C Library Functions - prank_special (3)

NAME

prank_special(3f) - [M_orderpack:RANK:PARTIAL] partially ranks an array in ASCENDING order (Insertion Sort)

Synopsis
Description
Options
Returns
Examples
Author
Maintainer
License

SYNOPSIS

Subroutine Prank_Special (INVALS, IRNGT, NORD)
     ${TYPE} (kind=${KIND}), Intent (In) :: INVALS(:)
     Integer, Intent (Out)               :: IRNGT(:)
     Integer, Intent (In)                :: NORD
Where ${TYPE}(kind=${KIND}) may be

Real(kind=real32)

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

DESCRIPTION

Partially ranks INVALS(). Returns IRNGT(1:NORD) filled with the indices of the lowest values in the array INVALS. More technically, it does a partial ranking of the array INVALS of order NORD.
NORD is restricted to the range 1 to size(IRNGT).
Internally, this version is not optimized for performance, and is thus not as difficult to read as some other ones.
The subroutine uses an insertion sort, limiting insertion to the first NORD values. It does not use any work array and is fastest when NORD is very small (2-5). but worst case behavior can easily happen (ie. if INVALS initially is inverse sorted). Therefore, In many cases, the refined Quick-sort method is faster.

OPTIONS

INVALS array to partially sort

NORD number of indices to return, restricted to 1 to size(IRNGT)

RETURNS

IRNGT indices of requested number (NORD) of lowest values in INVALS

EXAMPLES

Sample program:

   program demo_prank_special
   ! partially rank N lowest values in an array
   use M_orderpack, only : prank_special
   implicit none
   character(len=*),parameter :: g=’(*(g0,1x))’
   integer,allocatable :: INVALS(:)
   integer,allocatable :: irngt(:)
   integer :: nord
   INVALS=[10,5,7,1,4,5,6,8,9,10,1]
   nord=5
   allocate(irngt(nord))
      write(*,g)’ORIGINAL:’,INVALS
      call prank_special(INVALS,irngt,nord)
      write(*,g)’NUMBER OF INDICES TO RETURN:’,nord
      write(*,g)’RETURNED INDICES:’,irngt
      write(*,g)nord,’SMALLEST VALUES:’,INVALS(irngt(:nord))
   end program demo_prank_special

Results:

ORIGINAL: 10 5 7 1 4 5 6 8 9 10 1 NUMBER OF INDICES TO RETURN: 5 RETURNED INDICES: 4 11 5 2 6 5 SMALLEST VALUES: 1 1 4 5 5

AUTHOR

Michel Olagnon - Feb. 2000

MAINTAINER

John Urban, 2022.04.16

LICENSE

CC0-1.0

Nemo Release 3.1

prank_special (3)

July 22, 2023

Generated by manServer 1.08 from 6b61d88c-7949-4826-8381-3478cd195984 using man macros.

INVALS	array to partially sort
NORD	number of indices to return, restricted to 1 to size(IRNGT)