| Summary: | 碩士 === 東吳大學 === 資訊科學系 === 92 === The use of quorums is a well-known approach to reaching mutual exclusion in distributed computing systems. Employ quorum based concept in mutual exclusion means if each request is required to get consensus form a quorum of nodes in distributed system then it can enter a critical section. However, All quorums are formed to coterie set in the system. If it’s possible to find a coterie with minimum communication delay that reduces cost on waiting time for any requests to get permission in distributed systems. Fu introduced two related to measure call max-delay and mean-delay. She proposed polynomial-time algorithms for finding max-delay and mean-delay optimal coteries when the network topology is a tree and a ring. Then, Tsuchiya, Yamaguchi, Kikuno proposed polynomial-time revised algorithms with time complexity O(n3logn) to an arbitrary network topology. It’s efficient to reduce relative delays. In this paper, we will focus on max-delay problem and present an improved algorithm to reduce time complexity from O(n3logn) to O(n3). We also define a new availability evaluation method, which name is workable availability. It could be used in arbitrary network to measure and analyze the availability for any constructed coteries.
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