glicko2-php

A PHP implementation of Glicko2, a rating system for game ladders. Glicko2 is a refinement of the well-known Elo rating system that adds the concepts of rating deviation, volatility, and rating decay.

This is a fork of Guangcong Luo's version, going straight from the PDF and trying to match exactly what the PDF states. I also confirmed the test case mentioned in the PDF was accurate, I believe Luo's version was not accurate - Therefore I created this. This also keeps tracks of wins/losses/draws for players.

The original glicko2phplib was written by Noah Smith on 2011 June 7. That version contains significant mathematical errors. This is a fork by Guangcong Luo on 2012 Sept 28 that corrects these errors, and also updates it to be compatible with PHP 5. It should also work on PHP 4, although I have not tested that.

Usage

Glicko2Player([$rating = 1500 [, $rd = 350 [, $volatility = 0.06 [, $mu [, $phi [, $systemconstant = 0.50 ]]]]]])

For new players, use the default values for rating, rd, and volatility.

The systemconstant should be between 0.3 and 1.2, depending on system itself (this is game dependent, and must be set by estimation or experimentation)

Updating a Glicko2Player

Add wins, losses, and draws to a player:

$Alice = new Glicko2Player();
$Bob = new Glicko2Player();
$Charlie = new Glicko2Player();
$David = new Glicko2Player();

$Alice->AddWin($Bob);
$Alice->AddWin($Charlie)

$Bob->AddLoss($Alice);
$Bob->AddWin($Charlie);

$Charlie->AddLoss($Alice);
$Charlie->AddLoss($Bob);

$Alice->Update();
$Bob->Update();
$Charlie->Update();
$David->Update(); // David did not participate, but must be updated

PDF Test case (see: http://www.glicko.net/glicko/glicko2.pdf)

$Todd = new Glicko2Player(1500,200);
$Alice = new Glicko2Player(1400,30);
$Bob = new Glicko2Player(1550,100);
$Charlie = new Glicko2Player(1700,300);

$Todd->AddWin($Alice);
$Todd->AddLoss($Bob);
$Todd->AddLoss($Charlie);
$Todd->Update();

var_dump($Todd);
/*
object(Glicko2Player)#1 (9) {
  ["rating"]=> float(1464.0506705393)
  ["rd"]=> float(151.51652412386)
  ["vol"]=> float(0.059995984286488)
  ["mu"]=> float(-0.20694096667525)
  ["phi"]=> float(0.87219918813073)
  ["tau"]=> float(0.5)
  ["wins"]=> int(1)
  ["losses"]=> int(2)
  ["M":"Glicko2Player":private]=> array(0) {}
}
*/

License

GNU LGPL version 3.0