Author: Stan Arts
Date: 11:13:49 02/01/04
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On January 31, 2004 at 19:29:18, Jaime Benito de Valle Ruiz wrote: >I came across this position almost by accident. A few moves before this, my >"poor engine" was giving a huge score for white in no time, while Ruffian >sticked to draw. So I reanalized the whole thing. >Why can't Ruffian 1.05 find an easy 1.Qd5 and win? Null move? Special Pruning? > >[d]Q7/8/1p1K4/1p6/2k5/8/1P6/4q3 w - - > Neurosis 1.7 on PIII-550 with 32mb hash. Legal moves: 26 Static score: -87 Ply Score Time Nodes Best move and expected line ------------------------------------------------------------ 2 0 6 2681 Qc6+ Kb4 Qxb6 3 0 6 2962 Qc6+ Kb4 Qxb6 4 -83 17 14185 Qc6+ Kb4 Kc7 Qd2 Qxb2 4 -80 17 15932 Qd5+ Kb4 Qd4+ Ka5 Qc3+ Qxc3 bxc3 5 -2 28 21740 Qd5+ < + > Kb4 Kc6 Qe8+ Kxb6 5 0 28 24016 Qd5+ Kb4 Kc6 Qe8+ Kxb6 Qg6+ Kc7 Qc2+ Kb6 6 0 60 57851 Qd5+ Kb4 Kc6 Qe8+ Kxb6 Qg6+ Kc7 Qc2+ Kb6 Qg6+ Kc7 Qc2+ Kb6 7 786 115 107427 Qd5+ < + > Kb4 Qd3 Qe7+ Kxe7 Ka5 b4+ 7 796 143 133145 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 8 796 626 608058 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 9 796 1456 1313305 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 Qxb6 10 796 6663 6225046 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 Qxb6 11 799 12660 11988459 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qb1+ Kc4 Qc2+ Kb4 Kd5 Total nodes:28436153 n/sec:96400 (Q-nodes:3% max depth:20) My program does do some form of null-move pruning, but very conservative and "safe". (=not recursive, adaptive R=1 and R=2, a verificationsearch, using my evaluationfunction to deside to do a null-move or not, etc.) This usually works..but it does fail in this position with my program as well :( It's indeed a null-move/zugzwang problem position. Without any null- move at all it finds the winning score faster. : Legal moves: 26 Static score: -87 Ply Score Time Nodes Best move and expected line ------------------------------------------------------------ 2 0 5 2681 Qc6+ Kb4 Qxb6 3 0 5 2962 Qc6+ Kb4 Qxb6 4 -83 16 14099 Qc6+ Kb4 Kc7 Qd2 Qxb2 4 -80 16 15845 Qd5+ Kb4 Qd4+ Ka5 Qc3+ Qxc3 bxc3 5 1 27 25466 Qd5+ < + > Kb4 Qd3 Qa1 Qd4+ 5 790 27 26234 Qd5+ < + > Kb4 Qd3 Qa1 Qc3+ 5 790 33 31407 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 6 790 137 123881 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 7 796 302 273372 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 Qxb6 8 796 1362 1304206 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 Qxb6 9 796 2845 2695919 Qd5+ Kb4 Qd3 Qa1 Qc3+ Ka4 b3+ Ka3 Qxa1+ Kxb3 Qd4 Qxb6 Total nodes:5310333 n/sec:96500 (Q-nodes:3% max depth:18) Greetings Stan
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