Author: Ricardo Gibert
Date: 21:34:56 07/10/02
Go up one level in this thread
On July 10, 2002 at 22:04:44, Robert Hyatt wrote: >On July 10, 2002 at 20:42:45, Ricardo Gibert wrote: > >>On July 10, 2002 at 11:04:34, Sune Fischer wrote: >> >>>On July 10, 2002 at 09:30:30, Ricardo Gibert wrote: >>> >>>>On July 10, 2002 at 04:30:28, Sune Fischer wrote: >>>> >>>>>On July 10, 2002 at 01:02:38, Ricardo Gibert wrote: >>>>> >>>>>>I find it fascinating that so many very experienced computer chess programmers >>>>>>do not understand some rather fundamental properties of alpha-beta search. >>>>>> >>>>>>What RH ran into was actually quite predictable. As MF put it, "I'm surprised >>>>>>that you're surprised." >>>>> >>>>>In a PV search some of the nodes are searched twice, so if you get something >>>>>outside the zero window because of a collision, it slows you down as you have to >>>>>research, but it doesn't hurt you unless you get another collision while >>>>>researching. >>>>> >>>>>-S. >>>> >>>>This is not a property of using PVS. A normal alpha-beta search plus hash table >>>>does this too. >>> >>>How so? >>>I would say it does the opposite, since its about refuting moves. >> >>What either one of us has to say on this is really irrelevant. RH needs to >>conduct a more reasonable test. The manner in which he generated the collisions >>plus the use of PVS should be changed. > >How would you suggest generating the collisions? As far as dropping PVS >however, I disagree on. That is what I _use_ in real games. That is what >I want to understand the behavior of. I don't care about variants of >alpha/beta that I am not using myself (ie mtd(f) or something else that >is non-PVS). You are forcing a collision every 1000 nodes, but then the same position will not likely produce the same collision when the position is researched. You are testing something very different and valuable than if you were generating the collisions in a consistent way unless I have misunderstood what you were doing. I think studying alpha-beta first will afford a more precise understanding of what is going on. Start with the simple before moving on to the more complex. I just think it is better to be more methodical. > > > > >> >>> >>>But thinking further about it, the collision could also return a false score >>>outside alpha-beta, so the move is refuted when it should not be. I don't know >>>which is worse, but at least landing _inside_ is harmless as we just research, >>>which was my point. >>> >>>-S.
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