TrigZFinderInternal.cxx

Go to the documentation of this file.

/*
  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TrigZFinderInternal.h"
#include "PhiSlice.h"
 
 
 
TrigZFinderInternal::TrigZFinderInternal( const std::string& type, const std::string& name)
  : m_type (type),
    m_name (name)
{
  m_phiBinSize       = 0.2   ;
  m_usedphiBinSize   = m_phiBinSize   ;
  m_pixOnly          = false ;
  m_ROIphiWidth      = 0.2   ;
  m_minZBinSize      = 0.2   ;
  m_zBinSizeEtaCoeff = 0.1   ;
  m_dphideta         = -0.02 ;
  m_neighborMultiplier = 1.  ;
  m_numberOfPeaks    = 1     ;
  m_chargeAware      = true  ;
  m_zHistoPerPhi     = true  ;
  m_nFirstLayers     = 3     ;
  m_vrtxDistCut      = 0.    ;
  m_vrtxMixing       = 0.    ;
  m_nvrtxSeparation  = 0     ;
  m_preferCentralZ   = false ;
  m_trustSPprovider  = true  ;
  m_fullScanMode     = false ;
  m_tripletMode      = 0     ;
  m_tripletDZ        = 25.   ;
  m_tripletDK        = 0.005 ;
  m_halfTripletDK    = 0.5*m_tripletDK; // using this in internals avoids unnecessary multiplications when calculating curvature
  m_tripletDP        = 0.05  ;
 
  m_maxLayer         = 32;
 
  m_minVtxSignificance = 0;
  m_percentile         = 1;
  
  //  m_applyWeightThreshold = false;
  m_weightThreshold      = 0;
 
 
  m_IdScan_MaxNumLayers     = 20; // dphiEC depends on this value !!! 19 without IBL, 20 with IBL!!
  m_IdScan_LastBrlLayer     = 7;  // dphiBrl depends on this value
 
}
 
 
 
void TrigZFinderInternal::initializeInternal(long maxLayers, long lastBarrel )
{
  m_halfTripletDK = 0.5*m_tripletDK;
 
  m_IdScan_MaxNumLayers = maxLayers; 
  m_IdScan_LastBrlLayer = lastBarrel; 
 
  //initialize new/old layer number transform table
 
  if(maxLayers > 20) {
    int offsetEndcapPixels = lastBarrel + 1;
    int M = (maxLayers-offsetEndcapPixels)/2;
    for(int l=0;l<maxLayers;l++) {
      int oldL = l;
      if(l>lastBarrel) {
    oldL = l-offsetEndcapPixels;
    oldL = oldL < M ? oldL : oldL - M;
    oldL += offsetEndcapPixels;
      }
      m_new2old.push_back(oldL);
    }
    m_IdScan_MaxNumLayers = lastBarrel + M + 1;
  } else {
    for(int l=0;l<maxLayers;l++) m_new2old.push_back(l);
  }
 
 
  // std::cout << "m_IdScan_MaxNumLayers "    <<  m_IdScan_MaxNumLayers
  //        << "\tm_IdScan_LastBrlLayer "  <<  m_IdScan_LastBrlLayer << std::endl;
 
  // number of phi neighbours to look at
  //  if ( extraPhi.size()==0 ) 
 
  m_extraPhi = std::vector< std::vector<long> >( m_IdScan_MaxNumLayers, std::vector<long>(m_IdScan_MaxNumLayers) ); 
 
  // from TrigZFinder::initialize
  m_usedphiBinSize = m_phiBinSize;
  if ( m_usedphiBinSize < ZFinder_MinPhiSliceSize and ! m_forcePhiBinSize) m_usedphiBinSize = ZFinder_MinPhiSliceSize;
  if ( m_dphideta > 0 )                             m_dphideta *= -m_dphideta;
 
  m_invPhiSliceSize = 180./(M_PI*m_usedphiBinSize);
 
  for (long l1=0; l1<m_IdScan_MaxNumLayers-1; ++l1) {
    for (long l2=l1+1; l2<m_IdScan_MaxNumLayers; ++l2) {
      m_extraPhi[l1][l2]=1; // look at a single phi neighbour
    }
  }
 
