/data/refman/pasoursint/CMSSW_4_4_5_patch3/src/RecoParticleFlow/PFProducer/src/PFBlockAlgo.cc

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#include "RecoParticleFlow/PFProducer/interface/PFBlockAlgo.h"
#include "RecoParticleFlow/PFProducer/interface/Utils.h"
#include "RecoParticleFlow/PFClusterTools/interface/LinkByRecHit.h"
#include "DataFormats/ParticleFlowReco/interface/PFBlock.h"
#include "DataFormats/TrackReco/interface/Track.h"
#include "DataFormats/ParticleFlowReco/interface/PFDisplacedVertex.h" // gouzevitch

#include "DataFormats/ParticleFlowReco/interface/PFRecHit.h"

#include <stdexcept>
#include "TMath.h"

using namespace std;
using namespace reco;

//for debug only 
//#define PFLOW_DEBUG

const PFBlockAlgo::Mask PFBlockAlgo::dummyMask_;

PFBlockAlgo::PFBlockAlgo() : 
  blocks_( new reco::PFBlockCollection ),
  DPtovPtCut_(std::vector<double>(4,static_cast<double>(999.))),
  NHitCut_(std::vector<unsigned int>(4,static_cast<unsigned>(0))), 
  useIterTracking_(true),
  photonSelector_(0),
  debug_(false) {}



void PFBlockAlgo::setParameters( std::vector<double>& DPtovPtCut,
                                 std::vector<unsigned int>& NHitCut,
                                 bool useConvBremPFRecTracks,
                                 bool useIterTracking,
                                 int nuclearInteractionsPurity,
                                 bool useEGPhotons,
                                 std::vector<double>& photonSelectionCuts) {
  
  DPtovPtCut_    = DPtovPtCut;
  NHitCut_       = NHitCut;
  useIterTracking_ = useIterTracking;
  useConvBremPFRecTracks_ = useConvBremPFRecTracks;
  nuclearInteractionsPurity_ = nuclearInteractionsPurity;
  useEGPhotons_ = useEGPhotons;
  // Pt cut; Track iso (constant + slope), Ecal iso (constant + slope), HCAL iso (constant+slope), H/E
  if(useEGPhotons_)
    photonSelector_ = new PhotonSelectorAlgo(photonSelectionCuts[0],   
                                             photonSelectionCuts[1], photonSelectionCuts[2],   
                                             photonSelectionCuts[3], photonSelectionCuts[4],    
                                             photonSelectionCuts[5], photonSelectionCuts[6],    
                                             photonSelectionCuts[7],
                                             photonSelectionCuts[8],
                                             photonSelectionCuts[9],
                                             photonSelectionCuts[10]
                                             );


}

// Glowinski & Gouzevitch
void PFBlockAlgo::setUseOptimization(bool useKDTreeTrackEcalLinker)
{
  useKDTreeTrackEcalLinker_ = useKDTreeTrackEcalLinker;
}
// !Glowinski & Gouzevitch


PFBlockAlgo::~PFBlockAlgo() {

#ifdef PFLOW_DEBUG
  if(debug_)
    cout<<"~PFBlockAlgo - number of remaining elements: "
        <<elements_.size()<<endl;
#endif

  if(photonSelector_) delete photonSelector_;

}

void 
PFBlockAlgo::findBlocks() {

  // Glowinski & Gouzevitch
  if (useKDTreeTrackEcalLinker_) {
    TELinker_.process();
    THLinker_.process();
    PSELinker_.process();
  }
  // !Glowinski & Gouzevitch

  // the blocks have not been passed to the event, and need to be cleared
  if(blocks_.get() )blocks_->clear();
  else 
    blocks_.reset( new reco::PFBlockCollection );

  blocks_->reserve(elements_.size());
  for(IE ie = elements_.begin(); 
      ie != elements_.end();) {
    
#ifdef PFLOW_DEBUG
    if(debug_) {
      cout<<" PFBlockAlgo::findBlocks() ----------------------"<<endl;
      cout<<" element "<<**ie<<endl;
      cout<<" creating new block"<<endl;
    }
#endif

    blocks_->push_back( PFBlock() );
    
    vector< PFBlockLink > links;

    //    list< IE > used;
    ie = associate( elements_.end() , ie, links );

    packLinks( blocks_->back(), links );
  }
}




PFBlockAlgo::IE 
PFBlockAlgo::associate( IE last, 
                        IE next, 
                        vector<PFBlockLink>& links ) {

    
#ifdef PFLOW_DEBUG
  if(debug_ ) cout<<"PFBlockAlgo::associate start ----"<<endl;
#endif

  if( last!= elements_.end() ) {
    PFBlockLink::Type linktype = PFBlockLink::NONE;
    double dist = -1;
    PFBlock::LinkTest linktest = PFBlock::LINKTEST_RECHIT;
    link( *last, *next, linktype, linktest, dist ); 

    
    if(dist<-0.5) {
#ifdef PFLOW_DEBUG
      if(debug_ ) cout<<"link failed"<<endl;
#endif
      return ++next; // association failed
    }
    else {
      // add next element to the current pflowblock
      blocks_->back().addElement( *next );  

      // (*next)->setIndex( blocks_->back()->indexToLastElement() );
      
      // this is not necessary? 
      // next->setPFBlock(this);
      
      // create a link between next and last      
      links.push_back( PFBlockLink(linktype, 
                                   linktest,
                                   dist,
                                   (*last)->index(), 
                                   (*next)->index() ) );
      // not necessary ?
      //       next->connect( links_.size()-1 );
      //       last->connect( links_.size()-1 );      
    }
  }
  else {
    // add next element to this eflowblock
#ifdef PFLOW_DEBUG
    if(debug_ ) cout<<"adding to block element "<<(**next)<<endl;
#endif
    blocks_->back().addElement( *next );
    // (*next)->setIndex( blocks_->back()->indexToLastElement() );   
    // next->setPFBlock(this);
  }

  // recursive call: associate next and other unused elements 
  
  //   IE afterNext = next;
  //   ++afterNext;
  //  cout<<"last "<<**last<<" next "<<**next<<endl;
  
  for(IE ie = elements_.begin(); 
      ie != elements_.end();) {
    
    if( ie == last || ie == next ) {
      ++ie;
      continue;
    } 
    bool bTestLink = linkPrefilter(*next, *ie);

    if(!bTestLink) {
      ++ie;
      continue;
    }
    
    // *ie already included to a block
    if( (*ie)->locked() ) {
#ifdef PFLOW_DEBUG
      if(debug_ ) cout<<"element "<<(**ie)<<"already used"<<endl;
#endif
      ++ie;
      continue;
    }    
    
