PDE_filter_mapping.f90

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!
module pde_filter
  use num_types, only: rp
  use json_module, only: json_file
  use registry, only: neko_registry
  use field, only: field_t
  use coefs, only: coef_t
  use ax_product, only: ax_t, ax_helm_factory
  use krylov, only: ksp_t, ksp_monitor_t, krylov_solver_factory
  use precon, only: pc_t, precon_factory, precon_destroy
  use bc_list, only: bc_list_t
  use neumann, only: neumann_t
  use profiler, only: profiler_start_region, profiler_end_region
  use gather_scatter, only: gs_t, gs_op_add
  use pnpn_residual, only: pnpn_prs_res_t
  use mesh, only: mesh_t, neko_msh_max_zlbls, neko_msh_max_zlbl_len
  use registry, only: neko_registry
  use mapping, only: mapping_t
  use scratch_registry, only: neko_scratch_registry
  use field_math, only: field_copy, field_add3
  use coefs, only: coef_t
  use logger, only: neko_log, log_size
  use neko_config, only: neko_bcknd_device
  use dofmap, only: dofmap_t
  use jacobi, only: jacobi_t
  use device_jacobi, only: device_jacobi_t
  use sx_jacobi, only: sx_jacobi_t
  use utils, only: neko_error
  use device_math, only: device_cfill, device_subcol3, device_cmult
  use json_utils, only: json_get, json_get_or_default
  implicit none
  private
 
  type, public, extends(mapping_t) :: pde_filter_t
     class(ax_t), allocatable :: ax
     type(ksp_monitor_t) :: ksp_results(1)
     class(ksp_t), allocatable :: ksp_filt
     class(pc_t), allocatable :: pc_filt
     type(bc_list_t) :: bclst_filt
 
     ! Inputs from the user
     real(kind=rp) :: r
     real(kind=rp) :: abstol_filt
     integer :: ksp_max_iter
     character(len=:), allocatable :: ksp_solver
     ! > preconditioner type
     character(len=:), allocatable :: precon_type_filt
     integer :: ksp_n, n, i
 
 
 
   contains
     procedure, pass(this) :: init => pde_filter_init_from_json
     procedure, pass(this) :: init_from_attributes => &
          pde_filter_init_from_attributes
     procedure, pass(this) :: free => pde_filter_free
     procedure, pass(this) :: forward_mapping => pde_filter_forward_mapping
     ! TODO
     ! TALK TO NIELS, I think this is correct...
     ! but it's not exactly "chain ruling back"
     ! it's filtering the sensitivity
 
     ! UPDATE:
     ! After an email with Niels, we should be using the chain rule,
     ! not a sensitivity filter
     procedure, pass(this) :: backward_mapping => pde_filter_backward_mapping
  end type pde_filter_t
 
contains
 
  subroutine pde_filter_init_from_json(this, json, coef)
    class(pde_filter_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
    type(coef_t), intent(inout) :: coef
    real(kind=rp) :: r, tol
    integer :: max_iter
    character(len=:), allocatable :: ksp_solver, precon_type
 
    call json_get(json, 'r', r)
    call json_get_or_default(json, 'tol', tol, 0.0000000001_rp)
    call json_get_or_default(json, 'max_iter', max_iter, 200)
    call json_get_or_default(json, 'solver', ksp_solver, "cg")
    call json_get_or_default(json, 'preconditioner', precon_type, "jacobi")
 
    call this%init_base(json, coef)
    call this%init_from_attributes(coef, r, tol, max_iter, &
         ksp_solver, precon_type)
 
  end subroutine pde_filter_init_from_json
 
  subroutine pde_filter_init_from_attributes(this, coef, r, tol, max_iter, &
       ksp_solver, precon_type)
    class(pde_filter_t), intent(inout) :: this
    type(coef_t), intent(inout) :: coef
    real(kind=rp), intent(in) :: r, tol
    integer, intent(in) :: max_iter
    character(len=*), intent(in) :: ksp_solver, precon_type
    integer :: n
 
    this%r = r / (2.0_rp * sqrt(3.0_rp))
    this%abstol_filt = tol
    this%ksp_max_iter = max_iter
    this%ksp_solver = ksp_solver
    this%precon_type_filt = precon_type
 
    ! set the number of dofs
    n = this%coef%dof%size()
 
    ! init the bc list (all Neuman BCs, will remain empty)
    call this%bclst_filt%init()
 
    ! Setup backend dependent Ax routines
    call ax_helm_factory(this%Ax, full_formulation = .false.)
 
