Randward and Lamar: Randomizing the FF Heuristic

We present two planners, Randward and Lamar, which are respectively built upon the Downward and LAMA planners. The technique developed in these planners is to randomize heuristic construction so that heuristic plateaus are less frequent and the bias introduced by poor, arbitrary nondeterministic choices in heuristic construction is removed. Specifically, we randomize the FF heuristic, naming the resulting planner Randward, and with the addition of the landmark count heuristic, name it Lamar. Within the FF heuristic, we randomize planning graph construction, which is akin to a random-walk in the relaxed planning space. From this randomized planning graph, we extract a relaxed plan heuristic (exactly as would FF).