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Subject: Re: [OMPI users] Option to use only 7 cores out of 8 on each node
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2010-03-02 13:26:06

Eugene Loh wrote:

> Addepalli, Srirangam V wrote:
>> i tried using the following syntax with machinefile
>> mpirun -np 14 -npernode 7 -machinefile machinefile ven_nw.e <coll.dt5
> It "works" for me. I'm not using SGE, though.
> % cat machinefile
> % mpirun -tag-output -np 14 -npernode 7 -machinefile machinefile hostname

Incidentally, the key ingredient here is the "-npernode 7" part. The
machine file only needs enough slots. E.g., you could have had:

% cat machinefile
node0 slots=20
node1 slots=20

mpirun will see that there are enough slots on each node, but load only
7 up per node due to the -npernode switch.

That said, I don't know what's going wrong in your case -- only that
things work as advertised for me.