Deep Bxh6 sac

[jdart]

[d] 5r1k/1pq1bpp1/p6p/P1prPR2/8/4B1Q1/1PP3PP/R5K1 w - - 0 25

This is the end position of Vallejo Pons-Le Quang, Tromso 2013. That game was agreed drawn. But White can play Bxh6 here. It appears this isn't winning, but in the main line White comes out with Queen + Pawn vs two Rooks so there is some advantage (that line is Bxh6 gxh6 Qf4 Bg5 Rxg5 hxg5 Qf6+ Kh7 Ra3 Rd1+ Kf2 Rd2+ Ke1 Qd7 Rh3+ Qxh3 gxh3).

--Jon

[peter]

Hi Jon!

5r1k/1pq1bpp1/p6p/P1prPR2/8/4B1Q1/1PP3PP/R5K1 w - - 0 1

Analysis by asmFishW_2016-08-21_base:

25.Taf1 Dxa5 26.Df3 c4 27.Txf7 Txf7 28.Dxf7
+/- (0.71) Tiefe: 7 00:00:00 20kN
...

25.Dh3
+/= (0.38 ++) Tiefe: 26 00:00:07 195MN
25.Lxh6
+/= (0.45 ++) Tiefe: 26 00:00:09 245MN
...
25.Lxh6 gxh6 26.Df4 Dd7 27.Dxh6+ Kg8 28.Dh5 De6 29.Ta3 Td1+ 30.Kf2 Lh4+ 31.Tg3+ Lxg3+ 32.Kxg3 Tfd8 33.Tf6 T8d3+ 34.cxd3 Txd3+ 35.Kh4 Dc4+ 36.g4 Db3 37.Dg5+ Kf8 38.Dh6+ Ke7 39.Df4 Ke8 40.Kg5 Th3 41.Dd2 Th8 42.Td6 Tg8+ 43.Kf4 Da4+ 44.Ke3 Tg6 45.Txg6 fxg6 46.Kf3 Dc6+ 47.Kg3 De4 48.Dc3
+/- (1.06) Tiefe: 26 00:00:12 340MN
...
25.Lxh6 gxh6 26.Df4 Lg5 27.Txg5 hxg5 28.Df6+ Kh7 29.Ta3 Dd7 30.Th3+ Dxh3 31.gxh3 Tdd8 32.h4 gxh4 33.Dxh4+ Kg7 34.Dg4+ Kh6 35.Dh3+ Kg5 36.Df3 Tde8 37.Df6+ Kh5 38.Kf2 Te6 39.Dg7 Tfe8 40.Dxf7+ Kh6 41.Dxb7 Tf8+ 42.Ke3 Txe5+ 43.Kd3 Tf6 44.c3 Kg6 45.Dc8 Tfe6 46.Dg8+ Kf6 47.Df8+ Kg6 48.Df3 Tf6 49.Dg4+ Tg5 50.Dc4 Kg7 51.h4 Tgf5 52.Dg4+ Kh6 53.Kc2
+/- (1.48) Tiefe: 31 00:00:40 1217MN
changed from German to English abbrevations
25.Bxh6
+/- (1.55 ++) Depth: 32 00:00:56 1705MN
25.Bxh6 gxh6 26.Qf4 Bg5 27.Rxg5 hxg5 28.Qf6+ Kh7 29.Ra3 Qd7 30.Rh3+ Qxh3 31.gxh3 Rdd8 32.h4 gxh4 33.Qxh4+ Kg7 34.Qg4+ Kh6 35.Qh3+ Kg5 36.Qf3 f5 37.Qxb7 Rh8 38.Qg2+ Kf4 39.Qe2 Kg5 40.e6 Kf6 41.e7 Ra8 42.Qe3 c4 43.Qc5 Ke6 44.Qxc4+ Kxe7 45.h4 Rhd8 46.Kf2 Rac8 47.Qe2+ Kf7 48.Qxa6 Rxc2+ 49.Kf3
+/- (1.55) Depth: 32 00:00:59 1798MN
...
25.Bxh6 gxh6 26.Qf4 Qd7 27.Qxh6+ Kg8 28.Qh5 Qe6 29.Ra3 Rd1+ 30.Kf2 Bh4+ 31.Rg3+ Bxg3+ 32.Kxg3 Rfd8 33.Rf6 R1d3+ 34.cxd3 Rxd3+ 35.Kh4 Qc4+ 36.g4 Qb3 37.Qg5+ Kf8 38.Qh6+ Ke7 39.Qf4 Ke8 40.Kg5 Rh3 41.Qd2 Rd3 42.Qf2 Rd5 43.Rxf7 Rxe5+ 44.Rf5 Qg8+ 45.Kh4 Qh7+ 46.Kg3 Qe7 47.Rxe5 Qxe5+ 48.Qf4 Qxb2 49.Qe4+ Kf7 50.Qd5+ Kg6 51.Qh5+ Kg7 52.Qg5+ Kf7 53.Qxc5 Qb3+ 54.Kf4 Qb5 55.Qf5+ Kg7
+- (1.69) Depth: 34 00:02:06 3880MN

