Asynchronous parallel discrete event simulation

Complex models may have model components distributed over a network and generally require significant execution times. The field of parallel and distributed simulation has grown over the past fifteen years to accommodate the need of simulating the complex models using a distributed versus sequential method. In particular, asynchronous parallel discrete event simulation (PDES) has been widely studied, and yet we envision greater acceptance of this methodology as more readers are exposed to PDES introductions that carefully integrate real-world applications. With this in mind, we present two key methodologies (conservative and optimistic) which have been adopted as solutions to PDES systems. We discuss PDES terminology and methodology under the umbrella of the personal communications services application     

Parallel discrete event simulation with SIMULA

The area of Discrete Event Simulation (DES) is the least impacted by parallel processing even though most of its applications require tremendous amounts of processing time. The common approach of parallelizing individually special purpose programs leads to very limited improvements in performance. We propose here the parallelization of general DES applications written in SIMULA, as a part of an ongoing project that aims towards developing methodologies and architectures for parallel DES. SIMULA is a general purpose process oriented language whose structure allows the creation of processes which can participate in a quasi-parallel execution according to an interleaved fashion. Problems related to the process interference representation, parallel scheduling and process synchronization are defined and solved. To test and verify the theoretical results the parallel execution of experimental and real DES applications has been simulated. The results show that significant improvement in performance can be expected.     

Interactive discrete event simulation without programming

The development and implementation of an interactive discrete event simulation package is described. APHIDS (A Program to Help Interactively with Discrete Simulation) has been specifically designed with those inexperienced at system modelling in mind. As such, the package gently steers the user through the model definition stage of his problem and also provides a variety of output modes. APHIDS may be used at a number of different “complexity” levels reflecting the interests, abilities and needs of the user. The package is written almost entirely in ANSI minimal BASIC and, currently, has been implemented on at least two interactive minicomputer systems.     

Using Ada for discrete event simulation

The process interaction approach is proposed for developing a discrete simulation environment in Ada. The introduction of simulation facilities in Ada not only concerns the classical aspect of model building, but allows a new class of problems to be tackled, that is the testing of correctness of programs intended for real-time applications. In this paper attention is focused on the presentation of the process scheduling in the simulation context and on the definition of standard forms of interactions among processes. Simulation facilities are organized by making use of Ada's structuring concepts.     

User interfaces and discrete event simulation models

This paper examines features of user interfaces present in current discrete event simulation systems. A particular emphasis is placed on their data input capabilities and the presentation of simulation statistics. There has been a lot of work on developing visual simulation and animation. Little effort appears to have been invested in data input facilities. There has been considerable effort invested in the presentation of simulation results. This paper shows that this distribution of effort into the various interfaces lacks proper insight into the particular needs of simulation systems. A list of features to improve data input and model specification for existing simulation systems is derived. A list of issues that need to be tackled to make the presentation of simulation statistics more appropriate for the specifics of the simulation is given. The paper concludes with general comments concerning future research issues to be addressed.     

基于乐观策略的并行离散事件模拟研究

并行离散事件模拟（PDES）又称分布式模拟,通过将一个离散事件模拟程序在多个处理器上并行执行来提高模拟性能。乐观策略在解决并行模拟中各模拟部分之间的同步关系时具有较好的性能。介绍了基于乐观策略的并行离散事件模拟的原理,讨论了存在的问题,并给出相应的解决方法。     

Parallel discrete event simulation using shared memory

With traditional event-list techniques, evaluating a detailed discrete event simulation-model can often require hours or even days of computation time. By eliminating the event list and maintaining only sufficient synchronization to ensure causality, parallel simulation can potentially provide speedups that are linear in the numbers of processors. A set of shared-memory experiments using the Chandy-Misra distributed simulation algorithm, to simulate networks of queues is presented. Parameters of the study include queueing network topology and routing probabilities, number of processors, and assignment of network nodes to processors. These experiments show that Chandy-Misra distributed simulation is a questionable alternative to sequential simulation of most queuing network models.<>     

On the distributed orchestration of stochastic discrete event simulations

Discrete event simulations are a powerful technique for modeling stochastic systems with multiple components where interactions between these components are governed by the probability distribution functions associated with them. Complex discrete event simulations are often computationally intensive with long completion times. This paper describes our solution to the problem of orchestrating the execution of a stochastic, discrete event simulation where computational hot spots evolve spatially over time. Our performance benchmarks report on our ability to balance computational loads in these settings. Copyright © 2013 John Wiley & Sons, Ltd.     

并行离散事件模拟的同步机制研究

逻辑模拟在设计新系统的过程中起着重要作用,通过计算机进行模拟可以实时反馈输出结果,及早发现潜在的问题,进而缩短设计周期,降低研发成本。并行离散事件模拟通过分散计算量到并行机或者网络的多个节点来减少模拟时间,被视为解决模拟速度问题的有效途径。在影响模拟性能的因素中,各并行子系统之间的同步问题是直接影响并行性能的关键因素之一。探讨了并行离散事件模拟的同步机制,介绍了其基本原理、特点及存在的问题,并阐述了可能的改进方法。     

Web Services with generic simulation models for discrete event simulation

Today the Internet and the World Wide Web (WWW) are on the cusp of a paradigm shift. Up to now most actions in the WWW are sorts of human–computer interaction, but the introduction of the eXtensible Markup Language (XML) changed the perception. The Internet will be seen as a great space of information and with the use of XML and following technologies like Web Services, Grid Computing and Semantic Web the difference between human–machine interaction and machine–machine interaction vanishes. This work investigates the usefulness of XML in the simulation domain and uses Web Service technology to build the SimASP framework for discrete event simulation (DES).     

