! $Header$

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

subroutine dissipation_4_2 (var, ni, nj, nk, bb, gsize, offset, delta, epsilon, rhs)

  implicit none

  DECLARE_CCTK_PARAMETERS

  integer ::  ni, nj, nk
  CCTK_REAL, dimension(ni,nj,nk), intent(in) :: var
  CCTK_REAL, dimension(ni,nj,nk), intent(inout) :: rhs
  CCTK_INT, dimension(6), intent(in) :: bb
  CCTK_INT, dimension(3), intent(in) :: gsize
  CCTK_INT, dimension(6), intent(in) :: offset
  CCTK_REAL, dimension(3), intent(in) :: delta
  CCTK_REAL, intent(in) :: epsilon 

  CCTK_REAL :: zero = 0.0
  integer, parameter :: wp = kind(zero)
  CCTK_REAL, dimension(6,4) :: a
  CCTK_REAL :: idel

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

  call set_coeff ( a )

  if ( scale_with_h > 0 ) then
    idel = epsilon / ( 16 * delta(1) )
  else
    idel = epsilon / 16
  end if

  if ( bb(1) == 0 ) then
    il = 1 + gsize(1)
  else
    ol = offset(1)
!$omp parallel workshare
    rhs(1+ol,:,:) = rhs(1+ol,:,:) + &
                 ( a(1,1) * var(1+ol,:,:) + a(2,1) * var(2+ol,:,:) + &
                   a(3,1) * var(3+ol,:,:) ) * idel
    rhs(2+ol,:,:) = rhs(2+ol,:,:) + &
                 ( a(1,2) * var(1+ol,:,:) + a(2,2) * var(2+ol,:,:) + &
                   a(3,2) * var(3+ol,:,:) + a(4,2) * var(4+ol,:,:) ) * idel
    rhs(3+ol,:,:) = rhs(3+ol,:,:) + &
                 ( a(1,3) * var(1+ol,:,:) + a(2,3) * var(2+ol,:,:) + &
                   a(3,3) * var(3+ol,:,:) + a(4,3) * var(4+ol,:,:) + &
                   a(5,3) * var(5+ol,:,:) ) * idel
    rhs(4+ol,:,:) = rhs(4+ol,:,:) + &
                 ( a(2,4) * var(2+ol,:,:) + a(3,4) * var(3+ol,:,:) + &
                   a(4,4) * var(4+ol,:,:) + a(5,4) * var(5+ol,:,:) + &
                   a(6,4) * var(6+ol,:,:) ) * idel
!$omp end parallel workshare

    il = 5 + ol
  end if
  if ( bb(2) == 0 ) then
    ir = ni - gsize(1)
  else
    or = ni - offset(2)
!$omp parallel workshare
    rhs(or-3,:,:) = rhs(or-3,:,:) + &
                 ( a(2,4) * var(or-1,:,:) + a(3,4) * var(or-2,:,:) + &
                   a(4,4) * var(or-3,:,:) + a(5,4) * var(or-4,:,:) + &
                   a(6,4) * var(or-5,:,:) ) * idel
    rhs(or-2,:,:) = rhs(or-2,:,:) + &
                 ( a(1,3) * var(or,:,:) + a(2,3) * var(or-1,:,:) + &
                   a(3,3) * var(or-2,:,:) + a(4,3) * var(or-3,:,:) + &
                   a(5,3) * var(or-4,:,:) ) * idel
    rhs(or-1,:,:) = rhs(or-1,:,:) + &
                 ( a(1,2) * var(or,:,:) + a(2,2) * var(or-1,:,:) + &
                   a(3,2) * var(or-2,:,:) + a(4,2) * var(or-3,:,:) ) * idel
    rhs(or,:,:)   = rhs(or,:,:) + &
                 ( a(1,1) * var(or,:,:) + a(2,1) * var(or-1,:,:) + &
                   a(3,1) * var(or-2,:,:) ) * idel
!$omp end parallel workshare

    ir = or - 4
  end if
!$omp parallel workshare
  rhs(il:ir,:,:) = rhs(il:ir,:,:) + &
                   ( -6.0_wp * var(il:ir,:,:) + &
                      4.0_wp * ( var(il-1:ir-1,:,:) + &
                                 var(il+1:ir+1,:,:) ) - &
                               ( var(il-2:ir-2,:,:) + &
                                 var(il+2:ir+2,:,:) ) ) * idel
!$omp end parallel workshare

  if ( zero_derivs_y == 0 ) then
    call set_coeff ( a )
  
