[R-sig-Debian] Accessto OpenBLAS

[Dirk Eddelbuettel]

On 23 February 2012 at 09:08, Scott Raynaud wrote:
| So my experiments have confirmed that the binary version of
| OpenBLAS uses onlt two cores.  Should the compiled version
| use more?
| 
| I want figure out which package to utilize mulitiple cores in
| a UNIX environment.  Did some research on this a while back 
| but it's a bit fuzzy right now.  My main concern is there's a 
| warning about BLAS and multiple cores in the install docs.
| Will I run into problems?

Did you see the README?  

   4.Usages
   Link with libopenblas.a or -lopenblas for shared library.

   4.1 Set the number of threads with environment variables. for example,
   export OPENBLAS_NUM_THREADS=4
    or
   export GOTO_NUM_THREADS=4
    or 
   export OMP_NUM_THREADS=4
   
   The priorities are OPENBLAS_NUM_THREADS > GOTO_NUM_THREADS > OMP_NUM_THREADS.
   
   If you compile this lib with USE_OPENMP=1, you should only set OMP_NUM_THREADS environment variable.

Some BLAS libraries can respond to environment variables at run-time: MKL,
GotoBlas and hence OpenBlas.  For others such as Atlas this is fixed at
compile time.

Dirk

-- 
"Outside of a dog, a book is a man's best friend. Inside of a dog, it is too
dark to read." -- Groucho Marx