Dear all, I have a code where two processes (forming the original MPI_COMM_WORLD) each spawn one additional child process (using MPI_COMM_SELF as spawning group). Now I want to create an intra-comm that covers all of these four processes. For doing so, I initially merge the two inter-comms resulting from the spawn calls into two new intra-comms (by using MPI_Intercomm_merge()). Then I create via MPI_intercomm_create() a new inter-comm that connects these two by using the original world communicator as peer-com. Finally, I merge the resulting inter-comm into the desired intra-comm. When using Open MPI, my code (it's derived from the MPICH test spaiccreate2.c, see attachment) works fine on my local machine. However, when running it with MPICH-3.1.2, I get the following error message: PMPI_Intercomm_create(601).....: MPI_Intercomm_create(comm=0x84000006, local_leader=1, MPI_COMM_WORLD, remote_leader=1, tag=123, newintercomm=0x7fff8323ee3c) failed MPIR_Intercomm_create_impl(258): MPID_GPID_ToLpidArray(461).....: Internal MPI error: Unknown gpid (1809769587)0 Fatal error in PMPI_Intercomm_create: Internal MPI error!, error stack: PMPI_Intercomm_create(601).....: MPI_Intercomm_create(comm=0x84000004, local_leader=1, MPI_COMM_WORLD, remote_leader=0, tag=123, newintercomm=0x7fff6e0b4c7c) failed MPIR_Intercomm_create_impl(258): MPID_GPID_ToLpidArray(461).....: Internal MPI error: Unknown gpid (1607388239)0 Here are my questions: 1) Is the above mentioned approach the right way to reach my goal? 2) Is the semantics of the attached code MPI compliant? 3) What is the reason for the error message when using MPICH? Thanks in advance and with kind regards, Carsten -- Carsten Clauss www.par-tec.com _____________________________________ ParTec Cluster Competence Center GmbH Possartstrasse 20 D-81679 Muenchen Geschäftsführer RA. Dipl.-Ing. Bernhard Frohwitter Eingetragen beim Amtsgericht München HRB 151545 Steuer-Nr. 08/32305, Ust-ID DE235527064 _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss