An Algorithmic Evaluation of Optical Interconnection Networks

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Parallel architectures based on the optical interconnect technology are becoming more and more popular as reflected by the numerous optical computers that have been proposed in recent years. Optical computers have been shown to possess superior interconnect properties compared to their electrical counterparts. These architectures offer the potential of building affordable machines operating at extremely high speeds.The development of algorithms for the proposed optical architectures is complicated by the fact that some models support pipelined data transfer, other models have a heterogeneous interconnect topology, and yet other models use an asymmetric topology. Although algorithms have been designed for some of these models, this development is in its infancy. The developed algorithms are mainly for a limited set of fundamental problems, and even this level of development has been done for only a few of the proposed architectures. Further, the developed algorithms assume that the size of the architecture is a function of the problem size. This assumption is clearly invalid in practice. Typically, the problem size will be much larger than the size of the architecture. An important question is if the optical architecture algorithms that have been developed so far are scalable. That is, can they be efficiently extended to solve problems whose size is considerably larger than the machine size. In this project the base of known efficient algorithms for optical architectures will be significantly expanded. Special attention will be paid to scalable algorithms. A cross-architecture performance study from the algorithms point of view will be performed. This study will be conducted in the domains of fundamental data operations and image processing. Scalability study has been conducted in the past by various researchers on models such as the PRAM, meshes with buses, and so on. But little has been done for the optical models. Also, many of the past works (for example, on meshes with buses) have studied the scalability issue by simulating a machine of one size on a machine of different size. Such studies are restricted in their applicability. In this project the general scalability issue will be investigated and hence the scalability of algorithms will be explored directly. In particular, the following question will be addressed: As the size of the input increases arbitrarily, how do the speedup and efficiency of the algorithm under concern change?The problem domains of interest are fundamental data operations such as sorting, routing, selection, etc. and image processing operations such as clustering, template matching, histogram, FFT, etc. These operations have been chosen since they span a number of application domains. At least three optical architectures, namely, Arrays with Reconfigurable Optical Buses (AROBs), Optical Transpose Interconnection Systems (OTISs), and Partitionable Optical Passive Star (POPS) computers, will be considered. The algorithms and algorithmic techniques to be developed in this project can be expected to be applicable to other architectures as well.