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Old 2016-03-03, 02:24   #12
1997rj7
 
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Promoting to Knight loses:

h8=N Ng5
Nf7 Nxf7 (or Ng6 Nh7 mate)
Kg8 Bxg7
Kxg7

and its KBN against K.
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Old 2016-03-03, 03:21   #13
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I guess the idea is to promote h8=B, whereby white just deprived itself of its last freedom of movement. If black is not careful, it will be a stalemate next move. If black moves the dark squared bishop to give white's knight freedom of movement, it'll capture the LSB (and with check to boot), so it'll have to move the LSB, giving the white king the freedom of movement. If only I had access to 7-men TB :(
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Old 2016-03-03, 09:57   #14
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Quote:
Originally Posted by axn View Post
If only I had access to 7-men TB :(
...which certainly wasn't available in 1967!

According to the source where I found this problem, the tablebases indicate that after 1.h8=B! (that is indeed the composer's intended key) Bg4! Black has a tablebase win. Before tablebases this sort of pawnless ending with 3 minor pieces against 2 was generally assumed to be drawn, but the frequently incomprehensible play indicated by TBs show that this assumption was sometimes wrong. A pity for the composer's beautiful idea of self-paralysis in the position.
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Old 2016-03-03, 12:30   #15
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http://chessok.com/?page_id=361 says mate in 70...

[B]FEN[/B]: 3k1K/6NP/4b2b/8/4n/8/8/8 w - - 0 24
1. h8=B Bd7 2. Kf7 Nd6+ 3. Kf6 Bc1 4. Ne6+ Kc8 5. Nd4 Bb2 6. Kg6 Nb5 7. Nxb5[B]
FEN[/B]: 2k4B/3b4/6K1/1N6/8/8/1b6/8 b - - 0 7
Mate in 64 moves 1... Bxh8 2. Nd6+ Kc7 3. Ne4 Be5 4. Nc5 Bc8 5. Ne4 Bb2
6. Ng3 Kd6 7. Nf5+ Ke5 8. Ng7 Bb7 9. Ne8 Be4+ 10. Kf7 Bc2
11. Ng7 Bd4 12. Ne8 Bb3+ 13. Kg6 Kf4 14. Ng7 Kg4 15. Ne8 Bc2+
16. Kf7 Kg5 17. Ke6 Bb3+ 18. Kd6 Bf2 19. Nc7 Bg3+ 20. Kc6 Ba4+
21. Kb6 Kf5 22. Nb5 Bf2+ 23. Ka5 Bb3 24. Kb4 Be6 25. Kc3 Ke4
26. Nd6+ Kd5 27. Nc4 Bd4+ 28. Kb4 Bf7 29. Kb5 Bf2 30. Nb6+ Ke5
31. Nc4+ Kd4 32. Na5 Kd5 33. Nc4 Be8+ 34. Kb4 Kd4 35. Nb6 Be1+
36. Kb3 Kd3 37. Ka3 Bf7 38. Ka4 Kd4 39. Kb5 Be8+ 40. Ka6 Bc6
41. Nc8 Kc5 42. Ne7 Bg2 43. Nc8 Bh4 44. Na7 Bd8 45. Nc8 Kc6
46. Na7+ Kc7 47. Kb5 Kb7 48. Nc6 Bxc6+ 49. Kc5 Bc7 50. Kb4 Bb6
51. Kc3 Bb5 52. Kb3 Ba5 53. Ka2 Ba6 54. Kb3 Kb6 55. Ka4 Bc4
56. Ka3 Kb5 57. Kb2 Bb4 58. Ka1 Ba3 59. Kb1 Bd3+ 60. Ka2 Ka4
61. Ka1 Bc4 62. Kb1 Kb3 63. Ka1 Bb2+ 64. Kb1 Bd3#
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Old 2016-03-03, 23:57   #16
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Quote:
Originally Posted by Batalov View Post
That's a cool site! Thanks.
It would appear that White would get a draw under the 50 move rule, then.

EDIT: Oops, No, on closer inspection of that tablebase line, Black just gets the capture of the knight in time.

