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! $Header$

#include "cctk.h"
#include "cctk_Parameters.h"
#include "cctk_Functions.h"


subroutine dissipation_4_3_alt (var, lsh, gsh, lbnd, bb, gsize, &
                                delta, epsilon, dfl, npatches, patch, rhs)

  use dissipation_coeff

  implicit none

  DECLARE_CCTK_PARAMETERS
  DECLARE_CCTK_FUNCTIONS

  CCTK_INT, dimension(3), intent(in) ::  lsh, gsh, lbnd
  CCTK_INT :: ni, nj, nk
  CCTK_REAL, dimension(lsh(1),lsh(2),lsh(3)), intent(in) :: var
  CCTK_REAL, dimension(lsh(1),lsh(2),lsh(3)), intent(inout) :: rhs
  CCTK_INT, dimension(6), intent(in) :: bb
  CCTK_INT, dimension(3), intent(in) :: gsize
  CCTK_REAL, dimension(3), intent(in) :: delta
  CCTK_REAL, intent(in) :: epsilon
  CCTK_REAL, dimension(3), intent(in) :: dfl
  CCTK_INT, intent(in) :: npatches, patch

  CCTK_REAL :: zero = 0.0
  integer, parameter :: wp = kind(zero)
  integer :: i, j, k, center
  CCTK_REAL, dimension(:,:), allocatable :: atmp, d, b, h, tmp
  CCTK_REAL, dimension(:,:), pointer :: a
  CCTK_REAL :: idel

  CCTK_INT :: il, ir, jl, jr, kl, kr

  ni = lsh(1); nj = lsh(2); nk = lsh(3)

  if ( first ) then
    allocate ( savedx(npatches), savedy(npatches), savedz(npatches) )
    savedx = .false.; savedy = .false.; savedz = .false.
    allocate ( xcoeff(npatches), ycoeff(npatches), zcoeff(npatches) )
    first = .false.
  end if

  if ( .not. savedx(patch) ) then
    allocate ( atmp(ni,ni), d(ni,ni), b(ni,ni), h(ni,ni), tmp(ni,ni) )
    atmp = zero; d = zero; b = zero; h = zero; tmp = zero

    call set_bmatrix ( b, bb(1:2), lsh(1), gsh(1), lbnd(1), delta(1), dfl(1) )

    call set_hmatrix ( h, bb(1:2) )

    if ( any ( bb(1:2) == 0 ) ) then

      call set_dmatrix ( d, bb(1:2) )

      atmp = -transpose ( matmul ( h, matmul ( transpose(d), matmul ( b, d ) ) ) )

    else

      if ( lsh(1) /= gsh(1) ) then
        call CCTK_WARN(0, 'Internal error. Bounding box inconsistent with grid' )
      end if

      center = gsh(1) / 2
      ir = center + max(3,gsize(1))

      call set_dmatrix_half ( d(1:ir,1:ir), 1 )

      tmp(1:ir,1:ir) = -transpose ( &
                          matmul ( h(1:ir,1:ir), &
                                   matmul ( &
                                     transpose ( d(1:ir,1:ir) ), &
                                      matmul ( b(1:ir,1:ir), &
                                               d(1:ir,1:ir) ) ) ) )

      atmp(1:ir,1:center) = tmp(1:ir,1:center)

      il = center + 1 - max(3,gsize(1))
      d = zero
      call set_dmatrix_half ( d(il:ni,il:ni), 2 )
      tmp(il:ni,il:ni) = matmul ( b(il:ni,il:ni), d(il:ni,il:ni) )
      tmp(il:ni,il:ni) = matmul ( transpose ( d(il:ni,il:ni) ), tmp(il:ni,il:ni) )
      tmp(il:ni,il:ni) = matmul ( h(il:ni,il:ni), tmp(il:ni,il:ni) )
      tmp(il:ni,il:ni) = -transpose ( tmp(il:ni,il:ni) )

      atmp(il:ni,center+1:ni) = tmp(il:ni,center+1:ni)

    end if

    allocate ( xcoeff(patch)%coeff(ni,ni) )

    xcoeff(patch)%coeff = atmp

    savedx(patch) = .true.

