[mpich-discuss] MPIR_Request_complete(232): INTERNAL ERROR: unexpected value in case statement

[Jeff Hammond]

Thanks.  That solves my issue (both with the code and the reason I
wrote it).  It means that the statement on 486 about no restrictions
is not exactly correct, but and the standard is not a user guide, one
can only reason about it with the entire contents in cache.

Jeff

On Thu, Jan 15, 2015 at 10:18 PM, Thakur, Rajeev <thakur at mcs.anl.gov> wrote:
> pg 483, ln 44-45:  "Multiple threads completing the same request. A program
> in which two threads block, waiting on the same request, is erroneous."
>
> Rajeev
>
>
> On Jan 16, 2015, at 12:03 AM, Jeff Hammond <jeff.science at gmail.com>
>  wrote:
>
> MPI-3 page 483 says: "two concurrently running threads may make MPI
> calls and the outcome will be as if the calls executed in some order,
> even if their execution is interleaved."
>
> The outcome of my program where the calls execute in some order is
> well-defined: the first call completes the request and the second call
> returns immediately since req=MPI_REQUEST_NULL.
>
> Furthermore, MPI-3 page 486 says that MPI_THREAD_MULTIPLE is defined
> to mean "Multiple threads may call MPI, with no restrictions."
> Without restriction implies that data races are valid.  The prior
> statement ensures that the result of a program with MPI-related races
> is well-defined.
>
> Do you disagree with my interpretation of MPI-3?
>
> Jeff
>
> On Thu, Jan 15, 2015 at 9:41 PM, Thakur, Rajeev <thakur at mcs.anl.gov> wrote:
>
> 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 <jeff.science at gmail.com>
> 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
> jeff.science at gmail.com
> http://jeffhammond.github.io/
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>
> --
> Jeff Hammond
> jeff.science at gmail.com
> http://jeffhammond.github.io/
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-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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