Test position, Queen sac, that appears to be winning!

[Robert Flesher]

Does your favourite engine see axb6!!

[d]r1r3k1/p1Q4p/1n2qpp1/P2b4/2p4P/5PB1/3N2PK/R2R4 w - - 0 28

[perejaslav]

Analysis by Houdini 1.5a x64:


1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4 4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7 7.Bg3 Ke7
= (-0.11 ++) : 20/55 00:00:09
= (0.00) : 20/55 00:00:16

9 sec. for Houdini

[perejaslav]

IvanHoe and Rybka can find it immediately

[Robert Flesher]

Analysis by Houdini 1.5a x64:


1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4 4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7 7.Bg3 Ke7
= (-0.11 ++) : 20/55 00:00:09
= (0.00) : 20/55 00:00:16

9 sec. for Houdini

Yes, but they need to see a winning score, unless it's not winning?
I say it is winning!

[Robert Flesher]

Analysis by Houdini 1.5a x64:


1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4 4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7 7.Bg3 Ke7
= (-0.11 ++) : 20/55 00:00:09
= (0.00) : 20/55 00:00:16

9 sec. for Houdini

The point being, they do not see it's winning.



1. axb6 Rxc7 2. bxc7 Kf7 (2... Kg7 3. Ne4!! ) 3. Ne4!! Bxe4 4. fxe4 winning

[Robert Flesher]

DAMN! Given enough time the top engines see it winning.

[Terry McCracken]

DAMN! Given enough time the top engines see it winning.

Funny, this position is fairly easy for a human. It's one of those positions computers have trouble with.

[Martin Thoresen]

Not winning but definitely on good way there.

Houdini 1.5a 6CPU:

