001package net.sf.cpsolver.coursett.constraint;
002
003import java.util.ArrayList;
004import java.util.BitSet;
005import java.util.Collections;
006import java.util.HashMap;
007import java.util.HashSet;
008import java.util.List;
009import java.util.Set;
010import java.util.regex.Matcher;
011import java.util.regex.Pattern;
012
013import net.sf.cpsolver.coursett.Constants;
014import net.sf.cpsolver.coursett.model.Lecture;
015import net.sf.cpsolver.coursett.model.Placement;
016import net.sf.cpsolver.ifs.util.ToolBox;
017
018/**
019 * 
020 * The MaxBlock constraint checks for too big blocks of back-to-back classes of an instructor.<br>
021 * It has two parameters: a maximal length of a back-to-back block that is allowed and a minimal length of a break between two classes not to be considered in the same block.<br>
022 * Reference _MaxBlock:120:30_ translates to a maximal block of at most 2 hours (120 minutes) with classes not more than 30 minutes a part.<br>
023 * 
024 * @version CourseTT 1.2 (University Course Timetabling)<br>
025 *          Copyright (C) 2013 Matej Lukac<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 */
041public class MaxBlockFlexibleConstraint extends FlexibleConstraint {
042
043    // max number of slots between to classes to be considered Back-To-Back
044    private int iMaxBreakBetweenBTB; 
045    // max length of a block of classes taught Back-To-Back
046    private int iMaxBlockSlotsBTB;      
047    
048    /**
049     * 
050     * @param owner identifier of distribution preference the constraint was created for
051     * @param preference time preference ("R" for required, "P" for prohibited, "-2",
052     *            "-1", "1", "2" for soft preference)   
053     * @param reference parameters of the constraint in String form            
054     */
055    public MaxBlockFlexibleConstraint(Long id, String owner, String preference, String reference) {
056        super(id, owner, preference, reference);     
057        
058        Pattern pattern = null;
059        Matcher matcher = null;   
060        
061        // recognize Break constraint        
062        String patternString = "_(MaxBlock):([0-9]+):([0-9]+)_";
063        pattern = Pattern.compile(patternString);
064        matcher = pattern.matcher(reference);
065        if (matcher.find()) {       
066            iMaxBlockSlotsBTB = Integer.parseInt(matcher.group(2))/Constants.SLOT_LENGTH_MIN;
067            iMaxBreakBetweenBTB = Integer.parseInt(matcher.group(3))/Constants.SLOT_LENGTH_MIN;             
068            iConstraintType = FlexibleConstraint.FlexibleConstraintType.MAXBLOCK_BACKTOBACK;           
069        }  
070         
071    }
072    
073    @Override
074    public void computeConflicts(Placement value, Set<Placement> conflicts) {
075        if (!isHard())
076            return;       
077        
078        List<BitSet> weeks = getWeeks();
079        
080        // constraint is checked for every day in week
081        for (int dayCode : Constants.DAY_CODES) {
082            // constraint is checked for every week in semester (or for the whole semester)
083            for (BitSet week : weeks) {
084                boolean isProblem = false;
085                do {
086                    isProblem = false;
087                    // each blocks contains placements which are BTB 
088                    List<Block> blocks = getBlocks(dayCode, conflicts, value, null, week);
089                    for (Block block : blocks) {
090                        // if the block is not affected by the current placement, continue
091                        if (!block.getPlacements().contains(value)){
092                            continue;
093                        }
094                        Set<Placement> adepts = new HashSet<Placement>();                        
095                        // if there is only 1 placement in block, the block cannot be shortened
096                        // if placements of a block start at the same time, they intersect
097                        // this solves problem when between 2 classes is required MEET_TOGETHER  
098                        if (block.getNbrPlacements() == 1 || block.haveSameStartTime())
099                            continue;
100                        // if block is longer than maximum size, some of its placements are conflicts
101                        if (block.getLengthInSlots() > iMaxBlockSlotsBTB) {
102                            // classes from block are potential conflicts
103                            adepts.addAll(block.getPlacements());                            
104                            // do not set currently assigned value as conflict
105                            adepts.remove(value);
106                            isProblem = true;
107                            // pick random placement
108                            Placement conflict = ToolBox.random(adepts);
109                            if (conflict != null) {
110                                conflicts.add(conflict);
111                            }
112                        }
113                    }
114                } while (isProblem);
115            }
116        }
117    }
118    
119    public List<Block> getBlocks(int dayCode, Set<Placement> conflicts, Placement value, HashMap<Lecture, Placement> assignments, BitSet week) {     
120        List<Placement> toBeSorted = new ArrayList<Placement>(getRelevantPlacements(dayCode, conflicts, value, assignments, week));
121        Collections.sort(toBeSorted, new PlacementTimeComparator());  
122        
123        return mergeToBlocks(toBeSorted, iMaxBreakBetweenBTB);
124    } 
125
126    @Override
127    public double getNrViolations(Set<Placement> conflicts, HashMap<Lecture, Placement> assignments) {
128        List<BitSet> weeks = getWeeks();
129
130        int violatedBlocks = 0;
131        for (int dayCode : Constants.DAY_CODES) {
132            for (BitSet week : weeks) {
133                List<Block> blocks = getBlocks(dayCode, null, null, assignments, week);
134                for (Block block : blocks) {
135                    if (block.getNbrPlacements() == 1 || block.haveSameStartTime())
136                        continue;
137                    // violated if there is a block containing more than one
138                    // class longer than iMaxBlockSlotsBTB
139                    if (block.getLengthInSlots() > iMaxBlockSlotsBTB) {
140                        int blockLengthPenalty = block.getLengthInSlots() / iMaxBlockSlotsBTB;
141                        violatedBlocks += blockLengthPenalty;
142                    }
143                }
144            }
145        }
146        return violatedBlocks;
147    }
148
149}