Author: Robert Hyatt
Date: 06:39:30 12/26/99
Go up one level in this thread
On December 25, 1999 at 17:46:42, Gian-Carlo Pascutto wrote: >On December 25, 1999 at 13:27:45, John Hendrikx wrote: > >>I've tried adding null-moves as well, but haven't been very succesful. I >>need some more to go on before I can get it right, but I can't find good >>examples or descriptions of them. So far what I've tried is to try a >>null-move before doing any real moves at a certain level of the tree, and >>searching the null-move to the same depth as usual; > >Erm, this basically defeats the idea of a nullmove search: to get a cutoff >with *less* work. > >>my problem is that I >>don't know what to do with the returned score. From what I gathered one >>should create a cut-off when the score is 'not so good' even while doing >>two moves in a row.. > >I prefer to reverse this: when the other side is allowed to move twice and >a shallow search yields a score for us that is still enough for a beta cutoff, >we are quite certain we'd have gotten a beta cutoff if we did a full-depth >search. > >>it didn't work for me though. It was far slower (1.5 >>times) with the same results, and only a few dozen null-move cutoffs at >>6 plies orso. > >You should be getting over 50%. (at least, that the number I get) > >>Should null-moves be tried for both black and white? > >Your search shouldn't make any distinction between black and white. Using a >negamax-type search will make your program a lot less complicated. > >>> >>>1. hash table move >> >>Is that the same as the Principle Variation? >> > >No...there is only one principle variation, but all positions >have a best move. > >-- >GCP Actually, with alpha/beta they don't. If one position fails high, that means that the move at the previous ply was no good. If you search every move at ply=N, and each move is refuted by a move at ply=N+1 that fails high, then with alpha/beta you have absolutely no idea about which move is best at ply=N.
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