Code: Select all

  4/13	00:00	       1 374	687 000	-0,52	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Ne4 Bxe4 31.fxe4
  5/13	00:00	       1 852	926 000	-0,52	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Ne4 Bxe4 31.fxe4
  6/18	00:00	       3 142	628 000	-0,44	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8
  7/18	00:00	       4 236	353 000	-0,44	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8
  8/18	00:00	       5 546	396 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8 32.Rab1 Kg7
  9/18+	00:00	       9 258	356 000	-0,42	28.Qd6
  9/27+	00:00	      17 183	592 000	-0,29	28.Qd6
  9/27	00:00	      31 396	981 000	-0,38	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Bf5 32.Rd4 Bd3 33.Be7 Rc7 34.Re1 Rb8
 10/27	00:00	      40 783	1 132 000	-0,38	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Bf5 32.Rd4 Bd3 33.Be7 Rc7 34.Re1 Rb8
 11/27-	00:00	      76 134	1 812 000	-0,44	28.Qd6 Qxd6
 11/27	00:00	     123 710	2 524 000	-0,45	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Rc6 32.Rd2 Ra6 33.g4 Re8 34.Kg3 Kg7 35.h5 gxh5 36.gxh5
 12/28	00:00	     189 370	3 265 000	-0,40	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Rc6 32.Kg3 Kg7 33.Kf2 Nc5 34.Bxc5 Rxc5 35.Rd6 Re8 36.Re1
 13/29-	00:00	     474 843	5 521 000	-0,46	28.Qd6 Qxd6
 13/29	00:00	     724 202	6 705 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Nb5 Re3 33.Nc7 Rc8 34.Nb5 c3 35.Bf4 Re7 36.Nxa7 Rc4 37.Kg3 c2
 14/29	00:00	     902 577	7 338 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Nb5 Re3 33.Nc7 Rc8 34.Nb5 c3 35.Bf4 Re7 36.Nxa7 Rc4 37.Kg3 c2
 15/38	00:00	   1 613 190	9 379 000	-0,53	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Ba3 Ne5 33.Rab1 Reb8 34.Rxb8+ Rxb8 35.Be7 Rb2 36.Bxf6 Nxf3+ 37.Kg3 Nd2
 15/38	00:00	   2 849 279	10 916 000	-0,46	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Nd3 31.Qxf6 Nxc1 32.Rxd5 Qxf6 33.Nxf6+ Kg7 34.Be5 Rd8 35.Rb5 Kf7 36.Nxh7 Nd3 37.Ng5+ Kg8 38.Kg3 Nxe5 39.Rxe5
 16/38+	00:00	   3 866 878	11 753 000	-0,40	28.Qf4
 16/42+	00:00	   6 819 505	12 675 000	-0,27	28.Qf4
 16/48	00:01	  16 200 474	14 661 000	-0,27	28.Qf4 Nd7 29.Rac1 Rc6 30.Re1 Qf5 31.Qe3 Re6 32.Qd4 Rxe1 33.Rxe1 Qd3 34.Qxd3 cxd3 35.Re3 Nc5 36.Bd6 Rc8 37.a6 Nxa6 38.Rxd3 Bc6 39.Nb3 Bb5 40.Rd1 Rc2 41.Nd4
 17/48+	00:01	  18 277 718	14 799 000	-0,21	28.Qf4
 17/48	00:02	  27 462 049	15 515 000	-0,24	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kh1 Rf8 33.Rd5 c3 34.Bxe5 fxe5 35.Rxe5 Qc4 36.Qe3 Rc7 37.Re4 Qc5 38.Rd4 Qxa5 39.Qe6+ Kg7 40.Rd5 Qa3 41.Qe5+ Kg8 42.Qe6+ Rcf7
 18/48+	00:02	  30 496 667	15 623 000	-0,17	28.Qf4
 18/48	00:02	  38 253 619	15 569 000	-0,21	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.g3 Kg7 37.Kg2 Rcc8 38.a6 Re7 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4
 19/48	00:02	  41 547 098	15 695 000	-0,21	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.g3 Kg7 37.Kg2 Rcc8 38.a6 Re7 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4
 20/48	00:03	  48 233 454	15 992 000	-0,19	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.Kf1 Kg7 37.Kf2 Ree7 38.Kg3 Rc8 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4 Kf6 42.Kf3
 21/48	00:03	  58 783 289	16 301 000	-0,19	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.Kf1 Kg7 37.Kf2 Ree7 38.Kg3 Rc8 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4 Kf6 42.Kf3
 22/49+	00:05	  91 045 112	16 938 000	-0,12	28.Qf4
 22/49	00:06	  98 512 697	17 020 000	-0,18	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Re1 Rcc8 34.Qd4 a6 35.Bxe5 fxe5 36.Qc3 Rc5 37.Re4 Rec8 38.Rce1 Rd8 39.Rxe5 Rxe5 40.Rxe5 Rd1+ 41.Kf2 Qc6 42.h5
 22/49+	00:11	 197 399 636	17 798 000	 0,00	28.axb6
 22/61	00:22	 396 450 780	17 997 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 23/61	00:24	 436 740 426	18 065 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 24/61	00:28	 517 104 348	18 222 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 25/61	00:35	 654 141 477	18 408 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 26/66+	01:13	1 370 757 930	18 835 000	+0,06	28.axb6
 26/66+	01:45	1 991 377 609	18 948 000	+0,19	28.axb6
 26/68+	03:37	4 134 875 846	19 041 000	+0,47	28.axb6
 26/82	14:17	16 568 654 439	19 324 000	+1,14	28.axb6 Rxc7 29.bxc7 Rc8 30.Nb1 Qc6 31.Nc3 Rxc7 32.Rxd5 Rd7 33.Rxd7 Qxd7 34.Ne4 Qe7 35.Rc1 f5 36.Rxc4 fxe4 37.Rc8+ Kf7 38.Rc7 exf3 39.Rxe7+ Kxe7 40.gxf3 a5 41.Be1 a4 42.Kg3 Kd7 43.Kf4 a3 44.Ke4 Ke6 45.Bc3 h6 46.Ba1 g5 47.h5 Kd6
 27/82+	20:30	23 952 744 665	19 467 000	+1,23	28.axb6
 27/82-	23:29	27 496 630 234	19 516 000	+1,05	28.axb6 Rxc7
 27/82-	23:45	27 821 256 379	19 520 000	+0,87	28.axb6 Rxc7
 27/82	24:03	28 147 507 496	19 509 000	+0,97	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Kd2 f5 53.Rh3 Qb4+ 54.Ke2 Qb2+ 55.Kf1 Qb1+ 56.Be1 h5 57.Re3+
 28/82+	26:15	30 803 503 479	19 561 000	+1,05	28.axb6
 28/82	26:42	31 350 127 478	19 563 000	+0,93	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Ke2 h5 53.Re3+ Kd6 54.Rd3+ Ke6
 29/84+	31:30	37 157 282 525	19 653 000	+1,02	28.axb6
 29/84	33:46	39 907 517 671	19 695 000	+1,02	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Ke2 h5 53.Re3+ Kd6 54.Rd3+

Best move: axb6, Value: +1,02, Depth: 29/84, Time: 30:39,903, 39 907 517 671 Nodes, 19 695 kN/sec.

