core/reaction_methods/utils.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 "reaction_methods/SingleReaction.hpp"
 
#include <unordered_map>
 
namespace ReactionMethods {
 
/**
 * Calculates the logarithm of whole product of factorial expressions which
 * occur in the reaction ensemble acceptance probability.
 *
 * See @cite smith94c.
 */
double calculate_factorial_expression(
    SingleReaction const &reaction,
    std::unordered_map<int, int> const &particle_numbers);
 
/**
 * Calculates the logarithm of factorial expression which occurs in the constant
 * pH method with symmetric proposal probability.
 *
 * See @cite landsgesell17b for details.
 * zeta = 1 (see @cite smith94c) since we only perform one reaction
 * at one call of the function.
 */
double calculate_factorial_expression_cpH(
    SingleReaction const &reaction,
    std::unordered_map<int, int> const &particle_numbers);
 
/**
 * Calculates the logarithm of factorial expression which occurs in the reaction
 * ensemble acceptance probability
 */
double ln_factorial_Ni0_divided_by_factorial_Ni0_plus_nu_i(int Ni0, int nu_i);
 
} // namespace ReactionMethods