Interesting endgame in TCEC: Nirvana vs. Gaviota

[Guenther]

[pgn][Event "?"]
[Site "?"]
[Date "?"]
[Round "-"]
[White "?"]
[Black "?"]
[Result "*"]

1. c4 Nf6 2. Nc3 e6 3. d4 d5 4. Bg5 Be7 5. e3 h6 6. Bh4 O-O 7. Rc1 b6 8.
cxd5 Nxd5 9. Bxe7 Qxe7 10. Nf3 Bb7 11. Be2 Nf6 12. O-O Nbd7 13. Qb3 Rfd8
14. Rfd1 a6 15. Ne5 Nxe5 16. dxe5 Nd7 17. f4 Rac8 18. Kh1 Rb8 19. Qc4 Nf8
20. Ne4 Ng6 21. Kg1 Nh4 22. g3 Nf5 23. Kf2 Rd5 24. Rxd5 Bxd5 25. Qc2 Rd8
26. Rd1 a5 27. Qd3 Rd7 28. Qb5 Rd8 29. Nc3 Bb7 30. Rxd8+ Qxd8 31. Qd3 Qxd3
32. Bxd3 Ne7 33. a3 g5 34. Be2 Nd5 35. Ne4 gxf4 36. exf4 Kg7 37. Nd2 Ne7
38. g4 Bd5 39. Bd3 h5 40. g5 Bb7 41. Nf3 Bxf3 42. Kxf3 Ng6 43. Bb5 Nh4+ 44.
Ke4 Nf5 45. a4 Kh7 46. Be2 Kg6 47. Ba6 c6 48. Bc4 Kg7 49. Bd3 Nh4 50. Be2
Kg6 51. Bf1 Nf5 52. Bd3 Kg7 53. Kf3 Ne7 54. Be4
*[/pgn]

In the final position of the pgn excerpt, Gavota with Black thought it can now play b5 and completely missed the answer, which wins on the spot!
(even if it may appear that the position is already not good, 54...b5?? should be avoided)
It seems the killer answer is pruned away completely by a lot of programs. Humans with a certain strength of course know the motif.

8/4npk1/1pp1p3/p3P1Pp/P3BP2/5K2/1P5P/8 b - - 13 54

Scorpio 2.78-64 with 5men egbb (256MB only 1 thread) also does not see it, but it is not alone e.g. Texel 1.07-64 behaves the same
(analysis mode with stepping quickly through the pgn to fill hash until move 54)

