"numpy/core/tests/test_umath.py::TestComplexFunctions::()::test_branch_cuts",
 "numpy/core/tests/test_umath.py::TestComplexFunctions::()::test_branch_cuts_complex64",
 "numpy/core/tests/test_umath.py::TestComplexFunctions::()::test_loss_of_precision",

_________________ TestComplexFunctions.test_loss_of_precision _________________

self = <numpy.core.tests.test_umath.TestComplexFunctions object at 0x000000000ADC6C88>

    def test_loss_of_precision(self):
        for dtype in [np.complex64, np.complex_]:
>           self.check_loss_of_precision(dtype)

dtype      = <class 'numpy.complex64'>
self       = <numpy.core.tests.test_umath.TestComplexFunctions object at 0x000000000ADC6C88>

numpy\core\tests\test_umath.py:2637:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <numpy.core.tests.test_umath.TestComplexFunctions object at 0x000000000ADC6C88>
dtype = <class 'numpy.complex64'>

    def check_loss_of_precision(self, dtype):
        """Check loss of precision in complex arc* functions"""

        # Check against known-good functions

        info = np.finfo(dtype)
        real_dtype = dtype(0.).real.dtype
        eps = info.eps

        def check(x, rtol):
            x = x.astype(real_dtype)

            z = x.astype(dtype)
            d = np.absolute(np.arcsinh(x)/np.arcsinh(z).real - 1)
            assert_(np.all(d < rtol), (np.argmax(d), x[np.argmax(d)], d.max(),
                                      'arcsinh'))

            z = (1j*x).astype(dtype)
            d = np.absolute(np.arcsinh(x)/np.arcsin(z).imag - 1)
            assert_(np.all(d < rtol), (np.argmax(d), x[np.argmax(d)], d.max(),
                                      'arcsin'))

            z = x.astype(dtype)
            d = np.absolute(np.arctanh(x)/np.arctanh(z).real - 1)
            assert_(np.all(d < rtol), (np.argmax(d), x[np.argmax(d)], d.max(),
                                      'arctanh'))

            z = (1j*x).astype(dtype)
            d = np.absolute(np.arctanh(x)/np.arctan(z).imag - 1)
            assert_(np.all(d < rtol), (np.argmax(d), x[np.argmax(d)], d.max(),
                                      'arctan'))

        # The switchover was chosen as 1e-3; hence there can be up to
        # ~eps/1e-3 of relative cancellation error before it

        x_series = np.logspace(-20, -3.001, 200)
        x_basic = np.logspace(-2.999, 0, 10, endpoint=False)

        if dtype is np.longcomplex:
            # It's not guaranteed that the system-provided arc functions
            # are accurate down to a few epsilons. (Eg. on Linux 64-bit)
            # So, give more leeway for long complex tests here:
            check(x_series, 50*eps)
        else:
            check(x_series, 2.1*eps)
        check(x_basic, 2*eps/1e-3)

        # Check a few points

        z = np.array([1e-5*(1+1j)], dtype=dtype)
        p = 9.999999999333333333e-6 + 1.000000000066666666e-5j
        d = np.absolute(1-np.arctanh(z)/p)
>       assert_(np.all(d < 1e-15))
E       AssertionError

check      = <function TestComplexFunctions.check_loss_of_precision.<locals>.check at 0x000000000AEAF8C8>
d          = array([4.5474735e-08], dtype=float32)
dtype      = <class 'numpy.complex64'>
eps        = 1.1920929e-07
info       = finfo(resolution=1e-06, min=-3.4028235e+38, max=3.4028235e+38, dtype=float32)
p          = (9.999999999333333e-06+1.0000000000666667e-05j)
real_dtype = dtype('float32')
self       = <numpy.core.tests.test_umath.TestComplexFunctions object at 0x000000000ADC6C88>
x_basic    = array([0.00100231, 0.0019994 , 0.00398841, 0.0079561 , 0.01587084,
       0.0316592 , 0.06315387, 0.12597953, 0.25130435, 0.50130265])
x_series   = array([1.00000000e-20, 1.21736864e-20, 1.48198641e-20, 1.80412378e-20,
       2.19628372e-20, 2.67368693e-20, 3.254862...3.06526013e-04, 3.73155156e-04, 4.54267386e-04,
       5.53010871e-04, 6.73218092e-04, 8.19554595e-04, 9.97700064e-04])
z          = array([1.e-05+1.e-05j], dtype=complex64)

numpy\core\tests\test_umath.py:2602: AssertionError

Python 3.6.3 |Anaconda custom (64-bit)| (default, Oct 15 2017, 03:27:45)
 [MSC v.1900 64 bit (AMD64)] on win32