    if ( scale_with_h > 0 ) then
      idel = epsilon / ( 16 * delta(2) )
    else
      idel = epsilon / 16
    end if
  
    if ( bb(3) == 0 ) then
      jl = 1 + gsize(2)
    else
      ol = offset(3)
!$omp parallel workshare
      rhs(:,1+ol,:) = rhs(:,1+ol,:) + &
                   ( a(1,1) * var(:,1+ol,:) + a(2,1) * var(:,2+ol,:) + &
                     a(3,1) * var(:,3+ol,:) ) * idel
      rhs(:,2+ol,:) = rhs(:,2+ol,:) + &
                   ( a(1,2) * var(:,1+ol,:) + a(2,2) * var(:,2+ol,:) + &
                     a(3,2) * var(:,3+ol,:) + a(4,2) * var(:,4+ol,:) ) * idel
      rhs(:,3+ol,:) = rhs(:,3+ol,:) + &
                   ( a(1,3) * var(:,1+ol,:) + a(2,3) * var(:,2+ol,:) + &
                     a(3,3) * var(:,3+ol,:) + a(4,3) * var(:,4+ol,:) + &
                     a(5,3) * var(:,5+ol,:) ) * idel
      rhs(:,4+ol,:) = rhs(:,4+ol,:) + &
                   ( a(2,4) * var(:,2+ol,:) + a(3,4) * var(:,3+ol,:) + &
                     a(4,4) * var(:,4+ol,:) + a(5,4) * var(:,5+ol,:) + &
                     a(6,4) * var(:,6+ol,:) ) * idel
!$omp end parallel workshare
  
      jl = 5 + ol
    end if
    if ( bb(4) == 0 ) then
      jr = nj - gsize(2)
    else
      or = nj - offset(4)
!$omp parallel workshare
      rhs(:,or-3,:) = rhs(:,or-3,:) + &
                   ( a(2,4) * var(:,or-1,:) + a(3,4) * var(:,or-2,:) + &
                     a(4,4) * var(:,or-3,:) + a(5,4) * var(:,or-4,:) + &
                     a(6,4) * var(:,or-5,:) ) * idel
      rhs(:,or-2,:) = rhs(:,or-2,:) + &
                   ( a(1,3) * var(:,or,:) + a(2,3) * var(:,or-1,:) + &
                     a(3,3) * var(:,or-2,:) + a(4,3) * var(:,or-3,:) + &
                     a(5,3) * var(:,or-4,:) ) * idel
      rhs(:,or-1,:) = rhs(:,or-1,:) + &
                   ( a(1,2) * var(:,or,:) + a(2,2) * var(:,or-1,:) + &
                     a(3,2) * var(:,or-2,:) + a(4,2) * var(:,or-3,:) ) * idel
      rhs(:,or,:)   = rhs(:,or,:) + &
                   ( a(1,1) * var(:,or,:) + a(2,1) * var(:,or-1,:) + &
                     a(3,1) * var(:,or-2,:) ) * idel
!$omp end parallel workshare
  
      jr = or - 4
    end if
!$omp parallel workshare
    rhs(:,jl:jr,:) = rhs(:,jl:jr,:) + &
                     ( -6.0_wp * var(:,jl:jr,:) + &
                        4.0_wp * ( var(:,jl-1:jr-1,:) + &
                                   var(:,jl+1:jr+1,:) ) - &
                                 ( var(:,jl-2:jr-2,:) + &
                                   var(:,jl+2:jr+2,:) ) ) * idel
!$omp end parallel workshare
  end if

  if ( zero_derivs_z == 0 ) then
    call set_coeff ( a )
  
    if ( scale_with_h > 0 ) then
      idel = epsilon / ( 16 * delta(3) )
    else
      idel = epsilon / 16
    end if
  
    if ( bb(5) == 0 ) then
      kl = 1 + gsize(3)
    else
      ol = offset(5)
!$omp parallel workshare
      rhs(:,:,1+ol) = rhs(:,:,1+ol) + &
                   ( a(1,1) * var(:,:,1+ol) + a(2,1) * var(:,:,2+ol) + &
                     a(3,1) * var(:,:,3+ol) ) * idel
      rhs(:,:,2+ol) = rhs(:,:,2+ol) + &
                   ( a(1,2) * var(:,:,1+ol) + a(2,2) * var(:,:,2+ol) + &
                     a(3,2) * var(:,:,3+ol) + a(4,2) * var(:,:,4+ol) ) * idel
      rhs(:,:,3+ol) = rhs(:,:,3+ol) + &
                   ( a(1,3) * var(:,:,1+ol) + a(2,3) * var(:,:,2+ol) + &
                     a(3,3) * var(:,:,3+ol) + a(4,3) * var(:,:,4+ol) + &
                     a(5,3) * var(:,:,5+ol) ) * idel
      rhs(:,:,4+ol) = rhs(:,:,4+ol) + &
                   ( a(2,4) * var(:,:,2+ol) + a(3,4) * var(:,:,3+ol) + &
                     a(4,4) * var(:,:,4+ol) + a(5,4) * var(:,:,5+ol) + &
                     a(6,4) * var(:,:,6+ol) ) * idel
!$omp end parallel workshare
  
