[32] | 1 | package geniusweb.voting;
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| 2 |
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| 3 | import java.util.Collections;
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| 4 | import java.util.Comparator;
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| 5 | import java.util.HashMap;
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| 6 | import java.util.HashSet;
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| 7 | import java.util.Map;
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| 8 | import java.util.PriorityQueue;
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| 9 | import java.util.Set;
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| 10 | import java.util.stream.Collectors;
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| 11 |
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| 12 | import geniusweb.actions.PartyId;
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| 13 | import geniusweb.actions.Vote;
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| 14 | import geniusweb.actions.Votes;
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| 15 | import geniusweb.issuevalue.Bid;
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| 16 | import tudelft.utilities.immutablelist.FixedList;
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| 17 | import tudelft.utilities.immutablelist.ImmutableList;
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| 18 | import tudelft.utilities.immutablelist.PowerSet;
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| 19 |
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| 20 | /**
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| 21 | * Utility class. Typically contains all the votes collected from 1 round. Can
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| 22 | * find the best combinations of votes, eg to get the maximum consensus group
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| 23 | */
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| 24 | public class CollectedVotes {
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| 25 | private final Map<PartyId, Votes> allvotes;
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| 26 | private final Map<PartyId, Integer> powers;
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| 27 |
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| 28 | // caching
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| 29 | private transient Map<Bid, Set<Vote>> allBids = null;
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| 30 |
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| 31 | /**
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| 32 | *
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| 33 | * @param votesMap the {@link Votes} done for each party
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| 34 | * @param power the power of each party. The power is an integer number.
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| 35 | * In the voting process, the party powers add up to form
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| 36 | * the total voting power. This set may contain parties that
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| 37 | * are not in newmap.
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| 38 | */
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| 39 | public CollectedVotes(Map<PartyId, Votes> votesMap,
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| 40 | Map<PartyId, Integer> power) {
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| 41 | this.allvotes = new HashMap<>(votesMap);
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| 42 | this.powers = new HashMap<>(power);
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| 43 | if (!powers.keySet().containsAll(allvotes.keySet())) {
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| 44 | throw new IllegalArgumentException(
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| 45 | "All voting parties must have a power");
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| 46 | }
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| 47 | }
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| 48 |
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| 49 | /**
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| 50 | * @param votes additional set of votes for a new party that did not yet
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| 51 | * vote.
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| 52 | * @param power powers for the new party, can be null if power already set
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| 53 | * previously.
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| 54 | * @return new CollectedVotes with the new votes added.
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| 55 | */
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| 56 | public CollectedVotes with(Votes votes, Integer power) {
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| 57 | PartyId actor = votes.getActor();
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| 58 | if (allvotes.containsKey(actor))
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| 59 | throw new IllegalArgumentException(
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| 60 | "Party " + actor + " already voted");
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| 61 |
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| 62 | Map<PartyId, Integer> newpowers = new HashMap<>(powers);
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| 63 | if (!powers.containsKey(actor)) {
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| 64 | if (power == null)
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| 65 | throw new IllegalArgumentException(
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| 66 | "Power must be set for new actor " + actor);
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| 67 | newpowers.put(actor, power);
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| 68 | }
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| 69 |
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| 70 | Map<PartyId, Votes> newmap = new HashMap<>(allvotes);
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| 71 | newmap.put(actor, votes);
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| 72 | return new CollectedVotes(newmap, newpowers);
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| 73 | }
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| 74 |
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| 75 | /**
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| 76 | * @return all the votes placed so far
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| 77 | */
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| 78 | public Map<PartyId, Votes> getVotes() {
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| 79 | return Collections.unmodifiableMap(allvotes);
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| 80 | }
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| 81 |
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| 82 | /**
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| 83 | * @return the powers of all parties
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| 84 | */
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| 85 | public Map<PartyId, Integer> getPowers() {
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| 86 | return Collections.unmodifiableMap(powers);
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| 87 | }
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| 88 |
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| 89 | /**
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| 90 | * @return a map containing for each {@link Bid}s a subset of
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| 91 | * {@link PartyId}s that placed a satisfied vote for that bid, such
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| 92 | * that the subset has maximum power. Maximum power means that there
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| 93 | * is no other subset of satisfied votes for that bid with more
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| 94 | * group power. There may be other subsets of equal power for the
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| 95 | * bid. If there are no concensus possibilities at all for a bid,
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| 96 | * the bid is not placed in the map.
