001package org.cpsolver.instructor.constraints;
002
003import java.util.ArrayList;
004import java.util.List;
005import java.util.Set;
006
007import org.cpsolver.ifs.assignment.Assignment;
008import org.cpsolver.ifs.model.GlobalConstraint;
009import org.cpsolver.ifs.util.ToolBox;
010import org.cpsolver.instructor.model.Instructor.Context;
011import org.cpsolver.instructor.model.TeachingAssignment;
012import org.cpsolver.instructor.model.TeachingRequest;
013
014/**
015 * Instructor Constraint. This is the main constraint of the problem, ensuring that an instructor gets a consistent list of 
016 * assignments. It checks for instructor availability, maximal load, time conflicts, and whether the given assignments are of the same
017 * course (if desired).
018 * 
019 * @version IFS 1.3 (Instructor Sectioning)<br>
020 *          Copyright (C) 2016 Tomas Muller<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
036 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
037 */
038public class InstructorConstraint extends GlobalConstraint<TeachingRequest, TeachingAssignment> {
039    
040    /**
041     * Constructor
042     */
043    public InstructorConstraint() {}
044    
045    @Override
046    public void computeConflicts(Assignment<TeachingRequest, TeachingAssignment> assignment, TeachingAssignment value, Set<TeachingAssignment> conflicts) {
047        Context context = value.getInstructor().getContext(assignment);
048
049        // Check availability
050        if (context.getInstructor().getTimePreference(value.variable()).isProhibited()) {
051            conflicts.add(value);
052            return;
053        }
054
055        // Check for overlaps
056        for (TeachingAssignment ta : context.getAssignments()) {
057            if (ta.variable().equals(value.variable()) || conflicts.contains(ta))
058                continue;
059
060            if (ta.variable().overlaps(value.variable()))
061                conflicts.add(ta);
062        }
063
064        // Same course and/or common
065        if (value.variable().getCourse().isExclusive()) {
066            boolean sameCommon = value.variable().getCourse().isSameCommon();
067            for (TeachingAssignment ta : context.getAssignments()) {
068                if (ta.variable().equals(value.variable()) || conflicts.contains(ta))
069                    continue;
070
071                if (!ta.variable().sameCourse(value.variable()) || (sameCommon && !ta.variable().sameCommon(value.variable())))
072                    conflicts.add(ta);
073            }
074        } else if (value.variable().getCourse().isSameCommon()) {
075            for (TeachingAssignment ta : context.getAssignments()) {
076                if (ta.variable().equals(value.variable()) || conflicts.contains(ta))
077                    continue;
078                if (ta.variable().sameCourse(value.variable()) && !ta.variable().sameCommon(value.variable()))
079                    conflicts.add(ta);
080            }
081        }
082        
083        // Check load
084        float load = value.variable().getLoad();
085        List<TeachingAssignment> adepts = new ArrayList<TeachingAssignment>();
086        for (TeachingAssignment ta : context.getAssignments()) {
087            if (ta.variable().equals(value.variable()) || conflicts.contains(ta))
088                continue;
089
090            adepts.add(ta);
091            load += ta.variable().getLoad();
092        }
093        while (load > context.getInstructor().getMaxLoad()) {
094            if (adepts.isEmpty()) {
095                conflicts.add(value);
096                break;
097            }
098            TeachingAssignment conflict = ToolBox.random(adepts);
099            load -= conflict.variable().getLoad();
100            adepts.remove(conflict);
101            conflicts.add(conflict);
102        }
103    }
104    
105    @Override
106    public String getName() {
107        return "Instructor Constraint";
108    }
109    
110    @Override
111    public String toString() {
112        return getName();
113    }
114}