neko_api.f90

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! Copyright (c) 2022-2026, The Neko Authors
! All rights reserved.
!
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! are met:
!
!   * Redistributions of source code must retain the above copyright
!     notice, this list of conditions and the following disclaimer.
!
!   * Redistributions in binary form must reproduce the above
!     copyright notice, this list of conditions and the following
!     disclaimer in the documentation and/or other materials provided
!     with the distribution.
!
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!     contributors may be used to endorse or promote products derived
!     from this software without specific prior written permission.
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! THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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! COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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! POSSIBILITY OF SUCH DAMAGE.
!
module neko_api
  use neko
  use neko_api_user, only : neko_api_user_cb_register, &
       neko_api_user_cb_get_field
  use, intrinsic :: iso_c_binding
  implicit none
  private
 
contains
 
  subroutine neko_api_init() bind(c, name="neko_init")
 
    call neko_init()
 
  end subroutine neko_api_init
 
  subroutine neko_api_finalize() bind(c, name="neko_finalize")
 
    call neko_finalize()
 
  end subroutine neko_api_finalize
 
  subroutine neko_api_device_init() bind(c, name="neko_device_init")
 
    call device_init
 
  end subroutine neko_api_device_init
 
  subroutine neko_api_device_finalize() bind(c, name="neko_device_finalize")
 
    call device_finalize
 
  end subroutine neko_api_device_finalize
 
  subroutine neko_api_job_info() bind(c, name="neko_job_info")
    logical :: initialized
 
    call mpi_initialized(initialized)
 
    if (.not.initialized) then
       call neko_warning('Neko has not been initialised')
    else
       call neko_job_info()
       call neko_log%newline()
    end if
 
  end subroutine neko_api_job_info
 
  subroutine neko_api_registry_init() bind(c, name="neko_registry_init")
 
    call neko_registry%init()
 
  end subroutine neko_api_registry_init
 
  subroutine neko_api_registry_free() bind(c, name="neko_registry_free")
 
    call neko_registry%free()
 
  end subroutine neko_api_registry_free
 
  subroutine neko_api_case_allocate(case_iptr) &
       bind(c, name="neko_case_allocate")
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cp
 
    allocate(c)
    cp = c_loc(c)
    case_iptr = transfer(cp, 0_c_intptr_t)
 
  end subroutine neko_api_case_allocate
 
  subroutine neko_api_case_init(case_json, case_len, case_iptr) &
       bind(c, name="neko_case_init")
    type(c_ptr), intent(in) :: case_json
    integer(c_int), value :: case_len
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(json_file) :: json_case
    type(case_t), pointer :: C
    type(c_ptr) :: cp
 
    ! Check if the case has already been allocated
    ! e.g. if a user callback has been injected
    cp = transfer(case_iptr, c_null_ptr)
    if (c_associated(cp)) then
       call c_f_pointer(cp, c)
    else
       allocate(c)
       cp = c_loc(c)
       case_iptr = transfer(cp, 0_c_intptr_t)
    end if
 
    ! Convert passed in serialised JSON object into a Fortran
    ! character string and create a json_file object
    if (c_associated(case_json)) then
       block
         character(kind=c_char,len=case_len+1),pointer :: s
         character(len=:), allocatable :: fcase_json
         call c_f_pointer(case_json, s)
         fcase_json = s(1:case_len)
         call json_case%load_from_string(fcase_json)
         deallocate(fcase_json)
         nullify(s)
       end block
    end if
 
    !
    ! Create case
    !
    call c%init(json_case)
 
    !
    ! Create simulation components
    !
    call neko_simcomps%init(c)
 
  end subroutine neko_api_case_init
 
 
  subroutine neko_api_case_free(case_iptr) bind(c, name="neko_case_free")
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cp
 
    cp = transfer(case_iptr, c_null_ptr)
    if (c_associated(cp)) then
       call c_f_pointer(cp, c)
       call c%free()
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_case_free
 
  function neko_api_case_time(case_iptr) result(time) &
       bind(c, name="neko_case_time")
    integer(c_intptr_t), intent(inout) :: case_iptr
    real(kind=c_rp) :: time
    type(case_t), pointer :: c
    type(c_ptr) :: cptr
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       time = c%time%t
    else
       call neko_error('Invalid Neko case')
    end if
 
