[mpich-discuss] Problem reproducing an example from the MPI standard

[Pavan Balaji]

The example is correct, since it's in Fortran.  Your conversion to C is 
incorrect.  You probably want to use MPI_DOUBLE instead of MPI_REAL, and 
MPI_INT instead of MPI_INTEGER.

  -- Pavan

On 06/22/2013 11:49 AM, Jiri Simsa wrote:
> Hi,
>
> I tried implementing the Example 3.17 from the MPI 3.0 specification
> document using as follows:
>
> #include <assert.h>
> #include <mpi.h>
> #include <stdio.h>
>
> int main(int argc, char *argv[]) {
>    int myrank, size;
>    MPI_Status status;
>    MPI_Init(&argc, &argv );
>    MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
>    MPI_Comm_size(MPI_COMM_WORLD, &size);
>    assert(size == 3);
>    if (myrank == 0) {
>      /* code for process zero */
>      int i = 1;
>      MPI_Send(&i, 1, MPI_INTEGER, 2, 99, MPI_COMM_WORLD);
>    }
>    if (myrank == 1) {
>      /* code for process one */
>      double d = 3.14;
>      MPI_Send(&d, 1, MPI_REAL, 2, 99, MPI_COMM_WORLD);
>    }
>    if (myrank == 2) {
>      /* code for process two */
>      for (int i = 0; i < 2; i++) {
>        MPI_Probe(MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
>        printf("Probe matched %lld bytes from source %d.\n",
>               status.count, status.MPI_SOURCE);
>        if (status.MPI_SOURCE == 0) {
> int i;
> MPI_Recv(&i, 1, MPI_INTEGER, 0, 99, MPI_COMM_WORLD, &status);
> printf("Received integer '%d' from %d.\n", i, status.MPI_SOURCE);
>        } else {
> double d;
> MPI_Recv(&d, 1, MPI_REAL, 1, 99, MPI_COMM_WORLD, &status);
> printf("Received real '%f' from %d.\n", d, status.MPI_SOURCE);
>        }
>      }
>    }
>    MPI_Finalize();
>    return 0;
> }
>
> This example compiles without any warning with the MPICH-3.0.4 library.
> However, running:
>
> $ mpiexec -n 3 ./example
>
> leads to the following output:
>
> Probe matched 4 bytes from source 1.
> Received real '0.000000' from 1.
> Probe matched 4 bytes from source 0.
> Received integer '1' from 0.
>
> Could someone please let me know what is the problem with my program? I
> failed to see a problem there. Thank you.
>
> Best,
>
> --Jiri Simsa
>
>
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-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji