yac_core.F90

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! Copyright (c) 2024 The YAC Authors
!
! SPDX-License-Identifier: BSD-3-Clause
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
module yac_core
  use, intrinsic :: iso_c_binding, only : c_int, c_long, &
                                        & c_long_long, c_short, c_char, &
                                        & c_size_t, c_double, c_null_char, &
                                        & c_ptr, c_null_ptr
 
  implicit none
 
  public
 
  !------------------------------------------------
  ! Constants for Fortran-C interoperability
  !------------------------------------------------
 
  integer, parameter :: yac_mpi_fint_kind = yac_mpi_fint_fc_kind
  real(kind=c_double), parameter :: &
    yac_frac_mask_no_value = 133713371337.0_c_double
 
  !---------------
  ! Location enums
  !---------------
 
  enum, bind(c)
   enumerator :: yac_loc_cell   = 0
   enumerator :: yac_loc_corner = 1
   enumerator :: yac_loc_edge   = 2
  end enum
 
  !----------------------------------
  ! Handling of existing weight files
  !----------------------------------
 
  enum, bind(c)
   enumerator :: yac_weight_file_error     = 0
   enumerator :: yac_weight_file_keep      = 1
   enumerator :: yac_weight_file_overwrite = 2
  end enum
 
  !---------------------------
  ! Interpolation method enums
  !---------------------------
 
  enum, bind(c)
     enumerator :: yac_interp_avg_arithmetic = 0
     enumerator :: yac_interp_avg_dist       = 1
     enumerator :: yac_interp_avg_bary       = 2
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_ncc_avg  = 0
     enumerator :: yac_interp_ncc_dist = 1
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_nnn_avg    = 0
     enumerator :: yac_interp_nnn_dist   = 1
     enumerator :: yac_interp_nnn_gauss  = 2
     enumerator :: yac_interp_nnn_rbf    = 3
     enumerator :: yac_interp_nnn_zero   = 4
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_dnn_weight_avg   = 0
     enumerator :: yac_interp_dnn_weight_dist  = 1
     enumerator :: yac_interp_dnn_weight_gauss = 2
     enumerator :: yac_interp_dnn_weight_rbf   = 3
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_dnn_search_distance_fixed     = 0
     enumerator :: yac_interp_dnn_search_distance_cell_area = 1
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_conserv_destarea = 0
     enumerator :: yac_interp_conserv_fracarea = 1
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_spmap_avg  = 0
     enumerator :: yac_interp_spmap_dist = 1
  end enum
 
  enum, bind(c)
     enumerator :: yac_interp_spmap_none       = 0
     enumerator :: yac_interp_spmap_srcarea    = 1
     enumerator :: yac_interp_spmap_invtgtarea = 2
     enumerator :: yac_interp_spmap_fracarea   = 3
  end enum
 
  enum, bind(c)
    enumerator :: yac_interp_file_missing_error = 0
    enumerator :: yac_interp_file_missing_cont  = 1
  end enum
 
  enum, bind(c)
    enumerator :: yac_interp_file_success_stop = 0
    enumerator :: yac_interp_file_success_cont = 1
  end enum
 
  !------------------------------------
  ! Interpolation method default values
  !------------------------------------
 
  ! average
  integer(kind=c_int), parameter :: yac_interp_avg_weight_type_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_avg_partial_coverage_default_f = 0_c_int
 
  ! nearest corner cells
  integer(kind=c_int), parameter :: yac_interp_ncc_weight_type_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_ncc_partial_coverage_default_f = 0_c_int
 
  ! conserv
  integer(kind=c_int), parameter :: yac_interp_conserv_order_default_f = 1_c_int
  integer(kind=c_int), parameter :: yac_interp_conserv_enforced_conserv_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_conserv_partial_coverage_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_conserv_normalisation_default_f = 0_c_int
 
  ! creep
  integer(kind=c_int), parameter :: yac_interp_creep_distance_default_f = -1_c_int
 
  ! fixed
  real(kind=c_double), parameter :: yac_interp_fixed_value_default_f = huge(1.0_c_double)
 
  ! n-nearest-neighbour
  integer(kind=c_int), parameter    :: yac_interp_nnn_weighted_default_f = 0_c_int
  integer(kind=c_size_t), parameter :: yac_interp_nnn_n_default_f = 1_c_size_t
  real(kind=c_double), parameter    :: yac_interp_nnn_max_search_distance_default_f = 0.0_c_double
  real(kind=c_double), parameter    :: yac_interp_nnn_gauss_scale_default_f = 0.1_c_double
 
  ! distance-nearest-neighbour
  integer(kind=c_int), parameter :: yac_interp_dnn_weight_type_default_f = 1_c_int
  integer(kind=c_int), parameter :: yac_interp_dnn_search_distance_type_default_f = 1_c_int
  real(kind=c_double), parameter :: yac_interp_dnn_search_distance_default_f = 1.0_c_double
  real(kind=c_double), parameter :: yac_interp_dnn_scale_default_f = 0.0_c_double
  real(kind=c_double), parameter :: yac_interp_dnn_gauss_scale_default_f = 0.1_c_double
  real(kind=c_double), parameter :: yac_interp_dnn_rbf_scale_default_f = 1.487973e+01_c_double
 
  ! rbf
  integer(kind=c_size_t), parameter :: yac_interp_rbf_n_default_f = 9_c_size_t
  real(kind=c_double), parameter    :: yac_interp_rbf_max_search_distance_default_f = 0.0_c_double
  real(kind=c_double), parameter    :: yac_interp_rbf_scale_default_f = 1.487973e+01_c_double
  integer(kind=c_int), parameter    :: yac_interp_rbf_kernel_default_f = 0_c_int
 
  ! source-point mapping
  real(kind=c_double), parameter :: yac_interp_spmap_spread_distance_default_f = 0.0_c_double
  real(kind=c_double), parameter :: yac_interp_spmap_max_search_distance_default_f = 0.0_c_double
  integer(kind=c_int), parameter :: yac_interp_spmap_weighted_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_spmap_scale_type_default_f = 0_c_int
  real(kind=c_double), parameter :: yac_interp_spmap_sphere_radius_default_f = 1.0_c_double
  character(kind=c_char,len=*), parameter :: yac_interp_spmap_filename_default_f = "" // c_null_char
  character(kind=c_char,len=*), parameter :: yac_interp_spmap_varname_default_f = "" // c_null_char
  integer(kind=c_int), parameter :: yac_interp_spmap_min_global_id_default_f = 0_c_int
  type(c_ptr), parameter :: yac_interp_spmap_config_default_f = c_null_ptr
  type(c_ptr), parameter :: yac_interp_spmap_overwrite_default_f = c_null_ptr
 
