Re: error saving empty matrix in HDF5 format

[David Bateman]

Daprès Paul Kienzle <address@hidden> (le 03/03/2004):
> 
> On Mar 2, 2004, at 11:19 AM, David Bateman wrote:
> 
> >According to John W. Eaton <address@hidden> (on 03/02/04):
> >>I applied these changes, but I think maybe we should use Paul's
> >>suggestion of storing the dimensions in the attributes section.
> >
> >I agree, but we need to check that the empty array is available in
> >the hdf library. In any case this would just be a matter of fixing up
> >the ls-hdf5.cc{save_hdf5_empty, load_hdf5_empty} functions I added.
> >So a reasonable structure is there even in this patch...
> 
> It would be nice to have the data files not so heavily dependent
> on a particular release of hdf5.  Could you save it instead as an
> empty string or empty something else, but with the vector attribute
> empty_dims?  Or is nothing allowed to be empty?  How about
> an empty group?
> 
> Paul Kienzle
> address@hidden

Ok, looking at this again it seems that the discussion I pointed out
was about the possibility of including empty objects in the HDF files.
At the moment this is not even implemented.

So, not sure what the best thing to do here is, as there are no empty array
structures in HDF files... At the moment the structure is

<variable name> <GROUP> -- >  type "octave_value" <DATASET>
                           >  value <DATASET> 
                           >  OCTAVE_EMPTY_MATRIX <ATTRIBUTE>

where "OCTAVE_EMPTY_MATRIX" is a flag and "value" contains either the 
data of a non empty matrix or the dimensions of the matrix if
"OCATVE_EMPTY_MATRIX" is set. What we would like is 

<variable name> <GROUP> -- >  type "octave_value" <DATASET>
                           >  value "empty dataset" <DATASET> 
                           >  OCTAVE_EMPTY_MATRIX <ATTRIBUTE>

where OCTAVE_EMPTY_MATRIX is now an attribute containing the array dimensions.
However, this is not possible even with the latest versions of HDF5. Are
there any other choices that make sense?

Regards
David

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David Bateman                                address@hidden
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