So, it appears that for a machine of this type (dual quad core cpu's), this approach would be correct for my tests...

[jpummill@n1 bin]$ more my-hosts
n1 slots=8 max_slots=8

and subsequently, launch two jobs in this configuration...
/home/jpummill/openmpi-1.2.2/bin/mpirun --hostfile my-hosts -np 4 --byslot ./cg.C.4

It appears that this does avoid oversubscribing any particular core as I am not exceeding my core count by running just the two jobs requiring 4 cores each.

Thanks,

Jeff Pummill





George Bosilca wrote:
The cleaner way to define such an environment is by using the max-slots and/or slots options in the hostfile. Here is a FAQ entry about how Open MPI deal with these options (http://www.open-mpi.org/faq/?category=running#mpirun-scheduling).

  george.


On Oct 26, 2007, at 10:52 AM, Jeff Pummill wrote:

I am doing some testing on a variety of 8-core nodes in which I just want to execute a couple of executables and have them distributed to the available cores without overlapping. Typically, this would be done with a parameter like -machinefile machines, but I have no idea what names to put into the machines file as this is a single node with two quad core cpu's. As I am launching the jobs sans scheduler, I need to specify what cores to run on I would think to keep from overscheduling some cores while others receive nothing to do at all.

Simple suggestions? Maybe Open MPI takes care of this detail for me?

Thanks!

Jeff Pummill
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