    001package org.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 org.cpsolver.coursett.Constants;
    014import org.cpsolver.coursett.model.Lecture;
    015import org.cpsolver.coursett.model.Placement;
    016import org.cpsolver.ifs.assignment.Assignment;
    017import org.cpsolver.ifs.util.ToolBox;
    018
    019
    020/**
    021 *
    022 * The MaxBlock constraint checks for too big blocks of back-to-back classes of an instructor.<br>
    023 * 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>
    024 * 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>
    025 *
    026 * @version CourseTT 1.3 (University Course Timetabling)<br>
    027 *          Copyright (C) 2013 Matej Lukac<br>
    028 * <br>
    029 *          This library is free software; you can redistribute it and/or modify
    030 *          it under the terms of the GNU Lesser General Public License as
    031 *          published by the Free Software Foundation; either version 3 of the
    032 *          License, or (at your option) any later version. <br>
    033 * <br>
    034 *          This library is distributed in the hope that it will be useful, but
    035 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    036 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    037 *          Lesser General Public License for more details. <br>
    038 * <br>
    039 *          You should have received a copy of the GNU Lesser General Public
    040 *          License along with this library; if not see
    041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    042 */
    043public class MaxBlockFlexibleConstraint extends FlexibleConstraint {
    044
    045    // max number of slots between to classes to be considered Back-To-Back
    046    private int iMaxBreakBetweenBTB;
    047    // max length of a block of classes taught Back-To-Back
    048    protected int iMaxBlockSlotsBTB;
    049
    050    /**
    051     *
    052     * @param id constraint unique id
    053     * @param owner identifier of distribution preference the constraint was created for
    054     * @param preference time preference ("R" for required, "P" for prohibited, "-2",
    055     *            "-1", "1", "2" for soft preference)
    056     * @param reference parameters of the constraint in String form
    057     */
    058    public MaxBlockFlexibleConstraint(Long id, String owner, String preference, String reference) {
    059        super(id, owner, preference, reference);
    060
    061        Pattern pattern = null;
    062        Matcher matcher = null;
    063
    064        // recognize Break constraint
    065        String patternString = "_(MaxBlock):([0-9]+):([0-9]+)_";
    066        pattern = Pattern.compile(patternString);
    067        matcher = pattern.matcher(reference);
    068        if (matcher.find()) {
    069            iMaxBlockSlotsBTB = Integer.parseInt(matcher.group(2))/Constants.SLOT_LENGTH_MIN;
    070            iMaxBreakBetweenBTB = Integer.parseInt(matcher.group(3))/Constants.SLOT_LENGTH_MIN;
    071            iConstraintType = FlexibleConstraint.FlexibleConstraintType.MAXBLOCK_BACKTOBACK;
    072        }
    073
    074    }
    075
    076    @Override
    077    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
    078        if (!isHard())
    079            return;
    080
    081        List<BitSet> weeks = getWeeks();
    082
    083        // constraint is checked for every day in week
    084        for (int dayCode : Constants.DAY_CODES) {
    085            // constraint is checked for every week in semester (or for the whole semester)
    086            for (BitSet week : weeks) {
    087                boolean isProblem = false;
    088                do {
    089                    isProblem = false;
    090                    // each blocks contains placements which are BTB
    091                    List<Block> blocks = getBlocks(assignment, dayCode, conflicts, value, null, week);
    092                    for (Block block : blocks) {
    093                        // if the block is not affected by the current placement, continue
    094                        if (!block.getPlacements().contains(value)){
    095                            continue;
    096                        }
    097                        Set<Placement> adepts = new HashSet<Placement>();
    098                        // if there is only 1 placement in block, the block cannot be shortened
    099                        // if placements of a block start at the same time, they intersect
    100                        // this solves problem when between 2 classes is required MEET_TOGETHER
    101                        if (block.getNbrPlacements() == 1 || block.haveSameStartTime())
    102                            continue;
    103                        // if block is longer than maximum size, some of its placements are conflicts
    104                        if (block.getLengthInSlots() > iMaxBlockSlotsBTB) {
    105                            // classes from block are potential conflicts
    106                            adepts.addAll(block.getPlacements());
    107                            // do not set currently assigned value as conflict
    108                            adepts.remove(value);
    109                            isProblem = true;
    110                            // pick random placement
    111                            Placement conflict = ToolBox.random(adepts);
    112                            if (conflict != null) {
    113                                conflicts.add(conflict);
    114                            }
    115                        }
    116                    }
    117                } while (isProblem);
    118            }
    119        }
    120    }
    121
    122    public List<Block> getBlocks(Assignment<Lecture, Placement> assignment, int dayCode, Set<Placement> conflicts, Placement value, HashMap<Lecture, Placement> assignments, BitSet week) {
    123        List<Placement> toBeSorted = new ArrayList<Placement>(getRelevantPlacements(assignment, dayCode, conflicts, value, assignments, week));
    124        Collections.sort(toBeSorted, new PlacementTimeComparator());
    125
    126        return mergeToBlocks(toBeSorted, iMaxBreakBetweenBTB);
    127    }
    128
    129    @Override
    130    public double getNrViolations(Assignment<Lecture, Placement> assignment, Set<Placement> conflicts, HashMap<Lecture, Placement> assignments) {
    131        List<BitSet> weeks = getWeeks();
    132
    133        int violatedBlocks = 0;
    134        for (int dayCode : Constants.DAY_CODES) {
    135            for (BitSet week : weeks) {
    136                List<Block> blocks = getBlocks(assignment, dayCode, null, null, assignments, week);
    137                for (Block block : blocks) {
    138                    if (block.getNbrPlacements() == 1 || block.haveSameStartTime())
    139                        continue;
    140                    // violated if there is a block containing more than one
    141                    // class longer than iMaxBlockSlotsBTB
    142                    if (block.getLengthInSlots() > iMaxBlockSlotsBTB) {
    143                        int blockLengthPenalty = block.getLengthInSlots() / iMaxBlockSlotsBTB;
    144                        violatedBlocks += blockLengthPenalty;
    145                    }
    146                }
    147            }
    148        }
    149        return violatedBlocks;
    150    }
    151
    152}