An Unreal Engine implementation of the Glicko-2 player rating system.
The rating system has two components: the configuration and rating objects. The values in Glicko described all of the configurable components and can be changed in the project settings in Edit -> ProjectSettings -> UE Glicko; this includes the default rating values and system constants. Details of how to configure the rating system are described in the Glicko-2 paper.
New player ratings can be created as follows:
// Create a new Rating instance with the default rating
static const UGlickoSettings* Glicko = UGlickoSettings::GetGlickoSettings();
URating* r = URating::MakeRating(Glicko->DefaultRating);
// Create a new Rating instance with a specific rating
URating* r = URating::MakeRating(1500);
// Create a new Rating instance with a specific rating and deviation
URating* r = URating::MakeRating(1500, 200);
// Create a new Rating instance with a specific rating, deviation and volatility
URating* r = URating::MakeRating(1500, 310, 0.04);
In the Glicko rating system, player ratings are updated in batches. As described in the Glicko-2 paper, the ideal number of games in a rating period is 10-15. As such, the primary method for updating a rating is the URating::Update() method. This arguments to the URating::Update() method are a game count, an array of opponent ratings and the outcome of the games. As per the Glicko-2 paper, a victor has the score 1.0, a draw is scored as 0.5 and a loss is 0.0.
// The test player
URating* player = URating::MakeRating(1500, 200);
// Three opponents
URating* opponent1 = URating::MakeRating(1400, 30);
URating* opponent2 = URating::MakeRating(1550, 100);
URating* opponent3 = URating::MakeRating(1700, 300);
// Update the rating from the 3 games
TArray<FMatch> matches = TArray<FMatch>();
matches.Add(FMatch::MakeMatch(opponent1, 1.0));
matches.Add(FMatch::MakeMatch(opponent2, 0));
matches.Add(FMatch::MakeMatch(opponent3, 0));
player->Update(matches);
player->Apply();
A version of URating::Update() that takes a single opponent and game outcome can also be used. This method is useful in situations where the ratings are updated with each game, such as an online chess environment:
// Player1's rating
URating* player1 = URating::MakeRating(1500, 200);
// Player2's rating
URating* player2 = URating::MakeRating(1400, 30);
// Update the ratings based on a game in which player1 beat player2
player1->Update(FMatch::MakeMatch(player2, 1.0));
player2->Update(FMatch::MakeMatch(player1, 0.0));
player1->Apply();
player2->Apply();
If a player does not play any games during a rating period, the Glicko-2 document recommends that their rating deviation is updated based on the volatility, as described in Step 6 of the Glicko pdf. This can be achieved using the URating::Decay() function:
player->Decay();
After calling URating::Update() or URating::Decay(), the changes must be applied using the URating::Apply() method. This is necessary because updates to multiple URating instances may depend on each other and ratings should be not updated until all outcomes have been processed.
player->Apply();
This implementation of the Glicko-2 rating system is distributed under The MIT License.