Pythia8Hadronizer.cc

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#include <iostream>
#include <sstream>
#include <string>
#include <memory>
#include <stdint.h>
#include <vector>

#include "HepMC/GenEvent.h"
#include "HepMC/GenParticle.h"

#include "Pythia8/Pythia.h"
#include "Pythia8Plugins/HepMC2.h"

using namespace Pythia8;

#include "GeneratorInterface/Pythia8Interface/interface/Py8InterfaceBase.h"

#include "GeneratorInterface/Pythia8Interface/plugins/ReweightUserHooks.h"

// PS matchning prototype
//
#include "GeneratorInterface/Pythia8Interface/plugins/JetMatchingHook.h"
#include "Pythia8Plugins/JetMatching.h"
#include "Pythia8Plugins/aMCatNLOHooks.h"

#include "GeneratorInterface/Pythia8Interface/interface/MultiUserHook.h"

// Emission Veto Hooks
//
#include "Pythia8Plugins/PowhegHooks.h"
#include "GeneratorInterface/Pythia8Interface/plugins/EmissionVetoHook1.h"

//decay filter hook
#include "GeneratorInterface/Pythia8Interface/interface/ResonanceDecayFilterHook.h"

// EvtGen plugin
//
#include "Pythia8Plugins/EvtGen.h"

#include "FWCore/Concurrency/interface/SharedResourceNames.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"
#include "FWCore/ParameterSet/interface/FileInPath.h"

#include "SimDataFormats/GeneratorProducts/interface/HepMCProduct.h"
#include "SimDataFormats/GeneratorProducts/interface/GenRunInfoProduct.h"

#include "GeneratorInterface/Core/interface/GeneratorFilter.h"
#include "GeneratorInterface/Core/interface/HadronizerFilter.h"

#include "GeneratorInterface/Pythia8Interface/plugins/LHAupLesHouches.h"

#include "HepPID/ParticleIDTranslations.hh"

#include "GeneratorInterface/ExternalDecays/interface/ExternalDecayDriver.h"

namespace CLHEP {
  class HepRandomEngine;
}

using namespace gen;


class Pythia8Hadronizer : public Py8InterfaceBase {

  public:

    Pythia8Hadronizer(const edm::ParameterSet &params);
   ~Pythia8Hadronizer();
 
    bool initializeForInternalPartons() override;
    bool initializeForExternalPartons();
    
    bool generatePartonsAndHadronize() override;
    bool hadronize();

    virtual bool residualDecay();

    void finalizeEvent() override;

    void statistics() override;

    const char *classname() const override { return "Pythia8Hadronizer"; }
    
    GenLumiInfoHeader *getGenLumiInfoHeader() const override;
    
  private:

    virtual void doSetRandomEngine(CLHEP::HepRandomEngine* v) override { p8SetRandomEngine(v); }
    virtual std::vector<std::string> const& doSharedResources() const override { return p8SharedResources; }

    double       comEnergy;

    std::string LHEInputFileName;
    std::auto_ptr<LHAupLesHouches>  lhaUP;

    enum { PP, PPbar, ElectronPositron };
    int  fInitialState ; // pp, ppbar, or e-e+

    double fBeam1PZ;
    double fBeam2PZ;

    //helper class to allow multiple user hooks simultaneously
    std::auto_ptr<MultiUserHook> fMultiUserHook;
    
    // Reweight user hooks
    //
    std::auto_ptr<UserHooks> fReweightUserHook;
    std::auto_ptr<UserHooks> fReweightRapUserHook;  
    std::auto_ptr<UserHooks> fReweightPtHatRapUserHook;
        
    // PS matching prototype
    //
    std::auto_ptr<JetMatchingHook> fJetMatchingHook;
    std::auto_ptr<Pythia8::JetMatchingMadgraph> fJetMatchingPy8InternalHook;
    std::auto_ptr<Pythia8::amcnlo_unitarised_interface> fMergingHook;
    
    // Emission Veto Hooks
    //
    std::auto_ptr<PowhegHooks> fEmissionVetoHook;
    std::auto_ptr<EmissionVetoHook1> fEmissionVetoHook1;
    
