I was able to reproduce with my own test ( https://github.com/jeffhammond/HPCInfo/blob/master/mpi/bugs/iprobe-overflow....) with Intel MPI 2019, so I will report that bug to the Intel MPI team. It should be easy enough for them to figure out if this bug is from MPICH or not. 2139000000 iterations, 627.143272 seconds 2140000000 iterations, 627.436206 seconds 2141000000 iterations, 627.729135 seconds 2142000000 iterations, 628.022049 seconds 2143000000 iterations, 628.315015 seconds 2144000000 iterations, 628.608066 seconds 2145000000 iterations, 628.901065 seconds 2146000000 iterations, 629.193992 seconds 2147000000 iterations, 629.488107 seconds Abort(738833413) on node 0 (rank 0 in comm 0): Fatal error in PMPI_Iprobe: Invalid communicator, error stack: PMPI_Iprobe(123): MPI_Iprobe(src=MPI_ANY_SOURCE, tag=MPI_ANY_TAG, MPI_COMM_WORLD, flag=0x7ffdf75a396c, status=0x7ffdf75a3970) failed PMPI_Iprobe(90).: Invalid communicator Jeff, who works for Intel but knows more about MPICH than Intel MPI On Mon, Jan 21, 2019 at 11:19 AM Joachim Protze via discuss < [email protected]> wrote:

Hi all,

we detected the behavior with IntelMPI 2019 (which is based on MPICH 3.3). Reproducing it with MPICH-3.3 was not yet successful. But I fear, that our built of MPICH just not uses the necessary code path / build flags.

When calling MPI_Iprobe with the same communicator for ~2^31 times (which can take 10-30 minutes), the execution stops with:

Abort(201962501) on node 0 (rank 0 in comm 0): Fatal error in PMPI_Iprobe: Invalid communicator, error stack: PMPI_Iprobe(123): MPI_Iprobe(src=MPI_ANY_SOURCE, tag=MPI_ANY_TAG, MPI_COMM_WORLD, flag=0x7ffd925056c0, status=0x7ffd92505694) failed PMPI_Iprobe(90).: Invalid communicator

From my understanding of the referenced MPICH code lines, I guess, that the ref-count for MPI_COMM_WORLD overflows, which triggers this error message.

Best Joachim

-- Dipl.-Inf. Joachim Protze

IT Center Group: High Performance Computing Division: Computational Science and Engineering RWTH Aachen University Seffenter Weg 23 D 52074 Aachen (Germany) Tel: +49 241 80- 24765 Fax: +49 241 80-624765 [email protected] www.itc.rwth-aachen.de

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-- Jeff Hammond [email protected] http://jeffhammond.github.io/