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Subject: Re: [OMPI users] Simple MPI_Comm_spawn program hangs
From: Prakash Velayutham (prakash.velayutham_at_[hidden])
Date: 2007-12-01 18:36:15


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_at_bmi-xeon1-01:~/thesis/CS/Samples> ./master1
>> MASTER : spawning a slave ...
>> bmi-xeon1-01
>>
>> Any ideas why?
>>
>> Thanks,
>> Prakash
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
> --
> 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
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users