package edu.berkeley.nlp.util;

import java.util.Random;

public class NumUtils {
	// This random stuff should be deprecated. DON'T USE IT!
	@Deprecated
	private static Random random = new Random();

	@Deprecated
	public static Random getRandom() {
		return random;
	}

	@Deprecated
	public static void setRandom(long seed) {
		setRandom(new Random(seed));
	}

	@Deprecated
	public static void setRandom(Random random) {
		NumUtils.random = random;
	}

	@Deprecated
	public static double randDouble() {
		return random.nextDouble();
	}

	@Deprecated
	public static int randInt(int n) {
		return random.nextInt(n);
	}

	@Deprecated
	public static boolean randBernoulli(double p) {
		return random.nextDouble() < p;
	}

	@Deprecated
	public static int randMultinomial(double[] probs, Random random) {
		double v = random.nextDouble();
		double sum = 0;
		for (int i = 0; i < probs.length; i++) {
			sum += probs[i];
			if (v < sum)
				return i;
		}
		throw new RuntimeException(sum + " < " + v);
	}

	@Deprecated
	public static int randMultinomial(double[] probs) {
		return randMultinomial(probs, random);
	}

	public static boolean isFinite(double x) {
		return !Double.isNaN(x) && !Double.isInfinite(x);
	}

	public static void assertIsFinite(double x) {
		assert isFinite(x) : "Not finite: " + x;
	}

	public static void assertIsFinite(double[] xs) {
		for (double x : xs)
			assert isFinite(x) : "Not finite: " + Fmt.D(xs);
	}

	public static void assertIsFinite(double[][] xss) {
		for (double[] xs : xss)
			for (double x : xs)
				assert isFinite(x) : "Not finite: " + Fmt.D(xss);
	}

	public static boolean isProb(double x) {
		return x >= 0 && x <= 1 && !Double.isNaN(x);
	}

	public static void assertIsProb(double x) {
		assert isProb(x) : "Not a probability [0, 1]: " + x;
	}

	public static void assertEquals(double x, double y) {
		assertEquals(x, y, 1e-10);
	}

	public static void assertEquals(double x, double y, double tol) {
		assert Math.abs(x - y) < tol : x + " != " + y;
	}

	public static void assertNormalized(double[] p) {
		assertEquals(ListUtils.sum(p), 1);
	}

	public static void assertNormalized(double[] p, double tol) {
		assertEquals(ListUtils.sum(p), 1, tol);
	}

	// Vector, matrix operations {
	public static boolean normalize(float[] data) {
		float sum = 0;
		for (float x : data)
			sum += x;
		if (sum == 0)
			return false;
		for (int i = 0; i < data.length; i++)
			data[i] /= sum;
		return true;
	}

	public static boolean normalize(double[] data) {
		double sum = 0;
		for (double x : data)
			sum += x;
		if (sum == 0)
			return false;
		for (int i = 0; i < data.length; i++)
			data[i] /= sum;
		return true;
	}

	public static boolean normalize(double[][] data) {
		double sum = 0;
		for (double[] v : data)
			for (double x : v)
				sum += x;
		if (sum == 0)
			return false;
		for (double[] v : data)
			for (int i = 0; i < v.length; i++)
				v[i] /= sum;
		return true;
	}

	public static boolean normalizeEachRow(double[][] data) {
		boolean allRowsOkay = true;
		for (double[] row : data) {
			if (!NumUtils.normalize(row))
				allRowsOkay = false;
		}
		return allRowsOkay;
	}

	public static boolean normalize(double[][][] data) {
		double sum = 0;
		for (double[][] m : data)
			for (double[] v : m)
				for (double x : v)
					sum += x;
		if (sum == 0)
			return false;
		for (double[][] m : data)
			for (double[] v : m)
				for (int i = 0; i < v.length; i++)
					v[i] /= sum;
		return true;
	}

	public static boolean expNormalize(double[] probs) {
		// Input: log probabilities (unnormalized too)
		// Output: normalized probabilities
		// probs actually contains log probabilities; so we can add an arbitrary
		// constant to make
		// the largest log prob 0 to prevent overflow problems
		double max = Double.NEGATIVE_INFINITY;
		for (int i = 0; i < probs.length; i++)
			max = Math.max(max, probs[i]);
		for (int i = 0; i < probs.length; i++)
			probs[i] = Math.exp(probs[i] - max);
		return normalize(probs);
	}

	public static boolean expNormalize(double[][] probs) {
		double max = Double.NEGATIVE_INFINITY;
		for (double[] v : probs)
			for (int i = 0; i < v.length; i++)
				max = Math.max(max, v[i]);
		for (double[] v : probs)
			for (int i = 0; i < v.length; i++)
				v[i] = Math.exp(v[i] - max);
		return normalize(probs);
	}