    //resonance decay filter hook
    std::auto_ptr<ResonanceDecayFilterHook> fResonanceDecayFilterHook;
    
    int  EV1_nFinal;
    bool EV1_vetoOn;
    int  EV1_maxVetoCount;
    int  EV1_pThardMode;
    int  EV1_pTempMode;
    int  EV1_emittedMode;
    int  EV1_pTdefMode;
    bool EV1_MPIvetoOn;   

    static const std::vector<std::string> p8SharedResources;
    
    vector<float> DJR;
    int nME;
    int nMEFiltered;

    int nISRveto;
    int nFSRveto;
    
    std::vector<std::string> fSortedWeightKeys;

};

const std::vector<std::string> Pythia8Hadronizer::p8SharedResources = { edm::SharedResourceNames::kPythia8 };

Pythia8Hadronizer::Pythia8Hadronizer(const edm::ParameterSet &params) :
  Py8InterfaceBase(params),
  comEnergy(params.getParameter<double>("comEnergy")),
  LHEInputFileName(params.getUntrackedParameter<std::string>("LHEInputFileName","")),
  fInitialState(PP),
  nME(-1), nMEFiltered(-1), nISRveto(0), nFSRveto(0)
{

  // J.Y.: the following 3 parameters are hacked "for a reason"
  //
  if ( params.exists( "PPbarInitialState" ) )
  {
    if ( fInitialState == PP )
    {
      fInitialState = PPbar;
      edm::LogImportant("GeneratorInterface|Pythia8Interface")
      << "Pythia8 will be initialized for PROTON-ANTIPROTON INITIAL STATE. "
      << "This is a user-request change from the DEFAULT PROTON-PROTON initial state.";
    }
    else
    {   
      // probably need to throw on attempt to override ?
    }
  }   
  else if ( params.exists( "ElectronPositronInitialState" ) )
  {
    if ( fInitialState == PP )
    {
      fInitialState = ElectronPositron;
      edm::LogInfo("GeneratorInterface|Pythia8Interface")
      << "Pythia8 will be initialized for ELECTRON-POSITRON INITIAL STATE. "
      << "This is a user-request change from the DEFAULT PROTON-PROTON initial state.";
    }
    else
    {   
       // probably need to throw on attempt to override ?
    }
  }
  else if ( params.exists( "ElectronProtonInitialState" ) || params.exists( "PositronProtonInitialState" ) )
  {
    // throw on unknown initial state !
    throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" UNKNOWN INITIAL STATE. \n The allowed initial states are: PP, PPbar, ElectronPositron \n";
  }

  // Reweight user hook
  //
  if( params.exists( "reweightGen" ) )
    fReweightUserHook.reset(new PtHatReweightUserHook());
  if( params.exists( "reweightGenRap" ) )
  {
    edm::LogInfo("Pythia8Interface") << "Start setup for reweightGenRap";
    edm::ParameterSet rgrParams =
      params.getParameter<edm::ParameterSet>("reweightGenRap");
    fReweightRapUserHook.reset(
      new RapReweightUserHook(rgrParams.getParameter<std::string>("yLabSigmaFunc"),
                              rgrParams.getParameter<double>("yLabPower"),
                              rgrParams.getParameter<std::string>("yCMSigmaFunc"),
                              rgrParams.getParameter<double>("yCMPower"),
                              rgrParams.getParameter<double>("pTHatMin"),
                              rgrParams.getParameter<double>("pTHatMax"))
                         );
    edm::LogInfo("Pythia8Interface") << "End setup for reweightGenRap";
  }
  if( params.exists( "reweightGenPtHatRap" ) )
  {
    edm::LogInfo("Pythia8Interface") << "Start setup for reweightGenPtHatRap";
    edm::ParameterSet rgrParams =
      params.getParameter<edm::ParameterSet>("reweightGenPtHatRap");
    fReweightPtHatRapUserHook.reset(
      new PtHatRapReweightUserHook(rgrParams.getParameter<std::string>("yLabSigmaFunc"),
                                   rgrParams.getParameter<double>("yLabPower"),
                                   rgrParams.getParameter<std::string>("yCMSigmaFunc"),
                                   rgrParams.getParameter<double>("yCMPower"),
                                   rgrParams.getParameter<double>("pTHatMin"),
                                   rgrParams.getParameter<double>("pTHatMax"))
                              );
    edm::LogInfo("Pythia8Interface") << "End setup for reweightGenPtHatRap";
  }

  if( params.exists( "useUserHook" ) )
    throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" Obsolete parameter: useUserHook \n Please use the actual one instead \n";

