I'd like to voice a word of caution on the inclusion of optional szip
compression in netCDF4.1. Although I'm sure szip has technically merit
it further fragments the "netcdf format". The NetCDF FAQ lists 4 netCDF
format variants and szip will make that 6:
1. netCDF3 format
2. netCDF3 64-bit offset format
3. netCDF4 format (zlib or no compression)
4. netCDF4 classic model (zlib or no compression)
5. netCDF4 format (szip)
6. netCDF4 classic model (szip)
The reason I lump zlib with no compression is that when building NetCDF
libraries you need to decide whether to include szip in the build, with
the inherent license limitations it imposes. Therefore users will have
netCDF4 tools with or without szip support.
This is bound to discourage the adoption of netCDF4 in general and could
cause many data archival problems down the line. For instance, from my
perspective I am now asking myself what the CMIP5 archive's policy
should be on netCDF4 szip.
I'm not sure how to resolve this problem here but it's worth exposing.
Cheers,
Stephen.
---
Stephen Pascoe +44 (0)1235 445980
British Atmospheric Data Centre
Rutherford Appleton Laboratory
-----Original Message-----
From: netcdfgroup-bounces@xxxxxxxxxxxxxxxx
[mailto:netcdfgroup-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Ed Hartnett
Sent: 18 October 2009 12:15
To: netcdfgroup@xxxxxxxxxxxxxxxx
Subject: [netcdfgroup] please try out the netcdf daily snapshot for
opendap,hdf4-reading, hdf5-reading, szip compression, etc.
Howdy all!
Here at NetCDF World Headquarters, we are preparing the 4.1 release of
the netCDF C/Fortran libraries. There are many exciting new features in
this release, including:
* Remote data access with the new built-in opendap client.
* Reading of existing HDF4/HDF5 data archives with the netCDF C/Fortran
APIs.
* A completely rewritten ncgen, which now fully supports netCDF-4.
* Use of parallel-netcdf library to do parallel I/O on netCDF classic
and 64-bit offset format files.
* The nc-config script to help build netCDF programs.
* UDUNITS now distributed with netCDF.
* The ability to compress netCDF-4/HDF5 data with szip
compression. (JUST ADDED!)
Now would be a great time for our dedicated user community to download
the daily snapshot, let us know that it builds cleanly, and try out some
of the new features.
Get the latest snapshot here:
ftp://ftp.unidata.ucar.edu/pub/netcdf/snapshot/netcdf-4-daily.tar.gz
Build it according to instructions here:
http://www.unidata.ucar.edu/software/netcdf/docs_snapshot/netcdf-install
.html#Quick-Instructions
Report results (good or bad) to the support email address:
support-netcdf@xxxxxxxxxxxxxxxx
Thanks!
Ed
--
Ed Hartnett -- ed@xxxxxxxxxxxxxxxx
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