INTRODUCTION
---------------
Clasp_W is a modified version of the Clasp solver.
This distribution package is modified based on clasp-2.0.6.
It provides a window mechanism for stopping the solver
earlier when a relatively good solution is found.

For detailed information of Clasp, please look at
http://www.cs.uni-potsdam.de/clasp/

The Linux binaries is built on Ubuntu 11.10, please use
"ldd" to check whether the shared libraries are linked correctly.

LICENSE
---------------
clasp is part of the Potassco project hosted at SourceForge.
It is distributed under the GNU Public License. And Clasp_W
is a derived work based on clasp, so it is also distributed
as a whole under the GNU Public License. See COPYING.gpl for
details regarding the license.

For the Windows distribution, Cascade uses POSIX Threads for Windows v2.9.1,
which is under GNU Lesser Public License v2.1.

USAGE
---------------
clasp_w [options] [input-file]

Clasp_W takes an input file which must conforms to the standard
PB solver requirements (ref. http://www.cril.univ-artois.fr/PB09/solver_req.html)
If no input file is specified, Clasp_W will take input from the standard
input (Ctrl-D for EOF for Linux, and Ctrl-Z for Windows).

Options:
  -w default|<a>,<b>,<c>
    This option is only works when an objective function exists.
    If not, it taks no effect.
    
    By default, the -w option is not specified, the solver will
    terminate until the optimum solution is found.
    
    However, sometimes the user may want the solver to terminate
    earlier when it has already found a good solution. Clasp_W
    provides a window mechanism for early termination. Typically,
    the diagram of the best objective function to the time is like
    the following:
    
    obj func value
    |
  y2|----------------------------------------
    |                       /               |
  y1|-----------------------                |
    |             /|                        |
    |          --  |                        |
    |         /    |                        |
    |       -      |                        |
    |      /       |                        |
    |     /        |                        |
    |    /         |                        |
    |   /          |                        |
    |  /           |                        |
    | |            |                        |
    | /            |                        |
    |/             |                        |
    ____________________________________________ time
                  x1                       x2

    We want to terminate when the solver begins to find new solutions
    very slow. The window mechanism is like this:
      Suppose the current time & best value are x2,y2, and the time &
      best value at an previous time point are x1,y1. Here we fix the
      ratio of x1 to x2. If y1>d*y2, then we can judge the solver is
      entering the hard zone, and it will stop.
    
    The four parameters a,b,c respectively stands for:
      a:  Minimum timeout. The window mechanism will not work until the
          solving time is greater than a (in milliseconds).
      b:  The ratio of window size to x2, i.e. (x2-x1)/x2. Note that
          when x2 becomes large, (x2-x1) will increase too, and (x2-x1)
          should not be greater than b.
      c:  The ratio of x1 to x2, i.e. x1/x2.
  
  -s <value>
    This option can be used with -w option. This is to specify the start
    value point. The value passed to the window is the difference of <value>
    and the current best value. (negative differences will be considered
    as zero)