CylindricalLBFluxDensityProfileAtParticlePositions.cpp

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/*
 * Copyright (C) 2016-2022 The ESPResSo project
 *
 * This file is part of ESPResSo.
 *
 * ESPResSo 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.
 *
 * ESPResSo 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "CylindricalLBFluxDensityProfileAtParticlePositions.hpp"
 
#include "BoxGeometry.hpp"
#include "system/System.hpp"
#include "utils_histogram.hpp"
 
#include <utils/Histogram.hpp>
#include <utils/math/coordinate_transformation.hpp>
 
#include <boost/mpi/collectives/gather.hpp>
#include <boost/serialization/vector.hpp>
 
#include <utility>
#include <vector>
 
namespace Observables {
std::vector<double>
CylindricalLBFluxDensityProfileAtParticlePositions::evaluate(
    boost::mpi::communicator const &comm,
    ParticleReferenceRange const &local_particles,
    const ParticleObservables::traits<Particle> &traits) const {
  using pos_type = decltype(traits.position(std::declval<Particle>()));
  using flux_type = Utils::Vector3d;
 
  auto const buffer_size = local_particles.size();
  std::vector<pos_type> local_folded_positions{};
  std::vector<flux_type> local_flux_densities{};
  local_folded_positions.reserve(buffer_size);
  local_flux_densities.reserve(buffer_size);
 
  auto &system = System::get_system();
  auto const &box_geo = *system.box_geo;
  auto &lb = system.lb;
  lb.ghost_communication_pdf();
  lb.ghost_communication_vel();
 
  std::vector<Utils::Vector3d> unfolded_pos{};
  std::vector<Utils::Vector3d> folded_pos{};
  unfolded_pos.reserve(buffer_size);
  folded_pos.reserve(buffer_size);
  for (auto const &p : local_particles) {
    unfolded_pos.emplace_back(traits.position(p));
    folded_pos.emplace_back(box_geo.folded_position(traits.position(p)));
  }
  auto const interpolated_vel =
      lb.get_coupling_interpolated_velocities(folded_pos);
  auto const interpolated_rho = lb.get_interpolated_densities(unfolded_pos);
  auto vel_it = interpolated_vel.begin();
  auto rho_it = interpolated_rho.begin();
  for (auto const &pos : folded_pos) {
    auto const pos_shifted = pos - transform_params->center();
    auto const pos_cyl = Utils::transform_coordinate_cartesian_to_cylinder(
        pos_shifted, transform_params->axis(), transform_params->orientation());
    auto const flux_cyl = Utils::transform_vector_cartesian_to_cylinder(
        (*vel_it) * (*rho_it), transform_params->axis(), pos_shifted);
    local_folded_positions.emplace_back(pos_cyl);
    local_flux_densities.emplace_back(flux_cyl);
    ++vel_it;
    ++rho_it;
  }
 
  auto const [global_folded_positions, global_flux_densities] =
      detail::gather(comm, local_folded_positions, local_flux_densities);
 
  if (comm.rank() != 0) {
    return {};
  }
 
  Utils::CylindricalHistogram<double, 3> histogram(n_bins(), limits());
  detail::accumulate(histogram, global_folded_positions, global_flux_densities);
  return detail::normalize_by_bin_size(histogram);
}
} // namespace Observables