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[Spliffjiffer]

i did not participate but did further analysis and i think also that mate in 27 is correct !!?
one of the mainlines is this eg:
[d]rk1b4/p2p2p1/1P6/2R2P2/8/2K5/8/5B2 w - - 0 1
1. Rc8+ Kb7 2. Bg2+ Kxb6 3. Rxa8 Bf6+ 4. Kc4 Be7 5. Kd5 Bf6 6. Rf8 Ba1 7. Bf1 Bc3 8. Rf7 Kc7 9. Bb5 Kb6 10. Bxd7 Ba1 11. Bc6 Bf6 12. Rb7+ Ka5 13. Kc4 a6 14. Bg2 Ka4 15. Rb6 Ka3 16. Be4 a5 17. Rb3+ Ka2 18. Rc3 Bxc3 19. Kxc3 a4 20. Bc2 a3 21. Be4 Ka1 22. Kb3 a2 23. Kc2 g6 24. f6 g5 25. f7 g4 26. f8=Q g3 27. Qf6# 1-0

[Vinvin]

So what now? Preferable I would drop the position, give everyone 1 point for the trouble...

Yes, let's drop the position. This position is a mistake.

[Paloma]

[pgn][Event "?"]
[Site "?"]
[Date "2018.02.08"]
[Round "?"]
[White "Rebel_Hard"]
[Black "?"]
[Result "1-0"]
[Annotator "*"]
[SetUp "1"]
[FEN "rk1b4/p2p2p1/1P6/2R2P2/8/2K5/8/5B2 w - - 0 1"]
[PlyCount "53"]

{Kubbel, 1936} 1. Rc8+ {27#} Kb7 (1... Kxc8 $2 2. Ba6+ {22#}
Kb8 3. b7 Bb6 (3... Bf6+ 4. Kc4 Bb2 5. Kd5 Ba3 6. Ke5 Bb4 7. f6 g5
(7... g6 8. f7 {16#}) 8. Kf5 {16#}) 4. Kc4 Bc7 5. Kd5 Bg3 6. f6
gxf6 7. Ke4 $1 Bd6 8. Kf5 {16#}) 2. Bg2+ Kxb6 $1 (2... Kxc8 3. b7+ {14#} Kc7 4.
bxa8=Q Bf6+ 5. Kc4) 3. Rxa8 {25#} Bf6+ (3... Bg5 4. Kc4 Kc7 5. Kd5 Be3 6. Rg8
Bh6 7. Be4 Kb6 8. Ra8 Bd2 9. Rf8 Bc3 10. Bd3 Ba1 11. Bc2 a6 12. Rf7 Kb5 13.
Rxd7 Kb4 14. Rb7+ Kc3 15. Rxg7 Kxc2 16. Ra7) 4. Kc4 a5 (4... Bg5 5. Rf8 {23#} Kc7 6. Kd5) 5. Be4 {23#} Kc7 (5... Kc7 6. Rxa5 {25#} Kd8 7. Ra6 Be5 8. Kd5 {23#} Bc3 9. Bd3 Ke7 10. Bb5 {21#} Bb2
11. Rd6 Ba3 12. Rxd7+ {19#} Kf6 13. Bd3 Bb2 14. Rd6+ {17#} Kg5 15. Ke4 Bf6 16.
Be2 {15#} Kh6 17. Rxf6+) 6. Kd5 $1 a4 7. Bd3 a3 8. Rxa3 Kd8 9. Bb5 Bb2 10. f6
Ke8 11. fxg7 Bxg7 12. Bxd7+ {16#} Ke7 13. Ra6 Bb2 14. Ba4 Kf7 15. Re6 Ba3 16.
Be8+ Kf8 17. Bh5 Bb2 18. Re2 Bf6 19. Ke6 Kg7 20. Rg2+ Kh6 21. Kxf6 Kxh5 22.
Rg5+ Kh4 23. Kf5 Kh3 24. Kf4 Kh2 25. Kf3 Kh1 26. Kf2 Kh2 27. Rh5# 1-0
[/pgn]

[zullil]

Cfish feels it's Mate-in-26 (not 27 as I submitted originally). Here's what I can offer:

Code: Select all

Mate in 26  1. Rc8+ Kb7 2. Bg2+ Kxb6 3. Rxa8 Bf6+ 4. Kc4 Be5 5. Kd5 Bf6 6. Rf8 Ba1 7. Rf7 a5 8. Rxd7 a4 9. Bf1 a3 10. Rd6+ Kb7 11. Rc6 Bf6 12. Ba6+ Ka7 13. Bc4 Kb7 14. Kd6 Be5+ 15. Kd7 Bd4 16. Bd5 Ka7 17. Re6 a2 18. Bxa2 Bb6 19. Kc6 Ka6 20. Re4 Ka5 21. Bb3 Ka6 22. Bc4+ Ka7 23. Re7+ Bc7 24. Kxc7 Ka8 25. Re5 g5 26. Ra5# (depth 112)

I'll keep the search running, and the hash table full, for a bit more, in case anyone wants to explore options.

