Author: Tord Romstad
Date: 04:57:30 01/27/04
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On January 27, 2004 at 07:21:53, Ed Schröder wrote: >On January 26, 2004 at 11:10:55, Tord Romstad wrote: > >>Yes. That is why I don't do this at all nodes, but only when the evaluation >>function reports that the current position is "sufficiently close to >>quiescent" that it is safe to rely on the relatively simple SEE. >> >>Consider the simplest possible example: >> >>Assume that the side to move has no hanging, pinned or overloaded pieces, >>and that the opponent has an undefended hanging piece. If the static >>eval plus the value of the hanging piece is considerably bigger than >>beta, it is reasonably safe to return beta. This works even with >>a very simple SEE. > >Tord, > >I am probably doing something similar, to be sure can you demonstrate the above >with a (diagram) example? Sure. The following examples look rather artificial, but I still think they are good enough to illustrate the idea. Assume that the following position occurs with white to move in the qsearch, and that beta has a value close to zero: [d] 4k3/2b5/5q2/4P3/8/8/6K1/6Q1 w - - Instead of generating and searching any captures, my qsearch just returns a fail high score immediately in this position. Black's queen is hanging, capturing it will bring the score considerably above beta, and there are no "warning signs" for white (i.e. no hanging, pinned or overloaded pieces). If we move the white king or queen to h2, white's pawn on e5 is pinned. This is detected by my evaluation function. In such cases, I generate and search captures. If we move black's bishop to b6, I also generate and search the captures rather than returning a fail high score immediately, because now white's queen is also hanging. Does this resemble what you are doing? Tord
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