    deallocate ( atmp, d, b, h, tmp )

  end if

  a => xcoeff(patch)%coeff

  idel = epsilon / ( 64 * delta(1) )

  if ( bb(1) == 0 ) then

    il = 1 + gsize(1)

  else

    rhs(1,:,:) = rhs(1,:,:) + &
                 ( a(1,1) * var(1,:,:) + a(2,1) * var(2,:,:) + &
                   a(3,1) * var(3,:,:) + a(4,1) * var(4,:,:) ) * idel
    rhs(2,:,:) = rhs(2,:,:) + &
                 ( a(1,2) * var(1,:,:) + a(2,2) * var(2,:,:) + &
                   a(3,2) * var(3,:,:) + a(4,2) * var(4,:,:) + &
                   a(5,2) * var(5,:,:) + a(6,2) * var(6,:,:) + &
                   a(7,2) * var(7,:,:) + a(8,2) * var(8,:,:) ) * idel
    rhs(3,:,:) = rhs(3,:,:) + &
                 ( a(1,3) * var(1,:,:) + a(2,3) * var(2,:,:) + &
                   a(3,3) * var(3,:,:) + a(4,3) * var(4,:,:) + &
                   a(5,3) * var(5,:,:) + a(6,3) * var(6,:,:) + &
                   a(7,3) * var(7,:,:) + a(8,3) * var(8,:,:) ) * idel
    rhs(4,:,:) = rhs(4,:,:) + &
                 ( a(1,4) * var(1,:,:) + a(2,4) * var(2,:,:) + &
                   a(3,4) * var(3,:,:) + a(4,4) * var(4,:,:) + &
                   a(5,4) * var(5,:,:) + a(6,4) * var(6,:,:) + &
                   a(7,4) * var(7,:,:) + a(8,4) * var(8,:,:) ) * idel
    rhs(5,:,:) = rhs(5,:,:) + &
                 ( a(1,5) * var(1,:,:) + a(2,5) * var(2,:,:) + &
                   a(3,5) * var(3,:,:) + a(4,5) * var(4,:,:) + &
                   a(5,5) * var(5,:,:) + a(6,5) * var(6,:,:) + &
                   a(7,5) * var(7,:,:) + a(8,5) * var(8,:,:) ) * idel

    il = 6

  end if

  if ( bb(2) == 0 ) then

    ir = ni - gsize(1)

  else

    rhs(ni-4,:,:) = rhs(ni-4,:,:) + &
                    ( a(ni-7,ni-4) * var(ni-7,:,:) + &
                      a(ni-6,ni-4) * var(ni-6,:,:) + &
                      a(ni-5,ni-4) * var(ni-5,:,:) + &
                      a(ni-4,ni-4) * var(ni-4,:,:) + &
                      a(ni-3,ni-4) * var(ni-3,:,:) + &
                      a(ni-2,ni-4) * var(ni-2,:,:) + &
                      a(ni-1,ni-4) * var(ni-1,:,:) + &
                      a(ni,ni-4) * var(ni,:,:) ) * idel
    rhs(ni-3,:,:) = rhs(ni-3,:,:) + &
                    ( a(ni-7,ni-3) * var(ni-7,:,:) + &
                      a(ni-6,ni-3) * var(ni-6,:,:) + &
                      a(ni-5,ni-3) * var(ni-5,:,:) + &
                      a(ni-4,ni-3) * var(ni-4,:,:) + &
                      a(ni-3,ni-3) * var(ni-3,:,:) + &
                      a(ni-2,ni-3) * var(ni-2,:,:) + &
                      a(ni-1,ni-3) * var(ni-1,:,:) + &
                      a(ni,ni-3) * var(ni,:,:) ) * idel
    rhs(ni-2,:,:) = rhs(ni-2,:,:) + &
                    ( a(ni-7,ni-2) * var(ni-7,:,:) + &
                      a(ni-6,ni-2) * var(ni-6,:,:) + &
                      a(ni-5,ni-2) * var(ni-5,:,:) + &
                      a(ni-4,ni-2) * var(ni-4,:,:) + &
                      a(ni-3,ni-2) * var(ni-3,:,:) + &
                      a(ni-2,ni-2) * var(ni-2,:,:) + &
                      a(ni-1,ni-2) * var(ni-1,:,:) + &
                      a(ni,ni-2) * var(ni,:,:) ) * idel
    rhs(ni-1,:,:) = rhs(ni-1,:,:) + &
                    ( a(ni-7,ni-1) * var(ni-7,:,:) + &
                      a(ni-6,ni-1) * var(ni-6,:,:) + &
                      a(ni-5,ni-1) * var(ni-5,:,:) + &
                      a(ni-4,ni-1) * var(ni-4,:,:) + &
                      a(ni-3,ni-1) * var(ni-3,:,:) + &
                      a(ni-2,ni-1) * var(ni-2,:,:) + &
                      a(ni-1,ni-1) * var(ni-1,:,:) + &
                      a(ni,ni-1) * var(ni,:,:) ) * idel
    rhs(ni,:,:)   = rhs(ni,:,:) + &
                    ( a(ni-3,ni) * var(ni-3,:,:) + &
                      a(ni-2,ni) * var(ni-2,:,:) + &
                      a(ni-1,ni) * var(ni-1,:,:) + &
                      a(ni,ni) * var(ni,:,:) ) * idel

