lube_term_objective.f90

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!
! I promise I'll write this document properly in the future...
!
! But the Borval Peterson (I think) paper had an objective function
! that had 2 terms, dissipation and this term they claimed represented
! out of plane stresses.
! I never really understood that extra term, I also don't think it
! applies to 3D cases, but everyone includes it anyway.
!
! It appears to me to be basically a heuristic penality that targets
! non-binary designs
!
! so let's call
!
! F = \int |\nabla u|^2  + K \int \chi \u^2
!
!      | dissipation |     |"lube term"|
!
! I say "lube term" because they said it came from lubrication theory...
! Anyway, we can change all this later (especially the names!)
 
! If the objective function \int |\nabla u|^2,
! the corresponding adjoint forcing is \int \nabla v \cdot \nabla u
!
! for the lube term, the adjoint forcing is \chi u
!
! This has always annoyed me...
! because now I see one objective and one constraint
!
module lube_term_objective
  use objective, only: objective_t
  use design, only: design_t
  use brinkman_design, only: brinkman_design_t
  use simulation_m, only: simulation_t
  use adjoint_lube_source_term, only: adjoint_lube_source_term_t
  use adjoint_fluid_pnpn, only: adjoint_fluid_pnpn_t
  use num_types, only: rp
  use field, only: field_t
  use scratch_registry, only: neko_scratch_registry
  use neko_config, only: neko_bcknd_device
  use mask_ops, only: mask_exterior_const
  use utils, only: neko_error
  use json_module, only: json_file
  use json_utils, only: json_get_or_default
  use field_registry, only: neko_field_registry
  use coefs, only: coef_t
  use math, only: glsc2, copy
  use device_math, only: device_copy, device_glsc2
  use math_ext, only: glsc2_mask
  use field_math, only: field_col3, field_addcol3, field_cmult
  use, intrinsic :: iso_c_binding, only: c_ptr, c_null_ptr
  implicit none
  private
 
  type, public, extends(objective_t) :: lube_term_objective_t
     private
 
     real(kind=rp) :: k
 
     type(field_t), pointer :: u => null()
     type(field_t), pointer :: v => null()
     type(field_t), pointer :: w => null()
     type(coef_t), pointer :: c_xh => null()
     type(field_t), pointer :: brinkman_amplitude => null()
 
   contains
 
     procedure, public, pass(this) :: init_json_sim => lube_term_init_json_sim
     procedure, public, pass(this) :: init_from_attributes => &
          lube_term_init_attributes
     procedure, public, pass(this) :: free => lube_term_free
     procedure, public, pass(this) :: update_value => &
          lube_term_update_value
     procedure, public, pass(this) :: update_sensitivity => &
          lube_term_update_sensitivity
 
  end type lube_term_objective_t
 
contains
 
  subroutine lube_term_init_json_sim(this, json, design, simulation)
    class(lube_term_objective_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
    class(design_t), intent(in) :: design
    type(simulation_t), target, intent(inout) :: simulation
 
    character(len=:), allocatable :: mask_name
    character(len=:), allocatable :: name
    real(kind=rp) :: weight, k
 
    call json_get_or_default(json, "weight", weight, 1.0_rp)
    call json_get_or_default(json, "mask_name", mask_name, "")
    call json_get_or_default(json, "name", name, "Out of plane stresses")
    call json_get_or_default(json, "K", k, 1.0_rp)
 
    call this%init_from_attributes(design, simulation, weight, name, &
         mask_name, k)
  end subroutine lube_term_init_json_sim
 
  subroutine lube_term_init_attributes(this, design, simulation, weight, &
       name, mask_name, K)
    class(lube_term_objective_t), intent(inout) :: this
    class(design_t), intent(in) :: design
    type(simulation_t), target, intent(inout) :: simulation
    real(kind=rp), intent(in) :: weight
    character(len=*), intent(in) :: mask_name
    character(len=*), intent(in) :: name
    real(kind=rp), intent(in) :: k
    type(adjoint_lube_source_term_t) :: lube_term
 
    ! Call the base initializer
    call this%init_base(name, design%size(), weight, mask_name)
 