    
#ifdef PFLOW_DEBUG
    if(debug_ ) cout<<"calling associate "<<(**next)<<" & "<<(**ie)<<endl;
#endif
    ie = associate(next, ie, links);
  }       

#ifdef PFLOW_DEBUG
  if(debug_ ) {
    cout<<"**** deleting element "<<endl;
    cout<<**next<<endl;
  }
#endif
  delete *next;

#ifdef PFLOW_DEBUG
  if(debug_ ) {
    cout<<"**** removing element "<<endl;
  }
#endif

  IE iteratorToNextFreeElement = elements_.erase( next );

#ifdef PFLOW_DEBUG
  if(debug_ ) cout<<"PFBlockAlgo::associate stop ----"<<endl;
#endif

  return iteratorToNextFreeElement;
}



void 
PFBlockAlgo::packLinks( reco::PFBlock& block, 
                        const vector<PFBlockLink>& links ) const {
  
  
  const edm::OwnVector< reco::PFBlockElement >& els = block.elements();
  
  block.bookLinkData();

  unsigned elsize = els.size();
  unsigned ilStart = 0;
  //First Loop: update all link data
  for( unsigned i1=0; i1<elsize; ++i1 ) {
    for( unsigned i2=0; i2<i1; ++i2 ) {
      
      // no reflexive link
      //if( i1==i2 ) continue;
      
      double dist = -1;
      
      bool linked = false;
      PFBlock::LinkTest linktest 
        = PFBlock::LINKTEST_RECHIT; 

      // are these elements already linked ?
      // this can be optimized

      unsigned linksize = links.size();
      for( unsigned il = ilStart; il<linksize; ++il ) {
        // The following three lines exploits the increasing-element2 ordering of links.
        if ( links[il].element2() < i1 ) ilStart = il;
        if ( links[il].element2() > i1 ) break;
        if( (links[il].element1() == i2 && 
             links[il].element2() == i1) ) { // yes
          
          dist = links[il].dist();
          linked = true;

          //modif-beg     
          //retrieve type of test used to get distance
          linktest = links[il].test();
#ifdef PFLOW_DEBUG
          if( debug_ )
            cout << "Reading link vector: linktest used=" 
                 << linktest 
                 << " distance = " << dist 
                 << endl; 
#endif
          //modif-end
          
          break;
        } 
      }
      
      if(!linked) {
        PFBlockLink::Type linktype = PFBlockLink::NONE;
        bool bTestLink = linkPrefilter(&els[i1], &els[i2]);
        if (bTestLink) link( & els[i1], & els[i2], linktype, linktest, dist);
      }

      //loading link data according to link test used: RECHIT 
      //block.setLink( i1, i2, chi2, block.linkData() );
#ifdef PFLOW_DEBUG
      if( debug_ )
        cout << "Setting link between elements " << i1 << " and " << i2
             << " of dist =" << dist << " computed from link test "
             << linktest << endl;
#endif
      block.setLink( i1, i2, dist, block.linkData(), linktest );
    }
  }

}



void 
PFBlockAlgo::buildGraph() {
  // loop on all blocks and create a big graph
}



void 
PFBlockAlgo::link( const reco::PFBlockElement* el1, 
                   const reco::PFBlockElement* el2, 
                   PFBlockLink::Type& linktype, 
                   reco::PFBlock::LinkTest& linktest,
                   double& dist) const {
  
  // ACHTUNG!!!! If you introduce new links check that they are not desabled in linkPrefilter!!!!


  dist=-1.;
  linktest = PFBlock::LINKTEST_RECHIT; //rechit by default 

  PFBlockElement::Type type1 = el1->type();
  PFBlockElement::Type type2 = el2->type();

  linktype = static_cast<PFBlockLink::Type>
    ((1<< (type1-1) ) | (1<< (type2-1) ));

  if(debug_ ) std::cout << " PFBlockAlgo links type1 " << type1 << " type2 " << type2 << std::endl;

  PFBlockElement::Type lowType = type1;
  PFBlockElement::Type highType = type2;
  const PFBlockElement* lowEl = el1;
  const PFBlockElement* highEl = el2;
  
  if(type1>type2) {
    lowType = type2;
    highType = type1;
    lowEl = el2;
    highEl = el1;
  }
  
  switch(linktype) {
  // Track and preshower cluster links are not used for now - disable
  case PFBlockLink::PS1andECAL:
  case PFBlockLink::PS2andECAL:
    {
      // if(debug_ ) cout<< "PSandECAL" <<endl;
      PFClusterRef  psref = lowEl->clusterRef();
      PFClusterRef  ecalref = highEl->clusterRef();
      assert( !psref.isNull() );
      assert( !ecalref.isNull() );

      // Check if the linking has been done using the KDTree algo
      // Glowinski & Gouzevitch
      if ( useKDTreeTrackEcalLinker_ && lowEl->isMultilinksValide() ) { // KDTree algo
        const reco::PFMultilinksType& multilinks = lowEl->getMultilinks();
        
        double ecalPhi = ecalref->positionREP().Phi();
        double ecalEta = ecalref->positionREP().Eta();
        
        // Check if the link PS/Ecal exist
        reco::PFMultilinksType::const_iterator mlit = multilinks.begin();
        for (; mlit != multilinks.end(); ++mlit)
          if ((mlit->first == ecalPhi) && (mlit->second == ecalEta))
            break;
        
        // If the link exist, we fill dist and linktest. We use old algorithme method.
        if (mlit != multilinks.end()){
          double xPS = psref->position().X();
          double yPS = psref->position().Y();
          double xECAL  = ecalref->position().X();
          double yECAL  = ecalref->position().Y();

          dist = LinkByRecHit::computeDist(xECAL/1000.,yECAL/1000.,xPS/1000.  ,yPS/1000, false);
        }

      } else { //Old algorithm
        dist = LinkByRecHit::testECALAndPSByRecHit( *ecalref, *psref ,debug_);
      }

      //      linktest = PFBlock::LINKTEST_RECHIT;
      
      break;
    }
  case PFBlockLink::TRACKandECAL:
    {
      if(debug_ ) cout<<"TRACKandECAL"<<endl;

      PFRecTrackRef trackref = lowEl->trackRefPF();
      PFClusterRef  clusterref = highEl->clusterRef();
      assert( !trackref.isNull() );
      assert( !clusterref.isNull() );

      if(debug_ ) std::cout << " Track pt " << trackref->trackRef()->pt() << std::endl;

