Note from my first mail on this thread:
"As per MPI-2 p84, the command, argv, maxprocs, and info arguments to
MPI_COMM_SPAWN are only significant in the root process."
Specifically: MPI says that it doesn't matter what you put in argv on
any process other than the root. The argv from the root is the only
argv that matters.
By changing your application to use MPI_COMM_SELF, this effectively
makes every process the root, and therefore it launches 8 different
processes (each with their own MPI_COMM_WORLD). That's why you see 8
"rank 0"s. Yes, they're all rank 0, but from different
MPI_COMM_WORLD's. Additionally, none of those processes can
communicate with each other -- they can only communicate with their
parent, which, in this case, is one process from the original MPI
application that you ran (probably via mpirun).
Also note from my previous mail:
"If you want to launch N processes, each with different arguments, then
you need to use either multiple calls to MPI_COMM_SPAWN (i.e., each one
with a different argv), or MPI_COMM_SPAWN_MULTIPLE, where you can
specify an array of argv."
If you want these 8 processes to share a common MPI_COMM_WORLD, and you
only want one launch command, then you really need to use
MPI_COMM_SPAWN_MULTIPLE.
On Dec 6, 2004, at 11:32 AM, Gabriel Antoine Louis Paillard wrote:
> Now, after some modifications in the same code, finally I have
> the desired output (all processes received their argument), but the
> rank
> 0 executed 8 times the same thing.
>
>
> #include <stdio.h>
> #include <mpi.h>
>
> int slave ();
>
>
> int main(int argc,char *argv[])
> {
> int myrank;
> double starttime,endtime;
>
> MPI_Init(&argc, &argv);
> starttime = MPI_Wtime();
> MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
>
> switch(myrank) {
> case 0:
> slave(1);
> break;
> case 1:
> slave(7);
> break;
> case 2:
> slave(11);
> break;
> case 3:
> slave(13);
> break;
> case 4:
> slave(17);
> break;
> case 5:
> slave(19);
> break;
> case 6:
> slave(23);
> break;
> case 7:
> slave(29);
> break;
> }
> endtime = MPI_Wtime();
> printf("time: %1.15f\n", endtime-starttime);
>
> MPI_Finalize();
> exit(0);
> }
>
> int slave (unsigned long int argument)
> {
> char command[] = "Program";
> char **argv;
> int errcode;
> int err,mon_rang;
> MPI_Comm nouveau_monde;
>
> mon_rang=MPI_Comm_rank(MPI_COMM_WORLD, &mon_rang);
>
> argv=(char **)malloc(2*sizeof(char *));
> argv[0]=(char*)malloc(100*sizeof(char));
> sprintf(argv[0],"%ld",argument);
> argv[1] = NULL;
>
> MPI_Comm_set_errhandler(MPI_COMM_WORLD,MPI_ERRORS_RETURN);
>
> err=MPI_Comm_spawn(command,argv,8,MPI_INFO_NULL,mon_rang,MPI_COMM_SELF,
> &nouveau_monde,&errcode);
>
> return(0);
> }
>
> Thanks again,
>
> Gabriel Paillard
>
> _______________________________________________
> This list is archived at http://www.lam-mpi.org/MailArchives/lam/
>
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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