-DF uses a modified A* pathfinding algorithm.
-Tiles on the map that can be walked between are kept in groups.
-If you wall off an area, the game won't attempt to path there because the start and finish points are in different groups.
-A current bug with creatures that fly is that they won't use their ability to fly unless they could also walk there on foot instead.
-If you try to build a workshop in one walkable group of tiles, then the game won't list wood logs that are lying in a different walkable group. I get "No access to building material non-economic item" when I try to designate a wall in a small, empty room with a locked door. I can designate the wall if I unlock the door.
-Items in walled-off areas therefore don't cause an extra cpu or pathfinding hit.
-Hallways that lead towards a location where a dwarf wants to go, but dead-end before they get there, cause large pathfinding lag because they trick the pathfinding algorithm into exploring a false path.
-The pathfinding algorithm generally explores the easiest path first (a straight line).
-Laying out "high traffic" traffic designations helps FPS.
See
http://www.youtube.com/results?search_query=a+star+pathfinding&aq=fMy current fort is spherical, with food/booze storage, bedrooms, and meeting rooms at the core so dwarves only have to walk in straight lines to get to their destination. Workshops and industry rooms are on the outside of the sphere, at the end of radial spoke hallways.