InputInterpolationYAC.cc

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/* Copyright (C) 2024, 2025, 2026 PISM Authors
 *
 * This file is part of PISM.
 *
 * PISM is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
 *
 * PISM is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PISM; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
#include <cstddef>
#include <memory>
#include <vector>
#include <cmath>
 
#include "InputInterpolation.hh"
#include "Interpolation1D.hh"
#include "pism/util/VariableMetadata.hh"
#include "pism/util/projection.hh"
#include "pism/util/Grid.hh"
#include "pism/util/error_handling.hh"
#include "pism/util/Context.hh"
#include "pism/util/Logger.hh"
#include "pism/util/petscwrappers/Vec.hh"
#include "pism/util/array/Scalar.hh"
#include "pism/util/InputInterpolationYAC.hh"
#include "pism/util/pism_utilities.hh" // GlobalMin()
 
#if (Pism_USE_PROJ == 0)
#error "This code requires PROJ"
#endif
 
#include <proj.h>
 
#include "pism/util/Proj.hh"
#include "pism/util/LonLatGrid.hh"
 
#if (Pism_USE_YAC == 0)
#error "This code requires YAC"
#endif
 
extern "C" {
#include "yac.h"
}
 
namespace pism {
 
/*!
 * Define the PISM grid. Each PE defines its own subdomain.
 *
 * Returns the point ID that can be used to define a "field".
 */
int InputInterpolationYAC::define_grid(const std::vector<double> &x_cell,
                                       const std::vector<double> &y_cell,
                                       const std::string &grid_name,
                                       const std::string &projection) {
 
  if (projection.empty()) {
    throw pism::RuntimeError::formatted(
        PISM_ERROR_LOCATION, "grid '%s' has no projection information", grid_name.c_str());
  }
 
  // Shift x and y by half a grid spacing and add one more row and column to get
  // coordinates of corners of cells in the local sub-domain:
  std::vector<double> x_node(x_cell.size() + 1), y_node(y_cell.size() + 1);
  {
    // note: dx and dy may be negative here
    double dx = x_cell[1] - x_cell[0];
    double dy = y_cell[1] - y_cell[0];
 
    for (size_t k = 0; k < x_cell.size(); ++k) {
      x_node[k] = x_cell[k] - 0.5 * dx;
    }
    x_node.back() = x_cell.back() + 0.5 * dx;
 
    for (size_t k = 0; k < y_cell.size(); ++k) {
      y_node[k] = y_cell[k] - 0.5 * dy;
    }
    y_node.back() = y_cell.back() + 0.5 * dy;
  }
 
  // Compute lon,lat coordinates of cell centers:
  LonLatGrid cells(x_cell, y_cell, projection);
  // Compute lon,lat coordinates of cell corners:
  LonLatGrid nodes(x_node, y_node, projection);
 
  int point_id = 0;
  {
    int cyclic[] = { 0, 0 };
 
    int grid_id = 0;
 
    int n_nodes[2] = { (int)x_node.size(), (int)y_node.size() };
    yac_cdef_grid_curve2d(grid_name.c_str(), n_nodes, cyclic, nodes.lon.data(), nodes.lat.data(),
                          &grid_id);
 
    int n_cells[2] = { (int)x_cell.size(), (int)y_cell.size() };
    yac_cdef_points_curve2d(grid_id, n_cells, YAC_LOCATION_CELL, cells.lon.data(), cells.lat.data(),
                            &point_id);
  }
  return point_id;
}
 
/*!
 * Return the YAC field_id corresponding to a given PISM grid and its
 * projection info.
 *
 * @param[in] component_id YAC component ID
 * @param[in] pism_grid PISM's grid
 * @param[in] name string describing this grid and field
 */
int InputInterpolationYAC::define_field(int component_id, const std::vector<double> &x,
                                        const std::vector<double> &y,
                                        const std::string &proj_string, const std::string &name) {
 
  int point_id = define_grid(x, y, name, proj_string);
 
  const char *time_step_length = "1";
  const int point_set_size     = 1;
  const int collection_size    = 1;
 
  int field_id = 0;
  yac_cdef_field(name.c_str(), component_id, &point_id, point_set_size, collection_size,
                 time_step_length, YAC_TIME_UNIT_SECOND, &field_id);
  return field_id;
}
 