    ! Set the coefficient for the lube term
    this%K = k
 
    ! Grab the brinkman amplitude for the lube term
    select type (design)
    type is (brinkman_design_t)
       this%brinkman_amplitude => &
            neko_field_registry%get_field("brinkman_amplitude")
 
 
    class default
       call neko_error('Minimum dissipation only works with brinkman_design')
    end select
 
    this%u => neko_field_registry%get_field('u')
    this%v => neko_field_registry%get_field('v')
    this%w => neko_field_registry%get_field('w')
    this%c_Xh => simulation%neko_case%fluid%c_Xh
 
    ! if we have the lube term we need to initialize and append that too
 
    associate(f_adj_x => simulation%adjoint_fluid%f_adj_x, &
         f_adj_y => simulation%adjoint_fluid%f_adj_y, &
         f_adj_z => simulation%adjoint_fluid%f_adj_z, &
         c_xh => simulation%adjoint_fluid%c_Xh)
 
      call lube_term%init_from_components(f_adj_x, f_adj_y, f_adj_z, design, &
           this%k * this%weight, this%u, this%v, this%w, this%mask, &
           this%has_mask, c_xh)
 
    end associate
 
    ! append adjoint forcing term based on objective function
    select type (f => simulation%adjoint_fluid)
    type is (adjoint_fluid_pnpn_t)
       call f%source_term%add_source_term(lube_term)
    end select
 
  end subroutine lube_term_init_attributes
 
  subroutine lube_term_free(this)
    class(lube_term_objective_t), intent(inout) :: this
    call this%free_base()
 
    this%u => null()
    this%v => null()
    this%w => null()
    this%c_Xh => null()
    this%brinkman_amplitude => null()
 
  end subroutine lube_term_free
 
  subroutine lube_term_update_value(this, design)
    class(lube_term_objective_t), intent(inout) :: this
    class(design_t), intent(in) :: design
    type(field_t), pointer :: work
    integer :: temp_indices(1)
 
    call neko_scratch_registry%request_field(work, temp_indices(1))
 
    ! it's becoming so stupid to pass the whole fluid and adjoint and
    ! design through
    ! I feel like every objective function should have internal pointers to
    ! u,v,w and u_adj, v_adj, w_adj and perhaps the design
    ! (the whole design, so we get all the coeffients)
    call field_col3(work, this%u, this%brinkman_amplitude)
    call field_addcol3(work, this%v, this%brinkman_amplitude)
    call field_addcol3(work, this%w, this%brinkman_amplitude)
 
    if (this%has_mask) then
       if (neko_bcknd_device .eq. 1) then
          ! note, this could be done more elagantly by writing
          ! device_glsc2_mask
          call mask_exterior_const(work, this%mask, 0.0_rp)
          this%value = device_glsc2(work%x_d, this%c_Xh%B_d, design%size())
       else
          this%value = glsc2_mask(work%x, this%c_Xh%B, design%size(), &
               this%mask%mask, this%mask%size)
       end if
    else
       if (neko_bcknd_device .eq. 1) then
          this%value = device_glsc2(work%x_d, this%c_Xh%B_d, design%size())
       else
          this%value = glsc2(work%x, this%c_Xh%B, design%size())
       end if
    end if
    this%value = 0.5 * this%K * this%value
 
    call neko_scratch_registry%relinquish_field(temp_indices)
 
  end subroutine lube_term_update_value
 
  subroutine lube_term_update_sensitivity(this, design)
    class(lube_term_objective_t), intent(inout) :: this
    class(design_t), intent(in) :: design
    type(field_t), pointer :: work
    integer :: temp_indices(1)
 
    ! if we have the lube term we also get an extra term in the sensitivity
    ! K * u^2
    ! TODO
    ! omfg be so careful with non-dimensionalization etc
    ! I bet this is scaled a smidge wrong (ie, track if it's 1/2 or not etc)
    ! do this later
 
    call neko_scratch_registry%request_field(work, temp_indices(1))
 
    call field_col3(work, this%u, this%u)
    call field_addcol3(work, this%v, this%v)
    call field_addcol3(work, this%w, this%w)
    call field_cmult(work, this%K)
 
    if (neko_bcknd_device .eq. 1) then
       call device_copy(this%sensitivity%x_d, work%x_d, this%sensitivity%size())
    else
       call copy(this%sensitivity%x, work%x, this%sensitivity%size())
    end if
 
    call neko_scratch_registry%relinquish_field(temp_indices)
 
  end subroutine lube_term_update_sensitivity
 
end module lube_term_objective