Technical note: Efficient sorting routines in FORTRAN 77

A problem faced which arises in many computing applications is that of sorting the entries in a list into ascending sequence of their values. Efficient algorithms for sorting long lists usually require recursive techniques and are not straightforward to program in a non-recursive language such as FORTRAN 77. This paper describes three FORTRAN 77 implementations of the insertion sort, quicksort and modified quicksort algorithms. The first algorithm is suitable for short lists whilst the second two are suitable for longer lists. A detailed description of the removal of recursion from the quicksort algorithm by the use of stacks is presented. All of the implementations are believed to be efficient, and should prove useful in engineering applications. Some timing statistics are given to illustrate the utility of the subroutines presented. © 1984