Member Rankings

About

The Go Center operates an automatic player ranking system. The goal is easily enable players to choose opponents and handicaps so that both players have a challenging game.

Estimate

The ranking system is an opt-in system. You must go to the go center and estimate your rank at least once to get into the system.

At the Go Center, find the "Ranking Board" and touch it. You will get a dialog box where you select the range of your rank, then another dialog where you pick your specific rank. Many members have used their AGA or KGS rank as a starting estimate.

If you ever decide you'd like to take yourself out of the ranking system, then touch the Ranking Board again, and choose "No Rank".

dialogs

Playing Games

Your ranking is adjusted based on the games you play at the Go Center. For a game to included in the ranking calculation:

Playing with reasonable handicaps will result in games that more influence your ranking, and make the ranking more accurate. Games that are too predictable: even games played between players many ranks apart, or playing with much lower than appropriate handicap, will have little or no effect on your ranking.

Updates

Your rank at the time you start the game will be recorded with the game.

The system runs rankings periodically. Expect to see updates about once a week. However, the system is tuned for stability, and so rankings move relatively smoothly and slowly compared to some other systems (like KGS).

If you find that your ranking is off (perhaps you've been playing in RL and have advanced much, or you've been studying Joseki and fell behind...) You can always go to the Ranking Board in world and re-estimate your rank.

System Details

The Go Center uses an implementation of the GoR. This is the same system that is in use by the European Go Federation. The system is openly documented, well tested, and several open source software implementations exist.

In essence, for each game played, the system estimates likelihood of each player winning based on their current rating, and the game parameters. The number of points added or removed from a players rating is in proportion to how likely the actual outcome was against the prediction. The GoR web site has full details of the math.

Ratings and Ranks

GoR is a rating system in which each player is assigned a numerical rating. These correspond to the more conventional ranks in the following way: A rating of 2100 is equivalent to 1 dan, and each 100 points of rating added or removed is equivalent to one stone stronger or weaker. Since the ratings are kept to the point, ratings such as 2135 and 962 represent "strong 1 dan" and "weak 11 kyu".

The Go Center keeps and displays the more human friendly rank equivalent in most places. Further, the rank is a "filtered" version of the rating, which keeps the rank from oscillating back and forth if your strength is near the mid-point of two ranks.

Implementation

There are some differences in the Go Center's implementations from the GoR system as used by the EGF. Here are the full technical details for those who care.

Lower Bound: The Go Center does not use the rating of 100 as a lower bound on player's ranks. New players are started off at -900 which corresponds to 30 kyu.

Board Size: 13x13 and 9x9 games are included in the system. The effect on ratings is divided by a factor based on the board size. The weight of handicap stones on equalizing the ranks is similarly weighted, so each handicap stone on 13x13 makes up for about 2 ranks, and on 9x9, about 5.

Calculations: The 'a' and 'con' values are computed from simple polynomials, rather than GoR's tables. The values match the tables to high degree, but can be computed for the wider range of ratings