/data/refman/pasoursint/CMSSW_5_3_3/src/GeneratorInterface/LHEInterface/src/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 boost::shared_ptr<LHERunInfo> &runInfo,
                   std::istream &in) :
        runInfo(runInfo), counted(false), readAttemptCounter(0)
{
        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;

        int idwtup = runInfo->getHEPRUP()->IDWTUP;
        if (idwtup >= 0 && hepeup.XWGTUP < 0) {
                edm::LogWarning("Generator|LHEInterface")
                        << "Non-allowed egative 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 boost::shared_ptr<LHERunInfo> &runInfo,
                   const HEPEUP &hepeup) :
        runInfo(runInfo), hepeup(hepeup), counted(false), readAttemptCounter(0)
{
}

LHEEvent::LHEEvent(const boost::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) : 0),
        comments(comments), counted(false), readAttemptCounter(0)
{
}

LHEEvent::LHEEvent(const boost::shared_ptr<LHERunInfo> &runInfo,
                   const LHEEventProduct &product) :
        runInfo(runInfo), hepeup(product.hepeup()),
        pdf(product.pdf() ? new PDF(*product.pdf()) : 0),
        comments(product.comments_begin(), product.comments_end()),
        counted(false), readAttemptCounter(0)
{
}

LHEEvent::~LHEEvent()
{
}

template<typename T>
static inline void pop(std::vector<T> &vec, unsigned int index)
{
        unsigned int size = vec.size() - 1;
        std::memmove(&vec[index], &vec[index + 1], (size - index) * sizeof(T));
}

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];

        pop(hepeup.IDUP, index);
        pop(hepeup.ISTUP, index);
        pop(hepeup.MOTHUP, index);
        pop(hepeup.ICOLUP, index);
        pop(hepeup.PUP, index);
        pop(hepeup.VTIMUP, index);
        pop(hepeup.SPINUP, index);
        hepeup.NUP--;
        hepeup.resize();

        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::auto_ptr<HepMC::GenEvent> LHEEvent::asHepMCEvent() const
{
        std::auto_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 = 0;
        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 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