stencils.f90

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module stencils
 
    !       stencils defines indices for several types of stencils. These
    !       are useful for setting blocks in dRdw and dRdwPre depending
    !       on the type of equations  being solved
 
    use constants, only: inttype, realtype
    implicit none
 
    ! Euler stencils
    integer(kind=intType), parameter :: n_euler_pc = 7
    integer(kind=intType), parameter :: n_euler_drdw = 13
 
    integer(kind=intType), dimension(7, 3), target :: euler_pc_stencil
    integer(kind=intType), dimension(13, 3), target :: euler_drdw_stencil
 
    ! Viscous stencils
    integer(kind=intType), parameter :: n_visc_pc = 27
    integer(kind=intType), parameter :: n_visc_drdw = 33
 
    integer(kind=intType), dimension(27, 3), target :: visc_pc_stencil
    integer(kind=intType), dimension(33, 3), target :: visc_drdw_stencil
 
end module stencils
 
subroutine initialize_stencils
 
    use stencils
 
    implicit none
    integer(kind=intType) :: i, j, k, ii
 
    ! -------- Euler PC Stencil ---------
    euler_pc_stencil(1, :) = (/0, 0, 0/)
    euler_pc_stencil(2, :) = (/-1, 0, 0/)
    euler_pc_stencil(3, :) = (/1, 0, 0/)
    euler_pc_stencil(4, :) = (/0, -1, 0/)
    euler_pc_stencil(5, :) = (/0, 1, 0/)
    euler_pc_stencil(6, :) = (/0, 0, -1/)
    euler_pc_stencil(7, :) = (/0, 0, 1/)
 
    ! ---------- Euler drdw Stencil ---------
    euler_drdw_stencil(1, :) = (/0, 0, 0/)
    euler_drdw_stencil(2, :) = (/-2, 0, 0/)
    euler_drdw_stencil(3, :) = (/-1, 0, 0/)
    euler_drdw_stencil(4, :) = (/1, 0, 0/)
    euler_drdw_stencil(5, :) = (/2, 0, 0/)
    euler_drdw_stencil(6, :) = (/0, -2, 0/)
    euler_drdw_stencil(7, :) = (/0, -1, 0/)
    euler_drdw_stencil(8, :) = (/0, 1, 0/)
    euler_drdw_stencil(9, :) = (/0, 2, 0/)
    euler_drdw_stencil(10, :) = (/0, 0, -2/)
    euler_drdw_stencil(11, :) = (/0, 0, -1/)
    euler_drdw_stencil(12, :) = (/0, 0, 1/)
    euler_drdw_stencil(13, :) = (/0, 0, 2/)
 
    ! ---------- Visc PC Stencil -------
 
    ! Set the first 7 to the euler pc stencil
    visc_pc_stencil(1:7, :) = euler_pc_stencil
 
    ! And now for the remaining 20
    visc_pc_stencil(8, :) = (/-1, -1, -1/)
    visc_pc_stencil(9, :) = (/0, -1, -1/)
    visc_pc_stencil(10, :) = (/1, -1, -1/)
    visc_pc_stencil(11, :) = (/-1, 0, -1/)
    visc_pc_stencil(12, :) = (/1, 0, -1/)
    visc_pc_stencil(13, :) = (/-1, 1, -1/)
    visc_pc_stencil(14, :) = (/0, 1, -1/)
    visc_pc_stencil(15, :) = (/1, 1, -1/)
 
    visc_pc_stencil(16, :) = (/-1, -1, 0/)
    visc_pc_stencil(17, :) = (/1, -1, 0/)
    visc_pc_stencil(18, :) = (/-1, 1, 0/)
    visc_pc_stencil(19, :) = (/1, 1, 0/)
 
    visc_pc_stencil(20, :) = (/-1, -1, 1/)
    visc_pc_stencil(21, :) = (/0, -1, 1/)
    visc_pc_stencil(22, :) = (/1, -1, 1/)
    visc_pc_stencil(23, :) = (/-1, 0, 1/)
    visc_pc_stencil(24, :) = (/1, 0, 1/)
    visc_pc_stencil(25, :) = (/-1, 1, 1/)
    visc_pc_stencil(26, :) = (/0, 1, 1/)
    visc_pc_stencil(27, :) = (/1, 1, 1/)
 
    ! ------------ Visc dRdw Stencil -------------
    ! Dense 3x3x3 cube
    ii = 1
    do k = -1, 1
        do j = -1, 1
            do i = -1, 1
                visc_drdw_stencil(ii, :) = (/i, j, k/)
                ii = ii + 1
            end do
        end do
    end do
 
    ! Plus the 6 double halos
    visc_drdw_stencil(28, :) = (/-2, 0, 0/)
    visc_drdw_stencil(29, :) = (/2, 0, 0/)
    visc_drdw_stencil(30, :) = (/0, -2, 0/)
    visc_drdw_stencil(31, :) = (/0, 2, 0/)
    visc_drdw_stencil(32, :) = (/0, 0, -2/)
    visc_drdw_stencil(33, :) = (/0, 0, 2/)
 
end subroutine initialize_stencils