    ir = ni - 5

  end if

  do i = il, ir

    rhs(i,:,:) = rhs(i,:,:) + &
                   ( a(i-3,i) * var(i-3,:,:) + &
                     a(i-2,i) * var(i-2,:,:) + &
                     a(i-1,i) * var(i-1,:,:) + &
                     a(i,i) * var(i,:,:) + &
                     a(i+1,i) * var(i+1,:,:) + &
                     a(i+2,i) * var(i+2,:,:) + &
                     a(i+3,i) * var(i+3,:,:) ) * idel

  end do

  if ( zero_derivs_y == 0 ) then
    if ( .not. savedy(patch) ) then
      allocate ( atmp(nj,nj), d(nj,nj), b(nj,nj), h(nj,nj), tmp(nj,nj) )
      atmp = zero; d = zero; b = zero; h = zero; tmp = zero
  
      call set_bmatrix ( b, bb(3:4), lsh(2), gsh(2), lbnd(2), delta(2), dfl(2) )
    
      call set_hmatrix ( h, bb(3:4) )
  
      if ( any ( bb(3:4) == 0 ) ) then
  
        call set_dmatrix ( d, bb(3:4) )
  
        atmp = -transpose ( matmul ( h, matmul ( transpose(d), matmul ( b, d ) ) ) )
  
      else
  
        if ( lsh(2) /= gsh(2) ) then
          call CCTK_WARN(0, 'Internal error. Bounding box inconsistent with grid' )
        end if
  
        center = gsh(2) / 2
        jr = center + max(3,gsize(2))
  
        call set_dmatrix_half ( d(1:jr,1:jr), 1 )
  
        tmp(1:jr,1:jr) = -transpose ( &
                            matmul ( h(1:jr,1:jr), &
                                     matmul ( &
                                       transpose ( d(1:jr,1:jr) ), &
                                        matmul ( b(1:jr,1:jr), &
                                                 d(1:jr,1:jr) ) ) ) )
  
        atmp(1:jr,1:center) = tmp(1:jr,1:center)
  
        jl = center + 1 - max(3,gsize(2))
        d = zero
        call set_dmatrix_half ( d(jl:nj,jl:nj), 2 )
        tmp(jl:nj,jl:nj) = -transpose ( &
                              matmul ( h(jl:nj,jl:nj), &
                                       matmul ( &
                                         transpose ( d(jl:nj,jl:nj) ), &
                                         matmul ( b(jl:nj,jl:nj), &
                                                  d(jl:nj,jl:nj) ) ) ) )
  
        atmp(jl:nj,center+1:nj) = tmp(jl:nj,center+1:nj)
  
      end if

      allocate ( ycoeff(patch)%coeff(nj,nj) )

      ycoeff(patch)%coeff = atmp

      savedy(patch) = .true.

