LowPtGSFToPackedCandidateLinker.cc

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#include <string>

#include "DataFormats/Candidate/interface/Candidate.h"
#include "DataFormats/ParticleFlowCandidate/interface/PFCandidate.h"
#include "DataFormats/ParticleFlowCandidate/interface/PFCandidateFwd.h"
#include "DataFormats/GsfTrackReco/interface/GsfTrack.h"
#include "DataFormats/GsfTrackReco/interface/GsfTrackFwd.h"
#include "DataFormats/PatCandidates/interface/PackedCandidate.h"
#include "DataFormats/Common/interface/Association.h"
#include "FWCore/Framework/interface/global/EDProducer.h"
#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/Framework/interface/Frameworkfwd.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/Utilities/interface/Exception.h"
#include "DataFormats/ParticleFlowReco/interface/PreId.h"
#include "DataFormats/ParticleFlowReco/interface/PreIdFwd.h"
#include "DataFormats/EgammaReco/interface/ElectronSeed.h"
#include "DataFormats/EgammaReco/interface/ElectronSeedFwd.h"
#include "FWCore/Framework/interface/MakerMacros.h"

class LowPtGSFToPackedCandidateLinker : public edm::global::EDProducer<> {
public:
    explicit LowPtGSFToPackedCandidateLinker(const edm::ParameterSet&);
    ~LowPtGSFToPackedCandidateLinker() override;
    
    void produce(edm::StreamID, edm::Event&, const edm::EventSetup&) const override;
    static void fillDescriptions(edm::ConfigurationDescriptions&);
   
private:
    const edm::EDGetTokenT<reco::PFCandidateCollection> pfcands_;
    const edm::EDGetTokenT<pat::PackedCandidateCollection> packed_;
    const edm::EDGetTokenT<pat::PackedCandidateCollection> lost_tracks_;
    const edm::EDGetTokenT<reco::TrackCollection>          tracks_;
    const edm::EDGetTokenT<edm::Association<pat::PackedCandidateCollection> > pf2packed_;
    const edm::EDGetTokenT<edm::Association<pat::PackedCandidateCollection> > lost2trk_;
    const edm::EDGetTokenT< std::vector<reco::PreId> > preid_;  
    const edm::EDGetTokenT< std::vector<reco::GsfTrack> > gsftracks_;   
};

LowPtGSFToPackedCandidateLinker::LowPtGSFToPackedCandidateLinker(const edm::ParameterSet& iConfig) :
  pfcands_{consumes<reco::PFCandidateCollection>(iConfig.getParameter<edm::InputTag>("PFCandidates"))},
  packed_{consumes<pat::PackedCandidateCollection>(iConfig.getParameter<edm::InputTag>("packedCandidates"))},
  lost_tracks_{consumes<pat::PackedCandidateCollection>(iConfig.getParameter<edm::InputTag>("lostTracks"))},
  tracks_{consumes<reco::TrackCollection>(iConfig.getParameter<edm::InputTag>("tracks"))},
  pf2packed_{consumes<edm::Association<pat::PackedCandidateCollection> >(iConfig.getParameter<edm::InputTag>("packedCandidates"))},
  lost2trk_{consumes<edm::Association<pat::PackedCandidateCollection> >(iConfig.getParameter<edm::InputTag>("lostTracks"))},
  preid_{consumes<std::vector<reco::PreId> >(iConfig.getParameter<edm::InputTag>("gsfPreID"))},
  gsftracks_{consumes<std::vector<reco::GsfTrack> >(iConfig.getParameter<edm::InputTag>("gsfTracks"))} {     
        produces< edm::Association<pat::PackedCandidateCollection> > ("packedCandidates");
        produces< edm::Association<pat::PackedCandidateCollection> > ("lostTracks");
    }

LowPtGSFToPackedCandidateLinker::~LowPtGSFToPackedCandidateLinker() {}

void LowPtGSFToPackedCandidateLinker::produce(edm::StreamID, edm::Event& iEvent, const edm::EventSetup& iSetup) const {
    edm::Handle<reco::PFCandidateCollection> pfcands;
    iEvent.getByToken(pfcands_, pfcands);

    edm::Handle<pat::PackedCandidateCollection> packed;
    iEvent.getByToken(packed_, packed);

    edm::Handle<pat::PackedCandidateCollection> lost_tracks;
    iEvent.getByToken(lost_tracks_, lost_tracks);

    edm::Handle<edm::Association<pat::PackedCandidateCollection> > pf2packed;
    iEvent.getByToken(pf2packed_, pf2packed);

    edm::Handle<edm::Association<pat::PackedCandidateCollection> > lost2trk_assoc;
    iEvent.getByToken(lost2trk_, lost2trk_assoc);

    edm::Handle<std::vector<reco::GsfTrack> > gsftracks;
    iEvent.getByToken(gsftracks_, gsftracks);

    edm::Handle<reco::TrackCollection> tracks;
    iEvent.getByToken(tracks_, tracks);

    edm::Handle<std::vector<reco::PreId> > preid;
    iEvent.getByToken(preid_, preid);

