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Subject: Re: [OMPI users] Any scientific application heavily using MPI_Barrier?
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-03-05 10:25:30

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?

Jeff Squyres
Cisco Systems