      deallocate ( atmp, d, b, h, tmp )

    end if
  
    a => ycoeff(patch)%coeff

    idel = epsilon / ( 64 * delta(2) )
   
    if ( bb(3) == 0 ) then
  
      jl = 1 + gsize(2)
  
    else
  
      rhs(:,1,:) = rhs(:,1,:) + &
                   ( a(1,1) * var(:,1,:) + a(2,1) * var(:,2,:) + &
                     a(3,1) * var(:,3,:) + a(4,1) * var(:,4,:) ) * idel
      rhs(:,2,:) = rhs(:,2,:) + &
                   ( a(1,2) * var(:,1,:) + a(2,2) * var(:,2,:) + &
                     a(3,2) * var(:,3,:) + a(4,2) * var(:,4,:) + &
                     a(5,2) * var(:,5,:) + a(6,2) * var(:,6,:) + &
                     a(7,2) * var(:,7,:) + a(8,2) * var(:,8,:) ) * idel
      rhs(:,3,:) = rhs(:,3,:) + &
                   ( a(1,3) * var(:,1,:) + a(2,3) * var(:,2,:) + &
                     a(3,3) * var(:,3,:) + a(4,3) * var(:,4,:) + &
                     a(5,3) * var(:,5,:) + a(6,3) * var(:,6,:) + &
                     a(7,3) * var(:,7,:) + a(8,3) * var(:,8,:) ) * idel
      rhs(:,4,:) = rhs(:,4,:) + &
                   ( a(1,4) * var(:,1,:) + a(2,4) * var(:,2,:) + &
                     a(3,4) * var(:,3,:) + a(4,4) * var(:,4,:) + &
                     a(5,4) * var(:,5,:) + a(6,4) * var(:,6,:) + &
                     a(7,4) * var(:,7,:) + a(8,4) * var(:,8,:) ) * idel
      rhs(:,5,:) = rhs(:,5,:) + &
                   ( a(1,5) * var(:,1,:) + a(2,5) * var(:,2,:) + &
                     a(3,5) * var(:,3,:) + a(4,5) * var(:,4,:) + &
                     a(5,5) * var(:,5,:) + a(6,5) * var(:,6,:) + &
                     a(7,5) * var(:,7,:) + a(8,5) * var(:,8,:) ) * idel
  
      jl = 6
  
    end if
  
    if ( bb(4) == 0 ) then
  
      jr = nj - gsize(2)
  
    else
  
      rhs(:,nj-4,:) = rhs(:,nj-4,:) + &
                      ( a(nj-7,nj-4) * var(:,nj-7,:) + &
                        a(nj-6,nj-4) * var(:,nj-6,:) + &
                        a(nj-5,nj-4) * var(:,nj-5,:) + &
                        a(nj-4,nj-4) * var(:,nj-4,:) + &
                        a(nj-3,nj-4) * var(:,nj-3,:) + &
                        a(nj-2,nj-4) * var(:,nj-2,:) + &
                        a(nj-1,nj-4) * var(:,nj-1,:) + &
                        a(nj,nj-4) * var(:,nj,:) ) * idel
      rhs(:,nj-3,:) = rhs(:,nj-3,:) + &
                      ( a(nj-7,nj-3) * var(:,nj-7,:) + &
                        a(nj-6,nj-3) * var(:,nj-6,:) + &
                        a(nj-5,nj-3) * var(:,nj-5,:) + &
                        a(nj-4,nj-3) * var(:,nj-4,:) + &
                        a(nj-3,nj-3) * var(:,nj-3,:) + &
                        a(nj-2,nj-3) * var(:,nj-2,:) + &
                        a(nj-1,nj-3) * var(:,nj-1,:) + &
                        a(nj,nj-3) * var(:,nj,:) ) * idel
      rhs(:,nj-2,:) = rhs(:,nj-2,:) + &
                      ( a(nj-7,nj-2) * var(:,nj-7,:) + &
                        a(nj-6,nj-2) * var(:,nj-6,:) + &
                        a(nj-5,nj-2) * var(:,nj-5,:) + &
                        a(nj-4,nj-2) * var(:,nj-4,:) + &
                        a(nj-3,nj-2) * var(:,nj-3,:) + &
                        a(nj-2,nj-2) * var(:,nj-2,:) + &
                        a(nj-1,nj-2) * var(:,nj-1,:) + &
                        a(nj,nj-2) * var(:,nj,:) ) * idel
      rhs(:,nj-1,:) = rhs(:,nj-1,:) + &
                      ( a(nj-7,nj-1) * var(:,nj-7,:) + &
                        a(nj-6,nj-1) * var(:,nj-6,:) + &
                        a(nj-5,nj-1) * var(:,nj-5,:) + &
                        a(nj-4,nj-1) * var(:,nj-4,:) + &
                        a(nj-3,nj-1) * var(:,nj-3,:) + &
                        a(nj-2,nj-1) * var(:,nj-2,:) + &
                        a(nj-1,nj-1) * var(:,nj-1,:) + &
                        a(nj,nj-1) * var(:,nj,:) ) * idel
      rhs(:,nj,:)   = rhs(:,nj,:) + &
                      ( a(nj-3,nj) * var(:,nj-3,:) + &
                        a(nj-2,nj) * var(:,nj-2,:) + &
                        a(nj-1,nj) * var(:,nj-1,:) + &
                        a(nj,nj) * var(:,nj,:) ) * idel
  
