[mvapich-discuss] reduce in place

[Roland Schulz]

Hi,

the below program crashes in MPI_Reduce. It works fine in OpenMPI or an
equivalent version without MPI_IN_PLACE. Is MPI_IN_PLACE not supported with
MPI_Reduce?
Or do I call it wrong? Or is this a bug in mvapich?
It segfaults in 1.0.2 and 1.4 (with ofed 1.1).

Thanks Roland

==========
#include <mpi.h>
#include <stdlib.h>

int main(int argc, char** argv)
{
  double nr = 4;
  double *r = (double*)malloc(nr*sizeof(double));
  MPI_Comm comm_intra;
  int rank;

  MPI_Init(&argc,&argv);
  comm_intra = MPI_COMM_WORLD;
  MPI_Comm_rank(comm_intra, &rank);

  if (rank==0) {
    MPI_Reduce(MPI_IN_PLACE,r,nr,MPI_DOUBLE,MPI_SUM,0,
               comm_intra);
  } else {
    MPI_Reduce(r,NULL,nr,MPI_DOUBLE,MPI_SUM,0,comm_intra);
  }
  free(r);
  return 0;
}

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ORNL/UT Center for Molecular Biophysics cmb.ornl.gov
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