 
  long first_layer  = 0;
  long offset_layer = 1;
  if ( m_IdScan_MaxNumLayers<20 ) { 
    first_layer  = 1; 
    offset_layer = 0; 
  }
 
  long lyrcnt = 0;
  for (long l1=0; l1<m_IdScan_LastBrlLayer; ++l1) {
    for (long l2=l1+1; l2<=m_IdScan_LastBrlLayer; ++l2) {
      double dphi = ZF_dphiBrl[lyrcnt + 7*first_layer];
      dphi *= m_neighborMultiplier;
      m_extraPhi[l1][l2]=static_cast<long>( ceil(  sqrt(dphi*dphi+ZF_phiRes*ZF_phiRes*2) * m_invPhiSliceSize ) );
 
      //      std::cout << "test 1 " << l1 << " " << l2 << "\tmax : " <<  m_IdScan_MaxNumLayers << std::endl;
 
      if (m_extraPhi[l1][l2]<1) m_extraPhi[l1][l2]=1;
      //      std::cout << "Delta Phi between layers " << l1 << " and " << l2
      //        << " = "<< ZF_dphiBrl[lyrcnt] 
      //        << " rads ( " << m_extraPhi[l1][l2] << " bins including phi resln.)\n";
      lyrcnt++;
    }
  }
 
 
 
 
 
  for ( long lyrpair=12*first_layer ;  lyrpair<117; ++lyrpair ) {
 
    double dphi = ZF_dphiEC[lyrpair*4+2];
    long     l1 = (long)ZF_dphiEC[lyrpair*4] + offset_layer; 
    long     l2 = (long)ZF_dphiEC[lyrpair*4+1] + offset_layer; 
    double  eta = ZF_dphiEC[lyrpair*4+3];
    //   std::cout << "Delta Phi between layers " << l1 << " and " << l2 
    //        << " = " << dphi << " rads @ eta=" << eta
    //        << ". Extrapolate it to eta=0.9 to get ";
    dphi = dphi + m_dphideta * ( 0.9 - eta );
    dphi *= m_neighborMultiplier;
    m_extraPhi[l1][l2]=static_cast<long>(ceil(sqrt(dphi*dphi+ZF_phiRes*ZF_phiRes*2)*m_invPhiSliceSize));
 
    if (m_extraPhi[l1][l2]<1) m_extraPhi[l1][l2]=1;
 
    //    std::cout << "test 2 " << l1 << " " << l2 << "\tmax : " <<  m_IdScan_MaxNumLayers << std::endl;
 
    // std::cout << dphi << " rads ( " << m_extraPhi[l1][l2] << " bins including phi resln.)\n";
  }
 
}
 
 
 
 
 
double TrigZFinderInternal::computeZV(double r1, double z1, double r2, double z2) const {
  return (z2*r1-z1*r2)/(r1-r2);
}
 
double TrigZFinderInternal::computeZV(double r1, double p1, double z1,
    double r2, double p2, double z2) const {
 
  double x1, y1, x2, y2;
  //sincos( p1, &y1, &x1 );  x1 *= r1;  y1 *= r1;
  //sincos( p2, &y2, &x2 );  x2 *= r2;  y2 *= r2;
  x1 = r1 * cos(p1);
  x2 = r2 * cos(p2);
  y1 = r1 * sin(p1);
  y2 = r2 * sin(p2);
 