      // Check if the linking has been done using the KDTree algo
      // Glowinski & Gouzevitch
      if ( useKDTreeTrackEcalLinker_ && lowEl->isMultilinksValide() ) { //KDTree Algo

        const reco::PFMultilinksType& multilinks = lowEl->getMultilinks();
        double ecalphi = clusterref->positionREP().Phi();
        double ecaleta = clusterref->positionREP().Eta();

        // Check if the link Track/Ecal exist
        reco::PFMultilinksType::const_iterator mlit = multilinks.begin();
        for (; mlit != multilinks.end(); ++mlit)
          if ((mlit->first == ecalphi) && (mlit->second == ecaleta))
            break;

        
        // If the link exist, we fill dist and linktest. We use old algorithme method.
        if (mlit != multilinks.end()){


          //Should be something like this :
          //      const reco::PFRecTrack& track = *trackref;
          //instead of this :
          /*
          reco::PFRecTrack track (*trackref);
          const reco::PFTrajectoryPoint& atECAL_tmp = 
            (*trackref).extrapolatedPoint( reco::PFTrajectoryPoint::ECALShowerMax );
          if(std::abs(atECAL_tmp.positionREP().Eta())<1E-9 &&
             std::abs(atECAL_tmp.positionREP().Phi())<1E-9 &&
             atECAL_tmp.positionREP().R()<1E-9) 
            track.calculatePositionREP();
          */

          const reco::PFTrajectoryPoint& atECAL = 
            trackref->extrapolatedPoint( reco::PFTrajectoryPoint::ECALShowerMax );
          
          double tracketa = atECAL.positionREP().Eta();
          double trackphi = atECAL.positionREP().Phi();

          dist = LinkByRecHit::computeDist(ecaleta, ecalphi, tracketa, trackphi);
        }

      } else {// Old algorithm
        if ( trackref->extrapolatedPoint( reco::PFTrajectoryPoint::ECALShowerMax ).isValid() )
          dist = LinkByRecHit::testTrackAndClusterByRecHit( *trackref, *clusterref, false, debug_ );
        else
          dist = -1.;
      }

      if ( debug_ ) { 
        if( dist > 0. ) { 
          std::cout << " Here a link has been established"
                    << " between a track an Ecal with dist  " 
                    << dist <<  std::endl;
        } else
          std::cout << " No link found " << std::endl;
      }
      
      //     linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::TRACKandHCAL:
    {
      //      if(debug_ ) cout<<"TRACKandHCAL"<<endl;

      PFRecTrackRef trackref = lowEl->trackRefPF();
      PFClusterRef  clusterref = highEl->clusterRef();
      assert( !trackref.isNull() );
      assert( !clusterref.isNull() );

      // Check if the linking has been done using the KDTree algo
      // Glowinski & Gouzevitch
      if ( useKDTreeTrackEcalLinker_ && highEl->isMultilinksValide() ) { //KDTree Algo
        
        const reco::PFMultilinksType& multilinks = highEl->getMultilinks();

        /*
        reco::PFRecTrack track (*trackref);
        const reco::PFTrajectoryPoint& atHCALEntrance_tmp = 
          (*trackref).extrapolatedPoint( reco::PFTrajectoryPoint::HCALEntrance);
        if (std::abs(atHCALEntrance_tmp.positionREP().Eta())<1E-9 &&
            std::abs(atHCALEntrance_tmp.positionREP().Phi())<1E-9 &&
            atHCALEntrance_tmp.positionREP().R()<1E-9)   
          track.calculatePositionREP();
        */

        const reco::PFTrajectoryPoint& atHCAL = 
          trackref->extrapolatedPoint(reco::PFTrajectoryPoint::HCALEntrance);
        
          
        double tracketa = atHCAL.positionREP().Eta();
        double trackphi = atHCAL.positionREP().Phi();

        // Check if the link Track/Ecal exist
        reco::PFMultilinksType::const_iterator mlit = multilinks.begin();
        for (; mlit != multilinks.end(); ++mlit)
          if ((mlit->first == trackphi) && (mlit->second == tracketa))
            break;

        // If the link exist, we fill dist and linktest. We use old algorithme method.
        if (mlit != multilinks.end()){

          const reco::PFTrajectoryPoint& atHCALExit = 
            trackref->extrapolatedPoint(reco::PFTrajectoryPoint::HCALExit);
          double dHEta = atHCALExit.positionREP().Eta()-atHCAL.positionREP().Eta();
          double dHPhi = atHCALExit.positionREP().Phi()-atHCAL.positionREP().Phi(); 
          if ( dHPhi > M_PI ) dHPhi = dHPhi - 2.*M_PI;
          else if ( dHPhi < -M_PI ) dHPhi = dHPhi + 2.*M_PI; 
          tracketa += 0.1 * dHEta;
          trackphi += 0.1 * dHPhi;

          double clusterphi = clusterref->positionREP().Phi();
          double clustereta = clusterref->positionREP().Eta();
          
          dist = LinkByRecHit::computeDist(clustereta, clusterphi, tracketa, trackphi);
        }       

      } else {// Old algorithm
        if ( trackref->extrapolatedPoint( reco::PFTrajectoryPoint::HCALEntrance ).isValid() )
          dist = LinkByRecHit::testTrackAndClusterByRecHit( *trackref, *clusterref, false, debug_ );
        else
          dist = -1.;
      }

      //      linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::ECALandHCAL:
    {
      //       cout<<"ECALandHCAL"<<endl;
      PFClusterRef  ecalref = lowEl->clusterRef();
      PFClusterRef  hcalref = highEl->clusterRef();
      assert( !ecalref.isNull() );
      assert( !hcalref.isNull() );
      // PJ - 14-May-09 : A link by rechit is needed here !
      dist = testECALAndHCAL( *ecalref, *hcalref );
      // dist = -1.;
      //     linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::HFEMandHFHAD:
    {
      // cout<<"HFEMandHFHAD"<<endl;
      PFClusterRef  eref = lowEl->clusterRef();
      PFClusterRef  href = highEl->clusterRef();
      assert( !eref.isNull() );
      assert( !href.isNull() );
      dist = LinkByRecHit::testHFEMAndHFHADByRecHit( *eref, *href, debug_ );
      //    linktest = PFBlock::LINKTEST_RECHIT;
      break;      
    }