  // PS matching prototype
  //
  if ( params.exists("jetMatching") )
  {
    edm::ParameterSet jmParams =
      params.getUntrackedParameter<edm::ParameterSet>("jetMatching");
      std::string scheme = jmParams.getParameter<std::string>("scheme");
      if ( scheme == "Madgraph" || scheme == "MadgraphFastJet" )
      {
         fJetMatchingHook.reset(new JetMatchingHook( jmParams, &fMasterGen->info ));
      }
  }

  // Pythia8Interface emission veto
  //
  if ( params.exists("emissionVeto1") )
  {
    EV1_nFinal = -1;
    if(params.exists("EV1_nFinal")) EV1_nFinal = params.getParameter<int>("EV1_nFinal");
    EV1_vetoOn = true;
    if(params.exists("EV1_vetoOn")) EV1_vetoOn = params.getParameter<bool>("EV1_vetoOn");
    EV1_maxVetoCount = 10;
    if(params.exists("EV1_maxVetoCount")) EV1_maxVetoCount = params.getParameter<int>("EV1_maxVetoCount");
    EV1_pThardMode = 1;
    if(params.exists("EV1_pThardMode")) EV1_pThardMode = params.getParameter<int>("EV1_pThardMode");
    EV1_pTempMode = 0;
    if(params.exists("EV1_pTempMode")) EV1_pTempMode = params.getParameter<int>("EV1_pTempMode");
    if(EV1_pTempMode > 2 || EV1_pTempMode < 0)
      throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
        <<" Wrong value for EV1_pTempMode code\n";
    EV1_emittedMode = 0;
    if(params.exists("EV1_emittedMode")) EV1_emittedMode = params.getParameter<int>("EV1_emittedMode");
    EV1_pTdefMode = 1;
    if(params.exists("EV1_pTdefMode")) EV1_pTdefMode = params.getParameter<int>("EV1_pTdefMode");
    EV1_MPIvetoOn = false;
    if(params.exists("EV1_MPIvetoOn")) EV1_MPIvetoOn = params.getParameter<bool>("EV1_MPIvetoOn");
    fEmissionVetoHook1.reset(new EmissionVetoHook1(EV1_nFinal, EV1_vetoOn,
                               EV1_maxVetoCount, EV1_pThardMode, EV1_pTempMode,
                               EV1_emittedMode, EV1_pTdefMode, EV1_MPIvetoOn, 0));
  }
  
}


Pythia8Hadronizer::~Pythia8Hadronizer()
{
  
}

bool Pythia8Hadronizer::initializeForInternalPartons()
{
  
  bool status = false, status1 = false;
  
  if (lheFile_.empty()) {
    if ( fInitialState == PP ) // default
    {
      fMasterGen->settings.mode("Beams:idA", 2212);
      fMasterGen->settings.mode("Beams:idB", 2212);
    }
    else if ( fInitialState == PPbar )
    {
      fMasterGen->settings.mode("Beams:idA", 2212);
      fMasterGen->settings.mode("Beams:idB", -2212);
    }
    else if ( fInitialState == ElectronPositron )
    {
      fMasterGen->settings.mode("Beams:idA", 11);
      fMasterGen->settings.mode("Beams:idB", -11);
    }    
    else 
    {
      // throw on unknown initial state !
      throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
        <<" UNKNOWN INITIAL STATE. \n The allowed initial states are: PP, PPbar, ElectronPositron \n";
    }
    fMasterGen->settings.parm("Beams:eCM", comEnergy);
  }
  else {
    fMasterGen->settings.mode("Beams:frameType", 4);
    fMasterGen->settings.word("Beams:LHEF", lheFile_);
  }
  
  fMultiUserHook.reset(new MultiUserHook);
  
  if(fReweightUserHook.get()) fMultiUserHook->addHook(fReweightUserHook.get());
  if(fReweightRapUserHook.get()) fMultiUserHook->addHook(fReweightRapUserHook.get());
  if(fReweightPtHatRapUserHook.get()) fMultiUserHook->addHook(fReweightPtHatRapUserHook.get());
  if(fJetMatchingHook.get()) fMultiUserHook->addHook(fJetMatchingHook.get());
  if(fEmissionVetoHook1.get()) { 
    edm::LogInfo("Pythia8Interface") << "Turning on Emission Veto Hook 1 from CMSSW Pythia8Interface";
    fMultiUserHook->addHook(fEmissionVetoHook1.get());
  }
  
