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Alpha Beta Search how computers make decisions Elena Eneva 10 October 2001.

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Presentation on theme: "Alpha Beta Search how computers make decisions Elena Eneva 10 October 2001."— Presentation transcript:

1 Alpha Beta Search how computers make decisions Elena Eneva 10 October 2001

2 How humans make decisions Current situation at home Goal get to the cinema Options Cab Bike Bus Consequences Best choice Think ahead! slow convenient cheap fast inconvenient cheap LATE HAVE $ ON TIME NO $ ON TIME HAVE $ fast convenient expensive

3 How computers make decisions Current situation Goal get max # of points Options Cab Bike Bus Consequences Best choice Think ahead! +7 +13-3 slow -10 convenient +2 cheap +5 fast +10 inconvenient -2 cheap +5 fast +10 convenient +2 expensive -5

4 How computers play games 2 players Evil opponent Minimax strategy +2 +7 Rain -5 Flat tire Traffic -2 +13 +1 Wait 20 mins -12 Rain -2 Full -2 -3 -8 Rain -5 Flat tire -3 Lose keys -3 X

5 Minimax strategy +2 +7 Rain -5 Flat tire Traffic -2 +13 +1 Wait 20 mins -12 -3 -8 Rain -5 Alpha Beta Pruning Want to save time!

6 Summary Alpha Beta search – a decision making strategy for computers Minimax steps – computer versus evil opponent Pruning – saves time, lets you think further ahead The end.

7 How computers make decisions Current situation Goal get max # of points Options Bike Bus Cab Consequences Best choice Think ahead! slow -10 convenient +2 cheap +5 -3 +7 fast +10 inconvenient -2 cheap +5 +13 fast +10 convenient +2 expensive -5

8 Alpha Beta Pruning Minimax strategy -3 Rain -5 Lose keys -3 Flat tire -3 -8 Wait 20 mins -12 +1 +13 +7 Flat tire -5 Rain Traffic -2 +2 Want to save time!

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