TRT_TrackSegmentsMaker_BarrelCosmics.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/

//    TRT_TrackSegmentsMaker_BarrelCosmics.h, (c) ATLAS Detector software
 
#include "TRT_TrackSegmentsTool_xk/TRT_TrackSegmentsMaker_BarrelCosmics.h"
 
#include "TrkPseudoMeasurementOnTrack/PseudoMeasurementOnTrack.h"
#include "InDetRIO_OnTrack/TRT_DriftCircleOnTrack.h"
#include "TrkEventPrimitives/FitQuality.h"
#include "StoreGate/ReadHandle.h"
#include "InDetIdentifier/TRT_ID.h"
#include "TrkSurfaces/StraightLineSurface.h"
#include <cmath>

//   standard methods: constructor, initialize, finalize
 
InDet::TRT_TrackSegmentsMaker_BarrelCosmics::TRT_TrackSegmentsMaker_BarrelCosmics
(const std::string& t,const std::string& n,const IInterface* p)
  : AthAlgTool(t,n,p)
{
  declareInterface<ITRT_TrackSegmentsMaker>(this);
}
 
StatusCode InDet::TRT_TrackSegmentsMaker_BarrelCosmics::initialize() {
 
   ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::initialize(), March 2012"
                << ", magnetic field: " << (m_magneticField?"ON":"OFF")
                << " search bins: " << m_nBinsInX << ", " << m_nBinsInPhi);
 
  StatusCode sc = StatusCode::SUCCESS;
 
  // Initialize ReadHandle
  ATH_CHECK(m_driftCirclesName.initialize());
  // TRT
  if (detStore()->retrieve(m_trtid, "TRT_ID").isFailure()) {
    ATH_MSG_FATAL("Could not get TRT ID helper");
    return StatusCode::FAILURE;
  }
 
  if (m_minHitsForSeed<=0) m_minHitsForSeed = (int) ( 0.601 * m_minHitsForSegment );
  if (m_minHitsAboveTOT<=0) m_minHitsAboveTOT = (int) (0.751 * m_minHitsForSegment );
 
  ATH_MSG_DEBUG("m_minHitsForSegment = " << m_minHitsForSegment);
  ATH_MSG_DEBUG("m_minHitsForSeed    = " << m_minHitsForSeed);
  ATH_MSG_DEBUG("m_minHitsAboveTOT   = " << m_minHitsAboveTOT);
 
  if (m_minSeedTOT<0. || m_minSeedTOT>20.)
    ATH_MSG_WARNING("initialize(): are you sure about the MinimalTOTForSeedSearch setting? (set at " << m_minSeedTOT << ")");
 
  ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::initialize(), jobProperties: "
        << "MinimalNumberOfTRTHits " << m_minHitsForSegment << ", MinimalTOTForSeedSearch: " << m_minSeedTOT
        << ", m_minHitsForSeed: " << m_minHitsForSeed << ", m_minHitsAboveTOT: " << m_minHitsAboveTOT );
 
  return sc;
}
 
StatusCode InDet::TRT_TrackSegmentsMaker_BarrelCosmics::finalize() {
   return StatusCode::SUCCESS;
}

//   other methods inherited from ITRT_TrackSegmentsMaker: newEvent, newRegion, endEvent
 
std::unique_ptr<InDet::ITRT_TrackSegmentsMaker::IEventData> InDet::TRT_TrackSegmentsMaker_BarrelCosmics::newEvent(const EventContext& ctx) const {
 
  ATH_MSG_DEBUG( "InDet::TRT_TrackSegmentsMaker_BarrelCosmics::newEvent()");
 
