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34 lines
967 B
PHP
34 lines
967 B
PHP
<?php
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namespace Moserware\Skills\Elo;
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require_once(dirname(__FILE__) . "/../GameInfo.php");
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require_once(dirname(__FILE__) . "/../Numerics/GaussianDistribution.php");
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require_once(dirname(__FILE__) . "/KFactor.php");
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require_once(dirname(__FILE__) . "/TwoPlayerEloCalculator.php");
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use Moserware\Skills\GameInfo;
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use Moserware\Numerics\GaussianDistribution;
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class GaussianEloCalculator extends TwoPlayerEloCalculator
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{
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// From the paper
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const STABLE_KFACTOR = 24;
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public function __construct()
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{
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parent::__construct(new KFactor(self::STABLE_KFACTOR));
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}
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public function getPlayerWinProbability(GameInfo $gameInfo, $playerRating, $opponentRating)
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{
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$ratingDifference = $playerRating - $opponentRating;
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// See equation 1.1 in the TrueSkill paper
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return GaussianDistribution::cumulativeTo(
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$ratingDifference
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/
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(sqrt(2) * $gameInfo->getBeta()));
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}
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}
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?>
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