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// $Id: example_MyPythia.cc,v 1.3 2002/12/13 11:42:38 gcosmo Exp $
// ====================================================================
//   example_MyPythia.cc
//
//   sample event generation using Pythia and HepMC(CLHEP)
// ====================================================================

#include "CLHEP/HepMC/CBhepevt.h"
#include "CLHEP/HepMC/WriteHepMC.h"
#include "CLHEP/HepMC/ReadHepMC.h"
#include "CLHEP/HepMC/include/PythiaWrapper6_2.h"

#include <string>
#include <fstream>

// global parameters
hepev2_t hepev2_;
hepev3_t hepev3_;
hepev4_t hepev4_;
hepev5_t hepev5_;

int main() { 
  // initialize Pythia...
  // select W+gamma process (process number 20) 
  pysubs.msel= 0;
  pysubs.msub[20-1]= 1;
  // set random number seed (mandatory!)
  pydatr.mrpy[0]= 55122 ;
  // tell Pythia not to write multiple copies of particles in event record.
  pypars.mstp[128-1]= 2;
  // example of setting a Pythia parameter: set the top mass 
  pydat2.pmas[1-1][6-1]= 175;  
  // call pythia initialization
  call_pyinit( "CMS", "p", "p", 14000. );
  
  // prepare HepMC-HEPEVT interface...
  HepMC::CBhepevt* hepevtio= new HepMC::CBhepevt;
  
  std::ofstream to;
  std::string fname= "example_MyPythia.dat";
  to.open(fname.c_str(), std::ios::out);

  HepMC::writeComment(to, "generate sample pythia events...");
  for ( int i = 1; i <= 10; i++ ) {
    if ( i%50==1 ) std::cout << "Processing Event Number " 
			     << i << std::endl;
    call_pyevnt();  // generate one event with Pythia
    // pythia pyhepc routine converts common PYJETS in common HEPEVT
    call_pyhepc( 1 );
    
    HepMC::GenEvent* evt= new HepMC::GenEvent();
    hepevtio-> toGenEvent(evt, false);
    hepevtio-> clean(); // clear HEPEVT
    
    // add some information to the event
    evt-> set_event_number(i);
    evt-> set_signal_process_id(20);
    
    // write the event out to the ascii file
    to << evt;
    
    // we also need to delete the created event from memory
    delete evt;
  }

  // write out some information from Pythia to the screen
  call_pystat(1);
  to.close();
  delete hepevtio;
  
  return 0;
}