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Chess engine

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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.

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47-572: A chess engine is usually a back end with a command-line interface with no graphics or windowing . Engines are usually used with a front end, a windowed graphical user interface such as Chessbase or WinBoard that the user can interact with via a keyboard, mouse or touchscreen. This allows the user to play against multiple engines without learning a new user interface for each, and allows different engines to play against each other. Many chess engines are now available for mobile phones and tablets, making them even more accessible. The meaning of

94-531: A 'searching engine,' apparently referring to the software rather than the hardware. In December 1991, Computer-schach & Spiele referred to Chessbase 's recently released Fritz as a 'Schach-motor,' the German translation for 'chess engine.' By early 1993, Marty Hirsch was drawing a distinction between commercial chess programs such as Chessmaster 3000 or Battle Chess on the one hand, and 'chess engines' such as ChessGenius or his own MChess Pro on

141-581: A 3D interface, drew a four-game match against Garry Kasparov . Fritz 8, which appeared around this time, provided a 3D Spanish room setting for games to take place. Fritz 9 added a 3D virtual opponent, the Turk. In 2004, Fritz 8 added a Handicap and Fun mode, allowing players to choose the Elo rating and style that the engine will use. Chessbase native engines can use the Handicap feature: Chess Tiger , Crafty ,

188-765: A disassembled binary of Rybka . Due to the controversy , all these engines have been blacklisted from many tournaments and rating lists. Rybka in turn was accused of being based on Fruit , and in June 2011, the ICGA formally claimed Rybka was derived from Fruit and Crafty and banned Rybka from the International Computer Games Association World Computer Chess Championship, and revoked its previous victories (2007, 2008, 2009, and 2010). The ICGA received some criticism for this decision. Despite all this, Rybka

235-508: A green circle and bad moves with a red one. This version again uses the Rybka engine. Fritz 17 was released on November 12, 2019, and uses the Ginkgo engine, written by Frank Schneider. Fritz 18 was released on November 16, 2021. On March 30, 2022, Fritz 18 Neuronal was released that supplemented Fritz's handcrafted evaluation with an efficiently updatable neural network . In July 2021,

282-541: A program using a MuZero -derived algorithm could handle an unbounded state space . XBoard / Winboard was one of the earliest graphical user interfaces (GUI). Tim Mann created it to provide a GUI for the GNU Chess engine, but after that, other engines such as Crafty appeared which used the Winboard protocol. Eventually, the program Chessmaster included the option to import other Winboard engines in addition to

329-479: A separate UCI GUI of his own design, allowing UCI or Winboard engines to be imported into it. Convekta's Chess Assistant and Lokasoft's ChessPartner also added the ability to import Winboard and UCI engines into their products. Shane Hudson developed Shane's Chess Information Database , a free GUI for Linux, Mac and Windows. Martin Blume developed Arena, another free GUI for Linux and Windows. Lucas Monge entered

376-583: A uci_elo parameter include Houdini , Fritz 15–16, Rybka , Shredder , Hiarcs , Junior , Zappa , and Sjeng . GUIs such as Shredder , Chess Assistant , Convekta Aquarium, Hiarcs Chess Explorer, and Martin Blume's Arena have dropdown menus for setting the engine's uci_elo parameter. The Fritz family GUIs, Chess Assistant , and Aquarium also have independent means of limiting an engine's strength apparently based on an engine's ability to generate ranked lists of moves (called multipv for 'principle variation'). The results of computer tournaments give one view of

423-1003: A version of their database program including Fritz  4 as a separate engine. This was the first appearance of the Chessbase protocol. Soon after, they added the engines Junior and Shredder to their product line up, including engines in CB protocol as separate programs which could be installed in the Chessbase program or one of the other Fritz style GUI's. Fritz 1-14 were only issued as Chessbase engines, while Hiarcs , Nimzo, Chess Tiger and Crafty have been ported to Chessbase format even though they were UCI or Winboard engines. Recently, Chessbase has begun to include Universal Chess Interface (UCI) engines in their playing programs such as Komodo , Houdini , Fritz 15–16 and Rybka rather than convert them to Chessbase engines. In 2000, Stefan Meyer-Kahlen and Franz Huber released

470-460: Is a metaphor of a car 's engine . Thus a software engine is a complex subsystem . There is no formal guideline for what should be called an engine, but the term has become widespread in the software industry . Fritz (chess) Fritz is a German chess program originally developed for Chessbase by Frans Morsch based on his Quest program, ported to DOS, and then Windows by Mathias Feist. With version 13, Morsch retired, and his engine