  case PFBlockLink::TRACKandTRACK:
    {
      if(debug_ ) 
        cout<<"TRACKandTRACK"<<endl;
      dist = testLinkByVertex(lowEl, highEl);
      if(debug_ ) 
        std::cout << " PFBlockLink::TRACKandTRACK dist " << dist << std::endl;
      //   linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }

  case PFBlockLink::ECALandECAL:
      {
        
        PFClusterRef  ecal1ref = lowEl->clusterRef();
        PFClusterRef  ecal2ref = highEl->clusterRef();
        assert( !ecal1ref.isNull() );
        assert( !ecal2ref.isNull() );
        if(debug_)
          cout << " PFBlockLink::ECALandECAL" << endl;
        dist = testLinkBySuperCluster(ecal1ref,ecal2ref);
        break;
      }

  case PFBlockLink::ECALandGSF:
    {
      PFClusterRef  clusterref = lowEl->clusterRef();
      assert( !clusterref.isNull() );
      const reco::PFBlockElementGsfTrack *  GsfEl =  dynamic_cast<const reco::PFBlockElementGsfTrack*>(highEl);
      const PFRecTrack * myTrack =  &(GsfEl->GsftrackPF());
      if ( myTrack->extrapolatedPoint( reco::PFTrajectoryPoint::ECALShowerMax ).isValid() )
        dist = LinkByRecHit::testTrackAndClusterByRecHit( *myTrack, *clusterref, false, debug_ );
      else
        dist = -1.;
      //   linktest = PFBlock::LINKTEST_RECHIT;
      
      if ( debug_ ) {
        if ( dist > 0. ) {
          std::cout << " Here a link has been established" 
                    << " between a GSF track an Ecal with dist  " 
                    << dist <<  std::endl;
        } else {
          if(debug_ ) std::cout << " No link found " << std::endl;
        }
      }
      break;
    }
  case PFBlockLink::TRACKandGSF:
    {
      PFRecTrackRef trackref = lowEl->trackRefPF();
      assert( !trackref.isNull() );
      const reco::PFBlockElementGsfTrack *  GsfEl =  
        dynamic_cast<const reco::PFBlockElementGsfTrack*>(highEl);
      GsfPFRecTrackRef gsfref = GsfEl->GsftrackRefPF();
      reco::TrackRef kftrackref= (*trackref).trackRef();
      assert( !gsfref.isNull() );
      PFRecTrackRef refkf = (*gsfref).kfPFRecTrackRef();
      if(refkf.isNonnull()) {
        reco::TrackRef gsftrackref = (*refkf).trackRef();
        if (gsftrackref.isNonnull()&&kftrackref.isNonnull()) {
          if (kftrackref == gsftrackref) { 
            dist = 0.001;
          } else { 
            dist = -1.;
          }
        } else { 
          dist = -1.;
        }
      } else {
        dist = -1.;
      }
      
      
      if(useConvBremPFRecTracks_) {
        if(lowEl->isLinkedToDisplacedVertex()){
          vector<PFRecTrackRef> pfrectrack_vec = GsfEl->GsftrackRefPF()->convBremPFRecTrackRef();
          if(pfrectrack_vec.size() > 0){
            for(unsigned int iconv = 0; iconv <  pfrectrack_vec.size(); ++iconv) {
              if( lowEl->trackType(reco::PFBlockElement::T_FROM_GAMMACONV)) {
                // use track ref
                if(kftrackref == (*pfrectrack_vec[iconv]).trackRef()) {         
                  dist = 0.001;
                }
              } 
              else{
                // use the track base ref
                reco::TrackBaseRef newTrackBaseRef((*pfrectrack_vec[iconv]).trackRef());
                reco::TrackBaseRef elemTrackBaseRef(kftrackref);              
                if(newTrackBaseRef == elemTrackBaseRef){
                  dist = 0.001;
                } 
              }
            }
          }
        }
      }
 

      break;      
    }
         
  case PFBlockLink::GSFandBREM:
    {
      const reco::PFBlockElementGsfTrack * GsfEl  =  dynamic_cast<const reco::PFBlockElementGsfTrack*>(lowEl);
      const reco::PFBlockElementBrem * BremEl =  dynamic_cast<const reco::PFBlockElementBrem*>(highEl);
      GsfPFRecTrackRef gsfref = GsfEl->GsftrackRefPF();
      GsfPFRecTrackRef bremref = BremEl->GsftrackRefPF();
      assert( !gsfref.isNull() );
      assert( !bremref.isNull() );
      if (gsfref == bremref)  { 
        dist = 0.001;
      } else { 
        dist = -1.;
      }
      break;
    }
  case PFBlockLink::GSFandGSF:
    {
      const reco::PFBlockElementGsfTrack * lowGsfEl  =  
        dynamic_cast<const reco::PFBlockElementGsfTrack*>(lowEl);
      const reco::PFBlockElementGsfTrack * highGsfEl  =  
        dynamic_cast<const reco::PFBlockElementGsfTrack*>(highEl);
      
      GsfPFRecTrackRef lowgsfref = lowGsfEl->GsftrackRefPF();
      GsfPFRecTrackRef highgsfref = highGsfEl->GsftrackRefPF();
      assert( !lowgsfref.isNull() );
      assert( !highgsfref.isNull() );
      
      if( (lowGsfEl->trackType(reco::PFBlockElement::T_FROM_GAMMACONV) == false && 
           highGsfEl->trackType(reco::PFBlockElement::T_FROM_GAMMACONV)) ||
          (highGsfEl->trackType(reco::PFBlockElement::T_FROM_GAMMACONV) == false && 
           lowGsfEl->trackType(reco::PFBlockElement::T_FROM_GAMMACONV))) {
        if(lowgsfref->trackId() == highgsfref->trackId()) {
          dist = 0.001;
        }
        else {
          dist = -1.;
        }
      }
      break;
    }
  case PFBlockLink::ECALandBREM:
    {
      PFClusterRef  clusterref = lowEl->clusterRef();
      assert( !clusterref.isNull() );
      const reco::PFBlockElementBrem * BremEl =  
        dynamic_cast<const reco::PFBlockElementBrem*>(highEl);
      const PFRecTrack * myTrack = &(BremEl->trackPF());
      /*
      double DP = (BremEl->DeltaP())*(-1.);
      double SigmaDP = BremEl->SigmaDeltaP();
      double SignBremDp = DP/SigmaDP;
      */
      bool isBrem = true;
      if ( myTrack->extrapolatedPoint( reco::PFTrajectoryPoint::ECALShowerMax ).isValid() )
        dist = LinkByRecHit::testTrackAndClusterByRecHit( *myTrack, *clusterref, isBrem, debug_);
      else
        dist = -1.;
      if( debug_ && dist > 0. ) 
        std::cout << "ECALandBREM: dist testTrackAndClusterByRecHit " 
                  << dist << std::endl;
      //   linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::HCALandGSF:
    {
      PFClusterRef  clusterref = lowEl->clusterRef();
      assert( !clusterref.isNull() );
      const reco::PFBlockElementGsfTrack *  GsfEl =  dynamic_cast<const reco::PFBlockElementGsfTrack*>(highEl);
      const PFRecTrack * myTrack =  &(GsfEl->GsftrackPF());
      if ( myTrack->extrapolatedPoint( reco::PFTrajectoryPoint::HCALEntrance ).isValid() )
        dist = LinkByRecHit::testTrackAndClusterByRecHit( *myTrack, *clusterref, false, debug_ );
      else
        dist = -1.;

