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.
A viable approach for building large-scale quantum computers is to interlink small-scale quantum computers with a quantum network to create a larger distributed quantum computer. When designing quantum algorithms for ...
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ISBN:
(纸本)9781728186740
A viable approach for building large-scale quantum computers is to interlink small-scale quantum computers with a quantum network to create a larger distributed quantum computer. When designing quantum algorithms for such a distributed quantum computer, one can make use of the added parallelization and distribution abilities inherent in the system. An added difficulty to then overcome for distributed quantum computing is that a complex control system to orchestrate the various components is required. In this work, we aim to address these issues. We explicitly define what it means for a quantum algorithm to be distributed and then present various quantum algorithms that fit the definition. We discuss potential benefits and propose a high-level scheme for controlling the system. With this, we present our software framework called Interlin-q, a simulation platform that aims to simplify designing and verifying parallel and distributed quantum algorithms. We demonstrate Interlin-q by implementing some of the discussed algorithms using Interlin-q and layout future steps for developing Interlin-q into a control system for distributed quantum computers.
We describe two major developments in the General Network simulation Integration System (Genesis): the support for BGP protocol in large network simulations and distribution of the simulation memory among Genesis comp...
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ISBN:
(纸本)0769519709
We describe two major developments in the General Network simulation Integration System (Genesis): the support for BGP protocol in large network simulations and distribution of the simulation memory among Genesis component simulations. Genesis uses a high granularity synchronization mechanism between parallelsimulations simulating parts of a network. This mechanism uses checkpointed simulation state to iterate over the same time interval until convergence. It also replaces individual packet data for flows crossing the network partitions with statistical characterization of such flows over the synchronization time interval. We had achieved significant performance improvement over the sequential simulation for simulations with TCP and UDP traffic. However, this approach can not be used directly to simulate dynamic routing protocols that use underlying network for exchanging protocol information, as no packets are exchanged in Genesis between simulated network parts. We have developed a new mechanism to exchange and synchronize BGP routing data among distributed Genesis simulators. The extended Genesis allows simulations of more realistic network scenarios, including routing flows, in addition to TCP or UDP data traffic. Large memory size required by simulation software hinders the simulation of large-scale networks. Based on our new support of distributed BGP simulation, we developed an approach to construct and simulate networks on distributed memory using Genesis simulators in such a way that each participating processor possesses only data related to the part of the network it simulates. This solution supports simulations of large-scale networks on machines with modest memory size.
A methodology and its associated algorithms are presented for mapping a novel, field-based vehicular mobility model onto graphical processing unit computational platform for simulating mobility in large-scale road net...
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ISBN:
(纸本)9780769537139
A methodology and its associated algorithms are presented for mapping a novel, field-based vehicular mobility model onto graphical processing unit computational platform for simulating mobility in large-scale road networks. Of particular focus is the achievement of real-time execution, on desktop platforms, of vehicular mobility on road networks comprised of millions of nodes and links, and multi-million counts of simultaneously active vehicles. The methodology is realized in a system called GARFIELD, whose implementation details and performance study are described The runtime characteristics of a prototype implementation are presented that show real-time performance in simulations of networks at the scale of a few states of the US road networks.
This paper describes two forms of feedback in the simulation runtime of VHDL circuits that greatly influences performance. While circuit feedback and strongly connected components have been observed and documented as ...
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This paper describes two forms of feedback in the simulation runtime of VHDL circuits that greatly influences performance. While circuit feedback and strongly connected components have been observed and documented as detrimental influences to conservative parallel discrete event simulation (PDES) efficiency, that influence has never been quantified. Moreover, in this study, the phenomenon of induced feedback [1] was observed to diminish speedup to the same degree as explicit feedback. In this paper the influence of feedback on simulation runtime is analyzed and an O(n) algorithm for its elimination is presented. In addition, a metric for the quantification of feedback is introduced. By measuring feedback, it is possible to balance its influence on simulation runtime with that of other factors (e.g. load balance, number of processors, machine granularity, etc.) through the use of a cost-based partitioning approach. This paper reports significant improvements in runtime for three circuits due to the prevention of feedback using the partitioning algorithm presented. In addition, strong correlation between the feedback metric and conservative parallelsimulation overhead is demonstrated.
Teaching topics related to high performance computing and parallel and distributed computing in a hands-on manner is challenging, especially at introductory, undergraduate levels. There is a participation challenge du...
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ISBN:
(纸本)9781728159751
Teaching topics related to high performance computing and parallel and distributed computing in a hands-on manner is challenging, especially at introductory, undergraduate levels. There is a participation challenge due to the need to secure access to a platform on which students can learn via hands-on activities, which is not always possible. There are also pedagogic challenges. For instance, any particular platform provided to students imposes constraints on which learning objectives can be achieved. These challenges become steeper as the topics being taught target more heterogeneous, more distributed, and/or larger platforms, as needed to prepare students for using and developing Cyberinfrastructure. To address the above challenges, we have developed a set of pedagogic activities that can be integrated piecemeal in university courses, starting at freshman levels. These activities use simulation so that students can experience hands-on any relevant application and platform scenarios. This is achieved by capitalizing on the capabilities of the WRENCH and SimGrid simulation frameworks. After describing our approach and the pedagogic activities currently available, we present results from an evaluation performed in an undergraduate university course.
The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs auto...
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The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs automatically support time-synchronized communications between CSIM submodels running on different processors. This paper describes extensions to U.P.S. that allow the user to assist U.P.S. by providing additional 'process lookahead,' thereby reducing the frequency of synchronizations. The use and effect on performance of process lookahead is described for several models. In a mobile cellular communications model, the use of process lookahead results in up to a 60% improvement in speedup on 32 nodes of the IBM SP2. A factor of 3 improvement is obtained on a closed queueing network simulation running on 32 nodes of the Intel Paragon.
It is well known that the critical path provides an absolute lower bound on the execution time of a conservative parallel discrete event simulation. It stands to reason that optimal execution time can only be achieved...
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It is well known that the critical path provides an absolute lower bound on the execution time of a conservative parallel discrete event simulation. It stands to reason that optimal execution time can only be achieved by immediately executing each event on the critical path. However, dynamically identifying the critical event is difficult, if not impossible. In this paper, we examine several heuristics that might help to determine the critical event, and conduct a performance study to determine the effectiveness of using these heuristics for preferential scheduling.
Synchronization is often the dominant cost in conservative parallelsimulation, particularly in simulations of parallel computers, in which low-latency simulated communication requires frequent synchronization. We pre...
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Synchronization is often the dominant cost in conservative parallelsimulation, particularly in simulations of parallel computers, in which low-latency simulated communication requires frequent synchronization. We present and evaluate local barriers and predictive barrier scheduling, two techniques for reducing synchronization overhead in the simulation of message-passing multicomputers. Local barriers use nearest-neighbor synchronization to reduce waiting time at synchronization points. Predictive barrier scheduling, a novel technique that schedules synchronizations using both compile-time and runtime analysis, reduces the frequency of synchronization operations. In contrast to other work in this area, both techniques reduce synchronization overhead without decreasing the accuracy of network simulation. These techniques were evaluated by comparing their performance to that of periodic global synchronization. Experiments show that local barriers improve performance by up to 24% for communication-bound applications, while predictive barrier scheduling improves performance by up to 65% for applications with long local computation phases. Because the two techniques are complementary, we advocate a combined approach. This work was done in the context of parallel Proteus, a new parallel simulator of message-passing multicomputers.
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