In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the me...
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In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the mechanics of breaking event-time ties and has neither measured its extent nor considered its implications. Extant simulators (both serial and parallel) prohibit simultaneity either by user-specified event priorities or by an arbitrary (but well-documented) tie-breaking mechanism. We shall show, theoretically and empirically, that these strategies may lead to an invalid simulation. In doing so, we shall introduce the threshold of event simultaneity and use it to understand the semantics of simultaneity.
The Hierarchical Tool HIT is a software tool for hierarchical modeling and performance evaluation of discrete event systems. Besides analytical and numerical solution techniques HIT provides the evaluation of models b...
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ISBN:
(纸本)0818679654
The Hierarchical Tool HIT is a software tool for hierarchical modeling and performance evaluation of discrete event systems. Besides analytical and numerical solution techniques HIT provides the evaluation of models by sequential simulation. Here we present concepts for optimistic distributedsimulation of HIT-models by partitioning them with respect to subhierarchies. The main goals of the concept being presented are the preservation of model structure even in lower levels of the realization (e.g. use of the process view of simulation throughout all levels of abstraction) and distribution transparency on the modeling level (homogeneous model specification for all solution techniques).
Large-scale ecological simulations are natural candidates for distributed discrete event simulation. In optimistic simulation of spatially explicit models, a difficult problem arises when individuals migrate between p...
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ISBN:
(纸本)0818679654
Large-scale ecological simulations are natural candidates for distributed discrete event simulation. In optimistic simulation of spatially explicit models, a difficult problem arises when individuals migrate between physical regions simulated by different logical processes. We present a solution to this problem that uses shared object states. Shared states allow for efficient communication between LPs and for early detection of canceled events. We briefly describe an optimistic simulation environment called EcoKit, which operates on top of the WarpKit implementation of Time Warp. Our experiments with this system on a shared memory multiprocessor show that EcoKit promises to scale well both with the number of processors and the number of individuals simulated.
This paper presents the results of an experimental study to evaluate the effectiveness of multiple synchronization protocols and partitioning algorithms in reducing the execution time of switch-level models of VLSI ci...
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This paper presents the results of an experimental study to evaluate the effectiveness of multiple synchronization protocols and partitioning algorithms in reducing the execution time of switch-level models of VLSI circuits. Specific contributions of this paper include: (i) parallelizing an existing switch-level simulator such that the model can be executed using conservative and optimistic simulation protocols with minor changes, (ii) evaluating effectiveness of several partitioning algorithms for parallelsimulation, and (iii) demonstrating speedups with both consecutive and optimistic simulation protocols for seven circuits, ranging in size from 3 K transistors to about 87 K transistors.
In this paper an approach to provide Web-based framework for distributed execution of collaborative applications is presented. The work is a part of a wider on-going project whose aim is to make environmental simulati...
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ISBN:
(纸本)0818680431
In this paper an approach to provide Web-based framework for distributed execution of collaborative applications is presented. The work is a part of a wider on-going project whose aim is to make environmental simulation models publicly available to the Internet users. The Web computing skeleton has been constructed from prefabricated Web-enabled components with the ability to open and maintain Web connections and provide collaboration over the Internet. The case study illustrates how a single-user simulation system can be embedded in the skeleton, thus becoming widely available distributed application.
The IDES project at Sandia National Laboratories is developing a large scale portable parallel simulator for use in stockpile stewardship. IDES will use the Breathing-Time-Buckets synchronization protocol;to support I...
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The IDES project at Sandia National Laboratories is developing a large scale portable parallel simulator for use in stockpile stewardship. IDES will use the Breathing-Time-Buckets synchronization protocol;to support IDES development, this paper studies a performance model and describes performance experiments on expected workload and architectural parameters. A new parallel algorithm for terminating the window quickly is also described and analyzed.
The process interaction world view is widely used in the general simulation community for its expressive power and is supported by most modem simulation languages. In parallel discrete event simulation, however its us...
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ISBN:
(纸本)0818679654
The process interaction world view is widely used in the general simulation community for its expressive power and is supported by most modem simulation languages. In parallel discrete event simulation, however its use remains comparatively rare due to the perceived inefficiency (and difficulty) of parallel implementations. We present a new implementation strategy for parallel process-oriented simulation languages. This innovative, semantics-based approach directly addresses two common concerns of such languages. By concentrating on the intrinsic threads of control, we avoid the proliferation of simulation objects (and their associated costs) that might result from a naive translation. More fundamentally, the primary costs associated with process-oriented languages - those of context switching between stacks and, in an optimistic setting, of saving the state of these stacks - are entirely eliminated since our explicit use of continuations avoids the need for stacks in the first place. We similarly obtain cheap and natural thread pre-emption.
The problem of executing sequential programs in parallel using the optimistic algorithm Time Warp is considered. This is done by first mapping the sequential execution to a control tree and then assigning timestamps t...
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The problem of executing sequential programs in parallel using the optimistic algorithm Time Warp is considered. This is done by first mapping the sequential execution to a control tree and then assigning timestamps to each node in the tree. For such timestamps to be effective in either hardware or software they must be finite, this implies that they must be periodically rescaled to allow old timestamps to be reused. A number of timestamp representations are described and compared on the basis of their complexity;the frequency and cost of rescaling;and the cost of performing basic operations, including comparison and creation of new timestamps.
We propose in this paper two new asynchronous parallel algorithms for test set partitioned fault simulation. The algorithms are based on a new two-stage approach to parallelizing fault simulation for sequential VLSI c...
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We propose in this paper two new asynchronous parallel algorithms for test set partitioned fault simulation. The algorithms are based on a new two-stage approach to parallelizing fault simulation for sequential VLSI circuits in which the test set is partitioned among the available processors. These algorithms provide the same result as the previous synchronous two stage approach. However, due to the dynamic characteristics of these algorithms and due to the fact that there is very minimal redundant work, they run faster than the previous synchronous approach. A theoretical analysis comparing the various algorithms is also given to provide an insight into these algorithms. The implementations were done in MPI and are therefore portable to many parallel platforms. Results are shown for a shared memory multiprocessor.
The efficiency of parallel Discrete Event simulations that use the optimistic protocol is strongly dependent on the overhead incurred by rollbacks. This paper introduces a novel approach to rollback processing which l...
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The efficiency of parallel Discrete Event simulations that use the optimistic protocol is strongly dependent on the overhead incurred by rollbacks. This paper introduces a novel approach to rollback processing which limits the number of events rolled back as a result of a straggler or antimessage. The method, called Breadth-First Rollback (BFR), is suitable for spatially explicit problems where the space is discretized and distributed among processes and simulation objects move freely in the space. BFR uses incremental state saving, allowing the recovery of causal relationships between events during rollback. These relationships are then used to determine which events need to be rolled back. Our results demonstrate an almost linear speedup - a dramatic improvement over the traditional approach to rollback processing.
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