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Re: Matlab, Mex, FFTW3

From: Mike Miller
Subject: Re: Matlab, Mex, FFTW3
Date: Wed, 9 Dec 2015 10:25:14 -0500
User-agent: Mutt/1.5.24 (2015-08-30)

On Tue, Dec 08, 2015 at 19:17:01 +0100, Hugo Raguet wrote:
> Hello,
> I am switching from Octave to MATLAB, after having developed a series of
> tools for my research in the latter language. As is usual (or should be
> usual), I wrote the most time-consuming operations in C, interfaced with
> Mex.
> I have two specific questions, which I will justify below.
> 1) is it possible that a mex-file properly written for Matlab (i.e.
> fully deterministic behavior, no segmentation violation, etc.) would not
> behave correctly when compiled and used within Octave ?
> 2) are there known incompatibilities between Mex (either Matlab or
> Octave) and the famous library FFTW3 ?
> I am asking those questions because of the following observations:
> 1) Under Matlab, I encontered the following, very strange, bug:
> . In brief, I compile C codes linked with FFTW3, and the resulting
> mex-file crashes in very specific and odd circumstances. The same bug is
> not reproducible within Octave, but it is expected, given the extreme
> specificity of this bug.
> 2) However, I have a huge routine in mex, which by the way also uses
> FFTW3, which seems to work perfectly fine : deterministic behavior, no
> crash, results coherent with the data.
> Now when I use it within Octave, I get *sometimes* what looks like the
> same results as in Matlab, sometimes different results (still
> 'resembling' in some sense the Matlab results, but different), and
> sometimes it crashes.
> Any help, commentary, pointer, hint, idea concerning the above would be
> greatly appreciated.

You also asked here

which IMHO is the best place to ask. (Best to mention all

Not having a lot of information, I can only guess at answers:

1) anything is possible,
2) not that I know of.

You say your simple code example always crashes in Matlab but never in
Octave. Just a guess, but does Matlab link against a different ABI
version of FFTW than the one you are trying to link your mex file to?

No way to even speculate on the "huge routine" without diving into the

> PS: unrelated: where should I report very small errors, like typos in
> the French version of the GUI?

The bug tracker:


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