  end function neko_api_case_time
 
  function neko_api_case_end_time(case_iptr) result(end_time) &
       bind(c, name="neko_case_end_time")
    integer(c_intptr_t), intent(inout) :: case_iptr
    real(kind=c_rp) :: end_time
    type(case_t), pointer :: c
    type(c_ptr) :: cptr
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       end_time = c%time%end_time
    else
       call neko_error('Invalid Neko case')
    end if
 
  end function neko_api_case_end_time
 
  function neko_api_case_tstep(case_iptr) result(tstep) &
       bind(c, name="neko_case_tstep")
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: c
    type(c_ptr) :: cptr
    integer(c_int) :: tstep
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       tstep = c%time%tstep
    else
       call neko_error('Invalid Neko case')
    end if
 
  end function neko_api_case_tstep
 
  subroutine neko_api_solve(case_iptr) bind(c, name="neko_solve")
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cp
 
    cp = transfer(case_iptr, c_null_ptr)
    if (c_associated(cp)) then
       call c_f_pointer(cp, c)
       call neko_solve(c)
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_solve
 
  subroutine neko_api_step(case_iptr) &
       bind(c, name="neko_step")
    use time_step_controller, only : time_step_controller_t
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cptr
    type(json_file) :: dt_params
    type(time_step_controller_t), save, allocatable :: dt_controller
    real(kind=dp), save :: step_loop_start = 0.0_dp
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
 
       if (.not. allocated(dt_controller)) then
          allocate(dt_controller)
          call json_get(c%params, 'case.time', dt_params)
          call dt_controller%init(dt_params)
       end if
 
       if (c%time%tstep .eq. 0) then
          call simulation_init(c, dt_controller)
 
          step_loop_start = mpi_wtime()
       end if
 
       if (.not. c%time%is_done()) then
          call simulation_step(c, dt_controller, step_loop_start)
       end if
 
       if (c%time%is_done()) then
          call simulation_finalize(c)
          if (allocated(dt_controller)) then
             deallocate(dt_controller)
          end if
       end if
 
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_step
 
  subroutine neko_api_output_ctrl_execute(case_iptr, force_output) &
       bind(c, name="neko_output_ctrl_execute")
    integer(c_intptr_t), intent(inout) :: case_iptr
    logical(kind=c_bool), value :: force_output
    logical :: f_force_output
    type(case_t), pointer :: C
    type(c_ptr) :: cp
    type(time_state_t) :: f_time
 
    cp = transfer(case_iptr, c_null_ptr)
    if (c_associated(cp)) then
       call c_f_pointer(cp, c)
    else
       call neko_error('Invalid Neko case')
    end if
 
    f_force_output = transfer(force_output, f_force_output)
    call c%output_controller%execute(c%time, f_force_output)
 
  end subroutine neko_api_output_ctrl_execute
 
  function neko_api_field(field_name) result(field_ptr) &
       bind(c, name='neko_field')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: field
    type(c_ptr) :: field_ptr
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
 
    field_ptr = c_loc(field%x)
 
  end function neko_api_field
 
  function neko_api_field_order(field_name) result(field_lx) &
       bind(c, name='neko_field_order')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: field
    integer(c_int) :: field_lx
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
 
    field_lx = field%Xh%lx
 
  end function neko_api_field_order
 
  function neko_api_field_nelements(field_name) result(field_nelv) &
       bind(c, name='neko_field_nelements')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: field
    integer(c_int) :: field_nelv
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
 
    field_nelv = field%msh%nelv
 
  end function neko_api_field_nelements
 
  function neko_api_field_size(field_name) result(field_size) &
       bind(c, name='neko_field_size')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: field
    integer(c_int) :: field_size
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
 
    field_size = field%dof%size()
 
  end function neko_api_field_size
 
  subroutine neko_api_field_dofmap(field_name, dof_ptr, x_ptr, y_ptr, z_ptr) &
       bind(c, name='neko_field_dofmap')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    type(c_ptr), intent(inout) :: dof_ptr, x_ptr, y_ptr, z_ptr
    character(len=8192) :: name
    type(field_t), pointer :: field
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
    call neko_api_wrap_dofmap(field%dof, dof_ptr, x_ptr, y_ptr, z_ptr)
 
  end subroutine neko_api_field_dofmap
 
  subroutine neko_api_case_fluid_dofmap(case_iptr, dof_ptr, &
       x_ptr, y_ptr, z_ptr, size) bind(c, name='neko_case_fluid_dofmap')
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cptr
    type(c_ptr), intent(inout) :: dof_ptr, x_ptr, y_ptr, z_ptr
    integer, intent(inout) :: size
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       call neko_api_wrap_dofmap(c%fluid%dm_Xh, dof_ptr, x_ptr, y_ptr, z_ptr)
       size = c%fluid%dm_Xh%size()
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_case_fluid_dofmap
 
