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Subject: Re: [OMPI users] Machinefile option in opempi-1.3.2
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-06-19 22:40:43

If you do "man orte_hosts", you'll see a full explanation of how the various
machinefile options work.
The default mapper doesn't do any type of sorting - it is a round-robin
mapper that just works its way through the provided nodes. We don't reorder
them in any way.

However, it does depend on the number of slots we are told each node has, so
that might be what you are encountering. If you do a --display-map and send
it along, I might be able to spot the issue.


On Fri, Jun 19, 2009 at 1:35 PM, Rajesh Sudarsan <rsudarsan_at_[hidden]>wrote:

> Hi,
> I tested a simple hello world program on 5 nodes each with dual
> quad-core processors. I noticed that openmpi does not always follow
> the order of the processors indicated in the machinefile. Depending
> upon the number of processors requested, openmpi does some type of
> sorting to find the best node fit for a particular job and runs on
> them. Is there a way to make openmpi to turn off this sorting and
> strictly follow the order indicated in the machinefile?
> mpiexec supports three options to specify the machinefile -
> default-machinefile, hostfile, and machinefile. Can anyone tell what
> is the difference between these three options?
> Any help would be greatly appreciated.
> Thanks,
> Rajesh
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