 
  SG::ReadHandle<InDet::TRT_DriftCircleContainer> trtcontainer(m_driftCirclesName, ctx); // get TRT_DriftCircle list from StoreGate containers
 
  if (not trtcontainer.isValid()) {
     msg(MSG::ERROR) << "Could not find TRT_DriftCircles collection!" << endmsg;
     std::stringstream msg;
     msg << name() <<" no TRT drift circles : " << m_driftCirclesName.key();
     throw std::runtime_error(msg.str());
  }
 
  std::unique_ptr<TRT_TrackSegmentsMaker_BarrelCosmics::EventData>
     event_data = std::make_unique<TRT_TrackSegmentsMaker_BarrelCosmics::EventData>(trtcontainer.cptr());
 
  for(const auto *it : *trtcontainer) {
 
    const InDet::TRT_DriftCircleCollection *colNext=&(*it);
    if (!colNext) { msg(MSG::WARNING) << "newEvent(): !colNext " << endmsg; continue; }
 
    for (const auto *circleit : *colNext){
 
      if ( m_trtid->is_barrel((*circleit).identify()) ) { // TRT barrel
 
    event_data->m_listHits.push_back( circleit );
 
        double onMyTime = circleit->timeOverThreshold();
        if ( circleit->firstBinHigh()  && (circleit->trailingEdge() != 24) && (circleit->trailingEdge() != 0) ) onMyTime = ( (double) circleit->trailingEdge() + 1 ) * 3.125;
        if (onMyTime < m_minSeedTOT) continue;
 
        const Amg::Vector3D &center = circleit->detectorElement()->surface(circleit->identify()).center();
        event_data->m_listHitCenter.push_back( center );
      }
    }
  } // end trtcontainer loop
 
  if ( m_maxTotalHits && ((int)event_data->m_listHits.size()) > m_maxTotalHits ) {
     ATH_MSG_DEBUG( "skipping high occupancy event of " << event_data->m_listHits.size() << " barrel hits, limit at "
                    << m_maxTotalHits );
     event_data->clear();
  }
 
  ATH_MSG_DEBUG( "newEvent(): Number of TRT barrel hits: " << event_data->m_listHits.size()
                 << " Number of hits with TOT > " << m_minSeedTOT << ": " << event_data->m_listHitCenter.size() );
 
  return std::unique_ptr<InDet::ITRT_TrackSegmentsMaker::IEventData>(event_data.release());
}
 
std::unique_ptr<InDet::ITRT_TrackSegmentsMaker::IEventData>
InDet::TRT_TrackSegmentsMaker_BarrelCosmics::newRegion(const EventContext& ctx, const std::vector<IdentifierHash> &vTRT) const {
 
  ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::newRegion()" );
 
  SG::ReadHandle<InDet::TRT_DriftCircleContainer> trtcontainer(m_driftCirclesName, ctx);
  if (not trtcontainer.isValid()) {
    msg(MSG::ERROR) << "m_trtcontainer is empty!!!" << endmsg;
     std::stringstream msg;
     msg << name() <<" no TRT drift circles : " << m_driftCirclesName.key();
     throw std::runtime_error(msg.str());
  }
 
  std::unique_ptr<TRT_TrackSegmentsMaker_BarrelCosmics::EventData>
     event_data = std::make_unique<TRT_TrackSegmentsMaker_BarrelCosmics::EventData>(trtcontainer.cptr());
 
 
  for(auto d : vTRT) {
    for ( InDet::TRT_DriftCircleContainer::const_iterator w = trtcontainer->indexFind(d); w!=trtcontainer->end(); ++w ) {
      for(const auto *circleit : **w) {
 
        if(std::abs(m_trtid->barrel_ec( circleit->identify() ))!=1) continue;
 
        event_data->m_listHits.push_back(circleit);
 
        double onMyTime = circleit->timeOverThreshold();
        if ( circleit->firstBinHigh()  && (circleit->trailingEdge() != 24) && (circleit->trailingEdge() != 0) ) onMyTime = ( (double) circleit->trailingEdge() + 1 ) * 3.125;
        if (onMyTime < m_minSeedTOT) continue;
        const Amg::Vector3D &center = circleit->detectorElement()->surface(circleit->identify()).center();
        event_data->m_listHitCenter.push_back( center );
      }
    }
  }
 
  if ( m_maxTotalHits && ((int)event_data->m_listHits.size()) > m_maxTotalHits ) {
     ATH_MSG_DEBUG("skipping high occupancy event of " << event_data->m_listHits.size() << " barrel hits, limit at "
                   << m_maxTotalHits);
    event_data->clear();
  }
 
