27 Jan 2005
CS 3243 - Heuristics
20
Admissible heuristics
nA heuristic h(n) is admissible if for every node n,
n h(n) ≤ h*(n), where h*(n) is the true cost to reach the goal state from n.
nAn admissible heuristic never overestimates the cost to reach the goal, i.e., it is optimistic
nExample: hSLD(n) (never overestimates the actual road distance)
nTheorem: If h(n) is admissible, A* using TREE-SEARCH is optimal