Once solely the province of the human mind, chess is now played by both humans and machines. At first considered only a curiosity, the best chess playing programs like Shredder or Fritz have risen in ability to the point where they can seriously challenge and even defeat the best humans, and regularly defeat the average human Grandmaster.
Garry Kasparov, then ranked number one in the world, played a six-game match against IBM's chess computer Deep Blue in February 1996. Deep Blue shocked the world by winning the first game in Deep Blue - Kasparov, 1996, Game 1, but Kasparov convincingly won the match by winning three games and drawing two.
The six-game rematch in May 1997 was won by the machine (informally dubbed Deeper Blue) which was subsequently retired by IBM. The other programs running on general purpose hardware are generally weaker than Deep Blue was, but catching up, as computers get faster. In October 2002, Vladimir Kramnik drew in an eight-game match with the computer program Deep Fritz. In 2003, Kasparov drew both a six-game match with the computer program Deep Junior in February, and a four-game match against X3D Fritz in November.
The chess machine Hydra is the intellectual descendant of Deep Blue; and appears to be somewhat stronger than Deep Blue was. Certainly it is very much comparable in terms of positions analysed per second. Given the relative ease with which it beats the other programs, and the humans it has met, Hydra may be expected to beat any unaided human player in match play. In June 2005, Hydra scored a decisive victory over the then 7th ranked GM Michael Adams winning five games and drawing one game in a six game match.
Kasparov's loss to Deep Blue has inspired the creation of chess variants in which human intelligence can still overpower computer calculation. In particular Arimaa, which is played upon a standard 8×8 chessboard, is a game at which humans can beat the best efforts of programmers so far, even at fast time controls.
