How%20Computers%20Play%20Chess

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How Computers Play Chess
Artificial Intelligence 101

• Peter Barnum
• November 15, 2007

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• This raises the question Can a machine play
  chess? It could fairly easily be made to play a
  rather bad game. It would be bad because chess
  requires intelligence.
• Alan Turing 1946

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• The decisive game of the match was Game 2we saw
  something that went beyond out wildest
  expectationsThe machine refused to move to a
  position that had a decisive short-term advantage
  - showing a very human sense of danger.
• Garry Kasparov 1997

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What move should we make?
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How a computer decides
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How a computer decides
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How a computer decides
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How a computer decides
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How a computer decides
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How a computer decides
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Uh oh!
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Adversarial search

• If I make this move, whats the worst thing my
  opponent could do?

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Examining all possible moves

• Can I make a move that will allow me to win and
  prevent my opponent from winning?

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Wait, thats easy!
35
x35
x35
35N
For a game with 6 moves per player
35123,379,200,000,000,000,000 possibilities
If a computer can check one billion moves per
second, it would take over 100 years
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What to do?

• Can we avoid searching all possibilities?

• Can we pre-compute anything?

• Can we approximate the search?

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References

• Stuart Russell and Peter Norvig Artificial
  Intelligence A Modern Approach
• Stanford Encyclopedia of Philosophy