BM.h

// BM.h -- The back marking filter interface.  See "FC w/ BM",
// Technical Report AISL-48-93, June 1993, Patrick Prosser
// <pat@cs.strath.ac.uk>.

/*
 * 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: BM_8h-source.html,v 1.1 2005/05/25 12:37:18 tudor Exp $

#ifndef _CSP_FILTERS_BM_H
#define _CSP_FILTERS_BM_H


CSP_NAMESPACE_BEGIN(csp);
CSP_NAMESPACE_BEGIN(filters);


class CSP_API BM :
    public Filter
{
  public:
    BM(Problem& problem, Retraction& retraction) :
        Filter(L"Back Marking", L"BM", problem, retraction)
    {
        /* FIXME: Does BM really require that all the variables have
           the same domain size?  Can we make m_mcl a vector of arrays?  */
        size_t size = (**problem.beginVariables()).domain().size();
        m_mcl = new size_t [problem.variables() * size];
        m_mbl = new size_t [problem.variables()];
    }

    ~BM()
    {
        delete m_mbl;
        delete m_mcl;
    }

    virtual bool restoresArcConsistency() const { return false; }

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

  private:
    /* NOTE: The backmarking fiter doesn't work with dynamic CSPs,
       because the m_mcl & m_mbl arrays have fixed size.  */

    /* Maximum checking level.  When a consistency ckeck is performed
       between v[h] and v[i]=k, m_mcl[i,k] becomes h.  */
    size_t* m_mcl;

    /* Minimum backtracking level.  m_mbl[i] records the shallowest
       variable in the search tree that has been re-instantiated since
       we last visited v[i].  */
    size_t* m_mbl;

    BM(const BM&);

    BM& operator=(const BM&);
};


CSP_NAMESPACE_END(filters);
CSP_NAMESPACE_END(csp);


#endif // _CSP_FILTERS_BM_H

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