[Numpy-discussion] Fast sizes for FFT

[Robert McGibbon]

Alex Griffing pointed out on github that this feature was recently added to
scipy in https://github.com/scipy/scipy/pull/3144. Sweet!

-Robert

On Tue, Dec 23, 2014 at 6:47 PM, Charles R Harris <charlesr.harris at gmail.com
> wrote:

>
>
> On Tue, Dec 23, 2014 at 7:32 PM, Robert McGibbon <rmcgibbo at gmail.com>
> wrote:
>
>> Hey,
>>
>> The performance of fftpack depends very strongly on the array size --
>> sizes that are powers of two are good, but also powers of three, five and
>> seven, or numbers whose only prime factors are from (2,3,5,7). For problems
>> that can use padding, rounding up the size (using np.fft.fft(x,
>> n=size_with_padding)) to one of these multiples makes a big difference.
>>
>> Some other packages expose a function for calculating the next fast size,
>> e.g: http://ltfat.sourceforge.net/notes/ltfatnote017.pdf.
>>
>> Is there anything like this in numpy/scipy? If not, would this be a
>> reasonable feature to add?
>>
>>
> It would be nice to have, but an integrated system would combine it with
> padding and windowing. Might be worth putting together a package, somewhat
> like seaborn for plotting, that provides  a nicer interface to the fft
> module. Tracking downsampling/upsampling  and units would also be useful. I
> don't know if anyone has done something like that already...
>
> Chuck
>
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