I don't know (I'm a little new to this area), but I figured out how to get around the problem:
Using SGE and MVAPICH2, the "-env MV2_CPU_MAPPING 0:1....." option in mpiexec seems to do the trick.
So when calling the external program with mpiexec, I map the called
process to the current core rank, and it seems to stay distributed and
separated as I want.
Hope someone else finds this useful in the future.
> Date: Wed, 3 Mar 2010 13:13:01 +1100 > Subject: Re: [OMPI users] running external program on same processor (Fortran) > > Surely this is the problem of the scheduler that your system uses, > rather than MPI? > > > On Wed, 2010-03-03 at 00:48 +0000, abc def wrote: > > Hello, > > > > I wonder if someone can help. > > > > The situation is that I have an MPI-parallel fortran program. I run it > > and it's distributed on N cores, and each of these processes must call > > an external program. > > > > This external program is also an MPI program, however I want to run it > > in serial, on the core that is calling it, as if it were part of the > > fortran program. The fortran program waits until the external program > > has completed, and then continues. > > > > The problem is that this external program seems to run on any core, > > and not necessarily the (now idle) core that called it. This slows > > things down a lot as you get one core doing multiple tasks. > > > > Can anyone tell me how I can call the program and ensure it runs only > > on the core that's calling it? Note that there are several cores per > > node. I can ID the node by running the hostname command (I don't know > > a way to do this for individual cores). > > > > Thanks! > > > > ==== > > > > Extra information that might be helpful: > > > > If I simply run the external program from the command line (ie, type > > "/path/myprogram.ex <enter>"), it runs fine. If I run it within the > > fortran program by calling it via > > > > CALL SYSTEM("/path/myprogram.ex") > > > > it doesn't run at all (doesn't even start) and everything crashes. I > > don't know why this is. > > > > If I call it using mpiexec: > > > > CALL SYSTEM("mpiexec -n 1 /path/myprogram.ex") > > > > then it does work, but I get the problem that it can go on any core. > > > > ______________________________________________________________________ > > Do you want a Hotmail account? Sign-up now - Free > > _______________________________________________ > > users mailing list > > email@example.com > > http://www.open-mpi.org/mailman/listinfo.cgi/users > > _______________________________________________ > users mailing list > firstname.lastname@example.org > http://www.open-mpi.org/mailman/listinfo.cgi/users