  if (fMasterGen->settings.mode("POWHEG:veto") > 0 || fMasterGen->settings.mode("POWHEG:MPIveto") > 0) {

    if(fJetMatchingHook.get() || fEmissionVetoHook1.get())
      throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" Attempt to turn on PowhegHooks by pythia8 settings but there are incompatible hooks on \n Incompatible are : jetMatching, emissionVeto1 \n";

    fEmissionVetoHook.reset(new PowhegHooks());

    edm::LogInfo("Pythia8Interface") << "Turning on Emission Veto Hook from pythia8 code";
    fMultiUserHook->addHook(fEmissionVetoHook.get());
  }
  
  //adapted from main89.cc in pythia8 examples
  bool internalMatching = fMasterGen->settings.flag("JetMatching:merge");
  bool internalMerging = !(fMasterGen->settings.word("Merging:Process").compare("void")==0);
  
  if (internalMatching && internalMerging) {
    throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" Only one jet matching/merging scheme can be used at a time. \n";
  }
  
  if (internalMatching) {
    fJetMatchingPy8InternalHook.reset(new Pythia8::JetMatchingMadgraph);
    fMultiUserHook->addHook(fJetMatchingPy8InternalHook.get());
  }
  
  if (internalMerging) {
    int scheme = ( fMasterGen->settings.flag("Merging:doUMEPSTree")
                || fMasterGen->settings.flag("Merging:doUMEPSSubt")) ?
                1 :
                 ( ( fMasterGen->settings.flag("Merging:doUNLOPSTree")
                || fMasterGen->settings.flag("Merging:doUNLOPSSubt")
                || fMasterGen->settings.flag("Merging:doUNLOPSLoop")
                || fMasterGen->settings.flag("Merging:doUNLOPSSubtNLO")) ?
                2 :
                0 );
    fMergingHook.reset(new Pythia8::amcnlo_unitarised_interface(scheme));
    fMultiUserHook->addHook(fMergingHook.get());
  }
  
  bool resonanceDecayFilter = fMasterGen->settings.flag("ResonanceDecayFilter:filter");
  if (resonanceDecayFilter) {
    fResonanceDecayFilterHook.reset(new ResonanceDecayFilterHook);
    fMultiUserHook->addHook(fResonanceDecayFilterHook.get());
  }
  
  if (fMultiUserHook->nHooks()>0) {
    fMasterGen->setUserHooksPtr(fMultiUserHook.get());
  }

  edm::LogInfo("Pythia8Interface") << "Initializing MasterGen";
  status = fMasterGen->init();
  
  //clean up temp file
  if (!slhafile_.empty()) {
    std::remove(slhafile_.c_str());
  }  

  if ( pythiaPylistVerbosity > 10 )
  {
    if ( pythiaPylistVerbosity == 11 || pythiaPylistVerbosity == 13 )
           fMasterGen->settings.listAll();
    if ( pythiaPylistVerbosity == 12 || pythiaPylistVerbosity == 13 )
           fMasterGen->particleData.listAll();
  }

  // init decayer
  fDecayer->settings.flag("ProcessLevel:all", false ); // trick
  fDecayer->settings.flag("ProcessLevel:resonanceDecays", true );
  edm::LogInfo("Pythia8Interface") << "Initializing Decayer";
  status1 = fDecayer->init();

  if (useEvtGen) {
    edm::LogInfo("Pythia8Interface") << "Creating and initializing pythia8 EvtGen plugin";

    evtgenDecays.reset(new EvtGenDecays(fMasterGen.get(), evtgenDecFile.c_str(), evtgenPdlFile.c_str()));

    for (unsigned int i=0; i<evtgenUserFiles.size(); i++) {
      edm::FileInPath evtgenUserFile(evtgenUserFiles.at(i)); 
      evtgenDecays->readDecayFile(evtgenUserFile.fullPath().c_str());
    }

