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C Library Functions  - psort (3)

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NAME

psort(3f) - [M_orderpack:SORT:PARTIAL] partially sorts an array (Insertion Sort, generally for small or nearly sorted arrays)

CONTENTS

Synopsis
Description
Options
Examples
Author
Maintainer
License

SYNOPSIS

Subroutine Psort (INOUTVALS, NORD)

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

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

PSORT(3f) partially sorts INOUTVALS, bringing the NORD lowest values to the beginning of the array.

Internally, this subroutine uses an insertion sort, limiting insertion to the first NORD values. It does not use any work array and is faster when NORD is very small (2-5), but worst case behavior can happen fairly probably (initially inverse sorted). Therefore, in many cases, the refined quick-sort method is faster.

OPTIONS

INOUTVALS
	The array to partially sort
NORD	number of sorted values to return.

EXAMPLES

Sample program:

   program demo_psort
   ! partially sort an array
   use M_orderpack, only : psort
   implicit none
   character(len=*),parameter :: g=’(*(g0,1x))’
   integer :: nord

   int: block
      integer,allocatable :: ia(:)
      ia=[10,5,7,1,4,5,6,8,9,10,1]
      nord=5
      write(*,g)’Original.................:’,ia
      call psort(ia,nord)
      write(*,g)’Number of indices to sort:’,nord
      write(*,g)nord,’Lowest values..........:’,ia(:nord)
      write(*,g)’Entire array.............:’,ia
      write(*,g)
   endblock int
   char: block
      character(len=:),allocatable :: ca(:)
      integer :: i
      ca=[character(len=20) :: ’fan’,’a’,’car’,’be’,’egg’,’dam’,’gas’]
      nord=3
      write(*,g)’Original.................:’,(trim(ca(i)),i=1,size(ca))
      call psort(ca,nord)
      write(*,g)’Number of indices to sort:’,nord
      write(*,g)nord,’Lowest values..........:’,(trim(ca(i)),i=1,nord)
      write(*,g)’Entire array.............:’,(trim(ca(i)),i=1,size(ca))
      write(*,g)
   endblock char

   end program demo_psort

Results:

   Original.................: 10 5 7 1 4 5 6 8 9 10 1
   Number of indices to sort: 5
   5 Lowest values..........: 1 1 4 5 5
   Entire array.............: 1 1 4 5 5 10 7 8 9 10 6

   Original.................: fan a car be egg dam gas
   Number of indices to sort: 3
   3 Lowest values..........: a be car
   Entire array.............: a be car fan egg dam gas

AUTHOR

Michel Olagnon - Feb. 2000

MAINTAINER

John Urban, 2022.04.16

LICENSE

CC0-1.0

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Nemo Release 3.1

psort (3)

February 23, 2025

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