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psblas3/base/serial/aux/dmsort_dw.f90

174 lines
5.0 KiB
Fortran

!
! Parallel Sparse BLAS version 2.2
! (C) Copyright 2006 Salvatore Filippone University of Rome Tor Vergata
! Alfredo Buttari University of Rome Tor Vergata
!
! Redistribution and use in source and binary forms, with or without
! modification, are permitted provided that the following conditions
! are met:
! 1. Redistributions of source code must retain the above copyright
! notice, this list of conditions and the following disclaimer.
! 2. Redistributions in binary form must reproduce the above copyright
! notice, this list of conditions, and the following disclaimer in the
! documentation and/or other materials provided with the distribution.
! 3. The name of the PSBLAS group or the names of its contributors may
! not be used to endorse or promote products derived from this
! software without specific written permission.
!
! THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
! ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
! TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
! PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE PSBLAS GROUP OR ITS CONTRIBUTORS
! BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
! CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
! SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
! INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
! CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
! ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
! POSSIBILITY OF SUCH DAMAGE.
!
! File: msort_dw.f90
!
! Subroutine: msort_dw
! This subroutine sorts an integer array into ascending order.
!
! Arguments:
! n - integer Input: size of the array
! k - real(*) input: array of keys to be sorted
! l - integer(0:n+1) output: link list
! iret - integer output: 0 Normal termination
! 1 the array was already sorted
! *
! REFERENCES = (1) D. E. Knuth *
! The Art of Computer Programming, *
! vol.3: Sorting and Searching *
! Addison-Wesley, 1973 *
! *
! call msort_dw(n,x,iaux,iret)
!
! if (iret == 0) then
! lp = iaux(0)
! k = 1
! do
! if ((lp == 0).or.(k>n)) exit
! do
! if (lp >= k) exit
! lp = iaux(lp)
! end do
! iswap = x(lp)
! x(lp) = x(k)
! x(k) = iswap
! lswap = iaux(lp)
! iaux(lp) = iaux(k)
! iaux(k) = lp
! lp = lswap
! k = k + 1
! enddo
! end if
!
!
subroutine dmsort_dw(n,k,l,iret)
use psb_const_mod
implicit none
integer n, iret
real(psb_dpk_) :: k(n)
integer l(0:n+1)
!
integer p,q,s,t
intrinsic iabs,isign
! ..
iret = 0
! first step: we are preparing ordered sublists, exploiting
! what order was already in the input data; negative links
! mark the end of the sublists
l(0) = 1
t = n + 1
do p = 1,n - 1
if (k(p) >= k(p+1)) then
l(p) = p + 1
else
l(t) = - (p+1)
t = p
end if
end do
l(t) = 0
l(n) = 0
! see if the input was already sorted
if (l(n+1) == 0) then
iret = 1
return
else
l(n+1) = iabs(l(n+1))
end if
mergepass: do
! otherwise, begin a pass through the list.
! throughout all the subroutine we have:
! p, q: pointing to the sublists being merged
! s: pointing to the most recently processed record
! t: pointing to the end of previously completed sublist
s = 0
t = n + 1
p = l(s)
q = l(t)
if (q == 0) exit mergepass
outer: do
if (k(p) < k(q)) then
l(s) = isign(q,l(s))
s = q
q = l(q)
if (q > 0) then
do
if (k(p) >= k(q)) cycle outer
s = q
q = l(q)
if (q <= 0) exit
end do
end if
l(s) = p
s = t
do
t = p
p = l(p)
if (p <= 0) exit
end do
else
l(s) = isign(p,l(s))
s = p
p = l(p)
if (p>0) then
do
if (k(p) < k(q)) cycle outer
s = p
p = l(p)
if (p <= 0) exit
end do
end if
! otherwise, one sublist ended, and we append to it the rest
! of the other one.
l(s) = q
s = t
do
t = q
q = l(q)
if (q <= 0) exit
end do
end if
p = -p
q = -q
if (q == 0) then
l(s) = isign(p,l(s))
l(t) = 0
exit outer
end if
end do outer
end do mergepass
end subroutine dmsort_dw