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Subject: Re: [OMPI users] Low performance of Open MPI-1.3 over Gigabit
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-03-05 18:00:34

On Mar 5, 2009, at 1:29 PM, Jeff Squyres wrote:

> On Mar 5, 2009, at 1:54 AM, Sangamesh B wrote:
>> The fortran application I'm using here is the CPMD-3.11.
>> I don't think the processor is Nehalem:
>> Intel(R) Xeon(R) CPU X5472 @ 3.00GHz
>> Installation procedure was same on both the clusters. I've not set
>> mpi_affinity.
>> This is a memory intensive application, but this job was not using
>> that much amount of memory.
>> Regarding CPU & ELAPSED TIMEs, the CPU TIME should be greater than
>> ELAPSED TIME in general (for a parallel program). Right?
> It depends on exactly what you're reporting for ELAPSED time. Is
> that wall clock time? Or user time? Or something else?
> Ralph and I disagree on this point, but my opinion is that the only
> meaningful time reported in a parallel application is the wall clock
> time. The CPU time can be badly skewed by a variety of things, such
> as any filesystem IO, network activity (depending on whether you
> have an OS-bypass network or not), etc.

You have gradually worn me down on this point... :D

> --
> Jeff Squyres
> Cisco Systems
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