JetFitterRoutines.cxx

Go to the documentation of this file.

/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
/***************************************************************************
                          JetFitterRoutines.h  -  Description
                             -------------------
 
    begin : Februar 2007
    authors: Giacinto Piacquadio (University of Freiburg),
             Christian Weiser (University of Freiburg)
    email : nicola.giacinto.piacquadio@cern.ch,
            christian.weiser@cern.ch
    changes: new!
 
  2007 (c) Atlas Detector Software
 
  Look at the header file for more information.
     
 ***************************************************************************/
 
 
 
// to get AmgMatrix plugin:
#include "GeoPrimitives/GeoPrimitives.h"
 
#include "TrkJetVxFitter/JetFitterRoutines.h"
#include "VxVertex/RecVertex.h"
#include "VxJetVertex/VxJetCandidate.h"
#include "VxVertex/VxTrackAtVertex.h"
#include "VxJetVertex/VxVertexOnJetAxis.h"
#include "VxJetVertex/RecVertexPositions.h"
#include "VxJetVertex/VxClusteringTable.h"
#include "VxJetVertex/JetVtxParamDefs.h"
#include "VxJetVertex/PairOfVxVertexOnJetAxis.h"
#include "TrkJetVxFitter/KalmanVertexOnJetAxisUpdator.h"
#include "TrkJetVxFitter/KalmanVertexOnJetAxisSmoother.h"
#include "TrkJetVxFitter/JetFitterHelper.h"
#include "TrkJetVxFitter/JetFitterInitializationHelper.h"
#include "VxJetVertex/VxJetFitterDebugInfo.h"
 
#include "TrkNeutralParameters/NeutralParameters.h"
#include "TrkJetVxFitter/Utilities.h"
 
 
#include "TrkJetVxFitter/TrkDistanceFinderNeutralCharged.h"
#include "TrkJetVxFitter/TrkDistanceFinderNeutralNeutral.h"
 
#include <TMath.h>
#include <cmath>
#include <sstream>
#include <iostream>
#include <algorithm>
 
 
 
namespace Trk
{
 
  JetFitterRoutines::JetFitterRoutines(const std::string& t, const std::string& n, const IInterface*  p) :
    AthAlgTool(t,n,p),
    m_initializationHelper("Trk::JetFitterInitializationHelper", this),
    m_helper("Trk::JetFitterHelper", this),
    m_updator("Trk::KalmanVertexOnJetAxisUpdator", this),
    m_smoother("Trk::KalmanVertexOnJetAxisSmoother", this),
    m_minDistanceFinder("Trk::TrkDistanceFinderNeutralCharged/TrkDistanceFinderNeutralCharged", this),
    m_minDistanceFinderNeutral("Trk::TrkDistanceFinderNeutralNeutral/TrkDistanceFinderNeutralNeutral", this),
    m_fast(false),
    m_maxDRshift(.5),
    m_noPrimaryVertexRefit(false),
    m_maxR(1150.),//max R of ID
    m_maxZ(2727.)//max Z of ID
  { 
    declareProperty("KalmanVertexOnJetAxisUpdator",m_updator);
    declareProperty("KalmanVertexOnJetAxisSmoother",m_smoother);
    declareProperty("JetFitterHelper",m_helper);
    declareProperty("JetFitterInitializationHelper",m_initializationHelper);
    declareProperty("JetFitterMinimumDistanceFinder",m_minDistanceFinder);
    declareProperty("JetFitterMinimumDistanceFinderNeutral",m_minDistanceFinderNeutral);
    declareProperty("ID_maxR",m_maxR);
    declareProperty("ID_maxZ",m_maxZ);
    declareInterface< JetFitterRoutines >(this) ;
    declareProperty("BeFast",m_fast);
    declareProperty("maxDRshift",m_maxDRshift);
    declareProperty("noPrimaryVertexRefit",m_noPrimaryVertexRefit);
 
  }
 
 
    
  JetFitterRoutines::~JetFitterRoutines() = default;
 
 
  StatusCode JetFitterRoutines::initialize() {
    
    AthAlgTool::initialize().ignore();
    ATH_CHECK( m_fieldCacheCondObjInputKey.initialize() );
 
    //retrieving the udator itself   
    ATH_CHECK( m_helper.retrieve()  );    
 
    ATH_CHECK( m_initializationHelper.retrieve() );
 
    ATH_CHECK( m_minDistanceFinder.retrieve() );
 
    ATH_CHECK( m_minDistanceFinderNeutral.retrieve() );
    
    ATH_CHECK( m_updator.retrieve() );
 
    ATH_CHECK( m_smoother.retrieve() );
 
    return StatusCode::SUCCESS;
  }
 
 
  void JetFitterRoutines::initializeToMinDistancesToJetAxis(VxJetCandidate* myJetCandidate) const {
    
    ATH_MSG_DEBUG ("initializingToMinDistancesToJetAxis is now implemented! Will converge faster!!! Neutrals are fully supported...");
 
    VertexPositions & linVertexPositions=myJetCandidate->getLinearizationVertexPositions();
    Amg::VectorX linPositions=linVertexPositions.position();
    
    
    const Trk::RecVertexPositions & recVtxPosition=myJetCandidate->getRecVertexPositions();
    const Amg::VectorX & recPosition=recVtxPosition.position();
    
    Amg::Vector3D a(recPosition[Trk::jet_xv],
                    recPosition[Trk::jet_yv],
                    recPosition[Trk::jet_zv]);
 
    auto const sinRecJetTheta = std::sin(recPosition[Trk::jet_theta]);
    auto const sinRecJetPhi   = std::sin(recPosition[Trk::jet_phi]);
    auto const cosRecJetTheta = std::cos(recPosition[Trk::jet_theta]);
    auto const cosRecJetPhi   = std::cos(recPosition[Trk::jet_phi]);
 
    auto const absRecJetTheta = std::abs(recPosition[Trk::jet_theta]);
    auto const abssinRecJetTheta = std::abs(sinRecJetTheta);
    auto const abscosRecJetTheta = std::abs(cosRecJetTheta);
 
    Amg::Vector3D b(cosRecJetPhi*sinRecJetTheta,
                    sinRecJetPhi*sinRecJetTheta,
                    cosRecJetTheta);
    
    NeutralTrack myJetAxis(a,b);
 
    //Yes, but the seeding is more than just speed!
    const std::vector<VxVertexOnJetAxis*> & associatedVertices=myJetCandidate->getVerticesOnJetAxis();
    
