Time Warp's optimistic scheduling requires the maintenance of simulation state history to support rollback in the event of causality violations. State history, and the ability to rollback the simulation, can provi...
ISBN:
(纸本)9780818679650
Time Warp's optimistic scheduling requires the maintenance of simulation state history to support rollback in the event of causality violations. State history, and the ability to rollback the simulation, can provide unique functionality for human-in-the-loop simulation environments. This paper investigates the use of Time Warp to output valid simulation state in a near real-time manner, re-execute portions of the simulation, and interactively probe simulation values to ascertain underlying causes of transient behavior.A shared-memory, multi-threaded interactive simulation architecture is presented and the additional state saving requirements imposed by interactivity are examined. The shortcomings of existing state saving schemes lead us to propose Multiplexed State Saving (MSS). By interleaving checkpointing and incremental state logs MSS provides bounded rollback costs and asynchronous access to prior simulation state. The interaction algorithms and MSS form a scalable, bounded cost component suitable for use in a real-time interactive Time Warp system.
The proceedings contains 24 papers. Topics discussed include load balancing in parallelsimulation, asynchronous transfer mode networks, computer architecture, state saving and synchronization in parallelsimulation, ...
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The proceedings contains 24 papers. Topics discussed include load balancing in parallelsimulation, asynchronous transfer mode networks, computer architecture, state saving and synchronization in parallelsimulation, granularity and partitioning, logic circuits, queueing models, VHDL simulation.
Presented is a conservative algorithm for the parallelsimulation of billiard balls. A spatial approach to these simulations is commonly employed, in which the billiard table is partitioned into segments which are sim...
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Presented is a conservative algorithm for the parallelsimulation of billiard balls. A spatial approach to these simulations is commonly employed, in which the billiard table is partitioned into segments which are simulated by different processors. The conservative algorithm differs from previous approaches in that it makes use of shared variables to enable processors to ascertain the state of the computation at neighboring processors. The shared variable corresponds to a region at the boundary of the table segments. By making use of shared variables a significant speed-up is obtained.
Advances in massively parallel platforms are increasing the prospects for high performance discrete event simulation. Still the difficulty in parallel programming persists and there is increasing demand for high level...
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Advances in massively parallel platforms are increasing the prospects for high performance discrete event simulation. Still the difficulty in parallel programming persists and there is increasing demand for high level support for building discrete event models to execute on such platforms. We present a parallel DEVS-based (Discrete Event System Specification) simulation environment that can execute on distributed memory multicomputer systems with bench-marking results of a class of high resolution, large scale ecosystem models. Underlying the environment is a parallel container class library for hiding the details of message passing technology while providing high level abstractions for hierarchical, modular DEVS models. The C++ implementation working on the Thinking Machines CM-5 demonstrates that the desire for high level modeling support need not be irreconcilable with sustained high performance.
A new conservative algorithm for both parallel and sequential simulation of networks is described. The technique is motivated by the construction of a high performance simulator for ATM networks. It permits very fast ...
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A new conservative algorithm for both parallel and sequential simulation of networks is described. The technique is motivated by the construction of a high performance simulator for ATM networks. It permits very fast execution of models of ATM systems, both sequentially and in parallel. A simple analysis of the performance of the system is made. Initial performance results from parallel and sequential implementations are presented and compared with comparable results from an optimistic TimeWarp based simulator. It is shown that the conservative simulator performs well when the 'density' of messages in the simulated system is high, a condition which is likely to hold in many interesting ATM scenarios.
We investigate conservative parallel discrete event simulations for logical circuits on shared-memory multiprocessors. For a first estimation of the possible speedup, we extend the critical path analysis technique by ...
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We investigate conservative parallel discrete event simulations for logical circuits on shared-memory multiprocessors. For a first estimation of the possible speedup, we extend the critical path analysis technique by partitioning strategies. To incorporate overhead due to the management of data structures, we use a simulation on an ideal parallel machine (PRAM). This simulation can be directly executed on the SB-PRAM prototype, yielding both an implementation and a basis for data structure optimizations. One of the major tools to achieve these is the SB-PRAM's hardware support for parallel prefix operations. Our reimplementation of the PTHOR program on the SB-PRAM yields substantially higher speedups than before.
Most experimental studies of the performance of parallelsimulation protocols use speedup or number of events processed per unit time as the performance metric. Although helpful in evaluating the usefulness of paralle...
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Most experimental studies of the performance of parallelsimulation protocols use speedup or number of events processed per unit time as the performance metric. Although helpful in evaluating the usefulness of parallelsimulation for a given simulation model, these metrics tell us little about the efficiency of the simulation protocol used. In this paper, we describe an Ideal simulation Protocol (ISP), based on the concept of critical path, which experimentally computes the best possible execution time for a simulation model on a given parallel architecture. Since ISP computes the bound by actually executing the model on the given parallel architecture, it is much more realistic than that computed by a uniprocessor critical path analysis. The paper illustrates, using parameterized synthetic benchmarks, how an ISP-based performance evaluation can lead to much better insights into the performance of parallelsimulation protocols than what would be gained from speedup graphs alone.
Models of ATM communication systems were simulated on massively parallel SIMD computer. Fast simulations of ATM models are needed because the regimes of interest usually involve high volumes of traffic and low failure...
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Models of ATM communication systems were simulated on massively parallel SIMD computer. Fast simulations of ATM models are needed because the regimes of interest usually involve high volumes of traffic and low failure rates. Unexpected practical and theoretical difficulties, partly due to the massive parallelism and SIMD aspects, were encountered;this paper shows how to cope with them. In a replica-parallelsimulation of an ATM system, large variations in computed statistics are caused by small differences in the distribution of employed random number generators. A comparison of these distributions using a secondary statistical measure served to disambiguate the results.
Recently, a considerable amount of effort in the U.S. Department of Defense has been devoted to defining the High Level Architecture (HLA) for distributedsimulations. This paper describes the time management componen...
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Recently, a considerable amount of effort in the U.S. Department of Defense has been devoted to defining the High Level Architecture (HLA) for distributedsimulations. This paper describes the time management component of the HLA that defines the means by which individual simulations (called federates) advance through time. Time management includes synchronization mechanisms to ensure event ordering when this is needed. The principal challenge of the time management structure is to support interoperability among federates using different local time management mechanisms such as that used in DIS, conservative and optimistic mechanisms developed in the parallelsimulation community, and real-time hardware-in-the-loop simulations.
Many systems rely on the ability to rollback (or restore) parts of the system state to undo or recover from undesired or erroneous computations. Examples of such systems include fault tolerant systems with checkpointi...
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Many systems rely on the ability to rollback (or restore) parts of the system state to undo or recover from undesired or erroneous computations. Examples of such systems include fault tolerant systems with checkpointing, editors with undo capabilities, transaction and data base systems and optimistically synchronized parallel and distributedsimulations. An essential part of such systems is the state saving mechanism. It should not only allow efficient state saving, but also support efficient state restoration in case of roll back. Furthermore, it is often a requirement that this mechanism is transparent to the user. In this paper we present a method to implement a transparent incremental state saving mechanism in an optimistically synchronized parallel discrete event simulation system based on the Time Warp mechanism. The usefulness of this approach is demonstrated by simulations of large, detailed, realistic FCA and a DCA-like cellular phone systems.
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