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Subject: Re: [OMPI users] Any scientific application heavily using MPI_Barrier?
From: Ganesh (ganesh_at_[hidden])
Date: 2009-03-05 10:29:41


We have a paper on the very topic that Jeff just mentioned :

Subodh Sharma, Sarvani Vakkalanka, Ganesh Gopalakrishnan, Robert M.
Kirby, Rajeev Thakur, and William Gropp, `` A Formal Approach to Detect
Functionally Irrelevant Barriers in MPI Programs,'' Recent Advances in
Parallel Virtual Machine and Message Passing Interface (EuroPVM/MPI),
Dublin, Ireland, 2008, LNCS 5205, pp. 265-273.

This is available from http://www.cs.utah.edu/formal_verification/ under
Publications.

The "FIB" facility (ability to detect functionally irrelevant barriers)
exists in verification tool ISP which can be downloaded from here

http://www.cs.utah.edu/formal_verification/ISP-release

Ganesh

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?
>