Deep Blue (chess computer)

Deep Blue was a chess-playing computer developed by IBM. It is known for being the first computer chess-playing system to win both a chess game and a chess match against a reigning world champion under regular time controls.

Deep Blue won its first game against a world champion on 10 February 1996, when it defeated Garry Kasparov in game one of a six-game match. However, Kasparov won three and drew two of the following five games, defeating Deep Blue by a score of 4–2. Deep Blue was then heavily upgraded, and played Kasparov again in May 1997.[1] Deep Blue won game six, thereby winning the six-game rematch 3½–2½ and becoming the first computer system to defeat a reigning world champion in a match under standard chess tournament time controls.[2] Kasparov accused IBM of cheating[3] and demanded a rematch. IBM refused and dismantled Deep Blue.

Development for Deep Blue began in 1985 with the ChipTest project at Carnegie Mellon University. This project eventually evolved into Deep Thought, at which point the development team was hired by IBM.[4] The project evolved once more with the new name Deep Blue in 1989. Grandmaster Joel Benjamin was also part of the development team.


The project was started as ChipTest at Carnegie Mellon University by Feng-hsiung Hsu, followed by its successor, Deep Thought. After their graduation from Carnegie Mellon, Hsu, Thomas Anantharaman, and Murray Campbell from the Deep Thought team were hired by IBM Research to continue their quest to build a chess machine that could defeat the world champion.[5] Hsu and Campbell joined IBM in autumn 1989, with Anantharaman following later.[6] Anantharaman subsequently left IBM for Wall Street and Arthur Joseph Hoane joined the team to perform programming tasks.[7] Jerry Brody, a long-time employee of IBM Research, was recruited for the team in 1990.[8] The team was managed first by Randy Moulic, followed by Chung-Jen (C J) Tan.[9]

After Deep Thought's 1989 match against Kasparov, IBM held a contest to rename the chess machine and it became "Deep Blue", a play on IBM's nickname, "Big Blue".[10] After a scaled-down version of Deep Blue, Deep Blue Jr., played Grandmaster Joel Benjamin, Hsu and Campbell decided that Benjamin was the expert they were looking for to develop Deep Blue's opening book, and Benjamin was signed by IBM Research to assist with the preparations for Deep Blue's matches against Garry Kasparov.[11]

In 1995 "Deep Blue prototype" (actually Deep Thought II, renamed for PR reasons) played in the 8th World Computer Chess Championship. Deep Blue prototype played the computer program Wchess to a draw while Wchess was running on a personal computer. In round 5 Deep Blue prototype had the white pieces and lost to the computer program Fritz 3 in 39 moves while Fritz was running on an Intel Pentium 90 MHz personal computer. In the end of the championship Deep Blue prototype was tied for second place with the computer program Junior while Junior was running on a personal computer.[12]


Deep Blue employed custom VLSI chips to execute the alpha-beta search algorithm in parallel,[13] an example of GOFAI (Good Old-Fashioned Artificial Intelligence) rather than of deep learning which would come a decade later. It was a brute force approach, and one of its developers even denied that it was artificial intelligence at all.[14]

Deep Blue versus Kasparov

Deep Blue and Kasparov played each other on two occasions. The first match began on 10 February 1996, in which Deep Blue became the first machine to win a chess game against a reigning world champion (Garry Kasparov) under regular time controls. However, Kasparov won three and drew two of the following five games, beating Deep Blue by a score of 4–2 (wins count 1 point, draws count ½ point). The match concluded on 17 February 1996.

Deep Blue was then heavily upgraded (unofficially nicknamed "Deeper Blue")[15] and played Kasparov again in May 1997, winning the six-game rematch 3½–2½, ending on 11 May. Deep Blue won the deciding game six after Kasparov made a mistake in the opening, becoming the first computer system to defeat a reigning world champion in a match under standard chess tournament time controls.

The system derived its playing strength mainly from brute force computing power. It was a massively parallel, RS/6000 SP Thin P2SC-based system with 30 nodes, with each node containing a 120 MHz P2SC microprocessor, enhanced with 480 special purpose VLSI chess chips. Its chess playing program was written in C and ran under the AIX operating system. It was capable of evaluating 200 million positions per second, twice as fast as the 1996 version. In June 1997, Deep Blue was the 259th most powerful supercomputer according to the TOP500 list, achieving 11.38 GFLOPS on the High-Performance LINPACK benchmark.[16]

The Deep Blue chess computer that defeated Kasparov in 1997 would typically search to a depth of between six and eight moves to a maximum of twenty or even more moves in some situations.[17] David Levy and Monty Newborn estimate that one additional ply (half-move) increases the playing strength 50 to 70 Elo points.[18]