#define _COMPUTEX0_
 
#ifdef _COMPUTEX0_
  double slope = (y2-y1)/(x2-x1);
  double invslope = 1./slope;
  double x0 = (slope*x1-y1)/(slope+invslope);
  //double y0 = -1*x0*invslope;
  double d0sqr = x0*x0*(1+invslope*invslope);
  // s1 and s2 are the track lengths from the point of closest approach
  double s1 = sqrt(r1*r1-d0sqr);
  double s2 = sqrt(r2*r2-d0sqr); // or s1*(x1-x0)/(x2-x0)
#else
  double inv_dels = 1./sqrt( (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) );
  double dotrr = x1*x2 + y1*y2;
  double s1 = ( dotrr - r1*r1 ) * inv_dels;
  double s2 = ( r2*r2 - dotrr ) * inv_dels;
#endif
 
  return (z2*s1-z1*s2)/(s1-s2);
}
 
 
long TrigZFinderInternal::fillVectors(const std::vector<TrigSiSpacePointBase>& spVec, 
                      const IRoiDescriptor& roi,
                      std::vector<double>& phi, 
                      std::vector<double>& rho, 
                      std::vector<double>& zed, 
                      std::vector<long>& lyr, 
                      std::vector<long>& filledLayers, 
                      long& numPhiSlices ) const
{
 
  std::vector<bool> lcount( m_IdScan_MaxNumLayers, false );
 
  // full scan check
  std::vector<TrigSiSpacePointBase>::const_iterator SpItr = spVec.begin();
 
  long nSPs = spVec.size();
 
  // to shift the phi of space points as if the RoI starts at phi~0
  // assumes that RoI->phi0() and the SPs are in range [-pi,+pi]
  //
  double roiPhiMin, roiPhiMax;
 
  if ( m_fullScanMode || roi.isFullscan() ) { 
    roiPhiMin = -M_PI;
    roiPhiMax =  M_PI;
  }
  else { 
    // If we trust that all the SPs are properly input, we determine the RoI phi width
    //  using the SPs themselves.
    //  If the RoI phi range is wider than pi, we keep everything as usual.
    if ( m_trustSPprovider  &&  m_ROIphiWidth < M_PI )
    {
      double roiPhiPosMin( 9.9), roiPhiPosMax(0);
      double roiPhiNegMin(-9.9), roiPhiNegMax(0);  // least negative and most negative
      for(long i=0; i<nSPs; ++i, ++SpItr)
      {
        double spphi = SpItr->phi();
        if ( spphi>0  &&  spphi>roiPhiPosMax )  roiPhiPosMax = spphi;
        if ( spphi>0  &&  spphi<roiPhiPosMin )  roiPhiPosMin = spphi;
 
        if ( spphi<0  &&  spphi<roiPhiNegMax )  roiPhiNegMax = spphi;
        if ( spphi<0  &&  spphi>roiPhiNegMin )  roiPhiNegMin = spphi;
      }
 
      if ( roiPhiNegMax > roiPhiNegMin )  { 
        // if all SPs are in (0, pi):
        roiPhiMin = roiPhiPosMin; 
        roiPhiMax = roiPhiPosMax;
      }
      else if ( roiPhiPosMax < roiPhiPosMin )  { 
        // if all SPs are in (-pi, 0):
        roiPhiMin = roiPhiNegMax; 
        roiPhiMax = roiPhiNegMin; 
      }
      else if ( roiPhiPosMin - roiPhiNegMin < M_PI )  { 
        // if we have an RoI that covers phi=0 axis
        roiPhiMin = roiPhiNegMax; 
        roiPhiMax = roiPhiPosMax;
      }
      else  { 
        // if we have an RoI that covers phi=pi axis
        roiPhiMin = roiPhiPosMin; 
        roiPhiMax = roiPhiNegMin; 
      }
 
      roiPhiMin -= 1e-10;
      roiPhiMax += 1e-10;
 
      SpItr = spVec.begin();  // rewind the iterator 
    }
    else  {
 
      if ( roi.phiMinus()==roi.phiPlus() ) { 
        roiPhiMin = roi.phi()-0.5*m_ROIphiWidth;
        roiPhiMax = roi.phi()+0.5*m_ROIphiWidth;
        if(roiPhiMin<-M_PI) roiPhiMin+=2*M_PI;
        if(roiPhiMax>M_PI)  roiPhiMax-=2*M_PI;
      }
      else {
        // already wrapped by RoiDescriptor
        roiPhiMin = roi.phiMinus();
        roiPhiMax = roi.phiPlus();
      }
 
