Heuristic search planner 2.0

We describe the hsp2.0 planning algorithm that entered the second planning contest held at the Fifth International Conference on Artificial Intelligence Planning and Scheduling (AIPS'00). hsp2.0 is a domain-independent planning algorithm that implements the family of heuristic search planners that are characterized by the state space that is searched (either progression or regression space), the search algorithm used (variants of best-first search), and the heuristic function extracted from the problem representation. This general planner implements a scheduler that tries different variants concurrently with different (time) resource bounds. We also describe how hsp2.0 can be used as an optimal (and near-optimal) planning algorithm and compare its performance with two other optimal planners, stan and blackbox.