Matlab crashes using mex-Function and openMP

I have a problem using matlab mexfunction and openMP instructions. I found some related topics but none of them were able to help me.

I want to use openMP with a mex-Function to create a .mexw64 file. But when i use my matlab function, matlab crashes in a brutal way.

Theses are my codes:

C++ code

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

    void mexFunction(int nlhs,
        mxArray *plhs[],
        int nrhs,
        const mxArray *prhs[])

    {
        #pragma omp parallel default(shared)
        {

        }
        mexPrintf("Hi !\n", N);
    }

Matlab code:

    clear all, close all, clc;

    testopenMP();
    clear mex;

When i call my function testopenMP matlab crashes. But if I comment the "#pragma omp parallel" instruction, everything work fine:

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

    void mexFunction(int nlhs,
        mxArray *plhs[],
        int nrhs,
        const mxArray *prhs[])

    {
        //#pragma omp parallel default(shared)
        {

        }
        mexPrintf("Hi !\n", N);
    }

Another important point, with the pragma omp parallel intruction, sometimes the program works, and sometimes it crashes...

Do you have any ideas of what crashes matlab ? Any help is welcolme

[James Tursa]

What is N?

[Sushant Mahajan]

Did you find a solution? I am having the same issue with a MEX code in FORTRAN. It crashes if I compile with -fopenmp flag, but runs smoothly without -fopenmp

mex feature_on_sun_fortran.F90 FFLAGS="$FFLAGS -O3" LDFLAGS="$LDFLAGS -O3"

The code does not even have a OMP_PARALLEL construct, it only has

include 'omp_lib.h'

[Matthew Hopcroft]

I just discovered that having a mexPrintf statement inside a OMP PARALLEL construct causes the program to crash. Move the print statement outside the parallel construct and it runs fine.

[Junda]

I met the same issue. Seems like MEX does not support mexPrintf inside OpenMP parallel region. Litterally can't find a way to output any information inside parallel region.