Deep Blue's evaluation function was initially written in a generalized form, with many to-be-determined parameters (e.g. how important is a safe king position compared to a space advantage in the center, etc.). The optimal values for these parameters were then determined by the system itself, by analyzing thousands of master games. The evaluation function had been split into 8,000 parts, many of them designed for special positions. In the opening book there were over 4,000 positions and 700,000 grandmaster games. The endgame database contained many six-piece endgames and five or fewer piece positions. Before the second match, the chess knowledge of the program was fine-tuned by grandmaster Joel Benjamin. The opening library was provided by grandmasters Miguel Illescas, John Fedorowicz, and Nick de Firmian.[19] When Kasparov requested that he be allowed to study other games that Deep Blue had played so as to better understand his opponent, IBM refused. However, Kasparov did study many popular PC games to become familiar with computer gameplay in general.

Writer Nate Silver suggests that a bug in Deep Blue's software led to a seemingly random move (the 44th in the first game of the second match) which Kasparov misattributed to "superior intelligence".[20][21] Subsequently, Kasparov experienced a decline in performance due to anxiety in the following game.[21] Kasparov rejects this interpretation.[22]


Computer scientists believed that playing chess was a good measurement for the effectiveness of artificial intelligence, and by beating a world champion chess player, IBM showed that they had made significant progress.[23]

After the loss, Kasparov said that he sometimes saw deep intelligence and creativity in the machine's moves, suggesting that during the second game, human chess players had intervened on behalf of the machine, which would be a violation of the rules. IBM denied that it cheated, saying the only human intervention occurred between games. The rules provided for the developers to modify the program between games, an opportunity they said they used to shore up weaknesses in the computer's play that were revealed during the course of the match. Kasparov requested printouts of the machine's log files, but IBM refused, although the company later published the logs on the Internet.[24] Kasparov demanded a rematch, but IBM refused and dismantled Deep Blue.[25] Owing to an insufficient sample of games between Deep Blue and officially rated chess players, a chess rating for Deep Blue was not established.

In 2003 a documentary film was made that explored these claims. Entitled Game Over: Kasparov and the Machine, the film interviewed some people who suggest that Deep Blue's victory was a ploy by IBM to boost its stock value.[25]

One of the cultural impacts of Deep Blue was the creation of a new game called Arimaa designed to be much more difficult for computers than chess.[26]

One of the two racks that made up Deep Blue is on display at the National Museum of American History in their exhibit about the Information Age;[27] the other rack appears at the Computer History Museum in the "Artificial Intelligence and Robotics" gallery of the Revolution exhibit.[28] Reports that Deep Blue was sold to United Airlines appear to originate from confusion between Deep Blue itself and other RS6000/SP2 systems.[29]

Feng-hsiung Hsu later claimed in his book Behind Deep Blue that he had the rights to use the Deep Blue design to build a bigger machine independently of IBM to take Kasparov's rematch offer, but Kasparov refused a rematch.[30]

Deep Blue, with its capability of evaluating 200 million positions per second, was the fastest computer to face a world chess champion. Today, in computer-chess research and matches of world-class players against computers, the focus of play has often shifted to software chess programs, rather than using dedicated chess hardware. Modern chess programs like Houdini, Rybka, Deep Fritz or Deep Junior are more efficient than the programs during Deep Blue's era. In a November 2006 match between Deep Fritz and world chess champion Vladimir Kramnik, the program ran on a computer system containing a dual-core Intel Xeon 5160 CPU, capable of evaluating only 8 million positions per second, but searching to an average depth of 17 to 18 plies in the middlegame thanks to heuristics; it won 4–2.[31][32]

