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

subroutine deriv_gf_4_3_opt ( var, ni, nj, nk, dir, bb, gsize, delta, dvar )

  implicit none

  DECLARE_CCTK_FUNCTIONS
  DECLARE_CCTK_PARAMETERS

  CCTK_REAL, parameter :: zero = 0.0
  integer, parameter :: wp = kind(zero)
  CCTK_INT, intent(IN) :: ni, nj, nk
  CCTK_REAL, dimension(ni,nj,nk), intent(IN) :: var
  CCTK_INT, intent(IN) :: dir
  CCTK_INT, intent(IN) :: bb(2)
  CCTK_INT, intent(IN) :: gsize
  CCTK_REAL, intent(IN) :: delta
  CCTK_REAL, dimension(ni,nj,nk), intent(OUT) :: dvar

  CCTK_REAL, dimension(2), save :: a
  CCTK_REAL, dimension(7,5), save :: q 
  CCTK_REAL :: idel

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

  logical, save :: first = .true.

  if ( first ) then
    a(1) = 2.0_wp/3.0_wp; a(2) = -1.0_wp/12.0_wp

    q(1,1) = -2.09329763466349871588733_wp
    q(2,1) = 4.0398572053206615302160_wp
    q(3,1) = -3.0597858079809922953240_wp
    q(4,1) = 1.37319053865399486354933_wp
    q(5,1) = -0.25996430133016538255400_wp
    q(6,1) = 0.0_wp
    q(7,1) = 0.0_wp
    q(1,2) = -0.31641585285940445272297_wp
    q(2,2) = -0.53930788973980422327388_wp
    q(3,2) = 0.98517732028644343383297_wp
    q(4,2) = -0.05264665989297578146709_wp
    q(5,2) = -0.113807251750624235013258_wp
    q(6,2) = 0.039879767889849911803103_wp
    q(7,2) = -0.0028794339334846531588787_wp
    q(1,3) = 0.13026916185021164524452_wp
    q(2,3) = -0.87966858995059249256890_wp
    q(3,3) = 0.38609640961100070000134_wp
    q(4,3) = 0.31358369072435588745988_wp
    q(5,3) = 0.085318941913678384633511_wp
    q(6,3) = -0.039046615792734640274641_wp
    q(7,3) = 0.0034470016440805155042908_wp
    q(1,4) = -0.01724512193824647912172_wp
    q(2,4) = 0.16272288227127504381134_wp
    q(3,4) = -0.81349810248648813029217_wp
    q(4,4) = 0.13833269266479833215645_wp
    q(5,4) = 0.59743854328548053399616_wp
    q(6,4) = -0.066026434346299887619324_wp
    q(7,4) = -0.0017244594505194129307249_wp
    q(1,5) = -0.00883569468552192965061_wp
    q(2,5) = 0.03056074759203203857284_wp
    q(3,5) = 0.05021168274530854232278_wp
    q(4,5) = -0.66307364652444929534068_wp
    q(5,5) = 0.014878787464005191116088_wp
    q(6,5) = 0.65882706381707471953820_wp
    q(7,5) = -0.082568940408449266558615_wp

