content: import itertools
  
  import numpy as np
  from numpy.testing import assert_array_almost_equal
  
  import scipy
  from scipy.spatial.distance import cdist
  from sklearn.neighbors.dist_metrics import DistanceMetric
  from nose import SkipTest
  
  
  def cmp_version(version1, version2):
      version1 = tuple(map(int, version1.split('.')[:2]))
      version2 = tuple(map(int, version2.split('.')[:2]))
  
      if version1 < version2:
          return -1
      elif version1 > version2:
          return 1
      else:
          return 0
  
  
  class TestMetrics:
      def __init__(self, n1=20, n2=25, d=4, zero_frac=0.5,
                   rseed=0, dtype=np.float64):
          np.random.seed(rseed)
          self.X1 = np.random.random((n1, d)).astype(dtype)
          self.X2 = np.random.random((n2, d)).astype(dtype)
  
          # make boolean arrays: ones and zeros
          self.X1_bool = self.X1.round(0)
          self.X2_bool = self.X2.round(0)
  
          V = np.random.random((d, d))
          VI = np.dot(V, V.T)
  
          self.metrics = {'euclidean': {},
                          'cityblock': {},
                          'minkowski': dict(p=(1, 1.5, 2, 3)),
                          'chebyshev': {},
                          'seuclidean': dict(V=(np.random.random(d),)),
                          'wminkowski': dict(p=(1, 1.5, 3),
                                             w=(np.random.random(d),)),
                          'mahalanobis': dict(VI=(VI,)),
                          'hamming': {},
                          'canberra': {},
                          'braycurtis': {}}
  
          self.bool_metrics = ['matching', 'jaccard', 'dice',
                               'kulsinski', 'rogerstanimoto', 'russellrao',
                               'sokalmichener', 'sokalsneath']
  
      def test_cdist(self):
          for metric, argdict in self.metrics.items():
              keys = argdict.keys()
              for vals in itertools.product(*argdict.values()):
                  kwargs = dict(zip(keys, vals))
                  D_true = cdist(self.X1, self.X2, metric, **kwargs)
                  yield self.check_cdist, metric, kwargs, D_true
  
          for metric in self.bool_metrics:
              D_true = cdist(self.X1_bool, self.X2_bool, metric)
              yield self.check_cdist_bool, metric, D_true
  
      def check_cdist(self, metric, kwargs, D_true):
          if metric == 'canberra' and cmp_version(scipy.__version__, '0.9') <= 0:
              raise SkipTest("Canberra distance incorrect in scipy < 0.9")
          dm = DistanceMetric.get_metric(metric, **kwargs)
          D12 = dm.pairwise(self.X1, self.X2)
          assert_array_almost_equal(D12, D_true)
  
      def check_cdist_bool(self, metric, D_true):
          dm = DistanceMetric.get_metric(metric)
          D12 = dm.pairwise(self.X1_bool, self.X2_bool)
          assert_array_almost_equal(D12, D_true)
  
      def test_pdist(self):
          for metric, argdict in self.metrics.items():
              keys = argdict.keys()
              for vals in itertools.product(*argdict.values()):
                  kwargs = dict(zip(keys, vals))
                  D_true = cdist(self.X1, self.X1, metric, **kwargs)
                  yield self.check_pdist, metric, kwargs, D_true
  
          for metric in self.bool_metrics:
              D_true = cdist(self.X1_bool, self.X1_bool, metric)
              yield self.check_pdist_bool, metric, D_true
  
      def check_pdist(self, metric, kwargs, D_true):
          if metric == 'canberra' and cmp_version(scipy.__version__, '0.9') <= 0:
              raise SkipTest("Canberra distance incorrect in scipy < 0.9")
          dm = DistanceMetric.get_metric(metric, **kwargs)
          D12 = dm.pairwise(self.X1)
          assert_array_almost_equal(D12, D_true)
  
      def check_pdist_bool(self, metric, D_true):
          dm = DistanceMetric.get_metric(metric)
          D12 = dm.pairwise(self.X1_bool)
          assert_array_almost_equal(D12, D_true)
  
  
  def test_haversine_metric():
      def haversine_slow(x1, x2):
          return 2 * np.arcsin(np.sqrt(np.sin(0.5 * (x1[0] - x2[0])) ** 2
                                       + np.cos(x1[0]) * np.cos(x2[0]) *
                                       np.sin(0.5 * (x1[1] - x2[1])) ** 2))
  
      X = np.random.random((10, 2))
  
      haversine = DistanceMetric.get_metric("haversine")
  
      D1 = haversine.pairwise(X)
      D2 = np.zeros_like(D1)
      for i, x1 in enumerate(X):
          for j, x2 in enumerate(X):
              D2[i, j] = haversine_slow(x1, x2)
  
      assert_array_almost_equal(D1, D2)
      assert_array_almost_equal(haversine.dist_to_rdist(D1),
                                np.sin(0.5 * D2) ** 2)
  
  
  def test_pyfunc_metric():
      def dist_func(x1, x2, p):
          return np.sum((x1 - x2) ** p) ** (1. / p)
  
      X = np.random.random((10, 3))
  
      euclidean = DistanceMetric.get_metric("euclidean")
      pyfunc = DistanceMetric.get_metric("pyfunc", func=dist_func, p=2)
  
      D1 = euclidean.pairwise(X)
      D2 = pyfunc.pairwise(X)
  
      assert_array_almost_equal(D1, D2)
  
  
  if __name__ == '__main__':
      import nose
      nose.runmodule()
  