Without any deep knowledge in the subject details…

HDF5 is a container format that uses miscellaneous techniques
for the purpose of storing those data.
Some of them are e.g. binary trees, or chunking, or changing size of length 
values.

Even if the data is the very same and even if any reader will see the same data
there can still be many cases where the encapsulation might see differences.

A binary tree can see different layouts.
A chunking value can be tuned differently depending on platform, file system or 
even the used compiler.
A size of a length value might be selected differently by default.

A low level parsing of the container format will unveil what the origin is.
This is not a bug – instead that is a feature.

Maybe your invalid approach for the comparison is the real “bug”. ;-)

regards, Alex.


Managing Directors: Dr. Seok Cheol Kee, Andrea Weuffen, Wolfgang Vieweger
Von: Hdf-forum [mailto:[email protected]] Im Auftrag von 
Ekin Akoglu
Gesendet: Dienstag, 5. August 2014 15:15
An: HDF Users Discussion List
Betreff: [Hdf-forum] Identical HDF5 files according to "h5diff" differ in 
comparison with "diff" Unix command

Dear all,

For the two versions of the same HDF5 file, h5diff comparison outputs "0 
differences found"; however, when compared with the Unix "diff" command, they 
differ. This is creating inconvenience under version control system. Do you 
have any suggestions why diff and h5diff conflicts? As far as I remember, this 
was not the case in the past and I remember managing HDF5 data files without 
problems under GIT DVCS; however, I cannot recall which version of the HDF5 
library.

I tried this as below:

I compiled my Fortran program (using GNU Fortran 4.8.2) and ran it so as to 
create the HDF5 datafile as output. I moved the datafile to some other 
directory. Then I re-ran my program (without recompiling) and then compared the 
newly created HDF5 data file with the old one using "diff" tool in Mac OS X 
(10.9.4) and Linux (Debian Wheezy 7.6 x64) and they did differ. Why?

My HDF5 version is 1.8.12 and diff version is GNU diffutils 2.8.1.

Thank you in advance,

Ekin
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