  ! check
  character(kind=c_char,len=*), parameter :: yac_interp_check_constructor_key_default_f = "" // c_null_char
  character(kind=c_char,len=*), parameter :: yac_interp_check_do_search_key_default_f = "" // c_null_char
 
  ! user file
  integer(kind=c_int), parameter :: yac_interp_file_on_missing_file_default_f = 0_c_int
  integer(kind=c_int), parameter :: yac_interp_file_on_success_default_f = 1_c_int
 
  !---------------------------
  ! Interpolation weight enums
  !---------------------------
 
  enum, bind(c)
    enumerator :: yac_mapping_on_src = 0
    enumerator :: yac_mapping_on_tgt = 1
  end enum
 
  !------------------------------------------------
  ! Initialisation and finalization of MPI and yaxt
  !------------------------------------------------
 
  interface
 
    ! initialise MPI (if not already initialised)
    subroutine yac_mpi_init_c () &
      bind( c, name='yac_mpi_init' )
    end subroutine yac_mpi_init_c
 
    ! initialise yaxt
    subroutine yac_yaxt_init_c (comm) &
      bind( c, name='yac_yaxt_init_f2c' )
 
      import :: yac_mpi_fint_kind
 
      integer(kind=YAC_MPI_FINT_KIND), value :: comm
    end subroutine yac_yaxt_init_c
 
    ! check whether MPI is initialised
    function yac_mpi_is_initialised_c () &
      bind( c, name='yac_mpi_is_initialised' )
 
      use, intrinsic :: iso_c_binding
 
      integer(kind=c_int) :: yac_mpi_is_initialised_c
    end function yac_mpi_is_initialised_c
 
    ! free internal buffers and finalize yaxt
    subroutine yac_mpi_cleanup_c () &
      bind ( c, name="yac_mpi_cleanup" )
    end subroutine yac_mpi_cleanup_c
 
    ! finalize MPI (if initialised by YAC)
    subroutine yac_mpi_finalize_c () &
      bind( c, name='yac_mpi_finalize' )
    end subroutine yac_mpi_finalize_c
 
  end interface
 
  !-----------------------
  ! Handling of basic grid
  !-----------------------
 
  interface
 
    function yac_basic_grid_empty_new_c(name) &
      bind( c, name='yac_basic_grid_empty_new' )
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: name(*)
 
      type(c_ptr) :: yac_basic_grid_empty_new_c
    end function yac_basic_grid_empty_new_c
 
    subroutine yac_basic_grid_delete_c(grid) &
      bind( c, name='yac_basic_grid_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: grid
    end subroutine yac_basic_grid_delete_c
 
    function yac_basic_grid_get_data_size_c(grid, location) &
      bind( c, name='yac_basic_grid_get_data_size_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: grid
      integer(kind=c_int), value :: location
 
      integer(kind=c_size_t) :: yac_basic_grid_get_data_size_c
    end function yac_basic_grid_get_data_size_c
 
    function yac_basic_grid_add_coordinates_c( &
      grid, location, coordinates, count) &
      bind( c, name='yac_basic_grid_add_coordinates_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: grid
      integer(kind=c_int), value    :: location
      real(kind=c_double)           :: coordinates(*)
      integer(kind=c_size_t), value :: count
 
      integer(kind=c_size_t) :: yac_basic_grid_add_coordinates_c
    end function yac_basic_grid_add_coordinates_c
 
    function yac_basic_grid_add_coordinates_nocpy_c( &
      grid, location, coordinates) &
      bind( c, name='yac_basic_grid_add_coordinates_nocpy_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: grid
      integer(kind=c_int), value    :: location
      real(kind=c_double)           :: coordinates(*)
 
      integer(kind=c_size_t) :: yac_basic_grid_add_coordinates_nocpy_c
    end function yac_basic_grid_add_coordinates_nocpy_c
 
    function yac_basic_grid_add_mask_c( &
      grid, location, mask, count, name) &
      bind( c, name='yac_basic_grid_add_mask_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: grid
      integer(kind=c_int), value    :: location
      integer(kind=c_int)           :: mask(*)
      integer(kind=c_size_t), value :: count
      character(kind=c_char)        :: name(*)
 
      integer(kind=c_size_t) :: yac_basic_grid_add_mask_c
    end function yac_basic_grid_add_mask_c
 
    function yac_basic_grid_add_mask_nocpy_c( &
      grid, location, mask, name) &
      bind( c, name='yac_basic_grid_add_mask_nocpy_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: grid
      integer(kind=c_int), value    :: location
      integer(kind=c_int)           :: mask(*)
      character(kind=c_char)        :: name(*)
 
      integer(kind=c_size_t) :: yac_basic_grid_add_mask_nocpy_c
    end function yac_basic_grid_add_mask_nocpy_c
 
    function yac_basic_grid_reg_2d_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices) &
      bind( c, name='yac_basic_grid_reg_2d_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: name(*)
      integer(kind=c_size_t) :: nbr_vertices(2)
      integer(kind=c_int)    :: cyclic(2)
      real(kind=c_double)    :: lon_vertices(*)
      real(kind=c_double)    :: lat_vertices(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_reg_2d_new_c
    end function yac_basic_grid_reg_2d_new_c
 
    function yac_basic_grid_reg_2d_deg_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices) &
      bind( c, name='yac_basic_grid_reg_2d_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: name(*)
      integer(kind=c_size_t) :: nbr_vertices(2)
      integer(kind=c_int)    :: cyclic(2)
      real(kind=c_double)    :: lon_vertices(*)
      real(kind=c_double)    :: lat_vertices(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_reg_2d_deg_new_c
    end function yac_basic_grid_reg_2d_deg_new_c
 
    function yac_basic_grid_curve_2d_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices) &
      bind( c, name='yac_basic_grid_curve_2d_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: name(*)
      integer(kind=c_size_t) :: nbr_vertices(2)
      integer(kind=c_int)    :: cyclic(2)
      real(kind=c_double)    :: lon_vertices(*)
      real(kind=c_double)    :: lat_vertices(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_curve_2d_new_c
    end function yac_basic_grid_curve_2d_new_c
 
    function yac_basic_grid_curve_2d_deg_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices) &
      bind( c, name='yac_basic_grid_curve_2d_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: name(*)
      integer(kind=c_size_t) :: nbr_vertices(2)
      integer(kind=c_int)    :: cyclic(2)
      real(kind=c_double)    :: lon_vertices(*)
      real(kind=c_double)    :: lat_vertices(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_curve_2d_deg_new_c
    end function yac_basic_grid_curve_2d_deg_new_c
 
