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We consider snap-stabilizing algorithms in anonymous networks. Self-stabilizing algorithms are well known fault tolerant algorithms : a self-stabilizing algorithm will eventually recover from arbitrary transient faults. On the other hand, an algorithm is snap-stabilizing if it can withstand arbitrary initial values and immediately satisfy its safety requirement. It is a subset of self-stabilizing algorithms. Distributed tasks that are solvable with self-stabilizing algorithms in anonymous networks have already been characterized by Boldi and Vigna in [BV02b]. In this paper, we show how the more demanding snap-stabilizing algorithms can be handled with standard tools for (not stabilizing) algorithms in anonymous networks. We give a characterization of which tasks are solvable by snap-stabilizing algorithms in anonymous networks. We also present a snap-stabilizing version of Mazurkiewicz' enumeration algorithm. This work exposes, from a task-equivalence point of view, the complete correspondence in anonymous networks between self or snap-stabilizing tasks and distributed tasks with various termination detection requirements. |
