CandMergerCleanOthersByDR.cc

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//****************************************************************
//
// A simple class to combine two candidate collections into a single
// collection of ptrs to the candidates
// note: it is a std::vector as the candidates are from different 
// collections
//
// collection 1 is added fully while collection 2 is deltaR cross
// cleaned against collection 2
//
// usecase: getting a unified list of e/gammas + jets for jet core 
//          regional tracking
//
//****************************************************************


#include "FWCore/Framework/interface/Frameworkfwd.h"
#include "FWCore/Framework/interface/global/EDProducer.h"

#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/MakerMacros.h"

#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/Utilities/interface/StreamID.h"

#include "DataFormats/Candidate/interface/Candidate.h"
#include "DataFormats/Common/interface/View.h"
#include "DataFormats/Common/interface/Ptr.h"
#include "DataFormats/Math/interface/deltaR.h"

class CandMergerCleanOthersByDR : public edm::global::EDProducer<> {
public:
  explicit CandMergerCleanOthersByDR(const edm::ParameterSet&);
  ~CandMergerCleanOthersByDR(){}
  
  static void fillDescriptions(edm::ConfigurationDescriptions& descriptions);
  
private:
  void produce(edm::StreamID, edm::Event&, const edm::EventSetup&)const override;

private:  
  const edm::EDGetTokenT<edm::View<reco::Candidate> > coll1Token_;
  const edm::EDGetTokenT<edm::View<reco::Candidate> > coll2Token_;
  const float maxDR2ToClean_;

};


namespace {
  double pow2(double val){return val*val;}
}

CandMergerCleanOthersByDR::CandMergerCleanOthersByDR(const edm::ParameterSet& iConfig) :
  coll1Token_(consumes<edm::View<reco::Candidate>>(iConfig.getParameter<edm::InputTag>("coll1"))),
  coll2Token_(consumes<edm::View<reco::Candidate>>(iConfig.getParameter<edm::InputTag>("coll2"))),
  maxDR2ToClean_(pow2(iConfig.getParameter<double>("maxDRToClean")))
{
  produces<std::vector<edm::Ptr<reco::Candidate> > >();
}

namespace {
  template<typename T> edm::Handle<T> getHandle(const edm::Event& iEvent,
                        const edm::EDGetTokenT<T>& token)
  {
    edm::Handle<T> handle;
    iEvent.getByToken(token,handle);
    return handle;
  }
  
  bool hasDRMatch(const reco::Candidate& cand,const std::vector<std::pair<float,float> >& etaPhisToMatch,const float maxDR2)
  {
    const float candEta = cand.eta();
    const float candPhi = cand.phi();
    for(const auto& etaPhi : etaPhisToMatch){
      if(reco::deltaR2(candEta,candPhi,etaPhi.first,etaPhi.second)<=maxDR2){
    return true;
      }
    }
    return false;
  }
}

// ------------ method called to produce the data  ------------
void
CandMergerCleanOthersByDR::produce(edm::StreamID streamID, edm::Event& iEvent, const edm::EventSetup& iSetup)const
{
  auto outColl = std::make_unique<std::vector<edm::Ptr<reco::Candidate> > >();
  
  auto coll1Handle = getHandle(iEvent,coll1Token_); 
  auto coll2Handle = getHandle(iEvent,coll2Token_); 
  
  std::vector<std::pair<float,float> > coll1EtaPhis;
  for(size_t objNr=0;objNr<coll1Handle->size();objNr++){
    edm::Ptr<reco::Candidate> objPtr(coll1Handle,objNr);
    coll1EtaPhis.push_back({objPtr->eta(),objPtr->phi()}); //just to speed up the DR match
    outColl->push_back(objPtr);
  }
  for(size_t objNr=0;objNr<coll2Handle->size();objNr++){
    edm::Ptr<reco::Candidate> objPtr(coll2Handle,objNr);
    if(!hasDRMatch(*objPtr,coll1EtaPhis,maxDR2ToClean_)){
      outColl->push_back(objPtr);
    }
  }
    
  iEvent.put(std::move(outColl));
}

// ------------ method fills 'descriptions' with the allowed parameters for the module  ------------
void
CandMergerCleanOthersByDR::fillDescriptions(edm::ConfigurationDescriptions& descriptions) {
  
  edm::ParameterSetDescription desc;
  desc.add<edm::InputTag>("coll1", edm::InputTag("egammasForCoreTracking"));
  desc.add<edm::InputTag>("coll2", edm::InputTag("jetsForCoreTracking"));
  desc.add<double>("maxDRToClean", 0.05);
  descriptions.add("candMergerCleanOthersByDR", desc);
}

//define this as a plug-in
DEFINE_FWK_MODULE(CandMergerCleanOthersByDR);