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proceedings of the thirteenth workshop on parallel and distributed simulation

作者： Ernest H. Page The MITRE Corporation 1820 Dolley Madison Boulevard McLean VA

This year's installment of the PADS "community assessment" looks at previous assessments and considers some current directions in distributed simulation and their possible relationship to PADS.

ISBN: (纸本)9780769501550

This year's installment of the PADS "community assessment" looks at previous assessments and considers some current directions in distributed simulation and their possible relationship to PADS.

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Fast-software-checkpointing in optimistic simulation: embedding state saving into the event routine instructions

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 118-125页

作者： Quaglia, Francesco Universita' di Roma 'La Sapienza' Roma Italy

In this paper we present a software approach, namely Fast-Software-Checkpointing (FSC), to reduce the running time of the state saving protocol in optimistic parallel discrete event simulation. The idea behind FSC is to use the instructions performed during the execution of an event as part of the state saving protocol, hence the total number of instructions due to state saving is reduced. Under FSC the time for saving the state of a logical process prior to the execution of an event e requires an amount of time proportional to be amount of state variables not updated by e's execution, as only these variables must be copied. This outlines that FSC shows some dualism with respect to incremental state saving. We show, however, that there exists a basic difference between the two solutions as in FSC some of the state saving instructions are actually event routine instructions, while in incremental state saving they are only added and mixed to the latter ones. We also present a simple software architecture to support FSC and simulation results to demonstrate the effectiveness of such solution. The obtained data show that FSC, combined with a sparse state saving strategy, may represent the best checkpointing solution in case of both medium/small state granularity simulations and large state granularity simulations even with small (but non-minimal) portions of the state updated by event execution. FSC may result therefore suited for a wide class of simulation problems.

关键词： Computer simulation

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Experience in retrofitting a large sequential Ada simulator to two versions of time warp

Proceedings of the Workshop on Parallel and Distributed Simu...

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proceedings of the workshop on parallel and distributed simulation, PADS 1999年 74-81页

作者： Smith, Ray Andress, Randal Parsons, George M. TRW Systems & Information Technology Group

The Extended Air Defense Testbed (EADTB), is a comprehensive, high- and mixed-level-of-detail, environment for modeling weapon system entities and interactions. Due to the complexity of the models and large scenario sizes, in its current single-threaded form, EADTB is limited in run-time speed. Our goal is to speed up the simulation without re-architecture or re-implementation of the models which comprise 1.76 million lines of Ada code, and without altering model behavior or compromising repeatability and causality. Our work demonstrates that the use of 'optimistic scheduling' techniques and its derivatives, offers the best alternative for object-based systems like EADTB. Specifically we have retrofitted and integrated the same representative pseudo-EADTB prototype with two different object-oriented optimistic scheduling engines (SPEEDES and TEMPO/Thema). We discuss the required architectural and behavioral features of a simulation to allow this retrofit, the issues of C++ to Ada language interfaces, and the employment of the basic services of the optimistic scheduling engines in this environment. Experimental results suggest that order-of-magnitude speed-up is feasible through parallelization, and is scalable to larger experiments simply by adding hardware.

关键词： Computer simulation languages

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Performance of dynamic load balanced join algorithms in shared disk parallel database systems

Performance of dynamic load balanced join algorithms in shar...

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IEEE workshop on Future Trends of distributed Computing Systems

作者： Aekyung Moon Kyungho On Haengrae Cho Department of Computer Engineering Yeungnam University Kyongbuk South Korea

ISBN: (纸本)076950468X

parallel database systems are the key to high performance database processing. In this paper, we propose parallel join algorithms in shared disk parallel database systems, where all coupled nodes are connected via a high-speed network and share a common database at the disk level. The proposed algorithms are novel in the sense that they can provide a higher potential for dynamic load balancing with the inherent flexibility of the shared disk architecture. Using a parallel database simulation model, we evaluate the performance of the proposed algorithms under a wide variety of system configurations and database workloads.

关键词： Database systems Partitioning algorithms Tin Query processing High-speed networks Load management Moon Concurrent computing Data engineering Transaction databases

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Specification and simulation of a concurrent real-time system

International Workshop on Software Engineering for Parallel ...

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International workshop on Software Engineering for parallel and distributed Systems, proceedings 1999年 197-204页

作者： Li, Xiaoshan Univ of Macau Macau China

Interval Temporal Logic (ITL) is real-time logic for specifying and verifying real-time systems. In this paper, ITL is used to specify a concurrent real-time system: assembly line which is an abstract model of industrial robot control systems. We can specify the abstract properties of the system in ITL as well as the system design using the executable subset of ITL, Tempura. Comparing with other approaches, the first advantage of this methodology is that the concurrent real-time systems can be naturally specified in true concurrent model rather than interleaving model. The second is that the specification of system design is executable so that the simulation can be obtained in the same formal framework. Therefore, both the properties of the system and the consistency of specification can be checked before verification.

关键词： Real time systems

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Scheduling critical channels in conservative parallel discrete event simulation

Scheduling critical channels in conservative parallel discre...

