NaiveBoostIntegrator.cpp

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2020-2024  Laurent Forthomme
 *
 *  This program 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
 *  any later version.
 *
 *  This program 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/>.
 */
 
#include <boost/math/quadrature/naive_monte_carlo.hpp>
 
#include "CepGen/Integration/Integrand.h"
#include "CepGen/Integration/Integrator.h"
#include "CepGen/Modules/IntegratorFactory.h"
 
namespace cepgen {
  class NaiveBoostIntegrator final : public Integrator {
  public:
    explicit NaiveBoostIntegrator(const ParametersList& params) : Integrator(params) {}
 
    static ParametersDescription description() {
      auto desc = Integrator::description();
      desc.setDescription("\"Naive\" Boost integrator");
      return desc;
    }
 
    void setLimits(const std::vector<Limits>& lims) override {
      Integrator::setLimits(lims);
      bounds_.clear();
      std::transform(
          limits_.begin(), limits_.end(), std::back_inserter(bounds_), [](const auto& lim) { return lim.raw(); });
    }
    Value integrate(Integrand& integrand) override {
      checkLimits(integrand);
 
      auto funct = [&](const std::vector<double>& coord) -> double { return integrand.eval(coord); };
      boost::math::quadrature::naive_monte_carlo<double, decltype(funct)> mc(funct, bounds_, 1.e-2, true, 1);
      auto task = mc.integrate();
 
      return Value{task.get(), mc.current_error_estimate()};
    }
 
  private:
    std::vector<std::pair<double, double> > bounds_;
  };
}  // namespace cepgen
 
REGISTER_INTEGRATOR("Naive", NaiveBoostIntegrator);