Deep Blue

background chess: “the touchstone of the intellect” machine would model thinking, some say chess problem “sharply defined” First chess-playing machine: 1760’s Maezal Chess Automaton

minimax algoritm generate all possible moves by player and opponent a number of steps ahead outcomes generally reside in outermost leaves of trees depth of search -> program rating

limits initially tried to emulate humans human skills: pattern recognition and associative memory engineering approach, relies on computer’s strengths

Tuning Mechanisms hill climbing perform a lookahead search then adjusts the parameter best fit function of machine’s evaluation of positions and the true values

logistics 6 move lookahead: 38^12 = 9 billion billion moves each move lookahead worth about 400 rating points (world champions around 2,900)

Deep Blue features Hsu’s single chip move generator Anantharaman’s singular extension algorithm

Hsu’s “chess machines” evaluates 2 million positions per second 256 teamed together: 100 million positions per second 70% of chip devoted to evaluating positions

position evaluation separate value for pieces on different squares stored endgame positions position features from grandmasters

alpha-beta search eliminates bad moves from further consideration move ‘refuted’ if opponent can force a worst outcome than the previous estimation

singular extensions horizon problem looks 30 or 60 moves in certain situations, checks or piece exchanges fewer choices, deeper search

Kasparov 2.5 Deep Blue 3.5 May 3 – 11, 1997 blunder costs previously undefeated World Champion