Compilation with OmpSs-2 and OpenMP

[bsc-pm]

Compilation with OmpSs-2 and OpenMP

[rofirrim]

Hi @Z10Frank,

I think in this case you can use #pragma oss task for as described here

https://pm.bsc.es/ftp/ompss-2/doc/spec/directives/index.html#task-for-clause

Let me know if this is useful.

Kind regards,

[Z10Frank]

Hello,
thank you for your answer, I know the #pragma oss task for construct, but my purpose was rather to understand the compatibility with OpenMP itself.

The objective is to progressively "taskify" a load imbalanced part of an existing code that already uses OpenMP, in particular with parallel regions, omp for, omp simd. So a preliminary question is if the use of OmpSs-2 in this code would imply the substitution of all existing OpenMP pragmas with "equivalents" in OmpSs-2. Or if there is a way to switch between OpenMP and OmpSs-2 pragmas with an if condition.

[rofirrim]

The objective is to progressively "taskify" a load imbalanced part of an existing code that already uses OpenMP, in particular with parallel regions, omp for, omp simd. So a preliminary question is if the use of OmpSs-2 in this code would imply the substitution of all existing OpenMP pragmas with "equivalents" in OmpSs-2.

The OmpSs-2 compatibility with OpenMP is limited. It may happen that some constructs will require you to substitute/temporarily disable the unsupported OpenMP constructs.

Or if there is a way to switch between OpenMP and OmpSs-2 pragmas with an if condition.

Not sure what you mean by "if" condition here, one option is using the macro _OMPSS_2 so you can enable OpenMP or OmpSs-2 progressively in your code. This macro is enabled when you use --ompss-2 with Mercurium.

#if _OMPSS_2
#pragma oss task ...
#else 
#pragma omp ...
#endif

Hope this helps.

[Z10Frank]

Thank you!
To keep it in the archives, my test after the modifications:

#include <stdio.h>
#include <iostream>
#include <omp.h>

using namespace std;

int main(int argc, char *argv[])
{
    #ifndef _OMPSS_2
    #pragma omp parallel
    #endif
    {

    #ifndef _OMPSS_2
    //with OpenMP
    #pragma omp for
    for (int i=0; i<10; i++)
    {
        #pragma omp critical
        cout<<"Hello omp for from thread "<<omp_get_thread_num()<<" iteration "<<i<<"\n"<<endl;
    }

    #else
    // with OmpSs-2
    for (int i=0; i<10; i++)
    {
        #pragma oss task firstprivate(i)
        {
        #pragma oss critical
        {
            cout<<"Hello OmpSs-2/, iteration "<<i<<endl;
        }
        }
    }
    #endif

    } // end parallel region if OpenMP is used
    return 0;

}

To compile with OpenMP:

mpiicpc -o test_OpenMP -fopenmp test_OpenMP_OmpSs-2.cpp

To compile with OmpSs-2:

I_MPI_CXX=mcxx MPICH_CXX=mcxx OMPI_CXX=mcxx mpiicpc -o test_OmpSs-2 --ompss-2 test_OpenMP_OmpSs-2.cpp