	public static boolean expNormalize(double[][][] probs) {
		double max = Double.NEGATIVE_INFINITY;
		for (double[][] m : probs)
			for (double[] v : m)
				for (int i = 0; i < v.length; i++)
					max = Math.max(max, v[i]);
		for (double[][] m : probs)
			for (double[] v : m)
				for (int i = 0; i < v.length; i++)
					v[i] = Math.exp(v[i] - max);
		return normalize(probs);
	}

	public static int[][] toInt(double[][] data) {
		int[][] newdata = new int[data.length][];
		for (int r = 0; r < data.length; r++) {
			newdata[r] = new int[data[r].length];
			for (int c = 0; c < data[r].length; c++)
				newdata[r][c] = (int) data[r][c];
		}
		return newdata;
	}

	public static double l1Dist(double[] x, double[] y) {
		double sum = 0;
		for (int i = 0; i < x.length; i++)
			sum += Math.abs(x[i] - y[i]);
		return sum;
	}

	public static double lInfDist(double[] x, double[] y) {
		double max = 0;
		for (int i = 0; i < x.length; i++)
			max = Math.max(max, Math.abs(x[i] - y[i]));
		return max;
	}

	public static double l2Dist(double[] x, double[] y) {
		return Math.sqrt(l2DistSquared(x, y));
	}

	public static double l2DistSquared(double[] x, double[] y) {
		double sum = 0;
		for (int i = 0; i < x.length; i++)
			sum += (x[i] - y[i]) * (x[i] - y[i]);
		return sum;
	}

	public static double l2Norm(double[] x) {
		return Math.sqrt(l2NormSquared(x));
	}

	public static double l2NormSquared(double[] x) {
		double sum = 0;
		for (int i = 0; i < x.length; i++)
			sum += x[i] * x[i];
		return sum;
	}

	public static double[] l2NormalizedMut(double[] x) {
		double norm = l2Norm(x);
		if (norm > 0)
			ListUtils.multMut(x, 1.0 / norm);
		return x;
	}

	// If sum is 0, set to uniform
	// Return false if we had to set to uniform
	public static boolean normalizeForce(double[] data) {
		double sum = 0;
		for (double x : data)
			sum += x;
		if (sum == 0) {
			for (int i = 0; i < data.length; i++)
				data[i] = 1.0 / data.length;
			return false;
		} else {
			for (int i = 0; i < data.length; i++)
				data[i] /= sum;
			return true;
		}
	}

	public static double[][] transpose(double[][] mat) {
		int m = mat.length, n = mat[0].length;
		double[][] newMat = new double[n][m];
		for (int r = 0; r < m; r++)
			for (int c = 0; c < n; c++)
				newMat[c][r] = mat[r][c];
		return newMat;
	}

	public static double[][] elementWiseMult(double[][] mat1, double[][] mat2) {
		int m = mat1.length, n = mat1[0].length;
		double[][] newMat = new double[m][n];
		for (int r = 0; r < m; r++)
			for (int c = 0; c < n; c++)
				newMat[r][c] = mat1[r][c] * mat2[r][c];
		return newMat;
	}

	public static void scalarMult(double[][] mat, double x) {
		int m = mat.length, n = mat[0].length;
		for (int r = 0; r < m; r++)
			for (int c = 0; c < n; c++)
				mat[r][c] *= x;
	}

	public static double[][] copy(double[][] mat) {
		int m = mat.length;
		double[][] newMat = new double[m][];
		for (int r = 0; r < m; r++) {
			int n = mat[r].length;
			newMat[r] = new double[n];
			for (int c = 0; c < n; c++)
				newMat[r][c] = mat[r][c];
		}
		return newMat;
	}

	public static boolean equals(double x, double y) {
		return Math.abs(x - y) < 1e-10;
	}

	public static boolean equals(double x, double y, double tol) {
		return Math.abs(x - y) < tol;
	}

	public static double round(double x, int numPlaces) {
		double scale = Math.pow(10, numPlaces);
		return Math.round(x * scale) / scale;
	}

	public static double[] round(double[] vec, int numPlaces) {
		double[] newVec = new double[vec.length];
		double scale = Math.pow(10, numPlaces);
		for (int i = 0; i < vec.length; i++)
			newVec[i] = Math.round(vec[i] * scale) / scale;
		return newVec;
	}

	public static double bound(double x, double lower, double upper) {
		if (x < lower)
			return lower;
		if (x > upper)
			return upper;
		return x;
	}

	public static int bound(int x, int lower, int upper) {
		if (x < lower)
			return lower;
		if (x > upper)
			return upper;
		return x;
	}

