From: Steve Evans <trout <at> NETSPACE <dot> NET <dot> AU>
Date: 21 feb 1999
Subject: Re: Repetition rule in Chu Shogi mating problems

> Steve and I have been working on the D29 problem.
>
> I have finally come up with a superb 37-move mate (subject to Steve's
> final checking) that solves this problem (and fully explains the role
> of every piece in the problem). The only doubt I have, is that it
> pre-supposes that the repetition rule for mating problems (at least in
> the D document, or at least in D29), is that the DEFENDER must vary.
>
> What do people think of the plausibility of this being the intended
> rule?
>

I have (with the aid of my program) just found the solution to this
problem that does not require invocation the repetition rule (in any
form).

The problem D29 in the Middle Shogi Manual is as follows:

1, +BT, 9, +b / 12 / 1, FL, 10 / 12 / s, 11 / 12 / 6, +RC, 5 / l, 9, ky, 1
/ R, 9, BT, 1 / 2, +RC, 8, +G / 3, GB, 1, r, 3, s, 1, K / 6, +rc, 3, +rc,
+SM /

The 38 move solution is:

1. +RC-2j, +Gx2j;
2. S-2l, Kx2l (if K-1i 3. S-1k mate.);
3. Kyx2j, K-3l;
4. R-3k, K-4l;
5. +RC-6j, +RCx6j (if K-5l see below for mating sequence)
6. Ky-4j, K-5l;
7. R-5k, K-6l;
8. Kyx6j, K-7l;
9. R-7k, K-8l;
10. Ky-8j, K-9l;
11. Rx9k, K-10l;
12. Kyx10j, K-11l
13. S-11d+, FLx11d
14. R-11k, K-12l
15. Ky-10l, +SMx10l
16. R-11i, K-12k (here, and throughout the rest of the problem, if +SM -
11k then  +B x 11k mate)
17. +B-2a, K-12l (here, and throughout the rest of the problem, if K - 12j
then +B - 11j mate)
18. +B-2b, K-12k
19. +B-3b, K-12l
20. +B-3c, K-12k
21. +B-4c, K-12l
22. +B-4d, K-12k
23. +B-5d, K-12l
24. +B-5e, K-12k
25. +B-6e, K-12l
26. +B-6f, K-12k
27. +B-7f, K-12l
28. +B-7g, K-12k
29. +B-8g, K-12l
30. +B-8h, K-12k
31. +B-9h, K-12l
32. +B-9i, K-12k
33. +B-10i, K-12l
34. +B-10j, K-12k
35. Rx12i, +SM-12j
36. Rx12j, Kx12j
37. L-12d+, FL-12e
38. +Lx12e mate.

The alternative (switch-back) line from 5... is
5. ....  K-5l;
6. R-5k, K-4l;
7. Ky-4j, K-3l;
8. R-3k, K-2l;
9. Ky-2j mate.

This really is a brilliant problem, and worthy of the great Ito Kanju (if
it is his).

Many thanks to Colin Adams whose thoughts about continuing from move 17
with the slow advance of the +B at 1a, brought me back to this problem
after I had written it off as insoluble. His assistance was invaluable.
Colin's comments on some of the side-lines also appear above in brackets.


Steve Evans