    first = .false.
  end if

  idel = 1.0_wp / delta

  direction: select case (dir)
  case (0) direction
    if ( bb(1) == 0 ) then
      il = 1 + gsize
    else
      dvar(1,:,:) = ( q(1,1) * var(1,:,:) + q(2,1) * var(2,:,:) + &
                      q(3,1) * var(3,:,:) + q(4,1) * var(4,:,:) + &
                      q(5,1) * var(5,:,:) ) * idel
      dvar(2,:,:) = ( q(1,2) * var(1,:,:) + q(2,2) * var(2,:,:) + &
                      q(3,2) * var(3,:,:) + q(4,2) * var(4,:,:) + &
                      q(5,2) * var(5,:,:) + q(6,2) * var(6,:,:) + &
                      q(7,2) * var(7,:,:) ) * idel
      dvar(3,:,:) = ( q(1,3) * var(1,:,:) + q(2,3) * var(2,:,:) + &
                      q(3,3) * var(3,:,:) + q(4,3) * var(4,:,:) + &
                      q(5,3) * var(5,:,:) + q(6,3) * var(6,:,:) + &
                      q(7,3) * var(7,:,:) ) * idel
      dvar(4,:,:) = ( q(1,4) * var(1,:,:) + q(2,4) * var(2,:,:) + &
                      q(3,4) * var(3,:,:) + q(4,4) * var(4,:,:) + &
                      q(5,4) * var(5,:,:) + q(6,4) * var(6,:,:) + &
                      q(7,4) * var(7,:,:) ) * idel
      dvar(5,:,:) = ( q(1,5) * var(1,:,:) + q(2,5) * var(2,:,:) + &
                      q(3,5) * var(3,:,:) + q(4,5) * var(4,:,:) + &
                      q(5,5) * var(5,:,:) + q(6,5) * var(6,:,:) + &
                      q(7,5) * var(7,:,:) ) * idel
      il = 6
    end if
    if ( bb(2) == 0 ) then
      ir = ni - gsize
    else
      dvar(ni-4,:,:) = - ( q(1,5) * var(ni,:,:) + q(2,5) * var(ni-1,:,:) + &
                           q(3,5) * var(ni-2,:,:) + q(4,5) * var(ni-3,:,:) + &
                           q(5,5) * var(ni-4,:,:) + q(6,5) * var(ni-5,:,:) + &
                           q(7,5) * var(ni-6,:,:) ) * idel
      dvar(ni-3,:,:) = - ( q(1,4) * var(ni,:,:) + q(2,4) * var(ni-1,:,:) + &
                           q(3,4) * var(ni-2,:,:) + q(4,4) * var(ni-3,:,:) + &
                           q(5,4) * var(ni-4,:,:) + q(6,4) * var(ni-5,:,:) + &
                           q(7,4) * var(ni-6,:,:) ) * idel
      dvar(ni-2,:,:) = - ( q(1,3) * var(ni,:,:) + q(2,3) * var(ni-1,:,:) + &
                           q(3,3) * var(ni-2,:,:) + q(4,3) * var(ni-3,:,:) + &
                           q(5,3) * var(ni-4,:,:) + q(6,3) * var(ni-5,:,:) + &
                           q(7,3) * var(ni-6,:,:) ) * idel
      dvar(ni-1,:,:) = - ( q(1,2) * var(ni,:,:) + q(2,2) * var(ni-1,:,:) + &
                           q(3,2) * var(ni-2,:,:) + q(4,2) * var(ni-3,:,:) + &
                           q(5,2) * var(ni-4,:,:) + q(6,2) * var(ni-5,:,:) + &
                           q(7,2) * var(ni-6,:,:) ) * idel
      dvar(ni,:,:)   = - ( q(1,1) * var(ni,:,:) + q(2,1) * var(ni-1,:,:) + &
                           q(3,1) * var(ni-2,:,:) + q(4,1) * var(ni-3,:,:) + &
                           q(5,1) * var(ni-4,:,:) ) * idel
      ir = ni - 5
    end if
    dvar(il:ir,:,:) = ( a(1) * ( var(il+1:ir+1,:,:) - &
                                 var(il-1:ir-1,:,:) ) + &
                        a(2) * ( var(il+2:ir+2,:,:) - &
                                 var(il-2:ir-2,:,:) ) ) * idel
  case (1) direction
    if ( zero_derivs_y /= 0 ) then
      dvar = zero
    else
