Abstract
This paper considers perpetual exploration of anonymous cactus graphs with distinguishable cycles by a single mobile agent under the restriction that nodes have no storage (e.g., whiteboards or token places). A cactus with distinguishable cycles allows the agent to distinguish at each node the two incident edges contained in each cycle from other incident edges. This paper introduces the concept of snap-stabilization into the perpetual exploration and shows that snap-stabilizing perpetual exploration is possible when the agent has one-bit persistent memory. The exploration time of the presented algorithm exactly matches a trivial lower bound. This paper also shows the necessity of one-bit agent memory by showing that any oblivious (or memory-less) agent cannot explore a cactus graph even when it has only a single distinguishable cycle. Finally, this paper shows that snap-stabilizing perpetual exploration by an oblivious agent is possible when a cactus graph with distinguishable cycles has a sense of direction.
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This work was partially supported by JSPS KAKENHI Grant Numbers 19H04085, 19K11826, 20H04140, and 20KK0232.
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Shimoyama, K., Sudo, Y., Kakugawa, H., Masuzawa, T. (2022). Invited Paper: One Bit Agent Memory is Enough for Snap-Stabilizing Perpetual Exploration of Cactus Graphs with Distinguishable Cycles. In: Devismes, S., Petit, F., Altisen, K., Di Luna, G.A., Fernandez Anta, A. (eds) Stabilization, Safety, and Security of Distributed Systems. SSS 2022. Lecture Notes in Computer Science, vol 13751. Springer, Cham. https://doi.org/10.1007/978-3-031-21017-4_2
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