Author: Jorge Pichard
Date: 08:30:48 04/26/03
Go up one level in this thread
On April 26, 2003 at 09:08:33, Geoff wrote: >Hi > >I have been experimenting with a chess engine, very similar to TSCP 1.73 at the >moment. I came across this test position which should be a mate for white in 5 > >[D]1b6/kPp5/p1P5/R5Rr/P1N1P3/8/6p1/6Kb w - - 0 1 > >Solution is 1.g5-c5 h5-g5 2.c5-f5 g5-h5 3.f5-g5 h5xg5 4.a5xg5 a6-a5 5.g5xa5# > >This chess engine uses iterative deepening and a standard alpha Beta Search >using +/- infinity. According to my understanding it should spot the mate at Ply >10. An alpha beta search with a +/- infinity search window should not miss a >mate as the pruning is guarenteed to be perfect ? >Is my understanding wrong here or must this be a bug ? > >The thing that really puzzled me is that I tried version 1.81 where as far as I >can see the eval and search code is the same, but V 1.81 spots the mate at ply >10. > >Thanks for any thoughts on this > > regards Geoff > > > >1.73 Misses the checkmate ?? > >ply nodes score pv > 1 28 980 g5h5 > 2 95 115 g5g2 h1g2 > 3 676 640 g5g2 h5a5 c4a5 > 4 2032 576 a5a6 a7a6 g5h5 b8a7 > 5 11687 960 c4d6 c7d6 g5h5 a7b6 h5h1 > 6 41864 571 g5e5 h5g5 a5a6 a7a6 e5g5 b8a7 > 7 306957 880 g5f5 h5g5 c4d6 c7d6 f5g5 a7b6 g5g2 > 8 932164 576 g5f5 h5g5 f5e5 g5h5 a5a6 a7a6 e5h5 b8a7 > 9 7280073 786 g5f5 h5g5 a5a6 a7a6 f5g5 b8a7 g1h2 g2g1q g5g1 > 10 14031564 845 g5c5 h5g5 e4e5 g5e5 c4e5 a7b6 c5d5 b8a7 a5c5 a7b8 > >e4e5 is the wrong move !!! grrrrrrr > > >1.81 Spots the checkmate >ply nodes score pv > 1 28 980 g5h5 > 2 95 115 g5g2 h1g2 > 3 676 640 g5g2 h5a5 c4a5 > 4 2032 576 a5a6 a7a6 g5h5 b8a7 > 5 11687 960 c4d6 c7d6 g5h5 a7b6 h5h1 > 6 41876 571 g5e5 h5g5 a5a6 a7a6 e5g5 b8a7 > 7 307185 880 g5f5 h5g5 c4d6 c7d6 f5g5 a7b6 g5g2 > 8 935877 576 g5f5 h5g5 f5e5 g5h5 a5a6 a7a6 e5h5 b8a7 > 9 7330801 786 g5f5 h5g5 a5a6 a7a6 f5g5 b8a7 g1h2 g2g1q g5g1 > 10 13846050 9991 g5c5 h5g5 c5f5 g5h5 f5g5 h5g5 a5g5 a6a5 g5a5
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