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Detecting global predicates in distributed systems with clocks
 In Proceedings of the 11th International Workshop on Distributed Algorithms (WDAG’97
, 1997
"... This paper proposes a framework for detecting global state predicates in systems of processes with approximatelysynchronized realtime clocks. Timestamps from these clocks are used to de ne two orderings on events: \de nitely occurred before " and \possibly occurred before". These ..."
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Cited by 20 (2 self)
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This paper proposes a framework for detecting global state predicates in systems of processes with approximatelysynchronized realtime clocks. Timestamps from these clocks are used to de ne two orderings on events: \de nitely occurred before &quot; and \possibly occurred before&quot;. These orderings lead naturally to de nitions of 3 distinct detection modalities, i.e., 3 meanings of \predicate held during a computation&quot;, namely: Poss db db! ( \ possibly held&quot;), Def! ( \ de nitely held&quot;), and Inst ( \ de nitely held in a speci c global state&quot;). This paper de nes these modalities and gives e cient algorithms for detecting them. The algorithms are based on algorithms of Garg and Waldecker, Alagar and Venkatesan, Cooper and Marzullo, and Fromentin and Raynal. Complexity analysis shows that under reasonable assumptions, these realtimeclockbased detection algorithms are less expensive thandetection algorithms based on Lamport's happenedbefore ordering. Sample applications are given to illustrate the bene ts of this approach. Key words: global predicate detection, consistent global states, distributed debugging, realtime monitoring 1
Efficient Detection of Global Properties in Distributed Systems Using PartialOrder Methods
 IN PROCEEDINGS OF THE 12TH INTERNATIONAL CONFERENCE ON COMPUTERAIDED VERIFICATION (CAV), VOLUME 1855 OF LECTURE NOTES IN COMPUTER SCIENCE
, 2000
"... A new approach is presented for detecting whether a computation of an asynchronous distributed system satisfies Poss (read "possibly"), meaning the system could have passed through a global state satisfying property. Previous generalpurpose algorithms for this problem explicitly enumerate ..."
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Cited by 19 (1 self)
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A new approach is presented for detecting whether a computation of an asynchronous distributed system satisfies Poss (read "possibly"), meaning the system could have passed through a global state satisfying property. Previous generalpurpose algorithms for this problem explicitly enumerate the set of global states through which the system could have passed during the computation. The new approach is to represent this set symbolically, in particular, using ordered binary decision diagrams. We describe an implementation of this approach, suitable for offline detection of properties, and compare its performance to the enumerationbased algorithm of Alagar & Venkatesan. In typical cases, the new algorithm is signi cantly faster. We have measured over 400fold speedup in some cases.
Efficient Distributed Detection of Conjunctions of Local Predicates in Asynchronous Computations
 In Proceedings of the 8th IEEE Symposium on Parallel and Distributed Processing (SPDP
, 1995
"... Global predicate detection is a fundamental problem... ..."
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Cited by 16 (1 self)
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Global predicate detection is a fundamental problem...
Distributed predicate detection in a faulty environment
 In Proceedings of the 18th IEEE International Conference on Distributed Computing Systems (ICDCS98
, 1998
"... There has been very little research in distributed predicate detection for faulty, asynchronous environments. In this paper we define a class of predicates called set decreasing predicates which can be detected in such an environment. We introduce a set of failure detectors called infinitely often a ..."
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There has been very little research in distributed predicate detection for faulty, asynchronous environments. In this paper we define a class of predicates called set decreasing predicates which can be detected in such an environment. We introduce a set of failure detectors called infinitely often accurate detectors which are implementable in asynchronous systems. Based on these failure detectors we present an algorithm to detect conjunction of local predicates and sendmonotonic channel predicates. Since perfect failure detection is impossible in an asynchronous system, we cannot guarantee that our detection algorithm will not have false detections. However, if the predicate ever holds then it is guaranteed to be detected.
Secure Distributed Time for Secure Distributed Protocols
, 1994
"... The views and conclusions contained in this document are those of the authors and should not be interpreted as ..."
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Cited by 15 (9 self)
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The views and conclusions contained in this document are those of the authors and should not be interpreted as
Linear Space Algorithm for Online Detection of Global Predicates
 PROC. INTERNATIONAL WORKSHOP ON STRUCTURES IN CONCURRENCY THEORY (STRICT '95
, 1995
"... A fundamental problem in debugging and monitoring is detecting whether the state of a system satisfies some predicate. Cooper and Marzullo defined this problem as Possibly(\Phi) for distributed computations. This paper presents the first online algorithm using linear space which resolve this p ..."
