## main154

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    // main154.cc is a part of the PYTHIA event generator.
    // Copyright (C) 2025 Torbjorn Sjostrand.
    // PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
    // Please respect the MCnet Guidelines, see GUIDELINES for details.

    // Authors:
    //            Philip Ilten

    // Keywords:
    //            Merging
    //            Matching
    //            Powheg

    // An example where the HVQ POWHEGBOX matrix element binary is
    // interfaced directly with PYTHIA. For this example to run correctly
    // PYTHIA must be configured with the
    // --with-powheg=<path to directory containing only POWHEG libraries>
    // option. This will build plugin libraries of the name
    // libpythia8powheg<process name>.so in the library directory.
    // For these plugin libraries to build correctly, special compiler flags
    // must have been used when building the POWHEGBOX binaries. These are
    // "-rdynamic -fPIC". The following SED command will correctly
    // insert them into the relevant POWHEGBOX Makefile:
    //     sed -i "s/F77= gfortran/F77= gfortran -rdynamic -fPIC/g"
    //     Makefile
    // For this specific example the library libpythia8powheghvq.so must
    // have been built. A complete set of libraries can be built using the LCG
    // script available here:
    //     https://gitlab.cern.ch/sft/lcgcmake/-/blob/master/generators/
    //     powheg-box-v2/prepare.sh

    #include "Pythia8/Pythia.h"

    using namespace Pythia8;

    int main() {

      // PYTHIA and the POWHEG user hooks must still be configured, here
      // this is done via main154.cmnd. These settings are sensible
      // defaults, but Powheg:nFinal is dependent upon the POWHEG matrix
      // element being used and so must be changed as appropriate.
      Pythia pythia;
      pythia.readString(
        "Init:plugins = {libpythia8powheghvq.so::LHAupPowheg::set::main154.cmnd,"
        "libpythia8powhegHooks.so::PowhegHooks::set::main154.cmnd}");

      // Initialize PYTHIA, based on the specified settings.
      // If Pythia fails to initialize, exit with error.
      if (!pythia.init()) return 1;

      // Run PYTHIA. The random numbers are taken from the associated
      // PYTHIA random number generator.
      for (int iEvent = 0; iEvent < 100; ++iEvent) pythia.next();

      // End of run.
      pythia.stat();
      return 0;
    }