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proceedings of the 5th IEEE workshop on Challenges of Large Applications in distributed Environments, CLADE'07 2007年 1-10页

作者： Gardner, Jeffrey P. Connolly, Andrew McBride, Cameron Pittsburgh Supercomputing Center 300 S. Craig St. Pittsburgh PA 15213 University of Washington Department of Astronomy Seattle WA 98195 University of Pittsburgh Department of Physics and Astronomy 3941 O'Hara St. Pittsburgh PA 15260

ISBN: (纸本)1595937145

Virtual observatories will give astronomers easy access to anunprecedented amount of data. Extracting scientific knowledge from these data will increasingly demand both efficient algorithms as well as the power of parallel computers. Nearly all efficient analyses of large astronomical datasets use trees as their fundamental data structure. Writing efficient tree-based techniques, a task that is time-consuming even on single-processor computers, is exceedingly cumbersome on massively parallel platforms (MPPs). Most applications that run on MPPs are simulation codes, since the expense of developing them is offset by the fact that they will be used for many years by many researchers. In contrast, data analysis codes change far more rapidly, are often unique to individual researchers, and therefore accommodate little reuse. Consequently, the economics of the current high-performance computing development paradigm for MPPs does not favor data analysis applications. We have therefore built a library, called Ntropy, that provides a flexible, extensible, and easy-to-use way of developing tree-based data analysis algorithms for both serial and parallel platforms. Our experience has shown that not only does our library save development time, it can also deliver excellent serial performance and parallel scalability. Furthermore, Ntropy makes it easy for an astronomer with little or noparallel programming experience to quickly scale their application to a distributed multiprocessor environment. By minimizing development time for efficient and scalable data analysis, we enable wide-scale knowledge discovery on massive datasets. Copyright 2007 ACM.

关键词： Data reduction

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Adaptive checkpointing for time warp technique with a limited number of checkpoints

Adaptive checkpointing for time warp technique with a limite...

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International Conference on distributed Computing Systems workshop

作者： R. Suzuki S. Fukurnoto K. Iwasaki Graduate School of Engineering Tokyo Metropolitan University Tokyo Japan Shuto Daigaku Tokyo Hachioji Tokyo JP Graduate Sch. of Eng. Tokyo Metropolitan Univ. Japan

This paper discusses distributed checkpointing with "Time Warp techniques", a typical uncoordinated checkpointing technique that is often used in the parallel and distributed simulations. Relaxing the assumption of the previous model of Soliman et al., we show a discrete time model where the number of available checkpoints each process can hold is finite. In addition, we propose an adaptive distributed checkpointing technique, that gives an effective time arrangement of checkpoints for a recovery point distribution, and we give numerical examples.

关键词： Checkpointing Clocks Time warp simulation Analytical models distributed computing Conferences

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Stack-free process-oriented simulation 97

Stack-free process-oriented simulation

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proceedings of the eleventh workshop on parallel and distributed simulation

作者： C. J. M. Booth D. I. Bruce Defence Evaluation and Research Agency St. Andrews Road Malvern WORCS WR14 3PS UK

ISBN: (纸本)9780818679650

The process interaction world view is widely used in the general simulation community for its expressive power, and is supported by most modern simulation languages. In parallel discrete event simulation, however, its use remains comparatively rare due to the perceived inefficiency (and difficulty) of parallel *** present a new implementation strategy for parallel process-oriented simulation languages. This innovative, semantics-based approach directly addresses two common concerns of such languages. By concentrating on the intrinsic threads of control, we avoid the proliferation of simulation objects (and their associated costs) that might result from a naive translation. More fundamentally, the primary costs associated with process-oriented languages -- those of context switching between stacks and, in an optimistic setting, of saving the state of these stacks -- are entirely eliminated since our explicit use of continuations avoids the need for stacks in the first place. We similarly obtain cheap and natural thread preemption.