[Robert Flesher]

Not winning but definitely on good way there.

Houdini 1.5a 6CPU:

Code: Select all

  4/13	00:00	       1 374	687 000	-0,52	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Ne4 Bxe4 31.fxe4
  5/13	00:00	       1 852	926 000	-0,52	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Ne4 Bxe4 31.fxe4
  6/18	00:00	       3 142	628 000	-0,44	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8
  7/18	00:00	       4 236	353 000	-0,44	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8
  8/18	00:00	       5 546	396 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bc6 31.Nc3 Re8 32.Rab1 Kg7
  9/18+	00:00	       9 258	356 000	-0,42	28.Qd6
  9/27+	00:00	      17 183	592 000	-0,29	28.Qd6
  9/27	00:00	      31 396	981 000	-0,38	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Bf5 32.Rd4 Bd3 33.Be7 Rc7 34.Re1 Rb8
 10/27	00:00	      40 783	1 132 000	-0,38	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Bf5 32.Rd4 Bd3 33.Be7 Rc7 34.Re1 Rb8
 11/27-	00:00	      76 134	1 812 000	-0,44	28.Qd6 Qxd6
 11/27	00:00	     123 710	2 524 000	-0,45	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Rc6 32.Rd2 Ra6 33.g4 Re8 34.Kg3 Kg7 35.h5 gxh5 36.gxh5
 12/28	00:00	     189 370	3 265 000	-0,40	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Be6 31.Nc3 Rc6 32.Kg3 Kg7 33.Kf2 Nc5 34.Bxc5 Rxc5 35.Rd6 Re8 36.Re1
 13/29-	00:00	     474 843	5 521 000	-0,46	28.Qd6 Qxd6
 13/29	00:00	     724 202	6 705 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Nb5 Re3 33.Nc7 Rc8 34.Nb5 c3 35.Bf4 Re7 36.Nxa7 Rc4 37.Kg3 c2
 14/29	00:00	     902 577	7 338 000	-0,48	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Nb5 Re3 33.Nc7 Rc8 34.Nb5 c3 35.Bf4 Re7 36.Nxa7 Rc4 37.Kg3 c2
 15/38	00:00	   1 613 190	9 379 000	-0,53	28.Qd6 Qxd6 29.Bxd6 Nd7 30.Nb1 Bf7 31.Nc3 Re8 32.Ba3 Ne5 33.Rab1 Reb8 34.Rxb8+ Rxb8 35.Be7 Rb2 36.Bxf6 Nxf3+ 37.Kg3 Nd2
 15/38	00:00	   2 849 279	10 916 000	-0,46	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Nd3 31.Qxf6 Nxc1 32.Rxd5 Qxf6 33.Nxf6+ Kg7 34.Be5 Rd8 35.Rb5 Kf7 36.Nxh7 Nd3 37.Ng5+ Kg8 38.Kg3 Nxe5 39.Rxe5
 16/38+	00:00	   3 866 878	11 753 000	-0,40	28.Qf4
 16/42+	00:00	   6 819 505	12 675 000	-0,27	28.Qf4
 16/48	00:01	  16 200 474	14 661 000	-0,27	28.Qf4 Nd7 29.Rac1 Rc6 30.Re1 Qf5 31.Qe3 Re6 32.Qd4 Rxe1 33.Rxe1 Qd3 34.Qxd3 cxd3 35.Re3 Nc5 36.Bd6 Rc8 37.a6 Nxa6 38.Rxd3 Bc6 39.Nb3 Bb5 40.Rd1 Rc2 41.Nd4
 17/48+	00:01	  18 277 718	14 799 000	-0,21	28.Qf4
 17/48	00:02	  27 462 049	15 515 000	-0,24	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kh1 Rf8 33.Rd5 c3 34.Bxe5 fxe5 35.Rxe5 Qc4 36.Qe3 Rc7 37.Re4 Qc5 38.Rd4 Qxa5 39.Qe6+ Kg7 40.Rd5 Qa3 41.Qe5+ Kg8 42.Qe6+ Rcf7
 18/48+	00:02	  30 496 667	15 623 000	-0,17	28.Qf4
 18/48	00:02	  38 253 619	15 569 000	-0,21	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.g3 Kg7 37.Kg2 Rcc8 38.a6 Re7 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4
