Package solver.search.strategy.strategy

Source Code of solver.search.strategy.strategy.LastConflict

/**
*  Copyright (c) 1999-2014, Ecole des Mines de Nantes
*  All rights reserved.
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions are met:
*
*      * Redistributions of source code must retain the above copyright
*        notice, this list of conditions and the following disclaimer.
*      * Redistributions in binary form must reproduce the above copyright
*        notice, this list of conditions and the following disclaimer in the
*        documentation and/or other materials provided with the distribution.
*      * Neither the name of the Ecole des Mines de Nantes nor the
*        names of its contributors may be used to endorse or promote products
*        derived from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
*  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
*  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
*  DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
*  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
*  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
*  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
*  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
*  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
*  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package solver.search.strategy.strategy;

import solver.Solver;
import solver.exception.ContradictionException;
import solver.search.loop.monitors.IMonitorContradiction;
import solver.search.loop.monitors.IMonitorRestart;
import solver.search.loop.monitors.IMonitorSolution;
import solver.search.strategy.decision.Decision;
import solver.variables.Variable;

/**
* Last Conflict heuristic
* Composite heuristic which hacks a mainStrategy by forcing the
* use of variables involved in recent conflicts
*
* @author Jean-Guillaume Fages, Charles Prud'homme
*/
public class LastConflict extends AbstractStrategy<Variable> implements IMonitorRestart, IMonitorSolution, IMonitorContradiction {

    //***********************************************************************************
    // VARIABLES
    //***********************************************************************************

  protected Solver solver;
    protected AbstractStrategy<Variable> mainStrategy;
  protected boolean active;
  protected int nbCV;
  protected Variable[] conflictingVariables;

    //***********************************************************************************
    // CONSTRUCTORS
    //***********************************************************************************

    public LastConflict(Solver solver, AbstractStrategy<Variable> mainStrategy, int k) {
        super(mainStrategy.vars);
    assert k>0 : "parameter K of last conflict must be strictly positive!";
        this.solver = solver;
        this.mainStrategy = mainStrategy;
        solver.getSearchLoop().plugSearchMonitor(this);
    conflictingVariables = new Variable[k];
    nbCV = 0;
    active = false;
    }

    //***********************************************************************************
    // METHODS
    //***********************************************************************************

    @Override
    public void init() throws ContradictionException {
    mainStrategy.init();
    }

    @Override
    public Decision getDecision() {
    if(active){
      Variable decVar = firstNotInst();
      if (decVar != null) {
        Decision d = mainStrategy.computeDecision(decVar);
        if(d != null){
          return d;
        }
      }
    }
    active = true;
    return mainStrategy.getDecision();
    }

    //***********************************************************************************
    // Monitor
    //***********************************************************************************


    @Override
    public void onContradiction(ContradictionException cex) {
        Variable curDecVar = solver.getSearchLoop().getLastDecision().getDecisionVariable();
    if(nbCV>0 && conflictingVariables[nbCV-1]==curDecVar)return;
    if(inScope(curDecVar)){
      if(nbCV<conflictingVariables.length){
        conflictingVariables[nbCV++] = curDecVar;
      }else{
        assert nbCV==conflictingVariables.length;
        for(int i=0;i<nbCV-1;i++){
          conflictingVariables[i] = conflictingVariables[i+1];
        }
        conflictingVariables[nbCV-1] = curDecVar;
      }
    }
    }

    @Override
    public void beforeRestart() {}

    @Override
    public void afterRestart() {
    active = false;
    }

    @Override
    public void onSolution() {
    active = false;
    }

    //***********************************************************************************
    //***********************************************************************************

    private Variable firstNotInst() {
    for(int i=nbCV-1;i>=0;i--){
      if(!conflictingVariables[i].isInstantiated()){
        return conflictingVariables[i];
      }
    }
        return null;
    }

  private boolean inScope(Variable target){
    Variable[] scope = mainStrategy.vars;
    for(int v=0; v<scope.length; v++){
      if(scope[v].getId()==target.getId()){
        return true;
      }
    }
    return false;
  }
}
TOP

Related Classes of solver.search.strategy.strategy.LastConflict

TOP
Copyright © 2018 www.massapi.com. All rights reserved.
All source code are property of their respective owners. Java is a trademark of Sun Microsystems, Inc and owned by ORACLE Inc. Contact coftware#gmail.com.