[Spliffjiffer]

actually my originally suggestion of 4...a5 (also only move, omg) was completely wrong (only analysed for 5.bf1, that was really, really dirty !!!, sry for that)...
after 3...bf6+ 4.Kc4 a5 this is possible (at least) :
[d]rk1b4/p2p2p1/1P6/2R2P2/8/2K5/8/5B2 w - - 0 1
1. Rc8+ Kb7 2. Bg2+ Kxb6 3. Rxa8 Bf6+ 4. Kc4 a5 5. Bf3 a4 6. Rxa4 Kc7 7. Kd5 Kd8 8. Bh5 Kc7 9. Be2 Kd8 10. Bb5 Ke8 11. Ra7 Kf7 12. Rxd7+ g8 13. Rd6 Kh7 14. Rxf6 gxf6 15. Ke6 Kg7 16. Ba4 Kh6 17. Kxf6 Kh5 18. Ke6 Kg4 19. f6 Kf4 20. f7 Ke4 21. f8=Q Kd4 22. Qf2+ Kc3 23. Kd6 Kc4 24. Qe3 Kb4 25. Qb3+ Ka5 26. Qb5#

only candidate moves for a mate in 27 ( after 3...bf6+ 4.Kc4) are:
4...be7/g5/h4/e5/a1 and 4...Kc7
some of them or even all might also end up in a faster win, i dont know...if so we have probably a mate in 26 at least
everything else looses faster !

in general: quick bf3 and/or Kd5 (further kd6 sometimes) are the crtitical moves to mate most quickly

[zullil]

Cfish feels it's Mate-in-26 (not 27 as I submitted originally). Here's what I can offer:

Code: Select all

Mate in 26  1. Rc8+ Kb7 2. Bg2+ Kxb6 3. Rxa8 Bf6+ 4. Kc4 Be5 5. Kd5 Bf6 6. Rf8 Ba1 7. Rf7 a5 8. Rxd7 a4 9. Bf1 a3 10. Rd6+ Kb7 11. Rc6 Bf6 12. Ba6+ Ka7 13. Bc4 Kb7 14. Kd6 Be5+ 15. Kd7 Bd4 16. Bd5 Ka7 17. Re6 a2 18. Bxa2 Bb6 19. Kc6 Ka6 20. Re4 Ka5 21. Bb3 Ka6 22. Bc4+ Ka7 23. Re7+ Bc7 24. Kxc7 Ka8 25. Re5 g5 26. Ra5# (depth 112)

I'll keep the search running, and the hash table full, for a bit more, in case anyone wants to explore options.

[pgn]
[Result "1-0"]
[FEN "rk1b4/p2p2p1/1P6/2R2P2/8/2K5/8/5B2 w - - 0 1"]
[SetUp "1"]
1. Rc8+ Kb7 2. Bg2+ Kxb6 3. Rxa8 Bf6+ 4. Kc4 Be5 5. Kd5 Bf6 6. Rf8 Ba1 7.
Rf7 a5 8. Rxd7 a4 9. Bf1 a3 10. Rd6+ Kb7 11. Rc6 Bf6 12. Ba6+ Ka7 13. Bc4
Kb7 14. Kd6 Be5+ 15. Kd7 Bd4 16. Bd5 Ka7 17. Re6 a2 18. Bxa2 Bb6 19. Kc6
Ka6 20. Re4 Ka5 21. Bb3 Ka6 22. Bc4+ Ka7 23. Re7+ Bc7 24. Kxc7 Ka8 25. Re5
g5 26. Ra5#
{White mates} 1-0
[/pgn]

[Spliffjiffer]

very intersting Louis !...im investigating to verify you ...thx very much !

[Rebel]

Which would mean, provided M26 is correct, nobody had it right

[zullil]

Which would mean, provided M26 is correct, nobody had it right

Which engines even find Rc8+ on their own, i.e., without launching a browser and Googling the FEN?

[Spliffjiffer]

Komodo 11.2.2 does eg very very quickly ( with 5men sysygy at least)
...although i use my "special" settings i tryed "normal" komodo and it finds 1 rc8 practically instantly with 0.00 score...after about (lets say) 1-3 min the score rises quickly !