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxBegin=associatedVertices.begin();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxEnd=associatedVertices.end();
    
    if (associatedVertices.empty()) {//Was that your intention? to be checked... 15.03.2007
      SG::ReadCondHandle<AtlasFieldCacheCondObj> readHandle{m_fieldCacheCondObjInputKey};
      const AtlasFieldCacheCondObj* fieldCondObj{*readHandle};
      if (!readHandle.isValid() or !fieldCondObj) {
         std::stringstream msg;
         msg << "Failed to retrieve magmnetic field conditions data " << m_fieldCacheCondObjInputKey.key() << ".";
         throw std::runtime_error(msg.str());
      }
      MagField::AtlasFieldCache fieldCache;
      fieldCondObj->getInitializedCache (fieldCache);
      for (std::vector<VxVertexOnJetAxis*>::const_iterator VtxIter=VtxBegin;VtxIter!=VtxEnd;++VtxIter) {
        VxVertexOnJetAxis* myVertex=(*VtxIter);
        if (myVertex!=nullptr) {
          
          const std::vector<VxTrackAtVertex*> & tracksAtVertex=myVertex->getTracksAtVertex();
          if (tracksAtVertex.size()>1) { 
              ATH_MSG_DEBUG( "Warning in JetFitterInitializationHelper.Number of tracks at vertex is bigger than one, " 
                             << "even during initialization phase. Skipping this vertex (already initialized)..." );
          } 
          else if (tracksAtVertex.empty())
          {
            ATH_MSG_WARNING( "No track at vertex. Internal fitter error. Contact author (GP) ... " );
          }
          else
          {
            ATH_MSG_VERBOSE( " TrackAtVertexSize is: " << tracksAtVertex.size() );
            ATH_MSG_VERBOSE( " pointer to first element: " << tracksAtVertex[0] );
            ATH_MSG_VERBOSE( " pointer to initialPerigee: " << tracksAtVertex[0]->initialPerigee() );
 
        // RS 19.04.2011 try to fix coverity defect 22750
        const Trk::Perigee* ptr = dynamic_cast<const Trk::Perigee*>((tracksAtVertex[0]->initialPerigee()));
            if (ptr) 
            {
 
              double distOnAxis=-999.;
              std::pair<Amg::Vector3D,double> result;
              try {
                result=m_minDistanceFinder->getPointAndDistance(myJetAxis,*ptr,distOnAxis, fieldCache);
 
                double R=distOnAxis*sinRecJetTheta;
                double Z=distOnAxis*cosRecJetTheta;
 
                if (std::abs(R)>m_maxR)
                {
 
                  if (absRecJetTheta>1e-8)
                  {
                    ATH_MSG_DEBUG( " Closest distance of track to jet axis is outside ID envelope, R=" << R << ", setting to R= " << m_maxR );
                    distOnAxis=m_maxR /abssinRecJetTheta;
                  }
                }
 
                Z=distOnAxis*cosRecJetTheta;
                if (std::abs(Z)>m_maxZ)
                {
                  if (abscosRecJetTheta>1e-8)
                  {
                    ATH_MSG_DEBUG( " Closest distance of track to jet axis is outside ID envelope, Z=" << Z << ", setting to Z= " << m_maxZ );
                    distOnAxis=m_maxZ / cosRecJetTheta;
                  }
                }
                
                linPositions[numRow(myVertex->getNumVertex())]=distOnAxis;
                  
 
              } catch (Error::NewtonProblem e) {
                ATH_MSG_WARNING( "Problem with Newton finder " << e.p );
              } catch (...) {
                ATH_MSG_ERROR( "Could not catch error " );
              }
              ATH_MSG_DEBUG ("initializingToMinDistancesToJetAxis for vertex number... " << 
                             myVertex->getNumVertex() << " to distance " << distOnAxis << 
                             " distance to axis " <<  result.second);
            }
            // FIXME   THIS PART IS DEAD IN NEW TRACKING EDM:
            else if (dynamic_cast<const Trk::NeutralPerigee*>((tracksAtVertex[0]->initialPerigee()))!=nullptr)
            {
              double distOnAxis=-999.;
              std::pair<Amg::Vector3D,double> result;
 
              const Trk::NeutralPerigee * neutralTrack = 
                dynamic_cast<const Trk::NeutralPerigee*>((tracksAtVertex[0]->initialPerigee()));
              
              NeutralTrack myNeutralTrack(neutralTrack->position(),neutralTrack->momentum());
              
              result=m_minDistanceFinderNeutral->getPointAndDistance(myJetAxis,myNeutralTrack,distOnAxis);
 
              double R=distOnAxis*sinRecJetTheta;
              double Z=distOnAxis*cosRecJetTheta;
 
              if (std::abs(R)>m_maxR)
              {
                
                if (absRecJetTheta>1e-8)
                {
                  ATH_MSG_DEBUG( " Closest distance of track to jet axis is outside ID envelope, R=" << R << ", setting to R= " << m_maxR );
                  distOnAxis=m_maxR / abssinRecJetTheta;
                }
              }
              
              Z=distOnAxis*cosRecJetTheta;
              if (std::abs(Z)>m_maxZ)
              {
                if (abscosRecJetTheta>1e-8)
                {
                  ATH_MSG_DEBUG( " Closest distance of track to jet axis is outside ID envelope, Z=" << Z << ", setting to Z= " << m_maxZ );
                  distOnAxis=m_maxZ / cosRecJetTheta;
                }
              }
              
              linPositions[numRow(myVertex->getNumVertex())]=distOnAxis; 
              ATH_MSG_DEBUG( "initializingToMinDistancesToJetAxis for vertex from NEUTRAL number... " << 
                               myVertex->getNumVertex() << " to distance " << 
                               distOnAxis << " distance to axis " <<  result.second );
              
            }
            else 
            {
              ATH_MSG_WARNING( "Could not cast to neither CHARGED or NEUTRAL! This error is not FATAL" );
            }
          }
        } else {
          ATH_MSG_WARNING( "Warning in JetFitterInitializationHelper.Inconsistency found. Pointer to VxVertexOnJetAxis should be different from zero. Skipping track..." );
          throw ("Warning in JetFitterInitializationHelper.Inconsistency found. Pointer to VxVertexOnJetAxis should be different from zero. Skipping track...");
        }
      }
 
      linVertexPositions.setPosition(linPositions);
      
    } else {
      ATH_MSG_DEBUG ("No Associated Vertices found! no initialization to minimum distance is possible.");
    }
  }
 
  void JetFitterRoutines::performTheFit(VxJetCandidate* myJetCandidate,
                    int num_maxiterations,//default 20
                    bool treat_sign_flip,//default true
                    int num_signflip_maxiterations,//default 10
                    double deltachi2_convergence) const {//default 0.001
    
    bool isInitialized=this->checkJetCandidate(myJetCandidate);
    
    if (!isInitialized) {
      ATH_MSG_DEBUG ("JetFitter found the candidate was not correctly initialized. Not proceeding with the fitt...");
      return;
    }
    
 
    
    //linearization is DONE. now do fit with all the vertices (updating them through the knowledge coming from all the tracks parameters)
    
    int num_iteration_signflip=0;
    double lastchi2=-99.;
    bool converged=false;
 
    if (treat_sign_flip) {
      do {
 
    myJetCandidate->setRecVertexPositions(RecVertexPositions(myJetCandidate->getConstraintVertexPositions()));
 
