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Subject: Re: SEE for forward pruning in the Q. search - I'm confused!

Author: Robert Hyatt

Date: 15:26:59 08/12/99

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On August 12, 1999 at 15:53:55, Tom King wrote:

>On August 11, 1999 at 17:27:52, Bruce Moreland wrote:
>
>>
>>On August 11, 1999 at 16:12:07, Tom King wrote:
>>
>>>I must be missing something obvious with using SEE to prune
>>>in the Q. search. If I understand right, "losing" captures
>>>(according to the SEE) are pruned right out. But I fail to
>>>see how this won't screw up big time.
>>>
>>>Let's take an example. Now assume we have a white bishop on G5
>>>and a black knight on F6, and the knight is protected by a pawn on G7.
>>>Now the SEE might well assume that BxN is a loser (assuming that
>>>the bishop is worth a fraction more than the knight), because
>>>after BxN, gxB, white has lost a bishop for a knight. But it
>>>might be that this is in fact a very good capture, because it
>>>destroys black's kingside. And a program with the SEE Q. pruning
>>>might not want to play this? Am I missing something obvious
>>>here?
>>
>>Yes, a bishop is worth the same as a knight.
>>
>>bruce
>
>not in my program, it ain't ;-)
>
>anyhow is val[bishop]==val[knight]? I always thought that bishops were worth
>*slightly* more than a knight in general..


Nope.  Take any position with 8 pawns on both sides, and compare a bishop to a
knight.  Knight wins every time, because the bishop gets hemmed in.  That's why
I use bishop == knight (material) and then let the positional scores separate
them. IE bishop has more mobility than knight, it is more valuable.  Knight
stuck in a strong outpost where it can't be dislodged is much stronger than
a bishop.

Etc...



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