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psblas3/prec/impl/psb_d_sp_drop.f90

169 lines
5.8 KiB
Fortran

!
! Parallel Sparse BLAS version 3.5
! (C) Copyright 2006-2018
! Salvatore Filippone
! Alfredo Buttari
!
! 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.
!
! Moved here from AMG-AINV, original copyright below.
!
!
! AMG-AINV: Approximate Inverse plugin for
! AMG4PSBLAS version 1.0
!
! (C) Copyright 2020
!
! Salvatore Filippone 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 AMG4PSBLAS 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 AMG4PSBLAS 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 psb_d_sp_drop(idiag,nzrmax,sp_thresh,nz,iz,valz,info)
use psb_base_mod
implicit none
real(psb_dpk_), intent(in) :: sp_thresh
integer(psb_ipk_), intent(in) :: idiag, nzrmax
integer(psb_ipk_), intent(inout) :: nz
integer(psb_ipk_), intent(inout) :: iz(:)
real(psb_dpk_), intent(inout) :: valz(:)
integer(psb_ipk_), intent(out) :: info
!
integer(psb_ipk_) :: i, j, idf, nw
real(psb_dpk_) :: witem
integer(psb_ipk_) :: widx
real(psb_dpk_), allocatable :: xw(:)
integer(psb_ipk_), allocatable :: xwid(:), indx(:)
info = psb_success_
if (nz > min(size(iz),size(valz))) then
write(0,*) 'Serious size problem ',nz,size(iz),size(valz)
info = -2
return
end if
allocate(xw(nz),xwid(nz),indx(nz),stat=info)
if (info /= psb_success_) then
write(psb_err_unit,*) ' Memory allocation failure in sp_drop',nz,info
return
endif
! Always keep the diagonal element
idf = -1
do i=1, nz
if (iz(i) == idiag) then
idf = i
witem = valz(i)
widx = iz(i)
valz(i) = valz(1)
iz(i) = iz(1)
valz(1) = witem
iz(1) = widx
exit
end if
end do
if (idf == -1) then
xw(1:nz) = valz(1:nz)
call psb_qsort(xw(1:nz),indx(1:nz),dir=psb_asort_down_)
do i=1, nz
xwid(i) = iz(indx(i))
end do
nw = min(nz,nzrmax)
do
if (nw <= 1) exit
if (abs(xw(nw)) < sp_thresh) then
nw = nw - 1
else
exit
end if
end do
nw = max(nw, 1)
else
nw = nz-1
xw(1:nw) = valz(2:nz)
call psb_qsort(xw(1:nw),indx(1:nw),dir=psb_asort_down_)
nw = min(nw,nzrmax-1)
do
if (nw <= 1) exit
if (abs(xw(nw)) < sp_thresh) then
nw = nw - 1
else
exit
end if
end do
do i=1, nw
xwid(i) = iz(1+indx(i))
end do
nw = nw + 1
xw(nw) = valz(1)
xwid(nw) = iz(1)
end if
call psb_msort(xwid(1:nw),indx(1:nw),dir=psb_sort_up_)
do i=1, nw
valz(i) = xw(indx(i))
iz(i) = xwid(i)
end do
nz = nw
if (nz>nzrmax) write(0,*) 'in sp_drop: ',nw,nzrmax,nz
deallocate(xw,xwid,indx,stat=info)
if (info /= psb_success_) then
write(psb_err_unit,*) ' Memory deallocation failure in sp_drop',info
return
endif
return
end subroutine psb_d_sp_drop