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...
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ISBN:
(纸本)0818679654
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.
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.
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.
We investigate the causality issue in distributed virtual environments. Causality has been widely studied in parallel and distributed systems. However, most of the work in causality detection and preservation are from...
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This paper presents Maya, a multi-paradigm, scalable and extensible network modeling framework for emulating distributed applications. A novel three-tier architecture is proposed to integrate three disparate modeling ...
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ISBN:
(纸本)0769519709
This paper presents Maya, a multi-paradigm, scalable and extensible network modeling framework for emulating distributed applications. A novel three-tier architecture is proposed to integrate three disparate modeling paradigms, namely, discrete event models, analytical models and physical network interfaces into one unified framework of Maya. As the first effort to integrate all three paradigms into one framework, this paper discusses the implementations of Maya using Qualnet, fluid flow based TCP model and physical network interface. It addresses the performance issues involved in attaining the real time constraints imposed by distributed applications and demonstrates the effectiveness of using analytical models in Maya. Furthermore, it identifies the negative impact on real time performance through the computation intensive ordinary differential equation (ODE) solver in the fluid flow model. A new approach to interleaved executions of the fluid flow model is proposed to hide ODE solver turnaround time. As a result, the percentage of packets missing their deadlines has been reduced from more than 6% to less than 0.2%.
Performance models exist that reliably describe the execution time and efficiency of parallel discrete-event simulations executed in a synchronous iterative fashion. These performance models incorporate the effects of...
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Performance models exist that reliably describe the execution time and efficiency of parallel discrete-event simulations executed in a synchronous iterative fashion. These performance models incorporate the effects of processor heterogeneity, other processor load due to shared computational resources, application workload imbalance, and the use of speculative computation. This includes modeling the effects of predictive optimism, a technique for improving the accuracy of speculative assumptions. We extend these models to incorporate correlated workloads across the set of processors and validate the models with two different applications.
Recent experiments have shown that conservative methods can achieve good performance by exploiting the characteristics of the system being simulated. In this paper we focus on the interrelationship between run time an...
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ISBN:
(纸本)1565550552
Recent experiments have shown that conservative methods can achieve good performance by exploiting the characteristics of the system being simulated. In this paper we focus on the interrelationship between run time and synchronization requirements of a distributedsimulation. A metric that considers the effect of lookahead and the physical rate of transmission of messages, and an arrival approximation that models the effect of synchronization requirements on the run time are developed. It is shown that even when good lookahead is exploited in the system, poor run-time performance is achieved if an inefficient mapping of LPs to processors is used.
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.
Wireless networks' models differ from wired ones at least in the innovative dynamic effects of host-mobility and open-broadcast nature of the wireless medium. Topology changes due to simulated hosts' mobility ...
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ISBN:
(纸本)0769519709
Wireless networks' models differ from wired ones at least in the innovative dynamic effects of host-mobility and open-broadcast nature of the wireless medium. Topology changes due to simulated hosts' mobility map on causality effects in the "areas of influence" of each mobile device. The analysis of wireless networks Of interest today may include a potentially high number of simulated hosts, resulting in performance and scalability problems for discrete-event sequential simulation tools and methods, on a single physical execution unit (PEU). In a distributedsimulation, the main bottleneck becomes the communication and synchronization required to maintain the causality constrains between distributed model components. In this work we propose a HLA-based, dynamic mechanism for the runtime management and allocation of model entities in a distributedsimulation of wireless networks models, over a cluster of PEUs. By adopting a runtime evaluation of causal bindings between model entities we map the causal effects of virtual topology changes to dynamic migration of data structures. Preliminary results demonstrate that the prototype heuristics lead to a reduction in the percentage of external communication between the PEUs, limited overheads and performance enhancements for a worst-case scenario.
A number of optimistic synchronization schemes for parallelsimulation rely upon a global synchronization. The problem is to determine when every processor has completed all its work, and there are no messages in tran...
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ISBN:
(纸本)1565550552
A number of optimistic synchronization schemes for parallelsimulation rely upon a global synchronization. The problem is to determine when every processor has completed all its work, and there are no messages in transit in the system that will cause more work. Most previous solutions to the problem have used distributed termination algorithms, which are inherently serial;other parallel mechanisms may be inefficient. In this paper we describe an efficient parallel algorithm derived from a common `barrier' synchronization algorithm used in parallel processing. The algorithm's principle attraction is speed, and generality - it is designed to be used in contexts more general than parallel discrete-event simulation. To establish our claim to speed, we compare our algorithm's performance with the standard barrier algorithm, and find that its additional costs are not excessive. Our experiments are conducted using up to 256 processors on the Intel Touchstone Delta.
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