    }
 
  }
 
 
  double dphi = roiPhiMax-roiPhiMin;
 
  if ( dphi<0 ) dphi+=2*M_PI;
 
  numPhiSlices = long (ceil( dphi*m_invPhiSliceSize ));
 
 
  bool piBound=(roiPhiMin>roiPhiMax);
 
  int icount = 0;
 
  if(!piBound)
  {
    for(long i=0; i<nSPs; ++i, ++SpItr) 
    {
      if ( SpItr->layer()>m_maxLayer || (m_pixOnly && !SpItr->isPixel()) ) continue;
      double phi2 = SpItr->phi() - roiPhiMin;
 
      if ( phi2>=0 && phi2<dphi ) { // ensures space point is in ROI
        phi[icount] = phi2;
        rho[icount] = SpItr->r();
        zed[icount] = SpItr->z();
        lyr[icount] = m_new2old[SpItr->layer()];
        lcount[lyr[icount]]=true;
        ++icount;
      }
    }
  }
  else
  {
    for(long i=0; i<nSPs; ++i, ++SpItr) 
    {
      if ( SpItr->layer()>m_maxLayer || (m_pixOnly && !SpItr->isPixel()) ) continue;
      double phi2 = SpItr->phi() - roiPhiMin;
      if( phi2<0.0) phi2+=2*M_PI;
      if ( phi2>=0 && phi2<dphi ) { // ensures space point is in ROI
        phi[icount] = phi2;
        rho[icount] = SpItr->r();
        zed[icount] = SpItr->z();
        lyr[icount] = m_new2old[SpItr->layer()];
        lcount[lyr[icount]]=true;
        ++icount;
      }
    }
  }
 
  if ( icount<nSPs ) { 
 
    //    std::cout << "TrigZFinderInternal::fillVectors() filtered some spacepoints " << nSPs 
    //        << " -> " << icount << std::endl; 
    phi.resize(icount);
    rho.resize(icount);
    zed.resize(icount);
    lyr.resize(icount);
  }
 
 
  //   Store in filledLayers the layerNumber of those layers that contain hits.
  //   So, if there are hits in layers 1,3,8 filledLayers[0]=1, filledLayers[1]=3
  //   and filledLayers[2]=8 
  //
  long filled = 0;
 
  for ( long i=0; i<m_IdScan_MaxNumLayers; ++i ) {
    if ( lcount[i] ) {
      filledLayers[filled] = i;
      ++filled;
    }
  }
 
  //  std::cout << "SUTT NSP : " << phi.size() << " " << spVec.size() << std::endl;
  //  for ( unsigned i=0 ; i<phi.size() ; i++ ) { 
  //    std::cout << "SUTT SP : " << i << "\tphi " << phi[i] << "\tz " << zed[i] << "\tr " << rho[i] << std::endl; 
  //  }
 
  return filled;
}
 
 
 
 
std::vector<typename TrigZFinderInternal::vertex>* 
TrigZFinderInternal::findZInternal( const std::vector<TrigSiSpacePointBase>& spVec, 
                    const IRoiDescriptor& roi) const {
 
  std::vector<vertex>* output = new std::vector<vertex>();
 
  long nsp = spVec.size();
  if ( !nsp ) return output; //No points - return nothing
 
  //   Creating vectors of doubles/longs for storing phi,rho,z and layer of space points.
  //   filledLayers is used to know which of all layers contain space points
  //   and fill with relevant info...
  //
  std::vector<double> phi(nsp), rho(nsp), zed(nsp);
  std::vector<long>   lyr(nsp), filledLayers(m_IdScan_MaxNumLayers);
 
  long numPhiSlices = 0;
 
  long filled = this->fillVectors( spVec, roi, phi, rho, zed, lyr, filledLayers, numPhiSlices );
 
  nsp = phi.size();
 
  //  std::cout << "SUTT roi " << roi << "nsp: " << nsp << std::endl;
 
 
  double zMin = roi.zedMinus(); 
  double zMax = roi.zedPlus(); 
 
