001 package net.sf.cpsolver.exam.heuristics;
002
003 import java.text.DecimalFormat;
004 import java.util.ArrayList;
005 import java.util.Collection;
006 import java.util.List;
007 import java.util.Map;
008
009 import net.sf.cpsolver.exam.model.Exam;
010 import net.sf.cpsolver.exam.model.ExamPlacement;
011 import net.sf.cpsolver.exam.neighbours.ExamRandomMove;
012 import net.sf.cpsolver.exam.neighbours.ExamRoomMove;
013 import net.sf.cpsolver.exam.neighbours.ExamTimeMove;
014 import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
015 import net.sf.cpsolver.ifs.model.LazyNeighbour;
016 import net.sf.cpsolver.ifs.model.Neighbour;
017 import net.sf.cpsolver.ifs.model.LazyNeighbour.LazyNeighbourAcceptanceCriterion;
018 import net.sf.cpsolver.ifs.solution.Solution;
019 import net.sf.cpsolver.ifs.solution.SolutionListener;
020 import net.sf.cpsolver.ifs.solver.Solver;
021 import net.sf.cpsolver.ifs.util.DataProperties;
022 import net.sf.cpsolver.ifs.util.JProf;
023 import net.sf.cpsolver.ifs.util.Progress;
024 import net.sf.cpsolver.ifs.util.ToolBox;
025
026 import org.apache.log4j.Logger;
027
028 /**
029 * Greate deluge. In each iteration, one of the following three neighbourhoods
030 * is selected first
031 * <ul>
032 * <li>random move ({@link ExamRandomMove})
033 * <li>period swap ({@link ExamTimeMove})
034 * <li>room swap ({@link ExamRoomMove})
035 * </ul>
036 * , then a neighbour is generated and it is accepted if the value of the new
037 * solution is below certain bound. This bound is initialized to the
038 * GreatDeluge.UpperBoundRate × value of the best solution ever found.
039 * After each iteration, the bound is decreased by GreatDeluge.CoolRate (new
040 * bound equals to old bound × GreatDeluge.CoolRate). If the bound gets
041 * bellow GreatDeluge.LowerBoundRate × value of the best solution ever
042 * found, it is changed back to GreatDeluge.UpperBoundRate × value of the
043 * best solution ever found.
044 *
045 * If there was no improvement found between the bounds, the new bounds are
046 * changed to GreatDeluge.UpperBoundRate^2 and GreatDeluge.LowerBoundRate^2,
047 * GreatDeluge.UpperBoundRate^3 and GreatDeluge.LowerBoundRate^3, etc. till
048 * there is an improvement found. <br>
049 * <br>
050 *
051 * @version ExamTT 1.2 (Examination Timetabling)<br>
052 * Copyright (C) 2008 - 2010 Tomas Muller<br>
053 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
054 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
055 * <br>
056 * This library is free software; you can redistribute it and/or modify
057 * it under the terms of the GNU Lesser General Public License as
058 * published by the Free Software Foundation; either version 3 of the
059 * License, or (at your option) any later version. <br>
060 * <br>
061 * This library is distributed in the hope that it will be useful, but
062 * WITHOUT ANY WARRANTY; without even the implied warranty of
063 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
064 * Lesser General Public License for more details. <br>
065 * <br>
066 * You should have received a copy of the GNU Lesser General Public
067 * License along with this library; if not see
068 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
069 */
070 public class ExamGreatDeluge implements NeighbourSelection<Exam, ExamPlacement>, SolutionListener<Exam, ExamPlacement>, LazyNeighbourAcceptanceCriterion<Exam, ExamPlacement> {
071 private static Logger sLog = Logger.getLogger(ExamGreatDeluge.class);
072 private static DecimalFormat sDF2 = new DecimalFormat("0.00");
073 private static DecimalFormat sDF5 = new DecimalFormat("0.00000");
