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Subject: [OMPI users] Oversubscription of nodes with Torque and OpenMPI
From: Gans, Jason D (jgans_at_[hidden])
Date: 2013-11-22 11:32:44

Hello, I would like to run an instance of my application on every *core* of a small cluster. I am using Torque 2.5.12 to run jobs on the cluster. The cluster in question is a heterogeneous collection of machines that are all past their prime. Specifically, the number of cores ranges from 2-8. Here is the Torque "nodes" file: n0000 np=2 n0001 np=2 n0002 np=8 n0003 np=8 n0004 np=2 n0005 np=2 n0006 np=2 n0007 np=4 When I use openmpi-1.6.3, I can oversubscribe nodes but the tasks are allocated to nodes without regard to the number of cores on each node (specified by the "np=xx" in the nodes file). For example, when I run "mpirun -np 24 hostname", mpirun places three instances of "hostname" on each node, despite the fact that some nodes only have two processors and some have more. Is there a way to have OpenMPI "gracefully" oversubscribe nodes by allocating instances based on the "np=xx" information in the Torque nodes file? It this a Torque problem? p.s. I do get the desired behavior when I run *without* Torque and specify the following machine file to mpirun: n0000 slots=2 n0001 slots=2 n0002 slots=8 n0003 slots=8 n0004 slots=2 n0005 slots=2 n0006 slots=2 n0007 slots=4 Regards, Jason