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

Author: Omid David Tabibi

Date: 02:04:58 08/19/03

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On August 19, 2003 at 04:12:45, Tord Romstad wrote:

>On August 19, 2003 at 02:48:36, Omid David Tabibi wrote:
>>It seems that some programs use Static Exchange Evaluation in order to prune
>>losing captures in quiescence search.
>Not just some.  Almost all strong programs do this, I think.
>>In the following position, an SEE will deem the move 1.Rxd7 a losing capture, and it might
>>get pruned in quiescence. However, in fact this is a winning capture since Qf6 is attacked
>>after 1.Rxd7. How do such programs solve these kind of problems?
>They don't (or at least most don't).  On the other hand, the significant extra
>speed gained
>by not searching all captures help them find a lot of other tactics which they
>wouldn't have found.
>Try it yourself.  I am almost certain that you will find that excluding losing
>from the qsearch is a big win.

But a good SEE will be quite costly by itself. For example:

[D]3r2k1/pp1r1qpp/2pb4/5p2/3R1P2/8/PPPR2PP/3Q2K1 w - - 0 1

My engine has information about all attacked squares, e.g., it knows that d6 is
attacked by a white rook and defended by a black rook. However, I assume that an
SEE should be able to find out that Rxd6 is a winning capture. This needs a more
extensive processing of backed-up attacks (e.g., Rd4 is backed up by Rd2 which
is backed up by Qd1, and Rd7 is backed up by Rd8). I'm afraid this is too costly
a process.


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