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| 97 | */
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| 98 | public Map<Bid, Set<PartyId>> getMaxAgreements() {
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| 99 | Map<Bid, Set<PartyId>> agreements = new HashMap<>();
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| 100 | Map<Bid, Set<Vote>> allbidsmap = getAllBids();
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| 101 | for (Bid bid : allbidsmap.keySet()) {
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| 102 | Set<PartyId> max = getMaxPowerGroup(allbidsmap.get(bid));
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| 103 | if (!max.isEmpty())
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| 104 | agreements.put(bid, max);
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| 105 | }
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| 106 | return agreements;
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| 107 | }
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| 108 |
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| 109 | /**
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| 110 | * @return all bids that were voted on and the votes for that bid. This
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| 111 | * basically reverses keys and values in {@link #allvotes}
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| 112 | */
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| 113 | public Map<Bid, Set<Vote>> getAllBids() {
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| 114 | if (allBids == null)
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| 115 | allBids = getAllBids1();
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| 116 | return allBids;
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| 117 | }
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| 118 |
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| 119 | /**
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| 120 | *
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| 121 | * @param parties the parties to be removed
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| 122 | * @return new CollectedVotes without given parties
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| 123 | */
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| 124 | public CollectedVotes without(Set<PartyId> parties) {
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| 125 | Map<PartyId, Votes> newvotes = new HashMap<>(allvotes);
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| 126 | newvotes.keySet().removeAll(parties);
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| 127 | Map<PartyId, Integer> newpower = new HashMap<>(powers);
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| 128 | newpower.keySet().removeAll(parties);
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| 129 | return new CollectedVotes(newvotes, newpower);
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| 130 | }
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| 131 |
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| 132 | /**
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| 133 | *
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| 134 | * @param parties a list of parties
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| 135 | * @return total voting power of the parties
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| 136 | */
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| 137 | public Integer getTotalPower(Set<PartyId> parties) {
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| 138 | return parties.stream().map(p -> powers.get(p)).reduce(0, Integer::sum);
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| 139 | }
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| 140 |
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| 141 | /**
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| 142 | * Breath-first optimized search, similar as {@link #getMaxPowerGroup(Set)}
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| 143 | * but more efficient on average (remains to be proven). Notice that this
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| 144 | * algorithm may be more expensive particularly if there is no consensus at
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| 145 | * all, because of the added overhead of the breath-first search
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| 146 | *
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| 147 | * @param allvotes a list of all votes for a particular bid.
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| 148 | * @return a consensus-group with maximum power, so there is no other
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| 149 | * consensus group that has more power (but there may be other
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| 150 | * groups with same power). returns empty set if no consensus found
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| 151 | */
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| 152 | protected Set<PartyId> getMaxPowerGroupBreathFirst(Set<Vote> allvotes) {
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| 153 | /**
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| 154 | * queue that keeps the options for the breath-first search sorted from
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| 155 | * highest to lowest power of the voters.
