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Deep Blue

Kasparov vs. Deep Blue
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Kasparov vs. Deep Blue

Deep Blue was a chess playing computer developed by IBM.

Deep Blue was the first computer system to win a chess game against a reigning world champion (Garry Kasparov) under regular time controls. This first win occurred on February 10, 1996, and Deep Blue - Kasparov, 1996, Game 1 is a famous chess game. However, Kasparov won 3 games and drew 2 of the following games, beating Deep Blue by a score of 4-2.

Deep Blue was then heavily upgraded (unofficially nicknamed "Deeper Blue") and played Kasparov again in May 1997, winning the six-game rematch 3.5-2.5, ending on May 11th. The final game is at Deep Blue - Kasparov, 1997, Game 6. Deep Blue thus became the first computer system to defeat a reigning world champion in a match under standard chess tournament time controls.

The project was started as "ChipTest" at Carnegie Mellon University by Feng-hsiung Hsu; the computer system produced was named Deep Thought after the fictional computer of the same name from The Hitchhiker's Guide to the Galaxy. Hsu joined IBM in 1989 and worked with Murray Campbell on parallel computing problems. Deep Blue was developed out of this.

The system derives its playing strength mainly out of brute force computing power. It is a massively parallel, 30-node, RS/6000, SP-based computer system enhanced with 480 special purpose VLSI chess chips. Its chess playing program is written in C and runs under the AIX operating system. It was capable of evaluating 200,000,000 positions per second, twice as fast as the 1996 version. In June 1997, Deep Blue was the 259th most powerful supercomputer, although this did not take into account Deep Blue's special-purpose hardware for chess.

The Deeper Blue chess computer which defeated Kasparov in 1997 could search to a depth of 12 ply. Good human chess players look roughly 10 ply ahead. An increase in search depth of one ply corresponds on the average to an increase in playing strength of approximately 80 Elo points.

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 8000 parts, many of them designed for special positions. In the opening book there were over 4000 positions and 700000 grandmaster games. The endgame database contained many six piece endgames and all 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 the grandmasters Miguel Illescas, John Fedorovich and Nick De Firmian.

After the lost match, Kasparov said that he sometimes saw deep intelligence and creativity in the machine's moves, which he could not understand. He also suggested that humans may have helped the machine during the match. He demanded a rematch, but IBM declined and retired Deep Blue. In 2003 a documentary film was made that explored these claims entitled Game Over: Kasparov and the Machine.

In part these allegations were correct. The rules provided for the developers to modify the program between games, an opportunity they took with abandon. The code was modified between games to understand Kasparov's playstyle better, allowing it to avoid a trap in the final game that the AI had fallen for twice before.

Feng-hsiung Hsu later claimed in his book Behind Deep Blue: Building the Computer that Defeated the World Chess Champion 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 to agree to a rematch (see also Hsu's open letter about the rematch linked below).

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; the other rack appears at the Computer History Museum in their "Mastering The Game: A History of Computer Chess" exhibit.

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