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C Library Functions  - rank_unique (3)

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NAME

Rank_Unique(3f) - [M_orderpack:RANK:UNIQUE] ranks an array, with removal of duplicate entries (Merge-Sort)

CONTENTS

Synopsis
Description
Options
Examples
Author
Maintainer
License

SYNOPSIS

Subroutine rank_unique (INVALS, IRNGT, NUNI)

      ${TYPE} (Kind=${KIND}), Intent (In) :: INVALS(:)
      Integer, Intent (Out)               :: IRNGT(:)
      Integer, Intent (Out)               :: NUNI

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

o	Real(kind=real32)
o	Real(kind=real64)
o	Integer(kind=int8)
o	Integer(kind=int16)
o	Integer(kind=int32)
o	Integer(kind=int64)

DESCRIPTION

Ranks an array, removing duplicate entries.

Internally, RANK_UNIQUE(3f) performs a Merge-sort ranking of an array, with removal of duplicate entries.

The routine is similar to pure merge-sort ranking, but on the last pass, it discards indices that correspond to duplicate entries.

For performance reasons, the first two passes are taken out of the standard loop, and use dedicated coding.

OPTIONS

INVALS	array to index
IRNGT	rank index returned pointing to unique values
NUNI	the number of unique values found

EXAMPLES

Sample program:

   program demo_rank_unique
   ! rank an array, with removal of duplicate entries.
   use M_orderpack, only : rank_unique
   implicit none
   character(len=*),parameter :: g=’(*(g0,1x))’
   integer,allocatable :: INVALS(:)
   !
   INVALS=[10,5,7,1,4,5,6,8,9,10,1]
   call printme()
   INVALS=[-1,0,-2,0,-3,0,-4]
   call printme()
   contains
   subroutine printme()
   integer,allocatable :: irngt(:)
   integer :: nuni
      if(allocated(irngt))deallocate(irngt)
      allocate(irngt(size(INVALS)))
      write(*,g)’ORIGINAL:’,INVALS
      call rank_unique(INVALS,irngt,nuni)
      write(*,g)’NUMBER OF UNIQUE INDICES:’,nuni
      write(*,g)’RETURNED INDICES:’,irngt(:nuni)
      write(*,g)’SORTED DATA:’,INVALS(irngt(:nuni))
   end subroutine
   end program demo_rank_unique

Results:

   ORIGINAL: 10 5 7 1 4 5 6 8 9 10 1
   NUMBER OF UNIQUE INDICES: 8
   RETURNED INDICES: 4 5 2 7 3 8 9 1
   SORTED DATA: 1 4 5 6 7 8 9 10
   ORIGINAL: -1 0 -2 0 -3 0 -4
   NUMBER OF UNIQUE INDICES: 5
   RETURNED INDICES: 7 5 3 1 2
   SORTED DATA: -4 -3 -2 -1 0

AUTHOR

Michel Olagnon, 2000-2012

MAINTAINER

John Urban, 2022.04.16

LICENSE

CC0-1.0

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Nemo Release 3.1

rank_unique (3)

February 23, 2025

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