Author: Dieter Buerssner
Date: 07:58:27 04/23/01
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On April 23, 2001 at 10:11:00, Ulrich Tuerke wrote: >On April 23, 2001 at 09:48:40, Dann Corbit wrote: [...] >> >>Just like NULL MOVE or any selective element for searching, it will cause some >>problems to be solved more slowly. However, I suspect it will cause *most* >>problems to be solved faster. That is the way it works with every good idea. > >Completely agreed. The above mentioned risk arises essentially if you have >chosen your cut threshold (too) close to alpha. There can also be some other "risks", depending on what the qsearch does. E.g. When you don't allow stand-pats, where the side to move is in check. When you cut such nodes, depending on material gain and alpha, you can miss such situations. I try to be careful to do the pruning in qsearch in certain situations. When you capture the last pawn of the opponent, you can reach a draw score. An example (similar to what we discussed recently). KNNP vs. K will have an high material advantage. If you grap the P, the material gain is much less than the gain in score. Also, when reaching pawn endgames, I try to be careful. I think, this pruning idea saves less, than one could think. When you prune the node, all work, that would be needed for this node is a call to qsearch, and a call to eval (which will fail high). For the threshold, I use something based on largest positional advantage (dependant on the side). Of course, this won't give many cutoffs with Vincent's 20 pawns :-) Regards, Dieter
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