Author: Steve Timson
Date: 22:03:02 01/01/01
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>The other position is from a game against another program (ChesterX on >ICC): > >[D] 2n5/8/1p6/pK5p/2N2k1P/8/PP6/8 w - h6 > >Here Chester played a4, but the sac Nxb6 seems to be winning. It is not >easy to find. Crafty fails high at ply 17, after almost 5 minutes of search >(on a PIII/733): > > 17 4:53 ++ 48. Nxb6!! > 17 5:20 1.49 48. Nxb6 Nxb6 49. Kxb6 a4 50. Kb5 Kg3 > 51. Kxa4 Kxh4 52. b4 Kg4 53. b5 h4 > 54. Kb4 h3 55. b6 h2 56. b7 h1=Q 57. > b8=Q Qd5 > (2) 17-> 5:24 1.49 48. Nxb6 Nxb6 49. Kxb6 a4 50. Kb5 Kg3 > 51. Kxa4 Kxh4 52. b4 Kg4 53. b5 h4 > 54. Kb4 h3 55. b6 h2 56. b7 h1=Q 57. > b8=Q Qd5 > 18 6:34 1.55 48. Nxb6 Nxb6 49. Kxb6 Kg3 50. Kxa5 > Kxh4 51. b4 Kg4 52. b5 h4 53. b6 h3 > 54. b7 h2 55. b8=Q h1=Q 56. Qc8+ Kf4 > 57. Qc7+ Kf5 58. Qc5+ Ke6 59. Kb5 > 18-> 9:01 1.55 48. Nxb6 Nxb6 49. Kxb6 Kg3 50. Kxa5 > Kxh4 51. b4 Kg4 52. b5 h4 53. b6 h3 > 54. b7 h2 55. b8=Q h1=Q 56. Qc8+ Kf4 > 57. Qc7+ Kf5 58. Qc5+ Ke6 59. Kb5 > 19 11:39 1.55 48. Nxb6 Nxb6 49. Kxb6 Kg3 50. Kxa5 > Kxh4 51. b4 Kg4 52. b5 h4 53. b6 h3 > 54. b7 h2 55. b8=Q h1=Q 56. a4 Qc6 > 57. Qb5 Qc7+ 58. Kb4 Kf3 > >I'd be interested in any analysis or comments on these positions from other >players or programs. > >--Jon Chester actually switches back and forth between Nxb6 and a4 off and on. Here is what Chester thinks about the position: 5.44s 11 798445 +1.22 a4 Kg4 Nxb6 Nxb6 Kxb6 Kxh4 Kxa5 Kg5 b4 Kf5 Kb5 9.56s 11 1557836 +1.47 Nxb6 Nd6+ Kxa5 Kg4 Kb4 Kxh4 Kc5 Ne4+ Kd4 Ng5 Nd5 Nf3+ Ke4 Kg4 19.83s 12 3420369 +1.04 Nxb6 Nxb6 Kxb6 a4 Kb5 Kg4 Kxa4 Kxh4 b4 Kg5 b5 h4 24.28s 12 4204443 +1.41 a4 Kg4 Kc6 Ne7+ Kxb6 Kxh4 Kxa5 Kg5 b4 h4 Kb5 h3 a5 40.81s 13 7051588 +1.42 a4 Kg4 Nxb6 Nxb6 Kxb6 Kxh4 Kxa5 Kg5 b4 Kf6 Kb5 Ke5 a5 60.20s 13 10611289 +1.56 Nxb6 Nd6+ Kxa5 Nf5 b4 Nxh4 b5 Nf5 Nc4 Nd4 b6 Nc6+ Kb5 Nd4+ Kc5 Ke4 144.29s 14 25560357 +1.11 a4 Kg4 Kc6 Ne7+ Kxb6 Kxh4 Nxa5 Kg5 Kc5 h4 Nc4 h3 Nd2 Kf5 b4 270.51s 15 47645722 +0.98 a4 Kg4 Nxb6 Nxb6 Kxb6 Kxh4 Kxa5 Kg5 b4 h4 b5 h3 b6 h2 b7 h1=Q b8=Q Things start slowing down a lot right there. This is short of where Crafty makes its discovery of course. So, if I play a4 and then search Chester gives: 28.07s 13 4787825 -1.11 Kg4 Kc6 Ne7+ Kxb6 Kxh4 Nxa5 Kg5 Nc4 h4 Kc5 h3 Nd2 Kf5 b4 68.22s 14 11865384 -0.98 Kg4 Nxb6 Nxb6 Kxb6 Kxh4 Kxa5 Kg4 b4 h4 b5 h3 b6 h2 b7 ... 148.80s 15 26159174 -0.98 Kg4 Nxb6 Nxb6 Kxb6 Kxh4 Kxa5 Kg4 b4 h4 b5 h3 b6 h2 b7 ... 438.53s 16 77706614 -0.82 Kg4 Nxb6 Na7+ Kxa5 Kxh4 Ka6 Kg3 Kxa7 h4 Nc4 h3 Ne3 Kf2 Ng4+ Kg3 a5 Kxg4 a6 While if I play Nxb6: 49.54s 14 9073476 -0.98 Nxb6 Kxb6 Kg4 Kxa5 Kxh4 b4 Kg5 b5 h4 b6 h3 b7 h2 ... 64.64s 15 11979587 -0.87 Nxb6 Kxb6 a4 Kb5 Kg4 Kxa4 Kxh4 b4 Kg5 b5 h4 b6 h3 b7 h2 Kb4 h1=Q b8=Q 94.69s 16 17796917 -0.87 Nxb6 Kxb6 a4 Kb5 Kg4 Kxa4 Kxh4 b4 Kg5 b5 h4 b6 h3 b7 h2 ... 175.15s 17 33233917 -0.87 Nxb6 Kxb6 a4 Kb5 Kg4 Kxa4 Kxh4 b4 Kg5 b5 h4 b6 h3 b7 h2 Kb4 h1=Q b8=Q So basically Chester really can't make up its mind... :) It certainly sees them as roughly equivalent, at least to depths it can see in a reasonable time period, though I'd definitely believe Crafty over Chester. - Steve
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