001package org.cpsolver.exam.criteria;
002
003import java.util.Map;
004import java.util.Set;
005
006import org.cpsolver.exam.model.Exam;
007import org.cpsolver.exam.model.ExamPlacement;
008import org.cpsolver.ifs.assignment.Assignment;
009import org.cpsolver.ifs.util.DataProperties;
010
011
012/**
013 * Rotation penalty. I.e., an exam that has been in later period last times tries
014 * to be in an earlier period.
015 * <br><br>
016 * A weight for exam rotation penalty can be set by problem property
017 * Exams.RotationWeight, or in the input xml file, property examRotationWeight.
018 * 
019 * 
020 * <br>
021 * 
022 * @author  Tomáš Müller
023 * @version ExamTT 1.3 (Examination Timetabling)<br>
024 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
025 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
026 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
027 * <br>
028 *          This library is free software; you can redistribute it and/or modify
029 *          it under the terms of the GNU Lesser General Public License as
030 *          published by the Free Software Foundation; either version 3 of the
031 *          License, or (at your option) any later version. <br>
032 * <br>
033 *          This library is distributed in the hope that it will be useful, but
034 *          WITHOUT ANY WARRANTY; without even the implied warranty of
035 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
036 *          Lesser General Public License for more details. <br>
037 * <br>
038 *          You should have received a copy of the GNU Lesser General Public
039 *          License along with this library; if not see
040 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
041 */
042public class ExamRotationPenalty extends ExamCriterion {
043    
044    @Override
045    public ValueContext createAssignmentContext(Assignment<Exam, ExamPlacement> assignment) {
046        return new RotationContext(assignment);
047    }
048        
049    @Override
050    public String getWeightName() {
051        return "Exams.RotationWeight";
052    }
053    
054    @Override
055    public String getXmlWeightName() {
056        return "examRotationWeight";
057    }
058    
059    @Override
060    public double getWeightDefault(DataProperties config) {
061        return 0.001;
062    }
063
064    @Override
065    public double getValue(Assignment<Exam, ExamPlacement> assignment, ExamPlacement value, Set<ExamPlacement> conflicts) {
066        if (value.variable().getAveragePeriod() < 0) return 0;
067        return (1 + value.getPeriod().getIndex()) * (1 + value.variable().getAveragePeriod());
068    }
069    
070    public int nrAssignedExamsWithAvgPeriod(Assignment<Exam, ExamPlacement> assignment) {
071        return ((RotationContext)getContext(assignment)).nrAssignedExamsWithAvgPeriod();
072    }
073    
074    public double averagePeriod(Assignment<Exam, ExamPlacement> assignment) {
075        return ((RotationContext)getContext(assignment)).averagePeriod();
076    }
077    
078    @Override
079    public void getInfo(Assignment<Exam, ExamPlacement> assignment, Map<String, String> info) {
080        if (getValue(assignment) != 0.0) {
081            info.put(getName(), sDoubleFormat.format(Math.sqrt(getValue(assignment) / nrAssignedExamsWithAvgPeriod(assignment)) - 1));
082        }
083    }
084    
085    @Override
086    public String toString(Assignment<Exam, ExamPlacement> assignment) {
087        return "@P:" + sDoubleFormat.format((Math.sqrt(getValue(assignment) / nrAssignedExamsWithAvgPeriod(assignment)) - 1));
088    }
089    
090    protected class RotationContext extends ValueContext {
091        private int iAssignedExamsWithAvgPeriod = 0;
092        private double iAveragePeriod = 0.0;
093
094        public RotationContext(Assignment<Exam, ExamPlacement> assignment) {
095            super(assignment);
096            for (Exam exam: getModel().variables())
097                if (exam.getAveragePeriod() > 0) {
098                    ExamPlacement placement = assignment.getValue(exam);
099                    if (placement != null) {
100                        iAssignedExamsWithAvgPeriod ++;
101                        iAveragePeriod += exam.getAveragePeriod();
102                    }
103                }
104        }
105
106        @Override
107        public void assigned(Assignment<Exam, ExamPlacement> assignment, ExamPlacement value) {
108            super.assigned(assignment, value);
109            if (value.variable().getAveragePeriod() >= 0) {
110                iAssignedExamsWithAvgPeriod ++;
111                iAveragePeriod += value.variable().getAveragePeriod();
112            }
113        }
114
115        @Override
116        public void unassigned(Assignment<Exam, ExamPlacement> assignment, ExamPlacement value) {
117            super.unassigned(assignment, value);
118            if (value.variable().getAveragePeriod() >= 0) {
119                iAssignedExamsWithAvgPeriod --;
120                iAveragePeriod -= value.variable().getAveragePeriod();
121            }
122        }
123        
124        public int nrAssignedExamsWithAvgPeriod() {
125            return iAssignedExamsWithAvgPeriod;
126        }
127        
128        public double averagePeriod() {
129            return iAveragePeriod / iAssignedExamsWithAvgPeriod;
130        }
131    }
132}