main42_new.cc

// main42.cc is a part of the PYTHIA event generator.
// Copyright (C) 2015 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.

// Author: Mikhail Kirsanov, Mikhail.Kirsanov@cern.ch.
// This program illustrates how a file with HepMC events
// can be generated by Pythia8.
// Input and output files are specified on the command line, e.g. like
// ./main42.exe main42.cmnd hepmcout42.dat > out
// The main program contains no analysis; this is intended to happen later.
// It therefore "never" has to be recompiled to handle different tasks.

// WARNING: typically one needs 25 MB/100 events at the LHC.
// Therefore large event samples may be impractical.

#include <iostream>
#include "Pythia8/Pythia.h"
#include "Pythia8/Settings.h"

using namespace Pythia8;

int main(int argc, char* argv[]) {

  // Check that correct number of command-line arguments
  if (argc != 3) {
    cerr << " Unexpected number of command-line arguments. \n You are"
         << " expected to provide one input and one output file name. \n"
         << " Program stopped! " << endl;
    return 1;
  }

  // Check that the provided input name corresponds to an existing file.
  ifstream is(argv[1]);
  if (!is) {
    cerr << " Command-line file " << argv[1] << " was not found. \n"
         << " Program stopped! " << endl;
    return 1;
  }

  // Confirm that external files will be used for input and output.
  cout << "\n >>> PYTHIA settings will be read from file " << argv[1]
       << " <<< \n >>> HepMC events will be written to file "
       << argv[2] << " <<< \n" << endl;

  // Interface for conversion from Pythia8::Event to HepMC event.

  // Specify file where HepMC events will be stored.
  std::ofstream ascii_io(argv[2], std::ios::out);

  // Generator.
  Pythia pythia;
  pythia.settings.init("xmldoc/Index.xml");
  
  // Read in commands from external file.
  pythia.readFile(argv[1]);

  // Extract settings to be used in the main program.
  int    nEvent    = pythia.mode("Main:numberOfEvents");
  int    nAbort    = pythia.mode("Main:timesAllowErrors");

  // Initialization.
  pythia.init();

  // Begin event loop.
  int iAbort = 0;
  int totEv = 0;
  for (int iEvent = 0; iEvent < nEvent; ++iEvent) {

    // Generate event.
    if (!pythia.next()) {
      // If failure because reached end of file then exit event loop.
      if (pythia.info.atEndOfFile()) {
        cout << " Aborted since reached end of Les Houches Event File\n";
        break;
      }

      // First few failures write off as "acceptable" errors, then quit.
      if (++iAbort < nAbort) continue;
      cout << " Event generation aborted prematurely, owing to error!\n";
      break;
    }
    ++totEv;
    for (int i = 0; i < pythia.event.size(); ++i) {
      if (pythia.event[i].isFinal() && pythia.event[i].isCharged() && 
        abs(pythia.event[i].id()) == 1000010020) {
        ascii_io << pythia.event[i].id() << "\t" << pythia.event[i].pT() << "\t"; 
      ascii_io << pythia.event[i].pz() << "\t" << pythia.event[i].eta() << "\t" << pythia.event[i].y() << std::endl;
    }
    
    
  // End of event loop. Statistics.
  }
  }
  ascii_io << "#" << totEv << endl;
  // Done.
  return 0;
}