, 3), Permutation(1, 2)) >>> p.elements {(1 2 3), (1 3 2), (1 3), (2 3), (3), (3)(1 2)} """ return set(self._elements) @property def _elements(self): """Returns all the elements of the permutation group as a list Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> p = PermutationGroup(Permutation(1, 3), Permutation(1, 2)) >>> p._elements [(3), (3)(1 2), (1 3), (2 3), (1 2 3), (1 3 2)] """ return list(islice(self.generate(), None)) def derived_series(self): r"""Return the derived series for the group. Explanation =========== The derived series for a group `G` is defined as `G = G_0 > G_1 > G_2 > \ldots` where `G_i = [G_{i-1}, G_{i-1}]`, i.e. `G_i` is the derived subgroup of `G_{i-1}`, for `i\in\mathbb{N}`. When we have `G_k = G_{k-1}` for some `k\in\mathbb{N}`, the series terminates. Returns ======= A list of permutation groups containing the members of the derived series in the order `G = G_0, G_1, G_2, \ldots`. Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup, DihedralGroup) >>> A = AlternatingGroup(5) >>> len(A.derived_series()) 1 >>> S = SymmetricGroup(4) >>> len(S.derived_series()) 4 >>> S.derived_series()[1].is_subgroup(AlternatingGroup(4)) True >>> S.derived_series()[2].is_subgroup(DihedralGroup(2)) True See Also ======== derived_subgroup """ res = [self] current = self next = self.derived_subgroup() while not current.is_subgroup(next): res.append(next) current = next next = next.derived_subgroup() return res def derived_subgroup(self): r"""Compute the derived subgroup. Explanation =========== The derived subgroup, or commutator subgroup is the subgroup generated by all commutators `[g, h] = hgh^{-1}g^{-1}` for `g, h\in G` ; it is equal to the normal closure of the set of commutators of the generators ([1], p.28, [11]). Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2, 4, 3]) >>> b = Permutation([0, 1, 3, 2, 4]) >>> G = PermutationGroup([a, b]) >>> C = G.derived_subgroup() >>> list(C.generate(af=True)) [[0, 1, 2, 3, 4], [0, 1, 3, 4, 2], [0, 1, 4, 2, 3]] See Also ======== derived_series """ r = self._r gens = [p._array_form for p in self.generators] set_commutators = set() degree = self._degree rng = list(range(degree)) for i in range(r): for j in range(r): p1 = gens[i] p2 = gens[j] c = list(range(degree)) for k in rng: c[p2[p1[k]]] = p1[p2[k]] ct = tuple(c) if not ct in set_commutators: set_commutators.add(ct) cms = [_af_new(p) for p in set_commutators] G2 = self.normal_closure(cms) return G2 def generate(self, method="coset", af=False): """Return iterator to generate the elements of the group. Explanation =========== Iteration is done with one of these methods:: method='coset' using the Schreier-Sims coset representation method='dimino' using the Dimino method If ``af = True`` it yields the array form of the permutations Examples ======== >>> from sympy.combinatorics import PermutationGroup >>> from sympy.combinatorics.polyhedron import tetrahedron The permutation group given in the tetrahedron object is also true groups: >>> G = tetrahedron.pgroup >>> G.is_group True Also the group generated by the permutations in the tetrahedron pgroup -- even the first two -- is a proper group: >>> H = PermutationGroup(G[0], G[1]) >>> J = PermutationGroup(list(H.generate())); J PermutationGroup([ (0 1)(2 3), (1 2 3), (1 3 2), (0 3 1), (0 2 3), (0 3)(1 2), (0 1 3), (3)(0 2 1), (0 3 2), (3)(0 1 2), (0 2)(1 3)]) >>> _.is_group True """ if method == "coset": return self.generate_schreier_sims(af) elif method == "dimino": return self.generate_dimino(af) else: raise NotImplementedError('No generation defined for %s' % method) def generate_dimino(self, af=False): """Yield group elements using Dimino's algorithm. If ``af == True`` it yields the array form of the permutations. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([0, 2, 3, 1]) >>> g = PermutationGroup([a, b]) >>> list(g.generate_dimino(af=True)) [[0, 1, 2, 3], [0, 2, 1, 3], [0, 2, 3, 1], [0, 1, 3, 2], [0, 3, 2, 1], [0, 3, 1, 2]] References ========== .. [1] The Implementation of Various Algorithms for Permutation Groups in the Computer Algebra System: AXIOM, N.J. Doye, M.Sc. Thesis """ idn = list(range(self.degree)) order = 0 element_list = [idn] set_element_list = {tuple(idn)} if af: yield idn else: yield _af_new(idn) gens = [p._array_form for p in self.generators] for i in range(len(gens)): # D elements of the subgroup G_i generated by gens[:i] D = element_list[:] N = [idn] while N: A = N N = [] for a in A: for g in gens[:i + 1]: ag = _af_rmul(a, g) if tuple(ag) not in set_element_list: # produce G_i*g for d in D: order += 1 ap = _af_rmul(d, ag) if af: yield ap else: p = _af_new(ap) yield p element_list.append(ap) set_element_list.add(tuple(ap)) N.append(ap) self._order = len(element_list) def generate_schreier_sims(self, af=False): """Yield group elements using the Schreier-Sims representation in coset_rank order If ``af = True`` it yields the array form of the permutations Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([0, 2, 3, 1]) >>> g = PermutationGroup([a, b]) >>> list(g.generate_schreier_sims(af=True)) [[0, 1, 2, 3], [0, 2, 1, 3], [0, 3, 2, 1], [0, 1, 3, 2], [0, 2, 3, 1], [0, 3, 1, 2]] """ n = self._degree u = self.basic_transversals basic_orbits = self._basic_orbits if len(u) == 0: for x in self.generators: if af: yield x._array_form else: yield x return if len(u) == 1: for i in basic_orbits[0]: if af: yield u[0][i]._array_form else: yield u[0][i] return u = list(reversed(u)) basic_orbits = basic_orbits[::-1] # stg stack of group elements stg = [list(range(n))] posmax = [len(x) for x in u] n1 = len(posmax) - 1 pos = [0]*n1 h = 0 while 1: # backtrack when finished iterating over coset if pos[h] >= posmax[h]: if h == 0: return pos[h] = 0 h -= 1 stg.pop() continue p = _af_rmul(u[h][basic_orbits[h][pos[h]]]._array_form, stg[-1]) pos[h] += 1 stg.append(p) h += 1 if h == n1: if af: for i in basic_orbits[-1]: p = _af_rmul(u[-1][i]._array_form, stg[-1]) yield p else: for i in basic_orbits[-1]: p = _af_rmul(u[-1][i]._array_form, stg[-1]) p1 = _af_new(p) yield p1 stg.pop() h -= 1 @property def generators(self): """Returns the generators of the group. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.generators [(1 2), (2)(0 1)] """ return self._generators def contains(self, g, strict=True): """Test if permutation ``g`` belong to self, ``G``. Explanation =========== If ``g`` is an element of ``G`` it can be written as a product of factors drawn from the cosets of ``G``'s stabilizers. To see if ``g`` is one of the actual generators defining the group use ``G.has(g)``. If ``strict`` is not ``True``, ``g`` will be resized, if necessary, to match the size of permutations in ``self``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1, 2) >>> b = Permutation(2, 3, 1) >>> G = PermutationGroup(a, b, degree=5) >>> G.contains(G[0]) # trivial check True >>> elem = Permutation([[2, 3]], size=5) >>> G.contains(elem) True >>> G.contains(Permutation(4)(0, 1, 2, 3)) False If strict is False, a permutation will be resized, if necessary: >>> H = PermutationGroup(Permutation(5)) >>> H.contains(Permutation(3)) False >>> H.contains(Permutation(3), strict=False) True To test if a given permutation is present in the group: >>> elem in G.generators False >>> G.has(elem) False See Also ======== coset_factor, sympy.core.basic.Basic.has, __contains__ """ if not isinstance(g, Permutation): return False if g.size != self.degree: if strict: return False g = Permutation(g, size=self.degree) if g in self.generators: return True return bool(self.coset_factor(g.array_form, True)) @property def is_perfect(self): """Return ``True`` if the group is perfect. A group is perfect if it equals to its derived subgroup. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1,2,3)(4,5) >>> b = Permutation(1,2,3,4,5) >>> G = PermutationGroup([a, b]) >>> G.is_perfect False """ if self._is_perfect is None: self._is_perfect = self == self.derived_subgroup() return self._is_perfect @property def is_abelian(self): """Test if the group is Abelian. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.is_abelian False >>> a = Permutation([0, 2, 1]) >>> G = PermutationGroup([a]) >>> G.is_abelian True """ if self._is_abelian is not None: return self._is_abelian self._is_abelian = True gens = [p._array_form for p in self.generators] for x in gens: for y in gens: if y <= x: continue if not _af_commutes_with(x, y): self._is_abelian = False return False return True def abelian_invariants(self): """ Returns the abelian invariants for the given group. Let ``G`` be a nontrivial finite abelian group. Then G is isomorphic to the direct product of finitely many nontrivial cyclic groups of prime-power order. Explanation =========== The prime-powers that occur as the orders of the factors are uniquely determined by G. More precisely, the primes that occur in the orders of the factors in any such decomposition of ``G`` are exactly the primes that divide ``|G|`` and for any such prime ``p``, if the orders of the factors that are p-groups in one such decomposition of ``G`` are ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``, then the orders of the factors that are p-groups in any such decomposition of ``G`` are ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``. The uniquely determined integers ``p^{t_1} >= p^{t_2} >= ... p^{t_r}``, taken for all primes that divide ``|G|`` are called the invariants of the nontrivial group ``G`` as suggested in ([14], p. 542). Notes ===== We adopt the convention that the invariants of a trivial group are []. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.abelian_invariants() [2] >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(7) >>> G.abelian_invariants() [7] """ if self.is_trivial: return [] gns = self.generators inv = [] G = self H = G.derived_subgroup() Hgens = H.generators for p in primefactors(G.order()): ranks = [] while True: pows = [] for g in gns: elm = g**p if not H.contains(elm): pows.append(elm) K = PermutationGroup(Hgens + pows) if pows else H r = G.order()//K.order() G = K gns = pows if r == 1: break; ranks.append(multiplicity(p, r)) if ranks: pows = [1]*ranks[0] for i in ranks: for j in range(0, i): pows[j] = pows[j]*p inv.extend(pows) inv.sort() return inv def is_elementary(self, p): """Return ``True`` if the group is elementary abelian. An elementary abelian group is a finite abelian group, where every nontrivial element has order `p`, where `p` is a prime. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> G = PermutationGroup([a]) >>> G.is_elementary(2) True >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([3, 1, 2, 0]) >>> G = PermutationGroup([a, b]) >>> G.is_elementary(2) True >>> G.is_elementary(3) False """ return self.is_abelian and all(g.order() == p for g in self.generators) def _eval_is_alt_sym_naive(self, only_sym=False, only_alt=False): """A naive test using the group order.""" if only_sym and only_alt: raise ValueError( "Both {} and {} cannot be set to True" .format(only_sym, only_alt)) n = self.degree sym_order = 1 for i in range(2, n+1): sym_order *= i order = self.order() if order == sym_order: self._is_sym = True self._is_alt = False if only_alt: return False return True elif 2*order == sym_order: self._is_sym = False self._is_alt = True if only_sym: return False return True return False def _eval_is_alt_sym_monte_carlo(self, eps=0.05, perms=None): """A test using monte-carlo algorithm. Parameters ========== eps : float, optional The criterion for the incorrect ``False`` return. perms : list[Permutation], optional If explicitly given, it tests over the given candidats for testing. If ``None``, it randomly computes ``N_eps`` and chooses ``N_eps`` sample of the permutation from the group. See Also ======== _check_cycles_alt_sym """ if perms is None: n = self.degree if n < 17: c_n = 0.34 else: c_n = 0.57 d_n = (c_n*log(2))/log(n) N_eps = int(-log(eps)/d_n) perms = (self.random_pr() for i in range(N_eps)) return self._eval_is_alt_sym_monte_carlo(perms=perms) for perm in perms: if _check_cycles_alt_sym(perm): return True return False def is_alt_sym(self, eps=0.05, _random_prec=None): r"""Monte Carlo test for the symmetric/alternating group for degrees >= 8. Explanation =========== More specifically, it is one-sided Monte Carlo with the answer True (i.e., G is symmetric/alternating) guaranteed to be correct, and the answer False being incorrect with probability eps. For degree < 8, the order of the group is checked so the test is deterministic. Notes ===== The algorithm itself uses some nontrivial results from group theory and number theory: 1) If a transitive group ``G`` of degree ``n`` contains an element with a cycle of length ``n/2 < p < n-2`` for ``p`` a prime, ``G`` is the symmetric or alternating group ([1], pp. 81-82) 2) The proportion of elements in the symmetric/alternating group having the property described in 1) is approximately `\log(2)/\log(n)` ([1], p.82; [2], pp. 226-227). The helper function ``_check_cycles_alt_sym`` is used to go over the cycles in a permutation and look for ones satisfying 1). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.is_alt_sym() False See Also ======== _check_cycles_alt_sym """ if _random_prec is not None: N_eps = _random_prec['N_eps'] perms= (_random_prec[i] for i in range(N_eps)) return self._eval_is_alt_sym_monte_carlo(perms=perms) if self._is_sym or self._is_alt: return True if self._is_sym is False and self._is_alt is False: return False n = self.degree if n < 8: return self._eval_is_alt_sym_naive() elif self.is_transitive(): return self._eval_is_alt_sym_monte_carlo(eps=eps) self._is_sym, self._is_alt = False, False return False @property def is_nilpotent(self): """Test if the group is nilpotent. Explanation =========== A group `G` is nilpotent if it has a central series of finite length. Alternatively, `G` is nilpotent if its lower central series terminates with the trivial group. Every nilpotent group is also solvable ([1], p.29, [12]). Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) >>> C = CyclicGroup(6) >>> C.is_nilpotent True >>> S = SymmetricGroup(5) >>> S.is_nilpotent False See Also ======== lower_central_series, is_solvable """ if self._is_nilpotent is None: lcs = self.lower_central_series() terminator = lcs[len(lcs) - 1] gens = terminator.generators degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in gens): self._is_solvable = True self._is_nilpotent = True return True else: self._is_nilpotent = False return False else: return self._is_nilpotent def is_normal(self, gr, strict=True): """Test if ``G=self`` is a normal subgroup of ``gr``. Explanation =========== G is normal in gr if for each g2 in G, g1 in gr, ``g = g1*g2*g1**-1`` belongs to G It is sufficient to check this for each g1 in gr.generators and g2 in G.generators. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 2, 0]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G1 = PermutationGroup([a, Permutation([2, 0, 1])]) >>> G1.is_normal(G) True """ if not self.is_subgroup(gr, strict=strict): return False d_self = self.degree d_gr = gr.degree if self.is_trivial and (d_self == d_gr or not strict): return True if self._is_abelian: return True new_self = self.copy() if not strict and d_self != d_gr: if d_self < d_gr: new_self = PermGroup(new_self.generators + [Permutation(d_gr - 1)]) else: gr = PermGroup(gr.generators + [Permutation(d_self - 1)]) gens2 = [p._array_form for p in new_self.generators] gens1 = [p._array_form for p in gr.generators] for g1 in gens1: for g2 in gens2: p = _af_rmuln(g1, g2, _af_invert(g1)) if not new_self.coset_factor(p, True): return False return True def is_primitive(self, randomized=True): r"""Test if a group is primitive. Explanation =========== A permutation group ``G`` acting on a set ``S`` is called primitive if ``S`` contains no nontrivial block under the action of ``G`` (a block is nontrivial if its cardinality is more than ``1``). Notes ===== The algorithm is described in [1], p.83, and uses the function minimal_block to search for blocks of the form `\{0, k\}` for ``k`` ranging over representatives for the orbits of `G_0`, the stabilizer of ``0``. This algorithm has complexity `O(n^2)` where ``n`` is the degree of the group, and will perform badly if `G_0` is small. There are two implementations offered: one finds `G_0` deterministically using the function ``stabilizer``, and the other (default) produces random elements of `G_0` using ``random_stab``, hoping that they generate a subgroup of `G_0` with not too many more orbits than `G_0` (this is suggested in [1], p.83). Behavior is changed by the ``randomized`` flag. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.is_primitive() False See Also ======== minimal_block, random_stab """ if self._is_primitive is not None: return self._is_primitive if self.is_transitive() is False: return False if randomized: random_stab_gens = [] v = self.schreier_vector(0) for i in range(len(self)): random_stab_gens.append(self.random_stab(0, v)) stab = PermutationGroup(random_stab_gens) else: stab = self.stabilizer(0) orbits = stab.orbits() for orb in orbits: x = orb.pop() if x != 0 and any(e != 0 for e in self.minimal_block([0, x])): self._is_primitive = False return False self._is_primitive = True return True def minimal_blocks(self, randomized=True): ''' For a transitive group, return the list of all minimal block systems. If a group is intransitive, return `False`. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.named_groups import DihedralGroup >>> DihedralGroup(6).minimal_blocks() [[0, 1, 0, 1, 0, 1], [0, 1, 2, 0, 1, 2]] >>> G = PermutationGroup(Permutation(1,2,5)) >>> G.minimal_blocks() False See Also ======== minimal_block, is_transitive, is_primitive ''' def _number_blocks(blocks): # number the blocks of a block system # in order and return the number of # blocks and the tuple with the # reordering n = len(blocks) appeared = {} m = 0 b = [None]*n for i in range(n): if blocks[i] not in appeared: appeared[blocks[i]] = m b[i] = m m += 1 else: b[i] = appeared[blocks[i]] return tuple(b), m if not self.is_transitive(): return False blocks = [] num_blocks = [] rep_blocks = [] if randomized: random_stab_gens = [] v = self.schreier_vector(0) for i in range(len(self)): random_stab_gens.append(self.random_stab(0, v)) stab = PermutationGroup(random_stab_gens) else: stab = self.stabilizer(0) orbits = stab.orbits() for orb in orbits: x = orb.pop() if x != 0: block = self.minimal_block([0, x]) num_block, m = _number_blocks(block) # a representative block (containing 0) rep = {j for j in range(self.degree) if num_block[j] == 0} # check if the system is minimal with # respect to the already discovere ones minimal = True blocks_remove_mask = [False] * len(blocks) for i, r in enumerate(rep_blocks): if len(r) > len(rep) and rep.issubset(r): # i-th block system is not minimal blocks_remove_mask[i] = True elif len(r) < len(rep) and r.issubset(rep): # the system being checked is not minimal minimal = False break # remove non-minimal representative blocks blocks = [b for i, b in enumerate(blocks) if not blocks_remove_mask[i]] num_blocks = [n for i, n in enumerate(num_blocks) if not blocks_remove_mask[i]] rep_blocks = [r for i, r in enumerate(rep_blocks) if not blocks_remove_mask[i]] if minimal and num_block not in num_blocks: blocks.append(block) num_blocks.append(num_block) rep_blocks.append(rep) return blocks @property def is_solvable(self): """Test if the group is solvable. ``G`` is solvable if its derived series terminates with the trivial group ([1], p.29). Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(3) >>> S.is_solvable True See Also ======== is_nilpotent, derived_series """ if self._is_solvable is None: if self.order() % 2 != 0: return True ds = self.derived_series() terminator = ds[len(ds) - 1] gens = terminator.generators degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in gens): self._is_solvable = True return True else: self._is_solvable = False return False else: return self._is_solvable def is_subgroup(self, G, strict=True): """Return ``True`` if all elements of ``self`` belong to ``G``. If ``strict`` is ``False`` then if ``self``'s degree is smaller than ``G``'s, the elements will be resized to have the same degree. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup) Testing is strict by default: the degree of each group must be the same: >>> p = Permutation(0, 1, 2, 3, 4, 5) >>> G1 = PermutationGroup([Permutation(0, 1, 2), Permutation(0, 1)]) >>> G2 = PermutationGroup([Permutation(0, 2), Permutation(0, 1, 2)]) >>> G3 = PermutationGroup([p, p**2]) >>> assert G1.order() == G2.order() == G3.order() == 6 >>> G1.is_subgroup(G2) True >>> G1.is_subgroup(G3) False >>> G3.is_subgroup(PermutationGroup(G3[1])) False >>> G3.is_subgroup(PermutationGroup(G3[0])) True To ignore the size, set ``strict`` to ``False``: >>> S3 = SymmetricGroup(3) >>> S5 = SymmetricGroup(5) >>> S3.is_subgroup(S5, strict=False) True >>> C7 = CyclicGroup(7) >>> G = S5*C7 >>> S5.is_subgroup(G, False) True >>> C7.is_subgroup(G, 0) False """ if isinstance(G, SymmetricPermutationGroup): if self.degree != G.degree: return False return True if not isinstance(G, PermutationGroup): return False if self == G or self.generators[0]==Permutation(): return True if G.order() % self.order() != 0: return False if self.degree == G.degree or \ (self.degree < G.degree and not strict): gens = self.generators else: return False return all(G.contains(g, strict=strict) for g in gens) @property def is_polycyclic(self): """Return ``True`` if a group is polycyclic. A group is polycyclic if it has a subnormal series with cyclic factors. For finite groups, this is the same as if the group is solvable. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([2, 0, 1, 3]) >>> G = PermutationGroup([a, b]) >>> G.is_polycyclic True """ return self.is_solvable def is_transitive(self, strict=True): """Test if the group is transitive. Explanation =========== A group is transitive if it has a single orbit. If ``strict`` is ``False`` the group is transitive if it has a single orbit of length different from 1. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1, 3]) >>> b = Permutation([2, 0, 1, 3]) >>> G1 = PermutationGroup([a, b]) >>> G1.is_transitive() False >>> G1.is_transitive(strict=False) True >>> c = Permutation([2, 3, 0, 1]) >>> G2 = PermutationGroup([a, c]) >>> G2.is_transitive() True >>> d = Permutation([1, 0, 2, 3]) >>> e = Permutation([0, 1, 3, 2]) >>> G3 = PermutationGroup([d, e]) >>> G3.is_transitive() or G3.is_transitive(strict=False) False """ if self._is_transitive: # strict or not, if True then True return self._is_transitive if strict: if self._is_transitive is not None: # we only store strict=True return self._is_transitive ans = len(self.orbit(0)) == self.degree self._is_transitive = ans return ans got_orb = False for x in self.orbits(): if len(x) > 1: if got_orb: return False got_orb = True return got_orb @property def is_trivial(self): """Test if the group is the trivial group. This is true if the group contains only the identity permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> G = PermutationGroup([Permutation([0, 1, 2])]) >>> G.is_trivial True """ if self._is_trivial is None: self._is_trivial = len(self) == 1 and self[0].is_Identity return self._is_trivial def lower_central_series(self): r"""Return the lower central series for the group. The lower central series for a group `G` is the series `G = G_0 > G_1 > G_2 > \ldots` where `G_k = [G, G_{k-1}]`, i.e. every term after the first is equal to the commutator of `G` and the previous term in `G1` ([1], p.29). Returns ======= A list of permutation groups in the order `G = G_0, G_1, G_2, \ldots` Examples ======== >>> from sympy.combinatorics.named_groups import (AlternatingGroup, ... DihedralGroup) >>> A = AlternatingGroup(4) >>> len(A.lower_central_series()) 2 >>> A.lower_central_series()[1].is_subgroup(DihedralGroup(2)) True See Also ======== commutator, derived_series """ res = [self] current = self next = self.commutator(self, current) while not current.is_subgroup(next): res.append(next) current = next next = self.commutator(self, current) return res @property def max_div(self): """Maximum proper divisor of the degree of a permutation group. Explanation =========== Obviously, this is the degree divided by its minimal proper divisor (larger than ``1``, if one exists). As it is guaranteed to be prime, the ``sieve`` from ``sympy.ntheory`` is used. This function is also used as an optimization tool for the functions ``minimal_block`` and ``_union_find_merge``. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> G = PermutationGroup([Permutation([0, 2, 1, 3])]) >>> G.max_div 2 See Also ======== minimal_block, _union_find_merge """ if self._max_div is not None: return self._max_div n = self.degree if n == 1: return 1 for x in sieve: if n % x == 0: d = n//x self._max_div = d return d def minimal_block(self, points): r"""For a transitive group, finds the block system generated by ``points``. Explanation =========== If a group ``G`` acts on a set ``S``, a nonempty subset ``B`` of ``S`` is called a block under the action of ``G`` if for all ``g`` in ``G`` we have ``gB = B`` (``g`` fixes ``B``) or ``gB`` and ``B`` have no common points (``g`` moves ``B`` entirely). ([1], p.23; [6]). The distinct translates ``gB`` of a block ``B`` for ``g`` in ``G`` partition the set ``S`` and this set of translates is known as a block system. Moreover, we obviously have that all blocks in the partition have the same size, hence the block size divides ``|S|`` ([1], p.23). A ``G``-congruence is an equivalence relation ``~`` on the set ``S`` such that ``a ~ b`` implies ``g(a) ~ g(b)`` for all ``g`` in ``G``. For a transitive group, the equivalence classes of a ``G``-congruence and the blocks of a block system are the same thing ([1], p.23). The algorithm below checks the group for transitivity, and then finds the ``G``-congruence generated by the pairs ``(p_0, p_1), (p_0, p_2), ..., (p_0,p_{k-1})`` which is the same as finding the maximal block system (i.e., the one with minimum block size) such that ``p_0, ..., p_{k-1}`` are in the same block ([1], p.83). It is an implementation of Atkinson's algorithm, as suggested in [1], and manipulates an equivalence relation on the set ``S`` using a union-find data structure. The running time is just above `O(|points||S|)`. ([1], pp. 83-87; [7]). Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(10) >>> D.minimal_block([0, 5]) [0, 1, 2, 3, 4, 0, 1, 2, 3, 4] >>> D.minimal_block([0, 1]) [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] See Also ======== _union_find_rep, _union_find_merge, is_transitive, is_primitive """ if not self.is_transitive(): return False n = self.degree gens = self.generators # initialize the list of equivalence class representatives parents = list(range(n)) ranks = [1]*n not_rep = [] k = len(points) # the block size must divide the degree of the group if k > self.max_div: return [0]*n for i in range(k - 1): parents[points[i + 1]] = points[0] not_rep.append(points[i + 1]) ranks[points[0]] = k i = 0 len_not_rep = k - 1 while i < len_not_rep: gamma = not_rep[i] i += 1 for gen in gens: # find has side effects: performs path compression on the list # of representatives delta = self._union_find_rep(gamma, parents) # union has side effects: performs union by rank on the list # of representatives temp = self._union_find_merge(gen(gamma), gen(delta), ranks, parents, not_rep) if temp == -1: return [0]*n len_not_rep += temp for i in range(n): # force path compression to get the final state of the equivalence # relation self._union_find_rep(i, parents) # rewrite result so that block representatives are minimal new_reps = {} return [new_reps.setdefault(r, i) for i, r in enumerate(parents)] def conjugacy_class(self, x): r"""Return the conjugacy class of an element in the group. Explanation =========== The conjugacy class of an element ``g`` in a group ``G`` is the set of elements ``x`` in ``G`` that are conjugate with ``g``, i.e. for which ``g = xax^{-1}`` for some ``a`` in ``G``. Note that conjugacy is an equivalence relation, and therefore that conjugacy classes are partitions of ``G``. For a list of all the conjugacy classes of the group, use the conjugacy_classes() method. In a permutation group, each conjugacy class corresponds to a particular `cycle structure': for example, in ``S_3``, the conjugacy classes are: * the identity class, ``{()}`` * all transpositions, ``{(1 2), (1 3), (2 3)}`` * all 3-cycles, ``{(1 2 3), (1 3 2)}`` Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S3 = SymmetricGroup(3) >>> S3.conjugacy_class(Permutation(0, 1, 2)) {(0 1 2), (0 2 1)} Notes ===== This procedure computes the conjugacy class directly by finding the orbit of the element under conjugation in G. This algorithm is only feasible for permutation groups of relatively small order, but is like the orbit() function itself in that respect. """ # Ref: "Computing the conjugacy classes of finite groups"; Butler, G. # Groups '93 Galway/St Andrews; edited by Campbell, C. M. new_class = {x} last_iteration = new_class while len(last_iteration) > 0: this_iteration = set() for y in last_iteration: for s in self.generators: conjugated = s * y * (~s) if conjugated not in new_class: this_iteration.add(conjugated) new_class.update(last_iteration) last_iteration = this_iteration return new_class def conjugacy_classes(self): r"""Return the conjugacy classes of the group. Explanation =========== As described in the documentation for the .conjugacy_class() function, conjugacy is an equivalence relation on a group G which partitions the set of elements. This method returns a list of all these conjugacy classes of G. Examples ======== >>> from sympy.combinatorics import SymmetricGroup >>> SymmetricGroup(3).conjugacy_classes() [{(2)}, {(0 1 2), (0 2 1)}, {(0 2), (1 2), (2)(0 1)}] """ identity = _af_new(list(range(self.degree))) known_elements = {identity} classes = [known_elements.copy()] for x in self.generate(): if x not in known_elements: new_class = self.conjugacy_class(x) classes.append(new_class) known_elements.update(new_class) return classes def normal_closure(self, other, k=10): r"""Return the normal closure of a subgroup/set of permutations. Explanation =========== If ``S`` is a subset of a group ``G``, the normal closure of ``A`` in ``G`` is defined as the intersection of all normal subgroups of ``G`` that contain ``A`` ([1], p.14). Alternatively, it is the group generated by the conjugates ``x^{-1}yx`` for ``x`` a generator of ``G`` and ``y`` a generator of the subgroup ``\left\langle S\right\rangle`` generated by ``S`` (for some chosen generating set for ``\left\langle S\right\rangle``) ([1], p.73). Parameters ========== other a subgroup/list of permutations/single permutation k an implementation-specific parameter that determines the number of conjugates that are adjoined to ``other`` at once Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... CyclicGroup, AlternatingGroup) >>> S = SymmetricGroup(5) >>> C = CyclicGroup(5) >>> G = S.normal_closure(C) >>> G.order() 60 >>> G.is_subgroup(AlternatingGroup(5)) True See Also ======== commutator, derived_subgroup, random_pr Notes ===== The algorithm is described in [1], pp. 73-74; it makes use of the generation of random elements for permutation groups by the product replacement algorithm. """ if hasattr(other, 'generators'): degree = self.degree identity = _af_new(list(range(degree))) if all(g == identity for g in other.generators): return other Z = PermutationGroup(other.generators[:]) base, strong_gens = Z.schreier_sims_incremental() strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, basic_transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) self._random_pr_init(r=10, n=20) _loop = True while _loop: Z._random_pr_init(r=10, n=10) for i in range(k): g = self.random_pr() h = Z.random_pr() conj = h^g res = _strip(conj, base, basic_orbits, basic_transversals) if res[0] != identity or res[1] != len(base) + 1: gens = Z.generators gens.append(conj) Z = PermutationGroup(gens) strong_gens.append(conj) temp_base, temp_strong_gens = \ Z.schreier_sims_incremental(base, strong_gens) base, strong_gens = temp_base, temp_strong_gens strong_gens_distr = \ _distribute_gens_by_base(base, strong_gens) basic_orbits, basic_transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) _loop = False for g in self.generators: for h in Z.generators: conj = h^g res = _strip(conj, base, basic_orbits, basic_transversals) if res[0] != identity or res[1] != len(base) + 1: _loop = True break if _loop: break return Z elif hasattr(other, '__getitem__'): return self.normal_closure(PermutationGroup(other)) elif hasattr(other, 'array_form'): return self.normal_closure(PermutationGroup([other])) def orbit(self, alpha, action='tuples'): r"""Compute the orbit of alpha `\{g(\alpha) | g \in G\}` as a set. Explanation =========== The time complexity of the algorithm used here is `O(|Orb|*r)` where `|Orb|` is the size of the orbit and ``r`` is the number of generators of the group. For a more detailed analysis, see [1], p.78, [2], pp. 19-21. Here alpha can be a single point, or a list of points. If alpha is a single point, the ordinary orbit is computed. if alpha is a list of points, there are three available options: 'union' - computes the union of the orbits of the points in the list 'tuples' - computes the orbit of the list interpreted as an ordered tuple under the group action ( i.e., g((1,2,3)) = (g(1), g(2), g(3)) ) 'sets' - computes the orbit of the list interpreted as a sets Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 2, 0, 4, 5, 6, 3]) >>> G = PermutationGroup([a]) >>> G.orbit(0) {0, 1, 2} >>> G.orbit([0, 4], 'union') {0, 1, 2, 3, 4, 5, 6} See Also ======== orbit_transversal """ return _orbit(self.degree, self.generators, alpha, action) def orbit_rep(self, alpha, beta, schreier_vector=None): """Return a group element which sends ``alpha`` to ``beta``. Explanation =========== If ``beta`` is not in the orbit of ``alpha``, the function returns ``False``. This implementation makes use of the schreier vector. For a proof of correctness, see [1], p.80 Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> G = AlternatingGroup(5) >>> G.orbit_rep(0, 4) (0 4 1 2 3) See Also ======== schreier_vector """ if schreier_vector is None: schreier_vector = self.schreier_vector(alpha) if schreier_vector[beta] is None: return False k = schreier_vector[beta] gens = [x._array_form for x in self.generators] a = [] while k != -1: a.append(gens[k]) beta = gens[k].index(beta) # beta = (~gens[k])(beta) k = schreier_vector[beta] if a: return _af_new(_af_rmuln(*a)) else: return _af_new(list(range(self._degree))) def orbit_transversal(self, alpha, pairs=False): r"""Computes a transversal for the orbit of ``alpha`` as a set. Explanation =========== For a permutation group `G`, a transversal for the orbit `Orb = \{g(\alpha) | g \in G\}` is a set `\{g_\beta | g_\beta(\alpha) = \beta\}` for `\beta \in Orb`. Note that there may be more than one possible transversal. If ``pairs`` is set to ``True``, it returns the list of pairs `(\beta, g_\beta)`. For a proof of correctness, see [1], p.79 Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> G.orbit_transversal(0) [(5), (0 1 2 3 4 5), (0 5)(1 4)(2 3), (0 2 4)(1 3 5), (5)(0 4)(1 3), (0 3)(1 4)(2 5)] See Also ======== orbit """ return _orbit_transversal(self._degree, self.generators, alpha, pairs) def orbits(self, rep=False): """Return the orbits of ``self``, ordered according to lowest element in each orbit. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1, 5)(2, 3)(4, 0, 6) >>> b = Permutation(1, 5)(3, 4)(2, 6, 0) >>> G = PermutationGroup([a, b]) >>> G.orbits() [{0, 2, 3, 4, 6}, {1, 5}] """ return _orbits(self._degree, self._generators) def order(self): """Return the order of the group: the number of permutations that can be generated from elements of the group. The number of permutations comprising the group is given by ``len(group)``; the length of each permutation in the group is given by ``group.size``. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([1, 0, 2]) >>> G = PermutationGroup([a]) >>> G.degree 3 >>> len(G) 1 >>> G.order() 2 >>> list(G.generate()) [(2), (2)(0 1)] >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.order() 6 See Also ======== degree """ if self._order is not None: return self._order if self._is_sym: n = self._degree self._order = factorial(n) return self._order if self._is_alt: n = self._degree self._order = factorial(n)/2 return self._order basic_transversals = self.basic_transversals m = 1 for x in basic_transversals: m *= len(x) self._order = m return m def index(self, H): """ Returns the index of a permutation group. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation(1,2,3) >>> b =Permutation(3) >>> G = PermutationGroup([a]) >>> H = PermutationGroup([b]) >>> G.index(H) 3 """ if H.is_subgroup(self): return self.order()//H.order() @property def is_symmetric(self): """Return ``True`` if the group is symmetric. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> g = SymmetricGroup(5) >>> g.is_symmetric True >>> from sympy.combinatorics import Permutation, PermutationGroup >>> g = PermutationGroup( ... Permutation(0, 1, 2, 3, 4), ... Permutation(2, 3)) >>> g.is_symmetric True Notes ===== This uses a naive test involving the computation of the full group order. If you need more quicker taxonomy for large groups, you can use :meth:`PermutationGroup.is_alt_sym`. However, :meth:`PermutationGroup.is_alt_sym` may not be accurate and is not able to distinguish between an alternating group and a symmetric group. See Also ======== is_alt_sym """ _is_sym = self._is_sym if _is_sym is not None: return _is_sym n = self.degree if n >= 8: if self.is_transitive(): _is_alt_sym = self._eval_is_alt_sym_monte_carlo() if _is_alt_sym: if any(g.is_odd for g in self.generators): self._is_sym, self._is_alt = True, False return True self._is_sym, self._is_alt = False, True return False return self._eval_is_alt_sym_naive(only_sym=True) self._is_sym, self._is_alt = False, False return False return self._eval_is_alt_sym_naive(only_sym=True) @property def is_alternating(self): """Return ``True`` if the group is alternating. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> g = AlternatingGroup(5) >>> g.is_alternating True >>> from sympy.combinatorics import Permutation, PermutationGroup >>> g = PermutationGroup( ... Permutation(0, 1, 2, 3, 4), ... Permutation(2, 3, 4)) >>> g.is_alternating True Notes ===== This uses a naive test involving the computation of the full group order. If you need more quicker taxonomy for large groups, you can use :meth:`PermutationGroup.is_alt_sym`. However, :meth:`PermutationGroup.is_alt_sym` may not be accurate and is not able to distinguish between an alternating group and a symmetric group. See Also ======== is_alt_sym """ _is_alt = self._is_alt if _is_alt is not None: return _is_alt n = self.degree if n >= 8: if self.is_transitive(): _is_alt_sym = self._eval_is_alt_sym_monte_carlo() if _is_alt_sym: if all(g.is_even for g in self.generators): self._is_sym, self._is_alt = False, True return True self._is_sym, self._is_alt = True, False return False return self._eval_is_alt_sym_naive(only_alt=True) self._is_sym, self._is_alt = False, False return False return self._eval_is_alt_sym_naive(only_alt=True) @classmethod def _distinct_primes_lemma(cls, primes): """Subroutine to test if there is only one cyclic group for the order.""" primes = sorted(primes) l = len(primes) for i in range(l): for j in range(i+1, l): if primes[j] % primes[i] == 1: return None return True @property def is_cyclic(self): r""" Return ``True`` if the group is Cyclic. Examples ======== >>> from sympy.combinatorics.named_groups import AbelianGroup >>> G = AbelianGroup(3, 4) >>> G.is_cyclic True >>> G = AbelianGroup(4, 4) >>> G.is_cyclic False Notes ===== If the order of a group $n$ can be factored into the distinct primes $p_1, p_2, ... , p_s$ and if .. math:: \forall i, j \in \{1, 2, \ldots, s \}: p_i \not \equiv 1 \pmod {p_j} holds true, there is only one group of the order $n$ which is a cyclic group. [1]_ This is a generalization of the lemma that the group of order $15, 35, ...$ are cyclic. And also, these additional lemmas can be used to test if a group is cyclic if the order of the group is already found. - If the group is abelian and the order of the group is square-free, the group is cyclic. - If the order of the group is less than $6$ and is not $4$, the group is cyclic. - If the order of the group is prime, the group is cyclic. References ========== .. [1] 1978: John S. Rose: A Course on Group Theory, Introduction to Finite Group Theory: 1.4 """ if self._is_cyclic is not None: return self._is_cyclic if len(self.generators) == 1: self._is_cyclic = True self._is_abelian = True return True if self._is_abelian is False: self._is_cyclic = False return False order = self.order() if order < 6: self._is_abelian == True if order != 4: self._is_cyclic == True return True factors = factorint(order) if all(v == 1 for v in factors.values()): if self._is_abelian: self._is_cyclic = True return True primes = list(factors.keys()) if PermutationGroup._distinct_primes_lemma(primes) is True: self._is_cyclic = True self._is_abelian = True return True for p in factors: pgens = [] for g in self.generators: pgens.append(g**p) if self.index(self.subgroup(pgens)) != p: self._is_cyclic = False return False self._is_cyclic = True self._is_abelian = True return True def pointwise_stabilizer(self, points, incremental=True): r"""Return the pointwise stabilizer for a set of points. Explanation =========== For a permutation group `G` and a set of points `\{p_1, p_2,\ldots, p_k\}`, the pointwise stabilizer of `p_1, p_2, \ldots, p_k` is defined as `G_{p_1,\ldots, p_k} = \{g\in G | g(p_i) = p_i \forall i\in\{1, 2,\ldots,k\}\}` ([1],p20). It is a subgroup of `G`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(7) >>> Stab = S.pointwise_stabilizer([2, 3, 5]) >>> Stab.is_subgroup(S.stabilizer(2).stabilizer(3).stabilizer(5)) True See Also ======== stabilizer, schreier_sims_incremental Notes ===== When incremental == True, rather than the obvious implementation using successive calls to ``.stabilizer()``, this uses the incremental Schreier-Sims algorithm to obtain a base with starting segment - the given points. """ if incremental: base, strong_gens = self.schreier_sims_incremental(base=points) stab_gens = [] degree = self.degree for gen in strong_gens: if [gen(point) for point in points] == points: stab_gens.append(gen) if not stab_gens: stab_gens = _af_new(list(range(degree))) return PermutationGroup(stab_gens) else: gens = self._generators degree = self.degree for x in points: gens = _stabilizer(degree, gens, x) return PermutationGroup(gens) def make_perm(self, n, seed=None): """ Multiply ``n`` randomly selected permutations from pgroup together, starting with the identity permutation. If ``n`` is a list of integers, those integers will be used to select the permutations and they will be applied in L to R order: make_perm((A, B, C)) will give CBA(I) where I is the identity permutation. ``seed`` is used to set the seed for the random selection of permutations from pgroup. If this is a list of integers, the corresponding permutations from pgroup will be selected in the order give. This is mainly used for testing purposes. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a, b = [Permutation([1, 0, 3, 2]), Permutation([1, 3, 0, 2])] >>> G = PermutationGroup([a, b]) >>> G.make_perm(1, [0]) (0 1)(2 3) >>> G.make_perm(3, [0, 1, 0]) (0 2 3 1) >>> G.make_perm([0, 1, 0]) (0 2 3 1) See Also ======== random """ if is_sequence(n): if seed is not None: raise ValueError('If n is a sequence, seed should be None') n, seed = len(n), n else: try: n = int(n) except TypeError: raise ValueError('n must be an integer or a sequence.') randrange = _randrange(seed) # start with the identity permutation result = Permutation(list(range(self.degree))) m = len(self) for i in range(n): p = self[randrange(m)] result = rmul(result, p) return result def random(self, af=False): """Return a random group element """ rank = randrange(self.order()) return self.coset_unrank(rank, af) def random_pr(self, gen_count=11, iterations=50, _random_prec=None): """Return a random group element using product replacement. Explanation =========== For the details of the product replacement algorithm, see ``_random_pr_init`` In ``random_pr`` the actual 'product replacement' is performed. Notice that if the attribute ``_random_gens`` is empty, it needs to be initialized by ``_random_pr_init``. See Also ======== _random_pr_init """ if self._random_gens == []: self._random_pr_init(gen_count, iterations) random_gens = self._random_gens r = len(random_gens) - 1 # handle randomized input for testing purposes if _random_prec is None: s = randrange(r) t = randrange(r - 1) if t == s: t = r - 1 x = choice([1, 2]) e = choice([-1, 1]) else: s = _random_prec['s'] t = _random_prec['t'] if t == s: t = r - 1 x = _random_prec['x'] e = _random_prec['e'] if x == 1: random_gens[s] = _af_rmul(random_gens[s], _af_pow(random_gens[t], e)) random_gens[r] = _af_rmul(random_gens[r], random_gens[s]) else: random_gens[s] = _af_rmul(_af_pow(random_gens[t], e), random_gens[s]) random_gens[r] = _af_rmul(random_gens[s], random_gens[r]) return _af_new(random_gens[r]) def random_stab(self, alpha, schreier_vector=None, _random_prec=None): """Random element from the stabilizer of ``alpha``. The schreier vector for ``alpha`` is an optional argument used for speeding up repeated calls. The algorithm is described in [1], p.81 See Also ======== random_pr, orbit_rep """ if schreier_vector is None: schreier_vector = self.schreier_vector(alpha) if _random_prec is None: rand = self.random_pr() else: rand = _random_prec['rand'] beta = rand(alpha) h = self.orbit_rep(alpha, beta, schreier_vector) return rmul(~h, rand) def schreier_sims(self): """Schreier-Sims algorithm. Explanation =========== It computes the generators of the chain of stabilizers `G > G_{b_1} > .. > G_{b1,..,b_r} > 1` in which `G_{b_1,..,b_i}` stabilizes `b_1,..,b_i`, and the corresponding ``s`` cosets. An element of the group can be written as the product `h_1*..*h_s`. We use the incremental Schreier-Sims algorithm. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.schreier_sims() >>> G.basic_transversals [{0: (2)(0 1), 1: (2), 2: (1 2)}, {0: (2), 2: (0 2)}] """ if self._transversals: return self._schreier_sims() return def _schreier_sims(self, base=None): schreier = self.schreier_sims_incremental(base=base, slp_dict=True) base, strong_gens = schreier[:2] self._base = base self._strong_gens = strong_gens self._strong_gens_slp = schreier[2] if not base: self._transversals = [] self._basic_orbits = [] return strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, transversals, slps = _orbits_transversals_from_bsgs(base,\ strong_gens_distr, slp=True) # rewrite the indices stored in slps in terms of strong_gens for i, slp in enumerate(slps): gens = strong_gens_distr[i] for k in slp: slp[k] = [strong_gens.index(gens[s]) for s in slp[k]] self._transversals = transversals self._basic_orbits = [sorted(x) for x in basic_orbits] self._transversal_slp = slps def schreier_sims_incremental(self, base=None, gens=None, slp_dict=False): """Extend a sequence of points and generating set to a base and strong generating set. Parameters ========== base The sequence of points to be extended to a base. Optional parameter with default value ``[]``. gens The generating set to be extended to a strong generating set relative to the base obtained. Optional parameter with default value ``self.generators``. slp_dict If `True`, return a dictionary `{g: gens}` for each strong generator `g` where `gens` is a list of strong generators coming before `g` in `strong_gens`, such that the product of the elements of `gens` is equal to `g`. Returns ======= (base, strong_gens) ``base`` is the base obtained, and ``strong_gens`` is the strong generating set relative to it. The original parameters ``base``, ``gens`` remain unchanged. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> from sympy.combinatorics.testutil import _verify_bsgs >>> A = AlternatingGroup(7) >>> base = [2, 3] >>> seq = [2, 3] >>> base, strong_gens = A.schreier_sims_incremental(base=seq) >>> _verify_bsgs(A, base, strong_gens) True >>> base[:2] [2, 3] Notes ===== This version of the Schreier-Sims algorithm runs in polynomial time. There are certain assumptions in the implementation - if the trivial group is provided, ``base`` and ``gens`` are returned immediately, as any sequence of points is a base for the trivial group. If the identity is present in the generators ``gens``, it is removed as it is a redundant generator. The implementation is described in [1], pp. 90-93. See Also ======== schreier_sims, schreier_sims_random """ if base is None: base = [] if gens is None: gens = self.generators[:] degree = self.degree id_af = list(range(degree)) # handle the trivial group if len(gens) == 1 and gens[0].is_Identity: if slp_dict: return base, gens, {gens[0]: [gens[0]]} return base, gens # prevent side effects _base, _gens = base[:], gens[:] # remove the identity as a generator _gens = [x for x in _gens if not x.is_Identity] # make sure no generator fixes all base points for gen in _gens: if all(x == gen._array_form[x] for x in _base): for new in id_af: if gen._array_form[new] != new: break else: assert None # can this ever happen? _base.append(new) # distribute generators according to basic stabilizers strong_gens_distr = _distribute_gens_by_base(_base, _gens) strong_gens_slp = [] # initialize the basic stabilizers, basic orbits and basic transversals orbs = {} transversals = {} slps = {} base_len = len(_base) for i in range(base_len): transversals[i], slps[i] = _orbit_transversal(degree, strong_gens_distr[i], _base[i], pairs=True, af=True, slp=True) transversals[i] = dict(transversals[i]) orbs[i] = list(transversals[i].keys()) # main loop: amend the stabilizer chain until we have generators # for all stabilizers i = base_len - 1 while i >= 0: # this flag is used to continue with the main loop from inside # a nested loop continue_i = False # test the generators for being a strong generating set db = {} for beta, u_beta in list(transversals[i].items()): for j, gen in enumerate(strong_gens_distr[i]): gb = gen._array_form[beta] u1 = transversals[i][gb] g1 = _af_rmul(gen._array_form, u_beta) slp = [(i, g) for g in slps[i][beta]] slp = [(i, j)] + slp if g1 != u1: # test if the schreier generator is in the i+1-th # would-be basic stabilizer y = True try: u1_inv = db[gb] except KeyError: u1_inv = db[gb] = _af_invert(u1) schreier_gen = _af_rmul(u1_inv, g1) u1_inv_slp = slps[i][gb][:] u1_inv_slp.reverse() u1_inv_slp = [(i, (g,)) for g in u1_inv_slp] slp = u1_inv_slp + slp h, j, slp = _strip_af(schreier_gen, _base, orbs, transversals, i, slp=slp, slps=slps) if j <= base_len: # new strong generator h at level j y = False elif h: # h fixes all base points y = False moved = 0 while h[moved] == moved: moved += 1 _base.append(moved) base_len += 1 strong_gens_distr.append([]) if y is False: # if a new strong generator is found, update the # data structures and start over h = _af_new(h) strong_gens_slp.append((h, slp)) for l in range(i + 1, j): strong_gens_distr[l].append(h) transversals[l], slps[l] =\ _orbit_transversal(degree, strong_gens_distr[l], _base[l], pairs=True, af=True, slp=True) transversals[l] = dict(transversals[l]) orbs[l] = list(transversals[l].keys()) i = j - 1 # continue main loop using the flag continue_i = True if continue_i is True: break if continue_i is True: break if continue_i is True: continue i -= 1 strong_gens = _gens[:] if slp_dict: # create the list of the strong generators strong_gens and # rewrite the indices of strong_gens_slp in terms of the # elements of strong_gens for k, slp in strong_gens_slp: strong_gens.append(k) for i in range(len(slp)): s = slp[i] if isinstance(s[1], tuple): slp[i] = strong_gens_distr[s[0]][s[1][0]]**-1 else: slp[i] = strong_gens_distr[s[0]][s[1]] strong_gens_slp = dict(strong_gens_slp) # add the original generators for g in _gens: strong_gens_slp[g] = [g] return (_base, strong_gens, strong_gens_slp) strong_gens.extend([k for k, _ in strong_gens_slp]) return _base, strong_gens def schreier_sims_random(self, base=None, gens=None, consec_succ=10, _random_prec=None): r"""Randomized Schreier-Sims algorithm. Explanation =========== The randomized Schreier-Sims algorithm takes the sequence ``base`` and the generating set ``gens``, and extends ``base`` to a base, and ``gens`` to a strong generating set relative to that base with probability of a wrong answer at most `2^{-consec\_succ}`, provided the random generators are sufficiently random. Parameters ========== base The sequence to be extended to a base. gens The generating set to be extended to a strong generating set. consec_succ The parameter defining the probability of a wrong answer. _random_prec An internal parameter used for testing purposes. Returns ======= (base, strong_gens) ``base`` is the base and ``strong_gens`` is the strong generating set relative to it. Examples ======== >>> from sympy.combinatorics.testutil import _verify_bsgs >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(5) >>> base, strong_gens = S.schreier_sims_random(consec_succ=5) >>> _verify_bsgs(S, base, strong_gens) #doctest: +SKIP True Notes ===== The algorithm is described in detail in [1], pp. 97-98. It extends the orbits ``orbs`` and the permutation groups ``stabs`` to basic orbits and basic stabilizers for the base and strong generating set produced in the end. The idea of the extension process is to "sift" random group elements through the stabilizer chain and amend the stabilizers/orbits along the way when a sift is not successful. The helper function ``_strip`` is used to attempt to decompose a random group element according to the current state of the stabilizer chain and report whether the element was fully decomposed (successful sift) or not (unsuccessful sift). In the latter case, the level at which the sift failed is reported and used to amend ``stabs``, ``base``, ``gens`` and ``orbs`` accordingly. The halting condition is for ``consec_succ`` consecutive successful sifts to pass. This makes sure that the current ``base`` and ``gens`` form a BSGS with probability at least `1 - 1/\text{consec\_succ}`. See Also ======== schreier_sims """ if base is None: base = [] if gens is None: gens = self.generators base_len = len(base) n = self.degree # make sure no generator fixes all base points for gen in gens: if all(gen(x) == x for x in base): new = 0 while gen._array_form[new] == new: new += 1 base.append(new) base_len += 1 # distribute generators according to basic stabilizers strong_gens_distr = _distribute_gens_by_base(base, gens) # initialize the basic stabilizers, basic transversals and basic orbits transversals = {} orbs = {} for i in range(base_len): transversals[i] = dict(_orbit_transversal(n, strong_gens_distr[i], base[i], pairs=True)) orbs[i] = list(transversals[i].keys()) # initialize the number of consecutive elements sifted c = 0 # start sifting random elements while the number of consecutive sifts # is less than consec_succ while c < consec_succ: if _random_prec is None: g = self.random_pr() else: g = _random_prec['g'].pop() h, j = _strip(g, base, orbs, transversals) y = True # determine whether a new base point is needed if j <= base_len: y = False elif not h.is_Identity: y = False moved = 0 while h(moved) == moved: moved += 1 base.append(moved) base_len += 1 strong_gens_distr.append([]) # if the element doesn't sift, amend the strong generators and # associated stabilizers and orbits if y is False: for l in range(1, j): strong_gens_distr[l].append(h) transversals[l] = dict(_orbit_transversal(n, strong_gens_distr[l], base[l], pairs=True)) orbs[l] = list(transversals[l].keys()) c = 0 else: c += 1 # build the strong generating set strong_gens = strong_gens_distr[0][:] for gen in strong_gens_distr[1]: if gen not in strong_gens: strong_gens.append(gen) return base, strong_gens def schreier_vector(self, alpha): """Computes the schreier vector for ``alpha``. Explanation =========== The Schreier vector efficiently stores information about the orbit of ``alpha``. It can later be used to quickly obtain elements of the group that send ``alpha`` to a particular element in the orbit. Notice that the Schreier vector depends on the order in which the group generators are listed. For a definition, see [3]. Since list indices start from zero, we adopt the convention to use "None" instead of 0 to signify that an element doesn't belong to the orbit. For the algorithm and its correctness, see [2], pp.78-80. Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([2, 4, 6, 3, 1, 5, 0]) >>> b = Permutation([0, 1, 3, 5, 4, 6, 2]) >>> G = PermutationGroup([a, b]) >>> G.schreier_vector(0) [-1, None, 0, 1, None, 1, 0] See Also ======== orbit """ n = self.degree v = [None]*n v[alpha] = -1 orb = [alpha] used = [False]*n used[alpha] = True gens = self.generators r = len(gens) for b in orb: for i in range(r): temp = gens[i]._array_form[b] if used[temp] is False: orb.append(temp) used[temp] = True v[temp] = i return v def stabilizer(self, alpha): r"""Return the stabilizer subgroup of ``alpha``. Explanation =========== The stabilizer of `\alpha` is the group `G_\alpha = \{g \in G | g(\alpha) = \alpha\}`. For a proof of correctness, see [1], p.79. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> G.stabilizer(5) PermutationGroup([ (5)(0 4)(1 3)]) See Also ======== orbit """ return PermGroup(_stabilizer(self._degree, self._generators, alpha)) @property def strong_gens(self): r"""Return a strong generating set from the Schreier-Sims algorithm. Explanation =========== A generating set `S = \{g_1, g_2, ..., g_t\}` for a permutation group `G` is a strong generating set relative to the sequence of points (referred to as a "base") `(b_1, b_2, ..., b_k)` if, for `1 \leq i \leq k` we have that the intersection of the pointwise stabilizer `G^{(i+1)} := G_{b_1, b_2, ..., b_i}` with `S` generates the pointwise stabilizer `G^{(i+1)}`. The concepts of a base and strong generating set and their applications are discussed in depth in [1], pp. 87-89 and [2], pp. 55-57. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> D = DihedralGroup(4) >>> D.strong_gens [(0 1 2 3), (0 3)(1 2), (1 3)] >>> D.base [0, 1] See Also ======== base, basic_transversals, basic_orbits, basic_stabilizers """ if self._strong_gens == []: self.schreier_sims() return self._strong_gens def subgroup(self, gens): """ Return the subgroup generated by `gens` which is a list of elements of the group """ if not all([g in self for g in gens]): raise ValueError("The group doesn't contain the supplied generators") G = PermutationGroup(gens) return G def subgroup_search(self, prop, base=None, strong_gens=None, tests=None, init_subgroup=None): """Find the subgroup of all elements satisfying the property ``prop``. Explanation =========== This is done by a depth-first search with respect to base images that uses several tests to prune the search tree. Parameters ========== prop The property to be used. Has to be callable on group elements and always return ``True`` or ``False``. It is assumed that all group elements satisfying ``prop`` indeed form a subgroup. base A base for the supergroup. strong_gens A strong generating set for the supergroup. tests A list of callables of length equal to the length of ``base``. These are used to rule out group elements by partial base images, so that ``tests[l](g)`` returns False if the element ``g`` is known not to satisfy prop base on where g sends the first ``l + 1`` base points. init_subgroup if a subgroup of the sought group is known in advance, it can be passed to the function as this parameter. Returns ======= res The subgroup of all elements satisfying ``prop``. The generating set for this group is guaranteed to be a strong generating set relative to the base ``base``. Examples ======== >>> from sympy.combinatorics.named_groups import (SymmetricGroup, ... AlternatingGroup) >>> from sympy.combinatorics.testutil import _verify_bsgs >>> S = SymmetricGroup(7) >>> prop_even = lambda x: x.is_even >>> base, strong_gens = S.schreier_sims_incremental() >>> G = S.subgroup_search(prop_even, base=base, strong_gens=strong_gens) >>> G.is_subgroup(AlternatingGroup(7)) True >>> _verify_bsgs(G, base, G.generators) True Notes ===== This function is extremely lengthy and complicated and will require some careful attention. The implementation is described in [1], pp. 114-117, and the comments for the code here follow the lines of the pseudocode in the book for clarity. The complexity is exponential in general, since the search process by itself visits all members of the supergroup. However, there are a lot of tests which are used to prune the search tree, and users can define their own tests via the ``tests`` parameter, so in practice, and for some computations, it's not terrible. A crucial part in the procedure is the frequent base change performed (this is line 11 in the pseudocode) in order to obtain a new basic stabilizer. The book mentiones that this can be done by using ``.baseswap(...)``, however the current implementation uses a more straightforward way to find the next basic stabilizer - calling the function ``.stabilizer(...)`` on the previous basic stabilizer. """ # initialize BSGS and basic group properties def get_reps(orbits): # get the minimal element in the base ordering return [min(orbit, key = lambda x: base_ordering[x]) \ for orbit in orbits] def update_nu(l): temp_index = len(basic_orbits[l]) + 1 -\ len(res_basic_orbits_init_base[l]) # this corresponds to the element larger than all points if temp_index >= len(sorted_orbits[l]): nu[l] = base_ordering[degree] else: nu[l] = sorted_orbits[l][temp_index] if base is None: base, strong_gens = self.schreier_sims_incremental() base_len = len(base) degree = self.degree identity = _af_new(list(range(degree))) base_ordering = _base_ordering(base, degree) # add an element larger than all points base_ordering.append(degree) # add an element smaller than all points base_ordering.append(-1) # compute BSGS-related structures strong_gens_distr = _distribute_gens_by_base(base, strong_gens) basic_orbits, transversals = _orbits_transversals_from_bsgs(base, strong_gens_distr) # handle subgroup initialization and tests if init_subgroup is None: init_subgroup = PermutationGroup([identity]) if tests is None: trivial_test = lambda x: True tests = [] for i in range(base_len): tests.append(trivial_test) # line 1: more initializations. res = init_subgroup f = base_len - 1 l = base_len - 1 # line 2: set the base for K to the base for G res_base = base[:] # line 3: compute BSGS and related structures for K res_base, res_strong_gens = res.schreier_sims_incremental( base=res_base) res_strong_gens_distr = _distribute_gens_by_base(res_base, res_strong_gens) res_generators = res.generators res_basic_orbits_init_base = \ [_orbit(degree, res_strong_gens_distr[i], res_base[i])\ for i in range(base_len)] # initialize orbit representatives orbit_reps = [None]*base_len # line 4: orbit representatives for f-th basic stabilizer of K orbits = _orbits(degree, res_strong_gens_distr[f]) orbit_reps[f] = get_reps(orbits) # line 5: remove the base point from the representatives to avoid # getting the identity element as a generator for K orbit_reps[f].remove(base[f]) # line 6: more initializations c = [0]*base_len u = [identity]*base_len sorted_orbits = [None]*base_len for i in range(base_len): sorted_orbits[i] = basic_orbits[i][:] sorted_orbits[i].sort(key=lambda point: base_ordering[point]) # line 7: initializations mu = [None]*base_len nu = [None]*base_len # this corresponds to the element smaller than all points mu[l] = degree + 1 update_nu(l) # initialize computed words computed_words = [identity]*base_len # line 8: main loop while True: # apply all the tests while l < base_len - 1 and \ computed_words[l](base[l]) in orbit_reps[l] and \ base_ordering[mu[l]] < \ base_ordering[computed_words[l](base[l])] < \ base_ordering[nu[l]] and \ tests[l](computed_words): # line 11: change the (partial) base of K new_point = computed_words[l](base[l]) res_base[l] = new_point new_stab_gens = _stabilizer(degree, res_strong_gens_distr[l], new_point) res_strong_gens_distr[l + 1] = new_stab_gens # line 12: calculate minimal orbit representatives for the # l+1-th basic stabilizer orbits = _orbits(degree, new_stab_gens) orbit_reps[l + 1] = get_reps(orbits) # line 13: amend sorted orbits l += 1 temp_orbit = [computed_words[l - 1](point) for point in basic_orbits[l]] temp_orbit.sort(key=lambda point: base_ordering[point]) sorted_orbits[l] = temp_orbit # lines 14 and 15: update variables used minimality tests new_mu = degree + 1 for i in range(l): if base[l] in res_basic_orbits_init_base[i]: candidate = computed_words[i](base[i]) if base_ordering[candidate] > base_ordering[new_mu]: new_mu = candidate mu[l] = new_mu update_nu(l) # line 16: determine the new transversal element c[l] = 0 temp_point = sorted_orbits[l][c[l]] gamma = computed_words[l - 1]._array_form.index(temp_point) u[l] = transversals[l][gamma] # update computed words computed_words[l] = rmul(computed_words[l - 1], u[l]) # lines 17 & 18: apply the tests to the group element found g = computed_words[l] temp_point = g(base[l]) if l == base_len - 1 and \ base_ordering[mu[l]] < \ base_ordering[temp_point] < base_ordering[nu[l]] and \ temp_point in orbit_reps[l] and \ tests[l](computed_words) and \ prop(g): # line 19: reset the base of K res_generators.append(g) res_base = base[:] # line 20: recalculate basic orbits (and transversals) res_strong_gens.append(g) res_strong_gens_distr = _distribute_gens_by_base(res_base, res_strong_gens) res_basic_orbits_init_base = \ [_orbit(degree, res_strong_gens_distr[i], res_base[i]) \ for i in range(base_len)] # line 21: recalculate orbit representatives # line 22: reset the search depth orbit_reps[f] = get_reps(orbits) l = f # line 23: go up the tree until in the first branch not fully # searched while l >= 0 and c[l] == len(basic_orbits[l]) - 1: l = l - 1 # line 24: if the entire tree is traversed, return K if l == -1: return PermutationGroup(res_generators) # lines 25-27: update orbit representatives if l < f: # line 26 f = l c[l] = 0 # line 27 temp_orbits = _orbits(degree, res_strong_gens_distr[f]) orbit_reps[f] = get_reps(temp_orbits) # line 28: update variables used for minimality testing mu[l] = degree + 1 temp_index = len(basic_orbits[l]) + 1 - \ len(res_basic_orbits_init_base[l]) if temp_index >= len(sorted_orbits[l]): nu[l] = base_ordering[degree] else: nu[l] = sorted_orbits[l][temp_index] # line 29: set the next element from the current branch and update # accordingly c[l] += 1 if l == 0: gamma = sorted_orbits[l][c[l]] else: gamma = computed_words[l - 1]._array_form.index(sorted_orbits[l][c[l]]) u[l] = transversals[l][gamma] if l == 0: computed_words[l] = u[l] else: computed_words[l] = rmul(computed_words[l - 1], u[l]) @property def transitivity_degree(self): r"""Compute the degree of transitivity of the group. Explanation =========== A permutation group `G` acting on `\Omega = \{0, 1, ..., n-1\}` is ``k``-fold transitive, if, for any k points `(a_1, a_2, ..., a_k)\in\Omega` and any k points `(b_1, b_2, ..., b_k)\in\Omega` there exists `g\in G` such that `g(a_1)=b_1, g(a_2)=b_2, ..., g(a_k)=b_k` The degree of transitivity of `G` is the maximum ``k`` such that `G` is ``k``-fold transitive. ([8]) Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([1, 2, 0]) >>> b = Permutation([1, 0, 2]) >>> G = PermutationGroup([a, b]) >>> G.transitivity_degree 3 See Also ======== is_transitive, orbit """ if self._transitivity_degree is None: n = self.degree G = self # if G is k-transitive, a tuple (a_0,..,a_k) # can be brought to (b_0,...,b_(k-1), b_k) # where b_0,...,b_(k-1) are fixed points; # consider the group G_k which stabilizes b_0,...,b_(k-1) # if G_k is transitive on the subset excluding b_0,...,b_(k-1) # then G is (k+1)-transitive for i in range(n): orb = G.orbit(i) if len(orb) != n - i: self._transitivity_degree = i return i G = G.stabilizer(i) self._transitivity_degree = n return n else: return self._transitivity_degree def _p_elements_group(G, p): ''' For an abelian p-group G return the subgroup consisting of all elements of order p (and the identity) ''' gens = G.generators[:] gens = sorted(gens, key=lambda x: x.order(), reverse=True) gens_p = [g**(g.order()/p) for g in gens] gens_r = [] for i in range(len(gens)): x = gens[i] x_order = x.order() # x_p has order p x_p = x**(x_order/p) if i > 0: P = PermutationGroup(gens_p[:i]) else: P = PermutationGroup(G.identity) if x**(x_order/p) not in P: gens_r.append(x**(x_order/p)) else: # replace x by an element of order (x.order()/p) # so that gens still generates G g = P.generator_product(x_p, original=True) for s in g: x = x*s**-1 x_order = x_order/p # insert x to gens so that the sorting is preserved del gens[i] del gens_p[i] j = i - 1 while j < len(gens) and gens[j].order() >= x_order: j += 1 gens = gens[:j] + [x] + gens[j:] gens_p = gens_p[:j] + [x] + gens_p[j:] return PermutationGroup(gens_r) def _sylow_alt_sym(self, p): ''' Return a p-Sylow subgroup of a symmetric or an alternating group. Explanation =========== The algorithm for this is hinted at in [1], Chapter 4, Exercise 4. For Sym(n) with n = p^i, the idea is as follows. Partition the interval [0..n-1] into p equal parts, each of length p^(i-1): [0..p^(i-1)-1], [p^(i-1)..2*p^(i-1)-1]...[(p-1)*p^(i-1)..p^i-1]. Find a p-Sylow subgroup of Sym(p^(i-1)) (treated as a subgroup of ``self``) acting on each of the parts. Call the subgroups P_1, P_2...P_p. The generators for the subgroups P_2...P_p can be obtained from those of P_1 by applying a "shifting" permutation to them, that is, a permutation mapping [0..p^(i-1)-1] to the second part (the other parts are obtained by using the shift multiple times). The union of this permutation and the generators of P_1 is a p-Sylow subgroup of ``self``. For n not equal to a power of p, partition [0..n-1] in accordance with how n would be written in base p. E.g. for p=2 and n=11, 11 = 2^3 + 2^2 + 1 so the partition is [[0..7], [8..9], {10}]. To generate a p-Sylow subgroup, take the union of the generators for each of the parts. For the above example, {(0 1), (0 2)(1 3), (0 4), (1 5)(2 7)} from the first part, {(8 9)} from the second part and nothing from the third. This gives 4 generators in total, and the subgroup they generate is p-Sylow. Alternating groups are treated the same except when p=2. In this case, (0 1)(s s+1) should be added for an appropriate s (the start of a part) for each part in the partitions. See Also ======== sylow_subgroup, is_alt_sym ''' n = self.degree gens = [] identity = Permutation(n-1) # the case of 2-sylow subgroups of alternating groups # needs special treatment alt = p == 2 and all(g.is_even for g in self.generators) # find the presentation of n in base p coeffs = [] m = n while m > 0: coeffs.append(m % p) m = m // p power = len(coeffs)-1 # for a symmetric group, gens[:i] is the generating # set for a p-Sylow subgroup on [0..p**(i-1)-1]. For # alternating groups, the same is given by gens[:2*(i-1)] for i in range(1, power+1): if i == 1 and alt: # (0 1) shouldn't be added for alternating groups continue gen = Permutation([(j + p**(i-1)) % p**i for j in range(p**i)]) gens.append(identity*gen) if alt: gen = Permutation(0, 1)*gen*Permutation(0, 1)*gen gens.append(gen) # the first point in the current part (see the algorithm # description in the docstring) start = 0 while power > 0: a = coeffs[power] # make the permutation shifting the start of the first # part ([0..p^i-1] for some i) to the current one for s in range(a): shift = Permutation() if start > 0: for i in range(p**power): shift = shift(i, start + i) if alt: gen = Permutation(0, 1)*shift*Permutation(0, 1)*shift gens.append(gen) j = 2*(power - 1) else: j = power for i, gen in enumerate(gens[:j]): if alt and i % 2 == 1: continue # shift the generator to the start of the # partition part gen = shift*gen*shift gens.append(gen) start += p**power power = power-1 return gens def sylow_subgroup(self, p): ''' Return a p-Sylow subgroup of the group. The algorithm is described in [1], Chapter 4, Section 7 Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> D = DihedralGroup(6) >>> S = D.sylow_subgroup(2) >>> S.order() 4 >>> G = SymmetricGroup(6) >>> S = G.sylow_subgroup(5) >>> S.order() 5 >>> G1 = AlternatingGroup(3) >>> G2 = AlternatingGroup(5) >>> G3 = AlternatingGroup(9) >>> S1 = G1.sylow_subgroup(3) >>> S2 = G2.sylow_subgroup(3) >>> S3 = G3.sylow_subgroup(3) >>> len1 = len(S1.lower_central_series()) >>> len2 = len(S2.lower_central_series()) >>> len3 = len(S3.lower_central_series()) >>> len1 == len2 True >>> len1 < len3 True ''' from sympy.combinatorics.homomorphisms import ( orbit_homomorphism, block_homomorphism) from sympy.ntheory.primetest import isprime if not isprime(p): raise ValueError("p must be a prime") def is_p_group(G): # check if the order of G is a power of p # and return the power m = G.order() n = 0 while m % p == 0: m = m/p n += 1 if m == 1: return True, n return False, n def _sylow_reduce(mu, nu): # reduction based on two homomorphisms # mu and nu with trivially intersecting # kernels Q = mu.image().sylow_subgroup(p) Q = mu.invert_subgroup(Q) nu = nu.restrict_to(Q) R = nu.image().sylow_subgroup(p) return nu.invert_subgroup(R) order = self.order() if order % p != 0: return PermutationGroup([self.identity]) p_group, n = is_p_group(self) if p_group: return self if self.is_alt_sym(): return PermutationGroup(self._sylow_alt_sym(p)) # if there is a non-trivial orbit with size not divisible # by p, the sylow subgroup is contained in its stabilizer # (by orbit-stabilizer theorem) orbits = self.orbits() non_p_orbits = [o for o in orbits if len(o) % p != 0 and len(o) != 1] if non_p_orbits: G = self.stabilizer(list(non_p_orbits[0]).pop()) return G.sylow_subgroup(p) if not self.is_transitive(): # apply _sylow_reduce to orbit actions orbits = sorted(orbits, key = lambda x: len(x)) omega1 = orbits.pop() omega2 = orbits[0].union(*orbits) mu = orbit_homomorphism(self, omega1) nu = orbit_homomorphism(self, omega2) return _sylow_reduce(mu, nu) blocks = self.minimal_blocks() if len(blocks) > 1: # apply _sylow_reduce to block system actions mu = block_homomorphism(self, blocks[0]) nu = block_homomorphism(self, blocks[1]) return _sylow_reduce(mu, nu) elif len(blocks) == 1: block = list(blocks)[0] if any(e != 0 for e in block): # self is imprimitive mu = block_homomorphism(self, block) if not is_p_group(mu.image())[0]: S = mu.image().sylow_subgroup(p) return mu.invert_subgroup(S).sylow_subgroup(p) # find an element of order p g = self.random() g_order = g.order() while g_order % p != 0 or g_order == 0: g = self.random() g_order = g.order() g = g**(g_order // p) if order % p**2 != 0: return PermutationGroup(g) C = self.centralizer(g) while C.order() % p**n != 0: S = C.sylow_subgroup(p) s_order = S.order() Z = S.center() P = Z._p_elements_group(p) h = P.random() C_h = self.centralizer(h) while C_h.order() % p*s_order != 0: h = P.random() C_h = self.centralizer(h) C = C_h return C.sylow_subgroup(p) def _block_verify(H, L, alpha): delta = sorted(list(H.orbit(alpha))) H_gens = H.generators # p[i] will be the number of the block # delta[i] belongs to p = [-1]*len(delta) blocks = [-1]*len(delta) B = [[]] # future list of blocks u = [0]*len(delta) # u[i] in L s.t. alpha^u[i] = B[0][i] t = L.orbit_transversal(alpha, pairs=True) for a, beta in t: B[0].append(a) i_a = delta.index(a) p[i_a] = 0 blocks[i_a] = alpha u[i_a] = beta rho = 0 m = 0 # number of blocks - 1 while rho <= m: beta = B[rho][0] for g in H_gens: d = beta^g i_d = delta.index(d) sigma = p[i_d] if sigma < 0: # define a new block m += 1 sigma = m u[i_d] = u[delta.index(beta)]*g p[i_d] = sigma rep = d blocks[i_d] = rep newb = [rep] for gamma in B[rho][1:]: i_gamma = delta.index(gamma) d = gamma^g i_d = delta.index(d) if p[i_d] < 0: u[i_d] = u[i_gamma]*g p[i_d] = sigma blocks[i_d] = rep newb.append(d) else: # B[rho] is not a block s = u[i_gamma]*g*u[i_d]**(-1) return False, s B.append(newb) else: for h in B[rho][1:]: if not h^g in B[sigma]: # B[rho] is not a block s = u[delta.index(beta)]*g*u[i_d]**(-1) return False, s rho += 1 return True, blocks def _verify(H, K, phi, z, alpha): ''' Return a list of relators ``rels`` in generators ``gens`_h` that are mapped to ``H.generators`` by ``phi`` so that given a finite presentation <gens_k | rels_k> of ``K`` on a subset of ``gens_h`` <gens_h | rels_k + rels> is a finite presentation of ``H``. Explanation =========== ``H`` should be generated by the union of ``K.generators`` and ``z`` (a single generator), and ``H.stabilizer(alpha) == K``; ``phi`` is a canonical injection from a free group into a permutation group containing ``H``. The algorithm is described in [1], Chapter 6. Examples ======== >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.homomorphisms import homomorphism >>> from sympy.combinatorics.free_groups import free_group >>> from sympy.combinatorics.fp_groups import FpGroup >>> H = PermutationGroup(Permutation(0, 2), Permutation (1, 5)) >>> K = PermutationGroup(Permutation(5)(0, 2)) >>> F = free_group("x_0 x_1")[0] >>> gens = F.generators >>> phi = homomorphism(F, H, F.generators, H.generators) >>> rels_k = [gens[0]**2] # relators for presentation of K >>> z= Permutation(1, 5) >>> check, rels_h = H._verify(K, phi, z, 1) >>> check True >>> rels = rels_k + rels_h >>> G = FpGroup(F, rels) # presentation of H >>> G.order() == H.order() True See also ======== strong_presentation, presentation, stabilizer ''' orbit = H.orbit(alpha) beta = alpha^(z**-1) K_beta = K.stabilizer(beta) # orbit representatives of K_beta gammas = [alpha, beta] orbits = list({tuple(K_beta.orbit(o)) for o in orbit}) orbit_reps = [orb[0] for orb in orbits] for rep in orbit_reps: if rep not in gammas: gammas.append(rep) # orbit transversal of K betas = [alpha, beta] transversal = {alpha: phi.invert(H.identity), beta: phi.invert(z**-1)} for s, g in K.orbit_transversal(beta, pairs=True): if not s in transversal: transversal[s] = transversal[beta]*phi.invert(g) union = K.orbit(alpha).union(K.orbit(beta)) while (len(union) < len(orbit)): for gamma in gammas: if gamma in union: r = gamma^z if r not in union: betas.append(r) transversal[r] = transversal[gamma]*phi.invert(z) for s, g in K.orbit_transversal(r, pairs=True): if not s in transversal: transversal[s] = transversal[r]*phi.invert(g) union = union.union(K.orbit(r)) break # compute relators rels = [] for b in betas: k_gens = K.stabilizer(b).generators for y in k_gens: new_rel = transversal[b] gens = K.generator_product(y, original=True) for g in gens[::-1]: new_rel = new_rel*phi.invert(g) new_rel = new_rel*transversal[b]**-1 perm = phi(new_rel) try: gens = K.generator_product(perm, original=True) except ValueError: return False, perm for g in gens: new_rel = new_rel*phi.invert(g)**-1 if new_rel not in rels: rels.append(new_rel) for gamma in gammas: new_rel = transversal[gamma]*phi.invert(z)*transversal[gamma^z]**-1 perm = phi(new_rel) try: gens = K.generator_product(perm, original=True) except ValueError: return False, perm for g in gens: new_rel = new_rel*phi.invert(g)**-1 if new_rel not in rels: rels.append(new_rel) return True, rels def strong_presentation(G): ''' Return a strong finite presentation of `G`. The generators of the returned group are in the same order as the strong generators of `G`. The algorithm is based on Sims' Verify algorithm described in [1], Chapter 6. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> P = DihedralGroup(4) >>> G = P.strong_presentation() >>> P.order() == G.order() True See Also ======== presentation, _verify ''' from sympy.combinatorics.fp_groups import (FpGroup, simplify_presentation) from sympy.combinatorics.free_groups import free_group from sympy.combinatorics.homomorphisms import (block_homomorphism, homomorphism, GroupHomomorphism) strong_gens = G.strong_gens[:] stabs = G.basic_stabilizers[:] base = G.base[:] # injection from a free group on len(strong_gens) # generators into G gen_syms = [('x_%d'%i) for i in range(len(strong_gens))] F = free_group(', '.join(gen_syms))[0] phi = homomorphism(F, G, F.generators, strong_gens) H = PermutationGroup(G.identity) while stabs: alpha = base.pop() K = H H = stabs.pop() new_gens = [g for g in H.generators if g not in K] if K.order() == 1: z = new_gens.pop() rels = [F.generators[-1]**z.order()] intermediate_gens = [z] K = PermutationGroup(intermediate_gens) # add generators one at a time building up from K to H while new_gens: z = new_gens.pop() intermediate_gens = [z] + intermediate_gens K_s = PermutationGroup(intermediate_gens) orbit = K_s.orbit(alpha) orbit_k = K.orbit(alpha) # split into cases based on the orbit of K_s if orbit_k == orbit: if z in K: rel = phi.invert(z) perm = z else: t = K.orbit_rep(alpha, alpha^z) rel = phi.invert(z)*phi.invert(t)**-1 perm = z*t**-1 for g in K.generator_product(perm, original=True): rel = rel*phi.invert(g)**-1 new_rels = [rel] elif len(orbit_k) == 1: # `success` is always true because `strong_gens` # and `base` are already a verified BSGS. Later # this could be changed to start with a randomly # generated (potential) BSGS, and then new elements # would have to be appended to it when `success` # is false. success, new_rels = K_s._verify(K, phi, z, alpha) else: # K.orbit(alpha) should be a block # under the action of K_s on K_s.orbit(alpha) check, block = K_s._block_verify(K, alpha) if check: # apply _verify to the action of K_s # on the block system; for convenience, # add the blocks as additional points # that K_s should act on t = block_homomorphism(K_s, block) m = t.codomain.degree # number of blocks d = K_s.degree # conjugating with p will shift # permutations in t.image() to # higher numbers, e.g. # p*(0 1)*p = (m m+1) p = Permutation() for i in range(m): p *= Permutation(i, i+d) t_img = t.images # combine generators of K_s with their # action on the block system images = {g: g*p*t_img[g]*p for g in t_img} for g in G.strong_gens[:-len(K_s.generators)]: images[g] = g K_s_act = PermutationGroup(list(images.values())) f = GroupHomomorphism(G, K_s_act, images) K_act = PermutationGroup([f(g) for g in K.generators]) success, new_rels = K_s_act._verify(K_act, f.compose(phi), f(z), d) for n in new_rels: if not n in rels: rels.append(n) K = K_s group = FpGroup(F, rels) return simplify_presentation(group) def presentation(G, eliminate_gens=True): ''' Return an `FpGroup` presentation of the group. The algorithm is described in [1], Chapter 6.1. ''' from sympy.combinatorics.fp_groups import (FpGroup, simplify_presentation) from sympy.combinatorics.coset_table import CosetTable from sympy.combinatorics.free_groups import free_group from sympy.combinatorics.homomorphisms import homomorphism from itertools import product if G._fp_presentation: return G._fp_presentation if G._fp_presentation: return G._fp_presentation def _factor_group_by_rels(G, rels): if isinstance(G, FpGroup): rels.extend(G.relators) return FpGroup(G.free_group, list(set(rels))) return FpGroup(G, rels) gens = G.generators len_g = len(gens) if len_g == 1: order = gens[0].order() # handle the trivial group if order == 1: return free_group([])[0] F, x = free_group('x') return FpGroup(F, [x**order]) if G.order() > 20: half_gens = G.generators[0:(len_g+1)//2] else: half_gens = [] H = PermutationGroup(half_gens) H_p = H.presentation() len_h = len(H_p.generators) C = G.coset_table(H) n = len(C) # subgroup index gen_syms = [('x_%d'%i) for i in range(len(gens))] F = free_group(', '.join(gen_syms))[0] # mapping generators of H_p to those of F images = [F.generators[i] for i in range(len_h)] R = homomorphism(H_p, F, H_p.generators, images, check=False) # rewrite relators rels = R(H_p.relators) G_p = FpGroup(F, rels) # injective homomorphism from G_p into G T = homomorphism(G_p, G, G_p.generators, gens) C_p = CosetTable(G_p, []) C_p.table = [[None]*(2*len_g) for i in range(n)] # initiate the coset transversal transversal = [None]*n transversal[0] = G_p.identity # fill in the coset table as much as possible for i in range(2*len_h): C_p.table[0][i] = 0 gamma = 1 for alpha, x in product(range(0, n), range(2*len_g)): beta = C[alpha][x] if beta == gamma: gen = G_p.generators[x//2]**((-1)**(x % 2)) transversal[beta] = transversal[alpha]*gen C_p.table[alpha][x] = beta C_p.table[beta][x + (-1)**(x % 2)] = alpha gamma += 1 if gamma == n: break C_p.p = list(range(n)) beta = x = 0 while not C_p.is_complete(): # find the first undefined entry while C_p.table[beta][x] == C[beta][x]: x = (x + 1) % (2*len_g) if x == 0: beta = (beta + 1) % n # define a new relator gen = G_p.generators[x//2]**((-1)**(x % 2)) new_rel = transversal[beta]*gen*transversal[C[beta][x]]**-1 perm = T(new_rel) next = G_p.identity for s in H.generator_product(perm, original=True): next = next*T.invert(s)**-1 new_rel = new_rel*next # continue coset enumeration G_p = _factor_group_by_rels(G_p, [new_rel]) C_p.scan_and_fill(0, new_rel) C_p = G_p.coset_enumeration([], strategy="coset_table", draft=C_p, max_cosets=n, incomplete=True) G._fp_presentation = simplify_presentation(G_p) return G._fp_presentation def polycyclic_group(self): """ Return the PolycyclicGroup instance with below parameters: Explanation =========== * ``pc_sequence`` : Polycyclic sequence is formed by collecting all the missing generators between the adjacent groups in the derived series of given permutation group. * ``pc_series`` : Polycyclic series is formed by adding all the missing generators of ``der[i+1]`` in ``der[i]``, where ``der`` represents the derived series. * ``relative_order`` : A list, computed by the ratio of adjacent groups in pc_series. """ from sympy.combinatorics.pc_groups import PolycyclicGroup if not self.is_polycyclic: raise ValueError("The group must be solvable") der = self.derived_series() pc_series = [] pc_sequence = [] relative_order = [] pc_series.append(der[-1]) der.reverse() for i in range(len(der)-1): H = der[i] for g in der[i+1].generators: if g not in H: H = PermutationGroup([g] + H.generators) pc_series.insert(0, H) pc_sequence.insert(0, g) G1 = pc_series[0].order() G2 = pc_series[1].order() relative_order.insert(0, G1 // G2) return PolycyclicGroup(pc_sequence, pc_series, relative_order, collector=None) def _orbit(degree, generators, alpha, action='tuples'): r"""Compute the orbit of alpha `\{g(\alpha) | g \in G\}` as a set. Explanation =========== The time complexity of the algorithm used here is `O(|Orb|*r)` where `|Orb|` is the size of the orbit and ``r`` is the number of generators of the group. For a more detailed analysis, see [1], p.78, [2], pp. 19-21. Here alpha can be a single point, or a list of points. If alpha is a single point, the ordinary orbit is computed. if alpha is a list of points, there are three available options: 'union' - computes the union of the orbits of the points in the list 'tuples' - computes the orbit of the list interpreted as an ordered tuple under the group action ( i.e., g((1, 2, 3)) = (g(1), g(2), g(3)) ) 'sets' - computes the orbit of the list interpreted as a sets Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup, _orbit >>> a = Permutation([1, 2, 0, 4, 5, 6, 3]) >>> G = PermutationGroup([a]) >>> _orbit(G.degree, G.generators, 0) {0, 1, 2} >>> _orbit(G.degree, G.generators, [0, 4], 'union') {0, 1, 2, 3, 4, 5, 6} See Also ======== orbit, orbit_transversal """ if not hasattr(alpha, '__getitem__'): alpha = [alpha] gens = [x._array_form for x in generators] if len(alpha) == 1 or action == 'union': orb = alpha used = [False]*degree for el in alpha: used[el] = True for b in orb: for gen in gens: temp = gen[b] if used[temp] == False: orb.append(temp) used[temp] = True return set(orb) elif action == 'tuples': alpha = tuple(alpha) orb = [alpha] used = {alpha} for b in orb: for gen in gens: temp = tuple([gen[x] for x in b]) if temp not in used: orb.append(temp) used.add(temp) return set(orb) elif action == 'sets': alpha = frozenset(alpha) orb = [alpha] used = {alpha} for b in orb: for gen in gens: temp = frozenset([gen[x] for x in b]) if temp not in used: orb.append(temp) used.add(temp) return {tuple(x) for x in orb} def _orbits(degree, generators): """Compute the orbits of G. If ``rep=False`` it returns a list of sets else it returns a list of representatives of the orbits Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.perm_groups import _orbits >>> a = Permutation([0, 2, 1]) >>> b = Permutation([1, 0, 2]) >>> _orbits(a.size, [a, b]) [{0, 1, 2}] """ orbs = [] sorted_I = list(range(degree)) I = set(sorted_I) while I: i = sorted_I[0] orb = _orbit(degree, generators, i) orbs.append(orb) # remove all indices that are in this orbit I -= orb sorted_I = [i for i in sorted_I if i not in orb] return orbs def _orbit_transversal(degree, generators, alpha, pairs, af=False, slp=False): r"""Computes a transversal for the orbit of ``alpha`` as a set. Explanation =========== generators generators of the group ``G`` For a permutation group ``G``, a transversal for the orbit `Orb = \{g(\alpha) | g \in G\}` is a set `\{g_\beta | g_\beta(\alpha) = \beta\}` for `\beta \in Orb`. Note that there may be more than one possible transversal. If ``pairs`` is set to ``True``, it returns the list of pairs `(\beta, g_\beta)`. For a proof of correctness, see [1], p.79 if ``af`` is ``True``, the transversal elements are given in array form. If `slp` is `True`, a dictionary `{beta: slp_beta}` is returned for `\beta \in Orb` where `slp_beta` is a list of indices of the generators in `generators` s.t. if `slp_beta = [i_1 ... i_n]` `g_\beta = generators[i_n]*...*generators[i_1]`. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.perm_groups import _orbit_transversal >>> G = DihedralGroup(6) >>> _orbit_transversal(G.degree, G.generators, 0, False) [(5), (0 1 2 3 4 5), (0 5)(1 4)(2 3), (0 2 4)(1 3 5), (5)(0 4)(1 3), (0 3)(1 4)(2 5)] """ tr = [(alpha, list(range(degree)))] slp_dict = {alpha: []} used = [False]*degree used[alpha] = True gens = [x._array_form for x in generators] for x, px in tr: px_slp = slp_dict[x] for gen in gens: temp = gen[x] if used[temp] == False: slp_dict[temp] = [gens.index(gen)] + px_slp tr.append((temp, _af_rmul(gen, px))) used[temp] = True if pairs: if not af: tr = [(x, _af_new(y)) for x, y in tr] if not slp: return tr return tr, slp_dict if af: tr = [y for _, y in tr] if not slp: return tr return tr, slp_dict tr = [_af_new(y) for _, y in tr] if not slp: return tr return tr, slp_dict def _stabilizer(degree, generators, alpha): r"""Return the stabilizer subgroup of ``alpha``. Explanation =========== The stabilizer of `\alpha` is the group `G_\alpha = \{g \in G | g(\alpha) = \alpha\}`. For a proof of correctness, see [1], p.79. degree : degree of G generators : generators of G Examples ======== >>> from sympy.combinatorics.perm_groups import _stabilizer >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(6) >>> _stabilizer(G.degree, G.generators, 5) [(5)(0 4)(1 3), (5)] See Also ======== orbit """ orb = [alpha] table = {alpha: list(range(degree))} table_inv = {alpha: list(range(degree))} used = [False]*degree used[alpha] = True gens = [x._array_form for x in generators] stab_gens = [] for b in orb: for gen in gens: temp = gen[b] if used[temp] is False: gen_temp = _af_rmul(gen, table[b]) orb.append(temp) table[temp] = gen_temp table_inv[temp] = _af_invert(gen_temp) used[temp] = True else: schreier_gen = _af_rmuln(table_inv[temp], gen, table[b]) if schreier_gen not in stab_gens: stab_gens.append(schreier_gen) return [_af_new(x) for x in stab_gens] PermGroup = PermutationGroup class SymmetricPermutationGroup(Basic): """ The class defining the lazy form of SymmetricGroup. deg : int """ def __new__(cls, deg): deg = _sympify(deg) obj = Basic.__new__(cls, deg) obj._deg = deg obj._order = None return obj def __contains__(self, i): """Return ``True`` if *i* is contained in SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import Permutation, SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> Permutation(1, 2, 3) in G True """ if not isinstance(i, Permutation): raise TypeError("A SymmetricPermutationGroup contains only Permutations as " "elements, not elements of type %s" % type(i)) return i.size == self.degree def order(self): """ Return the order of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.order() 24 """ if self._order is not None: return self._order n = self._deg self._order = factorial(n) return self._order @property def degree(self): """ Return the degree of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.degree 4 """ return self._deg @property def identity(self): ''' Return the identity element of the SymmetricPermutationGroup. Examples ======== >>> from sympy.combinatorics import SymmetricPermutationGroup >>> G = SymmetricPermutationGroup(4) >>> G.identity() (3) ''' return _af_new(list(range(self._deg))) class Coset(Basic): """A left coset of a permutation group with respect to an element. Parameters ========== g : Permutation H : PermutationGroup dir : "+" or "-", If not specified by default it will be "+" here ``dir`` specified the type of coset "+" represent the right coset and "-" represent the left coset. G : PermutationGroup, optional The group which contains *H* as its subgroup and *g* as its element. If not specified, it would automatically become a symmetric group ``SymmetricPermutationGroup(g.size)`` and ``SymmetricPermutationGroup(H.degree)`` if ``g.size`` and ``H.degree`` are matching.``SymmetricPermutationGroup`` is a lazy form of SymmetricGroup used for representation purpose. """ def __new__(cls, g, H, G=None, dir="+"): g = _sympify(g) if not isinstance(g, Permutation): raise NotImplementedError H = _sympify(H) if not isinstance(H, PermutationGroup): raise NotImplementedError if G is not None: G = _sympify(G) if not isinstance(G, PermutationGroup) and not isinstance(G, SymmetricPermutationGroup): raise NotImplementedError if not H.is_subgroup(G): raise ValueError("{} must be a subgroup of {}.".format(H, G)) if g not in G: raise ValueError("{} must be an element of {}.".format(g, G)) else: g_size = g.size h_degree = H.degree if g_size != h_degree: raise ValueError( "The size of the permutation {} and the degree of " "the permutation group {} should be matching " .format(g, H)) G = SymmetricPermutationGroup(g.size) if isinstance(dir, str): dir = Symbol(dir) elif not isinstance(dir, Symbol): raise TypeError("dir must be of type basestring or " "Symbol, not %s" % type(dir)) if str(dir) not in ('+', '-'): raise ValueError("dir must be one of '+' or '-' not %s" % dir) obj = Basic.__new__(cls, g, H, G, dir) obj._dir = dir return obj @property def is_left_coset(self): """ Check if the coset is left coset that is ``gH``. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup, Coset >>> a = Permutation(1, 2) >>> b = Permutation(0, 1) >>> G = PermutationGroup([a, b]) >>> cst = Coset(a, G, dir="-") >>> cst.is_left_coset True """ return str(self._dir) == '-' @property def is_right_coset(self): """ Check if the coset is right coset that is ``Hg``. Examples ======== >>> from sympy.combinatorics import Permutation, PermutationGroup, Coset >>> a = Permutation(1, 2) >>> b = Permutation(0, 1) >>> G = PermutationGroup([a, b]) >>> cst = Coset(a, G, dir="+") >>> cst.is_right_coset True """ return str(self._dir) == '+' def as_list(self): """ Return all the elements of coset in the form of list. """ g = self.args[0] H = self.args[1] cst = [] if str(self._dir) == '+': for h in H.elements: cst.append(h*g) else: for h in H.elements: cst.append(g*h) return cst

63ed4e6adc5ac1d4a921424f2c62fef8853e61b9caab3fc64142548895f0d48d

import random from collections import defaultdict from sympy.core.parameters import global_parameters from sympy.core.basic import Atom from sympy.core.expr import Expr from sympy.core.compatibility import \ is_sequence, reduce, as_int, Iterable from sympy.core.numbers import Integer from sympy.core.sympify import _sympify from sympy.matrices import zeros from sympy.polys.polytools import lcm from sympy.utilities.iterables import (flatten, has_variety, minlex, has_dups, runs) from mpmath.libmp.libintmath import ifac from sympy.multipledispatch import dispatch def _af_rmul(a, b): """ Return the product b*a; input and output are array forms. The ith value is a[b[i]]. Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> _af_rmul(a, b) [1, 2, 0] >>> [a[b[i]] for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ``*`` operator: >>> a = Permutation(a) >>> b = Permutation(b) >>> list(a*b) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] See Also ======== rmul, _af_rmuln """ return [a[i] for i in b] def _af_rmuln(*abc): """ Given [a, b, c, ...] return the product of ...*c*b*a using array forms. The ith value is a[b[c[i]]]. Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> _af_rmul(a, b) [1, 2, 0] >>> [a[b[i]] for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ``*`` operator: >>> a = Permutation(a); b = Permutation(b) >>> list(a*b) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] See Also ======== rmul, _af_rmul """ a = abc m = len(a) if m == 3: p0, p1, p2 = a return [p0[p1[i]] for i in p2] if m == 4: p0, p1, p2, p3 = a return [p0[p1[p2[i]]] for i in p3] if m == 5: p0, p1, p2, p3, p4 = a return [p0[p1[p2[p3[i]]]] for i in p4] if m == 6: p0, p1, p2, p3, p4, p5 = a return [p0[p1[p2[p3[p4[i]]]]] for i in p5] if m == 7: p0, p1, p2, p3, p4, p5, p6 = a return [p0[p1[p2[p3[p4[p5[i]]]]]] for i in p6] if m == 8: p0, p1, p2, p3, p4, p5, p6, p7 = a return [p0[p1[p2[p3[p4[p5[p6[i]]]]]]] for i in p7] if m == 1: return a[0][:] if m == 2: a, b = a return [a[i] for i in b] if m == 0: raise ValueError("String must not be empty") p0 = _af_rmuln(*a[:m//2]) p1 = _af_rmuln(*a[m//2:]) return [p0[i] for i in p1] def _af_parity(pi): """ Computes the parity of a permutation in array form. Explanation =========== The parity of a permutation reflects the parity of the number of inversions in the permutation, i.e., the number of pairs of x and y such that x > y but p[x] < p[y]. Examples ======== >>> from sympy.combinatorics.permutations import _af_parity >>> _af_parity([0, 1, 2, 3]) 0 >>> _af_parity([3, 2, 0, 1]) 1 See Also ======== Permutation """ n = len(pi) a = [0] * n c = 0 for j in range(n): if a[j] == 0: c += 1 a[j] = 1 i = j while pi[i] != j: i = pi[i] a[i] = 1 return (n - c) % 2 def _af_invert(a): """ Finds the inverse, ~A, of a permutation, A, given in array form. Examples ======== >>> from sympy.combinatorics.permutations import _af_invert, _af_rmul >>> A = [1, 2, 0, 3] >>> _af_invert(A) [2, 0, 1, 3] >>> _af_rmul(_, A) [0, 1, 2, 3] See Also ======== Permutation, __invert__ """ inv_form = [0] * len(a) for i, ai in enumerate(a): inv_form[ai] = i return inv_form def _af_pow(a, n): """ Routine for finding powers of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation, _af_pow >>> p = Permutation([2, 0, 3, 1]) >>> p.order() 4 >>> _af_pow(p._array_form, 4) [0, 1, 2, 3] """ if n == 0: return list(range(len(a))) if n < 0: return _af_pow(_af_invert(a), -n) if n == 1: return a[:] elif n == 2: b = [a[i] for i in a] elif n == 3: b = [a[a[i]] for i in a] elif n == 4: b = [a[a[a[i]]] for i in a] else: # use binary multiplication b = list(range(len(a))) while 1: if n & 1: b = [b[i] for i in a] n -= 1 if not n: break if n % 4 == 0: a = [a[a[a[i]]] for i in a] n = n // 4 elif n % 2 == 0: a = [a[i] for i in a] n = n // 2 return b def _af_commutes_with(a, b): """ Checks if the two permutations with array forms given by ``a`` and ``b`` commute. Examples ======== >>> from sympy.combinatorics.permutations import _af_commutes_with >>> _af_commutes_with([1, 2, 0], [0, 2, 1]) False See Also ======== Permutation, commutes_with """ return not any(a[b[i]] != b[a[i]] for i in range(len(a) - 1)) class Cycle(dict): """ Wrapper around dict which provides the functionality of a disjoint cycle. Explanation =========== A cycle shows the rule to use to move subsets of elements to obtain a permutation. The Cycle class is more flexible than Permutation in that 1) all elements need not be present in order to investigate how multiple cycles act in sequence and 2) it can contain singletons: >>> from sympy.combinatorics.permutations import Perm, Cycle A Cycle will automatically parse a cycle given as a tuple on the rhs: >>> Cycle(1, 2)(2, 3) (1 3 2) The identity cycle, Cycle(), can be used to start a product: >>> Cycle()(1, 2)(2, 3) (1 3 2) The array form of a Cycle can be obtained by calling the list method (or passing it to the list function) and all elements from 0 will be shown: >>> a = Cycle(1, 2) >>> a.list() [0, 2, 1] >>> list(a) [0, 2, 1] If a larger (or smaller) range is desired use the list method and provide the desired size -- but the Cycle cannot be truncated to a size smaller than the largest element that is out of place: >>> b = Cycle(2, 4)(1, 2)(3, 1, 4)(1, 3) >>> b.list() [0, 2, 1, 3, 4] >>> b.list(b.size + 1) [0, 2, 1, 3, 4, 5] >>> b.list(-1) [0, 2, 1] Singletons are not shown when printing with one exception: the largest element is always shown -- as a singleton if necessary: >>> Cycle(1, 4, 10)(4, 5) (1 5 4 10) >>> Cycle(1, 2)(4)(5)(10) (1 2)(10) The array form can be used to instantiate a Permutation so other properties of the permutation can be investigated: >>> Perm(Cycle(1, 2)(3, 4).list()).transpositions() [(1, 2), (3, 4)] Notes ===== The underlying structure of the Cycle is a dictionary and although the __iter__ method has been redefined to give the array form of the cycle, the underlying dictionary items are still available with the such methods as items(): >>> list(Cycle(1, 2).items()) [(1, 2), (2, 1)] See Also ======== Permutation """ def __missing__(self, arg): """Enter arg into dictionary and return arg.""" return as_int(arg) def __iter__(self): yield from self.list() def __call__(self, *other): """Return product of cycles processed from R to L. Examples ======== >>> from sympy.combinatorics.permutations import Cycle as C >>> C(1, 2)(2, 3) (1 3 2) An instance of a Cycle will automatically parse list-like objects and Permutations that are on the right. It is more flexible than the Permutation in that all elements need not be present: >>> a = C(1, 2) >>> a(2, 3) (1 3 2) >>> a(2, 3)(4, 5) (1 3 2)(4 5) """ rv = Cycle(*other) for k, v in zip(list(self.keys()), [rv[self[k]] for k in self.keys()]): rv[k] = v return rv def list(self, size=None): """Return the cycles as an explicit list starting from 0 up to the greater of the largest value in the cycles and size. Truncation of trailing unmoved items will occur when size is less than the maximum element in the cycle; if this is desired, setting ``size=-1`` will guarantee such trimming. Examples ======== >>> from sympy.combinatorics.permutations import Cycle >>> p = Cycle(2, 3)(4, 5) >>> p.list() [0, 1, 3, 2, 5, 4] >>> p.list(10) [0, 1, 3, 2, 5, 4, 6, 7, 8, 9] Passing a length too small will trim trailing, unchanged elements in the permutation: >>> Cycle(2, 4)(1, 2, 4).list(-1) [0, 2, 1] """ if not self and size is None: raise ValueError('must give size for empty Cycle') if size is not None: big = max([i for i in self.keys() if self[i] != i] + [0]) size = max(size, big + 1) else: size = self.size return [self[i] for i in range(size)] def __repr__(self): """We want it to print as a Cycle, not as a dict. Examples ======== >>> from sympy.combinatorics import Cycle >>> Cycle(1, 2) (1 2) >>> print(_) (1 2) >>> list(Cycle(1, 2).items()) [(1, 2), (2, 1)] """ if not self: return 'Cycle()' cycles = Permutation(self).cyclic_form s = ''.join(str(tuple(c)) for c in cycles) big = self.size - 1 if not any(i == big for c in cycles for i in c): s += '(%s)' % big return 'Cycle%s' % s def __str__(self): """We want it to be printed in a Cycle notation with no comma in-between. Examples ======== >>> from sympy.combinatorics import Cycle >>> Cycle(1, 2) (1 2) >>> Cycle(1, 2, 4)(5, 6) (1 2 4)(5 6) """ if not self: return '()' cycles = Permutation(self).cyclic_form s = ''.join(str(tuple(c)) for c in cycles) big = self.size - 1 if not any(i == big for c in cycles for i in c): s += '(%s)' % big s = s.replace(',', '') return s def __init__(self, *args): """Load up a Cycle instance with the values for the cycle. Examples ======== >>> from sympy.combinatorics.permutations import Cycle >>> Cycle(1, 2, 6) (1 2 6) """ if not args: return if len(args) == 1: if isinstance(args[0], Permutation): for c in args[0].cyclic_form: self.update(self(*c)) return elif isinstance(args[0], Cycle): for k, v in args[0].items(): self[k] = v return args = [as_int(a) for a in args] if any(i < 0 for i in args): raise ValueError('negative integers are not allowed in a cycle.') if has_dups(args): raise ValueError('All elements must be unique in a cycle.') for i in range(-len(args), 0): self[args[i]] = args[i + 1] @property def size(self): if not self: return 0 return max(self.keys()) + 1 def copy(self): return Cycle(self) class Permutation(Atom): """ A permutation, alternatively known as an 'arrangement number' or 'ordering' is an arrangement of the elements of an ordered list into a one-to-one mapping with itself. The permutation of a given arrangement is given by indicating the positions of the elements after re-arrangement [2]_. For example, if one started with elements [x, y, a, b] (in that order) and they were reordered as [x, y, b, a] then the permutation would be [0, 1, 3, 2]. Notice that (in SymPy) the first element is always referred to as 0 and the permutation uses the indices of the elements in the original ordering, not the elements (a, b, etc...) themselves. >>> from sympy.combinatorics import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) Permutations Notation ===================== Permutations are commonly represented in disjoint cycle or array forms. Array Notation and 2-line Form ------------------------------------ In the 2-line form, the elements and their final positions are shown as a matrix with 2 rows: [0 1 2 ... n-1] [p(0) p(1) p(2) ... p(n-1)] Since the first line is always range(n), where n is the size of p, it is sufficient to represent the permutation by the second line, referred to as the "array form" of the permutation. This is entered in brackets as the argument to the Permutation class: >>> p = Permutation([0, 2, 1]); p Permutation([0, 2, 1]) Given i in range(p.size), the permutation maps i to i^p >>> [i^p for i in range(p.size)] [0, 2, 1] The composite of two permutations p*q means first apply p, then q, so i^(p*q) = (i^p)^q which is i^p^q according to Python precedence rules: >>> q = Permutation([2, 1, 0]) >>> [i^p^q for i in range(3)] [2, 0, 1] >>> [i^(p*q) for i in range(3)] [2, 0, 1] One can use also the notation p(i) = i^p, but then the composition rule is (p*q)(i) = q(p(i)), not p(q(i)): >>> [(p*q)(i) for i in range(p.size)] [2, 0, 1] >>> [q(p(i)) for i in range(p.size)] [2, 0, 1] >>> [p(q(i)) for i in range(p.size)] [1, 2, 0] Disjoint Cycle Notation ----------------------- In disjoint cycle notation, only the elements that have shifted are indicated. In the above case, the 2 and 1 switched places. This can be entered in two ways: >>> Permutation(1, 2) == Permutation([[1, 2]]) == p True Only the relative ordering of elements in a cycle matter: >>> Permutation(1,2,3) == Permutation(2,3,1) == Permutation(3,1,2) True The disjoint cycle notation is convenient when representing permutations that have several cycles in them: >>> Permutation(1, 2)(3, 5) == Permutation([[1, 2], [3, 5]]) True It also provides some economy in entry when computing products of permutations that are written in disjoint cycle notation: >>> Permutation(1, 2)(1, 3)(2, 3) Permutation([0, 3, 2, 1]) >>> _ == Permutation([[1, 2]])*Permutation([[1, 3]])*Permutation([[2, 3]]) True Caution: when the cycles have common elements between them then the order in which the permutations are applied matters. The convention is that the permutations are applied from *right to left*. In the following, the transposition of elements 2 and 3 is followed by the transposition of elements 1 and 2: >>> Permutation(1, 2)(2, 3) == Permutation([(1, 2), (2, 3)]) True >>> Permutation(1, 2)(2, 3).list() [0, 3, 1, 2] If the first and second elements had been swapped first, followed by the swapping of the second and third, the result would have been [0, 2, 3, 1]. If, for some reason, you want to apply the cycles in the order they are entered, you can simply reverse the order of cycles: >>> Permutation([(1, 2), (2, 3)][::-1]).list() [0, 2, 3, 1] Entering a singleton in a permutation is a way to indicate the size of the permutation. The ``size`` keyword can also be used. Array-form entry: >>> Permutation([[1, 2], [9]]) Permutation([0, 2, 1], size=10) >>> Permutation([[1, 2]], size=10) Permutation([0, 2, 1], size=10) Cyclic-form entry: >>> Permutation(1, 2, size=10) Permutation([0, 2, 1], size=10) >>> Permutation(9)(1, 2) Permutation([0, 2, 1], size=10) Caution: no singleton containing an element larger than the largest in any previous cycle can be entered. This is an important difference in how Permutation and Cycle handle the __call__ syntax. A singleton argument at the start of a Permutation performs instantiation of the Permutation and is permitted: >>> Permutation(5) Permutation([], size=6) A singleton entered after instantiation is a call to the permutation -- a function call -- and if the argument is out of range it will trigger an error. For this reason, it is better to start the cycle with the singleton: The following fails because there is no element 3: >>> Permutation(1, 2)(3) Traceback (most recent call last): ... IndexError: list index out of range This is ok: only the call to an out of range singleton is prohibited; otherwise the permutation autosizes: >>> Permutation(3)(1, 2) Permutation([0, 2, 1, 3]) >>> Permutation(1, 2)(3, 4) == Permutation(3, 4)(1, 2) True Equality testing ---------------- The array forms must be the same in order for permutations to be equal: >>> Permutation([1, 0, 2, 3]) == Permutation([1, 0]) False Identity Permutation -------------------- The identity permutation is a permutation in which no element is out of place. It can be entered in a variety of ways. All the following create an identity permutation of size 4: >>> I = Permutation([0, 1, 2, 3]) >>> all(p == I for p in [ ... Permutation(3), ... Permutation(range(4)), ... Permutation([], size=4), ... Permutation(size=4)]) True Watch out for entering the range *inside* a set of brackets (which is cycle notation): >>> I == Permutation([range(4)]) False Permutation Printing ==================== There are a few things to note about how Permutations are printed. 1) If you prefer one form (array or cycle) over another, you can set ``init_printing`` with the ``perm_cyclic`` flag. >>> from sympy import init_printing >>> p = Permutation(1, 2)(4, 5)(3, 4) >>> p Permutation([0, 2, 1, 4, 5, 3]) >>> init_printing(perm_cyclic=True, pretty_print=False) >>> p (1 2)(3 4 5) 2) Regardless of the setting, a list of elements in the array for cyclic form can be obtained and either of those can be copied and supplied as the argument to Permutation: >>> p.array_form [0, 2, 1, 4, 5, 3] >>> p.cyclic_form [[1, 2], [3, 4, 5]] >>> Permutation(_) == p True 3) Printing is economical in that as little as possible is printed while retaining all information about the size of the permutation: >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation([1, 0, 2, 3]) Permutation([1, 0, 2, 3]) >>> Permutation([1, 0, 2, 3], size=20) Permutation([1, 0], size=20) >>> Permutation([1, 0, 2, 4, 3, 5, 6], size=20) Permutation([1, 0, 2, 4, 3], size=20) >>> p = Permutation([1, 0, 2, 3]) >>> init_printing(perm_cyclic=True, pretty_print=False) >>> p (3)(0 1) >>> init_printing(perm_cyclic=False, pretty_print=False) The 2 was not printed but it is still there as can be seen with the array_form and size methods: >>> p.array_form [1, 0, 2, 3] >>> p.size 4 Short introduction to other methods =================================== The permutation can act as a bijective function, telling what element is located at a given position >>> q = Permutation([5, 2, 3, 4, 1, 0]) >>> q.array_form[1] # the hard way 2 >>> q(1) # the easy way 2 >>> {i: q(i) for i in range(q.size)} # showing the bijection {0: 5, 1: 2, 2: 3, 3: 4, 4: 1, 5: 0} The full cyclic form (including singletons) can be obtained: >>> p.full_cyclic_form [[0, 1], [2], [3]] Any permutation can be factored into transpositions of pairs of elements: >>> Permutation([[1, 2], [3, 4, 5]]).transpositions() [(1, 2), (3, 5), (3, 4)] >>> Permutation.rmul(*[Permutation([ti], size=6) for ti in _]).cyclic_form [[1, 2], [3, 4, 5]] The number of permutations on a set of n elements is given by n! and is called the cardinality. >>> p.size 4 >>> p.cardinality 24 A given permutation has a rank among all the possible permutations of the same elements, but what that rank is depends on how the permutations are enumerated. (There are a number of different methods of doing so.) The lexicographic rank is given by the rank method and this rank is used to increment a permutation with addition/subtraction: >>> p.rank() 6 >>> p + 1 Permutation([1, 0, 3, 2]) >>> p.next_lex() Permutation([1, 0, 3, 2]) >>> _.rank() 7 >>> p.unrank_lex(p.size, rank=7) Permutation([1, 0, 3, 2]) The product of two permutations p and q is defined as their composition as functions, (p*q)(i) = q(p(i)) [6]_. >>> p = Permutation([1, 0, 2, 3]) >>> q = Permutation([2, 3, 1, 0]) >>> list(q*p) [2, 3, 0, 1] >>> list(p*q) [3, 2, 1, 0] >>> [q(p(i)) for i in range(p.size)] [3, 2, 1, 0] The permutation can be 'applied' to any list-like object, not only Permutations: >>> p(['zero', 'one', 'four', 'two']) ['one', 'zero', 'four', 'two'] >>> p('zo42') ['o', 'z', '4', '2'] If you have a list of arbitrary elements, the corresponding permutation can be found with the from_sequence method: >>> Permutation.from_sequence('SymPy') Permutation([1, 3, 2, 0, 4]) See Also ======== Cycle References ========== .. [1] Skiena, S. 'Permutations.' 1.1 in Implementing Discrete Mathematics Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, pp. 3-16, 1990. .. [2] Knuth, D. E. The Art of Computer Programming, Vol. 4: Combinatorial Algorithms, 1st ed. Reading, MA: Addison-Wesley, 2011. .. [3] Wendy Myrvold and Frank Ruskey. 2001. Ranking and unranking permutations in linear time. Inf. Process. Lett. 79, 6 (September 2001), 281-284. DOI=10.1016/S0020-0190(01)00141-7 .. [4] D. L. Kreher, D. R. Stinson 'Combinatorial Algorithms' CRC Press, 1999 .. [5] Graham, R. L.; Knuth, D. E.; and Patashnik, O. Concrete Mathematics: A Foundation for Computer Science, 2nd ed. Reading, MA: Addison-Wesley, 1994. .. [6] https://en.wikipedia.org/wiki/Permutation#Product_and_inverse .. [7] https://en.wikipedia.org/wiki/Lehmer_code """ is_Permutation = True _array_form = None _cyclic_form = None _cycle_structure = None _size = None _rank = None def __new__(cls, *args, size=None, **kwargs): """ Constructor for the Permutation object from a list or a list of lists in which all elements of the permutation may appear only once. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) Permutations entered in array-form are left unaltered: >>> Permutation([0, 2, 1]) Permutation([0, 2, 1]) Permutations entered in cyclic form are converted to array form; singletons need not be entered, but can be entered to indicate the largest element: >>> Permutation([[4, 5, 6], [0, 1]]) Permutation([1, 0, 2, 3, 5, 6, 4]) >>> Permutation([[4, 5, 6], [0, 1], [19]]) Permutation([1, 0, 2, 3, 5, 6, 4], size=20) All manipulation of permutations assumes that the smallest element is 0 (in keeping with 0-based indexing in Python) so if the 0 is missing when entering a permutation in array form, an error will be raised: >>> Permutation([2, 1]) Traceback (most recent call last): ... ValueError: Integers 0 through 2 must be present. If a permutation is entered in cyclic form, it can be entered without singletons and the ``size`` specified so those values can be filled in, otherwise the array form will only extend to the maximum value in the cycles: >>> Permutation([[1, 4], [3, 5, 2]], size=10) Permutation([0, 4, 3, 5, 1, 2], size=10) >>> _.array_form [0, 4, 3, 5, 1, 2, 6, 7, 8, 9] """ if size is not None: size = int(size) #a) () #b) (1) = identity #c) (1, 2) = cycle #d) ([1, 2, 3]) = array form #e) ([[1, 2]]) = cyclic form #f) (Cycle) = conversion to permutation #g) (Permutation) = adjust size or return copy ok = True if not args: # a return cls._af_new(list(range(size or 0))) elif len(args) > 1: # c return cls._af_new(Cycle(*args).list(size)) if len(args) == 1: a = args[0] if isinstance(a, cls): # g if size is None or size == a.size: return a return cls(a.array_form, size=size) if isinstance(a, Cycle): # f return cls._af_new(a.list(size)) if not is_sequence(a): # b if size is not None and a + 1 > size: raise ValueError('size is too small when max is %s' % a) return cls._af_new(list(range(a + 1))) if has_variety(is_sequence(ai) for ai in a): ok = False else: ok = False if not ok: raise ValueError("Permutation argument must be a list of ints, " "a list of lists, Permutation or Cycle.") # safe to assume args are valid; this also makes a copy # of the args args = list(args[0]) is_cycle = args and is_sequence(args[0]) if is_cycle: # e args = [[int(i) for i in c] for c in args] else: # d args = [int(i) for i in args] # if there are n elements present, 0, 1, ..., n-1 should be present # unless a cycle notation has been provided. A 0 will be added # for convenience in case one wants to enter permutations where # counting starts from 1. temp = flatten(args) if has_dups(temp) and not is_cycle: raise ValueError('there were repeated elements.') temp = set(temp) if not is_cycle: if any(i not in temp for i in range(len(temp))): raise ValueError('Integers 0 through %s must be present.' % max(temp)) if size is not None and temp and max(temp) + 1 > size: raise ValueError('max element should not exceed %s' % (size - 1)) if is_cycle: # it's not necessarily canonical so we won't store # it -- use the array form instead c = Cycle() for ci in args: c = c(*ci) aform = c.list() else: aform = list(args) if size and size > len(aform): # don't allow for truncation of permutation which # might split a cycle and lead to an invalid aform # but do allow the permutation size to be increased aform.extend(list(range(len(aform), size))) return cls._af_new(aform) @classmethod def _af_new(cls, perm): """A method to produce a Permutation object from a list; the list is bound to the _array_form attribute, so it must not be modified; this method is meant for internal use only; the list ``a`` is supposed to be generated as a temporary value in a method, so p = Perm._af_new(a) is the only object to hold a reference to ``a``:: Examples ======== >>> from sympy.combinatorics.permutations import Perm >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> a = [2, 1, 3, 0] >>> p = Perm._af_new(a) >>> p Permutation([2, 1, 3, 0]) """ p = super().__new__(cls) p._array_form = perm p._size = len(perm) return p def _hashable_content(self): # the array_form (a list) is the Permutation arg, so we need to # return a tuple, instead return tuple(self.array_form) @property def array_form(self): """ Return a copy of the attribute _array_form Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[2, 0], [3, 1]]) >>> p.array_form [2, 3, 0, 1] >>> Permutation([[2, 0, 3, 1]]).array_form [3, 2, 0, 1] >>> Permutation([2, 0, 3, 1]).array_form [2, 0, 3, 1] >>> Permutation([[1, 2], [4, 5]]).array_form [0, 2, 1, 3, 5, 4] """ return self._array_form[:] def list(self, size=None): """Return the permutation as an explicit list, possibly trimming unmoved elements if size is less than the maximum element in the permutation; if this is desired, setting ``size=-1`` will guarantee such trimming. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation(2, 3)(4, 5) >>> p.list() [0, 1, 3, 2, 5, 4] >>> p.list(10) [0, 1, 3, 2, 5, 4, 6, 7, 8, 9] Passing a length too small will trim trailing, unchanged elements in the permutation: >>> Permutation(2, 4)(1, 2, 4).list(-1) [0, 2, 1] >>> Permutation(3).list(-1) [] """ if not self and size is None: raise ValueError('must give size for empty Cycle') rv = self.array_form if size is not None: if size > self.size: rv.extend(list(range(self.size, size))) else: # find first value from rhs where rv[i] != i i = self.size - 1 while rv: if rv[-1] != i: break rv.pop() i -= 1 return rv @property def cyclic_form(self): """ This is used to convert to the cyclic notation from the canonical notation. Singletons are omitted. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2]) >>> p.cyclic_form [[1, 3, 2]] >>> Permutation([1, 0, 2, 4, 3, 5]).cyclic_form [[0, 1], [3, 4]] See Also ======== array_form, full_cyclic_form """ if self._cyclic_form is not None: return list(self._cyclic_form) array_form = self.array_form unchecked = [True] * len(array_form) cyclic_form = [] for i in range(len(array_form)): if unchecked[i]: cycle = [] cycle.append(i) unchecked[i] = False j = i while unchecked[array_form[j]]: j = array_form[j] cycle.append(j) unchecked[j] = False if len(cycle) > 1: cyclic_form.append(cycle) assert cycle == list(minlex(cycle, is_set=True)) cyclic_form.sort() self._cyclic_form = cyclic_form[:] return cyclic_form @property def full_cyclic_form(self): """Return permutation in cyclic form including singletons. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> Permutation([0, 2, 1]).full_cyclic_form [[0], [1, 2]] """ need = set(range(self.size)) - set(flatten(self.cyclic_form)) rv = self.cyclic_form rv.extend([[i] for i in need]) rv.sort() return rv @property def size(self): """ Returns the number of elements in the permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([[3, 2], [0, 1]]).size 4 See Also ======== cardinality, length, order, rank """ return self._size def support(self): """Return the elements in permutation, P, for which P[i] != i. Examples ======== >>> from sympy.combinatorics import Permutation >>> p = Permutation([[3, 2], [0, 1], [4]]) >>> p.array_form [1, 0, 3, 2, 4] >>> p.support() [0, 1, 2, 3] """ a = self.array_form return [i for i, e in enumerate(a) if a[i] != i] def __add__(self, other): """Return permutation that is other higher in rank than self. The rank is the lexicographical rank, with the identity permutation having rank of 0. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> I = Permutation([0, 1, 2, 3]) >>> a = Permutation([2, 1, 3, 0]) >>> I + a.rank() == a True See Also ======== __sub__, inversion_vector """ rank = (self.rank() + other) % self.cardinality rv = self.unrank_lex(self.size, rank) rv._rank = rank return rv def __sub__(self, other): """Return the permutation that is other lower in rank than self. See Also ======== __add__ """ return self.__add__(-other) @staticmethod def rmul(*args): """ Return product of Permutations [a, b, c, ...] as the Permutation whose ith value is a(b(c(i))). a, b, c, ... can be Permutation objects or tuples. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> a = Permutation(a); b = Permutation(b) >>> list(Permutation.rmul(a, b)) [1, 2, 0] >>> [a(b(i)) for i in range(3)] [1, 2, 0] This handles the operands in reverse order compared to the ``*`` operator: >>> a = Permutation(a); b = Permutation(b) >>> list(a*b) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] Notes ===== All items in the sequence will be parsed by Permutation as necessary as long as the first item is a Permutation: >>> Permutation.rmul(a, [0, 2, 1]) == Permutation.rmul(a, b) True The reverse order of arguments will raise a TypeError. """ rv = args[0] for i in range(1, len(args)): rv = args[i]*rv return rv @classmethod def rmul_with_af(cls, *args): """ same as rmul, but the elements of args are Permutation objects which have _array_form """ a = [x._array_form for x in args] rv = cls._af_new(_af_rmuln(*a)) return rv def mul_inv(self, other): """ other*~self, self and other have _array_form """ a = _af_invert(self._array_form) b = other._array_form return self._af_new(_af_rmul(a, b)) def __rmul__(self, other): """This is needed to coerce other to Permutation in rmul.""" cls = type(self) return cls(other)*self def __mul__(self, other): """ Return the product a*b as a Permutation; the ith value is b(a(i)). Examples ======== >>> from sympy.combinatorics.permutations import _af_rmul, Permutation >>> a, b = [1, 0, 2], [0, 2, 1] >>> a = Permutation(a); b = Permutation(b) >>> list(a*b) [2, 0, 1] >>> [b(a(i)) for i in range(3)] [2, 0, 1] This handles operands in reverse order compared to _af_rmul and rmul: >>> al = list(a); bl = list(b) >>> _af_rmul(al, bl) [1, 2, 0] >>> [al[bl[i]] for i in range(3)] [1, 2, 0] It is acceptable for the arrays to have different lengths; the shorter one will be padded to match the longer one: >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> b*Permutation([1, 0]) Permutation([1, 2, 0]) >>> Permutation([1, 0])*b Permutation([2, 0, 1]) It is also acceptable to allow coercion to handle conversion of a single list to the left of a Permutation: >>> [0, 1]*a # no change: 2-element identity Permutation([1, 0, 2]) >>> [[0, 1]]*a # exchange first two elements Permutation([0, 1, 2]) You cannot use more than 1 cycle notation in a product of cycles since coercion can only handle one argument to the left. To handle multiple cycles it is convenient to use Cycle instead of Permutation: >>> [[1, 2]]*[[2, 3]]*Permutation([]) # doctest: +SKIP >>> from sympy.combinatorics.permutations import Cycle >>> Cycle(1, 2)(2, 3) (1 3 2) """ from sympy.combinatorics.perm_groups import PermutationGroup, Coset if isinstance(other, PermutationGroup): return Coset(self, other, dir='-') a = self.array_form # __rmul__ makes sure the other is a Permutation b = other.array_form if not b: perm = a else: b.extend(list(range(len(b), len(a)))) perm = [b[i] for i in a] + b[len(a):] return self._af_new(perm) def commutes_with(self, other): """ Checks if the elements are commuting. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([1, 4, 3, 0, 2, 5]) >>> b = Permutation([0, 1, 2, 3, 4, 5]) >>> a.commutes_with(b) True >>> b = Permutation([2, 3, 5, 4, 1, 0]) >>> a.commutes_with(b) False """ a = self.array_form b = other.array_form return _af_commutes_with(a, b) def __pow__(self, n): """ Routine for finding powers of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([2, 0, 3, 1]) >>> p.order() 4 >>> p**4 Permutation([0, 1, 2, 3]) """ if isinstance(n, Permutation): raise NotImplementedError( 'p**p is not defined; do you mean p^p (conjugate)?') n = int(n) return self._af_new(_af_pow(self.array_form, n)) def __rxor__(self, i): """Return self(i) when ``i`` is an int. Examples ======== >>> from sympy.combinatorics import Permutation >>> p = Permutation(1, 2, 9) >>> 2^p == p(2) == 9 True """ if int(i) == i: return self(i) else: raise NotImplementedError( "i^p = p(i) when i is an integer, not %s." % i) def __xor__(self, h): """Return the conjugate permutation ``~h*self*h` `. Explanation =========== If ``a`` and ``b`` are conjugates, ``a = h*b*~h`` and ``b = ~h*a*h`` and both have the same cycle structure. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation(1, 2, 9) >>> q = Permutation(6, 9, 8) >>> p*q != q*p True Calculate and check properties of the conjugate: >>> c = p^q >>> c == ~q*p*q and p == q*c*~q True The expression q^p^r is equivalent to q^(p*r): >>> r = Permutation(9)(4, 6, 8) >>> q^p^r == q^(p*r) True If the term to the left of the conjugate operator, i, is an integer then this is interpreted as selecting the ith element from the permutation to the right: >>> all(i^p == p(i) for i in range(p.size)) True Note that the * operator as higher precedence than the ^ operator: >>> q^r*p^r == q^(r*p)^r == Permutation(9)(1, 6, 4) True Notes ===== In Python the precedence rule is p^q^r = (p^q)^r which differs in general from p^(q^r) >>> q^p^r (9)(1 4 8) >>> q^(p^r) (9)(1 8 6) For a given r and p, both of the following are conjugates of p: ~r*p*r and r*p*~r. But these are not necessarily the same: >>> ~r*p*r == r*p*~r True >>> p = Permutation(1, 2, 9)(5, 6) >>> ~r*p*r == r*p*~r False The conjugate ~r*p*r was chosen so that ``p^q^r`` would be equivalent to ``p^(q*r)`` rather than ``p^(r*q)``. To obtain r*p*~r, pass ~r to this method: >>> p^~r == r*p*~r True """ if self.size != h.size: raise ValueError("The permutations must be of equal size.") a = [None]*self.size h = h._array_form p = self._array_form for i in range(self.size): a[h[i]] = h[p[i]] return self._af_new(a) def transpositions(self): """ Return the permutation decomposed into a list of transpositions. Explanation =========== It is always possible to express a permutation as the product of transpositions, see [1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[1, 2, 3], [0, 4, 5, 6, 7]]) >>> t = p.transpositions() >>> t [(0, 7), (0, 6), (0, 5), (0, 4), (1, 3), (1, 2)] >>> print(''.join(str(c) for c in t)) (0, 7)(0, 6)(0, 5)(0, 4)(1, 3)(1, 2) >>> Permutation.rmul(*[Permutation([ti], size=p.size) for ti in t]) == p True References ========== .. [1] https://en.wikipedia.org/wiki/Transposition_%28mathematics%29#Properties """ a = self.cyclic_form res = [] for x in a: nx = len(x) if nx == 2: res.append(tuple(x)) elif nx > 2: first = x[0] for y in x[nx - 1:0:-1]: res.append((first, y)) return res @classmethod def from_sequence(self, i, key=None): """Return the permutation needed to obtain ``i`` from the sorted elements of ``i``. If custom sorting is desired, a key can be given. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation.from_sequence('SymPy') (4)(0 1 3) >>> _(sorted("SymPy")) ['S', 'y', 'm', 'P', 'y'] >>> Permutation.from_sequence('SymPy', key=lambda x: x.lower()) (4)(0 2)(1 3) """ ic = list(zip(i, list(range(len(i))))) if key: ic.sort(key=lambda x: key(x[0])) else: ic.sort() return ~Permutation([i[1] for i in ic]) def __invert__(self): """ Return the inverse of the permutation. A permutation multiplied by its inverse is the identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([[2, 0], [3, 1]]) >>> ~p Permutation([2, 3, 0, 1]) >>> _ == p**-1 True >>> p*~p == ~p*p == Permutation([0, 1, 2, 3]) True """ return self._af_new(_af_invert(self._array_form)) def __iter__(self): """Yield elements from array form. Examples ======== >>> from sympy.combinatorics import Permutation >>> list(Permutation(range(3))) [0, 1, 2] """ yield from self.array_form def __repr__(self): from sympy.printing.repr import srepr return srepr(self) def __call__(self, *i): """ Allows applying a permutation instance as a bijective function. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([[2, 0], [3, 1]]) >>> p.array_form [2, 3, 0, 1] >>> [p(i) for i in range(4)] [2, 3, 0, 1] If an array is given then the permutation selects the items from the array (i.e. the permutation is applied to the array): >>> from sympy.abc import x >>> p([x, 1, 0, x**2]) [0, x**2, x, 1] """ # list indices can be Integer or int; leave this # as it is (don't test or convert it) because this # gets called a lot and should be fast if len(i) == 1: i = i[0] if not isinstance(i, Iterable): i = as_int(i) if i < 0 or i > self.size: raise TypeError( "{} should be an integer between 0 and {}" .format(i, self.size-1)) return self._array_form[i] # P([a, b, c]) if len(i) != self.size: raise TypeError( "{} should have the length {}.".format(i, self.size)) return [i[j] for j in self._array_form] # P(1, 2, 3) return self*Permutation(Cycle(*i), size=self.size) def atoms(self): """ Returns all the elements of a permutation Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 1, 2, 3, 4, 5]).atoms() {0, 1, 2, 3, 4, 5} >>> Permutation([[0, 1], [2, 3], [4, 5]]).atoms() {0, 1, 2, 3, 4, 5} """ return set(self.array_form) def apply(self, i): r"""Apply the permutation to an expression. Parameters ========== i : Expr It should be an integer between $0$ and $n-1$ where $n$ is the size of the permutation. If it is a symbol or a symbolic expression that can have integer values, an ``AppliedPermutation`` object will be returned which can represent an unevaluated function. Notes ===== Any permutation can be defined as a bijective function $\sigma : \{ 0, 1, ..., n-1 \} \rightarrow \{ 0, 1, ..., n-1 \}$ where $n$ denotes the size of the permutation. The definition may even be extended for any set with distinctive elements, such that the permutation can even be applied for real numbers or such, however, it is not implemented for now for computational reasons and the integrity with the group theory module. This function is similar to the ``__call__`` magic, however, ``__call__`` magic already has some other applications like permuting an array or attatching new cycles, which would not always be mathematically consistent. This also guarantees that the return type is a SymPy integer, which guarantees the safety to use assumptions. """ i = _sympify(i) if i.is_integer is False: raise NotImplementedError("{} should be an integer.".format(i)) n = self.size if (i < 0) == True or (i >= n) == True: raise NotImplementedError( "{} should be an integer between 0 and {}".format(i, n-1)) if i.is_Integer: return Integer(self._array_form[i]) return AppliedPermutation(self, i) def next_lex(self): """ Returns the next permutation in lexicographical order. If self is the last permutation in lexicographical order it returns None. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 3, 1, 0]) >>> p = Permutation([2, 3, 1, 0]); p.rank() 17 >>> p = p.next_lex(); p.rank() 18 See Also ======== rank, unrank_lex """ perm = self.array_form[:] n = len(perm) i = n - 2 while perm[i + 1] < perm[i]: i -= 1 if i == -1: return None else: j = n - 1 while perm[j] < perm[i]: j -= 1 perm[j], perm[i] = perm[i], perm[j] i += 1 j = n - 1 while i < j: perm[j], perm[i] = perm[i], perm[j] i += 1 j -= 1 return self._af_new(perm) @classmethod def unrank_nonlex(self, n, r): """ This is a linear time unranking algorithm that does not respect lexicographic order [3]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.unrank_nonlex(4, 5) Permutation([2, 0, 3, 1]) >>> Permutation.unrank_nonlex(4, -1) Permutation([0, 1, 2, 3]) See Also ======== next_nonlex, rank_nonlex """ def _unrank1(n, r, a): if n > 0: a[n - 1], a[r % n] = a[r % n], a[n - 1] _unrank1(n - 1, r//n, a) id_perm = list(range(n)) n = int(n) r = r % ifac(n) _unrank1(n, r, id_perm) return self._af_new(id_perm) def rank_nonlex(self, inv_perm=None): """ This is a linear time ranking algorithm that does not enforce lexicographic order [3]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank_nonlex() 23 See Also ======== next_nonlex, unrank_nonlex """ def _rank1(n, perm, inv_perm): if n == 1: return 0 s = perm[n - 1] t = inv_perm[n - 1] perm[n - 1], perm[t] = perm[t], s inv_perm[n - 1], inv_perm[s] = inv_perm[s], t return s + n*_rank1(n - 1, perm, inv_perm) if inv_perm is None: inv_perm = (~self).array_form if not inv_perm: return 0 perm = self.array_form[:] r = _rank1(len(perm), perm, inv_perm) return r def next_nonlex(self): """ Returns the next permutation in nonlex order [3]. If self is the last permutation in this order it returns None. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([2, 0, 3, 1]); p.rank_nonlex() 5 >>> p = p.next_nonlex(); p Permutation([3, 0, 1, 2]) >>> p.rank_nonlex() 6 See Also ======== rank_nonlex, unrank_nonlex """ r = self.rank_nonlex() if r == ifac(self.size) - 1: return None return self.unrank_nonlex(self.size, r + 1) def rank(self): """ Returns the lexicographic rank of the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank() 0 >>> p = Permutation([3, 2, 1, 0]) >>> p.rank() 23 See Also ======== next_lex, unrank_lex, cardinality, length, order, size """ if not self._rank is None: return self._rank rank = 0 rho = self.array_form[:] n = self.size - 1 size = n + 1 psize = int(ifac(n)) for j in range(size - 1): rank += rho[j]*psize for i in range(j + 1, size): if rho[i] > rho[j]: rho[i] -= 1 psize //= n n -= 1 self._rank = rank return rank @property def cardinality(self): """ Returns the number of all possible permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.cardinality 24 See Also ======== length, order, rank, size """ return int(ifac(self.size)) def parity(self): """ Computes the parity of a permutation. Explanation =========== The parity of a permutation reflects the parity of the number of inversions in the permutation, i.e., the number of pairs of x and y such that ``x > y`` but ``p[x] < p[y]``. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.parity() 0 >>> p = Permutation([3, 2, 0, 1]) >>> p.parity() 1 See Also ======== _af_parity """ if self._cyclic_form is not None: return (self.size - self.cycles) % 2 return _af_parity(self.array_form) @property def is_even(self): """ Checks if a permutation is even. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.is_even True >>> p = Permutation([3, 2, 1, 0]) >>> p.is_even True See Also ======== is_odd """ return not self.is_odd @property def is_odd(self): """ Checks if a permutation is odd. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.is_odd False >>> p = Permutation([3, 2, 0, 1]) >>> p.is_odd True See Also ======== is_even """ return bool(self.parity() % 2) @property def is_Singleton(self): """ Checks to see if the permutation contains only one number and is thus the only possible permutation of this set of numbers Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0]).is_Singleton True >>> Permutation([0, 1]).is_Singleton False See Also ======== is_Empty """ return self.size == 1 @property def is_Empty(self): """ Checks to see if the permutation is a set with zero elements Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([]).is_Empty True >>> Permutation([0]).is_Empty False See Also ======== is_Singleton """ return self.size == 0 @property def is_identity(self): return self.is_Identity @property def is_Identity(self): """ Returns True if the Permutation is an identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([]) >>> p.is_Identity True >>> p = Permutation([[0], [1], [2]]) >>> p.is_Identity True >>> p = Permutation([0, 1, 2]) >>> p.is_Identity True >>> p = Permutation([0, 2, 1]) >>> p.is_Identity False See Also ======== order """ af = self.array_form return not af or all(i == af[i] for i in range(self.size)) def ascents(self): """ Returns the positions of ascents in a permutation, ie, the location where p[i] < p[i+1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 0, 1, 3, 2]) >>> p.ascents() [1, 2] See Also ======== descents, inversions, min, max """ a = self.array_form pos = [i for i in range(len(a) - 1) if a[i] < a[i + 1]] return pos def descents(self): """ Returns the positions of descents in a permutation, ie, the location where p[i] > p[i+1] Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 0, 1, 3, 2]) >>> p.descents() [0, 3] See Also ======== ascents, inversions, min, max """ a = self.array_form pos = [i for i in range(len(a) - 1) if a[i] > a[i + 1]] return pos def max(self): """ The maximum element moved by the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([1, 0, 2, 3, 4]) >>> p.max() 1 See Also ======== min, descents, ascents, inversions """ max = 0 a = self.array_form for i in range(len(a)): if a[i] != i and a[i] > max: max = a[i] return max def min(self): """ The minimum element moved by the permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 4, 3, 2]) >>> p.min() 2 See Also ======== max, descents, ascents, inversions """ a = self.array_form min = len(a) for i in range(len(a)): if a[i] != i and a[i] < min: min = a[i] return min def inversions(self): """ Computes the number of inversions of a permutation. Explanation =========== An inversion is where i > j but p[i] < p[j]. For small length of p, it iterates over all i and j values and calculates the number of inversions. For large length of p, it uses a variation of merge sort to calculate the number of inversions. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3, 4, 5]) >>> p.inversions() 0 >>> Permutation([3, 2, 1, 0]).inversions() 6 See Also ======== descents, ascents, min, max References ========== .. [1] http://www.cp.eng.chula.ac.th/~piak/teaching/algo/algo2008/count-inv.htm """ inversions = 0 a = self.array_form n = len(a) if n < 130: for i in range(n - 1): b = a[i] for c in a[i + 1:]: if b > c: inversions += 1 else: k = 1 right = 0 arr = a[:] temp = a[:] while k < n: i = 0 while i + k < n: right = i + k * 2 - 1 if right >= n: right = n - 1 inversions += _merge(arr, temp, i, i + k, right) i = i + k * 2 k = k * 2 return inversions def commutator(self, x): """Return the commutator of ``self`` and ``x``: ``~x*~self*x*self`` If f and g are part of a group, G, then the commutator of f and g is the group identity iff f and g commute, i.e. fg == gf. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([0, 2, 3, 1]) >>> x = Permutation([2, 0, 3, 1]) >>> c = p.commutator(x); c Permutation([2, 1, 3, 0]) >>> c == ~x*~p*x*p True >>> I = Permutation(3) >>> p = [I + i for i in range(6)] >>> for i in range(len(p)): ... for j in range(len(p)): ... c = p[i].commutator(p[j]) ... if p[i]*p[j] == p[j]*p[i]: ... assert c == I ... else: ... assert c != I ... References ========== https://en.wikipedia.org/wiki/Commutator """ a = self.array_form b = x.array_form n = len(a) if len(b) != n: raise ValueError("The permutations must be of equal size.") inva = [None]*n for i in range(n): inva[a[i]] = i invb = [None]*n for i in range(n): invb[b[i]] = i return self._af_new([a[b[inva[i]]] for i in invb]) def signature(self): """ Gives the signature of the permutation needed to place the elements of the permutation in canonical order. The signature is calculated as (-1)^<number of inversions> Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2]) >>> p.inversions() 0 >>> p.signature() 1 >>> q = Permutation([0,2,1]) >>> q.inversions() 1 >>> q.signature() -1 See Also ======== inversions """ if self.is_even: return 1 return -1 def order(self): """ Computes the order of a permutation. When the permutation is raised to the power of its order it equals the identity permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([3, 1, 5, 2, 4, 0]) >>> p.order() 4 >>> (p**(p.order())) Permutation([], size=6) See Also ======== identity, cardinality, length, rank, size """ return reduce(lcm, [len(cycle) for cycle in self.cyclic_form], 1) def length(self): """ Returns the number of integers moved by a permutation. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 3, 2, 1]).length() 2 >>> Permutation([[0, 1], [2, 3]]).length() 4 See Also ======== min, max, support, cardinality, order, rank, size """ return len(self.support()) @property def cycle_structure(self): """Return the cycle structure of the permutation as a dictionary indicating the multiplicity of each cycle length. Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation(3).cycle_structure {1: 4} >>> Permutation(0, 4, 3)(1, 2)(5, 6).cycle_structure {2: 2, 3: 1} """ if self._cycle_structure: rv = self._cycle_structure else: rv = defaultdict(int) singletons = self.size for c in self.cyclic_form: rv[len(c)] += 1 singletons -= len(c) if singletons: rv[1] = singletons self._cycle_structure = rv return dict(rv) # make a copy @property def cycles(self): """ Returns the number of cycles contained in the permutation (including singletons). Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation([0, 1, 2]).cycles 3 >>> Permutation([0, 1, 2]).full_cyclic_form [[0], [1], [2]] >>> Permutation(0, 1)(2, 3).cycles 2 See Also ======== sympy.functions.combinatorial.numbers.stirling """ return len(self.full_cyclic_form) def index(self): """ Returns the index of a permutation. The index of a permutation is the sum of all subscripts j such that p[j] is greater than p[j+1]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([3, 0, 2, 1, 4]) >>> p.index() 2 """ a = self.array_form return sum([j for j in range(len(a) - 1) if a[j] > a[j + 1]]) def runs(self): """ Returns the runs of a permutation. An ascending sequence in a permutation is called a run [5]. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 5, 7, 3, 6, 0, 1, 4, 8]) >>> p.runs() [[2, 5, 7], [3, 6], [0, 1, 4, 8]] >>> q = Permutation([1,3,2,0]) >>> q.runs() [[1, 3], [2], [0]] """ return runs(self.array_form) def inversion_vector(self): """Return the inversion vector of the permutation. The inversion vector consists of elements whose value indicates the number of elements in the permutation that are lesser than it and lie on its right hand side. The inversion vector is the same as the Lehmer encoding of a permutation. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([4, 8, 0, 7, 1, 5, 3, 6, 2]) >>> p.inversion_vector() [4, 7, 0, 5, 0, 2, 1, 1] >>> p = Permutation([3, 2, 1, 0]) >>> p.inversion_vector() [3, 2, 1] The inversion vector increases lexicographically with the rank of the permutation, the -ith element cycling through 0..i. >>> p = Permutation(2) >>> while p: ... print('%s %s %s' % (p, p.inversion_vector(), p.rank())) ... p = p.next_lex() (2) [0, 0] 0 (1 2) [0, 1] 1 (2)(0 1) [1, 0] 2 (0 1 2) [1, 1] 3 (0 2 1) [2, 0] 4 (0 2) [2, 1] 5 See Also ======== from_inversion_vector """ self_array_form = self.array_form n = len(self_array_form) inversion_vector = [0] * (n - 1) for i in range(n - 1): val = 0 for j in range(i + 1, n): if self_array_form[j] < self_array_form[i]: val += 1 inversion_vector[i] = val return inversion_vector def rank_trotterjohnson(self): """ Returns the Trotter Johnson rank, which we get from the minimal change algorithm. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 1, 2, 3]) >>> p.rank_trotterjohnson() 0 >>> p = Permutation([0, 2, 1, 3]) >>> p.rank_trotterjohnson() 7 See Also ======== unrank_trotterjohnson, next_trotterjohnson """ if self.array_form == [] or self.is_Identity: return 0 if self.array_form == [1, 0]: return 1 perm = self.array_form n = self.size rank = 0 for j in range(1, n): k = 1 i = 0 while perm[i] != j: if perm[i] < j: k += 1 i += 1 j1 = j + 1 if rank % 2 == 0: rank = j1*rank + j1 - k else: rank = j1*rank + k - 1 return rank @classmethod def unrank_trotterjohnson(cls, size, rank): """ Trotter Johnson permutation unranking. See [4] section 2.4. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.unrank_trotterjohnson(5, 10) Permutation([0, 3, 1, 2, 4]) See Also ======== rank_trotterjohnson, next_trotterjohnson """ perm = [0]*size r2 = 0 n = ifac(size) pj = 1 for j in range(2, size + 1): pj *= j r1 = (rank * pj) // n k = r1 - j*r2 if r2 % 2 == 0: for i in range(j - 1, j - k - 1, -1): perm[i] = perm[i - 1] perm[j - k - 1] = j - 1 else: for i in range(j - 1, k, -1): perm[i] = perm[i - 1] perm[k] = j - 1 r2 = r1 return cls._af_new(perm) def next_trotterjohnson(self): """ Returns the next permutation in Trotter-Johnson order. If self is the last permutation it returns None. See [4] section 2.4. If it is desired to generate all such permutations, they can be generated in order more quickly with the ``generate_bell`` function. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation([3, 0, 2, 1]) >>> p.rank_trotterjohnson() 4 >>> p = p.next_trotterjohnson(); p Permutation([0, 3, 2, 1]) >>> p.rank_trotterjohnson() 5 See Also ======== rank_trotterjohnson, unrank_trotterjohnson, sympy.utilities.iterables.generate_bell """ pi = self.array_form[:] n = len(pi) st = 0 rho = pi[:] done = False m = n-1 while m > 0 and not done: d = rho.index(m) for i in range(d, m): rho[i] = rho[i + 1] par = _af_parity(rho[:m]) if par == 1: if d == m: m -= 1 else: pi[st + d], pi[st + d + 1] = pi[st + d + 1], pi[st + d] done = True else: if d == 0: m -= 1 st += 1 else: pi[st + d], pi[st + d - 1] = pi[st + d - 1], pi[st + d] done = True if m == 0: return None return self._af_new(pi) def get_precedence_matrix(self): """ Gets the precedence matrix. This is used for computing the distance between two permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> p = Permutation.josephus(3, 6, 1) >>> p Permutation([2, 5, 3, 1, 4, 0]) >>> p.get_precedence_matrix() Matrix([ [0, 0, 0, 0, 0, 0], [1, 0, 0, 0, 1, 0], [1, 1, 0, 1, 1, 1], [1, 1, 0, 0, 1, 0], [1, 0, 0, 0, 0, 0], [1, 1, 0, 1, 1, 0]]) See Also ======== get_precedence_distance, get_adjacency_matrix, get_adjacency_distance """ m = zeros(self.size) perm = self.array_form for i in range(m.rows): for j in range(i + 1, m.cols): m[perm[i], perm[j]] = 1 return m def get_precedence_distance(self, other): """ Computes the precedence distance between two permutations. Explanation =========== Suppose p and p' represent n jobs. The precedence metric counts the number of times a job j is preceded by job i in both p and p'. This metric is commutative. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([2, 0, 4, 3, 1]) >>> q = Permutation([3, 1, 2, 4, 0]) >>> p.get_precedence_distance(q) 7 >>> q.get_precedence_distance(p) 7 See Also ======== get_precedence_matrix, get_adjacency_matrix, get_adjacency_distance """ if self.size != other.size: raise ValueError("The permutations must be of equal size.") self_prec_mat = self.get_precedence_matrix() other_prec_mat = other.get_precedence_matrix() n_prec = 0 for i in range(self.size): for j in range(self.size): if i == j: continue if self_prec_mat[i, j] * other_prec_mat[i, j] == 1: n_prec += 1 d = self.size * (self.size - 1)//2 - n_prec return d def get_adjacency_matrix(self): """ Computes the adjacency matrix of a permutation. Explanation =========== If job i is adjacent to job j in a permutation p then we set m[i, j] = 1 where m is the adjacency matrix of p. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation.josephus(3, 6, 1) >>> p.get_adjacency_matrix() Matrix([ [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 1, 0], [0, 0, 0, 0, 0, 1], [0, 1, 0, 0, 0, 0], [1, 0, 0, 0, 0, 0], [0, 0, 0, 1, 0, 0]]) >>> q = Permutation([0, 1, 2, 3]) >>> q.get_adjacency_matrix() Matrix([ [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1], [0, 0, 0, 0]]) See Also ======== get_precedence_matrix, get_precedence_distance, get_adjacency_distance """ m = zeros(self.size) perm = self.array_form for i in range(self.size - 1): m[perm[i], perm[i + 1]] = 1 return m def get_adjacency_distance(self, other): """ Computes the adjacency distance between two permutations. Explanation =========== This metric counts the number of times a pair i,j of jobs is adjacent in both p and p'. If n_adj is this quantity then the adjacency distance is n - n_adj - 1 [1] [1] Reeves, Colin R. Landscapes, Operators and Heuristic search, Annals of Operational Research, 86, pp 473-490. (1999) Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2, 4]) >>> q = Permutation.josephus(4, 5, 2) >>> p.get_adjacency_distance(q) 3 >>> r = Permutation([0, 2, 1, 4, 3]) >>> p.get_adjacency_distance(r) 4 See Also ======== get_precedence_matrix, get_precedence_distance, get_adjacency_matrix """ if self.size != other.size: raise ValueError("The permutations must be of the same size.") self_adj_mat = self.get_adjacency_matrix() other_adj_mat = other.get_adjacency_matrix() n_adj = 0 for i in range(self.size): for j in range(self.size): if i == j: continue if self_adj_mat[i, j] * other_adj_mat[i, j] == 1: n_adj += 1 d = self.size - n_adj - 1 return d def get_positional_distance(self, other): """ Computes the positional distance between two permutations. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> p = Permutation([0, 3, 1, 2, 4]) >>> q = Permutation.josephus(4, 5, 2) >>> r = Permutation([3, 1, 4, 0, 2]) >>> p.get_positional_distance(q) 12 >>> p.get_positional_distance(r) 12 See Also ======== get_precedence_distance, get_adjacency_distance """ a = self.array_form b = other.array_form if len(a) != len(b): raise ValueError("The permutations must be of the same size.") return sum([abs(a[i] - b[i]) for i in range(len(a))]) @classmethod def josephus(cls, m, n, s=1): """Return as a permutation the shuffling of range(n) using the Josephus scheme in which every m-th item is selected until all have been chosen. The returned permutation has elements listed by the order in which they were selected. The parameter ``s`` stops the selection process when there are ``s`` items remaining and these are selected by continuing the selection, counting by 1 rather than by ``m``. Consider selecting every 3rd item from 6 until only 2 remain:: choices chosen ======== ====== 012345 01 345 2 01 34 25 01 4 253 0 4 2531 0 25314 253140 Examples ======== >>> from sympy.combinatorics import Permutation >>> Permutation.josephus(3, 6, 2).array_form [2, 5, 3, 1, 4, 0] References ========== .. [1] https://en.wikipedia.org/wiki/Flavius_Josephus .. [2] https://en.wikipedia.org/wiki/Josephus_problem .. [3] http://www.wou.edu/~burtonl/josephus.html """ from collections import deque m -= 1 Q = deque(list(range(n))) perm = [] while len(Q) > max(s, 1): for dp in range(m): Q.append(Q.popleft()) perm.append(Q.popleft()) perm.extend(list(Q)) return cls(perm) @classmethod def from_inversion_vector(cls, inversion): """ Calculates the permutation from the inversion vector. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> Permutation.from_inversion_vector([3, 2, 1, 0, 0]) Permutation([3, 2, 1, 0, 4, 5]) """ size = len(inversion) N = list(range(size + 1)) perm = [] try: for k in range(size): val = N[inversion[k]] perm.append(val) N.remove(val) except IndexError: raise ValueError("The inversion vector is not valid.") perm.extend(N) return cls._af_new(perm) @classmethod def random(cls, n): """ Generates a random permutation of length ``n``. Uses the underlying Python pseudo-random number generator. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> Permutation.random(2) in (Permutation([1, 0]), Permutation([0, 1])) True """ perm_array = list(range(n)) random.shuffle(perm_array) return cls._af_new(perm_array) @classmethod def unrank_lex(cls, size, rank): """ Lexicographic permutation unranking. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> init_printing(perm_cyclic=False, pretty_print=False) >>> a = Permutation.unrank_lex(5, 10) >>> a.rank() 10 >>> a Permutation([0, 2, 4, 1, 3]) See Also ======== rank, next_lex """ perm_array = [0] * size psize = 1 for i in range(size): new_psize = psize*(i + 1) d = (rank % new_psize) // psize rank -= d*psize perm_array[size - i - 1] = d for j in range(size - i, size): if perm_array[j] > d - 1: perm_array[j] += 1 psize = new_psize return cls._af_new(perm_array) def resize(self, n): """Resize the permutation to the new size ``n``. Parameters ========== n : int The new size of the permutation. Raises ====== ValueError If the permutation cannot be resized to the given size. This may only happen when resized to a smaller size than the original. Examples ======== >>> from sympy.combinatorics.permutations import Permutation Increasing the size of a permutation: >>> p = Permutation(0, 1, 2) >>> p = p.resize(5) >>> p (4)(0 1 2) Decreasing the size of the permutation: >>> p = p.resize(4) >>> p (3)(0 1 2) If resizing to the specific size breaks the cycles: >>> p.resize(2) Traceback (most recent call last): ... ValueError: The permutation can not be resized to 2 because the cycle (0, 1, 2) may break. """ aform = self.array_form l = len(aform) if n > l: aform += list(range(l, n)) return Permutation._af_new(aform) elif n < l: cyclic_form = self.full_cyclic_form new_cyclic_form = [] for cycle in cyclic_form: cycle_min = min(cycle) cycle_max = max(cycle) if cycle_min <= n-1: if cycle_max > n-1: raise ValueError( "The permutation can not be resized to {} " "because the cycle {} may break." .format(n, tuple(cycle))) new_cyclic_form.append(cycle) return Permutation(new_cyclic_form) return self # XXX Deprecated flag print_cyclic = None def _merge(arr, temp, left, mid, right): """ Merges two sorted arrays and calculates the inversion count. Helper function for calculating inversions. This method is for internal use only. """ i = k = left j = mid inv_count = 0 while i < mid and j <= right: if arr[i] < arr[j]: temp[k] = arr[i] k += 1 i += 1 else: temp[k] = arr[j] k += 1 j += 1 inv_count += (mid -i) while i < mid: temp[k] = arr[i] k += 1 i += 1 if j <= right: k += right - j + 1 j += right - j + 1 arr[left:k + 1] = temp[left:k + 1] else: arr[left:right + 1] = temp[left:right + 1] return inv_count Perm = Permutation _af_new = Perm._af_new class AppliedPermutation(Expr): """A permutation applied to a symbolic variable. Parameters ========== perm : Permutation x : Expr Examples ======== >>> from sympy import Symbol >>> from sympy.combinatorics import Permutation Creating a symbolic permutation function application: >>> x = Symbol('x') >>> p = Permutation(0, 1, 2) >>> p.apply(x) AppliedPermutation((0 1 2), x) >>> _.subs(x, 1) 2 """ def __new__(cls, perm, x, evaluate=None): if evaluate is None: evaluate = global_parameters.evaluate perm = _sympify(perm) x = _sympify(x) if not isinstance(perm, Permutation): raise ValueError("{} must be a Permutation instance." .format(perm)) if evaluate: if x.is_Integer: return perm.apply(x) obj = super().__new__(cls, perm, x) return obj @dispatch(Permutation, Permutation) def _eval_is_eq(lhs, rhs): if lhs._size != rhs._size: return None return lhs._array_form == rhs._array_form

dcbff30c138b49b2ba5c8435bedee7ec8b793900e080202fb10db1224d56aa56

from itertools import combinations from sympy.combinatorics.graycode import GrayCode from sympy.core import Basic class Subset(Basic): """ Represents a basic subset object. Explanation =========== We generate subsets using essentially two techniques, binary enumeration and lexicographic enumeration. The Subset class takes two arguments, the first one describes the initial subset to consider and the second describes the superset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset ['b'] >>> a.prev_binary().subset ['c'] """ _rank_binary = None _rank_lex = None _rank_graycode = None _subset = None _superset = None def __new__(cls, subset, superset): """ Default constructor. It takes the ``subset`` and its ``superset`` as its parameters. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.subset ['c', 'd'] >>> a.superset ['a', 'b', 'c', 'd'] >>> a.size 2 """ if len(subset) > len(superset): raise ValueError('Invalid arguments have been provided. The ' 'superset must be larger than the subset.') for elem in subset: if elem not in superset: raise ValueError('The superset provided is invalid as it does ' 'not contain the element {}'.format(elem)) obj = Basic.__new__(cls) obj._subset = subset obj._superset = superset return obj def iterate_binary(self, k): """ This is a helper function. It iterates over the binary subsets by ``k`` steps. This variable can be both positive or negative. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.iterate_binary(-2).subset ['d'] >>> a = Subset(['a', 'b', 'c'], ['a', 'b', 'c', 'd']) >>> a.iterate_binary(2).subset [] See Also ======== next_binary, prev_binary """ bin_list = Subset.bitlist_from_subset(self.subset, self.superset) n = (int(''.join(bin_list), 2) + k) % 2**self.superset_size bits = bin(n)[2:].rjust(self.superset_size, '0') return Subset.subset_from_bitlist(self.superset, bits) def next_binary(self): """ Generates the next binary ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset ['b'] >>> a = Subset(['a', 'b', 'c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_binary().subset [] See Also ======== prev_binary, iterate_binary """ return self.iterate_binary(1) def prev_binary(self): """ Generates the previous binary ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a', 'b', 'c', 'd']) >>> a.prev_binary().subset ['a', 'b', 'c', 'd'] >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.prev_binary().subset ['c'] See Also ======== next_binary, iterate_binary """ return self.iterate_binary(-1) def next_lexicographic(self): """ Generates the next lexicographically ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.next_lexicographic().subset ['d'] >>> a = Subset(['d'], ['a', 'b', 'c', 'd']) >>> a.next_lexicographic().subset [] See Also ======== prev_lexicographic """ i = self.superset_size - 1 indices = Subset.subset_indices(self.subset, self.superset) if i in indices: if i - 1 in indices: indices.remove(i - 1) else: indices.remove(i) i = i - 1 while not i in indices and i >= 0: i = i - 1 if i >= 0: indices.remove(i) indices.append(i+1) else: while i not in indices and i >= 0: i = i - 1 indices.append(i + 1) ret_set = [] super_set = self.superset for i in indices: ret_set.append(super_set[i]) return Subset(ret_set, super_set) def prev_lexicographic(self): """ Generates the previous lexicographically ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a', 'b', 'c', 'd']) >>> a.prev_lexicographic().subset ['d'] >>> a = Subset(['c','d'], ['a', 'b', 'c', 'd']) >>> a.prev_lexicographic().subset ['c'] See Also ======== next_lexicographic """ i = self.superset_size - 1 indices = Subset.subset_indices(self.subset, self.superset) while i not in indices and i >= 0: i = i - 1 if i - 1 in indices or i == 0: indices.remove(i) else: if i >= 0: indices.remove(i) indices.append(i - 1) indices.append(self.superset_size - 1) ret_set = [] super_set = self.superset for i in indices: ret_set.append(super_set[i]) return Subset(ret_set, super_set) def iterate_graycode(self, k): """ Helper function used for prev_gray and next_gray. It performs ``k`` step overs to get the respective Gray codes. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([1, 2, 3], [1, 2, 3, 4]) >>> a.iterate_graycode(3).subset [1, 4] >>> a.iterate_graycode(-2).subset [1, 2, 4] See Also ======== next_gray, prev_gray """ unranked_code = GrayCode.unrank(self.superset_size, (self.rank_gray + k) % self.cardinality) return Subset.subset_from_bitlist(self.superset, unranked_code) def next_gray(self): """ Generates the next Gray code ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([1, 2, 3], [1, 2, 3, 4]) >>> a.next_gray().subset [1, 3] See Also ======== iterate_graycode, prev_gray """ return self.iterate_graycode(1) def prev_gray(self): """ Generates the previous Gray code ordered subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([2, 3, 4], [1, 2, 3, 4, 5]) >>> a.prev_gray().subset [2, 3, 4, 5] See Also ======== iterate_graycode, next_gray """ return self.iterate_graycode(-1) @property def rank_binary(self): """ Computes the binary ordered rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset([], ['a','b','c','d']) >>> a.rank_binary 0 >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.rank_binary 3 See Also ======== iterate_binary, unrank_binary """ if self._rank_binary is None: self._rank_binary = int("".join( Subset.bitlist_from_subset(self.subset, self.superset)), 2) return self._rank_binary @property def rank_lexicographic(self): """ Computes the lexicographic ranking of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.rank_lexicographic 14 >>> a = Subset([2, 4, 5], [1, 2, 3, 4, 5, 6]) >>> a.rank_lexicographic 43 """ if self._rank_lex is None: def _ranklex(self, subset_index, i, n): if subset_index == [] or i > n: return 0 if i in subset_index: subset_index.remove(i) return 1 + _ranklex(self, subset_index, i + 1, n) return 2**(n - i - 1) + _ranklex(self, subset_index, i + 1, n) indices = Subset.subset_indices(self.subset, self.superset) self._rank_lex = _ranklex(self, indices, 0, self.superset_size) return self._rank_lex @property def rank_gray(self): """ Computes the Gray code ranking of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c','d'], ['a','b','c','d']) >>> a.rank_gray 2 >>> a = Subset([2, 4, 5], [1, 2, 3, 4, 5, 6]) >>> a.rank_gray 27 See Also ======== iterate_graycode, unrank_gray """ if self._rank_graycode is None: bits = Subset.bitlist_from_subset(self.subset, self.superset) self._rank_graycode = GrayCode(len(bits), start=bits).rank return self._rank_graycode @property def subset(self): """ Gets the subset represented by the current instance. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.subset ['c', 'd'] See Also ======== superset, size, superset_size, cardinality """ return self._subset @property def size(self): """ Gets the size of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.size 2 See Also ======== subset, superset, superset_size, cardinality """ return len(self.subset) @property def superset(self): """ Gets the superset of the subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.superset ['a', 'b', 'c', 'd'] See Also ======== subset, size, superset_size, cardinality """ return self._superset @property def superset_size(self): """ Returns the size of the superset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.superset_size 4 See Also ======== subset, superset, size, cardinality """ return len(self.superset) @property def cardinality(self): """ Returns the number of all possible subsets. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> a = Subset(['c', 'd'], ['a', 'b', 'c', 'd']) >>> a.cardinality 16 See Also ======== subset, superset, size, superset_size """ return 2**(self.superset_size) @classmethod def subset_from_bitlist(self, super_set, bitlist): """ Gets the subset defined by the bitlist. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.subset_from_bitlist(['a', 'b', 'c', 'd'], '0011').subset ['c', 'd'] See Also ======== bitlist_from_subset """ if len(super_set) != len(bitlist): raise ValueError("The sizes of the lists are not equal") ret_set = [] for i in range(len(bitlist)): if bitlist[i] == '1': ret_set.append(super_set[i]) return Subset(ret_set, super_set) @classmethod def bitlist_from_subset(self, subset, superset): """ Gets the bitlist corresponding to a subset. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.bitlist_from_subset(['c', 'd'], ['a', 'b', 'c', 'd']) '0011' See Also ======== subset_from_bitlist """ bitlist = ['0'] * len(superset) if type(subset) is Subset: subset = subset.subset for i in Subset.subset_indices(subset, superset): bitlist[i] = '1' return ''.join(bitlist) @classmethod def unrank_binary(self, rank, superset): """ Gets the binary ordered subset of the specified rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.unrank_binary(4, ['a', 'b', 'c', 'd']).subset ['b'] See Also ======== iterate_binary, rank_binary """ bits = bin(rank)[2:].rjust(len(superset), '0') return Subset.subset_from_bitlist(superset, bits) @classmethod def unrank_gray(self, rank, superset): """ Gets the Gray code ordered subset of the specified rank. Examples ======== >>> from sympy.combinatorics.subsets import Subset >>> Subset.unrank_gray(4, ['a', 'b', 'c']).subset ['a', 'b'] >>> Subset.unrank_gray(0, ['a', 'b', 'c']).subset [] See Also ======== iterate_graycode, rank_gray """ graycode_bitlist = GrayCode.unrank(len(superset), rank) return Subset.subset_from_bitlist(superset, graycode_bitlist) @classmethod def subset_indices(self, subset, superset): """Return indices of subset in superset in a list; the list is empty if all elements of ``subset`` are not in ``superset``. Examples ======== >>> from sympy.combinatorics import Subset >>> superset = [1, 3, 2, 5, 4] >>> Subset.subset_indices([3, 2, 1], superset) [1, 2, 0] >>> Subset.subset_indices([1, 6], superset) [] >>> Subset.subset_indices([], superset) [] """ a, b = superset, subset sb = set(b) d = {} for i, ai in enumerate(a): if ai in sb: d[ai] = i sb.remove(ai) if not sb: break else: return list() return [d[bi] for bi in b] def ksubsets(superset, k): """ Finds the subsets of size ``k`` in lexicographic order. This uses the itertools generator. Examples ======== >>> from sympy.combinatorics.subsets import ksubsets >>> list(ksubsets([1, 2, 3], 2)) [(1, 2), (1, 3), (2, 3)] >>> list(ksubsets([1, 2, 3, 4, 5], 2)) [(1, 2), (1, 3), (1, 4), (1, 5), (2, 3), (2, 4), \ (2, 5), (3, 4), (3, 5), (4, 5)] See Also ======== Subset """ return combinations(superset, k)

20ac75dbfc9626a110ee0fa806e0167795512db08e5b22f42c6e0f42ee37052f

from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.permutations import Permutation from sympy.utilities.iterables import uniq _af_new = Permutation._af_new def DirectProduct(*groups): """ Returns the direct product of several groups as a permutation group. Explanation =========== This is implemented much like the __mul__ procedure for taking the direct product of two permutation groups, but the idea of shifting the generators is realized in the case of an arbitrary number of groups. A call to DirectProduct(G1, G2, ..., Gn) is generally expected to be faster than a call to G1*G2*...*Gn (and thus the need for this algorithm). Examples ======== >>> from sympy.combinatorics.group_constructs import DirectProduct >>> from sympy.combinatorics.named_groups import CyclicGroup >>> C = CyclicGroup(4) >>> G = DirectProduct(C, C, C) >>> G.order() 64 See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.__mul__ """ degrees = [] gens_count = [] total_degree = 0 total_gens = 0 for group in groups: current_deg = group.degree current_num_gens = len(group.generators) degrees.append(current_deg) total_degree += current_deg gens_count.append(current_num_gens) total_gens += current_num_gens array_gens = [] for i in range(total_gens): array_gens.append(list(range(total_degree))) current_gen = 0 current_deg = 0 for i in range(len(gens_count)): for j in range(current_gen, current_gen + gens_count[i]): gen = ((groups[i].generators)[j - current_gen]).array_form array_gens[j][current_deg:current_deg + degrees[i]] = \ [x + current_deg for x in gen] current_gen += gens_count[i] current_deg += degrees[i] perm_gens = list(uniq([_af_new(list(a)) for a in array_gens])) return PermutationGroup(perm_gens, dups=False)

e606bdf433557bb0e9363559f9b0d58af0c56dde60895b16bda3bfe1546a88ff

from sympy.combinatorics.permutations import Permutation, _af_rmul, \ _af_invert, _af_new from sympy.combinatorics.perm_groups import PermutationGroup, _orbit, \ _orbit_transversal from sympy.combinatorics.util import _distribute_gens_by_base, \ _orbits_transversals_from_bsgs """ References for tensor canonicalization: [1] R. Portugal "Algorithmic simplification of tensor expressions", J. Phys. A 32 (1999) 7779-7789 [2] R. Portugal, B.F. Svaiter "Group-theoretic Approach for Symbolic Tensor Manipulation: I. Free Indices" arXiv:math-ph/0107031v1 [3] L.R.U. Manssur, R. Portugal "Group-theoretic Approach for Symbolic Tensor Manipulation: II. Dummy Indices" arXiv:math-ph/0107032v1 [4] xperm.c part of XPerm written by J. M. Martin-Garcia http://www.xact.es/index.html """ def dummy_sgs(dummies, sym, n): """ Return the strong generators for dummy indices. Parameters ========== dummies : List of dummy indices. `dummies[2k], dummies[2k+1]` are paired indices. In base form, the dummy indices are always in consecutive positions. sym : symmetry under interchange of contracted dummies:: * None no symmetry * 0 commuting * 1 anticommuting n : number of indices Examples ======== >>> from sympy.combinatorics.tensor_can import dummy_sgs >>> dummy_sgs(list(range(2, 8)), 0, 8) [[0, 1, 3, 2, 4, 5, 6, 7, 8, 9], [0, 1, 2, 3, 5, 4, 6, 7, 8, 9], [0, 1, 2, 3, 4, 5, 7, 6, 8, 9], [0, 1, 4, 5, 2, 3, 6, 7, 8, 9], [0, 1, 2, 3, 6, 7, 4, 5, 8, 9]] """ if len(dummies) > n: raise ValueError("List too large") res = [] # exchange of contravariant and covariant indices if sym is not None: for j in dummies[::2]: a = list(range(n + 2)) if sym == 1: a[n] = n + 1 a[n + 1] = n a[j], a[j + 1] = a[j + 1], a[j] res.append(a) # rename dummy indices for j in dummies[:-3:2]: a = list(range(n + 2)) a[j:j + 4] = a[j + 2], a[j + 3], a[j], a[j + 1] res.append(a) return res def _min_dummies(dummies, sym, indices): """ Return list of minima of the orbits of indices in group of dummies. See ``double_coset_can_rep`` for the description of ``dummies`` and ``sym``. ``indices`` is the initial list of dummy indices. Examples ======== >>> from sympy.combinatorics.tensor_can import _min_dummies >>> _min_dummies([list(range(2, 8))], [0], list(range(10))) [0, 1, 2, 2, 2, 2, 2, 2, 8, 9] """ num_types = len(sym) m = [] for dx in dummies: if dx: m.append(min(dx)) else: m.append(None) res = indices[:] for i in range(num_types): for c, i in enumerate(indices): for j in range(num_types): if i in dummies[j]: res[c] = m[j] break return res def _trace_S(s, j, b, S_cosets): """ Return the representative h satisfying s[h[b]] == j If there is not such a representative return None """ for h in S_cosets[b]: if s[h[b]] == j: return h return None def _trace_D(gj, p_i, Dxtrav): """ Return the representative h satisfying h[gj] == p_i If there is not such a representative return None """ for h in Dxtrav: if h[gj] == p_i: return h return None def _dumx_remove(dumx, dumx_flat, p0): """ remove p0 from dumx """ res = [] for dx in dumx: if p0 not in dx: res.append(dx) continue k = dx.index(p0) if k % 2 == 0: p0_paired = dx[k + 1] else: p0_paired = dx[k - 1] dx.remove(p0) dx.remove(p0_paired) dumx_flat.remove(p0) dumx_flat.remove(p0_paired) res.append(dx) def transversal2coset(size, base, transversal): a = [] j = 0 for i in range(size): if i in base: a.append(sorted(transversal[j].values())) j += 1 else: a.append([list(range(size))]) j = len(a) - 1 while a[j] == [list(range(size))]: j -= 1 return a[:j + 1] def double_coset_can_rep(dummies, sym, b_S, sgens, S_transversals, g): """ Butler-Portugal algorithm for tensor canonicalization with dummy indices. Parameters ========== dummies list of lists of dummy indices, one list for each type of index; the dummy indices are put in order contravariant, covariant [d0, -d0, d1, -d1, ...]. sym list of the symmetries of the index metric for each type. possible symmetries of the metrics * 0 symmetric * 1 antisymmetric * None no symmetry b_S base of a minimal slot symmetry BSGS. sgens generators of the slot symmetry BSGS. S_transversals transversals for the slot BSGS. g permutation representing the tensor. Returns ======= Return 0 if the tensor is zero, else return the array form of the permutation representing the canonical form of the tensor. Notes ===== A tensor with dummy indices can be represented in a number of equivalent ways which typically grows exponentially with the number of indices. To be able to establish if two tensors with many indices are equal becomes computationally very slow in absence of an efficient algorithm. The Butler-Portugal algorithm [3] is an efficient algorithm to put tensors in canonical form, solving the above problem. Portugal observed that a tensor can be represented by a permutation, and that the class of tensors equivalent to it under slot and dummy symmetries is equivalent to the double coset `D*g*S` (Note: in this documentation we use the conventions for multiplication of permutations p, q with (p*q)(i) = p[q[i]] which is opposite to the one used in the Permutation class) Using the algorithm by Butler to find a representative of the double coset one can find a canonical form for the tensor. To see this correspondence, let `g` be a permutation in array form; a tensor with indices `ind` (the indices including both the contravariant and the covariant ones) can be written as `t = T(ind[g[0]],..., ind[g[n-1]])`, where `n= len(ind)`; `g` has size `n + 2`, the last two indices for the sign of the tensor (trick introduced in [4]). A slot symmetry transformation `s` is a permutation acting on the slots `t -> T(ind[(g*s)[0]],..., ind[(g*s)[n-1]])` A dummy symmetry transformation acts on `ind` `t -> T(ind[(d*g)[0]],..., ind[(d*g)[n-1]])` Being interested only in the transformations of the tensor under these symmetries, one can represent the tensor by `g`, which transforms as `g -> d*g*s`, so it belongs to the coset `D*g*S`, or in other words to the set of all permutations allowed by the slot and dummy symmetries. Let us explain the conventions by an example. Given a tensor `T^{d3 d2 d1}{}_{d1 d2 d3}` with the slot symmetries `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}` `T^{a0 a1 a2 a3 a4 a5} = -T^{a4 a1 a2 a3 a0 a5}` and symmetric metric, find the tensor equivalent to it which is the lowest under the ordering of indices: lexicographic ordering `d1, d2, d3` and then contravariant before covariant index; that is the canonical form of the tensor. The canonical form is `-T^{d1 d2 d3}{}_{d1 d2 d3}` obtained using `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}`. To convert this problem in the input for this function, use the following ordering of the index names (- for covariant for short) `d1, -d1, d2, -d2, d3, -d3` `T^{d3 d2 d1}{}_{d1 d2 d3}` corresponds to `g = [4, 2, 0, 1, 3, 5, 6, 7]` where the last two indices are for the sign `sgens = [Permutation(0, 2)(6, 7), Permutation(0, 4)(6, 7)]` sgens[0] is the slot symmetry `-(0, 2)` `T^{a0 a1 a2 a3 a4 a5} = -T^{a2 a1 a0 a3 a4 a5}` sgens[1] is the slot symmetry `-(0, 4)` `T^{a0 a1 a2 a3 a4 a5} = -T^{a4 a1 a2 a3 a0 a5}` The dummy symmetry group D is generated by the strong base generators `[(0, 1), (2, 3), (4, 5), (0, 2)(1, 3), (0, 4)(1, 5)]` where the first three interchange covariant and contravariant positions of the same index (d1 <-> -d1) and the last two interchange the dummy indices themselves (d1 <-> d2). The dummy symmetry acts from the left `d = [1, 0, 2, 3, 4, 5, 6, 7]` exchange `d1 <-> -d1` `T^{d3 d2 d1}{}_{d1 d2 d3} == T^{d3 d2}{}_{d1}{}^{d1}{}_{d2 d3}` `g=[4, 2, 0, 1, 3, 5, 6, 7] -> [4, 2, 1, 0, 3, 5, 6, 7] = _af_rmul(d, g)` which differs from `_af_rmul(g, d)`. The slot symmetry acts from the right `s = [2, 1, 0, 3, 4, 5, 7, 6]` exchanges slots 0 and 2 and changes sign `T^{d3 d2 d1}{}_{d1 d2 d3} == -T^{d1 d2 d3}{}_{d1 d2 d3}` `g=[4,2,0,1,3,5,6,7] -> [0, 2, 4, 1, 3, 5, 7, 6] = _af_rmul(g, s)` Example in which the tensor is zero, same slot symmetries as above: `T^{d2}{}_{d1 d3}{}^{d1 d3}{}_{d2}` `= -T^{d3}{}_{d1 d3}{}^{d1 d2}{}_{d2}` under slot symmetry `-(0,4)`; `= T_{d3 d1}{}^{d3}{}^{d1 d2}{}_{d2}` under slot symmetry `-(0,2)`; `= T^{d3}{}_{d1 d3}{}^{d1 d2}{}_{d2}` symmetric metric; `= 0` since two of these lines have tensors differ only for the sign. The double coset D*g*S consists of permutations `h = d*g*s` corresponding to equivalent tensors; if there are two `h` which are the same apart from the sign, return zero; otherwise choose as representative the tensor with indices ordered lexicographically according to `[d1, -d1, d2, -d2, d3, -d3]` that is `rep = min(D*g*S) = min([d*g*s for d in D for s in S])` The indices are fixed one by one; first choose the lowest index for slot 0, then the lowest remaining index for slot 1, etc. Doing this one obtains a chain of stabilizers `S -> S_{b0} -> S_{b0,b1} -> ...` and `D -> D_{p0} -> D_{p0,p1} -> ...` where `[b0, b1, ...] = range(b)` is a base of the symmetric group; the strong base `b_S` of S is an ordered sublist of it; therefore it is sufficient to compute once the strong base generators of S using the Schreier-Sims algorithm; the stabilizers of the strong base generators are the strong base generators of the stabilizer subgroup. `dbase = [p0, p1, ...]` is not in general in lexicographic order, so that one must recompute the strong base generators each time; however this is trivial, there is no need to use the Schreier-Sims algorithm for D. The algorithm keeps a TAB of elements `(s_i, d_i, h_i)` where `h_i = d_i*g*s_i` satisfying `h_i[j] = p_j` for `0 <= j < i` starting from `s_0 = id, d_0 = id, h_0 = g`. The equations `h_0[0] = p_0, h_1[1] = p_1,...` are solved in this order, choosing each time the lowest possible value of p_i For `j < i` `d_i*g*s_i*S_{b_0,...,b_{i-1}}*b_j = D_{p_0,...,p_{i-1}}*p_j` so that for dx in `D_{p_0,...,p_{i-1}}` and sx in `S_{base[0],...,base[i-1]}` one has `dx*d_i*g*s_i*sx*b_j = p_j` Search for dx, sx such that this equation holds for `j = i`; it can be written as `s_i*sx*b_j = J, dx*d_i*g*J = p_j` `sx*b_j = s_i**-1*J; sx = trace(s_i**-1, S_{b_0,...,b_{i-1}})` `dx**-1*p_j = d_i*g*J; dx = trace(d_i*g*J, D_{p_0,...,p_{i-1}})` `s_{i+1} = s_i*trace(s_i**-1*J, S_{b_0,...,b_{i-1}})` `d_{i+1} = trace(d_i*g*J, D_{p_0,...,p_{i-1}})**-1*d_i` `h_{i+1}*b_i = d_{i+1}*g*s_{i+1}*b_i = p_i` `h_n*b_j = p_j` for all j, so that `h_n` is the solution. Add the found `(s, d, h)` to TAB1. At the end of the iteration sort TAB1 with respect to the `h`; if there are two consecutive `h` in TAB1 which differ only for the sign, the tensor is zero, so return 0; if there are two consecutive `h` which are equal, keep only one. Then stabilize the slot generators under `i` and the dummy generators under `p_i`. Assign `TAB = TAB1` at the end of the iteration step. At the end `TAB` contains a unique `(s, d, h)`, since all the slots of the tensor `h` have been fixed to have the minimum value according to the symmetries. The algorithm returns `h`. It is important that the slot BSGS has lexicographic minimal base, otherwise there is an `i` which does not belong to the slot base for which `p_i` is fixed by the dummy symmetry only, while `i` is not invariant from the slot stabilizer, so `p_i` is not in general the minimal value. This algorithm differs slightly from the original algorithm [3]: the canonical form is minimal lexicographically, and the BSGS has minimal base under lexicographic order. Equal tensors `h` are eliminated from TAB. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.tensor_can import double_coset_can_rep, get_transversals >>> gens = [Permutation(x) for x in [[2, 1, 0, 3, 4, 5, 7, 6], [4, 1, 2, 3, 0, 5, 7, 6]]] >>> base = [0, 2] >>> g = Permutation([4, 2, 0, 1, 3, 5, 6, 7]) >>> transversals = get_transversals(base, gens) >>> double_coset_can_rep([list(range(6))], [0], base, gens, transversals, g) [0, 1, 2, 3, 4, 5, 7, 6] >>> g = Permutation([4, 1, 3, 0, 5, 2, 6, 7]) >>> double_coset_can_rep([list(range(6))], [0], base, gens, transversals, g) 0 """ size = g.size g = g.array_form num_dummies = size - 2 indices = list(range(num_dummies)) all_metrics_with_sym = all([_ is not None for _ in sym]) num_types = len(sym) dumx = dummies[:] dumx_flat = [] for dx in dumx: dumx_flat.extend(dx) b_S = b_S[:] sgensx = [h._array_form for h in sgens] if b_S: S_transversals = transversal2coset(size, b_S, S_transversals) # strong generating set for D dsgsx = [] for i in range(num_types): dsgsx.extend(dummy_sgs(dumx[i], sym[i], num_dummies)) idn = list(range(size)) # TAB = list of entries (s, d, h) where h = _af_rmuln(d,g,s) # for short, in the following d*g*s means _af_rmuln(d,g,s) TAB = [(idn, idn, g)] for i in range(size - 2): b = i testb = b in b_S and sgensx if testb: sgensx1 = [_af_new(_) for _ in sgensx] deltab = _orbit(size, sgensx1, b) else: deltab = {b} # p1 = min(IMAGES) = min(Union D_p*h*deltab for h in TAB) if all_metrics_with_sym: md = _min_dummies(dumx, sym, indices) else: md = [min(_orbit(size, [_af_new( ddx) for ddx in dsgsx], ii)) for ii in range(size - 2)] p_i = min([min([md[h[x]] for x in deltab]) for s, d, h in TAB]) dsgsx1 = [_af_new(_) for _ in dsgsx] Dxtrav = _orbit_transversal(size, dsgsx1, p_i, False, af=True) \ if dsgsx else None if Dxtrav: Dxtrav = [_af_invert(x) for x in Dxtrav] # compute the orbit of p_i for ii in range(num_types): if p_i in dumx[ii]: # the orbit is made by all the indices in dum[ii] if sym[ii] is not None: deltap = dumx[ii] else: # the orbit is made by all the even indices if p_i # is even, by all the odd indices if p_i is odd p_i_index = dumx[ii].index(p_i) % 2 deltap = dumx[ii][p_i_index::2] break else: deltap = [p_i] TAB1 = [] while TAB: s, d, h = TAB.pop() if min([md[h[x]] for x in deltab]) != p_i: continue deltab1 = [x for x in deltab if md[h[x]] == p_i] # NEXT = s*deltab1 intersection (d*g)**-1*deltap dg = _af_rmul(d, g) dginv = _af_invert(dg) sdeltab = [s[x] for x in deltab1] gdeltap = [dginv[x] for x in deltap] NEXT = [x for x in sdeltab if x in gdeltap] # d, s satisfy # d*g*s*base[i-1] = p_{i-1}; using the stabilizers # d*g*s*S_{base[0],...,base[i-1]}*base[i-1] = # D_{p_0,...,p_{i-1}}*p_{i-1} # so that to find d1, s1 satisfying d1*g*s1*b = p_i # one can look for dx in D_{p_0,...,p_{i-1}} and # sx in S_{base[0],...,base[i-1]} # d1 = dx*d; s1 = s*sx # d1*g*s1*b = dx*d*g*s*sx*b = p_i for j in NEXT: if testb: # solve s1*b = j with s1 = s*sx for some element sx # of the stabilizer of ..., base[i-1] # sx*b = s**-1*j; sx = _trace_S(s, j,...) # s1 = s*trace_S(s**-1*j,...) s1 = _trace_S(s, j, b, S_transversals) if not s1: continue else: s1 = [s[ix] for ix in s1] else: s1 = s # assert s1[b] == j # invariant # solve d1*g*j = p_i with d1 = dx*d for some element dg # of the stabilizer of ..., p_{i-1} # dx**-1*p_i = d*g*j; dx**-1 = trace_D(d*g*j,...) # d1 = trace_D(d*g*j,...)**-1*d # to save an inversion in the inner loop; notice we did # Dxtrav = [perm_af_invert(x) for x in Dxtrav] out of the loop if Dxtrav: d1 = _trace_D(dg[j], p_i, Dxtrav) if not d1: continue else: if p_i != dg[j]: continue d1 = idn assert d1[dg[j]] == p_i # invariant d1 = [d1[ix] for ix in d] h1 = [d1[g[ix]] for ix in s1] # assert h1[b] == p_i # invariant TAB1.append((s1, d1, h1)) # if TAB contains equal permutations, keep only one of them; # if TAB contains equal permutations up to the sign, return 0 TAB1.sort(key=lambda x: x[-1]) prev = [0] * size while TAB1: s, d, h = TAB1.pop() if h[:-2] == prev[:-2]: if h[-1] != prev[-1]: return 0 else: TAB.append((s, d, h)) prev = h # stabilize the SGS sgensx = [h for h in sgensx if h[b] == b] if b in b_S: b_S.remove(b) _dumx_remove(dumx, dumx_flat, p_i) dsgsx = [] for i in range(num_types): dsgsx.extend(dummy_sgs(dumx[i], sym[i], num_dummies)) return TAB[0][-1] def canonical_free(base, gens, g, num_free): """ Canonicalization of a tensor with respect to free indices choosing the minimum with respect to lexicographical ordering in the free indices. Explanation =========== ``base``, ``gens`` BSGS for slot permutation group ``g`` permutation representing the tensor ``num_free`` number of free indices The indices must be ordered with first the free indices See explanation in double_coset_can_rep The algorithm is a variation of the one given in [2]. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import canonical_free >>> gens = [[1, 0, 2, 3, 5, 4], [2, 3, 0, 1, 4, 5],[0, 1, 3, 2, 5, 4]] >>> gens = [Permutation(h) for h in gens] >>> base = [0, 2] >>> g = Permutation([2, 1, 0, 3, 4, 5]) >>> canonical_free(base, gens, g, 4) [0, 3, 1, 2, 5, 4] Consider the product of Riemann tensors ``T = R^{a}_{d0}^{d1,d2}*R_{d2,d1}^{d0,b}`` The order of the indices is ``[a, b, d0, -d0, d1, -d1, d2, -d2]`` The permutation corresponding to the tensor is ``g = [0, 3, 4, 6, 7, 5, 2, 1, 8, 9]`` In particular ``a`` is position ``0``, ``b`` is in position ``9``. Use the slot symmetries to get `T` is a form which is the minimal in lexicographic order in the free indices ``a`` and ``b``, e.g. ``-R^{a}_{d0}^{d1,d2}*R^{b,d0}_{d2,d1}`` corresponding to ``[0, 3, 4, 6, 1, 2, 7, 5, 9, 8]`` >>> from sympy.combinatorics.tensor_can import riemann_bsgs, tensor_gens >>> base, gens = riemann_bsgs >>> size, sbase, sgens = tensor_gens(base, gens, [[], []], 0) >>> g = Permutation([0, 3, 4, 6, 7, 5, 2, 1, 8, 9]) >>> canonical_free(sbase, [Permutation(h) for h in sgens], g, 2) [0, 3, 4, 6, 1, 2, 7, 5, 9, 8] """ g = g.array_form size = len(g) if not base: return g[:] transversals = get_transversals(base, gens) for x in sorted(g[:-2]): if x not in base: base.append(x) h = g for i, transv in enumerate(transversals): h_i = [size]*num_free # find the element s in transversals[i] such that # _af_rmul(h, s) has its free elements with the lowest position in h s = None for sk in transv.values(): h1 = _af_rmul(h, sk) hi = [h1.index(ix) for ix in range(num_free)] if hi < h_i: h_i = hi s = sk if s: h = _af_rmul(h, s) return h def _get_map_slots(size, fixed_slots): res = list(range(size)) pos = 0 for i in range(size): if i in fixed_slots: continue res[i] = pos pos += 1 return res def _lift_sgens(size, fixed_slots, free, s): a = [] j = k = 0 fd = list(zip(fixed_slots, free)) fd = [y for x, y in sorted(fd)] num_free = len(free) for i in range(size): if i in fixed_slots: a.append(fd[k]) k += 1 else: a.append(s[j] + num_free) j += 1 return a def canonicalize(g, dummies, msym, *v): """ canonicalize tensor formed by tensors Parameters ========== g : permutation representing the tensor dummies : list representing the dummy indices it can be a list of dummy indices of the same type or a list of lists of dummy indices, one list for each type of index; the dummy indices must come after the free indices, and put in order contravariant, covariant [d0, -d0, d1,-d1,...] msym : symmetry of the metric(s) it can be an integer or a list; in the first case it is the symmetry of the dummy index metric; in the second case it is the list of the symmetries of the index metric for each type v : list, (base_i, gens_i, n_i, sym_i) for tensors of type `i` base_i, gens_i : BSGS for tensors of this type. The BSGS should have minimal base under lexicographic ordering; if not, an attempt is made do get the minimal BSGS; in case of failure, canonicalize_naive is used, which is much slower. n_i : number of tensors of type `i`. sym_i : symmetry under exchange of component tensors of type `i`. Both for msym and sym_i the cases are * None no symmetry * 0 commuting * 1 anticommuting Returns ======= 0 if the tensor is zero, else return the array form of the permutation representing the canonical form of the tensor. Algorithm ========= First one uses canonical_free to get the minimum tensor under lexicographic order, using only the slot symmetries. If the component tensors have not minimal BSGS, it is attempted to find it; if the attempt fails canonicalize_naive is used instead. Compute the residual slot symmetry keeping fixed the free indices using tensor_gens(base, gens, list_free_indices, sym). Reduce the problem eliminating the free indices. Then use double_coset_can_rep and lift back the result reintroducing the free indices. Examples ======== one type of index with commuting metric; `A_{a b}` and `B_{a b}` antisymmetric and commuting `T = A_{d0 d1} * B^{d0}{}_{d2} * B^{d2 d1}` `ord = [d0,-d0,d1,-d1,d2,-d2]` order of the indices g = [1, 3, 0, 5, 4, 2, 6, 7] `T_c = 0` >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, canonicalize, bsgs_direct_product >>> from sympy.combinatorics import Permutation >>> base2a, gens2a = get_symmetric_group_sgs(2, 1) >>> t0 = (base2a, gens2a, 1, 0) >>> t1 = (base2a, gens2a, 2, 0) >>> g = Permutation([1, 3, 0, 5, 4, 2, 6, 7]) >>> canonicalize(g, range(6), 0, t0, t1) 0 same as above, but with `B_{a b}` anticommuting `T_c = -A^{d0 d1} * B_{d0}{}^{d2} * B_{d1 d2}` can = [0,2,1,4,3,5,7,6] >>> t1 = (base2a, gens2a, 2, 1) >>> canonicalize(g, range(6), 0, t0, t1) [0, 2, 1, 4, 3, 5, 7, 6] two types of indices `[a,b,c,d,e,f]` and `[m,n]`, in this order, both with commuting metric `f^{a b c}` antisymmetric, commuting `A_{m a}` no symmetry, commuting `T = f^c{}_{d a} * f^f{}_{e b} * A_m{}^d * A^{m b} * A_n{}^a * A^{n e}` ord = [c,f,a,-a,b,-b,d,-d,e,-e,m,-m,n,-n] g = [0,7,3, 1,9,5, 11,6, 10,4, 13,2, 12,8, 14,15] The canonical tensor is `T_c = -f^{c a b} * f^{f d e} * A^m{}_a * A_{m d} * A^n{}_b * A_{n e}` can = [0,2,4, 1,6,8, 10,3, 11,7, 12,5, 13,9, 15,14] >>> base_f, gens_f = get_symmetric_group_sgs(3, 1) >>> base1, gens1 = get_symmetric_group_sgs(1) >>> base_A, gens_A = bsgs_direct_product(base1, gens1, base1, gens1) >>> t0 = (base_f, gens_f, 2, 0) >>> t1 = (base_A, gens_A, 4, 0) >>> dummies = [range(2, 10), range(10, 14)] >>> g = Permutation([0, 7, 3, 1, 9, 5, 11, 6, 10, 4, 13, 2, 12, 8, 14, 15]) >>> canonicalize(g, dummies, [0, 0], t0, t1) [0, 2, 4, 1, 6, 8, 10, 3, 11, 7, 12, 5, 13, 9, 15, 14] """ from sympy.combinatorics.testutil import canonicalize_naive if not isinstance(msym, list): if not msym in [0, 1, None]: raise ValueError('msym must be 0, 1 or None') num_types = 1 else: num_types = len(msym) if not all(msymx in [0, 1, None] for msymx in msym): raise ValueError('msym entries must be 0, 1 or None') if len(dummies) != num_types: raise ValueError( 'dummies and msym must have the same number of elements') size = g.size num_tensors = 0 v1 = [] for i in range(len(v)): base_i, gens_i, n_i, sym_i = v[i] # check that the BSGS is minimal; # this property is used in double_coset_can_rep; # if it is not minimal use canonicalize_naive if not _is_minimal_bsgs(base_i, gens_i): mbsgs = get_minimal_bsgs(base_i, gens_i) if not mbsgs: can = canonicalize_naive(g, dummies, msym, *v) return can base_i, gens_i = mbsgs v1.append((base_i, gens_i, [[]] * n_i, sym_i)) num_tensors += n_i if num_types == 1 and not isinstance(msym, list): dummies = [dummies] msym = [msym] flat_dummies = [] for dumx in dummies: flat_dummies.extend(dumx) if flat_dummies and flat_dummies != list(range(flat_dummies[0], flat_dummies[-1] + 1)): raise ValueError('dummies is not valid') # slot symmetry of the tensor size1, sbase, sgens = gens_products(*v1) if size != size1: raise ValueError( 'g has size %d, generators have size %d' % (size, size1)) free = [i for i in range(size - 2) if i not in flat_dummies] num_free = len(free) # g1 minimal tensor under slot symmetry g1 = canonical_free(sbase, sgens, g, num_free) if not flat_dummies: return g1 # save the sign of g1 sign = 0 if g1[-1] == size - 1 else 1 # the free indices are kept fixed. # Determine free_i, the list of slots of tensors which are fixed # since they are occupied by free indices, which are fixed. start = 0 for i in range(len(v)): free_i = [] base_i, gens_i, n_i, sym_i = v[i] len_tens = gens_i[0].size - 2 # for each component tensor get a list od fixed islots for j in range(n_i): # get the elements corresponding to the component tensor h = g1[start:(start + len_tens)] fr = [] # get the positions of the fixed elements in h for k in free: if k in h: fr.append(h.index(k)) free_i.append(fr) start += len_tens v1[i] = (base_i, gens_i, free_i, sym_i) # BSGS of the tensor with fixed free indices # if tensor_gens fails in gens_product, use canonicalize_naive size, sbase, sgens = gens_products(*v1) # reduce the permutations getting rid of the free indices pos_free = [g1.index(x) for x in range(num_free)] size_red = size - num_free g1_red = [x - num_free for x in g1 if x in flat_dummies] if sign: g1_red.extend([size_red - 1, size_red - 2]) else: g1_red.extend([size_red - 2, size_red - 1]) map_slots = _get_map_slots(size, pos_free) sbase_red = [map_slots[i] for i in sbase if i not in pos_free] sgens_red = [_af_new([map_slots[i] for i in y._array_form if i not in pos_free]) for y in sgens] dummies_red = [[x - num_free for x in y] for y in dummies] transv_red = get_transversals(sbase_red, sgens_red) g1_red = _af_new(g1_red) g2 = double_coset_can_rep( dummies_red, msym, sbase_red, sgens_red, transv_red, g1_red) if g2 == 0: return 0 # lift to the case with the free indices g3 = _lift_sgens(size, pos_free, free, g2) return g3 def perm_af_direct_product(gens1, gens2, signed=True): """ Direct products of the generators gens1 and gens2. Examples ======== >>> from sympy.combinatorics.tensor_can import perm_af_direct_product >>> gens1 = [[1, 0, 2, 3], [0, 1, 3, 2]] >>> gens2 = [[1, 0]] >>> perm_af_direct_product(gens1, gens2, False) [[1, 0, 2, 3, 4, 5], [0, 1, 3, 2, 4, 5], [0, 1, 2, 3, 5, 4]] >>> gens1 = [[1, 0, 2, 3, 5, 4], [0, 1, 3, 2, 4, 5]] >>> gens2 = [[1, 0, 2, 3]] >>> perm_af_direct_product(gens1, gens2, True) [[1, 0, 2, 3, 4, 5, 7, 6], [0, 1, 3, 2, 4, 5, 6, 7], [0, 1, 2, 3, 5, 4, 6, 7]] """ gens1 = [list(x) for x in gens1] gens2 = [list(x) for x in gens2] s = 2 if signed else 0 n1 = len(gens1[0]) - s n2 = len(gens2[0]) - s start = list(range(n1)) end = list(range(n1, n1 + n2)) if signed: gens1 = [gen[:-2] + end + [gen[-2] + n2, gen[-1] + n2] for gen in gens1] gens2 = [start + [x + n1 for x in gen] for gen in gens2] else: gens1 = [gen + end for gen in gens1] gens2 = [start + [x + n1 for x in gen] for gen in gens2] res = gens1 + gens2 return res def bsgs_direct_product(base1, gens1, base2, gens2, signed=True): """ Direct product of two BSGS. Parameters ========== base1 : base of the first BSGS. gens1 : strong generating sequence of the first BSGS. base2, gens2 : similarly for the second BSGS. signed : flag for signed permutations. Examples ======== >>> from sympy.combinatorics.tensor_can import (get_symmetric_group_sgs, bsgs_direct_product) >>> base1, gens1 = get_symmetric_group_sgs(1) >>> base2, gens2 = get_symmetric_group_sgs(2) >>> bsgs_direct_product(base1, gens1, base2, gens2) ([1], [(4)(1 2)]) """ s = 2 if signed else 0 n1 = gens1[0].size - s base = list(base1) base += [x + n1 for x in base2] gens1 = [h._array_form for h in gens1] gens2 = [h._array_form for h in gens2] gens = perm_af_direct_product(gens1, gens2, signed) size = len(gens[0]) id_af = list(range(size)) gens = [h for h in gens if h != id_af] if not gens: gens = [id_af] return base, [_af_new(h) for h in gens] def get_symmetric_group_sgs(n, antisym=False): """ Return base, gens of the minimal BSGS for (anti)symmetric tensor Parameters ========== ``n``: rank of the tensor ``antisym`` : bool ``antisym = False`` symmetric tensor ``antisym = True`` antisymmetric tensor Examples ======== >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs >>> get_symmetric_group_sgs(3) ([0, 1], [(4)(0 1), (4)(1 2)]) """ if n == 1: return [], [_af_new(list(range(3)))] gens = [Permutation(n - 1)(i, i + 1)._array_form for i in range(n - 1)] if antisym == 0: gens = [x + [n, n + 1] for x in gens] else: gens = [x + [n + 1, n] for x in gens] base = list(range(n - 1)) return base, [_af_new(h) for h in gens] riemann_bsgs = [0, 2], [Permutation(0, 1)(4, 5), Permutation(2, 3)(4, 5), Permutation(5)(0, 2)(1, 3)] def get_transversals(base, gens): """ Return transversals for the group with BSGS base, gens """ if not base: return [] stabs = _distribute_gens_by_base(base, gens) orbits, transversals = _orbits_transversals_from_bsgs(base, stabs) transversals = [{x: h._array_form for x, h in y.items()} for y in transversals] return transversals def _is_minimal_bsgs(base, gens): """ Check if the BSGS has minimal base under lexigographic order. base, gens BSGS Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import riemann_bsgs, _is_minimal_bsgs >>> _is_minimal_bsgs(*riemann_bsgs) True >>> riemann_bsgs1 = ([2, 0], ([Permutation(5)(0, 1)(4, 5), Permutation(5)(0, 2)(1, 3)])) >>> _is_minimal_bsgs(*riemann_bsgs1) False """ base1 = [] sgs1 = gens[:] size = gens[0].size for i in range(size): if not all(h._array_form[i] == i for h in sgs1): base1.append(i) sgs1 = [h for h in sgs1 if h._array_form[i] == i] return base1 == base def get_minimal_bsgs(base, gens): """ Compute a minimal GSGS base, gens BSGS If base, gens is a minimal BSGS return it; else return a minimal BSGS if it fails in finding one, it returns None TODO: use baseswap in the case in which if it fails in finding a minimal BSGS Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.tensor_can import get_minimal_bsgs >>> riemann_bsgs1 = ([2, 0], ([Permutation(5)(0, 1)(4, 5), Permutation(5)(0, 2)(1, 3)])) >>> get_minimal_bsgs(*riemann_bsgs1) ([0, 2], [(0 1)(4 5), (5)(0 2)(1 3), (2 3)(4 5)]) """ G = PermutationGroup(gens) base, gens = G.schreier_sims_incremental() if not _is_minimal_bsgs(base, gens): return None return base, gens def tensor_gens(base, gens, list_free_indices, sym=0): """ Returns size, res_base, res_gens BSGS for n tensors of the same type. Explanation =========== base, gens BSGS for tensors of this type list_free_indices list of the slots occupied by fixed indices for each of the tensors sym symmetry under commutation of two tensors sym None no symmetry sym 0 commuting sym 1 anticommuting Examples ======== >>> from sympy.combinatorics.tensor_can import tensor_gens, get_symmetric_group_sgs two symmetric tensors with 3 indices without free indices >>> base, gens = get_symmetric_group_sgs(3) >>> tensor_gens(base, gens, [[], []]) (8, [0, 1, 3, 4], [(7)(0 1), (7)(1 2), (7)(3 4), (7)(4 5), (7)(0 3)(1 4)(2 5)]) two symmetric tensors with 3 indices with free indices in slot 1 and 0 >>> tensor_gens(base, gens, [[1], [0]]) (8, [0, 4], [(7)(0 2), (7)(4 5)]) four symmetric tensors with 3 indices, two of which with free indices """ def _get_bsgs(G, base, gens, free_indices): """ return the BSGS for G.pointwise_stabilizer(free_indices) """ if not free_indices: return base[:], gens[:] else: H = G.pointwise_stabilizer(free_indices) base, sgs = H.schreier_sims_incremental() return base, sgs # if not base there is no slot symmetry for the component tensors # if list_free_indices.count([]) < 2 there is no commutation symmetry # so there is no resulting slot symmetry if not base and list_free_indices.count([]) < 2: n = len(list_free_indices) size = gens[0].size size = n * (gens[0].size - 2) + 2 return size, [], [_af_new(list(range(size)))] # if any(list_free_indices) one needs to compute the pointwise # stabilizer, so G is needed if any(list_free_indices): G = PermutationGroup(gens) else: G = None # no_free list of lists of indices for component tensors without fixed # indices no_free = [] size = gens[0].size id_af = list(range(size)) num_indices = size - 2 if not list_free_indices[0]: no_free.append(list(range(num_indices))) res_base, res_gens = _get_bsgs(G, base, gens, list_free_indices[0]) for i in range(1, len(list_free_indices)): base1, gens1 = _get_bsgs(G, base, gens, list_free_indices[i]) res_base, res_gens = bsgs_direct_product(res_base, res_gens, base1, gens1, 1) if not list_free_indices[i]: no_free.append(list(range(size - 2, size - 2 + num_indices))) size += num_indices nr = size - 2 res_gens = [h for h in res_gens if h._array_form != id_af] # if sym there are no commuting tensors stop here if sym is None or not no_free: if not res_gens: res_gens = [_af_new(id_af)] return size, res_base, res_gens # if the component tensors have moinimal BSGS, so is their direct # product P; the slot symmetry group is S = P*C, where C is the group # to (anti)commute the component tensors with no free indices # a stabilizer has the property S_i = P_i*C_i; # the BSGS of P*C has SGS_P + SGS_C and the base is # the ordered union of the bases of P and C. # If P has minimal BSGS, so has S with this base. base_comm = [] for i in range(len(no_free) - 1): ind1 = no_free[i] ind2 = no_free[i + 1] a = list(range(ind1[0])) a.extend(ind2) a.extend(ind1) base_comm.append(ind1[0]) a.extend(list(range(ind2[-1] + 1, nr))) if sym == 0: a.extend([nr, nr + 1]) else: a.extend([nr + 1, nr]) res_gens.append(_af_new(a)) res_base = list(res_base) # each base is ordered; order the union of the two bases for i in base_comm: if i not in res_base: res_base.append(i) res_base.sort() if not res_gens: res_gens = [_af_new(id_af)] return size, res_base, res_gens def gens_products(*v): """ Returns size, res_base, res_gens BSGS for n tensors of different types. Explanation =========== v is a sequence of (base_i, gens_i, free_i, sym_i) where base_i, gens_i BSGS of tensor of type `i` free_i list of the fixed slots for each of the tensors of type `i`; if there are `n_i` tensors of type `i` and none of them have fixed slots, `free = [[]]*n_i` sym 0 (1) if the tensors of type `i` (anti)commute among themselves Examples ======== >>> from sympy.combinatorics.tensor_can import get_symmetric_group_sgs, gens_products >>> base, gens = get_symmetric_group_sgs(2) >>> gens_products((base, gens, [[], []], 0)) (6, [0, 2], [(5)(0 1), (5)(2 3), (5)(0 2)(1 3)]) >>> gens_products((base, gens, [[1], []], 0)) (6, [2], [(5)(2 3)]) """ res_size, res_base, res_gens = tensor_gens(*v[0]) for i in range(1, len(v)): size, base, gens = tensor_gens(*v[i]) res_base, res_gens = bsgs_direct_product(res_base, res_gens, base, gens, 1) res_size = res_gens[0].size id_af = list(range(res_size)) res_gens = [h for h in res_gens if h != id_af] if not res_gens: res_gens = [id_af] return res_size, res_base, res_gens

