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Re: 20030618: NetCDF performance problems

>To: address@hidden
>From: Gottfried Necker <address@hidden>
>Subject: NetCDF performance problems.
>Organization: ?
>Keywords: 200306180911.h5I9BvLd025090 netCDF 3.5.1-beta10 Fujitsu VPP

Hi Gottfried,

> I used netcdf 3.5.1-beta10 (Fortran 90 interface) on a Fujitsu VPP
> 5000. The code was run in 32bit address mode. Depending on the file
> system type (nfs, local, striped) the program used enormous amounts of
> system cpu time, was waiting for i/o etc.
> Then I went back to netcdf 3.5.1-beta3 and the performance problems
> went away.
> 
> I guess this problem is caused by changes in the C i/o layer. If
> somebody has an idea, what has to be changed, I could try it again.

I'm very interested in this and would like more information about it.
We don't know of any changes from 3.5.1-beta3 to 3.5.1-beta10 that
would cause such a performance problem.  Did the problem occur with
only one of the file systems you mention (nfs, local, striped)?  Is it
possible to profile the program to see where it is when the cpu time
is being consumed?  We don't have access to a Fujitsu platform for
testing, so this problem may be difficult to isolate and fix without
more information.

Another possibility would be providing you with some versions between
beta3 and beta10 that would help isolate which changes caused the
problem.

Thanks.

--Russ

_____________________________________________________________________

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://my.unidata.ucar.edu