    function yac_basic_grid_unstruct_new_c( &
      name, nbr_vertices, nbr_cells, num_vertices_per_cell, &
      x_vertices, y_vertices, cell_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_int)           :: num_vertices_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_new_c
    end function yac_basic_grid_unstruct_new_c
 
    function yac_basic_grid_unstruct_deg_new_c( &
      name, nbr_vertices, nbr_cells, num_vertices_per_cell, &
      x_vertices, y_vertices, cell_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_int)           :: num_vertices_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_deg_new_c
    end function yac_basic_grid_unstruct_deg_new_c
 
    function yac_basic_grid_unstruct_ll_new_c( &
      name, nbr_vertices, nbr_cells, num_vertices_per_cell, &
      x_vertices, y_vertices, cell_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_ll_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_int)           :: num_vertices_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_ll_new_c
    end function yac_basic_grid_unstruct_ll_new_c
 
    function yac_basic_grid_unstruct_ll_deg_new_c( &
      name, nbr_vertices, nbr_cells, num_vertices_per_cell, &
      x_vertices, y_vertices, cell_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_ll_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_int)           :: num_vertices_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_ll_deg_new_c
    end function yac_basic_grid_unstruct_ll_deg_new_c
 
    function yac_basic_grid_unstruct_edge_new_c( &
      name, nbr_vertices, nbr_cells, nbr_edges, num_edges_per_cell, &
      x_vertices, y_vertices, cell_to_edge, edge_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_edge_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_size_t), value :: nbr_edges
      integer(kind=c_int)           :: num_edges_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_edge(*)
      integer(kind=c_int)           :: edge_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_edge_new_c
    end function yac_basic_grid_unstruct_edge_new_c
 
    function yac_basic_grid_unstruct_edge_deg_new_c( &
      name, nbr_vertices, nbr_cells, nbr_edges, num_edges_per_cell, &
      x_vertices, y_vertices, cell_to_edge, edge_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_edge_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_size_t), value :: nbr_edges
      integer(kind=c_int)           :: num_edges_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_edge(*)
      integer(kind=c_int)           :: edge_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_edge_deg_new_c
    end function yac_basic_grid_unstruct_edge_deg_new_c
 
    function yac_basic_grid_unstruct_edge_ll_new_c( &
      name, nbr_vertices, nbr_cells, nbr_edges, num_edges_per_cell, &
      x_vertices, y_vertices, cell_to_edge, edge_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_edge_ll_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_size_t), value :: nbr_edges
      integer(kind=c_int)           :: num_edges_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_edge(*)
      integer(kind=c_int)           :: edge_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_edge_ll_new_c
    end function yac_basic_grid_unstruct_edge_ll_new_c
 
    function yac_basic_grid_unstruct_edge_ll_deg_new_c( &
      name, nbr_vertices, nbr_cells, nbr_edges, num_edges_per_cell, &
      x_vertices, y_vertices, cell_to_edge, edge_to_vertex) &
      bind( c, name='yac_basic_grid_unstruct_edge_ll_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_vertices
      integer(kind=c_size_t), value :: nbr_cells
      integer(kind=c_size_t), value :: nbr_edges
      integer(kind=c_int)           :: num_edges_per_cell(*)
      real(kind=c_double)           :: x_vertices(*)
      real(kind=c_double)           :: y_vertices(*)
      integer(kind=c_int)           :: cell_to_edge(*)
      integer(kind=c_int)           :: edge_to_vertex(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_unstruct_edge_ll_deg_new_c
    end function yac_basic_grid_unstruct_edge_ll_deg_new_c
 
    function yac_basic_grid_cloud_new_c( &
      name, nbr_points, x_points, y_points) &
      bind( c, name='yac_basic_grid_cloud_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_points
      real(kind=c_double)           :: x_points(*)
      real(kind=c_double)           :: y_points(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_cloud_new_c
    end function yac_basic_grid_cloud_new_c
 
    function yac_basic_grid_cloud_deg_new_c( &
      name, nbr_points, x_points, y_points) &
      bind( c, name='yac_basic_grid_cloud_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)        :: name(*)
      integer(kind=c_size_t), value :: nbr_points
      real(kind=c_double)           :: x_points(*)
      real(kind=c_double)           :: y_points(*)
 
      ! struct yac_basic_grid *
      type(c_ptr) :: yac_basic_grid_cloud_deg_new_c
    end function yac_basic_grid_cloud_deg_new_c
 
    function yac_basic_grid_reg_2d_rot_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices, &
      north_pol_lon, north_pol_lat) &
      bind( c, name='yac_basic_grid_reg_2d_rot_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)     :: name(*)
      integer(kind=c_size_t)     :: nbr_vertices(2)
      integer(kind=c_int)        :: cyclic(2)
      real(kind=c_double)        :: lon_vertices(*)
      real(kind=c_double)        :: lat_vertices(*)
      real(kind=c_double), value :: north_pol_lon
      real(kind=c_double), value :: north_pol_lat
 
      type(c_ptr) :: yac_basic_grid_reg_2d_rot_new_c
    end function yac_basic_grid_reg_2d_rot_new_c
 
    function yac_basic_grid_reg_2d_rot_deg_new_c( &
      name, nbr_vertices, cyclic, lon_vertices, lat_vertices, &
      north_pol_lon, north_pol_lat) &
      bind( c, name='yac_basic_grid_reg_2d_rot_deg_new')
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)     :: name(*)
      integer(kind=c_size_t)     :: nbr_vertices(2)
      integer(kind=c_int)        :: cyclic(2)
      real(kind=c_double)        :: lon_vertices(*)
      real(kind=c_double)        :: lat_vertices(*)
      real(kind=c_double), value :: north_pol_lon
      real(kind=c_double), value :: north_pol_lat
 
      type(c_ptr) :: yac_basic_grid_reg_2d_rot_deg_new_c
    end function yac_basic_grid_reg_2d_rot_deg_new_c
 
    function yac_basic_grid_check_coordinates_c(grid, is_fatal) &
      bind( c, name='yac_basic_grid_check_coordinates' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: grid
      integer(kind=c_int), value :: is_fatal
 
      integer(kind=c_int) :: yac_basic_grid_check_coordinates_c
    end function yac_basic_grid_check_coordinates_c
 
    subroutine yac_basic_grid_compute_cell_areas_c(grid, cell_areas) &
      bind( c, name='yac_basic_grid_compute_cell_areas')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value  :: grid
      real(kind=c_double) :: cell_areas(*)
    end subroutine yac_basic_grid_compute_cell_areas_c
 
  end interface
 
  !------------------------------
  ! Handling of distributed grids
  !------------------------------
 
  interface
 
    function yac_dist_grid_pair_new_c(grid_a, grid_b, comm) &
      bind( c, name='yac_dist_grid_pair_new_f2c' )
 
      use, intrinsic :: iso_c_binding
      import :: yac_mpi_fint_kind
 
      type(c_ptr), value                     :: grid_a
      type(c_ptr), value                     :: grid_b
      integer(kind=YAC_MPI_FINT_KIND), value :: comm
 