074 private double iBound = 0.0;
075 private double iCoolRate = 0.99999995;
076 private long iIter;
077 private double iUpperBound;
078 private double iUpperBoundRate = 1.05;
079 private double iLowerBoundRate = 0.95;
080 private int iMoves = 0;
081 private int iAcceptedMoves = 0;
082 private int iNrIdle = 0;
083 private long iT0 = -1;
084 private long iLastImprovingIter = 0;
085 private double iBestValue = 0;
086 private Progress iProgress = null;
087
088 private List<NeighbourSelection<Exam, ExamPlacement>> iNeighbours = null;
089
090 /**
091 * Constructor. Following problem properties are considered:
092 * <ul>
093 * <li>GreatDeluge.CoolRate ... bound cooling rate (default 0.99999995)
094 * <li>GreatDeluge.UpperBoundRate ... bound upper bound relative to best
095 * solution ever found (default 1.05)
096 * <li>GreatDeluge.LowerBoundRate ... bound lower bound relative to best
097 * solution ever found (default 0.95)
098 * </ul>
099 *
100 * @param properties
101 * problem properties
102 */
103 @SuppressWarnings("unchecked")
104 public ExamGreatDeluge(DataProperties properties) {
105 iCoolRate = properties.getPropertyDouble("GreatDeluge.CoolRate", iCoolRate);
106 iUpperBoundRate = properties.getPropertyDouble("GreatDeluge.UpperBoundRate", iUpperBoundRate);
107 iLowerBoundRate = properties.getPropertyDouble("GreatDeluge.LowerBoundRate", iLowerBoundRate);
108 String neighbours = properties.getProperty("GreatDeluge.Neighbours",
109 ExamRandomMove.class.getName() + ";" +
110 ExamRoomMove.class.getName() + ";" +
111 ExamTimeMove.class.getName());
112 neighbours += ";" + properties.getProperty("GreatDeluge.AdditionalNeighbours", "");
113 iNeighbours = new ArrayList<NeighbourSelection<Exam,ExamPlacement>>();
114 for (String neighbour: neighbours.split("\\;")) {
115 if (neighbour == null || neighbour.isEmpty()) continue;
116 try {
117 Class<NeighbourSelection<Exam, ExamPlacement>> clazz = (Class<NeighbourSelection<Exam, ExamPlacement>>)Class.forName(neighbour);
118 iNeighbours.add(clazz.getConstructor(DataProperties.class).newInstance(properties));
119 } catch (Exception e) {
120 sLog.error("Unable to use " + neighbour + ": " + e.getMessage());
121 }
122 }
123 }
124
125 /** Initialization */
126 @Override
127 public void init(Solver<Exam, ExamPlacement> solver) {
128 iIter = -1;
129 solver.currentSolution().addSolutionListener(this);
130 for (NeighbourSelection<Exam, ExamPlacement> neighbour: iNeighbours)
131 neighbour.init(solver);
132 solver.setUpdateProgress(false);
133 iProgress = Progress.getInstance(solver.currentSolution().getModel());
134 }
135
136 /** Print some information */
137 protected void info(Solution<Exam, ExamPlacement> solution) {
138 sLog.info("Iter=" + iIter / 1000 + "k, NonImpIter=" + sDF2.format((iIter - iLastImprovingIter) / 1000.0)
139 + "k, Speed=" + sDF2.format(1000.0 * iIter / (JProf.currentTimeMillis() - iT0)) + " it/s");
140 sLog.info("Bound is " + sDF2.format(iBound) + ", " + "best value is " + sDF2.format(solution.getBestValue())
141 + " (" + sDF2.format(100.0 * iBound / solution.getBestValue()) + "%), " + "current value is "
142 + sDF2.format(solution.getModel().getTotalValue()) + " ("
143 + sDF2.format(100.0 * iBound / solution.getModel().getTotalValue()) + "%), " + "#idle=" + iNrIdle
144 + ", " + "Pacc=" + sDF5.format(100.0 * iAcceptedMoves / iMoves) + "%");
145 iAcceptedMoves = iMoves = 0;
146 }
147
148 /**
149 * Generate neighbour -- select neighbourhood randomly, select neighbour
150 */
151 public Neighbour<Exam, ExamPlacement> genMove(Solution<Exam, ExamPlacement> solution) {
