From help-octave-request at bevo dot che dot wisc dot edu  Sat Nov 20 20:12:27 1999
Subject: interest in HDF5 support in Octave?
From: stevenj at gil-galad dot mit dot edu
To: help-octave at bevo dot che dot wisc dot edu
Date: Sat, 20 Nov 1999 21:12:43 -0500 (EST)

Hello all,

I noted that "Use HDF for binary data" was on the project wishlist.  I am
interested in this too.  I am thinking about implementing it (and have
already done some work...see below) and wanted to gauge the interest of
other octave users and developers for this.

For those of you who don't know, HDF is a portable binary format and free
supporting library developed at NCSA in Illinois, and is designed for
storing large scientific datasets.

A single HDF file can contain many data sets, annotations, hierarchical
groups of data sets, and so on.  Supporting it in octave would mean the
ability to easily interchange data with a wide variety of other scientific
computing tools, projects, and visualization programs.  Standard formats
are good!

I have written an Octave plugin to import 1d/2d data slices from
multidimensional HDF5 files (and will be posting it to octave-sources in
the next few days, once I clean it up a bit).  But, what I would really
like to do is to add a new "-hdf5" option to the "save" and "load"
commands, allowing you to store all of your octave data (or a subset) in a
single HDF5 file.  I think this shouldn't be too hard to do.  (One can't
load arbitrary HDF files because octave doesn't support 3+ dimensional
data sets...so my slice importer will still be useful.)

HDF5, by the way, is a recent complete rewrite of HDF by NCSA, and is the
direction of future HDF development.  It has lots of advantages over HDF
such as a *much* cleaner interface and format, large (> 2GB) dataset
support, nice things like parallel I/O and reentrancy, and so on.  It is
incompatible with the old HDF format, but conversion tools exist.

The old HDF was under a BSD-like license, including the advertising clause
that makes it incompatible with the GPL.  HDF5, however, recently removed*
the advertising clause, partially at my instigation--I gave them Octave as
an example of something I would like to use HDF5 with but couldn't because
of licensing issues.

* Actually, they changed the advertising clause from a legal requirement
to a "request."  I checked to with Richard Stallman to make sure that the
resulting license was GPL-compatible, and he said that it was ("a request
can't conflict with anything").

Cordially,
Steven G. Johnson



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