_helpers.py 文件源码

def _ulps_away(value1, value2, num_bits=1):
    r"""Determines if ``value1`` is within ``n`` ULPs of ``value2``.

    Uses ``np.spacing`` to determine the unit of least precision (ULP)
    for ``value1`` and then checks that the different between the values
    does not exceed ``n`` ULPs.

    When ``value1 == 0`` or ``value2 == 0``, we instead check that the other
    is less than :math:`2^{-40}` (``_EPS``) in magnitude.

    .. note::

       There is also a Fortran implementation of this function, which
       will be used if it can be built.

    Args:
        value1 (float): The first value that being compared.
        value2 (float): The second value that being compared.
        num_bits (Optional[int]): The number of bits allowed to differ.
            Defaults to ``1``.

    Returns:
        bool: Predicate indicating if the values agree to ``n`` bits.
    """
    if value1 == 0.0:
        return abs(value2) < _EPS
    elif value2 == 0.0:
        return abs(value1) < _EPS
    else:
        local_epsilon = np.spacing(value1)  # pylint: disable=no-member
        return abs(value1 - value2) <= num_bits * abs(local_epsilon)