    ATH_MSG_DEBUG( myJetCandidate->getRecVertexPositions() );
    
    //linearization position is now stored in a different VertexPositions attached to the VxJetCandidate...
    m_initializationHelper->linearizeAllTracks(myJetCandidate,true);
 
    //now update all vertices with the new information
    updateAllVertices(myJetCandidate);
 
    //now do the chi2 update of all tracks after end of fit iterations
    //(this permits to invert the big weight matrix only once at the end!!)
    //  updateChi2AllVertices(myJetCandidate);
    
    num_iteration_signflip+=1;
    
    const RecVertexPositions & myRecPosition=myJetCandidate->getRecVertexPositions();
 
    const FitQuality & myFitQuality=myRecPosition.fitQuality();
 
    double actualchi2=myFitQuality.chiSquared();
 
    auto const absActLastChi2 = std::abs(actualchi2-lastchi2);
 
#ifdef JetFitterRoutines_DEBUG
    ATH_MSG_DEBUG( " last chi2 " << lastchi2 << " actual chi2 " << actualchi2 << " difference " << 
      absActLastChi2<< " < " << deltachi2_convergence << " ? " <<  " ndf " << myFitQuality.numberDoF() );
#endif
 
    if (absActLastChi2<deltachi2_convergence) {
      converged=true;
    } else {
 
          //GP 12.3.2012 Check that no vertex is outside the ID acceptance
          copyRecoPositionsToLinearizationPositions(*myJetCandidate);
 
    }
 
    lastchi2=actualchi2;
    
      } while ((!converged)&&num_iteration_signflip<num_signflip_maxiterations);
 
    
      if (converged) {
    ATH_MSG_VERBOSE( " For sign flip treatment there was convergence after " << num_iteration_signflip );
      } 
    }
    
    //    if (msgSvc()->outputLevel()== MSG::DEBUG||msgSvc()->outputLevel()== MSG::VERBOSE) {
#ifdef JetFitterRoutines_DEBUG
      ATH_MSG_DEBUG( "JetFitterRoutines: after convergence with sign flip treatment: " << myJetCandidate->getRecVertexPositions() );
#endif
      //    }
 
    int num_iteration=0;
    lastchi2=-99.;
    converged=false;
   
    do {
      
 
      myJetCandidate->setRecVertexPositions(RecVertexPositions(myJetCandidate->getConstraintVertexPositions()));
 
 
      //linearization position is now stored in a different VertexPositions attached to the VxJetCandidate...
      m_initializationHelper->linearizeAllTracks(myJetCandidate,false);
      
      //now update all vertices with the new information
      updateAllVertices(myJetCandidate);
 
      //now do the chi2 update of all tracks after end of fit iterations
      //(this permits to invert the big weight matrix only once at the end!!)
      //      updateChi2AllVertices(myJetCandidate);
 
      num_iteration+=1;
      
      const RecVertexPositions & myRecPosition=myJetCandidate->getRecVertexPositions();
 
      ATH_MSG_VERBOSE( " num_iteration (full fit): " << num_iteration << " det " << myRecPosition.covariancePosition().determinant() <<  " recVertex " << myJetCandidate->getRecVertexPositions() );
 
      const FitQuality & myFitQuality=myRecPosition.fitQuality();
      double actualchi2=myFitQuality.chiSquared(); 
      
      auto const absActLastChi2 = std::abs(actualchi2-lastchi2);      
 
      //    if (msgSvc()->outputLevel()== MSG::VERBOSE) {
#ifdef JetFitterRoutines_DEBUG
      ATH_MSG_DEBUG( " without sign flip: last chi2 " << lastchi2 << " actual chi2 " << actualchi2 << " difference " << 
    absActLastChi2 << " < " << deltachi2_convergence << " ? " <<  " ndf " << myFitQuality.numberDoF() );
#endif
      //    }
 
      if (absActLastChi2<deltachi2_convergence) {
    converged=true;
      } else {
    //now set the linearization position for the next step to the actual fitted vertex
          //GP 12.3.2012 Check that no vertex is outside the ID acceptance
          copyRecoPositionsToLinearizationPositions(*myJetCandidate);
          //OLD myJetCandidate->setLinearizationVertexPositions(myJetCandidate->getRecVertexPositions());
      }
      lastchi2=actualchi2;
      
    } while ((!converged)&&num_iteration<num_maxiterations);
    
    if (converged) {
      ATH_MSG_VERBOSE( " Fit without sign flip treatment there was convergence after " << num_iteration );
    } 
    
    //    if (msgSvc()->outputLevel()== MSG::VERBOSE) {
    #ifdef JetFitterRoutines_DEBUG
    ATH_MSG_DEBUG( "JetFitterRoutines: after convergence without sign flip treatment: " << myJetCandidate->getRecVertexPositions() );
    #endif
      //    }
    if (num_iteration>=num_maxiterations)
    {
      ATH_MSG_DEBUG( "There wasn't convergence in JetFitter after: " << num_maxiterations );
    }
 
    //now only the smoothing is missing as a last step... (updated momenta, chi2 + ndf of clusters,...)
    
    smoothAllVertices(myJetCandidate);
    
    Trk::VxJetFitterDebugInfo * & myDebugInfo=myJetCandidate->getDebugInfo();
    if (myDebugInfo!=nullptr) {
      delete myDebugInfo;
    }
    myDebugInfo=new VxJetFitterDebugInfo();
    myDebugInfo->setNumFitIterations(num_iteration);
    myDebugInfo->setSignFlipNumFitIterations(num_iteration_signflip);
 
  }
 
 
  void JetFitterRoutines::updateAllVertices(VxJetCandidate* myJetCandidate) const {
 
//    ATH_MSG_DEBUG( " Updating PV " );
 
    int n_iteration=0;
    
 
    if (!m_noPrimaryVertexRefit) {
      //new iteration
      VxVertexOnJetAxis* myPrimary=myJetCandidate->getPrimaryVertex();
      const std::vector<VxTrackAtVertex*> & primaryVectorTracks=myPrimary->getTracksAtVertex();
      
      const std::vector<VxTrackAtVertex*>::const_iterator primaryVectorTracksBegin=primaryVectorTracks.begin();
      const std::vector<VxTrackAtVertex*>::const_iterator primaryVectorTracksEnd=primaryVectorTracks.end();
    
      for (std::vector<VxTrackAtVertex*>::const_iterator  primaryVectorIter=primaryVectorTracksBegin;
       primaryVectorIter!=primaryVectorTracksEnd;++primaryVectorIter) {
    
    ATH_MSG_VERBOSE( " RecVertexPositions before update " << myJetCandidate->getRecVertexPositions() );
    
    if ((!m_fast)) {
      m_updator->add(*primaryVectorIter,myPrimary,myJetCandidate);
    } else {
      m_updator->addWithFastUpdate(*primaryVectorIter,myPrimary,myJetCandidate);
    }
 
        const RecVertexPositions & myRecPosition=myJetCandidate->getRecVertexPositions();
 
