001package org.cpsolver.ifs.termination;
002
003import org.cpsolver.ifs.model.Value;
004import org.cpsolver.ifs.model.Variable;
005import org.cpsolver.ifs.solution.Solution;
006import org.cpsolver.ifs.util.DataProperties;
007
008/**
009 * General implementation of termination condition for minimal perturbation
010 * problem. <br>
011 * <br>
012 * Solver stops when a timeout is reached (expressed either by the number of
013 * iterations or by a time) or when an acceptable complete (all variables are
014 * assigned) solution is found. The acceptance of a solution is expressed either
015 * by the minimal number of variables assigned to not-initial values or by the
016 * perturbations penalty. <br>
017 * <br>
018 * Parameters: <br>
019 * <table border='1' summary='Related Solver Parameters'>
020 * <tr>
021 * <th>Parameter</th>
022 * <th>Type</th>
023 * <th>Comment</th>
024 * </tr>
025 * <tr>
026 * <td>Termination.StopWhenComplete</td>
027 * <td>{@link Double}</td>
028 * <td>if true, solver stops when a complete solution is found</td>
029 * </tr>
030 * <tr>
031 * <td>Termination.MaxIters</td>
032 * <td>{@link Integer}</td>
033 * <td>if zero or positive, solver stops when the given number of iteration is
034 * reached</td>
035 * </tr>
036 * <tr>
037 * <td>Termination.TimeOut</td>
038 * <td>{@link Double}</td>
039 * <td>if zero or positive, solver stops when the given timeout (given in
040 * seconds) is reached</td>
041 * </tr>
042 * <tr>
043 * <td>Termination.MinPerturbances</td>
044 * <td>{@link Integer}</td>
045 * <td>if zero or positive, solver stops when the solution is complete and the
046 * number of variables with non-initial values is below or equal to this limit</td>
047 * </tr>
048 * <tr>
049 * <td>Termination.MinPerturbationPenalty</td>
050 * <td>{@link Double}</td>
051 * <td>if zero or positive, solver stops when the solution is complete and when
052 * the perturbation penaly of the solution is below or equal to this limit</td>
053 * </tr>
054 * </table>
055 * 
056 * @see org.cpsolver.ifs.solver.Solver
057 * @see org.cpsolver.ifs.perturbations.PerturbationsCounter
058 * 
059 * @version IFS 1.3 (Iterative Forward Search)<br>
060 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
061 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
062 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
063 * <br>
064 *          This library is free software; you can redistribute it and/or modify
065 *          it under the terms of the GNU Lesser General Public License as
066 *          published by the Free Software Foundation; either version 3 of the
067 *          License, or (at your option) any later version. <br>
068 * <br>
069 *          This library is distributed in the hope that it will be useful, but
070 *          WITHOUT ANY WARRANTY; without even the implied warranty of
071 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
072 *          Lesser General Public License for more details. <br>
073 * <br>
074 *          You should have received a copy of the GNU Lesser General Public
075 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
076 *
077 * @param <V> Variable
078 * @param <T> Value
079 **/
080public class MPPTerminationCondition<V extends Variable<V, T>, T extends Value<V, T>> implements
081        TerminationCondition<V, T> {
082    protected static org.apache.log4j.Logger sLogger = org.apache.log4j.Logger.getLogger(MPPTerminationCondition.class);
083    private int iMinPerturbances;
084    private int iMaxIter;
085    private double iTimeOut;
086    private double iMinPertPenalty;
087    private boolean iStopWhenComplete;
088
089    public MPPTerminationCondition(DataProperties properties) {
090        iMaxIter = properties.getPropertyInt("Termination.MaxIters", -1);
091        iTimeOut = properties.getPropertyDouble("Termination.TimeOut", -1.0);
092        iMinPerturbances = properties.getPropertyInt("Termination.MinPerturbances", -1);
093        iStopWhenComplete = properties.getPropertyBoolean("Termination.StopWhenComplete", false);
094        iMinPertPenalty = properties.getPropertyDouble("Termination.MinPerturbationPenalty", -1.0);
095    }
096
097    public MPPTerminationCondition(int maxIter, double timeout, int minPerturbances) {
098        iMaxIter = maxIter;
099        iMinPerturbances = minPerturbances;
100        iTimeOut = timeout;
101    }
102
103    @Override
104    public boolean canContinue(Solution<V, T> currentSolution) {
105        if (iMinPerturbances >= 0 && currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel()) == 0
106                && currentSolution.getModel().perturbVariables(currentSolution.getAssignment()).size() <= iMinPerturbances) {
107            sLogger.info("A complete solution with allowed number of perturbances found.");
108            return false;
109        }
110        if (iMinPertPenalty >= 0.0
111                && currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel()) == 0
112                && currentSolution.getPerturbationsCounter().getPerturbationPenalty(currentSolution.getAssignment(), currentSolution.getModel()) <= iMinPertPenalty) {
113            sLogger.info("A complete solution with allowed perturbation penalty found.");
114            return false;
115        }
116        if (iMaxIter >= 0 && currentSolution.getIteration() >= iMaxIter) {
117            sLogger.info("Maximum number of iteration reached.");
118            return false;
119        }
120        if (iTimeOut >= 0 && currentSolution.getTime() > iTimeOut) {
121            sLogger.info("Timeout reached.");
122            return false;
123        }
124        if (iStopWhenComplete || (iMaxIter < 0 && iTimeOut < 0)) {
125            boolean ret = (currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel()) != 0);
126            if (!ret)
127                sLogger.info("Complete solution found.");
128            return ret;
129        }
130        return true;
131    }
132
133}