Hi, > Also, I couldn't find an example to show how to or classic_format and hdf5 to > create the > Netcdf-4 classic format. > nf90_create(FILE_NAME, (nf90_classic_model|nf90_hdf5) doesn't work. Sorry, the documentation should be clearer. You can use: nf90_create(FILE_NAME, IOR(nf90_netcdf4, nf90_classic_model), ncid) > The confusion from netcdf is that it is vague from the online document on how > to generate a > Netcdf4 classic - when compiling the library for this, does one need hdf5 lib > at all? Yes, the hdf5 library is needed becasue a netCDF-4 classic model file is really an HDF5 file with an artifact to make sure it is readable by old programs lijnked to the netCDF-4 library. For an explanation, see this FAQ, and maybe some of the subsequent questions and answers: http://www.unidata.ucar.edu/netcdf/docs/faq.html#fv1 > Using your online example pres_temp_4D_wr.f90, I tried to modify the line into > call check( nf90_create(FILE_NAME, nf90_hdf5, ncid) ) > > now when I look at the file sizes, it is significanly larger (7 times), I > thought hdf5 should be smaller, anything wrong? > > -rw-rw-r-- 16867 Feb 10 10:55 pres_temp_4D.nc > -rw-rw-r-- 2784 Feb 10 10:38 pres_temp_4D.nc_nocompress netCDF-4 files are only smaller if compression is used when writing the data. Here's an answer to an FAQ on that: http://www.unidata.ucar.edu/netcdf/docs/faq.html#fv8 Compression is done on a variable-by-variable basis, so it's possible to use different compression levels on different variables. But if you just want to compress all variables in the file using the same compression level, the easiest way is using the nccopy utility, as in nccopy -d1 foo.nc foo-compressed.nc to use "deflation level" 1. Note that for small files, the compressed netCDF-4 files will actually be larger than uncompressed netCDF-3 (classic format) files, because the underlying HDF5 format has some fixed-size overhead. But for large datasets, compression will save space, at the expense of taking more time to read and write the data. I just tested the 4.1.3 nccopy on an example file for compression and got this: $ nccopy -d1 llnl.nc llnl-compressed.nc && ls -l llnl*.nc -rw-rw-r-- 1 russ ustaff 13802 Feb 15 14:58 llnl-compressed.nc -rw-rw-r-- 1 russ ustaff 32864 Oct 17 11:05 llnl.nc --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: PRD-617628 Department: Support netCDF Priority: Normal Status: Closed
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