  }
  
  //keep track of lhe weights
  //*FIXME* Sort them numerically since pythia does not preserve the original order
  //This will fail if weight names are not parseable as integers/
  //To be improved with future pythia release
  fSortedWeightKeys.clear();
  if (fMasterGen->info.initrwgt) {
    fSortedWeightKeys.reserve(fMasterGen->info.initrwgt->weights.size());
    
    std::vector<std::pair<int,std::string> > fWeightKeysTmp;
    fWeightKeysTmp.reserve(fMasterGen->info.initrwgt->weights.size());
    
    for (const auto &wgt : fMasterGen->info.initrwgt->weights) {
      fWeightKeysTmp.emplace_back(std::stoi(wgt.first),wgt.first);
    }
    
    std::sort(fWeightKeysTmp.begin(),fWeightKeysTmp.end());
    
    for (const auto &wgt : fWeightKeysTmp) {
      fSortedWeightKeys.push_back(wgt.second);
    }
  }

  return (status&&status1);
}


bool Pythia8Hadronizer::initializeForExternalPartons()
{

  edm::LogInfo("Pythia8Interface") << "Initializing for external partons";

  bool status = false, status1 = false;
  
  fMultiUserHook.reset(new MultiUserHook);
  
  if(fReweightUserHook.get()) fMultiUserHook->addHook(fReweightUserHook.get());
  if(fReweightRapUserHook.get()) fMultiUserHook->addHook(fReweightRapUserHook.get());
  if(fReweightPtHatRapUserHook.get()) fMultiUserHook->addHook(fReweightPtHatRapUserHook.get());
  if(fJetMatchingHook.get()) fMultiUserHook->addHook(fJetMatchingHook.get());
  if(fEmissionVetoHook1.get()) { 
    edm::LogInfo("Pythia8Interface") << "Turning on Emission Veto Hook 1 from CMSSW Pythia8Interface";
    fMultiUserHook->addHook(fEmissionVetoHook1.get());
  }
  
  if (fMasterGen->settings.mode("POWHEG:veto") > 0 || fMasterGen->settings.mode("POWHEG:MPIveto") > 0) {

    if(fJetMatchingHook.get() || fEmissionVetoHook1.get())
      throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" Attempt to turn on PowhegHooks by pythia8 settings but there are incompatible hooks on \n Incompatible are : jetMatching, emissionVeto1 \n";

    fEmissionVetoHook.reset(new PowhegHooks());

    edm::LogInfo("Pythia8Interface") << "Turning on Emission Veto Hook from pythia8 code";
    fMultiUserHook->addHook(fEmissionVetoHook.get());
  }
  
  //adapted from main89.cc in pythia8 examples
  bool internalMatching = fMasterGen->settings.flag("JetMatching:merge");
  bool internalMerging = !(fMasterGen->settings.word("Merging:Process").compare("void")==0);
  
  if (internalMatching && internalMerging) {
    throw edm::Exception(edm::errors::Configuration,"Pythia8Interface")
      <<" Only one jet matching/merging scheme can be used at a time. \n";
  }
  
  if (internalMatching) {
    fJetMatchingPy8InternalHook.reset(new Pythia8::JetMatchingMadgraph);
    fMultiUserHook->addHook(fJetMatchingPy8InternalHook.get());
  }
  
  if (internalMerging) {
    int scheme = ( fMasterGen->settings.flag("Merging:doUMEPSTree")
                || fMasterGen->settings.flag("Merging:doUMEPSSubt")) ?
                1 :
                 ( ( fMasterGen->settings.flag("Merging:doUNLOPSTree")
                || fMasterGen->settings.flag("Merging:doUNLOPSSubt")
                || fMasterGen->settings.flag("Merging:doUNLOPSLoop")
                || fMasterGen->settings.flag("Merging:doUNLOPSSubtNLO")) ?
                2 :
                0 );
    fMergingHook.reset(new Pythia8::amcnlo_unitarised_interface(scheme));
    fMultiUserHook->addHook(fMergingHook.get());
  }
  
  bool resonanceDecayFilter = fMasterGen->settings.flag("ResonanceDecayFilter:filter");
  if (resonanceDecayFilter) {
    fResonanceDecayFilterHook.reset(new ResonanceDecayFilterHook);
    fMultiUserHook->addHook(fResonanceDecayFilterHook.get());
  }
  
  if (fMultiUserHook->nHooks()>0) {
    fMasterGen->setUserHooksPtr(fMultiUserHook.get());
  }  
  
  if(LHEInputFileName != std::string()) {

    edm::LogInfo("Pythia8Interface") << "Initialize direct pythia8 reading from LHE file "
                                     << LHEInputFileName;
    edm::LogInfo("Pythia8Interface") << "Some LHE information can be not stored";
    fMasterGen->settings.mode("Beams:frameType", 4);
    fMasterGen->settings.word("Beams:LHEF", LHEInputFileName);
    status = fMasterGen->init();

