Load balancing is a crucial factor in achieving good performance for parallel discrete event simulations. We present a load balancing scheme that combines both static partitioning and dynamic load balancing. The stati...
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Load balancing is a crucial factor in achieving good performance for parallel discrete event simulations. We present a load balancing scheme that combines both static partitioning and dynamic load balancing. The static partitioning scheme maps simulation objects to logical processes before simulation starts while the dynamic load balancing scheme attempts to balance the load during runtime. The static scheme involves two steps. First, the simulation objects that contribute to small lookahead are merged together by using a merging algorithm. Then a partitioning algorithm is applied. The merging is needed to ensure a consistent performance for our dynamic scheme. Our dynamic scheme is tailor-made for an asynchronous simulation protocol that does not rely on null messages. The performance study on a supply chain simulation shows that the partitioning algorithm and dynamic load balancing are important in achieving good performance.
Testing distributed applications over the Internet is fraught with problems: due to the inability, to control a wide area network consistent, reproduceable performance experiments are not possible. Here a system is de...
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Testing distributed applications over the Internet is fraught with problems: due to the inability, to control a wide area network consistent, reproduceable performance experiments are not possible. Here a system is described that uses a parallel discrete event simulator that can act as a real-time network emulator. Real Internet Protocol (IP) traffic generated by application programs running on user workstations can interact with modelled traffic in the emulator, thus providing a controlled test environment for distributed applications. parallel execution enables the emulator to simulate large virtual networks and to model traffic interactions that could not be done in real-time sequentially. This paper gives an overview of the emulator and explores the various external data routing methods that the emulator supports. These routing methods allow the emulator to be operated in shared environments with certain constraints, as well as in dedicated test environments. Preliminary performance results are included.
We introduce a new time warp system called ROSS: Rensselaer's Optimistic simulation System. ROSS is an extremely modular kernel that is capable of achieving event rates as high as 1,250,000 events per second when ...
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We introduce a new time warp system called ROSS: Rensselaer's Optimistic simulation System. ROSS is an extremely modular kernel that is capable of achieving event rates as high as 1,250,000 events per second when simulating a wireless telephone network model (PCS) on a quad processor PC server. In a head-to-head comparison, we observe that ROSS out performs the Georgia Tech Time Warp (GTW) system on the same computing platform by up to 180%. ROSS only requires a small constant amount of memory buffers greater than the amount needed by the sequential simulation for a constant number of processors. The driving force behind these high-performance and low memory utilization results is the coupling of an efficient pointer-based implementation framework, Fujimoto's (1989) fast GVT algorithm for shared memory multiprocessors, reverse computation and the introduction of kernel processes (KPs). KPs lower fossil collection overheads by aggregating processed event lists. This aspect allows fossil collection to be done with greater frequency, thus lowering the overall memory necessary to sustain stable, efficient parallel execution.
Several scheduling algorithms have been proposed to determine the next event to be executed on a processor in a time warp parallel discrete event simulation. However none of them is specifically designed for simulatio...
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Several scheduling algorithms have been proposed to determine the next event to be executed on a processor in a time warp parallel discrete event simulation. However none of them is specifically designed for simulations where the execution time (or granularity) for different types of events has large variance. We present a grain sensitive scheduling algorithm which addresses this problem. In our solution, the scheduling decision depends on both timestamp and granularity values with the aim at giving higher priority to small grain events even if their timestamp is not the lowest one (i.e. the closest one to the commitment horizon of the simulation). This implicitly limits the optimism of the execution of large grain events that, if rolled back, would produce a large waste of CPU time. The algorithm is adaptive in that it relies on the dynamic recalculation of the length of a simulated time window within which the timestamp of any good candidate event for the scheduling falls in. If the window length is set to zero, then the algorithm behaves like the standard Lowest-Timestamp-First (LTF) scheduling algorithm. simulation results of a classical benchmark in several different configurations are reported for a performance comparison with LTF: these results demonstrate the effectiveness of our algorithm.
Summary form only given. It has been a little less than ten years since modeling and simulation (M&S) hit the knee on the curve. During these past few years a great deal of marketing of the potential of M&S ha...
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Summary form only given. It has been a little less than ten years since modeling and simulation (M&S) hit the knee on the curve. During these past few years a great deal of marketing of the potential of M&S has occurred, which resulted in a significant influx of funding for research and development (R&D) projects, especially in the area of distributedsimulation. One of the significant experiments in this area-the DARPA Synthetic Theater of War program-officially ended, bringing to an end one of the more robust experiments in distributedsimulation. We are now in a time where most of the M&S funding is targeted at production programs, with much fewer dollars going into R&D or experimentation. Although it is good that major programs are capitalizing on previous R&D efforts, it would not be true to say that the necessary R&D has been completed to realize the vision of distributedsimulation. It would be true to say that we now have a much better understanding of the issues. What is needed now is a period of reflection on the vision, where we are, what was done right, what hasn't worked well, and where we should be headed for the next five to ten years.
The proceedings contain 12 papers. The topics discussed include: WATIS2: design and application of an environment simulation system for test improvement of control software for automatic logistic systems;preliminary i...
ISBN:
(纸本)0769508375
The proceedings contain 12 papers. The topics discussed include: WATIS2: design and application of an environment simulation system for test improvement of control software for automatic logistic systems;preliminary investigations into distributed computing applications on a beowulf cluster;distributedsimulation over loosely coupled domains;distributed engineering plant simuiatiod stimulation environment accreditation of accuracy;scheduling for very large virtual environments and networked games using visibility and priorities;exploiting temporal uncertainty in time warp simulations;dynamic grid-based multicast group assignment in data distribution management;a hybrid approach to data distribution management;state of the HLN RTI;adapting a supply-chain simulation for HLA;a generic rollback manager for optimistic HLA simulations;HLA-based simulation within an interactive engineering environment;and an approach for stream retrieval over HLA-RTI in distributed virtual environments.
Recent demand for mobile telephone service have been growing rapidly while the electro-magnetic spectrum of frequencies allocated for this purpose remain limited. Any solution to the channel assignment problem is subj...
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ISBN:
(纸本)1581133049
Recent demand for mobile telephone service have been growing rapidly while the electro-magnetic spectrum of frequencies allocated for this purpose remain limited. Any solution to the channel assignment problem is subject to this limitation, as well as the interference constraints between adjacent channels in the spectrum. Channel allocation schemes provide a flexible and efficient access to bandwith in wireless and mobile communication systems. In this paper, we present an efficient distributed algorithm for dynamic channel allocation based upon multual exclusion model, where the channels are grouped by the number of cells in a cluster and each group of channels can not be shared concurrently within the cluster. We describe the algorithm, and report its performance several channel systems using different types of call arrival patterns. Our results indicate that significant low denial rate, low message complexity and low acquisition time can be obtained using our algorithm.
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