  ATH_MSG_DEBUG( "newRegion(): Number of TRT barrel hits: " << event_data->m_listHits.size()
                 << " Number of hits with TOT > " << m_minSeedTOT << ": " << event_data->m_listHitCenter.size() );
 
  return std::unique_ptr<InDet::ITRT_TrackSegmentsMaker::IEventData>(event_data.release());
}
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::endEvent (InDet::ITRT_TrackSegmentsMaker::IEventData &virt_event_data) const {
  TRT_TrackSegmentsMaker_BarrelCosmics::EventData &
     event_data  = TRT_TrackSegmentsMaker_BarrelCosmics::EventData::getPrivateEventData(virt_event_data);
 
  ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::endEvent()" );
 
  // elements of m_segments created by new have not been passed on
  if ( event_data.m_segmentDriftCirclesCount < event_data.m_segments.size() ) {
    msg(MSG::WARNING) << "endEvent() you called the function to create the segments but didn't retrieve them later??" << endmsg;
    msg(MSG::WARNING) << "endEvent() deleting remaining elements of m_segments" << endmsg;
    for (unsigned int i=event_data.m_segmentDriftCirclesCount; i<event_data.m_segments.size(); i++) delete event_data.m_segments[i];
  }
 
  }

//   segment finding algorithm function: find, calls findSeed
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::find(const EventContext &/*ctx*/,
                                                       InDet::ITRT_TrackSegmentsMaker::IEventData &virt_event_data,
                                                       InDet::TRT_DetElementLink_xk::TRT_DetElemUsedMap&) const {
  TRT_TrackSegmentsMaker_BarrelCosmics::EventData &
     event_data  = TRT_TrackSegmentsMaker_BarrelCosmics::EventData::getPrivateEventData(virt_event_data);
 
  if (!m_magneticField) { findOld(event_data); return; }
 
  ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::find()" );
 
 
  if ((int)event_data.m_listHitCenter.size()<m_minHitsAboveTOT) return;
 
  if (!event_data.m_segmentDriftCircles.empty()) { // debug only
    msg(MSG::WARNING) << "TRT_TrackSegmentsMaker_BarrelCosmics::find() probably called twice per event? or newEvent / newRegion have not been called. check your program" << endmsg;
    event_data.clear(); return;
  }
 
  std::vector<double> x0, phi, pivotX, pivotY, Xparabola, cotanParabola, InverseR;
  std::vector<int> nHitsPosY, nHitsNegY;
 
  // first find seeds
  int nIterations(15), countCalls(0);
  while (countCalls<150) {
 
    double xRange(1000.), phiRange(M_PI_4);
    double par[] = {0., M_PI_2, 0., 0., 0., 0., 0., 0.};
    int foundSeed(0);
 
    for (int i=0; i<nIterations; i++) {
 
      countCalls++;
      foundSeed = findSeed( par[0]-xRange, par[0]+xRange, par[1]-phiRange, par[1]+phiRange, par, event_data);
      if ( !foundSeed ) break;
 
      xRange /= 3.;
      phiRange /= 2.;
      if ( xRange < 0.01 || phiRange < 0.00001) break;
    }
    if (!foundSeed) break;
 
    if (m_magneticField) findSeedInverseR(par, event_data);
 
// remove the hits associated with this region, save this region, search again
    int countAssociatedHits[] = {0, 0};
    double cosphi = std::cos( par[1] );
    double sinphi = std::sqrt( 1. - cosphi*cosphi );
    double range = (m_magneticField) ? 10. : 2.; // BE CAREFULL ABOUT THIS RANGE, IT USED TO BE 2 BUT PERHAPS IT SHOULD BE INCREASED TO 10 in the case of magnetic field!
 
 
    double measx[200], measy[200];
    int countMeas(0);
 
    for (std::vector< Amg::Vector3D>::iterator it = event_data.m_listHitCenter.begin(); it!=event_data.m_listHitCenter.end(); ) {
 
      double a = (par[3]-it->x())*sinphi+(it->y()-par[4])*cosphi;
      double b = (m_magneticField) ? 0.5 * (std::pow(it->x()-par[3], 2.) + std::pow(it->y()-par[4], 2.) - std::pow(a, 2)) : 0.;
      if ( std::abs(a+par[2]*b) > range ) { ++it; continue; }
 
      if (m_magneticField && countMeas<200) { measx[countMeas] = it->x(); measy[countMeas] = it->y(); countMeas++; }
 
      countAssociatedHits[(it->y()>0)?0:1]++;
      it = event_data.m_listHitCenter.erase( it );
    }
 
    if ( countAssociatedHits[0]+countAssociatedHits[1] < m_minHitsAboveTOT ) continue;
 
    if (m_magneticField) segFit(measx, measy, countMeas, nullptr, par+3);
 
