LHEEvent.cc

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#include <algorithm>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <cstring>
#include <string>
#include <vector>
#include <memory>
#include <cmath>
 
#include "HepMC/GenEvent.h"
#include "HepMC/GenVertex.h"
#include "HepMC/GenParticle.h"
#include "HepMC/SimpleVector.h"
 
#include "FWCore/MessageLogger/interface/MessageLogger.h"
 
#include "SimDataFormats/GeneratorProducts/interface/LesHouches.h"
 
#include "GeneratorInterface/LHEInterface/interface/LHERunInfo.h"
#include "GeneratorInterface/LHEInterface/interface/LHEEvent.h"
 
static int skipWhitespace(std::istream &in) {
  int ch;
  do {
    ch = in.get();
  } while (std::isspace(ch));
  if (ch != std::istream::traits_type::eof())
    in.putback(ch);
  return ch;
}
 
namespace lhef {
 
  LHEEvent::LHEEvent(const std::shared_ptr<LHERunInfo> &runInfo, std::istream &in)
      : runInfo(runInfo),
        weights_(0),
        counted(false),
        readAttemptCounter(0),
        npLO_(-99),
        npNLO_(-99)
 
  {
    hepeup.NUP = 0;
    hepeup.XPDWUP.first = hepeup.XPDWUP.second = 0.0;
 
    in >> hepeup.NUP >> hepeup.IDPRUP >> hepeup.XWGTUP >> hepeup.SCALUP >> hepeup.AQEDUP >> hepeup.AQCDUP;
    if (!in.good())
      throw cms::Exception("InvalidFormat") << "Les Houches file contained invalid"
                                               " event header."
                                            << std::endl;
 
    // store the original value of XWGTUP for the user
    originalXWGTUP_ = hepeup.XWGTUP;
 
    int idwtup = runInfo->getHEPRUP()->IDWTUP;
    if (idwtup >= 0 && hepeup.XWGTUP < 0) {
      edm::LogWarning("Generator|LHEInterface") << "Non-allowed negative event weight encountered." << std::endl;
      hepeup.XWGTUP = std::abs(hepeup.XWGTUP);
    }
 
    if (std::abs(idwtup) == 3 && std::abs(hepeup.XWGTUP) != 1.) {
      edm::LogInfo("Generator|LHEInterface") << "Event weight not set to one for abs(IDWTUP) == 3" << std::endl;
      hepeup.XWGTUP = hepeup.XWGTUP > 0. ? 1.0 : -1.0;
    }
 
    hepeup.resize();
 
    for (int i = 0; i < hepeup.NUP; i++) {
      in >> hepeup.IDUP[i] >> hepeup.ISTUP[i] >> hepeup.MOTHUP[i].first >> hepeup.MOTHUP[i].second >>
          hepeup.ICOLUP[i].first >> hepeup.ICOLUP[i].second >> hepeup.PUP[i][0] >> hepeup.PUP[i][1] >>
          hepeup.PUP[i][2] >> hepeup.PUP[i][3] >> hepeup.PUP[i][4] >> hepeup.VTIMUP[i] >> hepeup.SPINUP[i];
      if (!in.good())
        throw cms::Exception("InvalidFormat") << "Les Houches file contained invalid event"
                                                 " in particle line "
                                              << (i + 1) << "." << std::endl;
    }
 
    while (skipWhitespace(in) == '#') {
      std::string line;
      std::getline(in, line);
      std::istringstream ss(line);
      std::string tag;
      ss >> tag;
      if (tag == "#pdf") {
        pdf.reset(new PDF);
        ss >> pdf->id.first >> pdf->id.second >> pdf->x.first >> pdf->x.second >> pdf->scalePDF >> pdf->xPDF.first >>
            pdf->xPDF.second;
        if (ss.bad()) {
          edm::LogWarning("Generator|LHEInterface") << "Les Houches event contained"
                                                       " unparseable PDF information."
                                                    << std::endl;
          pdf.reset();
        } else
          continue;
      }
      comments.push_back(line + "\n");
    }
 
    if (!in.eof())
      edm::LogWarning("Generator|LHEInterface") << "Les Houches file contained spurious"
                                                   " content after event data."
                                                << std::endl;
  }
 