        ATH_MSG_VERBOSE( " Determinant after PRIMARY VTX update: " << n_iteration <<  " det: "  << myRecPosition.covariancePosition().determinant() <<  " recVertex " << myJetCandidate->getRecVertexPositions() );
      }
    }
 
    n_iteration=0;
    
    // const RecVertexPositions & myRecPositionBeg=myJetCandidate->getRecVertexPositions();
 
    const std::vector<VxVertexOnJetAxis*> & associatedVertices=myJetCandidate->getVerticesOnJetAxis();
    
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxBegin=associatedVertices.begin();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxEnd=associatedVertices.end();
    
    for (std::vector<VxVertexOnJetAxis*>::const_iterator VtxIter=VtxBegin;VtxIter!=VtxEnd;++VtxIter) {
 
//      ATH_MSG_DEBUG( " Updating an SV along jet axis " );
 
      const std::vector<VxTrackAtVertex*> & tracksAtVertex=(*VtxIter)->getTracksAtVertex();
 
      const std::vector<VxTrackAtVertex*>::const_iterator TracksBegin=tracksAtVertex.begin();
      const std::vector<VxTrackAtVertex*>::const_iterator TracksEnd=tracksAtVertex.end();
      
      for (std::vector<VxTrackAtVertex*>::const_iterator  TrackVectorIter=TracksBegin;
       TrackVectorIter!=TracksEnd;++TrackVectorIter) {
    
    ATH_MSG_VERBOSE( " RecVertexPositions before update " << myJetCandidate->getRecVertexPositions() );
    
    if (!m_fast) {
      m_updator->add(*TrackVectorIter,*VtxIter,myJetCandidate);
    } else {
      m_updator->addWithFastUpdate(*TrackVectorIter,*VtxIter,myJetCandidate);
    }
 
        n_iteration+=1;
 
        const RecVertexPositions & myRecPosition=myJetCandidate->getRecVertexPositions();
 
        ATH_MSG_VERBOSE( " Determinant after sec update: " << n_iteration <<  " det: "  << myRecPosition.covariancePosition().determinant() <<  " recVertex " << myJetCandidate->getRecVertexPositions() );
      }
    }
 
     myJetCandidate->getRecVertexPositions().finalizePosition();
  }
 
 void JetFitterRoutines::smoothAllVertices(VxJetCandidate* myJetCandidate) const {
    //new iteration
    VxVertexOnJetAxis* myPrimary=myJetCandidate->getPrimaryVertex();
 
    if (!m_fast) {
      m_smoother->update(myPrimary,myJetCandidate);    
    } else {
      m_smoother->fastUpdate(myPrimary,myJetCandidate); 
    }
 
    const std::vector<VxVertexOnJetAxis*> & associatedVertices=myJetCandidate->getVerticesOnJetAxis();
    
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxBegin=associatedVertices.begin();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxEnd=associatedVertices.end();
    
    for (std::vector<VxVertexOnJetAxis*>::const_iterator VtxIter=VtxBegin;VtxIter!=VtxEnd;++VtxIter) {
      if (!m_fast) {
    m_smoother->update(*VtxIter,myJetCandidate);
      } else {
    m_smoother->fastUpdate(*VtxIter,myJetCandidate);
      }
    }
  }
 
 
 
 
  bool JetFitterRoutines::checkJetCandidate(VxJetCandidate* myJetCandidate) const {
    
    int sizeprimary(0);
 
    //check if primaryvertex exists
    const VxVertexOnJetAxis* myPrimary=myJetCandidate->getPrimaryVertex();
    if (myPrimary==nullptr) {
      ATH_MSG_WARNING( "No primary vertex found in VxJetCandidate class. Initialization was not done correctly..." );
      return false;
    }
 
    bool ok = true;
    if (myPrimary->getNumVertex() != -10) {
      ATH_MSG_WARNING("Numvertex of primary vertex not correctly initialized. "
                      "Not proceeding with the fit!");
      return false;
    }
 
    const std::vector<VxTrackAtVertex*>& primaryVectorTracks =
      myPrimary->getTracksAtVertex();
 
    sizeprimary = primaryVectorTracks.size();
    ok = std::ranges::none_of(primaryVectorTracks,[](const auto* track) { return track == nullptr; });
    if (not ok){
      ATH_MSG_WARNING("At least one of the VxTrackAtVertex is a null pointer. Not "
                      "proceeding with the fit!");
      return false;
    }
    
    // end if else rimary==0
 
    // check std::vector<VxVertexOnJetAxis*> (if pointers are not empty and if
    // all associated tracks are not empty)
    const std::vector<VxVertexOnJetAxis*>& tracksOfVertex =
      myJetCandidate->getVerticesOnJetAxis();
 
    auto badVertex = [](VxVertexOnJetAxis* pVertex) {
      return (pVertex == nullptr) or (pVertex->getNumVertex() < 0);
    };
    ok =
      (std::find_if(tracksOfVertex.begin(), tracksOfVertex.end(), badVertex) ==
       tracksOfVertex.end());
    if (not ok) {
      ATH_MSG_WARNING(
        "One of the VxTrackAtVertex is a null pointer or uninitialized. Not "
        "proceeding with the fit!"); // Two error messages combined into one
    }
    if (not ok) {
      return false;
    }
    
    //now check if there is some track at least to do the fit...
 
    if (tracksOfVertex.empty()&&sizeprimary==0) {
      ATH_MSG_DEBUG( "No tracks at primary, no tracks on jet axis. Not proceeding with the fit!" );
      return false;
    }
    
    //now check if the number of tracks corrisponds to the number of components of the recVertexPositions
    const Trk::RecVertexPositions & myRecVertexPositions=myJetCandidate->getRecVertexPositions();
 
    const Amg::VectorX& myPosition=myRecVertexPositions.position();
 
    if (static_cast<unsigned int>(tracksOfVertex.size()+5)!=static_cast<unsigned int>(myPosition.rows())) { 
        ATH_MSG_WARNING ( "The position matrix has " <<  myPosition.rows() 
                          << " components while " <<  tracksOfVertex.size()+5 
                          << " are expected. Not proceeding with the fit " );
    }
 
    const Amg::MatrixX & myErrorMatrix=myRecVertexPositions.covariancePosition();
 
    //check if symMatrix and myPosition are compatible (size matches)
    if (myPosition.rows()!=myErrorMatrix.rows()) {
      ATH_MSG_WARNING ("The dimension of the position vector and the covariance matrix does not match. Not performing fit...");
      return false;
    }
 
    //check if all the diagonal values of the covariance matrix are not zero
    for (int i=0;i<myPosition.rows();i++) {
      if (std::abs(myErrorMatrix(i,i))<1e-20) {
        ATH_MSG_WARNING ("Value of cov matrix component n. " << i << " has a value smaller than 1e-8. Not considered as possible. Not performing fit...");
        return false;
      }
    }
 
