On Mar 16, 2010, at 5:12 AM, abc def wrote: > 1. Since Spawn is non-blocking, but I need the parent to wait until the child > completes, I am thinking there must be a way to pass a variable from the > child to the parent just prior to the FINALIZE command in the child, to > signal that the parent can pick up the output files from the child. Am I > right in assuming that the message from the child to the parent will go to > the correct parent process? The value of "parent" in "CALL > MPI_COMM_GET_PARENT(parent, ierr)" is the same in all spawned processes, > which is why I ask this question.
Yes, you can MPI_SEND (etc.) between the parents and children, just like you would expect. Just be aware that the communicator between the parents and children is an *inter*communicator -- so you need to express the source/destination in terms of the "other" group. Check out the MPI spec for a description of intercommunicators. > 2. By launching the parent with the "--mca mpi_yield_when_idle 1" option, the > child should be able to take CPU power from any blocked parent process, thus > avoiding the busy-poll problem mentioned below. Somewhat. Note that the parents aren't blocked -- they *are* busy polling, but they call yield() in every pool loop. > If each host has 4 processors and I'm running on 2 hosts (ie, 8 processors in > total), then I also assume that the spawned child will launch on the same > host as the associated parent? If you have told Open MPI about 8 process slots and are using all of them, then spawned processes will start overlaying the original process slots -- effectively in the same order. -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