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Application-aware scheduling of a magnetohydrodynamics application in the legion metasystem

Proceedings of the Heterogeneous Computing Workshop, HCW

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proceedings of the Heterogeneous Computing workshop, HCW 2000年 216-228页

作者： Dail, Holly Obertelli, Graziano Berman, Francine Wolski, Rich Grimshaw, Andrew Univ of California San Diego San Diego United States

Computational Grids have become an important and popular computing platform for both scientific and commercial distributed computing communities. However, users of such systems typically find achievement of application execution performance remains challenging. Although Grid infrastructures such as Legion and Globus provide basic resource selection functionality, work allocation functionality, and scheduling mechanisms, applications must interpret system performance information in terms of their own requirements in order to develop performance-efficient schedules. We describe a new high-performance scheduler that incorporates dynamic system information, application requirements, and a detailed performance model in order to create performance efficient schedules. While the scheduler is designed to provide improved performance for a magneto hydrodynamics simulation in the Legion Computational Grid infrastructure, the design is generalizable to other systems and other data-parallel, iterative codes. We describe the adaptive performance model, resource selection strategies, and scheduling policies employed by the scheduler. We demonstrate the improvement in application performance achieved by the scheduler in dedicated and shared Legion environments.

关键词： distributed computer systems

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Improving lookahead in parallel discrete event simulations of large-scale applications using compiler analysis 01

Improving lookahead in parallel discrete event simulations o...

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proceedings of the fifteenth workshop on parallel and distributed simulation

作者： Ewa Deelman Rajive Bagrodia Rizos Sakellariou Vikram Adve ISI/USC UCLA Manchester University UIUC

ISBN: (纸本)9780769511047

This paper addresses the issue of efficient and accurate performance prediction of large-scale message-passing applications on high performance architectures using simulation. Such simulators are often based on parallel discrete event simulation, typically using the conservative protocol to synchronize the simulation threads. The paper considers how a compiler can be used to automatically extract information about the lookahead present in the application, and how this can be used to improve the performance of the null protocol used for synchronization. These techniques are implemented in the MPI-Sim simulator and dHPF compiler, which had previously been extended to work together for optimizing the simulation of local computational components of an application. The results shows that the availability of lookahead information improves the runtime of the simulator by factors ranging from 9% up to two orders of magnitude, with 30-60% improvements being typical for the real-world codes. The experiments also show that these improvements are directly correlated with reductions in the number of null messages required by the simulations.

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An architecture of decentralized control for multi-degrees of freedom parallel manipulator

An architecture of decentralized control for multi-degrees o...

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International workshop on Advanced Motion Control (AMC)

作者： T. Kageyama K. Ohnishi Department of System Design Engineering Keio University Yokohama Japan

Decentralized control is composed of more than two subsystems. Subsystems communicate each other to control the whole system. In this paper, information of mechanical constraint for a parallel manipulator is analyzed. When some joints of multi-degrees of freedom parallel manipulators are set to be passive, excessive interference force can be reduced. A case where one joint of 3-linked arms is set to be passive is treated. The influence of a passive joint to the tip of the arm is derived by the configuration and the calculated reference torque. In the active joints, the interference force information from other joints are used to compensate the effect of passive joint. Such information is also used for switching passive joints. As a result, the avoidance of singular point is realized. Taking advantage of a parallel manipulator which has redundant drive joints, fault compensation is achieved by extending the communication of subsystems. Comparison with centralized control represents the availability of the decentralized control system by simulation.

关键词： distributed control Control systems Manipulators parallel robots Interference Mechanical variables control Torque Control system synthesis Availability Orbital robotics

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Dynamic load balancing strategies for conservative parallel simulations 97

Dynamic load balancing strategies for conservative parallel ...

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proceedings of the eleventh workshop on parallel and distributed simulation

作者： Azzedine Boukerche Sajal K. Das Center for Research in Parallel and Distributed Computing Department of Computer Sciences University of North of Texas Denton TX

ISBN: (纸本)9780818679650

This paper studies the problem of load balancing for conservative parallel simulations for execution on a multicomputer. The synchronization protocol makes use of Chandy-Misra null-messages. We propose a dynamic load balancing algorithm which assumes no compile time knowledge about the workload parameters. It is based upon a process migration mechanism, and the notion of CPU-queue length, which indicates the workload at each *** examine two variations for the algorithm which we refer to as centralized and multi-level hierarchical methods, in the context of queueing network simulation of a torus. The torus was chosen because it of its many cycles aid in the formation of deadlock making it a stress test for any conservative synchronization protocols. Our experiments indicate that our dynamic load balancing schemes significantly reduce the run time of an optimized version of Chandy-Misra null message approach, and decreases by 30-40\% the synchronization overhead when compared to the use of a static partitioning algorithm. Significantly, the results obtained also indicate that the multi-level scheme always outperforms both the centralized load balancing approach and the static partitioning algorithm.

