The 2012 Arimaa World Championship

Overview: Each year a tournament is held to determine the best human Arimaa player in the world. The winner will receive an official Arimaa World Champion certificate. All participants will also receive a cash prize for each game they win. Spectators can watch some exciting Arimaa action and take part in a contest to predict the outcome of the games.

Registration begins 8PM EST Nov 7, 2011
Registration ends 8PM EST Jan 1, 2011
Ratings fixed 8PM EST Sunday Jan 8, 2012
First round begins Wednesday Jan 11, 2012; with one round per week
Tournament ends Late March 2012

Prizes: The total World Championship Prize Fund will be divided by the number of games in the tournament and that amount will be awarded to the winner of each game. In addition the 1st place winner will also receive an official Arimaa World Champion certificate.

Registration: This tournament is open to everyone. Interested players must register before the deadline mentioned above. The registration fee starts at $80 USD on the first day of registration and increases by $1 USD each day. 100% of the registration fees will be added to the prize fund. Players may unregister before the registration deadline to receive a full refund.

Resigning: There is no penalty for resigning a game, however resigning is discouraged and completing a game to the end is highly encouraged.

Commemorative Gear: Commemorative World Championship T-shirts listing the names of all participants and match-ups will be available for purchase after the event.

Location of games: All games will be played in the Arimaa gameroom over the Internet. The players are responsible for providing their own reliable computer and Internet connection. There will not be a rematch if a player loses a game due to problems with their computer or Internet connection or even the game client program. However, if there is a problem with the game server, the tournament director will consider a rematch.

Time of games: The players will play one game per week. The players will submit a web form to indicate what times they are available to play during the upcoming week. If a player does not submit the preferred times then any preferred times they had previously submitted will be used. If no preferred times have been provided then any time will be considered a preferred time. After 8pm EST Monday the players will be notified of the opponent they have been paired with for that round along with the scheduled time of the game. The players will have 24 hours to communicate with each other and agree to a new time and update their preferred times. On Tuesday after 8pm EST the tournament coordinator will run the scheduler to fix the final game time and notify both players of the scheduled game time. The earliest a game could begin is on 7pm EST Wednesday and the latest is on 5pm EST the following Monday. The final game times cannot be changed.

Forfeits: If a player does not show up for the game within 15 minute after the scheduled start time then that player will lose by forfeit. To claim the forfeit the player that showed up just needs to exit the game window after the 15 minutes are over. However, the player can choose to give the opponent more time by keeping the window open. A player losing by forfeit may not appeal for a rematch regardless of the reason for being late. Also the player who forfeits a game is automatically removed from the tournament and will not play in future rounds unless the player notifies the tournament director and the tournament director accepts the appeal.

Tournament format: A Floating Triple Elimination tournament

    The tournament coordinator runs a program which is used to pair the players, assign a bye in rounds with odd number of players and to select the color of each player.

    The pairing algorithm for the Floating Triple Elimination attempts to best meet the following constraints:

    1. Players are initially ranked based on WHRX ratings. A players WHRX rating is their WHRE rating if it is based on at least 5 games, otherwise their WHR rating if it is based on at least 5 games, otherwise their gameroom rating.
    2. Everyone plays until they have lost three times. At the end of each round, any player who has lost for the third time is eliminated.
    3. If an odd number of players remain, the bye must go to some player among the players with the fewest byes so far.
    4. For every number N, minimize the number of pairings occurring for the Nth time, without regard for any number of pairings occurring less than N times.
    5. Give any bye to a player with as few losses as possible.
    6. For every number N, minimize the number of pairings between players whose number of losses differ by N, without regard for any number of pairings between players whose number of losses differ by less than N.
    7. Calculate tournament performance ratings for all players on the basis of the Bradley-Terry model and all past games including those in which one player forfeited, but not both, plus, for each player, a virtual half-weighted draw against a fixed dummy player, identically rated against everyone. No existing ratings are used in the calculation.
    8. Give any bye to a player with an as high as possible tournament performance rating.
    9. Give any bye to a player who is as best seeded as possible.
    10. Based on a ranking of the non-eliminated players primarily by least number of losses, secondarily by tournament performance rating and thirdly by seed, maximize the sum of the squares of the differences in rank among paired players with equal number of losses minus the sum of the squares of the differences in rank among paired players with different number of losses.
    11. Color assignment is done as described later considering all games.
    12. All games are played according to the Arimaa Match Rules.

    This tournament format is designed only to clearly recognize a first place winner. Recognition of second and third place will be done based on number of games won. Ties for second and third place will not be broken with additional games and all players that tied for these positions will be recognized.

    Color Assignment:
    Color assignment within each pairing will be made on the basis of games each player has played within the tournament, including forfeits. The rules are given in order of strict priority, i.e. a later rule will apply only if no prior rule distinguishes between the players.

    1. Assign Gold to the player with a lower total of previous games as Gold minus previous games as Silver.
    2. Assign Gold to the player with fewer previous games as Gold among games between the two players.
    3. Break both color streaks. If possible give both players a different color then the color they played with in their most recent game.
    4. Break the color streak of the player with the longer streak.
    5. Swap colors with respect to the last time the two players played against each other.
    6. Assign color arbitrarily.

    Time controls: All games will be played with a time control of: 90s/5m/100/0/6h/5m.


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