Additional features in MKL_FFT's API

[RemiLehe]

Thanks again for making mkl_fft available!

Looking at the API, I was wondering if there were plans to expand the API, in order to try to optimize performance, especially:

• Are there plans to set the number of threads via the API, or is this set anyway via the environment variable MKL_NUM_THREADS?

• Would it be possible to add an argument out, so that the user can pass a pre-allocated numpy array to store the results? (I would expect this to lead to better performance in some cases, since there would be no allocation of memory when calling fft in this case.)

• Are there plans to add an alternative lower-level Python API (much like the C API), where users can create and commit a descriptor, and then call the DFTI routines (potentially many times), before finally destroying the descriptor. (Again, I would expect this to lead to better performance ; is that correct?)

[oleksandr-pavlyk]

@RemiLehe The in-place operation is supported with mkl_fft.fft(arg, overwrite_x=True), following somewhat clunky design of scipy.fftpack.

[oleksandr-pavlyk]

Regarding your last point. Yes, it is totally correct. Creating a descriptor can be as costly for 1D FFT as performing computations. mkl_fft attempts to cache 1D descriptors, so that repeated calls to FFT on arrays of the same size has better performance.

C API is an excellent suggestion.

[RemiLehe]

Great, thanks for your answers!
If an API similar to the C one is developed, I would be very interested indeed!