Author: Amir Ban
Date: 14:00:24 07/22/00
Go up one level in this thread
On July 22, 2000 at 16:19:07, Robert Hyatt wrote: >On July 22, 2000 at 16:03:59, Amir Ban wrote: > >>On July 22, 2000 at 15:32:26, Ed Schröder wrote: >> >>>On July 22, 2000 at 14:16:51, Andrew Dados wrote: >>> >>>>On July 22, 2000 at 14:11:20, Ed Schröder wrote: >>>> >>>>>On July 22, 2000 at 13:28:28, blass uri wrote: >>>>> >>>>>>Deeper blue had a positive evaluation before trading queens. >>>>>> >>>>>>The evaluation of Deeper blue was based on Deeper blue's logfile >>>>>> >>>>>>9(6) 3 T=46 34...Qxf1 >>>>>>10(6) 2 T=130 34...Qxf1 >>>>>>11(6) 2 T=168 34...Qxf1 >>>>>> >>>>>>The evaluation when deeper blue started to ponder (hash guess Rxf1) was >>>>>> >>>>>>7 (4) -30 >>>>>>7 (6) -66 >>>>>>8 (6) -50 >>>>>>9 (6) -50 >>>>>>10 (6) -50 >>>>>>11 (6) -48 >>>>>> >>>>>>Deeper blue lost 0.5 pawn in the evaluation and the only reason that I can >>>>>>explain it is that it is a root processor. >>>>>> >>>>>>I guess that something like this cannot happen to Deep Junior because it is >>>>>>probably more knowledge based program. >>>>>> >>>>>>Uri >>>>> >>>>>The behavior you describe is quite normal. After a queen exchange in the >>>>>next move often other more accurate tables are used which may cause such >>>>>score differences. I do the same in Rebel. That doesn't make the program >>>>>a root processor. A root processor is a program that totally (or to a >>>>>great extend) relies on the evaluation on the root. If you read the IBM >>>>>pages it is said DB has something similar (a short investigation at the >>>>>root). That makes DB no root processor. >>>>> >>>>>Ed >>>> >>>>What you just said is pretty much confirmation of preprocessing to me: >>>>'After a queen exchange in the next move often other more accurate tables are >>>>used []'... >>>>If it is done in the search - then no score differences should be seen; if it is >>>>done at root then it is clear preprocessing... >>>> >>>>-Andrew- >>> >>>Yes such ticks are preprocessing. And it helps. But note that in Rebel >>>only a few things are done this way not more than being < 0.5% of the >>>total knowledge. That makes Rebel not a root processor and DB neither >>>which was my reply to header of the subject. >>> >>>Ed >> >>I disagree. >> >>Even if only a small part is preprocessed, the effect here is huge: half a pawn. >>DB played 37... Qxf1+ into an even position and woke up a move later into a >>half-pawn disadvantage. This means that according to its own evaluation Qxf1 is >>a blunder and would never have been played if not for preprocessing. >> >>DB switched from Qe2 (-21) to Qxf1+ (+2) and then learned that it's actually >>Qxf1+ (-48). So Qe2 was clearly better by DB evaluation. >> >>Junior evaluates Qe2 and Qxf1+ as equals. >> >>Amir > >As I said before, there is more than one way to skin a cat. Cray Blitz did >exactly as described, because there I added a bonus for trading queens. But >once the trade was done, the bonus went away on the next search. > Same thing. This may not be preprocessing, but is equally bad. You play a move thinking it is best, only to find when evaluating the resulting position that your second-best move was better. If scores are not comparable, then they are meaningless. Amir P.S. Before somebody jumps on me with a position, I do have some minor dependency on root position in Junior. I don't like it, and will get rid of it eventually. >In Crafty, I have a smoothing function that can produce some ugly scoring >distortion. Ie if I am a piece ahead, the score will climb by a significant >amount each time a piece is traded. By the time I reach a position where I have >only one piece, the score may say +5. > >You don't have to do it this way. But I think it is better as it doesn't >introduce hashing inconsistencies... There is a downside when someone says >"hey, you are only up a pawn, why do you have +2.0?" and I say "that is because >all the pieces are gone..."
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