    //well, more checks in the future!!!
    
    return true;
 
  }//end method
 
  
  std::pair<double,bool> JetFitterRoutines::fastProbabilityOfMerging(const VxVertexOnJetAxis* firstVertex,
                                     const VxVertexOnJetAxis* secondVertex,
                                     const VxJetCandidate* myJetCandidate) const {
    //this method is for evaluating the probability of merging in a very fast (and rough) way
    //if above a threshold you should think about evaluating the "fullProbabilityOfMerging" :-)
 
    const VxVertexOnJetAxis * PrimaryVertex=myJetCandidate->getPrimaryVertex();
 
    if (firstVertex==PrimaryVertex) {
      return fastProbabilityOfMergingWithPrimary(secondVertex,myJetCandidate);
    } 
    if (secondVertex==PrimaryVertex) {
      return fastProbabilityOfMergingWithPrimary(firstVertex,myJetCandidate);
    }
 
    return fastProbabilityOfMergingNoPrimary(firstVertex,secondVertex,myJetCandidate);
    
  }
 
  
  std::pair<double,bool> JetFitterRoutines::fastProbabilityOfMergingWithPrimary(const VxVertexOnJetAxis* otherVertex,
                                        const VxJetCandidate* myJetCandidate) const {
    
 
    //first get a copy of all vertex positions (this you can't avoid I fear...)
    RecVertexPositions copyOfRecVertexPositions(myJetCandidate->getRecVertexPositions());
 
 
    double oldchi2=copyOfRecVertexPositions.fitQuality().chiSquared();
    double oldndf=copyOfRecVertexPositions.fitQuality().numberDoF();
 
    //#ifdef JetFitterRoutines_DEBUG2
    const Amg::VectorX & positionVector=copyOfRecVertexPositions.position();
    const Amg::MatrixX & positionCov=copyOfRecVertexPositions.covariancePosition();
    double phiold=positionVector(Trk::jet_phi);
    double thetaold=positionVector(Trk::jet_theta);
    double phierr=std::sqrt(positionCov(Trk::jet_phi,Trk::jet_phi));
    double thetaerr=std::sqrt(positionCov(Trk::jet_theta,Trk::jet_theta));
 
    //now do the merging of the second cluster to the primary vertex...
    m_helper->performKalmanConstraintToBePrimaryVertex(copyOfRecVertexPositions,
                               *otherVertex);
 
    double phinew=positionVector[Trk::jet_phi];
    double thetanew=positionVector[Trk::jet_theta];
    bool isshifted=
      std::pow((phinew-phiold)/phierr,2)+std::pow((thetanew-thetaold)/thetaerr,2)>m_maxDRshift*m_maxDRshift;
                   
    double chi2 = myJetCandidate->getPrimaryVertex()->fitQuality().chiSquared() + 
                  otherVertex->fitQuality().chiSquared() +
                  copyOfRecVertexPositions.fitQuality().chiSquared()-oldchi2;
    
    double ndf = copyOfRecVertexPositions.fitQuality().numberDoF()-oldndf + 
                 myJetCandidate->getPrimaryVertex()->fitQuality().numberDoF() +
                 otherVertex->fitQuality().numberDoF();
 
    if (chi2<0||ndf<0) {
      ATH_MSG_WARNING (" In the compatibility estimation chi2: " << chi2 << " ndf " << ndf << " giving back 0 prob ");
      return std::pair<double,bool>(0,isshifted);
    }
 
    return std::pair<double,bool>(TMath::Prob(chi2,(int)std::floor(ndf+0.5)),isshifted);
 
  }
 
  std::pair<double,bool> JetFitterRoutines::fastProbabilityOfMergingNoPrimary(const VxVertexOnJetAxis* firstVertex,
                                          const VxVertexOnJetAxis* secondVertex,
                                          const VxJetCandidate* myJetCandidate) const {
    
    //first get a copy of all vertex positions (this you can't avoid I fear...)
    RecVertexPositions copyOfRecVertexPositions(myJetCandidate->getRecVertexPositions());
    const FitQuality & copyOfRecVertexQuality=copyOfRecVertexPositions.fitQuality();
 
    double oldchi2=copyOfRecVertexQuality.chiSquared();
    double oldndf=copyOfRecVertexQuality.numberDoF();
 
    //#ifdef JetFitterRoutines_DEBUG2
    const Amg::VectorX & positionVector=copyOfRecVertexPositions.position();
    const Amg::MatrixX & positionCov=copyOfRecVertexPositions.covariancePosition();
    double phiold=positionVector(Trk::jet_phi);
    double thetaold=positionVector(Trk::jet_theta);
    double phierr=std::sqrt(positionCov(Trk::jet_phi,Trk::jet_phi));
    double thetaerr=std::sqrt(positionCov(Trk::jet_theta,Trk::jet_theta));
 
    
    //now do the merging of the second cluster to the primary vertex...
    m_helper->performKalmanConstraintToMergeVertices(copyOfRecVertexPositions,
                             *firstVertex,
                             *secondVertex);
 
    double phinew=positionVector[Trk::jet_phi];
    double thetanew=positionVector[Trk::jet_theta];
    bool isshifted=std::pow((phinew-phiold)/phierr,2)+std::pow((thetanew-thetaold)/thetaerr,2)>m_maxDRshift* m_maxDRshift;
 
    double chi2 = firstVertex->fitQuality().chiSquared() + 
                  secondVertex->fitQuality().chiSquared() +
                  copyOfRecVertexPositions.fitQuality().chiSquared()-oldchi2;
    
    
    double ndf = copyOfRecVertexPositions.fitQuality().numberDoF()-oldndf + 
                 firstVertex->fitQuality().numberDoF()+
                 secondVertex->fitQuality().numberDoF();
 
    if (chi2<0||ndf<0) {
      ATH_MSG_WARNING ("In the compatibility estimation chi2: " << chi2 << " ndf " << ndf << " giving back 0 prob");
      return std::pair<double,bool>(0,isshifted);
    }
 
    return std::pair<double,bool>(TMath::Prob(chi2,(int)std::floor(ndf+0.5)),isshifted);
 
 
  }
 
  double JetFitterRoutines::fullProbabilityOfMerging(const VxVertexOnJetAxis* firstVertex,
                            const VxVertexOnJetAxis* secondVertex,
                            const VxJetCandidate* myJetCandidate,
                            int num_maxiterations,
                            bool treat_sign_flip,
                            int num_signflip_maxiterations,
                            double deltachi2_convergence) const {
 
    
    if (firstVertex==nullptr||secondVertex==nullptr||myJetCandidate==nullptr) {
      ATH_MSG_WARNING ("zero pointer given to the full probability estimation. No estimation performed, zero prob returned ");
      return 0;
    }
 