See also


  1. "IBM's Deep Blue beats chess champion Garry Kasparov in 1997". NY Daily News. Retrieved 3 August 2017.
  2. Saletan, William (11 May 2007). "Chess Bump: The triumphant teamwork of humans and computers". Slate. Archived from the original on 13 May 2007.
  3. Hsu, Feng-Hsiung (2004). Behind Deep Blue: Building the Computer that Defeated the World Chess Champion (revised ed.). Princeton University Press. p. Preface page x. ISBN 9780691118185.
  4. "A Brief History of Deep Blue, IBM's Chess Computer". 29 July 2017. Retrieved 3 August 2017.
  5. Hsu 2002, pp.92–95
  6. Hsu 2002, p.107
  7. Hsu 2002, p.132
  8. IBM. "Deep Blue – Overview". IBM Research. Archived from the original on 12 December 2008. Retrieved 19 August 2008.
  9. Hsu 2002, p.136
  10. Hsu 2002, pp.126–127
  11. Hsu 2002, pp.160–161, 174, 177, 193
  12. Deep blue had white and lost to Fritz in 39 moves Archived 7 October 2008 at the Wayback Machine
  13. Hsu, Feng-hsiung; Campbell, Murray (1995). "Deep Blue System Overview" (PDF). Proceedings of the 9th international conference on Supercomputing. ACM. pp. 240–244.
  14. Press, Gil (7 February 2018). "The Brute Force of IBM Deep Blue And Google DeepMind". Retrieved 12 May 2018.
  15. IBM Research Game 2 Archived 19 October 2007 at the Wayback Machine, Deep Blue IBM
  16. TOP500 Super Computer List – June 1997 (201–300) Archived 13 February 2009 at the Wayback Machine
  17. Campbell 1998, p. 88.
  18. Levy & Newborn 1991, p. 192
  19. Weber, Bruce (18 May 1997). "What Deep Blue Learned in Chess School". The New York Times. ISSN 0362-4331. Retrieved 4 July 2017.
  20. Roberts, Jacob (2016). "Thinking Machines: The Search for Artificial Intelligence". Distillations. 2 (2): 14–23. Archived from the original on 19 August 2018. Retrieved 22 March 2018.
  21. Plumer, Brad (26 September 2012). "Nate Silver's 'The Signal and the Noise'". Archived from the original on 9 November 2012. Retrieved 5 January 2014.
  23. Greenemeier, Larry. "20 Years after Deep Blue: How AI Has Advanced Since Conquering Chess". Scientific American. Retrieved 29 June 2018.
  24. Deep Blue the Match Replay the games. IBM.
  25. 'Game Over' : Did IBM Cheat Kasparov? Archived 12 October 2007 at the Wayback Machine, by Mark Weeks,, June 2005.
  26. Deep Blue Cultural Impacts. Archived 30 March 2014 at the Wayback Machine IBM.
  27. "Deep Blue Supercomputer Tower". National Museum of American History. Retrieved 1 February 2019.
  28. Deep Blue II. Archived 3 July 2013 at the Wayback Machine Computer History Museum collections database. Retrieved 10 January 2014.
  29. "Deep Blue Skies: Ibm Helps Airline". Orlando Sentinel. 7 December 1997. Archived from the original on 11 May 2013.
  30. "Owen Williams replies to Feng-hsiung Hsu". The Week in Chess. 13 January 2000. Archived from the original on 29 July 2012. Retrieved 11 May 2012 Cite journal requires |journal= (help)
  31. "The last match man vs machine?". English translation of Spiegel Article. ChessBase. 23 November 2006. Archived from the original on 16 October 2012.
  32. "Chess champion loses to computer". BBC News. 5 December 2006. Archived from the original on 31 December 2007. Retrieved 4 May 2008.


  • Hsu, Feng-hsiung (2002). "Behind Deep Blue: Building the Computer that Defeated the World Chess Champion". Princeton University Press. ISBN 0-691-09065-3. Cite journal requires |journal= (help)
  • Levy, David; Newborn, Monty (1991). "How Computers Play Chess". Computer Science Press. ISBN 0-7167-8121-2. Cite journal requires |journal= (help)
  • Campbell, Murray (1998). "An Enjoyable Game". In Stork, D. G. (ed.). HAL's Legacy: 2001's Computer as Dream and Reality. Cambridge, Massachusetts: MIT Press.
  • Syed, Omar; Syed, Aamir (2003). "Arimaa – a New Game Designed to be Difficult for Computers". International Computer Games Association Journal 26: 138–139 Cite journal requires |journal= (help)

Further reading

  • Newborn, Monty (1997). "Kasparov versus Deep Blue: Computer Chess Comes of Age". Springer. ISBN 0-387-94820-1. Cite journal requires |journal= (help)
  • King, Daniel (1997). "Kasparov v. Deeper Blue: The Ultimate Man v. Machine Challenge". Batsford. ISBN 0-7134-8322-9. Cite journal requires |journal= (help)
  • Newborn, Monty (2002). Deep Blue. Springer. ISBN 0-387-95461-9.
  • Campbell, M.; Hoane, A. J.; Hsu, F. H. (2002). "Deep Blue". Artificial Intelligence. 134: 57–59. doi:10.1016/S0004-3702(01)00129-1.
  • Deep Blue player profile and games at
  •, IBM Research pages on Deep Blue
  •, IBM page with the computer logs from the games
  •, Open letter from Feng-hsiung Hsu on the aborted rematch with Kasparov, The Week in Chess Magazine, issue 270, 10 January 2000
  •, Open Letter from Owen Williams (Gary Kasparov's manager), responding to Feng-hsiung Hsu, 13 January 2000
  •, Deep Blue system described by Feng-hsiung Hsu, Murray Campbell and A. Joseph Hoane Jr.
  •, ICC Interview with Feng-Hsiung Hsu, an online interview with Hsu in 2002 (annotated)
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