  } else {

    lhaUP.reset(new LHAupLesHouches());
    lhaUP->setScalesFromLHEF(fMasterGen->settings.flag("Beams:setProductionScalesFromLHEF"));
    lhaUP->loadRunInfo(lheRunInfo());
    
    if ( fJetMatchingHook.get() )
    {
       fJetMatchingHook->init ( lheRunInfo() );
    }
    
    fMasterGen->settings.mode("Beams:frameType", 5);
    fMasterGen->setLHAupPtr(lhaUP.get());
    edm::LogInfo("Pythia8Interface") << "Initializing MasterGen";
    status = fMasterGen->init();
  }
  
  //clean up temp file
  if (!slhafile_.empty()) {
    std::remove(slhafile_.c_str());
  }  
  
  if ( pythiaPylistVerbosity > 10 )
  {
    if ( pythiaPylistVerbosity == 11 || pythiaPylistVerbosity == 13 )
           fMasterGen->settings.listAll();
    if ( pythiaPylistVerbosity == 12 || pythiaPylistVerbosity == 13 )
           fMasterGen->particleData.listAll();
  }

  // init decayer
  fDecayer->settings.flag("ProcessLevel:all", false ); // trick
  fDecayer->settings.flag("ProcessLevel:resonanceDecays", true );
  edm::LogInfo("Pythia8Interface") << "Initializing Decayer";
  status1 = fDecayer->init();

  if (useEvtGen) {
    edm::LogInfo("Pythia8Interface") << "Creating and initializing pythia8 EvtGen plugin";

    std::string evtgenpath(getenv("EVTGENDATA"));
    evtgenDecays.reset(new EvtGenDecays(fMasterGen.get(), evtgenDecFile.c_str(), evtgenPdlFile.c_str()));

    for (unsigned int i=0; i<evtgenUserFiles.size(); i++) {
      edm::FileInPath evtgenUserFile(evtgenUserFiles.at(i));
      evtgenDecays->readDecayFile(evtgenUserFile.fullPath().c_str());
    }

  }

  return (status&&status1);
}


void Pythia8Hadronizer::statistics()
{
  fMasterGen->stat();

  if(fEmissionVetoHook.get()) {
    edm::LogPrint("Pythia8Interface") << "\n"
      << "Number of ISR vetoed = " << nISRveto;
    edm::LogPrint("Pythia8Interface")
      << "Number of FSR vetoed = " << nFSRveto;
  }

  double xsec = fMasterGen->info.sigmaGen(); // cross section in mb
  xsec *= 1.0e9; // translate to pb (CMS/Gen "convention" as of May 2009)
  double err  = fMasterGen->info.sigmaErr(); // cross section err in mb
  err  *= 1.0e9; // translate to pb (CMS/Gen "convention" as of May 2009)
  runInfo().setInternalXSec(GenRunInfoProduct::XSec(xsec,err));
}


bool Pythia8Hadronizer::generatePartonsAndHadronize()
{

  DJR.resize(0);
  nME = -1;
  nMEFiltered = -1;
  
  if ( fJetMatchingHook.get() ) 
  {
    fJetMatchingHook->resetMatchingStatus(); 
    fJetMatchingHook->beforeHadronization( lheEvent() );
  }
  
  if (!fMasterGen->next()) return false;

  double mergeweight = fMasterGen.get()->info.mergingWeightNLO();
  if (fMergingHook.get()) {
    mergeweight *= fMergingHook->getNormFactor();
  }
  
  //protect against 0-weight from ckkw or similar
  if (std::abs(mergeweight)==0.)
  {
    event().reset();
    return false;
  }
  
  if (fJetMatchingPy8InternalHook.get()) {
    const std::vector<double> djrmatch = fJetMatchingPy8InternalHook->getDJR();
    //cap size of djr vector to save storage space (keep only up to first 6 elements)
    unsigned int ndjr = std::min(djrmatch.size(), std::vector<double>::size_type(6));
    for (unsigned int idjr=0; idjr<ndjr; ++idjr) {
      DJR.push_back(djrmatch[idjr]);
    }
    
    nME=fJetMatchingPy8InternalHook->nMEpartons().first;
    nMEFiltered=fJetMatchingPy8InternalHook->nMEpartons().second;
  }
  
  if (evtgenDecays.get()) evtgenDecays->decay();

  event().reset(new HepMC::GenEvent);
  bool py8hepmc =  toHepMC.fill_next_event( *(fMasterGen.get()), event().get());

  if (!py8hepmc) {
    return false;
  }
  
  //add ckkw/umeps/unlops merging weight
  if (mergeweight!=1.) {
    event()->weights()[0] *= mergeweight;
  }
  
  if (fEmissionVetoHook.get()) {
    nISRveto += fEmissionVetoHook->getNISRveto();
    nFSRveto += fEmissionVetoHook->getNFSRveto();  
  }
  
