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In the last three decades a considerable amount of research has been pursued in the efficient implementation of the pending event set (PES) associated with discrete-event simulation. The reason is simple: a fast event management has a very crucial impact in the total running time of both sequential and parallel simulations. This report focuses on this problem by studying the empirical performance of a number of solutions to the PES implementation in which we include a complete binary tree described in [26], 1 Introduction The PES is defined as the set of all the events generated during a discrete-event simulation and whose occurrence have not been simulated yet. In order to determine the next event to take place, it is necessary to extract the event with the least time from the PES. We call this operation extract-min. On the other hand, the occurrence of any event during the simulation can produce the insertion of new pending or future events in the PES; insert operation. These two b...

This paper identifies a number of issues that we believe are important for hardware/software codesign. The issues are illustrated by a small comprehensible example: a priority queue. Based on simulations of a real application, we suggest a combined hardware /software realization of the priority queue. 1 Introduction A priority queue is a data structure with a simple interface which in many applications is a performance bottleneck. For example, in event driven simulators, the operations on a priority queue may account for a significant fraction of the computation time. Since the interface to a priority queue is simple and well defined, it seems like an obvious candidate for hardware realization while leaving other parts of the application in software. Despite its simplicity the priority queue illustrates several issues that are also relevant in more complex and less transparent examples of hardware /software codesign: ffl the significance of an efficient interface between software an...

this paper we study the performance of the very first tournament based complete binary tree. We focus on discrete-event simulation and our results show that this unknown predecessor of heaps can be a more efficient alternative to the fastest pending event set implementations reported in the literature. We also extend the idea of binary tournaments to a (2; L)-tournament structure which exhibits the property of delaying the processing of events with larger timestamps whilst it keeps similar theoretical performance bounds to the native (2; 1)-structure or CBT. This property can be certainly useful in systems where many pending events are expected to be deleted or rescheduled during the simulation. 2 Tournament trees

Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.

Digital Equipment Corporation The event-manipulation system presented here consists of two major parts. The first part addresses the familiar problem of event scheduling efficiency when the number of scheduled events grows large. The second part deals with the less apparent problem of--providing efficiency and flexibility as scheduled events are accessed to he executed. Additional features and problems dealt with include the proper handling of simultaneous events; that certain events must be created, scheduled, and executed at the same points in simulated time; that infinite loops caused by the concatenation of such "zero-time " events are possible and must be diagnosed; that maintaining various event counts is practical and economical; and that a capability for handling "time-displaceable " events is desirable and possible.

Recently algorithms have been presented for the realization of event scheduling routines suitable for general purpose discrete event simulation systems. Sev-eral exhibited a performance superior to that of com-monly used simple linked list algorithms. In this paper a new event scheduling algorithm is presented which im-proves on two aspects of the best of the previously published algorithms. First, the new algorithm's per-formance is quite insensitive to skewed distributions, and second, its worst-case complexity is O(~/n), where n is the number of events in the set. Furthermore, tests conducted to estimate the average complexity showed it to be nearly independent of n. Key Words and Phrases: simulation, time flow mechanisms, event scanning mechanisms, multilinked

I sincerely thank my advisor Prof K. Gopinath for his guidance and support to complete this thesis. I also thank my organization, Accord Software and Systems for supporting me with time and resources to complete my thesis. I thank my organizational guide Mr.Purushotham for his whole-hearted support. I would also like to thank my supervisors Mr.Devanathan, Mr.Shashidhar and Mr.Rengasamy for their encouragement and support. I will always remember the sincere help that I received from my colleagues Prashanth Nayak and Yadunandan. I believe this has been possible due to the continued motivation and support Time management is one of the critical modules of safety-critical systems. Applications need strong assurance from the operating system that their hard real-time requirements are met. Partitioned system has recently evolved as a means to provide protection to safety critical applications running on an Avionics computer resource. Each partition has an application running strictly for a specified duration. These applications use the CPU on a cyclic basis. Applications running on a real-time systems request the service of time management in one way or the other. An application may request for a time-out while waiting for a resource, may

Cellular space modeling is becoming an increasingly important modeling paradigm for modeling complex systems with spatial-temporal behaviors. The growing demand for cellular space models has directed researchers to use different modeling formalisms, among which Discrete Event System Specification (DEVS) is widely used due to its formal modeling and simulation framework. The increasing complexity of systems to be modeled asks for cellular space models with large number of cells for modeling the systems ’ spatial-temporal behavior. Improving simulation performance becomes crucial for simulating large scale cellular space models. In this dissertation, we proposed a framework for improving simulation performance for large scale DEVS-based cellular space models. The framework has a layered structure, which includes modeling, simulation, and network layers corresponding to the DEVS-based modeling and simulation architecture. Based on this framework, we developed methods at each layer to overcome performance issues for simulating large scale cellular space models. Specifically, toincrease the runtime and memory efficiency for simulating large number of cells, we applied Dynamic Structure DEVS (DSDEVS) to cellular space modeling and carried out comprehensive

Abstract-- Dynamic Structure DEVS (DSDEVS) is an advanced modeling formalism that allows DEVS models and their couplings to be dynamically changed. The modeling power and advantages of DSDEVS have been well studied. However, the performance aspect of DSDEVS is generally overlooked. This paper provides a comprehensive performance measurement of DSDEVS for a large scale cellular space models. We consider both the modeling layer and simulation layer for performance analysis, and carry out performance measurement based on a token ring model and a fire spread model. The results shows that DS modeling can improve simulation performance for large scale cellular space models, due to the fact that it makes the simulation focus only on those active models, and thus be more efficient than when the entire cellular space is loaded. On the other hand, the DS overhead cannot be ignored and can become significant and even dominant when large number of cells are dynamically added/deleted.