Author: Tony Werten
Date: 23:31:32 12/20/02
Go up one level in this thread
On December 20, 2002 at 17:40:10, Vincent Diepeveen wrote: >On December 20, 2002 at 17:36:20, Tony Werten wrote: > >>On December 20, 2002 at 17:20:26, Uri Blass wrote: >> >>>On December 20, 2002 at 16:30:32, Vincent Diepeveen wrote: >>> >>>>On December 20, 2002 at 12:02:23, Uri Blass wrote: >>>> >>>>>On December 20, 2002 at 11:26:28, Richard Pijl wrote: >>>>> >>>>>>On December 20, 2002 at 10:54:01, Vincent Diepeveen wrote: >>>>>> >>>>>>>On December 20, 2002 at 08:23:59, Russell Reagan wrote: >>>>>>> >>>>>>>No futility is 100% different from lazy evaluation. >>>>>>> >>>>>>>Futility in fact selects less moves (in qsearch) >>>>>>>based upon alfa or beta and lazy evaluation gives >>>>>>>back a quick score a lot of the times. >>>>>> >>>>>>They are still related in a sense that both 'cut-off' the work to be done by >>>>>>saying that it can't get good enough to improve alpha, so better stop working on >>>>>>it. >>>>>>> >>>>>>>If you search a ply deeper a futile pruned move should not >>>>>>>get pruned, whereas a lazy evaluated position will give problems >>>>>>>no matter what depth you search. >>>>>>> >>>>>>>In contradiction to draughts where everything is seen fullwidth, >>>>>>>in computerchess the effect of futility can be very bad too, >>>>>>>because last 3 to 4 plies (R=2 versus R=3) the qsearch is returning >>>>>>>back a score instead of a full search. >>>>>>> >>>>>>>If that misses major problems then you are in trouble. >>>>>>> >>>>>>>The argumentation of Heinz that futility is correct, is using the >>>>>>>assumption that an evaluation doesn't get a big score for positional >>>>>>>matters. The problem is that todays top programs do give big scores >>>>>>>though. >>>>>> >>>>>>Although Baron is not a top program yet I'm starting to feel this. >>>>>>To be sure that the wrong nodes aren't getting pruned I wrote a little piece of >>>>>>test code. It returned the highest difference it found between the lazyeval >>>>>>score and the full eval score (but not with passers on the board, and not in the >>>>>>endgame). I added 20% to this and that was the threshold used for both lazyeval >>>>>>and futility pruning. It turned out that with every release of the Baron this >>>>>>value increased. >>>>>>Now I'm working on 0.99.4 and the margin was getting very large, more than 5 >>>>>>pawns. >>>>> >>>>>I think that it may be interesting to see the position that you talk about >>>>> >>>>>When do you see a difference of more than 4 pawns between the static evaluation >>>>>and the lazy evaluation? >>>> >>>>define lazy evaluation in this case. Just material component or >>>>a function that quickly estimates lazy eval? >>> >>>I think that the definition of lazy evaluation may be a function that quickly >>>estimates the real evaluation(not just material) >>> >>>The estimate can also say that the big evaluation need to be done in small part >>>of the cases (for example you can decide that if there are no pawns near the >>>king then king safety can get big scores so you cannot trust fast evaluation). >>> >>>> >>>>Note that just a diff of > 4 pawns is not interesting, only when it >>>>would modify alfa or beta it is; >>>> >>>>if lazy eval is 2 pawns white up and actual score is 3 pawns white up >>>>and beta is 1.5, then obviously it is not interesting. A cutoff is >>>>a cutoff, isn't it? >>>> >>>>Idem for <= alfa. >>>> >>>>The interesting thing is when your quick eval with a margin is >>>>at the other side of the bound (alfa or beta) than the real eval. >>>> >>>>In diep i produced a big graph and found out that 1% was wrong. >>> >>>If I understand correctly in 99% of the cases when lazy without margin was in >>>the wrong side of the bound lazy with margin was right. >>> >>>I am still surprised to read it >>>My question is if you evaluate tactical stuff like pins or forks because my >>>opinion is that positions when positional stuff worth more than 3 pawns are >>>rare. >> >>Don't forget that one side only has to be 1,5 pawn up and the other 1,5 pawn >>down. > >3 pawns up or 3 pawns down. A window of 3 pawns above beta and a window >of 3 pawns down alfa. > Yes, what I meant was that if material is equal and one side gets 1,5 pawn bonusses and one side gets 1,5 penalties then 3 pawns window is already reached. 1,5 pawns bonus or penalty is easily reached, but people think 3 pawns sounds so big. Tony > > >>Tony >> >>> >>>You say that you worked 3 monthes about your fast evaluation so the question is >>>in how many cases only material+margin of +3 is wrong. >>> >>> >>>Uri
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