  subroutine neko_api_wrap_dofmap(dm, dof_ptr, x_ptr, y_ptr, z_ptr)
    type(dofmap_t), target, intent(in) :: dm
    type(c_ptr), intent(inout) :: dof_ptr, x_ptr, y_ptr, z_ptr
 
    dof_ptr = c_loc(dm%dof)
    x_ptr = c_loc(dm%x)
    y_ptr = c_loc(dm%y)
    z_ptr = c_loc(dm%z)
 
  end subroutine neko_api_wrap_dofmap
 
  subroutine neko_api_field_space(field_name, lx, zg, &
       dr_inv, ds_inv, dt_inv, wx, wy, wz, dx, dy, dz) &
       bind(c, name='neko_field_space')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    integer, intent(inout) :: lx
    type(c_ptr), intent(inout) :: zg, dr_inv, ds_inv, dt_inv
    type(c_ptr), intent(inout) :: wx, wy, wz, dx, dy, dz
    character(len=8192) :: name
    type(field_t), pointer :: field
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_registry%get_field(trim(name(1:len)))
    call neko_api_wrap_space(field%Xh, lx, zg, dr_inv, ds_inv, dt_inv, &
         wx, wy, wz, dx, dy, dz)
 
  end subroutine neko_api_field_space
 
  subroutine neko_api_case_fluid_space(case_iptr, lx, zg, &
       dr_inv, ds_inv, dt_inv, wx, wy, wz, dx, dy, dz) &
       bind(c, name='neko_case_fluid_space')
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cptr
    integer, intent(inout) :: lx
    type(c_ptr), intent(inout) :: zg, dr_inv, ds_inv, dt_inv
    type(c_ptr), intent(inout) :: wx, wy, wz, dx, dy, dz
 
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       call neko_api_wrap_space(c%fluid%Xh, lx, zg, dr_inv, ds_inv, dt_inv, &
            wx, wy, wz, dx, dy, dz)
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_case_fluid_space
 
  subroutine neko_api_wrap_space(Xh, lx, zg, dr_inv, ds_inv, dt_inv, &
       wx, wy, wz, dx, dy, dz)
    type(space_t), target, intent(in) :: Xh
    integer, intent(inout) :: lx
    type(c_ptr), intent(inout) :: zg, dr_inv, ds_inv, dt_inv
    type(c_ptr), intent(inout) :: wx, wy, wz, dx, dy, dz
 
    lx = xh%lx
    zg = c_loc(xh%zg)
    dr_inv = c_loc(xh%dr_inv)
    ds_inv = c_loc(xh%ds_inv)
    dt_inv = c_loc(xh%dt_inv)
    wx = c_loc(xh%wx)
    wy = c_loc(xh%wy)
    wz = c_loc(xh%wz)
    dx = c_loc(xh%dx)
    dy = c_loc(xh%dy)
    dz = c_loc(xh%dz)
 
  end subroutine neko_api_wrap_space
 
  subroutine neko_api_case_fluid_coef(case_iptr, G11, G22, G33, G12, G13, G23, &
       mult, dxdr, dydr, dzdr, dxds, dyds, dzds, dxdt, dydt, dzdt, &
       drdx, drdy, drdz, dsdx, dsdy, dsdz, dtdx, dtdy, dtdz, &
       jac, B, area, nx, ny, nz) bind(c, name='neko_case_fluid_coef')
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(case_t), pointer :: C
    type(c_ptr) :: cptr
    type(c_ptr), intent(inout) :: G11, G22, G33, G12, G13, G23
    type(c_ptr), intent(inout) :: mult
    type(c_ptr), intent(inout) :: dxdr, dydr, dzdr
    type(c_ptr), intent(inout) :: dxds, dyds, dzds
    type(c_ptr), intent(inout) :: dxdt, dydt, dzdt
    type(c_ptr), intent(inout) :: drdx, drdy, drdz
    type(c_ptr), intent(inout) :: dsdx, dsdy, dsdz
    type(c_ptr), intent(inout) :: dtdx, dtdy, dtdz
    type(c_ptr), intent(inout) :: jac, B, area, nx, ny, nz
 
