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A framework for formalization and strictness analysis of simulation event orderings

simulation-TRANSACTIONS OF thE SOCIETY FOR MODELING AND simulation INTERNATIONAL 2005年第4期81卷 325-335页

作者： Teo, YM Onggo, BSS Singapore Massachusetts Inst Technol Alliance Singapore 117576 Singapore Natl Univ Singapore Dept Comp Sci Singapore 117543 Singapore

this article advocates the use of a formal framework for analyzing simulation performance. simulation performance is characterized based on the three simulation development process boundaries: physical system, simulation model, and simulator implementation. First, the authors formalize simulation event ordering using partially ordered set theory. A simulator implements a simulation event ordering and incurs implementation overheads when enforcing event ordering at runtime. Second, they apply their formalism to extract and formalize the simulation event orderings of both sequential and parallel simulations. third, they propose the relation stricter and a measure called strictness for comparing and quantifying the degree of event dependency of simulation event orderings, respectively. In contrast to the event parallelism measure, strictness is independent of time.

关键词： parallel and distributed simulation formalization event ordering strictness partially ordered set

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Optimizing parallel execution of detailed wireless network simulation 04

Optimizing parallel execution of detailed wireless network s...

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18th workshop on parallel and distributed simulation

作者： Ji, ZR Zhou, JL Takai, M Martin, J Bagrodia, R Univ Calif Los Angeles Parallel Comp Lab Los Angeles CA 90095 USA

ISBN: (纸本)0769521118

With parallel and Discrete Event simulation (PDES) techniques, the runtime performance of detailed wireless network simulation can be improved significantly without compromising fidelity of the simulation results. However modelling characteristics of wireless communications such as signal propagation and interference may severely hinder the potential speedup yielded by PDES. this paper proposes various optimization techniques to address three major concerns in achieving efficient parallel execution of wireless network simulation: i.e., (1) reducing communication and computation overhead of simulating signal propagation across multiple logical processes;(2) reducing synchronization overhead among logical processes;(3) minimizing event scheduling overhead within individual logical processes. these techniques have been implemented in a parallel version of GloMoSim and QualNet. the experimental results with mobile ad hoc networking scenarios demonstrate that the proposed optimization techniques can improve the performance of parallel wireless network simulation by up to an order of magnitude.

关键词： Wireless networks Discrete event simulation Computational modeling Runtime Wireless communication Interference Mobile communication Computer networks Concurrent computing Signal processing

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Optimistic synchronization in HLA-based distributed simulation

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simulation-TRANSACTIONS OF thE SOCIETY FOR MODELING AND simulation INTERNATIONAL 2005年第4期81卷 279-291页

作者： Wang, XG Turner, SJ Low, MYH Gan, BP Nanyang Technol Univ Sch Comp Engn Parallel & Distributed Comp Ctr Singapore 639798 Singapore Singapore Inst Mfg Technol Singapore 638075 Singapore

With the wide use of commercial off-the-shelf (COTS) simulation packages and the advent of the High Level Architecture (HLA) standard, it is desirable to build distributed simulations by linking various types of simulation models developed using best-fit COTS packages. While almost all current work on integrating COTS packages and the HLA is based on conservative synchronization, it is worthwhile to investigate the optimistic synchronization approach. the optimistic approach can exploit parallelism and achieve promising performance in situations where causality errors may occur but in fact seldom occur. the authors introduce a rollback controller using a middleware approach to handle the complex rollback procedure on behalf of the simulation model. A new time advance algorithm is proposed that can fully use the benefits of optimistic synchronization. the article also describes a scalability study showing the experimental results for the two synchronization approaches as the number of simulation components increases.

关键词： distributed simulation optimistic synchronization commercial-off-the-shelf (COTS) simulation packages high level architecture (HLA) rollback controller

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Toward grid-aware time warp

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simulation-TRANSACTIONS OF thE SOCIETY FOR MODELING AND simulation INTERNATIONAL 2005年第4期81卷 293-306页

作者： Iskra, KA van Albada, GD Sloot, PMA Univ Amsterdam Comp Syst Architecture & Programming Lab NL-1098 SJ Amsterdam Netherlands

the authors study the adaptation of an optimistic Time Warp kernel to cross-cluster computing on the Grid. Wide-area communication, the primary source of overhead, is offloaded onto dedicated routing processes. this allows the simulation processes to run at full speed and thus significantly decreases the performance gap caused by the wide-area distribution. Further improvements are obtained by employing message aggregation on the wide-area links and using a distributed global virtual time algorithm. the authors achieve many of their objectives for a cellular automaton simulation with lazy cancellation and moderate communication. High communication rates, especially with aggressive cancellation, present a challenge. this is confirmed by the experiments with synthetic loads. Even then, a satisfactory speedup can be achieved, provided that the computational grain of events is large enough.

关键词： optimistic parallel discrete event simulation grid computing message aggregation GVT algorithms

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Time-parallel simulation with approximative state matching

Time-parallel simulation with approximative state matching

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18th workshop on parallel and distributed simulation

作者： Kiesling, T Pohl, S Univ Bundeswehr Munchen Fak Informat D-85577 Neubiberg Germany

ISBN: (纸本)0769521118

Time-parallel simulation offers the potential of massive parallelization of a simulation application, due to the amount of achievable parallelism not being restricted by the decomposability of the state space of a simulation model. Unfortunately, the potential speedup of a time-parallel simulation highly depends on the ability to match final and initial states of adjacent time intervals. Depending on the properties of the underlying simulation model, it might be feasible to accept a simulation iteration, even if the states of adjacent time intervals do not match exactly. this leads to the concept of approximative state matching in time-parallel simulation, which is introduced in this paper Experiments with a prototypical implementation of a simple simulation model show encouraging results in terms of simulation speedup and introduced error.

