sd_interface.hpp

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/*
 * Copyright (C) 2010-2025 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
 
/** @file
 *  See @cite durlofsky87a for the Stokesian dynamics method used here.
 *  See @cite banchio03a and @cite brady88a for the thermalization method.
 */
 
#include <config/config.hpp>
 
#ifdef ESPRESSO_STOKESIAN_DYNAMICS
 
#include "PropagationMode.hpp"
#include "PropagationPredicate.hpp"
#include "thermostat.hpp"
 
#include <unordered_map>
 
struct PropagationPredicateStokesian {
  int modes;
  PropagationPredicateStokesian(int default_propagation) {
    modes = PropagationMode::TRANS_STOKESIAN;
    if (default_propagation & PropagationMode::TRANS_STOKESIAN) {
      modes |= PropagationMode::SYSTEM_DEFAULT;
    }
  }
 
  bool operator()(int prop) const { return (prop & modes); }
};
 
using ParticleRangeStokesian =
    ParticleRangeFiltered<PropagationPredicateStokesian>;
 
struct StokesianDynamics {
  double viscosity = 0.;
  std::unordered_map<int, double> radii = {};
  int flags = 0;
  StokesianDynamics() = default;
  StokesianDynamics(double viscosity, std::unordered_map<int, double> radii,
                    int flags);
 
  /**
   * Take the forces and torques on all particles and compute velocities.
   * Act globally on particles on all nodes; i.e. particle data is
   * gathered from all nodes and their velocities and angular velocities
   * are set according to the Stokesian Dynamics method.
   */
  void propagate_vel_pos(ParticleRangeStokesian const &particles,
                         StokesianThermostat const &stokesian, double time_step,
                         double kT) const;
 
private:
  /**
   * Buffer that holds the (translational and angular) velocities of the local
   * particles on each node, used for returning results.
   */
  mutable std::vector<double> v_sd = {};
  mutable std::vector<double> x_host = {};
  mutable std::vector<double> f_host = {};
  mutable std::vector<double> a_host = {};
};
 
enum class sd_flags : int {
  NONE = 0,
  SELF_MOBILITY = 1 << 0,
  PAIR_MOBILITY = 1 << 1,
  LUBRICATION = 1 << 2,
  FTS = 1 << 3
};
 
#endif // ESPRESSO_STOKESIAN_DYNAMICS