The Hierarchical Tool HIT is a software tool for hierarchical modeling and performance evaluation of discrete event systems. Besides analytical and numerical solution techniques HIT provides the evaluation of models b...
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ISBN:
(纸本)0818679654
The Hierarchical Tool HIT is a software tool for hierarchical modeling and performance evaluation of discrete event systems. Besides analytical and numerical solution techniques HIT provides the evaluation of models by sequential simulation. Here we present concepts for optimistic distributedsimulation of HIT-models by partitioning them with respect to subhierarchies. The main goals of the concept being presented are the preservation of model structure even in lower levels of the realization (e.g. use of the process view of simulation throughout all levels of abstraction) and distribution transparency on the modeling level (homogeneous model specification for all solution techniques).
Large-scale ecological simulations are natural candidates for distributed discrete event simulation. In optimistic simulation of spatially explicit models, a difficult problem arises when individuals migrate between p...
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ISBN:
(纸本)0818679654
Large-scale ecological simulations are natural candidates for distributed discrete event simulation. In optimistic simulation of spatially explicit models, a difficult problem arises when individuals migrate between physical regions simulated by different logical processes. We present a solution to this problem that uses shared object states. Shared states allow for efficient communication between LPs and for early detection of canceled events. We briefly describe an optimistic simulation environment called EcoKit, which operates on top of the WarpKit implementation of Time Warp. Our experiments with this system on a shared memory multiprocessor show that EcoKit promises to scale well both with the number of processors and the number of individuals simulated.
The GRISSLi coupling interface is a runtime library designed for the coupled computation of grid-based multidisciplinary applications. Established simulation programs, which are deleted to a single discipline, can be ...
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ISBN:
(纸本)0769500595
The GRISSLi coupling interface is a runtime library designed for the coupled computation of grid-based multidisciplinary applications. Established simulation programs, which are deleted to a single discipline, can be interconnected to a complex simulation system via the GRISSLi coupling interface without recoding the participating programs. We introduce a data model to establish the links between the (dynamic) grids and the attached coupling values in a single application program and to establish the mappings between grids and coupling values among different application programs. The user-specified consistency model is realized ruing asynchronous communication based on the MPI message passing standard Efficient communication is achieved by pre-computing an optimized communication schedule and overlapping communication with computation. Flexible coupling algorithms with adaptive grids and branches are supported in GRISSLi. We have developed a prototype implementation, which provides language bindings in ANSI C and Fortran, and runs currently on IBM RS/6000 SP Gray T3E, SGI Origin/Octane and HP-V Class. We verify the functionality and evaluate the performance of our library rising an industry relevant pilot application, the steel strip production process.
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.
Although there exist many approaches for classification of computer architectures, no system is able to distinguish parallel computers adequately yet. The first part of this paper is a brief survey of the main charact...
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ISBN:
(纸本)0769500595
Although there exist many approaches for classification of computer architectures, no system is able to distinguish parallel computers adequately yet. The first part of this paper is a brief survey of the main characteristics of various parallel architecture concepts and several approaches of classification. We realized that the idea of defining a sharp classification system is questionable in the world of parallel computing. But we also recognized important structural similarities of computing systems. So we introduce a modeling system, called rho (recursive hierarchical objects), which allows to describe the structure Of various computing systems hierarchically. However we do not aim at a new classification system but at a scheme for modeling parallel architectures.
A probabilistic scheduling policy for selecting the next event to be processed by a processor during optimistic parallel discrete event simulation is presented. This policy exploits the knowledge about statistical dis...
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A probabilistic scheduling policy for selecting the next event to be processed by a processor during optimistic parallel discrete event simulation is presented. This policy exploits the knowledge about statistical distributions of the difference between the timestamps of successively committed events of a logical process. simulation results are presented to demonstrate that under appropriate conditions probabilistic scheduling generates substantially fewer number of rollbacks compared to the lowest timestamp first scheduling policy.
One of the six categories of management services provided in the Run Time Infrastructure (RTI) to federated simulations is Time Management. Currently, it provides only two message ordering policies, that is, time stam...
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ISBN:
(纸本)0769511058
One of the six categories of management services provided in the Run Time Infrastructure (RTI) to federated simulations is Time Management. Currently, it provides only two message ordering policies, that is, time stamp ordering and receive ordering. Temporal anomalies occurred during the execution of federation due to the heterogeneous latencies in the communication network are nor handled in receive ordering. While time stamp ordering eliminates the temporal anomalies entirely, it incurs great communication latency and huge bandwidth requirement. This paper presents a new time management mechanism which provides a less costly message ordering service, namely causal ordering, to federates. It does not require the specification of lookahead and allows federates that do not require stringent message ordering properties to achieve much more efficient execution. A series of experiments has been carried out to benchmark the performance of this new time management mechanism and the results show that it incurs a slight overhead compared to receive ordering mechanism but achieves significant performance improvement over time stamp ordering mechanism.
We present a new conservative event-synchronization protocol, time-based synchronization, for parallel discrete-event simulation of mobile ad hoc wireless networks. Simulators that use our protocol proceed at a scaled...
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ISBN:
(纸本)0769520367
We present a new conservative event-synchronization protocol, time-based synchronization, for parallel discrete-event simulation of mobile ad hoc wireless networks. Simulators that use our protocol proceed at a scaled version of real time and send messages that correspond only to transmissions in the simulated network. We show that such simulators can maintain a constant execution time even as the sizes of the networks that they simulate grow. Moreover we show that these simulators, when executed on a custom parallel architecture, are capable of simulating many networks faster than real time.
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.
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