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A new interconnection network for massively parallel computing is introduced. This network is called an optical multi-mesh hypercube (OMMH) network. The OMMH integrates positive features of both hypercube (small diameter, high connectivity, symmetry, simple control and routing, fault tolerance, etc.) and mesh (constant node degree and scalability) topologies and at the same time circumvents their limitations (e.g., the lack of scalability of hypercubes, and the large diameter of meshes). The OMMH can maintain a constant node degree regardless of the increase in the network size. In addition, the flexibility of the OMMH network makes it well suited for optical implementations. This paper presents the OMMH topology, analyzes its architectural properties and potentials for massively parallel computing, and compares it to the hypercube. Moreover, it also presents a three-dimensional optical design methodology based on free-space optics. The proposed optical implementation has totally space-invariant connection patterns at every node, which enables the OMMH to be highly amenable to optical implementation using simple and efficient large space-bandwidth product space-invariant optical elements. >

Two important parameters of a network for massively parallel computers are scalability and modularity. Scalability has two aspects: size and time (or generation). Size scalability refers to the property that the size of the network can be increased with nominal effect on the existing configuration. Also, the increase in size is expected to result in a linear increase in performance. Time scalability implies that the communication capabilities of a network should be large enough to support the evolution of processing elements through generations. A modular network enables the construction of a large network out of many smaller ones. The lack of these two important parameters has limited the use of certain types of interconnection networks in the area of massively parallel computers. We present a new modular optical interconnection network, called an optical multimesh hypercube (OMMH), which is both size and time scalable. The OMMH combines positive features of both the hypercube (small diameter, high connectivity, symmetry, simple routing, and fault tolerance) and the torus (constant node degree and size scalability) networks. Also presented is a three-dimensional optical implementation of the OMMH network. A basic building block of the OMMH network is a hypercube module that is constructed with free-space optics to provide compact and high-density localized hypercube connections. The OMMH network is then constructed by the connection of such basic building blocks with multiwavelength optical fibers to realize torus connections. The proposed implementation methodology is intended to exploit the advantages of both space-invariant free-space and multiwavelength fiber-based optical interconnect technologies. The analysis of the proposed implementation shows that such a network is optically feasible in terms of the physical size and the optical power budget.

An important issue in the design of interconnection networks for massively parallel computers is scalability. Size-scalability refers to the property that the number of nodes in the network can be increased with negligible effect on the existing configuration and generation-scalability implies that the communication capabilities of a network should be large enough to support the evolution of processing elements through generations. The lack of size-scalability has limited the use of certain types of interconnection networks (e.g. hypercube) in the area of massively parallel computing. The authors present a new optical interconnection network, called an Optical Multi-Mesh Hypercube (OMMH), which is both size- and generation-scalable while combining positive features of both the hypercube (small diameter, high connectivity, symmetry, simple routing, and fault tolerance) and the mesh (constant node degree and scalability) networks. Also presented is a three-dimensional optical implementation methodology of the OMMH network. >

As an alternative to the hypercube, the binary de Bruijn (BdB) network is recently receiving much attention. The BdB not only provides a logarithmic diameter fault tolerance, and simple routing but also requires fewer links than the hypercube for the same network size. Additionally, a major advantage of the BdB network is a constant node degree: the number of edges per node is independent of the network size. This makes it very desirable for large scale parallel systems. However, due to its asymmetrical nature and global connectivity it is posing a major challenge for VLSI technology. Optics, owing to its three dimensional and global connectivity nature seems to be very suitable for implementing BdB networks. We present an implementation methodology for BdB networks. The distinctive feature of the proposed implementation methodology is partitionability of the network into a few primitive operations that can be efficiently implemented. We further show feasibility of the presented design methodology by proposing an optical implementation of the BdB network.