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Checkers |
English draughts, known simply as draughts in the United Kingdom and some other countries, and also called American checkers, straight checkers, or simply checkers, is a form of the draughts board game played on an 8×8 board with 12 pieces on each side that may only initially move and capture diagonally forwards. Only when a piece is "kinged" may it move backwards.
As in all draughts variants, English draughts is played by two people, on opposite sides of a playing board, alternating moves. One player has black pieces, and the other has white or red pieces. Most commonly, the board alternates between red and black. The opponent's pieces are captured by jumping over them.
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In tournament English draughts, a variation called three-move restriction is preferred. The first three moves are drawn at random from a set of accepted openings. Two games are played with the chosen opening, each player having a turn at either side. This tends to reduce the number of draws and can make for more exciting matches. Three-move restriction has been played in the United States championship since 1934. A two-move restriction was used from 1900 until 1934 in the United States and in the British Isles until the 1950s. Before 1900, championships were played without restriction: this style is called go-as-you-please (GAYP).
One rule of long standing that has fallen out of favor is the "huffing" rule. In this variation, jumping is not mandatory, but a piece that could have jumped, but failed to do so, may be taken — or "huffed" — by the opposing player at the beginning of his or her next turn. After huffing the offending piece, the opponent then takes his or her turn as normal. Huffing has been abolished by both the American Checker Federation and the English Draughts Association.
Three common misinterpretations of the rules are:
The first computer English draughts program was written by C. S. Strachey, M.A., National Research Development Corporation, London, in the early 1950s. 1
The second computer program was written in 1956 by Arthur Samuel, a researcher from IBM. Other than it being one of the most complicated game playing programs written at the time, it is also well known for being one of the first adaptive programs. It learned by playing games against modified versions of itself, with the victorious versions surviving. Samuel's program was far from mastering the game, although one win against a blind checkers master gave the general public the impression that it was very good.
In the 1990s, the strongest program was Chinook, written in 1989 by a team from the University of Alberta led by Jonathan Schaeffer. Marion Tinsley, world champion from 1955-1962 and from 1975-1991, won a match against the machine in 1992. In 1994, Tinsley had to resign in the middle of an even match for health reasons; he died shortly thereafter. In 1995, Chinook defended its man-machine title against Don Lafferty in a 32 game match where each had 1 win and 1 loss, and a record setting 30 draws. In 1996 Chinook won in the USA National Tournament by the widest margin ever, and was retired from play after that event. The man-machine title has not been contested since.
On July 2007, in an article published in Science Magazine, Chinook's developers announced that the program had been improved to the point where it could not lose a game.2 If no mistakes were made by either player, the game would always end in a draw. After eighteen years, they have mathematically proven a weak solution to the game of Checkers 3. Using between 200 desktop computers at the peak of the project down to around 50 later on, the team made just 1014 calculations to search from the initial position to a database of positions with at most 10 pieces.4
The number of legal positions in English draughts is estimated to be 1020, and it has a game-tree complexity of approximately 1031. By comparison, chess is estimated to have 1040 legal positions.
When draughts is generalized so that it can be played on an n-by-n board, the problem of determining if the first player has a win in a given position is EXPTIME-complete.
The July 2007 announcement by Chinook's team stating that the game had been solved must be understood in the sense that, with perfect play on both sides, the game will always finish with a draw. Yet, not all positions that could result from imperfect play have been analyzed. 5
This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
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