SAS+ Planning as Satisfiability
This work addresses the efficiency bottleneck in automated planning for AI systems, offering incremental improvements over existing methods.
The paper tackles the problem of planning as satisfiability by introducing a novel SAT encoding scheme (SASE) based on the SAS+ formalism, resulting in significant improvements in time and memory efficiency over state-of-the-art STRIPS-based encodings, as demonstrated through extensive experimental results.
Planning as satisfiability is a principal approach to planning with many eminent advantages. The existing planning as satisfiability techniques usually use encodings compiled from STRIPS. We introduce a novel SAT encoding scheme (SASE) based on the SAS+ formalism. The new scheme exploits the structural information in SAS+, resulting in an encoding that is both more compact and efficient for planning. We prove the correctness of the new encoding by establishing an isomorphism between the solution plans of SASE and that of STRIPS based encodings. We further analyze the transition variables newly introduced in SASE to explain why it accommodates modern SAT solving algorithms and improves performance. We give empirical statistical results to support our analysis. We also develop a number of techniques to further reduce the encoding size of SASE, and conduct experimental studies to show the strength of each individual technique. Finally, we report extensive experimental results to demonstrate significant improvements of SASE over the state-of-the-art STRIPS based encoding schemes in terms of both time and memory efficiency.