 
  //   The bin size of the z-histo -and hence the number of bins- 
  //   depends on the RoI's |eta| (to account for worsening z-resolution)
  //
  const double ZBinSize = m_minZBinSize + m_zBinSizeEtaCoeff*fabs(roi.eta());
  const double invZBinSize = 1./ZBinSize;
 
 
  const long HalfZhistoBins = long ( ceil( 0.5*(zMax-zMin)*invZBinSize ) );
  const long NumZhistoBins = 2*HalfZhistoBins;
 
  // number of phi bins to look at will get fewer as eta increases
  const long extraPhiNeg = static_cast<long> ( floor( (0.9 - fabs(roi.eta()))*m_dphideta*m_invPhiSliceSize*m_neighborMultiplier ) );
 
 
 
  //   These are the z-Histograms
  //   Two sets are defined: {n/z}Histo[0][phi][z] will be for positively bending tracks
  //                         {n/z}Histo[1][phi][z] will be for negatively bending tracks
  //
 
  long numZhistos = m_zHistoPerPhi ? numPhiSlices : 1 ;
 
  //  std::vector < std::vector < std::vector<long>   > >  nHisto( 2, std::vector < std::vector<long>   > (numZhistos, std::vector<long>  () ) );
  //  std::vector < std::vector < std::vector<double> > >  zHisto( 2, std::vector < std::vector<double> > (numZhistos, std::vector<double>() ) );
 
  std::vector < std::vector<long>   >  nHisto[2]; // the actual z histogram count of pairs
  std::vector < std::vector<double> >  zHisto[2]; // summed z position histograms
 
  for ( int i=2 ; i-- ;  ) { nHisto[i].clear();   nHisto[i].resize(numZhistos); } 
  for ( int i=2 ; i-- ;  ) { zHisto[i].clear();   zHisto[i].resize(numZhistos); } 
 
  //  std::vector< std::vector<long> >*   nHisto = m_nHisto;
  //  std::vector< std::vector<double> >* zHisto = m_zHisto;
 
  //  nMax = 0;
 
  //Make a vector of all the PhiSlice instances we need
  std::vector< PhiSlice* > allSlices( numPhiSlices );
  for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ )
  {
    allSlices[ sliceIndex ] = new PhiSlice( sliceIndex, ZBinSize, m_invPhiSliceSize,
                        m_tripletDZ, m_halfTripletDK, m_tripletDP, zMin, zMax,
                        m_IdScan_MaxNumLayers, m_IdScan_LastBrlLayer );
  }
 
  int allSlicesSize = allSlices.size();
 
  //Populate the slices
  for ( long pointIndex = 0; pointIndex < nsp; pointIndex++ )
  {
    int phiIndex = floor( phi[ pointIndex ] * m_invPhiSliceSize );
    if (phiIndex > allSlicesSize) {
      continue;
    }
    allSlices[ phiIndex ]->AddPoint( rho[ pointIndex ], zed[ pointIndex ], phi[ pointIndex ], lyr[ pointIndex ] );
  }
 
  //Read out the slices into flat structures for the whole layers
  std::vector< std::vector< double > > allLayerRhos, allLayerZs, allLayerPhis;
  allLayerRhos.resize( m_IdScan_MaxNumLayers );
  allLayerZs.resize( m_IdScan_MaxNumLayers );
  allLayerPhis.resize( m_IdScan_MaxNumLayers );
 
  std::vector< std::vector< int > > allSliceWidths( m_IdScan_MaxNumLayers, std::vector< int >( numPhiSlices + 1, 0 ) );
  for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ )
  {
    allSlices[ sliceIndex ]->MakeWideLayers( &allLayerRhos, &allLayerZs, &allLayerPhis, &allSliceWidths, filled, &filledLayers );
  }
 
  //One histogram per phi slice?
  if ( m_zHistoPerPhi )
  {
    //Allocate all the histograms
    for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ )
    {
      nHisto[0][sliceIndex].resize( NumZhistoBins + 1 );
      zHisto[0][sliceIndex].resize( NumZhistoBins + 1 );
    }
    if ( m_chargeAware ) {
      for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ ) {
      nHisto[1][sliceIndex].resize( NumZhistoBins + 1 );
      zHisto[1][sliceIndex].resize( NumZhistoBins + 1 );
      }
    }
    
