[Mne_analysis] Please read: Problem with MNE version 2.6.1 on Mac OSX

[Matti Hamalainen]

Dear all:

It turns out that there is a problem with MNE version 2.6.1 on the Mac  
OSX Intel platform. This problem may affects you if and only if *both*  
of the following are true:

(i) You are using MNE on the Mac OSX Intel platform.

(ii) Your MNE version is 2.6.1, compiled on May 5, 2009 or later. You  
can find this information in $MNE_ROOT/VERSION.

If both of the above are true, read on. Otherwise, you can ignore this  
email.

The problem has to do with the fact that at this version many of the  
MNE programs for Mac OSX Intel platform were compiled in 64-bit mode.  
It turns out that in this case the BLAS matrix multiplication routine  
sgemm *sometimes* produces incorrect results. I found this by looking  
at output from mne_compute_raw_inverse. The workaround was to revert  
to 32-bit compilation, which works correctly.

To get rid of the problem, download the newly compiled MNE 2.6.2 from  
the website. With help of Matlab and comparisons between mne_analyze/ 
mne_make_movie/mne_compute_raw_inverse and direct tests of matrix  
multiplication I verified that this version works correctly.

Again, you have nothing to worry about in this respect if you are  
running MNE on LINUX or Mac PowerPC or have an MNE version prior to  
May 5.

Thanks to Eliezer Kanal to bringing up the question about consistency  
between mne_analyze/mne_make_movie and mne_compute_raw_inverse, which  
lead to the discovery of this trouble.

Sorry for the inconvenience,
Matti


PS. The "dev" version common MNE software installation at the Martinos  
Center has been updated to 2.6.2. The "standard" version is unaffected.


---------

Matti Hamalainen, Ph.D.
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital

msh at nmr.mgh.harvard.edu






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