bad performance

[Joeckel, Patrick]

Dear parallel-netCDF developers and -users,

I recently finished a test implementation of
parallel-netCDF in our Chemistry-Climate-Model
using the recent version 1.0.3 of the library.

Running it on an IBM Power6 system

uname -a
Linux p6012 2.6.16.60-0.42.7.1-ppc64 #1 SMP Tue Nov 3 12:20:42 CET 2009 
ppc64 ppc64 ppc64 GNU/Linux

on 64 CPUs (i.e. 2 nodes), I detected that our "classical" gathering on 
one CPU and output through the serial netCDF interface
is - for a typical application - 4.5 times faster (wall clock for I/O 
output time step) than the parallel-netCDF implementation.

I guess (I hope !) that I am doing something wrong and further that you 
can help me.
I appreciate any suggestion and I am happy to provide more information 
that can help me to solve the problem.

Yours,

Patrick


-- 
------------------------------------------------------------------
 Dr. Patrick Joeckel
 Deutsches Zentrum fuer Luft- und Raumfahrt e.V.
 in der Helmholtz-Gemeinschaft
 Institut fuer Physik der Atmosphaere

 Muenchner Strasse 20
 Oberpfaffenhofen, D-82234 Wessling

 Phone : +49-8153-28-2565
 Fax   : +49-8153-28-1841
 E-mail: Patrick.Joeckel at dlr.de
 Web   : http://www.dlr.de/ipa/
------------------------------------------------------------------