197 lines
6.4 KiB
Python
197 lines
6.4 KiB
Python
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import scipy._lib.uarray as ua
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from . import _basic_backend
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from . import _realtransforms_backend
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from . import _fftlog_backend
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class _ScipyBackend:
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"""The default backend for fft calculations
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Notes
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-----
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We use the domain ``numpy.scipy`` rather than ``scipy`` because ``uarray``
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treats the domain as a hierarchy. This means the user can install a single
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backend for ``numpy`` and have it implement ``numpy.scipy.fft`` as well.
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"""
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__ua_domain__ = "numpy.scipy.fft"
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@staticmethod
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def __ua_function__(method, args, kwargs):
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fn = getattr(_basic_backend, method.__name__, None)
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if fn is None:
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fn = getattr(_realtransforms_backend, method.__name__, None)
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if fn is None:
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fn = getattr(_fftlog_backend, method.__name__, None)
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if fn is None:
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return NotImplemented
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return fn(*args, **kwargs)
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_named_backends = {
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'scipy': _ScipyBackend,
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}
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def _backend_from_arg(backend):
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"""Maps strings to known backends and validates the backend"""
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if isinstance(backend, str):
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try:
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backend = _named_backends[backend]
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except KeyError as e:
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raise ValueError(f'Unknown backend {backend}') from e
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if backend.__ua_domain__ != 'numpy.scipy.fft':
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raise ValueError('Backend does not implement "numpy.scipy.fft"')
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return backend
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def set_global_backend(backend, coerce=False, only=False, try_last=False):
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"""Sets the global fft backend
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This utility method replaces the default backend for permanent use. It
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will be tried in the list of backends automatically, unless the
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``only`` flag is set on a backend. This will be the first tried
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backend outside the :obj:`set_backend` context manager.
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Parameters
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----------
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backend : {object, 'scipy'}
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The backend to use.
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Can either be a ``str`` containing the name of a known backend
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{'scipy'} or an object that implements the uarray protocol.
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coerce : bool
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Whether to coerce input types when trying this backend.
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only : bool
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If ``True``, no more backends will be tried if this fails.
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Implied by ``coerce=True``.
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try_last : bool
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If ``True``, the global backend is tried after registered backends.
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Raises
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------
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ValueError: If the backend does not implement ``numpy.scipy.fft``.
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Notes
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-----
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This will overwrite the previously set global backend, which, by default, is
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the SciPy implementation.
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Examples
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--------
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We can set the global fft backend:
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>>> from scipy.fft import fft, set_global_backend
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>>> set_global_backend("scipy") # Sets global backend (default is "scipy").
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>>> fft([1]) # Calls the global backend
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array([1.+0.j])
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"""
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backend = _backend_from_arg(backend)
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ua.set_global_backend(backend, coerce=coerce, only=only, try_last=try_last)
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def register_backend(backend):
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"""
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Register a backend for permanent use.
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Registered backends have the lowest priority and will be tried after the
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global backend.
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Parameters
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----------
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backend : {object, 'scipy'}
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The backend to use.
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Can either be a ``str`` containing the name of a known backend
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{'scipy'} or an object that implements the uarray protocol.
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Raises
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------
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ValueError: If the backend does not implement ``numpy.scipy.fft``.
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Examples
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--------
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We can register a new fft backend:
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>>> from scipy.fft import fft, register_backend, set_global_backend
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>>> class NoopBackend: # Define an invalid Backend
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... __ua_domain__ = "numpy.scipy.fft"
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... def __ua_function__(self, func, args, kwargs):
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... return NotImplemented
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>>> set_global_backend(NoopBackend()) # Set the invalid backend as global
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>>> register_backend("scipy") # Register a new backend
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# The registered backend is called because
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# the global backend returns `NotImplemented`
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>>> fft([1])
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array([1.+0.j])
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>>> set_global_backend("scipy") # Restore global backend to default
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"""
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backend = _backend_from_arg(backend)
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ua.register_backend(backend)
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def set_backend(backend, coerce=False, only=False):
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"""Context manager to set the backend within a fixed scope.
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Upon entering the ``with`` statement, the given backend will be added to
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the list of available backends with the highest priority. Upon exit, the
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backend is reset to the state before entering the scope.
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Parameters
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----------
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backend : {object, 'scipy'}
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The backend to use.
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Can either be a ``str`` containing the name of a known backend
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{'scipy'} or an object that implements the uarray protocol.
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coerce : bool, optional
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Whether to allow expensive conversions for the ``x`` parameter. e.g.,
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copying a NumPy array to the GPU for a CuPy backend. Implies ``only``.
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only : bool, optional
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If only is ``True`` and this backend returns ``NotImplemented``, then a
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BackendNotImplemented error will be raised immediately. Ignoring any
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lower priority backends.
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Examples
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--------
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>>> import scipy.fft as fft
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>>> with fft.set_backend('scipy', only=True):
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... fft.fft([1]) # Always calls the scipy implementation
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array([1.+0.j])
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"""
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backend = _backend_from_arg(backend)
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return ua.set_backend(backend, coerce=coerce, only=only)
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def skip_backend(backend):
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"""Context manager to skip a backend within a fixed scope.
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Within the context of a ``with`` statement, the given backend will not be
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called. This covers backends registered both locally and globally. Upon
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exit, the backend will again be considered.
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Parameters
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----------
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backend : {object, 'scipy'}
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The backend to skip.
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Can either be a ``str`` containing the name of a known backend
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{'scipy'} or an object that implements the uarray protocol.
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Examples
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--------
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>>> import scipy.fft as fft
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>>> fft.fft([1]) # Calls default SciPy backend
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array([1.+0.j])
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>>> with fft.skip_backend('scipy'): # We explicitly skip the SciPy backend
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... fft.fft([1]) # leaving no implementation available
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Traceback (most recent call last):
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...
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BackendNotImplementedError: No selected backends had an implementation ...
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"""
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backend = _backend_from_arg(backend)
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return ua.skip_backend(backend)
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set_global_backend('scipy', try_last=True)
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