7980f821d4c2d10739349db72691d4e9292c8317bb12a550f1a34a0466e180f3

from sympy import isprime from sympy.combinatorics.perm_groups import PermutationGroup from sympy.printing.defaults import DefaultPrinting from sympy.combinatorics.free_groups import free_group class PolycyclicGroup(DefaultPrinting): is_group = True is_solvable = True def __init__(self, pc_sequence, pc_series, relative_order, collector=None): """ Parameters ========== pc_sequence : list A sequence of elements whose classes generate the cyclic factor groups of pc_series. pc_series : list A subnormal sequence of subgroups where each factor group is cyclic. relative_order : list The orders of factor groups of pc_series. collector : Collector By default, it is None. Collector class provides the polycyclic presentation with various other functionalities. """ self.pcgs = pc_sequence self.pc_series = pc_series self.relative_order = relative_order self.collector = Collector(self.pcgs, pc_series, relative_order) if not collector else collector def is_prime_order(self): return all(isprime(order) for order in self.relative_order) def length(self): return len(self.pcgs) class Collector(DefaultPrinting): """ References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.3 """ def __init__(self, pcgs, pc_series, relative_order, free_group_=None, pc_presentation=None): """ Most of the parameters for the Collector class are the same as for PolycyclicGroup. Others are described below. Parameters ========== free_group_ : tuple free_group_ provides the mapping of polycyclic generating sequence with the free group elements. pc_presentation : dict Provides the presentation of polycyclic groups with the help of power and conjugate relators. See Also ======== PolycyclicGroup """ self.pcgs = pcgs self.pc_series = pc_series self.relative_order = relative_order self.free_group = free_group('x:{}'.format(len(pcgs)))[0] if not free_group_ else free_group_ self.index = {s: i for i, s in enumerate(self.free_group.symbols)} self.pc_presentation = self.pc_relators() def minimal_uncollected_subword(self, word): r""" Returns the minimal uncollected subwords. Explanation =========== A word ``v`` defined on generators in ``X`` is a minimal uncollected subword of the word ``w`` if ``v`` is a subword of ``w`` and it has one of the following form * `v = {x_{i+1}}^{a_j}x_i` * `v = {x_{i+1}}^{a_j}{x_i}^{-1}` * `v = {x_i}^{a_j}` for `a_j` not in `\{1, \ldots, s-1\}`. Where, ``s`` is the power exponent of the corresponding generator. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x1, x2 = free_group("x1, x2") >>> word = x2**2*x1**7 >>> collector.minimal_uncollected_subword(word) ((x2, 2),) """ # To handle the case word = <identity> if not word: return None array = word.array_form re = self.relative_order index = self.index for i in range(len(array)): s1, e1 = array[i] if re[index[s1]] and (e1 < 0 or e1 > re[index[s1]]-1): return ((s1, e1), ) for i in range(len(array)-1): s1, e1 = array[i] s2, e2 = array[i+1] if index[s1] > index[s2]: e = 1 if e2 > 0 else -1 return ((s1, e1), (s2, e)) return None def relations(self): """ Separates the given relators of pc presentation in power and conjugate relations. Returns ======= (power_rel, conj_rel) Separates pc presentation into power and conjugate relations. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> power_rel, conj_rel = collector.relations() >>> power_rel {x0**2: (), x1**3: ()} >>> conj_rel {x0**-1*x1*x0: x1**2} See Also ======== pc_relators """ power_relators = {} conjugate_relators = {} for key, value in self.pc_presentation.items(): if len(key.array_form) == 1: power_relators[key] = value else: conjugate_relators[key] = value return power_relators, conjugate_relators def subword_index(self, word, w): """ Returns the start and ending index of a given subword in a word. Parameters ========== word : FreeGroupElement word defined on free group elements for a polycyclic group. w : FreeGroupElement subword of a given word, whose starting and ending index to be computed. Returns ======= (i, j) A tuple containing starting and ending index of ``w`` in the given word. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x1, x2 = free_group("x1, x2") >>> word = x2**2*x1**7 >>> w = x2**2*x1 >>> collector.subword_index(word, w) (0, 3) >>> w = x1**7 >>> collector.subword_index(word, w) (2, 9) """ low = -1 high = -1 for i in range(len(word)-len(w)+1): if word.subword(i, i+len(w)) == w: low = i high = i+len(w) break if low == high == -1: return -1, -1 return low, high def map_relation(self, w): """ Return a conjugate relation. Explanation =========== Given a word formed by two free group elements, the corresponding conjugate relation with those free group elements is formed and mapped with the collected word in the polycyclic presentation. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x0, x1 = free_group("x0, x1") >>> w = x1*x0 >>> collector.map_relation(w) x1**2 See Also ======== pc_presentation """ array = w.array_form s1 = array[0][0] s2 = array[1][0] key = ((s2, -1), (s1, 1), (s2, 1)) key = self.free_group.dtype(key) return self.pc_presentation[key] def collected_word(self, word): r""" Return the collected form of a word. Explanation =========== A word ``w`` is called collected, if `w = {x_{i_1}}^{a_1} * \ldots * {x_{i_r}}^{a_r}` with `i_1 < i_2< \ldots < i_r` and `a_j` is in `\{1, \ldots, {s_j}-1\}`. Otherwise w is uncollected. Parameters ========== word : FreeGroupElement An uncollected word. Returns ======= word A collected word of form `w = {x_{i_1}}^{a_1}, \ldots, {x_{i_r}}^{a_r}` with `i_1, i_2, \ldots, i_r` and `a_j \in \{1, \ldots, {s_j}-1\}`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.free_groups import free_group >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> F, x0, x1, x2, x3 = free_group("x0, x1, x2, x3") >>> word = x3*x2*x1*x0 >>> collected_word = collector.collected_word(word) >>> free_to_perm = {} >>> free_group = collector.free_group >>> for sym, gen in zip(free_group.symbols, collector.pcgs): ... free_to_perm[sym] = gen >>> G1 = PermutationGroup() >>> for w in word: ... sym = w[0] ... perm = free_to_perm[sym] ... G1 = PermutationGroup([perm] + G1.generators) >>> G2 = PermutationGroup() >>> for w in collected_word: ... sym = w[0] ... perm = free_to_perm[sym] ... G2 = PermutationGroup([perm] + G2.generators) >>> G1 == G2 True See Also ======== minimal_uncollected_subword """ free_group = self.free_group while True: w = self.minimal_uncollected_subword(word) if not w: break low, high = self.subword_index(word, free_group.dtype(w)) if low == -1: continue s1, e1 = w[0] if len(w) == 1: re = self.relative_order[self.index[s1]] q = e1 // re r = e1-q*re key = ((w[0][0], re), ) key = free_group.dtype(key) if self.pc_presentation[key]: presentation = self.pc_presentation[key].array_form sym, exp = presentation[0] word_ = ((w[0][0], r), (sym, q*exp)) word_ = free_group.dtype(word_) else: if r != 0: word_ = ((w[0][0], r), ) word_ = free_group.dtype(word_) else: word_ = None word = word.eliminate_word(free_group.dtype(w), word_) if len(w) == 2 and w[1][1] > 0: s2, e2 = w[1] s2 = ((s2, 1), ) s2 = free_group.dtype(s2) word_ = self.map_relation(free_group.dtype(w)) word_ = s2*word_**e1 word_ = free_group.dtype(word_) word = word.substituted_word(low, high, word_) elif len(w) == 2 and w[1][1] < 0: s2, e2 = w[1] s2 = ((s2, 1), ) s2 = free_group.dtype(s2) word_ = self.map_relation(free_group.dtype(w)) word_ = s2**-1*word_**e1 word_ = free_group.dtype(word_) word = word.substituted_word(low, high, word_) return word def pc_relators(self): r""" Return the polycyclic presentation. Explanation =========== There are two types of relations used in polycyclic presentation. * ``Power relations`` : Power relators are of the form `x_i^{re_i}`, where `i \in \{0, \ldots, \mathrm{len(pcgs)}\}`, ``x`` represents polycyclic generator and ``re`` is the corresponding relative order. * ``Conjugate relations`` : Conjugate relators are of the form `x_j^-1x_ix_j`, where `j < i \in \{0, \ldots, \mathrm{len(pcgs)}\}`. Returns ======= A dictionary with power and conjugate relations as key and their collected form as corresponding values. Notes ===== Identity Permutation is mapped with empty ``()``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> S = SymmetricGroup(49).sylow_subgroup(7) >>> der = S.derived_series() >>> G = der[len(der)-2] >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> pcgs = PcGroup.pcgs >>> len(pcgs) 6 >>> free_group = collector.free_group >>> pc_resentation = collector.pc_presentation >>> free_to_perm = {} >>> for s, g in zip(free_group.symbols, pcgs): ... free_to_perm[s] = g >>> for k, v in pc_resentation.items(): ... k_array = k.array_form ... if v != (): ... v_array = v.array_form ... lhs = Permutation() ... for gen in k_array: ... s = gen[0] ... e = gen[1] ... lhs = lhs*free_to_perm[s]**e ... if v == (): ... assert lhs.is_identity ... continue ... rhs = Permutation() ... for gen in v_array: ... s = gen[0] ... e = gen[1] ... rhs = rhs*free_to_perm[s]**e ... assert lhs == rhs """ free_group = self.free_group rel_order = self.relative_order pc_relators = {} perm_to_free = {} pcgs = self.pcgs for gen, s in zip(pcgs, free_group.generators): perm_to_free[gen**-1] = s**-1 perm_to_free[gen] = s pcgs = pcgs[::-1] series = self.pc_series[::-1] rel_order = rel_order[::-1] collected_gens = [] for i, gen in enumerate(pcgs): re = rel_order[i] relation = perm_to_free[gen]**re G = series[i] l = G.generator_product(gen**re, original = True) l.reverse() word = free_group.identity for g in l: word = word*perm_to_free[g] word = self.collected_word(word) pc_relators[relation] = word if word else () self.pc_presentation = pc_relators collected_gens.append(gen) if len(collected_gens) > 1: conj = collected_gens[len(collected_gens)-1] conjugator = perm_to_free[conj] for j in range(len(collected_gens)-1): conjugated = perm_to_free[collected_gens[j]] relation = conjugator**-1*conjugated*conjugator gens = conj**-1*collected_gens[j]*conj l = G.generator_product(gens, original = True) l.reverse() word = free_group.identity for g in l: word = word*perm_to_free[g] word = self.collected_word(word) pc_relators[relation] = word if word else () self.pc_presentation = pc_relators return pc_relators def exponent_vector(self, element): r""" Return the exponent vector of length equal to the length of polycyclic generating sequence. Explanation =========== For a given generator/element ``g`` of the polycyclic group, it can be represented as `g = {x_1}^{e_1}, \ldots, {x_n}^{e_n}`, where `x_i` represents polycyclic generators and ``n`` is the number of generators in the free_group equal to the length of pcgs. Parameters ========== element : Permutation Generator of a polycyclic group. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> G = SymmetricGroup(4) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> pcgs = PcGroup.pcgs >>> collector.exponent_vector(G[0]) [1, 0, 0, 0] >>> exp = collector.exponent_vector(G[1]) >>> g = Permutation() >>> for i in range(len(exp)): ... g = g*pcgs[i]**exp[i] if exp[i] else g >>> assert g == G[1] References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.1, Definition 8.4 """ free_group = self.free_group G = PermutationGroup() for g in self.pcgs: G = PermutationGroup([g] + G.generators) gens = G.generator_product(element, original = True) gens.reverse() perm_to_free = {} for sym, g in zip(free_group.generators, self.pcgs): perm_to_free[g**-1] = sym**-1 perm_to_free[g] = sym w = free_group.identity for g in gens: w = w*perm_to_free[g] word = self.collected_word(w) index = self.index exp_vector = [0]*len(free_group) word = word.array_form for t in word: exp_vector[index[t[0]]] = t[1] return exp_vector def depth(self, element): r""" Return the depth of a given element. Explanation =========== The depth of a given element ``g`` is defined by `\mathrm{dep}[g] = i` if `e_1 = e_2 = \ldots = e_{i-1} = 0` and `e_i != 0`, where ``e`` represents the exponent-vector. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> collector.depth(G[0]) 2 >>> collector.depth(G[1]) 1 References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of Computational Group Theory" Section 8.1.1, Definition 8.5 """ exp_vector = self.exponent_vector(element) return next((i+1 for i, x in enumerate(exp_vector) if x), len(self.pcgs)+1) def leading_exponent(self, element): r""" Return the leading non-zero exponent. Explanation =========== The leading exponent for a given element `g` is defined by `\mathrm{leading\_exponent}[g]` `= e_i`, if `\mathrm{depth}[g] = i`. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> collector.leading_exponent(G[1]) 1 """ exp_vector = self.exponent_vector(element) depth = self.depth(element) if depth != len(self.pcgs)+1: return exp_vector[depth-1] return None def _sift(self, z, g): h = g d = self.depth(h) while d < len(self.pcgs) and z[d-1] != 1: k = z[d-1] e = self.leading_exponent(h)*(self.leading_exponent(k))**-1 e = e % self.relative_order[d-1] h = k**-e*h d = self.depth(h) return h def induced_pcgs(self, gens): """ Parameters ========== gens : list A list of generators on which polycyclic subgroup is to be defined. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> S = SymmetricGroup(8) >>> G = S.sylow_subgroup(2) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> gens = [G[0], G[1]] >>> ipcgs = collector.induced_pcgs(gens) >>> [gen.order() for gen in ipcgs] [2, 2, 2] >>> G = S.sylow_subgroup(3) >>> PcGroup = G.polycyclic_group() >>> collector = PcGroup.collector >>> gens = [G[0], G[1]] >>> ipcgs = collector.induced_pcgs(gens) >>> [gen.order() for gen in ipcgs] [3] """ z = [1]*len(self.pcgs) G = gens while G: g = G.pop(0) h = self._sift(z, g) d = self.depth(h) if d < len(self.pcgs): for gen in z: if gen != 1: G.append(h**-1*gen**-1*h*gen) z[d-1] = h; z = [gen for gen in z if gen != 1] return z def constructive_membership_test(self, ipcgs, g): """ Return the exponent vector for induced pcgs. """ e = [0]*len(ipcgs) h = g d = self.depth(h) for i, gen in enumerate(ipcgs): while self.depth(gen) == d: f = self.leading_exponent(h)*self.leading_exponent(gen) f = f % self.relative_order[d-1] h = gen**(-f)*h e[i] = f d = self.depth(h) if h == 1: return e return False

b356a6b760fffb62e9f4a9615d26e6716ea5c1c47add792a123d95aba509a5d6

from sympy.combinatorics import Permutation as Perm from sympy.combinatorics.perm_groups import PermutationGroup from sympy.core import Basic, Tuple from sympy.core.compatibility import as_int from sympy.sets import FiniteSet from sympy.utilities.iterables import (minlex, unflatten, flatten) rmul = Perm.rmul class Polyhedron(Basic): """ Represents the polyhedral symmetry group (PSG). Explanation =========== The PSG is one of the symmetry groups of the Platonic solids. There are three polyhedral groups: the tetrahedral group of order 12, the octahedral group of order 24, and the icosahedral group of order 60. All doctests have been given in the docstring of the constructor of the object. References ========== .. [1] http://mathworld.wolfram.com/PolyhedralGroup.html """ _edges = None def __new__(cls, corners, faces=[], pgroup=[]): """ The constructor of the Polyhedron group object. Explanation =========== It takes up to three parameters: the corners, faces, and allowed transformations. The corners/vertices are entered as a list of arbitrary expressions that are used to identify each vertex. The faces are entered as a list of tuples of indices; a tuple of indices identifies the vertices which define the face. They should be entered in a cw or ccw order; they will be standardized by reversal and rotation to be give the lowest lexical ordering. If no faces are given then no edges will be computed. >>> from sympy.combinatorics.polyhedron import Polyhedron >>> Polyhedron(list('abc'), [(1, 2, 0)]).faces FiniteSet((0, 1, 2)) >>> Polyhedron(list('abc'), [(1, 0, 2)]).faces FiniteSet((0, 1, 2)) The allowed transformations are entered as allowable permutations of the vertices for the polyhedron. Instance of Permutations (as with faces) should refer to the supplied vertices by index. These permutation are stored as a PermutationGroup. Examples ======== >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.interactive import init_printing >>> from sympy.abc import w, x, y, z >>> init_printing(pretty_print=False, perm_cyclic=False) Here we construct the Polyhedron object for a tetrahedron. >>> corners = [w, x, y, z] >>> faces = [(0, 1, 2), (0, 2, 3), (0, 3, 1), (1, 2, 3)] Next, allowed transformations of the polyhedron must be given. This is given as permutations of vertices. Although the vertices of a tetrahedron can be numbered in 24 (4!) different ways, there are only 12 different orientations for a physical tetrahedron. The following permutations, applied once or twice, will generate all 12 of the orientations. (The identity permutation, Permutation(range(4)), is not included since it does not change the orientation of the vertices.) >>> pgroup = [Permutation([[0, 1, 2], [3]]), \ Permutation([[0, 1, 3], [2]]), \ Permutation([[0, 2, 3], [1]]), \ Permutation([[1, 2, 3], [0]]), \ Permutation([[0, 1], [2, 3]]), \ Permutation([[0, 2], [1, 3]]), \ Permutation([[0, 3], [1, 2]])] The Polyhedron is now constructed and demonstrated: >>> tetra = Polyhedron(corners, faces, pgroup) >>> tetra.size 4 >>> tetra.edges FiniteSet((0, 1), (0, 2), (0, 3), (1, 2), (1, 3), (2, 3)) >>> tetra.corners (w, x, y, z) It can be rotated with an arbitrary permutation of vertices, e.g. the following permutation is not in the pgroup: >>> tetra.rotate(Permutation([0, 1, 3, 2])) >>> tetra.corners (w, x, z, y) An allowed permutation of the vertices can be constructed by repeatedly applying permutations from the pgroup to the vertices. Here is a demonstration that applying p and p**2 for every p in pgroup generates all the orientations of a tetrahedron and no others: >>> all = ( (w, x, y, z), \ (x, y, w, z), \ (y, w, x, z), \ (w, z, x, y), \ (z, w, y, x), \ (w, y, z, x), \ (y, z, w, x), \ (x, z, y, w), \ (z, y, x, w), \ (y, x, z, w), \ (x, w, z, y), \ (z, x, w, y) ) >>> got = [] >>> for p in (pgroup + [p**2 for p in pgroup]): ... h = Polyhedron(corners) ... h.rotate(p) ... got.append(h.corners) ... >>> set(got) == set(all) True The make_perm method of a PermutationGroup will randomly pick permutations, multiply them together, and return the permutation that can be applied to the polyhedron to give the orientation produced by those individual permutations. Here, 3 permutations are used: >>> tetra.pgroup.make_perm(3) # doctest: +SKIP Permutation([0, 3, 1, 2]) To select the permutations that should be used, supply a list of indices to the permutations in pgroup in the order they should be applied: >>> use = [0, 0, 2] >>> p002 = tetra.pgroup.make_perm(3, use) >>> p002 Permutation([1, 0, 3, 2]) Apply them one at a time: >>> tetra.reset() >>> for i in use: ... tetra.rotate(pgroup[i]) ... >>> tetra.vertices (x, w, z, y) >>> sequentially = tetra.vertices Apply the composite permutation: >>> tetra.reset() >>> tetra.rotate(p002) >>> tetra.corners (x, w, z, y) >>> tetra.corners in all and tetra.corners == sequentially True Notes ===== Defining permutation groups --------------------------- It is not necessary to enter any permutations, nor is necessary to enter a complete set of transformations. In fact, for a polyhedron, all configurations can be constructed from just two permutations. For example, the orientations of a tetrahedron can be generated from an axis passing through a vertex and face and another axis passing through a different vertex or from an axis passing through the midpoints of two edges opposite of each other. For simplicity of presentation, consider a square -- not a cube -- with vertices 1, 2, 3, and 4: 1-----2 We could think of axes of rotation being: | | 1) through the face | | 2) from midpoint 1-2 to 3-4 or 1-3 to 2-4 3-----4 3) lines 1-4 or 2-3 To determine how to write the permutations, imagine 4 cameras, one at each corner, labeled A-D: A B A B 1-----2 1-----3 vertex index: | | | | 1 0 | | | | 2 1 3-----4 2-----4 3 2 C D C D 4 3 original after rotation along 1-4 A diagonal and a face axis will be chosen for the "permutation group" from which any orientation can be constructed. >>> pgroup = [] Imagine a clockwise rotation when viewing 1-4 from camera A. The new orientation is (in camera-order): 1, 3, 2, 4 so the permutation is given using the *indices* of the vertices as: >>> pgroup.append(Permutation((0, 2, 1, 3))) Now imagine rotating clockwise when looking down an axis entering the center of the square as viewed. The new camera-order would be 3, 1, 4, 2 so the permutation is (using indices): >>> pgroup.append(Permutation((2, 0, 3, 1))) The square can now be constructed: ** use real-world labels for the vertices, entering them in camera order ** for the faces we use zero-based indices of the vertices in *edge-order* as the face is traversed; neither the direction nor the starting point matter -- the faces are only used to define edges (if so desired). >>> square = Polyhedron((1, 2, 3, 4), [(0, 1, 3, 2)], pgroup) To rotate the square with a single permutation we can do: >>> square.rotate(square.pgroup[0]) >>> square.corners (1, 3, 2, 4) To use more than one permutation (or to use one permutation more than once) it is more convenient to use the make_perm method: >>> p011 = square.pgroup.make_perm([0, 1, 1]) # diag flip + 2 rotations >>> square.reset() # return to initial orientation >>> square.rotate(p011) >>> square.corners (4, 2, 3, 1) Thinking outside the box ------------------------ Although the Polyhedron object has a direct physical meaning, it actually has broader application. In the most general sense it is just a decorated PermutationGroup, allowing one to connect the permutations to something physical. For example, a Rubik's cube is not a proper polyhedron, but the Polyhedron class can be used to represent it in a way that helps to visualize the Rubik's cube. >>> from sympy.utilities.iterables import flatten, unflatten >>> from sympy import symbols >>> from sympy.combinatorics import RubikGroup >>> facelets = flatten([symbols(s+'1:5') for s in 'UFRBLD']) >>> def show(): ... pairs = unflatten(r2.corners, 2) ... print(pairs[::2]) ... print(pairs[1::2]) ... >>> r2 = Polyhedron(facelets, pgroup=RubikGroup(2)) >>> show() [(U1, U2), (F1, F2), (R1, R2), (B1, B2), (L1, L2), (D1, D2)] [(U3, U4), (F3, F4), (R3, R4), (B3, B4), (L3, L4), (D3, D4)] >>> r2.rotate(0) # cw rotation of F >>> show() [(U1, U2), (F3, F1), (U3, R2), (B1, B2), (L1, D1), (R3, R1)] [(L4, L2), (F4, F2), (U4, R4), (B3, B4), (L3, D2), (D3, D4)] Predefined Polyhedra ==================== For convenience, the vertices and faces are defined for the following standard solids along with a permutation group for transformations. When the polyhedron is oriented as indicated below, the vertices in a given horizontal plane are numbered in ccw direction, starting from the vertex that will give the lowest indices in a given face. (In the net of the vertices, indices preceded by "-" indicate replication of the lhs index in the net.) tetrahedron, tetrahedron_faces ------------------------------ 4 vertices (vertex up) net: 0 0-0 1 2 3-1 4 faces: (0, 1, 2) (0, 2, 3) (0, 3, 1) (1, 2, 3) cube, cube_faces ---------------- 8 vertices (face up) net: 0 1 2 3-0 4 5 6 7-4 6 faces: (0, 1, 2, 3) (0, 1, 5, 4) (1, 2, 6, 5) (2, 3, 7, 6) (0, 3, 7, 4) (4, 5, 6, 7) octahedron, octahedron_faces ---------------------------- 6 vertices (vertex up) net: 0 0 0-0 1 2 3 4-1 5 5 5-5 8 faces: (0, 1, 2) (0, 2, 3) (0, 3, 4) (0, 1, 4) (1, 2, 5) (2, 3, 5) (3, 4, 5) (1, 4, 5) dodecahedron, dodecahedron_faces -------------------------------- 20 vertices (vertex up) net: 0 1 2 3 4 -0 5 6 7 8 9 -5 14 10 11 12 13-14 15 16 17 18 19-15 12 faces: (0, 1, 2, 3, 4) (0, 1, 6, 10, 5) (1, 2, 7, 11, 6) (2, 3, 8, 12, 7) (3, 4, 9, 13, 8) (0, 4, 9, 14, 5) (5, 10, 16, 15, 14) (6, 10, 16, 17, 11) (7, 11, 17, 18, 12) (8, 12, 18, 19, 13) (9, 13, 19, 15, 14)(15, 16, 17, 18, 19) icosahedron, icosahedron_faces ------------------------------ 12 vertices (face up) net: 0 0 0 0 -0 1 2 3 4 5 -1 6 7 8 9 10 -6 11 11 11 11 -11 20 faces: (0, 1, 2) (0, 2, 3) (0, 3, 4) (0, 4, 5) (0, 1, 5) (1, 2, 6) (2, 3, 7) (3, 4, 8) (4, 5, 9) (1, 5, 10) (2, 6, 7) (3, 7, 8) (4, 8, 9) (5, 9, 10) (1, 6, 10) (6, 7, 11) (7, 8, 11) (8, 9, 11) (9, 10, 11) (6, 10, 11) >>> from sympy.combinatorics.polyhedron import cube >>> cube.edges FiniteSet((0, 1), (0, 3), (0, 4), (1, 2), (1, 5), (2, 3), (2, 6), (3, 7), (4, 5), (4, 7), (5, 6), (6, 7)) If you want to use letters or other names for the corners you can still use the pre-calculated faces: >>> corners = list('abcdefgh') >>> Polyhedron(corners, cube.faces).corners (a, b, c, d, e, f, g, h) References ========== .. [1] www.ocf.berkeley.edu/~wwu/articles/platonicsolids.pdf """ faces = [minlex(f, directed=False, is_set=True) for f in faces] corners, faces, pgroup = args = \ [Tuple(*a) for a in (corners, faces, pgroup)] obj = Basic.__new__(cls, *args) obj._corners = tuple(corners) # in order given obj._faces = FiniteSet(*faces) if pgroup and pgroup[0].size != len(corners): raise ValueError("Permutation size unequal to number of corners.") # use the identity permutation if none are given obj._pgroup = PermutationGroup( pgroup or [Perm(range(len(corners)))] ) return obj @property def corners(self): """ Get the corners of the Polyhedron. The method ``vertices`` is an alias for ``corners``. Examples ======== >>> from sympy.combinatorics import Polyhedron >>> from sympy.abc import a, b, c, d >>> p = Polyhedron(list('abcd')) >>> p.corners == p.vertices == (a, b, c, d) True See Also ======== array_form, cyclic_form """ return self._corners vertices = corners @property def array_form(self): """Return the indices of the corners. The indices are given relative to the original position of corners. Examples ======== >>> from sympy.combinatorics.polyhedron import tetrahedron >>> tetrahedron = tetrahedron.copy() >>> tetrahedron.array_form [0, 1, 2, 3] >>> tetrahedron.rotate(0) >>> tetrahedron.array_form [0, 2, 3, 1] >>> tetrahedron.pgroup[0].array_form [0, 2, 3, 1] See Also ======== corners, cyclic_form """ corners = list(self.args[0]) return [corners.index(c) for c in self.corners] @property def cyclic_form(self): """Return the indices of the corners in cyclic notation. The indices are given relative to the original position of corners. See Also ======== corners, array_form """ return Perm._af_new(self.array_form).cyclic_form @property def size(self): """ Get the number of corners of the Polyhedron. """ return len(self._corners) @property def faces(self): """ Get the faces of the Polyhedron. """ return self._faces @property def pgroup(self): """ Get the permutations of the Polyhedron. """ return self._pgroup @property def edges(self): """ Given the faces of the polyhedra we can get the edges. Examples ======== >>> from sympy.combinatorics import Polyhedron >>> from sympy.abc import a, b, c >>> corners = (a, b, c) >>> faces = [(0, 1, 2)] >>> Polyhedron(corners, faces).edges FiniteSet((0, 1), (0, 2), (1, 2)) """ if self._edges is None: output = set() for face in self.faces: for i in range(len(face)): edge = tuple(sorted([face[i], face[i - 1]])) output.add(edge) self._edges = FiniteSet(*output) return self._edges def rotate(self, perm): """ Apply a permutation to the polyhedron *in place*. The permutation may be given as a Permutation instance or an integer indicating which permutation from pgroup of the Polyhedron should be applied. This is an operation that is analogous to rotation about an axis by a fixed increment. Notes ===== When a Permutation is applied, no check is done to see if that is a valid permutation for the Polyhedron. For example, a cube could be given a permutation which effectively swaps only 2 vertices. A valid permutation (that rotates the object in a physical way) will be obtained if one only uses permutations from the ``pgroup`` of the Polyhedron. On the other hand, allowing arbitrary rotations (applications of permutations) gives a way to follow named elements rather than indices since Polyhedron allows vertices to be named while Permutation works only with indices. Examples ======== >>> from sympy.combinatorics import Polyhedron, Permutation >>> from sympy.combinatorics.polyhedron import cube >>> cube = cube.copy() >>> cube.corners (0, 1, 2, 3, 4, 5, 6, 7) >>> cube.rotate(0) >>> cube.corners (1, 2, 3, 0, 5, 6, 7, 4) A non-physical "rotation" that is not prohibited by this method: >>> cube.reset() >>> cube.rotate(Permutation([[1, 2]], size=8)) >>> cube.corners (0, 2, 1, 3, 4, 5, 6, 7) Polyhedron can be used to follow elements of set that are identified by letters instead of integers: >>> shadow = h5 = Polyhedron(list('abcde')) >>> p = Permutation([3, 0, 1, 2, 4]) >>> h5.rotate(p) >>> h5.corners (d, a, b, c, e) >>> _ == shadow.corners True >>> copy = h5.copy() >>> h5.rotate(p) >>> h5.corners == copy.corners False """ if not isinstance(perm, Perm): perm = self.pgroup[perm] # and we know it's valid else: if perm.size != self.size: raise ValueError('Polyhedron and Permutation sizes differ.') a = perm.array_form corners = [self.corners[a[i]] for i in range(len(self.corners))] self._corners = tuple(corners) def reset(self): """Return corners to their original positions. Examples ======== >>> from sympy.combinatorics.polyhedron import tetrahedron as T >>> T = T.copy() >>> T.corners (0, 1, 2, 3) >>> T.rotate(0) >>> T.corners (0, 2, 3, 1) >>> T.reset() >>> T.corners (0, 1, 2, 3) """ self._corners = self.args[0] def _pgroup_calcs(): """Return the permutation groups for each of the polyhedra and the face definitions: tetrahedron, cube, octahedron, dodecahedron, icosahedron, tetrahedron_faces, cube_faces, octahedron_faces, dodecahedron_faces, icosahedron_faces Explanation =========== (This author didn't find and didn't know of a better way to do it though there likely is such a way.) Although only 2 permutations are needed for a polyhedron in order to generate all the possible orientations, a group of permutations is provided instead. A set of permutations is called a "group" if:: a*b = c (for any pair of permutations in the group, a and b, their product, c, is in the group) a*(b*c) = (a*b)*c (for any 3 permutations in the group associativity holds) there is an identity permutation, I, such that I*a = a*I for all elements in the group a*b = I (the inverse of each permutation is also in the group) None of the polyhedron groups defined follow these definitions of a group. Instead, they are selected to contain those permutations whose powers alone will construct all orientations of the polyhedron, i.e. for permutations ``a``, ``b``, etc... in the group, ``a, a**2, ..., a**o_a``, ``b, b**2, ..., b**o_b``, etc... (where ``o_i`` is the order of permutation ``i``) generate all permutations of the polyhedron instead of mixed products like ``a*b``, ``a*b**2``, etc.... Note that for a polyhedron with n vertices, the valid permutations of the vertices exclude those that do not maintain its faces. e.g. the permutation BCDE of a square's four corners, ABCD, is a valid permutation while CBDE is not (because this would twist the square). Examples ======== The is_group checks for: closure, the presence of the Identity permutation, and the presence of the inverse for each of the elements in the group. This confirms that none of the polyhedra are true groups: >>> from sympy.combinatorics.polyhedron import ( ... tetrahedron, cube, octahedron, dodecahedron, icosahedron) ... >>> polyhedra = (tetrahedron, cube, octahedron, dodecahedron, icosahedron) >>> [h.pgroup.is_group for h in polyhedra] ... [True, True, True, True, True] Although tests in polyhedron's test suite check that powers of the permutations in the groups generate all permutations of the vertices of the polyhedron, here we also demonstrate the powers of the given permutations create a complete group for the tetrahedron: >>> from sympy.combinatorics import Permutation, PermutationGroup >>> for h in polyhedra[:1]: ... G = h.pgroup ... perms = set() ... for g in G: ... for e in range(g.order()): ... p = tuple((g**e).array_form) ... perms.add(p) ... ... perms = [Permutation(p) for p in perms] ... assert PermutationGroup(perms).is_group In addition to doing the above, the tests in the suite confirm that the faces are all present after the application of each permutation. References ========== .. [1] http://dogschool.tripod.com/trianglegroup.html """ def _pgroup_of_double(polyh, ordered_faces, pgroup): n = len(ordered_faces[0]) # the vertices of the double which sits inside a give polyhedron # can be found by tracking the faces of the outer polyhedron. # A map between face and the vertex of the double is made so that # after rotation the position of the vertices can be located fmap = dict(zip(ordered_faces, range(len(ordered_faces)))) flat_faces = flatten(ordered_faces) new_pgroup = [] for i, p in enumerate(pgroup): h = polyh.copy() h.rotate(p) c = h.corners # reorder corners in the order they should appear when # enumerating the faces reorder = unflatten([c[j] for j in flat_faces], n) # make them canonical reorder = [tuple(map(as_int, minlex(f, directed=False, is_set=True))) for f in reorder] # map face to vertex: the resulting list of vertices are the # permutation that we seek for the double new_pgroup.append(Perm([fmap[f] for f in reorder])) return new_pgroup tetrahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 1), # upper 3 (1, 2, 3), # bottom ] # cw from top # _t_pgroup = [ Perm([[1, 2, 3], [0]]), # cw from top Perm([[0, 1, 2], [3]]), # cw from front face Perm([[0, 3, 2], [1]]), # cw from back right face Perm([[0, 3, 1], [2]]), # cw from back left face Perm([[0, 1], [2, 3]]), # through front left edge Perm([[0, 2], [1, 3]]), # through front right edge Perm([[0, 3], [1, 2]]), # through back edge ] tetrahedron = Polyhedron( range(4), tetrahedron_faces, _t_pgroup) cube_faces = [ (0, 1, 2, 3), # upper (0, 1, 5, 4), (1, 2, 6, 5), (2, 3, 7, 6), (0, 3, 7, 4), # middle 4 (4, 5, 6, 7), # lower ] # U, D, F, B, L, R = up, down, front, back, left, right _c_pgroup = [Perm(p) for p in [ [1, 2, 3, 0, 5, 6, 7, 4], # cw from top, U [4, 0, 3, 7, 5, 1, 2, 6], # cw from F face [4, 5, 1, 0, 7, 6, 2, 3], # cw from R face [1, 0, 4, 5, 2, 3, 7, 6], # cw through UF edge [6, 2, 1, 5, 7, 3, 0, 4], # cw through UR edge [6, 7, 3, 2, 5, 4, 0, 1], # cw through UB edge [3, 7, 4, 0, 2, 6, 5, 1], # cw through UL edge [4, 7, 6, 5, 0, 3, 2, 1], # cw through FL edge [6, 5, 4, 7, 2, 1, 0, 3], # cw through FR edge [0, 3, 7, 4, 1, 2, 6, 5], # cw through UFL vertex [5, 1, 0, 4, 6, 2, 3, 7], # cw through UFR vertex [5, 6, 2, 1, 4, 7, 3, 0], # cw through UBR vertex [7, 4, 0, 3, 6, 5, 1, 2], # cw through UBL ]] cube = Polyhedron( range(8), cube_faces, _c_pgroup) octahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 4), (0, 1, 4), # top 4 (1, 2, 5), (2, 3, 5), (3, 4, 5), (1, 4, 5), # bottom 4 ] octahedron = Polyhedron( range(6), octahedron_faces, _pgroup_of_double(cube, cube_faces, _c_pgroup)) dodecahedron_faces = [ (0, 1, 2, 3, 4), # top (0, 1, 6, 10, 5), (1, 2, 7, 11, 6), (2, 3, 8, 12, 7), # upper 5 (3, 4, 9, 13, 8), (0, 4, 9, 14, 5), (5, 10, 16, 15, 14), (6, 10, 16, 17, 11), (7, 11, 17, 18, 12), # lower 5 (8, 12, 18, 19, 13), (9, 13, 19, 15, 14), (15, 16, 17, 18, 19) # bottom ] def _string_to_perm(s): rv = [Perm(range(20))] p = None for si in s: if si not in '01': count = int(si) - 1 else: count = 1 if si == '0': p = _f0 elif si == '1': p = _f1 rv.extend([p]*count) return Perm.rmul(*rv) # top face cw _f0 = Perm([ 1, 2, 3, 4, 0, 6, 7, 8, 9, 5, 11, 12, 13, 14, 10, 16, 17, 18, 19, 15]) # front face cw _f1 = Perm([ 5, 0, 4, 9, 14, 10, 1, 3, 13, 15, 6, 2, 8, 19, 16, 17, 11, 7, 12, 18]) # the strings below, like 0104 are shorthand for F0*F1*F0**4 and are # the remaining 4 face rotations, 15 edge permutations, and the # 10 vertex rotations. _dodeca_pgroup = [_f0, _f1] + [_string_to_perm(s) for s in ''' 0104 140 014 0410 010 1403 03104 04103 102 120 1304 01303 021302 03130 0412041 041204103 04120410 041204104 041204102 10 01 1402 0140 04102 0412 1204 1302 0130 03120'''.strip().split()] dodecahedron = Polyhedron( range(20), dodecahedron_faces, _dodeca_pgroup) icosahedron_faces = [ (0, 1, 2), (0, 2, 3), (0, 3, 4), (0, 4, 5), (0, 1, 5), (1, 6, 7), (1, 2, 7), (2, 7, 8), (2, 3, 8), (3, 8, 9), (3, 4, 9), (4, 9, 10), (4, 5, 10), (5, 6, 10), (1, 5, 6), (6, 7, 11), (7, 8, 11), (8, 9, 11), (9, 10, 11), (6, 10, 11)] icosahedron = Polyhedron( range(12), icosahedron_faces, _pgroup_of_double( dodecahedron, dodecahedron_faces, _dodeca_pgroup)) return (tetrahedron, cube, octahedron, dodecahedron, icosahedron, tetrahedron_faces, cube_faces, octahedron_faces, dodecahedron_faces, icosahedron_faces) # ----------------------------------------------------------------------- # Standard Polyhedron groups # # These are generated using _pgroup_calcs() above. However to save # import time we encode them explicitly here. # ----------------------------------------------------------------------- tetrahedron = Polyhedron( Tuple(0, 1, 2, 3), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 1, 3), Tuple(1, 2, 3)), Tuple( Perm(1, 2, 3), Perm(3)(0, 1, 2), Perm(0, 3, 2), Perm(0, 3, 1), Perm(0, 1)(2, 3), Perm(0, 2)(1, 3), Perm(0, 3)(1, 2) )) cube = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7), Tuple( Tuple(0, 1, 2, 3), Tuple(0, 1, 5, 4), Tuple(1, 2, 6, 5), Tuple(2, 3, 7, 6), Tuple(0, 3, 7, 4), Tuple(4, 5, 6, 7)), Tuple( Perm(0, 1, 2, 3)(4, 5, 6, 7), Perm(0, 4, 5, 1)(2, 3, 7, 6), Perm(0, 4, 7, 3)(1, 5, 6, 2), Perm(0, 1)(2, 4)(3, 5)(6, 7), Perm(0, 6)(1, 2)(3, 5)(4, 7), Perm(0, 6)(1, 7)(2, 3)(4, 5), Perm(0, 3)(1, 7)(2, 4)(5, 6), Perm(0, 4)(1, 7)(2, 6)(3, 5), Perm(0, 6)(1, 5)(2, 4)(3, 7), Perm(1, 3, 4)(2, 7, 5), Perm(7)(0, 5, 2)(3, 4, 6), Perm(0, 5, 7)(1, 6, 3), Perm(0, 7, 2)(1, 4, 6))) octahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 3, 4), Tuple(0, 1, 4), Tuple(1, 2, 5), Tuple(2, 3, 5), Tuple(3, 4, 5), Tuple(1, 4, 5)), Tuple( Perm(5)(1, 2, 3, 4), Perm(0, 4, 5, 2), Perm(0, 1, 5, 3), Perm(0, 1)(2, 4)(3, 5), Perm(0, 2)(1, 3)(4, 5), Perm(0, 3)(1, 5)(2, 4), Perm(0, 4)(1, 3)(2, 5), Perm(0, 5)(1, 4)(2, 3), Perm(0, 5)(1, 2)(3, 4), Perm(0, 4, 1)(2, 3, 5), Perm(0, 1, 2)(3, 4, 5), Perm(0, 2, 3)(1, 5, 4), Perm(0, 4, 3)(1, 5, 2))) dodecahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19), Tuple( Tuple(0, 1, 2, 3, 4), Tuple(0, 1, 6, 10, 5), Tuple(1, 2, 7, 11, 6), Tuple(2, 3, 8, 12, 7), Tuple(3, 4, 9, 13, 8), Tuple(0, 4, 9, 14, 5), Tuple(5, 10, 16, 15, 14), Tuple(6, 10, 16, 17, 11), Tuple(7, 11, 17, 18, 12), Tuple(8, 12, 18, 19, 13), Tuple(9, 13, 19, 15, 14), Tuple(15, 16, 17, 18, 19)), Tuple( Perm(0, 1, 2, 3, 4)(5, 6, 7, 8, 9)(10, 11, 12, 13, 14)(15, 16, 17, 18, 19), Perm(0, 5, 10, 6, 1)(2, 4, 14, 16, 11)(3, 9, 15, 17, 7)(8, 13, 19, 18, 12), Perm(0, 10, 17, 12, 3)(1, 6, 11, 7, 2)(4, 5, 16, 18, 8)(9, 14, 15, 19, 13), Perm(0, 6, 17, 19, 9)(1, 11, 18, 13, 4)(2, 7, 12, 8, 3)(5, 10, 16, 15, 14), Perm(0, 2, 12, 19, 14)(1, 7, 18, 15, 5)(3, 8, 13, 9, 4)(6, 11, 17, 16, 10), Perm(0, 4, 9, 14, 5)(1, 3, 13, 15, 10)(2, 8, 19, 16, 6)(7, 12, 18, 17, 11), Perm(0, 1)(2, 5)(3, 10)(4, 6)(7, 14)(8, 16)(9, 11)(12, 15)(13, 17)(18, 19), Perm(0, 7)(1, 2)(3, 6)(4, 11)(5, 12)(8, 10)(9, 17)(13, 16)(14, 18)(15, 19), Perm(0, 12)(1, 8)(2, 3)(4, 7)(5, 18)(6, 13)(9, 11)(10, 19)(14, 17)(15, 16), Perm(0, 8)(1, 13)(2, 9)(3, 4)(5, 12)(6, 19)(7, 14)(10, 18)(11, 15)(16, 17), Perm(0, 4)(1, 9)(2, 14)(3, 5)(6, 13)(7, 15)(8, 10)(11, 19)(12, 16)(17, 18), Perm(0, 5)(1, 14)(2, 15)(3, 16)(4, 10)(6, 9)(7, 19)(8, 17)(11, 13)(12, 18), Perm(0, 11)(1, 6)(2, 10)(3, 16)(4, 17)(5, 7)(8, 15)(9, 18)(12, 14)(13, 19), Perm(0, 18)(1, 12)(2, 7)(3, 11)(4, 17)(5, 19)(6, 8)(9, 16)(10, 13)(14, 15), Perm(0, 18)(1, 19)(2, 13)(3, 8)(4, 12)(5, 17)(6, 15)(7, 9)(10, 16)(11, 14), Perm(0, 13)(1, 19)(2, 15)(3, 14)(4, 9)(5, 8)(6, 18)(7, 16)(10, 12)(11, 17), Perm(0, 16)(1, 15)(2, 19)(3, 18)(4, 17)(5, 10)(6, 14)(7, 13)(8, 12)(9, 11), Perm(0, 18)(1, 17)(2, 16)(3, 15)(4, 19)(5, 12)(6, 11)(7, 10)(8, 14)(9, 13), Perm(0, 15)(1, 19)(2, 18)(3, 17)(4, 16)(5, 14)(6, 13)(7, 12)(8, 11)(9, 10), Perm(0, 17)(1, 16)(2, 15)(3, 19)(4, 18)(5, 11)(6, 10)(7, 14)(8, 13)(9, 12), Perm(0, 19)(1, 18)(2, 17)(3, 16)(4, 15)(5, 13)(6, 12)(7, 11)(8, 10)(9, 14), Perm(1, 4, 5)(2, 9, 10)(3, 14, 6)(7, 13, 16)(8, 15, 11)(12, 19, 17), Perm(19)(0, 6, 2)(3, 5, 11)(4, 10, 7)(8, 14, 17)(9, 16, 12)(13, 15, 18), Perm(0, 11, 8)(1, 7, 3)(4, 6, 12)(5, 17, 13)(9, 10, 18)(14, 16, 19), Perm(0, 7, 13)(1, 12, 9)(2, 8, 4)(5, 11, 19)(6, 18, 14)(10, 17, 15), Perm(0, 3, 9)(1, 8, 14)(2, 13, 5)(6, 12, 15)(7, 19, 10)(11, 18, 16), Perm(0, 14, 10)(1, 9, 16)(2, 13, 17)(3, 19, 11)(4, 15, 6)(7, 8, 18), Perm(0, 16, 7)(1, 10, 11)(2, 5, 17)(3, 14, 18)(4, 15, 12)(8, 9, 19), Perm(0, 16, 13)(1, 17, 8)(2, 11, 12)(3, 6, 18)(4, 10, 19)(5, 15, 9), Perm(0, 11, 15)(1, 17, 14)(2, 18, 9)(3, 12, 13)(4, 7, 19)(5, 6, 16), Perm(0, 8, 15)(1, 12, 16)(2, 18, 10)(3, 19, 5)(4, 13, 14)(6, 7, 17))) icosahedron = Polyhedron( Tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11), Tuple( Tuple(0, 1, 2), Tuple(0, 2, 3), Tuple(0, 3, 4), Tuple(0, 4, 5), Tuple(0, 1, 5), Tuple(1, 6, 7), Tuple(1, 2, 7), Tuple(2, 7, 8), Tuple(2, 3, 8), Tuple(3, 8, 9), Tuple(3, 4, 9), Tuple(4, 9, 10), Tuple(4, 5, 10), Tuple(5, 6, 10), Tuple(1, 5, 6), Tuple(6, 7, 11), Tuple(7, 8, 11), Tuple(8, 9, 11), Tuple(9, 10, 11), Tuple(6, 10, 11)), Tuple( Perm(11)(1, 2, 3, 4, 5)(6, 7, 8, 9, 10), Perm(0, 5, 6, 7, 2)(3, 4, 10, 11, 8), Perm(0, 1, 7, 8, 3)(4, 5, 6, 11, 9), Perm(0, 2, 8, 9, 4)(1, 7, 11, 10, 5), Perm(0, 3, 9, 10, 5)(1, 2, 8, 11, 6), Perm(0, 4, 10, 6, 1)(2, 3, 9, 11, 7), Perm(0, 1)(2, 5)(3, 6)(4, 7)(8, 10)(9, 11), Perm(0, 2)(1, 3)(4, 7)(5, 8)(6, 9)(10, 11), Perm(0, 3)(1, 9)(2, 4)(5, 8)(6, 11)(7, 10), Perm(0, 4)(1, 9)(2, 10)(3, 5)(6, 8)(7, 11), Perm(0, 5)(1, 4)(2, 10)(3, 6)(7, 9)(8, 11), Perm(0, 6)(1, 5)(2, 10)(3, 11)(4, 7)(8, 9), Perm(0, 7)(1, 2)(3, 6)(4, 11)(5, 8)(9, 10), Perm(0, 8)(1, 9)(2, 3)(4, 7)(5, 11)(6, 10), Perm(0, 9)(1, 11)(2, 10)(3, 4)(5, 8)(6, 7), Perm(0, 10)(1, 9)(2, 11)(3, 6)(4, 5)(7, 8), Perm(0, 11)(1, 6)(2, 10)(3, 9)(4, 8)(5, 7), Perm(0, 11)(1, 8)(2, 7)(3, 6)(4, 10)(5, 9), Perm(0, 11)(1, 10)(2, 9)(3, 8)(4, 7)(5, 6), Perm(0, 11)(1, 7)(2, 6)(3, 10)(4, 9)(5, 8), Perm(0, 11)(1, 9)(2, 8)(3, 7)(4, 6)(5, 10), Perm(0, 5, 1)(2, 4, 6)(3, 10, 7)(8, 9, 11), Perm(0, 1, 2)(3, 5, 7)(4, 6, 8)(9, 10, 11), Perm(0, 2, 3)(1, 8, 4)(5, 7, 9)(6, 11, 10), Perm(0, 3, 4)(1, 8, 10)(2, 9, 5)(6, 7, 11), Perm(0, 4, 5)(1, 3, 10)(2, 9, 6)(7, 8, 11), Perm(0, 10, 7)(1, 5, 6)(2, 4, 11)(3, 9, 8), Perm(0, 6, 8)(1, 7, 2)(3, 5, 11)(4, 10, 9), Perm(0, 7, 9)(1, 11, 4)(2, 8, 3)(5, 6, 10), Perm(0, 8, 10)(1, 7, 6)(2, 11, 5)(3, 9, 4), Perm(0, 9, 6)(1, 3, 11)(2, 8, 7)(4, 10, 5))) tetrahedron_faces = list(tuple(arg) for arg in tetrahedron.faces) cube_faces = list(tuple(arg) for arg in cube.faces) octahedron_faces = list(tuple(arg) for arg in octahedron.faces) dodecahedron_faces = list(tuple(arg) for arg in dodecahedron.faces) icosahedron_faces = list(tuple(arg) for arg in icosahedron.faces)

154b1e85fb2ec21248a0d65c1c0bc33949f23361183bf4e26e83094c9d58e7cf

import itertools from sympy.combinatorics.fp_groups import FpGroup, FpSubgroup, simplify_presentation from sympy.combinatorics.free_groups import FreeGroup from sympy.combinatorics.perm_groups import PermutationGroup from sympy.core.numbers import igcd from sympy.ntheory.factor_ import totient from sympy import S class GroupHomomorphism: ''' A class representing group homomorphisms. Instantiate using `homomorphism()`. References ========== .. [1] Holt, D., Eick, B. and O'Brien, E. (2005). Handbook of computational group theory. ''' def __init__(self, domain, codomain, images): self.domain = domain self.codomain = codomain self.images = images self._inverses = None self._kernel = None self._image = None def _invs(self): ''' Return a dictionary with `{gen: inverse}` where `gen` is a rewriting generator of `codomain` (e.g. strong generator for permutation groups) and `inverse` is an element of its preimage ''' image = self.image() inverses = {} for k in list(self.images.keys()): v = self.images[k] if not (v in inverses or v.is_identity): inverses[v] = k if isinstance(self.codomain, PermutationGroup): gens = image.strong_gens else: gens = image.generators for g in gens: if g in inverses or g.is_identity: continue w = self.domain.identity if isinstance(self.codomain, PermutationGroup): parts = image._strong_gens_slp[g][::-1] else: parts = g for s in parts: if s in inverses: w = w*inverses[s] else: w = w*inverses[s**-1]**-1 inverses[g] = w return inverses def invert(self, g): ''' Return an element of the preimage of ``g`` or of each element of ``g`` if ``g`` is a list. Explanation =========== If the codomain is an FpGroup, the inverse for equal elements might not always be the same unless the FpGroup's rewriting system is confluent. However, making a system confluent can be time-consuming. If it's important, try `self.codomain.make_confluent()` first. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.free_groups import FreeGroupElement if isinstance(g, (Permutation, FreeGroupElement)): if isinstance(self.codomain, FpGroup): g = self.codomain.reduce(g) if self._inverses is None: self._inverses = self._invs() image = self.image() w = self.domain.identity if isinstance(self.codomain, PermutationGroup): gens = image.generator_product(g)[::-1] else: gens = g # the following can't be "for s in gens:" # because that would be equivalent to # "for s in gens.array_form:" when g is # a FreeGroupElement. On the other hand, # when you call gens by index, the generator # (or inverse) at position i is returned. for i in range(len(gens)): s = gens[i] if s.is_identity: continue if s in self._inverses: w = w*self._inverses[s] else: w = w*self._inverses[s**-1]**-1 return w elif isinstance(g, list): return [self.invert(e) for e in g] def kernel(self): ''' Compute the kernel of `self`. ''' if self._kernel is None: self._kernel = self._compute_kernel() return self._kernel def _compute_kernel(self): from sympy import S G = self.domain G_order = G.order() if G_order is S.Infinity: raise NotImplementedError( "Kernel computation is not implemented for infinite groups") gens = [] if isinstance(G, PermutationGroup): K = PermutationGroup(G.identity) else: K = FpSubgroup(G, gens, normal=True) i = self.image().order() while K.order()*i != G_order: r = G.random() k = r*self.invert(self(r))**-1 if not k in K: gens.append(k) if isinstance(G, PermutationGroup): K = PermutationGroup(gens) else: K = FpSubgroup(G, gens, normal=True) return K def image(self): ''' Compute the image of `self`. ''' if self._image is None: values = list(set(self.images.values())) if isinstance(self.codomain, PermutationGroup): self._image = self.codomain.subgroup(values) else: self._image = FpSubgroup(self.codomain, values) return self._image def _apply(self, elem): ''' Apply `self` to `elem`. ''' if not elem in self.domain: if isinstance(elem, (list, tuple)): return [self._apply(e) for e in elem] raise ValueError("The supplied element doesn't belong to the domain") if elem.is_identity: return self.codomain.identity else: images = self.images value = self.codomain.identity if isinstance(self.domain, PermutationGroup): gens = self.domain.generator_product(elem, original=True) for g in gens: if g in self.images: value = images[g]*value else: value = images[g**-1]**-1*value else: i = 0 for _, p in elem.array_form: if p < 0: g = elem[i]**-1 else: g = elem[i] value = value*images[g]**p i += abs(p) return value def __call__(self, elem): return self._apply(elem) def is_injective(self): ''' Check if the homomorphism is injective ''' return self.kernel().order() == 1 def is_surjective(self): ''' Check if the homomorphism is surjective ''' from sympy import S im = self.image().order() oth = self.codomain.order() if im is S.Infinity and oth is S.Infinity: return None else: return im == oth def is_isomorphism(self): ''' Check if `self` is an isomorphism. ''' return self.is_injective() and self.is_surjective() def is_trivial(self): ''' Check is `self` is a trivial homomorphism, i.e. all elements are mapped to the identity. ''' return self.image().order() == 1 def compose(self, other): ''' Return the composition of `self` and `other`, i.e. the homomorphism phi such that for all g in the domain of `other`, phi(g) = self(other(g)) ''' if not other.image().is_subgroup(self.domain): raise ValueError("The image of `other` must be a subgroup of " "the domain of `self`") images = {g: self(other(g)) for g in other.images} return GroupHomomorphism(other.domain, self.codomain, images) def restrict_to(self, H): ''' Return the restriction of the homomorphism to the subgroup `H` of the domain. ''' if not isinstance(H, PermutationGroup) or not H.is_subgroup(self.domain): raise ValueError("Given H is not a subgroup of the domain") domain = H images = {g: self(g) for g in H.generators} return GroupHomomorphism(domain, self.codomain, images) def invert_subgroup(self, H): ''' Return the subgroup of the domain that is the inverse image of the subgroup ``H`` of the homomorphism image ''' if not H.is_subgroup(self.image()): raise ValueError("Given H is not a subgroup of the image") gens = [] P = PermutationGroup(self.image().identity) for h in H.generators: h_i = self.invert(h) if h_i not in P: gens.append(h_i) P = PermutationGroup(gens) for k in self.kernel().generators: if k*h_i not in P: gens.append(k*h_i) P = PermutationGroup(gens) return P def homomorphism(domain, codomain, gens, images=[], check=True): ''' Create (if possible) a group homomorphism from the group ``domain`` to the group ``codomain`` defined by the images of the domain's generators ``gens``. ``gens`` and ``images`` can be either lists or tuples of equal sizes. If ``gens`` is a proper subset of the group's generators, the unspecified generators will be mapped to the identity. If the images are not specified, a trivial homomorphism will be created. If the given images of the generators do not define a homomorphism, an exception is raised. If ``check`` is ``False``, don't check whether the given images actually define a homomorphism. ''' if not isinstance(domain, (PermutationGroup, FpGroup, FreeGroup)): raise TypeError("The domain must be a group") if not isinstance(codomain, (PermutationGroup, FpGroup, FreeGroup)): raise TypeError("The codomain must be a group") generators = domain.generators if any([g not in generators for g in gens]): raise ValueError("The supplied generators must be a subset of the domain's generators") if any([g not in codomain for g in images]): raise ValueError("The images must be elements of the codomain") if images and len(images) != len(gens): raise ValueError("The number of images must be equal to the number of generators") gens = list(gens) images = list(images) images.extend([codomain.identity]*(len(generators)-len(images))) gens.extend([g for g in generators if g not in gens]) images = dict(zip(gens,images)) if check and not _check_homomorphism(domain, codomain, images): raise ValueError("The given images do not define a homomorphism") return GroupHomomorphism(domain, codomain, images) def _check_homomorphism(domain, codomain, images): if hasattr(domain, 'relators'): rels = domain.relators else: gens = domain.presentation().generators rels = domain.presentation().relators identity = codomain.identity def _image(r): if r.is_identity: return identity else: w = identity r_arr = r.array_form i = 0 j = 0 # i is the index for r and j is for # r_arr. r_arr[j] is the tuple (sym, p) # where sym is the generator symbol # and p is the power to which it is # raised while r[i] is a generator # (not just its symbol) or the inverse of # a generator - hence the need for # both indices while i < len(r): power = r_arr[j][1] if isinstance(domain, PermutationGroup) and r[i] in gens: s = domain.generators[gens.index(r[i])] else: s = r[i] if s in images: w = w*images[s]**power elif s**-1 in images: w = w*images[s**-1]**power i += abs(power) j += 1 return w for r in rels: if isinstance(codomain, FpGroup): s = codomain.equals(_image(r), identity) if s is None: # only try to make the rewriting system # confluent when it can't determine the # truth of equality otherwise success = codomain.make_confluent() s = codomain.equals(_image(r), identity) if s is None and not success: raise RuntimeError("Can't determine if the images " "define a homomorphism. Try increasing " "the maximum number of rewriting rules " "(group._rewriting_system.set_max(new_value); " "the current value is stored in group._rewriting" "_system.maxeqns)") else: s = _image(r).is_identity if not s: return False return True def orbit_homomorphism(group, omega): ''' Return the homomorphism induced by the action of the permutation group ``group`` on the set ``omega`` that is closed under the action. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.named_groups import SymmetricGroup codomain = SymmetricGroup(len(omega)) identity = codomain.identity omega = list(omega) images = {g: identity*Permutation([omega.index(o^g) for o in omega]) for g in group.generators} group._schreier_sims(base=omega) H = GroupHomomorphism(group, codomain, images) if len(group.basic_stabilizers) > len(omega): H._kernel = group.basic_stabilizers[len(omega)] else: H._kernel = PermutationGroup([group.identity]) return H def block_homomorphism(group, blocks): ''' Return the homomorphism induced by the action of the permutation group ``group`` on the block system ``blocks``. The latter should be of the same form as returned by the ``minimal_block`` method for permutation groups, namely a list of length ``group.degree`` where the i-th entry is a representative of the block i belongs to. ''' from sympy.combinatorics import Permutation from sympy.combinatorics.named_groups import SymmetricGroup n = len(blocks) # number the blocks; m is the total number, # b is such that b[i] is the number of the block i belongs to, # p is the list of length m such that p[i] is the representative # of the i-th block m = 0 p = [] b = [None]*n for i in range(n): if blocks[i] == i: p.append(i) b[i] = m m += 1 for i in range(n): b[i] = b[blocks[i]] codomain = SymmetricGroup(m) # the list corresponding to the identity permutation in codomain identity = range(m) images = {g: Permutation([b[p[i]^g] for i in identity]) for g in group.generators} H = GroupHomomorphism(group, codomain, images) return H def group_isomorphism(G, H, isomorphism=True): ''' Compute an isomorphism between 2 given groups. Parameters ========== G : A finite ``FpGroup`` or a ``PermutationGroup``. First group. H : A finite ``FpGroup`` or a ``PermutationGroup`` Second group. isomorphism : bool This is used to avoid the computation of homomorphism when the user only wants to check if there exists an isomorphism between the groups. Returns ======= If isomorphism = False -- Returns a boolean. If isomorphism = True -- Returns a boolean and an isomorphism between `G` and `H`. Examples ======== >>> from sympy.combinatorics import Permutation >>> from sympy.combinatorics.perm_groups import PermutationGroup >>> from sympy.combinatorics.free_groups import free_group >>> from sympy.combinatorics.fp_groups import FpGroup >>> from sympy.combinatorics.homomorphisms import group_isomorphism >>> from sympy.combinatorics.named_groups import DihedralGroup, AlternatingGroup >>> D = DihedralGroup(8) >>> p = Permutation(0, 1, 2, 3, 4, 5, 6, 7) >>> P = PermutationGroup(p) >>> group_isomorphism(D, P) (False, None) >>> F, a, b = free_group("a, b") >>> G = FpGroup(F, [a**3, b**3, (a*b)**2]) >>> H = AlternatingGroup(4) >>> (check, T) = group_isomorphism(G, H) >>> check True >>> T(b*a*b**-1*a**-1*b**-1) (0 2 3) Notes ===== Uses the approach suggested by Robert Tarjan to compute the isomorphism between two groups. First, the generators of ``G`` are mapped to the elements of ``H`` and we check if the mapping induces an isomorphism. ''' if not isinstance(G, (PermutationGroup, FpGroup)): raise TypeError("The group must be a PermutationGroup or an FpGroup") if not isinstance(H, (PermutationGroup, FpGroup)): raise TypeError("The group must be a PermutationGroup or an FpGroup") if isinstance(G, FpGroup) and isinstance(H, FpGroup): G = simplify_presentation(G) H = simplify_presentation(H) # Two infinite FpGroups with the same generators are isomorphic # when the relators are same but are ordered differently. if G.generators == H.generators and (G.relators).sort() == (H.relators).sort(): if not isomorphism: return True return (True, homomorphism(G, H, G.generators, H.generators)) # `_H` is the permutation group isomorphic to `H`. _H = H g_order = G.order() h_order = H.order() if g_order is S.Infinity: raise NotImplementedError("Isomorphism methods are not implemented for infinite groups.") if isinstance(H, FpGroup): if h_order is S.Infinity: raise NotImplementedError("Isomorphism methods are not implemented for infinite groups.") _H, h_isomorphism = H._to_perm_group() if (g_order != h_order) or (G.is_abelian != H.is_abelian): if not isomorphism: return False return (False, None) if not isomorphism: # Two groups of the same cyclic numbered order # are isomorphic to each other. n = g_order if (igcd(n, totient(n))) == 1: return True # Match the generators of `G` with subsets of `_H` gens = list(G.generators) for subset in itertools.permutations(_H, len(gens)): images = list(subset) images.extend([_H.identity]*(len(G.generators)-len(images))) _images = dict(zip(gens,images)) if _check_homomorphism(G, _H, _images): if isinstance(H, FpGroup): images = h_isomorphism.invert(images) T = homomorphism(G, H, G.generators, images, check=False) if T.is_isomorphism(): # It is a valid isomorphism if not isomorphism: return True return (True, T) if not isomorphism: return False return (False, None) def is_isomorphic(G, H): ''' Check if the groups are isomorphic to each other Parameters ========== G : A finite ``FpGroup`` or a ``PermutationGroup`` First group. H : A finite ``FpGroup`` or a ``PermutationGroup`` Second group. Returns ======= boolean ''' return group_isomorphism(G, H, isomorphism=False)

9565b5f31f6b52a1711728114843fecc9843c6179d18e729c9945f8cee9e4b02

from sympy.core import Basic, Dict, sympify from sympy.core.compatibility import as_int, default_sort_key from sympy.core.sympify import _sympify from sympy.functions.combinatorial.numbers import bell from sympy.matrices import zeros from sympy.sets.sets import FiniteSet, Union from sympy.utilities.iterables import flatten, group from collections import defaultdict class Partition(FiniteSet): """ This class represents an abstract partition. A partition is a set of disjoint sets whose union equals a given set. See Also ======== sympy.utilities.iterables.partitions, sympy.utilities.iterables.multiset_partitions """ _rank = None _partition = None def __new__(cls, *partition): """ Generates a new partition object. This method also verifies if the arguments passed are valid and raises a ValueError if they are not. Examples ======== Creating Partition from Python lists: >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a Partition(FiniteSet(1, 2), FiniteSet(3)) >>> a.partition [[1, 2], [3]] >>> len(a) 2 >>> a.members (1, 2, 3) Creating Partition from Python sets: >>> Partition({1, 2, 3}, {4, 5}) Partition(FiniteSet(1, 2, 3), FiniteSet(4, 5)) Creating Partition from SymPy finite sets: >>> from sympy.sets.sets import FiniteSet >>> a = FiniteSet(1, 2, 3) >>> b = FiniteSet(4, 5) >>> Partition(a, b) Partition(FiniteSet(1, 2, 3), FiniteSet(4, 5)) """ args = [] dups = False for arg in partition: if isinstance(arg, list): as_set = set(arg) if len(as_set) < len(arg): dups = True break # error below arg = as_set args.append(_sympify(arg)) if not all(isinstance(part, FiniteSet) for part in args): raise ValueError( "Each argument to Partition should be " \ "a list, set, or a FiniteSet") # sort so we have a canonical reference for RGS U = Union(*args) if dups or len(U) < sum(len(arg) for arg in args): raise ValueError("Partition contained duplicate elements.") obj = FiniteSet.__new__(cls, *args) obj.members = tuple(U) obj.size = len(U) return obj def sort_key(self, order=None): """Return a canonical key that can be used for sorting. Ordering is based on the size and sorted elements of the partition and ties are broken with the rank. Examples ======== >>> from sympy.utilities.iterables import default_sort_key >>> from sympy.combinatorics.partitions import Partition >>> from sympy.abc import x >>> a = Partition([1, 2]) >>> b = Partition([3, 4]) >>> c = Partition([1, x]) >>> d = Partition(list(range(4))) >>> l = [d, b, a + 1, a, c] >>> l.sort(key=default_sort_key); l [Partition(FiniteSet(1, 2)), Partition(FiniteSet(1), FiniteSet(2)), Partition(FiniteSet(1, x)), Partition(FiniteSet(3, 4)), Partition(FiniteSet(0, 1, 2, 3))] """ if order is None: members = self.members else: members = tuple(sorted(self.members, key=lambda w: default_sort_key(w, order))) return tuple(map(default_sort_key, (self.size, members, self.rank))) @property def partition(self): """Return partition as a sorted list of lists. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> Partition([1], [2, 3]).partition [[1], [2, 3]] """ if self._partition is None: self._partition = sorted([sorted(p, key=default_sort_key) for p in self.args]) return self._partition def __add__(self, other): """ Return permutation whose rank is ``other`` greater than current rank, (mod the maximum rank for the set). Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a.rank 1 >>> (a + 1).rank 2 >>> (a + 100).rank 1 """ other = as_int(other) offset = self.rank + other result = RGS_unrank((offset) % RGS_enum(self.size), self.size) return Partition.from_rgs(result, self.members) def __sub__(self, other): """ Return permutation whose rank is ``other`` less than current rank, (mod the maximum rank for the set). Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3]) >>> a.rank 1 >>> (a - 1).rank 0 >>> (a - 100).rank 1 """ return self.__add__(-other) def __le__(self, other): """ Checks if a partition is less than or equal to the other based on rank. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3, 4, 5]) >>> b = Partition([1], [2, 3], [4], [5]) >>> a.rank, b.rank (9, 34) >>> a <= a True >>> a <= b True """ return self.sort_key() <= sympify(other).sort_key() def __lt__(self, other): """ Checks if a partition is less than the other. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3, 4, 5]) >>> b = Partition([1], [2, 3], [4], [5]) >>> a.rank, b.rank (9, 34) >>> a >> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3], [4, 5]) >>> a.rank 13 """ if self._rank is not None: return self._rank self._rank = RGS_rank(self.RGS) return self._rank @property def RGS(self): """ Returns the "restricted growth string" of the partition. Explanation =========== The RGS is returned as a list of indices, L, where L[i] indicates the block in which element i appears. For example, in a partition of 3 elements (a, b, c) into 2 blocks ([c], [a, b]) the RGS is [1, 1, 0]: "a" is in block 1, "b" is in block 1 and "c" is in block 0. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> a = Partition([1, 2], [3], [4, 5]) >>> a.members (1, 2, 3, 4, 5) >>> a.RGS (0, 0, 1, 2, 2) >>> a + 1 Partition(FiniteSet(1, 2), FiniteSet(3), FiniteSet(4), FiniteSet(5)) >>> _.RGS (0, 0, 1, 2, 3) """ rgs = {} partition = self.partition for i, part in enumerate(partition): for j in part: rgs[j] = i return tuple([rgs[i] for i in sorted( [i for p in partition for i in p], key=default_sort_key)]) @classmethod def from_rgs(self, rgs, elements): """ Creates a set partition from a restricted growth string. Explanation =========== The indices given in rgs are assumed to be the index of the element as given in elements *as provided* (the elements are not sorted by this routine). Block numbering starts from 0. If any block was not referenced in ``rgs`` an error will be raised. Examples ======== >>> from sympy.combinatorics.partitions import Partition >>> Partition.from_rgs([0, 1, 2, 0, 1], list('abcde')) Partition(FiniteSet(c), FiniteSet(a, d), FiniteSet(b, e)) >>> Partition.from_rgs([0, 1, 2, 0, 1], list('cbead')) Partition(FiniteSet(e), FiniteSet(a, c), FiniteSet(b, d)) >>> a = Partition([1, 4], [2], [3, 5]) >>> Partition.from_rgs(a.RGS, a.members) Partition(FiniteSet(1, 4), FiniteSet(2), FiniteSet(3, 5)) """ if len(rgs) != len(elements): raise ValueError('mismatch in rgs and element lengths') max_elem = max(rgs) + 1 partition = [[] for i in range(max_elem)] j = 0 for i in rgs: partition[i].append(elements[j]) j += 1 if not all(p for p in partition): raise ValueError('some blocks of the partition were empty.') return Partition(*partition) class IntegerPartition(Basic): """ This class represents an integer partition. Explanation =========== In number theory and combinatorics, a partition of a positive integer, ``n``, also called an integer partition, is a way of writing ``n`` as a list of positive integers that sum to n. Two partitions that differ only in the order of summands are considered to be the same partition; if order matters then the partitions are referred to as compositions. For example, 4 has five partitions: [4], [3, 1], [2, 2], [2, 1, 1], and [1, 1, 1, 1]; the compositions [1, 2, 1] and [1, 1, 2] are the same as partition [2, 1, 1]. See Also ======== sympy.utilities.iterables.partitions, sympy.utilities.iterables.multiset_partitions References ========== https://en.wikipedia.org/wiki/Partition_%28number_theory%29 """ _dict = None _keys = None def __new__(cls, partition, integer=None): """ Generates a new IntegerPartition object from a list or dictionary. Explantion ========== The partition can be given as a list of positive integers or a dictionary of (integer, multiplicity) items. If the partition is preceded by an integer an error will be raised if the partition does not sum to that given integer. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([5, 4, 3, 1, 1]) >>> a IntegerPartition(14, (5, 4, 3, 1, 1)) >>> print(a) [5, 4, 3, 1, 1] >>> IntegerPartition({1:3, 2:1}) IntegerPartition(5, (2, 1, 1, 1)) If the value that the partition should sum to is given first, a check will be made to see n error will be raised if there is a discrepancy: >>> IntegerPartition(10, [5, 4, 3, 1]) Traceback (most recent call last): ... ValueError: The partition is not valid """ if integer is not None: integer, partition = partition, integer if isinstance(partition, (dict, Dict)): _ = [] for k, v in sorted(list(partition.items()), reverse=True): if not v: continue k, v = as_int(k), as_int(v) _.extend([k]*v) partition = tuple(_) else: partition = tuple(sorted(map(as_int, partition), reverse=True)) sum_ok = False if integer is None: integer = sum(partition) sum_ok = True else: integer = as_int(integer) if not sum_ok and sum(partition) != integer: raise ValueError("Partition did not add to %s" % integer) if any(i < 1 for i in partition): raise ValueError("The summands must all be positive.") obj = Basic.__new__(cls, integer, partition) obj.partition = list(partition) obj.integer = integer return obj def prev_lex(self): """Return the previous partition of the integer, n, in lexical order, wrapping around to [1, ..., 1] if the partition is [n]. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> p = IntegerPartition([4]) >>> print(p.prev_lex()) [3, 1] >>> p.partition > p.prev_lex().partition True """ d = defaultdict(int) d.update(self.as_dict()) keys = self._keys if keys == [1]: return IntegerPartition({self.integer: 1}) if keys[-1] != 1: d[keys[-1]] -= 1 if keys[-1] == 2: d[1] = 2 else: d[keys[-1] - 1] = d[1] = 1 else: d[keys[-2]] -= 1 left = d[1] + keys[-2] new = keys[-2] d[1] = 0 while left: new -= 1 if left - new >= 0: d[new] += left//new left -= d[new]*new return IntegerPartition(self.integer, d) def next_lex(self): """Return the next partition of the integer, n, in lexical order, wrapping around to [n] if the partition is [1, ..., 1]. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> p = IntegerPartition([3, 1]) >>> print(p.next_lex()) [4] >>> p.partition < p.next_lex().partition True """ d = defaultdict(int) d.update(self.as_dict()) key = self._keys a = key[-1] if a == self.integer: d.clear() d[1] = self.integer elif a == 1: if d[a] > 1: d[a + 1] += 1 d[a] -= 2 else: b = key[-2] d[b + 1] += 1 d[1] = (d[b] - 1)*b d[b] = 0 else: if d[a] > 1: if len(key) == 1: d.clear() d[a + 1] = 1 d[1] = self.integer - a - 1 else: a1 = a + 1 d[a1] += 1 d[1] = d[a]*a - a1 d[a] = 0 else: b = key[-2] b1 = b + 1 d[b1] += 1 need = d[b]*b + d[a]*a - b1 d[a] = d[b] = 0 d[1] = need return IntegerPartition(self.integer, d) def as_dict(self): """Return the partition as a dictionary whose keys are the partition integers and the values are the multiplicity of that integer. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> IntegerPartition([1]*3 + [2] + [3]*4).as_dict() {1: 3, 2: 1, 3: 4} """ if self._dict is None: groups = group(self.partition, multiple=False) self._keys = [g[0] for g in groups] self._dict = dict(groups) return self._dict @property def conjugate(self): """ Computes the conjugate partition of itself. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([6, 3, 3, 2, 1]) >>> a.conjugate [5, 4, 3, 1, 1, 1] """ j = 1 temp_arr = list(self.partition) + [0] k = temp_arr[0] b = [0]*k while k > 0: while k > temp_arr[j]: b[k - 1] = j k -= 1 j += 1 return b def __lt__(self, other): """Return True if self is less than other when the partition is listed from smallest to biggest. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([3, 1]) >>> a < a False >>> b = a.next_lex() >>> a >> a == b False """ return list(reversed(self.partition)) < list(reversed(other.partition)) def __le__(self, other): """Return True if self is less than other when the partition is listed from smallest to biggest. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> a = IntegerPartition([4]) >>> a <= a True """ return list(reversed(self.partition)) <= list(reversed(other.partition)) def as_ferrers(self, char='#'): """ Prints the ferrer diagram of a partition. Examples ======== >>> from sympy.combinatorics.partitions import IntegerPartition >>> print(IntegerPartition([1, 1, 5]).as_ferrers()) ##### # # """ return "\n".join([char*i for i in self.partition]) def __str__(self): return str(list(self.partition)) def random_integer_partition(n, seed=None): """ Generates a random integer partition summing to ``n`` as a list of reverse-sorted integers. Examples ======== >>> from sympy.combinatorics.partitions import random_integer_partition For the following, a seed is given so a known value can be shown; in practice, the seed would not be given. >>> random_integer_partition(100, seed=[1, 1, 12, 1, 2, 1, 85, 1]) [85, 12, 2, 1] >>> random_integer_partition(10, seed=[1, 2, 3, 1, 5, 1]) [5, 3, 1, 1] >>> random_integer_partition(1) [1] """ from sympy.testing.randtest import _randint n = as_int(n) if n < 1: raise ValueError('n must be a positive integer') randint = _randint(seed) partition = [] while (n > 0): k = randint(1, n) mult = randint(1, n//k) partition.append((k, mult)) n -= k*mult partition.sort(reverse=True) partition = flatten([[k]*m for k, m in partition]) return partition def RGS_generalized(m): """ Computes the m + 1 generalized unrestricted growth strings and returns them as rows in matrix. Examples ======== >>> from sympy.combinatorics.partitions import RGS_generalized >>> RGS_generalized(6) Matrix([ [ 1, 1, 1, 1, 1, 1, 1], [ 1, 2, 3, 4, 5, 6, 0], [ 2, 5, 10, 17, 26, 0, 0], [ 5, 15, 37, 77, 0, 0, 0], [ 15, 52, 151, 0, 0, 0, 0], [ 52, 203, 0, 0, 0, 0, 0], [203, 0, 0, 0, 0, 0, 0]]) """ d = zeros(m + 1) for i in range(0, m + 1): d[0, i] = 1 for i in range(1, m + 1): for j in range(m): if j <= m - i: d[i, j] = j * d[i - 1, j] + d[i - 1, j + 1] else: d[i, j] = 0 return d def RGS_enum(m): """ RGS_enum computes the total number of restricted growth strings possible for a superset of size m. Examples ======== >>> from sympy.combinatorics.partitions import RGS_enum >>> from sympy.combinatorics.partitions import Partition >>> RGS_enum(4) 15 >>> RGS_enum(5) 52 >>> RGS_enum(6) 203 We can check that the enumeration is correct by actually generating the partitions. Here, the 15 partitions of 4 items are generated: >>> a = Partition(list(range(4))) >>> s = set() >>> for i in range(20): ... s.add(a) ... a += 1 ... >>> assert len(s) == 15 """ if (m < 1): return 0 elif (m == 1): return 1 else: return bell(m) def RGS_unrank(rank, m): """ Gives the unranked restricted growth string for a given superset size. Examples ======== >>> from sympy.combinatorics.partitions import RGS_unrank >>> RGS_unrank(14, 4) [0, 1, 2, 3] >>> RGS_unrank(0, 4) [0, 0, 0, 0] """ if m < 1: raise ValueError("The superset size must be >= 1") if rank < 0 or RGS_enum(m) <= rank: raise ValueError("Invalid arguments") L = [1] * (m + 1) j = 1 D = RGS_generalized(m) for i in range(2, m + 1): v = D[m - i, j] cr = j*v if cr <= rank: L[i] = j + 1 rank -= cr j += 1 else: L[i] = int(rank / v + 1) rank %= v return [x - 1 for x in L[1:]] def RGS_rank(rgs): """ Computes the rank of a restricted growth string. Examples ======== >>> from sympy.combinatorics.partitions import RGS_rank, RGS_unrank >>> RGS_rank([0, 1, 2, 1, 3]) 42 >>> RGS_rank(RGS_unrank(4, 7)) 4 """ rgs_size = len(rgs) rank = 0 D = RGS_generalized(rgs_size) for i in range(1, rgs_size): n = len(rgs[(i + 1):]) m = max(rgs[0:i]) rank += D[n, m + 1] * rgs[i] return rank

8623821dff0c0e6e9e487fee93f54fbf2677ac5735901ac5dd6cc51e85fff678

from sympy.combinatorics.permutations import Permutation, _af_invert, _af_rmul from sympy.ntheory import isprime rmul = Permutation.rmul _af_new = Permutation._af_new ############################################ # # Utilities for computational group theory # ############################################ def _base_ordering(base, degree): r""" Order `\{0, 1, ..., n-1\}` so that base points come first and in order. Parameters ========== ``base`` : the base ``degree`` : the degree of the associated permutation group Returns ======= A list ``base_ordering`` such that ``base_ordering[point]`` is the number of ``point`` in the ordering. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _base_ordering >>> S = SymmetricGroup(4) >>> S.schreier_sims() >>> _base_ordering(S.base, S.degree) [0, 1, 2, 3] Notes ===== This is used in backtrack searches, when we define a relation `<<` on the underlying set for a permutation group of degree `n`, `\{0, 1, ..., n-1\}`, so that if `(b_1, b_2, ..., b_k)` is a base we have `b_i << b_j` whenever `i<j` and `b_i << a` for all `i\in\{1,2, ..., k\}` and `a` is not in the base. The idea is developed and applied to backtracking algorithms in [1], pp.108-132. The points that are not in the base are taken in increasing order. References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" """ base_len = len(base) ordering = [0]*degree for i in range(base_len): ordering[base[i]] = i current = base_len for i in range(degree): if i not in base: ordering[i] = current current += 1 return ordering def _check_cycles_alt_sym(perm): """ Checks for cycles of prime length p with n/2 >> from sympy.combinatorics.util import _check_cycles_alt_sym >>> from sympy.combinatorics.permutations import Permutation >>> a = Permutation([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [11, 12]]) >>> _check_cycles_alt_sym(a) False >>> b = Permutation([[0, 1, 2, 3, 4, 5, 6], [7, 8, 9, 10]]) >>> _check_cycles_alt_sym(b) True See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.is_alt_sym """ n = perm.size af = perm.array_form current_len = 0 total_len = 0 used = set() for i in range(n//2): if not i in used and i < n//2 - total_len: current_len = 1 used.add(i) j = i while af[j] != i: current_len += 1 j = af[j] used.add(j) total_len += current_len if current_len > n//2 and current_len < n - 2 and isprime(current_len): return True return False def _distribute_gens_by_base(base, gens): r""" Distribute the group elements ``gens`` by membership in basic stabilizers. Explanation =========== Notice that for a base `(b_1, b_2, ..., b_k)`, the basic stabilizers are defined as `G^{(i)} = G_{b_1, ..., b_{i-1}}` for `i \in\{1, 2, ..., k\}`. Parameters ========== ``base`` : a sequence of points in `\{0, 1, ..., n-1\}` ``gens`` : a list of elements of a permutation group of degree `n`. Returns ======= List of length `k`, where `k` is the length of ``base``. The `i`-th entry contains those elements in ``gens`` which fix the first `i` elements of ``base`` (so that the `0`-th entry is equal to ``gens`` itself). If no element fixes the first `i` elements of ``base``, the `i`-th element is set to a list containing the identity element. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.util import _distribute_gens_by_base >>> D = DihedralGroup(3) >>> D.schreier_sims() >>> D.strong_gens [(0 1 2), (0 2), (1 2)] >>> D.base [0, 1] >>> _distribute_gens_by_base(D.base, D.strong_gens) [[(0 1 2), (0 2), (1 2)], [(1 2)]] See Also ======== _strong_gens_from_distr, _orbits_transversals_from_bsgs, _handle_precomputed_bsgs """ base_len = len(base) degree = gens[0].size stabs = [[] for _ in range(base_len)] max_stab_index = 0 for gen in gens: j = 0 while j < base_len - 1 and gen._array_form[base[j]] == base[j]: j += 1 if j > max_stab_index: max_stab_index = j for k in range(j + 1): stabs[k].append(gen) for i in range(max_stab_index + 1, base_len): stabs[i].append(_af_new(list(range(degree)))) return stabs def _handle_precomputed_bsgs(base, strong_gens, transversals=None, basic_orbits=None, strong_gens_distr=None): """ Calculate BSGS-related structures from those present. Explanation =========== The base and strong generating set must be provided; if any of the transversals, basic orbits or distributed strong generators are not provided, they will be calculated from the base and strong generating set. Parameters ========== ``base`` - the base ``strong_gens`` - the strong generators ``transversals`` - basic transversals ``basic_orbits`` - basic orbits ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Returns ======= ``(transversals, basic_orbits, strong_gens_distr)`` where ``transversals`` are the basic transversals, ``basic_orbits`` are the basic orbits, and ``strong_gens_distr`` are the strong generators distributed by membership in basic stabilizers. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> from sympy.combinatorics.util import _handle_precomputed_bsgs >>> D = DihedralGroup(3) >>> D.schreier_sims() >>> _handle_precomputed_bsgs(D.base, D.strong_gens, ... basic_orbits=D.basic_orbits) ([{0: (2), 1: (0 1 2), 2: (0 2)}, {1: (2), 2: (1 2)}], [[0, 1, 2], [1, 2]], [[(0 1 2), (0 2), (1 2)], [(1 2)]]) See Also ======== _orbits_transversals_from_bsgs, _distribute_gens_by_base """ if strong_gens_distr is None: strong_gens_distr = _distribute_gens_by_base(base, strong_gens) if transversals is None: if basic_orbits is None: basic_orbits, transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr) else: transversals = \ _orbits_transversals_from_bsgs(base, strong_gens_distr, transversals_only=True) else: if basic_orbits is None: base_len = len(base) basic_orbits = [None]*base_len for i in range(base_len): basic_orbits[i] = list(transversals[i].keys()) return transversals, basic_orbits, strong_gens_distr def _orbits_transversals_from_bsgs(base, strong_gens_distr, transversals_only=False, slp=False): """ Compute basic orbits and transversals from a base and strong generating set. Explanation =========== The generators are provided as distributed across the basic stabilizers. If the optional argument ``transversals_only`` is set to True, only the transversals are returned. Parameters ========== ``base`` - The base. ``strong_gens_distr`` - Strong generators distributed by membership in basic stabilizers. ``transversals_only`` - bool A flag switching between returning only the transversals and both orbits and transversals. ``slp`` - If ``True``, return a list of dictionaries containing the generator presentations of the elements of the transversals, i.e. the list of indices of generators from ``strong_gens_distr[i]`` such that their product is the relevant transversal element. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _distribute_gens_by_base >>> S = SymmetricGroup(3) >>> S.schreier_sims() >>> strong_gens_distr = _distribute_gens_by_base(S.base, S.strong_gens) >>> (S.base, strong_gens_distr) ([0, 1], [[(0 1 2), (2)(0 1), (1 2)], [(1 2)]]) See Also ======== _distribute_gens_by_base, _handle_precomputed_bsgs """ from sympy.combinatorics.perm_groups import _orbit_transversal base_len = len(base) degree = strong_gens_distr[0][0].size transversals = [None]*base_len slps = [None]*base_len if transversals_only is False: basic_orbits = [None]*base_len for i in range(base_len): transversals[i], slps[i] = _orbit_transversal(degree, strong_gens_distr[i], base[i], pairs=True, slp=True) transversals[i] = dict(transversals[i]) if transversals_only is False: basic_orbits[i] = list(transversals[i].keys()) if transversals_only: return transversals else: if not slp: return basic_orbits, transversals return basic_orbits, transversals, slps def _remove_gens(base, strong_gens, basic_orbits=None, strong_gens_distr=None): """ Remove redundant generators from a strong generating set. Parameters ========== ``base`` - a base ``strong_gens`` - a strong generating set relative to ``base`` ``basic_orbits`` - basic orbits ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Returns ======= A strong generating set with respect to ``base`` which is a subset of ``strong_gens``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import _remove_gens >>> from sympy.combinatorics.testutil import _verify_bsgs >>> S = SymmetricGroup(15) >>> base, strong_gens = S.schreier_sims_incremental() >>> new_gens = _remove_gens(base, strong_gens) >>> len(new_gens) 14 >>> _verify_bsgs(S, base, new_gens) True Notes ===== This procedure is outlined in [1],p.95. References ========== .. [1] Holt, D., Eick, B., O'Brien, E. "Handbook of computational group theory" """ from sympy.combinatorics.perm_groups import _orbit base_len = len(base) degree = strong_gens[0].size if strong_gens_distr is None: strong_gens_distr = _distribute_gens_by_base(base, strong_gens) if basic_orbits is None: basic_orbits = [] for i in range(base_len): basic_orbit = _orbit(degree, strong_gens_distr[i], base[i]) basic_orbits.append(basic_orbit) strong_gens_distr.append([]) res = strong_gens[:] for i in range(base_len - 1, -1, -1): gens_copy = strong_gens_distr[i][:] for gen in strong_gens_distr[i]: if gen not in strong_gens_distr[i + 1]: temp_gens = gens_copy[:] temp_gens.remove(gen) if temp_gens == []: continue temp_orbit = _orbit(degree, temp_gens, base[i]) if temp_orbit == basic_orbits[i]: gens_copy.remove(gen) res.remove(gen) return res def _strip(g, base, orbits, transversals): """ Attempt to decompose a permutation using a (possibly partial) BSGS structure. Explanation =========== This is done by treating the sequence ``base`` as an actual base, and the orbits ``orbits`` and transversals ``transversals`` as basic orbits and transversals relative to it. This process is called "sifting". A sift is unsuccessful when a certain orbit element is not found or when after the sift the decomposition doesn't end with the identity element. The argument ``transversals`` is a list of dictionaries that provides transversal elements for the orbits ``orbits``. Parameters ========== ``g`` - permutation to be decomposed ``base`` - sequence of points ``orbits`` - a list in which the ``i``-th entry is an orbit of ``base[i]`` under some subgroup of the pointwise stabilizer of ` `base[0], base[1], ..., base[i - 1]``. The groups themselves are implicit in this function since the only information we need is encoded in the orbits and transversals ``transversals`` - a list of orbit transversals associated with the orbits ``orbits``. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.permutations import Permutation >>> from sympy.combinatorics.util import _strip >>> S = SymmetricGroup(5) >>> S.schreier_sims() >>> g = Permutation([0, 2, 3, 1, 4]) >>> _strip(g, S.base, S.basic_orbits, S.basic_transversals) ((4), 5) Notes ===== The algorithm is described in [1],pp.89-90. The reason for returning both the current state of the element being decomposed and the level at which the sifting ends is that they provide important information for the randomized version of the Schreier-Sims algorithm. References ========== .. [1] Holt, D., Eick, B., O'Brien, E."Handbook of computational group theory" See Also ======== sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims sympy.combinatorics.perm_groups.PermutationGroup.schreier_sims_random """ h = g._array_form base_len = len(base) for i in range(base_len): beta = h[base[i]] if beta == base[i]: continue if beta not in orbits[i]: return _af_new(h), i + 1 u = transversals[i][beta]._array_form h = _af_rmul(_af_invert(u), h) return _af_new(h), base_len + 1 def _strip_af(h, base, orbits, transversals, j, slp=[], slps={}): """ optimized _strip, with h, transversals and result in array form if the stripped elements is the identity, it returns False, base_len + 1 j h[base[i]] == base[i] for i <= j """ base_len = len(base) for i in range(j+1, base_len): beta = h[base[i]] if beta == base[i]: continue if beta not in orbits[i]: if not slp: return h, i + 1 return h, i + 1, slp u = transversals[i][beta] if h == u: if not slp: return False, base_len + 1 return False, base_len + 1, slp h = _af_rmul(_af_invert(u), h) if slp: u_slp = slps[i][beta][:] u_slp.reverse() u_slp = [(i, (g,)) for g in u_slp] slp = u_slp + slp if not slp: return h, base_len + 1 return h, base_len + 1, slp def _strong_gens_from_distr(strong_gens_distr): """ Retrieve strong generating set from generators of basic stabilizers. This is just the union of the generators of the first and second basic stabilizers. Parameters ========== ``strong_gens_distr`` - strong generators distributed by membership in basic stabilizers Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> from sympy.combinatorics.util import (_strong_gens_from_distr, ... _distribute_gens_by_base) >>> S = SymmetricGroup(3) >>> S.schreier_sims() >>> S.strong_gens [(0 1 2), (2)(0 1), (1 2)] >>> strong_gens_distr = _distribute_gens_by_base(S.base, S.strong_gens) >>> _strong_gens_from_distr(strong_gens_distr) [(0 1 2), (2)(0 1), (1 2)] See Also ======== _distribute_gens_by_base """ if len(strong_gens_distr) == 1: return strong_gens_distr[0][:] else: result = strong_gens_distr[0] for gen in strong_gens_distr[1]: if gen not in result: result.append(gen) return result

8026745e91aed7a9e06c1461e66801e858648459e3b3010d6f91f590b762c781

from sympy.combinatorics.group_constructs import DirectProduct from sympy.combinatorics.perm_groups import PermutationGroup from sympy.combinatorics.permutations import Permutation _af_new = Permutation._af_new def AbelianGroup(*cyclic_orders): """ Returns the direct product of cyclic groups with the given orders. Explanation =========== According to the structure theorem for finite abelian groups ([1]), every finite abelian group can be written as the direct product of finitely many cyclic groups. Examples ======== >>> from sympy.combinatorics.named_groups import AbelianGroup >>> AbelianGroup(3, 4) PermutationGroup([ (6)(0 1 2), (3 4 5 6)]) >>> _.is_group True See Also ======== DirectProduct References ========== .. [1] http://groupprops.subwiki.org/wiki/Structure_theorem_for_finitely_generated_abelian_groups """ groups = [] degree = 0 order = 1 for size in cyclic_orders: degree += size order *= size groups.append(CyclicGroup(size)) G = DirectProduct(*groups) G._is_abelian = True G._degree = degree G._order = order return G def AlternatingGroup(n): """ Generates the alternating group on ``n`` elements as a permutation group. Explanation =========== For ``n > 2``, the generators taken are ``(0 1 2), (0 1 2 ... n-1)`` for ``n`` odd and ``(0 1 2), (1 2 ... n-1)`` for ``n`` even (See [1], p.31, ex.6.9.). After the group is generated, some of its basic properties are set. The cases ``n = 1, 2`` are handled separately. Examples ======== >>> from sympy.combinatorics.named_groups import AlternatingGroup >>> G = AlternatingGroup(4) >>> G.is_group True >>> a = list(G.generate_dimino()) >>> len(a) 12 >>> all(perm.is_even for perm in a) True See Also ======== SymmetricGroup, CyclicGroup, DihedralGroup References ========== .. [1] Armstrong, M. "Groups and Symmetry" """ # small cases are special if n in (1, 2): return PermutationGroup([Permutation([0])]) a = list(range(n)) a[0], a[1], a[2] = a[1], a[2], a[0] gen1 = a if n % 2: a = list(range(1, n)) a.append(0) gen2 = a else: a = list(range(2, n)) a.append(1) a.insert(0, 0) gen2 = a gens = [gen1, gen2] if gen1 == gen2: gens = gens[:1] G = PermutationGroup([_af_new(a) for a in gens], dups=False) if n < 4: G._is_abelian = True G._is_nilpotent = True else: G._is_abelian = False G._is_nilpotent = False if n < 5: G._is_solvable = True else: G._is_solvable = False G._degree = n G._is_transitive = True G._is_alt = True return G def CyclicGroup(n): """ Generates the cyclic group of order ``n`` as a permutation group. Explanation =========== The generator taken is the ``n``-cycle ``(0 1 2 ... n-1)`` (in cycle notation). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import CyclicGroup >>> G = CyclicGroup(6) >>> G.is_group True >>> G.order() 6 >>> list(G.generate_schreier_sims(af=True)) [[0, 1, 2, 3, 4, 5], [1, 2, 3, 4, 5, 0], [2, 3, 4, 5, 0, 1], [3, 4, 5, 0, 1, 2], [4, 5, 0, 1, 2, 3], [5, 0, 1, 2, 3, 4]] See Also ======== SymmetricGroup, DihedralGroup, AlternatingGroup """ a = list(range(1, n)) a.append(0) gen = _af_new(a) G = PermutationGroup([gen]) G._is_abelian = True G._is_nilpotent = True G._is_solvable = True G._degree = n G._is_transitive = True G._order = n return G def DihedralGroup(n): r""" Generates the dihedral group `D_n` as a permutation group. Explanation =========== The dihedral group `D_n` is the group of symmetries of the regular ``n``-gon. The generators taken are the ``n``-cycle ``a = (0 1 2 ... n-1)`` (a rotation of the ``n``-gon) and ``b = (0 n-1)(1 n-2)...`` (a reflection of the ``n``-gon) in cycle rotation. It is easy to see that these satisfy ``a**n = b**2 = 1`` and ``bab = ~a`` so they indeed generate `D_n` (See [1]). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import DihedralGroup >>> G = DihedralGroup(5) >>> G.is_group True >>> a = list(G.generate_dimino()) >>> [perm.cyclic_form for perm in a] [[], [[0, 1, 2, 3, 4]], [[0, 2, 4, 1, 3]], [[0, 3, 1, 4, 2]], [[0, 4, 3, 2, 1]], [[0, 4], [1, 3]], [[1, 4], [2, 3]], [[0, 1], [2, 4]], [[0, 2], [3, 4]], [[0, 3], [1, 2]]] See Also ======== SymmetricGroup, CyclicGroup, AlternatingGroup References ========== .. [1] https://en.wikipedia.org/wiki/Dihedral_group """ # small cases are special if n == 1: return PermutationGroup([Permutation([1, 0])]) if n == 2: return PermutationGroup([Permutation([1, 0, 3, 2]), Permutation([2, 3, 0, 1]), Permutation([3, 2, 1, 0])]) a = list(range(1, n)) a.append(0) gen1 = _af_new(a) a = list(range(n)) a.reverse() gen2 = _af_new(a) G = PermutationGroup([gen1, gen2]) # if n is a power of 2, group is nilpotent if n & (n-1) == 0: G._is_nilpotent = True else: G._is_nilpotent = False G._is_abelian = False G._is_solvable = True G._degree = n G._is_transitive = True G._order = 2*n return G def SymmetricGroup(n): """ Generates the symmetric group on ``n`` elements as a permutation group. Explanation =========== The generators taken are the ``n``-cycle ``(0 1 2 ... n-1)`` and the transposition ``(0 1)`` (in cycle notation). (See [1]). After the group is generated, some of its basic properties are set. Examples ======== >>> from sympy.combinatorics.named_groups import SymmetricGroup >>> G = SymmetricGroup(4) >>> G.is_group True >>> G.order() 24 >>> list(G.generate_schreier_sims(af=True)) [[0, 1, 2, 3], [1, 2, 3, 0], [2, 3, 0, 1], [3, 1, 2, 0], [0, 2, 3, 1], [1, 3, 0, 2], [2, 0, 1, 3], [3, 2, 0, 1], [0, 3, 1, 2], [1, 0, 2, 3], [2, 1, 3, 0], [3, 0, 1, 2], [0, 1, 3, 2], [1, 2, 0, 3], [2, 3, 1, 0], [3, 1, 0, 2], [0, 2, 1, 3], [1, 3, 2, 0], [2, 0, 3, 1], [3, 2, 1, 0], [0, 3, 2, 1], [1, 0, 3, 2], [2, 1, 0, 3], [3, 0, 2, 1]] See Also ======== CyclicGroup, DihedralGroup, AlternatingGroup References ========== .. [1] https://en.wikipedia.org/wiki/Symmetric_group#Generators_and_relations """ if n == 1: G = PermutationGroup([Permutation([0])]) elif n == 2: G = PermutationGroup([Permutation([1, 0])]) else: a = list(range(1, n)) a.append(0) gen1 = _af_new(a) a = list(range(n)) a[0], a[1] = a[1], a[0] gen2 = _af_new(a) G = PermutationGroup([gen1, gen2]) if n < 3: G._is_abelian = True G._is_nilpotent = True else: G._is_abelian = False G._is_nilpotent = False if n < 5: G._is_solvable = True else: G._is_solvable = False G._degree = n G._is_transitive = True G._is_sym = True return G def RubikGroup(n): """Return a group of Rubik's cube generators >>> from sympy.combinatorics.named_groups import RubikGroup >>> RubikGroup(2).is_group True """ from sympy.combinatorics.generators import rubik if n <= 1: raise ValueError("Invalid cube. n has to be greater than 1") return PermutationGroup(rubik(n))

b469c409285f40e99271b4fd2d8158e2101659962af8d7ff68794a281de4705b

from sympy import Integer from sympy.core import Symbol from sympy.utilities import public @public def approximants(l, X=Symbol('x'), simplify=False): """ Return a generator for consecutive Pade approximants for a series. It can also be used for computing the rational generating function of a series when possible, since the last approximant returned by the generator will be the generating function (if any). The input list can contain more complex expressions than integer or rational numbers; symbols may also be involved in the computation. An example below show how to compute the generating function of the whole Pascal triangle. The generator can be asked to apply the sympy.simplify function on each generated term, which will make the computation slower; however it may be useful when symbols are involved in the expressions. Examples ======== >>> from sympy.series import approximants >>> from sympy import lucas, fibonacci, symbols, binomial >>> g = [lucas(k) for k in range(16)] >>> [e for e in approximants(g)] [2, -4/(x - 2), (5*x - 2)/(3*x - 1), (x - 2)/(x**2 + x - 1)] >>> h = [fibonacci(k) for k in range(16)] >>> [e for e in approximants(h)] [x, -x/(x - 1), (x**2 - x)/(2*x - 1), -x/(x**2 + x - 1)] >>> x, t = symbols("x,t") >>> p=[sum(binomial(k,i)*x**i for i in range(k+1)) for k in range(16)] >>> y = approximants(p, t) >>> for k in range(3): print(next(y)) 1 (x + 1)/((-x - 1)*(t*(x + 1) + (x + 1)/(-x - 1))) nan >>> y = approximants(p, t, simplify=True) >>> for k in range(3): print(next(y)) 1 -1/(t*(x + 1) - 1) nan See Also ======== See function sympy.concrete.guess.guess_generating_function_rational and function mpmath.pade """ p1, q1 = [Integer(1)], [Integer(0)] p2, q2 = [Integer(0)], [Integer(1)] while len(l): b = 0 while l[b]==0: b += 1 if b == len(l): return m = [Integer(1)/l[b]] for k in range(b+1, len(l)): s = 0 for j in range(b, k): s -= l[j+1] * m[b-j-1] m.append(s/l[b]) l = m a, l[0] = l[0], 0 p = [0] * max(len(p2), b+len(p1)) q = [0] * max(len(q2), b+len(q1)) for k in range(len(p2)): p[k] = a*p2[k] for k in range(b, b+len(p1)): p[k] += p1[k-b] for k in range(len(q2)): q[k] = a*q2[k] for k in range(b, b+len(q1)): q[k] += q1[k-b] while p[-1]==0: p.pop() while q[-1]==0: q.pop() p1, p2 = p2, p q1, q2 = q2, q # yield result from sympy import denom, lcm, simplify as simp c = 1 for x in p: c = lcm(c, denom(x)) for x in q: c = lcm(c, denom(x)) out = ( sum(c*e*X**k for k, e in enumerate(p)) / sum(c*e*X**k for k, e in enumerate(q)) ) if simplify: yield(simp(out)) else: yield out return

d37dcd27945ef004b87aaf9c8667dcb77f8bcf6bc1a9d16a5ed9eb6f1b304f1d

""" Contains the base class for series Made using sequences in mind """ from sympy.core.expr import Expr from sympy.core.singleton import S from sympy.core.cache import cacheit class SeriesBase(Expr): """Base Class for series""" @property def interval(self): """The interval on which the series is defined""" raise NotImplementedError("(%s).interval" % self) @property def start(self): """The starting point of the series. This point is included""" raise NotImplementedError("(%s).start" % self) @property def stop(self): """The ending point of the series. This point is included""" raise NotImplementedError("(%s).stop" % self) @property def length(self): """Length of the series expansion""" raise NotImplementedError("(%s).length" % self) @property def variables(self): """Returns a tuple of variables that are bounded""" return () @property def free_symbols(self): """ This method returns the symbols in the object, excluding those that take on a specific value (i.e. the dummy symbols). """ return ({j for i in self.args for j in i.free_symbols} .difference(self.variables)) @cacheit def term(self, pt): """Term at point pt of a series""" if pt < self.start or pt > self.stop: raise IndexError("Index %s out of bounds %s" % (pt, self.interval)) return self._eval_term(pt) def _eval_term(self, pt): raise NotImplementedError("The _eval_term method should be added to" "%s to return series term so it is available" "when 'term' calls it." % self.func) def _ith_point(self, i): """ Returns the i'th point of a series If start point is negative infinity, point is returned from the end. Assumes the first point to be indexed zero. Examples ======== TODO """ if self.start is S.NegativeInfinity: initial = self.stop step = -1 else: initial = self.start step = 1 return initial + i*step def __iter__(self): i = 0 while i < self.length: pt = self._ith_point(i) yield self.term(pt) i += 1 def __getitem__(self, index): if isinstance(index, int): index = self._ith_point(index) return self.term(index) elif isinstance(index, slice): start, stop = index.start, index.stop if start is None: start = 0 if stop is None: stop = self.length return [self.term(self._ith_point(i)) for i in range(start, stop, index.step or 1)]

72b4a440ad7003a15000a2358ac946eaba40cef5a5cf581964fc76030a78dd08

from sympy.core.sympify import sympify def series(expr, x=None, x0=0, n=6, dir="+"): """Series expansion of expr around point `x = x0`. Parameters ========== expr : Expression The expression whose series is to be expanded. x : Symbol It is the variable of the expression to be calculated. x0 : Value The value around which ``x`` is calculated. Can be any value from ``-oo`` to ``oo``. n : Value The number of terms upto which the series is to be expanded. dir : String, optional The series-expansion can be bi-directional. If ``dir="+"``, then (x->x0+). If ``dir="-", then (x->x0-). For infinite ``x0`` (``oo`` or ``-oo``), the ``dir`` argument is determined from the direction of the infinity (i.e., ``dir="-"`` for ``oo``). Examples ======== >>> from sympy import series, tan, oo >>> from sympy.abc import x >>> f = tan(x) >>> series(f, x, 2, 6, "+") tan(2) + (1 + tan(2)**2)*(x - 2) + (x - 2)**2*(tan(2)**3 + tan(2)) + (x - 2)**3*(1/3 + 4*tan(2)**2/3 + tan(2)**4) + (x - 2)**4*(tan(2)**5 + 5*tan(2)**3/3 + 2*tan(2)/3) + (x - 2)**5*(2/15 + 17*tan(2)**2/15 + 2*tan(2)**4 + tan(2)**6) + O((x - 2)**6, (x, 2)) >>> series(f, x, 2, 3, "-") tan(2) + (2 - x)*(-tan(2)**2 - 1) + (2 - x)**2*(tan(2)**3 + tan(2)) + O((x - 2)**3, (x, 2)) >>> series(f, x, 2, oo, "+") Traceback (most recent call last): ... TypeError: 'Infinity' object cannot be interpreted as an integer Returns ======= Expr Series expansion of the expression about x0 See Also ======== sympy.core.expr.Expr.series: See the docstring of Expr.series() for complete details of this wrapper. """ expr = sympify(expr) return expr.series(x, x0, n, dir)

7075464506b36b86b2a88ea38ba38736475010c57b064a387f8bee8366ee1106

from sympy.core.sympify import sympify def aseries(expr, x=None, n=6, bound=0, hir=False): """ See the docstring of Expr.aseries() for complete details of this wrapper. """ expr = sympify(expr) return expr.aseries(x, n, bound, hir)

ecbf10de75ef3b36145a643cbaec3bd045061e5f9afb83f83953214eb1a9337d

""" Convergence acceleration / extrapolation methods for series and sequences. References: Carl M. Bender & Steven A. Orszag, "Advanced Mathematical Methods for Scientists and Engineers: Asymptotic Methods and Perturbation Theory", Springer 1999. (Shanks transformation: pp. 368-375, Richardson extrapolation: pp. 375-377.) """ from sympy import factorial, Integer, S def richardson(A, k, n, N): """ Calculate an approximation for lim k->oo A(k) using Richardson extrapolation with the terms A(n), A(n+1), ..., A(n+N+1). Choosing N ~= 2*n often gives good results. A simple example is to calculate exp(1) using the limit definition. This limit converges slowly; n = 100 only produces two accurate digits: >>> from sympy.abc import n >>> e = (1 + 1/n)**n >>> print(round(e.subs(n, 100).evalf(), 10)) 2.7048138294 Richardson extrapolation with 11 appropriately chosen terms gives a value that is accurate to the indicated precision: >>> from sympy import E >>> from sympy.series.acceleration import richardson >>> print(round(richardson(e, n, 10, 20).evalf(), 10)) 2.7182818285 >>> print(round(E.evalf(), 10)) 2.7182818285 Another useful application is to speed up convergence of series. Computing 100 terms of the zeta(2) series 1/k**2 yields only two accurate digits: >>> from sympy.abc import k, n >>> from sympy import Sum >>> A = Sum(k**-2, (k, 1, n)) >>> print(round(A.subs(n, 100).evalf(), 10)) 1.6349839002 Richardson extrapolation performs much better: >>> from sympy import pi >>> print(round(richardson(A, n, 10, 20).evalf(), 10)) 1.6449340668 >>> print(round(((pi**2)/6).evalf(), 10)) # Exact value 1.6449340668 """ s = S.Zero for j in range(0, N + 1): s += A.subs(k, Integer(n + j)).doit() * (n + j)**N * (-1)**(j + N) / \ (factorial(j) * factorial(N - j)) return s def shanks(A, k, n, m=1): """ Calculate an approximation for lim k->oo A(k) using the n-term Shanks transformation S(A)(n). With m > 1, calculate the m-fold recursive Shanks transformation S(S(...S(A)...))(n). The Shanks transformation is useful for summing Taylor series that converge slowly near a pole or singularity, e.g. for log(2): >>> from sympy.abc import k, n >>> from sympy import Sum, Integer >>> from sympy.series.acceleration import shanks >>> A = Sum(Integer(-1)**(k+1) / k, (k, 1, n)) >>> print(round(A.subs(n, 100).doit().evalf(), 10)) 0.6881721793 >>> print(round(shanks(A, n, 25).evalf(), 10)) 0.6931396564 >>> print(round(shanks(A, n, 25, 5).evalf(), 10)) 0.6931471806 The correct value is 0.6931471805599453094172321215. """ table = [A.subs(k, Integer(j)).doit() for j in range(n + m + 2)] table2 = table[:] for i in range(1, m + 1): for j in range(i, n + m + 1): x, y, z = table[j - 1], table[j], table[j + 1] table2[j] = (z*x - y**2) / (z + x - 2*y) table = table2[:] return table[n]

7e6503609ee98d51720d7e261f57f930c5a147cf7bbcad96b064446db53698d3

""" Limits ====== Implemented according to the PhD thesis http://www.cybertester.com/data/gruntz.pdf, which contains very thorough descriptions of the algorithm including many examples. We summarize here the gist of it. All functions are sorted according to how rapidly varying they are at infinity using the following rules. Any two functions f and g can be compared using the properties of L: L=lim log|f(x)| / log|g(x)| (for x -> oo) We define >, < ~ according to:: 1. f > g .... L=+-oo we say that: - f is greater than any power of g - f is more rapidly varying than g - f goes to infinity/zero faster than g 2. f < g .... L=0 we say that: - f is lower than any power of g 3. f ~ g .... L!=0, +-oo we say that: - both f and g are bounded from above and below by suitable integral powers of the other Examples ======== :: 2 < x < exp(x) < exp(x**2) < exp(exp(x)) 2 ~ 3 ~ -5 x ~ x**2 ~ x**3 ~ 1/x ~ x**m ~ -x exp(x) ~ exp(-x) ~ exp(2x) ~ exp(x)**2 ~ exp(x+exp(-x)) f ~ 1/f So we can divide all the functions into comparability classes (x and x^2 belong to one class, exp(x) and exp(-x) belong to some other class). In principle, we could compare any two functions, but in our algorithm, we don't compare anything below the class 2~3~-5 (for example log(x) is below this), so we set 2~3~-5 as the lowest comparability class. Given the function f, we find the list of most rapidly varying (mrv set) subexpressions of it. This list belongs to the same comparability class. Let's say it is {exp(x), exp(2x)}. Using the rule f ~ 1/f we find an element "w" (either from the list or a new one) from the same comparability class which goes to zero at infinity. In our example we set w=exp(-x) (but we could also set w=exp(-2x) or w=exp(-3x) ...). We rewrite the mrv set using w, in our case {1/w, 1/w^2}, and substitute it into f. Then we expand f into a series in w:: f = c0*w^e0 + c1*w^e1 + ... + O(w^en), where e0<e1<...<en, c0!=0 but for x->oo, lim f = lim c0*w^e0, because all the other terms go to zero, because w goes to zero faster than the ci and ei. So:: for e0>0, lim f = 0 for e0<0, lim f = +-oo (the sign depends on the sign of c0) for e0=0, lim f = lim c0 We need to recursively compute limits at several places of the algorithm, but as is shown in the PhD thesis, it always finishes. Important functions from the implementation: compare(a, b, x) compares "a" and "b" by computing the limit L. mrv(e, x) returns list of most rapidly varying (mrv) subexpressions of "e" rewrite(e, Omega, x, wsym) rewrites "e" in terms of w leadterm(f, x) returns the lowest power term in the series of f mrv_leadterm(e, x) returns the lead term (c0, e0) for e limitinf(e, x) computes lim e (for x->oo) limit(e, z, z0) computes any limit by converting it to the case x->oo All the functions are really simple and straightforward except rewrite(), which is the most difficult/complex part of the algorithm. When the algorithm fails, the bugs are usually in the series expansion (i.e. in SymPy) or in rewrite. This code is almost exact rewrite of the Maple code inside the Gruntz thesis. Debugging --------- Because the gruntz algorithm is highly recursive, it's difficult to figure out what went wrong inside a debugger. Instead, turn on nice debug prints by defining the environment variable SYMPY_DEBUG. For example: [user@localhost]: SYMPY_DEBUG=True ./bin/isympy In [1]: limit(sin(x)/x, x, 0) limitinf(_x*sin(1/_x), _x) = 1 +-mrv_leadterm(_x*sin(1/_x), _x) = (1, 0) | +-mrv(_x*sin(1/_x), _x) = set([_x]) | | +-mrv(_x, _x) = set([_x]) | | +-mrv(sin(1/_x), _x) = set([_x]) | | +-mrv(1/_x, _x) = set([_x]) | | +-mrv(_x, _x) = set([_x]) | +-mrv_leadterm(exp(_x)*sin(exp(-_x)), _x, set([exp(_x)])) = (1, 0) | +-rewrite(exp(_x)*sin(exp(-_x)), set([exp(_x)]), _x, _w) = (1/_w*sin(_w), -_x) | +-sign(_x, _x) = 1 | +-mrv_leadterm(1, _x) = (1, 0) +-sign(0, _x) = 0 +-limitinf(1, _x) = 1 And check manually which line is wrong. Then go to the source code and debug this function to figure out the exact problem. """ from sympy import cacheit from sympy.core import Basic, S, oo, I, Dummy, Wild, Mul from sympy.core.compatibility import reduce from sympy.functions import log, exp from sympy.series.order import Order from sympy.simplify.powsimp import powsimp, powdenest from sympy.utilities.misc import debug_decorator as debug from sympy.utilities.timeutils import timethis timeit = timethis('gruntz') def compare(a, b, x): """Returns "<" if a<b, "=" for a == b, ">" for a>b""" # log(exp(...)) must always be simplified here for termination la, lb = log(a), log(b) if isinstance(a, Basic) and isinstance(a, exp): la = a.args[0] if isinstance(b, Basic) and isinstance(b, exp): lb = b.args[0] c = limitinf(la/lb, x) if c == 0: return "<" elif c.is_infinite: return ">" else: return "=" class SubsSet(dict): """ Stores (expr, dummy) pairs, and how to rewrite expr-s. The gruntz algorithm needs to rewrite certain expressions in term of a new variable w. We cannot use subs, because it is just too smart for us. For example:: > Omega=[exp(exp(_p - exp(-_p))/(1 - 1/_p)), exp(exp(_p))] > O2=[exp(-exp(_p) + exp(-exp(-_p))*exp(_p)/(1 - 1/_p))/_w, 1/_w] > e = exp(exp(_p - exp(-_p))/(1 - 1/_p)) - exp(exp(_p)) > e.subs(Omega[0],O2[0]).subs(Omega[1],O2[1]) -1/w + exp(exp(p)*exp(-exp(-p))/(1 - 1/p)) is really not what we want! So we do it the hard way and keep track of all the things we potentially want to substitute by dummy variables. Consider the expression:: exp(x - exp(-x)) + exp(x) + x. The mrv set is {exp(x), exp(-x), exp(x - exp(-x))}. We introduce corresponding dummy variables d1, d2, d3 and rewrite:: d3 + d1 + x. This class first of all keeps track of the mapping expr->variable, i.e. will at this stage be a dictionary:: {exp(x): d1, exp(-x): d2, exp(x - exp(-x)): d3}. [It turns out to be more convenient this way round.] But sometimes expressions in the mrv set have other expressions from the mrv set as subexpressions, and we need to keep track of that as well. In this case, d3 is really exp(x - d2), so rewrites at this stage is:: {d3: exp(x-d2)}. The function rewrite uses all this information to correctly rewrite our expression in terms of w. In this case w can be chosen to be exp(-x), i.e. d2. The correct rewriting then is:: exp(-w)/w + 1/w + x. """ def __init__(self): self.rewrites = {} def __repr__(self): return super().__repr__() + ', ' + self.rewrites.__repr__() def __getitem__(self, key): if not key in self: self[key] = Dummy() return dict.__getitem__(self, key) def do_subs(self, e): """Substitute the variables with expressions""" for expr, var in self.items(): e = e.xreplace({var: expr}) return e def meets(self, s2): """Tell whether or not self and s2 have non-empty intersection""" return set(self.keys()).intersection(list(s2.keys())) != set() def union(self, s2, exps=None): """Compute the union of self and s2, adjusting exps""" res = self.copy() tr = {} for expr, var in s2.items(): if expr in self: if exps: exps = exps.xreplace({var: res[expr]}) tr[var] = res[expr] else: res[expr] = var for var, rewr in s2.rewrites.items(): res.rewrites[var] = rewr.xreplace(tr) return res, exps def copy(self): """Create a shallow copy of SubsSet""" r = SubsSet() r.rewrites = self.rewrites.copy() for expr, var in self.items(): r[expr] = var return r @debug def mrv(e, x): """Returns a SubsSet of most rapidly varying (mrv) subexpressions of 'e', and e rewritten in terms of these""" e = powsimp(e, deep=True, combine='exp') if not isinstance(e, Basic): raise TypeError("e should be an instance of Basic") if not e.has(x): return SubsSet(), e elif e == x: s = SubsSet() return s, s[x] elif e.is_Mul or e.is_Add: i, d = e.as_independent(x) # throw away x-independent terms if d.func != e.func: s, expr = mrv(d, x) return s, e.func(i, expr) a, b = d.as_two_terms() s1, e1 = mrv(a, x) s2, e2 = mrv(b, x) return mrv_max1(s1, s2, e.func(i, e1, e2), x) elif e.is_Pow: e1 = S.One while e.is_Pow: b1 = e.base e1 *= e.exp e = b1 if b1 == 1: return SubsSet(), b1 if e1.has(x): base_lim = limitinf(b1, x) if base_lim is S.One: return mrv(exp(e1 * (b1 - 1)), x) return mrv(exp(e1 * log(b1)), x) else: s, expr = mrv(b1, x) return s, expr**e1 elif isinstance(e, log): s, expr = mrv(e.args[0], x) return s, log(expr) elif isinstance(e, exp): # We know from the theory of this algorithm that exp(log(...)) may always # be simplified here, and doing so is vital for termination. if isinstance(e.args[0], log): return mrv(e.args[0].args[0], x) # if a product has an infinite factor the result will be # infinite if there is no zero, otherwise NaN; here, we # consider the result infinite if any factor is infinite li = limitinf(e.args[0], x) if any(_.is_infinite for _ in Mul.make_args(li)): s1 = SubsSet() e1 = s1[e] s2, e2 = mrv(e.args[0], x) su = s1.union(s2)[0] su.rewrites[e1] = exp(e2) return mrv_max3(s1, e1, s2, exp(e2), su, e1, x) else: s, expr = mrv(e.args[0], x) return s, exp(expr) elif e.is_Function: l = [mrv(a, x) for a in e.args] l2 = [s for (s, _) in l if s != SubsSet()] if len(l2) != 1: # e.g. something like BesselJ(x, x) raise NotImplementedError("MRV set computation for functions in" " several variables not implemented.") s, ss = l2[0], SubsSet() args = [ss.do_subs(x[1]) for x in l] return s, e.func(*args) elif e.is_Derivative: raise NotImplementedError("MRV set computation for derviatives" " not implemented yet.") return mrv(e.args[0], x) raise NotImplementedError( "Don't know how to calculate the mrv of '%s'" % e) def mrv_max3(f, expsf, g, expsg, union, expsboth, x): """Computes the maximum of two sets of expressions f and g, which are in the same comparability class, i.e. max() compares (two elements of) f and g and returns either (f, expsf) [if f is larger], (g, expsg) [if g is larger] or (union, expsboth) [if f, g are of the same class]. """ if not isinstance(f, SubsSet): raise TypeError("f should be an instance of SubsSet") if not isinstance(g, SubsSet): raise TypeError("g should be an instance of SubsSet") if f == SubsSet(): return g, expsg elif g == SubsSet(): return f, expsf elif f.meets(g): return union, expsboth c = compare(list(f.keys())[0], list(g.keys())[0], x) if c == ">": return f, expsf elif c == "<": return g, expsg else: if c != "=": raise ValueError("c should be =") return union, expsboth def mrv_max1(f, g, exps, x): """Computes the maximum of two sets of expressions f and g, which are in the same comparability class, i.e. mrv_max1() compares (two elements of) f and g and returns the set, which is in the higher comparability class of the union of both, if they have the same order of variation. Also returns exps, with the appropriate substitutions made. """ u, b = f.union(g, exps) return mrv_max3(f, g.do_subs(exps), g, f.do_subs(exps), u, b, x) @debug @cacheit @timeit def sign(e, x): """ Returns a sign of an expression e(x) for x->oo. :: e > 0 for x sufficiently large ... 1 e == 0 for x sufficiently large ... 0 e < 0 for x sufficiently large ... -1 The result of this function is currently undefined if e changes sign arbitrarily often for arbitrarily large x (e.g. sin(x)). Note that this returns zero only if e is *constantly* zero for x sufficiently large. [If e is constant, of course, this is just the same thing as the sign of e.] """ from sympy import sign as _sign if not isinstance(e, Basic): raise TypeError("e should be an instance of Basic") if e.is_positive: return 1 elif e.is_negative: return -1 elif e.is_zero: return 0 elif not e.has(x): return _sign(e) elif e == x: return 1 elif e.is_Mul: a, b = e.as_two_terms() sa = sign(a, x) if not sa: return 0 return sa * sign(b, x) elif isinstance(e, exp): return 1 elif e.is_Pow: s = sign(e.base, x) if s == 1: return 1 if e.exp.is_Integer: return s**e.exp elif isinstance(e, log): return sign(e.args[0] - 1, x) # if all else fails, do it the hard way c0, e0 = mrv_leadterm(e, x) return sign(c0, x) @debug @timeit @cacheit def limitinf(e, x, leadsimp=False): """Limit e(x) for x-> oo. If ``leadsimp`` is True, an attempt is made to simplify the leading term of the series expansion of ``e``. That may succeed even if ``e`` cannot be simplified. """ # rewrite e in terms of tractable functions only if not e.has(x): return e # e is a constant if e.has(Order): e = e.expand().removeO() if not x.is_positive or x.is_integer: # We make sure that x.is_positive is True and x.is_integer is None # so we get all the correct mathematical behavior from the expression. # We need a fresh variable. p = Dummy('p', positive=True) e = e.subs(x, p) x = p e = e.rewrite('tractable', deep=True, limitvar=x) e = powdenest(e) c0, e0 = mrv_leadterm(e, x) sig = sign(e0, x) if sig == 1: return S.Zero # e0>0: lim f = 0 elif sig == -1: # e0<0: lim f = +-oo (the sign depends on the sign of c0) if c0.match(I*Wild("a", exclude=[I])): return c0*oo s = sign(c0, x) # the leading term shouldn't be 0: if s == 0: raise ValueError("Leading term should not be 0") return s*oo elif sig == 0: if leadsimp: c0 = c0.simplify() return limitinf(c0, x, leadsimp) # e0=0: lim f = lim c0 else: raise ValueError("{} could not be evaluated".format(sig)) def moveup2(s, x): r = SubsSet() for expr, var in s.items(): r[expr.xreplace({x: exp(x)})] = var for var, expr in s.rewrites.items(): r.rewrites[var] = s.rewrites[var].xreplace({x: exp(x)}) return r def moveup(l, x): return [e.xreplace({x: exp(x)}) for e in l] @debug @timeit def calculate_series(e, x, logx=None): """ Calculates at least one term of the series of "e" in "x". This is a place that fails most often, so it is in its own function. """ from sympy.polys import cancel for t in e.lseries(x, logx=logx): t = cancel(t) if t.has(exp) and t.has(log): t = powdenest(t) if t.simplify(): break return t @debug @timeit @cacheit def mrv_leadterm(e, x): """Returns (c0, e0) for e.""" Omega = SubsSet() if not e.has(x): return (e, S.Zero) if Omega == SubsSet(): Omega, exps = mrv(e, x) if not Omega: # e really does not depend on x after simplification return exps, S.Zero if x in Omega: # move the whole omega up (exponentiate each term): Omega_up = moveup2(Omega, x) e_up = moveup([e], x)[0] exps_up = moveup([exps], x)[0] # NOTE: there is no need to move this down! e = e_up Omega = Omega_up exps = exps_up # # The positive dummy, w, is used here so log(w*2) etc. will expand; # a unique dummy is needed in this algorithm # # For limits of complex functions, the algorithm would have to be # improved, or just find limits of Re and Im components separately. # w = Dummy("w", real=True, positive=True) f, logw = rewrite(exps, Omega, x, w) series = calculate_series(f, w, logx=logw) return series.leadterm(w) def build_expression_tree(Omega, rewrites): r""" Helper function for rewrite. We need to sort Omega (mrv set) so that we replace an expression before we replace any expression in terms of which it has to be rewritten:: e1 ---> e2 ---> e3 \ -> e4 Here we can do e1, e2, e3, e4 or e1, e2, e4, e3. To do this we assemble the nodes into a tree, and sort them by height. This function builds the tree, rewrites then sorts the nodes. """ class Node: def ht(self): return reduce(lambda x, y: x + y, [x.ht() for x in self.before], 1) nodes = {} for expr, v in Omega: n = Node() n.before = [] n.var = v n.expr = expr nodes[v] = n for _, v in Omega: if v in rewrites: n = nodes[v] r = rewrites[v] for _, v2 in Omega: if r.has(v2): n.before.append(nodes[v2]) return nodes @debug @timeit def rewrite(e, Omega, x, wsym): """e(x) ... the function Omega ... the mrv set wsym ... the symbol which is going to be used for w Returns the rewritten e in terms of w and log(w). See test_rewrite1() for examples and correct results. """ from sympy import ilcm if not isinstance(Omega, SubsSet): raise TypeError("Omega should be an instance of SubsSet") if len(Omega) == 0: raise ValueError("Length can not be 0") # all items in Omega must be exponentials for t in Omega.keys(): if not isinstance(t, exp): raise ValueError("Value should be exp") rewrites = Omega.rewrites Omega = list(Omega.items()) nodes = build_expression_tree(Omega, rewrites) Omega.sort(key=lambda x: nodes[x[1]].ht(), reverse=True) # make sure we know the sign of each exp() term; after the loop, # g is going to be the "w" - the simplest one in the mrv set for g, _ in Omega: sig = sign(g.args[0], x) if sig != 1 and sig != -1: raise NotImplementedError('Result depends on the sign of %s' % sig) if sig == 1: wsym = 1/wsym # if g goes to oo, substitute 1/w # O2 is a list, which results by rewriting each item in Omega using "w" O2 = [] denominators = [] for f, var in Omega: c = limitinf(f.args[0]/g.args[0], x) if c.is_Rational: denominators.append(c.q) arg = f.args[0] if var in rewrites: if not isinstance(rewrites[var], exp): raise ValueError("Value should be exp") arg = rewrites[var].args[0] O2.append((var, exp((arg - c*g.args[0]).expand())*wsym**c)) # Remember that Omega contains subexpressions of "e". So now we find # them in "e" and substitute them for our rewriting, stored in O2 # the following powsimp is necessary to automatically combine exponentials, # so that the .xreplace() below succeeds: # TODO this should not be necessary f = powsimp(e, deep=True, combine='exp') for a, b in O2: f = f.xreplace({a: b}) for _, var in Omega: assert not f.has(var) # finally compute the logarithm of w (logw). logw = g.args[0] if sig == 1: logw = -logw # log(w)->log(1/w)=-log(w) # Some parts of sympy have difficulty computing series expansions with # non-integral exponents. The following heuristic improves the situation: exponent = reduce(ilcm, denominators, 1) f = f.subs({wsym: wsym**exponent}) logw /= exponent return f, logw def gruntz(e, z, z0, dir="+"): """ Compute the limit of e(z) at the point z0 using the Gruntz algorithm. z0 can be any expression, including oo and -oo. For dir="+" (default) it calculates the limit from the right (z->z0+) and for dir="-" the limit from the left (z->z0-). For infinite z0 (oo or -oo), the dir argument doesn't matter. This algorithm is fully described in the module docstring in the gruntz.py file. It relies heavily on the series expansion. Most frequently, gruntz() is only used if the faster limit() function (which uses heuristics) fails. """ if not z.is_symbol: raise NotImplementedError("Second argument must be a Symbol") # convert all limits to the limit z->oo; sign of z is handled in limitinf r = None if z0 == oo: e0 = e elif z0 == -oo: e0 = e.subs(z, -z) else: if str(dir) == "-": e0 = e.subs(z, z0 - 1/z) elif str(dir) == "+": e0 = e.subs(z, z0 + 1/z) else: raise NotImplementedError("dir must be '+' or '-'") try: r = limitinf(e0, z) except ValueError: r = limitinf(e0, z, leadsimp=True) # This is a bit of a heuristic for nice results... we always rewrite # tractable functions in terms of familiar intractable ones. # It might be nicer to rewrite the exactly to what they were initially, # but that would take some work to implement. return r.rewrite('intractable', deep=True)

7fb8f5541de050478d729516884b9bac61c2cf5e21939ec52bb18a2b00bd036e

from sympy.core.basic import Basic from sympy.core.cache import cacheit from sympy.core.compatibility import is_sequence, iterable, ordered from sympy.core.containers import Tuple from sympy.core.decorators import call_highest_priority from sympy.core.parameters import global_parameters from sympy.core.function import AppliedUndef from sympy.core.mul import Mul from sympy.core.numbers import Integer from sympy.core.relational import Eq from sympy.core.singleton import S, Singleton from sympy.core.symbol import Dummy, Symbol, Wild from sympy.core.sympify import sympify from sympy.polys import lcm, factor from sympy.sets.sets import Interval, Intersection from sympy.simplify import simplify from sympy.tensor.indexed import Idx from sympy.utilities.iterables import flatten from sympy import expand ############################################################################### # SEQUENCES # ############################################################################### class SeqBase(Basic): """Base class for sequences""" is_commutative = True _op_priority = 15 @staticmethod def _start_key(expr): """Return start (if possible) else S.Infinity. adapted from Set._infimum_key """ try: start = expr.start except (NotImplementedError, AttributeError, ValueError): start = S.Infinity return start def _intersect_interval(self, other): """Returns start and stop. Takes intersection over the two intervals. """ interval = Intersection(self.interval, other.interval) return interval.inf, interval.sup @property def gen(self): """Returns the generator for the sequence""" raise NotImplementedError("(%s).gen" % self) @property def interval(self): """The interval on which the sequence is defined""" raise NotImplementedError("(%s).interval" % self) @property def start(self): """The starting point of the sequence. This point is included""" raise NotImplementedError("(%s).start" % self) @property def stop(self): """The ending point of the sequence. This point is included""" raise NotImplementedError("(%s).stop" % self) @property def length(self): """Length of the sequence""" raise NotImplementedError("(%s).length" % self) @property def variables(self): """Returns a tuple of variables that are bounded""" return () @property def free_symbols(self): """ This method returns the symbols in the object, excluding those that take on a specific value (i.e. the dummy symbols). Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n, m >>> SeqFormula(m*n**2, (n, 0, 5)).free_symbols {m} """ return ({j for i in self.args for j in i.free_symbols .difference(self.variables)}) @cacheit def coeff(self, pt): """Returns the coefficient at point pt""" if pt < self.start or pt > self.stop: raise IndexError("Index %s out of bounds %s" % (pt, self.interval)) return self._eval_coeff(pt) def _eval_coeff(self, pt): raise NotImplementedError("The _eval_coeff method should be added to" "%s to return coefficient so it is available" "when coeff calls it." % self.func) def _ith_point(self, i): """Returns the i'th point of a sequence. If start point is negative infinity, point is returned from the end. Assumes the first point to be indexed zero. Examples ========= >>> from sympy import oo >>> from sympy.series.sequences import SeqPer bounded >>> SeqPer((1, 2, 3), (-10, 10))._ith_point(0) -10 >>> SeqPer((1, 2, 3), (-10, 10))._ith_point(5) -5 End is at infinity >>> SeqPer((1, 2, 3), (0, oo))._ith_point(5) 5 Starts at negative infinity >>> SeqPer((1, 2, 3), (-oo, 0))._ith_point(5) -5 """ if self.start is S.NegativeInfinity: initial = self.stop else: initial = self.start if self.start is S.NegativeInfinity: step = -1 else: step = 1 return initial + i*step def _add(self, other): """ Should only be used internally. self._add(other) returns a new, term-wise added sequence if self knows how to add with other, otherwise it returns ``None``. ``other`` should only be a sequence object. Used within :class:`SeqAdd` class. """ return None def _mul(self, other): """ Should only be used internally. self._mul(other) returns a new, term-wise multiplied sequence if self knows how to multiply with other, otherwise it returns ``None``. ``other`` should only be a sequence object. Used within :class:`SeqMul` class. """ return None def coeff_mul(self, other): """ Should be used when ``other`` is not a sequence. Should be defined to define custom behaviour. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n**2).coeff_mul(2) SeqFormula(2*n**2, (n, 0, oo)) Notes ===== '*' defines multiplication of sequences with sequences only. """ return Mul(self, other) def __add__(self, other): """Returns the term-wise addition of 'self' and 'other'. ``other`` should be a sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n**2) + SeqFormula(n**3) SeqFormula(n**3 + n**2, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot add sequence and %s' % type(other)) return SeqAdd(self, other) @call_highest_priority('__add__') def __radd__(self, other): return self + other def __sub__(self, other): """Returns the term-wise subtraction of 'self' and 'other'. ``other`` should be a sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n**2) - (SeqFormula(n)) SeqFormula(n**2 - n, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot subtract sequence and %s' % type(other)) return SeqAdd(self, -other) @call_highest_priority('__sub__') def __rsub__(self, other): return (-self) + other def __neg__(self): """Negates the sequence. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> -SeqFormula(n**2) SeqFormula(-n**2, (n, 0, oo)) """ return self.coeff_mul(-1) def __mul__(self, other): """Returns the term-wise multiplication of 'self' and 'other'. ``other`` should be a sequence. For ``other`` not being a sequence see :func:`coeff_mul` method. Examples ======== >>> from sympy import SeqFormula >>> from sympy.abc import n >>> SeqFormula(n**2) * (SeqFormula(n)) SeqFormula(n**3, (n, 0, oo)) """ if not isinstance(other, SeqBase): raise TypeError('cannot multiply sequence and %s' % type(other)) return SeqMul(self, other) @call_highest_priority('__mul__') def __rmul__(self, other): return self * other def __iter__(self): for i in range(self.length): pt = self._ith_point(i) yield self.coeff(pt) def __getitem__(self, index): if isinstance(index, int): index = self._ith_point(index) return self.coeff(index) elif isinstance(index, slice): start, stop = index.start, index.stop if start is None: start = 0 if stop is None: stop = self.length return [self.coeff(self._ith_point(i)) for i in range(start, stop, index.step or 1)] def find_linear_recurrence(self,n,d=None,gfvar=None): r""" Finds the shortest linear recurrence that satisfies the first n terms of sequence of order `\leq` n/2 if possible. If d is specified, find shortest linear recurrence of order `\leq` min(d, n/2) if possible. Returns list of coefficients ``[b(1), b(2), ...]`` corresponding to the recurrence relation ``x(n) = b(1)*x(n-1) + b(2)*x(n-2) + ...`` Returns ``[]`` if no recurrence is found. If gfvar is specified, also returns ordinary generating function as a function of gfvar. Examples ======== >>> from sympy import sequence, sqrt, oo, lucas >>> from sympy.abc import n, x, y >>> sequence(n**2).find_linear_recurrence(10, 2) [] >>> sequence(n**2).find_linear_recurrence(10) [3, -3, 1] >>> sequence(2**n).find_linear_recurrence(10) [2] >>> sequence(23*n**4+91*n**2).find_linear_recurrence(10) [5, -10, 10, -5, 1] >>> sequence(sqrt(5)*(((1 + sqrt(5))/2)**n - (-(1 + sqrt(5))/2)**(-n))/5).find_linear_recurrence(10) [1, 1] >>> sequence(x+y*(-2)**(-n), (n, 0, oo)).find_linear_recurrence(30) [1/2, 1/2] >>> sequence(3*5**n + 12).find_linear_recurrence(20,gfvar=x) ([6, -5], 3*(5 - 21*x)/((x - 1)*(5*x - 1))) >>> sequence(lucas(n)).find_linear_recurrence(15,gfvar=x) ([1, 1], (x - 2)/(x**2 + x - 1)) """ from sympy.matrices import Matrix x = [simplify(expand(t)) for t in self[:n]] lx = len(x) if d is None: r = lx//2 else: r = min(d,lx//2) coeffs = [] for l in range(1, r+1): l2 = 2*l mlist = [] for k in range(l): mlist.append(x[k:k+l]) m = Matrix(mlist) if m.det() != 0: y = simplify(m.LUsolve(Matrix(x[l:l2]))) if lx == l2: coeffs = flatten(y[::-1]) break mlist = [] for k in range(l,lx-l): mlist.append(x[k:k+l]) m = Matrix(mlist) if m*y == Matrix(x[l2:]): coeffs = flatten(y[::-1]) break if gfvar is None: return coeffs else: l = len(coeffs) if l == 0: return [], None else: n, d = x[l-1]*gfvar**(l-1), 1 - coeffs[l-1]*gfvar**l for i in range(l-1): n += x[i]*gfvar**i for j in range(l-i-1): n -= coeffs[i]*x[j]*gfvar**(i+j+1) d -= coeffs[i]*gfvar**(i+1) return coeffs, simplify(factor(n)/factor(d)) class EmptySequence(SeqBase, metaclass=Singleton): """Represents an empty sequence. The empty sequence is also available as a singleton as ``S.EmptySequence``. Examples ======== >>> from sympy import EmptySequence, SeqPer >>> from sympy.abc import x >>> EmptySequence EmptySequence >>> SeqPer((1, 2), (x, 0, 10)) + EmptySequence SeqPer((1, 2), (x, 0, 10)) >>> SeqPer((1, 2)) * EmptySequence EmptySequence >>> EmptySequence.coeff_mul(-1) EmptySequence """ @property def interval(self): return S.EmptySet @property def length(self): return S.Zero def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" return self def __iter__(self): return iter([]) class SeqExpr(SeqBase): """Sequence expression class. Various sequences should inherit from this class. Examples ======== >>> from sympy.series.sequences import SeqExpr >>> from sympy.abc import x >>> s = SeqExpr((1, 2, 3), (x, 0, 10)) >>> s.gen (1, 2, 3) >>> s.interval Interval(0, 10) >>> s.length 11 See Also ======== sympy.series.sequences.SeqPer sympy.series.sequences.SeqFormula """ @property def gen(self): return self.args[0] @property def interval(self): return Interval(self.args[1][1], self.args[1][2]) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return self.stop - self.start + 1 @property def variables(self): return (self.args[1][0],) class SeqPer(SeqExpr): """Represents a periodic sequence. The elements are repeated after a given period. Examples ======== >>> from sympy import SeqPer, oo >>> from sympy.abc import k >>> s = SeqPer((1, 2, 3), (0, 5)) >>> s.periodical (1, 2, 3) >>> s.period 3 For value at a particular point >>> s.coeff(3) 1 supports slicing >>> s[:] [1, 2, 3, 1, 2, 3] iterable >>> list(s) [1, 2, 3, 1, 2, 3] sequence starts from negative infinity >>> SeqPer((1, 2, 3), (-oo, 0))[0:6] [1, 2, 3, 1, 2, 3] Periodic formulas >>> SeqPer((k, k**2, k**3), (k, 0, oo))[0:6] [0, 1, 8, 3, 16, 125] See Also ======== sympy.series.sequences.SeqFormula """ def __new__(cls, periodical, limits=None): periodical = sympify(periodical) def _find_x(periodical): free = periodical.free_symbols if len(periodical.free_symbols) == 1: return free.pop() else: return Dummy('k') x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(periodical), 0, S.Infinity if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(periodical) start, stop = limits if not isinstance(x, (Symbol, Idx)) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) if start is S.NegativeInfinity and stop is S.Infinity: raise ValueError("Both the start and end value" "cannot be unbounded") limits = sympify((x, start, stop)) if is_sequence(periodical, Tuple): periodical = sympify(tuple(flatten(periodical))) else: raise ValueError("invalid period %s should be something " "like e.g (1, 2) " % periodical) if Interval(limits[1], limits[2]) is S.EmptySet: return S.EmptySequence return Basic.__new__(cls, periodical, limits) @property def period(self): return len(self.gen) @property def periodical(self): return self.gen def _eval_coeff(self, pt): if self.start is S.NegativeInfinity: idx = (self.stop - pt) % self.period else: idx = (pt - self.start) % self.period return self.periodical[idx].subs(self.variables[0], pt) def _add(self, other): """See docstring of SeqBase._add""" if isinstance(other, SeqPer): per1, lper1 = self.periodical, self.period per2, lper2 = other.periodical, other.period per_length = lcm(lper1, lper2) new_per = [] for x in range(per_length): ele1 = per1[x % lper1] ele2 = per2[x % lper2] new_per.append(ele1 + ele2) start, stop = self._intersect_interval(other) return SeqPer(new_per, (self.variables[0], start, stop)) def _mul(self, other): """See docstring of SeqBase._mul""" if isinstance(other, SeqPer): per1, lper1 = self.periodical, self.period per2, lper2 = other.periodical, other.period per_length = lcm(lper1, lper2) new_per = [] for x in range(per_length): ele1 = per1[x % lper1] ele2 = per2[x % lper2] new_per.append(ele1 * ele2) start, stop = self._intersect_interval(other) return SeqPer(new_per, (self.variables[0], start, stop)) def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" coeff = sympify(coeff) per = [x * coeff for x in self.periodical] return SeqPer(per, self.args[1]) class SeqFormula(SeqExpr): """Represents sequence based on a formula. Elements are generated using a formula. Examples ======== >>> from sympy import SeqFormula, oo, Symbol >>> n = Symbol('n') >>> s = SeqFormula(n**2, (n, 0, 5)) >>> s.formula n**2 For value at a particular point >>> s.coeff(3) 9 supports slicing >>> s[:] [0, 1, 4, 9, 16, 25] iterable >>> list(s) [0, 1, 4, 9, 16, 25] sequence starts from negative infinity >>> SeqFormula(n**2, (-oo, 0))[0:6] [0, 1, 4, 9, 16, 25] See Also ======== sympy.series.sequences.SeqPer """ def __new__(cls, formula, limits=None): formula = sympify(formula) def _find_x(formula): free = formula.free_symbols if len(free) == 1: return free.pop() elif not free: return Dummy('k') else: raise ValueError( " specify dummy variables for %s. If the formula contains" " more than one free symbol, a dummy variable should be" " supplied explicitly e.g., SeqFormula(m*n**2, (n, 0, 5))" % formula) x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(formula), 0, S.Infinity if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(formula) start, stop = limits if not isinstance(x, (Symbol, Idx)) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) if start is S.NegativeInfinity and stop is S.Infinity: raise ValueError("Both the start and end value " "cannot be unbounded") limits = sympify((x, start, stop)) if Interval(limits[1], limits[2]) is S.EmptySet: return S.EmptySequence return Basic.__new__(cls, formula, limits) @property def formula(self): return self.gen def _eval_coeff(self, pt): d = self.variables[0] return self.formula.subs(d, pt) def _add(self, other): """See docstring of SeqBase._add""" if isinstance(other, SeqFormula): form1, v1 = self.formula, self.variables[0] form2, v2 = other.formula, other.variables[0] formula = form1 + form2.subs(v2, v1) start, stop = self._intersect_interval(other) return SeqFormula(formula, (v1, start, stop)) def _mul(self, other): """See docstring of SeqBase._mul""" if isinstance(other, SeqFormula): form1, v1 = self.formula, self.variables[0] form2, v2 = other.formula, other.variables[0] formula = form1 * form2.subs(v2, v1) start, stop = self._intersect_interval(other) return SeqFormula(formula, (v1, start, stop)) def coeff_mul(self, coeff): """See docstring of SeqBase.coeff_mul""" coeff = sympify(coeff) formula = self.formula * coeff return SeqFormula(formula, self.args[1]) def expand(self, *args, **kwargs): return SeqFormula(expand(self.formula, *args, **kwargs), self.args[1]) class RecursiveSeq(SeqBase): """A finite degree recursive sequence. That is, a sequence a(n) that depends on a fixed, finite number of its previous values. The general form is a(n) = f(a(n - 1), a(n - 2), ..., a(n - d)) for some fixed, positive integer d, where f is some function defined by a SymPy expression. Parameters ========== recurrence : SymPy expression defining recurrence This is *not* an equality, only the expression that the nth term is equal to. For example, if :code:`a(n) = f(a(n - 1), ..., a(n - d))`, then the expression should be :code:`f(a(n - 1), ..., a(n - d))`. yn : applied undefined function Represents the nth term of the sequence as e.g. :code:`y(n)` where :code:`y` is an undefined function and `n` is the sequence index. n : symbolic argument The name of the variable that the recurrence is in, e.g., :code:`n` if the recurrence function is :code:`y(n)`. initial : iterable with length equal to the degree of the recurrence The initial values of the recurrence. start : start value of sequence (inclusive) Examples ======== >>> from sympy import Function, symbols >>> from sympy.series.sequences import RecursiveSeq >>> y = Function("y") >>> n = symbols("n") >>> fib = RecursiveSeq(y(n - 1) + y(n - 2), y(n), n, [0, 1]) >>> fib.coeff(3) # Value at a particular point 2 >>> fib[:6] # supports slicing [0, 1, 1, 2, 3, 5] >>> fib.recurrence # inspect recurrence Eq(y(n), y(n - 2) + y(n - 1)) >>> fib.degree # automatically determine degree 2 >>> for x in zip(range(10), fib): # supports iteration ... print(x) (0, 0) (1, 1) (2, 1) (3, 2) (4, 3) (5, 5) (6, 8) (7, 13) (8, 21) (9, 34) See Also ======== sympy.series.sequences.SeqFormula """ def __new__(cls, recurrence, yn, n, initial=None, start=0): if not isinstance(yn, AppliedUndef): raise TypeError("recurrence sequence must be an applied undefined function" ", found `{}`".format(yn)) if not isinstance(n, Basic) or not n.is_symbol: raise TypeError("recurrence variable must be a symbol" ", found `{}`".format(n)) if yn.args != (n,): raise TypeError("recurrence sequence does not match symbol") y = yn.func k = Wild("k", exclude=(n,)) degree = 0 # Find all applications of y in the recurrence and check that: # 1. The function y is only being used with a single argument; and # 2. All arguments are n + k for constant negative integers k. prev_ys = recurrence.find(y) for prev_y in prev_ys: if len(prev_y.args) != 1: raise TypeError("Recurrence should be in a single variable") shift = prev_y.args[0].match(n + k)[k] if not (shift.is_constant() and shift.is_integer and shift < 0): raise TypeError("Recurrence should have constant," " negative, integer shifts" " (found {})".format(prev_y)) if -shift > degree: degree = -shift if not initial: initial = [Dummy("c_{}".format(k)) for k in range(degree)] if len(initial) != degree: raise ValueError("Number of initial terms must equal degree") degree = Integer(degree) start = sympify(start) initial = Tuple(*(sympify(x) for x in initial)) seq = Basic.__new__(cls, recurrence, yn, n, initial, start) seq.cache = {y(start + k): init for k, init in enumerate(initial)} seq.degree = degree return seq @property def _recurrence(self): """Equation defining recurrence.""" return self.args[0] @property def recurrence(self): """Equation defining recurrence.""" return Eq(self.yn, self.args[0]) @property def yn(self): """Applied function representing the nth term""" return self.args[1] @property def y(self): """Undefined function for the nth term of the sequence""" return self.yn.func @property def n(self): """Sequence index symbol""" return self.args[2] @property def initial(self): """The initial values of the sequence""" return self.args[3] @property def start(self): """The starting point of the sequence. This point is included""" return self.args[4] @property def stop(self): """The ending point of the sequence. (oo)""" return S.Infinity @property def interval(self): """Interval on which sequence is defined.""" return (self.start, S.Infinity) def _eval_coeff(self, index): if index - self.start < len(self.cache): return self.cache[self.y(index)] for current in range(len(self.cache), index + 1): # Use xreplace over subs for performance. # See issue #10697. seq_index = self.start + current current_recurrence = self._recurrence.xreplace({self.n: seq_index}) new_term = current_recurrence.xreplace(self.cache) self.cache[self.y(seq_index)] = new_term return self.cache[self.y(self.start + current)] def __iter__(self): index = self.start while True: yield self._eval_coeff(index) index += 1 def sequence(seq, limits=None): """Returns appropriate sequence object. If ``seq`` is a sympy sequence, returns :class:`SeqPer` object otherwise returns :class:`SeqFormula` object. Examples ======== >>> from sympy import sequence >>> from sympy.abc import n >>> sequence(n**2, (n, 0, 5)) SeqFormula(n**2, (n, 0, 5)) >>> sequence((1, 2, 3), (n, 0, 5)) SeqPer((1, 2, 3), (n, 0, 5)) See Also ======== sympy.series.sequences.SeqPer sympy.series.sequences.SeqFormula """ seq = sympify(seq) if is_sequence(seq, Tuple): return SeqPer(seq, limits) else: return SeqFormula(seq, limits) ############################################################################### # OPERATIONS # ############################################################################### class SeqExprOp(SeqBase): """Base class for operations on sequences. Examples ======== >>> from sympy.series.sequences import SeqExprOp, sequence >>> from sympy.abc import n >>> s1 = sequence(n**2, (n, 0, 10)) >>> s2 = sequence((1, 2, 3), (n, 5, 10)) >>> s = SeqExprOp(s1, s2) >>> s.gen (n**2, (1, 2, 3)) >>> s.interval Interval(5, 10) >>> s.length 6 See Also ======== sympy.series.sequences.SeqAdd sympy.series.sequences.SeqMul """ @property def gen(self): """Generator for the sequence. returns a tuple of generators of all the argument sequences. """ return tuple(a.gen for a in self.args) @property def interval(self): """Sequence is defined on the intersection of all the intervals of respective sequences """ return Intersection(*(a.interval for a in self.args)) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def variables(self): """Cumulative of all the bound variables""" return tuple(flatten([a.variables for a in self.args])) @property def length(self): return self.stop - self.start + 1 class SeqAdd(SeqExprOp): """Represents term-wise addition of sequences. Rules: * The interval on which sequence is defined is the intersection of respective intervals of sequences. * Anything + :class:`EmptySequence` remains unchanged. * Other rules are defined in ``_add`` methods of sequence classes. Examples ======== >>> from sympy import EmptySequence, oo, SeqAdd, SeqPer, SeqFormula >>> from sympy.abc import n >>> SeqAdd(SeqPer((1, 2), (n, 0, oo)), EmptySequence) SeqPer((1, 2), (n, 0, oo)) >>> SeqAdd(SeqPer((1, 2), (n, 0, 5)), SeqPer((1, 2), (n, 6, 10))) EmptySequence >>> SeqAdd(SeqPer((1, 2), (n, 0, oo)), SeqFormula(n**2, (n, 0, oo))) SeqAdd(SeqFormula(n**2, (n, 0, oo)), SeqPer((1, 2), (n, 0, oo))) >>> SeqAdd(SeqFormula(n**3), SeqFormula(n**2)) SeqFormula(n**3 + n**2, (n, 0, oo)) See Also ======== sympy.series.sequences.SeqMul """ def __new__(cls, *args, **kwargs): evaluate = kwargs.get('evaluate', global_parameters.evaluate) # flatten inputs args = list(args) # adapted from sympy.sets.sets.Union def _flatten(arg): if isinstance(arg, SeqBase): if isinstance(arg, SeqAdd): return sum(map(_flatten, arg.args), []) else: return [arg] if iterable(arg): return sum(map(_flatten, arg), []) raise TypeError("Input must be Sequences or " " iterables of Sequences") args = _flatten(args) args = [a for a in args if a is not S.EmptySequence] # Addition of no sequences is EmptySequence if not args: return S.EmptySequence if Intersection(*(a.interval for a in args)) is S.EmptySet: return S.EmptySequence # reduce using known rules if evaluate: return SeqAdd.reduce(args) args = list(ordered(args, SeqBase._start_key)) return Basic.__new__(cls, *args) @staticmethod def reduce(args): """Simplify :class:`SeqAdd` using known rules. Iterates through all pairs and ask the constituent sequences if they can simplify themselves with any other constituent. Notes ===== adapted from ``Union.reduce`` """ new_args = True while new_args: for id1, s in enumerate(args): new_args = False for id2, t in enumerate(args): if id1 == id2: continue new_seq = s._add(t) # This returns None if s does not know how to add # with t. Returns the newly added sequence otherwise if new_seq is not None: new_args = [a for a in args if a not in (s, t)] new_args.append(new_seq) break if new_args: args = new_args break if len(args) == 1: return args.pop() else: return SeqAdd(args, evaluate=False) def _eval_coeff(self, pt): """adds up the coefficients of all the sequences at point pt""" return sum(a.coeff(pt) for a in self.args) class SeqMul(SeqExprOp): r"""Represents term-wise multiplication of sequences. Handles multiplication of sequences only. For multiplication with other objects see :func:`SeqBase.coeff_mul`. Rules: * The interval on which sequence is defined is the intersection of respective intervals of sequences. * Anything \* :class:`EmptySequence` returns :class:`EmptySequence`. * Other rules are defined in ``_mul`` methods of sequence classes. Examples ======== >>> from sympy import EmptySequence, oo, SeqMul, SeqPer, SeqFormula >>> from sympy.abc import n >>> SeqMul(SeqPer((1, 2), (n, 0, oo)), EmptySequence) EmptySequence >>> SeqMul(SeqPer((1, 2), (n, 0, 5)), SeqPer((1, 2), (n, 6, 10))) EmptySequence >>> SeqMul(SeqPer((1, 2), (n, 0, oo)), SeqFormula(n**2)) SeqMul(SeqFormula(n**2, (n, 0, oo)), SeqPer((1, 2), (n, 0, oo))) >>> SeqMul(SeqFormula(n**3), SeqFormula(n**2)) SeqFormula(n**5, (n, 0, oo)) See Also ======== sympy.series.sequences.SeqAdd """ def __new__(cls, *args, **kwargs): evaluate = kwargs.get('evaluate', global_parameters.evaluate) # flatten inputs args = list(args) # adapted from sympy.sets.sets.Union def _flatten(arg): if isinstance(arg, SeqBase): if isinstance(arg, SeqMul): return sum(map(_flatten, arg.args), []) else: return [arg] elif iterable(arg): return sum(map(_flatten, arg), []) raise TypeError("Input must be Sequences or " " iterables of Sequences") args = _flatten(args) # Multiplication of no sequences is EmptySequence if not args: return S.EmptySequence if Intersection(*(a.interval for a in args)) is S.EmptySet: return S.EmptySequence # reduce using known rules if evaluate: return SeqMul.reduce(args) args = list(ordered(args, SeqBase._start_key)) return Basic.__new__(cls, *args) @staticmethod def reduce(args): """Simplify a :class:`SeqMul` using known rules. Iterates through all pairs and ask the constituent sequences if they can simplify themselves with any other constituent. Notes ===== adapted from ``Union.reduce`` """ new_args = True while new_args: for id1, s in enumerate(args): new_args = False for id2, t in enumerate(args): if id1 == id2: continue new_seq = s._mul(t) # This returns None if s does not know how to multiply # with t. Returns the newly multiplied sequence otherwise if new_seq is not None: new_args = [a for a in args if a not in (s, t)] new_args.append(new_seq) break if new_args: args = new_args break if len(args) == 1: return args.pop() else: return SeqMul(args, evaluate=False) def _eval_coeff(self, pt): """multiplies the coefficients of all the sequences at point pt""" val = 1 for a in self.args: val *= a.coeff(pt) return val

53ec675f12ed86d53c3ce4201d982e01f27e6b10e33a0ad9d3df5319bcd926b3

from sympy.core import S, Symbol, Add, sympify, Expr, PoleError, Mul from sympy.core.exprtools import factor_terms from sympy.core.symbol import Dummy from sympy.functions.combinatorial.factorials import factorial from sympy.functions.special.gamma_functions import gamma from sympy.polys import PolynomialError, factor from sympy.series.order import Order from sympy.simplify.ratsimp import ratsimp from sympy.simplify.simplify import together from .gruntz import gruntz def limit(e, z, z0, dir="+"): """Computes the limit of ``e(z)`` at the point ``z0``. Parameters ========== e : expression, the limit of which is to be taken z : symbol representing the variable in the limit. Other symbols are treated as constants. Multivariate limits are not supported. z0 : the value toward which ``z`` tends. Can be any expression, including ``oo`` and ``-oo``. dir : string, optional (default: "+") The limit is bi-directional if ``dir="+-"``, from the right (z->z0+) if ``dir="+"``, and from the left (z->z0-) if ``dir="-"``. For infinite ``z0`` (``oo`` or ``-oo``), the ``dir`` argument is determined from the direction of the infinity (i.e., ``dir="-"`` for ``oo``). Examples ======== >>> from sympy import limit, sin, oo >>> from sympy.abc import x >>> limit(sin(x)/x, x, 0) 1 >>> limit(1/x, x, 0) # default dir='+' oo >>> limit(1/x, x, 0, dir="-") -oo >>> limit(1/x, x, 0, dir='+-') zoo >>> limit(1/x, x, oo) 0 Notes ===== First we try some heuristics for easy and frequent cases like "x", "1/x", "x**2" and similar, so that it's fast. For all other cases, we use the Gruntz algorithm (see the gruntz() function). See Also ======== limit_seq : returns the limit of a sequence. """ return Limit(e, z, z0, dir).doit(deep=False) def heuristics(e, z, z0, dir): """Computes the limit of an expression term-wise. Parameters are the same as for the ``limit`` function. Works with the arguments of expression ``e`` one by one, computing the limit of each and then combining the results. This approach works only for simple limits, but it is fast. """ from sympy.calculus.util import AccumBounds rv = None if abs(z0) is S.Infinity: rv = limit(e.subs(z, 1/z), z, S.Zero, "+" if z0 is S.Infinity else "-") if isinstance(rv, Limit): return elif e.is_Mul or e.is_Add or e.is_Pow or e.is_Function: r = [] for a in e.args: l = limit(a, z, z0, dir) if l.has(S.Infinity) and l.is_finite is None: if isinstance(e, Add): m = factor_terms(e) if not isinstance(m, Mul): # try together m = together(m) if not isinstance(m, Mul): # try factor if the previous methods failed m = factor(e) if isinstance(m, Mul): return heuristics(m, z, z0, dir) return return elif isinstance(l, Limit): return elif l is S.NaN: return else: r.append(l) if r: rv = e.func(*r) if rv is S.NaN and e.is_Mul and any(isinstance(rr, AccumBounds) for rr in r): r2 = [] e2 = [] for ii in range(len(r)): if isinstance(r[ii], AccumBounds): r2.append(r[ii]) else: e2.append(e.args[ii]) if len(e2) > 0: e3 = Mul(*e2).simplify() l = limit(e3, z, z0, dir) rv = l * Mul(*r2) if rv is S.NaN: try: rat_e = ratsimp(e) except PolynomialError: return if rat_e is S.NaN or rat_e == e: return return limit(rat_e, z, z0, dir) return rv class Limit(Expr): """Represents an unevaluated limit. Examples ======== >>> from sympy import Limit, sin >>> from sympy.abc import x >>> Limit(sin(x)/x, x, 0) Limit(sin(x)/x, x, 0) >>> Limit(1/x, x, 0, dir="-") Limit(1/x, x, 0, dir='-') """ def __new__(cls, e, z, z0, dir="+"): e = sympify(e) z = sympify(z) z0 = sympify(z0) if z0 is S.Infinity: dir = "-" elif z0 is S.NegativeInfinity: dir = "+" if isinstance(dir, str): dir = Symbol(dir) elif not isinstance(dir, Symbol): raise TypeError("direction must be of type basestring or " "Symbol, not %s" % type(dir)) if str(dir) not in ('+', '-', '+-'): raise ValueError("direction must be one of '+', '-' " "or '+-', not %s" % dir) obj = Expr.__new__(cls) obj._args = (e, z, z0, dir) return obj @property def free_symbols(self): e = self.args[0] isyms = e.free_symbols isyms.difference_update(self.args[1].free_symbols) isyms.update(self.args[2].free_symbols) return isyms def doit(self, **hints): """Evaluates the limit. Parameters ========== deep : bool, optional (default: True) Invoke the ``doit`` method of the expressions involved before taking the limit. hints : optional keyword arguments To be passed to ``doit`` methods; only used if deep is True. """ from sympy import Abs, exp, log, sign from sympy.calculus.util import AccumBounds e, z, z0, dir = self.args if z0 is S.ComplexInfinity: raise NotImplementedError("Limits at complex " "infinity are not implemented") if hints.get('deep', True): e = e.doit(**hints) z = z.doit(**hints) z0 = z0.doit(**hints) if e == z: return z0 if not e.has(z): return e cdir = 0 if str(dir) == "+": cdir = 1 elif str(dir) == "-": cdir = -1 def remove_abs(expr): if not expr.args: return expr newargs = tuple(remove_abs(arg) for arg in expr.args) if newargs != expr.args: expr = expr.func(*newargs) if isinstance(expr, Abs): sig = limit(expr.args[0], z, z0, dir) if sig.is_zero: sig = limit(1/expr.args[0], z, z0, dir) if sig.is_extended_real: if (sig < 0) == True: return -expr.args[0] elif (sig > 0) == True: return expr.args[0] return expr e = remove_abs(e) if e.is_meromorphic(z, z0): if abs(z0) is S.Infinity: newe = e.subs(z, -1/z) else: newe = e.subs(z, z + z0) try: coeff, ex = newe.leadterm(z, cdir) except (ValueError, NotImplementedError): pass else: if ex > 0: return S.Zero elif ex == 0: return coeff if str(dir) == "+" or not(int(ex) & 1): return S.Infinity*sign(coeff) elif str(dir) == "-": return S.NegativeInfinity*sign(coeff) else: return S.ComplexInfinity # gruntz fails on factorials but works with the gamma function # If no factorial term is present, e should remain unchanged. # factorial is defined to be zero for negative inputs (which # differs from gamma) so only rewrite for positive z0. if z0.is_extended_positive: e = e.rewrite(factorial, gamma) if e.is_Mul and abs(z0) is S.Infinity: e = factor_terms(e) u = Dummy('u', positive=True) if z0 is S.NegativeInfinity: inve = e.subs(z, -1/u) else: inve = e.subs(z, 1/u) try: f = inve.as_leading_term(u).gammasimp() if f.is_meromorphic(u, S.Zero): r = limit(f, u, S.Zero, "+") if isinstance(r, Limit): return self else: return r except (ValueError, NotImplementedError, PoleError): pass if e.is_Order: return Order(limit(e.expr, z, z0), *e.args[1:]) if e.is_Pow: if e.has(S.Infinity, S.NegativeInfinity, S.ComplexInfinity, S.NaN): return self b1, e1 = e.base, e.exp f1 = e1*log(b1) if f1.is_meromorphic(z, z0): res = limit(f1, z, z0) return exp(res) ex_lim = limit(e1, z, z0) base_lim = limit(b1, z, z0) if base_lim is S.One: if ex_lim in (S.Infinity, S.NegativeInfinity): res = limit(e1*(b1 - 1), z, z0) return exp(res) elif ex_lim.is_real: return S.One if base_lim in (S.Zero, S.Infinity, S.NegativeInfinity) and ex_lim is S.Zero: res = limit(f1, z, z0) return exp(res) if base_lim is S.NegativeInfinity: if ex_lim is S.NegativeInfinity: return S.Zero if ex_lim is S.Infinity: return S.ComplexInfinity if not isinstance(base_lim, AccumBounds) and not isinstance(ex_lim, AccumBounds): res = base_lim**ex_lim if res is not S.ComplexInfinity and not res.is_Pow: return res l = None try: if str(dir) == '+-': r = gruntz(e, z, z0, '+') l = gruntz(e, z, z0, '-') if l != r: raise ValueError("The limit does not exist since " "left hand limit = %s and right hand limit = %s" % (l, r)) else: r = gruntz(e, z, z0, dir) if r is S.NaN or l is S.NaN: raise PoleError() except (PoleError, ValueError): if l is not None: raise r = heuristics(e, z, z0, dir) if r is None: return self return r

468436b1499e66d2ade09cff6a77a7eff94c065ce9cb7f3db10be053d58dfb09

"""Limits of sequences""" from sympy.core.add import Add from sympy.core.function import PoleError from sympy.core.power import Pow from sympy.core.singleton import S from sympy.core.symbol import Dummy from sympy.core.sympify import sympify from sympy.functions.combinatorial.numbers import fibonacci from sympy.functions.combinatorial.factorials import factorial, subfactorial from sympy.functions.special.gamma_functions import gamma from sympy.functions.elementary.complexes import Abs from sympy.functions.elementary.miscellaneous import Max, Min from sympy.functions.elementary.trigonometric import cos, sin from sympy.series.limits import Limit def difference_delta(expr, n=None, step=1): """Difference Operator. Discrete analog of differential operator. Given a sequence x[n], returns the sequence x[n + step] - x[n]. Examples ======== >>> from sympy import difference_delta as dd >>> from sympy.abc import n >>> dd(n*(n + 1), n) 2*n + 2 >>> dd(n*(n + 1), n, 2) 4*n + 6 References ========== .. [1] https://reference.wolfram.com/language/ref/DifferenceDelta.html """ expr = sympify(expr) if n is None: f = expr.free_symbols if len(f) == 1: n = f.pop() elif len(f) == 0: return S.Zero else: raise ValueError("Since there is more than one variable in the" " expression, a variable must be supplied to" " take the difference of %s" % expr) step = sympify(step) if step.is_number is False or step.is_finite is False: raise ValueError("Step should be a finite number.") if hasattr(expr, '_eval_difference_delta'): result = expr._eval_difference_delta(n, step) if result: return result return expr.subs(n, n + step) - expr def dominant(expr, n): """Finds the dominant term in a sum, that is a term that dominates every other term. If limit(a/b, n, oo) is oo then a dominates b. If limit(a/b, n, oo) is 0 then b dominates a. Otherwise, a and b are comparable. If there is no unique dominant term, then returns ``None``. Examples ======== >>> from sympy import Sum >>> from sympy.series.limitseq import dominant >>> from sympy.abc import n, k >>> dominant(5*n**3 + 4*n**2 + n + 1, n) 5*n**3 >>> dominant(2**n + Sum(k, (k, 0, n)), n) 2**n See Also ======== sympy.series.limitseq.dominant """ terms = Add.make_args(expr.expand(func=True)) term0 = terms[-1] comp = [term0] # comparable terms for t in terms[:-1]: e = (term0 / t).gammasimp() l = limit_seq(e, n) if l is None: return None elif l.is_zero: term0 = t comp = [term0] elif l not in [S.Infinity, S.NegativeInfinity]: comp.append(t) if len(comp) > 1: return None return term0 def _limit_inf(expr, n): try: return Limit(expr, n, S.Infinity).doit(deep=False) except (NotImplementedError, PoleError): return None def _limit_seq(expr, n, trials): from sympy.concrete.summations import Sum for i in range(trials): if not expr.has(Sum): result = _limit_inf(expr, n) if result is not None: return result num, den = expr.as_numer_denom() if not den.has(n) or not num.has(n): result = _limit_inf(expr.doit(), n) if result is not None: return result return None num, den = (difference_delta(t.expand(), n) for t in [num, den]) expr = (num / den).gammasimp() if not expr.has(Sum): result = _limit_inf(expr, n) if result is not None: return result num, den = expr.as_numer_denom() num = dominant(num, n) if num is None: return None den = dominant(den, n) if den is None: return None expr = (num / den).gammasimp() def limit_seq(expr, n=None, trials=5): """Finds the limit of a sequence as index n tends to infinity. Parameters ========== expr : Expr SymPy expression for the n-th term of the sequence n : Symbol, optional The index of the sequence, an integer that tends to positive infinity. If None, inferred from the expression unless it has multiple symbols. trials: int, optional The algorithm is highly recursive. ``trials`` is a safeguard from infinite recursion in case the limit is not easily computed by the algorithm. Try increasing ``trials`` if the algorithm returns ``None``. Admissible Terms ================ The algorithm is designed for sequences built from rational functions, indefinite sums, and indefinite products over an indeterminate n. Terms of alternating sign are also allowed, but more complex oscillatory behavior is not supported. Examples ======== >>> from sympy import limit_seq, Sum, binomial >>> from sympy.abc import n, k, m >>> limit_seq((5*n**3 + 3*n**2 + 4) / (3*n**3 + 4*n - 5), n) 5/3 >>> limit_seq(binomial(2*n, n) / Sum(binomial(2*k, k), (k, 1, n)), n) 3/4 >>> limit_seq(Sum(k**2 * Sum(2**m/m, (m, 1, k)), (k, 1, n)) / (2**n*n), n) 4 See Also ======== sympy.series.limitseq.dominant References ========== .. [1] Computing Limits of Sequences - Manuel Kauers """ from sympy.concrete.summations import Sum from sympy.calculus.util import AccumulationBounds if n is None: free = expr.free_symbols if len(free) == 1: n = free.pop() elif not free: return expr else: raise ValueError("Expression has more than one variable. " "Please specify a variable.") elif n not in expr.free_symbols: return expr expr = expr.rewrite(fibonacci, S.GoldenRatio) expr = expr.rewrite(factorial, subfactorial, gamma) n_ = Dummy("n", integer=True, positive=True) n1 = Dummy("n", odd=True, positive=True) n2 = Dummy("n", even=True, positive=True) # If there is a negative term raised to a power involving n, or a # trigonometric function, then consider even and odd n separately. powers = (p.as_base_exp() for p in expr.atoms(Pow)) if (any(b.is_negative and e.has(n) for b, e in powers) or expr.has(cos, sin)): L1 = _limit_seq(expr.xreplace({n: n1}), n1, trials) if L1 is not None: L2 = _limit_seq(expr.xreplace({n: n2}), n2, trials) if L1 != L2: if L1.is_comparable and L2.is_comparable: return AccumulationBounds(Min(L1, L2), Max(L1, L2)) else: return None else: L1 = _limit_seq(expr.xreplace({n: n_}), n_, trials) if L1 is not None: return L1 else: if expr.is_Add: limits = [limit_seq(term, n, trials) for term in expr.args] if any(result is None for result in limits): return None else: return Add(*limits) # Maybe the absolute value is easier to deal with (though not if # it has a Sum). If it tends to 0, the limit is 0. elif not expr.has(Sum): lim = _limit_seq(Abs(expr.xreplace({n: n_})), n_, trials) if lim is not None and lim.is_zero: return S.Zero

8844cdb1f5e648976b6fbc504dc3502f1267e18e232d1f199091c7d0f3366078

"""Fourier Series""" from sympy import pi, oo, Wild from sympy.core.expr import Expr from sympy.core.add import Add from sympy.core.compatibility import is_sequence from sympy.core.containers import Tuple from sympy.core.singleton import S from sympy.core.symbol import Dummy, Symbol from sympy.core.sympify import sympify from sympy.functions.elementary.trigonometric import sin, cos, sinc from sympy.series.series_class import SeriesBase from sympy.series.sequences import SeqFormula from sympy.sets.sets import Interval from sympy.simplify.fu import TR2, TR1, TR10, sincos_to_sum def fourier_cos_seq(func, limits, n): """Returns the cos sequence in a Fourier series""" from sympy.integrals import integrate x, L = limits[0], limits[2] - limits[1] cos_term = cos(2*n*pi*x / L) formula = 2 * cos_term * integrate(func * cos_term, limits) / L a0 = formula.subs(n, S.Zero) / 2 return a0, SeqFormula(2 * cos_term * integrate(func * cos_term, limits) / L, (n, 1, oo)) def fourier_sin_seq(func, limits, n): """Returns the sin sequence in a Fourier series""" from sympy.integrals import integrate x, L = limits[0], limits[2] - limits[1] sin_term = sin(2*n*pi*x / L) return SeqFormula(2 * sin_term * integrate(func * sin_term, limits) / L, (n, 1, oo)) def _process_limits(func, limits): """ Limits should be of the form (x, start, stop). x should be a symbol. Both start and stop should be bounded. * If x is not given, x is determined from func. * If limits is None. Limit of the form (x, -pi, pi) is returned. Examples ======== >>> from sympy.series.fourier import _process_limits as pari >>> from sympy.abc import x >>> pari(x**2, (x, -2, 2)) (x, -2, 2) >>> pari(x**2, (-2, 2)) (x, -2, 2) >>> pari(x**2, None) (x, -pi, pi) """ def _find_x(func): free = func.free_symbols if len(free) == 1: return free.pop() elif not free: return Dummy('k') else: raise ValueError( " specify dummy variables for %s. If the function contains" " more than one free symbol, a dummy variable should be" " supplied explicitly e.g. FourierSeries(m*n**2, (n, -pi, pi))" % func) x, start, stop = None, None, None if limits is None: x, start, stop = _find_x(func), -pi, pi if is_sequence(limits, Tuple): if len(limits) == 3: x, start, stop = limits elif len(limits) == 2: x = _find_x(func) start, stop = limits if not isinstance(x, Symbol) or start is None or stop is None: raise ValueError('Invalid limits given: %s' % str(limits)) unbounded = [S.NegativeInfinity, S.Infinity] if start in unbounded or stop in unbounded: raise ValueError("Both the start and end value should be bounded") return sympify((x, start, stop)) def finite_check(f, x, L): def check_fx(exprs, x): return x not in exprs.free_symbols def check_sincos(_expr, x, L): if isinstance(_expr, (sin, cos)): sincos_args = _expr.args[0] if sincos_args.match(a*(pi/L)*x + b) is not None: return True else: return False _expr = sincos_to_sum(TR2(TR1(f))) add_coeff = _expr.as_coeff_add() a = Wild('a', properties=[lambda k: k.is_Integer, lambda k: k != S.Zero, ]) b = Wild('b', properties=[lambda k: x not in k.free_symbols, ]) for s in add_coeff[1]: mul_coeffs = s.as_coeff_mul()[1] for t in mul_coeffs: if not (check_fx(t, x) or check_sincos(t, x, L)): return False, f return True, _expr class FourierSeries(SeriesBase): r"""Represents Fourier sine/cosine series. This class only represents a fourier series. No computation is performed. For how to compute Fourier series, see the :func:`fourier_series` docstring. See Also ======== sympy.series.fourier.fourier_series """ def __new__(cls, *args): args = map(sympify, args) return Expr.__new__(cls, *args) @property def function(self): return self.args[0] @property def x(self): return self.args[1][0] @property def period(self): return (self.args[1][1], self.args[1][2]) @property def a0(self): return self.args[2][0] @property def an(self): return self.args[2][1] @property def bn(self): return self.args[2][2] @property def interval(self): return Interval(0, oo) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return oo @property def L(self): return abs(self.period[1] - self.period[0]) / 2 def _eval_subs(self, old, new): x = self.x if old.has(x): return self def truncate(self, n=3): """ Return the first n nonzero terms of the series. If n is None return an iterator. Parameters ========== n : int or None Amount of non-zero terms in approximation or None. Returns ======= Expr or iterator Approximation of function expanded into Fourier series. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x, (x, -pi, pi)) >>> s.truncate(4) 2*sin(x) - sin(2*x) + 2*sin(3*x)/3 - sin(4*x)/2 See Also ======== sympy.series.fourier.FourierSeries.sigma_approximation """ if n is None: return iter(self) terms = [] for t in self: if len(terms) == n: break if t is not S.Zero: terms.append(t) return Add(*terms) def sigma_approximation(self, n=3): r""" Return :math:`\sigma`-approximation of Fourier series with respect to order n. Sigma approximation adjusts a Fourier summation to eliminate the Gibbs phenomenon which would otherwise occur at discontinuities. A sigma-approximated summation for a Fourier series of a T-periodical function can be written as .. math:: s(\theta) = \frac{1}{2} a_0 + \sum _{k=1}^{m-1} \operatorname{sinc} \Bigl( \frac{k}{m} \Bigr) \cdot \left[ a_k \cos \Bigl( \frac{2\pi k}{T} \theta \Bigr) + b_k \sin \Bigl( \frac{2\pi k}{T} \theta \Bigr) \right], where :math:`a_0, a_k, b_k, k=1,\ldots,{m-1}` are standard Fourier series coefficients and :math:`\operatorname{sinc} \Bigl( \frac{k}{m} \Bigr)` is a Lanczos :math:`\sigma` factor (expressed in terms of normalized :math:`\operatorname{sinc}` function). Parameters ========== n : int Highest order of the terms taken into account in approximation. Returns ======= Expr Sigma approximation of function expanded into Fourier series. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x, (x, -pi, pi)) >>> s.sigma_approximation(4) 2*sin(x)*sinc(pi/4) - 2*sin(2*x)/pi + 2*sin(3*x)*sinc(3*pi/4)/3 See Also ======== sympy.series.fourier.FourierSeries.truncate Notes ===== The behaviour of :meth:`~sympy.series.fourier.FourierSeries.sigma_approximation` is different from :meth:`~sympy.series.fourier.FourierSeries.truncate` - it takes all nonzero terms of degree smaller than n, rather than first n nonzero ones. References ========== .. [1] https://en.wikipedia.org/wiki/Gibbs_phenomenon .. [2] https://en.wikipedia.org/wiki/Sigma_approximation """ terms = [sinc(pi * i / n) * t for i, t in enumerate(self[:n]) if t is not S.Zero] return Add(*terms) def shift(self, s): """Shift the function by a term independent of x. f(x) -> f(x) + s This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x**2, (x, -pi, pi)) >>> s.shift(1).truncate() -4*cos(x) + cos(2*x) + 1 + pi**2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) a0 = self.a0 + s sfunc = self.function + s return self.func(sfunc, self.args[1], (a0, self.an, self.bn)) def shiftx(self, s): """Shift x by a term independent of x. f(x) -> f(x + s) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x**2, (x, -pi, pi)) >>> s.shiftx(1).truncate() -4*cos(x + 1) + cos(2*x + 2) + pi**2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.subs(x, x + s) bn = self.bn.subs(x, x + s) sfunc = self.function.subs(x, x + s) return self.func(sfunc, self.args[1], (self.a0, an, bn)) def scale(self, s): """Scale the function by a term independent of x. f(x) -> s * f(x) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x**2, (x, -pi, pi)) >>> s.scale(2).truncate() -8*cos(x) + 2*cos(2*x) + 2*pi**2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.coeff_mul(s) bn = self.bn.coeff_mul(s) a0 = self.a0 * s sfunc = self.args[0] * s return self.func(sfunc, self.args[1], (a0, an, bn)) def scalex(self, s): """Scale x by a term independent of x. f(x) -> f(s*x) This is fast, if Fourier series of f(x) is already computed. Examples ======== >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> s = fourier_series(x**2, (x, -pi, pi)) >>> s.scalex(2).truncate() -4*cos(2*x) + cos(4*x) + pi**2/3 """ s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) an = self.an.subs(x, x * s) bn = self.bn.subs(x, x * s) sfunc = self.function.subs(x, x * s) return self.func(sfunc, self.args[1], (self.a0, an, bn)) def _eval_as_leading_term(self, x, cdir=0): for t in self: if t is not S.Zero: return t def _eval_term(self, pt): if pt == 0: return self.a0 return self.an.coeff(pt) + self.bn.coeff(pt) def __neg__(self): return self.scale(-1) def __add__(self, other): if isinstance(other, FourierSeries): if self.period != other.period: raise ValueError("Both the series should have same periods") x, y = self.x, other.x function = self.function + other.function.subs(y, x) if self.x not in function.free_symbols: return function an = self.an + other.an bn = self.bn + other.bn a0 = self.a0 + other.a0 return self.func(function, self.args[1], (a0, an, bn)) return Add(self, other) def __sub__(self, other): return self.__add__(-other) class FiniteFourierSeries(FourierSeries): r"""Represents Finite Fourier sine/cosine series. For how to compute Fourier series, see the :func:`fourier_series` docstring. Parameters ========== f : Expr Expression for finding fourier_series limits : ( x, start, stop) x is the independent variable for the expression f (start, stop) is the period of the fourier series exprs: (a0, an, bn) or Expr a0 is the constant term a0 of the fourier series an is a dictionary of coefficients of cos terms an[k] = coefficient of cos(pi*(k/L)*x) bn is a dictionary of coefficients of sin terms bn[k] = coefficient of sin(pi*(k/L)*x) or exprs can be an expression to be converted to fourier form Methods ======= This class is an extension of FourierSeries class. Please refer to sympy.series.fourier.FourierSeries for further information. See Also ======== sympy.series.fourier.FourierSeries sympy.series.fourier.fourier_series """ def __new__(cls, f, limits, exprs): f = sympify(f) limits = sympify(limits) exprs = sympify(exprs) if not (type(exprs) == Tuple and len(exprs) == 3): # exprs is not of form (a0, an, bn) # Converts the expression to fourier form c, e = exprs.as_coeff_add() rexpr = c + Add(*[TR10(i) for i in e]) a0, exp_ls = rexpr.expand(trig=False, power_base=False, power_exp=False, log=False).as_coeff_add() x = limits[0] L = abs(limits[2] - limits[1]) / 2 a = Wild('a', properties=[lambda k: k.is_Integer, lambda k: k is not S.Zero, ]) b = Wild('b', properties=[lambda k: x not in k.free_symbols, ]) an = dict() bn = dict() # separates the coefficients of sin and cos terms in dictionaries an, and bn for p in exp_ls: t = p.match(b * cos(a * (pi / L) * x)) q = p.match(b * sin(a * (pi / L) * x)) if t: an[t[a]] = t[b] + an.get(t[a], S.Zero) elif q: bn[q[a]] = q[b] + bn.get(q[a], S.Zero) else: a0 += p exprs = Tuple(a0, an, bn) return Expr.__new__(cls, f, limits, exprs) @property def interval(self): _length = 1 if self.a0 else 0 _length += max(set(self.an.keys()).union(set(self.bn.keys()))) + 1 return Interval(0, _length) @property def length(self): return self.stop - self.start def shiftx(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate().subs(x, x + s) sfunc = self.function.subs(x, x + s) return self.func(sfunc, self.args[1], _expr) def scale(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate() * s sfunc = self.function * s return self.func(sfunc, self.args[1], _expr) def scalex(self, s): s, x = sympify(s), self.x if x in s.free_symbols: raise ValueError("'%s' should be independent of %s" % (s, x)) _expr = self.truncate().subs(x, x * s) sfunc = self.function.subs(x, x * s) return self.func(sfunc, self.args[1], _expr) def _eval_term(self, pt): if pt == 0: return self.a0 _term = self.an.get(pt, S.Zero) * cos(pt * (pi / self.L) * self.x) \ + self.bn.get(pt, S.Zero) * sin(pt * (pi / self.L) * self.x) return _term def __add__(self, other): if isinstance(other, FourierSeries): return other.__add__(fourier_series(self.function, self.args[1],\ finite=False)) elif isinstance(other, FiniteFourierSeries): if self.period != other.period: raise ValueError("Both the series should have same periods") x, y = self.x, other.x function = self.function + other.function.subs(y, x) if self.x not in function.free_symbols: return function return fourier_series(function, limits=self.args[1]) def fourier_series(f, limits=None, finite=True): r"""Computes the Fourier trigonometric series expansion. Explanation =========== Fourier trigonometric series of $f(x)$ over the interval $(a, b)$ is defined as: .. math:: \frac{a_0}{2} + \sum_{n=1}^{\infty} (a_n \cos(\frac{2n \pi x}{L}) + b_n \sin(\frac{2n \pi x}{L})) where the coefficients are: .. math:: L = b - a .. math:: a_0 = \frac{2}{L} \int_{a}^{b}{f(x) dx} .. math:: a_n = \frac{2}{L} \int_{a}^{b}{f(x) \cos(\frac{2n \pi x}{L}) dx} .. math:: b_n = \frac{2}{L} \int_{a}^{b}{f(x) \sin(\frac{2n \pi x}{L}) dx} The condition whether the function $f(x)$ given should be periodic or not is more than necessary, because it is sufficient to consider the series to be converging to $f(x)$ only in the given interval, not throughout the whole real line. This also brings a lot of ease for the computation because you don't have to make $f(x)$ artificially periodic by wrapping it with piecewise, modulo operations, but you can shape the function to look like the desired periodic function only in the interval $(a, b)$, and the computed series will automatically become the series of the periodic version of $f(x)$. This property is illustrated in the examples section below. Parameters ========== limits : (sym, start, end), optional *sym* denotes the symbol the series is computed with respect to. *start* and *end* denotes the start and the end of the interval where the fourier series converges to the given function. Default range is specified as $-\pi$ and $\pi$. Returns ======= FourierSeries A symbolic object representing the Fourier trigonometric series. Examples ======== Computing the Fourier series of $f(x) = x^2$: >>> from sympy import fourier_series, pi >>> from sympy.abc import x >>> f = x**2 >>> s = fourier_series(f, (x, -pi, pi)) >>> s1 = s.truncate(n=3) >>> s1 -4*cos(x) + cos(2*x) + pi**2/3 Shifting of the Fourier series: >>> s.shift(1).truncate() -4*cos(x) + cos(2*x) + 1 + pi**2/3 >>> s.shiftx(1).truncate() -4*cos(x + 1) + cos(2*x + 2) + pi**2/3 Scaling of the Fourier series: >>> s.scale(2).truncate() -8*cos(x) + 2*cos(2*x) + 2*pi**2/3 >>> s.scalex(2).truncate() -4*cos(2*x) + cos(4*x) + pi**2/3 Computing the Fourier series of $f(x) = x$: This illustrates how truncating to the higher order gives better convergence. .. plot:: :context: reset :format: doctest :include-source: True >>> from sympy import fourier_series, pi, plot >>> from sympy.abc import x >>> f = x >>> s = fourier_series(f, (x, -pi, pi)) >>> s1 = s.truncate(n = 3) >>> s2 = s.truncate(n = 5) >>> s3 = s.truncate(n = 7) >>> p = plot(f, s1, s2, s3, (x, -pi, pi), show=False, legend=True) >>> p[0].line_color = (0, 0, 0) >>> p[0].label = 'x' >>> p[1].line_color = (0.7, 0.7, 0.7) >>> p[1].label = 'n=3' >>> p[2].line_color = (0.5, 0.5, 0.5) >>> p[2].label = 'n=5' >>> p[3].line_color = (0.3, 0.3, 0.3) >>> p[3].label = 'n=7' >>> p.show() This illustrates how the series converges to different sawtooth waves if the different ranges are specified. .. plot:: :context: close-figs :format: doctest :include-source: True >>> s1 = fourier_series(x, (x, -1, 1)).truncate(10) >>> s2 = fourier_series(x, (x, -pi, pi)).truncate(10) >>> s3 = fourier_series(x, (x, 0, 1)).truncate(10) >>> p = plot(x, s1, s2, s3, (x, -5, 5), show=False, legend=True) >>> p[0].line_color = (0, 0, 0) >>> p[0].label = 'x' >>> p[1].line_color = (0.7, 0.7, 0.7) >>> p[1].label = '[-1, 1]' >>> p[2].line_color = (0.5, 0.5, 0.5) >>> p[2].label = '[-pi, pi]' >>> p[3].line_color = (0.3, 0.3, 0.3) >>> p[3].label = '[0, 1]' >>> p.show() Notes ===== Computing Fourier series can be slow due to the integration required in computing an, bn. It is faster to compute Fourier series of a function by using shifting and scaling on an already computed Fourier series rather than computing again. e.g. If the Fourier series of ``x**2`` is known the Fourier series of ``x**2 - 1`` can be found by shifting by ``-1``. See Also ======== sympy.series.fourier.FourierSeries References ========== .. [1] https://mathworld.wolfram.com/FourierSeries.html """ f = sympify(f) limits = _process_limits(f, limits) x = limits[0] if x not in f.free_symbols: return f if finite: L = abs(limits[2] - limits[1]) / 2 is_finite, res_f = finite_check(f, x, L) if is_finite: return FiniteFourierSeries(f, limits, res_f) n = Dummy('n') center = (limits[1] + limits[2]) / 2 if center.is_zero: neg_f = f.subs(x, -x) if f == neg_f: a0, an = fourier_cos_seq(f, limits, n) bn = SeqFormula(0, (1, oo)) return FourierSeries(f, limits, (a0, an, bn)) elif f == -neg_f: a0 = S.Zero an = SeqFormula(0, (1, oo)) bn = fourier_sin_seq(f, limits, n) return FourierSeries(f, limits, (a0, an, bn)) a0, an = fourier_cos_seq(f, limits, n) bn = fourier_sin_seq(f, limits, n) return FourierSeries(f, limits, (a0, an, bn))

5844a3acac836e1030ec18ed03e3b63e1ca71213790653f69a4f9c62cfffe584

""" This module implements the Residue function and related tools for working with residues. """ from sympy import sympify from sympy.utilities.timeutils import timethis @timethis('residue') def residue(expr, x, x0): """ Finds the residue of ``expr`` at the point x=x0. The residue is defined as the coefficient of 1/(x-x0) in the power series expansion about x=x0. Examples ======== >>> from sympy import Symbol, residue, sin >>> x = Symbol("x") >>> residue(1/x, x, 0) 1 >>> residue(1/x**2, x, 0) 0 >>> residue(2/sin(x), x, 0) 2 This function is essential for the Residue Theorem [1]. References ========== .. [1] https://en.wikipedia.org/wiki/Residue_theorem """ # The current implementation uses series expansion to # calculate it. A more general implementation is explained in # the section 5.6 of the Bronstein's book {M. Bronstein: # Symbolic Integration I, Springer Verlag (2005)}. For purely # rational functions, the algorithm is much easier. See # sections 2.4, 2.5, and 2.7 (this section actually gives an # algorithm for computing any Laurent series coefficient for # a rational function). The theory in section 2.4 will help to # understand why the resultant works in the general algorithm. # For the definition of a resultant, see section 1.4 (and any # previous sections for more review). from sympy import collect, Mul, Order, S expr = sympify(expr) if x0 != 0: expr = expr.subs(x, x + x0) for n in [0, 1, 2, 4, 8, 16, 32]: s = expr.nseries(x, n=n) if not s.has(Order) or s.getn() >= 0: break s = collect(s.removeO(), x) if s.is_Add: args = s.args else: args = [s] res = S.Zero for arg in args: c, m = arg.as_coeff_mul(x) m = Mul(*m) if not (m == 1 or m == x or (m.is_Pow and m.exp.is_Integer)): raise NotImplementedError('term of unexpected form: %s' % m) if m == 1/x: res += c return res

2f39430a9d0224e848a62b0f493977273a4cc94f377d5a4fd9d626f0172e0b5a

"""Formal Power Series""" from collections import defaultdict from sympy import oo, zoo, nan from sympy.core.add import Add from sympy.core.compatibility import iterable from sympy.core.expr import Expr from sympy.core.function import Derivative, Function, expand from sympy.core.mul import Mul from sympy.core.numbers import Rational from sympy.core.relational import Eq from sympy.sets.sets import Interval from sympy.core.singleton import S from sympy.core.symbol import Wild, Dummy, symbols, Symbol from sympy.core.sympify import sympify from sympy.discrete.convolutions import convolution from sympy.functions.combinatorial.factorials import binomial, factorial, rf from sympy.functions.combinatorial.numbers import bell from sympy.functions.elementary.integers import floor, frac, ceiling from sympy.functions.elementary.miscellaneous import Min, Max from sympy.functions.elementary.piecewise import Piecewise from sympy.series.limits import Limit from sympy.series.order import Order from sympy.simplify.powsimp import powsimp from sympy.series.sequences import sequence from sympy.series.series_class import SeriesBase def rational_algorithm(f, x, k, order=4, full=False): """ Rational algorithm for computing formula of coefficients of Formal Power Series of a function. Applicable when f(x) or some derivative of f(x) is a rational function in x. :func:`rational_algorithm` uses :func:`~.apart` function for partial fraction decomposition. :func:`~.apart` by default uses 'undetermined coefficients method'. By setting ``full=True``, 'Bronstein's algorithm' can be used instead. Looks for derivative of a function up to 4'th order (by default). This can be overridden using order option. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import log, atan >>> from sympy.series.formal import rational_algorithm as ra >>> from sympy.abc import x, k >>> ra(1 / (1 - x), x, k) (1, 0, 0) >>> ra(log(1 + x), x, k) (-(-1)**(-k)/k, 0, 1) >>> ra(atan(x), x, k, full=True) ((-I*(-I)**(-k)/2 + I*I**(-k)/2)/k, 0, 1) Notes ===== By setting ``full=True``, range of admissible functions to be solved using ``rational_algorithm`` can be increased. This option should be used carefully as it can significantly slow down the computation as ``doit`` is performed on the :class:`~.RootSum` object returned by the :func:`~.apart` function. Use ``full=False`` whenever possible. See Also ======== sympy.polys.partfrac.apart References ========== .. [1] Formal Power Series - Dominik Gruntz, Wolfram Koepf .. [2] Power Series in Computer Algebra - Wolfram Koepf """ from sympy.polys import RootSum, apart from sympy.integrals import integrate diff = f ds = [] # list of diff for i in range(order + 1): if i: diff = diff.diff(x) if diff.is_rational_function(x): coeff, sep = S.Zero, S.Zero terms = apart(diff, x, full=full) if terms.has(RootSum): terms = terms.doit() for t in Add.make_args(terms): num, den = t.as_numer_denom() if not den.has(x): sep += t else: if isinstance(den, Mul): # m*(n*x - a)**j -> (n*x - a)**j ind = den.as_independent(x) den = ind[1] num /= ind[0] # (n*x - a)**j -> (x - b) den, j = den.as_base_exp() a, xterm = den.as_coeff_add(x) # term -> m/x**n if not a: sep += t continue xc = xterm[0].coeff(x) a /= -xc num /= xc**j ak = ((-1)**j * num * binomial(j + k - 1, k).rewrite(factorial) / a**(j + k)) coeff += ak # Hacky, better way? if coeff.is_zero: return None if (coeff.has(x) or coeff.has(zoo) or coeff.has(oo) or coeff.has(nan)): return None for j in range(i): coeff = (coeff / (k + j + 1)) sep = integrate(sep, x) sep += (ds.pop() - sep).limit(x, 0) # constant of integration return (coeff.subs(k, k - i), sep, i) else: ds.append(diff) return None def rational_independent(terms, x): """Returns a list of all the rationally independent terms. Examples ======== >>> from sympy import sin, cos >>> from sympy.series.formal import rational_independent >>> from sympy.abc import x >>> rational_independent([cos(x), sin(x)], x) [cos(x), sin(x)] >>> rational_independent([x**2, sin(x), x*sin(x), x**3], x) [x**3 + x**2, x*sin(x) + sin(x)] """ if not terms: return [] ind = terms[0:1] for t in terms[1:]: n = t.as_independent(x)[1] for i, term in enumerate(ind): d = term.as_independent(x)[1] q = (n / d).cancel() if q.is_rational_function(x): ind[i] += t break else: ind.append(t) return ind def simpleDE(f, x, g, order=4): r"""Generates simple DE. DE is of the form .. math:: f^k(x) + \sum\limits_{j=0}^{k-1} A_j f^j(x) = 0 where :math:`A_j` should be rational function in x. Generates DE's upto order 4 (default). DE's can also have free parameters. By increasing order, higher order DE's can be found. Yields a tuple of (DE, order). """ from sympy.solvers.solveset import linsolve a = symbols('a:%d' % (order)) def _makeDE(k): eq = f.diff(x, k) + Add(*[a[i]*f.diff(x, i) for i in range(0, k)]) DE = g(x).diff(x, k) + Add(*[a[i]*g(x).diff(x, i) for i in range(0, k)]) return eq, DE found = False for k in range(1, order + 1): eq, DE = _makeDE(k) eq = eq.expand() terms = eq.as_ordered_terms() ind = rational_independent(terms, x) if found or len(ind) == k: sol = dict(zip(a, (i for s in linsolve(ind, a[:k]) for i in s))) if sol: found = True DE = DE.subs(sol) DE = DE.as_numer_denom()[0] DE = DE.factor().as_coeff_mul(Derivative)[1][0] yield DE.collect(Derivative(g(x))), k def exp_re(DE, r, k): """Converts a DE with constant coefficients (explike) into a RE. Performs the substitution: .. math:: f^j(x) \\to r(k + j) Normalises the terms so that lowest order of a term is always r(k). Examples ======== >>> from sympy import Function, Derivative >>> from sympy.series.formal import exp_re >>> from sympy.abc import x, k >>> f, r = Function('f'), Function('r') >>> exp_re(-f(x) + Derivative(f(x)), r, k) -r(k) + r(k + 1) >>> exp_re(Derivative(f(x), x) + Derivative(f(x), (x, 2)), r, k) r(k) + r(k + 1) See Also ======== sympy.series.formal.hyper_re """ RE = S.Zero g = DE.atoms(Function).pop() mini = None for t in Add.make_args(DE): coeff, d = t.as_independent(g) if isinstance(d, Derivative): j = d.derivative_count else: j = 0 if mini is None or j < mini: mini = j RE += coeff * r(k + j) if mini: RE = RE.subs(k, k - mini) return RE def hyper_re(DE, r, k): """Converts a DE into a RE. Performs the substitution: .. math:: x^l f^j(x) \\to (k + 1 - l)_j . a_{k + j - l} Normalises the terms so that lowest order of a term is always r(k). Examples ======== >>> from sympy import Function, Derivative >>> from sympy.series.formal import hyper_re >>> from sympy.abc import x, k >>> f, r = Function('f'), Function('r') >>> hyper_re(-f(x) + Derivative(f(x)), r, k) (k + 1)*r(k + 1) - r(k) >>> hyper_re(-x*f(x) + Derivative(f(x), (x, 2)), r, k) (k + 2)*(k + 3)*r(k + 3) - r(k) See Also ======== sympy.series.formal.exp_re """ RE = S.Zero g = DE.atoms(Function).pop() x = g.atoms(Symbol).pop() mini = None for t in Add.make_args(DE.expand()): coeff, d = t.as_independent(g) c, v = coeff.as_independent(x) l = v.as_coeff_exponent(x)[1] if isinstance(d, Derivative): j = d.derivative_count else: j = 0 RE += c * rf(k + 1 - l, j) * r(k + j - l) if mini is None or j - l < mini: mini = j - l RE = RE.subs(k, k - mini) m = Wild('m') return RE.collect(r(k + m)) def _transformation_a(f, x, P, Q, k, m, shift): f *= x**(-shift) P = P.subs(k, k + shift) Q = Q.subs(k, k + shift) return f, P, Q, m def _transformation_c(f, x, P, Q, k, m, scale): f = f.subs(x, x**scale) P = P.subs(k, k / scale) Q = Q.subs(k, k / scale) m *= scale return f, P, Q, m def _transformation_e(f, x, P, Q, k, m): f = f.diff(x) P = P.subs(k, k + 1) * (k + m + 1) Q = Q.subs(k, k + 1) * (k + 1) return f, P, Q, m def _apply_shift(sol, shift): return [(res, cond + shift) for res, cond in sol] def _apply_scale(sol, scale): return [(res, cond / scale) for res, cond in sol] def _apply_integrate(sol, x, k): return [(res / ((cond + 1)*(cond.as_coeff_Add()[1].coeff(k))), cond + 1) for res, cond in sol] def _compute_formula(f, x, P, Q, k, m, k_max): """Computes the formula for f.""" from sympy.polys import roots sol = [] for i in range(k_max + 1, k_max + m + 1): if (i < 0) == True: continue r = f.diff(x, i).limit(x, 0) / factorial(i) if r.is_zero: continue kterm = m*k + i res = r p = P.subs(k, kterm) q = Q.subs(k, kterm) c1 = p.subs(k, 1/k).leadterm(k)[0] c2 = q.subs(k, 1/k).leadterm(k)[0] res *= (-c1 / c2)**k for r, mul in roots(p, k).items(): res *= rf(-r, k)**mul for r, mul in roots(q, k).items(): res /= rf(-r, k)**mul sol.append((res, kterm)) return sol def _rsolve_hypergeometric(f, x, P, Q, k, m): """Recursive wrapper to rsolve_hypergeometric. Returns a Tuple of (formula, series independent terms, maximum power of x in independent terms) if successful otherwise ``None``. See :func:`rsolve_hypergeometric` for details. """ from sympy.polys import lcm, roots from sympy.integrals import integrate # transformation - c proots, qroots = roots(P, k), roots(Q, k) all_roots = dict(proots) all_roots.update(qroots) scale = lcm([r.as_numer_denom()[1] for r, t in all_roots.items() if r.is_rational]) f, P, Q, m = _transformation_c(f, x, P, Q, k, m, scale) # transformation - a qroots = roots(Q, k) if qroots: k_min = Min(*qroots.keys()) else: k_min = S.Zero shift = k_min + m f, P, Q, m = _transformation_a(f, x, P, Q, k, m, shift) l = (x*f).limit(x, 0) if not isinstance(l, Limit) and l != 0: # Ideally should only be l != 0 return None qroots = roots(Q, k) if qroots: k_max = Max(*qroots.keys()) else: k_max = S.Zero ind, mp = S.Zero, -oo for i in range(k_max + m + 1): r = f.diff(x, i).limit(x, 0) / factorial(i) if r.is_finite is False: old_f = f f, P, Q, m = _transformation_a(f, x, P, Q, k, m, i) f, P, Q, m = _transformation_e(f, x, P, Q, k, m) sol, ind, mp = _rsolve_hypergeometric(f, x, P, Q, k, m) sol = _apply_integrate(sol, x, k) sol = _apply_shift(sol, i) ind = integrate(ind, x) ind += (old_f - ind).limit(x, 0) # constant of integration mp += 1 return sol, ind, mp elif r: ind += r*x**(i + shift) pow_x = Rational((i + shift), scale) if pow_x > mp: mp = pow_x # maximum power of x ind = ind.subs(x, x**(1/scale)) sol = _compute_formula(f, x, P, Q, k, m, k_max) sol = _apply_shift(sol, shift) sol = _apply_scale(sol, scale) return sol, ind, mp def rsolve_hypergeometric(f, x, P, Q, k, m): """Solves RE of hypergeometric type. Attempts to solve RE of the form Q(k)*a(k + m) - P(k)*a(k) Transformations that preserve Hypergeometric type: a. x**n*f(x): b(k + m) = R(k - n)*b(k) b. f(A*x): b(k + m) = A**m*R(k)*b(k) c. f(x**n): b(k + n*m) = R(k/n)*b(k) d. f(x**(1/m)): b(k + 1) = R(k*m)*b(k) e. f'(x): b(k + m) = ((k + m + 1)/(k + 1))*R(k + 1)*b(k) Some of these transformations have been used to solve the RE. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import exp, ln, S >>> from sympy.series.formal import rsolve_hypergeometric as rh >>> from sympy.abc import x, k >>> rh(exp(x), x, -S.One, (k + 1), k, 1) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> rh(ln(1 + x), x, k**2, k*(k + 1), k, 1) (Piecewise(((-1)**(k - 1)*factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) References ========== .. [1] Formal Power Series - Dominik Gruntz, Wolfram Koepf .. [2] Power Series in Computer Algebra - Wolfram Koepf """ result = _rsolve_hypergeometric(f, x, P, Q, k, m) if result is None: return None sol_list, ind, mp = result sol_dict = defaultdict(lambda: S.Zero) for res, cond in sol_list: j, mk = cond.as_coeff_Add() c = mk.coeff(k) if j.is_integer is False: res *= x**frac(j) j = floor(j) res = res.subs(k, (k - j) / c) cond = Eq(k % c, j % c) sol_dict[cond] += res # Group together formula for same conditions sol = [] for cond, res in sol_dict.items(): sol.append((res, cond)) sol.append((S.Zero, True)) sol = Piecewise(*sol) if mp is -oo: s = S.Zero elif mp.is_integer is False: s = ceiling(mp) else: s = mp + 1 # save all the terms of # form 1/x**k in ind if s < 0: ind += sum(sequence(sol * x**k, (k, s, -1))) s = S.Zero return (sol, ind, s) def _solve_hyper_RE(f, x, RE, g, k): """See docstring of :func:`rsolve_hypergeometric` for details.""" terms = Add.make_args(RE) if len(terms) == 2: gs = list(RE.atoms(Function)) P, Q = map(RE.coeff, gs) m = gs[1].args[0] - gs[0].args[0] if m < 0: P, Q = Q, P m = abs(m) return rsolve_hypergeometric(f, x, P, Q, k, m) def _solve_explike_DE(f, x, DE, g, k): """Solves DE with constant coefficients.""" from sympy.solvers import rsolve for t in Add.make_args(DE): coeff, d = t.as_independent(g) if coeff.free_symbols: return RE = exp_re(DE, g, k) init = {} for i in range(len(Add.make_args(RE))): if i: f = f.diff(x) init[g(k).subs(k, i)] = f.limit(x, 0) sol = rsolve(RE, g(k), init) if sol: return (sol / factorial(k), S.Zero, S.Zero) def _solve_simple(f, x, DE, g, k): """Converts DE into RE and solves using :func:`rsolve`.""" from sympy.solvers import rsolve RE = hyper_re(DE, g, k) init = {} for i in range(len(Add.make_args(RE))): if i: f = f.diff(x) init[g(k).subs(k, i)] = f.limit(x, 0) / factorial(i) sol = rsolve(RE, g(k), init) if sol: return (sol, S.Zero, S.Zero) def _transform_explike_DE(DE, g, x, order, syms): """Converts DE with free parameters into DE with constant coefficients.""" from sympy.solvers.solveset import linsolve eq = [] highest_coeff = DE.coeff(Derivative(g(x), x, order)) for i in range(order): coeff = DE.coeff(Derivative(g(x), x, i)) coeff = (coeff / highest_coeff).expand().collect(x) for t in Add.make_args(coeff): eq.append(t) temp = [] for e in eq: if e.has(x): break elif e.has(Symbol): temp.append(e) else: eq = temp if eq: sol = dict(zip(syms, (i for s in linsolve(eq, list(syms)) for i in s))) if sol: DE = DE.subs(sol) DE = DE.factor().as_coeff_mul(Derivative)[1][0] DE = DE.collect(Derivative(g(x))) return DE def _transform_DE_RE(DE, g, k, order, syms): """Converts DE with free parameters into RE of hypergeometric type.""" from sympy.solvers.solveset import linsolve RE = hyper_re(DE, g, k) eq = [] for i in range(1, order): coeff = RE.coeff(g(k + i)) eq.append(coeff) sol = dict(zip(syms, (i for s in linsolve(eq, list(syms)) for i in s))) if sol: m = Wild('m') RE = RE.subs(sol) RE = RE.factor().as_numer_denom()[0].collect(g(k + m)) RE = RE.as_coeff_mul(g)[1][0] for i in range(order): # smallest order should be g(k) if RE.coeff(g(k + i)) and i: RE = RE.subs(k, k - i) break return RE def solve_de(f, x, DE, order, g, k): """Solves the DE. Tries to solve DE by either converting into a RE containing two terms or converting into a DE having constant coefficients. Returns ======= formula : Expr ind : Expr Independent terms. order : int Examples ======== >>> from sympy import Derivative as D, Function >>> from sympy import exp, ln >>> from sympy.series.formal import solve_de >>> from sympy.abc import x, k >>> f = Function('f') >>> solve_de(exp(x), x, D(f(x), x) - f(x), 1, f, k) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> solve_de(ln(1 + x), x, (x + 1)*D(f(x), x, 2) + D(f(x)), 2, f, k) (Piecewise(((-1)**(k - 1)*factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) """ sol = None syms = DE.free_symbols.difference({g, x}) if syms: RE = _transform_DE_RE(DE, g, k, order, syms) else: RE = hyper_re(DE, g, k) if not RE.free_symbols.difference({k}): sol = _solve_hyper_RE(f, x, RE, g, k) if sol: return sol if syms: DE = _transform_explike_DE(DE, g, x, order, syms) if not DE.free_symbols.difference({x}): sol = _solve_explike_DE(f, x, DE, g, k) if sol: return sol def hyper_algorithm(f, x, k, order=4): """Hypergeometric algorithm for computing Formal Power Series. Steps: * Generates DE * Convert the DE into RE * Solves the RE Examples ======== >>> from sympy import exp, ln >>> from sympy.series.formal import hyper_algorithm >>> from sympy.abc import x, k >>> hyper_algorithm(exp(x), x, k) (Piecewise((1/factorial(k), Eq(Mod(k, 1), 0)), (0, True)), 1, 1) >>> hyper_algorithm(ln(1 + x), x, k) (Piecewise(((-1)**(k - 1)*factorial(k - 1)/RisingFactorial(2, k - 1), Eq(Mod(k, 1), 0)), (0, True)), x, 2) See Also ======== sympy.series.formal.simpleDE sympy.series.formal.solve_de """ g = Function('g') des = [] # list of DE's sol = None for DE, i in simpleDE(f, x, g, order): if DE is not None: sol = solve_de(f, x, DE, i, g, k) if sol: return sol if not DE.free_symbols.difference({x}): des.append(DE) # If nothing works # Try plain rsolve for DE in des: sol = _solve_simple(f, x, DE, g, k) if sol: return sol def _compute_fps(f, x, x0, dir, hyper, order, rational, full): """Recursive wrapper to compute fps. See :func:`compute_fps` for details. """ if x0 in [S.Infinity, S.NegativeInfinity]: dir = S.One if x0 is S.Infinity else -S.One temp = f.subs(x, 1/x) result = _compute_fps(temp, x, 0, dir, hyper, order, rational, full) if result is None: return None return (result[0], result[1].subs(x, 1/x), result[2].subs(x, 1/x)) elif x0 or dir == -S.One: if dir == -S.One: rep = -x + x0 rep2 = -x rep2b = x0 else: rep = x + x0 rep2 = x rep2b = -x0 temp = f.subs(x, rep) result = _compute_fps(temp, x, 0, S.One, hyper, order, rational, full) if result is None: return None return (result[0], result[1].subs(x, rep2 + rep2b), result[2].subs(x, rep2 + rep2b)) if f.is_polynomial(x): k = Dummy('k') ak = sequence(Coeff(f, x, k), (k, 1, oo)) xk = sequence(x**k, (k, 0, oo)) ind = f.coeff(x, 0) return ak, xk, ind # Break instances of Add # this allows application of different # algorithms on different terms increasing the # range of admissible functions. if isinstance(f, Add): result = False ak = sequence(S.Zero, (0, oo)) ind, xk = S.Zero, None for t in Add.make_args(f): res = _compute_fps(t, x, 0, S.One, hyper, order, rational, full) if res: if not result: result = True xk = res[1] if res[0].start > ak.start: seq = ak s, f = ak.start, res[0].start else: seq = res[0] s, f = res[0].start, ak.start save = Add(*[z[0]*z[1] for z in zip(seq[0:(f - s)], xk[s:f])]) ak += res[0] ind += res[2] + save else: ind += t if result: return ak, xk, ind return None # The symbolic term - symb, if present, is being separated from the function # Otherwise symb is being set to S.One syms = f.free_symbols.difference({x}) (f, symb) = expand(f).as_independent(*syms) if symb.is_zero: symb = S.One symb = powsimp(symb) result = None # from here on it's x0=0 and dir=1 handling k = Dummy('k') if rational: result = rational_algorithm(f, x, k, order, full) if result is None and hyper: result = hyper_algorithm(f, x, k, order) if result is None: return None ak = sequence(result[0], (k, result[2], oo)) xk_formula = powsimp(x**k * symb) xk = sequence(xk_formula, (k, 0, oo)) ind = powsimp(result[1] * symb) return ak, xk, ind def compute_fps(f, x, x0=0, dir=1, hyper=True, order=4, rational=True, full=False): """Computes the formula for Formal Power Series of a function. Tries to compute the formula by applying the following techniques (in order): * rational_algorithm * Hypergeometric algorithm Parameters ========== x : Symbol x0 : number, optional Point to perform series expansion about. Default is 0. dir : {1, -1, '+', '-'}, optional If dir is 1 or '+' the series is calculated from the right and for -1 or '-' the series is calculated from the left. For smooth functions this flag will not alter the results. Default is 1. hyper : {True, False}, optional Set hyper to False to skip the hypergeometric algorithm. By default it is set to False. order : int, optional Order of the derivative of ``f``, Default is 4. rational : {True, False}, optional Set rational to False to skip rational algorithm. By default it is set to True. full : {True, False}, optional Set full to True to increase the range of rational algorithm. See :func:`rational_algorithm` for details. By default it is set to False. Returns ======= ak : sequence Sequence of coefficients. xk : sequence Sequence of powers of x. ind : Expr Independent terms. mul : Pow Common terms. See Also ======== sympy.series.formal.rational_algorithm sympy.series.formal.hyper_algorithm """ f = sympify(f) x = sympify(x) if not f.has(x): return None x0 = sympify(x0) if dir == '+': dir = S.One elif dir == '-': dir = -S.One elif dir not in [S.One, -S.One]: raise ValueError("Dir must be '+' or '-'") else: dir = sympify(dir) return _compute_fps(f, x, x0, dir, hyper, order, rational, full) class Coeff(Function): """ Coeff(p, x, n) represents the nth coefficient of the polynomial p in x """ @classmethod def eval(cls, p, x, n): if p.is_polynomial(x) and n.is_integer: return p.coeff(x, n) class FormalPowerSeries(SeriesBase): """Represents Formal Power Series of a function. No computation is performed. This class should only to be used to represent a series. No checks are performed. For computing a series use :func:`fps`. See Also ======== sympy.series.formal.fps """ def __new__(cls, *args): args = map(sympify, args) return Expr.__new__(cls, *args) def __init__(self, *args): ak = args[4][0] k = ak.variables[0] self.ak_seq = sequence(ak.formula, (k, 1, oo)) self.fact_seq = sequence(factorial(k), (k, 1, oo)) self.bell_coeff_seq = self.ak_seq * self.fact_seq self.sign_seq = sequence((-1, 1), (k, 1, oo)) @property def function(self): return self.args[0] @property def x(self): return self.args[1] @property def x0(self): return self.args[2] @property def dir(self): return self.args[3] @property def ak(self): return self.args[4][0] @property def xk(self): return self.args[4][1] @property def ind(self): return self.args[4][2] @property def interval(self): return Interval(0, oo) @property def start(self): return self.interval.inf @property def stop(self): return self.interval.sup @property def length(self): return oo @property def infinite(self): """Returns an infinite representation of the series""" from sympy.concrete import Sum ak, xk = self.ak, self.xk k = ak.variables[0] inf_sum = Sum(ak.formula * xk.formula, (k, ak.start, ak.stop)) return self.ind + inf_sum def _get_pow_x(self, term): """Returns the power of x in a term.""" xterm, pow_x = term.as_independent(self.x)[1].as_base_exp() if not xterm.has(self.x): return S.Zero return pow_x def polynomial(self, n=6): """Truncated series as polynomial. Returns series expansion of ``f`` upto order ``O(x**n)`` as a polynomial(without ``O`` term). """ terms = [] sym = self.free_symbols for i, t in enumerate(self): xp = self._get_pow_x(t) if xp.has(*sym): xp = xp.as_coeff_add(*sym)[0] if xp >= n: break elif xp.is_integer is True and i == n + 1: break elif t is not S.Zero: terms.append(t) return Add(*terms) def truncate(self, n=6): """Truncated series. Returns truncated series expansion of f upto order ``O(x**n)``. If n is ``None``, returns an infinite iterator. """ if n is None: return iter(self) x, x0 = self.x, self.x0 pt_xk = self.xk.coeff(n) if x0 is S.NegativeInfinity: x0 = S.Infinity return self.polynomial(n) + Order(pt_xk, (x, x0)) def zero_coeff(self): return self._eval_term(0) def _eval_term(self, pt): try: pt_xk = self.xk.coeff(pt) pt_ak = self.ak.coeff(pt).simplify() # Simplify the coefficients except IndexError: term = S.Zero else: term = (pt_ak * pt_xk) if self.ind: ind = S.Zero sym = self.free_symbols for t in Add.make_args(self.ind): pow_x = self._get_pow_x(t) if pow_x.has(*sym): pow_x = pow_x.as_coeff_add(*sym)[0] if pt == 0 and pow_x < 1: ind += t elif pow_x >= pt and pow_x < pt + 1: ind += t term += ind return term.collect(self.x) def _eval_subs(self, old, new): x = self.x if old.has(x): return self def _eval_as_leading_term(self, x, cdir=0): for t in self: if t is not S.Zero: return t def _eval_derivative(self, x): f = self.function.diff(x) ind = self.ind.diff(x) pow_xk = self._get_pow_x(self.xk.formula) ak = self.ak k = ak.variables[0] if ak.formula.has(x): form = [] for e, c in ak.formula.args: temp = S.Zero for t in Add.make_args(e): pow_x = self._get_pow_x(t) temp += t * (pow_xk + pow_x) form.append((temp, c)) form = Piecewise(*form) ak = sequence(form.subs(k, k + 1), (k, ak.start - 1, ak.stop)) else: ak = sequence((ak.formula * pow_xk).subs(k, k + 1), (k, ak.start - 1, ak.stop)) return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def integrate(self, x=None, **kwargs): """Integrate Formal Power Series. Examples ======== >>> from sympy import fps, sin, integrate >>> from sympy.abc import x >>> f = fps(sin(x)) >>> f.integrate(x).truncate() -1 + x**2/2 - x**4/24 + O(x**6) >>> integrate(f, (x, 0, 1)) 1 - cos(1) """ from sympy.integrals import integrate if x is None: x = self.x elif iterable(x): return integrate(self.function, x) f = integrate(self.function, x) ind = integrate(self.ind, x) ind += (f - ind).limit(x, 0) # constant of integration pow_xk = self._get_pow_x(self.xk.formula) ak = self.ak k = ak.variables[0] if ak.formula.has(x): form = [] for e, c in ak.formula.args: temp = S.Zero for t in Add.make_args(e): pow_x = self._get_pow_x(t) temp += t / (pow_xk + pow_x + 1) form.append((temp, c)) form = Piecewise(*form) ak = sequence(form.subs(k, k - 1), (k, ak.start + 1, ak.stop)) else: ak = sequence((ak.formula / (pow_xk + 1)).subs(k, k - 1), (k, ak.start + 1, ak.stop)) return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def product(self, other, x=None, n=6): """Multiplies two Formal Power Series, using discrete convolution and return the truncated terms upto specified order. Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(sin(x)) >>> f2 = fps(exp(x)) >>> f1.product(f2, x).truncate(4) x + x**2 + x**3/3 + O(x**4) See Also ======== sympy.discrete.convolutions sympy.series.formal.FormalPowerSeriesProduct """ if x is None: x = self.x if n is None: return iter(self) other = sympify(other) if not isinstance(other, FormalPowerSeries): raise ValueError("Both series should be an instance of FormalPowerSeries" " class.") if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") elif self.x != other.x: raise ValueError("Both series should have the same symbol.") return FormalPowerSeriesProduct(self, other) def coeff_bell(self, n): r""" self.coeff_bell(n) returns a sequence of Bell polynomials of the second kind. Note that ``n`` should be a integer. The second kind of Bell polynomials (are sometimes called "partial" Bell polynomials or incomplete Bell polynomials) are defined as .. math:: B_{n,k}(x_1, x_2,\dotsc x_{n-k+1}) = \sum_{j_1+j_2+j_2+\dotsb=k \atop j_1+2j_2+3j_2+\dotsb=n} \frac{n!}{j_1!j_2!\dotsb j_{n-k+1}!} \left(\frac{x_1}{1!} \right)^{j_1} \left(\frac{x_2}{2!} \right)^{j_2} \dotsb \left(\frac{x_{n-k+1}}{(n-k+1)!} \right) ^{j_{n-k+1}}. * ``bell(n, k, (x1, x2, ...))`` gives Bell polynomials of the second kind, `B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1})`. See Also ======== sympy.functions.combinatorial.numbers.bell """ inner_coeffs = [bell(n, j, tuple(self.bell_coeff_seq[:n-j+1])) for j in range(1, n+1)] k = Dummy('k') return sequence(tuple(inner_coeffs), (k, 1, oo)) def compose(self, other, x=None, n=6): r""" Returns the truncated terms of the formal power series of the composed function, up to specified `n`. If `f` and `g` are two formal power series of two different functions, then the coefficient sequence ``ak`` of the composed formal power series `fp` will be as follows. .. math:: \sum\limits_{k=0}^{n} b_k B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1}) Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(sin(x)) >>> f1.compose(f2, x).truncate() 1 + x + x**2/2 - x**4/8 - x**5/15 + O(x**6) >>> f1.compose(f2, x).truncate(8) 1 + x + x**2/2 - x**4/8 - x**5/15 - x**6/240 + x**7/90 + O(x**8) See Also ======== sympy.functions.combinatorial.numbers.bell sympy.series.formal.FormalPowerSeriesCompose References ========== .. [1] Comtet, Louis: Advanced combinatorics; the art of finite and infinite expansions. Reidel, 1974. """ if x is None: x = self.x if n is None: return iter(self) other = sympify(other) if not isinstance(other, FormalPowerSeries): raise ValueError("Both series should be an instance of FormalPowerSeries" " class.") if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") elif self.x != other.x: raise ValueError("Both series should have the same symbol.") if other._eval_term(0).as_coeff_mul(other.x)[0] is not S.Zero: raise ValueError("The formal power series of the inner function should not have any " "constant coefficient term.") return FormalPowerSeriesCompose(self, other) def inverse(self, x=None, n=6): r""" Returns the truncated terms of the inverse of the formal power series, up to specified `n`. If `f` and `g` are two formal power series of two different functions, then the coefficient sequence ``ak`` of the composed formal power series `fp` will be as follows. .. math:: \sum\limits_{k=0}^{n} (-1)^{k} x_0^{-k-1} B_{n,k}(x_1, x_2, \dotsc, x_{n-k+1}) Parameters ========== n : Number, optional Specifies the order of the term up to which the polynomial should be truncated. Examples ======== >>> from sympy import fps, exp, cos >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(cos(x)) >>> f1.inverse(x).truncate() 1 - x + x**2/2 - x**3/6 + x**4/24 - x**5/120 + O(x**6) >>> f2.inverse(x).truncate(8) 1 + x**2/2 + 5*x**4/24 + 61*x**6/720 + O(x**8) See Also ======== sympy.functions.combinatorial.numbers.bell sympy.series.formal.FormalPowerSeriesInverse References ========== .. [1] Comtet, Louis: Advanced combinatorics; the art of finite and infinite expansions. Reidel, 1974. """ if x is None: x = self.x if n is None: return iter(self) if self._eval_term(0).is_zero: raise ValueError("Constant coefficient should exist for an inverse of a formal" " power series to exist.") return FormalPowerSeriesInverse(self) def __add__(self, other): other = sympify(other) if isinstance(other, FormalPowerSeries): if self.dir != other.dir: raise ValueError("Both series should be calculated from the" " same direction.") elif self.x0 != other.x0: raise ValueError("Both series should be calculated about the" " same point.") x, y = self.x, other.x f = self.function + other.function.subs(y, x) if self.x not in f.free_symbols: return f ak = self.ak + other.ak if self.ak.start > other.ak.start: seq = other.ak s, e = other.ak.start, self.ak.start else: seq = self.ak s, e = self.ak.start, other.ak.start save = Add(*[z[0]*z[1] for z in zip(seq[0:(e - s)], self.xk[s:e])]) ind = self.ind + other.ind + save return self.func(f, x, self.x0, self.dir, (ak, self.xk, ind)) elif not other.has(self.x): f = self.function + other ind = self.ind + other return self.func(f, self.x, self.x0, self.dir, (self.ak, self.xk, ind)) return Add(self, other) def __radd__(self, other): return self.__add__(other) def __neg__(self): return self.func(-self.function, self.x, self.x0, self.dir, (-self.ak, self.xk, -self.ind)) def __sub__(self, other): return self.__add__(-other) def __rsub__(self, other): return (-self).__add__(other) def __mul__(self, other): other = sympify(other) if other.has(self.x): return Mul(self, other) f = self.function * other ak = self.ak.coeff_mul(other) ind = self.ind * other return self.func(f, self.x, self.x0, self.dir, (ak, self.xk, ind)) def __rmul__(self, other): return self.__mul__(other) class FiniteFormalPowerSeries(FormalPowerSeries): """Base Class for Product, Compose and Inverse classes""" def __init__(self, *args): pass @property def ffps(self): return self.args[0] @property def gfps(self): return self.args[1] @property def f(self): return self.ffps.function @property def g(self): return self.gfps.function @property def infinite(self): raise NotImplementedError("No infinite version for an object of" " FiniteFormalPowerSeries class.") def _eval_terms(self, n): raise NotImplementedError("(%s)._eval_terms()" % self) def _eval_term(self, pt): raise NotImplementedError("By the current logic, one can get terms" "upto a certain order, instead of getting term by term.") def polynomial(self, n): return self._eval_terms(n) def truncate(self, n=6): ffps = self.ffps pt_xk = ffps.xk.coeff(n) x, x0 = ffps.x, ffps.x0 return self.polynomial(n) + Order(pt_xk, (x, x0)) def _eval_derivative(self, x): raise NotImplementedError def integrate(self, x): raise NotImplementedError class FormalPowerSeriesProduct(FiniteFormalPowerSeries): """Represents the product of two formal power series of two functions. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There are two differences between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesProduct` object. The first argument contains the two functions involved in the product. Also, the coefficient sequence contains both the coefficient sequence of the formal power series of the involved functions. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ def __init__(self, *args): ffps, gfps = self.ffps, self.gfps k = ffps.ak.variables[0] self.coeff1 = sequence(ffps.ak.formula, (k, 0, oo)) k = gfps.ak.variables[0] self.coeff2 = sequence(gfps.ak.formula, (k, 0, oo)) @property def function(self): """Function of the product of two formal power series.""" return self.f * self.g def _eval_terms(self, n): """ Returns the first `n` terms of the product formal power series. Term by term logic is implemented here. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(sin(x)) >>> f2 = fps(exp(x)) >>> fprod = f1.product(f2, x) >>> fprod._eval_terms(4) x**3/3 + x**2 + x See Also ======== sympy.series.formal.FormalPowerSeries.product """ coeff1, coeff2 = self.coeff1, self.coeff2 aks = convolution(coeff1[:n], coeff2[:n]) terms = [] for i in range(0, n): terms.append(aks[i] * self.ffps.xk.coeff(i)) return Add(*terms) class FormalPowerSeriesCompose(FiniteFormalPowerSeries): """Represents the composed formal power series of two functions. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There are two differences between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesCompose` object. The first argument contains the outer function and the inner function involved in the omposition. Also, the coefficient sequence contains the generic sequence which is to be multiplied by a custom ``bell_seq`` finite sequence. The finite terms will then be added up to get the final terms. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ @property def function(self): """Function for the composed formal power series.""" f, g, x = self.f, self.g, self.ffps.x return f.subs(x, g) def _eval_terms(self, n): """ Returns the first `n` terms of the composed formal power series. Term by term logic is implemented here. The coefficient sequence of the :obj:`FormalPowerSeriesCompose` object is the generic sequence. It is multiplied by ``bell_seq`` to get a sequence, whose terms are added up to get the final terms for the polynomial. Examples ======== >>> from sympy import fps, sin, exp >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(sin(x)) >>> fcomp = f1.compose(f2, x) >>> fcomp._eval_terms(6) -x**5/15 - x**4/8 + x**2/2 + x + 1 >>> fcomp._eval_terms(8) x**7/90 - x**6/240 - x**5/15 - x**4/8 + x**2/2 + x + 1 See Also ======== sympy.series.formal.FormalPowerSeries.compose sympy.series.formal.FormalPowerSeries.coeff_bell """ ffps, gfps = self.ffps, self.gfps terms = [ffps.zero_coeff()] for i in range(1, n): bell_seq = gfps.coeff_bell(i) seq = (ffps.bell_coeff_seq * bell_seq) terms.append(Add(*(seq[:i])) / ffps.fact_seq[i-1] * ffps.xk.coeff(i)) return Add(*terms) class FormalPowerSeriesInverse(FiniteFormalPowerSeries): """Represents the Inverse of a formal power series. No computation is performed. Terms are calculated using a term by term logic, instead of a point by point logic. There is a single difference between a :obj:`FormalPowerSeries` object and a :obj:`FormalPowerSeriesInverse` object. The coefficient sequence contains the generic sequence which is to be multiplied by a custom ``bell_seq`` finite sequence. The finite terms will then be added up to get the final terms. See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.FiniteFormalPowerSeries """ def __init__(self, *args): ffps = self.ffps k = ffps.xk.variables[0] inv = ffps.zero_coeff() inv_seq = sequence(inv ** (-(k + 1)), (k, 1, oo)) self.aux_seq = ffps.sign_seq * ffps.fact_seq * inv_seq @property def function(self): """Function for the inverse of a formal power series.""" f = self.f return 1 / f @property def g(self): raise ValueError("Only one function is considered while performing" "inverse of a formal power series.") @property def gfps(self): raise ValueError("Only one function is considered while performing" "inverse of a formal power series.") def _eval_terms(self, n): """ Returns the first `n` terms of the composed formal power series. Term by term logic is implemented here. The coefficient sequence of the `FormalPowerSeriesInverse` object is the generic sequence. It is multiplied by ``bell_seq`` to get a sequence, whose terms are added up to get the final terms for the polynomial. Examples ======== >>> from sympy import fps, exp, cos >>> from sympy.abc import x >>> f1 = fps(exp(x)) >>> f2 = fps(cos(x)) >>> finv1, finv2 = f1.inverse(), f2.inverse() >>> finv1._eval_terms(6) -x**5/120 + x**4/24 - x**3/6 + x**2/2 - x + 1 >>> finv2._eval_terms(8) 61*x**6/720 + 5*x**4/24 + x**2/2 + 1 See Also ======== sympy.series.formal.FormalPowerSeries.inverse sympy.series.formal.FormalPowerSeries.coeff_bell """ ffps = self.ffps terms = [ffps.zero_coeff()] for i in range(1, n): bell_seq = ffps.coeff_bell(i) seq = (self.aux_seq * bell_seq) terms.append(Add(*(seq[:i])) / ffps.fact_seq[i-1] * ffps.xk.coeff(i)) return Add(*terms) def fps(f, x=None, x0=0, dir=1, hyper=True, order=4, rational=True, full=False): """Generates Formal Power Series of f. Returns the formal series expansion of ``f`` around ``x = x0`` with respect to ``x`` in the form of a ``FormalPowerSeries`` object. Formal Power Series is represented using an explicit formula computed using different algorithms. See :func:`compute_fps` for the more details regarding the computation of formula. Parameters ========== x : Symbol, optional If x is None and ``f`` is univariate, the univariate symbols will be supplied, otherwise an error will be raised. x0 : number, optional Point to perform series expansion about. Default is 0. dir : {1, -1, '+', '-'}, optional If dir is 1 or '+' the series is calculated from the right and for -1 or '-' the series is calculated from the left. For smooth functions this flag will not alter the results. Default is 1. hyper : {True, False}, optional Set hyper to False to skip the hypergeometric algorithm. By default it is set to False. order : int, optional Order of the derivative of ``f``, Default is 4. rational : {True, False}, optional Set rational to False to skip rational algorithm. By default it is set to True. full : {True, False}, optional Set full to True to increase the range of rational algorithm. See :func:`rational_algorithm` for details. By default it is set to False. Examples ======== >>> from sympy import fps, ln, atan, sin >>> from sympy.abc import x, n Rational Functions >>> fps(ln(1 + x)).truncate() x - x**2/2 + x**3/3 - x**4/4 + x**5/5 + O(x**6) >>> fps(atan(x), full=True).truncate() x - x**3/3 + x**5/5 + O(x**6) Symbolic Functions >>> fps(x**n*sin(x**2), x).truncate(8) -x**(n + 6)/6 + x**(n + 2) + O(x**(n + 8)) See Also ======== sympy.series.formal.FormalPowerSeries sympy.series.formal.compute_fps """ f = sympify(f) if x is None: free = f.free_symbols if len(free) == 1: x = free.pop() elif not free: return f else: raise NotImplementedError("multivariate formal power series") result = compute_fps(f, x, x0, dir, hyper, order, rational, full) if result is None: return f return FormalPowerSeries(f, x, x0, dir, result)

ea177139aa1de3f6c399e78491604b67c106794bccb7b6a951acdfb9df5812c5

from sympy.core import S, sympify, Expr, Rational, Dummy from sympy.core import Add, Mul, expand_power_base, expand_log from sympy.core.cache import cacheit from sympy.core.compatibility import default_sort_key, is_sequence from sympy.core.containers import Tuple from sympy.sets.sets import Complement from sympy.utilities.iterables import uniq class Order(Expr): r""" Represents the limiting behavior of some function The order of a function characterizes the function based on the limiting behavior of the function as it goes to some limit. Only taking the limit point to be a number is currently supported. This is expressed in big O notation [1]_. The formal definition for the order of a function `g(x)` about a point `a` is such that `g(x) = O(f(x))` as `x \rightarrow a` if and only if for any `\delta > 0` there exists a `M > 0` such that `|g(x)| \leq M|f(x)|` for `|x-a| < \delta`. This is equivalent to `\lim_{x \rightarrow a} \sup |g(x)/f(x)| < \infty`. Let's illustrate it on the following example by taking the expansion of `\sin(x)` about 0: .. math :: \sin(x) = x - x^3/3! + O(x^5) where in this case `O(x^5) = x^5/5! - x^7/7! + \cdots`. By the definition of `O`, for any `\delta > 0` there is an `M` such that: .. math :: |x^5/5! - x^7/7! + ....| <= M|x^5| \text{ for } |x| < \delta or by the alternate definition: .. math :: \lim_{x \rightarrow 0} | (x^5/5! - x^7/7! + ....) / x^5| < \infty which surely is true, because .. math :: \lim_{x \rightarrow 0} | (x^5/5! - x^7/7! + ....) / x^5| = 1/5! As it is usually used, the order of a function can be intuitively thought of representing all terms of powers greater than the one specified. For example, `O(x^3)` corresponds to any terms proportional to `x^3, x^4,\ldots` and any higher power. For a polynomial, this leaves terms proportional to `x^2`, `x` and constants. Examples ======== >>> from sympy import O, oo, cos, pi >>> from sympy.abc import x, y >>> O(x + x**2) O(x) >>> O(x + x**2, (x, 0)) O(x) >>> O(x + x**2, (x, oo)) O(x**2, (x, oo)) >>> O(1 + x*y) O(1, x, y) >>> O(1 + x*y, (x, 0), (y, 0)) O(1, x, y) >>> O(1 + x*y, (x, oo), (y, oo)) O(x*y, (x, oo), (y, oo)) >>> O(1) in O(1, x) True >>> O(1, x) in O(1) False >>> O(x) in O(1, x) True >>> O(x**2) in O(x) True >>> O(x)*x O(x**2) >>> O(x) - O(x) O(x) >>> O(cos(x)) O(1) >>> O(cos(x), (x, pi/2)) O(x - pi/2, (x, pi/2)) References ========== .. [1] `Big O notation <https://en.wikipedia.org/wiki/Big_O_notation>`_ Notes ===== In ``O(f(x), x)`` the expression ``f(x)`` is assumed to have a leading term. ``O(f(x), x)`` is automatically transformed to ``O(f(x).as_leading_term(x),x)``. ``O(expr*f(x), x)`` is ``O(f(x), x)`` ``O(expr, x)`` is ``O(1)`` ``O(0, x)`` is 0. Multivariate O is also supported: ``O(f(x, y), x, y)`` is transformed to ``O(f(x, y).as_leading_term(x,y).as_leading_term(y), x, y)`` In the multivariate case, it is assumed the limits w.r.t. the various symbols commute. If no symbols are passed then all symbols in the expression are used and the limit point is assumed to be zero. """ is_Order = True __slots__ = () @cacheit def __new__(cls, expr, *args, **kwargs): expr = sympify(expr) if not args: if expr.is_Order: variables = expr.variables point = expr.point else: variables = list(expr.free_symbols) point = [S.Zero]*len(variables) else: args = list(args if is_sequence(args) else [args]) variables, point = [], [] if is_sequence(args[0]): for a in args: v, p = list(map(sympify, a)) variables.append(v) point.append(p) else: variables = list(map(sympify, args)) point = [S.Zero]*len(variables) if not all(v.is_symbol for v in variables): raise TypeError('Variables are not symbols, got %s' % variables) if len(list(uniq(variables))) != len(variables): raise ValueError('Variables are supposed to be unique symbols, got %s' % variables) if expr.is_Order: expr_vp = dict(expr.args[1:]) new_vp = dict(expr_vp) vp = dict(zip(variables, point)) for v, p in vp.items(): if v in new_vp.keys(): if p != new_vp[v]: raise NotImplementedError( "Mixing Order at different points is not supported.") else: new_vp[v] = p if set(expr_vp.keys()) == set(new_vp.keys()): return expr else: variables = list(new_vp.keys()) point = [new_vp[v] for v in variables] if expr is S.NaN: return S.NaN if any(x in p.free_symbols for x in variables for p in point): raise ValueError('Got %s as a point.' % point) if variables: if any(p != point[0] for p in point): raise NotImplementedError( "Multivariable orders at different points are not supported.") if point[0] is S.Infinity: s = {k: 1/Dummy() for k in variables} rs = {1/v: 1/k for k, v in s.items()} elif point[0] is S.NegativeInfinity: s = {k: -1/Dummy() for k in variables} rs = {-1/v: -1/k for k, v in s.items()} elif point[0] is not S.Zero: s = {k: Dummy() + point[0] for k in variables} rs = {v - point[0]: k - point[0] for k, v in s.items()} else: s = () rs = () expr = expr.subs(s) if expr.is_Add: expr = expr.factor() if s: args = tuple([r[0] for r in rs.items()]) else: args = tuple(variables) if len(variables) > 1: # XXX: better way? We need this expand() to # workaround e.g: expr = x*(x + y). # (x*(x + y)).as_leading_term(x, y) currently returns # x*y (wrong order term!). That's why we want to deal with # expand()'ed expr (handled in "if expr.is_Add" branch below). expr = expr.expand() old_expr = None while old_expr != expr: old_expr = expr if expr.is_Add: lst = expr.extract_leading_order(args) expr = Add(*[f.expr for (e, f) in lst]) elif expr: expr = expr.as_leading_term(*args) expr = expr.as_independent(*args, as_Add=False)[1] expr = expand_power_base(expr) expr = expand_log(expr) if len(args) == 1: # The definition of O(f(x)) symbol explicitly stated that # the argument of f(x) is irrelevant. That's why we can # combine some power exponents (only "on top" of the # expression tree for f(x)), e.g.: # x**p * (-x)**q -> x**(p+q) for real p, q. x = args[0] margs = list(Mul.make_args( expr.as_independent(x, as_Add=False)[1])) for i, t in enumerate(margs): if t.is_Pow: b, q = t.args if b in (x, -x) and q.is_real and not q.has(x): margs[i] = x**q elif b.is_Pow and not b.exp.has(x): b, r = b.args if b in (x, -x) and r.is_real: margs[i] = x**(r*q) elif b.is_Mul and b.args[0] is S.NegativeOne: b = -b if b.is_Pow and not b.exp.has(x): b, r = b.args if b in (x, -x) and r.is_real: margs[i] = x**(r*q) expr = Mul(*margs) expr = expr.subs(rs) if expr.is_Order: expr = expr.expr if not expr.has(*variables) and not expr.is_zero: expr = S.One # create Order instance: vp = dict(zip(variables, point)) variables.sort(key=default_sort_key) point = [vp[v] for v in variables] args = (expr,) + Tuple(*zip(variables, point)) obj = Expr.__new__(cls, *args) return obj def _eval_nseries(self, x, n, logx, cdir=0): return self @property def expr(self): return self.args[0] @property def variables(self): if self.args[1:]: return tuple(x[0] for x in self.args[1:]) else: return () @property def point(self): if self.args[1:]: return tuple(x[1] for x in self.args[1:]) else: return () @property def free_symbols(self): return self.expr.free_symbols | set(self.variables) def _eval_power(b, e): if e.is_Number and e.is_nonnegative: return b.func(b.expr ** e, *b.args[1:]) if e == O(1): return b return def as_expr_variables(self, order_symbols): if order_symbols is None: order_symbols = self.args[1:] else: if (not all(o[1] == order_symbols[0][1] for o in order_symbols) and not all(p == self.point[0] for p in self.point)): # pragma: no cover raise NotImplementedError('Order at points other than 0 ' 'or oo not supported, got %s as a point.' % self.point) if order_symbols and order_symbols[0][1] != self.point[0]: raise NotImplementedError( "Multiplying Order at different points is not supported.") order_symbols = dict(order_symbols) for s, p in dict(self.args[1:]).items(): if s not in order_symbols.keys(): order_symbols[s] = p order_symbols = sorted(order_symbols.items(), key=lambda x: default_sort_key(x[0])) return self.expr, tuple(order_symbols) def removeO(self): return S.Zero def getO(self): return self @cacheit def contains(self, expr): r""" Return True if expr belongs to Order(self.expr, \*self.variables). Return False if self belongs to expr. Return None if the inclusion relation cannot be determined (e.g. when self and expr have different symbols). """ from sympy import powsimp if expr.is_zero: return True if expr is S.NaN: return False point = self.point[0] if self.point else S.Zero if expr.is_Order: if (any(p != point for p in expr.point) or any(p != point for p in self.point)): return None if expr.expr == self.expr: # O(1) + O(1), O(1) + O(1, x), etc. return all([x in self.args[1:] for x in expr.args[1:]]) if expr.expr.is_Add: return all([self.contains(x) for x in expr.expr.args]) if self.expr.is_Add and point.is_zero: return any([self.func(x, *self.args[1:]).contains(expr) for x in self.expr.args]) if self.variables and expr.variables: common_symbols = tuple( [s for s in self.variables if s in expr.variables]) elif self.variables: common_symbols = self.variables else: common_symbols = expr.variables if not common_symbols: return None if (self.expr.is_Pow and len(self.variables) == 1 and self.variables == expr.variables): symbol = self.variables[0] other = expr.expr.as_independent(symbol, as_Add=False)[1] if (other.is_Pow and other.base == symbol and self.expr.base == symbol): if point.is_zero: rv = (self.expr.exp - other.exp).is_nonpositive if point.is_infinite: rv = (self.expr.exp - other.exp).is_nonnegative if rv is not None: return rv r = None ratio = self.expr/expr.expr ratio = powsimp(ratio, deep=True, combine='exp') for s in common_symbols: from sympy.series.limits import Limit l = Limit(ratio, s, point).doit(heuristics=False) if not isinstance(l, Limit): l = l != 0 else: l = None if r is None: r = l else: if r != l: return return r if self.expr.is_Pow and len(self.variables) == 1: symbol = self.variables[0] other = expr.as_independent(symbol, as_Add=False)[1] if (other.is_Pow and other.base == symbol and self.expr.base == symbol): if point.is_zero: rv = (self.expr.exp - other.exp).is_nonpositive if point.is_infinite: rv = (self.expr.exp - other.exp).is_nonnegative if rv is not None: return rv obj = self.func(expr, *self.args[1:]) return self.contains(obj) def __contains__(self, other): result = self.contains(other) if result is None: raise TypeError('contains did not evaluate to a bool') return result def _eval_subs(self, old, new): if old in self.variables: newexpr = self.expr.subs(old, new) i = self.variables.index(old) newvars = list(self.variables) newpt = list(self.point) if new.is_symbol: newvars[i] = new else: syms = new.free_symbols if len(syms) == 1 or old in syms: if old in syms: var = self.variables[i] else: var = syms.pop() # First, try to substitute self.point in the "new" # expr to see if this is a fixed point. # E.g. O(y).subs(y, sin(x)) point = new.subs(var, self.point[i]) if point != self.point[i]: from sympy.solvers.solveset import solveset d = Dummy() sol = solveset(old - new.subs(var, d), d) if isinstance(sol, Complement): e1 = sol.args[0] e2 = sol.args[1] sol = set(e1) - set(e2) res = [dict(zip((d, ), sol))] point = d.subs(res[0]).limit(old, self.point[i]) newvars[i] = var newpt[i] = point elif old not in syms: del newvars[i], newpt[i] if not syms and new == self.point[i]: newvars.extend(syms) newpt.extend([S.Zero]*len(syms)) else: return return Order(newexpr, *zip(newvars, newpt)) def _eval_conjugate(self): expr = self.expr._eval_conjugate() if expr is not None: return self.func(expr, *self.args[1:]) def _eval_derivative(self, x): return self.func(self.expr.diff(x), *self.args[1:]) or self def _eval_transpose(self): expr = self.expr._eval_transpose() if expr is not None: return self.func(expr, *self.args[1:]) def _sage_(self): #XXX: SAGE doesn't have Order yet. Let's return 0 instead. return Rational(0)._sage_() def __neg__(self): return self O = Order

