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
       memory  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 dependent 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 fragmentation 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).