This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.
>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