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Reaching the Goal in Real-Time Heuristic Search: Scrubbing Behavior is Unavoidable

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Real-time agent-centered heuristic search is a well-studied problem where an agent that can only reason locally about the world must travel to a goal location using bounded computation and memory at each step. Many algorithms have been proposed for this problem, and theoretical results have also been derived for the worst-case performance. Assuming sufficiently poor tie-breaking, among other conditions, we derive theoretical best-case bounds for reaching the goal using LRTA*, a canonical example of a real-time agent-centered heuristic search algorithm. We show that the number of steps required to reach the goal can grow asymptotically faster than the state space, resulting in a “scrubbing” when the agent repeatedly visits the same state. This theoretical result, supported by experimental data, encourages recent work in the field that uses novel tie-breaking schemas and/or perform different types of learning.

Citation

N. Sturtevant, V. Bulitko. "Reaching the Goal in Real-Time Heuristic Search: Scrubbing Behavior is Unavoidable". Symposium on Combinatorial Search, (ed: Stefan Edelkamp, Roman Barták), pp 166-174, August 2014.

Keywords: heuristic search, real-time, learning
Category: In Conference
Web Links: AAAI

BibTeX

@incollection{Sturtevant+Bulitko:SoCS14,
  author = {Nathan R. Sturtevant and Vadim Bulitko},
  title = {Reaching the Goal in Real-Time Heuristic Search: Scrubbing Behavior
    is Unavoidable},
  Editor = {Stefan Edelkamp, Roman Barták},
  Pages = {166-174},
  booktitle = {Symposium on Combinatorial Search},
  year = 2014,
}

Last Updated: July 09, 2020
Submitted by Sabina P

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