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[netCDF #UGK-599461]: creation ordering issue with coordinate variables in 4.1.2, 4.0.1

> Hello netcdf folks,
> 
> Some of our customers are starting to report issues with dimension and
> coordinate variable creation ordering, which I believe is what's referenced
> at
> 
> 
> http://www.unidata.ucar.edu/software/netcdf/docs/netcdf/NetCDF_002d4-Format.html
> 
> section "C.3.5 Dimension and Coordinate Variable Ordering".  My thinking is
> that this situation, when brought about by a 4.1.x netcdf library client,
> will result in a file that is unreadable by a 4.0.1 client (such as MATLAB,
> versions R2010b and R2011a).  Attached is sample code that reproduces the the
> situation when compiled with 4.0.1 and 4.1.2.
> 
> 4.0.1 clients can't open such files, erroring out in nc_open ==> ... read_var
> ==> pg_att_grpa, specifically bailing out at line nc4hdf.c:1655 because the
> HDF5 dataspace of the "_Netcdf4Dimid" attribute is scalar and therefore not
> one-dimensional.
> 
> Does this sound right?  If so, we have a couple of ideas on how our customers
> can proceed to deal with the situation, but I felt the need to check with you
> first.
> 
> 

Howdy John!

Sorry it took me so long to reply to your email, we got a little swamped for a 
few weeks.

The 4.0.1 release had some bugs in the handling of re-ordered coordinate 
variables, fixed in 4.1.x. So files produced by 4.1.x which do this coordinate 
variable re-ordering will not be readable to 4.0.x versions.

More seriously, we have recently learned that there will be other files that 
4.1.x produces which are not going to be understood by 4.0.x releases. This is 
because the HDF5 binary format is far more fluid than the classic netCDF 
format. The HDF5 file contains a number of independently versioned objects, and 
new versions of these objects are released from time to time in HDF5 releases. 
Files that contain these new versions will not be readable to older versions of 
HDF5.

The answer in all cases is to upgrade to the latest release of HDF5 and 
netCDF-4. This is now possible for DLL users as well as those on Unix 
platforms, since daily DLL snapshots of the C library, based on the latest HDF5 
DLLs, are now being released.

Thanks,

Ed

Ticket Details
===================
Ticket ID: UGK-599461
Department: Support netCDF
Priority: Critical
Status: Closed