Author: Miguel A. Ballicora
Date: 10:12:55 01/25/01
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On January 25, 2001 at 12:49:58, Edward Screven wrote: >On January 25, 2001 at 09:34:05, Robert Hyatt wrote: > >>On January 25, 2001 at 08:20:26, David Rasmussen wrote: >>>I mean, maybe many of the "unsound" pruning methods would be sounder if, instead >>>of just pruning, they just adjusted the resulting depth down. In that way, a >>>line would still be examined, only later. >> >> >>This is what null-move search does, in essence... > >we must think about the null move heuristic differently, because i >don't think its typical implementation is at all similar to what >david suggested. > >sure, there is a reduced depth search involved, but it's part >of the pruning test, not the pruning action. the pruning action >is all or none -- completely prune the move from the parent node >or search it in full. > >applying david's suggestion to a null move implementation would >mean reducing the search depth after a null move failed high >instead of simply returning immediately with a fail high. That is what I do with in my program Gaviota (not a good example since it is still a beginning project). Instead of returning beta I do depth = depth - R; I does not reduce the tree as much as classic null-move but still reduces enough. The advantage is that it is not fooled as easily by zugswang-type positions. A couple of plies more and it sees it. Some of the positions that have been posted here that are tough for excellent null-move programs Gaviota was ok. Probably not as good as null-move since zugswangs are rare but I just like it. Regards, Miguel > > - edward
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