      if ( bb(1) == 0 ) then
        jl = 1 + gsize
      else
        dvar(:,1,:) = ( q(1,1) * var(:,1,:) + q(2,1) * var(:,2,:) + &
                        q(3,1) * var(:,3,:) + q(4,1) * var(:,4,:) + &
                        q(5,1) * var(:,5,:) ) * idel
        dvar(:,2,:) = ( q(1,2) * var(:,1,:) + q(2,2) * var(:,2,:) + &
                        q(3,2) * var(:,3,:) + q(4,2) * var(:,4,:) + &
                        q(5,2) * var(:,5,:) + q(6,2) * var(:,6,:) + &
                        q(7,2) * var(:,7,:) ) * idel
        dvar(:,3,:) = ( q(1,3) * var(:,1,:) + q(2,3) * var(:,2,:) + &
                        q(3,3) * var(:,3,:) + q(4,3) * var(:,4,:) + &
                        q(5,3) * var(:,5,:) + q(6,3) * var(:,6,:) + &
                        q(7,3) * var(:,7,:) ) * idel
        dvar(:,4,:) = ( q(1,4) * var(:,1,:) + q(2,4) * var(:,2,:) + &
                        q(3,4) * var(:,3,:) + q(4,4) * var(:,4,:) + &
                        q(5,4) * var(:,5,:) + q(6,4) * var(:,6,:) + &
                        q(7,4) * var(:,7,:) ) * idel
        dvar(:,5,:) = ( q(1,5) * var(:,1,:) + q(2,5) * var(:,2,:) + &
                        q(3,5) * var(:,3,:) + q(4,5) * var(:,4,:) + &
                        q(5,5) * var(:,5,:) + q(6,5) * var(:,6,:) + &
                        q(7,5) * var(:,7,:) ) * idel
        jl = 6
      end if
      if ( bb(2) == 0 ) then
        jr = nj - gsize
      else
        dvar(:,nj-4,:) = - ( q(1,5) * var(:,nj,:) + q(2,5) * var(:,nj-1,:) + &
                             q(3,5) * var(:,nj-2,:) + q(4,5) * var(:,nj-3,:) + &
                             q(5,5) * var(:,nj-4,:) + q(6,5) * var(:,nj-5,:) + &
                             q(7,5) * var(:,nj-6,:) ) * idel
        dvar(:,nj-3,:) = - ( q(1,4) * var(:,nj,:) + q(2,4) * var(:,nj-1,:) + &
                             q(3,4) * var(:,nj-2,:) + q(4,4) * var(:,nj-3,:) + &
                             q(5,4) * var(:,nj-4,:) + q(6,4) * var(:,nj-5,:) + &
                             q(7,4) * var(:,nj-6,:) ) * idel
        dvar(:,nj-2,:) = - ( q(1,3) * var(:,nj,:) + q(2,3) * var(:,nj-1,:) + &
                             q(3,3) * var(:,nj-2,:) + q(4,3) * var(:,nj-3,:) + &
                             q(5,3) * var(:,nj-4,:) + q(6,3) * var(:,nj-5,:) + &
                             q(7,3) * var(:,nj-6,:) ) * idel
        dvar(:,nj-1,:) = - ( q(1,2) * var(:,nj,:) + q(2,2) * var(:,nj-1,:) + &
                             q(3,2) * var(:,nj-2,:) + q(4,2) * var(:,nj-3,:) + &
                             q(5,2) * var(:,nj-4,:) + q(6,2) * var(:,nj-5,:) + &
                             q(7,2) * var(:,nj-6,:) ) * idel
        dvar(:,nj,:)   = - ( q(1,1) * var(:,nj,:) + q(2,1) * var(:,nj-1,:) + &
                             q(3,1) * var(:,nj-2,:) + q(4,1) * var(:,nj-3,:) + &
                             q(5,1) * var(:,nj-4,:) ) * idel
        jr = nj - 5
      end if
      dvar(:,jl:jr,:) = ( a(1) * ( var(:,jl+1:jr+1,:) - &
                                   var(:,jl-1:jr-1,:) ) + &
                          a(2) * ( var(:,jl+2:jr+2,:) - &
                                   var(:,jl-2:jr-2,:) ) ) * idel
    end if
  case (2) direction
    if ( zero_derivs_z /= 0 ) then
      dvar = zero
