CDO

Hi,

When comparing several variables in 2 files, diffn is not reliable when variables are stored in different order. I get a warning message:

cdo diffn (Warning): Input streams have different parameters!

and the result is wrong.

In contrast, when explicitly extracting 1 variable out of each of the 2 files, diffn works properly.

I attach 2 files and the corresponding example to highlight the problem:

cdo diffn test_ham2.nc test_debugs.nc   #--> prints the above warning, and shows an erroneous result

cdo diffn -selname,RWETAS test_ham2.nc -selname,RWETAS test_debugs.nc  #--> no warning and the result is correct
cdo diffn -selname,RWETAI test_ham2.nc -selname,RWETAI test_debugs.nc    #--> no warning and the result is correct

I suspect that in the second case it only works because the pre-selection of the variable automatically sets the var code to 1 in both files, which implies that diffn actually relies on variable codes and not on variable names.

My cdo version: 1.6.2rc5

Is this a bug?