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       g11 = c_loc(c%fluid%c_Xh%G11)
       g22 = c_loc(c%fluid%c_Xh%G22)
       g33 = c_loc(c%fluid%c_Xh%G33)
       g12 = c_loc(c%fluid%c_Xh%G12)
       g13 = c_loc(c%fluid%c_Xh%G13)
       g23 = c_loc(c%fluid%c_Xh%G23)
       mult = c_loc(c%fluid%c_Xh%mult)
       dxdr = c_loc(c%fluid%c_Xh%dxdr)
       dydr = c_loc(c%fluid%c_Xh%dydr)
       dzdr = c_loc(c%fluid%c_Xh%dzdr)
       dxds = c_loc(c%fluid%c_Xh%dxds)
       dyds = c_loc(c%fluid%c_Xh%dyds)
       dzds = c_loc(c%fluid%c_Xh%dzds)
       dxdt = c_loc(c%fluid%c_Xh%dxdt)
       dydt = c_loc(c%fluid%c_Xh%dydt)
       dzdt = c_loc(c%fluid%c_Xh%dzdt)
       drdx = c_loc(c%fluid%c_Xh%drdx)
       drdy = c_loc(c%fluid%c_Xh%drdy)
       drdz = c_loc(c%fluid%c_Xh%drdz)
       dsdx = c_loc(c%fluid%c_Xh%dsdx)
       dsdy = c_loc(c%fluid%c_Xh%dsdy)
       dsdz = c_loc(c%fluid%c_Xh%dsdz)
       dtdx = c_loc(c%fluid%c_Xh%dtdx)
       dtdy = c_loc(c%fluid%c_Xh%dtdy)
       dtdz = c_loc(c%fluid%c_Xh%dtdz)
       jac = c_loc(c%fluid%c_Xh%jac)
       b = c_loc(c%fluid%c_Xh%B)
       area = c_loc(c%fluid%c_Xh%area)
       nx = c_loc(c%fluid%c_Xh%nx)
       ny = c_loc(c%fluid%c_Xh%ny)
       nz = c_loc(c%fluid%c_Xh%nz)
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_case_fluid_coef
 
  subroutine neko_api_user_setup(case_iptr, initial_cb, preprocess_cb, &
       compute_cb, dirichlet_cb, material_cb, source_cb) &
       bind(c, name='neko_user_setup')
    integer(c_intptr_t), intent(inout) :: case_iptr
    type(c_funptr), value :: initial_cb, preprocess_cb, compute_cb
    type(c_funptr), value :: dirichlet_cb, material_cb, source_cb
    type(case_t), pointer :: C
    type(c_ptr) :: cptr
 
    cptr = transfer(case_iptr, c_null_ptr)
    if (c_associated(cptr)) then
       call c_f_pointer(cptr, c)
       call neko_api_user_cb_register(c%user, initial_cb, preprocess_cb, &
            compute_cb, dirichlet_cb, material_cb, source_cb)
    else
       call neko_error('Invalid Neko case')
    end if
 
  end subroutine neko_api_user_setup
 
  function neko_api_user_cb_field_by_name(field_name) result(field_ptr) &
       bind(c, name='neko_cb_field_by_name')
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: field
    type(c_ptr) :: field_ptr
    integer :: len
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    field => neko_api_user_cb_get_field(trim(name(1:len)))
 
    field_ptr = c_loc(field%x)
 
  end function neko_api_user_cb_field_by_name
 
  function neko_api_user_cb_field_by_index(field_idx) &
       result(field_ptr) bind(c, name='neko_cb_field_by_index')
    integer, intent(in) :: field_idx
    type(field_t), pointer :: field
    type(c_ptr) :: field_ptr
 
    field => neko_api_user_cb_get_field(field_idx)
 
    field_ptr = c_loc(field%x)
 
  end function neko_api_user_cb_field_by_index
 
  function neko_api_user_cb_field_name_at_index(field_idx, field_name) &
       result(same_name) bind(c, name='neko_cb_field_name_at_index')
    integer, intent(in) :: field_idx
    character(kind=c_char), dimension(*), intent(in) :: field_name
    character(len=8192) :: name
    type(field_t), pointer :: f1, f2
    type(c_ptr) :: field_ptr
    integer :: len
    logical(c_bool) :: same_name
 
    len = 0
    do
       if (field_name(len+1) .eq. c_null_char) exit
       len = len + 1
       name(len:len) = field_name(len)
    end do
 
    f1 => neko_api_user_cb_get_field(field_idx)
    f2 => neko_api_user_cb_get_field(trim(name(1:len)))
 
    same_name = trim(f1%name) .eq. trim(f2%name)
 
  end function neko_api_user_cb_field_name_at_index
 
 
end module neko_api