Author: Omid David
Date: 12:42:36 07/15/02
Go up one level in this thread
On July 15, 2002 at 14:42:52, Robert Hyatt wrote: >On July 15, 2002 at 13:30:54, Gian-Carlo Pascutto wrote: > >>On July 15, 2002 at 13:11:09, Christophe Theron wrote: >> >>>Why does double null move prove that null move is a correct search method???? >>> >>>Doing two null moves in a row means going back to standard search (a search not >>>involving an illegal move like null move is). >>> >>>I fail to see how it legitimates null move. >> >>I think the idea is simply to show that you can nullmove and still >>have a correct search. (but only with double nullmove, not single) >> >>-- >>GCP > > >I think the discussion is pointless, myself. Null-move search is _not_ >equlvalent to non-null-move search. It demonstrably has more errors due to >reducing the depth on many sub-trees. > >The concept of "correct search" is therefore so abstract as to mean absolutely >nothing. double-null eliminates _some_ zugzwang problems, but not _all_. It >is obviously impossible to eliminate all of them, particularly when you are >whacking 6 plies off the tree depth and then drawing conclusiong about the >resulting sub-trees.. > >The only useful definition of "correct search" would be to somehow prove >that a null-move search to depth=D would produce the _same_ move as a >non-null-move search to depth=D, for all positions. This is simply not >possible. Well, all these ideas try to deal with zugzwangs. As I said before IMO the main null-move deficiency remains the horizon effect. However the gains from null-move pruning by far exceed the risks.
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