Author: Bruce Moreland
Date: 11:32:13 02/15/99
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On February 15, 1999 at 13:07:45, Dann Corbit wrote: >On February 15, 1999 at 12:47:56, Bruce Moreland wrote: >>Not every problem is solvable in a short time. If you search for 8 hours you >>are only searching a few more plies than if you search for 2 minutes. You're >>just doing a little more of the same old stuff. >> >>Maybe the pawn sacrifice doesn't work, but the argument against it is going to >>be a chess argument, not a "I searched this for a year and didn't find it" >>argument. >Well, that's clearly true. But I would argue that with 13 fullmoves lookahead, >there are not a lot of people who will out-think the computer. In other words, >as time goes by in computer assisted analysis, I think it increases the >probability that the computer's choice is correct, especially when both choices >are considered in detail. Considering them in detail in this case involved forcing a move at the root, which I don't think qualifies. A few days ago I made the argument that in a sense all moves that lead to mate are equally good. I think it was important to do it in that case since it appeared that there was an attempt to apply some absolute meaning to the notion of a best move. I think this argument would be tiresome if I invoked it in every circumstance. If someone shows a move that wins a rook, destroys counterplay, and leads to a position that any reasonable player would agree is won, I am not going to say that the solution is spoiled because there is another move that wins a pawn and may lead to a technical win. I think that there are many positions where computers can offer valid insights. And by this I mean that they find a good move and offer a convincing line. I think there are also many positions where you can let the computer search forever and it is still in the dark. Many of these are middlegame positions, but there seems to be another category that includes endgame positions of this sort. Perhaps 1. c5 does not win. I haven't looked at the analysis. But I've fiddled with the position a bit. 1. c5 is a pawn sacrifice. It is possible that other pawn sacrifices, or even a piece sacrifice, will follow from this position. I think that this kind of position is dangerous for computers and it is very likely that there is a win here and your computer won't be able to see it. You can burn through 13 full moves in an endgame very quickly. Put a bishop on the board, put the kings somewhere where they can't do much, and put a few pawns down for the other side, in such a fashion that they can't be simultaneously stopped by the bishop. This is a -1 position for the pawns, but after many moves by both sides one of them queens. >By supplying the pv for both possibilities, someone with a lot more chess >knowlege than I have can say, "Yes, there may be something here..." or "No, this >is clearly wrong. The position is Zugzwang here and so the computer simply did >not consider the proper choice..." >I will go so far as to say that unless a checkmate for one side or the other is >undeniably proven then any 'best move' candidate is in question. Here's why: >Imagine a 5 year old (non-prodigy) who has just learned the rules of chess. >They look ahead one ply at a time for the immediate move. They have a move that >would look best to them. But now, after 10 years of playing, the 15 year old is >much better. Perhaps she looks ahead 'n' moves. She would beat the 'best move' >of the 5 year old. Now, she faces a GM. The GM thinks ahead 'n'+2 or more >moves at all times. The GM's best move is better than her best move. The GM >faces a super GM. The super GM thinks one ply farther than the GM, on average >(or however the strategy is superior -- probably nobody knows). From the same >position, the Super GM's best move may be different than the GM's. Now, let's >take that Super GM and let them think on a move for a whole month. After >thinking it through very carefully, using database systems and computer programs >to assist, the Super GM's best move may not be the same move they chose >previously. > >In other words, a 'best move' is only 'best' compared to a worse move unless it >definitely and undeniably leads to mate. I think that in this case it is likely that 1. c5 is the only try for a win, and that this is one of those marginal positions where this can be seen by fairly weak humans (although the win itself may be harder to see), but that computers may have a hard time understanding. bruce
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