[Nordlandia]

This variation is pretty much forced.

[pgn][Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "New game"]
[Black "?"]
[Result "*"]
[SetUp "1"]
[FEN "5r1k/1pq1bpp1/p6p/P1prPR2/8/4B1Q1/1PP3PP/R5K1 w - - 0 25"]
[PlyCount "47"]

25. Bxh6 gxh6 26. Qf4 Bg5 27. Rxg5 hxg5 28. Qf6+ Kh7 29. Ra3 Rd1+ 30. Kf2 Rd2+
31. Ke1 Qd7 32. Rh3+ Qxh3 33. gxh3 Rdd8 34. h4 gxh4 35. Qxh4+ Kg6 36. Qg4+ Kh6
37. Qh3+ Kg7 38. Qg2+ Kh6 39. Qxb7 Rfe8 40. Qxa6+ Re6 41. Qe2 Rd5 42. Qe3+ Kg7
43. Qc3 c4 44. h4 Rexe5+ 45. Kf2 Rxa5 46. Qxc4 Rac5 47. Qg4+ Kf6 48. c4 *

[/pgn]Analysis by asmFishW_2016-08-20_bmi2:

+/- (0.94) (22.08.2016)

[d]8/5p2/5k2/2r1r3/2P3QP/8/1P3K2/8 b - - 0 48
Very complex ending

[bob]

[d] Very

This is the end position of Vallejo Pons-Le Quang, Tromso 2013. That game was agreed drawn. But White can play Bxh6 here. It appears this isn't winning, but in the main line White comes out with Queen + Pawn vs two Rooks so there is some advantage (that line is Bxh6 gxh6 Qf4 Bg5 Rxg5 hxg5 Qf6+ Kh7 Ra3 Rd1+ Kf2 Rd2+ Ke1 Qd7 Rh3+ Qxh3 gxh3).

--Jon

I don't follow. Q+P is not "some advantage" over two rooks. It is beyond difficult to win a QP vs RR ending unless the RR side has its king totally out of play, which is not the case in this position.

[jdart]

I meant, the material difference is Q+P vs RR, but there is other material present.

The line given by Jon Fredrik Åsvang leads to Q vs 3 pawns vs. RR and 1 pawn. It is by no means clear this is a win. But most engine evals will prefer the side with the Queen.

--Jon

[bob]

I meant, the material difference is Q+P vs RR, but there is other material present.

The line given by Jon Fredrik Åsvang leads to Q vs 3 pawns vs. RR and 1 pawn. It is by no means clear this is a win. But most engine evals will prefer the side with the Queen.

--Jon

Then perhaps I took your comment wrong ("there is some advantage"). What a program says is not always correct regarding which side is better, although they generally seem to find the right move most of the time.

Most consider two rooks better than a queen. Two rooks can overpower a queen and win pawns.

