    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 Break constraint checks for instructor lunch break or a break in general in between the given classes.<br>
    021 * It has three parameters: a start and an end time of a window in which the break is required / preferred, and a minimal length of a break that is needed.<br>
    022 * Reference _Break:132:162:30_ translates to a break of at least 30 minutes between 11 am (slot 132) and 1:30 pm (slot 162).<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 BreakFlexibleConstraint extends FlexibleConstraint {
    042
    043    // LunchBreak constraint parameters
    044    private int iBreakStart;
    045    private int iBreakEnd;
    046    private int iBreakLength;
    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 BreakFlexibleConstraint(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 = "_(Break):([0-9]+):([0-9]+):([0-9]+)_";
    063        pattern = Pattern.compile(patternString);
    064        matcher = pattern.matcher(reference);
    065        if (matcher.find()) {
    066            iBreakStart = Integer.parseInt(matcher.group(2));
    067            iBreakEnd = Integer.parseInt(matcher.group(3));
    068            iBreakLength = Integer.parseInt(matcher.group(4))/Constants.SLOT_LENGTH_MIN;
    069            iConstraintType = FlexibleConstraintType.BREAK;
    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        // checks only placements in the break time
    081        if (value.getTimeLocation().getStartSlot() <= iBreakEnd
    082                && value.getTimeLocation().getStartSlot() + value.getTimeLocation().getLength() > iBreakStart) {
    083
    084            for (int dayCode : Constants.DAY_CODES) {
    085                // checks only days affected by the placement
    086                if ((value.getTimeLocation().getDayCode() & dayCode) != 0) {
    087                    // constraint is checked for every week in semester (or for the whole semester)
    088                    for (BitSet week : weeks) {
    089                        boolean isProblem = false;
    090                        do {
    091                            Set<Placement> adepts = new HashSet<Placement>();
    092                            // each blocks contains placements which are BTB
    093                            // placements are BTB if there is less time between them than the minimal break length
    094                            List<Block> blocks = getBreakBlocks(dayCode, conflicts, value, null, week);
    095                            // determine possible conflicts from blocks' placements
    096                            getAdeptsLunchBreak(blocks, adepts);
    097                            if (adepts.isEmpty())
    098                                isProblem = false;
    099                            // currently assigned value shouldn't be added to conflicts if possible
    100                            if (adepts.size() >= 2)
    101                                adepts.remove(value);
    102                            // pick random placement
    103                            Placement conflict = ToolBox.random(adepts);
    104                            if (conflict != null) {
    105                                conflicts.add(conflict);
    106                            }
    107                        } while (isProblem);
    108                    }
    109                }
    110            }
    111        }
    112    }
    113
    114    /**
    115     * Creates a list of consecutive blocks with back-to-back classes.
    116     */
    117    public List<Block> getBreakBlocks(int dayCode, Set<Placement> conflicts, Placement value, HashMap<Lecture, Placement> assignments, BitSet week) {
    118
    119        List<Placement> toBeSorted = new ArrayList<Placement>(getRelevantPlacements(dayCode, conflicts, value, assignments, week));
    120        Collections.sort(toBeSorted, new PlacementTimeComparator());
    121
    122        return mergeToBlocks(toBeSorted, iBreakLength);
    123    }
    124
    125
    126
    127    /**
    128     * Method adds Placements from blocks to adepts if there is a possibility, that the placement caused constraint violation
    129     *
    130     * @param blocks placements in
    131     * @param adepts
    132     */
    133    private void getAdeptsLunchBreak(List<Block> blocks, Set<Placement> adepts) {
    134        List<Block> matchingBlocks = new ArrayList<Block>();
    135        for(Block block: blocks){
    136            // if block intersects with break interval, it will be used in conflict selection
    137            if (block.getStartSlotCurrentBlock() <= iBreakEnd && block.getEndSlotCurrentBlock() >= iBreakStart) matchingBlocks.add(block);
    138        }
    139        int size = matchingBlocks.size();
    140        // if there is none block intersecting with break interval, the constraint is satisfied
    141        // if there are at least 2 blocks intersecting with break interval, the constraint is satisfied,
    142        // because there must be a space between them, otherwise they would be in one block
    143        // if there is only one block intersecting with break interval, constraint might not be satisfied
    144        if (size == 1) {
    145            Block block = matchingBlocks.get(0);
    146            // check whether the block leaves enough space for break
    147            if (block.getStartSlotCurrentBlock() - iBreakStart >= iBreakLength || iBreakEnd - block.getEndSlotCurrentBlock() >= iBreakLength){
    148                return;
    149            // if it doesn't
    150            }else{
    151                // every placement intersecting with break interval might be potential conflict
    152                for (Placement p: block.getPlacements()){
    153                    if ( p.getTimeLocation().getStartSlot() <= iBreakEnd && p.getTimeLocation().getStartSlot()+ p.getTimeLocation().getLength() >= iBreakStart){
    154                        adepts.add(p);
    155                    }
    156                }
    157            }
    158        }
    159    }
    160
    161    @Override
    162    public double getNrViolations(Set<Placement> conflicts, HashMap<Lecture, Placement> assignments){
    163        List<BitSet> weeks = getWeeks();
    164
    165        int violatedDays = 0;
    166        for (int dayCode : Constants.DAY_CODES) {
    167            weekIteration: for (BitSet week : weeks) {
    168                Set<Placement> adepts = new HashSet<Placement>();
    169                List<Block> blocks = getBreakBlocks(dayCode, null, null, assignments, week);
    170                getAdeptsLunchBreak(blocks, adepts);
    171                if (!adepts.isEmpty())
    172                    violatedDays++;
    173                break weekIteration;
    174            }
    175        }
    176        return violatedDays;
    177    }
    178
    179}