inssor Interface

sort_special(3f) - [M_orderpack:SORT] Sorts array into ascending order
             (Insertion sort, generally for small or nearly sorted
             arrays)

  Subroutine Sort_Special (INOUTVALS)

   ${TYPE} (kind=${KIND}), Intent (InOut) :: INOUTVALS(:)

Where ${TYPE}(kind=${KIND}) may be

   o Real(kind=real32)
   o Real(kind=real64)
   o Integer(kind=int32)
   o Character(kind=selected_char_kind("DEFAULT"),len=*)

Sorts INOUTVALS() into ascending order (Insertion sort).

If certain requirements are met and performance is important this
procedure can be far faster, but SORT(3f) and ranking routines
RANK(3f) and RANK_BASIC(3f) are recommended for the general case.

This subroutine uses an Insertion sort. It does not use any work array
and is faster when INOUTVALS() is of very small size (< 20), or already
almost sorted; but worst case behavior can be triggered by commonly
encountered data order (e.g. initially inverse sorted). Therefore,
in many cases the Quick-sort or Merge-sort method is faster.

 INOUTVALS      array to sort

program demo_sort_special
! sort an array using insertion sort
use,intrinsic :: iso_fortran_env, only : int32, real32, real64
use M_orderpack, only : sort_special
implicit none
! an insertion sort is very efficient for very small arrays
! but generally slower than methods like quick-sort and merge-sort.
integer,parameter :: isz=2000
real(kind=real64) :: dd(isz), hi, low
   ! make an array of random values
   call random_seed()
   call random_number(dd)
   dd=dd*1000000.0-500000.0
   low= minval(dd)
   hi = maxval(dd)
   ! sort the data
   call sort_special(dd)
   ! cursory checks
   if(any(dd(1:isz-1) .gt. dd(2:isz)))stop 'ERROR: array not sorted'
   write(*,*)'check min:',dd(1).eq.low
   write(*,*)'check max:',dd(isz).eq.hi
   write(*,*)'PASSED: random array is now sorted'
end program demo_sort_special

 check min: T
 check max: T
 PASSED: random array is now sorted

Michel Olagnon - Apr. 2000

John Urban, 2022.04.16

CC0-1.0