Re: [OMPI users] Simple MPI_Comm_spawn program hangs

[Prakash Velayutham]

Thanks Edgar. I did not know that. Really?

Anyways, you are sure, an MPI job will work as a spawned process  
instead of "hostname"?

Thanks,
Prakash


On Dec 1, 2007, at 5:56 PM, Edgar Gabriel wrote:

MPI_Comm_spawn has to build an intercommunicator with the child  
process
that it spawns. Thus, you can not spawn a non-MPI job such as
/bin/hostname, since the parent process waits for some messages from  
the
child process(es) in order to set up the intercommunicator.

Thanks
Edgar

Prakash Velayutham wrote:
Hello,

Open MPI 1.2.4

I am trying to run a simple C program.

######################################################################################

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

void
main(int argc, char **argv)
{

        int             tag = 0;
        int             my_rank;
        int             num_proc;
        char            message_0[] = "hello slave, i'm your master";
        char            message_1[50];
        char            master_data[] = "slaves to work";
        int             array_of_errcodes[10];
        int             num;
        MPI_Status      status;
        MPI_Comm        inter_comm;
        MPI_Info        info;
        int             arr[1];
        int             rc1;

        MPI_Init(&argc, &argv);
        MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
        MPI_Comm_size(MPI_COMM_WORLD, &num_proc);

        printf("MASTER : spawning a slave ... \n");
        rc1 = MPI_Comm_spawn("/bin/hostname", MPI_ARGV_NULL, 1,
MPI_INFO_NULL, 0, MPI_COMM_WORLD, &inter_comm, arr);

        MPI_Finalize();
        exit(0);
}

######################################################################################


This program hangs as below:

prakash@bmi-xeon1-01:~/thesis/CS/Samples> ./master1
MASTER : spawning a slave ...
bmi-xeon1-01

Any ideas  why?

Thanks,
Prakash
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--
Edgar Gabriel
Assistant Professor
Parallel Software Technologies Lab      http://pstl.cs.uh.edu
Department of Computer Science          University of Houston
Philip G. Hoffman Hall, Room 524        Houston, TX-77204, USA
Tel: +1 (713) 743-3857                  Fax: +1 (713) 743-3335
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