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Solved: changing number of OpenBLAS threads from inside R

Claudia Beleites 
Dear all,

Simon has been making great progress on our attempts to trade off
implicit (by BLAS) and explicit (e.g. SNOW) parallelization.

One important missing point was the ability to change the number of
threads used by the BLAS during an R session. This gap is filled now for
OpenBLAS by package OpenBlasThreads (on
https://github.com/simonfullernuim/OpenBlasThreads; basically just one
line of C code).

He wrote a blog post about it:
http://hyperspec.wordpress.com/2012/07/26/altering-openblas-threads/
where he also gives alternative code that can be used with inline, so no
package installation is needed.

Note that OpenBLAS does not yet have this functionality implemented for
Windows, so obviously changing number of threads doesn't work there.

So far, we've been testing it on Ubuntu 64bit with manually installed
OpenBLAS as well as with installation from the Ubuntu sources, and we'd
be grateful if you could test it on different linux distros and let us
know whether it works.

Have a nice weekend,

Claudia and Simon