      //    linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::HCALandBREM:
    {
      PFClusterRef  clusterref = lowEl->clusterRef();
      assert( !clusterref.isNull() );
      const reco::PFBlockElementBrem * BremEl =  dynamic_cast<const reco::PFBlockElementBrem*>(highEl);
      const PFRecTrack * myTrack = &(BremEl->trackPF());
      bool isBrem = true;
      if ( myTrack->extrapolatedPoint( reco::PFTrajectoryPoint::HCALEntrance ).isValid() )
        dist = LinkByRecHit::testTrackAndClusterByRecHit( *myTrack, *clusterref, isBrem, debug_);
      else
        dist = -1.;
      break;
    }
  case PFBlockLink::SCandECAL:
    {
      PFClusterRef  clusterref = lowEl->clusterRef();

      assert( !clusterref.isNull() );
      
      const reco::PFBlockElementSuperCluster * scEl = 
        dynamic_cast<const reco::PFBlockElementSuperCluster*>(highEl);
      assert (!scEl->superClusterRef().isNull());
      dist = testSuperClusterPFCluster(scEl->superClusterRef(),
                                       clusterref);
      break;
    }
    /*
  // Links between the two preshower layers are not used for now - disable
  case PFBlockLink::PS1andPS2:
    {
      PFClusterRef  ps1ref = lowEl->clusterRef();
      PFClusterRef  ps2ref = highEl->clusterRef();
      assert( !ps1ref.isNull() );
      assert( !ps2ref.isNull() );
      // PJ - 14-May-09 : A link by rechit is needed here !
      // dist = testPS1AndPS2( *ps1ref, *ps2ref );
      dist = -1.;
      linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::TRACKandPS1:
  case PFBlockLink::TRACKandPS2:
    {
      //cout<<"TRACKandPS"<<endl;
      PFRecTrackRef trackref = lowEl->trackRefPF();
      PFClusterRef  clusterref = highEl->clusterRef();
      assert( !trackref.isNull() );
      assert( !clusterref.isNull() );
      // PJ - 14-May-09 : A link by rechit is needed here !
      dist = testTrackAndPS( *trackref, *clusterref );
      linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
    // GSF Track/Brem Track and preshower cluster links are not used for now - disable
  case PFBlockLink::PS1andGSF:
  case PFBlockLink::PS2andGSF:
    {
      PFClusterRef  psref = lowEl->clusterRef();
      assert( !psref.isNull() );
      const reco::PFBlockElementGsfTrack *  GsfEl =  dynamic_cast<const reco::PFBlockElementGsfTrack*>(highEl);
      const PFRecTrack * myTrack =  &(GsfEl->GsftrackPF());
      // PJ - 14-May-09 : A link by rechit is needed here !
      dist = testTrackAndPS( *myTrack, *psref );
      linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
  case PFBlockLink::PS1andBREM:
  case PFBlockLink::PS2andBREM:
    {
      PFClusterRef  psref = lowEl->clusterRef();
      assert( !psref.isNull() );
      const reco::PFBlockElementBrem * BremEl =  dynamic_cast<const reco::PFBlockElementBrem*>(highEl);
      const PFRecTrack * myTrack = &(BremEl->trackPF());
      // PJ - 14-May-09 : A link by rechit is needed here !
      dist = testTrackAndPS( *myTrack, *psref );
      linktest = PFBlock::LINKTEST_RECHIT;
      break;
    }
    */

  default:
    dist = -1.;
    //   linktest = PFBlock::LINKTEST_RECHIT;
    // cerr<<"link type not implemented yet: 0x"<<hex<<linktype<<dec<<endl;
    // assert(0);
    return;
  }
}

double
PFBlockAlgo::testTrackAndPS(const PFRecTrack& track, 
                            const PFCluster& ps)  const {

#ifdef PFLOW_DEBUG
  //   cout<<"entering testTrackAndPS"<<endl;
  // resolution of PS cluster dxdx and dydy from strip pitch and length
  double dx=0.;
  double dy=0.;
  
  unsigned layerid =0;
  // PS1: vertical strips  PS2: horizontal strips
  switch (ps.layer()) {
  case PFLayer::PS1:
    layerid = reco::PFTrajectoryPoint::PS1;
    
    // vertical strips in PS1, measure x with pitch precision
    dx = resPSpitch_;
    dy = resPSlength_; 
    break;
  case PFLayer::PS2:
    layerid = reco::PFTrajectoryPoint::PS2;
    // horizontal strips in PS2, measure y with pitch precision
    dy = resPSpitch_;
    dx = resPSlength_;
    break;
  default:
    break;
  }
  const reco::PFTrajectoryPoint& atPS
    = track.extrapolatedPoint( layerid );  
  // did not reach PS, cannot be associated with a cluster.
  if( ! atPS.isValid() ) return -1.;   
  
  double trackx = atPS.position().X();
  double tracky = atPS.position().Y();
  double trackz = atPS.position().Z(); // MDN jan 09
  
  // ps position  x, y
  double psx = ps.position().X();
  double psy = ps.position().Y();
  // MDN Jan 09: check that trackz and psz have the same sign
  double psz = ps.position().Z();
  if( trackz*psz < 0.) return -1.; 
  