Code: Select all

35	 -1.50 	125.5M	2:21.05	b6-b5 a4xb5 c6xb5 Be4-d3 b5-b4 b2-b3 Ne7-d5 Kf3-e4 a5-a4 b3xa4 Nd5-c3 Ke4-d4 Nc3xa4 f4-f5 e6xf5 Bd3xf5 b4-b3 Kd4-c4 b3-b2 Bf5-b1 Kg7-g8 Kc4-b3 Na4-b6 e5-e6 f7xe6 Kb3xb2 Nb6-c4 Kb2-c1 Kg8-f7 Bb1-d3 Nc4-e5 Bd3-e4 Ne5-c4 Kc1-c2 N
 34	 -1.31 	90.2M  	1:38.25	Kg7-g8 Be4-b1 Kg8-g7 Kf3-e3 Ne7-d5 Ke3-e4 Nd5-e7 Ke4-d4 Kg7-h8 Kd4-e3 Ne7-d5 Ke3-e4 Kh8-g7 Bb1-d3 Nd5-e7 Ke4-d4 Ne7-g6 Kd4-e3 Ng6-e7 Ke3-f3 Ne7-g6 Bd3-e4 Ng6-e7 Be4-c2 Ne7-g6 Kf3-e3 Ng6-e7 Ke3-d4 Kg7-f8 Bc2-e4 Kf8-g7 Kd4-d3 K
 34	 -1.32 	96.9M  	1:45.84	b6-b5 a4xb5 c6xb5 Be4-d3 b5-b4 b2-b3 Ne7-d5 Kf3-e4 a5-a4 b3xa4 Nd5-c3 Ke4-d4 Nc3xa4 f4-f5 e6xf5 Bd3xf5 b4-b3 Kd4-c4 b3-b2 Kc4-b3 Na4-b6 e5-e6 f7xe6 Bf5-b1 Nb6-d7 Kb3xb2 Nd7-c5 Kb2-c3 e6-e5 h2-h4 Kg7-f7 Kc3-b4 Nc5-a6 Kb4-b5 Na
 33	 -1.32 	84.7M  	1:32.56	Kg7-g8 Be4-b1 Kg8-g7 Kf3-e3 Ne7-d5 Ke3-e4 Nd5-e7 Ke4-d4 Kg7-h8 Kd4-e3 Ne7-d5 Ke3-e4 Kh8-g7 Bb1-d3 Nd5-e7 Ke4-d4 Ne7-g6 Kd4-e3 Ng6-e7 Ke3-f3 Ne7-g6 Bd3-e4 Ng6-h4 Kf3-f2 Nh4-g6 Kf2-e3 Ng6-e7 Be4-d3 Ne7-f5 Bd3xf5 e6xf5 Ke3-d4 Kg
 33	 -1.34 	72.9M  	1:19.80	b6-b5 a4xb5 c6xb5 Be4-d3 b5-b4 Bd3-c2 Kg7-g8 Kf3-e4 Ne7-f5 Ke4-d3 Kg8-g7 b2-b3 Nf5-h4 Kd3-c4 Nh4-g2 Kc4-b5 Ng2xf4 Kb5xa5 Nf4-h3 Ka5xb4 Nh3xg5 Bc2-d1 h5-h4 Kb4-c5 Ng5-e4 Kc5-d4 Ne4-g5 Bd1-g4 f7-f5 e5xf6 Kg7xf6 b3-b4 e6-e5 Kd4-
 32	 -1.32 	32.0M  	0:35.17	b6-b5 a4xb5 c6xb5 Be4-d3 b5-b4 Bd3-c2 Kg7-f8 b2-b3 Kf8-g8 Bc2-e4 Kg8-g7 Kf3-e3 Kg7-f8 Be4-c2 Kf8-g7 Ke3-e4 Ne7-f5 Ke4-d3 Nf5-h4 Kd3-c4 Nh4-g2 Kc4-b5 Ng2xf4 Kb5xa5 Nf4-h3 g5-g6 f7xg6 Ka5xb4 Nh3-f2 Kb4-c5 Nf2-g4 Kc5-d6 Kg7-f7 h
 31	 -0.80 	22.7M  	0:25.29	b6-b5 a4xb5 c6xb5 Be4-c2 a5-a4 Kf3-e4 Ne7-f5 Ke4-d3 h5-h4 Kd3-e4 Kg7-g6 h2-h3 Kg6-h5 Bc2-d1 Kh5-g6 Ke4-f3 Kg6-g7 Kf3-e2 Kg7-h7 Ke2-d3 Kh7-g6 Kd3-e4 Kg6-g7 Bd1-c2 Kg7-g8 Ke4-d3 Kg8-g7 Kd3-d2 Nf5-d4 Bc2-e4 b5-b4 Kd2-d3 a4-a3 b2
 30	 -0.80 	15.4M  	0:17.14	b6-b5 a4xb5 c6xb5 Be4-c2 a5-a4 Kf3-e4 Ne7-f5 Ke4-d3 h5-h4 Kd3-e4 Kg7-g6 h2-h3 Kg6-h5 Bc2-d1 Kh5-g6 Ke4-f3 Kg6-g7 Kf3-e2 Nf5-e7 Bd1-c2 Kg7-f8 Ke2-e3 Ne7-f5 Ke3-e4 Kf8-g8 Ke4-d3 Kg8-g7 Kd3-d2 Nf5-d4 Bc2-e4 b5-b4 Kd2-d3 Nd4-f5 B
 29	 -0.84 	14.5M  	0:16.14	b6-b5 a4xb5 c6xb5 Be4-c2 a5-a4 Kf3-e4 Ne7-f5 Ke4-d3 h5-h4 Kd3-e4 Kg7-g6 h2-h3 Kg6-h5 Ke4-d3 Nf5-e7 Bc2-d1 Kh5-g6 Kd3-e3 Ne7-d5 Ke3-f3 Kg6-h5 Bd1-c2 Nd5-e7 Kf3-e3 Ne7-d5 Ke3-e4 Nd5-e7 Ke4-f3 Ne7-f5 Bc2-e4 b5-b4 Be4xf5 e6xf5 Kf
 28	 -1.16 	11.7M  	0:13.07	b6-b5 a4xb5 c6xb5 Be4-c2 b5-b4 Kf3-e3 Ne7-d5 Ke3-e4 Nd5-e7 b2-b3 Ne7-f5 Ke4-d3 Nf5-h4 Kd3-c4 Nh4-g2 Kc4-b5 Ng2xf4 Kb5xa5 Nf4-g6 Bc2-d1 h5-h4 Ka5xb4 Ng6xe5 Kb4-c5 Ne5-d3 Kc5-c6 h4-h3 Kc6-b5 Nd3-e5 Bd1-e2
 27	 -0.86 	11.2M  	0:12.61	b6-b5 a4xb5 c6xb5 Be4-c2 b5-b4 Kf3-e3 Ne7-d5 Ke3-e4 Nd5-e7 b2-b3 Ne7-f5 Ke4-d3 Nf5-h4 Kd3-c4 Nh4-g2 Kc4-b5 Ng2xf4 Kb5xa5 Nf4-g6 Bc2-d1 h5-h4 Ka5xb4 Ng6xe5 Kb4-c5 Kg7-g6 Kc5-d6 f7-f6 Bd1-e2 Kg6xg5 Kd6xe6
 26	 -0.91 	9.13M  	0:10.18	b6-b5 Be4-b1 b5xa4 Bb1-c2 a4-a3 b2xa3 c6-c5 Bc2-e4 Ne7-g6 Kf3-e3 h5-h4 Be4-d3 Ng6-e7 Ke3-f3 Ne7-d5 Bd3-b5 Kg7-g6 Bb5-c4 Kg6-h5 Kf3-e4 Nd5-c3 Ke4-e3 Nc3-d5 Ke3-f3 Nd5-b6 Bc4-d3 Nb6-d5 h2-h3
 25	 -0.90 	7.52M  	0:08.28	b6-b5 Be4-b1 b5xa4 Bb1-c2 a4-a3 b2xa3 c6-c5 Kf3-e4 h5-h4 Bc2-d3 Kg7-g6 Bd3-c4 Ne7-f5 Ke4-f3 Kg6-h5 h2-h3 Kh5-g6 Kf3-f2 Kg6-g7 Bc4-d3 Kg7-h7 Kf2-f3 Kh7-g6 a3-a4 Kg6-g7 Bd3xf5 e6xf5 Kf3-e3 Kg7-g6 Ke3-f3 Kg6-g7
 24	 -0.88 	5.15M  	0:05.66	b6-b5 Kf3-e3 b5xa4 Be4-c2 Ne7-d5 Ke3-e4 a4-a3 b2xa3 Kg7-f8 Ke4-f3 Nd5-c3 Kf3-f2 Nc3-b5 a3-a4 Nb5-d4 Bc2-e4 c6-c5 Kf2-e3 Kf8-e7 g5-g6 f7xg6 Be4xg6 h5-h4 Bg6-e4 h4-h3 Ke3-d2
 23	 -1.08 	1.68M  	0:01.74	b6-b5 Be4-c2 b5-b4 b2-b3 Kg7-f8 Bc2-e4 Kf8-g7 Be4-d3 Kg7-f8 Bd3-b1 Kf8-g8 Kf3-g3 Kg8-g7 Bb1-e4 Kg7-f8 Kg3-h4 Ne7-g6 Kh4xh5 Ng6xf4 Kh5-h6 c6-c5 h2-h4 c5-c4 b3xc4 b4-b3 h4-h5 b3-b2 g5-g6 f7xg6
 22	 -1.03 	1.49M  	0:01.55	b6-b5 Be4-c2 b5-b4 b2-b3 Kg7-f8 Bc2-e4 Kf8-g7 Be4-d3 Kg7-f8 Bd3-b1 Kf8-g7 Bb1-e4 Kg7-f8 Kf3-e3 Ne7-d5 Ke3-d4 Nd5xf4 Be4xc6 Kf8-g7 Kd4-c5 Nf4-g6 Kc5-d6 Ng6-f4 Bc6-e4 h5-h4
 21	 -1.17 	1.31M  	0:01.37	b6-b5 Be4-c2 b5-b4 b2-b3 Kg7-f8 Bc2-e4 Kf8-g7 Kf3-g3 c6-c5 Kg3-f3 h5-h4 Kf3-g4 Ne7-d5 Be4-f3 Kg7-f8 Bf3-e2 Kf8-g7 Be2-d3 h4-h3 Bd3-b5 Kg7-g6 Kg4xh3 Nd5xf4 Kh3-g4
 20	 -1.08 	1.19M  	0:01.23	b6-b5 Be4-c2 b5-b4 b2-b3 Kg7-f8 Bc2-e4 Kf8-g7 Be4-d3 Ne7-g6 Kf3-e3 Ng6-e7 Ke3-f2 Ne7-g6 Kf2-f3 Ng6-e7 Bd3-e4 Kg7-f8 Kf3-f2 Ne7-d5 Kf2-g3 Kf8-g7 Kg3-h4 Nd5xf4 Be4xc6 Kg7-g6 Bc6-e4 Kg6-g7 h2-h3 Nf4-g6 Kh4xh5 Ng6xe5 h3-h4 f7-f5
