Deep Blue
background chess: “the touchstone of the intellect” 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 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)
Hsu’s single chip move generator Anantharaman’s singular extension algorithm
Hsu’s “chess machines” 256 teamed together: 100 million positions per second 70% of chip devoted to evaluating positions
position evaluation separate value for pieces on different squares 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
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
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