Difficult endgames

[Nordlandia]

| -1.15

[d]3r4/1p6/p1b5/5p1k/1R4p1/1P6/P1P1NP2/2K5 w - - 0 0

[Nordlandia]

SF is not certain.

[d]8/1r6/1PRP2pp/5p2/p4p2/P5k1/4K1P1/8 w - - bm Kd3

id "arasan18.191"; c0 "Seven of Seven (Stockfish 2.2.2 JA)-Halmatic (Deep Rybka 4.1), playchess.com 2012";

[Nordlandia]

Fairly complex endgame positions ->

BBP vs BRP

[d]5k2/8/3p2B1/3r2b1/3B2P1/8/4K3/8 w - - 0 85

[d]8/8/8/B2pkB2/6P1/5r2/4K3/b7 b - - 0 102

[d]8/5k2/2R1b3/4bp2/8/4BP2/4K3/8 w - - 0 79

[d]6k1/8/8/4Nb2/5p1b/1R6/1P4K1/8 b - - 0 41

[d]8/4bbk1/8/8/1R3p2/1P3N2/5K2/8 w - - 0 46

[d]1B6/7k/5n1p/7B/5P2/3r4/6K1/8 w - - 0 60

[d]8/8/6R1/4p3/3bk3/8/4bPN1/6K1 b - - 0 49

[d]8/8/4b1k1/6p1/1b6/6P1/6N1/5R1K w - - 0 54

[d]8/3B4/4P1p1/B4n2/4r3/1k6/3K4/8 b - - 0 57

[d]8/8/4p3/2k1B3/2r1nP2/8/2B5/2K5 b - - 0 5

Possible winning 8-man EGTB position.

[d]Q7/8/2p5/2k5/3b4/5KB1/2B5/q7 w - - 0 5

[d]8/8/P1p5/3k4/3b3B/p4K2/2B5/8 b - - 0 1

[peter]

Hi Jon!

...
Possible winning 8-man EGTB position.

[d]Q7/8/2p5/2k5/3b4/5KB1/2B5/q7 w - - 0 5

[d]8/8/P1p5/3k4/3b3B/p4K2/2B5/8 b - - 0 1

Did let SF with full Syzygys at 8'+2" play out all the positions, only the (two) last one(s) ended up drawn.

[pgn]
[Event "Stellung ausspielen (SF-McBrain2664POPCN"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Neue Partie"]
[Black "?"]
[Result "1/2-1/2"]
[FEN "8/8/P1p5/3k4/3b3B/p4K2/2B5/8 b - - 0 1"]
[SetUp "1"]

1...Kd6 2.Bg3+ Kc5 3.a7 a2 4.a8=Q a1=Q 5.Qf8+ Kb5 6.Qb8+ Kc4 7.Qg8+ Kb5 8.Kg4 Qc3 9.Qg6 Kb4 10.Bf4 Qc4 11.Be4 Bf6 12.Kg3 c5 13.Qe8 Bd4 14.Kg4 Qe2+ 15.Kf5 Qf1 16.Qb8+ Kc3 17.Qa7 Kb4 18.Qb7+ Kc3 19.Qa8 Kb4 20.Qb8+ Kc3 21.Qa7 Kb4 22.Qb7+ Kc3 23.Qa8 Kb4 24.Kg5 Qg1+ 25.Bg2 c4 26.Qb7+ Kc3 27.Qf3+ Kb2 28.Qe4 c3 1/2-1/2
[/pgn]

Will let run slow Backward to be sure, maybe TC was too short for this one

[peter]

Did let SF with full Syzygys at 8'+2" play out all the positions, only the (two) last one(s) ended up drawn.

[pgn]
[Event "Stellung ausspielen (SF-McBrain2664POPCN"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Neue Partie"]
[Black "?"]
[Result "1/2-1/2"]
[FEN "8/8/P1p5/3k4/3b3B/p4K2/2B5/8 b - - 0 1"]
[SetUp "1"]

1...Kd6 2.Bg3+ Kc5 3.a7 a2 4.a8=Q a1=Q 5.Qf8+ Kb5 6.Qb8+ Kc4 7.Qg8+ Kb5 8.Kg4 Qc3 9.Qg6 Kb4 10.Bf4 Qc4 11.Be4 Bf6 12.Kg3 c5 13.Qe8 Bd4 14.Kg4 Qe2+ 15.Kf5 Qf1 16.Qb8+ Kc3 17.Qa7 Kb4 18.Qb7+ Kc3 19.Qa8 Kb4 20.Qb8+ Kc3 21.Qa7 Kb4 22.Qb7+ Kc3 23.Qa8 Kb4 24.Kg5 Qg1+ 25.Bg2 c4 26.Qb7+ Kc3 27.Qf3+ Kb2 28.Qe4 c3 1/2-1/2
[/pgn]

Will let run slow Backward to be sure, maybe TC was too short for this one

One more game from first White deviaton of 150"/move- Backward, 8.Qb8+ instead fo Kg4, this time with 120'+30" at 24 threads and 16G hash, again full Syzygys loaded:

[pgn]
[Event "Stellung ausspielen (SF-McBrain2664POPCN"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Neue Partie"]
[Black "?"]
[Result "1/2-1/2"]
[FEN "8/8/P1p5/3k4/3b3B/p4K2/2B5/8 b - - 0 1"]
[SetUp "1"]

