Are you asking whether it's possible to determine all possible 1-move predecessors of a given position?
If so, then yes, that is pretty straightforward. E.g. the last move was either a pass, or a move by White, or a move by Black. For a move by White, it was either a suicide, so could be on any point in an empty region enclosed by Black, or it was no suicide and is one of the points occupied by White in the given position, possibly having captured a Black group in any of the adjacent empty regions enclosed by White.
Yeah, that what I'm asking (in a really bad way). I wonder, given a list of positions, how long it would take to build the transitions between them. I would imagine 19x19 would be a "practically forever" type thing.
It would take at least a nanosecond for each position. Given that 6x6 already has 62567386502084877, it would take at
least 724 days. To take "practically forever", 7x7 more than suffices:)
// did not know you couldn't do this for chess (paper even pointed to why)