Malte Helmert

Strengthening Canonical Pattern Databases with Structural Symmetries

2021 · Proceedings of the International Symposium on Combinatorial Search

Symmetry-based state space pruning techniques have proved to greatly improve heuristic search based classical planners. Similarly, abstraction heuristics in general and pattern databases in particular are key ingredients of such planners. However, only little work …

Unsolvability Certificates for Classical Planning

2017 · Proceedings of the International Conference on Automated Planning and Scheduling

The plans that planning systems generate for solvable planning tasks are routinely verified by independent validation tools. For unsolvable planning tasks, no such validation capabilities currently exist. We describe a family of certificates of unsolvability …

Best-Case and Worst-Case Behavior of Greedy Best-First Search

2018

We study the impact of tie-breaking on the behavior of greedy best-first search with a fixed state space and fixed heuristic. We prove that it is NP-complete to determine the number of states that need …