In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the me...
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In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the mechanics of breaking event-time ties and has neither measured its extent nor considered its implications. Extant simulators (both serial and parallel) prohibit simultaneity either by user-specified event priorities or by an arbitrary (but well-documented) tie-breaking mechanism. We shall show, theoretically and empirically, that these strategies may lead to an invalid simulation. In doing so, we shall introduce the threshold of event simultaneity and use it to understand the semantics of simultaneity.
One of the key factors for efficiency in distributedsimulation is the detection of model-inherent concurrency, which is related on the prediction of the future behavior of each logical simulation process. In this pap...
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One of the key factors for efficiency in distributedsimulation is the detection of model-inherent concurrency, which is related on the prediction of the future behavior of each logical simulation process. In this paper we present a generalization of traditional approaches to behavioral prediction which provides more accurate predictions in general and a high degree of scalability in terms of computational and communication overhead. We give a sequential implementation, prove its correctness using concepts from the analysis of real-time process networks and then show how these results can be used in distributedsimulation.
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...
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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/distributedsimulation 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 parallelsimulation system by providing a more flexible approach to synchronization.
The Data Distribution Management (DDM) service is one of the six services provided in the Runtime Infrastructure (RTI) of High Level Architecture (HLA). Its purpose is to perform data filtering and reduce irrelevant d...
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ISBN:
(纸本)0769511058
The Data Distribution Management (DDM) service is one of the six services provided in the Runtime Infrastructure (RTI) of High Level Architecture (HLA). Its purpose is to perform data filtering and reduce irrelevant data communicated between federates. The two DDM schemes proposed for RTI, region-based and grid-based DDM, are oriented to send as little irrelevant data to subscribers as possible, but only manage to filter part of this information and some irrelevant data is still being communicated. In a previous paper [3], we employed intelligent agents to perform data filtering in HLA, implemented an agent-based DDM in RTI (ARTI) and compared it with the other two filtering mechanisms. This paper reports on additional experiments, results and analysis using two scenarios, the AWACS sensing aircraft simulation and the air traffic control simulation scenario Experimental results show that compared with other mechanisms, the agent-based approach communicates only relevant data and minimizes network communication, and is also comparable in terms of time efficiency. Some guidelines on when the agent-based scheme can be used are also given.
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. How...
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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.
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 ...
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ISBN:
(纸本)0769500595
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.
The widespread use of sequential simulation in large scale parameter studies means that large cost savings can be made by improving the performance of these simulators. Sequential discrete event simulation systems usu...
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ISBN:
(纸本)0769523838
The widespread use of sequential simulation in large scale parameter studies means that large cost savings can be made by improving the performance of these simulators. Sequential discrete event simulation systems usually employ a central event list to manage future events. This is a priority queue ordered by event timestamps. Many different priority queue algorithms have been developed with the aim of improving simulator performance. Researchers developing asynchronous conservative parallel discrete event simulations have reported exceptional performance for their systems running sequentially in certain cases. This paper compares the performance of simulations using a selection of high performance central event list implementations to that achieved using techniques borrowed from the parallelsimulation community. Theoretical and empirical analysis of the algorithms is presented demonstrating the range of performance that can be achieved, and the benefits of employing parallelsimulation techniques in a sequential execution environment.
This paper describes Nops, a conservatively synchronized process-oriented parallelsimulation system. Nops is designed to support the programming model of the Telecommunications Description Language (TeD), with specia...
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This paper describes Nops, a conservatively synchronized process-oriented parallelsimulation system. Nops is designed to support the programming model of the Telecommunications Description Language (TeD), with special emphasis on scaling up to very large network models. We chronicle the decisions beyond Nops' design, describe that design, assess its raw performance relative to CSIM, Maisie, and GTW, and study its ability to scale to large models.
This paper proposes a critical path-like analyzer to predict the amount of memory consumed in a specific Chandy-Misra simulation: Segments of code are inserted into the existing sequential simulation program, and this...
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This paper proposes a critical path-like analyzer to predict the amount of memory consumed in a specific Chandy-Misra simulation: Segments of code are inserted into the existing sequential simulation program, and this modified simulation program is called a memory analyzer. The amount of memory needed in the corresponding Chandy-Misra simulation is computed along with the execution of the memory analyzer. Experiments to evaluate the analyzer are in progress.
Ten years ago, MITRE/CAASD built a realtime, Human-In-The-Loop (HITL) research laboratory. The focus of this lab is integration and human factors research for the air traffic control and aviation communities. The last...
ISBN:
(纸本)0769516084
Ten years ago, MITRE/CAASD built a realtime, Human-In-The-Loop (HITL) research laboratory. The focus of this lab is integration and human factors research for the air traffic control and aviation communities. The last ten years have been illuminating in terms of the evolution of laboratory capabilities, infrastructure, and corporate culture. This paper will describe the laboratory environment, its history and vision, and will also provide some examples of how distributedsimulation technology has been applied, and continues to evolve, in a real-world HITL simulation environment serving a broad range of research needs.
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