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 CHESS SOLVINGTournamentsRating lists1-Apr-2021
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MatPlus.Net Forum Misc Construction Challenge

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This came to my attention on Chess Stack Exchange.

Geir, I'm sorry to say this, but I found out today that your 32 ply position is BUSTED: 10. Kf2 works as an alternative to 10. Kg2.

However, Stockfish analysis confirms that your 25 ply position is sound, and thus still the record.

 (Read Only) pid=20430

White’s 9th move is Kxh1, so I am pretty sure 10.Kf2 is illegal. Otherwise I would agree that 10.Kf2 is a cook.

 (Read Only) pid=20442

Oh, my oh my! You're right, so it isn't busted. I accidentally swapped the king and the knight. My bad Geir!

 (Read Only) pid=20443

I have found a way to make 20, 21 or 25 plies without captures. The number of plies depends on how you treat threefold repetitions.

(= 9+7 )

1.h7 Rd8 2.Bf7 Rh8 3.Bg8 Kb8 4.Kb1 Kc7 5.Kc1 Kd6 6.Kd1 Ke5 7.Ke1 Kf4 8.Kf1 Kg3 9.Kg1 Kh3 10.Kh1 Kg3 11.Kg1 Kh3 12.Kh1 Kg3 13.Kg1 draw.

The reason this is all forced is that White wins if he gets to play Kg2, while Black wins if he gets to play Kh2. With Kg2 vs Kg4, White plays a5 to put Black in zugzwang, but with Kf1 vs Kh2, the pawn move only serves to delay the zugzwang by one move.

The question now is how long this line is to be considered. If you count the moves before any position is repeated, that is 20 plies (10...Kg3). If you include the move that makes the first repeated position, that is 21 plies (11.Kg1). If you count the moves to the threefold repetition, that is 25 plies (13.Kg1).

 (Read Only) pid=20476

My suggestion is that due to the theme, you should count
to the first unforced move of one side. And that would be the
automatic draw, for fuzzy values of "move" and "forced" :-)

 (Read Only) pid=20478

Hope I’m not making a dumb error here, but it seems to me that in the 3Rep study, White is safe as soon as he plays 9. Kg1. At that point he can freely advance Pa4 without risking loss. So the sequence of Nunn single moves ends at 18. That pawn still served a purpose in that it stopped Black dawdling on the 4th rank.

 (Read Only) pid=20479

9. Kg1 Kh3 10. a5 Kg3 11. Kf1 Kh2 B+ or 11. Kh1 Kf2 B+.

 (Read Only) pid=20480

Thanks, Joost. Sorry I was remembering the board wrong when I was cycling. I will have another look maybe later today when I'm freer.

 (Read Only) pid=20487
(49) Posted by Geir Sune Tallaksen Østmoe [Wednesday, Jan 20, 2021 22:46]

I just realized I can add two plies like this:

(= 9+7 )

1.Bh5 Rd1 2.h7 Rd8 etc.

 (Read Only) pid=20499

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MatPlus.Net Forum Misc Construction Challenge