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Subject: Re: [OMPI users] How to specify hosts for MPI_Comm_spawn
From: Mark Borgerding (markb_at_[hidden])
Date: 2008-08-04 11:45:28


Jeff Squyres wrote:
> On Aug 4, 2008, at 10:02 AM, Jeff Squyres wrote:
>
>> I *think* George Bosilca sent some sample code about this across one
>> of the OMPI lists (users or devel) a long time ago. I'm not 100%
>> sure about that, though...
>>
>> I unfortunately forget the trick that he used. :-\
>
>
> George is unable to send e-mail at the moment, but he asked me to send
> these links:
>
> http://www.lam-mpi.org/MailArchives/lam/2003/06/6226.php
> http://www.open-mpi.org/community/lists/users/2007/10/4327.php
>
> And a simple example:
>
> http://www.open-mpi.org/community/lists/users/2008/07/6168.php
>
> Hope that helps.
>
Thanks for all your help.

I'm afraid I still could not make the simple example spawn work on
remote hosts listed in host file. Everything stays local. At least on 1.2.x

But I think I've got a path forward. I've been able to use sockets and
MPI_Comm_join to create intercomms between the singleton and
mpirun-spawned children. The important step I was missing was
"orted --persistent --seed --scope public". Now the MPI_Comm_join calls
in different worlds can see each other. FWIW, this technique just works
in LAM, presumably because lamboot is an explicit step.

I've almost got my head wrapped around the technique in
http://www.open-mpi.org/community/lists/users/2007/10/4327.php
Are there any shortcuts I could take for the case where all the clients
are already in a group?

-- 
Mark Borgerding
3dB Labs, Inc
Innovate.  Develop.  Deliver.