Author: Tony Werten
Date: 23:08:15 12/04/05
Go up one level in this thread
On December 04, 2005 at 06:17:18, Uri Blass wrote: >On December 04, 2005 at 04:49:55, Tony Werten wrote: > >>On December 03, 2005 at 12:27:56, Robert Hyatt wrote: >> >>>On December 03, 2005 at 11:12:23, chandler yergin wrote: >>> >>>>New game >>>>[D]3Q4/bp3pp1/6k1/8/7R/6p1/B2p1PP1/q1rn2K1 w - - 0 1 >>>> >>>>Analysis by Shredder 8: >>>> >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 10/10 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 12/12 00:00:00 26kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 13/13 00:00:00 41kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 14/14 00:00:00 75kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 15/15 00:00:00 153kN >>>>1.Qd3+ f5 2.Qxg3+ >>>> +- (#14) Depth: 16/16 00:00:00 247kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Qxd2 >>>> +- (#11) Depth: 17/18 00:00:01 596kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ >>>> +- (#14) Depth: 18/54 00:07:23 166686kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 19/55 00:07:28 169067kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ >>>> +- (#14) Depth: 20/53 00:07:35 171711kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 21/56 00:07:42 174826kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 22/36 00:07:49 178326kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 23/38 00:08:03 184315kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 24/40 00:08:26 194168kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 25/43 00:08:56 207920kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 26/43 00:09:43 229005kN >>>>1.Qd3+ f5 2.Qxg3+ Kf6 3.Qd6+ Kg5 4.Rh5+ Kxh5 5.Bf7+ Kg5 6.Qg3+ Kf6 7.Qg6+ Ke5 >>>>8.Qe6+ Kf4 9.g3+ Kg4 10.Qg6+ Kf3 11.Qxf5+ >>>> +- (#14) Depth: 27/41 00:11:01 263041kN >>>> >>>>(, MyTown 03.12.2005) >>>> Which is what I said; deeper search confirms. >>>>I see no Bug, the Program found a Mate in 11 in .01 seconds >>>>I cut the analysis short. My error, not the Program. >>> >>> >>>You may not see the bug, or you may not understand the bug. But it is >>>absolutely a bug. >>> >>>Pick up _any_ AI textbook. Alpha/Beta is _guaranteed_ to return the same score >>>as a pure minimax search, only far faster. If a minimax search says "mate in >>>11", and there is no mate in 11 present, then that is a bug, nothing more, >>>nothing less. Many programs will find a mate that is sub-optimal (longer) but >>>if one finds one that is shorter than can be forced, it is simply a bug. >> >>Why would checkmate scores have to be exact ? >> >>You can choose to return (heuristic)checkmate scores from eval, with some bound >>on iteration depth. >> >> >>Tony > >I agree that in theory checkmate score do not have to be exact but I think that >practically when programs say shorter mate than the real mate it is because of >bugs. > >Note that usually evaluation is only an estimate for the real score and if a >program says 0.00 it does not mean that it is a draw. > >A program may have a function to see wins in pawn endgame(I do not have it) and >it may evaluate the following position as mate in 20 for white during the >search. > >[D]8/p3k3/8/8/8/8/PPPPK3/8 w - - 0 1 > >The reason that I believe that no program does it is because I see no practical >advantage from doing it because even if you evaluate it as winning and use it >for pruning you can give it a bonus of 50 pawns and have a rule to prune lines >when the evaluation is more than 50 pawns advantage unless you already found >advantage of more than 50 pawns for one side and you search for mate. I know at least 2 programs using it. Giving 50 pawns bonus is based on the same idea. The problem is what to do with different wins. Add a rook for white, and score would go up but how much ? Returning a checkmate score, where the distance to mate is based on the difficulty of the win is a lot easier. When searching, iteration depth will go up, and real checkmates pop up, because they are the only ones having a dtm below or equal to the iteration depth. One big point of attention though: You should first check wether the move leads to a draw by repetition before you return the heuristic checkmate score. Else you might allow a 3 fold repetition in a heuristicly won position. Very embarrasing when that happens at, oh say, a world championship. Tony > > >Uri
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