In [[computer science]], '''randomization function''' or '''randomizing function''' is a [[algorithm]] or [[procedure]] that implements a [[random]] [[function (mathematics)|function]] between two specific [[set (mathematics)|set]]s.
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Randomizing functions are central to the design of [[randomized algorithms]], that have good [[expected value (statistics)|expected]] performance for any input. For example, consider an algorithm like [[quicksort]], which has small expected running time for random inputs, but is very slow when the input data are presented in certain unfavorable orders. A randomizing function from the integers 1 to ''n'' to the integers 1 to ''n'' can be used used to rerrange the ''n'' input items in "random" order, before calling that algorithm. This modified algorithm will have small expected running time for ''any'' input.
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Randomizing functions are related to [[random number generator]]s and [[hash function]]s, but have somewhat different requirements and uses, and often need specific algorithms.
