Hi Marc, > I am finding a peculiar instance that when an identical netcdf file > is written via NCL (NetCDF 4 Classic, compression level 5,) on one > machine the file is 5.6GB but on the other computer its size is 9GB. > To the best of my knowledge, the files are identical when opened (type, > values, etc.) What is odder is that if I execute the NCL script (and > ensure they are using the same version of NCL) from the command line > instead of from the shell script, the file sizes are identical. > > Are there certain checks I am missing that I should try? > > I believe both machines are using the same NetCDF libraries, but could > that be the issue? Yes, that might explain what you are seeing. If you are not specifying how to chunk variables that are compressed, then default chunking is used. The algorithm for deciding what chunk sizes to use as a default has changed several times in different versions of the netCDF-4 library, as we discovered inefficiencies in default chunk sizes. One way to check this is with the "-s" and "-h" options of ncdump, assuming you have recent enough versions of ncdump to support the "-s" option. That will show you the chunk sizes along each dimension for each variable. If those turn out to be different, that could explain the huge difference in compression. If the chunk sizes are the same, I'm stumped. In the latter case, I would forward the question to NCL support, they may have an explanation (which I would like to hear about also). --Russ > Anyhow, I am somewhat stumped and believe it must be a machine environment > issue difference when both machines execute the shell script that calls > the NCL script to generate the netcdf. > > Any help you could lend would be greatly appreciated...thanks! > > -Marc > > Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: DTM-721292 Department: Support netCDF Priority: High Status: Closed
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