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workshop on Principles of Advanced and distributed simulation (PADS)

作者： R.M. Fujimoto College of Computing Georgia Institute of Technology Atlanta GA USA

parallel discrete event simulation algorithms are usually based on time stamp ordering of events. distributed virtual environment (DVE) applications such as DIS typically use unordered event delivery. A partial order called approximate time (AT) is proposed to order events in both domains, facilitating reuse of simulations across DVE and analysis applications. A variation on AT-order called approximate time causal (ATC) order is also described. Synchronisation algorithms to realize these orderings are presented as well as performance measurements on a workstation cluster. A long-term goal of this work is to use AT and ATC order to exploit temporal uncertainty in the model to achieve efficient conservative parallel simulation despite little or no lookahead, a long-standing problem in the field.

关键词： Uncertainty Discrete event simulation Computational modeling Virtual environment Analytical models distributed computing Educational institutions Concurrent computing Clustering algorithms Measurement

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On event ordering in parallel discrete event simulation

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 38-45页

作者： Ronngren, Robert Liljenstam, Michael Stockholm Sweden

Ordering of simultaneous events in DES is an important issue as it has an impact on modelling expressiveness, model correctness as well as causal dependencies. In sequential DES this is a problem which has attracted much attention over the years and most systems provide the user with tools to deal with such issues. This has also attracted some attention within the PDES community and we present an overview of these efforts. We have, however, not yet found a scheme which provides us with the desired functionality. Thus, we present and evaluate some simple schemes to achieve a well defined ordering of events and means to identify both causally dependent and independent events with identical timestamps in the context of optimistic simulations. These schemes should be applicable also to conservative PDES.

关键词： Computer simulation

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Case study: parallelizing a sequential simulation model

Case study: parallelizing a sequential simulation model

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： L. Bajaj R. Bagrodia R. Meyer Computer Science Department University of California Los Angeles Los Angeles CA USA

Most successful examples of parallel simulation models were developed for parallel execution, from the beginning. A number of simulation models are designed only for sequential simulation, even in languages like PARSEC, that support both sequential and parallel simulation algorithms. Converting such simulation models to a form that yields good performance with a parallel implementation can be non-trivial. We describe a case study showing this conversion process for a simulation model of replicated file systems. The details of the major steps taken in converting the simulation into a parallel simulation are presented: correctness changes; performance changes such as communication topology simplification and lookahead specification; and modeling changes to eliminate performance bottlenecks. The details and performance improvements of each step are presented.

关键词： Computer aided software engineering File systems Computational modeling Topology Costs Scalability Computer science Computer simulation Identity-based encryption Availability

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parallel simulation of incompressible fluids

Parallel simulation of incompressible fluids

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Euromicro workshop on parallel and distributed Processing

作者： A. Adelsbach I. Potikoglou T. Rauber G. Runter Fachbereich Informatik Universität des Saarlandes Saarbrucken Germany Institut für Informatik Universität Halle-Wittenberg Halle Germany

The simulation of incompressible fluids is one of the important problem classes in computational fluid dynamics. We consider a simulation algorithm for the convection in binary fluid mixtures, a problem where a quite simple model describes a very complex behavior. In a parallel implementation on an IBM SP2, we investigate several implementation strategies involving different data layouts and communication organizations.

关键词： Computational modeling Oceans Rivers Heating Grid computing Asynchronous communication Testing Computational fluid dynamics Identity-based encryption Navier-Stokes equations

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Performance prediction tools for parallel discrete-event simulation

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 148-155页

作者： Lim, Chu-Cheow Low, Yoke-Hean Gan, Boon-Ping Jain, Sanjay Cai, Wentong Hsu, Wen Jing Huang, Shell Ying Gintic Inst of Manufacturing Technology Singapore Singapore

We have developed a set of performance prediction tools which help to estimate the achievable speedups from parallelizing a sequential simulation. The tools focus on two important factors in the actual speedup of a parallel simulation program: (a) the simulation protocol used, and (b) the inherent parallelism in the simulation model. The first two tools are a performance/parallelism analyzer for a conservative, asynchronous simulation protocol, and a similar analyzer for a conservative, synchronous ('super-step') protocol. Each analyzer allows us to study how the speedup of a model changes with increasing number of processors, when a specific protocol is used. The third tool - a critical path analyzer - gives an ideal upper bound to the model's speedup. This paper gives an overview of the prediction tools, and reports the predictions from applying the tools to a discrete-event wafer fabrication simulation model. The predictions are close to speedups from actual parallel implementations. These tools help us to set realistic expectations of the speedup from a parallel simulation program, and to focus our work on issues which are more likely to yield performance improvement.

