[SciPy-User] [ANN] pyfftw-0.2 released

Sebastian Haase seb.haase@gmail....
Tue Feb 16 03:34:43 CST 2010


On Mon, Feb 15, 2010 at 11:23 PM, Jochen Schroeder <cycomanic@gmail.com> wrote:
<snip>
>> Also, most arrays allocated by malloc are *not* 16 bytes aligned on
>> Linux, because for allocated areas above a certain size, the glibc
>> malloc use mmap, and always "disalign" the allocated buffer. The
>> threshold is easily reached when working with big data.
>
> Just to clarify this is 32bit Linux, on 64bit malloc automatically aligns to
> 16bytes.

thanks, for the info!

> Well I looked at creating a more "traditional" API around fftw (something like
> y=fft(x)) but the performance benefit for relatively small arrays (in my
> experience ~2**12) was mainly eaten up by the creation of the output array.
> Because most of the stuff I do uses arrays of around that size and does a lot of ffts
> back and forth between two arrays (pulse propagation simulations if anyone is
> interested), I went with the current approach (it's probably possible to create
> some sort of memory pool to avoid the time of allocating arrays, is there
> something like this in numpy already?)
>
You should add an `out=None` option to fft, so that if `out` is not
`None` it only checks the shape, dtype and contiguity requirements.
At least that's what I did for my (old, fftw2) frontend.

-Sebastian


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