[SciPy-user] fftw3 wrappers

Lars Friedrich lfriedri@imtek...
Wed Aug 8 01:41:31 CDT 2007


Hi David,

thank you for your answer.

David Cournapeau wrote:
> Mmh, sorry, I missed that you were interested in multi dimensional fft, 
> this may explain the result. For 1d, fftw3 wrappers are almost always 
> faster than numpy, but not for multi dimensional

Maybe I just did not tell before... I thought this would not make any 
difference.

> What does scipy.show_config() tells you ?

...
fftw2_info:
   NOT AVAILABLE

fftw3_info:
   NOT AVAILABLE
...

> in my experience, scipy's fftw3 wrappers may or may not be faster than 
> numpy for multi dimensional fft, depending on your architecture (eg 
> Pentium 4 vs Pentium m vs Core Duo). This will change in the future, 
> because the problem is on scipy's side, not on fftw3 (fftw by itself is 
> certainly faster than what you get using numpy).
> 
> If I were you, this is what I would do:
>     - first, check whether you are really using fftw3 (using show_config)
>     - if you are, then maybe you can try with fftw2 instead of fftw3: 
> install fftw2 on your computer, and then rebuild scipy with FFTW3=None, 
> eg: FFTW3=None python setup.py build (you can check whether fftw2 is 
> picked instead of fftw3 by running first FFTW3 python setup.py config).
>     - if this is ok for you, you may try the Intel MKL instead. I have 
> never used it, but heard it is pretty efficient.
> 
> fftw2 has a pretty good chance of working better than fftw3 now because 
> it is more efficiently used by scipy. Hopefully, this will change soon 
> (there is a bit some work needed to improve the wrappers efficiency 
> wise: I am working on it).

I tend to wait for full fftw3-support... maybe I can help you? I started 
with checking out http://svn.scipy.org/svn/scipy/trunk, is this the 
right step?

Lars



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