关键词： Software prototyping

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Using ghosts for global topology knowledge in space-parallel distributed network simulations

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simulation-TRANSACTIONS OF thE SOCIETY FOR MODELING AND simulation INTERNATIONAL 2005年第4期81卷 267-277页

作者： Riley, GF Jaafar, TM Fujimoto, RM Ammar, MH Georgia Inst Technol Dept Elect & Comp Engn Atlanta GA 30332 USA Georgia Inst Technol Coll Comp Atlanta GA 30332 USA

the authors discuss an approach to federated network simulations that eases the burdens on the simulation developer in creating space-parallel simulations. Previous approaches have had difficulties that arise from the need for global topology knowledge when forwarding simulated packets between federates. In all but the simplest cases, proper packet-forwarding decisions between federates requires routing tables of size O(mn), where m is the number of nodes modeled in a particular federate, and n is the total number of network nodes in the entire topology. Furthermore, the benefits of the well-known NIx-Vector routing approach cannot be fully achieved without global knowledge of the overall topology. the authors overcome these difficulties by using a topology partitioning methodology that uses ghost nodes. they show experimentally that the memory overhead associated with ghosts is minimal relative to the overall memory footprint of the simulation.

关键词： network simulation distributed simulation large-scale simulation

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Event reconstruction in time warp 04

Event reconstruction in time warp

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18th workshop on parallel and distributed simulation

作者： Li, LJ Tropper, C McGill Univ Sch Comp Sci Montreal PQ Canada

ISBN: (纸本)0769521118

In optimistic simulations, checkpointing techniques are often used to reduce the overhead caused by state saving. In this paper, we propose event reconstruction as a technique with which to reduce the overhead caused by event saving, and compare its memory consumption and execution time to the results obtained by dynamic checkpointing. As the name implies, event reconstruction reconstructs input events and anti-events from the differences between adjacent states, and does not save input events in the event queue. For simulations with fine event granularity and small state size, such as the logic simulation of VLSI circuitry, event reconstruction can yield an improvement in execution time as well as a significant reduction in memory utilization when compared to dynamic checkpointing. Moreover, this technique facilitates load migration because only the state queue needs to be moved from one processor to another.

关键词： Checkpointing Circuit simulation Very large scale integration Discrete event simulation Costs Logic circuits Time warp simulation Heuristic algorithms Frequency Computer science

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Component-based distributed simulations. the way forward?

Component-based distributed simulations. The way forward?

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18th workshop on parallel and distributed simulation

作者： Verbraeck, A Delft Univ Technol Fac Technol Policy & Management Syst Engn Sect NL-2600 GA Delft Netherlands

ISBN: (纸本)0769521118

parallel simulation and distributed simulation sometimes appear to be two different worlds. Where parallel simulation aims at increasing the speed of a single model by distributing it over more processors, distributed simulation looks at ways to link entire models or federates that run on different computers. In the case of distributed simulation, the models themselves are hard to distribute, and often they each run on one processor as a monolithic model. this paper advocates to build the more traditional simulation models in such a way, that they can be easily distributed. As simulationists, we can learn from component-based theory from the software engineering field to prepare our models for distribution, and parts of our models for reuse. the results of several projects show that componentizing simulation models can have many advantages. the results also show that it is not easy to create models in a componentized way, and that current methods for simulation model building should be adapted.

关键词： Program processors

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Space uncertain simulation events: some concepts and an application to optimistic synchronization

Space uncertain simulation events: some concepts and an appl...

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18th workshop on parallel and distributed simulation

作者： Quaglia, F Beraldi, R Univ Roma La Sapienza Dipartimento Informat & Sistemist I-00198 Rome Italy

ISBN: (纸本)0769521118

the notion of temporal uncertainty, expressed as the possibility for an event to occur in an interval of simulation time, rather than at a specific instant, has been recently proposed and exploited in order to enhance the performance of parallel/distributed simulation systems. In this paper we propose the concept of "spatial uncertainty" expressed as the possibility for a simulation event to occur in one of a set of points within the simulated system space. How to handle/exploit space uncertain events in an optimistic simulation system is discussed. Also, experimental results for optimistic simulations of a Personal Communication System (PCS) modeled with space uncertain events are reported these results show the ability of spatial uncertainty to increase the performance of the parallel simulation system by providing a more flexible approach to synchronization.

关键词： Mobile telecommunication systems

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Formalization and strictness of simulation event orderings

Formalization and strictness of simulation event orderings

引用

18th workshop on parallel and distributed simulation

作者： Teo, YM Onggo, BSS Natl Univ Singapore Dept Comp Sci Singapore 117543 Singapore

ISBN: (纸本)0769521118

this paper advocates the use of a formal framework for analyzing simulation performance. simulation performance is characterized based on the three simulation development process boundaries: physical system, simulation model, and simulator implementation. Firstly, we formalize simulation event ordering using partially ordered set theory. A simulator implements a simulation event ordering, and incurs implementation overheads when enforcing event ordering at runtime. Secondly, we apply our formalism to extract and formalize the simulation event orderings of both sequential and parallel simulations. thirdly, we propose the relation stricter and a measure called strictness for comparing and quantifying the degree of event dependency of simulation event orderings respectively.

关键词： Simulators

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