 19/48	00:02	  41 547 098	15 695 000	-0,21	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.g3 Kg7 37.Kg2 Rcc8 38.a6 Re7 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4
 20/48	00:03	  48 233 454	15 992 000	-0,19	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.Kf1 Kg7 37.Kf2 Ree7 38.Kg3 Rc8 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4 Kf6 42.Kf3
 21/48	00:03	  58 783 289	16 301 000	-0,19	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Bxe5 fxe5 34.Rc3 Rc7 35.Rd5 Qc6 36.Kf1 Kg7 37.Kf2 Ree7 38.Kg3 Rc8 39.Rxe5 Qxe4 40.Rxe4 Rxe4 41.fxe4 Kf6 42.Kf3
 22/49+	00:05	  91 045 112	16 938 000	-0,12	28.Qf4
 22/49	00:06	  98 512 697	17 020 000	-0,18	28.Qf4 Nd7 29.Rac1 Ne5 30.Ne4 Bxe4 31.Qxe4 Rc6 32.Kg1 Re8 33.Re1 Rcc8 34.Qd4 a6 35.Bxe5 fxe5 36.Qc3 Rc5 37.Re4 Rec8 38.Rce1 Rd8 39.Rxe5 Rxe5 40.Rxe5 Rd1+ 41.Kf2 Qc6 42.h5
 22/49+	00:11	 197 399 636	17 798 000	 0,00	28.axb6
 22/61	00:22	 396 450 780	17 997 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 23/61	00:24	 436 740 426	18 065 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 24/61	00:28	 517 104 348	18 222 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 25/61	00:35	 654 141 477	18 408 000	 0,00	28.axb6 Rxc7 29.bxc7 Rc8 30.Nxc4 Bxc4 31.Rd8+ Kf7 32.Rad1 Ke7 33.Bd6+ Kf7 34.Bg3 Ke7
 26/66+	01:13	1 370 757 930	18 835 000	+0,06	28.axb6
 26/66+	01:45	1 991 377 609	18 948 000	+0,19	28.axb6
 26/68+	03:37	4 134 875 846	19 041 000	+0,47	28.axb6
 26/82	14:17	16 568 654 439	19 324 000	+1,14	28.axb6 Rxc7 29.bxc7 Rc8 30.Nb1 Qc6 31.Nc3 Rxc7 32.Rxd5 Rd7 33.Rxd7 Qxd7 34.Ne4 Qe7 35.Rc1 f5 36.Rxc4 fxe4 37.Rc8+ Kf7 38.Rc7 exf3 39.Rxe7+ Kxe7 40.gxf3 a5 41.Be1 a4 42.Kg3 Kd7 43.Kf4 a3 44.Ke4 Ke6 45.Bc3 h6 46.Ba1 g5 47.h5 Kd6
 27/82+	20:30	23 952 744 665	19 467 000	+1,23	28.axb6
 27/82-	23:29	27 496 630 234	19 516 000	+1,05	28.axb6 Rxc7
 27/82-	23:45	27 821 256 379	19 520 000	+0,87	28.axb6 Rxc7
 27/82	24:03	28 147 507 496	19 509 000	+0,97	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Kd2 f5 53.Rh3 Qb4+ 54.Ke2 Qb2+ 55.Kf1 Qb1+ 56.Be1 h5 57.Re3+
 28/82+	26:15	30 803 503 479	19 561 000	+1,05	28.axb6
 28/82	26:42	31 350 127 478	19 563 000	+0,93	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Ke2 h5 53.Re3+ Kd6 54.Rd3+ Ke6
 29/84+	31:30	37 157 282 525	19 653 000	+1,02	28.axb6
 29/84	33:46	39 907 517 671	19 695 000	+1,02	28.axb6 Rxc7 29.bxc7 Kf7 30.Ne4 Bxe4 31.fxe4 Rc8 32.Rd8 c3 33.Rad1 c2 34.Rc1 g5 35.h5 Rxc7 36.Bxc7 Qc4 37.Bg3 Qe2 38.Be1 Qxh5+ 39.Kg1 Qe2 40.Rd2 Qe3+ 41.Kh1 g4 42.Rdxc2 g3 43.Rc7+ Kg6 44.R7c3 Qh6+ 45.Kg1 Qh2+ 46.Kf1 Qh1+ 47.Ke2 Qxg2+ 48.Kd1 Qxe4 49.Rxg3+ Kf5 50.Rc5+ Ke6 51.Bf2 Qa4+ 52.Ke2 h5 53.Re3+ Kd6 54.Rd3+

Best move: axb6, Value: +1,02, Depth: 29/84, Time: 30:39,903, 39 907 517 671 Nodes, 19 695 kN/sec.