      ! struct yac_dist_grid_pair *
      type(c_ptr) :: yac_dist_grid_pair_new_c
    end function yac_dist_grid_pair_new_c
 
    subroutine yac_dist_grid_pair_delete_c(grid_pair) &
      bind( c, name='yac_dist_grid_pair_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: grid_pair
    end subroutine yac_dist_grid_pair_delete_c
 
  end interface
 
  !-------------------------------
  ! Handling of interpolation grid
  !-------------------------------
 
  interface
 
    function yac_interp_grid_new_c( dist_grid_pair,            &
                                    src_grid_name,             &
                                    tgt_grid_name,             &
                                    num_src_fields,            &
                                    src_field_locations,       &
                                    src_field_coordinate_idxs, &
                                    src_field_masks_idxs,      &
                                    tgt_field_location,        &
                                    tgt_field_coordinate_idx,  &
                                    tgt_field_masks_idx)        &
      bind( c, name='yac_interp_grid_new_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: dist_grid_pair
      character(kind=c_char)        :: src_grid_name(*)
      character(kind=c_char)        :: tgt_grid_name(*)
      integer(kind=c_size_t), value :: num_src_fields
      integer(kind=c_int)           :: src_field_locations(*)
      integer(kind=c_size_t)        :: src_field_coordinate_idxs(*)
      integer(kind=c_size_t)        :: src_field_masks_idxs(*)
      integer(kind=c_int), value    :: tgt_field_location
      integer(kind=c_size_t), value :: tgt_field_coordinate_idx
      integer(kind=c_size_t), value :: tgt_field_masks_idx
 
      ! struct yac_interp_grid *
      type(c_ptr) :: yac_interp_grid_new_c
    end function yac_interp_grid_new_c
 
    subroutine yac_interp_grid_delete_c(interp_grid) &
      bind( c, name='yac_interp_grid_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_grid
    end subroutine yac_interp_grid_delete_c
 
  end interface
 
  !---------------------------------------------------------------------
  ! Handling of datastructures required for extended spmap configuration
  !---------------------------------------------------------------------
 
  interface
 
    function yac_point_selection_bnd_circle_new_c( &
      center_lon, center_lat, inc_angle)           &
      bind( c, name='yac_point_selection_bnd_circle_new' )
 
      use, intrinsic :: iso_c_binding
 
      real(kind=c_double), value :: center_lon
      real(kind=c_double), value :: center_lat
      real(kind=c_double), value :: inc_angle
 
      ! struct yac_point_selection *
      type(c_ptr) :: yac_point_selection_bnd_circle_new_c
    end function yac_point_selection_bnd_circle_new_c
 
    subroutine yac_point_selection_delete_c(point_select) &
      bind( c, name='yac_point_selection_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_point_selection *
      type(c_ptr), value :: point_select
    end subroutine yac_point_selection_delete_c
 
    function yac_interp_spmap_config_new_c( &
      spread_distance, max_search_distance, &
      weight_type, scale_config)            &
      bind( c, name='yac_interp_spmap_config_new_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      real(kind=c_double), value :: spread_distance
      real(kind=c_double), value :: max_search_distance
      integer(kind=c_int), value :: weight_type
      ! struct yac_spmap_scale_config *
      type(c_ptr), value         :: scale_config
 
      ! struct yac_interp_spmap_config *
      type(c_ptr) :: yac_interp_spmap_config_new_c
    end function yac_interp_spmap_config_new_c
 
    subroutine yac_interp_spmap_config_delete_c(spmap_config) &
      bind( c, name='yac_interp_spmap_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_spmap_config *
      type(c_ptr), value :: spmap_config
    end subroutine yac_interp_spmap_config_delete_c
 
    function yac_spmap_scale_config_new_c(                          &
      scale_type, source_cell_area_config, target_cell_area_config) &
      bind( c, name='yac_spmap_scale_config_new_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      integer(kind=c_int), value :: scale_type
      ! struct yac_spmap_cell_area_config *
      type(c_ptr), value         :: source_cell_area_config
      ! struct yac_spmap_cell_area_config *
      type(c_ptr), value         :: target_cell_area_config
 
      ! struct yac_spmap_scale_config *
      type(c_ptr) :: yac_spmap_scale_config_new_c
    end function yac_spmap_scale_config_new_c
 
    subroutine yac_spmap_scale_config_delete_c(scale_config) &
      bind( c, name='yac_spmap_scale_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_spmap_scale_config *
      type(c_ptr), value :: scale_config
    end subroutine yac_spmap_scale_config_delete_c
 
    function yac_spmap_cell_area_config_yac_new_c(sphere_radius) &
      bind( c, name='yac_spmap_cell_area_config_yac_new' )
 
      use, intrinsic :: iso_c_binding
 
      real(kind=c_double), value :: sphere_radius
 
      ! struct yac_spmap_cell_area_config *
      type(c_ptr) :: yac_spmap_cell_area_config_yac_new_c
    end function yac_spmap_cell_area_config_yac_new_c
 
    function yac_spmap_cell_area_config_file_new_c( &
      filename, varname, min_global_id) &
      bind( c, name='yac_spmap_cell_area_config_file_new_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char)     :: filename(*)
      character(kind=c_char)     :: varname(*)
      integer(kind=c_int), value :: min_global_id
 
      ! struct yac_spmap_cell_area_config *
      type(c_ptr) :: yac_spmap_cell_area_config_file_new_c
    end function yac_spmap_cell_area_config_file_new_c
 
    subroutine yac_spmap_cell_area_config_delete_c(cell_area_config) &
      bind( c, name='yac_spmap_cell_area_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_spmap_cell_area_config *
      type(c_ptr), value :: cell_area_config
    end subroutine yac_spmap_cell_area_config_delete_c
 
    function yac_spmap_overwrite_config_new_c(src_point_selection, config) &
      bind( c, name='yac_spmap_overwrite_config_new' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_point_selection *
      type(c_ptr), value :: src_point_selection
      ! struct yac_interp_spmap_config *
      type(c_ptr), value :: config
 
