001package org.cpsolver.studentsct.online;
002
003import java.util.Set;
004
005import org.cpsolver.ifs.assignment.Assignment;
006import org.cpsolver.ifs.heuristics.RouletteWheelSelection;
007import org.cpsolver.ifs.model.GlobalConstraint;
008import org.cpsolver.studentsct.model.CourseRequest;
009import org.cpsolver.studentsct.model.Enrollment;
010import org.cpsolver.studentsct.model.Request;
011import org.cpsolver.studentsct.model.Section;
012import org.cpsolver.studentsct.online.expectations.OverExpectedCriterion;
013
014/**
015 * A global constraint limiting the over-expected penalization for a student.
016 * Only to be used during online scheduling (with the {@link OnlineSectioningModel}).
017 * 
018 * @author  Tomáš Müller
019 * @version StudentSct 1.3 (Student Sectioning)<br>
020 *          Copyright (C) 2014 Tomáš Müller<br>
021 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
022 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
023 * <br>
024 *          This library is free software; you can redistribute it and/or modify
025 *          it under the terms of the GNU Lesser General Public License as
026 *          published by the Free Software Foundation; either version 3 of the
027 *          License, or (at your option) any later version. <br>
028 * <br>
029 *          This library is distributed in the hope that it will be useful, but
030 *          WITHOUT ANY WARRANTY; without even the implied warranty of
031 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
032 *          Lesser General Public License for more details. <br>
033 * <br>
034 *          You should have received a copy of the GNU Lesser General Public
035 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
036 * 
037 */
038public class MaxOverExpectedConstraint extends GlobalConstraint<Request, Enrollment> {
039    private double iMaxOverExpected;
040
041    public MaxOverExpectedConstraint(double limit) {
042        iMaxOverExpected = limit;
043    }
044
045    @Override
046    public void computeConflicts(Assignment<Request, Enrollment> assignment, Enrollment value, Set<Enrollment> conflicts) {
047        if (!value.isCourseRequest()) return;
048        CourseRequest cr = (CourseRequest) value.variable();
049        OnlineSectioningModel model = (OnlineSectioningModel) getModel();
050
051        double basePenalty = model.getOverExpected(assignment, value, value, conflicts);
052
053        if (basePenalty > iMaxOverExpected) {
054            conflicts.add(value);
055            return;
056        }
057
058        RouletteWheelSelection<Enrollment> selection = new RouletteWheelSelection<Enrollment>();
059
060        for (Request r : cr.getStudent().getRequests()) {
061            Enrollment e = assignment.getValue(r);
062            if (e != null && !r.equals(value.variable()) && !conflicts.contains(e) && e.isCourseRequest()) {
063                double penalty = model.getOverExpected(assignment, e, value, conflicts);
064                if (penalty > 0.0)
065                    selection.add(e, penalty);
066            }
067        }
068
069        while (selection.getRemainingPoints() + basePenalty > iMaxOverExpected && selection.hasMoreElements()) {
070            conflicts.add(selection.nextElement());
071        }
072    }
073
074    @Override
075    public boolean inConflict(Assignment<Request, Enrollment> assignment, Enrollment value) {
076        if (!value.isCourseRequest()) return false;
077        OverExpectedCriterion over = ((OnlineSectioningModel)getModel()).getOverExpectedCriterion();
078        if (over == null) return false;
079
080        double penalty = 0.0;
081        for (Request r : value.getRequest().getStudent().getRequests()) {
082            Enrollment e = (r.equals(value.variable()) ? value : assignment.getValue(r));
083            if (e != null && e.isCourseRequest())
084                for (Section s : e.getSections())
085                    penalty += over.getOverExpected(assignment, s, e.getRequest());
086        }
087        return penalty > iMaxOverExpected;
088    }
089
090}