Ed Hartnett wrote:
Jeff Whitaker <jswhit@xxxxxxxxxxx> writes:
Ed: I'd like to try out the szip compression, but I only see
instructions on how to build with szip enabled. Are there any docs
yet showing to use szip instead of zlib for compression?
-Jeff
Howdy Jeff!
Can you tell me why you prefer szip to zlib deflation?
From C, use nc_def_var_szip to set up szip compression on a var (after
it is defined, but before any enddef is called.) There is also an
nc_inq_var_szip function, for completeness, but it is not necessary to
know that a variable is zipped when reading it, as the unpacking is
automatic. See the C docs for more:
http://www.unidata.ucar.edu/software/netcdf/docs_snapshot/netcdf-c.html#nc_005fdef_005fvar_005fszip
In F90, there are two new parameters to the nf90_def_var and
nf90_inquire functions, "option_mask" and "bits_per_pixel", which allow
you to turn on szip and control its operation. Documentation here:
http://www.unidata.ucar.edu/software/netcdf/docs_snapshot/netcdf-f90.html#NF90_005fDEF_005fVAR
Ed: From looking at the HDF5 docs I'm pretty sure you mean
pixels_per_block, not bits_per_pixel.
http://www.hdfgroup.org/HDF5/doc/RM/RM_H5P.html#Property-SetSzip
pixels_per_block is set internally by HDF5.
-Jeff
Please let me know how it works for you!
Thanks,
Ed
