Stockfish (chess)

Stockfish is an open sourceUCI chess engine, available for various desktop and mobile platforms. It is developed by Tord Romstad, Marco Costalba, Joona Kiiski and Gary Linscott, with many contributions from a community of open source developers.

Stockfish is consistently ranked first or near the top of most chess engine rating lists and is the strongest open source chess engine in the world. It won the unofficial world computer chess championships in 2013 and was a runner-up in 2014 and 2015. It is derived from Glaurung, an open source engine by Romstad.

Features

Stockfish can use up to 128 CPU cores in multiprocessor systems. The maximum size of its transposition table is 1 TB. Stockfish implements an advanced alpha-beta search and uses bitboards. Compared to other engines, it is characterized by its great search depth, due in part to more aggressive pruning and late move reductions.

Stockfish supports Chess960, which is one of the features that was inherited from Glaurung. The Syzygy tablebase support, previously available in a fork maintained by Ronald de Man, was integrated into Stockfish in 2014.

Chess

Chess is a two-player board game played on a chessboard, a checkered gameboard with 64 squares arranged in an eight-by-eight grid. Chess is played by millions of people worldwide, both amateurs and professionals.

Each player begins the game with 16 pieces: one king, one queen, two rooks, two knights, two bishops, and eight pawns. Each of the six piece types moves differently. The most powerful piece is the queen and the least powerful piece is the pawn. The objective is to 'checkmate' the opponent's king by placing it under an inescapable threat of capture. To this end, a player's pieces are used to attack and capture the opponent's pieces, while supporting their own. In addition to checkmate, the game can be won by voluntary resignation by the opponent, which typically occurs when too much material is lost, or if checkmate appears unavoidable. A game may also result in a draw in several ways.

Chess is believed to have originated in India, some time before the 7th century; the Indian game of chaturanga is also the likely ancestor of xiangqi and shogi. The pieces took on their current powers in Spain in the late 15th century; the rules were finally standardized in the 19th century.

Chess annotation symbols

When annotating chess games, commentators frequently use widely recognized annotation symbols. Question marks and exclamation points that denote a move as bad or good are ubiquitous in chess literature. Some publications intended for an international audience, such as the Chess Informant have a wide range of additional symbols that transcend language barriers.

The common symbols for evaluating the merits of a move are "??", "?", "?!", "!?", "!", and "!!". In these cases, the corresponding symbol is juxtaposed in the text immediately after the move (e.g. Re7? or Kh1!?, see algebraic chess notation).

Use of these annotation symbols is subjective, as different annotators use the same symbols differently. Moreover, an annotator's use of symbols is often influenced by the player's strength: a positional misjudgment that an annotator might give a "??" if played by a strong grandmaster might pass unremarked if played by a beginner.

Annotators' use of punctuation also may possibly be influenced by the result of the game (regardless of the actual quality of the move); one possible example came in the 11th game of the 1972 World Championship, when Spassky played an unexpected move, 14.Nb1, retreating the knight to its initial square. Spassky won the game, and several annotators gave the move two exclamation points. Edmar Mednis asserted that if Spassky had lost the game, the move would likely have been given two question marks instead.

Chess (Northwestern University)

Chess was a pioneering chess program from the 1970s, written by Larry Atkin and David Slate at Northwestern University. Chess ran on Control Data Corporation's line of supercomputers. Work on the program began in 1968. It dominated the first computer chess tournaments, such as the World Computer Chess Championship and ACM's North American Computer Chess Championship. Chess was the first published use of the bitboard data structure applied to the game of chess.

In 1976, Chess 4.5 won the Class B section of the Paul Masson American Chess Championship, the first time a computer was successful in a human tournament. The performance rating was 1950.

In February 1977 Chess 4.6, the only computer entry, surprised observers by winning the 84th Minnesota Open against competitors just under Master level. It achieved a USCF rating close to or at Expert, higher than previous programs' Class C or D, by winning five games and losing none. Stenberg (rated 1969) became the second Class A player to lose to a computer in a tournament game, the first being Jola.