 19	 -1.02 	813656	0:00.80	b6-b5 Be4-c2 b5-b4 b2-b3 Kg7-f8 Bc2-e4 Kf8-g7 Kf3-g3 Ne7-d5 Kg3-h4 Nd5xf4 Be4xc6 Kg7-g6 Bc6-e4 Kg6-g7 h2-h3 Nf4-g6 Kh4xh5 Ng6xe5 h3-h4 f7-f5
 19	 -1.20 	321926	0:00.31	Kg7-g8 Kf3-e2 Kg8-f8 Ke2-f2 Kf8-g7 Be4-d3 Ne7-g6 Kf2-g3 Ng6-e7 Bd3-e2 Ne7-f5 Kg3-f2 Kg7-g6 Be2-d3 h5-h4 Bd3-e4 c6-c5 Be4-d3 Kg6-h5 Bd3xf5 e6xf5 Kf2-e3 Kh5-g6 Ke3-d3 Kg6-g7 Kd3-c3 Kg7-f8 Kc3-d2 Kf8-g7 Kd2-d3 Kg7-h7 Kd3-e3 Kh7-g
 18	 -1.19 	230219	0:00.23	Kg7-g8 Kf3-e2 Kg8-f8 Ke2-f2 Kf8-g7 Be4-d3 Ne7-f5 Bd3xf5 e6xf5 Kf2-f3 Kg7-g8 Kf3-e2 Kg8-g7 Ke2-e3 Kg7-f8 h2-h3 Kf8-g7 Ke3-d4 Kg7-g6 Kd4-e3 Kg6-h7 Ke3-d2 Kh7-g7 Kd2-d3 Kg7-f8 Kd3-c2 Kf8-e8 Kc2-d2 Ke8-e7 Kd2-d3 Ke7-e6 Kd3-c4 Ke6-
 18	 -1.21 	211926	0:00.21	Kg7-h8 Kf3-e2 Kh8-g8 Ke2-d3 Kg8-g7 Kd3-d4 Ne7-f5 Kd4-c4 Nf5-e7 Kc4-d3 Ne7-d5 f4-f5 e6xf5 Be4xf5 h5-h4 Kd3-d4 Nd5-f4 Kd4-e3 Nf4-d5 Ke3-f3 c6-c5 Bf5-e4 Kg7-f8 Be4xd5
 17	 -1.19 	199092	0:00.20	Kg7-h8 Kf3-e2 Kh8-g8 Ke2-d3 Kg8-g7 Kd3-d4 Ne7-f5 Kd4-c4 Nf5-e7 Kc4-d3 Ne7-d5 f4-f5 e6xf5 Be4xf5 h5-h4 Kd3-d4 Nd5-f4 Kd4-e3 Kg7-f8
 17	 -1.26 	122169	0:00.12	Kg7-g8 Kf3-g3 Kg8-g7 Kg3-f2 Ne7-g6 Kf2-e3 Ng6-e7 Ke3-d4 Ne7-g6 f4-f5 c6-c5 Kd4-c4 e6xf5 Be4xf5 Ng6xe5 Kc4-b5 Ne5-g4 Kb5xb6 Ng4-e3 Bf5-e4 c5-c4
 16	 -1.18 	105574	0:00.11	Kg7-g8 Kf3-g3 Kg8-g7 Kg3-f2 Ne7-d5 f4-f5 e6xf5 Be4xf5 c6-c5 Kf2-f3 Nd5-e7 Bf5-e4 Ne7-g6 e5-e6 f7xe6 Kf3-e3 Ng6-e7 Ke3-f3 Ne7-d5 Kf3-e2 Kg7-f8
 16	 -1.18 	76287  	0:00.08	Kg7-g8 Kf3-g3 Kg8-g7 Be4-d3 Ne7-f5 Bd3xf5 e6xf5 Kg3-f3 Kg7-g8 Kf3-e2 Kg8-h7 Ke2-f2 Kh7-g7 Kf2-g3 b6-b5 a4xb5 c6xb5 Kg3-f3 b5-b4 Kf3-g2 Kg7-g6 h2-h4 Kg6-g7 Kg2-f3 Kg7-g6 Kf3-g3 a5-a4 Kg3-f2 Kg6-g7 Kf2-e1 Kg7-f8 Ke1-d2 a4-a3 Kd
 16	 -1.27 	99911  	0:00.10	b6-b5 a4xb5 c6xb5 Kf3-e3 a5-a4 Be4-c2 Ne7-f5 Ke3-d3 Nf5-e7 Kd3-d4 Ne7-g6 f4-f5 e6xf5 Bc2xf5 b5-b4 e5-e6 f7xe6 Bf5xe6 a4-a3
 15	 -1.18 	53770  	0:00.06	Kg7-g8 Kf3-g3 Kg8-g7 Be4-d3 Ne7-f5 Bd3xf5 e6xf5 Kg3-f3 Kg7-g8 Kf3-e2 Kg8-g7 Ke2-e3 Kg7-g6 Ke3-f2 Kg6-h7 Kf2-g2 Kh7-g6 Kg2-f3 Kg6-h7 Kf3-f2 Kh7-g7 Kf2-f3
 14	 -1.14 	43032  	0:00.05	Kg7-g8 Kf3-g3 Kg8-g7 Kg3-f2 Ne7-g6 Kf2-e3 Ng6-e7 Ke3-d4 Ne7-d5 f4-f5 e6xf5 Be4xf5 Nd5-f4 Kd4-e3 Nf4-d5 Ke3-f3 Kg7-h8 Bf5-e4 Kh8-g7 h2-h3 c6-c5 Be4xd5
 13	 -1.18 	26785  	0:00.04	Kg7-g8 Kf3-g3 Kg8-g7 Be4-d3 Ne7-f5 Bd3xf5 e6xf5 Kg3-f3 Kg7-g8 Kf3-e2 Kg8-f8 Ke2-e3 Kf8-e7 Ke3-d3 c6-c5 Kd3-c4 h5-h4 Kc4-b5 Ke7-e8 Kb5xb6 Ke8-d7 Kb6xa5 c5-c4 Ka5-b5
 12	 -1.16 	16460  	0:00.03	Kg7-g8 Kf3-g3 Kg8-g7 Be4-d3 Ne7-d5 Bd3-c4 Nd5-e7 Kg3-f2 Kg7-h7 Kf2-f3 Ne7-d5 Bc4xd5 c6xd5 Kf3-e3 Kh7-g6 Ke3-d2 Kg6-g7 h2-h3 Kg7-g6 Kd2-c2 Kg6-g7 Kc2-d3 Kg7-g6 h3-h4 Kg6-g7 Kd3-d4 Kg7-g6 Kd4-e3 Kg6-g7 Ke3-d3 Kg7-g6 b2-b3 Kg6-g
 11	 -1.18 	11959  	0:00.02	Kg7-g8 Kf3-e2 Kg8-g7 Ke2-f2 Ne7-g6 Kf2-e3 Ng6-e7 Be4-d3 Ne7-d5 Ke3-e4 c6-c5 f4-f5 b6-b5 f5xe6 f7xe6
 10	 -1.14 	11139  	0:00.02	Kg7-g8 Kf3-e2 Kg8-g7 Ke2-f2 Ne7-g6 Kf2-f3 Ng6-e7 Be4-d3 Ne7-d5 f4-f5 e6xf5 Bd3xf5 Kg7-h8 Bf5-e4 Kh8-g7 h2-h3 c6-c5 Be4xd5
  9	 -1.13 	9989    	0:00.01	Kg7-g8 Kf3-e2 Kg8-g7 Ke2-f2 Ne7-g6 Kf2-e3 Ng6-e7 Be4-d3 Ne7-d5 Ke3-f3 Nd5-e7
  9	 -1.28 	9233    	0:00.01	b6-b5 a4xb5 c6xb5 Kf3-e2 Ne7-f5 Be4xf5 e6xf5 Ke2-d3 Kg7-g6 Kd3-d4 Kg6-g7 Kd4-c3 Kg7-g8 Kc3-d3 h5-h4 h2-h3 Kg8-g7 Kd3-d4 b5-b4 Kd4-c5 b4-b3 Kc5-c4 a5-a4 Kc4-d3 Kg7-g6 Kd3-e3
  8	 -1.18 	7448    	0:00.01	b6-b5 a4xb5 c6xb5 Kf3-e2 a5-a4 Ke2-d3 Ne7-d5 f4-f5
  8	 -1.22 	6859    	0:00.01	Kg7-g8 Kf3-e2 Kg8-f8 Ke2-f2 Ne7-d5 Kf2-g3 b6-b5 a4xb5 c6xb5 Be4xd5 e6xd5 f4-f5 Kf8-g8 Kg3-f3 Kg8-g7 Kf3-f2 Kg7-h7 Kf2-f3 Kh7-g7
  7	 -1.07 	5109    	0:00.01	Kg7-g8 Kf3-e2 Kg8-g7 Ke2-d3 Ne7-d5 Kd3-c4 Nd5xf4 Be4xc6 Kg7-g6 Bc6-e4 Kg6xg5 Kc4-c3
  6	 -1.13 	3530    	0:00.00	Kg7-g8 Kf3-g3 Kg8-g7 Be4-d3 Ne7-d5 Kg3-f3 Nd5-e7
  5	 -1.05 	3069    	0:00.00	Kg7-g8 Kf3-g3 Kg8-g7 Be4-f3 Ne7-f5 Kg3-f2 c6-c5 Bf3xh5 Nf5-e3
  5	 -1.35 	2194    	0:00.00	b6-b5 a4xb5 c6xb5 h2-h3 b5-b4 b2-b3
  5	 -1.57 	2069    	0:00.00	Ne7-d5 Kf3-g3 b6-b5 f4-f5 b5xa4 f5xe6 f7xe6 Be4-d3
  4	 -1.25 	498      	0:00.00	Ne7-d5 Kf3-g3 Kg7-f8 Kg3-h4 Nd5xf4 h2-h3 c6-c5 g5-g6 f7xg6
  3	 -1.14 	229      	0:00.00	Ne7-d5 f4-f5 e6xf5 Be4xf5 Kg7-h8 Bf5-e4 Kh8-g7 h2-h3 c6-c5 Be4xd5
  2	 -1.14 	117      	0:00.00	Ne7-d5 f4-f5 e6xf5 Be4xf5 Kg7-h8 Bf5-e4 Kh8-g7 h2-h3 c6-c5 Be4xd5

