Pythia8Hadronizer.cc

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

#include <HepMC/GenEvent.h>
#include <HepMC/GenParticle.h>

#include <Pythia.h>
#include <HepMCInterface.h>

#include "GeneratorInterface/Pythia8Interface/interface/RandomP8.h"

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

#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"

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

#include "GeneratorInterface/Core/interface/ParameterCollector.h"
#include "GeneratorInterface/Core/interface/BaseHadronizer.h"
#include "GeneratorInterface/Core/interface/GeneratorFilter.h"
#include "GeneratorInterface/Core/interface/HadronizerFilter.h"
#include "GeneratorInterface/Core/interface/RNDMEngineAccess.h"

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

#include "HepPID/ParticleIDTranslations.hh"

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

using namespace gen;
using namespace Pythia8;

class Pythia8Hadronizer : public BaseHadronizer {
    public:
    Pythia8Hadronizer(const edm::ParameterSet &params);
    ~Pythia8Hadronizer();
 
    bool initializeForInternalPartons();
        bool initializeForExternalPartons();
    
    bool declareStableParticles(const std::vector<int> &pdgIds);
    bool declareSpecialSettings( const std::vector<std::string> );

    void statistics();

    bool generatePartonsAndHadronize();
        bool hadronize();
    bool decay();
    bool residualDecay();
    void finalizeEvent();

    const char *classname() const { return "Pythia8Hadronizer"; }

    private:
    ParameterCollector  parameters;

    double          comEnergy;
    unsigned int        pythiaPylistVerbosity;
    bool            pythiaHepMCVerbosity;
    unsigned int        maxEventsToPrint;

    string LHEInputFileName;

    bool            useUserHook;

    std::auto_ptr<LHAupLesHouches>      lhaUP;

    std::auto_ptr<Pythia>   pythia;
    Event           *pythiaEvent;
    HepMC::I_Pythia8    toHepMC;   

        UserHooks* UserHookPointer;
};


Pythia8Hadronizer::Pythia8Hadronizer(const edm::ParameterSet &params) :
        BaseHadronizer(params),
    parameters(params.getParameter<edm::ParameterSet>("PythiaParameters")),
    comEnergy(params.getParameter<double>("comEnergy")),
    pythiaPylistVerbosity(params.getUntrackedParameter<int>("pythiaPylistVerbosity", 0)),
    pythiaHepMCVerbosity(params.getUntrackedParameter<bool>("pythiaHepMCVerbosity", false)),
    maxEventsToPrint(params.getUntrackedParameter<int>("maxEventsToPrint", 0)),
    LHEInputFileName(params.getUntrackedParameter<string>("LHEInputFileName","")),
    useUserHook(false),
    UserHookPointer(0)
{
    if( params.exists( "useUserHook" ) )
      useUserHook = params.getParameter<bool>("useUserHook");
    randomEngine = &getEngineReference();
}

Pythia8Hadronizer::~Pythia8Hadronizer()
{
}

bool Pythia8Hadronizer::initializeForInternalPartons()
{
    //Old code that used Pythia8 own random engine
    //edm::Service<edm::RandomNumberGenerator> rng;
    //uint32_t seed = rng->mySeed();
    //Pythia8::Rndm::init(seed);

    RandomP8* RP8 = new RandomP8();

    pythia.reset(new Pythia);

    pythia->setRndmEnginePtr(RP8);
    if(useUserHook){
      UserHookPointer = new PtHatReweightUserHook();
      pythia->setUserHooksPtr(UserHookPointer);
    }

    pythiaEvent = &pythia->event;

    for(ParameterCollector::const_iterator line = parameters.begin();
        line != parameters.end(); ++line) {
        if (line->find("Random:") != std::string::npos)
            throw cms::Exception("PythiaError")
                << "Attempted to set random number "
                   "using Pythia commands.  Please use "
                   "the RandomNumberGeneratorService."
                << std::endl;

        if (!pythia->readString(*line))
            throw cms::Exception("PythiaError")
                << "Pythia 8 did not accept \""
                << *line << "\"." << std::endl;
    }

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

    pythia->init(2212, 2212, comEnergy);

    pythia->settings.listChanged();

    return true;
}


bool Pythia8Hadronizer::initializeForExternalPartons()
{

    std::cout << "Initializing for external partons" << std::endl;

    RandomP8* RP8 = new RandomP8();

    pythia.reset(new Pythia);

    pythia->setRndmEnginePtr(RP8);

    pythiaEvent = &pythia->event;

    for(ParameterCollector::const_iterator line = parameters.begin();
        line != parameters.end(); ++line) {
        if (line->find("Random:") != std::string::npos)
            throw cms::Exception("PythiaError")
                << "Attempted to set random number "
                   "using Pythia commands.  Please use "
                   "the RandomNumberGeneratorService."
                << std::endl;

        if (!pythia->readString(*line))
            throw cms::Exception("PythiaError")
                << "Pythia 8 did not accept \""
                << *line << "\"." << std::endl;
    }

