[Retros] Accidental retro

Theodore Hwa hwatheod at cs.stanford.edu
Mon Feb 13 21:56:34 EST 2006

On Mon, 13 Feb 2006 Pastmaker at aol.com wrote:


> Given a diagram position in which there is only one possible last move, is

> there now a program capable of determining that move for all such diagrams?

> (That was not the case some months ago if I recall correctly.)

I don't think there is (anyone, please feel free to correct me if you know
differently.) This would seem to be a quite difficult problem, in
general. But let me throw out some ideas here.

In a typical 'hard' retro problem, a set of pieces is locked within a set
of squares S, meaning that no piece currently in S can leave S unless some
outside piece moves into S. The key to unlocking the position is figuring
out the external manuever. The article
http://www.janko.at/Retros/Articles/Volet.htm is a good example of this.
Here S would be the rectangle with opposite corners c8 and h6, plus the
squares b7, f5, g5, h5.

A general solver, that solves in a reasonable time, would likely need to
have some kind of module that identifies such locked subsets, and then
looks for these external moves. I think this would be the next big step
in automated retro solving. Someday I do hope to implement this...


More information about the Retros mailing list