[Octave-bug-tracker] [bug #47478] parallel package: parcellfun() hangs when used with @fft2()

[Brett Merrick]

Follow-up Comment #7, bug #47478 (project octave):

Thanks for looking into it.

Olaf, I tried it and parcellfun does indeed work on fft2 when fft2 has not
been previously called in that Octave instance.

As to whether it is a smart or stupid thing to use parcellfun on fft2, my
quick tests suggest that that depends entirely on the matrix sizes involved.

On small matrices, straight calls to fft2 are much faster than via parcellfun.
On very large matrices, fft2 makes little use of the available cores, even
when I set: fftw("threads", 4). 
In such cases, it is faster -on my machine at least- to use parcellfun with 4
processes on fft2 with fftw("threads", 1), but only if the available RAM is
sufficient to prevent swap memory from being used. 

Your mileage may vary.

Thanks again for the help guys!

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