3f30f43004cc3632e33e2f465b919018be94a9cd944feb8fc27ce18bb4e4247f

def finite_diff(expression, variable, increment=1): """ Takes as input a polynomial expression and the variable used to construct it and returns the difference between function's value when the input is incremented to 1 and the original function value. If you want an increment other than one supply it as a third argument. Examples ======== >>> from sympy.abc import x, y, z >>> from sympy.series.kauers import finite_diff >>> finite_diff(x**2, x) 2*x + 1 >>> finite_diff(y**3 + 2*y**2 + 3*y + 4, y) 3*y**2 + 7*y + 6 >>> finite_diff(x**2 + 3*x + 8, x, 2) 4*x + 10 >>> finite_diff(z**3 + 8*z, z, 3) 9*z**2 + 27*z + 51 """ expression = expression.expand() expression2 = expression.subs(variable, variable + increment) expression2 = expression2.expand() return expression2 - expression def finite_diff_kauers(sum): """ Takes as input a Sum instance and returns the difference between the sum with the upper index incremented by 1 and the original sum. For example, if S(n) is a sum, then finite_diff_kauers will return S(n + 1) - S(n). Examples ======== >>> from sympy.series.kauers import finite_diff_kauers >>> from sympy import Sum >>> from sympy.abc import x, y, m, n, k >>> finite_diff_kauers(Sum(k, (k, 1, n))) n + 1 >>> finite_diff_kauers(Sum(1/k, (k, 1, n))) 1/(n + 1) >>> finite_diff_kauers(Sum((x*y**2), (x, 1, n), (y, 1, m))) (m + 1)**2*(n + 1) >>> finite_diff_kauers(Sum((x*y), (x, 1, m), (y, 1, n))) (m + 1)*(n + 1) """ function = sum.function for l in sum.limits: function = function.subs(l[0], l[- 1] + 1) return function

0607859c45509e32175013678990c98684543b1f679756914d2de9fad97e066a

""" Expand Hypergeometric (and Meijer G) functions into named special functions. The algorithm for doing this uses a collection of lookup tables of hypergeometric functions, and various of their properties, to expand many hypergeometric functions in terms of special functions. It is based on the following paper: Kelly B. Roach. Meijer G Function Representations. In: Proceedings of the 1997 International Symposium on Symbolic and Algebraic Computation, pages 205-211, New York, 1997. ACM. It is described in great(er) detail in the Sphinx documentation. """ # SUMMARY OF EXTENSIONS FOR MEIJER G FUNCTIONS # # o z**rho G(ap, bq; z) = G(ap + rho, bq + rho; z) # # o denote z*d/dz by D # # o It is helpful to keep in mind that ap and bq play essentially symmetric # roles: G(1/z) has slightly altered parameters, with ap and bq interchanged. # # o There are four shift operators: # A_J = b_J - D, J = 1, ..., n # B_J = 1 - a_j + D, J = 1, ..., m # C_J = -b_J + D, J = m+1, ..., q # D_J = a_J - 1 - D, J = n+1, ..., p # # A_J, C_J increment b_J # B_J, D_J decrement a_J # # o The corresponding four inverse-shift operators are defined if there # is no cancellation. Thus e.g. an index a_J (upper or lower) can be # incremented if a_J != b_i for i = 1, ..., q. # # o Order reduction: if b_j - a_i is a non-negative integer, where # j <= m and i > n, the corresponding quotient of gamma functions reduces # to a polynomial. Hence the G function can be expressed using a G-function # of lower order. # Similarly if j > m and i <= n. # # Secondly, there are paired index theorems [Adamchik, The evaluation of # integrals of Bessel functions via G-function identities]. Suppose there # are three parameters a, b, c, where a is an a_i, i <= n, b is a b_j, # j <= m and c is a denominator parameter (i.e. a_i, i > n or b_j, j > m). # Suppose further all three differ by integers. # Then the order can be reduced. # TODO work this out in detail. # # o An index quadruple is called suitable if its order cannot be reduced. # If there exists a sequence of shift operators transforming one index # quadruple into another, we say one is reachable from the other. # # o Deciding if one index quadruple is reachable from another is tricky. For # this reason, we use hand-built routines to match and instantiate formulas. # from collections import defaultdict from itertools import product from sympy import SYMPY_DEBUG from sympy.core import (S, Dummy, symbols, sympify, Tuple, expand, I, pi, Mul, EulerGamma, oo, zoo, expand_func, Add, nan, Expr, Rational) from sympy.core.compatibility import default_sort_key, reduce from sympy.core.mod import Mod from sympy.functions import (exp, sqrt, root, log, lowergamma, cos, besseli, gamma, uppergamma, expint, erf, sin, besselj, Ei, Ci, Si, Shi, sinh, cosh, Chi, fresnels, fresnelc, polar_lift, exp_polar, floor, ceiling, rf, factorial, lerchphi, Piecewise, re, elliptic_k, elliptic_e) from sympy.functions.elementary.complexes import polarify, unpolarify from sympy.functions.special.hyper import (hyper, HyperRep_atanh, HyperRep_power1, HyperRep_power2, HyperRep_log1, HyperRep_asin1, HyperRep_asin2, HyperRep_sqrts1, HyperRep_sqrts2, HyperRep_log2, HyperRep_cosasin, HyperRep_sinasin, meijerg) from sympy.polys import poly, Poly from sympy.series import residue from sympy.simplify import simplify # type: ignore from sympy.simplify.powsimp import powdenest from sympy.utilities.iterables import sift # function to define "buckets" def _mod1(x): # TODO see if this can work as Mod(x, 1); this will require # different handling of the "buckets" since these need to # be sorted and that fails when there is a mixture of # integers and expressions with parameters. With the current # Mod behavior, Mod(k, 1) == Mod(1, 1) == 0 if k is an integer. # Although the sorting can be done with Basic.compare, this may # still require different handling of the sorted buckets. if x.is_Number: return Mod(x, 1) c, x = x.as_coeff_Add() return Mod(c, 1) + x # leave add formulae at the top for easy reference def add_formulae(formulae): """ Create our knowledge base. """ from sympy.matrices import Matrix a, b, c, z = symbols('a b c, z', cls=Dummy) def add(ap, bq, res): func = Hyper_Function(ap, bq) formulae.append(Formula(func, z, res, (a, b, c))) def addb(ap, bq, B, C, M): func = Hyper_Function(ap, bq) formulae.append(Formula(func, z, None, (a, b, c), B, C, M)) # Luke, Y. L. (1969), The Special Functions and Their Approximations, # Volume 1, section 6.2 # 0F0 add((), (), exp(z)) # 1F0 add((a, ), (), HyperRep_power1(-a, z)) # 2F1 addb((a, a - S.Half), (2*a, ), Matrix([HyperRep_power2(a, z), HyperRep_power2(a + S.Half, z)/2]), Matrix([[1, 0]]), Matrix([[(a - S.Half)*z/(1 - z), (S.Half - a)*z/(1 - z)], [a/(1 - z), a*(z - 2)/(1 - z)]])) addb((1, 1), (2, ), Matrix([HyperRep_log1(z), 1]), Matrix([[-1/z, 0]]), Matrix([[0, z/(z - 1)], [0, 0]])) addb((S.Half, 1), (S('3/2'), ), Matrix([HyperRep_atanh(z), 1]), Matrix([[1, 0]]), Matrix([[Rational(-1, 2), 1/(1 - z)/2], [0, 0]])) addb((S.Half, S.Half), (S('3/2'), ), Matrix([HyperRep_asin1(z), HyperRep_power1(Rational(-1, 2), z)]), Matrix([[1, 0]]), Matrix([[Rational(-1, 2), S.Half], [0, z/(1 - z)/2]])) addb((a, S.Half + a), (S.Half, ), Matrix([HyperRep_sqrts1(-a, z), -HyperRep_sqrts2(-a - S.Half, z)]), Matrix([[1, 0]]), Matrix([[0, -a], [z*(-2*a - 1)/2/(1 - z), S.Half - z*(-2*a - 1)/(1 - z)]])) # A. P. Prudnikov, Yu. A. Brychkov and O. I. Marichev (1990). # Integrals and Series: More Special Functions, Vol. 3,. # Gordon and Breach Science Publisher addb([a, -a], [S.Half], Matrix([HyperRep_cosasin(a, z), HyperRep_sinasin(a, z)]), Matrix([[1, 0]]), Matrix([[0, -a], [a*z/(1 - z), 1/(1 - z)/2]])) addb([1, 1], [3*S.Half], Matrix([HyperRep_asin2(z), 1]), Matrix([[1, 0]]), Matrix([[(z - S.Half)/(1 - z), 1/(1 - z)/2], [0, 0]])) # Complete elliptic integrals K(z) and E(z), both a 2F1 function addb([S.Half, S.Half], [S.One], Matrix([elliptic_k(z), elliptic_e(z)]), Matrix([[2/pi, 0]]), Matrix([[Rational(-1, 2), -1/(2*z-2)], [Rational(-1, 2), S.Half]])) addb([Rational(-1, 2), S.Half], [S.One], Matrix([elliptic_k(z), elliptic_e(z)]), Matrix([[0, 2/pi]]), Matrix([[Rational(-1, 2), -1/(2*z-2)], [Rational(-1, 2), S.Half]])) # 3F2 addb([Rational(-1, 2), 1, 1], [S.Half, 2], Matrix([z*HyperRep_atanh(z), HyperRep_log1(z), 1]), Matrix([[Rational(-2, 3), -S.One/(3*z), Rational(2, 3)]]), Matrix([[S.Half, 0, z/(1 - z)/2], [0, 0, z/(z - 1)], [0, 0, 0]])) # actually the formula for 3/2 is much nicer ... addb([Rational(-1, 2), 1, 1], [2, 2], Matrix([HyperRep_power1(S.Half, z), HyperRep_log2(z), 1]), Matrix([[Rational(4, 9) - 16/(9*z), 4/(3*z), 16/(9*z)]]), Matrix([[z/2/(z - 1), 0, 0], [1/(2*(z - 1)), 0, S.Half], [0, 0, 0]])) # 1F1 addb([1], [b], Matrix([z**(1 - b) * exp(z) * lowergamma(b - 1, z), 1]), Matrix([[b - 1, 0]]), Matrix([[1 - b + z, 1], [0, 0]])) addb([a], [2*a], Matrix([z**(S.Half - a)*exp(z/2)*besseli(a - S.Half, z/2) * gamma(a + S.Half)/4**(S.Half - a), z**(S.Half - a)*exp(z/2)*besseli(a + S.Half, z/2) * gamma(a + S.Half)/4**(S.Half - a)]), Matrix([[1, 0]]), Matrix([[z/2, z/2], [z/2, (z/2 - 2*a)]])) mz = polar_lift(-1)*z addb([a], [a + 1], Matrix([mz**(-a)*a*lowergamma(a, mz), a*exp(z)]), Matrix([[1, 0]]), Matrix([[-a, 1], [0, z]])) # This one is redundant. add([Rational(-1, 2)], [S.Half], exp(z) - sqrt(pi*z)*(-I)*erf(I*sqrt(z))) # Added to get nice results for Laplace transform of Fresnel functions # http://functions.wolfram.com/07.22.03.6437.01 # Basic rule #add([1], [Rational(3, 4), Rational(5, 4)], # sqrt(pi) * (cos(2*sqrt(polar_lift(-1)*z))*fresnelc(2*root(polar_lift(-1)*z,4)/sqrt(pi)) + # sin(2*sqrt(polar_lift(-1)*z))*fresnels(2*root(polar_lift(-1)*z,4)/sqrt(pi))) # / (2*root(polar_lift(-1)*z,4))) # Manually tuned rule addb([1], [Rational(3, 4), Rational(5, 4)], Matrix([ sqrt(pi)*(I*sinh(2*sqrt(z))*fresnels(2*root(z, 4)*exp(I*pi/4)/sqrt(pi)) + cosh(2*sqrt(z))*fresnelc(2*root(z, 4)*exp(I*pi/4)/sqrt(pi))) * exp(-I*pi/4)/(2*root(z, 4)), sqrt(pi)*root(z, 4)*(sinh(2*sqrt(z))*fresnelc(2*root(z, 4)*exp(I*pi/4)/sqrt(pi)) + I*cosh(2*sqrt(z))*fresnels(2*root(z, 4)*exp(I*pi/4)/sqrt(pi))) *exp(-I*pi/4)/2, 1 ]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 4), 1, Rational(1, 4)], [ z, Rational(1, 4), 0], [ 0, 0, 0]])) # 2F2 addb([S.Half, a], [Rational(3, 2), a + 1], Matrix([a/(2*a - 1)*(-I)*sqrt(pi/z)*erf(I*sqrt(z)), a/(2*a - 1)*(polar_lift(-1)*z)**(-a)* lowergamma(a, polar_lift(-1)*z), a/(2*a - 1)*exp(z)]), Matrix([[1, -1, 0]]), Matrix([[Rational(-1, 2), 0, 1], [0, -a, 1], [0, 0, z]])) # We make a "basis" of four functions instead of three, and give EulerGamma # an extra slot (it could just be a coefficient to 1). The advantage is # that this way Polys will not see multivariate polynomials (it treats # EulerGamma as an indeterminate), which is *way* faster. addb([1, 1], [2, 2], Matrix([Ei(z) - log(z), exp(z), 1, EulerGamma]), Matrix([[1/z, 0, 0, -1/z]]), Matrix([[0, 1, -1, 0], [0, z, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]])) # 0F1 add((), (S.Half, ), cosh(2*sqrt(z))) addb([], [b], Matrix([gamma(b)*z**((1 - b)/2)*besseli(b - 1, 2*sqrt(z)), gamma(b)*z**(1 - b/2)*besseli(b, 2*sqrt(z))]), Matrix([[1, 0]]), Matrix([[0, 1], [z, (1 - b)]])) # 0F3 x = 4*z**Rational(1, 4) def fp(a, z): return besseli(a, x) + besselj(a, x) def fm(a, z): return besseli(a, x) - besselj(a, x) # TODO branching addb([], [S.Half, a, a + S.Half], Matrix([fp(2*a - 1, z), fm(2*a, z)*z**Rational(1, 4), fm(2*a - 1, z)*sqrt(z), fp(2*a, z)*z**Rational(3, 4)]) * 2**(-2*a)*gamma(2*a)*z**((1 - 2*a)/4), Matrix([[1, 0, 0, 0]]), Matrix([[0, 1, 0, 0], [0, S.Half - a, 1, 0], [0, 0, S.Half, 1], [z, 0, 0, 1 - a]])) x = 2*(4*z)**Rational(1, 4)*exp_polar(I*pi/4) addb([], [a, a + S.Half, 2*a], (2*sqrt(polar_lift(-1)*z))**(1 - 2*a)*gamma(2*a)**2 * Matrix([besselj(2*a - 1, x)*besseli(2*a - 1, x), x*(besseli(2*a, x)*besselj(2*a - 1, x) - besseli(2*a - 1, x)*besselj(2*a, x)), x**2*besseli(2*a, x)*besselj(2*a, x), x**3*(besseli(2*a, x)*besselj(2*a - 1, x) + besseli(2*a - 1, x)*besselj(2*a, x))]), Matrix([[1, 0, 0, 0]]), Matrix([[0, Rational(1, 4), 0, 0], [0, (1 - 2*a)/2, Rational(-1, 2), 0], [0, 0, 1 - 2*a, Rational(1, 4)], [-32*z, 0, 0, 1 - a]])) # 1F2 addb([a], [a - S.Half, 2*a], Matrix([z**(S.Half - a)*besseli(a - S.Half, sqrt(z))**2, z**(1 - a)*besseli(a - S.Half, sqrt(z)) *besseli(a - Rational(3, 2), sqrt(z)), z**(Rational(3, 2) - a)*besseli(a - Rational(3, 2), sqrt(z))**2]), Matrix([[-gamma(a + S.Half)**2/4**(S.Half - a), 2*gamma(a - S.Half)*gamma(a + S.Half)/4**(1 - a), 0]]), Matrix([[1 - 2*a, 1, 0], [z/2, S.Half - a, S.Half], [0, z, 0]])) addb([S.Half], [b, 2 - b], pi*(1 - b)/sin(pi*b)* Matrix([besseli(1 - b, sqrt(z))*besseli(b - 1, sqrt(z)), sqrt(z)*(besseli(-b, sqrt(z))*besseli(b - 1, sqrt(z)) + besseli(1 - b, sqrt(z))*besseli(b, sqrt(z))), besseli(-b, sqrt(z))*besseli(b, sqrt(z))]), Matrix([[1, 0, 0]]), Matrix([[b - 1, S.Half, 0], [z, 0, z], [0, S.Half, -b]])) addb([S.Half], [Rational(3, 2), Rational(3, 2)], Matrix([Shi(2*sqrt(z))/2/sqrt(z), sinh(2*sqrt(z))/2/sqrt(z), cosh(2*sqrt(z))]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 2), S.Half, 0], [0, Rational(-1, 2), S.Half], [0, 2*z, 0]])) # FresnelS # Basic rule #add([Rational(3, 4)], [Rational(3, 2),Rational(7, 4)], 6*fresnels( exp(pi*I/4)*root(z,4)*2/sqrt(pi) ) / ( pi * (exp(pi*I/4)*root(z,4)*2/sqrt(pi))**3 ) ) # Manually tuned rule addb([Rational(3, 4)], [Rational(3, 2), Rational(7, 4)], Matrix( [ fresnels( exp( pi*I/4)*root( z, 4)*2/sqrt( pi) ) / ( pi * (exp(pi*I/4)*root(z, 4)*2/sqrt(pi))**3 ), sinh(2*sqrt(z))/sqrt(z), cosh(2*sqrt(z)) ]), Matrix([[6, 0, 0]]), Matrix([[Rational(-3, 4), Rational(1, 16), 0], [ 0, Rational(-1, 2), 1], [ 0, z, 0]])) # FresnelC # Basic rule #add([Rational(1, 4)], [S.Half,Rational(5, 4)], fresnelc( exp(pi*I/4)*root(z,4)*2/sqrt(pi) ) / ( exp(pi*I/4)*root(z,4)*2/sqrt(pi) ) ) # Manually tuned rule addb([Rational(1, 4)], [S.Half, Rational(5, 4)], Matrix( [ sqrt( pi)*exp( -I*pi/4)*fresnelc( 2*root(z, 4)*exp(I*pi/4)/sqrt(pi))/(2*root(z, 4)), cosh(2*sqrt(z)), sinh(2*sqrt(z))*sqrt(z) ]), Matrix([[1, 0, 0]]), Matrix([[Rational(-1, 4), Rational(1, 4), 0 ], [ 0, 0, 1 ], [ 0, z, S.Half]])) # 2F3 # XXX with this five-parameter formula is pretty slow with the current # Formula.find_instantiations (creates 2!*3!*3**(2+3) ~ 3000 # instantiations ... But it's not too bad. addb([a, a + S.Half], [2*a, b, 2*a - b + 1], gamma(b)*gamma(2*a - b + 1) * (sqrt(z)/2)**(1 - 2*a) * Matrix([besseli(b - 1, sqrt(z))*besseli(2*a - b, sqrt(z)), sqrt(z)*besseli(b, sqrt(z))*besseli(2*a - b, sqrt(z)), sqrt(z)*besseli(b - 1, sqrt(z))*besseli(2*a - b + 1, sqrt(z)), besseli(b, sqrt(z))*besseli(2*a - b + 1, sqrt(z))]), Matrix([[1, 0, 0, 0]]), Matrix([[0, S.Half, S.Half, 0], [z/2, 1 - b, 0, z/2], [z/2, 0, b - 2*a, z/2], [0, S.Half, S.Half, -2*a]])) # (C/f above comment about eulergamma in the basis). addb([1, 1], [2, 2, Rational(3, 2)], Matrix([Chi(2*sqrt(z)) - log(2*sqrt(z)), cosh(2*sqrt(z)), sqrt(z)*sinh(2*sqrt(z)), 1, EulerGamma]), Matrix([[1/z, 0, 0, 0, -1/z]]), Matrix([[0, S.Half, 0, Rational(-1, 2), 0], [0, 0, 1, 0, 0], [0, z, S.Half, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]])) # 3F3 # This is rule: http://functions.wolfram.com/07.31.03.0134.01 # Initial reason to add it was a nice solution for # integrate(erf(a*z)/z**2, z) and same for erfc and erfi. # Basic rule # add([1, 1, a], [2, 2, a+1], (a/(z*(a-1)**2)) * # (1 - (-z)**(1-a) * (gamma(a) - uppergamma(a,-z)) # - (a-1) * (EulerGamma + uppergamma(0,-z) + log(-z)) # - exp(z))) # Manually tuned rule addb([1, 1, a], [2, 2, a+1], Matrix([a*(log(-z) + expint(1, -z) + EulerGamma)/(z*(a**2 - 2*a + 1)), a*(-z)**(-a)*(gamma(a) - uppergamma(a, -z))/(a - 1)**2, a*exp(z)/(a**2 - 2*a + 1), a/(z*(a**2 - 2*a + 1))]), Matrix([[1-a, 1, -1/z, 1]]), Matrix([[-1,0,-1/z,1], [0,-a,1,0], [0,0,z,0], [0,0,0,-1]])) def add_meijerg_formulae(formulae): from sympy.matrices import Matrix a, b, c, z = list(map(Dummy, 'abcz')) rho = Dummy('rho') def add(an, ap, bm, bq, B, C, M, matcher): formulae.append(MeijerFormula(an, ap, bm, bq, z, [a, b, c, rho], B, C, M, matcher)) def detect_uppergamma(func): x = func.an[0] y, z = func.bm swapped = False if not _mod1((x - y).simplify()): swapped = True (y, z) = (z, y) if _mod1((x - z).simplify()) or x - z > 0: return None l = [y, x] if swapped: l = [x, y] return {rho: y, a: x - y}, G_Function([x], [], l, []) add([a + rho], [], [rho, a + rho], [], Matrix([gamma(1 - a)*z**rho*exp(z)*uppergamma(a, z), gamma(1 - a)*z**(a + rho)]), Matrix([[1, 0]]), Matrix([[rho + z, -1], [0, a + rho]]), detect_uppergamma) def detect_3113(func): """http://functions.wolfram.com/07.34.03.0984.01""" x = func.an[0] u, v, w = func.bm if _mod1((u - v).simplify()) == 0: if _mod1((v - w).simplify()) == 0: return sig = (S.Half, S.Half, S.Zero) x1, x2, y = u, v, w else: if _mod1((x - u).simplify()) == 0: sig = (S.Half, S.Zero, S.Half) x1, y, x2 = u, v, w else: sig = (S.Zero, S.Half, S.Half) y, x1, x2 = u, v, w if (_mod1((x - x1).simplify()) != 0 or _mod1((x - x2).simplify()) != 0 or _mod1((x - y).simplify()) != S.Half or x - x1 > 0 or x - x2 > 0): return return {a: x}, G_Function([x], [], [x - S.Half + t for t in sig], []) s = sin(2*sqrt(z)) c_ = cos(2*sqrt(z)) S_ = Si(2*sqrt(z)) - pi/2 C = Ci(2*sqrt(z)) add([a], [], [a, a, a - S.Half], [], Matrix([sqrt(pi)*z**(a - S.Half)*(c_*S_ - s*C), sqrt(pi)*z**a*(s*S_ + c_*C), sqrt(pi)*z**a]), Matrix([[-2, 0, 0]]), Matrix([[a - S.Half, -1, 0], [z, a, S.Half], [0, 0, a]]), detect_3113) def make_simp(z): """ Create a function that simplifies rational functions in ``z``. """ def simp(expr): """ Efficiently simplify the rational function ``expr``. """ numer, denom = expr.as_numer_denom() numer = numer.expand() # denom = denom.expand() # is this needed? c, numer, denom = poly(numer, z).cancel(poly(denom, z)) return c * numer.as_expr() / denom.as_expr() return simp def debug(*args): if SYMPY_DEBUG: for a in args: print(a, end="") print() class Hyper_Function(Expr): """ A generalized hypergeometric function. """ def __new__(cls, ap, bq): obj = super().__new__(cls) obj.ap = Tuple(*list(map(expand, ap))) obj.bq = Tuple(*list(map(expand, bq))) return obj @property def args(self): return (self.ap, self.bq) @property def sizes(self): return (len(self.ap), len(self.bq)) @property def gamma(self): """ Number of upper parameters that are negative integers This is a transformation invariant. """ return sum(bool(x.is_integer and x.is_negative) for x in self.ap) def _hashable_content(self): return super()._hashable_content() + (self.ap, self.bq) def __call__(self, arg): return hyper(self.ap, self.bq, arg) def build_invariants(self): """ Compute the invariant vector. Explanation =========== The invariant vector is: (gamma, ((s1, n1), ..., (sk, nk)), ((t1, m1), ..., (tr, mr))) where gamma is the number of integer a < 0, s1 < ... < sk nl is the number of parameters a_i congruent to sl mod 1 t1 < ... < tr ml is the number of parameters b_i congruent to tl mod 1 If the index pair contains parameters, then this is not truly an invariant, since the parameters cannot be sorted uniquely mod1. Examples ======== >>> from sympy.simplify.hyperexpand import Hyper_Function >>> from sympy import S >>> ap = (S.Half, S.One/3, S(-1)/2, -2) >>> bq = (1, 2) Here gamma = 1, k = 3, s1 = 0, s2 = 1/3, s3 = 1/2 n1 = 1, n2 = 1, n2 = 2 r = 1, t1 = 0 m1 = 2: >>> Hyper_Function(ap, bq).build_invariants() (1, ((0, 1), (1/3, 1), (1/2, 2)), ((0, 2),)) """ abuckets, bbuckets = sift(self.ap, _mod1), sift(self.bq, _mod1) def tr(bucket): bucket = list(bucket.items()) if not any(isinstance(x[0], Mod) for x in bucket): bucket.sort(key=lambda x: default_sort_key(x[0])) bucket = tuple([(mod, len(values)) for mod, values in bucket if values]) return bucket return (self.gamma, tr(abuckets), tr(bbuckets)) def difficulty(self, func): """ Estimate how many steps it takes to reach ``func`` from self. Return -1 if impossible. """ if self.gamma != func.gamma: return -1 oabuckets, obbuckets, abuckets, bbuckets = [sift(params, _mod1) for params in (self.ap, self.bq, func.ap, func.bq)] diff = 0 for bucket, obucket in [(abuckets, oabuckets), (bbuckets, obbuckets)]: for mod in set(list(bucket.keys()) + list(obucket.keys())): if (not mod in bucket) or (not mod in obucket) \ or len(bucket[mod]) != len(obucket[mod]): return -1 l1 = list(bucket[mod]) l2 = list(obucket[mod]) l1.sort() l2.sort() for i, j in zip(l1, l2): diff += abs(i - j) return diff def _is_suitable_origin(self): """ Decide if ``self`` is a suitable origin. Explanation =========== A function is a suitable origin iff: * none of the ai equals bj + n, with n a non-negative integer * none of the ai is zero * none of the bj is a non-positive integer Note that this gives meaningful results only when none of the indices are symbolic. """ for a in self.ap: for b in self.bq: if (a - b).is_integer and (a - b).is_negative is False: return False for a in self.ap: if a == 0: return False for b in self.bq: if b.is_integer and b.is_nonpositive: return False return True class G_Function(Expr): """ A Meijer G-function. """ def __new__(cls, an, ap, bm, bq): obj = super().__new__(cls) obj.an = Tuple(*list(map(expand, an))) obj.ap = Tuple(*list(map(expand, ap))) obj.bm = Tuple(*list(map(expand, bm))) obj.bq = Tuple(*list(map(expand, bq))) return obj @property def args(self): return (self.an, self.ap, self.bm, self.bq) def _hashable_content(self): return super()._hashable_content() + self.args def __call__(self, z): return meijerg(self.an, self.ap, self.bm, self.bq, z) def compute_buckets(self): """ Compute buckets for the fours sets of parameters. Explanation =========== We guarantee that any two equal Mod objects returned are actually the same, and that the buckets are sorted by real part (an and bq descendending, bm and ap ascending). Examples ======== >>> from sympy.simplify.hyperexpand import G_Function >>> from sympy.abc import y >>> from sympy import S >>> a, b = [1, 3, 2, S(3)/2], [1 + y, y, 2, y + 3] >>> G_Function(a, b, [2], [y]).compute_buckets() ({0: [3, 2, 1], 1/2: [3/2]}, {0: [2], y: [y, y + 1, y + 3]}, {0: [2]}, {y: [y]}) """ dicts = pan, pap, pbm, pbq = [defaultdict(list) for i in range(4)] for dic, lis in zip(dicts, (self.an, self.ap, self.bm, self.bq)): for x in lis: dic[_mod1(x)].append(x) for dic, flip in zip(dicts, (True, False, False, True)): for m, items in dic.items(): x0 = items[0] items.sort(key=lambda x: x - x0, reverse=flip) dic[m] = items return tuple([dict(w) for w in dicts]) @property def signature(self): return (len(self.an), len(self.ap), len(self.bm), len(self.bq)) # Dummy variable. _x = Dummy('x') class Formula: """ This class represents hypergeometric formulae. Explanation =========== Its data members are: - z, the argument - closed_form, the closed form expression - symbols, the free symbols (parameters) in the formula - func, the function - B, C, M (see _compute_basis) Examples ======== >>> from sympy.abc import a, b, z >>> from sympy.simplify.hyperexpand import Formula, Hyper_Function >>> func = Hyper_Function((a/2, a/3 + b, (1+a)/2), (a, b, (a+b)/7)) >>> f = Formula(func, z, None, [a, b]) """ def _compute_basis(self, closed_form): """ Compute a set of functions B=(f1, ..., fn), a nxn matrix M and a 1xn matrix C such that: closed_form = C B z d/dz B = M B. """ from sympy.matrices import Matrix, eye, zeros afactors = [_x + a for a in self.func.ap] bfactors = [_x + b - 1 for b in self.func.bq] expr = _x*Mul(*bfactors) - self.z*Mul(*afactors) poly = Poly(expr, _x) n = poly.degree() - 1 b = [closed_form] for _ in range(n): b.append(self.z*b[-1].diff(self.z)) self.B = Matrix(b) self.C = Matrix([[1] + [0]*n]) m = eye(n) m = m.col_insert(0, zeros(n, 1)) l = poly.all_coeffs()[1:] l.reverse() self.M = m.row_insert(n, -Matrix([l])/poly.all_coeffs()[0]) def __init__(self, func, z, res, symbols, B=None, C=None, M=None): z = sympify(z) res = sympify(res) symbols = [x for x in sympify(symbols) if func.has(x)] self.z = z self.symbols = symbols self.B = B self.C = C self.M = M self.func = func # TODO with symbolic parameters, it could be advantageous # (for prettier answers) to compute a basis only *after* # instantiation if res is not None: self._compute_basis(res) @property def closed_form(self): return reduce(lambda s,m: s+m[0]*m[1], zip(self.C, self.B), S.Zero) def find_instantiations(self, func): """ Find substitutions of the free symbols that match ``func``. Return the substitution dictionaries as a list. Note that the returned instantiations need not actually match, or be valid! """ from sympy.solvers import solve ap = func.ap bq = func.bq if len(ap) != len(self.func.ap) or len(bq) != len(self.func.bq): raise TypeError('Cannot instantiate other number of parameters') symbol_values = [] for a in self.symbols: if a in self.func.ap.args: symbol_values.append(ap) elif a in self.func.bq.args: symbol_values.append(bq) else: raise ValueError("At least one of the parameters of the " "formula must be equal to %s" % (a,)) base_repl = [dict(list(zip(self.symbols, values))) for values in product(*symbol_values)] abuckets, bbuckets = [sift(params, _mod1) for params in [ap, bq]] a_inv, b_inv = [{a: len(vals) for a, vals in bucket.items()} for bucket in [abuckets, bbuckets]] critical_values = [[0] for _ in self.symbols] result = [] _n = Dummy() for repl in base_repl: symb_a, symb_b = [sift(params, lambda x: _mod1(x.xreplace(repl))) for params in [self.func.ap, self.func.bq]] for bucket, obucket in [(abuckets, symb_a), (bbuckets, symb_b)]: for mod in set(list(bucket.keys()) + list(obucket.keys())): if (not mod in bucket) or (not mod in obucket) \ or len(bucket[mod]) != len(obucket[mod]): break for a, vals in zip(self.symbols, critical_values): if repl[a].free_symbols: continue exprs = [expr for expr in obucket[mod] if expr.has(a)] repl0 = repl.copy() repl0[a] += _n for expr in exprs: for target in bucket[mod]: n0, = solve(expr.xreplace(repl0) - target, _n) if n0.free_symbols: raise ValueError("Value should not be true") vals.append(n0) else: values = [] for a, vals in zip(self.symbols, critical_values): a0 = repl[a] min_ = floor(min(vals)) max_ = ceiling(max(vals)) values.append([a0 + n for n in range(min_, max_ + 1)]) result.extend(dict(list(zip(self.symbols, l))) for l in product(*values)) return result class FormulaCollection: """ A collection of formulae to use as origins. """ def __init__(self): """ Doing this globally at module init time is a pain ... """ self.symbolic_formulae = {} self.concrete_formulae = {} self.formulae = [] add_formulae(self.formulae) # Now process the formulae into a helpful form. # These dicts are indexed by (p, q). for f in self.formulae: sizes = f.func.sizes if len(f.symbols) > 0: self.symbolic_formulae.setdefault(sizes, []).append(f) else: inv = f.func.build_invariants() self.concrete_formulae.setdefault(sizes, {})[inv] = f def lookup_origin(self, func): """ Given the suitable target ``func``, try to find an origin in our knowledge base. Examples ======== >>> from sympy.simplify.hyperexpand import (FormulaCollection, ... Hyper_Function) >>> f = FormulaCollection() >>> f.lookup_origin(Hyper_Function((), ())).closed_form exp(_z) >>> f.lookup_origin(Hyper_Function([1], ())).closed_form HyperRep_power1(-1, _z) >>> from sympy import S >>> i = Hyper_Function([S('1/4'), S('3/4 + 4')], [S.Half]) >>> f.lookup_origin(i).closed_form HyperRep_sqrts1(-1/4, _z) """ inv = func.build_invariants() sizes = func.sizes if sizes in self.concrete_formulae and \ inv in self.concrete_formulae[sizes]: return self.concrete_formulae[sizes][inv] # We don't have a concrete formula. Try to instantiate. if not sizes in self.symbolic_formulae: return None # Too bad... possible = [] for f in self.symbolic_formulae[sizes]: repls = f.find_instantiations(func) for repl in repls: func2 = f.func.xreplace(repl) if not func2._is_suitable_origin(): continue diff = func2.difficulty(func) if diff == -1: continue possible.append((diff, repl, f, func2)) # find the nearest origin possible.sort(key=lambda x: x[0]) for _, repl, f, func2 in possible: f2 = Formula(func2, f.z, None, [], f.B.subs(repl), f.C.subs(repl), f.M.subs(repl)) if not any(e.has(S.NaN, oo, -oo, zoo) for e in [f2.B, f2.M, f2.C]): return f2 return None class MeijerFormula: """ This class represents a Meijer G-function formula. Its data members are: - z, the argument - symbols, the free symbols (parameters) in the formula - func, the function - B, C, M (c/f ordinary Formula) """ def __init__(self, an, ap, bm, bq, z, symbols, B, C, M, matcher): an, ap, bm, bq = [Tuple(*list(map(expand, w))) for w in [an, ap, bm, bq]] self.func = G_Function(an, ap, bm, bq) self.z = z self.symbols = symbols self._matcher = matcher self.B = B self.C = C self.M = M @property def closed_form(self): return reduce(lambda s,m: s+m[0]*m[1], zip(self.C, self.B), S.Zero) def try_instantiate(self, func): """ Try to instantiate the current formula to (almost) match func. This uses the _matcher passed on init. """ if func.signature != self.func.signature: return None res = self._matcher(func) if res is not None: subs, newfunc = res return MeijerFormula(newfunc.an, newfunc.ap, newfunc.bm, newfunc.bq, self.z, [], self.B.subs(subs), self.C.subs(subs), self.M.subs(subs), None) class MeijerFormulaCollection: """ This class holds a collection of meijer g formulae. """ def __init__(self): formulae = [] add_meijerg_formulae(formulae) self.formulae = defaultdict(list) for formula in formulae: self.formulae[formula.func.signature].append(formula) self.formulae = dict(self.formulae) def lookup_origin(self, func): """ Try to find a formula that matches func. """ if not func.signature in self.formulae: return None for formula in self.formulae[func.signature]: res = formula.try_instantiate(func) if res is not None: return res class Operator: """ Base class for operators to be applied to our functions. Explanation =========== These operators are differential operators. They are by convention expressed in the variable D = z*d/dz (although this base class does not actually care). Note that when the operator is applied to an object, we typically do *not* blindly differentiate but instead use a different representation of the z*d/dz operator (see make_derivative_operator). To subclass from this, define a __init__ method that initializes a self._poly variable. This variable stores a polynomial. By convention the generator is z*d/dz, and acts to the right of all coefficients. Thus this poly x**2 + 2*z*x + 1 represents the differential operator (z*d/dz)**2 + 2*z**2*d/dz. This class is used only in the implementation of the hypergeometric function expansion algorithm. """ def apply(self, obj, op): """ Apply ``self`` to the object ``obj``, where the generator is ``op``. Examples ======== >>> from sympy.simplify.hyperexpand import Operator >>> from sympy.polys.polytools import Poly >>> from sympy.abc import x, y, z >>> op = Operator() >>> op._poly = Poly(x**2 + z*x + y, x) >>> op.apply(z**7, lambda f: f.diff(z)) y*z**7 + 7*z**7 + 42*z**5 """ coeffs = self._poly.all_coeffs() coeffs.reverse() diffs = [obj] for c in coeffs[1:]: diffs.append(op(diffs[-1])) r = coeffs[0]*diffs[0] for c, d in zip(coeffs[1:], diffs[1:]): r += c*d return r class MultOperator(Operator): """ Simply multiply by a "constant" """ def __init__(self, p): self._poly = Poly(p, _x) class ShiftA(Operator): """ Increment an upper index. """ def __init__(self, ai): ai = sympify(ai) if ai == 0: raise ValueError('Cannot increment zero upper index.') self._poly = Poly(_x/ai + 1, _x) def __str__(self): return '<Increment upper %s.>' % (1/self._poly.all_coeffs()[0]) class ShiftB(Operator): """ Decrement a lower index. """ def __init__(self, bi): bi = sympify(bi) if bi == 1: raise ValueError('Cannot decrement unit lower index.') self._poly = Poly(_x/(bi - 1) + 1, _x) def __str__(self): return '<Decrement lower %s.>' % (1/self._poly.all_coeffs()[0] + 1) class UnShiftA(Operator): """ Decrement an upper index. """ def __init__(self, ap, bq, i, z): """ Note: i counts from zero! """ ap, bq, i = list(map(sympify, [ap, bq, i])) self._ap = ap self._bq = bq self._i = i ap = list(ap) bq = list(bq) ai = ap.pop(i) - 1 if ai == 0: raise ValueError('Cannot decrement unit upper index.') m = Poly(z*ai, _x) for a in ap: m *= Poly(_x + a, _x) A = Dummy('A') n = D = Poly(ai*A - ai, A) for b in bq: n *= D + (b - 1).as_poly(A) b0 = -n.nth(0) if b0 == 0: raise ValueError('Cannot decrement upper index: ' 'cancels with lower') n = Poly(Poly(n.all_coeffs()[:-1], A).as_expr().subs(A, _x/ai + 1), _x) self._poly = Poly((n - m)/b0, _x) def __str__(self): return '<Decrement upper index #%s of %s, %s.>' % (self._i, self._ap, self._bq) class UnShiftB(Operator): """ Increment a lower index. """ def __init__(self, ap, bq, i, z): """ Note: i counts from zero! """ ap, bq, i = list(map(sympify, [ap, bq, i])) self._ap = ap self._bq = bq self._i = i ap = list(ap) bq = list(bq) bi = bq.pop(i) + 1 if bi == 0: raise ValueError('Cannot increment -1 lower index.') m = Poly(_x*(bi - 1), _x) for b in bq: m *= Poly(_x + b - 1, _x) B = Dummy('B') D = Poly((bi - 1)*B - bi + 1, B) n = Poly(z, B) for a in ap: n *= (D + a.as_poly(B)) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment index: cancels with upper') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, _x/(bi - 1) + 1), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment lower index #%s of %s, %s.>' % (self._i, self._ap, self._bq) class MeijerShiftA(Operator): """ Increment an upper b index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(bi - _x, _x) def __str__(self): return '<Increment upper b=%s.>' % (self._poly.all_coeffs()[1]) class MeijerShiftB(Operator): """ Decrement an upper a index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(1 - bi + _x, _x) def __str__(self): return '<Decrement upper a=%s.>' % (1 - self._poly.all_coeffs()[1]) class MeijerShiftC(Operator): """ Increment a lower b index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(-bi + _x, _x) def __str__(self): return '<Increment lower b=%s.>' % (-self._poly.all_coeffs()[1]) class MeijerShiftD(Operator): """ Decrement a lower a index. """ def __init__(self, bi): bi = sympify(bi) self._poly = Poly(bi - 1 - _x, _x) def __str__(self): return '<Decrement lower a=%s.>' % (self._poly.all_coeffs()[1] + 1) class MeijerUnShiftA(Operator): """ Decrement an upper b index. """ def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) bi = bm.pop(i) - 1 m = Poly(1, _x) for b in bm: m *= Poly(b - _x, _x) for b in bq: m *= Poly(_x - b, _x) A = Dummy('A') D = Poly(bi - A, A) n = Poly(z, A) for a in an: n *= (D + 1 - a) for a in ap: n *= (-D + a - 1) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot decrement upper b index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], A).as_expr().subs(A, bi - _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Decrement upper b index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftB(Operator): """ Increment an upper a index. """ def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) ai = an.pop(i) + 1 m = Poly(z, _x) for a in an: m *= Poly(1 - a + _x, _x) for a in ap: m *= Poly(a - 1 - _x, _x) B = Dummy('B') D = Poly(B + ai - 1, B) n = Poly(1, B) for b in bm: n *= (-D + b) for b in bq: n *= (D - b) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment upper a index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, 1 - ai + _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment upper a index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftC(Operator): """ Decrement a lower b index. """ # XXX this is "essentially" the same as MeijerUnShiftA. This "essentially" # can be made rigorous using the functional equation G(1/z) = G'(z), # where G' denotes a G function of slightly altered parameters. # However, sorting out the details seems harder than just coding it # again. def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) bi = bq.pop(i) - 1 m = Poly(1, _x) for b in bm: m *= Poly(b - _x, _x) for b in bq: m *= Poly(_x - b, _x) C = Dummy('C') D = Poly(bi + C, C) n = Poly(z, C) for a in an: n *= (D + 1 - a) for a in ap: n *= (-D + a - 1) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot decrement lower b index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], C).as_expr().subs(C, _x - bi), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Decrement lower b index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class MeijerUnShiftD(Operator): """ Increment a lower a index. """ # XXX This is essentially the same as MeijerUnShiftA. # See comment at MeijerUnShiftC. def __init__(self, an, ap, bm, bq, i, z): """ Note: i counts from zero! """ an, ap, bm, bq, i = list(map(sympify, [an, ap, bm, bq, i])) self._an = an self._ap = ap self._bm = bm self._bq = bq self._i = i an = list(an) ap = list(ap) bm = list(bm) bq = list(bq) ai = ap.pop(i) + 1 m = Poly(z, _x) for a in an: m *= Poly(1 - a + _x, _x) for a in ap: m *= Poly(a - 1 - _x, _x) B = Dummy('B') # - this is the shift operator `D_I` D = Poly(ai - 1 - B, B) n = Poly(1, B) for b in bm: n *= (-D + b) for b in bq: n *= (D - b) b0 = n.nth(0) if b0 == 0: raise ValueError('Cannot increment lower a index (cancels)') n = Poly(Poly(n.all_coeffs()[:-1], B).as_expr().subs( B, ai - 1 - _x), _x) self._poly = Poly((m - n)/b0, _x) def __str__(self): return '<Increment lower a index #%s of %s, %s, %s, %s.>' % (self._i, self._an, self._ap, self._bm, self._bq) class ReduceOrder(Operator): """ Reduce Order by cancelling an upper and a lower index. """ def __new__(cls, ai, bj): """ For convenience if reduction is not possible, return None. """ ai = sympify(ai) bj = sympify(bj) n = ai - bj if not n.is_Integer or n < 0: return None if bj.is_integer and bj.is_nonpositive: return None expr = Operator.__new__(cls) p = S.One for k in range(n): p *= (_x + bj + k)/(bj + k) expr._poly = Poly(p, _x) expr._a = ai expr._b = bj return expr @classmethod def _meijer(cls, b, a, sign): """ Cancel b + sign*s and a + sign*s This is for meijer G functions. """ b = sympify(b) a = sympify(a) n = b - a if n.is_negative or not n.is_Integer: return None expr = Operator.__new__(cls) p = S.One for k in range(n): p *= (sign*_x + a + k) expr._poly = Poly(p, _x) if sign == -1: expr._a = b expr._b = a else: expr._b = Add(1, a - 1, evaluate=False) expr._a = Add(1, b - 1, evaluate=False) return expr @classmethod def meijer_minus(cls, b, a): return cls._meijer(b, a, -1) @classmethod def meijer_plus(cls, a, b): return cls._meijer(1 - a, 1 - b, 1) def __str__(self): return '<Reduce order by cancelling upper %s with lower %s.>' % \ (self._a, self._b) def _reduce_order(ap, bq, gen, key): """ Order reduction algorithm used in Hypergeometric and Meijer G """ ap = list(ap) bq = list(bq) ap.sort(key=key) bq.sort(key=key) nap = [] # we will edit bq in place operators = [] for a in ap: op = None for i in range(len(bq)): op = gen(a, bq[i]) if op is not None: bq.pop(i) break if op is None: nap.append(a) else: operators.append(op) return nap, bq, operators def reduce_order(func): """ Given the hypergeometric function ``func``, find a sequence of operators to reduces order as much as possible. Explanation =========== Return (newfunc, [operators]), where applying the operators to the hypergeometric function newfunc yields func. Examples ======== >>> from sympy.simplify.hyperexpand import reduce_order, Hyper_Function >>> reduce_order(Hyper_Function((1, 2), (3, 4))) (Hyper_Function((1, 2), (3, 4)), []) >>> reduce_order(Hyper_Function((1,), (1,))) (Hyper_Function((), ()), [<Reduce order by cancelling upper 1 with lower 1.>]) >>> reduce_order(Hyper_Function((2, 4), (3, 3))) (Hyper_Function((2,), (3,)), [<Reduce order by cancelling upper 4 with lower 3.>]) """ nap, nbq, operators = _reduce_order(func.ap, func.bq, ReduceOrder, default_sort_key) return Hyper_Function(Tuple(*nap), Tuple(*nbq)), operators def reduce_order_meijer(func): """ Given the Meijer G function parameters, ``func``, find a sequence of operators that reduces order as much as possible. Return newfunc, [operators]. Examples ======== >>> from sympy.simplify.hyperexpand import (reduce_order_meijer, ... G_Function) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [3, 4], [1, 2]))[0] G_Function((4, 3), (5, 6), (3, 4), (2, 1)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [3, 4], [1, 8]))[0] G_Function((3,), (5, 6), (3, 4), (1,)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [7, 5], [1, 5]))[0] G_Function((3,), (), (), (1,)) >>> reduce_order_meijer(G_Function([3, 4], [5, 6], [7, 5], [5, 3]))[0] G_Function((), (), (), ()) """ nan, nbq, ops1 = _reduce_order(func.an, func.bq, ReduceOrder.meijer_plus, lambda x: default_sort_key(-x)) nbm, nap, ops2 = _reduce_order(func.bm, func.ap, ReduceOrder.meijer_minus, default_sort_key) return G_Function(nan, nap, nbm, nbq), ops1 + ops2 def make_derivative_operator(M, z): """ Create a derivative operator, to be passed to Operator.apply. """ def doit(C): r = z*C.diff(z) + C*M r = r.applyfunc(make_simp(z)) return r return doit def apply_operators(obj, ops, op): """ Apply the list of operators ``ops`` to object ``obj``, substituting ``op`` for the generator. """ res = obj for o in reversed(ops): res = o.apply(res, op) return res def devise_plan(target, origin, z): """ Devise a plan (consisting of shift and un-shift operators) to be applied to the hypergeometric function ``target`` to yield ``origin``. Returns a list of operators. Examples ======== >>> from sympy.simplify.hyperexpand import devise_plan, Hyper_Function >>> from sympy.abc import z Nothing to do: >>> devise_plan(Hyper_Function((1, 2), ()), Hyper_Function((1, 2), ()), z) [] >>> devise_plan(Hyper_Function((), (1, 2)), Hyper_Function((), (1, 2)), z) [] Very simple plans: >>> devise_plan(Hyper_Function((2,), ()), Hyper_Function((1,), ()), z) [<Increment upper 1.>] >>> devise_plan(Hyper_Function((), (2,)), Hyper_Function((), (1,)), z) [<Increment lower index #0 of [], [1].>] Several buckets: >>> from sympy import S >>> devise_plan(Hyper_Function((1, S.Half), ()), ... Hyper_Function((2, S('3/2')), ()), z) #doctest: +NORMALIZE_WHITESPACE [<Decrement upper index #0 of [3/2, 1], [].>, <Decrement upper index #0 of [2, 3/2], [].>] A slightly more complicated plan: >>> devise_plan(Hyper_Function((1, 3), ()), Hyper_Function((2, 2), ()), z) [<Increment upper 2.>, <Decrement upper index #0 of [2, 2], [].>] Another more complicated plan: (note that the ap have to be shifted first!) >>> devise_plan(Hyper_Function((1, -1), (2,)), Hyper_Function((3, -2), (4,)), z) [<Decrement lower 3.>, <Decrement lower 4.>, <Decrement upper index #1 of [-1, 2], [4].>, <Decrement upper index #1 of [-1, 3], [4].>, <Increment upper -2.>] """ abuckets, bbuckets, nabuckets, nbbuckets = [sift(params, _mod1) for params in (target.ap, target.bq, origin.ap, origin.bq)] if len(list(abuckets.keys())) != len(list(nabuckets.keys())) or \ len(list(bbuckets.keys())) != len(list(nbbuckets.keys())): raise ValueError('%s not reachable from %s' % (target, origin)) ops = [] def do_shifts(fro, to, inc, dec): ops = [] for i in range(len(fro)): if to[i] - fro[i] > 0: sh = inc ch = 1 else: sh = dec ch = -1 while to[i] != fro[i]: ops += [sh(fro, i)] fro[i] += ch return ops def do_shifts_a(nal, nbk, al, aother, bother): """ Shift us from (nal, nbk) to (al, nbk). """ return do_shifts(nal, al, lambda p, i: ShiftA(p[i]), lambda p, i: UnShiftA(p + aother, nbk + bother, i, z)) def do_shifts_b(nal, nbk, bk, aother, bother): """ Shift us from (nal, nbk) to (nal, bk). """ return do_shifts(nbk, bk, lambda p, i: UnShiftB(nal + aother, p + bother, i, z), lambda p, i: ShiftB(p[i])) for r in sorted(list(abuckets.keys()) + list(bbuckets.keys()), key=default_sort_key): al = () nal = () bk = () nbk = () if r in abuckets: al = abuckets[r] nal = nabuckets[r] if r in bbuckets: bk = bbuckets[r] nbk = nbbuckets[r] if len(al) != len(nal) or len(bk) != len(nbk): raise ValueError('%s not reachable from %s' % (target, origin)) al, nal, bk, nbk = [sorted(list(w), key=default_sort_key) for w in [al, nal, bk, nbk]] def others(dic, key): l = [] for k, value in dic.items(): if k != key: l += list(dic[k]) return l aother = others(nabuckets, r) bother = others(nbbuckets, r) if len(al) == 0: # there can be no complications, just shift the bs as we please ops += do_shifts_b([], nbk, bk, aother, bother) elif len(bk) == 0: # there can be no complications, just shift the as as we please ops += do_shifts_a(nal, [], al, aother, bother) else: namax = nal[-1] amax = al[-1] if nbk[0] - namax <= 0 or bk[0] - amax <= 0: raise ValueError('Non-suitable parameters.') if namax - amax > 0: # we are going to shift down - first do the as, then the bs ops += do_shifts_a(nal, nbk, al, aother, bother) ops += do_shifts_b(al, nbk, bk, aother, bother) else: # we are going to shift up - first do the bs, then the as ops += do_shifts_b(nal, nbk, bk, aother, bother) ops += do_shifts_a(nal, bk, al, aother, bother) nabuckets[r] = al nbbuckets[r] = bk ops.reverse() return ops def try_shifted_sum(func, z): """ Try to recognise a hypergeometric sum that starts from k > 0. """ abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) if len(abuckets[S.Zero]) != 1: return None r = abuckets[S.Zero][0] if r <= 0: return None if not S.Zero in bbuckets: return None l = list(bbuckets[S.Zero]) l.sort() k = l[0] if k <= 0: return None nap = list(func.ap) nap.remove(r) nbq = list(func.bq) nbq.remove(k) k -= 1 nap = [x - k for x in nap] nbq = [x - k for x in nbq] ops = [] for n in range(r - 1): ops.append(ShiftA(n + 1)) ops.reverse() fac = factorial(k)/z**k for a in nap: fac /= rf(a, k) for b in nbq: fac *= rf(b, k) ops += [MultOperator(fac)] p = 0 for n in range(k): m = z**n/factorial(n) for a in nap: m *= rf(a, n) for b in nbq: m /= rf(b, n) p += m return Hyper_Function(nap, nbq), ops, -p def try_polynomial(func, z): """ Recognise polynomial cases. Returns None if not such a case. Requires order to be fully reduced. """ abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) a0 = abuckets[S.Zero] b0 = bbuckets[S.Zero] a0.sort() b0.sort() al0 = [x for x in a0 if x <= 0] bl0 = [x for x in b0 if x <= 0] if bl0 and all(a < bl0[-1] for a in al0): return oo if not al0: return None a = al0[-1] fac = 1 res = S.One for n in Tuple(*list(range(-a))): fac *= z fac /= n + 1 for a in func.ap: fac *= a + n for b in func.bq: fac /= b + n res += fac return res def try_lerchphi(func): """ Try to find an expression for Hyper_Function ``func`` in terms of Lerch Transcendents. Return None if no such expression can be found. """ # This is actually quite simple, and is described in Roach's paper, # section 18. # We don't need to implement the reduction to polylog here, this # is handled by expand_func. from sympy.matrices import Matrix, zeros from sympy.polys import apart # First we need to figure out if the summation coefficient is a rational # function of the summation index, and construct that rational function. abuckets, bbuckets = sift(func.ap, _mod1), sift(func.bq, _mod1) paired = {} for key, value in abuckets.items(): if key != 0 and not key in bbuckets: return None bvalue = bbuckets[key] paired[key] = (list(value), list(bvalue)) bbuckets.pop(key, None) if bbuckets != {}: return None if not S.Zero in abuckets: return None aints, bints = paired[S.Zero] # Account for the additional n! in denominator paired[S.Zero] = (aints, bints + [1]) t = Dummy('t') numer = S.One denom = S.One for key, (avalue, bvalue) in paired.items(): if len(avalue) != len(bvalue): return None # Note that since order has been reduced fully, all the b are # bigger than all the a they differ from by an integer. In particular # if there are any negative b left, this function is not well-defined. for a, b in zip(avalue, bvalue): if (a - b).is_positive: k = a - b numer *= rf(b + t, k) denom *= rf(b, k) else: k = b - a numer *= rf(a, k) denom *= rf(a + t, k) # Now do a partial fraction decomposition. # We assemble two structures: a list monomials of pairs (a, b) representing # a*t**b (b a non-negative integer), and a dict terms, where # terms[a] = [(b, c)] means that there is a term b/(t-a)**c. part = apart(numer/denom, t) args = Add.make_args(part) monomials = [] terms = {} for arg in args: numer, denom = arg.as_numer_denom() if not denom.has(t): p = Poly(numer, t) if not p.is_monomial: raise TypeError("p should be monomial") ((b, ), a) = p.LT() monomials += [(a/denom, b)] continue if numer.has(t): raise NotImplementedError('Need partial fraction decomposition' ' with linear denominators') indep, [dep] = denom.as_coeff_mul(t) n = 1 if dep.is_Pow: n = dep.exp dep = dep.base if dep == t: a == 0 elif dep.is_Add: a, tmp = dep.as_independent(t) b = 1 if tmp != t: b, _ = tmp.as_independent(t) if dep != b*t + a: raise NotImplementedError('unrecognised form %s' % dep) a /= b indep *= b**n else: raise NotImplementedError('unrecognised form of partial fraction') terms.setdefault(a, []).append((numer/indep, n)) # Now that we have this information, assemble our formula. All the # monomials yield rational functions and go into one basis element. # The terms[a] are related by differentiation. If the largest exponent is # n, we need lerchphi(z, k, a) for k = 1, 2, ..., n. # deriv maps a basis to its derivative, expressed as a C(z)-linear # combination of other basis elements. deriv = {} coeffs = {} z = Dummy('z') monomials.sort(key=lambda x: x[1]) mon = {0: 1/(1 - z)} if monomials: for k in range(monomials[-1][1]): mon[k + 1] = z*mon[k].diff(z) for a, n in monomials: coeffs.setdefault(S.One, []).append(a*mon[n]) for a, l in terms.items(): for c, k in l: coeffs.setdefault(lerchphi(z, k, a), []).append(c) l.sort(key=lambda x: x[1]) for k in range(2, l[-1][1] + 1): deriv[lerchphi(z, k, a)] = [(-a, lerchphi(z, k, a)), (1, lerchphi(z, k - 1, a))] deriv[lerchphi(z, 1, a)] = [(-a, lerchphi(z, 1, a)), (1/(1 - z), S.One)] trans = {} for n, b in enumerate([S.One] + list(deriv.keys())): trans[b] = n basis = [expand_func(b) for (b, _) in sorted(list(trans.items()), key=lambda x:x[1])] B = Matrix(basis) C = Matrix([[0]*len(B)]) for b, c in coeffs.items(): C[trans[b]] = Add(*c) M = zeros(len(B)) for b, l in deriv.items(): for c, b2 in l: M[trans[b], trans[b2]] = c return Formula(func, z, None, [], B, C, M) def build_hypergeometric_formula(func): """ Create a formula object representing the hypergeometric function ``func``. """ # We know that no `ap` are negative integers, otherwise "detect poly" # would have kicked in. However, `ap` could be empty. In this case we can # use a different basis. # I'm not aware of a basis that works in all cases. from sympy import zeros, Matrix, eye z = Dummy('z') if func.ap: afactors = [_x + a for a in func.ap] bfactors = [_x + b - 1 for b in func.bq] expr = _x*Mul(*bfactors) - z*Mul(*afactors) poly = Poly(expr, _x) n = poly.degree() basis = [] M = zeros(n) for k in range(n): a = func.ap[0] + k basis += [hyper([a] + list(func.ap[1:]), func.bq, z)] if k < n - 1: M[k, k] = -a M[k, k + 1] = a B = Matrix(basis) C = Matrix([[1] + [0]*(n - 1)]) derivs = [eye(n)] for k in range(n): derivs.append(M*derivs[k]) l = poly.all_coeffs() l.reverse() res = [0]*n for k, c in enumerate(l): for r, d in enumerate(C*derivs[k]): res[r] += c*d for k, c in enumerate(res): M[n - 1, k] = -c/derivs[n - 1][0, n - 1]/poly.all_coeffs()[0] return Formula(func, z, None, [], B, C, M) else: # Since there are no `ap`, none of the `bq` can be non-positive # integers. basis = [] bq = list(func.bq[:]) for i in range(len(bq)): basis += [hyper([], bq, z)] bq[i] += 1 basis += [hyper([], bq, z)] B = Matrix(basis) n = len(B) C = Matrix([[1] + [0]*(n - 1)]) M = zeros(n) M[0, n - 1] = z/Mul(*func.bq) for k in range(1, n): M[k, k - 1] = func.bq[k - 1] M[k, k] = -func.bq[k - 1] return Formula(func, z, None, [], B, C, M) def hyperexpand_special(ap, bq, z): """ Try to find a closed-form expression for hyper(ap, bq, z), where ``z`` is supposed to be a "special" value, e.g. 1. This function tries various of the classical summation formulae (Gauss, Saalschuetz, etc). """ # This code is very ad-hoc. There are many clever algorithms # (notably Zeilberger's) related to this problem. # For now we just want a few simple cases to work. p, q = len(ap), len(bq) z_ = z z = unpolarify(z) if z == 0: return S.One if p == 2 and q == 1: # 2F1 a, b, c = ap + bq if z == 1: # Gauss return gamma(c - a - b)*gamma(c)/gamma(c - a)/gamma(c - b) if z == -1 and simplify(b - a + c) == 1: b, a = a, b if z == -1 and simplify(a - b + c) == 1: # Kummer if b.is_integer and b.is_negative: return 2*cos(pi*b/2)*gamma(-b)*gamma(b - a + 1) \ /gamma(-b/2)/gamma(b/2 - a + 1) else: return gamma(b/2 + 1)*gamma(b - a + 1) \ /gamma(b + 1)/gamma(b/2 - a + 1) # TODO tons of more formulae # investigate what algorithms exist return hyper(ap, bq, z_) _collection = None def _hyperexpand(func, z, ops0=[], z0=Dummy('z0'), premult=1, prem=0, rewrite='default'): """ Try to find an expression for the hypergeometric function ``func``. Explanation =========== The result is expressed in terms of a dummy variable ``z0``. Then it is multiplied by ``premult``. Then ``ops0`` is applied. ``premult`` must be a*z**prem for some a independent of ``z``. """ if z.is_zero: return S.One z = polarify(z, subs=False) if rewrite == 'default': rewrite = 'nonrepsmall' def carryout_plan(f, ops): C = apply_operators(f.C.subs(f.z, z0), ops, make_derivative_operator(f.M.subs(f.z, z0), z0)) from sympy import eye C = apply_operators(C, ops0, make_derivative_operator(f.M.subs(f.z, z0) + prem*eye(f.M.shape[0]), z0)) if premult == 1: C = C.applyfunc(make_simp(z0)) r = reduce(lambda s,m: s+m[0]*m[1], zip(C, f.B.subs(f.z, z0)), S.Zero)*premult res = r.subs(z0, z) if rewrite: res = res.rewrite(rewrite) return res # TODO # The following would be possible: # *) PFD Duplication (see Kelly Roach's paper) # *) In a similar spirit, try_lerchphi() can be generalised considerably. global _collection if _collection is None: _collection = FormulaCollection() debug('Trying to expand hypergeometric function ', func) # First reduce order as much as possible. func, ops = reduce_order(func) if ops: debug(' Reduced order to ', func) else: debug(' Could not reduce order.') # Now try polynomial cases res = try_polynomial(func, z0) if res is not None: debug(' Recognised polynomial.') p = apply_operators(res, ops, lambda f: z0*f.diff(z0)) p = apply_operators(p*premult, ops0, lambda f: z0*f.diff(z0)) return unpolarify(simplify(p).subs(z0, z)) # Try to recognise a shifted sum. p = S.Zero res = try_shifted_sum(func, z0) if res is not None: func, nops, p = res debug(' Recognised shifted sum, reduced order to ', func) ops += nops # apply the plan for poly p = apply_operators(p, ops, lambda f: z0*f.diff(z0)) p = apply_operators(p*premult, ops0, lambda f: z0*f.diff(z0)) p = simplify(p).subs(z0, z) # Try special expansions early. if unpolarify(z) in [1, -1] and (len(func.ap), len(func.bq)) == (2, 1): f = build_hypergeometric_formula(func) r = carryout_plan(f, ops).replace(hyper, hyperexpand_special) if not r.has(hyper): return r + p # Try to find a formula in our collection formula = _collection.lookup_origin(func) # Now try a lerch phi formula if formula is None: formula = try_lerchphi(func) if formula is None: debug(' Could not find an origin. ', 'Will return answer in terms of ' 'simpler hypergeometric functions.') formula = build_hypergeometric_formula(func) debug(' Found an origin: ', formula.closed_form, ' ', formula.func) # We need to find the operators that convert formula into func. ops += devise_plan(func, formula.func, z0) # Now carry out the plan. r = carryout_plan(formula, ops) + p return powdenest(r, polar=True).replace(hyper, hyperexpand_special) def devise_plan_meijer(fro, to, z): """ Find operators to convert G-function ``fro`` into G-function ``to``. Explanation =========== It is assumed that ``fro`` and ``to`` have the same signatures, and that in fact any corresponding pair of parameters differs by integers, and a direct path is possible. I.e. if there are parameters a1 b1 c1 and a2 b2 c2 it is assumed that a1 can be shifted to a2, etc. The only thing this routine determines is the order of shifts to apply, nothing clever will be tried. It is also assumed that ``fro`` is suitable. Examples ======== >>> from sympy.simplify.hyperexpand import (devise_plan_meijer, ... G_Function) >>> from sympy.abc import z Empty plan: >>> devise_plan_meijer(G_Function([1], [2], [3], [4]), ... G_Function([1], [2], [3], [4]), z) [] Very simple plans: >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([1], [], [], []), z) [<Increment upper a index #0 of [0], [], [], [].>] >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([-1], [], [], []), z) [<Decrement upper a=0.>] >>> devise_plan_meijer(G_Function([], [1], [], []), ... G_Function([], [2], [], []), z) [<Increment lower a index #0 of [], [1], [], [].>] Slightly more complicated plans: >>> devise_plan_meijer(G_Function([0], [], [], []), ... G_Function([2], [], [], []), z) [<Increment upper a index #0 of [1], [], [], [].>, <Increment upper a index #0 of [0], [], [], [].>] >>> devise_plan_meijer(G_Function([0], [], [0], []), ... G_Function([-1], [], [1], []), z) [<Increment upper b=0.>, <Decrement upper a=0.>] Order matters: >>> devise_plan_meijer(G_Function([0], [], [0], []), ... G_Function([1], [], [1], []), z) [<Increment upper a index #0 of [0], [], [1], [].>, <Increment upper b=0.>] """ # TODO for now, we use the following simple heuristic: inverse-shift # when possible, shift otherwise. Give up if we cannot make progress. def try_shift(f, t, shifter, diff, counter): """ Try to apply ``shifter`` in order to bring some element in ``f`` nearer to its counterpart in ``to``. ``diff`` is +/- 1 and determines the effect of ``shifter``. Counter is a list of elements blocking the shift. Return an operator if change was possible, else None. """ for idx, (a, b) in enumerate(zip(f, t)): if ( (a - b).is_integer and (b - a)/diff > 0 and all(a != x for x in counter)): sh = shifter(idx) f[idx] += diff return sh fan = list(fro.an) fap = list(fro.ap) fbm = list(fro.bm) fbq = list(fro.bq) ops = [] change = True while change: change = False op = try_shift(fan, to.an, lambda i: MeijerUnShiftB(fan, fap, fbm, fbq, i, z), 1, fbm + fbq) if op is not None: ops += [op] change = True continue op = try_shift(fap, to.ap, lambda i: MeijerUnShiftD(fan, fap, fbm, fbq, i, z), 1, fbm + fbq) if op is not None: ops += [op] change = True continue op = try_shift(fbm, to.bm, lambda i: MeijerUnShiftA(fan, fap, fbm, fbq, i, z), -1, fan + fap) if op is not None: ops += [op] change = True continue op = try_shift(fbq, to.bq, lambda i: MeijerUnShiftC(fan, fap, fbm, fbq, i, z), -1, fan + fap) if op is not None: ops += [op] change = True continue op = try_shift(fan, to.an, lambda i: MeijerShiftB(fan[i]), -1, []) if op is not None: ops += [op] change = True continue op = try_shift(fap, to.ap, lambda i: MeijerShiftD(fap[i]), -1, []) if op is not None: ops += [op] change = True continue op = try_shift(fbm, to.bm, lambda i: MeijerShiftA(fbm[i]), 1, []) if op is not None: ops += [op] change = True continue op = try_shift(fbq, to.bq, lambda i: MeijerShiftC(fbq[i]), 1, []) if op is not None: ops += [op] change = True continue if fan != list(to.an) or fap != list(to.ap) or fbm != list(to.bm) or \ fbq != list(to.bq): raise NotImplementedError('Could not devise plan.') ops.reverse() return ops _meijercollection = None def _meijergexpand(func, z0, allow_hyper=False, rewrite='default', place=None): """ Try to find an expression for the Meijer G function specified by the G_Function ``func``. If ``allow_hyper`` is True, then returning an expression in terms of hypergeometric functions is allowed. Currently this just does Slater's theorem. If expansions exist both at zero and at infinity, ``place`` can be set to ``0`` or ``zoo`` for the preferred choice. """ global _meijercollection if _meijercollection is None: _meijercollection = MeijerFormulaCollection() if rewrite == 'default': rewrite = None func0 = func debug('Try to expand Meijer G function corresponding to ', func) # We will play games with analytic continuation - rather use a fresh symbol z = Dummy('z') func, ops = reduce_order_meijer(func) if ops: debug(' Reduced order to ', func) else: debug(' Could not reduce order.') # Try to find a direct formula f = _meijercollection.lookup_origin(func) if f is not None: debug(' Found a Meijer G formula: ', f.func) ops += devise_plan_meijer(f.func, func, z) # Now carry out the plan. C = apply_operators(f.C.subs(f.z, z), ops, make_derivative_operator(f.M.subs(f.z, z), z)) C = C.applyfunc(make_simp(z)) r = C*f.B.subs(f.z, z) r = r[0].subs(z, z0) return powdenest(r, polar=True) debug(" Could not find a direct formula. Trying Slater's theorem.") # TODO the following would be possible: # *) Paired Index Theorems # *) PFD Duplication # (See Kelly Roach's paper for details on either.) # # TODO Also, we tend to create combinations of gamma functions that can be # simplified. def can_do(pbm, pap): """ Test if slater applies. """ for i in pbm: if len(pbm[i]) > 1: l = 0 if i in pap: l = len(pap[i]) if l + 1 < len(pbm[i]): return False return True def do_slater(an, bm, ap, bq, z, zfinal): # zfinal is the value that will eventually be substituted for z. # We pass it to _hyperexpand to improve performance. func = G_Function(an, bm, ap, bq) _, pbm, pap, _ = func.compute_buckets() if not can_do(pbm, pap): return S.Zero, False cond = len(an) + len(ap) < len(bm) + len(bq) if len(an) + len(ap) == len(bm) + len(bq): cond = abs(z) < 1 if cond is False: return S.Zero, False res = S.Zero for m in pbm: if len(pbm[m]) == 1: bh = pbm[m][0] fac = 1 bo = list(bm) bo.remove(bh) for bj in bo: fac *= gamma(bj - bh) for aj in an: fac *= gamma(1 + bh - aj) for bj in bq: fac /= gamma(1 + bh - bj) for aj in ap: fac /= gamma(aj - bh) nap = [1 + bh - a for a in list(an) + list(ap)] nbq = [1 + bh - b for b in list(bo) + list(bq)] k = polar_lift(S.NegativeOne**(len(ap) - len(bm))) harg = k*zfinal # NOTE even though k "is" +-1, this has to be t/k instead of # t*k ... we are using polar numbers for consistency! premult = (t/k)**bh hyp = _hyperexpand(Hyper_Function(nap, nbq), harg, ops, t, premult, bh, rewrite=None) res += fac * hyp else: b_ = pbm[m][0] ki = [bi - b_ for bi in pbm[m][1:]] u = len(ki) li = [ai - b_ for ai in pap[m][:u + 1]] bo = list(bm) for b in pbm[m]: bo.remove(b) ao = list(ap) for a in pap[m][:u]: ao.remove(a) lu = li[-1] di = [l - k for (l, k) in zip(li, ki)] # We first work out the integrand: s = Dummy('s') integrand = z**s for b in bm: if not Mod(b, 1) and b.is_Number: b = int(round(b)) integrand *= gamma(b - s) for a in an: integrand *= gamma(1 - a + s) for b in bq: integrand /= gamma(1 - b + s) for a in ap: integrand /= gamma(a - s) # Now sum the finitely many residues: # XXX This speeds up some cases - is it a good idea? integrand = expand_func(integrand) for r in range(int(round(lu))): resid = residue(integrand, s, b_ + r) resid = apply_operators(resid, ops, lambda f: z*f.diff(z)) res -= resid # Now the hypergeometric term. au = b_ + lu k = polar_lift(S.NegativeOne**(len(ao) + len(bo) + 1)) harg = k*zfinal premult = (t/k)**au nap = [1 + au - a for a in list(an) + list(ap)] + [1] nbq = [1 + au - b for b in list(bm) + list(bq)] hyp = _hyperexpand(Hyper_Function(nap, nbq), harg, ops, t, premult, au, rewrite=None) C = S.NegativeOne**(lu)/factorial(lu) for i in range(u): C *= S.NegativeOne**di[i]/rf(lu - li[i] + 1, di[i]) for a in an: C *= gamma(1 - a + au) for b in bo: C *= gamma(b - au) for a in ao: C /= gamma(a - au) for b in bq: C /= gamma(1 - b + au) res += C*hyp return res, cond t = Dummy('t') slater1, cond1 = do_slater(func.an, func.bm, func.ap, func.bq, z, z0) def tr(l): return [1 - x for x in l] for op in ops: op._poly = Poly(op._poly.subs({z: 1/t, _x: -_x}), _x) slater2, cond2 = do_slater(tr(func.bm), tr(func.an), tr(func.bq), tr(func.ap), t, 1/z0) slater1 = powdenest(slater1.subs(z, z0), polar=True) slater2 = powdenest(slater2.subs(t, 1/z0), polar=True) if not isinstance(cond2, bool): cond2 = cond2.subs(t, 1/z) m = func(z) if m.delta > 0 or \ (m.delta == 0 and len(m.ap) == len(m.bq) and (re(m.nu) < -1) is not False and polar_lift(z0) == polar_lift(1)): # The condition delta > 0 means that the convergence region is # connected. Any expression we find can be continued analytically # to the entire convergence region. # The conditions delta==0, p==q, re(nu) < -1 imply that G is continuous # on the positive reals, so the values at z=1 agree. if cond1 is not False: cond1 = True if cond2 is not False: cond2 = True if cond1 is True: slater1 = slater1.rewrite(rewrite or 'nonrep') else: slater1 = slater1.rewrite(rewrite or 'nonrepsmall') if cond2 is True: slater2 = slater2.rewrite(rewrite or 'nonrep') else: slater2 = slater2.rewrite(rewrite or 'nonrepsmall') if cond1 is not False and cond2 is not False: # If one condition is False, there is no choice. if place == 0: cond2 = False if place == zoo: cond1 = False if not isinstance(cond1, bool): cond1 = cond1.subs(z, z0) if not isinstance(cond2, bool): cond2 = cond2.subs(z, z0) def weight(expr, cond): if cond is True: c0 = 0 elif cond is False: c0 = 1 else: c0 = 2 if expr.has(oo, zoo, -oo, nan): # XXX this actually should not happen, but consider # S('meijerg(((0, -1/2, 0, -1/2, 1/2), ()), ((0,), # (-1/2, -1/2, -1/2, -1)), exp_polar(I*pi))/4') c0 = 3 return (c0, expr.count(hyper), expr.count_ops()) w1 = weight(slater1, cond1) w2 = weight(slater2, cond2) if min(w1, w2) <= (0, 1, oo): if w1 < w2: return slater1 else: return slater2 if max(w1[0], w2[0]) <= 1 and max(w1[1], w2[1]) <= 1: return Piecewise((slater1, cond1), (slater2, cond2), (func0(z0), True)) # We couldn't find an expression without hypergeometric functions. # TODO it would be helpful to give conditions under which the integral # is known to diverge. r = Piecewise((slater1, cond1), (slater2, cond2), (func0(z0), True)) if r.has(hyper) and not allow_hyper: debug(' Could express using hypergeometric functions, ' 'but not allowed.') if not r.has(hyper) or allow_hyper: return r return func0(z0) def hyperexpand(f, allow_hyper=False, rewrite='default', place=None): """ Expand hypergeometric functions. If allow_hyper is True, allow partial simplification (that is a result different from input, but still containing hypergeometric functions). If a G-function has expansions both at zero and at infinity, ``place`` can be set to ``0`` or ``zoo`` to indicate the preferred choice. Examples ======== >>> from sympy.simplify.hyperexpand import hyperexpand >>> from sympy.functions import hyper >>> from sympy.abc import z >>> hyperexpand(hyper([], [], z)) exp(z) Non-hyperegeometric parts of the expression and hypergeometric expressions that are not recognised are left unchanged: >>> hyperexpand(1 + hyper([1, 1, 1], [], z)) hyper((1, 1, 1), (), z) + 1 """ f = sympify(f) def do_replace(ap, bq, z): r = _hyperexpand(Hyper_Function(ap, bq), z, rewrite=rewrite) if r is None: return hyper(ap, bq, z) else: return r def do_meijer(ap, bq, z): r = _meijergexpand(G_Function(ap[0], ap[1], bq[0], bq[1]), z, allow_hyper, rewrite=rewrite, place=place) if not r.has(nan, zoo, oo, -oo): return r return f.replace(hyper, do_replace).replace(meijerg, do_meijer)

9757d440686b51570176973fdb0aaf5b5fcbc34bd1bdc319c324164204422a18

""" Optimizations of the expression tree representation for better CSE opportunities. """ from sympy.core import Add, Basic, Mul from sympy.core.basic import preorder_traversal from sympy.core.singleton import S from sympy.utilities.iterables import default_sort_key def sub_pre(e): """ Replace y - x with -(x - y) if -1 can be extracted from y - x. """ # replacing Add, A, from which -1 can be extracted with -1*-A adds = [a for a in e.atoms(Add) if a.could_extract_minus_sign()] reps = {} ignore = set() for a in adds: na = -a if na.is_Mul: # e.g. MatExpr ignore.add(a) continue reps[a] = Mul._from_args([S.NegativeOne, na]) e = e.xreplace(reps) # repeat again for persisting Adds but mark these with a leading 1, -1 # e.g. y - x -> 1*-1*(x - y) if isinstance(e, Basic): negs = {} for a in sorted(e.atoms(Add), key=default_sort_key): if a in ignore: continue if a in reps: negs[a] = reps[a] elif a.could_extract_minus_sign(): negs[a] = Mul._from_args([S.One, S.NegativeOne, -a]) e = e.xreplace(negs) return e def sub_post(e): """ Replace 1*-1*x with -x. """ replacements = [] for node in preorder_traversal(e): if isinstance(node, Mul) and \ node.args[0] is S.One and node.args[1] is S.NegativeOne: replacements.append((node, -Mul._from_args(node.args[2:]))) for node, replacement in replacements: e = e.xreplace({node: replacement}) return e

ea1de60622e3707d7965d962f692b4e2346663147cb860dce0bb5f00c6b9e52d

from collections import defaultdict from sympy.core import (Basic, S, Add, Mul, Pow, Symbol, sympify, expand_func, Function, Dummy, Expr, factor_terms, expand_power_exp, Eq) from sympy.core.compatibility import iterable, ordered, as_int from sympy.core.parameters import global_parameters from sympy.core.function import (expand_log, count_ops, _mexpand, _coeff_isneg, nfloat, expand_mul) from sympy.core.numbers import Float, I, pi, Rational, Integer from sympy.core.relational import Relational from sympy.core.rules import Transform from sympy.core.sympify import _sympify from sympy.functions import gamma, exp, sqrt, log, exp_polar, re from sympy.functions.combinatorial.factorials import CombinatorialFunction from sympy.functions.elementary.complexes import unpolarify, Abs from sympy.functions.elementary.exponential import ExpBase from sympy.functions.elementary.hyperbolic import HyperbolicFunction from sympy.functions.elementary.integers import ceiling from sympy.functions.elementary.piecewise import Piecewise, piecewise_fold from sympy.functions.elementary.trigonometric import TrigonometricFunction from sympy.functions.special.bessel import besselj, besseli, besselk, jn, bessely from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.polys import together, cancel, factor from sympy.simplify.combsimp import combsimp from sympy.simplify.cse_opts import sub_pre, sub_post from sympy.simplify.powsimp import powsimp from sympy.simplify.radsimp import radsimp, fraction, collect_abs from sympy.simplify.sqrtdenest import sqrtdenest from sympy.simplify.trigsimp import trigsimp, exptrigsimp from sympy.utilities.iterables import has_variety, sift import mpmath def separatevars(expr, symbols=[], dict=False, force=False): """ Separates variables in an expression, if possible. By default, it separates with respect to all symbols in an expression and collects constant coefficients that are independent of symbols. Explanation =========== If ``dict=True`` then the separated terms will be returned in a dictionary keyed to their corresponding symbols. By default, all symbols in the expression will appear as keys; if symbols are provided, then all those symbols will be used as keys, and any terms in the expression containing other symbols or non-symbols will be returned keyed to the string 'coeff'. (Passing None for symbols will return the expression in a dictionary keyed to 'coeff'.) If ``force=True``, then bases of powers will be separated regardless of assumptions on the symbols involved. Notes ===== The order of the factors is determined by Mul, so that the separated expressions may not necessarily be grouped together. Although factoring is necessary to separate variables in some expressions, it is not necessary in all cases, so one should not count on the returned factors being factored. Examples ======== >>> from sympy.abc import x, y, z, alpha >>> from sympy import separatevars, sin >>> separatevars((x*y)**y) (x*y)**y >>> separatevars((x*y)**y, force=True) x**y*y**y >>> e = 2*x**2*z*sin(y)+2*z*x**2 >>> separatevars(e) 2*x**2*z*(sin(y) + 1) >>> separatevars(e, symbols=(x, y), dict=True) {'coeff': 2*z, x: x**2, y: sin(y) + 1} >>> separatevars(e, [x, y, alpha], dict=True) {'coeff': 2*z, alpha: 1, x: x**2, y: sin(y) + 1} If the expression is not really separable, or is only partially separable, separatevars will do the best it can to separate it by using factoring. >>> separatevars(x + x*y - 3*x**2) -x*(3*x - y - 1) If the expression is not separable then expr is returned unchanged or (if dict=True) then None is returned. >>> eq = 2*x + y*sin(x) >>> separatevars(eq) == eq True >>> separatevars(2*x + y*sin(x), symbols=(x, y), dict=True) is None True """ expr = sympify(expr) if dict: return _separatevars_dict(_separatevars(expr, force), symbols) else: return _separatevars(expr, force) def _separatevars(expr, force): if isinstance(expr, Abs): arg = expr.args[0] if arg.is_Mul and not arg.is_number: s = separatevars(arg, dict=True, force=force) if s is not None: return Mul(*map(expr.func, s.values())) else: return expr if len(expr.free_symbols) < 2: return expr # don't destroy a Mul since much of the work may already be done if expr.is_Mul: args = list(expr.args) changed = False for i, a in enumerate(args): args[i] = separatevars(a, force) changed = changed or args[i] != a if changed: expr = expr.func(*args) return expr # get a Pow ready for expansion if expr.is_Pow: expr = Pow(separatevars(expr.base, force=force), expr.exp) # First try other expansion methods expr = expr.expand(mul=False, multinomial=False, force=force) _expr, reps = posify(expr) if force else (expr, {}) expr = factor(_expr).subs(reps) if not expr.is_Add: return expr # Find any common coefficients to pull out args = list(expr.args) commonc = args[0].args_cnc(cset=True, warn=False)[0] for i in args[1:]: commonc &= i.args_cnc(cset=True, warn=False)[0] commonc = Mul(*commonc) commonc = commonc.as_coeff_Mul()[1] # ignore constants commonc_set = commonc.args_cnc(cset=True, warn=False)[0] # remove them for i, a in enumerate(args): c, nc = a.args_cnc(cset=True, warn=False) c = c - commonc_set args[i] = Mul(*c)*Mul(*nc) nonsepar = Add(*args) if len(nonsepar.free_symbols) > 1: _expr = nonsepar _expr, reps = posify(_expr) if force else (_expr, {}) _expr = (factor(_expr)).subs(reps) if not _expr.is_Add: nonsepar = _expr return commonc*nonsepar def _separatevars_dict(expr, symbols): if symbols: if not all(t.is_Atom for t in symbols): raise ValueError("symbols must be Atoms.") symbols = list(symbols) elif symbols is None: return {'coeff': expr} else: symbols = list(expr.free_symbols) if not symbols: return None ret = {i: [] for i in symbols + ['coeff']} for i in Mul.make_args(expr): expsym = i.free_symbols intersection = set(symbols).intersection(expsym) if len(intersection) > 1: return None if len(intersection) == 0: # There are no symbols, so it is part of the coefficient ret['coeff'].append(i) else: ret[intersection.pop()].append(i) # rebuild for k, v in ret.items(): ret[k] = Mul(*v) return ret def _is_sum_surds(p): args = p.args if p.is_Add else [p] for y in args: if not ((y**2).is_Rational and y.is_extended_real): return False return True def posify(eq): """Return ``eq`` (with generic symbols made positive) and a dictionary containing the mapping between the old and new symbols. Explanation =========== Any symbol that has positive=None will be replaced with a positive dummy symbol having the same name. This replacement will allow more symbolic processing of expressions, especially those involving powers and logarithms. A dictionary that can be sent to subs to restore ``eq`` to its original symbols is also returned. >>> from sympy import posify, Symbol, log, solve >>> from sympy.abc import x >>> posify(x + Symbol('p', positive=True) + Symbol('n', negative=True)) (_x + n + p, {_x: x}) >>> eq = 1/x >>> log(eq).expand() log(1/x) >>> log(posify(eq)[0]).expand() -log(_x) >>> p, rep = posify(eq) >>> log(p).expand().subs(rep) -log(x) It is possible to apply the same transformations to an iterable of expressions: >>> eq = x**2 - 4 >>> solve(eq, x) [-2, 2] >>> eq_x, reps = posify([eq, x]); eq_x [_x**2 - 4, _x] >>> solve(*eq_x) [2] """ eq = sympify(eq) if iterable(eq): f = type(eq) eq = list(eq) syms = set() for e in eq: syms = syms.union(e.atoms(Symbol)) reps = {} for s in syms: reps.update({v: k for k, v in posify(s)[1].items()}) for i, e in enumerate(eq): eq[i] = e.subs(reps) return f(eq), {r: s for s, r in reps.items()} reps = {s: Dummy(s.name, positive=True, **s.assumptions0) for s in eq.free_symbols if s.is_positive is None} eq = eq.subs(reps) return eq, {r: s for s, r in reps.items()} def hypersimp(f, k): """Given combinatorial term f(k) simplify its consecutive term ratio i.e. f(k+1)/f(k). The input term can be composed of functions and integer sequences which have equivalent representation in terms of gamma special function. Explanation =========== The algorithm performs three basic steps: 1. Rewrite all functions in terms of gamma, if possible. 2. Rewrite all occurrences of gamma in terms of products of gamma and rising factorial with integer, absolute constant exponent. 3. Perform simplification of nested fractions, powers and if the resulting expression is a quotient of polynomials, reduce their total degree. If f(k) is hypergeometric then as result we arrive with a quotient of polynomials of minimal degree. Otherwise None is returned. For more information on the implemented algorithm refer to: 1. W. Koepf, Algorithms for m-fold Hypergeometric Summation, Journal of Symbolic Computation (1995) 20, 399-417 """ f = sympify(f) g = f.subs(k, k + 1) / f g = g.rewrite(gamma) if g.has(Piecewise): g = piecewise_fold(g) g = g.args[-1][0] g = expand_func(g) g = powsimp(g, deep=True, combine='exp') if g.is_rational_function(k): return simplify(g, ratio=S.Infinity) else: return None def hypersimilar(f, g, k): """ Returns True if ``f`` and ``g`` are hyper-similar. Explanation =========== Similarity in hypergeometric sense means that a quotient of f(k) and g(k) is a rational function in ``k``. This procedure is useful in solving recurrence relations. For more information see hypersimp(). """ f, g = list(map(sympify, (f, g))) h = (f/g).rewrite(gamma) h = h.expand(func=True, basic=False) return h.is_rational_function(k) def signsimp(expr, evaluate=None): """Make all Add sub-expressions canonical wrt sign. Explanation =========== If an Add subexpression, ``a``, can have a sign extracted, as determined by could_extract_minus_sign, it is replaced with Mul(-1, a, evaluate=False). This allows signs to be extracted from powers and products. Examples ======== >>> from sympy import signsimp, exp, symbols >>> from sympy.abc import x, y >>> i = symbols('i', odd=True) >>> n = -1 + 1/x >>> n/x/(-n)**2 - 1/n/x (-1 + 1/x)/(x*(1 - 1/x)**2) - 1/(x*(-1 + 1/x)) >>> signsimp(_) 0 >>> x*n + x*-n x*(-1 + 1/x) + x*(1 - 1/x) >>> signsimp(_) 0 Since powers automatically handle leading signs >>> (-2)**i -2**i signsimp can be used to put the base of a power with an integer exponent into canonical form: >>> n**i (-1 + 1/x)**i By default, signsimp doesn't leave behind any hollow simplification: if making an Add canonical wrt sign didn't change the expression, the original Add is restored. If this is not desired then the keyword ``evaluate`` can be set to False: >>> e = exp(y - x) >>> signsimp(e) == e True >>> signsimp(e, evaluate=False) exp(-(x - y)) """ if evaluate is None: evaluate = global_parameters.evaluate expr = sympify(expr) if not isinstance(expr, (Expr, Relational)) or expr.is_Atom: return expr e = sub_post(sub_pre(expr)) if not isinstance(e, (Expr, Relational)) or e.is_Atom: return e if e.is_Add: return e.func(*[signsimp(a, evaluate) for a in e.args]) if evaluate: e = e.xreplace({m: -(-m) for m in e.atoms(Mul) if -(-m) != m}) return e def simplify(expr, ratio=1.7, measure=count_ops, rational=False, inverse=False, doit=True, **kwargs): """Simplifies the given expression. Explanation =========== Simplification is not a well defined term and the exact strategies this function tries can change in the future versions of SymPy. If your algorithm relies on "simplification" (whatever it is), try to determine what you need exactly - is it powsimp()?, radsimp()?, together()?, logcombine()?, or something else? And use this particular function directly, because those are well defined and thus your algorithm will be robust. Nonetheless, especially for interactive use, or when you don't know anything about the structure of the expression, simplify() tries to apply intelligent heuristics to make the input expression "simpler". For example: >>> from sympy import simplify, cos, sin >>> from sympy.abc import x, y >>> a = (x + x**2)/(x*sin(y)**2 + x*cos(y)**2) >>> a (x**2 + x)/(x*sin(y)**2 + x*cos(y)**2) >>> simplify(a) x + 1 Note that we could have obtained the same result by using specific simplification functions: >>> from sympy import trigsimp, cancel >>> trigsimp(a) (x**2 + x)/x >>> cancel(_) x + 1 In some cases, applying :func:`simplify` may actually result in some more complicated expression. The default ``ratio=1.7`` prevents more extreme cases: if (result length)/(input length) > ratio, then input is returned unmodified. The ``measure`` parameter lets you specify the function used to determine how complex an expression is. The function should take a single argument as an expression and return a number such that if expression ``a`` is more complex than expression ``b``, then ``measure(a) > measure(b)``. The default measure function is :func:`~.count_ops`, which returns the total number of operations in the expression. For example, if ``ratio=1``, ``simplify`` output can't be longer than input. :: >>> from sympy import sqrt, simplify, count_ops, oo >>> root = 1/(sqrt(2)+3) Since ``simplify(root)`` would result in a slightly longer expression, root is returned unchanged instead:: >>> simplify(root, ratio=1) == root True If ``ratio=oo``, simplify will be applied anyway:: >>> count_ops(simplify(root, ratio=oo)) > count_ops(root) True Note that the shortest expression is not necessary the simplest, so setting ``ratio`` to 1 may not be a good idea. Heuristically, the default value ``ratio=1.7`` seems like a reasonable choice. You can easily define your own measure function based on what you feel should represent the "size" or "complexity" of the input expression. Note that some choices, such as ``lambda expr: len(str(expr))`` may appear to be good metrics, but have other problems (in this case, the measure function may slow down simplify too much for very large expressions). If you don't know what a good metric would be, the default, ``count_ops``, is a good one. For example: >>> from sympy import symbols, log >>> a, b = symbols('a b', positive=True) >>> g = log(a) + log(b) + log(a)*log(1/b) >>> h = simplify(g) >>> h log(a*b**(1 - log(a))) >>> count_ops(g) 8 >>> count_ops(h) 5 So you can see that ``h`` is simpler than ``g`` using the count_ops metric. However, we may not like how ``simplify`` (in this case, using ``logcombine``) has created the ``b**(log(1/a) + 1)`` term. A simple way to reduce this would be to give more weight to powers as operations in ``count_ops``. We can do this by using the ``visual=True`` option: >>> print(count_ops(g, visual=True)) 2*ADD + DIV + 4*LOG + MUL >>> print(count_ops(h, visual=True)) 2*LOG + MUL + POW + SUB >>> from sympy import Symbol, S >>> def my_measure(expr): ... POW = Symbol('POW') ... # Discourage powers by giving POW a weight of 10 ... count = count_ops(expr, visual=True).subs(POW, 10) ... # Every other operation gets a weight of 1 (the default) ... count = count.replace(Symbol, type(S.One)) ... return count >>> my_measure(g) 8 >>> my_measure(h) 14 >>> 15./8 > 1.7 # 1.7 is the default ratio True >>> simplify(g, measure=my_measure) -log(a)*log(b) + log(a) + log(b) Note that because ``simplify()`` internally tries many different simplification strategies and then compares them using the measure function, we get a completely different result that is still different from the input expression by doing this. If ``rational=True``, Floats will be recast as Rationals before simplification. If ``rational=None``, Floats will be recast as Rationals but the result will be recast as Floats. If rational=False(default) then nothing will be done to the Floats. If ``inverse=True``, it will be assumed that a composition of inverse functions, such as sin and asin, can be cancelled in any order. For example, ``asin(sin(x))`` will yield ``x`` without checking whether x belongs to the set where this relation is true. The default is False. Note that ``simplify()`` automatically calls ``doit()`` on the final expression. You can avoid this behavior by passing ``doit=False`` as an argument. """ def shorter(*choices): """ Return the choice that has the fewest ops. In case of a tie, the expression listed first is selected. """ if not has_variety(choices): return choices[0] return min(choices, key=measure) def done(e): rv = e.doit() if doit else e return shorter(rv, collect_abs(rv)) expr = sympify(expr) kwargs = dict( ratio=kwargs.get('ratio', ratio), measure=kwargs.get('measure', measure), rational=kwargs.get('rational', rational), inverse=kwargs.get('inverse', inverse), doit=kwargs.get('doit', doit)) # no routine for Expr needs to check for is_zero if isinstance(expr, Expr) and expr.is_zero: return S.Zero _eval_simplify = getattr(expr, '_eval_simplify', None) if _eval_simplify is not None: return _eval_simplify(**kwargs) original_expr = expr = collect_abs(signsimp(expr)) if not isinstance(expr, Basic) or not expr.args: # XXX: temporary hack return expr if inverse and expr.has(Function): expr = inversecombine(expr) if not expr.args: # simplified to atomic return expr # do deep simplification handled = Add, Mul, Pow, ExpBase expr = expr.replace( # here, checking for x.args is not enough because Basic has # args but Basic does not always play well with replace, e.g. # when simultaneous is True found expressions will be masked # off with a Dummy but not all Basic objects in an expression # can be replaced with a Dummy lambda x: isinstance(x, Expr) and x.args and not isinstance( x, handled), lambda x: x.func(*[simplify(i, **kwargs) for i in x.args]), simultaneous=False) if not isinstance(expr, handled): return done(expr) if not expr.is_commutative: expr = nc_simplify(expr) # TODO: Apply different strategies, considering expression pattern: # is it a purely rational function? Is there any trigonometric function?... # See also https://github.com/sympy/sympy/pull/185. # rationalize Floats floats = False if rational is not False and expr.has(Float): floats = True expr = nsimplify(expr, rational=True) expr = bottom_up(expr, lambda w: getattr(w, 'normal', lambda: w)()) expr = Mul(*powsimp(expr).as_content_primitive()) _e = cancel(expr) expr1 = shorter(_e, _mexpand(_e).cancel()) # issue 6829 expr2 = shorter(together(expr, deep=True), together(expr1, deep=True)) if ratio is S.Infinity: expr = expr2 else: expr = shorter(expr2, expr1, expr) if not isinstance(expr, Basic): # XXX: temporary hack return expr expr = factor_terms(expr, sign=False) from sympy.simplify.hyperexpand import hyperexpand from sympy.functions.special.bessel import BesselBase from sympy import Sum, Product, Integral from sympy.functions.elementary.complexes import sign # must come before `Piecewise` since this introduces more `Piecewise` terms if expr.has(sign): expr = expr.rewrite(Abs) # Deal with Piecewise separately to avoid recursive growth of expressions if expr.has(Piecewise): # Fold into a single Piecewise expr = piecewise_fold(expr) # Apply doit, if doit=True expr = done(expr) # Still a Piecewise? if expr.has(Piecewise): # Fold into a single Piecewise, in case doit lead to some # expressions being Piecewise expr = piecewise_fold(expr) # kroneckersimp also affects Piecewise if expr.has(KroneckerDelta): expr = kroneckersimp(expr) # Still a Piecewise? if expr.has(Piecewise): from sympy.functions.elementary.piecewise import piecewise_simplify # Do not apply doit on the segments as it has already # been done above, but simplify expr = piecewise_simplify(expr, deep=True, doit=False) # Still a Piecewise? if expr.has(Piecewise): # Try factor common terms expr = shorter(expr, factor_terms(expr)) # As all expressions have been simplified above with the # complete simplify, nothing more needs to be done here return expr # hyperexpand automatically only works on hypergeometric terms # Do this after the Piecewise part to avoid recursive expansion expr = hyperexpand(expr) if expr.has(KroneckerDelta): expr = kroneckersimp(expr) if expr.has(BesselBase): expr = besselsimp(expr) if expr.has(TrigonometricFunction, HyperbolicFunction): expr = trigsimp(expr, deep=True) if expr.has(log): expr = shorter(expand_log(expr, deep=True), logcombine(expr)) if expr.has(CombinatorialFunction, gamma): # expression with gamma functions or non-integer arguments is # automatically passed to gammasimp expr = combsimp(expr) if expr.has(Sum): expr = sum_simplify(expr, **kwargs) if expr.has(Integral): expr = expr.xreplace({ i: factor_terms(i) for i in expr.atoms(Integral)}) if expr.has(Product): expr = product_simplify(expr) from sympy.physics.units import Quantity from sympy.physics.units.util import quantity_simplify if expr.has(Quantity): expr = quantity_simplify(expr) short = shorter(powsimp(expr, combine='exp', deep=True), powsimp(expr), expr) short = shorter(short, cancel(short)) short = shorter(short, factor_terms(short), expand_power_exp(expand_mul(short))) if short.has(TrigonometricFunction, HyperbolicFunction, ExpBase): short = exptrigsimp(short) # get rid of hollow 2-arg Mul factorization hollow_mul = Transform( lambda x: Mul(*x.args), lambda x: x.is_Mul and len(x.args) == 2 and x.args[0].is_Number and x.args[1].is_Add and x.is_commutative) expr = short.xreplace(hollow_mul) numer, denom = expr.as_numer_denom() if denom.is_Add: n, d = fraction(radsimp(1/denom, symbolic=False, max_terms=1)) if n is not S.One: expr = (numer*n).expand()/d if expr.could_extract_minus_sign(): n, d = fraction(expr) if d != 0: expr = signsimp(-n/(-d)) if measure(expr) > ratio*measure(original_expr): expr = original_expr # restore floats if floats and rational is None: expr = nfloat(expr, exponent=False) return done(expr) def sum_simplify(s, **kwargs): """Main function for Sum simplification""" from sympy.concrete.summations import Sum from sympy.core.function import expand if not isinstance(s, Add): s = s.xreplace({a: sum_simplify(a, **kwargs) for a in s.atoms(Add) if a.has(Sum)}) s = expand(s) if not isinstance(s, Add): return s terms = s.args s_t = [] # Sum Terms o_t = [] # Other Terms for term in terms: sum_terms, other = sift(Mul.make_args(term), lambda i: isinstance(i, Sum), binary=True) if not sum_terms: o_t.append(term) continue other = [Mul(*other)] s_t.append(Mul(*(other + [s._eval_simplify(**kwargs) for s in sum_terms]))) result = Add(sum_combine(s_t), *o_t) return result def sum_combine(s_t): """Helper function for Sum simplification Attempts to simplify a list of sums, by combining limits / sum function's returns the simplified sum """ from sympy.concrete.summations import Sum used = [False] * len(s_t) for method in range(2): for i, s_term1 in enumerate(s_t): if not used[i]: for j, s_term2 in enumerate(s_t): if not used[j] and i != j: temp = sum_add(s_term1, s_term2, method) if isinstance(temp, Sum) or isinstance(temp, Mul): s_t[i] = temp s_term1 = s_t[i] used[j] = True result = S.Zero for i, s_term in enumerate(s_t): if not used[i]: result = Add(result, s_term) return result def factor_sum(self, limits=None, radical=False, clear=False, fraction=False, sign=True): """Return Sum with constant factors extracted. If ``limits`` is specified then ``self`` is the summand; the other keywords are passed to ``factor_terms``. Examples ======== >>> from sympy import Sum >>> from sympy.abc import x, y >>> from sympy.simplify.simplify import factor_sum >>> s = Sum(x*y, (x, 1, 3)) >>> factor_sum(s) y*Sum(x, (x, 1, 3)) >>> factor_sum(s.function, s.limits) y*Sum(x, (x, 1, 3)) """ # XXX deprecate in favor of direct call to factor_terms from sympy.concrete.summations import Sum kwargs = dict(radical=radical, clear=clear, fraction=fraction, sign=sign) expr = Sum(self, *limits) if limits else self return factor_terms(expr, **kwargs) def sum_add(self, other, method=0): """Helper function for Sum simplification""" from sympy.concrete.summations import Sum from sympy import Mul #we know this is something in terms of a constant * a sum #so we temporarily put the constants inside for simplification #then simplify the result def __refactor(val): args = Mul.make_args(val) sumv = next(x for x in args if isinstance(x, Sum)) constant = Mul(*[x for x in args if x != sumv]) return Sum(constant * sumv.function, *sumv.limits) if isinstance(self, Mul): rself = __refactor(self) else: rself = self if isinstance(other, Mul): rother = __refactor(other) else: rother = other if type(rself) == type(rother): if method == 0: if rself.limits == rother.limits: return factor_sum(Sum(rself.function + rother.function, *rself.limits)) elif method == 1: if simplify(rself.function - rother.function) == 0: if len(rself.limits) == len(rother.limits) == 1: i = rself.limits[0][0] x1 = rself.limits[0][1] y1 = rself.limits[0][2] j = rother.limits[0][0] x2 = rother.limits[0][1] y2 = rother.limits[0][2] if i == j: if x2 == y1 + 1: return factor_sum(Sum(rself.function, (i, x1, y2))) elif x1 == y2 + 1: return factor_sum(Sum(rself.function, (i, x2, y1))) return Add(self, other) def product_simplify(s): """Main function for Product simplification""" from sympy.concrete.products import Product terms = Mul.make_args(s) p_t = [] # Product Terms o_t = [] # Other Terms for term in terms: if isinstance(term, Product): p_t.append(term) else: o_t.append(term) used = [False] * len(p_t) for method in range(2): for i, p_term1 in enumerate(p_t): if not used[i]: for j, p_term2 in enumerate(p_t): if not used[j] and i != j: if isinstance(product_mul(p_term1, p_term2, method), Product): p_t[i] = product_mul(p_term1, p_term2, method) used[j] = True result = Mul(*o_t) for i, p_term in enumerate(p_t): if not used[i]: result = Mul(result, p_term) return result def product_mul(self, other, method=0): """Helper function for Product simplification""" from sympy.concrete.products import Product if type(self) == type(other): if method == 0: if self.limits == other.limits: return Product(self.function * other.function, *self.limits) elif method == 1: if simplify(self.function - other.function) == 0: if len(self.limits) == len(other.limits) == 1: i = self.limits[0][0] x1 = self.limits[0][1] y1 = self.limits[0][2] j = other.limits[0][0] x2 = other.limits[0][1] y2 = other.limits[0][2] if i == j: if x2 == y1 + 1: return Product(self.function, (i, x1, y2)) elif x1 == y2 + 1: return Product(self.function, (i, x2, y1)) return Mul(self, other) def _nthroot_solve(p, n, prec): """ helper function for ``nthroot`` It denests ``p**Rational(1, n)`` using its minimal polynomial """ from sympy.polys.numberfields import _minimal_polynomial_sq from sympy.solvers import solve while n % 2 == 0: p = sqrtdenest(sqrt(p)) n = n // 2 if n == 1: return p pn = p**Rational(1, n) x = Symbol('x') f = _minimal_polynomial_sq(p, n, x) if f is None: return None sols = solve(f, x) for sol in sols: if abs(sol - pn).n() < 1./10**prec: sol = sqrtdenest(sol) if _mexpand(sol**n) == p: return sol def logcombine(expr, force=False): """ Takes logarithms and combines them using the following rules: - log(x) + log(y) == log(x*y) if both are positive - a*log(x) == log(x**a) if x is positive and a is real If ``force`` is ``True`` then the assumptions above will be assumed to hold if there is no assumption already in place on a quantity. For example, if ``a`` is imaginary or the argument negative, force will not perform a combination but if ``a`` is a symbol with no assumptions the change will take place. Examples ======== >>> from sympy import Symbol, symbols, log, logcombine, I >>> from sympy.abc import a, x, y, z >>> logcombine(a*log(x) + log(y) - log(z)) a*log(x) + log(y) - log(z) >>> logcombine(a*log(x) + log(y) - log(z), force=True) log(x**a*y/z) >>> x,y,z = symbols('x,y,z', positive=True) >>> a = Symbol('a', real=True) >>> logcombine(a*log(x) + log(y) - log(z)) log(x**a*y/z) The transformation is limited to factors and/or terms that contain logs, so the result depends on the initial state of expansion: >>> eq = (2 + 3*I)*log(x) >>> logcombine(eq, force=True) == eq True >>> logcombine(eq.expand(), force=True) log(x**2) + I*log(x**3) See Also ======== posify: replace all symbols with symbols having positive assumptions sympy.core.function.expand_log: expand the logarithms of products and powers; the opposite of logcombine """ def f(rv): if not (rv.is_Add or rv.is_Mul): return rv def gooda(a): # bool to tell whether the leading ``a`` in ``a*log(x)`` # could appear as log(x**a) return (a is not S.NegativeOne and # -1 *could* go, but we disallow (a.is_extended_real or force and a.is_extended_real is not False)) def goodlog(l): # bool to tell whether log ``l``'s argument can combine with others a = l.args[0] return a.is_positive or force and a.is_nonpositive is not False other = [] logs = [] log1 = defaultdict(list) for a in Add.make_args(rv): if isinstance(a, log) and goodlog(a): log1[()].append(([], a)) elif not a.is_Mul: other.append(a) else: ot = [] co = [] lo = [] for ai in a.args: if ai.is_Rational and ai < 0: ot.append(S.NegativeOne) co.append(-ai) elif isinstance(ai, log) and goodlog(ai): lo.append(ai) elif gooda(ai): co.append(ai) else: ot.append(ai) if len(lo) > 1: logs.append((ot, co, lo)) elif lo: log1[tuple(ot)].append((co, lo[0])) else: other.append(a) # if there is only one log in other, put it with the # good logs if len(other) == 1 and isinstance(other[0], log): log1[()].append(([], other.pop())) # if there is only one log at each coefficient and none have # an exponent to place inside the log then there is nothing to do if not logs and all(len(log1[k]) == 1 and log1[k][0] == [] for k in log1): return rv # collapse multi-logs as far as possible in a canonical way # TODO: see if x*log(a)+x*log(a)*log(b) -> x*log(a)*(1+log(b))? # -- in this case, it's unambiguous, but if it were were a log(c) in # each term then it's arbitrary whether they are grouped by log(a) or # by log(c). So for now, just leave this alone; it's probably better to # let the user decide for o, e, l in logs: l = list(ordered(l)) e = log(l.pop(0).args[0]**Mul(*e)) while l: li = l.pop(0) e = log(li.args[0]**e) c, l = Mul(*o), e if isinstance(l, log): # it should be, but check to be sure log1[(c,)].append(([], l)) else: other.append(c*l) # logs that have the same coefficient can multiply for k in list(log1.keys()): log1[Mul(*k)] = log(logcombine(Mul(*[ l.args[0]**Mul(*c) for c, l in log1.pop(k)]), force=force), evaluate=False) # logs that have oppositely signed coefficients can divide for k in ordered(list(log1.keys())): if not k in log1: # already popped as -k continue if -k in log1: # figure out which has the minus sign; the one with # more op counts should be the one num, den = k, -k if num.count_ops() > den.count_ops(): num, den = den, num other.append( num*log(log1.pop(num).args[0]/log1.pop(den).args[0], evaluate=False)) else: other.append(k*log1.pop(k)) return Add(*other) return bottom_up(expr, f) def inversecombine(expr): """Simplify the composition of a function and its inverse. Explanation =========== No attention is paid to whether the inverse is a left inverse or a right inverse; thus, the result will in general not be equivalent to the original expression. Examples ======== >>> from sympy.simplify.simplify import inversecombine >>> from sympy import asin, sin, log, exp >>> from sympy.abc import x >>> inversecombine(asin(sin(x))) x >>> inversecombine(2*log(exp(3*x))) 6*x """ def f(rv): if rv.is_Function and hasattr(rv, "inverse"): if (len(rv.args) == 1 and len(rv.args[0].args) == 1 and isinstance(rv.args[0], rv.inverse(argindex=1))): rv = rv.args[0].args[0] return rv return bottom_up(expr, f) def walk(e, *target): """Iterate through the args that are the given types (target) and return a list of the args that were traversed; arguments that are not of the specified types are not traversed. Examples ======== >>> from sympy.simplify.simplify import walk >>> from sympy import Min, Max >>> from sympy.abc import x, y, z >>> list(walk(Min(x, Max(y, Min(1, z))), Min)) [Min(x, Max(y, Min(1, z)))] >>> list(walk(Min(x, Max(y, Min(1, z))), Min, Max)) [Min(x, Max(y, Min(1, z))), Max(y, Min(1, z)), Min(1, z)] See Also ======== bottom_up """ if isinstance(e, target): yield e for i in e.args: yield from walk(i, *target) def bottom_up(rv, F, atoms=False, nonbasic=False): """Apply ``F`` to all expressions in an expression tree from the bottom up. If ``atoms`` is True, apply ``F`` even if there are no args; if ``nonbasic`` is True, try to apply ``F`` to non-Basic objects. """ args = getattr(rv, 'args', None) if args is not None: if args: args = tuple([bottom_up(a, F, atoms, nonbasic) for a in args]) if args != rv.args: rv = rv.func(*args) rv = F(rv) elif atoms: rv = F(rv) else: if nonbasic: try: rv = F(rv) except TypeError: pass return rv def kroneckersimp(expr): """ Simplify expressions with KroneckerDelta. The only simplification currently attempted is to identify multiplicative cancellation: Examples ======== >>> from sympy import KroneckerDelta, kroneckersimp >>> from sympy.abc import i >>> kroneckersimp(1 + KroneckerDelta(0, i) * KroneckerDelta(1, i)) 1 """ def args_cancel(args1, args2): for i1 in range(2): for i2 in range(2): a1 = args1[i1] a2 = args2[i2] a3 = args1[(i1 + 1) % 2] a4 = args2[(i2 + 1) % 2] if Eq(a1, a2) is S.true and Eq(a3, a4) is S.false: return True return False def cancel_kronecker_mul(m): from sympy.utilities.iterables import subsets args = m.args deltas = [a for a in args if isinstance(a, KroneckerDelta)] for delta1, delta2 in subsets(deltas, 2): args1 = delta1.args args2 = delta2.args if args_cancel(args1, args2): return 0*m return m if not expr.has(KroneckerDelta): return expr if expr.has(Piecewise): expr = expr.rewrite(KroneckerDelta) newexpr = expr expr = None while newexpr != expr: expr = newexpr newexpr = expr.replace(lambda e: isinstance(e, Mul), cancel_kronecker_mul) return expr def besselsimp(expr): """ Simplify bessel-type functions. Explanation =========== This routine tries to simplify bessel-type functions. Currently it only works on the Bessel J and I functions, however. It works by looking at all such functions in turn, and eliminating factors of "I" and "-1" (actually their polar equivalents) in front of the argument. Then, functions of half-integer order are rewritten using strigonometric functions and functions of integer order (> 1) are rewritten using functions of low order. Finally, if the expression was changed, compute factorization of the result with factor(). >>> from sympy import besselj, besseli, besselsimp, polar_lift, I, S >>> from sympy.abc import z, nu >>> besselsimp(besselj(nu, z*polar_lift(-1))) exp(I*pi*nu)*besselj(nu, z) >>> besselsimp(besseli(nu, z*polar_lift(-I))) exp(-I*pi*nu/2)*besselj(nu, z) >>> besselsimp(besseli(S(-1)/2, z)) sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z)) >>> besselsimp(z*besseli(0, z) + z*(besseli(2, z))/2 + besseli(1, z)) 3*z*besseli(0, z)/2 """ # TODO # - better algorithm? # - simplify (cos(pi*b)*besselj(b,z) - besselj(-b,z))/sin(pi*b) ... # - use contiguity relations? def replacer(fro, to, factors): factors = set(factors) def repl(nu, z): if factors.intersection(Mul.make_args(z)): return to(nu, z) return fro(nu, z) return repl def torewrite(fro, to): def tofunc(nu, z): return fro(nu, z).rewrite(to) return tofunc def tominus(fro): def tofunc(nu, z): return exp(I*pi*nu)*fro(nu, exp_polar(-I*pi)*z) return tofunc orig_expr = expr ifactors = [I, exp_polar(I*pi/2), exp_polar(-I*pi/2)] expr = expr.replace( besselj, replacer(besselj, torewrite(besselj, besseli), ifactors)) expr = expr.replace( besseli, replacer(besseli, torewrite(besseli, besselj), ifactors)) minusfactors = [-1, exp_polar(I*pi)] expr = expr.replace( besselj, replacer(besselj, tominus(besselj), minusfactors)) expr = expr.replace( besseli, replacer(besseli, tominus(besseli), minusfactors)) z0 = Dummy('z') def expander(fro): def repl(nu, z): if (nu % 1) == S.Half: return simplify(trigsimp(unpolarify( fro(nu, z0).rewrite(besselj).rewrite(jn).expand( func=True)).subs(z0, z))) elif nu.is_Integer and nu > 1: return fro(nu, z).expand(func=True) return fro(nu, z) return repl expr = expr.replace(besselj, expander(besselj)) expr = expr.replace(bessely, expander(bessely)) expr = expr.replace(besseli, expander(besseli)) expr = expr.replace(besselk, expander(besselk)) def _bessel_simp_recursion(expr): def _use_recursion(bessel, expr): while True: bessels = expr.find(lambda x: isinstance(x, bessel)) try: for ba in sorted(bessels, key=lambda x: re(x.args[0])): a, x = ba.args bap1 = bessel(a+1, x) bap2 = bessel(a+2, x) if expr.has(bap1) and expr.has(bap2): expr = expr.subs(ba, 2*(a+1)/x*bap1 - bap2) break else: return expr except (ValueError, TypeError): return expr if expr.has(besselj): expr = _use_recursion(besselj, expr) if expr.has(bessely): expr = _use_recursion(bessely, expr) return expr expr = _bessel_simp_recursion(expr) if expr != orig_expr: expr = expr.factor() return expr def nthroot(expr, n, max_len=4, prec=15): """ Compute a real nth-root of a sum of surds. Parameters ========== expr : sum of surds n : integer max_len : maximum number of surds passed as constants to ``nsimplify`` Algorithm ========= First ``nsimplify`` is used to get a candidate root; if it is not a root the minimal polynomial is computed; the answer is one of its roots. Examples ======== >>> from sympy.simplify.simplify import nthroot >>> from sympy import sqrt >>> nthroot(90 + 34*sqrt(7), 3) sqrt(7) + 3 """ expr = sympify(expr) n = sympify(n) p = expr**Rational(1, n) if not n.is_integer: return p if not _is_sum_surds(expr): return p surds = [] coeff_muls = [x.as_coeff_Mul() for x in expr.args] for x, y in coeff_muls: if not x.is_rational: return p if y is S.One: continue if not (y.is_Pow and y.exp == S.Half and y.base.is_integer): return p surds.append(y) surds.sort() surds = surds[:max_len] if expr < 0 and n % 2 == 1: p = (-expr)**Rational(1, n) a = nsimplify(p, constants=surds) res = a if _mexpand(a**n) == _mexpand(-expr) else p return -res a = nsimplify(p, constants=surds) if _mexpand(a) is not _mexpand(p) and _mexpand(a**n) == _mexpand(expr): return _mexpand(a) expr = _nthroot_solve(expr, n, prec) if expr is None: return p return expr def nsimplify(expr, constants=(), tolerance=None, full=False, rational=None, rational_conversion='base10'): """ Find a simple representation for a number or, if there are free symbols or if ``rational=True``, then replace Floats with their Rational equivalents. If no change is made and rational is not False then Floats will at least be converted to Rationals. Explanation =========== For numerical expressions, a simple formula that numerically matches the given numerical expression is sought (and the input should be possible to evalf to a precision of at least 30 digits). Optionally, a list of (rationally independent) constants to include in the formula may be given. A lower tolerance may be set to find less exact matches. If no tolerance is given then the least precise value will set the tolerance (e.g. Floats default to 15 digits of precision, so would be tolerance=10**-15). With ``full=True``, a more extensive search is performed (this is useful to find simpler numbers when the tolerance is set low). When converting to rational, if rational_conversion='base10' (the default), then convert floats to rationals using their base-10 (string) representation. When rational_conversion='exact' it uses the exact, base-2 representation. Examples ======== >>> from sympy import nsimplify, sqrt, GoldenRatio, exp, I, pi >>> nsimplify(4/(1+sqrt(5)), [GoldenRatio]) -2 + 2*GoldenRatio >>> nsimplify((1/(exp(3*pi*I/5)+1))) 1/2 - I*sqrt(sqrt(5)/10 + 1/4) >>> nsimplify(I**I, [pi]) exp(-pi/2) >>> nsimplify(pi, tolerance=0.01) 22/7 >>> nsimplify(0.333333333333333, rational=True, rational_conversion='exact') 6004799503160655/18014398509481984 >>> nsimplify(0.333333333333333, rational=True) 1/3 See Also ======== sympy.core.function.nfloat """ try: return sympify(as_int(expr)) except (TypeError, ValueError): pass expr = sympify(expr).xreplace({ Float('inf'): S.Infinity, Float('-inf'): S.NegativeInfinity, }) if expr is S.Infinity or expr is S.NegativeInfinity: return expr if rational or expr.free_symbols: return _real_to_rational(expr, tolerance, rational_conversion) # SymPy's default tolerance for Rationals is 15; other numbers may have # lower tolerances set, so use them to pick the largest tolerance if None # was given if tolerance is None: tolerance = 10**-min([15] + [mpmath.libmp.libmpf.prec_to_dps(n._prec) for n in expr.atoms(Float)]) # XXX should prec be set independent of tolerance or should it be computed # from tolerance? prec = 30 bprec = int(prec*3.33) constants_dict = {} for constant in constants: constant = sympify(constant) v = constant.evalf(prec) if not v.is_Float: raise ValueError("constants must be real-valued") constants_dict[str(constant)] = v._to_mpmath(bprec) exprval = expr.evalf(prec, chop=True) re, im = exprval.as_real_imag() # safety check to make sure that this evaluated to a number if not (re.is_Number and im.is_Number): return expr def nsimplify_real(x): orig = mpmath.mp.dps xv = x._to_mpmath(bprec) try: # We'll be happy with low precision if a simple fraction if not (tolerance or full): mpmath.mp.dps = 15 rat = mpmath.pslq([xv, 1]) if rat is not None: return Rational(-int(rat[1]), int(rat[0])) mpmath.mp.dps = prec newexpr = mpmath.identify(xv, constants=constants_dict, tol=tolerance, full=full) if not newexpr: raise ValueError if full: newexpr = newexpr[0] expr = sympify(newexpr) if x and not expr: # don't let x become 0 raise ValueError if expr.is_finite is False and not xv in [mpmath.inf, mpmath.ninf]: raise ValueError return expr finally: # even though there are returns above, this is executed # before leaving mpmath.mp.dps = orig try: if re: re = nsimplify_real(re) if im: im = nsimplify_real(im) except ValueError: if rational is None: return _real_to_rational(expr, rational_conversion=rational_conversion) return expr rv = re + im*S.ImaginaryUnit # if there was a change or rational is explicitly not wanted # return the value, else return the Rational representation if rv != expr or rational is False: return rv return _real_to_rational(expr, rational_conversion=rational_conversion) def _real_to_rational(expr, tolerance=None, rational_conversion='base10'): """ Replace all reals in expr with rationals. Examples ======== >>> from sympy.simplify.simplify import _real_to_rational >>> from sympy.abc import x >>> _real_to_rational(.76 + .1*x**.5) sqrt(x)/10 + 19/25 If rational_conversion='base10', this uses the base-10 string. If rational_conversion='exact', the exact, base-2 representation is used. >>> _real_to_rational(0.333333333333333, rational_conversion='exact') 6004799503160655/18014398509481984 >>> _real_to_rational(0.333333333333333) 1/3 """ expr = _sympify(expr) inf = Float('inf') p = expr reps = {} reduce_num = None if tolerance is not None and tolerance < 1: reduce_num = ceiling(1/tolerance) for fl in p.atoms(Float): key = fl if reduce_num is not None: r = Rational(fl).limit_denominator(reduce_num) elif (tolerance is not None and tolerance >= 1 and fl.is_Integer is False): r = Rational(tolerance*round(fl/tolerance) ).limit_denominator(int(tolerance)) else: if rational_conversion == 'exact': r = Rational(fl) reps[key] = r continue elif rational_conversion != 'base10': raise ValueError("rational_conversion must be 'base10' or 'exact'") r = nsimplify(fl, rational=False) # e.g. log(3).n() -> log(3) instead of a Rational if fl and not r: r = Rational(fl) elif not r.is_Rational: if fl == inf or fl == -inf: r = S.ComplexInfinity elif fl < 0: fl = -fl d = Pow(10, int(mpmath.log(fl)/mpmath.log(10))) r = -Rational(str(fl/d))*d elif fl > 0: d = Pow(10, int(mpmath.log(fl)/mpmath.log(10))) r = Rational(str(fl/d))*d else: r = Integer(0) reps[key] = r return p.subs(reps, simultaneous=True) def clear_coefficients(expr, rhs=S.Zero): """Return `p, r` where `p` is the expression obtained when Rational additive and multiplicative coefficients of `expr` have been stripped away in a naive fashion (i.e. without simplification). The operations needed to remove the coefficients will be applied to `rhs` and returned as `r`. Examples ======== >>> from sympy.simplify.simplify import clear_coefficients >>> from sympy.abc import x, y >>> from sympy import Dummy >>> expr = 4*y*(6*x + 3) >>> clear_coefficients(expr - 2) (y*(2*x + 1), 1/6) When solving 2 or more expressions like `expr = a`, `expr = b`, etc..., it is advantageous to provide a Dummy symbol for `rhs` and simply replace it with `a`, `b`, etc... in `r`. >>> rhs = Dummy('rhs') >>> clear_coefficients(expr, rhs) (y*(2*x + 1), _rhs/12) >>> _[1].subs(rhs, 2) 1/6 """ was = None free = expr.free_symbols if expr.is_Rational: return (S.Zero, rhs - expr) while expr and was != expr: was = expr m, expr = ( expr.as_content_primitive() if free else factor_terms(expr).as_coeff_Mul(rational=True)) rhs /= m c, expr = expr.as_coeff_Add(rational=True) rhs -= c expr = signsimp(expr, evaluate = False) if _coeff_isneg(expr): expr = -expr rhs = -rhs return expr, rhs def nc_simplify(expr, deep=True): ''' Simplify a non-commutative expression composed of multiplication and raising to a power by grouping repeated subterms into one power. Priority is given to simplifications that give the fewest number of arguments in the end (for example, in a*b*a*b*c*a*b*c simplifying to (a*b)**2*c*a*b*c gives 5 arguments while a*b*(a*b*c)**2 has 3). If ``expr`` is a sum of such terms, the sum of the simplified terms is returned. Keyword argument ``deep`` controls whether or not subexpressions nested deeper inside the main expression are simplified. See examples below. Setting `deep` to `False` can save time on nested expressions that don't need simplifying on all levels. Examples ======== >>> from sympy import symbols >>> from sympy.simplify.simplify import nc_simplify >>> a, b, c = symbols("a b c", commutative=False) >>> nc_simplify(a*b*a*b*c*a*b*c) a*b*(a*b*c)**2 >>> expr = a**2*b*a**4*b*a**4 >>> nc_simplify(expr) a**2*(b*a**4)**2 >>> nc_simplify(a*b*a*b*c**2*(a*b)**2*c**2) ((a*b)**2*c**2)**2 >>> nc_simplify(a*b*a*b + 2*a*c*a**2*c*a**2*c*a) (a*b)**2 + 2*(a*c*a)**3 >>> nc_simplify(b**-1*a**-1*(a*b)**2) a*b >>> nc_simplify(a**-1*b**-1*c*a) (b*a)**(-1)*c*a >>> expr = (a*b*a*b)**2*a*c*a*c >>> nc_simplify(expr) (a*b)**4*(a*c)**2 >>> nc_simplify(expr, deep=False) (a*b*a*b)**2*(a*c)**2 ''' from sympy.matrices.expressions import (MatrixExpr, MatAdd, MatMul, MatPow, MatrixSymbol) from sympy.core.exprtools import factor_nc if isinstance(expr, MatrixExpr): expr = expr.doit(inv_expand=False) _Add, _Mul, _Pow, _Symbol = MatAdd, MatMul, MatPow, MatrixSymbol else: _Add, _Mul, _Pow, _Symbol = Add, Mul, Pow, Symbol # =========== Auxiliary functions ======================== def _overlaps(args): # Calculate a list of lists m such that m[i][j] contains the lengths # of all possible overlaps between args[:i+1] and args[i+1+j:]. # An overlap is a suffix of the prefix that matches a prefix # of the suffix. # For example, let expr=c*a*b*a*b*a*b*a*b. Then m[3][0] contains # the lengths of overlaps of c*a*b*a*b with a*b*a*b. The overlaps # are a*b*a*b, a*b and the empty word so that m[3][0]=[4,2,0]. # All overlaps rather than only the longest one are recorded # because this information helps calculate other overlap lengths. m = [[([1, 0] if a == args[0] else [0]) for a in args[1:]]] for i in range(1, len(args)): overlaps = [] j = 0 for j in range(len(args) - i - 1): overlap = [] for v in m[i-1][j+1]: if j + i + 1 + v < len(args) and args[i] == args[j+i+1+v]: overlap.append(v + 1) overlap += [0] overlaps.append(overlap) m.append(overlaps) return m def _reduce_inverses(_args): # replace consecutive negative powers by an inverse # of a product of positive powers, e.g. a**-1*b**-1*c # will simplify to (a*b)**-1*c; # return that new args list and the number of negative # powers in it (inv_tot) inv_tot = 0 # total number of inverses inverses = [] args = [] for arg in _args: if isinstance(arg, _Pow) and arg.args[1] < 0: inverses = [arg**-1] + inverses inv_tot += 1 else: if len(inverses) == 1: args.append(inverses[0]**-1) elif len(inverses) > 1: args.append(_Pow(_Mul(*inverses), -1)) inv_tot -= len(inverses) - 1 inverses = [] args.append(arg) if inverses: args.append(_Pow(_Mul(*inverses), -1)) inv_tot -= len(inverses) - 1 return inv_tot, tuple(args) def get_score(s): # compute the number of arguments of s # (including in nested expressions) overall # but ignore exponents if isinstance(s, _Pow): return get_score(s.args[0]) elif isinstance(s, (_Add, _Mul)): return sum([get_score(a) for a in s.args]) return 1 def compare(s, alt_s): # compare two possible simplifications and return a # "better" one if s != alt_s and get_score(alt_s) < get_score(s): return alt_s return s # ======================================================== if not isinstance(expr, (_Add, _Mul, _Pow)) or expr.is_commutative: return expr args = expr.args[:] if isinstance(expr, _Pow): if deep: return _Pow(nc_simplify(args[0]), args[1]).doit() else: return expr elif isinstance(expr, _Add): return _Add(*[nc_simplify(a, deep=deep) for a in args]).doit() else: # get the non-commutative part c_args, args = expr.args_cnc() com_coeff = Mul(*c_args) if com_coeff != 1: return com_coeff*nc_simplify(expr/com_coeff, deep=deep) inv_tot, args = _reduce_inverses(args) # if most arguments are negative, work with the inverse # of the expression, e.g. a**-1*b*a**-1*c**-1 will become # (c*a*b**-1*a)**-1 at the end so can work with c*a*b**-1*a invert = False if inv_tot > len(args)/2: invert = True args = [a**-1 for a in args[::-1]] if deep: args = tuple(nc_simplify(a) for a in args) m = _overlaps(args) # simps will be {subterm: end} where `end` is the ending # index of a sequence of repetitions of subterm; # this is for not wasting time with subterms that are part # of longer, already considered sequences simps = {} post = 1 pre = 1 # the simplification coefficient is the number of # arguments by which contracting a given sequence # would reduce the word; e.g. in a*b*a*b*c*a*b*c, # contracting a*b*a*b to (a*b)**2 removes 3 arguments # while a*b*c*a*b*c to (a*b*c)**2 removes 6. It's # better to contract the latter so simplification # with a maximum simplification coefficient will be chosen max_simp_coeff = 0 simp = None # information about future simplification for i in range(1, len(args)): simp_coeff = 0 l = 0 # length of a subterm p = 0 # the power of a subterm if i < len(args) - 1: rep = m[i][0] start = i # starting index of the repeated sequence end = i+1 # ending index of the repeated sequence if i == len(args)-1 or rep == [0]: # no subterm is repeated at this stage, at least as # far as the arguments are concerned - there may be # a repetition if powers are taken into account if (isinstance(args[i], _Pow) and not isinstance(args[i].args[0], _Symbol)): subterm = args[i].args[0].args l = len(subterm) if args[i-l:i] == subterm: # e.g. a*b in a*b*(a*b)**2 is not repeated # in args (= [a, b, (a*b)**2]) but it # can be matched here p += 1 start -= l if args[i+1:i+1+l] == subterm: # e.g. a*b in (a*b)**2*a*b p += 1 end += l if p: p += args[i].args[1] else: continue else: l = rep[0] # length of the longest repeated subterm at this point start -= l - 1 subterm = args[start:end] p = 2 end += l if subterm in simps and simps[subterm] >= start: # the subterm is part of a sequence that # has already been considered continue # count how many times it's repeated while end < len(args): if l in m[end-1][0]: p += 1 end += l elif isinstance(args[end], _Pow) and args[end].args[0].args == subterm: # for cases like a*b*a*b*(a*b)**2*a*b p += args[end].args[1] end += 1 else: break # see if another match can be made, e.g. # for b*a**2 in b*a**2*b*a**3 or a*b in # a**2*b*a*b pre_exp = 0 pre_arg = 1 if start - l >= 0 and args[start-l+1:start] == subterm[1:]: if isinstance(subterm[0], _Pow): pre_arg = subterm[0].args[0] exp = subterm[0].args[1] else: pre_arg = subterm[0] exp = 1 if isinstance(args[start-l], _Pow) and args[start-l].args[0] == pre_arg: pre_exp = args[start-l].args[1] - exp start -= l p += 1 elif args[start-l] == pre_arg: pre_exp = 1 - exp start -= l p += 1 post_exp = 0 post_arg = 1 if end + l - 1 < len(args) and args[end:end+l-1] == subterm[:-1]: if isinstance(subterm[-1], _Pow): post_arg = subterm[-1].args[0] exp = subterm[-1].args[1] else: post_arg = subterm[-1] exp = 1 if isinstance(args[end+l-1], _Pow) and args[end+l-1].args[0] == post_arg: post_exp = args[end+l-1].args[1] - exp end += l p += 1 elif args[end+l-1] == post_arg: post_exp = 1 - exp end += l p += 1 # Consider a*b*a**2*b*a**2*b*a: # b*a**2 is explicitly repeated, but note # that in this case a*b*a is also repeated # so there are two possible simplifications: # a*(b*a**2)**3*a**-1 or (a*b*a)**3 # The latter is obviously simpler. # But in a*b*a**2*b**2*a**2 the simplifications are # a*(b*a**2)**2 and (a*b*a)**3*a in which case # it's better to stick with the shorter subterm if post_exp and exp % 2 == 0 and start > 0: exp = exp/2 _pre_exp = 1 _post_exp = 1 if isinstance(args[start-1], _Pow) and args[start-1].args[0] == post_arg: _post_exp = post_exp + exp _pre_exp = args[start-1].args[1] - exp elif args[start-1] == post_arg: _post_exp = post_exp + exp _pre_exp = 1 - exp if _pre_exp == 0 or _post_exp == 0: if not pre_exp: start -= 1 post_exp = _post_exp pre_exp = _pre_exp pre_arg = post_arg subterm = (post_arg**exp,) + subterm[:-1] + (post_arg**exp,) simp_coeff += end-start if post_exp: simp_coeff -= 1 if pre_exp: simp_coeff -= 1 simps[subterm] = end if simp_coeff > max_simp_coeff: max_simp_coeff = simp_coeff simp = (start, _Mul(*subterm), p, end, l) pre = pre_arg**pre_exp post = post_arg**post_exp if simp: subterm = _Pow(nc_simplify(simp[1], deep=deep), simp[2]) pre = nc_simplify(_Mul(*args[:simp[0]])*pre, deep=deep) post = post*nc_simplify(_Mul(*args[simp[3]:]), deep=deep) simp = pre*subterm*post if pre != 1 or post != 1: # new simplifications may be possible but no need # to recurse over arguments simp = nc_simplify(simp, deep=False) else: simp = _Mul(*args) if invert: simp = _Pow(simp, -1) # see if factor_nc(expr) is simplified better if not isinstance(expr, MatrixExpr): f_expr = factor_nc(expr) if f_expr != expr: alt_simp = nc_simplify(f_expr, deep=deep) simp = compare(simp, alt_simp) else: simp = simp.doit(inv_expand=False) return simp def dotprodsimp(expr, withsimp=False): """Simplification for a sum of products targeted at the kind of blowup that occurs during summation of products. Intended to reduce expression blowup during matrix multiplication or other similar operations. Only works with algebraic expressions and does not recurse into non. Parameters ========== withsimp : bool, optional Specifies whether a flag should be returned along with the expression to indicate roughly whether simplification was successful. It is used in ``MatrixArithmetic._eval_pow_by_recursion`` to avoid attempting to simplify an expression repetitively which does not simplify. """ def count_ops_alg(expr): """Optimized count algebraic operations with no recursion into non-algebraic args that ``core.function.count_ops`` does. Also returns whether rational functions may be present according to negative exponents of powers or non-number fractions. Returns ======= ops, ratfunc : int, bool ``ops`` is the number of algebraic operations starting at the top level expression (not recursing into non-alg children). ``ratfunc`` specifies whether the expression MAY contain rational functions which ``cancel`` MIGHT optimize. """ ops = 0 args = [expr] ratfunc = False while args: a = args.pop() if not isinstance(a, Basic): continue if a.is_Rational: if a is not S.One: # -1/3 = NEG + DIV ops += bool (a.p < 0) + bool (a.q != 1) elif a.is_Mul: if _coeff_isneg(a): ops += 1 if a.args[0] is S.NegativeOne: a = a.as_two_terms()[1] else: a = -a n, d = fraction(a) if n.is_Integer: ops += 1 + bool (n < 0) args.append(d) # won't be -Mul but could be Add elif d is not S.One: if not d.is_Integer: args.append(d) ratfunc=True ops += 1 args.append(n) # could be -Mul else: ops += len(a.args) - 1 args.extend(a.args) elif a.is_Add: laargs = len(a.args) negs = 0 for ai in a.args: if _coeff_isneg(ai): negs += 1 ai = -ai args.append(ai) ops += laargs - (negs != laargs) # -x - y = NEG + SUB elif a.is_Pow: ops += 1 args.append(a.base) if not ratfunc: ratfunc = a.exp.is_negative is not False return ops, ratfunc def nonalg_subs_dummies(expr, dummies): """Substitute dummy variables for non-algebraic expressions to avoid evaluation of non-algebraic terms that ``polys.polytools.cancel`` does. """ if not expr.args: return expr if expr.is_Add or expr.is_Mul or expr.is_Pow: args = None for i, a in enumerate(expr.args): c = nonalg_subs_dummies(a, dummies) if c is a: continue if args is None: args = list(expr.args) args[i] = c if args is None: return expr return expr.func(*args) return dummies.setdefault(expr, Dummy()) simplified = False # doesn't really mean simplified, rather "can simplify again" if isinstance(expr, Basic) and (expr.is_Add or expr.is_Mul or expr.is_Pow): expr2 = expr.expand(deep=True, modulus=None, power_base=False, power_exp=False, mul=True, log=False, multinomial=True, basic=False) if expr2 != expr: expr = expr2 simplified = True exprops, ratfunc = count_ops_alg(expr) if exprops >= 6: # empirically tested cutoff for expensive simplification if ratfunc: dummies = {} expr2 = nonalg_subs_dummies(expr, dummies) if expr2 is expr or count_ops_alg(expr2)[0] >= 6: # check again after substitution expr3 = cancel(expr2) if expr3 != expr2: expr = expr3.subs([(d, e) for e, d in dummies.items()]) simplified = True # very special case: x/(x-1) - 1/(x-1) -> 1 elif (exprops == 5 and expr.is_Add and expr.args [0].is_Mul and expr.args [1].is_Mul and expr.args [0].args [-1].is_Pow and expr.args [1].args [-1].is_Pow and expr.args [0].args [-1].exp is S.NegativeOne and expr.args [1].args [-1].exp is S.NegativeOne): expr2 = together (expr) expr2ops = count_ops_alg(expr2)[0] if expr2ops < exprops: expr = expr2 simplified = True else: simplified = True return (expr, simplified) if withsimp else expr

87332005ca78b461da90cbc74b0568b8a67818df30d6e7ffdb97e41f6294405f

"""Tools for applying functions to specified parts of expressions. """ from sympy.core import sympify def use(expr, func, level=0, args=(), kwargs={}): """ Use ``func`` to transform ``expr`` at the given level. Examples ======== >>> from sympy import use, expand >>> from sympy.abc import x, y >>> f = (x + y)**2*x + 1 >>> use(f, expand, level=2) x*(x**2 + 2*x*y + y**2) + 1 >>> expand(f) x**3 + 2*x**2*y + x*y**2 + 1 """ def _use(expr, level): if not level: return func(expr, *args, **kwargs) else: if expr.is_Atom: return expr else: level -= 1 _args = [] for arg in expr.args: _args.append(_use(arg, level)) return expr.__class__(*_args) return _use(sympify(expr), level)

6c1b4a8bf7bd8ff6aa680c23c9ba36060aaba78928c502ea4ac98624b79c1988

from collections import defaultdict from sympy import SYMPY_DEBUG from sympy.core import expand_power_base, sympify, Add, S, Mul, Derivative, Pow, symbols, expand_mul from sympy.core.add import _unevaluated_Add from sympy.core.compatibility import iterable, ordered, default_sort_key from sympy.core.parameters import global_parameters from sympy.core.exprtools import Factors, gcd_terms from sympy.core.function import _mexpand from sympy.core.mul import _keep_coeff, _unevaluated_Mul from sympy.core.numbers import Rational from sympy.functions import exp, sqrt, log from sympy.functions.elementary.complexes import Abs from sympy.polys import gcd from sympy.simplify.sqrtdenest import sqrtdenest def collect(expr, syms, func=None, evaluate=None, exact=False, distribute_order_term=True): """ Collect additive terms of an expression. Explanation =========== This function collects additive terms of an expression with respect to a list of expression up to powers with rational exponents. By the term symbol here are meant arbitrary expressions, which can contain powers, products, sums etc. In other words symbol is a pattern which will be searched for in the expression's terms. The input expression is not expanded by :func:`collect`, so user is expected to provide an expression is an appropriate form. This makes :func:`collect` more predictable as there is no magic happening behind the scenes. However, it is important to note, that powers of products are converted to products of powers using the :func:`~.expand_power_base` function. There are two possible types of output. First, if ``evaluate`` flag is set, this function will return an expression with collected terms or else it will return a dictionary with expressions up to rational powers as keys and collected coefficients as values. Examples ======== >>> from sympy import S, collect, expand, factor, Wild >>> from sympy.abc import a, b, c, x, y This function can collect symbolic coefficients in polynomials or rational expressions. It will manage to find all integer or rational powers of collection variable:: >>> collect(a*x**2 + b*x**2 + a*x - b*x + c, x) c + x**2*(a + b) + x*(a - b) The same result can be achieved in dictionary form:: >>> d = collect(a*x**2 + b*x**2 + a*x - b*x + c, x, evaluate=False) >>> d[x**2] a + b >>> d[x] a - b >>> d[S.One] c You can also work with multivariate polynomials. However, remember that this function is greedy so it will care only about a single symbol at time, in specification order:: >>> collect(x**2 + y*x**2 + x*y + y + a*y, [x, y]) x**2*(y + 1) + x*y + y*(a + 1) Also more complicated expressions can be used as patterns:: >>> from sympy import sin, log >>> collect(a*sin(2*x) + b*sin(2*x), sin(2*x)) (a + b)*sin(2*x) >>> collect(a*x*log(x) + b*(x*log(x)), x*log(x)) x*(a + b)*log(x) You can use wildcards in the pattern:: >>> w = Wild('w1') >>> collect(a*x**y - b*x**y, w**y) x**y*(a - b) It is also possible to work with symbolic powers, although it has more complicated behavior, because in this case power's base and symbolic part of the exponent are treated as a single symbol:: >>> collect(a*x**c + b*x**c, x) a*x**c + b*x**c >>> collect(a*x**c + b*x**c, x**c) x**c*(a + b) However if you incorporate rationals to the exponents, then you will get well known behavior:: >>> collect(a*x**(2*c) + b*x**(2*c), x**c) x**(2*c)*(a + b) Note also that all previously stated facts about :func:`collect` function apply to the exponential function, so you can get:: >>> from sympy import exp >>> collect(a*exp(2*x) + b*exp(2*x), exp(x)) (a + b)*exp(2*x) If you are interested only in collecting specific powers of some symbols then set ``exact`` flag in arguments:: >>> collect(a*x**7 + b*x**7, x, exact=True) a*x**7 + b*x**7 >>> collect(a*x**7 + b*x**7, x**7, exact=True) x**7*(a + b) You can also apply this function to differential equations, where derivatives of arbitrary order can be collected. Note that if you collect with respect to a function or a derivative of a function, all derivatives of that function will also be collected. Use ``exact=True`` to prevent this from happening:: >>> from sympy import Derivative as D, collect, Function >>> f = Function('f') (x) >>> collect(a*D(f,x) + b*D(f,x), D(f,x)) (a + b)*Derivative(f(x), x) >>> collect(a*D(D(f,x),x) + b*D(D(f,x),x), f) (a + b)*Derivative(f(x), (x, 2)) >>> collect(a*D(D(f,x),x) + b*D(D(f,x),x), D(f,x), exact=True) a*Derivative(f(x), (x, 2)) + b*Derivative(f(x), (x, 2)) >>> collect(a*D(f,x) + b*D(f,x) + a*f + b*f, f) (a + b)*f(x) + (a + b)*Derivative(f(x), x) Or you can even match both derivative order and exponent at the same time:: >>> collect(a*D(D(f,x),x)**2 + b*D(D(f,x),x)**2, D(f,x)) (a + b)*Derivative(f(x), (x, 2))**2 Finally, you can apply a function to each of the collected coefficients. For example you can factorize symbolic coefficients of polynomial:: >>> f = expand((x + a + 1)**3) >>> collect(f, x, factor) x**3 + 3*x**2*(a + 1) + 3*x*(a + 1)**2 + (a + 1)**3 .. note:: Arguments are expected to be in expanded form, so you might have to call :func:`~.expand` prior to calling this function. See Also ======== collect_const, collect_sqrt, rcollect """ from sympy.core.assumptions import assumptions from sympy.utilities.iterables import sift from sympy.core.symbol import Dummy, Wild expr = sympify(expr) syms = [sympify(i) for i in (syms if iterable(syms) else [syms])] # replace syms[i] if it is not x, -x or has Wild symbols cond = lambda x: x.is_Symbol or (-x).is_Symbol or bool( x.atoms(Wild)) _, nonsyms = sift(syms, cond, binary=True) if nonsyms: reps = dict(zip(nonsyms, [Dummy(**assumptions(i)) for i in nonsyms])) syms = [reps.get(s, s) for s in syms] rv = collect(expr.subs(reps), syms, func=func, evaluate=evaluate, exact=exact, distribute_order_term=distribute_order_term) urep = {v: k for k, v in reps.items()} if not isinstance(rv, dict): return rv.xreplace(urep) else: return {urep.get(k, k).xreplace(urep): v.xreplace(urep) for k, v in rv.items()} if evaluate is None: evaluate = global_parameters.evaluate def make_expression(terms): product = [] for term, rat, sym, deriv in terms: if deriv is not None: var, order = deriv while order > 0: term, order = Derivative(term, var), order - 1 if sym is None: if rat is S.One: product.append(term) else: product.append(Pow(term, rat)) else: product.append(Pow(term, rat*sym)) return Mul(*product) def parse_derivative(deriv): # scan derivatives tower in the input expression and return # underlying function and maximal differentiation order expr, sym, order = deriv.expr, deriv.variables[0], 1 for s in deriv.variables[1:]: if s == sym: order += 1 else: raise NotImplementedError( 'Improve MV Derivative support in collect') while isinstance(expr, Derivative): s0 = expr.variables[0] for s in expr.variables: if s != s0: raise NotImplementedError( 'Improve MV Derivative support in collect') if s0 == sym: expr, order = expr.expr, order + len(expr.variables) else: break return expr, (sym, Rational(order)) def parse_term(expr): """Parses expression expr and outputs tuple (sexpr, rat_expo, sym_expo, deriv) where: - sexpr is the base expression - rat_expo is the rational exponent that sexpr is raised to - sym_expo is the symbolic exponent that sexpr is raised to - deriv contains the derivatives the the expression For example, the output of x would be (x, 1, None, None) the output of 2**x would be (2, 1, x, None). """ rat_expo, sym_expo = S.One, None sexpr, deriv = expr, None if expr.is_Pow: if isinstance(expr.base, Derivative): sexpr, deriv = parse_derivative(expr.base) else: sexpr = expr.base if expr.exp.is_Number: rat_expo = expr.exp else: coeff, tail = expr.exp.as_coeff_Mul() if coeff.is_Number: rat_expo, sym_expo = coeff, tail else: sym_expo = expr.exp elif isinstance(expr, exp): arg = expr.args[0] if arg.is_Rational: sexpr, rat_expo = S.Exp1, arg elif arg.is_Mul: coeff, tail = arg.as_coeff_Mul(rational=True) sexpr, rat_expo = exp(tail), coeff elif isinstance(expr, Derivative): sexpr, deriv = parse_derivative(expr) return sexpr, rat_expo, sym_expo, deriv def parse_expression(terms, pattern): """Parse terms searching for a pattern. Terms is a list of tuples as returned by parse_terms; Pattern is an expression treated as a product of factors. """ pattern = Mul.make_args(pattern) if len(terms) < len(pattern): # pattern is longer than matched product # so no chance for positive parsing result return None else: pattern = [parse_term(elem) for elem in pattern] terms = terms[:] # need a copy elems, common_expo, has_deriv = [], None, False for elem, e_rat, e_sym, e_ord in pattern: if elem.is_Number and e_rat == 1 and e_sym is None: # a constant is a match for everything continue for j in range(len(terms)): if terms[j] is None: continue term, t_rat, t_sym, t_ord = terms[j] # keeping track of whether one of the terms had # a derivative or not as this will require rebuilding # the expression later if t_ord is not None: has_deriv = True if (term.match(elem) is not None and (t_sym == e_sym or t_sym is not None and e_sym is not None and t_sym.match(e_sym) is not None)): if exact is False: # we don't have to be exact so find common exponent # for both expression's term and pattern's element expo = t_rat / e_rat if common_expo is None: # first time common_expo = expo else: # common exponent was negotiated before so # there is no chance for a pattern match unless # common and current exponents are equal if common_expo != expo: common_expo = 1 else: # we ought to be exact so all fields of # interest must match in every details if e_rat != t_rat or e_ord != t_ord: continue # found common term so remove it from the expression # and try to match next element in the pattern elems.append(terms[j]) terms[j] = None break else: # pattern element not found return None return [_f for _f in terms if _f], elems, common_expo, has_deriv if evaluate: if expr.is_Add: o = expr.getO() or 0 expr = expr.func(*[ collect(a, syms, func, True, exact, distribute_order_term) for a in expr.args if a != o]) + o elif expr.is_Mul: return expr.func(*[ collect(term, syms, func, True, exact, distribute_order_term) for term in expr.args]) elif expr.is_Pow: b = collect( expr.base, syms, func, True, exact, distribute_order_term) return Pow(b, expr.exp) syms = [expand_power_base(i, deep=False) for i in syms] order_term = None if distribute_order_term: order_term = expr.getO() if order_term is not None: if order_term.has(*syms): order_term = None else: expr = expr.removeO() summa = [expand_power_base(i, deep=False) for i in Add.make_args(expr)] collected, disliked = defaultdict(list), S.Zero for product in summa: c, nc = product.args_cnc(split_1=False) args = list(ordered(c)) + nc terms = [parse_term(i) for i in args] small_first = True for symbol in syms: if SYMPY_DEBUG: print("DEBUG: parsing of expression %s with symbol %s " % ( str(terms), str(symbol)) ) if isinstance(symbol, Derivative) and small_first: terms = list(reversed(terms)) small_first = not small_first result = parse_expression(terms, symbol) if SYMPY_DEBUG: print("DEBUG: returned %s" % str(result)) if result is not None: if not symbol.is_commutative: raise AttributeError("Can not collect noncommutative symbol") terms, elems, common_expo, has_deriv = result # when there was derivative in current pattern we # will need to rebuild its expression from scratch if not has_deriv: margs = [] for elem in elems: if elem[2] is None: e = elem[1] else: e = elem[1]*elem[2] margs.append(Pow(elem[0], e)) index = Mul(*margs) else: index = make_expression(elems) terms = expand_power_base(make_expression(terms), deep=False) index = expand_power_base(index, deep=False) collected[index].append(terms) break else: # none of the patterns matched disliked += product # add terms now for each key collected = {k: Add(*v) for k, v in collected.items()} if disliked is not S.Zero: collected[S.One] = disliked if order_term is not None: for key, val in collected.items(): collected[key] = val + order_term if func is not None: collected = { key: func(val) for key, val in collected.items()} if evaluate: return Add(*[key*val for key, val in collected.items()]) else: return collected def rcollect(expr, *vars): """ Recursively collect sums in an expression. Examples ======== >>> from sympy.simplify import rcollect >>> from sympy.abc import x, y >>> expr = (x**2*y + x*y + x + y)/(x + y) >>> rcollect(expr, y) (x + y*(x**2 + x + 1))/(x + y) See Also ======== collect, collect_const, collect_sqrt """ if expr.is_Atom or not expr.has(*vars): return expr else: expr = expr.__class__(*[rcollect(arg, *vars) for arg in expr.args]) if expr.is_Add: return collect(expr, vars) else: return expr def collect_sqrt(expr, evaluate=None): """Return expr with terms having common square roots collected together. If ``evaluate`` is False a count indicating the number of sqrt-containing terms will be returned and, if non-zero, the terms of the Add will be returned, else the expression itself will be returned as a single term. If ``evaluate`` is True, the expression with any collected terms will be returned. Note: since I = sqrt(-1), it is collected, too. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import collect_sqrt >>> from sympy.abc import a, b >>> r2, r3, r5 = [sqrt(i) for i in [2, 3, 5]] >>> collect_sqrt(a*r2 + b*r2) sqrt(2)*(a + b) >>> collect_sqrt(a*r2 + b*r2 + a*r3 + b*r3) sqrt(2)*(a + b) + sqrt(3)*(a + b) >>> collect_sqrt(a*r2 + b*r2 + a*r3 + b*r5) sqrt(3)*a + sqrt(5)*b + sqrt(2)*(a + b) If evaluate is False then the arguments will be sorted and returned as a list and a count of the number of sqrt-containing terms will be returned: >>> collect_sqrt(a*r2 + b*r2 + a*r3 + b*r5, evaluate=False) ((sqrt(3)*a, sqrt(5)*b, sqrt(2)*(a + b)), 3) >>> collect_sqrt(a*sqrt(2) + b, evaluate=False) ((b, sqrt(2)*a), 1) >>> collect_sqrt(a + b, evaluate=False) ((a + b,), 0) See Also ======== collect, collect_const, rcollect """ if evaluate is None: evaluate = global_parameters.evaluate # this step will help to standardize any complex arguments # of sqrts coeff, expr = expr.as_content_primitive() vars = set() for a in Add.make_args(expr): for m in a.args_cnc()[0]: if m.is_number and ( m.is_Pow and m.exp.is_Rational and m.exp.q == 2 or m is S.ImaginaryUnit): vars.add(m) # we only want radicals, so exclude Number handling; in this case # d will be evaluated d = collect_const(expr, *vars, Numbers=False) hit = expr != d if not evaluate: nrad = 0 # make the evaluated args canonical args = list(ordered(Add.make_args(d))) for i, m in enumerate(args): c, nc = m.args_cnc() for ci in c: # XXX should this be restricted to ci.is_number as above? if ci.is_Pow and ci.exp.is_Rational and ci.exp.q == 2 or \ ci is S.ImaginaryUnit: nrad += 1 break args[i] *= coeff if not (hit or nrad): args = [Add(*args)] return tuple(args), nrad return coeff*d def collect_abs(expr): """Return ``expr`` with arguments of multiple Abs in a term collected under a single instance. Examples ======== >>> from sympy.simplify.radsimp import collect_abs >>> from sympy.abc import x >>> collect_abs(abs(x + 1)/abs(x**2 - 1)) Abs((x + 1)/(x**2 - 1)) >>> collect_abs(abs(1/x)) Abs(1/x) """ def _abs(mul): from sympy.core.mul import _mulsort c, nc = mul.args_cnc() a = [] o = [] for i in c: if isinstance(i, Abs): a.append(i.args[0]) elif isinstance(i, Pow) and isinstance(i.base, Abs) and i.exp.is_real: a.append(i.base.args[0]**i.exp) else: o.append(i) if len(a) < 2 and not any(i.exp.is_negative for i in a if isinstance(i, Pow)): return mul absarg = Mul(*a) A = Abs(absarg) args = [A] args.extend(o) if not A.has(Abs): args.extend(nc) return Mul(*args) if not isinstance(A, Abs): # reevaluate and make it unevaluated A = Abs(absarg, evaluate=False) args[0] = A _mulsort(args) args.extend(nc) # nc always go last return Mul._from_args(args, is_commutative=not nc) return expr.replace( lambda x: isinstance(x, Mul), lambda x: _abs(x)).replace( lambda x: isinstance(x, Pow), lambda x: _abs(x)) def collect_const(expr, *vars, Numbers=True): """A non-greedy collection of terms with similar number coefficients in an Add expr. If ``vars`` is given then only those constants will be targeted. Although any Number can also be targeted, if this is not desired set ``Numbers=False`` and no Float or Rational will be collected. Parameters ========== expr : sympy expression This parameter defines the expression the expression from which terms with similar coefficients are to be collected. A non-Add expression is returned as it is. vars : variable length collection of Numbers, optional Specifies the constants to target for collection. Can be multiple in number. Numbers : bool Specifies to target all instance of :class:`sympy.core.numbers.Number` class. If ``Numbers=False``, then no Float or Rational will be collected. Returns ======= expr : Expr Returns an expression with similar coefficient terms collected. Examples ======== >>> from sympy import sqrt >>> from sympy.abc import s, x, y, z >>> from sympy.simplify.radsimp import collect_const >>> collect_const(sqrt(3) + sqrt(3)*(1 + sqrt(2))) sqrt(3)*(sqrt(2) + 2) >>> collect_const(sqrt(3)*s + sqrt(7)*s + sqrt(3) + sqrt(7)) (sqrt(3) + sqrt(7))*(s + 1) >>> s = sqrt(2) + 2 >>> collect_const(sqrt(3)*s + sqrt(3) + sqrt(7)*s + sqrt(7)) (sqrt(2) + 3)*(sqrt(3) + sqrt(7)) >>> collect_const(sqrt(3)*s + sqrt(3) + sqrt(7)*s + sqrt(7), sqrt(3)) sqrt(7) + sqrt(3)*(sqrt(2) + 3) + sqrt(7)*(sqrt(2) + 2) The collection is sign-sensitive, giving higher precedence to the unsigned values: >>> collect_const(x - y - z) x - (y + z) >>> collect_const(-y - z) -(y + z) >>> collect_const(2*x - 2*y - 2*z, 2) 2*(x - y - z) >>> collect_const(2*x - 2*y - 2*z, -2) 2*x - 2*(y + z) See Also ======== collect, collect_sqrt, rcollect """ if not expr.is_Add: return expr recurse = False if not vars: recurse = True vars = set() for a in expr.args: for m in Mul.make_args(a): if m.is_number: vars.add(m) else: vars = sympify(vars) if not Numbers: vars = [v for v in vars if not v.is_Number] vars = list(ordered(vars)) for v in vars: terms = defaultdict(list) Fv = Factors(v) for m in Add.make_args(expr): f = Factors(m) q, r = f.div(Fv) if r.is_one: # only accept this as a true factor if # it didn't change an exponent from an Integer # to a non-Integer, e.g. 2/sqrt(2) -> sqrt(2) # -- we aren't looking for this sort of change fwas = f.factors.copy() fnow = q.factors if not any(k in fwas and fwas[k].is_Integer and not fnow[k].is_Integer for k in fnow): terms[v].append(q.as_expr()) continue terms[S.One].append(m) args = [] hit = False uneval = False for k in ordered(terms): v = terms[k] if k is S.One: args.extend(v) continue if len(v) > 1: v = Add(*v) hit = True if recurse and v != expr: vars.append(v) else: v = v[0] # be careful not to let uneval become True unless # it must be because it's going to be more expensive # to rebuild the expression as an unevaluated one if Numbers and k.is_Number and v.is_Add: args.append(_keep_coeff(k, v, sign=True)) uneval = True else: args.append(k*v) if hit: if uneval: expr = _unevaluated_Add(*args) else: expr = Add(*args) if not expr.is_Add: break return expr def radsimp(expr, symbolic=True, max_terms=4): r""" Rationalize the denominator by removing square roots. Explanation =========== The expression returned from radsimp must be used with caution since if the denominator contains symbols, it will be possible to make substitutions that violate the assumptions of the simplification process: that for a denominator matching a + b*sqrt(c), a != +/-b*sqrt(c). (If there are no symbols, this assumptions is made valid by collecting terms of sqrt(c) so the match variable ``a`` does not contain ``sqrt(c)``.) If you do not want the simplification to occur for symbolic denominators, set ``symbolic`` to False. If there are more than ``max_terms`` radical terms then the expression is returned unchanged. Examples ======== >>> from sympy import radsimp, sqrt, Symbol, pprint >>> from sympy import factor_terms, fraction, signsimp >>> from sympy.simplify.radsimp import collect_sqrt >>> from sympy.abc import a, b, c >>> radsimp(1/(2 + sqrt(2))) (2 - sqrt(2))/2 >>> x,y = map(Symbol, 'xy') >>> e = ((2 + 2*sqrt(2))*x + (2 + sqrt(8))*y)/(2 + sqrt(2)) >>> radsimp(e) sqrt(2)*(x + y) No simplification beyond removal of the gcd is done. One might want to polish the result a little, however, by collecting square root terms: >>> r2 = sqrt(2) >>> r5 = sqrt(5) >>> ans = radsimp(1/(y*r2 + x*r2 + a*r5 + b*r5)); pprint(ans) ___ ___ ___ ___ \/ 5 *a + \/ 5 *b - \/ 2 *x - \/ 2 *y ------------------------------------------ 2 2 2 2 5*a + 10*a*b + 5*b - 2*x - 4*x*y - 2*y >>> n, d = fraction(ans) >>> pprint(factor_terms(signsimp(collect_sqrt(n))/d, radical=True)) ___ ___ \/ 5 *(a + b) - \/ 2 *(x + y) ------------------------------------------ 2 2 2 2 5*a + 10*a*b + 5*b - 2*x - 4*x*y - 2*y If radicals in the denominator cannot be removed or there is no denominator, the original expression will be returned. >>> radsimp(sqrt(2)*x + sqrt(2)) sqrt(2)*x + sqrt(2) Results with symbols will not always be valid for all substitutions: >>> eq = 1/(a + b*sqrt(c)) >>> eq.subs(a, b*sqrt(c)) 1/(2*b*sqrt(c)) >>> radsimp(eq).subs(a, b*sqrt(c)) nan If ``symbolic=False``, symbolic denominators will not be transformed (but numeric denominators will still be processed): >>> radsimp(eq, symbolic=False) 1/(a + b*sqrt(c)) """ from sympy.simplify.simplify import signsimp syms = symbols("a:d A:D") def _num(rterms): # return the multiplier that will simplify the expression described # by rterms [(sqrt arg, coeff), ... ] a, b, c, d, A, B, C, D = syms if len(rterms) == 2: reps = dict(list(zip([A, a, B, b], [j for i in rterms for j in i]))) return ( sqrt(A)*a - sqrt(B)*b).xreplace(reps) if len(rterms) == 3: reps = dict(list(zip([A, a, B, b, C, c], [j for i in rterms for j in i]))) return ( (sqrt(A)*a + sqrt(B)*b - sqrt(C)*c)*(2*sqrt(A)*sqrt(B)*a*b - A*a**2 - B*b**2 + C*c**2)).xreplace(reps) elif len(rterms) == 4: reps = dict(list(zip([A, a, B, b, C, c, D, d], [j for i in rterms for j in i]))) return ((sqrt(A)*a + sqrt(B)*b - sqrt(C)*c - sqrt(D)*d)*(2*sqrt(A)*sqrt(B)*a*b - A*a**2 - B*b**2 - 2*sqrt(C)*sqrt(D)*c*d + C*c**2 + D*d**2)*(-8*sqrt(A)*sqrt(B)*sqrt(C)*sqrt(D)*a*b*c*d + A**2*a**4 - 2*A*B*a**2*b**2 - 2*A*C*a**2*c**2 - 2*A*D*a**2*d**2 + B**2*b**4 - 2*B*C*b**2*c**2 - 2*B*D*b**2*d**2 + C**2*c**4 - 2*C*D*c**2*d**2 + D**2*d**4)).xreplace(reps) elif len(rterms) == 1: return sqrt(rterms[0][0]) else: raise NotImplementedError def ispow2(d, log2=False): if not d.is_Pow: return False e = d.exp if e.is_Rational and e.q == 2 or symbolic and denom(e) == 2: return True if log2: q = 1 if e.is_Rational: q = e.q elif symbolic: d = denom(e) if d.is_Integer: q = d if q != 1 and log(q, 2).is_Integer: return True return False def handle(expr): # Handle first reduces to the case # expr = 1/d, where d is an add, or d is base**p/2. # We do this by recursively calling handle on each piece. from sympy.simplify.simplify import nsimplify n, d = fraction(expr) if expr.is_Atom or (d.is_Atom and n.is_Atom): return expr elif not n.is_Atom: n = n.func(*[handle(a) for a in n.args]) return _unevaluated_Mul(n, handle(1/d)) elif n is not S.One: return _unevaluated_Mul(n, handle(1/d)) elif d.is_Mul: return _unevaluated_Mul(*[handle(1/d) for d in d.args]) # By this step, expr is 1/d, and d is not a mul. if not symbolic and d.free_symbols: return expr if ispow2(d): d2 = sqrtdenest(sqrt(d.base))**numer(d.exp) if d2 != d: return handle(1/d2) elif d.is_Pow and (d.exp.is_integer or d.base.is_positive): # (1/d**i) = (1/d)**i return handle(1/d.base)**d.exp if not (d.is_Add or ispow2(d)): return 1/d.func(*[handle(a) for a in d.args]) # handle 1/d treating d as an Add (though it may not be) keep = True # keep changes that are made # flatten it and collect radicals after checking for special # conditions d = _mexpand(d) # did it change? if d.is_Atom: return 1/d # is it a number that might be handled easily? if d.is_number: _d = nsimplify(d) if _d.is_Number and _d.equals(d): return 1/_d while True: # collect similar terms collected = defaultdict(list) for m in Add.make_args(d): # d might have become non-Add p2 = [] other = [] for i in Mul.make_args(m): if ispow2(i, log2=True): p2.append(i.base if i.exp is S.Half else i.base**(2*i.exp)) elif i is S.ImaginaryUnit: p2.append(S.NegativeOne) else: other.append(i) collected[tuple(ordered(p2))].append(Mul(*other)) rterms = list(ordered(list(collected.items()))) rterms = [(Mul(*i), Add(*j)) for i, j in rterms] nrad = len(rterms) - (1 if rterms[0][0] is S.One else 0) if nrad < 1: break elif nrad > max_terms: # there may have been invalid operations leading to this point # so don't keep changes, e.g. this expression is troublesome # in collecting terms so as not to raise the issue of 2834: # r = sqrt(sqrt(5) + 5) # eq = 1/(sqrt(5)*r + 2*sqrt(5)*sqrt(-sqrt(5) + 5) + 5*r) keep = False break if len(rterms) > 4: # in general, only 4 terms can be removed with repeated squaring # but other considerations can guide selection of radical terms # so that radicals are removed if all([x.is_Integer and (y**2).is_Rational for x, y in rterms]): nd, d = rad_rationalize(S.One, Add._from_args( [sqrt(x)*y for x, y in rterms])) n *= nd else: # is there anything else that might be attempted? keep = False break from sympy.simplify.powsimp import powsimp, powdenest num = powsimp(_num(rterms)) n *= num d *= num d = powdenest(_mexpand(d), force=symbolic) if d.is_Atom: break if not keep: return expr return _unevaluated_Mul(n, 1/d) coeff, expr = expr.as_coeff_Add() expr = expr.normal() old = fraction(expr) n, d = fraction(handle(expr)) if old != (n, d): if not d.is_Atom: was = (n, d) n = signsimp(n, evaluate=False) d = signsimp(d, evaluate=False) u = Factors(_unevaluated_Mul(n, 1/d)) u = _unevaluated_Mul(*[k**v for k, v in u.factors.items()]) n, d = fraction(u) if old == (n, d): n, d = was n = expand_mul(n) if d.is_Number or d.is_Add: n2, d2 = fraction(gcd_terms(_unevaluated_Mul(n, 1/d))) if d2.is_Number or (d2.count_ops() <= d.count_ops()): n, d = [signsimp(i) for i in (n2, d2)] if n.is_Mul and n.args[0].is_Number: n = n.func(*n.args) return coeff + _unevaluated_Mul(n, 1/d) def rad_rationalize(num, den): """ Rationalize ``num/den`` by removing square roots in the denominator; num and den are sum of terms whose squares are positive rationals. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import rad_rationalize >>> rad_rationalize(sqrt(3), 1 + sqrt(2)/3) (-sqrt(3) + sqrt(6)/3, -7/9) """ if not den.is_Add: return num, den g, a, b = split_surds(den) a = a*sqrt(g) num = _mexpand((a - b)*num) den = _mexpand(a**2 - b**2) return rad_rationalize(num, den) def fraction(expr, exact=False): """Returns a pair with expression's numerator and denominator. If the given expression is not a fraction then this function will return the tuple (expr, 1). This function will not make any attempt to simplify nested fractions or to do any term rewriting at all. If only one of the numerator/denominator pair is needed then use numer(expr) or denom(expr) functions respectively. >>> from sympy import fraction, Rational, Symbol >>> from sympy.abc import x, y >>> fraction(x/y) (x, y) >>> fraction(x) (x, 1) >>> fraction(1/y**2) (1, y**2) >>> fraction(x*y/2) (x*y, 2) >>> fraction(Rational(1, 2)) (1, 2) This function will also work fine with assumptions: >>> k = Symbol('k', negative=True) >>> fraction(x * y**k) (x, y**(-k)) If we know nothing about sign of some exponent and ``exact`` flag is unset, then structure this exponent's structure will be analyzed and pretty fraction will be returned: >>> from sympy import exp, Mul >>> fraction(2*x**(-y)) (2, x**y) >>> fraction(exp(-x)) (1, exp(x)) >>> fraction(exp(-x), exact=True) (exp(-x), 1) The ``exact`` flag will also keep any unevaluated Muls from being evaluated: >>> u = Mul(2, x + 1, evaluate=False) >>> fraction(u) (2*x + 2, 1) >>> fraction(u, exact=True) (2*(x + 1), 1) """ expr = sympify(expr) numer, denom = [], [] for term in Mul.make_args(expr): if term.is_commutative and (term.is_Pow or isinstance(term, exp)): b, ex = term.as_base_exp() if ex.is_negative: if ex is S.NegativeOne: denom.append(b) elif exact: if ex.is_constant(): denom.append(Pow(b, -ex)) else: numer.append(term) else: denom.append(Pow(b, -ex)) elif ex.is_positive: numer.append(term) elif not exact and ex.is_Mul: n, d = term.as_numer_denom() if n != 1: numer.append(n) denom.append(d) else: numer.append(term) elif term.is_Rational and not term.is_Integer: if term.p != 1: numer.append(term.p) denom.append(term.q) else: numer.append(term) return Mul(*numer, evaluate=not exact), Mul(*denom, evaluate=not exact) def numer(expr): return fraction(expr)[0] def denom(expr): return fraction(expr)[1] def fraction_expand(expr, **hints): return expr.expand(frac=True, **hints) def numer_expand(expr, **hints): a, b = fraction(expr) return a.expand(numer=True, **hints) / b def denom_expand(expr, **hints): a, b = fraction(expr) return a / b.expand(denom=True, **hints) expand_numer = numer_expand expand_denom = denom_expand expand_fraction = fraction_expand def split_surds(expr): """ Split an expression with terms whose squares are positive rationals into a sum of terms whose surds squared have gcd equal to g and a sum of terms with surds squared prime with g. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.radsimp import split_surds >>> split_surds(3*sqrt(3) + sqrt(5)/7 + sqrt(6) + sqrt(10) + sqrt(15)) (3, sqrt(2) + sqrt(5) + 3, sqrt(5)/7 + sqrt(10)) """ args = sorted(expr.args, key=default_sort_key) coeff_muls = [x.as_coeff_Mul() for x in args] surds = [x[1]**2 for x in coeff_muls if x[1].is_Pow] surds.sort(key=default_sort_key) g, b1, b2 = _split_gcd(*surds) g2 = g if not b2 and len(b1) >= 2: b1n = [x/g for x in b1] b1n = [x for x in b1n if x != 1] # only a common factor has been factored; split again g1, b1n, b2 = _split_gcd(*b1n) g2 = g*g1 a1v, a2v = [], [] for c, s in coeff_muls: if s.is_Pow and s.exp == S.Half: s1 = s.base if s1 in b1: a1v.append(c*sqrt(s1/g2)) else: a2v.append(c*s) else: a2v.append(c*s) a = Add(*a1v) b = Add(*a2v) return g2, a, b def _split_gcd(*a): """ Split the list of integers ``a`` into a list of integers, ``a1`` having ``g = gcd(a1)``, and a list ``a2`` whose elements are not divisible by ``g``. Returns ``g, a1, a2``. Examples ======== >>> from sympy.simplify.radsimp import _split_gcd >>> _split_gcd(55, 35, 22, 14, 77, 10) (5, [55, 35, 10], [22, 14, 77]) """ g = a[0] b1 = [g] b2 = [] for x in a[1:]: g1 = gcd(g, x) if g1 == 1: b2.append(x) else: g = g1 b1.append(x) return g, b1, b2

35102055e5581845da44d59a64f8df8ca3602e598978cfa2698213b7e62a5d2b

"""Tools for manipulation of expressions using paths. """ from sympy.core import Basic class EPath: r""" Manipulate expressions using paths. EPath grammar in EBNF notation:: literal ::= /[A-Za-z_][A-Za-z_0-9]*/ number ::= /-?\d+/ type ::= literal attribute ::= literal "?" all ::= "*" slice ::= "[" number? (":" number? (":" number?)?)? "]" range ::= all | slice query ::= (type | attribute) ("|" (type | attribute))* selector ::= range | query range? path ::= "/" selector ("/" selector)* See the docstring of the epath() function. """ __slots__ = ("_path", "_epath") def __new__(cls, path): """Construct new EPath. """ if isinstance(path, EPath): return path if not path: raise ValueError("empty EPath") _path = path if path[0] == '/': path = path[1:] else: raise NotImplementedError("non-root EPath") epath = [] for selector in path.split('/'): selector = selector.strip() if not selector: raise ValueError("empty selector") index = 0 for c in selector: if c.isalnum() or c == '_' or c == '|' or c == '?': index += 1 else: break attrs = [] types = [] if index: elements = selector[:index] selector = selector[index:] for element in elements.split('|'): element = element.strip() if not element: raise ValueError("empty element") if element.endswith('?'): attrs.append(element[:-1]) else: types.append(element) span = None if selector == '*': pass else: if selector.startswith('['): try: i = selector.index(']') except ValueError: raise ValueError("expected ']', got EOL") _span, span = selector[1:i], [] if ':' not in _span: span = int(_span) else: for elt in _span.split(':', 3): if not elt: span.append(None) else: span.append(int(elt)) span = slice(*span) selector = selector[i + 1:] if selector: raise ValueError("trailing characters in selector") epath.append((attrs, types, span)) obj = object.__new__(cls) obj._path = _path obj._epath = epath return obj def __repr__(self): return "%s(%r)" % (self.__class__.__name__, self._path) def _get_ordered_args(self, expr): """Sort ``expr.args`` using printing order. """ if expr.is_Add: return expr.as_ordered_terms() elif expr.is_Mul: return expr.as_ordered_factors() else: return expr.args def _hasattrs(self, expr, attrs): """Check if ``expr`` has any of ``attrs``. """ for attr in attrs: if not hasattr(expr, attr): return False return True def _hastypes(self, expr, types): """Check if ``expr`` is any of ``types``. """ _types = [ cls.__name__ for cls in expr.__class__.mro() ] return bool(set(_types).intersection(types)) def _has(self, expr, attrs, types): """Apply ``_hasattrs`` and ``_hastypes`` to ``expr``. """ if not (attrs or types): return True if attrs and self._hasattrs(expr, attrs): return True if types and self._hastypes(expr, types): return True return False def apply(self, expr, func, args=None, kwargs=None): """ Modify parts of an expression selected by a path. Examples ======== >>> from sympy.simplify.epathtools import EPath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = EPath("/*/[0]/Symbol") >>> expr = [((x, 1), 2), ((3, y), z)] >>> path.apply(expr, lambda expr: expr**2) [((x**2, 1), 2), ((3, y**2), z)] >>> path = EPath("/*/*/Symbol") >>> expr = t + sin(x + 1) + cos(x + y + E) >>> path.apply(expr, lambda expr: 2*expr) t + sin(2*x + 1) + cos(2*x + 2*y + E) """ def _apply(path, expr, func): if not path: return func(expr) else: selector, path = path[0], path[1:] attrs, types, span = selector if isinstance(expr, Basic): if not expr.is_Atom: args, basic = self._get_ordered_args(expr), True else: return expr elif hasattr(expr, '__iter__'): args, basic = expr, False else: return expr args = list(args) if span is not None: if type(span) == slice: indices = range(*span.indices(len(args))) else: indices = [span] else: indices = range(len(args)) for i in indices: try: arg = args[i] except IndexError: continue if self._has(arg, attrs, types): args[i] = _apply(path, arg, func) if basic: return expr.func(*args) else: return expr.__class__(args) _args, _kwargs = args or (), kwargs or {} _func = lambda expr: func(expr, *_args, **_kwargs) return _apply(self._epath, expr, _func) def select(self, expr): """ Retrieve parts of an expression selected by a path. Examples ======== >>> from sympy.simplify.epathtools import EPath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = EPath("/*/[0]/Symbol") >>> expr = [((x, 1), 2), ((3, y), z)] >>> path.select(expr) [x, y] >>> path = EPath("/*/*/Symbol") >>> expr = t + sin(x + 1) + cos(x + y + E) >>> path.select(expr) [x, x, y] """ result = [] def _select(path, expr): if not path: result.append(expr) else: selector, path = path[0], path[1:] attrs, types, span = selector if isinstance(expr, Basic): args = self._get_ordered_args(expr) elif hasattr(expr, '__iter__'): args = expr else: return if span is not None: if type(span) == slice: args = args[span] else: try: args = [args[span]] except IndexError: return for arg in args: if self._has(arg, attrs, types): _select(path, arg) _select(self._epath, expr) return result def epath(path, expr=None, func=None, args=None, kwargs=None): r""" Manipulate parts of an expression selected by a path. Explanation =========== This function allows to manipulate large nested expressions in single line of code, utilizing techniques to those applied in XML processing standards (e.g. XPath). If ``func`` is ``None``, :func:`epath` retrieves elements selected by the ``path``. Otherwise it applies ``func`` to each matching element. Note that it is more efficient to create an EPath object and use the select and apply methods of that object, since this will compile the path string only once. This function should only be used as a convenient shortcut for interactive use. This is the supported syntax: * select all: ``/*`` Equivalent of ``for arg in args:``. * select slice: ``/[0]`` or ``/[1:5]`` or ``/[1:5:2]`` Supports standard Python's slice syntax. * select by type: ``/list`` or ``/list|tuple`` Emulates ``isinstance()``. * select by attribute: ``/__iter__?`` Emulates ``hasattr()``. Parameters ========== path : str | EPath A path as a string or a compiled EPath. expr : Basic | iterable An expression or a container of expressions. func : callable (optional) A callable that will be applied to matching parts. args : tuple (optional) Additional positional arguments to ``func``. kwargs : dict (optional) Additional keyword arguments to ``func``. Examples ======== >>> from sympy.simplify.epathtools import epath >>> from sympy import sin, cos, E >>> from sympy.abc import x, y, z, t >>> path = "/*/[0]/Symbol" >>> expr = [((x, 1), 2), ((3, y), z)] >>> epath(path, expr) [x, y] >>> epath(path, expr, lambda expr: expr**2) [((x**2, 1), 2), ((3, y**2), z)] >>> path = "/*/*/Symbol" >>> expr = t + sin(x + 1) + cos(x + y + E) >>> epath(path, expr) [x, x, y] >>> epath(path, expr, lambda expr: 2*expr) t + sin(2*x + 1) + cos(2*x + 2*y + E) """ _epath = EPath(path) if expr is None: return _epath if func is None: return _epath.select(expr) else: return _epath.apply(expr, func, args, kwargs)

a8029e2ba01f3f74c6531cab6bd69f7a122ed75d8ecd345234e2d91eddb775f4

from sympy.core import Mul from sympy.core.basic import preorder_traversal from sympy.core.function import count_ops from sympy.functions.combinatorial.factorials import binomial, factorial from sympy.functions import gamma from sympy.simplify.gammasimp import gammasimp, _gammasimp from sympy.utilities.timeutils import timethis @timethis('combsimp') def combsimp(expr): r""" Simplify combinatorial expressions. Explanation =========== This function takes as input an expression containing factorials, binomials, Pochhammer symbol and other "combinatorial" functions, and tries to minimize the number of those functions and reduce the size of their arguments. The algorithm works by rewriting all combinatorial functions as gamma functions and applying gammasimp() except simplification steps that may make an integer argument non-integer. See docstring of gammasimp for more information. Then it rewrites expression in terms of factorials and binomials by rewriting gammas as factorials and converting (a+b)!/a!b! into binomials. If expression has gamma functions or combinatorial functions with non-integer argument, it is automatically passed to gammasimp. Examples ======== >>> from sympy.simplify import combsimp >>> from sympy import factorial, binomial, symbols >>> n, k = symbols('n k', integer = True) >>> combsimp(factorial(n)/factorial(n - 3)) n*(n - 2)*(n - 1) >>> combsimp(binomial(n+1, k+1)/binomial(n, k)) (n + 1)/(k + 1) """ expr = expr.rewrite(gamma, piecewise=False) if any(isinstance(node, gamma) and not node.args[0].is_integer for node in preorder_traversal(expr)): return gammasimp(expr); expr = _gammasimp(expr, as_comb = True) expr = _gamma_as_comb(expr) return expr def _gamma_as_comb(expr): """ Helper function for combsimp. Rewrites expression in terms of factorials and binomials """ expr = expr.rewrite(factorial) from .simplify import bottom_up def f(rv): if not rv.is_Mul: return rv rvd = rv.as_powers_dict() nd_fact_args = [[], []] # numerator, denominator for k in rvd: if isinstance(k, factorial) and rvd[k].is_Integer: if rvd[k].is_positive: nd_fact_args[0].extend([k.args[0]]*rvd[k]) else: nd_fact_args[1].extend([k.args[0]]*-rvd[k]) rvd[k] = 0 if not nd_fact_args[0] or not nd_fact_args[1]: return rv hit = False for m in range(2): i = 0 while i < len(nd_fact_args[m]): ai = nd_fact_args[m][i] for j in range(i + 1, len(nd_fact_args[m])): aj = nd_fact_args[m][j] sum = ai + aj if sum in nd_fact_args[1 - m]: hit = True nd_fact_args[1 - m].remove(sum) del nd_fact_args[m][j] del nd_fact_args[m][i] rvd[binomial(sum, ai if count_ops(ai) < count_ops(aj) else aj)] += ( -1 if m == 0 else 1) break else: i += 1 if hit: return Mul(*([k**rvd[k] for k in rvd] + [factorial(k) for k in nd_fact_args[0]]))/Mul(*[factorial(k) for k in nd_fact_args[1]]) return rv return bottom_up(expr, f)

