variables/SolutionProbability.h

// SolutionProbability.h -- The `minimum/maximum solution probability'
// variable ordering heuristic interface.

/*
 * Copyright (C) 2004 Tudor Hulubei <tudor@hulubei.net>.
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2, or (at
 * your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA,
 * 02111-1307, USA.
 */

// $Id: variables_2SolutionProbability_8h-source.html,v 1.1 2005/05/25 12:37:18 tudor Exp $

#ifndef _CSP_HEURISTICS_VARIABLE_SolutionProbability_H
#define _CSP_HEURISTICS_VARIABLE_SolutionProbability_H


#include "../../caches/DomainSizes.h"


//#define SP_VAR_LOOK_AROUND 1


#ifdef SP_VAR_LOOK_AROUND
#include <gmpxx.h>
#endif


CSP_NAMESPACE_BEGIN(csp);
CSP_NAMESPACE_BEGIN(heuristics);
CSP_NAMESPACE_BEGIN(variables);


/*
 * This variable ordering heuristic should select the variables that,
 * when instantiated, maximizes the probability of finding a solution
 * in the remaining subproblem.  The heuristic works by computing the
 * set of active constraints in which the problem's uninstantiated
 * variables are involved, and multiplying their probabilities of
 * being satisfied, either based on the initial set of allowed tuples
 * or the current one (in the dynamic version).  This computation is
 * performed n times (with n the number of uninstantiated variables),
 * each time with a different variable and its constraints being taken
 * out of the set, so that we can calculate the probability of finding
 * a solution in the remaining problem.  Obviously, both the static
 * and the dynamic version of this heuristic are very expensive.
 */
class CSP_API SolutionProbability :
    public VariableOH
{
  public:
#ifdef SP_VAR_LOOK_AROUND
    typedef mpf_class Real;
#else
    typedef long double Real;
#endif

    enum Preference
    {
        Minimum,

        Maximum
    };

    SolutionProbability(
        Decomposition& decomposition,
        const vector<pair<double, double> >& intervals,
        double quality = 1,
        Preference preference = Minimum,
        bool dynamic = false);

    virtual void select(vlist_type& selectable, vlist_type& selected);

  private:
    SolutionProbability(const SolutionProbability&);

    SolutionProbability& operator=(const SolutionProbability&);

    ulonglong maxTuples(const Constraint& constraint);

    Real constraintProbability(const Constraint& constraint);

    void computeProbabilities(
        const Decomposition::ActiveConstraintsSet& acs,
        const Decomposition::ActiveVariablesSet& avs);

    void computeMaxTuples(
        const Decomposition::ActiveConstraintsSet& acs);

    void computeValueProbabilities(
        const Decomposition::ActiveVariablesSet& avs);

    void clearCaches();

    Real subproblemSolutionProbability(
        const Decomposition::ActiveConstraintsSet& acs) const;

    Real multiplyProbabilities(const Variable& variable) const;

    typedef hash_map<const Constraint*, Real> cp_type;

    typedef hash_map<const Constraint*, ulonglong> mt_type;

    typedef hash_map<const Value*, Real> vp_type;

    typedef hash_map<const Variable*, vp_type*> vs_type;

    cp_type m_constraintProbabilities;

    mt_type m_maxTuples;

    vs_type m_valueProbabilities;

    caches::DomainSizes m_domainSizes;

    Preference m_preference;

    bool m_dynamic;

    Real m_precision;
};


CSP_NAMESPACE_END(variables);
CSP_NAMESPACE_END(heuristics);
CSP_NAMESPACE_END(csp);


#endif // _CSP_HEURISTICS_VARIABLE_SolutionProbability_H

// Local Variables:
// mode: C++
// End:

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