      kl = 5 + ol
    end if
    if ( bb(6) == 0 ) then
      kr = nk - gsize(3)
    else
      or = nk - offset(6)
!$omp parallel workshare
      rhs(:,:,or-3) = rhs(:,:,or-3) + &
                   ( a(2,4) * var(:,:,or-1) + a(3,4) * var(:,:,or-2) + &
                     a(4,4) * var(:,:,or-3) + a(5,4) * var(:,:,or-4) + &
                     a(6,4) * var(:,:,or-5) ) * idel
      rhs(:,:,or-2) = rhs(:,:,or-2) + &
                   ( a(1,3) * var(:,:,or) + a(2,3) * var(:,:,or-1) + &
                     a(3,3) * var(:,:,or-2) + a(4,3) * var(:,:,or-3) + &
                     a(5,3) * var(:,:,or-4) ) * idel
      rhs(:,:,or-1) = rhs(:,:,or-1) + &
                   ( a(1,2) * var(:,:,or) + a(2,2) * var(:,:,or-1) + &
                     a(3,2) * var(:,:,or-2) + a(4,2) * var(:,:,or-3) ) * idel
      rhs(:,:,or)   = rhs(:,:,or) + &
                   ( a(1,1) * var(:,:,or) + a(2,1) * var(:,:,or-1) + &
                     a(3,1) * var(:,:,or-2) ) * idel
!$omp end parallel workshare
  
      kr = or - 4
    end if
!$omp parallel workshare
    rhs(:,:,kl:kr) = rhs(:,:,kl:kr) + &
                     ( -6.0_wp * var(:,:,kl:kr) + &
                        4.0_wp * ( var(:,:,kl-1:kr-1) + &
                                   var(:,:,kl+1:kr+1) ) - &
                                 ( var(:,:,kl-2:kr-2) + &
                                   var(:,:,kl+2:kr+2) ) ) * idel
!$omp end parallel workshare
  end if

contains

  subroutine set_coeff ( a )

    implicit none

    CCTK_REAL, dimension(6,4), intent(OUT) :: a
    CCTK_REAL :: zero = 0.0
    integer, parameter :: wp = kind(zero)

    a(1,1) = -2.8235294117647058823529411764705882352941176470588_wp
    a(2,1) = 5.6470588235294117647058823529411764705882352941176_wp
    a(3,1) = -2.8235294117647058823529411764705882352941176470588_wp
    a(4,1) = 0.0_wp
    a(5,1) = 0.0_wp
    a(6,1) = 0.0_wp
    a(1,2) = 1.6271186440677966101694915254237288135593220338983_wp
    a(2,2) = -4.0677966101694915254237288135593220338983050847458_wp
    a(3,2) = 3.2542372881355932203389830508474576271186440677966_wp
    a(4,2) = -0.81355932203389830508474576271186440677966101694915_wp
    a(5,2) = 0.0_wp
    a(6,2) = 0.0_wp
    a(1,3) = -1.1162790697674418604651162790697674418604651162791_wp
    a(2,3) = 4.4651162790697674418604651162790697674418604651163_wp
    a(3,3) = -6.6976744186046511627906976744186046511627906976744_wp
    a(4,3) = 4.4651162790697674418604651162790697674418604651163_wp
    a(5,3) = -1.1162790697674418604651162790697674418604651162791_wp
    a(6,3) = 0.0_wp
    a(1,4) = 0.0_wp
    a(2,4) = -0.97959183673469387755102040816326530612244897959184_wp
    a(3,4) = 3.9183673469387755102040816326530612244897959183673_wp
    a(4,4) = -5.8775510204081632653061224489795918367346938775510_wp
    a(5,4) = 3.9183673469387755102040816326530612244897959183673_wp
    a(6,4) = -0.97959183673469387755102040816326530612244897959184_wp

  end subroutine set_coeff

end subroutine dissipation_4_2