      ! struct yac_spmap_overwrite_config *
      type(c_ptr) :: yac_spmap_overwrite_config_new_c
    end function yac_spmap_overwrite_config_new_c
 
    subroutine yac_spmap_overwrite_config_delete_c(overwrite_config) &
      bind( c, name='yac_spmap_overwrite_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_spmap_overwrite_config *
      type(c_ptr), value :: overwrite_config
    end subroutine yac_spmap_overwrite_config_delete_c
 
    subroutine yac_spmap_overwrite_configs_delete_c(overwrite_configs) &
      bind( c, name='yac_spmap_overwrite_configs_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_spmap_overwrite_config **
      type(c_ptr), value :: overwrite_configs
    end subroutine yac_spmap_overwrite_configs_delete_c
 
  end interface
 
  !----------------------------------------------------
  ! Handling of interpolation method configurations
  !----------------------------------------------------
 
  interface
 
    function yac_interp_method_config_default_from_name_new_c(method_name) &
      bind( c, name='yac_interp_method_config_default_from_name_new' )
 
      use, intrinsic :: iso_c_binding
 
      character(kind=c_char) :: method_name(*)
 
      ! struct yac_interp_method_config *
      type(c_ptr) :: yac_interp_method_config_default_from_name_new_c
    end function yac_interp_method_config_default_from_name_new_c
 
    subroutine yac_interp_method_config_delete_c(config) &
      bind( c, name='yac_interp_method_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config *
      type(c_ptr), value :: config
    end subroutine yac_interp_method_config_delete_c
 
    subroutine yac_interp_method_config_set_param_str_c( &
      config, path, value) &
      bind( c, name='yac_interp_method_config_set_param_str' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config *
      type(c_ptr), value     :: config
      character(kind=c_char) :: path(*)
      character(kind=c_char) :: value(*)
    end subroutine yac_interp_method_config_set_param_str_c
 
    subroutine yac_interp_method_config_set_param_int_c( &
      config, path, value) &
      bind( c, name='yac_interp_method_config_set_param_int' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config *
      type(c_ptr), value         :: config
      character(kind=c_char)     :: path(*)
      integer(kind=c_int), value :: value
    end subroutine yac_interp_method_config_set_param_int_c
 
    subroutine yac_interp_method_config_set_param_dble_c( &
      config, path, value) &
      bind( c, name='yac_interp_method_config_set_param_dble' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config *
      type(c_ptr), value         :: config
      character(kind=c_char)     :: path(*)
      real(kind=c_double), value :: value
    end subroutine yac_interp_method_config_set_param_dble_c
 
    function yac_interp_method_config_get_param_int_c(config, path) &
      bind( c, name='yac_interp_method_config_get_param_int' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config const *
      type(c_ptr), value     :: config
      character(kind=c_char) :: path(*)
 
      integer(kind=c_int) :: yac_interp_method_config_get_param_int_c
    end function yac_interp_method_config_get_param_int_c
 
    function yac_interp_method_config_get_param_dble_c(config, path) &
      bind( c, name='yac_interp_method_config_get_param_dble' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config const *
      type(c_ptr), value     :: config
      character(kind=c_char) :: path(*)
 
      real(kind=c_double) :: yac_interp_method_config_get_param_dble_c
    end function yac_interp_method_config_get_param_dble_c
 
    subroutine yac_interp_method_config_get_param_str_c( &
      config, path, buf, buflen) &
      bind( c, name='yac_interp_method_config_get_param_str_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config const *
      type(c_ptr), value         :: config
      character(kind=c_char)     :: path(*)
      character(kind=c_char)     :: buf(*)
      integer(kind=c_int), value :: buflen
    end subroutine yac_interp_method_config_get_param_str_c
 
    function yac_interp_method_config_get_list_size_c(config, path) &
      bind( c, name='yac_interp_method_config_get_list_size' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config const *
      type(c_ptr), value     :: config
      character(kind=c_char) :: path(*)
      ! size_t (returned as c_size_t)
      integer(kind=c_size_t) :: yac_interp_method_config_get_list_size_c
    end function yac_interp_method_config_get_list_size_c
 
    function yac_interp_method_config_append_list_element_c(config, path) &
      bind( c, name='yac_interp_method_config_append_list_element' )
 
      use, intrinsic :: iso_c_binding
 
      ! struct yac_interp_method_config *
      type(c_ptr), value     :: config
      character(kind=c_char) :: path(*)
      ! zero-based index of the new element (size_t)
      integer(kind=c_size_t) :: yac_interp_method_config_append_list_element_c
    end function yac_interp_method_config_append_list_element_c
 
    subroutine yac_interp_stack_config_add_c( &
      interp_stack_config, method_config) &
      bind( c, name='yac_interp_stack_config_add' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
      type(c_ptr), value :: method_config
    end subroutine yac_interp_stack_config_add_c
 
  end interface
 
  !--------------------------------
  ! Handling of interpolation stack
  !--------------------------------
 
  interface
 
    function yac_interp_stack_config_new_c() &
      bind( c, name='yac_interp_stack_config_new' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr) :: yac_interp_stack_config_new_c
    end function yac_interp_stack_config_new_c
 
    function yac_interp_stack_config_copy_c(interp_stack_config) &
      bind( c, name='yac_interp_stack_config_copy' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
 
      type(c_ptr) :: yac_interp_stack_config_copy_c
    end function yac_interp_stack_config_copy_c
 
    subroutine yac_interp_stack_config_delete_c(interp_stack_config) &
      bind( c, name='yac_interp_stack_config_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
    end subroutine yac_interp_stack_config_delete_c
 
    subroutine yac_interp_stack_config_add_average_c( &
      interp_stack_config, reduction_type, partial_coverage) &
      bind( c, name='yac_interp_stack_config_add_average_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      integer(kind=c_int), value :: reduction_type
      integer(kind=c_int), value :: partial_coverage
    end subroutine yac_interp_stack_config_add_average_c
 
    subroutine yac_interp_stack_config_add_ncc_c( &
      interp_stack_config, weight_type, partial_coverage) &
      bind( c, name='yac_interp_stack_config_add_ncc_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      integer(kind=c_int), value :: weight_type
      integer(kind=c_int), value :: partial_coverage
    end subroutine yac_interp_stack_config_add_ncc_c
 
