    001package org.cpsolver.coursett.constraint;
    002
    003import java.util.ArrayList;
    004import java.util.Collections;
    005import java.util.Comparator;
    006import java.util.HashSet;
    007import java.util.Iterator;
    008import java.util.List;
    009import java.util.Set;
    010
    011import org.cpsolver.coursett.Constants;
    012import org.cpsolver.coursett.model.Lecture;
    013import org.cpsolver.coursett.model.Placement;
    014import org.cpsolver.coursett.model.TimeLocation;
    015import org.cpsolver.ifs.assignment.Assignment;
    016import org.cpsolver.ifs.assignment.context.AssignmentConstraintContext;
    017import org.cpsolver.ifs.assignment.context.ConstraintWithContext;
    018import org.cpsolver.ifs.model.WeakeningConstraint;
    019import org.cpsolver.ifs.util.DataProperties;
    020
    021
    022/**
    023 * Minimize number of used groups of time within a set of classes. <br>
    024 * <br>
    025 *
    026 * This constraint implements the following distribution/group constraints: <br>
    027 * <br>
    028 *
    029 * MIN_GRUSE(10x1h) (Minimize Use Of 1h Groups)<br>
    030 * Minimize number of groups of time that are used by the given classes. The
    031 * time is spread into the following 10 groups of one hour: 7:30a-8:30a,
    032 * 8:30a-9:30a, 9:30a-10:30a, ... 4:30p-5:30p. <br>
    033 * <br>
    034 *
    035 * MIN_GRUSE(5x2h) (Minimize Use Of 2h Groups)<br>
    036 * Minimize number of groups of time that are used by the given classes. The
    037 * time is spread into the following 5 groups of two hours: 7:30a-9:30a,
    038 * 9:30a-11:30a, 11:30a-1:30p, 1:30p-3:30p, 3:30p-5:30p. <br>
    039 * <br>
    040 *
    041 * MIN_GRUSE(3x3h) (Minimize Use Of 3h Groups)<br>
    042 * Minimize number of groups of time that are used by the given classes. The
    043 * time is spread into the following 3 groups: 7:30a-10:30a, 10:30a-2:30p,
    044 * 2:30p-5:30p. <br>
    045 * <br>
    046 *
    047 * MIN_GRUSE(2x5h) (Minimize Use Of 5h Groups)<br>
    048 * Minimize number of groups of time that are used by the given classes. The
    049 * time is spread into the following 2 groups: 7:30a-12:30a, 12:30a-5:30p.
    050 *
    051 * @version CourseTT 1.3 (University Course Timetabling)<br>
    052 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    053 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    054 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    055 * <br>
    056 *          This library is free software; you can redistribute it and/or modify
    057 *          it under the terms of the GNU Lesser General Public License as
    058 *          published by the Free Software Foundation; either version 3 of the
    059 *          License, or (at your option) any later version. <br>
    060 * <br>
    061 *          This library is distributed in the hope that it will be useful, but
    062 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    063 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    064 *          Lesser General Public License for more details. <br>
    065 * <br>
    066 *          You should have received a copy of the GNU Lesser General Public
    067 *          License along with this library; if not see
    068 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    069 */
    070
    071public class MinimizeNumberOfUsedGroupsOfTime extends ConstraintWithContext<Lecture, Placement, MinimizeNumberOfUsedGroupsOfTime.MinimizeNumberOfUsedGroupsOfTimeContext> implements WeakeningConstraint<Lecture, Placement> {
    072    private int iUnassignmentsToWeaken = 250;
    073    private GroupOfTime iGroupsOfTime[];
    074
    075    private String iName = null;
    076
    077    public static GroupOfTime[] sGroups2of5h = new GroupOfTime[] {
    078            new GroupOfTime(Constants.time2slot(7, 30), Constants.time2slot(12, 30), Constants.DAY_CODE_ALL),
    079            new GroupOfTime(Constants.time2slot(12, 30), Constants.time2slot(17, 30), Constants.DAY_CODE_ALL), };
    080    public static GroupOfTime[] sGroups3of3h = new GroupOfTime[] {
    081            new GroupOfTime(Constants.time2slot(7, 30), Constants.time2slot(10, 30), Constants.DAY_CODE_ALL),
    082            new GroupOfTime(Constants.time2slot(10, 30), Constants.time2slot(14, 30), Constants.DAY_CODE_ALL),
