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Subject: Re: Futility Pruning

Author: Tony Werten

Date: 09:06:15 12/20/02

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On December 20, 2002 at 10:54:01, Vincent Diepeveen wrote:

>
>Where lazy evaluation was easy for me to proof incorrect, with regard to
>futility pruning it is harder to judge.

Futility pruning cannot be correct either. Or rather, if it was correct it
wouldn't save any nodes.

Futility assumes that a move cannot bring the score to alfa. If futility is
correct and you would make the move, you would get into quiescence, evaluate,
get a score>=beta back and return. So no nodes saved.

The only time you save nodes, is when evaluate does not give back score>=beta,
ie when the assumption that the last move could not bring the score to alfa is
wrong.

So futility pruning can only saves nodes when it's wrong.

Tony




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