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[netCDF #DKW-240688]: nc_rename_var(), nc_rename_dim() bugs in netCDF4?

Hi Charlie,

> A user has pointed out a serious problem with ncrename.
> As best as I can tell, this traces back to a netCDF4 library bug.
> Please investigate and let me know if this is true or not.

You're right, this looks fairly serious. We haven't finished
determining the scope of the bug, but we'll let you know soon. A 
posting to netcdfgroup may be needed to warn users not to trust
coordinate data in coordinate variables that have been renamed.

Thanks for reporting the bug.

--Russ

> The bug apparently affects (at least) versions 4.3.1--4.3.2 of the
> netCDF4 library (and current snapshots).
> This bug corrupts values contained in netCDF4 arrays (not scalars)
> that are renamed or that utilize dimensions that are renamed.
> In other words, renaming variables and dimensions succeeds
> yet it corrupts the values contained by the affected array variables.
> This bug corrupts affected variables by replacing their values with the
> default _FillValue for that variable's type.
> Attached is a file whose values are corrupted when either the
> dimension or the variables or both are renamed.
> 
> ncks -O -4 -v lat -C -h -m -M ~/nco/data/in.nc ~/bug.nc # Create test
> ncrename -O -v lat,tal ~/bug.nc ~/foo.nc # Broken
> ncrename -O -d lat,tal ~/bug.nc ~/foo.nc # Broken
> ncrename -O -d lat,tal -v lat,tal ~/bug.nc ~/foo.nc # Broken
> ncks --cdl ~/foo.nc
> 
> The only known workaround is to convert the file to netCDF3 first,
> then rename as intended, then convert back. I checked renaming of
> groups and attributes in netCDF4 files and these operations both
> perform as intended. So the problem appears to be only with with
> renaming dimensions and renaming array variables in netCDF4 files.
> 
> Thanks!
> Charlie
> 
> zender@givre:~$ ncks --cdl ~/bug.nc
> netcdf bug {
> dimensions:
> lat = 2 ;
> 
> variables:
> float lat(lat) ;
> 
> data:
> lat = -90, 90 ;
> 
> } // group /
> zender@givre:~$ ncrename -O -v lat,tal ~/bug.nc ~/foo.nc
> ncrename: In total renamed 0 attributes, 0 dimensions, 0 groups, and 1
> variable
> zender@givre:~$ ncks --cdl ~/foo.nc
> netcdf foo {
> dimensions:
> lat = 2 ;
> 
> variables:
> float tal(lat) ;
> 
> // global attributes:
> :history = "Wed Oct  8 10:24:15 2014: ncrename -O -v lat,tal
> /home/zender/bug.nc /home/zender/foo.nc" ;
> 
> data:
> tal = 9.96921e+36, 9.96921e+36 ;
> 
> } // group /
> zender@givre:~$
> 
> --
> Charlie Zender, Earth System Sci. & Computer Sci.
> University of California, Irvine 949-891-2429 )'(
> 
> 

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: DKW-240688
Department: Support netCDF
Priority: Normal
Status: Closed