Quicksort revisited

H.D. Mills and R.C. Linger (1986) propose adding the datatype set to existing programming languages. During some investigations using sets, it became apparent that Quicksort can be written without using stacks (or recursion). Using sets can lead to efficient multiprocessor usage, because if the elements of a set can be processed in any order, they can frequently be processed simultaneously. An example of the possibilities is an intelligent disk control unit based on External Quicksort, using four processors and four read/write heads., The control unit can sort a large disk file in about 1/3 of the time taken by the one-processor version