Hello Martin, that is the problem with positions like this. Houdini is not correct IMHO. This looks clearly winning, it's better to move the pieces yourself (even using the engine to guide you if needed) and then after a few forcing moves it may begin to see the light. Although, I could be wrong, it would not be the first time, but I think it's unlikely here. The black queen is badly overworked and I cannot see how black can hold.

[Eelco de Groot]

Given enough time, Rainbow Serpent can find 3. Ne4. But to see it to the end of a Bishop endgame is too hard, at least on limited hardware of the Athlon. Serpent gets no further that +0.16 when running at half the processor to depth 29. It becomes more clear when I start another search in parallel five plies deeper along the PV, in multi PV, now a Bishop endgame at the end of the PV that looks winning. Checking this endgame in a third copy of the Shredder GUI, with Shredder and Shredder bitbases, it is quickly winning, but the evaluation function of Stockfish gives no more than approximately pawn and a half as a static evaluation. If you take some "jumps" like with this simulation of three engines checking points along the PV, this maybe is less risky if the line is reasonably forced, you should maybe be able to "create" higher scores or if you had some very specialized endgame knowledge, but that is probably too cumbersome.


[D]r1r3k1/p1Q4p/1n2qpp1/P2b4/2p4P/5PB1/3N2PK/R2R4 w - -

Engine: Rainbow Serpent 2.0 Build 081 (Athlon 2009 MHz, 256 MB)
by Romstad, Costalba, Kiiski

11/14 0:00 -1.01-- 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bc6
4.Nc3 Ne5 5.Bxe5 fxe5 6.Re1 Re8
7.Kg3 Kf7 (89.554) 163

11/14 0:00 -1.01 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bc6
4.Nc3 Ne5 5.Bxe5 fxe5 6.Re1 Re8
7.Kg3 Kf7 (121.017) 198

12/13 0:00 -1.13 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bc6
4.Nc3 Ne5 5.Bxe5 fxe5 6.Re1 Re8
7.Red1 (153.216) 228

13/15 0:00 -0.92++ 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bc6
4.Rd4 Ne5 5.Bxe5 fxe5 6.Rxc4 Bd5
7.Rxc8+ Rxc8 8.Nd2 (252.190) 293

13/14 0:00 -0.96 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Kg7 5.Kg3 Nc5 6.Rab1 Nb3 7.Re1 Re8 (291.304) 310

14/16 0:01 -1.01 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.Re1 Kf7 6.Rab1 Nb3 7.Kg3 Re8
8.Kf2 Nxa5 (447.489) 362

15/16 0:01 -1.13-- 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.Re1 Kf7 6.Rab1 Nb3 7.Kg3 Nxa5
8.Rb5 Rd8 (688.344) 408

15/16 0:02 -1.13 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.g4 Nb3 6.Ra2 Re8 7.Kg3 Rad8
8.Re2 Nxa5 (981.266) 436

16/17 0:02 -1.17 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.g4 Nb3 6.Ra2 Re8 7.Kg3 Kg7
8.Re2 Rad8 9.a6 (1.203.204) 455

17/19 0:04 -1.13 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.g4 Kf7 6.Kg3 Nd3 7.Rab1 Rd8
8.Rb7+ Rd7 9.Rdb1 Re8 10.Nd5 (2.008.261) 488

18/20 0:06 -1.17 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.g4 Kg7 6.Re1 Bf7 7.Kg2 Nd3
8.Re7 Re8 9.Rb1 Rad8 10.Rxe8 Rxe8 (3.220.618) 508

19/20 0:14 -1.25-- 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.g4 Kg7 6.Re1 Bf7 7.Kg2 Nd3
8.Re7 Re8 9.Rb1 Rxe7 10.Bxe7 Re8 (7.738.778) 526

19/21 0:18 -1.14++ 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Be6
4.Nc3 Nc5 5.Bxc5 Rxc5 6.Ne4 Rc7
7.Nxf6+ Kg7 8.Ne4 c3 9.Rdc1 c2
10.Kg3 Rd8 11.Kf4 (9.824.653) 529

19/20 0:21 -1.21 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bf7
4.Nc3 Nc5 5.Be7 f5 6.g4 Nb3 7.Ra2 Re8
8.Re2 fxg4 9.fxg4 Nxa5 10.Kg3 Nc6 (11.644.768) 531

