[Retros] distance-PG-

[Francois Labelle]

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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist1.pair.net/pipermail/retros/attachments/20160907/f1051ed2/attachment.html>