Texel 1.07-64 also with 256MB and 1 thread

Code: Select all

 28	 -0.27 	256.7M	5:25.11	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5e7 e4d4 e7g6 d4e3 g6e7 d3e4
 28	 -0.25 	243.1M	5:07.98	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5e7 e4d4 e7g6 d4e3 g6e7 d3e4 e7g6 e4f3
 27	 -0.40 	154.8M	3:16.10	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5e7 e4d4 e7g6 d4e3 g6e7
 26	 -0.37 	94.2M  	2:01.36	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4d3 e2f4 d3c4 f4g6 c4d4 g6f4 d4c5 f4g6 c5d6 g6f4 f5e4 h4h3 e4f5 f4e6 f5h3 e6g5 h3g2 g5e6 g2d5 e6f4 d5e4 g7h6
 25	 -0.33 	66.0M  	1:23.41	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4d3 e2f4 d3c4 f4g6 c4d4 g6f4 d4c5 f4g6 f5e4 g6e5 c5b5 h4h3 b5a5 e5g4 e4f5 g4h2 f5h3 g7g6
 24	 -0.39 	34.3M  	0:43.44	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4d3 e2c1 d3c4 c1e2 f5e4 e2c3 e4c2 c3e2 c4c5 e2g1 g5g6 g1f3 c5d6 f3h2 g6f7 g7f7 e5e6 f7f6 e6e7 f6f7 c2e4
 24	 -0.30 	30.0M  	0:38.01	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4d3 e2c1 d3c4 c1e2 f5e4 e2c3 e4c2
 23	 -0.15 	21.2M  	0:26.98	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4d3 e2c1 d3c4 c1e2 f5e4 e2c3 e4c2 c3e2 c4d5 e2g1 g5g6 f7g6 c2e4 g1e2
 23	 -0.10 	18.5M  	0:23.53	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 e5e6 f7e6 f5e6 a5a4 b3a4 c3a4 e6f5 a4c5 f3e3 h5h4 e3d4 c5b3 d4d3 b3a5 f5e4 a5b3 d3e3 b3a5 e3d4 a5b3 d4d5 b3d2 h2h3 b4b3
 22	 -0.25 	12.8M  	0:16.25	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 e5e6 f7e6 f5e6 a5a4 b3a4 c3a4 e6f5 a4c5 f3e3 h5h4 e3d4 c5b3 d4d3 b3a5 f5e4 a5b3 d3e3 b3a5 e3d4 a5b3 d4d5 b3d2 h2h3 d2e4
 22	 -0.08 	11.8M  	0:14.96	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 e5e6 f7e6 f5e6 a5a4 b3a4 c3a4 f3g3 a4c5 e6f5 g7f7 g3h4 c5e6 h4h5 e6g7 h5g4 g7f5 g4f5 b4b3 h2h4 b3b2
 21	 -0.23 	8.59M  	0:10.76	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 e5e6 f7e6 f5e6 a5a4 b3a4 c3a4 f3g3 a4c5 e6f5 g7f7 g3h4 c5e6 h4h5 e6g7 h5g4 g7f5 g4f5 b4b3 h2h4 b3b2
 21	 -0.14 	8.17M  	0:10.25	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 e5e6 f7e6 f5e6 a5a4 b3a4 c3a4 f3g3 a4c5
 20	 -0.29 	5.76M  	0:07.22	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5c3 f3e3 h5h4 e3d3 c3d5 d3d4 d5e7 f5e4 e7g6 d4c5 g6e5 c5b5 e5g4 b5a5 g4f2
 19	 -0.31 	3.43M  	0:04.32	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 g7f8 f4f5 d5c3 e4d4 e6f5 d3f5 f8e7 d4c5 c3e2 h2h4 e2c1 f5c2 e7e6 c5b6 e6e5 b6a5
 19	 -0.39 	2.11M  	0:02.69	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 g7f8 f4f5 d5c3 e4d4 e6f5 d3f5 f8e7 e5e6 f7e6 f5d3 a5a4 b3a4 c3a4 d3c2 a4b2 d4c5
 18	 -0.24 	1.44M  	0:01.85	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 g7f8 f4f5 d5c3 e4d4 e6f5 d3f5 f8e7 d4c5 c3e2 e5e6 f7e6 f5d3 e2c3 g5g6 e7f6 h2h4
 18	 -0.25 	1.21M  	0:01.55	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5c3 e4d4 h5h4 f4f5 e6f5 d3f5 a5a4 b3a4 c3a4 d4c4
 17	 -0.10 	1.01M  	0:01.30	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 h2h4 d5c3 d3c2 c3d5 f4f5 e6f5 c2f5 d5e7 f5e4 e7g6 e4g6 g7g6 f3e4 g6g7
 16	  0.00 	823164	0:01.08	b6b5 a4b5 c6b5 e4d3 e7f5 f3e4 b5b4 b2b3 h5h4 d3c4 g7g6 c4d3 g6g7
 15	 -0.14 	525720	0:00.69	b6b5 f3e3 b5a4 e3d4 h5h4 e4c2 h4h3 c2a4 e7d5 a4c6 d5f4 d4e4 f4e2 e4e3 e2c1 e3d4 c1b3
 15	 -0.10 	354865	0:00.45	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 b5b4 d4c4 a4a3 b2a3 b4a3 c4b3 e7g6 f4f5 e6f5 e4f5 g6e5 b3a3 e5f3
 14	 -0.25 	261682	0:00.34	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 e7g6 d4c5 g6f4 c5b5 f4h3 g5g6 h3f2 e4f3 f7g6 b5a4 f2d3
 13	 -0.13 	190788	0:00.25	b6b5 f3e3 b5a4 e3d4 g7f8 d4c5 f8g7 e4c6 e7g6 c6a4 g6f4 a4c2 h5h4 c5c6
 13	 -0.27 	90389  	0:00.12	b6b5 b2b3 b5a4 b3a4 e7d5 h2h4 d5b4 f4f5
 12	 -0.12 	38907  	0:00.05	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 b5b4 d4c4 a4a3 c4b3 a3b2 b3b2 e7g6 e4g6 g7g6 b2b3 g6f5
 11	 -0.12 	28434  	0:00.04	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 b5b4 d4c4 a4a3 c4b3 a3b2 b3b2 e7g6 e4g6 g7g6 b2b3 g6f5
 11	+0.05 	27084  	0:00.04	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 b5b4 d4c4 a4a3 b2a3 b4a3 c4b3 e7g6 e4g6 g7g6 b3a3 g6f5
 11	 -0.26 	18209  	0:00.02	b6b5 a4b5 c6b5 f3e3 a5a4 e3d4 b5b4 d4c4 a4a3 b2a3 b4a3 c4b3
 10	 -0.10 	10089  	0:00.01	b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 f3g3 a5a4 g3h4 g7g6 h4g3 b5b4
  9	 -0.10 	7159    	0:00.01	b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 f3g3 a5a4 g3h4 g7g6 h4g3 b5b4
  8	 -0.10 	5949    	0:00.00	b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 f3g3 a5a4 g3h4 g7g6 h4g3 b5b4
  8	 -0.15 	2985    	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 d3e4 d5e7 h2h3 h5h4 f3e3 e7d5 e4d5 e6d5 e3d4
  7	+0.02 	2684    	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4
  7	+0.05 	2346    	0:00.00	b6b5 a4b5 c6b5 f3g3 a5a4 g3h4 e7g6 h4g3 b5b4
  6	 -0.10 	1649    	0:00.00	b6b5 a4b5 c6b5 f3g3 b5b4 g3h4 e7g6 h4g3 g6e7
  6	 -0.06 	1288    	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 h2h4 a5a4
  6	 -0.21 	667      	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 h2h4 a5a4
  5	 -0.36 	375      	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 h2h4 a5a4
  4	 -0.28 	249      	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 h2h4 a5a4
  4	 -0.38 	155      	0:00.00	b6b5 a4b5 c6b5 e4d3 b5b4 h2h4 a5a4
  4	 -0.39 	121      	0:00.00	e7d5 f3g3 d5e7 g3h4 e7g6 h4h5 g6f4 h5g4 f4g6 h2h4 g6e5 g4f4 e5g6 f4g3 g6e7 h4h5 f7f5 e4d3 e7d5 g3f3 d5b4 d3c4 b4d5 c4e2 e6e5
  3	 -0.39 	89        	0:00.00	e7d5 f3g3 d5e7 g3h4 e7g6 h4h5 g6f4 h5g4 f4g6 h2h4 g6e5 g4f4 e5g6 f4g3 g6e7 h4h5 f7f5 e4d3 e7d5 g3f3 d5b4 d3c4 b4d5 c4e2 e6e5
  2	 -0.39 	36        	0:00.00	e7d5 f3g3 d5e7 g3h4 e7g6 h4h5 g6f4 h5g4 f4g6 h2h4 g6e5 g4f4 e5g6 f4g3 g6e7 h4h5 f7f5 e4d3 e7d5 g3f3 d5b4 d3c4 b4d5 c4e2 e6e5
  1	+0.20 	20        	0:00.00	e7d5 f3g3 d5e7 g3h4 e7g6 h4h5 g6f4 h5g4 f4g6 h2h4 g6e5 g4f4 e5g6 f4g3 g6e7 h4h5 f7f5 e4d3 e7d5 g3f3

[jeffreyan11]

A tricky one for sure. Laser dev with 1GB, 1 thread, 5-man Syzygy, starting directly from the position in question finds it at depth 30:

Code: Select all

info depth 1 seldepth 1 score cp -18 time 1 nodes 18 nps 18000 tbhits 0 hashfull 0 pv e7d5
info depth 2 seldepth 3 score cp -18 time 1 nodes 60 nps 60000 tbhits 0 hashfull 0 pv e7d5 e4d5
info depth 3 seldepth 3 score cp -18 time 1 nodes 104 nps 104000 tbhits 0 hashfull 0 pv e7d5 e4d5 c6d5
info depth 4 seldepth 5 score cp -22 time 1 nodes 227 nps 227000 tbhits 0 hashfull 0 pv e7d5 e4d5 c6d5 h2h4
info depth 5 seldepth 6 score cp -19 time 1 nodes 684 nps 684000 tbhits 0 hashfull 0 pv e7d5 h2h4 b6b5 e4d5 e6d5
info depth 6 seldepth 8 score cp -32 upperbound time 2 nodes 1897 nps 948500 tbhits 0 hashfull 0 pv e7d5 e4d5
info depth 6 seldepth 8 score cp -32 time 2 nodes 2599 nps 1299500 tbhits 0 hashfull 0 pv b6b5 a4b5 c6b5 f3e3 e7d5 e4d5 e6d5
info depth 7 seldepth 9 score cp -22 time 3 nodes 4616 nps 1538666 tbhits 0 hashfull 0 pv e7d5 e4d5 c6d5 f3e3 g7g6 e3d4 g6f5
info depth 8 seldepth 11 score cp -24 time 4 nodes 7267 nps 1816750 tbhits 0 hashfull 0 pv e7d5 h2h4 d5b4 f3e3 c6c5 b2b3 b4d5 e4d5 e6d5
info depth 9 seldepth 14 score cp -35 time 10 nodes 19255 nps 1925500 tbhits 0 hashfull 0 pv b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 h2h4 g7g6 f3e3
info depth 10 seldepth 15 score cp -23 time 18 nodes 36067 nps 2003722 tbhits 0 hashfull 0 pv b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 h2h4 a5a4 f3e3 b5b4
info depth 11 seldepth 16 score cp -30 time 35 nodes 76256 nps 2178742 tbhits 0 hashfull 0 pv b6b5 a4b5 c6b5 e4d3 e7f5 d3f5 e6f5 f3g3 a5a4 g3h4 g7g6 h4g3
info depth 12 seldepth 18 score cp -17 lowerbound time 56 nodes 122039 nps 2179267 tbhits 0 hashfull 0 pv e7d5
info depth 12 seldepth 18 score cp -19 time 62 nodes 138054 nps 2226677 tbhits 0 hashfull 0 pv e7d5 b2b3 d5e7 h2h4 e7d5 f4f5 e6f5 e4f5 d5e7 f5e4 e7g6 e4g6
info depth 13 seldepth 21 score cp -30 time 111 nodes 245413 nps 2210927 tbhits 0 hashfull 0 pv b6b5 a4b5 c6b5 e4d3 b5b4 d3c2 e7f5 c2f5 e6f5 b2b3 a5a4 b3a4 b4b3 a4a5
info depth 14 seldepth 24 score cp -23 time 165 nodes 362291 nps 2195703 tbhits 0 hashfull 1 pv b6b5 e4d3 b5a4 d3c2 a4a3 b2a3 e7d5 f4f5 e6f5 c2f5 d5b6 e5e6 f7e6 f5e6 g7g6 h2h4 b6d5
info depth 15 seldepth 24 score cp -27 time 256 nodes 572491 nps 2236292 tbhits 0 hashfull 1 pv g7f8 f3g3 f8g7 g3h4 e7d5 h4h5 d5f4 h5g4 f4g6 e4g6 f7g6 h2h4 b6b5 b2b3 b5a4 b3a4
info depth 16 seldepth 25 score cp -22 time 364 nodes 821760 nps 2257582 tbhits 0 hashfull 2 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5e7 f3f4 h5h4 e5e6 e7f5 f4f5 f7e6 f5e6 g7g6
info depth 17 seldepth 25 score cp -27 time 475 nodes 1076512 nps 2266341 tbhits 0 hashfull 3 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5e7 e4d4 h5h4 d3e4 h4h3 d4e3 e7f5 e4f5 e6f5 e3d4 g7g6
info depth 18 seldepth 26 score cp -25 time 587 nodes 1338480 nps 2280204 tbhits 0 hashfull 4 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 g7f8 f4f5 d5c3 e4d4 e6f5 d3f5 f8e7 d4c5 h5h4 c5b6 a5a4 b3a4 c3a4 b6b5
info depth 19 seldepth 30 score cp -27 time 747 nodes 1710661 nps 2290041 tbhits 0 hashfull 5 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 h5h4 f4f5 d5c3 e4d4 e6f5 d3f5 c3e2 d4e3 e2c3 e5e6 f7e6 f5e6 g7g6 e3f4 c3e2 f4g4
info depth 20 seldepth 30 score cp -23 time 1062 nodes 2425097 nps 2283518 tbhits 6 hashfull 8 pv b6b5 a4b5 c6b5 e4d3 b5b4 d3c2 h5h4 b2b3 e7f5 c2f5 e6f5 f3e3 h4h3 e3d4 g7g6 d4c4 g6h5 c4d3 h5g6 d3d4 g6h5 d4c4
info depth 21 seldepth 30 score cp -16 time 1684 nodes 3843622 nps 2282435 tbhits 15 hashfull 13 pv b6b5 a4b5 c6b5 e4d3 b5b4 d3c2 h5h4 b2b3 e7f5 c2f5 e6f5 f3e3 h4h3 e3d3 g7g6 d3d4 g6h5 d4e3 h5g4 e5e6 f7e6 g5g6 g4h5
info depth 22 seldepth 30 score cp -26 upperbound time 2449 nodes 5632646 nps 2299977 tbhits 64 hashfull 20 pv b6b5 a4b5
info depth 22 seldepth 30 score cp -26 time 2555 nodes 5883385 nps 2302694 tbhits 64 hashfull 20 pv b6b5 a4b5 c6b5 e4d3 b5b4 d3c2 e7d5 b2b3 d5c3 h2h4 c3b5 f3e4 b5c3 e4d4 c3e2 d4e3 e2c3 f4f5 e6f5 c2f5 c3d5 e3d4 d5e7 f5e4 e7g6
info depth 23 seldepth 32 score cp -23 time 2882 nodes 6666424 nps 2313124 tbhits 119 hashfull 23 pv b6b5 a4b5 c6b5 e4d3 b5b4 d3c2 e7d5 b2b3 d5c3 h2h4 c3b5 f3e4 b5c3 e4d4 c3e2 d4e3 e2c3 f4f5 e6f5 c2f5 c3d5 e3d4 d5e7 f5e4 e7g6 e4g6 g7g6 d4e4 a5a4 b3a4
info depth 24 seldepth 34 score cp -23 time 3534 nodes 8176343 nps 2313622 tbhits 182 hashfull 28 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5e7 f5d3 e7c6 f3e4 h5h4 d3c4 g7g6 e4f4 c6d4 f4g4 h4h3 c4d5 d4e6 d5e6 f7e6 g4f4 a5a4
info depth 25 seldepth 38 score cp -27 time 7342 nodes 17245503 nps 2348883 tbhits 1831 hashfull 62 pv g7f8 f3g3 f8g7 g3h4 e7g6 h4h5 g6f4 h5g4 f4g6 h2h4 g6e5 g4f4 e5g6 f4g3 g6e7 h4h5 f7f5 e4c2 e7d5 c2d3 d5b4 d3c4 b4d5 c4d5 c6d5 g3f4 d5d4 f4e5 d4d3 e5e6
info depth 26 seldepth 45 score cp -18 lowerbound time 24370 nodes 58196337 nps 2388031 tbhits 8178 hashfull 202 pv b6b5
info depth 26 seldepth 45 score cp -18 time 25113 nodes 59919657 nps 2386001 tbhits 8190 hashfull 207 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5c3 e4d4 h5h4 f4f5 e6f5 d3f5 c3d1 d4e4 d1c3 e4e3 c3d5 e3d4 d5f4 d4c5 f4g6 e5e6 f7e6 f5e6 g6e5 c5d6 e5f3
info depth 27 seldepth 45 score cp -19 time 26786 nodes 63610108 nps 2374752 tbhits 8357 hashfull 218 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f3e4 d5c3 e4d4 h5h4 f4f5 e6f5 d3f5 c3d1 d4e4 d1c3 e4e3 c3d5 e3d4 d5f4 d4c5 f4e2 f5e4 e2c1 e4c2 c1e2 c2b1 e2c1 c5c4 c1e2 b1e4
info depth 28 seldepth 45 score cp -19 time 29017 nodes 68796212 nps 2370893 tbhits 9659 hashfull 233 pv b6b5 a4b5 c6b5 e4d3 b5b4 b2b3 e7d5 f4f5 e6f5 d3f5 d5e7 f5d3 e7c6 f3e4 h5h4 d3b5 c6d8 e4f5 d8e6 b5c4 e6d4 f5g4 g7g6 h2h3 d4c6 c4d3 g6g7 d3e4 c6e5 g4h4 a5a4 b3a4 b4b3
info depth 29 seldepth 48 score cp -28 upperbound time 33080 nodes 78401568 nps 2370059 tbhits 12980 hashfull 260 pv b6b5 a4b5
info depth 29 seldepth 52 score cp -29 time 63784 nodes 151003353 nps 2367417 tbhits 23537 hashfull 462 pv b6b5 b2b4 a5b4 a4a5 c6c5 a5a6 e7c8 f3e3 h5h4 f4f5 c8a7 f5f6 g7f8 h2h3 f8e8 g5g6 f7g6 e4g6 e8d7 g6e4 d7e8 e4d3 e8f8 d3g6 a7c6 g6e4 c6a7 e3f4 c5c4 e4f3 b4b3 f3e4
info depth 30 seldepth 58 score cp -38 upperbound time 106921 nodes 255763240 nps 2392076 tbhits 44933 hashfull 648 pv b6b5 b2b4
info depth 30 seldepth 62 score cp -38 time 134201 nodes 322097202 nps 2400110 tbhits 51388 hashfull 734 pv e7d5 e4d3 d5b4 d3e2 b4d5 f3g3 g7g6 e2d3 g6g7 h2h4 d5e7 d3e4 b6b5 b2b4 b5a4 b4a5 a4a3 e4b1 c6c5 a5a6 e7c6 g3f2 g7f8 f2e2 f8e7 e2d2 e7d7 d2c3 d7c7 c3b3 c7b6 b3a3
info depth 31 seldepth 66 score cp -46 upperbound time 183300 nodes 435852472 nps 2377809 tbhits 67968 hashfull 848 pv e7d5 e4d3
info depth 31 seldepth 66 score cp -45 time 250904 nodes 596243887 nps 2376382 tbhits 101602 hashfull 926 pv e7d5 e4d3 d5c7 d3e2 b6b5 f3f2 h5h4 e2f3 c7d5 f3d5 e6d5 f4f5 b5a4 f2e3 c6c5 h2h3 g7h7 e3f4 d5d4 f4e4 h7g8 e4d3 g8g7 d3c4 g7g8 f5f6 g8h7 c4c5 d4d3 e5e6 f7e6

