[Retros] Two little SPG-challenges
elkies at math.harvard.edu
Mon Nov 15 13:53:10 EST 2004
M> I would wish the programmers of Natch & Co. would provide a switch,
M> which forces the detection of shorter solutions.
M> Is there any specific reason not to do so?
N> If all else fails you can ask Natch to solve the same position
N> in 6.5, 6.0, etc.
> I know. (And hopefully enough all SPGs which are marked 'C+'
> in journals or databases are tested that way :-)).
> For my two toy examples this approach doesn't require much additional
> time. But for longer SPGs (where the solving time might be e.g.
> 3 weeks) it would be nice to know that no shorter solutions exist.
I don't have any first-hand experience with Natch, but I imagine
that for most SPG's in N, once Natch has solved it in N moves
it would still take only a fraction of the time to check
for solutions in N-0.5 or N-1.0, and a tiny fraction
for even shorter solutions. For all I know, it might not even
save that much time for this search to be done together with
the full-length solution.
N> There are quite a few SPG's satisfying this condition
N> where the K-trek is motivated by parity. Some years ago
N> I composed one in which the Black King makes 15 of Black's
N> 19 moves and goes back home to be checkmated.
M> Does that mean you managed to improve/prolong your entry to
M> the 1st Retro List Quick Composition Tourney 1997 on this list?
M> where the ratio was 9 out of 14 black moves made by black king?
No, the SPG I have in mind is even earlier, see for instance
Unlike the 1997 SPG, this one was not constrained by the condition
that the other side also move its King during the K-trek.
More information about the Retros