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

[Jiri Simsa]

Nevermind.

I was incorrectly using the MPI_REAL data type. After replacing it with the
MPI_DOUBLE data type the program was as expected.


On Sat, Jun 22, 2013 at 12:49 PM, Jiri Simsa <jsimsa at cs.cmu.edu> 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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