    ! set up krylov solver
    call krylov_solver_factory(this%ksp_filt, n, this%ksp_solver, &
         this%ksp_max_iter, this%abstol_filt)
 
    ! set up preconditioner
    call filter_precon_factory(this%pc_filt, this%ksp_filt, &
         this%coef, this%coef%dof, this%coef%gs_h, this%bclst_filt, &
         this%precon_type_filt)
 
  end subroutine pde_filter_init_from_attributes
 
  subroutine pde_filter_free(this)
    class(pde_filter_t), intent(inout) :: this
 
    if (allocated(this%Ax)) then
       deallocate(this%Ax)
    end if
 
    if (allocated(this%ksp_filt)) then
       call this%ksp_filt%free()
       deallocate(this%ksp_filt)
    end if
 
    if (allocated(this%pc_filt)) then
       call precon_destroy(this%pc_filt)
       deallocate(this%pc_filt)
    end if
 
    call this%bclst_filt%free()
 
    call this%free_base()
 
  end subroutine pde_filter_free
 
  subroutine pde_filter_forward_mapping(this, X_out, X_in)
    class(pde_filter_t), intent(inout) :: this
    type(field_t), intent(in) :: X_in
    type(field_t), intent(inout) :: X_out
    integer :: n, i
    type(field_t), pointer :: RHS, d_X_out
    character(len=LOG_SIZE) :: log_buf
    integer :: temp_indices(2)
 
    n = this%coef%dof%size()
    call neko_scratch_registry%request_field(rhs, temp_indices(1), .false.)
    call neko_scratch_registry%request_field(d_x_out, temp_indices(2), .false.)
    ! in a similar fasion to pressure/velocity, we will solve for d_X_out.
 
    ! to improve convergence, we use X_in as an initial guess for X_out.
    ! so X_out = X_in + d_X_in.
 
    ! Defining the operator A = -r^2 \nabla^2 + I
    ! the system changes from:
    ! A (X_out) = X_in
    ! to
    ! A (d_X_out) = X_in - A(X_in)
 
    ! set up Helmholtz operators and RHS
    if (neko_bcknd_device .eq. 1) then
       call device_cfill(this%coef%h1_d, this%r**2, n)
       call device_cfill(this%coef%h2_d, 1.0_rp, n)
    else
       ! h1 is already negative in its definition
       this%coef%h1 = this%r**2
       ! ax_helm includes the mass matrix in h2
       this%coef%h2 = 1.0_rp
    end if
    this%coef%ifh2 = .true.
 
    ! compute the A(X_in) component of the RHS
    ! (note, to be safe with the inout intent we first copy X_in to the
    !  temporary d_X_out)
    call field_copy(d_x_out, x_in)
    call this%Ax%compute(rhs%x, d_x_out%x, this%coef, this%coef%msh, &
         this%coef%Xh)
 
    if (neko_bcknd_device .eq. 1) then
       call device_subcol3(rhs%x_d, x_in%x_d, this%coef%B_d, n)
       call device_cmult(rhs%x_d, -1.0_rp, n)
    else
       do i = 1, n
          ! mass matrix should be included here
          rhs%x(i,1,1,1) = x_in%x(i,1,1,1) * this%coef%B(i,1,1,1) &
               - rhs%x(i,1,1,1)
       end do
    end if
 
    ! gather scatter
    call this%coef%gs_h%op(rhs, gs_op_add)
 
    ! set BCs
    call this%bclst_filt%apply_scalar(rhs%x, n)
 
    ! Solve Helmholtz equation
    call profiler_start_region('filter solve')
    this%ksp_results(1) = &
         this%ksp_filt%solve(this%Ax, d_x_out, rhs%x, n, this%coef, &
         this%bclst_filt, this%coef%gs_h)
 
    call profiler_end_region
 
    ! add result
    call field_add3(x_out, x_in, d_x_out)
    ! update preconditioner (needed?)
    call this%pc_filt%update()
 
    ! write it all out
    call neko_log%message('Filter')
 
    write(log_buf, '(A,A,A)') 'Iterations:   ',&
         'Start residual:     ', 'Final residual:'
    call neko_log%message(log_buf)
    write(log_buf, '(I11,3x, E15.7,5x, E15.7)') this%ksp_results%iter, &
         this%ksp_results%res_start, this%ksp_results%res_final
    call neko_log%message(log_buf)
 
    call neko_scratch_registry%relinquish_field(temp_indices)
 