  // double chi2 = (psx-trackx)*(psx-trackx)/(dx*dx + trackresolx*trackresolx)
  //  + (psy-tracky)*(psy-tracky)/(dy*dy + trackresoly*trackresoly);

  double dist = std::sqrt( (psx-trackx)*(psx-trackx)
                         + (psy-tracky)*(psy-tracky));  
  if(debug_) cout<<"testTrackAndPS "<< dist <<" "<<endl;
  if(debug_){
    cout<<" trackx " << trackx 
        <<" tracky " << tracky 
        <<" psx "    <<  psx   
        <<" psy "    << psy    
        << endl;
  }
#endif
  
  // Return -1. as long as no link by rechit is available
  return -1.;
}

double
PFBlockAlgo::testECALAndHCAL(const PFCluster& ecal, 
                             const PFCluster& hcal)  const {
  
  //   cout<<"entering testECALAndHCAL"<<endl;
  
  double dist = fabs(ecal.positionREP().Eta()) > 2.5 ?
    LinkByRecHit::computeDist( ecal.positionREP().Eta(),
                               ecal.positionREP().Phi(), 
                               hcal.positionREP().Eta(), 
                               hcal.positionREP().Phi() )
    : 
    -1.;

#ifdef PFLOW_DEBUG
  if(debug_) cout<<"testECALAndHCAL "<< dist <<" "<<endl;
  if(debug_){
    cout<<" ecaleta " << ecal.positionREP().Eta()
        <<" ecalphi " << ecal.positionREP().Phi()
        <<" hcaleta " << hcal.positionREP().Eta()
        <<" hcalphi " << hcal.positionREP().Phi()
  }
#endif

  if ( dist < 0.2 ) return dist; 
 
  // Need to implement a link by RecHit
  return -1.;
}

double
PFBlockAlgo::testLinkBySuperCluster(const PFClusterRef& ecal1, 
                                    const PFClusterRef& ecal2)  const {
  
  //  cout<<"entering testECALAndECAL "<< pfcRefSCMap_.size() << endl;
  
  double dist = -1;
  
  // the first one is not in any super cluster
  int testindex=pfcSCVec_[ecal1.key()];
  if(testindex == -1.) return dist;
  //  if(itcheck==pfcRefSCMap_.end()) return dist;
  // now retrieve the of PFclusters in this super cluster  

  const std::vector<reco::PFClusterRef> & thePFClusters(scpfcRefs_[testindex]);
  
  unsigned npf=thePFClusters.size();
  for(unsigned i=0;i<npf;++i)
    {
      if(thePFClusters[i]==ecal2) // yes they are in the same SC 
        {
          dist=LinkByRecHit::computeDist( ecal1->positionREP().Eta(),
                                          ecal1->positionREP().Phi(), 
                                          ecal2->positionREP().Eta(), 
                                          ecal2->positionREP().Phi() );
//        std::cout << " DETA " << fabs(ecal1->positionREP().Eta()-ecal2->positionREP().Eta()) << std::endl;
//        if(fabs(ecal1->positionREP().Eta()-ecal2->positionREP().Eta())>0.2)
//          {
//            std::cout <<  " Super Cluster " <<  *(superClusters_[testindex]) << std::endl;
//            std::cout <<  " Cluster1 " <<  *ecal1 << std::endl;
//            std::cout <<  " Cluster2 " <<  *ecal2 << std::endl;
//            ClusterClusterMapping::checkOverlap(*ecal1,superClusters_,0.01,true);
//            ClusterClusterMapping::checkOverlap(*ecal2,superClusters_,0.01,true);
//          }
          return dist;
        }
    }
  return dist;
}


double
PFBlockAlgo::testSuperClusterPFCluster(const SuperClusterRef& ecal1, 
                                       const PFClusterRef& ecal2)  const {
  
  //  cout<<"entering testECALAndECAL "<< pfcRefSCMap_.size() << endl;
  
  double dist = -1;
  
  bool overlap=ClusterClusterMapping::overlap(*ecal1,*ecal2);
  
  if(overlap)   {
    dist=LinkByRecHit::computeDist( ecal1->position().eta(),
                                    ecal1->position().phi(), 
                                    ecal2->positionREP().Eta(), 
                                    ecal2->positionREP().Phi() );
    return dist;
  }
  return dist;
}



double
PFBlockAlgo::testPS1AndPS2(const PFCluster& ps1, 
                           const PFCluster& ps2)  const {
  
#ifdef PFLOW_DEBUG
  //   cout<<"entering testPS1AndPS2"<<endl;
  
  // compute chi2 in y, z using swimming formulae
  // y2 = y1 * z2/z1   and x2 = x1 *z2/z1
  
  // ps position1  x, y, z
  double x1 = ps1.position().X();
  double y1 = ps1.position().Y();
  double z1 = ps1.position().Z();
  double x2 = ps2.position().X();
  double y2 = ps2.position().Y();
  double z2 = ps2.position().Z();
  // MDN Bug correction Jan 09: check that z1 and z2 have the same sign!
  if (z1*z2<0.) -1.;
  // swim to PS2
  double scale = z2/z1;
  double x1atPS2 = x1*scale;
  double y1atPS2 = y1*scale;
  // resolution of PS cluster dxdx and dydy from strip pitch and length
  // vertical strips in PS1, measure x with pitch precision
  double dx1dx1 = resPSpitch_*resPSpitch_*scale*scale;
  double dy1dy1 = resPSlength_*resPSlength_*scale*scale;
  // horizontal strips in PS2 , measure y with pitch precision
  double dy2dy2 = resPSpitch_*resPSpitch_;
  double dx2dx2 = resPSlength_*resPSlength_;
  
  // double chi2 = (x2-x1atPS2)*(x2-x1atPS2)/(dx1dx1 + dx2dx2) 
  //  + (y2-y1atPS2)*(y2-y1atPS2)/(dy1dy1 + dy2dy2);
  
  double dist = std::sqrt( (x2-x1atPS2)*(x2-x1atPS2)
                         + (y2-y1atPS2)*(y2-y1atPS2));
    
  if(debug_) cout<<"testPS1AndPS2 "<<dist<<" "<<endl;
  if(debug_){
    cout<<" x1atPS2 "<< x1atPS2 << " dx1 "<<resPSpitch_*scale
        <<" y1atPS2 "<< y1atPS2 << " dy1 "<<resPSlength_*scale<< endl
        <<" x2 " <<x2  << " dx2 "<<resPSlength_
        <<" y2 " << y2 << " dy2 "<<resPSpitch_<< endl;
  }
#endif

  // Need a link by rechit here
  return -1.; 
}



double
PFBlockAlgo::testLinkByVertex( const reco::PFBlockElement* elt1, 
                               const reco::PFBlockElement* elt2) const {