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Cited by 14 (0 self)
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A fundamental problem in debugging and monitoring is detecting whether the state of a system satisfies some predicate. Cooper and Marzullo defined this problem as Possibly(\Phi) for distributed computations. This paper presents the first online algorithm using linear space which resolve this problem in the general case, improving all existing algorithms both in time and space. It is particularly interesting for the detection of Possibly(\Phi) on potentially infinite computations. To our knowledge, it also the only algorithm of detection which do not make use of vectors of timestamps. The presented algorithm is based on a structural properties of the consistent cuts lattice, leading to a new structure to study distributed computations: the consistent cuts tree.
Detecting Temporal Logic Predicates on the HappenedBefore Model
 In Proc. of the International Parallel and Distributed Processing Symposium (IPDPS), Fort
, 2001
"... in distributed computing. In this paper we describe new predicate detection algorithms for certain temporal logic predicates. We use a temporal logic, CTL, for specifying properties of a distributed computation and interpret it on a finite lattice of global states. We present solutions to the predic ..."
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Cited by 14 (6 self)
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in distributed computing. In this paper we describe new predicate detection algorithms for certain temporal logic predicates. We use a temporal logic, CTL, for specifying properties of a distributed computation and interpret it on a finite lattice of global states. We present solutions to the predicate detection of linear and observerindependent predicates under EG and AG operators of CTL. For linear predicates we develop polynomialtime predicate detection algorithms which exploit the structure of finite distributive lattices. For observerindependent predicates we prove that predicate detection is NPcomplete under EG operator and coNPcomplete under AG operator. We also present polynomialtime algorithms for a CTL operator called until , for which such algorithms did not exist. Finally, our work unifies many earlier results in predicate detection in a single framework.
Monitoring Functions on Global States of Distributed Programs
 Journal of Parallel and Distributed Computing
, 1994
"... The domain of a global function is the set of all global states of an execution of a distributed program. We show how to monitor a program in order to determine if there exists a global state in which the sum x 1 +x 2 + : : : +xN exceeds some constant K, where x i is defined in process i. We examin ..."
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The domain of a global function is the set of all global states of an execution of a distributed program. We show how to monitor a program in order to determine if there exists a global state in which the sum x 1 +x 2 + : : : +xN exceeds some constant K, where x i is defined in process i. We examine the cases where x i is an integer variable and where x i is a boolean variable. For both cases we provide algorithms, prove their correctness and analyze their complexity. 1 Introduction As a distributed program executes, each process proceeds through a sequence of local states. The set S of all local states is partially ordered by Lamport's happens before relation[Lam78], denoted by !. A global state is a subset of S in which no two elements are ordered by !. Given a global state c of some execution, it is impossible to determine if c actually occurred in an execution. However, it is known that c is consistent with some global state that did occur in the execution [CL85, Mat89]. In ot...
Observation and Control for Debugging Distributed Computations
 In Proceedings of the International Workshop on Automated Debugging (AADEBUG
, 1997
"... Ipresent a general framework for observing and controlling a distributedcomputation and its applications to distributed debugging. Algorithms for observation are useful in distributed debugging to stop a distributed program under certain undesirable global conditions. Ipresent the main ideas require ..."
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Ipresent a general framework for observing and controlling a distributedcomputation and its applications to distributed debugging. Algorithms for observation are useful in distributed debugging to stop a distributed program under certain undesirable global conditions. Ipresent the main ideas required for developing e cient algorithms for observation. Algorithms for control are useful in debugging to restrict the behavior of the distributed program to suspicious executions. It is also useful when a programmer wants to test a distributed program under certain conditions. I present di erent models and their limitations for controlling distributed computations. 1
Some Optimal Algorithms for Decomposed Partially Ordered Sets
 Information Processing Letters
, 1992
"... We describe two problems and their optimal solutions for partially ordered sets. We first describe an optimal algorithm for computing the largest antichain of a partially ordered set given its decomposition into its chains. Our algorithm requires O(n 2 m) comparisons where n is the number of cha ..."
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We describe two problems and their optimal solutions for partially ordered sets. We first describe an optimal algorithm for computing the largest antichain of a partially ordered set given its decomposition into its chains. Our algorithm requires O(n 2 m) comparisons where n is the number of chains and m is the maximum number of elements in any chain. We also give an adversary argument to prove that this is a lower bound. Our second problem requires us to find if the given poset is a total order. Our optimal algorithm requires O(mn log n) comparisons. These algorithms have applications in distributed debugging and recovery in distributed systems. Keywords: Partiallyordered sets, Distributed debugging 1. Introduction Let (S; !) be any partially ordered finite set. We are given a decomposition of S into n sets P 0 ; :::P n\Gamma1 such that for any i, P i is a chain of size at most m. We call such a structure a decomposed poset. These structures arise in distributed systems, becau...