	// }

	public static double entropy(double[] probs) {
		double e = 0;
		for (double p : probs) {
			if (p > 0)
				e += -p * Math.log(p);
		}
		return e;
	}

	// Suppose we have a joint probability distribution p(X, Y)
	// and we want to calculate the conditional entropy
	// H(Y | X) = -\sum_x \sum_y p(x, y) \log p(y | x)
	// For a fixed x, we input y -> p(X=x, Y=y)
	// and get out the contribution to H(Y|X).
	// If we sum over all values of X, we get the desired result.
	public static double condEntropy(double[] probs) {
		double sum = ListUtils.sum(probs); // This is p(X) = \sum_y P(X, Y=y)
		double e = 0;
		for (double p : probs) {
			if (p > 0)
				e += -p * Math.log(p / sum);
		}
		assertIsFinite(sum);
		return e;
	}

	public static double condEntropy(double[][] probs) {
		double sum = 0;
		for (int i = 0; i < probs.length; i++)
			sum += condEntropy(probs[i]);
		return sum;
	}

	// Return log(gamma(xx))
	private static double[] logGammaCoeff = { 76.18009172947146,
			-86.50532032941677, 24.01409824083091, -1.231739572450155,
			0.1208650973866179e-2, -0.5395239384953e-5 };

	public static double logGamma(double xx) {
		double x, y, tmp, ser;
		y = x = xx;
		tmp = x + 5.5;
		tmp -= (x + 0.5) * Math.log(tmp);
		ser = 1.000000000190015;
		for (int j = 0; j <= 5; j++)
			ser += logGammaCoeff[j] / ++y;
		return -tmp + Math.log(2.5066282746310005 * ser / x);
	}

	// Return log factorial(n) = logGamma(n+1)
	// Cache small values
	private static double[] cachedLogFactorial = null;
	private static int numCachedLogFactorial = 1024;

	public static double logFactorial(int n) {
		if (n < numCachedLogFactorial) {
			if (cachedLogFactorial == null) {
				cachedLogFactorial = new double[numCachedLogFactorial];
				for (int i = 1; i < numCachedLogFactorial; i++) {
					cachedLogFactorial[i] = cachedLogFactorial[i - 1]
							+ Math.log(i);
				}
			}
			return cachedLogFactorial[n];
		}
		return logGamma(n + 1);
	}

	public static double logChoose(int n, int k) {
		return logFactorial(n) - logFactorial(k) - logFactorial(n - k);
	}

	/**
	 * Stolen from Radford Neal's fbm package. digamma(x) is defined as (d/dx)
	 * log Gamma(x). It is computed here using an asymptotic expansion when x>5.
	 * For x<=5, the recurrence relation digamma(x) = digamma(x+1) - 1/x is used
	 * repeatedly. See Venables & Ripley, Modern Applied Statistics with S-Plus,
	 * pp. 151-152. COMPUTE THE DIGAMMA FUNCTION. Returns -inf if the argument
	 * is an integer less than or equal to zero.
	 */
	public static double digamma(double x) {
		assert x > 0 : x;
		double r, f, t;
		r = 0;
		while (x <= 5) {
			r -= 1 / x;
			x += 1;
		}
		f = 1 / (x * x);
		t = f
				* (-1 / 12.0 + f
						* (1 / 120.0 + f
								* (-1 / 252.0 + f
										* (1 / 240.0 + f
												* (-1 / 132.0 + f
														* (691 / 32760.0 + f
																* (-1 / 12.0 + f * 3617 / 8160.0)))))));
		return r + Math.log(x) - 0.5 / x + t;
	}

	// Return log(exp(a)+exp(b))
	private static double logMaxValue = Math.log(Double.MAX_VALUE);

	public static double logAdd(double a, double b) {
		if (a > b) {
			if (Double.isInfinite(b) || a - b > logMaxValue)
				return a;
			return b + Math.log(1 + Math.exp(a - b));
		} else {
			if (Double.isInfinite(a) || b - a > logMaxValue)
				return b;
			return a + Math.log(1 + Math.exp(b - a));
		}
	}

	// Fast exponential
	// http://martin.ankerl.com/2007/10/04/optimized-pow-approximation-for-java-and-c-c/
	public static double fastExp(double val) {
		final long tmp = (long) (1512775 * val + (1072693248 - 60801));
		return Double.longBitsToDouble(tmp << 32);
	}

	public static double fastLog(double val) {
		final double x = (Double.doubleToLongBits(val) >> 32);
		return (x - 1072632447) / 1512775;
	}
}
