Succinct Set-Encoding for State-Space Search

Abstract

We introduce the level-ordered edge sequence (LOES), a succinct encoding for state-sets based on prefix-trees. For use in state-space search, we give algorithms for member testing and element hashing with runtime dependent only on state size, as well as time and memory efficient construction of and iteration over such sets. Finally we compare LOES to binary decision diagrams (BDDs) and explicitly packed set-representation over a range of IPC planning problems. Our results show LOES produces succinct set-encodings for a wider range of planning problems than both BDDs and explicit state representation, increasing the number of problems that can be solved cost-optimally.