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Subject: [OMPI users] Bad MPI_Bcast behaviour when running over openib
From: Ake Sandgren (ake.sandgren_at_[hidden])
Date: 2009-09-11 07:18:24


Hi!

The following code shows a bad behaviour when running over openib.

Openmpi: 1.3.3
With openib it dies with "error polling HP CQ with status WORK REQUEST
FLUSHED ERROR status number 5 ", with tcp or shmem it works as expected.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "mpi.h"

int main(int argc, char *argv[])
{
    int rank;
    int n;

    MPI_Init( &argc, &argv );

    MPI_Comm_rank( MPI_COMM_WORLD, &rank );

    fprintf(stderr, "I am %d at %d\n", rank, time(NULL));
    fflush(stderr);

    n = 4;
    MPI_Bcast(&n, 1, MPI_INTEGER, 0, MPI_COMM_WORLD);
    fprintf(stderr, "I am %d at %d\n", rank, time(NULL));
    fflush(stderr);
    if (rank == 0) {
        sleep(60);
    }
    MPI_Barrier(MPI_COMM_WORLD);

    MPI_Finalize( );
    exit(0);
}

I know about the internal openmpi reason for it do behave as it does.
But i think that it should be allowed to behave as it does.

This example is a bit engineered but there are codes where a similar
situation can occur, i.e. the Bcast sender doing lots of other work
after the Bcast before the next MPI call. VASP is a candidate for this.

-- 
Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
Internet: ake_at_[hidden]   Phone: +46 90 7866134 Fax: +46 90 7866126
Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se