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10th Annual acm symposium on principles of distributed computing, PODC 1991

作者： Gilon, Kami Peleg, David Department of Applied Mathematics and Computer Science Weizmann Institute Rehovot76100 Israel

ISBN: (纸本)0897914392

This paper handles the problem of designing a deterministic dictionary structure in a distributed system. The structure is required to be compact (namely, store only a single copy of each data item) and memory balanced, and to have efficient access protocols. Several structures are presented, achieving near-optimal performance with respect to memory requirements and communication complexity. © 1991 acm

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SPECIFYING GRACEFUL DEGRADATION

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IEEE TRANSACTIONS ON PARALLEL AND distributed SYSTEMS 1991年第1期2卷 93-104页

作者： HERLIHY, MP WING, JM CARNEGIE MELLON UNIV SCH COMP SCIPITTSBURGHPA 15213

Complex programs are often required to display graceful degradation, reacting adaptively to changes in the environment. Under ideal circumstances, the program's behavior satisfies a set of application-dependent constraints. In the presence of events such as failures, timing anomalies, synchronization conflicts, or security breaches, certain constraints may become difficult or impossible to satisfy, and the application designer may choose to relax them as long as the resulting behavior is sufficiently "close" to the preferred behavior. This paper describes the relaxation lattice method, a new approach to specifying graceful degradation for a large class of programs. A relaxation lattice is a lattice of specifications parameterized by a set of constraints, where the stronger the set of constraints, the more restrictive the specification. While a program is able to satisfy its strongest set of constraints, it satisfies its preferred specification, but if changes to the environment force it to satisfy a weaker set, then it will permit additional "weakly consistent" computations which are undesired but tolerated. The use of relaxation lattices is illustrated by specifications for programs that tolerate 1) faults, such as site crashes and network partitions, 2) timing anomalies, such as attempting to read a value "too soon" after it was written, 3) synchronization conflicts, such as choosing the oldest "unlocked" item from a queue, and 4) security breaches, such as acquiring unauthorized capabilities. A preliminary version of this paper appeared in the proceedings of the Sixth acm SIGACT-SIGOPS symposium on principles of distributed computing [17].

关键词： CONCURRENCY distributed computing FAULT TOLERANCE FORMAL SPECIFICATION LARCH

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Resiliency of interactive distributed tasks 91

Resiliency of interactive distributed tasks

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10th Annual acm symposium on principles of distributed computing, PODC 1991

作者： Chor, Benny Nelson, Lee-Bath Department of Computer Science Technion Haifa32000 Israel

ISBN: (纸本)0897914392

Interaction is a fundamental notion in computation. In many cases, important properties are revealed by considering the interactive aspects of problems. In this work, we examine the power and limitations of interaction in the context of fault-tolerant, asynchronous distributed computing. We focus on two models of interprocess communication - shared memory, and message passing. Interactive distributed tasks naturally occur in many distributed systems. In such a task, each of n processors receives a local input, responds with some local output, then receives a second input (possibly depending on the response), responds to i t, and so on. Different processors can be at different stages simultaneously, so that additional inputs are received by fast processors while slow processors are still working on early inputs. Interactive distributed tasks have strong expressive power. They include, for example, both decision tasks and sequential systems as special cases. The main result of this work is an exact characterization of the interactive tasks which can be solved by randomized t-resilient protocols. The major tool we use in the characterization is a directed acyclic graph that is associated with an interactive task. Properties of this graph are used to determine the resiliency of the task, and to devise a "generic" resilient algorithm which solves such tasks. © 1991 acm

关键词： Message passing

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Dynamic node reconfiguration in a parallel-distributed environment 91

Dynamic node reconfiguration in a parallel-distributed envir...

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proceedings of the Third acm SIGPLAN symposium on principles and Practice of Parallel Programming - PPOPP

作者： Feeley, Michael J. Bershad, Brian N. Chase, Jeffrey S. Levy, Henry M. Department of Computer Science and Engineering University of Washington Seattle 98195 WA United States

ISBN: (纸本)0897913906

Idle workstations in a network represent a significant computing potential. In particular, their processing power can be used by parallel-distributed programs that treat the network as a loosely-coupled multiprocessor. But the set of machines free to participate in load sharing changes over time as users come and go from their workstations. To make full use of the available resources, parallel-distributed applications in the network must reconfigure to adapt to these changes as they run. This paper describes a node reconfiguration facility for Amber, an object-based parallel programming system for networks of multiprocessors. We describe system support that allows a parallel Amber application to adapt to changing network conditions by expanding to make use of new nodes as they become idle, and by contracting as nodes become busy. A key characteristic of Amber's node reconfiguration is that it is handled at the user level in the Amber runtime system it does not depend on a kernel-level process migration facility. Our experiments with Amber show that node reconfiguration can be implemented easily and efficiently in a runtime library. © 1991 Association for computing Machinery. All Rights Reserved.

关键词： Amber

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proceedings of the 9th Annual acm symposium on principles of distributed computing

Proceedings of the 9th Annual ACM Symposium on Principles of...

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proceedings of the 9th Annual acm symposium on principles of distributed computing

This conference proceedings contains 27 papers. The main subjects are shared memory multiprocessors, achievement of causal consistency, semantics of distributed services, storage management, message-passing systems, clock synchronization algorithms, high speed network control, analysis of communication protocols, reasoning about probabilistic algorithms, and totally asynchronous systems.

