JMASE分布式仿真功能的设计与实现

联合建模与仿真环境（JMASE）是一个用于工程级和交战级的仿真与建模环境,目前只支持串行仿真。为了提高仿真运行速度,该文提出利用支持并行与分布式仿真的KD-PARSE仿真引擎,将JMASE分布到多个节点上的方法。在分析JMASE通信机制和调度机制的基础上,设计和实现了调度服务演员和代理演员使JMASE具有分布式仿真的功能。文章最后通过一个简单例子验证了JMASE的分布式仿真功能,结果表明仿真效率有明显提高。     

JMASE与HLA仿真系统的互连研究

JMASE是一个建模与仿真的支撑环境，主要用于构建分析和测试领域所需要的工程级和交战级数字系统模型和仿真系统，它采用的是基于事件的仿真调度机制，通过端口消息进行通信。JMASE提供了灵活易用而且功能强大的开发工具、配置工具、执行工具和分析工具支持建模与仿真的全过程，还提供一系列的公共服务方便模型的开发，极大地促进了模型与仿真的重用以及互操作。该文在介绍JMASE基本概念、特点和功能的基础上，基于JMASE的事件调度机制和数据日志服务以及HLA的接口规范开发了一个JMASE—HLA框架，实现了JMASE仿真系统与HLA仿真系统的互连。     

NS仿真实时事件调度的性能分析

分析NS的仿真（NSE）实现所采用的实时事件调度方法,把NSE的同步过程对离散事件的处理看作一个修改的排队系统,建立实时事件调度的排队模型。把同步时间点处的等待事件看作嵌入Markov过程,得到等待事件的分布,进而得到任意时刻等待事件的分布。通过求得离散事件等待期间完成的服务数与在离散事件到达的前一同步时刻到达的其他离散事件数的等待时间的条件概率分布,得到离散事件的等待时间的分布。     

分布离散事件仿真的集中同步算法

分布离散事件仿真和一般的离散事件仿真不同,它没有公共的时钟和事件表,通过分布在多台主机上的仿真模型进行消息传递来实现世界中的事件的并发执行。同步算法是分离散事件离散事件仿真中确保模型之间发生的因果关系正确性的机制。文中提出了一种集中同步算法,它采用建立模型之间的关联关系和仿真控制节点的方法,来对仿真模型之间的交互事件和仿真模型内部事件进行调度。其实现机制简单,避免了死锁的产生,并能实现事件的并发执行。文中最后对在WindowsNT环境下实现该算法进行了探讨。     

集成化企业模型并行仿真系统中的仿真时钟

深入探讨了集成化企业模型并行仿真系统中的仿真时钟管理机制，解决了多个子过程共同使用一个独占型资源时的时钟同步问题和多事件仿真中活动数量限制造成的时钟同步问题以及多个线程之间的时钟同步问题。     

通用电子战M＆S支撑环境设计与实现

随着大规模先进分布仿真技术的兴起和现代仿真技术领域的不断拓展，仿真的规模和复杂性与日俱增。传统的面向过程的建模与仿真，由于不同对象和过程之间的相互耦合，已远远无法满足像电子战这种实体众多、关系错综复杂的大型系统仿真的需求。联合建模与仿真环境（JMASE）基于面向对象理论和技术，通过定义一系列标准、服务和模型接口及提供一组工具集，实现了模型开发、测试与分析过程的一体化和标准化，促进了不同领域仿真模型的互操作和可重用，有效地解决了复杂大系统M＆S所面临的困难，为用户提供了一个开放的、面向对象的通用电子战M＆S支撑环境。     

半实物仿真系统中的实时控制技术

从三个时间定量指标出发,对半实物仿真中实时控制技术作简要的总结。首先从仿真顿时控制的角度介绍了顿时平衡、进程调度、时间同步和实时通信技术,然后从仿真过程控制的角度对几种典型的仿真控制框架加以分析,并分别给出了具体的精度指标。     

并行仿真运行信息记录分析工具的设计与实现

如何提高并行离散事件仿真应用程序的运行质量一直是开发人员所关心的问题,设计了一个记录分析工具.为达到记录过程高效、数据完备的目的,使用节点代理顺序记录等技术可以记录并行离散事件和应用程序的运行信息,可以用于可视化显示和分析,开发人员通过使用上述工具能快速查看事件调度序列拓扑图、事件态势分布以及获取程序改进建议等信息,继而修改代码以提高程序运行质量.最后对工具的有效性进行了验证.     

