ENH: Determine current fft backend in use (for specified inputs)

Is your feature request related to a problem? Please describe.

I would like a way to know which backend (e.g. scipy’s own fft or pyfftw.interfaces.scipy_fft) would be used when e.g. scipy.fft.fft(some_specified_object) is called. (See below for a proposed API.)

The reason is that I would like my library to use the explicit pyfftw class-based API iff the end user has configured the pyfftw backend on scipy (via scipy.fft.set_backend or a variant thereof), thus reusing the configuration on scipy and avoiding a separate configuration knob on my library.

Describe the solution you’d like.

A possible API would be something like scipy.fft.fft.get_backend(*args, **kwargs) returning the backend that scipy.fft.fft(*args, **kwargs) would dispatch to (as an object compatible with set_backend, so either “scipy” or pyfftw.interfaces.scipy_fft, in the case above).

Describe alternatives you’ve considered.

No response

Additional context (e.g. screenshots, GIFs)

No response

[hameerabbasi]

@anntzer I’m in the process of releasing wheels for 3.9 and 3.10. If you need examples, there are many in the Quansight-Labs/unumpy repo.

[anntzer]

The point is to have deterministic behavior.