content: # Authors: Gael Varoquaux <gael.varoquaux@normalesup.org>
  #          Justin Vincent
  #          Lars Buitinck
  # License: BSD 3 clause
  
  import numpy as np
  
  from nose.tools import assert_equal
  from nose.tools import assert_false
  from nose.tools import assert_true
  from numpy.testing import (assert_almost_equal,
                             assert_array_almost_equal)
  
  from sklearn.utils.fixes import divide, expit
  from sklearn.utils.fixes import astype
  
  
  def test_expit():
      # Check numerical stability of expit (logistic function).
  
      # Simulate our previous Cython implementation, based on
      #http://fa.bianp.net/blog/2013/numerical-optimizers-for-logistic-regression
      assert_almost_equal(expit(1000.), 1. / (1. + np.exp(-1000.)), decimal=16)
      assert_almost_equal(expit(-1000.), np.exp(-1000.) / (1. + np.exp(-1000.)),
                          decimal=16)
  
      x = np.arange(10)
      out = np.zeros_like(x, dtype=np.float32)
      assert_array_almost_equal(expit(x), expit(x, out=out))
  
  
  def test_divide():
      assert_equal(divide(.6, 1), .600000000000)
  
  
  def test_astype_copy_memory():
      a_int32 = np.ones(3, np.int32)
  
      # Check that dtype conversion works
      b_float32 = astype(a_int32, dtype=np.float32, copy=False)
      assert_equal(b_float32.dtype, np.float32)
  
      # Changing dtype forces a copy even if copy=False
      assert_false(np.may_share_memory(b_float32, a_int32))
  
      # Check that copy can be skipped if requested dtype match
      c_int32 = astype(a_int32, dtype=np.int32, copy=False)
      assert_true(c_int32 is a_int32)
  
      # Check that copy can be forced, and is the case by default:
      d_int32 = astype(a_int32, dtype=np.int32, copy=True)
      assert_false(np.may_share_memory(d_int32, a_int32))
  
      e_int32 = astype(a_int32, dtype=np.int32)
      assert_false(np.may_share_memory(e_int32, a_int32))
  