Dear all,
I want to share with you the follow issue with the OpenMPI shipped with the
latest Ubuntu Artful. It is OpenMPI 2.1.1 compiled with
option --enable-heterogeneous.
Looking at this issue https://github.com/open-mpi/ompi/issues/171, it
appears that this option is broken and should not be used.
This option is being used in Debian/Ubuntu since 2010 (
http://changelogs.ubuntu.com/changelogs/pool/universe/o/ope
nmpi/openmpi_2.1.1-6/changelog) and is still used so far. Apparently,
nobody complained so far.
However, now I complain :-)
I've found a simple example for which this option causes invalid results in
OpenMPI.
int A = 666, B = 42;
MPI_Irecv(&A, 1, MPI_INT, MPI_ANY_SOURCE, tag, comm, &req);
MPI_Send(&B, 1, MPI_INT, my_rank, tag, comm);
MPI_Wait(&req, &status);
# After that, when compiled with --enable-heterogeneous, we have A != B
This happens with just a single process. The full example is in attachment
(to be run with "mpirun -n 1 ./bug_openmpi_artful").
I extracted and simplified the code from the Zoltan library with which I
initially noticed the issue.
I find it annoying that Ubuntu distributes a broken OpenMPI.
I've also tested OpenMPI 2.1.1, 2.1.2 and 3.0.0 and using
--enable-heterogeneous causes the bug systematically.
Finally, my points/questions are:
- To share with you this small example in case you want to debug it
- What is the status of issue https://github.com/open-mpi/ompi/issues/171 ?
Is this option still considered broken?
If yes, I encourage you to remove it or mark as deprecated to avoid this
kind of mistake in the future.
- To get the feedback of OpenMPI developers on the use of this option,
which might convince the Debian/Ubuntu maintainer to remove this flag.
I have opened a bug on Ubuntu for it https://bugs.launchpad.net/
ubuntu/+source/openmpi/+bug/1731938
Thanks!
Xavier
--
Dr Xavier BESSERON
Research associate
FSTC, University of Luxembourg
Campus Belval, Office MNO E04 0415-040
Phone: +352 46 66 44 5418
http://luxdem.uni.lu/
#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[])
{
int rc;
rc = MPI_Init(&argc, &argv);
if (rc != MPI_SUCCESS) abort();
int my_rank;
rc = MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
if (rc != MPI_SUCCESS) abort();
int A = 666;
int B = 42;
printf("[BEFORE] A = %d - B = %d\n", A, B);
int tag = 2999;
MPI_Comm comm = MPI_COMM_WORLD;
MPI_Status status;
MPI_Request req;
rc = MPI_Irecv(&A, 1, MPI_INT, MPI_ANY_SOURCE, tag, comm, &req);
if (rc != MPI_SUCCESS) abort();
rc = MPI_Send(&B, 1, MPI_INT, my_rank, tag, comm);
if (rc != MPI_SUCCESS) abort();
rc = MPI_Wait(&req, &status);
if (rc != MPI_SUCCESS) abort();
printf("[AFTER] A = %d - B = %d\n", A, B);
if ( A != B )
{
printf("Error!!!\n");
}
rc = MPI_Finalize();
if (rc != MPI_SUCCESS) abort();
return 0;
}
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