The proceedings contain 40 papers. The topics discussed include: fair and efficient dead reckoning-based update dissemination for distributed virtual environments;multi-level parallelism for time- and cost-efficient p...
ISBN:
(纸本)9780769547145
The proceedings contain 40 papers. The topics discussed include: fair and efficient dead reckoning-based update dissemination for distributed virtual environments;multi-level parallelism for time- and cost-efficient parallel discrete event simulation on GPUs;dynamically adjusting core frequencies to accelerate time warp simulations in many-core processors;HLA-based parallelsimulation: a case study;cloud-based simulation: the state-of-the-art computer simulation paradigm;vector time management based on topology information for HLA/RTI;a simplified belonging tree for optimizing information transmission on large-scale distributedsimulations;performance analysis of a multithreaded PDEs simulator on multicore clusters;enhancement of collaborative interest management mechanism for P2P networked virtual environment;parallelsimulation of large-scale artificial society on CPU/GPU mixed architecture;and SEMSim: a distributed architecture for multi-scale traffic simulation.
This paper focuses on conservative simulation using distributed-shared memory for inter-processor communication. JavaSpaces, a special service of Java Jini, provides a shared persistent memory for simulation message c...
ISBN:
(纸本)0769516084
This paper focuses on conservative simulation using distributed-shared memory for inter-processor communication. JavaSpaces, a special service of Java Jini, provides a shared persistent memory for simulation message communication among processors. Two benchmark programs written using our SPaDES/Java parallelsimulation library are used. The first program is a linear pipeline system representing a loosely-coupled open system. The PHOLD program represents a strongly-connected closed system. Experiments are carried out using a cluster of Pentium II PCs. We used a combination of Wood Turner carrier null, flushing and demand-driven algorithms for null message synchronization. To optimize message communication, we replace SPaDES/Java inter-processor communication implemented using Java's Remote Method Invocation (RMI) with one JavaSpace. For PHOLD (16x16, 16) running on eight processors, this change reduces simulation runtime by more than half, null message overhead reduces by a further 15%, and event rate more than doubled. Based on our memory analysis methodology, the memory, cost of null message synchronization for PHOLD is less than 9% of the total memory needed by, the simulation.
In this paper the performance of the Chandy-Misra algorithm in distributedsimulation has been studied in the context of a particular simulation applications a cellular network. The logical process structure under the...
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ISBN:
(纸本)0818684577
In this paper the performance of the Chandy-Misra algorithm in distributedsimulation has been studied in the context of a particular simulation applications a cellular network. The logical process structure under the algorithm is modified in such a way that the excessive synchronisation caused by the algorithm can be avoided. The synchronisation is minimised by reducing the number of connections between logical processes (LP). The concept of a neighbourhood of an LP is defined in such way that an LP is connected via logical channels only to those LPs that belong to its neighbourhood. A broadcast messages method is proposed to solve the communication between non-connected logical processes, i.e. those outside the neighbourhood. simulation experiments are carried out in a previously implemented distributedsimulation environment, Diworse. A GSM network is used as a simulation application where target of the simulation is to obtain estimates for the channel utilisation. Carrier per interference (C/I) values for GSM channels are used for determining the need for handovers. Execution time of the simulation and deviations in the C/I values are measured for completely connected and broadcast message methods in order to find but the effect of connection reduction. The results indicate that the broadcast messages method enables significantly faster simulation. With the GSM application the proposed method has only a negligible distorting effect to the simulation.
Synchronization is a significant cost in many parallel programs, and can be a major bottleneck if it is handled in a centralized fashion using traditional shared-memory constructs such as barriers. In a parallel time-...
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ISBN:
(纸本)1565550552
Synchronization is a significant cost in many parallel programs, and can be a major bottleneck if it is handled in a centralized fashion using traditional shared-memory constructs such as barriers. In a parallel time-stepped simulation, the use of global synchronization primitives limits scalability, increases the sensitivity to load imbalance, and reduces the potential for exploiting locality to improve cache behavior. This paper presents the results of an initial one-application study quantifying the costs and performance benefits of distributed, nearest neighbors synchronization. The application studied, MP3D, is a particle-based wind tunnel simulation. Our results for this one application on current shared-memory multiprocessors show a significant decrease in synchronization time using these techniques. We prototyped an application-independent library that implements distributed synchronization. The library allows a variety of parallelsimulations to exploit these techniques without increasing the application programming beyond that of conventional approaches.
In traditional distributedsimulation schemes, entire simulation needs to be restarted if any of the participating LP crashes. This is highly undesirable for long running simulations. Some form of fault-tolerance is r...