Last fiddled with by Brian-E on 2016-03-04 at 00:21
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Old 2016-03-04, 02:26   #17
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In 2014, it seems, there was a 7-men EGTB available on the web (with some restrictions). For the 6-men, we have to get white to lose a piece. It is interesting that Stockfish (v.5 or 7) doesn't ever consider the 1.h8=B! Bg4! line, -- but if prompted evaluates it as a much better (or apparently an easier calculable) path forward.
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Old 2016-03-04, 05:42   #18
LaurV
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Without any analysis, the pawn has to be promoted to a knight.
Why? Because it is the only piece that can move, and because the puzzle has to have a "unique" solution, and because it can not be promoted to a king or to itself, and there is nothing a bishop or a rook can do, which a queen can not do (therefore, promoting it to a bishop or rook would be equivalent to promote it to a queen, which would imply multiple - and trivial - solution). So, puzzle solved, logically. No chess analysis.

Yes, I have read the OP's comment that meantime the puzzle was proved to be black win, and I ignored it. No, I didn't read all the comments, and spoilers, and I didn't make any analysis. I am going to do the former two right now, but still no analysis, I don't expect to bring in anything new
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Old 2016-03-04, 06:01   #19
LaurV
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Quote:
Originally Posted by 1997rj7 View Post
Promoting to Knight loses:

h8=N Ng5
Nf7 Nxf7 (or Ng6 Nh7 mate)
Kg8 Bxg7
Kxg7

and its KBN against K.
Careful! KBN against K is draw according with the current rules (in the general position, you may need more than 50 moves to mate). Can you mate him here in less than 50 moves, considering that the king is cornered? This is in itself, another puzzle. And if so, how? (edit, remark that you are in the opposite-color corner, for the bishop)

Last fiddled with by LaurV on 2016-03-04 at 06:33
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Old 2016-03-04, 06:44   #20
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Quote:
h8=B(!)
Grrr... haha, totally didn't think to that! Good one!
\
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Old 2016-03-04, 12:10   #21
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Quote:
Originally Posted by LaurV View Post
Without any analysis, the pawn has to be promoted to a knight.
Why? Because it is the only piece that can move, and because the puzzle has to have a "unique" solution, and because it can not be promoted to a king or to itself, and there is nothing a bishop or a rook can do, which a queen can not do (therefore, promoting it to a bishop or rook would be equivalent to promote it to a queen, which would imply multiple - and trivial - solution). So, puzzle solved, logically. No chess analysis.

Yes, I have read the OP's comment that meantime the puzzle was proved to be black win, and I ignored it. No, I didn't read all the comments, and spoilers, and I didn't make any analysis. I am going to do the former two right now, but still no analysis, I don't expect to bring in anything new
This is an interesting post because you write down your thinking before actually analysing anything and you approach it in quite an original way.

The point where your logical reasoning falls down - a failure to consider the rare circumstances when a bishop or rook's being only part of a queen can actually work in their favour - go to the heart of the beauty of the study, I think. (And you've clearly seen that too by now.)

Quote:
Originally Posted by LaurV View Post
Careful! KBN against K is draw according with the current rules (in the general position, you may need more than 50 moves to mate). Can you mate him here in less than 50 moves, considering that the king is cornered? This is in itself, another puzzle. And if so, how? (edit, remark that you are in the opposite-color corner, for the bishop)
I believe that in the worst position for the KBN, it takes 32 moves to mate with perfect play. So KBN vs K is a win, period. The fact that it is not easy if you haven't mastered the method is illustrated by the fact that three years ago the then women's world champion Anna Ushenina failed to win it in a game at the Women's Grand Prix in Geneva. This was very embarrassing.
http://www.chessgames.com/perl/chessgame?gid=1716505
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Old 2016-03-04, 13:39   #22
LaurV
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I know how to mate if the king is on a side or on thew second line and I have the opposition, in about 20 moves. But for the hack of me I don't know (and never tried hard) how to bring the enemy king on a side, with KBN, if he wants to stay on the middle of the board, in 30 moves. Maybe I will dedicate some time to this in the near future. Anyhow, in a real match, this is completely useless.

I studied the final of the game you linked. Even at a fast skimming over the moves, I can accurately identify the mistakes which were done, once the enemy king was on a side. I assume the game was played fast-time? (white in crisis of time?) Otherwise I can't explain mistakes done by a world class player... (Oh, well... women... )
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