  //fill additional weights for systematic uncertainties
  //this is a hack because pythia does not currently provide ordered access to the weights
  //*FIXME* to be improved with future pythia version
  for (const string &key : fSortedWeightKeys) {
    double wgt = (*fMasterGen->info.weights_detailed)[key];
    event()->weights().push_back(wgt);
  }

  return true;
  
}


bool Pythia8Hadronizer::hadronize()
{
  DJR.resize(0);
  nME = -1;
  nMEFiltered = -1;
  if(LHEInputFileName == std::string()) lhaUP->loadEvent(lheEvent());

  if ( fJetMatchingHook.get() ) 
  {
    fJetMatchingHook->resetMatchingStatus(); 
    fJetMatchingHook->beforeHadronization( lheEvent() );
  }

  bool py8next = fMasterGen->next();

  double mergeweight = fMasterGen.get()->info.mergingWeightNLO();
  if (fMergingHook.get()) {
    mergeweight *= fMergingHook->getNormFactor();
  }
  
  
  //protect against 0-weight from ckkw or similar
  if (!py8next || std::abs(mergeweight)==0.)
  {
    lheEvent()->count( lhef::LHERunInfo::kSelected, 1.0, mergeweight );
    event().reset();
    return false;
  }
  
  if (fJetMatchingPy8InternalHook.get()) {
    const std::vector<double> djrmatch = fJetMatchingPy8InternalHook->getDJR();
    //cap size of djr vector to save storage space (keep only up to first 6 elements)
    unsigned int ndjr = std::min(djrmatch.size(), std::vector<double>::size_type(6));
    for (unsigned int idjr=0; idjr<ndjr; ++idjr) {
      DJR.push_back(djrmatch[idjr]);
    }
    
    nME=fJetMatchingPy8InternalHook->nMEpartons().first;
    nMEFiltered=fJetMatchingPy8InternalHook->nMEpartons().second;
  }
  
  // update LHE matching statistics
  //
  lheEvent()->count( lhef::LHERunInfo::kAccepted, 1.0, mergeweight );

  if (evtgenDecays.get()) evtgenDecays->decay();

  event().reset(new HepMC::GenEvent);
  bool py8hepmc =  toHepMC.fill_next_event( *(fMasterGen.get()), event().get());
  if (!py8hepmc) {
    return false;
  }
  
  //add ckkw/umeps/unlops merging weight
  if (mergeweight!=1.) {
    event()->weights()[0] *= mergeweight;
  }

  if (fEmissionVetoHook.get()) {
    nISRveto += fEmissionVetoHook->getNISRveto();
    nFSRveto += fEmissionVetoHook->getNFSRveto();  
  }

  return true;

}


bool Pythia8Hadronizer::residualDecay()
{

  Event* pythiaEvent = &(fMasterGen->event);

  int NPartsBeforeDecays = pythiaEvent->size();
  int NPartsAfterDecays = event().get()->particles_size();

  if(NPartsAfterDecays == NPartsBeforeDecays) return true;

  bool result = true;

  for ( int ipart=NPartsAfterDecays; ipart>NPartsBeforeDecays; ipart-- )
  {

    HepMC::GenParticle* part = event().get()->barcode_to_particle( ipart );

    if ( part->status() == 1 && (fDecayer->particleData).canDecay(part->pdg_id()) )
    {
      fDecayer->event.reset();
      Particle py8part(  part->pdg_id(), 93, 0, 0, 0, 0, 0, 0,
                         part->momentum().x(),
                         part->momentum().y(),
                         part->momentum().z(),
                         part->momentum().t(),
                         part->generated_mass() );
      HepMC::GenVertex* ProdVtx = part->production_vertex();
      py8part.vProd( ProdVtx->position().x(), ProdVtx->position().y(),
                     ProdVtx->position().z(), ProdVtx->position().t() );
      py8part.tau( (fDecayer->particleData).tau0( part->pdg_id() ) );
      fDecayer->event.append( py8part );
      int nentries = fDecayer->event.size();
      if ( !fDecayer->event[nentries-1].mayDecay() ) continue;
      fDecayer->next();
      int nentries1 = fDecayer->event.size();
      if ( nentries1 <= nentries ) continue; //same number of particles, no decays...

