org.chocosolver.solver.search.loop.move.MoveBinaryLDS Maven / Gradle / Ivy
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2022, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.search.loop.move;
import org.chocosolver.memory.IEnvironment;
import org.chocosolver.memory.IStateInt;
import org.chocosolver.solver.Solver;
import org.chocosolver.solver.search.strategy.decision.Decision;
import org.chocosolver.solver.search.strategy.decision.DecisionPath;
import org.chocosolver.solver.search.strategy.strategy.AbstractStrategy;
/**
* A move dedicated to run an Limited Discrepancy Search[1] (LDS) with binary decisions.
*
* [1]:W.D. Harvey and M.L.Ginsberg, Limited Discrepancy Search, IJCAI-95.
*
* Created by cprudhom on 07/10/15.
* Project: choco.
* @author Charles Prud'homme
* @since 07/10/15
*/
public class MoveBinaryLDS extends MoveBinaryDFS {
/**
* current discrepancy, maintained incrementally
*/
protected IStateInt dis;
/**
* max discrepancy allowed
*/
protected int DIS;
/**
* Create a DFS with binary decisions
*
* @param strategy how (binary) decisions are selected
* @param discrepancy maximum discrepancy
* @param environment backtracking environment
*/
public MoveBinaryLDS(AbstractStrategy strategy, int discrepancy, IEnvironment environment) {
super(strategy);
this.dis = environment.makeInt(0);
this.DIS = discrepancy;
}
@Override
public boolean init() {
dis.set(0);
return super.init();
}
@Override
public boolean repair(Solver solver) {
solver.getMeasures().incBackTrackCount();
solver.getEnvironment().worldPop();
boolean repaired = rewind(solver);
// increase the discrepancy max, if allowed, when the root node is reached
Decision head = solver.getDecisionPath().getLastDecision();
if (head.getPosition() == topDecisionPosition && dis.get() < DIS) {
dis.add(1);
solver.restart();
repaired = true;
}
return repaired;
}
@Override
protected boolean rewind(Solver solver) {
boolean repaired = false;
DecisionPath path = solver.getDecisionPath();
Decision head = path.getLastDecision();
while (!repaired && head.getPosition() != topDecisionPosition) {
solver.setJumpTo(solver.getJumpTo()-1);
if (dis.get() > 0 && solver.getJumpTo() <= 0 && head.hasNext()) {
solver.getEnvironment().worldPush();
repaired = true;
dis.add(-1);
} else {
prevDecision(solver);
}
head = solver.getDecisionPath().getLastDecision();
}
return repaired;
}
}