CuhreIntegrator.cpp

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2022-2024  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 <cuba.h>
 
#include "CepGen/Core/Exception.h"
#include "CepGen/Integration/Integrand.h"
#include "CepGen/Modules/IntegratorFactory.h"
#include "CepGenAddOns/CubaWrapper/Integrator.h"
 
namespace cepgen {
  namespace cuba {
    class CuhreIntegrator final : public Integrator {
    public:
      explicit CuhreIntegrator(const ParametersList& params) : Integrator(params), key_(steer<int>("key")) {
        CG_DEBUG("Integrator:build") << "Cuba-Cuhre integrator built.";
      }
 
      static ParametersDescription description() {
        auto desc = Integrator::description();
        desc.setDescription("Cuba implementation of the Cuhre algorithm");
        desc.add<int>("key", 0).setDescription(
            "basic integration rule:\n"
            "key = 7, 9, 11, 13 selects the cubature rule of degree key. Note that the degree-11\n"
            "rule is available only in 3 dimensions, the degree-13 rule only in 2 dimensions.\n"
            "For other values, the default rule is taken, which is the degree-13 rule in 2 dimensions,\n"
            "the degree-11 rule in 3 dimensions, and the degree-9 rule otherwise.");
        return desc;
      }
 
      Value integrate() override {
        int nregions, neval, fail;
        double integral, error, prob;
 
        Cuhre(gIntegrand->size(),
              ncomp_,
              cuba_integrand,
              nullptr,
              nvec_,
              epsrel_,
              epsabs_,
              verbose_,
              mineval_,
              maxeval_,
              key_,
              nullptr,  // statefile
              nullptr,  // spin
              &nregions,
              &neval,
              &fail,
              &integral,
              &error,
              &prob);
 
        CG_DEBUG("CuhreIntegrator:integrate")
            << "Number of regions needed: " << nregions << ".\nNumber of function evaluations: " << neval
            << "\nError flag: " << fail << ".";
 
        return Value{integral, error};
      }
 
    private:
      const int key_;
    };
  }  // namespace cuba
}  // namespace cepgen
using CuhreIntegratorCuba = cepgen::cuba::CuhreIntegrator;
REGISTER_INTEGRATOR("cuba_cuhre", CuhreIntegratorCuba);