[MikeB]

[snip]
In the final position of the pgn excerpt, Gavota with Black thought it can now play b5 and completely missed the answer, which wins on the spot!
(even if it may appear that the position is already not good, 54...b5?? should be avoided)
It seems the killer answer is pruned away completely by a lot of programs. Humans with a certain strength of course know the motif.


Scorpio 2.78-64 with 5men egbb (256MB only 1 thread) also does not see it, but it is not alone e.g. Texel 1.07-64 behaves the same
(analysis mode with stepping quickly through the pgn to fill hash until move 54)
[snip]

clean start:
[d]8/4npk1/1pp1p3/p3P1Pp/P3BP2/5K2/1P5P/8 b - - 13 54
SF-McBrain 3.1dev

Code: Select all

dep	score	nodes	time	(not shown:  tbhits	knps	seldep)
 36	+0.51 	1.62G	1:14.85	Kf8 Bd3 Kg7 Be2 Kg6 Ke4 Nf5 Bf1 Ne7 Bd3 Nd5 Be2 Ne7 Kf3 Nd5 Bd3+ Kg7 Kg3 Ne3 Be2 Kg6 h3 Nd5 Kf3 Nb4 h4 Nd5 b3 Kg7 Kg3 Nc3 Bxh5 b5 Bg4 bxa4 bxa4 Nxa4 h5 Nc5 
 35	+0.51 	1.47G	1:08.72	Kf8 Bd3 Kg7 Kf2 Nd5 Kg3 Ne7 Be2 Kg6 Bc4 Kg7 Bd3 Nd5 Be2 Kg6 Kf3 Ne7 Bc4 Nd5 Kg3 Kh7 Bf1 Kg7 Kf3 Kg6 Ke4 Nc7 Be2 Nd5 Bd3 Nb4 Bf1 Nd5 Be2 Nc7 Bc4 Nd5 
 34	+0.51 	1.17G	0:55.44	Nd5 Bd3 Ne7 Kf2 Nd5 Kg3 Ne7 Kf3 Nd5 Be2 Ne7 Kg3 Kg6 h3 Nf5+ Kg2 Ne7 Bd3+ Kg7 Kf2 Nd5 Kf3 Ne7 Kg3 Kg8 Be4 Kg7 Kf3 Nd5 h4 Ne7 Kg3 Nd5 Bg2 b5 Bf3 Kg6 f5+ Kxf5 
 33	+0.52 	962.4M	0:45.98	Nd5 Bd3 Ne7 Kf2 Nd5 Kg3 Ne7 Kf3 Nd5 Be2 Ne7 Kg3 Kg6 h3 Nf5+ Kg2 Ne7 h4 Nd5 Kg3 Ne7 Kf2 Nd5 Bd3+ Kg7 Kf3 Ne7 Bc2 Kg8 Kf2 Kg7 Be4 Nd5 Kg3 Ne7 b3 Kf8 Bf3 Nf5+ Kh3 
 33	+0.57!	846.1M	0:40.66	Nd5! 
 33	+0.65!	762.4M	0:36.86	Nd5! 
 32	+0.72 	567.1M	0:27.76	Nd5 h4 Ne7 Kg3 Nd5 Bf3 Kg6 b3 Nc3 Kf2 Nd5 Be4+ Kg7 f5 exf5 Bxf5 b5 Be4 bxa4 bxa4 Kf8 Kg3 Nb4 Kf3 c5 Ke3 Ke7 Bf3 Ke6 Bxh5 Nd5+ Ke4 Nc3+ Kd3 Nxa4 Kc4 Nb2+ Kxc5 Nd3+ Kb5 Nxe5 Bd1 Kf5 Kxa5 
 32	+0.67!	466.0M	0:23.27	Nd5! 
 32	+0.75?	439.6M	0:22.12	Nd5 h4? 
 31	+0.66 	288.3M	0:14.98	Nd5 h4 Ne7 Bd3 Kf8 Kg3 Kg7 Be2 Nf5+ Kh3 Kg6 Bd3 Kg7 Bxf5 exf5 Kg3 Kf8 b3 Kg7 Kf3 Kf8 Ke3 Ke8 Kf2 Kf8 Ke2 Kg7 Ke3 Kf8 Kd2 Kg7 Kc2 Kf8 Kc3 Ke7 Kd3 Kd7 Ke2 
 31	+0.65?	253.1M	0:13.27	Nd5 h4? 
 30	+0.56 	223.7M	0:11.84	Nd5 h4 Ne7 Bd3 Kf8 Kg3 Nf5+ Bxf5 exf5 b3 Kg7 Kf2 Kf8 Ke3 Ke7 Kd3 Kd7 Kc4 Ke6 Kc3 Kd5 b4 axb4+ Kxb4 Ke6 a5 c5+ Kb5 bxa5 Kxc5 a4 Kb4 a3 Kb3 Kd5 Kxa3 
 30	+0.55?	183.0M	0:09.86	Nd5 h4? 
 30	+0.48?	123.5M	0:06.97	Nd5 h4? 
 29	+0.41 	111.0M	0:06.19	Nd5 Bd3 Nb4 Bc4 Nd5 h4 Nb4 Be2 Nd5 Bd3 Kf8 Kg3 Kg7 Bc4 Kg6 Be2 Nb4 Kf2 Kg7 Ke3 Nd5+ Kf3 Nb4 Ke4 Kg6 Bc4 Nd5 Kf3 Kg7 Bxd5 
 28	+0.41 	103.8M	0:05.83	Nd5 h4 Ne7 Bc2 Nd5 Bd3 Kf8 Kg3 Kg7 Bc4 Kg6 Be2 Ne7 Kf2 Nd5 Kf3 Kg7 Kg3 Kg6 Bc4 Nb4 Kf3 Kg7 Ke4 Nd5 Be2 Ne7 Bxh5 Nf5 Be2 
 27	+0.41 	90.9M  	0:05.03	Nd5 h4 Ne7 Bc2 Nd5 Bd3 Kf8 Kg3 Kg7 Bc4 Kg6 Be2 Nb4 Kf2 Kg7 Kf3 Nd5 Kg3 Kg6 Bc4 Nb4 Kf3 Kg7 Ke4 Nd5 Bd3 Kg6 Be2 Nb4 
 26	+0.41 	65.1M  	0:03.63	Nd5 h4 Kf8 Bd3 Kg7 Kg3 Ne7 Be4 Nd5 Bf3 Kg6 Be2 Ne7 Kf3 Nd5 Bc4 Kg7 Bd3 Ne7 Be4 Nd5 Kg3 Ne7 Bf3 Kg6 Kf2 b5 Be4+ Kg7 
 25	+0.41 	32.4M  	0:01.77	Nd5 Bc2 Nb4 Bd1 Nd5 Be2 Kg6 Bd3+ Kg7 Kg3 Ne3 Be4 Nd5 Kf3 Kf8 Bc2 Kg7 Bd3 Kf8 Be2 Kg7 Ba6 Ne7 Ke4 Nd5 Bd3 Nb4 
 24	+0.41 	20.3M  	0:01.00	Nd5 Bc2 Kf8 Bd3 Kg7 Kg3 Ne3 Be4 Nd5 Kf3 Kf8 h4 Kg7 Kg3 Ne7 Bf3 Kg6 Kf2 Nd5 Be4+ Kg7 Kf3 Kf8 f5 exf5 
 23	+0.41 	17.0M  	0:00.85	Nd5 Bd3 Nb4 Bc4 Nd5 Be2 Kg6 Kg3 Ne7 Bd3+ Kg7 Kf3 Nd5 Ke4 Nb4 Be2 Kg6 h4 Nd5 Bd3 Ne7 Ke3+ Kg7 Kf3 Nd5 Kg3 Ne7 Be4 Nd5 
 22	+0.41 	12.4M  	0:00.61	Nd5 Bd3 Nb4 Bc4 Nd5 Be2 Kg6 Kg3 Ne7 Kf2 Kf5 Kf3 Kg6 Bc4 Nd5 h4 Kg7 Be2 Kg6 Bd3+ Kg7 Kg3 Ne7 Be2 Kg6 
 21	+0.41 	11.3M  	0:00.55	Nd5 Bd3 Nb4 Bc4 Nd5 Be2 Kg6 Kg3 Ne7 Kf2 Kf5 Kf3 Kg6 Bc4 Nd5 h4 Nb4 Ke4 Nd5 Bd3 Ne7 Ke3+ Kg7 Kf3 
 20	+0.49 	6.91M  	0:00.35	Kf8 Bd3 Nd5 Kg3 Kg7 Be4 Ne7 Kh4 Ng6+ Kxh5 Nxf4+ Kg4 Ng6 Bxg6 fxg6 h4 Kf7 b3 Kg7 Kf4 Kf7 Ke4 Kg7 Kd4 Kf7 Kd3 Ke7 
 19	+0.48 	5.01M  	0:00.26	Kf8 Bd3 Nd5 Bc4 Kg7 Be2 Kg6 Bd3+ Kg7 Ke4 Nb4 Be2 Kg6 h4 Nd5 Bf3 Ne7 Kd3 Nd5 Kd4 Nxf4 Bxc6 Kg7 Be4 
 18	+0.43 	4.22M  	0:00.21	Nd5 Kg3 Ne7 Kf2 Nd5 Kf3 Ne7 Bd3 Nd5 Kg3 Nb4 Be4 Nd5 Bf3 Kg6 Be2 Nb4 Bd1 b5 Kh4 Nd5 
 17	+0.45 	3.95M  	0:00.20	Nd5 Kg3 Ne7 Kf2 Nd5 Kf3 Ne7 Bc2 Nd5 f5 exf5 Bxf5 Ne7 Bd3 Ng6 Ke4 Nf8 Be2 Kg6 
 16	+0.36 	1.32M  	0:00.07	b5 Bd3 b4 Ke4 Nd5 Bc2 h4 Bd3 Kf8 Kf3 Nb6 b3 Nd5 Kg4 Ke7 Be4 c5 Bxd5 exd5 
 15	+0.34 	957048	0:00.05	b5 Bd3 b4 Ke4 Nd5 Bc2 Kf8 Kd4 Nxf4 Kc5 Nh3 Kxc6 Nxg5 Kb5 Nf3 Bd1 Nxe5 Kxa5 
 14	+0.26 	804030	0:00.04	b5 axb5 cxb5 Bd3 b4 Bc2 Kf8 Ke4 Nf5 Bd1 Ke7 Bb3 h4 Ba4 h3 Bb5 
 13	+0.29 	705441	0:00.04	b5 Bd3 b4 Ke4 Nd5 Bc2 Kf8 Bd1 h4 Bb3 Ne7 Kf3 Ke8 Bc4 Nd5 
 12	+0.26 	400040	0:00.02	b5 axb5 cxb5 Bd3 b4 b3 Nd5 Ke4 Kf8 h4 Ke7 f5 Nc3+ Kd4 
 11	+0.30 	241192	0:00.02	b5 Bd3 b4 Bc2 Nd5 Be4 Kf8 h4 Kg7 b3 Ne7 Kg3 Nd5 
 10	+0.40 	197945	0:00.01	b5 b4 axb4 a5 c5 a6 Nc8 f5 c4 Ke3 exf5 
  9	+0.38 	81310  	0:00.01	b5 Bd3 b4 Ke4 Nd5 h4 Nb6 b3 Nd5 
  8	+0.31 	22011  	0:00.00	b5 b3 bxa4 bxa4 c5 Bd3 Nd5 h4 
  7	+0.50 	9217    	0:00.00	b5 axb5 cxb5 Ke3 a4 Bf3 Kg6 
  6	+0.55 	6873    	0:00.00	b5 axb5 cxb5 Ke3 a4 Bf3 
  5	+0.58 	3576    	0:00.00	b5 axb5 cxb5 Bd3 b4 
  4	+0.54 	1763    	0:00.00	Nd5 h4 b5 Bxd5 
  3	+0.48 	1517    	0:00.00	Nd5 Bxd5 cxd5 
  2	+0.48 	1038    	0:00.00	Nd5 Bxd5 
  1	+0.48 	720      	0:00.00	Nd5 
  0	# 

