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Subject: Re: [OMPI users] MPI jobs ending up in one node
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-03-13 09:47:11

Hmmm...your comments don't sound like anything relating to Open MPI.
Are you sure you are not using some other MPI?

Our mpiexec isn't a script, for example, nor do we have anything named


On Mar 13, 2009, at 4:00 AM, Peter Teoh wrote:

> I saw the following problem posed somewhere - can anyone shed some
> light? Thanks.
> I have a cluster of 8-sock quad core systems running Redhat 5.2. It
> seems that whenever I try to run multiple MPI jobs to a single node
> all the jobs end up running on the same processors. For example, if I
> were to submit 4 8-way jobs to a single box they all end up in CPUs 0
> to 7, leaving 8 to 31 idle.
> I then tried all sorts of I_MPI_PIN_PROCESSOR_LIST combinations but
> short of explicitly listing out the processors at each run, they all
> end up still hanging on to CPUs 0-7. Browsing through the mpiexec
> script, I realise that it is doing a taskset on each run.
> As my jobs are all submitted through a scheduler (PBS in this case) I
> cannot possibly know at job submission time which CPUs are not used.
> So is there a simple way to tell mpiexec to set the taskset affinity
> correctly at each run so that it will choose only the idle processors?
> Thanks.
> --
> Regards,
> Peter Teoh
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