001package org.cpsolver.studentsct.heuristics;
002
003import java.util.ArrayList;
004import java.util.List;
005import java.util.Set;
006
007import org.cpsolver.ifs.assignment.Assignment;
008import org.cpsolver.ifs.extension.ConflictStatistics;
009import org.cpsolver.ifs.extension.Extension;
010import org.cpsolver.ifs.extension.MacPropagation;
011import org.cpsolver.ifs.extension.ViolatedInitials;
012import org.cpsolver.ifs.heuristics.GeneralValueSelection;
013import org.cpsolver.ifs.heuristics.ValueSelection;
014import org.cpsolver.ifs.solution.Solution;
015import org.cpsolver.ifs.solver.Solver;
016import org.cpsolver.ifs.util.DataProperties;
017import org.cpsolver.ifs.util.ToolBox;
018import org.cpsolver.studentsct.StudentSectioningModel;
019import org.cpsolver.studentsct.model.Enrollment;
020import org.cpsolver.studentsct.model.Request;
021import org.cpsolver.studentsct.model.Student;
022
023
024/**
025 * Enrollment selection criterion. It is similar to
026 * {@link GeneralValueSelection}, however, it is not allowed to assign a
027 * enrollment to a dummy student {@link Student#isDummy()} that is conflicting
028 * with an enrollment of a real student.
029 * 
030 * @version StudentSct 1.3 (Student Sectioning)<br>
031 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
032 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
033 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
034 * <br>
035 *          This library is free software; you can redistribute it and/or modify
036 *          it under the terms of the GNU Lesser General Public License as
037 *          published by the Free Software Foundation; either version 3 of the
038 *          License, or (at your option) any later version. <br>
039 * <br>
040 *          This library is distributed in the hope that it will be useful, but
041 *          WITHOUT ANY WARRANTY; without even the implied warranty of
042 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
043 *          Lesser General Public License for more details. <br>
044 * <br>
045 *          You should have received a copy of the GNU Lesser General Public
046 *          License along with this library; if not see
047 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
048 */
049public class EnrollmentSelection implements ValueSelection<Request, Enrollment> {
050    private double iRandomWalkProb = 0.0;
051    private double iInitialSelectionProb = 0.0;
052    private double iGoodSelectionProb = 0.0;
053    private int iMPPLimit = -1;
054
055    private double iWeightDeltaInitialAssignment = 0.0;
056    private double iWeightPotentialConflicts = 0.0;
057    private double iWeightWeightedCoflicts = 0.0;
058    private double iWeightCoflicts = 1.0;
059    private double iWeightValue = 0.0;
060
061    protected int iTabuSize = 0;
062    protected List<Enrollment> iTabu = null;
063    protected int iTabuPos = 0;
064
065    private boolean iMPP = false;
066    private ConflictStatistics<Request, Enrollment> iStat = null;
067    private MacPropagation<Request, Enrollment> iProp = null;
068    private ViolatedInitials<Request, Enrollment> iViolatedInitials = null;
069
070    public EnrollmentSelection() {
071    }
072
073    /**
074     * Constructor
075     * 
076     * @param properties
077     *            input configuration
078     */
079    public EnrollmentSelection(DataProperties properties) {
080        iMPP = properties.getPropertyBoolean("General.MPP", false);
081        if (iMPP) {
082            iMPPLimit = properties.getPropertyInt("Value.MPPLimit", -1);
083            iInitialSelectionProb = properties.getPropertyDouble("Value.InitialSelectionProb", 0.75);
084            iWeightDeltaInitialAssignment = properties.getPropertyDouble("Value.WeightDeltaInitialAssignments", 0.0);
085        }
086        iGoodSelectionProb = properties.getPropertyDouble("Value.GoodSelectionProb", 0.00);
087        iWeightWeightedCoflicts = properties.getPropertyDouble("Value.WeightWeightedConflicts", 1.0);
088        iWeightPotentialConflicts = properties.getPropertyDouble("Value.WeightPotentialConflicts", 0.0);
089
090        iRandomWalkProb = properties.getPropertyDouble("Value.RandomWalkProb", 0.0);
