!
!
! AMG4PSBLAS version 1.0
! Algebraic Multigrid Package
! based on PSBLAS (Parallel Sparse BLAS version 3.5)
!
! (C) Copyright 2020
!
! Salvatore Filippone
! Pasqua D'Ambra
! Fabio Durastante
!
! 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.
!
!
!
! File: amg_c_soc1_map__bld.f90
!
! Subroutine: amg_c_soc1_map_bld
! Version: complex
!
! This routine builds the tentative prolongator based on the
! strength of connection aggregation algorithm presented in
!
! M. Brezina and P. Vanek, A black-box iterative solver based on a
! two-level Schwarz method, Computing, 63 (1999), 233-263.
! P. Vanek, J. Mandel and M. Brezina, Algebraic Multigrid by Smoothed
! Aggregation for Second and Fourth Order Elliptic Problems, Computing, 56
! (1996), 179-196.
!
! Note: upon exit
!
! Arguments:
! a - type(psb_cspmat_type).
! The sparse matrix structure containing the local part of the
! matrix to be preconditioned.
! desc_a - type(psb_desc_type), input.
! The communication descriptor of a.
! p - type(amg_cprec_type), input/output.
! The preconditioner data structure; upon exit it contains
! the multilevel hierarchy of prolongators, restrictors
! and coarse matrices.
! info - integer, output.
! Error code.
!
!
!
subroutine amg_c_soc1_map_bld(iorder,theta,clean_zeros,a,desc_a,nlaggr,ilaggr,info)
use psb_base_mod
use amg_base_prec_type
use amg_c_inner_mod
implicit none
! Arguments
integer(psb_ipk_), intent(in) :: iorder
logical, intent(in) :: clean_zeros
type(psb_cspmat_type), intent(in) :: a
type(psb_desc_type), intent(in) :: desc_a
real(psb_spk_), intent(in) :: theta
integer(psb_lpk_), allocatable, intent(out) :: ilaggr(:),nlaggr(:)
integer(psb_ipk_), intent(out) :: info
! Local variables
integer(psb_ipk_), allocatable :: ils(:), neigh(:), irow(:), icol(:),&
& ideg(:), idxs(:)
integer(psb_lpk_), allocatable :: tmpaggr(:)
complex(psb_spk_), allocatable :: val(:), diag(:)
integer(psb_ipk_) :: icnt,nlp,k,n,ia,isz,nr, nc, naggr,i,j,m, nz, ilg, ii, ip
type(psb_c_csr_sparse_mat) :: acsr
real(psb_spk_) :: cpling, tcl
logical :: disjoint
integer(psb_ipk_) :: debug_level, debug_unit,err_act
integer(psb_ipk_) :: ictxt,np,me
integer(psb_ipk_) :: nrow, ncol, n_ne
integer(psb_lpk_) :: nrglob
character(len=20) :: name, ch_err
info=psb_success_
name = 'amg_soc1_map_bld'
call psb_erractionsave(err_act)
if (psb_errstatus_fatal()) then
info = psb_err_internal_error_; goto 9999
end if
debug_unit = psb_get_debug_unit()
debug_level = psb_get_debug_level()
!
ictxt=desc_a%get_context()
call psb_info(ictxt,me,np)
nrow = desc_a%get_local_rows()
ncol = desc_a%get_local_cols()
nrglob = desc_a%get_global_rows()
nr = a%get_nrows()
nc = a%get_ncols()
allocate(ilaggr(nr),neigh(nr),ideg(nr),idxs(nr),&
& icol(nc),val(nc),stat=info)
if(info /= psb_success_) then
info=psb_err_alloc_request_
call psb_errpush(info,name,i_err=(/2*nr,izero,izero,izero,izero/),&
& a_err='integer')
goto 9999
end if
diag = a%get_diag(info)
if(info /= psb_success_) then
info=psb_err_from_subroutine_
call psb_errpush(info,name,a_err='psb_sp_getdiag')
goto 9999
end if
call a%cp_to(acsr)
if (clean_zeros) call acsr%clean_zeros(info)
if (iorder == amg_aggr_ord_nat_) then
do i=1, nr
ilaggr(i) = -(nr+1)
idxs(i) = i
end do
else
do i=1, nr
ilaggr(i) = -(nr+1)
ideg(i) = acsr%irp(i+1) - acsr%irp(i)
end do
call psb_msort(ideg,ix=idxs,dir=psb_sort_down_)
end if
!
! Phase one: Start with disjoint groups.
!
naggr = 0
icnt = 0
step1: do ii=1, nr
i = idxs(ii)
if ((i<1).or.(i>nr)) then
info=psb_err_internal_error_
call psb_errpush(info,name)
goto 9999
end if
if (ilaggr(i) == -(nr+1)) then
nz = (acsr%irp(i+1)-acsr%irp(i))
if ((nz<0).or.(nz>size(icol))) then
info=psb_err_internal_error_
call psb_errpush(info,name)
goto 9999
end if
icol(1:nz) = acsr%ja(acsr%irp(i):acsr%irp(i+1)-1)
val(1:nz) = acsr%val(acsr%irp(i):acsr%irp(i+1)-1)
!
