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Subject: Re: [OMPI users] Guaranteed run rank 0 on a given machine?
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-12-10 17:50:51


David Mathog wrote:

>Also, in my limited testing --host and -hostfile seem to be mutually
>exclusive.
>
No. You can use both together. Indeed, the mpirun man page even has
examples of this (though personally, I don't see having a use for
this). I think the idea was you might use a hostfile to define the
nodes in your cluster and an mpirun command line that uses --host to
select specific nodes from the file.

>That is reasonable, but it isn't clear that it is intended.
> Example, with a hostfile containing one entry for "monkey02.cluster
>slots=1":
>
>mpirun --host monkey01 --mca plm_rsh_agent rsh hostname
>monkey01.cluster
>
>
Okay.

>mpirun --host monkey02 --mca plm_rsh_agent rsh hostname
>monkey02.cluster
>
>
Okay.

>mpirun -hostfile /usr/common/etc/openmpi.machines.test1 \
> --mca plm_rsh_agent rsh hostname
>monkey02.cluster
>
>
Okay.

>mpirun --host monkey01 \
> -hostfile /usr/commom/etc/openmpi.machines.test1 \
> --mca plm_rsh_agent rsh hostname
>--------------------------------------------------------------------------
>There are no allocated resources for the application
> hostname
>that match the requested mapping:
>
>
>Verify that you have mapped the allocated resources properly using the
>--host or --hostfile specification.
>--------------------------------------------------------------------------
>
>
Right. Your hostfile has monkey02. On the command line, you specify
monkey01, but that's not in your hostfile. That's a problem. Just like
on the mpirun man page.