[[Image:Abramowitz&Stegun.page97.agr.jpg|thumb|Part of a 20th century precomputed [[mathematical table]] of [[common logarithm]]s.]]
In [[algorithms]], '''precomputation''' is the act of performing an initial [[computation]] before [[Run time (program lifecycle phase)|run time]] to generate resultsa [[lookup table]] that can be used by an algorithm to avoid repeated computation each time it is executed. Precomputation is often used in algorithms that depend on the results of expensive computations that don't depend on the input of the algorithm. A trivial example of precomputation is the use of [[hardcoded]] mathematical constants, such as [[Pi|π]] and [[E_(mathematical_constant)|e]], rather than computing their approximations to the necessary precision at run time.
