| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 //
27 //////////////////////////////////////////////////////////////////////////
28 // Matt.Dobbs@Cern.CH, December 1999
29 // November 2000, updated to use Pythia 6.1
30 // example of generating events with Pythia
31 // using HepMC/PythiaWrapper.h
32 // Events are read into the HepMC event record from the FORTRAN HEPEVT
33 // common block using the IO_HEPEVT strategy and then output to file in
34 // ascii format using the IO_Ascii strategy.
35 //////////////////////////////////////////////////////////////////////////
36 // To Compile: go to the HepMC directory and type:
37 // gmake examples/example_MyPythia.exe
38 //
39 // In this example the precision and number of entries for the HEPEVT
40 // fortran common block are explicitly defined to correspond to those
41 // used in the Pythia version of the HEPEVT common block.
42 //
43 // If you get funny output from HEPEVT in your own code, probably you have
44 // set these values incorrectly!
45 //
46
47 #include <iostream>
48 #include "HepMC/PythiaWrapper.h"
49 #include "HepMC/IO_HEPEVT.h"
50 #include "HepMC/IO_GenEvent.h"
51 #include "HepMC/GenEvent.h"
52
53 int main() {
54 //
55 //........................................HEPEVT
56 // Pythia 6.1 uses HEPEVT with 4000 entries and 8-byte floating point
57 // numbers. We need to explicitly pass this information to the
58 // HEPEVT_Wrapper.
59 //
60 HepMC::HEPEVT_Wrapper::set_max_number_entries(4000);
61 HepMC::HEPEVT_Wrapper::set_sizeof_real(8);
62 //
63 //........................................PYTHIA INITIALIZATIONS
64 // (Some platforms may require the initialization of pythia PYDATA block
65 // data as external - if you get pythia initialization errors try
66 // commenting in/out the below call to initpydata() )
67 // initpydata();
68 //
69 // Select W+gamma process (process number 20)
70 // (here we have to be careful of C/F77 differences: arrays in C
71 // start at 0, F77 at 1, so we need to subtract 1 from the process #)
72 pysubs.msel=0;
73 pysubs.msub[20-1] = 1;
74 // set random number seed (mandatory!)
75 pydatr.mrpy[0]=55122 ;
76 // Tell Pythia not to write multiple copies of particles in event record.
77 pypars.mstp[128-1] = 2;
78 // Example of setting a Pythia parameter: set the top mass
79 pydat2.pmas[1-1][6-1]= 175;
80 //
81 // Call pythia initialization
82 call_pyinit( "CMS", "p", "p", 14000. );
83
84 //........................................HepMC INITIALIZATIONS
85 //
86 // Instantiate an IO strategy for reading from HEPEVT.
87 HepMC::IO_HEPEVT hepevtio;
88 //
89 // Instantial an IO strategy to write the data to file - it uses the
90 // same ParticleDataTable
91 HepMC::IO_GenEvent ascii_io("example_MyPythia.dat",std::ios::out);
92 //
93 //........................................EVENT LOOP
94 for ( int i = 1; i <= 10; i++ ) {
95 if ( i%50==1 ) std::cout << "Processing Event Number "
96 << i << std::endl;
97 call_pyevnt(); // generate one event with Pythia
98 // pythia pyhepc routine converts common PYJETS in common HEPEVT
99 call_pyhepc( 1 );
100 HepMC::GenEvent* evt = hepevtio.read_next_event();
101 // add some information to the event
102 evt->set_event_number(i);
103 evt->set_signal_process_id(20);
104 // write the event out to the ascii file
105 ascii_io << evt;
106 // we also need to delete the created event from memory
107 delete evt;
108 }
109 //........................................TERMINATION
110 // write out some information from Pythia to the screen
111 call_pystat( 1 );
112
113 return 0;
114 }