517-590: Is a series of introductory chess programs based on the Fritz engine. Each program provides basic tutorials and games based on one aspect of chess, allowing children to learn the basic rules easily without overwhelming them with too many options at once. Games follow Prince Fritz, the son of King White, and his cousin Bianca, as Chesster the rat (among others) teaches them the fundamentals of chess so that they can defeat King Black. There are three programs available in

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564-413: Is also sixth on the same list, with a rating of 3097. Fritz has not kept up with modern advances, attaining only 14th on the 2013 CCRL rating list and not participating in any world championships since 2004. The 2013 release of Deep Fritz 14 switched engines from the original author Frans Morsch's to Pandix, written by Gyula Horváth. A long-time participant in world computer championships since 1984, Pandix

611-405: 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 analyze and to acquire a better positional understanding. A chess engine often uses a vast previously-computed opening "book" to increase its playing strength for

658-719: Is still included on many rating lists, such as CCRL and CEGT, in addition to Houdini , a derivative of the IPPOLIT derivative Robbolito, and Fire, a derivative of Houdini. In addition, Fat Fritz 2 , a derivative of Stockfish, is also included on most of the rating lists. There are a number of factors that vary among the chess engine rating lists: These differences affect the results, and make direct comparisons between rating lists difficult. Current rating lists and rating list organizations include: Historic rating lists and rating list organizations include: Engines can be tested by measuring their performance on specific positions. Typical

705-403: Is the use of test suites where for each given position there is one best move to find. These positions can be geared towards positional, tactical or endgame play. The Nolot test suite, for instance, focuses on deep sacrifices. The BT2450 and BT2630 test suites measure the tactical capability of a chess engine and have been used by REBEL . There is also a general test suite called Brilliancy which

752-524: The Universal Chess Interface , a more detailed protocol that introduced a wider set of features. Chessbase soon after dropped support for Winboard engines, and added support for UCI to their engine GUI's and Chessbase programs. Most of the top engines are UCI these days: Stockfish , Komodo , Leela Chess Zero , Houdini , Fritz 15-16, Rybka , Shredder , Fruit , Critter , Ivanhoe and Ruffian. From 1998,

799-503: The computer hardware the engines use, in an attempt to measure the strength differences of the engines only. These lists provide not only a ranking, but also margins of error on the given ratings. The ratings on the rating lists, although calculated by using the Elo system (or similar rating methods), have no direct relation to FIDE Elo ratings or to other chess federation ratings of human players. Except for some man versus machine games which

846-414: The endgame . An endgame tablebase includes all possible endgame positions with a small amount 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. The tablebase identifies for every position the move which will win the fastest against an optimal defense, or the move that will lose

893-631: The Fritz engine, Hiarcs , Houdini , Junior , Rybka , Shredder and Zappa . Some UCI engines can also make use of Handicap, e.g. Fruit and Stockfish . On June 23, 2005, in the ABC Times Square studios, the AI Accoona Toolbar , driven by a Fritz 9 prototype, drew against the then FIDE World Champion Rustam Kasimdzhanov . From November 25 to December 5, 2006 Deep Fritz played a six-game match against Kramnik in Bonn . Fritz

940-539: The German company Data Becker released the program 3D Schach Genie, containing the Shredder engine and Fritz interface. The German company Purple Hills sold Fritz 6 through 12 as Profi Schach 1 through 7. British Excalibur Publishing has published Fritz 9 through 14. American book publisher Simon & Schuster featured the Fritz engine in their Extreme Chess program, as have German game publisher TopWare Interactive in their Battle vs. Chess game. Fritz and Chesster

987-612: The German company Millenium 2000 briefly moved from dedicated chess computers into the software market, developing the Millennium Chess System (MCS) protocol for a series of CD's containing ChessGenius or Shredder , but after 2001 ceased releasing new software. A more longstanding engine protocol has been used by the Dutch company, Lokasoft, which eventually took over the marketing of Ed Schröder's Rebel . Chess engines increase in playing strength continually. This

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1034-789: The King engine which was included. In 1995, Chessbase began offering the Fritz engine as a separate program within the Chessbase database program and within the Fritz GUI. Soon after, they added the Junior and Shredder engines to their product line up, packaging them within the same GUI as was used for Fritz. In the late 1990s, the Fritz GUI was able to run Winboard engines via an adapter, but after 2000, Chessbase simply added support for UCI engines, and no longer invested much effort in Winboard. In 2000, Stefan Meyer-Kahlen started selling Shredder in

1081-526: The SSDF had organized many years ago (when engines were far from today's strength), there is no calibration between any of these rating lists and player pools. Hence, the results which matter are the ranks and the differences between the ratings, and not the absolute values. Missing from many rating lists are IPPOLIT and its derivatives. Although very strong and open source , there are allegations from commercial software interests that they were derived from

