One of the difficulties inherent to conservative parallel discrete event simulation (PDES) is the need for extraction and explicit specification of the lookahead. In this paper we propose a simulator design which allo...
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ISBN:
(纸本)9780769516080
One of the difficulties inherent to conservative parallel discrete event simulation (PDES) is the need for extraction and explicit specification of the lookahead. In this paper we propose a simulator design which allows users to build simulation models with lookahead transparently. This is based on the cooperation between PDES experts and the users, and on the reusability of model components. We introduce the principal design of the simulator and give the results related to its lookahead.
The proceedings contain 36 papers. The special focus in this conference is on Experimental Tools, Theoretical Tools, Probabilistic Computational Models, Computer simulation, Sequence Design and Algorithms. The topics ...
ISBN:
(纸本)3540437754
The proceedings contain 36 papers. The special focus in this conference is on Experimental Tools, Theoretical Tools, Probabilistic Computational Models, Computer simulation, Sequence Design and Algorithms. The topics include: An object oriented simulation of real occurring molecular biological processes for DNA computing and its experimental verification;towards optimization of PCR protocol in DNA computing;DNA computing in microreactors;cascadable hybridisation transfer of specific DNA between microreactor selection modules;boundary components of thickened graphs;population computation and majority inference in test tube;biomolecular computation in virtual test tubes;developing support system for sequence design in DNA computing;an evolutionary algorithm for optimizing bit set selection;solving knapsack problems in a sticker based model;a proposal of DNA computing on beads with application to sat problems;aqueous solutions of algorithmic problems;solutions of shortest path problems by concentration control;another realization of aqueous computing with peptide nucleic acid;experimental conformation of the basic principles of length-only discrimination;experimental construction of very large scale DNA databases with associative search capability;a realization of information gate by using enterococcus faecalis pheromone system;programmed mutagenesis is a universal model of computation;DNA-based parallel computation of simple arithmetic;variants with an enhanced membrane handling;towards an electronic implementation of membrane computing and a universal time-varying distributed h system of degree.
parallelsimulations using optimistic synchronization strategies such as Time Warp, operate with no regard to global synchronization since this results in greater parallelism and lower synchronization cost. However, l...
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ISBN:
(纸本)9780769516080
parallelsimulations using optimistic synchronization strategies such as Time Warp, operate with no regard to global synchronization since this results in greater parallelism and lower synchronization cost. However, like virtual memory, the parallel simulators may end up thrashing instead of performing useful work. The complication in using a Time Warp simulator is then to configure it suitably for good performance and avoid thrashing. Unfortunately, the optimal configuration is not generally static among different applications or even throughout an entire run of a single application. Thus, online feedback control systems are deployed to govern the adjustment of input parameters in our Time Warp simulation kernel. The design and implementation of effective feedback control systems can be difficult; the extra processing is pure overhead that must be absorbed by any performance gains delivered. The problem is further complicated when attempting to build a simulation kernel that is designed efficiently to operate with many different applications. In this paper, we introduce a control-centric architecture that is used to monitor and manage different parts of a Time Warp simulator. Specifically, we extend concepts from control theory such as adaptive control and stability, to better understand and design hierarchically-distributed run-time control systems for Time Warp based parallelsimulation.
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)9780769516080
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.
We investigate the causality issue in distributed virtual environments. Causality has been widely studied in parallel and distributed systems. However, most of the work in causality detection and preservation are from...
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ISBN:
(纸本)9780769516080
We investigate the causality issue in distributed virtual environments. Causality has been widely studied in parallel and distributed systems. However, most of the work in causality detection and preservation are from a logical time system point of view, which are not generally suitable for distributed virtual environments due to the high cost of the proposed schemes to preserve causality. In this paper, first, critical causal order is defined, which is a relaxation of the "happened before"-based causal relation. Then, causal receive order delivery is proposed with the advantage that both the real-time property of distributed virtual environments and the critical causal order relationship among events are preserved. Finally, an algorithm to achieve causal receive order delivery is given. Our algorithm is easy to implement, and it results in little extra traffic on the network.
We present a case study in which we apply parallelsimulation methods and interoperability techniques to network simulations for simulation-based on-line control of military communication networks. The on-line simulat...