7e51bf655cdc6a8bbe60c10138c6204747ba3d7f28108a3ec75bdab3c055b72c

from sympy.core import Add, Expr, Mul, S, sympify from sympy.core.function import _mexpand, count_ops, expand_mul from sympy.core.symbol import Dummy from sympy.functions import root, sign, sqrt from sympy.polys import Poly, PolynomialError from sympy.utilities import default_sort_key def is_sqrt(expr): """Return True if expr is a sqrt, otherwise False.""" return expr.is_Pow and expr.exp.is_Rational and abs(expr.exp) is S.Half def sqrt_depth(p): """Return the maximum depth of any square root argument of p. >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import sqrt_depth Neither of these square roots contains any other square roots so the depth is 1: >>> sqrt_depth(1 + sqrt(2)*(1 + sqrt(3))) 1 The sqrt(3) is contained within a square root so the depth is 2: >>> sqrt_depth(1 + sqrt(2)*sqrt(1 + sqrt(3))) 2 """ if p is S.ImaginaryUnit: return 1 if p.is_Atom: return 0 elif p.is_Add or p.is_Mul: return max([sqrt_depth(x) for x in p.args], key=default_sort_key) elif is_sqrt(p): return sqrt_depth(p.base) + 1 else: return 0 def is_algebraic(p): """Return True if p is comprised of only Rationals or square roots of Rationals and algebraic operations. Examples ======== >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import is_algebraic >>> from sympy import cos >>> is_algebraic(sqrt(2)*(3/(sqrt(7) + sqrt(5)*sqrt(2)))) True >>> is_algebraic(sqrt(2)*(3/(sqrt(7) + sqrt(5)*cos(2)))) False """ if p.is_Rational: return True elif p.is_Atom: return False elif is_sqrt(p) or p.is_Pow and p.exp.is_Integer: return is_algebraic(p.base) elif p.is_Add or p.is_Mul: return all(is_algebraic(x) for x in p.args) else: return False def _subsets(n): """ Returns all possible subsets of the set (0, 1, ..., n-1) except the empty set, listed in reversed lexicographical order according to binary representation, so that the case of the fourth root is treated last. Examples ======== >>> from sympy.simplify.sqrtdenest import _subsets >>> _subsets(2) [[1, 0], [0, 1], [1, 1]] """ if n == 1: a = [[1]] elif n == 2: a = [[1, 0], [0, 1], [1, 1]] elif n == 3: a = [[1, 0, 0], [0, 1, 0], [1, 1, 0], [0, 0, 1], [1, 0, 1], [0, 1, 1], [1, 1, 1]] else: b = _subsets(n - 1) a0 = [x + [0] for x in b] a1 = [x + [1] for x in b] a = a0 + [[0]*(n - 1) + [1]] + a1 return a def sqrtdenest(expr, max_iter=3): """Denests sqrts in an expression that contain other square roots if possible, otherwise returns the expr unchanged. This is based on the algorithms of [1]. Examples ======== >>> from sympy.simplify.sqrtdenest import sqrtdenest >>> from sympy import sqrt >>> sqrtdenest(sqrt(5 + 2 * sqrt(6))) sqrt(2) + sqrt(3) See Also ======== sympy.solvers.solvers.unrad References ========== .. [1] http://researcher.watson.ibm.com/researcher/files/us-fagin/symb85.pdf .. [2] D. J. Jeffrey and A. D. Rich, 'Symplifying Square Roots of Square Roots by Denesting' (available at http://www.cybertester.com/data/denest.pdf) """ expr = expand_mul(sympify(expr)) for i in range(max_iter): z = _sqrtdenest0(expr) if expr == z: return expr expr = z return expr def _sqrt_match(p): """Return [a, b, r] for p.match(a + b*sqrt(r)) where, in addition to matching, sqrt(r) also has then maximal sqrt_depth among addends of p. Examples ======== >>> from sympy.functions.elementary.miscellaneous import sqrt >>> from sympy.simplify.sqrtdenest import _sqrt_match >>> _sqrt_match(1 + sqrt(2) + sqrt(2)*sqrt(3) + 2*sqrt(1+sqrt(5))) [1 + sqrt(2) + sqrt(6), 2, 1 + sqrt(5)] """ from sympy.simplify.radsimp import split_surds p = _mexpand(p) if p.is_Number: res = (p, S.Zero, S.Zero) elif p.is_Add: pargs = sorted(p.args, key=default_sort_key) sqargs = [x**2 for x in pargs] if all(sq.is_Rational and sq.is_positive for sq in sqargs): r, b, a = split_surds(p) res = a, b, r return list(res) # to make the process canonical, the argument is included in the tuple # so when the max is selected, it will be the largest arg having a # given depth v = [(sqrt_depth(x), x, i) for i, x in enumerate(pargs)] nmax = max(v, key=default_sort_key) if nmax[0] == 0: res = [] else: # select r depth, _, i = nmax r = pargs.pop(i) v.pop(i) b = S.One if r.is_Mul: bv = [] rv = [] for x in r.args: if sqrt_depth(x) < depth: bv.append(x) else: rv.append(x) b = Mul._from_args(bv) r = Mul._from_args(rv) # collect terms comtaining r a1 = [] b1 = [b] for x in v: if x[0] < depth: a1.append(x[1]) else: x1 = x[1] if x1 == r: b1.append(1) else: if x1.is_Mul: x1args = list(x1.args) if r in x1args: x1args.remove(r) b1.append(Mul(*x1args)) else: a1.append(x[1]) else: a1.append(x[1]) a = Add(*a1) b = Add(*b1) res = (a, b, r**2) else: b, r = p.as_coeff_Mul() if is_sqrt(r): res = (S.Zero, b, r**2) else: res = [] return list(res) class SqrtdenestStopIteration(StopIteration): pass def _sqrtdenest0(expr): """Returns expr after denesting its arguments.""" if is_sqrt(expr): n, d = expr.as_numer_denom() if d is S.One: # n is a square root if n.base.is_Add: args = sorted(n.base.args, key=default_sort_key) if len(args) > 2 and all((x**2).is_Integer for x in args): try: return _sqrtdenest_rec(n) except SqrtdenestStopIteration: pass expr = sqrt(_mexpand(Add(*[_sqrtdenest0(x) for x in args]))) return _sqrtdenest1(expr) else: n, d = [_sqrtdenest0(i) for i in (n, d)] return n/d if isinstance(expr, Add): cs = [] args = [] for arg in expr.args: c, a = arg.as_coeff_Mul() cs.append(c) args.append(a) if all(c.is_Rational for c in cs) and all(is_sqrt(arg) for arg in args): return _sqrt_ratcomb(cs, args) if isinstance(expr, Expr): args = expr.args if args: return expr.func(*[_sqrtdenest0(a) for a in args]) return expr def _sqrtdenest_rec(expr): """Helper that denests the square root of three or more surds. Explanation =========== It returns the denested expression; if it cannot be denested it throws SqrtdenestStopIteration Algorithm: expr.base is in the extension Q_m = Q(sqrt(r_1),..,sqrt(r_k)); split expr.base = a + b*sqrt(r_k), where `a` and `b` are on Q_(m-1) = Q(sqrt(r_1),..,sqrt(r_(k-1))); then a**2 - b**2*r_k is on Q_(m-1); denest sqrt(a**2 - b**2*r_k) and so on. See [1], section 6. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import _sqrtdenest_rec >>> _sqrtdenest_rec(sqrt(-72*sqrt(2) + 158*sqrt(5) + 498)) -sqrt(10) + sqrt(2) + 9 + 9*sqrt(5) >>> w=-6*sqrt(55)-6*sqrt(35)-2*sqrt(22)-2*sqrt(14)+2*sqrt(77)+6*sqrt(10)+65 >>> _sqrtdenest_rec(sqrt(w)) -sqrt(11) - sqrt(7) + sqrt(2) + 3*sqrt(5) """ from sympy.simplify.radsimp import radsimp, rad_rationalize, split_surds if not expr.is_Pow: return sqrtdenest(expr) if expr.base < 0: return sqrt(-1)*_sqrtdenest_rec(sqrt(-expr.base)) g, a, b = split_surds(expr.base) a = a*sqrt(g) if a < b: a, b = b, a c2 = _mexpand(a**2 - b**2) if len(c2.args) > 2: g, a1, b1 = split_surds(c2) a1 = a1*sqrt(g) if a1 < b1: a1, b1 = b1, a1 c2_1 = _mexpand(a1**2 - b1**2) c_1 = _sqrtdenest_rec(sqrt(c2_1)) d_1 = _sqrtdenest_rec(sqrt(a1 + c_1)) num, den = rad_rationalize(b1, d_1) c = _mexpand(d_1/sqrt(2) + num/(den*sqrt(2))) else: c = _sqrtdenest1(sqrt(c2)) if sqrt_depth(c) > 1: raise SqrtdenestStopIteration ac = a + c if len(ac.args) >= len(expr.args): if count_ops(ac) >= count_ops(expr.base): raise SqrtdenestStopIteration d = sqrtdenest(sqrt(ac)) if sqrt_depth(d) > 1: raise SqrtdenestStopIteration num, den = rad_rationalize(b, d) r = d/sqrt(2) + num/(den*sqrt(2)) r = radsimp(r) return _mexpand(r) def _sqrtdenest1(expr, denester=True): """Return denested expr after denesting with simpler methods or, that failing, using the denester.""" from sympy.simplify.simplify import radsimp if not is_sqrt(expr): return expr a = expr.base if a.is_Atom: return expr val = _sqrt_match(a) if not val: return expr a, b, r = val # try a quick numeric denesting d2 = _mexpand(a**2 - b**2*r) if d2.is_Rational: if d2.is_positive: z = _sqrt_numeric_denest(a, b, r, d2) if z is not None: return z else: # fourth root case # sqrtdenest(sqrt(3 + 2*sqrt(3))) = # sqrt(2)*3**(1/4)/2 + sqrt(2)*3**(3/4)/2 dr2 = _mexpand(-d2*r) dr = sqrt(dr2) if dr.is_Rational: z = _sqrt_numeric_denest(_mexpand(b*r), a, r, dr2) if z is not None: return z/root(r, 4) else: z = _sqrt_symbolic_denest(a, b, r) if z is not None: return z if not denester or not is_algebraic(expr): return expr res = sqrt_biquadratic_denest(expr, a, b, r, d2) if res: return res # now call to the denester av0 = [a, b, r, d2] z = _denester([radsimp(expr**2)], av0, 0, sqrt_depth(expr))[0] if av0[1] is None: return expr if z is not None: if sqrt_depth(z) == sqrt_depth(expr) and count_ops(z) > count_ops(expr): return expr return z return expr def _sqrt_symbolic_denest(a, b, r): """Given an expression, sqrt(a + b*sqrt(b)), return the denested expression or None. Explanation =========== If r = ra + rb*sqrt(rr), try replacing sqrt(rr) in ``a`` with (y**2 - ra)/rb, and if the result is a quadratic, ca*y**2 + cb*y + cc, and (cb + b)**2 - 4*ca*cc is 0, then sqrt(a + b*sqrt(r)) can be rewritten as sqrt(ca*(sqrt(r) + (cb + b)/(2*ca))**2). Examples ======== >>> from sympy.simplify.sqrtdenest import _sqrt_symbolic_denest, sqrtdenest >>> from sympy import sqrt, Symbol >>> from sympy.abc import x >>> a, b, r = 16 - 2*sqrt(29), 2, -10*sqrt(29) + 55 >>> _sqrt_symbolic_denest(a, b, r) sqrt(11 - 2*sqrt(29)) + sqrt(5) If the expression is numeric, it will be simplified: >>> w = sqrt(sqrt(sqrt(3) + 1) + 1) + 1 + sqrt(2) >>> sqrtdenest(sqrt((w**2).expand())) 1 + sqrt(2) + sqrt(1 + sqrt(1 + sqrt(3))) Otherwise, it will only be simplified if assumptions allow: >>> w = w.subs(sqrt(3), sqrt(x + 3)) >>> sqrtdenest(sqrt((w**2).expand())) sqrt((sqrt(sqrt(sqrt(x + 3) + 1) + 1) + 1 + sqrt(2))**2) Notice that the argument of the sqrt is a square. If x is made positive then the sqrt of the square is resolved: >>> _.subs(x, Symbol('x', positive=True)) sqrt(sqrt(sqrt(x + 3) + 1) + 1) + 1 + sqrt(2) """ a, b, r = map(sympify, (a, b, r)) rval = _sqrt_match(r) if not rval: return None ra, rb, rr = rval if rb: y = Dummy('y', positive=True) try: newa = Poly(a.subs(sqrt(rr), (y**2 - ra)/rb), y) except PolynomialError: return None if newa.degree() == 2: ca, cb, cc = newa.all_coeffs() cb += b if _mexpand(cb**2 - 4*ca*cc).equals(0): z = sqrt(ca*(sqrt(r) + cb/(2*ca))**2) if z.is_number: z = _mexpand(Mul._from_args(z.as_content_primitive())) return z def _sqrt_numeric_denest(a, b, r, d2): r"""Helper that denest $\sqrt{a + b \sqrt{r}}, d^2 = a^2 - b^2 r > 0$ If it cannot be denested, it returns ``None``. """ d = sqrt(d2) s = a + d # sqrt_depth(res) <= sqrt_depth(s) + 1 # sqrt_depth(expr) = sqrt_depth(r) + 2 # there is denesting if sqrt_depth(s) + 1 < sqrt_depth(r) + 2 # if s**2 is Number there is a fourth root if sqrt_depth(s) < sqrt_depth(r) + 1 or (s**2).is_Rational: s1, s2 = sign(s), sign(b) if s1 == s2 == -1: s1 = s2 = 1 res = (s1 * sqrt(a + d) + s2 * sqrt(a - d)) * sqrt(2) / 2 return res.expand() def sqrt_biquadratic_denest(expr, a, b, r, d2): """denest expr = sqrt(a + b*sqrt(r)) where a, b, r are linear combinations of square roots of positive rationals on the rationals (SQRR) and r > 0, b != 0, d2 = a**2 - b**2*r > 0 If it cannot denest it returns None. Explanation =========== Search for a solution A of type SQRR of the biquadratic equation 4*A**4 - 4*a*A**2 + b**2*r = 0 (1) sqd = sqrt(a**2 - b**2*r) Choosing the sqrt to be positive, the possible solutions are A = sqrt(a/2 +/- sqd/2) Since a, b, r are SQRR, then a**2 - b**2*r is a SQRR, so if sqd can be denested, it is done by _sqrtdenest_rec, and the result is a SQRR. Similarly for A. Examples of solutions (in both cases a and sqd are positive): Example of expr with solution sqrt(a/2 + sqd/2) but not solution sqrt(a/2 - sqd/2): expr = sqrt(-sqrt(15) - sqrt(2)*sqrt(-sqrt(5) + 5) - sqrt(3) + 8) a = -sqrt(15) - sqrt(3) + 8; sqd = -2*sqrt(5) - 2 + 4*sqrt(3) Example of expr with solution sqrt(a/2 - sqd/2) but not solution sqrt(a/2 + sqd/2): w = 2 + r2 + r3 + (1 + r3)*sqrt(2 + r2 + 5*r3) expr = sqrt((w**2).expand()) a = 4*sqrt(6) + 8*sqrt(2) + 47 + 28*sqrt(3) sqd = 29 + 20*sqrt(3) Define B = b/2*A; eq.(1) implies a = A**2 + B**2*r; then expr**2 = a + b*sqrt(r) = (A + B*sqrt(r))**2 Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import _sqrt_match, sqrt_biquadratic_denest >>> z = sqrt((2*sqrt(2) + 4)*sqrt(2 + sqrt(2)) + 5*sqrt(2) + 8) >>> a, b, r = _sqrt_match(z**2) >>> d2 = a**2 - b**2*r >>> sqrt_biquadratic_denest(z, a, b, r, d2) sqrt(2) + sqrt(sqrt(2) + 2) + 2 """ from sympy.simplify.radsimp import radsimp, rad_rationalize if r <= 0 or d2 < 0 or not b or sqrt_depth(expr.base) < 2: return None for x in (a, b, r): for y in x.args: y2 = y**2 if not y2.is_Integer or not y2.is_positive: return None sqd = _mexpand(sqrtdenest(sqrt(radsimp(d2)))) if sqrt_depth(sqd) > 1: return None x1, x2 = [a/2 + sqd/2, a/2 - sqd/2] # look for a solution A with depth 1 for x in (x1, x2): A = sqrtdenest(sqrt(x)) if sqrt_depth(A) > 1: continue Bn, Bd = rad_rationalize(b, _mexpand(2*A)) B = Bn/Bd z = A + B*sqrt(r) if z < 0: z = -z return _mexpand(z) return None def _denester(nested, av0, h, max_depth_level): """Denests a list of expressions that contain nested square roots. Explanation =========== Algorithm based on <http://www.almaden.ibm.com/cs/people/fagin/symb85.pdf>. It is assumed that all of the elements of 'nested' share the same bottom-level radicand. (This is stated in the paper, on page 177, in the paragraph immediately preceding the algorithm.) When evaluating all of the arguments in parallel, the bottom-level radicand only needs to be denested once. This means that calling _denester with x arguments results in a recursive invocation with x+1 arguments; hence _denester has polynomial complexity. However, if the arguments were evaluated separately, each call would result in two recursive invocations, and the algorithm would have exponential complexity. This is discussed in the paper in the middle paragraph of page 179. """ from sympy.simplify.simplify import radsimp if h > max_depth_level: return None, None if av0[1] is None: return None, None if (av0[0] is None and all(n.is_Number for n in nested)): # no arguments are nested for f in _subsets(len(nested)): # test subset 'f' of nested p = _mexpand(Mul(*[nested[i] for i in range(len(f)) if f[i]])) if f.count(1) > 1 and f[-1]: p = -p sqp = sqrt(p) if sqp.is_Rational: return sqp, f # got a perfect square so return its square root. # Otherwise, return the radicand from the previous invocation. return sqrt(nested[-1]), [0]*len(nested) else: R = None if av0[0] is not None: values = [av0[:2]] R = av0[2] nested2 = [av0[3], R] av0[0] = None else: values = list(filter(None, [_sqrt_match(expr) for expr in nested])) for v in values: if v[2]: # Since if b=0, r is not defined if R is not None: if R != v[2]: av0[1] = None return None, None else: R = v[2] if R is None: # return the radicand from the previous invocation return sqrt(nested[-1]), [0]*len(nested) nested2 = [_mexpand(v[0]**2) - _mexpand(R*v[1]**2) for v in values] + [R] d, f = _denester(nested2, av0, h + 1, max_depth_level) if not f: return None, None if not any(f[i] for i in range(len(nested))): v = values[-1] return sqrt(v[0] + _mexpand(v[1]*d)), f else: p = Mul(*[nested[i] for i in range(len(nested)) if f[i]]) v = _sqrt_match(p) if 1 in f and f.index(1) < len(nested) - 1 and f[len(nested) - 1]: v[0] = -v[0] v[1] = -v[1] if not f[len(nested)]: # Solution denests with square roots vad = _mexpand(v[0] + d) if vad <= 0: # return the radicand from the previous invocation. return sqrt(nested[-1]), [0]*len(nested) if not(sqrt_depth(vad) <= sqrt_depth(R) + 1 or (vad**2).is_Number): av0[1] = None return None, None sqvad = _sqrtdenest1(sqrt(vad), denester=False) if not (sqrt_depth(sqvad) <= sqrt_depth(R) + 1): av0[1] = None return None, None sqvad1 = radsimp(1/sqvad) res = _mexpand(sqvad/sqrt(2) + (v[1]*sqrt(R)*sqvad1/sqrt(2))) return res, f # sign(v[1])*sqrt(_mexpand(v[1]**2*R*vad1/2))), f else: # Solution requires a fourth root s2 = _mexpand(v[1]*R) + d if s2 <= 0: return sqrt(nested[-1]), [0]*len(nested) FR, s = root(_mexpand(R), 4), sqrt(s2) return _mexpand(s/(sqrt(2)*FR) + v[0]*FR/(sqrt(2)*s)), f def _sqrt_ratcomb(cs, args): """Denest rational combinations of radicals. Based on section 5 of [1]. Examples ======== >>> from sympy import sqrt >>> from sympy.simplify.sqrtdenest import sqrtdenest >>> z = sqrt(1+sqrt(3)) + sqrt(3+3*sqrt(3)) - sqrt(10+6*sqrt(3)) >>> sqrtdenest(z) 0 """ from sympy.simplify.radsimp import radsimp # check if there exists a pair of sqrt that can be denested def find(a): n = len(a) for i in range(n - 1): for j in range(i + 1, n): s1 = a[i].base s2 = a[j].base p = _mexpand(s1 * s2) s = sqrtdenest(sqrt(p)) if s != sqrt(p): return s, i, j indices = find(args) if indices is None: return Add(*[c * arg for c, arg in zip(cs, args)]) s, i1, i2 = indices c2 = cs.pop(i2) args.pop(i2) a1 = args[i1] # replace a2 by s/a1 cs[i1] += radsimp(c2 * s / a1.base) return _sqrt_ratcomb(cs, args)

dedea045629a9e7426b27000dd5ed4e0484979f8f2fe6e670f98a1a6aff17940

from collections import defaultdict from sympy.core.function import expand_log, count_ops from sympy.core import sympify, Basic, Dummy, S, Add, Mul, Pow, expand_mul, factor_terms from sympy.core.compatibility import ordered, default_sort_key, reduce from sympy.core.numbers import Integer, Rational from sympy.core.mul import prod, _keep_coeff from sympy.core.rules import Transform from sympy.functions import exp_polar, exp, log, root, polarify, unpolarify from sympy.polys import lcm, gcd from sympy.ntheory.factor_ import multiplicity def powsimp(expr, deep=False, combine='all', force=False, measure=count_ops): """ reduces expression by combining powers with similar bases and exponents. Explanation =========== If ``deep`` is ``True`` then powsimp() will also simplify arguments of functions. By default ``deep`` is set to ``False``. If ``force`` is ``True`` then bases will be combined without checking for assumptions, e.g. sqrt(x)*sqrt(y) -> sqrt(x*y) which is not true if x and y are both negative. You can make powsimp() only combine bases or only combine exponents by changing combine='base' or combine='exp'. By default, combine='all', which does both. combine='base' will only combine:: a a a 2x x x * y => (x*y) as well as things like 2 => 4 and combine='exp' will only combine :: a b (a + b) x * x => x combine='exp' will strictly only combine exponents in the way that used to be automatic. Also use deep=True if you need the old behavior. When combine='all', 'exp' is evaluated first. Consider the first example below for when there could be an ambiguity relating to this. This is done so things like the second example can be completely combined. If you want 'base' combined first, do something like powsimp(powsimp(expr, combine='base'), combine='exp'). Examples ======== >>> from sympy import powsimp, exp, log, symbols >>> from sympy.abc import x, y, z, n >>> powsimp(x**y*x**z*y**z, combine='all') x**(y + z)*y**z >>> powsimp(x**y*x**z*y**z, combine='exp') x**(y + z)*y**z >>> powsimp(x**y*x**z*y**z, combine='base', force=True) x**y*(x*y)**z >>> powsimp(x**z*x**y*n**z*n**y, combine='all', force=True) (n*x)**(y + z) >>> powsimp(x**z*x**y*n**z*n**y, combine='exp') n**(y + z)*x**(y + z) >>> powsimp(x**z*x**y*n**z*n**y, combine='base', force=True) (n*x)**y*(n*x)**z >>> x, y = symbols('x y', positive=True) >>> powsimp(log(exp(x)*exp(y))) log(exp(x)*exp(y)) >>> powsimp(log(exp(x)*exp(y)), deep=True) x + y Radicals with Mul bases will be combined if combine='exp' >>> from sympy import sqrt >>> x, y = symbols('x y') Two radicals are automatically joined through Mul: >>> a=sqrt(x*sqrt(y)) >>> a*a**3 == a**4 True But if an integer power of that radical has been autoexpanded then Mul does not join the resulting factors: >>> a**4 # auto expands to a Mul, no longer a Pow x**2*y >>> _*a # so Mul doesn't combine them x**2*y*sqrt(x*sqrt(y)) >>> powsimp(_) # but powsimp will (x*sqrt(y))**(5/2) >>> powsimp(x*y*a) # but won't when doing so would violate assumptions x*y*sqrt(x*sqrt(y)) """ from sympy.matrices.expressions.matexpr import MatrixSymbol def recurse(arg, **kwargs): _deep = kwargs.get('deep', deep) _combine = kwargs.get('combine', combine) _force = kwargs.get('force', force) _measure = kwargs.get('measure', measure) return powsimp(arg, _deep, _combine, _force, _measure) expr = sympify(expr) if (not isinstance(expr, Basic) or isinstance(expr, MatrixSymbol) or ( expr.is_Atom or expr in (exp_polar(0), exp_polar(1)))): return expr if deep or expr.is_Add or expr.is_Mul and _y not in expr.args: expr = expr.func(*[recurse(w) for w in expr.args]) if expr.is_Pow: return recurse(expr*_y, deep=False)/_y if not expr.is_Mul: return expr # handle the Mul if combine in ('exp', 'all'): # Collect base/exp data, while maintaining order in the # non-commutative parts of the product c_powers = defaultdict(list) nc_part = [] newexpr = [] coeff = S.One for term in expr.args: if term.is_Rational: coeff *= term continue if term.is_Pow: term = _denest_pow(term) if term.is_commutative: b, e = term.as_base_exp() if deep: b, e = [recurse(i) for i in [b, e]] if b.is_Pow or isinstance(b, exp): # don't let smthg like sqrt(x**a) split into x**a, 1/2 # or else it will be joined as x**(a/2) later b, e = b**e, S.One c_powers[b].append(e) else: # This is the logic that combines exponents for equal, # but non-commutative bases: A**x*A**y == A**(x+y). if nc_part: b1, e1 = nc_part[-1].as_base_exp() b2, e2 = term.as_base_exp() if (b1 == b2 and e1.is_commutative and e2.is_commutative): nc_part[-1] = Pow(b1, Add(e1, e2)) continue nc_part.append(term) # add up exponents of common bases for b, e in ordered(iter(c_powers.items())): # allow 2**x/4 -> 2**(x - 2); don't do this when b and e are # Numbers since autoevaluation will undo it, e.g. # 2**(1/3)/4 -> 2**(1/3 - 2) -> 2**(1/3)/4 if (b and b.is_Rational and not all(ei.is_Number for ei in e) and \ coeff is not S.One and b not in (S.One, S.NegativeOne)): m = multiplicity(abs(b), abs(coeff)) if m: e.append(m) coeff /= b**m c_powers[b] = Add(*e) if coeff is not S.One: if coeff in c_powers: c_powers[coeff] += S.One else: c_powers[coeff] = S.One # convert to plain dictionary c_powers = dict(c_powers) # check for base and inverted base pairs be = list(c_powers.items()) skip = set() # skip if we already saw them for b, e in be: if b in skip: continue bpos = b.is_positive or b.is_polar if bpos: binv = 1/b if b != binv and binv in c_powers: if b.as_numer_denom()[0] is S.One: c_powers.pop(b) c_powers[binv] -= e else: skip.add(binv) e = c_powers.pop(binv) c_powers[b] -= e # check for base and negated base pairs be = list(c_powers.items()) _n = S.NegativeOne for b, e in be: if (b.is_Symbol or b.is_Add) and -b in c_powers and b in c_powers: if (b.is_positive is not None or e.is_integer): if e.is_integer or b.is_negative: c_powers[-b] += c_powers.pop(b) else: # (-b).is_positive so use its e e = c_powers.pop(-b) c_powers[b] += e if _n in c_powers: c_powers[_n] += e else: c_powers[_n] = e # filter c_powers and convert to a list c_powers = [(b, e) for b, e in c_powers.items() if e] # ============================================================== # check for Mul bases of Rational powers that can be combined with # separated bases, e.g. x*sqrt(x*y)*sqrt(x*sqrt(x*y)) -> # (x*sqrt(x*y))**(3/2) # ---------------- helper functions def ratq(x): '''Return Rational part of x's exponent as it appears in the bkey. ''' return bkey(x)[0][1] def bkey(b, e=None): '''Return (b**s, c.q), c.p where e -> c*s. If e is not given then it will be taken by using as_base_exp() on the input b. e.g. x**3/2 -> (x, 2), 3 x**y -> (x**y, 1), 1 x**(2*y/3) -> (x**y, 3), 2 exp(x/2) -> (exp(a), 2), 1 ''' if e is not None: # coming from c_powers or from below if e.is_Integer: return (b, S.One), e elif e.is_Rational: return (b, Integer(e.q)), Integer(e.p) else: c, m = e.as_coeff_Mul(rational=True) if c is not S.One: if m.is_integer: return (b, Integer(c.q)), m*Integer(c.p) return (b**m, Integer(c.q)), Integer(c.p) else: return (b**e, S.One), S.One else: return bkey(*b.as_base_exp()) def update(b): '''Decide what to do with base, b. If its exponent is now an integer multiple of the Rational denominator, then remove it and put the factors of its base in the common_b dictionary or update the existing bases if necessary. If it has been zeroed out, simply remove the base. ''' newe, r = divmod(common_b[b], b[1]) if not r: common_b.pop(b) if newe: for m in Mul.make_args(b[0]**newe): b, e = bkey(m) if b not in common_b: common_b[b] = 0 common_b[b] += e if b[1] != 1: bases.append(b) # ---------------- end of helper functions # assemble a dictionary of the factors having a Rational power common_b = {} done = [] bases = [] for b, e in c_powers: b, e = bkey(b, e) if b in common_b: common_b[b] = common_b[b] + e else: common_b[b] = e if b[1] != 1 and b[0].is_Mul: bases.append(b) bases.sort(key=default_sort_key) # this makes tie-breaking canonical bases.sort(key=measure, reverse=True) # handle longest first for base in bases: if base not in common_b: # it may have been removed already continue b, exponent = base last = False # True when no factor of base is a radical qlcm = 1 # the lcm of the radical denominators while True: bstart = b qstart = qlcm bb = [] # list of factors ee = [] # (factor's expo. and it's current value in common_b) for bi in Mul.make_args(b): bib, bie = bkey(bi) if bib not in common_b or common_b[bib] < bie: ee = bb = [] # failed break ee.append([bie, common_b[bib]]) bb.append(bib) if ee: # find the number of integral extractions possible # e.g. [(1, 2), (2, 2)] -> min(2/1, 2/2) -> 1 min1 = ee[0][1]//ee[0][0] for i in range(1, len(ee)): rat = ee[i][1]//ee[i][0] if rat < 1: break min1 = min(min1, rat) else: # update base factor counts # e.g. if ee = [(2, 5), (3, 6)] then min1 = 2 # and the new base counts will be 5-2*2 and 6-2*3 for i in range(len(bb)): common_b[bb[i]] -= min1*ee[i][0] update(bb[i]) # update the count of the base # e.g. x**2*y*sqrt(x*sqrt(y)) the count of x*sqrt(y) # will increase by 4 to give bkey (x*sqrt(y), 2, 5) common_b[base] += min1*qstart*exponent if (last # no more radicals in base or len(common_b) == 1 # nothing left to join with or all(k[1] == 1 for k in common_b) # no rad's in common_b ): break # see what we can exponentiate base by to remove any radicals # so we know what to search for # e.g. if base were x**(1/2)*y**(1/3) then we should # exponentiate by 6 and look for powers of x and y in the ratio # of 2 to 3 qlcm = lcm([ratq(bi) for bi in Mul.make_args(bstart)]) if qlcm == 1: break # we are done b = bstart**qlcm qlcm *= qstart if all(ratq(bi) == 1 for bi in Mul.make_args(b)): last = True # we are going to be done after this next pass # this base no longer can find anything to join with and # since it was longer than any other we are done with it b, q = base done.append((b, common_b.pop(base)*Rational(1, q))) # update c_powers and get ready to continue with powsimp c_powers = done # there may be terms still in common_b that were bases that were # identified as needing processing, so remove those, too for (b, q), e in common_b.items(): if (b.is_Pow or isinstance(b, exp)) and \ q is not S.One and not b.exp.is_Rational: b, be = b.as_base_exp() b = b**(be/q) else: b = root(b, q) c_powers.append((b, e)) check = len(c_powers) c_powers = dict(c_powers) assert len(c_powers) == check # there should have been no duplicates # ============================================================== # rebuild the expression newexpr = expr.func(*(newexpr + [Pow(b, e) for b, e in c_powers.items()])) if combine == 'exp': return expr.func(newexpr, expr.func(*nc_part)) else: return recurse(expr.func(*nc_part), combine='base') * \ recurse(newexpr, combine='base') elif combine == 'base': # Build c_powers and nc_part. These must both be lists not # dicts because exp's are not combined. c_powers = [] nc_part = [] for term in expr.args: if term.is_commutative: c_powers.append(list(term.as_base_exp())) else: nc_part.append(term) # Pull out numerical coefficients from exponent if assumptions allow # e.g., 2**(2*x) => 4**x for i in range(len(c_powers)): b, e = c_powers[i] if not (all(x.is_nonnegative for x in b.as_numer_denom()) or e.is_integer or force or b.is_polar): continue exp_c, exp_t = e.as_coeff_Mul(rational=True) if exp_c is not S.One and exp_t is not S.One: c_powers[i] = [Pow(b, exp_c), exp_t] # Combine bases whenever they have the same exponent and # assumptions allow # first gather the potential bases under the common exponent c_exp = defaultdict(list) for b, e in c_powers: if deep: e = recurse(e) c_exp[e].append(b) del c_powers # Merge back in the results of the above to form a new product c_powers = defaultdict(list) for e in c_exp: bases = c_exp[e] # calculate the new base for e if len(bases) == 1: new_base = bases[0] elif e.is_integer or force: new_base = expr.func(*bases) else: # see which ones can be joined unk = [] nonneg = [] neg = [] for bi in bases: if bi.is_negative: neg.append(bi) elif bi.is_nonnegative: nonneg.append(bi) elif bi.is_polar: nonneg.append( bi) # polar can be treated like non-negative else: unk.append(bi) if len(unk) == 1 and not neg or len(neg) == 1 and not unk: # a single neg or a single unk can join the rest nonneg.extend(unk + neg) unk = neg = [] elif neg: # their negative signs cancel in groups of 2*q if we know # that e = p/q else we have to treat them as unknown israt = False if e.is_Rational: israt = True else: p, d = e.as_numer_denom() if p.is_integer and d.is_integer: israt = True if israt: neg = [-w for w in neg] unk.extend([S.NegativeOne]*len(neg)) else: unk.extend(neg) neg = [] del israt # these shouldn't be joined for b in unk: c_powers[b].append(e) # here is a new joined base new_base = expr.func(*(nonneg + neg)) # if there are positive parts they will just get separated # again unless some change is made def _terms(e): # return the number of terms of this expression # when multiplied out -- assuming no joining of terms if e.is_Add: return sum([_terms(ai) for ai in e.args]) if e.is_Mul: return prod([_terms(mi) for mi in e.args]) return 1 xnew_base = expand_mul(new_base, deep=False) if len(Add.make_args(xnew_base)) < _terms(new_base): new_base = factor_terms(xnew_base) c_powers[new_base].append(e) # break out the powers from c_powers now c_part = [Pow(b, ei) for b, e in c_powers.items() for ei in e] # we're done return expr.func(*(c_part + nc_part)) else: raise ValueError("combine must be one of ('all', 'exp', 'base').") def powdenest(eq, force=False, polar=False): r""" Collect exponents on powers as assumptions allow. Explanation =========== Given ``(bb**be)**e``, this can be simplified as follows: * if ``bb`` is positive, or * ``e`` is an integer, or * ``|be| < 1`` then this simplifies to ``bb**(be*e)`` Given a product of powers raised to a power, ``(bb1**be1 * bb2**be2...)**e``, simplification can be done as follows: - if e is positive, the gcd of all bei can be joined with e; - all non-negative bb can be separated from those that are negative and their gcd can be joined with e; autosimplification already handles this separation. - integer factors from powers that have integers in the denominator of the exponent can be removed from any term and the gcd of such integers can be joined with e Setting ``force`` to ``True`` will make symbols that are not explicitly negative behave as though they are positive, resulting in more denesting. Setting ``polar`` to ``True`` will do simplifications on the Riemann surface of the logarithm, also resulting in more denestings. When there are sums of logs in exp() then a product of powers may be obtained e.g. ``exp(3*(log(a) + 2*log(b)))`` - > ``a**3*b**6``. Examples ======== >>> from sympy.abc import a, b, x, y, z >>> from sympy import Symbol, exp, log, sqrt, symbols, powdenest >>> powdenest((x**(2*a/3))**(3*x)) (x**(2*a/3))**(3*x) >>> powdenest(exp(3*x*log(2))) 2**(3*x) Assumptions may prevent expansion: >>> powdenest(sqrt(x**2)) sqrt(x**2) >>> p = symbols('p', positive=True) >>> powdenest(sqrt(p**2)) p No other expansion is done. >>> i, j = symbols('i,j', integer=True) >>> powdenest((x**x)**(i + j)) # -X-> (x**x)**i*(x**x)**j x**(x*(i + j)) But exp() will be denested by moving all non-log terms outside of the function; this may result in the collapsing of the exp to a power with a different base: >>> powdenest(exp(3*y*log(x))) x**(3*y) >>> powdenest(exp(y*(log(a) + log(b)))) (a*b)**y >>> powdenest(exp(3*(log(a) + log(b)))) a**3*b**3 If assumptions allow, symbols can also be moved to the outermost exponent: >>> i = Symbol('i', integer=True) >>> powdenest(((x**(2*i))**(3*y))**x) ((x**(2*i))**(3*y))**x >>> powdenest(((x**(2*i))**(3*y))**x, force=True) x**(6*i*x*y) >>> powdenest(((x**(2*a/3))**(3*y/i))**x) ((x**(2*a/3))**(3*y/i))**x >>> powdenest((x**(2*i)*y**(4*i))**z, force=True) (x*y**2)**(2*i*z) >>> n = Symbol('n', negative=True) >>> powdenest((x**i)**y, force=True) x**(i*y) >>> powdenest((n**i)**x, force=True) (n**i)**x """ from sympy.simplify.simplify import posify if force: eq, rep = posify(eq) return powdenest(eq, force=False).xreplace(rep) if polar: eq, rep = polarify(eq) return unpolarify(powdenest(unpolarify(eq, exponents_only=True)), rep) new = powsimp(sympify(eq)) return new.xreplace(Transform( _denest_pow, filter=lambda m: m.is_Pow or isinstance(m, exp))) _y = Dummy('y') def _denest_pow(eq): """ Denest powers. This is a helper function for powdenest that performs the actual transformation. """ from sympy.simplify.simplify import logcombine b, e = eq.as_base_exp() if b.is_Pow or isinstance(b.func, exp) and e != 1: new = b._eval_power(e) if new is not None: eq = new b, e = new.as_base_exp() # denest exp with log terms in exponent if b is S.Exp1 and e.is_Mul: logs = [] other = [] for ei in e.args: if any(isinstance(ai, log) for ai in Add.make_args(ei)): logs.append(ei) else: other.append(ei) logs = logcombine(Mul(*logs)) return Pow(exp(logs), Mul(*other)) _, be = b.as_base_exp() if be is S.One and not (b.is_Mul or b.is_Rational and b.q != 1 or b.is_positive): return eq # denest eq which is either pos**e or Pow**e or Mul**e or # Mul(b1**e1, b2**e2) # handle polar numbers specially polars, nonpolars = [], [] for bb in Mul.make_args(b): if bb.is_polar: polars.append(bb.as_base_exp()) else: nonpolars.append(bb) if len(polars) == 1 and not polars[0][0].is_Mul: return Pow(polars[0][0], polars[0][1]*e)*powdenest(Mul(*nonpolars)**e) elif polars: return Mul(*[powdenest(bb**(ee*e)) for (bb, ee) in polars]) \ *powdenest(Mul(*nonpolars)**e) if b.is_Integer: # use log to see if there is a power here logb = expand_log(log(b)) if logb.is_Mul: c, logb = logb.args e *= c base = logb.args[0] return Pow(base, e) # if b is not a Mul or any factor is an atom then there is nothing to do if not b.is_Mul or any(s.is_Atom for s in Mul.make_args(b)): return eq # let log handle the case of the base of the argument being a Mul, e.g. # sqrt(x**(2*i)*y**(6*i)) -> x**i*y**(3**i) if x and y are positive; we # will take the log, expand it, and then factor out the common powers that # now appear as coefficient. We do this manually since terms_gcd pulls out # fractions, terms_gcd(x+x*y/2) -> x*(y + 2)/2 and we don't want the 1/2; # gcd won't pull out numerators from a fraction: gcd(3*x, 9*x/2) -> x but # we want 3*x. Neither work with noncommutatives. def nc_gcd(aa, bb): a, b = [i.as_coeff_Mul() for i in [aa, bb]] c = gcd(a[0], b[0]).as_numer_denom()[0] g = Mul(*(a[1].args_cnc(cset=True)[0] & b[1].args_cnc(cset=True)[0])) return _keep_coeff(c, g) glogb = expand_log(log(b)) if glogb.is_Add: args = glogb.args g = reduce(nc_gcd, args) if g != 1: cg, rg = g.as_coeff_Mul() glogb = _keep_coeff(cg, rg*Add(*[a/g for a in args])) # now put the log back together again if isinstance(glogb, log) or not glogb.is_Mul: if glogb.args[0].is_Pow or isinstance(glogb.args[0], exp): glogb = _denest_pow(glogb.args[0]) if (abs(glogb.exp) < 1) == True: return Pow(glogb.base, glogb.exp*e) return eq # the log(b) was a Mul so join any adds with logcombine add = [] other = [] for a in glogb.args: if a.is_Add: add.append(a) else: other.append(a) return Pow(exp(logcombine(Mul(*add))), e*Mul(*other))

0bf150af2b5a340b38eeeac388b9b62ce263c692768c3b697e04659a984923ce

from sympy.core import Function, S, Mul, Pow, Add from sympy.core.compatibility import ordered, default_sort_key from sympy.core.function import count_ops, expand_func from sympy.functions.combinatorial.factorials import binomial from sympy.functions import gamma, sqrt, sin from sympy.polys import factor, cancel from sympy.utilities.iterables import sift, uniq def gammasimp(expr): r""" Simplify expressions with gamma functions. Explanation =========== This function takes as input an expression containing gamma functions or functions that can be rewritten in terms of gamma functions and tries to minimize the number of those functions and reduce the size of their arguments. The algorithm works by rewriting all gamma functions as expressions involving rising factorials (Pochhammer symbols) and applies recurrence relations and other transformations applicable to rising factorials, to reduce their arguments, possibly letting the resulting rising factorial to cancel. Rising factorials with the second argument being an integer are expanded into polynomial forms and finally all other rising factorial are rewritten in terms of gamma functions. Then the following two steps are performed. 1. Reduce the number of gammas by applying the reflection theorem gamma(x)*gamma(1-x) == pi/sin(pi*x). 2. Reduce the number of gammas by applying the multiplication theorem gamma(x)*gamma(x+1/n)*...*gamma(x+(n-1)/n) == C*gamma(n*x). It then reduces the number of prefactors by absorbing them into gammas where possible and expands gammas with rational argument. All transformation rules can be found (or was derived from) here: .. [1] http://functions.wolfram.com/GammaBetaErf/Pochhammer/17/01/02/ .. [2] http://functions.wolfram.com/GammaBetaErf/Pochhammer/27/01/0005/ Examples ======== >>> from sympy.simplify import gammasimp >>> from sympy import gamma, Symbol >>> from sympy.abc import x >>> n = Symbol('n', integer = True) >>> gammasimp(gamma(x)/gamma(x - 3)) (x - 3)*(x - 2)*(x - 1) >>> gammasimp(gamma(n + 3)) gamma(n + 3) """ expr = expr.rewrite(gamma) return _gammasimp(expr, as_comb = False) def _gammasimp(expr, as_comb): """ Helper function for gammasimp and combsimp. Explanation =========== Simplifies expressions written in terms of gamma function. If as_comb is True, it tries to preserve integer arguments. See docstring of gammasimp for more information. This was part of combsimp() in combsimp.py. """ expr = expr.replace(gamma, lambda n: _rf(1, (n - 1).expand())) if as_comb: expr = expr.replace(_rf, lambda a, b: gamma(b + 1)) else: expr = expr.replace(_rf, lambda a, b: gamma(a + b)/gamma(a)) def rule(n, k): coeff, rewrite = S.One, False cn, _n = n.as_coeff_Add() if _n and cn.is_Integer and cn: coeff *= _rf(_n + 1, cn)/_rf(_n - k + 1, cn) rewrite = True n = _n # this sort of binomial has already been removed by # rising factorials but is left here in case the order # of rule application is changed if k.is_Add: ck, _k = k.as_coeff_Add() if _k and ck.is_Integer and ck: coeff *= _rf(n - ck - _k + 1, ck)/_rf(_k + 1, ck) rewrite = True k = _k if count_ops(k) > count_ops(n - k): rewrite = True k = n - k if rewrite: return coeff*binomial(n, k) expr = expr.replace(binomial, rule) def rule_gamma(expr, level=0): """ Simplify products of gamma functions further. """ if expr.is_Atom: return expr def gamma_rat(x): # helper to simplify ratios of gammas was = x.count(gamma) xx = x.replace(gamma, lambda n: _rf(1, (n - 1).expand() ).replace(_rf, lambda a, b: gamma(a + b)/gamma(a))) if xx.count(gamma) < was: x = xx return x def gamma_factor(x): # return True if there is a gamma factor in shallow args if isinstance(x, gamma): return True if x.is_Add or x.is_Mul: return any(gamma_factor(xi) for xi in x.args) if x.is_Pow and (x.exp.is_integer or x.base.is_positive): return gamma_factor(x.base) return False # recursion step if level == 0: expr = expr.func(*[rule_gamma(x, level + 1) for x in expr.args]) level += 1 if not expr.is_Mul: return expr # non-commutative step if level == 1: args, nc = expr.args_cnc() if not args: return expr if nc: return rule_gamma(Mul._from_args(args), level + 1)*Mul._from_args(nc) level += 1 # pure gamma handling, not factor absorption if level == 2: T, F = sift(expr.args, gamma_factor, binary=True) gamma_ind = Mul(*F) d = Mul(*T) nd, dd = d.as_numer_denom() for ipass in range(2): args = list(ordered(Mul.make_args(nd))) for i, ni in enumerate(args): if ni.is_Add: ni, dd = Add(*[ rule_gamma(gamma_rat(a/dd), level + 1) for a in ni.args] ).as_numer_denom() args[i] = ni if not dd.has(gamma): break nd = Mul(*args) if ipass == 0 and not gamma_factor(nd): break nd, dd = dd, nd # now process in reversed order expr = gamma_ind*nd/dd if not (expr.is_Mul and (gamma_factor(dd) or gamma_factor(nd))): return expr level += 1 # iteration until constant if level == 3: while True: was = expr expr = rule_gamma(expr, 4) if expr == was: return expr numer_gammas = [] denom_gammas = [] numer_others = [] denom_others = [] def explicate(p): if p is S.One: return None, [] b, e = p.as_base_exp() if e.is_Integer: if isinstance(b, gamma): return True, [b.args[0]]*e else: return False, [b]*e else: return False, [p] newargs = list(ordered(expr.args)) while newargs: n, d = newargs.pop().as_numer_denom() isg, l = explicate(n) if isg: numer_gammas.extend(l) elif isg is False: numer_others.extend(l) isg, l = explicate(d) if isg: denom_gammas.extend(l) elif isg is False: denom_others.extend(l) # =========== level 2 work: pure gamma manipulation ========= if not as_comb: # Try to reduce the number of gamma factors by applying the # reflection formula gamma(x)*gamma(1-x) = pi/sin(pi*x) for gammas, numer, denom in [( numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: new = [] while gammas: g1 = gammas.pop() if g1.is_integer: new.append(g1) continue for i, g2 in enumerate(gammas): n = g1 + g2 - 1 if not n.is_Integer: continue numer.append(S.Pi) denom.append(sin(S.Pi*g1)) gammas.pop(i) if n > 0: for k in range(n): numer.append(1 - g1 + k) elif n < 0: for k in range(-n): denom.append(-g1 - k) break else: new.append(g1) # /!\ updating IN PLACE gammas[:] = new # Try to reduce the number of gammas by using the duplication # theorem to cancel an upper and lower: gamma(2*s)/gamma(s) = # 2**(2*s + 1)/(4*sqrt(pi))*gamma(s + 1/2). Although this could # be done with higher argument ratios like gamma(3*x)/gamma(x), # this would not reduce the number of gammas as in this case. for ng, dg, no, do in [(numer_gammas, denom_gammas, numer_others, denom_others), (denom_gammas, numer_gammas, denom_others, numer_others)]: while True: for x in ng: for y in dg: n = x - 2*y if n.is_Integer: break else: continue break else: break ng.remove(x) dg.remove(y) if n > 0: for k in range(n): no.append(2*y + k) elif n < 0: for k in range(-n): do.append(2*y - 1 - k) ng.append(y + S.Half) no.append(2**(2*y - 1)) do.append(sqrt(S.Pi)) # Try to reduce the number of gamma factors by applying the # multiplication theorem (used when n gammas with args differing # by 1/n mod 1 are encountered). # # run of 2 with args differing by 1/2 # # >>> gammasimp(gamma(x)*gamma(x+S.Half)) # 2*sqrt(2)*2**(-2*x - 1/2)*sqrt(pi)*gamma(2*x) # # run of 3 args differing by 1/3 (mod 1) # # >>> gammasimp(gamma(x)*gamma(x+S(1)/3)*gamma(x+S(2)/3)) # 6*3**(-3*x - 1/2)*pi*gamma(3*x) # >>> gammasimp(gamma(x)*gamma(x+S(1)/3)*gamma(x+S(5)/3)) # 2*3**(-3*x - 1/2)*pi*(3*x + 2)*gamma(3*x) # def _run(coeffs): # find runs in coeffs such that the difference in terms (mod 1) # of t1, t2, ..., tn is 1/n u = list(uniq(coeffs)) for i in range(len(u)): dj = ([((u[j] - u[i]) % 1, j) for j in range(i + 1, len(u))]) for one, j in dj: if one.p == 1 and one.q != 1: n = one.q got = [i] get = list(range(1, n)) for d, j in dj: m = n*d if m.is_Integer and m in get: get.remove(m) got.append(j) if not get: break else: continue for i, j in enumerate(got): c = u[j] coeffs.remove(c) got[i] = c return one.q, got[0], got[1:] def _mult_thm(gammas, numer, denom): # pull off and analyze the leading coefficient from each gamma arg # looking for runs in those Rationals # expr -> coeff + resid -> rats[resid] = coeff rats = {} for g in gammas: c, resid = g.as_coeff_Add() rats.setdefault(resid, []).append(c) # look for runs in Rationals for each resid keys = sorted(rats, key=default_sort_key) for resid in keys: coeffs = list(sorted(rats[resid])) new = [] while True: run = _run(coeffs) if run is None: break # process the sequence that was found: # 1) convert all the gamma functions to have the right # argument (could be off by an integer) # 2) append the factors corresponding to the theorem # 3) append the new gamma function n, ui, other = run # (1) for u in other: con = resid + u - 1 for k in range(int(u - ui)): numer.append(con - k) con = n*(resid + ui) # for (2) and (3) # (2) numer.append((2*S.Pi)**(S(n - 1)/2)* n**(S.Half - con)) # (3) new.append(con) # restore resid to coeffs rats[resid] = [resid + c for c in coeffs] + new # rebuild the gamma arguments g = [] for resid in keys: g += rats[resid] # /!\ updating IN PLACE gammas[:] = g for l, numer, denom in [(numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: _mult_thm(l, numer, denom) # =========== level >= 2 work: factor absorption ========= if level >= 2: # Try to absorb factors into the gammas: x*gamma(x) -> gamma(x + 1) # and gamma(x)/(x - 1) -> gamma(x - 1) # This code (in particular repeated calls to find_fuzzy) can be very # slow. def find_fuzzy(l, x): if not l: return S1, T1 = compute_ST(x) for y in l: S2, T2 = inv[y] if T1 != T2 or (not S1.intersection(S2) and (S1 != set() or S2 != set())): continue # XXX we want some simplification (e.g. cancel or # simplify) but no matter what it's slow. a = len(cancel(x/y).free_symbols) b = len(x.free_symbols) c = len(y.free_symbols) # TODO is there a better heuristic? if a == 0 and (b > 0 or c > 0): return y # We thus try to avoid expensive calls by building the following # "invariants": For every factor or gamma function argument # - the set of free symbols S # - the set of functional components T # We will only try to absorb if T1==T2 and (S1 intersect S2 != emptyset # or S1 == S2 == emptyset) inv = {} def compute_ST(expr): if expr in inv: return inv[expr] return (expr.free_symbols, expr.atoms(Function).union( {e.exp for e in expr.atoms(Pow)})) def update_ST(expr): inv[expr] = compute_ST(expr) for expr in numer_gammas + denom_gammas + numer_others + denom_others: update_ST(expr) for gammas, numer, denom in [( numer_gammas, numer_others, denom_others), (denom_gammas, denom_others, numer_others)]: new = [] while gammas: g = gammas.pop() cont = True while cont: cont = False y = find_fuzzy(numer, g) if y is not None: numer.remove(y) if y != g: numer.append(y/g) update_ST(y/g) g += 1 cont = True y = find_fuzzy(denom, g - 1) if y is not None: denom.remove(y) if y != g - 1: numer.append((g - 1)/y) update_ST((g - 1)/y) g -= 1 cont = True new.append(g) # /!\ updating IN PLACE gammas[:] = new # =========== rebuild expr ================================== return Mul(*[gamma(g) for g in numer_gammas]) \ / Mul(*[gamma(g) for g in denom_gammas]) \ * Mul(*numer_others) / Mul(*denom_others) # (for some reason we cannot use Basic.replace in this case) was = factor(expr) expr = rule_gamma(was) if expr != was: expr = factor(expr) expr = expr.replace(gamma, lambda n: expand_func(gamma(n)) if n.is_Rational else gamma(n)) return expr class _rf(Function): @classmethod def eval(cls, a, b): if b.is_Integer: if not b: return S.One n, result = int(b), S.One if n > 0: for i in range(n): result *= a + i return result elif n < 0: for i in range(1, -n + 1): result *= a - i return 1/result else: if b.is_Add: c, _b = b.as_coeff_Add() if c.is_Integer: if c > 0: return _rf(a, _b)*_rf(a + _b, c) elif c < 0: return _rf(a, _b)/_rf(a + _b + c, -c) if a.is_Add: c, _a = a.as_coeff_Add() if c.is_Integer: if c > 0: return _rf(_a, b)*_rf(_a + b, c)/_rf(_a, c) elif c < 0: return _rf(_a, b)*_rf(_a + c, -c)/_rf(_a + b + c, -c)

e381b806646ed3ea8fd1280303b457cfb59c29dfc4986c44aaab050d544235dd

from collections import defaultdict from sympy.core import (sympify, Basic, S, Expr, expand_mul, factor_terms, Mul, Dummy, igcd, FunctionClass, Add, symbols, Wild, expand) from sympy.core.cache import cacheit from sympy.core.compatibility import reduce, iterable, SYMPY_INTS from sympy.core.function import count_ops, _mexpand from sympy.core.numbers import I, Integer from sympy.functions import sin, cos, exp, cosh, tanh, sinh, tan, cot, coth from sympy.functions.elementary.hyperbolic import HyperbolicFunction from sympy.functions.elementary.trigonometric import TrigonometricFunction from sympy.polys import Poly, factor, cancel, parallel_poly_from_expr from sympy.polys.domains import ZZ from sympy.polys.polyerrors import PolificationFailed from sympy.polys.polytools import groebner from sympy.simplify.cse_main import cse from sympy.strategies.core import identity from sympy.strategies.tree import greedy from sympy.utilities.misc import debug def trigsimp_groebner(expr, hints=[], quick=False, order="grlex", polynomial=False): """ Simplify trigonometric expressions using a groebner basis algorithm. Explanation =========== This routine takes a fraction involving trigonometric or hyperbolic expressions, and tries to simplify it. The primary metric is the total degree. Some attempts are made to choose the simplest possible expression of the minimal degree, but this is non-rigorous, and also very slow (see the ``quick=True`` option). If ``polynomial`` is set to True, instead of simplifying numerator and denominator together, this function just brings numerator and denominator into a canonical form. This is much faster, but has potentially worse results. However, if the input is a polynomial, then the result is guaranteed to be an equivalent polynomial of minimal degree. The most important option is hints. Its entries can be any of the following: - a natural number - a function - an iterable of the form (func, var1, var2, ...) - anything else, interpreted as a generator A number is used to indicate that the search space should be increased. A function is used to indicate that said function is likely to occur in a simplified expression. An iterable is used indicate that func(var1 + var2 + ...) is likely to occur in a simplified . An additional generator also indicates that it is likely to occur. (See examples below). This routine carries out various computationally intensive algorithms. The option ``quick=True`` can be used to suppress one particularly slow step (at the expense of potentially more complicated results, but never at the expense of increased total degree). Examples ======== >>> from sympy.abc import x, y >>> from sympy import sin, tan, cos, sinh, cosh, tanh >>> from sympy.simplify.trigsimp import trigsimp_groebner Suppose you want to simplify ``sin(x)*cos(x)``. Naively, nothing happens: >>> ex = sin(x)*cos(x) >>> trigsimp_groebner(ex) sin(x)*cos(x) This is because ``trigsimp_groebner`` only looks for a simplification involving just ``sin(x)`` and ``cos(x)``. You can tell it to also try ``2*x`` by passing ``hints=[2]``: >>> trigsimp_groebner(ex, hints=[2]) sin(2*x)/2 >>> trigsimp_groebner(sin(x)**2 - cos(x)**2, hints=[2]) -cos(2*x) Increasing the search space this way can quickly become expensive. A much faster way is to give a specific expression that is likely to occur: >>> trigsimp_groebner(ex, hints=[sin(2*x)]) sin(2*x)/2 Hyperbolic expressions are similarly supported: >>> trigsimp_groebner(sinh(2*x)/sinh(x)) 2*cosh(x) Note how no hints had to be passed, since the expression already involved ``2*x``. The tangent function is also supported. You can either pass ``tan`` in the hints, to indicate that tan should be tried whenever cosine or sine are, or you can pass a specific generator: >>> trigsimp_groebner(sin(x)/cos(x), hints=[tan]) tan(x) >>> trigsimp_groebner(sinh(x)/cosh(x), hints=[tanh(x)]) tanh(x) Finally, you can use the iterable form to suggest that angle sum formulae should be tried: >>> ex = (tan(x) + tan(y))/(1 - tan(x)*tan(y)) >>> trigsimp_groebner(ex, hints=[(tan, x, y)]) tan(x + y) """ # TODO # - preprocess by replacing everything by funcs we can handle # - optionally use cot instead of tan # - more intelligent hinting. # For example, if the ideal is small, and we have sin(x), sin(y), # add sin(x + y) automatically... ? # - algebraic numbers ... # - expressions of lowest degree are not distinguished properly # e.g. 1 - sin(x)**2 # - we could try to order the generators intelligently, so as to influence # which monomials appear in the quotient basis # THEORY # ------ # Ratsimpmodprime above can be used to "simplify" a rational function # modulo a prime ideal. "Simplify" mainly means finding an equivalent # expression of lower total degree. # # We intend to use this to simplify trigonometric functions. To do that, # we need to decide (a) which ring to use, and (b) modulo which ideal to # simplify. In practice, (a) means settling on a list of "generators" # a, b, c, ..., such that the fraction we want to simplify is a rational # function in a, b, c, ..., with coefficients in ZZ (integers). # (2) means that we have to decide what relations to impose on the # generators. There are two practical problems: # (1) The ideal has to be *prime* (a technical term). # (2) The relations have to be polynomials in the generators. # # We typically have two kinds of generators: # - trigonometric expressions, like sin(x), cos(5*x), etc # - "everything else", like gamma(x), pi, etc. # # Since this function is trigsimp, we will concentrate on what to do with # trigonometric expressions. We can also simplify hyperbolic expressions, # but the extensions should be clear. # # One crucial point is that all *other* generators really should behave # like indeterminates. In particular if (say) "I" is one of them, then # in fact I**2 + 1 = 0 and we may and will compute non-sensical # expressions. However, we can work with a dummy and add the relation # I**2 + 1 = 0 to our ideal, then substitute back in the end. # # Now regarding trigonometric generators. We split them into groups, # according to the argument of the trigonometric functions. We want to # organise this in such a way that most trigonometric identities apply in # the same group. For example, given sin(x), cos(2*x) and cos(y), we would # group as [sin(x), cos(2*x)] and [cos(y)]. # # Our prime ideal will be built in three steps: # (1) For each group, compute a "geometrically prime" ideal of relations. # Geometrically prime means that it generates a prime ideal in # CC[gens], not just ZZ[gens]. # (2) Take the union of all the generators of the ideals for all groups. # By the geometric primality condition, this is still prime. # (3) Add further inter-group relations which preserve primality. # # Step (1) works as follows. We will isolate common factors in the # argument, so that all our generators are of the form sin(n*x), cos(n*x) # or tan(n*x), with n an integer. Suppose first there are no tan terms. # The ideal [sin(x)**2 + cos(x)**2 - 1] is geometrically prime, since # X**2 + Y**2 - 1 is irreducible over CC. # Now, if we have a generator sin(n*x), than we can, using trig identities, # express sin(n*x) as a polynomial in sin(x) and cos(x). We can add this # relation to the ideal, preserving geometric primality, since the quotient # ring is unchanged. # Thus we have treated all sin and cos terms. # For tan(n*x), we add a relation tan(n*x)*cos(n*x) - sin(n*x) = 0. # (This requires of course that we already have relations for cos(n*x) and # sin(n*x).) It is not obvious, but it seems that this preserves geometric # primality. # XXX A real proof would be nice. HELP! # Sketch that <S**2 + C**2 - 1, C*T - S> is a prime ideal of # CC[S, C, T]: # - it suffices to show that the projective closure in CP**3 is # irreducible # - using the half-angle substitutions, we can express sin(x), tan(x), # cos(x) as rational functions in tan(x/2) # - from this, we get a rational map from CP**1 to our curve # - this is a morphism, hence the curve is prime # # Step (2) is trivial. # # Step (3) works by adding selected relations of the form # sin(x + y) - sin(x)*cos(y) - sin(y)*cos(x), etc. Geometric primality is # preserved by the same argument as before. def parse_hints(hints): """Split hints into (n, funcs, iterables, gens).""" n = 1 funcs, iterables, gens = [], [], [] for e in hints: if isinstance(e, (SYMPY_INTS, Integer)): n = e elif isinstance(e, FunctionClass): funcs.append(e) elif iterable(e): iterables.append((e[0], e[1:])) # XXX sin(x+2y)? # Note: we go through polys so e.g. # sin(-x) -> -sin(x) -> sin(x) gens.extend(parallel_poly_from_expr( [e[0](x) for x in e[1:]] + [e[0](Add(*e[1:]))])[1].gens) else: gens.append(e) return n, funcs, iterables, gens def build_ideal(x, terms): """ Build generators for our ideal. ``Terms`` is an iterable with elements of the form (fn, coeff), indicating that we have a generator fn(coeff*x). If any of the terms is trigonometric, sin(x) and cos(x) are guaranteed to appear in terms. Similarly for hyperbolic functions. For tan(n*x), sin(n*x) and cos(n*x) are guaranteed. """ I = [] y = Dummy('y') for fn, coeff in terms: for c, s, t, rel in ( [cos, sin, tan, cos(x)**2 + sin(x)**2 - 1], [cosh, sinh, tanh, cosh(x)**2 - sinh(x)**2 - 1]): if coeff == 1 and fn in [c, s]: I.append(rel) elif fn == t: I.append(t(coeff*x)*c(coeff*x) - s(coeff*x)) elif fn in [c, s]: cn = fn(coeff*y).expand(trig=True).subs(y, x) I.append(fn(coeff*x) - cn) return list(set(I)) def analyse_gens(gens, hints): """ Analyse the generators ``gens``, using the hints ``hints``. The meaning of ``hints`` is described in the main docstring. Return a new list of generators, and also the ideal we should work with. """ # First parse the hints n, funcs, iterables, extragens = parse_hints(hints) debug('n=%s' % n, 'funcs:', funcs, 'iterables:', iterables, 'extragens:', extragens) # We just add the extragens to gens and analyse them as before gens = list(gens) gens.extend(extragens) # remove duplicates funcs = list(set(funcs)) iterables = list(set(iterables)) gens = list(set(gens)) # all the functions we can do anything with allfuncs = {sin, cos, tan, sinh, cosh, tanh} # sin(3*x) -> ((3, x), sin) trigterms = [(g.args[0].as_coeff_mul(), g.func) for g in gens if g.func in allfuncs] # Our list of new generators - start with anything that we cannot # work with (i.e. is not a trigonometric term) freegens = [g for g in gens if g.func not in allfuncs] newgens = [] trigdict = {} for (coeff, var), fn in trigterms: trigdict.setdefault(var, []).append((coeff, fn)) res = [] # the ideal for key, val in trigdict.items(): # We have now assembeled a dictionary. Its keys are common # arguments in trigonometric expressions, and values are lists of # pairs (fn, coeff). x0, (fn, coeff) in trigdict means that we # need to deal with fn(coeff*x0). We take the rational gcd of the # coeffs, call it ``gcd``. We then use x = x0/gcd as "base symbol", # all other arguments are integral multiples thereof. # We will build an ideal which works with sin(x), cos(x). # If hint tan is provided, also work with tan(x). Moreover, if # n > 1, also work with sin(k*x) for k <= n, and similarly for cos # (and tan if the hint is provided). Finally, any generators which # the ideal does not work with but we need to accommodate (either # because it was in expr or because it was provided as a hint) # we also build into the ideal. # This selection process is expressed in the list ``terms``. # build_ideal then generates the actual relations in our ideal, # from this list. fns = [x[1] for x in val] val = [x[0] for x in val] gcd = reduce(igcd, val) terms = [(fn, v/gcd) for (fn, v) in zip(fns, val)] fs = set(funcs + fns) for c, s, t in ([cos, sin, tan], [cosh, sinh, tanh]): if any(x in fs for x in (c, s, t)): fs.add(c) fs.add(s) for fn in fs: for k in range(1, n + 1): terms.append((fn, k)) extra = [] for fn, v in terms: if fn == tan: extra.append((sin, v)) extra.append((cos, v)) if fn in [sin, cos] and tan in fs: extra.append((tan, v)) if fn == tanh: extra.append((sinh, v)) extra.append((cosh, v)) if fn in [sinh, cosh] and tanh in fs: extra.append((tanh, v)) terms.extend(extra) x = gcd*Mul(*key) r = build_ideal(x, terms) res.extend(r) newgens.extend({fn(v*x) for fn, v in terms}) # Add generators for compound expressions from iterables for fn, args in iterables: if fn == tan: # Tan expressions are recovered from sin and cos. iterables.extend([(sin, args), (cos, args)]) elif fn == tanh: # Tanh expressions are recovered from sihn and cosh. iterables.extend([(sinh, args), (cosh, args)]) else: dummys = symbols('d:%i' % len(args), cls=Dummy) expr = fn( Add(*dummys)).expand(trig=True).subs(list(zip(dummys, args))) res.append(fn(Add(*args)) - expr) if myI in gens: res.append(myI**2 + 1) freegens.remove(myI) newgens.append(myI) return res, freegens, newgens myI = Dummy('I') expr = expr.subs(S.ImaginaryUnit, myI) subs = [(myI, S.ImaginaryUnit)] num, denom = cancel(expr).as_numer_denom() try: (pnum, pdenom), opt = parallel_poly_from_expr([num, denom]) except PolificationFailed: return expr debug('initial gens:', opt.gens) ideal, freegens, gens = analyse_gens(opt.gens, hints) debug('ideal:', ideal) debug('new gens:', gens, " -- len", len(gens)) debug('free gens:', freegens, " -- len", len(gens)) # NOTE we force the domain to be ZZ to stop polys from injecting generators # (which is usually a sign of a bug in the way we build the ideal) if not gens: return expr G = groebner(ideal, order=order, gens=gens, domain=ZZ) debug('groebner basis:', list(G), " -- len", len(G)) # If our fraction is a polynomial in the free generators, simplify all # coefficients separately: from sympy.simplify.ratsimp import ratsimpmodprime if freegens and pdenom.has_only_gens(*set(gens).intersection(pdenom.gens)): num = Poly(num, gens=gens+freegens).eject(*gens) res = [] for monom, coeff in num.terms(): ourgens = set(parallel_poly_from_expr([coeff, denom])[1].gens) # We compute the transitive closure of all generators that can # be reached from our generators through relations in the ideal. changed = True while changed: changed = False for p in ideal: p = Poly(p) if not ourgens.issuperset(p.gens) and \ not p.has_only_gens(*set(p.gens).difference(ourgens)): changed = True ourgens.update(p.exclude().gens) # NOTE preserve order! realgens = [x for x in gens if x in ourgens] # The generators of the ideal have now been (implicitly) split # into two groups: those involving ourgens and those that don't. # Since we took the transitive closure above, these two groups # live in subgrings generated by a *disjoint* set of variables. # Any sensible groebner basis algorithm will preserve this disjoint # structure (i.e. the elements of the groebner basis can be split # similarly), and and the two subsets of the groebner basis then # form groebner bases by themselves. (For the smaller generating # sets, of course.) ourG = [g.as_expr() for g in G.polys if g.has_only_gens(*ourgens.intersection(g.gens))] res.append(Mul(*[a**b for a, b in zip(freegens, monom)]) * \ ratsimpmodprime(coeff/denom, ourG, order=order, gens=realgens, quick=quick, domain=ZZ, polynomial=polynomial).subs(subs)) return Add(*res) # NOTE The following is simpler and has less assumptions on the # groebner basis algorithm. If the above turns out to be broken, # use this. return Add(*[Mul(*[a**b for a, b in zip(freegens, monom)]) * \ ratsimpmodprime(coeff/denom, list(G), order=order, gens=gens, quick=quick, domain=ZZ) for monom, coeff in num.terms()]) else: return ratsimpmodprime( expr, list(G), order=order, gens=freegens+gens, quick=quick, domain=ZZ, polynomial=polynomial).subs(subs) _trigs = (TrigonometricFunction, HyperbolicFunction) def trigsimp(expr, **opts): """ reduces expression by using known trig identities Explanation =========== method: - Determine the method to use. Valid choices are 'matching' (default), 'groebner', 'combined', and 'fu'. If 'matching', simplify the expression recursively by targeting common patterns. If 'groebner', apply an experimental groebner basis algorithm. In this case further options are forwarded to ``trigsimp_groebner``, please refer to its docstring. If 'combined', first run the groebner basis algorithm with small default parameters, then run the 'matching' algorithm. 'fu' runs the collection of trigonometric transformations described by Fu, et al. (see the `fu` docstring). Examples ======== >>> from sympy import trigsimp, sin, cos, log >>> from sympy.abc import x >>> e = 2*sin(x)**2 + 2*cos(x)**2 >>> trigsimp(e) 2 Simplification occurs wherever trigonometric functions are located. >>> trigsimp(log(e)) log(2) Using `method="groebner"` (or `"combined"`) might lead to greater simplification. The old trigsimp routine can be accessed as with method 'old'. >>> from sympy import coth, tanh >>> t = 3*tanh(x)**7 - 2/coth(x)**7 >>> trigsimp(t, method='old') == t True >>> trigsimp(t) tanh(x)**7 """ from sympy.simplify.fu import fu expr = sympify(expr) _eval_trigsimp = getattr(expr, '_eval_trigsimp', None) if _eval_trigsimp is not None: return _eval_trigsimp(**opts) old = opts.pop('old', False) if not old: opts.pop('deep', None) opts.pop('recursive', None) method = opts.pop('method', 'matching') else: method = 'old' def groebnersimp(ex, **opts): def traverse(e): if e.is_Atom: return e args = [traverse(x) for x in e.args] if e.is_Function or e.is_Pow: args = [trigsimp_groebner(x, **opts) for x in args] return e.func(*args) new = traverse(ex) if not isinstance(new, Expr): return new return trigsimp_groebner(new, **opts) trigsimpfunc = { 'fu': (lambda x: fu(x, **opts)), 'matching': (lambda x: futrig(x)), 'groebner': (lambda x: groebnersimp(x, **opts)), 'combined': (lambda x: futrig(groebnersimp(x, polynomial=True, hints=[2, tan]))), 'old': lambda x: trigsimp_old(x, **opts), }[method] return trigsimpfunc(expr) def exptrigsimp(expr): """ Simplifies exponential / trigonometric / hyperbolic functions. Examples ======== >>> from sympy import exptrigsimp, exp, cosh, sinh >>> from sympy.abc import z >>> exptrigsimp(exp(z) + exp(-z)) 2*cosh(z) >>> exptrigsimp(cosh(z) - sinh(z)) exp(-z) """ from sympy.simplify.fu import hyper_as_trig, TR2i from sympy.simplify.simplify import bottom_up def exp_trig(e): # select the better of e, and e rewritten in terms of exp or trig # functions choices = [e] if e.has(*_trigs): choices.append(e.rewrite(exp)) choices.append(e.rewrite(cos)) return min(*choices, key=count_ops) newexpr = bottom_up(expr, exp_trig) def f(rv): if not rv.is_Mul: return rv commutative_part, noncommutative_part = rv.args_cnc() # Since as_powers_dict loses order information, # if there is more than one noncommutative factor, # it should only be used to simplify the commutative part. if (len(noncommutative_part) > 1): return f(Mul(*commutative_part))*Mul(*noncommutative_part) rvd = rv.as_powers_dict() newd = rvd.copy() def signlog(expr, sign=1): if expr is S.Exp1: return sign, 1 elif isinstance(expr, exp): return sign, expr.args[0] elif sign == 1: return signlog(-expr, sign=-1) else: return None, None ee = rvd[S.Exp1] for k in rvd: if k.is_Add and len(k.args) == 2: # k == c*(1 + sign*E**x) c = k.args[0] sign, x = signlog(k.args[1]/c) if not x: continue m = rvd[k] newd[k] -= m if ee == -x*m/2: # sinh and cosh newd[S.Exp1] -= ee ee = 0 if sign == 1: newd[2*c*cosh(x/2)] += m else: newd[-2*c*sinh(x/2)] += m elif newd[1 - sign*S.Exp1**x] == -m: # tanh del newd[1 - sign*S.Exp1**x] if sign == 1: newd[-c/tanh(x/2)] += m else: newd[-c*tanh(x/2)] += m else: newd[1 + sign*S.Exp1**x] += m newd[c] += m return Mul(*[k**newd[k] for k in newd]) newexpr = bottom_up(newexpr, f) # sin/cos and sinh/cosh ratios to tan and tanh, respectively if newexpr.has(HyperbolicFunction): e, f = hyper_as_trig(newexpr) newexpr = f(TR2i(e)) if newexpr.has(TrigonometricFunction): newexpr = TR2i(newexpr) # can we ever generate an I where there was none previously? if not (newexpr.has(I) and not expr.has(I)): expr = newexpr return expr #-------------------- the old trigsimp routines --------------------- def trigsimp_old(expr, *, first=True, **opts): """ Reduces expression by using known trig identities. Notes ===== deep: - Apply trigsimp inside all objects with arguments recursive: - Use common subexpression elimination (cse()) and apply trigsimp recursively (this is quite expensive if the expression is large) method: - Determine the method to use. Valid choices are 'matching' (default), 'groebner', 'combined', 'fu' and 'futrig'. If 'matching', simplify the expression recursively by pattern matching. If 'groebner', apply an experimental groebner basis algorithm. In this case further options are forwarded to ``trigsimp_groebner``, please refer to its docstring. If 'combined', first run the groebner basis algorithm with small default parameters, then run the 'matching' algorithm. 'fu' runs the collection of trigonometric transformations described by Fu, et al. (see the `fu` docstring) while `futrig` runs a subset of Fu-transforms that mimic the behavior of `trigsimp`. compare: - show input and output from `trigsimp` and `futrig` when different, but returns the `trigsimp` value. Examples ======== >>> from sympy import trigsimp, sin, cos, log, cot >>> from sympy.abc import x >>> e = 2*sin(x)**2 + 2*cos(x)**2 >>> trigsimp(e, old=True) 2 >>> trigsimp(log(e), old=True) log(2*sin(x)**2 + 2*cos(x)**2) >>> trigsimp(log(e), deep=True, old=True) log(2) Using `method="groebner"` (or `"combined"`) can sometimes lead to a lot more simplification: >>> e = (-sin(x) + 1)/cos(x) + cos(x)/(-sin(x) + 1) >>> trigsimp(e, old=True) (1 - sin(x))/cos(x) + cos(x)/(1 - sin(x)) >>> trigsimp(e, method="groebner", old=True) 2/cos(x) >>> trigsimp(1/cot(x)**2, compare=True, old=True) futrig: tan(x)**2 cot(x)**(-2) """ old = expr if first: if not expr.has(*_trigs): return expr trigsyms = set().union(*[t.free_symbols for t in expr.atoms(*_trigs)]) if len(trigsyms) > 1: from sympy.simplify.simplify import separatevars d = separatevars(expr) if d.is_Mul: d = separatevars(d, dict=True) or d if isinstance(d, dict): expr = 1 for k, v in d.items(): # remove hollow factoring was = v v = expand_mul(v) opts['first'] = False vnew = trigsimp(v, **opts) if vnew == v: vnew = was expr *= vnew old = expr else: if d.is_Add: for s in trigsyms: r, e = expr.as_independent(s) if r: opts['first'] = False expr = r + trigsimp(e, **opts) if not expr.is_Add: break old = expr recursive = opts.pop('recursive', False) deep = opts.pop('deep', False) method = opts.pop('method', 'matching') def groebnersimp(ex, deep, **opts): def traverse(e): if e.is_Atom: return e args = [traverse(x) for x in e.args] if e.is_Function or e.is_Pow: args = [trigsimp_groebner(x, **opts) for x in args] return e.func(*args) if deep: ex = traverse(ex) return trigsimp_groebner(ex, **opts) trigsimpfunc = { 'matching': (lambda x, d: _trigsimp(x, d)), 'groebner': (lambda x, d: groebnersimp(x, d, **opts)), 'combined': (lambda x, d: _trigsimp(groebnersimp(x, d, polynomial=True, hints=[2, tan]), d)) }[method] if recursive: w, g = cse(expr) g = trigsimpfunc(g[0], deep) for sub in reversed(w): g = g.subs(sub[0], sub[1]) g = trigsimpfunc(g, deep) result = g else: result = trigsimpfunc(expr, deep) if opts.get('compare', False): f = futrig(old) if f != result: print('\tfutrig:', f) return result def _dotrig(a, b): """Helper to tell whether ``a`` and ``b`` have the same sorts of symbols in them -- no need to test hyperbolic patterns against expressions that have no hyperbolics in them.""" return a.func == b.func and ( a.has(TrigonometricFunction) and b.has(TrigonometricFunction) or a.has(HyperbolicFunction) and b.has(HyperbolicFunction)) _trigpat = None def _trigpats(): global _trigpat a, b, c = symbols('a b c', cls=Wild) d = Wild('d', commutative=False) # for the simplifications like sinh/cosh -> tanh: # DO NOT REORDER THE FIRST 14 since these are assumed to be in this # order in _match_div_rewrite. matchers_division = ( (a*sin(b)**c/cos(b)**c, a*tan(b)**c, sin(b), cos(b)), (a*tan(b)**c*cos(b)**c, a*sin(b)**c, sin(b), cos(b)), (a*cot(b)**c*sin(b)**c, a*cos(b)**c, sin(b), cos(b)), (a*tan(b)**c/sin(b)**c, a/cos(b)**c, sin(b), cos(b)), (a*cot(b)**c/cos(b)**c, a/sin(b)**c, sin(b), cos(b)), (a*cot(b)**c*tan(b)**c, a, sin(b), cos(b)), (a*(cos(b) + 1)**c*(cos(b) - 1)**c, a*(-sin(b)**2)**c, cos(b) + 1, cos(b) - 1), (a*(sin(b) + 1)**c*(sin(b) - 1)**c, a*(-cos(b)**2)**c, sin(b) + 1, sin(b) - 1), (a*sinh(b)**c/cosh(b)**c, a*tanh(b)**c, S.One, S.One), (a*tanh(b)**c*cosh(b)**c, a*sinh(b)**c, S.One, S.One), (a*coth(b)**c*sinh(b)**c, a*cosh(b)**c, S.One, S.One), (a*tanh(b)**c/sinh(b)**c, a/cosh(b)**c, S.One, S.One), (a*coth(b)**c/cosh(b)**c, a/sinh(b)**c, S.One, S.One), (a*coth(b)**c*tanh(b)**c, a, S.One, S.One), (c*(tanh(a) + tanh(b))/(1 + tanh(a)*tanh(b)), tanh(a + b)*c, S.One, S.One), ) matchers_add = ( (c*sin(a)*cos(b) + c*cos(a)*sin(b) + d, sin(a + b)*c + d), (c*cos(a)*cos(b) - c*sin(a)*sin(b) + d, cos(a + b)*c + d), (c*sin(a)*cos(b) - c*cos(a)*sin(b) + d, sin(a - b)*c + d), (c*cos(a)*cos(b) + c*sin(a)*sin(b) + d, cos(a - b)*c + d), (c*sinh(a)*cosh(b) + c*sinh(b)*cosh(a) + d, sinh(a + b)*c + d), (c*cosh(a)*cosh(b) + c*sinh(a)*sinh(b) + d, cosh(a + b)*c + d), ) # for cos(x)**2 + sin(x)**2 -> 1 matchers_identity = ( (a*sin(b)**2, a - a*cos(b)**2), (a*tan(b)**2, a*(1/cos(b))**2 - a), (a*cot(b)**2, a*(1/sin(b))**2 - a), (a*sin(b + c), a*(sin(b)*cos(c) + sin(c)*cos(b))), (a*cos(b + c), a*(cos(b)*cos(c) - sin(b)*sin(c))), (a*tan(b + c), a*((tan(b) + tan(c))/(1 - tan(b)*tan(c)))), (a*sinh(b)**2, a*cosh(b)**2 - a), (a*tanh(b)**2, a - a*(1/cosh(b))**2), (a*coth(b)**2, a + a*(1/sinh(b))**2), (a*sinh(b + c), a*(sinh(b)*cosh(c) + sinh(c)*cosh(b))), (a*cosh(b + c), a*(cosh(b)*cosh(c) + sinh(b)*sinh(c))), (a*tanh(b + c), a*((tanh(b) + tanh(c))/(1 + tanh(b)*tanh(c)))), ) # Reduce any lingering artifacts, such as sin(x)**2 changing # to 1-cos(x)**2 when sin(x)**2 was "simpler" artifacts = ( (a - a*cos(b)**2 + c, a*sin(b)**2 + c, cos), (a - a*(1/cos(b))**2 + c, -a*tan(b)**2 + c, cos), (a - a*(1/sin(b))**2 + c, -a*cot(b)**2 + c, sin), (a - a*cosh(b)**2 + c, -a*sinh(b)**2 + c, cosh), (a - a*(1/cosh(b))**2 + c, a*tanh(b)**2 + c, cosh), (a + a*(1/sinh(b))**2 + c, a*coth(b)**2 + c, sinh), # same as above but with noncommutative prefactor (a*d - a*d*cos(b)**2 + c, a*d*sin(b)**2 + c, cos), (a*d - a*d*(1/cos(b))**2 + c, -a*d*tan(b)**2 + c, cos), (a*d - a*d*(1/sin(b))**2 + c, -a*d*cot(b)**2 + c, sin), (a*d - a*d*cosh(b)**2 + c, -a*d*sinh(b)**2 + c, cosh), (a*d - a*d*(1/cosh(b))**2 + c, a*d*tanh(b)**2 + c, cosh), (a*d + a*d*(1/sinh(b))**2 + c, a*d*coth(b)**2 + c, sinh), ) _trigpat = (a, b, c, d, matchers_division, matchers_add, matchers_identity, artifacts) return _trigpat def _replace_mul_fpowxgpow(expr, f, g, rexp, h, rexph): """Helper for _match_div_rewrite. Replace f(b_)**c_*g(b_)**(rexp(c_)) with h(b)**rexph(c) if f(b_) and g(b_) are both positive or if c_ is an integer. """ # assert expr.is_Mul and expr.is_commutative and f != g fargs = defaultdict(int) gargs = defaultdict(int) args = [] for x in expr.args: if x.is_Pow or x.func in (f, g): b, e = x.as_base_exp() if b.is_positive or e.is_integer: if b.func == f: fargs[b.args[0]] += e continue elif b.func == g: gargs[b.args[0]] += e continue args.append(x) common = set(fargs) & set(gargs) hit = False while common: key = common.pop() fe = fargs.pop(key) ge = gargs.pop(key) if fe == rexp(ge): args.append(h(key)**rexph(fe)) hit = True else: fargs[key] = fe gargs[key] = ge if not hit: return expr while fargs: key, e = fargs.popitem() args.append(f(key)**e) while gargs: key, e = gargs.popitem() args.append(g(key)**e) return Mul(*args) _idn = lambda x: x _midn = lambda x: -x _one = lambda x: S.One def _match_div_rewrite(expr, i): """helper for __trigsimp""" if i == 0: expr = _replace_mul_fpowxgpow(expr, sin, cos, _midn, tan, _idn) elif i == 1: expr = _replace_mul_fpowxgpow(expr, tan, cos, _idn, sin, _idn) elif i == 2: expr = _replace_mul_fpowxgpow(expr, cot, sin, _idn, cos, _idn) elif i == 3: expr = _replace_mul_fpowxgpow(expr, tan, sin, _midn, cos, _midn) elif i == 4: expr = _replace_mul_fpowxgpow(expr, cot, cos, _midn, sin, _midn) elif i == 5: expr = _replace_mul_fpowxgpow(expr, cot, tan, _idn, _one, _idn) # i in (6, 7) is skipped elif i == 8: expr = _replace_mul_fpowxgpow(expr, sinh, cosh, _midn, tanh, _idn) elif i == 9: expr = _replace_mul_fpowxgpow(expr, tanh, cosh, _idn, sinh, _idn) elif i == 10: expr = _replace_mul_fpowxgpow(expr, coth, sinh, _idn, cosh, _idn) elif i == 11: expr = _replace_mul_fpowxgpow(expr, tanh, sinh, _midn, cosh, _midn) elif i == 12: expr = _replace_mul_fpowxgpow(expr, coth, cosh, _midn, sinh, _midn) elif i == 13: expr = _replace_mul_fpowxgpow(expr, coth, tanh, _idn, _one, _idn) else: return None return expr def _trigsimp(expr, deep=False): # protect the cache from non-trig patterns; we only allow # trig patterns to enter the cache if expr.has(*_trigs): return __trigsimp(expr, deep) return expr @cacheit def __trigsimp(expr, deep=False): """recursive helper for trigsimp""" from sympy.simplify.fu import TR10i if _trigpat is None: _trigpats() a, b, c, d, matchers_division, matchers_add, \ matchers_identity, artifacts = _trigpat if expr.is_Mul: # do some simplifications like sin/cos -> tan: if not expr.is_commutative: com, nc = expr.args_cnc() expr = _trigsimp(Mul._from_args(com), deep)*Mul._from_args(nc) else: for i, (pattern, simp, ok1, ok2) in enumerate(matchers_division): if not _dotrig(expr, pattern): continue newexpr = _match_div_rewrite(expr, i) if newexpr is not None: if newexpr != expr: expr = newexpr break else: continue # use SymPy matching instead res = expr.match(pattern) if res and res.get(c, 0): if not res[c].is_integer: ok = ok1.subs(res) if not ok.is_positive: continue ok = ok2.subs(res) if not ok.is_positive: continue # if "a" contains any of trig or hyperbolic funcs with # argument "b" then skip the simplification if any(w.args[0] == res[b] for w in res[a].atoms( TrigonometricFunction, HyperbolicFunction)): continue # simplify and finish: expr = simp.subs(res) break # process below if expr.is_Add: args = [] for term in expr.args: if not term.is_commutative: com, nc = term.args_cnc() nc = Mul._from_args(nc) term = Mul._from_args(com) else: nc = S.One term = _trigsimp(term, deep) for pattern, result in matchers_identity: res = term.match(pattern) if res is not None: term = result.subs(res) break args.append(term*nc) if args != expr.args: expr = Add(*args) expr = min(expr, expand(expr), key=count_ops) if expr.is_Add: for pattern, result in matchers_add: if not _dotrig(expr, pattern): continue expr = TR10i(expr) if expr.has(HyperbolicFunction): res = expr.match(pattern) # if "d" contains any trig or hyperbolic funcs with # argument "a" or "b" then skip the simplification; # this isn't perfect -- see tests if res is None or not (a in res and b in res) or any( w.args[0] in (res[a], res[b]) for w in res[d].atoms( TrigonometricFunction, HyperbolicFunction)): continue expr = result.subs(res) break # Reduce any lingering artifacts, such as sin(x)**2 changing # to 1 - cos(x)**2 when sin(x)**2 was "simpler" for pattern, result, ex in artifacts: if not _dotrig(expr, pattern): continue # Substitute a new wild that excludes some function(s) # to help influence a better match. This is because # sometimes, for example, 'a' would match sec(x)**2 a_t = Wild('a', exclude=[ex]) pattern = pattern.subs(a, a_t) result = result.subs(a, a_t) m = expr.match(pattern) was = None while m and was != expr: was = expr if m[a_t] == 0 or \ -m[a_t] in m[c].args or m[a_t] + m[c] == 0: break if d in m and m[a_t]*m[d] + m[c] == 0: break expr = result.subs(m) m = expr.match(pattern) m.setdefault(c, S.Zero) elif expr.is_Mul or expr.is_Pow or deep and expr.args: expr = expr.func(*[_trigsimp(a, deep) for a in expr.args]) try: if not expr.has(*_trigs): raise TypeError e = expr.atoms(exp) new = expr.rewrite(exp, deep=deep) if new == e: raise TypeError fnew = factor(new) if fnew != new: new = sorted([new, factor(new)], key=count_ops)[0] # if all exp that were introduced disappeared then accept it if not (new.atoms(exp) - e): expr = new except TypeError: pass return expr #------------------- end of old trigsimp routines -------------------- def futrig(e, *, hyper=True, **kwargs): """Return simplified ``e`` using Fu-like transformations. This is not the "Fu" algorithm. This is called by default from ``trigsimp``. By default, hyperbolics subexpressions will be simplified, but this can be disabled by setting ``hyper=False``. Examples ======== >>> from sympy import trigsimp, tan, sinh, tanh >>> from sympy.simplify.trigsimp import futrig >>> from sympy.abc import x >>> trigsimp(1/tan(x)**2) tan(x)**(-2) >>> futrig(sinh(x)/tanh(x)) cosh(x) """ from sympy.simplify.fu import hyper_as_trig from sympy.simplify.simplify import bottom_up e = sympify(e) if not isinstance(e, Basic): return e if not e.args: return e old = e e = bottom_up(e, _futrig) if hyper and e.has(HyperbolicFunction): e, f = hyper_as_trig(e) e = f(bottom_up(e, _futrig)) if e != old and e.is_Mul and e.args[0].is_Rational: # redistribute leading coeff on 2-arg Add e = Mul(*e.as_coeff_Mul()) return e def _futrig(e): """Helper for futrig.""" from sympy.simplify.fu import ( TR1, TR2, TR3, TR2i, TR10, L, TR10i, TR8, TR6, TR15, TR16, TR111, TR5, TRmorrie, TR11, _TR11, TR14, TR22, TR12) from sympy.core.compatibility import _nodes if not e.has(TrigonometricFunction): return e if e.is_Mul: coeff, e = e.as_independent(TrigonometricFunction) else: coeff = None Lops = lambda x: (L(x), x.count_ops(), _nodes(x), len(x.args), x.is_Add) trigs = lambda x: x.has(TrigonometricFunction) tree = [identity, ( TR3, # canonical angles TR1, # sec-csc -> cos-sin TR12, # expand tan of sum lambda x: _eapply(factor, x, trigs), TR2, # tan-cot -> sin-cos [identity, lambda x: _eapply(_mexpand, x, trigs)], TR2i, # sin-cos ratio -> tan lambda x: _eapply(lambda i: factor(i.normal()), x, trigs), TR14, # factored identities TR5, # sin-pow -> cos_pow TR10, # sin-cos of sums -> sin-cos prod TR11, _TR11, TR6, # reduce double angles and rewrite cos pows lambda x: _eapply(factor, x, trigs), TR14, # factored powers of identities [identity, lambda x: _eapply(_mexpand, x, trigs)], TR10i, # sin-cos products > sin-cos of sums TRmorrie, [identity, TR8], # sin-cos products -> sin-cos of sums [identity, lambda x: TR2i(TR2(x))], # tan -> sin-cos -> tan [ lambda x: _eapply(expand_mul, TR5(x), trigs), lambda x: _eapply( expand_mul, TR15(x), trigs)], # pos/neg powers of sin [ lambda x: _eapply(expand_mul, TR6(x), trigs), lambda x: _eapply( expand_mul, TR16(x), trigs)], # pos/neg powers of cos TR111, # tan, sin, cos to neg power -> cot, csc, sec [identity, TR2i], # sin-cos ratio to tan [identity, lambda x: _eapply( expand_mul, TR22(x), trigs)], # tan-cot to sec-csc TR1, TR2, TR2i, [identity, lambda x: _eapply( factor_terms, TR12(x), trigs)], # expand tan of sum )] e = greedy(tree, objective=Lops)(e) if coeff is not None: e = coeff * e return e def _is_Expr(e): """_eapply helper to tell whether ``e`` and all its args are Exprs.""" from sympy import Derivative if isinstance(e, Derivative): return _is_Expr(e.expr) if not isinstance(e, Expr): return False return all(_is_Expr(i) for i in e.args) def _eapply(func, e, cond=None): """Apply ``func`` to ``e`` if all args are Exprs else only apply it to those args that *are* Exprs.""" if not isinstance(e, Expr): return e if _is_Expr(e) or not e.args: return func(e) return e.func(*[ _eapply(func, ei) if (cond is None or cond(ei)) else ei for ei in e.args])

99eb4868fae8df81d96636f8d8b7e2d8e496eb20494cb78c3e7f605caba04a7e

""" Tools for doing common subexpression elimination. """ from sympy.core import Basic, Mul, Add, Pow, sympify, Symbol from sympy.core.compatibility import iterable from sympy.core.containers import Tuple, OrderedSet from sympy.core.exprtools import factor_terms from sympy.core.function import _coeff_isneg from sympy.core.singleton import S from sympy.utilities.iterables import numbered_symbols, sift, \ topological_sort, ordered from . import cse_opts # (preprocessor, postprocessor) pairs which are commonly useful. They should # each take a sympy expression and return a possibly transformed expression. # When used in the function ``cse()``, the target expressions will be transformed # by each of the preprocessor functions in order. After the common # subexpressions are eliminated, each resulting expression will have the # postprocessor functions transform them in *reverse* order in order to undo the # transformation if necessary. This allows the algorithm to operate on # a representation of the expressions that allows for more optimization # opportunities. # ``None`` can be used to specify no transformation for either the preprocessor or # postprocessor. basic_optimizations = [(cse_opts.sub_pre, cse_opts.sub_post), (factor_terms, None)] # sometimes we want the output in a different format; non-trivial # transformations can be put here for users # =============================================================== def reps_toposort(r): """Sort replacements ``r`` so (k1, v1) appears before (k2, v2) if k2 is in v1's free symbols. This orders items in the way that cse returns its results (hence, in order to use the replacements in a substitution option it would make sense to reverse the order). Examples ======== >>> from sympy.simplify.cse_main import reps_toposort >>> from sympy.abc import x, y >>> from sympy import Eq >>> for l, r in reps_toposort([(x, y + 1), (y, 2)]): ... print(Eq(l, r)) ... Eq(y, 2) Eq(x, y + 1) """ r = sympify(r) E = [] for c1, (k1, v1) in enumerate(r): for c2, (k2, v2) in enumerate(r): if k1 in v2.free_symbols: E.append((c1, c2)) return [r[i] for i in topological_sort((range(len(r)), E))] def cse_separate(r, e): """Move expressions that are in the form (symbol, expr) out of the expressions and sort them into the replacements using the reps_toposort. Examples ======== >>> from sympy.simplify.cse_main import cse_separate >>> from sympy.abc import x, y, z >>> from sympy import cos, exp, cse, Eq, symbols >>> x0, x1 = symbols('x:2') >>> eq = (x + 1 + exp((x + 1)/(y + 1)) + cos(y + 1)) >>> cse([eq, Eq(x, z + 1), z - 2], postprocess=cse_separate) in [ ... [[(x0, y + 1), (x, z + 1), (x1, x + 1)], ... [x1 + exp(x1/x0) + cos(x0), z - 2]], ... [[(x1, y + 1), (x, z + 1), (x0, x + 1)], ... [x0 + exp(x0/x1) + cos(x1), z - 2]]] ... True """ d = sift(e, lambda w: w.is_Equality and w.lhs.is_Symbol) r = r + [w.args for w in d[True]] e = d[False] return [reps_toposort(r), e] # ====end of cse postprocess idioms=========================== def preprocess_for_cse(expr, optimizations): """ Preprocess an expression to optimize for common subexpression elimination. Parameters ========== expr : sympy expression The target expression to optimize. optimizations : list of (callable, callable) pairs The (preprocessor, postprocessor) pairs. Returns ======= expr : sympy expression The transformed expression. """ for pre, post in optimizations: if pre is not None: expr = pre(expr) return expr def postprocess_for_cse(expr, optimizations): """ Postprocess an expression after common subexpression elimination to return the expression to canonical sympy form. Parameters ========== expr : sympy expression The target expression to transform. optimizations : list of (callable, callable) pairs, optional The (preprocessor, postprocessor) pairs. The postprocessors will be applied in reversed order to undo the effects of the preprocessors correctly. Returns ======= expr : sympy expression The transformed expression. """ for pre, post in reversed(optimizations): if post is not None: expr = post(expr) return expr class FuncArgTracker: """ A class which manages a mapping from functions to arguments and an inverse mapping from arguments to functions. """ def __init__(self, funcs): # To minimize the number of symbolic comparisons, all function arguments # get assigned a value number. self.value_numbers = {} self.value_number_to_value = [] # Both of these maps use integer indices for arguments / functions. self.arg_to_funcset = [] self.func_to_argset = [] for func_i, func in enumerate(funcs): func_argset = OrderedSet() for func_arg in func.args: arg_number = self.get_or_add_value_number(func_arg) func_argset.add(arg_number) self.arg_to_funcset[arg_number].add(func_i) self.func_to_argset.append(func_argset) def get_args_in_value_order(self, argset): """ Return the list of arguments in sorted order according to their value numbers. """ return [self.value_number_to_value[argn] for argn in sorted(argset)] def get_or_add_value_number(self, value): """ Return the value number for the given argument. """ nvalues = len(self.value_numbers) value_number = self.value_numbers.setdefault(value, nvalues) if value_number == nvalues: self.value_number_to_value.append(value) self.arg_to_funcset.append(OrderedSet()) return value_number def stop_arg_tracking(self, func_i): """ Remove the function func_i from the argument to function mapping. """ for arg in self.func_to_argset[func_i]: self.arg_to_funcset[arg].remove(func_i) def get_common_arg_candidates(self, argset, min_func_i=0): """Return a dict whose keys are function numbers. The entries of the dict are the number of arguments said function has in common with ``argset``. Entries have at least 2 items in common. All keys have value at least ``min_func_i``. """ from collections import defaultdict count_map = defaultdict(lambda: 0) funcsets = [self.arg_to_funcset[arg] for arg in argset] # As an optimization below, we handle the largest funcset separately from # the others. largest_funcset = max(funcsets, key=len) for funcset in funcsets: if largest_funcset is funcset: continue for func_i in funcset: if func_i >= min_func_i: count_map[func_i] += 1 # We pick the smaller of the two containers (count_map, largest_funcset) # to iterate over to reduce the number of iterations needed. (smaller_funcs_container, larger_funcs_container) = sorted( [largest_funcset, count_map], key=len) for func_i in smaller_funcs_container: # Not already in count_map? It can't possibly be in the output, so # skip it. if count_map[func_i] < 1: continue if func_i in larger_funcs_container: count_map[func_i] += 1 return {k: v for k, v in count_map.items() if v >= 2} def get_subset_candidates(self, argset, restrict_to_funcset=None): """ Return a set of functions each of which whose argument list contains ``argset``, optionally filtered only to contain functions in ``restrict_to_funcset``. """ iarg = iter(argset) indices = OrderedSet( fi for fi in self.arg_to_funcset[next(iarg)]) if restrict_to_funcset is not None: indices &= restrict_to_funcset for arg in iarg: indices &= self.arg_to_funcset[arg] return indices def update_func_argset(self, func_i, new_argset): """ Update a function with a new set of arguments. """ new_args = OrderedSet(new_argset) old_args = self.func_to_argset[func_i] for deleted_arg in old_args - new_args: self.arg_to_funcset[deleted_arg].remove(func_i) for added_arg in new_args - old_args: self.arg_to_funcset[added_arg].add(func_i) self.func_to_argset[func_i].clear() self.func_to_argset[func_i].update(new_args) class Unevaluated: def __init__(self, func, args): self.func = func self.args = args def __str__(self): return "Uneval<{}>({})".format( self.func, ", ".join(str(a) for a in self.args)) def as_unevaluated_basic(self): return self.func(*self.args, evaluate=False) @property def free_symbols(self): return set().union(*[a.free_symbols for a in self.args]) __repr__ = __str__ def match_common_args(func_class, funcs, opt_subs): """ Recognize and extract common subexpressions of function arguments within a set of function calls. For instance, for the following function calls:: x + z + y sin(x + y) this will extract a common subexpression of `x + y`:: w = x + y w + z sin(w) The function we work with is assumed to be associative and commutative. Parameters ========== func_class: class The function class (e.g. Add, Mul) funcs: list of functions A list of function calls. opt_subs: dict A dictionary of substitutions which this function may update. """ # Sort to ensure that whole-function subexpressions come before the items # that use them. funcs = sorted(funcs, key=lambda f: len(f.args)) arg_tracker = FuncArgTracker(funcs) changed = OrderedSet() for i in range(len(funcs)): common_arg_candidates_counts = arg_tracker.get_common_arg_candidates( arg_tracker.func_to_argset[i], min_func_i=i + 1) # Sort the candidates in order of match size. # This makes us try combining smaller matches first. common_arg_candidates = OrderedSet(sorted( common_arg_candidates_counts.keys(), key=lambda k: (common_arg_candidates_counts[k], k))) while common_arg_candidates: j = common_arg_candidates.pop(last=False) com_args = arg_tracker.func_to_argset[i].intersection( arg_tracker.func_to_argset[j]) if len(com_args) <= 1: # This may happen if a set of common arguments was already # combined in a previous iteration. continue # For all sets, replace the common symbols by the function # over them, to allow recursive matches. diff_i = arg_tracker.func_to_argset[i].difference(com_args) if diff_i: # com_func needs to be unevaluated to allow for recursive matches. com_func = Unevaluated( func_class, arg_tracker.get_args_in_value_order(com_args)) com_func_number = arg_tracker.get_or_add_value_number(com_func) arg_tracker.update_func_argset(i, diff_i | OrderedSet([com_func_number])) changed.add(i) else: # Treat the whole expression as a CSE. # # The reason this needs to be done is somewhat subtle. Within # tree_cse(), to_eliminate only contains expressions that are # seen more than once. The problem is unevaluated expressions # do not compare equal to the evaluated equivalent. So # tree_cse() won't mark funcs[i] as a CSE if we use an # unevaluated version. com_func_number = arg_tracker.get_or_add_value_number(funcs[i]) diff_j = arg_tracker.func_to_argset[j].difference(com_args) arg_tracker.update_func_argset(j, diff_j | OrderedSet([com_func_number])) changed.add(j) for k in arg_tracker.get_subset_candidates( com_args, common_arg_candidates): diff_k = arg_tracker.func_to_argset[k].difference(com_args) arg_tracker.update_func_argset(k, diff_k | OrderedSet([com_func_number])) changed.add(k) if i in changed: opt_subs[funcs[i]] = Unevaluated(func_class, arg_tracker.get_args_in_value_order(arg_tracker.func_to_argset[i])) arg_tracker.stop_arg_tracking(i) def opt_cse(exprs, order='canonical'): """Find optimization opportunities in Adds, Muls, Pows and negative coefficient Muls. Parameters ========== exprs : list of sympy expressions The expressions to optimize. order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. For large expressions where speed is a concern, use the setting order='none'. Returns ======= opt_subs : dictionary of expression substitutions The expression substitutions which can be useful to optimize CSE. Examples ======== >>> from sympy.simplify.cse_main import opt_cse >>> from sympy.abc import x >>> opt_subs = opt_cse([x**-2]) >>> k, v = list(opt_subs.keys())[0], list(opt_subs.values())[0] >>> print((k, v.as_unevaluated_basic())) (x**(-2), 1/(x**2)) """ from sympy.matrices.expressions import MatAdd, MatMul, MatPow opt_subs = dict() adds = OrderedSet() muls = OrderedSet() seen_subexp = set() def _find_opts(expr): if not isinstance(expr, (Basic, Unevaluated)): return if expr.is_Atom or expr.is_Order: return if iterable(expr): list(map(_find_opts, expr)) return if expr in seen_subexp: return expr seen_subexp.add(expr) list(map(_find_opts, expr.args)) if _coeff_isneg(expr): neg_expr = -expr if not neg_expr.is_Atom: opt_subs[expr] = Unevaluated(Mul, (S.NegativeOne, neg_expr)) seen_subexp.add(neg_expr) expr = neg_expr if isinstance(expr, (Mul, MatMul)): muls.add(expr) elif isinstance(expr, (Add, MatAdd)): adds.add(expr) elif isinstance(expr, (Pow, MatPow)): base, exp = expr.base, expr.exp if _coeff_isneg(exp): opt_subs[expr] = Unevaluated(Pow, (Pow(base, -exp), -1)) for e in exprs: if isinstance(e, (Basic, Unevaluated)): _find_opts(e) # split muls into commutative commutative_muls = OrderedSet() for m in muls: c, nc = m.args_cnc(cset=False) if c: c_mul = m.func(*c) if nc: if c_mul == 1: new_obj = m.func(*nc) else: new_obj = m.func(c_mul, m.func(*nc), evaluate=False) opt_subs[m] = new_obj if len(c) > 1: commutative_muls.add(c_mul) match_common_args(Add, adds, opt_subs) match_common_args(Mul, commutative_muls, opt_subs) return opt_subs def tree_cse(exprs, symbols, opt_subs=None, order='canonical', ignore=()): """Perform raw CSE on expression tree, taking opt_subs into account. Parameters ========== exprs : list of sympy expressions The expressions to reduce. symbols : infinite iterator yielding unique Symbols The symbols used to label the common subexpressions which are pulled out. opt_subs : dictionary of expression substitutions The expressions to be substituted before any CSE action is performed. order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. For large expressions where speed is a concern, use the setting order='none'. ignore : iterable of Symbols Substitutions containing any Symbol from ``ignore`` will be ignored. """ from sympy.matrices.expressions import MatrixExpr, MatrixSymbol, MatMul, MatAdd from sympy.polys.rootoftools import RootOf if opt_subs is None: opt_subs = dict() ## Find repeated sub-expressions to_eliminate = set() seen_subexp = set() excluded_symbols = set() def _find_repeated(expr): if not isinstance(expr, (Basic, Unevaluated)): return if isinstance(expr, RootOf): return if isinstance(expr, Basic) and (expr.is_Atom or expr.is_Order): if expr.is_Symbol: excluded_symbols.add(expr) return if iterable(expr): args = expr else: if expr in seen_subexp: for ign in ignore: if ign in expr.free_symbols: break else: to_eliminate.add(expr) return seen_subexp.add(expr) if expr in opt_subs: expr = opt_subs[expr] args = expr.args list(map(_find_repeated, args)) for e in exprs: if isinstance(e, Basic): _find_repeated(e) ## Rebuild tree # Remove symbols from the generator that conflict with names in the expressions. symbols = (symbol for symbol in symbols if symbol not in excluded_symbols) replacements = [] subs = dict() def _rebuild(expr): if not isinstance(expr, (Basic, Unevaluated)): return expr if not expr.args: return expr if iterable(expr): new_args = [_rebuild(arg) for arg in expr] return expr.func(*new_args) if expr in subs: return subs[expr] orig_expr = expr if expr in opt_subs: expr = opt_subs[expr] # If enabled, parse Muls and Adds arguments by order to ensure # replacement order independent from hashes if order != 'none': if isinstance(expr, (Mul, MatMul)): c, nc = expr.args_cnc() if c == [1]: args = nc else: args = list(ordered(c)) + nc elif isinstance(expr, (Add, MatAdd)): args = list(ordered(expr.args)) else: args = expr.args else: args = expr.args new_args = list(map(_rebuild, args)) if isinstance(expr, Unevaluated) or new_args != args: new_expr = expr.func(*new_args) else: new_expr = expr if orig_expr in to_eliminate: try: sym = next(symbols) except StopIteration: raise ValueError("Symbols iterator ran out of symbols.") if isinstance(orig_expr, MatrixExpr): sym = MatrixSymbol(sym.name, orig_expr.rows, orig_expr.cols) subs[orig_expr] = sym replacements.append((sym, new_expr)) return sym else: return new_expr reduced_exprs = [] for e in exprs: if isinstance(e, Basic): reduced_e = _rebuild(e) else: reduced_e = e reduced_exprs.append(reduced_e) return replacements, reduced_exprs def cse(exprs, symbols=None, optimizations=None, postprocess=None, order='canonical', ignore=()): """ Perform common subexpression elimination on an expression. Parameters ========== exprs : list of sympy expressions, or a single sympy expression The expressions to reduce. symbols : infinite iterator yielding unique Symbols The symbols used to label the common subexpressions which are pulled out. The ``numbered_symbols`` generator is useful. The default is a stream of symbols of the form "x0", "x1", etc. This must be an infinite iterator. optimizations : list of (callable, callable) pairs The (preprocessor, postprocessor) pairs of external optimization functions. Optionally 'basic' can be passed for a set of predefined basic optimizations. Such 'basic' optimizations were used by default in old implementation, however they can be really slow on larger expressions. Now, no pre or post optimizations are made by default. postprocess : a function which accepts the two return values of cse and returns the desired form of output from cse, e.g. if you want the replacements reversed the function might be the following lambda: lambda r, e: return reversed(r), e order : string, 'none' or 'canonical' The order by which Mul and Add arguments are processed. If set to 'canonical', arguments will be canonically ordered. If set to 'none', ordering will be faster but dependent on expressions hashes, thus machine dependent and variable. For large expressions where speed is a concern, use the setting order='none'. ignore : iterable of Symbols Substitutions containing any Symbol from ``ignore`` will be ignored. Returns ======= replacements : list of (Symbol, expression) pairs All of the common subexpressions that were replaced. Subexpressions earlier in this list might show up in subexpressions later in this list. reduced_exprs : list of sympy expressions The reduced expressions with all of the replacements above. Examples ======== >>> from sympy import cse, SparseMatrix >>> from sympy.abc import x, y, z, w >>> cse(((w + x + y + z)*(w + y + z))/(w + x)**3) ([(x0, y + z), (x1, w + x)], [(w + x0)*(x0 + x1)/x1**3]) Note that currently, y + z will not get substituted if -y - z is used. >>> cse(((w + x + y + z)*(w - y - z))/(w + x)**3) ([(x0, w + x)], [(w - y - z)*(x0 + y + z)/x0**3]) List of expressions with recursive substitutions: >>> m = SparseMatrix([x + y, x + y + z]) >>> cse([(x+y)**2, x + y + z, y + z, x + z + y, m]) ([(x0, x + y), (x1, x0 + z)], [x0**2, x1, y + z, x1, Matrix([ [x0], [x1]])]) Note: the type and mutability of input matrices is retained. >>> isinstance(_[1][-1], SparseMatrix) True The user may disallow substitutions containing certain symbols: >>> cse([y**2*(x + 1), 3*y**2*(x + 1)], ignore=(y,)) ([(x0, x + 1)], [x0*y**2, 3*x0*y**2]) """ from sympy.matrices import (MatrixBase, Matrix, ImmutableMatrix, SparseMatrix, ImmutableSparseMatrix) if isinstance(exprs, (int, float)): exprs = sympify(exprs) # Handle the case if just one expression was passed. if isinstance(exprs, (Basic, MatrixBase)): exprs = [exprs] copy = exprs temp = [] for e in exprs: if isinstance(e, (Matrix, ImmutableMatrix)): temp.append(Tuple(*e._mat)) elif isinstance(e, (SparseMatrix, ImmutableSparseMatrix)): temp.append(Tuple(*e._smat.items())) else: temp.append(e) exprs = temp del temp if optimizations is None: optimizations = list() elif optimizations == 'basic': optimizations = basic_optimizations # Preprocess the expressions to give us better optimization opportunities. reduced_exprs = [preprocess_for_cse(e, optimizations) for e in exprs] if symbols is None: symbols = numbered_symbols(cls=Symbol) else: # In case we get passed an iterable with an __iter__ method instead of # an actual iterator. symbols = iter(symbols) # Find other optimization opportunities. opt_subs = opt_cse(reduced_exprs, order) # Main CSE algorithm. replacements, reduced_exprs = tree_cse(reduced_exprs, symbols, opt_subs, order, ignore) # Postprocess the expressions to return the expressions to canonical form. exprs = copy for i, (sym, subtree) in enumerate(replacements): subtree = postprocess_for_cse(subtree, optimizations) replacements[i] = (sym, subtree) reduced_exprs = [postprocess_for_cse(e, optimizations) for e in reduced_exprs] # Get the matrices back for i, e in enumerate(exprs): if isinstance(e, (Matrix, ImmutableMatrix)): reduced_exprs[i] = Matrix(e.rows, e.cols, reduced_exprs[i]) if isinstance(e, ImmutableMatrix): reduced_exprs[i] = reduced_exprs[i].as_immutable() elif isinstance(e, (SparseMatrix, ImmutableSparseMatrix)): m = SparseMatrix(e.rows, e.cols, {}) for k, v in reduced_exprs[i]: m[k] = v if isinstance(e, ImmutableSparseMatrix): m = m.as_immutable() reduced_exprs[i] = m if postprocess is None: return replacements, reduced_exprs return postprocess(replacements, reduced_exprs)

daa9e086514933f6bdcd1d99ff39fd392d2ebd56fbe575774ab4e0421f77ffbe

from collections import defaultdict from sympy.core.add import Add from sympy.core.basic import S from sympy.core.compatibility import ordered from sympy.core.expr import Expr from sympy.core.exprtools import Factors, gcd_terms, factor_terms from sympy.core.function import expand_mul from sympy.core.mul import Mul from sympy.core.numbers import pi, I from sympy.core.power import Pow from sympy.core.symbol import Dummy from sympy.core.sympify import sympify from sympy.functions.combinatorial.factorials import binomial from sympy.functions.elementary.hyperbolic import ( cosh, sinh, tanh, coth, sech, csch, HyperbolicFunction) from sympy.functions.elementary.trigonometric import ( cos, sin, tan, cot, sec, csc, sqrt, TrigonometricFunction) from sympy.ntheory.factor_ import perfect_power from sympy.polys.polytools import factor from sympy.simplify.simplify import bottom_up from sympy.strategies.tree import greedy from sympy.strategies.core import identity, debug from sympy import SYMPY_DEBUG # ================== Fu-like tools =========================== def TR0(rv): """Simplification of rational polynomials, trying to simplify the expression, e.g. combine things like 3*x + 2*x, etc.... """ # although it would be nice to use cancel, it doesn't work # with noncommutatives return rv.normal().factor().expand() def TR1(rv): """Replace sec, csc with 1/cos, 1/sin Examples ======== >>> from sympy.simplify.fu import TR1, sec, csc >>> from sympy.abc import x >>> TR1(2*csc(x) + sec(x)) 1/cos(x) + 2/sin(x) """ def f(rv): if isinstance(rv, sec): a = rv.args[0] return S.One/cos(a) elif isinstance(rv, csc): a = rv.args[0] return S.One/sin(a) return rv return bottom_up(rv, f) def TR2(rv): """Replace tan and cot with sin/cos and cos/sin Examples ======== >>> from sympy.simplify.fu import TR2 >>> from sympy.abc import x >>> from sympy import tan, cot, sin, cos >>> TR2(tan(x)) sin(x)/cos(x) >>> TR2(cot(x)) cos(x)/sin(x) >>> TR2(tan(tan(x) - sin(x)/cos(x))) 0 """ def f(rv): if isinstance(rv, tan): a = rv.args[0] return sin(a)/cos(a) elif isinstance(rv, cot): a = rv.args[0] return cos(a)/sin(a) return rv return bottom_up(rv, f) def TR2i(rv, half=False): """Converts ratios involving sin and cos as follows:: sin(x)/cos(x) -> tan(x) sin(x)/(cos(x) + 1) -> tan(x/2) if half=True Examples ======== >>> from sympy.simplify.fu import TR2i >>> from sympy.abc import x, a >>> from sympy import sin, cos >>> TR2i(sin(x)/cos(x)) tan(x) Powers of the numerator and denominator are also recognized >>> TR2i(sin(x)**2/(cos(x) + 1)**2, half=True) tan(x/2)**2 The transformation does not take place unless assumptions allow (i.e. the base must be positive or the exponent must be an integer for both numerator and denominator) >>> TR2i(sin(x)**a/(cos(x) + 1)**a) (cos(x) + 1)**(-a)*sin(x)**a """ def f(rv): if not rv.is_Mul: return rv n, d = rv.as_numer_denom() if n.is_Atom or d.is_Atom: return rv def ok(k, e): # initial filtering of factors return ( (e.is_integer or k.is_positive) and ( k.func in (sin, cos) or (half and k.is_Add and len(k.args) >= 2 and any(any(isinstance(ai, cos) or ai.is_Pow and ai.base is cos for ai in Mul.make_args(a)) for a in k.args)))) n = n.as_powers_dict() ndone = [(k, n.pop(k)) for k in list(n.keys()) if not ok(k, n[k])] if not n: return rv d = d.as_powers_dict() ddone = [(k, d.pop(k)) for k in list(d.keys()) if not ok(k, d[k])] if not d: return rv # factoring if necessary def factorize(d, ddone): newk = [] for k in d: if k.is_Add and len(k.args) > 1: knew = factor(k) if half else factor_terms(k) if knew != k: newk.append((k, knew)) if newk: for i, (k, knew) in enumerate(newk): del d[k] newk[i] = knew newk = Mul(*newk).as_powers_dict() for k in newk: v = d[k] + newk[k] if ok(k, v): d[k] = v else: ddone.append((k, v)) del newk factorize(n, ndone) factorize(d, ddone) # joining t = [] for k in n: if isinstance(k, sin): a = cos(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])**n[k]) n[k] = d[a] = None elif half: a1 = 1 + a if a1 in d and d[a1] == n[k]: t.append((tan(k.args[0]/2))**n[k]) n[k] = d[a1] = None elif isinstance(k, cos): a = sin(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])**-n[k]) n[k] = d[a] = None elif half and k.is_Add and k.args[0] is S.One and \ isinstance(k.args[1], cos): a = sin(k.args[1].args[0], evaluate=False) if a in d and d[a] == n[k] and (d[a].is_integer or \ a.is_positive): t.append(tan(a.args[0]/2)**-n[k]) n[k] = d[a] = None if t: rv = Mul(*(t + [b**e for b, e in n.items() if e]))/\ Mul(*[b**e for b, e in d.items() if e]) rv *= Mul(*[b**e for b, e in ndone])/Mul(*[b**e for b, e in ddone]) return rv return bottom_up(rv, f) def TR3(rv): """Induced formula: example sin(-a) = -sin(a) Examples ======== >>> from sympy.simplify.fu import TR3 >>> from sympy.abc import x, y >>> from sympy import pi >>> from sympy import cos >>> TR3(cos(y - x*(y - x))) cos(x*(x - y) + y) >>> cos(pi/2 + x) -sin(x) >>> cos(30*pi/2 + x) -cos(x) """ from sympy.simplify.simplify import signsimp # Negative argument (already automatic for funcs like sin(-x) -> -sin(x) # but more complicated expressions can use it, too). Also, trig angles # between pi/4 and pi/2 are not reduced to an angle between 0 and pi/4. # The following are automatically handled: # Argument of type: pi/2 +/- angle # Argument of type: pi +/- angle # Argument of type : 2k*pi +/- angle def f(rv): if not isinstance(rv, TrigonometricFunction): return rv rv = rv.func(signsimp(rv.args[0])) if not isinstance(rv, TrigonometricFunction): return rv if (rv.args[0] - S.Pi/4).is_positive is (S.Pi/2 - rv.args[0]).is_positive is True: fmap = {cos: sin, sin: cos, tan: cot, cot: tan, sec: csc, csc: sec} rv = fmap[rv.func](S.Pi/2 - rv.args[0]) return rv return bottom_up(rv, f) def TR4(rv): """Identify values of special angles. a= 0 pi/6 pi/4 pi/3 pi/2 ---------------------------------------------------- cos(a) 0 1/2 sqrt(2)/2 sqrt(3)/2 1 sin(a) 1 sqrt(3)/2 sqrt(2)/2 1/2 0 tan(a) 0 sqt(3)/3 1 sqrt(3) -- Examples ======== >>> from sympy import pi >>> from sympy import cos, sin, tan, cot >>> for s in (0, pi/6, pi/4, pi/3, pi/2): ... print('%s %s %s %s' % (cos(s), sin(s), tan(s), cot(s))) ... 1 0 0 zoo sqrt(3)/2 1/2 sqrt(3)/3 sqrt(3) sqrt(2)/2 sqrt(2)/2 1 1 1/2 sqrt(3)/2 sqrt(3) sqrt(3)/3 0 1 zoo 0 """ # special values at 0, pi/6, pi/4, pi/3, pi/2 already handled return rv def _TR56(rv, f, g, h, max, pow): """Helper for TR5 and TR6 to replace f**2 with h(g**2) Options ======= max : controls size of exponent that can appear on f e.g. if max=4 then f**4 will be changed to h(g**2)**2. pow : controls whether the exponent must be a perfect power of 2 e.g. if pow=True (and max >= 6) then f**6 will not be changed but f**8 will be changed to h(g**2)**4 >>> from sympy.simplify.fu import _TR56 as T >>> from sympy.abc import x >>> from sympy import sin, cos >>> h = lambda x: 1 - x >>> T(sin(x)**3, sin, cos, h, 4, False) sin(x)**3 >>> T(sin(x)**6, sin, cos, h, 6, False) (1 - cos(x)**2)**3 >>> T(sin(x)**6, sin, cos, h, 6, True) sin(x)**6 >>> T(sin(x)**8, sin, cos, h, 10, True) (1 - cos(x)**2)**4 """ def _f(rv): # I'm not sure if this transformation should target all even powers # or only those expressible as powers of 2. Also, should it only # make the changes in powers that appear in sums -- making an isolated # change is not going to allow a simplification as far as I can tell. if not (rv.is_Pow and rv.base.func == f): return rv if not rv.exp.is_real: return rv if (rv.exp < 0) == True: return rv if (rv.exp > max) == True: return rv if rv.exp == 2: return h(g(rv.base.args[0])**2) else: if rv.exp == 4: e = 2 elif not pow: if rv.exp % 2: return rv e = rv.exp//2 else: p = perfect_power(rv.exp) if not p: return rv e = rv.exp//2 return h(g(rv.base.args[0])**2)**e return bottom_up(rv, _f) def TR5(rv, max=4, pow=False): """Replacement of sin**2 with 1 - cos(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR5 >>> from sympy.abc import x >>> from sympy import sin >>> TR5(sin(x)**2) 1 - cos(x)**2 >>> TR5(sin(x)**-2) # unchanged sin(x)**(-2) >>> TR5(sin(x)**4) (1 - cos(x)**2)**2 """ return _TR56(rv, sin, cos, lambda x: 1 - x, max=max, pow=pow) def TR6(rv, max=4, pow=False): """Replacement of cos**2 with 1 - sin(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR6 >>> from sympy.abc import x >>> from sympy import cos >>> TR6(cos(x)**2) 1 - sin(x)**2 >>> TR6(cos(x)**-2) #unchanged cos(x)**(-2) >>> TR6(cos(x)**4) (1 - sin(x)**2)**2 """ return _TR56(rv, cos, sin, lambda x: 1 - x, max=max, pow=pow) def TR7(rv): """Lowering the degree of cos(x)**2. Examples ======== >>> from sympy.simplify.fu import TR7 >>> from sympy.abc import x >>> from sympy import cos >>> TR7(cos(x)**2) cos(2*x)/2 + 1/2 >>> TR7(cos(x)**2 + 1) cos(2*x)/2 + 3/2 """ def f(rv): if not (rv.is_Pow and rv.base.func == cos and rv.exp == 2): return rv return (1 + cos(2*rv.base.args[0]))/2 return bottom_up(rv, f) def TR8(rv, first=True): """Converting products of ``cos`` and/or ``sin`` to a sum or difference of ``cos`` and or ``sin`` terms. Examples ======== >>> from sympy.simplify.fu import TR8 >>> from sympy import cos, sin >>> TR8(cos(2)*cos(3)) cos(5)/2 + cos(1)/2 >>> TR8(cos(2)*sin(3)) sin(5)/2 + sin(1)/2 >>> TR8(sin(2)*sin(3)) -cos(5)/2 + cos(1)/2 """ def f(rv): if not ( rv.is_Mul or rv.is_Pow and rv.base.func in (cos, sin) and (rv.exp.is_integer or rv.base.is_positive)): return rv if first: n, d = [expand_mul(i) for i in rv.as_numer_denom()] newn = TR8(n, first=False) newd = TR8(d, first=False) if newn != n or newd != d: rv = gcd_terms(newn/newd) if rv.is_Mul and rv.args[0].is_Rational and \ len(rv.args) == 2 and rv.args[1].is_Add: rv = Mul(*rv.as_coeff_Mul()) return rv args = {cos: [], sin: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (cos, sin): args[a.func].append(a.args[0]) elif (a.is_Pow and a.exp.is_Integer and a.exp > 0 and \ a.base.func in (cos, sin)): # XXX this is ok but pathological expression could be handled # more efficiently as in TRmorrie args[a.base.func].extend([a.base.args[0]]*a.exp) else: args[None].append(a) c = args[cos] s = args[sin] if not (c and s or len(c) > 1 or len(s) > 1): return rv args = args[None] n = min(len(c), len(s)) for i in range(n): a1 = s.pop() a2 = c.pop() args.append((sin(a1 + a2) + sin(a1 - a2))/2) while len(c) > 1: a1 = c.pop() a2 = c.pop() args.append((cos(a1 + a2) + cos(a1 - a2))/2) if c: args.append(cos(c.pop())) while len(s) > 1: a1 = s.pop() a2 = s.pop() args.append((-cos(a1 + a2) + cos(a1 - a2))/2) if s: args.append(sin(s.pop())) return TR8(expand_mul(Mul(*args))) return bottom_up(rv, f) def TR9(rv): """Sum of ``cos`` or ``sin`` terms as a product of ``cos`` or ``sin``. Examples ======== >>> from sympy.simplify.fu import TR9 >>> from sympy import cos, sin >>> TR9(cos(1) + cos(2)) 2*cos(1/2)*cos(3/2) >>> TR9(cos(1) + 2*sin(1) + 2*sin(2)) cos(1) + 4*sin(3/2)*cos(1/2) If no change is made by TR9, no re-arrangement of the expression will be made. For example, though factoring of common term is attempted, if the factored expression wasn't changed, the original expression will be returned: >>> TR9(cos(3) + cos(3)*cos(2)) cos(3) + cos(2)*cos(3) """ def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # cos(a)+/-cos(b) can be combined into a product of cosines and # sin(a)+/-sin(b) can be combined into a product of cosine and # sine. # # If there are more than two args, the pairs which "work" will # have a gcd extractable and the remaining two terms will have # the above structure -- all pairs must be checked to find the # ones that work. args that don't have a common set of symbols # are skipped since this doesn't lead to a simpler formula and # also has the arbitrariness of combining, for example, the x # and y term instead of the y and z term in something like # cos(x) + cos(y) + cos(z). if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add(*[_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(*args) if not split: return rv gcd, n1, n2, a, b, iscos = split # application of rule if possible if iscos: if n1 == n2: return gcd*n1*2*cos((a + b)/2)*cos((a - b)/2) if n1 < 0: a, b = b, a return -2*gcd*sin((a + b)/2)*sin((a - b)/2) else: if n1 == n2: return gcd*n1*2*sin((a + b)/2)*cos((a - b)/2) if n1 < 0: a, b = b, a return 2*gcd*cos((a + b)/2)*sin((a - b)/2) return process_common_addends(rv, do) # DON'T sift by free symbols return bottom_up(rv, f) def TR10(rv, first=True): """Separate sums in ``cos`` and ``sin``. Examples ======== >>> from sympy.simplify.fu import TR10 >>> from sympy.abc import a, b, c >>> from sympy import cos, sin >>> TR10(cos(a + b)) -sin(a)*sin(b) + cos(a)*cos(b) >>> TR10(sin(a + b)) sin(a)*cos(b) + sin(b)*cos(a) >>> TR10(sin(a + b + c)) (-sin(a)*sin(b) + cos(a)*cos(b))*sin(c) + \ (sin(a)*cos(b) + sin(b)*cos(a))*cos(c) """ def f(rv): if not rv.func in (cos, sin): return rv f = rv.func arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: if f == sin: return sin(a)*TR10(cos(b), first=False) + \ cos(a)*TR10(sin(b), first=False) else: return cos(a)*TR10(cos(b), first=False) - \ sin(a)*TR10(sin(b), first=False) else: if f == sin: return sin(a)*cos(b) + cos(a)*sin(b) else: return cos(a)*cos(b) - sin(a)*sin(b) return rv return bottom_up(rv, f) def TR10i(rv): """Sum of products to function of sum. Examples ======== >>> from sympy.simplify.fu import TR10i >>> from sympy import cos, sin, sqrt >>> from sympy.abc import x >>> TR10i(cos(1)*cos(3) + sin(1)*sin(3)) cos(2) >>> TR10i(cos(1)*sin(3) + sin(1)*cos(3) + cos(3)) cos(3) + sin(4) >>> TR10i(sqrt(2)*cos(x)*x + sqrt(6)*sin(x)*x) 2*sqrt(2)*x*sin(x + pi/6) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # args which can be expressed as A*(cos(a)*cos(b)+/-sin(a)*sin(b)) # or B*(cos(a)*sin(b)+/-cos(b)*sin(a)) can be combined into # A*f(a+/-b) where f is either sin or cos. # # If there are more than two args, the pairs which "work" will have # a gcd extractable and the remaining two terms will have the above # structure -- all pairs must be checked to find the ones that # work. if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add(*[_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(*args, two=True) if not split: return rv gcd, n1, n2, a, b, same = split # identify and get c1 to be cos then apply rule if possible if same: # coscos, sinsin gcd = n1*gcd if n1 == n2: return gcd*cos(a - b) return gcd*cos(a + b) else: #cossin, cossin gcd = n1*gcd if n1 == n2: return gcd*sin(a + b) return gcd*sin(b - a) rv = process_common_addends( rv, do, lambda x: tuple(ordered(x.free_symbols))) # need to check for inducible pairs in ratio of sqrt(3):1 that # appeared in different lists when sorting by coefficient while rv.is_Add: byrad = defaultdict(list) for a in rv.args: hit = 0 if a.is_Mul: for ai in a.args: if ai.is_Pow and ai.exp is S.Half and \ ai.base.is_Integer: byrad[ai].append(a) hit = 1 break if not hit: byrad[S.One].append(a) # no need to check all pairs -- just check for the onees # that have the right ratio args = [] for a in byrad: for b in [_ROOT3*a, _invROOT3]: if b in byrad: for i in range(len(byrad[a])): if byrad[a][i] is None: continue for j in range(len(byrad[b])): if byrad[b][j] is None: continue was = Add(byrad[a][i] + byrad[b][j]) new = do(was) if new != was: args.append(new) byrad[a][i] = None byrad[b][j] = None break if args: rv = Add(*(args + [Add(*[_f for _f in v if _f]) for v in byrad.values()])) else: rv = do(rv) # final pass to resolve any new inducible pairs break return rv return bottom_up(rv, f) def TR11(rv, base=None): """Function of double angle to product. The ``base`` argument can be used to indicate what is the un-doubled argument, e.g. if 3*pi/7 is the base then cosine and sine functions with argument 6*pi/7 will be replaced. Examples ======== >>> from sympy.simplify.fu import TR11 >>> from sympy import cos, sin, pi >>> from sympy.abc import x >>> TR11(sin(2*x)) 2*sin(x)*cos(x) >>> TR11(cos(2*x)) -sin(x)**2 + cos(x)**2 >>> TR11(sin(4*x)) 4*(-sin(x)**2 + cos(x)**2)*sin(x)*cos(x) >>> TR11(sin(4*x/3)) 4*(-sin(x/3)**2 + cos(x/3)**2)*sin(x/3)*cos(x/3) If the arguments are simply integers, no change is made unless a base is provided: >>> TR11(cos(2)) cos(2) >>> TR11(cos(4), 2) -sin(2)**2 + cos(2)**2 There is a subtle issue here in that autosimplification will convert some higher angles to lower angles >>> cos(6*pi/7) + cos(3*pi/7) -cos(pi/7) + cos(3*pi/7) The 6*pi/7 angle is now pi/7 but can be targeted with TR11 by supplying the 3*pi/7 base: >>> TR11(_, 3*pi/7) -sin(3*pi/7)**2 + cos(3*pi/7)**2 + cos(3*pi/7) """ def f(rv): if not rv.func in (cos, sin): return rv if base: f = rv.func t = f(base*2) co = S.One if t.is_Mul: co, t = t.as_coeff_Mul() if not t.func in (cos, sin): return rv if rv.args[0] == t.args[0]: c = cos(base) s = sin(base) if f is cos: return (c**2 - s**2)/co else: return 2*c*s/co return rv elif not rv.args[0].is_Number: # make a change if the leading coefficient's numerator is # divisible by 2 c, m = rv.args[0].as_coeff_Mul(rational=True) if c.p % 2 == 0: arg = c.p//2*m/c.q c = TR11(cos(arg)) s = TR11(sin(arg)) if rv.func == sin: rv = 2*s*c else: rv = c**2 - s**2 return rv return bottom_up(rv, f) def _TR11(rv): """ Helper for TR11 to find half-arguments for sin in factors of num/den that appear in cos or sin factors in the den/num. Examples ======== >>> from sympy.simplify.fu import TR11, _TR11 >>> from sympy import cos, sin >>> from sympy.abc import x >>> TR11(sin(x/3)/(cos(x/6))) sin(x/3)/cos(x/6) >>> _TR11(sin(x/3)/(cos(x/6))) 2*sin(x/6) >>> TR11(sin(x/6)/(sin(x/3))) sin(x/6)/sin(x/3) >>> _TR11(sin(x/6)/(sin(x/3))) 1/(2*cos(x/6)) """ def f(rv): if not isinstance(rv, Expr): return rv def sincos_args(flat): # find arguments of sin and cos that # appears as bases in args of flat # and have Integer exponents args = defaultdict(set) for fi in Mul.make_args(flat): b, e = fi.as_base_exp() if e.is_Integer and e > 0: if b.func in (cos, sin): args[b.func].add(b.args[0]) return args num_args, den_args = map(sincos_args, rv.as_numer_denom()) def handle_match(rv, num_args, den_args): # for arg in sin args of num_args, look for arg/2 # in den_args and pass this half-angle to TR11 # for handling in rv for narg in num_args[sin]: half = narg/2 if half in den_args[cos]: func = cos elif half in den_args[sin]: func = sin else: continue rv = TR11(rv, half) den_args[func].remove(half) return rv # sin in num, sin or cos in den rv = handle_match(rv, num_args, den_args) # sin in den, sin or cos in num rv = handle_match(rv, den_args, num_args) return rv return bottom_up(rv, f) def TR12(rv, first=True): """Separate sums in ``tan``. Examples ======== >>> from sympy.abc import x, y >>> from sympy import tan >>> from sympy.simplify.fu import TR12 >>> TR12(tan(x + y)) (tan(x) + tan(y))/(-tan(x)*tan(y) + 1) """ def f(rv): if not rv.func == tan: return rv arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: tb = TR12(tan(b), first=False) else: tb = tan(b) return (tan(a) + tb)/(1 - tan(a)*tb) return rv return bottom_up(rv, f) def TR12i(rv): """Combine tan arguments as (tan(y) + tan(x))/(tan(x)*tan(y) - 1) -> -tan(x + y). Examples ======== >>> from sympy.simplify.fu import TR12i >>> from sympy import tan >>> from sympy.abc import a, b, c >>> ta, tb, tc = [tan(i) for i in (a, b, c)] >>> TR12i((ta + tb)/(-ta*tb + 1)) tan(a + b) >>> TR12i((ta + tb)/(ta*tb - 1)) -tan(a + b) >>> TR12i((-ta - tb)/(ta*tb - 1)) tan(a + b) >>> eq = (ta + tb)/(-ta*tb + 1)**2*(-3*ta - 3*tc)/(2*(ta*tc - 1)) >>> TR12i(eq.expand()) -3*tan(a + b)*tan(a + c)/(2*(tan(a) + tan(b) - 1)) """ from sympy import factor def f(rv): if not (rv.is_Add or rv.is_Mul or rv.is_Pow): return rv n, d = rv.as_numer_denom() if not d.args or not n.args: return rv dok = {} def ok(di): m = as_f_sign_1(di) if m: g, f, s = m if s is S.NegativeOne and f.is_Mul and len(f.args) == 2 and \ all(isinstance(fi, tan) for fi in f.args): return g, f d_args = list(Mul.make_args(d)) for i, di in enumerate(d_args): m = ok(di) if m: g, t = m s = Add(*[_.args[0] for _ in t.args]) dok[s] = S.One d_args[i] = g continue if di.is_Add: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One elif di.is_Pow and (di.exp.is_integer or di.base.is_positive): m = ok(di.base) if m: g, t = m s = Add(*[_.args[0] for _ in t.args]) dok[s] = di.exp d_args[i] = g**di.exp else: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One if not dok: return rv def ok(ni): if ni.is_Add and len(ni.args) == 2: a, b = ni.args if isinstance(a, tan) and isinstance(b, tan): return a, b n_args = list(Mul.make_args(factor_terms(n))) hit = False for i, ni in enumerate(n_args): m = ok(ni) if not m: m = ok(-ni) if m: n_args[i] = S.NegativeOne else: if ni.is_Add: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue elif ni.is_Pow and ( ni.exp.is_integer or ni.base.is_positive): m = ok(ni.base) if m: n_args[i] = S.One else: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue else: continue else: n_args[i] = S.One hit = True s = Add(*[_.args[0] for _ in m]) ed = dok[s] newed = ed.extract_additively(S.One) if newed is not None: if newed: dok[s] = newed else: dok.pop(s) n_args[i] *= -tan(s) if hit: rv = Mul(*n_args)/Mul(*d_args)/Mul(*[(Add(*[ tan(a) for a in i.args]) - 1)**e for i, e in dok.items()]) return rv return bottom_up(rv, f) def TR13(rv): """Change products of ``tan`` or ``cot``. Examples ======== >>> from sympy.simplify.fu import TR13 >>> from sympy import tan, cot >>> TR13(tan(3)*tan(2)) -tan(2)/tan(5) - tan(3)/tan(5) + 1 >>> TR13(cot(3)*cot(2)) cot(2)*cot(5) + 1 + cot(3)*cot(5) """ def f(rv): if not rv.is_Mul: return rv # XXX handle products of powers? or let power-reducing handle it? args = {tan: [], cot: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (tan, cot): args[a.func].append(a.args[0]) else: args[None].append(a) t = args[tan] c = args[cot] if len(t) < 2 and len(c) < 2: return rv args = args[None] while len(t) > 1: t1 = t.pop() t2 = t.pop() args.append(1 - (tan(t1)/tan(t1 + t2) + tan(t2)/tan(t1 + t2))) if t: args.append(tan(t.pop())) while len(c) > 1: t1 = c.pop() t2 = c.pop() args.append(1 + cot(t1)*cot(t1 + t2) + cot(t2)*cot(t1 + t2)) if c: args.append(cot(c.pop())) return Mul(*args) return bottom_up(rv, f) def TRmorrie(rv): """Returns cos(x)*cos(2*x)*...*cos(2**(k-1)*x) -> sin(2**k*x)/(2**k*sin(x)) Examples ======== >>> from sympy.simplify.fu import TRmorrie, TR8, TR3 >>> from sympy.abc import x >>> from sympy import Mul, cos, pi >>> TRmorrie(cos(x)*cos(2*x)) sin(4*x)/(4*sin(x)) >>> TRmorrie(7*Mul(*[cos(x) for x in range(10)])) 7*sin(12)*sin(16)*cos(5)*cos(7)*cos(9)/(64*sin(1)*sin(3)) Sometimes autosimplification will cause a power to be not recognized. e.g. in the following, cos(4*pi/7) automatically simplifies to -cos(3*pi/7) so only 2 of the 3 terms are recognized: >>> TRmorrie(cos(pi/7)*cos(2*pi/7)*cos(4*pi/7)) -sin(3*pi/7)*cos(3*pi/7)/(4*sin(pi/7)) A touch by TR8 resolves the expression to a Rational >>> TR8(_) -1/8 In this case, if eq is unsimplified, the answer is obtained directly: >>> eq = cos(pi/9)*cos(2*pi/9)*cos(3*pi/9)*cos(4*pi/9) >>> TRmorrie(eq) 1/16 But if angles are made canonical with TR3 then the answer is not simplified without further work: >>> TR3(eq) sin(pi/18)*cos(pi/9)*cos(2*pi/9)/2 >>> TRmorrie(_) sin(pi/18)*sin(4*pi/9)/(8*sin(pi/9)) >>> TR8(_) cos(7*pi/18)/(16*sin(pi/9)) >>> TR3(_) 1/16 The original expression would have resolve to 1/16 directly with TR8, however: >>> TR8(eq) 1/16 References ========== .. [1] https://en.wikipedia.org/wiki/Morrie%27s_law """ def f(rv, first=True): if not rv.is_Mul: return rv if first: n, d = rv.as_numer_denom() return f(n, 0)/f(d, 0) args = defaultdict(list) coss = {} other = [] for c in rv.args: b, e = c.as_base_exp() if e.is_Integer and isinstance(b, cos): co, a = b.args[0].as_coeff_Mul() args[a].append(co) coss[b] = e else: other.append(c) new = [] for a in args: c = args[a] c.sort() no = [] while c: k = 0 cc = ci = c[0] while cc in c: k += 1 cc *= 2 if k > 1: newarg = sin(2**k*ci*a)/2**k/sin(ci*a) # see how many times this can be taken take = None ccs = [] for i in range(k): cc /= 2 key = cos(a*cc, evaluate=False) ccs.append(cc) take = min(coss[key], take or coss[key]) # update exponent counts for i in range(k): cc = ccs.pop() key = cos(a*cc, evaluate=False) coss[key] -= take if not coss[key]: c.remove(cc) new.append(newarg**take) else: no.append(c.pop(0)) c[:] = no if new: rv = Mul(*(new + other + [ cos(k*a, evaluate=False) for a in args for k in args[a]])) return rv return bottom_up(rv, f) def TR14(rv, first=True): """Convert factored powers of sin and cos identities into simpler expressions. Examples ======== >>> from sympy.simplify.fu import TR14 >>> from sympy.abc import x, y >>> from sympy import cos, sin >>> TR14((cos(x) - 1)*(cos(x) + 1)) -sin(x)**2 >>> TR14((sin(x) - 1)*(sin(x) + 1)) -cos(x)**2 >>> p1 = (cos(x) + 1)*(cos(x) - 1) >>> p2 = (cos(y) - 1)*2*(cos(y) + 1) >>> p3 = (3*(cos(y) - 1))*(3*(cos(y) + 1)) >>> TR14(p1*p2*p3*(x - 1)) -18*(x - 1)*sin(x)**2*sin(y)**4 """ def f(rv): if not rv.is_Mul: return rv if first: # sort them by location in numerator and denominator # so the code below can just deal with positive exponents n, d = rv.as_numer_denom() if d is not S.One: newn = TR14(n, first=False) newd = TR14(d, first=False) if newn != n or newd != d: rv = newn/newd return rv other = [] process = [] for a in rv.args: if a.is_Pow: b, e = a.as_base_exp() if not (e.is_integer or b.is_positive): other.append(a) continue a = b else: e = S.One m = as_f_sign_1(a) if not m or m[1].func not in (cos, sin): if e is S.One: other.append(a) else: other.append(a**e) continue g, f, si = m process.append((g, e.is_Number, e, f, si, a)) # sort them to get like terms next to each other process = list(ordered(process)) # keep track of whether there was any change nother = len(other) # access keys keys = (g, t, e, f, si, a) = list(range(6)) while process: A = process.pop(0) if process: B = process[0] if A[e].is_Number and B[e].is_Number: # both exponents are numbers if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = min(A[e], B[e]) # reinsert any remainder # the B will likely sort after A so check it first if B[e] != take: rem = [B[i] for i in keys] rem[e] -= take process.insert(0, rem) elif A[e] != take: rem = [A[i] for i in keys] rem[e] -= take process.insert(0, rem) if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]*B[g]*t(A[f].args[0])**2)**take) continue elif A[e] == B[e]: # both exponents are equal symbols if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = A[e] if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]*B[g]*t(A[f].args[0])**2)**take) continue # either we are done or neither condition above applied other.append(A[a]**A[e]) if len(other) != nother: rv = Mul(*other) return rv return bottom_up(rv, f) def TR15(rv, max=4, pow=False): """Convert sin(x)*-2 to 1 + cot(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR15 >>> from sympy.abc import x >>> from sympy import sin >>> TR15(1 - 1/sin(x)**2) -cot(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, sin)): return rv ia = 1/rv a = _TR56(ia, sin, cot, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR16(rv, max=4, pow=False): """Convert cos(x)*-2 to 1 + tan(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR16 >>> from sympy.abc import x >>> from sympy import cos >>> TR16(1 - 1/cos(x)**2) -tan(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, cos)): return rv ia = 1/rv a = _TR56(ia, cos, tan, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR111(rv): """Convert f(x)**-i to g(x)**i where either ``i`` is an integer or the base is positive and f, g are: tan, cot; sin, csc; or cos, sec. Examples ======== >>> from sympy.simplify.fu import TR111 >>> from sympy.abc import x >>> from sympy import tan >>> TR111(1 - 1/tan(x)**2) 1 - cot(x)**2 """ def f(rv): if not ( isinstance(rv, Pow) and (rv.base.is_positive or rv.exp.is_integer and rv.exp.is_negative)): return rv if isinstance(rv.base, tan): return cot(rv.base.args[0])**-rv.exp elif isinstance(rv.base, sin): return csc(rv.base.args[0])**-rv.exp elif isinstance(rv.base, cos): return sec(rv.base.args[0])**-rv.exp return rv return bottom_up(rv, f) def TR22(rv, max=4, pow=False): """Convert tan(x)**2 to sec(x)**2 - 1 and cot(x)**2 to csc(x)**2 - 1. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR22 >>> from sympy.abc import x >>> from sympy import tan, cot >>> TR22(1 + tan(x)**2) sec(x)**2 >>> TR22(1 + cot(x)**2) csc(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and rv.base.func in (cot, tan)): return rv rv = _TR56(rv, tan, sec, lambda x: x - 1, max=max, pow=pow) rv = _TR56(rv, cot, csc, lambda x: x - 1, max=max, pow=pow) return rv return bottom_up(rv, f) def TRpower(rv): """Convert sin(x)**n and cos(x)**n with positive n to sums. Examples ======== >>> from sympy.simplify.fu import TRpower >>> from sympy.abc import x >>> from sympy import cos, sin >>> TRpower(sin(x)**6) -15*cos(2*x)/32 + 3*cos(4*x)/16 - cos(6*x)/32 + 5/16 >>> TRpower(sin(x)**3*cos(2*x)**4) (3*sin(x)/4 - sin(3*x)/4)*(cos(4*x)/2 + cos(8*x)/8 + 3/8) References ========== .. [1] https://en.wikipedia.org/wiki/List_of_trigonometric_identities#Power-reduction_formulae """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, (sin, cos))): return rv b, n = rv.as_base_exp() x = b.args[0] if n.is_Integer and n.is_positive: if n.is_odd and isinstance(b, cos): rv = 2**(1-n)*Add(*[binomial(n, k)*cos((n - 2*k)*x) for k in range((n + 1)/2)]) elif n.is_odd and isinstance(b, sin): rv = 2**(1-n)*(-1)**((n-1)/2)*Add(*[binomial(n, k)* (-1)**k*sin((n - 2*k)*x) for k in range((n + 1)/2)]) elif n.is_even and isinstance(b, cos): rv = 2**(1-n)*Add(*[binomial(n, k)*cos((n - 2*k)*x) for k in range(n/2)]) elif n.is_even and isinstance(b, sin): rv = 2**(1-n)*(-1)**(n/2)*Add(*[binomial(n, k)* (-1)**k*cos((n - 2*k)*x) for k in range(n/2)]) if n.is_even: rv += 2**(-n)*binomial(n, n/2) return rv return bottom_up(rv, f) def L(rv): """Return count of trigonometric functions in expression. Examples ======== >>> from sympy.simplify.fu import L >>> from sympy.abc import x >>> from sympy import cos, sin >>> L(cos(x)+sin(x)) 2 """ return S(rv.count(TrigonometricFunction)) # ============== end of basic Fu-like tools ===================== if SYMPY_DEBUG: (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22 )= list(map(debug, (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22))) # tuples are chains -- (f, g) -> lambda x: g(f(x)) # lists are choices -- [f, g] -> lambda x: min(f(x), g(x), key=objective) CTR1 = [(TR5, TR0), (TR6, TR0), identity] CTR2 = (TR11, [(TR5, TR0), (TR6, TR0), TR0]) CTR3 = [(TRmorrie, TR8, TR0), (TRmorrie, TR8, TR10i, TR0), identity] CTR4 = [(TR4, TR10i), identity] RL1 = (TR4, TR3, TR4, TR12, TR4, TR13, TR4, TR0) # XXX it's a little unclear how this one is to be implemented # see Fu paper of reference, page 7. What is the Union symbol referring to? # The diagram shows all these as one chain of transformations, but the # text refers to them being applied independently. Also, a break # if L starts to increase has not been implemented. RL2 = [ (TR4, TR3, TR10, TR4, TR3, TR11), (TR5, TR7, TR11, TR4), (CTR3, CTR1, TR9, CTR2, TR4, TR9, TR9, CTR4), identity, ] def fu(rv, measure=lambda x: (L(x), x.count_ops())): """Attempt to simplify expression by using transformation rules given in the algorithm by Fu et al. :func:`fu` will try to minimize the objective function ``measure``. By default this first minimizes the number of trig terms and then minimizes the number of total operations. Examples ======== >>> from sympy.simplify.fu import fu >>> from sympy import cos, sin, tan, pi, S, sqrt >>> from sympy.abc import x, y, a, b >>> fu(sin(50)**2 + cos(50)**2 + sin(pi/6)) 3/2 >>> fu(sqrt(6)*cos(x) + sqrt(2)*sin(x)) 2*sqrt(2)*sin(x + pi/3) CTR1 example >>> eq = sin(x)**4 - cos(y)**2 + sin(y)**2 + 2*cos(x)**2 >>> fu(eq) cos(x)**4 - 2*cos(y)**2 + 2 CTR2 example >>> fu(S.Half - cos(2*x)/2) sin(x)**2 CTR3 example >>> fu(sin(a)*(cos(b) - sin(b)) + cos(a)*(sin(b) + cos(b))) sqrt(2)*sin(a + b + pi/4) CTR4 example >>> fu(sqrt(3)*cos(x)/2 + sin(x)/2) sin(x + pi/3) Example 1 >>> fu(1-sin(2*x)**2/4-sin(y)**2-cos(x)**4) -cos(x)**2 + cos(y)**2 Example 2 >>> fu(cos(4*pi/9)) sin(pi/18) >>> fu(cos(pi/9)*cos(2*pi/9)*cos(3*pi/9)*cos(4*pi/9)) 1/16 Example 3 >>> fu(tan(7*pi/18)+tan(5*pi/18)-sqrt(3)*tan(5*pi/18)*tan(7*pi/18)) -sqrt(3) Objective function example >>> fu(sin(x)/cos(x)) # default objective function tan(x) >>> fu(sin(x)/cos(x), measure=lambda x: -x.count_ops()) # maximize op count sin(x)/cos(x) References ========== .. [1] https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.657.2478&rep=rep1&type=pdf """ fRL1 = greedy(RL1, measure) fRL2 = greedy(RL2, measure) was = rv rv = sympify(rv) if not isinstance(rv, Expr): return rv.func(*[fu(a, measure=measure) for a in rv.args]) rv = TR1(rv) if rv.has(tan, cot): rv1 = fRL1(rv) if (measure(rv1) < measure(rv)): rv = rv1 if rv.has(tan, cot): rv = TR2(rv) if rv.has(sin, cos): rv1 = fRL2(rv) rv2 = TR8(TRmorrie(rv1)) rv = min([was, rv, rv1, rv2], key=measure) return min(TR2i(rv), rv, key=measure) def process_common_addends(rv, do, key2=None, key1=True): """Apply ``do`` to addends of ``rv`` that (if ``key1=True``) share at least a common absolute value of their coefficient and the value of ``key2`` when applied to the argument. If ``key1`` is False ``key2`` must be supplied and will be the only key applied. """ # collect by absolute value of coefficient and key2 absc = defaultdict(list) if key1: for a in rv.args: c, a = a.as_coeff_Mul() if c < 0: c = -c a = -a # put the sign on `a` absc[(c, key2(a) if key2 else 1)].append(a) elif key2: for a in rv.args: absc[(S.One, key2(a))].append(a) else: raise ValueError('must have at least one key') args = [] hit = False for k in absc: v = absc[k] c, _ = k if len(v) > 1: e = Add(*v, evaluate=False) new = do(e) if new != e: e = new hit = True args.append(c*e) else: args.append(c*v[0]) if hit: rv = Add(*args) return rv fufuncs = ''' TR0 TR1 TR2 TR3 TR4 TR5 TR6 TR7 TR8 TR9 TR10 TR10i TR11 TR12 TR13 L TR2i TRmorrie TR12i TR14 TR15 TR16 TR111 TR22'''.split() FU = dict(list(zip(fufuncs, list(map(locals().get, fufuncs))))) def _roots(): global _ROOT2, _ROOT3, _invROOT3 _ROOT2, _ROOT3 = sqrt(2), sqrt(3) _invROOT3 = 1/_ROOT3 _ROOT2 = None def trig_split(a, b, two=False): """Return the gcd, s1, s2, a1, a2, bool where If two is False (default) then:: a + b = gcd*(s1*f(a1) + s2*f(a2)) where f = cos if bool else sin else: if bool, a + b was +/- cos(a1)*cos(a2) +/- sin(a1)*sin(a2) and equals n1*gcd*cos(a - b) if n1 == n2 else n1*gcd*cos(a + b) else a + b was +/- cos(a1)*sin(a2) +/- sin(a1)*cos(a2) and equals n1*gcd*sin(a + b) if n1 = n2 else n1*gcd*sin(b - a) Examples ======== >>> from sympy.simplify.fu import trig_split >>> from sympy.abc import x, y, z >>> from sympy import cos, sin, sqrt >>> trig_split(cos(x), cos(y)) (1, 1, 1, x, y, True) >>> trig_split(2*cos(x), -2*cos(y)) (2, 1, -1, x, y, True) >>> trig_split(cos(x)*sin(y), cos(y)*sin(y)) (sin(y), 1, 1, x, y, True) >>> trig_split(cos(x), -sqrt(3)*sin(x), two=True) (2, 1, -1, x, pi/6, False) >>> trig_split(cos(x), sin(x), two=True) (sqrt(2), 1, 1, x, pi/4, False) >>> trig_split(cos(x), -sin(x), two=True) (sqrt(2), 1, -1, x, pi/4, False) >>> trig_split(sqrt(2)*cos(x), -sqrt(6)*sin(x), two=True) (2*sqrt(2), 1, -1, x, pi/6, False) >>> trig_split(-sqrt(6)*cos(x), -sqrt(2)*sin(x), two=True) (-2*sqrt(2), 1, 1, x, pi/3, False) >>> trig_split(cos(x)/sqrt(6), sin(x)/sqrt(2), two=True) (sqrt(6)/3, 1, 1, x, pi/6, False) >>> trig_split(-sqrt(6)*cos(x)*sin(y), -sqrt(2)*sin(x)*sin(y), two=True) (-2*sqrt(2)*sin(y), 1, 1, x, pi/3, False) >>> trig_split(cos(x), sin(x)) >>> trig_split(cos(x), sin(z)) >>> trig_split(2*cos(x), -sin(x)) >>> trig_split(cos(x), -sqrt(3)*sin(x)) >>> trig_split(cos(x)*cos(y), sin(x)*sin(z)) >>> trig_split(cos(x)*cos(y), sin(x)*sin(y)) >>> trig_split(-sqrt(6)*cos(x), sqrt(2)*sin(x)*sin(y), two=True) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() a, b = [Factors(i) for i in (a, b)] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() n1 = n2 = 1 if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -n1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n2 = -n2 a, b = [i.as_expr() for i in (ua, ub)] def pow_cos_sin(a, two): """Return ``a`` as a tuple (r, c, s) such that ``a = (r or 1)*(c or 1)*(s or 1)``. Three arguments are returned (radical, c-factor, s-factor) as long as the conditions set by ``two`` are met; otherwise None is returned. If ``two`` is True there will be one or two non-None values in the tuple: c and s or c and r or s and r or s or c with c being a cosine function (if possible) else a sine, and s being a sine function (if possible) else oosine. If ``two`` is False then there will only be a c or s term in the tuple. ``two`` also require that either two cos and/or sin be present (with the condition that if the functions are the same the arguments are different or vice versa) or that a single cosine or a single sine be present with an optional radical. If the above conditions dictated by ``two`` are not met then None is returned. """ c = s = None co = S.One if a.is_Mul: co, a = a.as_coeff_Mul() if len(a.args) > 2 or not two: return None if a.is_Mul: args = list(a.args) else: args = [a] a = args.pop(0) if isinstance(a, cos): c = a elif isinstance(a, sin): s = a elif a.is_Pow and a.exp is S.Half: # autoeval doesn't allow -1/2 co *= a else: return None if args: b = args[0] if isinstance(b, cos): if c: s = b else: c = b elif isinstance(b, sin): if s: c = b else: s = b elif b.is_Pow and b.exp is S.Half: co *= b else: return None return co if co is not S.One else None, c, s elif isinstance(a, cos): c = a elif isinstance(a, sin): s = a if c is None and s is None: return co = co if co is not S.One else None return co, c, s # get the parts m = pow_cos_sin(a, two) if m is None: return coa, ca, sa = m m = pow_cos_sin(b, two) if m is None: return cob, cb, sb = m # check them if (not ca) and cb or ca and isinstance(ca, sin): coa, ca, sa, cob, cb, sb = cob, cb, sb, coa, ca, sa n1, n2 = n2, n1 if not two: # need cos(x) and cos(y) or sin(x) and sin(y) c = ca or sa s = cb or sb if not isinstance(c, s.func): return None return gcd, n1, n2, c.args[0], s.args[0], isinstance(c, cos) else: if not coa and not cob: if (ca and cb and sa and sb): if isinstance(ca, sa.func) is not isinstance(cb, sb.func): return args = {j.args for j in (ca, sa)} if not all(i.args in args for i in (cb, sb)): return return gcd, n1, n2, ca.args[0], sa.args[0], isinstance(ca, sa.func) if ca and sa or cb and sb or \ two and (ca is None and sa is None or cb is None and sb is None): return c = ca or sa s = cb or sb if c.args != s.args: return if not coa: coa = S.One if not cob: cob = S.One if coa is cob: gcd *= _ROOT2 return gcd, n1, n2, c.args[0], pi/4, False elif coa/cob == _ROOT3: gcd *= 2*cob return gcd, n1, n2, c.args[0], pi/3, False elif coa/cob == _invROOT3: gcd *= 2*coa return gcd, n1, n2, c.args[0], pi/6, False def as_f_sign_1(e): """If ``e`` is a sum that can be written as ``g*(a + s)`` where ``s`` is ``+/-1``, return ``g``, ``a``, and ``s`` where ``a`` does not have a leading negative coefficient. Examples ======== >>> from sympy.simplify.fu import as_f_sign_1 >>> from sympy.abc import x >>> as_f_sign_1(x + 1) (1, x, 1) >>> as_f_sign_1(x - 1) (1, x, -1) >>> as_f_sign_1(-x + 1) (-1, x, -1) >>> as_f_sign_1(-x - 1) (-1, x, 1) >>> as_f_sign_1(2*x + 2) (2, x, 1) """ if not e.is_Add or len(e.args) != 2: return # exact match a, b = e.args if a in (S.NegativeOne, S.One): g = S.One if b.is_Mul and b.args[0].is_Number and b.args[0] < 0: a, b = -a, -b g = -g return g, b, a # gcd match a, b = [Factors(i) for i in e.args] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -1 n2 = 1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n1 = 1 n2 = -1 else: n1 = n2 = 1 a, b = [i.as_expr() for i in (ua, ub)] if a is S.One: a, b = b, a n1, n2 = n2, n1 if n1 == -1: gcd = -gcd n2 = -n2 if b is S.One: return gcd, a, n2 def _osborne(e, d): """Replace all hyperbolic functions with trig functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, HyperbolicFunction): return rv a = rv.args[0] a = a*d if not a.is_Add else Add._from_args([i*d for i in a.args]) if isinstance(rv, sinh): return I*sin(a) elif isinstance(rv, cosh): return cos(a) elif isinstance(rv, tanh): return I*tan(a) elif isinstance(rv, coth): return cot(a)/I elif isinstance(rv, sech): return sec(a) elif isinstance(rv, csch): return csc(a)/I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def _osbornei(e, d): """Replace all trig functions with hyperbolic functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, TrigonometricFunction): return rv const, x = rv.args[0].as_independent(d, as_Add=True) a = x.xreplace({d: S.One}) + const*I if isinstance(rv, sin): return sinh(a)/I elif isinstance(rv, cos): return cosh(a) elif isinstance(rv, tan): return tanh(a)/I elif isinstance(rv, cot): return coth(a)*I elif isinstance(rv, sec): return sech(a) elif isinstance(rv, csc): return csch(a)*I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def hyper_as_trig(rv): """Return an expression containing hyperbolic functions in terms of trigonometric functions. Any trigonometric functions initially present are replaced with Dummy symbols and the function to undo the masking and the conversion back to hyperbolics is also returned. It should always be true that:: t, f = hyper_as_trig(expr) expr == f(t) Examples ======== >>> from sympy.simplify.fu import hyper_as_trig, fu >>> from sympy.abc import x >>> from sympy import cosh, sinh >>> eq = sinh(x)**2 + cosh(x)**2 >>> t, f = hyper_as_trig(eq) >>> f(fu(t)) cosh(2*x) References ========== .. [1] https://en.wikipedia.org/wiki/Hyperbolic_function """ from sympy.simplify.simplify import signsimp from sympy.simplify.radsimp import collect # mask off trig functions trigs = rv.atoms(TrigonometricFunction) reps = [(t, Dummy()) for t in trigs] masked = rv.xreplace(dict(reps)) # get inversion substitutions in place reps = [(v, k) for k, v in reps] d = Dummy() return _osborne(masked, d), lambda x: collect(signsimp( _osbornei(x, d).xreplace(dict(reps))), S.ImaginaryUnit) def sincos_to_sum(expr): """Convert products and powers of sin and cos to sums. Explanation =========== Applied power reduction TRpower first, then expands products, and converts products to sums with TR8. Examples ======== >>> from sympy.simplify.fu import sincos_to_sum >>> from sympy.abc import x >>> from sympy import cos, sin >>> sincos_to_sum(16*sin(x)**3*cos(2*x)**2) 7*sin(x) - 5*sin(3*x) + 3*sin(5*x) - sin(7*x) """ if not expr.has(cos, sin): return expr else: return TR8(expand_mul(TRpower(expr)))

55e107182ad69fdd4bea9061664d2eaebfee9062558cb6462b580df38506facc

""" This module cooks up a docstring when imported. Its only purpose is to be displayed in the sphinx documentation. """ from sympy import latex, Eq, hyper from sympy.simplify.hyperexpand import FormulaCollection c = FormulaCollection() doc = "" for f in c.formulae: obj = Eq(hyper(f.func.ap, f.func.bq, f.z), f.closed_form.rewrite('nonrepsmall')) doc += ".. math::\n %s\n" % latex(obj) __doc__ = doc

1ab8af4bff62a9ce031d149a748a0b74ec49773e9eb9dcad3d90fc3c5830a346

from itertools import combinations_with_replacement from sympy.core import symbols, Add, Dummy from sympy.core.numbers import Rational from sympy.polys import cancel, ComputationFailed, parallel_poly_from_expr, reduced, Poly from sympy.polys.monomials import Monomial, monomial_div from sympy.polys.polyerrors import DomainError, PolificationFailed from sympy.utilities.misc import debug def ratsimp(expr): """ Put an expression over a common denominator, cancel and reduce. Examples ======== >>> from sympy import ratsimp >>> from sympy.abc import x, y >>> ratsimp(1/x + 1/y) (x + y)/(x*y) """ f, g = cancel(expr).as_numer_denom() try: Q, r = reduced(f, [g], field=True, expand=False) except ComputationFailed: return f/g return Add(*Q) + cancel(r/g) def ratsimpmodprime(expr, G, *gens, quick=True, polynomial=False, **args): """ Simplifies a rational expression ``expr`` modulo the prime ideal generated by ``G``. ``G`` should be a Groebner basis of the ideal. Examples ======== >>> from sympy.simplify.ratsimp import ratsimpmodprime >>> from sympy.abc import x, y >>> eq = (x + y**5 + y)/(x - y) >>> ratsimpmodprime(eq, [x*y**5 - x - y], x, y, order='lex') (-x**2 - x*y - x - y)/(-x**2 + x*y) If ``polynomial`` is ``False``, the algorithm computes a rational simplification which minimizes the sum of the total degrees of the numerator and the denominator. If ``polynomial`` is ``True``, this function just brings numerator and denominator into a canonical form. This is much faster, but has potentially worse results. References ========== .. [1] M. Monagan, R. Pearce, Rational Simplification Modulo a Polynomial Ideal, http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.163.6984 (specifically, the second algorithm) """ from sympy import solve debug('ratsimpmodprime', expr) # usual preparation of polynomials: num, denom = cancel(expr).as_numer_denom() try: polys, opt = parallel_poly_from_expr([num, denom] + G, *gens, **args) except PolificationFailed: return expr domain = opt.domain if domain.has_assoc_Field: opt.domain = domain.get_field() else: raise DomainError( "can't compute rational simplification over %s" % domain) # compute only once leading_monomials = [g.LM(opt.order) for g in polys[2:]] tested = set() def staircase(n): """ Compute all monomials with degree less than ``n`` that are not divisible by any element of ``leading_monomials``. """ if n == 0: return [1] S = [] for mi in combinations_with_replacement(range(len(opt.gens)), n): m = [0]*len(opt.gens) for i in mi: m[i] += 1 if all([monomial_div(m, lmg) is None for lmg in leading_monomials]): S.append(m) return [Monomial(s).as_expr(*opt.gens) for s in S] + staircase(n - 1) def _ratsimpmodprime(a, b, allsol, N=0, D=0): r""" Computes a rational simplification of ``a/b`` which minimizes the sum of the total degrees of the numerator and the denominator. Explanation =========== The algorithm proceeds by looking at ``a * d - b * c`` modulo the ideal generated by ``G`` for some ``c`` and ``d`` with degree less than ``a`` and ``b`` respectively. The coefficients of ``c`` and ``d`` are indeterminates and thus the coefficients of the normalform of ``a * d - b * c`` are linear polynomials in these indeterminates. If these linear polynomials, considered as system of equations, have a nontrivial solution, then `\frac{a}{b} \equiv \frac{c}{d}` modulo the ideal generated by ``G``. So, by construction, the degree of ``c`` and ``d`` is less than the degree of ``a`` and ``b``, so a simpler representation has been found. After a simpler representation has been found, the algorithm tries to reduce the degree of the numerator and denominator and returns the result afterwards. As an extension, if quick=False, we look at all possible degrees such that the total degree is less than *or equal to* the best current solution. We retain a list of all solutions of minimal degree, and try to find the best one at the end. """ c, d = a, b steps = 0 maxdeg = a.total_degree() + b.total_degree() if quick: bound = maxdeg - 1 else: bound = maxdeg while N + D <= bound: if (N, D) in tested: break tested.add((N, D)) M1 = staircase(N) M2 = staircase(D) debug('%s / %s: %s, %s' % (N, D, M1, M2)) Cs = symbols("c:%d" % len(M1), cls=Dummy) Ds = symbols("d:%d" % len(M2), cls=Dummy) ng = Cs + Ds c_hat = Poly( sum([Cs[i] * M1[i] for i in range(len(M1))]), opt.gens + ng) d_hat = Poly( sum([Ds[i] * M2[i] for i in range(len(M2))]), opt.gens + ng) r = reduced(a * d_hat - b * c_hat, G, opt.gens + ng, order=opt.order, polys=True)[1] S = Poly(r, gens=opt.gens).coeffs() sol = solve(S, Cs + Ds, particular=True, quick=True) if sol and not all([s == 0 for s in sol.values()]): c = c_hat.subs(sol) d = d_hat.subs(sol) # The "free" variables occurring before as parameters # might still be in the substituted c, d, so set them # to the value chosen before: c = c.subs(dict(list(zip(Cs + Ds, [1] * (len(Cs) + len(Ds)))))) d = d.subs(dict(list(zip(Cs + Ds, [1] * (len(Cs) + len(Ds)))))) c = Poly(c, opt.gens) d = Poly(d, opt.gens) if d == 0: raise ValueError('Ideal not prime?') allsol.append((c_hat, d_hat, S, Cs + Ds)) if N + D != maxdeg: allsol = [allsol[-1]] break steps += 1 N += 1 D += 1 if steps > 0: c, d, allsol = _ratsimpmodprime(c, d, allsol, N, D - steps) c, d, allsol = _ratsimpmodprime(c, d, allsol, N - steps, D) return c, d, allsol # preprocessing. this improves performance a bit when deg(num) # and deg(denom) are large: num = reduced(num, G, opt.gens, order=opt.order)[1] denom = reduced(denom, G, opt.gens, order=opt.order)[1] if polynomial: return (num/denom).cancel() c, d, allsol = _ratsimpmodprime( Poly(num, opt.gens, domain=opt.domain), Poly(denom, opt.gens, domain=opt.domain), []) if not quick and allsol: debug('Looking for best minimal solution. Got: %s' % len(allsol)) newsol = [] for c_hat, d_hat, S, ng in allsol: sol = solve(S, ng, particular=True, quick=False) newsol.append((c_hat.subs(sol), d_hat.subs(sol))) c, d = min(newsol, key=lambda x: len(x[0].terms()) + len(x[1].terms())) if not domain.is_Field: cn, c = c.clear_denoms(convert=True) dn, d = d.clear_denoms(convert=True) r = Rational(cn, dn) else: r = Rational(1) return (c*r.q)/(d*r.p)

cab556bc3f59419547746c326c3d37caedeaaa73a68a721e961ad6c1290d80bf

from typing import Any, Set from itertools import permutations from sympy.combinatorics import Permutation from sympy.core import ( Basic, Expr, Function, diff, Pow, Mul, Add, Atom, Lambda, S, Tuple, Dict ) from sympy.core.cache import cacheit from sympy.core.compatibility import reduce from sympy.core.symbol import Symbol, Dummy from sympy.core.symbol import Str from sympy.core.sympify import _sympify from sympy.functions import factorial from sympy.matrices import ImmutableDenseMatrix as Matrix from sympy.simplify import simplify from sympy.solvers import solve from sympy.utilities.exceptions import SymPyDeprecationWarning # TODO you are a bit excessive in the use of Dummies # TODO dummy point, literal field # TODO too often one needs to call doit or simplify on the output, check the # tests and find out why from sympy.tensor.array import ImmutableDenseNDimArray class Manifold(Atom): """A mathematical manifold. Explanation =========== A manifold is a topological space that locally resembles Euclidean space near each point [1]. This class does not provide any means to study the topological characteristics of the manifold that it represents, though. Parameters ========== name : str The name of the manifold. dim : int The dimension of the manifold. Examples ======== >>> from sympy.diffgeom import Manifold >>> m = Manifold('M', 2) >>> m M >>> m.dim 2 References ========== .. [1] https://en.wikipedia.org/wiki/Manifold """ def __new__(cls, name, dim, **kwargs): if not isinstance(name, Str): name = Str(name) dim = _sympify(dim) obj = super().__new__(cls, name, dim) obj.patches = _deprecated_list( "Manifold.patches", "external container for registry", 19321, "1.7", [] ) return obj @property def name(self): return self.args[0] @property def dim(self): return self.args[1] class Patch(Atom): """A patch on a manifold. Explanation =========== Coordinate patch, or patch in short, is a simply-connected open set around a point in the manifold [1]. On a manifold one can have many patches that do not always include the whole manifold. On these patches coordinate charts can be defined that permit the parameterization of any point on the patch in terms of a tuple of real numbers (the coordinates). This class does not provide any means to study the topological characteristics of the patch that it represents. Parameters ========== name : str The name of the patch. manifold : Manifold The manifold on which the patch is defined. Examples ======== >>> from sympy.diffgeom import Manifold, Patch >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> p P >>> p.dim 2 References ========== .. [1] G. Sussman, J. Wisdom, W. Farr, Functional Differential Geometry (2013) """ def __new__(cls, name, manifold, **kwargs): if not isinstance(name, Str): name = Str(name) obj = super().__new__(cls, name, manifold) obj.manifold.patches.append(obj) # deprecated obj.coord_systems = _deprecated_list( "Patch.coord_systems", "external container for registry", 19321, "1.7", [] ) return obj @property def name(self): return self.args[0] @property def manifold(self): return self.args[1] @property def dim(self): return self.manifold.dim class CoordSystem(Atom): """A coordinate system defined on the patch. Explanation =========== Coordinate system is a system that uses one or more coordinates to uniquely determine the position of the points or other geometric elements on a manifold [1]. By passing Symbols to *symbols* parameter, user can define the name and assumptions of coordinate symbols of the coordinate system. If not passed, these symbols are generated automatically and are assumed to be real valued. By passing *relations* parameter, user can define the tranform relations of coordinate systems. Inverse transformation and indirect transformation can be found automatically. If this parameter is not passed, coordinate transformation cannot be done. Parameters ========== name : str The name of the coordinate system. patch : Patch The patch where the coordinate system is defined. symbols : list of Symbols, optional Defines the names and assumptions of coordinate symbols. relations : dict, optional - key : tuple of two strings, who are the names of systems where the coordinates transform from and transform to. - value : Lambda returning the transformed coordinates. Examples ======== >>> from sympy import symbols, pi, Lambda, Matrix, sqrt, atan2, cos, sin >>> from sympy.diffgeom import Manifold, Patch, CoordSystem >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> x, y = symbols('x y', real=True) >>> r, theta = symbols('r theta', nonnegative=True) >>> relation_dict = { ... ('Car2D', 'Pol'): Lambda((x, y), Matrix([sqrt(x**2 + y**2), atan2(y, x)])), ... ('Pol', 'Car2D'): Lambda((r, theta), Matrix([r*cos(theta), r*sin(theta)])) ... } >>> Car2D = CoordSystem('Car2D', p, [x, y], relation_dict) >>> Pol = CoordSystem('Pol', p, [r, theta], relation_dict) >>> Car2D Car2D >>> Car2D.dim 2 >>> Car2D.symbols [x, y] >>> Car2D.transformation(Pol) Lambda((x, y), Matrix([ [sqrt(x**2 + y**2)], [ atan2(y, x)]])) >>> Car2D.transform(Pol) Matrix([ [sqrt(x**2 + y**2)], [ atan2(y, x)]]) >>> Car2D.transform(Pol, [1, 2]) Matrix([ [sqrt(5)], [atan(2)]]) >>> Pol.jacobian(Car2D) Matrix([ [cos(theta), -r*sin(theta)], [sin(theta), r*cos(theta)]]) >>> Pol.jacobian(Car2D, [1, pi/2]) Matrix([ [0, -1], [1, 0]]) References ========== .. [1] https://en.wikipedia.org/wiki/Coordinate_system """ def __new__(cls, name, patch, symbols=None, relations={}, **kwargs): if not isinstance(name, Str): name = Str(name) # canonicallize the symbols if symbols is None: names = kwargs.get('names', None) if names is None: symbols = Tuple( *[Symbol('%s_%s' % (name.name, i), real=True) for i in range(patch.dim)] ) else: SymPyDeprecationWarning( feature="Class signature 'names' of CoordSystem", useinstead="class signature 'symbols'", issue=19321, deprecated_since_version="1.7" ).warn() symbols = Tuple( *[Symbol(n, real=True) for n in names] ) else: syms = [] for s in symbols: if isinstance(s, Symbol): syms.append(Symbol(s.name, **s._assumptions.generator)) elif isinstance(s, str): SymPyDeprecationWarning( feature="Passing str as coordinate symbol's name", useinstead="Symbol which contains the name and assumption for coordinate symbol", issue=19321, deprecated_since_version="1.7" ).warn() syms.append(Symbol(s, real=True)) symbols = Tuple(*syms) # canonicallize the relations rel_temp = {} for k,v in relations.items(): s1, s2 = k if not isinstance(s1, Str): s1 = Str(s1) if not isinstance(s2, Str): s2 = Str(s2) key = Tuple(s1, s2) rel_temp[key] = v relations = Dict(rel_temp) # construct the object obj = super().__new__(cls, name, patch, symbols, relations) # Add deprecated attributes obj.transforms = _deprecated_dict( "Mutable CoordSystem.transforms", "'relations' parameter in class signature", 19321, "1.7", {} ) obj._names = [str(n) for n in symbols] obj.patch.coord_systems.append(obj) # deprecated obj._dummies = [Dummy(str(n)) for n in symbols] # deprecated obj._dummy = Dummy() return obj @property def name(self): return self.args[0] @property def patch(self): return self.args[1] @property def manifold(self): return self.patch.manifold @property def symbols(self): return [ CoordinateSymbol( self, i, **s._assumptions.generator ) for i,s in enumerate(self.args[2]) ] @property def relations(self): return self.args[3] @property def dim(self): return self.patch.dim ########################################################################## # Finding transformation relation ########################################################################## def transformation(self, sys): """ Return coordinate transform relation from *self* to *sys* as Lambda. """ if self.relations != sys.relations: raise TypeError( "Two coordinate systems have different relations") key = Tuple(self.name, sys.name) if key in self.relations: return self.relations[key] elif key[::-1] in self.relations: return self._inverse_transformation(sys, self) else: return self._indirect_transformation(self, sys) @staticmethod def _inverse_transformation(sys1, sys2): # Find the transformation relation from sys2 to sys1 forward_transform = sys1.transform(sys2) forward_syms, forward_results = forward_transform.args inv_syms = [i.as_dummy() for i in forward_syms] inv_results = solve( [t[0] - t[1] for t in zip(inv_syms, forward_results)], list(forward_syms), dict=True)[0] inv_results = [inv_results[s] for s in forward_syms] signature = tuple(inv_syms) expr = Matrix(inv_results) return Lambda(signature, expr) @classmethod @cacheit def _indirect_transformation(cls, sys1, sys2): # Find the transformation relation between two indirectly connected coordinate systems path = cls._dijkstra(sys1, sys2) Lambdas = [] for i in range(len(path) - 1): s1, s2 = path[i], path[i + 1] Lambdas.append(s1.transformation(s2)) syms = Lambdas[-1].signature expr = syms for l in reversed(Lambdas): expr = l(*expr) return Lambda(syms, expr) @staticmethod def _dijkstra(sys1, sys2): # Use Dijkstra algorithm to find the shortest path between two indirectly-connected # coordinate systems relations = sys1.relations graph = {} for s1, s2 in relations.keys(): if s1 not in graph: graph[s1] = {s2} else: graph[s1].add(s2) if s2 not in graph: graph[s2] = {s1} else: graph[s2].add(s1) path_dict = {sys:[0, [], 0] for sys in graph} # minimum distance, path, times of visited def visit(sys): path_dict[sys][2] = 1 for newsys in graph[sys]: distance = path_dict[sys][0] + 1 if path_dict[newsys][0] >= distance or not path_dict[newsys][1]: path_dict[newsys][0] = distance path_dict[newsys][1] = [i for i in path_dict[sys][1]] path_dict[newsys][1].append(sys) visit(sys1) while True: min_distance = max(path_dict.values(), key=lambda x:x[0])[0] newsys = None for sys, lst in path_dict.items(): if 0 < lst[0] <= min_distance and not lst[2]: min_distance = lst[0] newsys = sys if newsys is None: break visit(newsys) result = path_dict[sys2][1] result.append(sys2) if result == [sys2]: raise KeyError("Two coordinate systems are not connected.") return result def connect_to(self, to_sys, from_coords, to_exprs, inverse=True, fill_in_gaps=False): SymPyDeprecationWarning( feature="CoordSystem.connect_to", useinstead="new instance generated with new 'transforms' parameter", issue=19321, deprecated_since_version="1.7" ).warn() from_coords, to_exprs = dummyfy(from_coords, to_exprs) self.transforms[to_sys] = Matrix(from_coords), Matrix(to_exprs) if inverse: to_sys.transforms[self] = self._inv_transf(from_coords, to_exprs) if fill_in_gaps: self._fill_gaps_in_transformations() @staticmethod def _inv_transf(from_coords, to_exprs): # Will be removed when connect_to is removed inv_from = [i.as_dummy() for i in from_coords] inv_to = solve( [t[0] - t[1] for t in zip(inv_from, to_exprs)], list(from_coords), dict=True)[0] inv_to = [inv_to[fc] for fc in from_coords] return Matrix(inv_from), Matrix(inv_to) @staticmethod def _fill_gaps_in_transformations(): # Will be removed when connect_to is removed raise NotImplementedError ########################################################################## # Coordinate transformations ########################################################################## def transform(self, sys, coordinates=None): """ Return the result of coordinate transformation from *self* to *sys*. If coordinates are not given, coordinate symbols of *self* are used. """ if coordinates is None: coordinates = Matrix(self.symbols) else: coordinates = Matrix(coordinates) if self != sys: transf = self.transformation(sys) coordinates = transf(*coordinates) return coordinates def coord_tuple_transform_to(self, to_sys, coords): """Transform ``coords`` to coord system ``to_sys``.""" SymPyDeprecationWarning( feature="CoordSystem.coord_tuple_transform_to", useinstead="CoordSystem.transform", issue=19321, deprecated_since_version="1.7" ).warn() coords = Matrix(coords) if self != to_sys: transf = self.transforms[to_sys] coords = transf[1].subs(list(zip(transf[0], coords))) return coords def jacobian(self, sys, coordinates=None): """ Return the jacobian matrix of a transformation. """ result = self.transform(sys).jacobian(self.symbols) if coordinates is not None: result = result.subs(list(zip(self.symbols, coordinates))) return result jacobian_matrix = jacobian def jacobian_determinant(self, sys, coordinates=None): """Return the jacobian determinant of a transformation.""" return self.jacobian(sys, coordinates).det() ########################################################################## # Points ########################################################################## def point(self, coords): """Create a ``Point`` with coordinates given in this coord system.""" return Point(self, coords) def point_to_coords(self, point): """Calculate the coordinates of a point in this coord system.""" return point.coords(self) ########################################################################## # Base fields. ########################################################################## def base_scalar(self, coord_index): """Return ``BaseScalarField`` that takes a point and returns one of the coordinates.""" return BaseScalarField(self, coord_index) coord_function = base_scalar def base_scalars(self): """Returns a list of all coordinate functions. For more details see the ``base_scalar`` method of this class.""" return [self.base_scalar(i) for i in range(self.dim)] coord_functions = base_scalars def base_vector(self, coord_index): """Return a basis vector field. The basis vector field for this coordinate system. It is also an operator on scalar fields.""" return BaseVectorField(self, coord_index) def base_vectors(self): """Returns a list of all base vectors. For more details see the ``base_vector`` method of this class.""" return [self.base_vector(i) for i in range(self.dim)] def base_oneform(self, coord_index): """Return a basis 1-form field. The basis one-form field for this coordinate system. It is also an operator on vector fields.""" return Differential(self.coord_function(coord_index)) def base_oneforms(self): """Returns a list of all base oneforms. For more details see the ``base_oneform`` method of this class.""" return [self.base_oneform(i) for i in range(self.dim)] class CoordinateSymbol(Symbol): """A symbol which denotes an abstract value of i-th coordinate of the coordinate system with given context. Explanation =========== Each coordinates in coordinate system are represented by unique symbol, such as x, y, z in Cartesian coordinate system. You may not construct this class directly. Instead, use `symbols` method of CoordSystem. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import symbols >>> from sympy.diffgeom import Manifold, Patch, CoordSystem >>> m = Manifold('M', 2) >>> p = Patch('P', m) >>> _x, _y = symbols('x y', nonnegative=True) >>> C = CoordSystem('C', p, [_x, _y]) >>> x, y = C.symbols >>> x.name 'x' >>> x.coord_sys == C True >>> x.index 0 >>> x.is_nonnegative True """ def __new__(cls, coord_sys, index, **assumptions): name = coord_sys.args[2][index].name obj = super().__new__(cls, name, **assumptions) obj.coord_sys = coord_sys obj.index = index return obj def __getnewargs__(self): return (self.coord_sys, self.index) def _hashable_content(self): return ( self.coord_sys, self.index ) + tuple(sorted(self.assumptions0.items())) class Point(Basic): """Point defined in a coordinate system. Explanation =========== Mathematically, point is defined in the manifold and does not have any coordinates by itself. Coordinate system is what imbues the coordinates to the point by coordinate chart. However, due to the difficulty of realizing such logic, you must supply a coordinate system and coordinates to define a Point here. The usage of this object after its definition is independent of the coordinate system that was used in order to define it, however due to limitations in the simplification routines you can arrive at complicated expressions if you use inappropriate coordinate systems. Parameters ========== coord_sys : CoordSystem coords : list The coordinates of the point. Examples ======== >>> from sympy import pi >>> from sympy.diffgeom import Point >>> from sympy.diffgeom.rn import R2, R2_r, R2_p >>> rho, theta = R2_p.symbols >>> p = Point(R2_p, [rho, 3*pi/4]) >>> p.manifold == R2 True >>> p.coords() Matrix([ [ rho], [3*pi/4]]) >>> p.coords(R2_r) Matrix([ [-sqrt(2)*rho/2], [ sqrt(2)*rho/2]]) """ def __new__(cls, coord_sys, coords, **kwargs): coords = Matrix(coords) obj = super().__new__(cls, coord_sys, coords) obj._coord_sys = coord_sys obj._coords = coords return obj @property def patch(self): return self._coord_sys.patch @property def manifold(self): return self._coord_sys.manifold @property def dim(self): return self.manifold.dim def coords(self, sys=None): """ Coordinates of the point in given coordinate system. If coordinate system is not passed, it returns the coordinates in the coordinate system in which the poin was defined. """ if sys is None: return self._coords else: return self._coord_sys.transform(sys, self._coords) @property def free_symbols(self): return self._coords.free_symbols class BaseScalarField(Expr): """Base scalar field over a manifold for a given coordinate system. Explanation =========== A scalar field takes a point as an argument and returns a scalar. A base scalar field of a coordinate system takes a point and returns one of the coordinates of that point in the coordinate system in question. To define a scalar field you need to choose the coordinate system and the index of the coordinate. The use of the scalar field after its definition is independent of the coordinate system in which it was defined, however due to limitations in the simplification routines you may arrive at more complicated expression if you use unappropriate coordinate systems. You can build complicated scalar fields by just building up SymPy expressions containing ``BaseScalarField`` instances. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import Function, pi >>> from sympy.diffgeom import BaseScalarField >>> from sympy.diffgeom.rn import R2_r, R2_p >>> rho, _ = R2_p.symbols >>> point = R2_p.point([rho, 0]) >>> fx, fy = R2_r.base_scalars() >>> ftheta = BaseScalarField(R2_r, 1) >>> fx(point) rho >>> fy(point) 0 >>> (fx**2+fy**2).rcall(point) rho**2 >>> g = Function('g') >>> fg = g(ftheta-pi) >>> fg.rcall(point) g(-pi) """ is_commutative = True def __new__(cls, coord_sys, index, **kwargs): index = _sympify(index) obj = super().__new__(cls, coord_sys, index) obj._coord_sys = coord_sys obj._index = index return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def patch(self): return self.coord_sys.patch @property def manifold(self): return self.coord_sys.manifold @property def dim(self): return self.manifold.dim def __call__(self, *args): """Evaluating the field at a point or doing nothing. If the argument is a ``Point`` instance, the field is evaluated at that point. The field is returned itself if the argument is any other object. It is so in order to have working recursive calling mechanics for all fields (check the ``__call__`` method of ``Expr``). """ point = args[0] if len(args) != 1 or not isinstance(point, Point): return self coords = point.coords(self._coord_sys) # XXX Calling doit is necessary with all the Subs expressions # XXX Calling simplify is necessary with all the trig expressions return simplify(coords[self._index]).doit() # XXX Workaround for limitations on the content of args free_symbols = set() # type: Set[Any] def doit(self): return self class BaseVectorField(Expr): r"""Base vector field over a manifold for a given coordinate system. Explanation =========== A vector field is an operator taking a scalar field and returning a directional derivative (which is also a scalar field). A base vector field is the same type of operator, however the derivation is specifically done with respect to a chosen coordinate. To define a base vector field you need to choose the coordinate system and the index of the coordinate. The use of the vector field after its definition is independent of the coordinate system in which it was defined, however due to limitations in the simplification routines you may arrive at more complicated expression if you use unappropriate coordinate systems. Parameters ========== coord_sys : CoordSystem index : integer Examples ======== >>> from sympy import Function >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import BaseVectorField >>> from sympy import pprint >>> x, y = R2_r.symbols >>> rho, theta = R2_p.symbols >>> fx, fy = R2_r.base_scalars() >>> point_p = R2_p.point([rho, theta]) >>> point_r = R2_r.point([x, y]) >>> g = Function('g') >>> s_field = g(fx, fy) >>> v = BaseVectorField(R2_r, 1) >>> pprint(v(s_field)) / d \| |---(g(x, xi))|| \dxi /|xi=y >>> pprint(v(s_field).rcall(point_r).doit()) d --(g(x, y)) dy >>> pprint(v(s_field).rcall(point_p)) / d \| |---(g(rho*cos(theta), xi))|| \dxi /|xi=rho*sin(theta) """ is_commutative = False def __new__(cls, coord_sys, index, **kwargs): index = _sympify(index) obj = super().__new__(cls, coord_sys, index) obj._coord_sys = coord_sys obj._index = index return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def patch(self): return self.coord_sys.patch @property def manifold(self): return self.coord_sys.manifold @property def dim(self): return self.manifold.dim def __call__(self, scalar_field): """Apply on a scalar field. The action of a vector field on a scalar field is a directional differentiation. If the argument is not a scalar field an error is raised. """ if covariant_order(scalar_field) or contravariant_order(scalar_field): raise ValueError('Only scalar fields can be supplied as arguments to vector fields.') if scalar_field is None: return self base_scalars = list(scalar_field.atoms(BaseScalarField)) # First step: e_x(x+r**2) -> e_x(x) + 2*r*e_x(r) d_var = self._coord_sys._dummy # TODO: you need a real dummy function for the next line d_funcs = [Function('_#_%s' % i)(d_var) for i, b in enumerate(base_scalars)] d_result = scalar_field.subs(list(zip(base_scalars, d_funcs))) d_result = d_result.diff(d_var) # Second step: e_x(x) -> 1 and e_x(r) -> cos(atan2(x, y)) coords = self._coord_sys.symbols d_funcs_deriv = [f.diff(d_var) for f in d_funcs] d_funcs_deriv_sub = [] for b in base_scalars: jac = self._coord_sys.jacobian(b._coord_sys, coords) d_funcs_deriv_sub.append(jac[b._index, self._index]) d_result = d_result.subs(list(zip(d_funcs_deriv, d_funcs_deriv_sub))) # Remove the dummies result = d_result.subs(list(zip(d_funcs, base_scalars))) result = result.subs(list(zip(coords, self._coord_sys.coord_functions()))) return result.doit() def _find_coords(expr): # Finds CoordinateSystems existing in expr fields = expr.atoms(BaseScalarField, BaseVectorField) result = set() for f in fields: result.add(f._coord_sys) return result class Commutator(Expr): r"""Commutator of two vector fields. Explanation =========== The commutator of two vector fields `v_1` and `v_2` is defined as the vector field `[v_1, v_2]` that evaluated on each scalar field `f` is equal to `v_1(v_2(f)) - v_2(v_1(f))`. Examples ======== >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import Commutator >>> from sympy.simplify import simplify >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> e_r = R2_p.base_vector(0) >>> c_xy = Commutator(e_x, e_y) >>> c_xr = Commutator(e_x, e_r) >>> c_xy 0 Unfortunately, the current code is not able to compute everything: >>> c_xr Commutator(e_x, e_rho) >>> simplify(c_xr(fy**2)) -2*cos(theta)*y**2/(x**2 + y**2) """ def __new__(cls, v1, v2): if (covariant_order(v1) or contravariant_order(v1) != 1 or covariant_order(v2) or contravariant_order(v2) != 1): raise ValueError( 'Only commutators of vector fields are supported.') if v1 == v2: return S.Zero coord_sys = set().union(*[_find_coords(v) for v in (v1, v2)]) if len(coord_sys) == 1: # Only one coordinate systems is used, hence it is easy enough to # actually evaluate the commutator. if all(isinstance(v, BaseVectorField) for v in (v1, v2)): return S.Zero bases_1, bases_2 = [list(v.atoms(BaseVectorField)) for v in (v1, v2)] coeffs_1 = [v1.expand().coeff(b) for b in bases_1] coeffs_2 = [v2.expand().coeff(b) for b in bases_2] res = 0 for c1, b1 in zip(coeffs_1, bases_1): for c2, b2 in zip(coeffs_2, bases_2): res += c1*b1(c2)*b2 - c2*b2(c1)*b1 return res else: obj = super().__new__(cls, v1, v2) obj._v1 = v1 # deprecated assignment obj._v2 = v2 # deprecated assignment return obj @property def v1(self): return self.args[0] @property def v2(self): return self.args[1] def __call__(self, scalar_field): """Apply on a scalar field. If the argument is not a scalar field an error is raised. """ return self.v1(self.v2(scalar_field)) - self.v2(self.v1(scalar_field)) class Differential(Expr): r"""Return the differential (exterior derivative) of a form field. Explanation =========== The differential of a form (i.e. the exterior derivative) has a complicated definition in the general case. The differential `df` of the 0-form `f` is defined for any vector field `v` as `df(v) = v(f)`. Examples ======== >>> from sympy import Function >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import Differential >>> from sympy import pprint >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> g = Function('g') >>> s_field = g(fx, fy) >>> dg = Differential(s_field) >>> dg d(g(x, y)) >>> pprint(dg(e_x)) / d \| |---(g(xi, y))|| \dxi /|xi=x >>> pprint(dg(e_y)) / d \| |---(g(x, xi))|| \dxi /|xi=y Applying the exterior derivative operator twice always results in: >>> Differential(dg) 0 """ is_commutative = False def __new__(cls, form_field): if contravariant_order(form_field): raise ValueError( 'A vector field was supplied as an argument to Differential.') if isinstance(form_field, Differential): return S.Zero else: obj = super().__new__(cls, form_field) obj._form_field = form_field # deprecated assignment return obj @property def form_field(self): return self.args[0] def __call__(self, *vector_fields): """Apply on a list of vector_fields. Explanation =========== If the number of vector fields supplied is not equal to 1 + the order of the form field inside the differential the result is undefined. For 1-forms (i.e. differentials of scalar fields) the evaluation is done as `df(v)=v(f)`. However if `v` is ``None`` instead of a vector field, the differential is returned unchanged. This is done in order to permit partial contractions for higher forms. In the general case the evaluation is done by applying the form field inside the differential on a list with one less elements than the number of elements in the original list. Lowering the number of vector fields is achieved through replacing each pair of fields by their commutator. If the arguments are not vectors or ``None``s an error is raised. """ if any((contravariant_order(a) != 1 or covariant_order(a)) and a is not None for a in vector_fields): raise ValueError('The arguments supplied to Differential should be vector fields or Nones.') k = len(vector_fields) if k == 1: if vector_fields[0]: return vector_fields[0].rcall(self._form_field) return self else: # For higher form it is more complicated: # Invariant formula: # https://en.wikipedia.org/wiki/Exterior_derivative#Invariant_formula # df(v1, ... vn) = +/- vi(f(v1..no i..vn)) # +/- f([vi,vj],v1..no i, no j..vn) f = self._form_field v = vector_fields ret = 0 for i in range(k): t = v[i].rcall(f.rcall(*v[:i] + v[i + 1:])) ret += (-1)**i*t for j in range(i + 1, k): c = Commutator(v[i], v[j]) if c: # TODO this is ugly - the Commutator can be Zero and # this causes the next line to fail t = f.rcall(*(c,) + v[:i] + v[i + 1:j] + v[j + 1:]) ret += (-1)**(i + j)*t return ret class TensorProduct(Expr): """Tensor product of forms. Explanation =========== The tensor product permits the creation of multilinear functionals (i.e. higher order tensors) out of lower order fields (e.g. 1-forms and vector fields). However, the higher tensors thus created lack the interesting features provided by the other type of product, the wedge product, namely they are not antisymmetric and hence are not form fields. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> TensorProduct(dx, dy)(e_x, e_y) 1 >>> TensorProduct(dx, dy)(e_y, e_x) 0 >>> TensorProduct(dx, fx*dy)(fx*e_x, e_y) x**2 >>> TensorProduct(e_x, e_y)(fx**2, fy**2) 4*x*y >>> TensorProduct(e_y, dx)(fy) dx You can nest tensor products. >>> tp1 = TensorProduct(dx, dy) >>> TensorProduct(tp1, dx)(e_x, e_y, e_x) 1 You can make partial contraction for instance when 'raising an index'. Putting ``None`` in the second argument of ``rcall`` means that the respective position in the tensor product is left as it is. >>> TP = TensorProduct >>> metric = TP(dx, dx) + 3*TP(dy, dy) >>> metric.rcall(e_y, None) 3*dy Or automatically pad the args with ``None`` without specifying them. >>> metric.rcall(e_y) 3*dy """ def __new__(cls, *args): scalar = Mul(*[m for m in args if covariant_order(m) + contravariant_order(m) == 0]) multifields = [m for m in args if covariant_order(m) + contravariant_order(m)] if multifields: if len(multifields) == 1: return scalar*multifields[0] return scalar*super().__new__(cls, *multifields) else: return scalar def __call__(self, *fields): """Apply on a list of fields. If the number of input fields supplied is not equal to the order of the tensor product field, the list of arguments is padded with ``None``'s. The list of arguments is divided in sublists depending on the order of the forms inside the tensor product. The sublists are provided as arguments to these forms and the resulting expressions are given to the constructor of ``TensorProduct``. """ tot_order = covariant_order(self) + contravariant_order(self) tot_args = len(fields) if tot_args != tot_order: fields = list(fields) + [None]*(tot_order - tot_args) orders = [covariant_order(f) + contravariant_order(f) for f in self._args] indices = [sum(orders[:i + 1]) for i in range(len(orders) - 1)] fields = [fields[i:j] for i, j in zip([0] + indices, indices + [None])] multipliers = [t[0].rcall(*t[1]) for t in zip(self._args, fields)] return TensorProduct(*multipliers) class WedgeProduct(TensorProduct): """Wedge product of forms. Explanation =========== In the context of integration only completely antisymmetric forms make sense. The wedge product permits the creation of such forms. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import WedgeProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> WedgeProduct(dx, dy)(e_x, e_y) 1 >>> WedgeProduct(dx, dy)(e_y, e_x) -1 >>> WedgeProduct(dx, fx*dy)(fx*e_x, e_y) x**2 >>> WedgeProduct(e_x, e_y)(fy, None) -e_x You can nest wedge products. >>> wp1 = WedgeProduct(dx, dy) >>> WedgeProduct(wp1, dx)(e_x, e_y, e_x) 0 """ # TODO the calculation of signatures is slow # TODO you do not need all these permutations (neither the prefactor) def __call__(self, *fields): """Apply on a list of vector_fields. The expression is rewritten internally in terms of tensor products and evaluated.""" orders = (covariant_order(e) + contravariant_order(e) for e in self.args) mul = 1/Mul(*(factorial(o) for o in orders)) perms = permutations(fields) perms_par = (Permutation( p).signature() for p in permutations(list(range(len(fields))))) tensor_prod = TensorProduct(*self.args) return mul*Add(*[tensor_prod(*p[0])*p[1] for p in zip(perms, perms_par)]) class LieDerivative(Expr): """Lie derivative with respect to a vector field. Explanation =========== The transport operator that defines the Lie derivative is the pushforward of the field to be derived along the integral curve of the field with respect to which one derives. Examples ======== >>> from sympy.diffgeom.rn import R2_r, R2_p >>> from sympy.diffgeom import (LieDerivative, TensorProduct) >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> e_rho, e_theta = R2_p.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> LieDerivative(e_x, fy) 0 >>> LieDerivative(e_x, fx) 1 >>> LieDerivative(e_x, e_x) 0 The Lie derivative of a tensor field by another tensor field is equal to their commutator: >>> LieDerivative(e_x, e_rho) Commutator(e_x, e_rho) >>> LieDerivative(e_x + e_y, fx) 1 >>> tp = TensorProduct(dx, dy) >>> LieDerivative(e_x, tp) LieDerivative(e_x, TensorProduct(dx, dy)) >>> LieDerivative(e_x, tp) LieDerivative(e_x, TensorProduct(dx, dy)) """ def __new__(cls, v_field, expr): expr_form_ord = covariant_order(expr) if contravariant_order(v_field) != 1 or covariant_order(v_field): raise ValueError('Lie derivatives are defined only with respect to' ' vector fields. The supplied argument was not a ' 'vector field.') if expr_form_ord > 0: obj = super().__new__(cls, v_field, expr) # deprecated assignments obj._v_field = v_field obj._expr = expr return obj if expr.atoms(BaseVectorField): return Commutator(v_field, expr) else: return v_field.rcall(expr) @property def v_field(self): return self.args[0] @property def expr(self): return self.args[1] def __call__(self, *args): v = self.v_field expr = self.expr lead_term = v(expr(*args)) rest = Add(*[Mul(*args[:i] + (Commutator(v, args[i]),) + args[i + 1:]) for i in range(len(args))]) return lead_term - rest class BaseCovarDerivativeOp(Expr): """Covariant derivative operator with respect to a base vector. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import BaseCovarDerivativeOp >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> ch = metric_to_Christoffel_2nd(TP(dx, dx) + TP(dy, dy)) >>> ch [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> cvd = BaseCovarDerivativeOp(R2_r, 0, ch) >>> cvd(fx) 1 >>> cvd(fx*e_x) e_x """ def __new__(cls, coord_sys, index, christoffel): index = _sympify(index) christoffel = ImmutableDenseNDimArray(christoffel) obj = super().__new__(cls, coord_sys, index, christoffel) # deprecated assignments obj._coord_sys = coord_sys obj._index = index obj._christoffel = christoffel return obj @property def coord_sys(self): return self.args[0] @property def index(self): return self.args[1] @property def christoffel(self): return self.args[2] def __call__(self, field): """Apply on a scalar field. The action of a vector field on a scalar field is a directional differentiation. If the argument is not a scalar field the behaviour is undefined. """ if covariant_order(field) != 0: raise NotImplementedError() field = vectors_in_basis(field, self._coord_sys) wrt_vector = self._coord_sys.base_vector(self._index) wrt_scalar = self._coord_sys.coord_function(self._index) vectors = list(field.atoms(BaseVectorField)) # First step: replace all vectors with something susceptible to # derivation and do the derivation # TODO: you need a real dummy function for the next line d_funcs = [Function('_#_%s' % i)(wrt_scalar) for i, b in enumerate(vectors)] d_result = field.subs(list(zip(vectors, d_funcs))) d_result = wrt_vector(d_result) # Second step: backsubstitute the vectors in d_result = d_result.subs(list(zip(d_funcs, vectors))) # Third step: evaluate the derivatives of the vectors derivs = [] for v in vectors: d = Add(*[(self._christoffel[k, wrt_vector._index, v._index] *v._coord_sys.base_vector(k)) for k in range(v._coord_sys.dim)]) derivs.append(d) to_subs = [wrt_vector(d) for d in d_funcs] # XXX: This substitution can fail when there are Dummy symbols and the # cache is disabled: https://github.com/sympy/sympy/issues/17794 result = d_result.subs(list(zip(to_subs, derivs))) # Remove the dummies result = result.subs(list(zip(d_funcs, vectors))) return result.doit() class CovarDerivativeOp(Expr): """Covariant derivative operator. Examples ======== >>> from sympy.diffgeom.rn import R2_r >>> from sympy.diffgeom import CovarDerivativeOp >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> fx, fy = R2_r.base_scalars() >>> e_x, e_y = R2_r.base_vectors() >>> dx, dy = R2_r.base_oneforms() >>> ch = metric_to_Christoffel_2nd(TP(dx, dx) + TP(dy, dy)) >>> ch [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> cvd = CovarDerivativeOp(fx*e_x, ch) >>> cvd(fx) x >>> cvd(fx*e_x) x*e_x """ def __new__(cls, wrt, christoffel): if len({v._coord_sys for v in wrt.atoms(BaseVectorField)}) > 1: raise NotImplementedError() if contravariant_order(wrt) != 1 or covariant_order(wrt): raise ValueError('Covariant derivatives are defined only with ' 'respect to vector fields. The supplied argument ' 'was not a vector field.') obj = super().__new__(cls, wrt, christoffel) # deprecated assigments obj._wrt = wrt obj._christoffel = christoffel return obj @property def wrt(self): return self.args[0] @property def christoffel(self): return self.args[1] def __call__(self, field): vectors = list(self._wrt.atoms(BaseVectorField)) base_ops = [BaseCovarDerivativeOp(v._coord_sys, v._index, self._christoffel) for v in vectors] return self._wrt.subs(list(zip(vectors, base_ops))).rcall(field) ############################################################################### # Integral curves on vector fields ############################################################################### def intcurve_series(vector_field, param, start_point, n=6, coord_sys=None, coeffs=False): r"""Return the series expansion for an integral curve of the field. Explanation =========== Integral curve is a function `\gamma` taking a parameter in `R` to a point in the manifold. It verifies the equation: `V(f)\big(\gamma(t)\big) = \frac{d}{dt}f\big(\gamma(t)\big)` where the given ``vector_field`` is denoted as `V`. This holds for any value `t` for the parameter and any scalar field `f`. This equation can also be decomposed of a basis of coordinate functions `V(f_i)\big(\gamma(t)\big) = \frac{d}{dt}f_i\big(\gamma(t)\big) \quad \forall i` This function returns a series expansion of `\gamma(t)` in terms of the coordinate system ``coord_sys``. The equations and expansions are necessarily done in coordinate-system-dependent way as there is no other way to represent movement between points on the manifold (i.e. there is no such thing as a difference of points for a general manifold). Parameters ========== vector_field the vector field for which an integral curve will be given param the argument of the function `\gamma` from R to the curve start_point the point which corresponds to `\gamma(0)` n the order to which to expand coord_sys the coordinate system in which to expand coeffs (default False) - if True return a list of elements of the expansion Examples ======== Use the predefined R2 manifold: >>> from sympy.abc import t, x, y >>> from sympy.diffgeom.rn import R2_p, R2_r >>> from sympy.diffgeom import intcurve_series Specify a starting point and a vector field: >>> start_point = R2_r.point([x, y]) >>> vector_field = R2_r.e_x Calculate the series: >>> intcurve_series(vector_field, t, start_point, n=3) Matrix([ [t + x], [ y]]) Or get the elements of the expansion in a list: >>> series = intcurve_series(vector_field, t, start_point, n=3, coeffs=True) >>> series[0] Matrix([ [x], [y]]) >>> series[1] Matrix([ [t], [0]]) >>> series[2] Matrix([ [0], [0]]) The series in the polar coordinate system: >>> series = intcurve_series(vector_field, t, start_point, ... n=3, coord_sys=R2_p, coeffs=True) >>> series[0] Matrix([ [sqrt(x**2 + y**2)], [ atan2(y, x)]]) >>> series[1] Matrix([ [t*x/sqrt(x**2 + y**2)], [ -t*y/(x**2 + y**2)]]) >>> series[2] Matrix([ [t**2*(-x**2/(x**2 + y**2)**(3/2) + 1/sqrt(x**2 + y**2))/2], [ t**2*x*y/(x**2 + y**2)**2]]) See Also ======== intcurve_diffequ """ if contravariant_order(vector_field) != 1 or covariant_order(vector_field): raise ValueError('The supplied field was not a vector field.') def iter_vfield(scalar_field, i): """Return ``vector_field`` called `i` times on ``scalar_field``.""" return reduce(lambda s, v: v.rcall(s), [vector_field, ]*i, scalar_field) def taylor_terms_per_coord(coord_function): """Return the series for one of the coordinates.""" return [param**i*iter_vfield(coord_function, i).rcall(start_point)/factorial(i) for i in range(n)] coord_sys = coord_sys if coord_sys else start_point._coord_sys coord_functions = coord_sys.coord_functions() taylor_terms = [taylor_terms_per_coord(f) for f in coord_functions] if coeffs: return [Matrix(t) for t in zip(*taylor_terms)] else: return Matrix([sum(c) for c in taylor_terms]) def intcurve_diffequ(vector_field, param, start_point, coord_sys=None): r"""Return the differential equation for an integral curve of the field. Explanation =========== Integral curve is a function `\gamma` taking a parameter in `R` to a point in the manifold. It verifies the equation: `V(f)\big(\gamma(t)\big) = \frac{d}{dt}f\big(\gamma(t)\big)` where the given ``vector_field`` is denoted as `V`. This holds for any value `t` for the parameter and any scalar field `f`. This function returns the differential equation of `\gamma(t)` in terms of the coordinate system ``coord_sys``. The equations and expansions are necessarily done in coordinate-system-dependent way as there is no other way to represent movement between points on the manifold (i.e. there is no such thing as a difference of points for a general manifold). Parameters ========== vector_field the vector field for which an integral curve will be given param the argument of the function `\gamma` from R to the curve start_point the point which corresponds to `\gamma(0)` coord_sys the coordinate system in which to give the equations Returns ======= a tuple of (equations, initial conditions) Examples ======== Use the predefined R2 manifold: >>> from sympy.abc import t >>> from sympy.diffgeom.rn import R2, R2_p, R2_r >>> from sympy.diffgeom import intcurve_diffequ Specify a starting point and a vector field: >>> start_point = R2_r.point([0, 1]) >>> vector_field = -R2.y*R2.e_x + R2.x*R2.e_y Get the equation: >>> equations, init_cond = intcurve_diffequ(vector_field, t, start_point) >>> equations [f_1(t) + Derivative(f_0(t), t), -f_0(t) + Derivative(f_1(t), t)] >>> init_cond [f_0(0), f_1(0) - 1] The series in the polar coordinate system: >>> equations, init_cond = intcurve_diffequ(vector_field, t, start_point, R2_p) >>> equations [Derivative(f_0(t), t), Derivative(f_1(t), t) - 1] >>> init_cond [f_0(0) - 1, f_1(0) - pi/2] See Also ======== intcurve_series """ if contravariant_order(vector_field) != 1 or covariant_order(vector_field): raise ValueError('The supplied field was not a vector field.') coord_sys = coord_sys if coord_sys else start_point._coord_sys gammas = [Function('f_%d' % i)(param) for i in range( start_point._coord_sys.dim)] arbitrary_p = Point(coord_sys, gammas) coord_functions = coord_sys.coord_functions() equations = [simplify(diff(cf.rcall(arbitrary_p), param) - vector_field.rcall(cf).rcall(arbitrary_p)) for cf in coord_functions] init_cond = [simplify(cf.rcall(arbitrary_p).subs(param, 0) - cf.rcall(start_point)) for cf in coord_functions] return equations, init_cond ############################################################################### # Helpers ############################################################################### def dummyfy(args, exprs): # TODO Is this a good idea? d_args = Matrix([s.as_dummy() for s in args]) reps = dict(zip(args, d_args)) d_exprs = Matrix([_sympify(expr).subs(reps) for expr in exprs]) return d_args, d_exprs ############################################################################### # Helpers ############################################################################### def contravariant_order(expr, _strict=False): """Return the contravariant order of an expression. Examples ======== >>> from sympy.diffgeom import contravariant_order >>> from sympy.diffgeom.rn import R2 >>> from sympy.abc import a >>> contravariant_order(a) 0 >>> contravariant_order(a*R2.x + 2) 0 >>> contravariant_order(a*R2.x*R2.e_y + R2.e_x) 1 """ # TODO move some of this to class methods. # TODO rewrite using the .as_blah_blah methods if isinstance(expr, Add): orders = [contravariant_order(e) for e in expr.args] if len(set(orders)) != 1: raise ValueError('Misformed expression containing contravariant fields of varying order.') return orders[0] elif isinstance(expr, Mul): orders = [contravariant_order(e) for e in expr.args] not_zero = [o for o in orders if o != 0] if len(not_zero) > 1: raise ValueError('Misformed expression containing multiplication between vectors.') return 0 if not not_zero else not_zero[0] elif isinstance(expr, Pow): if covariant_order(expr.base) or covariant_order(expr.exp): raise ValueError( 'Misformed expression containing a power of a vector.') return 0 elif isinstance(expr, BaseVectorField): return 1 elif isinstance(expr, TensorProduct): return sum(contravariant_order(a) for a in expr.args) elif not _strict or expr.atoms(BaseScalarField): return 0 else: # If it does not contain anything related to the diffgeom module and it is _strict return -1 def covariant_order(expr, _strict=False): """Return the covariant order of an expression. Examples ======== >>> from sympy.diffgeom import covariant_order >>> from sympy.diffgeom.rn import R2 >>> from sympy.abc import a >>> covariant_order(a) 0 >>> covariant_order(a*R2.x + 2) 0 >>> covariant_order(a*R2.x*R2.dy + R2.dx) 1 """ # TODO move some of this to class methods. # TODO rewrite using the .as_blah_blah methods if isinstance(expr, Add): orders = [covariant_order(e) for e in expr.args] if len(set(orders)) != 1: raise ValueError('Misformed expression containing form fields of varying order.') return orders[0] elif isinstance(expr, Mul): orders = [covariant_order(e) for e in expr.args] not_zero = [o for o in orders if o != 0] if len(not_zero) > 1: raise ValueError('Misformed expression containing multiplication between forms.') return 0 if not not_zero else not_zero[0] elif isinstance(expr, Pow): if covariant_order(expr.base) or covariant_order(expr.exp): raise ValueError( 'Misformed expression containing a power of a form.') return 0 elif isinstance(expr, Differential): return covariant_order(*expr.args) + 1 elif isinstance(expr, TensorProduct): return sum(covariant_order(a) for a in expr.args) elif not _strict or expr.atoms(BaseScalarField): return 0 else: # If it does not contain anything related to the diffgeom module and it is _strict return -1 ############################################################################### # Coordinate transformation functions ############################################################################### def vectors_in_basis(expr, to_sys): """Transform all base vectors in base vectors of a specified coord basis. While the new base vectors are in the new coordinate system basis, any coefficients are kept in the old system. Examples ======== >>> from sympy.diffgeom import vectors_in_basis >>> from sympy.diffgeom.rn import R2_r, R2_p >>> vectors_in_basis(R2_r.e_x, R2_p) -y*e_theta/(x**2 + y**2) + x*e_rho/sqrt(x**2 + y**2) >>> vectors_in_basis(R2_p.e_r, R2_r) sin(theta)*e_y + cos(theta)*e_x """ vectors = list(expr.atoms(BaseVectorField)) new_vectors = [] for v in vectors: cs = v._coord_sys jac = cs.jacobian(to_sys, cs.coord_functions()) new = (jac.T*Matrix(to_sys.base_vectors()))[v._index] new_vectors.append(new) return expr.subs(list(zip(vectors, new_vectors))) ############################################################################### # Coordinate-dependent functions ############################################################################### def twoform_to_matrix(expr): """Return the matrix representing the twoform. For the twoform `w` return the matrix `M` such that `M[i,j]=w(e_i, e_j)`, where `e_i` is the i-th base vector field for the coordinate system in which the expression of `w` is given. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import twoform_to_matrix, TensorProduct >>> TP = TensorProduct >>> twoform_to_matrix(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) Matrix([ [1, 0], [0, 1]]) >>> twoform_to_matrix(R2.x*TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) Matrix([ [x, 0], [0, 1]]) >>> twoform_to_matrix(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy) - TP(R2.dx, R2.dy)/2) Matrix([ [ 1, 0], [-1/2, 1]]) """ if covariant_order(expr) != 2 or contravariant_order(expr): raise ValueError('The input expression is not a two-form.') coord_sys = _find_coords(expr) if len(coord_sys) != 1: raise ValueError('The input expression concerns more than one ' 'coordinate systems, hence there is no unambiguous ' 'way to choose a coordinate system for the matrix.') coord_sys = coord_sys.pop() vectors = coord_sys.base_vectors() expr = expr.expand() matrix_content = [[expr.rcall(v1, v2) for v1 in vectors] for v2 in vectors] return Matrix(matrix_content) def metric_to_Christoffel_1st(expr): """Return the nested list of Christoffel symbols for the given metric. This returns the Christoffel symbol of first kind that represents the Levi-Civita connection for the given metric. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Christoffel_1st, TensorProduct >>> TP = TensorProduct >>> metric_to_Christoffel_1st(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> metric_to_Christoffel_1st(R2.x*TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[1/2, 0], [0, 0]], [[0, 0], [0, 0]]] """ matrix = twoform_to_matrix(expr) if not matrix.is_symmetric(): raise ValueError( 'The two-form representing the metric is not symmetric.') coord_sys = _find_coords(expr).pop() deriv_matrices = [matrix.applyfunc(lambda a: d(a)) for d in coord_sys.base_vectors()] indices = list(range(coord_sys.dim)) christoffel = [[[(deriv_matrices[k][i, j] + deriv_matrices[j][i, k] - deriv_matrices[i][j, k])/2 for k in indices] for j in indices] for i in indices] return ImmutableDenseNDimArray(christoffel) def metric_to_Christoffel_2nd(expr): """Return the nested list of Christoffel symbols for the given metric. This returns the Christoffel symbol of second kind that represents the Levi-Civita connection for the given metric. Examples ======== >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Christoffel_2nd, TensorProduct >>> TP = TensorProduct >>> metric_to_Christoffel_2nd(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[0, 0], [0, 0]], [[0, 0], [0, 0]]] >>> metric_to_Christoffel_2nd(R2.x*TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[1/(2*x), 0], [0, 0]], [[0, 0], [0, 0]]] """ ch_1st = metric_to_Christoffel_1st(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) # XXX workaround, inverting a matrix does not work if it contains non # symbols #matrix = twoform_to_matrix(expr).inv() matrix = twoform_to_matrix(expr) s_fields = set() for e in matrix: s_fields.update(e.atoms(BaseScalarField)) s_fields = list(s_fields) dums = coord_sys.symbols matrix = matrix.subs(list(zip(s_fields, dums))).inv().subs(list(zip(dums, s_fields))) # XXX end of workaround christoffel = [[[Add(*[matrix[i, l]*ch_1st[l, j, k] for l in indices]) for k in indices] for j in indices] for i in indices] return ImmutableDenseNDimArray(christoffel) def metric_to_Riemann_components(expr): """Return the components of the Riemann tensor expressed in a given basis. Given a metric it calculates the components of the Riemann tensor in the canonical basis of the coordinate system in which the metric expression is given. Examples ======== >>> from sympy import exp >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Riemann_components, TensorProduct >>> TP = TensorProduct >>> metric_to_Riemann_components(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[[[0, 0], [0, 0]], [[0, 0], [0, 0]]], [[[0, 0], [0, 0]], [[0, 0], [0, 0]]]] >>> non_trivial_metric = exp(2*R2.r)*TP(R2.dr, R2.dr) + \ R2.r**2*TP(R2.dtheta, R2.dtheta) >>> non_trivial_metric exp(2*rho)*TensorProduct(drho, drho) + rho**2*TensorProduct(dtheta, dtheta) >>> riemann = metric_to_Riemann_components(non_trivial_metric) >>> riemann[0, :, :, :] [[[0, 0], [0, 0]], [[0, exp(-2*rho)*rho], [-exp(-2*rho)*rho, 0]]] >>> riemann[1, :, :, :] [[[0, -1/rho], [1/rho, 0]], [[0, 0], [0, 0]]] """ ch_2nd = metric_to_Christoffel_2nd(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) deriv_ch = [[[[d(ch_2nd[i, j, k]) for d in coord_sys.base_vectors()] for k in indices] for j in indices] for i in indices] riemann_a = [[[[deriv_ch[rho][sig][nu][mu] - deriv_ch[rho][sig][mu][nu] for nu in indices] for mu in indices] for sig in indices] for rho in indices] riemann_b = [[[[Add(*[ch_2nd[rho, l, mu]*ch_2nd[l, sig, nu] - ch_2nd[rho, l, nu]*ch_2nd[l, sig, mu] for l in indices]) for nu in indices] for mu in indices] for sig in indices] for rho in indices] riemann = [[[[riemann_a[rho][sig][mu][nu] + riemann_b[rho][sig][mu][nu] for nu in indices] for mu in indices] for sig in indices] for rho in indices] return ImmutableDenseNDimArray(riemann) def metric_to_Ricci_components(expr): """Return the components of the Ricci tensor expressed in a given basis. Given a metric it calculates the components of the Ricci tensor in the canonical basis of the coordinate system in which the metric expression is given. Examples ======== >>> from sympy import exp >>> from sympy.diffgeom.rn import R2 >>> from sympy.diffgeom import metric_to_Ricci_components, TensorProduct >>> TP = TensorProduct >>> metric_to_Ricci_components(TP(R2.dx, R2.dx) + TP(R2.dy, R2.dy)) [[0, 0], [0, 0]] >>> non_trivial_metric = exp(2*R2.r)*TP(R2.dr, R2.dr) + \ R2.r**2*TP(R2.dtheta, R2.dtheta) >>> non_trivial_metric exp(2*rho)*TensorProduct(drho, drho) + rho**2*TensorProduct(dtheta, dtheta) >>> metric_to_Ricci_components(non_trivial_metric) [[1/rho, 0], [0, exp(-2*rho)*rho]] """ riemann = metric_to_Riemann_components(expr) coord_sys = _find_coords(expr).pop() indices = list(range(coord_sys.dim)) ricci = [[Add(*[riemann[k, i, k, j] for k in indices]) for j in indices] for i in indices] return ImmutableDenseNDimArray(ricci) ############################################################################### # Classes for deprecation ############################################################################### class _deprecated_container: # This class gives deprecation warning. # When deprecated features are completely deleted, this should be removed as well. # See https://github.com/sympy/sympy/pull/19368 def __init__(self, feature, useinstead, issue, version, data): super().__init__(data) self.feature = feature self.useinstead = useinstead self.issue = issue self.version = version def warn(self): SymPyDeprecationWarning( feature=self.feature, useinstead=self.useinstead, issue=self.issue, deprecated_since_version=self.version).warn() def __iter__(self): self.warn() return super().__iter__() def __getitem__(self, key): self.warn() return super().__getitem__(key) def __contains__(self, key): self.warn() return super().__contains__(key) class _deprecated_list(_deprecated_container, list): pass class _deprecated_dict(_deprecated_container, dict): pass

e41fcf0c8e414118cb92fc5bd29ab382457035653c415a29bdf5ac158d9c48c9

""" AST nodes specific to the C family of languages """ from sympy.codegen.ast import ( Attribute, Declaration, Node, String, Token, Type, none, FunctionCall, CodeBlock ) from sympy.core.basic import Basic from sympy.core.containers import Tuple from sympy.core.sympify import sympify void = Type('void') restrict = Attribute('restrict') # guarantees no pointer aliasing volatile = Attribute('volatile') static = Attribute('static') def alignof(arg): """ Generate of FunctionCall instance for calling 'alignof' """ return FunctionCall('alignof', [String(arg) if isinstance(arg, str) else arg]) def sizeof(arg): """ Generate of FunctionCall instance for calling 'sizeof' Examples ======== >>> from sympy.codegen.ast import real >>> from sympy.codegen.cnodes import sizeof >>> from sympy.printing import ccode >>> ccode(sizeof(real)) 'sizeof(double)' """ return FunctionCall('sizeof', [String(arg) if isinstance(arg, str) else arg]) class CommaOperator(Basic): """ Represents the comma operator in C """ def __new__(cls, *args): return Basic.__new__(cls, *[sympify(arg) for arg in args]) class Label(Node): """ Label for use with e.g. goto statement. Examples ======== >>> from sympy import Symbol >>> from sympy.codegen.cnodes import Label, PreIncrement >>> from sympy.printing import ccode >>> print(ccode(Label('foo'))) foo: >>> print(ccode(Label('bar', [PreIncrement(Symbol('a'))]))) bar: ++(a); """ __slots__ = ('name', 'body') defaults = {'body': none} _construct_name = String @classmethod def _construct_body(cls, itr): if isinstance(itr, CodeBlock): return itr else: return CodeBlock(*itr) class goto(Token): """ Represents goto in C """ __slots__ = ('label',) _construct_label = Label class PreDecrement(Basic): """ Represents the pre-decrement operator Examples ======== >>> from sympy.abc import x >>> from sympy.codegen.cnodes import PreDecrement >>> from sympy.printing import ccode >>> ccode(PreDecrement(x)) '--(x)' """ nargs = 1 class PostDecrement(Basic): """ Represents the post-decrement operator """ nargs = 1 class PreIncrement(Basic): """ Represents the pre-increment operator """ nargs = 1 class PostIncrement(Basic): """ Represents the post-increment operator """ nargs = 1 class struct(Node): """ Represents a struct in C """ __slots__ = ('name', 'declarations') defaults = {'name': none} _construct_name = String @classmethod def _construct_declarations(cls, args): return Tuple(*[Declaration(arg) for arg in args]) class union(struct): """ Represents a union in C """