  //  cout << "Test link by vertex between" << endl << *elt1 << endl << " and " << endl << *elt2 << endl;

  double result=-1.;

  reco::PFBlockElement::TrackType T_TO_DISP = reco::PFBlockElement::T_TO_DISP;
  reco::PFBlockElement::TrackType T_FROM_DISP = reco::PFBlockElement::T_FROM_DISP;
  PFDisplacedTrackerVertexRef ni1_TO_DISP = elt1->displacedVertexRef(T_TO_DISP);
  PFDisplacedTrackerVertexRef ni2_TO_DISP = elt2->displacedVertexRef(T_TO_DISP);
  PFDisplacedTrackerVertexRef ni1_FROM_DISP = elt1->displacedVertexRef(T_FROM_DISP);
  PFDisplacedTrackerVertexRef ni2_FROM_DISP = elt2->displacedVertexRef(T_FROM_DISP);
  
  if( ni1_TO_DISP.isNonnull() && ni2_FROM_DISP.isNonnull())
    if( ni1_TO_DISP == ni2_FROM_DISP ) { result = 1.0; return result; }

  if( ni1_FROM_DISP.isNonnull() && ni2_TO_DISP.isNonnull())
    if( ni1_FROM_DISP == ni2_TO_DISP ) { result = 1.0; return result; }

  if( ni1_FROM_DISP.isNonnull() && ni2_FROM_DISP.isNonnull())
    if( ni1_FROM_DISP == ni2_FROM_DISP ) { result = 1.0; return result; }
    
  
  if (  elt1->trackType(reco::PFBlockElement::T_FROM_GAMMACONV)  &&
             elt2->trackType(reco::PFBlockElement::T_FROM_GAMMACONV)  ) {
    
    if(debug_ ) std::cout << " testLinkByVertex On Conversions " << std::endl;
    
    if ( elt1->convRef().isNonnull() && elt2->convRef().isNonnull() ) {
      if(debug_ ) std::cout << " PFBlockAlgo.cc testLinkByVertex  Cconversion Refs are non null  " << std::endl;      
      if ( elt1->convRef() ==  elt2->convRef() ) {
        result=1.0;
        if(debug_ ) std::cout << " testLinkByVertex  Cconversion Refs are equal  " << std::endl;      
        return result;
      }
    } 
    
  }
  
  if (  elt1->trackType(reco::PFBlockElement::T_FROM_V0)  &&
             elt2->trackType(reco::PFBlockElement::T_FROM_V0)  ) {
    if(debug_ ) std::cout << " testLinkByVertex On V0 " << std::endl;
    if ( elt1->V0Ref().isNonnull() && elt2->V0Ref().isNonnull() ) {
      if(debug_ ) std::cout << " PFBlockAlgo.cc testLinkByVertex  V0 Refs are non null  " << std::endl;
      if ( elt1->V0Ref() ==  elt2->V0Ref() ) {
        result=1.0;
        if(debug_ ) std::cout << " testLinkByVertex  V0 Refs are equal  " << std::endl;
        return result;
      }
    }
  }

  return result;
}



void 
PFBlockAlgo::checkMaskSize( const reco::PFRecTrackCollection& tracks,
                            const reco::GsfPFRecTrackCollection& gsftracks, 
                            const reco::PFClusterCollection&  ecals,
                            const reco::PFClusterCollection&  hcals,
                            const reco::PFClusterCollection&  hfems,
                            const reco::PFClusterCollection&  hfhads,
                            const reco::PFClusterCollection&  pss, 
                            const reco::PhotonCollection&  egphh, 
                            const Mask& trackMask, 
                            const Mask& gsftrackMask,  
                            const Mask& ecalMask,
                            const Mask& hcalMask, 
                            const Mask& hfemMask,
                            const Mask& hfhadMask,                    
                            const Mask& psMask,
                            const Mask& phMask) const {

  if( !trackMask.empty() && 
      trackMask.size() != tracks.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the track mask is different ";
    err += "from the size of the track vector.";
    throw std::length_error( err.c_str() );
  }

  if( !gsftrackMask.empty() && 
      gsftrackMask.size() != gsftracks.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the gsf track mask is different ";
    err += "from the size of the gsftrack vector.";
    throw std::length_error( err.c_str() );
  }

  if( !ecalMask.empty() && 
      ecalMask.size() != ecals.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the ecal mask is different ";
    err += "from the size of the ecal clusters vector.";
    throw std::length_error( err.c_str() );
  }
  
  if( !hcalMask.empty() && 
      hcalMask.size() != hcals.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the hcal mask is different ";
    err += "from the size of the hcal clusters vector.";
    throw std::length_error( err.c_str() );
  }

  if( !hfemMask.empty() && 
      hfemMask.size() != hfems.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the hfem mask is different ";
    err += "from the size of the hfem clusters vector.";
    throw std::length_error( err.c_str() );
  }

  if( !hfhadMask.empty() && 
      hfhadMask.size() != hfhads.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the hfhad mask is different ";
    err += "from the size of the hfhad clusters vector.";
    throw std::length_error( err.c_str() );
  }

  if( !psMask.empty() && 
      psMask.size() != pss.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the ps mask is different ";
    err += "from the size of the ps clusters vector.";
    throw std::length_error( err.c_str() );
  }
  
    if( !phMask.empty() && 
      phMask.size() != egphh.size() ) {
    string err = "PFBlockAlgo::setInput: ";
    err += "The size of the photon mask is different ";
    err += "from the size of the photon vector.";
    throw std::length_error( err.c_str() );
  }

}


std::ostream& operator<<(std::ostream& out, const PFBlockAlgo& a) {
  if(! out) return out;
  
  out<<"====== Particle Flow Block Algorithm ======= ";
  out<<endl;
  out<<"number of unassociated elements : "<<a.elements_.size()<<endl;
  out<<endl;
  
  for(PFBlockAlgo::IEC ie = a.elements_.begin(); 
      ie != a.elements_.end(); ++ie) {
    out<<"\t"<<**ie <<endl;
  }