and part B is how long does an engine take to find b4!

[d]8/4npk1/2p1p3/pp2P1Pp/P3BP2/5K2/1P5P/8 w - - 0 1

clean start:

Code: Select all

dep	score	nodes	time	(not shown:  tbhits	knps	seldep)
 39	+7.09 	5.62G	3:38.83	b4 axb4 a5 c5 a6 Nc8 h4 Kg8 Ke3 Kg7 Kd2 Na7 Bd3 c4 Be4 Nc8 Bc6 Na7 Bf3 Kg6 Be4+ Kg7 Kc2 Nc8 Kb1 Kf8 Bf3 Kg7 Bxh5 Na7 Kc2 Nc6 Bf3 Na7 h5 Kh8 h6 Kg8 Kb2 b3 Kc3 Kh8 Be4 b2 Kxb2 b4 Bf3 Nb5 Be2 c3+ Ka2 Na7 Kb3 c2 Kb2 c1=Q+ Kxc1 Kh7 
 39	+6.60!	4.60G	3:00.54	b4! 
 39	+6.02!	3.45G	2:15.70	b4! 
 38	+5.45 	2.62G	1:42.11	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 a6 Nc8 Bd3 c4 Be4 Na7 Kd4 b3 Kc3 Nc8 f5 exf5 Bxf5 Na7 Kb2 Kg8 e6 fxe6 Bxe6+ Kf8 Bd5 Kg7 Kc3 Nc8 Bc6 Na7 Bf3 Kg6 Kb2 Nc8 Be4+ Kg7 Bc6 Na7 Be8 b4 Bxh5 Nc6 Bd1 Kf8 Bf3 Na7 h5 Nb5 Bd5 
 37	+5.45 	2.45G	1:35.33	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 a6 Nc8 Bd3 c4 Be4 Na7 Kd4 b3 Kc3 Nc8 f5 exf5 Bxf5 Na7 Kb2 Kg8 e6 fxe6 Bxe6+ Kf8 Bd5 Kg7 Kc3 Nc8 Bc6 Na7 Bf3 Kh7 Bxh5 b4+ Kb2 Nb5 Bf3 Kg7 Bd5 c3+ Kxb3 Nd4+ Ka2 Nb5 Bc4 c2 Kb2 
 37	+4.89!	2.02G	1:18.99	b4! 
 37	+4.45!	1.61G	1:03.88	b4! 
 36	+4.02 	1.27G	0:50.25	b4 axb4 a5 c5 Ke2 Nc8 h4 Na7 Kd2 Nc8 a6 c4 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6 Kg6 Kc2 Kg7 Bd5 Kg6 Be4+ Kf7 Kb2 b3 Bb7 Kg6 Bf3 Nc8 Bc6 Na7 Be8+ Kh7 Bxh5 Nc8 Be8 Na7 h5 Kg7 Bg6 
 35	+4.01 	1.08G	0:43.02	b4 axb4 a5 c5 Ke2 Nc8 h4 Na7 Kd2 Nc8 Kc2 Na7 a6 Nc8 Kb2 Na7 Kb3 Nc8 Bf3 Kg6 Be2 Na7 Bd3+ Kg7 Kb2 c4 Be4 Nc8 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6 Kg6 Kc2 Kg7 Bd5 Kg6 Be4+ Kf7 Kb2 Ke6 Bf3 Kf7 Bxh5+ Kg7 Kc2 Nc8 Be8 Na7 h5 Kg8 Kb2 Kf8 Bg6  
 35	+3.74!	755.9M	0:30.23	b4! 
 35	+3.21!	596.4M	0:24.05	b4! 
 35	+2.80!	513.0M	0:20.74	b4! 
 35	+2.49!	408.7M	0:16.53	b4! 
 35	+2.25!	384.6M	0:15.57	b4! 
 34	+2.02 	361.6M	0:14.67	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke2 Kg7 Bf3 Kg6 Bg2 c4 Be4+ Kg7 Ke3 Na7 Kd2 Nc8 Bc6 Na7 Bf3 Kg6 Kc2 Nc8 Bb7 b3+ Kc3 Na7 Be4+ Kg7 f5 exf5 Bxf5 Nc6 e6 fxe6 Bxe6 Na7 Bd5 Nc8 Bc6 Na7 Bf3 Kg6 Be4+ Kf7 Kb2 Ke6 Bf3 b4 Be2 c3+ Kxb3 
 33	+2.02 	217.1M	0:08.69	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke2 Kg7 Bf3 Kg6 Bg2 c4 Be4+ Kg7 Ke3 Na7 Kd4 Nc8 Kc5 b3 Kd4 Na7 Kc3 Nc8 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6 Nc6 Bd5 Na7 Kb2 Kg6 Bf3 Nc8 Bc6 Na7 
 32	+1.82 	187.0M	0:07.45	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke2 Kg7 Kd2 Na7 Ke3 Nc8 Bd3 c4 Be4 b3 Kd4 Kg8 f5 exf5 Bxf5 Na7 Kc3 Kf8 e6 fxe6 Bxe6 Kg7 Bd5 Kf8 Kb2 Kg7 Bf3 Kg6 Be4+ Kf7 Kc3 Nc8 Bd5+ Kg7 Bc6 b4+ Kxb4 
 31	+1.81 	144.8M	0:05.80	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke2 Kg7 Kd2 Na7 Ke3 Nc8 Bd3 Na7 Kd2 c4 Be4 Nc8 Ke3 b3 Kd4 Kg8 Kc3 Kg7 f5 exf5 Bxf5 Na7 e6 Kf8 exf7 Kxf7 Be4 Kg8 Bd5+ Kf8 Bf3 Kg7 Kb2 Kg6 
 30	+1.80 	111.8M	0:04.47	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke2 Kg7 Kd2 Na7 Bd3 c4 Be4 Nc8 Ke3 Na7 Kd4 Nc8 Kc5 b3 Kd4 Kf8 Kc3 Kg7 f5 exf5 Bxf5 Na7 e6 Kf8 exf7 Kxf7 Be4 Nc8 Bf3 Kg6 Bc6 Na7 Be8+ Kf5 Kb2 b4 Bxh5 
