The compression gains must be extremely data dependent.
Here are the results for the compression of a dataset that consists of
32bit floats of a collection of many meteorological fields from the NCAR CCM3:
35577060 bytes ENSANNAVG-0105.nc
26739972 bytes ENSANNAVG-0105.nc.bz2
The compression is very small.
Phil
On Wed, Aug 09, 2000 at 08:03:50AM -0600, Roy Mendelssohn wrote:
> There was some question as to how well Bzip2 would compress floating
> point data. We just did a test on a large NetCDF file, containing a
> years worth of global, 1-degree six-hourly pressure fields, so that
> the data is floating point. here are the sizes from a Unix ls
> command (i.e in 512 byte units).
>
> raw.nc 380,551,616
>
> raw.nc.Z 143,716,211
>
> raw.nc.bz2 55,633,062
>
>
>
> Bzip2 gave about the same 7:1 compression that Russ reported, and
> roughly 3 times better that Unix compress.
>
--
----------------------------------------
Phil Rasch, Climate Modeling Section, National Center for Atmospheric Research
P.O. Box 3000, Boulder CO 80307
internet: pjr@xxxxxxxx, http://www.cgd.ucar.edu/cms/pjr
Phone: 303-497-1368, FAX: 303-497-1324
