On Oct 16, 2008, at 5:33 PM, Jeff Squyres wrote:

main() { MPI_INIT(); spawn_threads(8, thread_main, NULL); wait_for_threads(); MPI_FINALIZE(); }

void thread_main(void *arg) { MPI_Comm comm1; MPI_THREAD_REGISTER(MPI_COMM_SELF, my_thread_id, 8, comm1); spawn_threads(8, secondary_thread_main, comm1); }

void secondary_thread_main(void *arg) { MPI_Comm comm2, parent = (MPI_Comm) arg; MPI_THREAD_REGISTER(parent, my_thread_id, 8, &comm2); }

Never mind -- this was a bad example. The grouping above is guaranteed because of the unique values of the parent communicator. Hmm. Something still bugs me about this, but I can't quite put my finger on it. I'll therefore shut up about this specific point until I can be clear about it. :-) -- Jeff Squyres Cisco Systems