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Subject: Re: [OMPI users] Any scientific application heavily using MPI_Barrier?
From: Gerry Creager (gerry.creager_at_[hidden])
Date: 2009-03-05 10:33:31


We've been playing with it in a coupled atmosphere-ocean model to allow
the two to synchronize and exchange data. The models have differing
levels of physics complexity and the time step requirements are
significantly different. To sync them up we have to know where the
timesteps are identical, stop the process, exchange data and continue.
We've been playing with barrier to help.

gc

Jeff Squyres wrote:
> On Mar 5, 2009, at 9:29 AM, Shanyuan Gao wrote:
>
>> I am doing some research on MPI barrier operations. And I am ready
>> to do some performance test.
>> I wonder if there are any applications that using barriers a lot.
>> Please let me know if there
>> is any. Any comments are welcomed. Thanks!
>>
>
>
> I don't remember who originally said it, but I've repeated the
> statement: any MPI program that relies on a barrier for correctness is
> an incorrect MPI application.
>
> There's anecdotal evidence that throwing in a barrier every once in a
> while can help reduce unexpected messages (and other things), and
> therefore improve performance a bit. But that's very application
> dependent, and usually not frequent.
>
> Why do you want to do a barrier? Particularly one that sounds like it
> might be in your critical performance path?
>

-- 
Gerry Creager -- gerry.creager_at_[hidden]
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
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