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Thread Subject: omp_get_num_threads() (again)

Subject: omp_get_num_threads() (again)

From: Sebastiaan

Date: 29 May, 2008 13:48:02

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The omp_get_num_threads() does not work properly, as well as
similar functions for getting the maximum number of threads etc.

The problem is that omp_get_num_threads() always returns 1,
no matter to what maxNumCompThreads() is set in Matlab.

This was previously reported in this newsgroup:
http://www.mathworks.com/matlabcentral/newsreader/view_thread/157701#416259

The solution given there is to:
>> setenv('OMP_NUM_THREADS','2')
>> maxNumCompThreads(2)

However, this does not work for me in 2008a and 2007b
(x86_64 Linux). The observation by CPU usage is however,
that the loops are parallellized properly.

I would like to use omp_get_num_threads() to default to a
(faster) sequential code when only 1 thread is used.

This is a test listing I used, compiled with Intel C
compiler version 10.

Thanks,
Sebastiaan

#include "mex.h"
#include <omp.h>

void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const
mxArray* prhs[])
{
mexPrintf("Num threads %d.\n", omp_get_num_threads());
}

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Tag	Applied By	Date/Time
openmp	Sebastiaan	29 May, 2008 09:50:25
omp	Sebastiaan	29 May, 2008 09:50:25
mex	Sebastiaan	29 May, 2008 09:50:25

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