abstract strategy Abstract strategy games admit a number of definitions which distinguish these from strategy games in general, mostly involving no or minimal narrative theme, outcomes determined only by player choice (with no randomness), and perfect information ...

board game Board games are tabletop games that typically use . These pieces are moved or placed on a pre-marked board (playing surface) and often include elements of table, card, role-playing, and miniatures games as well. Many board games feature a co ...

s, candidate moves are moves which, upon initial observation of the position, seem to warrant further analysis. Although in theory the idea of candidate moves can be applied to games such as

checkers Checkers (American English), also known as draughts (; British English), is a group of strategy board games for two players which involve diagonal moves of uniform game pieces and mandatory captures by jumping over opponent pieces. Checkers ...

, go, and

xiangqi ''Xiangqi'' (; ), also called Chinese chess or elephant chess, is a strategy board game for two players. It is the most popular board game in China. ''Xiangqi'' is in the same family of games as '' shogi'', '' janggi'', Western chess, '' c ...

, it is most often used in the context of

chess Chess is a board game for two players, called White and Black, each controlling an army of chess pieces in their color, with the objective to checkmate the opponent's king. It is sometimes called international chess or Western chess to dist ...

History

The idea of candidate moves was first put forth by Grandmaster

Alexander Kotov Alexander Alexandrovich Kotov (Алекса́ндр Алекса́ндрович Ко́тов; – 8 January 1981) was a Soviet chess grandmaster and author. He was a Soviet chess champion, a two-time world title Candidate, and a prolific write ...

in his book ''Think Like a Grandmaster''. In it, Kotov recommended looking for several moves that seemed feasible – the so-called candidate moves – and then analyzing those moves one at a time. Although this idea had been practiced by expert chess players for some time, it had never been explicitly articulated, and was relatively unknown to players at the amateur level. The idea quickly caught on, and is now considered standard practice among chess players at all levels. Many beginning players are taught about candidate moves as soon as they learn to play the game, and there are numerous references to the idea in other chess books.

Finding candidate moves

Finding the correct candidate moves is often one of the most difficult aspects of becoming a better chess player. Kotov, as well as other teachers, recommend using a system of

pattern recognition Pattern recognition is the automated recognition of patterns and regularities in data. It has applications in statistical data analysis, signal processing, image analysis, information retrieval, bioinformatics, data compression, computer graphics ...

, looking at the elements of the current position to determine what might be a feasible move. For example, if a player notices that his opponent's

king King is the title given to a male monarch in a variety of contexts. The female equivalent is queen, which title is also given to the consort of a king. *In the context of prehistory, antiquity and contemporary indigenous peoples, the tit ...

is on the g8 square, and that his

knight A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the church or the country, especially in a military capacity. Knighthood finds origins in the Gr ...

is on f3, then a candidate move might be Ng5, a fairly common beginning to a sacrifice. Once a player has found a good number of candidate moves (every position is different, although four to six moves is usually the norm), a player may then begin to systematically analyze these moves. The idea behind candidate moves is to help structure one's analysis and prevent it from becoming jumbled; inexperienced players who do not carefully consider candidate moves will often find themselves jumping between lines of analysis haphazardly.

Computer chess

The ability of humans to find candidate moves remains one of the main differences between them and computers. Although early chess programmers made admirable efforts to make computers able to select candidate moves (see Type A versus Type B programs), they never played particularly well, and were soon supplanted by computers using brute-force algorithms (Shenk, 2006). The addition of alpha–beta algorithms made the latter type even more feasible. Many acknowledged that computers were simply not capable of performing the complex pattern recognition that was required to find appropriate candidate moves, and that it was easier to have computers perform simple exhaustive searches. Today, most chess programs still rely mainly on brute-force searches, but as search algorithms have improved, today's

chess engine In computer chess, a chess engine is a computer program that analyzes chess or chess variant positions, and generates a move or list of moves that it regards as strongest. A chess engine is usually a back end with a command-line interface wit ...

s seem more and more to be using candidate moves in their analysis. Hydra and

AlphaZero AlphaZero is a computer program developed by artificial intelligence research company DeepMind to master the games of chess, shogi and go. This algorithm uses an approach similar to AlphaGo Zero. On December 5, 2017, the DeepMind team re ...

, for example, are widely considered to be a "Type B" (candidate move finding) computer.

References

{{chess Chess terminology Computer chess