      jr = nj - 5
  
    end if
  
    do j = jl, jr
  
      rhs(:,j,:) = rhs(:,j,:) + &
                     ( a(j-3,j) * var(:,j-3,:) + &
                       a(j-2,j) * var(:,j-2,:) + &
                       a(j-1,j) * var(:,j-1,:) + &
                       a(j,j) * var(:,j,:) + &
                       a(j+1,j) * var(:,j+1,:) + &
                       a(j+2,j) * var(:,j+2,:) + &
                       a(j+3,j) * var(:,j+3,:) ) * idel
  
    end do
  
  end if

  if ( zero_derivs_z == 0 ) then
    if ( .not. savedz(patch) ) then
      allocate ( atmp(nk,nk), d(nk,nk), b(nk,nk), h(nk,nk), tmp(nk,nk) )
      atmp = zero; d = zero; b = zero; h = zero; tmp = zero
  
      call set_bmatrix ( b, bb(5:6), lsh(3), gsh(3), lbnd(3), delta(3), dfl(3) )
  
      call set_hmatrix ( h, bb(5:6) )
  
      if ( any ( bb(5:6) == 0 ) ) then
  
        call set_dmatrix ( d, bb(5:6) )
  
        atmp = -transpose ( matmul ( h, matmul ( transpose(d), matmul ( b, d ) ) ) )
  
      else
  
        if ( lsh(3) /= gsh(3) ) then
          call CCTK_WARN(0, 'Internal error. Bounding box inconsistent with grid' )
        end if
  
        center = gsh(3) / 2
        kr = center + max(3,gsize(3))
  
        call set_dmatrix_half ( d(1:kr,1:kr), 1 )
  
        tmp(1:kr,1:kr) = matmul ( b(1:kr,1:kr), d(1:kr,1:kr) )
        tmp(1:kr,1:kr) = matmul ( transpose ( d(1:kr,1:kr) ), tmp(1:kr,1:kr) )
        tmp(1:kr,1:kr) = matmul ( h(1:kr,1:kr), tmp(1:kr,1:kr) )
        tmp(1:kr,1:kr) = -transpose ( tmp(1:kr,1:kr) )
  
        atmp(1:kr,1:center) = tmp(1:kr,1:center)
  
        kl = center + 1 - max(3,gsize(3))
        d = zero
        call set_dmatrix_half ( d(kl:nk,kl:nk), 2 )
        tmp(kl:nk,kl:nk) = -transpose ( &
                              matmul ( h(kl:nk,kl:nk), &
                                       matmul ( &
                                         transpose ( d(kl:nk,kl:nk) ), &
                                         matmul ( b(kl:nk,kl:nk), &
                                                  d(kl:nk,kl:nk) ) ) ) )
  
        atmp(kl:nk,center+1:nk) = tmp(kl:nk,center+1:nk)
  
      end if

      allocate ( zcoeff(patch)%coeff(nk,nk) )

      zcoeff(patch)%coeff = atmp

      savedz(patch) = .true.

