What is Glicko system?

In patch 7.33 valve announced ” we’re switching to a different algorithm called Glicko, which should let you quickly and accurately get matched with other players at a similar skill level”, but what does that mean acutally?

Glicko is a matchmaking algorithm used in competitive games to assign ratings to players based on their performance in matches against other players. The algorithm was developed by Dr. Mark Glickman in the late 1990s as an improvement over the Elo rating system, which is widely used in chess.

The Glicko system uses a player’s rating and volatility (how consistent they are in their performance) to calculate their expected performance in a match against another player. After a match is played, the algorithm updates the player’s rating and volatility based on the outcome of the match and the ratings of the opponent.

One of the benefits of the Glicko system is that it can account for the uncertainty in a player’s rating, which is particularly important for new players or players who haven’t played many matches. The system assigns a rating deviation to each player that represents the amount of uncertainty in their rating.

Dota 2 recently announced that it has adopted a new matchmaking algorithm called Glicko. The goal of this new algorithm is to improve the accuracy and speed of matchmaking, allowing players to more quickly and accurately be matched with other players at a similar skill level.

The Glicko algorithm takes into account a player’s Rank Confidence, which is a measure of how certain the algorithm is about a player’s skill level. By factoring in Rank Confidence, the algorithm can make more accurate decisions about rank gains and losses.

As part of the switch to the new matchmaking system, all players will be placed back into a short calibration mode, initially seeded by their previous rank. However, calibration will no longer be a fixed number of matches. Instead, a player will be considered calibrated whenever their Rank Confidence is above a certain threshold.

It’s likely that players may end up with a different medal than they had before, but they should still expect to be matched with players of a similar skill level. In addition, matches will no longer have a fixed MMR gain/loss, but will be variable based on a number of factors, including the Ranks and Rank Confidence of the participants. However, to prevent particularly negative outcomes, the gain/loss per match will be capped.

Furthermore, a player’s Rank Confidence will slowly lower over time if the player does not play matches. Dota 2 has been running both matchmaking systems simultaneously behind the scenes for a while now to help build confidence in these changes.

While accurate MMR is only one of many factors that impact match quality, the Dota 2 development team is interested in hearing feedback from players on these changes. Overall, the Glicko matchmaking system has the potential to greatly improve the matchmaking experience for Dota 2 players.