/*!
 * Extract the "local" (corresponding to the current sub-domain) grid subset.
 */
static std::vector<double> grid_subset(int xs, int xm, const std::vector<double> &coords) {
  std::vector<double> result(xm);
  for (int k = 0; k < xm; ++k) {
    result[k] = coords[xs + k];
  }
 
  return result;
}
 
static double dx_estimate(Proj &mapping, double x1, double x2, double y) {
  PJ_COORD p1 = proj_coord(0, 0, 0, 0), p2 = proj_coord(0, 0, 0, 0);
  p1.lp = {proj_torad(x1), proj_torad(y)};
  p2.lp = {proj_torad(x2), proj_torad(y)};
 
  return proj_lp_dist(mapping, p1, p2);
}
 
static double dx_min(const std::string &proj_string,
                     const std::vector<double> &x,
                     const std::vector<double> &y) {
  size_t Nx = x.size();
  size_t Ny = y.size();
 
  Proj mapping(proj_string, "EPSG:4326");
 
  double dx = dx_estimate(mapping, x[0], x[1], y[0]);
  for (size_t j = 0; j < Ny; ++j) {   // y
    for (size_t i = 1; i < Nx; ++i) { // x; note: starts from 1
      dx = std::min(dx, dx_estimate(mapping, x[i-1], x[i], y[j]));
    }
  }
  return dx;
}
 
static double dy_estimate(Proj &mapping, double x, double y1, double y2) {
  PJ_COORD p1 = proj_coord(0, 0, 0, 0), p2 = proj_coord(0, 0, 0, 0);
  p1.lp = {proj_torad(x), proj_torad(y1)};
  p2.lp = {proj_torad(x), proj_torad(y2)};
 
  return proj_lp_dist(mapping, p1, p2);
}
 
static double dy_min(const std::string &proj_string,
                     const std::vector<double> &x,
                     const std::vector<double> &y) {
  size_t Nx = x.size();
  size_t Ny = y.size();
 
  Proj mapping(proj_string, "EPSG:4326");
 
  double dy = dy_estimate(mapping, x[0], x[1], y[0]);
  for (size_t i = 0; i < Nx; ++i) { // x
    for (size_t j = 1; j < Ny; ++j) { // y; note: starts from 1
      dy = std::min(dy, dy_estimate(mapping, x[i], y[j-1], y[j]));
    }
  }
  return dy;
}
 
InputInterpolationYAC::InputInterpolationYAC(const pism::Grid &target_grid,
                                             const pism::File &input_file,
                                             const std::string &variable_name,
                                             InterpolationType type)
    : m_instance_id(0), m_source_field_id(0), m_target_field_id(0) {
  auto ctx = target_grid.ctx();
 
  std::string target_proj_params = target_grid.get_mapping_info()["proj_params"];
 
  if (target_proj_params.empty()) {
    throw RuntimeError::formatted(PISM_ERROR_LOCATION, "internal grid projection is not known");
  }
 
  try {
    auto log = ctx->log();
 
    auto source_grid_name = grid_name(input_file, variable_name, ctx->unit_system(),
                                      type == PIECEWISE_CONSTANT);
 
    log->message(
        2, "* Initializing 2D interpolation on the sphere from '%s' to the internal grid...\n",
        source_grid_name.c_str());
 
    grid::InputGridInfo source_grid_info(input_file, variable_name, ctx->unit_system(),
                                         pism::grid::CELL_CENTER);
 
    auto source_grid_mapping = mapping_info_from_file(input_file, variable_name, ctx->unit_system());
 
    std::string grid_mapping_name = source_grid_mapping["grid_mapping_name"];
 
    log->message(2, "Input grid:\n");
    if (not grid_mapping_name.empty()) {
      log->message(2, " Grid mapping: %s\n", grid_mapping_name.c_str());
    }
 
    std::string source_proj_params = source_grid_mapping["proj_params"];
    if (not source_proj_params.empty()) {
      log->message(2, " PROJ string: '%s'\n", source_proj_params.c_str());
    }
    source_grid_info.report(*log, 2, ctx->unit_system());
 
    grid::Parameters P(*ctx->config(), source_grid_info.x.size(), source_grid_info.y.size(),
                       source_grid_info.Lx, source_grid_info.Ly);
 
