Download Deep Blue - UMBC CSEE

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