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Show 38 identical elements). and ease of programmtng (programs which run on one el m nt will run on any other element, eliminating the need to develop special software for each different element). The Butterfly is typical in some ways of a modem commercial multiprocessor. It is built of "off-the-shelf' components (for the most part) and is designed to support general-purpose computing over a wide range of applications. It is composed of the Butterfly hardware, an operating system, and an interface to the outside world. That interface is not relevant to this dissertation and affects only the practical aspects of actually communicating with the Butterfly. Nothing more will be said about it h ere, although it is vecy important to the practical use of the machine. The operating system and the hardware are intimately connected and cannot be fully understood independently. The remainder of this chapter is devoted to a general description of the hardware and some of the operating system functions, a detailed description of those aspects of the Butterfly which have the most impact on logic programming implementation, and a summacy of how these aspects relate to the implementation. 3.1 General Characteristics This discussion of the Butterfly design is in two parts. The first part describes the hardware of the machine, and the second treats software aspects. These descriptions are not exhaustive, but give an adequate description of the Butterfly for the purposes of this discussion. References to more detailed explications are given where appropriate. 3.1.1 Hardware The Butterfly hardware comprises two sub-systems. The processor nodes are the processing elements which form the computational engine of the machine, and the Butterfly switch forms the communication system which connects them. 3.1.1.1 Processor Nodes. A Butterfly comprises 1 to 256 processor nodes. Unlike hypercubes, which can only have numbers of PEs which are powers of two. and mesh-connected architectures which must grow by rows or columns. a Butterfly can grow in single-node increments. A typical Butterfly node consist s of an |