1128-585: The U.S. and Fritz throughout the rest of the world. In 1995, Fritz 3 won the World Computer Chess Championship in Hong Kong, beating an early version of Deep Blue . This was the first time that a program running on a consumer-level microcomputer defeated the mainframes that had previously dominated this event. In 1998, Fritz 5 was released including a Friend mode which would cause the engine to adjust its strength of play over

1175-583: The basis for what became known as the Chess Engine Communication Protocol or Winboard engines, originally a subset of the GNU Chess command line interface. Also in 1994, Stephen J. Edwards released the Portable Game Notation (PGN) specification. It mentions PGN reading programs not needing to have a "full chess engine." It also mentions three "graphical user interfaces" (GUI): XBoard , pgnRead and Slappy

1222-668: The complexity, and the contribution it has made to chess make it the most important game ever played." Some chess engines have been developed to play chess variants , adding the necessary code to simulate non-standard chess pieces , or to analyze play on non-standard boards. ChessV and Fairy-Max , for example, are both capable of playing variants on a chessboard up to 12×8 in size, such as Capablanca Chess (10×8 board). For larger boards, however, there are few chess engines that can play effectively, and indeed chess games played on an unbounded chessboard ( infinite chess ) are virtually untouched by chess-playing software, although theoretically

1269-578: The course of a game based on the level the opponent appeared to be playing. Fritz 5.32 was released soon after replacing the 16-bit architecture with a 32-bit one. In 2002, Deep Fritz drew the Brains in Bahrain match against Vladimir Kramnik 4–4. Fritz 7, which was released that year, included the ability to play on the Playchess server. In November 2003, X3D Fritz , a version of Deep Fritz with

1316-485: The database. By the mid-2000s, engines had become so strong that they were able to beat even the best human players. Except for entertainment purposes, especially using engines with limited strength, matches between humans and engines are now rare; engines are increasingly regarded as tools for analysis rather than as opponents. Common Winboard engines would include Crafty , ProDeo (based on Rebel ), Chenard, Zarkov and Phalanx. In 1995, Chessbase released

1363-480: The developers of the open source Stockfish chess engine filed a lawsuit against Chessbase alleging that Fat Fritz 2.0 is a derivative of Stockfish and is in violation of a "central obligation" of Stockfish's GNU General Public License . In November 2022, a settlement was reached in which it was agreed that the license obligations of the GPL-3.0 for the products Fat Fritz 2 and Houdini 6 have not been complied with. In

1410-443: The field with the free Lucas Chess GUI. All three can handle both UCI and Winboard engines. On Android, Aart Bik came out with Chess for Android, another free GUI, and Gerhard Kalab's Chess PGN Master and Peter Osterlund's Droidfish can also serve as GUIs for engines. The Computer Chess Wiki lists many chess GUIs. Software engine A software engine is a core component of a complex software system . The word "engine"

1457-529: The first several moves, up to possibly 20 moves or more in deeply analyzed lines. Some chess engines maintain a database of chess positions, along with previously-computed evaluations and best moves—in effect, a kind of "dictionary" of recurring chess positions. Since these positions are pre-computed, the engine merely plays one of the indicated moves in the database, thereby saving computing time, resulting in stronger, faster play. Some chess engines use endgame tablebases to increase their playing strength during

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1504-468: The future, Chessbase will comply with the license terms and to adequately inform the public about the use of the Stockfish software in its products. The American company Viva Media , now a division of Encore, Inc. has been licensed to sell many versions of the Fritz engine and GUI combination. British game publisher Eidos Interactive (now part of Square Enix Europe ) published Fritz 6 and 7. In 1998,

1551-416: The late 2010s, free and open source programs have largely displaced commercial programs as the strongest engines in tournaments. Current tournaments include: Historic tournaments include: Chess engine rating lists aim to provide statistically significant measures of relative engine strength. These lists play multiple games between engines. Some also standardize the opening books, the time controls , and

1598-400: The most widely-used testing framework for chess engines. By the late 1990s, the top engines had become so strong that few players stood a chance of winning a game against them. To give players more of a chance, engines began to include settings to adjust or limit their strength. In 2000, when Stefan Meyer-Kahlen and Franz Huber released the Universal Chess Interface protocol they included

1645-510: The other. In his characterization, commercial chess programs were low in price, had fancy graphics, but did not place high on the SSDF ( Swedish Chess Computer Association ) rating lists while engines were more expensive, and did have high ratings. In 1994, Shay Bushinsky was working on an early version of his Junior program. He wanted to focus on the chess playing part rather than the graphics, and so asked Tim Mann how he could get Junior to communicate with Winboard . Tim's answer formed

