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Subject: Re: [OMPI docs] Behavior of --host and --hostfile flags on mpirun
From: Kelly Black (kjblack_at_[hidden])
Date: 2013-10-11 16:31:07


Dear Jeff,

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

Thanks for the info on the network interface. I did not realize that.

Sincerely,
Kel

_______________________________________________________
Kelly Black Phone: (315) 600-8334
Clarkson University Fax: (315) 268-2371
Department of Math. & C.S.
PO Box 5815
Potsdam, NY 13699-5815
USA

On Fri, Oct 11, 2013 at 4:10 PM, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]
> wrote:

> Also, it's more common to use a hostfile *or* the --host option. It's
> fairly uncommon to use both.
>
> As to whether one should use FQDN or a basename, it doesn't matter to MPI.
> If the system resolves the name, OMPI can use it.
>
> Finally, a point that is worth noting (because so many people make the
> wrong assumption): the hostnames that are listed in the hostfile or --host
> option have nothing to do with what network interfaces are used for MPI
> traffic. The hosts specified by the hostfile (or --hosts) are *only* used
> to determine on which nodes MPI processes are launched. The determination
> of which network interfaces are used are controlled by other MCA parameters
> (e.g., the "btl" MCA parameter, and various mca_btl_*_if_include /
> mca_btl_*_if_exclude MCA parameters).
>
>
> On Oct 11, 2013, at 1:57 PM, Kelly Black <kjblack_at_[hidden]> wrote:
>
> > Dear Shao-Ching,
> >
> > oops, I see what you mean. Sorry, I got sloppy and in a hurry. I should
> have the slots= flag in that file.
> >
> > Sincerely,
> > Kel
> >
> > _______________________________________________________
> > Kelly Black Phone: (315) 600-8334
> > Clarkson University Fax: (315) 268-2371
> > Department of Math. & C.S.
> > PO Box 5815
> > Potsdam, NY 13699-5815
> > USA
> >
> >
> > On Fri, Oct 11, 2013 at 1:54 PM, Kelly Black <kjblack_at_[hidden]> wrote:
> > Hello,
> >
> > I thought that the "slots" flag was optional in the host file format
> where the slots option gives the max no. of slots?
> >
> > -Kel
> >
> > _______________________________________________________
> > Kelly Black Phone: (315) 600-8334
> > Clarkson University Fax: (315) 268-2371
> > Department of Math. & C.S.
> > PO Box 5815
> > Potsdam, NY 13699-5815
> > USA
> >
> >
> > On Fri, Oct 11, 2013 at 1:24 PM, Shao-Ching Huang <huangsc_at_[hidden]>
> wrote:
> > Kel:
> >
> > I believe the ompi hostfile format is:
> >
> > # myhosts.txt
> > thingOne.clarkson.edu slots=4
> > thingTwo.clarkson.edu slots=4
> >
> > Shao-Ching
> >
> >
> > On Fri, Oct 11, 2013 at 10:21 AM, Ralph Castain <rhc_at_[hidden]>
> wrote:
> > I *think* that should work, but I haven't personally tested it.
> >
> > On Oct 11, 2013, at 9:27 AM, Kelly Black <kjblack_at_[hidden]> wrote:
> >
> >> Hello,
> >>
> >> I have a question about the --host and --hostfile flags used by mpirun.
> Do you have to use fully qualified host names in the arguments to the
> --host option if the fully qualified domain name is given in the host file?
> >>
> >> For example, if I have a host file like this:
> >>
> >> # myhosts.txt
> >> thingOne.clarkson.edu=4
> >> thingTwo.clarkson.edu=4
> >>
> >> Can I then use the following command?
> >>
> >> mpirun --hostfile myhosts.txt --host thingOne -np 3 bubba
> >>
> >> Sincerely,
> >> kel
> >> _______________________________________________________
> >> Kelly Black Phone: (315) 600-8334
> >> Clarkson University Fax: (315) 268-2371
> >> Department of Math. & C.S.
> >> PO Box 5815
> >> Potsdam, NY 13699-5815
> >> USA
> >> _______________________________________________
> >> docs mailing list
> >> docs_at_[hidden]
> >> http://www.open-mpi.org/mailman/listinfo.cgi/docs
> >
> >
> > _______________________________________________
> > docs mailing list
> > docs_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/docs
> >
> >
> >
> > _______________________________________________
> > docs mailing list
> > docs_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/docs
>
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
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