      deallocate ( atmp, d, b, h, tmp )

    end if
  
    a => zcoeff(patch)%coeff

    idel = epsilon / ( 64 * delta(3) )
  
    if ( bb(5) == 0 ) then
  
      kl = 1 + gsize(3)
  
    else
  
      rhs(:,:,1) = rhs(:,:,1) + &
                   ( a(1,1) * var(:,:,1) + a(2,1) * var(:,:,2) + &
                     a(3,1) * var(:,:,3) + a(4,1) * var(:,:,4) ) * idel
      rhs(:,:,2) = rhs(:,:,2) + &
                   ( a(1,2) * var(:,:,1) + a(2,2) * var(:,:,2) + &
                     a(3,2) * var(:,:,3) + a(4,2) * var(:,:,4) + &
                     a(5,2) * var(:,:,5) + a(6,2) * var(:,:,6) + &
                     a(7,2) * var(:,:,7) + a(8,2) * var(:,:,8) ) * idel
      rhs(:,:,3) = rhs(:,:,3) + &
                   ( a(1,3) * var(:,:,1) + a(2,3) * var(:,:,2) + &
                     a(3,3) * var(:,:,3) + a(4,3) * var(:,:,4) + &
                     a(5,3) * var(:,:,5) + a(6,3) * var(:,:,6) + &
                     a(7,3) * var(:,:,7) + a(8,3) * var(:,:,8) ) * idel
      rhs(:,:,4) = rhs(:,:,4) + &
                   ( a(1,4) * var(:,:,1) + a(2,4) * var(:,:,2) + &
                     a(3,4) * var(:,:,3) + a(4,4) * var(:,:,4) + &
                     a(5,4) * var(:,:,5) + a(6,4) * var(:,:,6) + &
                     a(7,4) * var(:,:,7) + a(8,4) * var(:,:,8) ) * idel
      rhs(:,:,5) = rhs(:,:,5) + &
                   ( a(1,5) * var(:,:,1) + a(2,5) * var(:,:,2) + &
                     a(3,5) * var(:,:,3) + a(4,5) * var(:,:,4) + &
                     a(5,5) * var(:,:,5) + a(6,5) * var(:,:,6) + &
                     a(7,5) * var(:,:,7) + a(8,5) * var(:,:,8) ) * idel
  
      kl = 6
  
    end if
  
    if ( bb(6) == 0 ) then
  
      kr = nk - gsize(3)
  
    else
  
      rhs(:,:,nk-4) = rhs(:,:,nk-4) + &
                      ( a(nk-7,nk-4) * var(:,:,nk-7) + &
                        a(nk-6,nk-4) * var(:,:,nk-6) + &
                        a(nk-5,nk-4) * var(:,:,nk-5) + &
                        a(nk-4,nk-4) * var(:,:,nk-4) + &
                        a(nk-3,nk-4) * var(:,:,nk-3) + &
                        a(nk-2,nk-4) * var(:,:,nk-2) + &
                        a(nk-1,nk-4) * var(:,:,nk-1) + &
                        a(nk,nk-4) * var(:,:,nk) ) * idel
      rhs(:,:,nk-3) = rhs(:,:,nk-3) + &
                      ( a(nk-7,nk-3) * var(:,:,nk-7) + &
                        a(nk-6,nk-3) * var(:,:,nk-6) + &
                        a(nk-5,nk-3) * var(:,:,nk-5) + &
                        a(nk-4,nk-3) * var(:,:,nk-4) + &
                        a(nk-3,nk-3) * var(:,:,nk-3) + &
                        a(nk-2,nk-3) * var(:,:,nk-2) + &
                        a(nk-1,nk-3) * var(:,:,nk-1) + &
                        a(nk,nk-3) * var(:,:,nk) ) * idel
      rhs(:,:,nk-2) = rhs(:,:,nk-2) + &
                      ( a(nk-7,nk-2) * var(:,:,nk-7) + &
                        a(nk-6,nk-2) * var(:,:,nk-6) + &
                        a(nk-5,nk-2) * var(:,:,nk-5) + &
                        a(nk-4,nk-2) * var(:,:,nk-4) + &
                        a(nk-3,nk-2) * var(:,:,nk-3) + &
                        a(nk-2,nk-2) * var(:,:,nk-2) + &
                        a(nk-1,nk-2) * var(:,:,nk-1) + &
                        a(nk,nk-2) * var(:,:,nk) ) * idel
      rhs(:,:,nk-1) = rhs(:,:,nk-1) + &
                      ( a(nk-7,nk-1) * var(:,:,nk-7) + &
                        a(nk-6,nk-1) * var(:,:,nk-6) + &
                        a(nk-5,nk-1) * var(:,:,nk-5) + &
                        a(nk-4,nk-1) * var(:,:,nk-4) + &
                        a(nk-3,nk-1) * var(:,:,nk-3) + &
                        a(nk-2,nk-1) * var(:,:,nk-2) + &
                        a(nk-1,nk-1) * var(:,:,nk-1) + &
                        a(nk,nk-1) * var(:,:,nk) ) * idel
      rhs(:,:,nk)   = rhs(:,:,nk) + &
                      ( a(nk-3,nk) * var(:,:,nk-3) + &
                        a(nk-2,nk) * var(:,:,nk-2) + &
                        a(nk-1,nk) * var(:,:,nk-1) + &
                        a(nk,nk) * var(:,:,nk) ) * idel
  