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： Z. Xiao B. Unger R. Simmonds J. Cleary Computer Science Department University of Calgary Canada Comuter Science Department University of Waikato New Zealand

This paper introduces the Critical Channel Traversing (CCT) algorithm, a new scheduling algorithm for both sequential and parallel discrete event simulation. CCT is a general conservative algorithm that is aimed at the simulation of low-granularity network models on shared-memory multiprocessor computers. An implementation of the CCT algorithm within a kernel called TasKit has demonstrated excellent performance for large ATM network simulations when compared to previous sequential, optimistic and conservative kernels. TasKit has achieved two to three times speedup on a single processor with respect to a splay tree central-event-list based sequential kernel. On a 16 processor (R8000) Silicon Graphics PowerChallenge, TasKit has achieved an event-rate of 1.2 million events per second and a speedup of 26 relative to the sequential kernel for a large ATM network model. Performance is achieved through a multi-level scheduling scheme that supports the scheduling of large grains of computation even with low-granularity events. Performance is also enhanced by supporting good cache behavior and automatic load balancing. The paper describes the algorithm and its motivation, proves its correctness and briefly presents performance results for TasKit.

关键词： Kernel Processor scheduling Scheduling algorithm Computational modeling Discrete event simulation Computer simulation Computer networks Tree graphs Silicon Graphics

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Optimism: not just for event execution any more

Optimism: not just for event execution any more

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： C.H. Young R. Radhakrishnan P.A. Wilsey Department of ECECS University of Cincinnati Cincinnati OH USA

Optimism is a technique used by the Time Warp paradigm to make decisions about event execution under uncertainty. While the benefits of throttling the optimism of Time Warp have been studied, the benefits of extending optimism to operations besides event execution are presented. Specifically, we discuss how optimism can be mapped to fossil collection which has traditionally been assumed to be a non-recoverable operation that must be performed under global control. Optimistic Fossil Collection (OFC) is a technique for fossil collection that does not require global control. However, as states are fossil collected optimistically, a recovery mechanism is required to recover from errors. Performance results show that Time Warp using OFC can improve the performance of simulations on a network of workstations. Another benefit of OFC is that the simulation checkpoints provide for fault tolerance in more than just fossil collection.

关键词： Time warp simulation Uncertainty Optimization methods Protocols Workstations Fault tolerant systems Discrete event simulation Contracts Checkpointing Memory management

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Exploiting temporal uncertainty in parallel and distributed simulations 99

Exploiting temporal uncertainty in parallel and distributed ...

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proceedings of the thirteenth workshop on parallel and distributed simulation

作者： Richard M. Fujimoto College of Computing Georgia Institute of Technology Atlanta GA

ISBN: (纸本)9780769501550

parallel discrete event simulation algorithms are usually based on time stamp ordering of events. distributed virtual environment (DVE) applications such as DIS typically use unordered event delivery. A partial order called approximate time (AT) is proposed to order events in both domains, facilitating reuse of simulations across DVE and analysis applications. A variation on AT-order called approximate time causal (ATC) order is also described. Synchronization algorithms to realize these orderings are presented as well as performance measurements on a workstation cluster. A long-term goal of this work is to use AT and ATC order to exploit temporal uncertainty in the model to achieve efficient conservative parallel simulation despite little or no lookahead, a longstanding problem in the field.

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On the performance of nearest-neighbors load balancing algorithms in parallel systems

On the performance of nearest-neighbors load balancing algor...

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Euromicro workshop on parallel and distributed Processing

作者： A. Cortes A. Ripoll M.A. Senar P. Pons E. Luque Computer Architectures and Operating Systems Group Universitat Autònoma Barcelona Barcelona Spain

DASUD (Diffusion Algorithm Searching Unbalanced Domains) is a totally distributed load-balancing algorithm which belongs to the nearest-neighbors class. DASUD detects unbalanced domains (a processor and its immediate neighbors) and corrects this situation by allowing load movements between non-connected processors. DASUD has been evaluated by comparison with two well-known nearest-neighbors load balancing strategies, namely, the GDE (Generalized Dimension Exchange) and the SID (Sender Initiated Diffusion) by considering a large set of initial load distributions. These distributions were applied to ring, tents and hypercube topologies, and the number of processors ranged from 8 to 128. From these experiments we have observed that DASUD outperforms the other strategies used in the comparison as it provides the best trade-off between the balance degree obtained at the final state and the number of iterations required to reach this state.

关键词： Load management Iterative algorithms Concurrent computing Computer architecture Operating systems Topology parallel processing Plasma simulation Partial differential equations distributed computing

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Fast-software-checkpointing in optimistic simulation: embedding state saving into the event routine instructions

Fast-software-checkpointing in optimistic simulation: embedd...

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workshop on Principles of Advanced and distributed simulation (PADS)

作者： F. Quaglia Dipartimento di Informatica e Sistemistica Università di Roma La Sapienza Roma Italy

We present a software approach, namely fast-software-checkpointing (FSC), to reduce the running time of the state saving protocol in optimistic parallel discrete event simulation. The idea behind FSC is to use the instructions performed during the execution of an event as part of the state saving protocol, hence the total number of instructions due to state saving is reduced. Under FSC the time for saving the state of a logical process prior to the execution of an event E requires an amount of time proportional to the amount of state variables not updated by E's execution, as only these variables must be copied. This outlines that FSC shows some dualism with respect to incremental state saving. We show, however that there exists a basic difference between the two solutions as in FSC some of the state saving instructions are actually event routine instructions, while in incremental state saving they are only added and mixed to the latter ones. We also present a simple software architecture to support FSC and simulation results to demonstrate the effectiveness of such solution. The obtained data show that FSC, combined with a sparse state saving strategy may represent the best checkpointing solution in case of both medium/small state granularity simulations and large state granularity simulations even with small (but non-minimal) portions of the state updated by event execution. FSC may result therefore suited for a wide class of simulation problems.

关键词： Discrete event simulation Power capacitors Checkpointing Protocols Remuneration

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