I would say the program is erroneous. It is calling MPI_Wait concurrently on the same request, i.e., you are completing one operation twice. You can call MPI_Wait concurrently, but with different requests. Rajeev On Jan 15, 2015, at 11:32 PM, Jeff Hammond <[email protected]> wrote:

I am trying to run the following program. It's obviously a silly program but I wrote it to make an argument about the MPI standard. I don't believe it violates the MPI standard, but please let me know if I am mistaken.

smakramu-mobl:MPI jrhammon$ cat wait-race.c #include <stdio.h> #include <omp.h> #include <mpi.h>

int main(int argc, char * argv[]) { int provided; MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &provided); if (provided<MPI_THREAD_MULTIPLE) { printf("inadequate thread support\n"); MPI_Finalize(); }

MPI_Request req; MPI_Ibarrier(MPI_COMM_WORLD, &req); //req = MPI_REQUEST_NULL; #pragma omp parallel num_threads(2) shared(req) { MPI_Wait(&req, MPI_STATUS_IGNORE); }

printf("test finished\n"); MPI_Finalize(); return 0; }

I compile the program with MPICH git master and GCC 4.9.2 from about a week ago:

smakramu-mobl:MPI jrhammon$ mpicc -fopenmp -g -Wall wait-race.c

smakramu-mobl:MPI jrhammon$ mpichversion MPICH Version: 3.2a2 MPICH Release date: unreleased development copy MPICH Device: ch3:nemesis MPICH configure: CC=gcc-4.9 CXX=g++-4.9 FC=gfortran-4.9 F77=gfortran-4.9 --disable-cxx --enable-fortran --enable-threads=runtime --enable-g=dbg --with-pm=hydra --prefix=/opt/mpich/dev/gcc/default --enable-wrapper-rpath --enable-static --enable-shared MPICH CC: gcc-4.9 -g -O2 MPICH CXX: no -g MPICH F77: gfortran-4.9 -g -O2 MPICH FC: gfortran-4.9 -g -O2

Sometimes the program runs fine:

smakramu-mobl:MPI jrhammon$ mpiexec -n 2 ./a.out test finished test finished

And sometimes it fails like this:

smakramu-mobl:MPI jrhammon$ mpiexec -n 2 ./a.out test finished Fatal error in MPI_Wait: Internal MPI error!, error stack: MPI_Wait(187).............: MPI_Wait(request=0x7fff5b51ee88, status=0x1) failed MPIR_Wait_impl(84)........: MPIR_Request_complete(232): INTERNAL ERROR: unexpected value in case statement (value=78309520)

So either my program violates the MPI standard or there's a bug in MPICH. Please let me know which it is.

Thanks,

Jeff

-- Jeff Hammond [email protected] http://jeffhammond.github.io/ _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss

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