charge_neutrality.hpp

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/*
 * Copyright (C) 2010-2022 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/>.
 */
#ifndef UTILS_CHECKS_CHARGE_NEUTRALITY_HPP
#define UTILS_CHECKS_CHARGE_NEUTRALITY_HPP
 
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/sum_kahan.hpp>
 
#include <cmath>
#include <limits>
#include <stdexcept>
 
namespace Utils {
template <typename ParticleRange>
bool check_charge_neutrality(ParticleRange &prange) {
  using namespace boost::accumulators;
  using KahanSum = accumulator_set<double, features<tag::sum_kahan>>;
 
  KahanSum q_sum;
  auto q_min = std::numeric_limits<double>::infinity();
  constexpr auto relative_tolerance = 2e-12;
 
  for (auto const &p : prange) {
    auto const &q = p.q();
 
    if (q != 0.0) {
      q_sum(q);
      q_min = std::min(q_min, std::abs(q));
    }
  }
 
  auto const excess_ratio = std::abs(sum_kahan(q_sum)) / q_min;
 
  return excess_ratio <= relative_tolerance;
}
} // namespace Utils
#endif