Author: David Rudel
Date: 10:00:34 05/14/05
Go up one level in this thread
KK, I think you have both the situation and Stephen's response wrong. Possibly it is a language barrier problem [I do not know if English is your native language], but you say >You admitted that you don't use it. What Stephen actually said is >>I have a Bookup database with 1.3MM moves in it, all input manually by me over >>the past 15-years. Given that size, I never use the automatic backsolve >>function. The only thing Stephen is saying he doesn't use is the AUTOMATIC backsolve. I am sure he still backsolves after inputting a new set of moves, he just doesn't do it after each one is put in separately]. Since Stephen goes on to say how helpful and useful the backsolving feature is, it seems that there either must be a language barrier here or a willful interest in selective reading. To answer some of your other questions: Bookup backsolves both the numeric assessments [that is the assessment an engine would place if it had all the assessments from all the moves later in the tree] and the Human evaluation [informator symbols] assessments that you enter based on literature or your own evaluation of the material. It also backsolves the total number of variations past a position. It handles all your transposition concerns because Bookup is a positional database, so all it cares about is whether a certain position with a certain assessment is reached with best play from both sides [exactly the min-max method]. However, it will show all move orders and do other transposition gymnastics if you wish. I do not know what your beef is with Backsolving, but the claim is that backsolving is a much better method of finding the correct evaluation of a position than using statistical inference based on a selection of human games. In this contention, backsolving has a lot to be said for it. As for how a move done at move 30 can be a refutation to a choice chosen at move 12, that is the nature of chess. You make a choice at move 12 and that choice, with what is known to be good play from both sides, leads to a certain position well down the road. If someone finds a new move in that position, an improvement has to be found to save the line. That improvement may be hard to find going back until the choice made on move 12. Now, the numbers 12 and 30 in the above are a bit of hyperbole, but the general idea is still valid. Here is an example in a somewhat popular variation of the slav: 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.e3 Bf5 5.Bd3 Bxd3 If one were just looking at databases, Bg5 would be the overwhelming choice here, statistically Black has a huge advantage with Bg5, so why does a world-class GM play Bxd3 against Karpov? 6. Qxd3 e6 7.O-O Nbd7 8.Nc3 Bb4 9. Bd2 And here is where we get to the answer. From this position, WHite does very well [statistically] agaisnt everything except... 9...a5 So, since a5 is not an obvious move, you will have many games where Black choses something else and White does well. Since this is a very large branch of this opening, it will skew 5...Bxd3 to look unfavorable [and 4.e3 to look favorable]. However, Black does very well in the one variation 9...a5, so if you had entered all the main lines into bookup and your engine correctly evaluated the end-nodes correctly, backsolving would show this whole line to be rather lackluster for White, whereas statistics will show it to be reasonably good. Another example is the Winawer Counter-gambit, 1.d4 d5 2.c4 c6 3.Nc3 e5!?. This variation scored very well for Black for a few years until Kasparov found a REFUTATION on 7 plies later.
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