001 package net.sf.cpsolver.studentsct.heuristics.selection;
002
003 import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
004 import net.sf.cpsolver.ifs.heuristics.ValueSelection;
005 import net.sf.cpsolver.ifs.heuristics.VariableSelection;
006 import net.sf.cpsolver.ifs.model.Neighbour;
007 import net.sf.cpsolver.ifs.model.SimpleNeighbour;
008 import net.sf.cpsolver.ifs.solution.Solution;
009 import net.sf.cpsolver.ifs.solver.Solver;
010 import net.sf.cpsolver.ifs.util.DataProperties;
011 import net.sf.cpsolver.ifs.util.Progress;
012 import net.sf.cpsolver.studentsct.model.Enrollment;
013 import net.sf.cpsolver.studentsct.model.Request;
014
015 /**
016 * Use the provided variable and value selection for some time.
017 * The provided variable and value selection is used for the
018 * number of iterations equal to the number of all
019 * variables in the problem. If a complete solution is found,
020 * the neighbour selection is stopped (it returns null).
021 *
022 * <br><br>
023 * Parameters:
024 * <br>
025 * <table border='1'><tr><th>Parameter</th><th>Type</th><th>Comment</th></tr>
026 * <tr><td>Neighbour.StandardIterations</td><td>{@link Long}</td><td>Number of iterations to perform. If -1, number of iterations is set to the number of unassigned variables.</td></tr>
027 * </table>
028 * <br><br>
029 *
030 * @version
031 * StudentSct 1.1 (Student Sectioning)<br>
032 * Copyright (C) 2007 Tomáš Müller<br>
033 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
034 * Lazenska 391, 76314 Zlin, Czech Republic<br>
035 * <br>
036 * This library is free software; you can redistribute it and/or
037 * modify it under the terms of the GNU Lesser General Public
038 * License as published by the Free Software Foundation; either
039 * version 2.1 of the License, or (at your option) any later version.
040 * <br><br>
041 * This library is distributed in the hope that it will be useful,
042 * but WITHOUT ANY WARRANTY; without even the implied warranty of
043 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
044 * Lesser General Public License for more details.
045 * <br><br>
046 * You should have received a copy of the GNU Lesser General Public
047 * License along with this library; if not, write to the Free Software
048 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
049 */
050 public class StandardSelection implements NeighbourSelection {
051 private static org.apache.log4j.Logger sLog = org.apache.log4j.Logger.getLogger(StandardSelection.class);
052 private long iIteration = 0;
053 private ValueSelection iValueSelection = null;
054 private VariableSelection iVariableSelection = null;
055 protected long iNrIterations = -1;
056
057 /**
058 * Constructor (variable and value selection are expected to be already initialized).
059 * @param properties configuration
060 * @param variableSelection variable selection
061 * @param valueSelection value selection
062 */
063 public StandardSelection(DataProperties properties, VariableSelection variableSelection, ValueSelection valueSelection) {
064 iVariableSelection = variableSelection;
065 iValueSelection = valueSelection;
066 }
067
068 /** Initialization */
069 public void init(Solver solver) {
070 iIteration = solver.currentSolution().getIteration();
071 iNrIterations = solver.getProperties().getPropertyLong("Neighbour.StandardIterations", -1);
072 if (iNrIterations>0)
073 Progress.getInstance(solver.currentSolution().getModel()).setPhase("Ifs...", iNrIterations);
074 }
075
076 /**
077 * Employ the provided {@link VariableSelection} and {@link ValueSelection} and return the
078 * selected value as {@link SimpleNeighbour}. The selection is stopped (null is returned)
079 * after the number of iterations equal to the number of variables in the problem
080 * or when a complete solution is found.
081 */
082 public Neighbour selectNeighbour(Solution solution) {
083 if (iNrIterations<0) {
084 iNrIterations = solution.getModel().unassignedVariables().size();
085 Progress.getInstance(solution.getModel()).setPhase("Ifs...", iNrIterations);
086 }
087 if (solution.getModel().unassignedVariables().isEmpty() || solution.getIteration()>=iIteration+iNrIterations) return null;
088 Progress.getInstance(solution.getModel()).incProgress();
089 for (int i=0;i<10;i++) {
090 Request request = (Request)iVariableSelection.selectVariable(solution);
091 Enrollment enrollment = (request==null?null:(Enrollment)iValueSelection.selectValue(solution, request));
092 if (enrollment!=null && !enrollment.variable().getModel().conflictValues(enrollment).contains(enrollment))
093 return new SimpleNeighbour(request, enrollment);
094 }
095 return null;
096 }
097
098 }