  LHEEvent::LHEEvent(const std::shared_ptr<LHERunInfo> &runInfo, const HEPEUP &hepeup)
      : runInfo(runInfo), hepeup(hepeup), counted(false), readAttemptCounter(0), npLO_(-99), npNLO_(-99) {}
 
  LHEEvent::LHEEvent(const std::shared_ptr<LHERunInfo> &runInfo,
                     const HEPEUP &hepeup,
                     const LHEEventProduct::PDF *pdf,
                     const std::vector<std::string> &comments)
      : runInfo(runInfo),
        hepeup(hepeup),
        pdf(pdf ? new PDF(*pdf) : nullptr),
        comments(comments),
        counted(false),
        readAttemptCounter(0),
        npLO_(-99),
        npNLO_(-99) {}
 
  LHEEvent::LHEEvent(const std::shared_ptr<LHERunInfo> &runInfo, const LHEEventProduct &product)
      : runInfo(runInfo),
        hepeup(product.hepeup()),
        pdf(product.pdf() ? new PDF(*product.pdf()) : nullptr),
        weights_(product.weights()),
        comments(product.comments_begin(), product.comments_end()),
        counted(false),
        readAttemptCounter(0),
        originalXWGTUP_(product.originalXWGTUP()),
        scales_(product.scales()),
        npLO_(product.npLO()),
        npNLO_(product.npNLO()) {}
 
  LHEEvent::~LHEEvent() {}
 
  void LHEEvent::removeParticle(HEPEUP &hepeup, int index) {
    index--;
    if (index < 0 || index >= hepeup.NUP) {
      edm::LogError("Generator|LHEInterface")
          << "removeParticle: Index " << (index + 1) << " out of bounds." << std::endl;
      return;
    }
 
    std::pair<int, int> mo = hepeup.MOTHUP[index];
 
    hepeup.IDUP.erase(hepeup.IDUP.begin() + index);
    hepeup.ISTUP.erase(hepeup.ISTUP.begin() + index);
    hepeup.MOTHUP.erase(hepeup.MOTHUP.begin() + index);
    hepeup.ICOLUP.erase(hepeup.ICOLUP.begin() + index);
    hepeup.PUP.erase(hepeup.PUP.begin() + index);
    hepeup.VTIMUP.erase(hepeup.VTIMUP.begin() + index);
    hepeup.SPINUP.erase(hepeup.SPINUP.begin() + index);
 
    hepeup.NUP--;
 
    index++;
    for (int i = 0; i < hepeup.NUP; i++) {
      if (hepeup.MOTHUP[i].first == index) {
        if (hepeup.MOTHUP[i].second > 0)
          edm::LogError("Generator|LHEInterface")
              << "removeParticle: Particle " << (i + 2) << " has two mothers." << std::endl;
        hepeup.MOTHUP[i] = mo;
      }
 
      if (hepeup.MOTHUP[i].first > index)
        hepeup.MOTHUP[i].first--;
      if (hepeup.MOTHUP[i].second > index)
        hepeup.MOTHUP[i].second--;
    }
  }
 
  void LHEEvent::removeResonances(const std::vector<int> &ids) {
    for (int i = 1; i <= hepeup.NUP; i++) {
      int id = std::abs(hepeup.IDUP[i - 1]);
      if (hepeup.MOTHUP[i - 1].first > 0 && hepeup.MOTHUP[i - 1].second > 0 &&
          std::find(ids.begin(), ids.end(), id) != ids.end())
        removeParticle(hepeup, i--);
    }
  }
 