    083            new GroupOfTime(Constants.time2slot(14, 30), Constants.time2slot(17, 30), Constants.DAY_CODE_ALL) };
    084    public static GroupOfTime[] sGroups5of2h = new GroupOfTime[] {
    085            new GroupOfTime(Constants.time2slot(7, 30), Constants.time2slot(9, 30), Constants.DAY_CODE_ALL),
    086            new GroupOfTime(Constants.time2slot(9, 30), Constants.time2slot(11, 30), Constants.DAY_CODE_ALL),
    087            new GroupOfTime(Constants.time2slot(11, 30), Constants.time2slot(13, 30), Constants.DAY_CODE_ALL),
    088            new GroupOfTime(Constants.time2slot(13, 30), Constants.time2slot(15, 30), Constants.DAY_CODE_ALL),
    089            new GroupOfTime(Constants.time2slot(15, 30), Constants.time2slot(17, 30), Constants.DAY_CODE_ALL) };
    090    public static GroupOfTime[] sGroups10of1h = new GroupOfTime[] {
    091            new GroupOfTime(Constants.time2slot(7, 30), Constants.time2slot(8, 30), Constants.DAY_CODE_ALL),
    092            new GroupOfTime(Constants.time2slot(8, 30), Constants.time2slot(9, 30), Constants.DAY_CODE_ALL),
    093            new GroupOfTime(Constants.time2slot(9, 30), Constants.time2slot(10, 30), Constants.DAY_CODE_ALL),
    094            new GroupOfTime(Constants.time2slot(10, 30), Constants.time2slot(11, 30), Constants.DAY_CODE_ALL),
    095            new GroupOfTime(Constants.time2slot(11, 30), Constants.time2slot(12, 30), Constants.DAY_CODE_ALL),
    096            new GroupOfTime(Constants.time2slot(12, 30), Constants.time2slot(13, 30), Constants.DAY_CODE_ALL),
    097            new GroupOfTime(Constants.time2slot(13, 30), Constants.time2slot(14, 30), Constants.DAY_CODE_ALL),
    098            new GroupOfTime(Constants.time2slot(14, 30), Constants.time2slot(15, 30), Constants.DAY_CODE_ALL),
    099            new GroupOfTime(Constants.time2slot(15, 30), Constants.time2slot(16, 30), Constants.DAY_CODE_ALL),
    100            new GroupOfTime(Constants.time2slot(16, 30), Constants.time2slot(17, 30), Constants.DAY_CODE_ALL) };
    101
    102    public MinimizeNumberOfUsedGroupsOfTime(DataProperties config, String name, GroupOfTime[] groupsOfTime) {
    103        iGroupsOfTime = groupsOfTime;
    104        iUnassignmentsToWeaken = config.getPropertyInt("MinimizeNumberOfUsedGroupsOfTime.Unassignments2Weaken", iUnassignmentsToWeaken);
    105        iName = name;
    106    }
    107
    108    public int estimateLimit() {
    109        int nrSlotsUsed = 0;
    110        int minSlotsUsed = 0;
    111        boolean firstLecture = true;
    112        for (Lecture lecture : variables()) {
    113            boolean first = true;
    114            int minSlotsUsedThisLecture = 0;
    115            for (TimeLocation time : lecture.timeLocations()) {
    116                int min = 0;
    117                for (int i = 0; i < iGroupsOfTime.length; i++) {
    118                    if (iGroupsOfTime[i].overlap(time))
    119                        min++;
    120                }
    121                if (first) {
    122                    nrSlotsUsed += time.getLength() * time.getNrMeetings();
    123                    minSlotsUsedThisLecture = min;
    124                    first = false;
    125                } else {
    126                    minSlotsUsedThisLecture = Math.min(minSlotsUsedThisLecture, min);
    127                }
    128            }
    129            if (firstLecture) {
    130                minSlotsUsed = minSlotsUsedThisLecture;
    131                firstLecture = false;
    132            } else {
    133                minSlotsUsed = Math.min(minSlotsUsed, minSlotsUsedThisLecture);
    134            }
    135        }
    136        return Math.max(Math.max(1, (int) Math.ceil(((double) nrSlotsUsed) / iGroupsOfTime[0].size())), minSlotsUsed);
    137    }
    138
    139    @Override
    140    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement placement, Set<Placement> conflicts) {
    141        MinimizeNumberOfUsedGroupsOfTimeContext context = getContext(assignment);
    142        int overLimit = context.getOverLimit(placement);
    143        if (overLimit > 0) {
    144            TimeLocation time = placement.getTimeLocation();
    145
    146            List<List<Placement>> adepts = new ArrayList<List<Placement>>();