    else
      if ( bb(1) == 0 ) then
        kl = 1 + gsize
      else
        dvar(:,:,1) = ( q(1,1) * var(:,:,1) + q(2,1) * var(:,:,2) + &
                        q(3,1) * var(:,:,3) + q(4,1) * var(:,:,4) + &
                        q(5,1) * var(:,:,5) ) * idel
        dvar(:,:,2) = ( q(1,2) * var(:,:,1) + q(2,2) * var(:,:,2) + &
                        q(3,2) * var(:,:,3) + q(4,2) * var(:,:,4) + &
                        q(5,2) * var(:,:,5) + q(6,2) * var(:,:,6) + &
                        q(7,2) * var(:,:,7) ) * idel
        dvar(:,:,3) = ( q(1,3) * var(:,:,1) + q(2,3) * var(:,:,2) + &
                        q(3,3) * var(:,:,3) + q(4,3) * var(:,:,4) + &
                        q(5,3) * var(:,:,5) + q(6,3) * var(:,:,6) + &
                        q(7,3) * var(:,:,7) ) * idel
        dvar(:,:,4) = ( q(1,4) * var(:,:,1) + q(2,4) * var(:,:,2) + &
                        q(3,4) * var(:,:,3) + q(4,4) * var(:,:,4) + &
                        q(5,4) * var(:,:,5) + q(6,4) * var(:,:,6) + &
                        q(7,4) * var(:,:,7) ) * idel
        dvar(:,:,5) = ( q(1,5) * var(:,:,1) + q(2,5) * var(:,:,2) + &
                        q(3,5) * var(:,:,3) + q(4,5) * var(:,:,4) + &
                        q(5,5) * var(:,:,5) + q(6,5) * var(:,:,6) + &
                        q(7,5) * var(:,:,7) ) * idel
        kl = 6
      end if
      if ( bb(2) == 0 ) then
        kr = nk - gsize
      else 
        dvar(:,:,nk-4) = - ( q(1,5) * var(:,:,nk) + q(2,5) * var(:,:,nk-1) + &
                             q(3,5) * var(:,:,nk-2) + q(4,5) * var(:,:,nk-3) + &
                             q(5,5) * var(:,:,nk-4) + q(6,5) * var(:,:,nk-5) + &
                             q(7,5) * var(:,:,nk-6) ) * idel
        dvar(:,:,nk-3) = - ( q(1,4) * var(:,:,nk) + q(2,4) * var(:,:,nk-1) + &
                             q(3,4) * var(:,:,nk-2) + q(4,4) * var(:,:,nk-3) + &
                             q(5,4) * var(:,:,nk-4) + q(6,4) * var(:,:,nk-5) + &
                             q(7,4) * var(:,:,nk-6) ) * idel
        dvar(:,:,nk-2) = - ( q(1,3) * var(:,:,nk) + q(2,3) * var(:,:,nk-1) + &
                             q(3,3) * var(:,:,nk-2) + q(4,3) * var(:,:,nk-3) + &
                             q(5,3) * var(:,:,nk-4) + q(6,3) * var(:,:,nk-5) + &
                             q(7,3) * var(:,:,nk-6) ) * idel
        dvar(:,:,nk-1) = - ( q(1,2) * var(:,:,nk) + q(2,2) * var(:,:,nk-1) + &
                             q(3,2) * var(:,:,nk-2) + q(4,2) * var(:,:,nk-3) + &
                             q(5,2) * var(:,:,nk-4) + q(6,2) * var(:,:,nk-5) + &
                             q(7,2) * var(:,:,nk-6) ) * idel
        dvar(:,:,nk)   = - ( q(1,1) * var(:,:,nk) + q(2,1) * var(:,:,nk-1) + &
                             q(3,1) * var(:,:,nk-2) + q(4,1) * var(:,:,nk-3) + &
                             q(5,1) * var(:,:,nk-4) ) * idel
        kr = nk - 5
      end if
      dvar(:,:,kl:kr) = ( a(1) * ( var(:,:,kl+1:kr+1) - &
                                   var(:,:,kl-1:kr-1) ) + &
                          a(2) * ( var(:,:,kl+2:kr+2) - &
                                   var(:,:,kl-2:kr-2) ) ) * idel
    end if
  end select direction
end subroutine deriv_gf_4_3_opt