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