VegasIntegrator.cpp

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2021-2024  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/Integration/Integrand.h"
#include "CepGen/Modules/IntegratorFactory.h"
#include "CepGenAddOns/CubaWrapper/Integrator.h"
#include "cuba.h"
 
namespace cepgen {
  namespace cuba {
    class VegasIntegrator : public Integrator {
    public:
      explicit VegasIntegrator(const ParametersList& params)
          : Integrator(params),
            nstart_(steer<int>("NStart")),
            nincrease_(steer<int>("NIncrease")),
            nbatch_(steer<int>("NBatch")),
            gridno_(steer<int>("GridNo")) {
        CG_DEBUG("Integrator:build") << "Cuba-VEGAS integrator built.";
      }
 
      static ParametersDescription description() {
        auto desc = Integrator::description();
        desc.setDescription("Cuba implementation of the VEGAS algorithm");
        desc.add<int>("NStart", 1000).setDescription("number of integrand evaluations per iteration to start with");
        desc.add<int>("NIncrease", 500).setDescription("increase in the number of integrand evaluations per iteration");
        desc.add<int>("NBatch", 1000)
            .setDescription("number of points sent in one MathLink packet to be sampled by Mathematica");
        desc.add<int>("GridNo", 0).setDescription("slot in the internal grid table");
        return desc;
      }
 
      Value integrate() override {
        int neval, fail;
        double integral, error, prob;
 
        Vegas(gIntegrand->size(),
              ncomp_,
              cuba_integrand,
              nullptr,
              nvec_,
              epsrel_,
              epsabs_,
              verbose_,
              rnd_gen_->parameters().get<unsigned long long>("seed"),
              mineval_,
              maxeval_,
              nstart_,
              nincrease_,
              nbatch_,
              gridno_,
              nullptr,
              nullptr,
              &neval,
              &fail,
              &integral,
              &error,
              &prob);
        return Value{integral, error};
      }
 
    private:
      const int nstart_, nincrease_, nbatch_;
      const int gridno_;
    };
  }  // namespace cuba
}  // namespace cepgen
using VegasIntegratorCuba = cepgen::cuba::VegasIntegrator;
REGISTER_INTEGRATOR("cuba_vegas", VegasIntegratorCuba);