Improving efficiency in social services with discrete event simulation

The Kentucky Cabinet for Health and Family Services’ main office in Louisville, Kentucky deals with hundreds of clients with various needs each day. The office provides food stamps, child care assistance, and financial support among other services. A simulation model of the intake process was developed and analyzed in order to investigate various alternatives concerning process flow, staffing, and layout. The simulation model shows long wait times for clients coming into the system to receive benefits. Working with a state budget during variable economic times leaves no room for hiring new workers, so changes must come from within. The flexibility of the simulation model allows for experiments on the system to be created and observed. This paper describes the simulation model, the analysis of alternatives with the model, and the changes implemented in the system as a result of the analysis.     

Modelling complex manufacturing systems using discrete event simulation

This paper presents an approach in simulating complex manufacturing systems. The approach is founded on developing several general purpose simulation generators for an assembly station, a manufacturing cell, and an inventory transfer function. These simulation generators can then be linked together to create a model of a complex manufacturing system. A typical manufacturing system is modelled using these simulation generators and the results summarized.     

Predicting the performance of synchronous discrete event simulation

We develop a model to predict the performance of synchronous discrete event simulation. Our model considers the two most important factors for the performance of synchronous simulation: load balancing and communication. The effect of load balancing in a synchronous simulation is computed using probability distribution models. We derive a formula that computes the cost of synchronous simulation by combining a communication model called LogGP and computation granularity. Even though the formula is simple, it is effective in capturing the most important factors for the synchronous simulation. The formula helps us to predict the maximum speed up achievable by synchronous simulation. In order to examine the prediction model, we have simulated several large ISCAS logic circuits and a simple PCS network simulation on an SGI Origin 2000 and Terascale Computing System (TCS) at the Pittsburgh Supercomputing Center. The results of the experiment show that our performance model accurately predicts the performance of synchronous simulation. The performance model developed is used to analyze the effect of several factors that may improve the performance of synchronous simulation. The factors include problem size, load balancing, granularity, communication overhead, and partitioning.     

A note on filtering in queueing networks and discrete event dynamic systems

In this short tutorial paper, we give a simple Bayesian derivation of the optimal filtering formula for queueing networks. No measure theoretic knowledge is needed.     

Formal approach to fault diagnosis in distributed discrete event systems with OBDD

In this paper, we study the fault diagnosis problem for distributed discrete event systems. The model assumes that the system is composed of distributed components which are modeled in labeled Petri nets and interact with each other via sets of common resources (places). Further, a component’s own access to a common resource is an observable event. Based on the diagnoser approach proposed by Sampath et al., a distributed fault diagnosis algorithm with communication is presented. The distributed algorithm assumes that the local diagnosis process can exchange messages upon the occurrence of observable events. We prove the distributed diagnosis algorithm is correct in the sense that it recovers the same diagnostic information as the centralized diagnosis algorithm. Furthermore, we introduce the ordered binary decision diagrams (OBDD) in order to manage the state explosion problem in state estimation of the system.     

PL/I as a discrete event simulation tool

The programming language PL/I is considered as a most useful and portable discrete event simulation tool. This paper discusses design facilities required in simulation languages, making use of a model described in PL/I. The problem of queues, parallelism and synchronization in a simulator is solved. The structure of the simulator is considered.     

Predicting nuclear power-plant operator performance using discrete event simulation

A study was conducted to evaluate the use of discrete event simulation (DES) to predict human performance in a nuclear power plant control room environment. Computer simulation models of two disturbance scenarios were built using a simulation software program, Micro Saint. In parallel, data were also collected at a full-scope training simulator at the Halden man-machine laboratory (HAMMLAB) in Halden, Norway, using crews of commercial nuclear power plant operators from the Loviisa nuclear power plant in Loviisa, Finland. Comparisons were made between predicted operator performance data generated by the simulation models and crew performance in the HAMMLAB experiment to determine the degree of agreement between the simulated data and the data from operators. The models were then used to extrapolate advanced control room conditions and alarm systems that were not tested in the HAMMLAB experiment. This report summarizes these findings and provides recommendations for improvements to the DES approach for use by a regulatory agency.     

A context-based object-oriented application framework for discrete event simulation

Applying object-oriented programming (OOP) to construct simulation programs has gained momentum in the research community. Major research efforts involved with object-oriented paradigm adopted in discrete-event simulation are reviewed in this paper, along with a simulation application framework proposed which provides special reusability mechanisms. This object-oriented simulation framework consists of three object elements, that is, model, service and scheduler. The relations and interactions among these elements are also demonstrated. In addition, the abstraction of a model under such a framework is reached by a special concept and implementation, referred to as the simulation context. Each simulation context is used to model a component sub-system, e.g. the control or physical flows of a manufacturing system. A practical system, CSIMT+ +, is also developed to validate the feasibility of such a simulation application framework. Furthermore, various forms of application models based on this framework are also illustrated.     

Generating non-standard random distributions for discrete event simulation systems

This paper introduces a novel method for generating non-standard random distributions. These distributions are required when the system cannot be modelled accurately using conventional probabilistic distributions. In the proposed method, the desired random distribution is built by splitting the density function into smaller segments which are individually approximated with simple polynomial functions. Then, the inverse transformation method is used to form the final random distribution function. This paper presents also new criteria for expediting the selection of the correct segment. The complexity of the proposed process for segment selection is O(log M), where M is the number of segments. An example of the application of the proposed method to simulation of disk access patterns for performance evaluation of computer systems is provided.