FixHepMC.cxx File Reference

#include "EvgenProdTools/FixHepMC.h"
#include "TruthUtils/HepMCHelpers.h"
#include "AtlasHepMC/GenVertex.h"
#include "AtlasHepMC/GenEvent.h"
#include <vector>

Include dependency graph for FixHepMC.cxx:

Go to the source code of this file.

Functions
Event reduction functions
static void	reduce (HepMC::GenEvent *ge, HepMC::GenParticle *gp)
	Remove an unwanted particle from the event, collapsing the graph structure consistently.
void	reduce (HepMC::GenEvent *ge, std::vector< HepMC::GenParticlePtr > toremove)
	Remove unwanted particles from the event, collapsing the graph structure consistently.

Function Documentation

reduce() [1/2]

void reduce ( HepMC::GenEvent * ge, HepMC::GenParticle * gp )

inlinestatic

Remove an unwanted particle from the event, collapsing the graph structure consistently.

Note

The disconnected end vertex will be picked up by the final "sweeper" loop if necessary.

We do the reassigning this way since GV::add_particle_*() modifies the end vertex

Todo

Can we be a bit more efficient rather than having to run over all vertices every time? Or allow disabling of this clean-up, with a single clean being run at the end of filtering.

Todo

Todo

Use neater looping via vertices_match (or iterated vertex_match)

Todo

Todo

Also look for and report changes in number of no-parent and no-child vertices

Definition at line 39 of file FixHepMC.cxx.

                                                                    {
    // Do nothing if for some reason this particle is not actually in this event
    if (gp->parent_event() != ge) return;
 
    // Get start and end vertices
    HepMC::GenVertex* vstart = gp->production_vertex();
    HepMC::GenVertex* vend = gp->end_vertex();
 
    // Disconnect the unwanted particle from its vertices and delete it
    if (vstart != nullptr) vstart->remove_particle(gp);
    if (vend != nullptr) vend->remove_particle(gp);
    delete gp;
 
    // If start/end vertices are valid and distinct, and this was the only particle that
    // connected them, then reassign the end vertex decay products to the start vertex
    // and rewrite the vertex position as most appropriate.
    if (vstart != nullptr && vend != nullptr && vend != vstart) {
      bool is_only_link = true;
      for (auto pchild=vstart->particles_out_const_begin();pchild!=vstart->particles_out_const_end();++pchild) {
        if ((*pchild)->end_vertex() == vend) is_only_link = false;
      }
      if (is_only_link) {
        if (vend->position() != HepMC::FourVector())
          vstart->set_position(vend->position()); //< @todo Always use end position if defined... ok?
        while (vend->particles_out_size() > 0) {
          vstart->add_particle_out(*vend->particles_out_const_begin());
        }
        while (vend->particles_in_size() > 0) {
          vstart->add_particle_in(*vend->particles_in_const_begin());
        }
      }
    }
 
    // Sweep up any vertices orphaned by the particle removal
    std::vector<HepMC::GenVertex*> orphaned_vtxs;
    for (HepMC::GenEvent::vertex_const_iterator vi = ge->vertices_begin(); vi != ge->vertices_end(); ++vi) {
      if ((*vi)->particles_in_size() == 0 && (*vi)->particles_out_size() == 0) orphaned_vtxs.push_back(*vi);
    }
    for (HepMC::GenVertex* gv : orphaned_vtxs) delete gv;
  }

reduce() [2/2]

void reduce ( HepMC::GenEvent * ge, std::vector< HepMC::GenParticlePtr > toremove )

inline

Remove unwanted particles from the event, collapsing the graph structure consistently.

Definition at line 87 of file FixHepMC.cxx.

                                                                                 {
    while (toremove.size()) {
      auto gp = toremove.back();
      toremove.pop_back();
      reduce(ge, gp);
    }
  }