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C Library Functions  - sort (3)

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NAME

sort(3f) - [M_orderpack:SORT] Sorts array into ascending order (Quick-sort)

CONTENTS

Synopsis
Description
Options
Examples
Author
Maintainer
License

SYNOPSIS

Subroutine Sort (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=*)

DESCRIPTION

Sorts INOUTVALS into ascending order (Quick-sort)

This version is not optimized for performance, and is thus not as difficult to read as some other ones.

Internally, This subroutine uses Quick-sort in a recursive implementation, and insertion sort for the last steps with small subsets. It does not use any work array.

The Quick-sort chooses a "pivot" in the set, and explores the array from both ends, looking for a value > pivot with the increasing index, for a value <= pivot with the decreasing index, and swapping them when it has found one of each. The array is then subdivided in two subsets:

       { values <= pivot} {pivot} {values > pivot}

It then recursively calls the procedure to sort each subset. When the size of the subarray is small enough, it switches to an insertion sort that is faster for very small sets.

OPTIONS

INOUTVALS
	array to sort

EXAMPLES

Sample program:

   program demo_sort
   ! sort array in ascending order
   use,intrinsic :: iso_fortran_env, only : int32, real32, real64
   use M_orderpack, only : sort
   implicit none
   ! an insertion sort is very efficient for very small arrays
   ! but generally slower than methods like quick-sort and merge-sort.
   real(kind=real64) :: valsd(2000)
   integer           :: i
      call random_seed()
      call random_number(valsd)
      valsd=valsd*1000000.0-500000.0
      call sort(valsd)
      do i=1,size(valsd)-1
         if (valsd(i+1).lt.valsd(i))then
            write(*,*)’not sorted’
            stop 3
         endif
      enddo
      write(*,*)’random arrays are now sorted’
   end program demo_sort

Results:

    random arrays are now sorted

AUTHOR

Michel Olagnon - Apr. 2000

MAINTAINER

John Urban, 2022.04.16

LICENSE

CC0-1.0

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Nemo Release 3.1

sort (3)

July 22, 2023

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