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Trent Parker
18-11-2008, 03:51 PM
3K4/1p5p/1p6/8/8/1B6/1p6/b1k3B1 w - - 0 50

White to play and force mate in twenty something moves.

Miranda
18-11-2008, 03:53 PM
twenty something?

I'm not even going to try.

Trent Parker
18-11-2008, 03:55 PM
Come on Miranda! its all forced!

Miranda
18-11-2008, 04:07 PM
Um.... black bishop gives check?

Miranda
18-11-2008, 04:08 PM
IDK about you, but to me, forced mate = check, check, check (repeat as many times as needed) checkmate.

:lol:

Igor_Goldenberg
18-11-2008, 04:19 PM
I got it in 19 moves, might've missed some better defence without the chess board in front of me, even I can't see where black could play better

1. Be3+ Kb1
2. Bh6 b5
3. Ke7 b4
4. Kf6 b5
5. Kg5 Kc1
6. Kf5(or Kg4)+ Kb1
7. Kf4 Kc1
8. Ke4(f3)+ Kb1
9. Ke3 Kc1
10. Kd3+ Kb1
11. Bd5 b3
12 .Bxb3 b4
13. Bd5 b3
14. Kc3 Ka2
15 Bxb3+ Kb1 (15...Ka3 16.Bf8#)
16. Be3 h5
17. Bc4 h4
18. Kb3 h3
19. Bd3#
If 3...b6, then Kf6-f5-f4 and checkmate one move earlier.

Kaitlin
18-11-2008, 05:30 PM
Waits patiently for someone to put a PNG up :twiddlesthumbs:

Igor_Goldenberg
18-11-2008, 06:48 PM
I don't know how to do pgn from the setup position (e.g. not initial one). I put it in chessbase, saved as pgn and tried to upload, but uploader ignores the FEN

black
18-11-2008, 10:52 PM
I got it in 19 moves, might've missed some better defence without the chess board in front of me, even I can't see where black could play better

1. Be3+ Kb1
2. Bh6 b5
3. Ke7 b4
4. Kf6 b5
5. Kg5 Kc1
6. Kf5(or Kg4)+ Kb1
7. Kf4 Kc1
8. Ke4(f3)+ Kb1
9. Ke3 Kc1
10. Kd3+ Kb1
11. Bd5 b3
12 .Bxb3 b4
13. Bd5 b3
14. Kc3 Ka2
15 Bxb3+ Kb1 (15...Ka3 16.Bf8#)
16. Be3 h5
17. Bc4 h4
18. Kb3 h3
19. Bd3#
If 3...b6, then Kf6-f5-f4 and checkmate one move earlier.

I got this too. Since the question asks for 21 moves, perhaps white can shuffle the light-square bishop along the a6-f1 diagonal until black promotes, then deliver the Bd3# (Or Be2-d1-c2#; or a similar idea depending how far back you move that bishop from b3...).

Inefficient moves within the logic of chess, but this satisfies the question.

Incidentally, if black chooses to play b7-b6 instead of b7-b5 then white can mate one move faster; but can still satisfy the question with a shuffle until move 21. That is, so long as black plays h7-h6 etc. If black plays h7-h5 (and continues with ideal play from then on), then white will need to deliver mate on move 20.

By the same reasoning, the main line given by Igor, and my suggestion to shuffle until promotion, only works with black playing h7-h5. If h7-h6 then white can make the mate on move 21 with the pawn on h2, or shuffle a move longer and do mate on the 22nd move.

Unless I missed something!?

I don't see the point for extending the solution beyond best play. Nice concept in the given problem though.

Zwischenzug
19-11-2008, 12:51 AM
Success!

1. Be3+ Kb1 2. Bh6 b5 3. Ke7 b4 (If 3...b6, then Kf6-f5-f4 and checkmate one move earlier) 4. Kf6 b5 5. Kg5 Kc1 6. Kf5+ Kb1 7. Kf4 Kc1 8. Ke4+ Kb1 9. Ke3 Kc1 10. Kd3+ Kb1 11. Bd5 b3 12. Bxb3 b4 13. Bd5 b3 14. Kc3 Ka2 15. Bxb3+ Kb1 (15...Ka3 16.Bf8#) 16. Be3 h5 17. Bc4 h4 18. Kb3 h3 19. Bd3#

Igor_Goldenberg
19-11-2008, 10:31 AM
Thanks. So, you put FEN in pgn statement, then it starts from that position.

Igor_Goldenberg
19-11-2008, 10:33 AM
I got this too. Since the question asks for 21 moves
I wasn't looking for white to make it longer, only for black to prolong the agony.
Interesting, Rybka was puffing for almost half an hour, but came out only with += line and got nowhere near the solution (which is not very difficult for human being). After being humiliated by a computer so many times, I finally felt vindicated.:lol:

Miranda
19-11-2008, 01:12 PM
haha... I would never have seen that. never.

meh.

perhaps one day...

Space_Dude
28-11-2008, 04:31 PM
Waits patiently for someone to put a PNG up :twiddlesthumbs:
Agreed!

Miranda
28-11-2008, 04:35 PM
Agreed!
Look at post 10.

Space_Dude
29-11-2008, 05:10 PM
Success!

1. Be3+ Kb1 2. Bh6 b5 3. Ke7 b4 (If 3...b6, then Kf6-f5-f4 and checkmate one move earlier) 4. Kf6 b5 5. Kg5 Kc1 6. Kf5+ Kb1 7. Kf4 Kc1 8. Ke4+ Kb1 9. Ke3 Kc1 10. Kd3+ Kb1 11. Bd5 b3 12. Bxb3 b4 13. Bd5 b3 14. Kc3 Ka2 15. Bxb3+ Kb1 (15...Ka3 16.Bf8#) 16. Be3 h5 17. Bc4 h4 18. Kb3 h3 19. Bd3#
Freaky...

Trent Parker
03-12-2008, 08:27 AM
Wow thanks Igor! thats a different answer than I have

Igor_Goldenberg
03-12-2008, 09:12 AM
Wow thanks Igor! thats a different answer than I have
Trent,
What's your answer?