Causality and atomicity in distributed computations

  • Authors:

  • Ajay D. Kshemkalyani

  • Affiliations:

  • Department of Electrical Engineering and Computer Science (MC 154), University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL

  • Venue:
  • Distributed Computing
  • Year:
  • 1998

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Abstract

In a distributed system, high-level actions can be modeled by nonatomic events. This paper proposes causality relations between distributed nonatomic events and provides efficient testing conditions for the relations. The relations provide a fine-grained granularity to specify causality relations between distributed nonatomic events. The set of relations between nonatomic events is complete in first-order predicate logic, using only the causality relation between atomic events. For a pair of distributed nonatomic events X and Y, the evaluation of any of the causality relations requires |NX| × |NY| integer comparisons, where |NX| and |NY|, respectively, are the number of nodes on which the two nonatomic events X and Y occur. In this paper, we show that this polynomial complexity of evaluation can by simplified to a linear complexity using properties of partial orders. Specifically, we show that most relations can be evaluated in min(|NX|,|NY|) integer comparisons, some in |NX| integer comparisons, and the others in |NY| integer comparisons. During the derivation of the efficient testing conditions, we also define special system execution prefixes associated with distributed nonatomic events and examine their knowledge-theoretic significance.