    //Populate the histograms
    for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ )  {
      allSlices[ sliceIndex ]->GetHistogram( &( nHisto[0][sliceIndex] ), &( zHisto[0][sliceIndex] ),
                         &( nHisto[1][sliceIndex] ), &( zHisto[1][sliceIndex] ),
                         m_extraPhi, extraPhiNeg, m_nFirstLayers, m_tripletMode, m_chargeAware, nHisto, zHisto );
      
      //Note the extra arguments here - pointers to the whole histogram collection
      //This allows the filling of neighbouring slice histograms as required, but breaks thread safety
      
      delete allSlices[ sliceIndex ];
    }
  }
  else {
    //Allocate the z-axis histograms
    nHisto[0][0].resize( NumZhistoBins + 1 );
    zHisto[0][0].resize( NumZhistoBins + 1 );
    if ( m_chargeAware )  {
      nHisto[1][0].resize( NumZhistoBins + 1 );
      zHisto[1][0].resize( NumZhistoBins + 1 );
    }
    
    //Populate the histogram - fast and memory-efficient, but not thread safe (use MakeHistogram for thread safety)
    for ( unsigned int sliceIndex = 0; sliceIndex < numPhiSlices; sliceIndex++ ) {
      allSlices[ sliceIndex ]->GetHistogram( &( nHisto[0][0] ), &( zHisto[0][0] ),
          &( nHisto[1][0] ), &( zHisto[1][0] ),
          m_extraPhi, extraPhiNeg, m_nFirstLayers, m_tripletMode, m_chargeAware );
 
      delete allSlices[ sliceIndex ];
    }
  }
  
 
 
 
  double pedestal = 0;
 
  if ( m_weightThreshold>0 ) { 
 
    int count = 0; 
 
    for ( long zpm=0; zpm<1 || ( m_chargeAware && zpm<2 ) ; ++zpm ) {
 
      for(std::vector< std::vector<long> >::iterator nfiter = nHisto[zpm].begin(); nfiter!=nHisto[zpm].end(); ++nfiter) {
 
        if((*nfiter).empty()) continue; // only check the filled zHistos
        if((*nfiter).size() <= 2 ) continue;// this is only a protection : with proper inputs to zfinder, it is always satisfied
 
        for(std::vector<long>::iterator niter=nfiter->begin()+2; niter!=nfiter->end(); ++niter ) {
          if ( *niter>=0 ) { 
            count++;
            pedestal += *(niter) + *(niter-1) + *(niter-2);
          }
        }
      }
    }
 
    if ( count>0 ) pedestal /= count;
    
  }
 
 
 
  double bg = 0; 
      
  if ( m_minVtxSignificance > 0 ) { 
 
    if ( !m_chargeAware ) {  
 
      std::vector<long>& n = nHisto[0][0];
      
      std::vector<long>  n3( nHisto[0][0].size()-2, 0);
      
      for( unsigned i=n.size()-2 ; i-- ;  ) n3[i] = ( n[i+2] + n[i+1] + n[i] );
      std::sort( n3.begin(), n3.end() );
      
      unsigned nmax = unsigned(n3.size()*m_percentile);
 
      for( unsigned i=nmax ; i-- ;  ) bg += n3[i];
      
      if ( nmax>0 ) bg /= nmax;
      
    }
  }
 
 
 
  //   Now the nHisto's are filled; find the 3 consecutive bins with the highest number of entries...
  //
 
  std::vector<double>  zoutput;
  std::vector<double>  woutput;
 
