Author: Omid David Tabibi
Date: 13:07:54 11/27/02
Go up one level in this thread
On November 27, 2002 at 15:55:04, Uri Blass wrote: >On November 27, 2002 at 15:15:50, Robert Hyatt wrote: > >>On November 27, 2002 at 13:48:50, Frank Phillips wrote: >> >>>On November 26, 2002 at 20:02:06, Robert Hyatt wrote: >>> >>>>On November 26, 2002 at 16:21:00, Omid David Tabibi wrote: >>>> >>>>>On November 26, 2002 at 15:58:06, Gian-Carlo Pascutto wrote: >>>>> >>>>>>On November 26, 2002 at 15:55:56, Omid David Tabibi wrote: >>>>>> >>>>>>>So it is reasonable that on every program starting from a certain depth >adaptive null-move pruning will always construct a smaller search tree. >>>>>> >>>>>>Don't you mean the other way around? >>>>>> >>>>> >>>>>Yes :-) >>>>> >>>>>Starting from a certain depth, verified null-move pruning will always construct >>>>>a smaller search tree than the adaptive one. >>>>> >>>>> >>>>> >>>>>>-- >>>>>>GCP >>>> >>>> >>>> I am doing some testing now. First thing I noticed is that for WAC, the >>>>time-squared >>>>measurement went down very significantly for your algorithm. And I have not >>>>modified >>>>anything such as turning null-move off when low material happens, since your >>>>idea will >>>>catch the zug problems. >>> >>>Have you tried Fine70? >>> >>>Frank >> >>Yes... and I told Omid that this is a strange case as if I allow null-move in >>pawn-only >>endings, which turns it on for fine 70 of course, things get wrecked inside the >>search >>somehow. A 45 ply search fails to see that Kb1 wins where normally an 18-19 ply >>search is enough... > >No surprise > >The idea is productive for detecting cases when there is one zugzwang but not >for cases when there is more than one zugzwang. > >It is a bad idea to use it for pawn endgame. >If you want to use it to be theoretically sound(to see everything after enough >plies) then you need always to do verification search and not only in cases that >verify=true. > >It may be possible to do verification search to reduced depth when >verify=false(for example by depth-=3; instead of depth--;) >if you want to protect yourself against the danger of zugzwangs in the middle >game and only if you detect a zugzwang to search again to bigger depth. > In the subtree of a fail-high reported node, standard null-ove pruning is used, which is susceptible to zugzwangs. So the algorithm might not detect a series of zugzwangs in a variation, in special positions. I thought that such exceptional positions might exist, and that's why I wrote "detect most zugzwangs" ("most" instead of "all"). Anyway, in the extreme endgames, I believe it'd be better to turn off null-move pruning altogether, since the cost of the re-searches might be too much. However, using a reduction of 2 on fail-high reports, we can allow using verified null-move pruning also in the subtree, without ending up with a large tree. This method should be completely zugzwang-proof. >Uri
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