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Subject: Re: [OMPI users] difference between single and double precision
From: Peter Kjellström (cap_at_[hidden])
Date: 2010-12-06 10:01:16


On Monday 06 December 2010 15:03:13 Mathieu Gontier wrote:
> Hi,
>
> A small update.
> My colleague made a mistake and there is no arithmetic performance
> issue. Sorry for bothering you.
>
> Nevertheless, one can observed some differences between MPICH and
> OpenMPI from 25% to 100% depending on the options we are using into our
> software. Tests are lead on a single SGI node on 6 or 12 processes, and
> thus, I am focused on the sm option.

A few previous threads on sm performance have been related to what /tmp is.
OpenMPI relies on (or at least used to rely on) this being backed by page
cache (tmpfs, a local ext3 or similar). I'm not sure what the behaviour is in
the latest version but then again you didn't say which version you've tried.

/Peter