    subroutine yac_interp_stack_config_add_dnn_c( &
      interp_stack_config, type, search_distance_type, search_distance, scale) &
      bind( c, name='yac_interp_stack_config_add_dnn_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      integer(kind=c_int), value :: type
      integer(kind=c_int), value :: search_distance_type
      real(kind=c_double), value :: search_distance
      real(kind=c_double), value :: scale
    end subroutine yac_interp_stack_config_add_dnn_c
 
    subroutine yac_interp_stack_config_add_nnn_c( &
      interp_stack_config, type, n, max_search_distance, scale) &
      bind( c, name='yac_interp_stack_config_add_nnn_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: interp_stack_config
      integer(kind=c_int), value    :: type
      integer(kind=c_size_t), value :: n
      real(kind=c_double), value    :: max_search_distance
      real(kind=c_double), value    :: scale
    end subroutine yac_interp_stack_config_add_nnn_c
 
    subroutine yac_interp_stack_config_add_rbf_c( &
      interp_stack_config, n, max_search_distance, scale) &
      bind( c, name='yac_interp_stack_config_add_rbf' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: interp_stack_config
      integer(kind=c_size_t), value :: n
      real(kind=c_double), value    :: max_search_distance
      real(kind=c_double), value    :: scale
    end subroutine yac_interp_stack_config_add_rbf_c
 
    subroutine yac_interp_stack_config_add_conservative_c(            &
      interp_stack_config, order, enforced_conserv, partial_coverage, &
      normalisation) &
      bind( c, name='yac_interp_stack_config_add_conservative_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      integer(kind=c_int), value :: order
      integer(kind=c_int), value :: enforced_conserv
      integer(kind=c_int), value :: partial_coverage
      integer(kind=c_int), value :: normalisation
    end subroutine yac_interp_stack_config_add_conservative_c
 
    subroutine yac_interp_stack_config_add_spmap_ext_c( &
      interp_stack_config, default_config, overwrite_configs) &
      bind( c, name='yac_interp_stack_config_add_spmap_ext' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
      type(c_ptr), value :: default_config
      type(c_ptr), value :: overwrite_configs
    end subroutine yac_interp_stack_config_add_spmap_ext_c
 
    subroutine yac_interp_stack_config_add_spmap_c( &
      interp_stack_config, spread_distance, max_search_distance, &
      weight_type, scale_type, &
      src_sphere_radius, src_filename, src_varname, src_min_global_id, &
      tgt_sphere_radius, tgt_filename, tgt_varname, tgt_min_global_id) &
      bind( c, name='yac_interp_stack_config_add_spmap_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      real(kind=c_double), value :: spread_distance
      real(kind=c_double), value :: max_search_distance
      integer(kind=c_int), value :: weight_type
      integer(kind=c_int), value :: scale_type
      real(kind=c_double), value :: src_sphere_radius
      character(kind=c_char)     :: src_filename(*)
      character(kind=c_char)     :: src_varname(*)
      integer(kind=c_int), value :: src_min_global_id
      real(kind=c_double), value :: tgt_sphere_radius
      character(kind=c_char)     :: tgt_filename(*)
      character(kind=c_char)     :: tgt_varname(*)
      integer(kind=c_int), value :: tgt_min_global_id
    end subroutine yac_interp_stack_config_add_spmap_c
 
    subroutine yac_interp_stack_config_add_hcsbb_c(interp_stack_config) &
      bind( c, name='yac_interp_stack_config_add_hcsbb' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
    end subroutine yac_interp_stack_config_add_hcsbb_c
 
    subroutine yac_interp_stack_config_add_user_file_c( &
      interp_stack_config, filename, on_missing_file, on_success) &
      bind( c, name='yac_interp_stack_config_add_user_file_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      character(kind=c_char)     :: filename(*)
      integer(kind=c_int), value :: on_missing_file
      integer(kind=c_int), value :: on_success
    end subroutine yac_interp_stack_config_add_user_file_c
 
    subroutine yac_interp_stack_config_add_fixed_c( &
      interp_stack_config, value) &
      bind( c, name='yac_interp_stack_config_add_fixed' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      real(kind=c_double), value :: value
    end subroutine yac_interp_stack_config_add_fixed_c
 
    subroutine yac_interp_stack_config_add_creep_c( &
      interp_stack_config, n) &
      bind( c, name='yac_interp_stack_config_add_creep' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value         :: interp_stack_config
      integer(kind=c_int), value :: n
    end subroutine yac_interp_stack_config_add_creep_c
 
    subroutine yac_interp_stack_config_add_check_c( &
      interp_stack_config, constructor_key, do_search_key) &
      bind( c, name='yac_interp_stack_config_add_check' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value     :: interp_stack_config
      character(kind=c_char) :: constructor_key(*)
      character(kind=c_char) :: do_search_key(*)
    end subroutine yac_interp_stack_config_add_check_c
 
    function yac_interp_stack_config_compare_c(a, b) &
      bind( c, name='yac_interp_stack_config_compare' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: a
      type(c_ptr), value :: b
 
      integer(kind=c_int) :: yac_interp_stack_config_compare_c
    end function yac_interp_stack_config_compare_c
 
    function yac_interp_stack_config_generate_c(interp_stack_config) &
      bind( c, name='yac_interp_stack_config_generate' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_stack_config
 
      ! struct interp_method **
      type(c_ptr) :: yac_interp_stack_config_generate_c
    end function yac_interp_stack_config_generate_c
 
  end interface
 
  !----------------------------------
  ! Handling of interpolation methods
  !----------------------------------
 
  interface
 
    function yac_interp_method_do_search_c(interp_method_stack, interp_grid) &
      bind( c, name='yac_interp_method_do_search' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_method_stack
      type(c_ptr), value :: interp_grid
 