      kr = nk - 5
  
    end if
  
    do k = kl, kr
  
      rhs(:,:,k) = rhs(:,:,k) + &
                     ( a(k-3,k) * var(:,:,k-3) + &
                       a(k-2,k) * var(:,:,k-2) + &
                       a(k-1,k) * var(:,:,k-1) + &
                       a(k,k) * var(:,:,k) + &
                       a(k+1,k) * var(:,:,k+1) + &
                       a(k+2,k) * var(:,:,k+2) + &
                       a(k+3,k) * var(:,:,k+3) ) * idel
  
    end do
  
  end if

contains

  subroutine set_dmatrix ( d, bb )

    implicit none

    CCTK_REAL, dimension(:,:), intent(out) :: d
    CCTK_INT, dimension(2), intent(in) :: bb
    CCTK_INT :: n
    CCTK_REAL, dimension(4), save :: ac = (/ -1.0_wp, 3.0_wp, -3.0_wp, 1.0_wp /)
    CCTK_INT :: i

    n = size(d,1)

    if ( any(bb /= 0) ) then

      if ( bb(1) /= 0 ) then

        d(1,1:4) = ac
        d(2,1:4) = ac

        do i = 3, n-1
          d(i,i-2:i+1) = ac
        end do

        d(n,n-2:n) = ac(1:3)

      else

        d(1,1:3) = ac(2:4)

        do i = 2, n-2
          d(i,i-1:i+2) = ac
        end do

        d(n-1,n-3:n) = ac
        d(n,n-3:n) = ac

      end if

    else

      d(1,1:2) = ac(3:4)
      d(2,1:3) = ac(2:4)

      do i = 3, n-1
        d(i,i-2:i+1) = ac
      end do

      d(n,n-2:n) = ac(1:3)

    end if

  end subroutine set_dmatrix


  subroutine set_dmatrix_half ( d, part )

    implicit none

    CCTK_REAL, dimension(:,:), intent(out) :: d
    integer, intent(in) :: part
    CCTK_INT :: n
    CCTK_REAL, dimension(4), save :: ac = (/ -1.0_wp, 3.0_wp, -3.0_wp, 1.0_wp /)
    CCTK_INT :: i

    n = size(d,1)

    if ( part == 1 ) then

      d(1,1:4) = ac
      d(2,1:4) = ac

      do i = 3, n-1
        d(i,i-2:i+1) = ac
      end do

      d(n,n-2:n) = ac(1:3)

    else if ( part == 2 ) then

      d(1,1:3) = ac(2:4)

      do i = 2, n-2
        d(i,i-1:i+2) = ac
      end do

      d(n-1,n-3:n) = ac
      d(n,n-3:n) = ac

    end if

  end subroutine set_dmatrix_half


  subroutine set_bmatrix ( b, bb, lsh, gsh, lbnd, h, dfl )

    implicit none

    CCTK_REAL, dimension(:,:), intent(out) :: b
    CCTK_INT, dimension(2), intent(in) :: bb
    CCTK_INT, intent(in) :: lsh, gsh, lbnd
    CCTK_REAL, intent(in) :: h, dfl
    CCTK_INT :: n
    CCTK_INT :: i
    CCTK_REAL :: xp

