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Subject: Re: [OMPI users] scaling problem with openmpi
From: Peter Kjellstrom (cap_at_[hidden])
Date: 2009-05-19 11:19:13

On Tuesday 19 May 2009, Roman Martonak wrote:
> On Tue, May 19, 2009 at 3:29 PM, Peter Kjellstrom <cap_at_[hidden]> wrote:
> > On Tuesday 19 May 2009, Roman Martonak wrote:
> > ...
> >> openmpi-1.3.2                           time per one MD step is 3.66 s
> >>  = ALL TO ALL COMM           102033. BYTES               4221.  =
> >>  = ALL TO ALL COMM             7.802  MB/S          55.200 SEC  =
> With TASKGROUP=2 the summary looks as follows
> = ALL TO ALL COMM 231821. BYTES 4221. =
> = ALL TO ALL COMM 82.716 MB/S 11.830 SEC =

Wow, according to this it takes 1/5th the time to do the same number (4221) of
alltoalls if the size is (roughly) doubled... (ten times better performance
with the larger transfer size)

Something is not quite right, could you possibly try to run just the alltoalls
like I suggested in my previous e-mail?