001    package net.sf.cpsolver.coursett.criteria;
002    
003    import java.util.Collection;
004    import java.util.HashSet;
005    import java.util.Set;
006    
007    import net.sf.cpsolver.coursett.Constants;
008    import net.sf.cpsolver.coursett.constraint.InstructorConstraint;
009    import net.sf.cpsolver.coursett.model.Lecture;
010    import net.sf.cpsolver.coursett.model.Placement;
011    import net.sf.cpsolver.coursett.model.TimetableModel;
012    
013    import net.sf.cpsolver.ifs.util.DataProperties;
014    
015    /**
016     * Bact-to-back instructor preferences. This criterion counts cases when an instructor
017     * has to teach two classes in two rooms that are too far a part. This objective
018     * is counter by the {@link InstructorConstraint}
019     * (see {@link InstructorConstraint#getDistancePreference(Placement, Placement)}).
020     * <br>
021     * 
022     * @version CourseTT 1.2 (University Course Timetabling)<br>
023     *          Copyright (C) 2006 - 2011 Tomas Muller<br>
024     *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
025     *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
026     * <br>
027     *          This library is free software; you can redistribute it and/or modify
028     *          it under the terms of the GNU Lesser General Public License as
029     *          published by the Free Software Foundation; either version 3 of the
030     *          License, or (at your option) any later version. <br>
031     * <br>
032     *          This library is distributed in the hope that it will be useful, but
033     *          WITHOUT ANY WARRANTY; without even the implied warranty of
034     *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
035     *          Lesser General Public License for more details. <br>
036     * <br>
037     *          You should have received a copy of the GNU Lesser General Public
038     *          License along with this library; if not see
039     *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
040     */
041    public class BackToBackInstructorPreferences extends TimetablingCriterion {
042        
043        public BackToBackInstructorPreferences() {
044            iValueUpdateType = ValueUpdateType.NoUpdate;
045        }
046        
047        @Override
048        public double getWeightDefault(DataProperties config) {
049            return Constants.sPreferenceLevelDiscouraged * config.getPropertyDouble("Comparator.DistanceInstructorPreferenceWeight", 1.0);
050        }
051        
052        @Override
053        public String getPlacementSelectionWeightName() {
054            return "Placement.DistanceInstructorPreferenceWeight";
055        }
056        
057        protected int penalty(Placement value) {
058            int ret = 0;
059            for (InstructorConstraint ic: value.variable().getInstructorConstraints()) {
060                ret += ic.getPreference(value);
061            }
062            return ret;
063        }
064        
065        @Override
066        public double getValue(Placement value, Set<Placement> conflicts) {
067            double ret = penalty(value);
068            if (conflicts != null)
069                for (Placement conflict: conflicts)
070                    ret -= penalty(conflict);
071            return ret;
072        }
073    
074        @Override
075        public double getValue(Collection<Lecture> variables) {
076            double ret = 0;
077            Set<InstructorConstraint> constraints = new HashSet<InstructorConstraint>();
078            for (Lecture lect: variables) {
079                for (InstructorConstraint ic: lect.getInstructorConstraints()) {
080                    if (!constraints.add(ic)) continue;
081                    ret += ic.getPreference();
082                }
083            }
084            return ret;
085        }
086        
087        @Override
088        protected double[] computeBounds() {
089            double[] bounds = new double[] { 0.0, 0.0 };
090            for (InstructorConstraint ic: ((TimetableModel)getModel()).getInstructorConstraints())
091                bounds[1] += ic.getWorstPreference();
092            return bounds;
093        }
094        
095        @Override
096        public double[] getBounds(Collection<Lecture> variables) {
097            double[] bounds = new double[] { 0.0, 0.0 };
098            Set<InstructorConstraint> constraints = new HashSet<InstructorConstraint>();
099            for (Lecture lect: variables) {
100                for (InstructorConstraint ic: lect.getInstructorConstraints()) {
101                    if (!constraints.add(ic)) continue;
102                    bounds[1] += ic.getWorstPreference();
103                }
104            }
105            return bounds;
106        }
107    }