1692-403: The parameters uci_limitstrength and uci_elo allowing engine authors to offer a variety of levels rated in accordance with Elo rating , as calibrated by one of the rating lists. Most GUIs for UCI engines allow users to set this Elo rating within the menus. Even engines that have not adopted this parameter will sometimes have an adjustable strength parameter (e.g. Stockfish 11). Engines which have

1739-425: The participation of over 50,000 people from more than 75 countries, deciding their moves by plurality vote . The game lasted four months, ending after Kasparov's 62nd move when he announced a forced checkmate in 28 moves found with the computer program Deep Junior . The World Team voters resigned on October 22. After the game, Kasparov said: "It is the greatest game in the history of chess. The sheer number of ideas,

1786-526: The relative strengths of chess engines. However, tournaments do not play a statistically significant number of games for accurate strength determination. In fact, the number of games that need to be played between fairly evenly matched engines, in order to achieve significance, runs into the thousands and is, therefore, impractical within the framework of a tournament. Most tournaments also allow any types of hardware, so only engine/hardware combinations are being compared. Historically, commercial programs have been

1833-415: The slowest against an optimal offense. Such tablebases are available for all chess endgames with seven pieces or fewer (trivial endgame positions are excluded, such as six white pieces versus a lone black king ). When the maneuvering 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

1880-399: The software code. As of June 2017, a total of more than 745 years of CPU time has been used to play more than 485 million chess games, with the results being used to make small and incremental improvements to the chess-playing software. In 2019, Ethereal author Andrew Grant started the distributed computing testing framework OpenBench, based upon Stockfish's testing framework, and it is now

1927-451: The strongest engines. If an amateur engine wins a tournament or otherwise performs well (for example, Zappa in 2005), then it is quickly commercialized. Titles gained in these tournaments garner much prestige for the winning programs, and are thus used for marketing purposes. However, after the rise of volunteer distributed computing projects such as Leela Chess Zero and Stockfish and testing frameworks such as FishTest and OpenBench in

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1974-403: The term "chess engine" has evolved over time. In 1986, Linda and Tony Scherzer entered their program Bebe into the 4th World Computer Chess Championship , running it on "Chess Engine," their brand name for the chess computer hardware made, and marketed by their company Sys-10, Inc. By 1990 the developers of Deep Blue , Feng-hsiung Hsu and Murray Campbell , were writing of giving their program

2021-497: The use of an endgame tablebase, and in many cases can fall foul of the fifty-move rule as a result. Many engines use permanent brain (continuing to calculate during the opponent's turn) as a method to increase their strength. Distributed computing is also used to improve the software code of chess engines. In 2013, the developers of the Stockfish chess playing program started using distributed computing to make improvements in

2068-698: Was able to win 4–2. In this match, Kramnik blundered away game 2, allowing a mate in one. On SSDF 's September 2010 rating list, Deep Fritz 12 placed sixth with a rating of 3110, 135 points higher than Deep Junior 10.1, and 103 points lower than no. 1 ranked Deep Rybka 3 x64. Deep Fritz 11 is eighth on the same list, with a rating of 3073. On the December 2010 edition of the CCRL rating list, Deep Fritz 12 placed sixth with an Elo rating of 3088, 29 points higher than Deep Junior 11.1a x64, and 174 points lower than no. 1 ranked Deep Rybka 4 x64. Deep Fritz 11

2115-595: Was compiled mostly from How to Reassess Your Chess Workbook . The Strategic Test Suite (STS) tests an engine's strategical strength. Another modern test suite is Nightmare II which contains 30 chess puzzles. In 1999, Garry Kasparov played a chess game called "Kasparov versus the World" over the Internet , hosted by the MSN Gaming Zone . Both sides used computer (chess engine) assistance. The "World Team" included

2162-507: Was first replaced by Gyula Horvath's Pandix, and then with Fritz 15, Vasik Rajlich 's Rybka . The latest version of the consumer product is Fritz 18 Neuronal. This version supports 64-bit hardware and multiprocessing by default. In 1991, the German company ChessBase approached the Dutch chess programmer Frans Morsch about writing a chess engine to add to the database program which they sold. Morsch adapted his Quest program, and ChessBase released it for sale that year as Knightstalker in

2209-465: Was substantially rewritten in 2009, and has been a strong contender since then. Fritz 15 was released on November 25, 2015, with new features, including switching to Vasik Rajlich's famous Rybka engine. Handicap and Fun mode was dropped, but there is now a function for pawn and piece handicaps (e.g. ceding pawn and move). Fritz 16 was released on November 12, 2017, with a new Easy game mode which provides for assisted calculation marking good moves with

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