关键词： Computer simulation

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Combining periodic and probabilistic checkpointing in optimistic simulation

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 109-116页

作者： Quaglia, Francesco Universita' di Roma 'La Sapienza' Roma Italy

This paper presents a checkpointing scheme for optimistic simulation which is a mixed approach between periodic and probabilistic checkpointing. The latter, basing on statistical data collected during the simulation, aims at recording as checkpoints states of a logical process that have high probability to be restored due to rollback (this is done in order to make those states immediately available). The periodic part prevents performance degradation due to state reconstruction (coasting forward) cost whenever the collected statistics do not allow to identify states highly likely to be restored. Hence, this scheme can be seen as a highly general solution to tackle the checkpoint problem in optimistic simulation. A performance comparison with previous solutions is carried out through a simulation study of a store-and-forward communication network in a two-dimensional torus topology.

关键词： Computer simulation

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Efficient optimistic parallel simulations using reverse computation

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 126-135页

作者： Carothers, Christopher D. Perumalla, Kalyan S. Fujimoto, Richard M. Rensselaer Polytechnic Inst Troy United States

In optimistic parallel simulations, state-saving techniques have been traditionally used to realize rollback. In this article, we propose reverse computation as an alternative approach, and compare its execution performance against that of state-saving. Using compiler techniques, we describe an approach to automatically generate reversible computations, and to optimize them to transparently reap the performance benefits of reverse computation. For certain fine-grain models, such as queuing network models, we show that reverse computation can yield significant improvement in execution speed coupled with significant reduction in memory utilization, as compared to traditional state-saving. On sample models using reverse computation, we observe as much as three-fold improvement in execution speed over traditional state-saving.

关键词： Computer simulation

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Exploiting model independence for parallel PCS network simulation

Exploiting model independence for parallel PCS network simul...

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： A. Boukerche S.K. Das A. Fabbri O. Yildiz Center for Research in Wireless Computing (CReW) Department of Computer Science University of North Texas Denton TX USA

We present a parallel simulator (SWiMNet) for PCS networks using a combination of optimistic and conservative paradigms. The proposed methodology exploits event precomputation permitted by model independence within the PCS components. The low percentage of blocked calls is exploited in the channel allocation simulation of precomputed events by means of an optimistic approach. Experiments were conducted with various call arrival rates and mobile host densities on a cluster of Pentium workstations. Performance results indicate that the SWiMNet achieves a speedup of 6 employing 8 workstations, and a speedup of 12 with 16 workstations.

关键词： Personal communication networks Object oriented modeling Computational modeling Computer simulation Discrete event simulation Workstations Concurrent computing Wireless networks Frequency conversion Computer networks

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Time Warp simulation on clumps

Time Warp simulation on clumps

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： G.D. Sharma R. Radhakrishnan U.K.V. Rajasekaran N. Abu-Ghazaleh P.A. Wilsey Department of ECECS University of Cincinnati Cincinnati OH USA Department of Computer Science State University of New York Binghamton NY USA

Traditionally, parallel discrete-event simulators based on the Time Warp synchronization protocol have been implemented using either the shared memory programming model or the distributed memory, message passing programming model. This was because the preferred hardware platform was either a shared memory multiprocessor workstation or a network of uniprocessor workstations. However, with the advent of clumps (cluster of shared memory multiprocessors), a change in this dichotomous view becomes necessary. We explore the design and implementation issues involved in exploiting this new platform for Time Warp simulations. Specifically, we present two generic strategies for implementing Time Warp simulators on clumps. In addition, we present our experiences in implementing these strategies on an extant distributed memory, message passing Time Warp simulator (WARPED). Preliminary performance results comparing the modified clump-specific simulation kernel to the unmodified distributed memory, message passing simulation kernel are also presented.

关键词： Time warp simulation Message passing Workstations Computational modeling Kernel Hardware Costs parallel programming Bandwidth Delay

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Performance prediction of a parallel simulator

Performance prediction of a parallel simulator

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： J. Liu D. Nicol B. Premore A. Poplawski Department of Computer Science Dartmouth College Hanover NH USA

There are at least three major obstacles thwarting widespread adoption of parallel discrete-event simulation: lack of need; lack of tools; and lack of predictability in behavior and performance. The plain truth is that most simulation studies can be adequately done on ordinary serial computers. parallel simulation tools are products of research efforts, and simply do not stand up to the demands of modern software engineering. The results of 20 years of research in parallel simulation reveal it to be a highly complex endeavour, with performance results very much dependent on implementation details and model characteristics. The Scalable simulation Framework (SSF) is an effort to address some these concerns. It addresses lack of need in two ways; it provides a modeling API that is attractive both for serial and parallel simulation, with parallel execution requiring no change to the model, and it targets large-scale telecommunication system modeling, an application area that requires the computational capabilities of parallelism. We address the concern over unpredictable behavior. We show how we measured the internal overheads of the Dartmouth implementation of the SSF API (DaSSF), and how those measurements can be used to predict the performance of a given model, using given features of the simulator, without having to run, or even build, the model.

关键词： Predictive models Computational modeling Large-scale systems Software engineering Computer science Educational institutions Discrete event simulation Computer simulation Concurrent computing Telecommunication computing

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