Editing Partial evaluation (section)

{{Short description|Technique for program optimization}}
{{Distinguish|partial application}}
{{More footnotes|date=May 2013}}
{{Evaluation strategy}}

In [[computing]], '''partial evaluation''' is a technique for several different types of [[optimization (computer science)|program optimization]] by [[Specialization (logic)|specialization]]. The most straightforward application is to produce new programs that run faster than the originals while being guaranteed to behave in the same way.

A [[computer program]] ''prog'' is seen as a [[map (mathematics)|map]]ping of input data into output data:

<math display="block">prog : I_\text{static} \times I_\text{dynamic} \to O,</math>

where <math>I_\text{static}</math>, the ''static data'', is the part of the input data known at compile time.

The partial evaluator transforms <math>\langle prog, I_\text{static}\rangle</math> into <math>prog^* : I_\text{dynamic} \to O</math> by precomputing all static input at compile time. <math>prog^*</math> is called the "residual program" and should run more efficiently than the original program. The act of partial evaluation is said to "residualize" <math>prog</math> to <math>prog^*</math>.