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In traditional distributedsimulation schemes, entire simulation needs to be restarted if any of the participating LP crashes. This is highly undesirable for long running simulations. Some form of fault-tolerance is required to minimize the wasted computation. In this paper, a rollback based optimistic fault-tolerance scheme is integrated with an optimistic distributedsimulation scheme. In rollback recovery schemes, checkpoints are periodically saved on stable storage. After a crash, these saved checkpoints are used to restart the computation. We make use of the novel insight that a failure can be modeled as a straggler event with the receive time equal to the virtual time of the last checkpoint saved on stable storage. This results in saving of implementation efforts, as well as reduced overheads. We define stable global virtual time (SGVT), as the virtual time such that no state with a lower timestamp will ever be rolled back despite crash failures. A simple change is made in existing GVT algorithms to compute SGVT. Our use of transitive dependency tracking eliminates antimessages. LPs are clubbed in clusters to minimize stable storage access time.
A flexible simulator has been developed to simulate a two-level metropolitan area network which uses wormhole routing. To accurately model the nature of wormhole routing, the simulator performs discrete-byte rather th...
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A flexible simulator has been developed to simulate a two-level metropolitan area network which uses wormhole routing. To accurately model the nature of wormhole routing, the simulator performs discrete-byte rather than discrete-packet simulation. Despite the increased computational workload that this implies, it has been possible to create a simulator with acceptable performance by writing it in Maisie, a parallel discrete-event simulation language. The simulator provides an accurate model of an actual high-speed, source-routing, wormhole network (the Murinet) and is the first such simulator. The paper describes the simulator and reports on the performance of parallel implementations of the simulator on a 24-node IBM SP 2 multicomputer. The parallel implementations yielded reasonable speedups. For instance, on 12 nodes, the conservative algorithm yielded a speed-up of about 6 whereas an optimistic algorithm yielded a speed-up of about 4.
The Local Time Warp (LTW) model was one of the novel approaches to distributedsimulation presented in early 90s. While several similar schemes had emerged afterwards, no implementation and performance analysis of LTW...
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ISBN:
(纸本)9780769528984
The Local Time Warp (LTW) model was one of the novel approaches to distributedsimulation presented in early 90s. While several similar schemes had emerged afterwards, no implementation and performance analysis of LTW were offered. This paper provides an implementation and performance analysis of the Local Time Warp model on a Beowulf Cluster using Message Passing Interface (MPI). Cluster computing matches well with the Local Time Warp model due to its partitioning of the simulation entities and assigning them to clusters of processors. This paper presents a distributedsimulation engine called BG-LTW which is a clustered-based implementation of the model. Further, the implementation features and its performance are provided. The obtained results suggest that for large-scale simulations local time warp outperforms its global counterpart.
Over-optimistic execution has long been identified as a major performance bottleneck in Time Warp based parallelsimulation systems. An appropriate throttle or control of optimism can improve performance by reducing t...
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Over-optimistic execution has long been identified as a major performance bottleneck in Time Warp based parallelsimulation systems. An appropriate throttle or control of optimism can improve performance by reducing the number of rollbacks. However, the design of an appropriate throttle is a difficult task, as correct computations on the critical path may be blocked, thus increasing the overall execution time. In this paper we build a cost model for throttled execution that involves both rollback probability and probability for an event computation being on the critical path. The model can estimate an appropriate size of time window for a throttled execution using statistics collected from the purely optimistic execution. The model is validated by an experimental study with a set of synthetic workloads.
The event horizon is a very important concept that is useful for both parallel and sequential discrete-event simulations. By exploiting the event horizon, parallelsimulations can process events in a manner that is ri...
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ISBN:
(纸本)9781565550278
The event horizon is a very important concept that is useful for both parallel and sequential discrete-event simulations. By exploiting the event horizon, parallelsimulations can process events in a manner that is risk-free (i.e., no antimessages) in adaptable “breathing” time cycles with variable time widths. Additionally, exploiting the event horizon can greatly reduce the event list management overhead that is common to virtually all discrete-event *** paper develops an analytic model describing the event horizon from first principles using equilibrium considerations and the hold model (where each event, when consumed, generates a single new event with future-time statistics described by a known probability function). Exponential and Beta-density functions are used to verify the mathematics presented in this paper.
Faster-than-real-time simulation (FRTS) can be used for the performance evaluation of systems behavior in real time, providing significant capabilities for studying systems with a time-varying behavior. FRTS enables m...
ISBN:
(纸本)0769516084
Faster-than-real-time simulation (FRTS) can be used for the performance evaluation of systems behavior in real time, providing significant capabilities for studying systems with a time-varying behavior. FRTS enables model validation through comparing simulation results with the corresponding system observations. However, experimentation proves to be rather demanding, as both delivering output results and ensuring their reliability must be accomplished within a predetermined time frame. Output analysis of system observations and model results and relevant timing issues are discussed. A method is introduced that determines whether it is possible to execute the "optimal" faster-than-real-time experiment, in which case multiple replications are scheduled for execution, or a compromise has to be made between the ability to predict for the long future and the degree of reliability achieved for predictions. FRTS experimental results are also presented to support the effectiveness of the proposed method.
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