Re: [netcdfgroup] please try out the netcdf daily snapshot for opendap, hdf4-reading, hdf5-reading, szip compression, etc.

• To: Ed Hartnett <ed@xxxxxxxxxxxxxxxx>
• Subject: Re: [netcdfgroup] please try out the netcdf daily snapshot for opendap, hdf4-reading, hdf5-reading, szip compression, etc.
• From: Jeff Whitaker <jswhit@xxxxxxxxxxx>
• Date: Mon, 19 Oct 2009 07:27:21 -0600

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?

Ed: I don' really - I was just responding to your call to test stuff.

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

Please let me know how it works for you!

OK, I will.

-Jeff

Thanks,

Ed

• References:
  • [netcdfgroup] please try out the netcdf daily snapshot for opendap, hdf4-reading, hdf5-reading, szip compression, etc.
    • From: Ed Hartnett
  • Re: [netcdfgroup] please try out the netcdf daily snapshot for opendap, hdf4-reading, hdf5-reading, szip compression, etc.
    • From: Jeff Whitaker
  • Re: [netcdfgroup] please try out the netcdf daily snapshot for opendap, hdf4-reading, hdf5-reading, szip compression, etc.
    • From: Ed Hartnett