    P.x0 = source_grid_info.x0;
    P.y0 = source_grid_info.y0;
    P.registration = grid::CELL_CENTER;
    P.variable_name = variable_name;
    P.vertical_grid_from_options(*ctx->config());
    P.ownership_ranges_from_options(*ctx->config(), ctx->size());
 
    auto source_grid = std::make_shared<Grid>(ctx, P);
 
    source_grid->set_mapping_info(source_grid_mapping);
 
    if (source_proj_params.empty()) {
      throw RuntimeError::formatted(PISM_ERROR_LOCATION,
                                    "unsupported or missing projection info for the grid '%s'",
                                    source_grid_name.c_str());
    }
 
    m_buffer = std::make_shared<pism::array::Scalar>(source_grid, variable_name);
 
    std::string target_grid_name = "internal for " + source_grid_name;
    {
      // Initialize YAC:
      {
        yac_cinit_comm_instance(PETSC_COMM_WORLD, &m_instance_id);
        yac_cdef_calendar(YAC_YEAR_OF_365_DAYS);
        // Note: zero-padding of months and days *is* required.
        yac_cdef_datetime_instance(m_instance_id, "-1-01-01", "+1-01-01");
      }
 
      // Define components: this has to be done using *one* call
      // (cannot call yac_cdef_comp?_instance() more than once)
      const int n_comps               = 2;
      const char *comp_names[n_comps] = { "source_component", "target_component" };
      int comp_ids[n_comps]           = { 0, 0 };
      yac_cdef_comps_instance(m_instance_id, comp_names, n_comps, comp_ids);
 
      double source_grid_spacing = 0.0;
      log->message(2, "Defining the source grid (%s)...\n", source_grid_name.c_str());
      {
        auto x = grid_subset(source_grid->xs(), source_grid->xm(), source_grid_info.x);
        auto y = grid_subset(source_grid->ys(), source_grid->ym(), source_grid_info.y);
 
        m_source_field_id = define_field(
            comp_ids[0], x, y, source_proj_params, source_grid_name);
 
        double dx = 0.0;
        double dy = 0.0;
        if (source_grid_info.longitude_latitude) {
          dx = dx_min(source_proj_params, x, y);
          dy = dy_min(source_proj_params, x, y);
        } else {
          dx = std::abs(x[1] - x[0]);
          dy = std::abs(y[1] - y[0]);
        }
        source_grid_spacing = GlobalMin(ctx->com(), std::min(dx, dy));
        log->message(2, " Source grid spacing: ~%3.3f m\n", source_grid_spacing);
      }
 
      double target_grid_spacing = 0.0;
      log->message(2, "Defining the target grid (%s)...\n", target_grid_name.c_str());
      {
        auto x = grid_subset(target_grid.xs(), target_grid.xm(), target_grid.x());
        auto y = grid_subset(target_grid.ys(), target_grid.ym(), target_grid.y());
 
        m_target_field_id = define_field(
            comp_ids[1], x, y, target_proj_params, target_grid_name);
 
        target_grid_spacing = GlobalMin(ctx->com(), std::min(target_grid.dx(), target_grid.dy()));
        log->message(2, " Target grid spacing: %3.3f m\n", target_grid_spacing);
      }
 
      // Define the interpolation stack:
      {
        std::string method;
        int interp_stack_id = 0;
        yac_cget_interp_stack_config(&interp_stack_id);
 
        if (type == PIECEWISE_CONSTANT) {
          method = "nearest neighbor";
 
