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From: Glen Kaukola (glen_at_[hidden])
Date: 2006-02-02 08:55:52

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)

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

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.