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