Thanks Maarten and Francesc,
The "sleep" experiment seems definitive. In fact, I found the
following in the HDF5 User Guide,
----------------
Name: H5Pset_obj_track_times
Signature:
herr_t H5Pset_obj_track_times( hid_t ocpl_id, hbool_t track_times )
Purpose:
Sets the recording of times associated with an object.
---------------
So at a low level this can be controlled. I guess I will go that
route, trying to open access to this functionality. Any suggestions /
warnings will be appreciated. Thanks,
Matt
On Tue, Mar 23, 2010 at 9:50 AM, Francesc Alted <fal...@pytables.org> wrote:
> A Tuesday 23 March 2010 14:17:29 Matt Calder escrigué:
>> Maarten,
>>
>> Thanks for the pointer to h5diff. Unfortunately, it shows no
>> difference in the files. Any idea how a timestamp might find its way
>> into the file? Or where I might look for an answer? I'm guessing this
>> is happening at the hdf5 rather than the pytable level.
>
> This is my guess too. The script below generates identical files:
>
> ---------------------------------------
> import tables
> import numpy
> import time
>
> # Define simple table
> table1 = numpy.array([[(0,0,0), (1,0,0)], [(0,1,0), (0,0,1)]], {'names':
> ('r','g','b'), 'formats': ('f4', 'f4', 'f4')})
> # Write table to a file
> h5file = tables.openFile("/tmp/file1.h5", "w", PYTABLES_SYS_ATTRS=False)
> h5file.createTable("/", "table1", description = table1)
> h5file.close()
>
> #time.sleep(1)
>
> # Write same table to another file
> h5file = tables.openFile("/tmp/file2.h5", "w", PYTABLES_SYS_ATTRS=False)
> h5file.createTable("/", "table1", description = table1)
> h5file.close()
> ---------------
>
> [notice how I've disabled pytables' system attributes, just in case]
>
> $ diff /tmp/file1.h5 /tmp/file2.h5
> $
>
> but if I uncomment the `time.sleep(1)` line, the files differ:
>
> $ diff /tmp/file1.h5 /tmp/file2.h5
> Els fitxers /tmp/file1.h5 i /tmp/file2.h5 difereixen
> $
>
> Object IDs are also identical:
>
> $ h5ls -i /tmp/file1.h5
> HDF5 "/tmp/file1.h5" {
> GROUP "/" {
> OBJECTID { 33554433 }
> DATASET "table1" {
> DATATYPE H5T_COMPOUND {
> H5T_IEEE_F32LE "r";
> H5T_IEEE_F32LE "g";
> H5T_IEEE_F32LE "b";
> }
> DATASPACE SIMPLE { ( 4 ) / ( H5S_UNLIMITED ) }
> OBJECTID { 83886081 }
> [...]
>
> $ h5ls -i /tmp/file2.h5
> HDF5 "/tmp/file2.h5" {
> GROUP "/" {
> OBJECTID { 33554433 }
> DATASET "table1" {
> DATATYPE H5T_COMPOUND {
> H5T_IEEE_F32LE "r";
> H5T_IEEE_F32LE "g";
> H5T_IEEE_F32LE "b";
> }
> DATASPACE SIMPLE { ( 4 ) / ( H5S_UNLIMITED ) }
> OBJECTID { 83886081 }
> [...]
>
> Mmh, I am afraid that you will need to use another way to check whether the
> files are identical or not.
>
> --
> Francesc Alted
>
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