Candidate move
Encyclopedia
In abstract strategy board game
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, Go
, and Xiangqi
, it is most often used in the context of chess
.
Alexander Kotov
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 doctrine among chess players at all levels. Many beginning players are taught about candidate moves as soon as they learn to play the game, and the idea is often referenced in other chess books.
, 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
is on the g8 square
, and that his Knight
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.
. 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 Alphabeta
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 engines seem more and more to be using candidate moves in their analysis. Hydra
, for example, is widely considered to be a "Type B" (candidate move finding) computer.
Board game
A board game is a game which involves counters or pieces being moved on a pre-marked surface or "board", according to a set of rules. Games may be based on pure strategy, chance or a mixture of the two, and usually have a goal which a player aims to achieve...
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, Go
Go (board game)
Go , is an ancient board game for two players that originated in China more than 2,000 years ago...
, and Xiangqi
Xiangqi
Xiangqi is a two-player Chinese board game in the same family as Western chess, chaturanga, shogi, Indian chess and janggi. The present-day form of Xiangqi originated in China and is therefore commonly called Chinese chess in English. Xiangqi is one of the most popular board games in China...
, it is most often used in the context of chess
Chess
Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...
.
History
The idea of candidate moves was first put forth by GrandmasterInternational Grandmaster
The title Grandmaster is awarded to strong chess players by the world chess organization FIDE. Apart from World Champion, Grandmaster is the highest title a chess player can attain....
Alexander Kotov
Alexander Kotov
Alexander Alexandrovich Kotov was a Soviet chess grandmaster and author. He was a Soviet champion, a two-time world title Candidate, and a prolific chess author. Kotov served in high posts in the Soviet Chess Federation and most of his books were written during the period of Cold War between the...
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 doctrine among chess players at all levels. Many beginning players are taught about candidate moves as soon as they learn to play the game, and the idea is often referenced 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 recognitionPattern recognition
In machine learning, pattern recognition is the assignment of some sort of output value to a given input value , according to some specific algorithm. An example of pattern recognition is classification, which attempts to assign each input value to one of a given set of classes...
, 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 (chess)
In chess, the king is the most important piece. The object of the game is to trap the opponent's king so that its escape is not possible . If a player's king is threatened with capture, it is said to be in check, and the player must remove the threat of capture on the next move. If this cannot be...
is on the g8 square
Algebraic chess notation
Algebraic notation is a method for recording and describing the moves in a game of chess. It is now standard among all chess organizations and most books, magazines, and newspapers...
, and that his Knight
Knight (chess)
The knight is a piece in the game of chess, representing a knight . It is normally represented by a horse's head and neck. Each player starts with two knights, which begin on the row closest to the player, one square from the corner...
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 computersComputer chess
Computer chess is computer architecture encompassing hardware and software capable of playing chess autonomously without human guidance. Computer chess acts as solo entertainment , as aids to chess analysis, for computer chess competitions, and as research to provide insights into human...
. 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
Brute-force search
In computer science, brute-force search or exhaustive search, also known as generate and test, is a trivial but very general problem-solving technique that consists of systematically enumerating all possible candidates for the solution and checking whether each candidate satisfies the problem's...
(Shenk, 2006). The addition of Alphabeta
Alpha-beta pruning
Alpha-beta pruning is a search algorithm which seeks to decrease the number of nodes that are evaluated by the minimax algorithm in its search tree. It is an adversarial search algorithm used commonly for machine playing of two-player games...
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 engines seem more and more to be using candidate moves in their analysis. Hydra
Hydra (chess)
Hydra was a chess machine, designed by a team with Dr. Christian "Chrilly" Donninger, Dr. Ulf Lorenz, GM Christopher Lutz and Muhammad Nasir Ali. Since 2006 the development team consised only of Donninger and Lutz. Hydra was under the patronage of the PAL Group and Sheikh Tahnoon Bin Zayed Al...
, for example, is widely considered to be a "Type B" (candidate move finding) computer.