  void LHEEvent::count(LHERunInfo::CountMode mode, double weight, double matchWeight) {
    if (counted)
      edm::LogWarning("Generator|LHEInterface") << "LHEEvent::count called twice on same event!" << std::endl;
 
    runInfo->count(hepeup.IDPRUP, mode, hepeup.XWGTUP, weight, matchWeight);
 
    counted = true;
  }
 
  void LHEEvent::fillPdfInfo(HepMC::PdfInfo *info) const {
    if (pdf.get()) {
      info->set_id1(pdf->id.first);
      info->set_id2(pdf->id.second);
      info->set_x1(pdf->x.first);
      info->set_x2(pdf->x.second);
      info->set_pdf1(pdf->xPDF.first);
      info->set_pdf2(pdf->xPDF.second);
      info->set_scalePDF(pdf->scalePDF);
    } else if (hepeup.NUP >= 2) {
      const HEPRUP *heprup = getHEPRUP();
      info->set_id1(hepeup.IDUP[0] == 21 ? 0 : hepeup.IDUP[0]);
      info->set_id2(hepeup.IDUP[1] == 21 ? 0 : hepeup.IDUP[1]);
      info->set_x1(std::abs(hepeup.PUP[0][2] / heprup->EBMUP.first));
      info->set_x2(std::abs(hepeup.PUP[1][2] / heprup->EBMUP.second));
      info->set_pdf1(-1.0);
      info->set_pdf2(-1.0);
      info->set_scalePDF(hepeup.SCALUP);
    } else {
      info->set_x1(-1.0);
      info->set_x2(-1.0);
      info->set_pdf1(-1.0);
      info->set_pdf2(-1.0);
      info->set_scalePDF(hepeup.SCALUP);
    }
  }
 
  void LHEEvent::fillEventInfo(HepMC::GenEvent *event) const {
    event->set_signal_process_id(hepeup.IDPRUP);
    event->set_event_scale(hepeup.SCALUP);
    event->set_alphaQED(hepeup.AQEDUP);
    event->set_alphaQCD(hepeup.AQCDUP);
  }
 
  std::unique_ptr<HepMC::GenEvent> LHEEvent::asHepMCEvent() const {
    std::unique_ptr<HepMC::GenEvent> hepmc(new HepMC::GenEvent);
 
    hepmc->set_signal_process_id(hepeup.IDPRUP);
    hepmc->set_event_scale(hepeup.SCALUP);
    hepmc->set_alphaQED(hepeup.AQEDUP);
    hepmc->set_alphaQCD(hepeup.AQCDUP);
 
    unsigned int nup = hepeup.NUP;  // particles in event
 
    // any particles in HEPEUP block?
    if (!nup) {
      edm::LogWarning("Generator|LHEInterface") << "Les Houches Event does not contain any partons. "
                                                << "Not much to convert.";
      return hepmc;
    }
 
    // stores (pointers to) converted particles
    std::vector<HepMC::GenParticle *> genParticles;
    std::vector<HepMC::GenVertex *> genVertices;
 
    // I. convert particles
    for (unsigned int i = 0; i < nup; i++)
      genParticles.push_back(makeHepMCParticle(i));
 
    // II. loop again to build vertices
    for (unsigned int i = 0; i < nup; i++) {
      unsigned int mother1 = hepeup.MOTHUP.at(i).first;
      unsigned int mother2 = hepeup.MOTHUP.at(i).second;
      double cTau = hepeup.VTIMUP.at(i);  // decay time
 
      // current particle has a mother? --- Sorry, parent! We're PC.
      if (mother1) {
        mother1--;  // FORTRAN notation!
        if (mother2)
          mother2--;
        else
          mother2 = mother1;
 
        HepMC::GenParticle *in_par = genParticles.at(mother1);
        HepMC::GenVertex *current_vtx = in_par->end_vertex();  // vertex of first mother
 
        if (!current_vtx) {
          current_vtx = new HepMC::GenVertex(HepMC::FourVector(0, 0, 0, cTau));
 
