_float_utils.py

#!/usr/bin/env python
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import numpy as np

__all__ = [
    "__upcast_float16_array",
    "__downcast_float128_array",
    "__supported_array_or_not_implemented",
]


def __upcast_float16_array(x):
    """
    Used in _scipy_fft to upcast float16 to float32,
    instead of float64, as mkl_fft would do
    """
    if hasattr(x, "dtype"):
        xdt = x.dtype
        if xdt == np.half:
            # no half-precision routines, so convert to single precision
            return np.asarray(x, dtype=np.float32)
        if xdt == np.longdouble and not xdt == np.float64:
            raise ValueError("type %s is not supported" % xdt)
    if not isinstance(x, np.ndarray):
        __x = np.asarray(x)
        xdt = __x.dtype
        if xdt == np.half:
            # no half-precision routines, so convert to single precision
            return np.asarray(__x, dtype=np.float32)
        if xdt == np.longdouble and not xdt == np.float64:
            raise ValueError("type %s is not supported" % xdt)
        return __x
    return x


def __downcast_float128_array(x):
    """
    Used in _numpy_fft to unsafely downcast float128/complex256 to
    complex128, instead of raising an error
    """
    if hasattr(x, "dtype"):
        xdt = x.dtype
        if xdt == np.longdouble and not xdt == np.float64:
            return np.asarray(x, dtype=np.float64)
        elif xdt == np.clongdouble and not xdt == np.complex128:
            return np.asarray(x, dtype=np.complex128)
    if not isinstance(x, np.ndarray):
        __x = np.asarray(x)
        xdt = __x.dtype
        if xdt == np.longdouble and not xdt == np.float64:
            return np.asarray(x, dtype=np.float64)
        elif xdt == np.clongdouble and not xdt == np.complex128:
            return np.asarray(x, dtype=np.complex128)
        return __x
    return x


def __supported_array_or_not_implemented(x):
    """
    Used in _scipy_fft_backend to convert array to float32,
    float64, complex64, or complex128 type or return NotImplemented
    """
    __x = np.asarray(x)
    black_list = [np.half]
    if hasattr(np, "float128"):
        black_list.append(np.float128)
    if hasattr(np, "complex256"):
        black_list.append(np.complex256)
    if __x.dtype in black_list:
        return NotImplemented
    return __x