7ea671bab2fca64a2d592c8f137a7460a29848eb7c40afa0cb1c0176202f1380

import bisect import itertools from functools import reduce from collections import defaultdict from sympy import Indexed, IndexedBase, Tuple, Sum, Add, S, Integer, diagonalize_vector, DiagMatrix from sympy.combinatorics import Permutation from sympy.core.basic import Basic from sympy.core.compatibility import accumulate, default_sort_key from sympy.core.mul import Mul from sympy.core.sympify import _sympify from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.matrices.expressions import (MatAdd, MatMul, Trace, Transpose, MatrixSymbol) from sympy.matrices.expressions.matexpr import MatrixExpr, MatrixElement from sympy.tensor.array import NDimArray class _CodegenArrayAbstract(Basic): @property def subranks(self): """ Returns the ranks of the objects in the uppermost tensor product inside the current object. In case no tensor products are contained, return the atomic ranks. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayTensorProduct, CodegenArrayContraction >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> P = MatrixSymbol("P", 3, 3) Important: do not confuse the rank of the matrix with the rank of an array. >>> tp = CodegenArrayTensorProduct(M, N, P) >>> tp.subranks [2, 2, 2] >>> co = CodegenArrayContraction(tp, (1, 2), (3, 4)) >>> co.subranks [2, 2, 2] """ return self._subranks[:] def subrank(self): """ The sum of ``subranks``. """ return sum(self.subranks) @property def shape(self): return self._shape class CodegenArrayContraction(_CodegenArrayAbstract): r""" This class is meant to represent contractions of arrays in a form easily processable by the code printers. """ def __new__(cls, expr, *contraction_indices, **kwargs): contraction_indices = _sort_contraction_indices(contraction_indices) expr = _sympify(expr) if len(contraction_indices) == 0: return expr if isinstance(expr, CodegenArrayContraction): return cls._flatten(expr, *contraction_indices) obj = Basic.__new__(cls, expr, *contraction_indices) obj._subranks = _get_subranks(expr) obj._mapping = _get_mapping_from_subranks(obj._subranks) free_indices_to_position = {i: i for i in range(sum(obj._subranks)) if all([i not in cind for cind in contraction_indices])} obj._free_indices_to_position = free_indices_to_position shape = expr.shape cls._validate(expr, *contraction_indices) if shape: shape = tuple(shp for i, shp in enumerate(shape) if not any(i in j for j in contraction_indices)) obj._shape = shape return obj def __mul__(self, other): if other == 1: return self else: raise NotImplementedError("Product of N-dim arrays is not uniquely defined. Use another method.") def __rmul__(self, other): if other == 1: return self else: raise NotImplementedError("Product of N-dim arrays is not uniquely defined. Use another method.") @staticmethod def _validate(expr, *contraction_indices): shape = expr.shape if shape is None: return # Check that no contraction happens when the shape is mismatched: for i in contraction_indices: if len({shape[j] for j in i if shape[j] != -1}) != 1: raise ValueError("contracting indices of different dimensions") @classmethod def _push_indices_down(cls, contraction_indices, indices): flattened_contraction_indices = [j for i in contraction_indices for j in i] flattened_contraction_indices.sort() transform = _build_push_indices_down_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) @classmethod def _push_indices_up(cls, contraction_indices, indices): flattened_contraction_indices = [j for i in contraction_indices for j in i] flattened_contraction_indices.sort() transform = _build_push_indices_up_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) def split_multiple_contractions(self): """ Recognize multiple contractions and attempt at rewriting them as paired-contractions. """ from sympy import ask, Q contraction_indices = self.contraction_indices if isinstance(self.expr, CodegenArrayTensorProduct): args = list(self.expr.args) else: args = [self.expr] # TODO: unify API, best location in CodegenArrayTensorProduct subranks = [get_rank(i) for i in args] # TODO: unify API mapping = _get_mapping_from_subranks(subranks) reverse_mapping = {v:k for k, v in mapping.items()} new_contraction_indices = [] for indl, links in enumerate(contraction_indices): if len(links) <= 2: new_contraction_indices.append(links) continue # Check multiple contractions: # # Examples: # # * `A_ij b_j0 C_jk` ===> `A*DiagMatrix(b)*C` # # Care for: # - matrix being diagonalized (i.e. `A_ii`) # - vectors being diagonalized (i.e. `a_i0`) # Also consider the case of diagonal matrices being contracted: current_dimension = self.expr.shape[links[0]] tuple_links = [mapping[i] for i in links] arg_indices, arg_positions = zip(*tuple_links) args_updates = {} if len(arg_indices) != len(set(arg_indices)): # Maybe trace should be supported? raise NotImplementedError not_vectors = [] vectors = [] for arg_ind, arg_pos in tuple_links: mat = args[arg_ind] other_arg_pos = 1-arg_pos other_arg_abs = reverse_mapping[arg_ind, other_arg_pos] if (((1 not in mat.shape) and (not ask(Q.diagonal(mat)))) or ((current_dimension == 1) is True and mat.shape != (1, 1)) or any([other_arg_abs in l for li, l in enumerate(contraction_indices) if li != indl]) ): not_vectors.append((arg_ind, arg_pos)) continue args_updates[arg_ind] = diagonalize_vector(mat) vectors.append((arg_ind, arg_pos)) vectors.append((arg_ind, 1-arg_pos)) if len(not_vectors) > 2: new_contraction_indices.append(links) continue if len(not_vectors) == 0: new_sequence = vectors[:1] + vectors[2:] elif len(not_vectors) == 1: new_sequence = not_vectors[:1] + vectors[:-1] else: new_sequence = not_vectors[:1] + vectors + not_vectors[1:] for i in range(0, len(new_sequence) - 1, 2): arg1, pos1 = new_sequence[i] arg2, pos2 = new_sequence[i+1] if arg1 == arg2: raise NotImplementedError continue abspos1 = reverse_mapping[arg1, pos1] abspos2 = reverse_mapping[arg2, pos2] new_contraction_indices.append((abspos1, abspos2)) for ind, newarg in args_updates.items(): args[ind] = newarg return CodegenArrayContraction( CodegenArrayTensorProduct(*args), *new_contraction_indices ) def flatten_contraction_of_diagonal(self): if not isinstance(self.expr, CodegenArrayDiagonal): return self contraction_down = self.expr._push_indices_down(self.expr.diagonal_indices, self.contraction_indices) new_contraction_indices = [] diagonal_indices = self.expr.diagonal_indices[:] for i in contraction_down: contraction_group = list(i) for j in i: diagonal_with = [k for k in diagonal_indices if j in k] contraction_group.extend([l for k in diagonal_with for l in k]) diagonal_indices = [k for k in diagonal_indices if k not in diagonal_with] new_contraction_indices.append(sorted(set(contraction_group))) new_contraction_indices = CodegenArrayDiagonal._push_indices_up(diagonal_indices, new_contraction_indices) return CodegenArrayContraction( CodegenArrayDiagonal( self.expr.expr, *diagonal_indices ), *new_contraction_indices ) @staticmethod def _get_free_indices_to_position_map(free_indices, contraction_indices): free_indices_to_position = {} flattened_contraction_indices = [j for i in contraction_indices for j in i] counter = 0 for ind in free_indices: while counter in flattened_contraction_indices: counter += 1 free_indices_to_position[ind] = counter counter += 1 return free_indices_to_position @staticmethod def _get_index_shifts(expr): """ Get the mapping of indices at the positions before the contraction occurs. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(M, N), [1, 2]) >>> cg._get_index_shifts(cg) [0, 2] Indeed, ``cg`` after the contraction has two dimensions, 0 and 1. They need to be shifted by 0 and 2 to get the corresponding positions before the contraction (that is, 0 and 3). """ inner_contraction_indices = expr.contraction_indices all_inner = [j for i in inner_contraction_indices for j in i] all_inner.sort() # TODO: add API for total rank and cumulative rank: total_rank = _get_subrank(expr) inner_rank = len(all_inner) outer_rank = total_rank - inner_rank shifts = [0 for i in range(outer_rank)] counter = 0 pointer = 0 for i in range(outer_rank): while pointer < inner_rank and counter >= all_inner[pointer]: counter += 1 pointer += 1 shifts[i] += pointer counter += 1 return shifts @staticmethod def _convert_outer_indices_to_inner_indices(expr, *outer_contraction_indices): shifts = CodegenArrayContraction._get_index_shifts(expr) outer_contraction_indices = tuple(tuple(shifts[j] + j for j in i) for i in outer_contraction_indices) return outer_contraction_indices @staticmethod def _flatten(expr, *outer_contraction_indices): inner_contraction_indices = expr.contraction_indices outer_contraction_indices = CodegenArrayContraction._convert_outer_indices_to_inner_indices(expr, *outer_contraction_indices) contraction_indices = inner_contraction_indices + outer_contraction_indices return CodegenArrayContraction(expr.expr, *contraction_indices) def _get_contraction_tuples(self): r""" Return tuples containing the argument index and position within the argument of the index position. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(A, B), (1, 2)) >>> cg._get_contraction_tuples() [[(0, 1), (1, 0)]] Here the contraction pair `(1, 2)` meaning that the 2nd and 3rd indices of the tensor product `A\otimes B` are contracted, has been transformed into `(0, 1)` and `(1, 0)`, identifying the same indices in a different notation. `(0, 1)` is the second index (1) of the first argument (i.e. 0 or `A`). `(1, 0)` is the first index (i.e. 0) of the second argument (i.e. 1 or `B`). """ mapping = self._mapping return [[mapping[j] for j in i] for i in self.contraction_indices] @staticmethod def _contraction_tuples_to_contraction_indices(expr, contraction_tuples): # TODO: check that `expr` has `.subranks`: ranks = expr.subranks cumulative_ranks = [0] + list(accumulate(ranks)) return [tuple(cumulative_ranks[j]+k for j, k in i) for i in contraction_tuples] @property def free_indices(self): return self._free_indices[:] @property def free_indices_to_position(self): return dict(self._free_indices_to_position) @property def expr(self): return self.args[0] @property def contraction_indices(self): return self.args[1:] def _contraction_indices_to_components(self): expr = self.expr if not isinstance(expr, CodegenArrayTensorProduct): raise NotImplementedError("only for contractions of tensor products") ranks = expr.subranks mapping = {} counter = 0 for i, rank in enumerate(ranks): for j in range(rank): mapping[counter] = (i, j) counter += 1 return mapping def sort_args_by_name(self): """ Sort arguments in the tensor product so that their order is lexicographical. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) >>> cg = parse_matrix_expression(C*D*A*B) >>> cg CodegenArrayContraction(CodegenArrayTensorProduct(C, D, A, B), (1, 2), (3, 4), (5, 6)) >>> cg.sort_args_by_name() CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (0, 7), (1, 2), (5, 6)) """ expr = self.expr if not isinstance(expr, CodegenArrayTensorProduct): return self args = expr.args sorted_data = sorted(enumerate(args), key=lambda x: default_sort_key(x[1])) pos_sorted, args_sorted = zip(*sorted_data) reordering_map = {i: pos_sorted.index(i) for i, arg in enumerate(args)} contraction_tuples = self._get_contraction_tuples() contraction_tuples = [[(reordering_map[j], k) for j, k in i] for i in contraction_tuples] c_tp = CodegenArrayTensorProduct(*args_sorted) new_contr_indices = self._contraction_tuples_to_contraction_indices( c_tp, contraction_tuples ) return CodegenArrayContraction(c_tp, *new_contr_indices) def _get_contraction_links(self): r""" Returns a dictionary of links between arguments in the tensor product being contracted. See the example for an explanation of the values. Examples ======== >>> from sympy import MatrixSymbol >>> from sympy.abc import N >>> from sympy.codegen.array_utils import parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) Matrix multiplications are pairwise contractions between neighboring matrices: `A_{ij} B_{jk} C_{kl} D_{lm}` >>> cg = parse_matrix_expression(A*B*C*D) >>> cg CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (1, 2), (3, 4), (5, 6)) >>> cg._get_contraction_links() {0: {1: (1, 0)}, 1: {0: (0, 1), 1: (2, 0)}, 2: {0: (1, 1), 1: (3, 0)}, 3: {0: (2, 1)}} This dictionary is interpreted as follows: argument in position 0 (i.e. matrix `A`) has its second index (i.e. 1) contracted to `(1, 0)`, that is argument in position 1 (matrix `B`) on the first index slot of `B`, this is the contraction provided by the index `j` from `A`. The argument in position 1 (that is, matrix `B`) has two contractions, the ones provided by the indices `j` and `k`, respectively the first and second indices (0 and 1 in the sub-dict). The link `(0, 1)` and `(2, 0)` respectively. `(0, 1)` is the index slot 1 (the 2nd) of argument in position 0 (that is, `A_{\ldot j}`), and so on. """ args, dlinks = _get_contraction_links([self], self.subranks, *self.contraction_indices) return dlinks def get_shape(expr): if hasattr(expr, "shape"): return expr.shape return () class CodegenArrayTensorProduct(_CodegenArrayAbstract): r""" Class to represent the tensor product of array-like objects. """ def __new__(cls, *args): args = [_sympify(arg) for arg in args] args = cls._flatten(args) ranks = [_get_subrank(arg) for arg in args] if len(args) == 1: return args[0] # If there are contraction objects inside, transform the whole # expression into `CodegenArrayContraction`: contractions = {i: arg for i, arg in enumerate(args) if isinstance(arg, CodegenArrayContraction)} if contractions: cumulative_ranks = list(accumulate([0] + ranks))[:-1] tp = cls(*[arg.expr if isinstance(arg, CodegenArrayContraction) else arg for arg in args]) contraction_indices = [tuple(cumulative_ranks[i] + k for k in j) for i, arg in contractions.items() for j in arg.contraction_indices] return CodegenArrayContraction(tp, *contraction_indices) #newargs = [i for i in args if hasattr(i, "shape")] #coeff = reduce(lambda x, y: x*y, [i for i in args if not hasattr(i, "shape")], S.One) #newargs[0] *= coeff obj = Basic.__new__(cls, *args) obj._subranks = ranks shapes = [get_shape(i) for i in args] if any(i is None for i in shapes): obj._shape = None else: obj._shape = tuple(j for i in shapes for j in i) return obj @classmethod def _flatten(cls, args): args = [i for arg in args for i in (arg.args if isinstance(arg, cls) else [arg])] return args class CodegenArrayElementwiseAdd(_CodegenArrayAbstract): r""" Class for elementwise array additions. """ def __new__(cls, *args): args = [_sympify(arg) for arg in args] obj = Basic.__new__(cls, *args) ranks = [get_rank(arg) for arg in args] ranks = list(set(ranks)) if len(ranks) != 1: raise ValueError("summing arrays of different ranks") obj._subranks = ranks shapes = [arg.shape for arg in args] if len({i for i in shapes if i is not None}) > 1: raise ValueError("mismatching shapes in addition") if any(i is None for i in shapes): obj._shape = None else: obj._shape = shapes[0] return obj class CodegenArrayPermuteDims(_CodegenArrayAbstract): r""" Class to represent permutation of axes of arrays. Examples ======== >>> from sympy.codegen.array_utils import CodegenArrayPermuteDims >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> cg = CodegenArrayPermuteDims(M, [1, 0]) The object ``cg`` represents the transposition of ``M``, as the permutation ``[1, 0]`` will act on its indices by switching them: `M_{ij} \Rightarrow M_{ji}` This is evident when transforming back to matrix form: >>> from sympy.codegen.array_utils import recognize_matrix_expression >>> recognize_matrix_expression(cg) M.T >>> N = MatrixSymbol("N", 3, 2) >>> cg = CodegenArrayPermuteDims(N, [1, 0]) >>> cg.shape (2, 3) """ def __new__(cls, expr, permutation): from sympy.combinatorics import Permutation expr = _sympify(expr) permutation = Permutation(permutation) plist = permutation.array_form if plist == sorted(plist): return expr obj = Basic.__new__(cls, expr, permutation) obj._subranks = [get_rank(expr)] shape = expr.shape if shape is None: obj._shape = None else: obj._shape = tuple(shape[permutation(i)] for i in range(len(shape))) return obj @property def expr(self): return self.args[0] @property def permutation(self): return self.args[1] def nest_permutation(self): r""" Nest the permutation down the expression tree. Examples ======== >>> from sympy.codegen.array_utils import (CodegenArrayPermuteDims, CodegenArrayTensorProduct, nest_permutation) >>> from sympy import MatrixSymbol >>> M = MatrixSymbol("M", 3, 3) >>> N = MatrixSymbol("N", 3, 3) >>> cg = CodegenArrayPermuteDims(CodegenArrayTensorProduct(M, N), [1, 0, 3, 2]) >>> cg CodegenArrayPermuteDims(CodegenArrayTensorProduct(M, N), (0 1)(2 3)) >>> nest_permutation(cg) CodegenArrayTensorProduct(CodegenArrayPermuteDims(M, (0 1)), CodegenArrayPermuteDims(N, (0 1))) In ``cg`` both ``M`` and ``N`` are transposed. The cyclic representation of the permutation after the tensor product is `(0 1)(2 3)`. After nesting it down the expression tree, the usual transposition permutation `(0 1)` appears. """ expr = self.expr if isinstance(expr, CodegenArrayTensorProduct): # Check if the permutation keeps the subranks separated: subranks = expr.subranks subrank = expr.subrank() l = list(range(subrank)) p = [self.permutation(i) for i in l] dargs = {} counter = 0 for i, arg in zip(subranks, expr.args): p0 = p[counter:counter+i] counter += i s0 = sorted(p0) if not all([s0[j+1]-s0[j] == 1 for j in range(len(s0)-1)]): # Cross-argument permutations, impossible to nest the object: return self subpermutation = [p0.index(j) for j in s0] dargs[s0[0]] = CodegenArrayPermuteDims(arg, subpermutation) # Read the arguments sorting the according to the keys of the dict: args = [dargs[i] for i in sorted(dargs)] return CodegenArrayTensorProduct(*args) elif isinstance(expr, CodegenArrayContraction): # Invert tree hierarchy: put the contraction above. cycles = self.permutation.cyclic_form newcycles = CodegenArrayContraction._convert_outer_indices_to_inner_indices(expr, *cycles) newpermutation = Permutation(newcycles) new_contr_indices = [tuple(newpermutation(j) for j in i) for i in expr.contraction_indices] return CodegenArrayContraction(CodegenArrayPermuteDims(expr.expr, newpermutation), *new_contr_indices) elif isinstance(expr, CodegenArrayElementwiseAdd): return CodegenArrayElementwiseAdd(*[CodegenArrayPermuteDims(arg, self.permutation) for arg in expr.args]) return self def nest_permutation(expr): if isinstance(expr, CodegenArrayPermuteDims): return expr.nest_permutation() else: return expr class CodegenArrayDiagonal(_CodegenArrayAbstract): r""" Class to represent the diagonal operator. In a 2-dimensional array it returns the diagonal, this looks like the operation: `A_{ij} \rightarrow A_{ii}` The diagonal over axes 1 and 2 (the second and third) of the tensor product of two 2-dimensional arrays `A \otimes B` is `\Big[ A_{ab} B_{cd} \Big]_{abcd} \rightarrow \Big[ A_{ai} B_{id} \Big]_{adi}` In this last example the array expression has been reduced from 4-dimensional to 3-dimensional. Notice that no contraction has occurred, rather there is a new index `i` for the diagonal, contraction would have reduced the array to 2 dimensions. Notice that the diagonalized out dimensions are added as new dimensions at the end of the indices. """ def __new__(cls, expr, *diagonal_indices): expr = _sympify(expr) diagonal_indices = [Tuple(*sorted(i)) for i in diagonal_indices] if isinstance(expr, CodegenArrayDiagonal): return cls._flatten(expr, *diagonal_indices) shape = expr.shape if shape is not None: diagonal_indices = [i for i in diagonal_indices if len(i) > 1] cls._validate(expr, *diagonal_indices) #diagonal_indices = cls._remove_trivial_dimensions(shape, *diagonal_indices) # Get new shape: shp1 = tuple(shp for i,shp in enumerate(shape) if not any(i in j for j in diagonal_indices)) shp2 = tuple(shape[i[0]] for i in diagonal_indices) shape = shp1 + shp2 if len(diagonal_indices) == 0: return expr obj = Basic.__new__(cls, expr, *diagonal_indices) obj._subranks = _get_subranks(expr) obj._shape = shape return obj @staticmethod def _validate(expr, *diagonal_indices): # Check that no diagonalization happens on indices with mismatched # dimensions: shape = expr.shape for i in diagonal_indices: if len({shape[j] for j in i}) != 1: raise ValueError("diagonalizing indices of different dimensions") @staticmethod def _remove_trivial_dimensions(shape, *diagonal_indices): return [tuple(j for j in i) for i in diagonal_indices if shape[i[0]] != 1] @property def expr(self): return self.args[0] @property def diagonal_indices(self): return self.args[1:] @staticmethod def _flatten(expr, *outer_diagonal_indices): inner_diagonal_indices = expr.diagonal_indices all_inner = [j for i in inner_diagonal_indices for j in i] all_inner.sort() # TODO: add API for total rank and cumulative rank: total_rank = _get_subrank(expr) inner_rank = len(all_inner) outer_rank = total_rank - inner_rank shifts = [0 for i in range(outer_rank)] counter = 0 pointer = 0 for i in range(outer_rank): while pointer < inner_rank and counter >= all_inner[pointer]: counter += 1 pointer += 1 shifts[i] += pointer counter += 1 outer_diagonal_indices = tuple(tuple(shifts[j] + j for j in i) for i in outer_diagonal_indices) diagonal_indices = inner_diagonal_indices + outer_diagonal_indices return CodegenArrayDiagonal(expr.expr, *diagonal_indices) @classmethod def _push_indices_down(cls, diagonal_indices, indices): flattened_contraction_indices = [j for i in diagonal_indices for j in i[1:]] flattened_contraction_indices.sort() transform = _build_push_indices_down_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) @classmethod def _push_indices_up(cls, diagonal_indices, indices): flattened_contraction_indices = [j for i in diagonal_indices for j in i[1:]] flattened_contraction_indices.sort() transform = _build_push_indices_up_func_transformation(flattened_contraction_indices) return _apply_recursively_over_nested_lists(transform, indices) def transform_to_product(self): from sympy import ask, Q diagonal_indices = self.diagonal_indices if isinstance(self.expr, CodegenArrayContraction): # invert Diagonal and Contraction: diagonal_down = CodegenArrayContraction._push_indices_down( self.expr.contraction_indices, diagonal_indices ) newexpr = CodegenArrayDiagonal( self.expr.expr, *diagonal_down ).transform_to_product() contraction_up = newexpr._push_indices_up( diagonal_down, self.expr.contraction_indices ) return CodegenArrayContraction( newexpr, *contraction_up ) if not isinstance(self.expr, CodegenArrayTensorProduct): return self args = list(self.expr.args) # TODO: unify API subranks = [get_rank(i) for i in args] # TODO: unify API mapping = _get_mapping_from_subranks(subranks) new_contraction_indices = [] drop_diagonal_indices = [] for indl, links in enumerate(diagonal_indices): if len(links) > 2: continue # Also consider the case of diagonal matrices being contracted: current_dimension = self.expr.shape[links[0]] if current_dimension == 1: drop_diagonal_indices.append(indl) continue tuple_links = [mapping[i] for i in links] arg_indices, arg_positions = zip(*tuple_links) if len(arg_indices) != len(set(arg_indices)): # Maybe trace should be supported? raise NotImplementedError args_updates = {} count_nondiagonal = 0 last = None expression_is_square = False # Check that all args are vectors: for arg_ind, arg_pos in tuple_links: mat = args[arg_ind] if 1 in mat.shape and mat.shape != (1, 1): args_updates[arg_ind] = DiagMatrix(mat) last = arg_ind else: expression_is_square = True if not ask(Q.diagonal(mat)): count_nondiagonal += 1 if count_nondiagonal > 1: break if count_nondiagonal > 1: continue # TODO: if count_nondiagonal == 0 then the sub-expression can be recognized as HadamardProduct. for arg_ind, newmat in args_updates.items(): if not expression_is_square and arg_ind == last: continue #pass args[arg_ind] = newmat drop_diagonal_indices.append(indl) new_contraction_indices.append(links) new_diagonal_indices = CodegenArrayContraction._push_indices_up( new_contraction_indices, [e for i, e in enumerate(diagonal_indices) if i not in drop_diagonal_indices] ) return CodegenArrayDiagonal( CodegenArrayContraction( CodegenArrayTensorProduct(*args), *new_contraction_indices ), *new_diagonal_indices ) def get_rank(expr): if isinstance(expr, (MatrixExpr, MatrixElement)): return 2 if isinstance(expr, _CodegenArrayAbstract): return len(expr.shape) if isinstance(expr, NDimArray): return expr.rank() if isinstance(expr, Indexed): return expr.rank if isinstance(expr, IndexedBase): shape = expr.shape if shape is None: return -1 else: return len(shape) if isinstance(expr, _RecognizeMatOp): return expr.rank() if isinstance(expr, _RecognizeMatMulLines): return expr.rank() return 0 def _get_subrank(expr): if isinstance(expr, _CodegenArrayAbstract): return expr.subrank() return get_rank(expr) def _get_subranks(expr): if isinstance(expr, _CodegenArrayAbstract): return expr.subranks else: return [get_rank(expr)] def _get_mapping_from_subranks(subranks): mapping = {} counter = 0 for i, rank in enumerate(subranks): for j in range(rank): mapping[counter] = (i, j) counter += 1 return mapping def _get_contraction_links(args, subranks, *contraction_indices): mapping = _get_mapping_from_subranks(subranks) contraction_tuples = [[mapping[j] for j in i] for i in contraction_indices] dlinks = defaultdict(dict) for links in contraction_tuples: if len(links) == 2: (arg1, pos1), (arg2, pos2) = links dlinks[arg1][pos1] = (arg2, pos2) dlinks[arg2][pos2] = (arg1, pos1) continue return args, dict(dlinks) def _sort_contraction_indices(pairing_indices): pairing_indices = [Tuple(*sorted(i)) for i in pairing_indices] pairing_indices.sort(key=lambda x: min(x)) return pairing_indices def _get_diagonal_indices(flattened_indices): axes_contraction = defaultdict(list) for i, ind in enumerate(flattened_indices): if isinstance(ind, (int, Integer)): # If the indices is a number, there can be no diagonal operation: continue axes_contraction[ind].append(i) axes_contraction = {k: v for k, v in axes_contraction.items() if len(v) > 1} # Put the diagonalized indices at the end: ret_indices = [i for i in flattened_indices if i not in axes_contraction] diag_indices = list(axes_contraction) diag_indices.sort(key=lambda x: flattened_indices.index(x)) diagonal_indices = [tuple(axes_contraction[i]) for i in diag_indices] ret_indices += diag_indices ret_indices = tuple(ret_indices) return diagonal_indices, ret_indices def _get_argindex(subindices, ind): for i, sind in enumerate(subindices): if ind == sind: return i if isinstance(sind, (set, frozenset)) and ind in sind: return i raise IndexError("%s not found in %s" % (ind, subindices)) def _codegen_array_parse(expr): if isinstance(expr, Sum): function = expr.function summation_indices = expr.variables subexpr, subindices = _codegen_array_parse(function) # Check dimensional consistency: shape = subexpr.shape if shape: for ind, istart, iend in expr.limits: i = _get_argindex(subindices, ind) if istart != 0 or iend+1 != shape[i]: raise ValueError("summation index and array dimension mismatch: %s" % ind) contraction_indices = [] subindices = list(subindices) if isinstance(subexpr, CodegenArrayDiagonal): diagonal_indices = list(subexpr.diagonal_indices) dindices = subindices[-len(diagonal_indices):] subindices = subindices[:-len(diagonal_indices)] for index in summation_indices: if index in dindices: position = dindices.index(index) contraction_indices.append(diagonal_indices[position]) diagonal_indices[position] = None diagonal_indices = [i for i in diagonal_indices if i is not None] for i, ind in enumerate(subindices): if ind in summation_indices: pass if diagonal_indices: subexpr = CodegenArrayDiagonal(subexpr.expr, *diagonal_indices) else: subexpr = subexpr.expr axes_contraction = defaultdict(list) for i, ind in enumerate(subindices): if ind in summation_indices: axes_contraction[ind].append(i) subindices[i] = None for k, v in axes_contraction.items(): contraction_indices.append(tuple(v)) free_indices = [i for i in subindices if i is not None] indices_ret = list(free_indices) indices_ret.sort(key=lambda x: free_indices.index(x)) return CodegenArrayContraction( subexpr, *contraction_indices, free_indices=free_indices ), tuple(indices_ret) if isinstance(expr, Mul): args, indices = zip(*[_codegen_array_parse(arg) for arg in expr.args]) # Check if there are KroneckerDelta objects: kronecker_delta_repl = {} for arg in args: if not isinstance(arg, KroneckerDelta): continue # Diagonalize two indices: i, j = arg.indices kindices = set(arg.indices) if i in kronecker_delta_repl: kindices.update(kronecker_delta_repl[i]) if j in kronecker_delta_repl: kindices.update(kronecker_delta_repl[j]) kindices = frozenset(kindices) for index in kindices: kronecker_delta_repl[index] = kindices # Remove KroneckerDelta objects, their relations should be handled by # CodegenArrayDiagonal: newargs = [] newindices = [] for arg, loc_indices in zip(args, indices): if isinstance(arg, KroneckerDelta): continue newargs.append(arg) newindices.append(loc_indices) flattened_indices = [kronecker_delta_repl.get(j, j) for i in newindices for j in i] diagonal_indices, ret_indices = _get_diagonal_indices(flattened_indices) tp = CodegenArrayTensorProduct(*newargs) if diagonal_indices: return (CodegenArrayDiagonal(tp, *diagonal_indices), ret_indices) else: return tp, ret_indices if isinstance(expr, MatrixElement): indices = expr.args[1:] diagonal_indices, ret_indices = _get_diagonal_indices(indices) if diagonal_indices: return (CodegenArrayDiagonal(expr.args[0], *diagonal_indices), ret_indices) else: return expr.args[0], ret_indices if isinstance(expr, Indexed): indices = expr.indices diagonal_indices, ret_indices = _get_diagonal_indices(indices) if diagonal_indices: return (CodegenArrayDiagonal(expr.base, *diagonal_indices), ret_indices) else: return expr.args[0], ret_indices if isinstance(expr, IndexedBase): raise NotImplementedError if isinstance(expr, KroneckerDelta): return expr, expr.indices if isinstance(expr, Add): args, indices = zip(*[_codegen_array_parse(arg) for arg in expr.args]) args = list(args) # Check if all indices are compatible. Otherwise expand the dimensions: index0set = set(indices[0]) index0 = indices[0] for i in range(1, len(args)): if set(indices[i]) != index0set: raise NotImplementedError("indices must be the same") permutation = Permutation([index0.index(j) for j in indices[i]]) # Perform index permutations: args[i] = CodegenArrayPermuteDims(args[i], permutation) return CodegenArrayElementwiseAdd(*args), index0 return expr, () def parse_matrix_expression(expr: MatrixExpr) -> Basic: if isinstance(expr, MatMul): args_nonmat = [] args = [] for arg in expr.args: if isinstance(arg, MatrixExpr): args.append(arg) else: args_nonmat.append(arg) contractions = [(2*i+1, 2*i+2) for i in range(len(args)-1)] scalar = Mul.fromiter(args_nonmat) if scalar == 1: tprod = CodegenArrayTensorProduct( *[parse_matrix_expression(arg) for arg in args]) else: tprod = CodegenArrayTensorProduct( scalar, *[parse_matrix_expression(arg) for arg in args]) return CodegenArrayContraction( tprod, *contractions ) elif isinstance(expr, MatAdd): return CodegenArrayElementwiseAdd( *[parse_matrix_expression(arg) for arg in expr.args] ) elif isinstance(expr, Transpose): return CodegenArrayPermuteDims( parse_matrix_expression(expr.args[0]), [1, 0] ) elif isinstance(expr, Trace): inner_expr = parse_matrix_expression(expr.arg) return CodegenArrayContraction(inner_expr, (0, len(inner_expr.shape) - 1)) else: return expr def parse_indexed_expression(expr, first_indices=None): r""" Parse indexed expression into a form useful for code generation. Examples ======== >>> from sympy.codegen.array_utils import parse_indexed_expression >>> from sympy import MatrixSymbol, Sum, symbols >>> i, j, k, d = symbols("i j k d") >>> M = MatrixSymbol("M", d, d) >>> N = MatrixSymbol("N", d, d) Recognize the trace in summation form: >>> expr = Sum(M[i, i], (i, 0, d-1)) >>> parse_indexed_expression(expr) CodegenArrayContraction(M, (0, 1)) Recognize the extraction of the diagonal by using the same index `i` on both axes of the matrix: >>> expr = M[i, i] >>> parse_indexed_expression(expr) CodegenArrayDiagonal(M, (0, 1)) This function can help perform the transformation expressed in two different mathematical notations as: `\sum_{j=0}^{N-1} A_{i,j} B_{j,k} \Longrightarrow \mathbf{A}\cdot \mathbf{B}` Recognize the matrix multiplication in summation form: >>> expr = Sum(M[i, j]*N[j, k], (j, 0, d-1)) >>> parse_indexed_expression(expr) CodegenArrayContraction(CodegenArrayTensorProduct(M, N), (1, 2)) Specify that ``k`` has to be the starting index: >>> parse_indexed_expression(expr, first_indices=[k]) CodegenArrayPermuteDims(CodegenArrayContraction(CodegenArrayTensorProduct(M, N), (1, 2)), (0 1)) """ result, indices = _codegen_array_parse(expr) if not first_indices: return result for i in first_indices: if i not in indices: first_indices.remove(i) #raise ValueError("index %s not found or not a free index" % i) first_indices.extend([i for i in indices if i not in first_indices]) permutation = [first_indices.index(i) for i in indices] return CodegenArrayPermuteDims(result, permutation) def _has_multiple_lines(expr): if isinstance(expr, _RecognizeMatMulLines): return True if isinstance(expr, _RecognizeMatOp): return expr.multiple_lines return False class _RecognizeMatOp: """ Class to help parsing matrix multiplication lines. """ def __init__(self, operator, args): self.operator = operator self.args = args if any(_has_multiple_lines(arg) for arg in args): multiple_lines = True else: multiple_lines = False self.multiple_lines = multiple_lines def rank(self): if self.operator == Trace: return 0 # TODO: check return 2 def __repr__(self): op = self.operator if op == MatMul: s = "*" elif op == MatAdd: s = "+" else: s = op.__name__ return "_RecognizeMatOp(%s, %s)" % (s, repr(self.args)) return "_RecognizeMatOp(%s)" % (s.join(repr(i) for i in self.args)) def __eq__(self, other): if not isinstance(other, type(self)): return False if self.operator != other.operator: return False if self.args != other.args: return False return True def __iter__(self): return iter(self.args) class _RecognizeMatMulLines(list): """ This class handles multiple parsed multiplication lines. """ def __new__(cls, args): if len(args) == 1: return args[0] return list.__new__(cls, args) def rank(self): return reduce(lambda x, y: x*y, [get_rank(i) for i in self], S.One) def __repr__(self): return "_RecognizeMatMulLines(%s)" % super().__repr__() def _support_function_tp1_recognize(contraction_indices, args): if not isinstance(args, list): args = [args] subranks = [get_rank(i) for i in args] coeff = reduce(lambda x, y: x*y, [arg for arg, srank in zip(args, subranks) if srank == 0], S.One) mapping = _get_mapping_from_subranks(subranks) reverse_mapping = {v:k for k, v in mapping.items()} args, dlinks = _get_contraction_links(args, subranks, *contraction_indices) flatten_contractions = [j for i in contraction_indices for j in i] total_rank = sum(subranks) # TODO: turn `free_indices` into a list? free_indices = {i: i for i in range(total_rank) if i not in flatten_contractions} return_list = [] while dlinks: if free_indices: first_index, starting_argind = min(free_indices.items(), key=lambda x: x[1]) free_indices.pop(first_index) starting_argind, starting_pos = mapping[starting_argind] else: # Maybe a Trace first_index = None starting_argind = min(dlinks) starting_pos = 0 current_argind, current_pos = starting_argind, starting_pos matmul_args = [] last_index = None while True: elem = args[current_argind] if current_pos == 1: elem = _RecognizeMatOp(Transpose, [elem]) matmul_args.append(elem) other_pos = 1 - current_pos if current_argind not in dlinks: other_absolute = reverse_mapping[current_argind, other_pos] free_indices.pop(other_absolute, None) break link_dict = dlinks.pop(current_argind) if other_pos not in link_dict: if free_indices: last_index = [i for i, j in free_indices.items() if mapping[j] == (current_argind, other_pos)][0] else: last_index = None break if len(link_dict) > 2: raise NotImplementedError("not a matrix multiplication line") # Get the last element of `link_dict` as the next link. The last # element is the correct start for trace expressions: current_argind, current_pos = link_dict[other_pos] if current_argind == starting_argind: # This is a trace: if len(matmul_args) > 1: matmul_args = [_RecognizeMatOp(Trace, [_RecognizeMatOp(MatMul, matmul_args)])] elif args[current_argind].shape != (1, 1): matmul_args = [_RecognizeMatOp(Trace, matmul_args)] break dlinks.pop(starting_argind, None) free_indices.pop(last_index, None) return_list.append(_RecognizeMatOp(MatMul, matmul_args)) if coeff != 1: # Let's inject the coefficient: return_list[0].args.insert(0, coeff) return _RecognizeMatMulLines(return_list) def recognize_matrix_expression(expr): r""" Recognize matrix expressions in codegen objects. If more than one matrix multiplication line have been detected, return a list with the matrix expressions. Examples ======== >>> from sympy import MatrixSymbol, Sum >>> from sympy.abc import i, j, k, l, N >>> from sympy.codegen.array_utils import CodegenArrayContraction, CodegenArrayTensorProduct >>> from sympy.codegen.array_utils import recognize_matrix_expression, parse_indexed_expression, parse_matrix_expression >>> A = MatrixSymbol("A", N, N) >>> B = MatrixSymbol("B", N, N) >>> C = MatrixSymbol("C", N, N) >>> D = MatrixSymbol("D", N, N) >>> expr = Sum(A[i, j]*B[j, k], (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) A*B >>> cg = parse_indexed_expression(expr, first_indices=[k]) >>> recognize_matrix_expression(cg) (A*B).T Transposition is detected: >>> expr = Sum(A[j, i]*B[j, k], (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) A.T*B >>> cg = parse_indexed_expression(expr, first_indices=[k]) >>> recognize_matrix_expression(cg) (A.T*B).T Detect the trace: >>> expr = Sum(A[i, i], (i, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) Trace(A) Recognize some more complex traces: >>> expr = Sum(A[i, j]*B[j, i], (i, 0, N-1), (j, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) Trace(A*B) More complicated expressions: >>> expr = Sum(A[i, j]*B[k, j]*A[l, k], (j, 0, N-1), (k, 0, N-1)) >>> cg = parse_indexed_expression(expr) >>> recognize_matrix_expression(cg) A*B.T*A.T Expressions constructed from matrix expressions do not contain literal indices, the positions of free indices are returned instead: >>> expr = A*B >>> cg = parse_matrix_expression(expr) >>> recognize_matrix_expression(cg) A*B If more than one line of matrix multiplications is detected, return separate matrix multiplication factors: >>> cg = CodegenArrayContraction(CodegenArrayTensorProduct(A, B, C, D), (1, 2), (5, 6)) >>> recognize_matrix_expression(cg) [A*B, C*D] The two lines have free indices at axes 0, 3 and 4, 7, respectively. """ # TODO: expr has to be a CodegenArray... type rec = _recognize_matrix_expression(expr) return _unfold_recognized_expr(rec) def _recognize_matrix_expression(expr): if isinstance(expr, CodegenArrayContraction): # Apply some transformations: expr = expr.flatten_contraction_of_diagonal() expr = expr.split_multiple_contractions() args = _recognize_matrix_expression(expr.expr) contraction_indices = expr.contraction_indices if isinstance(args, _RecognizeMatOp) and args.operator == MatAdd: addends = [] for arg in args.args: addends.append(_support_function_tp1_recognize(contraction_indices, arg)) return _RecognizeMatOp(MatAdd, addends) elif isinstance(args, _RecognizeMatMulLines): return _support_function_tp1_recognize(contraction_indices, args) return _support_function_tp1_recognize(contraction_indices, [args]) elif isinstance(expr, CodegenArrayElementwiseAdd): add_args = [] for arg in expr.args: add_args.append(_recognize_matrix_expression(arg)) return _RecognizeMatOp(MatAdd, add_args) elif isinstance(expr, (MatrixSymbol, IndexedBase)): return expr elif isinstance(expr, CodegenArrayPermuteDims): if expr.permutation.array_form == [1, 0]: return _RecognizeMatOp(Transpose, [_recognize_matrix_expression(expr.expr)]) elif isinstance(expr.expr, CodegenArrayTensorProduct): ranks = expr.expr.subranks newrange = [expr.permutation(i) for i in range(sum(ranks))] newpos = [] counter = 0 for rank in ranks: newpos.append(newrange[counter:counter+rank]) counter += rank newargs = [] for pos, arg in zip(newpos, expr.expr.args): if pos == sorted(pos): newargs.append((_recognize_matrix_expression(arg), pos[0])) elif len(pos) == 2: newargs.append((_RecognizeMatOp(Transpose, [_recognize_matrix_expression(arg)]), pos[0])) else: raise NotImplementedError newargs.sort(key=lambda x: x[1]) newargs = [i[0] for i in newargs] return _RecognizeMatMulLines(newargs) else: raise NotImplementedError elif isinstance(expr, CodegenArrayTensorProduct): args = [_recognize_matrix_expression(arg) for arg in expr.args] multiple_lines = [_has_multiple_lines(arg) for arg in args] if any(multiple_lines): if any(a.operator != MatAdd for i, a in enumerate(args) if multiple_lines[i] and isinstance(a, _RecognizeMatOp)): raise NotImplementedError getargs = lambda x: x.args if isinstance(x, _RecognizeMatOp) else list(x) expand_args = [getargs(arg) if multiple_lines[i] else [arg] for i, arg in enumerate(args)] it = itertools.product(*expand_args) ret = _RecognizeMatOp(MatAdd, [_RecognizeMatMulLines([k for j in i for k in (j if isinstance(j, _RecognizeMatMulLines) else [j])]) for i in it]) return ret return _RecognizeMatMulLines(args) elif isinstance(expr, CodegenArrayDiagonal): pexpr = expr.transform_to_product() if expr == pexpr: return expr return _recognize_matrix_expression(pexpr) elif isinstance(expr, Transpose): return expr elif isinstance(expr, MatrixExpr): return expr return expr def _suppress_trivial_dims_in_tensor_product(mat_list): # Recognize expressions like [x, y] with shape (k, 1, k, 1) as `x*y.T`. # The matrix expression has to be equivalent to the tensor product of the matrices, with trivial dimensions (i.e. dim=1) dropped. # That is, add contractions over trivial dimensions: mat_11 = [] mat_k1 = [] for mat in mat_list: if mat.shape == (1, 1): mat_11.append(mat) elif 1 in mat.shape: if mat.shape[0] == 1: mat_k1.append(mat.T) else: mat_k1.append(mat) else: return mat_list if len(mat_k1) > 2: return mat_list a = MatMul.fromiter(mat_k1[:1]) b = MatMul.fromiter(mat_k1[1:]) x = MatMul.fromiter(mat_11) return a*x*b.T def _unfold_recognized_expr(expr): if isinstance(expr, _RecognizeMatOp): return expr.operator(*[_unfold_recognized_expr(i) for i in expr.args]) elif isinstance(expr, _RecognizeMatMulLines): unfolded = [_unfold_recognized_expr(i) for i in expr] mat_list = [i for i in unfolded if isinstance(i, MatrixExpr)] scalar_list = [i for i in unfolded if i not in mat_list] scalar = Mul.fromiter(scalar_list) mat_list = [i.doit() for i in mat_list] mat_list = [i for i in mat_list if not (i.shape == (1, 1) and i.is_Identity)] if mat_list: mat_list[0] *= scalar if len(mat_list) == 1: return mat_list[0].doit() else: return _suppress_trivial_dims_in_tensor_product(mat_list) else: return scalar else: return expr def _apply_recursively_over_nested_lists(func, arr): if isinstance(arr, (tuple, list, Tuple)): return tuple(_apply_recursively_over_nested_lists(func, i) for i in arr) elif isinstance(arr, Tuple): return Tuple.fromiter(_apply_recursively_over_nested_lists(func, i) for i in arr) else: return func(arr) def _build_push_indices_up_func_transformation(flattened_contraction_indices): shifts = {0: 0} i = 0 cumulative = 0 while i < len(flattened_contraction_indices): j = 1 while i+j < len(flattened_contraction_indices): if flattened_contraction_indices[i] + j != flattened_contraction_indices[i+j]: break j += 1 cumulative += j shifts[flattened_contraction_indices[i]] = cumulative i += j shift_keys = sorted(shifts.keys()) def func(idx): return shifts[shift_keys[bisect.bisect_right(shift_keys, idx)-1]] def transform(j): if j in flattened_contraction_indices: return None else: return j - func(j) return transform def _build_push_indices_down_func_transformation(flattened_contraction_indices): N = flattened_contraction_indices[-1]+2 shifts = [i for i in range(N) if i not in flattened_contraction_indices] def transform(j): if j < len(shifts): return shifts[j] else: return j + shifts[-1] - len(shifts) + 1 return transform

9a00e866fba102613418c91f5e9295fef7da15cefed39ca180fb376eea1fb675

""" Additional AST nodes for operations on matrices. The nodes in this module are meant to represent optimization of matrix expressions within codegen's target languages that cannot be represented by SymPy expressions. As an example, we can use :meth:`sympy.codegen.rewriting.optimize` and the ``matin_opt`` optimization provided in :mod:`sympy.codegen.rewriting` to transform matrix multiplication under certain assumptions: >>> from sympy import symbols, MatrixSymbol >>> n = symbols('n', integer=True) >>> A = MatrixSymbol('A', n, n) >>> x = MatrixSymbol('x', n, 1) >>> expr = A**(-1) * x >>> from sympy.assumptions import assuming, Q >>> from sympy.codegen.rewriting import matinv_opt, optimize >>> with assuming(Q.fullrank(A)): ... optimize(expr, [matinv_opt]) MatrixSolve(A, vector=x) """ from .ast import Token from sympy.matrices import MatrixExpr from sympy.core.sympify import sympify class MatrixSolve(Token, MatrixExpr): """Represents an operation to solve a linear matrix equation. Parameters ========== matrix : MatrixSymbol Matrix representing the coefficients of variables in the linear equation. This matrix must be square and full-rank (i.e. all columns must be linearly independent) for the solving operation to be valid. vector : MatrixSymbol One-column matrix representing the solutions to the equations represented in ``matrix``. Examples ======== >>> from sympy import symbols, MatrixSymbol >>> from sympy.codegen.matrix_nodes import MatrixSolve >>> n = symbols('n', integer=True) >>> A = MatrixSymbol('A', n, n) >>> x = MatrixSymbol('x', n, 1) >>> from sympy.printing.pycode import NumPyPrinter >>> NumPyPrinter().doprint(MatrixSolve(A, x)) 'numpy.linalg.solve(A, x)' >>> from sympy.printing import octave_code >>> octave_code(MatrixSolve(A, x)) 'A \\\\ x' """ __slots__ = ('matrix', 'vector') _construct_matrix = staticmethod(sympify) @property def shape(self): return self.vector.shape

af2a3731ef0028c090a6a0908bd2ba653a6c17a26cec5b11a4473d1ab5369c2b

""" This file contains some classical ciphers and routines implementing a linear-feedback shift register (LFSR) and the Diffie-Hellman key exchange. .. warning:: This module is intended for educational purposes only. Do not use the functions in this module for real cryptographic applications. If you wish to encrypt real data, we recommend using something like the `cryptography <https://cryptography.io/en/latest/>`_ module. """ from string import whitespace, ascii_uppercase as uppercase, printable from functools import reduce import warnings from itertools import cycle from sympy import nextprime from sympy.core import Rational, Symbol from sympy.core.numbers import igcdex, mod_inverse, igcd from sympy.core.compatibility import as_int from sympy.matrices import Matrix from sympy.ntheory import isprime, primitive_root, factorint from sympy.polys.domains import FF from sympy.polys.polytools import gcd, Poly from sympy.utilities.misc import filldedent, translate from sympy.utilities.iterables import uniq, multiset from sympy.testing.randtest import _randrange, _randint class NonInvertibleCipherWarning(RuntimeWarning): """A warning raised if the cipher is not invertible.""" def __init__(self, msg): self.fullMessage = msg def __str__(self): return '\n\t' + self.fullMessage def warn(self, stacklevel=2): warnings.warn(self, stacklevel=stacklevel) def AZ(s=None): """Return the letters of ``s`` in uppercase. In case more than one string is passed, each of them will be processed and a list of upper case strings will be returned. Examples ======== >>> from sympy.crypto.crypto import AZ >>> AZ('Hello, world!') 'HELLOWORLD' >>> AZ('Hello, world!'.split()) ['HELLO', 'WORLD'] See Also ======== check_and_join """ if not s: return uppercase t = type(s) is str if t: s = [s] rv = [check_and_join(i.upper().split(), uppercase, filter=True) for i in s] if t: return rv[0] return rv bifid5 = AZ().replace('J', '') bifid6 = AZ() + '0123456789' bifid10 = printable def padded_key(key, symbols): """Return a string of the distinct characters of ``symbols`` with those of ``key`` appearing first. A ValueError is raised if a) there are duplicate characters in ``symbols`` or b) there are characters in ``key`` that are not in ``symbols``. Examples ======== >>> from sympy.crypto.crypto import padded_key >>> padded_key('PUPPY', 'OPQRSTUVWXY') 'PUYOQRSTVWX' >>> padded_key('RSA', 'ARTIST') Traceback (most recent call last): ... ValueError: duplicate characters in symbols: T """ syms = list(uniq(symbols)) if len(syms) != len(symbols): extra = ''.join(sorted({ i for i in symbols if symbols.count(i) > 1})) raise ValueError('duplicate characters in symbols: %s' % extra) extra = set(key) - set(syms) if extra: raise ValueError( 'characters in key but not symbols: %s' % ''.join( sorted(extra))) key0 = ''.join(list(uniq(key))) # remove from syms characters in key0 return key0 + translate(''.join(syms), None, key0) def check_and_join(phrase, symbols=None, filter=None): """ Joins characters of ``phrase`` and if ``symbols`` is given, raises an error if any character in ``phrase`` is not in ``symbols``. Parameters ========== phrase String or list of strings to be returned as a string. symbols Iterable of characters allowed in ``phrase``. If ``symbols`` is ``None``, no checking is performed. Examples ======== >>> from sympy.crypto.crypto import check_and_join >>> check_and_join('a phrase') 'a phrase' >>> check_and_join('a phrase'.upper().split()) 'APHRASE' >>> check_and_join('a phrase!'.upper().split(), 'ARE', filter=True) 'ARAE' >>> check_and_join('a phrase!'.upper().split(), 'ARE') Traceback (most recent call last): ... ValueError: characters in phrase but not symbols: "!HPS" """ rv = ''.join(''.join(phrase)) if symbols is not None: symbols = check_and_join(symbols) missing = ''.join(list(sorted(set(rv) - set(symbols)))) if missing: if not filter: raise ValueError( 'characters in phrase but not symbols: "%s"' % missing) rv = translate(rv, None, missing) return rv def _prep(msg, key, alp, default=None): if not alp: if not default: alp = AZ() msg = AZ(msg) key = AZ(key) else: alp = default else: alp = ''.join(alp) key = check_and_join(key, alp, filter=True) msg = check_and_join(msg, alp, filter=True) return msg, key, alp def cycle_list(k, n): """ Returns the elements of the list ``range(n)`` shifted to the left by ``k`` (so the list starts with ``k`` (mod ``n``)). Examples ======== >>> from sympy.crypto.crypto import cycle_list >>> cycle_list(3, 10) [3, 4, 5, 6, 7, 8, 9, 0, 1, 2] """ k = k % n return list(range(k, n)) + list(range(k)) ######## shift cipher examples ############ def encipher_shift(msg, key, symbols=None): """ Performs shift cipher encryption on plaintext msg, and returns the ciphertext. Parameters ========== key : int The secret key. msg : str Plaintext of upper-case letters. Returns ======= str Ciphertext of upper-case letters. Examples ======== >>> from sympy.crypto.crypto import encipher_shift, decipher_shift >>> msg = "GONAVYBEATARMY" >>> ct = encipher_shift(msg, 1); ct 'HPOBWZCFBUBSNZ' To decipher the shifted text, change the sign of the key: >>> encipher_shift(ct, -1) 'GONAVYBEATARMY' There is also a convenience function that does this with the original key: >>> decipher_shift(ct, 1) 'GONAVYBEATARMY' Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L1`` of corresponding integers. 2. Compute from the list ``L1`` a new list ``L2``, given by adding ``(k mod 26)`` to each element in ``L1``. 3. Compute from the list ``L2`` a string ``ct`` of corresponding letters. The shift cipher is also called the Caesar cipher, after Julius Caesar, who, according to Suetonius, used it with a shift of three to protect messages of military significance. Caesar's nephew Augustus reportedly used a similar cipher, but with a right shift of 1. References ========== .. [1] https://en.wikipedia.org/wiki/Caesar_cipher .. [2] http://mathworld.wolfram.com/CaesarsMethod.html See Also ======== decipher_shift """ msg, _, A = _prep(msg, '', symbols) shift = len(A) - key % len(A) key = A[shift:] + A[:shift] return translate(msg, key, A) def decipher_shift(msg, key, symbols=None): """ Return the text by shifting the characters of ``msg`` to the left by the amount given by ``key``. Examples ======== >>> from sympy.crypto.crypto import encipher_shift, decipher_shift >>> msg = "GONAVYBEATARMY" >>> ct = encipher_shift(msg, 1); ct 'HPOBWZCFBUBSNZ' To decipher the shifted text, change the sign of the key: >>> encipher_shift(ct, -1) 'GONAVYBEATARMY' Or use this function with the original key: >>> decipher_shift(ct, 1) 'GONAVYBEATARMY' """ return encipher_shift(msg, -key, symbols) def encipher_rot13(msg, symbols=None): """ Performs the ROT13 encryption on a given plaintext ``msg``. Explanation =========== ROT13 is a substitution cipher which substitutes each letter in the plaintext message for the letter furthest away from it in the English alphabet. Equivalently, it is just a Caeser (shift) cipher with a shift key of 13 (midway point of the alphabet). References ========== .. [1] https://en.wikipedia.org/wiki/ROT13 See Also ======== decipher_rot13 encipher_shift """ return encipher_shift(msg, 13, symbols) def decipher_rot13(msg, symbols=None): """ Performs the ROT13 decryption on a given plaintext ``msg``. Explanation ============ ``decipher_rot13`` is equivalent to ``encipher_rot13`` as both ``decipher_shift`` with a key of 13 and ``encipher_shift`` key with a key of 13 will return the same results. Nonetheless, ``decipher_rot13`` has nonetheless been explicitly defined here for consistency. Examples ======== >>> from sympy.crypto.crypto import encipher_rot13, decipher_rot13 >>> msg = 'GONAVYBEATARMY' >>> ciphertext = encipher_rot13(msg);ciphertext 'TBANILORNGNEZL' >>> decipher_rot13(ciphertext) 'GONAVYBEATARMY' >>> encipher_rot13(msg) == decipher_rot13(msg) True >>> msg == decipher_rot13(ciphertext) True """ return decipher_shift(msg, 13, symbols) ######## affine cipher examples ############ def encipher_affine(msg, key, symbols=None, _inverse=False): r""" Performs the affine cipher encryption on plaintext ``msg``, and returns the ciphertext. Explanation =========== Encryption is based on the map `x \rightarrow ax+b` (mod `N`) where ``N`` is the number of characters in the alphabet. Decryption is based on the map `x \rightarrow cx+d` (mod `N`), where `c = a^{-1}` (mod `N`) and `d = -a^{-1}b` (mod `N`). In particular, for the map to be invertible, we need `\mathrm{gcd}(a, N) = 1` and an error will be raised if this is not true. Parameters ========== msg : str Characters that appear in ``symbols``. a, b : int, int A pair integers, with ``gcd(a, N) = 1`` (the secret key). symbols String of characters (default = uppercase letters). When no symbols are given, ``msg`` is converted to upper case letters and all other characters are ignored. Returns ======= ct String of characters (the ciphertext message) Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L1`` of corresponding integers. 2. Compute from the list ``L1`` a new list ``L2``, given by replacing ``x`` by ``a*x + b (mod N)``, for each element ``x`` in ``L1``. 3. Compute from the list ``L2`` a string ``ct`` of corresponding letters. This is a straightforward generalization of the shift cipher with the added complexity of requiring 2 characters to be deciphered in order to recover the key. References ========== .. [1] https://en.wikipedia.org/wiki/Affine_cipher See Also ======== decipher_affine """ msg, _, A = _prep(msg, '', symbols) N = len(A) a, b = key assert gcd(a, N) == 1 if _inverse: c = mod_inverse(a, N) d = -b*c a, b = c, d B = ''.join([A[(a*i + b) % N] for i in range(N)]) return translate(msg, A, B) def decipher_affine(msg, key, symbols=None): r""" Return the deciphered text that was made from the mapping, `x \rightarrow ax+b` (mod `N`), where ``N`` is the number of characters in the alphabet. Deciphering is done by reciphering with a new key: `x \rightarrow cx+d` (mod `N`), where `c = a^{-1}` (mod `N`) and `d = -a^{-1}b` (mod `N`). Examples ======== >>> from sympy.crypto.crypto import encipher_affine, decipher_affine >>> msg = "GO NAVY BEAT ARMY" >>> key = (3, 1) >>> encipher_affine(msg, key) 'TROBMVENBGBALV' >>> decipher_affine(_, key) 'GONAVYBEATARMY' See Also ======== encipher_affine """ return encipher_affine(msg, key, symbols, _inverse=True) def encipher_atbash(msg, symbols=None): r""" Enciphers a given ``msg`` into its Atbash ciphertext and returns it. Explanation =========== Atbash is a substitution cipher originally used to encrypt the Hebrew alphabet. Atbash works on the principle of mapping each alphabet to its reverse / counterpart (i.e. a would map to z, b to y etc.) Atbash is functionally equivalent to the affine cipher with ``a = 25`` and ``b = 25`` See Also ======== decipher_atbash """ return encipher_affine(msg, (25, 25), symbols) def decipher_atbash(msg, symbols=None): r""" Deciphers a given ``msg`` using Atbash cipher and returns it. Explanation =========== ``decipher_atbash`` is functionally equivalent to ``encipher_atbash``. However, it has still been added as a separate function to maintain consistency. Examples ======== >>> from sympy.crypto.crypto import encipher_atbash, decipher_atbash >>> msg = 'GONAVYBEATARMY' >>> encipher_atbash(msg) 'TLMZEBYVZGZINB' >>> decipher_atbash(msg) 'TLMZEBYVZGZINB' >>> encipher_atbash(msg) == decipher_atbash(msg) True >>> msg == encipher_atbash(encipher_atbash(msg)) True References ========== .. [1] https://en.wikipedia.org/wiki/Atbash See Also ======== encipher_atbash """ return decipher_affine(msg, (25, 25), symbols) #################### substitution cipher ########################### def encipher_substitution(msg, old, new=None): r""" Returns the ciphertext obtained by replacing each character that appears in ``old`` with the corresponding character in ``new``. If ``old`` is a mapping, then new is ignored and the replacements defined by ``old`` are used. Explanation =========== This is a more general than the affine cipher in that the key can only be recovered by determining the mapping for each symbol. Though in practice, once a few symbols are recognized the mappings for other characters can be quickly guessed. Examples ======== >>> from sympy.crypto.crypto import encipher_substitution, AZ >>> old = 'OEYAG' >>> new = '034^6' >>> msg = AZ("go navy! beat army!") >>> ct = encipher_substitution(msg, old, new); ct '60N^V4B3^T^RM4' To decrypt a substitution, reverse the last two arguments: >>> encipher_substitution(ct, new, old) 'GONAVYBEATARMY' In the special case where ``old`` and ``new`` are a permutation of order 2 (representing a transposition of characters) their order is immaterial: >>> old = 'NAVY' >>> new = 'ANYV' >>> encipher = lambda x: encipher_substitution(x, old, new) >>> encipher('NAVY') 'ANYV' >>> encipher(_) 'NAVY' The substitution cipher, in general, is a method whereby "units" (not necessarily single characters) of plaintext are replaced with ciphertext according to a regular system. >>> ords = dict(zip('abc', ['\\%i' % ord(i) for i in 'abc'])) >>> print(encipher_substitution('abc', ords)) \97\98\99 References ========== .. [1] https://en.wikipedia.org/wiki/Substitution_cipher """ return translate(msg, old, new) ###################################################################### #################### Vigenere cipher examples ######################## ###################################################################### def encipher_vigenere(msg, key, symbols=None): """ Performs the Vigenere cipher encryption on plaintext ``msg``, and returns the ciphertext. Examples ======== >>> from sympy.crypto.crypto import encipher_vigenere, AZ >>> key = "encrypt" >>> msg = "meet me on monday" >>> encipher_vigenere(msg, key) 'QRGKKTHRZQEBPR' Section 1 of the Kryptos sculpture at the CIA headquarters uses this cipher and also changes the order of the the alphabet [2]_. Here is the first line of that section of the sculpture: >>> from sympy.crypto.crypto import decipher_vigenere, padded_key >>> alp = padded_key('KRYPTOS', AZ()) >>> key = 'PALIMPSEST' >>> msg = 'EMUFPHZLRFAXYUSDJKZLDKRNSHGNFIVJ' >>> decipher_vigenere(msg, key, alp) 'BETWEENSUBTLESHADINGANDTHEABSENC' Explanation =========== The Vigenere cipher is named after Blaise de Vigenere, a sixteenth century diplomat and cryptographer, by a historical accident. Vigenere actually invented a different and more complicated cipher. The so-called *Vigenere cipher* was actually invented by Giovan Batista Belaso in 1553. This cipher was used in the 1800's, for example, during the American Civil War. The Confederacy used a brass cipher disk to implement the Vigenere cipher (now on display in the NSA Museum in Fort Meade) [1]_. The Vigenere cipher is a generalization of the shift cipher. Whereas the shift cipher shifts each letter by the same amount (that amount being the key of the shift cipher) the Vigenere cipher shifts a letter by an amount determined by the key (which is a word or phrase known only to the sender and receiver). For example, if the key was a single letter, such as "C", then the so-called Vigenere cipher is actually a shift cipher with a shift of `2` (since "C" is the 2nd letter of the alphabet, if you start counting at `0`). If the key was a word with two letters, such as "CA", then the so-called Vigenere cipher will shift letters in even positions by `2` and letters in odd positions are left alone (shifted by `0`, since "A" is the 0th letter, if you start counting at `0`). ALGORITHM: INPUT: ``msg``: string of characters that appear in ``symbols`` (the plaintext) ``key``: a string of characters that appear in ``symbols`` (the secret key) ``symbols``: a string of letters defining the alphabet OUTPUT: ``ct``: string of characters (the ciphertext message) STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``key`` a list ``L1`` of corresponding integers. Let ``n1 = len(L1)``. 2. Compute from the string ``msg`` a list ``L2`` of corresponding integers. Let ``n2 = len(L2)``. 3. Break ``L2`` up sequentially into sublists of size ``n1``; the last sublist may be smaller than ``n1`` 4. For each of these sublists ``L`` of ``L2``, compute a new list ``C`` given by ``C[i] = L[i] + L1[i] (mod N)`` to the ``i``-th element in the sublist, for each ``i``. 5. Assemble these lists ``C`` by concatenation into a new list of length ``n2``. 6. Compute from the new list a string ``ct`` of corresponding letters. Once it is known that the key is, say, `n` characters long, frequency analysis can be applied to every `n`-th letter of the ciphertext to determine the plaintext. This method is called *Kasiski examination* (although it was first discovered by Babbage). If they key is as long as the message and is comprised of randomly selected characters -- a one-time pad -- the message is theoretically unbreakable. The cipher Vigenere actually discovered is an "auto-key" cipher described as follows. ALGORITHM: INPUT: ``key``: a string of letters (the secret key) ``msg``: string of letters (the plaintext message) OUTPUT: ``ct``: string of upper-case letters (the ciphertext message) STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L2`` of corresponding integers. Let ``n2 = len(L2)``. 2. Let ``n1`` be the length of the key. Append to the string ``key`` the first ``n2 - n1`` characters of the plaintext message. Compute from this string (also of length ``n2``) a list ``L1`` of integers corresponding to the letter numbers in the first step. 3. Compute a new list ``C`` given by ``C[i] = L1[i] + L2[i] (mod N)``. 4. Compute from the new list a string ``ct`` of letters corresponding to the new integers. To decipher the auto-key ciphertext, the key is used to decipher the first ``n1`` characters and then those characters become the key to decipher the next ``n1`` characters, etc...: >>> m = AZ('go navy, beat army! yes you can'); m 'GONAVYBEATARMYYESYOUCAN' >>> key = AZ('gold bug'); n1 = len(key); n2 = len(m) >>> auto_key = key + m[:n2 - n1]; auto_key 'GOLDBUGGONAVYBEATARMYYE' >>> ct = encipher_vigenere(m, auto_key); ct 'MCYDWSHKOGAMKZCELYFGAYR' >>> n1 = len(key) >>> pt = [] >>> while ct: ... part, ct = ct[:n1], ct[n1:] ... pt.append(decipher_vigenere(part, key)) ... key = pt[-1] ... >>> ''.join(pt) == m True References ========== .. [1] https://en.wikipedia.org/wiki/Vigenere_cipher .. [2] http://web.archive.org/web/20071116100808/ .. [3] http://filebox.vt.edu/users/batman/kryptos.html (short URL: https://goo.gl/ijr22d) """ msg, key, A = _prep(msg, key, symbols) map = {c: i for i, c in enumerate(A)} key = [map[c] for c in key] N = len(map) k = len(key) rv = [] for i, m in enumerate(msg): rv.append(A[(map[m] + key[i % k]) % N]) rv = ''.join(rv) return rv def decipher_vigenere(msg, key, symbols=None): """ Decode using the Vigenere cipher. Examples ======== >>> from sympy.crypto.crypto import decipher_vigenere >>> key = "encrypt" >>> ct = "QRGK kt HRZQE BPR" >>> decipher_vigenere(ct, key) 'MEETMEONMONDAY' """ msg, key, A = _prep(msg, key, symbols) map = {c: i for i, c in enumerate(A)} N = len(A) # normally, 26 K = [map[c] for c in key] n = len(K) C = [map[c] for c in msg] rv = ''.join([A[(-K[i % n] + c) % N] for i, c in enumerate(C)]) return rv #################### Hill cipher ######################## def encipher_hill(msg, key, symbols=None, pad="Q"): r""" Return the Hill cipher encryption of ``msg``. Explanation =========== The Hill cipher [1]_, invented by Lester S. Hill in the 1920's [2]_, was the first polygraphic cipher in which it was practical (though barely) to operate on more than three symbols at once. The following discussion assumes an elementary knowledge of matrices. First, each letter is first encoded as a number starting with 0. Suppose your message `msg` consists of `n` capital letters, with no spaces. This may be regarded an `n`-tuple M of elements of `Z_{26}` (if the letters are those of the English alphabet). A key in the Hill cipher is a `k x k` matrix `K`, all of whose entries are in `Z_{26}`, such that the matrix `K` is invertible (i.e., the linear transformation `K: Z_{N}^k \rightarrow Z_{N}^k` is one-to-one). Parameters ========== msg Plaintext message of `n` upper-case letters. key A `k \times k` invertible matrix `K`, all of whose entries are in `Z_{26}` (or whatever number of symbols are being used). pad Character (default "Q") to use to make length of text be a multiple of ``k``. Returns ======= ct Ciphertext of upper-case letters. Notes ===== ALGORITHM: STEPS: 0. Number the letters of the alphabet from 0, ..., N 1. Compute from the string ``msg`` a list ``L`` of corresponding integers. Let ``n = len(L)``. 2. Break the list ``L`` up into ``t = ceiling(n/k)`` sublists ``L_1``, ..., ``L_t`` of size ``k`` (with the last list "padded" to ensure its size is ``k``). 3. Compute new list ``C_1``, ..., ``C_t`` given by ``C[i] = K*L_i`` (arithmetic is done mod N), for each ``i``. 4. Concatenate these into a list ``C = C_1 + ... + C_t``. 5. Compute from ``C`` a string ``ct`` of corresponding letters. This has length ``k*t``. References ========== .. [1] https://en.wikipedia.org/wiki/Hill_cipher .. [2] Lester S. Hill, Cryptography in an Algebraic Alphabet, The American Mathematical Monthly Vol.36, June-July 1929, pp.306-312. See Also ======== decipher_hill """ assert key.is_square assert len(pad) == 1 msg, pad, A = _prep(msg, pad, symbols) map = {c: i for i, c in enumerate(A)} P = [map[c] for c in msg] N = len(A) k = key.cols n = len(P) m, r = divmod(n, k) if r: P = P + [map[pad]]*(k - r) m += 1 rv = ''.join([A[c % N] for j in range(m) for c in list(key*Matrix(k, 1, [P[i] for i in range(k*j, k*(j + 1))]))]) return rv def decipher_hill(msg, key, symbols=None): """ Deciphering is the same as enciphering but using the inverse of the key matrix. Examples ======== >>> from sympy.crypto.crypto import encipher_hill, decipher_hill >>> from sympy import Matrix >>> key = Matrix([[1, 2], [3, 5]]) >>> encipher_hill("meet me on monday", key) 'UEQDUEODOCTCWQ' >>> decipher_hill(_, key) 'MEETMEONMONDAY' When the length of the plaintext (stripped of invalid characters) is not a multiple of the key dimension, extra characters will appear at the end of the enciphered and deciphered text. In order to decipher the text, those characters must be included in the text to be deciphered. In the following, the key has a dimension of 4 but the text is 2 short of being a multiple of 4 so two characters will be added. >>> key = Matrix([[1, 1, 1, 2], [0, 1, 1, 0], ... [2, 2, 3, 4], [1, 1, 0, 1]]) >>> msg = "ST" >>> encipher_hill(msg, key) 'HJEB' >>> decipher_hill(_, key) 'STQQ' >>> encipher_hill(msg, key, pad="Z") 'ISPK' >>> decipher_hill(_, key) 'STZZ' If the last two characters of the ciphertext were ignored in either case, the wrong plaintext would be recovered: >>> decipher_hill("HD", key) 'ORMV' >>> decipher_hill("IS", key) 'UIKY' See Also ======== encipher_hill """ assert key.is_square msg, _, A = _prep(msg, '', symbols) map = {c: i for i, c in enumerate(A)} C = [map[c] for c in msg] N = len(A) k = key.cols n = len(C) m, r = divmod(n, k) if r: C = C + [0]*(k - r) m += 1 key_inv = key.inv_mod(N) rv = ''.join([A[p % N] for j in range(m) for p in list(key_inv*Matrix( k, 1, [C[i] for i in range(k*j, k*(j + 1))]))]) return rv #################### Bifid cipher ######################## def encipher_bifid(msg, key, symbols=None): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. This is the version of the Bifid cipher that uses an `n \times n` Polybius square. Parameters ========== msg Plaintext string. key Short string for key. Duplicate characters are ignored and then it is padded with the characters in ``symbols`` that were not in the short key. symbols `n \times n` characters defining the alphabet. (default is string.printable) Returns ======= ciphertext Ciphertext using Bifid5 cipher without spaces. See Also ======== decipher_bifid, encipher_bifid5, encipher_bifid6 References ========== .. [1] https://en.wikipedia.org/wiki/Bifid_cipher """ msg, key, A = _prep(msg, key, symbols, bifid10) long_key = ''.join(uniq(key)) or A n = len(A)**.5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) N = int(n) if len(long_key) < N**2: long_key = list(long_key) + [x for x in A if x not in long_key] # the fractionalization row_col = {ch: divmod(i, N) for i, ch in enumerate(long_key)} r, c = zip(*[row_col[x] for x in msg]) rc = r + c ch = {i: ch for ch, i in row_col.items()} rv = ''.join(ch[i] for i in zip(rc[::2], rc[1::2])) return rv def decipher_bifid(msg, key, symbols=None): r""" Performs the Bifid cipher decryption on ciphertext ``msg``, and returns the plaintext. This is the version of the Bifid cipher that uses the `n \times n` Polybius square. Parameters ========== msg Ciphertext string. key Short string for key. Duplicate characters are ignored and then it is padded with the characters in symbols that were not in the short key. symbols `n \times n` characters defining the alphabet. (default=string.printable, a `10 \times 10` matrix) Returns ======= deciphered Deciphered text. Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_bifid, decipher_bifid, AZ) Do an encryption using the bifid5 alphabet: >>> alp = AZ().replace('J', '') >>> ct = AZ("meet me on monday!") >>> key = AZ("gold bug") >>> encipher_bifid(ct, key, alp) 'IEILHHFSTSFQYE' When entering the text or ciphertext, spaces are ignored so it can be formatted as desired. Re-entering the ciphertext from the preceding, putting 4 characters per line and padding with an extra J, does not cause problems for the deciphering: >>> decipher_bifid(''' ... IEILH ... HFSTS ... FQYEJ''', key, alp) 'MEETMEONMONDAY' When no alphabet is given, all 100 printable characters will be used: >>> key = '' >>> encipher_bifid('hello world!', key) 'bmtwmg-bIo*w' >>> decipher_bifid(_, key) 'hello world!' If the key is changed, a different encryption is obtained: >>> key = 'gold bug' >>> encipher_bifid('hello world!', 'gold_bug') 'hg2sfuei7t}w' And if the key used to decrypt the message is not exact, the original text will not be perfectly obtained: >>> decipher_bifid(_, 'gold pug') 'heldo~wor6d!' """ msg, _, A = _prep(msg, '', symbols, bifid10) long_key = ''.join(uniq(key)) or A n = len(A)**.5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) N = int(n) if len(long_key) < N**2: long_key = list(long_key) + [x for x in A if x not in long_key] # the reverse fractionalization row_col = { ch: divmod(i, N) for i, ch in enumerate(long_key)} rc = [i for c in msg for i in row_col[c]] n = len(msg) rc = zip(*(rc[:n], rc[n:])) ch = {i: ch for ch, i in row_col.items()} rv = ''.join(ch[i] for i in rc) return rv def bifid_square(key): """Return characters of ``key`` arranged in a square. Examples ======== >>> from sympy.crypto.crypto import ( ... bifid_square, AZ, padded_key, bifid5) >>> bifid_square(AZ().replace('J', '')) Matrix([ [A, B, C, D, E], [F, G, H, I, K], [L, M, N, O, P], [Q, R, S, T, U], [V, W, X, Y, Z]]) >>> bifid_square(padded_key(AZ('gold bug!'), bifid5)) Matrix([ [G, O, L, D, B], [U, A, C, E, F], [H, I, K, M, N], [P, Q, R, S, T], [V, W, X, Y, Z]]) See Also ======== padded_key """ A = ''.join(uniq(''.join(key))) n = len(A)**.5 if n != int(n): raise ValueError( 'Length of alphabet (%s) is not a square number.' % len(A)) n = int(n) f = lambda i, j: Symbol(A[n*i + j]) rv = Matrix(n, n, f) return rv def encipher_bifid5(msg, key): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. Explanation =========== This is the version of the Bifid cipher that uses the `5 \times 5` Polybius square. The letter "J" is ignored so it must be replaced with something else (traditionally an "I") before encryption. ALGORITHM: (5x5 case) STEPS: 0. Create the `5 \times 5` Polybius square ``S`` associated to ``key`` as follows: a) moving from left-to-right, top-to-bottom, place the letters of the key into a `5 \times 5` matrix, b) if the key has less than 25 letters, add the letters of the alphabet not in the key until the `5 \times 5` square is filled. 1. Create a list ``P`` of pairs of numbers which are the coordinates in the Polybius square of the letters in ``msg``. 2. Let ``L1`` be the list of all first coordinates of ``P`` (length of ``L1 = n``), let ``L2`` be the list of all second coordinates of ``P`` (so the length of ``L2`` is also ``n``). 3. Let ``L`` be the concatenation of ``L1`` and ``L2`` (length ``L = 2*n``), except that consecutive numbers are paired ``(L[2*i], L[2*i + 1])``. You can regard ``L`` as a list of pairs of length ``n``. 4. Let ``C`` be the list of all letters which are of the form ``S[i, j]``, for all ``(i, j)`` in ``L``. As a string, this is the ciphertext of ``msg``. Parameters ========== msg : str Plaintext string. Converted to upper case and filtered of anything but all letters except J. key Short string for key; non-alphabetic letters, J and duplicated characters are ignored and then, if the length is less than 25 characters, it is padded with other letters of the alphabet (in alphabetical order). Returns ======= ct Ciphertext (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_bifid5, decipher_bifid5) "J" will be omitted unless it is replaced with something else: >>> round_trip = lambda m, k: \ ... decipher_bifid5(encipher_bifid5(m, k), k) >>> key = 'a' >>> msg = "JOSIE" >>> round_trip(msg, key) 'OSIE' >>> round_trip(msg.replace("J", "I"), key) 'IOSIE' >>> j = "QIQ" >>> round_trip(msg.replace("J", j), key).replace(j, "J") 'JOSIE' Notes ===== The Bifid cipher was invented around 1901 by Felix Delastelle. It is a *fractional substitution* cipher, where letters are replaced by pairs of symbols from a smaller alphabet. The cipher uses a `5 \times 5` square filled with some ordering of the alphabet, except that "J" is replaced with "I" (this is a so-called Polybius square; there is a `6 \times 6` analog if you add back in "J" and also append onto the usual 26 letter alphabet, the digits 0, 1, ..., 9). According to Helen Gaines' book *Cryptanalysis*, this type of cipher was used in the field by the German Army during World War I. See Also ======== decipher_bifid5, encipher_bifid """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid5) key = padded_key(key, bifid5) return encipher_bifid(msg, '', key) def decipher_bifid5(msg, key): r""" Return the Bifid cipher decryption of ``msg``. Explanation =========== This is the version of the Bifid cipher that uses the `5 \times 5` Polybius square; the letter "J" is ignored unless a ``key`` of length 25 is used. Parameters ========== msg Ciphertext string. key Short string for key; duplicated characters are ignored and if the length is less then 25 characters, it will be padded with other letters from the alphabet omitting "J". Non-alphabetic characters are ignored. Returns ======= plaintext Plaintext from Bifid5 cipher (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import encipher_bifid5, decipher_bifid5 >>> key = "gold bug" >>> encipher_bifid5('meet me on friday', key) 'IEILEHFSTSFXEE' >>> encipher_bifid5('meet me on monday', key) 'IEILHHFSTSFQYE' >>> decipher_bifid5(_, key) 'MEETMEONMONDAY' """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid5) key = padded_key(key, bifid5) return decipher_bifid(msg, '', key) def bifid5_square(key=None): r""" 5x5 Polybius square. Produce the Polybius square for the `5 \times 5` Bifid cipher. Examples ======== >>> from sympy.crypto.crypto import bifid5_square >>> bifid5_square("gold bug") Matrix([ [G, O, L, D, B], [U, A, C, E, F], [H, I, K, M, N], [P, Q, R, S, T], [V, W, X, Y, Z]]) """ if not key: key = bifid5 else: _, key, _ = _prep('', key.upper(), None, bifid5) key = padded_key(key, bifid5) return bifid_square(key) def encipher_bifid6(msg, key): r""" Performs the Bifid cipher encryption on plaintext ``msg``, and returns the ciphertext. This is the version of the Bifid cipher that uses the `6 \times 6` Polybius square. Parameters ========== msg Plaintext string (digits okay). key Short string for key (digits okay). If ``key`` is less than 36 characters long, the square will be filled with letters A through Z and digits 0 through 9. Returns ======= ciphertext Ciphertext from Bifid cipher (all caps, no spaces). See Also ======== decipher_bifid6, encipher_bifid """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid6) key = padded_key(key, bifid6) return encipher_bifid(msg, '', key) def decipher_bifid6(msg, key): r""" Performs the Bifid cipher decryption on ciphertext ``msg``, and returns the plaintext. This is the version of the Bifid cipher that uses the `6 \times 6` Polybius square. Parameters ========== msg Ciphertext string (digits okay); converted to upper case key Short string for key (digits okay). If ``key`` is less than 36 characters long, the square will be filled with letters A through Z and digits 0 through 9. All letters are converted to uppercase. Returns ======= plaintext Plaintext from Bifid cipher (all caps, no spaces). Examples ======== >>> from sympy.crypto.crypto import encipher_bifid6, decipher_bifid6 >>> key = "gold bug" >>> encipher_bifid6('meet me on monday at 8am', key) 'KFKLJJHF5MMMKTFRGPL' >>> decipher_bifid6(_, key) 'MEETMEONMONDAYAT8AM' """ msg, key, _ = _prep(msg.upper(), key.upper(), None, bifid6) key = padded_key(key, bifid6) return decipher_bifid(msg, '', key) def bifid6_square(key=None): r""" 6x6 Polybius square. Produces the Polybius square for the `6 \times 6` Bifid cipher. Assumes alphabet of symbols is "A", ..., "Z", "0", ..., "9". Examples ======== >>> from sympy.crypto.crypto import bifid6_square >>> key = "gold bug" >>> bifid6_square(key) Matrix([ [G, O, L, D, B, U], [A, C, E, F, H, I], [J, K, M, N, P, Q], [R, S, T, V, W, X], [Y, Z, 0, 1, 2, 3], [4, 5, 6, 7, 8, 9]]) """ if not key: key = bifid6 else: _, key, _ = _prep('', key.upper(), None, bifid6) key = padded_key(key, bifid6) return bifid_square(key) #################### RSA ############################# def _decipher_rsa_crt(i, d, factors): """Decipher RSA using chinese remainder theorem from the information of the relatively-prime factors of the modulus. Parameters ========== i : integer Ciphertext d : integer The exponent component. factors : list of relatively-prime integers The integers given must be coprime and the product must equal the modulus component of the original RSA key. Examples ======== How to decrypt RSA with CRT: >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key >>> primes = [61, 53] >>> e = 17 >>> args = primes + [e] >>> puk = rsa_public_key(*args) >>> prk = rsa_private_key(*args) >>> from sympy.crypto.crypto import encipher_rsa, _decipher_rsa_crt >>> msg = 65 >>> crt_primes = primes >>> encrypted = encipher_rsa(msg, puk) >>> decrypted = _decipher_rsa_crt(encrypted, prk[1], primes) >>> decrypted 65 """ from sympy.ntheory.modular import crt moduluses = [pow(i, d, p) for p in factors] result = crt(factors, moduluses) if not result: raise ValueError("CRT failed") return result[0] def _rsa_key(*args, public=True, private=True, totient='Euler', index=None, multipower=None): r"""A private subroutine to generate RSA key Parameters ========== public, private : bool, optional Flag to generate either a public key, a private key. totient : 'Euler' or 'Carmichael' Different notation used for totient. multipower : bool, optional Flag to bypass warning for multipower RSA. """ from sympy.ntheory import totient as _euler from sympy.ntheory import reduced_totient as _carmichael if len(args) < 2: return False if totient not in ('Euler', 'Carmichael'): raise ValueError( "The argument totient={} should either be " \ "'Euler', 'Carmichalel'." \ .format(totient)) if totient == 'Euler': _totient = _euler else: _totient = _carmichael if index is not None: index = as_int(index) if totient != 'Carmichael': raise ValueError( "Setting the 'index' keyword argument requires totient" "notation to be specified as 'Carmichael'.") primes, e = args[:-1], args[-1] if any(not isprime(p) for p in primes): new_primes = [] for i in primes: new_primes.extend(factorint(i, multiple=True)) primes = new_primes n = reduce(lambda i, j: i*j, primes) tally = multiset(primes) if all(v == 1 for v in tally.values()): multiple = list(tally.keys()) phi = _totient._from_distinct_primes(*multiple) else: if not multipower: NonInvertibleCipherWarning( 'Non-distinctive primes found in the factors {}. ' 'The cipher may not be decryptable for some numbers ' 'in the complete residue system Z[{}], but the cipher ' 'can still be valid if you restrict the domain to be ' 'the reduced residue system Z*[{}]. You can pass ' 'the flag multipower=True if you want to suppress this ' 'warning.' .format(primes, n, n) ).warn() phi = _totient._from_factors(tally) if igcd(e, phi) == 1: if public and not private: if isinstance(index, int): e = e % phi e += index * phi return n, e if private and not public: d = mod_inverse(e, phi) if isinstance(index, int): d += index * phi return n, d return False def rsa_public_key(*args, **kwargs): r"""Return the RSA *public key* pair, `(n, e)` Parameters ========== args : naturals If specified as `p, q, e` where `p` and `q` are distinct primes and `e` is a desired public exponent of the RSA, `n = p q` and `e` will be verified against the totient `\phi(n)` (Euler totient) or `\lambda(n)` (Carmichael totient) to be `\gcd(e, \phi(n)) = 1` or `\gcd(e, \lambda(n)) = 1`. If specified as `p_1, p_2, ..., p_n, e` where `p_1, p_2, ..., p_n` are specified as primes, and `e` is specified as a desired public exponent of the RSA, it will be able to form a multi-prime RSA, which is a more generalized form of the popular 2-prime RSA. It can also be possible to form a single-prime RSA by specifying the argument as `p, e`, which can be considered a trivial case of a multiprime RSA. Furthermore, it can be possible to form a multi-power RSA by specifying two or more pairs of the primes to be same. However, unlike the two-distinct prime RSA or multi-prime RSA, not every numbers in the complete residue system (`\mathbb{Z}_n`) will be decryptable since the mapping `\mathbb{Z}_{n} \rightarrow \mathbb{Z}_{n}` will not be bijective. (Only except for the trivial case when `e = 1` or more generally, .. math:: e \in \left \{ 1 + k \lambda(n) \mid k \in \mathbb{Z} \land k \geq 0 \right \} when RSA reduces to the identity.) However, the RSA can still be decryptable for the numbers in the reduced residue system (`\mathbb{Z}_n^{\times}`), since the mapping `\mathbb{Z}_{n}^{\times} \rightarrow \mathbb{Z}_{n}^{\times}` can still be bijective. If you pass a non-prime integer to the arguments `p_1, p_2, ..., p_n`, the particular number will be prime-factored and it will become either a multi-prime RSA or a multi-power RSA in its canonical form, depending on whether the product equals its radical or not. `p_1 p_2 ... p_n = \text{rad}(p_1 p_2 ... p_n)` totient : bool, optional If ``'Euler'``, it uses Euler's totient `\phi(n)` which is :meth:`sympy.ntheory.factor_.totient` in SymPy. If ``'Carmichael'``, it uses Carmichael's totient `\lambda(n)` which is :meth:`sympy.ntheory.factor_.reduced_totient` in SymPy. Unlike private key generation, this is a trivial keyword for public key generation because `\gcd(e, \phi(n)) = 1 \iff \gcd(e, \lambda(n)) = 1`. index : nonnegative integer, optional Returns an arbitrary solution of a RSA public key at the index specified at `0, 1, 2, ...`. This parameter needs to be specified along with ``totient='Carmichael'``. Similarly to the non-uniquenss of a RSA private key as described in the ``index`` parameter documentation in :meth:`rsa_private_key`, RSA public key is also not unique and there is an infinite number of RSA public exponents which can behave in the same manner. From any given RSA public exponent `e`, there are can be an another RSA public exponent `e + k \lambda(n)` where `k` is an integer, `\lambda` is a Carmichael's totient function. However, considering only the positive cases, there can be a principal solution of a RSA public exponent `e_0` in `0 < e_0 < \lambda(n)`, and all the other solutions can be canonicalzed in a form of `e_0 + k \lambda(n)`. ``index`` specifies the `k` notation to yield any possible value an RSA public key can have. An example of computing any arbitrary RSA public key: >>> from sympy.crypto.crypto import rsa_public_key >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=0) (3233, 17) >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=1) (3233, 797) >>> rsa_public_key(61, 53, 17, totient='Carmichael', index=2) (3233, 1577) multipower : bool, optional Any pair of non-distinct primes found in the RSA specification will restrict the domain of the cryptosystem, as noted in the explaination of the parameter ``args``. SymPy RSA key generator may give a warning before dispatching it as a multi-power RSA, however, you can disable the warning if you pass ``True`` to this keyword. Returns ======= (n, e) : int, int `n` is a product of any arbitrary number of primes given as the argument. `e` is relatively prime (coprime) to the Euler totient `\phi(n)`. False Returned if less than two arguments are given, or `e` is not relatively prime to the modulus. Examples ======== >>> from sympy.crypto.crypto import rsa_public_key A public key of a two-prime RSA: >>> p, q, e = 3, 5, 7 >>> rsa_public_key(p, q, e) (15, 7) >>> rsa_public_key(p, q, 30) False A public key of a multiprime RSA: >>> primes = [2, 3, 5, 7, 11, 13] >>> e = 7 >>> args = primes + [e] >>> rsa_public_key(*args) (30030, 7) Notes ===== Although the RSA can be generalized over any modulus `n`, using two large primes had became the most popular specification because a product of two large primes is usually the hardest to factor relatively to the digits of `n` can have. However, it may need further understanding of the time complexities of each prime-factoring algorithms to verify the claim. See Also ======== rsa_private_key encipher_rsa decipher_rsa References ========== .. [1] https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29 .. [2] http://cacr.uwaterloo.ca/techreports/2006/cacr2006-16.pdf .. [3] https://link.springer.com/content/pdf/10.1007%2FBFb0055738.pdf .. [4] http://www.itiis.org/digital-library/manuscript/1381 """ return _rsa_key(*args, public=True, private=False, **kwargs) def rsa_private_key(*args, **kwargs): r"""Return the RSA *private key* pair, `(n, d)` Parameters ========== args : naturals The keyword is identical to the ``args`` in :meth:`rsa_public_key`. totient : bool, optional If ``'Euler'``, it uses Euler's totient convention `\phi(n)` which is :meth:`sympy.ntheory.factor_.totient` in SymPy. If ``'Carmichael'``, it uses Carmichael's totient convention `\lambda(n)` which is :meth:`sympy.ntheory.factor_.reduced_totient` in SymPy. There can be some output differences for private key generation as examples below. Example using Euler's totient: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Euler') (3233, 2753) Example using Carmichael's totient: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Carmichael') (3233, 413) index : nonnegative integer, optional Returns an arbitrary solution of a RSA private key at the index specified at `0, 1, 2, ...`. This parameter needs to be specified along with ``totient='Carmichael'``. RSA private exponent is a non-unique solution of `e d \mod \lambda(n) = 1` and it is possible in any form of `d + k \lambda(n)`, where `d` is an another already-computed private exponent, and `\lambda` is a Carmichael's totient function, and `k` is any integer. However, considering only the positive cases, there can be a principal solution of a RSA private exponent `d_0` in `0 < d_0 < \lambda(n)`, and all the other solutions can be canonicalzed in a form of `d_0 + k \lambda(n)`. ``index`` specifies the `k` notation to yield any possible value an RSA private key can have. An example of computing any arbitrary RSA private key: >>> from sympy.crypto.crypto import rsa_private_key >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=0) (3233, 413) >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=1) (3233, 1193) >>> rsa_private_key(61, 53, 17, totient='Carmichael', index=2) (3233, 1973) multipower : bool, optional The keyword is identical to the ``multipower`` in :meth:`rsa_public_key`. Returns ======= (n, d) : int, int `n` is a product of any arbitrary number of primes given as the argument. `d` is the inverse of `e` (mod `\phi(n)`) where `e` is the exponent given, and `\phi` is a Euler totient. False Returned if less than two arguments are given, or `e` is not relatively prime to the totient of the modulus. Examples ======== >>> from sympy.crypto.crypto import rsa_private_key A private key of a two-prime RSA: >>> p, q, e = 3, 5, 7 >>> rsa_private_key(p, q, e) (15, 7) >>> rsa_private_key(p, q, 30) False A private key of a multiprime RSA: >>> primes = [2, 3, 5, 7, 11, 13] >>> e = 7 >>> args = primes + [e] >>> rsa_private_key(*args) (30030, 823) See Also ======== rsa_public_key encipher_rsa decipher_rsa References ========== .. [1] https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29 .. [2] http://cacr.uwaterloo.ca/techreports/2006/cacr2006-16.pdf .. [3] https://link.springer.com/content/pdf/10.1007%2FBFb0055738.pdf .. [4] http://www.itiis.org/digital-library/manuscript/1381 """ return _rsa_key(*args, public=False, private=True, **kwargs) def _encipher_decipher_rsa(i, key, factors=None): n, d = key if not factors: return pow(i, d, n) def _is_coprime_set(l): is_coprime_set = True for i in range(len(l)): for j in range(i+1, len(l)): if igcd(l[i], l[j]) != 1: is_coprime_set = False break return is_coprime_set prod = reduce(lambda i, j: i*j, factors) if prod == n and _is_coprime_set(factors): return _decipher_rsa_crt(i, d, factors) return _encipher_decipher_rsa(i, key, factors=None) def encipher_rsa(i, key, factors=None): r"""Encrypt the plaintext with RSA. Parameters ========== i : integer The plaintext to be encrypted for. key : (n, e) where n, e are integers `n` is the modulus of the key and `e` is the exponent of the key. The encryption is computed by `i^e \bmod n`. The key can either be a public key or a private key, however, the message encrypted by a public key can only be decrypted by a private key, and vice versa, as RSA is an asymmetric cryptography system. factors : list of coprime integers This is identical to the keyword ``factors`` in :meth:`decipher_rsa`. Notes ===== Some specifications may make the RSA not cryptographically meaningful. For example, `0`, `1` will remain always same after taking any number of exponentiation, thus, should be avoided. Furthermore, if `i^e < n`, `i` may easily be figured out by taking `e` th root. And also, specifying the exponent as `1` or in more generalized form as `1 + k \lambda(n)` where `k` is an nonnegative integer, `\lambda` is a carmichael totient, the RSA becomes an identity mapping. Examples ======== >>> from sympy.crypto.crypto import encipher_rsa >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key Public Key Encryption: >>> p, q, e = 3, 5, 7 >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> encipher_rsa(msg, puk) 3 Private Key Encryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> msg = 12 >>> encipher_rsa(msg, prk) 3 Encryption using chinese remainder theorem: >>> encipher_rsa(msg, prk, factors=[p, q]) 3 """ return _encipher_decipher_rsa(i, key, factors=factors) def decipher_rsa(i, key, factors=None): r"""Decrypt the ciphertext with RSA. Parameters ========== i : integer The ciphertext to be decrypted for. key : (n, d) where n, d are integers `n` is the modulus of the key and `d` is the exponent of the key. The decryption is computed by `i^d \bmod n`. The key can either be a public key or a private key, however, the message encrypted by a public key can only be decrypted by a private key, and vice versa, as RSA is an asymmetric cryptography system. factors : list of coprime integers As the modulus `n` created from RSA key generation is composed of arbitrary prime factors `n = {p_1}^{k_1}{p_2}^{k_2}...{p_n}^{k_n}` where `p_1, p_2, ..., p_n` are distinct primes and `k_1, k_2, ..., k_n` are positive integers, chinese remainder theorem can be used to compute `i^d \bmod n` from the fragmented modulo operations like .. math:: i^d \bmod {p_1}^{k_1}, i^d \bmod {p_2}^{k_2}, ... , i^d \bmod {p_n}^{k_n} or like .. math:: i^d \bmod {p_1}^{k_1}{p_2}^{k_2}, i^d \bmod {p_3}^{k_3}, ... , i^d \bmod {p_n}^{k_n} as long as every moduli does not share any common divisor each other. The raw primes used in generating the RSA key pair can be a good option. Note that the speed advantage of using this is only viable for very large cases (Like 2048-bit RSA keys) since the overhead of using pure python implementation of :meth:`sympy.ntheory.modular.crt` may overcompensate the theoritical speed advantage. Notes ===== See the ``Notes`` section in the documentation of :meth:`encipher_rsa` Examples ======== >>> from sympy.crypto.crypto import decipher_rsa, encipher_rsa >>> from sympy.crypto.crypto import rsa_public_key, rsa_private_key Public Key Encryption and Decryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> new_msg = encipher_rsa(msg, prk) >>> new_msg 3 >>> decipher_rsa(new_msg, puk) 12 Private Key Encryption and Decryption: >>> p, q, e = 3, 5, 7 >>> prk = rsa_private_key(p, q, e) >>> puk = rsa_public_key(p, q, e) >>> msg = 12 >>> new_msg = encipher_rsa(msg, puk) >>> new_msg 3 >>> decipher_rsa(new_msg, prk) 12 Decryption using chinese remainder theorem: >>> decipher_rsa(new_msg, prk, factors=[p, q]) 12 See Also ======== encipher_rsa """ return _encipher_decipher_rsa(i, key, factors=factors) #################### kid krypto (kid RSA) ############################# def kid_rsa_public_key(a, b, A, B): r""" Kid RSA is a version of RSA useful to teach grade school children since it does not involve exponentiation. Explanation =========== Alice wants to talk to Bob. Bob generates keys as follows. Key generation: * Select positive integers `a, b, A, B` at random. * Compute `M = a b - 1`, `e = A M + a`, `d = B M + b`, `n = (e d - 1)//M`. * The *public key* is `(n, e)`. Bob sends these to Alice. * The *private key* is `(n, d)`, which Bob keeps secret. Encryption: If `p` is the plaintext message then the ciphertext is `c = p e \pmod n`. Decryption: If `c` is the ciphertext message then the plaintext is `p = c d \pmod n`. Examples ======== >>> from sympy.crypto.crypto import kid_rsa_public_key >>> a, b, A, B = 3, 4, 5, 6 >>> kid_rsa_public_key(a, b, A, B) (369, 58) """ M = a*b - 1 e = A*M + a d = B*M + b n = (e*d - 1)//M return n, e def kid_rsa_private_key(a, b, A, B): """ Compute `M = a b - 1`, `e = A M + a`, `d = B M + b`, `n = (e d - 1) / M`. The *private key* is `d`, which Bob keeps secret. Examples ======== >>> from sympy.crypto.crypto import kid_rsa_private_key >>> a, b, A, B = 3, 4, 5, 6 >>> kid_rsa_private_key(a, b, A, B) (369, 70) """ M = a*b - 1 e = A*M + a d = B*M + b n = (e*d - 1)//M return n, d def encipher_kid_rsa(msg, key): """ Here ``msg`` is the plaintext and ``key`` is the public key. Examples ======== >>> from sympy.crypto.crypto import ( ... encipher_kid_rsa, kid_rsa_public_key) >>> msg = 200 >>> a, b, A, B = 3, 4, 5, 6 >>> key = kid_rsa_public_key(a, b, A, B) >>> encipher_kid_rsa(msg, key) 161 """ n, e = key return (msg*e) % n def decipher_kid_rsa(msg, key): """ Here ``msg`` is the plaintext and ``key`` is the private key. Examples ======== >>> from sympy.crypto.crypto import ( ... kid_rsa_public_key, kid_rsa_private_key, ... decipher_kid_rsa, encipher_kid_rsa) >>> a, b, A, B = 3, 4, 5, 6 >>> d = kid_rsa_private_key(a, b, A, B) >>> msg = 200 >>> pub = kid_rsa_public_key(a, b, A, B) >>> pri = kid_rsa_private_key(a, b, A, B) >>> ct = encipher_kid_rsa(msg, pub) >>> decipher_kid_rsa(ct, pri) 200 """ n, d = key return (msg*d) % n #################### Morse Code ###################################### morse_char = { ".-": "A", "-...": "B", "-.-.": "C", "-..": "D", ".": "E", "..-.": "F", "--.": "G", "....": "H", "..": "I", ".---": "J", "-.-": "K", ".-..": "L", "--": "M", "-.": "N", "---": "O", ".--.": "P", "--.-": "Q", ".-.": "R", "...": "S", "-": "T", "..-": "U", "...-": "V", ".--": "W", "-..-": "X", "-.--": "Y", "--..": "Z", "-----": "0", ".----": "1", "..---": "2", "...--": "3", "....-": "4", ".....": "5", "-....": "6", "--...": "7", "---..": "8", "----.": "9", ".-.-.-": ".", "--..--": ",", "---...": ":", "-.-.-.": ";", "..--..": "?", "-....-": "-", "..--.-": "_", "-.--.": "(", "-.--.-": ")", ".----.": "'", "-...-": "=", ".-.-.": "+", "-..-.": "/", ".--.-.": "@", "...-..-": "$", "-.-.--": "!"} char_morse = {v: k for k, v in morse_char.items()} def encode_morse(msg, sep='|', mapping=None): """ Encodes a plaintext into popular Morse Code with letters separated by ``sep`` and words by a double ``sep``. Examples ======== >>> from sympy.crypto.crypto import encode_morse >>> msg = 'ATTACK RIGHT FLANK' >>> encode_morse(msg) '.-|-|-|.-|-.-.|-.-||.-.|..|--.|....|-||..-.|.-..|.-|-.|-.-' References ========== .. [1] https://en.wikipedia.org/wiki/Morse_code """ mapping = mapping or char_morse assert sep not in mapping word_sep = 2*sep mapping[" "] = word_sep suffix = msg and msg[-1] in whitespace # normalize whitespace msg = (' ' if word_sep else '').join(msg.split()) # omit unmapped chars chars = set(''.join(msg.split())) ok = set(mapping.keys()) msg = translate(msg, None, ''.join(chars - ok)) morsestring = [] words = msg.split() for word in words: morseword = [] for letter in word: morseletter = mapping[letter] morseword.append(morseletter) word = sep.join(morseword) morsestring.append(word) return word_sep.join(morsestring) + (word_sep if suffix else '') def decode_morse(msg, sep='|', mapping=None): """ Decodes a Morse Code with letters separated by ``sep`` (default is '|') and words by `word_sep` (default is '||) into plaintext. Examples ======== >>> from sympy.crypto.crypto import decode_morse >>> mc = '--|---|...-|.||.|.-|...|-' >>> decode_morse(mc) 'MOVE EAST' References ========== .. [1] https://en.wikipedia.org/wiki/Morse_code """ mapping = mapping or morse_char word_sep = 2*sep characterstring = [] words = msg.strip(word_sep).split(word_sep) for word in words: letters = word.split(sep) chars = [mapping[c] for c in letters] word = ''.join(chars) characterstring.append(word) rv = " ".join(characterstring) return rv #################### LFSRs ########################################## def lfsr_sequence(key, fill, n): r""" This function creates an LFSR sequence. Parameters ========== key : list A list of finite field elements, `[c_0, c_1, \ldots, c_k].` fill : list The list of the initial terms of the LFSR sequence, `[x_0, x_1, \ldots, x_k].` n Number of terms of the sequence that the function returns. Returns ======= L The LFSR sequence defined by `x_{n+1} = c_k x_n + \ldots + c_0 x_{n-k}`, for `n \leq k`. Notes ===== S. Golomb [G]_ gives a list of three statistical properties a sequence of numbers `a = \{a_n\}_{n=1}^\infty`, `a_n \in \{0,1\}`, should display to be considered "random". Define the autocorrelation of `a` to be .. math:: C(k) = C(k,a) = \lim_{N\rightarrow \infty} {1\over N}\sum_{n=1}^N (-1)^{a_n + a_{n+k}}. In the case where `a` is periodic with period `P` then this reduces to .. math:: C(k) = {1\over P}\sum_{n=1}^P (-1)^{a_n + a_{n+k}}. Assume `a` is periodic with period `P`. - balance: .. math:: \left|\sum_{n=1}^P(-1)^{a_n}\right| \leq 1. - low autocorrelation: .. math:: C(k) = \left\{ \begin{array}{cc} 1,& k = 0,\\ \epsilon, & k \ne 0. \end{array} \right. (For sequences satisfying these first two properties, it is known that `\epsilon = -1/P` must hold.) - proportional runs property: In each period, half the runs have length `1`, one-fourth have length `2`, etc. Moreover, there are as many runs of `1`'s as there are of `0`'s. Examples ======== >>> from sympy.crypto.crypto import lfsr_sequence >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> lfsr_sequence(key, fill, 10) [1 mod 2, 1 mod 2, 0 mod 2, 1 mod 2, 0 mod 2, 1 mod 2, 1 mod 2, 0 mod 2, 0 mod 2, 1 mod 2] References ========== .. [G] Solomon Golomb, Shift register sequences, Aegean Park Press, Laguna Hills, Ca, 1967 """ if not isinstance(key, list): raise TypeError("key must be a list") if not isinstance(fill, list): raise TypeError("fill must be a list") p = key[0].mod F = FF(p) s = fill k = len(fill) L = [] for i in range(n): s0 = s[:] L.append(s[0]) s = s[1:k] x = sum([int(key[i]*s0[i]) for i in range(k)]) s.append(F(x)) return L # use [x.to_int() for x in L] for int version def lfsr_autocorrelation(L, P, k): """ This function computes the LFSR autocorrelation function. Parameters ========== L A periodic sequence of elements of `GF(2)`. L must have length larger than P. P The period of L. k : int An integer `k` (`0 < k < P`). Returns ======= autocorrelation The k-th value of the autocorrelation of the LFSR L. Examples ======== >>> from sympy.crypto.crypto import ( ... lfsr_sequence, lfsr_autocorrelation) >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_autocorrelation(s, 15, 7) -1/15 >>> lfsr_autocorrelation(s, 15, 0) 1 """ if not isinstance(L, list): raise TypeError("L (=%s) must be a list" % L) P = int(P) k = int(k) L0 = L[:P] # slices makes a copy L1 = L0 + L0[:k] L2 = [(-1)**(L1[i].to_int() + L1[i + k].to_int()) for i in range(P)] tot = sum(L2) return Rational(tot, P) def lfsr_connection_polynomial(s): """ This function computes the LFSR connection polynomial. Parameters ========== s A sequence of elements of even length, with entries in a finite field. Returns ======= C(x) The connection polynomial of a minimal LFSR yielding s. This implements the algorithm in section 3 of J. L. Massey's article [M]_. Examples ======== >>> from sympy.crypto.crypto import ( ... lfsr_sequence, lfsr_connection_polynomial) >>> from sympy.polys.domains import FF >>> F = FF(2) >>> fill = [F(1), F(1), F(0), F(1)] >>> key = [F(1), F(0), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x**4 + x + 1 >>> fill = [F(1), F(0), F(0), F(1)] >>> key = [F(1), F(1), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x**3 + 1 >>> fill = [F(1), F(0), F(1)] >>> key = [F(1), F(1), F(0)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x**3 + x**2 + 1 >>> fill = [F(1), F(0), F(1)] >>> key = [F(1), F(0), F(1)] >>> s = lfsr_sequence(key, fill, 20) >>> lfsr_connection_polynomial(s) x**3 + x + 1 References ========== .. [M] James L. Massey, "Shift-Register Synthesis and BCH Decoding." IEEE Trans. on Information Theory, vol. 15(1), pp. 122-127, Jan 1969. """ # Initialization: p = s[0].mod x = Symbol("x") C = 1*x**0 B = 1*x**0 m = 1 b = 1*x**0 L = 0 N = 0 while N < len(s): if L > 0: dC = Poly(C).degree() r = min(L + 1, dC + 1) coeffsC = [C.subs(x, 0)] + [C.coeff(x**i) for i in range(1, dC + 1)] d = (s[N].to_int() + sum([coeffsC[i]*s[N - i].to_int() for i in range(1, r)])) % p if L == 0: d = s[N].to_int()*x**0 if d == 0: m += 1 N += 1 if d > 0: if 2*L > N: C = (C - d*((b**(p - 2)) % p)*x**m*B).expand() m += 1 N += 1 else: T = C C = (C - d*((b**(p - 2)) % p)*x**m*B).expand() L = N + 1 - L m = 1 b = d B = T N += 1 dC = Poly(C).degree() coeffsC = [C.subs(x, 0)] + [C.coeff(x**i) for i in range(1, dC + 1)] return sum([coeffsC[i] % p*x**i for i in range(dC + 1) if coeffsC[i] is not None]) #################### ElGamal ############################# def elgamal_private_key(digit=10, seed=None): r""" Return three number tuple as private key. Explanation =========== Elgamal encryption is based on the mathmatical problem called the Discrete Logarithm Problem (DLP). For example, `a^{b} \equiv c \pmod p` In general, if ``a`` and ``b`` are known, ``ct`` is easily calculated. If ``b`` is unknown, it is hard to use ``a`` and ``ct`` to get ``b``. Parameters ========== digit : int Minimum number of binary digits for key. Returns ======= tuple : (p, r, d) p = prime number. r = primitive root. d = random number. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import elgamal_private_key >>> from sympy.ntheory import is_primitive_root, isprime >>> a, b, _ = elgamal_private_key() >>> isprime(a) True >>> is_primitive_root(b, a) True """ randrange = _randrange(seed) p = nextprime(2**digit) return p, primitive_root(p), randrange(2, p) def elgamal_public_key(key): r""" Return three number tuple as public key. Parameters ========== key : (p, r, e) Tuple generated by ``elgamal_private_key``. Returns ======= tuple : (p, r, e) `e = r**d \bmod p` `d` is a random number in private key. Examples ======== >>> from sympy.crypto.crypto import elgamal_public_key >>> elgamal_public_key((1031, 14, 636)) (1031, 14, 212) """ p, r, e = key return p, r, pow(r, e, p) def encipher_elgamal(i, key, seed=None): r""" Encrypt message with public key. Explanation =========== ``i`` is a plaintext message expressed as an integer. ``key`` is public key (p, r, e). In order to encrypt a message, a random number ``a`` in ``range(2, p)`` is generated and the encryped message is returned as `c_{1}` and `c_{2}` where: `c_{1} \equiv r^{a} \pmod p` `c_{2} \equiv m e^{a} \pmod p` Parameters ========== msg int of encoded message. key Public key. Returns ======= tuple : (c1, c2) Encipher into two number. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import encipher_elgamal, elgamal_private_key, elgamal_public_key >>> pri = elgamal_private_key(5, seed=[3]); pri (37, 2, 3) >>> pub = elgamal_public_key(pri); pub (37, 2, 8) >>> msg = 36 >>> encipher_elgamal(msg, pub, seed=[3]) (8, 6) """ p, r, e = key if i < 0 or i >= p: raise ValueError( 'Message (%s) should be in range(%s)' % (i, p)) randrange = _randrange(seed) a = randrange(2, p) return pow(r, a, p), i*pow(e, a, p) % p def decipher_elgamal(msg, key): r""" Decrypt message with private key. `msg = (c_{1}, c_{2})` `key = (p, r, d)` According to extended Eucliden theorem, `u c_{1}^{d} + p n = 1` `u \equiv 1/{{c_{1}}^d} \pmod p` `u c_{2} \equiv \frac{1}{c_{1}^d} c_{2} \equiv \frac{1}{r^{ad}} c_{2} \pmod p` `\frac{1}{r^{ad}} m e^a \equiv \frac{1}{r^{ad}} m {r^{d a}} \equiv m \pmod p` Examples ======== >>> from sympy.crypto.crypto import decipher_elgamal >>> from sympy.crypto.crypto import encipher_elgamal >>> from sympy.crypto.crypto import elgamal_private_key >>> from sympy.crypto.crypto import elgamal_public_key >>> pri = elgamal_private_key(5, seed=[3]) >>> pub = elgamal_public_key(pri); pub (37, 2, 8) >>> msg = 17 >>> decipher_elgamal(encipher_elgamal(msg, pub), pri) == msg True """ p, _, d = key c1, c2 = msg u = igcdex(c1**d, p)[0] return u * c2 % p ################ Diffie-Hellman Key Exchange ######################### def dh_private_key(digit=10, seed=None): r""" Return three integer tuple as private key. Explanation =========== Diffie-Hellman key exchange is based on the mathematical problem called the Discrete Logarithm Problem (see ElGamal). Diffie-Hellman key exchange is divided into the following steps: * Alice and Bob agree on a base that consist of a prime ``p`` and a primitive root of ``p`` called ``g`` * Alice choses a number ``a`` and Bob choses a number ``b`` where ``a`` and ``b`` are random numbers in range `[2, p)`. These are their private keys. * Alice then publicly sends Bob `g^{a} \pmod p` while Bob sends Alice `g^{b} \pmod p` * They both raise the received value to their secretly chosen number (``a`` or ``b``) and now have both as their shared key `g^{ab} \pmod p` Parameters ========== digit Minimum number of binary digits required in key. Returns ======= tuple : (p, g, a) p = prime number. g = primitive root of p. a = random number from 2 through p - 1. Notes ===== For testing purposes, the ``seed`` parameter may be set to control the output of this routine. See sympy.testing.randtest._randrange. Examples ======== >>> from sympy.crypto.crypto import dh_private_key >>> from sympy.ntheory import isprime, is_primitive_root >>> p, g, _ = dh_private_key() >>> isprime(p) True >>> is_primitive_root(g, p) True >>> p, g, _ = dh_private_key(5) >>> isprime(p) True >>> is_primitive_root(g, p) True """ p = nextprime(2**digit) g = primitive_root(p) randrange = _randrange(seed) a = randrange(2, p) return p, g, a def dh_public_key(key): r""" Return three number tuple as public key. This is the tuple that Alice sends to Bob. Parameters ========== key : (p, g, a) A tuple generated by ``dh_private_key``. Returns ======= tuple : int, int, int A tuple of `(p, g, g^a \mod p)` with `p`, `g` and `a` given as parameters.s Examples ======== >>> from sympy.crypto.crypto import dh_private_key, dh_public_key >>> p, g, a = dh_private_key(); >>> _p, _g, x = dh_public_key((p, g, a)) >>> p == _p and g == _g True >>> x == pow(g, a, p) True """ p, g, a = key return p, g, pow(g, a, p) def dh_shared_key(key, b): """ Return an integer that is the shared key. This is what Bob and Alice can both calculate using the public keys they received from each other and their private keys. Parameters ========== key : (p, g, x) Tuple `(p, g, x)` generated by ``dh_public_key``. b Random number in the range of `2` to `p - 1` (Chosen by second key exchange member (Bob)). Returns ======= int A shared key. Examples ======== >>> from sympy.crypto.crypto import ( ... dh_private_key, dh_public_key, dh_shared_key) >>> prk = dh_private_key(); >>> p, g, x = dh_public_key(prk); >>> sk = dh_shared_key((p, g, x), 1000) >>> sk == pow(x, 1000, p) True """ p, _, x = key if 1 >= b or b >= p: raise ValueError(filldedent(''' Value of b should be greater 1 and less than prime %s.''' % p)) return pow(x, b, p) ################ Goldwasser-Micali Encryption ######################### def _legendre(a, p): """ Returns the legendre symbol of a and p assuming that p is a prime. i.e. 1 if a is a quadratic residue mod p -1 if a is not a quadratic residue mod p 0 if a is divisible by p Parameters ========== a : int The number to test. p : prime The prime to test ``a`` against. Returns ======= int Legendre symbol (a / p). """ sig = pow(a, (p - 1)//2, p) if sig == 1: return 1 elif sig == 0: return 0 else: return -1 def _random_coprime_stream(n, seed=None): randrange = _randrange(seed) while True: y = randrange(n) if gcd(y, n) == 1: yield y def gm_private_key(p, q, a=None): """ Check if ``p`` and ``q`` can be used as private keys for the Goldwasser-Micali encryption. The method works roughly as follows. Explanation =========== $\\cdot$ Pick two large primes $p$ and $q$. $\\cdot$ Call their product $N$. $\\cdot$ Given a message as an integer $i$, write $i$ in its bit representation $b_0$ , $\\dotsc$ , $b_n$ . $\\cdot$ For each $k$ , if $b_k$ = 0: let $a_k$ be a random square (quadratic residue) modulo $p q$ such that $jacobi \\_symbol(a, p q) = 1$ if $b_k$ = 1: let $a_k$ be a random non-square (non-quadratic residue) modulo $p q$ such that $jacobi \\_ symbol(a, p q) = 1$ returns [$a_1$ , $a_2$ , $\\dotsc$ ] $b_k$ can be recovered by checking whether or not $a_k$ is a residue. And from the $b_k$ 's, the message can be reconstructed. The idea is that, while $jacobi \\_ symbol(a, p q)$ can be easily computed (and when it is equal to $-1$ will tell you that $a$ is not a square mod $p q$ ), quadratic residuosity modulo a composite number is hard to compute without knowing its factorization. Moreover, approximately half the numbers coprime to $p q$ have $jacobi \\_ symbol$ equal to $1$ . And among those, approximately half are residues and approximately half are not. This maximizes the entropy of the code. Parameters ========== p, q, a Initialization variables. Returns ======= tuple : (p, q) The input value ``p`` and ``q``. Raises ====== ValueError If ``p`` and ``q`` are not distinct odd primes. """ if p == q: raise ValueError("expected distinct primes, " "got two copies of %i" % p) elif not isprime(p) or not isprime(q): raise ValueError("first two arguments must be prime, " "got %i of %i" % (p, q)) elif p == 2 or q == 2: raise ValueError("first two arguments must not be even, " "got %i of %i" % (p, q)) return p, q def gm_public_key(p, q, a=None, seed=None): """ Compute public keys for ``p`` and ``q``. Note that in Goldwasser-Micali Encryption, public keys are randomly selected. Parameters ========== p, q, a : int, int, int Initialization variables. Returns ======= tuple : (a, N) ``a`` is the input ``a`` if it is not ``None`` otherwise some random integer coprime to ``p`` and ``q``. ``N`` is the product of ``p`` and ``q``. """ p, q = gm_private_key(p, q) N = p * q if a is None: randrange = _randrange(seed) while True: a = randrange(N) if _legendre(a, p) == _legendre(a, q) == -1: break else: if _legendre(a, p) != -1 or _legendre(a, q) != -1: return False return (a, N) def encipher_gm(i, key, seed=None): """ Encrypt integer 'i' using public_key 'key' Note that gm uses random encryption. Parameters ========== i : int The message to encrypt. key : (a, N) The public key. Returns ======= list : list of int The randomized encrypted message. """ if i < 0: raise ValueError( "message must be a non-negative " "integer: got %d instead" % i) a, N = key bits = [] while i > 0: bits.append(i % 2) i //= 2 gen = _random_coprime_stream(N, seed) rev = reversed(bits) encode = lambda b: next(gen)**2*pow(a, b) % N return [ encode(b) for b in rev ] def decipher_gm(message, key): """ Decrypt message 'message' using public_key 'key'. Parameters ========== message : list of int The randomized encrypted message. key : (p, q) The private key. Returns ======= int The encrypted message. """ p, q = key res = lambda m, p: _legendre(m, p) > 0 bits = [res(m, p) * res(m, q) for m in message] m = 0 for b in bits: m <<= 1 m += not b return m ########### RailFence Cipher ############# def encipher_railfence(message,rails): """ Performs Railfence Encryption on plaintext and returns ciphertext Examples ======== >>> from sympy.crypto.crypto import encipher_railfence >>> message = "hello world" >>> encipher_railfence(message,3) 'horel ollwd' Parameters ========== message : string, the message to encrypt. rails : int, the number of rails. Returns ======= The Encrypted string message. References ========== .. [1] https://en.wikipedia.org/wiki/Rail_fence_cipher """ r = list(range(rails)) p = cycle(r + r[-2:0:-1]) return ''.join(sorted(message, key=lambda i: next(p))) def decipher_railfence(ciphertext,rails): """ Decrypt the message using the given rails Examples ======== >>> from sympy.crypto.crypto import decipher_railfence >>> decipher_railfence("horel ollwd",3) 'hello world' Parameters ========== message : string, the message to encrypt. rails : int, the number of rails. Returns ======= The Decrypted string message. """ r = list(range(rails)) p = cycle(r + r[-2:0:-1]) idx = sorted(range(len(ciphertext)), key=lambda i: next(p)) res = [''] * len(ciphertext) for i, c in zip(idx, ciphertext): res[i] = c return ''.join(res) ################ Blum-Goldwasser cryptosystem ######################### def bg_private_key(p, q): """ Check if p and q can be used as private keys for the Blum-Goldwasser cryptosystem. Explanation =========== The three necessary checks for p and q to pass so that they can be used as private keys: 1. p and q must both be prime 2. p and q must be distinct 3. p and q must be congruent to 3 mod 4 Parameters ========== p, q The keys to be checked. Returns ======= p, q Input values. Raises ====== ValueError If p and q do not pass the above conditions. """ if not isprime(p) or not isprime(q): raise ValueError("the two arguments must be prime, " "got %i and %i" %(p, q)) elif p == q: raise ValueError("the two arguments must be distinct, " "got two copies of %i. " %p) elif (p - 3) % 4 != 0 or (q - 3) % 4 != 0: raise ValueError("the two arguments must be congruent to 3 mod 4, " "got %i and %i" %(p, q)) return p, q def bg_public_key(p, q): """ Calculates public keys from private keys. Explanation =========== The function first checks the validity of private keys passed as arguments and then returns their product. Parameters ========== p, q The private keys. Returns ======= N The public key. """ p, q = bg_private_key(p, q) N = p * q return N def encipher_bg(i, key, seed=None): """ Encrypts the message using public key and seed. Explanation =========== ALGORITHM: 1. Encodes i as a string of L bits, m. 2. Select a random element r, where 1 < r < key, and computes x = r^2 mod key. 3. Use BBS pseudo-random number generator to generate L random bits, b, using the initial seed as x. 4. Encrypted message, c_i = m_i XOR b_i, 1 <= i <= L. 5. x_L = x^(2^L) mod key. 6. Return (c, x_L) Parameters ========== i Message, a non-negative integer key The public key Returns ======= Tuple (encrypted_message, x_L) Raises ====== ValueError If i is negative. """ if i < 0: raise ValueError( "message must be a non-negative " "integer: got %d instead" % i) enc_msg = [] while i > 0: enc_msg.append(i % 2) i //= 2 enc_msg.reverse() L = len(enc_msg) r = _randint(seed)(2, key - 1) x = r**2 % key x_L = pow(int(x), int(2**L), int(key)) rand_bits = [] for _ in range(L): rand_bits.append(x % 2) x = x**2 % key encrypt_msg = [m ^ b for (m, b) in zip(enc_msg, rand_bits)] return (encrypt_msg, x_L) def decipher_bg(message, key): """ Decrypts the message using private keys. Explanation =========== ALGORITHM: 1. Let, c be the encrypted message, y the second number received, and p and q be the private keys. 2. Compute, r_p = y^((p+1)/4 ^ L) mod p and r_q = y^((q+1)/4 ^ L) mod q. 3. Compute x_0 = (q(q^-1 mod p)r_p + p(p^-1 mod q)r_q) mod N. 4. From, recompute the bits using the BBS generator, as in the encryption algorithm. 5. Compute original message by XORing c and b. Parameters ========== message Tuple of encrypted message and a non-negative integer. key Tuple of private keys. Returns ======= orig_msg The original message """ p, q = key encrypt_msg, y = message public_key = p * q L = len(encrypt_msg) p_t = ((p + 1)/4)**L q_t = ((q + 1)/4)**L r_p = pow(int(y), int(p_t), int(p)) r_q = pow(int(y), int(q_t), int(q)) x = (q * mod_inverse(q, p) * r_p + p * mod_inverse(p, q) * r_q) % public_key orig_bits = [] for _ in range(L): orig_bits.append(x % 2) x = x**2 % public_key orig_msg = 0 for (m, b) in zip(encrypt_msg, orig_bits): orig_msg = orig_msg * 2 orig_msg += (m ^ b) return orig_msg

995dbc94b5fcf1e2a06ce72aa655d2eeb83c6caff96e7299dfaf4e7e8a024e22

from sympy.core.add import Add from sympy.core.compatibility import ordered from sympy.core.function import expand_log from sympy.core.power import Pow from sympy.core.singleton import S from sympy.core.symbol import Dummy from sympy.functions.elementary.exponential import (LambertW, exp, log) from sympy.functions.elementary.miscellaneous import root from sympy.polys.polyroots import roots from sympy.polys.polytools import Poly, factor from sympy.core.function import _mexpand from sympy.simplify.simplify import separatevars from sympy.simplify.radsimp import collect from sympy.simplify.simplify import powsimp from sympy.solvers.solvers import solve, _invert from sympy.utilities.iterables import uniq def _filtered_gens(poly, symbol): """process the generators of ``poly``, returning the set of generators that have ``symbol``. If there are two generators that are inverses of each other, prefer the one that has no denominator. Examples ======== >>> from sympy.solvers.bivariate import _filtered_gens >>> from sympy import Poly, exp >>> from sympy.abc import x >>> _filtered_gens(Poly(x + 1/x + exp(x)), x) {x, exp(x)} """ gens = {g for g in poly.gens if symbol in g.free_symbols} for g in list(gens): ag = 1/g if g in gens and ag in gens: if ag.as_numer_denom()[1] is not S.One: g = ag gens.remove(g) return gens def _mostfunc(lhs, func, X=None): """Returns the term in lhs which contains the most of the func-type things e.g. log(log(x)) wins over log(x) if both terms appear. ``func`` can be a function (exp, log, etc...) or any other SymPy object, like Pow. If ``X`` is not ``None``, then the function returns the term composed with the most ``func`` having the specified variable. Examples ======== >>> from sympy.solvers.bivariate import _mostfunc >>> from sympy.functions.elementary.exponential import exp >>> from sympy.abc import x, y >>> _mostfunc(exp(x) + exp(exp(x) + 2), exp) exp(exp(x) + 2) >>> _mostfunc(exp(x) + exp(exp(y) + 2), exp) exp(exp(y) + 2) >>> _mostfunc(exp(x) + exp(exp(y) + 2), exp, x) exp(x) >>> _mostfunc(x, exp, x) is None True >>> _mostfunc(exp(x) + exp(x*y), exp, x) exp(x) """ fterms = [tmp for tmp in lhs.atoms(func) if (not X or X.is_Symbol and X in tmp.free_symbols or not X.is_Symbol and tmp.has(X))] if len(fterms) == 1: return fterms[0] elif fterms: return max(list(ordered(fterms)), key=lambda x: x.count(func)) return None def _linab(arg, symbol): """Return ``a, b, X`` assuming ``arg`` can be written as ``a*X + b`` where ``X`` is a symbol-dependent factor and ``a`` and ``b`` are independent of ``symbol``. Examples ======== >>> from sympy.functions.elementary.exponential import exp >>> from sympy.solvers.bivariate import _linab >>> from sympy.abc import x, y >>> from sympy import S >>> _linab(S(2), x) (2, 0, 1) >>> _linab(2*x, x) (2, 0, x) >>> _linab(y + y*x + 2*x, x) (y + 2, y, x) >>> _linab(3 + 2*exp(x), x) (2, 3, exp(x)) """ from sympy.core.exprtools import factor_terms arg = factor_terms(arg.expand()) ind, dep = arg.as_independent(symbol) if arg.is_Mul and dep.is_Add: a, b, x = _linab(dep, symbol) return ind*a, ind*b, x if not arg.is_Add: b = 0 a, x = ind, dep else: b = ind a, x = separatevars(dep).as_independent(symbol, as_Add=False) if x.could_extract_minus_sign(): a = -a x = -x return a, b, x def _lambert(eq, x): """ Given an expression assumed to be in the form ``F(X, a..f) = a*log(b*X + c) + d*X + f = 0`` where X = g(x) and x = g^-1(X), return the Lambert solution, ``x = g^-1(-c/b + (a/d)*W(d/(a*b)*exp(c*d/a/b)*exp(-f/a)))``. """ eq = _mexpand(expand_log(eq)) mainlog = _mostfunc(eq, log, x) if not mainlog: return [] # violated assumptions other = eq.subs(mainlog, 0) if isinstance(-other, log): eq = (eq - other).subs(mainlog, mainlog.args[0]) mainlog = mainlog.args[0] if not isinstance(mainlog, log): return [] # violated assumptions other = -(-other).args[0] eq += other if not x in other.free_symbols: return [] # violated assumptions d, f, X2 = _linab(other, x) logterm = collect(eq - other, mainlog) a = logterm.as_coefficient(mainlog) if a is None or x in a.free_symbols: return [] # violated assumptions logarg = mainlog.args[0] b, c, X1 = _linab(logarg, x) if X1 != X2: return [] # violated assumptions # invert the generator X1 so we have x(u) u = Dummy('rhs') xusolns = solve(X1 - u, x) # There are infinitely many branches for LambertW # but only branches for k = -1 and 0 might be real. The k = 0 # branch is real and the k = -1 branch is real if the LambertW argumen # in in range [-1/e, 0]. Since `solve` does not return infinite # solutions we will only include the -1 branch if it tests as real. # Otherwise, inclusion of any LambertW in the solution indicates to # the user that there are imaginary solutions corresponding to # different k values. lambert_real_branches = [-1, 0] sol = [] # solution of the given Lambert equation is like # sol = -c/b + (a/d)*LambertW(arg, k), # where arg = d/(a*b)*exp((c*d-b*f)/a/b) and k in lambert_real_branches. # Instead of considering the single arg, `d/(a*b)*exp((c*d-b*f)/a/b)`, # the individual `p` roots obtained when writing `exp((c*d-b*f)/a/b)` # as `exp(A/p) = exp(A)**(1/p)`, where `p` is an Integer, are used. # calculating args for LambertW num, den = ((c*d-b*f)/a/b).as_numer_denom() p, den = den.as_coeff_Mul() e = exp(num/den) t = Dummy('t') args = [d/(a*b)*t for t in roots(t**p - e, t).keys()] # calculating solutions from args for arg in args: for k in lambert_real_branches: w = LambertW(arg, k) if k and not w.is_real: continue rhs = -c/b + (a/d)*w for xu in xusolns: sol.append(xu.subs(u, rhs)) return sol def _solve_lambert(f, symbol, gens): """Return solution to ``f`` if it is a Lambert-type expression else raise NotImplementedError. For ``f(X, a..f) = a*log(b*X + c) + d*X - f = 0`` the solution for ``X`` is ``X = -c/b + (a/d)*W(d/(a*b)*exp(c*d/a/b)*exp(f/a))``. There are a variety of forms for `f(X, a..f)` as enumerated below: 1a1) if B**B = R for R not in [0, 1] (since those cases would already be solved before getting here) then log of both sides gives log(B) + log(log(B)) = log(log(R)) and X = log(B), a = 1, b = 1, c = 0, d = 1, f = log(log(R)) 1a2) if B*(b*log(B) + c)**a = R then log of both sides gives log(B) + a*log(b*log(B) + c) = log(R) and X = log(B), d=1, f=log(R) 1b) if a*log(b*B + c) + d*B = R and X = B, f = R 2a) if (b*B + c)*exp(d*B + g) = R then log of both sides gives log(b*B + c) + d*B + g = log(R) and X = B, a = 1, f = log(R) - g 2b) if g*exp(d*B + h) - b*B = c then the log form is log(g) + d*B + h - log(b*B + c) = 0 and X = B, a = -1, f = -h - log(g) 3) if d*p**(a*B + g) - b*B = c then the log form is log(d) + (a*B + g)*log(p) - log(b*B + c) = 0 and X = B, a = -1, d = a*log(p), f = -log(d) - g*log(p) """ def _solve_even_degree_expr(expr, t, symbol): """Return the unique solutions of equations derived from ``expr`` by replacing ``t`` with ``+/- symbol``. Parameters ========== expr : Expr The expression which includes a dummy variable t to be replaced with +symbol and -symbol. symbol : Symbol The symbol for which a solution is being sought. Returns ======= List of unique solution of the two equations generated by replacing ``t`` with positive and negative ``symbol``. Notes ===== If ``expr = 2*log(t) + x/2` then solutions for ``2*log(x) + x/2 = 0`` and ``2*log(-x) + x/2 = 0`` are returned by this function. Though this may seem counter-intuitive, one must note that the ``expr`` being solved here has been derived from a different expression. For an expression like ``eq = x**2*g(x) = 1``, if we take the log of both sides we obtain ``log(x**2) + log(g(x)) = 0``. If x is positive then this simplifies to ``2*log(x) + log(g(x)) = 0``; the Lambert-solving routines will return solutions for this, but we must also consider the solutions for ``2*log(-x) + log(g(x))`` since those must also be a solution of ``eq`` which has the same value when the ``x`` in ``x**2`` is negated. If `g(x)` does not have even powers of symbol then we don't want to replace the ``x`` there with ``-x``. So the role of the ``t`` in the expression received by this function is to mark where ``+/-x`` should be inserted before obtaining the Lambert solutions. """ nlhs, plhs = [ expr.xreplace({t: sgn*symbol}) for sgn in (-1, 1)] sols = _solve_lambert(nlhs, symbol, gens) if plhs != nlhs: sols.extend(_solve_lambert(plhs, symbol, gens)) # uniq is needed for a case like # 2*log(t) - log(-z**2) + log(z + log(x) + log(z)) # where subtituting t with +/-x gives all the same solution; # uniq, rather than list(set()), is used to maintain canonical # order return list(uniq(sols)) nrhs, lhs = f.as_independent(symbol, as_Add=True) rhs = -nrhs lamcheck = [tmp for tmp in gens if (tmp.func in [exp, log] or (tmp.is_Pow and symbol in tmp.exp.free_symbols))] if not lamcheck: raise NotImplementedError() if lhs.is_Add or lhs.is_Mul: # replacing all even_degrees of symbol with dummy variable t # since these will need special handling; non-Add/Mul do not # need this handling t = Dummy('t', **symbol.assumptions0) lhs = lhs.replace( lambda i: # find symbol**even i.is_Pow and i.base == symbol and i.exp.is_even, lambda i: # replace t**even t**i.exp) if lhs.is_Add and lhs.has(t): t_indep = lhs.subs(t, 0) t_term = lhs - t_indep _rhs = rhs - t_indep if not t_term.is_Add and _rhs and not ( t_term.has(S.ComplexInfinity, S.NaN)): eq = expand_log(log(t_term) - log(_rhs)) return _solve_even_degree_expr(eq, t, symbol) elif lhs.is_Mul and rhs: # this needs to happen whether t is present or not lhs = expand_log(log(lhs), force=True) rhs = log(rhs) if lhs.has(t) and lhs.is_Add: # it expanded from Mul to Add eq = lhs - rhs return _solve_even_degree_expr(eq, t, symbol) # restore symbol in lhs lhs = lhs.xreplace({t: symbol}) lhs = powsimp(factor(lhs, deep=True)) # make sure we have inverted as completely as possible r = Dummy() i, lhs = _invert(lhs - r, symbol) rhs = i.xreplace({r: rhs}) # For the first forms: # # 1a1) B**B = R will arrive here as B*log(B) = log(R) # lhs is Mul so take log of both sides: # log(B) + log(log(B)) = log(log(R)) # 1a2) B*(b*log(B) + c)**a = R will arrive unchanged so # lhs is Mul, so take log of both sides: # log(B) + a*log(b*log(B) + c) = log(R) # 1b) d*log(a*B + b) + c*B = R will arrive unchanged so # lhs is Add, so isolate c*B and expand log of both sides: # log(c) + log(B) = log(R - d*log(a*B + b)) soln = [] if not soln: mainlog = _mostfunc(lhs, log, symbol) if mainlog: if lhs.is_Mul and rhs != 0: soln = _lambert(log(lhs) - log(rhs), symbol) elif lhs.is_Add: other = lhs.subs(mainlog, 0) if other and not other.is_Add and [ tmp for tmp in other.atoms(Pow) if symbol in tmp.free_symbols]: if not rhs: diff = log(other) - log(other - lhs) else: diff = log(lhs - other) - log(rhs - other) soln = _lambert(expand_log(diff), symbol) else: #it's ready to go soln = _lambert(lhs - rhs, symbol) # For the next forms, # # collect on main exp # 2a) (b*B + c)*exp(d*B + g) = R # lhs is mul, so take log of both sides: # log(b*B + c) + d*B = log(R) - g # 2b) g*exp(d*B + h) - b*B = R # lhs is add, so add b*B to both sides, # take the log of both sides and rearrange to give # log(R + b*B) - d*B = log(g) + h if not soln: mainexp = _mostfunc(lhs, exp, symbol) if mainexp: lhs = collect(lhs, mainexp) if lhs.is_Mul and rhs != 0: soln = _lambert(expand_log(log(lhs) - log(rhs)), symbol) elif lhs.is_Add: # move all but mainexp-containing term to rhs other = lhs.subs(mainexp, 0) mainterm = lhs - other rhs = rhs - other if (mainterm.could_extract_minus_sign() and rhs.could_extract_minus_sign()): mainterm *= -1 rhs *= -1 diff = log(mainterm) - log(rhs) soln = _lambert(expand_log(diff), symbol) # For the last form: # # 3) d*p**(a*B + g) - b*B = c # collect on main pow, add b*B to both sides, # take log of both sides and rearrange to give # a*B*log(p) - log(b*B + c) = -log(d) - g*log(p) if not soln: mainpow = _mostfunc(lhs, Pow, symbol) if mainpow and symbol in mainpow.exp.free_symbols: lhs = collect(lhs, mainpow) if lhs.is_Mul and rhs != 0: # b*B = 0 soln = _lambert(expand_log(log(lhs) - log(rhs)), symbol) elif lhs.is_Add: # move all but mainpow-containing term to rhs other = lhs.subs(mainpow, 0) mainterm = lhs - other rhs = rhs - other diff = log(mainterm) - log(rhs) soln = _lambert(expand_log(diff), symbol) if not soln: raise NotImplementedError('%s does not appear to have a solution in ' 'terms of LambertW' % f) return list(ordered(soln)) def bivariate_type(f, x, y, *, first=True): """Given an expression, f, 3 tests will be done to see what type of composite bivariate it might be, options for u(x, y) are:: x*y x+y x*y+x x*y+y If it matches one of these types, ``u(x, y)``, ``P(u)`` and dummy variable ``u`` will be returned. Solving ``P(u)`` for ``u`` and equating the solutions to ``u(x, y)`` and then solving for ``x`` or ``y`` is equivalent to solving the original expression for ``x`` or ``y``. If ``x`` and ``y`` represent two functions in the same variable, e.g. ``x = g(t)`` and ``y = h(t)``, then if ``u(x, y) - p`` can be solved for ``t`` then these represent the solutions to ``P(u) = 0`` when ``p`` are the solutions of ``P(u) = 0``. Only positive values of ``u`` are considered. Examples ======== >>> from sympy.solvers.solvers import solve >>> from sympy.solvers.bivariate import bivariate_type >>> from sympy.abc import x, y >>> eq = (x**2 - 3).subs(x, x + y) >>> bivariate_type(eq, x, y) (x + y, _u**2 - 3, _u) >>> uxy, pu, u = _ >>> usol = solve(pu, u); usol [sqrt(3)] >>> [solve(uxy - s) for s in solve(pu, u)] [[{x: -y + sqrt(3)}]] >>> all(eq.subs(s).equals(0) for sol in _ for s in sol) True """ u = Dummy('u', positive=True) if first: p = Poly(f, x, y) f = p.as_expr() _x = Dummy() _y = Dummy() rv = bivariate_type(Poly(f.subs({x: _x, y: _y}), _x, _y), _x, _y, first=False) if rv: reps = {_x: x, _y: y} return rv[0].xreplace(reps), rv[1].xreplace(reps), rv[2] return p = f f = p.as_expr() # f(x*y) args = Add.make_args(p.as_expr()) new = [] for a in args: a = _mexpand(a.subs(x, u/y)) free = a.free_symbols if x in free or y in free: break new.append(a) else: return x*y, Add(*new), u def ok(f, v, c): new = _mexpand(f.subs(v, c)) free = new.free_symbols return None if (x in free or y in free) else new # f(a*x + b*y) new = [] d = p.degree(x) if p.degree(y) == d: a = root(p.coeff_monomial(x**d), d) b = root(p.coeff_monomial(y**d), d) new = ok(f, x, (u - b*y)/a) if new is not None: return a*x + b*y, new, u # f(a*x*y + b*y) new = [] d = p.degree(x) if p.degree(y) == d: for itry in range(2): a = root(p.coeff_monomial(x**d*y**d), d) b = root(p.coeff_monomial(y**d), d) new = ok(f, x, (u - b*y)/a/y) if new is not None: return a*x*y + b*y, new, u x, y = y, x

6979c6ce6a257f2ae9f98793ac839436534e4ab9bddc03a0420acae110359871

r""" This module is intended for solving recurrences or, in other words, difference equations. Currently supported are linear, inhomogeneous equations with polynomial or rational coefficients. The solutions are obtained among polynomials, rational functions, hypergeometric terms, or combinations of hypergeometric term which are pairwise dissimilar. ``rsolve_X`` functions were meant as a low level interface for ``rsolve`` which would use Mathematica's syntax. Given a recurrence relation: .. math:: a_{k}(n) y(n+k) + a_{k-1}(n) y(n+k-1) + ... + a_{0}(n) y(n) = f(n) where `k > 0` and `a_{i}(n)` are polynomials in `n`. To use ``rsolve_X`` we need to put all coefficients in to a list ``L`` of `k+1` elements the following way: ``L = [a_{0}(n), ..., a_{k-1}(n), a_{k}(n)]`` where ``L[i]``, for `i=0, \ldots, k`, maps to `a_{i}(n) y(n+i)` (`y(n+i)` is implicit). For example if we would like to compute `m`-th Bernoulli polynomial up to a constant (example was taken from rsolve_poly docstring), then we would use `b(n+1) - b(n) = m n^{m-1}` recurrence, which has solution `b(n) = B_m + C`. Then ``L = [-1, 1]`` and `f(n) = m n^(m-1)` and finally for `m=4`: >>> from sympy import Symbol, bernoulli, rsolve_poly >>> n = Symbol('n', integer=True) >>> rsolve_poly([-1, 1], 4*n**3, n) C0 + n**4 - 2*n**3 + n**2 >>> bernoulli(4, n) n**4 - 2*n**3 + n**2 - 1/30 For the sake of completeness, `f(n)` can be: [1] a polynomial -> rsolve_poly [2] a rational function -> rsolve_ratio [3] a hypergeometric function -> rsolve_hyper """ from collections import defaultdict from sympy.core.singleton import S from sympy.core.numbers import Rational, I from sympy.core.symbol import Symbol, Wild, Dummy from sympy.core.relational import Equality from sympy.core.add import Add from sympy.core.mul import Mul from sympy.core import sympify from sympy.simplify import simplify, hypersimp, hypersimilar # type: ignore from sympy.solvers import solve, solve_undetermined_coeffs from sympy.polys import Poly, quo, gcd, lcm, roots, resultant from sympy.functions import binomial, factorial, FallingFactorial, RisingFactorial from sympy.matrices import Matrix, casoratian from sympy.concrete import product from sympy.core.compatibility import default_sort_key from sympy.utilities.iterables import numbered_symbols def rsolve_poly(coeffs, f, n, **hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f`, where `f` is a polynomial, we seek for all polynomial solutions over field `K` of characteristic zero. The algorithm performs two basic steps: (1) Compute degree `N` of the general polynomial solution. (2) Find all polynomials of degree `N` or less of `\operatorname{L} y = f`. There are two methods for computing the polynomial solutions. If the degree bound is relatively small, i.e. it's smaller than or equal to the order of the recurrence, then naive method of undetermined coefficients is being used. This gives system of algebraic equations with `N+1` unknowns. In the other case, the algorithm performs transformation of the initial equation to an equivalent one, for which the system of algebraic equations has only `r` indeterminates. This method is quite sophisticated (in comparison with the naive one) and was invented together by Abramov, Bronstein and Petkovsek. It is possible to generalize the algorithm implemented here to the case of linear q-difference and differential equations. Lets say that we would like to compute `m`-th Bernoulli polynomial up to a constant. For this we can use `b(n+1) - b(n) = m n^{m-1}` recurrence, which has solution `b(n) = B_m + C`. For example: >>> from sympy import Symbol, rsolve_poly >>> n = Symbol('n', integer=True) >>> rsolve_poly([-1, 1], 4*n**3, n) C0 + n**4 - 2*n**3 + n**2 References ========== .. [1] S. A. Abramov, M. Bronstein and M. Petkovsek, On polynomial solutions of linear operator equations, in: T. Levelt, ed., Proc. ISSAC '95, ACM Press, New York, 1995, 290-296. .. [2] M. Petkovsek, Hypergeometric solutions of linear recurrences with polynomial coefficients, J. Symbolic Computation, 14 (1992), 243-264. .. [3] M. Petkovsek, H. S. Wilf, D. Zeilberger, A = B, 1996. """ f = sympify(f) if not f.is_polynomial(n): return None homogeneous = f.is_zero r = len(coeffs) - 1 coeffs = [Poly(coeff, n) for coeff in coeffs] polys = [Poly(0, n)]*(r + 1) terms = [(S.Zero, S.NegativeInfinity)]*(r + 1) for i in range(r + 1): for j in range(i, r + 1): polys[i] += coeffs[j]*(binomial(j, i).as_poly(n)) if not polys[i].is_zero: (exp,), coeff = polys[i].LT() terms[i] = (coeff, exp) d = b = terms[0][1] for i in range(1, r + 1): if terms[i][1] > d: d = terms[i][1] if terms[i][1] - i > b: b = terms[i][1] - i d, b = int(d), int(b) x = Dummy('x') degree_poly = S.Zero for i in range(r + 1): if terms[i][1] - i == b: degree_poly += terms[i][0]*FallingFactorial(x, i) nni_roots = list(roots(degree_poly, x, filter='Z', predicate=lambda r: r >= 0).keys()) if nni_roots: N = [max(nni_roots)] else: N = [] if homogeneous: N += [-b - 1] else: N += [f.as_poly(n).degree() - b, -b - 1] N = int(max(N)) if N < 0: if homogeneous: if hints.get('symbols', False): return (S.Zero, []) else: return S.Zero else: return None if N <= r: C = [] y = E = S.Zero for i in range(N + 1): C.append(Symbol('C' + str(i))) y += C[i] * n**i for i in range(r + 1): E += coeffs[i].as_expr()*y.subs(n, n + i) solutions = solve_undetermined_coeffs(E - f, C, n) if solutions is not None: C = [c for c in C if (c not in solutions)] result = y.subs(solutions) else: return None # TBD else: A = r U = N + A + b + 1 nni_roots = list(roots(polys[r], filter='Z', predicate=lambda r: r >= 0).keys()) if nni_roots != []: a = max(nni_roots) + 1 else: a = S.Zero def _zero_vector(k): return [S.Zero] * k def _one_vector(k): return [S.One] * k def _delta(p, k): B = S.One D = p.subs(n, a + k) for i in range(1, k + 1): B *= Rational(i - k - 1, i) D += B * p.subs(n, a + k - i) return D alpha = {} for i in range(-A, d + 1): I = _one_vector(d + 1) for k in range(1, d + 1): I[k] = I[k - 1] * (x + i - k + 1)/k alpha[i] = S.Zero for j in range(A + 1): for k in range(d + 1): B = binomial(k, i + j) D = _delta(polys[j].as_expr(), k) alpha[i] += I[k]*B*D V = Matrix(U, A, lambda i, j: int(i == j)) if homogeneous: for i in range(A, U): v = _zero_vector(A) for k in range(1, A + b + 1): if i - k < 0: break B = alpha[k - A].subs(x, i - k) for j in range(A): v[j] += B * V[i - k, j] denom = alpha[-A].subs(x, i) for j in range(A): V[i, j] = -v[j] / denom else: G = _zero_vector(U) for i in range(A, U): v = _zero_vector(A) g = S.Zero for k in range(1, A + b + 1): if i - k < 0: break B = alpha[k - A].subs(x, i - k) for j in range(A): v[j] += B * V[i - k, j] g += B * G[i - k] denom = alpha[-A].subs(x, i) for j in range(A): V[i, j] = -v[j] / denom G[i] = (_delta(f, i - A) - g) / denom P, Q = _one_vector(U), _zero_vector(A) for i in range(1, U): P[i] = (P[i - 1] * (n - a - i + 1)/i).expand() for i in range(A): Q[i] = Add(*[(v*p).expand() for v, p in zip(V[:, i], P)]) if not homogeneous: h = Add(*[(g*p).expand() for g, p in zip(G, P)]) C = [Symbol('C' + str(i)) for i in range(A)] g = lambda i: Add(*[c*_delta(q, i) for c, q in zip(C, Q)]) if homogeneous: E = [g(i) for i in range(N + 1, U)] else: E = [g(i) + _delta(h, i) for i in range(N + 1, U)] if E != []: solutions = solve(E, *C) if not solutions: if homogeneous: if hints.get('symbols', False): return (S.Zero, []) else: return S.Zero else: return None else: solutions = {} if homogeneous: result = S.Zero else: result = h for c, q in list(zip(C, Q)): if c in solutions: s = solutions[c]*q C.remove(c) else: s = c*q result += s.expand() if hints.get('symbols', False): return (result, C) else: return result def rsolve_ratio(coeffs, f, n, **hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f`, where `f` is a polynomial, we seek for all rational solutions over field `K` of characteristic zero. This procedure accepts only polynomials, however if you are interested in solving recurrence with rational coefficients then use ``rsolve`` which will pre-process the given equation and run this procedure with polynomial arguments. The algorithm performs two basic steps: (1) Compute polynomial `v(n)` which can be used as universal denominator of any rational solution of equation `\operatorname{L} y = f`. (2) Construct new linear difference equation by substitution `y(n) = u(n)/v(n)` and solve it for `u(n)` finding all its polynomial solutions. Return ``None`` if none were found. Algorithm implemented here is a revised version of the original Abramov's algorithm, developed in 1989. The new approach is much simpler to implement and has better overall efficiency. This method can be easily adapted to q-difference equations case. Besides finding rational solutions alone, this functions is an important part of Hyper algorithm were it is used to find particular solution of inhomogeneous part of a recurrence. Examples ======== >>> from sympy.abc import x >>> from sympy.solvers.recurr import rsolve_ratio >>> rsolve_ratio([-2*x**3 + x**2 + 2*x - 1, 2*x**3 + x**2 - 6*x, ... - 2*x**3 - 11*x**2 - 18*x - 9, 2*x**3 + 13*x**2 + 22*x + 8], 0, x) C2*(2*x - 3)/(2*(x**2 - 1)) References ========== .. [1] S. A. Abramov, Rational solutions of linear difference and q-difference equations with polynomial coefficients, in: T. Levelt, ed., Proc. ISSAC '95, ACM Press, New York, 1995, 285-289 See Also ======== rsolve_hyper """ f = sympify(f) if not f.is_polynomial(n): return None coeffs = list(map(sympify, coeffs)) r = len(coeffs) - 1 A, B = coeffs[r], coeffs[0] A = A.subs(n, n - r).expand() h = Dummy('h') res = resultant(A, B.subs(n, n + h), n) if not res.is_polynomial(h): p, q = res.as_numer_denom() res = quo(p, q, h) nni_roots = list(roots(res, h, filter='Z', predicate=lambda r: r >= 0).keys()) if not nni_roots: return rsolve_poly(coeffs, f, n, **hints) else: C, numers = S.One, [S.Zero]*(r + 1) for i in range(int(max(nni_roots)), -1, -1): d = gcd(A, B.subs(n, n + i), n) A = quo(A, d, n) B = quo(B, d.subs(n, n - i), n) C *= Mul(*[d.subs(n, n - j) for j in range(i + 1)]) denoms = [C.subs(n, n + i) for i in range(r + 1)] for i in range(r + 1): g = gcd(coeffs[i], denoms[i], n) numers[i] = quo(coeffs[i], g, n) denoms[i] = quo(denoms[i], g, n) for i in range(r + 1): numers[i] *= Mul(*(denoms[:i] + denoms[i + 1:])) result = rsolve_poly(numers, f * Mul(*denoms), n, **hints) if result is not None: if hints.get('symbols', False): return (simplify(result[0] / C), result[1]) else: return simplify(result / C) else: return None def rsolve_hyper(coeffs, f, n, **hints): r""" Given linear recurrence operator `\operatorname{L}` of order `k` with polynomial coefficients and inhomogeneous equation `\operatorname{L} y = f` we seek for all hypergeometric solutions over field `K` of characteristic zero. The inhomogeneous part can be either hypergeometric or a sum of a fixed number of pairwise dissimilar hypergeometric terms. The algorithm performs three basic steps: (1) Group together similar hypergeometric terms in the inhomogeneous part of `\operatorname{L} y = f`, and find particular solution using Abramov's algorithm. (2) Compute generating set of `\operatorname{L}` and find basis in it, so that all solutions are linearly independent. (3) Form final solution with the number of arbitrary constants equal to dimension of basis of `\operatorname{L}`. Term `a(n)` is hypergeometric if it is annihilated by first order linear difference equations with polynomial coefficients or, in simpler words, if consecutive term ratio is a rational function. The output of this procedure is a linear combination of fixed number of hypergeometric terms. However the underlying method can generate larger class of solutions - D'Alembertian terms. Note also that this method not only computes the kernel of the inhomogeneous equation, but also reduces in to a basis so that solutions generated by this procedure are linearly independent Examples ======== >>> from sympy.solvers import rsolve_hyper >>> from sympy.abc import x >>> rsolve_hyper([-1, -1, 1], 0, x) C0*(1/2 - sqrt(5)/2)**x + C1*(1/2 + sqrt(5)/2)**x >>> rsolve_hyper([-1, 1], 1 + x, x) C0 + x*(x + 1)/2 References ========== .. [1] M. Petkovsek, Hypergeometric solutions of linear recurrences with polynomial coefficients, J. Symbolic Computation, 14 (1992), 243-264. .. [2] M. Petkovsek, H. S. Wilf, D. Zeilberger, A = B, 1996. """ coeffs = list(map(sympify, coeffs)) f = sympify(f) r, kernel, symbols = len(coeffs) - 1, [], set() if not f.is_zero: if f.is_Add: similar = {} for g in f.expand().args: if not g.is_hypergeometric(n): return None for h in similar.keys(): if hypersimilar(g, h, n): similar[h] += g break else: similar[g] = S.Zero inhomogeneous = [] for g, h in similar.items(): inhomogeneous.append(g + h) elif f.is_hypergeometric(n): inhomogeneous = [f] else: return None for i, g in enumerate(inhomogeneous): coeff, polys = S.One, coeffs[:] denoms = [S.One]*(r + 1) s = hypersimp(g, n) for j in range(1, r + 1): coeff *= s.subs(n, n + j - 1) p, q = coeff.as_numer_denom() polys[j] *= p denoms[j] = q for j in range(r + 1): polys[j] *= Mul(*(denoms[:j] + denoms[j + 1:])) R = rsolve_poly(polys, Mul(*denoms), n) if not (R is None or R is S.Zero): inhomogeneous[i] *= R else: return None result = Add(*inhomogeneous) else: result = S.Zero Z = Dummy('Z') p, q = coeffs[0], coeffs[r].subs(n, n - r + 1) p_factors = [z for z in roots(p, n).keys()] q_factors = [z for z in roots(q, n).keys()] factors = [(S.One, S.One)] for p in p_factors: for q in q_factors: if p.is_integer and q.is_integer and p <= q: continue else: factors += [(n - p, n - q)] p = [(n - p, S.One) for p in p_factors] q = [(S.One, n - q) for q in q_factors] factors = p + factors + q for A, B in factors: polys, degrees = [], [] D = A*B.subs(n, n + r - 1) for i in range(r + 1): a = Mul(*[A.subs(n, n + j) for j in range(i)]) b = Mul(*[B.subs(n, n + j) for j in range(i, r)]) poly = quo(coeffs[i]*a*b, D, n) polys.append(poly.as_poly(n)) if not poly.is_zero: degrees.append(polys[i].degree()) if degrees: d, poly = max(degrees), S.Zero else: return None for i in range(r + 1): coeff = polys[i].nth(d) if coeff is not S.Zero: poly += coeff * Z**i for z in roots(poly, Z).keys(): if z.is_zero: continue (C, s) = rsolve_poly([polys[i].as_expr()*z**i for i in range(r + 1)], 0, n, symbols=True) if C is not None and C is not S.Zero: symbols |= set(s) ratio = z * A * C.subs(n, n + 1) / B / C ratio = simplify(ratio) # If there is a nonnegative root in the denominator of the ratio, # this indicates that the term y(n_root) is zero, and one should # start the product with the term y(n_root + 1). n0 = 0 for n_root in roots(ratio.as_numer_denom()[1], n).keys(): if n_root.has(I): return None elif (n0 < (n_root + 1)) == True: n0 = n_root + 1 K = product(ratio, (n, n0, n - 1)) if K.has(factorial, FallingFactorial, RisingFactorial): K = simplify(K) if casoratian(kernel + [K], n, zero=False) != 0: kernel.append(K) kernel.sort(key=default_sort_key) sk = list(zip(numbered_symbols('C'), kernel)) if sk: for C, ker in sk: result += C * ker else: return None if hints.get('symbols', False): # XXX: This returns the symbols in a non-deterministic order symbols |= {s for s, k in sk} return (result, list(symbols)) else: return result def rsolve(f, y, init=None): r""" Solve univariate recurrence with rational coefficients. Given `k`-th order linear recurrence `\operatorname{L} y = f`, or equivalently: .. math:: a_{k}(n) y(n+k) + a_{k-1}(n) y(n+k-1) + \cdots + a_{0}(n) y(n) = f(n) where `a_{i}(n)`, for `i=0, \ldots, k`, are polynomials or rational functions in `n`, and `f` is a hypergeometric function or a sum of a fixed number of pairwise dissimilar hypergeometric terms in `n`, finds all solutions or returns ``None``, if none were found. Initial conditions can be given as a dictionary in two forms: (1) ``{ n_0 : v_0, n_1 : v_1, ..., n_m : v_m}`` (2) ``{y(n_0) : v_0, y(n_1) : v_1, ..., y(n_m) : v_m}`` or as a list ``L`` of values: ``L = [v_0, v_1, ..., v_m]`` where ``L[i] = v_i``, for `i=0, \ldots, m`, maps to `y(n_i)`. Examples ======== Lets consider the following recurrence: .. math:: (n - 1) y(n + 2) - (n^2 + 3 n - 2) y(n + 1) + 2 n (n + 1) y(n) = 0 >>> from sympy import Function, rsolve >>> from sympy.abc import n >>> y = Function('y') >>> f = (n - 1)*y(n + 2) - (n**2 + 3*n - 2)*y(n + 1) + 2*n*(n + 1)*y(n) >>> rsolve(f, y(n)) 2**n*C0 + C1*factorial(n) >>> rsolve(f, y(n), {y(0):0, y(1):3}) 3*2**n - 3*factorial(n) See Also ======== rsolve_poly, rsolve_ratio, rsolve_hyper """ if isinstance(f, Equality): f = f.lhs - f.rhs n = y.args[0] k = Wild('k', exclude=(n,)) # Preprocess user input to allow things like # y(n) + a*(y(n + 1) + y(n - 1))/2 f = f.expand().collect(y.func(Wild('m', integer=True))) h_part = defaultdict(list) i_part = [] for g in Add.make_args(f): coeff, dep = g.as_coeff_mul(y.func) if not dep: i_part.append(coeff) continue for h in dep: if h.is_Function and h.func == y.func: result = h.args[0].match(n + k) if result is not None: h_part[int(result[k])].append(coeff) continue raise ValueError( "'%s(%s + k)' expected, got '%s'" % (y.func, n, h)) for k in h_part: h_part[k] = Add(*h_part[k]) h_part.default_factory = lambda: 0 i_part = Add(*i_part) for k, coeff in h_part.items(): h_part[k] = simplify(coeff) common = S.One if not i_part.is_zero and not i_part.is_hypergeometric(n) and \ not (i_part.is_Add and all(map(lambda x: x.is_hypergeometric(n), i_part.expand().args))): raise ValueError("The independent term should be a sum of hypergeometric functions, got '%s'" % i_part) for coeff in h_part.values(): if coeff.is_rational_function(n): if not coeff.is_polynomial(n): common = lcm(common, coeff.as_numer_denom()[1], n) else: raise ValueError( "Polynomial or rational function expected, got '%s'" % coeff) i_numer, i_denom = i_part.as_numer_denom() if i_denom.is_polynomial(n): common = lcm(common, i_denom, n) if common is not S.One: for k, coeff in h_part.items(): numer, denom = coeff.as_numer_denom() h_part[k] = numer*quo(common, denom, n) i_part = i_numer*quo(common, i_denom, n) K_min = min(h_part.keys()) if K_min < 0: K = abs(K_min) H_part = defaultdict(lambda: S.Zero) i_part = i_part.subs(n, n + K).expand() common = common.subs(n, n + K).expand() for k, coeff in h_part.items(): H_part[k + K] = coeff.subs(n, n + K).expand() else: H_part = h_part K_max = max(H_part.keys()) coeffs = [H_part[i] for i in range(K_max + 1)] result = rsolve_hyper(coeffs, -i_part, n, symbols=True) if result is None: return None solution, symbols = result if init == {} or init == []: init = None if symbols and init is not None: if isinstance(init, list): init = {i: init[i] for i in range(len(init))} equations = [] for k, v in init.items(): try: i = int(k) except TypeError: if k.is_Function and k.func == y.func: i = int(k.args[0]) else: raise ValueError("Integer or term expected, got '%s'" % k) eq = solution.subs(n, i) - v if eq.has(S.NaN): eq = solution.limit(n, i) - v equations.append(eq) result = solve(equations, *symbols) if not result: return None else: solution = solution.subs(result) return solution

582902239582005a55a76cf702ba605404b6fb238f1258a08d9bd066c7e8a215

""" This module contains functions to: - solve a single equation for a single variable, in any domain either real or complex. - solve a single transcendental equation for a single variable in any domain either real or complex. (currently supports solving in real domain only) - solve a system of linear equations with N variables and M equations. - solve a system of Non Linear Equations with N variables and M equations """ from sympy.core.sympify import sympify from sympy.core import (S, Pow, Dummy, pi, Expr, Wild, Mul, Equality, Add) from sympy.core.containers import Tuple from sympy.core.numbers import I, Number, Rational, oo from sympy.core.function import (Lambda, expand_complex, AppliedUndef, expand_log) from sympy.core.mod import Mod from sympy.core.numbers import igcd from sympy.core.relational import Eq, Ne, Relational from sympy.core.symbol import Symbol, _uniquely_named_symbol from sympy.core.sympify import _sympify from sympy.simplify.simplify import simplify, fraction, trigsimp from sympy.simplify import powdenest, logcombine from sympy.functions import (log, Abs, tan, cot, sin, cos, sec, csc, exp, acos, asin, acsc, asec, arg, piecewise_fold, Piecewise) from sympy.functions.elementary.trigonometric import (TrigonometricFunction, HyperbolicFunction) from sympy.functions.elementary.miscellaneous import real_root from sympy.logic.boolalg import And from sympy.sets import (FiniteSet, EmptySet, imageset, Interval, Intersection, Union, ConditionSet, ImageSet, Complement, Contains) from sympy.sets.sets import Set, ProductSet from sympy.matrices import Matrix, MatrixBase from sympy.ntheory import totient from sympy.ntheory.factor_ import divisors from sympy.ntheory.residue_ntheory import discrete_log, nthroot_mod from sympy.polys import (roots, Poly, degree, together, PolynomialError, RootOf, factor, lcm, gcd) from sympy.polys.polyerrors import CoercionFailed from sympy.polys.polytools import invert from sympy.polys.solvers import (sympy_eqs_to_ring, solve_lin_sys, PolyNonlinearError) from sympy.solvers.solvers import (checksol, denoms, unrad, _simple_dens, recast_to_symbols) from sympy.solvers.polysys import solve_poly_system from sympy.solvers.inequalities import solve_univariate_inequality from sympy.utilities import filldedent from sympy.utilities.iterables import numbered_symbols, has_dups from sympy.calculus.util import periodicity, continuous_domain from sympy.core.compatibility import ordered, default_sort_key, is_sequence from types import GeneratorType from collections import defaultdict class NonlinearError(ValueError): """Raised when unexpectedly encountering nonlinear equations""" pass _rc = Dummy("R", real=True), Dummy("C", complex=True) def _masked(f, *atoms): """Return ``f``, with all objects given by ``atoms`` replaced with Dummy symbols, ``d``, and the list of replacements, ``(d, e)``, where ``e`` is an object of type given by ``atoms`` in which any other instances of atoms have been recursively replaced with Dummy symbols, too. The tuples are ordered so that if they are applied in sequence, the origin ``f`` will be restored. Examples ======== >>> from sympy import cos >>> from sympy.abc import x >>> from sympy.solvers.solveset import _masked >>> f = cos(cos(x) + 1) >>> f, reps = _masked(cos(1 + cos(x)), cos) >>> f _a1 >>> reps [(_a1, cos(_a0 + 1)), (_a0, cos(x))] >>> for d, e in reps: ... f = f.xreplace({d: e}) >>> f cos(cos(x) + 1) """ sym = numbered_symbols('a', cls=Dummy, real=True) mask = [] for a in ordered(f.atoms(*atoms)): for i in mask: a = a.replace(*i) mask.append((a, next(sym))) for i, (o, n) in enumerate(mask): f = f.replace(o, n) mask[i] = (n, o) mask = list(reversed(mask)) return f, mask def _invert(f_x, y, x, domain=S.Complexes): r""" Reduce the complex valued equation ``f(x) = y`` to a set of equations ``{g(x) = h_1(y), g(x) = h_2(y), ..., g(x) = h_n(y) }`` where ``g(x)`` is a simpler function than ``f(x)``. The return value is a tuple ``(g(x), set_h)``, where ``g(x)`` is a function of ``x`` and ``set_h`` is the set of function ``{h_1(y), h_2(y), ..., h_n(y)}``. Here, ``y`` is not necessarily a symbol. The ``set_h`` contains the functions, along with the information about the domain in which they are valid, through set operations. For instance, if ``y = Abs(x) - n`` is inverted in the real domain, then ``set_h`` is not simply `{-n, n}` as the nature of `n` is unknown; rather, it is: `Intersection([0, oo) {n}) U Intersection((-oo, 0], {-n})` By default, the complex domain is used which means that inverting even seemingly simple functions like ``exp(x)`` will give very different results from those obtained in the real domain. (In the case of ``exp(x)``, the inversion via ``log`` is multi-valued in the complex domain, having infinitely many branches.) If you are working with real values only (or you are not sure which function to use) you should probably set the domain to ``S.Reals`` (or use `invert\_real` which does that automatically). Examples ======== >>> from sympy.solvers.solveset import invert_complex, invert_real >>> from sympy.abc import x, y >>> from sympy import exp When does exp(x) == y? >>> invert_complex(exp(x), y, x) (x, ImageSet(Lambda(_n, I*(2*_n*pi + arg(y)) + log(Abs(y))), Integers)) >>> invert_real(exp(x), y, x) (x, Intersection(FiniteSet(log(y)), Reals)) When does exp(x) == 1? >>> invert_complex(exp(x), 1, x) (x, ImageSet(Lambda(_n, 2*_n*I*pi), Integers)) >>> invert_real(exp(x), 1, x) (x, FiniteSet(0)) See Also ======== invert_real, invert_complex """ x = sympify(x) if not x.is_Symbol: raise ValueError("x must be a symbol") f_x = sympify(f_x) if x not in f_x.free_symbols: raise ValueError("Inverse of constant function doesn't exist") y = sympify(y) if x in y.free_symbols: raise ValueError("y should be independent of x ") if domain.is_subset(S.Reals): x1, s = _invert_real(f_x, FiniteSet(y), x) else: x1, s = _invert_complex(f_x, FiniteSet(y), x) if not isinstance(s, FiniteSet) or x1 != x: return x1, s # Avoid adding gratuitous intersections with S.Complexes. Actual # conditions should be handled by the respective inverters. if domain is S.Complexes: return x1, s else: return x1, s.intersection(domain) invert_complex = _invert def invert_real(f_x, y, x, domain=S.Reals): """ Inverts a real-valued function. Same as _invert, but sets the domain to ``S.Reals`` before inverting. """ return _invert(f_x, y, x, domain) def _invert_real(f, g_ys, symbol): """Helper function for _invert.""" if f == symbol: return (f, g_ys) n = Dummy('n', real=True) if hasattr(f, 'inverse') and not isinstance(f, ( TrigonometricFunction, HyperbolicFunction, )): if len(f.args) > 1: raise ValueError("Only functions with one argument are supported.") return _invert_real(f.args[0], imageset(Lambda(n, f.inverse()(n)), g_ys), symbol) if isinstance(f, Abs): return _invert_abs(f.args[0], g_ys, symbol) if f.is_Add: # f = g + h g, h = f.as_independent(symbol) if g is not S.Zero: return _invert_real(h, imageset(Lambda(n, n - g), g_ys), symbol) if f.is_Mul: # f = g*h g, h = f.as_independent(symbol) if g is not S.One: return _invert_real(h, imageset(Lambda(n, n/g), g_ys), symbol) if f.is_Pow: base, expo = f.args base_has_sym = base.has(symbol) expo_has_sym = expo.has(symbol) if not expo_has_sym: res = imageset(Lambda(n, real_root(n, expo)), g_ys) if expo.is_rational: numer, denom = expo.as_numer_denom() if denom % 2 == 0: base_positive = solveset(base >= 0, symbol, S.Reals) res = imageset(Lambda(n, real_root(n, expo) ), g_ys.intersect( Interval.Ropen(S.Zero, S.Infinity))) _inv, _set = _invert_real(base, res, symbol) return (_inv, _set.intersect(base_positive)) elif numer % 2 == 0: n = Dummy('n') neg_res = imageset(Lambda(n, -n), res) return _invert_real(base, res + neg_res, symbol) else: return _invert_real(base, res, symbol) else: if not base.is_positive: raise ValueError("x**w where w is irrational is not " "defined for negative x") return _invert_real(base, res, symbol) if not base_has_sym: rhs = g_ys.args[0] if base.is_positive: return _invert_real(expo, imageset(Lambda(n, log(n, base, evaluate=False)), g_ys), symbol) elif base.is_negative: from sympy.core.power import integer_log s, b = integer_log(rhs, base) if b: return _invert_real(expo, FiniteSet(s), symbol) else: return _invert_real(expo, S.EmptySet, symbol) elif base.is_zero: one = Eq(rhs, 1) if one == S.true: # special case: 0**x - 1 return _invert_real(expo, FiniteSet(0), symbol) elif one == S.false: return _invert_real(expo, S.EmptySet, symbol) if isinstance(f, TrigonometricFunction): if isinstance(g_ys, FiniteSet): def inv(trig): if isinstance(f, (sin, csc)): F = asin if isinstance(f, sin) else acsc return (lambda a: n*pi + (-1)**n*F(a),) if isinstance(f, (cos, sec)): F = acos if isinstance(f, cos) else asec return ( lambda a: 2*n*pi + F(a), lambda a: 2*n*pi - F(a),) if isinstance(f, (tan, cot)): return (lambda a: n*pi + f.inverse()(a),) n = Dummy('n', integer=True) invs = S.EmptySet for L in inv(f): invs += Union(*[imageset(Lambda(n, L(g)), S.Integers) for g in g_ys]) return _invert_real(f.args[0], invs, symbol) return (f, g_ys) def _invert_complex(f, g_ys, symbol): """Helper function for _invert.""" if f == symbol: return (f, g_ys) n = Dummy('n') if f.is_Add: # f = g + h g, h = f.as_independent(symbol) if g is not S.Zero: return _invert_complex(h, imageset(Lambda(n, n - g), g_ys), symbol) if f.is_Mul: # f = g*h g, h = f.as_independent(symbol) if g is not S.One: if g in {S.NegativeInfinity, S.ComplexInfinity, S.Infinity}: return (h, S.EmptySet) return _invert_complex(h, imageset(Lambda(n, n/g), g_ys), symbol) if hasattr(f, 'inverse') and \ not isinstance(f, TrigonometricFunction) and \ not isinstance(f, HyperbolicFunction) and \ not isinstance(f, exp): if len(f.args) > 1: raise ValueError("Only functions with one argument are supported.") return _invert_complex(f.args[0], imageset(Lambda(n, f.inverse()(n)), g_ys), symbol) if isinstance(f, exp): if isinstance(g_ys, FiniteSet): exp_invs = Union(*[imageset(Lambda(n, I*(2*n*pi + arg(g_y)) + log(Abs(g_y))), S.Integers) for g_y in g_ys if g_y != 0]) return _invert_complex(f.args[0], exp_invs, symbol) return (f, g_ys) def _invert_abs(f, g_ys, symbol): """Helper function for inverting absolute value functions. Returns the complete result of inverting an absolute value function along with the conditions which must also be satisfied. If it is certain that all these conditions are met, a `FiniteSet` of all possible solutions is returned. If any condition cannot be satisfied, an `EmptySet` is returned. Otherwise, a `ConditionSet` of the solutions, with all the required conditions specified, is returned. """ if not g_ys.is_FiniteSet: # this could be used for FiniteSet, but the # results are more compact if they aren't, e.g. # ConditionSet(x, Contains(n, Interval(0, oo)), {-n, n}) vs # Union(Intersection(Interval(0, oo), {n}), Intersection(Interval(-oo, 0), {-n})) # for the solution of abs(x) - n pos = Intersection(g_ys, Interval(0, S.Infinity)) parg = _invert_real(f, pos, symbol) narg = _invert_real(-f, pos, symbol) if parg[0] != narg[0]: raise NotImplementedError return parg[0], Union(narg[1], parg[1]) # check conditions: all these must be true. If any are unknown # then return them as conditions which must be satisfied unknown = [] for a in g_ys.args: ok = a.is_nonnegative if a.is_Number else a.is_positive if ok is None: unknown.append(a) elif not ok: return symbol, S.EmptySet if unknown: conditions = And(*[Contains(i, Interval(0, oo)) for i in unknown]) else: conditions = True n = Dummy('n', real=True) # this is slightly different than above: instead of solving # +/-f on positive values, here we solve for f on +/- g_ys g_x, values = _invert_real(f, Union( imageset(Lambda(n, n), g_ys), imageset(Lambda(n, -n), g_ys)), symbol) return g_x, ConditionSet(g_x, conditions, values) def domain_check(f, symbol, p): """Returns False if point p is infinite or any subexpression of f is infinite or becomes so after replacing symbol with p. If none of these conditions is met then True will be returned. Examples ======== >>> from sympy import Mul, oo >>> from sympy.abc import x >>> from sympy.solvers.solveset import domain_check >>> g = 1/(1 + (1/(x + 1))**2) >>> domain_check(g, x, -1) False >>> domain_check(x**2, x, 0) True >>> domain_check(1/x, x, oo) False * The function relies on the assumption that the original form of the equation has not been changed by automatic simplification. >>> domain_check(x/x, x, 0) # x/x is automatically simplified to 1 True * To deal with automatic evaluations use evaluate=False: >>> domain_check(Mul(x, 1/x, evaluate=False), x, 0) False """ f, p = sympify(f), sympify(p) if p.is_infinite: return False return _domain_check(f, symbol, p) def _domain_check(f, symbol, p): # helper for domain check if f.is_Atom and f.is_finite: return True elif f.subs(symbol, p).is_infinite: return False else: return all([_domain_check(g, symbol, p) for g in f.args]) def _is_finite_with_finite_vars(f, domain=S.Complexes): """ Return True if the given expression is finite. For symbols that don't assign a value for `complex` and/or `real`, the domain will be used to assign a value; symbols that don't assign a value for `finite` will be made finite. All other assumptions are left unmodified. """ def assumptions(s): A = s.assumptions0 A.setdefault('finite', A.get('finite', True)) if domain.is_subset(S.Reals): # if this gets set it will make complex=True, too A.setdefault('real', True) else: # don't change 'real' because being complex implies # nothing about being real A.setdefault('complex', True) return A reps = {s: Dummy(**assumptions(s)) for s in f.free_symbols} return f.xreplace(reps).is_finite def _is_function_class_equation(func_class, f, symbol): """ Tests whether the equation is an equation of the given function class. The given equation belongs to the given function class if it is comprised of functions of the function class which are multiplied by or added to expressions independent of the symbol. In addition, the arguments of all such functions must be linear in the symbol as well. Examples ======== >>> from sympy.solvers.solveset import _is_function_class_equation >>> from sympy import tan, sin, tanh, sinh, exp >>> from sympy.abc import x >>> from sympy.functions.elementary.trigonometric import (TrigonometricFunction, ... HyperbolicFunction) >>> _is_function_class_equation(TrigonometricFunction, exp(x) + tan(x), x) False >>> _is_function_class_equation(TrigonometricFunction, tan(x) + sin(x), x) True >>> _is_function_class_equation(TrigonometricFunction, tan(x**2), x) False >>> _is_function_class_equation(TrigonometricFunction, tan(x + 2), x) True >>> _is_function_class_equation(HyperbolicFunction, tanh(x) + sinh(x), x) True """ if f.is_Mul or f.is_Add: return all(_is_function_class_equation(func_class, arg, symbol) for arg in f.args) if f.is_Pow: if not f.exp.has(symbol): return _is_function_class_equation(func_class, f.base, symbol) else: return False if not f.has(symbol): return True if isinstance(f, func_class): try: g = Poly(f.args[0], symbol) return g.degree() <= 1 except PolynomialError: return False else: return False def _solve_as_rational(f, symbol, domain): """ solve rational functions""" f = together(f, deep=True) g, h = fraction(f) if not h.has(symbol): try: return _solve_as_poly(g, symbol, domain) except NotImplementedError: # The polynomial formed from g could end up having # coefficients in a ring over which finding roots # isn't implemented yet, e.g. ZZ[a] for some symbol a return ConditionSet(symbol, Eq(f, 0), domain) except CoercionFailed: # contained oo, zoo or nan return S.EmptySet else: valid_solns = _solveset(g, symbol, domain) invalid_solns = _solveset(h, symbol, domain) return valid_solns - invalid_solns class _SolveTrig1Error(Exception): """Raised when _solve_trig1 heuristics do not apply""" def _solve_trig(f, symbol, domain): """Function to call other helpers to solve trigonometric equations """ sol = None try: sol = _solve_trig1(f, symbol, domain) except _SolveTrig1Error: try: sol = _solve_trig2(f, symbol, domain) except ValueError: raise NotImplementedError(filldedent(''' Solution to this kind of trigonometric equations is yet to be implemented''')) return sol def _solve_trig1(f, symbol, domain): """Primary solver for trigonometric and hyperbolic equations Returns either the solution set as a ConditionSet (auto-evaluated to a union of ImageSets if no variables besides 'symbol' are involved) or raises _SolveTrig1Error if f == 0 can't be solved. Notes ===== Algorithm: 1. Do a change of variable x -> mu*x in arguments to trigonometric and hyperbolic functions, in order to reduce them to small integers. (This step is crucial to keep the degrees of the polynomials of step 4 low.) 2. Rewrite trigonometric/hyperbolic functions as exponentials. 3. Proceed to a 2nd change of variable, replacing exp(I*x) or exp(x) by y. 4. Solve the resulting rational equation. 5. Use invert_complex or invert_real to return to the original variable. 6. If the coefficients of 'symbol' were symbolic in nature, add the necessary consistency conditions in a ConditionSet. """ # Prepare change of variable x = Dummy('x') if _is_function_class_equation(HyperbolicFunction, f, symbol): cov = exp(x) inverter = invert_real if domain.is_subset(S.Reals) else invert_complex else: cov = exp(I*x) inverter = invert_complex f = trigsimp(f) f_original = f trig_functions = f.atoms(TrigonometricFunction, HyperbolicFunction) trig_arguments = [e.args[0] for e in trig_functions] # trigsimp may have reduced the equation to an expression # that is independent of 'symbol' (e.g. cos**2+sin**2) if not any(a.has(symbol) for a in trig_arguments): return solveset(f_original, symbol, domain) denominators = [] numerators = [] for ar in trig_arguments: try: poly_ar = Poly(ar, symbol) except PolynomialError: raise _SolveTrig1Error("trig argument is not a polynomial") if poly_ar.degree() > 1: # degree >1 still bad raise _SolveTrig1Error("degree of variable must not exceed one") if poly_ar.degree() == 0: # degree 0, don't care continue c = poly_ar.all_coeffs()[0] # got the coefficient of 'symbol' numerators.append(fraction(c)[0]) denominators.append(fraction(c)[1]) mu = lcm(denominators)/gcd(numerators) f = f.subs(symbol, mu*x) f = f.rewrite(exp) f = together(f) g, h = fraction(f) y = Dummy('y') g, h = g.expand(), h.expand() g, h = g.subs(cov, y), h.subs(cov, y) if g.has(x) or h.has(x): raise _SolveTrig1Error("change of variable not possible") solns = solveset_complex(g, y) - solveset_complex(h, y) if isinstance(solns, ConditionSet): raise _SolveTrig1Error("polynomial has ConditionSet solution") if isinstance(solns, FiniteSet): if any(isinstance(s, RootOf) for s in solns): raise _SolveTrig1Error("polynomial results in RootOf object") # revert the change of variable cov = cov.subs(x, symbol/mu) result = Union(*[inverter(cov, s, symbol)[1] for s in solns]) # In case of symbolic coefficients, the solution set is only valid # if numerator and denominator of mu are non-zero. if mu.has(Symbol): syms = (mu).atoms(Symbol) munum, muden = fraction(mu) condnum = munum.as_independent(*syms, as_Add=False)[1] condden = muden.as_independent(*syms, as_Add=False)[1] cond = And(Ne(condnum, 0), Ne(condden, 0)) else: cond = True # Actual conditions are returned as part of the ConditionSet. Adding an # intersection with C would only complicate some solution sets due to # current limitations of intersection code. (e.g. #19154) if domain is S.Complexes: # This is a slight abuse of ConditionSet. Ideally this should # be some kind of "PiecewiseSet". (See #19507 discussion) return ConditionSet(symbol, cond, result) else: return ConditionSet(symbol, cond, Intersection(result, domain)) elif solns is S.EmptySet: return S.EmptySet else: raise _SolveTrig1Error("polynomial solutions must form FiniteSet") def _solve_trig2(f, symbol, domain): """Secondary helper to solve trigonometric equations, called when first helper fails """ from sympy import ilcm, expand_trig, degree f = trigsimp(f) f_original = f trig_functions = f.atoms(sin, cos, tan, sec, cot, csc) trig_arguments = [e.args[0] for e in trig_functions] denominators = [] numerators = [] # todo: This solver can be extended to hyperbolics if the # analogous change of variable to tanh (instead of tan) # is used. if not trig_functions: return ConditionSet(symbol, Eq(f_original, 0), domain) # todo: The pre-processing below (extraction of numerators, denominators, # gcd, lcm, mu, etc.) should be updated to the enhanced version in # _solve_trig1. (See #19507) for ar in trig_arguments: try: poly_ar = Poly(ar, symbol) except PolynomialError: raise ValueError("give up, we can't solve if this is not a polynomial in x") if poly_ar.degree() > 1: # degree >1 still bad raise ValueError("degree of variable inside polynomial should not exceed one") if poly_ar.degree() == 0: # degree 0, don't care continue c = poly_ar.all_coeffs()[0] # got the coefficient of 'symbol' try: numerators.append(Rational(c).p) denominators.append(Rational(c).q) except TypeError: return ConditionSet(symbol, Eq(f_original, 0), domain) x = Dummy('x') # ilcm() and igcd() require more than one argument if len(numerators) > 1: mu = Rational(2)*ilcm(*denominators)/igcd(*numerators) else: assert len(numerators) == 1 mu = Rational(2)*denominators[0]/numerators[0] f = f.subs(symbol, mu*x) f = f.rewrite(tan) f = expand_trig(f) f = together(f) g, h = fraction(f) y = Dummy('y') g, h = g.expand(), h.expand() g, h = g.subs(tan(x), y), h.subs(tan(x), y) if g.has(x) or h.has(x): return ConditionSet(symbol, Eq(f_original, 0), domain) solns = solveset(g, y, S.Reals) - solveset(h, y, S.Reals) if isinstance(solns, FiniteSet): result = Union(*[invert_real(tan(symbol/mu), s, symbol)[1] for s in solns]) dsol = invert_real(tan(symbol/mu), oo, symbol)[1] if degree(h) > degree(g): # If degree(denom)>degree(num) then there result = Union(result, dsol) # would be another sol at Lim(denom-->oo) return Intersection(result, domain) elif solns is S.EmptySet: return S.EmptySet else: return ConditionSet(symbol, Eq(f_original, 0), S.Reals) def _solve_as_poly(f, symbol, domain=S.Complexes): """ Solve the equation using polynomial techniques if it already is a polynomial equation or, with a change of variables, can be made so. """ result = None if f.is_polynomial(symbol): solns = roots(f, symbol, cubics=True, quartics=True, quintics=True, domain='EX') num_roots = sum(solns.values()) if degree(f, symbol) <= num_roots: result = FiniteSet(*solns.keys()) else: poly = Poly(f, symbol) solns = poly.all_roots() if poly.degree() <= len(solns): result = FiniteSet(*solns) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: poly = Poly(f) if poly is None: result = ConditionSet(symbol, Eq(f, 0), domain) gens = [g for g in poly.gens if g.has(symbol)] if len(gens) == 1: poly = Poly(poly, gens[0]) gen = poly.gen deg = poly.degree() poly = Poly(poly.as_expr(), poly.gen, composite=True) poly_solns = FiniteSet(*roots(poly, cubics=True, quartics=True, quintics=True).keys()) if len(poly_solns) < deg: result = ConditionSet(symbol, Eq(f, 0), domain) if gen != symbol: y = Dummy('y') inverter = invert_real if domain.is_subset(S.Reals) else invert_complex lhs, rhs_s = inverter(gen, y, symbol) if lhs == symbol: result = Union(*[rhs_s.subs(y, s) for s in poly_solns]) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: result = ConditionSet(symbol, Eq(f, 0), domain) if result is not None: if isinstance(result, FiniteSet): # this is to simplify solutions like -sqrt(-I) to sqrt(2)/2 # - sqrt(2)*I/2. We are not expanding for solution with symbols # or undefined functions because that makes the solution more complicated. # For example, expand_complex(a) returns re(a) + I*im(a) if all([s.atoms(Symbol, AppliedUndef) == set() and not isinstance(s, RootOf) for s in result]): s = Dummy('s') result = imageset(Lambda(s, expand_complex(s)), result) if isinstance(result, FiniteSet) and domain != S.Complexes: # Avoid adding gratuitous intersections with S.Complexes. Actual # conditions should be handled elsewhere. result = result.intersection(domain) return result else: return ConditionSet(symbol, Eq(f, 0), domain) def _has_rational_power(expr, symbol): """ Returns (bool, den) where bool is True if the term has a non-integer rational power and den is the denominator of the expression's exponent. Examples ======== >>> from sympy.solvers.solveset import _has_rational_power >>> from sympy import sqrt >>> from sympy.abc import x >>> _has_rational_power(sqrt(x), x) (True, 2) >>> _has_rational_power(x**2, x) (False, 1) """ a, p, q = Wild('a'), Wild('p'), Wild('q') pattern_match = expr.match(a*p**q) or {} if pattern_match.get(a, S.Zero).is_zero: return (False, S.One) elif p not in pattern_match.keys(): return (False, S.One) elif isinstance(pattern_match[q], Rational) \ and pattern_match[p].has(symbol): if not pattern_match[q].q == S.One: return (True, pattern_match[q].q) if not isinstance(pattern_match[a], Pow) \ or isinstance(pattern_match[a], Mul): return (False, S.One) else: return _has_rational_power(pattern_match[a], symbol) def _solve_radical(f, symbol, solveset_solver): """ Helper function to solve equations with radicals """ res = unrad(f) eq, cov = res if res else (f, []) if not cov: result = solveset_solver(eq, symbol) - \ Union(*[solveset_solver(g, symbol) for g in denoms(f, symbol)]) else: y, yeq = cov if not solveset_solver(y - I, y): yreal = Dummy('yreal', real=True) yeq = yeq.xreplace({y: yreal}) eq = eq.xreplace({y: yreal}) y = yreal g_y_s = solveset_solver(yeq, symbol) f_y_sols = solveset_solver(eq, y) result = Union(*[imageset(Lambda(y, g_y), f_y_sols) for g_y in g_y_s]) if isinstance(result, Complement) or isinstance(result,ConditionSet): solution_set = result else: f_set = [] # solutions for FiniteSet c_set = [] # solutions for ConditionSet for s in result: if checksol(f, symbol, s): f_set.append(s) else: c_set.append(s) solution_set = FiniteSet(*f_set) + ConditionSet(symbol, Eq(f, 0), FiniteSet(*c_set)) return solution_set def _solve_abs(f, symbol, domain): """ Helper function to solve equation involving absolute value function """ if not domain.is_subset(S.Reals): raise ValueError(filldedent(''' Absolute values cannot be inverted in the complex domain.''')) p, q, r = Wild('p'), Wild('q'), Wild('r') pattern_match = f.match(p*Abs(q) + r) or {} f_p, f_q, f_r = [pattern_match.get(i, S.Zero) for i in (p, q, r)] if not (f_p.is_zero or f_q.is_zero): domain = continuous_domain(f_q, symbol, domain) q_pos_cond = solve_univariate_inequality(f_q >= 0, symbol, relational=False, domain=domain, continuous=True) q_neg_cond = q_pos_cond.complement(domain) sols_q_pos = solveset_real(f_p*f_q + f_r, symbol).intersect(q_pos_cond) sols_q_neg = solveset_real(f_p*(-f_q) + f_r, symbol).intersect(q_neg_cond) return Union(sols_q_pos, sols_q_neg) else: return ConditionSet(symbol, Eq(f, 0), domain) def solve_decomposition(f, symbol, domain): """ Function to solve equations via the principle of "Decomposition and Rewriting". Examples ======== >>> from sympy import exp, sin, Symbol, pprint, S >>> from sympy.solvers.solveset import solve_decomposition as sd >>> x = Symbol('x') >>> f1 = exp(2*x) - 3*exp(x) + 2 >>> sd(f1, x, S.Reals) FiniteSet(0, log(2)) >>> f2 = sin(x)**2 + 2*sin(x) + 1 >>> pprint(sd(f2, x, S.Reals), use_unicode=False) 3*pi {2*n*pi + ---- | n in Integers} 2 >>> f3 = sin(x + 2) >>> pprint(sd(f3, x, S.Reals), use_unicode=False) {2*n*pi - 2 | n in Integers} U {2*n*pi - 2 + pi | n in Integers} """ from sympy.solvers.decompogen import decompogen from sympy.calculus.util import function_range # decompose the given function g_s = decompogen(f, symbol) # `y_s` represents the set of values for which the function `g` is to be # solved. # `solutions` represent the solutions of the equations `g = y_s` or # `g = 0` depending on the type of `y_s`. # As we are interested in solving the equation: f = 0 y_s = FiniteSet(0) for g in g_s: frange = function_range(g, symbol, domain) y_s = Intersection(frange, y_s) result = S.EmptySet if isinstance(y_s, FiniteSet): for y in y_s: solutions = solveset(Eq(g, y), symbol, domain) if not isinstance(solutions, ConditionSet): result += solutions else: if isinstance(y_s, ImageSet): iter_iset = (y_s,) elif isinstance(y_s, Union): iter_iset = y_s.args elif y_s is EmptySet: # y_s is not in the range of g in g_s, so no solution exists #in the given domain return EmptySet for iset in iter_iset: new_solutions = solveset(Eq(iset.lamda.expr, g), symbol, domain) dummy_var = tuple(iset.lamda.expr.free_symbols)[0] (base_set,) = iset.base_sets if isinstance(new_solutions, FiniteSet): new_exprs = new_solutions elif isinstance(new_solutions, Intersection): if isinstance(new_solutions.args[1], FiniteSet): new_exprs = new_solutions.args[1] for new_expr in new_exprs: result += ImageSet(Lambda(dummy_var, new_expr), base_set) if result is S.EmptySet: return ConditionSet(symbol, Eq(f, 0), domain) y_s = result return y_s def _solveset(f, symbol, domain, _check=False): """Helper for solveset to return a result from an expression that has already been sympify'ed and is known to contain the given symbol.""" # _check controls whether the answer is checked or not from sympy.simplify.simplify import signsimp from sympy.logic.boolalg import BooleanTrue if isinstance(f, BooleanTrue): return domain orig_f = f if f.is_Mul: coeff, f = f.as_independent(symbol, as_Add=False) if coeff in {S.ComplexInfinity, S.NegativeInfinity, S.Infinity}: f = together(orig_f) elif f.is_Add: a, h = f.as_independent(symbol) m, h = h.as_independent(symbol, as_Add=False) if m not in {S.ComplexInfinity, S.Zero, S.Infinity, S.NegativeInfinity}: f = a/m + h # XXX condition `m != 0` should be added to soln # assign the solvers to use solver = lambda f, x, domain=domain: _solveset(f, x, domain) inverter = lambda f, rhs, symbol: _invert(f, rhs, symbol, domain) result = EmptySet if f.expand().is_zero: return domain elif not f.has(symbol): return EmptySet elif f.is_Mul and all(_is_finite_with_finite_vars(m, domain) for m in f.args): # if f(x) and g(x) are both finite we can say that the solution of # f(x)*g(x) == 0 is same as Union(f(x) == 0, g(x) == 0) is not true in # general. g(x) can grow to infinitely large for the values where # f(x) == 0. To be sure that we are not silently allowing any # wrong solutions we are using this technique only if both f and g are # finite for a finite input. result = Union(*[solver(m, symbol) for m in f.args]) elif _is_function_class_equation(TrigonometricFunction, f, symbol) or \ _is_function_class_equation(HyperbolicFunction, f, symbol): result = _solve_trig(f, symbol, domain) elif isinstance(f, arg): a = f.args[0] result = solveset_real(a > 0, symbol) elif f.is_Piecewise: expr_set_pairs = f.as_expr_set_pairs(domain) for (expr, in_set) in expr_set_pairs: if in_set.is_Relational: in_set = in_set.as_set() solns = solver(expr, symbol, in_set) result += solns elif isinstance(f, Eq): result = solver(Add(f.lhs, - f.rhs, evaluate=False), symbol, domain) elif f.is_Relational: if not domain.is_subset(S.Reals): raise NotImplementedError(filldedent(''' Inequalities in the complex domain are not supported. Try the real domain by setting domain=S.Reals''')) try: result = solve_univariate_inequality( f, symbol, domain=domain, relational=False) except NotImplementedError: result = ConditionSet(symbol, f, domain) return result elif _is_modular(f, symbol): result = _solve_modular(f, symbol, domain) else: lhs, rhs_s = inverter(f, 0, symbol) if lhs == symbol: # do some very minimal simplification since # repeated inversion may have left the result # in a state that other solvers (e.g. poly) # would have simplified; this is done here # rather than in the inverter since here it # is only done once whereas there it would # be repeated for each step of the inversion if isinstance(rhs_s, FiniteSet): rhs_s = FiniteSet(*[Mul(* signsimp(i).as_content_primitive()) for i in rhs_s]) result = rhs_s elif isinstance(rhs_s, FiniteSet): for equation in [lhs - rhs for rhs in rhs_s]: if equation == f: if any(_has_rational_power(g, symbol)[0] for g in equation.args) or _has_rational_power( equation, symbol)[0]: result += _solve_radical(equation, symbol, solver) elif equation.has(Abs): result += _solve_abs(f, symbol, domain) else: result_rational = _solve_as_rational(equation, symbol, domain) if isinstance(result_rational, ConditionSet): # may be a transcendental type equation result += _transolve(equation, symbol, domain) else: result += result_rational else: result += solver(equation, symbol) elif rhs_s is not S.EmptySet: result = ConditionSet(symbol, Eq(f, 0), domain) if isinstance(result, ConditionSet): if isinstance(f, Expr): num, den = f.as_numer_denom() else: num, den = f, S.One if den.has(symbol): _result = _solveset(num, symbol, domain) if not isinstance(_result, ConditionSet): singularities = _solveset(den, symbol, domain) result = _result - singularities if _check: if isinstance(result, ConditionSet): # it wasn't solved or has enumerated all conditions # -- leave it alone return result # whittle away all but the symbol-containing core # to use this for testing if isinstance(orig_f, Expr): fx = orig_f.as_independent(symbol, as_Add=True)[1] fx = fx.as_independent(symbol, as_Add=False)[1] else: fx = orig_f if isinstance(result, FiniteSet): # check the result for invalid solutions result = FiniteSet(*[s for s in result if isinstance(s, RootOf) or domain_check(fx, symbol, s)]) return result def _is_modular(f, symbol): """ Helper function to check below mentioned types of modular equations. ``A - Mod(B, C) = 0`` A -> This can or cannot be a function of symbol. B -> This is surely a function of symbol. C -> It is an integer. Parameters ========== f : Expr The equation to be checked. symbol : Symbol The concerned variable for which the equation is to be checked. Examples ======== >>> from sympy import symbols, exp, Mod >>> from sympy.solvers.solveset import _is_modular as check >>> x, y = symbols('x y') >>> check(Mod(x, 3) - 1, x) True >>> check(Mod(x, 3) - 1, y) False >>> check(Mod(x, 3)**2 - 5, x) False >>> check(Mod(x, 3)**2 - y, x) False >>> check(exp(Mod(x, 3)) - 1, x) False >>> check(Mod(3, y) - 1, y) False """ if not f.has(Mod): return False # extract modterms from f. modterms = list(f.atoms(Mod)) return (len(modterms) == 1 and # only one Mod should be present modterms[0].args[0].has(symbol) and # B-> function of symbol modterms[0].args[1].is_integer and # C-> to be an integer. any(isinstance(term, Mod) for term in list(_term_factors(f))) # free from other funcs ) def _invert_modular(modterm, rhs, n, symbol): """ Helper function to invert modular equation. ``Mod(a, m) - rhs = 0`` Generally it is inverted as (a, ImageSet(Lambda(n, m*n + rhs), S.Integers)). More simplified form will be returned if possible. If it is not invertible then (modterm, rhs) is returned. The following cases arise while inverting equation ``Mod(a, m) - rhs = 0``: 1. If a is symbol then m*n + rhs is the required solution. 2. If a is an instance of ``Add`` then we try to find two symbol independent parts of a and the symbol independent part gets tranferred to the other side and again the ``_invert_modular`` is called on the symbol dependent part. 3. If a is an instance of ``Mul`` then same as we done in ``Add`` we separate out the symbol dependent and symbol independent parts and transfer the symbol independent part to the rhs with the help of invert and again the ``_invert_modular`` is called on the symbol dependent part. 4. If a is an instance of ``Pow`` then two cases arise as following: - If a is of type (symbol_indep)**(symbol_dep) then the remainder is evaluated with the help of discrete_log function and then the least period is being found out with the help of totient function. period*n + remainder is the required solution in this case. For reference: (https://en.wikipedia.org/wiki/Euler's_theorem) - If a is of type (symbol_dep)**(symbol_indep) then we try to find all primitive solutions list with the help of nthroot_mod function. m*n + rem is the general solution where rem belongs to solutions list from nthroot_mod function. Parameters ========== modterm, rhs : Expr The modular equation to be inverted, ``modterm - rhs = 0`` symbol : Symbol The variable in the equation to be inverted. n : Dummy Dummy variable for output g_n. Returns ======= A tuple (f_x, g_n) is being returned where f_x is modular independent function of symbol and g_n being set of values f_x can have. Examples ======== >>> from sympy import symbols, exp, Mod, Dummy, S >>> from sympy.solvers.solveset import _invert_modular as invert_modular >>> x, y = symbols('x y') >>> n = Dummy('n') >>> invert_modular(Mod(exp(x), 7), S(5), n, x) (Mod(exp(x), 7), 5) >>> invert_modular(Mod(x, 7), S(5), n, x) (x, ImageSet(Lambda(_n, 7*_n + 5), Integers)) >>> invert_modular(Mod(3*x + 8, 7), S(5), n, x) (x, ImageSet(Lambda(_n, 7*_n + 6), Integers)) >>> invert_modular(Mod(x**4, 7), S(5), n, x) (x, EmptySet) >>> invert_modular(Mod(2**(x**2 + x + 1), 7), S(2), n, x) (x**2 + x + 1, ImageSet(Lambda(_n, 3*_n + 1), Naturals0)) """ a, m = modterm.args if rhs.is_real is False or any(term.is_real is False for term in list(_term_factors(a))): # Check for complex arguments return modterm, rhs if abs(rhs) >= abs(m): # if rhs has value greater than value of m. return symbol, EmptySet if a == symbol: return symbol, ImageSet(Lambda(n, m*n + rhs), S.Integers) if a.is_Add: # g + h = a g, h = a.as_independent(symbol) if g is not S.Zero: x_indep_term = rhs - Mod(g, m) return _invert_modular(Mod(h, m), Mod(x_indep_term, m), n, symbol) if a.is_Mul: # g*h = a g, h = a.as_independent(symbol) if g is not S.One: x_indep_term = rhs*invert(g, m) return _invert_modular(Mod(h, m), Mod(x_indep_term, m), n, symbol) if a.is_Pow: # base**expo = a base, expo = a.args if expo.has(symbol) and not base.has(symbol): # remainder -> solution independent of n of equation. # m, rhs are made coprime by dividing igcd(m, rhs) try: remainder = discrete_log(m / igcd(m, rhs), rhs, a.base) except ValueError: # log does not exist return modterm, rhs # period -> coefficient of n in the solution and also referred as # the least period of expo in which it is repeats itself. # (a**(totient(m)) - 1) divides m. Here is link of theorem: # (https://en.wikipedia.org/wiki/Euler's_theorem) period = totient(m) for p in divisors(period): # there might a lesser period exist than totient(m). if pow(a.base, p, m / igcd(m, a.base)) == 1: period = p break # recursion is not applied here since _invert_modular is currently # not smart enough to handle infinite rhs as here expo has infinite # rhs = ImageSet(Lambda(n, period*n + remainder), S.Naturals0). return expo, ImageSet(Lambda(n, period*n + remainder), S.Naturals0) elif base.has(symbol) and not expo.has(symbol): try: remainder_list = nthroot_mod(rhs, expo, m, all_roots=True) if remainder_list == []: return symbol, EmptySet except (ValueError, NotImplementedError): return modterm, rhs g_n = EmptySet for rem in remainder_list: g_n += ImageSet(Lambda(n, m*n + rem), S.Integers) return base, g_n return modterm, rhs def _solve_modular(f, symbol, domain): r""" Helper function for solving modular equations of type ``A - Mod(B, C) = 0``, where A can or cannot be a function of symbol, B is surely a function of symbol and C is an integer. Currently ``_solve_modular`` is only able to solve cases where A is not a function of symbol. Parameters ========== f : Expr The modular equation to be solved, ``f = 0`` symbol : Symbol The variable in the equation to be solved. domain : Set A set over which the equation is solved. It has to be a subset of Integers. Returns ======= A set of integer solutions satisfying the given modular equation. A ``ConditionSet`` if the equation is unsolvable. Examples ======== >>> from sympy.solvers.solveset import _solve_modular as solve_modulo >>> from sympy import S, Symbol, sin, Intersection, Interval >>> from sympy.core.mod import Mod >>> x = Symbol('x') >>> solve_modulo(Mod(5*x - 8, 7) - 3, x, S.Integers) ImageSet(Lambda(_n, 7*_n + 5), Integers) >>> solve_modulo(Mod(5*x - 8, 7) - 3, x, S.Reals) # domain should be subset of integers. ConditionSet(x, Eq(Mod(5*x + 6, 7) - 3, 0), Reals) >>> solve_modulo(-7 + Mod(x, 5), x, S.Integers) EmptySet >>> solve_modulo(Mod(12**x, 21) - 18, x, S.Integers) ImageSet(Lambda(_n, 6*_n + 2), Naturals0) >>> solve_modulo(Mod(sin(x), 7) - 3, x, S.Integers) # not solvable ConditionSet(x, Eq(Mod(sin(x), 7) - 3, 0), Integers) >>> solve_modulo(3 - Mod(x, 5), x, Intersection(S.Integers, Interval(0, 100))) Intersection(ImageSet(Lambda(_n, 5*_n + 3), Integers), Range(0, 101, 1)) """ # extract modterm and g_y from f unsolved_result = ConditionSet(symbol, Eq(f, 0), domain) modterm = list(f.atoms(Mod))[0] rhs = -S.One*(f.subs(modterm, S.Zero)) if f.as_coefficients_dict()[modterm].is_negative: # checks if coefficient of modterm is negative in main equation. rhs *= -S.One if not domain.is_subset(S.Integers): return unsolved_result if rhs.has(symbol): # TODO Case: A-> function of symbol, can be extended here # in future. return unsolved_result n = Dummy('n', integer=True) f_x, g_n = _invert_modular(modterm, rhs, n, symbol) if f_x == modterm and g_n == rhs: return unsolved_result if f_x == symbol: if domain is not S.Integers: return domain.intersect(g_n) return g_n if isinstance(g_n, ImageSet): lamda_expr = g_n.lamda.expr lamda_vars = g_n.lamda.variables base_sets = g_n.base_sets sol_set = _solveset(f_x - lamda_expr, symbol, S.Integers) if isinstance(sol_set, FiniteSet): tmp_sol = EmptySet for sol in sol_set: tmp_sol += ImageSet(Lambda(lamda_vars, sol), *base_sets) sol_set = tmp_sol else: sol_set = ImageSet(Lambda(lamda_vars, sol_set), *base_sets) return domain.intersect(sol_set) return unsolved_result def _term_factors(f): """ Iterator to get the factors of all terms present in the given equation. Parameters ========== f : Expr Equation that needs to be addressed Returns ======= Factors of all terms present in the equation. Examples ======== >>> from sympy import symbols >>> from sympy.solvers.solveset import _term_factors >>> x = symbols('x') >>> list(_term_factors(-2 - x**2 + x*(x + 1))) [-2, -1, x**2, x, x + 1] """ for add_arg in Add.make_args(f): yield from Mul.make_args(add_arg) def _solve_exponential(lhs, rhs, symbol, domain): r""" Helper function for solving (supported) exponential equations. Exponential equations are the sum of (currently) at most two terms with one or both of them having a power with a symbol-dependent exponent. For example .. math:: 5^{2x + 3} - 5^{3x - 1} .. math:: 4^{5 - 9x} - e^{2 - x} Parameters ========== lhs, rhs : Expr The exponential equation to be solved, `lhs = rhs` symbol : Symbol The variable in which the equation is solved domain : Set A set over which the equation is solved. Returns ======= A set of solutions satisfying the given equation. A ``ConditionSet`` if the equation is unsolvable or if the assumptions are not properly defined, in that case a different style of ``ConditionSet`` is returned having the solution(s) of the equation with the desired assumptions. Examples ======== >>> from sympy.solvers.solveset import _solve_exponential as solve_expo >>> from sympy import symbols, S >>> x = symbols('x', real=True) >>> a, b = symbols('a b') >>> solve_expo(2**x + 3**x - 5**x, 0, x, S.Reals) # not solvable ConditionSet(x, Eq(2**x + 3**x - 5**x, 0), Reals) >>> solve_expo(a**x - b**x, 0, x, S.Reals) # solvable but incorrect assumptions ConditionSet(x, (a > 0) & (b > 0), FiniteSet(0)) >>> solve_expo(3**(2*x) - 2**(x + 3), 0, x, S.Reals) FiniteSet(-3*log(2)/(-2*log(3) + log(2))) >>> solve_expo(2**x - 4**x, 0, x, S.Reals) FiniteSet(0) * Proof of correctness of the method The logarithm function is the inverse of the exponential function. The defining relation between exponentiation and logarithm is: .. math:: {\log_b x} = y \enspace if \enspace b^y = x Therefore if we are given an equation with exponent terms, we can convert every term to its corresponding logarithmic form. This is achieved by taking logarithms and expanding the equation using logarithmic identities so that it can easily be handled by ``solveset``. For example: .. math:: 3^{2x} = 2^{x + 3} Taking log both sides will reduce the equation to .. math:: (2x)\log(3) = (x + 3)\log(2) This form can be easily handed by ``solveset``. """ unsolved_result = ConditionSet(symbol, Eq(lhs - rhs, 0), domain) newlhs = powdenest(lhs) if lhs != newlhs: # it may also be advantageous to factor the new expr return _solveset(factor(newlhs - rhs), symbol, domain) # try again with _solveset if not (isinstance(lhs, Add) and len(lhs.args) == 2): # solving for the sum of more than two powers is possible # but not yet implemented return unsolved_result if rhs != 0: return unsolved_result a, b = list(ordered(lhs.args)) a_term = a.as_independent(symbol)[1] b_term = b.as_independent(symbol)[1] a_base, a_exp = a_term.base, a_term.exp b_base, b_exp = b_term.base, b_term.exp from sympy.functions.elementary.complexes import im if domain.is_subset(S.Reals): conditions = And( a_base > 0, b_base > 0, Eq(im(a_exp), 0), Eq(im(b_exp), 0)) else: conditions = And( Ne(a_base, 0), Ne(b_base, 0)) L, R = map(lambda i: expand_log(log(i), force=True), (a, -b)) solutions = _solveset(L - R, symbol, domain) return ConditionSet(symbol, conditions, solutions) def _is_exponential(f, symbol): r""" Return ``True`` if one or more terms contain ``symbol`` only in exponents, else ``False``. Parameters ========== f : Expr The equation to be checked symbol : Symbol The variable in which the equation is checked Examples ======== >>> from sympy import symbols, cos, exp >>> from sympy.solvers.solveset import _is_exponential as check >>> x, y = symbols('x y') >>> check(y, y) False >>> check(x**y - 1, y) True >>> check(x**y*2**y - 1, y) True >>> check(exp(x + 3) + 3**x, x) True >>> check(cos(2**x), x) False * Philosophy behind the helper The function extracts each term of the equation and checks if it is of exponential form w.r.t ``symbol``. """ rv = False for expr_arg in _term_factors(f): if symbol not in expr_arg.free_symbols: continue if (isinstance(expr_arg, Pow) and symbol not in expr_arg.base.free_symbols or isinstance(expr_arg, exp)): rv = True # symbol in exponent else: return False # dependent on symbol in non-exponential way return rv def _solve_logarithm(lhs, rhs, symbol, domain): r""" Helper to solve logarithmic equations which are reducible to a single instance of `\log`. Logarithmic equations are (currently) the equations that contains `\log` terms which can be reduced to a single `\log` term or a constant using various logarithmic identities. For example: .. math:: \log(x) + \log(x - 4) can be reduced to: .. math:: \log(x(x - 4)) Parameters ========== lhs, rhs : Expr The logarithmic equation to be solved, `lhs = rhs` symbol : Symbol The variable in which the equation is solved domain : Set A set over which the equation is solved. Returns ======= A set of solutions satisfying the given equation. A ``ConditionSet`` if the equation is unsolvable. Examples ======== >>> from sympy import symbols, log, S >>> from sympy.solvers.solveset import _solve_logarithm as solve_log >>> x = symbols('x') >>> f = log(x - 3) + log(x + 3) >>> solve_log(f, 0, x, S.Reals) FiniteSet(sqrt(10), -sqrt(10)) * Proof of correctness A logarithm is another way to write exponent and is defined by .. math:: {\log_b x} = y \enspace if \enspace b^y = x When one side of the equation contains a single logarithm, the equation can be solved by rewriting the equation as an equivalent exponential equation as defined above. But if one side contains more than one logarithm, we need to use the properties of logarithm to condense it into a single logarithm. Take for example .. math:: \log(2x) - 15 = 0 contains single logarithm, therefore we can directly rewrite it to exponential form as .. math:: x = \frac{e^{15}}{2} But if the equation has more than one logarithm as .. math:: \log(x - 3) + \log(x + 3) = 0 we use logarithmic identities to convert it into a reduced form Using, .. math:: \log(a) + \log(b) = \log(ab) the equation becomes, .. math:: \log((x - 3)(x + 3)) This equation contains one logarithm and can be solved by rewriting to exponents. """ new_lhs = logcombine(lhs, force=True) new_f = new_lhs - rhs return _solveset(new_f, symbol, domain) def _is_logarithmic(f, symbol): r""" Return ``True`` if the equation is in the form `a\log(f(x)) + b\log(g(x)) + ... + c` else ``False``. Parameters ========== f : Expr The equation to be checked symbol : Symbol The variable in which the equation is checked Returns ======= ``True`` if the equation is logarithmic otherwise ``False``. Examples ======== >>> from sympy import symbols, tan, log >>> from sympy.solvers.solveset import _is_logarithmic as check >>> x, y = symbols('x y') >>> check(log(x + 2) - log(x + 3), x) True >>> check(tan(log(2*x)), x) False >>> check(x*log(x), x) False >>> check(x + log(x), x) False >>> check(y + log(x), x) True * Philosophy behind the helper The function extracts each term and checks whether it is logarithmic w.r.t ``symbol``. """ rv = False for term in Add.make_args(f): saw_log = False for term_arg in Mul.make_args(term): if symbol not in term_arg.free_symbols: continue if isinstance(term_arg, log): if saw_log: return False # more than one log in term saw_log = True else: return False # dependent on symbol in non-log way if saw_log: rv = True return rv def _transolve(f, symbol, domain): r""" Function to solve transcendental equations. It is a helper to ``solveset`` and should be used internally. ``_transolve`` currently supports the following class of equations: - Exponential equations - Logarithmic equations Parameters ========== f : Any transcendental equation that needs to be solved. This needs to be an expression, which is assumed to be equal to ``0``. symbol : The variable for which the equation is solved. This needs to be of class ``Symbol``. domain : A set over which the equation is solved. This needs to be of class ``Set``. Returns ======= Set A set of values for ``symbol`` for which ``f`` is equal to zero. An ``EmptySet`` is returned if ``f`` does not have solutions in respective domain. A ``ConditionSet`` is returned as unsolved object if algorithms to evaluate complete solution are not yet implemented. How to use ``_transolve`` ========================= ``_transolve`` should not be used as an independent function, because it assumes that the equation (``f``) and the ``symbol`` comes from ``solveset`` and might have undergone a few modification(s). To use ``_transolve`` as an independent function the equation (``f``) and the ``symbol`` should be passed as they would have been by ``solveset``. Examples ======== >>> from sympy.solvers.solveset import _transolve as transolve >>> from sympy.solvers.solvers import _tsolve as tsolve >>> from sympy import symbols, S, pprint >>> x = symbols('x', real=True) # assumption added >>> transolve(5**(x - 3) - 3**(2*x + 1), x, S.Reals) FiniteSet(-(log(3) + 3*log(5))/(-log(5) + 2*log(3))) How ``_transolve`` works ======================== ``_transolve`` uses two types of helper functions to solve equations of a particular class: Identifying helpers: To determine whether a given equation belongs to a certain class of equation or not. Returns either ``True`` or ``False``. Solving helpers: Once an equation is identified, a corresponding helper either solves the equation or returns a form of the equation that ``solveset`` might better be able to handle. * Philosophy behind the module The purpose of ``_transolve`` is to take equations which are not already polynomial in their generator(s) and to either recast them as such through a valid transformation or to solve them outright. A pair of helper functions for each class of supported transcendental functions are employed for this purpose. One identifies the transcendental form of an equation and the other either solves it or recasts it into a tractable form that can be solved by ``solveset``. For example, an equation in the form `ab^{f(x)} - cd^{g(x)} = 0` can be transformed to `\log(a) + f(x)\log(b) - \log(c) - g(x)\log(d) = 0` (under certain assumptions) and this can be solved with ``solveset`` if `f(x)` and `g(x)` are in polynomial form. How ``_transolve`` is better than ``_tsolve`` ============================================= 1) Better output ``_transolve`` provides expressions in a more simplified form. Consider a simple exponential equation >>> f = 3**(2*x) - 2**(x + 3) >>> pprint(transolve(f, x, S.Reals), use_unicode=False) -3*log(2) {------------------} -2*log(3) + log(2) >>> pprint(tsolve(f, x), use_unicode=False) / 3 \ | --------| | log(2/9)| [-log\2 /] 2) Extensible The API of ``_transolve`` is designed such that it is easily extensible, i.e. the code that solves a given class of equations is encapsulated in a helper and not mixed in with the code of ``_transolve`` itself. 3) Modular ``_transolve`` is designed to be modular i.e, for every class of equation a separate helper for identification and solving is implemented. This makes it easy to change or modify any of the method implemented directly in the helpers without interfering with the actual structure of the API. 4) Faster Computation Solving equation via ``_transolve`` is much faster as compared to ``_tsolve``. In ``solve``, attempts are made computing every possibility to get the solutions. This series of attempts makes solving a bit slow. In ``_transolve``, computation begins only after a particular type of equation is identified. How to add new class of equations ================================= Adding a new class of equation solver is a three-step procedure: - Identify the type of the equations Determine the type of the class of equations to which they belong: it could be of ``Add``, ``Pow``, etc. types. Separate internal functions are used for each type. Write identification and solving helpers and use them from within the routine for the given type of equation (after adding it, if necessary). Something like: .. code-block:: python def add_type(lhs, rhs, x): .... if _is_exponential(lhs, x): new_eq = _solve_exponential(lhs, rhs, x) .... rhs, lhs = eq.as_independent(x) if lhs.is_Add: result = add_type(lhs, rhs, x) - Define the identification helper. - Define the solving helper. Apart from this, a few other things needs to be taken care while adding an equation solver: - Naming conventions: Name of the identification helper should be as ``_is_class`` where class will be the name or abbreviation of the class of equation. The solving helper will be named as ``_solve_class``. For example: for exponential equations it becomes ``_is_exponential`` and ``_solve_expo``. - The identifying helpers should take two input parameters, the equation to be checked and the variable for which a solution is being sought, while solving helpers would require an additional domain parameter. - Be sure to consider corner cases. - Add tests for each helper. - Add a docstring to your helper that describes the method implemented. The documentation of the helpers should identify: - the purpose of the helper, - the method used to identify and solve the equation, - a proof of correctness - the return values of the helpers """ def add_type(lhs, rhs, symbol, domain): """ Helper for ``_transolve`` to handle equations of ``Add`` type, i.e. equations taking the form as ``a*f(x) + b*g(x) + .... = c``. For example: 4**x + 8**x = 0 """ result = ConditionSet(symbol, Eq(lhs - rhs, 0), domain) # check if it is exponential type equation if _is_exponential(lhs, symbol): result = _solve_exponential(lhs, rhs, symbol, domain) # check if it is logarithmic type equation elif _is_logarithmic(lhs, symbol): result = _solve_logarithm(lhs, rhs, symbol, domain) return result result = ConditionSet(symbol, Eq(f, 0), domain) # invert_complex handles the call to the desired inverter based # on the domain specified. lhs, rhs_s = invert_complex(f, 0, symbol, domain) if isinstance(rhs_s, FiniteSet): assert (len(rhs_s.args)) == 1 rhs = rhs_s.args[0] if lhs.is_Add: result = add_type(lhs, rhs, symbol, domain) else: result = rhs_s return result def solveset(f, symbol=None, domain=S.Complexes): r"""Solves a given inequality or equation with set as output Parameters ========== f : Expr or a relational. The target equation or inequality symbol : Symbol The variable for which the equation is solved domain : Set The domain over which the equation is solved Returns ======= Set A set of values for `symbol` for which `f` is True or is equal to zero. An `EmptySet` is returned if `f` is False or nonzero. A `ConditionSet` is returned as unsolved object if algorithms to evaluate complete solution are not yet implemented. `solveset` claims to be complete in the solution set that it returns. Raises ====== NotImplementedError The algorithms to solve inequalities in complex domain are not yet implemented. ValueError The input is not valid. RuntimeError It is a bug, please report to the github issue tracker. Notes ===== Python interprets 0 and 1 as False and True, respectively, but in this function they refer to solutions of an expression. So 0 and 1 return the Domain and EmptySet, respectively, while True and False return the opposite (as they are assumed to be solutions of relational expressions). See Also ======== solveset_real: solver for real domain solveset_complex: solver for complex domain Examples ======== >>> from sympy import exp, sin, Symbol, pprint, S, Eq >>> from sympy.solvers.solveset import solveset, solveset_real * The default domain is complex. Not specifying a domain will lead to the solving of the equation in the complex domain (and this is not affected by the assumptions on the symbol): >>> x = Symbol('x') >>> pprint(solveset(exp(x) - 1, x), use_unicode=False) {2*n*I*pi | n in Integers} >>> x = Symbol('x', real=True) >>> pprint(solveset(exp(x) - 1, x), use_unicode=False) {2*n*I*pi | n in Integers} * If you want to use `solveset` to solve the equation in the real domain, provide a real domain. (Using ``solveset_real`` does this automatically.) >>> R = S.Reals >>> x = Symbol('x') >>> solveset(exp(x) - 1, x, R) FiniteSet(0) >>> solveset_real(exp(x) - 1, x) FiniteSet(0) The solution is unaffected by assumptions on the symbol: >>> p = Symbol('p', positive=True) >>> pprint(solveset(p**2 - 4)) {-2, 2} When a conditionSet is returned, symbols with assumptions that would alter the set are replaced with more generic symbols: >>> i = Symbol('i', imaginary=True) >>> solveset(Eq(i**2 + i*sin(i), 1), i, domain=S.Reals) ConditionSet(_R, Eq(_R**2 + _R*sin(_R) - 1, 0), Reals) * Inequalities can be solved over the real domain only. Use of a complex domain leads to a NotImplementedError. >>> solveset(exp(x) > 1, x, R) Interval.open(0, oo) """ f = sympify(f) symbol = sympify(symbol) if f is S.true: return domain if f is S.false: return S.EmptySet if not isinstance(f, (Expr, Relational, Number)): raise ValueError("%s is not a valid SymPy expression" % f) if not isinstance(symbol, (Expr, Relational)) and symbol is not None: raise ValueError("%s is not a valid SymPy symbol" % symbol) if not isinstance(domain, Set): raise ValueError("%s is not a valid domain" %(domain)) free_symbols = f.free_symbols if symbol is None and not free_symbols: b = Eq(f, 0) if b is S.true: return domain elif b is S.false: return S.EmptySet else: raise NotImplementedError(filldedent(''' relationship between value and 0 is unknown: %s''' % b)) if symbol is None: if len(free_symbols) == 1: symbol = free_symbols.pop() elif free_symbols: raise ValueError(filldedent(''' The independent variable must be specified for a multivariate equation.''')) elif not isinstance(symbol, Symbol): f, s, swap = recast_to_symbols([f], [symbol]) # the xreplace will be needed if a ConditionSet is returned return solveset(f[0], s[0], domain).xreplace(swap) # solveset should ignore assumptions on symbols if symbol not in _rc: x = _rc[0] if domain.is_subset(S.Reals) else _rc[1] rv = solveset(f.xreplace({symbol: x}), x, domain) # try to use the original symbol if possible try: _rv = rv.xreplace({x: symbol}) except TypeError: _rv = rv if rv.dummy_eq(_rv): rv = _rv return rv # Abs has its own handling method which avoids the # rewriting property that the first piece of abs(x) # is for x >= 0 and the 2nd piece for x < 0 -- solutions # can look better if the 2nd condition is x <= 0. Since # the solution is a set, duplication of results is not # an issue, e.g. {y, -y} when y is 0 will be {0} f, mask = _masked(f, Abs) f = f.rewrite(Piecewise) # everything that's not an Abs for d, e in mask: # everything *in* an Abs e = e.func(e.args[0].rewrite(Piecewise)) f = f.xreplace({d: e}) f = piecewise_fold(f) return _solveset(f, symbol, domain, _check=True) def solveset_real(f, symbol): return solveset(f, symbol, S.Reals) def solveset_complex(f, symbol): return solveset(f, symbol, S.Complexes) def _solveset_multi(eqs, syms, domains): '''Basic implementation of a multivariate solveset. For internal use (not ready for public consumption)''' rep = {} for sym, dom in zip(syms, domains): if dom is S.Reals: rep[sym] = Symbol(sym.name, real=True) eqs = [eq.subs(rep) for eq in eqs] syms = [sym.subs(rep) for sym in syms] syms = tuple(syms) if len(eqs) == 0: return ProductSet(*domains) if len(syms) == 1: sym = syms[0] domain = domains[0] solsets = [solveset(eq, sym, domain) for eq in eqs] solset = Intersection(*solsets) return ImageSet(Lambda((sym,), (sym,)), solset).doit() eqs = sorted(eqs, key=lambda eq: len(eq.free_symbols & set(syms))) for n in range(len(eqs)): sols = [] all_handled = True for sym in syms: if sym not in eqs[n].free_symbols: continue sol = solveset(eqs[n], sym, domains[syms.index(sym)]) if isinstance(sol, FiniteSet): i = syms.index(sym) symsp = syms[:i] + syms[i+1:] domainsp = domains[:i] + domains[i+1:] eqsp = eqs[:n] + eqs[n+1:] for s in sol: eqsp_sub = [eq.subs(sym, s) for eq in eqsp] sol_others = _solveset_multi(eqsp_sub, symsp, domainsp) fun = Lambda((symsp,), symsp[:i] + (s,) + symsp[i:]) sols.append(ImageSet(fun, sol_others).doit()) else: all_handled = False if all_handled: return Union(*sols) def solvify(f, symbol, domain): """Solves an equation using solveset and returns the solution in accordance with the `solve` output API. Returns ======= We classify the output based on the type of solution returned by `solveset`. Solution | Output ---------------------------------------- FiniteSet | list ImageSet, | list (if `f` is periodic) Union | EmptySet | empty list Others | None Raises ====== NotImplementedError A ConditionSet is the input. Examples ======== >>> from sympy.solvers.solveset import solvify >>> from sympy.abc import x >>> from sympy import S, tan, sin, exp >>> solvify(x**2 - 9, x, S.Reals) [-3, 3] >>> solvify(sin(x) - 1, x, S.Reals) [pi/2] >>> solvify(tan(x), x, S.Reals) [0] >>> solvify(exp(x) - 1, x, S.Complexes) >>> solvify(exp(x) - 1, x, S.Reals) [0] """ solution_set = solveset(f, symbol, domain) result = None if solution_set is S.EmptySet: result = [] elif isinstance(solution_set, ConditionSet): raise NotImplementedError('solveset is unable to solve this equation.') elif isinstance(solution_set, FiniteSet): result = list(solution_set) else: period = periodicity(f, symbol) if period is not None: solutions = S.EmptySet iter_solutions = () if isinstance(solution_set, ImageSet): iter_solutions = (solution_set,) elif isinstance(solution_set, Union): if all(isinstance(i, ImageSet) for i in solution_set.args): iter_solutions = solution_set.args for solution in iter_solutions: solutions += solution.intersect(Interval(0, period, False, True)) if isinstance(solutions, FiniteSet): result = list(solutions) else: solution = solution_set.intersect(domain) if isinstance(solution, FiniteSet): result += solution return result ############################################################################### ################################ LINSOLVE ##################################### ############################################################################### def linear_coeffs(eq, *syms, **_kw): """Return a list whose elements are the coefficients of the corresponding symbols in the sum of terms in ``eq``. The additive constant is returned as the last element of the list. Raises ====== NonlinearError The equation contains a nonlinear term Examples ======== >>> from sympy.solvers.solveset import linear_coeffs >>> from sympy.abc import x, y, z >>> linear_coeffs(3*x + 2*y - 1, x, y) [3, 2, -1] It is not necessary to expand the expression: >>> linear_coeffs(x + y*(z*(x*3 + 2) + 3), x) [3*y*z + 1, y*(2*z + 3)] But if there are nonlinear or cross terms -- even if they would cancel after simplification -- an error is raised so the situation does not pass silently past the caller's attention: >>> eq = 1/x*(x - 1) + 1/x >>> linear_coeffs(eq.expand(), x) [0, 1] >>> linear_coeffs(eq, x) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: 1/x >>> linear_coeffs(x*(y + 1) - x*y, x, y) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: x*(y + 1) """ d = defaultdict(list) eq = _sympify(eq) symset = set(syms) has = eq.free_symbols & symset if not has: return [S.Zero]*len(syms) + [eq] c, terms = eq.as_coeff_add(*has) d[0].extend(Add.make_args(c)) for t in terms: m, f = t.as_coeff_mul(*has) if len(f) != 1: break f = f[0] if f in symset: d[f].append(m) elif f.is_Add: d1 = linear_coeffs(f, *has, **{'dict': True}) d[0].append(m*d1.pop(0)) for xf, vf in d1.items(): d[xf].append(m*vf) else: break else: for k, v in d.items(): d[k] = Add(*v) if not _kw: return [d.get(s, S.Zero) for s in syms] + [d[0]] return d # default is still list but this won't matter raise NonlinearError('nonlinear term encountered: %s' % t) def linear_eq_to_matrix(equations, *symbols): r""" Converts a given System of Equations into Matrix form. Here `equations` must be a linear system of equations in `symbols`. Element M[i, j] corresponds to the coefficient of the jth symbol in the ith equation. The Matrix form corresponds to the augmented matrix form. For example: .. math:: 4x + 2y + 3z = 1 .. math:: 3x + y + z = -6 .. math:: 2x + 4y + 9z = 2 This system would return `A` & `b` as given below: :: [ 4 2 3 ] [ 1 ] A = [ 3 1 1 ] b = [-6 ] [ 2 4 9 ] [ 2 ] The only simplification performed is to convert `Eq(a, b) -> a - b`. Raises ====== NonlinearError The equations contain a nonlinear term. ValueError The symbols are not given or are not unique. Examples ======== >>> from sympy import linear_eq_to_matrix, symbols >>> c, x, y, z = symbols('c, x, y, z') The coefficients (numerical or symbolic) of the symbols will be returned as matrices: >>> eqns = [c*x + z - 1 - c, y + z, x - y] >>> A, b = linear_eq_to_matrix(eqns, [x, y, z]) >>> A Matrix([ [c, 0, 1], [0, 1, 1], [1, -1, 0]]) >>> b Matrix([ [c + 1], [ 0], [ 0]]) This routine does not simplify expressions and will raise an error if nonlinearity is encountered: >>> eqns = [ ... (x**2 - 3*x)/(x - 3) - 3, ... y**2 - 3*y - y*(y - 4) + x - 4] >>> linear_eq_to_matrix(eqns, [x, y]) Traceback (most recent call last): ... NonlinearError: The term (x**2 - 3*x)/(x - 3) is nonlinear in {x, y} Simplifying these equations will discard the removable singularity in the first, reveal the linear structure of the second: >>> [e.simplify() for e in eqns] [x - 3, x + y - 4] Any such simplification needed to eliminate nonlinear terms must be done before calling this routine. """ if not symbols: raise ValueError(filldedent(''' Symbols must be given, for which coefficients are to be found. ''')) if hasattr(symbols[0], '__iter__'): symbols = symbols[0] for i in symbols: if not isinstance(i, Symbol): raise ValueError(filldedent(''' Expecting a Symbol but got %s ''' % i)) if has_dups(symbols): raise ValueError('Symbols must be unique') equations = sympify(equations) if isinstance(equations, MatrixBase): equations = list(equations) elif isinstance(equations, (Expr, Eq)): equations = [equations] elif not is_sequence(equations): raise ValueError(filldedent(''' Equation(s) must be given as a sequence, Expr, Eq or Matrix. ''')) A, b = [], [] for i, f in enumerate(equations): if isinstance(f, Equality): f = f.rewrite(Add, evaluate=False) coeff_list = linear_coeffs(f, *symbols) b.append(-coeff_list.pop()) A.append(coeff_list) A, b = map(Matrix, (A, b)) return A, b def linsolve(system, *symbols): r""" Solve system of N linear equations with M variables; both underdetermined and overdetermined systems are supported. The possible number of solutions is zero, one or infinite. Zero solutions throws a ValueError, whereas infinite solutions are represented parametrically in terms of the given symbols. For unique solution a FiniteSet of ordered tuples is returned. All Standard input formats are supported: For the given set of Equations, the respective input types are given below: .. math:: 3x + 2y - z = 1 .. math:: 2x - 2y + 4z = -2 .. math:: 2x - y + 2z = 0 * Augmented Matrix Form, `system` given below: :: [3 2 -1 1] system = [2 -2 4 -2] [2 -1 2 0] * List Of Equations Form `system = [3x + 2y - z - 1, 2x - 2y + 4z + 2, 2x - y + 2z]` * Input A & b Matrix Form (from Ax = b) are given as below: :: [3 2 -1 ] [ 1 ] A = [2 -2 4 ] b = [ -2 ] [2 -1 2 ] [ 0 ] `system = (A, b)` Symbols can always be passed but are actually only needed when 1) a system of equations is being passed and 2) the system is passed as an underdetermined matrix and one wants to control the name of the free variables in the result. An error is raised if no symbols are used for case 1, but if no symbols are provided for case 2, internally generated symbols will be provided. When providing symbols for case 2, there should be at least as many symbols are there are columns in matrix A. The algorithm used here is Gauss-Jordan elimination, which results, after elimination, in a row echelon form matrix. Returns ======= A FiniteSet containing an ordered tuple of values for the unknowns for which the `system` has a solution. (Wrapping the tuple in FiniteSet is used to maintain a consistent output format throughout solveset.) Returns EmptySet, if the linear system is inconsistent. Raises ====== ValueError The input is not valid. The symbols are not given. Examples ======== >>> from sympy import Matrix, linsolve, symbols >>> x, y, z = symbols("x, y, z") >>> A = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 10]]) >>> b = Matrix([3, 6, 9]) >>> A Matrix([ [1, 2, 3], [4, 5, 6], [7, 8, 10]]) >>> b Matrix([ [3], [6], [9]]) >>> linsolve((A, b), [x, y, z]) FiniteSet((-1, 2, 0)) * Parametric Solution: In case the system is underdetermined, the function will return a parametric solution in terms of the given symbols. Those that are free will be returned unchanged. e.g. in the system below, `z` is returned as the solution for variable z; it can take on any value. >>> A = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) >>> b = Matrix([3, 6, 9]) >>> linsolve((A, b), x, y, z) FiniteSet((z - 1, 2 - 2*z, z)) If no symbols are given, internally generated symbols will be used. The `tau0` in the 3rd position indicates (as before) that the 3rd variable -- whatever it's named -- can take on any value: >>> linsolve((A, b)) FiniteSet((tau0 - 1, 2 - 2*tau0, tau0)) * List of Equations as input >>> Eqns = [3*x + 2*y - z - 1, 2*x - 2*y + 4*z + 2, - x + y/2 - z] >>> linsolve(Eqns, x, y, z) FiniteSet((1, -2, -2)) * Augmented Matrix as input >>> aug = Matrix([[2, 1, 3, 1], [2, 6, 8, 3], [6, 8, 18, 5]]) >>> aug Matrix([ [2, 1, 3, 1], [2, 6, 8, 3], [6, 8, 18, 5]]) >>> linsolve(aug, x, y, z) FiniteSet((3/10, 2/5, 0)) * Solve for symbolic coefficients >>> a, b, c, d, e, f = symbols('a, b, c, d, e, f') >>> eqns = [a*x + b*y - c, d*x + e*y - f] >>> linsolve(eqns, x, y) FiniteSet(((-b*f + c*e)/(a*e - b*d), (a*f - c*d)/(a*e - b*d))) * A degenerate system returns solution as set of given symbols. >>> system = Matrix(([0, 0, 0], [0, 0, 0], [0, 0, 0])) >>> linsolve(system, x, y) FiniteSet((x, y)) * For an empty system linsolve returns empty set >>> linsolve([], x) EmptySet * An error is raised if, after expansion, any nonlinearity is detected: >>> linsolve([x*(1/x - 1), (y - 1)**2 - y**2 + 1], x, y) FiniteSet((1, 1)) >>> linsolve([x**2 - 1], x) Traceback (most recent call last): ... NonlinearError: nonlinear term encountered: x**2 """ if not system: return S.EmptySet # If second argument is an iterable if symbols and hasattr(symbols[0], '__iter__'): symbols = symbols[0] sym_gen = isinstance(symbols, GeneratorType) b = None # if we don't get b the input was bad syms_needed_msg = None # unpack system if hasattr(system, '__iter__'): # 1). (A, b) if len(system) == 2 and isinstance(system[0], MatrixBase): A, b = system # 2). (eq1, eq2, ...) if not isinstance(system[0], MatrixBase): if sym_gen or not symbols: raise ValueError(filldedent(''' When passing a system of equations, the explicit symbols for which a solution is being sought must be given as a sequence, too. ''')) eqs = system try: eqs, ring = sympy_eqs_to_ring(eqs, symbols) except PolynomialError as exc: # e.g. cos(x) contains an element of the set of generators raise NonlinearError(str(exc)) try: sol = solve_lin_sys(eqs, ring, _raw=False) except PolyNonlinearError as exc: raise NonlinearError(str(exc)) if sol is None: return S.EmptySet sol = FiniteSet(Tuple(*(sol.get(sym, sym) for sym in symbols))) return sol elif isinstance(system, MatrixBase) and not ( symbols and not isinstance(symbols, GeneratorType) and isinstance(symbols[0], MatrixBase)): # 3). A augmented with b A, b = system[:, :-1], system[:, -1:] if b is None: raise ValueError("Invalid arguments") syms_needed_msg = syms_needed_msg or 'columns of A' if sym_gen: symbols = [next(symbols) for i in range(A.cols)] if any(set(symbols) & (A.free_symbols | b.free_symbols)): raise ValueError(filldedent(''' At least one of the symbols provided already appears in the system to be solved. One way to avoid this is to use Dummy symbols in the generator, e.g. numbered_symbols('%s', cls=Dummy) ''' % symbols[0].name.rstrip('1234567890'))) if not symbols: symbols = [Dummy() for _ in range(A.cols)] name = _uniquely_named_symbol('tau', (A, b), compare=lambda i: str(i).rstrip('1234567890')).name gen = numbered_symbols(name) else: gen = None # This is just a wrapper for solve_lin_sys eqs = [] rows = A.tolist() for rowi, bi in zip(rows, b): terms = [elem * sym for elem, sym in zip(rowi, symbols) if elem] terms.append(-bi) eqs.append(Add(*terms)) eqs, ring = sympy_eqs_to_ring(eqs, symbols) sol = solve_lin_sys(eqs, ring, _raw=False) if sol is None: return S.EmptySet #sol = {sym:val for sym, val in sol.items() if sym != val} sol = FiniteSet(Tuple(*(sol.get(sym, sym) for sym in symbols))) if gen is not None: solsym = sol.free_symbols rep = {sym: next(gen) for sym in symbols if sym in solsym} sol = sol.subs(rep) return sol ############################################################################## # ------------------------------nonlinsolve ---------------------------------# ############################################################################## def _return_conditionset(eqs, symbols): # return conditionset eqs = (Eq(lhs, 0) for lhs in eqs) condition_set = ConditionSet( Tuple(*symbols), And(*eqs), S.Complexes**len(symbols)) return condition_set def substitution(system, symbols, result=[{}], known_symbols=[], exclude=[], all_symbols=None): r""" Solves the `system` using substitution method. It is used in `nonlinsolve`. This will be called from `nonlinsolve` when any equation(s) is non polynomial equation. Parameters ========== system : list of equations The target system of equations symbols : list of symbols to be solved. The variable(s) for which the system is solved known_symbols : list of solved symbols Values are known for these variable(s) result : An empty list or list of dict If No symbol values is known then empty list otherwise symbol as keys and corresponding value in dict. exclude : Set of expression. Mostly denominator expression(s) of the equations of the system. Final solution should not satisfy these expressions. all_symbols : known_symbols + symbols(unsolved). Returns ======= A FiniteSet of ordered tuple of values of `all_symbols` for which the `system` has solution. Order of values in the tuple is same as symbols present in the parameter `all_symbols`. If parameter `all_symbols` is None then same as symbols present in the parameter `symbols`. Please note that general FiniteSet is unordered, the solution returned here is not simply a FiniteSet of solutions, rather it is a FiniteSet of ordered tuple, i.e. the first & only argument to FiniteSet is a tuple of solutions, which is ordered, & hence the returned solution is ordered. Also note that solution could also have been returned as an ordered tuple, FiniteSet is just a wrapper `{}` around the tuple. It has no other significance except for the fact it is just used to maintain a consistent output format throughout the solveset. Raises ====== ValueError The input is not valid. The symbols are not given. AttributeError The input symbols are not `Symbol` type. Examples ======== >>> from sympy.core.symbol import symbols >>> x, y = symbols('x, y', real=True) >>> from sympy.solvers.solveset import substitution >>> substitution([x + y], [x], [{y: 1}], [y], set([]), [x, y]) FiniteSet((-1, 1)) * when you want soln should not satisfy eq `x + 1 = 0` >>> substitution([x + y], [x], [{y: 1}], [y], set([x + 1]), [y, x]) EmptySet >>> substitution([x + y], [x], [{y: 1}], [y], set([x - 1]), [y, x]) FiniteSet((1, -1)) >>> substitution([x + y - 1, y - x**2 + 5], [x, y]) FiniteSet((-3, 4), (2, -1)) * Returns both real and complex solution >>> x, y, z = symbols('x, y, z') >>> from sympy import exp, sin >>> substitution([exp(x) - sin(y), y**2 - 4], [x, y]) FiniteSet((ImageSet(Lambda(_n, 2*_n*I*pi + log(sin(2))), Integers), 2), (ImageSet(Lambda(_n, I*(2*_n*pi + pi) + log(sin(2))), Integers), -2)) >>> eqs = [z**2 + exp(2*x) - sin(y), -3 + exp(-y)] >>> substitution(eqs, [y, z]) FiniteSet((-log(3), sqrt(-exp(2*x) - sin(log(3)))), (-log(3), -sqrt(-exp(2*x) - sin(log(3)))), (ImageSet(Lambda(_n, 2*_n*I*pi - log(3)), Integers), ImageSet(Lambda(_n, sqrt(-exp(2*x) + sin(2*_n*I*pi - log(3)))), Integers)), (ImageSet(Lambda(_n, 2*_n*I*pi - log(3)), Integers), ImageSet(Lambda(_n, -sqrt(-exp(2*x) + sin(2*_n*I*pi - log(3)))), Integers))) """ from sympy import Complement from sympy.core.compatibility import is_sequence if not system: return S.EmptySet if not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise ValueError(filldedent(msg)) if not is_sequence(symbols): msg = ('symbols should be given as a sequence, e.g. a list.' 'Not type %s: %s') raise TypeError(filldedent(msg % (type(symbols), symbols))) if not getattr(symbols[0], 'is_Symbol', False): msg = ('Iterable of symbols must be given as ' 'second argument, not type %s: %s') raise ValueError(filldedent(msg % (type(symbols[0]), symbols[0]))) # By default `all_symbols` will be same as `symbols` if all_symbols is None: all_symbols = symbols old_result = result # storing complements and intersection for particular symbol complements = {} intersections = {} # when total_solveset_call equals total_conditionset # it means that solveset failed to solve all eqs. total_conditionset = -1 total_solveset_call = -1 def _unsolved_syms(eq, sort=False): """Returns the unsolved symbol present in the equation `eq`. """ free = eq.free_symbols unsolved = (free - set(known_symbols)) & set(all_symbols) if sort: unsolved = list(unsolved) unsolved.sort(key=default_sort_key) return unsolved # end of _unsolved_syms() # sort such that equation with the fewest potential symbols is first. # means eq with less number of variable first in the list. eqs_in_better_order = list( ordered(system, lambda _: len(_unsolved_syms(_)))) def add_intersection_complement(result, intersection_dict, complement_dict): # If solveset has returned some intersection/complement # for any symbol, it will be added in the final solution. final_result = [] for res in result: res_copy = res for key_res, value_res in res.items(): intersect_set, complement_set = None, None for key_sym, value_sym in intersection_dict.items(): if key_sym == key_res: intersect_set = value_sym for key_sym, value_sym in complement_dict.items(): if key_sym == key_res: complement_set = value_sym if intersect_set or complement_set: new_value = FiniteSet(value_res) if intersect_set and intersect_set != S.Complexes: new_value = Intersection(new_value, intersect_set) if complement_set: new_value = Complement(new_value, complement_set) if new_value is S.EmptySet: res_copy = None break elif new_value.is_FiniteSet and len(new_value) == 1: res_copy[key_res] = set(new_value).pop() else: res_copy[key_res] = new_value if res_copy is not None: final_result.append(res_copy) return final_result # end of def add_intersection_complement() def _extract_main_soln(sym, sol, soln_imageset): """Separate the Complements, Intersections, ImageSet lambda expr and its base_set. """ # if there is union, then need to check # Complement, Intersection, Imageset. # Order should not be changed. if isinstance(sol, Complement): # extract solution and complement complements[sym] = sol.args[1] sol = sol.args[0] # complement will be added at the end # using `add_intersection_complement` method if isinstance(sol, Intersection): # Interval/Set will be at 0th index always if sol.args[0] not in (S.Reals, S.Complexes): # Sometimes solveset returns soln with intersection # S.Reals or S.Complexes. We don't consider that # intersection. intersections[sym] = sol.args[0] sol = sol.args[1] # after intersection and complement Imageset should # be checked. if isinstance(sol, ImageSet): soln_imagest = sol expr2 = sol.lamda.expr sol = FiniteSet(expr2) soln_imageset[expr2] = soln_imagest # if there is union of Imageset or other in soln. # no testcase is written for this if block if isinstance(sol, Union): sol_args = sol.args sol = S.EmptySet # We need in sequence so append finteset elements # and then imageset or other. for sol_arg2 in sol_args: if isinstance(sol_arg2, FiniteSet): sol += sol_arg2 else: # ImageSet, Intersection, complement then # append them directly sol += FiniteSet(sol_arg2) if not isinstance(sol, FiniteSet): sol = FiniteSet(sol) return sol, soln_imageset # end of def _extract_main_soln() # helper function for _append_new_soln def _check_exclude(rnew, imgset_yes): rnew_ = rnew if imgset_yes: # replace all dummy variables (Imageset lambda variables) # with zero before `checksol`. Considering fundamental soln # for `checksol`. rnew_copy = rnew.copy() dummy_n = imgset_yes[0] for key_res, value_res in rnew_copy.items(): rnew_copy[key_res] = value_res.subs(dummy_n, 0) rnew_ = rnew_copy # satisfy_exclude == true if it satisfies the expr of `exclude` list. try: # something like : `Mod(-log(3), 2*I*pi)` can't be # simplified right now, so `checksol` returns `TypeError`. # when this issue is fixed this try block should be # removed. Mod(-log(3), 2*I*pi) == -log(3) satisfy_exclude = any( checksol(d, rnew_) for d in exclude) except TypeError: satisfy_exclude = None return satisfy_exclude # end of def _check_exclude() # helper function for _append_new_soln def _restore_imgset(rnew, original_imageset, newresult): restore_sym = set(rnew.keys()) & \ set(original_imageset.keys()) for key_sym in restore_sym: img = original_imageset[key_sym] rnew[key_sym] = img if rnew not in newresult: newresult.append(rnew) # end of def _restore_imgset() def _append_eq(eq, result, res, delete_soln, n=None): u = Dummy('u') if n: eq = eq.subs(n, 0) satisfy = checksol(u, u, eq, minimal=True) if satisfy is False: delete_soln = True res = {} else: result.append(res) return result, res, delete_soln def _append_new_soln(rnew, sym, sol, imgset_yes, soln_imageset, original_imageset, newresult, eq=None): """If `rnew` (A dict <symbol: soln>) contains valid soln append it to `newresult` list. `imgset_yes` is (base, dummy_var) if there was imageset in previously calculated result(otherwise empty tuple). `original_imageset` is dict of imageset expr and imageset from this result. `soln_imageset` dict of imageset expr and imageset of new soln. """ satisfy_exclude = _check_exclude(rnew, imgset_yes) delete_soln = False # soln should not satisfy expr present in `exclude` list. if not satisfy_exclude: local_n = None # if it is imageset if imgset_yes: local_n = imgset_yes[0] base = imgset_yes[1] if sym and sol: # when `sym` and `sol` is `None` means no new # soln. In that case we will append rnew directly after # substituting original imagesets in rnew values if present # (second last line of this function using _restore_imgset) dummy_list = list(sol.atoms(Dummy)) # use one dummy `n` which is in # previous imageset local_n_list = [ local_n for i in range( 0, len(dummy_list))] dummy_zip = zip(dummy_list, local_n_list) lam = Lambda(local_n, sol.subs(dummy_zip)) rnew[sym] = ImageSet(lam, base) if eq is not None: newresult, rnew, delete_soln = _append_eq( eq, newresult, rnew, delete_soln, local_n) elif eq is not None: newresult, rnew, delete_soln = _append_eq( eq, newresult, rnew, delete_soln) elif soln_imageset: rnew[sym] = soln_imageset[sol] # restore original imageset _restore_imgset(rnew, original_imageset, newresult) else: newresult.append(rnew) elif satisfy_exclude: delete_soln = True rnew = {} _restore_imgset(rnew, original_imageset, newresult) return newresult, delete_soln # end of def _append_new_soln() def _new_order_result(result, eq): # separate first, second priority. `res` that makes `eq` value equals # to zero, should be used first then other result(second priority). # If it is not done then we may miss some soln. first_priority = [] second_priority = [] for res in result: if not any(isinstance(val, ImageSet) for val in res.values()): if eq.subs(res) == 0: first_priority.append(res) else: second_priority.append(res) if first_priority or second_priority: return first_priority + second_priority return result def _solve_using_known_values(result, solver): """Solves the system using already known solution (result contains the dict <symbol: value>). solver is `solveset_complex` or `solveset_real`. """ # stores imageset <expr: imageset(Lambda(n, expr), base)>. soln_imageset = {} total_solvest_call = 0 total_conditionst = 0 # sort such that equation with the fewest potential symbols is first. # means eq with less variable first for index, eq in enumerate(eqs_in_better_order): newresult = [] original_imageset = {} # if imageset expr is used to solve other symbol imgset_yes = False result = _new_order_result(result, eq) for res in result: got_symbol = set() # symbols solved in one iteration if soln_imageset: # find the imageset and use its expr. for key_res, value_res in res.items(): if isinstance(value_res, ImageSet): res[key_res] = value_res.lamda.expr original_imageset[key_res] = value_res dummy_n = value_res.lamda.expr.atoms(Dummy).pop() (base,) = value_res.base_sets imgset_yes = (dummy_n, base) # update eq with everything that is known so far eq2 = eq.subs(res).expand() unsolved_syms = _unsolved_syms(eq2, sort=True) if not unsolved_syms: if res: newresult, delete_res = _append_new_soln( res, None, None, imgset_yes, soln_imageset, original_imageset, newresult, eq2) if delete_res: # `delete_res` is true, means substituting `res` in # eq2 doesn't return `zero` or deleting the `res` # (a soln) since it staisfies expr of `exclude` # list. result.remove(res) continue # skip as it's independent of desired symbols depen1, depen2 = (eq2.rewrite(Add)).as_independent(*unsolved_syms) if (depen1.has(Abs) or depen2.has(Abs)) and solver == solveset_complex: # Absolute values cannot be inverted in the # complex domain continue soln_imageset = {} for sym in unsolved_syms: not_solvable = False try: soln = solver(eq2, sym) total_solvest_call += 1 soln_new = S.EmptySet if isinstance(soln, Complement): # separate solution and complement complements[sym] = soln.args[1] soln = soln.args[0] # complement will be added at the end if isinstance(soln, Intersection): # Interval will be at 0th index always if soln.args[0] != Interval(-oo, oo): # sometimes solveset returns soln # with intersection S.Reals, to confirm that # soln is in domain=S.Reals intersections[sym] = soln.args[0] soln_new += soln.args[1] soln = soln_new if soln_new else soln if index > 0 and solver == solveset_real: # one symbol's real soln , another symbol may have # corresponding complex soln. if not isinstance(soln, (ImageSet, ConditionSet)): soln += solveset_complex(eq2, sym) except NotImplementedError: # If sovleset is not able to solve equation `eq2`. Next # time we may get soln using next equation `eq2` continue if isinstance(soln, ConditionSet): soln = S.EmptySet # don't do `continue` we may get soln # in terms of other symbol(s) not_solvable = True total_conditionst += 1 if soln is not S.EmptySet: soln, soln_imageset = _extract_main_soln( sym, soln, soln_imageset) for sol in soln: # sol is not a `Union` since we checked it # before this loop sol, soln_imageset = _extract_main_soln( sym, sol, soln_imageset) sol = set(sol).pop() free = sol.free_symbols if got_symbol and any([ ss in free for ss in got_symbol ]): # sol depends on previously solved symbols # then continue continue rnew = res.copy() # put each solution in res and append the new result # in the new result list (solution for symbol `s`) # along with old results. for k, v in res.items(): if isinstance(v, Expr): # if any unsolved symbol is present # Then subs known value rnew[k] = v.subs(sym, sol) # and add this new solution if soln_imageset: # replace all lambda variables with 0. imgst = soln_imageset[sol] rnew[sym] = imgst.lamda( *[0 for i in range(0, len( imgst.lamda.variables))]) else: rnew[sym] = sol newresult, delete_res = _append_new_soln( rnew, sym, sol, imgset_yes, soln_imageset, original_imageset, newresult) if delete_res: # deleting the `res` (a soln) since it staisfies # eq of `exclude` list result.remove(res) # solution got for sym if not not_solvable: got_symbol.add(sym) # next time use this new soln if newresult: result = newresult return result, total_solvest_call, total_conditionst # end def _solve_using_know_values() new_result_real, solve_call1, cnd_call1 = _solve_using_known_values( old_result, solveset_real) new_result_complex, solve_call2, cnd_call2 = _solve_using_known_values( old_result, solveset_complex) # when `total_solveset_call` is equals to `total_conditionset` # means solvest fails to solve all the eq. # return conditionset in this case total_conditionset += (cnd_call1 + cnd_call2) total_solveset_call += (solve_call1 + solve_call2) if total_conditionset == total_solveset_call and total_solveset_call != -1: return _return_conditionset(eqs_in_better_order, all_symbols) # overall result result = new_result_real + new_result_complex result_all_variables = [] result_infinite = [] for res in result: if not res: # means {None : None} continue # If length < len(all_symbols) means infinite soln. # Some or all the soln is dependent on 1 symbol. # eg. {x: y+2} then final soln {x: y+2, y: y} if len(res) < len(all_symbols): solved_symbols = res.keys() unsolved = list(filter( lambda x: x not in solved_symbols, all_symbols)) for unsolved_sym in unsolved: res[unsolved_sym] = unsolved_sym result_infinite.append(res) if res not in result_all_variables: result_all_variables.append(res) if result_infinite: # we have general soln # eg : [{x: -1, y : 1}, {x : -y , y: y}] then # return [{x : -y, y : y}] result_all_variables = result_infinite if intersections or complements: result_all_variables = add_intersection_complement( result_all_variables, intersections, complements) # convert to ordered tuple result = S.EmptySet for r in result_all_variables: temp = [r[symb] for symb in all_symbols] result += FiniteSet(tuple(temp)) return result # end of def substitution() def _solveset_work(system, symbols): soln = solveset(system[0], symbols[0]) if isinstance(soln, FiniteSet): _soln = FiniteSet(*[tuple((s,)) for s in soln]) return _soln else: return FiniteSet(tuple(FiniteSet(soln))) def _handle_positive_dimensional(polys, symbols, denominators): from sympy.polys.polytools import groebner # substitution method where new system is groebner basis of the system _symbols = list(symbols) _symbols.sort(key=default_sort_key) basis = groebner(polys, _symbols, polys=True) new_system = [] for poly_eq in basis: new_system.append(poly_eq.as_expr()) result = [{}] result = substitution( new_system, symbols, result, [], denominators) return result # end of def _handle_positive_dimensional() def _handle_zero_dimensional(polys, symbols, system): # solve 0 dimensional poly system using `solve_poly_system` result = solve_poly_system(polys, *symbols) # May be some extra soln is added because # we used `unrad` in `_separate_poly_nonpoly`, so # need to check and remove if it is not a soln. result_update = S.EmptySet for res in result: dict_sym_value = dict(list(zip(symbols, res))) if all(checksol(eq, dict_sym_value) for eq in system): result_update += FiniteSet(res) return result_update # end of def _handle_zero_dimensional() def _separate_poly_nonpoly(system, symbols): polys = [] polys_expr = [] nonpolys = [] denominators = set() poly = None for eq in system: # Store denom expression if it contains symbol denominators.update(_simple_dens(eq, symbols)) # try to remove sqrt and rational power without_radicals = unrad(simplify(eq)) if without_radicals: eq_unrad, cov = without_radicals if not cov: eq = eq_unrad if isinstance(eq, Expr): eq = eq.as_numer_denom()[0] poly = eq.as_poly(*symbols, extension=True) elif simplify(eq).is_number: continue if poly is not None: polys.append(poly) polys_expr.append(poly.as_expr()) else: nonpolys.append(eq) return polys, polys_expr, nonpolys, denominators # end of def _separate_poly_nonpoly() def nonlinsolve(system, *symbols): r""" Solve system of N nonlinear equations with M variables, which means both under and overdetermined systems are supported. Positive dimensional system is also supported (A system with infinitely many solutions is said to be positive-dimensional). In Positive dimensional system solution will be dependent on at least one symbol. Returns both real solution and complex solution(If system have). The possible number of solutions is zero, one or infinite. Parameters ========== system : list of equations The target system of equations symbols : list of Symbols symbols should be given as a sequence eg. list Returns ======= A FiniteSet of ordered tuple of values of `symbols` for which the `system` has solution. Order of values in the tuple is same as symbols present in the parameter `symbols`. Please note that general FiniteSet is unordered, the solution returned here is not simply a FiniteSet of solutions, rather it is a FiniteSet of ordered tuple, i.e. the first & only argument to FiniteSet is a tuple of solutions, which is ordered, & hence the returned solution is ordered. Also note that solution could also have been returned as an ordered tuple, FiniteSet is just a wrapper `{}` around the tuple. It has no other significance except for the fact it is just used to maintain a consistent output format throughout the solveset. For the given set of Equations, the respective input types are given below: .. math:: x*y - 1 = 0 .. math:: 4*x**2 + y**2 - 5 = 0 `system = [x*y - 1, 4*x**2 + y**2 - 5]` `symbols = [x, y]` Raises ====== ValueError The input is not valid. The symbols are not given. AttributeError The input symbols are not `Symbol` type. Examples ======== >>> from sympy.core.symbol import symbols >>> from sympy.solvers.solveset import nonlinsolve >>> x, y, z = symbols('x, y, z', real=True) >>> nonlinsolve([x*y - 1, 4*x**2 + y**2 - 5], [x, y]) FiniteSet((-1, -1), (-1/2, -2), (1/2, 2), (1, 1)) 1. Positive dimensional system and complements: >>> from sympy import pprint >>> from sympy.polys.polytools import is_zero_dimensional >>> a, b, c, d = symbols('a, b, c, d', extended_real=True) >>> eq1 = a + b + c + d >>> eq2 = a*b + b*c + c*d + d*a >>> eq3 = a*b*c + b*c*d + c*d*a + d*a*b >>> eq4 = a*b*c*d - 1 >>> system = [eq1, eq2, eq3, eq4] >>> is_zero_dimensional(system) False >>> pprint(nonlinsolve(system, [a, b, c, d]), use_unicode=False) -1 1 1 -1 {(---, -d, -, {d} \ {0}), (-, -d, ---, {d} \ {0})} d d d d >>> nonlinsolve([(x+y)**2 - 4, x + y - 2], [x, y]) FiniteSet((2 - y, y)) 2. If some of the equations are non-polynomial then `nonlinsolve` will call the `substitution` function and return real and complex solutions, if present. >>> from sympy import exp, sin >>> nonlinsolve([exp(x) - sin(y), y**2 - 4], [x, y]) FiniteSet((ImageSet(Lambda(_n, 2*_n*I*pi + log(sin(2))), Integers), 2), (ImageSet(Lambda(_n, I*(2*_n*pi + pi) + log(sin(2))), Integers), -2)) 3. If system is non-linear polynomial and zero-dimensional then it returns both solution (real and complex solutions, if present) using `solve_poly_system`: >>> from sympy import sqrt >>> nonlinsolve([x**2 - 2*y**2 -2, x*y - 2], [x, y]) FiniteSet((-2, -1), (2, 1), (-sqrt(2)*I, sqrt(2)*I), (sqrt(2)*I, -sqrt(2)*I)) 4. `nonlinsolve` can solve some linear (zero or positive dimensional) system (because it uses the `groebner` function to get the groebner basis and then uses the `substitution` function basis as the new `system`). But it is not recommended to solve linear system using `nonlinsolve`, because `linsolve` is better for general linear systems. >>> nonlinsolve([x + 2*y -z - 3, x - y - 4*z + 9 , y + z - 4], [x, y, z]) FiniteSet((3*z - 5, 4 - z, z)) 5. System having polynomial equations and only real solution is solved using `solve_poly_system`: >>> e1 = sqrt(x**2 + y**2) - 10 >>> e2 = sqrt(y**2 + (-x + 10)**2) - 3 >>> nonlinsolve((e1, e2), (x, y)) FiniteSet((191/20, -3*sqrt(391)/20), (191/20, 3*sqrt(391)/20)) >>> nonlinsolve([x**2 + 2/y - 2, x + y - 3], [x, y]) FiniteSet((1, 2), (1 - sqrt(5), 2 + sqrt(5)), (1 + sqrt(5), 2 - sqrt(5))) >>> nonlinsolve([x**2 + 2/y - 2, x + y - 3], [y, x]) FiniteSet((2, 1), (2 - sqrt(5), 1 + sqrt(5)), (2 + sqrt(5), 1 - sqrt(5))) 6. It is better to use symbols instead of Trigonometric Function or Function (e.g. replace `sin(x)` with symbol, replace `f(x)` with symbol and so on. Get soln from `nonlinsolve` and then using `solveset` get the value of `x`) How nonlinsolve is better than old solver `_solve_system` : =========================================================== 1. A positive dimensional system solver : nonlinsolve can return solution for positive dimensional system. It finds the Groebner Basis of the positive dimensional system(calling it as basis) then we can start solving equation(having least number of variable first in the basis) using solveset and substituting that solved solutions into other equation(of basis) to get solution in terms of minimum variables. Here the important thing is how we are substituting the known values and in which equations. 2. Real and Complex both solutions : nonlinsolve returns both real and complex solution. If all the equations in the system are polynomial then using `solve_poly_system` both real and complex solution is returned. If all the equations in the system are not polynomial equation then goes to `substitution` method with this polynomial and non polynomial equation(s), to solve for unsolved variables. Here to solve for particular variable solveset_real and solveset_complex is used. For both real and complex solution function `_solve_using_know_values` is used inside `substitution` function.(`substitution` function will be called when there is any non polynomial equation(s) is present). When solution is valid then add its general solution in the final result. 3. Complement and Intersection will be added if any : nonlinsolve maintains dict for complements and Intersections. If solveset find complements or/and Intersection with any Interval or set during the execution of `substitution` function ,then complement or/and Intersection for that variable is added before returning final solution. """ from sympy.polys.polytools import is_zero_dimensional if not system: return S.EmptySet if not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise ValueError(filldedent(msg)) if hasattr(symbols[0], '__iter__'): symbols = symbols[0] if not is_sequence(symbols) or not symbols: msg = ('Symbols must be given, for which solution of the ' 'system is to be found.') raise IndexError(filldedent(msg)) system, symbols, swap = recast_to_symbols(system, symbols) if swap: soln = nonlinsolve(system, symbols) return FiniteSet(*[tuple(i.xreplace(swap) for i in s) for s in soln]) if len(system) == 1 and len(symbols) == 1: return _solveset_work(system, symbols) # main code of def nonlinsolve() starts from here polys, polys_expr, nonpolys, denominators = _separate_poly_nonpoly( system, symbols) if len(symbols) == len(polys): # If all the equations in the system are poly if is_zero_dimensional(polys, symbols): # finite number of soln (Zero dimensional system) try: return _handle_zero_dimensional(polys, symbols, system) except NotImplementedError: # Right now it doesn't fail for any polynomial system of # equation. If `solve_poly_system` fails then `substitution` # method will handle it. result = substitution( polys_expr, symbols, exclude=denominators) return result # positive dimensional system res = _handle_positive_dimensional(polys, symbols, denominators) if res is EmptySet and any(not p.domain.is_Exact for p in polys): raise NotImplementedError("Equation not in exact domain. Try converting to rational") else: return res else: # If all the equations are not polynomial. # Use `substitution` method for the system result = substitution( polys_expr + nonpolys, symbols, exclude=denominators) return result

