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Subject: [OMPI users] Core ids not coming properly
From: Kranthi Kumar (kranthipls_at_[hidden])
Date: 2013-02-15 11:34:11

Hello Sir

Here below is the code which I wrote using hwloc for getting the bindings
of the processes.
I tested this code on SDSC Gordon Super Computer which has Open MPI 1.4.3
and on TACC Stampede which uses intel's MPI library IMPI.
With Open MPI I get all the core ids for all the processes as 0. Using
Intel MPI library I get different coreids. I tried even binding the
in the command line using taskset. Open MPI gives me core id 0 for all the
processes whereas IMPI gives me correct bindings.
Please look into this

#include <stdio.h>
#include <sched.h>
#include <math.h>
#include "mpi.h"
#include <hwloc.h>
int main(int argc, char* argv[])
    int rank, size;
    cpu_set_t mask;
    long num;
    int proc_num(long num);

    hwloc_topology_t topology;
    hwloc_cpuset_t cpuset;
    hwloc_obj_t obj;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    hwloc_topology_init ( &topology);
    hwloc_topology_load ( topology);

    hwloc_bitmap_t set = hwloc_bitmap_alloc();
    hwloc_obj_t pu;
    int err;

    err = hwloc_get_proc_cpubind(topology, getpid(), set,
    if (err) {
    printf ("Error Cannot find\n"), exit(1);

    pu = hwloc_get_pu_obj_by_os_index(topology, hwloc_bitmap_first(set));
    printf ("Hello World, I am %d and pid: %d

    return 0;
Thank You