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GPCF Library
The Greater Peoria Chess Foundation Library
You may check one or two books out for up to two weeks and then return the book(s) or request renewal for another two weeks. Please do not write in any of the books, or mark pages. Please leave the book in the same condition for future users. The books may be picked up at Peoria Academy on Tuesdays, Hult on Fridays or the Lakeview Chess club on Monday nights.
E-mail your requests to: Mike Leali.
Swiss Tournament Pairings
The Swiss System is the pairing system used in most chess tournaments in the US. It allows an unlimited number of players to participate over any number of rounds and produces a reasonable result leading towards a tournament winner.
Ideally, a Swiss Tournament should have enough rounds, so that if every game were decisive, there would be a clear champion. Like a knock-out tournament, where all losers go home, raising 2 to the power of the number of rounds played yields the maximum number of players the tournament can accomodate and guarantee a clear first place winner. For example, a 4 round tournament can produce a clear winner if there are no more than 2^4 or 16 players. Likewise, a 5-round tournament can support 32 players and guarantee a clear winner.
In practice the number of draws among the leaders modifies the number so often a clear winner is determined even if there are more players than ideal. There are also modifications that the tournament director can make to speed up the process of determining a winner, called Accelerated Pairings.
The basic rules for pairing (there are more details than presented here - see the USCF Official Rules for a complete explanation) are as follows.
1) Players are not allowed to play the same player twice in the same tournament. Round Robin pairings should be used if it expected that it will be necessary for players to play each other more than once.
2) Players are placed into score groups. In general, players within the same score group are eleigble to play each other.
3) Players within a score group are sorted by rating. If there are an odd number of players in a score group, the lowest rated player in the score group will be paired with the highest rated player in the next or lower score group. In the first round, or in the last score group in later rounds, the odd player is given a bye. Note that the bye goes to the lowest rated player. Unrated players are not given a bye unless there is no other legal pairing with that score group.
4) The top half of the score group plays the bottom half of the score group. Specifically, the top player in the top half plays the top player in the bottom half, and so on, with the lowest player in the top half playing the lowest player in the bottom half. For this purpose, unrated players are listed after all the rated players and paired as if they had a low rating.
5) If adjustments need to be made, the lower section players are moved, the upper half players retain their relative positions. Adjustments may be required if two players are paired who have played each other previously in the tournament. Adjustments may also be made to correct colors where there is a color imbalance (one player has played more of one color than his opponent), or to alternate colors (ideally a player who played white in one round is due black the next, etc).
Before the early 1990s, most pairings were made manually. Since then, most tournaments are paired by computer according to the same rules. The first computer pairing program used in a national scholastic chess tournament was in Peoria in the 1989 US K-9 Championship with a program written by Murrel Rhodes. Since then, a number of pairing and Tournament Direction programs have been sold commercially. The GPCF uses the Swiss-sys. Bloomington-Normal chess directors use the Win-swiss system.
Tie-Breaks
Money prizes are always split when more than one player ties for a tournament prize, but some non-monitary prizes, for example trophies, cannot be split and so some way must be devised to determine who among those with the same score should most equitably receive the prize. There have been many tie-break systems devised to try and accomplish this task. There is no perfect tie-break system, all have strengths and weaknesses. Tournament directors try to find the one that they believe is the most fair for their tournament.
When tie-breaks are used they are announced ahead of the start of the tournament. The one's used can be found in the tournament annoucements and fliers and should also be posted at the tournament site. Frequently one tie-break system may not break all the ties and most tournaments use several tie-breaks, caluclated in sequence, to determine the final tournament rank of the players.
The following lists of tie-breaks are among the most popular:
Solkoff
Modified_Median
Sonneborn-Berger
Performance_of_Opposition
Average_Opposition
Kashdan
Links
Greater Peoria Chess Federation (GPCF)
Bloomington-Normal Scholastic Chess
Chess Teachers (Chicago)
United States Chess Federation (USCF)
Illinois Chess Assocaition (ICA)
Illinois Valley Chess Club (LaSalle-Peru)
Colley's Chess Club
