Beating LM-Cut with hmax (Sometimes): Fork-Decoupled State Space Search
نویسندگان
چکیده
Factored planning decouples planning tasks into subsets (factors) of state variables. The traditional focus is on handling complex cross-factor interactions. Departing from this, we introduce a form of target-profile factoring, forcing the crossfactor interactions to take the form of a fork, with several leaf factors and one potentially very large root factor. We show that forward state space search gracefully extends to such structure, by augmenting regular search on the root factor with maintenance of the cheapest compliant paths within each leaf factor. We analyze how to guarantee optimality. Connecting to standard heuristics, the performance improvements relative to A∗ are substantial, and sometimes dramatic: In four IPC benchmark domains, fork-decoupled state space search outperforms standard state space search even when using h in the former vs. LM-cut in the latter.
منابع مشابه
Beyond Forks: Finding and Ranking Star Factorings for Decoupled Search
Star-topology decoupling is a recent search reduction method for forward state space search. The idea basically is to automatically identify a star factoring, then search only over the center component in the star, avoiding interleavings across leaf components. The framework can handle complex star topologies, yet prior work on decoupled search considered only factoring strategies identifying f...
متن کاملSymbolic Leaf Representation in Decoupled Search
Star-Topology Decoupled Search has recently been introduced in classical planning. It splits the planning task into a set of components whose dependencies take a star structure, where one center component interacts with possibly many leaf components. Here we address a weakness of decoupled search, namely large leaf components, whose state space is enumerated explicitly. We propose a symbolic re...
متن کاملOn State-Dominance Criteria in Fork-Decoupled Search
Fork-decoupled search is a recent approach to classical planning that exploits fork structures, where a single center component provides preconditions for several leaf components. The decoupled states in this search consist of a center state, along with a price for every leaf state. Given this, when does one decoupled state dominate another? Such statedominance criteria can be used to prune dom...
متن کاملFrom Fork Decoupling to Star-Topology Decoupling
Fork decoupling is a recent approach to exploiting problem structure in state space search. The problem is assumed to take the form of a fork, where a single (large) center component provides preconditions for several (small) leaf components. The leaves are then conditionally independent in the sense that, given a fixed center path π , the compliant leaf moves – those leaf moves enabled by the ...
متن کاملOptimal Planning for Delete-Free Tasks with Incremental LM-Cut
Optimal plans of delete-free planning tasks are interesting both in domains that have no delete effects and as the relaxation heuristic h in general planning. Many heuristics for optimal and satisficing planning approximate the h heuristic, which is well-informed and admissible but intractable to compute. In this work, branch-and-bound and IDA∗ search are used in a search space tailored to dele...
متن کامل