TrackingAlg.cpp

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// Local includes
#include "Hit.h"
#include "Track.h"
 
// Framework includes
#include <Gaudi/Accumulators.h>
#include <Gaudi/Functional/Transformer.h>
 
// STD includes
#include <cmath>
#include <numbers>
#include <vector>
 
namespace Gaudi::Example::TinyExperiment {

  class TrackingAlg : public Functional::Transformer<Tracks( Hits const& )> {
  public:
    TrackingAlg( const std::string& name, ISvcLocator* pSvcLocator )
        : Transformer( name, pSvcLocator, { { "HitsLocation", "/Event/Hits" } },
                       { "TracksLocation", "/Event/Tracks" } ) {}
 
    Tracks operator()( Hits const& hits ) const override {
      // hough transform, actually only computing theta, and not dealing properly with borders of bins
      std::vector<unsigned int> bins( m_nBins, 0 );
      for ( auto const& hit : hits ) {
        auto theta = std::atan( hit.y / hit.x );
        auto index = static_cast<unsigned int>( ( theta + std::numbers::pi_v<float> / 2 ) / std::numbers::pi_v<float> *
                                                m_nBins );
        ++bins.at( index );
      }
      // extract tracks
      Tracks tracks;
      tracks.reserve( hits.size() / 10 );
      for ( unsigned int n = 0; n < m_nBins; n++ ) {
        if ( bins[n] >= m_sensibility ) {
          tracks.emplace_back( -std::numbers::pi_v<float> / 2 +
                               ( std::numbers::pi_v<float> * ( n + 0.5f ) ) / m_nBins );
          ++n_tracks;
        }
      }
      return tracks;
    }
 
  private:
    Gaudi::Property<unsigned int> m_nBins{ this, "NumberBins", 180, "Number of bins in the Hough Transform for theta" };
    Gaudi::Property<unsigned int> m_sensibility{ this, "Sensibility", 6,
                                                 "How many hits do we want for considering we have a track ?" };
    mutable Gaudi::Accumulators::Counter<> n_tracks{ this, "Number of Tracks" };
  };
 
  DECLARE_COMPONENT( TrackingAlg )
 
} // namespace Gaudi::Example::TinyExperiment