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[netCDF #AGE-229844]: netCDF-4 problems

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  • Subject: [netCDF #AGE-229844]: netCDF-4 problems
  • Date: Fri, 25 Apr 2008 07:55:28 -0600
> I have extended the CDO package to support reading and
> writing netCDF-4 data with the classic model.
> The compression works fine and it's very useful for us!
> I think an netCDF-4 interface for SZIP compression would
> also very useful because it's very fast.

I agree, and szip will probably be added in a future version of netcdf-4. But
the 4.0 version needs to go out first! ;-)

> But I have two problems with the netCDF-4 libray. I use the
> daily snapshot2008030613.
> Could you tell me how I can check that the opened (read)
> netCDF dataset really has the classic model?

There is an nc_inq_format function:
http://www.unidata.ucar.edu/software/netcdf/netcdf-4/newdocs/netcdf-c.html#index-nc_005finq_005fformat-110

It tells you that a file is one of the following:
#define NC_FORMAT_CLASSIC (1)
#define NC_FORMAT_64BIT   (2)
#define NC_FORMAT_NETCDF4 (3)
#define NC_FORMAT_NETCDF4_CLASSIC  (4) /* create netcdf-4 files, with
NC_CLASSIC_MODEL. */

> The second problem is that I can't read large files on 32-bit Linux.
> I can write large files in classic, 64-bit offset and netCDF-4 classic
> but the reading failed with "File too large". It works only if i
> compile the netCDF-4 library without netcdf-4 support.

We are currently working on a large file bug, so perhaps you have encountered
it. Give us a few days and try the snapshot again.

If you can easily reduce your code to a test such as the code in
nc_test/tst_large.c we could see about adding it to the netcdf test suite,
which would be very helpful as well, and would ensure that netCDF continues to
work for your exact case.

Can you tell me what the CDO is, or point me to a web page? Is it the climate
metadata system, or am I confusing my TLAs?

How was your experience extending the CDO from netCDF classic to netCDF-4
classic? Easy? Hard? As painful as root canal? Any comments would be welcome.

Thanks,

Ed

Ticket Details
===================
Ticket ID: AGE-229844
Department: Support netCDF
Priority: Normal
Status: Open