all_compare.hpp

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/*
 * Copyright (C) 2017-2022 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_MPI_ALL_COMPARED_HPP
#define UTILS_MPI_ALL_COMPARED_HPP
 
#include <boost/mpi/collectives/all_reduce.hpp>
#include <boost/mpi/collectives/broadcast.hpp>
 
namespace Utils {
namespace Mpi {
 
/**
 * @brief Compare values on all nodes.
 *
 * @param comm The communicator to operate on.
 * @param value the value to compare.
 *
 * @tparam T the type of value.
 *
 * Returns true iff all ranks in comm called
 * the function with the same value.
 * T has to be serializeable.
 */
template <typename T>
bool all_compare(boost::mpi::communicator const &comm, T const &value) {
  T root_value{};
 
  /* Arbitrary pick the value on rank 0, and broadcast it */
  if (comm.rank() == 0) {
    root_value = value;
  }
 
  boost::mpi::broadcast(comm, root_value, 0);
 
  bool is_same = false;
  boost::mpi::all_reduce(comm, value == root_value, is_same,
                         std::logical_and<bool>());
 
  return is_same;
}
} // namespace Mpi
} // namespace Utils
 
#endif