AW: [Retros] Massacre SPGs

[Gerd Wilts]

Francois Labelle wrote:


> The missing PG is:

>

> wKg1, bKf8, bBd7


Very interesting!


> It'd be really interesting to know what your program thought for this SPG:

>

> - If it saw 0 solutions, then your program had a bug.

> - If it saw >= 2 solutions, then *my* program has a bug and I'd very much

> like to know about it! (Alternatively people can try to find a cook by

> hand if they're so inclined).

>

> The PG does have the unusual property that the surviving piece is black,

> i.e. it's a (1+2), all the 17 others are (2+1).


I now remember that even though we had some very powerful hardware available
at that time (1994), we had to split the calculation in two cases:
(xwhite,xblack) = (2,2) and (3,1) (xwhite = number of non-capturing white
moves)
I assume that we did the calculation only for the first case. This means
that your program verified the 17 PGs with (2+1) pieces and it found
a new one with (1+2) pieces!


> x=5 has not yet been done, so there is still hope that a dualfree PG

> with two Kings only exists!

>

> I wonder, would that be dismissed as a simple curiosity, or is it the holy

> grail of retrograde analysis?


I guess that many people would consider this as a simple curiosity rather
than as the "holy grail", but from a theoretically point of view I would
really like to know if such a PG exists.


> I started the computation.


Good luck!

Gerd