e550a4452e5c95ebe56244e1588b39c16741db74e8a21a9287ce29fd39236fcb

""" This module contains pdsolve() and different helper functions that it uses. It is heavily inspired by the ode module and hence the basic infrastructure remains the same. **Functions in this module** These are the user functions in this module: - pdsolve() - Solves PDE's - classify_pde() - Classifies PDEs into possible hints for dsolve(). - pde_separate() - Separate variables in partial differential equation either by additive or multiplicative separation approach. These are the helper functions in this module: - pde_separate_add() - Helper function for searching additive separable solutions. - pde_separate_mul() - Helper function for searching multiplicative separable solutions. **Currently implemented solver methods** The following methods are implemented for solving partial differential equations. See the docstrings of the various pde_hint() functions for more information on each (run help(pde)): - 1st order linear homogeneous partial differential equations with constant coefficients. - 1st order linear general partial differential equations with constant coefficients. - 1st order linear partial differential equations with variable coefficients. """ from itertools import combinations_with_replacement from sympy.simplify import simplify # type: ignore from sympy.core import Add, S from sympy.core.compatibility import reduce, is_sequence from sympy.core.function import Function, expand, AppliedUndef, Subs from sympy.core.relational import Equality, Eq from sympy.core.symbol import Symbol, Wild, symbols from sympy.functions import exp from sympy.integrals.integrals import Integral from sympy.utilities.iterables import has_dups from sympy.utilities.misc import filldedent from sympy.solvers.deutils import _preprocess, ode_order, _desolve from sympy.solvers.solvers import solve from sympy.simplify.radsimp import collect import operator allhints = ( "1st_linear_constant_coeff_homogeneous", "1st_linear_constant_coeff", "1st_linear_constant_coeff_Integral", "1st_linear_variable_coeff" ) def pdsolve(eq, func=None, hint='default', dict=False, solvefun=None, **kwargs): """ Solves any (supported) kind of partial differential equation. **Usage** pdsolve(eq, f(x,y), hint) -> Solve partial differential equation eq for function f(x,y), using method hint. **Details** ``eq`` can be any supported partial differential equation (see the pde docstring for supported methods). This can either be an Equality, or an expression, which is assumed to be equal to 0. ``f(x,y)`` is a function of two variables whose derivatives in that variable make up the partial differential equation. In many cases it is not necessary to provide this; it will be autodetected (and an error raised if it couldn't be detected). ``hint`` is the solving method that you want pdsolve to use. Use classify_pde(eq, f(x,y)) to get all of the possible hints for a PDE. The default hint, 'default', will use whatever hint is returned first by classify_pde(). See Hints below for more options that you can use for hint. ``solvefun`` is the convention used for arbitrary functions returned by the PDE solver. If not set by the user, it is set by default to be F. **Hints** Aside from the various solving methods, there are also some meta-hints that you can pass to pdsolve(): "default": This uses whatever hint is returned first by classify_pde(). This is the default argument to pdsolve(). "all": To make pdsolve apply all relevant classification hints, use pdsolve(PDE, func, hint="all"). This will return a dictionary of hint:solution terms. If a hint causes pdsolve to raise the NotImplementedError, value of that hint's key will be the exception object raised. The dictionary will also include some special keys: - order: The order of the PDE. See also ode_order() in deutils.py - default: The solution that would be returned by default. This is the one produced by the hint that appears first in the tuple returned by classify_pde(). "all_Integral": This is the same as "all", except if a hint also has a corresponding "_Integral" hint, it only returns the "_Integral" hint. This is useful if "all" causes pdsolve() to hang because of a difficult or impossible integral. This meta-hint will also be much faster than "all", because integrate() is an expensive routine. See also the classify_pde() docstring for more info on hints, and the pde docstring for a list of all supported hints. **Tips** - You can declare the derivative of an unknown function this way: >>> from sympy import Function, Derivative >>> from sympy.abc import x, y # x and y are the independent variables >>> f = Function("f")(x, y) # f is a function of x and y >>> # fx will be the partial derivative of f with respect to x >>> fx = Derivative(f, x) >>> # fy will be the partial derivative of f with respect to y >>> fy = Derivative(f, y) - See test_pde.py for many tests, which serves also as a set of examples for how to use pdsolve(). - pdsolve always returns an Equality class (except for the case when the hint is "all" or "all_Integral"). Note that it is not possible to get an explicit solution for f(x, y) as in the case of ODE's - Do help(pde.pde_hintname) to get help more information on a specific hint Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, Eq >>> from sympy.abc import x, y >>> f = Function('f') >>> u = f(x, y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> eq = Eq(1 + (2*(ux/u)) + (3*(uy/u)), 0) >>> pdsolve(eq) Eq(f(x, y), F(3*x - 2*y)*exp(-2*x/13 - 3*y/13)) """ if not solvefun: solvefun = Function('F') # See the docstring of _desolve for more details. hints = _desolve(eq, func=func, hint=hint, simplify=True, type='pde', **kwargs) eq = hints.pop('eq', False) all_ = hints.pop('all', False) if all_: # TODO : 'best' hint should be implemented when adequate # number of hints are added. pdedict = {} failed_hints = {} gethints = classify_pde(eq, dict=True) pdedict.update({'order': gethints['order'], 'default': gethints['default']}) for hint in hints: try: rv = _helper_simplify(eq, hint, hints[hint]['func'], hints[hint]['order'], hints[hint][hint], solvefun) except NotImplementedError as detail: failed_hints[hint] = detail else: pdedict[hint] = rv pdedict.update(failed_hints) return pdedict else: return _helper_simplify(eq, hints['hint'], hints['func'], hints['order'], hints[hints['hint']], solvefun) def _helper_simplify(eq, hint, func, order, match, solvefun): """Helper function of pdsolve that calls the respective pde functions to solve for the partial differential equations. This minimizes the computation in calling _desolve multiple times. """ if hint.endswith("_Integral"): solvefunc = globals()[ "pde_" + hint[:-len("_Integral")]] else: solvefunc = globals()["pde_" + hint] return _handle_Integral(solvefunc(eq, func, order, match, solvefun), func, order, hint) def _handle_Integral(expr, func, order, hint): r""" Converts a solution with integrals in it into an actual solution. Simplifies the integral mainly using doit() """ if hint.endswith("_Integral"): return expr elif hint == "1st_linear_constant_coeff": return simplify(expr.doit()) else: return expr def classify_pde(eq, func=None, dict=False, *, prep=True, **kwargs): """ Returns a tuple of possible pdsolve() classifications for a PDE. The tuple is ordered so that first item is the classification that pdsolve() uses to solve the PDE by default. In general, classifications near the beginning of the list will produce better solutions faster than those near the end, though there are always exceptions. To make pdsolve use a different classification, use pdsolve(PDE, func, hint=<classification>). See also the pdsolve() docstring for different meta-hints you can use. If ``dict`` is true, classify_pde() will return a dictionary of hint:match expression terms. This is intended for internal use by pdsolve(). Note that because dictionaries are ordered arbitrarily, this will most likely not be in the same order as the tuple. You can get help on different hints by doing help(pde.pde_hintname), where hintname is the name of the hint without "_Integral". See sympy.pde.allhints or the sympy.pde docstring for a list of all supported hints that can be returned from classify_pde. Examples ======== >>> from sympy.solvers.pde import classify_pde >>> from sympy import Function, Eq >>> from sympy.abc import x, y >>> f = Function('f') >>> u = f(x, y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> eq = Eq(1 + (2*(ux/u)) + (3*(uy/u)), 0) >>> classify_pde(eq) ('1st_linear_constant_coeff_homogeneous',) """ if func and len(func.args) != 2: raise NotImplementedError("Right now only partial " "differential equations of two variables are supported") if prep or func is None: prep, func_ = _preprocess(eq, func) if func is None: func = func_ if isinstance(eq, Equality): if eq.rhs != 0: return classify_pde(eq.lhs - eq.rhs, func) eq = eq.lhs f = func.func x = func.args[0] y = func.args[1] fx = f(x,y).diff(x) fy = f(x,y).diff(y) # TODO : For now pde.py uses support offered by the ode_order function # to find the order with respect to a multi-variable function. An # improvement could be to classify the order of the PDE on the basis of # individual variables. order = ode_order(eq, f(x,y)) # hint:matchdict or hint:(tuple of matchdicts) # Also will contain "default":<default hint> and "order":order items. matching_hints = {'order': order} if not order: if dict: matching_hints["default"] = None return matching_hints else: return () eq = expand(eq) a = Wild('a', exclude = [f(x,y)]) b = Wild('b', exclude = [f(x,y), fx, fy, x, y]) c = Wild('c', exclude = [f(x,y), fx, fy, x, y]) d = Wild('d', exclude = [f(x,y), fx, fy, x, y]) e = Wild('e', exclude = [f(x,y), fx, fy]) n = Wild('n', exclude = [x, y]) # Try removing the smallest power of f(x,y) # from the highest partial derivatives of f(x,y) reduced_eq = None if eq.is_Add: var = set(combinations_with_replacement((x,y), order)) dummyvar = var.copy() power = None for i in var: coeff = eq.coeff(f(x,y).diff(*i)) if coeff != 1: match = coeff.match(a*f(x,y)**n) if match and match[a]: power = match[n] dummyvar.remove(i) break dummyvar.remove(i) for i in dummyvar: coeff = eq.coeff(f(x,y).diff(*i)) if coeff != 1: match = coeff.match(a*f(x,y)**n) if match and match[a] and match[n] < power: power = match[n] if power: den = f(x,y)**power reduced_eq = Add(*[arg/den for arg in eq.args]) if not reduced_eq: reduced_eq = eq if order == 1: reduced_eq = collect(reduced_eq, f(x, y)) r = reduced_eq.match(b*fx + c*fy + d*f(x,y) + e) if r: if not r[e]: ## Linear first-order homogeneous partial-differential ## equation with constant coefficients r.update({'b': b, 'c': c, 'd': d}) matching_hints["1st_linear_constant_coeff_homogeneous"] = r else: if r[b]**2 + r[c]**2 != 0: ## Linear first-order general partial-differential ## equation with constant coefficients r.update({'b': b, 'c': c, 'd': d, 'e': e}) matching_hints["1st_linear_constant_coeff"] = r matching_hints[ "1st_linear_constant_coeff_Integral"] = r else: b = Wild('b', exclude=[f(x, y), fx, fy]) c = Wild('c', exclude=[f(x, y), fx, fy]) d = Wild('d', exclude=[f(x, y), fx, fy]) r = reduced_eq.match(b*fx + c*fy + d*f(x,y) + e) if r: r.update({'b': b, 'c': c, 'd': d, 'e': e}) matching_hints["1st_linear_variable_coeff"] = r # Order keys based on allhints. retlist = [] for i in allhints: if i in matching_hints: retlist.append(i) if dict: # Dictionaries are ordered arbitrarily, so make note of which # hint would come first for pdsolve(). Use an ordered dict in Py 3. matching_hints["default"] = None matching_hints["ordered_hints"] = tuple(retlist) for i in allhints: if i in matching_hints: matching_hints["default"] = i break return matching_hints else: return tuple(retlist) def checkpdesol(pde, sol, func=None, solve_for_func=True): """ Checks if the given solution satisfies the partial differential equation. pde is the partial differential equation which can be given in the form of an equation or an expression. sol is the solution for which the pde is to be checked. This can also be given in an equation or an expression form. If the function is not provided, the helper function _preprocess from deutils is used to identify the function. If a sequence of solutions is passed, the same sort of container will be used to return the result for each solution. The following methods are currently being implemented to check if the solution satisfies the PDE: 1. Directly substitute the solution in the PDE and check. If the solution hasn't been solved for f, then it will solve for f provided solve_for_func hasn't been set to False. If the solution satisfies the PDE, then a tuple (True, 0) is returned. Otherwise a tuple (False, expr) where expr is the value obtained after substituting the solution in the PDE. However if a known solution returns False, it may be due to the inability of doit() to simplify it to zero. Examples ======== >>> from sympy import Function, symbols >>> from sympy.solvers.pde import checkpdesol, pdsolve >>> x, y = symbols('x y') >>> f = Function('f') >>> eq = 2*f(x,y) + 3*f(x,y).diff(x) + 4*f(x,y).diff(y) >>> sol = pdsolve(eq) >>> assert checkpdesol(eq, sol)[0] >>> eq = x*f(x,y) + f(x,y).diff(x) >>> checkpdesol(eq, sol) (False, (x*F(4*x - 3*y) - 6*F(4*x - 3*y)/25 + 4*Subs(Derivative(F(_xi_1), _xi_1), _xi_1, 4*x - 3*y))*exp(-6*x/25 - 8*y/25)) """ # Converting the pde into an equation if not isinstance(pde, Equality): pde = Eq(pde, 0) # If no function is given, try finding the function present. if func is None: try: _, func = _preprocess(pde.lhs) except ValueError: funcs = [s.atoms(AppliedUndef) for s in ( sol if is_sequence(sol, set) else [sol])] funcs = set().union(funcs) if len(funcs) != 1: raise ValueError( 'must pass func arg to checkpdesol for this case.') func = funcs.pop() # If the given solution is in the form of a list or a set # then return a list or set of tuples. if is_sequence(sol, set): return type(sol)([checkpdesol( pde, i, func=func, solve_for_func=solve_for_func) for i in sol]) # Convert solution into an equation if not isinstance(sol, Equality): sol = Eq(func, sol) elif sol.rhs == func: sol = sol.reversed # Try solving for the function solved = sol.lhs == func and not sol.rhs.has(func) if solve_for_func and not solved: solved = solve(sol, func) if solved: if len(solved) == 1: return checkpdesol(pde, Eq(func, solved[0]), func=func, solve_for_func=False) else: return checkpdesol(pde, [Eq(func, t) for t in solved], func=func, solve_for_func=False) # try direct substitution of the solution into the PDE and simplify if sol.lhs == func: pde = pde.lhs - pde.rhs s = simplify(pde.subs(func, sol.rhs).doit()) return s is S.Zero, s raise NotImplementedError(filldedent(''' Unable to test if %s is a solution to %s.''' % (sol, pde))) def pde_1st_linear_constant_coeff_homogeneous(eq, func, order, match, solvefun): r""" Solves a first order linear homogeneous partial differential equation with constant coefficients. The general form of this partial differential equation is .. math:: a \frac{\partial f(x,y)}{\partial x} + b \frac{\partial f(x,y)}{\partial y} + c f(x,y) = 0 where `a`, `b` and `c` are constants. The general solution is of the form: .. math:: f(x, y) = F(- a y + b x ) e^{- \frac{c (a x + b y)}{a^2 + b^2}} and can be found in SymPy with ``pdsolve``:: >>> from sympy.solvers import pdsolve >>> from sympy.abc import x, y, a, b, c >>> from sympy import Function, pprint >>> f = Function('f') >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = a*ux + b*uy + c*u >>> pprint(genform) d d a*--(f(x, y)) + b*--(f(x, y)) + c*f(x, y) dx dy >>> pprint(pdsolve(genform)) -c*(a*x + b*y) --------------- 2 2 a + b f(x, y) = F(-a*y + b*x)*e Examples ======== >>> from sympy import pdsolve >>> from sympy import Function, pprint >>> from sympy.abc import x,y >>> f = Function('f') >>> pdsolve(f(x,y) + f(x,y).diff(x) + f(x,y).diff(y)) Eq(f(x, y), F(x - y)*exp(-x/2 - y/2)) >>> pprint(pdsolve(f(x,y) + f(x,y).diff(x) + f(x,y).diff(y))) x y - - - - 2 2 f(x, y) = F(x - y)*e References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ # TODO : For now homogeneous first order linear PDE's having # two variables are implemented. Once there is support for # solving systems of ODE's, this can be extended to n variables. f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] return Eq(f(x,y), exp(-S(d)/(b**2 + c**2)*(b*x + c*y))*solvefun(c*x - b*y)) def pde_1st_linear_constant_coeff(eq, func, order, match, solvefun): r""" Solves a first order linear partial differential equation with constant coefficients. The general form of this partial differential equation is .. math:: a \frac{\partial f(x,y)}{\partial x} + b \frac{\partial f(x,y)}{\partial y} + c f(x,y) = G(x,y) where `a`, `b` and `c` are constants and `G(x, y)` can be an arbitrary function in `x` and `y`. The general solution of the PDE is: .. math:: f(x, y) = \left. \left[F(\eta) + \frac{1}{a^2 + b^2} \int\limits^{a x + b y} G\left(\frac{a \xi + b \eta}{a^2 + b^2}, \frac{- a \eta + b \xi}{a^2 + b^2} \right) e^{\frac{c \xi}{a^2 + b^2}}\, d\xi\right] e^{- \frac{c \xi}{a^2 + b^2}} \right|_{\substack{\eta=- a y + b x\\ \xi=a x + b y }}\, , where `F(\eta)` is an arbitrary single-valued function. The solution can be found in SymPy with ``pdsolve``:: >>> from sympy.solvers import pdsolve >>> from sympy.abc import x, y, a, b, c >>> from sympy import Function, pprint >>> f = Function('f') >>> G = Function('G') >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = a*ux + b*uy + c*u - G(x,y) >>> pprint(genform) d d a*--(f(x, y)) + b*--(f(x, y)) + c*f(x, y) - G(x, y) dx dy >>> pprint(pdsolve(genform, hint='1st_linear_constant_coeff_Integral')) // a*x + b*y \ || / | || | | || | c*xi | || | ------- | || | 2 2 | || | /a*xi + b*eta -a*eta + b*xi\ a + b | || | G|------------, -------------|*e d(xi)| || | | 2 2 2 2 | | || | \ a + b a + b / | || | | || / | || | f(x, y) = ||F(eta) + -------------------------------------------------------|* || 2 2 | \\ a + b / <BLANKLINE> \| || || || || || || || || -c*xi || -------|| 2 2|| a + b || e || || /|eta=-a*y + b*x, xi=a*x + b*y Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, pprint, exp >>> from sympy.abc import x,y >>> f = Function('f') >>> eq = -2*f(x,y).diff(x) + 4*f(x,y).diff(y) + 5*f(x,y) - exp(x + 3*y) >>> pdsolve(eq) Eq(f(x, y), (F(4*x + 2*y) + exp(x/2 + 4*y)/15)*exp(x/2 - y)) References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ # TODO : For now homogeneous first order linear PDE's having # two variables are implemented. Once there is support for # solving systems of ODE's, this can be extended to n variables. xi, eta = symbols("xi eta") f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] e = -match[match['e']] expterm = exp(-S(d)/(b**2 + c**2)*xi) functerm = solvefun(eta) solvedict = solve((b*x + c*y - xi, c*x - b*y - eta), x, y) # Integral should remain as it is in terms of xi, # doit() should be done in _handle_Integral. genterm = (1/S(b**2 + c**2))*Integral( (1/expterm*e).subs(solvedict), (xi, b*x + c*y)) return Eq(f(x,y), Subs(expterm*(functerm + genterm), (eta, xi), (c*x - b*y, b*x + c*y))) def pde_1st_linear_variable_coeff(eq, func, order, match, solvefun): r""" Solves a first order linear partial differential equation with variable coefficients. The general form of this partial differential equation is .. math:: a(x, y) \frac{\partial f(x, y)}{\partial x} + b(x, y) \frac{\partial f(x, y)}{\partial y} + c(x, y) f(x, y) = G(x, y) where `a(x, y)`, `b(x, y)`, `c(x, y)` and `G(x, y)` are arbitrary functions in `x` and `y`. This PDE is converted into an ODE by making the following transformation: 1. `\xi` as `x` 2. `\eta` as the constant in the solution to the differential equation `\frac{dy}{dx} = -\frac{b}{a}` Making the previous substitutions reduces it to the linear ODE .. math:: a(\xi, \eta)\frac{du}{d\xi} + c(\xi, \eta)u - G(\xi, \eta) = 0 which can be solved using ``dsolve``. >>> from sympy.abc import x, y >>> from sympy import Function, pprint >>> a, b, c, G, f= [Function(i) for i in ['a', 'b', 'c', 'G', 'f']] >>> u = f(x,y) >>> ux = u.diff(x) >>> uy = u.diff(y) >>> genform = a(x, y)*u + b(x, y)*ux + c(x, y)*uy - G(x,y) >>> pprint(genform) d d -G(x, y) + a(x, y)*f(x, y) + b(x, y)*--(f(x, y)) + c(x, y)*--(f(x, y)) dx dy Examples ======== >>> from sympy.solvers.pde import pdsolve >>> from sympy import Function, pprint >>> from sympy.abc import x,y >>> f = Function('f') >>> eq = x*(u.diff(x)) - y*(u.diff(y)) + y**2*u - y**2 >>> pdsolve(eq) Eq(f(x, y), F(x*y)*exp(y**2/2) + 1) References ========== - Viktor Grigoryan, "Partial Differential Equations" Math 124A - Fall 2010, pp.7 """ from sympy.integrals.integrals import integrate from sympy.solvers.ode import dsolve xi, eta = symbols("xi eta") f = func.func x = func.args[0] y = func.args[1] b = match[match['b']] c = match[match['c']] d = match[match['d']] e = -match[match['e']] if not d: # To deal with cases like b*ux = e or c*uy = e if not (b and c): if c: try: tsol = integrate(e/c, y) except NotImplementedError: raise NotImplementedError("Unable to find a solution" " due to inability of integrate") else: return Eq(f(x,y), solvefun(x) + tsol) if b: try: tsol = integrate(e/b, x) except NotImplementedError: raise NotImplementedError("Unable to find a solution" " due to inability of integrate") else: return Eq(f(x,y), solvefun(y) + tsol) if not c: # To deal with cases when c is 0, a simpler method is used. # The PDE reduces to b*(u.diff(x)) + d*u = e, which is a linear ODE in x plode = f(x).diff(x)*b + d*f(x) - e sol = dsolve(plode, f(x)) syms = sol.free_symbols - plode.free_symbols - {x, y} rhs = _simplify_variable_coeff(sol.rhs, syms, solvefun, y) return Eq(f(x, y), rhs) if not b: # To deal with cases when b is 0, a simpler method is used. # The PDE reduces to c*(u.diff(y)) + d*u = e, which is a linear ODE in y plode = f(y).diff(y)*c + d*f(y) - e sol = dsolve(plode, f(y)) syms = sol.free_symbols - plode.free_symbols - {x, y} rhs = _simplify_variable_coeff(sol.rhs, syms, solvefun, x) return Eq(f(x, y), rhs) dummy = Function('d') h = (c/b).subs(y, dummy(x)) sol = dsolve(dummy(x).diff(x) - h, dummy(x)) if isinstance(sol, list): sol = sol[0] solsym = sol.free_symbols - h.free_symbols - {x, y} if len(solsym) == 1: solsym = solsym.pop() etat = (solve(sol, solsym)[0]).subs(dummy(x), y) ysub = solve(eta - etat, y)[0] deq = (b*(f(x).diff(x)) + d*f(x) - e).subs(y, ysub) final = (dsolve(deq, f(x), hint='1st_linear')).rhs if isinstance(final, list): final = final[0] finsyms = final.free_symbols - deq.free_symbols - {x, y} rhs = _simplify_variable_coeff(final, finsyms, solvefun, etat) return Eq(f(x, y), rhs) else: raise NotImplementedError("Cannot solve the partial differential equation due" " to inability of constantsimp") def _simplify_variable_coeff(sol, syms, func, funcarg): r""" Helper function to replace constants by functions in 1st_linear_variable_coeff """ eta = Symbol("eta") if len(syms) == 1: sym = syms.pop() final = sol.subs(sym, func(funcarg)) else: for key, sym in enumerate(syms): final = sol.subs(sym, func(funcarg)) return simplify(final.subs(eta, funcarg)) def pde_separate(eq, fun, sep, strategy='mul'): """Separate variables in partial differential equation either by additive or multiplicative separation approach. It tries to rewrite an equation so that one of the specified variables occurs on a different side of the equation than the others. :param eq: Partial differential equation :param fun: Original function F(x, y, z) :param sep: List of separated functions [X(x), u(y, z)] :param strategy: Separation strategy. You can choose between additive separation ('add') and multiplicative separation ('mul') which is default. Examples ======== >>> from sympy import E, Eq, Function, pde_separate, Derivative as D >>> from sympy.abc import x, t >>> u, X, T = map(Function, 'uXT') >>> eq = Eq(D(u(x, t), x), E**(u(x, t))*D(u(x, t), t)) >>> pde_separate(eq, u(x, t), [X(x), T(t)], strategy='add') [exp(-X(x))*Derivative(X(x), x), exp(T(t))*Derivative(T(t), t)] >>> eq = Eq(D(u(x, t), x, 2), D(u(x, t), t, 2)) >>> pde_separate(eq, u(x, t), [X(x), T(t)], strategy='mul') [Derivative(X(x), (x, 2))/X(x), Derivative(T(t), (t, 2))/T(t)] See Also ======== pde_separate_add, pde_separate_mul """ do_add = False if strategy == 'add': do_add = True elif strategy == 'mul': do_add = False else: raise ValueError('Unknown strategy: %s' % strategy) if isinstance(eq, Equality): if eq.rhs != 0: return pde_separate(Eq(eq.lhs - eq.rhs, 0), fun, sep, strategy) else: return pde_separate(Eq(eq, 0), fun, sep, strategy) if eq.rhs != 0: raise ValueError("Value should be 0") # Handle arguments orig_args = list(fun.args) subs_args = [] for s in sep: for j in range(0, len(s.args)): subs_args.append(s.args[j]) if do_add: functions = reduce(operator.add, sep) else: functions = reduce(operator.mul, sep) # Check whether variables match if len(subs_args) != len(orig_args): raise ValueError("Variable counts do not match") # Check for duplicate arguments like [X(x), u(x, y)] if has_dups(subs_args): raise ValueError("Duplicate substitution arguments detected") # Check whether the variables match if set(orig_args) != set(subs_args): raise ValueError("Arguments do not match") # Substitute original function with separated... result = eq.lhs.subs(fun, functions).doit() # Divide by terms when doing multiplicative separation if not do_add: eq = 0 for i in result.args: eq += i/functions result = eq svar = subs_args[0] dvar = subs_args[1:] return _separate(result, svar, dvar) def pde_separate_add(eq, fun, sep): """ Helper function for searching additive separable solutions. Consider an equation of two independent variables x, y and a dependent variable w, we look for the product of two functions depending on different arguments: `w(x, y, z) = X(x) + y(y, z)` Examples ======== >>> from sympy import E, Eq, Function, pde_separate_add, Derivative as D >>> from sympy.abc import x, t >>> u, X, T = map(Function, 'uXT') >>> eq = Eq(D(u(x, t), x), E**(u(x, t))*D(u(x, t), t)) >>> pde_separate_add(eq, u(x, t), [X(x), T(t)]) [exp(-X(x))*Derivative(X(x), x), exp(T(t))*Derivative(T(t), t)] """ return pde_separate(eq, fun, sep, strategy='add') def pde_separate_mul(eq, fun, sep): """ Helper function for searching multiplicative separable solutions. Consider an equation of two independent variables x, y and a dependent variable w, we look for the product of two functions depending on different arguments: `w(x, y, z) = X(x)*u(y, z)` Examples ======== >>> from sympy import Function, Eq, pde_separate_mul, Derivative as D >>> from sympy.abc import x, y >>> u, X, Y = map(Function, 'uXY') >>> eq = Eq(D(u(x, y), x, 2), D(u(x, y), y, 2)) >>> pde_separate_mul(eq, u(x, y), [X(x), Y(y)]) [Derivative(X(x), (x, 2))/X(x), Derivative(Y(y), (y, 2))/Y(y)] """ return pde_separate(eq, fun, sep, strategy='mul') def _separate(eq, dep, others): """Separate expression into two parts based on dependencies of variables.""" # FIRST PASS # Extract derivatives depending our separable variable... terms = set() for term in eq.args: if term.is_Mul: for i in term.args: if i.is_Derivative and not i.has(*others): terms.add(term) continue elif term.is_Derivative and not term.has(*others): terms.add(term) # Find the factor that we need to divide by div = set() for term in terms: ext, sep = term.expand().as_independent(dep) # Failed? if sep.has(*others): return None div.add(ext) # FIXME: Find lcm() of all the divisors and divide with it, instead of # current hack :( # https://github.com/sympy/sympy/issues/4597 if len(div) > 0: final = 0 for term in eq.args: eqn = 0 for i in div: eqn += term / i final += simplify(eqn) eq = final # SECOND PASS - separate the derivatives div = set() lhs = rhs = 0 for term in eq.args: # Check, whether we have already term with independent variable... if not term.has(*others): lhs += term continue # ...otherwise, try to separate temp, sep = term.expand().as_independent(dep) # Failed? if sep.has(*others): return None # Extract the divisors div.add(sep) rhs -= term.expand() # Do the division fulldiv = reduce(operator.add, div) lhs = simplify(lhs/fulldiv).expand() rhs = simplify(rhs/fulldiv).expand() # ...and check whether we were successful :) if lhs.has(*others) or rhs.has(dep): return None return [lhs, rhs]

41628ff36fc8874595494c5e1678fcbb8aae32012e79e69320be404666a9dd9e

"""Utility functions for classifying and solving ordinary and partial differential equations. Contains ======== _preprocess ode_order _desolve """ from sympy.core import Pow from sympy.core.function import Derivative, AppliedUndef from sympy.core.relational import Equality from sympy.core.symbol import Wild def _preprocess(expr, func=None, hint='_Integral'): """Prepare expr for solving by making sure that differentiation is done so that only func remains in unevaluated derivatives and (if hint doesn't end with _Integral) that doit is applied to all other derivatives. If hint is None, don't do any differentiation. (Currently this may cause some simple differential equations to fail.) In case func is None, an attempt will be made to autodetect the function to be solved for. >>> from sympy.solvers.deutils import _preprocess >>> from sympy import Derivative, Function >>> from sympy.abc import x, y, z >>> f, g = map(Function, 'fg') If f(x)**p == 0 and p>0 then we can solve for f(x)=0 >>> _preprocess((f(x).diff(x)-4)**5, f(x)) (Derivative(f(x), x) - 4, f(x)) Apply doit to derivatives that contain more than the function of interest: >>> _preprocess(Derivative(f(x) + x, x)) (Derivative(f(x), x) + 1, f(x)) Do others if the differentiation variable(s) intersect with those of the function of interest or contain the function of interest: >>> _preprocess(Derivative(g(x), y, z), f(y)) (0, f(y)) >>> _preprocess(Derivative(f(y), z), f(y)) (0, f(y)) Do others if the hint doesn't end in '_Integral' (the default assumes that it does): >>> _preprocess(Derivative(g(x), y), f(x)) (Derivative(g(x), y), f(x)) >>> _preprocess(Derivative(f(x), y), f(x), hint='') (0, f(x)) Don't do any derivatives if hint is None: >>> eq = Derivative(f(x) + 1, x) + Derivative(f(x), y) >>> _preprocess(eq, f(x), hint=None) (Derivative(f(x) + 1, x) + Derivative(f(x), y), f(x)) If it's not clear what the function of interest is, it must be given: >>> eq = Derivative(f(x) + g(x), x) >>> _preprocess(eq, g(x)) (Derivative(f(x), x) + Derivative(g(x), x), g(x)) >>> try: _preprocess(eq) ... except ValueError: print("A ValueError was raised.") A ValueError was raised. """ if isinstance(expr, Pow): # if f(x)**p=0 then f(x)=0 (p>0) if (expr.exp).is_positive: expr = expr.base derivs = expr.atoms(Derivative) if not func: funcs = set().union(*[d.atoms(AppliedUndef) for d in derivs]) if len(funcs) != 1: raise ValueError('The function cannot be ' 'automatically detected for %s.' % expr) func = funcs.pop() fvars = set(func.args) if hint is None: return expr, func reps = [(d, d.doit()) for d in derivs if not hint.endswith('_Integral') or d.has(func) or set(d.variables) & fvars] eq = expr.subs(reps) return eq, func def ode_order(expr, func): """ Returns the order of a given differential equation with respect to func. This function is implemented recursively. Examples ======== >>> from sympy import Function >>> from sympy.solvers.deutils import ode_order >>> from sympy.abc import x >>> f, g = map(Function, ['f', 'g']) >>> ode_order(f(x).diff(x, 2) + f(x).diff(x)**2 + ... f(x).diff(x), f(x)) 2 >>> ode_order(f(x).diff(x, 2) + g(x).diff(x, 3), f(x)) 2 >>> ode_order(f(x).diff(x, 2) + g(x).diff(x, 3), g(x)) 3 """ a = Wild('a', exclude=[func]) if expr.match(a): return 0 if isinstance(expr, Derivative): if expr.args[0] == func: return len(expr.variables) else: order = 0 for arg in expr.args[0].args: order = max(order, ode_order(arg, func) + len(expr.variables)) return order else: order = 0 for arg in expr.args: order = max(order, ode_order(arg, func)) return order def _desolve(eq, func=None, hint="default", ics=None, simplify=True, *, prep=True, **kwargs): """This is a helper function to dsolve and pdsolve in the ode and pde modules. If the hint provided to the function is "default", then a dict with the following keys are returned 'func' - It provides the function for which the differential equation has to be solved. This is useful when the expression has more than one function in it. 'default' - The default key as returned by classifier functions in ode and pde.py 'hint' - The hint given by the user for which the differential equation is to be solved. If the hint given by the user is 'default', then the value of 'hint' and 'default' is the same. 'order' - The order of the function as returned by ode_order 'match' - It returns the match as given by the classifier functions, for the default hint. If the hint provided to the function is not "default" and is not in ('all', 'all_Integral', 'best'), then a dict with the above mentioned keys is returned along with the keys which are returned when dict in classify_ode or classify_pde is set True If the hint given is in ('all', 'all_Integral', 'best'), then this function returns a nested dict, with the keys, being the set of classified hints returned by classifier functions, and the values being the dict of form as mentioned above. Key 'eq' is a common key to all the above mentioned hints which returns an expression if eq given by user is an Equality. See Also ======== classify_ode(ode.py) classify_pde(pde.py) """ if isinstance(eq, Equality): eq = eq.lhs - eq.rhs # preprocess the equation and find func if not given if prep or func is None: eq, func = _preprocess(eq, func) prep = False # type is an argument passed by the solve functions in ode and pde.py # that identifies whether the function caller is an ordinary # or partial differential equation. Accordingly corresponding # changes are made in the function. type = kwargs.get('type', None) xi = kwargs.get('xi') eta = kwargs.get('eta') x0 = kwargs.get('x0', 0) terms = kwargs.get('n') if type == 'ode': from sympy.solvers.ode import classify_ode, allhints classifier = classify_ode string = 'ODE ' dummy = '' elif type == 'pde': from sympy.solvers.pde import classify_pde, allhints classifier = classify_pde string = 'PDE ' dummy = 'p' # Magic that should only be used internally. Prevents classify_ode from # being called more than it needs to be by passing its results through # recursive calls. if kwargs.get('classify', True): hints = classifier(eq, func, dict=True, ics=ics, xi=xi, eta=eta, n=terms, x0=x0, prep=prep) else: # Here is what all this means: # # hint: The hint method given to _desolve() by the user. # hints: The dictionary of hints that match the DE, along with other # information (including the internal pass-through magic). # default: The default hint to return, the first hint from allhints # that matches the hint; obtained from classify_ode(). # match: Dictionary containing the match dictionary for each hint # (the parts of the DE for solving). When going through the # hints in "all", this holds the match string for the current # hint. # order: The order of the DE, as determined by ode_order(). hints = kwargs.get('hint', {'default': hint, hint: kwargs['match'], 'order': kwargs['order']}) if not hints['default']: # classify_ode will set hints['default'] to None if no hints match. if hint not in allhints and hint != 'default': raise ValueError("Hint not recognized: " + hint) elif hint not in hints['ordered_hints'] and hint != 'default': raise ValueError(string + str(eq) + " does not match hint " + hint) # If dsolve can't solve the purely algebraic equation then dsolve will raise # ValueError elif hints['order'] == 0: raise ValueError( str(eq) + " is not a solvable differential equation in " + str(func)) else: raise NotImplementedError(dummy + "solve" + ": Cannot solve " + str(eq)) if hint == 'default': return _desolve(eq, func, ics=ics, hint=hints['default'], simplify=simplify, prep=prep, x0=x0, classify=False, order=hints['order'], match=hints[hints['default']], xi=xi, eta=eta, n=terms, type=type) elif hint in ('all', 'all_Integral', 'best'): retdict = {} gethints = set(hints) - {'order', 'default', 'ordered_hints'} if hint == 'all_Integral': for i in hints: if i.endswith('_Integral'): gethints.remove(i[:-len('_Integral')]) # special cases for k in ["1st_homogeneous_coeff_best", "1st_power_series", "lie_group", "2nd_power_series_ordinary", "2nd_power_series_regular"]: if k in gethints: gethints.remove(k) for i in gethints: sol = _desolve(eq, func, ics=ics, hint=i, x0=x0, simplify=simplify, prep=prep, classify=False, n=terms, order=hints['order'], match=hints[i], type=type) retdict[i] = sol retdict['all'] = True retdict['eq'] = eq return retdict elif hint not in allhints: # and hint not in ('default', 'ordered_hints'): raise ValueError("Hint not recognized: " + hint) elif hint not in hints: raise ValueError(string + str(eq) + " does not match hint " + hint) else: # Key added to identify the hint needed to solve the equation hints['hint'] = hint hints.update({'func': func, 'eq': eq}) return hints

fa495579c64fa1f211572a6625d7654afad8c46be569e839f71d86bd4b7b5811

"""Solvers of systems of polynomial equations. """ from sympy.core import S from sympy.polys import Poly, groebner, roots from sympy.polys.polytools import parallel_poly_from_expr from sympy.polys.polyerrors import (ComputationFailed, PolificationFailed, CoercionFailed) from sympy.simplify import rcollect from sympy.utilities import default_sort_key, postfixes from sympy.utilities.misc import filldedent class SolveFailed(Exception): """Raised when solver's conditions weren't met. """ def solve_poly_system(seq, *gens, **args): """ Solve a system of polynomial equations. Parameters ========== seq: a list/tuple/set Listing all the equations that are needed to be solved gens: generators generators of the equations in seq for which we want the solutions args: Keyword arguments Special options for solving the equations Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq Examples ======== >>> from sympy import solve_poly_system >>> from sympy.abc import x, y >>> solve_poly_system([x*y - 2*y, 2*y**2 - x**2], x, y) [(0, 0), (2, -sqrt(2)), (2, sqrt(2))] """ try: polys, opt = parallel_poly_from_expr(seq, *gens, **args) except PolificationFailed as exc: raise ComputationFailed('solve_poly_system', len(seq), exc) if len(polys) == len(opt.gens) == 2: f, g = polys if all(i <= 2 for i in f.degree_list() + g.degree_list()): try: return solve_biquadratic(f, g, opt) except SolveFailed: pass return solve_generic(polys, opt) def solve_biquadratic(f, g, opt): """Solve a system of two bivariate quadratic polynomial equations. Parameters ========== f: a single Expr or Poly First equation g: a single Expr or Poly Second Equation opt: an Options object For specifying keyword arguments and generators Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq. Examples ======== >>> from sympy.polys import Options, Poly >>> from sympy.abc import x, y >>> from sympy.solvers.polysys import solve_biquadratic >>> NewOption = Options((x, y), {'domain': 'ZZ'}) >>> a = Poly(y**2 - 4 + x, y, x, domain='ZZ') >>> b = Poly(y*2 + 3*x - 7, y, x, domain='ZZ') >>> solve_biquadratic(a, b, NewOption) [(1/3, 3), (41/27, 11/9)] >>> a = Poly(y + x**2 - 3, y, x, domain='ZZ') >>> b = Poly(-y + x - 4, y, x, domain='ZZ') >>> solve_biquadratic(a, b, NewOption) [(7/2 - sqrt(29)/2, -sqrt(29)/2 - 1/2), (sqrt(29)/2 + 7/2, -1/2 + \ sqrt(29)/2)] """ G = groebner([f, g]) if len(G) == 1 and G[0].is_ground: return None if len(G) != 2: raise SolveFailed x, y = opt.gens p, q = G if not p.gcd(q).is_ground: # not 0-dimensional raise SolveFailed p = Poly(p, x, expand=False) p_roots = [rcollect(expr, y) for expr in roots(p).keys()] q = q.ltrim(-1) q_roots = list(roots(q).keys()) solutions = [] for q_root in q_roots: for p_root in p_roots: solution = (p_root.subs(y, q_root), q_root) solutions.append(solution) return sorted(solutions, key=default_sort_key) def solve_generic(polys, opt): """ Solve a generic system of polynomial equations. Returns all possible solutions over C[x_1, x_2, ..., x_m] of a set F = { f_1, f_2, ..., f_n } of polynomial equations, using Groebner basis approach. For now only zero-dimensional systems are supported, which means F can have at most a finite number of solutions. The algorithm works by the fact that, supposing G is the basis of F with respect to an elimination order (here lexicographic order is used), G and F generate the same ideal, they have the same set of solutions. By the elimination property, if G is a reduced, zero-dimensional Groebner basis, then there exists an univariate polynomial in G (in its last variable). This can be solved by computing its roots. Substituting all computed roots for the last (eliminated) variable in other elements of G, new polynomial system is generated. Applying the above procedure recursively, a finite number of solutions can be found. The ability of finding all solutions by this procedure depends on the root finding algorithms. If no solutions were found, it means only that roots() failed, but the system is solvable. To overcome this difficulty use numerical algorithms instead. Parameters ========== polys: a list/tuple/set Listing all the polynomial equations that are needed to be solved opt: an Options object For specifying keyword arguments and generators Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in seq References ========== .. [Buchberger01] B. Buchberger, Groebner Bases: A Short Introduction for Systems Theorists, In: R. Moreno-Diaz, B. Buchberger, J.L. Freire, Proceedings of EUROCAST'01, February, 2001 .. [Cox97] D. Cox, J. Little, D. O'Shea, Ideals, Varieties and Algorithms, Springer, Second Edition, 1997, pp. 112 Examples ======== >>> from sympy.polys import Poly, Options >>> from sympy.solvers.polysys import solve_generic >>> from sympy.abc import x, y >>> NewOption = Options((x, y), {'domain': 'ZZ'}) >>> a = Poly(x - y + 5, x, y, domain='ZZ') >>> b = Poly(x + y - 3, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(-1, 4)] >>> a = Poly(x - 2*y + 5, x, y, domain='ZZ') >>> b = Poly(2*x - y - 3, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(11/3, 13/3)] >>> a = Poly(x**2 + y, x, y, domain='ZZ') >>> b = Poly(x + y*4, x, y, domain='ZZ') >>> solve_generic([a, b], NewOption) [(0, 0), (1/4, -1/16)] """ def _is_univariate(f): """Returns True if 'f' is univariate in its last variable. """ for monom in f.monoms(): if any(monom[:-1]): return False return True def _subs_root(f, gen, zero): """Replace generator with a root so that the result is nice. """ p = f.as_expr({gen: zero}) if f.degree(gen) >= 2: p = p.expand(deep=False) return p def _solve_reduced_system(system, gens, entry=False): """Recursively solves reduced polynomial systems. """ if len(system) == len(gens) == 1: zeros = list(roots(system[0], gens[-1]).keys()) return [(zero,) for zero in zeros] basis = groebner(system, gens, polys=True) if len(basis) == 1 and basis[0].is_ground: if not entry: return [] else: return None univariate = list(filter(_is_univariate, basis)) if len(univariate) == 1: f = univariate.pop() else: raise NotImplementedError(filldedent(''' only zero-dimensional systems supported (finite number of solutions) ''')) gens = f.gens gen = gens[-1] zeros = list(roots(f.ltrim(gen)).keys()) if not zeros: return [] if len(basis) == 1: return [(zero,) for zero in zeros] solutions = [] for zero in zeros: new_system = [] new_gens = gens[:-1] for b in basis[:-1]: eq = _subs_root(b, gen, zero) if eq is not S.Zero: new_system.append(eq) for solution in _solve_reduced_system(new_system, new_gens): solutions.append(solution + (zero,)) if solutions and len(solutions[0]) != len(gens): raise NotImplementedError(filldedent(''' only zero-dimensional systems supported (finite number of solutions) ''')) return solutions try: result = _solve_reduced_system(polys, opt.gens, entry=True) except CoercionFailed: raise NotImplementedError if result is not None: return sorted(result, key=default_sort_key) else: return None def solve_triangulated(polys, *gens, **args): """ Solve a polynomial system using Gianni-Kalkbrenner algorithm. The algorithm proceeds by computing one Groebner basis in the ground domain and then by iteratively computing polynomial factorizations in appropriately constructed algebraic extensions of the ground domain. Parameters ========== polys: a list/tuple/set Listing all the equations that are needed to be solved gens: generators generators of the equations in polys for which we want the solutions args: Keyword arguments Special options for solving the equations Returns ======= List[Tuple] A List of tuples. Solutions for symbols that satisfy the equations listed in polys Examples ======== >>> from sympy.solvers.polysys import solve_triangulated >>> from sympy.abc import x, y, z >>> F = [x**2 + y + z - 1, x + y**2 + z - 1, x + y + z**2 - 1] >>> solve_triangulated(F, x, y, z) [(0, 0, 1), (0, 1, 0), (1, 0, 0)] References ========== 1. Patrizia Gianni, Teo Mora, Algebraic Solution of System of Polynomial Equations using Groebner Bases, AAECC-5 on Applied Algebra, Algebraic Algorithms and Error-Correcting Codes, LNCS 356 247--257, 1989 """ G = groebner(polys, gens, polys=True) G = list(reversed(G)) domain = args.get('domain') if domain is not None: for i, g in enumerate(G): G[i] = g.set_domain(domain) f, G = G[0].ltrim(-1), G[1:] dom = f.get_domain() zeros = f.ground_roots() solutions = set() for zero in zeros: solutions.add(((zero,), dom)) var_seq = reversed(gens[:-1]) vars_seq = postfixes(gens[1:]) for var, vars in zip(var_seq, vars_seq): _solutions = set() for values, dom in solutions: H, mapping = [], list(zip(vars, values)) for g in G: _vars = (var,) + vars if g.has_only_gens(*_vars) and g.degree(var) != 0: h = g.ltrim(var).eval(dict(mapping)) if g.degree(var) == h.degree(): H.append(h) p = min(H, key=lambda h: h.degree()) zeros = p.ground_roots() for zero in zeros: if not zero.is_Rational: dom_zero = dom.algebraic_field(zero) else: dom_zero = dom _solutions.add(((zero,) + values, dom_zero)) solutions = _solutions solutions = list(solutions) for i, (solution, _) in enumerate(solutions): solutions[i] = solution return sorted(solutions, key=default_sort_key)

2e1fd921dca5bc48d487b2c42feb036a6b6763ddafd9cc48952cb3e3e966f952

"""Tools for solving inequalities and systems of inequalities. """ from sympy.core import Symbol, Dummy, sympify from sympy.core.compatibility import iterable from sympy.core.exprtools import factor_terms from sympy.core.relational import Relational, Eq, Ge, Lt from sympy.sets import Interval from sympy.sets.sets import FiniteSet, Union, EmptySet, Intersection from sympy.core.singleton import S from sympy.core.function import expand_mul from sympy.functions import Abs from sympy.logic import And from sympy.polys import Poly, PolynomialError, parallel_poly_from_expr from sympy.polys.polyutils import _nsort from sympy.utilities.iterables import sift from sympy.utilities.misc import filldedent def solve_poly_inequality(poly, rel): """Solve a polynomial inequality with rational coefficients. Examples ======== >>> from sympy import Poly >>> from sympy.abc import x >>> from sympy.solvers.inequalities import solve_poly_inequality >>> solve_poly_inequality(Poly(x, x, domain='ZZ'), '==') [FiniteSet(0)] >>> solve_poly_inequality(Poly(x**2 - 1, x, domain='ZZ'), '!=') [Interval.open(-oo, -1), Interval.open(-1, 1), Interval.open(1, oo)] >>> solve_poly_inequality(Poly(x**2 - 1, x, domain='ZZ'), '==') [FiniteSet(-1), FiniteSet(1)] See Also ======== solve_poly_inequalities """ if not isinstance(poly, Poly): raise ValueError( 'For efficiency reasons, `poly` should be a Poly instance') if poly.as_expr().is_number: t = Relational(poly.as_expr(), 0, rel) if t is S.true: return [S.Reals] elif t is S.false: return [S.EmptySet] else: raise NotImplementedError( "could not determine truth value of %s" % t) reals, intervals = poly.real_roots(multiple=False), [] if rel == '==': for root, _ in reals: interval = Interval(root, root) intervals.append(interval) elif rel == '!=': left = S.NegativeInfinity for right, _ in reals + [(S.Infinity, 1)]: interval = Interval(left, right, True, True) intervals.append(interval) left = right else: if poly.LC() > 0: sign = +1 else: sign = -1 eq_sign, equal = None, False if rel == '>': eq_sign = +1 elif rel == '<': eq_sign = -1 elif rel == '>=': eq_sign, equal = +1, True elif rel == '<=': eq_sign, equal = -1, True else: raise ValueError("'%s' is not a valid relation" % rel) right, right_open = S.Infinity, True for left, multiplicity in reversed(reals): if multiplicity % 2: if sign == eq_sign: intervals.insert( 0, Interval(left, right, not equal, right_open)) sign, right, right_open = -sign, left, not equal else: if sign == eq_sign and not equal: intervals.insert( 0, Interval(left, right, True, right_open)) right, right_open = left, True elif sign != eq_sign and equal: intervals.insert(0, Interval(left, left)) if sign == eq_sign: intervals.insert( 0, Interval(S.NegativeInfinity, right, True, right_open)) return intervals def solve_poly_inequalities(polys): """Solve polynomial inequalities with rational coefficients. Examples ======== >>> from sympy.solvers.inequalities import solve_poly_inequalities >>> from sympy.polys import Poly >>> from sympy.abc import x >>> solve_poly_inequalities((( ... Poly(x**2 - 3), ">"), ( ... Poly(-x**2 + 1), ">"))) Union(Interval.open(-oo, -sqrt(3)), Interval.open(-1, 1), Interval.open(sqrt(3), oo)) """ from sympy import Union return Union(*[s for p in polys for s in solve_poly_inequality(*p)]) def solve_rational_inequalities(eqs): """Solve a system of rational inequalities with rational coefficients. Examples ======== >>> from sympy.abc import x >>> from sympy import Poly >>> from sympy.solvers.inequalities import solve_rational_inequalities >>> solve_rational_inequalities([[ ... ((Poly(-x + 1), Poly(1, x)), '>='), ... ((Poly(-x + 1), Poly(1, x)), '<=')]]) FiniteSet(1) >>> solve_rational_inequalities([[ ... ((Poly(x), Poly(1, x)), '!='), ... ((Poly(-x + 1), Poly(1, x)), '>=')]]) Union(Interval.open(-oo, 0), Interval.Lopen(0, 1)) See Also ======== solve_poly_inequality """ result = S.EmptySet for _eqs in eqs: if not _eqs: continue global_intervals = [Interval(S.NegativeInfinity, S.Infinity)] for (numer, denom), rel in _eqs: numer_intervals = solve_poly_inequality(numer*denom, rel) denom_intervals = solve_poly_inequality(denom, '==') intervals = [] for numer_interval in numer_intervals: for global_interval in global_intervals: interval = numer_interval.intersect(global_interval) if interval is not S.EmptySet: intervals.append(interval) global_intervals = intervals intervals = [] for global_interval in global_intervals: for denom_interval in denom_intervals: global_interval -= denom_interval if global_interval is not S.EmptySet: intervals.append(global_interval) global_intervals = intervals if not global_intervals: break for interval in global_intervals: result = result.union(interval) return result def reduce_rational_inequalities(exprs, gen, relational=True): """Reduce a system of rational inequalities with rational coefficients. Examples ======== >>> from sympy import Symbol >>> from sympy.solvers.inequalities import reduce_rational_inequalities >>> x = Symbol('x', real=True) >>> reduce_rational_inequalities([[x**2 <= 0]], x) Eq(x, 0) >>> reduce_rational_inequalities([[x + 2 > 0]], x) -2 < x >>> reduce_rational_inequalities([[(x + 2, ">")]], x) -2 < x >>> reduce_rational_inequalities([[x + 2]], x) Eq(x, -2) This function find the non-infinite solution set so if the unknown symbol is declared as extended real rather than real then the result may include finiteness conditions: >>> y = Symbol('y', extended_real=True) >>> reduce_rational_inequalities([[y + 2 > 0]], y) (-2 < y) & (y < oo) """ exact = True eqs = [] solution = S.Reals if exprs else S.EmptySet for _exprs in exprs: _eqs = [] for expr in _exprs: if isinstance(expr, tuple): expr, rel = expr else: if expr.is_Relational: expr, rel = expr.lhs - expr.rhs, expr.rel_op else: expr, rel = expr, '==' if expr is S.true: numer, denom, rel = S.Zero, S.One, '==' elif expr is S.false: numer, denom, rel = S.One, S.One, '==' else: numer, denom = expr.together().as_numer_denom() try: (numer, denom), opt = parallel_poly_from_expr( (numer, denom), gen) except PolynomialError: raise PolynomialError(filldedent(''' only polynomials and rational functions are supported in this context. ''')) if not opt.domain.is_Exact: numer, denom, exact = numer.to_exact(), denom.to_exact(), False domain = opt.domain.get_exact() if not (domain.is_ZZ or domain.is_QQ): expr = numer/denom expr = Relational(expr, 0, rel) solution &= solve_univariate_inequality(expr, gen, relational=False) else: _eqs.append(((numer, denom), rel)) if _eqs: eqs.append(_eqs) if eqs: solution &= solve_rational_inequalities(eqs) exclude = solve_rational_inequalities([[((d, d.one), '==') for i in eqs for ((n, d), _) in i if d.has(gen)]]) solution -= exclude if not exact and solution: solution = solution.evalf() if relational: solution = solution.as_relational(gen) return solution def reduce_abs_inequality(expr, rel, gen): """Reduce an inequality with nested absolute values. Examples ======== >>> from sympy import Abs, Symbol >>> from sympy.solvers.inequalities import reduce_abs_inequality >>> x = Symbol('x', real=True) >>> reduce_abs_inequality(Abs(x - 5) - 3, '<', x) (2 < x) & (x < 8) >>> reduce_abs_inequality(Abs(x + 2)*3 - 13, '<', x) (-19/3 < x) & (x < 7/3) See Also ======== reduce_abs_inequalities """ if gen.is_extended_real is False: raise TypeError(filldedent(''' can't solve inequalities with absolute values containing non-real variables. ''')) def _bottom_up_scan(expr): exprs = [] if expr.is_Add or expr.is_Mul: op = expr.func for arg in expr.args: _exprs = _bottom_up_scan(arg) if not exprs: exprs = _exprs else: args = [] for expr, conds in exprs: for _expr, _conds in _exprs: args.append((op(expr, _expr), conds + _conds)) exprs = args elif expr.is_Pow: n = expr.exp if not n.is_Integer: raise ValueError("Only Integer Powers are allowed on Abs.") _exprs = _bottom_up_scan(expr.base) for expr, conds in _exprs: exprs.append((expr**n, conds)) elif isinstance(expr, Abs): _exprs = _bottom_up_scan(expr.args[0]) for expr, conds in _exprs: exprs.append(( expr, conds + [Ge(expr, 0)])) exprs.append((-expr, conds + [Lt(expr, 0)])) else: exprs = [(expr, [])] return exprs exprs = _bottom_up_scan(expr) mapping = {'<': '>', '<=': '>='} inequalities = [] for expr, conds in exprs: if rel not in mapping.keys(): expr = Relational( expr, 0, rel) else: expr = Relational(-expr, 0, mapping[rel]) inequalities.append([expr] + conds) return reduce_rational_inequalities(inequalities, gen) def reduce_abs_inequalities(exprs, gen): """Reduce a system of inequalities with nested absolute values. Examples ======== >>> from sympy import Abs, Symbol >>> from sympy.solvers.inequalities import reduce_abs_inequalities >>> x = Symbol('x', extended_real=True) >>> reduce_abs_inequalities([(Abs(3*x - 5) - 7, '<'), ... (Abs(x + 25) - 13, '>')], x) (-2/3 < x) & (x < 4) & (((-oo < x) & (x < -38)) | ((-12 < x) & (x < oo))) >>> reduce_abs_inequalities([(Abs(x - 4) + Abs(3*x - 5) - 7, '<')], x) (1/2 < x) & (x < 4) See Also ======== reduce_abs_inequality """ return And(*[ reduce_abs_inequality(expr, rel, gen) for expr, rel in exprs ]) def solve_univariate_inequality(expr, gen, relational=True, domain=S.Reals, continuous=False): """Solves a real univariate inequality. Parameters ========== expr : Relational The target inequality gen : Symbol The variable for which the inequality is solved relational : bool A Relational type output is expected or not domain : Set The domain over which the equation is solved continuous: bool True if expr is known to be continuous over the given domain (and so continuous_domain() doesn't need to be called on it) Raises ====== NotImplementedError The solution of the inequality cannot be determined due to limitation in :func:`sympy.solvers.solveset.solvify`. Notes ===== Currently, we cannot solve all the inequalities due to limitations in :func:`sympy.solvers.solveset.solvify`. Also, the solution returned for trigonometric inequalities are restricted in its periodic interval. See Also ======== sympy.solvers.solveset.solvify: solver returning solveset solutions with solve's output API Examples ======== >>> from sympy.solvers.inequalities import solve_univariate_inequality >>> from sympy import Symbol, sin, Interval, S >>> x = Symbol('x') >>> solve_univariate_inequality(x**2 >= 4, x) ((2 <= x) & (x < oo)) | ((x <= -2) & (-oo < x)) >>> solve_univariate_inequality(x**2 >= 4, x, relational=False) Union(Interval(-oo, -2), Interval(2, oo)) >>> domain = Interval(0, S.Infinity) >>> solve_univariate_inequality(x**2 >= 4, x, False, domain) Interval(2, oo) >>> solve_univariate_inequality(sin(x) > 0, x, relational=False) Interval.open(0, pi) """ from sympy import im from sympy.calculus.util import (continuous_domain, periodicity, function_range) from sympy.solvers.solvers import denoms from sympy.solvers.solveset import solvify, solveset # This keeps the function independent of the assumptions about `gen`. # `solveset` makes sure this function is called only when the domain is # real. _gen = gen _domain = domain if gen.is_extended_real is False: rv = S.EmptySet return rv if not relational else rv.as_relational(_gen) elif gen.is_extended_real is None: gen = Dummy('gen', extended_real=True) try: expr = expr.xreplace({_gen: gen}) except TypeError: raise TypeError(filldedent(''' When gen is real, the relational has a complex part which leads to an invalid comparison like I < 0. ''')) rv = None if expr is S.true: rv = domain elif expr is S.false: rv = S.EmptySet else: e = expr.lhs - expr.rhs period = periodicity(e, gen) if period == S.Zero: e = expand_mul(e) const = expr.func(e, 0) if const is S.true: rv = domain elif const is S.false: rv = S.EmptySet elif period is not None: frange = function_range(e, gen, domain) rel = expr.rel_op if rel == '<' or rel == '<=': if expr.func(frange.sup, 0): rv = domain elif not expr.func(frange.inf, 0): rv = S.EmptySet elif rel == '>' or rel == '>=': if expr.func(frange.inf, 0): rv = domain elif not expr.func(frange.sup, 0): rv = S.EmptySet inf, sup = domain.inf, domain.sup if sup - inf is S.Infinity: domain = Interval(0, period, False, True).intersect(_domain) _domain = domain if rv is None: n, d = e.as_numer_denom() try: if gen not in n.free_symbols and len(e.free_symbols) > 1: raise ValueError # this might raise ValueError on its own # or it might give None... solns = solvify(e, gen, domain) if solns is None: # in which case we raise ValueError raise ValueError except (ValueError, NotImplementedError): # replace gen with generic x since it's # univariate anyway raise NotImplementedError(filldedent(''' The inequality, %s, cannot be solved using solve_univariate_inequality. ''' % expr.subs(gen, Symbol('x')))) expanded_e = expand_mul(e) def valid(x): # this is used to see if gen=x satisfies the # relational by substituting it into the # expanded form and testing against 0, e.g. # if expr = x*(x + 1) < 2 then e = x*(x + 1) - 2 # and expanded_e = x**2 + x - 2; the test is # whether a given value of x satisfies # x**2 + x - 2 < 0 # # expanded_e, expr and gen used from enclosing scope v = expanded_e.subs(gen, expand_mul(x)) try: r = expr.func(v, 0) except TypeError: r = S.false if r in (S.true, S.false): return r if v.is_extended_real is False: return S.false else: v = v.n(2) if v.is_comparable: return expr.func(v, 0) # not comparable or couldn't be evaluated raise NotImplementedError( 'relationship did not evaluate: %s' % r) singularities = [] for d in denoms(expr, gen): singularities.extend(solvify(d, gen, domain)) if not continuous: domain = continuous_domain(expanded_e, gen, domain) include_x = '=' in expr.rel_op and expr.rel_op != '!=' try: discontinuities = set(domain.boundary - FiniteSet(domain.inf, domain.sup)) # remove points that are not between inf and sup of domain critical_points = FiniteSet(*(solns + singularities + list( discontinuities))).intersection( Interval(domain.inf, domain.sup, domain.inf not in domain, domain.sup not in domain)) if all(r.is_number for r in critical_points): reals = _nsort(critical_points, separated=True)[0] else: sifted = sift(critical_points, lambda x: x.is_extended_real) if sifted[None]: # there were some roots that weren't known # to be real raise NotImplementedError try: reals = sifted[True] if len(reals) > 1: reals = list(sorted(reals)) except TypeError: raise NotImplementedError except NotImplementedError: raise NotImplementedError('sorting of these roots is not supported') # If expr contains imaginary coefficients, only take real # values of x for which the imaginary part is 0 make_real = S.Reals if im(expanded_e) != S.Zero: check = True im_sol = FiniteSet() try: a = solveset(im(expanded_e), gen, domain) if not isinstance(a, Interval): for z in a: if z not in singularities and valid(z) and z.is_extended_real: im_sol += FiniteSet(z) else: start, end = a.inf, a.sup for z in _nsort(critical_points + FiniteSet(end)): valid_start = valid(start) if start != end: valid_z = valid(z) pt = _pt(start, z) if pt not in singularities and pt.is_extended_real and valid(pt): if valid_start and valid_z: im_sol += Interval(start, z) elif valid_start: im_sol += Interval.Ropen(start, z) elif valid_z: im_sol += Interval.Lopen(start, z) else: im_sol += Interval.open(start, z) start = z for s in singularities: im_sol -= FiniteSet(s) except (TypeError): im_sol = S.Reals check = False if isinstance(im_sol, EmptySet): raise ValueError(filldedent(''' %s contains imaginary parts which cannot be made 0 for any value of %s satisfying the inequality, leading to relations like I < 0. ''' % (expr.subs(gen, _gen), _gen))) make_real = make_real.intersect(im_sol) sol_sets = [S.EmptySet] start = domain.inf if start in domain and valid(start) and start.is_finite: sol_sets.append(FiniteSet(start)) for x in reals: end = x if valid(_pt(start, end)): sol_sets.append(Interval(start, end, True, True)) if x in singularities: singularities.remove(x) else: if x in discontinuities: discontinuities.remove(x) _valid = valid(x) else: # it's a solution _valid = include_x if _valid: sol_sets.append(FiniteSet(x)) start = end end = domain.sup if end in domain and valid(end) and end.is_finite: sol_sets.append(FiniteSet(end)) if valid(_pt(start, end)): sol_sets.append(Interval.open(start, end)) if im(expanded_e) != S.Zero and check: rv = (make_real).intersect(_domain) else: rv = Intersection( (Union(*sol_sets)), make_real, _domain).subs(gen, _gen) return rv if not relational else rv.as_relational(_gen) def _pt(start, end): """Return a point between start and end""" if not start.is_infinite and not end.is_infinite: pt = (start + end)/2 elif start.is_infinite and end.is_infinite: pt = S.Zero else: if (start.is_infinite and start.is_extended_positive is None or end.is_infinite and end.is_extended_positive is None): raise ValueError('cannot proceed with unsigned infinite values') if (end.is_infinite and end.is_extended_negative or start.is_infinite and start.is_extended_positive): start, end = end, start # if possible, use a multiple of self which has # better behavior when checking assumptions than # an expression obtained by adding or subtracting 1 if end.is_infinite: if start.is_extended_positive: pt = start*2 elif start.is_extended_negative: pt = start*S.Half else: pt = start + 1 elif start.is_infinite: if end.is_extended_positive: pt = end*S.Half elif end.is_extended_negative: pt = end*2 else: pt = end - 1 return pt def _solve_inequality(ie, s, linear=False): """Return the inequality with s isolated on the left, if possible. If the relationship is non-linear, a solution involving And or Or may be returned. False or True are returned if the relationship is never True or always True, respectively. If `linear` is True (default is False) an `s`-dependent expression will be isolated on the left, if possible but it will not be solved for `s` unless the expression is linear in `s`. Furthermore, only "safe" operations which don't change the sense of the relationship are applied: no division by an unsigned value is attempted unless the relationship involves Eq or Ne and no division by a value not known to be nonzero is ever attempted. Examples ======== >>> from sympy import Eq, Symbol >>> from sympy.solvers.inequalities import _solve_inequality as f >>> from sympy.abc import x, y For linear expressions, the symbol can be isolated: >>> f(x - 2 < 0, x) x < 2 >>> f(-x - 6 < x, x) x > -3 Sometimes nonlinear relationships will be False >>> f(x**2 + 4 < 0, x) False Or they may involve more than one region of values: >>> f(x**2 - 4 < 0, x) (-2 < x) & (x < 2) To restrict the solution to a relational, set linear=True and only the x-dependent portion will be isolated on the left: >>> f(x**2 - 4 < 0, x, linear=True) x**2 < 4 Division of only nonzero quantities is allowed, so x cannot be isolated by dividing by y: >>> y.is_nonzero is None # it is unknown whether it is 0 or not True >>> f(x*y < 1, x) x*y < 1 And while an equality (or inequality) still holds after dividing by a non-zero quantity >>> nz = Symbol('nz', nonzero=True) >>> f(Eq(x*nz, 1), x) Eq(x, 1/nz) the sign must be known for other inequalities involving > or <: >>> f(x*nz <= 1, x) nz*x <= 1 >>> p = Symbol('p', positive=True) >>> f(x*p <= 1, x) x <= 1/p When there are denominators in the original expression that are removed by expansion, conditions for them will be returned as part of the result: >>> f(x < x*(2/x - 1), x) (x < 1) & Ne(x, 0) """ from sympy.solvers.solvers import denoms if s not in ie.free_symbols: return ie if ie.rhs == s: ie = ie.reversed if ie.lhs == s and s not in ie.rhs.free_symbols: return ie def classify(ie, s, i): # return True or False if ie evaluates when substituting s with # i else None (if unevaluated) or NaN (when there is an error # in evaluating) try: v = ie.subs(s, i) if v is S.NaN: return v elif v not in (True, False): return return v except TypeError: return S.NaN rv = None oo = S.Infinity expr = ie.lhs - ie.rhs try: p = Poly(expr, s) if p.degree() == 0: rv = ie.func(p.as_expr(), 0) elif not linear and p.degree() > 1: # handle in except clause raise NotImplementedError except (PolynomialError, NotImplementedError): if not linear: try: rv = reduce_rational_inequalities([[ie]], s) except PolynomialError: rv = solve_univariate_inequality(ie, s) # remove restrictions wrt +/-oo that may have been # applied when using sets to simplify the relationship okoo = classify(ie, s, oo) if okoo is S.true and classify(rv, s, oo) is S.false: rv = rv.subs(s < oo, True) oknoo = classify(ie, s, -oo) if (oknoo is S.true and classify(rv, s, -oo) is S.false): rv = rv.subs(-oo < s, True) rv = rv.subs(s > -oo, True) if rv is S.true: rv = (s <= oo) if okoo is S.true else (s < oo) if oknoo is not S.true: rv = And(-oo < s, rv) else: p = Poly(expr) conds = [] if rv is None: e = p.as_expr() # this is in expanded form # Do a safe inversion of e, moving non-s terms # to the rhs and dividing by a nonzero factor if # the relational is Eq/Ne; for other relationals # the sign must also be positive or negative rhs = 0 b, ax = e.as_independent(s, as_Add=True) e -= b rhs -= b ef = factor_terms(e) a, e = ef.as_independent(s, as_Add=False) if (a.is_zero != False or # don't divide by potential 0 a.is_negative == a.is_positive is None and # if sign is not known then ie.rel_op not in ('!=', '==')): # reject if not Eq/Ne e = ef a = S.One rhs /= a if a.is_positive: rv = ie.func(e, rhs) else: rv = ie.reversed.func(e, rhs) # return conditions under which the value is # valid, too. beginning_denoms = denoms(ie.lhs) | denoms(ie.rhs) current_denoms = denoms(rv) for d in beginning_denoms - current_denoms: c = _solve_inequality(Eq(d, 0), s, linear=linear) if isinstance(c, Eq) and c.lhs == s: if classify(rv, s, c.rhs) is S.true: # rv is permitting this value but it shouldn't conds.append(~c) for i in (-oo, oo): if (classify(rv, s, i) is S.true and classify(ie, s, i) is not S.true): conds.append(s < i if i is oo else i < s) conds.append(rv) return And(*conds) def _reduce_inequalities(inequalities, symbols): # helper for reduce_inequalities poly_part, abs_part = {}, {} other = [] for inequality in inequalities: expr, rel = inequality.lhs, inequality.rel_op # rhs is 0 # check for gens using atoms which is more strict than free_symbols to # guard against EX domain which won't be handled by # reduce_rational_inequalities gens = expr.atoms(Symbol) if len(gens) == 1: gen = gens.pop() else: common = expr.free_symbols & symbols if len(common) == 1: gen = common.pop() other.append(_solve_inequality(Relational(expr, 0, rel), gen)) continue else: raise NotImplementedError(filldedent(''' inequality has more than one symbol of interest. ''')) if expr.is_polynomial(gen): poly_part.setdefault(gen, []).append((expr, rel)) else: components = expr.find(lambda u: u.has(gen) and ( u.is_Function or u.is_Pow and not u.exp.is_Integer)) if components and all(isinstance(i, Abs) for i in components): abs_part.setdefault(gen, []).append((expr, rel)) else: other.append(_solve_inequality(Relational(expr, 0, rel), gen)) poly_reduced = [] abs_reduced = [] for gen, exprs in poly_part.items(): poly_reduced.append(reduce_rational_inequalities([exprs], gen)) for gen, exprs in abs_part.items(): abs_reduced.append(reduce_abs_inequalities(exprs, gen)) return And(*(poly_reduced + abs_reduced + other)) def reduce_inequalities(inequalities, symbols=[]): """Reduce a system of inequalities with rational coefficients. Examples ======== >>> from sympy.abc import x, y >>> from sympy.solvers.inequalities import reduce_inequalities >>> reduce_inequalities(0 <= x + 3, []) (-3 <= x) & (x < oo) >>> reduce_inequalities(0 <= x + y*2 - 1, [x]) (x < oo) & (x >= 1 - 2*y) """ if not iterable(inequalities): inequalities = [inequalities] inequalities = [sympify(i) for i in inequalities] gens = set().union(*[i.free_symbols for i in inequalities]) if not iterable(symbols): symbols = [symbols] symbols = (set(symbols) or gens) & gens if any(i.is_extended_real is False for i in symbols): raise TypeError(filldedent(''' inequalities cannot contain symbols that are not real. ''')) # make vanilla symbol real recast = {i: Dummy(i.name, extended_real=True) for i in gens if i.is_extended_real is None} inequalities = [i.xreplace(recast) for i in inequalities] symbols = {i.xreplace(recast) for i in symbols} # prefilter keep = [] for i in inequalities: if isinstance(i, Relational): i = i.func(i.lhs.as_expr() - i.rhs.as_expr(), 0) elif i not in (True, False): i = Eq(i, 0) if i == True: continue elif i == False: return S.false if i.lhs.is_number: raise NotImplementedError( "could not determine truth value of %s" % i) keep.append(i) inequalities = keep del keep # solve system rv = _reduce_inequalities(inequalities, symbols) # restore original symbols and return return rv.xreplace({v: k for k, v in recast.items()})

27d45b731ee4f7e2f96b62eaaf80d520e37cfd204dc9a7fec1446d6a2e0455ef

""" This module contain solvers for all kinds of equations: - algebraic or transcendental, use solve() - recurrence, use rsolve() - differential, use dsolve() - nonlinear (numerically), use nsolve() (you will need a good starting point) """ from sympy import divisors, binomial, expand_func from sympy.core.assumptions import check_assumptions from sympy.core.compatibility import (iterable, is_sequence, ordered, default_sort_key) from sympy.core.sympify import sympify from sympy.core import (S, Add, Symbol, Equality, Dummy, Expr, Mul, Pow, Unequality, Wild) from sympy.core.exprtools import factor_terms from sympy.core.function import (expand_mul, expand_log, Derivative, AppliedUndef, UndefinedFunction, nfloat, Function, expand_power_exp, _mexpand, expand) from sympy.integrals.integrals import Integral from sympy.core.numbers import ilcm, Float, Rational from sympy.core.relational import Relational from sympy.core.logic import fuzzy_not from sympy.core.power import integer_log from sympy.logic.boolalg import And, Or, BooleanAtom from sympy.core.basic import preorder_traversal from sympy.functions import (log, exp, LambertW, cos, sin, tan, acos, asin, atan, Abs, re, im, arg, sqrt, atan2) from sympy.functions.elementary.trigonometric import (TrigonometricFunction, HyperbolicFunction) from sympy.simplify import (simplify, collect, powsimp, posify, # type: ignore powdenest, nsimplify, denom, logcombine, sqrtdenest, fraction, separatevars) from sympy.simplify.sqrtdenest import sqrt_depth from sympy.simplify.fu import TR1, TR2i from sympy.matrices.common import NonInvertibleMatrixError from sympy.matrices import Matrix, zeros from sympy.polys import roots, cancel, factor, Poly, degree from sympy.polys.polyerrors import GeneratorsNeeded, PolynomialError from sympy.polys.solvers import sympy_eqs_to_ring, solve_lin_sys from sympy.functions.elementary.piecewise import piecewise_fold, Piecewise from sympy.utilities.lambdify import lambdify from sympy.utilities.misc import filldedent from sympy.utilities.iterables import (cartes, connected_components, flatten, generate_bell, uniq, sift) from sympy.utilities.decorator import conserve_mpmath_dps from mpmath import findroot from sympy.solvers.polysys import solve_poly_system from sympy.solvers.inequalities import reduce_inequalities from types import GeneratorType from collections import defaultdict import warnings def recast_to_symbols(eqs, symbols): """ Return (e, s, d) where e and s are versions of *eqs* and *symbols* in which any non-Symbol objects in *symbols* have been replaced with generic Dummy symbols and d is a dictionary that can be used to restore the original expressions. Examples ======== >>> from sympy.solvers.solvers import recast_to_symbols >>> from sympy import symbols, Function >>> x, y = symbols('x y') >>> fx = Function('f')(x) >>> eqs, syms = [fx + 1, x, y], [fx, y] >>> e, s, d = recast_to_symbols(eqs, syms); (e, s, d) ([_X0 + 1, x, y], [_X0, y], {_X0: f(x)}) The original equations and symbols can be restored using d: >>> assert [i.xreplace(d) for i in eqs] == eqs >>> assert [d.get(i, i) for i in s] == syms """ if not iterable(eqs) and iterable(symbols): raise ValueError('Both eqs and symbols must be iterable') new_symbols = list(symbols) swap_sym = {} for i, s in enumerate(symbols): if not isinstance(s, Symbol) and s not in swap_sym: swap_sym[s] = Dummy('X%d' % i) new_symbols[i] = swap_sym[s] new_f = [] for i in eqs: isubs = getattr(i, 'subs', None) if isubs is not None: new_f.append(isubs(swap_sym)) else: new_f.append(i) swap_sym = {v: k for k, v in swap_sym.items()} return new_f, new_symbols, swap_sym def _ispow(e): """Return True if e is a Pow or is exp.""" return isinstance(e, Expr) and (e.is_Pow or isinstance(e, exp)) def _simple_dens(f, symbols): # when checking if a denominator is zero, we can just check the # base of powers with nonzero exponents since if the base is zero # the power will be zero, too. To keep it simple and fast, we # limit simplification to exponents that are Numbers dens = set() for d in denoms(f, symbols): if d.is_Pow and d.exp.is_Number: if d.exp.is_zero: continue # foo**0 is never 0 d = d.base dens.add(d) return dens def denoms(eq, *symbols): """ Return (recursively) set of all denominators that appear in *eq* that contain any symbol in *symbols*; if *symbols* are not provided then all denominators will be returned. Examples ======== >>> from sympy.solvers.solvers import denoms >>> from sympy.abc import x, y, z >>> denoms(x/y) {y} >>> denoms(x/(y*z)) {y, z} >>> denoms(3/x + y/z) {x, z} >>> denoms(x/2 + y/z) {2, z} If *symbols* are provided then only denominators containing those symbols will be returned: >>> denoms(1/x + 1/y + 1/z, y, z) {y, z} """ pot = preorder_traversal(eq) dens = set() for p in pot: # Here p might be Tuple or Relational # Expr subtrees (e.g. lhs and rhs) will be traversed after by pot if not isinstance(p, Expr): continue den = denom(p) if den is S.One: continue for d in Mul.make_args(den): dens.add(d) if not symbols: return dens elif len(symbols) == 1: if iterable(symbols[0]): symbols = symbols[0] rv = [] for d in dens: free = d.free_symbols if any(s in free for s in symbols): rv.append(d) return set(rv) def checksol(f, symbol, sol=None, **flags): """ Checks whether sol is a solution of equation f == 0. Explanation =========== Input can be either a single symbol and corresponding value or a dictionary of symbols and values. When given as a dictionary and flag ``simplify=True``, the values in the dictionary will be simplified. *f* can be a single equation or an iterable of equations. A solution must satisfy all equations in *f* to be considered valid; if a solution does not satisfy any equation, False is returned; if one or more checks are inconclusive (and none are False) then None is returned. Examples ======== >>> from sympy import symbols >>> from sympy.solvers import checksol >>> x, y = symbols('x,y') >>> checksol(x**4 - 1, x, 1) True >>> checksol(x**4 - 1, x, 0) False >>> checksol(x**2 + y**2 - 5**2, {x: 3, y: 4}) True To check if an expression is zero using ``checksol()``, pass it as *f* and send an empty dictionary for *symbol*: >>> checksol(x**2 + x - x*(x + 1), {}) True None is returned if ``checksol()`` could not conclude. flags: 'numerical=True (default)' do a fast numerical check if ``f`` has only one symbol. 'minimal=True (default is False)' a very fast, minimal testing. 'warn=True (default is False)' show a warning if checksol() could not conclude. 'simplify=True (default)' simplify solution before substituting into function and simplify the function before trying specific simplifications 'force=True (default is False)' make positive all symbols without assumptions regarding sign. """ from sympy.physics.units import Unit minimal = flags.get('minimal', False) if sol is not None: sol = {symbol: sol} elif isinstance(symbol, dict): sol = symbol else: msg = 'Expecting (sym, val) or ({sym: val}, None) but got (%s, %s)' raise ValueError(msg % (symbol, sol)) if iterable(f): if not f: raise ValueError('no functions to check') rv = True for fi in f: check = checksol(fi, sol, **flags) if check: continue if check is False: return False rv = None # don't return, wait to see if there's a False return rv if isinstance(f, Poly): f = f.as_expr() elif isinstance(f, (Equality, Unequality)): if f.rhs in (S.true, S.false): f = f.reversed B, E = f.args if isinstance(B, BooleanAtom): f = f.subs(sol) if not f.is_Boolean: return else: f = f.rewrite(Add, evaluate=False) if isinstance(f, BooleanAtom): return bool(f) elif not f.is_Relational and not f: return True if sol and not f.free_symbols & set(sol.keys()): # if f(y) == 0, x=3 does not set f(y) to zero...nor does it not return None illegal = {S.NaN, S.ComplexInfinity, S.Infinity, S.NegativeInfinity} if any(sympify(v).atoms() & illegal for k, v in sol.items()): return False was = f attempt = -1 numerical = flags.get('numerical', True) while 1: attempt += 1 if attempt == 0: val = f.subs(sol) if isinstance(val, Mul): val = val.as_independent(Unit)[0] if val.atoms() & illegal: return False elif attempt == 1: if not val.is_number: if not val.is_constant(*list(sol.keys()), simplify=not minimal): return False # there are free symbols -- simple expansion might work _, val = val.as_content_primitive() val = _mexpand(val.as_numer_denom()[0], recursive=True) elif attempt == 2: if minimal: return if flags.get('simplify', True): for k in sol: sol[k] = simplify(sol[k]) # start over without the failed expanded form, possibly # with a simplified solution val = simplify(f.subs(sol)) if flags.get('force', True): val, reps = posify(val) # expansion may work now, so try again and check exval = _mexpand(val, recursive=True) if exval.is_number: # we can decide now val = exval else: # if there are no radicals and no functions then this can't be # zero anymore -- can it? pot = preorder_traversal(expand_mul(val)) seen = set() saw_pow_func = False for p in pot: if p in seen: continue seen.add(p) if p.is_Pow and not p.exp.is_Integer: saw_pow_func = True elif p.is_Function: saw_pow_func = True elif isinstance(p, UndefinedFunction): saw_pow_func = True if saw_pow_func: break if saw_pow_func is False: return False if flags.get('force', True): # don't do a zero check with the positive assumptions in place val = val.subs(reps) nz = fuzzy_not(val.is_zero) if nz is not None: # issue 5673: nz may be True even when False # so these are just hacks to keep a false positive # from being returned # HACK 1: LambertW (issue 5673) if val.is_number and val.has(LambertW): # don't eval this to verify solution since if we got here, # numerical must be False return None # add other HACKs here if necessary, otherwise we assume # the nz value is correct return not nz break if val == was: continue elif val.is_Rational: return val == 0 if numerical and val.is_number: return (abs(val.n(18).n(12, chop=True)) < 1e-9) is S.true was = val if flags.get('warn', False): warnings.warn("\n\tWarning: could not verify solution %s." % sol) # returns None if it can't conclude # TODO: improve solution testing def solve(f, *symbols, **flags): r""" Algebraically solves equations and systems of equations. Explanation =========== Currently supported: - polynomial - transcendental - piecewise combinations of the above - systems of linear and polynomial equations - systems containing relational expressions Examples ======== The output varies according to the input and can be seen by example: >>> from sympy import solve, Poly, Eq, Function, exp >>> from sympy.abc import x, y, z, a, b >>> f = Function('f') Boolean or univariate Relational: >>> solve(x < 3) (-oo < x) & (x < 3) To always get a list of solution mappings, use flag dict=True: >>> solve(x - 3, dict=True) [{x: 3}] >>> sol = solve([x - 3, y - 1], dict=True) >>> sol [{x: 3, y: 1}] >>> sol[0][x] 3 >>> sol[0][y] 1 To get a list of *symbols* and set of solution(s) use flag set=True: >>> solve([x**2 - 3, y - 1], set=True) ([x, y], {(-sqrt(3), 1), (sqrt(3), 1)}) Single expression and single symbol that is in the expression: >>> solve(x - y, x) [y] >>> solve(x - 3, x) [3] >>> solve(Eq(x, 3), x) [3] >>> solve(Poly(x - 3), x) [3] >>> solve(x**2 - y**2, x, set=True) ([x], {(-y,), (y,)}) >>> solve(x**4 - 1, x, set=True) ([x], {(-1,), (1,), (-I,), (I,)}) Single expression with no symbol that is in the expression: >>> solve(3, x) [] >>> solve(x - 3, y) [] Single expression with no symbol given. In this case, all free *symbols* will be selected as potential *symbols* to solve for. If the equation is univariate then a list of solutions is returned; otherwise - as is the case when *symbols* are given as an iterable of length greater than 1 - a list of mappings will be returned: >>> solve(x - 3) [3] >>> solve(x**2 - y**2) [{x: -y}, {x: y}] >>> solve(z**2*x**2 - z**2*y**2) [{x: -y}, {x: y}, {z: 0}] >>> solve(z**2*x - z**2*y**2) [{x: y**2}, {z: 0}] When an object other than a Symbol is given as a symbol, it is isolated algebraically and an implicit solution may be obtained. This is mostly provided as a convenience to save you from replacing the object with a Symbol and solving for that Symbol. It will only work if the specified object can be replaced with a Symbol using the subs method: >>> solve(f(x) - x, f(x)) [x] >>> solve(f(x).diff(x) - f(x) - x, f(x).diff(x)) [x + f(x)] >>> solve(f(x).diff(x) - f(x) - x, f(x)) [-x + Derivative(f(x), x)] >>> solve(x + exp(x)**2, exp(x), set=True) ([exp(x)], {(-sqrt(-x),), (sqrt(-x),)}) >>> from sympy import Indexed, IndexedBase, Tuple, sqrt >>> A = IndexedBase('A') >>> eqs = Tuple(A[1] + A[2] - 3, A[1] - A[2] + 1) >>> solve(eqs, eqs.atoms(Indexed)) {A[1]: 1, A[2]: 2} * To solve for a symbol implicitly, use implicit=True: >>> solve(x + exp(x), x) [-LambertW(1)] >>> solve(x + exp(x), x, implicit=True) [-exp(x)] * It is possible to solve for anything that can be targeted with subs: >>> solve(x + 2 + sqrt(3), x + 2) [-sqrt(3)] >>> solve((x + 2 + sqrt(3), x + 4 + y), y, x + 2) {y: -2 + sqrt(3), x + 2: -sqrt(3)} * Nothing heroic is done in this implicit solving so you may end up with a symbol still in the solution: >>> eqs = (x*y + 3*y + sqrt(3), x + 4 + y) >>> solve(eqs, y, x + 2) {y: -sqrt(3)/(x + 3), x + 2: -2*x/(x + 3) - 6/(x + 3) + sqrt(3)/(x + 3)} >>> solve(eqs, y*x, x) {x: -y - 4, x*y: -3*y - sqrt(3)} * If you attempt to solve for a number remember that the number you have obtained does not necessarily mean that the value is equivalent to the expression obtained: >>> solve(sqrt(2) - 1, 1) [sqrt(2)] >>> solve(x - y + 1, 1) # /!\ -1 is targeted, too [x/(y - 1)] >>> [_.subs(z, -1) for _ in solve((x - y + 1).subs(-1, z), 1)] [-x + y] * To solve for a function within a derivative, use ``dsolve``. Single expression and more than one symbol: * When there is a linear solution: >>> solve(x - y**2, x, y) [(y**2, y)] >>> solve(x**2 - y, x, y) [(x, x**2)] >>> solve(x**2 - y, x, y, dict=True) [{y: x**2}] * When undetermined coefficients are identified: * That are linear: >>> solve((a + b)*x - b + 2, a, b) {a: -2, b: 2} * That are nonlinear: >>> solve((a + b)*x - b**2 + 2, a, b, set=True) ([a, b], {(-sqrt(2), sqrt(2)), (sqrt(2), -sqrt(2))}) * If there is no linear solution, then the first successful attempt for a nonlinear solution will be returned: >>> solve(x**2 - y**2, x, y, dict=True) [{x: -y}, {x: y}] >>> solve(x**2 - y**2/exp(x), x, y, dict=True) [{x: 2*LambertW(-y/2)}, {x: 2*LambertW(y/2)}] >>> solve(x**2 - y**2/exp(x), y, x) [(-x*sqrt(exp(x)), x), (x*sqrt(exp(x)), x)] Iterable of one or more of the above: * Involving relationals or bools: >>> solve([x < 3, x - 2]) Eq(x, 2) >>> solve([x > 3, x - 2]) False * When the system is linear: * With a solution: >>> solve([x - 3], x) {x: 3} >>> solve((x + 5*y - 2, -3*x + 6*y - 15), x, y) {x: -3, y: 1} >>> solve((x + 5*y - 2, -3*x + 6*y - 15), x, y, z) {x: -3, y: 1} >>> solve((x + 5*y - 2, -3*x + 6*y - z), z, x, y) {x: 2 - 5*y, z: 21*y - 6} * Without a solution: >>> solve([x + 3, x - 3]) [] * When the system is not linear: >>> solve([x**2 + y -2, y**2 - 4], x, y, set=True) ([x, y], {(-2, -2), (0, 2), (2, -2)}) * If no *symbols* are given, all free *symbols* will be selected and a list of mappings returned: >>> solve([x - 2, x**2 + y]) [{x: 2, y: -4}] >>> solve([x - 2, x**2 + f(x)], {f(x), x}) [{x: 2, f(x): -4}] * If any equation does not depend on the symbol(s) given, it will be eliminated from the equation set and an answer may be given implicitly in terms of variables that were not of interest: >>> solve([x - y, y - 3], x) {x: y} **Additional Examples** ``solve()`` with check=True (default) will run through the symbol tags to elimate unwanted solutions. If no assumptions are included, all possible solutions will be returned: >>> from sympy import Symbol, solve >>> x = Symbol("x") >>> solve(x**2 - 1) [-1, 1] By using the positive tag, only one solution will be returned: >>> pos = Symbol("pos", positive=True) >>> solve(pos**2 - 1) [1] Assumptions are not checked when ``solve()`` input involves relationals or bools. When the solutions are checked, those that make any denominator zero are automatically excluded. If you do not want to exclude such solutions, then use the check=False option: >>> from sympy import sin, limit >>> solve(sin(x)/x) # 0 is excluded [pi] If check=False, then a solution to the numerator being zero is found: x = 0. In this case, this is a spurious solution since $\sin(x)/x$ has the well known limit (without dicontinuity) of 1 at x = 0: >>> solve(sin(x)/x, check=False) [0, pi] In the following case, however, the limit exists and is equal to the value of x = 0 that is excluded when check=True: >>> eq = x**2*(1/x - z**2/x) >>> solve(eq, x) [] >>> solve(eq, x, check=False) [0] >>> limit(eq, x, 0, '-') 0 >>> limit(eq, x, 0, '+') 0 **Disabling High-Order Explicit Solutions** When solving polynomial expressions, you might not want explicit solutions (which can be quite long). If the expression is univariate, ``CRootOf`` instances will be returned instead: >>> solve(x**3 - x + 1) [-1/((-1/2 - sqrt(3)*I/2)*(3*sqrt(69)/2 + 27/2)**(1/3)) - (-1/2 - sqrt(3)*I/2)*(3*sqrt(69)/2 + 27/2)**(1/3)/3, -(-1/2 + sqrt(3)*I/2)*(3*sqrt(69)/2 + 27/2)**(1/3)/3 - 1/((-1/2 + sqrt(3)*I/2)*(3*sqrt(69)/2 + 27/2)**(1/3)), -(3*sqrt(69)/2 + 27/2)**(1/3)/3 - 1/(3*sqrt(69)/2 + 27/2)**(1/3)] >>> solve(x**3 - x + 1, cubics=False) [CRootOf(x**3 - x + 1, 0), CRootOf(x**3 - x + 1, 1), CRootOf(x**3 - x + 1, 2)] If the expression is multivariate, no solution might be returned: >>> solve(x**3 - x + a, x, cubics=False) [] Sometimes solutions will be obtained even when a flag is False because the expression could be factored. In the following example, the equation can be factored as the product of a linear and a quadratic factor so explicit solutions (which did not require solving a cubic expression) are obtained: >>> eq = x**3 + 3*x**2 + x - 1 >>> solve(eq, cubics=False) [-1, -1 + sqrt(2), -sqrt(2) - 1] **Solving Equations Involving Radicals** Because of SymPy's use of the principle root, some solutions to radical equations will be missed unless check=False: >>> from sympy import root >>> eq = root(x**3 - 3*x**2, 3) + 1 - x >>> solve(eq) [] >>> solve(eq, check=False) [1/3] In the above example, there is only a single solution to the equation. Other expressions will yield spurious roots which must be checked manually; roots which give a negative argument to odd-powered radicals will also need special checking: >>> from sympy import real_root, S >>> eq = root(x, 3) - root(x, 5) + S(1)/7 >>> solve(eq) # this gives 2 solutions but misses a 3rd [CRootOf(7*x**5 - 7*x**3 + 1, 1)**15, CRootOf(7*x**5 - 7*x**3 + 1, 2)**15] >>> sol = solve(eq, check=False) >>> [abs(eq.subs(x,i).n(2)) for i in sol] [0.48, 0.e-110, 0.e-110, 0.052, 0.052] The first solution is negative so ``real_root`` must be used to see that it satisfies the expression: >>> abs(real_root(eq.subs(x, sol[0])).n(2)) 0.e-110 If the roots of the equation are not real then more care will be necessary to find the roots, especially for higher order equations. Consider the following expression: >>> expr = root(x, 3) - root(x, 5) We will construct a known value for this expression at x = 3 by selecting the 1-th root for each radical: >>> expr1 = root(x, 3, 1) - root(x, 5, 1) >>> v = expr1.subs(x, -3) The ``solve`` function is unable to find any exact roots to this equation: >>> eq = Eq(expr, v); eq1 = Eq(expr1, v) >>> solve(eq, check=False), solve(eq1, check=False) ([], []) The function ``unrad``, however, can be used to get a form of the equation for which numerical roots can be found: >>> from sympy.solvers.solvers import unrad >>> from sympy import nroots >>> e, (p, cov) = unrad(eq) >>> pvals = nroots(e) >>> inversion = solve(cov, x)[0] >>> xvals = [inversion.subs(p, i) for i in pvals] Although ``eq`` or ``eq1`` could have been used to find ``xvals``, the solution can only be verified with ``expr1``: >>> z = expr - v >>> [xi.n(chop=1e-9) for xi in xvals if abs(z.subs(x, xi).n()) < 1e-9] [] >>> z1 = expr1 - v >>> [xi.n(chop=1e-9) for xi in xvals if abs(z1.subs(x, xi).n()) < 1e-9] [-3.0] Parameters ========== f : - a single Expr or Poly that must be zero - an Equality - a Relational expression - a Boolean - iterable of one or more of the above symbols : (object(s) to solve for) specified as - none given (other non-numeric objects will be used) - single symbol - denested list of symbols (e.g., ``solve(f, x, y)``) - ordered iterable of symbols (e.g., ``solve(f, [x, y])``) flags : dict=True (default is False) Return list (perhaps empty) of solution mappings. set=True (default is False) Return list of symbols and set of tuple(s) of solution(s). exclude=[] (default) Do not try to solve for any of the free symbols in exclude; if expressions are given, the free symbols in them will be extracted automatically. check=True (default) If False, do not do any testing of solutions. This can be useful if you want to include solutions that make any denominator zero. numerical=True (default) Do a fast numerical check if *f* has only one symbol. minimal=True (default is False) A very fast, minimal testing. warn=True (default is False) Show a warning if ``checksol()`` could not conclude. simplify=True (default) Simplify all but polynomials of order 3 or greater before returning them and (if check is not False) use the general simplify function on the solutions and the expression obtained when they are substituted into the function which should be zero. force=True (default is False) Make positive all symbols without assumptions regarding sign. rational=True (default) Recast Floats as Rational; if this option is not used, the system containing Floats may fail to solve because of issues with polys. If rational=None, Floats will be recast as rationals but the answer will be recast as Floats. If the flag is False then nothing will be done to the Floats. manual=True (default is False) Do not use the polys/matrix method to solve a system of equations, solve them one at a time as you might "manually." implicit=True (default is False) Allows ``solve`` to return a solution for a pattern in terms of other functions that contain that pattern; this is only needed if the pattern is inside of some invertible function like cos, exp, ect. particular=True (default is False) Instructs ``solve`` to try to find a particular solution to a linear system with as many zeros as possible; this is very expensive. quick=True (default is False) When using particular=True, use a fast heuristic to find a solution with many zeros (instead of using the very slow method guaranteed to find the largest number of zeros possible). cubics=True (default) Return explicit solutions when cubic expressions are encountered. quartics=True (default) Return explicit solutions when quartic expressions are encountered. quintics=True (default) Return explicit solutions (if possible) when quintic expressions are encountered. See Also ======== rsolve: For solving recurrence relationships dsolve: For solving differential equations """ # keeping track of how f was passed since if it is a list # a dictionary of results will be returned. ########################################################################### def _sympified_list(w): return list(map(sympify, w if iterable(w) else [w])) bare_f = not iterable(f) ordered_symbols = (symbols and symbols[0] and (isinstance(symbols[0], Symbol) or is_sequence(symbols[0], include=GeneratorType) ) ) f, symbols = (_sympified_list(w) for w in [f, symbols]) if isinstance(f, list): f = [s for s in f if s is not S.true and s is not True] implicit = flags.get('implicit', False) # preprocess symbol(s) ########################################################################### if not symbols: # get symbols from equations symbols = set().union(*[fi.free_symbols for fi in f]) if len(symbols) < len(f): for fi in f: pot = preorder_traversal(fi) for p in pot: if isinstance(p, AppliedUndef): flags['dict'] = True # better show symbols symbols.add(p) pot.skip() # don't go any deeper symbols = list(symbols) ordered_symbols = False elif len(symbols) == 1 and iterable(symbols[0]): symbols = symbols[0] # remove symbols the user is not interested in exclude = flags.pop('exclude', set()) if exclude: if isinstance(exclude, Expr): exclude = [exclude] exclude = set().union(*[e.free_symbols for e in sympify(exclude)]) symbols = [s for s in symbols if s not in exclude] # preprocess equation(s) ########################################################################### for i, fi in enumerate(f): if isinstance(fi, (Equality, Unequality)): if 'ImmutableDenseMatrix' in [type(a).__name__ for a in fi.args]: fi = fi.lhs - fi.rhs else: L, R = fi.args if isinstance(R, BooleanAtom): L, R = R, L if isinstance(L, BooleanAtom): if isinstance(fi, Unequality): L = ~L if R.is_Relational: fi = ~R if L is S.false else R elif R.is_Symbol: return L elif R.is_Boolean and (~R).is_Symbol: return ~L else: raise NotImplementedError(filldedent(''' Unanticipated argument of Eq when other arg is True or False. ''')) else: fi = fi.rewrite(Add, evaluate=False) f[i] = fi if fi.is_Relational: return reduce_inequalities(f, symbols=symbols) if isinstance(fi, Poly): f[i] = fi.as_expr() # rewrite hyperbolics in terms of exp f[i] = f[i].replace(lambda w: isinstance(w, HyperbolicFunction), lambda w: w.rewrite(exp)) # if we have a Matrix, we need to iterate over its elements again if f[i].is_Matrix: bare_f = False f.extend(list(f[i])) f[i] = S.Zero # if we can split it into real and imaginary parts then do so freei = f[i].free_symbols if freei and all(s.is_extended_real or s.is_imaginary for s in freei): fr, fi = f[i].as_real_imag() # accept as long as new re, im, arg or atan2 are not introduced had = f[i].atoms(re, im, arg, atan2) if fr and fi and fr != fi and not any( i.atoms(re, im, arg, atan2) - had for i in (fr, fi)): if bare_f: bare_f = False f[i: i + 1] = [fr, fi] # real/imag handling ----------------------------- if any(isinstance(fi, (bool, BooleanAtom)) for fi in f): if flags.get('set', False): return [], set() return [] for i, fi in enumerate(f): # Abs while True: was = fi fi = fi.replace(Abs, lambda arg: separatevars(Abs(arg)).rewrite(Piecewise) if arg.has(*symbols) else Abs(arg)) if was == fi: break for e in fi.find(Abs): if e.has(*symbols): raise NotImplementedError('solving %s when the argument ' 'is not real or imaginary.' % e) # arg fi = fi.replace(arg, lambda a: arg(a).rewrite(atan2).rewrite(atan)) # save changes f[i] = fi # see if re(s) or im(s) appear freim = [fi for fi in f if fi.has(re, im)] if freim: irf = [] for s in symbols: if s.is_real or s.is_imaginary: continue # neither re(x) nor im(x) will appear # if re(s) or im(s) appear, the auxiliary equation must be present if any(fi.has(re(s), im(s)) for fi in freim): irf.append((s, re(s) + S.ImaginaryUnit*im(s))) if irf: for s, rhs in irf: for i, fi in enumerate(f): f[i] = fi.xreplace({s: rhs}) f.append(s - rhs) symbols.extend([re(s), im(s)]) if bare_f: bare_f = False flags['dict'] = True # end of real/imag handling ----------------------------- symbols = list(uniq(symbols)) if not ordered_symbols: # we do this to make the results returned canonical in case f # contains a system of nonlinear equations; all other cases should # be unambiguous symbols = sorted(symbols, key=default_sort_key) # we can solve for non-symbol entities by replacing them with Dummy symbols f, symbols, swap_sym = recast_to_symbols(f, symbols) # this is needed in the next two events symset = set(symbols) # get rid of equations that have no symbols of interest; we don't # try to solve them because the user didn't ask and they might be # hard to solve; this means that solutions may be given in terms # of the eliminated equations e.g. solve((x-y, y-3), x) -> {x: y} newf = [] for fi in f: # let the solver handle equations that.. # - have no symbols but are expressions # - have symbols of interest # - have no symbols of interest but are constant # but when an expression is not constant and has no symbols of # interest, it can't change what we obtain for a solution from # the remaining equations so we don't include it; and if it's # zero it can be removed and if it's not zero, there is no # solution for the equation set as a whole # # The reason for doing this filtering is to allow an answer # to be obtained to queries like solve((x - y, y), x); without # this mod the return value is [] ok = False if fi.free_symbols & symset: ok = True else: if fi.is_number: if fi.is_Number: if fi.is_zero: continue return [] ok = True else: if fi.is_constant(): ok = True if ok: newf.append(fi) if not newf: return [] f = newf del newf # mask off any Object that we aren't going to invert: Derivative, # Integral, etc... so that solving for anything that they contain will # give an implicit solution seen = set() non_inverts = set() for fi in f: pot = preorder_traversal(fi) for p in pot: if not isinstance(p, Expr) or isinstance(p, Piecewise): pass elif (isinstance(p, bool) or not p.args or p in symset or p.is_Add or p.is_Mul or p.is_Pow and not implicit or p.is_Function and not implicit) and p.func not in (re, im): continue elif not p in seen: seen.add(p) if p.free_symbols & symset: non_inverts.add(p) else: continue pot.skip() del seen non_inverts = dict(list(zip(non_inverts, [Dummy() for _ in non_inverts]))) f = [fi.subs(non_inverts) for fi in f] # Both xreplace and subs are needed below: xreplace to force substitution # inside Derivative, subs to handle non-straightforward substitutions non_inverts = [(v, k.xreplace(swap_sym).subs(swap_sym)) for k, v in non_inverts.items()] # rationalize Floats floats = False if flags.get('rational', True) is not False: for i, fi in enumerate(f): if fi.has(Float): floats = True f[i] = nsimplify(fi, rational=True) # capture any denominators before rewriting since # they may disappear after the rewrite, e.g. issue 14779 flags['_denominators'] = _simple_dens(f[0], symbols) # Any embedded piecewise functions need to be brought out to the # top level so that the appropriate strategy gets selected. # However, this is necessary only if one of the piecewise # functions depends on one of the symbols we are solving for. def _has_piecewise(e): if e.is_Piecewise: return e.has(*symbols) return any([_has_piecewise(a) for a in e.args]) for i, fi in enumerate(f): if _has_piecewise(fi): f[i] = piecewise_fold(fi) # # try to get a solution ########################################################################### if bare_f: solution = _solve(f[0], *symbols, **flags) else: solution = _solve_system(f, symbols, **flags) # # postprocessing ########################################################################### # Restore masked-off objects if non_inverts: def _do_dict(solution): return {k: v.subs(non_inverts) for k, v in solution.items()} for i in range(1): if isinstance(solution, dict): solution = _do_dict(solution) break elif solution and isinstance(solution, list): if isinstance(solution[0], dict): solution = [_do_dict(s) for s in solution] break elif isinstance(solution[0], tuple): solution = [tuple([v.subs(non_inverts) for v in s]) for s in solution] break else: solution = [v.subs(non_inverts) for v in solution] break elif not solution: break else: raise NotImplementedError(filldedent(''' no handling of %s was implemented''' % solution)) # Restore original "symbols" if a dictionary is returned. # This is not necessary for # - the single univariate equation case # since the symbol will have been removed from the solution; # - the nonlinear poly_system since that only supports zero-dimensional # systems and those results come back as a list # # ** unless there were Derivatives with the symbols, but those were handled # above. if swap_sym: symbols = [swap_sym.get(k, k) for k in symbols] if isinstance(solution, dict): solution = {swap_sym.get(k, k): v.subs(swap_sym) for k, v in solution.items()} elif solution and isinstance(solution, list) and isinstance(solution[0], dict): for i, sol in enumerate(solution): solution[i] = {swap_sym.get(k, k): v.subs(swap_sym) for k, v in sol.items()} # undo the dictionary solutions returned when the system was only partially # solved with poly-system if all symbols are present if ( not flags.get('dict', False) and solution and ordered_symbols and not isinstance(solution, dict) and all(isinstance(sol, dict) for sol in solution) ): solution = [tuple([r.get(s, s) for s in symbols]) for r in solution] # Get assumptions about symbols, to filter solutions. # Note that if assumptions about a solution can't be verified, it is still # returned. check = flags.get('check', True) # restore floats if floats and solution and flags.get('rational', None) is None: solution = nfloat(solution, exponent=False) if check and solution: # assumption checking warn = flags.get('warn', False) got_None = [] # solutions for which one or more symbols gave None no_False = [] # solutions for which no symbols gave False if isinstance(solution, tuple): # this has already been checked and is in as_set form return solution elif isinstance(solution, list): if isinstance(solution[0], tuple): for sol in solution: for symb, val in zip(symbols, sol): test = check_assumptions(val, **symb.assumptions0) if test is False: break if test is None: got_None.append(sol) else: no_False.append(sol) elif isinstance(solution[0], dict): for sol in solution: a_None = False for symb, val in sol.items(): test = check_assumptions(val, **symb.assumptions0) if test: continue if test is False: break a_None = True else: no_False.append(sol) if a_None: got_None.append(sol) else: # list of expressions for sol in solution: test = check_assumptions(sol, **symbols[0].assumptions0) if test is False: continue no_False.append(sol) if test is None: got_None.append(sol) elif isinstance(solution, dict): a_None = False for symb, val in solution.items(): test = check_assumptions(val, **symb.assumptions0) if test: continue if test is False: no_False = None break a_None = True else: no_False = solution if a_None: got_None.append(solution) elif isinstance(solution, (Relational, And, Or)): if len(symbols) != 1: raise ValueError("Length should be 1") if warn and symbols[0].assumptions0: warnings.warn(filldedent(""" \tWarning: assumptions about variable '%s' are not handled currently.""" % symbols[0])) # TODO: check also variable assumptions for inequalities else: raise TypeError('Unrecognized solution') # improve the checker solution = no_False if warn and got_None: warnings.warn(filldedent(""" \tWarning: assumptions concerning following solution(s) can't be checked:""" + '\n\t' + ', '.join(str(s) for s in got_None))) # # done ########################################################################### as_dict = flags.get('dict', False) as_set = flags.get('set', False) if not as_set and isinstance(solution, list): # Make sure that a list of solutions is ordered in a canonical way. solution.sort(key=default_sort_key) if not as_dict and not as_set: return solution or [] # return a list of mappings or [] if not solution: solution = [] else: if isinstance(solution, dict): solution = [solution] elif iterable(solution[0]): solution = [dict(list(zip(symbols, s))) for s in solution] elif isinstance(solution[0], dict): pass else: if len(symbols) != 1: raise ValueError("Length should be 1") solution = [{symbols[0]: s} for s in solution] if as_dict: return solution assert as_set if not solution: return [], set() k = list(ordered(solution[0].keys())) return k, {tuple([s[ki] for ki in k]) for s in solution} def _solve(f, *symbols, **flags): """ Return a checked solution for *f* in terms of one or more of the symbols. A list should be returned except for the case when a linear undetermined-coefficients equation is encountered (in which case a dictionary is returned). If no method is implemented to solve the equation, a NotImplementedError will be raised. In the case that conversion of an expression to a Poly gives None a ValueError will be raised. """ not_impl_msg = "No algorithms are implemented to solve equation %s" if len(symbols) != 1: soln = None free = f.free_symbols ex = free - set(symbols) if len(ex) != 1: ind, dep = f.as_independent(*symbols) ex = ind.free_symbols & dep.free_symbols if len(ex) == 1: ex = ex.pop() try: # soln may come back as dict, list of dicts or tuples, or # tuple of symbol list and set of solution tuples soln = solve_undetermined_coeffs(f, symbols, ex, **flags) except NotImplementedError: pass if soln: if flags.get('simplify', True): if isinstance(soln, dict): for k in soln: soln[k] = simplify(soln[k]) elif isinstance(soln, list): if isinstance(soln[0], dict): for d in soln: for k in d: d[k] = simplify(d[k]) elif isinstance(soln[0], tuple): soln = [tuple(simplify(i) for i in j) for j in soln] else: raise TypeError('unrecognized args in list') elif isinstance(soln, tuple): sym, sols = soln soln = sym, {tuple(simplify(i) for i in j) for j in sols} else: raise TypeError('unrecognized solution type') return soln # find first successful solution failed = [] got_s = set() result = [] for s in symbols: xi, v = solve_linear(f, symbols=[s]) if xi == s: # no need to check but we should simplify if desired if flags.get('simplify', True): v = simplify(v) vfree = v.free_symbols if got_s and any([ss in vfree for ss in got_s]): # sol depends on previously solved symbols: discard it continue got_s.add(xi) result.append({xi: v}) elif xi: # there might be a non-linear solution if xi is not 0 failed.append(s) if not failed: return result for s in failed: try: soln = _solve(f, s, **flags) for sol in soln: if got_s and any([ss in sol.free_symbols for ss in got_s]): # sol depends on previously solved symbols: discard it continue got_s.add(s) result.append({s: sol}) except NotImplementedError: continue if got_s: return result else: raise NotImplementedError(not_impl_msg % f) symbol = symbols[0] #expand binomials only if it has the unknown symbol f = f.replace(lambda e: isinstance(e, binomial) and e.has(symbol), lambda e: expand_func(e)) # /!\ capture this flag then set it to False so that no checking in # recursive calls will be done; only the final answer is checked flags['check'] = checkdens = check = flags.pop('check', True) # build up solutions if f is a Mul if f.is_Mul: result = set() for m in f.args: if m in {S.NegativeInfinity, S.ComplexInfinity, S.Infinity}: result = set() break soln = _solve(m, symbol, **flags) result.update(set(soln)) result = list(result) if check: # all solutions have been checked but now we must # check that the solutions do not set denominators # in any factor to zero dens = flags.get('_denominators', _simple_dens(f, symbols)) result = [s for s in result if all(not checksol(den, {symbol: s}, **flags) for den in dens)] # set flags for quick exit at end; solutions for each # factor were already checked and simplified check = False flags['simplify'] = False elif f.is_Piecewise: result = set() for i, (expr, cond) in enumerate(f.args): if expr.is_zero: raise NotImplementedError( 'solve cannot represent interval solutions') candidates = _solve(expr, symbol, **flags) # the explicit condition for this expr is the current cond # and none of the previous conditions args = [~c for _, c in f.args[:i]] + [cond] cond = And(*args) for candidate in candidates: if candidate in result: # an unconditional value was already there continue try: v = cond.subs(symbol, candidate) _eval_simplify = getattr(v, '_eval_simplify', None) if _eval_simplify is not None: # unconditionally take the simpification of v v = _eval_simplify(ratio=2, measure=lambda x: 1) except TypeError: # incompatible type with condition(s) continue if v == False: continue if v == True: result.add(candidate) else: result.add(Piecewise( (candidate, v), (S.NaN, True))) # set flags for quick exit at end; solutions for each # piece were already checked and simplified check = False flags['simplify'] = False else: # first see if it really depends on symbol and whether there # is only a linear solution f_num, sol = solve_linear(f, symbols=symbols) if f_num.is_zero or sol is S.NaN: return [] elif f_num.is_Symbol: # no need to check but simplify if desired if flags.get('simplify', True): sol = simplify(sol) return [sol] poly = None # check for a single non-symbol generator dums = f_num.atoms(Dummy) D = f_num.replace( lambda i: isinstance(i, Add) and symbol in i.free_symbols, lambda i: Dummy()) if not D.is_Dummy: dgen = D.atoms(Dummy) - dums if len(dgen) == 1: d = dgen.pop() w = Wild('g') gen = f_num.match(D.xreplace({d: w}))[w] spart = gen.as_independent(symbol)[1].as_base_exp()[0] if spart == symbol: try: poly = Poly(f_num, spart) except PolynomialError: pass result = False # no solution was obtained msg = '' # there is no failure message # Poly is generally robust enough to convert anything to # a polynomial and tell us the different generators that it # contains, so we will inspect the generators identified by # polys to figure out what to do. # try to identify a single generator that will allow us to solve this # as a polynomial, followed (perhaps) by a change of variables if the # generator is not a symbol try: if poly is None: poly = Poly(f_num) if poly is None: raise ValueError('could not convert %s to Poly' % f_num) except GeneratorsNeeded: simplified_f = simplify(f_num) if simplified_f != f_num: return _solve(simplified_f, symbol, **flags) raise ValueError('expression appears to be a constant') gens = [g for g in poly.gens if g.has(symbol)] def _as_base_q(x): """Return (b**e, q) for x = b**(p*e/q) where p/q is the leading Rational of the exponent of x, e.g. exp(-2*x/3) -> (exp(x), 3) """ b, e = x.as_base_exp() if e.is_Rational: return b, e.q if not e.is_Mul: return x, 1 c, ee = e.as_coeff_Mul() if c.is_Rational and c is not S.One: # c could be a Float return b**ee, c.q return x, 1 if len(gens) > 1: # If there is more than one generator, it could be that the # generators have the same base but different powers, e.g. # >>> Poly(exp(x) + 1/exp(x)) # Poly(exp(-x) + exp(x), exp(-x), exp(x), domain='ZZ') # # If unrad was not disabled then there should be no rational # exponents appearing as in # >>> Poly(sqrt(x) + sqrt(sqrt(x))) # Poly(sqrt(x) + x**(1/4), sqrt(x), x**(1/4), domain='ZZ') bases, qs = list(zip(*[_as_base_q(g) for g in gens])) bases = set(bases) if len(bases) > 1 or not all(q == 1 for q in qs): funcs = {b for b in bases if b.is_Function} trig = {_ for _ in funcs if isinstance(_, TrigonometricFunction)} other = funcs - trig if not other and len(funcs.intersection(trig)) > 1: newf = None if f_num.is_Add and len(f_num.args) == 2: # check for sin(x)**p = cos(x)**p _args = f_num.args t = a, b = [i.atoms(Function).intersection( trig) for i in _args] if all(len(i) == 1 for i in t): a, b = [i.pop() for i in t] if isinstance(a, cos): a, b = b, a _args = _args[::-1] if isinstance(a, sin) and isinstance(b, cos ) and a.args[0] == b.args[0]: # sin(x) + cos(x) = 0 -> tan(x) + 1 = 0 newf, _d = (TR2i(_args[0]/_args[1]) + 1 ).as_numer_denom() if not _d.is_Number: newf = None if newf is None: newf = TR1(f_num).rewrite(tan) if newf != f_num: # don't check the rewritten form --check # solutions in the un-rewritten form below flags['check'] = False result = _solve(newf, symbol, **flags) flags['check'] = check # just a simple case - see if replacement of single function # clears all symbol-dependent functions, e.g. # log(x) - log(log(x) - 1) - 3 can be solved even though it has # two generators. if result is False and funcs: funcs = list(ordered(funcs)) # put shallowest function first f1 = funcs[0] t = Dummy('t') # perform the substitution ftry = f_num.subs(f1, t) # if no Functions left, we can proceed with usual solve if not ftry.has(symbol): cv_sols = _solve(ftry, t, **flags) cv_inv = _solve(t - f1, symbol, **flags)[0] sols = list() for sol in cv_sols: sols.append(cv_inv.subs(t, sol)) result = list(ordered(sols)) if result is False: msg = 'multiple generators %s' % gens else: # e.g. case where gens are exp(x), exp(-x) u = bases.pop() t = Dummy('t') inv = _solve(u - t, symbol, **flags) if isinstance(u, (Pow, exp)): # this will be resolved by factor in _tsolve but we might # as well try a simple expansion here to get things in # order so something like the following will work now without # having to factor: # # >>> eq = (exp(I*(-x-2))+exp(I*(x+2))) # >>> eq.subs(exp(x),y) # fails # exp(I*(-x - 2)) + exp(I*(x + 2)) # >>> eq.expand().subs(exp(x),y) # works # y**I*exp(2*I) + y**(-I)*exp(-2*I) def _expand(p): b, e = p.as_base_exp() e = expand_mul(e) return expand_power_exp(b**e) ftry = f_num.replace( lambda w: w.is_Pow or isinstance(w, exp), _expand).subs(u, t) if not ftry.has(symbol): soln = _solve(ftry, t, **flags) sols = list() for sol in soln: for i in inv: sols.append(i.subs(t, sol)) result = list(ordered(sols)) elif len(gens) == 1: # There is only one generator that we are interested in, but # there may have been more than one generator identified by # polys (e.g. for symbols other than the one we are interested # in) so recast the poly in terms of our generator of interest. # Also use composite=True with f_num since Poly won't update # poly as documented in issue 8810. poly = Poly(f_num, gens[0], composite=True) # if we aren't on the tsolve-pass, use roots if not flags.pop('tsolve', False): soln = None deg = poly.degree() flags['tsolve'] = True solvers = {k: flags.get(k, True) for k in ('cubics', 'quartics', 'quintics')} soln = roots(poly, **solvers) if sum(soln.values()) < deg: # e.g. roots(32*x**5 + 400*x**4 + 2032*x**3 + # 5000*x**2 + 6250*x + 3189) -> {} # so all_roots is used and RootOf instances are # returned *unless* the system is multivariate # or high-order EX domain. try: soln = poly.all_roots() except NotImplementedError: if not flags.get('incomplete', True): raise NotImplementedError( filldedent(''' Neither high-order multivariate polynomials nor sorting of EX-domain polynomials is supported. If you want to see any results, pass keyword incomplete=True to solve; to see numerical values of roots for univariate expressions, use nroots. ''')) else: pass else: soln = list(soln.keys()) if soln is not None: u = poly.gen if u != symbol: try: t = Dummy('t') iv = _solve(u - t, symbol, **flags) soln = list(ordered({i.subs(t, s) for i in iv for s in soln})) except NotImplementedError: # perhaps _tsolve can handle f_num soln = None else: check = False # only dens need to be checked if soln is not None: if len(soln) > 2: # if the flag wasn't set then unset it since high-order # results are quite long. Perhaps one could base this # decision on a certain critical length of the # roots. In addition, wester test M2 has an expression # whose roots can be shown to be real with the # unsimplified form of the solution whereas only one of # the simplified forms appears to be real. flags['simplify'] = flags.get('simplify', False) result = soln # fallback if above fails # ----------------------- if result is False: # try unrad if flags.pop('_unrad', True): try: u = unrad(f_num, symbol) except (ValueError, NotImplementedError): u = False if u: eq, cov = u if cov: isym, ieq = cov inv = _solve(ieq, symbol, **flags)[0] rv = {inv.subs(isym, xi) for xi in _solve(eq, isym, **flags)} else: try: rv = set(_solve(eq, symbol, **flags)) except NotImplementedError: rv = None if rv is not None: result = list(ordered(rv)) # if the flag wasn't set then unset it since unrad results # can be quite long or of very high order flags['simplify'] = flags.get('simplify', False) else: pass # for coverage # try _tsolve if result is False: flags.pop('tsolve', None) # allow tsolve to be used on next pass try: soln = _tsolve(f_num, symbol, **flags) if soln is not None: result = soln except PolynomialError: pass # ----------- end of fallback ---------------------------- if result is False: raise NotImplementedError('\n'.join([msg, not_impl_msg % f])) if flags.get('simplify', True): result = list(map(simplify, result)) # we just simplified the solution so we now set the flag to # False so the simplification doesn't happen again in checksol() flags['simplify'] = False if checkdens: # reject any result that makes any denom. affirmatively 0; # if in doubt, keep it dens = _simple_dens(f, symbols) result = [s for s in result if all(not checksol(d, {symbol: s}, **flags) for d in dens)] if check: # keep only results if the check is not False result = [r for r in result if checksol(f_num, {symbol: r}, **flags) is not False] return result def _solve_system(exprs, symbols, **flags): if not exprs: return [] if flags.pop('_split', True): # Split the system into connected components V = exprs symsset = set(symbols) exprsyms = {e: e.free_symbols & symsset for e in exprs} E = [] for n, e1 in enumerate(exprs): for e2 in exprs[:n]: # Equations are connected if they share a symbol if exprsyms[e1] & exprsyms[e2]: E.append((e1, e2)) G = V, E subexprs = connected_components(G) if len(subexprs) > 1: subsols = [] for subexpr in subexprs: subsyms = set() for e in subexpr: subsyms |= exprsyms[e] subsyms = list(ordered(subsyms)) # use canonical subset to solve these equations # since there may be redundant equations in the set: # take the first equation of several that may have the # same sub-maximal free symbols of interest; the # other equations that weren't used should be checked # to see that they did not fail -- does the solver # take care of that? choices = sift(subexpr, lambda x: tuple(ordered(exprsyms[x]))) subexpr = choices.pop(tuple(ordered(subsyms)), []) for k in choices: subexpr.append(next(ordered(choices[k]))) flags['_split'] = False # skip split step subsol = _solve_system(subexpr, subsyms, **flags) if not isinstance(subsol, list): subsol = [subsol] subsols.append(subsol) # Full solution is cartesion product of subsystems sols = [] for soldicts in cartes(*subsols): sols.append(dict(item for sd in soldicts for item in sd.items())) # Return a list with one dict as just the dict if len(sols) == 1: return sols[0] return sols polys = [] dens = set() failed = [] result = False linear = False manual = flags.get('manual', False) checkdens = check = flags.get('check', True) for j, g in enumerate(exprs): dens.update(_simple_dens(g, symbols)) i, d = _invert(g, *symbols) g = d - i g = g.as_numer_denom()[0] if manual: failed.append(g) continue poly = g.as_poly(*symbols, extension=True) if poly is not None: polys.append(poly) else: failed.append(g) if not polys: solved_syms = [] else: if all(p.is_linear for p in polys): n, m = len(polys), len(symbols) matrix = zeros(n, m + 1) for i, poly in enumerate(polys): for monom, coeff in poly.terms(): try: j = monom.index(1) matrix[i, j] = coeff except ValueError: matrix[i, m] = -coeff # returns a dictionary ({symbols: values}) or None if flags.pop('particular', False): result = minsolve_linear_system(matrix, *symbols, **flags) else: result = solve_linear_system(matrix, *symbols, **flags) if failed: if result: solved_syms = list(result.keys()) else: solved_syms = [] else: linear = True else: if len(symbols) > len(polys): from sympy.utilities.iterables import subsets free = set().union(*[p.free_symbols for p in polys]) free = list(ordered(free.intersection(symbols))) got_s = set() result = [] for syms in subsets(free, len(polys)): try: # returns [] or list of tuples of solutions for syms res = solve_poly_system(polys, *syms) if res: for r in res: skip = False for r1 in r: if got_s and any([ss in r1.free_symbols for ss in got_s]): # sol depends on previously # solved symbols: discard it skip = True if not skip: got_s.update(syms) result.extend([dict(list(zip(syms, r)))]) except NotImplementedError: pass if got_s: solved_syms = list(got_s) else: raise NotImplementedError('no valid subset found') else: try: result = solve_poly_system(polys, *symbols) if result: solved_syms = symbols # we don't know here if the symbols provided # were given or not, so let solve resolve that. # A list of dictionaries is going to always be # returned from here. result = [dict(list(zip(solved_syms, r))) for r in result] except NotImplementedError: failed.extend([g.as_expr() for g in polys]) solved_syms = [] result = None if result: if isinstance(result, dict): result = [result] else: result = [{}] if failed: # For each failed equation, see if we can solve for one of the # remaining symbols from that equation. If so, we update the # solution set and continue with the next failed equation, # repeating until we are done or we get an equation that can't # be solved. def _ok_syms(e, sort=False): rv = (e.free_symbols - solved_syms) & legal if sort: rv = list(rv) rv.sort(key=default_sort_key) return rv solved_syms = set(solved_syms) # set of symbols we have solved for legal = set(symbols) # what we are interested in # sort so equation with the fewest potential symbols is first u = Dummy() # used in solution checking for eq in ordered(failed, lambda _: len(_ok_syms(_))): newresult = [] bad_results = [] got_s = set() hit = False for r in result: # update eq with everything that is known so far eq2 = eq.subs(r) # if check is True then we see if it satisfies this # equation, otherwise we just accept it if check and r: b = checksol(u, u, eq2, minimal=True) if b is not None: # this solution is sufficient to know whether # it is valid or not so we either accept or # reject it, then continue if b: newresult.append(r) else: bad_results.append(r) continue # search for a symbol amongst those available that # can be solved for ok_syms = _ok_syms(eq2, sort=True) if not ok_syms: if r: newresult.append(r) break # skip as it's independent of desired symbols for s in ok_syms: try: soln = _solve(eq2, s, **flags) except NotImplementedError: continue # put each solution in r and append the now-expanded # result in the new result list; use copy since the # solution for s in being added in-place for sol in soln: if got_s and any([ss in sol.free_symbols for ss in got_s]): # sol depends on previously solved symbols: discard it continue rnew = r.copy() for k, v in r.items(): rnew[k] = v.subs(s, sol) # and add this new solution rnew[s] = sol newresult.append(rnew) hit = True got_s.add(s) if not hit: raise NotImplementedError('could not solve %s' % eq2) else: result = newresult for b in bad_results: if b in result: result.remove(b) default_simplify = bool(failed) # rely on system-solvers to simplify if flags.get('simplify', default_simplify): for r in result: for k in r: r[k] = simplify(r[k]) flags['simplify'] = False # don't need to do so in checksol now if checkdens: result = [r for r in result if not any(checksol(d, r, **flags) for d in dens)] if check and not linear: result = [r for r in result if not any(checksol(e, r, **flags) is False for e in exprs)] result = [r for r in result if r] if linear and result: result = result[0] return result def solve_linear(lhs, rhs=0, symbols=[], exclude=[]): r""" Return a tuple derived from ``f = lhs - rhs`` that is one of the following: ``(0, 1)``, ``(0, 0)``, ``(symbol, solution)``, ``(n, d)``. Explanation =========== ``(0, 1)`` meaning that ``f`` is independent of the symbols in *symbols* that are not in *exclude*. ``(0, 0)`` meaning that there is no solution to the equation amongst the symbols given. If the first element of the tuple is not zero, then the function is guaranteed to be dependent on a symbol in *symbols*. ``(symbol, solution)`` where symbol appears linearly in the numerator of ``f``, is in *symbols* (if given), and is not in *exclude* (if given). No simplification is done to ``f`` other than a ``mul=True`` expansion, so the solution will correspond strictly to a unique solution. ``(n, d)`` where ``n`` and ``d`` are the numerator and denominator of ``f`` when the numerator was not linear in any symbol of interest; ``n`` will never be a symbol unless a solution for that symbol was found (in which case the second element is the solution, not the denominator). Examples ======== >>> from sympy.core.power import Pow >>> from sympy.polys.polytools import cancel ``f`` is independent of the symbols in *symbols* that are not in *exclude*: >>> from sympy.solvers.solvers import solve_linear >>> from sympy.abc import x, y, z >>> from sympy import cos, sin >>> eq = y*cos(x)**2 + y*sin(x)**2 - y # = y*(1 - 1) = 0 >>> solve_linear(eq) (0, 1) >>> eq = cos(x)**2 + sin(x)**2 # = 1 >>> solve_linear(eq) (0, 1) >>> solve_linear(x, exclude=[x]) (0, 1) The variable ``x`` appears as a linear variable in each of the following: >>> solve_linear(x + y**2) (x, -y**2) >>> solve_linear(1/x - y**2) (x, y**(-2)) When not linear in ``x`` or ``y`` then the numerator and denominator are returned: >>> solve_linear(x**2/y**2 - 3) (x**2 - 3*y**2, y**2) If the numerator of the expression is a symbol, then ``(0, 0)`` is returned if the solution for that symbol would have set any denominator to 0: >>> eq = 1/(1/x - 2) >>> eq.as_numer_denom() (x, 1 - 2*x) >>> solve_linear(eq) (0, 0) But automatic rewriting may cause a symbol in the denominator to appear in the numerator so a solution will be returned: >>> (1/x)**-1 x >>> solve_linear((1/x)**-1) (x, 0) Use an unevaluated expression to avoid this: >>> solve_linear(Pow(1/x, -1, evaluate=False)) (0, 0) If ``x`` is allowed to cancel in the following expression, then it appears to be linear in ``x``, but this sort of cancellation is not done by ``solve_linear`` so the solution will always satisfy the original expression without causing a division by zero error. >>> eq = x**2*(1/x - z**2/x) >>> solve_linear(cancel(eq)) (x, 0) >>> solve_linear(eq) (x**2*(1 - z**2), x) A list of symbols for which a solution is desired may be given: >>> solve_linear(x + y + z, symbols=[y]) (y, -x - z) A list of symbols to ignore may also be given: >>> solve_linear(x + y + z, exclude=[x]) (y, -x - z) (A solution for ``y`` is obtained because it is the first variable from the canonically sorted list of symbols that had a linear solution.) """ if isinstance(lhs, Equality): if rhs: raise ValueError(filldedent(''' If lhs is an Equality, rhs must be 0 but was %s''' % rhs)) rhs = lhs.rhs lhs = lhs.lhs dens = None eq = lhs - rhs n, d = eq.as_numer_denom() if not n: return S.Zero, S.One free = n.free_symbols if not symbols: symbols = free else: bad = [s for s in symbols if not s.is_Symbol] if bad: if len(bad) == 1: bad = bad[0] if len(symbols) == 1: eg = 'solve(%s, %s)' % (eq, symbols[0]) else: eg = 'solve(%s, *%s)' % (eq, list(symbols)) raise ValueError(filldedent(''' solve_linear only handles symbols, not %s. To isolate non-symbols use solve, e.g. >>> %s <<<. ''' % (bad, eg))) symbols = free.intersection(symbols) symbols = symbols.difference(exclude) if not symbols: return S.Zero, S.One # derivatives are easy to do but tricky to analyze to see if they # are going to disallow a linear solution, so for simplicity we # just evaluate the ones that have the symbols of interest derivs = defaultdict(list) for der in n.atoms(Derivative): csym = der.free_symbols & symbols for c in csym: derivs[c].append(der) all_zero = True for xi in sorted(symbols, key=default_sort_key): # canonical order # if there are derivatives in this var, calculate them now if isinstance(derivs[xi], list): derivs[xi] = {der: der.doit() for der in derivs[xi]} newn = n.subs(derivs[xi]) dnewn_dxi = newn.diff(xi) # dnewn_dxi can be nonzero if it survives differentation by any # of its free symbols free = dnewn_dxi.free_symbols if dnewn_dxi and (not free or any(dnewn_dxi.diff(s) for s in free)): all_zero = False if dnewn_dxi is S.NaN: break if xi not in dnewn_dxi.free_symbols: vi = -1/dnewn_dxi*(newn.subs(xi, 0)) if dens is None: dens = _simple_dens(eq, symbols) if not any(checksol(di, {xi: vi}, minimal=True) is True for di in dens): # simplify any trivial integral irep = [(i, i.doit()) for i in vi.atoms(Integral) if i.function.is_number] # do a slight bit of simplification vi = expand_mul(vi.subs(irep)) return xi, vi if all_zero: return S.Zero, S.One if n.is_Symbol: # no solution for this symbol was found return S.Zero, S.Zero return n, d def minsolve_linear_system(system, *symbols, **flags): r""" Find a particular solution to a linear system. Explanation =========== In particular, try to find a solution with the minimal possible number of non-zero variables using a naive algorithm with exponential complexity. If ``quick=True``, a heuristic is used. """ quick = flags.get('quick', False) # Check if there are any non-zero solutions at all s0 = solve_linear_system(system, *symbols, **flags) if not s0 or all(v == 0 for v in s0.values()): return s0 if quick: # We just solve the system and try to heuristically find a nice # solution. s = solve_linear_system(system, *symbols) def update(determined, solution): delete = [] for k, v in solution.items(): solution[k] = v.subs(determined) if not solution[k].free_symbols: delete.append(k) determined[k] = solution[k] for k in delete: del solution[k] determined = {} update(determined, s) while s: # NOTE sort by default_sort_key to get deterministic result k = max((k for k in s.values()), key=lambda x: (len(x.free_symbols), default_sort_key(x))) x = max(k.free_symbols, key=default_sort_key) if len(k.free_symbols) != 1: determined[x] = S.Zero else: val = solve(k)[0] if val == 0 and all(v.subs(x, val) == 0 for v in s.values()): determined[x] = S.One else: determined[x] = val update(determined, s) return determined else: # We try to select n variables which we want to be non-zero. # All others will be assumed zero. We try to solve the modified system. # If there is a non-trivial solution, just set the free variables to # one. If we do this for increasing n, trying all combinations of # variables, we will find an optimal solution. # We speed up slightly by starting at one less than the number of # variables the quick method manages. from itertools import combinations from sympy.utilities.misc import debug N = len(symbols) bestsol = minsolve_linear_system(system, *symbols, quick=True) n0 = len([x for x in bestsol.values() if x != 0]) for n in range(n0 - 1, 1, -1): debug('minsolve: %s' % n) thissol = None for nonzeros in combinations(list(range(N)), n): subm = Matrix([system.col(i).T for i in nonzeros] + [system.col(-1).T]).T s = solve_linear_system(subm, *[symbols[i] for i in nonzeros]) if s and not all(v == 0 for v in s.values()): subs = [(symbols[v], S.One) for v in nonzeros] for k, v in s.items(): s[k] = v.subs(subs) for sym in symbols: if sym not in s: if symbols.index(sym) in nonzeros: s[sym] = S.One else: s[sym] = S.Zero thissol = s break if thissol is None: break bestsol = thissol return bestsol def solve_linear_system(system, *symbols, **flags): r""" Solve system of $N$ linear equations with $M$ variables, which means both under- and overdetermined systems are supported. Explanation =========== The possible number of solutions is zero, one, or infinite. Respectively, this procedure will return None or a dictionary with solutions. In the case of underdetermined systems, all arbitrary parameters are skipped. This may cause a situation in which an empty dictionary is returned. In that case, all symbols can be assigned arbitrary values. Input to this function is a $N\times M + 1$ matrix, which means it has to be in augmented form. If you prefer to enter $N$ equations and $M$ unknowns then use ``solve(Neqs, *Msymbols)`` instead. Note: a local copy of the matrix is made by this routine so the matrix that is passed will not be modified. The algorithm used here is fraction-free Gaussian elimination, which results, after elimination, in an upper-triangular matrix. Then solutions are found using back-substitution. This approach is more efficient and compact than the Gauss-Jordan method. Examples ======== >>> from sympy import Matrix, solve_linear_system >>> from sympy.abc import x, y Solve the following system:: x + 4 y == 2 -2 x + y == 14 >>> system = Matrix(( (1, 4, 2), (-2, 1, 14))) >>> solve_linear_system(system, x, y) {x: -6, y: 2} A degenerate system returns an empty dictionary: >>> system = Matrix(( (0,0,0), (0,0,0) )) >>> solve_linear_system(system, x, y) {} """ assert system.shape[1] == len(symbols) + 1 # This is just a wrapper for solve_lin_sys eqs = list(system * Matrix(symbols + (-1,))) eqs, ring = sympy_eqs_to_ring(eqs, symbols) sol = solve_lin_sys(eqs, ring, _raw=False) if sol is not None: sol = {sym:val for sym, val in sol.items() if sym != val} return sol def solve_undetermined_coeffs(equ, coeffs, sym, **flags): r""" Solve equation of a type $p(x; a_1, \ldots, a_k) = q(x)$ where both $p$ and $q$ are univariate polynomials that depend on $k$ parameters. Explanation =========== The result of this function is a dictionary with symbolic values of those parameters with respect to coefficients in $q$. This function accepts both equations class instances and ordinary SymPy expressions. Specification of parameters and variables is obligatory for efficiency and simplicity reasons. Examples ======== >>> from sympy import Eq >>> from sympy.abc import a, b, c, x >>> from sympy.solvers import solve_undetermined_coeffs >>> solve_undetermined_coeffs(Eq(2*a*x + a+b, x), [a, b], x) {a: 1/2, b: -1/2} >>> solve_undetermined_coeffs(Eq(a*c*x + a+b, x), [a, b], x) {a: 1/c, b: -1/c} """ if isinstance(equ, Equality): # got equation, so move all the # terms to the left hand side equ = equ.lhs - equ.rhs equ = cancel(equ).as_numer_denom()[0] system = list(collect(equ.expand(), sym, evaluate=False).values()) if not any(equ.has(sym) for equ in system): # consecutive powers in the input expressions have # been successfully collected, so solve remaining # system using Gaussian elimination algorithm return solve(system, *coeffs, **flags) else: return None # no solutions def solve_linear_system_LU(matrix, syms): """ Solves the augmented matrix system using ``LUsolve`` and returns a dictionary in which solutions are keyed to the symbols of *syms* as ordered. Explanation =========== The matrix must be invertible. Examples ======== >>> from sympy import Matrix >>> from sympy.abc import x, y, z >>> from sympy.solvers.solvers import solve_linear_system_LU >>> solve_linear_system_LU(Matrix([ ... [1, 2, 0, 1], ... [3, 2, 2, 1], ... [2, 0, 0, 1]]), [x, y, z]) {x: 1/2, y: 1/4, z: -1/2} See Also ======== LUsolve """ if matrix.rows != matrix.cols - 1: raise ValueError("Rows should be equal to columns - 1") A = matrix[:matrix.rows, :matrix.rows] b = matrix[:, matrix.cols - 1:] soln = A.LUsolve(b) solutions = {} for i in range(soln.rows): solutions[syms[i]] = soln[i, 0] return solutions def det_perm(M): """ Return the determinant of *M* by using permutations to select factors. Explanation =========== For sizes larger than 8 the number of permutations becomes prohibitively large, or if there are no symbols in the matrix, it is better to use the standard determinant routines (e.g., ``M.det()``.) See Also ======== det_minor det_quick """ args = [] s = True n = M.rows list_ = getattr(M, '_mat', None) if list_ is None: list_ = flatten(M.tolist()) for perm in generate_bell(n): fac = [] idx = 0 for j in perm: fac.append(list_[idx + j]) idx += n term = Mul(*fac) # disaster with unevaluated Mul -- takes forever for n=7 args.append(term if s else -term) s = not s return Add(*args) def det_minor(M): """ Return the ``det(M)`` computed from minors without introducing new nesting in products. See Also ======== det_perm det_quick """ n = M.rows if n == 2: return M[0, 0]*M[1, 1] - M[1, 0]*M[0, 1] else: return sum([(1, -1)[i % 2]*Add(*[M[0, i]*d for d in Add.make_args(det_minor(M.minor_submatrix(0, i)))]) if M[0, i] else S.Zero for i in range(n)]) def det_quick(M, method=None): """ Return ``det(M)`` assuming that either there are lots of zeros or the size of the matrix is small. If this assumption is not met, then the normal Matrix.det function will be used with method = ``method``. See Also ======== det_minor det_perm """ if any(i.has(Symbol) for i in M): if M.rows < 8 and all(i.has(Symbol) for i in M): return det_perm(M) return det_minor(M) else: return M.det(method=method) if method else M.det() def inv_quick(M): """Return the inverse of ``M``, assuming that either there are lots of zeros or the size of the matrix is small. """ from sympy.matrices import zeros if not all(i.is_Number for i in M): if not any(i.is_Number for i in M): det = lambda _: det_perm(_) else: det = lambda _: det_minor(_) else: return M.inv() n = M.rows d = det(M) if d == S.Zero: raise NonInvertibleMatrixError("Matrix det == 0; not invertible") ret = zeros(n) s1 = -1 for i in range(n): s = s1 = -s1 for j in range(n): di = det(M.minor_submatrix(i, j)) ret[j, i] = s*di/d s = -s return ret # these are functions that have multiple inverse values per period multi_inverses = { sin: lambda x: (asin(x), S.Pi - asin(x)), cos: lambda x: (acos(x), 2*S.Pi - acos(x)), } def _tsolve(eq, sym, **flags): """ Helper for ``_solve`` that solves a transcendental equation with respect to the given symbol. Various equations containing powers and logarithms, can be solved. There is currently no guarantee that all solutions will be returned or that a real solution will be favored over a complex one. Either a list of potential solutions will be returned or None will be returned (in the case that no method was known to get a solution for the equation). All other errors (like the inability to cast an expression as a Poly) are unhandled. Examples ======== >>> from sympy import log >>> from sympy.solvers.solvers import _tsolve as tsolve >>> from sympy.abc import x >>> tsolve(3**(2*x + 5) - 4, x) [-5/2 + log(2)/log(3), (-5*log(3)/2 + log(2) + I*pi)/log(3)] >>> tsolve(log(x) + 2*x, x) [LambertW(2)/2] """ if 'tsolve_saw' not in flags: flags['tsolve_saw'] = [] if eq in flags['tsolve_saw']: return None else: flags['tsolve_saw'].append(eq) rhs, lhs = _invert(eq, sym) if lhs == sym: return [rhs] try: if lhs.is_Add: # it's time to try factoring; powdenest is used # to try get powers in standard form for better factoring f = factor(powdenest(lhs - rhs)) if f.is_Mul: return _solve(f, sym, **flags) if rhs: f = logcombine(lhs, force=flags.get('force', True)) if f.count(log) != lhs.count(log): if isinstance(f, log): return _solve(f.args[0] - exp(rhs), sym, **flags) return _tsolve(f - rhs, sym, **flags) elif lhs.is_Pow: if lhs.exp.is_Integer: if lhs - rhs != eq: return _solve(lhs - rhs, sym, **flags) if sym not in lhs.exp.free_symbols: return _solve(lhs.base - rhs**(1/lhs.exp), sym, **flags) # _tsolve calls this with Dummy before passing the actual number in. if any(t.is_Dummy for t in rhs.free_symbols): raise NotImplementedError # _tsolve will call here again... # a ** g(x) == 0 if not rhs: # f(x)**g(x) only has solutions where f(x) == 0 and g(x) != 0 at # the same place sol_base = _solve(lhs.base, sym, **flags) return [s for s in sol_base if lhs.exp.subs(sym, s) != 0] # a ** g(x) == b if not lhs.base.has(sym): if lhs.base == 0: return _solve(lhs.exp, sym, **flags) if rhs != 0 else [] # Gets most solutions... if lhs.base == rhs.as_base_exp()[0]: # handles case when bases are equal sol = _solve(lhs.exp - rhs.as_base_exp()[1], sym, **flags) else: # handles cases when bases are not equal and exp # may or may not be equal sol = _solve(exp(log(lhs.base)*lhs.exp)-exp(log(rhs)), sym, **flags) # Check for duplicate solutions def equal(expr1, expr2): _ = Dummy() eq = checksol(expr1 - _, _, expr2) if eq is None: if nsimplify(expr1) != nsimplify(expr2): return False # they might be coincidentally the same # so check more rigorously eq = expr1.equals(expr2) return eq # Guess a rational exponent e_rat = nsimplify(log(abs(rhs))/log(abs(lhs.base))) e_rat = simplify(posify(e_rat)[0]) n, d = fraction(e_rat) if expand(lhs.base**n - rhs**d) == 0: sol = [s for s in sol if not equal(lhs.exp.subs(sym, s), e_rat)] sol.extend(_solve(lhs.exp - e_rat, sym, **flags)) return list(ordered(set(sol))) # f(x) ** g(x) == c else: sol = [] logform = lhs.exp*log(lhs.base) - log(rhs) if logform != lhs - rhs: try: sol.extend(_solve(logform, sym, **flags)) except NotImplementedError: pass # Collect possible solutions and check with substitution later. check = [] if rhs == 1: # f(x) ** g(x) = 1 -- g(x)=0 or f(x)=+-1 check.extend(_solve(lhs.exp, sym, **flags)) check.extend(_solve(lhs.base - 1, sym, **flags)) check.extend(_solve(lhs.base + 1, sym, **flags)) elif rhs.is_Rational: for d in (i for i in divisors(abs(rhs.p)) if i != 1): e, t = integer_log(rhs.p, d) if not t: continue # rhs.p != d**b for s in divisors(abs(rhs.q)): if s**e== rhs.q: r = Rational(d, s) check.extend(_solve(lhs.base - r, sym, **flags)) check.extend(_solve(lhs.base + r, sym, **flags)) check.extend(_solve(lhs.exp - e, sym, **flags)) elif rhs.is_irrational: b_l, e_l = lhs.base.as_base_exp() n, d = (e_l*lhs.exp).as_numer_denom() b, e = sqrtdenest(rhs).as_base_exp() check = [sqrtdenest(i) for i in (_solve(lhs.base - b, sym, **flags))] check.extend([sqrtdenest(i) for i in (_solve(lhs.exp - e, sym, **flags))]) if e_l*d != 1: check.extend(_solve(b_l**n - rhs**(e_l*d), sym, **flags)) for s in check: ok = checksol(eq, sym, s) if ok is None: ok = eq.subs(sym, s).equals(0) if ok: sol.append(s) return list(ordered(set(sol))) elif lhs.is_Function and len(lhs.args) == 1: if lhs.func in multi_inverses: # sin(x) = 1/3 -> x - asin(1/3) & x - (pi - asin(1/3)) soln = [] for i in multi_inverses[lhs.func](rhs): soln.extend(_solve(lhs.args[0] - i, sym, **flags)) return list(ordered(soln)) elif lhs.func == LambertW: return _solve(lhs.args[0] - rhs*exp(rhs), sym, **flags) rewrite = lhs.rewrite(exp) if rewrite != lhs: return _solve(rewrite - rhs, sym, **flags) except NotImplementedError: pass # maybe it is a lambert pattern if flags.pop('bivariate', True): # lambert forms may need some help being recognized, e.g. changing # 2**(3*x) + x**3*log(2)**3 + 3*x**2*log(2)**2 + 3*x*log(2) + 1 # to 2**(3*x) + (x*log(2) + 1)**3 g = _filtered_gens(eq.as_poly(), sym) up_or_log = set() for gi in g: if isinstance(gi, exp) or isinstance(gi, log): up_or_log.add(gi) elif gi.is_Pow: gisimp = powdenest(expand_power_exp(gi)) if gisimp.is_Pow and sym in gisimp.exp.free_symbols: up_or_log.add(gi) eq_down = expand_log(expand_power_exp(eq)).subs( dict(list(zip(up_or_log, [0]*len(up_or_log))))) eq = expand_power_exp(factor(eq_down, deep=True) + (eq - eq_down)) rhs, lhs = _invert(eq, sym) if lhs.has(sym): try: poly = lhs.as_poly() g = _filtered_gens(poly, sym) _eq = lhs - rhs sols = _solve_lambert(_eq, sym, g) # use a simplified form if it satisfies eq # and has fewer operations for n, s in enumerate(sols): ns = nsimplify(s) if ns != s and ns.count_ops() <= s.count_ops(): ok = checksol(_eq, sym, ns) if ok is None: ok = _eq.subs(sym, ns).equals(0) if ok: sols[n] = ns return sols except NotImplementedError: # maybe it's a convoluted function if len(g) == 2: try: gpu = bivariate_type(lhs - rhs, *g) if gpu is None: raise NotImplementedError g, p, u = gpu flags['bivariate'] = False inversion = _tsolve(g - u, sym, **flags) if inversion: sol = _solve(p, u, **flags) return list(ordered({i.subs(u, s) for i in inversion for s in sol})) except NotImplementedError: pass else: pass if flags.pop('force', True): flags['force'] = False pos, reps = posify(lhs - rhs) if rhs == S.ComplexInfinity: return [] for u, s in reps.items(): if s == sym: break else: u = sym if pos.has(u): try: soln = _solve(pos, u, **flags) return list(ordered([s.subs(reps) for s in soln])) except NotImplementedError: pass else: pass # here for coverage return # here for coverage # TODO: option for calculating J numerically @conserve_mpmath_dps def nsolve(*args, dict=False, **kwargs): r""" Solve a nonlinear equation system numerically: ``nsolve(f, [args,] x0, modules=['mpmath'], **kwargs)``. Explanation =========== ``f`` is a vector function of symbolic expressions representing the system. *args* are the variables. If there is only one variable, this argument can be omitted. ``x0`` is a starting vector close to a solution. Use the modules keyword to specify which modules should be used to evaluate the function and the Jacobian matrix. Make sure to use a module that supports matrices. For more information on the syntax, please see the docstring of ``lambdify``. If the keyword arguments contain ``dict=True`` (default is False) ``nsolve`` will return a list (perhaps empty) of solution mappings. This might be especially useful if you want to use ``nsolve`` as a fallback to solve since using the dict argument for both methods produces return values of consistent type structure. Please note: to keep this consistent with ``solve``, the solution will be returned in a list even though ``nsolve`` (currently at least) only finds one solution at a time. Overdetermined systems are supported. Examples ======== >>> from sympy import Symbol, nsolve >>> import mpmath >>> mpmath.mp.dps = 15 >>> x1 = Symbol('x1') >>> x2 = Symbol('x2') >>> f1 = 3 * x1**2 - 2 * x2**2 - 1 >>> f2 = x1**2 - 2 * x1 + x2**2 + 2 * x2 - 8 >>> print(nsolve((f1, f2), (x1, x2), (-1, 1))) Matrix([[-1.19287309935246], [1.27844411169911]]) For one-dimensional functions the syntax is simplified: >>> from sympy import sin, nsolve >>> from sympy.abc import x >>> nsolve(sin(x), x, 2) 3.14159265358979 >>> nsolve(sin(x), 2) 3.14159265358979 To solve with higher precision than the default, use the prec argument: >>> from sympy import cos >>> nsolve(cos(x) - x, 1) 0.739085133215161 >>> nsolve(cos(x) - x, 1, prec=50) 0.73908513321516064165531208767387340401341175890076 >>> cos(_) 0.73908513321516064165531208767387340401341175890076 To solve for complex roots of real functions, a nonreal initial point must be specified: >>> from sympy import I >>> nsolve(x**2 + 2, I) 1.4142135623731*I ``mpmath.findroot`` is used and you can find their more extensive documentation, especially concerning keyword parameters and available solvers. Note, however, that functions which are very steep near the root, the verification of the solution may fail. In this case you should use the flag ``verify=False`` and independently verify the solution. >>> from sympy import cos, cosh >>> f = cos(x)*cosh(x) - 1 >>> nsolve(f, 3.14*100) Traceback (most recent call last): ... ValueError: Could not find root within given tolerance. (1.39267e+230 > 2.1684e-19) >>> ans = nsolve(f, 3.14*100, verify=False); ans 312.588469032184 >>> f.subs(x, ans).n(2) 2.1e+121 >>> (f/f.diff(x)).subs(x, ans).n(2) 7.4e-15 One might safely skip the verification if bounds of the root are known and a bisection method is used: >>> bounds = lambda i: (3.14*i, 3.14*(i + 1)) >>> nsolve(f, bounds(100), solver='bisect', verify=False) 315.730061685774 Alternatively, a function may be better behaved when the denominator is ignored. Since this is not always the case, however, the decision of what function to use is left to the discretion of the user. >>> eq = x**2/(1 - x)/(1 - 2*x)**2 - 100 >>> nsolve(eq, 0.46) Traceback (most recent call last): ... ValueError: Could not find root within given tolerance. (10000 > 2.1684e-19) Try another starting point or tweak arguments. >>> nsolve(eq.as_numer_denom()[0], 0.46) 0.46792545969349058 """ # there are several other SymPy functions that use method= so # guard against that here if 'method' in kwargs: raise ValueError(filldedent(''' Keyword "method" should not be used in this context. When using some mpmath solvers directly, the keyword "method" is used, but when using nsolve (and findroot) the keyword to use is "solver".''')) if 'prec' in kwargs: prec = kwargs.pop('prec') import mpmath mpmath.mp.dps = prec else: prec = None # keyword argument to return result as a dictionary as_dict = dict from builtins import dict # to unhide the builtin # interpret arguments if len(args) == 3: f = args[0] fargs = args[1] x0 = args[2] if iterable(fargs) and iterable(x0): if len(x0) != len(fargs): raise TypeError('nsolve expected exactly %i guess vectors, got %i' % (len(fargs), len(x0))) elif len(args) == 2: f = args[0] fargs = None x0 = args[1] if iterable(f): raise TypeError('nsolve expected 3 arguments, got 2') elif len(args) < 2: raise TypeError('nsolve expected at least 2 arguments, got %i' % len(args)) else: raise TypeError('nsolve expected at most 3 arguments, got %i' % len(args)) modules = kwargs.get('modules', ['mpmath']) if iterable(f): f = list(f) for i, fi in enumerate(f): if isinstance(fi, Equality): f[i] = fi.lhs - fi.rhs f = Matrix(f).T if iterable(x0): x0 = list(x0) if not isinstance(f, Matrix): # assume it's a sympy expression if isinstance(f, Equality): f = f.lhs - f.rhs syms = f.free_symbols if fargs is None: fargs = syms.copy().pop() if not (len(syms) == 1 and (fargs in syms or fargs[0] in syms)): raise ValueError(filldedent(''' expected a one-dimensional and numerical function''')) # the function is much better behaved if there is no denominator # but sending the numerator is left to the user since sometimes # the function is better behaved when the denominator is present # e.g., issue 11768 f = lambdify(fargs, f, modules) x = sympify(findroot(f, x0, **kwargs)) if as_dict: return [{fargs: x}] return x if len(fargs) > f.cols: raise NotImplementedError(filldedent(''' need at least as many equations as variables''')) verbose = kwargs.get('verbose', False) if verbose: print('f(x):') print(f) # derive Jacobian J = f.jacobian(fargs) if verbose: print('J(x):') print(J) # create functions f = lambdify(fargs, f.T, modules) J = lambdify(fargs, J, modules) # solve the system numerically x = findroot(f, x0, J=J, **kwargs) if as_dict: return [dict(zip(fargs, [sympify(xi) for xi in x]))] return Matrix(x) def _invert(eq, *symbols, **kwargs): """ Return tuple (i, d) where ``i`` is independent of *symbols* and ``d`` contains symbols. Explanation =========== ``i`` and ``d`` are obtained after recursively using algebraic inversion until an uninvertible ``d`` remains. If there are no free symbols then ``d`` will be zero. Some (but not necessarily all) solutions to the expression ``i - d`` will be related to the solutions of the original expression. Examples ======== >>> from sympy.solvers.solvers import _invert as invert >>> from sympy import sqrt, cos >>> from sympy.abc import x, y >>> invert(x - 3) (3, x) >>> invert(3) (3, 0) >>> invert(2*cos(x) - 1) (1/2, cos(x)) >>> invert(sqrt(x) - 3) (3, sqrt(x)) >>> invert(sqrt(x) + y, x) (-y, sqrt(x)) >>> invert(sqrt(x) + y, y) (-sqrt(x), y) >>> invert(sqrt(x) + y, x, y) (0, sqrt(x) + y) If there is more than one symbol in a power's base and the exponent is not an Integer, then the principal root will be used for the inversion: >>> invert(sqrt(x + y) - 2) (4, x + y) >>> invert(sqrt(x + y) - 2) (4, x + y) If the exponent is an Integer, setting ``integer_power`` to True will force the principal root to be selected: >>> invert(x**2 - 4, integer_power=True) (2, x) """ eq = sympify(eq) if eq.args: # make sure we are working with flat eq eq = eq.func(*eq.args) free = eq.free_symbols if not symbols: symbols = free if not free & set(symbols): return eq, S.Zero dointpow = bool(kwargs.get('integer_power', False)) lhs = eq rhs = S.Zero while True: was = lhs while True: indep, dep = lhs.as_independent(*symbols) # dep + indep == rhs if lhs.is_Add: # this indicates we have done it all if indep.is_zero: break lhs = dep rhs -= indep # dep * indep == rhs else: # this indicates we have done it all if indep is S.One: break lhs = dep rhs /= indep # collect like-terms in symbols if lhs.is_Add: terms = {} for a in lhs.args: i, d = a.as_independent(*symbols) terms.setdefault(d, []).append(i) if any(len(v) > 1 for v in terms.values()): args = [] for d, i in terms.items(): if len(i) > 1: args.append(Add(*i)*d) else: args.append(i[0]*d) lhs = Add(*args) # if it's a two-term Add with rhs = 0 and two powers we can get the # dependent terms together, e.g. 3*f(x) + 2*g(x) -> f(x)/g(x) = -2/3 if lhs.is_Add and not rhs and len(lhs.args) == 2 and \ not lhs.is_polynomial(*symbols): a, b = ordered(lhs.args) ai, ad = a.as_independent(*symbols) bi, bd = b.as_independent(*symbols) if any(_ispow(i) for i in (ad, bd)): a_base, a_exp = ad.as_base_exp() b_base, b_exp = bd.as_base_exp() if a_base == b_base: # a = -b lhs = powsimp(powdenest(ad/bd)) rhs = -bi/ai else: rat = ad/bd _lhs = powsimp(ad/bd) if _lhs != rat: lhs = _lhs rhs = -bi/ai elif ai == -bi: if isinstance(ad, Function) and ad.func == bd.func: if len(ad.args) == len(bd.args) == 1: lhs = ad.args[0] - bd.args[0] elif len(ad.args) == len(bd.args): # should be able to solve # f(x, y) - f(2 - x, 0) == 0 -> x == 1 raise NotImplementedError( 'equal function with more than 1 argument') else: raise ValueError( 'function with different numbers of args') elif lhs.is_Mul and any(_ispow(a) for a in lhs.args): lhs = powsimp(powdenest(lhs)) if lhs.is_Function: if hasattr(lhs, 'inverse') and len(lhs.args) == 1: # -1 # f(x) = g -> x = f (g) # # /!\ inverse should not be defined if there are multiple values # for the function -- these are handled in _tsolve # rhs = lhs.inverse()(rhs) lhs = lhs.args[0] elif isinstance(lhs, atan2): y, x = lhs.args lhs = 2*atan(y/(sqrt(x**2 + y**2) + x)) elif lhs.func == rhs.func: if len(lhs.args) == len(rhs.args) == 1: lhs = lhs.args[0] rhs = rhs.args[0] elif len(lhs.args) == len(rhs.args): # should be able to solve # f(x, y) == f(2, 3) -> x == 2 # f(x, x + y) == f(2, 3) -> x == 2 raise NotImplementedError( 'equal function with more than 1 argument') else: raise ValueError( 'function with different numbers of args') if rhs and lhs.is_Pow and lhs.exp.is_Integer and lhs.exp < 0: lhs = 1/lhs rhs = 1/rhs # base**a = b -> base = b**(1/a) if # a is an Integer and dointpow=True (this gives real branch of root) # a is not an Integer and the equation is multivariate and the # base has more than 1 symbol in it # The rationale for this is that right now the multi-system solvers # doesn't try to resolve generators to see, for example, if the whole # system is written in terms of sqrt(x + y) so it will just fail, so we # do that step here. if lhs.is_Pow and ( lhs.exp.is_Integer and dointpow or not lhs.exp.is_Integer and len(symbols) > 1 and len(lhs.base.free_symbols & set(symbols)) > 1): rhs = rhs**(1/lhs.exp) lhs = lhs.base if lhs == was: break return rhs, lhs def unrad(eq, *syms, **flags): """ Remove radicals with symbolic arguments and return (eq, cov), None, or raise an error. Explanation =========== None is returned if there are no radicals to remove. NotImplementedError is raised if there are radicals and they cannot be removed or if the relationship between the original symbols and the change of variable needed to rewrite the system as a polynomial cannot be solved. Otherwise the tuple, ``(eq, cov)``, is returned where: *eq*, ``cov`` *eq* is an equation without radicals (in the symbol(s) of interest) whose solutions are a superset of the solutions to the original expression. *eq* might be rewritten in terms of a new variable; the relationship to the original variables is given by ``cov`` which is a list containing ``v`` and ``v**p - b`` where ``p`` is the power needed to clear the radical and ``b`` is the radical now expressed as a polynomial in the symbols of interest. For example, for sqrt(2 - x) the tuple would be ``(c, c**2 - 2 + x)``. The solutions of *eq* will contain solutions to the original equation (if there are any). *syms* An iterable of symbols which, if provided, will limit the focus of radical removal: only radicals with one or more of the symbols of interest will be cleared. All free symbols are used if *syms* is not set. *flags* are used internally for communication during recursive calls. Two options are also recognized: ``take``, when defined, is interpreted as a single-argument function that returns True if a given Pow should be handled. Radicals can be removed from an expression if: * All bases of the radicals are the same; a change of variables is done in this case. * If all radicals appear in one term of the expression. * There are only four terms with sqrt() factors or there are less than four terms having sqrt() factors. * There are only two terms with radicals. Examples ======== >>> from sympy.solvers.solvers import unrad >>> from sympy.abc import x >>> from sympy import sqrt, Rational, root >>> unrad(sqrt(x)*x**Rational(1, 3) + 2) (x**5 - 64, []) >>> unrad(sqrt(x) + root(x + 1, 3)) (x**3 - x**2 - 2*x - 1, []) >>> eq = sqrt(x) + root(x, 3) - 2 >>> unrad(eq) (_p**3 + _p**2 - 2, [_p, _p**6 - x]) """ uflags = dict(check=False, simplify=False) def _cov(p, e): if cov: # XXX - uncovered oldp, olde = cov if Poly(e, p).degree(p) in (1, 2): cov[:] = [p, olde.subs(oldp, _solve(e, p, **uflags)[0])] else: raise NotImplementedError else: cov[:] = [p, e] def _canonical(eq, cov): if cov: # change symbol to vanilla so no solutions are eliminated p, e = cov rep = {p: Dummy(p.name)} eq = eq.xreplace(rep) cov = [p.xreplace(rep), e.xreplace(rep)] # remove constants and powers of factors since these don't change # the location of the root; XXX should factor or factor_terms be used? eq = factor_terms(_mexpand(eq.as_numer_denom()[0], recursive=True), clear=True) if eq.is_Mul: args = [] for f in eq.args: if f.is_number: continue if f.is_Pow and _take(f, True): args.append(f.base) else: args.append(f) eq = Mul(*args) # leave as Mul for more efficient solving # make the sign canonical free = eq.free_symbols if len(free) == 1: if eq.coeff(free.pop()**degree(eq)).could_extract_minus_sign(): eq = -eq elif eq.could_extract_minus_sign(): eq = -eq return eq, cov def _Q(pow): # return leading Rational of denominator of Pow's exponent c = pow.as_base_exp()[1].as_coeff_Mul()[0] if not c.is_Rational: return S.One return c.q # define the _take method that will determine whether a term is of interest def _take(d, take_int_pow): # return True if coefficient of any factor's exponent's den is not 1 for pow in Mul.make_args(d): if not (pow.is_Symbol or pow.is_Pow): continue b, e = pow.as_base_exp() if not b.has(*syms): continue if not take_int_pow and _Q(pow) == 1: continue free = pow.free_symbols if free.intersection(syms): return True return False _take = flags.setdefault('_take', _take) cov, nwas, rpt = [flags.setdefault(k, v) for k, v in sorted(dict(cov=[], n=None, rpt=0).items())] # preconditioning eq = powdenest(factor_terms(eq, radical=True, clear=True)) if isinstance(eq, Relational): eq, d = eq, 1 else: eq, d = eq.as_numer_denom() eq = _mexpand(eq, recursive=True) if eq.is_number: return syms = set(syms) or eq.free_symbols poly = eq.as_poly() gens = [g for g in poly.gens if _take(g, True)] if not gens: return # check for trivial case # - already a polynomial in integer powers if all(_Q(g) == 1 for g in gens): if (len(gens) == len(poly.gens) and d!=1): return eq, [] else: return # - an exponent has a symbol of interest (don't handle) if any(g.as_base_exp()[1].has(*syms) for g in gens): return def _rads_bases_lcm(poly): # if all the bases are the same or all the radicals are in one # term, `lcm` will be the lcm of the denominators of the # exponents of the radicals lcm = 1 rads = set() bases = set() for g in poly.gens: if not _take(g, False): continue q = _Q(g) if q != 1: rads.add(g) lcm = ilcm(lcm, q) bases.add(g.base) return rads, bases, lcm rads, bases, lcm = _rads_bases_lcm(poly) if not rads: return covsym = Dummy('p', nonnegative=True) # only keep in syms symbols that actually appear in radicals; # and update gens newsyms = set() for r in rads: newsyms.update(syms & r.free_symbols) if newsyms != syms: syms = newsyms gens = [g for g in gens if g.free_symbols & syms] # get terms together that have common generators drad = dict(list(zip(rads, list(range(len(rads)))))) rterms = {(): []} args = Add.make_args(poly.as_expr()) for t in args: if _take(t, False): common = set(t.as_poly().gens).intersection(rads) key = tuple(sorted([drad[i] for i in common])) else: key = () rterms.setdefault(key, []).append(t) others = Add(*rterms.pop(())) rterms = [Add(*rterms[k]) for k in rterms.keys()] # the output will depend on the order terms are processed, so # make it canonical quickly rterms = list(reversed(list(ordered(rterms)))) ok = False # we don't have a solution yet depth = sqrt_depth(eq) if len(rterms) == 1 and not (rterms[0].is_Add and lcm > 2): eq = rterms[0]**lcm - ((-others)**lcm) ok = True else: if len(rterms) == 1 and rterms[0].is_Add: rterms = list(rterms[0].args) if len(bases) == 1: b = bases.pop() if len(syms) > 1: free = b.free_symbols x = {g for g in gens if g.is_Symbol} & free if not x: x = free x = ordered(x) else: x = syms x = list(x)[0] try: inv = _solve(covsym**lcm - b, x, **uflags) if not inv: raise NotImplementedError eq = poly.as_expr().subs(b, covsym**lcm).subs(x, inv[0]) _cov(covsym, covsym**lcm - b) return _canonical(eq, cov) except NotImplementedError: pass else: # no longer consider integer powers as generators gens = [g for g in gens if _Q(g) != 1] if len(rterms) == 2: if not others: eq = rterms[0]**lcm - (-rterms[1])**lcm ok = True elif not log(lcm, 2).is_Integer: # the lcm-is-power-of-two case is handled below r0, r1 = rterms if flags.get('_reverse', False): r1, r0 = r0, r1 i0 = _rads0, _bases0, lcm0 = _rads_bases_lcm(r0.as_poly()) i1 = _rads1, _bases1, lcm1 = _rads_bases_lcm(r1.as_poly()) for reverse in range(2): if reverse: i0, i1 = i1, i0 r0, r1 = r1, r0 _rads1, _, lcm1 = i1 _rads1 = Mul(*_rads1) t1 = _rads1**lcm1 c = covsym**lcm1 - t1 for x in syms: try: sol = _solve(c, x, **uflags) if not sol: raise NotImplementedError neweq = r0.subs(x, sol[0]) + covsym*r1/_rads1 + \ others tmp = unrad(neweq, covsym) if tmp: eq, newcov = tmp if newcov: newp, newc = newcov _cov(newp, c.subs(covsym, _solve(newc, covsym, **uflags)[0])) else: _cov(covsym, c) else: eq = neweq _cov(covsym, c) ok = True break except NotImplementedError: if reverse: raise NotImplementedError( 'no successful change of variable found') else: pass if ok: break elif len(rterms) == 3: # two cube roots and another with order less than 5 # (so an analytical solution can be found) or a base # that matches one of the cube root bases info = [_rads_bases_lcm(i.as_poly()) for i in rterms] RAD = 0 BASES = 1 LCM = 2 if info[0][LCM] != 3: info.append(info.pop(0)) rterms.append(rterms.pop(0)) elif info[1][LCM] != 3: info.append(info.pop(1)) rterms.append(rterms.pop(1)) if info[0][LCM] == info[1][LCM] == 3: if info[1][BASES] != info[2][BASES]: info[0], info[1] = info[1], info[0] rterms[0], rterms[1] = rterms[1], rterms[0] if info[1][BASES] == info[2][BASES]: eq = rterms[0]**3 + (rterms[1] + rterms[2] + others)**3 ok = True elif info[2][LCM] < 5: # a*root(A, 3) + b*root(B, 3) + others = c a, b, c, d, A, B = [Dummy(i) for i in 'abcdAB'] # zz represents the unraded expression into which the # specifics for this case are substituted zz = (c - d)*(A**3*a**9 + 3*A**2*B*a**6*b**3 - 3*A**2*a**6*c**3 + 9*A**2*a**6*c**2*d - 9*A**2*a**6*c*d**2 + 3*A**2*a**6*d**3 + 3*A*B**2*a**3*b**6 + 21*A*B*a**3*b**3*c**3 - 63*A*B*a**3*b**3*c**2*d + 63*A*B*a**3*b**3*c*d**2 - 21*A*B*a**3*b**3*d**3 + 3*A*a**3*c**6 - 18*A*a**3*c**5*d + 45*A*a**3*c**4*d**2 - 60*A*a**3*c**3*d**3 + 45*A*a**3*c**2*d**4 - 18*A*a**3*c*d**5 + 3*A*a**3*d**6 + B**3*b**9 - 3*B**2*b**6*c**3 + 9*B**2*b**6*c**2*d - 9*B**2*b**6*c*d**2 + 3*B**2*b**6*d**3 + 3*B*b**3*c**6 - 18*B*b**3*c**5*d + 45*B*b**3*c**4*d**2 - 60*B*b**3*c**3*d**3 + 45*B*b**3*c**2*d**4 - 18*B*b**3*c*d**5 + 3*B*b**3*d**6 - c**9 + 9*c**8*d - 36*c**7*d**2 + 84*c**6*d**3 - 126*c**5*d**4 + 126*c**4*d**5 - 84*c**3*d**6 + 36*c**2*d**7 - 9*c*d**8 + d**9) def _t(i): b = Mul(*info[i][RAD]) return cancel(rterms[i]/b), Mul(*info[i][BASES]) aa, AA = _t(0) bb, BB = _t(1) cc = -rterms[2] dd = others eq = zz.xreplace(dict(zip( (a, A, b, B, c, d), (aa, AA, bb, BB, cc, dd)))) ok = True # handle power-of-2 cases if not ok: if log(lcm, 2).is_Integer and (not others and len(rterms) == 4 or len(rterms) < 4): def _norm2(a, b): return a**2 + b**2 + 2*a*b if len(rterms) == 4: # (r0+r1)**2 - (r2+r3)**2 r0, r1, r2, r3 = rterms eq = _norm2(r0, r1) - _norm2(r2, r3) ok = True elif len(rterms) == 3: # (r1+r2)**2 - (r0+others)**2 r0, r1, r2 = rterms eq = _norm2(r1, r2) - _norm2(r0, others) ok = True elif len(rterms) == 2: # r0**2 - (r1+others)**2 r0, r1 = rterms eq = r0**2 - _norm2(r1, others) ok = True new_depth = sqrt_depth(eq) if ok else depth rpt += 1 # XXX how many repeats with others unchanging is enough? if not ok or ( nwas is not None and len(rterms) == nwas and new_depth is not None and new_depth == depth and rpt > 3): raise NotImplementedError('Cannot remove all radicals') flags.update(dict(cov=cov, n=len(rterms), rpt=rpt)) neq = unrad(eq, *syms, **flags) if neq: eq, cov = neq eq, cov = _canonical(eq, cov) return eq, cov from sympy.solvers.bivariate import ( bivariate_type, _solve_lambert, _filtered_gens)

