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)