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Subject: Re: [OMPI users] Strange behaviour of SGE+OpenMPI
From: Dave Love (d.love_at_[hidden])
Date: 2009-03-31 14:50:27

Rolf Vandevaart <Rolf.Vandevaart_at_[hidden]> writes:

>> However, I found that if I explicitly specify the "-machinefile
>> $TMPDIR/machines", all 8 mpi processes were spawned within a single
>> node, i.e. node0002.

I had that sort of behaviour recently when the tight integration was
broken on the installation we'd been given, and it took me a long time
to spot. [Is the orte_leave_session_attached fix relevant here?]

> And for what it is worth, as you have seen,
> you do not need to specify a machines file. Open MPI will use the
> ones that were allocated by SGE.

Yes, but there's a problem with the recommended (as far as I remember)
setup, with one slot per node to ensure a single job per node. In that
case, you have no control over allocation -- -bynode and -byslot are
equivalent, which apparently can badly affect some codes. We're
currently using a starter to generate a hosts file for that reason
(complicated by having dual- and quad-core nodes) and would welcome a
better idea.