    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}