Author: Robert Hyatt
Date: 06:24:40 08/06/99
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On August 06, 1999 at 00:55:40, KarinsDad wrote: >On August 05, 1999 at 23:02:00, Robert Hyatt wrote: > >[snip] >> >> >>that isn't the case I am looking at. I have a position that is a mate in 220 >>plies, or 110 moves. If I play it 'perfectly' I will make only one pawn move >>at move 90, but I will draw because at move 50 no pawn pushes have been played. >>In this position, I can push a pawn at ply=20, but if I do so, I won't be able >>to push it again until ply=130. And that is 10 plies too deep and again I draw >>if I push it at 20. But if I wait to ply 40 to push it, I can still push it >>again at ply=130, and now I am 'home free' with no chance of a draw, although >>the total mate is probably going to be much longer than 220 plies, since I had >>to avoid the optimal path to avoid the 50-move draws... >> >>That is the problem I don't see a way to solve, ever... >> > >Well, this problem cannot be solved with the current tablebases. > >And, since it cannot be solved with them, the best you can do is attempt to >accidentally find a solution. In the case you specify, the program would find a >potential solution at ply 20, but as it got further down the search, it would >find that this does not solve the problem and a draw will result. > maybe or maybe not. Remember that I do a search while probing egtb files. And this search is aware of repetitions and 50-move draws. So I won't blindly play a mate in N that actually is an instant draw... >The problem you specify could be solved with a tablebase that had win preserving >moves (for 50 move rule only) in it. The reason is that a win preserving move by >definition is one that resets the counter and leads to mate. It does not matter >how many moves down below it the mate occurs since you know by definition that >somewhere down the 100 ply you will either mate or you will find another win >preserving move. Note: a win preserving move would have the distance to reseting >the counter, not the distance to mate. the problem is not "this move preserves a win because there is a useful capture in 35 plies from this point"... the problem is that between here and 35 plies into the future there are a _lot_ of positions. And any of them could repeat a previous position that we have already passed twice... I think the 'path' problem is simply impossible unless the program is able to search the game from the beginning, all by itself. If we expect the computer to take over a human-played game at some point, it is _always_ going to make such mistakes... > >So, the problem is solvable (at least for those positions where it CAN be >solved). For positions where it cannot be solved, it doesn't matter. They are >already a draw and they will stay that way unless the opponent blunders. > >KarinsDad :)
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