ABOUT HDF4.1 Beta 1
December 6, 1996
INTRODUCTION
This document describes the differences between HDF 4.0r2 and
HDF 4.1b1. It is written for people who are familiar with
previous releases of HDF and wish to migrate to HDF 4.1b1.
The release notes provide more in-depth information concerning
the topics discussed here. For documentation, please refer
to the HDF 4.0r2 documentation which can be found on the NCSA
ftp server (ftp.ncsa.uiuc.edu) in the directory
/HDF/Documentation/HDF4.0r2.
First-time HDF users are encouraged to read the FAQ in this
release for more information about HDF. Users can also look
at the home page for HDF at:
http://hdf.ncsa.uiuc.edu/
If you have any questions or comments, please send them to:
hdfhelp@ncsa.uiuc.edu
CONTENTS
- New Features and Changes
- Platforms Tested
- Known Problems
- Important Fixes
New Features and Changes:
-------------------------
o Attributes are now supported in both the vdata and vgroup
APIs. In the vdata API, attributes can be attached to either
vdata fields or vdatas; in the vgroup API, attributes can be
attached to vgroups. This new functionality can be used
to attach attributes to vdatas and vgroups created by earlier
versions of the HDF library. However, the old versions of
the HDF library cannot read the new version vdatas and vgroups.
A vdata/vgroup having attributes will become a new version
vdata/vgroup. For more information, please refer to the file
../release_notes/vattr.txt, as well as the man pages for the
new functions.
o Data chunking is now supported in SD scientific data sets.
When data chunking is used, an n-dimensional SDS is stored
as a series of n-dimensional chunks, improving performance on
certain types of partial read operations.
New routines for creating and manipulating chunked SD
scientific data sets have been provided, and two preexisting
SD I/O routines, SDreaddata and SDwritedata, have also been
modified to work with chunked SDSs. For more information, please
refer to the file ../release_notes/sd_chunk_examples.txt, as
well as the man page for sd_chunk.
More information will be included in the HDF 4.1 documentation,
which will be available with the release of HDF 4.1.
o Due to certain limitations in the way compressed SDS datasets are stored,
data which has been compressed is not completely writable in ways that
uncompressed datasets are. The "rules" for writing to a compressed
dataset are as follows:
(1) Write an entire dataset that is to be compressed. i.e. build the
dataset entirely in memory, then write it out with a single call.
(2) Append to a compressed dataset. i.e. write to a compressed dataset
that has already been written out by adding to the unlimited
dimension for that dataset.
(3) For users of HDF 4.1, write to any subset of a compressed dataset
that is also chunked.
Please refer to the ../release_notes/comp_SDS.txt file for more information.
o A new file, ../release_notes/compile.txt, contains instructions on
compiling applications on the supported platforms. If you encounter
problems with it, please let us know at hdfhelp@ncsa.uiuc.edu.
o SGI has changed some compiler default settings in IRIX 6.2.
We decided to explicitly define the settings of various ABI related
options. For the 64 bit OS ("uname -s" returns IRIX64), HDF uses
"-64 -mips4" code. For the traditional 32 bit OS ("uname -s" returns
IRIX), HDF uses "-32 -mips2". To use n32 mode on IRIX64, HDF uses
"-n32 -mips3" code. Note that in the previous release (4.0r2), HDF
used only "-n32". In IRIX 6.1 and before, "-n32" defaulted to
"-mips4" code but in IRIX 6.2, it defaults to mips3 or mips4 code.
We decided to explicitly set it to "-n32 -mips3". Therefore,
applications linking with the HDF library must be compiled with
the same explicit ABI options.
Platforms Tested:
-----------------
HDF 4.1b1 has been tested on the following platforms:
DEC Alpha/Digital Unix 3.2
DEC Alpha/OpenVMS AXP v6.2
DEC VAX OpenVMS v6.2
Free BSD 2.2
HP-UX 9.03
IRIX 5.3
IRIX 6.2_64
IRIX 6.2_n32
Linux ELF 1.2.13 (C only)
Macintosh PowerPC (C only) (not ready yet)
SP2 4.1
Solaris 2.5
SunOS 4.1.3
Windows NT/95 (C only)
YMP 9.0.2asC
Known Problems:
---------------
o With the SD interface, you are unable to overwrite
existing compressed data, that is not stored in
"chunked" form. This is due to compression algorithms
not being suitable for "local" modifications in a compressed
datastream. For more information, please refer to
the ../release_notes/comp_SDS.txt file.
o With 4.0r1p1, you could type "hdp list -a
to get a list of the file attributes associated with
a file. This does not currently work.
o There are no plans to add the DF24writeref function
to the DF24 interface. This function will be removed
from the documentation.
o When running "make test" on OpenVMS, Test 3 (float32) of the
chunking tests fails, and has therefore been commented out.
o When running the tests on Window NT/95, Test 2 (uint16) of the
chunking tests fails, and will be commented out.
Important Fixes:
----------------
o If you opened a file in Read Only mode with the SD interface
(using SDstart), it would create the file if the file did not
exist. This no longer occurs.
o HDF 4.0r2 did not recognize JPEG images created by HDF 3.3r4.
This has been fixed.
See the ../release_notes/bug_fixed.txt file for more information
on bugs fixed in this release.