      ! struct yac_interp_weights *
      type(c_ptr) :: yac_interp_method_do_search_c
    end function yac_interp_method_do_search_c
 
    subroutine yac_interp_method_delete_c(interp_method_stack) &
      bind( c, name='yac_interp_method_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_method_stack
    end subroutine yac_interp_method_delete_c
 
    subroutine yac_interp_method_cleanup_c() &
      bind( c, name='yac_interp_method_cleanup' )
 
    end subroutine yac_interp_method_cleanup_c
 
  end interface
 
  !----------------------------------
  ! Handling of collection selections
  !----------------------------------
 
  interface
 
    subroutine yac_collection_selection_delete_c(collection_selection) &
      bind( c, name='yac_collection_selection_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: collection_selection
    end subroutine yac_collection_selection_delete_c
 
  end interface
 
  !---------------------------------------------------
  ! Handling of interpolation generation configuration
  !---------------------------------------------------
 
  interface
 
    function yac_interpolation_gen_config_new_c() result(config) &
      bind(c, name='yac_interpolation_gen_config_new')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr) :: config
    end function yac_interpolation_gen_config_new_c
 
    subroutine yac_interpolation_gen_config_delete_c(config) &
      bind(c, name='yac_interpolation_gen_config_delete')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
    end subroutine yac_interpolation_gen_config_delete_c
 
    function yac_interpolation_gen_config_copy_c(src) result(copy) &
      bind(c, name='yac_interpolation_gen_config_copy')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: src
      type(c_ptr) :: copy
    end function yac_interpolation_gen_config_copy_c
 
    subroutine yac_interpolation_gen_config_set_reorder_c(config, reorder) &
      bind(c, name='yac_interpolation_gen_config_set_reorder_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      integer(kind=c_int), value :: reorder
    end subroutine yac_interpolation_gen_config_set_reorder_c
 
    subroutine yac_interpolation_gen_config_set_collection_size_c( &
      config, collection_size) &
      bind(c, name='yac_interpolation_gen_config_set_collection_size')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      integer(kind=c_size_t), value :: collection_size
    end subroutine yac_interpolation_gen_config_set_collection_size_c
 
    subroutine yac_interpolation_gen_config_set_collection_selection_c(&
      config, collection_selection) &
      bind(c, name='yac_interpolation_gen_config_set_collection_selection')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      type(c_ptr), value :: collection_selection
    end subroutine yac_interpolation_gen_config_set_collection_selection_c
 
    subroutine yac_interpolation_gen_config_set_frac_mask_fallback_value_c( &
      config, frac_mask_fallback_value) &
      bind(c, name='yac_interpolation_gen_config_set_frac_mask_fallback_value')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      real(kind=c_double), value :: frac_mask_fallback_value
    end subroutine yac_interpolation_gen_config_set_frac_mask_fallback_value_c
 
    subroutine yac_interpolation_gen_config_set_scaling_factor_c( &
      config, scaling_factor) &
      bind(c, name='yac_interpolation_gen_config_set_scaling_factor')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      real(kind=c_double), value :: scaling_factor
    end subroutine yac_interpolation_gen_config_set_scaling_factor_c
 
    subroutine yac_interpolation_gen_config_set_scaling_summand_c( &
      config, scaling_summand) &
      bind(c, name='yac_interpolation_gen_config_set_scaling_summand')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      real(kind=c_double), value :: scaling_summand
    end subroutine yac_interpolation_gen_config_set_scaling_summand_c
 
    subroutine yac_interpolation_gen_config_set_yaxt_exchanger_name_c( &
      config, yaxt_exchanger_name) &
      bind(c, name='yac_interpolation_gen_config_set_yaxt_exchanger_name_f2c')
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: config
      character(kind=c_char) :: yaxt_exchanger_name(*)
    end subroutine yac_interpolation_gen_config_set_yaxt_exchanger_name_c
 
  end interface
 
  !----------------------------------
  ! Handling of interpolation weights
  !----------------------------------
 
  interface
 
    subroutine yac_interp_weights_delete_c(interp_weights) &
      bind( c, name='yac_interp_weights_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp_weights
    end subroutine yac_interp_weights_delete_c
 
    subroutine yac_interp_weights_write_to_file_c(interp_weights, &
                                                  filename,       &
                                                  src_grid_name,  &
                                                  tgt_grid_name,  &
                                                  src_grid_size,  &
                                                  tgt_grid_size,  &
                                                  on_existing)    &
      bind( c, name='yac_interp_weights_write_to_file' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: interp_weights
      character(kind=c_char)        :: filename(*)
      character(kind=c_char)        :: src_grid_name(*)
      character(kind=c_char)        :: tgt_grid_name(*)
      integer(kind=c_size_t), value :: src_grid_size
      integer(kind=c_size_t), value :: tgt_grid_size
      integer(kind=c_int), value    :: on_existing
    end subroutine yac_interp_weights_write_to_file_c
 
    function yac_interp_weights_get_interpolation_c( &
      interp_weights, reorder, collection_size, frac_mask_fallback_value, &
      scaling_factor, scaling_summand, yaxt_exchanger_name, &
      is_source, is_target) &
      bind( c, name='yac_interp_weights_get_interpolation_f2c' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: interp_weights
      integer(kind=c_int), value    :: reorder
      integer(kind=c_size_t), value :: collection_size
      real(kind=c_double), value    :: frac_mask_fallback_value
      real(kind=c_double), value    :: scaling_factor
      real(kind=c_double), value    :: scaling_summand
      character(kind=c_char)        :: yaxt_exchanger_name
      integer(kind=c_int), value    :: is_source
      integer(kind=c_int), value    :: is_target
 
      ! struct yac_interpolation *
      type(c_ptr) :: yac_interp_weights_get_interpolation_c
    end function yac_interp_weights_get_interpolation_c
 
    function yac_interp_weights_get_interpolation_ext_c( &
      interp_weights, interpolation_gen_config, is_source, is_target) &
      bind( c, name='yac_interp_weights_get_interpolation_ext' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value            :: interp_weights
      type(c_ptr), value            :: interpolation_gen_config
      integer(kind=c_int), value    :: is_source
      integer(kind=c_int), value    :: is_target
 
      ! struct yac_interpolation *
      type(c_ptr) :: yac_interp_weights_get_interpolation_ext_c
    end function yac_interp_weights_get_interpolation_ext_c
 
  end interface
 
  !---------------------------
  ! Handling of interpolations
  !---------------------------
 
  interface
 
    subroutine yac_interpolation_delete_c(interp) &
      bind( c, name='yac_interpolation_delete' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
    end subroutine yac_interpolation_delete_c
 
    subroutine yac_interpolation_execute_c( &
      interp, src_fields, tgt_field) &
      bind( c, name='yac_interpolation_execute' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: src_fields
      type(c_ptr), value :: tgt_field
    end subroutine yac_interpolation_execute_c
 
    subroutine yac_interpolation_execute_frac_c( &
      interp, src_fields, src_frac_masks, tgt_field) &
      bind( c, name='yac_interpolation_execute_frac' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: src_fields
      type(c_ptr), value :: src_frac_masks
      type(c_ptr), value :: tgt_field
    end subroutine yac_interpolation_execute_frac_c
 
    subroutine yac_interpolation_execute_put_c(interp, src_fields) &
      bind( c, name='yac_interpolation_execute_put' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: src_fields
    end subroutine yac_interpolation_execute_put_c
 
