Noam Elkies elkies at math.harvard.edu
Mon Oct 7 11:34:48 EDT 2002

A few more discovered or double checkmates with a promoted piece:

# a2N/Ra1 in 6.5:
1 a4 c6 2 a5 Qb6 3 a:b6 Kd8 4 ba b6 5 a:b8=N Bb7! 6 R:a8 Ba6 7 N:a6#
(C+ 30 msec.)

## g2N/Rh1 in 6.5:
1 g4 d5 2 g5 Qd6 3 g6 Q:h2 4 gh Qd6 5 h:g8=N e5 6 R:h8 Be7 7 Nf6##
(C+ 1.1 sec.)

## g2N/h2Q(R) in 10.5:
1 g4 a5 2 g5 a4 3 g6 a3 4 gh ab 5 h:g8=N Rh6 6 h4 Rc6 7 h5 e6
8 h6 Qe7 9 h7 Qd6 10 h8=Q(R) Be7 11 Nf6## (both C+, 240 msec. each)

# g2B/h2Q(R) in 10.5:
1 g4 a5 2 g5 a4 3 g6 a3 4 gh ab 5 h:g8=B Rh6 6 h4 Rc6 7 h5 e6
8 h6 Qf6 9 h7 Be7 10 h8=Q(R) Kf8 11 Bh7# (both C+, 240 msec. each)

Note that the 10.5-movers show double or discovered checks
with *both* units promoted. There are seven kinds of batteries
(Q/[RBN], R/[BN], B/[RN]), each of which can give either double
or discovered checkmate. If each of these involves two promoted
pawns, and we keep track of both, we get a total of 14*8*7=784
SPG tasks. Add to that the cases where only one pawn is promoted,
and the total number of tasks comes to about a thousand. Yet another