MPI segmentation fault on Stampede

job.sh

#!/usr/bin/env bash
#SBATCH -J mpi_seg_fault
#SBATCH -n 16
#SBATCH -p normal
#SBATCH -t 48:00:00

ibrun ./a.out

mpi_seg_fault.c

#include <mpi.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
    int num = 1;
    int total;
    unsigned long count = 0;
    int rank;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    for (;;) {
        MPI_Allreduce(&num, &total, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
        if (++count % 1000000 == 0 && rank == 0) {
            printf("Count: %lu\n", count);
        }
    }
    MPI_Finalize();
}