    subroutine yac_interpolation_execute_put_frac_c( &
      interp, src_fields, src_frac_masks) &
      bind( c, name='yac_interpolation_execute_put_frac' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: src_fields
      type(c_ptr), value :: src_frac_masks
    end subroutine yac_interpolation_execute_put_frac_c
 
    subroutine yac_interpolation_execute_get_c(interp, tgt_field) &
      bind( c, name='yac_interpolation_execute_get' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: tgt_field
    end subroutine yac_interpolation_execute_get_c
 
    subroutine yac_interpolation_execute_get_async_c(interp, tgt_field) &
      bind( c, name='yac_interpolation_execute_get_async' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
      type(c_ptr), value :: tgt_field
    end subroutine yac_interpolation_execute_get_async_c
 
    function yac_interpolation_execute_put_test_c(interp) &
      bind( c, name='yac_interpolation_execute_put_test' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
 
      integer(kind=c_int) :: yac_interpolation_execute_put_test_c
    end function yac_interpolation_execute_put_test_c
 
    function yac_interpolation_execute_get_test_c(interp) &
      bind( c, name='yac_interpolation_execute_get_test' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
 
      integer(kind=c_int) :: yac_interpolation_execute_get_test_c
    end function yac_interpolation_execute_get_test_c
 
    subroutine yac_interpolation_execute_wait_c(interp) &
      bind( c, name='yac_interpolation_execute_wait' )
 
      use, intrinsic :: iso_c_binding
 
      type(c_ptr), value :: interp
    end subroutine yac_interpolation_execute_wait_c
 
    function yac_interpolation_get_const_frac_mask_no_value_c() &
      bind( c, name='yac_interpolation_get_const_frac_mask_no_value_c2f' )
 
      use, intrinsic :: iso_c_binding
 
      real(kind=c_double) :: &
        yac_interpolation_get_const_frac_mask_no_value_c
    end function yac_interpolation_get_const_frac_mask_no_value_c
 
    function yac_interpolation_get_const_frac_mask_undef_c() &
      bind( c, name='yac_interpolation_get_const_frac_mask_undef_c2f' )
 
      use, intrinsic :: iso_c_binding
 
      real(kind=c_double) :: &
        yac_interpolation_get_const_frac_mask_undef_c
    end function yac_interpolation_get_const_frac_mask_undef_c
 
  end interface
 
  !--------------------
  ! Abort functionality
  !--------------------
 
  interface
 
     subroutine yac_abort_message_c ( text, file, line ) &
           bind( c, name='yac_abort_message' )
 
       use, intrinsic :: iso_c_binding, only : c_int, c_char
 
       character ( kind=c_char ), dimension(*) :: text
       character ( kind=c_char ), dimension(*) :: file
       integer ( kind=c_int ), value           :: line
 
     end subroutine yac_abort_message_c
 
  end interface
 
  !---------------------------------
  ! Setting of callback routines for
  ! check interpolation method
  !---------------------------------
 
  interface
 
     subroutine yac_interp_method_check_add_constructor_callback_c ( &
       constructor_callback, user_data, key ) &
       bind( c, name='yac_interp_method_check_add_constructor_callback' )
 
       use, intrinsic :: iso_c_binding, only : c_funptr, c_ptr, c_char
 
       type(c_funptr), value                   :: constructor_callback
       type(c_ptr), value                      :: user_data
       character ( kind=c_char ), dimension(*) :: key
 
     end subroutine yac_interp_method_check_add_constructor_callback_c
 
     subroutine yac_interp_method_check_add_do_search_callback_c ( &
       do_search_callback, user_data, key ) &
       bind( c, name='yac_interp_method_check_add_do_search_callback' )
 
       use, intrinsic :: iso_c_binding, only : c_funptr, c_ptr, c_char
 
       type(c_funptr), value                   :: do_search_callback
       type(c_ptr), value                      :: user_data
       character ( kind=c_char ), dimension(*) :: key
 
     end subroutine yac_interp_method_check_add_do_search_callback_c
 
  end interface
 
contains
 
  !----------------------------------
  ! Handling of collection selections
  !----------------------------------
 
  function yac_collection_selection_new_c(collection_size, &
                                          selection_indices)
 
    use, intrinsic :: iso_c_binding
 
    implicit none
 
    integer(kind=c_size_t), intent(in) :: collection_size
    integer(kind=c_size_t), target, optional, intent(in) :: selection_indices(*)
    type(c_ptr) :: yac_collection_selection_new_c
 
    interface
      function yac_collection_selection_new_c_(collection_size, &
                                               selection_indices) &
        bind( c, name='yac_collection_selection_new' )
 
        use, intrinsic :: iso_c_binding
 
        integer(kind=c_size_t), value :: collection_size
        type(c_ptr), value            :: selection_indices
 
        type(c_ptr) :: yac_collection_selection_new_c_
      end function yac_collection_selection_new_c_
    end interface
 
    if (present(selection_indices)) then
      yac_collection_selection_new_c = &
        yac_collection_selection_new_c_( &
          collection_size, c_loc(selection_indices))
    else
      yac_collection_selection_new_c = &
        yac_collection_selection_new_c_( &
          collection_size, c_null_ptr)
    end if
 
  end function yac_collection_selection_new_c
 
  !----------------------------------
  ! Core version query
  !----------------------------------
 
  function yac_get_core_version_c () result (version_string)
 
    use, intrinsic :: iso_c_binding, only : c_ptr, c_char, &
        c_f_pointer, c_size_t
 
    implicit none
 
    interface
      function yac_get_core_version_c_ () &
        bind( c, name='yac_get_core_version' )
        use, intrinsic :: iso_c_binding, only : c_ptr
        type(c_ptr) :: yac_get_core_version_c_
      end function yac_get_core_version_c_
    end interface
 
    interface
      function strlen_c(str_ptr) bind ( C, name = "strlen" ) result(len)
        use, intrinsic :: iso_c_binding
        type(c_ptr), value      :: str_ptr
        integer(kind=c_size_t)  :: len
      end function strlen_c
    end interface
 
    type(c_ptr)                    :: c_string_ptr
    character(len=:), allocatable  :: version_string
    character(kind=c_char), dimension(:), pointer :: chars
    integer(kind=c_size_t)         :: i, slen
 
    c_string_ptr = yac_get_core_version_c_()
    slen = strlen_c(c_string_ptr)
    call c_f_pointer(c_string_ptr, chars, [ slen ])
    allocate(character(len=slen) :: version_string)
    do i = 1, slen
      version_string(i:i) = chars(i)
    end do
 
  end function yac_get_core_version_c
 
end module yac_core