GSLIntegrator.cpp

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2013-2024  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 "CepGen/Core/Exception.h"
#include "CepGen/Core/ParametersList.h"
#include "CepGen/Integration/GSLIntegrator.h"
#include "CepGen/Integration/Integrand.h"
#include "CepGen/Modules/RandomGeneratorFactory.h"
 
namespace cepgen {
  GSLIntegrator::GSLIntegrator(const ParametersList& params) : Integrator(params) {
    CG_DEBUG("Integrator:build") << "Random numbers generator: " << gsl_rng_name(rnd_gen_->engine<gsl_rng>()) << ".";
  }
 
  void GSLIntegrator::setIntegrand(Integrand& integrand) {
    //--- specify the integrand through the GSL wrapper
    funct_ = [&](double* x, size_t ndim, void*) -> double { return integrand.eval(std::vector<double>(x, x + ndim)); };
    function_ = utils::GSLMonteFunctionWrapper<decltype(funct_)>::build(funct_, integrand.size());
    if (!function_)
      throw CG_FATAL("GSLIntegrator:setIntegrand") << "Integrand was not properly set.";
    if (function_->dim <= 0)
      throw CG_FATAL("GSLIntegrator:setIntegrand") << "Invalid phase space dimension: " << function_->dim << ".";
 
    CG_DEBUG("GSLIntegrator:setIntegrand") << "Number of integration dimensions: " << function_->dim << ".";
 
    checkLimits(integrand);  // check the integration bounds
  }
 
  void GSLIntegrator::setLimits(const std::vector<Limits>& lims) {
    Integrator::setLimits(lims);
    xlow_.clear();
    xhigh_.clear();
    for (const auto& lim : limits_) {
      xlow_.emplace_back(lim.min());
      xhigh_.emplace_back(lim.max());
    }
  }
 
  ParametersDescription GSLIntegrator::description() {
    auto desc = Integrator::description();
    desc.add<ParametersDescription>("randomGenerator", RandomGeneratorFactory::get().describeParameters("gsl"));
    return desc;
  }
}  // namespace cepgen