ppmd(1) [debian man page]
ppmd(1) utils ppmd(1) NAME
ppmd - file-to-file compressor SYNTAX
ppmd [e|d] [switches] filename...|wildcard... DESCRIPTION
It is written for embedding in user programs mainly and it is not intended for immediate use. I was interested in speed and performance improvements of abstract PPM model [1-6] only, without tuning it to particular data types, therefore compressor works good enough for texts, but it is not so good for nonhomogeneous files (executables) and for noisy analog data (sounds, pictures etc.). Program is very mem- ory consuming, you can choose balance between execution speed and memory economy, on one hand, and compression performance, on another hand, with the help of model order selection option (-o). OPTIONS
-d Delete file[s] after processing, default: disabled. -s Silent mode. -fName Set output file name to Name. -mN Use N MB memory - [1,256], default: 10. The PPMII algorithm might need a lot of memory, especially when used on large files and/or used with large model order. If ppmd needs more memory than you give it, the compression will be worse. The exact effect is depen- dent on the -r option. -oN Set model order to N - [2,16], default: 4. Bigger model orders almost surely results in better compression and surely more memory and CPU usage. -r{0,1,2} Methods of restoration of model correctness at memory insufficiency: '-r0 - restart model from scratch'. This method is not optimal for any type of data sources, but it works fast and efficient in average, so it is the recommended method (default). '-r1 - cut off model'. This method is optimal for quasistationary sources when the period of stationarity is much larger than period between cutoffs. As a rule, it gives better results, but it is slower than other methods and it is unstable against fragmen- tation of memory heap at high model orders and low memory. '-r2 - freeze model'. This method is optimal for stationary sources (show me such source when You will find it ;-)). It is fast and efficient for such sources. EXAMPLES
To run this program the standard way type: ppmd e /tmp/myfile Alternatively you can run it as: ppmd -e -o 16 /tmp/myfile AUTHORS
PPMd was written by Dmitry Shkarin <dmitry.shkarin@mtu-net.ru> and Dmitry Subbotin. SEE ALSO
gzip(1), bzip2(1), lzma(1). 10.1 2011-07-25 ppmd(1)
Check Out this Related Man Page
BZZ(1) DjVuLibre-3.5 BZZ(1) NAME
bzz - DjVu general purpose compression utility. SYNOPSIS
Encoding: bzz -e[blocksize] inputfile outputfile Decoding: bzz -d inputfile outputfile DESCRIPTION
The first form of the command line (option -e) compresses the data from file inputfile and writes the compressed data into outputfile. The second form of the command line (option -d) decompressed file inputfile and writes the output to outputfile. OPTIONS
-d Decoding mode. -e[blocksize] Encoding mode. The optional argument blocksize specifies the size of the input file blocks processed by the Burrows-Wheeler trans- form expressed in kilobytes. The default block sizes is 2048 KB. The maximal block size is 4096 KB. Specifying a larger block size usually produces higher compression ratios and increases the memory requirements of both the encoder and decoder. It is use- less to specify a block size that is larger than the input file. ALGORITHMS
The Burrows-Wheeler transform is performed using a combination of the Karp-Miller-Rosenberg and the Bentley-Sedgewick algorithms. This is comparable to (Sadakane, DCC 98) with a slightly more flexible ranking scheme. Symbols are then ordered according to a running estimate of their occurrence frequencies. The symbol ranks are then coded using a simple fixed tree and the ZP binary adaptive coder (Bottou, DCC 98). The Burrows-Wheeler transform is also used in the well known compressor bzip2. The originality of bzz is the use of the ZP adaptive coder. The adaptation noise can cost up to 5 percent in file size, but this penalty is usually offset by the benefits of adaptation. PERFORMANCE
The following table shows comparative results (in bits per character) on the Canterbury Corpus ( http://corpus.canterbury.ac.nz ). The very good bzz performance on the spreadsheet file excl puts the weighted average ahead of much more sophisticated compressors such as fsmx. +-------------------------------------------------------------------------------------------------------------+ | Compression performance | | text fax csrc excl sprc tech poem html lisp man play Weighted Average | +-------------------------------------------------------------------------------------------------------------+ | compress 3.27 0.97 3.56 2.41 4.21 3.06 3.38 3.68 3.90 4.43 3.51 2.55 3.31 | | gzip -9 2.85 0.82 2.24 1.63 2.67 2.71 3.23 2.59 2.65 3.31 3.12 2.08 2.53 | | bzip2 -9 2.27 0.78 2.18 1.01 2.70 2.02 2.42 2.48 2.79 3.33 2.53 1.54 2.23 | | ppmd 2.31 0.99 2.11 1.08 2.68 2.19 2.48 2.38 2.43 3.00 2.53 1.65 2.20 | | fsmx 2.10 0.79 1.89 1.48 2.52 1.84 2.21 2.24 2.29 2.91 2.35 1.63 2.06 | | bzz 2.25 0.76 2.13 0.78 2.67 2.00 2.40 2.52 2.60 3.19 2.52 1.44 2.16 | +-------------------------------------------------------------------------------------------------------------+ Note that DjVu contributors have several entries in this table. Program compress was written some time ago by Joe Orost. Program ppmd is an improvement of the PPM-C method invented by Paul Howard. CREDITS
Program bzz was written by Leon Bottou <leonb@users.sourceforge.net> and was then improved by Andrei Erofeev <andrew_erofeev@yahoo.com>, Bill Riemers <docbill@sourceforge.net> and many others. SEE ALSO
djvu(1), compress(1), gzip(1), bzip2(1) DjVuLibre-3.5 10/11/2001 BZZ(1)