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parallel Discrete-Event simulation (PDES): a case study in design, development, and performance using SPEEDES 95

Parallel Discrete-Event Simulation (PDES): a case study in d...

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proceedings of the ninth workshop on parallel and distributed simulation

作者： Frederick Wieland Eric Blair Tony Zukas The MITRE Corporation 7525 Colshire Dr. McLean VA

ISBN: (纸本)9780818671203

Can parallel simulations efficiently exploit a network of workstations? Why haven't PDES models followed standard modeling methodologies? Will the field of PDES survive, and if so, in what form? Researchers in the PDES field have addressed these questions and others in a series of papers published in the last few years [1,2,3,4]. The purpose of this paper is to shed light on these questions, by documenting an actual case study of the development of an optimistically synchronized PDES application on a network of workstations. This paper is unique in that its focus is not necessarily on performance, but on the whole process of developing a model, from the physical system being simulated, through its conceptual design, validation, implementation, and, of course, its performance. This paper also presents the first reported performance results indicating the impact of risk on performance. The results suggest that the optimal value of risk is sensitive to the latency parameters of the communications network.

关键词： performance network of workstations implementation aerospace simulation validation flight simulation aerospace computing communications network SPEEDES discrete event simulation conceptual design parallel discrete-event simulation optimistically synchronized PDES operations research

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Site-based mapping for parallel proxy servers with fewer TCP connections

Site-based mapping for parallel proxy servers with fewer TCP...

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International Conference on distributed Computing Systems workshop

作者： K.Y. Wong K.F. Law K.H. Yeung Department of Electrical Engineering City University of Engineering Hong Kong China

There are many mapping schemes proposed in previous research on parallel proxy servers. The operations of these schemes are mainly URL-based, and therefore cannot fully benefit from the new persistent connection feature of HTTP/1.1. We propose a site-based mapping scheme that forwards all requests targeting on the same Web site to the same proxy server. The scheme then allows the proxy to use a single persistent connection to serve many client requests. The major advantage of the scheme is the reduction in the number of connection establishments. This reduction can save network bandwidth and reduce the user-experienced latency. simulation results show that the proposed site-based scheme reduces 40%-70% of the connection setups and teardowns when compared to a traditional URL-based mapping scheme.

关键词： distributed computing Conferences

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Global Virtual Time and distributed synchronization 95

Global Virtual Time and distributed synchronization

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proceedings of the ninth workshop on parallel and distributed simulation

作者： Jeffrey S. Steinman Craig A. Lee Linda F. Wilson David M. Nicol Jet Propulation Laboratory California Inst. of Technology 4800 Oak Grove Drive Mail Stop 525-3960 Pasadena CA The Aerospace Corporation 2350 East E1 Segundo Blvd. Mail Stop M1-102 El Segundo CA ICASE NASA Langley Research Center Mail Stop 132C Hampton VA College of William and Mary Dept. of Computer Science Williamsburg VA

ISBN: (纸本)9780818671203

Global Virtual Time (GVT) is the fundamental synchronization concept in optimistic simulations. It is defined as the earliest time tag within the set of unprocessed pending events in distributed simulation. A number of techniques for determining GVT have been proposed in recent years, each having their own intrinsic properties. However, most of these techniques either focus on specific types of simulation problems or assume specific hardware support. This paper specifically addresses the GVT problem in the context of the following area• Scalability• Efficiency• Portability• Flow control• Interactive support•Real time useA new GVT algorithm, called SPEEDES GVT, has been developed in the Synchronous parallel Environment for Emulation and Discrete-Event simulation (SPEEDES) framework. The new algorithm runs periodically but does not disrupt event processing. It provides flow control by processing events risk-free while flushing out messages during the GVT computation. SPEEDES GVT is built from a set of global reduction operations that are easily implementable on any hardware system.

关键词： flow control SPEEDES GVT software fault tolerance global reduction operations parallel programming Synchronous parallel Environment for Emulation and Discrete-Event simulation framework message passing scalability event processing SPEEDES framework real time use interactive support distributed simulation optimistic simulations unprocessed pending events real-time systems portability efficiency global virtual time distributed synchronization synchronisation fundamental synchronization concept digital simulation GVT computation

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