091        iWeightCoflicts = properties.getPropertyDouble("Value.WeightConflicts", 1.0);
092        iWeightValue = properties.getPropertyDouble("Value.WeightValue", 0.0);
093        iTabuSize = properties.getPropertyInt("Value.Tabu", 0);
094        if (iTabuSize > 0)
095            iTabu = new ArrayList<Enrollment>(iTabuSize);
096    }
097
098    /** Initialization */
099    @Override
100    public void init(Solver<Request, Enrollment> solver) {
101        for (Extension<Request, Enrollment> extension : solver.getExtensions()) {
102            if (ConflictStatistics.class.isInstance(extension))
103                iStat = (ConflictStatistics<Request, Enrollment>) extension;
104            if (MacPropagation.class.isInstance(extension))
105                iProp = (MacPropagation<Request, Enrollment>) extension;
106            if (ViolatedInitials.class.isInstance(extension))
107                iViolatedInitials = (ViolatedInitials<Request, Enrollment>) extension;
108        }
109    }
110
111    /** true, if it is allowed to assign given value 
112     * @param assignment current assignment
113     * @param value given value
114     * @return true if it is allowed
115     **/
116    public boolean isAllowed(Assignment<Request, Enrollment> assignment, Enrollment value) {
117        return isAllowed(assignment, value, null);
118    }
119
120    /** true, if it is allowed to assign given value 
121     * @param assignment current assignment
122     * @param value given value
123     * @param conflicts conflicting assignments
124     * @return true if it is allowed
125     **/
126    public boolean isAllowed(Assignment<Request, Enrollment> assignment, Enrollment value, Set<Enrollment> conflicts) {
127        if (value == null)
128            return true;
129        StudentSectioningModel model = (StudentSectioningModel) value.variable().getModel();
130        if (model.getNrLastLikeRequests(false) == 0 || model.getNrRealRequests(false) == 0)
131            return true;
132        Request request = value.variable();
133        if (request.getStudent().isDummy()) {
134            if (conflicts == null)
135                conflicts = value.variable().getModel().conflictValues(assignment, value);
136            for (Enrollment conflict : conflicts) {
137                if (!conflict.getRequest().getStudent().isDummy())
138                    return false;
139            }
140        } else {
141            if (conflicts == null)
142                conflicts = value.variable().getModel().conflictValues(assignment, value);
143            if (conflicts.size() > (assignment.getValue(request) == null ? 1 : 0))
144                return false;
145        }
146        return true;
147    }
148
149    /** Value selection */
150    @Override
151    public Enrollment selectValue(Solution<Request, Enrollment> solution, Request selectedVariable) {
152        Assignment<Request, Enrollment> assignment = solution.getAssignment();
153        if (iMPP) {
154            if (selectedVariable.getInitialAssignment() != null) {
155                if (solution.getModel().unassignedVariables(assignment).isEmpty()) {
156                    if (solution.getModel().perturbVariables(assignment).size() <= iMPPLimit)
157                        iMPPLimit = solution.getModel().perturbVariables(assignment).size() - 1;
158                }
159                if (iMPPLimit >= 0 && solution.getModel().perturbVariables(assignment).size() > iMPPLimit) {
160                    if (isAllowed(assignment, selectedVariable.getInitialAssignment()))
161                        return selectedVariable.getInitialAssignment();
162                }
163                if (selectedVariable.getInitialAssignment() != null && ToolBox.random() <= iInitialSelectionProb) {
164                    if (isAllowed(assignment, selectedVariable.getInitialAssignment()))
165                        return selectedVariable.getInitialAssignment();
166                }
167            }
168        }
169
170        List<Enrollment> values = selectedVariable.values(assignment);
171        if (ToolBox.random() <= iRandomWalkProb) {
172            Enrollment value = ToolBox.random(values);
173            if (isAllowed(assignment, value))
174                return value;
