[SciPy-User] [OT] looking for fft

Matt Newville newville@cars.uchicago....
Wed Apr 17 18:49:41 CDT 2013


Hi Neal,

On Wed, Apr 17, 2013 at 9:08 AM, Neal Becker <ndbecker2@gmail.com> wrote:
> I'm looking for some fft code that has:
>
> 1. commercial-friendly license
> 2. seperates construction (which involves costly trig functions) from repeated
> use (which should use only multiply-add)
>
> An example of (2) is fftw, but that doesn't meet (1).
>
> I've seen plenty of examples that have (1) but not (2) - these use fft as a
> function, which has no state.  fft should be written as a class, where in the
> constructor all the trig functions are determined.

I believe the code in the numpy.fft module sort of does this -- uses
fftpack, and automatically calls the initialization routine (cfftfi)
and caches the result for subsequent calls with the same array length.

You don't actually need to make an explicit call to cfftfi(), as you
would with C/Fortran, but this routine is only called once (per array
length).  See
    https://github.com/numpy/numpy/blob/master/numpy/fft/fftpack.py#L55

--Matt Newville <newville at cars.uchicago.edu>


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