amg4psblas/mlprec/impl/smoother/mld_d_jac_smoother_apply_vect.f90

!!$
!!$ 
!!$                           MLD2P4  version 2.0
!!$  MultiLevel Domain Decomposition Parallel Preconditioners Package
!!$             based on PSBLAS (Parallel Sparse BLAS version 3.3)
!!$  
!!$  (C) Copyright 2008, 2010, 2012, 2015
!!$
!!$                      Salvatore Filippone  University of Rome Tor Vergata
!!$                      Alfredo Buttari      CNRS-IRIT, Toulouse
!!$                      Pasqua D'Ambra       ICAR-CNR, Naples
!!$                      Daniela di Serafino  Second University of Naples
!!$ 
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!!$
subroutine mld_d_jac_smoother_apply_vect(alpha,sm,x,beta,y,desc_data,trans,& 
     & sweeps,work,info,init,initu)
  
  use psb_base_mod
  use mld_d_jac_smoother, mld_protect_name => mld_d_jac_smoother_apply_vect
  implicit none 
  type(psb_desc_type), intent(in)                 :: desc_data
  class(mld_d_jac_smoother_type), intent(inout) :: sm
  type(psb_d_vect_type),intent(inout)           :: x
  type(psb_d_vect_type),intent(inout)           :: y
  real(psb_dpk_),intent(in)                      :: alpha,beta
  character(len=1),intent(in)                     :: trans
  integer(psb_ipk_), intent(in)                   :: sweeps
  real(psb_dpk_),target, intent(inout)           :: work(:)
  integer(psb_ipk_), intent(out)                  :: info
  character, intent(in), optional                :: init
  type(psb_d_vect_type),intent(inout), optional   :: initu

  integer(psb_ipk_)    :: n_row,n_col
  type(psb_d_vect_type)  :: tx, ty
  real(psb_dpk_), pointer :: aux(:)
  integer(psb_ipk_)  :: ictxt,np,me,i, err_act
  character          :: trans_, init_
  character(len=20)  :: name='d_jac_smoother_apply_v'

  call psb_erractionsave(err_act)

  info = psb_success_

  
  if (present(init)) then
    init_ = psb_toupper(init)
  else
    init_='Z'
  end if

  trans_ = psb_toupper(trans)
  select case(trans_)
  case('N')
  case('T','C')
  case default
    call psb_errpush(psb_err_iarg_invalid_i_,name)
    goto 9999
  end select

  if (.not.allocated(sm%sv)) then 
    info = 1121
    call psb_errpush(info,name)
    goto 9999
  end if

  n_row = desc_data%get_local_rows()
  n_col = desc_data%get_local_cols()

  if (4*n_col <= size(work)) then 
    aux => work(:)
  else
    allocate(aux(4*n_col),stat=info)
    if (info /= psb_success_) then 
      info=psb_err_alloc_request_
      call psb_errpush(info,name,& 
           & i_err=(/4*n_col,izero,izero,izero,izero/),&
           & a_err='real(psb_dpk_)')
      goto 9999      
    end if
  endif
  
  if ((.not.sm%sv%is_iterative()).and.((sweeps == 1).or.(sm%nnz_nd_tot==0))) then 
    !  if .not.sv%is_iterative, there's no need to pass init
    call sm%sv%apply(alpha,x,beta,y,desc_data,trans_,aux,info) 
    
    if (info /= psb_success_) then
      call psb_errpush(psb_err_internal_error_,&
           & name,a_err='Error in sub_aply Jacobi Sweeps = 1')
      goto 9999
    endif
    
  else if (sweeps >= 0) then 
    !
    !
    ! Apply multiple sweeps of a block-Jacobi solver
    ! to compute an approximate solution of a linear system.
    !
    !
    call psb_geasb(tx,desc_data,info,mold=x%v,scratch=.true.)
    call psb_geasb(ty,desc_data,info,mold=x%v,scratch=.true.)


    !
    !  Unroll  the first iteration and fold it inside SELECT CASE
    !  this will save one AXPBY and one SPMM when INIT=Z, and will be
    !  significant when sweeps=1 (a common case)
    !
    select case (init_)
    case('Z') 

      call sm%sv%apply(done,x,dzero,ty,desc_data,trans_,aux,info,init='Z') 
      
    case('Y')
      call psb_geaxpby(done,x,dzero,tx,desc_data,info)
      call psb_geaxpby(done,y,dzero,ty,desc_data,info)
      call psb_spmm(-done,sm%nd,ty,done,tx,desc_data,info,work=aux,trans=trans_)
      call sm%sv%apply(done,tx,dzero,ty,desc_data,trans_,aux,info,init='Y') 

    case('U')
      if (.not.present(initu)) then
        call psb_errpush(psb_err_internal_error_,name,&
             & a_err='missing initu to smoother_apply')
        goto 9999
      end if
      call psb_geaxpby(done,x,dzero,tx,desc_data,info)
      call psb_geaxpby(done,initu,dzero,ty,desc_data,info)
      call psb_spmm(-done,sm%nd,ty,done,tx,desc_data,info,work=aux,trans=trans_)
      call sm%sv%apply(done,tx,dzero,ty,desc_data,trans_,aux,info,init='Y') 

    case default
      call psb_errpush(psb_err_internal_error_,name,&
           & a_err='wrong  init to smoother_apply')
      goto 9999
    end select
    
    do i=1, sweeps-1
      !
      ! Compute Y(j+1) = D^(-1)*(X-ND*Y(j)), where D and ND are the
      ! block diagonal part and the remaining part of the local matrix
      ! and Y(j) is the approximate solution at sweep j.
      !
      call psb_geaxpby(done,x,dzero,tx,desc_data,info)
      call psb_spmm(-done,sm%nd,ty,done,tx,desc_data,info,work=aux,trans=trans_)

      if (info /= psb_success_) exit

      call sm%sv%apply(done,tx,dzero,ty,desc_data,trans_,aux,info,init='Y') 

      if (info /= psb_success_) exit
    end do

    if (info == psb_success_) call psb_geaxpby(alpha,ty,beta,y,desc_data,info)

    if (info /= psb_success_) then 
      info=psb_err_internal_error_
      call psb_errpush(info,name,& 
           & a_err='subsolve with Jacobi sweeps > 1')
      goto 9999      
    end if

    call tx%free(info) 
    if (info == psb_success_) call ty%free(info) 
    if (info /= psb_success_) then 
      info=psb_err_internal_error_
      call psb_errpush(info,name,& 
           & a_err='final cleanup with Jacobi sweeps > 1')
      goto 9999      
    end if

  else

    info = psb_err_iarg_neg_
    call psb_errpush(info,name,&
         & i_err=(/itwo,sweeps,izero,izero,izero/))
    goto 9999

  endif

  if (.not.(4*n_col <= size(work))) then 
    deallocate(aux)
  endif

  call psb_erractionrestore(err_act)
  return

9999 call psb_error_handler(err_act)

  return

end subroutine mld_d_jac_smoother_apply_vect