RI: Small: Integrating Paradigms for Approximate Stochastic Planning

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A fundamental challenge for Artificial Intelligence is sequential decision making under uncertainty, a task where automated algorithms lag far behind human-level intelligence. The primary reason for the disparity is curse of dimensionality - the number of states is exponential in the problem features. Recent advances that restrict decision-theoretic computation to a reachable subset of state space have scaled to moderately-sized problems, but proven ineffective in scaling to real problems. On the other hand, probabilistic planners based on deterministic planning might scale up, but with a massive loss in solution quality.This project is investigating several methods to scale probabilistic planning to real-sized problems. We combine decision-theoretic analysis, basis function approximation and the classical AI planning techniques, to develop a series of highly scalable planners. A common theme in our techniques is the use of deterministic plans to automatically obtain domain abstractions in the form of 'good' or 'bad' properties, or intermediate subgoals. The project introduces and exploits a principled collaboration between decision theory and classical planning techniques, thus retaining the benefits of both - high quality as well as high performance. Experiments show that our new planner solves difficult planning competition problems using orders of magnitude less memory outputting high quality policies.Our research also proposes effective solutions to long-standing problems of generating a set of basis functions and computing a hierarchical problem decomposition. Both basis function approximation and hierarchical decomposition are popular in existing literature for speeding up planning, but they are not fully automated - a human is required to specify the basis functions and the hierarchy. We provide novel, domain-independent solutions that remove this additional human effort. Our research addresses several long standing challenges in AI, like scaling stochastic planning, and automatically generating basis functions and subgoal hierarchies. We expect to produce state-of-the-art planners that will be effective in large and complex real world scenarios, e.g., planetary exploration, military operations planning, and robotic decision making.