1 problem(s) found in 1547 milliseconds (displaying 1 problem(s)). [PROBID='P1338392'] [download as LaTeX]

1 - P1338392

J.Lois-70 JT 2016-2017

Special Prize

(9+9) C+

Draw exists in 1.0 move.

PG in 13.0

**Andrew Buchanan**J.Lois-70 JT 2016-2017

Special Prize

(9+9) C+

Draw exists in 1.0 move.

PG in 13.0

1. Sf3 b5 2. Sd4 Lb7 3. Sxb5 Lxg2 4. Sxa7 Sc6 5. Sxc6 Lxf1 6. Sxd8 Lxe2 7. Sxf7 Lxd1 8. Sh6 Lxc2 9. Sxg8 Lxb1 10. Txb1 Txg8 11. Ta1 Th8 12. Tb1 Tg8 13. Ta1 Th8 then 14. Tb1 Tg8= draw by 3Rep

**Keywords:**Unique Proof Game, Draw by repetition, Homebase (2), Constrained problem, Castling

**Genre:**Retro

**FEN:**r3kb1r/2ppp1pp/8/8/8/8/PP1P1P1P/R1B1K2R

**Input:**A.Buchanan, 2017-08-30

**Last update:**A.Buchanan, 2021-06-05 more...

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The problems of this query have been registered by the following contributors:

A.Buchanan (1)
Henrik Juel: 1.Sf3 b5 2.Sd4 Lb7 3.Sxb5 Lxg2 4.Sxa7 Sc6 5.Sxc6 Lxf1 6.Sxd8 Lxe2 7.Sxf7 Lxd1 8.Sh6 Lxc2 9.Sxg8 Lxb1 10.Txb1 Txg8 11.Ta1 Th8 12.Tb1 Tg8 13.Ta1 Th814.Tb1 Tg8 draws by three repetitions

Judge J. Lois:

The problem is well explained by the author:

“The position at 10.0 is SPG in 10.0. Following this, only the two rooks which have moved can move, to avoid disrupting the remaining castling rights.

Validation cases:

(1) Show that E is indeed a unique SPG in 10.0. Observe that the unique solution does not repeat a position for the third time until 14.0.

(2) Show that E has no solutions in a smaller number of moves. (Checking 8.5, 9.0 & 9.5 is sufficient.)

(3) Show that D cannot be reached even non-uniquely in 9.0 moves or less.

(4) Show that none of the 6 positions after a single reversible White move from D can be reached even non-uniquely in 9.5 moves or less.

(5) Show that none of the other 6x11-1=65 positions after 1.0 reversible moves from D can be reached even non-uniquely in 10.0 moves or less. (In fact (5) implies (4) implies (3)) In the context of the condition "draw in 1.0", the problem is indeed SPG. "PG" would incorrectly suggest that a shorter solution exists”.

An excellent problem. (2017-08-30)

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