Rassul Ayani

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In Time Warp optimistic discrete event simulation, there exists a need to occasionally save the states of the logical processes. The state saving often constitutes a substantial overhead. However it is not necessary to save each state of a logical process since states can be restored from earlier states by re-executing intermediate events. In this paper, we(More)
Priority queues are used in many applications including real-time systems, operating systems, and simulations. Their implementation may have a profound effect on the performance of such applications. In this article, we study the performance of well-known sequential priority queue implementations and the recently proposed parallel access priority queues.(More)
This paper focuses on an experimental analysis of the performance and scalability of cluster-based web servers. We carry out the comparative studies using two experimental platforms, namely, a hardware testbed consisting of 16 PCs, and a trace-driven discrete-event simulator. Dispatcher and web server service times used in the simulator are determined by(More)
The two main approaches to parallel discrete event simulation – conservative and optimistic – are likely to encounter some limitations when the size and complexity of the simulation system increases. For such large scale simulations, the conservative approach appears to be limited by blocking overhead and sensitivity to lookahead, whereas the(More)
Creating simulation models via composition of predefined and reusable components is an efficient way of reducing costs and time associated with the simulation model development process. However, in order to successfully compose models one has to solve the issues of syntactic and semantic composability of components. HLA is the most widely used architecture(More)
A new priority queue implementation, the Lazy Queue, is presented in this paper. It is tailored to handle the pending event set encountered in discrete event simulation. The Lazy Queue is a multi-list variety where the sorting process is delayed until a point near the time where the elements are to be dequeued. The queue access time has been measured and(More)
The implementation of the pending event set (PES) is crucial to the execution speed of discrete event simulation programs. This paper studies the implementation of the PES in the context of simulations executing on parallel computers using the Time Warp mechanism. We present a scheme for implementing Time Warsp's PES based on well-known data structures for(More)
The High Level Architecture (HLA) is a standardized framework for distributed simulation that promotes reuse and interoperability of simulation components (federates). Federates are processes which communicate with each other in the simulation via the Run Time Infrastructure (RTI). When running a large scale simulation over many nodes/workstations, some may(More)