A coterie is a set of subsets (called quorums) of the processes in a distributed system such that any two quorums intersect with each other and is mainly used to solve the mutualexclusion problem in a quorum-based al...
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A coterie is a set of subsets (called quorums) of the processes in a distributed system such that any two quorums intersect with each other and is mainly used to solve the mutualexclusion problem in a quorum-based algorithm. The choice of a coterie sensitively affects the performance of the algorithm and it is known that nondominated (ND) coteries achieve good performance in terms of criteria such as availability and load. On the other hand, grid coteries have some other attractive features: 1) A quorum size is small, which implies a low message complexity, and 2) a quorum is constructible on the fly, which benefits a low space complexity. However, they are not ND coteries unfortunately. To construct ND coteries having the favorite features of grid coteries, we introduce the transversal merge operation that transforms a dominated coterie into an ND coterie and apply it to grid coteries. We call the constructed ND coteries ND grid coteries. These ND grid coteries have availability higher than the original ones, inheriting the above desirable features from them. To demonstrate this fact, we then investigate their quorum size, load, and availability, and propose a dynamic quorum construction algorithm for an ND grid coterie.
The modeling and analysis experience with process algebras has shown the necessity of extending them with priority, probabilistic internal/external choice, and time while preserving compositionality. The purpose of th...
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The modeling and analysis experience with process algebras has shown the necessity of extending them with priority, probabilistic internal/external choice, and time while preserving compositionality. The purpose of this paper is to make a further step by introducing a way to express performance measures, in order to allow the modeler to capture the QoS metrics of interest. We show that the standard technique of expressing stationary and transient performance measures as weighted sums of state probabilities and transition frequencies can be imported in the process algebra framework. Technically speaking, if we denote by n is an element of N the number of performance measures of interest, in this paper we define a family of extended Markovian process algebras with generative master-reactive slaves synchronization mechanism called EMPA(grn) including probabilities, priorities, exponentially distributed durations, and sequences of rewards of length n. Then we show that the Markovian bisimulation equivalence similar to(MBn) is a congruence for EMPA(grn) which preserves the specified performance measures and we give a sound and complete axiomatization for finite EMPA(grn) terms. Finally, we present a case study conducted with the software tool TwoTowers in which we contrast the average performance of a selection of distributed algorithms for mutualexclusion modeled with EMPA(grn). (C) 2002 Elsevier Science B.V. All rights reserved.
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