          // add vertex to event
          genVertices.push_back(current_vtx);
        }
 
        for (unsigned int j = mother1; j <= mother2; j++)  // set mother-daughter relations
          if (!genParticles.at(j)->end_vertex())
            current_vtx->add_particle_in(genParticles.at(j));
 
        // connect THIS outgoing particle to current vertex
        current_vtx->add_particle_out(genParticles.at(i));
      }
    }
 
    checkHepMCTree(hepmc.get());
 
    // III. restore color flow
    // ok, nobody knows how to do it so far...
 
    // IV. fill run information
    const HEPRUP *heprup = getHEPRUP();
 
    // set beam particles
    HepMC::GenParticle *b1 = new HepMC::GenParticle(
        HepMC::FourVector(0.0, 0.0, +heprup->EBMUP.first, heprup->EBMUP.first), heprup->IDBMUP.first);
    HepMC::GenParticle *b2 = new HepMC::GenParticle(
        HepMC::FourVector(0.0, 0.0, -heprup->EBMUP.second, heprup->EBMUP.second), heprup->IDBMUP.second);
    b1->set_status(3);
    b2->set_status(3);
 
    HepMC::GenVertex *v1 = new HepMC::GenVertex();
    HepMC::GenVertex *v2 = new HepMC::GenVertex();
    v1->add_particle_in(b1);
    v2->add_particle_in(b2);
 
    hepmc->add_vertex(v1);
    hepmc->add_vertex(v2);
    hepmc->set_beam_particles(b1, b2);
 
    // first two particles have to be the hard partons going into the interaction
    if (genParticles.size() >= 2) {
      if (!genParticles.at(0)->production_vertex() && !genParticles.at(1)->production_vertex()) {
        v1->add_particle_out(genParticles.at(0));
        v2->add_particle_out(genParticles.at(1));
      } else
        edm::LogWarning("Generator|LHEInterface") << "Initial partons do already have a"
                                                     " production vertex. "
                                                  << std::endl
                                                  << "Beam particles not connected.";
    } else
      edm::LogWarning("Generator|LHEInterface") << "Can't find any initial partons to be"
                                                   " connected to the beam particles.";
 
    for (std::vector<HepMC::GenVertex *>::const_iterator iter = genVertices.begin(); iter != genVertices.end(); ++iter)
      hepmc->add_vertex(*iter);
 
    // do some more consistency checks
    for (unsigned int i = 0; i < nup; i++) {
      if (!genParticles.at(i)->parent_event()) {
        edm::LogWarning("Generator|LHEInterface") << "Not all LHE particles could be stored"
                                                     "  stored in the HepMC event. "
                                                  << std::endl
                                                  << "Check the mother-daughter relations"
                                                     " in the given LHE input file.";
        break;
      }
    }
 
    hepmc->set_signal_process_vertex(const_cast<HepMC::GenVertex *>(findSignalVertex(hepmc.get(), false)));
 
    return hepmc;
  }
 
  HepMC::GenParticle *LHEEvent::makeHepMCParticle(unsigned int i) const {
    HepMC::GenParticle *particle = new HepMC::GenParticle(
        HepMC::FourVector(hepeup.PUP.at(i)[0], hepeup.PUP.at(i)[1], hepeup.PUP.at(i)[2], hepeup.PUP.at(i)[3]),
        hepeup.IDUP.at(i));
 
    int status = hepeup.ISTUP.at(i);
 
    particle->set_generated_mass(hepeup.PUP.at(i)[4]);
    particle->set_status(status > 0 ? (status == 2 ? 3 : status) : 3);
 
    return particle;
  }
 
  bool LHEEvent::checkHepMCTree(const HepMC::GenEvent *event) {
    double px = 0, py = 0, pz = 0, E = 0;
 
    for (HepMC::GenEvent::particle_const_iterator iter = event->particles_begin(); iter != event->particles_end();
         iter++) {
      int status = (*iter)->status();
      HepMC::FourVector fv = (*iter)->momentum();
 
