What is massively parallel computing, and why is it important?

HY should there be an issue of Dcedalus devoted to computation? Because there is a significant technology transition that is taking place in computers, and since it radically changes the cost and capabilities of information processing, it is likely to change our lives. The new technology is called massively parallel computing. On one hand, it is just a set of engineering ideas: a way of reorganizing the structure of the computer so that it can do many things at once. These ideas are simple and, in retrospect, obvious. On the other hand, the implication of these ideas is that the computer revolution has not yet begun to reach its limits. By the end of this article I will be writing about strange and unlikely sounding things, like home robots and virtual worlds. These things sound unlikely because significant technical advances?such as the automo bile, television, the computer?generally have surprising conse quences. It is always easiest to believe in a future that is a minor extrapolation of current-day trends. Such an extrapolated present is unlikely to happen in a time of rapid technological change. To help make this point and to set the ground for explaining the technology of parallel processing, I will begin with a story of how some simple ideas about reorganizing the flow of processing had a profound effect on our present-day lives. In the 1790s, just before Thomas Jefferson was elected president, the United States was in danger of getting into a war with the French. At that time, most of the rifles used by the US militia were made in France. In hopes of encouraging the development of an American