Hi Carsten,

I have written a minimal MPI program that does nothing:

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

int main(int argc, char* argv[]) {

    int my_id, other_id, size;
    int length = 1, tag = 1;
    int myvalue, othervalue;
    MPI_Status satus;

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

    printf("\n[size is %d and rank is %d]\n", size, my_id);

    MPI_Finalize();

    return 0;
}

I compile it like:

mpicc -Wall -ansi -o mpiTest mpiTest.c

Then I run it with:

mpirun -v -np 5 mpiTest

But it prints

[size is 1 and rank is 0]
21168 mpiTest running on n0 (o)

[size is 1 and rank is 0]
21169 mpiTest running on n0 (o)

[size is 1 and rank is 0]
21170 mpiTest running on n0 (o)

[size is 1 and rank is 0]
21171 mpiTest running on n0 (o)

[size is 1 and rank is 0]
21172 mpiTest running on n0 (o)

followed by:

-----------------------------------------------------------------------------
It seems that [at least] one of the processes that was started with
mpirun did not invoke MPI_INIT before quitting (it is possible that
more than one process did not invoke MPI_INIT -- mpirun was only
notified of the first one, which was on node n0).

mpirun can *only* be used with MPI programs (i.e., programs that
invoke MPI_INIT and MPI_FINALIZE). You can use the "lamexec" program
to run non-MPI programs over the lambooted nodes.
-----------------------------------------------------------------------------

Any ideas what probably is the problem?

Regards,
Al

On 10/10/07, Carsten Kutzner <ckutzne@gwdg.de> wrote:

Altu 59 wrote:
> Hi,
>
> I want to write an MPI program that is comprised of 5 nodes.
> Can I test this with lam on one machine?
>
> How can I create 5 nodes on one machine? Is it even possible?
Hi Al,

just boot LAM without arguments ('lamboot') and let mpirun know the
number of processes you want, e.g.

mpirun -np 5 myprog.x

That should do exactly what you want.
Carsten
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