Editing Parallel computing (section)

===Flynn's taxonomy===
{{Main|Flynn's taxonomy}}
[[Michael J. Flynn]] created one of the earliest classification systems for parallel (and sequential) computers and programs, now known as [[Flynn's taxonomy]]. Flynn classified programs and computers by whether they were operating using a single set or multiple sets of instructions, and whether or not those instructions were using a single set or multiple sets of data.

{{Flynn's taxonomy}}

The single-instruction-single-data (SISD) classification is equivalent to an entirely sequential program. The single-instruction-multiple-data (SIMD) classification is analogous to doing the same operation repeatedly over a large data set. This is commonly done in [[signal processing]] applications. Multiple-instruction-single-data (MISD) is a rarely used classification. While computer architectures to deal with this were devised (such as [[systolic array]]s), few applications that fit this class materialized. Multiple-instruction-multiple-data (MIMD) programs are by far the most common type of parallel programs.

According to [[David A. Patterson (scientist)|David A. Patterson]] and [[John L. Hennessy]], "Some machines are hybrids of these categories, of course, but this classic model has survived because it is simple, easy to understand, and gives a good first approximation. It is also—perhaps because of its understandability—the most widely used scheme."<ref>Patterson and Hennessy, p.&nbsp;748.</ref>