Re: [OMPI users] MPI_Comm_spawn, caller uses CPU while waiting for spawned processes

[Eugene Loh]

Nicolas Bock wrote: On Fri, Dec 4, 2009 at 10:29, Eugene Loh <eugene....@sun.com> wrote: I think you might observe a world of difference if the master issued some non-blocking call and then intermixed MPI_Test calls with sleep calls.  You should see *much* more subservient behavior.  As I remember, putting such passivity into OMPI is on somebody's to-do list, but just not very high. could you give me more details? Nope, sorry.  I'm going to drop out here.  The basic idea was something like: MPI_Irecv(); while ( !flag ) {   nanosleep(...);   MPI_Test(...&flag...); } but I was hoping to "leave the rest to the reader". I can't figure out how to do this. I could see that one way to implement what you are describing is: in slave.c: MPI_Send() to rank 0 in master.c MPI_IRecv() from the spawned processes while (1) {  MPI_Test(); } I can't figure out how to find the ranks that MPI_Comm_spawn() used. What's the source argument in MPI_IRecv() supposed to be?