125b7cab1477fa0901681cd031d9cd8b30882465b3e85a56ba9585313f42c370

from sympy import Order, S, log, limit, lcm_list, im, re, Dummy from sympy.core import Add, Mul, Pow from sympy.core.basic import Basic from sympy.core.compatibility import iterable from sympy.core.expr import AtomicExpr, Expr from sympy.core.function import expand_mul from sympy.core.numbers import _sympifyit, oo from sympy.core.relational import is_le, is_lt, is_ge, is_gt from sympy.core.sympify import _sympify from sympy.functions.elementary.miscellaneous import Min, Max from sympy.logic.boolalg import And from sympy.sets.sets import (Interval, Intersection, FiniteSet, Union, Complement, EmptySet) from sympy.sets.fancysets import ImageSet from sympy.solvers.inequalities import solve_univariate_inequality from sympy.utilities import filldedent from sympy.multipledispatch import dispatch def continuous_domain(f, symbol, domain): """ Returns the intervals in the given domain for which the function is continuous. This method is limited by the ability to determine the various singularities and discontinuities of the given function. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the intervals are to be determined. domain : Interval The domain over which the continuity of the symbol has to be checked. Examples ======== >>> from sympy import Symbol, S, tan, log, pi, sqrt >>> from sympy.sets import Interval >>> from sympy.calculus.util import continuous_domain >>> x = Symbol('x') >>> continuous_domain(1/x, x, S.Reals) Union(Interval.open(-oo, 0), Interval.open(0, oo)) >>> continuous_domain(tan(x), x, Interval(0, pi)) Union(Interval.Ropen(0, pi/2), Interval.Lopen(pi/2, pi)) >>> continuous_domain(sqrt(x - 2), x, Interval(-5, 5)) Interval(2, 5) >>> continuous_domain(log(2*x - 1), x, S.Reals) Interval.open(1/2, oo) Returns ======= Interval Union of all intervals where the function is continuous. Raises ====== NotImplementedError If the method to determine continuity of such a function has not yet been developed. """ from sympy.solvers.inequalities import solve_univariate_inequality from sympy.solvers.solveset import _has_rational_power from sympy.calculus.singularities import singularities if domain.is_subset(S.Reals): constrained_interval = domain for atom in f.atoms(Pow): predicate, denomin = _has_rational_power(atom, symbol) if predicate and denomin == 2: constraint = solve_univariate_inequality(atom.base >= 0, symbol).as_set() constrained_interval = Intersection(constraint, constrained_interval) for atom in f.atoms(log): constraint = solve_univariate_inequality(atom.args[0] > 0, symbol).as_set() constrained_interval = Intersection(constraint, constrained_interval) return constrained_interval - singularities(f, symbol, domain) def function_range(f, symbol, domain): """ Finds the range of a function in a given domain. This method is limited by the ability to determine the singularities and determine limits. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the range of function is to be determined. domain : Interval The domain under which the range of the function has to be found. Examples ======== >>> from sympy import Symbol, S, exp, log, pi, sqrt, sin, tan >>> from sympy.sets import Interval >>> from sympy.calculus.util import function_range >>> x = Symbol('x') >>> function_range(sin(x), x, Interval(0, 2*pi)) Interval(-1, 1) >>> function_range(tan(x), x, Interval(-pi/2, pi/2)) Interval(-oo, oo) >>> function_range(1/x, x, S.Reals) Union(Interval.open(-oo, 0), Interval.open(0, oo)) >>> function_range(exp(x), x, S.Reals) Interval.open(0, oo) >>> function_range(log(x), x, S.Reals) Interval(-oo, oo) >>> function_range(sqrt(x), x , Interval(-5, 9)) Interval(0, 3) Returns ======= Interval Union of all ranges for all intervals under domain where function is continuous. Raises ====== NotImplementedError If any of the intervals, in the given domain, for which function is continuous are not finite or real, OR if the critical points of the function on the domain can't be found. """ from sympy.solvers.solveset import solveset if isinstance(domain, EmptySet): return S.EmptySet period = periodicity(f, symbol) if period == S.Zero: # the expression is constant wrt symbol return FiniteSet(f.expand()) if period is not None: if isinstance(domain, Interval): if (domain.inf - domain.sup).is_infinite: domain = Interval(0, period) elif isinstance(domain, Union): for sub_dom in domain.args: if isinstance(sub_dom, Interval) and \ ((sub_dom.inf - sub_dom.sup).is_infinite): domain = Interval(0, period) intervals = continuous_domain(f, symbol, domain) range_int = S.EmptySet if isinstance(intervals,(Interval, FiniteSet)): interval_iter = (intervals,) elif isinstance(intervals, Union): interval_iter = intervals.args else: raise NotImplementedError(filldedent(''' Unable to find range for the given domain. ''')) for interval in interval_iter: if isinstance(interval, FiniteSet): for singleton in interval: if singleton in domain: range_int += FiniteSet(f.subs(symbol, singleton)) elif isinstance(interval, Interval): vals = S.EmptySet critical_points = S.EmptySet critical_values = S.EmptySet bounds = ((interval.left_open, interval.inf, '+'), (interval.right_open, interval.sup, '-')) for is_open, limit_point, direction in bounds: if is_open: critical_values += FiniteSet(limit(f, symbol, limit_point, direction)) vals += critical_values else: vals += FiniteSet(f.subs(symbol, limit_point)) solution = solveset(f.diff(symbol), symbol, interval) if not iterable(solution): raise NotImplementedError( 'Unable to find critical points for {}'.format(f)) if isinstance(solution, ImageSet): raise NotImplementedError( 'Infinite number of critical points for {}'.format(f)) critical_points += solution for critical_point in critical_points: vals += FiniteSet(f.subs(symbol, critical_point)) left_open, right_open = False, False if critical_values is not S.EmptySet: if critical_values.inf == vals.inf: left_open = True if critical_values.sup == vals.sup: right_open = True range_int += Interval(vals.inf, vals.sup, left_open, right_open) else: raise NotImplementedError(filldedent(''' Unable to find range for the given domain. ''')) return range_int def not_empty_in(finset_intersection, *syms): """ Finds the domain of the functions in `finite_set` in which the `finite_set` is not-empty Parameters ========== finset_intersection : The unevaluated intersection of FiniteSet containing real-valued functions with Union of Sets syms : Tuple of symbols Symbol for which domain is to be found Raises ====== NotImplementedError The algorithms to find the non-emptiness of the given FiniteSet are not yet implemented. ValueError The input is not valid. RuntimeError It is a bug, please report it to the github issue tracker (https://github.com/sympy/sympy/issues). Examples ======== >>> from sympy import FiniteSet, Interval, not_empty_in, oo >>> from sympy.abc import x >>> not_empty_in(FiniteSet(x/2).intersect(Interval(0, 1)), x) Interval(0, 2) >>> not_empty_in(FiniteSet(x, x**2).intersect(Interval(1, 2)), x) Union(Interval(1, 2), Interval(-sqrt(2), -1)) >>> not_empty_in(FiniteSet(x**2/(x + 2)).intersect(Interval(1, oo)), x) Union(Interval.Lopen(-2, -1), Interval(2, oo)) """ # TODO: handle piecewise defined functions # TODO: handle transcendental functions # TODO: handle multivariate functions if len(syms) == 0: raise ValueError("One or more symbols must be given in syms.") if finset_intersection is S.EmptySet: return S.EmptySet if isinstance(finset_intersection, Union): elm_in_sets = finset_intersection.args[0] return Union(not_empty_in(finset_intersection.args[1], *syms), elm_in_sets) if isinstance(finset_intersection, FiniteSet): finite_set = finset_intersection _sets = S.Reals else: finite_set = finset_intersection.args[1] _sets = finset_intersection.args[0] if not isinstance(finite_set, FiniteSet): raise ValueError('A FiniteSet must be given, not %s: %s' % (type(finite_set), finite_set)) if len(syms) == 1: symb = syms[0] else: raise NotImplementedError('more than one variables %s not handled' % (syms,)) def elm_domain(expr, intrvl): """ Finds the domain of an expression in any given interval """ from sympy.solvers.solveset import solveset _start = intrvl.start _end = intrvl.end _singularities = solveset(expr.as_numer_denom()[1], symb, domain=S.Reals) if intrvl.right_open: if _end is S.Infinity: _domain1 = S.Reals else: _domain1 = solveset(expr < _end, symb, domain=S.Reals) else: _domain1 = solveset(expr <= _end, symb, domain=S.Reals) if intrvl.left_open: if _start is S.NegativeInfinity: _domain2 = S.Reals else: _domain2 = solveset(expr > _start, symb, domain=S.Reals) else: _domain2 = solveset(expr >= _start, symb, domain=S.Reals) # domain in the interval expr_with_sing = Intersection(_domain1, _domain2) expr_domain = Complement(expr_with_sing, _singularities) return expr_domain if isinstance(_sets, Interval): return Union(*[elm_domain(element, _sets) for element in finite_set]) if isinstance(_sets, Union): _domain = S.EmptySet for intrvl in _sets.args: _domain_element = Union(*[elm_domain(element, intrvl) for element in finite_set]) _domain = Union(_domain, _domain_element) return _domain def periodicity(f, symbol, check=False): """ Tests the given function for periodicity in the given symbol. Parameters ========== f : Expr. The concerned function. symbol : Symbol The variable for which the period is to be determined. check : Boolean, optional The flag to verify whether the value being returned is a period or not. Returns ======= period The period of the function is returned. `None` is returned when the function is aperiodic or has a complex period. The value of `0` is returned as the period of a constant function. Raises ====== NotImplementedError The value of the period computed cannot be verified. Notes ===== Currently, we do not support functions with a complex period. The period of functions having complex periodic values such as `exp`, `sinh` is evaluated to `None`. The value returned might not be the "fundamental" period of the given function i.e. it may not be the smallest periodic value of the function. The verification of the period through the `check` flag is not reliable due to internal simplification of the given expression. Hence, it is set to `False` by default. Examples ======== >>> from sympy import Symbol, sin, cos, tan, exp >>> from sympy.calculus.util import periodicity >>> x = Symbol('x') >>> f = sin(x) + sin(2*x) + sin(3*x) >>> periodicity(f, x) 2*pi >>> periodicity(sin(x)*cos(x), x) pi >>> periodicity(exp(tan(2*x) - 1), x) pi/2 >>> periodicity(sin(4*x)**cos(2*x), x) pi >>> periodicity(exp(x), x) """ from sympy.core.mod import Mod from sympy.core.relational import Relational from sympy.functions.elementary.exponential import exp from sympy.functions.elementary.complexes import Abs from sympy.functions.elementary.trigonometric import ( TrigonometricFunction, sin, cos, csc, sec) from sympy.simplify.simplify import simplify from sympy.solvers.decompogen import decompogen from sympy.polys.polytools import degree temp = Dummy('x', real=True) f = f.subs(symbol, temp) symbol = temp def _check(orig_f, period): '''Return the checked period or raise an error.''' new_f = orig_f.subs(symbol, symbol + period) if new_f.equals(orig_f): return period else: raise NotImplementedError(filldedent(''' The period of the given function cannot be verified. When `%s` was replaced with `%s + %s` in `%s`, the result was `%s` which was not recognized as being the same as the original function. So either the period was wrong or the two forms were not recognized as being equal. Set check=False to obtain the value.''' % (symbol, symbol, period, orig_f, new_f))) orig_f = f period = None if isinstance(f, Relational): f = f.lhs - f.rhs f = simplify(f) if symbol not in f.free_symbols: return S.Zero if isinstance(f, TrigonometricFunction): try: period = f.period(symbol) except NotImplementedError: pass if isinstance(f, Abs): arg = f.args[0] if isinstance(arg, (sec, csc, cos)): # all but tan and cot might have a # a period that is half as large # so recast as sin arg = sin(arg.args[0]) period = periodicity(arg, symbol) if period is not None and isinstance(arg, sin): # the argument of Abs was a trigonometric other than # cot or tan; test to see if the half-period # is valid. Abs(arg) has behaviour equivalent to # orig_f, so use that for test: orig_f = Abs(arg) try: return _check(orig_f, period/2) except NotImplementedError as err: if check: raise NotImplementedError(err) # else let new orig_f and period be # checked below if isinstance(f, exp): f = f.func(expand_mul(f.args[0])) if im(f) != 0: period_real = periodicity(re(f), symbol) period_imag = periodicity(im(f), symbol) if period_real is not None and period_imag is not None: period = lcim([period_real, period_imag]) if f.is_Pow: base, expo = f.args base_has_sym = base.has(symbol) expo_has_sym = expo.has(symbol) if base_has_sym and not expo_has_sym: period = periodicity(base, symbol) elif expo_has_sym and not base_has_sym: period = periodicity(expo, symbol) else: period = _periodicity(f.args, symbol) elif f.is_Mul: coeff, g = f.as_independent(symbol, as_Add=False) if isinstance(g, TrigonometricFunction) or coeff is not S.One: period = periodicity(g, symbol) else: period = _periodicity(g.args, symbol) elif f.is_Add: k, g = f.as_independent(symbol) if k is not S.Zero: return periodicity(g, symbol) period = _periodicity(g.args, symbol) elif isinstance(f, Mod): a, n = f.args if a == symbol: period = n elif isinstance(a, TrigonometricFunction): period = periodicity(a, symbol) #check if 'f' is linear in 'symbol' elif (a.is_polynomial(symbol) and degree(a, symbol) == 1 and symbol not in n.free_symbols): period = Abs(n / a.diff(symbol)) elif period is None: from sympy.solvers.decompogen import compogen g_s = decompogen(f, symbol) num_of_gs = len(g_s) if num_of_gs > 1: for index, g in enumerate(reversed(g_s)): start_index = num_of_gs - 1 - index g = compogen(g_s[start_index:], symbol) if g != orig_f and g != f: # Fix for issue 12620 period = periodicity(g, symbol) if period is not None: break if period is not None: if check: return _check(orig_f, period) return period return None def _periodicity(args, symbol): """ Helper for `periodicity` to find the period of a list of simpler functions. It uses the `lcim` method to find the least common period of all the functions. Parameters ========== args : Tuple of Symbol All the symbols present in a function. symbol : Symbol The symbol over which the function is to be evaluated. Returns ======= period The least common period of the function for all the symbols of the function. None if for at least one of the symbols the function is aperiodic """ periods = [] for f in args: period = periodicity(f, symbol) if period is None: return None if period is not S.Zero: periods.append(period) if len(periods) > 1: return lcim(periods) if periods: return periods[0] def lcim(numbers): """Returns the least common integral multiple of a list of numbers. The numbers can be rational or irrational or a mixture of both. `None` is returned for incommensurable numbers. Parameters ========== numbers : list Numbers (rational and/or irrational) for which lcim is to be found. Returns ======= number lcim if it exists, otherwise `None` for incommensurable numbers. Examples ======== >>> from sympy import S, pi >>> from sympy.calculus.util import lcim >>> lcim([S(1)/2, S(3)/4, S(5)/6]) 15/2 >>> lcim([2*pi, 3*pi, pi, pi/2]) 6*pi >>> lcim([S(1), 2*pi]) """ result = None if all(num.is_irrational for num in numbers): factorized_nums = list(map(lambda num: num.factor(), numbers)) factors_num = list( map(lambda num: num.as_coeff_Mul(), factorized_nums)) term = factors_num[0][1] if all(factor == term for coeff, factor in factors_num): common_term = term coeffs = [coeff for coeff, factor in factors_num] result = lcm_list(coeffs) * common_term elif all(num.is_rational for num in numbers): result = lcm_list(numbers) else: pass return result def is_convex(f, *syms, domain=S.Reals): """Determines the convexity of the function passed in the argument. Parameters ========== f : Expr The concerned function. syms : Tuple of symbols The variables with respect to which the convexity is to be determined. domain : Interval, optional The domain over which the convexity of the function has to be checked. If unspecified, S.Reals will be the default domain. Returns ======= Boolean The method returns `True` if the function is convex otherwise it returns `False`. Raises ====== NotImplementedError The check for the convexity of multivariate functions is not implemented yet. Notes ===== To determine concavity of a function pass `-f` as the concerned function. To determine logarithmic convexity of a function pass log(f) as concerned function. To determine logartihmic concavity of a function pass -log(f) as concerned function. Currently, convexity check of multivariate functions is not handled. Examples ======== >>> from sympy import symbols, exp, oo, Interval >>> from sympy.calculus.util import is_convex >>> x = symbols('x') >>> is_convex(exp(x), x) True >>> is_convex(x**3, x, domain = Interval(-1, oo)) False References ========== .. [1] https://en.wikipedia.org/wiki/Convex_function .. [2] http://www.ifp.illinois.edu/~angelia/L3_convfunc.pdf .. [3] https://en.wikipedia.org/wiki/Logarithmically_convex_function .. [4] https://en.wikipedia.org/wiki/Logarithmically_concave_function .. [5] https://en.wikipedia.org/wiki/Concave_function """ if len(syms) > 1: raise NotImplementedError( "The check for the convexity of multivariate functions is not implemented yet.") f = _sympify(f) var = syms[0] condition = f.diff(var, 2) < 0 if solve_univariate_inequality(condition, var, False, domain): return False return True def stationary_points(f, symbol, domain=S.Reals): """ Returns the stationary points of a function (where derivative of the function is 0) in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for which the stationary points are to be determined. domain : Interval The domain over which the stationary points have to be checked. If unspecified, S.Reals will be the default domain. Returns ======= Set A set of stationary points for the function. If there are no stationary point, an EmptySet is returned. Examples ======== >>> from sympy import Symbol, S, sin, pi, pprint, stationary_points >>> from sympy.sets import Interval >>> x = Symbol('x') >>> stationary_points(1/x, x, S.Reals) EmptySet >>> pprint(stationary_points(sin(x), x), use_unicode=False) pi 3*pi {2*n*pi + -- | n in Integers} U {2*n*pi + ---- | n in Integers} 2 2 >>> stationary_points(sin(x),x, Interval(0, 4*pi)) FiniteSet(pi/2, 3*pi/2, 5*pi/2, 7*pi/2) """ from sympy import solveset, diff if isinstance(domain, EmptySet): return S.EmptySet domain = continuous_domain(f, symbol, domain) set = solveset(diff(f, symbol), symbol, domain) return set def maximum(f, symbol, domain=S.Reals): """ Returns the maximum value of a function in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for maximum value needs to be determined. domain : Interval The domain over which the maximum have to be checked. If unspecified, then Global maximum is returned. Returns ======= number Maximum value of the function in given domain. Examples ======== >>> from sympy import Symbol, S, sin, cos, pi, maximum >>> from sympy.sets import Interval >>> x = Symbol('x') >>> f = -x**2 + 2*x + 5 >>> maximum(f, x, S.Reals) 6 >>> maximum(sin(x), x, Interval(-pi, pi/4)) sqrt(2)/2 >>> maximum(sin(x)*cos(x), x) 1/2 """ from sympy import Symbol if isinstance(symbol, Symbol): if isinstance(domain, EmptySet): raise ValueError("Maximum value not defined for empty domain.") return function_range(f, symbol, domain).sup else: raise ValueError("%s is not a valid symbol." % symbol) def minimum(f, symbol, domain=S.Reals): """ Returns the minimum value of a function in the given domain. Parameters ========== f : Expr The concerned function. symbol : Symbol The variable for minimum value needs to be determined. domain : Interval The domain over which the minimum have to be checked. If unspecified, then Global minimum is returned. Returns ======= number Minimum value of the function in the given domain. Examples ======== >>> from sympy import Symbol, S, sin, cos, minimum >>> from sympy.sets import Interval >>> x = Symbol('x') >>> f = x**2 + 2*x + 5 >>> minimum(f, x, S.Reals) 4 >>> minimum(sin(x), x, Interval(2, 3)) sin(3) >>> minimum(sin(x)*cos(x), x) -1/2 """ from sympy import Symbol if isinstance(symbol, Symbol): if isinstance(domain, EmptySet): raise ValueError("Minimum value not defined for empty domain.") return function_range(f, symbol, domain).inf else: raise ValueError("%s is not a valid symbol." % symbol) class AccumulationBounds(AtomicExpr): r""" # Note AccumulationBounds has an alias: AccumBounds AccumulationBounds represent an interval `[a, b]`, which is always closed at the ends. Here `a` and `b` can be any value from extended real numbers. The intended meaning of AccummulationBounds is to give an approximate location of the accumulation points of a real function at a limit point. Let `a` and `b` be reals such that a <= b. `\left\langle a, b\right\rangle = \{x \in \mathbb{R} \mid a \le x \le b\}` `\left\langle -\infty, b\right\rangle = \{x \in \mathbb{R} \mid x \le b\} \cup \{-\infty, \infty\}` `\left\langle a, \infty \right\rangle = \{x \in \mathbb{R} \mid a \le x\} \cup \{-\infty, \infty\}` `\left\langle -\infty, \infty \right\rangle = \mathbb{R} \cup \{-\infty, \infty\}` `oo` and `-oo` are added to the second and third definition respectively, since if either `-oo` or `oo` is an argument, then the other one should be included (though not as an end point). This is forced, since we have, for example, `1/AccumBounds(0, 1) = AccumBounds(1, oo)`, and the limit at `0` is not one-sided. As x tends to `0-`, then `1/x -> -oo`, so `-oo` should be interpreted as belonging to `AccumBounds(1, oo)` though it need not appear explicitly. In many cases it suffices to know that the limit set is bounded. However, in some other cases more exact information could be useful. For example, all accumulation values of cos(x) + 1 are non-negative. (AccumBounds(-1, 1) + 1 = AccumBounds(0, 2)) A AccumulationBounds object is defined to be real AccumulationBounds, if its end points are finite reals. Let `X`, `Y` be real AccumulationBounds, then their sum, difference, product are defined to be the following sets: `X + Y = \{ x+y \mid x \in X \cap y \in Y\}` `X - Y = \{ x-y \mid x \in X \cap y \in Y\}` `X * Y = \{ x*y \mid x \in X \cap y \in Y\}` There is, however, no consensus on Interval division. `X / Y = \{ z \mid \exists x \in X, y \in Y \mid y \neq 0, z = x/y\}` Note: According to this definition the quotient of two AccumulationBounds may not be a AccumulationBounds object but rather a union of AccumulationBounds. Note ==== The main focus in the interval arithmetic is on the simplest way to calculate upper and lower endpoints for the range of values of a function in one or more variables. These barriers are not necessarily the supremum or infimum, since the precise calculation of those values can be difficult or impossible. Examples ======== >>> from sympy import AccumBounds, sin, exp, log, pi, E, S, oo >>> from sympy.abc import x >>> AccumBounds(0, 1) + AccumBounds(1, 2) AccumBounds(1, 3) >>> AccumBounds(0, 1) - AccumBounds(0, 2) AccumBounds(-2, 1) >>> AccumBounds(-2, 3)*AccumBounds(-1, 1) AccumBounds(-3, 3) >>> AccumBounds(1, 2)*AccumBounds(3, 5) AccumBounds(3, 10) The exponentiation of AccumulationBounds is defined as follows: If 0 does not belong to `X` or `n > 0` then `X^n = \{ x^n \mid x \in X\}` otherwise `X^n = \{ x^n \mid x \neq 0, x \in X\} \cup \{-\infty, \infty\}` Here for fractional `n`, the part of `X` resulting in a complex AccumulationBounds object is neglected. >>> AccumBounds(-1, 4)**(S(1)/2) AccumBounds(0, 2) >>> AccumBounds(1, 2)**2 AccumBounds(1, 4) >>> AccumBounds(-1, oo)**(-1) AccumBounds(-oo, oo) Note: `<a, b>^2` is not same as `<a, b>*<a, b>` >>> AccumBounds(-1, 1)**2 AccumBounds(0, 1) >>> AccumBounds(1, 3) < 4 True >>> AccumBounds(1, 3) < -1 False Some elementary functions can also take AccumulationBounds as input. A function `f` evaluated for some real AccumulationBounds `<a, b>` is defined as `f(\left\langle a, b\right\rangle) = \{ f(x) \mid a \le x \le b \}` >>> sin(AccumBounds(pi/6, pi/3)) AccumBounds(1/2, sqrt(3)/2) >>> exp(AccumBounds(0, 1)) AccumBounds(1, E) >>> log(AccumBounds(1, E)) AccumBounds(0, 1) Some symbol in an expression can be substituted for a AccumulationBounds object. But it doesn't necessarily evaluate the AccumulationBounds for that expression. Same expression can be evaluated to different values depending upon the form it is used for substitution. For example: >>> (x**2 + 2*x + 1).subs(x, AccumBounds(-1, 1)) AccumBounds(-1, 4) >>> ((x + 1)**2).subs(x, AccumBounds(-1, 1)) AccumBounds(0, 4) References ========== .. [1] https://en.wikipedia.org/wiki/Interval_arithmetic .. [2] http://fab.cba.mit.edu/classes/S62.12/docs/Hickey_interval.pdf Notes ===== Do not use ``AccumulationBounds`` for floating point interval arithmetic calculations, use ``mpmath.iv`` instead. """ is_extended_real = True def __new__(cls, min, max): min = _sympify(min) max = _sympify(max) # Only allow real intervals (use symbols with 'is_extended_real=True'). if not min.is_extended_real or not max.is_extended_real: raise ValueError("Only real AccumulationBounds are supported") # Make sure that the created AccumBounds object will be valid. if max.is_comparable and min.is_comparable: if max < min: raise ValueError( "Lower limit should be smaller than upper limit") if max == min: return max return Basic.__new__(cls, min, max) # setting the operation priority _op_priority = 11.0 def _eval_is_real(self): if self.min.is_real and self.max.is_real: return True @property def min(self): """ Returns the minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).min 1 """ return self.args[0] @property def max(self): """ Returns the maximum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).max 3 """ return self.args[1] @property def delta(self): """ Returns the difference of maximum possible value attained by AccumulationBounds object and minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).delta 2 """ return self.max - self.min @property def mid(self): """ Returns the mean of maximum possible value attained by AccumulationBounds object and minimum possible value attained by AccumulationBounds object. Examples ======== >>> from sympy import AccumBounds >>> AccumBounds(1, 3).mid 2 """ return (self.min + self.max) / 2 @_sympifyit('other', NotImplemented) def _eval_power(self, other): return self.__pow__(other) @_sympifyit('other', NotImplemented) def __add__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds( Add(self.min, other.min), Add(self.max, other.max)) if other is S.Infinity and self.min is S.NegativeInfinity or \ other is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif other.is_extended_real: if self.min is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif self.min is S.NegativeInfinity: return AccumBounds(-oo, self.max + other) elif self.max is S.Infinity: return AccumBounds(self.min + other, oo) else: return AccumBounds(Add(self.min, other), Add(self.max, other)) return Add(self, other, evaluate=False) return NotImplemented __radd__ = __add__ def __neg__(self): return AccumBounds(-self.max, -self.min) @_sympifyit('other', NotImplemented) def __sub__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds( Add(self.min, -other.max), Add(self.max, -other.min)) if other is S.NegativeInfinity and self.min is S.NegativeInfinity or \ other is S.Infinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif other.is_extended_real: if self.min is S.NegativeInfinity and self.max is S.Infinity: return AccumBounds(-oo, oo) elif self.min is S.NegativeInfinity: return AccumBounds(-oo, self.max - other) elif self.max is S.Infinity: return AccumBounds(self.min - other, oo) else: return AccumBounds( Add(self.min, -other), Add(self.max, -other)) return Add(self, -other, evaluate=False) return NotImplemented @_sympifyit('other', NotImplemented) def __rsub__(self, other): return self.__neg__() + other @_sympifyit('other', NotImplemented) def __mul__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): return AccumBounds(Min(Mul(self.min, other.min), Mul(self.min, other.max), Mul(self.max, other.min), Mul(self.max, other.max)), Max(Mul(self.min, other.min), Mul(self.min, other.max), Mul(self.max, other.min), Mul(self.max, other.max))) if other is S.Infinity: if self.min.is_zero: return AccumBounds(0, oo) if self.max.is_zero: return AccumBounds(-oo, 0) if other is S.NegativeInfinity: if self.min.is_zero: return AccumBounds(-oo, 0) if self.max.is_zero: return AccumBounds(0, oo) if other.is_extended_real: if other.is_zero: if self == AccumBounds(-oo, oo): return AccumBounds(-oo, oo) if self.max is S.Infinity: return AccumBounds(0, oo) if self.min is S.NegativeInfinity: return AccumBounds(-oo, 0) return S.Zero if other.is_extended_positive: return AccumBounds( Mul(self.min, other), Mul(self.max, other)) elif other.is_extended_negative: return AccumBounds( Mul(self.max, other), Mul(self.min, other)) if isinstance(other, Order): return other return Mul(self, other, evaluate=False) return NotImplemented __rmul__ = __mul__ @_sympifyit('other', NotImplemented) def __truediv__(self, other): if isinstance(other, Expr): if isinstance(other, AccumBounds): if other.min.is_positive or other.max.is_negative: return self * AccumBounds(1/other.max, 1/other.min) if (self.min.is_extended_nonpositive and self.max.is_extended_nonnegative and other.min.is_extended_nonpositive and other.max.is_extended_nonnegative): if self.min.is_zero and other.min.is_zero: return AccumBounds(0, oo) if self.max.is_zero and other.min.is_zero: return AccumBounds(-oo, 0) return AccumBounds(-oo, oo) if self.max.is_extended_negative: if other.min.is_extended_negative: if other.max.is_zero: return AccumBounds(self.max / other.min, oo) if other.max.is_extended_positive: # the actual answer is a Union of AccumBounds, # Union(AccumBounds(-oo, self.max/other.max), # AccumBounds(self.max/other.min, oo)) return AccumBounds(-oo, oo) if other.min.is_zero and other.max.is_extended_positive: return AccumBounds(-oo, self.max / other.max) if self.min.is_extended_positive: if other.min.is_extended_negative: if other.max.is_zero: return AccumBounds(-oo, self.min / other.min) if other.max.is_extended_positive: # the actual answer is a Union of AccumBounds, # Union(AccumBounds(-oo, self.min/other.min), # AccumBounds(self.min/other.max, oo)) return AccumBounds(-oo, oo) if other.min.is_zero and other.max.is_extended_positive: return AccumBounds(self.min / other.max, oo) elif other.is_extended_real: if other is S.Infinity or other is S.NegativeInfinity: if self == AccumBounds(-oo, oo): return AccumBounds(-oo, oo) if self.max is S.Infinity: return AccumBounds(Min(0, other), Max(0, other)) if self.min is S.NegativeInfinity: return AccumBounds(Min(0, -other), Max(0, -other)) if other.is_extended_positive: return AccumBounds(self.min / other, self.max / other) elif other.is_extended_negative: return AccumBounds(self.max / other, self.min / other) if (1 / other) is S.ComplexInfinity: return Mul(self, 1 / other, evaluate=False) else: return Mul(self, 1 / other) return NotImplemented @_sympifyit('other', NotImplemented) def __rtruediv__(self, other): if isinstance(other, Expr): if other.is_extended_real: if other.is_zero: return S.Zero if (self.min.is_extended_nonpositive and self.max.is_extended_nonnegative): if self.min.is_zero: if other.is_extended_positive: return AccumBounds(Mul(other, 1 / self.max), oo) if other.is_extended_negative: return AccumBounds(-oo, Mul(other, 1 / self.max)) if self.max.is_zero: if other.is_extended_positive: return AccumBounds(-oo, Mul(other, 1 / self.min)) if other.is_extended_negative: return AccumBounds(Mul(other, 1 / self.min), oo) return AccumBounds(-oo, oo) else: return AccumBounds(Min(other / self.min, other / self.max), Max(other / self.min, other / self.max)) return Mul(other, 1 / self, evaluate=False) else: return NotImplemented @_sympifyit('other', NotImplemented) def __pow__(self, other): from sympy.functions.elementary.miscellaneous import real_root if isinstance(other, Expr): if other is S.Infinity: if self.min.is_extended_nonnegative: if self.max < 1: return S.Zero if self.min > 1: return S.Infinity return AccumBounds(0, oo) elif self.max.is_extended_negative: if self.min > -1: return S.Zero if self.max < -1: return FiniteSet(-oo, oo) return AccumBounds(-oo, oo) else: if self.min > -1: if self.max < 1: return S.Zero return AccumBounds(0, oo) return AccumBounds(-oo, oo) if other is S.NegativeInfinity: return (1 / self)**oo if other.is_extended_real and other.is_number: if other.is_zero: return S.One if other.is_Integer: if self.min.is_extended_positive: return AccumBounds( Min(self.min ** other, self.max ** other), Max(self.min ** other, self.max ** other)) elif self.max.is_extended_negative: return AccumBounds( Min(self.max ** other, self.min ** other), Max(self.max ** other, self.min ** other)) if other % 2 == 0: if other.is_extended_negative: if self.min.is_zero: return AccumBounds(self.max**other, oo) if self.max.is_zero: return AccumBounds(self.min**other, oo) return AccumBounds(0, oo) return AccumBounds( S.Zero, Max(self.min**other, self.max**other)) else: if other.is_extended_negative: if self.min.is_zero: return AccumBounds(self.max**other, oo) if self.max.is_zero: return AccumBounds(-oo, self.min**other) return AccumBounds(-oo, oo) return AccumBounds(self.min**other, self.max**other) num, den = other.as_numer_denom() if num == S.One: if den % 2 == 0: if S.Zero in self: if self.min.is_extended_negative: return AccumBounds(0, real_root(self.max, den)) return AccumBounds(real_root(self.min, den), real_root(self.max, den)) if den!=1: num_pow = self**num return num_pow**(1 / den) return AccumBounds(-oo, oo) return NotImplemented def __abs__(self): if self.max.is_extended_negative: return self.__neg__() elif self.min.is_extended_negative: return AccumBounds(S.Zero, Max(abs(self.min), self.max)) else: return self def __contains__(self, other): """ Returns True if other is contained in self, where other belongs to extended real numbers, False if not contained, otherwise TypeError is raised. Examples ======== >>> from sympy import AccumBounds, oo >>> 1 in AccumBounds(-1, 3) True -oo and oo go together as limits (in AccumulationBounds). >>> -oo in AccumBounds(1, oo) True >>> oo in AccumBounds(-oo, 0) True """ other = _sympify(other) if other is S.Infinity or other is S.NegativeInfinity: if self.min is S.NegativeInfinity or self.max is S.Infinity: return True return False rv = And(self.min <= other, self.max >= other) if rv not in (True, False): raise TypeError("input failed to evaluate") return rv def intersection(self, other): """ Returns the intersection of 'self' and 'other'. Here other can be an instance of FiniteSet or AccumulationBounds. Parameters ========== other: AccumulationBounds Another AccumulationBounds object with which the intersection has to be computed. Returns ======= AccumulationBounds Intersection of 'self' and 'other'. Examples ======== >>> from sympy import AccumBounds, FiniteSet >>> AccumBounds(1, 3).intersection(AccumBounds(2, 4)) AccumBounds(2, 3) >>> AccumBounds(1, 3).intersection(AccumBounds(4, 6)) EmptySet >>> AccumBounds(1, 4).intersection(FiniteSet(1, 2, 5)) FiniteSet(1, 2) """ if not isinstance(other, (AccumBounds, FiniteSet)): raise TypeError( "Input must be AccumulationBounds or FiniteSet object") if isinstance(other, FiniteSet): fin_set = S.EmptySet for i in other: if i in self: fin_set = fin_set + FiniteSet(i) return fin_set if self.max < other.min or self.min > other.max: return S.EmptySet if self.min <= other.min: if self.max <= other.max: return AccumBounds(other.min, self.max) if self.max > other.max: return other if other.min <= self.min: if other.max < self.max: return AccumBounds(self.min, other.max) if other.max > self.max: return self def union(self, other): # TODO : Devise a better method for Union of AccumBounds # this method is not actually correct and # can be made better if not isinstance(other, AccumBounds): raise TypeError( "Input must be AccumulationBounds or FiniteSet object") if self.min <= other.min and self.max >= other.min: return AccumBounds(self.min, Max(self.max, other.max)) if other.min <= self.min and other.max >= self.min: return AccumBounds(other.min, Max(self.max, other.max)) @dispatch(AccumulationBounds, AccumulationBounds) # type: ignore # noqa:F811 def _eval_is_le(lhs, rhs): # noqa:F811 if is_le(lhs.max, rhs.min): return True if is_gt(lhs.min, rhs.max): return False @dispatch(AccumulationBounds, Basic) # type: ignore # noqa:F811 def _eval_is_le(lhs, rhs): # noqa: F811 """ Returns True if range of values attained by `self` AccumulationBounds object is greater than the range of values attained by `other`, where other may be any value of type AccumulationBounds object or extended real number value, False if `other` satisfies the same property, else an unevaluated Relational. Examples ======== >>> from sympy import AccumBounds, oo >>> AccumBounds(1, 3) > AccumBounds(4, oo) False >>> AccumBounds(1, 4) > AccumBounds(3, 4) AccumBounds(1, 4) > AccumBounds(3, 4) >>> AccumBounds(1, oo) > -1 True """ if not rhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(rhs), rhs)) elif rhs.is_comparable: if is_le(lhs.max, rhs): return True if is_gt(lhs.min, rhs): return False @dispatch(AccumulationBounds, AccumulationBounds) def _eval_is_ge(lhs, rhs): # noqa:F811 if is_ge(lhs.min, rhs.max): return True if is_lt(lhs.max, rhs.min): return False @dispatch(AccumulationBounds, Expr) # type:ignore def _eval_is_ge(lhs, rhs): # noqa: F811 """ Returns True if range of values attained by `lhs` AccumulationBounds object is less that the range of values attained by `rhs`, where other may be any value of type AccumulationBounds object or extended real number value, False if `rhs` satisfies the same property, else an unevaluated Relational. Examples ======== >>> from sympy import AccumBounds, oo >>> AccumBounds(1, 3) >= AccumBounds(4, oo) False >>> AccumBounds(1, 4) >= AccumBounds(3, 4) AccumBounds(1, 4) >= AccumBounds(3, 4) >>> AccumBounds(1, oo) >= 1 True """ if not rhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(rhs), rhs)) elif rhs.is_comparable: if is_ge(lhs.min, rhs): return True if is_lt(lhs.max, rhs): return False @dispatch(Expr, AccumulationBounds) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 if not lhs.is_extended_real: raise TypeError( "Invalid comparison of %s %s" % (type(lhs), lhs)) elif lhs.is_comparable: if is_le(rhs.max, lhs): return True if is_gt(rhs.min, lhs): return False @dispatch(AccumulationBounds, AccumulationBounds) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 if is_ge(lhs.min, rhs.max): return True if is_lt(lhs.max, rhs.min): return False # setting an alias for AccumulationBounds AccumBounds = AccumulationBounds

cb53b82ad984aa09934edfa2044d7e26a9f507a4ed59cb19979d31434af9427d

from sympy.tensor import Indexed from sympy import Integral, Dummy, sympify, Tuple class IndexedIntegral(Integral): """ Experimental class to test integration by indexed variables. Usage is analogue to ``Integral``, it simply adds awareness of integration over indices. Contraction of non-identical index symbols referring to the same ``IndexedBase`` is not yet supported. Examples ======== >>> from sympy.sandbox.indexed_integrals import IndexedIntegral >>> from sympy import IndexedBase, symbols >>> A = IndexedBase('A') >>> i, j = symbols('i j', integer=True) >>> ii = IndexedIntegral(A[i], A[i]) >>> ii Integral(_A[i], _A[i]) >>> ii.doit() A[i]**2/2 If the indices are different, indexed objects are considered to be different variables: >>> i2 = IndexedIntegral(A[j], A[i]) >>> i2 Integral(A[j], _A[i]) >>> i2.doit() A[i]*A[j] """ def __new__(cls, function, *limits, **assumptions): repl, limits = IndexedIntegral._indexed_process_limits(limits) function = sympify(function) function = function.xreplace(repl) obj = Integral.__new__(cls, function, *limits, **assumptions) obj._indexed_repl = repl obj._indexed_reverse_repl = {val: key for key, val in repl.items()} return obj def doit(self): res = super().doit() return res.xreplace(self._indexed_reverse_repl) @staticmethod def _indexed_process_limits(limits): repl = {} newlimits = [] for i in limits: if isinstance(i, (tuple, list, Tuple)): v = i[0] vrest = i[1:] else: v = i vrest = () if isinstance(v, Indexed): if v not in repl: r = Dummy(str(v)) repl[v] = r newlimits.append((r,)+vrest) else: newlimits.append(i) return repl, newlimits

d6b3a9921058d13b3a5171efaa34567e10ce2f0221951c83af4caf2e7414c18e

""" Generic SymPy-Independent Strategies """ from sympy.core.compatibility import get_function_name identity = lambda x: x def exhaust(rule): """ Apply a rule repeatedly until it has no effect """ def exhaustive_rl(expr): new, old = rule(expr), expr while new != old: new, old = rule(new), new return new return exhaustive_rl def memoize(rule): """ Memoized version of a rule """ cache = {} def memoized_rl(expr): if expr in cache: return cache[expr] else: result = rule(expr) cache[expr] = result return result return memoized_rl def condition(cond, rule): """ Only apply rule if condition is true """ def conditioned_rl(expr): if cond(expr): return rule(expr) else: return expr return conditioned_rl def chain(*rules): """ Compose a sequence of rules so that they apply to the expr sequentially """ def chain_rl(expr): for rule in rules: expr = rule(expr) return expr return chain_rl def debug(rule, file=None): """ Print out before and after expressions each time rule is used """ if file is None: from sys import stdout file = stdout def debug_rl(*args, **kwargs): expr = args[0] result = rule(*args, **kwargs) if result != expr: file.write("Rule: %s\n" % get_function_name(rule)) file.write("In: %s\nOut: %s\n\n"%(expr, result)) return result return debug_rl def null_safe(rule): """ Return original expr if rule returns None """ def null_safe_rl(expr): result = rule(expr) if result is None: return expr else: return result return null_safe_rl def tryit(rule, exception): """ Return original expr if rule raises exception """ def try_rl(expr): try: return rule(expr) except exception: return expr return try_rl def do_one(*rules): """ Try each of the rules until one works. Then stop. """ def do_one_rl(expr): for rl in rules: result = rl(expr) if result != expr: return result return expr return do_one_rl def switch(key, ruledict): """ Select a rule based on the result of key called on the function """ def switch_rl(expr): rl = ruledict.get(key(expr), identity) return rl(expr) return switch_rl def minimize(*rules, objective=identity): """ Select result of rules that minimizes objective >>> from sympy.strategies import minimize >>> inc = lambda x: x + 1 >>> dec = lambda x: x - 1 >>> rl = minimize(inc, dec) >>> rl(4) 3 >>> rl = minimize(inc, dec, objective=lambda x: -x) # maximize >>> rl(4) 5 """ def minrule(expr): return min([rule(expr) for rule in rules], key=objective) return minrule

1e1ed6be8c816053f910f8055fe5ed2e445fedf8ac067a1b31de13e8baecc02a

from functools import partial from sympy.strategies import chain, minimize import sympy.strategies.branch as branch from sympy.strategies.branch import yieldify identity = lambda x: x def treeapply(tree, join, leaf=identity): """ Apply functions onto recursive containers (tree) join - a dictionary mapping container types to functions e.g. ``{list: minimize, tuple: chain}`` Keys are containers/iterables. Values are functions [a] -> a. Examples ======== >>> from sympy.strategies.tree import treeapply >>> tree = [(3, 2), (4, 1)] >>> treeapply(tree, {list: max, tuple: min}) 2 >>> add = lambda *args: sum(args) >>> def mul(*args): ... total = 1 ... for arg in args: ... total *= arg ... return total >>> treeapply(tree, {list: mul, tuple: add}) 25 """ for typ in join: if isinstance(tree, typ): return join[typ](*map(partial(treeapply, join=join, leaf=leaf), tree)) return leaf(tree) def greedy(tree, objective=identity, **kwargs): """ Execute a strategic tree. Select alternatives greedily Trees ----- Nodes in a tree can be either function - a leaf list - a selection among operations tuple - a sequence of chained operations Textual examples ---------------- Text: Run f, then run g, e.g. ``lambda x: g(f(x))`` Code: ``(f, g)`` Text: Run either f or g, whichever minimizes the objective Code: ``[f, g]`` Textx: Run either f or g, whichever is better, then run h Code: ``([f, g], h)`` Text: Either expand then simplify or try factor then foosimp. Finally print Code: ``([(expand, simplify), (factor, foosimp)], print)`` Objective --------- "Better" is determined by the objective keyword. This function makes choices to minimize the objective. It defaults to the identity. Examples ======== >>> from sympy.strategies.tree import greedy >>> inc = lambda x: x + 1 >>> dec = lambda x: x - 1 >>> double = lambda x: 2*x >>> tree = [inc, (dec, double)] # either inc or dec-then-double >>> fn = greedy(tree) >>> fn(4) # lowest value comes from the inc 5 >>> fn(1) # lowest value comes from dec then double 0 This function selects between options in a tuple. The result is chosen that minimizes the objective function. >>> fn = greedy(tree, objective=lambda x: -x) # maximize >>> fn(4) # highest value comes from the dec then double 6 >>> fn(1) # highest value comes from the inc 2 Greediness ---------- This is a greedy algorithm. In the example: ([a, b], c) # do either a or b, then do c the choice between running ``a`` or ``b`` is made without foresight to c """ optimize = partial(minimize, objective=objective) return treeapply(tree, {list: optimize, tuple: chain}, **kwargs) def allresults(tree, leaf=yieldify): """ Execute a strategic tree. Return all possibilities. Returns a lazy iterator of all possible results Exhaustiveness -------------- This is an exhaustive algorithm. In the example ([a, b], [c, d]) All of the results from (a, c), (b, c), (a, d), (b, d) are returned. This can lead to combinatorial blowup. See sympy.strategies.greedy for details on input """ return treeapply(tree, {list: branch.multiplex, tuple: branch.chain}, leaf=leaf) def brute(tree, objective=identity, **kwargs): return lambda expr: min(tuple(allresults(tree, **kwargs)(expr)), key=objective)

02d0ea37d52030f3e60fbd8e3a296de3f14ad6e43ffa1167feff7c68785636d3

from . import rl from .core import do_one, exhaust, switch from .traverse import top_down def subs(d, **kwargs): """ Full simultaneous exact substitution Examples ======== >>> from sympy.strategies.tools import subs >>> from sympy import Basic >>> mapping = {1: 4, 4: 1, Basic(5): Basic(6, 7)} >>> expr = Basic(1, Basic(2, 3), Basic(4, Basic(5))) >>> subs(mapping)(expr) Basic(4, Basic(2, 3), Basic(1, Basic(6, 7))) """ if d: return top_down(do_one(*map(rl.subs, *zip(*d.items()))), **kwargs) else: return lambda x: x def canon(*rules, **kwargs): """ Strategy for canonicalization Apply each rule in a bottom_up fashion through the tree. Do each one in turn. Keep doing this until there is no change. """ return exhaust(top_down(exhaust(do_one(*rules)), **kwargs)) def typed(ruletypes): """ Apply rules based on the expression type inputs: ruletypes -- a dict mapping {Type: rule} >>> from sympy.strategies import rm_id, typed >>> from sympy import Add, Mul >>> rm_zeros = rm_id(lambda x: x==0) >>> rm_ones = rm_id(lambda x: x==1) >>> remove_idents = typed({Add: rm_zeros, Mul: rm_ones}) """ return switch(type, ruletypes)

3e1c3f1edbf42774ed9ae9bb9735f766a712de69cbc05db2e934161a7325ddc0

""" Generic Rules for SymPy This file assumes knowledge of Basic and little else. """ from sympy.utilities.iterables import sift from .util import new # Functions that create rules def rm_id(isid, new=new): """ Create a rule to remove identities isid - fn :: x -> Bool --- whether or not this element is an identity >>> from sympy.strategies import rm_id >>> from sympy import Basic >>> remove_zeros = rm_id(lambda x: x==0) >>> remove_zeros(Basic(1, 0, 2)) Basic(1, 2) >>> remove_zeros(Basic(0, 0)) # If only identites then we keep one Basic(0) See Also: unpack """ def ident_remove(expr): """ Remove identities """ ids = list(map(isid, expr.args)) if sum(ids) == 0: # No identities. Common case return expr elif sum(ids) != len(ids): # there is at least one non-identity return new(expr.__class__, *[arg for arg, x in zip(expr.args, ids) if not x]) else: return new(expr.__class__, expr.args[0]) return ident_remove def glom(key, count, combine): """ Create a rule to conglomerate identical args >>> from sympy.strategies import glom >>> from sympy import Add >>> from sympy.abc import x >>> key = lambda x: x.as_coeff_Mul()[1] >>> count = lambda x: x.as_coeff_Mul()[0] >>> combine = lambda cnt, arg: cnt * arg >>> rl = glom(key, count, combine) >>> rl(Add(x, -x, 3*x, 2, 3, evaluate=False)) 3*x + 5 Wait, how are key, count and combine supposed to work? >>> key(2*x) x >>> count(2*x) 2 >>> combine(2, x) 2*x """ def conglomerate(expr): """ Conglomerate together identical args x + x -> 2x """ groups = sift(expr.args, key) counts = {k: sum(map(count, args)) for k, args in groups.items()} newargs = [combine(cnt, mat) for mat, cnt in counts.items()] if set(newargs) != set(expr.args): return new(type(expr), *newargs) else: return expr return conglomerate def sort(key, new=new): """ Create a rule to sort by a key function >>> from sympy.strategies import sort >>> from sympy import Basic >>> sort_rl = sort(str) >>> sort_rl(Basic(3, 1, 2)) Basic(1, 2, 3) """ def sort_rl(expr): return new(expr.__class__, *sorted(expr.args, key=key)) return sort_rl def distribute(A, B): """ Turns an A containing Bs into a B of As where A, B are container types >>> from sympy.strategies import distribute >>> from sympy import Add, Mul, symbols >>> x, y = symbols('x,y') >>> dist = distribute(Mul, Add) >>> expr = Mul(2, x+y, evaluate=False) >>> expr 2*(x + y) >>> dist(expr) 2*x + 2*y """ def distribute_rl(expr): for i, arg in enumerate(expr.args): if isinstance(arg, B): first, b, tail = expr.args[:i], expr.args[i], expr.args[i+1:] return B(*[A(*(first + (arg,) + tail)) for arg in b.args]) return expr return distribute_rl def subs(a, b): """ Replace expressions exactly """ def subs_rl(expr): if expr == a: return b else: return expr return subs_rl # Functions that are rules def unpack(expr): """ Rule to unpack singleton args >>> from sympy.strategies import unpack >>> from sympy import Basic >>> unpack(Basic(2)) 2 """ if len(expr.args) == 1: return expr.args[0] else: return expr def flatten(expr, new=new): """ Flatten T(a, b, T(c, d), T2(e)) to T(a, b, c, d, T2(e)) """ cls = expr.__class__ args = [] for arg in expr.args: if arg.__class__ == cls: args.extend(arg.args) else: args.append(arg) return new(expr.__class__, *args) def rebuild(expr): """ Rebuild a SymPy tree This function recursively calls constructors in the expression tree. This forces canonicalization and removes ugliness introduced by the use of Basic.__new__ """ if expr.is_Atom: return expr else: return expr.func(*list(map(rebuild, expr.args)))

0e13e7049e51c3fc73846881b527224f257e1f6ce19718236158eb347fa02f29

"""Strategies to Traverse a Tree.""" from sympy.strategies.util import basic_fns from sympy.strategies.core import chain, do_one def top_down(rule, fns=basic_fns): """Apply a rule down a tree running it on the top nodes first.""" return chain(rule, lambda expr: sall(top_down(rule, fns), fns)(expr)) def bottom_up(rule, fns=basic_fns): """Apply a rule down a tree running it on the bottom nodes first.""" return chain(lambda expr: sall(bottom_up(rule, fns), fns)(expr), rule) def top_down_once(rule, fns=basic_fns): """Apply a rule down a tree - stop on success.""" return do_one(rule, lambda expr: sall(top_down(rule, fns), fns)(expr)) def bottom_up_once(rule, fns=basic_fns): """Apply a rule up a tree - stop on success.""" return do_one(lambda expr: sall(bottom_up(rule, fns), fns)(expr), rule) def sall(rule, fns=basic_fns): """Strategic all - apply rule to args.""" op, new, children, leaf = map(fns.get, ('op', 'new', 'children', 'leaf')) def all_rl(expr): if leaf(expr): return expr else: args = map(rule, children(expr)) return new(op(expr), *args) return all_rl

d0e6d9fa0d43122d60d3b005fabe93f35978a2f1b05bb1ea713ae39243aa8034

from sympy import Basic new = Basic.__new__ def assoc(d, k, v): d = d.copy() d[k] = v return d basic_fns = {'op': type, 'new': Basic.__new__, 'leaf': lambda x: not isinstance(x, Basic) or x.is_Atom, 'children': lambda x: x.args} expr_fns = assoc(basic_fns, 'new', lambda op, *args: op(*args))

81c2ee6523a14b167fb3fd56f704089ee5baacba2e8d5196cb103ae97eaf911c

""" This module provides convenient functions to transform sympy expressions to lambda functions which can be used to calculate numerical values very fast. """ from typing import Any, Dict, Iterable import inspect import keyword import textwrap import linecache from sympy.utilities.exceptions import SymPyDeprecationWarning from sympy.core.compatibility import (exec_, is_sequence, iterable, NotIterable, builtins) from sympy.utilities.misc import filldedent from sympy.utilities.decorator import doctest_depends_on __doctest_requires__ = {('lambdify',): ['numpy', 'tensorflow']} # Default namespaces, letting us define translations that can't be defined # by simple variable maps, like I => 1j MATH_DEFAULT = {} # type: Dict[str, Any] MPMATH_DEFAULT = {} # type: Dict[str, Any] NUMPY_DEFAULT = {"I": 1j} # type: Dict[str, Any] SCIPY_DEFAULT = {"I": 1j} # type: Dict[str, Any] TENSORFLOW_DEFAULT = {} # type: Dict[str, Any] SYMPY_DEFAULT = {} # type: Dict[str, Any] NUMEXPR_DEFAULT = {} # type: Dict[str, Any] # These are the namespaces the lambda functions will use. # These are separate from the names above because they are modified # throughout this file, whereas the defaults should remain unmodified. MATH = MATH_DEFAULT.copy() MPMATH = MPMATH_DEFAULT.copy() NUMPY = NUMPY_DEFAULT.copy() SCIPY = SCIPY_DEFAULT.copy() TENSORFLOW = TENSORFLOW_DEFAULT.copy() SYMPY = SYMPY_DEFAULT.copy() NUMEXPR = NUMEXPR_DEFAULT.copy() # Mappings between sympy and other modules function names. MATH_TRANSLATIONS = { "ceiling": "ceil", "E": "e", "ln": "log", } # NOTE: This dictionary is reused in Function._eval_evalf to allow subclasses # of Function to automatically evalf. MPMATH_TRANSLATIONS = { "Abs": "fabs", "elliptic_k": "ellipk", "elliptic_f": "ellipf", "elliptic_e": "ellipe", "elliptic_pi": "ellippi", "ceiling": "ceil", "chebyshevt": "chebyt", "chebyshevu": "chebyu", "E": "e", "I": "j", "ln": "log", #"lowergamma":"lower_gamma", "oo": "inf", #"uppergamma":"upper_gamma", "LambertW": "lambertw", "MutableDenseMatrix": "matrix", "ImmutableDenseMatrix": "matrix", "conjugate": "conj", "dirichlet_eta": "altzeta", "Ei": "ei", "Shi": "shi", "Chi": "chi", "Si": "si", "Ci": "ci", "RisingFactorial": "rf", "FallingFactorial": "ff", } NUMPY_TRANSLATIONS = {} # type: Dict[str, str] SCIPY_TRANSLATIONS = {} # type: Dict[str, str] TENSORFLOW_TRANSLATIONS = {} # type: Dict[str, str] NUMEXPR_TRANSLATIONS = {} # type: Dict[str, str] # Available modules: MODULES = { "math": (MATH, MATH_DEFAULT, MATH_TRANSLATIONS, ("from math import *",)), "mpmath": (MPMATH, MPMATH_DEFAULT, MPMATH_TRANSLATIONS, ("from mpmath import *",)), "numpy": (NUMPY, NUMPY_DEFAULT, NUMPY_TRANSLATIONS, ("import numpy; from numpy import *; from numpy.linalg import *",)), "scipy": (SCIPY, SCIPY_DEFAULT, SCIPY_TRANSLATIONS, ("import numpy; import scipy; from scipy import *; from scipy.special import *",)), "tensorflow": (TENSORFLOW, TENSORFLOW_DEFAULT, TENSORFLOW_TRANSLATIONS, ("import tensorflow",)), "sympy": (SYMPY, SYMPY_DEFAULT, {}, ( "from sympy.functions import *", "from sympy.matrices import *", "from sympy import Integral, pi, oo, nan, zoo, E, I",)), "numexpr" : (NUMEXPR, NUMEXPR_DEFAULT, NUMEXPR_TRANSLATIONS, ("import_module('numexpr')", )), } def _import(module, reload=False): """ Creates a global translation dictionary for module. The argument module has to be one of the following strings: "math", "mpmath", "numpy", "sympy", "tensorflow". These dictionaries map names of python functions to their equivalent in other modules. """ # Required despite static analysis claiming it is not used from sympy.external import import_module # noqa:F401 try: namespace, namespace_default, translations, import_commands = MODULES[ module] except KeyError: raise NameError( "'%s' module can't be used for lambdification" % module) # Clear namespace or exit if namespace != namespace_default: # The namespace was already generated, don't do it again if not forced. if reload: namespace.clear() namespace.update(namespace_default) else: return for import_command in import_commands: if import_command.startswith('import_module'): module = eval(import_command) if module is not None: namespace.update(module.__dict__) continue else: try: exec_(import_command, {}, namespace) continue except ImportError: pass raise ImportError( "can't import '%s' with '%s' command" % (module, import_command)) # Add translated names to namespace for sympyname, translation in translations.items(): namespace[sympyname] = namespace[translation] # For computing the modulus of a sympy expression we use the builtin abs # function, instead of the previously used fabs function for all # translation modules. This is because the fabs function in the math # module does not accept complex valued arguments. (see issue 9474). The # only exception, where we don't use the builtin abs function is the # mpmath translation module, because mpmath.fabs returns mpf objects in # contrast to abs(). if 'Abs' not in namespace: namespace['Abs'] = abs # Used for dynamically generated filenames that are inserted into the # linecache. _lambdify_generated_counter = 1 @doctest_depends_on(modules=('numpy', 'tensorflow', ), python_version=(3,)) def lambdify(args: Iterable, expr, modules=None, printer=None, use_imps=True, dummify=False): """Convert a SymPy expression into a function that allows for fast numeric evaluation. .. warning:: This function uses ``exec``, and thus shouldn't be used on unsanitized input. .. versionchanged:: 1.7.0 Passing a set for the *args* parameter is deprecated as sets are unordered. Use an ordered iterable such as a list or tuple. Explanation =========== For example, to convert the SymPy expression ``sin(x) + cos(x)`` to an equivalent NumPy function that numerically evaluates it: >>> from sympy import sin, cos, symbols, lambdify >>> import numpy as np >>> x = symbols('x') >>> expr = sin(x) + cos(x) >>> expr sin(x) + cos(x) >>> f = lambdify(x, expr, 'numpy') >>> a = np.array([1, 2]) >>> f(a) [1.38177329 0.49315059] The primary purpose of this function is to provide a bridge from SymPy expressions to numerical libraries such as NumPy, SciPy, NumExpr, mpmath, and tensorflow. In general, SymPy functions do not work with objects from other libraries, such as NumPy arrays, and functions from numeric libraries like NumPy or mpmath do not work on SymPy expressions. ``lambdify`` bridges the two by converting a SymPy expression to an equivalent numeric function. The basic workflow with ``lambdify`` is to first create a SymPy expression representing whatever mathematical function you wish to evaluate. This should be done using only SymPy functions and expressions. Then, use ``lambdify`` to convert this to an equivalent function for numerical evaluation. For instance, above we created ``expr`` using the SymPy symbol ``x`` and SymPy functions ``sin`` and ``cos``, then converted it to an equivalent NumPy function ``f``, and called it on a NumPy array ``a``. Parameters ========== args : List[Symbol] A variable or a list of variables whose nesting represents the nesting of the arguments that will be passed to the function. Variables can be symbols, undefined functions, or matrix symbols. >>> from sympy import Eq >>> from sympy.abc import x, y, z The list of variables should match the structure of how the arguments will be passed to the function. Simply enclose the parameters as they will be passed in a list. To call a function like ``f(x)`` then ``[x]`` should be the first argument to ``lambdify``; for this case a single ``x`` can also be used: >>> f = lambdify(x, x + 1) >>> f(1) 2 >>> f = lambdify([x], x + 1) >>> f(1) 2 To call a function like ``f(x, y)`` then ``[x, y]`` will be the first argument of the ``lambdify``: >>> f = lambdify([x, y], x + y) >>> f(1, 1) 2 To call a function with a single 3-element tuple like ``f((x, y, z))`` then ``[(x, y, z)]`` will be the first argument of the ``lambdify``: >>> f = lambdify([(x, y, z)], Eq(z**2, x**2 + y**2)) >>> f((3, 4, 5)) True If two args will be passed and the first is a scalar but the second is a tuple with two arguments then the items in the list should match that structure: >>> f = lambdify([x, (y, z)], x + y + z) >>> f(1, (2, 3)) 6 expr : Expr An expression, list of expressions, or matrix to be evaluated. Lists may be nested. If the expression is a list, the output will also be a list. >>> f = lambdify(x, [x, [x + 1, x + 2]]) >>> f(1) [1, [2, 3]] If it is a matrix, an array will be returned (for the NumPy module). >>> from sympy import Matrix >>> f = lambdify(x, Matrix([x, x + 1])) >>> f(1) [[1] [2]] Note that the argument order here (variables then expression) is used to emulate the Python ``lambda`` keyword. ``lambdify(x, expr)`` works (roughly) like ``lambda x: expr`` (see :ref:`lambdify-how-it-works` below). modules : str, optional Specifies the numeric library to use. If not specified, *modules* defaults to: - ``["scipy", "numpy"]`` if SciPy is installed - ``["numpy"]`` if only NumPy is installed - ``["math", "mpmath", "sympy"]`` if neither is installed. That is, SymPy functions are replaced as far as possible by either ``scipy`` or ``numpy`` functions if available, and Python's standard library ``math``, or ``mpmath`` functions otherwise. *modules* can be one of the following types: - The strings ``"math"``, ``"mpmath"``, ``"numpy"``, ``"numexpr"``, ``"scipy"``, ``"sympy"``, or ``"tensorflow"``. This uses the corresponding printer and namespace mapping for that module. - A module (e.g., ``math``). This uses the global namespace of the module. If the module is one of the above known modules, it will also use the corresponding printer and namespace mapping (i.e., ``modules=numpy`` is equivalent to ``modules="numpy"``). - A dictionary that maps names of SymPy functions to arbitrary functions (e.g., ``{'sin': custom_sin}``). - A list that contains a mix of the arguments above, with higher priority given to entries appearing first (e.g., to use the NumPy module but override the ``sin`` function with a custom version, you can use ``[{'sin': custom_sin}, 'numpy']``). dummify : bool, optional Whether or not the variables in the provided expression that are not valid Python identifiers are substituted with dummy symbols. This allows for undefined functions like ``Function('f')(t)`` to be supplied as arguments. By default, the variables are only dummified if they are not valid Python identifiers. Set ``dummify=True`` to replace all arguments with dummy symbols (if ``args`` is not a string) - for example, to ensure that the arguments do not redefine any built-in names. Examples ======== >>> from sympy.utilities.lambdify import implemented_function >>> from sympy import sqrt, sin, Matrix >>> from sympy import Function >>> from sympy.abc import w, x, y, z >>> f = lambdify(x, x**2) >>> f(2) 4 >>> f = lambdify((x, y, z), [z, y, x]) >>> f(1,2,3) [3, 2, 1] >>> f = lambdify(x, sqrt(x)) >>> f(4) 2.0 >>> f = lambdify((x, y), sin(x*y)**2) >>> f(0, 5) 0.0 >>> row = lambdify((x, y), Matrix((x, x + y)).T, modules='sympy') >>> row(1, 2) Matrix([[1, 3]]) ``lambdify`` can be used to translate SymPy expressions into mpmath functions. This may be preferable to using ``evalf`` (which uses mpmath on the backend) in some cases. >>> f = lambdify(x, sin(x), 'mpmath') >>> f(1) 0.8414709848078965 Tuple arguments are handled and the lambdified function should be called with the same type of arguments as were used to create the function: >>> f = lambdify((x, (y, z)), x + y) >>> f(1, (2, 4)) 3 The ``flatten`` function can be used to always work with flattened arguments: >>> from sympy.utilities.iterables import flatten >>> args = w, (x, (y, z)) >>> vals = 1, (2, (3, 4)) >>> f = lambdify(flatten(args), w + x + y + z) >>> f(*flatten(vals)) 10 Functions present in ``expr`` can also carry their own numerical implementations, in a callable attached to the ``_imp_`` attribute. This can be used with undefined functions using the ``implemented_function`` factory: >>> f = implemented_function(Function('f'), lambda x: x+1) >>> func = lambdify(x, f(x)) >>> func(4) 5 ``lambdify`` always prefers ``_imp_`` implementations to implementations in other namespaces, unless the ``use_imps`` input parameter is False. Usage with Tensorflow: >>> import tensorflow as tf >>> from sympy import Max, sin, lambdify >>> from sympy.abc import x >>> f = Max(x, sin(x)) >>> func = lambdify(x, f, 'tensorflow') After tensorflow v2, eager execution is enabled by default. If you want to get the compatible result across tensorflow v1 and v2 as same as this tutorial, run this line. >>> tf.compat.v1.enable_eager_execution() If you have eager execution enabled, you can get the result out immediately as you can use numpy. If you pass tensorflow objects, you may get an ``EagerTensor`` object instead of value. >>> result = func(tf.constant(1.0)) >>> print(result) tf.Tensor(1.0, shape=(), dtype=float32) >>> print(result.__class__) <class 'tensorflow.python.framework.ops.EagerTensor'> You can use ``.numpy()`` to get the numpy value of the tensor. >>> result.numpy() 1.0 >>> var = tf.Variable(2.0) >>> result = func(var) # also works for tf.Variable and tf.Placeholder >>> result.numpy() 2.0 And it works with any shape array. >>> tensor = tf.constant([[1.0, 2.0], [3.0, 4.0]]) >>> result = func(tensor) >>> result.numpy() [[1. 2.] [3. 4.]] Notes ===== - For functions involving large array calculations, numexpr can provide a significant speedup over numpy. Please note that the available functions for numexpr are more limited than numpy but can be expanded with ``implemented_function`` and user defined subclasses of Function. If specified, numexpr may be the only option in modules. The official list of numexpr functions can be found at: https://numexpr.readthedocs.io/en/latest/user_guide.html#supported-functions - In previous versions of SymPy, ``lambdify`` replaced ``Matrix`` with ``numpy.matrix`` by default. As of SymPy 1.0 ``numpy.array`` is the default. To get the old default behavior you must pass in ``[{'ImmutableDenseMatrix': numpy.matrix}, 'numpy']`` to the ``modules`` kwarg. >>> from sympy import lambdify, Matrix >>> from sympy.abc import x, y >>> import numpy >>> array2mat = [{'ImmutableDenseMatrix': numpy.matrix}, 'numpy'] >>> f = lambdify((x, y), Matrix([x, y]), modules=array2mat) >>> f(1, 2) [[1] [2]] - In the above examples, the generated functions can accept scalar values or numpy arrays as arguments. However, in some cases the generated function relies on the input being a numpy array: >>> from sympy import Piecewise >>> from sympy.testing.pytest import ignore_warnings >>> f = lambdify(x, Piecewise((x, x <= 1), (1/x, x > 1)), "numpy") >>> with ignore_warnings(RuntimeWarning): ... f(numpy.array([-1, 0, 1, 2])) [-1. 0. 1. 0.5] >>> f(0) Traceback (most recent call last): ... ZeroDivisionError: division by zero In such cases, the input should be wrapped in a numpy array: >>> with ignore_warnings(RuntimeWarning): ... float(f(numpy.array([0]))) 0.0 Or if numpy functionality is not required another module can be used: >>> f = lambdify(x, Piecewise((x, x <= 1), (1/x, x > 1)), "math") >>> f(0) 0 .. _lambdify-how-it-works: How it works ============ When using this function, it helps a great deal to have an idea of what it is doing. At its core, lambdify is nothing more than a namespace translation, on top of a special printer that makes some corner cases work properly. To understand lambdify, first we must properly understand how Python namespaces work. Say we had two files. One called ``sin_cos_sympy.py``, with .. code:: python # sin_cos_sympy.py from sympy import sin, cos def sin_cos(x): return sin(x) + cos(x) and one called ``sin_cos_numpy.py`` with .. code:: python # sin_cos_numpy.py from numpy import sin, cos def sin_cos(x): return sin(x) + cos(x) The two files define an identical function ``sin_cos``. However, in the first file, ``sin`` and ``cos`` are defined as the SymPy ``sin`` and ``cos``. In the second, they are defined as the NumPy versions. If we were to import the first file and use the ``sin_cos`` function, we would get something like >>> from sin_cos_sympy import sin_cos # doctest: +SKIP >>> sin_cos(1) # doctest: +SKIP cos(1) + sin(1) On the other hand, if we imported ``sin_cos`` from the second file, we would get >>> from sin_cos_numpy import sin_cos # doctest: +SKIP >>> sin_cos(1) # doctest: +SKIP 1.38177329068 In the first case we got a symbolic output, because it used the symbolic ``sin`` and ``cos`` functions from SymPy. In the second, we got a numeric result, because ``sin_cos`` used the numeric ``sin`` and ``cos`` functions from NumPy. But notice that the versions of ``sin`` and ``cos`` that were used was not inherent to the ``sin_cos`` function definition. Both ``sin_cos`` definitions are exactly the same. Rather, it was based on the names defined at the module where the ``sin_cos`` function was defined. The key point here is that when function in Python references a name that is not defined in the function, that name is looked up in the "global" namespace of the module where that function is defined. Now, in Python, we can emulate this behavior without actually writing a file to disk using the ``exec`` function. ``exec`` takes a string containing a block of Python code, and a dictionary that should contain the global variables of the module. It then executes the code "in" that dictionary, as if it were the module globals. The following is equivalent to the ``sin_cos`` defined in ``sin_cos_sympy.py``: >>> import sympy >>> module_dictionary = {'sin': sympy.sin, 'cos': sympy.cos} >>> exec(''' ... def sin_cos(x): ... return sin(x) + cos(x) ... ''', module_dictionary) >>> sin_cos = module_dictionary['sin_cos'] >>> sin_cos(1) cos(1) + sin(1) and similarly with ``sin_cos_numpy``: >>> import numpy >>> module_dictionary = {'sin': numpy.sin, 'cos': numpy.cos} >>> exec(''' ... def sin_cos(x): ... return sin(x) + cos(x) ... ''', module_dictionary) >>> sin_cos = module_dictionary['sin_cos'] >>> sin_cos(1) 1.38177329068 So now we can get an idea of how ``lambdify`` works. The name "lambdify" comes from the fact that we can think of something like ``lambdify(x, sin(x) + cos(x), 'numpy')`` as ``lambda x: sin(x) + cos(x)``, where ``sin`` and ``cos`` come from the ``numpy`` namespace. This is also why the symbols argument is first in ``lambdify``, as opposed to most SymPy functions where it comes after the expression: to better mimic the ``lambda`` keyword. ``lambdify`` takes the input expression (like ``sin(x) + cos(x)``) and 1. Converts it to a string 2. Creates a module globals dictionary based on the modules that are passed in (by default, it uses the NumPy module) 3. Creates the string ``"def func({vars}): return {expr}"``, where ``{vars}`` is the list of variables separated by commas, and ``{expr}`` is the string created in step 1., then ``exec``s that string with the module globals namespace and returns ``func``. In fact, functions returned by ``lambdify`` support inspection. So you can see exactly how they are defined by using ``inspect.getsource``, or ``??`` if you are using IPython or the Jupyter notebook. >>> f = lambdify(x, sin(x) + cos(x)) >>> import inspect >>> print(inspect.getsource(f)) def _lambdifygenerated(x): return (sin(x) + cos(x)) This shows us the source code of the function, but not the namespace it was defined in. We can inspect that by looking at the ``__globals__`` attribute of ``f``: >>> f.__globals__['sin'] <ufunc 'sin'> >>> f.__globals__['cos'] <ufunc 'cos'> >>> f.__globals__['sin'] is numpy.sin True This shows us that ``sin`` and ``cos`` in the namespace of ``f`` will be ``numpy.sin`` and ``numpy.cos``. Note that there are some convenience layers in each of these steps, but at the core, this is how ``lambdify`` works. Step 1 is done using the ``LambdaPrinter`` printers defined in the printing module (see :mod:`sympy.printing.lambdarepr`). This allows different SymPy expressions to define how they should be converted to a string for different modules. You can change which printer ``lambdify`` uses by passing a custom printer in to the ``printer`` argument. Step 2 is augmented by certain translations. There are default translations for each module, but you can provide your own by passing a list to the ``modules`` argument. For instance, >>> def mysin(x): ... print('taking the sin of', x) ... return numpy.sin(x) ... >>> f = lambdify(x, sin(x), [{'sin': mysin}, 'numpy']) >>> f(1) taking the sin of 1 0.8414709848078965 The globals dictionary is generated from the list by merging the dictionary ``{'sin': mysin}`` and the module dictionary for NumPy. The merging is done so that earlier items take precedence, which is why ``mysin`` is used above instead of ``numpy.sin``. If you want to modify the way ``lambdify`` works for a given function, it is usually easiest to do so by modifying the globals dictionary as such. In more complicated cases, it may be necessary to create and pass in a custom printer. Finally, step 3 is augmented with certain convenience operations, such as the addition of a docstring. Understanding how ``lambdify`` works can make it easier to avoid certain gotchas when using it. For instance, a common mistake is to create a lambdified function for one module (say, NumPy), and pass it objects from another (say, a SymPy expression). For instance, say we create >>> from sympy.abc import x >>> f = lambdify(x, x + 1, 'numpy') Now if we pass in a NumPy array, we get that array plus 1 >>> import numpy >>> a = numpy.array([1, 2]) >>> f(a) [2 3] But what happens if you make the mistake of passing in a SymPy expression instead of a NumPy array: >>> f(x + 1) x + 2 This worked, but it was only by accident. Now take a different lambdified function: >>> from sympy import sin >>> g = lambdify(x, x + sin(x), 'numpy') This works as expected on NumPy arrays: >>> g(a) [1.84147098 2.90929743] But if we try to pass in a SymPy expression, it fails >>> try: ... g(x + 1) ... # NumPy release after 1.17 raises TypeError instead of ... # AttributeError ... except (AttributeError, TypeError): ... raise AttributeError() # doctest: +IGNORE_EXCEPTION_DETAIL Traceback (most recent call last): ... AttributeError: Now, let's look at what happened. The reason this fails is that ``g`` calls ``numpy.sin`` on the input expression, and ``numpy.sin`` does not know how to operate on a SymPy object. **As a general rule, NumPy functions do not know how to operate on SymPy expressions, and SymPy functions do not know how to operate on NumPy arrays. This is why lambdify exists: to provide a bridge between SymPy and NumPy.** However, why is it that ``f`` did work? That's because ``f`` doesn't call any functions, it only adds 1. So the resulting function that is created, ``def _lambdifygenerated(x): return x + 1`` does not depend on the globals namespace it is defined in. Thus it works, but only by accident. A future version of ``lambdify`` may remove this behavior. Be aware that certain implementation details described here may change in future versions of SymPy. The API of passing in custom modules and printers will not change, but the details of how a lambda function is created may change. However, the basic idea will remain the same, and understanding it will be helpful to understanding the behavior of lambdify. **In general: you should create lambdified functions for one module (say, NumPy), and only pass it input types that are compatible with that module (say, NumPy arrays).** Remember that by default, if the ``module`` argument is not provided, ``lambdify`` creates functions using the NumPy and SciPy namespaces. """ from sympy.core.symbol import Symbol # If the user hasn't specified any modules, use what is available. if modules is None: try: _import("scipy") except ImportError: try: _import("numpy") except ImportError: # Use either numpy (if available) or python.math where possible. # XXX: This leads to different behaviour on different systems and # might be the reason for irreproducible errors. modules = ["math", "mpmath", "sympy"] else: modules = ["numpy"] else: modules = ["numpy", "scipy"] # Get the needed namespaces. namespaces = [] # First find any function implementations if use_imps: namespaces.append(_imp_namespace(expr)) # Check for dict before iterating if isinstance(modules, (dict, str)) or not hasattr(modules, '__iter__'): namespaces.append(modules) else: # consistency check if _module_present('numexpr', modules) and len(modules) > 1: raise TypeError("numexpr must be the only item in 'modules'") namespaces += list(modules) # fill namespace with first having highest priority namespace = {} # type: Dict[str, Any] for m in namespaces[::-1]: buf = _get_namespace(m) namespace.update(buf) if hasattr(expr, "atoms"): #Try if you can extract symbols from the expression. #Move on if expr.atoms in not implemented. syms = expr.atoms(Symbol) for term in syms: namespace.update({str(term): term}) if printer is None: if _module_present('mpmath', namespaces): from sympy.printing.pycode import MpmathPrinter as Printer # type: ignore elif _module_present('scipy', namespaces): from sympy.printing.pycode import SciPyPrinter as Printer # type: ignore elif _module_present('numpy', namespaces): from sympy.printing.pycode import NumPyPrinter as Printer # type: ignore elif _module_present('numexpr', namespaces): from sympy.printing.lambdarepr import NumExprPrinter as Printer # type: ignore elif _module_present('tensorflow', namespaces): from sympy.printing.tensorflow import TensorflowPrinter as Printer # type: ignore elif _module_present('sympy', namespaces): from sympy.printing.pycode import SymPyPrinter as Printer # type: ignore else: from sympy.printing.pycode import PythonCodePrinter as Printer # type: ignore user_functions = {} for m in namespaces[::-1]: if isinstance(m, dict): for k in m: user_functions[k] = k printer = Printer({'fully_qualified_modules': False, 'inline': True, 'allow_unknown_functions': True, 'user_functions': user_functions}) if isinstance(args, set): SymPyDeprecationWarning( feature="The list of arguments is a `set`. This leads to unpredictable results", useinstead=": Convert set into list or tuple", issue=20013, deprecated_since_version="1.6.3" ).warn() # Get the names of the args, for creating a docstring if not iterable(args): args = (args,) names = [] # Grab the callers frame, for getting the names by inspection (if needed) callers_local_vars = inspect.currentframe().f_back.f_locals.items() # type: ignore for n, var in enumerate(args): if hasattr(var, 'name'): names.append(var.name) else: # It's an iterable. Try to get name by inspection of calling frame. name_list = [var_name for var_name, var_val in callers_local_vars if var_val is var] if len(name_list) == 1: names.append(name_list[0]) else: # Cannot infer name with certainty. arg_# will have to do. names.append('arg_' + str(n)) # Create the function definition code and execute it funcname = '_lambdifygenerated' if _module_present('tensorflow', namespaces): funcprinter = _TensorflowEvaluatorPrinter(printer, dummify) # type: _EvaluatorPrinter else: funcprinter = _EvaluatorPrinter(printer, dummify) funcstr = funcprinter.doprint(funcname, args, expr) # Collect the module imports from the code printers. imp_mod_lines = [] for mod, keys in (getattr(printer, 'module_imports', None) or {}).items(): for k in keys: if k not in namespace: ln = "from %s import %s" % (mod, k) try: exec_(ln, {}, namespace) except ImportError: # Tensorflow 2.0 has issues with importing a specific # function from its submodule. # https://github.com/tensorflow/tensorflow/issues/33022 ln = "%s = %s.%s" % (k, mod, k) exec_(ln, {}, namespace) imp_mod_lines.append(ln) # Provide lambda expression with builtins, and compatible implementation of range namespace.update({'builtins':builtins, 'range':range}) funclocals = {} # type: Dict[str, Any] global _lambdify_generated_counter filename = '<lambdifygenerated-%s>' % _lambdify_generated_counter _lambdify_generated_counter += 1 c = compile(funcstr, filename, 'exec') exec_(c, namespace, funclocals) # mtime has to be None or else linecache.checkcache will remove it linecache.cache[filename] = (len(funcstr), None, funcstr.splitlines(True), filename) # type: ignore func = funclocals[funcname] # Apply the docstring sig = "func({})".format(", ".join(str(i) for i in names)) sig = textwrap.fill(sig, subsequent_indent=' '*8) expr_str = str(expr) if len(expr_str) > 78: expr_str = textwrap.wrap(expr_str, 75)[0] + '...' func.__doc__ = ( "Created with lambdify. Signature:\n\n" "{sig}\n\n" "Expression:\n\n" "{expr}\n\n" "Source code:\n\n" "{src}\n\n" "Imported modules:\n\n" "{imp_mods}" ).format(sig=sig, expr=expr_str, src=funcstr, imp_mods='\n'.join(imp_mod_lines)) return func def _module_present(modname, modlist): if modname in modlist: return True for m in modlist: if hasattr(m, '__name__') and m.__name__ == modname: return True return False def _get_namespace(m): """ This is used by _lambdify to parse its arguments. """ if isinstance(m, str): _import(m) return MODULES[m][0] elif isinstance(m, dict): return m elif hasattr(m, "__dict__"): return m.__dict__ else: raise TypeError("Argument must be either a string, dict or module but it is: %s" % m) def lambdastr(args, expr, printer=None, dummify=None): """ Returns a string that can be evaluated to a lambda function. Examples ======== >>> from sympy.abc import x, y, z >>> from sympy.utilities.lambdify import lambdastr >>> lambdastr(x, x**2) 'lambda x: (x**2)' >>> lambdastr((x,y,z), [z,y,x]) 'lambda x,y,z: ([z, y, x])' Although tuples may not appear as arguments to lambda in Python 3, lambdastr will create a lambda function that will unpack the original arguments so that nested arguments can be handled: >>> lambdastr((x, (y, z)), x + y) 'lambda _0,_1: (lambda x,y,z: (x + y))(_0,_1[0],_1[1])' """ # Transforming everything to strings. from sympy.matrices import DeferredVector from sympy import Dummy, sympify, Symbol, Function, flatten, Derivative, Basic if printer is not None: if inspect.isfunction(printer): lambdarepr = printer else: if inspect.isclass(printer): lambdarepr = lambda expr: printer().doprint(expr) else: lambdarepr = lambda expr: printer.doprint(expr) else: #XXX: This has to be done here because of circular imports from sympy.printing.lambdarepr import lambdarepr def sub_args(args, dummies_dict): if isinstance(args, str): return args elif isinstance(args, DeferredVector): return str(args) elif iterable(args): dummies = flatten([sub_args(a, dummies_dict) for a in args]) return ",".join(str(a) for a in dummies) else: # replace these with Dummy symbols if isinstance(args, (Function, Symbol, Derivative)): dummies = Dummy() dummies_dict.update({args : dummies}) return str(dummies) else: return str(args) def sub_expr(expr, dummies_dict): expr = sympify(expr) # dict/tuple are sympified to Basic if isinstance(expr, Basic): expr = expr.xreplace(dummies_dict) # list is not sympified to Basic elif isinstance(expr, list): expr = [sub_expr(a, dummies_dict) for a in expr] return expr # Transform args def isiter(l): return iterable(l, exclude=(str, DeferredVector, NotIterable)) def flat_indexes(iterable): n = 0 for el in iterable: if isiter(el): for ndeep in flat_indexes(el): yield (n,) + ndeep else: yield (n,) n += 1 if dummify is None: dummify = any(isinstance(a, Basic) and a.atoms(Function, Derivative) for a in ( args if isiter(args) else [args])) if isiter(args) and any(isiter(i) for i in args): dum_args = [str(Dummy(str(i))) for i in range(len(args))] indexed_args = ','.join([ dum_args[ind[0]] + ''.join(["[%s]" % k for k in ind[1:]]) for ind in flat_indexes(args)]) lstr = lambdastr(flatten(args), expr, printer=printer, dummify=dummify) return 'lambda %s: (%s)(%s)' % (','.join(dum_args), lstr, indexed_args) dummies_dict = {} if dummify: args = sub_args(args, dummies_dict) else: if isinstance(args, str): pass elif iterable(args, exclude=DeferredVector): args = ",".join(str(a) for a in args) # Transform expr if dummify: if isinstance(expr, str): pass else: expr = sub_expr(expr, dummies_dict) expr = lambdarepr(expr) return "lambda %s: (%s)" % (args, expr) class _EvaluatorPrinter: def __init__(self, printer=None, dummify=False): self._dummify = dummify #XXX: This has to be done here because of circular imports from sympy.printing.lambdarepr import LambdaPrinter if printer is None: printer = LambdaPrinter() if inspect.isfunction(printer): self._exprrepr = printer else: if inspect.isclass(printer): printer = printer() self._exprrepr = printer.doprint #if hasattr(printer, '_print_Symbol'): # symbolrepr = printer._print_Symbol #if hasattr(printer, '_print_Dummy'): # dummyrepr = printer._print_Dummy # Used to print the generated function arguments in a standard way self._argrepr = LambdaPrinter().doprint def doprint(self, funcname, args, expr): """Returns the function definition code as a string.""" from sympy import Dummy funcbody = [] if not iterable(args): args = [args] argstrs, expr = self._preprocess(args, expr) # Generate argument unpacking and final argument list funcargs = [] unpackings = [] for argstr in argstrs: if iterable(argstr): funcargs.append(self._argrepr(Dummy())) unpackings.extend(self._print_unpacking(argstr, funcargs[-1])) else: funcargs.append(argstr) funcsig = 'def {}({}):'.format(funcname, ', '.join(funcargs)) # Wrap input arguments before unpacking funcbody.extend(self._print_funcargwrapping(funcargs)) funcbody.extend(unpackings) funcbody.append('return ({})'.format(self._exprrepr(expr))) funclines = [funcsig] funclines.extend(' ' + line for line in funcbody) return '\n'.join(funclines) + '\n' @classmethod def _is_safe_ident(cls, ident): return isinstance(ident, str) and ident.isidentifier() \ and not keyword.iskeyword(ident) def _preprocess(self, args, expr): """Preprocess args, expr to replace arguments that do not map to valid Python identifiers. Returns string form of args, and updated expr. """ from sympy import Dummy, Function, flatten, Derivative, ordered, Basic from sympy.matrices import DeferredVector from sympy.core.symbol import uniquely_named_symbol from sympy.core.expr import Expr # Args of type Dummy can cause name collisions with args # of type Symbol. Force dummify of everything in this # situation. dummify = self._dummify or any( isinstance(arg, Dummy) for arg in flatten(args)) argstrs = [None]*len(args) for arg, i in reversed(list(ordered(zip(args, range(len(args)))))): if iterable(arg): s, expr = self._preprocess(arg, expr) elif isinstance(arg, DeferredVector): s = str(arg) elif isinstance(arg, Basic) and arg.is_symbol: s = self._argrepr(arg) if dummify or not self._is_safe_ident(s): dummy = Dummy() if isinstance(expr, Expr): dummy = uniquely_named_symbol( dummy.name, expr, modify=lambda s: '_' + s) s = self._argrepr(dummy) expr = self._subexpr(expr, {arg: dummy}) elif dummify or isinstance(arg, (Function, Derivative)): dummy = Dummy() s = self._argrepr(dummy) expr = self._subexpr(expr, {arg: dummy}) else: s = str(arg) argstrs[i] = s return argstrs, expr def _subexpr(self, expr, dummies_dict): from sympy.matrices import DeferredVector from sympy import sympify expr = sympify(expr) xreplace = getattr(expr, 'xreplace', None) if xreplace is not None: expr = xreplace(dummies_dict) else: if isinstance(expr, DeferredVector): pass elif isinstance(expr, dict): k = [self._subexpr(sympify(a), dummies_dict) for a in expr.keys()] v = [self._subexpr(sympify(a), dummies_dict) for a in expr.values()] expr = dict(zip(k, v)) elif isinstance(expr, tuple): expr = tuple(self._subexpr(sympify(a), dummies_dict) for a in expr) elif isinstance(expr, list): expr = [self._subexpr(sympify(a), dummies_dict) for a in expr] return expr def _print_funcargwrapping(self, args): """Generate argument wrapping code. args is the argument list of the generated function (strings). Return value is a list of lines of code that will be inserted at the beginning of the function definition. """ return [] def _print_unpacking(self, unpackto, arg): """Generate argument unpacking code. arg is the function argument to be unpacked (a string), and unpackto is a list or nested lists of the variable names (strings) to unpack to. """ def unpack_lhs(lvalues): return '[{}]'.format(', '.join( unpack_lhs(val) if iterable(val) else val for val in lvalues)) return ['{} = {}'.format(unpack_lhs(unpackto), arg)] class _TensorflowEvaluatorPrinter(_EvaluatorPrinter): def _print_unpacking(self, lvalues, rvalue): """Generate argument unpacking code. This method is used when the input value is not interable, but can be indexed (see issue #14655). """ from sympy import flatten def flat_indexes(elems): n = 0 for el in elems: if iterable(el): for ndeep in flat_indexes(el): yield (n,) + ndeep else: yield (n,) n += 1 indexed = ', '.join('{}[{}]'.format(rvalue, ']['.join(map(str, ind))) for ind in flat_indexes(lvalues)) return ['[{}] = [{}]'.format(', '.join(flatten(lvalues)), indexed)] def _imp_namespace(expr, namespace=None): """ Return namespace dict with function implementations We need to search for functions in anything that can be thrown at us - that is - anything that could be passed as ``expr``. Examples include sympy expressions, as well as tuples, lists and dicts that may contain sympy expressions. Parameters ---------- expr : object Something passed to lambdify, that will generate valid code from ``str(expr)``. namespace : None or mapping Namespace to fill. None results in new empty dict Returns ------- namespace : dict dict with keys of implemented function names within ``expr`` and corresponding values being the numerical implementation of function Examples ======== >>> from sympy.abc import x >>> from sympy.utilities.lambdify import implemented_function, _imp_namespace >>> from sympy import Function >>> f = implemented_function(Function('f'), lambda x: x+1) >>> g = implemented_function(Function('g'), lambda x: x*10) >>> namespace = _imp_namespace(f(g(x))) >>> sorted(namespace.keys()) ['f', 'g'] """ # Delayed import to avoid circular imports from sympy.core.function import FunctionClass if namespace is None: namespace = {} # tuples, lists, dicts are valid expressions if is_sequence(expr): for arg in expr: _imp_namespace(arg, namespace) return namespace elif isinstance(expr, dict): for key, val in expr.items(): # functions can be in dictionary keys _imp_namespace(key, namespace) _imp_namespace(val, namespace) return namespace # sympy expressions may be Functions themselves func = getattr(expr, 'func', None) if isinstance(func, FunctionClass): imp = getattr(func, '_imp_', None) if imp is not None: name = expr.func.__name__ if name in namespace and namespace[name] != imp: raise ValueError('We found more than one ' 'implementation with name ' '"%s"' % name) namespace[name] = imp # and / or they may take Functions as arguments if hasattr(expr, 'args'): for arg in expr.args: _imp_namespace(arg, namespace) return namespace def implemented_function(symfunc, implementation): """ Add numerical ``implementation`` to function ``symfunc``. ``symfunc`` can be an ``UndefinedFunction`` instance, or a name string. In the latter case we create an ``UndefinedFunction`` instance with that name. Be aware that this is a quick workaround, not a general method to create special symbolic functions. If you want to create a symbolic function to be used by all the machinery of SymPy you should subclass the ``Function`` class. Parameters ---------- symfunc : ``str`` or ``UndefinedFunction`` instance If ``str``, then create new ``UndefinedFunction`` with this as name. If ``symfunc`` is an Undefined function, create a new function with the same name and the implemented function attached. implementation : callable numerical implementation to be called by ``evalf()`` or ``lambdify`` Returns ------- afunc : sympy.FunctionClass instance function with attached implementation Examples ======== >>> from sympy.abc import x >>> from sympy.utilities.lambdify import lambdify, implemented_function >>> f = implemented_function('f', lambda x: x+1) >>> lam_f = lambdify(x, f(x)) >>> lam_f(4) 5 """ # Delayed import to avoid circular imports from sympy.core.function import UndefinedFunction # if name, create function to hold implementation kwargs = {} if isinstance(symfunc, UndefinedFunction): kwargs = symfunc._kwargs symfunc = symfunc.__name__ if isinstance(symfunc, str): # Keyword arguments to UndefinedFunction are added as attributes to # the created class. symfunc = UndefinedFunction( symfunc, _imp_=staticmethod(implementation), **kwargs) elif not isinstance(symfunc, UndefinedFunction): raise ValueError(filldedent(''' symfunc should be either a string or an UndefinedFunction instance.''')) return symfunc

a53ba351df1b9660ac721ffc99f61a04975b9ee024eb120a5f519c84e63cbaa9

from collections import defaultdict, OrderedDict from itertools import ( combinations, combinations_with_replacement, permutations, product, product as cartes ) import random from operator import gt from sympy.core import Basic # this is the logical location of these functions from sympy.core.compatibility import ( as_int, default_sort_key, is_sequence, iterable, ordered ) from sympy.utilities.enumerative import ( multiset_partitions_taocp, list_visitor, MultisetPartitionTraverser) def is_palindromic(s, i=0, j=None): """return True if the sequence is the same from left to right as it is from right to left in the whole sequence (default) or in the Python slice ``s[i: j]``; else False. Examples ======== >>> from sympy.utilities.iterables import is_palindromic >>> is_palindromic([1, 0, 1]) True >>> is_palindromic('abcbb') False >>> is_palindromic('abcbb', 1) False Normal Python slicing is performed in place so there is no need to create a slice of the sequence for testing: >>> is_palindromic('abcbb', 1, -1) True >>> is_palindromic('abcbb', -4, -1) True See Also ======== sympy.ntheory.digits.is_palindromic: tests integers """ i, j, _ = slice(i, j).indices(len(s)) m = (j - i)//2 # if length is odd, middle element will be ignored return all(s[i + k] == s[j - 1 - k] for k in range(m)) def flatten(iterable, levels=None, cls=None): """ Recursively denest iterable containers. >>> from sympy.utilities.iterables import flatten >>> flatten([1, 2, 3]) [1, 2, 3] >>> flatten([1, 2, [3]]) [1, 2, 3] >>> flatten([1, [2, 3], [4, 5]]) [1, 2, 3, 4, 5] >>> flatten([1.0, 2, (1, None)]) [1.0, 2, 1, None] If you want to denest only a specified number of levels of nested containers, then set ``levels`` flag to the desired number of levels:: >>> ls = [[(-2, -1), (1, 2)], [(0, 0)]] >>> flatten(ls, levels=1) [(-2, -1), (1, 2), (0, 0)] If cls argument is specified, it will only flatten instances of that class, for example: >>> from sympy.core import Basic >>> class MyOp(Basic): ... pass ... >>> flatten([MyOp(1, MyOp(2, 3))], cls=MyOp) [1, 2, 3] adapted from https://kogs-www.informatik.uni-hamburg.de/~meine/python_tricks """ from sympy.tensor.array import NDimArray if levels is not None: if not levels: return iterable elif levels > 0: levels -= 1 else: raise ValueError( "expected non-negative number of levels, got %s" % levels) if cls is None: reducible = lambda x: is_sequence(x, set) else: reducible = lambda x: isinstance(x, cls) result = [] for el in iterable: if reducible(el): if hasattr(el, 'args') and not isinstance(el, NDimArray): el = el.args result.extend(flatten(el, levels=levels, cls=cls)) else: result.append(el) return result def unflatten(iter, n=2): """Group ``iter`` into tuples of length ``n``. Raise an error if the length of ``iter`` is not a multiple of ``n``. """ if n < 1 or len(iter) % n: raise ValueError('iter length is not a multiple of %i' % n) return list(zip(*(iter[i::n] for i in range(n)))) def reshape(seq, how): """Reshape the sequence according to the template in ``how``. Examples ======== >>> from sympy.utilities import reshape >>> seq = list(range(1, 9)) >>> reshape(seq, [4]) # lists of 4 [[1, 2, 3, 4], [5, 6, 7, 8]] >>> reshape(seq, (4,)) # tuples of 4 [(1, 2, 3, 4), (5, 6, 7, 8)] >>> reshape(seq, (2, 2)) # tuples of 4 [(1, 2, 3, 4), (5, 6, 7, 8)] >>> reshape(seq, (2, [2])) # (i, i, [i, i]) [(1, 2, [3, 4]), (5, 6, [7, 8])] >>> reshape(seq, ((2,), [2])) # etc.... [((1, 2), [3, 4]), ((5, 6), [7, 8])] >>> reshape(seq, (1, [2], 1)) [(1, [2, 3], 4), (5, [6, 7], 8)] >>> reshape(tuple(seq), ([[1], 1, (2,)],)) (([[1], 2, (3, 4)],), ([[5], 6, (7, 8)],)) >>> reshape(tuple(seq), ([1], 1, (2,))) (([1], 2, (3, 4)), ([5], 6, (7, 8))) >>> reshape(list(range(12)), [2, [3], {2}, (1, (3,), 1)]) [[0, 1, [2, 3, 4], {5, 6}, (7, (8, 9, 10), 11)]] """ m = sum(flatten(how)) n, rem = divmod(len(seq), m) if m < 0 or rem: raise ValueError('template must sum to positive number ' 'that divides the length of the sequence') i = 0 container = type(how) rv = [None]*n for k in range(len(rv)): rv[k] = [] for hi in how: if type(hi) is int: rv[k].extend(seq[i: i + hi]) i += hi else: n = sum(flatten(hi)) hi_type = type(hi) rv[k].append(hi_type(reshape(seq[i: i + n], hi)[0])) i += n rv[k] = container(rv[k]) return type(seq)(rv) def group(seq, multiple=True): """ Splits a sequence into a list of lists of equal, adjacent elements. Examples ======== >>> from sympy.utilities.iterables import group >>> group([1, 1, 1, 2, 2, 3]) [[1, 1, 1], [2, 2], [3]] >>> group([1, 1, 1, 2, 2, 3], multiple=False) [(1, 3), (2, 2), (3, 1)] >>> group([1, 1, 3, 2, 2, 1], multiple=False) [(1, 2), (3, 1), (2, 2), (1, 1)] See Also ======== multiset """ if not seq: return [] current, groups = [seq[0]], [] for elem in seq[1:]: if elem == current[-1]: current.append(elem) else: groups.append(current) current = [elem] groups.append(current) if multiple: return groups for i, current in enumerate(groups): groups[i] = (current[0], len(current)) return groups def _iproduct2(iterable1, iterable2): '''Cartesian product of two possibly infinite iterables''' it1 = iter(iterable1) it2 = iter(iterable2) elems1 = [] elems2 = [] sentinel = object() def append(it, elems): e = next(it, sentinel) if e is not sentinel: elems.append(e) n = 0 append(it1, elems1) append(it2, elems2) while n <= len(elems1) + len(elems2): for m in range(n-len(elems1)+1, len(elems2)): yield (elems1[n-m], elems2[m]) n += 1 append(it1, elems1) append(it2, elems2) def iproduct(*iterables): ''' Cartesian product of iterables. Generator of the cartesian product of iterables. This is analogous to itertools.product except that it works with infinite iterables and will yield any item from the infinite product eventually. Examples ======== >>> from sympy.utilities.iterables import iproduct >>> sorted(iproduct([1,2], [3,4])) [(1, 3), (1, 4), (2, 3), (2, 4)] With an infinite iterator: >>> from sympy import S >>> (3,) in iproduct(S.Integers) True >>> (3, 4) in iproduct(S.Integers, S.Integers) True .. seealso:: `itertools.product <https://docs.python.org/3/library/itertools.html#itertools.product>`_ ''' if len(iterables) == 0: yield () return elif len(iterables) == 1: for e in iterables[0]: yield (e,) elif len(iterables) == 2: yield from _iproduct2(*iterables) else: first, others = iterables[0], iterables[1:] for ef, eo in _iproduct2(first, iproduct(*others)): yield (ef,) + eo def multiset(seq): """Return the hashable sequence in multiset form with values being the multiplicity of the item in the sequence. Examples ======== >>> from sympy.utilities.iterables import multiset >>> multiset('mississippi') {'i': 4, 'm': 1, 'p': 2, 's': 4} See Also ======== group """ rv = defaultdict(int) for s in seq: rv[s] += 1 return dict(rv) def postorder_traversal(node, keys=None): """ Do a postorder traversal of a tree. This generator recursively yields nodes that it has visited in a postorder fashion. That is, it descends through the tree depth-first to yield all of a node's children's postorder traversal before yielding the node itself. Parameters ========== node : sympy expression The expression to traverse. keys : (default None) sort key(s) The key(s) used to sort args of Basic objects. When None, args of Basic objects are processed in arbitrary order. If key is defined, it will be passed along to ordered() as the only key(s) to use to sort the arguments; if ``key`` is simply True then the default keys of ``ordered`` will be used (node count and default_sort_key). Yields ====== subtree : sympy expression All of the subtrees in the tree. Examples ======== >>> from sympy.utilities.iterables import postorder_traversal >>> from sympy.abc import w, x, y, z The nodes are returned in the order that they are encountered unless key is given; simply passing key=True will guarantee that the traversal is unique. >>> list(postorder_traversal(w + (x + y)*z)) # doctest: +SKIP [z, y, x, x + y, z*(x + y), w, w + z*(x + y)] >>> list(postorder_traversal(w + (x + y)*z, keys=True)) [w, z, x, y, x + y, z*(x + y), w + z*(x + y)] """ if isinstance(node, Basic): args = node.args if keys: if keys != True: args = ordered(args, keys, default=False) else: args = ordered(args) for arg in args: yield from postorder_traversal(arg, keys) elif iterable(node): for item in node: yield from postorder_traversal(item, keys) yield node def interactive_traversal(expr): """Traverse a tree asking a user which branch to choose. """ from sympy.printing import pprint RED, BRED = '\033[0;31m', '\033[1;31m' GREEN, BGREEN = '\033[0;32m', '\033[1;32m' YELLOW, BYELLOW = '\033[0;33m', '\033[1;33m' # noqa BLUE, BBLUE = '\033[0;34m', '\033[1;34m' # noqa MAGENTA, BMAGENTA = '\033[0;35m', '\033[1;35m'# noqa CYAN, BCYAN = '\033[0;36m', '\033[1;36m' # noqa END = '\033[0m' def cprint(*args): print("".join(map(str, args)) + END) def _interactive_traversal(expr, stage): if stage > 0: print() cprint("Current expression (stage ", BYELLOW, stage, END, "):") print(BCYAN) pprint(expr) print(END) if isinstance(expr, Basic): if expr.is_Add: args = expr.as_ordered_terms() elif expr.is_Mul: args = expr.as_ordered_factors() else: args = expr.args elif hasattr(expr, "__iter__"): args = list(expr) else: return expr n_args = len(args) if not n_args: return expr for i, arg in enumerate(args): cprint(GREEN, "[", BGREEN, i, GREEN, "] ", BLUE, type(arg), END) pprint(arg) print() if n_args == 1: choices = '0' else: choices = '0-%d' % (n_args - 1) try: choice = input("Your choice [%s,f,l,r,d,?]: " % choices) except EOFError: result = expr print() else: if choice == '?': cprint(RED, "%s - select subexpression with the given index" % choices) cprint(RED, "f - select the first subexpression") cprint(RED, "l - select the last subexpression") cprint(RED, "r - select a random subexpression") cprint(RED, "d - done\n") result = _interactive_traversal(expr, stage) elif choice in ['d', '']: result = expr elif choice == 'f': result = _interactive_traversal(args[0], stage + 1) elif choice == 'l': result = _interactive_traversal(args[-1], stage + 1) elif choice == 'r': result = _interactive_traversal(random.choice(args), stage + 1) else: try: choice = int(choice) except ValueError: cprint(BRED, "Choice must be a number in %s range\n" % choices) result = _interactive_traversal(expr, stage) else: if choice < 0 or choice >= n_args: cprint(BRED, "Choice must be in %s range\n" % choices) result = _interactive_traversal(expr, stage) else: result = _interactive_traversal(args[choice], stage + 1) return result return _interactive_traversal(expr, 0) def ibin(n, bits=None, str=False): """Return a list of length ``bits`` corresponding to the binary value of ``n`` with small bits to the right (last). If bits is omitted, the length will be the number required to represent ``n``. If the bits are desired in reversed order, use the ``[::-1]`` slice of the returned list. If a sequence of all bits-length lists starting from ``[0, 0,..., 0]`` through ``[1, 1, ..., 1]`` are desired, pass a non-integer for bits, e.g. ``'all'``. If the bit *string* is desired pass ``str=True``. Examples ======== >>> from sympy.utilities.iterables import ibin >>> ibin(2) [1, 0] >>> ibin(2, 4) [0, 0, 1, 0] If all lists corresponding to 0 to 2**n - 1, pass a non-integer for bits: >>> bits = 2 >>> for i in ibin(2, 'all'): ... print(i) (0, 0) (0, 1) (1, 0) (1, 1) If a bit string is desired of a given length, use str=True: >>> n = 123 >>> bits = 10 >>> ibin(n, bits, str=True) '0001111011' >>> ibin(n, bits, str=True)[::-1] # small bits left '1101111000' >>> list(ibin(3, 'all', str=True)) ['000', '001', '010', '011', '100', '101', '110', '111'] """ if n < 0: raise ValueError("negative numbers are not allowed") n = as_int(n) if bits is None: bits = 0 else: try: bits = as_int(bits) except ValueError: bits = -1 else: if n.bit_length() > bits: raise ValueError( "`bits` must be >= {}".format(n.bit_length())) if not str: if bits >= 0: return [1 if i == "1" else 0 for i in bin(n)[2:].rjust(bits, "0")] else: return variations(list(range(2)), n, repetition=True) else: if bits >= 0: return bin(n)[2:].rjust(bits, "0") else: return (bin(i)[2:].rjust(n, "0") for i in range(2**n)) def variations(seq, n, repetition=False): r"""Returns a generator of the n-sized variations of ``seq`` (size N). ``repetition`` controls whether items in ``seq`` can appear more than once; Examples ======== ``variations(seq, n)`` will return `\frac{N!}{(N - n)!}` permutations without repetition of ``seq``'s elements: >>> from sympy.utilities.iterables import variations >>> list(variations([1, 2], 2)) [(1, 2), (2, 1)] ``variations(seq, n, True)`` will return the `N^n` permutations obtained by allowing repetition of elements: >>> list(variations([1, 2], 2, repetition=True)) [(1, 1), (1, 2), (2, 1), (2, 2)] If you ask for more items than are in the set you get the empty set unless you allow repetitions: >>> list(variations([0, 1], 3, repetition=False)) [] >>> list(variations([0, 1], 3, repetition=True))[:4] [(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1)] .. seealso:: `itertools.permutations <https://docs.python.org/3/library/itertools.html#itertools.permutations>`_, `itertools.product <https://docs.python.org/3/library/itertools.html#itertools.product>`_ """ if not repetition: seq = tuple(seq) if len(seq) < n: return yield from permutations(seq, n) else: if n == 0: yield () else: yield from product(seq, repeat=n) def subsets(seq, k=None, repetition=False): r"""Generates all `k`-subsets (combinations) from an `n`-element set, ``seq``. A `k`-subset of an `n`-element set is any subset of length exactly `k`. The number of `k`-subsets of an `n`-element set is given by ``binomial(n, k)``, whereas there are `2^n` subsets all together. If `k` is ``None`` then all `2^n` subsets will be returned from shortest to longest. Examples ======== >>> from sympy.utilities.iterables import subsets ``subsets(seq, k)`` will return the `\frac{n!}{k!(n - k)!}` `k`-subsets (combinations) without repetition, i.e. once an item has been removed, it can no longer be "taken": >>> list(subsets([1, 2], 2)) [(1, 2)] >>> list(subsets([1, 2])) [(), (1,), (2,), (1, 2)] >>> list(subsets([1, 2, 3], 2)) [(1, 2), (1, 3), (2, 3)] ``subsets(seq, k, repetition=True)`` will return the `\frac{(n - 1 + k)!}{k!(n - 1)!}` combinations *with* repetition: >>> list(subsets([1, 2], 2, repetition=True)) [(1, 1), (1, 2), (2, 2)] If you ask for more items than are in the set you get the empty set unless you allow repetitions: >>> list(subsets([0, 1], 3, repetition=False)) [] >>> list(subsets([0, 1], 3, repetition=True)) [(0, 0, 0), (0, 0, 1), (0, 1, 1), (1, 1, 1)] """ if k is None: for k in range(len(seq) + 1): yield from subsets(seq, k, repetition) else: if not repetition: yield from combinations(seq, k) else: yield from combinations_with_replacement(seq, k) def filter_symbols(iterator, exclude): """ Only yield elements from `iterator` that do not occur in `exclude`. Parameters ========== iterator : iterable iterator to take elements from exclude : iterable elements to exclude Returns ======= iterator : iterator filtered iterator """ exclude = set(exclude) for s in iterator: if s not in exclude: yield s def numbered_symbols(prefix='x', cls=None, start=0, exclude=[], *args, **assumptions): """ Generate an infinite stream of Symbols consisting of a prefix and increasing subscripts provided that they do not occur in ``exclude``. Parameters ========== prefix : str, optional The prefix to use. By default, this function will generate symbols of the form "x0", "x1", etc. cls : class, optional The class to use. By default, it uses ``Symbol``, but you can also use ``Wild`` or ``Dummy``. start : int, optional The start number. By default, it is 0. Returns ======= sym : Symbol The subscripted symbols. """ exclude = set(exclude or []) if cls is None: # We can't just make the default cls=Symbol because it isn't # imported yet. from sympy import Symbol cls = Symbol while True: name = '%s%s' % (prefix, start) s = cls(name, *args, **assumptions) if s not in exclude: yield s start += 1 def capture(func): """Return the printed output of func(). ``func`` should be a function without arguments that produces output with print statements. >>> from sympy.utilities.iterables import capture >>> from sympy import pprint >>> from sympy.abc import x >>> def foo(): ... print('hello world!') ... >>> 'hello' in capture(foo) # foo, not foo() True >>> capture(lambda: pprint(2/x)) '2\\n-\\nx\\n' """ from sympy.core.compatibility import StringIO import sys stdout = sys.stdout sys.stdout = file = StringIO() try: func() finally: sys.stdout = stdout return file.getvalue() def sift(seq, keyfunc, binary=False): """ Sift the sequence, ``seq`` according to ``keyfunc``. Returns ======= When ``binary`` is ``False`` (default), the output is a dictionary where elements of ``seq`` are stored in a list keyed to the value of keyfunc for that element. If ``binary`` is True then a tuple with lists ``T`` and ``F`` are returned where ``T`` is a list containing elements of seq for which ``keyfunc`` was ``True`` and ``F`` containing those elements for which ``keyfunc`` was ``False``; a ValueError is raised if the ``keyfunc`` is not binary. Examples ======== >>> from sympy.utilities import sift >>> from sympy.abc import x, y >>> from sympy import sqrt, exp, pi, Tuple >>> sift(range(5), lambda x: x % 2) {0: [0, 2, 4], 1: [1, 3]} sift() returns a defaultdict() object, so any key that has no matches will give []. >>> sift([x], lambda x: x.is_commutative) {True: [x]} >>> _[False] [] Sometimes you will not know how many keys you will get: >>> sift([sqrt(x), exp(x), (y**x)**2], ... lambda x: x.as_base_exp()[0]) {E: [exp(x)], x: [sqrt(x)], y: [y**(2*x)]} Sometimes you expect the results to be binary; the results can be unpacked by setting ``binary`` to True: >>> sift(range(4), lambda x: x % 2, binary=True) ([1, 3], [0, 2]) >>> sift(Tuple(1, pi), lambda x: x.is_rational, binary=True) ([1], [pi]) A ValueError is raised if the predicate was not actually binary (which is a good test for the logic where sifting is used and binary results were expected): >>> unknown = exp(1) - pi # the rationality of this is unknown >>> args = Tuple(1, pi, unknown) >>> sift(args, lambda x: x.is_rational, binary=True) Traceback (most recent call last): ... ValueError: keyfunc gave non-binary output The non-binary sifting shows that there were 3 keys generated: >>> set(sift(args, lambda x: x.is_rational).keys()) {None, False, True} If you need to sort the sifted items it might be better to use ``ordered`` which can economically apply multiple sort keys to a sequence while sorting. See Also ======== ordered """ if not binary: m = defaultdict(list) for i in seq: m[keyfunc(i)].append(i) return m sift = F, T = [], [] for i in seq: try: sift[keyfunc(i)].append(i) except (IndexError, TypeError): raise ValueError('keyfunc gave non-binary output') return T, F def take(iter, n): """Return ``n`` items from ``iter`` iterator. """ return [ value for _, value in zip(range(n), iter) ] def dict_merge(*dicts): """Merge dictionaries into a single dictionary. """ merged = {} for dict in dicts: merged.update(dict) return merged def common_prefix(*seqs): """Return the subsequence that is a common start of sequences in ``seqs``. >>> from sympy.utilities.iterables import common_prefix >>> common_prefix(list(range(3))) [0, 1, 2] >>> common_prefix(list(range(3)), list(range(4))) [0, 1, 2] >>> common_prefix([1, 2, 3], [1, 2, 5]) [1, 2] >>> common_prefix([1, 2, 3], [1, 3, 5]) [1] """ if any(not s for s in seqs): return [] elif len(seqs) == 1: return seqs[0] i = 0 for i in range(min(len(s) for s in seqs)): if not all(seqs[j][i] == seqs[0][i] for j in range(len(seqs))): break else: i += 1 return seqs[0][:i] def common_suffix(*seqs): """Return the subsequence that is a common ending of sequences in ``seqs``. >>> from sympy.utilities.iterables import common_suffix >>> common_suffix(list(range(3))) [0, 1, 2] >>> common_suffix(list(range(3)), list(range(4))) [] >>> common_suffix([1, 2, 3], [9, 2, 3]) [2, 3] >>> common_suffix([1, 2, 3], [9, 7, 3]) [3] """ if any(not s for s in seqs): return [] elif len(seqs) == 1: return seqs[0] i = 0 for i in range(-1, -min(len(s) for s in seqs) - 1, -1): if not all(seqs[j][i] == seqs[0][i] for j in range(len(seqs))): break else: i -= 1 if i == -1: return [] else: return seqs[0][i + 1:] def prefixes(seq): """ Generate all prefixes of a sequence. Examples ======== >>> from sympy.utilities.iterables import prefixes >>> list(prefixes([1,2,3,4])) [[1], [1, 2], [1, 2, 3], [1, 2, 3, 4]] """ n = len(seq) for i in range(n): yield seq[:i + 1] def postfixes(seq): """ Generate all postfixes of a sequence. Examples ======== >>> from sympy.utilities.iterables import postfixes >>> list(postfixes([1,2,3,4])) [[4], [3, 4], [2, 3, 4], [1, 2, 3, 4]] """ n = len(seq) for i in range(n): yield seq[n - i - 1:] def topological_sort(graph, key=None): r""" Topological sort of graph's vertices. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph to be sorted topologically. key : callable[T] (optional) Ordering key for vertices on the same level. By default the natural (e.g. lexicographic) ordering is used (in this case the base type must implement ordering relations). Examples ======== Consider a graph:: +---+ +---+ +---+ | 7 |\ | 5 | | 3 | +---+ \ +---+ +---+ | _\___/ ____ _/ | | / \___/ \ / | V V V V | +----+ +---+ | | 11 | | 8 | | +----+ +---+ | | | \____ ___/ _ | | \ \ / / \ | V \ V V / V V +---+ \ +---+ | +----+ | 2 | | | 9 | | | 10 | +---+ | +---+ | +----+ \________/ where vertices are integers. This graph can be encoded using elementary Python's data structures as follows:: >>> V = [2, 3, 5, 7, 8, 9, 10, 11] >>> E = [(7, 11), (7, 8), (5, 11), (3, 8), (3, 10), ... (11, 2), (11, 9), (11, 10), (8, 9)] To compute a topological sort for graph ``(V, E)`` issue:: >>> from sympy.utilities.iterables import topological_sort >>> topological_sort((V, E)) [3, 5, 7, 8, 11, 2, 9, 10] If specific tie breaking approach is needed, use ``key`` parameter:: >>> topological_sort((V, E), key=lambda v: -v) [7, 5, 11, 3, 10, 8, 9, 2] Only acyclic graphs can be sorted. If the input graph has a cycle, then ``ValueError`` will be raised:: >>> topological_sort((V, E + [(10, 7)])) Traceback (most recent call last): ... ValueError: cycle detected References ========== .. [1] https://en.wikipedia.org/wiki/Topological_sorting """ V, E = graph L = [] S = set(V) E = list(E) for v, u in E: S.discard(u) if key is None: key = lambda value: value S = sorted(S, key=key, reverse=True) while S: node = S.pop() L.append(node) for u, v in list(E): if u == node: E.remove((u, v)) for _u, _v in E: if v == _v: break else: kv = key(v) for i, s in enumerate(S): ks = key(s) if kv > ks: S.insert(i, v) break else: S.append(v) if E: raise ValueError("cycle detected") else: return L def strongly_connected_components(G): r""" Strongly connected components of a directed graph in reverse topological order. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph whose strongly connected components are to be found. Examples ======== Consider a directed graph (in dot notation):: digraph { A -> B A -> C B -> C C -> B B -> D } where vertices are the letters A, B, C and D. This graph can be encoded using Python's elementary data structures as follows:: >>> V = ['A', 'B', 'C', 'D'] >>> E = [('A', 'B'), ('A', 'C'), ('B', 'C'), ('C', 'B'), ('B', 'D')] The strongly connected components of this graph can be computed as >>> from sympy.utilities.iterables import strongly_connected_components >>> strongly_connected_components((V, E)) [['D'], ['B', 'C'], ['A']] This also gives the components in reverse topological order. Since the subgraph containing B and C has a cycle they must be together in a strongly connected component. A and D are connected to the rest of the graph but not in a cyclic manner so they appear as their own strongly connected components. Notes ===== The vertices of the graph must be hashable for the data structures used. If the vertices are unhashable replace them with integer indices. This function uses Tarjan's algorithm to compute the strongly connected components in `O(|V|+|E|)` (linear) time. References ========== .. [1] https://en.wikipedia.org/wiki/Strongly_connected_component .. [2] https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm See Also ======== sympy.utilities.iterables.connected_components """ # Map from a vertex to its neighbours V, E = G Gmap = {vi: [] for vi in V} for v1, v2 in E: Gmap[v1].append(v2) # Non-recursive Tarjan's algorithm: lowlink = {} indices = {} stack = OrderedDict() callstack = [] components = [] nomore = object() def start(v): index = len(stack) indices[v] = lowlink[v] = index stack[v] = None callstack.append((v, iter(Gmap[v]))) def finish(v1): # Finished a component? if lowlink[v1] == indices[v1]: component = [stack.popitem()[0]] while component[-1] is not v1: component.append(stack.popitem()[0]) components.append(component[::-1]) v2, _ = callstack.pop() if callstack: v1, _ = callstack[-1] lowlink[v1] = min(lowlink[v1], lowlink[v2]) for v in V: if v in indices: continue start(v) while callstack: v1, it1 = callstack[-1] v2 = next(it1, nomore) # Finished children of v1? if v2 is nomore: finish(v1) # Recurse on v2 elif v2 not in indices: start(v2) elif v2 in stack: lowlink[v1] = min(lowlink[v1], indices[v2]) # Reverse topological sort order: return components def connected_components(G): r""" Connected components of an undirected graph or weakly connected components of a directed graph. Parameters ========== graph : tuple[list, list[tuple[T, T]] A tuple consisting of a list of vertices and a list of edges of a graph whose connected components are to be found. Examples ======== Given an undirected graph:: graph { A -- B C -- D } We can find the connected components using this function if we include each edge in both directions:: >>> from sympy.utilities.iterables import connected_components >>> V = ['A', 'B', 'C', 'D'] >>> E = [('A', 'B'), ('B', 'A'), ('C', 'D'), ('D', 'C')] >>> connected_components((V, E)) [['A', 'B'], ['C', 'D']] The weakly connected components of a directed graph can found the same way. Notes ===== The vertices of the graph must be hashable for the data structures used. If the vertices are unhashable replace them with integer indices. This function uses Tarjan's algorithm to compute the connected components in `O(|V|+|E|)` (linear) time. References ========== .. [1] https://en.wikipedia.org/wiki/Connected_component_(graph_theory) .. [2] https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm See Also ======== sympy.utilities.iterables.strongly_connected_components """ # Duplicate edges both ways so that the graph is effectively undirected # and return the strongly connected components: V, E = G E_undirected = [] for v1, v2 in E: E_undirected.extend([(v1, v2), (v2, v1)]) return strongly_connected_components((V, E_undirected)) def rotate_left(x, y): """ Left rotates a list x by the number of steps specified in y. Examples ======== >>> from sympy.utilities.iterables import rotate_left >>> a = [0, 1, 2] >>> rotate_left(a, 1) [1, 2, 0] """ if len(x) == 0: return [] y = y % len(x) return x[y:] + x[:y] def rotate_right(x, y): """ Right rotates a list x by the number of steps specified in y. Examples ======== >>> from sympy.utilities.iterables import rotate_right >>> a = [0, 1, 2] >>> rotate_right(a, 1) [2, 0, 1] """ if len(x) == 0: return [] y = len(x) - y % len(x) return x[y:] + x[:y] def least_rotation(x): ''' Returns the number of steps of left rotation required to obtain lexicographically minimal string/list/tuple, etc. Examples ======== >>> from sympy.utilities.iterables import least_rotation, rotate_left >>> a = [3, 1, 5, 1, 2] >>> least_rotation(a) 3 >>> rotate_left(a, _) [1, 2, 3, 1, 5] References ========== .. [1] https://en.wikipedia.org/wiki/Lexicographically_minimal_string_rotation ''' S = x + x # Concatenate string to it self to avoid modular arithmetic f = [-1] * len(S) # Failure function k = 0 # Least rotation of string found so far for j in range(1,len(S)): sj = S[j] i = f[j-k-1] while i != -1 and sj != S[k+i+1]: if sj < S[k+i+1]: k = j-i-1 i = f[i] if sj != S[k+i+1]: if sj < S[k]: k = j f[j-k] = -1 else: f[j-k] = i+1 return k def multiset_combinations(m, n, g=None): """ Return the unique combinations of size ``n`` from multiset ``m``. Examples ======== >>> from sympy.utilities.iterables import multiset_combinations >>> from itertools import combinations >>> [''.join(i) for i in multiset_combinations('baby', 3)] ['abb', 'aby', 'bby'] >>> def count(f, s): return len(list(f(s, 3))) The number of combinations depends on the number of letters; the number of unique combinations depends on how the letters are repeated. >>> s1 = 'abracadabra' >>> s2 = 'banana tree' >>> count(combinations, s1), count(multiset_combinations, s1) (165, 23) >>> count(combinations, s2), count(multiset_combinations, s2) (165, 54) """ if g is None: if type(m) is dict: if n > sum(m.values()): return g = [[k, m[k]] for k in ordered(m)] else: m = list(m) if n > len(m): return try: m = multiset(m) g = [(k, m[k]) for k in ordered(m)] except TypeError: m = list(ordered(m)) g = [list(i) for i in group(m, multiple=False)] del m if sum(v for k, v in g) < n or not n: yield [] else: for i, (k, v) in enumerate(g): if v >= n: yield [k]*n v = n - 1 for v in range(min(n, v), 0, -1): for j in multiset_combinations(None, n - v, g[i + 1:]): rv = [k]*v + j if len(rv) == n: yield rv def multiset_permutations(m, size=None, g=None): """ Return the unique permutations of multiset ``m``. Examples ======== >>> from sympy.utilities.iterables import multiset_permutations >>> from sympy import factorial >>> [''.join(i) for i in multiset_permutations('aab')] ['aab', 'aba', 'baa'] >>> factorial(len('banana')) 720 >>> len(list(multiset_permutations('banana'))) 60 """ if g is None: if type(m) is dict: g = [[k, m[k]] for k in ordered(m)] else: m = list(ordered(m)) g = [list(i) for i in group(m, multiple=False)] del m do = [gi for gi in g if gi[1] > 0] SUM = sum([gi[1] for gi in do]) if not do or size is not None and (size > SUM or size < 1): if size < 1: yield [] return elif size == 1: for k, v in do: yield [k] elif len(do) == 1: k, v = do[0] v = v if size is None else (size if size <= v else 0) yield [k for i in range(v)] elif all(v == 1 for k, v in do): for p in permutations([k for k, v in do], size): yield list(p) else: size = size if size is not None else SUM for i, (k, v) in enumerate(do): do[i][1] -= 1 for j in multiset_permutations(None, size - 1, do): if j: yield [k] + j do[i][1] += 1 def _partition(seq, vector, m=None): """ Return the partition of seq as specified by the partition vector. Examples ======== >>> from sympy.utilities.iterables import _partition >>> _partition('abcde', [1, 0, 1, 2, 0]) [['b', 'e'], ['a', 'c'], ['d']] Specifying the number of bins in the partition is optional: >>> _partition('abcde', [1, 0, 1, 2, 0], 3) [['b', 'e'], ['a', 'c'], ['d']] The output of _set_partitions can be passed as follows: >>> output = (3, [1, 0, 1, 2, 0]) >>> _partition('abcde', *output) [['b', 'e'], ['a', 'c'], ['d']] See Also ======== combinatorics.partitions.Partition.from_rgs """ if m is None: m = max(vector) + 1 elif type(vector) is int: # entered as m, vector vector, m = m, vector p = [[] for i in range(m)] for i, v in enumerate(vector): p[v].append(seq[i]) return p def _set_partitions(n): """Cycle through all partions of n elements, yielding the current number of partitions, ``m``, and a mutable list, ``q`` such that element[i] is in part q[i] of the partition. NOTE: ``q`` is modified in place and generally should not be changed between function calls. Examples ======== >>> from sympy.utilities.iterables import _set_partitions, _partition >>> for m, q in _set_partitions(3): ... print('%s %s %s' % (m, q, _partition('abc', q, m))) 1 [0, 0, 0] [['a', 'b', 'c']] 2 [0, 0, 1] [['a', 'b'], ['c']] 2 [0, 1, 0] [['a', 'c'], ['b']] 2 [0, 1, 1] [['a'], ['b', 'c']] 3 [0, 1, 2] [['a'], ['b'], ['c']] Notes ===== This algorithm is similar to, and solves the same problem as, Algorithm 7.2.1.5H, from volume 4A of Knuth's The Art of Computer Programming. Knuth uses the term "restricted growth string" where this code refers to a "partition vector". In each case, the meaning is the same: the value in the ith element of the vector specifies to which part the ith set element is to be assigned. At the lowest level, this code implements an n-digit big-endian counter (stored in the array q) which is incremented (with carries) to get the next partition in the sequence. A special twist is that a digit is constrained to be at most one greater than the maximum of all the digits to the left of it. The array p maintains this maximum, so that the code can efficiently decide when a digit can be incremented in place or whether it needs to be reset to 0 and trigger a carry to the next digit. The enumeration starts with all the digits 0 (which corresponds to all the set elements being assigned to the same 0th part), and ends with 0123...n, which corresponds to each set element being assigned to a different, singleton, part. This routine was rewritten to use 0-based lists while trying to preserve the beauty and efficiency of the original algorithm. References ========== .. [1] Nijenhuis, Albert and Wilf, Herbert. (1978) Combinatorial Algorithms, 2nd Ed, p 91, algorithm "nexequ". Available online from https://www.math.upenn.edu/~wilf/website/CombAlgDownld.html (viewed November 17, 2012). """ p = [0]*n q = [0]*n nc = 1 yield nc, q while nc != n: m = n while 1: m -= 1 i = q[m] if p[i] != 1: break q[m] = 0 i += 1 q[m] = i m += 1 nc += m - n p[0] += n - m if i == nc: p[nc] = 0 nc += 1 p[i - 1] -= 1 p[i] += 1 yield nc, q def multiset_partitions(multiset, m=None): """ Return unique partitions of the given multiset (in list form). If ``m`` is None, all multisets will be returned, otherwise only partitions with ``m`` parts will be returned. If ``multiset`` is an integer, a range [0, 1, ..., multiset - 1] will be supplied. Examples ======== >>> from sympy.utilities.iterables import multiset_partitions >>> list(multiset_partitions([1, 2, 3, 4], 2)) [[[1, 2, 3], [4]], [[1, 2, 4], [3]], [[1, 2], [3, 4]], [[1, 3, 4], [2]], [[1, 3], [2, 4]], [[1, 4], [2, 3]], [[1], [2, 3, 4]]] >>> list(multiset_partitions([1, 2, 3, 4], 1)) [[[1, 2, 3, 4]]] Only unique partitions are returned and these will be returned in a canonical order regardless of the order of the input: >>> a = [1, 2, 2, 1] >>> ans = list(multiset_partitions(a, 2)) >>> a.sort() >>> list(multiset_partitions(a, 2)) == ans True >>> a = range(3, 1, -1) >>> (list(multiset_partitions(a)) == ... list(multiset_partitions(sorted(a)))) True If m is omitted then all partitions will be returned: >>> list(multiset_partitions([1, 1, 2])) [[[1, 1, 2]], [[1, 1], [2]], [[1, 2], [1]], [[1], [1], [2]]] >>> list(multiset_partitions([1]*3)) [[[1, 1, 1]], [[1], [1, 1]], [[1], [1], [1]]] Counting ======== The number of partitions of a set is given by the bell number: >>> from sympy import bell >>> len(list(multiset_partitions(5))) == bell(5) == 52 True The number of partitions of length k from a set of size n is given by the Stirling Number of the 2nd kind: >>> from sympy.functions.combinatorial.numbers import stirling >>> stirling(5, 2) == len(list(multiset_partitions(5, 2))) == 15 True These comments on counting apply to *sets*, not multisets. Notes ===== When all the elements are the same in the multiset, the order of the returned partitions is determined by the ``partitions`` routine. If one is counting partitions then it is better to use the ``nT`` function. See Also ======== partitions sympy.combinatorics.partitions.Partition sympy.combinatorics.partitions.IntegerPartition sympy.functions.combinatorial.numbers.nT """ # This function looks at the supplied input and dispatches to # several special-case routines as they apply. if type(multiset) is int: n = multiset if m and m > n: return multiset = list(range(n)) if m == 1: yield [multiset[:]] return # If m is not None, it can sometimes be faster to use # MultisetPartitionTraverser.enum_range() even for inputs # which are sets. Since the _set_partitions code is quite # fast, this is only advantageous when the overall set # partitions outnumber those with the desired number of parts # by a large factor. (At least 60.) Such a switch is not # currently implemented. for nc, q in _set_partitions(n): if m is None or nc == m: rv = [[] for i in range(nc)] for i in range(n): rv[q[i]].append(multiset[i]) yield rv return if len(multiset) == 1 and isinstance(multiset, str): multiset = [multiset] if not has_variety(multiset): # Only one component, repeated n times. The resulting # partitions correspond to partitions of integer n. n = len(multiset) if m and m > n: return if m == 1: yield [multiset[:]] return x = multiset[:1] for size, p in partitions(n, m, size=True): if m is None or size == m: rv = [] for k in sorted(p): rv.extend([x*k]*p[k]) yield rv else: multiset = list(ordered(multiset)) n = len(multiset) if m and m > n: return if m == 1: yield [multiset[:]] return # Split the information of the multiset into two lists - # one of the elements themselves, and one (of the same length) # giving the number of repeats for the corresponding element. elements, multiplicities = zip(*group(multiset, False)) if len(elements) < len(multiset): # General case - multiset with more than one distinct element # and at least one element repeated more than once. if m: mpt = MultisetPartitionTraverser() for state in mpt.enum_range(multiplicities, m-1, m): yield list_visitor(state, elements) else: for state in multiset_partitions_taocp(multiplicities): yield list_visitor(state, elements) else: # Set partitions case - no repeated elements. Pretty much # same as int argument case above, with same possible, but # currently unimplemented optimization for some cases when # m is not None for nc, q in _set_partitions(n): if m is None or nc == m: rv = [[] for i in range(nc)] for i in range(n): rv[q[i]].append(i) yield [[multiset[j] for j in i] for i in rv] def partitions(n, m=None, k=None, size=False): """Generate all partitions of positive integer, n. Parameters ========== m : integer (default gives partitions of all sizes) limits number of parts in partition (mnemonic: m, maximum parts) k : integer (default gives partitions number from 1 through n) limits the numbers that are kept in the partition (mnemonic: k, keys) size : bool (default False, only partition is returned) when ``True`` then (M, P) is returned where M is the sum of the multiplicities and P is the generated partition. Each partition is represented as a dictionary, mapping an integer to the number of copies of that integer in the partition. For example, the first partition of 4 returned is {4: 1}, "4: one of them". Examples ======== >>> from sympy.utilities.iterables import partitions The numbers appearing in the partition (the key of the returned dict) are limited with k: >>> for p in partitions(6, k=2): # doctest: +SKIP ... print(p) {2: 3} {1: 2, 2: 2} {1: 4, 2: 1} {1: 6} The maximum number of parts in the partition (the sum of the values in the returned dict) are limited with m (default value, None, gives partitions from 1 through n): >>> for p in partitions(6, m=2): # doctest: +SKIP ... print(p) ... {6: 1} {1: 1, 5: 1} {2: 1, 4: 1} {3: 2} References ========== .. [1] modified from Tim Peter's version to allow for k and m values: http://code.activestate.com/recipes/218332-generator-for-integer-partitions/ See Also ======== sympy.combinatorics.partitions.Partition sympy.combinatorics.partitions.IntegerPartition """ if (n <= 0 or m is not None and m < 1 or k is not None and k < 1 or m and k and m*k < n): # the empty set is the only way to handle these inputs # and returning {} to represent it is consistent with # the counting convention, e.g. nT(0) == 1. if size: yield 0, {} else: yield {} return if m is None: m = n else: m = min(m, n) if n == 0: if size: yield 1, {0: 1} else: yield {0: 1} return k = min(k or n, n) n, m, k = as_int(n), as_int(m), as_int(k) q, r = divmod(n, k) ms = {k: q} keys = [k] # ms.keys(), from largest to smallest if r: ms[r] = 1 keys.append(r) room = m - q - bool(r) if size: yield sum(ms.values()), ms.copy() else: yield ms.copy() while keys != [1]: # Reuse any 1's. if keys[-1] == 1: del keys[-1] reuse = ms.pop(1) room += reuse else: reuse = 0 while 1: # Let i be the smallest key larger than 1. Reuse one # instance of i. i = keys[-1] newcount = ms[i] = ms[i] - 1 reuse += i if newcount == 0: del keys[-1], ms[i] room += 1 # Break the remainder into pieces of size i-1. i -= 1 q, r = divmod(reuse, i) need = q + bool(r) if need > room: if not keys: return continue ms[i] = q keys.append(i) if r: ms[r] = 1 keys.append(r) break room -= need if size: yield sum(ms.values()), ms.copy() else: yield ms.copy() def ordered_partitions(n, m=None, sort=True): """Generates ordered partitions of integer ``n``. Parameters ========== m : integer (default None) The default value gives partitions of all sizes else only those with size m. In addition, if ``m`` is not None then partitions are generated *in place* (see examples). sort : bool (default True) Controls whether partitions are returned in sorted order when ``m`` is not None; when False, the partitions are returned as fast as possible with elements sorted, but when m|n the partitions will not be in ascending lexicographical order. Examples ======== >>> from sympy.utilities.iterables import ordered_partitions All partitions of 5 in ascending lexicographical: >>> for p in ordered_partitions(5): ... print(p) [1, 1, 1, 1, 1] [1, 1, 1, 2] [1, 1, 3] [1, 2, 2] [1, 4] [2, 3] [5] Only partitions of 5 with two parts: >>> for p in ordered_partitions(5, 2): ... print(p) [1, 4] [2, 3] When ``m`` is given, a given list objects will be used more than once for speed reasons so you will not see the correct partitions unless you make a copy of each as it is generated: >>> [p for p in ordered_partitions(7, 3)] [[1, 1, 1], [1, 1, 1], [1, 1, 1], [2, 2, 2]] >>> [list(p) for p in ordered_partitions(7, 3)] [[1, 1, 5], [1, 2, 4], [1, 3, 3], [2, 2, 3]] When ``n`` is a multiple of ``m``, the elements are still sorted but the partitions themselves will be *unordered* if sort is False; the default is to return them in ascending lexicographical order. >>> for p in ordered_partitions(6, 2): ... print(p) [1, 5] [2, 4] [3, 3] But if speed is more important than ordering, sort can be set to False: >>> for p in ordered_partitions(6, 2, sort=False): ... print(p) [1, 5] [3, 3] [2, 4] References ========== .. [1] Generating Integer Partitions, [online], Available: https://jeromekelleher.net/generating-integer-partitions.html .. [2] Jerome Kelleher and Barry O'Sullivan, "Generating All Partitions: A Comparison Of Two Encodings", [online], Available: https://arxiv.org/pdf/0909.2331v2.pdf """ if n < 1 or m is not None and m < 1: # the empty set is the only way to handle these inputs # and returning {} to represent it is consistent with # the counting convention, e.g. nT(0) == 1. yield [] return if m is None: # The list `a`'s leading elements contain the partition in which # y is the biggest element and x is either the same as y or the # 2nd largest element; v and w are adjacent element indices # to which x and y are being assigned, respectively. a = [1]*n y = -1 v = n while v > 0: v -= 1 x = a[v] + 1 while y >= 2 * x: a[v] = x y -= x v += 1 w = v + 1 while x <= y: a[v] = x a[w] = y yield a[:w + 1] x += 1 y -= 1 a[v] = x + y y = a[v] - 1 yield a[:w] elif m == 1: yield [n] elif n == m: yield [1]*n else: # recursively generate partitions of size m for b in range(1, n//m + 1): a = [b]*m x = n - b*m if not x: if sort: yield a elif not sort and x <= m: for ax in ordered_partitions(x, sort=False): mi = len(ax) a[-mi:] = [i + b for i in ax] yield a a[-mi:] = [b]*mi else: for mi in range(1, m): for ax in ordered_partitions(x, mi, sort=True): a[-mi:] = [i + b for i in ax] yield a a[-mi:] = [b]*mi def binary_partitions(n): """ Generates the binary partition of n. A binary partition consists only of numbers that are powers of two. Each step reduces a `2^{k+1}` to `2^k` and `2^k`. Thus 16 is converted to 8 and 8. Examples ======== >>> from sympy.utilities.iterables import binary_partitions >>> for i in binary_partitions(5): ... print(i) ... [4, 1] [2, 2, 1] [2, 1, 1, 1] [1, 1, 1, 1, 1] References ========== .. [1] TAOCP 4, section 7.2.1.5, problem 64 """ from math import ceil, log pow = int(2**(ceil(log(n, 2)))) sum = 0 partition = [] while pow: if sum + pow <= n: partition.append(pow) sum += pow pow >>= 1 last_num = len(partition) - 1 - (n & 1) while last_num >= 0: yield partition if partition[last_num] == 2: partition[last_num] = 1 partition.append(1) last_num -= 1 continue partition.append(1) partition[last_num] >>= 1 x = partition[last_num + 1] = partition[last_num] last_num += 1 while x > 1: if x <= len(partition) - last_num - 1: del partition[-x + 1:] last_num += 1 partition[last_num] = x else: x >>= 1 yield [1]*n def has_dups(seq): """Return True if there are any duplicate elements in ``seq``. Examples ======== >>> from sympy.utilities.iterables import has_dups >>> from sympy import Dict, Set >>> has_dups((1, 2, 1)) True >>> has_dups(range(3)) False >>> all(has_dups(c) is False for c in (set(), Set(), dict(), Dict())) True """ from sympy.core.containers import Dict from sympy.sets.sets import Set if isinstance(seq, (dict, set, Dict, Set)): return False uniq = set() return any(True for s in seq if s in uniq or uniq.add(s)) def has_variety(seq): """Return True if there are any different elements in ``seq``. Examples ======== >>> from sympy.utilities.iterables import has_variety >>> has_variety((1, 2, 1)) True >>> has_variety((1, 1, 1)) False """ for i, s in enumerate(seq): if i == 0: sentinel = s else: if s != sentinel: return True return False def uniq(seq, result=None): """ Yield unique elements from ``seq`` as an iterator. The second parameter ``result`` is used internally; it is not necessary to pass anything for this. Note: changing the sequence during iteration will raise a RuntimeError if the size of the sequence is known; if you pass an iterator and advance the iterator you will change the output of this routine but there will be no warning. Examples ======== >>> from sympy.utilities.iterables import uniq >>> dat = [1, 4, 1, 5, 4, 2, 1, 2] >>> type(uniq(dat)) in (list, tuple) False >>> list(uniq(dat)) [1, 4, 5, 2] >>> list(uniq(x for x in dat)) [1, 4, 5, 2] >>> list(uniq([[1], [2, 1], [1]])) [[1], [2, 1]] """ try: n = len(seq) except TypeError: n = None def check(): # check that size of seq did not change during iteration; # if n == None the object won't support size changing, e.g. # an iterator can't be changed if n is not None and len(seq) != n: raise RuntimeError('sequence changed size during iteration') try: seen = set() result = result or [] for i, s in enumerate(seq): if not (s in seen or seen.add(s)): yield s check() except TypeError: if s not in result: yield s check() result.append(s) if hasattr(seq, '__getitem__'): yield from uniq(seq[i + 1:], result) else: yield from uniq(seq, result) def generate_bell(n): """Return permutations of [0, 1, ..., n - 1] such that each permutation differs from the last by the exchange of a single pair of neighbors. The ``n!`` permutations are returned as an iterator. In order to obtain the next permutation from a random starting permutation, use the ``next_trotterjohnson`` method of the Permutation class (which generates the same sequence in a different manner). Examples ======== >>> from itertools import permutations >>> from sympy.utilities.iterables import generate_bell >>> from sympy import zeros, Matrix This is the sort of permutation used in the ringing of physical bells, and does not produce permutations in lexicographical order. Rather, the permutations differ from each other by exactly one inversion, and the position at which the swapping occurs varies periodically in a simple fashion. Consider the first few permutations of 4 elements generated by ``permutations`` and ``generate_bell``: >>> list(permutations(range(4)))[:5] [(0, 1, 2, 3), (0, 1, 3, 2), (0, 2, 1, 3), (0, 2, 3, 1), (0, 3, 1, 2)] >>> list(generate_bell(4))[:5] [(0, 1, 2, 3), (0, 1, 3, 2), (0, 3, 1, 2), (3, 0, 1, 2), (3, 0, 2, 1)] Notice how the 2nd and 3rd lexicographical permutations have 3 elements out of place whereas each "bell" permutation always has only two elements out of place relative to the previous permutation (and so the signature (+/-1) of a permutation is opposite of the signature of the previous permutation). How the position of inversion varies across the elements can be seen by tracing out where the largest number appears in the permutations: >>> m = zeros(4, 24) >>> for i, p in enumerate(generate_bell(4)): ... m[:, i] = Matrix([j - 3 for j in list(p)]) # make largest zero >>> m.print_nonzero('X') [XXX XXXXXX XXXXXX XXX] [XX XX XXXX XX XXXX XX XX] [X XXXX XX XXXX XX XXXX X] [ XXXXXX XXXXXX XXXXXX ] See Also ======== sympy.combinatorics.permutations.Permutation.next_trotterjohnson References ========== .. [1] https://en.wikipedia.org/wiki/Method_ringing .. [2] https://stackoverflow.com/questions/4856615/recursive-permutation/4857018 .. [3] http://programminggeeks.com/bell-algorithm-for-permutation/ .. [4] https://en.wikipedia.org/wiki/Steinhaus%E2%80%93Johnson%E2%80%93Trotter_algorithm .. [5] Generating involutions, derangements, and relatives by ECO Vincent Vajnovszki, DMTCS vol 1 issue 12, 2010 """ n = as_int(n) if n < 1: raise ValueError('n must be a positive integer') if n == 1: yield (0,) elif n == 2: yield (0, 1) yield (1, 0) elif n == 3: yield from [(0, 1, 2), (0, 2, 1), (2, 0, 1), (2, 1, 0), (1, 2, 0), (1, 0, 2)] else: m = n - 1 op = [0] + [-1]*m l = list(range(n)) while True: yield tuple(l) # find biggest element with op big = None, -1 # idx, value for i in range(n): if op[i] and l[i] > big[1]: big = i, l[i] i, _ = big if i is None: break # there are no ops left # swap it with neighbor in the indicated direction j = i + op[i] l[i], l[j] = l[j], l[i] op[i], op[j] = op[j], op[i] # if it landed at the end or if the neighbor in the same # direction is bigger then turn off op if j == 0 or j == m or l[j + op[j]] > l[j]: op[j] = 0 # any element bigger to the left gets +1 op for i in range(j): if l[i] > l[j]: op[i] = 1 # any element bigger to the right gets -1 op for i in range(j + 1, n): if l[i] > l[j]: op[i] = -1 def generate_involutions(n): """ Generates involutions. An involution is a permutation that when multiplied by itself equals the identity permutation. In this implementation the involutions are generated using Fixed Points. Alternatively, an involution can be considered as a permutation that does not contain any cycles with a length that is greater than two. Examples ======== >>> from sympy.utilities.iterables import generate_involutions >>> list(generate_involutions(3)) [(0, 1, 2), (0, 2, 1), (1, 0, 2), (2, 1, 0)] >>> len(list(generate_involutions(4))) 10 References ========== .. [1] http://mathworld.wolfram.com/PermutationInvolution.html """ idx = list(range(n)) for p in permutations(idx): for i in idx: if p[p[i]] != i: break else: yield p def generate_derangements(perm): """ Routine to generate unique derangements. TODO: This will be rewritten to use the ECO operator approach once the permutations branch is in master. Examples ======== >>> from sympy.utilities.iterables import generate_derangements >>> list(generate_derangements([0, 1, 2])) [[1, 2, 0], [2, 0, 1]] >>> list(generate_derangements([0, 1, 2, 3])) [[1, 0, 3, 2], [1, 2, 3, 0], [1, 3, 0, 2], [2, 0, 3, 1], \ [2, 3, 0, 1], [2, 3, 1, 0], [3, 0, 1, 2], [3, 2, 0, 1], \ [3, 2, 1, 0]] >>> list(generate_derangements([0, 1, 1])) [] See Also ======== sympy.functions.combinatorial.factorials.subfactorial """ for p in multiset_permutations(perm): if not any(i == j for i, j in zip(perm, p)): yield p def necklaces(n, k, free=False): """ A routine to generate necklaces that may (free=True) or may not (free=False) be turned over to be viewed. The "necklaces" returned are comprised of ``n`` integers (beads) with ``k`` different values (colors). Only unique necklaces are returned. Examples ======== >>> from sympy.utilities.iterables import necklaces, bracelets >>> def show(s, i): ... return ''.join(s[j] for j in i) The "unrestricted necklace" is sometimes also referred to as a "bracelet" (an object that can be turned over, a sequence that can be reversed) and the term "necklace" is used to imply a sequence that cannot be reversed. So ACB == ABC for a bracelet (rotate and reverse) while the two are different for a necklace since rotation alone cannot make the two sequences the same. (mnemonic: Bracelets can be viewed Backwards, but Not Necklaces.) >>> B = [show('ABC', i) for i in bracelets(3, 3)] >>> N = [show('ABC', i) for i in necklaces(3, 3)] >>> set(N) - set(B) {'ACB'} >>> list(necklaces(4, 2)) [(0, 0, 0, 0), (0, 0, 0, 1), (0, 0, 1, 1), (0, 1, 0, 1), (0, 1, 1, 1), (1, 1, 1, 1)] >>> [show('.o', i) for i in bracelets(4, 2)] ['....', '...o', '..oo', '.o.o', '.ooo', 'oooo'] References ========== .. [1] http://mathworld.wolfram.com/Necklace.html """ return uniq(minlex(i, directed=not free) for i in variations(list(range(k)), n, repetition=True)) def bracelets(n, k): """Wrapper to necklaces to return a free (unrestricted) necklace.""" return necklaces(n, k, free=True) def generate_oriented_forest(n): """ This algorithm generates oriented forests. An oriented graph is a directed graph having no symmetric pair of directed edges. A forest is an acyclic graph, i.e., it has no cycles. A forest can also be described as a disjoint union of trees, which are graphs in which any two vertices are connected by exactly one simple path. Examples ======== >>> from sympy.utilities.iterables import generate_oriented_forest >>> list(generate_oriented_forest(4)) [[0, 1, 2, 3], [0, 1, 2, 2], [0, 1, 2, 1], [0, 1, 2, 0], \ [0, 1, 1, 1], [0, 1, 1, 0], [0, 1, 0, 1], [0, 1, 0, 0], [0, 0, 0, 0]] References ========== .. [1] T. Beyer and S.M. Hedetniemi: constant time generation of rooted trees, SIAM J. Computing Vol. 9, No. 4, November 1980 .. [2] https://stackoverflow.com/questions/1633833/oriented-forest-taocp-algorithm-in-python """ P = list(range(-1, n)) while True: yield P[1:] if P[n] > 0: P[n] = P[P[n]] else: for p in range(n - 1, 0, -1): if P[p] != 0: target = P[p] - 1 for q in range(p - 1, 0, -1): if P[q] == target: break offset = p - q for i in range(p, n + 1): P[i] = P[i - offset] break else: break def minlex(seq, directed=True, is_set=False, small=None): """ Return a tuple representing the rotation of the sequence in which the lexically smallest elements appear first, e.g. `cba ->acb`. If ``directed`` is False then the smaller of the sequence and the reversed sequence is returned, e.g. `cba -> abc`. For more efficient processing, ``is_set`` can be set to True if there are no duplicates in the sequence. If the smallest element is known at the time of calling, it can be passed as ``small`` and the calculation of the smallest element will be omitted. Examples ======== >>> from sympy.combinatorics.polyhedron import minlex >>> minlex((1, 2, 0)) (0, 1, 2) >>> minlex((1, 0, 2)) (0, 2, 1) >>> minlex((1, 0, 2), directed=False) (0, 1, 2) >>> minlex('11010011000', directed=True) '00011010011' >>> minlex('11010011000', directed=False) '00011001011' """ is_str = isinstance(seq, str) seq = list(seq) if small is None: small = min(seq, key=default_sort_key) if is_set: i = seq.index(small) if not directed: n = len(seq) p = (i + 1) % n m = (i - 1) % n if default_sort_key(seq[p]) > default_sort_key(seq[m]): seq = list(reversed(seq)) i = n - i - 1 if i: seq = rotate_left(seq, i) best = seq else: count = seq.count(small) if count == 1 and directed: best = rotate_left(seq, seq.index(small)) else: # if not directed, and not a set, we can't just # pass this off to minlex with is_set True since # peeking at the neighbor may not be sufficient to # make the decision so we continue... best = seq for i in range(count): seq = rotate_left(seq, seq.index(small, count != 1)) if seq < best: best = seq # it's cheaper to rotate now rather than search # again for these in reversed order so we test # the reverse now if not directed: seq = rotate_left(seq, 1) seq = list(reversed(seq)) if seq < best: best = seq seq = list(reversed(seq)) seq = rotate_right(seq, 1) # common return if is_str: return ''.join(best) return tuple(best) def runs(seq, op=gt): """Group the sequence into lists in which successive elements all compare the same with the comparison operator, ``op``: op(seq[i + 1], seq[i]) is True from all elements in a run. Examples ======== >>> from sympy.utilities.iterables import runs >>> from operator import ge >>> runs([0, 1, 2, 2, 1, 4, 3, 2, 2]) [[0, 1, 2], [2], [1, 4], [3], [2], [2]] >>> runs([0, 1, 2, 2, 1, 4, 3, 2, 2], op=ge) [[0, 1, 2, 2], [1, 4], [3], [2, 2]] """ cycles = [] seq = iter(seq) try: run = [next(seq)] except StopIteration: return [] while True: try: ei = next(seq) except StopIteration: break if op(ei, run[-1]): run.append(ei) continue else: cycles.append(run) run = [ei] if run: cycles.append(run) return cycles def kbins(l, k, ordered=None): """ Return sequence ``l`` partitioned into ``k`` bins. Examples ======== >>> from __future__ import print_function The default is to give the items in the same order, but grouped into k partitions without any reordering: >>> from sympy.utilities.iterables import kbins >>> for p in kbins(list(range(5)), 2): ... print(p) ... [[0], [1, 2, 3, 4]] [[0, 1], [2, 3, 4]] [[0, 1, 2], [3, 4]] [[0, 1, 2, 3], [4]] The ``ordered`` flag is either None (to give the simple partition of the elements) or is a 2 digit integer indicating whether the order of the bins and the order of the items in the bins matters. Given:: A = [[0], [1, 2]] B = [[1, 2], [0]] C = [[2, 1], [0]] D = [[0], [2, 1]] the following values for ``ordered`` have the shown meanings:: 00 means A == B == C == D 01 means A == B 10 means A == D 11 means A == A >>> for ordered_flag in [None, 0, 1, 10, 11]: ... print('ordered = %s' % ordered_flag) ... for p in kbins(list(range(3)), 2, ordered=ordered_flag): ... print(' %s' % p) ... ordered = None [[0], [1, 2]] [[0, 1], [2]] ordered = 0 [[0, 1], [2]] [[0, 2], [1]] [[0], [1, 2]] ordered = 1 [[0], [1, 2]] [[0], [2, 1]] [[1], [0, 2]] [[1], [2, 0]] [[2], [0, 1]] [[2], [1, 0]] ordered = 10 [[0, 1], [2]] [[2], [0, 1]] [[0, 2], [1]] [[1], [0, 2]] [[0], [1, 2]] [[1, 2], [0]] ordered = 11 [[0], [1, 2]] [[0, 1], [2]] [[0], [2, 1]] [[0, 2], [1]] [[1], [0, 2]] [[1, 0], [2]] [[1], [2, 0]] [[1, 2], [0]] [[2], [0, 1]] [[2, 0], [1]] [[2], [1, 0]] [[2, 1], [0]] See Also ======== partitions, multiset_partitions """ def partition(lista, bins): # EnricoGiampieri's partition generator from # https://stackoverflow.com/questions/13131491/ # partition-n-items-into-k-bins-in-python-lazily if len(lista) == 1 or bins == 1: yield [lista] elif len(lista) > 1 and bins > 1: for i in range(1, len(lista)): for part in partition(lista[i:], bins - 1): if len([lista[:i]] + part) == bins: yield [lista[:i]] + part if ordered is None: yield from partition(l, k) elif ordered == 11: for pl in multiset_permutations(l): pl = list(pl) yield from partition(pl, k) elif ordered == 00: yield from multiset_partitions(l, k) elif ordered == 10: for p in multiset_partitions(l, k): for perm in permutations(p): yield list(perm) elif ordered == 1: for kgot, p in partitions(len(l), k, size=True): if kgot != k: continue for li in multiset_permutations(l): rv = [] i = j = 0 li = list(li) for size, multiplicity in sorted(p.items()): for m in range(multiplicity): j = i + size rv.append(li[i: j]) i = j yield rv else: raise ValueError( 'ordered must be one of 00, 01, 10 or 11, not %s' % ordered) def permute_signs(t): """Return iterator in which the signs of non-zero elements of t are permuted. Examples ======== >>> from sympy.utilities.iterables import permute_signs >>> list(permute_signs((0, 1, 2))) [(0, 1, 2), (0, -1, 2), (0, 1, -2), (0, -1, -2)] """ for signs in cartes(*[(1, -1)]*(len(t) - t.count(0))): signs = list(signs) yield type(t)([i*signs.pop() if i else i for i in t]) def signed_permutations(t): """Return iterator in which the signs of non-zero elements of t and the order of the elements are permuted. Examples ======== >>> from sympy.utilities.iterables import signed_permutations >>> list(signed_permutations((0, 1, 2))) [(0, 1, 2), (0, -1, 2), (0, 1, -2), (0, -1, -2), (0, 2, 1), (0, -2, 1), (0, 2, -1), (0, -2, -1), (1, 0, 2), (-1, 0, 2), (1, 0, -2), (-1, 0, -2), (1, 2, 0), (-1, 2, 0), (1, -2, 0), (-1, -2, 0), (2, 0, 1), (-2, 0, 1), (2, 0, -1), (-2, 0, -1), (2, 1, 0), (-2, 1, 0), (2, -1, 0), (-2, -1, 0)] """ return (type(t)(i) for j in permutations(t) for i in permute_signs(j)) def rotations(s, dir=1): """Return a generator giving the items in s as list where each subsequent list has the items rotated to the left (default) or right (dir=-1) relative to the previous list. Examples ======== >>> from sympy.utilities.iterables import rotations >>> list(rotations([1,2,3])) [[1, 2, 3], [2, 3, 1], [3, 1, 2]] >>> list(rotations([1,2,3], -1)) [[1, 2, 3], [3, 1, 2], [2, 3, 1]] """ seq = list(s) for i in range(len(seq)): yield seq seq = rotate_left(seq, dir) def roundrobin(*iterables): """roundrobin recipe taken from itertools documentation: https://docs.python.org/2/library/itertools.html#recipes roundrobin('ABC', 'D', 'EF') --> A D E B F C Recipe credited to George Sakkis """ import itertools nexts = itertools.cycle(iter(it).__next__ for it in iterables) pending = len(iterables) while pending: try: for next in nexts: yield next() except StopIteration: pending -= 1 nexts = itertools.cycle(itertools.islice(nexts, pending))

5359449d9fa55e2073811b9613b9650fed082e07901a1adcae6351f1c89be9c9

""" This is a shim file to provide backwards compatibility (cxxcode.py was renamed to cxx.py in SymPy 1.7). """ from sympy.utilities.exceptions import SymPyDeprecationWarning SymPyDeprecationWarning( feature="importing from sympy.printing.cxxcode", useinstead="Import from sympy.printing.cxx", issue=20256, deprecated_since_version="1.7").warn() from .cxx import (cxxcode, reserved, CXX98CodePrinter, # noqa:F401 CXX11CodePrinter, CXX17CodePrinter, cxx_code_printers)

4a4d988f93d7e42793ea8df31f1f99542d6425303b610333c17a632709547ae7

"""A module providing information about the necessity of brackets""" from sympy.core.function import _coeff_isneg # Default precedence values for some basic types PRECEDENCE = { "Lambda": 1, "Xor": 10, "Or": 20, "And": 30, "Relational": 35, "Add": 40, "Mul": 50, "Pow": 60, "Func": 70, "Not": 100, "Atom": 1000, "BitwiseOr": 36, "BitwiseXor": 37, "BitwiseAnd": 38 } # A dictionary assigning precedence values to certain classes. These values are # treated like they were inherited, so not every single class has to be named # here. # Do not use this with printers other than StrPrinter PRECEDENCE_VALUES = { "Equivalent": PRECEDENCE["Xor"], "Xor": PRECEDENCE["Xor"], "Implies": PRECEDENCE["Xor"], "Or": PRECEDENCE["Or"], "And": PRECEDENCE["And"], "Add": PRECEDENCE["Add"], "Pow": PRECEDENCE["Pow"], "Relational": PRECEDENCE["Relational"], "Sub": PRECEDENCE["Add"], "Not": PRECEDENCE["Not"], "Function" : PRECEDENCE["Func"], "NegativeInfinity": PRECEDENCE["Add"], "MatAdd": PRECEDENCE["Add"], "MatPow": PRECEDENCE["Pow"], "MatrixSolve": PRECEDENCE["Mul"], "TensAdd": PRECEDENCE["Add"], # As soon as `TensMul` is a subclass of `Mul`, remove this: "TensMul": PRECEDENCE["Mul"], "HadamardProduct": PRECEDENCE["Mul"], "HadamardPower": PRECEDENCE["Pow"], "KroneckerProduct": PRECEDENCE["Mul"], "Equality": PRECEDENCE["Mul"], "Unequality": PRECEDENCE["Mul"], } # Sometimes it's not enough to assign a fixed precedence value to a # class. Then a function can be inserted in this dictionary that takes # an instance of this class as argument and returns the appropriate # precedence value. # Precedence functions def precedence_Mul(item): if _coeff_isneg(item): return PRECEDENCE["Add"] return PRECEDENCE["Mul"] def precedence_Rational(item): if item.p < 0: return PRECEDENCE["Add"] return PRECEDENCE["Mul"] def precedence_Integer(item): if item.p < 0: return PRECEDENCE["Add"] return PRECEDENCE["Atom"] def precedence_Float(item): if item < 0: return PRECEDENCE["Add"] return PRECEDENCE["Atom"] def precedence_PolyElement(item): if item.is_generator: return PRECEDENCE["Atom"] elif item.is_ground: return precedence(item.coeff(1)) elif item.is_term: return PRECEDENCE["Mul"] else: return PRECEDENCE["Add"] def precedence_FracElement(item): if item.denom == 1: return precedence_PolyElement(item.numer) else: return PRECEDENCE["Mul"] def precedence_UnevaluatedExpr(item): return precedence(item.args[0]) PRECEDENCE_FUNCTIONS = { "Integer": precedence_Integer, "Mul": precedence_Mul, "Rational": precedence_Rational, "Float": precedence_Float, "PolyElement": precedence_PolyElement, "FracElement": precedence_FracElement, "UnevaluatedExpr": precedence_UnevaluatedExpr, } def precedence(item): """Returns the precedence of a given object. This is the precedence for StrPrinter. """ if hasattr(item, "precedence"): return item.precedence try: mro = item.__class__.__mro__ except AttributeError: return PRECEDENCE["Atom"] for i in mro: n = i.__name__ if n in PRECEDENCE_FUNCTIONS: return PRECEDENCE_FUNCTIONS[n](item) elif n in PRECEDENCE_VALUES: return PRECEDENCE_VALUES[n] return PRECEDENCE["Atom"] PRECEDENCE_TRADITIONAL = PRECEDENCE.copy() PRECEDENCE_TRADITIONAL['Integral'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Sum'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Product'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Limit'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Derivative'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['TensorProduct'] = PRECEDENCE["Mul"] PRECEDENCE_TRADITIONAL['Transpose'] = PRECEDENCE["Pow"] PRECEDENCE_TRADITIONAL['Adjoint'] = PRECEDENCE["Pow"] PRECEDENCE_TRADITIONAL['Dot'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Cross'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Gradient'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Divergence'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Curl'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Laplacian'] = PRECEDENCE["Mul"] - 1 PRECEDENCE_TRADITIONAL['Union'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['Intersection'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['Complement'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['SymmetricDifference'] = PRECEDENCE['Xor'] PRECEDENCE_TRADITIONAL['ProductSet'] = PRECEDENCE['Xor'] def precedence_traditional(item): """Returns the precedence of a given object according to the traditional rules of mathematics. This is the precedence for the LaTeX and pretty printer. """ # Integral, Sum, Product, Limit have the precedence of Mul in LaTeX, # the precedence of Atom for other printers: from sympy.core.expr import UnevaluatedExpr if isinstance(item, UnevaluatedExpr): return precedence_traditional(item.args[0]) n = item.__class__.__name__ if n in PRECEDENCE_TRADITIONAL: return PRECEDENCE_TRADITIONAL[n] return precedence(item)

a6d9f063126be68c772c6e130836d1220c6c0a291a56f1335816aa2292135177

from sympy.printing.mathml import mathml from sympy.utilities.mathml import c2p import tempfile import subprocess def print_gtk(x, start_viewer=True): """Print to Gtkmathview, a gtk widget capable of rendering MathML. Needs libgtkmathview-bin""" with tempfile.NamedTemporaryFile('w') as file: file.write(c2p(mathml(x), simple=True)) file.flush() if start_viewer: subprocess.check_call(('mathmlviewer', file.name))

5bc85f19902188d42d8dc16766e92de828c8b07056502212bde859aadb9effcc

""" Python code printers This module contains python code printers for plain python as well as NumPy & SciPy enabled code. """ from collections import defaultdict from itertools import chain from sympy.core import S from .precedence import precedence from .codeprinter import CodePrinter _kw_py2and3 = { 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield', 'None' # 'None' is actually not in Python 2's keyword.kwlist } _kw_only_py2 = {'exec', 'print'} _kw_only_py3 = {'False', 'nonlocal', 'True'} _known_functions = { 'Abs': 'abs', } _known_functions_math = { 'acos': 'acos', 'acosh': 'acosh', 'asin': 'asin', 'asinh': 'asinh', 'atan': 'atan', 'atan2': 'atan2', 'atanh': 'atanh', 'ceiling': 'ceil', 'cos': 'cos', 'cosh': 'cosh', 'erf': 'erf', 'erfc': 'erfc', 'exp': 'exp', 'expm1': 'expm1', 'factorial': 'factorial', 'floor': 'floor', 'gamma': 'gamma', 'hypot': 'hypot', 'loggamma': 'lgamma', 'log': 'log', 'ln': 'log', 'log10': 'log10', 'log1p': 'log1p', 'log2': 'log2', 'sin': 'sin', 'sinh': 'sinh', 'Sqrt': 'sqrt', 'tan': 'tan', 'tanh': 'tanh' } # Not used from ``math``: [copysign isclose isfinite isinf isnan ldexp frexp pow modf # radians trunc fmod fsum gcd degrees fabs] _known_constants_math = { 'Exp1': 'e', 'Pi': 'pi', 'E': 'e' # Only in python >= 3.5: # 'Infinity': 'inf', # 'NaN': 'nan' } def _print_known_func(self, expr): known = self.known_functions[expr.__class__.__name__] return '{name}({args})'.format(name=self._module_format(known), args=', '.join(map(lambda arg: self._print(arg), expr.args))) def _print_known_const(self, expr): known = self.known_constants[expr.__class__.__name__] return self._module_format(known) class AbstractPythonCodePrinter(CodePrinter): printmethod = "_pythoncode" language = "Python" reserved_words = _kw_py2and3.union(_kw_only_py3) modules = None # initialized to a set in __init__ tab = ' ' _kf = dict(chain( _known_functions.items(), [(k, 'math.' + v) for k, v in _known_functions_math.items()] )) _kc = {k: 'math.'+v for k, v in _known_constants_math.items()} _operators = {'and': 'and', 'or': 'or', 'not': 'not'} _default_settings = dict( CodePrinter._default_settings, user_functions={}, precision=17, inline=True, fully_qualified_modules=True, contract=False, standard='python3', ) def __init__(self, settings=None): super().__init__(settings) # Python standard handler std = self._settings['standard'] if std is None: import sys std = 'python{}'.format(sys.version_info.major) if std not in ('python2', 'python3'): raise ValueError('Unrecognized python standard : {}'.format(std)) self.standard = std self.module_imports = defaultdict(set) # Known functions and constants handler self.known_functions = dict(self._kf, **(settings or {}).get( 'user_functions', {})) self.known_constants = dict(self._kc, **(settings or {}).get( 'user_constants', {})) def _declare_number_const(self, name, value): return "%s = %s" % (name, value) def _module_format(self, fqn, register=True): parts = fqn.split('.') if register and len(parts) > 1: self.module_imports['.'.join(parts[:-1])].add(parts[-1]) if self._settings['fully_qualified_modules']: return fqn else: return fqn.split('(')[0].split('[')[0].split('.')[-1] def _format_code(self, lines): return lines def _get_statement(self, codestring): return "{}".format(codestring) def _get_comment(self, text): return " # {}".format(text) def _expand_fold_binary_op(self, op, args): """ This method expands a fold on binary operations. ``functools.reduce`` is an example of a folded operation. For example, the expression `A + B + C + D` is folded into `((A + B) + C) + D` """ if len(args) == 1: return self._print(args[0]) else: return "%s(%s, %s)" % ( self._module_format(op), self._expand_fold_binary_op(op, args[:-1]), self._print(args[-1]), ) def _expand_reduce_binary_op(self, op, args): """ This method expands a reductin on binary operations. Notice: this is NOT the same as ``functools.reduce``. For example, the expression `A + B + C + D` is reduced into: `(A + B) + (C + D)` """ if len(args) == 1: return self._print(args[0]) else: N = len(args) Nhalf = N // 2 return "%s(%s, %s)" % ( self._module_format(op), self._expand_reduce_binary_op(args[:Nhalf]), self._expand_reduce_binary_op(args[Nhalf:]), ) def _get_einsum_string(self, subranks, contraction_indices): letters = self._get_letter_generator_for_einsum() contraction_string = "" counter = 0 d = {j: min(i) for i in contraction_indices for j in i} indices = [] for rank_arg in subranks: lindices = [] for i in range(rank_arg): if counter in d: lindices.append(d[counter]) else: lindices.append(counter) counter += 1 indices.append(lindices) mapping = {} letters_free = [] letters_dum = [] for i in indices: for j in i: if j not in mapping: l = next(letters) mapping[j] = l else: l = mapping[j] contraction_string += l if j in d: if l not in letters_dum: letters_dum.append(l) else: letters_free.append(l) contraction_string += "," contraction_string = contraction_string[:-1] return contraction_string, letters_free, letters_dum def _print_NaN(self, expr): return "float('nan')" def _print_Infinity(self, expr): return "float('inf')" def _print_NegativeInfinity(self, expr): return "float('-inf')" def _print_ComplexInfinity(self, expr): return self._print_NaN(expr) def _print_Mod(self, expr): PREC = precedence(expr) return ('{} % {}'.format(*map(lambda x: self.parenthesize(x, PREC), expr.args))) def _print_Piecewise(self, expr): result = [] i = 0 for arg in expr.args: e = arg.expr c = arg.cond if i == 0: result.append('(') result.append('(') result.append(self._print(e)) result.append(')') result.append(' if ') result.append(self._print(c)) result.append(' else ') i += 1 result = result[:-1] if result[-1] == 'True': result = result[:-2] result.append(')') else: result.append(' else None)') return ''.join(result) def _print_Relational(self, expr): "Relational printer for Equality and Unequality" op = { '==' :'equal', '!=' :'not_equal', '<' :'less', '<=' :'less_equal', '>' :'greater', '>=' :'greater_equal', } if expr.rel_op in op: lhs = self._print(expr.lhs) rhs = self._print(expr.rhs) return '({lhs} {op} {rhs})'.format(op=expr.rel_op, lhs=lhs, rhs=rhs) return super()._print_Relational(expr) def _print_ITE(self, expr): from sympy.functions.elementary.piecewise import Piecewise return self._print(expr.rewrite(Piecewise)) def _print_Sum(self, expr): loops = ( 'for {i} in range({a}, {b}+1)'.format( i=self._print(i), a=self._print(a), b=self._print(b)) for i, a, b in expr.limits) return '(builtins.sum({function} {loops}))'.format( function=self._print(expr.function), loops=' '.join(loops)) def _print_ImaginaryUnit(self, expr): return '1j' def _print_KroneckerDelta(self, expr): a, b = expr.args return '(1 if {a} == {b} else 0)'.format( a = self._print(a), b = self._print(b) ) def _print_MatrixBase(self, expr): name = expr.__class__.__name__ func = self.known_functions.get(name, name) return "%s(%s)" % (func, self._print(expr.tolist())) _print_SparseMatrix = \ _print_MutableSparseMatrix = \ _print_ImmutableSparseMatrix = \ _print_Matrix = \ _print_DenseMatrix = \ _print_MutableDenseMatrix = \ _print_ImmutableMatrix = \ _print_ImmutableDenseMatrix = \ lambda self, expr: self._print_MatrixBase(expr) def _indent_codestring(self, codestring): return '\n'.join([self.tab + line for line in codestring.split('\n')]) def _print_FunctionDefinition(self, fd): body = '\n'.join(map(lambda arg: self._print(arg), fd.body)) return "def {name}({parameters}):\n{body}".format( name=self._print(fd.name), parameters=', '.join([self._print(var.symbol) for var in fd.parameters]), body=self._indent_codestring(body) ) def _print_While(self, whl): body = '\n'.join(map(lambda arg: self._print(arg), whl.body)) return "while {cond}:\n{body}".format( cond=self._print(whl.condition), body=self._indent_codestring(body) ) def _print_Declaration(self, decl): return '%s = %s' % ( self._print(decl.variable.symbol), self._print(decl.variable.value) ) def _print_Return(self, ret): arg, = ret.args return 'return %s' % self._print(arg) def _print_Print(self, prnt): print_args = ', '.join(map(lambda arg: self._print(arg), prnt.print_args)) if prnt.format_string != None: # Must be '!= None', cannot be 'is not None' print_args = '{} % ({})'.format( self._print(prnt.format_string), print_args) if prnt.file != None: # Must be '!= None', cannot be 'is not None' print_args += ', file=%s' % self._print(prnt.file) if self.standard == 'python2': return 'print %s' % print_args return 'print(%s)' % print_args def _print_Stream(self, strm): if str(strm.name) == 'stdout': return self._module_format('sys.stdout') elif str(strm.name) == 'stderr': return self._module_format('sys.stderr') else: return self._print(strm.name) def _print_NoneToken(self, arg): return 'None' def _hprint_Pow(self, expr, rational=False, sqrt='math.sqrt'): """Printing helper function for ``Pow`` Notes ===== This only preprocesses the ``sqrt`` as math formatter Examples ======== >>> from sympy.functions import sqrt >>> from sympy.printing.pycode import PythonCodePrinter >>> from sympy.abc import x Python code printer automatically looks up ``math.sqrt``. >>> printer = PythonCodePrinter({'standard':'python3'}) >>> printer._hprint_Pow(sqrt(x), rational=True) 'x**(1/2)' >>> printer._hprint_Pow(sqrt(x), rational=False) 'math.sqrt(x)' >>> printer._hprint_Pow(1/sqrt(x), rational=True) 'x**(-1/2)' >>> printer._hprint_Pow(1/sqrt(x), rational=False) '1/math.sqrt(x)' Using sqrt from numpy or mpmath >>> printer._hprint_Pow(sqrt(x), sqrt='numpy.sqrt') 'numpy.sqrt(x)' >>> printer._hprint_Pow(sqrt(x), sqrt='mpmath.sqrt') 'mpmath.sqrt(x)' See Also ======== sympy.printing.str.StrPrinter._print_Pow """ PREC = precedence(expr) if expr.exp == S.Half and not rational: func = self._module_format(sqrt) arg = self._print(expr.base) return '{func}({arg})'.format(func=func, arg=arg) if expr.is_commutative: if -expr.exp is S.Half and not rational: func = self._module_format(sqrt) num = self._print(S.One) arg = self._print(expr.base) return "{num}/{func}({arg})".format( num=num, func=func, arg=arg) base_str = self.parenthesize(expr.base, PREC, strict=False) exp_str = self.parenthesize(expr.exp, PREC, strict=False) return "{}**{}".format(base_str, exp_str) class PythonCodePrinter(AbstractPythonCodePrinter): def _print_sign(self, e): return '(0.0 if {e} == 0 else {f}(1, {e}))'.format( f=self._module_format('math.copysign'), e=self._print(e.args[0])) def _print_Not(self, expr): PREC = precedence(expr) return self._operators['not'] + self.parenthesize(expr.args[0], PREC) def _print_Indexed(self, expr): base = expr.args[0] index = expr.args[1:] return "{}[{}]".format(str(base), ", ".join([self._print(ind) for ind in index])) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational) def _print_Rational(self, expr): if self.standard == 'python2': return '{}./{}.'.format(expr.p, expr.q) return '{}/{}'.format(expr.p, expr.q) def _print_Half(self, expr): return self._print_Rational(expr) def _print_frac(self, expr): from sympy import Mod return self._print_Mod(Mod(expr.args[0], 1)) _print_lowergamma = CodePrinter._print_not_supported _print_uppergamma = CodePrinter._print_not_supported _print_fresnelc = CodePrinter._print_not_supported _print_fresnels = CodePrinter._print_not_supported for k in PythonCodePrinter._kf: setattr(PythonCodePrinter, '_print_%s' % k, _print_known_func) for k in _known_constants_math: setattr(PythonCodePrinter, '_print_%s' % k, _print_known_const) def pycode(expr, **settings): """ Converts an expr to a string of Python code Parameters ========== expr : Expr A SymPy expression. fully_qualified_modules : bool Whether or not to write out full module names of functions (``math.sin`` vs. ``sin``). default: ``True``. standard : str or None, optional If 'python2', Python 2 sematics will be used. If 'python3', Python 3 sematics will be used. If None, the standard will be automatically detected. Default is 'python3'. And this parameter may be removed in the future. Examples ======== >>> from sympy import tan, Symbol >>> from sympy.printing.pycode import pycode >>> pycode(tan(Symbol('x')) + 1) 'math.tan(x) + 1' """ return PythonCodePrinter(settings).doprint(expr) _not_in_mpmath = 'log1p log2'.split() _in_mpmath = [(k, v) for k, v in _known_functions_math.items() if k not in _not_in_mpmath] _known_functions_mpmath = dict(_in_mpmath, **{ 'beta': 'beta', 'frac': 'frac', 'fresnelc': 'fresnelc', 'fresnels': 'fresnels', 'sign': 'sign', 'loggamma': 'loggamma', }) _known_constants_mpmath = { 'Exp1': 'e', 'Pi': 'pi', 'GoldenRatio': 'phi', 'EulerGamma': 'euler', 'Catalan': 'catalan', 'NaN': 'nan', 'Infinity': 'inf', 'NegativeInfinity': 'ninf' } def _unpack_integral_limits(integral_expr): """ helper function for _print_Integral that - accepts an Integral expression - returns a tuple of - a list variables of integration - a list of tuples of the upper and lower limits of integration """ integration_vars = [] limits = [] for integration_range in integral_expr.limits: if len(integration_range) == 3: integration_var, lower_limit, upper_limit = integration_range else: raise NotImplementedError("Only definite integrals are supported") integration_vars.append(integration_var) limits.append((lower_limit, upper_limit)) return integration_vars, limits class MpmathPrinter(PythonCodePrinter): """ Lambda printer for mpmath which maintains precision for floats """ printmethod = "_mpmathcode" language = "Python with mpmath" _kf = dict(chain( _known_functions.items(), [(k, 'mpmath.' + v) for k, v in _known_functions_mpmath.items()] )) _kc = {k: 'mpmath.'+v for k, v in _known_constants_mpmath.items()} def _print_Float(self, e): # XXX: This does not handle setting mpmath.mp.dps. It is assumed that # the caller of the lambdified function will have set it to sufficient # precision to match the Floats in the expression. # Remove 'mpz' if gmpy is installed. args = str(tuple(map(int, e._mpf_))) return '{func}({args})'.format(func=self._module_format('mpmath.mpf'), args=args) def _print_Rational(self, e): return "{func}({p})/{func}({q})".format( func=self._module_format('mpmath.mpf'), q=self._print(e.q), p=self._print(e.p) ) def _print_Half(self, e): return self._print_Rational(e) def _print_uppergamma(self, e): return "{}({}, {}, {})".format( self._module_format('mpmath.gammainc'), self._print(e.args[0]), self._print(e.args[1]), self._module_format('mpmath.inf')) def _print_lowergamma(self, e): return "{}({}, 0, {})".format( self._module_format('mpmath.gammainc'), self._print(e.args[0]), self._print(e.args[1])) def _print_log2(self, e): return '{0}({1})/{0}(2)'.format( self._module_format('mpmath.log'), self._print(e.args[0])) def _print_log1p(self, e): return '{}({}+1)'.format( self._module_format('mpmath.log'), self._print(e.args[0])) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational, sqrt='mpmath.sqrt') def _print_Integral(self, e): integration_vars, limits = _unpack_integral_limits(e) return "{}(lambda {}: {}, {})".format( self._module_format("mpmath.quad"), ", ".join(map(self._print, integration_vars)), self._print(e.args[0]), ", ".join("(%s, %s)" % tuple(map(self._print, l)) for l in limits)) for k in MpmathPrinter._kf: setattr(MpmathPrinter, '_print_%s' % k, _print_known_func) for k in _known_constants_mpmath: setattr(MpmathPrinter, '_print_%s' % k, _print_known_const) _not_in_numpy = 'erf erfc factorial gamma loggamma'.split() _in_numpy = [(k, v) for k, v in _known_functions_math.items() if k not in _not_in_numpy] _known_functions_numpy = dict(_in_numpy, **{ 'acos': 'arccos', 'acosh': 'arccosh', 'asin': 'arcsin', 'asinh': 'arcsinh', 'atan': 'arctan', 'atan2': 'arctan2', 'atanh': 'arctanh', 'exp2': 'exp2', 'sign': 'sign', 'logaddexp': 'logaddexp', 'logaddexp2': 'logaddexp2', }) _known_constants_numpy = { 'Exp1': 'e', 'Pi': 'pi', 'EulerGamma': 'euler_gamma', 'NaN': 'nan', 'Infinity': 'PINF', 'NegativeInfinity': 'NINF' } class NumPyPrinter(PythonCodePrinter): """ Numpy printer which handles vectorized piecewise functions, logical operators, etc. """ printmethod = "_numpycode" language = "Python with NumPy" _kf = dict(chain( PythonCodePrinter._kf.items(), [(k, 'numpy.' + v) for k, v in _known_functions_numpy.items()] )) _kc = {k: 'numpy.'+v for k, v in _known_constants_numpy.items()} def _print_seq(self, seq): "General sequence printer: converts to tuple" # Print tuples here instead of lists because numba supports # tuples in nopython mode. delimiter=', ' return '({},)'.format(delimiter.join(self._print(item) for item in seq)) def _print_MatMul(self, expr): "Matrix multiplication printer" if expr.as_coeff_matrices()[0] is not S.One: expr_list = expr.as_coeff_matrices()[1]+[(expr.as_coeff_matrices()[0])] return '({})'.format(').dot('.join(self._print(i) for i in expr_list)) return '({})'.format(').dot('.join(self._print(i) for i in expr.args)) def _print_MatPow(self, expr): "Matrix power printer" return '{}({}, {})'.format(self._module_format('numpy.linalg.matrix_power'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_Inverse(self, expr): "Matrix inverse printer" return '{}({})'.format(self._module_format('numpy.linalg.inv'), self._print(expr.args[0])) def _print_DotProduct(self, expr): # DotProduct allows any shape order, but numpy.dot does matrix # multiplication, so we have to make sure it gets 1 x n by n x 1. arg1, arg2 = expr.args if arg1.shape[0] != 1: arg1 = arg1.T if arg2.shape[1] != 1: arg2 = arg2.T return "%s(%s, %s)" % (self._module_format('numpy.dot'), self._print(arg1), self._print(arg2)) def _print_MatrixSolve(self, expr): return "%s(%s, %s)" % (self._module_format('numpy.linalg.solve'), self._print(expr.matrix), self._print(expr.vector)) def _print_ZeroMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.zeros'), self._print(expr.shape)) def _print_OneMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.ones'), self._print(expr.shape)) def _print_FunctionMatrix(self, expr): from sympy.core.function import Lambda from sympy.abc import i, j lamda = expr.lamda if not isinstance(lamda, Lambda): lamda = Lambda((i, j), lamda(i, j)) return '{}(lambda {}: {}, {})'.format(self._module_format('numpy.fromfunction'), ', '.join(self._print(arg) for arg in lamda.args[0]), self._print(lamda.args[1]), self._print(expr.shape)) def _print_HadamardProduct(self, expr): func = self._module_format('numpy.multiply') return ''.join('{}({}, '.format(func, self._print(arg)) \ for arg in expr.args[:-1]) + "{}{}".format(self._print(expr.args[-1]), ')' * (len(expr.args) - 1)) def _print_KroneckerProduct(self, expr): func = self._module_format('numpy.kron') return ''.join('{}({}, '.format(func, self._print(arg)) \ for arg in expr.args[:-1]) + "{}{}".format(self._print(expr.args[-1]), ')' * (len(expr.args) - 1)) def _print_Adjoint(self, expr): return '{}({}({}))'.format( self._module_format('numpy.conjugate'), self._module_format('numpy.transpose'), self._print(expr.args[0])) def _print_DiagonalOf(self, expr): vect = '{}({})'.format( self._module_format('numpy.diag'), self._print(expr.arg)) return '{}({}, (-1, 1))'.format( self._module_format('numpy.reshape'), vect) def _print_DiagMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.diagflat'), self._print(expr.args[0])) def _print_DiagonalMatrix(self, expr): return '{}({}, {}({}, {}))'.format(self._module_format('numpy.multiply'), self._print(expr.arg), self._module_format('numpy.eye'), self._print(expr.shape[0]), self._print(expr.shape[1])) def _print_Piecewise(self, expr): "Piecewise function printer" exprs = '[{}]'.format(','.join(self._print(arg.expr) for arg in expr.args)) conds = '[{}]'.format(','.join(self._print(arg.cond) for arg in expr.args)) # If [default_value, True] is a (expr, cond) sequence in a Piecewise object # it will behave the same as passing the 'default' kwarg to select() # *as long as* it is the last element in expr.args. # If this is not the case, it may be triggered prematurely. return '{}({}, {}, default={})'.format( self._module_format('numpy.select'), conds, exprs, self._print(S.NaN)) def _print_Relational(self, expr): "Relational printer for Equality and Unequality" op = { '==' :'equal', '!=' :'not_equal', '<' :'less', '<=' :'less_equal', '>' :'greater', '>=' :'greater_equal', } if expr.rel_op in op: lhs = self._print(expr.lhs) rhs = self._print(expr.rhs) return '{op}({lhs}, {rhs})'.format(op=self._module_format('numpy.'+op[expr.rel_op]), lhs=lhs, rhs=rhs) return super()._print_Relational(expr) def _print_And(self, expr): "Logical And printer" # We have to override LambdaPrinter because it uses Python 'and' keyword. # If LambdaPrinter didn't define it, we could use StrPrinter's # version of the function and add 'logical_and' to NUMPY_TRANSLATIONS. return '{}.reduce(({}))'.format(self._module_format('numpy.logical_and'), ','.join(self._print(i) for i in expr.args)) def _print_Or(self, expr): "Logical Or printer" # We have to override LambdaPrinter because it uses Python 'or' keyword. # If LambdaPrinter didn't define it, we could use StrPrinter's # version of the function and add 'logical_or' to NUMPY_TRANSLATIONS. return '{}.reduce(({}))'.format(self._module_format('numpy.logical_or'), ','.join(self._print(i) for i in expr.args)) def _print_Not(self, expr): "Logical Not printer" # We have to override LambdaPrinter because it uses Python 'not' keyword. # If LambdaPrinter didn't define it, we would still have to define our # own because StrPrinter doesn't define it. return '{}({})'.format(self._module_format('numpy.logical_not'), ','.join(self._print(i) for i in expr.args)) def _print_Pow(self, expr, rational=False): # XXX Workaround for negative integer power error from sympy.core.power import Pow if expr.exp.is_integer and expr.exp.is_negative: expr = Pow(expr.base, expr.exp.evalf(), evaluate=False) return self._hprint_Pow(expr, rational=rational, sqrt='numpy.sqrt') def _print_Min(self, expr): return '{}(({}), axis=0)'.format(self._module_format('numpy.amin'), ','.join(self._print(i) for i in expr.args)) def _print_Max(self, expr): return '{}(({}), axis=0)'.format(self._module_format('numpy.amax'), ','.join(self._print(i) for i in expr.args)) def _print_arg(self, expr): return "%s(%s)" % (self._module_format('numpy.angle'), self._print(expr.args[0])) def _print_im(self, expr): return "%s(%s)" % (self._module_format('numpy.imag'), self._print(expr.args[0])) def _print_Mod(self, expr): return "%s(%s)" % (self._module_format('numpy.mod'), ', '.join( map(lambda arg: self._print(arg), expr.args))) def _print_re(self, expr): return "%s(%s)" % (self._module_format('numpy.real'), self._print(expr.args[0])) def _print_sinc(self, expr): return "%s(%s)" % (self._module_format('numpy.sinc'), self._print(expr.args[0]/S.Pi)) def _print_MatrixBase(self, expr): func = self.known_functions.get(expr.__class__.__name__, None) if func is None: func = self._module_format('numpy.array') return "%s(%s)" % (func, self._print(expr.tolist())) def _print_Identity(self, expr): shape = expr.shape if all([dim.is_Integer for dim in shape]): return "%s(%s)" % (self._module_format('numpy.eye'), self._print(expr.shape[0])) else: raise NotImplementedError("Symbolic matrix dimensions are not yet supported for identity matrices") def _print_BlockMatrix(self, expr): return '{}({})'.format(self._module_format('numpy.block'), self._print(expr.args[0].tolist())) def _print_CodegenArrayTensorProduct(self, expr): array_list = [j for i, arg in enumerate(expr.args) for j in (self._print(arg), "[%i, %i]" % (2*i, 2*i+1))] return "%s(%s)" % (self._module_format('numpy.einsum'), ", ".join(array_list)) def _print_CodegenArrayContraction(self, expr): from sympy.codegen.array_utils import CodegenArrayTensorProduct base = expr.expr contraction_indices = expr.contraction_indices if not contraction_indices: return self._print(base) if isinstance(base, CodegenArrayTensorProduct): counter = 0 d = {j: min(i) for i in contraction_indices for j in i} indices = [] for rank_arg in base.subranks: lindices = [] for i in range(rank_arg): if counter in d: lindices.append(d[counter]) else: lindices.append(counter) counter += 1 indices.append(lindices) elems = ["%s, %s" % (self._print(arg), ind) for arg, ind in zip(base.args, indices)] return "%s(%s)" % ( self._module_format('numpy.einsum'), ", ".join(elems) ) raise NotImplementedError() def _print_CodegenArrayDiagonal(self, expr): diagonal_indices = list(expr.diagonal_indices) if len(diagonal_indices) > 1: # TODO: this should be handled in sympy.codegen.array_utils, # possibly by creating the possibility of unfolding the # CodegenArrayDiagonal object into nested ones. Same reasoning for # the array contraction. raise NotImplementedError if len(diagonal_indices[0]) != 2: raise NotImplementedError return "%s(%s, 0, axis1=%s, axis2=%s)" % ( self._module_format("numpy.diagonal"), self._print(expr.expr), diagonal_indices[0][0], diagonal_indices[0][1], ) def _print_CodegenArrayPermuteDims(self, expr): return "%s(%s, %s)" % ( self._module_format("numpy.transpose"), self._print(expr.expr), self._print(expr.permutation.array_form), ) def _print_CodegenArrayElementwiseAdd(self, expr): return self._expand_fold_binary_op('numpy.add', expr.args) _print_lowergamma = CodePrinter._print_not_supported _print_uppergamma = CodePrinter._print_not_supported _print_fresnelc = CodePrinter._print_not_supported _print_fresnels = CodePrinter._print_not_supported for k in NumPyPrinter._kf: setattr(NumPyPrinter, '_print_%s' % k, _print_known_func) for k in NumPyPrinter._kc: setattr(NumPyPrinter, '_print_%s' % k, _print_known_const) _known_functions_scipy_special = { 'erf': 'erf', 'erfc': 'erfc', 'besselj': 'jv', 'bessely': 'yv', 'besseli': 'iv', 'besselk': 'kv', 'cosm1': 'cosm1', 'factorial': 'factorial', 'gamma': 'gamma', 'loggamma': 'gammaln', 'digamma': 'psi', 'RisingFactorial': 'poch', 'jacobi': 'eval_jacobi', 'gegenbauer': 'eval_gegenbauer', 'chebyshevt': 'eval_chebyt', 'chebyshevu': 'eval_chebyu', 'legendre': 'eval_legendre', 'hermite': 'eval_hermite', 'laguerre': 'eval_laguerre', 'assoc_laguerre': 'eval_genlaguerre', 'beta': 'beta', 'LambertW' : 'lambertw', } _known_constants_scipy_constants = { 'GoldenRatio': 'golden_ratio', 'Pi': 'pi', } class SciPyPrinter(NumPyPrinter): language = "Python with SciPy" _kf = dict(chain( NumPyPrinter._kf.items(), [(k, 'scipy.special.' + v) for k, v in _known_functions_scipy_special.items()] )) _kc =dict(chain( NumPyPrinter._kc.items(), [(k, 'scipy.constants.' + v) for k, v in _known_constants_scipy_constants.items()] )) def _print_SparseMatrix(self, expr): i, j, data = [], [], [] for (r, c), v in expr._smat.items(): i.append(r) j.append(c) data.append(v) return "{name}(({data}, ({i}, {j})), shape={shape})".format( name=self._module_format('scipy.sparse.coo_matrix'), data=data, i=i, j=j, shape=expr.shape ) _print_ImmutableSparseMatrix = _print_SparseMatrix # SciPy's lpmv has a different order of arguments from assoc_legendre def _print_assoc_legendre(self, expr): return "{0}({2}, {1}, {3})".format( self._module_format('scipy.special.lpmv'), self._print(expr.args[0]), self._print(expr.args[1]), self._print(expr.args[2])) def _print_lowergamma(self, expr): return "{0}({2})*{1}({2}, {3})".format( self._module_format('scipy.special.gamma'), self._module_format('scipy.special.gammainc'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_uppergamma(self, expr): return "{0}({2})*{1}({2}, {3})".format( self._module_format('scipy.special.gamma'), self._module_format('scipy.special.gammaincc'), self._print(expr.args[0]), self._print(expr.args[1])) def _print_fresnels(self, expr): return "{}({})[0]".format( self._module_format("scipy.special.fresnel"), self._print(expr.args[0])) def _print_fresnelc(self, expr): return "{}({})[1]".format( self._module_format("scipy.special.fresnel"), self._print(expr.args[0])) def _print_airyai(self, expr): return "{}({})[0]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airyaiprime(self, expr): return "{}({})[1]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airybi(self, expr): return "{}({})[2]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_airybiprime(self, expr): return "{}({})[3]".format( self._module_format("scipy.special.airy"), self._print(expr.args[0])) def _print_Integral(self, e): integration_vars, limits = _unpack_integral_limits(e) if len(limits) == 1: # nicer (but not necessary) to prefer quad over nquad for 1D case module_str = self._module_format("scipy.integrate.quad") limit_str = "%s, %s" % tuple(map(self._print, limits[0])) else: module_str = self._module_format("scipy.integrate.nquad") limit_str = "({})".format(", ".join( "(%s, %s)" % tuple(map(self._print, l)) for l in limits)) return "{}(lambda {}: {}, {})[0]".format( module_str, ", ".join(map(self._print, integration_vars)), self._print(e.args[0]), limit_str) for k in SciPyPrinter._kf: setattr(SciPyPrinter, '_print_%s' % k, _print_known_func) for k in SciPyPrinter._kc: setattr(SciPyPrinter, '_print_%s' % k, _print_known_const) class SymPyPrinter(AbstractPythonCodePrinter): language = "Python with SymPy" def _print_Function(self, expr): mod = expr.func.__module__ or '' return '%s(%s)' % (self._module_format(mod + ('.' if mod else '') + expr.func.__name__), ', '.join(map(lambda arg: self._print(arg), expr.args))) def _print_Pow(self, expr, rational=False): return self._hprint_Pow(expr, rational=rational, sqrt='sympy.sqrt')

d5abad2058348a36008c41c78a7dd78c4addbbcb434c56bb31355fc6ceee9b5b

""" A Printer for generating readable representation of most sympy classes. """ from typing import Any, Dict from sympy.core import S, Rational, Pow, Basic, Mul, Number from sympy.core.mul import _keep_coeff from .printer import Printer, print_function from sympy.printing.precedence import precedence, PRECEDENCE from mpmath.libmp import prec_to_dps, to_str as mlib_to_str from sympy.utilities import default_sort_key class StrPrinter(Printer): printmethod = "_sympystr" _default_settings = { "order": None, "full_prec": "auto", "sympy_integers": False, "abbrev": False, "perm_cyclic": True, "min": None, "max": None, } # type: Dict[str, Any] _relationals = dict() # type: Dict[str, str] def parenthesize(self, item, level, strict=False): if (precedence(item) < level) or ((not strict) and precedence(item) <= level): return "(%s)" % self._print(item) else: return self._print(item) def stringify(self, args, sep, level=0): return sep.join([self.parenthesize(item, level) for item in args]) def emptyPrinter(self, expr): if isinstance(expr, str): return expr elif isinstance(expr, Basic): return repr(expr) else: return str(expr) def _print_Add(self, expr, order=None): terms = self._as_ordered_terms(expr, order=order) PREC = precedence(expr) l = [] for term in terms: t = self._print(term) if t.startswith('-'): sign = "-" t = t[1:] else: sign = "+" if precedence(term) < PREC: l.extend([sign, "(%s)" % t]) else: l.extend([sign, t]) sign = l.pop(0) if sign == '+': sign = "" return sign + ' '.join(l) def _print_BooleanTrue(self, expr): return "True" def _print_BooleanFalse(self, expr): return "False" def _print_Not(self, expr): return '~%s' %(self.parenthesize(expr.args[0],PRECEDENCE["Not"])) def _print_And(self, expr): return self.stringify(expr.args, " & ", PRECEDENCE["BitwiseAnd"]) def _print_Or(self, expr): return self.stringify(expr.args, " | ", PRECEDENCE["BitwiseOr"]) def _print_Xor(self, expr): return self.stringify(expr.args, " ^ ", PRECEDENCE["BitwiseXor"]) def _print_AppliedPredicate(self, expr): return '%s(%s)' % (self._print(expr.func), self._print(expr.arg)) def _print_Basic(self, expr): l = [self._print(o) for o in expr.args] return expr.__class__.__name__ + "(%s)" % ", ".join(l) def _print_BlockMatrix(self, B): if B.blocks.shape == (1, 1): self._print(B.blocks[0, 0]) return self._print(B.blocks) def _print_Catalan(self, expr): return 'Catalan' def _print_ComplexInfinity(self, expr): return 'zoo' def _print_ConditionSet(self, s): args = tuple([self._print(i) for i in (s.sym, s.condition)]) if s.base_set is S.UniversalSet: return 'ConditionSet(%s, %s)' % args args += (self._print(s.base_set),) return 'ConditionSet(%s, %s, %s)' % args def _print_Derivative(self, expr): dexpr = expr.expr dvars = [i[0] if i[1] == 1 else i for i in expr.variable_count] return 'Derivative(%s)' % ", ".join(map(lambda arg: self._print(arg), [dexpr] + dvars)) def _print_dict(self, d): keys = sorted(d.keys(), key=default_sort_key) items = [] for key in keys: item = "%s: %s" % (self._print(key), self._print(d[key])) items.append(item) return "{%s}" % ", ".join(items) def _print_Dict(self, expr): return self._print_dict(expr) def _print_RandomDomain(self, d): if hasattr(d, 'as_boolean'): return 'Domain: ' + self._print(d.as_boolean()) elif hasattr(d, 'set'): return ('Domain: ' + self._print(d.symbols) + ' in ' + self._print(d.set)) else: return 'Domain on ' + self._print(d.symbols) def _print_Dummy(self, expr): return '_' + expr.name def _print_EulerGamma(self, expr): return 'EulerGamma' def _print_Exp1(self, expr): return 'E' def _print_ExprCondPair(self, expr): return '(%s, %s)' % (self._print(expr.expr), self._print(expr.cond)) def _print_Function(self, expr): return expr.func.__name__ + "(%s)" % self.stringify(expr.args, ", ") def _print_GoldenRatio(self, expr): return 'GoldenRatio' def _print_TribonacciConstant(self, expr): return 'TribonacciConstant' def _print_ImaginaryUnit(self, expr): return 'I' def _print_Infinity(self, expr): return 'oo' def _print_Integral(self, expr): def _xab_tostr(xab): if len(xab) == 1: return self._print(xab[0]) else: return self._print((xab[0],) + tuple(xab[1:])) L = ', '.join([_xab_tostr(l) for l in expr.limits]) return 'Integral(%s, %s)' % (self._print(expr.function), L) def _print_Interval(self, i): fin = 'Interval{m}({a}, {b})' a, b, l, r = i.args if a.is_infinite and b.is_infinite: m = '' elif a.is_infinite and not r: m = '' elif b.is_infinite and not l: m = '' elif not l and not r: m = '' elif l and r: m = '.open' elif l: m = '.Lopen' else: m = '.Ropen' return fin.format(**{'a': a, 'b': b, 'm': m}) def _print_AccumulationBounds(self, i): return "AccumBounds(%s, %s)" % (self._print(i.min), self._print(i.max)) def _print_Inverse(self, I): return "%s**(-1)" % self.parenthesize(I.arg, PRECEDENCE["Pow"]) def _print_Lambda(self, obj): expr = obj.expr sig = obj.signature if len(sig) == 1 and sig[0].is_symbol: sig = sig[0] return "Lambda(%s, %s)" % (self._print(sig), self._print(expr)) def _print_LatticeOp(self, expr): args = sorted(expr.args, key=default_sort_key) return expr.func.__name__ + "(%s)" % ", ".join(self._print(arg) for arg in args) def _print_Limit(self, expr): e, z, z0, dir = expr.args if str(dir) == "+": return "Limit(%s, %s, %s)" % tuple(map(self._print, (e, z, z0))) else: return "Limit(%s, %s, %s, dir='%s')" % tuple(map(self._print, (e, z, z0, dir))) def _print_list(self, expr): return "[%s]" % self.stringify(expr, ", ") def _print_MatrixBase(self, expr): return expr._format_str(self) def _print_MatrixElement(self, expr): return self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) \ + '[%s, %s]' % (self._print(expr.i), self._print(expr.j)) def _print_MatrixSlice(self, expr): def strslice(x, dim): x = list(x) if x[2] == 1: del x[2] if x[0] == 0: x[0] = '' if x[1] == dim: x[1] = '' return ':'.join(map(lambda arg: self._print(arg), x)) return (self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) + '[' + strslice(expr.rowslice, expr.parent.rows) + ', ' + strslice(expr.colslice, expr.parent.cols) + ']') def _print_DeferredVector(self, expr): return expr.name def _print_Mul(self, expr): prec = precedence(expr) # Check for unevaluated Mul. In this case we need to make sure the # identities are visible, multiple Rational factors are not combined # etc so we display in a straight-forward form that fully preserves all # args and their order. args = expr.args if args[0] is S.One or any(isinstance(arg, Number) for arg in args[1:]): factors = [self.parenthesize(a, prec, strict=False) for a in args] return '*'.join(factors) c, e = expr.as_coeff_Mul() if c < 0: expr = _keep_coeff(-c, e) sign = "-" else: sign = "" a = [] # items in the numerator b = [] # items that are in the denominator (if any) pow_paren = [] # Will collect all pow with more than one base element and exp = -1 if self.order not in ('old', 'none'): args = expr.as_ordered_factors() else: # use make_args in case expr was something like -x -> x args = Mul.make_args(expr) # Gather args for numerator/denominator for item in args: if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative: if item.exp != -1: b.append(Pow(item.base, -item.exp, evaluate=False)) else: if len(item.args[0].args) != 1 and isinstance(item.base, Mul): # To avoid situations like #14160 pow_paren.append(item) b.append(Pow(item.base, -item.exp)) elif item.is_Rational and item is not S.Infinity: if item.p != 1: a.append(Rational(item.p)) if item.q != 1: b.append(Rational(item.q)) else: a.append(item) a = a or [S.One] a_str = [self.parenthesize(x, prec, strict=False) for x in a] b_str = [self.parenthesize(x, prec, strict=False) for x in b] # To parenthesize Pow with exp = -1 and having more than one Symbol for item in pow_paren: if item.base in b: b_str[b.index(item.base)] = "(%s)" % b_str[b.index(item.base)] if not b: return sign + '*'.join(a_str) elif len(b) == 1: return sign + '*'.join(a_str) + "/" + b_str[0] else: return sign + '*'.join(a_str) + "/(%s)" % '*'.join(b_str) def _print_MatMul(self, expr): c, m = expr.as_coeff_mmul() sign = "" if c.is_number: re, im = c.as_real_imag() if im.is_zero and re.is_negative: expr = _keep_coeff(-c, m) sign = "-" elif re.is_zero and im.is_negative: expr = _keep_coeff(-c, m) sign = "-" return sign + '*'.join( [self.parenthesize(arg, precedence(expr)) for arg in expr.args] ) def _print_ElementwiseApplyFunction(self, expr): return "{}.({})".format( expr.function, self._print(expr.expr), ) def _print_NaN(self, expr): return 'nan' def _print_NegativeInfinity(self, expr): return '-oo' def _print_Order(self, expr): if not expr.variables or all(p is S.Zero for p in expr.point): if len(expr.variables) <= 1: return 'O(%s)' % self._print(expr.expr) else: return 'O(%s)' % self.stringify((expr.expr,) + expr.variables, ', ', 0) else: return 'O(%s)' % self.stringify(expr.args, ', ', 0) def _print_Ordinal(self, expr): return expr.__str__() def _print_Cycle(self, expr): return expr.__str__() def _print_Permutation(self, expr): from sympy.combinatorics.permutations import Permutation, Cycle from sympy.utilities.exceptions import SymPyDeprecationWarning perm_cyclic = Permutation.print_cyclic if perm_cyclic is not None: SymPyDeprecationWarning( feature="Permutation.print_cyclic = {}".format(perm_cyclic), useinstead="init_printing(perm_cyclic={})" .format(perm_cyclic), issue=15201, deprecated_since_version="1.6").warn() else: perm_cyclic = self._settings.get("perm_cyclic", True) if perm_cyclic: if not expr.size: return '()' # before taking Cycle notation, see if the last element is # a singleton and move it to the head of the string s = Cycle(expr)(expr.size - 1).__repr__()[len('Cycle'):] last = s.rfind('(') if not last == 0 and ',' not in s[last:]: s = s[last:] + s[:last] s = s.replace(',', '') return s else: s = expr.support() if not s: if expr.size < 5: return 'Permutation(%s)' % self._print(expr.array_form) return 'Permutation([], size=%s)' % self._print(expr.size) trim = self._print(expr.array_form[:s[-1] + 1]) + ', size=%s' % self._print(expr.size) use = full = self._print(expr.array_form) if len(trim) < len(full): use = trim return 'Permutation(%s)' % use def _print_Subs(self, obj): expr, old, new = obj.args if len(obj.point) == 1: old = old[0] new = new[0] return "Subs(%s, %s, %s)" % ( self._print(expr), self._print(old), self._print(new)) def _print_TensorIndex(self, expr): return expr._print() def _print_TensorHead(self, expr): return expr._print() def _print_Tensor(self, expr): return expr._print() def _print_TensMul(self, expr): # prints expressions like "A(a)", "3*A(a)", "(1+x)*A(a)" sign, args = expr._get_args_for_traditional_printer() return sign + "*".join( [self.parenthesize(arg, precedence(expr)) for arg in args] ) def _print_TensAdd(self, expr): return expr._print() def _print_PermutationGroup(self, expr): p = [' %s' % self._print(a) for a in expr.args] return 'PermutationGroup([\n%s])' % ',\n'.join(p) def _print_Pi(self, expr): return 'pi' def _print_PolyRing(self, ring): return "Polynomial ring in %s over %s with %s order" % \ (", ".join(map(lambda rs: self._print(rs), ring.symbols)), self._print(ring.domain), self._print(ring.order)) def _print_FracField(self, field): return "Rational function field in %s over %s with %s order" % \ (", ".join(map(lambda fs: self._print(fs), field.symbols)), self._print(field.domain), self._print(field.order)) def _print_FreeGroupElement(self, elm): return elm.__str__() def _print_GaussianElement(self, poly): return "(%s + %s*I)" % (poly.x, poly.y) def _print_PolyElement(self, poly): return poly.str(self, PRECEDENCE, "%s**%s", "*") def _print_FracElement(self, frac): if frac.denom == 1: return self._print(frac.numer) else: numer = self.parenthesize(frac.numer, PRECEDENCE["Mul"], strict=True) denom = self.parenthesize(frac.denom, PRECEDENCE["Atom"], strict=True) return numer + "/" + denom def _print_Poly(self, expr): ATOM_PREC = PRECEDENCE["Atom"] - 1 terms, gens = [], [ self.parenthesize(s, ATOM_PREC) for s in expr.gens ] for monom, coeff in expr.terms(): s_monom = [] for i, exp in enumerate(monom): if exp > 0: if exp == 1: s_monom.append(gens[i]) else: s_monom.append(gens[i] + "**%d" % exp) s_monom = "*".join(s_monom) if coeff.is_Add: if s_monom: s_coeff = "(" + self._print(coeff) + ")" else: s_coeff = self._print(coeff) else: if s_monom: if coeff is S.One: terms.extend(['+', s_monom]) continue if coeff is S.NegativeOne: terms.extend(['-', s_monom]) continue s_coeff = self._print(coeff) if not s_monom: s_term = s_coeff else: s_term = s_coeff + "*" + s_monom if s_term.startswith('-'): terms.extend(['-', s_term[1:]]) else: terms.extend(['+', s_term]) if terms[0] in ['-', '+']: modifier = terms.pop(0) if modifier == '-': terms[0] = '-' + terms[0] format = expr.__class__.__name__ + "(%s, %s" from sympy.polys.polyerrors import PolynomialError try: format += ", modulus=%s" % expr.get_modulus() except PolynomialError: format += ", domain='%s'" % expr.get_domain() format += ")" for index, item in enumerate(gens): if len(item) > 2 and (item[:1] == "(" and item[len(item) - 1:] == ")"): gens[index] = item[1:len(item) - 1] return format % (' '.join(terms), ', '.join(gens)) def _print_UniversalSet(self, p): return 'UniversalSet' def _print_AlgebraicNumber(self, expr): if expr.is_aliased: return self._print(expr.as_poly().as_expr()) else: return self._print(expr.as_expr()) def _print_Pow(self, expr, rational=False): """Printing helper function for ``Pow`` Parameters ========== rational : bool, optional If ``True``, it will not attempt printing ``sqrt(x)`` or ``x**S.Half`` as ``sqrt``, and will use ``x**(1/2)`` instead. See examples for additional details Examples ======== >>> from sympy.functions import sqrt >>> from sympy.printing.str import StrPrinter >>> from sympy.abc import x How ``rational`` keyword works with ``sqrt``: >>> printer = StrPrinter() >>> printer._print_Pow(sqrt(x), rational=True) 'x**(1/2)' >>> printer._print_Pow(sqrt(x), rational=False) 'sqrt(x)' >>> printer._print_Pow(1/sqrt(x), rational=True) 'x**(-1/2)' >>> printer._print_Pow(1/sqrt(x), rational=False) '1/sqrt(x)' Notes ===== ``sqrt(x)`` is canonicalized as ``Pow(x, S.Half)`` in SymPy, so there is no need of defining a separate printer for ``sqrt``. Instead, it should be handled here as well. """ PREC = precedence(expr) if expr.exp is S.Half and not rational: return "sqrt(%s)" % self._print(expr.base) if expr.is_commutative: if -expr.exp is S.Half and not rational: # Note: Don't test "expr.exp == -S.Half" here, because that will # match -0.5, which we don't want. return "%s/sqrt(%s)" % tuple(map(lambda arg: self._print(arg), (S.One, expr.base))) if expr.exp is -S.One: # Similarly to the S.Half case, don't test with "==" here. return '%s/%s' % (self._print(S.One), self.parenthesize(expr.base, PREC, strict=False)) e = self.parenthesize(expr.exp, PREC, strict=False) if self.printmethod == '_sympyrepr' and expr.exp.is_Rational and expr.exp.q != 1: # the parenthesized exp should be '(Rational(a, b))' so strip parens, # but just check to be sure. if e.startswith('(Rational'): return '%s**%s' % (self.parenthesize(expr.base, PREC, strict=False), e[1:-1]) return '%s**%s' % (self.parenthesize(expr.base, PREC, strict=False), e) def _print_UnevaluatedExpr(self, expr): return self._print(expr.args[0]) def _print_MatPow(self, expr): PREC = precedence(expr) return '%s**%s' % (self.parenthesize(expr.base, PREC, strict=False), self.parenthesize(expr.exp, PREC, strict=False)) def _print_Integer(self, expr): if self._settings.get("sympy_integers", False): return "S(%s)" % (expr) return str(expr.p) def _print_Integers(self, expr): return 'Integers' def _print_Naturals(self, expr): return 'Naturals' def _print_Naturals0(self, expr): return 'Naturals0' def _print_Rationals(self, expr): return 'Rationals' def _print_Reals(self, expr): return 'Reals' def _print_Complexes(self, expr): return 'Complexes' def _print_EmptySet(self, expr): return 'EmptySet' def _print_EmptySequence(self, expr): return 'EmptySequence' def _print_int(self, expr): return str(expr) def _print_mpz(self, expr): return str(expr) def _print_Rational(self, expr): if expr.q == 1: return str(expr.p) else: if self._settings.get("sympy_integers", False): return "S(%s)/%s" % (expr.p, expr.q) return "%s/%s" % (expr.p, expr.q) def _print_PythonRational(self, expr): if expr.q == 1: return str(expr.p) else: return "%d/%d" % (expr.p, expr.q) def _print_Fraction(self, expr): if expr.denominator == 1: return str(expr.numerator) else: return "%s/%s" % (expr.numerator, expr.denominator) def _print_mpq(self, expr): if expr.denominator == 1: return str(expr.numerator) else: return "%s/%s" % (expr.numerator, expr.denominator) def _print_Float(self, expr): prec = expr._prec if prec < 5: dps = 0 else: dps = prec_to_dps(expr._prec) if self._settings["full_prec"] is True: strip = False elif self._settings["full_prec"] is False: strip = True elif self._settings["full_prec"] == "auto": strip = self._print_level > 1 low = self._settings["min"] if "min" in self._settings else None high = self._settings["max"] if "max" in self._settings else None rv = mlib_to_str(expr._mpf_, dps, strip_zeros=strip, min_fixed=low, max_fixed=high) if rv.startswith('-.0'): rv = '-0.' + rv[3:] elif rv.startswith('.0'): rv = '0.' + rv[2:] if rv.startswith('+'): # e.g., +inf -> inf rv = rv[1:] return rv def _print_Relational(self, expr): charmap = { "==": "Eq", "!=": "Ne", ":=": "Assignment", '+=': "AddAugmentedAssignment", "-=": "SubAugmentedAssignment", "*=": "MulAugmentedAssignment", "/=": "DivAugmentedAssignment", "%=": "ModAugmentedAssignment", } if expr.rel_op in charmap: return '%s(%s, %s)' % (charmap[expr.rel_op], self._print(expr.lhs), self._print(expr.rhs)) return '%s %s %s' % (self.parenthesize(expr.lhs, precedence(expr)), self._relationals.get(expr.rel_op) or expr.rel_op, self.parenthesize(expr.rhs, precedence(expr))) def _print_ComplexRootOf(self, expr): return "CRootOf(%s, %d)" % (self._print_Add(expr.expr, order='lex'), expr.index) def _print_RootSum(self, expr): args = [self._print_Add(expr.expr, order='lex')] if expr.fun is not S.IdentityFunction: args.append(self._print(expr.fun)) return "RootSum(%s)" % ", ".join(args) def _print_GroebnerBasis(self, basis): cls = basis.__class__.__name__ exprs = [self._print_Add(arg, order=basis.order) for arg in basis.exprs] exprs = "[%s]" % ", ".join(exprs) gens = [ self._print(gen) for gen in basis.gens ] domain = "domain='%s'" % self._print(basis.domain) order = "order='%s'" % self._print(basis.order) args = [exprs] + gens + [domain, order] return "%s(%s)" % (cls, ", ".join(args)) def _print_set(self, s): items = sorted(s, key=default_sort_key) args = ', '.join(self._print(item) for item in items) if not args: return "set()" return '{%s}' % args def _print_frozenset(self, s): if not s: return "frozenset()" return "frozenset(%s)" % self._print_set(s) def _print_Sum(self, expr): def _xab_tostr(xab): if len(xab) == 1: return self._print(xab[0]) else: return self._print((xab[0],) + tuple(xab[1:])) L = ', '.join([_xab_tostr(l) for l in expr.limits]) return 'Sum(%s, %s)' % (self._print(expr.function), L) def _print_Symbol(self, expr): return expr.name _print_MatrixSymbol = _print_Symbol _print_RandomSymbol = _print_Symbol def _print_Identity(self, expr): return "I" def _print_ZeroMatrix(self, expr): return "0" def _print_OneMatrix(self, expr): return "1" def _print_Predicate(self, expr): return "Q.%s" % expr.name def _print_str(self, expr): return str(expr) def _print_tuple(self, expr): if len(expr) == 1: return "(%s,)" % self._print(expr[0]) else: return "(%s)" % self.stringify(expr, ", ") def _print_Tuple(self, expr): return self._print_tuple(expr) def _print_Transpose(self, T): return "%s.T" % self.parenthesize(T.arg, PRECEDENCE["Pow"]) def _print_Uniform(self, expr): return "Uniform(%s, %s)" % (self._print(expr.a), self._print(expr.b)) def _print_Quantity(self, expr): if self._settings.get("abbrev", False): return "%s" % expr.abbrev return "%s" % expr.name def _print_Quaternion(self, expr): s = [self.parenthesize(i, PRECEDENCE["Mul"], strict=True) for i in expr.args] a = [s[0]] + [i+"*"+j for i, j in zip(s[1:], "ijk")] return " + ".join(a) def _print_Dimension(self, expr): return str(expr) def _print_Wild(self, expr): return expr.name + '_' def _print_WildFunction(self, expr): return expr.name + '_' def _print_Zero(self, expr): if self._settings.get("sympy_integers", False): return "S(0)" return "0" def _print_DMP(self, p): from sympy.core.sympify import SympifyError try: if p.ring is not None: # TODO incorporate order return self._print(p.ring.to_sympy(p)) except SympifyError: pass cls = p.__class__.__name__ rep = self._print(p.rep) dom = self._print(p.dom) ring = self._print(p.ring) return "%s(%s, %s, %s)" % (cls, rep, dom, ring) def _print_DMF(self, expr): return self._print_DMP(expr) def _print_Object(self, obj): return 'Object("%s")' % obj.name def _print_IdentityMorphism(self, morphism): return 'IdentityMorphism(%s)' % morphism.domain def _print_NamedMorphism(self, morphism): return 'NamedMorphism(%s, %s, "%s")' % \ (morphism.domain, morphism.codomain, morphism.name) def _print_Category(self, category): return 'Category("%s")' % category.name def _print_Manifold(self, manifold): return manifold.name.name def _print_Patch(self, patch): return patch.name.name def _print_CoordSystem(self, coords): return coords.name.name def _print_BaseScalarField(self, field): return field._coord_sys.symbols[field._index].name def _print_BaseVectorField(self, field): return 'e_%s' % field._coord_sys.symbols[field._index].name def _print_Differential(self, diff): field = diff._form_field if hasattr(field, '_coord_sys'): return 'd%s' % field._coord_sys.symbols[field._index].name else: return 'd(%s)' % self._print(field) def _print_Tr(self, expr): #TODO : Handle indices return "%s(%s)" % ("Tr", self._print(expr.args[0])) def _print_Str(self, s): return self._print(s.name) @print_function(StrPrinter) def sstr(expr, **settings): """Returns the expression as a string. For large expressions where speed is a concern, use the setting order='none'. If abbrev=True setting is used then units are printed in abbreviated form. Examples ======== >>> from sympy import symbols, Eq, sstr >>> a, b = symbols('a b') >>> sstr(Eq(a + b, 0)) 'Eq(a + b, 0)' """ p = StrPrinter(settings) s = p.doprint(expr) return s class StrReprPrinter(StrPrinter): """(internal) -- see sstrrepr""" def _print_str(self, s): return repr(s) def _print_Str(self, s): # Str does not to be printed same as str here return "%s(%s)" % (s.__class__.__name__, self._print(s.name)) @print_function(StrReprPrinter) def sstrrepr(expr, **settings): """return expr in mixed str/repr form i.e. strings are returned in repr form with quotes, and everything else is returned in str form. This function could be useful for hooking into sys.displayhook """ p = StrReprPrinter(settings) s = p.doprint(expr) return s