    // collection sizes, for reference
    const size_t npf = pfcands->size();
    const size_t npacked = packed->size();
    const size_t nlost = lost_tracks->size();
    const size_t ntracks = tracks->size();
    const size_t ngsf = gsftracks->size();

    //store index mapping in vectors for easy and fast access
    std::vector<size_t> trk2packed(ntracks, npacked);
    std::vector<size_t> trk2lost(ntracks, nlost);

    //store auxiliary mappings for association
    std::vector<int> gsf2pack(ngsf, -1);
    std::vector<int> gsf2lost(ngsf, -1);

    //electrons will never store their track (they store the Gsf track)
    //map PackedPF <--> Track
    for(unsigned int icand=0; icand < npf; ++icand) {
        edm::Ref<reco::PFCandidateCollection> pf_ref(pfcands,icand);
        const reco::PFCandidate &cand = pfcands->at(icand); 
        auto packed_ref = (*pf2packed)[pf_ref];
        if(cand.charge() && packed_ref.isNonnull() && cand.trackRef().isNonnull() 
             && cand.trackRef().id() == tracks.id() ) { 
            size_t trkid = cand.trackRef().index();
            size_t packid = packed_ref.index();
            trk2packed[trkid] = packid;
        }
    }

    //map LostTrack <--> Track
    for(unsigned int itrk=0; itrk < ntracks; ++itrk) {
        reco::TrackRef key(tracks, itrk);
        pat::PackedCandidateRef lostTrack = (*lost2trk_assoc)[key];
        if(lostTrack.isNonnull()) {
            size_t ilost = lostTrack.index(); //assumes that LostTracks are all made from the same track collection
            trk2lost[itrk] = ilost;
        }
    }   

    //map Track --> GSF and fill GSF --> PackedCandidates and GSF --> Lost associations
    for(unsigned int igsf=0; igsf < ngsf; ++igsf) {
        reco::GsfTrackRef gref(gsftracks, igsf);
        reco::TrackRef trk = preid->at(
            gref->seedRef().castTo<reco::ElectronSeedRef>().index()
            ).trackRef();
        size_t trkid = trk.index();

        if(trk2packed[trkid] != npacked) {
            gsf2pack[igsf] = trk2packed[trkid];
        } 
        if(trk2lost[trkid] != nlost) {
            gsf2lost[igsf] = trk2lost[trkid];
        }
    }

    // create output collections from the mappings
    auto assoc_gsf2pack = std::make_unique< edm::Association<pat::PackedCandidateCollection> >(packed);
    edm::Association<pat::PackedCandidateCollection>::Filler gsf2pack_filler(*assoc_gsf2pack);
    gsf2pack_filler.insert(gsftracks, gsf2pack.begin(), gsf2pack.end());
    gsf2pack_filler.fill(); 
    iEvent.put(std::move(assoc_gsf2pack), "packedCandidates");   

    auto assoc_gsf2lost = std::make_unique< edm::Association<pat::PackedCandidateCollection> >(lost_tracks);
    edm::Association<pat::PackedCandidateCollection>::Filler gsf2lost_filler(*assoc_gsf2lost);
    gsf2lost_filler.insert(gsftracks, gsf2lost.begin(), gsf2lost.end());
    gsf2lost_filler.fill();
    iEvent.put(std::move(assoc_gsf2lost), "lostTracks");
}

void LowPtGSFToPackedCandidateLinker::fillDescriptions(edm::ConfigurationDescriptions& descriptions) {
    edm::ParameterSetDescription desc;
    desc.add<edm::InputTag>("PFCandidates", edm::InputTag("particleFlow"));
    desc.add<edm::InputTag>("packedCandidates", edm::InputTag("packedPFCandidates"));
    desc.add<edm::InputTag>("lostTracks", edm::InputTag("lostTracks"));
    desc.add<edm::InputTag>("tracks", edm::InputTag("generalTracks"));
    desc.add<edm::InputTag>("gsfPreID", edm::InputTag("lowPtGsfElectronSeeds"));
    desc.add<edm::InputTag>("gsfTracks", edm::InputTag("lowPtGsfEleGsfTracks"));
    descriptions.add("lowPtGsfLinksDefault", desc);
}

DEFINE_FWK_MODULE(LowPtGSFToPackedCandidateLinker);