Re: error saving empty matrix in HDF5 format

[John W. Eaton]

On  3-Mar-2004, David Bateman <address@hidden> wrote:

| 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?

I don't know what the best solution is.

Unfortunately, since HDF does not handle zero-length dimensions
directly, that means that we have to insert kluges for every N-d
type.  For example, it seems that with the latest CVS I can save and
reload an empty N-d numeric array, but not an empty N-d cell array.

Perhaps we need to get the attention of the HDF people and get them to
handle zero-length dimensions?

jwe