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From: Carsten Kutzner (ckutzne_at_[hidden])
Date: 2006-02-02 12:28:05


Hi Glen,

what setup have you used for doing the benchmarks? I mean,
what type of Ethernet switch, which network cards, which
linux kernel. I am asking because it looks weird to me that
the 4 CPU OpenMPI job is taking longer than the 2 CPU job,
and that the 8 CPU job is faster again. Maybe the network
settings can be optimized?

Regards,
  Carsten

On Thu, 2 Feb 2006, Glen Kaukola wrote:

> Hi everyone,
>
> I recently took Open MPI (1.0.2a4) for a spin and thought you all might
> like to see how it's currently stacking up against MPICH (1.2.7p1). The
> benchmark I used was the EPA's CMAQ (Community Multiscale Air Quality)
> model.
>
> Now bear in mind my results aren't completely scientific. For one thing
> I'd need to run a series of jobs and take the averages. Forgive me if
> I'm too lazy to do that. I also didn't go through the trouble of
> completely isolating my jobs while they were running. However, I did
> monitor them pretty closely and I'm fairly certain no jobs from other
> users crept in on the machines I was using.
>
> Anyway, without further ado, here are my results (in h:mm):
>
> Open MPI
> 1 cpu job: 2:38
> 2 cpu job: 1:26
> 4 cpu job: 1:38
> 8 cpu job: 1:08
> 36 cpu job: 3:09
>
> MPICH
> 1 cpu job: 2:38
> 2 cpu job: 1:27
> 4 cpu job: 0:48
> 8 cpu job: 0:32
>
> And while Open MPI does seem a bit slower, one real nice thing I can say
> is that a 16+ cpu job runs without a hitch. I could never get away with
> that while using MPICH, as the jobs would just crash. Whether MPICH is
> at fault, or the CMAQ code is buggy, or gigabit ethernet just isn't good
> enough, I really couldn't say. But Open MPI sure doesn't seem to have
> that problem.
>
> It's also rather odd how the 4 cpu Open MPI job takes longer than the 2
> cpu Open MPI job. In fact that's slightly faster compared to the first
> time I ran a 4 cpu Open MPI job (I couldn't believe it the first time so
> I reran that one).
>
> And on a totally unrelated note, after swapping out MPICH for Open MPI,
> I can't seem to background my scripts. When I do my shell (bash) tells
> me the job has stopped. Somewhat annoying.
>
> Anyway, keep up the good work. I'll be paying close attention, and
> hopefully see some speedups in the not too distant future.
>
>
> Glen
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