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| 156 | */
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| 157 | PriorityQueue<Set<Vote>> queue = new PriorityQueue<>(
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| 158 | new Comparator<Set<Vote>>() {
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| 159 | @Override
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| 160 | public int compare(Set<Vote> vs1, Set<Vote> vs2) {
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| 161 | Set<PartyId> parties1 = vs1.stream()
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| 162 | .map(vote -> vote.getActor())
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| 163 | .collect(Collectors.toSet());
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| 164 | Set<PartyId> parties2 = vs2.stream()
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| 165 | .map(vote -> vote.getActor())
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| 166 | .collect(Collectors.toSet());
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| 167 | return getTotalPower(parties1)
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| 168 | .compareTo(getTotalPower(parties2));
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| 169 | }
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| 170 | });
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| 171 | queue.add(allvotes);
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| 172 |
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| 173 | while (!queue.isEmpty()) {
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| 174 | // try one with the highest power
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| 175 | Set<Vote> vs = queue.poll();
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| 176 | if (isViable(vs))
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| 177 | return getParties(vs);
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| 178 | if (vs.size() > 1) {
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| 179 | // vote can be splitted. push all new subsets
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| 180 | for (Vote vote : vs) {
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| 181 | Set<Vote> subvotes = new HashSet<>(vs);
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| 182 | subvotes.remove(vote);
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| 183 | // avoid duplicate work. Since this has a removed party,
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| 184 | // and assuming power of each party >=1,
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| 185 | // we can not already have checked subvotes
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| 186 | if (!queue.contains(subvotes))
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| 187 | queue.add(subvotes);
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| 188 | }
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| 189 | }
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| 190 |
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| 191 | }
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| 192 | return Collections.emptySet();
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| 193 | }
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| 194 |
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| 195 | /**
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| 196 | *
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| 197 | * @param votes a list of all votes for a particular bid. The parties that
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| 198 | * placed the votes are called 'voters'
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| 199 | * @return a consensus-group with maximum power, so there is no other
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| 200 | * consensus group that has more power (but there may be other
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| 201 | * groups with same power). returns empty set if no consensus found
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| 202 | */
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| 203 | protected Set<PartyId> getMaxPowerGroup(Set<Vote> votes) {
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| 204 | Set<PartyId> maxgroup = Collections.emptySet();
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| 205 | Integer maxpower = 0;
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| 206 |
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| 207 | for (Set<PartyId> parties : getConsensusGroups(votes)) {
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| 208 | Integer power = getTotalPower(parties);
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| 209 | if (power > maxpower) {
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| 210 | maxgroup = parties;
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| 211 | maxpower = power;
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| 212 | }
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| 213 | }
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| 214 | return maxgroup;
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| 215 | }
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| 216 |
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| 217 | /**
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| 218 | *
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| 219 | * @param votes a set of {@link Votes} for one single {@link Bid}. It is
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| 220 | * assumed all votes are by different parties.
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| 221 | * @return all subsets sets of parties that create a viable consensus vote.
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| 222 | * A viable consensus voteset VS is a subset of the votes, such that
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| 223 | * <ol>
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| 224 | * <li>|VS| ≥ 2
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| 225 | * <li>TP = The sum of the powers of the parties in VS
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| 226 | * <li>forall v in VS: v_minpower ≤ TP ≤ v_maxpower
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| 227 | * </ol>
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| 228 | * Notice that this algorithm works in exponential space
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| 229 | * (=expensive) and not suited for large numbers of parties. Should
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| 230 | * work fine for up to 10 parties.
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| 231 | */
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| 232 | protected Set<Set<PartyId>> getConsensusGroups(Set<Vote> votes) {
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| 233 | Set<Set<PartyId>> groups = new HashSet<>();
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| 234 |
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| 235 | PowerSet<Vote> allVotePermutations = new PowerSet<Vote>(
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| 236 | new FixedList<Vote>(votes));
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| 237 | // check each possible subset.
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| 238 | // TODO stream this
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| 239 | for (ImmutableList<Vote> voteList : allVotePermutations) {
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| 240 | if (isViable(voteList)) {
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| 241 | groups.add(getParties(voteList));
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| 242 | }
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| 243 | }
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| 244 | return groups;
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| 245 | }
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| 246 |
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| 247 | /**
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| 248 | *
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| 249 | * @param voteList a list of votes for a single bid.
