[SciPy-Dev] fftconvolve speedup / non powers of two

Pauli Virtanen pav@iki...
Sat Feb 11 06:46:17 CST 2012

11.02.2012 11:52, Nicolas Rougier kirjoitti:
> FFTW documentation (http://www.fftw.org/fftw2_doc/fftw_3.html) states that:
> "FFTW is best at handling sizes of the form 2^a*3^b*5^c*7^d*11^e*13^f, where e+f is either 0 or 1."
> But the code from fftconvolve is only using (internally) sizes that are
> power of two, is there a specific reason ?

The underlying library is not FFTW, so the FFTW documentation does not

However, IIRC, FFTPACK had factorizations for 2^a*3^b*5^c, so there
might be room for similar improvement. However, one would need to check
if there are some additional restrictions.

Pauli Virtanen

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