Although the origins of parallel computing go back to the last century,
it was only in the 1970s that parallel and vector computers became
available to the scientific community. The first of these machines-the
64 processor llliac IV and the vector computers built by Texas
Instruments, Control Data Corporation, and then CRA Y Research
Corporation-had a somewhat limited impact. They were few in number and
available mostly to workers in a few government laboratories. By now,
however, the trickle has become a flood. There are over 200 large-scale
vector computers now installed, not only in government laboratories but
also in universities and in an increasing diversity of industries.
Moreover, the National Science Foundation's Super- computing Centers
have made large vector computers widely available to the academic
community. In addition, smaller, very cost-effective vector computers
are being manufactured by a number of companies. Parallelism in
computers has also progressed rapidly. The largest super- computers now
consist of several vector processors working in parallel. Although the
number of processors in such machines is still relatively small (up to
8), it is expected that an increasing number of processors will be added
in the near future (to a total of 16 or 32). Moreover, there are a
myriad of research projects to build machines with hundreds, thousands,
or even more processors. Indeed, several companies are now selling
parallel machines, some with as many as hundreds, or even tens of
thousands, of processors.