 
 
  end subroutine pde_filter_forward_mapping
 
  ! TODO
  ! this really confuses me!
  ! it's not really a chain rule back, it's just a filtering of the sensitivity
  ! ?
  !
  ! Update:
  ! After an email exchange with Niels:
  ! We DON'T want to be filtering the sensitivity, this IS just the chain rule.
  ! So to the best of my knowledge, we're just applying the same filter
  ! on the sensitivity field.
  !
  ! Niels did mention the order of the RHS assembly should be reversed however.
  ! I'm not exactly sure how this applies to us, but it should be brought up
  ! in the next group meeting.
  subroutine pde_filter_backward_mapping(this, sens_out, sens_in, X_in)
    class(pde_filter_t), intent(inout) :: this
    type(field_t), intent(in) :: X_in
    type(field_t), intent(in) :: sens_in
    type(field_t), intent(inout) :: sens_out
    integer :: n, i
    type(field_t), pointer :: RHS, delta ! I'm so sorry for this notation..
    integer :: temp_indices(2)
    character(len=LOG_SIZE) :: log_buf
 
    n = this%coef%dof%size()
 
    call neko_scratch_registry%request_field(rhs, temp_indices(1), .false.)
    call neko_scratch_registry%request_field(delta, temp_indices(2), .false.)
 
    ! set up Helmholtz operators and RHS
    if (neko_bcknd_device .eq. 1) then
       call device_cfill(this%coef%h1_d, this%r**2, n)
       call device_cfill(this%coef%h2_d, 1.0_rp, n)
    else
       ! h1 is already negative in its definition
       this%coef%h1 = this%r**2
       ! ax_helm includes the mass matrix in h2
       this%coef%h2 = 1.0_rp
    end if
    this%coef%ifh2 = .true.
 
    ! compute the A(sens_in) component of the RHS
    ! (note, to be safe with the inout intent we first copy sens_in to the
    !  temporary delta)
    call field_copy(delta, sens_in)
    call this%Ax%compute(rhs%x, delta%x, this%coef, this%coef%msh, &
         this%coef%Xh)
 
    if (neko_bcknd_device .eq. 1) then
       call device_subcol3(rhs%x_d, sens_in%x_d, this%coef%B_d, n)
       call device_cmult(rhs%x_d, -1.0_rp, n)
    else
       do i = 1, n
          ! mass matrix should be included here
          rhs%x(i,1,1,1) = sens_in%x(i,1,1,1) * this%coef%B(i,1,1,1) &
               - rhs%x(i,1,1,1)
       end do
    end if
 
    ! gather scatter
    call this%coef%gs_h%op(rhs, gs_op_add)
 
    ! set BCs
    call this%bclst_filt%apply_scalar(rhs%x, n)
 
    ! Solve Helmholtz equation
    call profiler_start_region('filter solve')
    this%ksp_results(1) = &
         this%ksp_filt%solve(this%Ax, delta, rhs%x, n, this%coef, &
         this%bclst_filt, this%coef%gs_h)
 
    ! add result
    call field_add3(sens_out, sens_in, delta)
 
    call profiler_end_region
 
    ! update preconditioner (needed?)
    call this%pc_filt%update()
 
    ! write it all out
    call neko_log%message('Filter')
 
    write(log_buf, '(A,A,A)') 'Iterations:   ',&
         'Start residual:     ', 'Final residual:'
    call neko_log%message(log_buf)
    write(log_buf, '(I11,3x, E15.7,5x, E15.7)') this%ksp_results%iter, &
         this%ksp_results%res_start, this%ksp_results%res_final
    call neko_log%message(log_buf)
 
    call neko_scratch_registry%relinquish_field(temp_indices)
 
  end subroutine pde_filter_backward_mapping
 
  subroutine filter_precon_factory(pc, ksp, coef, dof, gs, bclst, pctype)
 
    implicit none
    class(pc_t), allocatable, target, intent(inout) :: pc
    class(ksp_t), target, intent(inout) :: ksp
    type(coef_t), target, intent(in) :: coef
    type(dofmap_t), target, intent(in) :: dof
    type(gs_t), target, intent(inout) :: gs
    type(bc_list_t), target, intent(inout) :: bclst
    character(len=*) :: pctype
 
    call precon_factory(pc, pctype)
 
    select type (pcp => pc)
    type is (jacobi_t)
       call pcp%init(coef, dof, gs)
    type is (sx_jacobi_t)
       call pcp%init(coef, dof, gs)
    type is (device_jacobi_t)
       call pcp%init(coef, dof, gs)
    end select
 
    call ksp%set_pc(pc)
 
  end subroutine filter_precon_factory
 
end module pde_filter