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Subject: Re: [OMPI users] Performance difference on OpenMPI, IntelMPI and ScaliMPI
From: Terry Dontje (Terry.Dontje_at_[hidden])
Date: 2009-08-05 10:06:35


A comment to the below. I meant the 2x performance was for shared
memory communications.

--td
> Message: 3
> Date: Wed, 05 Aug 2009 09:55:42 -0400
> From: Terry Dontje <Terry.Dontje_at_[hidden]>
> Subject: Re: [OMPI users] Performance difference on OpenMPI, IntelMPI
> and ScaliMPI
> To: users_at_[hidden]
> Message-ID: <4A798F5E.3000002_at_[hidden]>
> Content-Type: text/plain; CHARSET=US-ASCII; format=flowed
>
> We've found on certain applications binding to processors can have up to
> a 2x difference. ScaliMPI automatically binds processes by socket so if
> you are not running a one process per cpu job each process will land on
> a different socket.
>
> OMPI defaults to not binding at all. You may want to try and use the
> rankfile option (see manpage) and see if that helps any.
>
> If the above doesn't improve anything the next question is do you know
> what the sizes of the messages are? For very small messages I believe
> Scali shows a 2x better performance than Intel and OMPI (I think this is
> due to a fastpath optimization).