[pymvpa] how to do multiprocessing in pymvpa?

Michael Hanke mih at debian.org
Mon Feb 4 18:06:29 UTC 2013

Hi Meng,

On Mon, Feb 04, 2013 at 05:57:17PM +0000, Meng Liang wrote:
> However, it does not work on Mac. I googled but didn't find much
> relevant info about it - I got the feeling that pprocess is not
> supported in Mac. Is it true? If so, doesn't that mean running pymvpa
> on Mac machines cannot utilize multi-core computation?

It should work just fine on a Mac. Did you make multiple CPU-cores
available to the VM?

> Finally, an irrelevant question: is the value of 'radius' parameter in
> the Searchlight command in millimeter? It says so in Pymvpa
> documentation (
> http://www.pymvpa.org/modref/mvpa.measures.searchlight.html ). But in
> a given example on Pymvpa website, it seems to suggest that the value
> of 'radius' means the number of voxels (
> http://www.pymvpa.org/examples/searchlight_minimal.html ): "# setup
> searchlight with 2 voxels radius" and "sl = sphere_searchlight(cv,
> radius=2, space='myspace',...". It's a bit confusing to me...

The radius used to be in mm, but we have changed this after the 0.4
series (that is the version whose documentation you are citing).
Afterwards the radius is in 'elements'


> Also, do you know if multi-core support is also available for other
> commands other than searchlight? I find that cross-validation with
> large number of permutations is also quite slow - it would be good if
> multi-core support is also implemented in the permutation scenario. 

This is something we are working on, but isn't available yet.



Michael Hanke

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