      // incoming particles
      if (status == 3 && *iter != event->beam_particles().first && *iter != event->beam_particles().second) {
        px -= fv.px();
        py -= fv.py();
        pz -= fv.pz();
        E -= fv.e();
      }
 
      // outgoing particles
      if (status == 1) {
        px += fv.px();
        py += fv.py();
        pz += fv.pz();
        E += fv.e();
      }
    }
 
    if (px * px + py * py + pz * pz + E * E > 0.1) {
      edm::LogWarning("Generator|LHEInterface")
          << "Energy-momentum badly conserved. " << std::setprecision(3) << "sum p_i  = [" << std::setw(7) << E << ", "
          << std::setw(7) << px << ", " << std::setw(7) << py << ", " << std::setw(7) << pz << "]";
 
      return false;
    }
 
    return true;
  }
 
  const HepMC::GenVertex *LHEEvent::findSignalVertex(const HepMC::GenEvent *event, bool status3) {
    double largestMass2 = -9.0e-30;
    const HepMC::GenVertex *vertex = nullptr;
    for (HepMC::GenEvent::vertex_const_iterator iter = event->vertices_begin(); iter != event->vertices_end(); ++iter) {
      if ((*iter)->particles_in_size() < 2)
        continue;
      if ((*iter)->particles_out_size() < 1 ||
          ((*iter)->particles_out_size() == 1 &&
           (!(*(*iter)->particles_out_const_begin())->end_vertex() ||
            !(*(*iter)->particles_out_const_begin())->end_vertex()->particles_out_size())))
        continue;
 
      double px = 0.0, py = 0.0, pz = 0.0, E = 0.0;
      bool hadStatus3 = false;
      for (HepMC::GenVertex::particles_out_const_iterator iter2 = (*iter)->particles_out_const_begin();
           iter2 != (*iter)->particles_out_const_end();
           ++iter2) {
        hadStatus3 = hadStatus3 || (*iter2)->status() == 3;
        px += (*iter2)->momentum().px();
        py += (*iter2)->momentum().py();
        pz += (*iter2)->momentum().pz();
        E += (*iter2)->momentum().e();
      }
      if (status3 && !hadStatus3)
        continue;
 
      double mass2 = E * E - (px * px + py * py + pz * pz);
      if (mass2 > largestMass2) {
        vertex = *iter;
        largestMass2 = mass2;
      }
    }
 
    return vertex;
  }
 
  static void fixSubTree(HepMC::GenVertex *vertex,
                         HepMC::FourVector &_time,
                         std::set<const HepMC::GenVertex *> &visited) {
    HepMC::FourVector time = _time;
    HepMC::FourVector curTime = vertex->position();
    bool needsFixup = curTime.t() < time.t();
 
    if (!visited.insert(vertex).second && !needsFixup)
      return;
 
    if (needsFixup)
      vertex->set_position(time);
    else
      time = curTime;
 
    for (HepMC::GenVertex::particles_out_const_iterator iter = vertex->particles_out_const_begin();
         iter != vertex->particles_out_const_end();
         ++iter) {
      HepMC::GenVertex *endVertex = (*iter)->end_vertex();
      if (endVertex)
        fixSubTree(endVertex, time, visited);
    }
  }
 
  void LHEEvent::fixHepMCEventTimeOrdering(HepMC::GenEvent *event) {
    std::set<const HepMC::GenVertex *> visited;
    HepMC::FourVector zeroTime;
    for (HepMC::GenEvent::vertex_iterator iter = event->vertices_begin(); iter != event->vertices_end(); ++iter)
      fixSubTree(*iter, zeroTime, visited);
  }
 
}  // namespace lhef