1...Kd6 2.Bg3+ Kc5 3.a7 a2 4.a8=Q a1=Q 5.Qf8+ Kb5 6.Qb8+ Kc4 7.Qg8+ Kb5 8.Qb8+ Kc4 9.Qb3+ Kc5 10.Bd3 Qc3 11.Qd1 Kb6 12.Kg2 Be5 13.Bf2+ Bd4 14.Bg3 Be5 15.Be1 Qb2+ 16.Be2 Kc7 17.Qd3 Bd6 18.Bf2 Qg7+ 19.Kf1 Qa1+ 20.Bd1 Qc1 21.Be3 Qa1 22.Bf2 Qc1 23.Qd4 Qb1 24.Be1 Qf5+ 1/2-1/2
[/pgn]

[Nordlandia]

Peter Martan -> considering QBB vs QB is winning 7-man position, there is reason to believe QBB vs QBP is winning 8-man position.

[d]Q7/8/2p5/2k5/3b4/5KB1/2B5/q7 w - - 0 5

[peter]

Peter Martan -> considering QBB vs QB is winning 7-man position, there is reason to believe QBB vs QBP is winning 8-man position.

[d]Q7/8/2p5/2k5/3b4/5KB1/2B5/q7 w - - 0 5

Only if you consider the P+ to be irrelevant

Show your winning line, Jon

[Nordlandia]

Peter Martan -> considering QBB vs QB is winning 7-man position, there is reason to believe QBB vs QBP is winning 8-man position.

[d]Q7/8/2p5/2k5/3b4/5KB1/2B5/q7 w - - 0 5

Only if you consider the P+ to be irrelevant

Show your winning line, Jon

It's mate in 7 without c6 pawn so there certainly reason to believe QBB vs QBP is forced mate in some positions.

[pgn][Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "1-0"]
[SetUp "1"]
[FEN "Q7/8/8/2k5/3b4/5KB1/2B5/q7 w - -"]

1.Qc8+ Kb5 2.Bd3+ Ka5 3.Qa6+ Kb4 4.Bd6+ Bc5 5.Qc4+ Ka3 6.Bxc5+ Kb2 7.Qc2# 1-0[/pgn]

[peter]

It's mate in 7 without c6 pawn so there certainly reason to believe QBB vs QBP is forced mate in some positions.

I didn't mean the winning line without the pawn, Jon, if you think the pawn doesn't matter, you have to show a winning line to the position in which 7 pieces are reached again.
How in any other way can you come to the conclusion, the pawn wouldn't matter

[Nordlandia]

This complex 8-man position occured between SF Dev and K11 on Galaxy S8+ equipped with 5-men syzygy.

K11.2 and SF Dev is slightly above +1 in evaluation. It's not known if this is won or lost with good play.

[d]8/3b4/6k1/8/1R5p/1P1N1Kb1/8/8 b - - 0 54

[d]4rbk1/1pp2ppp/p1b2n2/8/8/P1N2N1P/1P3PP1/R2R2K1 w - - 0 23

[pgn][Event "Chess for Android Game"]
[Site "Norge"]
[Date "2017.07.17"]
[Round "?"]
[White "Self"]
[Black "Chess for Android"]
[Result "*"]
[SetUp "1"]
[FEN "4rbk1/1pp2ppp/p1b2n2/8/8/P1N2N1P/1P3PP1/R2R2K1 w - - 0 23"]
[PlyCount "118"]
[EventDate "2017.??.??"]

23. Re1 Bd6 24. Rxe8+ Bxe8 25. Nd2 g6 26. Nc4 Be7 27. Ne5 Kf8 28. Rd1 Bd6 29.
Re1 h5 30. Kf1 c5 31. f4 b5 32. Kf2 b4 33. Nb1 h4 34. axb4 cxb4 35. Nd2 Nh5 36.
Ne4 Bb8 37. Kf3 f6 38. Nd3 f5 39. Nec5 Bc6+ 40. Kf2 Ba7 41. Re6 Nxf4 42. Nxf4
Bxc5+ 43. Ke1 Bb7 44. Rxg6 Kf7 45. Rh6 Be4 46. Ke2 a5 47. Ra6 Bd4 48. b3 Be5
49. Nd3 Bg3 50. Rxa5 Bxg2 51. Rxf5+ Kg6 52. Rb5 Bxh3 53. Kf3 Bd7 54. Rxb4 Kf6
55. Rb6+ Kf5 56. Ra6 Bc7 57. Nc5 Be8 58. Rh6 Kg5 59. Rh8 Bh5+ 60. Kg2 Be5 61.
Ne4+ Kg6 62. Rg8+ Bg7 63. Nd6 Kh7 64. Rc8 Bg4 65. Re8 Bf6 66. Ne4 Bg7 67. Ng5+
Kg6 68. Nf3 h3+ 69. Kg3 Kf7 70. Re4 Bc8 71. b4 Bb7 72. Re2 Ba6 73. Ng5+ Kf8 74.
Re3 h2 75. Kxh2 Bb2 76. Ne6+ Kg8 77. Kg3 Kf7 78. Nf4 Bf6 79. Nd5 Bb2 80. Rf3+
Kg8 81. Kf4 Kh8 *

[/pgn]

Lichess analysis - https://lichess.org/79gHh6uM#44