Hi Douglas, this an answer to my question on the paraview-mailinglist.
I have the same problem with paraview, that it simply waits for more to do in client-server(MPI) mode, but is running on 100%. Different MPI-Implementations seem to behave different here. Using MPICH2 for example does not result in 100% cpu-time for paraview while waiting. I desperate to know if that is possible with open-mpi, too. These FAQs where interesting, but did not help: http://www.open-mpi.org/faq/?category=running#oversubscribing http://www.open-mpi.org/faq/?category=running#force-aggressive-degraded Greetings Jens Eugene Loh schrieb: > Douglas Guptill wrote: > >> Hi: >> >> I am using openmpi-1.2.8 to run a 2 processor job on an Intel >> Quad-core cpu. Opsys is Debian etch. I am reaonably sure that, most >> of the time, one process is waiting for results from the other. The >> code is fortran 90, and uses mpi_send and mpi_recv. Yet >> "gnome-system-monitor" shows 2 cpus at 100%. >> >> So I read, and re-read, the FAQs, and found the mpi_yield_when_idle >> flag, and tried it: >> >> mpirun --host localhost,localhost,localhost,localhost --mca btl >> sm,self --mca mpi_yield_when_idle 1 --byslot -np 2 >> /home/dguptill/software/sopale_nested_2008-10-24/bin/sopale_nested_openmpi-intel-noopt >> >> >> And still get, for each run, two cpus are at 100%. >> >> My goal is to get the system to a minimum usage state, where only one >> cpu is being used, if one process is waiting for results from the >> other. >> >> Can anyone suggest if this is possible, and if so, how? >> >> > I'm no expert on this, but I've played with the same problem. I think I > did this on Solaris, but perhaps the behavior is the same on other OSes. > > One issue is that "yield" might mean "yield if there is someone else > ready to run". Like a traffic sign: if someone else is there, you > yield. If no one else is there, there's no way to tell that someone is > yielding. > > Next, even if someone else is trying to run, "yield" doesn't give give > up the CPU 100%. It's still rather pesky. > > So, one question is whether you really want to have an idle CPU. Do > you, or do you simply want another process, if there is one, to be able > to run? > > Not a real answer to your question, but hopefully this helps. > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users >
