Permutator.cc

/*
 *  MoMEMta: a modular implementation of the Matrix Element Method
 *  Copyright (C) 2016  Universite catholique de Louvain (UCL), Belgium
 *
 *  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
 *  (at your option) 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 <momemta/ParameterSet.h>
#include <momemta/Module.h>
#include <momemta/Types.h>

#include <algorithm>
#include <cmath>
#include <numeric>

#include <TMath.h>

class Permutator: public Module {
    public:

        Permutator(PoolPtr pool, const ParameterSet& parameters): Module(pool, parameters.getModuleName()) {

            m_ps_point = get<double>(parameters.get<InputTag>("ps_point"));

            auto particle_tags = parameters.get<std::vector<InputTag>>("inputs");
            for (auto& t: particle_tags)
                m_inputs.push_back(get<LorentzVector>(t));

            std::vector<uint32_t> tmp(m_inputs.size());
            std::iota(tmp.begin(), tmp.end(), 0);

            do {
                perm_indices.push_back(tmp);
            } while (std::next_permutation(tmp.begin(), tmp.end()));

            (*m_output).resize(m_inputs.size());
        };

        virtual Status work() override {
            double psPoint = *m_ps_point;

            size_t chosen_perm = std::lround(psPoint * (perm_indices.size() - 1));

            for (size_t i = 0; i < m_inputs.size(); i++)
                (*m_output)[i] = *m_inputs[perm_indices[chosen_perm][i]];

            return Status::OK;
        }

    private:
        std::vector<std::vector<uint32_t>> perm_indices;

        // Inputs
        Value<double> m_ps_point;
        std::vector<Value<LorentzVector>> m_inputs;

        // Outputs
        std::shared_ptr<std::vector<LorentzVector>> m_output = produce<std::vector<LorentzVector>>("output");
};

REGISTER_MODULE(Permutator)
    .Input("ps_point")
    .Inputs("inputs")
    .Output("output");