    //copy the VxJetCandidate into a new object (this is expensive...)
    VxJetCandidate newJetCandidate(*myJetCandidate);
 
 
    //first find correspondence between old first and secondVertex and new ones (horrible,but...)
 
    std::map<const VxVertexOnJetAxis*,VxVertexOnJetAxis*> oldToNewVtxPointers;
 
    
    const std::vector<VxVertexOnJetAxis*> vectorOfOldJetCand=myJetCandidate->getVerticesOnJetAxis();
    const std::vector<VxVertexOnJetAxis*> vectorOfNewJetCand=newJetCandidate.getVerticesOnJetAxis();
    
    const VxVertexOnJetAxis* primaryOfFirst=myJetCandidate->getPrimaryVertex();
    VxVertexOnJetAxis* primaryOfSecond=newJetCandidate.getPrimaryVertex();
 
    if (primaryOfFirst==nullptr||primaryOfSecond==nullptr) {
      ATH_MSG_WARNING ("Empty primary vertex found when estimating fullProbOfMerging. 0 prob returned.");
      return 0;
    }
 
    oldToNewVtxPointers[primaryOfFirst]=primaryOfSecond;
 
    unsigned int sizeOfVertices=vectorOfOldJetCand.size();
    if (vectorOfNewJetCand.size()!=sizeOfVertices) {
      ATH_MSG_WARNING ("Old and new track of vertices do not match during fullProbOfMerging. 0 prob returned.");
      return 0;
    }
 
    for (unsigned int s=0;s<sizeOfVertices;s++) {
      const VxVertexOnJetAxis* pointer1=vectorOfOldJetCand[s];
      VxVertexOnJetAxis* pointer2=vectorOfNewJetCand[s];
      if (pointer1==nullptr||pointer2==nullptr) {
    ATH_MSG_WARNING ("One of the pointers of the original or copied vector of vertices is empty during fullProbOfMerging. Skipping it...");
      } else {
    oldToNewVtxPointers[pointer1]=pointer2;
      }
    }
 
    //now merge firstVertex and secondVertex
    VxVertexOnJetAxis* newFirstVertex=oldToNewVtxPointers[firstVertex];
    VxVertexOnJetAxis* newSecondVertex=oldToNewVtxPointers[secondVertex];
 
    if (newFirstVertex==nullptr||newSecondVertex==nullptr) {
      ATH_MSG_WARNING ("No correspondence to the given firstVertex or secondVertex in fullProbOfMerging. Returning 0 prob.");
      return 0.;
    }
 
    VxVertexOnJetAxis & commonVertex=m_helper->mergeVerticesInJetCandidate(*newFirstVertex,
                                       *newSecondVertex,
                                       newJetCandidate);
 
    //now you need to update the numbering scheme
    m_initializationHelper->updateTrackNumbering(&newJetCandidate);
    
    performTheFit(&newJetCandidate,num_maxiterations,
          treat_sign_flip,
          num_signflip_maxiterations,
          deltachi2_convergence);
 
    //    const FitQuality & qualityOfMergedVertex=commonVertex.fitQuality();
 
#ifdef JetFitterRoutines_DEBUG
    ATH_MSG_DEBUG( " End estimating full prob of merging... chi2 " << commonVertex.fitQuality().chiSquared() << " ndf " << commonVertex.fitQuality().numberDoF() );
#endif
 
    return (double)TMath::Prob(commonVertex.fitQuality().chiSquared(),
                  (int)std::floor(commonVertex.fitQuality().numberDoF()+0.5));
 
  }
 
  void JetFitterRoutines::fillTableWithFullProbOfMerging(VxJetCandidate* myJetCandidate,
                             int num_maxiterations,
                             bool treat_sign_flip,
                             int num_signflip_maxiterations,
                             double deltachi2_convergence,
                             double threshold_probability) const {
    fillTableWithProbOfMerging(myJetCandidate,
                   true,
                   num_maxiterations,
                   treat_sign_flip,
                   num_signflip_maxiterations,
                   deltachi2_convergence,
                   threshold_probability);
  }
 
  void JetFitterRoutines::fillTableWithFastProbOfMerging(VxJetCandidate* myJetCandidate) const {
    fillTableWithProbOfMerging(myJetCandidate,false);
  }
 
 
  void JetFitterRoutines::fillTableWithProbOfMerging(VxJetCandidate* myJetCandidate,
                             bool fullcomputation,
                             int num_maxiterations,
                             bool treat_sign_flip,
                             int num_signflip_maxiterations,
                             double deltachi2_convergence,
                             double threshold_probability) const {
    
    if (myJetCandidate==nullptr) {
      ATH_MSG_WARNING( "VxJetCandidate provided is a zero pointer. No compatibility table calculated." );
      return;
    }
    
    //first create the compatibility table object...
    Trk::VxClusteringTable* & clusteringTablePtr(myJetCandidate->getClusteringTable());
    if (clusteringTablePtr!=nullptr) {
      delete clusteringTablePtr;
    }
    clusteringTablePtr=new Trk::VxClusteringTable();
 
    double highestprobability(0.);
 
    VxVertexOnJetAxis* primaryVertex=myJetCandidate->getPrimaryVertex();
 
    if (primaryVertex==nullptr) {
    ATH_MSG_WARNING( "VxJetCandidate provided has no primary vertex. No compatibility table calculated." );
    return;
    } 
 
    primaryVertex->setCompatibilityToPrimaryVtx(1);//stupid but assign prob 1 to primary vtx for consistency
 
    const std::vector<VxVertexOnJetAxis*> & tracksOnJetAxis=myJetCandidate->getVerticesOnJetAxis();
 
    //now evaluate probability of cluster forming with primary vertex
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxBegin=tracksOnJetAxis.begin();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxEnd=tracksOnJetAxis.end();
    
    for (std::vector<VxVertexOnJetAxis*>::const_iterator VtxIter=VtxBegin;
     VtxIter!=VtxEnd;++VtxIter) {
 
      std::pair<double,bool> fastProbabilityAndNonLinearity=fastProbabilityOfMerging(primaryVertex,
                                             *VtxIter,
                                             myJetCandidate);
      
      
      ATH_MSG_VERBOSE ("Fast probability of merging between primary and " << 
                   (*VtxIter)->getNumVertex() << " is " << fastProbabilityAndNonLinearity.first);
      
#ifdef JetFitterRoutines_DEBUG2  
      ATH_MSG_DEBUG( "Fast probability of merging between primary and " << 
    (*VtxIter)->getNumVertex() << " is " << fastProbabilityAndNonLinearity.first <<  " and is max DR " << 
    fastProbabilityAndNonLinearity.second );
#endif  
 
      if (fullcomputation) {
    if (fastProbabilityAndNonLinearity.first>threshold_probability) {
      if (fastProbabilityAndNonLinearity.first>highestprobability/100.&&fastProbabilityAndNonLinearity.second) {
        
        double fullProbability=fullProbabilityOfMerging(primaryVertex,*VtxIter,
                               myJetCandidate,num_maxiterations,
                               treat_sign_flip,
                               num_signflip_maxiterations,
                               deltachi2_convergence);
        
