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Subject: Re: [OMPI docs] Behavior of --host and --hostfile flags on mpirun
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-10-11 17:05:49

On Oct 11, 2013, at 4:31 PM, Kelly Black <kjblack_at_[hidden]> wrote:

> Yeah, it never occurred to me to use both, but when I was double checking things on the Open MPI website I came across a blurb that said that when used together the behavior is different. The documentation said that if the names in the --host command are not contained in the host file then the mpirun command fails.

Correct. We basically use the --host as a filter on the hostfile. If the --host argument isn't a proper subset of the hostfile, OMPI errors.

> It was not clear if you do not use a fully qualified name in one but not the other how it would be handled.

I'm not sure. Like Ralph said, I *think* it works. I *think* OMPI may actually resolve all names first, and then do comparisons/filtering with IP addresses.

You might want to give it a whirl and see what happens...?

Jeff Squyres
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