When should we use Radix sort?

Question

It seems Radix sort has a very good average case performance, i.e. O(kN): http://en.wikipedia.org/wiki/Radix_sort

Yet it seems like most people are still using Quick Sort - why is this?

Answer 1

Radix sort is harder to generalize than most other sorting algorithms. It requires fixed size keys, and some standard way of breaking the keys into pieces. Thus it never finds its way into libraries.

Answer 2

The other answers here fail to give examples of when radix sort is actually used.

An example is when creating a "suffix array" using the skew DC3 algorithm (Kärkkäinen-Sanders-Burkhardt). The algorithm is only linear-time if the sorting algorithm is linear-time, and radix sort is necessary and useful here because the keys are short by construction (3-tuples of integers).