    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}