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<p>This paper discusses detection of global predicates in a distributed program. Earlieralgorithms for detection of global predicates proposed by Chandy and Lamport (1985)work only for stable predicates. A predicate is stable if it does not turn false once itbecomes true. Our algorithms detect even unstable predicates, without excessiveoverhead. In the past, such predicates have been regarded as too difficult to detect.The predicates are specified by using a logic described formally in this paper. We discussdetection of weak conjunctive predicates that are formed by conjunction of predicateslocal to processes in the system. Our detection methods will detect whether such apredicate is true for any interleaving of events in the system, regardless of whether thepredicate is stable. Also, any predicate that can be reduced to a set of weak conjunctivepredicates is detectable. This class of predicates captures many global predicates thatare of interest to a programmer. The message complexity of our algorithm is bounded bythe number of messages used by the program. The main applications of our results are indebugging and testing of distributed programs. Our algorithms have been incorporated ina distributed debugger that runs on a network of Sun workstations in UNIX.</p>
Index Termscommunication complexity; program debugging; distributed memory systems; programtesting; Unix; weak unstable predicates; distributed programs; global predicates; weakconjunctive predicates; message complexity; debugging; testing; distributed debugger;Sun workstations; UNIX; distributed algorithms

B. Waldecker and V. Garg, "Detection of Weak Unstable Predicates in Distributed Programs," in IEEE Transactions on Parallel & Distributed Systems, vol. 5, no. , pp. 299-307, 1994.
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