[Vinvin]

...
+/- (1.55) Depth: 32 00:00:59 1798MN

30 Mnodes/sec, what's that machine ?

[peter]

25. Bxh6 gxh6 26. Qf4 Bg5 27. Rxg5 hxg5 28. Qf6+ Kh7 29. Ra3 Rd1+ 30. Kf2 Rd2+
31. Ke1 Qd7 32. Rh3+ Qxh3 33. gxh3 Rdd8 34. h4 gxh4 35. Qxh4+ Kg6 36. Qg4+ Kh6
37. Qh3+ Kg7 38. Qg2+ Kh6 39. Qxb7 Rfe8 40. Qxa6+ Re6 41. Qe2 Rd5 42. Qe3+ Kg7
43. Qc3 c4 44. h4 Rexe5+ 45. Kf2 Rxa5 46. Qxc4 Rac5 47. Qg4+ Kf6 48. c4 *

44.a6 instead of h4:

5r1k/1pq1bpp1/p6p/P1prPR2/8/4B1Q1/1PP3PP/R5K1 w - - 0 25

25. Bxh6 gxh6 26. Qf4 Bg5 27. Rxg5 hxg5 28. Qf6+ Kh7 29. Ra3 Rd1+ 30. Kf2 Rd2+
31. Ke1 Qd7 32. Rh3+ Qxh3 33. gxh3 Rdd8 34. h4 gxh4 35. Qxh4+ Kg6 36. Qg4+ Kh6
37. Qh3+ Kg7 38. Qg2+ Kh6 39. Qxb7 Rfe8 40. Qxa6+ Re6 41. Qe2 Rd5 42. Qe3+ Kg7
43. Qc3 c4

44. a6 Rxa6 45. Qxc4 Rxe5+ 46. Kd2 Rd6+ 47. Kc3 Ree6 48. Qh4 f5 49.
b4 Rc6+ 50. Kd2 Rcd6+ 51. Kc1 Rf6 52. Qf4 Rde6 53. b5 Re4 54. Qg3+ Kf8 55. Qa3+
Kg7 56. b6 Re1+ 57. Kd2 Rb1 58. Qe7+ Kg6 59. b7 Rfb6 60. h4 Rxb7 61. Qg5+ Kh7
62. Qxf5+

[d]r5k/8/5Q2/7P/8/2PK4/1r6 b - - 0 1

Analysis by asmFishW_2016-08-21_base:

62...Kg7 63.Qg4+ Kh6 64.Qf4+ Kg6 65.c4 R7b2+ 66.Ke3 Rb3+ 67.Kd4 Rd1+ 68.Kc5 Rbb1 69.Qg5+ Kh7 70.Kc6 Rf1 71.c5 Ra1 72.Qh5+ Kg7 73.Qg4+ Kh7 74.Qe4+ Kh6 75.Qd4 Kg6 76.Qd3+ Kg7 77.Qg3+ Kf7 78.Qb3+ Kg7 79.Qb2+ Rf6+ 80.Kb5 Raa6 81.Qd4 Kh6 82.Qd5 Kg6 83.Qe5 Kh7 84.Qe4+ Kh6 85.Qe3+ Kg7 86.Qc3 Kh6 87.Qc1+ Kg6 88.Qd2 Kh7 89.Qg5 Rae6 90.Qh5+ Kg8 91.Qg4+ Kh8 92.Kc4 Re1 93.Qh5+ Kg7 94.Qg5+ Rg6 95.Qf4 Ree6
+/- (1.52) Depth: 44 00:02:36 6251MN, tb=65371545

but it's a drawn Lomonosov- position

Yet the question for the best 25th white move is to be answered clearly, I guess.
The question, if you want to go on playing at all, if you're not sure, that you will win, is a one of its own always, isn't it?
There are many people for sure, who don't want to play chess, even if they could be sure to win.

[peter]

12 cores at 2,7GHz and 24 threads, Vincent