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Subject: Re: [OMPI users] Option to use only 7 cores out of 8 on each node
From: Dave Love (d.love_at_[hidden])
Date: 2010-03-04 13:02:54

"Addepalli, Srirangam V" <srirangam.v.addepalli_at_[hidden]> writes:

> It works after creating a new pe and even from the command prompt with
> out using SGE.

You shouldn't need anything special -- I don't. (It's common to run,
say, one process per core for benchmarking.) Running

  mpirun -tag-output -np 14 -npernode 7 hostname

in 16 slots in the following PE (which confines the run to our 8-core
nodes) it shows 7 processes on each of 2 nodes. The nodes have
exclusive access for MPI jobs, but I don't think that's relevant.

  pe_name openmpi-8
  slots 999
  user_lists NONE
  xuser_lists NONE
  start_proc_args /bin/true
  stop_proc_args /bin/true
  allocation_rule 8
  control_slaves TRUE
  job_is_first_task FALSE
  urgency_slots min
  accounting_summary FALSE

In this case, you'd get the same effect allocating processes -bynode as
using -npernode.