Chess engine

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A chess engine is a computer program that can play the game of chess.

Contents

[edit] Interface

Traditionally, the term chess engine referred to a chess playing program that did not have its own user interface. Typically they ran on user interfaces such as XBoard on Linux or WinBoard on Windows. Nowadays, many commercial engines, historically sold tightly integrated with their own interface, now allow additional engines to be loaded. Popular examples include the Chessmaster and Chessbase family of engines.

[edit] Protocols

The command line interface of GNU Chess became the initial de facto standard, first supported by XBoard. There is now a newer protocol, the Universal Chess Interface.[1]

Many engines support both protocols. Both protocols have their supporters, although Universal Chess Interface has an edge on usability for end-users.

[edit] Increasing strength

Chess engines increase in playing strength each year. This is partly due to the increase in processing power that enables calculations to be made to ever greater depths in a given time. In addition, programming techniques have improved enabling the engines to be more selective in the lines that they analyse and to acquire a better positional understanding.

Some chess engines use endgame tablebases to increase their playing strength during the endgame. An endgame tablebase is a database of all possible endgame positions with small groups of material. Each position is conclusively determined as a win, loss, or draw for the player whose turn it is to move, and the number of moves to the end with best play by both sides. Endgame tablebases in all cases identify the absolute best move in all positions included (identifying the move that wins fastest against perfect defense, or the move that loses slowest against optimal opposition). Such tablebases are available for all 3-6 man positions (counting the kings) and some 7-man combinations. When the manoevering in an ending to achieve an irreversible improvement takes more moves than the horizon of calculation of a chess engine, an engine is not guaranteed to find the best move without the use of an endgame tablebase, and in many cases can fall foul of the 50 move rule etc. as a result. Some experts have pointed out the potential for faulty use of endgame tablebases by programmers, leading to worse play.

[edit] Comparison between engines

[edit] Tournaments

The results of computer tournaments such as the World Computer Chess Championship give one view of the relative strengths of chess engines. However, tournaments do not play a statistically significant number of games for accurate strength determination. Most tournaments also allow any types of hardware, so only engine/hardware combinations are being compared.

Historically, commercial programs have been the strongest engines. The 2006 WCCC was won by Junior. The top four programs were commercial engines but Spike, a freely available engine, finished joint 5th. [2] To some extent, this is a self-fulfulling prophesy; if an amateur engine wins a tournament or otherwise performs well (for example, Zappa in 2005), then it is quickly commercialized.

[edit] Chess engine rating lists

Chess engine rating lists aim to provide statistically significant measures of relative engine strength. These lists play multiple games between engines on standard hardware platforms, so that results are statistically significant and processor differences are factored out. These lists not only provide a ranking, but also margins of error on the given ratings. Also rating lists typically play games continuously, publishing many updates per year, compared to tournaments which only take place annually.

[edit] Engine categories

[edit] Freely available chess engines

[edit] Pedagogical engines

These open source chess programs were expressly written to teach the craft of chess programming.

[edit] Commercial programs

These chess programs are sold commercially. Most of these also include their own user interface.

[edit] Personal programs

These programs are personal or research projects which may have competed in tournaments or online, but are otherwise unavailable to the public.

[edit] Dedicated hardware

These chess playing systems include custom hardware or run on supercomputers.

[edit] Commercial dedicated computers

In the 1980s and early 1990s, there was a competitive market for strong dedicated chess computers. Many form-factors were sold, from handheld peg-board computers to wooden auto-sensory boards with state-of-the-art processors. This market changed in the mid-90s when the economical embedded processors in dedicated chess computers could no longer compete with the fast processors in personal computers. Nowadays, most dedicated units sold are of beginner and intermediate strength.

  • Chess Challenger, a line of chess computers sold by Fidelity Electronics from 1980 to 1992. These models won the first four World Microcomputer Chess Championships.
  • Chessmachine, an ARM-based dedicated computer, which could run two engines:
  • Mephisto, a line of chess computers sold by Hegner & Glaser. The units programmed by Richard Lang won six consecutive World Microcomputer Chess Championships.
  • Novag sold a line of tactically strong computers, including the Constellation and Sapphire brands
  • Saitek sold mid-range units of intermediate strength
  • Excalibur sells a current line of intermediate strength units

[edit] Historical programs

These chess programs run on obsolete hardware.

[edit] See also

[edit] External links

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