 
#ifdef JetFitterRoutines_DEBUG2     
        ATH_MSG_DEBUG( "Full probability of merging with primary is " << fullProbability );
#endif
 
        ATH_MSG_DEBUG ("Full probability of merging with primary is " << fullProbability);
        
        //store this fullProbability into the VxClusteringTable of myJetCandidate
        
        clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(primaryVertex,*VtxIter),fullProbability);
        if (fullProbability>highestprobability) {
          highestprobability=fullProbability;
        }
        (*VtxIter)->setCompatibilityToPrimaryVtx(fullProbability);
      } else {
        clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(primaryVertex,*VtxIter),fastProbabilityAndNonLinearity.first);
        (*VtxIter)->setCompatibilityToPrimaryVtx(fastProbabilityAndNonLinearity.first);     
      }
    } else {
      (*VtxIter)->setCompatibilityToPrimaryVtx(fastProbabilityAndNonLinearity.first);
    }
      } else {
    if (fastProbabilityAndNonLinearity.first>threshold_probability) {
      clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(primaryVertex,*VtxIter),fastProbabilityAndNonLinearity.first);
      if (fastProbabilityAndNonLinearity.first>highestprobability) {
        highestprobability=fastProbabilityAndNonLinearity.first;
      }
    }
    (*VtxIter)->setCompatibilityToPrimaryVtx(fastProbabilityAndNonLinearity.first);
      }
    }//end first iteration over tracks for compatibility with primary vertex
    
    //now all the remaining combination have to be tested...
 
    for (std::vector<Trk::VxVertexOnJetAxis*>::const_iterator VtxIter2=VtxBegin;
     VtxIter2!=VtxEnd;++VtxIter2) {
      for (std::vector<Trk::VxVertexOnJetAxis*>::const_iterator VtxIter1=VtxBegin;
       VtxIter1!=VtxIter2;++VtxIter1) {
    
    std::pair<double,bool> fastProbabilityAndNonLinearity=fastProbabilityOfMerging(*VtxIter1,
                                               *VtxIter2,
                                               myJetCandidate);
    
    
    
       ATH_MSG_VERBOSE ("Fast probability of merging between vtx n " <<  (*VtxIter1)->getNumVertex()<<
                        " and " << (*VtxIter2)->getNumVertex() << " is " << 
                        fastProbabilityAndNonLinearity.first << " and is max DR " <<
                    fastProbabilityAndNonLinearity.second);
 
#ifdef JetFitterRoutines_DEBUG2  
    ATH_MSG_DEBUG( "Fast probability of merging between vtx n " <<  (*VtxIter1)->getNumVertex() << " and " << 
      (*VtxIter2)->getNumVertex() << " is " << fastProbabilityAndNonLinearity.first << " and is max DR " << 
      fastProbabilityAndNonLinearity.second );
#endif  
    if (fullcomputation) {
      if (fastProbabilityAndNonLinearity.first>threshold_probability) {
        if (fastProbabilityAndNonLinearity.first>highestprobability/100.&&fastProbabilityAndNonLinearity.second) {
          double fullProbability=fullProbabilityOfMerging(*VtxIter1,*VtxIter2,
                                 myJetCandidate,num_maxiterations,
                                 treat_sign_flip,
                                 num_signflip_maxiterations,
                                 deltachi2_convergence);
          
 
#ifdef JetFitterRoutines_DEBUG2     
          ATH_MSG_DEBUG( "Full probability of merging is " << fullProbability );
#endif
 
          ATH_MSG_VERBOSE ("Full probability of merging is " << fullProbability);
          
          //store this fullProbability into the VxClusteringTable of myJetCandidate
          
          clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(*VtxIter1,*VtxIter2),fullProbability);
          if (fullProbability>highestprobability) {
        highestprobability=fullProbability;
          }
        } else {
          clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(*VtxIter1,*VtxIter2),fastProbabilityAndNonLinearity.first);
        }
      }
    } else {
      if (fastProbabilityAndNonLinearity.first>threshold_probability) {
        clusteringTablePtr->setCompatibilityOfTo(PairOfVxVertexOnJetAxis(*VtxIter1,*VtxIter2),fastProbabilityAndNonLinearity.first);
        if (fastProbabilityAndNonLinearity.first>highestprobability) {
          highestprobability=fastProbabilityAndNonLinearity.first;
        }
      }
    }
      }//end first vtx loop
    }//end second vtx loop
    
  }//end fillTableWithFullProbOfMerging() method
 
  void JetFitterRoutines::deleteVertexFromJetCandidate(VxVertexOnJetAxis* vertexToDelete,
                               VxJetCandidate* myJetCandidate) const {
    if (vertexToDelete==myJetCandidate->getPrimaryVertex()) {
      ATH_MSG_WARNING ("YOU ARE deleting the primary vertex. This is not possible... ");
      return;
    }
 
    // now you need to *delete* the second vertex in copyOfRecVertexPositions and 
    // in copyOfLinearizationPositions
    const Amg::VectorX & recPosition=myJetCandidate->getRecVertexPositions().position();
    const Amg::VectorX & linPosition=myJetCandidate->getLinearizationVertexPositions().position();
    const Amg::VectorX & constraintPosition=myJetCandidate->getConstraintVertexPositions().position();
    const Amg::MatrixX & covPosition=myJetCandidate->getRecVertexPositions().covariancePosition();
    const Amg::MatrixX & covConstraintPosition=myJetCandidate->getConstraintVertexPositions().covariancePosition();
   
    int numbVertex=numRow(vertexToDelete->getNumVertex());
    //call the function which deletes a single row (they're in the anonymous namespace, in Utilities.h)
    Amg::VectorX reducedRecPositions=deleteRowFromVector(recPosition,numbVertex);
    Amg::VectorX reducedLinPositions=deleteRowFromVector(linPosition,numbVertex);
    Amg::VectorX reducedConstraintPositions=deleteRowFromVector(constraintPosition,numbVertex);
    Amg::MatrixX reducedCovPositions=deleteRowFromSymMatrix(covPosition,numbVertex);
    Amg::MatrixX reducedConstraintCovPositions=deleteRowFromSymMatrix(covConstraintPosition,numbVertex);
 
    myJetCandidate->setRecVertexPositions(RecVertexPositions(reducedRecPositions,
                                 reducedCovPositions,
                                 0.,0.));
    myJetCandidate->setConstraintVertexPositions(RecVertexPositions(reducedConstraintPositions,
                                    reducedConstraintCovPositions,
                                    0.,0.));
    myJetCandidate->setLinearizationVertexPositions(VertexPositions(reducedLinPositions));
 
 
 
    //make a copy of the VxTrackAtVertex vector in myJetCandidate to delete some of the elements
      
