AC3.h

// AC3.h -- The AC-3 filter interface.

/*
 * Copyright (C) 1998 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: AC3_8h-source.html,v 1.1 2005/05/25 12:37:18 tudor Exp $

#ifndef _CSP_FILTERS_AC3_H
#define _CSP_FILTERS_AC3_H


CSP_NAMESPACE_BEGIN(csp);
CSP_NAMESPACE_BEGIN(filters);


class CSP_API AC3 :
    public Filter
{
  public:
    AC3(Problem& problem, Retraction& retraction) :
        Filter(L"Arc Consistency 3", L"AC-3", problem, retraction) {}
    ~AC3() {}

    virtual bool init(
        const vlist_type& uninstantiatedVariables,
        bool propagate = true);
    virtual void done() { Filter::done(); }

    virtual bool restoresArcConsistency() const { return true; }

    virtual bool propagate(
        const vlist_type& uninstantiatedVariables,
        const vlist_type& modifiedVariables,
        const bool keepChanges = true);

    virtual wostream& print(wostream& wos) const;

  private:
    AC3(const AC3&);

    AC3& operator=(const AC3&);

    void insertInQueue(
        const Variable& variable0,
        const Variable& variable1,
        Constraint& constraint);

    void popFromQueue(
        const Variable& variable0,
        const Variable& variable1,
        const Constraint& constraint);

    bool isInQueue(
        const Variable& variable0,
        const Variable& variable1,
        const Constraint& constraint);

    void addRelatedConstraints(Variable& variable, const Constraint& unwanted);

    void addActiveConstraintPairs(const Variable& variable);

    Domain m_diffs;

    struct Edge
    {
        Constraint* m_constraint;

        bool m_reversed;
    };

    deque<Edge> m_queue;

    hash_set<const Constraint*> m_inQueueAsIJ;

    hash_set<const Constraint*> m_inQueueAsJI;
};


CSP_NAMESPACE_END(filters);
CSP_NAMESPACE_END(csp);


#endif // _CSP_FILTERS_AC3_H

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