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v02i024: ncompress - (Ver. 4.2.3) an improved file compressor, Part00/02

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Peter Jannesen

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Aug 28, 1992, 6:35:59 PM8/28/92

Submitted-by: Peter Jannesen <pe...@ncs.nl>
Posting-number: Volume 2, Issue 24
Archive-name: ncompress/part00

Environment: UNIX

Tested Environments:
Sun 3 & 4, SunOS 4.0.3 & 4.1.1, cc & gcc
SCO Xenix 2.3.4 & gcc 1.40.
SCO OpenDesktop 1.1, gcc 2.0 compiler
486, ISC UNIX 3.0
ESIX System 5.3.2 Rev D, gcc 1.39
IBM 3090 600J, AIX/370 1.2.1
RS6000/530 (AIX 3.1.5 & 3.2)
MIPS, Mips OS 4.51
Next, NeXTOS
HP720/HP-UX 8.07
HP400/HP-UX 7.05 & 8.00
HP900/847, HP/UX 8.0
AT&T 3b1, 3.51m O/S.
Decstation 5000, Ultrix 4.2
DEC Alpha/OSF-1

Dates:
Submission Received: April 6 1992
Reviews Returned: April 30 1992
Revised Submission Received: Jun 23 1992
Reviews Returned: July 29 1992
Revised Submission Received: Aug 5 1992
Accepted: Aug 26 1992

Author's Summary:
-----------------

This is version 4.2 of (N)compress (an improved version of compress 4.1).

Compress is a fast, simple LZW file compressor. Compress does not have
the highest compression rate, but it is one of the fastest programs to
compress data. Compress is the defacto standard in the UNIX community
for compressing files.

'build' is a menu driven shell script for compiling, testing and
installing (N)compress. So to build and install (N)compress all you have to
do is run build. Build will first test your system for default
settings. The current compile settings are stored in a special file
called compress.def.

For user with problems with build there is a default makefile included
called 'Makefile.def'. Also build is capable te generate a Makefile with
all options (option genmake).

(N)compress 4.2 has a special, fast compression hash algorithm. This
algorithm uses more memory than the old hash table. If you don't want
the faster hash table algorithm set 'Memory free for compress' below
800000.

zcmp, zdiff, zmore were copied from version 4.1 without any changes.

The output of (N)compress 4.2 is fully compatible with that of compress 3.0.
In other words, the output of (N)compress 4.2 may be fed into uncompress 3.0 or
the output of compress 3.0 may be fed into uncompress 4.2.

The output of (N)compress 4.2 is not compatible with that of
compress 2.0. However, compress 4.2 still accepts the output of
compress 2.0. To generate output that is compatible with compress
2.0, use the undocumented "-C" flag.

Reviewers' Comments:
--------------------

Overall, this went very well. After reading the README, everything
seemed clear. I ran build, everything went fine, and apart from a
couple of points, it compiled & ran cleanly. Some of the
spelling/typing in the build script left a bit to be desired though.

------------------------------------------------------------------------------

This package is completely compatible with the SCO Unix 3.2v2 system
'compress' and adds a nice recursive feature. This version of compress
is faster than the supplied version with the differences becoming larger
as the file size grows (my perl.tar went from 35.1 user seconds to 16.5).
I am inpressed by this higher efficiency.

While the installed size, for me, was almost twice the size - from 14000
to 26684, I don't see this as any reason that it should not replace your
system 'compress', or at the very least augment it. Software Developement
House programers would want to use it as an augment, as it is very easy
to get hooked on the added features. The extra programs 'zdiff' & 'zmore'
are very good and useful.

------------------------------------------------------------------------------

Ncompress 4.2.3 is a new version of compress compatible with earlier
versions and generally faster although real time comparisons vary
considerably across platforms and cpu load. The program is easy to
configure, compile and install.

------------------------------------------------------------------------------

compress 4.2 is a welcome update to the venerable compress
utility that is used so heavily on the net. A number of
annoying minor bugs have been fixed that present problems
with older versions of compress on some newer platforms.

The package seems to be documented fully, and includes brief
descriptions of the algorithms and their potential patent status.

Aside from some rather annoying spelling mistakes and format
botches in the build procedure user-interface, the new version
of compress builds cleanly, and produces a version of compress
that's about 30% faster than the stock 3.51m compress.

One annoyance worthy of note: the build procedure does a good
job of configuring the compress compile process, but doesn't
bother to seek out incompatibilities in the ancilliary shell
scripts. In particular, it doesn't notice when the system
doesn't support "more"; it will not substitute "pg" into
the "zmore" script.

------------------------------------------------------------------------------

The product does the job it claims to without any errors that I was able
to detect. It is compatible with the existing compression software
that we have been using (version 4.0, from volume 2, issue 27 of
mod.sources).

This version claims to have a performance gain, but I was unable to verify
that against version 4.0, however, this may be due to the data that
I was compressing (a 7MB cpio file of C sourc efiles), or to some
difference with respect to the OS/hardware combination. It certainly
did not loose any significant amount of performance.

Compress 4.2 is the newest version of the standard file compression
mechanism utilized throughout USENET. Once it is offically available
it will replace our existing compression mechanism.

------------------------------------------------------------------------------

Compress is a public-domain implementaion of LZW file compression.
This is a cleanup version of the venerable UNIX compress utility. It
comes with menu driven script which eases compilation and
installation. This version provides a special fast compression hash
algorithm which seems to be the one algorithmic addition of this
version over the previous ones.

------------------------------------------------------------------------------

This excellent piece of software passes our review specifications
with flying colors. This has become a standard piece of software
at ealier revisions, and now in its lastest revision is the same tried
and true compression program it was before. Although the bug fixes are
minor, I am gald it is being maintained and is being put into review under
our system.

------------------------------------------------------------------------------

compress 4.2 offers some performance improvements over compress 4.0,
and adds a flag to compress recursively in a directory tree. People
creating UNIX distributions should use this version, but the new
features are not important enough that end users need to rush to
upgrade.

------------------------------------------------------------------------------

Compress 4.2 is a drop in replacement for whichever version of compress that
you are currently running. Using the faster hash table algorithm it normally
runs twice as fast as Sun's compress (compress 4.0). Without this algorithm,
it is about 40% faster than Sun's compress. No compatability problems were
found between this verion of compress and Sun's.

This version would be of most use to people who are compressing lots of data
(eg images). If you use compress a lot (particularly on large files), using
Compress 4.2 will save you a considerably amount of time. Where possible, I
would suggect allowing compress to use its faster hash table compression for
speed.

exit 0 # Just in case...
--
Andrew Patrick acting as Comp.Sources.Reviewed Moderator
Department of Communications, Ottawa, CANADA
c...@calvin.dgbt.doc.CA

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