Author: Martin Giepmans
Date: 05:47:02 12/19/02
Go up one level in this thread
On December 19, 2002 at 01:46:01, Uri Blass wrote: >On December 18, 2002 at 22:19:24, Martin Giepmans wrote: > >>On December 18, 2002 at 21:51:20, Omid David Tabibi wrote: >> >>>On December 18, 2002 at 21:44:09, Martin Giepmans wrote: >>> >>>><snip> >>>>>>I don't understand what you are trying to say. >>>>>>Without a research (if the verification search with reduced depth doesn't >>>>>>give a cutoff) verification search would be pointless. >>>>> >>>>>The verification search goes deeper than the null-move search, so it might find >>>>>tactical errors overlooked by the null-move search, and correct them (without >>>>>any need for a re-search). >>>>> >>>> >>>>No need for a research ?????????? >>>>It's late, I guess we are talking about two different things? >>> >>>No we aren't :-) >>> >>>When we have a fail-high report, we simply reduce the depth, and continue a >>>regular search, as if nothing has happened. Because this regular search (which >>>can be called verification search) goes deeper, it might find out threats beyond >>>null-move search's horizon. In that case, you would get the correct result even >>>if you don't do a re-search! >>> >>Yes, we _were_ talking about 2 different things :) >>My thing is verification search, yours is what I would call "de-extension". >>One difference is that de-extensions are symmetrical (you reduce depth for >>both colors) while (standard) verification search is essentially asymmetrical. >> >>I think it's possible that at least some of the readers of your article >>got confused here and implemented something in their programs that you >>didn't intend. Perhaps that explains why in many cases your method didn't >>seem to work. >> >>Martin > >I do not understand >How can you reduce depth for only one color? > >There is only one varaible with the name depth in my program. > >Uri That's right, but the effect is asymmetrical. It's the same with nullmove. Suppose a program has white and only uses nullmove on ply 2. The effect is that it may overlook a good continuation for white, but _not_ for black. Nullmove pruning is (in effect) asymmetrical. Standard verification search (always research) is also asymmetrical. If you leave out the research it becomes symmetrical: it may overlook good continuations for _both_ sides. I think there is a fundamental difference between vs with and without research. Martin
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