ind-set.cpp

/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2002
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
 *  Permission is hereby granted, free of charge, to any person obtaining
 *  a copy of this software and associated documentation files (the
 *  "Software"), to deal in the Software without restriction, including
 *  without limitation the rights to use, copy, modify, merge, publish,
 *  distribute, sublicense, and/or sell copies of the Software, and to
 *  permit persons to whom the Software is furnished to do so, subject to
 *  the following conditions:
 *
 *  The above copyright notice and this permission notice shall be
 *  included in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */

#include <gecode/driver.hh>
#include <gecode/int.hh>
#include <gecode/minimodel.hh>

using namespace Gecode;

/**
 * \name %Graph specification for independent sets
 *
 * \relates IndSet
 */
//@{
/// %Graph specification
class Graph {
public:
  const int  n_v; ///< Number of vertices
  const int  n_e; ///< Number of edges
  const int* e;   ///< Arrays of edges (as vertex pairs)
  Graph(const int n_v0, const int n_e0, const int* e0)
    : n_v(n_v0), n_e(n_e0), e(e0) {}
};

const int e_20_10[] = {
  0, 4,  2,12,  12,14,  18,19,   7,10,
  9,12,  5,11,   6,15,   3,18,   7,16
};

const Graph g_20_10(20,10,e_20_10);

const int e_40_20[] = {
  21,30,   11,30,   19,38,   20,25,   11,24,
  20,33,    8,39,    4, 5,    6,16,    5,32,
  0, 9,    5,24,   25,28,   36,38,   14,20,
  19,25,   11,22,   13,30,    7,36,   15,33
};

const Graph g_40_20(40, 20, e_40_20);
//@}


/**
 * \brief %Example: Independent sets in a graph
 *
 * \ingroup Example
 *
 */
class IndSet : public IntMaximizeScript {
protected:
  /// %Graph used
  const Graph& g;
  /// Whether vertex included in independent set
  BoolVarArray v;
  /// How many elements has indipendent set
  IntVar       k;
public:
  /// Actual model
  IndSet(const SizeOptions& opt)
    : IntMaximizeScript(opt),
      g(opt.size() == 0 ?  g_20_10 : g_40_20),
      v(*this,g.n_v,0,1), k(*this,0,g.n_v) {
    const int* e = g.e;
    for (int i = g.n_e; i--; ) {
      const int* e1 = e++; const int* e2 = e++;
      rel(*this, v[*e1], BOT_AND, v[*e2], 0);
    }
    linear(*this, v, IRT_EQ, k);
    branch(*this, v, BOOL_VAR_NONE(), BOOL_VAL_MIN());
  }

  /// Constructor for cloning \a s
  IndSet(IndSet& s) : IntMaximizeScript(s), g(s.g) {
    v.update(*this, s.v);
    k.update(*this, s.k);
  }
  /// Copy during cloning
  virtual Space*
  copy(void) {
    return new IndSet(*this);
  }
  /// Print solution
  virtual void
  print(std::ostream& os) const {
    os << "\tk = " << k << std::endl
       << "\tv[] = " << v << std::endl;
  }
  /// Return solution cost
  virtual IntVar cost(void) const {
    return k;
  }
};


/** \brief Main-function
 *  \relates IndSet
 */
int
main(int argc, char* argv[]) {
  SizeOptions opt("IndSet");
  opt.solutions(0);
  opt.size(1);
  opt.iterations(2000);
  opt.parse(argc,argv);
  IntMaximizeScript::run<IndSet,BAB,SizeOptions>(opt);
  return 0;
}

// STATISTICS: example-any