152 while (true) {
153 incIter(solution);
154 NeighbourSelection<Exam, ExamPlacement> ns = iNeighbours.get(ToolBox.random(iNeighbours.size()));
155 Neighbour<Exam, ExamPlacement> n = ns.selectNeighbour(solution);
156 if (n != null)
157 return n;
158 }
159 }
160
161 /** Accept neighbour */
162 protected boolean accept(Solution<Exam, ExamPlacement> solution, Neighbour<Exam, ExamPlacement> neighbour) {
163 if (neighbour instanceof LazyNeighbour) {
164 ((LazyNeighbour<Exam, ExamPlacement>)neighbour).setAcceptanceCriterion(this);
165 return true;
166 }
167 return (neighbour.value() <= 0 || solution.getModel().getTotalValue() + neighbour.value() <= iBound);
168 }
169
170 /** Accept lazy neighbour */
171 @Override
172 public boolean accept(LazyNeighbour<Exam, ExamPlacement> neighbour, double value) {
173 return (value <= 0.0 || neighbour.getModel().getTotalValue() <= iBound);
174 }
175
176 /** Increment iteration count, update bound */
177 protected void incIter(Solution<Exam, ExamPlacement> solution) {
178 if (iIter < 0) {
179 iIter = 0;
180 iLastImprovingIter = 0;
181 iT0 = JProf.currentTimeMillis();
182 iBound = (solution.getBestValue() > 0.0 ? iUpperBoundRate * solution.getBestValue() : solution
183 .getBestValue()
184 / iUpperBoundRate);
185 iUpperBound = iBound;
186 iNrIdle = 0;
187 iProgress.setPhase("Great deluge [" + (1 + iNrIdle) + "]...");
188 } else {
189 iIter++;
190 if (solution.getBestValue() >= 0.0)
191 iBound *= iCoolRate;
192 else
193 iBound /= iCoolRate;
194 }
195 if (iIter % 100000 == 0) {
196 info(solution);
197 }
198 double lowerBound = (solution.getBestValue() >= 0.0 ? Math.pow(iLowerBoundRate, 1 + iNrIdle)
199 * solution.getBestValue() : solution.getBestValue() / Math.pow(iLowerBoundRate, 1 + iNrIdle));
200 if (iBound < lowerBound) {
201 iNrIdle++;
202 sLog.info(" -<[" + iNrIdle + "]>- ");
203 iBound = Math.max(solution.getBestValue() + 2.0, (solution.getBestValue() >= 0.0 ? Math.pow(
204 iUpperBoundRate, iNrIdle)
205 * solution.getBestValue() : solution.getBestValue() / Math.pow(iUpperBoundRate, iNrIdle)));
206 iUpperBound = iBound;
207 iProgress.setPhase("Great deluge [" + (1 + iNrIdle) + "]...");
208 }
209 iProgress.setProgress(100 - Math.round(100.0 * (iBound - lowerBound) / (iUpperBound - lowerBound)));
210 }
211
212 /**
213 * A neighbour is generated randomly untill an acceptable one is found.
214 */
215 @Override
216 public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
217 Neighbour<Exam, ExamPlacement> neighbour = null;
218 while ((neighbour = genMove(solution)) != null) {
219 iMoves++;
220 if (accept(solution, neighbour)) {
221 iAcceptedMoves++;
222 break;
223 }
224 }
225 return (neighbour == null ? null : neighbour);
226 }
227
228 /** Update last improving iteration count */
229 @Override
230 public void bestSaved(Solution<Exam, ExamPlacement> solution) {
231 if (Math.abs(iBestValue - solution.getBestValue()) >= 1.0) {
232 iLastImprovingIter = iIter;
233 iNrIdle = 0;
234 iBestValue = solution.getBestValue();
235 }
236 }
237
238 @Override
239 public void solutionUpdated(Solution<Exam, ExamPlacement> solution) {
240 }
241
242 @Override
243 public void getInfo(Solution<Exam, ExamPlacement> solution, Map<String, String> info) {
244 }
245
246 @Override
247 public void getInfo(Solution<Exam, ExamPlacement> solution, Map<String, String> info, Collection<Exam> variables) {
248 }
249
250 @Override
251 public void bestCleared(Solution<Exam, ExamPlacement> solution) {
252 }
253
254 @Override
255 public void bestRestored(Solution<Exam, ExamPlacement> solution) {
256 }
257 }