13Alpha-beta Pruning Use with minimax for eliminating the nodes that looks badEach node will keep the lower limit and upper limitof possible score, called alpha and beta value[alpha,beta]Will follow the rules to stop expanding nodes
14Rules for Terminating search on nodes Stop below any MIN node have a beta value less thanor equal to alpha value of any of its MAX ancestorsStop below any MAX node have an alpha value greater thanor equal to beta value of any of its MIN ancestors
43Standard Board Size: 8x8 = 64 squares Depth: about 60 movesBranching factor: varied 0-20Estimated search time for depth 32 = 3 daysEstimated search time for depth 60 = 2,100 years
44Game playing Tactic Opening (around move 1-12) Use opening book Mid game (around move 13 – 35)Use Evaluation functionEnd game (around move 36-end)Use exhaustive search
45Opening There are 3 ways of opening in Othello. Use statistic records for 100,000+ games to determinewhich opening win the most.
46Mid Game Evaluation function use heuristics to give score to board positionDon’t play on certain squarePrefer cornerWant great mobilityEdge and corner patternsEvaluation function is the key to strong Othello program