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ISBN:
(纸本)9780769516080
We present a case study in which we apply parallelsimulation methods and interoperability techniques to network simulations for simulation-based on-line control of military communication networks. The on-line simulations model actual military networks, including wired shipboard sub-networks connected via satellite links, and wireless mobile devices. The modeled scenario depicts the communication requirements of an amphibious landing where a complex network connects troops ashore and naval vessels. The simulations use a heterogeneous set of tools, including ns2 models for shipboard wired networks, and GloMoSim models for the wireless devices. In this paper, we document the challenges we encountered in applying parallel and interoperable simulation methods, and describe our solutions. We describe our experiences in addressing the interoperability problems that naturally arose due to the heterogeneity of scenario models. We also present a preliminary study on the scalability of real-time performance of parallel network simulations, which is crucial for on-line simulations. Salient system characteristics of the subject military network scenarios are described for the benefit of exposure to the modeling and simulation research community. Our exercise not only highlights the relevance of parallel and distributedsimulation techniques to an important real-life problem, but also demonstrates the feasibility of applying those techniques in a practical setting.
Lookback is defined as the ability of a logical process to change its past locally (without involving other logical processes). Logical processes with lookback are able to process out-of-timestamp order events, enabli...
ISBN:
(纸本)9780769516080
Lookback is defined as the ability of a logical process to change its past locally (without involving other logical processes). Logical processes with lookback are able to process out-of-timestamp order events, enabling new synchronization protocols for the parallel discrete event simulation. Two of such protocols, LB-GVT (LookBack-Global Virtual Time) and LB-EIT (LookBack-Earliest Input Time), are presented and their performance on the Closed Queuing Network (CQN) simulation is discussed. We also discuss in detail the relation between lookahead and lookback. Finally, we demonstrate that lookback allows conservative simulations to circumvent the speedup limit imposed by the critical path.
In this paper we discuss and compare three differentcausality inconsistency tracking mechanisms in support ofpreemptive rollback in optimistic parallelsimulation onmyrinet clusters. These mechanisms exhibit different...
ISBN:
(纸本)9780769518534
In this paper we discuss and compare three differentcausality inconsistency tracking mechanisms in support ofpreemptive rollback in optimistic parallelsimulation onmyrinet clusters. These mechanisms exhibit different communication/processing overhead and also different effectivenessin revealing causality inconsistency of the currentlyexecuted simulation event. By the results of an empiricalstudy on a classical simulation benchmark we have foundsome trade-offs between these mechanisms, pointing out indicationsof application contexts for which each mechanismis expected to be well tailored.
A technique called updateable simulations is proposed to reduce the time to complete multiple executions of a discrete event simulation program. This technique updates the results of a prior simulation run rather than...
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ISBN:
(纸本)9780769516080
A technique called updateable simulations is proposed to reduce the time to complete multiple executions of a discrete event simulation program. This technique updates the results of a prior simulation run rather than re-execute the entire simulation to take into account variations in the underlying simulation model. A framework for creating updateable simulations is presented. This framework is applied to the problem of simulating a set of cascaded ATM multiplexers and a network of ATM switches. Performance measurements of sequential and parallel implementations of these simulations on a shared memory multiprocessor are presented, demonstrating that updateable simulations can yield substantial reductions in the time required to complete multiple simulation runs if there is much similarity among the runs.
Rapid growth in wireless communication systems motivates the development of technology supporting the simulation of large-scale wireless systems. However, it is widely recognized that wireless communications do not ha...
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ISBN:
(纸本)9780769516080
Rapid growth in wireless communication systems motivates the development of technology supporting the simulation of large-scale wireless systems. However, it is widely recognized that wireless communications do not have substantial "lookahead" needed by conservative synchronization protocols. This paper focuses on identifying and exploiting lookahead for such models. We find lookahead in three ways, exploiting characteristics of low power networks, the transceiver logic, and the way in which protocol stacks are typically constructed. We show how these observations allow a variety of conservative synchronization protocols to take advantage of lookahead, describe a synchronization method we use, and empirically examine the performance this method offers on a large-scale simulation of a sensor network intended for homeland defense scenarios
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