PAQ7 released

I just posted my newest compressor, PAQ7, to
http://cs.fit.edu/~mmahoney/compression/#paq7
Compression is similar to PAQAR but about 3 times faster (still very
slow). It includes models for color .bmp, .tiff, and .jpeg images, so
gives better compression on these (but not as good as WInRK or Stuffit
- how they do this well eludes me). It lacks a dictionary and a x86
model so compression is a bit worse than PAsQDa on English text and
32-bit WIndows .exe and .dll files.

This is a complete rewrite of PAQ6. It differs primarily in that it
replaces the gradient descent model mixer with a neural network, which
can be accelerated using MMX assembler (thus the better speed). For
non x86-32 machines or if you don't have NASM you can compile with
-DNOASM (1/3 slower). I tested it under WIndows, Linux and Sparc
Solaris for archive compatibility.

I will let Werner test on the maximumcompression.com corpus but in my
own tests it takes first place on ohs.doc (due to a large embedded
jpeg, which Stuffit missed), and english.dic, and second place on a
couple other files.

I don't know how Stuffit models jpeg (I haven't seen their patent) but
what I did was partially decode the image back to the DCT coefficients
to provide context for the Huffman coded data.

I plan to add more models to PAQ8 but I wanted to get something
released this year.

-- Matt Mahoney

.

Relevant Pages

  • Re: Emailing Documents from Word 2007
    ... first choose what ever email client you desire. ... now while in find locate the created document and if you use either StuffIt, stuffit Deluxe, or even from finder locate create .zip. ... IF you know the person the other end uses a Mac and owns Stuffit Deluxe, Stuffit, Or Stuffit Expander; the ideal for mat is .sitx it compress the to 1/2 the size of .zip file. ... That was actually the most compressed method of file compression ever created. ...
    (microsoft.public.mac.office.word)
  • Re: Fixpoint for LZH
    ... >> It is possible that several schemes may have a fixed point, ... zip appears to be fundamentally different from Stuffit ... but whether a compression scheme has a fixed point. ... I did a bit of experimentation with WinZip. ...
    (sci.math)
  • StuffIt and ZipMagic Family of products Directory traversal
    ... StuffIt and ZipMagic Family of products Directory ... designed to meet any level of compression needs; ... What is Directory traversal in archivers? ... you can find it from Hamid Network Security Team: ...
    (Bugtraq)
  • Re: compressing word documents to send as email attachments
    ... users with the paid-for version of Stuffit should be able to improve ... content in the file and adjust its compression algorithm accordingly. ... If it's still too big after saving as .docx, the problem is the pictures. ... How can I compress a large word document in order to send it via email ...
    (microsoft.public.mac.office.word)
  • Re: Fixpoint for LZH
    ... >> It is possible that several schemes may have a fixed point, ... zip appears to be fundamentally different from Stuffit ... after it leaves the file alone the decompressor will ... but whether a compression scheme has a fixed point. ...
    (sci.math)