Re: 20030618: NetCDF performance problems

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

Gottfried,

The performance problem you were seeing with many extra calls to
px_pgin and px_pgout functions was caused by the following change
described in the RELEASE_NOTES:

        Initialized a pointer in putget.m4 (used to generate
        putget.c) that was involved in uninitialized memory
        references when nc_test is run under Purify.  Two
        users had reported seeing crashes resulting from this
        problem in their applications.

Some of the initializations of pointers added to fix this other
problem were unnecessary and at least one changed the behavior of the
library.  I reverted the putget.m4 and putget.c files back to the
versions that appeared in netCDF-3.5.1-beta5 and that seemed to fix
the performance problems.

Now we will have to determine if there are still any significant
uninitialized memory references and, if so, find a better fix for them.

At your convenience, could you check that the proposed fix corrects
the performance problem you were seeing?  Please use the new beta
release

  ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf-3.5.1-beta11.tar.Z

or just copy the libsrc/putget.m4 and libsrc/putget.c files from the
beta5 version to the same place in the beta10 version and rebuild.

Thanks again for finding and reporting the problem!

--Russ

_____________________________________________________________________

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