 
 
  while((int)zoutput.size() < m_numberOfPeaks) {
 
    long maxh=0;  // was 1 before triplets were introduced
    long binMax=0;
    long bending=0, bestPhi=0;
    long ztest;
 
    for ( long zpm=0; zpm<1 || ( m_chargeAware && zpm<2 ) ; ++zpm ) {
 
      std::vector< std::vector<long> >::iterator nfiter = nHisto[zpm].begin(); 
      for( ; nfiter!=nHisto[zpm].end() ; ++nfiter) {
 
        if((*nfiter).empty()) continue; // only check the filled zHistos
        if((*nfiter).size() <= 2 ) continue;// this is only a protection : with proper inputs to zfinder, it is always satisfied
    
        for(std::vector<long>::iterator niter=(*nfiter).begin()+2; niter!=(*nfiter).end(); ++niter ) {
      
          ztest = *(niter-2) + *(niter-1) + *(niter);
          if ( ztest <= 0 || ztest < maxh ) continue;
          if ( ztest >= maxh ) { // && ztest>m_weightThreshold ) {
            long bintest = niter-(*nfiter).begin()-1;
            if ( ztest > maxh ||
         // for two candidates at same "height", prefer the more central one
         (m_preferCentralZ && std::abs( bintest - HalfZhistoBins ) < std::abs( binMax - HalfZhistoBins ) ) ) {
              maxh = ztest;
              binMax = bintest;
              bestPhi = nfiter-nHisto[zpm].begin();
              bending = zpm;
            }
          }
    }// end of niter loop
      }
    }
 
    // nMax = maxh;
    if ( maxh==0 || ( m_tripletMode==0 && maxh<2 ) ) {
      break;
    }
    
    //   ...and compute the "entries-weighted" average bin position
    
    double weightedMax = ( zHisto[bending][bestPhi][binMax] +
               zHisto[bending][bestPhi][binMax+1] +
               zHisto[bending][bestPhi][binMax-1] ) /maxh;
    
    if ( m_numberOfPeaks>0 ) { 
      nHisto[bending][bestPhi][binMax]   = -1;
      nHisto[bending][bestPhi][binMax-1] = -1;
      nHisto[bending][bestPhi][binMax+1] = -1;
      zHisto[bending][bestPhi][binMax]   = 0;
      zHisto[bending][bestPhi][binMax-1] = 0;
      zHisto[bending][bestPhi][binMax+1] = 0;
    }
    
    int closestVtx = -1; // find the closest vertex already put into the output list
    float dist2closestVtx = 1000; // should be larger than m_ZFinder_MaxZ*2
    for ( size_t iv = 0; iv < zoutput.size(); ++iv ) {
      if ( fabs(weightedMax-zoutput[iv]) < dist2closestVtx ) {
    closestVtx = iv;
    dist2closestVtx = fabs(weightedMax-zoutput[iv]); 
      }
    }
    
    if ( dist2closestVtx < m_nvrtxSeparation*ZBinSize || dist2closestVtx < fabs(weightedMax)*m_vrtxDistCut ) {
      zoutput[closestVtx] = m_vrtxMixing * weightedMax + (1.0 - m_vrtxMixing) * zoutput[closestVtx] ;
      woutput[closestVtx] = m_vrtxMixing * maxh        + (1.0 - m_vrtxMixing) * woutput[closestVtx] ;
    }  
    else  {
      
      bool addvtx = true;
      double significance = 0;
      if ( bg>0 ) { 
    significance = (maxh-bg)/std::sqrt(bg);
    if ( significance < m_minVtxSignificance ) break; // if this vertex is not significant then no subsequent vertex could be either  
      }
      
      if ( addvtx ) { 
    zoutput.push_back( weightedMax );
    woutput.push_back( maxh );
      }
    }
    
  }
  
  
  
  
  
  
  if ( m_weightThreshold>0 ) { 
    for ( unsigned i=0 ; i<zoutput.size() ; i++ ) { 
      output->push_back( vertex( woutput[i] - pedestal, zoutput[i] ) ); 
    }
  }
  else {
    for ( unsigned i=0 ; i<zoutput.size() ; i++ ) { 
      output->push_back( vertex( zoutput[i], woutput[i] - pedestal ) ); 
    }
  }
  
  //  std::cout << "SUTT zoutput size " << zoutput.size() << "\t" << roi << std::endl;
  //  for ( unsigned i=0 ; i<zoutput.size() ; i++ ) std::cout << "SUTT zoutput        " << i << "\t" << zoutput[i] << std::endl;
  
  return output;
 
}