Performance Modeling and Analysis of OTIS Networks

The most determining factors of the performance of a uniprocessor system are its architecture and the technology in which it is implemented. But when a number of such processors are interconnected to form a multiprocessor system, the performance of the whole system is significantly influenced by the nature in which the processors transfer data between each other; e.g. the technology, topology, switching technique and routing algorithm of the interconnection network. The present study focuses on a specific optoelectronic architecture for the interconnection of processors in a multiprocessor system, the OTIS (stands for Optical Transpose Interconnection System) architecture. In the OTIS architecture, free space optics is used for the interconnection of physically distant processing nodes and electronic interconnections are used for nodes that are closer. OTIS-based architectures appear to have the potential to be an interesting option for future generations of multiprocessing systems. But before any further observations on the potentials of these architectures can be made, further analysis of their performance is necessary. This is the objective of the work presented in this thesis. Previous work has been mainly focused on the algorithmic properties of OTIS networks. The aim of this project is to model and evaluate the performance of OTIS networks in sight of realistic parameters such as average message latency and network bandwidth. Of the different classes of OTIS networks, this study has been concentrated on the OTIS-hypercube network. Initially, adaptive and deterministic deadlock-free routing algorithms are suggested for this network. The effect of different design parameters on the performance of this architecture is evaluated through simulation experiments for different network sizes, routing algorithms, numbers of virtual channels, traffic patterns, traffic generation rates and message lengths. Many analytical models have been proposed for the performance of networks such as the hypercube and mesh networks. Such models can serve as a more appropriate and compact method to display, and refer to, the performance characteristics of the corresponding networks. But no such model has been reported, to our best knowledge, for OTIS-based networks in the literature. An accurate analytical performance model of such networks has been proposed in this work for wormhole switching in the cubical OTIS networks. The proposed model is validated through simulation experiments to serve as verification of its accuracy. We then utilize the proposed model to further study performance issues in OTIS-cubes under different technological implementation constraints.