[Numpy-discussion] Fast sizes for FFT

[Julian Taylor]

I still have the plan to add this function as public api to numpy's fft
helper functions, though I didn't get to it yet.
Its a relative simple task if someone wants to contribute.

On 24.12.2014 04:33, Robert McGibbon wrote:
> 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 <mailto:charlesr.harris at gmail.com>> wrote:
> 
> 
> 
>     On Tue, Dec 23, 2014 at 7:32 PM, Robert McGibbon <rmcgibbo at gmail.com
>     <mailto: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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