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Subject: Re: Quiescence Search - Additional Q

Author: Angrim

Date: 13:32:45 02/12/03

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On February 12, 2003 at 01:06:06, Nathan Thom wrote:

>On February 11, 2003 at 20:57:16, Nathan Thom wrote:
>
>>Ive just finished implementing a Q search for LittleThought, and was trying to
>>get a feel for my node stats compared with other engines out there. What % of
>>the total nodes searched are Q nodes in varying kinds of positions? eg opening,
>>middle game, end game etc.
>>
>>I have a feeling my q nodes are way way too many :)
>
>In alot of examples ive seen, an evaluation is done right at the start of the Q
>function and if it gives a beta cutoff it returns. I dont understand this. Isnt
>the whole point of Q search to prevent scoring unstable positions? If the score
>for this position exceeds beta, it may be that it just did QxQ say. That will
>give a large eval as one side just lost the Q but the other still has theirs.
>But, if the Q search had a chance to continue, it would see that the Q can be
>recaptured immediately.
>
>What gives?

If the previous move was QxQ then the side to move has just lost a Q.
If they exceed beta without even trying to recapture, then they return
because recapturing should only improve their position.

Angrim



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