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* Copyright 2011 BetaSteward_at_googlemail.com. All rights reserved.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list
* of conditions and the following disclaimer in the documentation and/or other materials
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package mage.server.rating;
import java.util.Date;
/**
*
* @author Quercitron
*/
public class GlickoRatingSystem {
// rating deviation will grow back from 50 to max 350 in 2 years
public static final double C = 0.00137934314767061324980397708525;
public static final double BaseRating = 1500;
public static final double BaseRD = 350;
public static final double MinRD = 30;
private static final double Q = Math.log(10) / 400;
public static GlickoRating getInitialRating() {
return new GlickoRating(GlickoRatingSystem.BaseRating, GlickoRatingSystem.BaseRD, 0);
}
public static int getDisplayedRating(GlickoRating rating) {
long currentTime = new Date().getTime();
double updatedRatingDeviation = getUpdatedRD(rating, currentTime);
return (int) Math.max(rating.getRating() - 2 * updatedRatingDeviation, 0);
}
public static int getDefaultDisplayedRating() {
return getDisplayedRating(getInitialRating());
}
public void updateRating(GlickoRating playerRating, GlickoRating opponentRating, double outcome, long gameTimeMs) {
playerRating.setRatingDeviation(getUpdatedRD(playerRating, gameTimeMs));
opponentRating.setRatingDeviation(getUpdatedRD(opponentRating, gameTimeMs));
GlickoRating newPlayerRating = getNewRating(playerRating, opponentRating, outcome);
GlickoRating newOpponentRating = getNewRating(opponentRating, playerRating, 1 - outcome);
playerRating.setRating(newPlayerRating.getRating());
playerRating.setRatingDeviation(newPlayerRating.getRatingDeviation());
playerRating.setLastGameTimeMs(gameTimeMs);
opponentRating.setRating(newOpponentRating.getRating());
opponentRating.setRatingDeviation(newOpponentRating.getRatingDeviation());
opponentRating.setLastGameTimeMs(gameTimeMs);
}
private static double getUpdatedRD(GlickoRating rating, long gameTimeMs) {
double newRatingDeviation;
if (rating.getLastGameTimeMs() != 0)
{
double newRD = Math.sqrt(
rating.getRatingDeviation() * rating.getRatingDeviation()
+ C * C * Math.max(gameTimeMs - rating.getLastGameTimeMs(), 0));
newRatingDeviation = Math.max(Math.min(BaseRD, newRD), MinRD);
}
else
{
newRatingDeviation = BaseRD;
}
return newRatingDeviation;
}
private GlickoRating getNewRating(GlickoRating playerRating, GlickoRating opponentRating, double outcome) {
double RD = playerRating.getRatingDeviation();
double g = gFunc(opponentRating.getRatingDeviation());
double p = -g * (playerRating.getRating() - opponentRating.getRating()) / 400;
double e = 1 / (1 + Math.pow(10, p));
double d2 = 1 / (Q * Q * g * g * e * (1 - e));
// todo: set minimum K?
double newRating = playerRating.getRating() + Q / (1 / RD / RD + 1 / d2) * g * (outcome - e);
double newRD = Math.sqrt(1 / (1 / RD / RD + 1 / d2));
return new GlickoRating(newRating, newRD);
}
private double gFunc(double rd) {
return 1 / Math.sqrt(1 + 3 * Q * Q * rd * rd / Math.PI / Math.PI);
}
}