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Subject: Re: [OMPI devel] Open-MPI build of NAMD launched from srun over 20% slowed than with mpirun
From: Hjelm, Nathan T (hjelmn_at_[hidden])
Date: 2013-09-05 10:23:44


I assume that process binding is enabled for both mpirun and srun? If not that could account for a difference between the runtimes.

-Nathan
________________________________________
From: devel [devel-bounces_at_[hidden]] on behalf of Ralph Castain [rhc_at_[hidden]]
Sent: Thursday, September 05, 2013 8:19 AM
To: Open MPI Developers
Subject: Re: [OMPI devel] Open-MPI build of NAMD launched from srun over 20% slowed than with mpirun

No, nothing significant there. Afraid I've exhausted my thoughts on why the difference might exist.

Anyone else care to chime in?

On Sep 4, 2013, at 9:34 PM, Christopher Samuel <samuel_at_[hidden]> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi Ralph,
>
> On 05/09/13 12:50, Ralph Castain wrote:
>
>> Jeff and I were looking at a similar issue today and suddenly
>> realized that the mappings were different - i.e., what ranks are
>> on what nodes differs depending on how you launch. You might want
>> to check if that's the issue here as well. Just launch the
>> attached program using mpirun vs srun and check to see if the maps
>> are the same or not.
>
> Very interesting, the ranks to node mappings are identical in all
> cases (mpirun and srun for 1.6.5 and my test 1.7.3 snapshot) but what
> is different is as follows.
>
>
> For the 1.6.5 build I see mpirun report:
>
> number 0 universe size 64 universe envar 64
>
> whereas srun report:
>
> number 1 universe size 64 universe envar NULL
>
>
>
> For the 1.7.3 snapshot both report "number 0" so the only difference
> there is that mpirun has:
>
> envar 64
>
> whereas srun has:
>
> envar NULL
>
>
> Are these differences significant?
>
> I'm intrigued that the problem child (srun 1.6.5) is the only one
> where number is 1.
>
> All the best,
> Chris
> - --
> Christopher Samuel Senior Systems Administrator
> VLSCI - Victorian Life Sciences Computation Initiative
> Email: samuel_at_[hidden] Phone: +61 (0)3 903 55545
> http://www.vlsci.org.au/ http://twitter.com/vlsci
>
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