What is "partial evaluation"

n. (context comptheory English) A technique for program optimization by specialization, so as to produce new programs which run faster than the originals while guaranteed to behave in the same way.

In computing, partial evaluation is a technique for several different types of program optimization by specialization. The most straightforward application is to produce new programs which run faster than the originals while being guaranteed to behave in the same way.

A computer program, prog, is seen as a mapping of input data into output data:

prog : I × I → O

I, the static data, is the part of the input data known at compile time.

The partial evaluator transforms ⟨prog, I⟩ into prog : I → O by precomputing all static input at compile time. prog is called the "residual program" and should run more efficiently than the original program. The act of partial evaluation is said to "residualize" prog to prog.