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