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## Matlab, Mex, FFTW3

**From**: |
Hugo Raguet |

**Subject**: |
Matlab, Mex, FFTW3 |

**Date**: |
Tue, 8 Dec 2015 19:17:01 +0100 |

**User-agent**: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |

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:
http://stackoverflow.com/questions/33921437/fftw-within-mex-crashes-with-very-odd-behavior
. 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.
Best,
Hugo Raguet
PS: unrelated: where should I report very small errors, like typos in
the French version of the GUI?

**Matlab, Mex, FFTW3**,
*Hugo Raguet* **<=**