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Subject: Re: [OMPI users] 50% performance reduction due to OpenMPI v 1.3.2 forcing all MPI traffic over Ethernet instead of using Infiniband
From: Don Kerr (Don.Kerr_at_[hidden])
Date: 2009-06-22 22:56:38


On 06/22/09 22:36, Jim Kress ORG wrote:
> Is there an environment variable (or variables) I can set to do the
> equivalent?
>
OMPI_MCA_mpi_show_mca_params

see: http://www.open-mpi.org/faq/?category=tuning#setting-mca-params
> Jim
>
>
>
> On Mon, 2009-06-22 at 19:40 -0600, Ralph Castain wrote:
>
>> Sounds very strange, indeed. You might want to check that your app is
>> actually getting the MCA param that you think it is. Try adding:
>>
>> -mca mpi_show_mca_params file,env
>>
>> to your cmd line. This will cause rank=0 to output the MCA params it
>> thinks were set via the default files and/or environment (including
>> cmd line).
>>
>> Ralph
>>
>> On Jun 22, 2009, at 6:14 PM, Jim Kress ORG wrote:
>>
>>
>>> For the app I am using, ORCA (a Quantum Chemistry program), when it
>>> was
>>> compiled using openMPI 1.2.8 and run under 1.2.8 with the following in
>>> the openmpi-mca-params.conf file:
>>>
>>> btl=self,openib
>>>
>>> the app ran fine with no traffic over my Ethernet network and all
>>> traffic over my Infiniband network.
>>>
>>> However, now that ORCA has been recompiled with openMPI v1.3.2 and run
>>> under 1.3.2 (using the same openmpi-mca-params.conf file), the
>>> performance has been reduced by 50% and all the MPI traffic is going
>>> over the Ethernet network.
>>>
>>> As a matter of fact, the openMPI v1.3.2 performance now looks exactly
>>> like the performance I get if I use MPICH 1.2.7.
>>>
>>> Anyone have any ideas:
>>>
>>> 1) How could this have happened?
>>>
>>> 2) How can I fix it?
>>>
>>> a 50% reduction in performance is just not acceptable. Ideas/
>>> suggestions would be appreciated.
>>>
>>> Jim
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>
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>
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