Author: Miguel A. Ballicora
Date: 14:02:28 01/30/02
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On January 30, 2002 at 16:11:07, Uri Blass wrote: >On January 30, 2002 at 15:22:09, Gerd Isenberg wrote: > >>>Are we sure that this blind spot is caused by null move? I tried switching >>>off null move completely and it makes very little difference to what my program >>>does in this position. My score still starts out at -1.something for black then >>>goes to +1.something, then goes back to -1.something before drifting back up to >>>around +0.9, all in the first 5 minutes of search (up to depth 20). Does anyone >>>else find that null move doesn't make much difference here? Obviously using null >>>move helps with the number of nodes, but it doesn't change the scores very much >>>at all. >>> >>>Andrew >> >>Use the position one move before. This position should be Nullmove sensitive: >> >>[D] 8/8/1p1r1k2/p1pPN1p1/P3KnP1/1P6/8/3R4 b - - bm Nxd5 >> >>If i use Nullmove here, but no confirmation-Search, IsiChess finds Nxd5 in about >>three minutes. > >I do not understand it. > >How is it possible to find Nxd5 with null move pruning without confirmation >search? >It seems impossible to do it. I do not know what a confirmatory search is (I guess I can imagine, something like YACE) but I think of 3 possible ways: 1) reduce depth, rather than pruning (Gaviota) 2) double nullmove (Diep) 3) apply only nullmove when depth is < x plies. x could be something like 7 etc. This one I think is Crafty, according to some posts in the past (IIRC). When you search so deep, there is one point where moves close to the root are not nullmoved anymore. Solution to nullmove problems are just delayed. Regards, Miguel > >after searching the line Nxd5 Rxd5 Re6 that is not the main line the computer is >going to find that there is no threat and prune the line. > >I expect normal null mover never to find it even after 3 years because it is >going to say the following: > >1)The score after moves like Rd8 or Ne2 is about +1 for white > >2)Nxd5 Rxd5 Re6 has no threat in other words the score after Nxd5 Rxd5 Re6 when >it is black to move is better than +1 for white and the conclusion is that the >computer does not need to search Nxd5 Rxd5 Re6 > >3)The score after Nxd5 Rxd5 not Re6 is also better than 1 pawn for white > >conclusion Nxd5 is worse than Rd8 and is not the right move. > >Uri
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