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Deep Blue

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

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Deep Blue

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  1. Deep Blue

  2. 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

  3. 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

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

  5. 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

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

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

  8. 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

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

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

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

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

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