  
  //   const PFBlockCollection& blocks = a.blocks();

  const std::auto_ptr< reco::PFBlockCollection >& blocks
    = a.blocks(); 
    
  if(!blocks.get() ) {
    out<<"blocks already transfered"<<endl;
  }
  else {
    out<<"number of blocks : "<<blocks->size()<<endl;
    out<<endl;
    
    for(PFBlockAlgo::IBC ib=blocks->begin(); 
        ib != blocks->end(); ++ib) {
      out<<(*ib)<<endl;
    }
  }

  return out;
}

bool 
PFBlockAlgo::goodPtResolution( const reco::TrackRef& trackref) {

  double P = trackref->p();
  double Pt = trackref->pt();
  double DPt = trackref->ptError();
  unsigned int NHit = trackref->hitPattern().trackerLayersWithMeasurement();
  unsigned int NLostHit = trackref->hitPattern().trackerLayersWithoutMeasurement();
  unsigned int LostHits = trackref->numberOfLostHits();
  double sigmaHad = sqrt(1.20*1.20/P+0.06*0.06) / (1.+LostHits);

  // iteration 1,2,3,4,5 correspond to algo = 1/4,5,6,7,8,9
  unsigned int Algo = 0; 
  switch (trackref->algo()) {
  case TrackBase::ctf:
  case TrackBase::iter0:
  case TrackBase::iter1:
  case TrackBase::iter2:
    Algo = 0;
    break;
  case TrackBase::iter3:
    Algo = 1;
    break;
  case TrackBase::iter4:
    Algo = 2;
    break;
  case TrackBase::iter5:
    Algo = 3;
    break;
  case TrackBase::iter6:
    Algo = 4;
    break;
  default:
    Algo = useIterTracking_ ? 5 : 0;
    break;
  }

  // Protection against 0 momentum tracks
  if ( P < 0.05 ) return false;

  // Temporary : Reject all tracking iteration beyond 5th step. 
  if ( Algo > 4 ) return false;
 
  if (debug_) cout << " PFBlockAlgo: PFrecTrack->Track Pt= "
                   << Pt << " DPt = " << DPt << endl;
  if ( ( DPtovPtCut_[Algo] > 0. && 
         DPt/Pt > DPtovPtCut_[Algo]*sigmaHad ) || 
       NHit < NHitCut_[Algo] ) { 
    // (Algo >= 3 && LostHits != 0) ) {
    if (debug_) cout << " PFBlockAlgo: skip badly measured track"
                     << ", P = " << P 
                     << ", Pt = " << Pt 
                     << " DPt = " << DPt 
                     << ", N(hits) = " << NHit << " (Lost : " << LostHits << "/" << NLostHit << ")"
                     << ", Algo = " << Algo
                     << endl;
    if (debug_) cout << " cut is DPt/Pt < " << DPtovPtCut_[Algo] * sigmaHad << endl;
    if (debug_) cout << " cut is NHit >= " << NHitCut_[Algo] << endl;
    /*
    std::cout << "Track REJECTED : ";
    std::cout << ", P = " << P 
              << ", Pt = " << Pt 
              << " DPt = " << DPt 
              << ", N(hits) = " << NHit << " (Lost : " << LostHits << "/" << NLostHit << ")"
              << ", Algo = " << Algo
              << std::endl;
    */
    return false;
  }

  /*
  std::cout << "Track Accepted : ";
  std::cout << ", P = " << P 
       << ", Pt = " << Pt 
       << " DPt = " << DPt 
       << ", N(hits) = " << NHit << " (Lost : " << LostHits << "/" << NLostHit << ")"
       << ", Algo = " << Algo
       << std::endl;
  */
  return true;
}

int
PFBlockAlgo::muAssocToTrack( const reco::TrackRef& trackref,
                             const edm::Handle<reco::MuonCollection>& muonh) const {
  if(muonh.isValid() ) {
    for(unsigned j=0;j<muonh->size(); ++j) {
      reco::MuonRef muonref( muonh, j );
      if (muonref->track().isNonnull()) 
        if( muonref->track() == trackref ) return j;
    }
  }
  return -1; // not found
}

int 
PFBlockAlgo::muAssocToTrack( const reco::TrackRef& trackref,
                             const edm::OrphanHandle<reco::MuonCollection>& muonh) const {
  if(muonh.isValid() ) {
    for(unsigned j=0;j<muonh->size(); ++j) {
      reco::MuonRef muonref( muonh, j );
      if (muonref->track().isNonnull())
        if( muonref->track() == trackref ) return j;
    }
  }
  return -1; // not found
}


// This prefilter avoid to call associate when not necessary.
// ACHTUNG!!!! If you introduce new links check that they are not desables here
inline bool
PFBlockAlgo::linkPrefilter(const reco::PFBlockElement* last, const reco::PFBlockElement* next) const {

  PFBlockElement::Type type1 = (last)->type();
  PFBlockElement::Type type2 = (next)->type();

  if( type1==type2 ) {
    // cannot link 2 elements of the same type. 
    // except if the elements are 2 tracks or 2 ECAL
    if( type1!=PFBlockElement::TRACK && type1!=PFBlockElement::GSF &&
        type1!=PFBlockElement::ECAL) {
      return false;
    }

    if (type1==PFBlockElement::ECAL && bNoSuperclus_) return false;

    // cannot link two primary tracks  (except if they come from a V0)
    if( type1 ==PFBlockElement::TRACK) {
      if ( !((last)->isLinkedToDisplacedVertex()) || !((next)->isLinkedToDisplacedVertex())) 
      return false;
    }
  }

  if ((type1 == PFBlockElement::PS1 || type1 == PFBlockElement::PS2) && (type2 != PFBlockElement::ECAL)) return false;
  if ((type2 == PFBlockElement::PS1 || type2 == PFBlockElement::PS2) && (type1 != PFBlockElement::ECAL)) return false;
  if ((type1 == PFBlockElement::HFEM && type2 != PFBlockElement::HFHAD) || (type1 == PFBlockElement::HFHAD && type2 != PFBlockElement::HFEM)) return false;

  if (useKDTreeTrackEcalLinker_){ 
  
    if ( type1 == PFBlockElement::TRACK && type2 == PFBlockElement::ECAL)
      if ( last->isMultilinksValide()  && last->getMultilinks().size()==0 ) return false;
    if ( type2 == PFBlockElement::TRACK && type1 == PFBlockElement::ECAL)
      if ( next->isMultilinksValide() && next->getMultilinks().size()==0 ) return false;
    if ( type1 == PFBlockElement::PS1 || type1 == PFBlockElement::PS2)
      if ( last->isMultilinksValide()  && last->getMultilinks().size()==0 ) return false;
    if ( type2 == PFBlockElement::PS1 || type2 == PFBlockElement::PS2)
      if ( next->isMultilinksValide() && next->getMultilinks().size()==0 ) return false;

  }

  return true;

}