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Subject: Re: Static Exchange Evaluation (SEE) for pruning in quiescence (?)

Author: Robert Hyatt

Date: 15:19:05 08/20/03

Go up one level in this thread


On August 20, 2003 at 07:36:37, Bo Persson wrote:

>On August 19, 2003 at 08:07:07, Uri Blass wrote:
>
>>On August 19, 2003 at 08:05:39, Uri Blass wrote:
>>
>>>On August 19, 2003 at 07:43:08, Bo Persson wrote:
>>>
>>>>On August 19, 2003 at 06:19:59, Joost Buijs wrote:
>>>>
>>>>>
>>>>>To me it looks wrong to skip losing captures from the quiescence search if the
>>>>>losing captures are determined by a SEE that is wrong in some cases, e.g. pinned
>>>>>pieces. If you use the SEE for move ordering purposes only this problem doesn't
>>>>>exist.
>>>>
>>>>But it is always only an approximation, you just want it to be good enough to
>>>>avoid flat out blunders.
>>>>
>>>>In a position like this
>>>>
>>>>[D]8/1p6/r1r5/8/8/8/8/R1R5 w - - 0 1
>>>>
>>>>SEE will believe that the black rooks are both defended, but they are not. This
>>>>is not a "pin", but an "overload" which is still missed. You just can't get it
>>>>all (cheap).
>>>>
>>>>
>>>>Bo Persson
>>>
>>>They are defended.
>>>
>>>Rxa6 Rxa6
>>>
>>>if you want a better example then it is better to put a pawn at b6 and not only
>>>at b7.
>>>
>>>Uri
>>
>>It is still wrong because Rxa6 Rxc1
>>
>>It is better to put 2 knights and not 2 rooks to show that SEE may miss a good
>>capture by white.
>
>Yes, you are right. My point was that if SEE is used to resolve captures on a
>specific square, you miss the fact that a single piece can be involved in
>several of these "shoot outs". In real play it often cannot, at least not
>simultaneously.
>
>That another piece might be pinned doesn't make that much of a difference.
>
>Bo Persson
>
>

I think that overloaded pieces, and pins, both contribute to the inaccuracy of
SEE.  I've handled pins in the past, but I don't now.  I've never tried
overloaded pieces as it is too complicated to figure out that "if I capture
here with this piece, then I lose material over _there_ because I have one
less defender than I need now."


>>
>>Uri



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