Anytime versus Real-Time Heuristic Search for On-Line Planning

Abstract

Many AI systems, such as robots, must plan under time constraints. The most popular search approach applied in robotics so far is anytime search, in which the algorithm quickly finds a suboptimal plan, and then continues to find better and better plans as time passes, until eventually converging on an optimal plan. However, the time until the first plan is returned is not controllable, so such methods inherently involve idling the system's operation before `real' execution can begin. Real-time search methods provide hard real-time bounds on action selection time, yet to our knowledge, they have not yet been demonstrated for robotic systems. In this work, we compare anytime and real-time heuristic search methods in their ability to allow agents to achieve goals quickly.Our results suggest that real-time search is more broadly applicable and often achieves goals faster than anytime search, while anytime search finds shorter plans and does not suffer from dead-ends.