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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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simulation of task graph systems in heterogeneous computing environments

Simulation of task graph systems in heterogeneous computing ...

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Heterogeneous Computing workshop

作者： N. Lopez-Benitez Ja-Young Hyon Department of Computer Science College of Engineering Texas Tech University Lubbock TX USA

This paper describes a simulation tool for the analysis of complex jobs described in the form of task graphs. The simulation procedure relies on the PN-based topological representation of the task graph that takes advantage of directly modeling precedence constraints and other characteristics inherent in generalized stochastic Petri nets (GSPN). The GSPN representation is enhanced with enabling functions that govern the sequence of firings of transitions representing execution of tasks. The regulated flow of activity is carried out observing not only precedence constraints but specific allocation heuristics and communication delays. The tool is useful in evaluating different heuristics described by the corresponding implemented algorithm, or using a deterministic time-span given by a Gantt chart.

关键词： Computational modeling Delay estimation Analytical models Computer simulation Petri nets distributed computing Optimization methods Discrete event simulation Computer science Educational institutions

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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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On event ordering in parallel discrete event simulation

On event ordering in parallel discrete event simulation

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： R. Ronngren M. Liljenstam Department of Teleinformatics Royal Institute of Technology 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： Discrete event simulation Context modeling Job shop scheduling Packaging machines Manufacturing systems Time measurement Kernel Costs

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GVT and scheduling in space time memory based techniques

GVT and scheduling in space time memory based techniques

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： A. Fabbri Department of Computer Sciences University of North Texas Denton TX USA

We present two GVT computation algorithms for PDES techniques with event based activities, relying on a space-time memory abstraction. Algorithm 2 involves a modification in the activity control, and is based on an epoch coloring scheme. The effect of the modification is assessed through an experimental study on a simulator implemented in the Linda coordination language. Experiments are performed on a cluster of workstations, and show that the modified activity control discipline is able to enhance performance.

关键词： Data structures Discrete event simulation Computational modeling Workstations Clustering algorithms Processor scheduling Electrical capacitance tomography History Concurrent computing

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Scheduling critical channels in conservative 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 20-28页

作者： Xiao, Z. Unger, B. Simmonds, R. Cleary, J. Univ of Calgary Calgary Canada

This paper introduces the Critical Channel Traversing (CCT) algorithm, a new scheduling algorithm for both sequential and parallel discrete event simulation. CCT is a general conservative algorithm that is aimed at the simulation of low-granularity network models on shared-memory multi-processor computers. An implementation of the CCT algorithm within a kernel called TasKit has demonstrated excellent performance for large ATM network simulations when compared to previous sequential, optimistic and conservative kernels. TasKit has achieved two to three times speedup on a single processor with respect to a splay tree central-event-list based sequential kernel. On a 16 processor (R8000) Silicon Graphics PowerChallenge, TasKit has achieved an event-rate of 1.2 million events per second and a speedup of 26 relative to the sequential kernel for a large ATM network model. Performance is achieved through a multi-level scheduling scheme that supports the scheduling of large grains of computation even with low-granularity events. Performance is also enhanced by supporting good cache behavior and automatic load balancing. The paper describes the algorithm and its motivation, proves its correctness and briefly presents performance results for TasKit.

关键词： Algorithms

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MPI code encapsulating using parallel CORBA object

MPI code encapsulating using parallel CORBA object

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International Symposium on High Performance distributed Computing

作者： C. Rene T. Priol IRISA/IFSIC Rennes France IRISA/INRIA Rennes France

This paper describes a technique that allows an MPI code to be encapsulated into a component. Our technique is based on an extension to the Common Object Request Broker Architecture (CORBA) from the OMG (Object Management Group). The proposed extensions do not modify the CORBA core infrastructure (the Object Request Broker) so that it can fully co-exist with existing CORBA applications. An MPI code is seen as a new kind of CORBA object that hides most of the cumbersome problems when dealing with parallelism. Such technique can be used to connect MPI codes to existing CORBA software infrastructures which are now being developed in the framework of several research and development projects such as JACO3, JULIUS or TENT from DLR. To illustrate the concept of parallel CORBA object, we present a virtual reality application that is made of the coupling of a light simulation application (radiosity) and a visualisation tool using VRML and Java.

关键词： Computational modeling parallel processing Application software Computer simulation Numerical simulation Middleware distributed processing Concurrent computing Iris Research and development

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The High Level Architecture and beyond: technology challenges

The High Level Architecture and beyond: technology challenge...

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： J.S. Dahmann U.S. Defense Modeling and Simulation Office USA

The High Level Architecture (HLA) provides the specification of a software architecture for distributed simulation. The baseline definition of the HLA includes the HLA Rules, The HLA Interface Specification, and the HLA Object Model Template. The HLA Rules are a set of 10 basic rules that define the responsibilities and relationships among the components of an HLA federation. The HLA Interface Specification provides a specification of the functional interfaces between HLA federates and the HLA Runtime Infrastructure. The HLA OMT provides a common presentation format for HLA simulation and Federation Object Models. The HLA was developed over the past three years. It is in the process of being applied with simulations developed for analysis, training and test and evaluation and incorporated into industry standards for distributed simulation by both the Object Management Group and the IEEE. This paper provides a discussion of key areas where there are technology challenges in the future implementation and application of the HLA.

关键词： Electrical capacitance tomography Runtime Application software Industrial training Management training Computer architecture Computational modeling Computer simulation Hip Testing

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Combining periodic and probabilistic checkpointing in optimistic simulation

Combining periodic and probabilistic checkpointing in optimi...

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： F. Quaglia Dipartimento di Informatica e Sistemistica Universitá 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 based 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： Checkpointing Costs Discrete event simulation Processor scheduling Protocols Remuneration Statistics Time warp simulation

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