      part->set_status(2);

      result = toHepMC.fill_next_event( *(fDecayer.get()), event().get(), -1, true, part);

    }
  }

  return result;

}


void Pythia8Hadronizer::finalizeEvent()
{
  bool lhe = lheEvent() != 0;

  // now create the GenEventInfo product from the GenEvent and fill
  // the missing pieces
  eventInfo().reset( new GenEventInfoProduct( event().get() ) );

  // in pythia pthat is used to subdivide samples into different bins
  // in LHE mode the binning is done by the external ME generator
  // which is likely not pthat, so only filling it for Py6 internal mode
  if (!lhe) {
    eventInfo()->setBinningValues(std::vector<double>(1, fMasterGen->info.pTHat()));
  }
  
  eventInfo()->setDJR(DJR);
  eventInfo()->setNMEPartons(nME);
  eventInfo()->setNMEPartonsFiltered(nMEFiltered);

  //******** Verbosity ********

  if (maxEventsToPrint > 0 &&
      (pythiaPylistVerbosity || pythiaHepMCVerbosity ||
                                pythiaHepMCVerbosityParticles) ) {
    maxEventsToPrint--;
    if (pythiaPylistVerbosity) {
      fMasterGen->info.list(std::cout); 
      fMasterGen->event.list(std::cout);
    } 

    if (pythiaHepMCVerbosity) {
      std::cout << "Event process = "
                << fMasterGen->info.code() << "\n"
                << "----------------------" << std::endl;
      event()->print();
    }
    if (pythiaHepMCVerbosityParticles) {
      std::cout << "Event process = "
                << fMasterGen->info.code() << "\n"
                << "----------------------" << std::endl;
      ascii_io->write_event(event().get());
    }
  }
}

GenLumiInfoHeader *Pythia8Hadronizer::getGenLumiInfoHeader() const {
  GenLumiInfoHeader *genLumiInfoHeader = BaseHadronizer::getGenLumiInfoHeader();
  
  //fill lhe headers
  //*FIXME* initrwgt header is corrupt due to pythia bug
  for (const std::string &key : fMasterGen->info.headerKeys()) {
    genLumiInfoHeader->lheHeaders().emplace_back(key,fMasterGen->info.header(key));
  }
  
  //fill weight names
  //*FIXME* to be improved with future pythia version to avoid need
  //for re-sorting weights
  //Note that weight group names are not available in all cases currently
  //due to an issue in the weightgroup handling in pythia
  genLumiInfoHeader->weightNames().reserve(fSortedWeightKeys.size() + 1);
  genLumiInfoHeader->weightNames().push_back("nominal");
  for (const std::string &key : fSortedWeightKeys) {
    std::string weightgroupname;
    for (const auto &wgtgrp : fMasterGen->info.initrwgt->weightgroups) {
      if (wgtgrp.second.weights.count(key)) {
        if (!wgtgrp.first.empty()) {
          weightgroupname = wgtgrp.first;
        }
        else if (wgtgrp.second.attributes.count("type")) {
          weightgroupname = wgtgrp.second.attributes.find("type")->second;
        }
        break;
      }
    }
    
    std::ostringstream weightname;
    weightname << "LHE, id = " << key << ", ";
    if (!weightgroupname.empty()) {
      weightname << weightgroupname << ", ";
    }
    weightname<< fMasterGen->info.initrwgt->weights[key].contents;
    genLumiInfoHeader->weightNames().push_back(weightname.str());
  }

  return genLumiInfoHeader;
}

typedef edm::GeneratorFilter<Pythia8Hadronizer, ExternalDecayDriver> Pythia8GeneratorFilter;
DEFINE_FWK_MODULE(Pythia8GeneratorFilter);


typedef edm::HadronizerFilter<Pythia8Hadronizer, ExternalDecayDriver> Pythia8HadronizerFilter;
DEFINE_FWK_MODULE(Pythia8HadronizerFilter);