paq8jd is an open source (GPL) file compressor and archiver.
Last update Feb. 12, 2007 by Matt Mahoney.

Contents of paq8jd.zip:

readme.txt - this file (updated 2/12/07)
paq8jd.exe - Win32 (MinGW g++) executable for Pentium MMX and higher
paq-8jd_intel.exe - Win32 executable (compiled by Johan de Bock with Intel C++ from http://uclc.info )
paq8jdsse.exe - Win32 executable linked with paq7asmsse.asm for Pentium 4 or higher
paq8jd32 - 32 bit Linux executable (compiled by Giorgio Tani)
paq8jd64 - 64 bit Linux executable

paq8jd.cpp - C++ source code for all versions
paq7asm.asm - NASM/YASM assembler code for Pentium MMX or higher
paq7asmsse.asm - NASM/YASM for Pentium 4 (SSE2) or higher in 32 bit mode
paq7asm-x86_64.asm - YASM for x86-64 bit processors (tested in 64 bit Linux)
paq7asm-x86_64.o - above, assembled for 64 bit Linux.

paq8jd can be compiled for other processors without the assembler
code using the -DNOASM option (but it will run slower).
The assembler code is the same for all paq7/8 versions.

paq8jd was written by Matt Mahoney (as paq8f) with improvements by
Bill Pettis (based on improvements by Alexander Ratushnyak and
Przemyslaw Skibinski in the paq8hp* series) and Serge Osnach (additional
models).  The assembler code was ported to 64 bit by Matthew Fite and 32 
bit SSE2 by wowtiger.

Other contributors to the PAQ project: Berto Destasio (tuning earlier
models for better compression), Johan de Bock (benchmarking, compiling
fast exectuables), David A. Scott (arithmetic coder improvements),
Fabio Buffoni (speed optimizations), Jason Schmidt (compression
improvements), Rudi Cilibrasi (text modeling), and Pavel L. Holoborodko
(PGM image modeling), and Jari Aalto (licensing/distribution).

This work would not be possible without the benchmarking efforts of
Marcus Hutter (Hutter prize), Werner Bergmans (maximumcompression.com)
Johan de Bock (UCLC), Berto Destasio (Emilcont benchmark), Stephan Busch
(Squeeze Chart), Leonid A. Broukhis (Calgary Corpus Challenge),
and Black Fox.

paq8jd and paq8f formats are supported in PeaZip by Giorgio Tani.
A similar (but rewritten) context mixing algorithm is used in
WinRK 3.0.3 (pwcm mode) by Malcolm Taylor.  Modified versions of 
PAQ (faster but less compression) are used in UDA and WinUDA by dwing,
and in xml-wrt by Przemyslaw Skibinski.
