Author: Tord Romstad
Date: 10:14:11 01/21/04
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On January 21, 2004 at 12:52:47, Charles Roberson wrote: > The qsearch algorithm allows the ability to "pass" in such a case, and >others, the qsearch will not catch undefended pieces. It isn't necessary to always allow the side to move to pass in the qsearch. I sometimes don't allow passing when the side to move has more than one piece hanging. In such cases, I search moves which brings one of the hanging pieces to a safe square in addition to captures and checks. I have found that using the evaluation function to decide what to do in the qsearch can be a rather powerful technique. With some effort, it is possible to write a qsearch which is both faster *and* more reliable than a plain stand pat + winning/equal captures qsearch. What I do is to collect as much information as possible about hanging, pinned, trapped and overloaded pieces as possible in the evaluation function. If the tactical complexity is low, I sometimes just return the value of the static eval plus the SEE value of capturing the biggest hanging piece for the opponent, without searching any moves at all. In more complicated positions, relying only on the SEE is too risky, and I search all winning and equal captures. If the position is really wild, I don't trust my SEE at all, and searches all captures (even those which appear to lose material). Furthermore, king safety and the presence of promising-looking force is used to the decide whether checks should be searched. Tord
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