Author: Ed Schröder
Date: 14:16:25 11/28/00
Go up one level in this thread
On November 28, 2000 at 14:38:33, Robert Hyatt wrote: >On November 28, 2000 at 14:12:53, Peter McKenzie wrote: > >>On November 28, 2000 at 13:44:15, Robert Hyatt wrote: >> >>>On November 28, 2000 at 12:47:00, Mogens Larsen wrote: >>> >>>>On November 28, 2000 at 12:12:12, Mogens Larsen wrote: >>>> >>>>>On November 28, 2000 at 11:50:12, Dann Corbit wrote: >>>>> >>>>>>On November 28, 2000 at 10:30:00, Robert Hyatt wrote: >>>>>>[snip] >>>>>>To add a bit, here is an output from a chess engine for one of the WAC >>>>>>positions: >>>>>> >>>>>>Middlegame phase. >>>>>> 2 -173 4 525 e5c6 d6c6 >>>>>> 2 -173 4 1232 e5c6 d6c6 >>>>>> 3 -188 5 1569 e5c6 d6c6 f6h5 >>>>>> 3 -187 6 4205 g3g6 ! >>>>>> 3 -123 6 4577 g3g6 >>>>>> 3 -122 7 6316 f6h5 ! >>>>>> 3 -101 7 7444 f6e8 ! >>>>>> 3 -17 7 7746 f6e8 d6e5 d4e5 d8e8 >>>>>> 4 -17 7 8247 f6e8 d6e5 d4e5 d8e8 >>>>>> 4 -17 8 10898 f6e8 d6e5 d4e5 d8e8 >>>>>> 5 -12 8 11626 f6e8 d6e5 d4e5 d8e8 a1d1 >>>>>> 5 -11 11 22518 g3g6 ! >>>>>> 5 383 14 33800 g3g6 !! >>>>>> 5 999996 14 34042 g3g6 d6e5 >>>>>> 5 999996 15 34369 g3g6 d6e5 >>>>>>Learning score: 999996 best: 36 depth:5 hash: F45FB3C8 >>>>>> >>>>>>Notice that it 'found' g6 at ply 3. Was it 'solved'? Obviously not. Why not? >>>>>>Because it had no idea how good the position was. Because of this, the choice >>>>>>was easily abandoned at later ply. Given enough time, it found the right move >>>>>>for the right reason and stuck to it. >>>> >>>>That is an obvious case but you're oversimplifying the question at hand. First >>>>of all it found the move at ply 5 for the same reasons as at ply 3, ie. better >>>>evaluation than other possibilities. You conclude that it found the right move >>>>because the evaluation is improving (rapidly), because you know that it should. >>>> >>>>The fact that the score explodes is irrelevant as it depends on the position, >>>>eg. finding a mating sequence or finding a slightly better move. So going from >>>>-167 to 11 slowly as an example is just as valid as -11 to 383 rapidly. It >>>>depends on the nature of the position and the depth of the correct variation. >>>>Guessing the correct first move in a long variation with a high score is even >>>>more suspicious IMO. The evaluation score isn't a right reason by itself. >>>> >>>>My interpretation of right reason is an improvement in score as the PV >>>>approaches the "correct" variation. The Gandalf case doesn't justify this "right >>>>reason" conclusively, but it's very close. I find my interpretation easy to >>>>understand, independent of position type and free of suspicious speculation. >>>> >>>>Mogens. >>> >>> >>>I don't have any "suspicious speculation" in this case. Only a strong feeling >>>that "right move, wrong reason" is not convincing me of very much. IE on ICC >>>the other night we had a long discussion about a move Crafty had played. The >>>GM (Don't remember who it was not, but not Roman) said "Rd4 was beautiful... >>>I am very impressed that the program saw it as it led to a crushing position >>>for it." I looked at the log and told the group discussing this "The score was >>>very bad for it at that point... it actually thought that move was best, but >>>that it was losing the game... until it failed high on the 'pondering search' >>>after playing it." We all agreed that it was just "lucky" there that it found >>>a move that turned into a win, even though it had no idea when it played it how >>>it would turn out... >> >>Remember the saying that goes something like, 'good players tend to get lucky' ? >> >>I think thats what this whole thing boils down to. If you (a program or a >>human) have a few clues about what is going on, then you are likely to play good >>moves. And as Larsen said: 'Good moves win chess games, not good positions'. >> >>I wouldn't get too carried away with this 'right reason' stuff, I think it over >>simplifies things. > >Counterpoint would say that "right move and nothing else" also over-simplifies >things. Because the question is "do you play the right move for the wrong >reason and later discover it is winning more often than when you play the >right move for the wrong reason and later discover the bottom drops out?" > >We have all (most everybody anyway) always counted a test position right if >the key move was found. And that is not a bad way of measuring very large test >suite results (IE WAC, ECM, etc...) because the "wrong reason" has to catch up >with you statistically. But on a very small (Nolot) suite, or even on a single >position from a small suite, I think a "microscope" is a good analysis tool. > >I personally don't feel very "safe" if my program is doing something good for >the completely wrong reason(s) it found... yes, I like to see it do the right >thing, period. But those "wrong reason" cases cause me to remember that for >every right move, wrong reason, there will also be wrong move, wrong reason >cases as well. Rebel from the start position will frequently switch from 1.d4 to 1.e4 Does it play 1.e4 or 1.d4 for the wrong reason? Ed >>> >>>That was my point. Yes it played the right move. No it didn't understand >>>why. It played it fully expecting to lose. It could have played any of >>>_several_ moves and _still_ expected to lose. It just _happened_ to pick the >>>right one. In this case, for a reason (weak opponent pawn) that had _nothing_ >>>to do with how the game actually progressed and was won by that move. >>> >>>I chalked that one up to heads or tails and heads came up _that_ time. Next >>>time it could well be tails and it goes down in brilliant flames...
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