 29	+1.79 	85.1M  	0:03.40	b4 axb4 a5 c5 h4 Nc8 Ke3 Na7 a6 Nc8 Bd3 Na7 Kd2 c4 Be4 Nc8 Ke3 Na7 Kd4 Nc8 Kc5 b3 Kd4 Kf8 Kc3 Kg7 f5 exf5 Bxf5 Na7 e6 Kf8 exf7 Kxf7 Be4 Ke6 Bf3 Ke5 Bxh5 b4+ Kb2 
 28	+1.79 	73.1M  	0:02.91	b4 axb4 a5 c5 h4 Nc8 Ke3 Na7 a6 Nc8 Bd3 Na7 Kd2 c4 Be4 Nc8 Ke3 b3 Kd4 Kf8 Kc3 Kg7 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6 Kg6 Bd5 Kf5 Kb2 Nc8 Bc6 Na7 Be8 b4 Bxh5 Nb5 Be2 c3+ Kxb3 Nd4+ Kxb4 Nxe2 
 27	+1.78 	62.5M  	0:02.49	b4 axb4 a5 c5 h4 Nc8 Ke3 Na7 Kd2 Nc8 Kc2 c4 a6 Na7 Kd2 Nc8 Ke3 b3 Kd4 Na7 Kc3 Nc8 f5 exf5 Bxf5 Na7 e6 Kf8 exf7 Kxf7 Be4 Ke6 Bf3 Ke5 Bxh5 b4+ Kb2 Nb5 Bf7 
 26	+1.43 	41.8M  	0:01.68	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 Kd3 c4+ Kc2 Nc8 a6 Na7 Kd2 Nc8 Ke3 b3 Kd4 Kf8 Kc3 Kg7 Bf3 Kg6 Bc6 Na7 Be4+ Kg7 f5 exf5 Bxf5 Kf8 e6 fxe6 Bxe6 Kg7 Bd5 Kg6 Bf3 Kf5 Bxh5 
 25	+1.43 	33.8M  	0:01.36	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 Kd3 c4+ Kc2 Nc8 a6 Na7 Kd2 Nc8 Ke3 b3 Kd4 Kf8 Kc3 Kg7 Bf3 Kg6 Bc6 Na7 Be4+ Kg7 f5 exf5 Bxf5 Kf8 e6 fxe6 Bxe6 Kg7 Bd5 
 24	+1.27 	26.5M  	0:01.07	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 a6 Nc8 Kd2 c4 Ke3 Na7 Kd4 Nc8 Kc5 b3 Kd4 Na7 Kc3 Nc8 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6 Kg6 Bd5 Kf5 Kb2 Ke5 Bf7 
 23	+1.02 	21.1M  	0:00.86	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 a6 c4 Kd4 Nc8 Kc5 b3 Kd4 Kg8 f5 exf5 Bxf5 Na7 e6 fxe6 Bxe6+ Kg7 Bd5 Kg6 Kc3 Kf5 Kb2 Nc8 Bf3 
 22	+0.77 	16.6M  	0:00.68	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 a6 Nc8 Kd2 Na7 Kd3 Nc8 Bf3 Kg6 Bb7 Na7 Be4+ Kg7 Bf3 c4+ Kd4 b3 Kc3 Kg6 Kb2 Nc8 Be4+ Kg7 Kc3 Na7 f5 exf5 Bxf5 Kf8 e6 fxe6 Bxe6 Ke7 Bf5 
 21	+1.04 	10.7M  	0:00.45	b4 axb4 a5 c5 Ke3 Nc8 h4 Na7 Kd3 Nc8 Bf3 Kg6 Bb7 Na7 Be4+ Kg7 a6 Nc8 Kc2 c4 Kd2 Na7 Ke3 Kf8 Kd4 Kg7 Bf3 Kg6 
 20	+0.96 	9.07M  	0:00.39	b4 axb4 a5 c5 h4 Nc8 Ke3 Na7 Kd3 c4+ Kd4 Kg8 Bf3 Kg7 a6 b3 Kc3 Kg6 Kb2 Nc8 Be4+ Kg7 Kc3 Na7 Kb4 Kf8 Bf3 Kg7 Bb7 Kg6 Be4+ Kg7 Kc3 Nc8 Bb7 
 19	+1.04 	6.91M  	0:00.30	b4 axb4 a5 c5 a6 Nc8 h4 Kf8 Ke3 Kg7 Bb7 Na7 Bf3 Kg6 Be4+ Kg7 Ke2 c4 Kd2 Kf8 Kc2 Kg7 Kb2 Kf8 Bf3 
 18	+0.27 	2.81M  	0:00.13	axb5 cxb5 Bd3 b4 Bc2 Ng6 Ke4 Ne7 Kd4 Ng6 Ke3 Ne7 Ke4 Nc6 Kd3 Ne7 Kc4 Nd5 Kb5 Nxf4 Kxa5 b3 Bxb3 
 17	+0.27 	1.85M  	0:00.09	axb5 cxb5 Bd3 b4 Bc2 Nd5 Ke4 Ne7 Kd4 Ng6 Ke3 Ne7 Ke4 Nf5 Kd3 Ne7 Kc4 Nd5 Kb5 Nxf4 
 16	+0.30 	1.52M  	0:00.08	axb5 cxb5 Bd3 b4 Bc2 Nc6 Ke3 Ne7 Ke4 Nf5 Kd3 Ne7 Kc4 Nd5 Kb5 Nxf4 Kxa5 
 15	+0.35 	1.40M  	0:00.07	axb5 cxb5 Bd3 b4 Bc2 Nc6 Ke3 Ne7 Ke4 Nf5 Kd3 h4 Ke4 Kf8 Bb3 
 14	+0.45 	735946	0:00.04	Ke3 bxa4 Bc2 Nd5+ Ke4 a3 bxa3 Kf8 h4 Ke7 Bb3 Nc3+ Kd3 Nd5 Bxd5 cxd5 Kd4 Kf8 a4 Kg7 
 13	+0.46 	494380	0:00.03	Ke3 bxa4 Bc2 a3 bxa3 Nd5+ Ke4 Kf8 h4 Ke7 Bb3 Nc3+ Kd3 Nd5 Bxd5 cxd5 Kd4 
 12	+0.40 	377801	0:00.02	Ke3 bxa4 Bc2 Nd5+ Ke4 a3 bxa3 Kf8 Bb3 a4 Bc4 Ke7 Bxd5 cxd5+ Kd4 Kd7 Kc5 h4 Kb4 
 11	+0.40 	275396	0:00.02	Ke3 bxa4 Bc2 Nd5+ Ke4 a3 bxa3 Kf8 Bb3 a4 Bxd5 cxd5+ Kd4 Ke7 Kc5 h4 h3 Kd7 
 10	+0.41 	134314	0:00.01	Bd3 bxa4 Bc2 a3 bxa3 Nd5 Ke4 Nc3+ Kd4 Ne2+ Kc5 Nxf4 Kxc6 
z