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Subject: Re: [OMPI users] what is a "node"?
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-08-30 08:07:43


In the OMPI v1.6 series, you can use the processor affinity options. And you can use --report-bindings to show exactly where processes were bound. For example:

-----
% mpirun -np 4 --bind-to-core --report-bindings -bycore uptime
[svbu-mpi056:18904] MCW rank 0 bound to socket 0[core 0]: [B . . .][. . . .]
[svbu-mpi056:18904] MCW rank 1 bound to socket 0[core 1]: [. B . .][. . . .]
[svbu-mpi056:18904] MCW rank 2 bound to socket 0[core 2]: [. . B .][. . . .]
[svbu-mpi056:18904] MCW rank 3 bound to socket 0[core 3]: [. . . B][. . . .]
 05:06:13 up 7 days, 6:57, 1 user, load average: 0.29, 0.10, 0.03
 05:06:13 up 7 days, 6:57, 1 user, load average: 0.29, 0.10, 0.03
 05:06:13 up 7 days, 6:57, 1 user, load average: 0.29, 0.10, 0.03
 05:06:13 up 7 days, 6:57, 1 user, load average: 0.29, 0.10, 0.03
%
-----

I bound each process to a single core, and mapped them on a round-robin basis by core. Hence, all 4 processes ended up on their own cores on a single processor socket.

The --report-bindings output shows that this particular machine has 2 sockets, each with 4 cores.

On Aug 30, 2012, at 5:37 AM, Zbigniew Koza wrote:

> Hi,
>
> consider this specification:
>
> "Curie fat consists in 360 nodes which contains 4 eight cores CPU Nehalem-EX clocked at 2.27 GHz, let 32 cores / node and 11520 cores for the full fat configuration"
>
> Suppose I would like to run some performance tests just on a single processor rather than 4 of them.
> Is there a way to do this?
> I'm afraid specifying that I need 1 cluster node with 8 MPI prcesses
> will result in OS distributing these 8 processes among 4
> processors forming the node, and this is not what I'm after.
>
> Z Koza
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users

-- 
Jeff Squyres
jsquyres_at_[hidden]
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