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| 250 | * @return true if this votelist satisfies the requirements of all
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| 251 | * participants and there are ≥ 2 parties
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| 252 | */
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| 253 | private boolean isViable(Iterable<Vote> voteList) {
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| 254 | Set<PartyId> parties = getParties(voteList);
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| 255 | Integer totalpower = getTotalPower(parties);
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| 256 | return parties.size() >= 2 && totalpower >= getMinPower(voteList)
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| 257 | && totalpower <= getMaxPower(voteList);
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| 258 | }
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| 259 |
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| 260 | /**
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| 261 | * @param voteList list of all {@link Vote}s
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| 262 | * @return all parties that did a vote
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| 263 | */
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| 264 | public static Set<PartyId> getParties(Iterable<Vote> voteList) {
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| 265 | Set<PartyId> parties = new HashSet<>();
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| 266 | for (Vote vote : voteList) {
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| 267 | parties.add(vote.getActor());
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| 268 | }
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| 269 | return parties;
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| 270 | }
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| 271 |
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| 272 | /**
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| 273 | *
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| 274 | * @param votes a list of {@link Vote}s on one Bid. All parties must be
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| 275 | * known
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| 276 | * @return the minimum voting power needed for this group, so that all can
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| 277 | * accept. This is equal to the max of the vote.getMinPower
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| 278 | */
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| 279 | private Integer getMinPower(Iterable<Vote> votes) {
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| 280 | int max = 0;
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| 281 | for (Vote vote : votes) {
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| 282 | max = Math.max(max, vote.getMinPower());
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| 283 | }
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| 284 | return max;
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| 285 | }
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| 286 |
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| 287 | /**
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| 288 | *
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| 289 | * @param votes a list of {@link Vote}s on one Bid. All parties must be
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| 290 | * known
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| 291 | * @return the maximum voting power needed for this group, so that all can
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| 292 | * accept. This is equal to the min of the vote.getMaxPower
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| 293 | */
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| 294 | private Integer getMaxPower(Iterable<Vote> votes) {
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| 295 | int min = Integer.MAX_VALUE;
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| 296 | for (Vote vote : votes) {
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| 297 | min = Math.min(min, vote.getMaxPower());
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| 298 | }
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| 299 | return min;
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| 300 | }
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| 301 |
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| 302 | private Map<Bid, Set<Vote>> getAllBids1() {
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| 303 | Map<Bid, Set<Vote>> bids = new HashMap<>();
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| 304 | for (Votes votes : allvotes.values()) {
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| 305 | for (Vote vote : votes.getVotes()) {
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| 306 | Bid bid = vote.getBid();
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| 307 | Set<Vote> list = bids.get(bid);
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| 308 | if (list == null)
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| 309 | list = new HashSet<Vote>();
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| 310 | list.add(vote);
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| 311 | bids.put(bid, list);
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| 312 | }
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| 313 | }
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| 314 | return bids;
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| 315 | }
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| 316 |
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| 317 | @Override
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| 318 | public int hashCode() {
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| 319 | final int prime = 31;
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| 320 | int result = 1;
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| 321 | result = prime * result
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| 322 | + ((allvotes == null) ? 0 : allvotes.hashCode());
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| 323 | result = prime * result + ((powers == null) ? 0 : powers.hashCode());
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| 324 | return result;
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| 325 | }
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| 326 |
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| 327 | @Override
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| 328 | public boolean equals(Object obj) {
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| 329 | if (this == obj)
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| 330 | return true;
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| 331 | if (obj == null)
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| 332 | return false;
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| 333 | if (getClass() != obj.getClass())
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| 334 | return false;
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| 335 | CollectedVotes other = (CollectedVotes) obj;
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| 336 | if (allvotes == null) {
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| 337 | if (other.allvotes != null)
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| 338 | return false;
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| 339 | } else if (!allvotes.equals(other.allvotes))
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| 340 | return false;
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| 341 | if (powers == null) {
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| 342 | if (other.powers != null)
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| 343 | return false;
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| 344 | } else if (!powers.equals(other.powers))
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| 345 | return false;
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| 346 | return true;
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| 347 | }
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| 348 |
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| 349 | @Override
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| 350 | public String toString() {
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| 351 | return "CollectedVotes[" + allvotes + "," + powers + "]";
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| 352 | }
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| 353 |
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| 354 | }
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