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> > Hello, > > > > I have a quick question about netCDF4 on OS X. Specifically, the > > performance of reading netCDF4 files. This appears to be extremely > > slow; in the following (approximate) timings, I am using a GHRSST > > format AMSRE SST file in netCDF3 format (amsre.nc3) and the same file > > converted manually to a netCDF4 file (with zlib on, shuffle on and > > chunking off), called amsre.nc4. > > > > I have BOTH the nc3 and nc4 libraries and utillities installed (so I > > call them ncdump3 / ncdump4....) > > > > Time to ncdump3 amsre.nc3 -> about 1 second > > Time to ncdump4 amsre.nc4 (with zlib off) -> about 2 seconds > > Time to ncdump4 amsre.nc4 (with zlib on) -> 4 MINUTES!!!!!! > > Time to gzip amsre.nc3 -> about 1 second > > > > Clearly, there is a problem with the zlib implementation on my version > > of netCDF4 (4.0.3-beta). It takes about 300 times longer to read the > > netCDF4 file with the ncdump4, than to convert it to netCDF3 and read > > it from there! > > > > I am using netcdf3 (3.6.3), apple OS X 10.5.6 (intel) > > > > I don't doubt that I have just missed something, but just in case, I > > thought I should report this. > > > > Do have any suggestions? > > > > Many thanks > > > > Dave Poulter > > > > David J. S. Poulter, Satellite Oceanographer > > National Oceanography Centre, Southampton > > European Way, Southampton, SO14 3ZH, UK > > Tel: +44(0)23 80596107 > > E-mail: address@hidden > > > Howdy Dave! Any progress on this? Did you resolve your performance problems with netCDF-4 by setting chunksizes? I suggest you get the just-released version 4.0.1 which offers several performance enhancements that might help your performance. Get the release here: ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf-4.0.1.tar.gz If you try the new release, please let me know if it works for you, and if it helps with your performance. Thanks, Ed Ticket Details =================== Ticket ID: UZM-707371 Department: Support netCDF Priority: Normal Status: Closed