Author: Bas Hamstra
Date: 18:40:12 06/01/01
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On June 01, 2001 at 16:13:41, Scott Gasch wrote: >Hi all, > >I have some questions about recapture extensions. > >First of all, what is the point? I assume to extend in a position where a >recapture move is the only reasonable move so as to see further beyond the >forced exchange. Somewhat like singular extensions or one legal reply >extensions, I think a properly done recapture extension should not be too >expensive. I'd also expect that a well done recapture extension would improve >the tactical strength of the engine. > >Well, I've been trying to get a good recapture extension working on my engine >for a while now. I've tried a bunch of different recapture definitions / >conditions. Most recently I did: > > 1. last move was a capture and this move captures the last moved piece > 2. this is the first capture considered (weighed by SEE) > 3. do not allow two recaptures in a row > 4. this move restores the material balance to what it was at the root. > >...in which case I extended 1/2 ply. Since I am expecting better tactical >ability with the recapture turned on, I test it with the ECM suite. Every time >I try, my results are worse with the recapture turned on than with no recapture. > >I know that a bunch of other engines are doing recapture... so there must be a >good idea there somewhere. Can anyone address these questions or propose a >solid recapture condition? > >Thanks, >Scott I do recaptures of equal value to the same square. The idea is to reduce horizon effect, a disaster can be pushed over the horizon by for example exchanging a knight for a knight, if you do nothing about it. Recaptures of non equal value will probably affect the score, so less important to extend. Does it help much? Well, not in my case. With it turned on, I solve a few wacs extra, and lose some others. Net effect zero. I leave it turned on, in the hope that it has some effect in real games, but am not 100% sure. Best regards, Bas.
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