    147            for (int i = 0; i < iGroupsOfTime.length; i++) {
    148                GroupOfTime groupOfTime = iGroupsOfTime[i];
    149                Set<Placement> usage = context.getUsage(i);
    150                if (groupOfTime.overlap(time) || usage.isEmpty())
    151                    continue;
    152                boolean canUnassign = true;
    153                List<Placement> placementsToUnassign = new ArrayList<Placement>(usage.size());
    154                for (Placement p : usage) {
    155                    Lecture l = p.variable();
    156                    if (l.isCommitted()) {
    157                        canUnassign = false;
    158                        break;
    159                    }
    160                    if (!conflicts.contains(p))
    161                        placementsToUnassign.add(p);
    162                }
    163                if (!canUnassign)
    164                    continue;
    165                adepts.add(placementsToUnassign);
    166            }
    167            if (adepts.size() < overLimit) {
    168                conflicts.add(placement);
    169            } else {
    170                Collections.sort(adepts, new Comparator<List<Placement>>() {
    171                    @Override
    172                    public int compare(List<Placement> c1, List<Placement> c2) {
    173                        return Double.compare(c1.size(), c2.size());
    174                    }
    175                });
    176                for (int i = 0; i < overLimit; i++) {
    177                    conflicts.addAll(adepts.get(i));
    178                }
    179            }
    180        }
    181    }
    182
    183    public String getConstraintName() {
    184        return "MIN_GRUSE(" + iName + ")";
    185    }
    186
    187    @Override
    188    public String getName() {
    189        return "Minimize number of used groups of time (" + iName + ")";
    190    }
    191
    192    private static class GroupOfTime {
    193        private int iStartSlot = 0;
    194        private int iEndSlot = 0;
    195        private int iDays = 0;
    196
    197        public GroupOfTime(int startSlot, int endSlot, int days) {
    198            iStartSlot = startSlot;
    199            iEndSlot = endSlot;
    200            iDays = days;
    201        }
    202
    203        public int getStartSlot() {
    204            return iStartSlot;
    205        }
    206
    207        public int getEndSlot() {
    208            return iEndSlot;
    209        }
    210
    211        public int getDays() {
    212            return iDays;
    213        }
    214
    215        public int nrDays() {
    216            int ret = 0;
    217            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
    218                if ((getDays() & Constants.DAY_CODES[i]) != 0)
    219                    ret++;
    220            }
    221            return ret;
    222        }
    223
    224        public int size() {
    225            return (getEndSlot() - getStartSlot()) * nrDays();
    226        }
    227
    228        public boolean overlap(TimeLocation timeLocation) {
    229            if ((timeLocation.getDayCode() & iDays) == 0)
    230                return false;
    231            int end = Math.min(iEndSlot, timeLocation.getStartSlot() + timeLocation.getLength());
    232            int start = Math.max(iStartSlot, timeLocation.getStartSlot());
    233            int nrSharedSlots = (end < start ? 0 : end - start);
    234            return (nrSharedSlots > 0);
    235        }
    236    }
    237
    238    @Override
    239    public String toString() {
    240        StringBuffer sb = new StringBuffer();
    241        sb.append("Minimize Use Of "
    242                + (Constants.SLOT_LENGTH_MIN * (iGroupsOfTime[0].getEndSlot() - iGroupsOfTime[0].getStartSlot()))
    243                + "min Groups between ");
    244        for (Iterator<Lecture> e = variables().iterator(); e.hasNext();) {
    245            Lecture v = e.next();
    246            sb.append(v.getName());
    247            if (e.hasNext())
    248                sb.append(", ");
    249        }
    250        return sb.toString();
    251    }
    252
    253    @Override
