Incremental Data Structures

[Philipp Garcia <phil@xxxxxxxxxx>]

I have a question for those that have written go-playing programs that
use incremental updates to maintain data structure like string-lists,
liberties lists, etc... When you take-back a move, do you "undo" the
modifications to the data structures OR do you revert back to a copy of
the data structure before the move that you are taking back was placed?
If you "undo" the modifications, how do you store "undo" information. Is
it log based similar to how modern databases work? Or does logic direct
the "undo"? If you revert back to a copy, do you really save enough CPU
cycles to even justify using incremental structures rather than a full
re-computation?