State Space Search
Intelligence and the Future
Intelligence is partly about "thinking ahead"
A complicated problem is solved a piece at a time, or an action at a time. Steps interact
Looking ahead gets complicated fast
AI has spent a long time thinking about this problem, and has found some fairly fancy techniques
Ultimately P ≠ NP (probably), so must abstract or approximate
Computers Search Good
A computer can construct future states from current states quickly and perfectly
Humans are bad at this; "easy" AI might want to leverage this
Problems like route-finding, scheduling, planning, puzzle-solving, games, robotics have gone there
Pattern-matching, machine learning, etc can be augmented with search
State Spaces
A state is a situation. It is static in time
A state space is a graph of situations.
The neighbors of a state s in a state space are the graph edges — states that can be reached from s by some atomic action
Road Maps and State Spaces
In a fancy road map, the states are junctions on the map. The state space is literally the graph of roads and junctions
An AI could proceed heuristically toward the goal by always choosing the route that gets closer to it
Dead-ends and side-trips are a big problem, though
Search The Map
To find a short route, it's probably better to look at least a little ahead: traverse the graph a bit and see where you end up
Watch out for backtracking and loops: use a stop list
Ultimately, this is BFS / DFS / Dijkstra search
Problem is usually boring for modern computers