Jim,
if i understand correctly, George point is that OpenMPI is currently
correct with respect to the MPI standard :
MPI_DATATYPE_NULL is *not* a predefined datatype, hence it is not
(expected to be) a committed datatype,
and hence it cannot be used in MPI_Alltoallw (regardless the
corresponding count is zero).
an other way to put this is mpich could/should have failed and/or you
were lucky it worked.
George and Jeff,
do you feel any need to ask MPI Forum to clarify this point ?
Cheers,
Gilles
On 1/13/2016 12:14 PM, Jim Edwards wrote:
Sorry there was a mistake in that code,
stypes and rtypes should be of type MPI_Datatype not integer
however the result is the same.
*** An error occurred in MPI_Alltoallw
*** reported by process [204406785,1]
*** on communicator MPI_COMM_WORLD
*** MPI_ERR_TYPE: invalid datatype
On Tue, Jan 12, 2016 at 7:55 PM, Jim Edwards <jedwa...@ucar.edu
<mailto:jedwa...@ucar.edu>> wrote:
Maybe the example is too simple. Here is another one which
when run on two tasks sends two integers from each task to
task 0. Task 1 receives nothing. This works with mpich and impi
but fails with openmpi.
#include <stdio.h>
#include <mpi.h>
my_mpi_test(int rank, int ntasks)
{
MPI_Datatype stype, rtype;
int sbuf[2];
int rbuf[4];
int slen[ntasks], sdisp[ntasks], stypes[ntasks], rlen[ntasks],
rdisp[ntasks], rtypes[ntasks];
sbuf[0]=rank;
sbuf[1]=ntasks+rank;
slen[0]=2;
slen[1]=0;
stypes[0]=MPI_INT;
stypes[1]=MPI_DATATYPE_NULL;
sdisp[0]=0;
sdisp[1]=4;
if(rank==0){
rlen[0]=2;
rlen[1]=2;
rtypes[0]=MPI_INT;
rtypes[1]=MPI_INT;
rdisp[0]=0;
rdisp[1]=8;
}else{
rlen[0]=0;
rlen[1]=0;
rtypes[0]=MPI_DATATYPE_NULL;
rtypes[1]=MPI_DATATYPE_NULL;
rdisp[0]=0;
rdisp[1]=0;
}
MPI_Alltoallw(sbuf, slen, sdisp, stypes, rbuf, rlen, rdisp,
rtypes, MPI_COMM_WORLD);
if(rank==0){
printf("%d %d %d %d\n",rbuf[0],rbuf[1],rbuf[2],rbuf[3]);
}
int main(int argc, char **argv)
{
int rank, ntasks;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD, &ntasks);
printf("rank %d ntasks %d\n",rank, ntasks);
my_mpi_test(rank,ntasks);
MPI_Finalize();
}
--
Jim Edwards
CESM Software Engineer
National Center for Atmospheric Research
Boulder, CO
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