The 2011 Arimaa Open Classic and World Championship

Overview: Each year a tournament is held to determine the best human Arimaa player in the world. The tournament is conducted in two phases. First there is a swiss format tournament which is open to everyone and referred to as the Open Classic or preliminary. The top 8 performers from this phase move on to the second phase which is a floating double elimination format tournament referred to as the World Championship or finals.

Schedule:

Registration begins	Nov 1, 2010
Registration ends	6PM EST Saturday Jan 1, 2011
Ratings fixed	8PM EST Sunday Jan 2, 2011
First round begins	Wednesday Jan 5, 2011; with one round per week
Tournament ends	Late March 2011

Prizes:

• 1st place winner will receive:
  1. an official Arimaa World Champion certificate
  2. the 1st place cash prize from the Prize Fund.
  3. a $100 gift certificate towards purchase of games from Z-Man Games¹.
  4. a yearly membership on LittleGolem.net (value of 19 EUR)
  5. the WYPS game in your language of choice (value of 29 EUR)
• 2nd place winner will receive:
  1. the 2nd place cash prize from the Prize Fund.
  2. a $50 gift certificate towards purchase of games from Z-Man Games¹.
  3. a yearly membership on LittleGolem.net (value of 19 EUR)
• 3rd place winner will receive:
  1. the 3rd place cash prize from the Prize Fund.
  2. $25 gift certificate towards purchase of games from Z-Man Games¹.
  3. a yearly membership on LittleGolem.net (value of 19 EUR)
• The total cash from 'Game Winners' portion of the Prize Fund will be divided by the number of games in the finals and that amount will be awarded to the winner of each game.

Registration: This tournament is open to everyone. Interested players must register before the deadline mentioned above. All players are expected to make a contribution of $10 USD to the prize fund. If this would be a hardship for you, you may request to have it waived. If you find out later that you are unable to participate, a refund of the registration fee can be requested before the event starts. The top 8 finishers from this tournament are considered the top human Arimaa players and are the primary candidates to defend the Arimaa Challenge. They may be invited to help defend the Arimaa Challenge if willing and able to do so.

Withdrawing: Once the tournament begins players are highly discouraged from withdrawing. There is a penalty of $20 USD for withdrawing from the tournament.

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

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 7pm 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 7pm 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 tournament directors accepts the appeal.

Tournament format: Swiss preliminary to select the top 8 performers followed by a Floating Double Elimination final

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 Swiss preliminary attempts to best meet the following objectives:

1. The number of rounds to be played is determined by the number of participants and is declared before the start of the Swiss. The following table is used to determine the number of rounds.

   # of players	# of rounds	# of wins needed
   1-8	0	0
   9-11	3	1
   12-15	4	2
   16-23	5	3
   24-35	6	4
   36-55	7	5

2. The players are initially ranked based on higher WHR ratings. Ties broken by lower gameroom rating uncertainty then further broken by greater number of games played and finally by older joined date/time.
3. Two players may play each other only once.
4. Players are paired with others of the same score, or nearest score.
5. Color assignment is done as described in a later section.
6. The player order is determined by the aggregate of points won: 1 point for a win and 0 point for a loss (draws are not possible). A player whose opponent fails to appear for a scheduled game receives a win and the opponent a lose. Ties are broken by sum of opponent score from highest to lowest. Ties are further broken by pre-tournament rating from highest to lowest. Ties are further broken by unique random number assigned at start of round.
7. Sum of opponent score (SoS) is calculated as follows:

     P = wins[this player]
     foreach opponent in list_of_opponents[this_player]
       O = wins[opponent]
       T = 1/(1+10^(F*(P-O)/(N+1)))
       SoS += T
   
     where:
       N = Number of rounds that have been played
       F = factor determined by the standard deviation of player ratings
         = 0.5 + stdev(player_ratings)/100
   

8. Pair the players from the top of the list to the bottom as follows: If the player is in the top half of the score group and has not already been paired then try to pair the player against the player in the bottom half of the score group starting at the same relative position in the bottom half as the player is in the top half. If a pair cannot be made then continue down the list within the same score group. After reaching the bottom of the score group then work upwards within the same score group. If a match cannot be found within the same score group then work down the list starting from the top of the next score group.
9. If the player is in the bottom half of the score group and has not already been paired then pair the player against the next player below them in the list and continue down the list until a pair is found.
10. If there is a an odd number of players the player at the very bottom of the list gets a bye.
11. All games are played according to the Arimaa Match Rules.

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

1. Players are initially ranked based on performance in the Open Classic. Ties broken by WHR ratings.
2. Everyone plays until they have lost two times. At the end of each round, any player who has lost for the second 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. Minimize the number of pairings occurring for the Nth time. ...
5. Minimize the number of pairings occurring for the fourth time.
6. Minimize the number of pairings occurring for the third time.
7. Minimize the number of pairings occurring for the second time.
8. Give the bye to the player with the fewest losses.
9. Give the bye to the player with the best ranking in the preliminary.
10. Minimize the number of pairings between players whose number of losses differ by N, etc.
11. Based on a ranking of the non-eliminated players primarily by least number of losses and secondarily 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.
12. Color assignment is done as described later considering all games including the Swiss preliminary.
13. 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. In case of ties for second place addition games will be played to break the tie. A two-way tie for second will be broken by a one-game playoff. A three-way tie for second will be broken by first pairing the two players eliminated in the second-to-last round and the winner playing the last eliminated player. A two-way tie for third will be broken by a one-game playoff. In these tie breaker games the colors are assigned as described in the next section considering all games including the Swiss preliminary.

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 in the Swiss preliminary will be played with a time control of: 60s/5m/75/0/4h/4m. All games in the FDE final will be played with a time control of: 90s/5m/75/0/6h/5m.

Notes:

• The games must be played in one sitting and cannot be adjourned.
• A player will not be allowed to take back a move once it has been submitted.
• The games will contribute to the players' ratings.
• Players are forbidden from using advice or suggestions from others or programs while playing the games. Any player doing so will be eliminated from the championship matches and will not be allowed to take part in future matches for two years.
• The tournament coordinator will carry out the tournament in compliance with the stated rules and does not make any decisions that will effect the course of the tournament. A player may serve as the coordinator.
• The tournament director will serve as the arbitrator in case of disputes. Should a dispute arise about the outcome of a game, the director will review the game and decide if the game should be replayed. A player may not serve as the director.
• The director will also make the final decision on matters of pairing and color assignment. However, the pairings and color assignments are done as much as possible using a program and the need for intervention should be rare.
• The director may require any player to have a web-cam turned on for monitoring during the games. Also the director may send a representative to be present with any player during the games. A player who does not comply will lose by forfeit.
• All decisions made by the director shall be considered final and binding by all parties. The director does not need to look at previous similar cases for precedence and nor does the decision of the director set a precedence for future cases. However, the director is expected to be consistent between rulings and completely unbiased.
• Omar and Aamir Syed reserve the rights to modify the championship tournament details in the future to resolve any logistical problems that may arise.

¹ The gift certificate from Z-Man Games must be used in one order. If the order amount including shipping exceeds the value of the gift certificate the difference must be paid for separately. The gift certificate is not transferable. The order should not be placed through the online shop (though you can use that to check prices and availability). A special contact address will be provided to redeem the gift certificate.

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