GeneratorAlg.cpp

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#include "IRandomGenSvc.h"
#include "MCTrack.h"
 
#include <Gaudi/Accumulators.h>
#include <Gaudi/Functional/Transformer.h>
 
#include <cmath>
#include <random>
 
namespace Gaudi::Example::TinyExperiment {
 
  class GeneratorAlg : public Functional::Transformer<MCTracks( EventContext const& )> {
  public:
    GeneratorAlg( const std::string& name, ISvcLocator* pSvcLocator )
        : Transformer( name, pSvcLocator, { "MCTracksLocation", "/Event/MCTracks" } ) {}
 
    MCTracks operator()( EventContext const& ctx ) const override {
      MCTracks tracks;
      tracks.reserve( m_nbTracksToGenerate );
      std::normal_distribution dist( 0.0f, (float)M_PI / 4 ); // µ, σ
      auto                     engine = m_rndSvc->getEngine( ctx.evt() );
      for ( unsigned int i = 0; i < m_nbTracksToGenerate; i++ ) {
        auto theta = dist( engine );
        m_thetas += theta;
        tracks.emplace_back( theta );
      }
      return tracks;
    };
 
  private:
    ServiceHandle<IRandomGenSvc>                    m_rndSvc{ this, "RandomGenSvc", "RandomGenSvc",
                                           "A service providing a thread safe random number generator" };
    Gaudi::Property<unsigned int>                   m_nbTracksToGenerate{ this, "NbTracksToGenerate", 10 };
    mutable Gaudi::Accumulators::AveragingCounter<> m_thetas{ this, "Theta values" };
  };
 
  DECLARE_COMPONENT( GeneratorAlg )
 
} // namespace Gaudi::Example::TinyExperiment