Author: Tony Werten
Date: 14:36:20 12/20/02
Go up one level in this thread
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. 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
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.