    254    public void weaken(Assignment<Lecture, Placement> assignment) {
    255        getContext(assignment).weaken();
    256    }
    257
    258    @Override
    259    public void weaken(Assignment<Lecture, Placement> assignment, Placement value) {
    260        getContext(assignment).weaken(value);
    261    }
    262
    263    @Override
    264    public MinimizeNumberOfUsedGroupsOfTimeContext createAssignmentContext(Assignment<Lecture, Placement> assignment) {
    265        return new MinimizeNumberOfUsedGroupsOfTimeContext(assignment);
    266    }
    267
    268    public class MinimizeNumberOfUsedGroupsOfTimeContext implements AssignmentConstraintContext<Lecture, Placement> {
    269        private long iUnassignment = 0;
    270        private int iLimit = 1;
    271        private Set<Placement> iUsage[];
    272
    273        @SuppressWarnings("unchecked")
    274        public MinimizeNumberOfUsedGroupsOfTimeContext(Assignment<Lecture, Placement> assignment) {
    275            iUsage = new HashSet[iGroupsOfTime.length];
    276            for (int i = 0; i < iUsage.length; i++)
    277                iUsage[i] = new HashSet<Placement>();
    278            for (Lecture lecture: variables()) {
    279                Placement placement = assignment.getValue(lecture);
    280                if (placement != null)
    281                    assigned(assignment, placement);
    282            }
    283            iLimit = Math.max(currentUsage(), estimateLimit());
    284        }
    285
    286        @Override
    287        public void assigned(Assignment<Lecture, Placement> assignment, Placement placement) {
    288            TimeLocation time = placement.getTimeLocation();
    289            for (int i = 0; i < iGroupsOfTime.length; i++) {
    290                GroupOfTime groupOfTime = iGroupsOfTime[i];
    291                Set<Placement> usage = iUsage[i];
    292                if (groupOfTime.overlap(time))
    293                    usage.add(placement);
    294            }
    295        }
    296
    297        @Override
    298        public void unassigned(Assignment<Lecture, Placement> assignment, Placement placement) {
    299            TimeLocation time = placement.getTimeLocation();
    300            for (int i = 0; i < iGroupsOfTime.length; i++) {
    301                GroupOfTime groupOfTime = iGroupsOfTime[i];
    302                Set<Placement> usage = iUsage[i];
    303                if (groupOfTime.overlap(time))
    304                    usage.remove(placement);
    305            }
    306        }
    307
    308        public int currentUsage() {
    309            int ret = 0;
    310            for (int i = 0; i < iUsage.length; i++)
    311                if (!iUsage[i].isEmpty())
    312                    ret++;
    313            return ret;
    314        }
    315
    316        public boolean isOverLimit(Placement placement) {
    317            return getOverLimit(placement) > 0;
    318        }
    319
    320        public int getOverLimit(Placement placement) {
    321            if (iUnassignmentsToWeaken == 0)
    322                return 0; // not working
    323
    324            Lecture lecture = placement.variable();
    325            TimeLocation time = placement.getTimeLocation();
    326
    327            if (lecture.isCommitted())
    328                return 0; // commited class
    329
    330            int usage = 0;
    331            for (int i = 0; i < iGroupsOfTime.length; i++) {
    332                GroupOfTime groupOfTime = iGroupsOfTime[i];
    333                if (!iUsage[i].isEmpty() || groupOfTime.overlap(time))
    334                    usage++;
    335            }
    336
    337            return usage - iLimit;
    338        }
    339
    340        public void weaken() {
    341            iUnassignment++;
    342            if (iUnassignmentsToWeaken > 0 && iUnassignment % iUnassignmentsToWeaken == 0)
    343                iLimit++;
    344        }
    345
    346        public void weaken(Placement value) {
    347            if (isOverLimit(value))
    348                iLimit += getOverLimit(value);
    349        }
    350
    351        public Set<Placement> getUsage(int slot) {
    352            return iUsage[slot];
    353        }
    354    }
    355
    356}