JMASE中光电/红外环境仿真研究

光电／红外环境是指战场状态下各种目标对象所处的光电／红外辐射环境,包括太阳辐射、自身辐射、以及其它一些背景辐射。JMASE是一个建模与仿真支撑环境,主要用于构建分析和测试领域所需要的工程级和交战级数字系统模型和仿真系统。JMASE提供了灵活易用而且功能强大的开发工具、配置工具、执行工具和分析工具支持建模与仿真的全过程,还提供一系列的公共服务方便模型的开发,极大地促进了模型与仿真的重用以及互操作。该文研究了JMASE中光电／红外环境仿真系统原理,利用面向对象的设计方法实现了光电／红外环境仿真。     

一种基于回调滞后的事件定序新算法

在分布式虚拟环境(DVE)中，各节点的时间和事件处理顺序的不一致，将严重影响仿真结果。为解决这些不一致问题，分析了DVE中不一致问题产生的原因，给出了一种软件时钟同步的方法，解决了时间一致性问题；提出了一个基于回调滞后的事件定序新算法，解决了因网络延迟而造成的事件处理顺序的不一致问题。将这些方法初步应用于分布交互仿真系统一综合仿真系统(Synthetic Simulation Sysem，SSS)中，系统的运行结果证明了这些方法的有效性。     

Simulation-based optimization vs. mathematical programming: A hybrid approach for optimizing scheduling problems

With the increasing computing power of modern processors, exact solution methods (solvers) for the optimization of scheduling problems become more and more important. Based on the mixed integer programming (MIP) formulation of a scheduling problem, it will be analyzed how powerful the present solvers of this problem class are and up to which complexity real scheduling problems are manageable. For this, initially some common benchmark problems are investigated to find out the boundaries for practical application. Then, the acquired results will be compared with the results of a conventional simulation-based optimization approach under comparable time restrictions. As a next step, the general advantages and disadvantages of both approaches were analyzed. As the result, a coupling of the discrete event simulation system and an MIP solver is presented. This coupling automatically generates an MIP-formulation for the present simulation model which can be solved externally by an MIP solver. After the external optimization process follows a backward transformation of the results into the simulation system. All features of the simulation system (like Gantt-Charts, etc.) could be used to check or to illustrate these results. To perform the coupling for a wide range of simulation models, it has to be defined which general constraints the model has to satisfy.     

Parameterized Time Warp (PTW): An Integrated Adaptive Solution to Optimistic PDES

Time Warp is an optimistic synchronization protocol used for parallel discrete event simulation. While Time Warp has the potential to reduce the execution time of large simulations, it has been plagued by a variety of problems, namely: 1. Instability due to thrashing effects caused by echoing and cascading rollbacks. 2. Memory bottlenecks due to state saving and excessive optimism. 3. Inefficient scheduling algorithms for scheduling Time Warp processes on each processing node. These problems have inhibited the widespread use of Time Warp as a general purpose synchronization algorithm. The general trend of researchers attempting to solve these problems has been to statically limit the optimism of Time Warp. Unfortunately, these attempts have achieved only limited success. This is because a static set of parameters may perform well for one simulation but not for another. This paper attacks the problem using adaptive mechanisms to control optimism, using an index of performance called useful work. This research presents solutions for the above mentioned problems, by: 1. Stabilizing Time Warp using adaptive bounded time windows. 2. Reducing memory usage and overall execution time by using an adaptive mechanism to vary the checkpoint interval. 3. Scheduling Time Warp processes with the useful work parameter to favor more productive processes. Using this new performance index called Useful Work, several modifications to Time Warp are implemented to stabilize and improve Time Warp. Thus, this new improved Time Warp synchronization mechanism termed Parameterized Time Warp provides an integrated adaptive solution to optimistic Parallel Discrete Event Simulation. Empirical work showing that PTW outperforms an equivalent Time Warp simulation executing under similar partitioning and load conditions is also presented.     

EPA网络控制系统丢包分析

针对基于时钟同步技术的时分调度网络控制系统工作方式,分析了基于EPA协议的网络丢包原理.建立在不同实时性要求情况下EPA网络系统的丢包模型,并且分析了时钟偏差抖动为马尔科夫链时,通信周期、时间片长度以及时钟同步精度对系统稳定性的影响.提出了提升EPA系统实时性的方法.最后对EPA系统的稳定性进行了分析.     

Domain-specific discrete event modelling and simulation using graph transformation

Graph transformation is being increasingly used to express the semantics of domain-specific visual languages since its graphical nature makes rules intuitive. However, many application domains require an explicit handling of time to accurately represent the behaviour of a real system and to obtain useful simulation metrics to measure throughputs, utilization times and average delays. Inspired by the vast knowledge and experience accumulated by the discrete event simulation community, we propose a novel way of adding explicit time to graph transformation rules. In particular, we take the event scheduling discrete simulation world view and provide rules with the ability to schedule the occurrence of other rules in the future. Hence, our work combines standard, efficient techniques for discrete event simulation (based on the handling of a future event set) and the intuitive, visual nature of graph transformation. Moreover, we show how our formalism can be used to give semantics to other timed approaches and provide an implementation on top of the rewriting logic system Maude.