Showing papers on "Wait-for graph published in 1991"

Deadlock problems in a multidatabase environment

Abstract: A deadlock detection algorithm and a deadlock prevention algorithm in a multidatabase environment are introduced. The deadlock detection algorithm is based on the potential conflict graph (PCG) introduced by Y. Breitbart et al. (1990). The deadlock prevention algorithm is based on the value data protocol discussed. The correctness of both algorithms is proved, and their performance is discussed. >

Distributed algorithm for communication deadlock detection

Abstract: In a distributed system, a set of processes may sometimes get involved in a communication deadlock. This is a situation where each process in the group waits for some process to communicate with it, but no other process is attempting communication. A new algorithm for deadlock detection in the communication model is presented. The proposed scheme is based on a new approach to the problem of distributed knot detection, which appears to be more efficient and simpler than existing ones. The resulting deadlock detection algorithm has the feature that when it terminates, the initiator knows all the processes that have caused the deadlock and may subsequently proceed to deadlock resolution.

Graph Rewriting Systems and their Application to Network Reliability Analysis

Abstract: We propose a new kind of Graph Rewriting Systems (GRS) that provide a theoretical foundation for using the reduction methods to analyze network reliability, and give the critical pair lemma in this paper.

Constructing protocol converters with guaranteed service

Abstract: The authors consider the conformity property, i.e. that the protocol converters providing communication between different networks meets the service specified by the designer, in constructing protocol converters. Using the top-down approach, an algorithm consisting of the following five steps is proposed to construct a protocol converter: (1) construction of a system graph from the given input; (2) removal of states and transitions that violate the synchronization requirements from the system graph constructed previously; (3) enforcement of liveness requirement on the system graph; (4) verification of the system graph against the service specification; and (5) derivation of a protocol converter from the system graph. The protocol converter so constructed is guaranteed not only to satisfy the conformity property, but also to be free from both deadlock and livelock. >

A distributed algorithm for resource deadlock detection

Abstract: A simple algorithm for the problem of deadlock detection in distributed systems is presented. In the proposed algorithm, the authors do not use probe messages to detect deadlock. Instead the authors use the update message whose function is twofold: first to modify the wait-for variables and second to check the occurrence of deadlock. The proposed algorithm ensures that only one process in the deadlock cycle will detect it, thus simplifying the resolution problem. All true deadlocks are detected in finite time and no false deadlocks are reported. An informal proof of correctness of the algorithm and an example are also presented. >

Efficient techniques for deadlock resolution in distributed systems

Abstract: Resolving a deadlock in a computer system involves choosing processes to terminate or roll back so that the deadlock is eliminated. It is widely known that the problem of finding the minimum number of processes to abort is NP-complete. Two polynomial-time heuristics to resolve deadlocks, the edge cycle method and a method based on enumerating the cycles in the wait-for-graph, are discussed. Simulation results are presented that show these heuristics perform better than several previously reported heuristics. >

Utilities for building and optimizing a computational graph for algorithmic decomposition

Abstract: This document describes a utility to construct and evaluate an optimized execution graph from the tapefile generated by the ADOL-C automatic differentiation software. It describes the format of the ADOL-C tapefile, the data structures used in building and storing the graph, and the optimizations performed in transforming the computation trace stored in the tape into an efficient graph representation. In particular, we eliminate assignments, increase granularity by hoisting'' chains of unary operations, and remove so-called dead roots -- intermediate values that have no influence on the dependent. Examples show that the optimized graphs contain up to 50% fewer nodes than a graph that would be an exact analogue of the ADOL-C tape. We also describe an attempt at generating compiled code for the graph evaluation as an alternative to interpretative approaches to evaluating the graph. 3 refs., 11 figs., 5 tabs.

Specification and implementation of Actors with graph rewriting

Abstract: We are investigating the use of graph rewriting for the specification and implementation of object-based concurrent systems Graph rewriting is a powerful framework in which to specify and implement such systems because the visual, graph-based notation more closely fits the programmer's visual image of object-based concurrent systems than textual notation, an image in which objects are represented as nodes or clusters of nodes in a graph and communication links are represented as edges in the same graph, and graph-rewriting presents an efficient implementation of object-based concurrent systems

Aspects of the parallel program execution: work, time and the current state

Abstract: The main focus in debugging and monitoring program execution is given as the notion of time. In particular, the progress of the execution, which is interpreted as useful computation, is addressed. The authors describe two interpretations, or views, of the causality graph which complement each other in the display of the propagation of the execution. The causality graph is the graph constructed from the partial order which reflects the execution of a parallel program. Additional processing of the causality graph is necessary in order to retrieve these views. This additional processing is essential since the complete, detailed display of the graph is unrealistic for programs of reasonable size. From the causality graph two notions are extracted: the notion of time slice and the notion of work. The definition of a unit of work and what this notion means for the application is provided by the user, and serves as an additional attribute of computation and resource nodes in the graph. These nodes are used for the generation of the views described. >

ANIGRAF: An Interactive System for the Animation of Graph Rewriting Systems with Priorities

Abstract: A PGRS is a finite set of rewriting rules, which do not modify the underlying graph, but only the labels attached to vertices or edges. There is a priority relation between rules, so when two occurrences of rules are overlapping in a graph, the rule with minor priority (if the rules are comparable) can not be applied to the graph. When the occurrences are not overlapping, both rules can be selected ; so checking whether a rule can be applied to a part of the graph does not require global informations.