HepMcTupleWriterTool.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
// HepMcTupleWriterTool.cxx 
// Implementation file for class HepMcTupleWriterTool
// Author: S.Binet<binet@cern.ch>
 
// FrameWork includes
#include "GaudiKernel/ITHistSvc.h"
#include "Gaudi/Property.h"
#include "GaudiKernel/GaudiException.h"
 
// ROOT includes
#include "TTree.h"
 
// CLHEP includes
#include "GeneratorObjects/McEventCollection.h"
#include "CLHEP/Units/SystemOfUnits.h"
 
// McParticleTools includes
#include "HepMcTupleWriterTool.h"
 
HepMcTupleWriterTool::HepMcTupleWriterTool( const std::string& type, 
                        const std::string& name, 
                        const IInterface* parent ) : 
  base_class( type, name, parent ),
  m_tupleSvc ( "THistSvc",     name ),
  m_tuple    ( nullptr )
{
  //
  // Property declaration
  // 
 
  declareProperty( "Output", 
           m_outputFileName = "hepmc.root", 
           "Name of the output file which will contain the HepMC tuple"
           "\nEx: hepmc.root" );
  m_outputFileName.declareUpdateHandler( &HepMcTupleWriterTool::setupBackend, this );
 
  declareProperty( "OutputStream", 
           m_outputStreamName = "hepmc", 
           "Name of the stream which will contain the HepMC tuple"
           "\nEx: hepmc" );
 
  declareProperty( "McEvents",
           m_mcEventsName = "GEN_EVENT",
           "Input location of the McEventCollection to write out" );
}
 
HepMcTupleWriterTool::~HepMcTupleWriterTool()
{ 
  ATH_MSG_DEBUG("Calling destructor");
}
 
StatusCode HepMcTupleWriterTool::initialize()
{
  ATH_MSG_INFO("Initializing " << name() << "...");
 
  // Get pointer to StoreGateSvc and cache it :
  if ( !evtStore().retrieve().isSuccess() ) {
    ATH_MSG_ERROR("Unable to retrieve pointer to StoreGateSvc");
    return StatusCode::FAILURE;
  }
 
  // Get pointer to ITHistSvc and cache it :
  if ( !m_tupleSvc.retrieve().isSuccess() ) {
    ATH_MSG_ERROR("Unable to retrieve pointer to ITHistSvc");
    return StatusCode::FAILURE;
  }
 
  // setup backend
  setupBackend(m_outputFileName);
 
  // book tuple
  bookTuple();
 
  return StatusCode::SUCCESS;
}
 
StatusCode HepMcTupleWriterTool::finalize()
{
  ATH_MSG_INFO("Finalizing " << name() << "...");
  return StatusCode::SUCCESS;
}
 
StatusCode HepMcTupleWriterTool::execute()
{
  // retrieve the McEventCollection
  const McEventCollection * mcEvts = nullptr;
  if ( evtStore()->retrieve( mcEvts, m_mcEventsName ).isFailure() || nullptr == mcEvts ) {
    ATH_MSG_ERROR("Could not retrieve a McEventCollection at [" << m_mcEventsName << "] !!");
    return StatusCode::FAILURE;
  }
 
  if ( mcEvts->empty() ) {
    ATH_MSG_WARNING("McEventCollection at ["<<m_mcEventsName<<"] is EMPTY !!");
    return StatusCode::FAILURE;
  }
 
  const HepMC::GenEvent * evt = mcEvts->front();
  if ( !evt ) {
    ATH_MSG_ERROR("Retrieved NULL pointer to HepMC::GenEvent !!");
    return StatusCode::FAILURE;
  }
 
  return write(evt);
}
 
 
StatusCode HepMcTupleWriterTool::write( const HepMC::GenEvent* evt )
{
  m_particles.m_nParticles = std::min<std::size_t>( s_nMax, evt->particles_size() );
  std::size_t i = 0;
  for (const auto& p: *evt)
  {
    if (i == static_cast<std::size_t>(m_particles.m_nParticles)) break;
    i++;
    const HepMC::FourVector mom = p->momentum();
    m_particles.m_px [i] = mom.px();
    m_particles.m_py [i] = mom.py();
    m_particles.m_pz [i] = mom.pz();
    m_particles.m_m  [i] = mom.m();
    m_particles.m_ene[i] = mom.e();
 
    m_particles.m_pdgId[i]   = p->pdg_id();
    m_particles.m_status[i]  = p->status();
    m_particles.m_barcode[i] = HepMC::barcode(p);
  }
  // commit event
  m_tuple->Fill();
 
  return StatusCode::SUCCESS;
}
 
 
void HepMcTupleWriterTool::setupBackend( Gaudi::Details::PropertyBase& /*m_outputFileName*/ )
{
  SmartIF<IProperty> tSvc{m_tupleSvc.get()};
  if ( !tSvc ) {
    ATH_MSG_ERROR("Could not retrieve THistSvc handle !!");
    throw GaudiException( "Could not retrieve THistSvc",   name(),   StatusCode::FAILURE );
  }
 
  const std::string streamName = m_outputStreamName.value();
 
  const std::string propName = "Output";
  StringArrayProperty outputFileName;
  outputFileName.assign( tSvc->getProperty( propName ) );
  std::vector<std::string> updatedProp( outputFileName.value() );
  updatedProp.push_back
    ( streamName+" DATAFILE='"+m_outputFileName.value()+"' "
      "TYP='ROOT' "
      "OPT='RECREATE'" );
  outputFileName.set( updatedProp );
  outputFileName.setName( propName );
  if ( !tSvc->setProperty( outputFileName ).isSuccess() ) {
    ATH_MSG_ERROR("Could not configure the THistSvc's output filename ["<< m_outputFileName.value() << "] !!");
    throw GaudiException( "Could not configure THistSvc output file !!",   name(),  StatusCode::FAILURE );
  }
 
  }
 
void HepMcTupleWriterTool::bookTuple()
{
  const std::string streamName = m_outputStreamName.value();
  TTree* t = new TTree("hepmc","HepMC validation tuple");
  if ( !m_tupleSvc->regTree( "/" + streamName + "/hepmc", t ).isSuccess() ) {
    ATH_MSG_ERROR("Could not register HepMC validation tuple !!");
    delete t; t = nullptr;
    throw GaudiException( "Could not register HepMC validation tuple !!",  name(),  StatusCode::FAILURE );
  }
 
  // booking branches
  t->Branch( "nParts", &m_particles.m_nParticles, "nParts/I" );
 
  t->Branch( "px", m_particles.m_px.data(),  "px[nParts]/D" );
  t->Branch( "py", m_particles.m_py.data(),  "py[nParts]/D" );
  t->Branch( "pz", m_particles.m_pz.data(),  "pz[nParts]/D" );
  t->Branch( "m",  m_particles.m_m.data(),   "m[nParts]/D"  );
  t->Branch( "e",  m_particles.m_ene.data(), "e[nParts]/D"  );
 
  t->Branch( "pdgId", m_particles.m_pdgId.data(),   "pdgId[nParts]/I" );
  t->Branch( "sc",    m_particles.m_status.data(),  "sc[nParts]/I" );
  t->Branch( "bc",    m_particles.m_barcode.data(), "bc[nParts]/I" );
 
  m_tuple = t;
}