A great deal of research in the area of distributed discrete event simulation has focussed on evaluating the performance of variants of conservative and optimistic methods on different types of applications. Applicati...
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ISBN:
(纸本)1565550277
A great deal of research in the area of distributed discrete event simulation has focussed on evaluating the performance of variants of conservative and optimistic methods on different types of applications. Application characteristics like lookahead, communication patterns, etc. have been found to affect the suitability of a specific protocol to simulate a given model. For many systems, it may be the case that different subsystems possess contradictory characteristics such that whereas some subsystems may be simulated efficiently using a conservative protocol, others may be more amenable to optimistic methods. Furthermore, the suitability of a protocol for a given subsystem may change dynamically. We propose a parallelsimulation protocol that allows different parts of a system to be simulated using different protocols, allowing these protocols to be switched dynamically. A proof of correctness is presented, along with some preliminary performance discussion.
In this contribution an implemented prototype of an object server on a parallel computer is described. In the first phase a model iras been proposed and simulated in Ada'95. Based on obtained experiences with run-...
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ISBN:
(纸本)0818681489
In this contribution an implemented prototype of an object server on a parallel computer is described. In the first phase a model iras been proposed and simulated in Ada'95. Based on obtained experiences with run-time features of the simulation program a corresponding prototype has been implemented in C++, tested, and the obtained results have been compared with results of the simulation.
In distributedsimulations, such as multi-player distributed virtual environments (DVE), power consumption traditionally has not been a major design factor. However, emerging battery-operated mobile computing platform...
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ISBN:
(纸本)0769519709
In distributedsimulations, such as multi-player distributed virtual environments (DVE), power consumption traditionally has not been a major design factor. However, emerging battery-operated mobile computing platforms require revisiting DVE implementation approaches for maximizing power efficiency. In this paper we explore some implications of power considerations in DVE implementation over mobile handhelds connected by wireless networks. We focus on the state dissemination problem in DVEs and propose a new power-aware dead reckoning framework for power-efficient state dissemination. We highlight a fundamental tradeoff between state consistency and power consumption, and present an adaptive dead reckoning algorithm that attempts to dynamically optimize the tradeoff at runtime. We present a quantitative evaluation of our approach using a synthetic DVE benchmark application.
This paper investigates issues concerning federations of sequential and/or parallel simulators. An approach is proposed for creating federated simulations by defining a global conceptual model of the entire simulation...
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This paper investigates issues concerning federations of sequential and/or parallel simulators. An approach is proposed for creating federated simulations by defining a global conceptual model of the entire simulation, and then mapping individual entities of the conceptual model to implementations within individual federates. Proxy entities are defined as a means for linking entities that are mapped to different federates. Using this approach, an implementation of a federation of optimistic simulators is examined. Issues concerning the adaptation of optimistic simulators to a federated system are discussed. The performance of the federated system utilizing runtime infrastructure (RTI) software executing on a shared memory multiprocessor (SMP) is compared with a native (non-federated) SMP-based optimistic parallel simulator. It is demonstrated that a well designed federated simulation system can yield performance comparable to a native, parallelsimulation engine, but important implementation issues must be properly addressed.
One of the promises of parallelized discrete-event simulation is that it might provide significant speedups over sequential simulation. In reality, high performance cannot be achieved unless the system is fine-tuned t...
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One of the promises of parallelized discrete-event simulation is that it might provide significant speedups over sequential simulation. In reality, high performance cannot be achieved unless the system is fine-tuned to balance computation, communication, and synchronization requirements. In this paper, we discuss our experiments in automated load balancing using the SPEEDES simulation framework. Specifically, we examine three mapping algorithms that use run-time measurements. Using simulation models of queuing networks and the National Airspace System, we investigate (i) the use of run-time data to guide mapping, (ii) the utility of considering communication costs in a mapping algorithm, (iii) the degree to which computational 'hot-spots' ought to be broken up in the linearization, and (iv) the relative execution costs of the different algorithms. We compare the performance of the three algorithms using results from the Intel Paragon.
The unthrottled optimism underlying the Time Warp (TW) parallelsimulation protocol can lead to excessive aggressiveness in memory consumption due to saving state histories, and waste of CPU cycles due to overoptimist...
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ISBN:
(纸本)081867931X
The unthrottled optimism underlying the Time Warp (TW) parallelsimulation protocol can lead to excessive aggressiveness in memory consumption due to saving state histories, and waste of CPU cycles due to overoptimistically progressing simulations that eventually have to be ''rolled back''. Furthermore, in TW simulations executing in distributed memory environments, the communication overhead induced by the rollback mechanism can cause pathological overall simulation performance. In this work direct optimism control mechanisms are used to overcome these shortcomings by probabilistically controlling simulation progression based on the forecasted time stamp of forthcoming messages. Several forecast methods are presented and their performance is compared for very large Petri net simulation models executed with the TW protocol on the Meiko CS-2.
Several mathematical and algorithmic problems that have arisen in discrete event simulations of large systems are described. The simulated systems belong to the areas of computational physics, queueing networks, and e...
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ISBN:
(纸本)1565550552
Several mathematical and algorithmic problems that have arisen in discrete event simulations of large systems are described. The simulated systems belong to the areas of computational physics, queueing networks, and econometric models.
simulation performance is dominated by lookahead in null message-based conservative time management of parallel discrete event simulation (PDES). This paper proposes a scheme for software execution path prediction to ...
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The performance of any mobile network is highly influenced by the mobility patterns of nodes in the network. In fact mobility behavior is the most important environmental factor that determines performance and influen...
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ISBN:
(纸本)9780769531595
The performance of any mobile network is highly influenced by the mobility patterns of nodes in the network. In fact mobility behavior is the most important environmental factor that determines performance and influences network design. Thus it is important that we develop models that 1. accurately capture the mobility of nodes, while at the same time 2. are amenable to mathematical analysis and/or efficient simulation. In the past, the wireless networking community relied on simple models such as random walk [3] and random waypoint [2]. However, the first of these models was found to be too simplistic although very useful in analysis and simulation. The latter, on the other hand was widely accepted and used in simulations. However, recently it was disvcovered that practitioners had severely misued it in simulations [4]. That and the growing appreciation that random waypoint is unrealistic has led to significant activities recently focusing on the development of parsimonious and accurate models describing the movement of nodes in mobile wireless networks. These have included efforts to model connectivity within sparse mobile networks associated with people and vehicles, and with the movement of units in miliatary settings. This talk will provide some of the early history in modeling mobility, including some of the failures described above. The talk will then describe the more recent application of a wide range of techniques to account for mobility. These range from Markov chains to ODE-based fluid models [6], from the use of exponetial, lognormal, and heavy-tailed distributions [1]to geometric weighted Gaussian distributions for intercontact times [5], and from the use of discrete state models to continuous state PDE-based models. The goal of the talk is to provide a better understanding of the issues underlying the accurate modeling of mobiltiy, recent progress in addressing these issues and the challenges that different approaches place on simulation.
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