Interactive simulation of battles is a valuable took for training. The behavior and movement of hundreds or thousands of entities (tanks, trucks, airplanes, missiles, etc.) is currently simulated using dozens or more ...
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ISBN:
(纸本)0818678798
Interactive simulation of battles is a valuable took for training. The behavior and movement of hundreds or thousands of entities (tanks, trucks, airplanes, missiles, etc.) is currently simulated using dozens or more workstations on geographically distributed LANs connected by WANs. The simulated entities can move, fire weapons, receive ''radio'' messages, etc. The terrain that they traverse may change dynamically, for example due to rains turning dirt roads into mud or bombs forming craters. Thus the entities need to receive frequent information about the state of the terrain and the location and state of other entities. Typically, information is updated several times a second. As the number of simulated entities grows, the number of messages that need to be sent per unit of time can grow to unmanageable numbers. One approach to reducing the number of messages is to keep track of what entities need to know about which other entities and only send information to the entities that need to know. For example, tanks in Germany need not know about a change of course of a ship in the Pacific. This technique for reducing messages is known as interest management. Caltech and its Jet Propulsion Laboratory have implemented a simulation of this type on several large-scale parallel computers, exploiting both the compute pourer and the fast messaging fabric of such systems. The application is implemented using a heterogeneous approach. Some nodes are used to simulate entities, some to manage a database of terrain information, some to provide interest management functions, and some to route messages to the entities that do need to receive the information. Some of these tasks require more memory than others, some require faster processing capability. Thus the application is heterogeneous both in its functional decomposition and to a smaller extent in the characteristics of the hardware that is used to run each function. In addition, workstations are used to run the Graphical User
The unthrottled optimism underlying the Time Warp (TW) parallelsimulation protocol can lead to excessive aggressiveness in memory consumption due to saving state histories, and waste of CPU cycles due to overoptimist...
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The unthrottled optimism underlying the Time Warp (TW) parallelsimulation protocol can lead to excessive aggressiveness in memory consumption due to saving state histories, and waste of CPU cycles due to overoptimistically progressing simulations that eventually have to be "rolled back". Furthermore, in TW simulations executing in distributed memory environments, the communication overhead induced by the rollback mechanism can cause pathological overall simulation performance. In this work direct optimism control mechanisms are used to overcome these shortcomings by probabilistically controlling simulation progression based on the forecasted time stamp of forthcoming messages. Several forecast methods are presented and their performance is compared for very large Petri net simulation models executed with the TW protocol on the Meiko CS-2.
The paper presents the tolerant, hybrid synchronization schema and its benefits for the parallel and distributedsimulation of interconnected computer networks. The hybrid schema combines conservative and optimistic s...
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The paper presents the tolerant, hybrid synchronization schema and its benefits for the parallel and distributedsimulation of interconnected computer networks. The hybrid schema combines conservative and optimistic synchronization approaches by using lookahead for scheduling special events and using the flexibility of time warp in certain cases. In addition to these classical approaches the introduction of the "tolerance" allows the distributed modules to simulate further ahead than guaranteed by the conservative synchronization schema. This results in significantly smaller simulation runtimes and many other benefits.
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 bre...
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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. Exant simulators (both serial and parallel) prohibit simultaneity either by user-specified event priorities or by an arbitrary (but well-documented) tie-breaking mechanism. We show, theoretically and empirically, that these strategies may lead to an invalid simulation. In doing so, we introduce the threshold of event simultaneity and use it to understand the semantics of simultaneity.
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 ...
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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 work load and architectural parameters. A new parallel algorithm for terminating the window quickly is also described and analyzed.
We propose 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 whi...
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We propose 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.
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: parallelizing an existing switch-level simulator such that the model can be executed using conservative and optimistic simulation protocols with minor changes; evaluating effectiveness of several partitioning algorithms for parallelsimulation; and demonstrating speedups with both conservative and optimistic simulation protocols for seven circuits, ranging in size from 3 K transistors to about 87 K transistors.
Performance analysis of distributed systems may be performed on different levels of abstraction. An accurate but time-consuming method is the construction of a simulation model which includes the different subsystems,...
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Performance analysis of distributed systems may be performed on different levels of abstraction. An accurate but time-consuming method is the construction of a simulation model which includes the different subsystems, the communication system, and the load profile. In particular, this approach seems to be very powerful for real-time systems because of the inherent possibility of precise calculations of delays and processing times. A VHDL-based approach is presented which supports the performance analysis of mixed discrete-continuous distributed systems.
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.
The proceedings contain 21 papers. The special focus in this conference is on Evolutionary Approaches to Issues in Biology and Economics. The topics include: Simulating pricing behaviours using a genetic algorithm;bio...
ISBN:
(纸本)3540634762
The proceedings contain 21 papers. The special focus in this conference is on Evolutionary Approaches to Issues in Biology and Economics. The topics include: Simulating pricing behaviours using a genetic algorithm;biologically inspired computational ecologies;modelling bounded rationality using evolutionary techniques;the abstract theory of evolution of the living;an evolutionary algorithm for single objective nonlinear constrained optimization problems;on recombinative sampling;the evolution of mutation, plasticity and culture in cyclically changing environments;on the structure and transformation of landscapes;island model genetic algorithms and linearly separable problems;empirical validation of the performance of a class of transient detector;the construction and evaluation of decision trees;paralleldistributed genetic programming applied to the evolution of natural language recognisers;scheduling planned maintenance of the south wales region of the national grid;solving generic scheduling problems with a distributed genetic algorithm;directing the search of evolutionary and neighbourhood-search optimisers for the flowshop sequencing problem with an idle-time heuristic;multiobjective genetic algorithms for pump scheduling in water supply;use of rules and preferences for schedule builders in genetic algorithms for production scheduling;a voxel based approach to evolutionary shape optimisation;an evolutionary, agent-assisted strategy for conceptual design space decomposition and task scheduling with use of classifier systems.
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