Author: Peter McKenzie
Date: 11:12:53 11/28/00
Go up one level in this thread
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. > >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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