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Subject: Re: Futility Pruning off?

Author: Uri Blass

Date: 22:01:16 01/21/04

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On January 21, 2004 at 18:25:54, Tord Romstad wrote:

>On January 21, 2004 at 14:59:23, Robert Hyatt wrote:
>
>>On January 21, 2004 at 12:45:59, Tord Romstad wrote:
>>
>>>On January 21, 2004 at 05:02:37, Robert Allgeuer wrote:
>>>
>>>>Do I conclude correctly that futilty pruning is off? Is there a specific reason
>>>>for that?
>>>
>>>Possibly that it simply doesn't work very well?  The idea has always looked
>>>dubious to me, and my own experiments confirm this.  There is a speedup, but
>>>it is not worth the risks.
>>>
>>>As always, the results may vary from engine to engine, but I suppose Bob has
>>>found that it doesn't work for him either.
>>>
>>>Tord
>>
>>
>>Correct.  I didn't like it myself after lots of testing.  It looks good on
>>test sets, but you don't win games by doing well on test sets.
>
>That's precisely what I found, too.
>
>In general I am very sceptical about pruning schemes which prune moves before
>they
>are made.   At that time, we simply don't know enough about the moves to be able
>to prune safely.

I do not understand it.

Suppose that the opponent has a big material advantage so you think the only
hope to get the score above alpha is by a capture or checkmate.

Suppose that captures and checks did not return score above alpha.
Do you think that it is a bad idea to prune other moves before you make
them(espacially for program that are using fail hard like Crafty and not fail
soft)?

Uri



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