Subversion Repositories hepmc

//////////////////////////////////////////////////////////////////////////

// Matt.Dobbs@Cern.CH, December 1999

// November 2000, updated to use Pythia 6.1

// example of generating events with Pythia

// using HepMC/PythiaWrapper.h 

// Events are read into the HepMC event record from the FORTRAN HEPEVT 

// common block using the IO_HEPEVT strategy and then output to file in

// ascii format using the IO_Ascii strategy.

//////////////////////////////////////////////////////////////////////////

/// To Compile: go to the HepMC directory and type:

/// gmake examples/example_MyPythia.exe

///

/// In this example the precision and number of entries for the HEPEVT 

/// fortran common block are explicitly defined to correspond to those 

/// used in the Pythia version of the HEPEVT common block. 

///

/// If you get funny output from HEPEVT in your own code, probably you have

/// set these values incorrectly!

///

#include <iostream>

#include "HepMC/PythiaWrapper.h"

#include "HepMC/IO_HEPEVT.h"

#include "HepMC/IO_Ascii.h"

#include "HepMC/GenEvent.h"

#include "PythiaHelper.h"

int main() {

    //

    //........................................HEPEVT

    // Pythia 6.1 uses HEPEVT with 4000 entries and 8-byte floating point

    //  numbers. We need to explicitly pass this information to the 

    //  HEPEVT_Wrapper.

    //

    HepMC::HEPEVT_Wrapper::set_max_number_entries(4000);

    HepMC::HEPEVT_Wrapper::set_sizeof_real(8);

    //

    //........................................PYTHIA INITIALIZATIONS

    initPythia();

    //........................................HepMC INITIALIZATIONS

    //

    // Instantiate an IO strategy for reading from HEPEVT.

    HepMC::IO_HEPEVT hepevtio;

    //

    { // begin scope of ascii_io

        // Instantiate an IO strategy to write the data to file 

        HepMC::IO_Ascii ascii_io("example_MyPythia.dat",std::ios::out);

        //

        //........................................EVENT LOOP

        for ( int i = 1; i <= 100; 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 = hepevtio.read_next_event();

            // add some information to the event

            evt->set_event_number(i);

            evt->set_signal_process_id(20);

            // set number of multi parton interactions

            evt->set_mpi( pypars.msti[31-1] );

            // write the event out to the ascii file

            ascii_io << evt;

            // we also need to delete the created event from memory

            delete evt;

        }

        //........................................TERMINATION

        // write out some information from Pythia to the screen

        call_pystat( 1 );    

    } // end scope of ascii_io

    return 0;

}