关键词： Computer Systems, Digital

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distributed control for PARIS 90

Distributed control for PARIS

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proceedings of the 9th Annual acm symposium on principles of distributed computing

作者： Awerbuch, Baruch Cidon, Israel Gopal, Inder Kaplan, Marc Kutten, Shay Dept of Mathematics and Lab for Computer Science MIT Cambridge MA United States

ISBN: (纸本)9780897914048

We describe the control protocols of the PARIS experimental network. This high bandwidth network for integrated communication (data, voice, video) is currently operational as a laboratory prototype. It will also be deployed within the AURORA Testbed that is part of the NSF/DARPA Gigabit Networking program. The high bandwidth dicates the need of specialized hardware to support faster packet handling and control protocols. A new network control architecture is presented which exploits the specialized hardware in order to support the expected real time needs of future traffic. In particular, since control information can be distributed quickly, decisions can be made based upon more complete and accurate information. In some respects, this has the effect of having the benefits of centralized control (e.g. easier bandwidth resource allocation to connections), while retaining the fault-tolerance and scalability of a distributed architecture.

关键词： Computer networks

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distributed variable server for atomic unification 90

Distributed variable server for atomic unification

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proceedings of the 9th Annual acm symposium on principles of distributed computing

作者： Kleinman, Alon Moses, Yoram Shapiro, Ehud Weizmann Inst of Science Rehovot Israel

ISBN: (纸本)9780897914048

Processes in concurrent logic programs communicate and synchronize using shared single-assignment variables. Communication is performed via unification operations, while synchronization is performed through input matching. The more expressive concurrent logic languages employ atomic unification as the basic communication primitive. Atomic unification can be thought of as an atomic transaction that either fails with no trace or succeeds in writing on all of the necessary writable variables occurring in the unification instance. This paper presents a distributed variable server algorithm that can be used as the key component in a distributed implementation of concurrent logic languages with atomic unification. The variable server provides an abstraction in which processes can act as if all of the shared variables are local. It thus allows programs to be written for a shared memory model and executed in a system in which memory is distributed. We rigorously specify the requirements the variable server must fulfill, present an algorithm satisfying the specification, and prove its correctness with respect to the specification. The algorithm has been implemented for the language Flat Concurrent Prolog (FCP) and is incorporated in the distributed version of the Logix system.

关键词： Computer systems, Digital

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Virtual time II. Storage management in distributed simulation

Virtual time II. Storage management in distributed simulatio...

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proceedings of the 9th Annual acm symposium on principles of distributed computing

作者： Jefferson, David UCLA

The main contribution of this paper is the Cancelback Protocol, an extension of the Time Warp mechanism that handles storage management. It includes both fossil collection, the recovery of storage for messages and states that can never again influence the computation, and cancelback, the recovery of storage assigned to messages and states at times so far in the future that their memory would be better used for more immediate purposes. It guarantees that Time Warp is optimal in its storage requirements when run in shared memory, i.e. Time Warp will successfully complete a simulation using no more space than it would take to execute the same simulation with the sequential event list algorithm. This is better by a factor of two than the only previously published result. Without this protocol (or equivalent) Time Warp's behavior can be unstable;hence it should be considered an essential part of Time Warp mechanism, rather than simply a refinement. In addition we also prove that asynchronous conservative algorithms, including all of the Chandy-Misra-Bryant (CMB) mechanisms, are not optimal;they cannot necessarily execute a simulation in the same amount of space as a sequential execution. In some cases a simulation requiring space n+k when executed sequentially might require O(nk) space when executed on n processors by CMB.

关键词： Computer Simulation

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LAZY REPLICATION - EXPLOITING THE SEMANTICS OF distributed SERVICES 90

LAZY REPLICATION - EXPLOITING THE SEMANTICS OF DISTRIBUTED S...

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9TH ANNUAL SYMP OF THE ASSOC FOR computing MACHINERY : principles OF distributed computing

作者： LADIN, R LISKOV, B SHRIRA, L Digital Equipment Corp. One Kendall Square Cambridge MA MIT Laboratory for Computer Science 545 Technology Square Cambridge MA

ISBN: (纸本)089791404X

To provide high availability for services such as mail or bulletin boards, data must be replicated. One way to guarantee consistency of replicated data is to force service operations to occur in the same order at all sites, but this approach is expensive. In this paper, we propose lazy replication as a way to preserve consistency by exploiting the semantics of the service's operations to relax the constraints on ordering. Three kinds of operations are supported: operations for which the clients define the required order dynamically during the execution, operations for which the service defines the order, and operations that must be globally ordered with respect to both client ordered and service ordered operations. The method performs well in terms of response time, amount of stored state, number of messages, and availability. It is especially well suited to applications in which most operations require only the client-defined order.

关键词： Computer systems, Digital

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Supporting shared data structures on distributed memory architectures 90

Supporting shared data structures on distributed memory arch...

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2nd acm SIGPLAN symposium on principles and Practice of Parallel Programming, PPOPP 1990

作者： Koelbel, Charles Mehrotra, Piyush Van Rosendale, John Department of Computer Science Purdue University West LafayetteIN47907 United States ICASE NASA Langley Research Center HamptonVA23665 United States

ISBN: (纸本)0897913507

Programming nonshared memory systems is more difficult than programming shared memory systems, since there is no support for shared data structures. Current programming languages for distributed memory architectures force the user to decompose all data structures into separate pieces, with each piece "owned" by one of the processors in the machine, and with all communication explicitly specified by low-level message-passing primitives. This paper presents a new prograrnming environment for distributed memory architectures, providing a global name space and allowing direct access to remote parts of data values. We describe the analysis and program transformations required to implement this environment, and present the efficiency of the resulting code on the NCUBE/7 and IPSC/2 hypercubes. © 1990 acm.

关键词： Message passing

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