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        @Override
044        public double getWeightDefault(DataProperties config) {
045            return Constants.sPreferenceLevelDiscouraged * config.getPropertyDouble("Comparator.DistanceInstructorPreferenceWeight", 1.0);
046        }
047        
048        @Override
049        public String getPlacementSelectionWeightName() {
050            return "Placement.DistanceInstructorPreferenceWeight";
051        }
052        
053        protected int penalty(Placement value) {
054            int ret = 0;
055            for (InstructorConstraint ic: value.variable().getInstructorConstraints()) {
056                ret += ic.getPreference(value);
057            }
058            return ret;
059        }
060        
061        @Override
062        public double getValue(Placement value, Set<Placement> conflicts) {
063            double ret = penalty(value);
064            if (conflicts != null)
065                for (Placement conflict: conflicts)
066                    ret -= penalty(conflict);
067            return ret;
068        }
069    
070        @Override
071        public double getValue(Collection<Lecture> variables) {
072            double ret = 0;
073            Set<InstructorConstraint> constraints = new HashSet<InstructorConstraint>();
074            for (Lecture lect: variables) {
075                for (InstructorConstraint ic: lect.getInstructorConstraints()) {
076                    if (!constraints.add(ic)) continue;
077                    ret += ic.getPreference();
078                }
079            }
080            return ret;
081        }
082        
083        @Override
084        protected void computeBounds() {
085            iBounds = new double[] { 0.0, 0.0 };
086            for (InstructorConstraint ic: ((TimetableModel)getModel()).getInstructorConstraints())
087                iBounds[1] += ic.getWorstPreference();
088        }
089        
090        @Override
091        public double[] getBounds(Collection<Lecture> variables) {
092            double[] bounds = new double[] { 0.0, 0.0 };
093            Set<InstructorConstraint> constraints = new HashSet<InstructorConstraint>();
094            for (Lecture lect: variables) {
095                for (InstructorConstraint ic: lect.getInstructorConstraints()) {
096                    if (!constraints.add(ic)) continue;
097                    bounds[1] += ic.getWorstPreference();
098                }
099            }
100            return bounds;
101        }
102    }