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psblas3/base/serial/aux/ssr.f90

360 lines
9.0 KiB
Fortran

!!$
!!$ Parallel Sparse BLAS version 3.0
!!$ (C) Copyright 2006, 2007, 2008, 2009, 2010, 2012
!!$ Salvatore Filippone University of Rome Tor Vergata
!!$ Alfredo Buttari CNRS-IRIT, Toulouse
!!$
!!$ 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.
!!$
!!$
subroutine ssr(n,x,dir)
use psb_serial_mod
implicit none
!
! Quicksort.
! Adapted from a number of sources, including Don Knuth's TAOCP.
!
! .. Scalar Arguments ..
integer(psb_ipk_), intent(in) :: n, dir
real(psb_spk_) :: x(n)
! ..
! .. Local Scalars ..
real(psb_spk_) :: piv, xt, xk
integer(psb_ipk_) :: i, j, ilx, iux, istp, lpiv
integer(psb_ipk_) :: n1, n2
integer(psb_ipk_), parameter :: maxstack=64,nparms=3,ithrs=16
integer(psb_ipk_) :: istack(nparms,maxstack)
! ..
!
! small inputs will only get through insertion sort.
!
select case(dir)
case(psb_sort_up_)
if (n > ithrs) then
!
! Init stack pointer
!
istp = 1
istack(1,istp) = 1
istack(2,istp) = n
do
if (istp <= 0) exit
ilx = istack(1,istp)
iux = istack(2,istp)
istp = istp - 1
!
! Choose a pivot with median-of-three heuristics, leave it
! in the LPIV location
!
i = ilx
j = iux
lpiv = (i+j)/2
piv = x(lpiv)
if (piv < x(i)) then
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
if (piv > x(j)) then
xt = x(j)
x(j) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
if (piv < x(i)) then
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
!
! now piv is correct; place it into first location
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
i = ilx - 1
j = iux + 1
outer_up: do
in_up1: do
i = i + 1
xk = x(i)
if (xk >= piv) exit in_up1
end do in_up1
!
! Ensure finite termination for next loop
!
xt = xk
x(i) = piv
in_up2:do
j = j - 1
xk = x(j)
if (xk <= piv) exit in_up2
end do in_up2
x(i) = xt
if (j > i) then
xt = x(i)
x(i) = x(j)
x(j) = xt
else
exit outer_up
end if
end do outer_up
if (i == ilx) then
if (x(i) /= piv) then
call psb_errpush(psb_err_internal_error_,r_name='ssr',a_err='impossible pivot condition')
call psb_error()
endif
i = i + 1
endif
n1 = (i-1)-ilx+1
n2 = iux-(i)+1
if (n1 > n2) then
if (n1 > ithrs) then
istp = istp + 1
istack(1,istp) = ilx
istack(2,istp) = i-1
else
call sisr_up(n1,x(ilx:i-1))
endif
if (n2 > ithrs) then
istp = istp + 1
istack(1,istp) = i
istack(2,istp) = iux
else
call sisr_up(n2,x(i:iux))
endif
else
if (n2 > ithrs) then
istp = istp + 1
istack(1,istp) = i
istack(2,istp) = iux
else
call sisr_up(n2,x(i:iux))
endif
if (n1 > ithrs) then
istp = istp + 1
istack(1,istp) = ilx
istack(2,istp) = i-1
else
call sisr_up(n1,x(ilx:i-1))
endif
endif
enddo
else
call sisr_up(n,x)
endif
case(psb_sort_down_)
if (n > ithrs) then
!
! Init stack pointer
!
istp = 1
istack(1,istp) = 1
istack(2,istp) = n
do
if (istp <= 0) exit
ilx = istack(1,istp)
iux = istack(2,istp)
istp = istp - 1
!
! Choose a pivot with median-of-three heuristics, leave it
! in the LPIV location
!
i = ilx
j = iux
lpiv = (i+j)/2
piv = x(lpiv)
if (piv > x(i)) then
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
if (piv < x(j)) then
xt = x(j)
x(j) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
if (piv > x(i)) then
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
piv = x(lpiv)
endif
!
! now piv is correct; place it into first location
xt = x(i)
x(i) = x(lpiv)
x(lpiv) = xt
i = ilx - 1
j = iux + 1
outer_dw: do
in_dw1: do
i = i + 1
xk = x(i)
if (xk <= piv) exit in_dw1
end do in_dw1
!
! Ensure finite termination for next loop
!
xt = xk
x(i) = piv
in_dw2:do
j = j - 1
xk = x(j)
if (xk >= piv) exit in_dw2
end do in_dw2
x(i) = xt
if (j > i) then
xt = x(i)
x(i) = x(j)
x(j) = xt
else
exit outer_dw
end if
end do outer_dw
if (i == ilx) then
if (x(i) /= piv) then
call psb_errpush(psb_err_internal_error_,r_name='ssr',a_err='impossible pivot condition')
call psb_error()
endif
i = i + 1
endif
n1 = (i-1)-ilx+1
n2 = iux-(i)+1
if (n1 > n2) then
if (n1 > ithrs) then
istp = istp + 1
istack(1,istp) = ilx
istack(2,istp) = i-1
else
call sisr_dw(n1,x(ilx:i-1))
endif
if (n2 > ithrs) then
istp = istp + 1
istack(1,istp) = i
istack(2,istp) = iux
else
call sisr_dw(n2,x(i:iux))
endif
else
if (n2 > ithrs) then
istp = istp + 1
istack(1,istp) = i
istack(2,istp) = iux
else
call sisr_dw(n2,x(i:iux))
endif
if (n1 > ithrs) then
istp = istp + 1
istack(1,istp) = ilx
istack(2,istp) = i-1
else
call sisr_dw(n1,x(ilx:i-1))
endif
endif
enddo
else
call sisr_dw(n,x)
endif
case default
call psb_errpush(psb_err_internal_error_,r_name='ssr',a_err='wrong dir')
call psb_error()
end select
return
contains
subroutine sisr_up(n,x)
implicit none
integer(psb_ipk_) :: n
real(psb_spk_) :: x(n)
integer(psb_ipk_) :: i,j
real(psb_spk_) :: xx
do j=n-1,1,-1
if (x(j+1) < x(j)) then
xx = x(j)
i=j+1
do
x(i-1) = x(i)
i = i+1
if (i>n) exit
if (x(i) >= xx) exit
end do
x(i-1) = xx
endif
enddo
end subroutine sisr_up
subroutine sisr_dw(n,x)
implicit none
integer(psb_ipk_) :: n
real(psb_spk_) :: x(n)
integer(psb_ipk_) :: i,j
real(psb_spk_) :: xx
do j=n-1,1,-1
if (x(j+1) > x(j)) then
xx = x(j)
i=j+1
do
x(i-1) = x(i)
i = i+1
if (i>n) exit
if (x(i) <= xx) exit
end do
x(i-1) = xx
endif
enddo
end subroutine sisr_dw
end subroutine ssr