    //PAY ATTENTION: here you are modifying the vector of tracks DIRECTLY...
    std::vector<VxTrackAtVertex*>* tracksAtJetCandidate(myJetCandidate->vxTrackAtVertex());
    // RS 19.04.2011 attempt to fix coverity defect 22750
    // const std::vector<VxTrackAtVertex*>::iterator TracksBegin=tracksAtJetCandidate->begin();
    // std::vector<VxTrackAtVertex*>::iterator TracksEnd=tracksAtJetCandidate->end();
 
    
    const std::vector<VxTrackAtVertex*> & tracksAtVtx(vertexToDelete->getTracksAtVertex());
 
    const std::vector<VxTrackAtVertex*>::const_iterator TracksAtVtxBegin=tracksAtVtx.begin();
    const std::vector<VxTrackAtVertex*>::const_iterator TracksAtVtxEnd=tracksAtVtx.end();
 
    int numberOfTracksBefore=tracksAtJetCandidate->size();
    int numberOfTracksToDelete=tracksAtVtx.size();
 
    for (std::vector<VxTrackAtVertex*>::const_iterator TracksAtVtxIter=TracksAtVtxBegin;
     TracksAtVtxIter!=TracksAtVtxEnd;
     ++TracksAtVtxIter) {
 
      // RS 19.04.2011 attempt to fix coverity defect 22750
      std::vector<VxTrackAtVertex*>::iterator TracksBegin=tracksAtJetCandidate->begin();
      std::vector<VxTrackAtVertex*>::iterator TracksEnd=tracksAtJetCandidate->end();
      for (std::vector<VxTrackAtVertex*>::iterator TracksIter=TracksBegin;TracksIter!=TracksEnd;) {
    
    if (*TracksIter==*TracksAtVtxIter) {
      Trk::VxTrackAtVertex* oldPointer=*TracksIter;
      TracksIter=tracksAtJetCandidate->erase(TracksIter);
      delete oldPointer;
      oldPointer=nullptr;
      TracksEnd=tracksAtJetCandidate->end();
      break; 
    } 
      ++TracksIter;
    
      }
    }
 
    if (numberOfTracksBefore-numberOfTracksToDelete!=(int)myJetCandidate->vxTrackAtVertex()->size()) {
      ATH_MSG_DEBUG( " MISMATCH in JetFitterRoutines: the jetcandidate had: " << numberOfTracksBefore << " tracks " << 
    " and " << numberOfTracksToDelete << " to delete = " << myJetCandidate->vxTrackAtVertex()->size() << " tracks left! " );
    }
 
 
    //now as a last step you need to delete the vertex you're not using anymore...
    
    std::vector<VxVertexOnJetAxis*> copyOfVerticesAtJetCandidate=myJetCandidate->getVerticesOnJetAxis();
 
    const std::vector<VxVertexOnJetAxis*>::iterator VerticesBegin=copyOfVerticesAtJetCandidate.begin();
    std::vector<VxVertexOnJetAxis*>::iterator VerticesEnd=copyOfVerticesAtJetCandidate.end();
     
    bool found=false;
    
    //have a variable to store the vector of tracks which then need to be removed (copy)...
    //    std::vector<VxTrackAtVertex*> tracksToRemove=vertexToDelete->getTracksAtVertex();
 
    for (std::vector<VxVertexOnJetAxis*>::iterator VerticesIter=VerticesBegin;VerticesIter!=VerticesEnd;) {
      if ((*VerticesIter)==vertexToDelete) {
    delete *VerticesIter;
    VerticesIter=copyOfVerticesAtJetCandidate.erase(VerticesIter);
    VerticesEnd=copyOfVerticesAtJetCandidate.end();
    found=true;
    break;
      } 
    ++VerticesIter;
      
    }
    
    if (!found) {
      ATH_MSG_WARNING( "Could not find the vertex to delete... Very strange... Check!!! " );
    }
 
    //update myJetCandidate with the new vector of tracks
    myJetCandidate->setVerticesOnJetAxis(copyOfVerticesAtJetCandidate);
   
    //update the numbering scheme
    m_initializationHelper->updateTrackNumbering(myJetCandidate);
 
  }
 
  void JetFitterRoutines::copyRecoPositionsToLinearizationPositions(VxJetCandidate & myJetCandidate) const
  {
 
    const VertexPositions & newLinVertexPositions=myJetCandidate.getRecVertexPositions();
    Amg::VectorX linPositions=newLinVertexPositions.position();
    
    const std::vector<VxVertexOnJetAxis*> & associatedVertices=myJetCandidate.getVerticesOnJetAxis();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxBegin=associatedVertices.begin();
    const std::vector<VxVertexOnJetAxis*>::const_iterator VtxEnd=associatedVertices.end();
    
    for (std::vector<VxVertexOnJetAxis*>::const_iterator VtxIter=VtxBegin;VtxIter!=VtxEnd;++VtxIter) {
      VxVertexOnJetAxis* myVertex=(*VtxIter);
      if (myVertex!=nullptr) {
        
        double distOnAxis=linPositions[numRow(myVertex->getNumVertex())];
  
    auto const sinLinJetTheta = std::sin(linPositions[Trk::jet_theta]);
    auto const cosLinJetTheta = std::cos(linPositions[Trk::jet_theta]);       
 
    auto const absLinJetTheta = std::abs(linPositions[Trk::jet_theta]);
    auto const abssinLinJetTheta = std::abs(sinLinJetTheta);
    auto const abscosLinJetTheta = std::abs(cosLinJetTheta);
 
        double R=distOnAxis*sinLinJetTheta;
        double Z=distOnAxis*cosLinJetTheta;
        if (std::abs(R)>m_maxR)
        {
          if (absLinJetTheta>1e-8)
          {
            ATH_MSG_DEBUG (" Closest distance of track to jet axis is outside ID envelope, R=" << R << ", setting to R= " << m_maxR);
            distOnAxis=m_maxR / abssinLinJetTheta;
          }
        }
        
        Z=distOnAxis*cosLinJetTheta;
        if (std::abs(Z)>m_maxZ)
        {
          if (abscosLinJetTheta>1e-8)
          {
            ATH_MSG_DEBUG( " Closest distance of track to jet axis is outside ID envelope, Z=" << Z << ", setting to Z= " << m_maxZ );
            distOnAxis=m_maxZ / cosLinJetTheta;
          }
        }
        
        linPositions[numRow(myVertex->getNumVertex())]=distOnAxis;
      }
    }
    
    VertexPositions & linVertexPositions=myJetCandidate.getLinearizationVertexPositions();
    linVertexPositions.setPosition(linPositions);
    //now set the linearization position for the next step to the actual fitted vertex
    //OLD CODE BEFORE CHECKS
    //myJetCandidate->setLinearizationVertexPositions(myJetCandidate->getRecVertexPositions());
  }
  
}//end namespace