KRBKB and ACM USCCC #6

[Steven J. Edwards]

The Association for Computing Machinery has held annual computer chess
championships for about a quarter century, although it is not known if
any more will be arranged. Anyway, back in 1976 at ACM USCCC #6, an
example of the KRBKB endgame appeared in an exhibition game between
the program Treefrog (by Hanson, Calnek, and Crook from the University
of Waterloo) and IM David Levy. The position was reported in an
article by Monty Newborn reprinted in _The Best of Creative Computing
Vol. 2_ (ISBN 0-916688-03).

With Black (Levy) to move, the position was:

:: :: :: ::
:: :: :: bK
:: :: :: ::
:: :: :: ::wB
:: ::wK:: ::
:: :: :: ::
:: :: :: ::
bBwR:: :: ::

The game was drawn by agreement as White (Treefrog) was unable to make
any progress.

With the KRBKB distance to mate/loss database now available, we can
see the fastest way for White to win:

FEN: 8/6k1/8/7B/4K3/8/8/bR6 b - - 0 1
Evaluation: Loss in 11

1. ... Bc3 2. Kf5 Ba5 {Bd2 Kf8} 3. Ke6 {Rb2 Rb5 Rb7+ Rg1+} Bc3 {Bd2} 4. Rg1+
Kh6 5. Bd1 {Be2 Bf3} Bd4 6. Rg2 Ba1 {Ba7 Bb2 Bb6 Bc3 Bc5 Be3 Bf2 Bg7 Bh8 Kh7}
7. Kf7 Bb2 {Bc3 Bd4 Be5 Bh8} 8. Rg6+ Kh7 9. Bc2 {Ra6 Rb6 Rc6 Rd6 Re6 Rg5} Bg7
10. Bb1 {Bd3 Be4 Bf5 Ra6+ Rb6+ Rc6+ Rd6+ Re6+} Ba1 {Bb2 Bc3 Bd4 Be5 Bf6 Bf8
Kh8} 11. Ra6+ {Rb6+ Rc6+ Rd6+ Re6+ Rf6+} Kh8 12. Ra8# {Rh6#}

-- Steven (s...@mv.mv.com)