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Subject: Re: [OMPI users] excluding hosts
From: David Turner (dpturner_at_[hidden])
Date: 2010-04-06 18:59:16


Hi Ralph,

> Are you using a scheduler of some kind? If so, you can add this to your default mca param file:

Yes, we are running torque/moab.

> orte_allocation_required = 1
>
> This will prevent anyone running without having an allocation. You can also set

Ah. An "allocation". Not much info on this on the open-mpi website.
I believe this is what we will want, to prevent mpirun on login nodes.

> rmaps_base_no_schedule_local = 1
>
> which tells mpirun not to schedule any MPI procs on the local node.

In our batch environment, mpirun will be executing on one of the
compute nodes. That is, we don't have dedicated MOM nodes.
Therefore, I think we will want to schedule (at least) one MPI
task on the same node. Actually, when somebody wants to run
(for example) 256 tasks packed on 32 8-core nodes, I think we'll
need mpirun to share a *core* with one of the MPI tasks. The above
option would prevent that, correct?

> Does that solve the problem?

I'll give it a try and let you know. Thanks!

> Ralph
>
>
> On Apr 6, 2010, at 3:28 PM, David Turner wrote:
>
>> Hi,
>>
>> Our cluster has a handful of login nodes, and then a bunch of
>> compute nodes. OpenMPI is installed in a global file system
>> visible from both sets of nodes. This means users can type
>> "mpirun" from an interactive prompt, and quickly oversubscribe
>> the login node.
>>
>> So, is there a way to explicitly exclude hosts from consideration
>> for mpirun? To prevent (what is usually accidental) running
>> MPI apps on our login nodes? Thanks!
>>
>> --
>> Best regards,
>>
>> David Turner
>> User Services Group email: dpturner_at_[hidden]
>> NERSC Division phone: (510) 486-4027
>> Lawrence Berkeley Lab fax: (510) 486-4316
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> _______________________________________________
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-- 
Best regards,
David Turner
User Services Group        email: dpturner_at_[hidden]
NERSC Division             phone: (510) 486-4027
Lawrence Berkeley Lab        fax: (510) 486-4316