energy.cpp

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/*
 * Copyright (C) 2010-2026 The ESPResSo project
 * Copyright (C) 2002,2003,2004,2005,2006,2007,2008,2009,2010
 *   Max-Planck-Institute for Polymer Research, Theory Group
 *
 * 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 <config/config.hpp>
 
#include "BoxGeometry.hpp"
#include "Observable_stat.hpp"
#include "Particle.hpp"
#include "cell_system/CellStructure.hpp"
#include "constraints/Constraints.hpp"
#include "energy_inline.hpp"
#include "nonbonded_interactions/nonbonded_interaction_data.hpp"
#include "short_range_loop.hpp"
#include "system/GpuParticleData.hpp"
#include "system/System.hpp"
 
#include "electrostatics/coulomb.hpp"
#include "magnetostatics/dipoles.hpp"
 
#include <cmath>
#include <cstddef>
#include <memory>
#include <optional>
#include <span>
#include <vector>
 
namespace System {
 
std::shared_ptr<Observable_stat> System::calculate_energy() {
 
  auto obs_energy_ptr = std::make_shared<Observable_stat>(
      1ul, static_cast<std::size_t>(bonded_ias->get_next_key()),
      nonbonded_ias->get_max_seen_particle_type());
 
  if (long_range_interactions_sanity_checks()) {
    return obs_energy_ptr;
  }
 
  auto &obs_energy = *obs_energy_ptr;
#if defined(ESPRESSO_CUDA) and                                                 \
    (defined(ESPRESSO_ELECTROSTATICS) or defined(ESPRESSO_DIPOLES))
  gpu->clear_energy_on_device();
  gpu->update();
#endif
  on_observable_calc();
 
  auto const local_parts = cell_structure->local_particles();
 
  for (auto const &p : local_parts) {
    obs_energy.kinetic_lin[0] += translational_kinetic_energy(p);
    obs_energy.kinetic_rot[0] += rotational_kinetic_energy(p);
  }
 
  auto const coulomb_kernel = coulomb.pair_energy_kernel();
  auto const dipoles_kernel = dipoles.pair_energy_kernel();
 
  short_range_loop(
      [this, coulomb_kernel_ptr = get_ptr(coulomb_kernel), &obs_energy](
          Particle const &p1, int bond_id, std::span<Particle *> partners) {
        auto const &iaparams = *bonded_ias->at(bond_id);
        auto const result = calc_bonded_energy(iaparams, p1, partners, *box_geo,
                                               coulomb_kernel_ptr);
        if (result) {
          obs_energy.bonded_contribution(bond_id)[0] += result.value();
          return false;
        }
        return true;
      },
      [coulomb_kernel_ptr = get_ptr(coulomb_kernel),
       dipoles_kernel_ptr = get_ptr(dipoles_kernel), this,
       &obs_energy](Particle const &p1, Particle const &p2, Distance const &d) {
        auto const &ia_params =
            nonbonded_ias->get_ia_param(p1.type(), p2.type());
        add_non_bonded_pair_energy(
            p1, p2, d.vec21, sqrt(d.dist2), d.dist2, ia_params, *bonded_ias,
            coulomb, coulomb_kernel_ptr, dipoles_kernel_ptr, obs_energy);
      },
      *cell_structure, maximal_cutoff(), bonded_ias->maximal_cutoff());
 
#ifdef ESPRESSO_ELECTROSTATICS
  /* calculate k-space part of electrostatic interaction. */
  obs_energy.coulomb[1] = coulomb.calc_energy_long_range();
#endif
 
#ifdef ESPRESSO_DIPOLES
  /* calculate k-space part of magnetostatic interaction. */
  obs_energy.dipolar[1] = dipoles.calc_energy_long_range();
#endif
 
  constraints->add_energy(local_parts, get_sim_time(), obs_energy);
 
#if defined(ESPRESSO_CUDA) and                                                 \
    (defined(ESPRESSO_ELECTROSTATICS) or defined(ESPRESSO_DIPOLES))
  auto const energy_host = gpu->copy_energy_to_host();
  if (!obs_energy.coulomb.empty())
    obs_energy.coulomb[1] += static_cast<double>(energy_host.coulomb);
  if (!obs_energy.dipolar.empty())
    obs_energy.dipolar[1] += static_cast<double>(energy_host.dipolar);
#endif
 
  obs_energy.mpi_reduce();
  return obs_energy_ptr;
  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
}
 
double System::particle_short_range_energy_contribution(int pid) {
  if (cell_structure->get_resort_particles()) {
    cell_structure->update_ghosts_and_resort_particle(get_global_ghost_flags());
  }
 
  auto ret = 0.0;
  if (auto const p = cell_structure->get_local_particle(pid)) {
    auto const coulomb_kernel = coulomb.pair_energy_kernel();
    auto kernel = [&ret, this](Particle const &p, Particle const &p1,
                               Utils::Vector3d const &vec) {
#ifdef ESPRESSO_EXCLUSIONS
      if (not do_nonbonded(p, p1))
        return;
#endif
      auto const &ia_params = nonbonded_ias->get_ia_param(p.type(), p1.type());
      // Add energy for current particle pair to result
      ret += calc_non_bonded_pair_energy(p, p1, ia_params, vec, vec.norm(),
                                         *bonded_ias, coulomb, nullptr);
    };
    cell_structure->run_on_particle_short_range_neighbors(*p, kernel);
  }
  return ret;
}
 
std::optional<double> System::particle_bond_energy(int pid, int bond_id,
                                                   std::vector<int> partners) {
  if (cell_structure->get_resort_particles()) {
    cell_structure->update_ghosts_and_resort_particle(get_global_ghost_flags());
  }
  Particle const *p = cell_structure->get_local_particle(pid);
  if (not p or p->is_ghost())
    return {}; // not available on this MPI rank or ghost
  auto const &iaparams = *bonded_ias->at(bond_id);
  try {
    auto resolved_partners = cell_structure->resolve_bond_partners(partners);
    auto const coulomb_kernel = coulomb.pair_energy_kernel();
    return calc_bonded_energy(
        iaparams, *p,
        std::span(resolved_partners.data(), resolved_partners.size()), *box_geo,
        get_ptr(coulomb_kernel));
  } catch (const BondResolutionError &) {
    bond_broken_error(p->id(), partners);
    return {};
  }
}
 
} // namespace System