1b1105d5621f94f3528653ab65cf0065c87623a1b10e56e92261ea5fad7f3f9a

def pprint_nodes(subtrees): """ Prettyprints systems of nodes. Examples ======== >>> from sympy.printing.tree import pprint_nodes >>> print(pprint_nodes(["a", "b1\\nb2", "c"])) +-a +-b1 | b2 +-c """ def indent(s, type=1): x = s.split("\n") r = "+-%s\n" % x[0] for a in x[1:]: if a == "": continue if type == 1: r += "| %s\n" % a else: r += " %s\n" % a return r if not subtrees: return "" f = "" for a in subtrees[:-1]: f += indent(a) f += indent(subtrees[-1], 2) return f def print_node(node, assumptions=True): """ Returns information about the "node". This includes class name, string representation and assumptions. Parameters ========== assumptions : bool, optional See the ``assumptions`` keyword in ``tree`` """ s = "%s: %s\n" % (node.__class__.__name__, str(node)) if assumptions: d = node._assumptions else: d = None if d: for a in sorted(d): v = d[a] if v is None: continue s += "%s: %s\n" % (a, v) return s def tree(node, assumptions=True): """ Returns a tree representation of "node" as a string. It uses print_node() together with pprint_nodes() on node.args recursively. Parameters ========== asssumptions : bool, optional The flag to decide whether to print out all the assumption data (such as ``is_integer`, ``is_real``) associated with the expression or not. Enabling the flag makes the result verbose, and the printed result may not be determinisitic because of the randomness used in backtracing the assumptions. See Also ======== print_tree """ subtrees = [] for arg in node.args: subtrees.append(tree(arg, assumptions=assumptions)) s = print_node(node, assumptions=assumptions) + pprint_nodes(subtrees) return s def print_tree(node, assumptions=True): """ Prints a tree representation of "node". Parameters ========== asssumptions : bool, optional The flag to decide whether to print out all the assumption data (such as ``is_integer`, ``is_real``) associated with the expression or not. Enabling the flag makes the result verbose, and the printed result may not be determinisitic because of the randomness used in backtracing the assumptions. Examples ======== >>> from sympy.printing import print_tree >>> from sympy import Symbol >>> x = Symbol('x', odd=True) >>> y = Symbol('y', even=True) Printing with full assumptions information: >>> print_tree(y**x) Pow: y**x +-Symbol: y | algebraic: True | commutative: True | complex: True | even: True | extended_real: True | finite: True | hermitian: True | imaginary: False | infinite: False | integer: True | irrational: False | noninteger: False | odd: False | rational: True | real: True | transcendental: False +-Symbol: x algebraic: True commutative: True complex: True even: False extended_nonzero: True extended_real: True finite: True hermitian: True imaginary: False infinite: False integer: True irrational: False noninteger: False nonzero: True odd: True rational: True real: True transcendental: False zero: False Hiding the assumptions: >>> print_tree(y**x, assumptions=False) Pow: y**x +-Symbol: y +-Symbol: x See Also ======== tree """ print(tree(node, assumptions=assumptions))

7667356eadb26d9f12aa8ea8875ab411fa95b54016d741f82bf7a12e2827b5a0

""" Rust code printer The `RustCodePrinter` converts SymPy expressions into Rust expressions. A complete code generator, which uses `rust_code` extensively, can be found in `sympy.utilities.codegen`. The `codegen` module can be used to generate complete source code files. """ # Possible Improvement # # * make sure we follow Rust Style Guidelines_ # * make use of pattern matching # * better support for reference # * generate generic code and use trait to make sure they have specific methods # * use crates_ to get more math support # - num_ # + BigInt_, BigUint_ # + Complex_ # + Rational64_, Rational32_, BigRational_ # # .. _crates: https://crates.io/ # .. _Guidelines: https://github.com/rust-lang/rust/tree/master/src/doc/style # .. _num: http://rust-num.github.io/num/num/ # .. _BigInt: http://rust-num.github.io/num/num/bigint/struct.BigInt.html # .. _BigUint: http://rust-num.github.io/num/num/bigint/struct.BigUint.html # .. _Complex: http://rust-num.github.io/num/num/complex/struct.Complex.html # .. _Rational32: http://rust-num.github.io/num/num/rational/type.Rational32.html # .. _Rational64: http://rust-num.github.io/num/num/rational/type.Rational64.html # .. _BigRational: http://rust-num.github.io/num/num/rational/type.BigRational.html from typing import Any, Dict from sympy.core import S, Rational, Float, Lambda from sympy.printing.codeprinter import CodePrinter # Rust's methods for integer and float can be found at here : # # * `Rust - Primitive Type f64 <https://doc.rust-lang.org/std/primitive.f64.html>`_ # * `Rust - Primitive Type i64 <https://doc.rust-lang.org/std/primitive.i64.html>`_ # # Function Style : # # 1. args[0].func(args[1:]), method with arguments # 2. args[0].func(), method without arguments # 3. args[1].func(), method without arguments (e.g. (e, x) => x.exp()) # 4. func(args), function with arguments # dictionary mapping sympy function to (argument_conditions, Rust_function). # Used in RustCodePrinter._print_Function(self) # f64 method in Rust known_functions = { # "": "is_nan", # "": "is_infinite", # "": "is_finite", # "": "is_normal", # "": "classify", "floor": "floor", "ceiling": "ceil", # "": "round", # "": "trunc", # "": "fract", "Abs": "abs", "sign": "signum", # "": "is_sign_positive", # "": "is_sign_negative", # "": "mul_add", "Pow": [(lambda base, exp: exp == -S.One, "recip", 2), # 1.0/x (lambda base, exp: exp == S.Half, "sqrt", 2), # x ** 0.5 (lambda base, exp: exp == -S.Half, "sqrt().recip", 2), # 1/(x ** 0.5) (lambda base, exp: exp == Rational(1, 3), "cbrt", 2), # x ** (1/3) (lambda base, exp: base == S.One*2, "exp2", 3), # 2 ** x (lambda base, exp: exp.is_integer, "powi", 1), # x ** y, for i32 (lambda base, exp: not exp.is_integer, "powf", 1)], # x ** y, for f64 "exp": [(lambda exp: True, "exp", 2)], # e ** x "log": "ln", # "": "log", # number.log(base) # "": "log2", # "": "log10", # "": "to_degrees", # "": "to_radians", "Max": "max", "Min": "min", # "": "hypot", # (x**2 + y**2) ** 0.5 "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", # "": "sin_cos", # "": "exp_m1", # e ** x - 1 # "": "ln_1p", # ln(1 + x) "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "asinh": "asinh", "acosh": "acosh", "atanh": "atanh", } # i64 method in Rust # known_functions_i64 = { # "": "min_value", # "": "max_value", # "": "from_str_radix", # "": "count_ones", # "": "count_zeros", # "": "leading_zeros", # "": "trainling_zeros", # "": "rotate_left", # "": "rotate_right", # "": "swap_bytes", # "": "from_be", # "": "from_le", # "": "to_be", # to big endian # "": "to_le", # to little endian # "": "checked_add", # "": "checked_sub", # "": "checked_mul", # "": "checked_div", # "": "checked_rem", # "": "checked_neg", # "": "checked_shl", # "": "checked_shr", # "": "checked_abs", # "": "saturating_add", # "": "saturating_sub", # "": "saturating_mul", # "": "wrapping_add", # "": "wrapping_sub", # "": "wrapping_mul", # "": "wrapping_div", # "": "wrapping_rem", # "": "wrapping_neg", # "": "wrapping_shl", # "": "wrapping_shr", # "": "wrapping_abs", # "": "overflowing_add", # "": "overflowing_sub", # "": "overflowing_mul", # "": "overflowing_div", # "": "overflowing_rem", # "": "overflowing_neg", # "": "overflowing_shl", # "": "overflowing_shr", # "": "overflowing_abs", # "Pow": "pow", # "Abs": "abs", # "sign": "signum", # "": "is_positive", # "": "is_negnative", # } # These are the core reserved words in the Rust language. Taken from: # http://doc.rust-lang.org/grammar.html#keywords reserved_words = ['abstract', 'alignof', 'as', 'become', 'box', 'break', 'const', 'continue', 'crate', 'do', 'else', 'enum', 'extern', 'false', 'final', 'fn', 'for', 'if', 'impl', 'in', 'let', 'loop', 'macro', 'match', 'mod', 'move', 'mut', 'offsetof', 'override', 'priv', 'proc', 'pub', 'pure', 'ref', 'return', 'Self', 'self', 'sizeof', 'static', 'struct', 'super', 'trait', 'true', 'type', 'typeof', 'unsafe', 'unsized', 'use', 'virtual', 'where', 'while', 'yield'] class RustCodePrinter(CodePrinter): """A printer to convert python expressions to strings of Rust code""" printmethod = "_rust_code" language = "Rust" _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'contract': True, 'dereference': set(), 'error_on_reserved': False, 'reserved_word_suffix': '_', 'inline': False, } # type: Dict[str, Any] def __init__(self, settings={}): CodePrinter.__init__(self, settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}) self.known_functions.update(userfuncs) self._dereference = set(settings.get('dereference', [])) self.reserved_words = set(reserved_words) def _rate_index_position(self, p): return p*5 def _get_statement(self, codestring): return "%s;" % codestring def _get_comment(self, text): return "// %s" % text def _declare_number_const(self, name, value): return "const %s: f64 = %s;" % (name, value) def _format_code(self, lines): return self.indent_code(lines) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for i in range(rows) for j in range(cols)) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] loopstart = "for %(var)s in %(start)s..%(end)s {" for i in indices: # Rust arrays start at 0 and end at dimension-1 open_lines.append(loopstart % { 'var': self._print(i), 'start': self._print(i.lower), 'end': self._print(i.upper + 1)}) close_lines.append("}") return open_lines, close_lines def _print_caller_var(self, expr): if len(expr.args) > 1: # for something like `sin(x + y + z)`, # make sure we can get '(x + y + z).sin()' # instead of 'x + y + z.sin()' return '(' + self._print(expr) + ')' elif expr.is_number: return self._print(expr, _type=True) else: return self._print(expr) def _print_Function(self, expr): """ basic function for printing `Function` Function Style : 1. args[0].func(args[1:]), method with arguments 2. args[0].func(), method without arguments 3. args[1].func(), method without arguments (e.g. (e, x) => x.exp()) 4. func(args), function with arguments """ if expr.func.__name__ in self.known_functions: cond_func = self.known_functions[expr.func.__name__] func = None style = 1 if isinstance(cond_func, str): func = cond_func else: for cond, func, style in cond_func: if cond(*expr.args): break if func is not None: if style == 1: ret = "%(var)s.%(method)s(%(args)s)" % { 'var': self._print_caller_var(expr.args[0]), 'method': func, 'args': self.stringify(expr.args[1:], ", ") if len(expr.args) > 1 else '' } elif style == 2: ret = "%(var)s.%(method)s()" % { 'var': self._print_caller_var(expr.args[0]), 'method': func, } elif style == 3: ret = "%(var)s.%(method)s()" % { 'var': self._print_caller_var(expr.args[1]), 'method': func, } else: ret = "%(func)s(%(args)s)" % { 'func': func, 'args': self.stringify(expr.args, ", "), } return ret elif hasattr(expr, '_imp_') and isinstance(expr._imp_, Lambda): # inlined function return self._print(expr._imp_(*expr.args)) else: return self._print_not_supported(expr) def _print_Pow(self, expr): if expr.base.is_integer and not expr.exp.is_integer: expr = type(expr)(Float(expr.base), expr.exp) return self._print(expr) return self._print_Function(expr) def _print_Float(self, expr, _type=False): ret = super()._print_Float(expr) if _type: return ret + '_f64' else: return ret def _print_Integer(self, expr, _type=False): ret = super()._print_Integer(expr) if _type: return ret + '_i32' else: return ret def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) return '%d_f64/%d.0' % (p, q) def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) def _print_Indexed(self, expr): # calculate index for 1d array dims = expr.shape elem = S.Zero offset = S.One for i in reversed(range(expr.rank)): elem += expr.indices[i]*offset offset *= dims[i] return "%s[%s]" % (self._print(expr.base.label), self._print(elem)) def _print_Idx(self, expr): return expr.label.name def _print_Dummy(self, expr): return expr.name def _print_Exp1(self, expr, _type=False): return "E" def _print_Pi(self, expr, _type=False): return 'PI' def _print_Infinity(self, expr, _type=False): return 'INFINITY' def _print_NegativeInfinity(self, expr, _type=False): return 'NEG_INFINITY' def _print_BooleanTrue(self, expr, _type=False): return "true" def _print_BooleanFalse(self, expr, _type=False): return "false" def _print_bool(self, expr, _type=False): return str(expr).lower() def _print_NaN(self, expr, _type=False): return "NAN" def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) {" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines[-1] += " else {" else: lines[-1] += " else if (%s) {" % self._print(c) code0 = self._print(e) lines.append(code0) lines.append("}") if self._settings['inline']: return " ".join(lines) else: return "\n".join(lines) def _print_ITE(self, expr): from sympy.functions import Piecewise _piecewise = Piecewise((expr.args[1], expr.args[0]), (expr.args[2], True)) return self._print(_piecewise) def _print_MatrixBase(self, A): if A.cols == 1: return "[%s]" % ", ".join(self._print(a) for a in A) else: raise ValueError("Full Matrix Support in Rust need Crates (https://crates.io/keywords/matrix).") def _print_SparseMatrix(self, mat): # do not allow sparse matrices to be made dense return self._print_not_supported(mat) def _print_MatrixElement(self, expr): return "%s[%s]" % (expr.parent, expr.j + expr.i*expr.parent.shape[1]) def _print_Symbol(self, expr): name = super()._print_Symbol(expr) if expr in self._dereference: return '(*%s)' % name else: return name def _print_Assignment(self, expr): from sympy.tensor.indexed import IndexedBase lhs = expr.lhs rhs = expr.rhs if self._settings["contract"] and (lhs.has(IndexedBase) or rhs.has(IndexedBase)): # Here we check if there is looping to be done, and if so # print the required loops. return self._doprint_loops(rhs, lhs) else: lhs_code = self._print(lhs) rhs_code = self._print(rhs) return self._get_statement("%s = %s" % (lhs_code, rhs_code)) def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) tab = " " inc_token = ('{', '(', '{\n', '(\n') dec_token = ('}', ')') code = [ line.lstrip(' \t') for line in code ] increase = [ int(any(map(line.endswith, inc_token))) for line in code ] decrease = [ int(any(map(line.startswith, dec_token))) for line in code ] pretty = [] level = 0 for n, line in enumerate(code): if line == '' or line == '\n': pretty.append(line) continue level -= decrease[n] pretty.append("%s%s" % (tab*level, line)) level += increase[n] return pretty def rust_code(expr, assign_to=None, **settings): """Converts an expr to a string of Rust code Parameters ========== expr : Expr A sympy expression to be converted. assign_to : optional When given, the argument is used as the name of the variable to which the expression is assigned. Can be a string, ``Symbol``, ``MatrixSymbol``, or ``Indexed`` type. This is helpful in case of line-wrapping, or for expressions that generate multi-line statements. precision : integer, optional The precision for numbers such as pi [default=15]. user_functions : dict, optional A dictionary where the keys are string representations of either ``FunctionClass`` or ``UndefinedFunction`` instances and the values are their desired C string representations. Alternatively, the dictionary value can be a list of tuples i.e. [(argument_test, cfunction_string)]. See below for examples. dereference : iterable, optional An iterable of symbols that should be dereferenced in the printed code expression. These would be values passed by address to the function. For example, if ``dereference=[a]``, the resulting code would print ``(*a)`` instead of ``a``. human : bool, optional If True, the result is a single string that may contain some constant declarations for the number symbols. If False, the same information is returned in a tuple of (symbols_to_declare, not_supported_functions, code_text). [default=True]. contract: bool, optional If True, ``Indexed`` instances are assumed to obey tensor contraction rules and the corresponding nested loops over indices are generated. Setting contract=False will not generate loops, instead the user is responsible to provide values for the indices in the code. [default=True]. Examples ======== >>> from sympy import rust_code, symbols, Rational, sin, ceiling, Abs, Function >>> x, tau = symbols("x, tau") >>> rust_code((2*tau)**Rational(7, 2)) '8*1.4142135623731*tau.powf(7_f64/2.0)' >>> rust_code(sin(x), assign_to="s") 's = x.sin();' Simple custom printing can be defined for certain types by passing a dictionary of {"type" : "function"} to the ``user_functions`` kwarg. Alternatively, the dictionary value can be a list of tuples i.e. [(argument_test, cfunction_string)]. >>> custom_functions = { ... "ceiling": "CEIL", ... "Abs": [(lambda x: not x.is_integer, "fabs", 4), ... (lambda x: x.is_integer, "ABS", 4)], ... "func": "f" ... } >>> func = Function('func') >>> rust_code(func(Abs(x) + ceiling(x)), user_functions=custom_functions) '(fabs(x) + x.CEIL()).f()' ``Piecewise`` expressions are converted into conditionals. If an ``assign_to`` variable is provided an if statement is created, otherwise the ternary operator is used. Note that if the ``Piecewise`` lacks a default term, represented by ``(expr, True)`` then an error will be thrown. This is to prevent generating an expression that may not evaluate to anything. >>> from sympy import Piecewise >>> expr = Piecewise((x + 1, x > 0), (x, True)) >>> print(rust_code(expr, tau)) tau = if (x > 0) { x + 1 } else { x }; Support for loops is provided through ``Indexed`` types. With ``contract=True`` these expressions will be turned into loops, whereas ``contract=False`` will just print the assignment expression that should be looped over: >>> from sympy import Eq, IndexedBase, Idx >>> len_y = 5 >>> y = IndexedBase('y', shape=(len_y,)) >>> t = IndexedBase('t', shape=(len_y,)) >>> Dy = IndexedBase('Dy', shape=(len_y-1,)) >>> i = Idx('i', len_y-1) >>> e=Eq(Dy[i], (y[i+1]-y[i])/(t[i+1]-t[i])) >>> rust_code(e.rhs, assign_to=e.lhs, contract=False) 'Dy[i] = (y[i + 1] - y[i])/(t[i + 1] - t[i]);' Matrices are also supported, but a ``MatrixSymbol`` of the same dimensions must be provided to ``assign_to``. Note that any expression that can be generated normally can also exist inside a Matrix: >>> from sympy import Matrix, MatrixSymbol >>> mat = Matrix([x**2, Piecewise((x + 1, x > 0), (x, True)), sin(x)]) >>> A = MatrixSymbol('A', 3, 1) >>> print(rust_code(mat, A)) A = [x.powi(2), if (x > 0) { x + 1 } else { x }, x.sin()]; """ return RustCodePrinter(settings).doprint(expr, assign_to) def print_rust_code(expr, **settings): """Prints Rust representation of the given expression.""" print(rust_code(expr, **settings))

13ad35f79d34139f8dd984ed7c3b6fc764a631493817e041242011d9b230b4ed

""" C++ code printer """ from itertools import chain from sympy.codegen.ast import Type, none from .c import C89CodePrinter, C99CodePrinter # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import cxxcode # noqa:F401 # from http://en.cppreference.com/w/cpp/keyword reserved = { 'C++98': [ 'and', 'and_eq', 'asm', 'auto', 'bitand', 'bitor', 'bool', 'break', 'case', 'catch,', 'char', 'class', 'compl', 'const', 'const_cast', 'continue', 'default', 'delete', 'do', 'double', 'dynamic_cast', 'else', 'enum', 'explicit', 'export', 'extern', 'false', 'float', 'for', 'friend', 'goto', 'if', 'inline', 'int', 'long', 'mutable', 'namespace', 'new', 'not', 'not_eq', 'operator', 'or', 'or_eq', 'private', 'protected', 'public', 'register', 'reinterpret_cast', 'return', 'short', 'signed', 'sizeof', 'static', 'static_cast', 'struct', 'switch', 'template', 'this', 'throw', 'true', 'try', 'typedef', 'typeid', 'typename', 'union', 'unsigned', 'using', 'virtual', 'void', 'volatile', 'wchar_t', 'while', 'xor', 'xor_eq' ] } reserved['C++11'] = reserved['C++98'][:] + [ 'alignas', 'alignof', 'char16_t', 'char32_t', 'constexpr', 'decltype', 'noexcept', 'nullptr', 'static_assert', 'thread_local' ] reserved['C++17'] = reserved['C++11'][:] reserved['C++17'].remove('register') # TM TS: atomic_cancel, atomic_commit, atomic_noexcept, synchronized # concepts TS: concept, requires # module TS: import, module _math_functions = { 'C++98': { 'Mod': 'fmod', 'ceiling': 'ceil', }, 'C++11': { 'gamma': 'tgamma', }, 'C++17': { 'beta': 'beta', 'Ei': 'expint', 'zeta': 'riemann_zeta', } } # from http://en.cppreference.com/w/cpp/header/cmath for k in ('Abs', 'exp', 'log', 'log10', 'sqrt', 'sin', 'cos', 'tan', # 'Pow' 'asin', 'acos', 'atan', 'atan2', 'sinh', 'cosh', 'tanh', 'floor'): _math_functions['C++98'][k] = k.lower() for k in ('asinh', 'acosh', 'atanh', 'erf', 'erfc'): _math_functions['C++11'][k] = k.lower() def _attach_print_method(cls, sympy_name, func_name): meth_name = '_print_%s' % sympy_name if hasattr(cls, meth_name): raise ValueError("Edit method (or subclass) instead of overwriting.") def _print_method(self, expr): return '{}{}({})'.format(self._ns, func_name, ', '.join(map(self._print, expr.args))) _print_method.__doc__ = "Prints code for %s" % k setattr(cls, meth_name, _print_method) def _attach_print_methods(cls, cont): for sympy_name, cxx_name in cont[cls.standard].items(): _attach_print_method(cls, sympy_name, cxx_name) class _CXXCodePrinterBase: printmethod = "_cxxcode" language = 'C++' _ns = 'std::' # namespace def __init__(self, settings=None): super().__init__(settings or {}) def _print_Max(self, expr): from sympy import Max if len(expr.args) == 1: return self._print(expr.args[0]) return "%smax(%s, %s)" % (self._ns, expr.args[0], self._print(Max(*expr.args[1:]))) def _print_Min(self, expr): from sympy import Min if len(expr.args) == 1: return self._print(expr.args[0]) return "%smin(%s, %s)" % (self._ns, expr.args[0], self._print(Min(*expr.args[1:]))) def _print_using(self, expr): if expr.alias == none: return 'using %s' % expr.type else: raise ValueError("C++98 does not support type aliases") class CXX98CodePrinter(_CXXCodePrinterBase, C89CodePrinter): standard = 'C++98' reserved_words = set(reserved['C++98']) # _attach_print_methods(CXX98CodePrinter, _math_functions) class CXX11CodePrinter(_CXXCodePrinterBase, C99CodePrinter): standard = 'C++11' reserved_words = set(reserved['C++11']) type_mappings = dict(chain( CXX98CodePrinter.type_mappings.items(), { Type('int8'): ('int8_t', {'cstdint'}), Type('int16'): ('int16_t', {'cstdint'}), Type('int32'): ('int32_t', {'cstdint'}), Type('int64'): ('int64_t', {'cstdint'}), Type('uint8'): ('uint8_t', {'cstdint'}), Type('uint16'): ('uint16_t', {'cstdint'}), Type('uint32'): ('uint32_t', {'cstdint'}), Type('uint64'): ('uint64_t', {'cstdint'}), Type('complex64'): ('std::complex<float>', {'complex'}), Type('complex128'): ('std::complex<double>', {'complex'}), Type('bool'): ('bool', None), }.items() )) def _print_using(self, expr): if expr.alias == none: return super()._print_using(expr) else: return 'using %(alias)s = %(type)s' % expr.kwargs(apply=self._print) # _attach_print_methods(CXX11CodePrinter, _math_functions) class CXX17CodePrinter(_CXXCodePrinterBase, C99CodePrinter): standard = 'C++17' reserved_words = set(reserved['C++17']) _kf = dict(C99CodePrinter._kf, **_math_functions['C++17']) def _print_beta(self, expr): return self._print_math_func(expr) def _print_Ei(self, expr): return self._print_math_func(expr) def _print_zeta(self, expr): return self._print_math_func(expr) # _attach_print_methods(CXX17CodePrinter, _math_functions) cxx_code_printers = { 'c++98': CXX98CodePrinter, 'c++11': CXX11CodePrinter, 'c++17': CXX17CodePrinter }

87f685c022e66623460379d2592826df4c8b0fd146e255692247df5bc1dc0a6b

''' Use llvmlite to create executable functions from Sympy expressions This module requires llvmlite (https://github.com/numba/llvmlite). ''' import ctypes from sympy.external import import_module from sympy.printing.printer import Printer from sympy import S, IndexedBase from sympy.utilities.decorator import doctest_depends_on llvmlite = import_module('llvmlite') if llvmlite: ll = import_module('llvmlite.ir').ir llvm = import_module('llvmlite.binding').binding llvm.initialize() llvm.initialize_native_target() llvm.initialize_native_asmprinter() __doctest_requires__ = {('llvm_callable'): ['llvmlite']} class LLVMJitPrinter(Printer): '''Convert expressions to LLVM IR''' def __init__(self, module, builder, fn, *args, **kwargs): self.func_arg_map = kwargs.pop("func_arg_map", {}) if not llvmlite: raise ImportError("llvmlite is required for LLVMJITPrinter") super().__init__(*args, **kwargs) self.fp_type = ll.DoubleType() self.module = module self.builder = builder self.fn = fn self.ext_fn = {} # keep track of wrappers to external functions self.tmp_var = {} def _add_tmp_var(self, name, value): self.tmp_var[name] = value def _print_Number(self, n): return ll.Constant(self.fp_type, float(n)) def _print_Integer(self, expr): return ll.Constant(self.fp_type, float(expr.p)) def _print_Symbol(self, s): val = self.tmp_var.get(s) if not val: # look up parameter with name s val = self.func_arg_map.get(s) if not val: raise LookupError("Symbol not found: %s" % s) return val def _print_Pow(self, expr): base0 = self._print(expr.base) if expr.exp == S.NegativeOne: return self.builder.fdiv(ll.Constant(self.fp_type, 1.0), base0) if expr.exp == S.Half: fn = self.ext_fn.get("sqrt") if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type]) fn = ll.Function(self.module, fn_type, "sqrt") self.ext_fn["sqrt"] = fn return self.builder.call(fn, [base0], "sqrt") if expr.exp == 2: return self.builder.fmul(base0, base0) exp0 = self._print(expr.exp) fn = self.ext_fn.get("pow") if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type, self.fp_type]) fn = ll.Function(self.module, fn_type, "pow") self.ext_fn["pow"] = fn return self.builder.call(fn, [base0, exp0], "pow") def _print_Mul(self, expr): nodes = [self._print(a) for a in expr.args] e = nodes[0] for node in nodes[1:]: e = self.builder.fmul(e, node) return e def _print_Add(self, expr): nodes = [self._print(a) for a in expr.args] e = nodes[0] for node in nodes[1:]: e = self.builder.fadd(e, node) return e # TODO - assumes all called functions take one double precision argument. # Should have a list of math library functions to validate this. def _print_Function(self, expr): name = expr.func.__name__ e0 = self._print(expr.args[0]) fn = self.ext_fn.get(name) if not fn: fn_type = ll.FunctionType(self.fp_type, [self.fp_type]) fn = ll.Function(self.module, fn_type, name) self.ext_fn[name] = fn return self.builder.call(fn, [e0], name) def emptyPrinter(self, expr): raise TypeError("Unsupported type for LLVM JIT conversion: %s" % type(expr)) # Used when parameters are passed by array. Often used in callbacks to # handle a variable number of parameters. class LLVMJitCallbackPrinter(LLVMJitPrinter): def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) def _print_Indexed(self, expr): array, idx = self.func_arg_map[expr.base] offset = int(expr.indices[0].evalf()) array_ptr = self.builder.gep(array, [ll.Constant(ll.IntType(32), offset)]) fp_array_ptr = self.builder.bitcast(array_ptr, ll.PointerType(self.fp_type)) value = self.builder.load(fp_array_ptr) return value def _print_Symbol(self, s): val = self.tmp_var.get(s) if val: return val array, idx = self.func_arg_map.get(s, [None, 0]) if not array: raise LookupError("Symbol not found: %s" % s) array_ptr = self.builder.gep(array, [ll.Constant(ll.IntType(32), idx)]) fp_array_ptr = self.builder.bitcast(array_ptr, ll.PointerType(self.fp_type)) value = self.builder.load(fp_array_ptr) return value # ensure lifetime of the execution engine persists (else call to compiled # function will seg fault) exe_engines = [] # ensure names for generated functions are unique link_names = set() current_link_suffix = 0 class LLVMJitCode: def __init__(self, signature): self.signature = signature self.fp_type = ll.DoubleType() self.module = ll.Module('mod1') self.fn = None self.llvm_arg_types = [] self.llvm_ret_type = self.fp_type self.param_dict = {} # map symbol name to LLVM function argument self.link_name = '' def _from_ctype(self, ctype): if ctype == ctypes.c_int: return ll.IntType(32) if ctype == ctypes.c_double: return self.fp_type if ctype == ctypes.POINTER(ctypes.c_double): return ll.PointerType(self.fp_type) if ctype == ctypes.c_void_p: return ll.PointerType(ll.IntType(32)) if ctype == ctypes.py_object: return ll.PointerType(ll.IntType(32)) print("Unhandled ctype = %s" % str(ctype)) def _create_args(self, func_args): """Create types for function arguments""" self.llvm_ret_type = self._from_ctype(self.signature.ret_type) self.llvm_arg_types = \ [self._from_ctype(a) for a in self.signature.arg_ctypes] def _create_function_base(self): """Create function with name and type signature""" global link_names, current_link_suffix default_link_name = 'jit_func' current_link_suffix += 1 self.link_name = default_link_name + str(current_link_suffix) link_names.add(self.link_name) fn_type = ll.FunctionType(self.llvm_ret_type, self.llvm_arg_types) self.fn = ll.Function(self.module, fn_type, name=self.link_name) def _create_param_dict(self, func_args): """Mapping of symbolic values to function arguments""" for i, a in enumerate(func_args): self.fn.args[i].name = str(a) self.param_dict[a] = self.fn.args[i] def _create_function(self, expr): """Create function body and return LLVM IR""" bb_entry = self.fn.append_basic_block('entry') builder = ll.IRBuilder(bb_entry) lj = LLVMJitPrinter(self.module, builder, self.fn, func_arg_map=self.param_dict) ret = self._convert_expr(lj, expr) lj.builder.ret(self._wrap_return(lj, ret)) strmod = str(self.module) return strmod def _wrap_return(self, lj, vals): # Return a single double if there is one return value, # else return a tuple of doubles. # Don't wrap return value in this case if self.signature.ret_type == ctypes.c_double: return vals[0] # Use this instead of a real PyObject* void_ptr = ll.PointerType(ll.IntType(32)) # Create a wrapped double: PyObject* PyFloat_FromDouble(double v) wrap_type = ll.FunctionType(void_ptr, [self.fp_type]) wrap_fn = ll.Function(lj.module, wrap_type, "PyFloat_FromDouble") wrapped_vals = [lj.builder.call(wrap_fn, [v]) for v in vals] if len(vals) == 1: final_val = wrapped_vals[0] else: # Create a tuple: PyObject* PyTuple_Pack(Py_ssize_t n, ...) # This should be Py_ssize_t tuple_arg_types = [ll.IntType(32)] tuple_arg_types.extend([void_ptr]*len(vals)) tuple_type = ll.FunctionType(void_ptr, tuple_arg_types) tuple_fn = ll.Function(lj.module, tuple_type, "PyTuple_Pack") tuple_args = [ll.Constant(ll.IntType(32), len(wrapped_vals))] tuple_args.extend(wrapped_vals) final_val = lj.builder.call(tuple_fn, tuple_args) return final_val def _convert_expr(self, lj, expr): try: # Match CSE return data structure. if len(expr) == 2: tmp_exprs = expr[0] final_exprs = expr[1] if len(final_exprs) != 1 and self.signature.ret_type == ctypes.c_double: raise NotImplementedError("Return of multiple expressions not supported for this callback") for name, e in tmp_exprs: val = lj._print(e) lj._add_tmp_var(name, val) except TypeError: final_exprs = [expr] vals = [lj._print(e) for e in final_exprs] return vals def _compile_function(self, strmod): global exe_engines llmod = llvm.parse_assembly(strmod) pmb = llvm.create_pass_manager_builder() pmb.opt_level = 2 pass_manager = llvm.create_module_pass_manager() pmb.populate(pass_manager) pass_manager.run(llmod) target_machine = \ llvm.Target.from_default_triple().create_target_machine() exe_eng = llvm.create_mcjit_compiler(llmod, target_machine) exe_eng.finalize_object() exe_engines.append(exe_eng) if False: print("Assembly") print(target_machine.emit_assembly(llmod)) fptr = exe_eng.get_function_address(self.link_name) return fptr class LLVMJitCodeCallback(LLVMJitCode): def __init__(self, signature): super().__init__(signature) def _create_param_dict(self, func_args): for i, a in enumerate(func_args): if isinstance(a, IndexedBase): self.param_dict[a] = (self.fn.args[i], i) self.fn.args[i].name = str(a) else: self.param_dict[a] = (self.fn.args[self.signature.input_arg], i) def _create_function(self, expr): """Create function body and return LLVM IR""" bb_entry = self.fn.append_basic_block('entry') builder = ll.IRBuilder(bb_entry) lj = LLVMJitCallbackPrinter(self.module, builder, self.fn, func_arg_map=self.param_dict) ret = self._convert_expr(lj, expr) if self.signature.ret_arg: output_fp_ptr = builder.bitcast(self.fn.args[self.signature.ret_arg], ll.PointerType(self.fp_type)) for i, val in enumerate(ret): index = ll.Constant(ll.IntType(32), i) output_array_ptr = builder.gep(output_fp_ptr, [index]) builder.store(val, output_array_ptr) builder.ret(ll.Constant(ll.IntType(32), 0)) # return success else: lj.builder.ret(self._wrap_return(lj, ret)) strmod = str(self.module) return strmod class CodeSignature: def __init__(self, ret_type): self.ret_type = ret_type self.arg_ctypes = [] # Input argument array element index self.input_arg = 0 # For the case output value is referenced through a parameter rather # than the return value self.ret_arg = None def _llvm_jit_code(args, expr, signature, callback_type): """Create a native code function from a Sympy expression""" if callback_type is None: jit = LLVMJitCode(signature) else: jit = LLVMJitCodeCallback(signature) jit._create_args(args) jit._create_function_base() jit._create_param_dict(args) strmod = jit._create_function(expr) if False: print("LLVM IR") print(strmod) fptr = jit._compile_function(strmod) return fptr @doctest_depends_on(modules=('llvmlite', 'scipy')) def llvm_callable(args, expr, callback_type=None): '''Compile function from a Sympy expression Expressions are evaluated using double precision arithmetic. Some single argument math functions (exp, sin, cos, etc.) are supported in expressions. Parameters ========== args : List of Symbol Arguments to the generated function. Usually the free symbols in the expression. Currently each one is assumed to convert to a double precision scalar. expr : Expr, or (Replacements, Expr) as returned from 'cse' Expression to compile. callback_type : string Create function with signature appropriate to use as a callback. Currently supported: 'scipy.integrate' 'scipy.integrate.test' 'cubature' Returns ======= Compiled function that can evaluate the expression. Examples ======== >>> import sympy.printing.llvmjitcode as jit >>> from sympy.abc import a >>> e = a*a + a + 1 >>> e1 = jit.llvm_callable([a], e) >>> e.subs(a, 1.1) # Evaluate via substitution 3.31000000000000 >>> e1(1.1) # Evaluate using JIT-compiled code 3.3100000000000005 Callbacks for integration functions can be JIT compiled. >>> import sympy.printing.llvmjitcode as jit >>> from sympy.abc import a >>> from sympy import integrate >>> from scipy.integrate import quad >>> e = a*a >>> e1 = jit.llvm_callable([a], e, callback_type='scipy.integrate') >>> integrate(e, (a, 0.0, 2.0)) 2.66666666666667 >>> quad(e1, 0.0, 2.0)[0] 2.66666666666667 The 'cubature' callback is for the Python wrapper around the cubature package ( https://github.com/saullocastro/cubature ) and ( http://ab-initio.mit.edu/wiki/index.php/Cubature ) There are two signatures for the SciPy integration callbacks. The first ('scipy.integrate') is the function to be passed to the integration routine, and will pass the signature checks. The second ('scipy.integrate.test') is only useful for directly calling the function using ctypes variables. It will not pass the signature checks for scipy.integrate. The return value from the cse module can also be compiled. This can improve the performance of the compiled function. If multiple expressions are given to cse, the compiled function returns a tuple. The 'cubature' callback handles multiple expressions (set `fdim` to match in the integration call.) >>> import sympy.printing.llvmjitcode as jit >>> from sympy import cse >>> from sympy.abc import x,y >>> e1 = x*x + y*y >>> e2 = 4*(x*x + y*y) + 8.0 >>> after_cse = cse([e1,e2]) >>> after_cse ([(x0, x**2), (x1, y**2)], [x0 + x1, 4*x0 + 4*x1 + 8.0]) >>> j1 = jit.llvm_callable([x,y], after_cse) >>> j1(1.0, 2.0) (5.0, 28.0) ''' if not llvmlite: raise ImportError("llvmlite is required for llvmjitcode") signature = CodeSignature(ctypes.py_object) arg_ctypes = [] if callback_type is None: for _ in args: arg_ctype = ctypes.c_double arg_ctypes.append(arg_ctype) elif callback_type == 'scipy.integrate' or callback_type == 'scipy.integrate.test': signature.ret_type = ctypes.c_double arg_ctypes = [ctypes.c_int, ctypes.POINTER(ctypes.c_double)] arg_ctypes_formal = [ctypes.c_int, ctypes.c_double] signature.input_arg = 1 elif callback_type == 'cubature': arg_ctypes = [ctypes.c_int, ctypes.POINTER(ctypes.c_double), ctypes.c_void_p, ctypes.c_int, ctypes.POINTER(ctypes.c_double) ] signature.ret_type = ctypes.c_int signature.input_arg = 1 signature.ret_arg = 4 else: raise ValueError("Unknown callback type: %s" % callback_type) signature.arg_ctypes = arg_ctypes fptr = _llvm_jit_code(args, expr, signature, callback_type) if callback_type and callback_type == 'scipy.integrate': arg_ctypes = arg_ctypes_formal cfunc = ctypes.CFUNCTYPE(signature.ret_type, *arg_ctypes)(fptr) return cfunc

92660d821a3ff9220ca9bd043b0e90ca4630395cbf8e3760bab2bf272d3e71fd

""" A few practical conventions common to all printers. """ import re from sympy.core.compatibility import Iterable from sympy import Derivative _name_with_digits_p = re.compile(r'^([a-zA-Z]+)([0-9]+)$') def split_super_sub(text): """Split a symbol name into a name, superscripts and subscripts The first part of the symbol name is considered to be its actual 'name', followed by super- and subscripts. Each superscript is preceded with a "^" character or by "__". Each subscript is preceded by a "_" character. The three return values are the actual name, a list with superscripts and a list with subscripts. Examples ======== >>> from sympy.printing.conventions import split_super_sub >>> split_super_sub('a_x^1') ('a', ['1'], ['x']) >>> split_super_sub('var_sub1__sup_sub2') ('var', ['sup'], ['sub1', 'sub2']) """ if not text: return text, [], [] pos = 0 name = None supers = [] subs = [] while pos < len(text): start = pos + 1 if text[pos:pos + 2] == "__": start += 1 pos_hat = text.find("^", start) if pos_hat < 0: pos_hat = len(text) pos_usc = text.find("_", start) if pos_usc < 0: pos_usc = len(text) pos_next = min(pos_hat, pos_usc) part = text[pos:pos_next] pos = pos_next if name is None: name = part elif part.startswith("^"): supers.append(part[1:]) elif part.startswith("__"): supers.append(part[2:]) elif part.startswith("_"): subs.append(part[1:]) else: raise RuntimeError("This should never happen.") # make a little exception when a name ends with digits, i.e. treat them # as a subscript too. m = _name_with_digits_p.match(name) if m: name, sub = m.groups() subs.insert(0, sub) return name, supers, subs def requires_partial(expr): """Return whether a partial derivative symbol is required for printing This requires checking how many free variables there are, filtering out the ones that are integers. Some expressions don't have free variables. In that case, check its variable list explicitly to get the context of the expression. """ if isinstance(expr, Derivative): return requires_partial(expr.expr) if not isinstance(expr.free_symbols, Iterable): return len(set(expr.variables)) > 1 return sum(not s.is_integer for s in expr.free_symbols) > 1

8e7eb188f89152bd63e88a65e06d76d41e26b0b1e4e9df569746680fc178dbb9

""" A Printer which converts an expression into its LaTeX equivalent. """ from typing import Any, Dict import itertools from sympy.core import Add, Float, Mod, Mul, Number, S, Symbol from sympy.core.alphabets import greeks from sympy.core.containers import Tuple from sympy.core.function import _coeff_isneg, AppliedUndef, Derivative from sympy.core.operations import AssocOp from sympy.core.sympify import SympifyError from sympy.logic.boolalg import true # sympy.printing imports from sympy.printing.precedence import precedence_traditional from sympy.printing.printer import Printer, print_function from sympy.printing.conventions import split_super_sub, requires_partial from sympy.printing.precedence import precedence, PRECEDENCE import mpmath.libmp as mlib from mpmath.libmp import prec_to_dps from sympy.core.compatibility import default_sort_key from sympy.utilities.iterables import has_variety import re # Hand-picked functions which can be used directly in both LaTeX and MathJax # Complete list at # https://docs.mathjax.org/en/latest/tex.html#supported-latex-commands # This variable only contains those functions which sympy uses. accepted_latex_functions = ['arcsin', 'arccos', 'arctan', 'sin', 'cos', 'tan', 'sinh', 'cosh', 'tanh', 'sqrt', 'ln', 'log', 'sec', 'csc', 'cot', 'coth', 're', 'im', 'frac', 'root', 'arg', ] tex_greek_dictionary = { 'Alpha': 'A', 'Beta': 'B', 'Gamma': r'\Gamma', 'Delta': r'\Delta', 'Epsilon': 'E', 'Zeta': 'Z', 'Eta': 'H', 'Theta': r'\Theta', 'Iota': 'I', 'Kappa': 'K', 'Lambda': r'\Lambda', 'Mu': 'M', 'Nu': 'N', 'Xi': r'\Xi', 'omicron': 'o', 'Omicron': 'O', 'Pi': r'\Pi', 'Rho': 'P', 'Sigma': r'\Sigma', 'Tau': 'T', 'Upsilon': r'\Upsilon', 'Phi': r'\Phi', 'Chi': 'X', 'Psi': r'\Psi', 'Omega': r'\Omega', 'lamda': r'\lambda', 'Lamda': r'\Lambda', 'khi': r'\chi', 'Khi': r'X', 'varepsilon': r'\varepsilon', 'varkappa': r'\varkappa', 'varphi': r'\varphi', 'varpi': r'\varpi', 'varrho': r'\varrho', 'varsigma': r'\varsigma', 'vartheta': r'\vartheta', } other_symbols = {'aleph', 'beth', 'daleth', 'gimel', 'ell', 'eth', 'hbar', 'hslash', 'mho', 'wp'} # Variable name modifiers modifier_dict = { # Accents 'mathring': lambda s: r'\mathring{'+s+r'}', 'ddddot': lambda s: r'\ddddot{'+s+r'}', 'dddot': lambda s: r'\dddot{'+s+r'}', 'ddot': lambda s: r'\ddot{'+s+r'}', 'dot': lambda s: r'\dot{'+s+r'}', 'check': lambda s: r'\check{'+s+r'}', 'breve': lambda s: r'\breve{'+s+r'}', 'acute': lambda s: r'\acute{'+s+r'}', 'grave': lambda s: r'\grave{'+s+r'}', 'tilde': lambda s: r'\tilde{'+s+r'}', 'hat': lambda s: r'\hat{'+s+r'}', 'bar': lambda s: r'\bar{'+s+r'}', 'vec': lambda s: r'\vec{'+s+r'}', 'prime': lambda s: "{"+s+"}'", 'prm': lambda s: "{"+s+"}'", # Faces 'bold': lambda s: r'\boldsymbol{'+s+r'}', 'bm': lambda s: r'\boldsymbol{'+s+r'}', 'cal': lambda s: r'\mathcal{'+s+r'}', 'scr': lambda s: r'\mathscr{'+s+r'}', 'frak': lambda s: r'\mathfrak{'+s+r'}', # Brackets 'norm': lambda s: r'\left\|{'+s+r'}\right\|', 'avg': lambda s: r'\left\langle{'+s+r'}\right\rangle', 'abs': lambda s: r'\left|{'+s+r'}\right|', 'mag': lambda s: r'\left|{'+s+r'}\right|', } greek_letters_set = frozenset(greeks) _between_two_numbers_p = ( re.compile(r'[0-9][} ]*$'), # search re.compile(r'[{ ]*[-+0-9]'), # match ) def latex_escape(s): """ Escape a string such that latex interprets it as plaintext. We can't use verbatim easily with mathjax, so escaping is easier. Rules from https://tex.stackexchange.com/a/34586/41112. """ s = s.replace('\\', r'\textbackslash') for c in '&%$#_{}': s = s.replace(c, '\\' + c) s = s.replace('~', r'\textasciitilde') s = s.replace('^', r'\textasciicircum') return s class LatexPrinter(Printer): printmethod = "_latex" _default_settings = { "full_prec": False, "fold_frac_powers": False, "fold_func_brackets": False, "fold_short_frac": None, "inv_trig_style": "abbreviated", "itex": False, "ln_notation": False, "long_frac_ratio": None, "mat_delim": "[", "mat_str": None, "mode": "plain", "mul_symbol": None, "order": None, "symbol_names": {}, "root_notation": True, "mat_symbol_style": "plain", "imaginary_unit": "i", "gothic_re_im": False, "decimal_separator": "period", "perm_cyclic": True, "parenthesize_super": True, "min": None, "max": None, } # type: Dict[str, Any] def __init__(self, settings=None): Printer.__init__(self, settings) if 'mode' in self._settings: valid_modes = ['inline', 'plain', 'equation', 'equation*'] if self._settings['mode'] not in valid_modes: raise ValueError("'mode' must be one of 'inline', 'plain', " "'equation' or 'equation*'") if self._settings['fold_short_frac'] is None and \ self._settings['mode'] == 'inline': self._settings['fold_short_frac'] = True mul_symbol_table = { None: r" ", "ldot": r" \,.\, ", "dot": r" \cdot ", "times": r" \times " } try: self._settings['mul_symbol_latex'] = \ mul_symbol_table[self._settings['mul_symbol']] except KeyError: self._settings['mul_symbol_latex'] = \ self._settings['mul_symbol'] try: self._settings['mul_symbol_latex_numbers'] = \ mul_symbol_table[self._settings['mul_symbol'] or 'dot'] except KeyError: if (self._settings['mul_symbol'].strip() in ['', ' ', '\\', '\\,', '\\:', '\\;', '\\quad']): self._settings['mul_symbol_latex_numbers'] = \ mul_symbol_table['dot'] else: self._settings['mul_symbol_latex_numbers'] = \ self._settings['mul_symbol'] self._delim_dict = {'(': ')', '[': ']'} imaginary_unit_table = { None: r"i", "i": r"i", "ri": r"\mathrm{i}", "ti": r"\text{i}", "j": r"j", "rj": r"\mathrm{j}", "tj": r"\text{j}", } try: self._settings['imaginary_unit_latex'] = \ imaginary_unit_table[self._settings['imaginary_unit']] except KeyError: self._settings['imaginary_unit_latex'] = \ self._settings['imaginary_unit'] def _add_parens(self, s): return r"\left({}\right)".format(s) # TODO: merge this with the above, which requires a lot of test changes def _add_parens_lspace(self, s): return r"\left( {}\right)".format(s) def parenthesize(self, item, level, is_neg=False, strict=False): prec_val = precedence_traditional(item) if is_neg and strict: return self._add_parens(self._print(item)) if (prec_val < level) or ((not strict) and prec_val <= level): return self._add_parens(self._print(item)) else: return self._print(item) def parenthesize_super(self, s): """ Protect superscripts in s If the parenthesize_super option is set, protect with parentheses, else wrap in braces. """ if "^" in s: if self._settings['parenthesize_super']: return self._add_parens(s) else: return "{{{}}}".format(s) return s def doprint(self, expr): tex = Printer.doprint(self, expr) if self._settings['mode'] == 'plain': return tex elif self._settings['mode'] == 'inline': return r"$%s$" % tex elif self._settings['itex']: return r"$$%s$$" % tex else: env_str = self._settings['mode'] return r"\begin{%s}%s\end{%s}" % (env_str, tex, env_str) def _needs_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when printed, False otherwise. For example: a + b => True; a => False; 10 => False; -10 => True. """ return not ((expr.is_Integer and expr.is_nonnegative) or (expr.is_Atom and (expr is not S.NegativeOne and expr.is_Rational is False))) def _needs_function_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when passed as an argument to a function, False otherwise. This is a more liberal version of _needs_brackets, in that many expressions which need to be wrapped in brackets when added/subtracted/raised to a power do not need them when passed to a function. Such an example is a*b. """ if not self._needs_brackets(expr): return False else: # Muls of the form a*b*c... can be folded if expr.is_Mul and not self._mul_is_clean(expr): return True # Pows which don't need brackets can be folded elif expr.is_Pow and not self._pow_is_clean(expr): return True # Add and Function always need brackets elif expr.is_Add or expr.is_Function: return True else: return False def _needs_mul_brackets(self, expr, first=False, last=False): """ Returns True if the expression needs to be wrapped in brackets when printed as part of a Mul, False otherwise. This is True for Add, but also for some container objects that would not need brackets when appearing last in a Mul, e.g. an Integral. ``last=True`` specifies that this expr is the last to appear in a Mul. ``first=True`` specifies that this expr is the first to appear in a Mul. """ from sympy import Integral, Product, Sum if expr.is_Mul: if not first and _coeff_isneg(expr): return True elif precedence_traditional(expr) < PRECEDENCE["Mul"]: return True elif expr.is_Relational: return True if expr.is_Piecewise: return True if any([expr.has(x) for x in (Mod,)]): return True if (not last and any([expr.has(x) for x in (Integral, Product, Sum)])): return True return False def _needs_add_brackets(self, expr): """ Returns True if the expression needs to be wrapped in brackets when printed as part of an Add, False otherwise. This is False for most things. """ if expr.is_Relational: return True if any([expr.has(x) for x in (Mod,)]): return True if expr.is_Add: return True return False def _mul_is_clean(self, expr): for arg in expr.args: if arg.is_Function: return False return True def _pow_is_clean(self, expr): return not self._needs_brackets(expr.base) def _do_exponent(self, expr, exp): if exp is not None: return r"\left(%s\right)^{%s}" % (expr, exp) else: return expr def _print_Basic(self, expr): ls = [self._print(o) for o in expr.args] return self._deal_with_super_sub(expr.__class__.__name__) + \ r"\left(%s\right)" % ", ".join(ls) def _print_bool(self, e): return r"\text{%s}" % e _print_BooleanTrue = _print_bool _print_BooleanFalse = _print_bool def _print_NoneType(self, e): return r"\text{%s}" % e def _print_Add(self, expr, order=None): terms = self._as_ordered_terms(expr, order=order) tex = "" for i, term in enumerate(terms): if i == 0: pass elif _coeff_isneg(term): tex += " - " term = -term else: tex += " + " term_tex = self._print(term) if self._needs_add_brackets(term): term_tex = r"\left(%s\right)" % term_tex tex += term_tex return tex def _print_Cycle(self, expr): from sympy.combinatorics.permutations import Permutation if expr.size == 0: return r"\left( \right)" expr = Permutation(expr) expr_perm = expr.cyclic_form siz = expr.size if expr.array_form[-1] == siz - 1: expr_perm = expr_perm + [[siz - 1]] term_tex = '' for i in expr_perm: term_tex += str(i).replace(',', r"\;") term_tex = term_tex.replace('[', r"\left( ") term_tex = term_tex.replace(']', r"\right)") return term_tex def _print_Permutation(self, expr): from sympy.combinatorics.permutations import Permutation from sympy.utilities.exceptions import SymPyDeprecationWarning perm_cyclic = Permutation.print_cyclic if perm_cyclic is not None: SymPyDeprecationWarning( feature="Permutation.print_cyclic = {}".format(perm_cyclic), useinstead="init_printing(perm_cyclic={})" .format(perm_cyclic), issue=15201, deprecated_since_version="1.6").warn() else: perm_cyclic = self._settings.get("perm_cyclic", True) if perm_cyclic: return self._print_Cycle(expr) if expr.size == 0: return r"\left( \right)" lower = [self._print(arg) for arg in expr.array_form] upper = [self._print(arg) for arg in range(len(lower))] row1 = " & ".join(upper) row2 = " & ".join(lower) mat = r" \\ ".join((row1, row2)) return r"\begin{pmatrix} %s \end{pmatrix}" % mat def _print_AppliedPermutation(self, expr): perm, var = expr.args return r"\sigma_{%s}(%s)" % (self._print(perm), self._print(var)) def _print_Float(self, expr): # Based off of that in StrPrinter dps = prec_to_dps(expr._prec) strip = False if self._settings['full_prec'] else True low = self._settings["min"] if "min" in self._settings else None high = self._settings["max"] if "max" in self._settings else None str_real = mlib.to_str(expr._mpf_, dps, strip_zeros=strip, min_fixed=low, max_fixed=high) # Must always have a mul symbol (as 2.5 10^{20} just looks odd) # thus we use the number separator separator = self._settings['mul_symbol_latex_numbers'] if 'e' in str_real: (mant, exp) = str_real.split('e') if exp[0] == '+': exp = exp[1:] if self._settings['decimal_separator'] == 'comma': mant = mant.replace('.','{,}') return r"%s%s10^{%s}" % (mant, separator, exp) elif str_real == "+inf": return r"\infty" elif str_real == "-inf": return r"- \infty" else: if self._settings['decimal_separator'] == 'comma': str_real = str_real.replace('.','{,}') return str_real def _print_Cross(self, expr): vec1 = expr._expr1 vec2 = expr._expr2 return r"%s \times %s" % (self.parenthesize(vec1, PRECEDENCE['Mul']), self.parenthesize(vec2, PRECEDENCE['Mul'])) def _print_Curl(self, expr): vec = expr._expr return r"\nabla\times %s" % self.parenthesize(vec, PRECEDENCE['Mul']) def _print_Divergence(self, expr): vec = expr._expr return r"\nabla\cdot %s" % self.parenthesize(vec, PRECEDENCE['Mul']) def _print_Dot(self, expr): vec1 = expr._expr1 vec2 = expr._expr2 return r"%s \cdot %s" % (self.parenthesize(vec1, PRECEDENCE['Mul']), self.parenthesize(vec2, PRECEDENCE['Mul'])) def _print_Gradient(self, expr): func = expr._expr return r"\nabla %s" % self.parenthesize(func, PRECEDENCE['Mul']) def _print_Laplacian(self, expr): func = expr._expr return r"\triangle %s" % self.parenthesize(func, PRECEDENCE['Mul']) def _print_Mul(self, expr): from sympy.core.power import Pow from sympy.physics.units import Quantity from sympy.simplify import fraction separator = self._settings['mul_symbol_latex'] numbersep = self._settings['mul_symbol_latex_numbers'] def convert(expr): if not expr.is_Mul: return str(self._print(expr)) else: if self.order not in ('old', 'none'): args = expr.as_ordered_factors() else: args = list(expr.args) # If quantities are present append them at the back args = sorted(args, key=lambda x: isinstance(x, Quantity) or (isinstance(x, Pow) and isinstance(x.base, Quantity))) return convert_args(args) def convert_args(args): _tex = last_term_tex = "" for i, term in enumerate(args): term_tex = self._print(term) if self._needs_mul_brackets(term, first=(i == 0), last=(i == len(args) - 1)): term_tex = r"\left(%s\right)" % term_tex if _between_two_numbers_p[0].search(last_term_tex) and \ _between_two_numbers_p[1].match(term_tex): # between two numbers _tex += numbersep elif _tex: _tex += separator _tex += term_tex last_term_tex = term_tex return _tex # Check for unevaluated Mul. In this case we need to make sure the # identities are visible, multiple Rational factors are not combined # etc so we display in a straight-forward form that fully preserves all # args and their order. # XXX: _print_Pow calls this routine with instances of Pow... if isinstance(expr, Mul): args = expr.args if args[0] is S.One or any(isinstance(arg, Number) for arg in args[1:]): return convert_args(args) include_parens = False if _coeff_isneg(expr): expr = -expr tex = "- " if expr.is_Add: tex += "(" include_parens = True else: tex = "" numer, denom = fraction(expr, exact=True) if denom is S.One and Pow(1, -1, evaluate=False) not in expr.args: # use the original expression here, since fraction() may have # altered it when producing numer and denom tex += convert(expr) else: snumer = convert(numer) sdenom = convert(denom) ldenom = len(sdenom.split()) ratio = self._settings['long_frac_ratio'] if self._settings['fold_short_frac'] and ldenom <= 2 and \ "^" not in sdenom: # handle short fractions if self._needs_mul_brackets(numer, last=False): tex += r"\left(%s\right) / %s" % (snumer, sdenom) else: tex += r"%s / %s" % (snumer, sdenom) elif ratio is not None and \ len(snumer.split()) > ratio*ldenom: # handle long fractions if self._needs_mul_brackets(numer, last=True): tex += r"\frac{1}{%s}%s\left(%s\right)" \ % (sdenom, separator, snumer) elif numer.is_Mul: # split a long numerator a = S.One b = S.One for x in numer.args: if self._needs_mul_brackets(x, last=False) or \ len(convert(a*x).split()) > ratio*ldenom or \ (b.is_commutative is x.is_commutative is False): b *= x else: a *= x if self._needs_mul_brackets(b, last=True): tex += r"\frac{%s}{%s}%s\left(%s\right)" \ % (convert(a), sdenom, separator, convert(b)) else: tex += r"\frac{%s}{%s}%s%s" \ % (convert(a), sdenom, separator, convert(b)) else: tex += r"\frac{1}{%s}%s%s" % (sdenom, separator, snumer) else: tex += r"\frac{%s}{%s}" % (snumer, sdenom) if include_parens: tex += ")" return tex def _print_Pow(self, expr): # Treat x**Rational(1,n) as special case if expr.exp.is_Rational and abs(expr.exp.p) == 1 and expr.exp.q != 1 \ and self._settings['root_notation']: base = self._print(expr.base) expq = expr.exp.q if expq == 2: tex = r"\sqrt{%s}" % base elif self._settings['itex']: tex = r"\root{%d}{%s}" % (expq, base) else: tex = r"\sqrt[%d]{%s}" % (expq, base) if expr.exp.is_negative: return r"\frac{1}{%s}" % tex else: return tex elif self._settings['fold_frac_powers'] \ and expr.exp.is_Rational \ and expr.exp.q != 1: base = self.parenthesize(expr.base, PRECEDENCE['Pow']) p, q = expr.exp.p, expr.exp.q # issue #12886: add parentheses for superscripts raised to powers if expr.base.is_Symbol: base = self.parenthesize_super(base) if expr.base.is_Function: return self._print(expr.base, exp="%s/%s" % (p, q)) return r"%s^{%s/%s}" % (base, p, q) elif expr.exp.is_Rational and expr.exp.is_negative and \ expr.base.is_commutative: # special case for 1^(-x), issue 9216 if expr.base == 1: return r"%s^{%s}" % (expr.base, expr.exp) # things like 1/x return self._print_Mul(expr) else: if expr.base.is_Function: return self._print(expr.base, exp=self._print(expr.exp)) else: tex = r"%s^{%s}" return self._helper_print_standard_power(expr, tex) def _helper_print_standard_power(self, expr, template): exp = self._print(expr.exp) # issue #12886: add parentheses around superscripts raised # to powers base = self.parenthesize(expr.base, PRECEDENCE['Pow']) if expr.base.is_Symbol: base = self.parenthesize_super(base) elif (isinstance(expr.base, Derivative) and base.startswith(r'\left(') and re.match(r'\\left\(\\d?d?dot', base) and base.endswith(r'\right)')): # don't use parentheses around dotted derivative base = base[6: -7] # remove outermost added parens return template % (base, exp) def _print_UnevaluatedExpr(self, expr): return self._print(expr.args[0]) def _print_Sum(self, expr): if len(expr.limits) == 1: tex = r"\sum_{%s=%s}^{%s} " % \ tuple([self._print(i) for i in expr.limits[0]]) else: def _format_ineq(l): return r"%s \leq %s \leq %s" % \ tuple([self._print(s) for s in (l[1], l[0], l[2])]) tex = r"\sum_{\substack{%s}} " % \ str.join('\\\\', [_format_ineq(l) for l in expr.limits]) if isinstance(expr.function, Add): tex += r"\left(%s\right)" % self._print(expr.function) else: tex += self._print(expr.function) return tex def _print_Product(self, expr): if len(expr.limits) == 1: tex = r"\prod_{%s=%s}^{%s} " % \ tuple([self._print(i) for i in expr.limits[0]]) else: def _format_ineq(l): return r"%s \leq %s \leq %s" % \ tuple([self._print(s) for s in (l[1], l[0], l[2])]) tex = r"\prod_{\substack{%s}} " % \ str.join('\\\\', [_format_ineq(l) for l in expr.limits]) if isinstance(expr.function, Add): tex += r"\left(%s\right)" % self._print(expr.function) else: tex += self._print(expr.function) return tex def _print_BasisDependent(self, expr): from sympy.vector import Vector o1 = [] if expr == expr.zero: return expr.zero._latex_form if isinstance(expr, Vector): items = expr.separate().items() else: items = [(0, expr)] for system, vect in items: inneritems = list(vect.components.items()) inneritems.sort(key=lambda x: x[0].__str__()) for k, v in inneritems: if v == 1: o1.append(' + ' + k._latex_form) elif v == -1: o1.append(' - ' + k._latex_form) else: arg_str = '(' + self._print(v) + ')' o1.append(' + ' + arg_str + k._latex_form) outstr = (''.join(o1)) if outstr[1] != '-': outstr = outstr[3:] else: outstr = outstr[1:] return outstr def _print_Indexed(self, expr): tex_base = self._print(expr.base) tex = '{'+tex_base+'}'+'_{%s}' % ','.join( map(self._print, expr.indices)) return tex def _print_IndexedBase(self, expr): return self._print(expr.label) def _print_Derivative(self, expr): if requires_partial(expr.expr): diff_symbol = r'\partial' else: diff_symbol = r'd' tex = "" dim = 0 for x, num in reversed(expr.variable_count): dim += num if num == 1: tex += r"%s %s" % (diff_symbol, self._print(x)) else: tex += r"%s %s^{%s}" % (diff_symbol, self.parenthesize_super(self._print(x)), self._print(num)) if dim == 1: tex = r"\frac{%s}{%s}" % (diff_symbol, tex) else: tex = r"\frac{%s^{%s}}{%s}" % (diff_symbol, self._print(dim), tex) if any(_coeff_isneg(i) for i in expr.args): return r"%s %s" % (tex, self.parenthesize(expr.expr, PRECEDENCE["Mul"], is_neg=True, strict=True)) return r"%s %s" % (tex, self.parenthesize(expr.expr, PRECEDENCE["Mul"], is_neg=False, strict=True)) def _print_Subs(self, subs): expr, old, new = subs.args latex_expr = self._print(expr) latex_old = (self._print(e) for e in old) latex_new = (self._print(e) for e in new) latex_subs = r'\\ '.join( e[0] + '=' + e[1] for e in zip(latex_old, latex_new)) return r'\left. %s \right|_{\substack{ %s }}' % (latex_expr, latex_subs) def _print_Integral(self, expr): tex, symbols = "", [] # Only up to \iiiint exists if len(expr.limits) <= 4 and all(len(lim) == 1 for lim in expr.limits): # Use len(expr.limits)-1 so that syntax highlighters don't think # \" is an escaped quote tex = r"\i" + "i"*(len(expr.limits) - 1) + "nt" symbols = [r"\, d%s" % self._print(symbol[0]) for symbol in expr.limits] else: for lim in reversed(expr.limits): symbol = lim[0] tex += r"\int" if len(lim) > 1: if self._settings['mode'] != 'inline' \ and not self._settings['itex']: tex += r"\limits" if len(lim) == 3: tex += "_{%s}^{%s}" % (self._print(lim[1]), self._print(lim[2])) if len(lim) == 2: tex += "^{%s}" % (self._print(lim[1])) symbols.insert(0, r"\, d%s" % self._print(symbol)) return r"%s %s%s" % (tex, self.parenthesize(expr.function, PRECEDENCE["Mul"], is_neg=any(_coeff_isneg(i) for i in expr.args), strict=True), "".join(symbols)) def _print_Limit(self, expr): e, z, z0, dir = expr.args tex = r"\lim_{%s \to " % self._print(z) if str(dir) == '+-' or z0 in (S.Infinity, S.NegativeInfinity): tex += r"%s}" % self._print(z0) else: tex += r"%s^%s}" % (self._print(z0), self._print(dir)) if isinstance(e, AssocOp): return r"%s\left(%s\right)" % (tex, self._print(e)) else: return r"%s %s" % (tex, self._print(e)) def _hprint_Function(self, func): r''' Logic to decide how to render a function to latex - if it is a recognized latex name, use the appropriate latex command - if it is a single letter, just use that letter - if it is a longer name, then put \operatorname{} around it and be mindful of undercores in the name ''' func = self._deal_with_super_sub(func) if func in accepted_latex_functions: name = r"\%s" % func elif len(func) == 1 or func.startswith('\\'): name = func else: name = r"\operatorname{%s}" % func return name def _print_Function(self, expr, exp=None): r''' Render functions to LaTeX, handling functions that LaTeX knows about e.g., sin, cos, ... by using the proper LaTeX command (\sin, \cos, ...). For single-letter function names, render them as regular LaTeX math symbols. For multi-letter function names that LaTeX does not know about, (e.g., Li, sech) use \operatorname{} so that the function name is rendered in Roman font and LaTeX handles spacing properly. expr is the expression involving the function exp is an exponent ''' func = expr.func.__name__ if hasattr(self, '_print_' + func) and \ not isinstance(expr, AppliedUndef): return getattr(self, '_print_' + func)(expr, exp) else: args = [str(self._print(arg)) for arg in expr.args] # How inverse trig functions should be displayed, formats are: # abbreviated: asin, full: arcsin, power: sin^-1 inv_trig_style = self._settings['inv_trig_style'] # If we are dealing with a power-style inverse trig function inv_trig_power_case = False # If it is applicable to fold the argument brackets can_fold_brackets = self._settings['fold_func_brackets'] and \ len(args) == 1 and \ not self._needs_function_brackets(expr.args[0]) inv_trig_table = [ "asin", "acos", "atan", "acsc", "asec", "acot", "asinh", "acosh", "atanh", "acsch", "asech", "acoth", ] # If the function is an inverse trig function, handle the style if func in inv_trig_table: if inv_trig_style == "abbreviated": pass elif inv_trig_style == "full": func = "arc" + func[1:] elif inv_trig_style == "power": func = func[1:] inv_trig_power_case = True # Can never fold brackets if we're raised to a power if exp is not None: can_fold_brackets = False if inv_trig_power_case: if func in accepted_latex_functions: name = r"\%s^{-1}" % func else: name = r"\operatorname{%s}^{-1}" % func elif exp is not None: func_tex = self._hprint_Function(func) func_tex = self.parenthesize_super(func_tex) name = r'%s^{%s}' % (func_tex, exp) else: name = self._hprint_Function(func) if can_fold_brackets: if func in accepted_latex_functions: # Wrap argument safely to avoid parse-time conflicts # with the function name itself name += r" {%s}" else: name += r"%s" else: name += r"{\left(%s \right)}" if inv_trig_power_case and exp is not None: name += r"^{%s}" % exp return name % ",".join(args) def _print_UndefinedFunction(self, expr): return self._hprint_Function(str(expr)) def _print_ElementwiseApplyFunction(self, expr): return r"{%s}_{\circ}\left({%s}\right)" % ( self._print(expr.function), self._print(expr.expr), ) @property def _special_function_classes(self): from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.functions.special.gamma_functions import gamma, lowergamma from sympy.functions.special.beta_functions import beta from sympy.functions.special.delta_functions import DiracDelta from sympy.functions.special.error_functions import Chi return {KroneckerDelta: r'\delta', gamma: r'\Gamma', lowergamma: r'\gamma', beta: r'\operatorname{B}', DiracDelta: r'\delta', Chi: r'\operatorname{Chi}'} def _print_FunctionClass(self, expr): for cls in self._special_function_classes: if issubclass(expr, cls) and expr.__name__ == cls.__name__: return self._special_function_classes[cls] return self._hprint_Function(str(expr)) def _print_Lambda(self, expr): symbols, expr = expr.args if len(symbols) == 1: symbols = self._print(symbols[0]) else: symbols = self._print(tuple(symbols)) tex = r"\left( %s \mapsto %s \right)" % (symbols, self._print(expr)) return tex def _print_IdentityFunction(self, expr): return r"\left( x \mapsto x \right)" def _hprint_variadic_function(self, expr, exp=None): args = sorted(expr.args, key=default_sort_key) texargs = [r"%s" % self._print(symbol) for symbol in args] tex = r"\%s\left(%s\right)" % (str(expr.func).lower(), ", ".join(texargs)) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex _print_Min = _print_Max = _hprint_variadic_function def _print_floor(self, expr, exp=None): tex = r"\left\lfloor{%s}\right\rfloor" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_ceiling(self, expr, exp=None): tex = r"\left\lceil{%s}\right\rceil" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_log(self, expr, exp=None): if not self._settings["ln_notation"]: tex = r"\log{\left(%s \right)}" % self._print(expr.args[0]) else: tex = r"\ln{\left(%s \right)}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_Abs(self, expr, exp=None): tex = r"\left|{%s}\right|" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex _print_Determinant = _print_Abs def _print_re(self, expr, exp=None): if self._settings['gothic_re_im']: tex = r"\Re{%s}" % self.parenthesize(expr.args[0], PRECEDENCE['Atom']) else: tex = r"\operatorname{{re}}{{{}}}".format(self.parenthesize(expr.args[0], PRECEDENCE['Atom'])) return self._do_exponent(tex, exp) def _print_im(self, expr, exp=None): if self._settings['gothic_re_im']: tex = r"\Im{%s}" % self.parenthesize(expr.args[0], PRECEDENCE['Atom']) else: tex = r"\operatorname{{im}}{{{}}}".format(self.parenthesize(expr.args[0], PRECEDENCE['Atom'])) return self._do_exponent(tex, exp) def _print_Not(self, e): from sympy import Equivalent, Implies if isinstance(e.args[0], Equivalent): return self._print_Equivalent(e.args[0], r"\not\Leftrightarrow") if isinstance(e.args[0], Implies): return self._print_Implies(e.args[0], r"\not\Rightarrow") if (e.args[0].is_Boolean): return r"\neg \left(%s\right)" % self._print(e.args[0]) else: return r"\neg %s" % self._print(e.args[0]) def _print_LogOp(self, args, char): arg = args[0] if arg.is_Boolean and not arg.is_Not: tex = r"\left(%s\right)" % self._print(arg) else: tex = r"%s" % self._print(arg) for arg in args[1:]: if arg.is_Boolean and not arg.is_Not: tex += r" %s \left(%s\right)" % (char, self._print(arg)) else: tex += r" %s %s" % (char, self._print(arg)) return tex def _print_And(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\wedge") def _print_Or(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\vee") def _print_Xor(self, e): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, r"\veebar") def _print_Implies(self, e, altchar=None): return self._print_LogOp(e.args, altchar or r"\Rightarrow") def _print_Equivalent(self, e, altchar=None): args = sorted(e.args, key=default_sort_key) return self._print_LogOp(args, altchar or r"\Leftrightarrow") def _print_conjugate(self, expr, exp=None): tex = r"\overline{%s}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_polar_lift(self, expr, exp=None): func = r"\operatorname{polar\_lift}" arg = r"{\left(%s \right)}" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (func, exp, arg) else: return r"%s%s" % (func, arg) def _print_ExpBase(self, expr, exp=None): # TODO should exp_polar be printed differently? # what about exp_polar(0), exp_polar(1)? tex = r"e^{%s}" % self._print(expr.args[0]) return self._do_exponent(tex, exp) def _print_elliptic_k(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"K^{%s}%s" % (exp, tex) else: return r"K%s" % tex def _print_elliptic_f(self, expr, exp=None): tex = r"\left(%s\middle| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"F^{%s}%s" % (exp, tex) else: return r"F%s" % tex def _print_elliptic_e(self, expr, exp=None): if len(expr.args) == 2: tex = r"\left(%s\middle| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"E^{%s}%s" % (exp, tex) else: return r"E%s" % tex def _print_elliptic_pi(self, expr, exp=None): if len(expr.args) == 3: tex = r"\left(%s; %s\middle| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1]), self._print(expr.args[2])) else: tex = r"\left(%s\middle| %s\right)" % \ (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\Pi^{%s}%s" % (exp, tex) else: return r"\Pi%s" % tex def _print_beta(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\operatorname{B}^{%s}%s" % (exp, tex) else: return r"\operatorname{B}%s" % tex def _print_uppergamma(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\Gamma^{%s}%s" % (exp, tex) else: return r"\Gamma%s" % tex def _print_lowergamma(self, expr, exp=None): tex = r"\left(%s, %s\right)" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"\gamma^{%s}%s" % (exp, tex) else: return r"\gamma%s" % tex def _hprint_one_arg_func(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (self._print(expr.func), exp, tex) else: return r"%s%s" % (self._print(expr.func), tex) _print_gamma = _hprint_one_arg_func def _print_Chi(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\operatorname{Chi}^{%s}%s" % (exp, tex) else: return r"\operatorname{Chi}%s" % tex def _print_expint(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[1]) nu = self._print(expr.args[0]) if exp is not None: return r"\operatorname{E}_{%s}^{%s}%s" % (nu, exp, tex) else: return r"\operatorname{E}_{%s}%s" % (nu, tex) def _print_fresnels(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"S^{%s}%s" % (exp, tex) else: return r"S%s" % tex def _print_fresnelc(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"C^{%s}%s" % (exp, tex) else: return r"C%s" % tex def _print_subfactorial(self, expr, exp=None): tex = r"!%s" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"\left(%s\right)^{%s}" % (tex, exp) else: return tex def _print_factorial(self, expr, exp=None): tex = r"%s!" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_factorial2(self, expr, exp=None): tex = r"%s!!" % self.parenthesize(expr.args[0], PRECEDENCE["Func"]) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_binomial(self, expr, exp=None): tex = r"{\binom{%s}{%s}}" % (self._print(expr.args[0]), self._print(expr.args[1])) if exp is not None: return r"%s^{%s}" % (tex, exp) else: return tex def _print_RisingFactorial(self, expr, exp=None): n, k = expr.args base = r"%s" % self.parenthesize(n, PRECEDENCE['Func']) tex = r"{%s}^{\left(%s\right)}" % (base, self._print(k)) return self._do_exponent(tex, exp) def _print_FallingFactorial(self, expr, exp=None): n, k = expr.args sub = r"%s" % self.parenthesize(k, PRECEDENCE['Func']) tex = r"{\left(%s\right)}_{%s}" % (self._print(n), sub) return self._do_exponent(tex, exp) def _hprint_BesselBase(self, expr, exp, sym): tex = r"%s" % (sym) need_exp = False if exp is not None: if tex.find('^') == -1: tex = r"%s^{%s}" % (tex, exp) else: need_exp = True tex = r"%s_{%s}\left(%s\right)" % (tex, self._print(expr.order), self._print(expr.argument)) if need_exp: tex = self._do_exponent(tex, exp) return tex def _hprint_vec(self, vec): if not vec: return "" s = "" for i in vec[:-1]: s += "%s, " % self._print(i) s += self._print(vec[-1]) return s def _print_besselj(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'J') def _print_besseli(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'I') def _print_besselk(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'K') def _print_bessely(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'Y') def _print_yn(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'y') def _print_jn(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'j') def _print_hankel1(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'H^{(1)}') def _print_hankel2(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'H^{(2)}') def _print_hn1(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'h^{(1)}') def _print_hn2(self, expr, exp=None): return self._hprint_BesselBase(expr, exp, 'h^{(2)}') def _hprint_airy(self, expr, exp=None, notation=""): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"%s^{%s}%s" % (notation, exp, tex) else: return r"%s%s" % (notation, tex) def _hprint_airy_prime(self, expr, exp=None, notation=""): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"{%s^\prime}^{%s}%s" % (notation, exp, tex) else: return r"%s^\prime%s" % (notation, tex) def _print_airyai(self, expr, exp=None): return self._hprint_airy(expr, exp, 'Ai') def _print_airybi(self, expr, exp=None): return self._hprint_airy(expr, exp, 'Bi') def _print_airyaiprime(self, expr, exp=None): return self._hprint_airy_prime(expr, exp, 'Ai') def _print_airybiprime(self, expr, exp=None): return self._hprint_airy_prime(expr, exp, 'Bi') def _print_hyper(self, expr, exp=None): tex = r"{{}_{%s}F_{%s}\left(\begin{matrix} %s \\ %s \end{matrix}" \ r"\middle| {%s} \right)}" % \ (self._print(len(expr.ap)), self._print(len(expr.bq)), self._hprint_vec(expr.ap), self._hprint_vec(expr.bq), self._print(expr.argument)) if exp is not None: tex = r"{%s}^{%s}" % (tex, exp) return tex def _print_meijerg(self, expr, exp=None): tex = r"{G_{%s, %s}^{%s, %s}\left(\begin{matrix} %s & %s \\" \ r"%s & %s \end{matrix} \middle| {%s} \right)}" % \ (self._print(len(expr.ap)), self._print(len(expr.bq)), self._print(len(expr.bm)), self._print(len(expr.an)), self._hprint_vec(expr.an), self._hprint_vec(expr.aother), self._hprint_vec(expr.bm), self._hprint_vec(expr.bother), self._print(expr.argument)) if exp is not None: tex = r"{%s}^{%s}" % (tex, exp) return tex def _print_dirichlet_eta(self, expr, exp=None): tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\eta^{%s}%s" % (exp, tex) return r"\eta%s" % tex def _print_zeta(self, expr, exp=None): if len(expr.args) == 2: tex = r"\left(%s, %s\right)" % tuple(map(self._print, expr.args)) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\zeta^{%s}%s" % (exp, tex) return r"\zeta%s" % tex def _print_stieltjes(self, expr, exp=None): if len(expr.args) == 2: tex = r"_{%s}\left(%s\right)" % tuple(map(self._print, expr.args)) else: tex = r"_{%s}" % self._print(expr.args[0]) if exp is not None: return r"\gamma%s^{%s}" % (tex, exp) return r"\gamma%s" % tex def _print_lerchphi(self, expr, exp=None): tex = r"\left(%s, %s, %s\right)" % tuple(map(self._print, expr.args)) if exp is None: return r"\Phi%s" % tex return r"\Phi^{%s}%s" % (exp, tex) def _print_polylog(self, expr, exp=None): s, z = map(self._print, expr.args) tex = r"\left(%s\right)" % z if exp is None: return r"\operatorname{Li}_{%s}%s" % (s, tex) return r"\operatorname{Li}_{%s}^{%s}%s" % (s, exp, tex) def _print_jacobi(self, expr, exp=None): n, a, b, x = map(self._print, expr.args) tex = r"P_{%s}^{\left(%s,%s\right)}\left(%s\right)" % (n, a, b, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_gegenbauer(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"C_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_chebyshevt(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"T_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_chebyshevu(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"U_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_legendre(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"P_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_assoc_legendre(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"P_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_hermite(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"H_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_laguerre(self, expr, exp=None): n, x = map(self._print, expr.args) tex = r"L_{%s}\left(%s\right)" % (n, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_assoc_laguerre(self, expr, exp=None): n, a, x = map(self._print, expr.args) tex = r"L_{%s}^{\left(%s\right)}\left(%s\right)" % (n, a, x) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_Ynm(self, expr, exp=None): n, m, theta, phi = map(self._print, expr.args) tex = r"Y_{%s}^{%s}\left(%s,%s\right)" % (n, m, theta, phi) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def _print_Znm(self, expr, exp=None): n, m, theta, phi = map(self._print, expr.args) tex = r"Z_{%s}^{%s}\left(%s,%s\right)" % (n, m, theta, phi) if exp is not None: tex = r"\left(" + tex + r"\right)^{%s}" % (exp) return tex def __print_mathieu_functions(self, character, args, prime=False, exp=None): a, q, z = map(self._print, args) sup = r"^{\prime}" if prime else "" exp = "" if not exp else "^{%s}" % exp return r"%s%s\left(%s, %s, %s\right)%s" % (character, sup, a, q, z, exp) def _print_mathieuc(self, expr, exp=None): return self.__print_mathieu_functions("C", expr.args, exp=exp) def _print_mathieus(self, expr, exp=None): return self.__print_mathieu_functions("S", expr.args, exp=exp) def _print_mathieucprime(self, expr, exp=None): return self.__print_mathieu_functions("C", expr.args, prime=True, exp=exp) def _print_mathieusprime(self, expr, exp=None): return self.__print_mathieu_functions("S", expr.args, prime=True, exp=exp) def _print_Rational(self, expr): if expr.q != 1: sign = "" p = expr.p if expr.p < 0: sign = "- " p = -p if self._settings['fold_short_frac']: return r"%s%d / %d" % (sign, p, expr.q) return r"%s\frac{%d}{%d}" % (sign, p, expr.q) else: return self._print(expr.p) def _print_Order(self, expr): s = self._print(expr.expr) if expr.point and any(p != S.Zero for p in expr.point) or \ len(expr.variables) > 1: s += '; ' if len(expr.variables) > 1: s += self._print(expr.variables) elif expr.variables: s += self._print(expr.variables[0]) s += r'\rightarrow ' if len(expr.point) > 1: s += self._print(expr.point) else: s += self._print(expr.point[0]) return r"O\left(%s\right)" % s def _print_Symbol(self, expr, style='plain'): if expr in self._settings['symbol_names']: return self._settings['symbol_names'][expr] return self._deal_with_super_sub(expr.name, style=style) _print_RandomSymbol = _print_Symbol def _deal_with_super_sub(self, string, style='plain'): if '{' in string: name, supers, subs = string, [], [] else: name, supers, subs = split_super_sub(string) name = translate(name) supers = [translate(sup) for sup in supers] subs = [translate(sub) for sub in subs] # apply the style only to the name if style == 'bold': name = "\\mathbf{{{}}}".format(name) # glue all items together: if supers: name += "^{%s}" % " ".join(supers) if subs: name += "_{%s}" % " ".join(subs) return name def _print_Relational(self, expr): if self._settings['itex']: gt = r"\gt" lt = r"\lt" else: gt = ">" lt = "<" charmap = { "==": "=", ">": gt, "<": lt, ">=": r"\geq", "<=": r"\leq", "!=": r"\neq", } return "%s %s %s" % (self._print(expr.lhs), charmap[expr.rel_op], self._print(expr.rhs)) def _print_Piecewise(self, expr): ecpairs = [r"%s & \text{for}\: %s" % (self._print(e), self._print(c)) for e, c in expr.args[:-1]] if expr.args[-1].cond == true: ecpairs.append(r"%s & \text{otherwise}" % self._print(expr.args[-1].expr)) else: ecpairs.append(r"%s & \text{for}\: %s" % (self._print(expr.args[-1].expr), self._print(expr.args[-1].cond))) tex = r"\begin{cases} %s \end{cases}" return tex % r" \\".join(ecpairs) def _print_MatrixBase(self, expr): lines = [] for line in range(expr.rows): # horrible, should be 'rows' lines.append(" & ".join([self._print(i) for i in expr[line, :]])) mat_str = self._settings['mat_str'] if mat_str is None: if self._settings['mode'] == 'inline': mat_str = 'smallmatrix' else: if (expr.cols <= 10) is True: mat_str = 'matrix' else: mat_str = 'array' out_str = r'\begin{%MATSTR%}%s\end{%MATSTR%}' out_str = out_str.replace('%MATSTR%', mat_str) if mat_str == 'array': out_str = out_str.replace('%s', '{' + 'c'*expr.cols + '}%s') if self._settings['mat_delim']: left_delim = self._settings['mat_delim'] right_delim = self._delim_dict[left_delim] out_str = r'\left' + left_delim + out_str + \ r'\right' + right_delim return out_str % r"\\".join(lines) def _print_MatrixElement(self, expr): return self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True)\ + '_{%s, %s}' % (self._print(expr.i), self._print(expr.j)) def _print_MatrixSlice(self, expr): def latexslice(x, dim): x = list(x) if x[2] == 1: del x[2] if x[0] == 0: x[0] = None if x[1] == dim: x[1] = None return ':'.join(self._print(xi) if xi is not None else '' for xi in x) return (self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True) + r'\left[' + latexslice(expr.rowslice, expr.parent.rows) + ', ' + latexslice(expr.colslice, expr.parent.cols) + r'\right]') def _print_BlockMatrix(self, expr): return self._print(expr.blocks) def _print_Transpose(self, expr): mat = expr.arg from sympy.matrices import MatrixSymbol if not isinstance(mat, MatrixSymbol): return r"\left(%s\right)^{T}" % self._print(mat) else: return "%s^{T}" % self.parenthesize(mat, precedence_traditional(expr), True) def _print_Trace(self, expr): mat = expr.arg return r"\operatorname{tr}\left(%s \right)" % self._print(mat) def _print_Adjoint(self, expr): mat = expr.arg from sympy.matrices import MatrixSymbol if not isinstance(mat, MatrixSymbol): return r"\left(%s\right)^{\dagger}" % self._print(mat) else: return r"%s^{\dagger}" % self._print(mat) def _print_MatMul(self, expr): from sympy import MatMul, Mul parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) args = expr.args if isinstance(args[0], Mul): args = args[0].as_ordered_factors() + list(args[1:]) else: args = list(args) if isinstance(expr, MatMul) and _coeff_isneg(expr): if args[0] == -1: args = args[1:] else: args[0] = -args[0] return '- ' + ' '.join(map(parens, args)) else: return ' '.join(map(parens, args)) def _print_Mod(self, expr, exp=None): if exp is not None: return r'\left(%s\bmod{%s}\right)^{%s}' % \ (self.parenthesize(expr.args[0], PRECEDENCE['Mul'], strict=True), self._print(expr.args[1]), exp) return r'%s\bmod{%s}' % (self.parenthesize(expr.args[0], PRECEDENCE['Mul'], strict=True), self._print(expr.args[1])) def _print_HadamardProduct(self, expr): args = expr.args prec = PRECEDENCE['Pow'] parens = self.parenthesize return r' \circ '.join( map(lambda arg: parens(arg, prec, strict=True), args)) def _print_HadamardPower(self, expr): if precedence_traditional(expr.exp) < PRECEDENCE["Mul"]: template = r"%s^{\circ \left({%s}\right)}" else: template = r"%s^{\circ {%s}}" return self._helper_print_standard_power(expr, template) def _print_KroneckerProduct(self, expr): args = expr.args prec = PRECEDENCE['Pow'] parens = self.parenthesize return r' \otimes '.join( map(lambda arg: parens(arg, prec, strict=True), args)) def _print_MatPow(self, expr): base, exp = expr.base, expr.exp from sympy.matrices import MatrixSymbol if not isinstance(base, MatrixSymbol): return "\\left(%s\\right)^{%s}" % (self._print(base), self._print(exp)) else: return "%s^{%s}" % (self._print(base), self._print(exp)) def _print_MatrixSymbol(self, expr): return self._print_Symbol(expr, style=self._settings[ 'mat_symbol_style']) def _print_ZeroMatrix(self, Z): return r"\mathbb{0}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{0}" def _print_OneMatrix(self, O): return r"\mathbb{1}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{1}" def _print_Identity(self, I): return r"\mathbb{I}" if self._settings[ 'mat_symbol_style'] == 'plain' else r"\mathbf{I}" def _print_PermutationMatrix(self, P): perm_str = self._print(P.args[0]) return "P_{%s}" % perm_str def _print_NDimArray(self, expr): if expr.rank() == 0: return self._print(expr[()]) mat_str = self._settings['mat_str'] if mat_str is None: if self._settings['mode'] == 'inline': mat_str = 'smallmatrix' else: if (expr.rank() == 0) or (expr.shape[-1] <= 10): mat_str = 'matrix' else: mat_str = 'array' block_str = r'\begin{%MATSTR%}%s\end{%MATSTR%}' block_str = block_str.replace('%MATSTR%', mat_str) if self._settings['mat_delim']: left_delim = self._settings['mat_delim'] right_delim = self._delim_dict[left_delim] block_str = r'\left' + left_delim + block_str + \ r'\right' + right_delim if expr.rank() == 0: return block_str % "" level_str = [[]] + [[] for i in range(expr.rank())] shape_ranges = [list(range(i)) for i in expr.shape] for outer_i in itertools.product(*shape_ranges): level_str[-1].append(self._print(expr[outer_i])) even = True for back_outer_i in range(expr.rank()-1, -1, -1): if len(level_str[back_outer_i+1]) < expr.shape[back_outer_i]: break if even: level_str[back_outer_i].append( r" & ".join(level_str[back_outer_i+1])) else: level_str[back_outer_i].append( block_str % (r"\\".join(level_str[back_outer_i+1]))) if len(level_str[back_outer_i+1]) == 1: level_str[back_outer_i][-1] = r"\left[" + \ level_str[back_outer_i][-1] + r"\right]" even = not even level_str[back_outer_i+1] = [] out_str = level_str[0][0] if expr.rank() % 2 == 1: out_str = block_str % out_str return out_str def _printer_tensor_indices(self, name, indices, index_map={}): out_str = self._print(name) last_valence = None prev_map = None for index in indices: new_valence = index.is_up if ((index in index_map) or prev_map) and \ last_valence == new_valence: out_str += "," if last_valence != new_valence: if last_valence is not None: out_str += "}" if index.is_up: out_str += "{}^{" else: out_str += "{}_{" out_str += self._print(index.args[0]) if index in index_map: out_str += "=" out_str += self._print(index_map[index]) prev_map = True else: prev_map = False last_valence = new_valence if last_valence is not None: out_str += "}" return out_str def _print_Tensor(self, expr): name = expr.args[0].args[0] indices = expr.get_indices() return self._printer_tensor_indices(name, indices) def _print_TensorElement(self, expr): name = expr.expr.args[0].args[0] indices = expr.expr.get_indices() index_map = expr.index_map return self._printer_tensor_indices(name, indices, index_map) def _print_TensMul(self, expr): # prints expressions like "A(a)", "3*A(a)", "(1+x)*A(a)" sign, args = expr._get_args_for_traditional_printer() return sign + "".join( [self.parenthesize(arg, precedence(expr)) for arg in args] ) def _print_TensAdd(self, expr): a = [] args = expr.args for x in args: a.append(self.parenthesize(x, precedence(expr))) a.sort() s = ' + '.join(a) s = s.replace('+ -', '- ') return s def _print_TensorIndex(self, expr): return "{}%s{%s}" % ( "^" if expr.is_up else "_", self._print(expr.args[0]) ) def _print_PartialDerivative(self, expr): if len(expr.variables) == 1: return r"\frac{\partial}{\partial {%s}}{%s}" % ( self._print(expr.variables[0]), self.parenthesize(expr.expr, PRECEDENCE["Mul"], False) ) else: return r"\frac{\partial^{%s}}{%s}{%s}" % ( len(expr.variables), " ".join([r"\partial {%s}" % self._print(i) for i in expr.variables]), self.parenthesize(expr.expr, PRECEDENCE["Mul"], False) ) def _print_UniversalSet(self, expr): return r"\mathbb{U}" def _print_frac(self, expr, exp=None): if exp is None: return r"\operatorname{frac}{\left(%s\right)}" % self._print(expr.args[0]) else: return r"\operatorname{frac}{\left(%s\right)}^{%s}" % ( self._print(expr.args[0]), exp) def _print_tuple(self, expr): if self._settings['decimal_separator'] == 'comma': sep = ";" elif self._settings['decimal_separator'] == 'period': sep = "," else: raise ValueError('Unknown Decimal Separator') if len(expr) == 1: # 1-tuple needs a trailing separator return self._add_parens_lspace(self._print(expr[0]) + sep) else: return self._add_parens_lspace( (sep + r" \ ").join([self._print(i) for i in expr])) def _print_TensorProduct(self, expr): elements = [self._print(a) for a in expr.args] return r' \otimes '.join(elements) def _print_WedgeProduct(self, expr): elements = [self._print(a) for a in expr.args] return r' \wedge '.join(elements) def _print_Tuple(self, expr): return self._print_tuple(expr) def _print_list(self, expr): if self._settings['decimal_separator'] == 'comma': return r"\left[ %s\right]" % \ r"; \ ".join([self._print(i) for i in expr]) elif self._settings['decimal_separator'] == 'period': return r"\left[ %s\right]" % \ r", \ ".join([self._print(i) for i in expr]) else: raise ValueError('Unknown Decimal Separator') def _print_dict(self, d): keys = sorted(d.keys(), key=default_sort_key) items = [] for key in keys: val = d[key] items.append("%s : %s" % (self._print(key), self._print(val))) return r"\left\{ %s\right\}" % r", \ ".join(items) def _print_Dict(self, expr): return self._print_dict(expr) def _print_DiracDelta(self, expr, exp=None): if len(expr.args) == 1 or expr.args[1] == 0: tex = r"\delta\left(%s\right)" % self._print(expr.args[0]) else: tex = r"\delta^{\left( %s \right)}\left( %s \right)" % ( self._print(expr.args[1]), self._print(expr.args[0])) if exp: tex = r"\left(%s\right)^{%s}" % (tex, exp) return tex def _print_SingularityFunction(self, expr): shift = self._print(expr.args[0] - expr.args[1]) power = self._print(expr.args[2]) tex = r"{\left\langle %s \right\rangle}^{%s}" % (shift, power) return tex def _print_Heaviside(self, expr, exp=None): tex = r"\theta\left(%s\right)" % self._print(expr.args[0]) if exp: tex = r"\left(%s\right)^{%s}" % (tex, exp) return tex def _print_KroneckerDelta(self, expr, exp=None): i = self._print(expr.args[0]) j = self._print(expr.args[1]) if expr.args[0].is_Atom and expr.args[1].is_Atom: tex = r'\delta_{%s %s}' % (i, j) else: tex = r'\delta_{%s, %s}' % (i, j) if exp is not None: tex = r'\left(%s\right)^{%s}' % (tex, exp) return tex def _print_LeviCivita(self, expr, exp=None): indices = map(self._print, expr.args) if all(x.is_Atom for x in expr.args): tex = r'\varepsilon_{%s}' % " ".join(indices) else: tex = r'\varepsilon_{%s}' % ", ".join(indices) if exp: tex = r'\left(%s\right)^{%s}' % (tex, exp) return tex def _print_RandomDomain(self, d): if hasattr(d, 'as_boolean'): return '\\text{Domain: }' + self._print(d.as_boolean()) elif hasattr(d, 'set'): return ('\\text{Domain: }' + self._print(d.symbols) + '\\text{ in }' + self._print(d.set)) elif hasattr(d, 'symbols'): return '\\text{Domain on }' + self._print(d.symbols) else: return self._print(None) def _print_FiniteSet(self, s): items = sorted(s.args, key=default_sort_key) return self._print_set(items) def _print_set(self, s): items = sorted(s, key=default_sort_key) if self._settings['decimal_separator'] == 'comma': items = "; ".join(map(self._print, items)) elif self._settings['decimal_separator'] == 'period': items = ", ".join(map(self._print, items)) else: raise ValueError('Unknown Decimal Separator') return r"\left\{%s\right\}" % items _print_frozenset = _print_set def _print_Range(self, s): dots = object() if s.has(Symbol): return self._print_Basic(s) if s.start.is_infinite and s.stop.is_infinite: if s.step.is_positive: printset = dots, -1, 0, 1, dots else: printset = dots, 1, 0, -1, dots elif s.start.is_infinite: printset = dots, s[-1] - s.step, s[-1] elif s.stop.is_infinite: it = iter(s) printset = next(it), next(it), dots elif len(s) > 4: it = iter(s) printset = next(it), next(it), dots, s[-1] else: printset = tuple(s) return (r"\left\{" + r", ".join(self._print(el) if el is not dots else r'\ldots' for el in printset) + r"\right\}") def __print_number_polynomial(self, expr, letter, exp=None): if len(expr.args) == 2: if exp is not None: return r"%s_{%s}^{%s}\left(%s\right)" % (letter, self._print(expr.args[0]), exp, self._print(expr.args[1])) return r"%s_{%s}\left(%s\right)" % (letter, self._print(expr.args[0]), self._print(expr.args[1])) tex = r"%s_{%s}" % (letter, self._print(expr.args[0])) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_bernoulli(self, expr, exp=None): return self.__print_number_polynomial(expr, "B", exp) def _print_bell(self, expr, exp=None): if len(expr.args) == 3: tex1 = r"B_{%s, %s}" % (self._print(expr.args[0]), self._print(expr.args[1])) tex2 = r"\left(%s\right)" % r", ".join(self._print(el) for el in expr.args[2]) if exp is not None: tex = r"%s^{%s}%s" % (tex1, exp, tex2) else: tex = tex1 + tex2 return tex return self.__print_number_polynomial(expr, "B", exp) def _print_fibonacci(self, expr, exp=None): return self.__print_number_polynomial(expr, "F", exp) def _print_lucas(self, expr, exp=None): tex = r"L_{%s}" % self._print(expr.args[0]) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_tribonacci(self, expr, exp=None): return self.__print_number_polynomial(expr, "T", exp) def _print_SeqFormula(self, s): dots = object() if len(s.start.free_symbols) > 0 or len(s.stop.free_symbols) > 0: return r"\left\{%s\right\}_{%s=%s}^{%s}" % ( self._print(s.formula), self._print(s.variables[0]), self._print(s.start), self._print(s.stop) ) if s.start is S.NegativeInfinity: stop = s.stop printset = (dots, s.coeff(stop - 3), s.coeff(stop - 2), s.coeff(stop - 1), s.coeff(stop)) elif s.stop is S.Infinity or s.length > 4: printset = s[:4] printset.append(dots) else: printset = tuple(s) return (r"\left[" + r", ".join(self._print(el) if el is not dots else r'\ldots' for el in printset) + r"\right]") _print_SeqPer = _print_SeqFormula _print_SeqAdd = _print_SeqFormula _print_SeqMul = _print_SeqFormula def _print_Interval(self, i): if i.start == i.end: return r"\left\{%s\right\}" % self._print(i.start) else: if i.left_open: left = '(' else: left = '[' if i.right_open: right = ')' else: right = ']' return r"\left%s%s, %s\right%s" % \ (left, self._print(i.start), self._print(i.end), right) def _print_AccumulationBounds(self, i): return r"\left\langle %s, %s\right\rangle" % \ (self._print(i.min), self._print(i.max)) def _print_Union(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \cup ".join(args_str) def _print_Complement(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \setminus ".join(args_str) def _print_Intersection(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \cap ".join(args_str) def _print_SymmetricDifference(self, u): prec = precedence_traditional(u) args_str = [self.parenthesize(i, prec) for i in u.args] return r" \triangle ".join(args_str) def _print_ProductSet(self, p): prec = precedence_traditional(p) if len(p.sets) >= 1 and not has_variety(p.sets): return self.parenthesize(p.sets[0], prec) + "^{%d}" % len(p.sets) return r" \times ".join( self.parenthesize(set, prec) for set in p.sets) def _print_EmptySet(self, e): return r"\emptyset" def _print_Naturals(self, n): return r"\mathbb{N}" def _print_Naturals0(self, n): return r"\mathbb{N}_0" def _print_Integers(self, i): return r"\mathbb{Z}" def _print_Rationals(self, i): return r"\mathbb{Q}" def _print_Reals(self, i): return r"\mathbb{R}" def _print_Complexes(self, i): return r"\mathbb{C}" def _print_ImageSet(self, s): expr = s.lamda.expr sig = s.lamda.signature xys = ((self._print(x), self._print(y)) for x, y in zip(sig, s.base_sets)) xinys = r" , ".join(r"%s \in %s" % xy for xy in xys) return r"\left\{%s\; |\; %s\right\}" % (self._print(expr), xinys) def _print_ConditionSet(self, s): vars_print = ', '.join([self._print(var) for var in Tuple(s.sym)]) if s.base_set is S.UniversalSet: return r"\left\{%s \mid %s \right\}" % \ (vars_print, self._print(s.condition)) return r"\left\{%s \mid %s \in %s \wedge %s \right\}" % ( vars_print, vars_print, self._print(s.base_set), self._print(s.condition)) def _print_ComplexRegion(self, s): vars_print = ', '.join([self._print(var) for var in s.variables]) return r"\left\{%s\; |\; %s \in %s \right\}" % ( self._print(s.expr), vars_print, self._print(s.sets)) def _print_Contains(self, e): return r"%s \in %s" % tuple(self._print(a) for a in e.args) def _print_FourierSeries(self, s): return self._print_Add(s.truncate()) + r' + \ldots' def _print_FormalPowerSeries(self, s): return self._print_Add(s.infinite) def _print_FiniteField(self, expr): return r"\mathbb{F}_{%s}" % expr.mod def _print_IntegerRing(self, expr): return r"\mathbb{Z}" def _print_RationalField(self, expr): return r"\mathbb{Q}" def _print_RealField(self, expr): return r"\mathbb{R}" def _print_ComplexField(self, expr): return r"\mathbb{C}" def _print_PolynomialRing(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) return r"%s\left[%s\right]" % (domain, symbols) def _print_FractionField(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) return r"%s\left(%s\right)" % (domain, symbols) def _print_PolynomialRingBase(self, expr): domain = self._print(expr.domain) symbols = ", ".join(map(self._print, expr.symbols)) inv = "" if not expr.is_Poly: inv = r"S_<^{-1}" return r"%s%s\left[%s\right]" % (inv, domain, symbols) def _print_Poly(self, poly): cls = poly.__class__.__name__ terms = [] for monom, coeff in poly.terms(): s_monom = '' for i, exp in enumerate(monom): if exp > 0: if exp == 1: s_monom += self._print(poly.gens[i]) else: s_monom += self._print(pow(poly.gens[i], exp)) if coeff.is_Add: if s_monom: s_coeff = r"\left(%s\right)" % self._print(coeff) else: s_coeff = self._print(coeff) else: if s_monom: if coeff is S.One: terms.extend(['+', s_monom]) continue if coeff is S.NegativeOne: terms.extend(['-', s_monom]) continue s_coeff = self._print(coeff) if not s_monom: s_term = s_coeff else: s_term = s_coeff + " " + s_monom if s_term.startswith('-'): terms.extend(['-', s_term[1:]]) else: terms.extend(['+', s_term]) if terms[0] in ['-', '+']: modifier = terms.pop(0) if modifier == '-': terms[0] = '-' + terms[0] expr = ' '.join(terms) gens = list(map(self._print, poly.gens)) domain = "domain=%s" % self._print(poly.get_domain()) args = ", ".join([expr] + gens + [domain]) if cls in accepted_latex_functions: tex = r"\%s {\left(%s \right)}" % (cls, args) else: tex = r"\operatorname{%s}{\left( %s \right)}" % (cls, args) return tex def _print_ComplexRootOf(self, root): cls = root.__class__.__name__ if cls == "ComplexRootOf": cls = "CRootOf" expr = self._print(root.expr) index = root.index if cls in accepted_latex_functions: return r"\%s {\left(%s, %d\right)}" % (cls, expr, index) else: return r"\operatorname{%s} {\left(%s, %d\right)}" % (cls, expr, index) def _print_RootSum(self, expr): cls = expr.__class__.__name__ args = [self._print(expr.expr)] if expr.fun is not S.IdentityFunction: args.append(self._print(expr.fun)) if cls in accepted_latex_functions: return r"\%s {\left(%s\right)}" % (cls, ", ".join(args)) else: return r"\operatorname{%s} {\left(%s\right)}" % (cls, ", ".join(args)) def _print_PolyElement(self, poly): mul_symbol = self._settings['mul_symbol_latex'] return poly.str(self, PRECEDENCE, "{%s}^{%d}", mul_symbol) def _print_FracElement(self, frac): if frac.denom == 1: return self._print(frac.numer) else: numer = self._print(frac.numer) denom = self._print(frac.denom) return r"\frac{%s}{%s}" % (numer, denom) def _print_euler(self, expr, exp=None): m, x = (expr.args[0], None) if len(expr.args) == 1 else expr.args tex = r"E_{%s}" % self._print(m) if exp is not None: tex = r"%s^{%s}" % (tex, exp) if x is not None: tex = r"%s\left(%s\right)" % (tex, self._print(x)) return tex def _print_catalan(self, expr, exp=None): tex = r"C_{%s}" % self._print(expr.args[0]) if exp is not None: tex = r"%s^{%s}" % (tex, exp) return tex def _print_UnifiedTransform(self, expr, s, inverse=False): return r"\mathcal{{{}}}{}_{{{}}}\left[{}\right]\left({}\right)".format(s, '^{-1}' if inverse else '', self._print(expr.args[1]), self._print(expr.args[0]), self._print(expr.args[2])) def _print_MellinTransform(self, expr): return self._print_UnifiedTransform(expr, 'M') def _print_InverseMellinTransform(self, expr): return self._print_UnifiedTransform(expr, 'M', True) def _print_LaplaceTransform(self, expr): return self._print_UnifiedTransform(expr, 'L') def _print_InverseLaplaceTransform(self, expr): return self._print_UnifiedTransform(expr, 'L', True) def _print_FourierTransform(self, expr): return self._print_UnifiedTransform(expr, 'F') def _print_InverseFourierTransform(self, expr): return self._print_UnifiedTransform(expr, 'F', True) def _print_SineTransform(self, expr): return self._print_UnifiedTransform(expr, 'SIN') def _print_InverseSineTransform(self, expr): return self._print_UnifiedTransform(expr, 'SIN', True) def _print_CosineTransform(self, expr): return self._print_UnifiedTransform(expr, 'COS') def _print_InverseCosineTransform(self, expr): return self._print_UnifiedTransform(expr, 'COS', True) def _print_DMP(self, p): try: if p.ring is not None: # TODO incorporate order return self._print(p.ring.to_sympy(p)) except SympifyError: pass return self._print(repr(p)) def _print_DMF(self, p): return self._print_DMP(p) def _print_Object(self, object): return self._print(Symbol(object.name)) def _print_LambertW(self, expr): if len(expr.args) == 1: return r"W\left(%s\right)" % self._print(expr.args[0]) return r"W_{%s}\left(%s\right)" % \ (self._print(expr.args[1]), self._print(expr.args[0])) def _print_Morphism(self, morphism): domain = self._print(morphism.domain) codomain = self._print(morphism.codomain) return "%s\\rightarrow %s" % (domain, codomain) def _print_TransferFunction(self, expr): from sympy.core import Mul, Pow num, den = expr.num, expr.den res = Mul(num, Pow(den, -1, evaluate=False), evaluate=False) return self._print_Mul(res) def _print_Series(self, expr): args = list(expr.args) parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) return ' '.join(map(parens, args)) def _print_Parallel(self, expr): args = list(expr.args) parens = lambda x: self.parenthesize(x, precedence_traditional(expr), False) return ' '.join(map(parens, args)) def _print_Feedback(self, expr): from sympy.physics.control import TransferFunction, Parallel, Series num, tf = expr.num, TransferFunction(1, 1, expr.num.var) num_arg_list = list(num.args) if isinstance(num, Series) else [num] den_arg_list = list(expr.den.args) if isinstance(expr.den, Series) else [expr.den] if isinstance(num, Series) and isinstance(expr.den, Series): den = Parallel(tf, Series(*num_arg_list, *den_arg_list)) elif isinstance(num, Series) and isinstance(expr.den, TransferFunction): if expr.den == tf: den = Parallel(tf, Series(*num_arg_list)) else: den = Parallel(tf, Series(*num_arg_list, expr.den)) elif isinstance(num, TransferFunction) and isinstance(expr.den, Series): if num == tf: den = Parallel(tf, Series(*den_arg_list)) else: den = Parallel(tf, Series(num, *den_arg_list)) else: if num == tf: den = Parallel(tf, *den_arg_list) elif expr.den == tf: den = Parallel(tf, *num_arg_list) else: den = Parallel(tf, Series(*num_arg_list, *den_arg_list)) numer = self._print(num) denom = self._print(den) return r"\frac{%s}{%s}" % (numer, denom) def _print_NamedMorphism(self, morphism): pretty_name = self._print(Symbol(morphism.name)) pretty_morphism = self._print_Morphism(morphism) return "%s:%s" % (pretty_name, pretty_morphism) def _print_IdentityMorphism(self, morphism): from sympy.categories import NamedMorphism return self._print_NamedMorphism(NamedMorphism( morphism.domain, morphism.codomain, "id")) def _print_CompositeMorphism(self, morphism): # All components of the morphism have names and it is thus # possible to build the name of the composite. component_names_list = [self._print(Symbol(component.name)) for component in morphism.components] component_names_list.reverse() component_names = "\\circ ".join(component_names_list) + ":" pretty_morphism = self._print_Morphism(morphism) return component_names + pretty_morphism def _print_Category(self, morphism): return r"\mathbf{{{}}}".format(self._print(Symbol(morphism.name))) def _print_Diagram(self, diagram): if not diagram.premises: # This is an empty diagram. return self._print(S.EmptySet) latex_result = self._print(diagram.premises) if diagram.conclusions: latex_result += "\\Longrightarrow %s" % \ self._print(diagram.conclusions) return latex_result def _print_DiagramGrid(self, grid): latex_result = "\\begin{array}{%s}\n" % ("c" * grid.width) for i in range(grid.height): for j in range(grid.width): if grid[i, j]: latex_result += latex(grid[i, j]) latex_result += " " if j != grid.width - 1: latex_result += "& " if i != grid.height - 1: latex_result += "\\\\" latex_result += "\n" latex_result += "\\end{array}\n" return latex_result def _print_FreeModule(self, M): return '{{{}}}^{{{}}}'.format(self._print(M.ring), self._print(M.rank)) def _print_FreeModuleElement(self, m): # Print as row vector for convenience, for now. return r"\left[ {} \right]".format(",".join( '{' + self._print(x) + '}' for x in m)) def _print_SubModule(self, m): return r"\left\langle {} \right\rangle".format(",".join( '{' + self._print(x) + '}' for x in m.gens)) def _print_ModuleImplementedIdeal(self, m): return r"\left\langle {} \right\rangle".format(",".join( '{' + self._print(x) + '}' for [x] in m._module.gens)) def _print_Quaternion(self, expr): # TODO: This expression is potentially confusing, # shall we print it as `Quaternion( ... )`? s = [self.parenthesize(i, PRECEDENCE["Mul"], strict=True) for i in expr.args] a = [s[0]] + [i+" "+j for i, j in zip(s[1:], "ijk")] return " + ".join(a) def _print_QuotientRing(self, R): # TODO nicer fractions for few generators... return r"\frac{{{}}}{{{}}}".format(self._print(R.ring), self._print(R.base_ideal)) def _print_QuotientRingElement(self, x): return r"{{{}}} + {{{}}}".format(self._print(x.data), self._print(x.ring.base_ideal)) def _print_QuotientModuleElement(self, m): return r"{{{}}} + {{{}}}".format(self._print(m.data), self._print(m.module.killed_module)) def _print_QuotientModule(self, M): # TODO nicer fractions for few generators... return r"\frac{{{}}}{{{}}}".format(self._print(M.base), self._print(M.killed_module)) def _print_MatrixHomomorphism(self, h): return r"{{{}}} : {{{}}} \to {{{}}}".format(self._print(h._sympy_matrix()), self._print(h.domain), self._print(h.codomain)) def _print_Manifold(self, manifold): string = manifold.name.name if '{' in string: name, supers, subs = string, [], [] else: name, supers, subs = split_super_sub(string) name = translate(name) supers = [translate(sup) for sup in supers] subs = [translate(sub) for sub in subs] name = r'\text{%s}' % name if supers: name += "^{%s}" % " ".join(supers) if subs: name += "_{%s}" % " ".join(subs) return name def _print_Patch(self, patch): return r'\text{%s}_{%s}' % (self._print(patch.name), self._print(patch.manifold)) def _print_CoordSystem(self, coordsys): return r'\text{%s}^{\text{%s}}_{%s}' % ( self._print(coordsys.name), self._print(coordsys.patch.name), self._print(coordsys.manifold) ) def _print_CovarDerivativeOp(self, cvd): return r'\mathbb{\nabla}_{%s}' % self._print(cvd._wrt) def _print_BaseScalarField(self, field): string = field._coord_sys.symbols[field._index].name return r'\mathbf{{{}}}'.format(self._print(Symbol(string))) def _print_BaseVectorField(self, field): string = field._coord_sys.symbols[field._index].name return r'\partial_{{{}}}'.format(self._print(Symbol(string))) def _print_Differential(self, diff): field = diff._form_field if hasattr(field, '_coord_sys'): string = field._coord_sys.symbols[field._index].name return r'\operatorname{{d}}{}'.format(self._print(Symbol(string))) else: string = self._print(field) return r'\operatorname{{d}}\left({}\right)'.format(string) def _print_Tr(self, p): # TODO: Handle indices contents = self._print(p.args[0]) return r'\operatorname{{tr}}\left({}\right)'.format(contents) def _print_totient(self, expr, exp=None): if exp is not None: return r'\left(\phi\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\phi\left(%s\right)' % self._print(expr.args[0]) def _print_reduced_totient(self, expr, exp=None): if exp is not None: return r'\left(\lambda\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\lambda\left(%s\right)' % self._print(expr.args[0]) def _print_divisor_sigma(self, expr, exp=None): if len(expr.args) == 2: tex = r"_%s\left(%s\right)" % tuple(map(self._print, (expr.args[1], expr.args[0]))) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\sigma^{%s}%s" % (exp, tex) return r"\sigma%s" % tex def _print_udivisor_sigma(self, expr, exp=None): if len(expr.args) == 2: tex = r"_%s\left(%s\right)" % tuple(map(self._print, (expr.args[1], expr.args[0]))) else: tex = r"\left(%s\right)" % self._print(expr.args[0]) if exp is not None: return r"\sigma^*^{%s}%s" % (exp, tex) return r"\sigma^*%s" % tex def _print_primenu(self, expr, exp=None): if exp is not None: return r'\left(\nu\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\nu\left(%s\right)' % self._print(expr.args[0]) def _print_primeomega(self, expr, exp=None): if exp is not None: return r'\left(\Omega\left(%s\right)\right)^{%s}' % \ (self._print(expr.args[0]), exp) return r'\Omega\left(%s\right)' % self._print(expr.args[0]) def _print_Str(self, s): return str(s.name) def _print_float(self, expr): return self._print(Float(expr)) def _print_int(self, expr): return str(expr) def _print_mpz(self, expr): return str(expr) def _print_mpq(self, expr): return str(expr) def emptyPrinter(self, expr): # default to just printing as monospace, like would normally be shown s = super().emptyPrinter(expr) return r"\mathtt{\text{%s}}" % latex_escape(s) def translate(s): r''' Check for a modifier ending the string. If present, convert the modifier to latex and translate the rest recursively. Given a description of a Greek letter or other special character, return the appropriate latex. Let everything else pass as given. >>> from sympy.printing.latex import translate >>> translate('alphahatdotprime') "{\\dot{\\hat{\\alpha}}}'" ''' # Process the rest tex = tex_greek_dictionary.get(s) if tex: return tex elif s.lower() in greek_letters_set: return "\\" + s.lower() elif s in other_symbols: return "\\" + s else: # Process modifiers, if any, and recurse for key in sorted(modifier_dict.keys(), key=lambda k:len(k), reverse=True): if s.lower().endswith(key) and len(s) > len(key): return modifier_dict[key](translate(s[:-len(key)])) return s @print_function(LatexPrinter) def latex(expr, **settings): r"""Convert the given expression to LaTeX string representation. Parameters ========== full_prec: boolean, optional If set to True, a floating point number is printed with full precision. fold_frac_powers : boolean, optional Emit ``^{p/q}`` instead of ``^{\frac{p}{q}}`` for fractional powers. fold_func_brackets : boolean, optional Fold function brackets where applicable. fold_short_frac : boolean, optional Emit ``p / q`` instead of ``\frac{p}{q}`` when the denominator is simple enough (at most two terms and no powers). The default value is ``True`` for inline mode, ``False`` otherwise. inv_trig_style : string, optional How inverse trig functions should be displayed. Can be one of ``abbreviated``, ``full``, or ``power``. Defaults to ``abbreviated``. itex : boolean, optional Specifies if itex-specific syntax is used, including emitting ``$$...$$``. ln_notation : boolean, optional If set to ``True``, ``\ln`` is used instead of default ``\log``. long_frac_ratio : float or None, optional The allowed ratio of the width of the numerator to the width of the denominator before the printer breaks off long fractions. If ``None`` (the default value), long fractions are not broken up. mat_delim : string, optional The delimiter to wrap around matrices. Can be one of ``[``, ``(``, or the empty string. Defaults to ``[``. mat_str : string, optional Which matrix environment string to emit. ``smallmatrix``, ``matrix``, ``array``, etc. Defaults to ``smallmatrix`` for inline mode, ``matrix`` for matrices of no more than 10 columns, and ``array`` otherwise. mode: string, optional Specifies how the generated code will be delimited. ``mode`` can be one of ``plain``, ``inline``, ``equation`` or ``equation*``. If ``mode`` is set to ``plain``, then the resulting code will not be delimited at all (this is the default). If ``mode`` is set to ``inline`` then inline LaTeX ``$...$`` will be used. If ``mode`` is set to ``equation`` or ``equation*``, the resulting code will be enclosed in the ``equation`` or ``equation*`` environment (remember to import ``amsmath`` for ``equation*``), unless the ``itex`` option is set. In the latter case, the ``$$...$$`` syntax is used. mul_symbol : string or None, optional The symbol to use for multiplication. Can be one of ``None``, ``ldot``, ``dot``, or ``times``. order: string, optional Any of the supported monomial orderings (currently ``lex``, ``grlex``, or ``grevlex``), ``old``, and ``none``. This parameter does nothing for Mul objects. Setting order to ``old`` uses the compatibility ordering for Add defined in Printer. For very large expressions, set the ``order`` keyword to ``none`` if speed is a concern. symbol_names : dictionary of strings mapped to symbols, optional Dictionary of symbols and the custom strings they should be emitted as. root_notation : boolean, optional If set to ``False``, exponents of the form 1/n are printed in fractonal form. Default is ``True``, to print exponent in root form. mat_symbol_style : string, optional Can be either ``plain`` (default) or ``bold``. If set to ``bold``, a MatrixSymbol A will be printed as ``\mathbf{A}``, otherwise as ``A``. imaginary_unit : string, optional String to use for the imaginary unit. Defined options are "i" (default) and "j". Adding "r" or "t" in front gives ``\mathrm`` or ``\text``, so "ri" leads to ``\mathrm{i}`` which gives `\mathrm{i}`. gothic_re_im : boolean, optional If set to ``True``, `\Re` and `\Im` is used for ``re`` and ``im``, respectively. The default is ``False`` leading to `\operatorname{re}` and `\operatorname{im}`. decimal_separator : string, optional Specifies what separator to use to separate the whole and fractional parts of a floating point number as in `2.5` for the default, ``period`` or `2{,}5` when ``comma`` is specified. Lists, sets, and tuple are printed with semicolon separating the elements when ``comma`` is chosen. For example, [1; 2; 3] when ``comma`` is chosen and [1,2,3] for when ``period`` is chosen. parenthesize_super : boolean, optional If set to ``False``, superscripted expressions will not be parenthesized when powered. Default is ``True``, which parenthesizes the expression when powered. min: Integer or None, optional Sets the lower bound for the exponent to print floating point numbers in fixed-point format. max: Integer or None, optional Sets the upper bound for the exponent to print floating point numbers in fixed-point format. Notes ===== Not using a print statement for printing, results in double backslashes for latex commands since that's the way Python escapes backslashes in strings. >>> from sympy import latex, Rational >>> from sympy.abc import tau >>> latex((2*tau)**Rational(7,2)) '8 \\sqrt{2} \\tau^{\\frac{7}{2}}' >>> print(latex((2*tau)**Rational(7,2))) 8 \sqrt{2} \tau^{\frac{7}{2}} Examples ======== >>> from sympy import latex, pi, sin, asin, Integral, Matrix, Rational, log >>> from sympy.abc import x, y, mu, r, tau Basic usage: >>> print(latex((2*tau)**Rational(7,2))) 8 \sqrt{2} \tau^{\frac{7}{2}} ``mode`` and ``itex`` options: >>> print(latex((2*mu)**Rational(7,2), mode='plain')) 8 \sqrt{2} \mu^{\frac{7}{2}} >>> print(latex((2*tau)**Rational(7,2), mode='inline')) $8 \sqrt{2} \tau^{7 / 2}$ >>> print(latex((2*mu)**Rational(7,2), mode='equation*')) \begin{equation*}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation*} >>> print(latex((2*mu)**Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2*mu)**Rational(7,2), mode='equation', itex=True)) $$8 \sqrt{2} \mu^{\frac{7}{2}}$$ >>> print(latex((2*mu)**Rational(7,2), mode='plain')) 8 \sqrt{2} \mu^{\frac{7}{2}} >>> print(latex((2*tau)**Rational(7,2), mode='inline')) $8 \sqrt{2} \tau^{7 / 2}$ >>> print(latex((2*mu)**Rational(7,2), mode='equation*')) \begin{equation*}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation*} >>> print(latex((2*mu)**Rational(7,2), mode='equation')) \begin{equation}8 \sqrt{2} \mu^{\frac{7}{2}}\end{equation} >>> print(latex((2*mu)**Rational(7,2), mode='equation', itex=True)) $$8 \sqrt{2} \mu^{\frac{7}{2}}$$ Fraction options: >>> print(latex((2*tau)**Rational(7,2), fold_frac_powers=True)) 8 \sqrt{2} \tau^{7/2} >>> print(latex((2*tau)**sin(Rational(7,2)))) \left(2 \tau\right)^{\sin{\left(\frac{7}{2} \right)}} >>> print(latex((2*tau)**sin(Rational(7,2)), fold_func_brackets=True)) \left(2 \tau\right)^{\sin {\frac{7}{2}}} >>> print(latex(3*x**2/y)) \frac{3 x^{2}}{y} >>> print(latex(3*x**2/y, fold_short_frac=True)) 3 x^{2} / y >>> print(latex(Integral(r, r)/2/pi, long_frac_ratio=2)) \frac{\int r\, dr}{2 \pi} >>> print(latex(Integral(r, r)/2/pi, long_frac_ratio=0)) \frac{1}{2 \pi} \int r\, dr Multiplication options: >>> print(latex((2*tau)**sin(Rational(7,2)), mul_symbol="times")) \left(2 \times \tau\right)^{\sin{\left(\frac{7}{2} \right)}} Trig options: >>> print(latex(asin(Rational(7,2)))) \operatorname{asin}{\left(\frac{7}{2} \right)} >>> print(latex(asin(Rational(7,2)), inv_trig_style="full")) \arcsin{\left(\frac{7}{2} \right)} >>> print(latex(asin(Rational(7,2)), inv_trig_style="power")) \sin^{-1}{\left(\frac{7}{2} \right)} Matrix options: >>> print(latex(Matrix(2, 1, [x, y]))) \left[\begin{matrix}x\\y\end{matrix}\right] >>> print(latex(Matrix(2, 1, [x, y]), mat_str = "array")) \left[\begin{array}{c}x\\y\end{array}\right] >>> print(latex(Matrix(2, 1, [x, y]), mat_delim="(")) \left(\begin{matrix}x\\y\end{matrix}\right) Custom printing of symbols: >>> print(latex(x**2, symbol_names={x: 'x_i'})) x_i^{2} Logarithms: >>> print(latex(log(10))) \log{\left(10 \right)} >>> print(latex(log(10), ln_notation=True)) \ln{\left(10 \right)} ``latex()`` also supports the builtin container types :class:`list`, :class:`tuple`, and :class:`dict`: >>> print(latex([2/x, y], mode='inline')) $\left[ 2 / x, \ y\right]$ Unsupported types are rendered as monospaced plaintext: >>> print(latex(int)) \mathtt{\text{<class 'int'>}} >>> print(latex("plain % text")) \mathtt{\text{plain \% text}} See :ref:`printer_method_example` for an example of how to override this behavior for your own types by implementing ``_latex``. .. versionchanged:: 1.7.0 Unsupported types no longer have their ``str`` representation treated as valid latex. """ return LatexPrinter(settings).doprint(expr) def print_latex(expr, **settings): """Prints LaTeX representation of the given expression. Takes the same settings as ``latex()``.""" print(latex(expr, **settings)) def multiline_latex(lhs, rhs, terms_per_line=1, environment="align*", use_dots=False, **settings): r""" This function generates a LaTeX equation with a multiline right-hand side in an ``align*``, ``eqnarray`` or ``IEEEeqnarray`` environment. Parameters ========== lhs : Expr Left-hand side of equation rhs : Expr Right-hand side of equation terms_per_line : integer, optional Number of terms per line to print. Default is 1. environment : "string", optional Which LaTeX wnvironment to use for the output. Options are "align*" (default), "eqnarray", and "IEEEeqnarray". use_dots : boolean, optional If ``True``, ``\\dots`` is added to the end of each line. Default is ``False``. Examples ======== >>> from sympy import multiline_latex, symbols, sin, cos, exp, log, I >>> x, y, alpha = symbols('x y alpha') >>> expr = sin(alpha*y) + exp(I*alpha) - cos(log(y)) >>> print(multiline_latex(x, expr)) \begin{align*} x = & e^{i \alpha} \\ & + \sin{\left(\alpha y \right)} \\ & - \cos{\left(\log{\left(y \right)} \right)} \end{align*} Using at most two terms per line: >>> print(multiline_latex(x, expr, 2)) \begin{align*} x = & e^{i \alpha} + \sin{\left(\alpha y \right)} \\ & - \cos{\left(\log{\left(y \right)} \right)} \end{align*} Using ``eqnarray`` and dots: >>> print(multiline_latex(x, expr, terms_per_line=2, environment="eqnarray", use_dots=True)) \begin{eqnarray} x & = & e^{i \alpha} + \sin{\left(\alpha y \right)} \dots\nonumber\\ & & - \cos{\left(\log{\left(y \right)} \right)} \end{eqnarray} Using ``IEEEeqnarray``: >>> print(multiline_latex(x, expr, environment="IEEEeqnarray")) \begin{IEEEeqnarray}{rCl} x & = & e^{i \alpha} \nonumber\\ & & + \sin{\left(\alpha y \right)} \nonumber\\ & & - \cos{\left(\log{\left(y \right)} \right)} \end{IEEEeqnarray} Notes ===== All optional parameters from ``latex`` can also be used. """ # Based on code from https://github.com/sympy/sympy/issues/3001 l = LatexPrinter(**settings) if environment == "eqnarray": result = r'\begin{eqnarray}' + '\n' first_term = '& = &' nonumber = r'\nonumber' end_term = '\n\\end{eqnarray}' doubleet = True elif environment == "IEEEeqnarray": result = r'\begin{IEEEeqnarray}{rCl}' + '\n' first_term = '& = &' nonumber = r'\nonumber' end_term = '\n\\end{IEEEeqnarray}' doubleet = True elif environment == "align*": result = r'\begin{align*}' + '\n' first_term = '= &' nonumber = '' end_term = '\n\\end{align*}' doubleet = False else: raise ValueError("Unknown environment: {}".format(environment)) dots = '' if use_dots: dots=r'\dots' terms = rhs.as_ordered_terms() n_terms = len(terms) term_count = 1 for i in range(n_terms): term = terms[i] term_start = '' term_end = '' sign = '+' if term_count > terms_per_line: if doubleet: term_start = '& & ' else: term_start = '& ' term_count = 1 if term_count == terms_per_line: # End of line if i < n_terms-1: # There are terms remaining term_end = dots + nonumber + r'\\' + '\n' else: term_end = '' if term.as_ordered_factors()[0] == -1: term = -1*term sign = r'-' if i == 0: # beginning if sign == '+': sign = '' result += r'{:s} {:s}{:s} {:s} {:s}'.format(l.doprint(lhs), first_term, sign, l.doprint(term), term_end) else: result += r'{:s}{:s} {:s} {:s}'.format(term_start, sign, l.doprint(term), term_end) term_count += 1 result += end_term return result

0da82ef731f8bba722e818a5fd0144d60b4c3433b29b085cff3d9c256e38f143

"""Printing subsystem driver SymPy's printing system works the following way: Any expression can be passed to a designated Printer who then is responsible to return an adequate representation of that expression. **The basic concept is the following:** 1. Let the object print itself if it knows how. 2. Take the best fitting method defined in the printer. 3. As fall-back use the emptyPrinter method for the printer. Which Method is Responsible for Printing? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The whole printing process is started by calling ``.doprint(expr)`` on the printer which you want to use. This method looks for an appropriate method which can print the given expression in the given style that the printer defines. While looking for the method, it follows these steps: 1. **Let the object print itself if it knows how.** The printer looks for a specific method in every object. The name of that method depends on the specific printer and is defined under ``Printer.printmethod``. For example, StrPrinter calls ``_sympystr`` and LatexPrinter calls ``_latex``. Look at the documentation of the printer that you want to use. The name of the method is specified there. This was the original way of doing printing in sympy. Every class had its own latex, mathml, str and repr methods, but it turned out that it is hard to produce a high quality printer, if all the methods are spread out that far. Therefore all printing code was combined into the different printers, which works great for built-in sympy objects, but not that good for user defined classes where it is inconvenient to patch the printers. 2. **Take the best fitting method defined in the printer.** The printer loops through expr classes (class + its bases), and tries to dispatch the work to ``_print_<EXPR_CLASS>`` e.g., suppose we have the following class hierarchy:: Basic | Atom | Number | Rational then, for ``expr=Rational(...)``, the Printer will try to call printer methods in the order as shown in the figure below:: p._print(expr) | |-- p._print_Rational(expr) | |-- p._print_Number(expr) | |-- p._print_Atom(expr) | `-- p._print_Basic(expr) if ``._print_Rational`` method exists in the printer, then it is called, and the result is returned back. Otherwise, the printer tries to call ``._print_Number`` and so on. 3. **As a fall-back use the emptyPrinter method for the printer.** As fall-back ``self.emptyPrinter`` will be called with the expression. If not defined in the Printer subclass this will be the same as ``str(expr)``. .. _printer_example: Example of Custom Printer ^^^^^^^^^^^^^^^^^^^^^^^^^ In the example below, we have a printer which prints the derivative of a function in a shorter form. .. code-block:: python from sympy import Symbol from sympy.printing.latex import LatexPrinter, print_latex from sympy.core.function import UndefinedFunction, Function class MyLatexPrinter(LatexPrinter): \"\"\"Print derivative of a function of symbols in a shorter form. \"\"\" def _print_Derivative(self, expr): function, *vars = expr.args if not isinstance(type(function), UndefinedFunction) or \\ not all(isinstance(i, Symbol) for i in vars): return super()._print_Derivative(expr) # If you want the printer to work correctly for nested # expressions then use self._print() instead of str() or latex(). # See the example of nested modulo below in the custom printing # method section. return "{}_{{{}}}".format( self._print(Symbol(function.func.__name__)), ''.join(self._print(i) for i in vars)) def print_my_latex(expr): \"\"\" Most of the printers define their own wrappers for print(). These wrappers usually take printer settings. Our printer does not have any settings. \"\"\" print(MyLatexPrinter().doprint(expr)) y = Symbol("y") x = Symbol("x") f = Function("f") expr = f(x, y).diff(x, y) # Print the expression using the normal latex printer and our custom # printer. print_latex(expr) print_my_latex(expr) The output of the code above is:: \\frac{\\partial^{2}}{\\partial x\\partial y} f{\\left(x,y \\right)} f_{xy} .. _printer_method_example: Example of Custom Printing Method ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In the example below, the latex printing of the modulo operator is modified. This is done by overriding the method ``_latex`` of ``Mod``. >>> from sympy import Symbol, Mod, Integer >>> from sympy.printing.latex import print_latex >>> # Always use printer._print() >>> class ModOp(Mod): ... def _latex(self, printer): ... a, b = [printer._print(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) Comparing the output of our custom operator to the builtin one: >>> x = Symbol('x') >>> m = Symbol('m') >>> print_latex(Mod(x, m)) x\\bmod{m} >>> print_latex(ModOp(x, m)) \\operatorname{Mod}{\\left( x,m \\right)} Common mistakes ~~~~~~~~~~~~~~~ It's important to always use ``self._print(obj)`` to print subcomponents of an expression when customizing a printer. Mistakes include: 1. Using ``self.doprint(obj)`` instead: >>> # This example does not work properly, as only the outermost call may use >>> # doprint. >>> class ModOpModeWrong(Mod): ... def _latex(self, printer): ... a, b = [printer.doprint(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This fails when the `mode` argument is passed to the printer: >>> print_latex(ModOp(x, m), mode='inline') # ok $\\operatorname{Mod}{\\left( x,m \\right)}$ >>> print_latex(ModOpModeWrong(x, m), mode='inline') # bad $\\operatorname{Mod}{\\left( $x$,$m$ \\right)}$ 2. Using ``str(obj)`` instead: >>> class ModOpNestedWrong(Mod): ... def _latex(self, printer): ... a, b = [str(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This fails on nested objects: >>> # Nested modulo. >>> print_latex(ModOp(ModOp(x, m), Integer(7))) # ok \\operatorname{Mod}{\\left( \\operatorname{Mod}{\\left( x,m \\right)},7 \\right)} >>> print_latex(ModOpNestedWrong(ModOpNestedWrong(x, m), Integer(7))) # bad \\operatorname{Mod}{\\left( ModOpNestedWrong(x, m),7 \\right)} 3. Using ``LatexPrinter()._print(obj)`` instead. >>> from sympy.printing.latex import LatexPrinter >>> class ModOpSettingsWrong(Mod): ... def _latex(self, printer): ... a, b = [LatexPrinter()._print(i) for i in self.args] ... return r"\\operatorname{Mod}{\\left( %s,%s \\right)}" % (a,b) This causes all the settings to be discarded in the subobjects. As an example, the ``full_prec`` setting which shows floats to full precision is ignored: >>> from sympy import Float >>> print_latex(ModOp(Float(1) * x, m), full_prec=True) # ok \\operatorname{Mod}{\\left( 1.00000000000000 x,m \\right)} >>> print_latex(ModOpSettingsWrong(Float(1) * x, m), full_prec=True) # bad \\operatorname{Mod}{\\left( 1.0 x,m \\right)} """ from typing import Any, Dict, Type import inspect from contextlib import contextmanager from functools import cmp_to_key, update_wrapper from sympy import Basic, Add from sympy.core.core import BasicMeta from sympy.core.function import AppliedUndef, UndefinedFunction, Function @contextmanager def printer_context(printer, **kwargs): original = printer._context.copy() try: printer._context.update(kwargs) yield finally: printer._context = original class Printer: """ Generic printer Its job is to provide infrastructure for implementing new printers easily. If you want to define your custom Printer or your custom printing method for your custom class then see the example above: printer_example_ . """ _global_settings = {} # type: Dict[str, Any] _default_settings = {} # type: Dict[str, Any] printmethod = None # type: str @classmethod def _get_initial_settings(cls): settings = cls._default_settings.copy() for key, val in cls._global_settings.items(): if key in cls._default_settings: settings[key] = val return settings def __init__(self, settings=None): self._str = str self._settings = self._get_initial_settings() self._context = dict() # mutable during printing if settings is not None: self._settings.update(settings) if len(self._settings) > len(self._default_settings): for key in self._settings: if key not in self._default_settings: raise TypeError("Unknown setting '%s'." % key) # _print_level is the number of times self._print() was recursively # called. See StrPrinter._print_Float() for an example of usage self._print_level = 0 @classmethod def set_global_settings(cls, **settings): """Set system-wide printing settings. """ for key, val in settings.items(): if val is not None: cls._global_settings[key] = val @property def order(self): if 'order' in self._settings: return self._settings['order'] else: raise AttributeError("No order defined.") def doprint(self, expr): """Returns printer's representation for expr (as a string)""" return self._str(self._print(expr)) def _print(self, expr, **kwargs): """Internal dispatcher Tries the following concepts to print an expression: 1. Let the object print itself if it knows how. 2. Take the best fitting method defined in the printer. 3. As fall-back use the emptyPrinter method for the printer. """ self._print_level += 1 try: # If the printer defines a name for a printing method # (Printer.printmethod) and the object knows for itself how it # should be printed, use that method. if (self.printmethod and hasattr(expr, self.printmethod) and not isinstance(expr, BasicMeta)): return getattr(expr, self.printmethod)(self, **kwargs) # See if the class of expr is known, or if one of its super # classes is known, and use that print function # Exception: ignore the subclasses of Undefined, so that, e.g., # Function('gamma') does not get dispatched to _print_gamma classes = type(expr).__mro__ if AppliedUndef in classes: classes = classes[classes.index(AppliedUndef):] if UndefinedFunction in classes: classes = classes[classes.index(UndefinedFunction):] # Another exception: if someone subclasses a known function, e.g., # gamma, and changes the name, then ignore _print_gamma if Function in classes: i = classes.index(Function) classes = tuple(c for c in classes[:i] if \ c.__name__ == classes[0].__name__ or \ c.__name__.endswith("Base")) + classes[i:] for cls in classes: printmethod = '_print_' + cls.__name__ if hasattr(self, printmethod): return getattr(self, printmethod)(expr, **kwargs) # Unknown object, fall back to the emptyPrinter. return self.emptyPrinter(expr) finally: self._print_level -= 1 def emptyPrinter(self, expr): return str(expr) def _as_ordered_terms(self, expr, order=None): """A compatibility function for ordering terms in Add. """ order = order or self.order if order == 'old': return sorted(Add.make_args(expr), key=cmp_to_key(Basic._compare_pretty)) elif order == 'none': return list(expr.args) else: return expr.as_ordered_terms(order=order) class _PrintFunction: """ Function wrapper to replace ``**settings`` in the signature with printer defaults """ def __init__(self, f, print_cls: Type[Printer]): # find all the non-setting arguments params = list(inspect.signature(f).parameters.values()) assert params.pop(-1).kind == inspect.Parameter.VAR_KEYWORD self.__other_params = params self.__print_cls = print_cls update_wrapper(self, f) def __repr__(self) -> str: return repr(self.__wrapped__) # type:ignore def __call__(self, *args, **kwargs): return self.__wrapped__(*args, **kwargs) @property def __signature__(self) -> inspect.Signature: settings = self.__print_cls._get_initial_settings() return inspect.Signature( parameters=self.__other_params + [ inspect.Parameter(k, inspect.Parameter.KEYWORD_ONLY, default=v) for k, v in settings.items() ], return_annotation=self.__wrapped__.__annotations__.get('return', inspect.Signature.empty) # type:ignore ) def print_function(print_cls): """ A decorator to replace kwargs with the printer settings in __signature__ """ def decorator(f): return _PrintFunction(f, print_cls) return decorator

27dc6e30be2b6370cd1eece613d2cc7aae83e2bbe428f8569882ba3cfb9b7f9a

from sympy.core.containers import Tuple from types import FunctionType class TableForm: r""" Create a nice table representation of data. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]]) >>> print(t) 5 7 4 2 10 3 You can use the SymPy's printing system to produce tables in any format (ascii, latex, html, ...). >>> print(t.as_latex()) \begin{tabular}{l l} $5$ & $7$ \\ $4$ & $2$ \\ $10$ & $3$ \\ \end{tabular} """ def __init__(self, data, **kwarg): """ Creates a TableForm. Parameters: data ... 2D data to be put into the table; data can be given as a Matrix headings ... gives the labels for rows and columns: Can be a single argument that applies to both dimensions: - None ... no labels - "automatic" ... labels are 1, 2, 3, ... Can be a list of labels for rows and columns: The labels for each dimension can be given as None, "automatic", or [l1, l2, ...] e.g. ["automatic", None] will number the rows [default: None] alignments ... alignment of the columns with: - "left" or "<" - "center" or "^" - "right" or ">" When given as a single value, the value is used for all columns. The row headings (if given) will be right justified unless an explicit alignment is given for it and all other columns. [default: "left"] formats ... a list of format strings or functions that accept 3 arguments (entry, row number, col number) and return a string for the table entry. (If a function returns None then the _print method will be used.) wipe_zeros ... Don't show zeros in the table. [default: True] pad ... the string to use to indicate a missing value (e.g. elements that are None or those that are missing from the end of a row (i.e. any row that is shorter than the rest is assumed to have missing values). When None, nothing will be shown for values that are missing from the end of a row; values that are None, however, will be shown. [default: None] Examples ======== >>> from sympy import TableForm, Symbol >>> TableForm([[5, 7], [4, 2], [10, 3]]) 5 7 4 2 10 3 >>> TableForm([list('.'*i) for i in range(1, 4)], headings='automatic') | 1 2 3 --------- 1 | . 2 | . . 3 | . . . >>> TableForm([[Symbol('.'*(j if not i%2 else 1)) for i in range(3)] ... for j in range(4)], alignments='rcl') . . . . .. . .. ... . ... """ from sympy import Symbol, S, Matrix from sympy.core.sympify import SympifyError # We only support 2D data. Check the consistency: if isinstance(data, Matrix): data = data.tolist() _h = len(data) # fill out any short lines pad = kwarg.get('pad', None) ok_None = False if pad is None: pad = " " ok_None = True pad = Symbol(pad) _w = max(len(line) for line in data) for i, line in enumerate(data): if len(line) != _w: line.extend([pad]*(_w - len(line))) for j, lj in enumerate(line): if lj is None: if not ok_None: lj = pad else: try: lj = S(lj) except SympifyError: lj = Symbol(str(lj)) line[j] = lj data[i] = line _lines = Tuple(*data) headings = kwarg.get("headings", [None, None]) if headings == "automatic": _headings = [range(1, _h + 1), range(1, _w + 1)] else: h1, h2 = headings if h1 == "automatic": h1 = range(1, _h + 1) if h2 == "automatic": h2 = range(1, _w + 1) _headings = [h1, h2] allow = ('l', 'r', 'c') alignments = kwarg.get("alignments", "l") def _std_align(a): a = a.strip().lower() if len(a) > 1: return {'left': 'l', 'right': 'r', 'center': 'c'}.get(a, a) else: return {'<': 'l', '>': 'r', '^': 'c'}.get(a, a) std_align = _std_align(alignments) if std_align in allow: _alignments = [std_align]*_w else: _alignments = [] for a in alignments: std_align = _std_align(a) _alignments.append(std_align) if std_align not in ('l', 'r', 'c'): raise ValueError('alignment "%s" unrecognized' % alignments) if _headings[0] and len(_alignments) == _w + 1: _head_align = _alignments[0] _alignments = _alignments[1:] else: _head_align = 'r' if len(_alignments) != _w: raise ValueError( 'wrong number of alignments: expected %s but got %s' % (_w, len(_alignments))) _column_formats = kwarg.get("formats", [None]*_w) _wipe_zeros = kwarg.get("wipe_zeros", True) self._w = _w self._h = _h self._lines = _lines self._headings = _headings self._head_align = _head_align self._alignments = _alignments self._column_formats = _column_formats self._wipe_zeros = _wipe_zeros def __repr__(self): from .str import sstr return sstr(self, order=None) def __str__(self): from .str import sstr return sstr(self, order=None) def as_matrix(self): """Returns the data of the table in Matrix form. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]], headings='automatic') >>> t | 1 2 -------- 1 | 5 7 2 | 4 2 3 | 10 3 >>> t.as_matrix() Matrix([ [ 5, 7], [ 4, 2], [10, 3]]) """ from sympy import Matrix return Matrix(self._lines) def as_str(self): # XXX obsolete ? return str(self) def as_latex(self): from .latex import latex return latex(self) def _sympystr(self, p): """ Returns the string representation of 'self'. Examples ======== >>> from sympy import TableForm >>> t = TableForm([[5, 7], [4, 2], [10, 3]]) >>> s = t.as_str() """ column_widths = [0] * self._w lines = [] for line in self._lines: new_line = [] for i in range(self._w): # Format the item somehow if needed: s = str(line[i]) if self._wipe_zeros and (s == "0"): s = " " w = len(s) if w > column_widths[i]: column_widths[i] = w new_line.append(s) lines.append(new_line) # Check heading: if self._headings[0]: self._headings[0] = [str(x) for x in self._headings[0]] _head_width = max([len(x) for x in self._headings[0]]) if self._headings[1]: new_line = [] for i in range(self._w): # Format the item somehow if needed: s = str(self._headings[1][i]) w = len(s) if w > column_widths[i]: column_widths[i] = w new_line.append(s) self._headings[1] = new_line format_str = [] def _align(align, w): return '%%%s%ss' % ( ("-" if align == "l" else ""), str(w)) format_str = [_align(align, w) for align, w in zip(self._alignments, column_widths)] if self._headings[0]: format_str.insert(0, _align(self._head_align, _head_width)) format_str.insert(1, '|') format_str = ' '.join(format_str) + '\n' s = [] if self._headings[1]: d = self._headings[1] if self._headings[0]: d = [""] + d first_line = format_str % tuple(d) s.append(first_line) s.append("-" * (len(first_line) - 1) + "\n") for i, line in enumerate(lines): d = [l if self._alignments[j] != 'c' else l.center(column_widths[j]) for j, l in enumerate(line)] if self._headings[0]: l = self._headings[0][i] l = (l if self._head_align != 'c' else l.center(_head_width)) d = [l] + d s.append(format_str % tuple(d)) return ''.join(s)[:-1] # don't include trailing newline def _latex(self, printer): """ Returns the string representation of 'self'. """ # Check heading: if self._headings[1]: new_line = [] for i in range(self._w): # Format the item somehow if needed: new_line.append(str(self._headings[1][i])) self._headings[1] = new_line alignments = [] if self._headings[0]: self._headings[0] = [str(x) for x in self._headings[0]] alignments = [self._head_align] alignments.extend(self._alignments) s = r"\begin{tabular}{" + " ".join(alignments) + "}\n" if self._headings[1]: d = self._headings[1] if self._headings[0]: d = [""] + d first_line = " & ".join(d) + r" \\" + "\n" s += first_line s += r"\hline" + "\n" for i, line in enumerate(self._lines): d = [] for j, x in enumerate(line): if self._wipe_zeros and (x in (0, "0")): d.append(" ") continue f = self._column_formats[j] if f: if isinstance(f, FunctionType): v = f(x, i, j) if v is None: v = printer._print(x) else: v = f % x d.append(v) else: v = printer._print(x) d.append("$%s$" % v) if self._headings[0]: d = [self._headings[0][i]] + d s += " & ".join(d) + r" \\" + "\n" s += r"\end{tabular}" return s

b1d1f05f9d617f22ecc79254ccc8b7d1b06f6e1c1f8c62d34e38ebc1f6858667

""" C code printer The C89CodePrinter & C99CodePrinter converts single sympy expressions into single C expressions, using the functions defined in math.h where possible. A complete code generator, which uses ccode extensively, can be found in sympy.utilities.codegen. The codegen module can be used to generate complete source code files that are compilable without further modifications. """ from typing import Any, Dict, Tuple from functools import wraps from itertools import chain from sympy.core import S from sympy.codegen.ast import ( Assignment, Pointer, Variable, Declaration, Type, real, complex_, integer, bool_, float32, float64, float80, complex64, complex128, intc, value_const, pointer_const, int8, int16, int32, int64, uint8, uint16, uint32, uint64, untyped, none ) from sympy.printing.codeprinter import CodePrinter, requires from sympy.printing.precedence import precedence, PRECEDENCE from sympy.sets.fancysets import Range # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import ccode, print_ccode # noqa:F401 # dictionary mapping sympy function to (argument_conditions, C_function). # Used in C89CodePrinter._print_Function(self) known_functions_C89 = { "Abs": [(lambda x: not x.is_integer, "fabs"), (lambda x: x.is_integer, "abs")], "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", "exp": "exp", "log": "log", "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "floor": "floor", "ceiling": "ceil", } known_functions_C99 = dict(known_functions_C89, **{ 'exp2': 'exp2', 'expm1': 'expm1', 'log10': 'log10', 'log2': 'log2', 'log1p': 'log1p', 'Cbrt': 'cbrt', 'hypot': 'hypot', 'fma': 'fma', 'loggamma': 'lgamma', 'erfc': 'erfc', 'Max': 'fmax', 'Min': 'fmin', "asinh": "asinh", "acosh": "acosh", "atanh": "atanh", "erf": "erf", "gamma": "tgamma", }) # These are the core reserved words in the C language. Taken from: # http://en.cppreference.com/w/c/keyword reserved_words = [ 'auto', 'break', 'case', 'char', 'const', 'continue', 'default', 'do', 'double', 'else', 'enum', 'extern', 'float', 'for', 'goto', 'if', 'int', 'long', 'register', 'return', 'short', 'signed', 'sizeof', 'static', 'struct', 'entry', # never standardized, we'll leave it here anyway 'switch', 'typedef', 'union', 'unsigned', 'void', 'volatile', 'while' ] reserved_words_c99 = ['inline', 'restrict'] def get_math_macros(): """ Returns a dictionary with math-related macros from math.h/cmath Note that these macros are not strictly required by the C/C++-standard. For MSVC they are enabled by defining "_USE_MATH_DEFINES" (preferably via a compilation flag). Returns ======= Dictionary mapping sympy expressions to strings (macro names) """ from sympy.codegen.cfunctions import log2, Sqrt from sympy.functions.elementary.exponential import log from sympy.functions.elementary.miscellaneous import sqrt return { S.Exp1: 'M_E', log2(S.Exp1): 'M_LOG2E', 1/log(2): 'M_LOG2E', log(2): 'M_LN2', log(10): 'M_LN10', S.Pi: 'M_PI', S.Pi/2: 'M_PI_2', S.Pi/4: 'M_PI_4', 1/S.Pi: 'M_1_PI', 2/S.Pi: 'M_2_PI', 2/sqrt(S.Pi): 'M_2_SQRTPI', 2/Sqrt(S.Pi): 'M_2_SQRTPI', sqrt(2): 'M_SQRT2', Sqrt(2): 'M_SQRT2', 1/sqrt(2): 'M_SQRT1_2', 1/Sqrt(2): 'M_SQRT1_2' } def _as_macro_if_defined(meth): """ Decorator for printer methods When a Printer's method is decorated using this decorator the expressions printed will first be looked for in the attribute ``math_macros``, and if present it will print the macro name in ``math_macros`` followed by a type suffix for the type ``real``. e.g. printing ``sympy.pi`` would print ``M_PIl`` if real is mapped to float80. """ @wraps(meth) def _meth_wrapper(self, expr, **kwargs): if expr in self.math_macros: return '%s%s' % (self.math_macros[expr], self._get_math_macro_suffix(real)) else: return meth(self, expr, **kwargs) return _meth_wrapper class C89CodePrinter(CodePrinter): """A printer to convert python expressions to strings of c code""" printmethod = "_ccode" language = "C" standard = "C89" reserved_words = set(reserved_words) _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, 'contract': True, 'dereference': set(), 'error_on_reserved': False, 'reserved_word_suffix': '_', } # type: Dict[str, Any] type_aliases = { real: float64, complex_: complex128, integer: intc } type_mappings = { real: 'double', intc: 'int', float32: 'float', float64: 'double', integer: 'int', bool_: 'bool', int8: 'int8_t', int16: 'int16_t', int32: 'int32_t', int64: 'int64_t', uint8: 'int8_t', uint16: 'int16_t', uint32: 'int32_t', uint64: 'int64_t', } # type: Dict[Type, Any] type_headers = { bool_: {'stdbool.h'}, int8: {'stdint.h'}, int16: {'stdint.h'}, int32: {'stdint.h'}, int64: {'stdint.h'}, uint8: {'stdint.h'}, uint16: {'stdint.h'}, uint32: {'stdint.h'}, uint64: {'stdint.h'}, } # Macros needed to be defined when using a Type type_macros = {} # type: Dict[Type, Tuple[str, ...]] type_func_suffixes = { float32: 'f', float64: '', float80: 'l' } type_literal_suffixes = { float32: 'F', float64: '', float80: 'L' } type_math_macro_suffixes = { float80: 'l' } math_macros = None _ns = '' # namespace, C++ uses 'std::' # known_functions-dict to copy _kf = known_functions_C89 # type: Dict[str, Any] def __init__(self, settings=None): settings = settings or {} if self.math_macros is None: self.math_macros = settings.pop('math_macros', get_math_macros()) self.type_aliases = dict(chain(self.type_aliases.items(), settings.pop('type_aliases', {}).items())) self.type_mappings = dict(chain(self.type_mappings.items(), settings.pop('type_mappings', {}).items())) self.type_headers = dict(chain(self.type_headers.items(), settings.pop('type_headers', {}).items())) self.type_macros = dict(chain(self.type_macros.items(), settings.pop('type_macros', {}).items())) self.type_func_suffixes = dict(chain(self.type_func_suffixes.items(), settings.pop('type_func_suffixes', {}).items())) self.type_literal_suffixes = dict(chain(self.type_literal_suffixes.items(), settings.pop('type_literal_suffixes', {}).items())) self.type_math_macro_suffixes = dict(chain(self.type_math_macro_suffixes.items(), settings.pop('type_math_macro_suffixes', {}).items())) super().__init__(settings) self.known_functions = dict(self._kf, **settings.get('user_functions', {})) self._dereference = set(settings.get('dereference', [])) self.headers = set() self.libraries = set() self.macros = set() def _rate_index_position(self, p): return p*5 def _get_statement(self, codestring): """ Get code string as a statement - i.e. ending with a semicolon. """ return codestring if codestring.endswith(';') else codestring + ';' def _get_comment(self, text): return "// {}".format(text) def _declare_number_const(self, name, value): type_ = self.type_aliases[real] var = Variable(name, type=type_, value=value.evalf(type_.decimal_dig), attrs={value_const}) decl = Declaration(var) return self._get_statement(self._print(decl)) def _format_code(self, lines): return self.indent_code(lines) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for i in range(rows) for j in range(cols)) @_as_macro_if_defined def _print_Mul(self, expr, **kwargs): return super()._print_Mul(expr, **kwargs) @_as_macro_if_defined def _print_Pow(self, expr): if "Pow" in self.known_functions: return self._print_Function(expr) PREC = precedence(expr) suffix = self._get_func_suffix(real) if expr.exp == -1: literal_suffix = self._get_literal_suffix(real) return '1.0%s/%s' % (literal_suffix, self.parenthesize(expr.base, PREC)) elif expr.exp == 0.5: return '%ssqrt%s(%s)' % (self._ns, suffix, self._print(expr.base)) elif expr.exp == S.One/3 and self.standard != 'C89': return '%scbrt%s(%s)' % (self._ns, suffix, self._print(expr.base)) else: return '%spow%s(%s, %s)' % (self._ns, suffix, self._print(expr.base), self._print(expr.exp)) def _print_Mod(self, expr): num, den = expr.args if num.is_integer and den.is_integer: return "(({}) % ({}))".format(self._print(num), self._print(den)) else: return self._print_math_func(expr, known='fmod') def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) suffix = self._get_literal_suffix(real) return '%d.0%s/%d.0%s' % (p, suffix, q, suffix) def _print_Indexed(self, expr): # calculate index for 1d array offset = getattr(expr.base, 'offset', S.Zero) strides = getattr(expr.base, 'strides', None) indices = expr.indices if strides is None or isinstance(strides, str): dims = expr.shape shift = S.One temp = tuple() if strides == 'C' or strides is None: traversal = reversed(range(expr.rank)) indices = indices[::-1] elif strides == 'F': traversal = range(expr.rank) for i in traversal: temp += (shift,) shift *= dims[i] strides = temp flat_index = sum([x[0]*x[1] for x in zip(indices, strides)]) + offset return "%s[%s]" % (self._print(expr.base.label), self._print(flat_index)) def _print_Idx(self, expr): return self._print(expr.label) @_as_macro_if_defined def _print_NumberSymbol(self, expr): return super()._print_NumberSymbol(expr) def _print_Infinity(self, expr): return 'HUGE_VAL' def _print_NegativeInfinity(self, expr): return '-HUGE_VAL' def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] if expr.has(Assignment): for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) {" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines.append("else {") else: lines.append("else if (%s) {" % self._print(c)) code0 = self._print(e) lines.append(code0) lines.append("}") return "\n".join(lines) else: # The piecewise was used in an expression, need to do inline # operators. This has the downside that inline operators will # not work for statements that span multiple lines (Matrix or # Indexed expressions). ecpairs = ["((%s) ? (\n%s\n)\n" % (self._print(c), self._print(e)) for e, c in expr.args[:-1]] last_line = ": (\n%s\n)" % self._print(expr.args[-1].expr) return ": ".join(ecpairs) + last_line + " ".join([")"*len(ecpairs)]) def _print_ITE(self, expr): from sympy.functions import Piecewise _piecewise = Piecewise((expr.args[1], expr.args[0]), (expr.args[2], True)) return self._print(_piecewise) def _print_MatrixElement(self, expr): return "{}[{}]".format(self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True), expr.j + expr.i*expr.parent.shape[1]) def _print_Symbol(self, expr): name = super()._print_Symbol(expr) if expr in self._settings['dereference']: return '(*{})'.format(name) else: return name def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) def _print_sinc(self, expr): from sympy.functions.elementary.trigonometric import sin from sympy.core.relational import Ne from sympy.functions import Piecewise _piecewise = Piecewise( (sin(expr.args[0]) / expr.args[0], Ne(expr.args[0], 0)), (1, True)) return self._print(_piecewise) def _print_For(self, expr): target = self._print(expr.target) if isinstance(expr.iterable, Range): start, stop, step = expr.iterable.args else: raise NotImplementedError("Only iterable currently supported is Range") body = self._print(expr.body) return ('for ({target} = {start}; {target} < {stop}; {target} += ' '{step}) {{\n{body}\n}}').format(target=target, start=start, stop=stop, step=step, body=body) def _print_sign(self, func): return '((({0}) > 0) - (({0}) < 0))'.format(self._print(func.args[0])) def _print_Max(self, expr): if "Max" in self.known_functions: return self._print_Function(expr) def inner_print_max(args): # The more natural abstraction of creating if len(args) == 1: # and printing smaller Max objects is slow return self._print(args[0]) # when there are many arguments. half = len(args) // 2 return "((%(a)s > %(b)s) ? %(a)s : %(b)s)" % { 'a': inner_print_max(args[:half]), 'b': inner_print_max(args[half:]) } return inner_print_max(expr.args) def _print_Min(self, expr): if "Min" in self.known_functions: return self._print_Function(expr) def inner_print_min(args): # The more natural abstraction of creating if len(args) == 1: # and printing smaller Min objects is slow return self._print(args[0]) # when there are many arguments. half = len(args) // 2 return "((%(a)s < %(b)s) ? %(a)s : %(b)s)" % { 'a': inner_print_min(args[:half]), 'b': inner_print_min(args[half:]) } return inner_print_min(expr.args) def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) tab = " " inc_token = ('{', '(', '{\n', '(\n') dec_token = ('}', ')') code = [line.lstrip(' \t') for line in code] increase = [int(any(map(line.endswith, inc_token))) for line in code] decrease = [int(any(map(line.startswith, dec_token))) for line in code] pretty = [] level = 0 for n, line in enumerate(code): if line == '' or line == '\n': pretty.append(line) continue level -= decrease[n] pretty.append("%s%s" % (tab*level, line)) level += increase[n] return pretty def _get_func_suffix(self, type_): return self.type_func_suffixes[self.type_aliases.get(type_, type_)] def _get_literal_suffix(self, type_): return self.type_literal_suffixes[self.type_aliases.get(type_, type_)] def _get_math_macro_suffix(self, type_): alias = self.type_aliases.get(type_, type_) dflt = self.type_math_macro_suffixes.get(alias, '') return self.type_math_macro_suffixes.get(type_, dflt) def _print_Type(self, type_): self.headers.update(self.type_headers.get(type_, set())) self.macros.update(self.type_macros.get(type_, set())) return self._print(self.type_mappings.get(type_, type_.name)) def _print_Declaration(self, decl): from sympy.codegen.cnodes import restrict var = decl.variable val = var.value if var.type == untyped: raise ValueError("C does not support untyped variables") if isinstance(var, Pointer): result = '{vc}{t} *{pc} {r}{s}'.format( vc='const ' if value_const in var.attrs else '', t=self._print(var.type), pc=' const' if pointer_const in var.attrs else '', r='restrict ' if restrict in var.attrs else '', s=self._print(var.symbol) ) elif isinstance(var, Variable): result = '{vc}{t} {s}'.format( vc='const ' if value_const in var.attrs else '', t=self._print(var.type), s=self._print(var.symbol) ) else: raise NotImplementedError("Unknown type of var: %s" % type(var)) if val != None: # Must be "!= None", cannot be "is not None" result += ' = %s' % self._print(val) return result def _print_Float(self, flt): type_ = self.type_aliases.get(real, real) self.macros.update(self.type_macros.get(type_, set())) suffix = self._get_literal_suffix(type_) num = str(flt.evalf(type_.decimal_dig)) if 'e' not in num and '.' not in num: num += '.0' num_parts = num.split('e') num_parts[0] = num_parts[0].rstrip('0') if num_parts[0].endswith('.'): num_parts[0] += '0' return 'e'.join(num_parts) + suffix @requires(headers={'stdbool.h'}) def _print_BooleanTrue(self, expr): return 'true' @requires(headers={'stdbool.h'}) def _print_BooleanFalse(self, expr): return 'false' def _print_Element(self, elem): if elem.strides == None: # Must be "== None", cannot be "is None" if elem.offset != None: # Must be "!= None", cannot be "is not None" raise ValueError("Expected strides when offset is given") idxs = ']['.join(map(lambda arg: self._print(arg), elem.indices)) else: global_idx = sum([i*s for i, s in zip(elem.indices, elem.strides)]) if elem.offset != None: # Must be "!= None", cannot be "is not None" global_idx += elem.offset idxs = self._print(global_idx) return "{symb}[{idxs}]".format( symb=self._print(elem.symbol), idxs=idxs ) def _print_CodeBlock(self, expr): """ Elements of code blocks printed as statements. """ return '\n'.join([self._get_statement(self._print(i)) for i in expr.args]) def _print_While(self, expr): return 'while ({condition}) {{\n{body}\n}}'.format(**expr.kwargs( apply=lambda arg: self._print(arg))) def _print_Scope(self, expr): return '{\n%s\n}' % self._print_CodeBlock(expr.body) @requires(headers={'stdio.h'}) def _print_Print(self, expr): return 'printf({fmt}, {pargs})'.format( fmt=self._print(expr.format_string), pargs=', '.join(map(lambda arg: self._print(arg), expr.print_args)) ) def _print_FunctionPrototype(self, expr): pars = ', '.join(map(lambda arg: self._print(Declaration(arg)), expr.parameters)) return "%s %s(%s)" % ( tuple(map(lambda arg: self._print(arg), (expr.return_type, expr.name))) + (pars,) ) def _print_FunctionDefinition(self, expr): return "%s%s" % (self._print_FunctionPrototype(expr), self._print_Scope(expr)) def _print_Return(self, expr): arg, = expr.args return 'return %s' % self._print(arg) def _print_CommaOperator(self, expr): return '(%s)' % ', '.join(map(lambda arg: self._print(arg), expr.args)) def _print_Label(self, expr): if expr.body == none: return '%s:' % str(expr.name) if len(expr.body.args) == 1: return '%s:\n%s' % (str(expr.name), self._print_CodeBlock(expr.body)) return '%s:\n{\n%s\n}' % (str(expr.name), self._print_CodeBlock(expr.body)) def _print_goto(self, expr): return 'goto %s' % expr.label.name def _print_PreIncrement(self, expr): arg, = expr.args return '++(%s)' % self._print(arg) def _print_PostIncrement(self, expr): arg, = expr.args return '(%s)++' % self._print(arg) def _print_PreDecrement(self, expr): arg, = expr.args return '--(%s)' % self._print(arg) def _print_PostDecrement(self, expr): arg, = expr.args return '(%s)--' % self._print(arg) def _print_struct(self, expr): return "%(keyword)s %(name)s {\n%(lines)s}" % dict( keyword=expr.__class__.__name__, name=expr.name, lines=';\n'.join( [self._print(decl) for decl in expr.declarations] + ['']) ) def _print_BreakToken(self, _): return 'break' def _print_ContinueToken(self, _): return 'continue' _print_union = _print_struct class C99CodePrinter(C89CodePrinter): standard = 'C99' reserved_words = set(reserved_words + reserved_words_c99) type_mappings=dict(chain(C89CodePrinter.type_mappings.items(), { complex64: 'float complex', complex128: 'double complex', }.items())) type_headers = dict(chain(C89CodePrinter.type_headers.items(), { complex64: {'complex.h'}, complex128: {'complex.h'} }.items())) # known_functions-dict to copy _kf = known_functions_C99 # type: Dict[str, Any] # functions with versions with 'f' and 'l' suffixes: _prec_funcs = ('fabs fmod remainder remquo fma fmax fmin fdim nan exp exp2' ' expm1 log log10 log2 log1p pow sqrt cbrt hypot sin cos tan' ' asin acos atan atan2 sinh cosh tanh asinh acosh atanh erf' ' erfc tgamma lgamma ceil floor trunc round nearbyint rint' ' frexp ldexp modf scalbn ilogb logb nextafter copysign').split() def _print_Infinity(self, expr): return 'INFINITY' def _print_NegativeInfinity(self, expr): return '-INFINITY' def _print_NaN(self, expr): return 'NAN' # tgamma was already covered by 'known_functions' dict @requires(headers={'math.h'}, libraries={'m'}) @_as_macro_if_defined def _print_math_func(self, expr, nest=False, known=None): if known is None: known = self.known_functions[expr.__class__.__name__] if not isinstance(known, str): for cb, name in known: if cb(*expr.args): known = name break else: raise ValueError("No matching printer") try: return known(self, *expr.args) except TypeError: suffix = self._get_func_suffix(real) if self._ns + known in self._prec_funcs else '' if nest: args = self._print(expr.args[0]) if len(expr.args) > 1: paren_pile = '' for curr_arg in expr.args[1:-1]: paren_pile += ')' args += ', {ns}{name}{suffix}({next}'.format( ns=self._ns, name=known, suffix=suffix, next = self._print(curr_arg) ) args += ', %s%s' % ( self._print(expr.func(expr.args[-1])), paren_pile ) else: args = ', '.join(map(lambda arg: self._print(arg), expr.args)) return '{ns}{name}{suffix}({args})'.format( ns=self._ns, name=known, suffix=suffix, args=args ) def _print_Max(self, expr): return self._print_math_func(expr, nest=True) def _print_Min(self, expr): return self._print_math_func(expr, nest=True) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] loopstart = "for (int %(var)s=%(start)s; %(var)s<%(end)s; %(var)s++){" # C99 for i in indices: # C arrays start at 0 and end at dimension-1 open_lines.append(loopstart % { 'var': self._print(i.label), 'start': self._print(i.lower), 'end': self._print(i.upper + 1)}) close_lines.append("}") return open_lines, close_lines for k in ('Abs Sqrt exp exp2 expm1 log log10 log2 log1p Cbrt hypot fma' ' loggamma sin cos tan asin acos atan atan2 sinh cosh tanh asinh acosh ' 'atanh erf erfc loggamma gamma ceiling floor').split(): setattr(C99CodePrinter, '_print_%s' % k, C99CodePrinter._print_math_func) class C11CodePrinter(C99CodePrinter): @requires(headers={'stdalign.h'}) def _print_alignof(self, expr): arg, = expr.args return 'alignof(%s)' % self._print(arg) c_code_printers = { 'c89': C89CodePrinter, 'c99': C99CodePrinter, 'c11': C11CodePrinter }

7a26db2a5cd10577fbe4e1bb04202e46545654d23dcdd57393af4fff8a7d9a0d

from .pycode import ( PythonCodePrinter, MpmathPrinter, # MpmathPrinter is imported for backward compatibility NumPyPrinter # NumPyPrinter is imported for backward compatibility ) from sympy.utilities import default_sort_key __all__ = [ 'PythonCodePrinter', 'MpmathPrinter', 'NumPyPrinter', 'LambdaPrinter', 'NumPyPrinter', 'lambdarepr', ] class LambdaPrinter(PythonCodePrinter): """ This printer converts expressions into strings that can be used by lambdify. """ printmethod = "_lambdacode" def _print_And(self, expr): result = ['('] for arg in sorted(expr.args, key=default_sort_key): result.extend(['(', self._print(arg), ')']) result.append(' and ') result = result[:-1] result.append(')') return ''.join(result) def _print_Or(self, expr): result = ['('] for arg in sorted(expr.args, key=default_sort_key): result.extend(['(', self._print(arg), ')']) result.append(' or ') result = result[:-1] result.append(')') return ''.join(result) def _print_Not(self, expr): result = ['(', 'not (', self._print(expr.args[0]), '))'] return ''.join(result) def _print_BooleanTrue(self, expr): return "True" def _print_BooleanFalse(self, expr): return "False" def _print_ITE(self, expr): result = [ '((', self._print(expr.args[1]), ') if (', self._print(expr.args[0]), ') else (', self._print(expr.args[2]), '))' ] return ''.join(result) def _print_NumberSymbol(self, expr): return str(expr) def _print_Pow(self, expr, **kwargs): # XXX Temporary workaround. Should python math printer be # isolated from PythonCodePrinter? return super(PythonCodePrinter, self)._print_Pow(expr, **kwargs) # numexpr works by altering the string passed to numexpr.evaluate # rather than by populating a namespace. Thus a special printer... class NumExprPrinter(LambdaPrinter): # key, value pairs correspond to sympy name and numexpr name # functions not appearing in this dict will raise a TypeError printmethod = "_numexprcode" _numexpr_functions = { 'sin' : 'sin', 'cos' : 'cos', 'tan' : 'tan', 'asin': 'arcsin', 'acos': 'arccos', 'atan': 'arctan', 'atan2' : 'arctan2', 'sinh' : 'sinh', 'cosh' : 'cosh', 'tanh' : 'tanh', 'asinh': 'arcsinh', 'acosh': 'arccosh', 'atanh': 'arctanh', 'ln' : 'log', 'log': 'log', 'exp': 'exp', 'sqrt' : 'sqrt', 'Abs' : 'abs', 'conjugate' : 'conj', 'im' : 'imag', 're' : 'real', 'where' : 'where', 'complex' : 'complex', 'contains' : 'contains', } def _print_ImaginaryUnit(self, expr): return '1j' def _print_seq(self, seq, delimiter=', '): # simplified _print_seq taken from pretty.py s = [self._print(item) for item in seq] if s: return delimiter.join(s) else: return "" def _print_Function(self, e): func_name = e.func.__name__ nstr = self._numexpr_functions.get(func_name, None) if nstr is None: # check for implemented_function if hasattr(e, '_imp_'): return "(%s)" % self._print(e._imp_(*e.args)) else: raise TypeError("numexpr does not support function '%s'" % func_name) return "%s(%s)" % (nstr, self._print_seq(e.args)) def _print_Piecewise(self, expr): "Piecewise function printer" exprs = [self._print(arg.expr) for arg in expr.args] conds = [self._print(arg.cond) for arg in expr.args] # If [default_value, True] is a (expr, cond) sequence in a Piecewise object # it will behave the same as passing the 'default' kwarg to select() # *as long as* it is the last element in expr.args. # If this is not the case, it may be triggered prematurely. ans = [] parenthesis_count = 0 is_last_cond_True = False for cond, expr in zip(conds, exprs): if cond == 'True': ans.append(expr) is_last_cond_True = True break else: ans.append('where(%s, %s, ' % (cond, expr)) parenthesis_count += 1 if not is_last_cond_True: # simplest way to put a nan but raises # 'RuntimeWarning: invalid value encountered in log' ans.append('log(-1)') return ''.join(ans) + ')' * parenthesis_count def blacklisted(self, expr): raise TypeError("numexpr cannot be used with %s" % expr.__class__.__name__) # blacklist all Matrix printing _print_SparseMatrix = \ _print_MutableSparseMatrix = \ _print_ImmutableSparseMatrix = \ _print_Matrix = \ _print_DenseMatrix = \ _print_MutableDenseMatrix = \ _print_ImmutableMatrix = \ _print_ImmutableDenseMatrix = \ blacklisted # blacklist some python expressions _print_list = \ _print_tuple = \ _print_Tuple = \ _print_dict = \ _print_Dict = \ blacklisted def doprint(self, expr): lstr = super().doprint(expr) return "evaluate('%s', truediv=True)" % lstr for k in NumExprPrinter._numexpr_functions: setattr(NumExprPrinter, '_print_%s' % k, NumExprPrinter._print_Function) def lambdarepr(expr, **settings): """ Returns a string usable for lambdifying. """ return LambdaPrinter(settings).doprint(expr)

b446d20e585feb73df58019aa6d696abfc62d6fe5ab2a73a72dd820b2a82ccc8

""" Mathematica code printer """ from typing import Any, Dict, Set, Tuple from sympy.core import Basic, Expr, Float from sympy.printing.codeprinter import CodePrinter from sympy.printing.precedence import precedence # Used in MCodePrinter._print_Function(self) known_functions = { "exp": [(lambda x: True, "Exp")], "log": [(lambda x: True, "Log")], "sin": [(lambda x: True, "Sin")], "cos": [(lambda x: True, "Cos")], "tan": [(lambda x: True, "Tan")], "cot": [(lambda x: True, "Cot")], "sec": [(lambda x: True, "Sec")], "csc": [(lambda x: True, "Csc")], "asin": [(lambda x: True, "ArcSin")], "acos": [(lambda x: True, "ArcCos")], "atan": [(lambda x: True, "ArcTan")], "acot": [(lambda x: True, "ArcCot")], "asec": [(lambda x: True, "ArcSec")], "acsc": [(lambda x: True, "ArcCsc")], "atan2": [(lambda *x: True, "ArcTan")], "sinh": [(lambda x: True, "Sinh")], "cosh": [(lambda x: True, "Cosh")], "tanh": [(lambda x: True, "Tanh")], "coth": [(lambda x: True, "Coth")], "sech": [(lambda x: True, "Sech")], "csch": [(lambda x: True, "Csch")], "asinh": [(lambda x: True, "ArcSinh")], "acosh": [(lambda x: True, "ArcCosh")], "atanh": [(lambda x: True, "ArcTanh")], "acoth": [(lambda x: True, "ArcCoth")], "asech": [(lambda x: True, "ArcSech")], "acsch": [(lambda x: True, "ArcCsch")], "conjugate": [(lambda x: True, "Conjugate")], "Max": [(lambda *x: True, "Max")], "Min": [(lambda *x: True, "Min")], "erf": [(lambda x: True, "Erf")], "erf2": [(lambda *x: True, "Erf")], "erfc": [(lambda x: True, "Erfc")], "erfi": [(lambda x: True, "Erfi")], "erfinv": [(lambda x: True, "InverseErf")], "erfcinv": [(lambda x: True, "InverseErfc")], "erf2inv": [(lambda *x: True, "InverseErf")], "expint": [(lambda *x: True, "ExpIntegralE")], "Ei": [(lambda x: True, "ExpIntegralEi")], "fresnelc": [(lambda x: True, "FresnelC")], "fresnels": [(lambda x: True, "FresnelS")], "gamma": [(lambda x: True, "Gamma")], "uppergamma": [(lambda *x: True, "Gamma")], "polygamma": [(lambda *x: True, "PolyGamma")], "loggamma": [(lambda x: True, "LogGamma")], "beta": [(lambda *x: True, "Beta")], "Ci": [(lambda x: True, "CosIntegral")], "Si": [(lambda x: True, "SinIntegral")], "Chi": [(lambda x: True, "CoshIntegral")], "Shi": [(lambda x: True, "SinhIntegral")], "li": [(lambda x: True, "LogIntegral")], "factorial": [(lambda x: True, "Factorial")], "factorial2": [(lambda x: True, "Factorial2")], "subfactorial": [(lambda x: True, "Subfactorial")], "catalan": [(lambda x: True, "CatalanNumber")], "harmonic": [(lambda *x: True, "HarmonicNumber")], "RisingFactorial": [(lambda *x: True, "Pochhammer")], "FallingFactorial": [(lambda *x: True, "FactorialPower")], "laguerre": [(lambda *x: True, "LaguerreL")], "assoc_laguerre": [(lambda *x: True, "LaguerreL")], "hermite": [(lambda *x: True, "HermiteH")], "jacobi": [(lambda *x: True, "JacobiP")], "gegenbauer": [(lambda *x: True, "GegenbauerC")], "chebyshevt": [(lambda *x: True, "ChebyshevT")], "chebyshevu": [(lambda *x: True, "ChebyshevU")], "legendre": [(lambda *x: True, "LegendreP")], "assoc_legendre": [(lambda *x: True, "LegendreP")], "mathieuc": [(lambda *x: True, "MathieuC")], "mathieus": [(lambda *x: True, "MathieuS")], "mathieucprime": [(lambda *x: True, "MathieuCPrime")], "mathieusprime": [(lambda *x: True, "MathieuSPrime")], "stieltjes": [(lambda x: True, "StieltjesGamma")], "elliptic_e": [(lambda *x: True, "EllipticE")], "elliptic_f": [(lambda *x: True, "EllipticE")], "elliptic_k": [(lambda x: True, "EllipticK")], "elliptic_pi": [(lambda *x: True, "EllipticPi")], "zeta": [(lambda *x: True, "Zeta")], "besseli": [(lambda *x: True, "BesselI")], "besselj": [(lambda *x: True, "BesselJ")], "besselk": [(lambda *x: True, "BesselK")], "bessely": [(lambda *x: True, "BesselY")], "hankel1": [(lambda *x: True, "HankelH1")], "hankel2": [(lambda *x: True, "HankelH2")], "airyai": [(lambda x: True, "AiryAi")], "airybi": [(lambda x: True, "AiryBi")], "airyaiprime": [(lambda x: True, "AiryAiPrime")], "airybiprime": [(lambda x: True, "AiryBiPrime")], "polylog": [(lambda *x: True, "PolyLog")], "lerchphi": [(lambda *x: True, "LerchPhi")], "gcd": [(lambda *x: True, "GCD")], "lcm": [(lambda *x: True, "LCM")], "jn": [(lambda *x: True, "SphericalBesselJ")], "yn": [(lambda *x: True, "SphericalBesselY")], "hyper": [(lambda *x: True, "HypergeometricPFQ")], "meijerg": [(lambda *x: True, "MeijerG")], "appellf1": [(lambda *x: True, "AppellF1")], "DiracDelta": [(lambda x: True, "DiracDelta")], "Heaviside": [(lambda x: True, "HeavisideTheta")], "KroneckerDelta": [(lambda *x: True, "KroneckerDelta")], } class MCodePrinter(CodePrinter): """A printer to convert python expressions to strings of the Wolfram's Mathematica code """ printmethod = "_mcode" language = "Wolfram Language" _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 15, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, } # type: Dict[str, Any] _number_symbols = set() # type: Set[Tuple[Expr, Float]] _not_supported = set() # type: Set[Basic] def __init__(self, settings={}): """Register function mappings supplied by user""" CodePrinter.__init__(self, settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}).copy() for k, v in userfuncs.items(): if not isinstance(v, list): userfuncs[k] = [(lambda *x: True, v)] self.known_functions.update(userfuncs) def _format_code(self, lines): return lines def _print_Pow(self, expr): PREC = precedence(expr) return '%s^%s' % (self.parenthesize(expr.base, PREC), self.parenthesize(expr.exp, PREC)) def _print_Mul(self, expr): PREC = precedence(expr) c, nc = expr.args_cnc() res = super()._print_Mul(expr.func(*c)) if nc: res += '*' res += '**'.join(self.parenthesize(a, PREC) for a in nc) return res def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op return "{} {} {}".format(lhs_code, op, rhs_code) # Primitive numbers def _print_Zero(self, expr): return '0' def _print_One(self, expr): return '1' def _print_NegativeOne(self, expr): return '-1' def _print_Half(self, expr): return '1/2' def _print_ImaginaryUnit(self, expr): return 'I' # Infinity and invalid numbers def _print_Infinity(self, expr): return 'Infinity' def _print_NegativeInfinity(self, expr): return '-Infinity' def _print_ComplexInfinity(self, expr): return 'ComplexInfinity' def _print_NaN(self, expr): return 'Indeterminate' # Mathematical constants def _print_Exp1(self, expr): return 'E' def _print_Pi(self, expr): return 'Pi' def _print_GoldenRatio(self, expr): return 'GoldenRatio' def _print_TribonacciConstant(self, expr): expanded = expr.expand(func=True) PREC = precedence(expr) return self.parenthesize(expanded, PREC) def _print_EulerGamma(self, expr): return 'EulerGamma' def _print_Catalan(self, expr): return 'Catalan' def _print_list(self, expr): return '{' + ', '.join(self.doprint(a) for a in expr) + '}' _print_tuple = _print_list _print_Tuple = _print_list def _print_ImmutableDenseMatrix(self, expr): return self.doprint(expr.tolist()) def _print_ImmutableSparseMatrix(self, expr): from sympy.core.compatibility import default_sort_key def print_rule(pos, val): return '{} -> {}'.format( self.doprint((pos[0]+1, pos[1]+1)), self.doprint(val)) def print_data(): items = sorted(expr._smat.items(), key=default_sort_key) return '{' + \ ', '.join(print_rule(k, v) for k, v in items) + \ '}' def print_dims(): return self.doprint(expr.shape) return 'SparseArray[{}, {}]'.format(print_data(), print_dims()) def _print_ImmutableDenseNDimArray(self, expr): return self.doprint(expr.tolist()) def _print_ImmutableSparseNDimArray(self, expr): def print_string_list(string_list): return '{' + ', '.join(a for a in string_list) + '}' def to_mathematica_index(*args): """Helper function to change Python style indexing to Pathematica indexing. Python indexing (0, 1 ... n-1) -> Mathematica indexing (1, 2 ... n) """ return tuple(i + 1 for i in args) def print_rule(pos, val): """Helper function to print a rule of Mathematica""" return '{} -> {}'.format(self.doprint(pos), self.doprint(val)) def print_data(): """Helper function to print data part of Mathematica sparse array. It uses the fourth notation ``SparseArray[data,{d1,d2,...}]`` from https://reference.wolfram.com/language/ref/SparseArray.html ``data`` must be formatted with rule. """ return print_string_list( [print_rule( to_mathematica_index(*(expr._get_tuple_index(key))), value) for key, value in sorted(expr._sparse_array.items())] ) def print_dims(): """Helper function to print dimensions part of Mathematica sparse array. It uses the fourth notation ``SparseArray[data,{d1,d2,...}]`` from https://reference.wolfram.com/language/ref/SparseArray.html """ return self.doprint(expr.shape) return 'SparseArray[{}, {}]'.format(print_data(), print_dims()) def _print_Function(self, expr): if expr.func.__name__ in self.known_functions: cond_mfunc = self.known_functions[expr.func.__name__] for cond, mfunc in cond_mfunc: if cond(*expr.args): return "%s[%s]" % (mfunc, self.stringify(expr.args, ", ")) elif (expr.func.__name__ in self._rewriteable_functions and self._rewriteable_functions[expr.func.__name__] in self.known_functions): # Simple rewrite to supported function possible return self._print(expr.rewrite(self._rewriteable_functions[expr.func.__name__])) return expr.func.__name__ + "[%s]" % self.stringify(expr.args, ", ") _print_MinMaxBase = _print_Function def _print_LambertW(self, expr): if len(expr.args) == 1: return "ProductLog[{}]".format(self._print(expr.args[0])) return "ProductLog[{}, {}]".format( self._print(expr.args[1]), self._print(expr.args[0])) def _print_Integral(self, expr): if len(expr.variables) == 1 and not expr.limits[0][1:]: args = [expr.args[0], expr.variables[0]] else: args = expr.args return "Hold[Integrate[" + ', '.join(self.doprint(a) for a in args) + "]]" def _print_Sum(self, expr): return "Hold[Sum[" + ', '.join(self.doprint(a) for a in expr.args) + "]]" def _print_Derivative(self, expr): dexpr = expr.expr dvars = [i[0] if i[1] == 1 else i for i in expr.variable_count] return "Hold[D[" + ', '.join(self.doprint(a) for a in [dexpr] + dvars) + "]]" def _get_comment(self, text): return "(* {} *)".format(text) def mathematica_code(expr, **settings): r"""Converts an expr to a string of the Wolfram Mathematica code Examples ======== >>> from sympy import mathematica_code as mcode, symbols, sin >>> x = symbols('x') >>> mcode(sin(x).series(x).removeO()) '(1/120)*x^5 - 1/6*x^3 + x' """ return MCodePrinter(settings).doprint(expr)

4c4d60548399b611a0a8fafcf738e5d0db6fb629d78253cd25a227b2c8e67c28

""" Fortran code printer The FCodePrinter converts single sympy expressions into single Fortran expressions, using the functions defined in the Fortran 77 standard where possible. Some useful pointers to Fortran can be found on wikipedia: https://en.wikipedia.org/wiki/Fortran Most of the code below is based on the "Professional Programmer\'s Guide to Fortran77" by Clive G. Page: http://www.star.le.ac.uk/~cgp/prof77.html Fortran is a case-insensitive language. This might cause trouble because SymPy is case sensitive. So, fcode adds underscores to variable names when it is necessary to make them different for Fortran. """ from typing import Dict, Any from collections import defaultdict from itertools import chain import string from sympy.codegen.ast import ( Assignment, Declaration, Pointer, value_const, float32, float64, float80, complex64, complex128, int8, int16, int32, int64, intc, real, integer, bool_, complex_ ) from sympy.codegen.fnodes import ( allocatable, isign, dsign, cmplx, merge, literal_dp, elemental, pure, intent_in, intent_out, intent_inout ) from sympy.core import S, Add, N, Float, Symbol from sympy.core.function import Function from sympy.core.relational import Eq from sympy.sets import Range from sympy.printing.codeprinter import CodePrinter from sympy.printing.precedence import precedence, PRECEDENCE from sympy.printing.printer import printer_context # These are defined in the other file so we can avoid importing sympy.codegen # from the top-level 'import sympy'. Export them here as well. from sympy.printing.codeprinter import fcode, print_fcode # noqa:F401 known_functions = { "sin": "sin", "cos": "cos", "tan": "tan", "asin": "asin", "acos": "acos", "atan": "atan", "atan2": "atan2", "sinh": "sinh", "cosh": "cosh", "tanh": "tanh", "log": "log", "exp": "exp", "erf": "erf", "Abs": "abs", "conjugate": "conjg", "Max": "max", "Min": "min", } class FCodePrinter(CodePrinter): """A printer to convert sympy expressions to strings of Fortran code""" printmethod = "_fcode" language = "Fortran" type_aliases = { integer: int32, real: float64, complex_: complex128, } type_mappings = { intc: 'integer(c_int)', float32: 'real*4', # real(kind(0.e0)) float64: 'real*8', # real(kind(0.d0)) float80: 'real*10', # real(kind(????)) complex64: 'complex*8', complex128: 'complex*16', int8: 'integer*1', int16: 'integer*2', int32: 'integer*4', int64: 'integer*8', bool_: 'logical' } type_modules = { intc: {'iso_c_binding': 'c_int'} } _default_settings = { 'order': None, 'full_prec': 'auto', 'precision': 17, 'user_functions': {}, 'human': True, 'allow_unknown_functions': False, 'source_format': 'fixed', 'contract': True, 'standard': 77, 'name_mangling' : True, } # type: Dict[str, Any] _operators = { 'and': '.and.', 'or': '.or.', 'xor': '.neqv.', 'equivalent': '.eqv.', 'not': '.not. ', } _relationals = { '!=': '/=', } def __init__(self, settings=None): if not settings: settings = {} self.mangled_symbols = {} # Dict showing mapping of all words self.used_name = [] self.type_aliases = dict(chain(self.type_aliases.items(), settings.pop('type_aliases', {}).items())) self.type_mappings = dict(chain(self.type_mappings.items(), settings.pop('type_mappings', {}).items())) super().__init__(settings) self.known_functions = dict(known_functions) userfuncs = settings.get('user_functions', {}) self.known_functions.update(userfuncs) # leading columns depend on fixed or free format standards = {66, 77, 90, 95, 2003, 2008} if self._settings['standard'] not in standards: raise ValueError("Unknown Fortran standard: %s" % self._settings[ 'standard']) self.module_uses = defaultdict(set) # e.g.: use iso_c_binding, only: c_int @property def _lead(self): if self._settings['source_format'] == 'fixed': return {'code': " ", 'cont': " @ ", 'comment': "C "} elif self._settings['source_format'] == 'free': return {'code': "", 'cont': " ", 'comment': "! "} else: raise ValueError("Unknown source format: %s" % self._settings['source_format']) def _print_Symbol(self, expr): if self._settings['name_mangling'] == True: if expr not in self.mangled_symbols: name = expr.name while name.lower() in self.used_name: name += '_' self.used_name.append(name.lower()) if name == expr.name: self.mangled_symbols[expr] = expr else: self.mangled_symbols[expr] = Symbol(name) expr = expr.xreplace(self.mangled_symbols) name = super()._print_Symbol(expr) return name def _rate_index_position(self, p): return -p*5 def _get_statement(self, codestring): return codestring def _get_comment(self, text): return "! {}".format(text) def _declare_number_const(self, name, value): return "parameter ({} = {})".format(name, self._print(value)) def _print_NumberSymbol(self, expr): # A Number symbol that is not implemented here or with _printmethod # is registered and evaluated self._number_symbols.add((expr, Float(expr.evalf(self._settings['precision'])))) return str(expr) def _format_code(self, lines): return self._wrap_fortran(self.indent_code(lines)) def _traverse_matrix_indices(self, mat): rows, cols = mat.shape return ((i, j) for j in range(cols) for i in range(rows)) def _get_loop_opening_ending(self, indices): open_lines = [] close_lines = [] for i in indices: # fortran arrays start at 1 and end at dimension var, start, stop = map(self._print, [i.label, i.lower + 1, i.upper + 1]) open_lines.append("do %s = %s, %s" % (var, start, stop)) close_lines.append("end do") return open_lines, close_lines def _print_sign(self, expr): from sympy import Abs arg, = expr.args if arg.is_integer: new_expr = merge(0, isign(1, arg), Eq(arg, 0)) elif (arg.is_complex or arg.is_infinite): new_expr = merge(cmplx(literal_dp(0), literal_dp(0)), arg/Abs(arg), Eq(Abs(arg), literal_dp(0))) else: new_expr = merge(literal_dp(0), dsign(literal_dp(1), arg), Eq(arg, literal_dp(0))) return self._print(new_expr) def _print_Piecewise(self, expr): if expr.args[-1].cond != True: # We need the last conditional to be a True, otherwise the resulting # function may not return a result. raise ValueError("All Piecewise expressions must contain an " "(expr, True) statement to be used as a default " "condition. Without one, the generated " "expression may not evaluate to anything under " "some condition.") lines = [] if expr.has(Assignment): for i, (e, c) in enumerate(expr.args): if i == 0: lines.append("if (%s) then" % self._print(c)) elif i == len(expr.args) - 1 and c == True: lines.append("else") else: lines.append("else if (%s) then" % self._print(c)) lines.append(self._print(e)) lines.append("end if") return "\n".join(lines) elif self._settings["standard"] >= 95: # Only supported in F95 and newer: # The piecewise was used in an expression, need to do inline # operators. This has the downside that inline operators will # not work for statements that span multiple lines (Matrix or # Indexed expressions). pattern = "merge({T}, {F}, {COND})" code = self._print(expr.args[-1].expr) terms = list(expr.args[:-1]) while terms: e, c = terms.pop() expr = self._print(e) cond = self._print(c) code = pattern.format(T=expr, F=code, COND=cond) return code else: # `merge` is not supported prior to F95 raise NotImplementedError("Using Piecewise as an expression using " "inline operators is not supported in " "standards earlier than Fortran95.") def _print_MatrixElement(self, expr): return "{}({}, {})".format(self.parenthesize(expr.parent, PRECEDENCE["Atom"], strict=True), expr.i + 1, expr.j + 1) def _print_Add(self, expr): # purpose: print complex numbers nicely in Fortran. # collect the purely real and purely imaginary parts: pure_real = [] pure_imaginary = [] mixed = [] for arg in expr.args: if arg.is_number and arg.is_real: pure_real.append(arg) elif arg.is_number and arg.is_imaginary: pure_imaginary.append(arg) else: mixed.append(arg) if pure_imaginary: if mixed: PREC = precedence(expr) term = Add(*mixed) t = self._print(term) if t.startswith('-'): sign = "-" t = t[1:] else: sign = "+" if precedence(term) < PREC: t = "(%s)" % t return "cmplx(%s,%s) %s %s" % ( self._print(Add(*pure_real)), self._print(-S.ImaginaryUnit*Add(*pure_imaginary)), sign, t, ) else: return "cmplx(%s,%s)" % ( self._print(Add(*pure_real)), self._print(-S.ImaginaryUnit*Add(*pure_imaginary)), ) else: return CodePrinter._print_Add(self, expr) def _print_Function(self, expr): # All constant function args are evaluated as floats prec = self._settings['precision'] args = [N(a, prec) for a in expr.args] eval_expr = expr.func(*args) if not isinstance(eval_expr, Function): return self._print(eval_expr) else: return CodePrinter._print_Function(self, expr.func(*args)) def _print_Mod(self, expr): # NOTE : Fortran has the functions mod() and modulo(). modulo() behaves # the same wrt to the sign of the arguments as Python and SymPy's # modulus computations (% and Mod()) but is not available in Fortran 66 # or Fortran 77, thus we raise an error. if self._settings['standard'] in [66, 77]: msg = ("Python % operator and SymPy's Mod() function are not " "supported by Fortran 66 or 77 standards.") raise NotImplementedError(msg) else: x, y = expr.args return " modulo({}, {})".format(self._print(x), self._print(y)) def _print_ImaginaryUnit(self, expr): # purpose: print complex numbers nicely in Fortran. return "cmplx(0,1)" def _print_int(self, expr): return str(expr) def _print_Mul(self, expr): # purpose: print complex numbers nicely in Fortran. if expr.is_number and expr.is_imaginary: return "cmplx(0,%s)" % ( self._print(-S.ImaginaryUnit*expr) ) else: return CodePrinter._print_Mul(self, expr) def _print_Pow(self, expr): PREC = precedence(expr) if expr.exp == -1: return '%s/%s' % ( self._print(literal_dp(1)), self.parenthesize(expr.base, PREC) ) elif expr.exp == 0.5: if expr.base.is_integer: # Fortran intrinsic sqrt() does not accept integer argument if expr.base.is_Number: return 'sqrt(%s.0d0)' % self._print(expr.base) else: return 'sqrt(dble(%s))' % self._print(expr.base) else: return 'sqrt(%s)' % self._print(expr.base) else: return CodePrinter._print_Pow(self, expr) def _print_Rational(self, expr): p, q = int(expr.p), int(expr.q) return "%d.0d0/%d.0d0" % (p, q) def _print_Float(self, expr): printed = CodePrinter._print_Float(self, expr) e = printed.find('e') if e > -1: return "%sd%s" % (printed[:e], printed[e + 1:]) return "%sd0" % printed def _print_Relational(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) op = expr.rel_op op = op if op not in self._relationals else self._relationals[op] return "{} {} {}".format(lhs_code, op, rhs_code) def _print_Indexed(self, expr): inds = [ self._print(i) for i in expr.indices ] return "%s(%s)" % (self._print(expr.base.label), ", ".join(inds)) def _print_Idx(self, expr): return self._print(expr.label) def _print_AugmentedAssignment(self, expr): lhs_code = self._print(expr.lhs) rhs_code = self._print(expr.rhs) return self._get_statement("{0} = {0} {1} {2}".format( *map(lambda arg: self._print(arg), [lhs_code, expr.binop, rhs_code]))) def _print_sum_(self, sm): params = self._print(sm.array) if sm.dim != None: # Must use '!= None', cannot use 'is not None' params += ', ' + self._print(sm.dim) if sm.mask != None: # Must use '!= None', cannot use 'is not None' params += ', mask=' + self._print(sm.mask) return '%s(%s)' % (sm.__class__.__name__.rstrip('_'), params) def _print_product_(self, prod): return self._print_sum_(prod) def _print_Do(self, do): excl = ['concurrent'] if do.step == 1: excl.append('step') step = '' else: step = ', {step}' return ( 'do {concurrent}{counter} = {first}, {last}'+step+'\n' '{body}\n' 'end do\n' ).format( concurrent='concurrent ' if do.concurrent else '', **do.kwargs(apply=lambda arg: self._print(arg), exclude=excl) ) def _print_ImpliedDoLoop(self, idl): step = '' if idl.step == 1 else ', {step}' return ('({expr}, {counter} = {first}, {last}'+step+')').format( **idl.kwargs(apply=lambda arg: self._print(arg)) ) def _print_For(self, expr): target = self._print(expr.target) if isinstance(expr.iterable, Range): start, stop, step = expr.iterable.args else: raise NotImplementedError("Only iterable currently supported is Range") body = self._print(expr.body) return ('do {target} = {start}, {stop}, {step}\n' '{body}\n' 'end do').format(target=target, start=start, stop=stop, step=step, body=body) def _print_Type(self, type_): type_ = self.type_aliases.get(type_, type_) type_str = self.type_mappings.get(type_, type_.name) module_uses = self.type_modules.get(type_) if module_uses: for k, v in module_uses: self.module_uses[k].add(v) return type_str def _print_Element(self, elem): return '{symbol}({idxs})'.format( symbol=self._print(elem.symbol), idxs=', '.join(map(lambda arg: self._print(arg), elem.indices)) ) def _print_Extent(self, ext): return str(ext) def _print_Declaration(self, expr): var = expr.variable val = var.value dim = var.attr_params('dimension') intents = [intent in var.attrs for intent in (intent_in, intent_out, intent_inout)] if intents.count(True) == 0: intent = '' elif intents.count(True) == 1: intent = ', intent(%s)' % ['in', 'out', 'inout'][intents.index(True)] else: raise ValueError("Multiple intents specified for %s" % self) if isinstance(var, Pointer): raise NotImplementedError("Pointers are not available by default in Fortran.") if self._settings["standard"] >= 90: result = '{t}{vc}{dim}{intent}{alloc} :: {s}'.format( t=self._print(var.type), vc=', parameter' if value_const in var.attrs else '', dim=', dimension(%s)' % ', '.join(map(lambda arg: self._print(arg), dim)) if dim else '', intent=intent, alloc=', allocatable' if allocatable in var.attrs else '', s=self._print(var.symbol) ) if val != None: # Must be "!= None", cannot be "is not None" result += ' = %s' % self._print(val) else: if value_const in var.attrs or val: raise NotImplementedError("F77 init./parameter statem. req. multiple lines.") result = ' '.join(map(lambda arg: self._print(arg), [var.type, var.symbol])) return result def _print_Infinity(self, expr): return '(huge(%s) + 1)' % self._print(literal_dp(0)) def _print_While(self, expr): return 'do while ({condition})\n{body}\nend do'.format(**expr.kwargs( apply=lambda arg: self._print(arg))) def _print_BooleanTrue(self, expr): return '.true.' def _print_BooleanFalse(self, expr): return '.false.' def _pad_leading_columns(self, lines): result = [] for line in lines: if line.startswith('!'): result.append(self._lead['comment'] + line[1:].lstrip()) else: result.append(self._lead['code'] + line) return result def _wrap_fortran(self, lines): """Wrap long Fortran lines Argument: lines -- a list of lines (without \\n character) A comment line is split at white space. Code lines are split with a more complex rule to give nice results. """ # routine to find split point in a code line my_alnum = set("_+-." + string.digits + string.ascii_letters) my_white = set(" \t()") def split_pos_code(line, endpos): if len(line) <= endpos: return len(line) pos = endpos split = lambda pos: \ (line[pos] in my_alnum and line[pos - 1] not in my_alnum) or \ (line[pos] not in my_alnum and line[pos - 1] in my_alnum) or \ (line[pos] in my_white and line[pos - 1] not in my_white) or \ (line[pos] not in my_white and line[pos - 1] in my_white) while not split(pos): pos -= 1 if pos == 0: return endpos return pos # split line by line and add the split lines to result result = [] if self._settings['source_format'] == 'free': trailing = ' &' else: trailing = '' for line in lines: if line.startswith(self._lead['comment']): # comment line if len(line) > 72: pos = line.rfind(" ", 6, 72) if pos == -1: pos = 72 hunk = line[:pos] line = line[pos:].lstrip() result.append(hunk) while line: pos = line.rfind(" ", 0, 66) if pos == -1 or len(line) < 66: pos = 66 hunk = line[:pos] line = line[pos:].lstrip() result.append("%s%s" % (self._lead['comment'], hunk)) else: result.append(line) elif line.startswith(self._lead['code']): # code line pos = split_pos_code(line, 72) hunk = line[:pos].rstrip() line = line[pos:].lstrip() if line: hunk += trailing result.append(hunk) while line: pos = split_pos_code(line, 65) hunk = line[:pos].rstrip() line = line[pos:].lstrip() if line: hunk += trailing result.append("%s%s" % (self._lead['cont'], hunk)) else: result.append(line) return result def indent_code(self, code): """Accepts a string of code or a list of code lines""" if isinstance(code, str): code_lines = self.indent_code(code.splitlines(True)) return ''.join(code_lines) free = self._settings['source_format'] == 'free' code = [ line.lstrip(' \t') for line in code ] inc_keyword = ('do ', 'if(', 'if ', 'do\n', 'else', 'program', 'interface') dec_keyword = ('end do', 'enddo', 'end if', 'endif', 'else', 'end program', 'end interface') increase = [ int(any(map(line.startswith, inc_keyword))) for line in code ] decrease = [ int(any(map(line.startswith, dec_keyword))) for line in code ] continuation = [ int(any(map(line.endswith, ['&', '&\n']))) for line in code ] level = 0 cont_padding = 0 tabwidth = 3 new_code = [] for i, line in enumerate(code): if line == '' or line == '\n': new_code.append(line) continue level -= decrease[i] if free: padding = " "*(level*tabwidth + cont_padding) else: padding = " "*level*tabwidth line = "%s%s" % (padding, line) if not free: line = self._pad_leading_columns([line])[0] new_code.append(line) if continuation[i]: cont_padding = 2*tabwidth else: cont_padding = 0 level += increase[i] if not free: return self._wrap_fortran(new_code) return new_code def _print_GoTo(self, goto): if goto.expr: # computed goto return "go to ({labels}), {expr}".format( labels=', '.join(map(lambda arg: self._print(arg), goto.labels)), expr=self._print(goto.expr) ) else: lbl, = goto.labels return "go to %s" % self._print(lbl) def _print_Program(self, prog): return ( "program {name}\n" "{body}\n" "end program\n" ).format(**prog.kwargs(apply=lambda arg: self._print(arg))) def _print_Module(self, mod): return ( "module {name}\n" "{declarations}\n" "\ncontains\n\n" "{definitions}\n" "end module\n" ).format(**mod.kwargs(apply=lambda arg: self._print(arg))) def _print_Stream(self, strm): if strm.name == 'stdout' and self._settings["standard"] >= 2003: self.module_uses['iso_c_binding'].add('stdint=>input_unit') return 'input_unit' elif strm.name == 'stderr' and self._settings["standard"] >= 2003: self.module_uses['iso_c_binding'].add('stdint=>error_unit') return 'error_unit' else: if strm.name == 'stdout': return '*' else: return strm.name def _print_Print(self, ps): if ps.format_string != None: # Must be '!= None', cannot be 'is not None' fmt = self._print(ps.format_string) else: fmt = "*" return "print {fmt}, {iolist}".format(fmt=fmt, iolist=', '.join( map(lambda arg: self._print(arg), ps.print_args))) def _print_Return(self, rs): arg, = rs.args return "{result_name} = {arg}".format( result_name=self._context.get('result_name', 'sympy_result'), arg=self._print(arg) ) def _print_FortranReturn(self, frs): arg, = frs.args if arg: return 'return %s' % self._print(arg) else: return 'return' def _head(self, entity, fp, **kwargs): bind_C_params = fp.attr_params('bind_C') if bind_C_params is None: bind = '' else: bind = ' bind(C, name="%s")' % bind_C_params[0] if bind_C_params else ' bind(C)' result_name = self._settings.get('result_name', None) return ( "{entity}{name}({arg_names}){result}{bind}\n" "{arg_declarations}" ).format( entity=entity, name=self._print(fp.name), arg_names=', '.join([self._print(arg.symbol) for arg in fp.parameters]), result=(' result(%s)' % result_name) if result_name else '', bind=bind, arg_declarations='\n'.join(map(lambda arg: self._print(Declaration(arg)), fp.parameters)) ) def _print_FunctionPrototype(self, fp): entity = "{} function ".format(self._print(fp.return_type)) return ( "interface\n" "{function_head}\n" "end function\n" "end interface" ).format(function_head=self._head(entity, fp)) def _print_FunctionDefinition(self, fd): if elemental in fd.attrs: prefix = 'elemental ' elif pure in fd.attrs: prefix = 'pure ' else: prefix = '' entity = "{} function ".format(self._print(fd.return_type)) with printer_context(self, result_name=fd.name): return ( "{prefix}{function_head}\n" "{body}\n" "end function\n" ).format( prefix=prefix, function_head=self._head(entity, fd), body=self._print(fd.body) ) def _print_Subroutine(self, sub): return ( '{subroutine_head}\n' '{body}\n' 'end subroutine\n' ).format( subroutine_head=self._head('subroutine ', sub), body=self._print(sub.body) ) def _print_SubroutineCall(self, scall): return 'call {name}({args})'.format( name=self._print(scall.name), args=', '.join(map(lambda arg: self._print(arg), scall.subroutine_args)) ) def _print_use_rename(self, rnm): return "%s => %s" % tuple(map(lambda arg: self._print(arg), rnm.args)) def _print_use(self, use): result = 'use %s' % self._print(use.namespace) if use.rename != None: # Must be '!= None', cannot be 'is not None' result += ', ' + ', '.join([self._print(rnm) for rnm in use.rename]) if use.only != None: # Must be '!= None', cannot be 'is not None' result += ', only: ' + ', '.join([self._print(nly) for nly in use.only]) return result def _print_BreakToken(self, _): return 'exit' def _print_ContinueToken(self, _): return 'cycle' def _print_ArrayConstructor(self, ac): fmtstr = "[%s]" if self._settings["standard"] >= 2003 else '(/%s/)' return fmtstr % ', '.join(map(lambda arg: self._print(arg), ac.elements))