Author: Vincent Diepeveen
Date: 14:40:10 12/20/02
Go up one level in this thread
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. >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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