mirror of
https://github.com/furyfire/trueskill.git
synced 2024-09-20 07:22:15 +00:00
105 lines
3.9 KiB
PHP
105 lines
3.9 KiB
PHP
<?php
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namespace Moserware\Skills\Elo;
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require_once(dirname(__FILE__) . "/../PairwiseComparison.php");
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require_once(dirname(__FILE__) . "/../RankSorter.php");
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require_once(dirname(__FILE__) . "/../SkillCalculator.php");
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require_once(dirname(__FILE__) . "/../PlayersRange.php");
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require_once(dirname(__FILE__) . "/../TeamsRange.php");
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use Moserware\Skills\PairwiseComparison;
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use Moserware\Skills\RankSorter;
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use Moserware\Skills\SkillCalculator;
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use Moserware\Skills\SkillCalculatorSupportedOptions;
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use Moserware\Skills\PlayersRange;
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use Moserware\Skills\TeamsRange;
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abstract class TwoPlayerEloCalculator extends SkillCalculator
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{
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protected $_kFactor;
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protected function __construct(KFactor $kFactor)
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{
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parent::__construct(SkillCalculatorSupportedOptions::NONE, TeamsRange::exactly(2), PlayersRange::exactly(1));
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$this->_kFactor = $kFactor;
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}
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public function calculateNewRatings($gameInfo,
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array $teamsOfPlayerToRatings,
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array $teamRanks)
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{
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$this->validateTeamCountAndPlayersCountPerTeam($teamsOfPlayerToRatings);
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RankSorter::sort($teamsOfPlayerToRatings, $teamRanks);
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$result = array();
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$isDraw = ($teamRanks[0] === $teamRanks[1]);
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$team1 = $teamsOfPlayerToRatings[0];
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$team2 = $teamsOfPlayerToRatings[1];
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$player1 = each($team1);
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$player2 = each($team2);
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$player1Rating = $player1["value"]->getMean();
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$player2Rating = $player2["value"]->getMean();
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$result[$player1["key"]] = $this->calculateNewRating($gameInfo, $player1Rating, $player2Rating, $isDraw ? PairwiseComparison::DRAW : PairwiseComparison::WIN);
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$result[$player2["key"]] = $this->calculateNewRating($gameInfo, $player2Rating, $player1Rating, $isDraw ? PairwiseComparison::DRAW : PairwiseComparison::LOSE);
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return $result;
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}
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protected function calculateNewRating($gameInfo, $selfRating, $opponentRating, $selfToOpponentComparison)
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{
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$expectedProbability = $this->getPlayerWinProbability($gameInfo, $selfRating, $opponentRating);
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$actualProbability = $this->getScoreFromComparison($selfToOpponentComparison);
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$k = $this->_kFactor->getValueForRating($selfRating);
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$ratingChange = $k * ($actualProbability - $expectedProbability);
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$newRating = $selfRating + $ratingChange;
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return new EloRating($newRating);
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}
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private static function getScoreFromComparison($comparison)
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{
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switch ($comparison)
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{
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case PairwiseComparison::WIN:
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return 1;
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case PairwiseComparison::DRAW:
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return 0.5;
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case PairwiseComparison::LOSE:
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return 0;
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default:
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throw new Exception("Unexpected comparison");
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}
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}
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public abstract function getPlayerWinProbability($gameInfo, $playerRating, $opponentRating);
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public function calculateMatchQuality($gameInfo, array $teamsOfPlayerToRatings)
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{
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validateTeamCountAndPlayersCountPerTeam($teamsOfPlayerToRatings);
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$team1 = $teamsOfPlayerToRatings[0];
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$team2 = $teamsOfPlayerToRatings[1];
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$player1 = $team1[0];
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$player2 = $team2[0];
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$player1Rating = $player1[1]->getMean();
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$player2Rating = $player2[1]->getMean();
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$ratingDifference = $player1Rating - $player2Rating;
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// The TrueSkill paper mentions that they used s1 - s2 (rating difference) to
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// determine match quality. I convert that to a percentage as a delta from 50%
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// using the cumulative density function of the specific curve being used
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$deltaFrom50Percent = abs(getPlayerWinProbability($gameInfo, $player1Rating, $player2Rating) - 0.5);
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return (0.5 - $deltaFrom50Percent) / 0.5;
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}
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}
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?>
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