[mpich-discuss] problem with MPI_Get_count() for very long (but legal length) messages.

[Dave Goodell]

Barry,

Thanks for letting us know.  Skimming the code in the implementation,  
nothing obviously wrong is jumping out at me.  So I'll file a ticket  
for this and add the test case as a regression test.

-Dave

On Feb 5, 2010, at 2:28 PM, Barry Smith wrote:

>
> #include "mpi.h"
> #include "stdlib.h"
>
> #undef __FUNCT__
> #define __FUNCT__ "main"
> int main(int argc,char **argv)
> {
>  int ierr;
>  int    size,rank;
>  int            cnt  = 433438806;
>  MPI_Status     status;
>  long long int  *cols;
>
>  MPI_Init(&argc,&argv);
>  ierr = MPI_Comm_size(MPI_COMM_WORLD,&size);
>  ierr = MPI_Comm_rank(MPI_COMM_WORLD,&rank);
>
>  cols = (long long int*) malloc(cnt*sizeof(long long));
>  if (rank == 0) {
>    ierr = MPI_Send(cols,cnt,MPI_LONG_LONG_INT,1,0,MPI_COMM_WORLD);
>
>  } else {
>    ierr = MPI_Recv(cols,cnt,MPI_LONG_LONG_INT, 
> 0,0,MPI_COMM_WORLD,&status);
>    ierr = MPI_Get_count(&status,MPI_LONG_LONG_INT,&cnt);
>    printf("count %d\n",cnt);
>  }
>  ierr = MPI_Finalize();
>  return 0;
> }
>
> crush is a 64 bit system with 64 bit pointers.
>
> crush:/usr> which mpicc
> /soft/apps/packages/mpich2-1.2.1-gcc/bin/mpicc
> crush:/usr> which mpiexec
> /soft/apps/packages/mpich2-1.2.1-gcc/bin/mpiexec
>
> crush:~> mpicc mpitest.c
> mpitest.c: In function ‘main’:
> mpitest.c:25: warning: incompatible implicit declaration of built-in  
> function ‘printf’
> crush:~> mpiexec -n 2 a.out
> count -103432106
>
> I've had this problem reported to me by two completely different  
> PETSc users so it is a real problem, not just academic. My guess is  
> you don't use a long long int in the intermediate computations  
> needed to get the final value for count.
>
> To cheer you up, when I run with openMPI it runs forever sucking  
> down 100% CPU trying to send the messages :-)
>
>  Barry
>
>
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