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).