dipoles_inline.hpp

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/*
 * Copyright (C) 2010-2026 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/>.
 */
 
#pragma once
 
#include <config/config.hpp>
 
#include "magnetostatics/dipoles.hpp"
#include "magnetostatics/dp3m.hpp"
#include "magnetostatics/solver.hpp"
 
#include "Particle.hpp"
 
#include "actor/traits.hpp"
#include "actor/visitors.hpp"
 
#include <utils/Vector.hpp>
#include <utils/math/tensor_product.hpp>
#include <utils/matrix.hpp>
 
#include <functional>
#include <optional>
#include <variant>
 
namespace Dipoles {
 
struct ShortRangeForceKernel {
 
  using kernel_type = Solver::ShortRangeForceKernel;
  using result_type = std::optional<kernel_type>;
 
#ifdef ESPRESSO_DIPOLES
  template <typename T>
  result_type operator()(std::shared_ptr<T> const &) const {
    return {};
  }
 
#ifdef ESPRESSO_DP3M
  result_type operator()(std::shared_ptr<DipolarP3M> const &ptr) const {
    auto const &actor = *ptr;
    return kernel_type{
        [&actor](double d1d2, Utils::Vector3d const &dip1,
                 Utils::Vector3d const &dip2,
#ifdef ESPRESSO_DIPOLE_FIELD_TRACKING
                 Utils::Vector3d &dip_fld_p1, Utils::Vector3d &dip_fld_p2,
#endif
                 Utils::Vector3d const &d, double dist, double dist2) {
          return actor.pair_force(d1d2, dip1, dip2,
#ifdef ESPRESSO_DIPOLE_FIELD_TRACKING
                                  dip_fld_p1, dip_fld_p2,
#endif
                                  d, dist, dist2);
        }};
  }
#endif // ESPRESSO_DP3M
 
  result_type
  operator()(std::shared_ptr<DipolarLayerCorrection> const &ptr) const {
    return std::visit(*this, ptr->base_solver);
  }
#endif // ESPRESSO_DIPOLES
};
 
struct ShortRangeEnergyKernel {
 
  using kernel_type = Solver::ShortRangeEnergyKernel;
  using result_type = std::optional<kernel_type>;
 
#ifdef ESPRESSO_DIPOLES
  template <typename T>
  result_type operator()(std::shared_ptr<T> const &) const {
    return {};
  }
 
#ifdef ESPRESSO_DP3M
  result_type operator()(std::shared_ptr<DipolarP3M> const &ptr) const {
    auto const &actor = *ptr;
    return kernel_type{
        [&actor](Utils::Vector3d const &dip1, Utils::Vector3d const &dip2,
                 Utils::Vector3d const &d, double dist, double dist2) {
          return actor.pair_energy(dip1, dip2, d, dist, dist2);
        }};
  }
#endif // ESPRESSO_DP3M
 
  result_type
  operator()(std::shared_ptr<DipolarLayerCorrection> const &ptr) const {
    return std::visit(*this, ptr->base_solver);
  }
#endif // ESPRESSO_DIPOLES
};
 
struct ShortRangePressureKernel {
 
  using kernel_type = Solver::ShortRangePressureKernel;
  using result_type = std::optional<kernel_type>;
 
#ifdef ESPRESSO_DIPOLES
  template <typename T>
  result_type operator()(std::shared_ptr<T> const &) const {
    return {};
  }
 
#ifdef ESPRESSO_DP3M
  result_type operator()(std::shared_ptr<DipolarP3M> const &ptr) const {
    return kernel_type{
        [&actor = std::as_const(*ptr)
#ifdef ESPRESSO_DIPOLE_FIELD_TRACKING
             ,
         dip_fld_p1 = Utils::Vector3d{}, dip_fld_p2 = Utils::Vector3d{}
#endif
    ](double d1d2, Utils::Vector3d const &dip1, Utils::Vector3d const &dip2,
        Utils::Vector3d const &d, double dist, double dist2) mutable {
          // dipole-dipole force is not central (unlike Coulomb), so the
          // separation-first convention used elsewhere in the pairwise
          // pressure kernel (non-bonded, DPD) must be matched explicitly
          auto const pf = actor.pair_force(d1d2, dip1, dip2,
#ifdef ESPRESSO_DIPOLE_FIELD_TRACKING
                                           dip_fld_p1, dip_fld_p2,
#endif
                                           d, dist, dist2);
          return Utils::tensor_product(d, pf.f);
        }};
  }
#endif // ESPRESSO_DP3M
 
  result_type
  operator()(std::shared_ptr<DipolarLayerCorrection> const &ptr) const {
    return std::visit(*this, ptr->base_solver);
  }
#endif // ESPRESSO_DIPOLES
};
 
inline std::optional<Solver::ShortRangeForceKernel>
Solver::pair_force_kernel() const {
#ifdef ESPRESSO_DIPOLES
  if (auto &solver = impl->solver; solver.has_value()) {
    auto const visitor = Dipoles::ShortRangeForceKernel();
    return std::visit(visitor, *solver);
  }
#endif // ESPRESSO_DIPOLES
  return std::nullopt;
}
 
inline std::optional<Solver::ShortRangeEnergyKernel>
Solver::pair_energy_kernel() const {
#ifdef ESPRESSO_DIPOLES
  if (auto &solver = impl->solver; solver.has_value()) {
    auto const visitor = Dipoles::ShortRangeEnergyKernel();
    return std::visit(visitor, *solver);
  }
#endif // ESPRESSO_DIPOLES
  return std::nullopt;
}
 
inline std::optional<Solver::ShortRangePressureKernel>
Solver::pair_pressure_kernel() const {
#ifdef ESPRESSO_DIPOLES
  if (auto &solver = impl->solver; solver.has_value()) {
    auto const visitor = Dipoles::ShortRangePressureKernel();
    return std::visit(visitor, *solver);
  }
#endif // ESPRESSO_DIPOLES
  return std::nullopt;
}
 
} // namespace Dipoles