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.
A distributed algorithm is introduced for the analysis of large continuous time Markov chains (CTMCs) by combining in some sense numerical solution techniques and simulation. CTMCs are described as a set of processes ...
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A distributed algorithm is introduced for the analysis of large continuous time Markov chains (CTMCs) by combining in some sense numerical solution techniques and simulation. CTMCs are described as a set of processes communicating via message passing. The state of a process is described by a probability distribution over a set of reachable states rather than by a single state. simulation is used to determine event times and messages types to be exchanged, whereas transitions are realized by vector matrix products as in iterative numerical analysis techniques. In this way, the state space explosion of numerical analysis is avoided, but it is still possible to determine more detailed results than with simulation. parallelization of the algorithm is realized applying a conservative synchronization scheme, which exploits the possibility of precomputing event times as already proposed for parallelsimulation of CTMCs. In contrast to a pure simulation approach, the amount of computation is increased, whereas the amount of communication keeps constant. Hence it is possible to achieve even on a workstation cluster a significant speedup.
We present a novel approach to parallel discrete event simulation based on the Cilk model of multithreaded computation. Cilk's runtime system not only manages the low-level aspects of program execution, but also p...
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We present a novel approach to parallel discrete event simulation based on the Cilk model of multithreaded computation. Cilk's runtime system not only manages the low-level aspects of program execution, but also provides the user with an algorithmic model of performance which can be used to predict the execution time of a parallelsimulation. Moreover, a Cilk application can `scale down' to run on a single processor with nearly the same performance as that of serial code. A conservative parallel discrete event simulation algorithm has been developed in which communication between logical processes is achieved using Cilk's virtual memory model, dag consistent shared memory. The simulation executes in cycles, where each cycle involves a divide and conquer computation. Although local lookahead information can be exploited, the algorithm is robust in that it also calculates a global simulation time for each cycle. It can therefore be used for applications where zero lookahead may occur.
We present a conservative strategy for spatially decomposed parallel discrete event battlefield simulation. The traditional null message algorithm provides a foundation from which a mapping to generic simulation attri...
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We present a conservative strategy for spatially decomposed parallel discrete event battlefield simulation. The traditional null message algorithm provides a foundation from which a mapping to generic simulation attributes can be made. We informally discuss preservation of logical correctness and freedom from deadlock. Experimental results demonstrate the potential execution time savings when load imbalance is not dominant;more importantly, they highlight improvement opportunities in spite of potential load imbalance. The net result is that a very reasonable performance gain can be delivered for little effort in a way that supports good simulation system design principles. The approach is straightforward and can be easily implemented as part of a more general sequential or parallelsimulation support environment. While the approach is expressed in terms of battlefield simulation, its essence applies to many simulation applications.
Multi-resolution representation of simulated entities is considered essential for a growing portion of distributedsimulations. Heretofore, modelers have represented entities at just one level of resolution, or have r...
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Multi-resolution representation of simulated entities is considered essential for a growing portion of distributedsimulations. Heretofore, modelers have represented entities at just one level of resolution, or have represented concurrent representations in an inconsistent manner. We address the question of the cost of maintaining multiple, concurrent representations. We present a brief overview of our concept of a Multiple Resolution Entity (MRE) and Attribute Dependency Graph (ADG) both originally described elsewhere, and then compare simulation and consistency costs of some approaches, including our own MRE/ADG-based approach, to multi-resolution modeling. The cost analysis presented here is the first known analysis of its type, and will provide a basis for simulation designers to determine the best, and most cost-effective approach to supporting simulation of entities at different levels of resolution concurrently.
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