          // use nearest neighbor interpolation to interpolate integer fields:
          {
            // nearest neighbor
            int n_neighbors            = 1; // only one neighbor
            double scaling             = 1.0;
            double max_search_distance = 0.0; // unlimited
            yac_cadd_interp_stack_config_nnn(interp_stack_id, YAC_NNN_DIST, n_neighbors,
                                             max_search_distance, scaling);
          }
        } else {
          int partial_coverage = 0;
          if (source_grid_spacing < target_grid_spacing) {
            method = "1st order conservative";
 
            int order                = 1;
            int enforce_conservation = 1;
 
            yac_cadd_interp_stack_config_conservative(interp_stack_id, order, enforce_conservation,
                                                      partial_coverage, YAC_CONSERV_DESTAREA);
          } else {
            method = "weighted average of source cell nodes";
 
            // use average over source grid nodes containing a target point as a backup:
            yac_cadd_interp_stack_config_average(interp_stack_id, YAC_AVG_BARY, partial_coverage);
          }
 
          {
            // nearest neighbor as a fallback
            int n_neighbors            = 1;
            double scaling             = 1.0;
            double max_search_distance = 0.0; // unlimited
            yac_cadd_interp_stack_config_nnn(interp_stack_id, YAC_NNN_DIST, n_neighbors,
                                             max_search_distance, scaling);
          }
        }
 
        log->message(2, "Interpolation method: %s\n", method.c_str());
 
        // Define the coupling between fields:
        const int src_lag = 0;
        const int tgt_lag = 0;
        yac_cdef_couple_instance(m_instance_id,
                                 "source_component",       // source component name
                                 source_grid_name.c_str(), // source grid name
                                 source_grid_name.c_str(), // source field name
                                 "target_component",       // target component name
                                 target_grid_name.c_str(), // target grid name
                                 target_grid_name.c_str(), // target field name
                                 "1",                      // time step length in units below
                                 YAC_TIME_UNIT_SECOND,     // time step length units
                                 YAC_REDUCTION_TIME_NONE,  // reduction in time (for
                                                           // asynchronous coupling)
                                 interp_stack_id, src_lag, tgt_lag);
 
        // free the interpolation stack config now that we defined the coupling
        yac_cfree_interp_stack_config(interp_stack_id);
      }
 
      double start = MPI_Wtime();
      yac_cenddef_instance(m_instance_id);
      double end = MPI_Wtime();
      log->message(2, "Initialized interpolation from %s in %f seconds.\n",
                   source_grid_name.c_str(), end - start);
    }
  } catch (pism::RuntimeError &e) {
    e.add_context("initializing interpolation from %s to the internal grid",
                  input_file.name().c_str());
    throw;
  }
}
 
InputInterpolationYAC::~InputInterpolationYAC() {
  yac_cfinalize_instance(m_instance_id);
}
 
double InputInterpolationYAC::interpolate(const pism::array::Scalar &source,
                                          pism::petsc::Vec &target) const {
 
  pism::petsc::VecArray input_array(source.vec());
  pism::petsc::VecArray output_array(target);
 
  double *send_field_    = input_array.get();
  double **send_field[1] = { &send_field_ };
 
  double *recv_field[1] = { output_array.get() };
 
  int ierror          = 0;
  int send_info       = 0;
  int recv_info       = 0;
  int collection_size = 1;
  double start        = MPI_Wtime();
  yac_cexchange(m_source_field_id, m_target_field_id, collection_size, send_field, recv_field,
                &send_info, &recv_info, &ierror);
  double end = MPI_Wtime();
 
  return end - start;
}
 
 
void InputInterpolationYAC::regrid(const pism::File &file, pism::array::Scalar &output) const {
 
  double time_spent =
      InputInterpolation::regrid(output.metadata(0), file, -1, *output.grid(), output.vec());
 
  auto log = output.grid()->ctx()->log();
 
  log->message(2, "Interpolation took %f seconds.\n", time_spent);
}
 
 
double InputInterpolationYAC::regrid_impl(const VariableMetadata &metadata,
                                          const pism::File &file, int record_index,
                                          const Grid & /* target_grid (unused) */,
                                          petsc::Vec &output) const {
 
  // set metadata to help the following call find the variable, convert units, etc
  m_buffer->metadata(0) = metadata;
  m_buffer->read(file, record_index);
 
  double time_spent = interpolate(*m_buffer, output);
 
  return time_spent;
}
 
} // namespace pism