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Subject: Re: [OMPI users] Performance Issues with OpenMPI v1.5.1 MPI_Barrieron Windows XP SP3
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2011-02-24 06:37:50


You should:

- do N warmup barriers
- start the timers
- do M barriers (M should be a lot)
- stop the timers
- divide the time by M

Benchmarking is tricky to get right.

Sent from my PDA. No type good.

On Feb 23, 2011, at 11:54 PM, "Li Zuwei" <lzuwei_at_[hidden]> wrote:

> Dear Users,
>
> I'm measuring barrier synchronization performance on the v1.5.1 build of OpenMPI. I am currently trying to measure synchronization performance on a single node, with 5 processes. I'm getting pretty weak results as follows:
>
> Testing procedure - initialize the timer at the start of the barrier, stop the timer when the process break from the barrier. Cycle through N number of times and calculate the average.
>
> 1 Node 5 processes: 299.38ms
> 1 Node 7 processes: 513.95ms
> 1 Node 10 processes: 749.94ms
>
> I am wondering if this is the expected performance on a single nodes. I presume Open MPI automatically uses Shared Memory for barrier synchronization on a single node which I think should be able to provide better performance when running on a single node. Is there a way to determine what transport layer I am using and I would greatly appreciate tips on how can I tune this performance.
>
> Regards,
> Zuwei
>
>
>
>
>
>
>
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