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

    if(LHEInputFileName != string()) {

      cout << endl;
      cout << "LHE Input File Name = " << LHEInputFileName << endl;
      cout << endl;
      pythia->init(LHEInputFileName);

    } else {

      lhaUP.reset(new LHAupLesHouches());
      lhaUP->loadRunInfo(lheRunInfo());
      pythia->init(lhaUP.get());

    }

    return true;
}


#if 0
// naive Pythia8 HepMC status fixup
static int getStatus(const HepMC::GenParticle *p)
{
    int status = p->status();
    if (status > 0)
        return status;
    else if (status > -30 && status < 0)
        return 3;
    else
        return 2;
}
#endif

bool Pythia8Hadronizer::declareStableParticles(const std::vector<int> &pdgIds)
{

   for ( size_t i=0; i<pdgIds.size(); i++ )
   {
      // FIXME: need to double check if PID's are the same in Py6 & Py8,
      //        because the HepPDT translation tool is actually for **Py6** 
      // 
      int PyID = HepPID::translatePDTtoPythia( pdgIds[i] ); 
      std::ostringstream pyCard ;
      pyCard << PyID <<":mayDecay=false";
      pythia->readString( pyCard.str() );
      // alternative:
      // set the 2nd input argument warn=false 
      // - this way Py8 will NOT print warnings about unknown particle code(s)
      // pythia->readString( pyCard.str(), false )
   }
   
   return true;

}
bool Pythia8Hadronizer::declareSpecialSettings( const std::vector<std::string> )
{
   return true;
}


void Pythia8Hadronizer::statistics()
{
    pythia->statistics();

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

bool Pythia8Hadronizer::generatePartonsAndHadronize()
{
    if (!pythia->next())
        return false;

    event().reset(new HepMC::GenEvent);
    toHepMC.fill_next_event(*pythiaEvent, event().get());

    return true;
}

bool Pythia8Hadronizer::hadronize()
{
    if(LHEInputFileName == string()) {
      //cout << "start loading event" << endl;
      lhaUP->loadEvent(lheEvent());
      //cout << "finish loading event" << endl;
    }

    if (!pythia->next())
        return false;

    // update LHE matching statistics
    //
    lheEvent()->count( lhef::LHERunInfo::kAccepted );

    event().reset(new HepMC::GenEvent);
    toHepMC.fill_next_event(*pythiaEvent, event().get());

    return true;
}

bool Pythia8Hadronizer::decay()
{
    return true;
}

bool Pythia8Hadronizer::residualDecay()
{
    return true;
}

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

  event()->set_signal_process_id(pythia->info.code());
  event()->set_event_scale(pythia->info.pTHat());   //FIXME

  // Putting pdf info into the HepMC record
  // There is the overloaded pythia8 HepMCInterface method fill_next_event
  // that does this, but CMSSW GeneratorInterface does not fill HepMC
  // record according to the HepMC convention (stores f(x) instead of x*f(x)
  // and converts gluon PDG ID to zero). For this reason we use the
  // method fill_next_event (above) that does NOT this and fill pdf info here
  //
  int id1 = pythia->info.id1();
  int id2 = pythia->info.id2();
  if (id1 == 21) id1 = 0;
  if (id2 == 21) id2 = 0;
  double x1 = pythia->info.x1();
  double x2 = pythia->info.x2();
  double Q = pythia->info.QRen();
  double pdf1 = pythia->info.pdf1() / pythia->info.x1();
  double pdf2 = pythia->info.pdf2() / pythia->info.x2();
  event()->set_pdf_info(HepMC::PdfInfo(id1,id2,x1,x2,Q,pdf1,pdf2));

  // Storing weights. Will be moved to pythia8 HepMCInterface
  //
  if (lhe && std::abs(lheRunInfo()->getHEPRUP()->IDWTUP) == 4)
    // translate mb to pb (CMS/Gen "convention" as of May 2009)
    event()->weights().push_back( pythia->info.weight() * 1.0e9 );
  else
    event()->weights().push_back( pythia->info.weight() );
  //
  // Below is the weight to be used in the case of reweighting by UserHook
  // This is a temporary solution. It requires the explicit conversion of
  // the pointer. In future versions (>150) the additional factor introduced
  // in the UserHook will be stored by pythia. Also, putting the weights
  // into the HepMC record will be made in the pythia8 HepMCInterface
  //
  if(useUserHook)
    event()->weights().push_back(1./((PtHatReweightUserHook*)UserHookPointer)->getFactor());

  // 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, pythia->info.pTHat()));
  }

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

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

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

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

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