[Retros] distance-PG-
Francois Labelle
flab at wismuth.com
Wed Sep 7 17:20:19 EDT 2016
roberto osorio wrote:
> ----------------------------------------------------------------------------------------------------------------
> "find a sound PG performing a **distance of SQR1125 ending in checkmate*"*
> ----------------------------------------------------------------------------------------------------------------
sqrt(1125)/sqrt(5) = 15, so we're looking for 15 single knight moves.
I found 31 such sound PGs with my computer, for example:
r1b1kb1r/ppN1pppp/7n/8/8/8/PPP1PPP1/RNBQK2R in 7.5 moves
1. Nf3 Nf6 2. Ne5 Ne4 3. Nxd7 Nxd2 4. Nxb8 Nxf1 5. Nc6 Nxh2 6. Nxd8 Ng4
7. Ne6 Nh6 8. Nxc7#
Amusingly I found exactly 1 mate PG in 7.5 moves with one knights-only
solution, and one which isn't:
rnb1kb1r/p1N1pppp/8/8/8/8/PPP2PPP/RN1QKBnR in 7.5 moves:
1. Nf3 Nf6 2. Ne5 Ne4 3. Nxd7 Nxd2 4. Nc5 Nb3 5. Nxb7 Nxc1 6. Nxd8 Nxe2
7. Ne6 Ng1 8. Nxc7#
1. d4 b6 2. Bh6 Nxh6 3. Nf3 Nf5 4. Ne5 Nxd4 5. Nxd7 Nxe2 6. Nxb6 Qd5 7.
Nxd5 Ng1 8. Nxc7#
So if we're looking for a composing challenge with a unique "solution",
then this can be one.
Nicolas Dupont wrote:
> Thanks François. The shortest I'm able to produce yet is NC#(38,0,0)
> in 9.0:
>
> 1. Pa2-a4 Ph7-h5 2. Pa4-a5 Th8-h6 3. Pa5-a6 Th6-f6
> 4. Ta1-a5 Tf6-f5 5. Ta5-e5 Pd7-d5 6. Ph2-h4 Dd8-d6
> 7. Th1-h3 Dd6-g6 8. Th3-e3 Pf7-f6 9. Pf2-f3 Dg6-g3#
>
> Maybe there are not too many capture-free mate PG (sound!), so that
> you might compute all of them till such a bound?
I don't have the numbers but I suspect that the fraction of games that
are capture-free is still too large to provide a significant speed-up.
At least not enough to compensate the exponential increase from 6.0 to
9.0 moves.
François
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