LesHouchesReader.hh

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#pragma once
 
#include <string>
#include <numeric>
 
#include "LHEF/LHEF.h"
 
#include "HEJ/EventReader.hh"
#include "HEJ/stream.hh"
 
namespace HEJ {
 
  class LesHouchesReader : public EventReader{
  public:
    explicit LesHouchesReader(std::string const & filename);
 
    bool read_event() override;
 
    std::string const & header() const override {
      return reader_.headerBlock;
    }
 
    LHEF::HEPRUP const & heprup() const override {
      return reader_.heprup;
    }
 
    LHEF::HEPEUP const & hepeup() const override {
      return reader_.hepeup;
    }
 
    std::optional<size_t> number_events() const override {
      std::size_t start = header().rfind("Number of Events");
      start = header().find_first_of("123456789", start);
      if(start == std::string::npos) {
        return {};
      }
      const std::size_t end = header().find_first_not_of("0123456789", start);
      return std::stoi(header().substr(start, end - start));
    }
 
    double scalefactor() const override {
      if (generator_==Generator::Sherpa) {
        const std::size_t num_trials = std::accumulate(
          num_trials_.begin(), num_trials_.end(), 0
        );
        return 1./static_cast<double>(num_trials);
      }
      else
        return 1.;
    }
 
  private:
    enum class Generator{
      HEJ,
      HEJFOG,
      Sherpa,
      MG,
      unknown
    };
 
    bool calculate_XSECUP() {
      return calculate_XSECUP_;
    }
    Generator get_generator(
      LHEF::HEPRUP const & heprup, std::string const & header
    );
 
    istream stream_;
    LHEF::Reader reader_;
    std::vector<size_t> num_trials_;
    Generator generator_;
    bool calculate_XSECUP_;
  };
 
} // namespace HEJ