2.1 Introduction

This chapter surveys activities related to parallel computing that took place around the time that CP was an active project, primarily during the 1980s. The major areas that are covered are hardware, software, research projects, and production uses of parallel computers. In each case, there is no attempt to present a comprehensive list or survey of all the work that was done in that area. Rather, the attempt is to identify some of the major events during the period.

There are two major motivations for creating and using parallel computer architectures. The first is that, as surveyed in Section 1.2 parallelism is the only avenue to achieve vastly higher speeds than are possible now from a single processor. This was the primary motivation for initiating CP. Table 2.1 demonstrates dramatically the rather slow increase in speed of single-processor systems for one particular brand of supercomputer, CRAYs,  the most popular supercomputer in the world. Figure 2.1 (Color Plate) shows a more comprehensive sample of computer performance, measured in operations per second, from the 1940s extrapolated through the year 2000.

Figure 2.1: Historical trends of peak computer performance. In some cases, we have scaled up parallel performance to correspond to a configuration that would cost approximately $20 million.

A second motivation for the use of parallel architectures is that they should be considerably cheaper than sequential machines for systems of moderate speeds; that is, not necessarily supercomputers but instead minicomputers or mini-supercomputers would be cheaper to produce for a given performance level than the equivalent sequential system.

  
Table 2.1: Cycle Times

At the beginning of the 1980s, the goals of research in parallel computer architectures were to achieve much higher speeds than could be obtained from sequential architectures and to get much better price performance through the use of parallelism than would be possible from sequential machines.