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The rating system takes the official games database of http://renju.net as input data and performs calculation on daily basis. Ratings are calculated starting from earliest tournament, proceeding further, tournament by tournament. Tournaments with invalid data (such as invalid end date) are skipped until their data is corrected by administrators. For every tournament the system calculates rating difference for every player's game (Rdiff) and then applies those differences to player's rating when the tournament is over. Rating calculation formula ---------------------------- Rdiff = K*(Sa-Se) where Rdiff - rating difference for single game K - K factor (depends on type of rating: established or provisional, see below) Sa - actual score (0 for loss, 1 for win and 0.5 for draw) Se - expected score (see formula below) The expected score is calculated as following: Se = 1/(1+10^((R2-R1)/400)) where R1 - is player's rating (player whose rating is calculated) R2 - is opponent's rating Established and Provisional ratings ------------------------------------ If the player has 10 or more games against Established players and gained 3 points from Established players, then such player has Established rating. Other players have Provisional rating. Provisional rating is calculated by formula: Rp = Ra + 400*(W-L)/N where Ra - average rating of established opponents W - number of wins L - number of losses N - number of games (all versus established) K factor. --------- K factor is a coefficient which defines maximum rating deviation from player's game result. For Established player playing versus another Established player the K factor = 32 |