[gmx-developers] gmx_fft_2d_real() output size

[Benson Muite]

Hi,

Might it be worth trying Spiral?

https://users.ece.cmu.edu/~franzf/papers/fftx-ecp-poster2019_rows.pdf

http://users.ece.cmu.edu/~franzf/papers/08510983_Spiral_IEEE_Final.pdf

http://www.spiral.net/doc/usermanual/gettingstarted.html#installing-spiral

Benson

On 8/10/19 6:56 PM, Erik Lindahl wrote:
> Hi Peter,
>
> All our FFTs employ the same standard output formats as used by e.g. 
> FFTW and and MKL, so for the full documentation it's probably easiest 
> to read there.
>
> Short story: All values are stored as proper real+complex parts (i.e., 
> 2 real values), so depending on input size the output array might be 
> larger. For in-place R2C transforms that usually means padding (but 
> not out-of-place ones).
>
> Cheers,
>
> Erik
>
> On Sat, Aug 10, 2019 at 10:36 AM Peter Kasson <kasson at virginia.edu 
> <mailto:kasson at virginia.edu>> wrote:
>
>     Hi developers,
>       The doxygen docs are a little ambiguous on gmx_fft_2d_real(),
>     and the source doesn't offer much clarification because we're
>     wrapping external libraries. Given a real-to-complex 2D FFT on a
>     grid of size x by y, is the output a complex grid of size x by y
>     also?  There are comments about in-place FFT (which I'm not doing)
>     taking a 5*4 real array and writing a 5*2 complex array.
>
>     (The context of this is trying to compute power spectra for an
>     analysis routine.)
>
>     Thanks,
>     --Peter
>
>     ----------------------------------------------------------------------
>     Peter Kasson, MD, PhD
>     Associate Professor
>     Departments of Molecular Physiology and Biological Physics
>     and of Biomedical Engineering
>     University of Virginia
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>
> -- 
> Erik Lindahl <erik.lindahl at dbb.su.se <mailto:erik.lindahl at dbb.su.se>>
> Professor of Biophysics, Dept. Biochemistry & Biophysics, Stockholm 
> University
> Science for Life Laboratory, Box 1031, 17121 Solna, Sweden
>
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