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<div class="PlainText">I believe that your code is correct. I’ve gone through it to simplify things a bit (attached) and see the same errors as you. That’s probably a bug in MPICH that needs to be fixed unless someone else comes along and says that for MPI_INTERCOMM_CREATE
to work, all processes must be in the same peer_comm, which doesn’t seem to be what the standard says to me. I’ll create a ticket and add you as a CC so you can keep track of things.<br>
<br>
In the meantime, you can avoid this problem by using one of the other ways of setting up communication between two group of processes. You can use the connect/accept functions as per this ticket:
<a href="http://trac.mpich.org/projects/mpich/ticket/495">http://trac.mpich.org/projects/mpich/ticket/495</a> or you can change the way you spawn processes to have all processes in MPI_COMM_WORLD be involved in spawning the new processes. I don’t know if that
will actually work for your application, but it’s a stopgap measure while we fix this bug.<br>
<br>
Thanks,<br>
Wesley<br>
<br>
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> On Sep 26, 2014, at 10:50 AM, Carsten Clauss <c.clauss@fz-juelich.de> wrote:<br>
> <br>
> Dear all,<br>
> <br>
> 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).<br>
> <br>
> Now I want to create an intra-comm that covers all of these four processes.<br>
> <br>
> 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()).<br>
> <br>
> Then I create via MPI_intercomm_create() a new inter-comm that connects these two by using the original world communicator as peer-com.<br>
> <br>
> Finally, I merge the resulting inter-comm into the desired intra-comm.<br>
> <br>
> When using Open MPI, my code (it's derived from the MPICH test spaiccreate2.c, see attachment) works fine on my local machine.<br>
> However, when running it with MPICH-3.1.2, I get the following error message:<br>
> <br>
> PMPI_Intercomm_create(601).....: MPI_Intercomm_create(comm=0x84000006, local_leader=1, MPI_COMM_WORLD, remote_leader=1, tag=123, newintercomm=0x7fff8323ee3c) failed<br>
> MPIR_Intercomm_create_impl(258):<br>
> MPID_GPID_ToLpidArray(461).....: Internal MPI error: Unknown gpid (1809769587)0<br>
> Fatal error in PMPI_Intercomm_create: Internal MPI error!, error stack:<br>
> PMPI_Intercomm_create(601).....: MPI_Intercomm_create(comm=0x84000004, local_leader=1, MPI_COMM_WORLD, remote_leader=0, tag=123, newintercomm=0x7fff6e0b4c7c) failed<br>
> MPIR_Intercomm_create_impl(258):<br>
> MPID_GPID_ToLpidArray(461).....: Internal MPI error: Unknown gpid (1607388239)0<br>
> <br>
> Here are my questions:<br>
> 1) Is the above mentioned approach the right way to reach my goal?<br>
> 2) Is the semantics of the attached code MPI compliant?<br>
> 3) What is the reason for the error message when using MPICH?<br>
> <br>
> Thanks in advance and with kind regards,<br>
> Carsten<br>
> <br>
> -- <br>
> Carsten Clauss<br>
> <a href="http://www.par-tec.com">www.par-tec.com</a><br>
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