Author: Uri Blass
Date: 14:52:45 01/30/02
Go up one level in this thread
On January 30, 2002 at 17:02:28, Miguel A. Ballicora wrote: >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) I am not sure if I understand the meaning of confirmation search but 1 and 2 seem to me similiar to confirmation search. I understand that confirmation search means searching to reduced depth and only if you find a zunzwang search to full depth. 1 is similiar to confirmation search and the only difference may be that in 1 you never search to full depth after searching to reduced depth. 2 is also basically the same as 1 because you search the line null null to a reduced depth. >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). I do not know but I think that it is not in Crafty. Crafy falled into the trap. I also do not think that 3 is a good idea. you can save a lot of time by pruning moves that are close to the root and has no threat. Uri
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