elementwise_filter.f90

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module elementwise_filter
  use num_types, only : rp
  use filter, only: filter_t
  use math, only : rzero, rone, copy
  use field, only : field_t
  use coefs, only : coef_t
  use utils, only : neko_error
  use neko_config, only : neko_bcknd_device
  use json_module, only : json_file
  use json_utils, only : json_get_or_default, json_get
  use speclib, only : zwgll, legendre_poly
  use matrix, only : matrix_t
  use mxm_wrapper, only : mxm
  use tensor, only : tnsr3d, trsp
  use device, only : device_map, device_free, device_memcpy, host_to_device
  use device_math, only : device_cfill
  use, intrinsic :: iso_c_binding, only : c_ptr, c_null_ptr, c_associated
  implicit none
  private
 
  type, public, extends(filter_t) :: elementwise_filter_t
     character(len=:), allocatable :: filter_type
     integer :: nx
     integer :: nt
     real(kind=rp), allocatable :: fh(:,:), fht(:,:)
     type(c_ptr) :: fh_d = c_null_ptr
     type(c_ptr) :: fht_d = c_null_ptr
     real(kind=rp), allocatable :: transfer(:)
   contains
     procedure, pass(this) :: init => elementwise_filter_init_from_json
     procedure, pass(this) :: init_from_components => &
          elementwise_filter_init_from_components
     procedure, pass(this) :: free => elementwise_filter_free
     procedure, pass(this) :: build_1d
     procedure, pass(this) :: apply => elementwise_field_filter_3d
  end type elementwise_filter_t
 
contains
  subroutine elementwise_filter_init_from_json(this, json, coef)
    class(elementwise_filter_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
    type(coef_t), intent(in) :: coef
    real(kind=rp), allocatable :: transfer(:)
    character(len=:), allocatable :: filter_type
 
    ! Filter assumes lx = ly = lz
    call this%init_base(json, coef)
 
    call this%init_from_components(coef%dof%xh%lx)
 
    call json_get_or_default(json, "filter.elementwise_filter_type", &
         this%filter_type, "nonBoyd")
 
    if (json%valid_path('filter.transfer_function')) then
       call json_get(json, 'filter.transfer_function', transfer)
       if (size(transfer) .eq. coef%dof%xh%lx) then
          this%transfer = transfer
       else
          call neko_error("The transfer function of the elementwise " // &
               "filter must correspond the order of the polynomial")
       end if
       call this%build_1d()
    end if
 
  end subroutine elementwise_filter_init_from_json
 
  subroutine elementwise_filter_init_from_components(this, nx)
    class(elementwise_filter_t), intent(inout) :: this
    integer :: nx
 
    this%nx = nx
    this%nt = nx ! initialize as if nothing is filtered yet
 
    allocate(this%fh(nx, nx))
    allocate(this%fht(nx, nx))
    allocate(this%transfer(nx))
 
    call rzero(this%fh, nx*nx)
    call rzero(this%fht, nx*nx)
    call rone(this%transfer, nx) ! initialize as if nothing is filtered yet
 
    if (neko_bcknd_device .eq. 1) then
       call device_map(this%fh, this%fh_d, this%nx * this%nx)
       call device_map(this%fht, this%fht_d, this%nx * this%nx)
       call device_cfill(this%fh_d, 0.0_rp, this%nx * this%nx)
       call device_cfill(this%fht_d, 0.0_rp, this%nx * this%nx)
    end if
 
  end subroutine elementwise_filter_init_from_components
 
  subroutine elementwise_filter_free(this)
    class(elementwise_filter_t), intent(inout) :: this
 
    if (allocated(this%filter_type)) then
       deallocate(this%filter_type)
    end if
 
    if (allocated(this%fh)) then
       deallocate(this%fh)
    end if
 
    if (allocated(this%fht)) then
       deallocate(this%fht)
    end if
 
    if (allocated(this%transfer)) then
       deallocate(this%transfer)
    end if
 
    if (c_associated(this%fh_d)) then
       call device_free(this%fh_d)
    end if
 
    if (c_associated(this%fht_d)) then
       call device_free(this%fht_d)
    end if
 
    this%filter_type = ""
    this%nx = 0
    this%nt = 0
 
    call this%free_base()
 
  end subroutine elementwise_filter_free
 
  subroutine build_1d(this)
    class(elementwise_filter_t), intent(inout) :: this
 
    call build_1d_cpu(this%fh, this%fht, this%transfer, &
         this%nx, this%filter_type)
    if (neko_bcknd_device .eq. 1) then
       call device_memcpy(this%fh, this%fh_d, &
            this%nx * this%nx, host_to_device, sync = .false.)
       call device_memcpy(this%fht, this%fht_d, &
            this%nx * this%nx, host_to_device, sync = .false.)
    end if
 
  end subroutine build_1d
 
  subroutine elementwise_field_filter_3d(this, F_out, F_in)
    class(elementwise_filter_t), intent(inout) :: this
    type(field_t), intent(inout) :: F_out
    type(field_t), intent(in) :: F_in
 
    ! F_out = fh x fh x fh x F_in
    call tnsr3d(f_out%x, this%nx, f_in%x, this%nx, this%fh, this%fht, this%fht, &
         this%coef%msh%nelv)
 
  end subroutine elementwise_field_filter_3d
 
  subroutine build_1d_cpu(fh, fht, transfer, nx, filter_type)
    integer, intent(in) :: nx
    real(kind=rp), intent(inout) :: fh(nx, nx), fht(nx, nx)
    real(kind=rp), intent(in) :: transfer(nx)
    real(kind=rp) :: diag(nx, nx), rmult(nx), lj(nx), zpts(nx)
    type(matrix_t) :: phi, pht
    integer :: n, i, j, k
    real(kind=rp) :: z
    character(len=*), intent(in) :: filter_type
 
    call phi%init(nx, nx)
    call pht%init(nx, nx)
 
    call zwgll(zpts, rmult, nx)
 
    n = nx-1
    do j = 1, nx
       z = zpts(j)
       call legendre_poly(lj, z, n)
       select case (filter_type)
       case("Boyd")
          pht%x(1,j) = lj(1)
          pht%x(2,j) = lj(2)
          do k=3,nx
             pht%x(k,j) = lj(k)-lj(k-2)
          end do
       case("nonBoyd")
          pht%x(:,j) = lj
       end select
    end do
 
    call trsp(phi%x, nx, pht%x, nx)
    pht%x = phi%x
 
    call pht%inverse(0) ! "0" for cpu implementation
 
    diag = 0.0_rp
 
    do i=1,nx
       diag(i,i) = transfer(i)
    end do
 
    call mxm (diag, nx, pht%x, nx, fh, nx) !          -1
    call mxm (phi%x, nx, fh, nx, pht%x, nx) !     V D V
 
    call copy (fh, pht%x, nx*nx)
    call trsp (fht, nx, fh, nx)
 
  end subroutine build_1d_cpu
 
end module elementwise_filter