175        }
176        if (iProp != null && assignment.getValue(selectedVariable) == null && ToolBox.random() <= iGoodSelectionProb) {
177            Set<Enrollment> goodValues = iProp.goodValues(assignment, selectedVariable);
178            if (!goodValues.isEmpty())
179                values = new ArrayList<Enrollment>(goodValues);
180        }
181        if (values.size() == 1) {
182            Enrollment value = values.get(0);
183            if (isAllowed(assignment, value))
184                return value;
185            else
186                return null;
187        }
188
189        List<Enrollment> bestValues = null;
190        double bestWeightedSum = 0;
191
192        for (Enrollment value : values) {
193            if (iTabu != null && iTabu.contains(value))
194                continue;
195            if (assignment.getValue(selectedVariable) != null && assignment.getValue(selectedVariable).equals(value))
196                continue;
197
198            Set<Enrollment> conf = solution.getModel().conflictValues(assignment, value);
199            if (conf.contains(value))
200                continue;
201
202            if (!isAllowed(assignment, value, conf))
203                continue;
204
205            double weightedConflicts = (iStat == null || iWeightWeightedCoflicts == 0.0 ? 0.0 : iStat.countRemovals(solution.getIteration(), conf, value));
206            double potentialConflicts = (iStat == null || iWeightPotentialConflicts == 0.0 ? 0.0 : iStat.countPotentialConflicts(assignment, solution.getIteration(), value, 3));
207
208            long deltaInitialAssignments = 0;
209            if (iMPP && iWeightDeltaInitialAssignment != 0.0) {
210                if (iViolatedInitials != null) {
211                    Set<Enrollment> violations = iViolatedInitials.getViolatedInitials(value);
212                    if (violations != null) {
213                        for (Enrollment aValue : violations) {
214                            if (assignment.getValue(aValue.variable()) == null || assignment.getValue(aValue.variable()).equals(aValue))
215                                deltaInitialAssignments += 2;
216                        }
217                    }
218                }
219                for (Enrollment aValue : conf) {
220                    if (aValue.variable().getInitialAssignment() != null)
221                        deltaInitialAssignments--;
222                }
223                if (selectedVariable.getInitialAssignment() != null
224                        && !selectedVariable.getInitialAssignment().equals(value)) {
225                    deltaInitialAssignments++;
226                }
227                if (iMPPLimit >= 0 && (solution.getModel().perturbVariables(assignment).size() + deltaInitialAssignments) > iMPPLimit)
228                    continue;
229            }
230
231            double weightedSum = (iWeightDeltaInitialAssignment * deltaInitialAssignments)
232                    + (iWeightPotentialConflicts * potentialConflicts) + (iWeightWeightedCoflicts * weightedConflicts)
233                    + (iWeightCoflicts * conf.size())
234                    + (iWeightValue * value.toDouble(assignment));
235
236            if (bestValues == null || bestWeightedSum > weightedSum) {
237                bestWeightedSum = weightedSum;
238                if (bestValues == null)
239                    bestValues = new ArrayList<Enrollment>();
240                else
241                    bestValues.clear();
242                bestValues.add(value);
243            } else {
244                if (bestWeightedSum == weightedSum)
245                    bestValues.add(value);
246            }
247        }
248
249        Enrollment selectedValue = (bestValues == null ? null : ToolBox.random(bestValues));
250        if (selectedValue == null)
251            selectedValue = ToolBox.random(values);
252        if (iTabu != null) {
253            if (iTabu.size() == iTabuPos)
254                iTabu.add(selectedValue);
255            else
256                iTabu.set(iTabuPos, selectedValue);
257            iTabuPos = (iTabuPos + 1) % iTabuSize;
258        }
259        return (bestValues == null ? null : selectedValue);
260    }
261
262}