Author: Dieter Buerssner
Date: 11:36:36 10/14/01
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On October 14, 2001 at 14:15:43, Rafael Andrist wrote: >If an underpromotion is clearly worse than the promotion to a queen, this line >will be pruned anyway (Nullmove+AlphaBeta). Problems are IMO only these cases, >where the score of the promotions is nearly equal (mostly because the promoted >piece can be captured, as in example given by Eduard). I agree, that this is the most likely case. >So it is sufficient to >include a rule like: if all promotions have (nearly) equal scores, prefer the >promotion to a queen (or to the piece with the highest value from the ones with >equal score). I think, this won't be sufficient. It is not easy to explain for me. Let me start again with my hash table argument. I think, we all have seen cases, where an engine can find the correct solution to a problem at different depthes, when different hash table sizes are used. Both cases can occure: the misleading hash info was overwritten, or, luckily, the hash info that leads to the correct solution was still there. This can make the scores very different at the same search depth (I don't mean few centipawns). And sooner or later, due to this, we will see wrong underpromotions again. I think, almost all chess engines will do some window dependent pruning. This can yield in the same problem, because in general, we will search the different moves with different bounds. Regards, Dieter
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