Re: netcdf-4.0-beta1 release now available on netCDF web site...

  • To: Ed Hartnett <ed@xxxxxxxxxxxxxxxx>
  • Subject: Re: netcdf-4.0-beta1 release now available on netCDF web site...
  • From: Jeff Whitaker <jswhit@xxxxxxxxxxx>
  • Date: Tue, 24 Apr 2007 20:01:59 -0600
Ed Hartnett wrote:
Jeff Whitaker <jswhit@xxxxxxxxxxx> writes:

Ed:  Thanks!  beta1 works fine and passes all the tests with my python
module.  However, ncdump appears to be broken - every netcdf-4 file I
try results in something like this:

ncdump: HDF error

It seems to work fine with netcdf-3 files however.

Howdy Jeff!

In this release, ncdump and ncgen can handle netCDF-4 files as long as
they conform to the classic model.

That is, as long as you don't use user-defined types and the new
atomic types, it should work fine. (Ncdump does handle groups
correctly, but not yet ncgen.)

This is tested with the ncdump tests, when the script
is run in the ncdump directory. This script causes ncgen to create
some netCDF-4/HDF5 files from the same CDL scripts that are used to
test the netCDF-3 ncgen/ncdump stuff. Then the script feeds the
resulting data files back to ncdump to make sure that the same CDL
output results.

For example:

bash-3.00$ ../ncgen/ncgen -v3 -b -o ../ncgen/c0.cdl
bash-3.00$ ./ncdump netcdf c0 {
        Dr = UNLIMITED ; // (2 currently)
        D1 = 1 ;
        D2 = 2 ;
        D3 = 3 ;
        dim-name-dashes = 4 ; = 5 ;
        char c ;
                c:att-name-dashes = 4 ;
       = 5 ;

Do your files conform to the classic model?

Ed:  Yes, they do.  ncdump crashes on every netcdf4_classic file I give it.

I'll try running the test and send you the results.


Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/PSD1        FAX   : (303)497-6449
325 Broadway                Boulder, CO, USA 80305-3328

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From owner-netcdfgroup@xxxxxxxxxxxxxxxx    16 Wed, Sep
Date:    Wed, 16 Sep 1992 22:38:37 EDT
From: RIVERS@xxxxxxxxxxxxxxxxxxx (Mark Rivers)
To: netcdfgroup@xxxxxxxxxxxxxxxx
Subject: Data compression
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Are there any plans to add data compression to netCDF? We are strongly leaning
towards switching from our present (local) data file format to netCDF. The only
feature which we will have to give up is data compression. We are presently
using either run-length encoding or a simple form of linear predictive coding.
Both of these are loss-free. Linear predictive coding typically reduces the size of our 32 bit integer data files by a factor of 3, which is significant.

It seems like it could be a very worthwhile addition.

Mark Rivers                              (516) 282-7708 or 5626
Building 815 rivers@xxxxxxxxxxxxxxxxxxx (Internet) Brookhaven National Laboratory rivers@bnl (Bitnet) Upton, NY 11973 BNLX26::RIVERS (Physnet)