quantumsampling.h

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/*
 *
 *    Copyright (c) 2020,2022
 *      SMASH Team
 *
 *    GNU General Public License (GPLv3 or later)
 *
 */
 
#ifndef SRC_INCLUDE_SMASH_QUANTUMSAMPLING_H_
#define SRC_INCLUDE_SMASH_QUANTUMSAMPLING_H_
 
#include <map>
 
#include "gsl/gsl_multiroots.h"
#include "gsl/gsl_vector.h"
 
#include "smash/pdgcode.h"
#include "smash/random.h"
 
namespace smash {
 
class QuantumSampling {
 public:
  QuantumSampling(const std::map<PdgCode, int>& initial_multiplicities,
                  double volume, double temperature);
 
  struct ParametersForMaximumMomentumRootFinder {
    double mass;
    double temperature;
    double effective_chemical_potential;
    double statistics;
  };
 
  static double p_max_root_equation(double p, double mass, double temperature,
                                    double effective_chemical_potential,
                                    double statistics);
 
  static int p_max_root_equation_for_GSL(const gsl_vector* roots_array,
                                         void* parameters,
                                         gsl_vector* function);
 
  static void print_state_p_max(unsigned int iter,
                                gsl_multiroot_fsolver* solver);
 
  static int find_p_at_maximum_of_the_distribution(
      double mass, double temperature, double effective_chemical_potential,
      double statistics, double p_max_initial_guess, double solution_precision,
      double* p_max);
 
  static double maximum_of_the_distribution(double mass, double temperature,
                                            double effective_chemical_potential,
                                            double statistics,
                                            double solution_precision);
 
  double sample(const PdgCode pdg);
 
 private:
  std::map<PdgCode, double> effective_chemical_potentials_;
  std::map<PdgCode, double> distribution_function_maximums_;
  const double volume_;
  const double temperature_;
};
 
}  // namespace smash
 
#endif  // SRC_INCLUDE_SMASH_QUANTUMSAMPLING_H_