[Retros] Two little SPG-challenges

[Mario Richter]

Hello,

I wrote: 

>> I would wish the programmers of Natch & Co. would provide a switch,

>> which forces the detection of shorter solutions.

>> Is there any specific reason not to do so?


to which Noam replied:


> If all else fails you can ask Natch to solve the same position

> 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.

So the question remains: Is there a special reason that such a switch
is not offered?


>> Construct an SPG (with a unique solution),

>> where this king has made as many moves as possible.



> There are quite a few SPG's satisfying this condition

> where the K-trek is motivated by parity.  Some years ago

> I composed one in which the Black King makes 15 of Black's

> 19 moves and goes back home to be checkmated.  


Does that mean you managed to improve/prolong your entry to
the 1st Retro List Quick Composition Tourney 1997 on this list?
(fen=KnQ1kbnr/1p1ppppp/p1p5/2B5/8/1PP5/P1P1PPPP/RN3BNR,
http://www.janko.at/Retros/RML/1997/N00-Tourney.htm), where the
ratio was 9 out of 14 black moves made by black king?


> If I remember right, the record length of a King's parity trek

> now stands at 19.


Joost wrote (thanks for pointing out this!):

> There is a Hashimoto composition, published in Problemesis, where

> the black king captures a rook on h1, and then goes back. His

> roundtrip is about 24 moves long, if I'm not mistaken.


Maybe you both are referring to:

R31 - Satoshi Hashimoto
Problemesis 20, Apr. 2001

    a   b   c   d   e   f   g   h
  +---+---+---+---+---+---+---+---+
8 |*r | . |*b | . |*k |*b |*n |*r | 8
  +---+---+---+---+---+---+---+---+
7 |*p |*p | . |*p |*p |*p |*p |*p | 7
  +---+---+---+---+---+---+---+---+
6 | R | . |*p | . |   | . |*n | . | 6
  +---+---+---+---+---+---+---+---+
5 | . | B | . |   | . |   | . |   | 5
  +---+---+---+---+---+---+---+---+
4 |   | . | K | . |   | B |   | . | 4
  +---+---+---+---+---+---+---+---+
3 | . | N | . |   | P |   | P |   | 3
  +---+---+---+---+---+---+---+---+
2 | P | P | P | . | P | P |   | P | 2
  +---+---+---+---+---+---+---+---+
1 | N |   | . | Q | . |   | . |   | 1  (15+15)
  +---+---+---+---+---+---+---+---+
    a   b   c   d   e   f   g   h


fen=/r1b1kbnr/pp1ppppp/R1p3n1/1B6/2K2B2/1N2P1P1/PPP1PP1P/N2Q4  

Proof game in 24.0 moves 

(s. e.g. http://www.janko.at/Retros/Problemesis/N20.htm)

where 18 out of 24 moves are made by the black king?


greetings
  mario