{I,S,D}SORTQ ( order, n, x, incx )
order character*1 On entry, order specifies the operation to be performed as follows: If order = 'A' or 'a', x is sorted in ascending sequence If order = 'D' or 'd', x is sorted in descending sequence On exit, order is unchanged. n integer*4 On entry, the length of vector x. On exit, n is unchanged. x integer*4 | real*4 | real*8 On entry, a length n vector of data to be sorted. On exit, x is overwritten by a length n vector of sorted data. incx integer*4 On entry, incx specifies the distance between elements of vector x. incx must be positive. On exit, incx is unchanged.
The _SORTQ routines sort a vector of data using the quicksort algorithm. Data is sorted in ascending order if order is 'A' or 'a' and in descending order if order is 'D' or 'd'. The quicksort algorithm is implemented by recursing until the partition size is less than sixteen. At that point a simple replacement sort is used to sort the elements of the partition.
REAL*4 DATA( 100 ) N = 100 CALL SSORTQ( 'A',N,DATA,1 ) This FORTRAN code sorts a 100 element single real vector.