20/20 0:26 -1.29-- 1.Qd6 Qxd6 2.Bxd6 Nd7 3.Nb1 Bf7
4.Nc3 Nc5 5.Be7 f5 6.g4 Nb3 7.Ra2 Re8
8.Re2 fxg4 9.fxg4 Nxa5 10.Kg3 Nc6 (14.095.822) 535

20/09 0:50 -1.13++ 1.axb6 Rxc7 2.bxc7 Rf8 3.Ne4 Bxe4
4.fxe4 Kf7 5.Rd8 (27.003.240) 537

20/09 0:56 -1.05++ 1.axb6 Rxc7 2.bxc7 Rf8 3.Ne4 Bxe4
4.fxe4 a5 5.Rd8 (30.714.928) 540

20/09 1:02 -0.88++ 1.axb6 Rxc7 2.bxc7 Qe8 3.Rac1 Rc8
4.Nxc4 Bxf3 5.gxf3 (34.230.974) 544

20/11 1:11 -0.56++ 1.axb6 Rxc7 2.bxc7 Qe8 3.Rac1 Qe2
4.Ne4 Qb2 5.Rxd5 Qxc1 6.Rd8+ (39.044.023) 546

20/26 1:47 -0.12 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kg7 5.Rad1 Rxc7 6.Bxc7 Bb5
7.Ra1 a6 8.Rc1 g5 9.Bg3 gxh4 10.Bxh4 h5
11.Rc7+ Kg6 12.Bf2 a5 13.Rc5 Qe2 (59.090.853) 548

21/27 2:11 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kg7 5.Rad1 Ba6 6.R8d7+ Kf8
7.Rd8+ Ke7 8.R1d6 Qf5 9.Rd5 Qc2
10.R5d7+ Ke6 11.Rd6+ Kf7 12.R8d7+ Ke8
13.Rd8+ Ke7 14.R6d7+ (72.164.212) 549

22/13 3:00 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (99.604.797) 551

23/13 3:52 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (127.596.861) 548

24/13 5:03 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (166.185.935) 547

25/13 9:04 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (295.152.356) 542

26/13 16:24 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (527.662.887) 535

27/13 26:36 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (755.283.857) 473

28/13 59:25 0.00 1.axb6 Rxc7 2.bxc7 Rc8 3.Nxc4 Bxc4
4.Rd8+ Kf7 5.Rad1 Ke7 6.Bd6+ Kf7
7.Bg3 (1.318.131.632) 369

29/11 124:08 +0.08++ 1.axb6 Rxc7 2.bxc7 Rc8 3.Ne4 Kf8
4.Nc3 Bb7 5.Rd8+ Kf7 6.Rxa7 (2.424.403.435) 325

29/05 272:51 +0.16++ 1.axb6 Rxc7 2.bxc7 a6 3.Ne4 (5.040.876.366) 307

best move: a5xb6 time: 282:43.860 min n/s: 307.364 nodes: 5.214.031.956


[FEN "r1r3k1/p1Q4p/1n2qpp1/P2b4/2p4P/5PB1/3N2PK/R2R4 w - -"]

1. axb6 Rxc7 2. bxc7 Rc8 3. Ne4 *

Two best moves:

[D]2r3k1/p1P4p/4qpp1/3b4/2p1N2P/5PB1/6PK/R2R4 b - -

Engine: Rainbow Serpent 2.0 Build 081 (Athlon 2009 MHz, 64 MB)
by Romstad, Costalba, Kiiski

29 269:07 -1.61 3...Bxe4 4.Rd8+ Kf7 5.fxe4 Ke7
6.Rxc8 Qxc8 7.Rd1 a5 8.Rd8 Qxd8
9.cxd8Q+ Kxd8 10.Be1 a4 11.Kg3 Kc7
12.Bc3 f5 13.exf5 gxf5 14.Kf4 a3
15.Kxf5 Kc6
{[D]8/7p/2k5/5K2/2p4P/p1B5/6P1/8 w - - 0 1 +/-
This is a won endgame}

29 269:07 -2.46 3...Kg7 4.Nd6 Rxc7 5.Re1 Rd7 6.Rxe6 Bxe6
7.Ra6 c3 8.Rc6 a5 9.Ne4 Bd5 10.Rxc3 a4
11.Nc5 Ra7 12.Ra3 Bc6 13.Bf2 Kf7
14.Kg3 Ra8 15.Kf4 Rd8 (5.110.464.567) 316

best move: Bd5xe4 time: 280:43.281 min n/s: 328.988 nodes: 5.541.203.371