    CCTK_REAL :: zero = 0.0
    integer, parameter :: wp = kind(zero)

    n = size(b,1)
    xp = ( gsh - 1 ) * dfl - 1

    do i = 1, n
      b(i,i) = bf ( real(i+lbnd-1,wp), xp, real(gsh-1,wp), h )
    end do

  end subroutine set_bmatrix
    

  subroutine set_hmatrix ( h, bb )

    implicit none

    CCTK_REAL, dimension(:,:), intent(out) :: h
    CCTK_INT, dimension(2), intent(in) :: bb
    CCTK_INT :: n, i

    CCTK_REAL :: zero = 0.0
    integer, parameter :: wp = kind(zero)

    n = size(h,1)

    do i = 1, n
      h(i,i) = 1.0_wp
    end do

    if ( bb(1) /= 0 ) then
      h(1:5,1:5) = sigma ( )
    end if

    if ( bb(2) /= 0 ) then
      h(n:n-4:-1,n:n-4:-1) = sigma ( )
    end if

  end subroutine set_hmatrix
    
  function bf ( x, xp, xmax, h )

    implicit none

    CCTK_REAL :: bf
    CCTK_REAL, intent(in) :: x, xp, xmax, h

    CCTK_REAL :: zero = 0.0
    integer, parameter :: wp = kind(zero)

    if ( x < xp ) then
      bf = ( 1.0_wp - h ) / xp * x + h
    else if ( x > xmax - xp ) then
      bf = ( h - 1.0_wp ) / xp * ( x + xp - xmax ) + 1
    else
      bf = 1.0_wp
    end if

  end function bf

  function sigma ( )

    implicit none

    CCTK_REAL, dimension(5,5) :: sigma

    CCTK_REAL :: zero = 0.0
    integer, parameter :: wp = kind(zero)

    sigma(1,1) = 4.186595370392226897362216859769846226369_wp
    sigma(2,1) = 0.0_wp
    sigma(3,1) = 0.0_wp
    sigma(4,1) = 0.0_wp
    sigma(5,1) = 0.0_wp
    sigma(1,2) = 0.0_wp
    sigma(2,2) = 0.6725191921225620731888714836983116420871_wp
    sigma(3,2) = 0.3613418181134949259370502966736306984367_wp
    sigma(4,2) = -0.2021316117293899791481674539631879662707_wp
    sigma(5,2) = 0.03455320708729270824077678274955265350304_wp
    sigma(1,3) = 0.0_wp
    sigma(2,3) = 0.3613418181134949259370502966736306984367_wp
    sigma(3,3) = 0.7206133711630147057720442098623847362950_wp
    sigma(4,3) = 0.1376472340546569368321616389764958792591_wp
    sigma(5,3) = -0.04136405531324488624637892257286207044784_wp
    sigma(1,4) = 0.0_wp
    sigma(2,4) = -0.2021316117293899791481674539631879662707_wp
    sigma(3,4) = 0.1376472340546569368321616389764958792591_wp
    sigma(4,4) = 0.9578653607931026822074133441449909689509_wp
    sigma(5,4) = 0.02069353627247161734563597102894256809696_wp
    sigma(1,5) = 0.0_wp
    sigma(2,5) = 0.03455320708729270824077678274955265350304_wp
    sigma(3,5) = -0.04136405531324488624637892257286207044784_wp
    sigma(4,5) = 0.02069353627247161734563597102894256809696_wp
    sigma(5,5) = 0.9908272703370861473007798925906968380654_wp

  end function sigma

end subroutine dissipation_4_3_alt