! Build the set of all strongly coupled nodes
!
ip = 0
do k=1, nz
j = icol(k)
if ((1<=j).and.(j<=nr)) then
if (abs(val(k)) > theta*sqrt(abs(diag(i)*diag(j)))) then
ip = ip + 1
icol(ip) = icol(k)
end if
end if
enddo
!
! If the whole strongly coupled neighborhood of I is
! as yet unconnected, turn it into the next aggregate.
! Same if ip==0 (in which case, neighborhood only
! contains I even if it does not look like it from matrix)
!
disjoint = all(ilaggr(icol(1:ip)) == -(nr+1)).or.(ip==0)
if (disjoint) then
icnt = icnt + 1
naggr = naggr + 1
do k=1, ip
ilaggr(icol(k)) = naggr
end do
ilaggr(i) = naggr
end if
endif
enddo step1
if (debug_level >= psb_debug_outer_) then
write(debug_unit,*) me,' ',trim(name),&
& ' Check 1:',count(ilaggr == -(nr+1))
end if
!
! Phase two: join the neighbours
!
tmpaggr = ilaggr
step2: do ii=1,nr
i = idxs(ii)
if (ilaggr(i) == -(nr+1)) then
nz = (acsr%irp(i+1)-acsr%irp(i))
if (nz == 1) cycle step2
icol(1:nz) = acsr%ja(acsr%irp(i):acsr%irp(i+1)-1)
val(1:nz) = acsr%val(acsr%irp(i):acsr%irp(i+1)-1)
!
! Find the most strongly connected neighbour that is
! already aggregated, if any, and join its aggregate
!
cpling = szero
ip = 0
do k=1, nz
j = icol(k)
if ((1<=j).and.(j<=nr)) then
if ((abs(val(k)) > theta*sqrt(abs(diag(i)*diag(j))))&
& .and. (tmpaggr(j) > 0).and. (abs(val(k)) > cpling)) then
ip = k
cpling = abs(val(k))
end if
end if
enddo
if (ip > 0) then
ilaggr(i) = ilaggr(icol(ip))
end if
end if
end do step2
!
! Phase three: sweep over leftovers, if any
!
step3: do ii=1,nr
i = idxs(ii)
if (ilaggr(i) < 0) then
nz = (acsr%irp(i+1)-acsr%irp(i))
if (nz == 1) cycle step3
icol(1:nz) = acsr%ja(acsr%irp(i):acsr%irp(i+1)-1)
val(1:nz) = acsr%val(acsr%irp(i):acsr%irp(i+1)-1)
!
! Find its strongly connected neighbourhood not
! already aggregated, and make it into a new aggregate.
!
cpling = szero
ip = 0
do k=1, nz
j = icol(k)
if ((1<=j).and.(j<=nr)) then
if ((abs(val(k)) > theta*sqrt(abs(diag(i)*diag(j))))&
& .and. (ilaggr(j) < 0)) then
ip = ip + 1
icol(ip) = icol(k)
end if
end if
enddo
if (ip > 0) then
icnt = icnt + 1
naggr = naggr + 1
ilaggr(i) = naggr
do k=1, ip
ilaggr(icol(k)) = naggr
end do
else
!
! This should not happen: we did not even connect with ourselves,
! but it's not a singleton.
!
naggr = naggr + 1
ilaggr(i) = naggr
end if
end if
end do step3
! Any leftovers?
do i=1, nr
if (ilaggr(i) < 0) then
nz = (acsr%irp(i+1)-acsr%irp(i))
if (nz == 1) then
! Mark explicitly as a singleton so that
! it will be ignored in map_to_tprol.
! Need to use -(nrglob+nr) to make sure
! it's still negative when shifted and combined with
! other processes.
ilaggr(i) = -(nrglob+nr)
else
info=psb_err_internal_error_
call psb_errpush(info,name,a_err='Fatal error: non-singleton leftovers')
goto 9999
endif
end if
end do
if (naggr > ncol) then
!write(0,*) name,'Error : naggr > ncol',naggr,ncol
info=psb_err_internal_error_
call psb_errpush(info,name,a_err='Fatal error: naggr>ncol')
goto 9999
end if
call psb_realloc(ncol,ilaggr,info)
if (info /= psb_success_) then
info=psb_err_from_subroutine_
ch_err='psb_realloc'
call psb_errpush(info,name,a_err=ch_err)
goto 9999
end if
allocate(nlaggr(np),stat=info)
if (info /= psb_success_) then
info=psb_err_alloc_request_
call psb_errpush(info,name,i_err=(/np,izero,izero,izero,izero/),&
& a_err='integer')
goto 9999
end if
nlaggr(:) = 0
nlaggr(me+1) = naggr
call psb_sum(ictxt,nlaggr(1:np))
call acsr%free()
call psb_erractionrestore(err_act)
return
9999 call psb_error_handler(err_act)
return
end subroutine amg_c_soc1_map_bld