/**
* Shuffles the song proposals at weighted random. For every position in the list
*
* <pre>
* P[song choosen] = shifted_vote / votesSum
* </pre>
*
* The votes get shifted to be pure positive and stretched, so that higher ratings are more
* probable to appear first
*
* <pre>
* shifted_vote = (vote[song] + 1)<sup>STRETCH_FACTOR</sup>
* </pre>
*
* @param votes The song votes
* @return The shuffled song list
*/
private List<BaseSong<BaseArtist, BaseAlbum>> getShuffledSongsAtWeightedRandom(
Map<BaseSong<BaseArtist, BaseAlbum>, Double> votes) {
final double STRETCH_FACTOR = 4.0f;
Map<BaseSong<BaseArtist, BaseAlbum>, Double> remainingVotes =
new HashMap<BaseSong<BaseArtist, BaseAlbum>, Double>(votes);
// Calculate the total vote sum
double voteSum = 0.0d;
for (Map.Entry<BaseSong<BaseArtist, BaseAlbum>, Double> entry : remainingVotes.entrySet()) {
double adjustedVote =
Math.pow(entry.getValue() + 1.0d, STRETCH_FACTOR); // to not have negative votes
remainingVotes.put(entry.getKey(), adjustedVote);
voteSum += adjustedVote;
}
// Shuffle songs
List<BaseSong<BaseArtist, BaseAlbum>> ret =
new ArrayList<BaseSong<BaseArtist, BaseAlbum>>(votes.size());
while (ret.size() < votes.size()) {
// Search the next weighted random song
double rand = RandomProvider.getRandom().nextDouble() * voteSum;
for (Map.Entry<BaseSong<BaseArtist, BaseAlbum>, Double> entry : remainingVotes.entrySet()) {
if (rand <= entry.getValue()) {
// Add the song
ret.add(entry.getKey());
// Reduce the search space for the next round
remainingVotes.remove(entry.getKey());
voteSum -= entry.getValue();
break;
} else {
rand -= entry.getValue();
}
}
}
return ret;
}
/**
* Returns the set of songs which are proposed by the agents.
*
* @param proposalTimes
* @return The songs
*/
private List<BaseSong<BaseArtist, BaseAlbum>> getProposedSongs(AgentsTiming proposalTimes) {
Set<IAgent> agents = agentManager.getAgents();
// Using set here to ensure no duplicate entries
Set<BaseSong<BaseArtist, BaseAlbum>> proposedSongs =
new HashSet<BaseSong<BaseArtist, BaseAlbum>>(SONG_PROPOSAL_USAGE_COUNT * agents.size());
for (IAgent agent : agents) {
throwIfAborted();
StopWatch stopWatch = StopWatch.start();
List<BaseSong<BaseArtist, BaseAlbum>> agentProposals =
new ArrayList<BaseSong<BaseArtist, BaseAlbum>>(agent.suggestSongs(SONG_PROPOSAL_COUNT));
// Get #SONG_PROPOSAL_USAGE_COUNT items of them at random
while (agentProposals.size() > SONG_PROPOSAL_USAGE_COUNT) {
agentProposals.remove(RandomProvider.getRandom().nextInt(agentProposals.size()));
}
proposedSongs.addAll(agentProposals);
proposalTimes.addAgentTiming(agent, stopWatch.stop());
}
return new ArrayList<BaseSong<BaseArtist, BaseAlbum>>(proposedSongs);
}