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From: Peter Kjellström (cap_at_[hidden])
Date: 2006-01-04 02:58:26


Hello Carsten,

Have you considered the possibility that this is the effect of a non-optimal
ethernet switch? I don't know how many nodes you need to reproduce it on or
if you even have physical access (and opportunity) but popping in another
decent 16-port switch for a testrun might be interesting.

just my .02 euros,
 Peter

On Tuesday 03 January 2006 18:45, Carsten Kutzner wrote:
> On Tue, 3 Jan 2006, Graham E Fagg wrote:
> > Do you have any tools such as Vampir (or its Intel equivalent) available
> > to get a time line graph ? (even jumpshot of one of the bad cases such as
> > the 128/32 for 256 floats below would help).
>
> Hi Graham,
>
> I have attached an slog file of an all-to-all run for 1024 floats (ompi
> tuned alltoall). I could not get clog files for >32 processes - is this
> perhaps a limitation of MPE? So I decided to take the case 32 CPUs on
> 32 nodes which is performance-critical as well. From the run output you
> can see that 2 of the 5 tries yield a fast execution while the others
> are slow (see below).
>
> Carsten
>
>
>
> ckutzne_at_node001:~/mpe> mpirun -hostfile ./bhost1 -np 32 ./phas_mpe.x
> Alltoall Test on 32 CPUs. 5 repetitions.
> --- New category (first test not counted) ---
> MPI: sending 1024 floats ( 4096 bytes) to 32 processes ( 1
> times) took ... 0.00690 seconds
> ---------------------------------------------
> MPI: sending 1024 floats ( 4096 bytes) to 32 processes ( 1
> times) took ... 0.00320 seconds MPI: sending 1024 floats ( 4096
> bytes) to 32 processes ( 1 times) took ... 0.26392 seconds ! MPI:
> sending 1024 floats ( 4096 bytes) to 32 processes ( 1 times)
> took ... 0.26868 seconds ! MPI: sending 1024 floats ( 4096 bytes)
> to 32 processes ( 1 times) took ... 0.26398 seconds ! MPI: sending
> 1024 floats ( 4096 bytes) to 32 processes ( 1 times) took ...
> 0.00339 seconds Summary (5-run average, timer resolution 0.000001):
> 1024 floats took 0.160632 (0.143644) seconds. Min: 0.003200 max:
> 0.268681 Writing logfile....
> Finished writing logfile.

-- 
------------------------------------------------------------
  Peter Kjellström               |
  National Supercomputer Centre  |
  Sweden                         | http://www.nsc.liu.se


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