Author: Robert Hyatt
Date: 13:19:07 07/22/00
Go up one level in this thread
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. 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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