    ATH_MSG_DEBUG("countAssociatedHits " << countAssociatedHits[0] << " "
                  << countAssociatedHits[1] << " m_minHitsAboveTOT " << m_minHitsAboveTOT );
    x0.push_back( par[0] ); phi.push_back( par[1] ); nHitsPosY.push_back( countAssociatedHits[0] ); nHitsNegY.push_back( countAssociatedHits[1] );
 
    pivotX.push_back( par[3] ); pivotY.push_back( par[4] ); Xparabola.push_back( par[5] ); cotanParabola.push_back( par[6] ); InverseR.push_back( par[7] );
  } // end for (int i=0; i<nIterations; i++) loop
// end finding seeds
 
// save all TRT hits for found segments
 
  int nFoundSegments = x0.size(); if (nFoundSegments>10) nFoundSegments = 10; // number of found segments
  {
     for (int i=0; i<nFoundSegments; i++) {
        event_data.m_segmentDriftCircles.emplace_back();
     }
  }
 
  double window = (m_magneticField) ? 4. : 2.; // change for magnetic field
  double residual;
 
  for (unsigned int i=0; i<event_data.m_listHits.size(); i++) {
 
    const Amg::Vector3D &center = event_data.m_listHits[i]->detectorElement()->surface(event_data.m_listHits[i]->identify()).center();
    for (int j=0; j<nFoundSegments; j++) {
 
      if (nHitsPosY[j]<5 && center.y()>0.) continue;
      if (nHitsNegY[j]<5 && center.y()<0.) continue;
 
          if (m_magneticField) {
        double sinphi = std::sqrt(1./(1+cotanParabola[j]*cotanParabola[j]));
        double cosphi = std::sqrt(1.-sinphi*sinphi); if (cotanParabola[j]<0.) cosphi *= -1.;
        double a = (pivotX[j]+Xparabola[j]-center.x())*sinphi+(center.y()-pivotY[j])*cosphi;
            double b = 0.5 * (std::pow(center.x()-pivotX[j], 2.) + std::pow(center.y()-pivotY[j], 2.) - std::pow(a, 2)) ;
            residual = a + InverseR[j] * b;
 
          } else {
                double cosphi = std::cos(phi[j]);
                double sinphi = std::sqrt(1.-cosphi*cosphi);
                residual = (x0[j]-center.x())*sinphi+center.y()*cosphi;
          }
 
      if (std::abs(residual)<window) {
        event_data.m_segmentDriftCircles[j].push_back(event_data.m_listHits[i]);
        break;
      }
    }
  }
  // end saving TRT hits
 
 
 
  // merge segments: can be simple: if 2 of them similar values of impact par -> copy hits from the second vector into the first one and clear the second one
  // XXXXXXXX to do: determine the optimal merging parameters
 
  if (m_mergeSegments) { // merge segments, not yet tested properly
 
     if (x0.size()>1) {
        int mergeI = 0;
    int mergeJ = 0;
    double mergeX0(100.), mergePhi(0.1);
        for (int i=0; i<nFoundSegments; i++) {
           for (int j=i+1; j<nFoundSegments; j++) {
              if ( std::abs(x0[i]-x0[j])<mergeX0 && std::abs(phi[i]-phi[j])<mergePhi ) {
                 mergeI = i;
                 mergeJ = j;
                 mergeX0 = std::abs(x0[i]-x0[j]);
                 mergePhi = std::abs(phi[i]-phi[j]);
              }
           }
    }
        if (mergeI != mergeJ) {
           ATH_MSG_DEBUG("Merge segments " << mergeI << " and " << mergeJ << " of size "
                         << event_data.m_segmentDriftCircles[mergeI].size() << ", " << event_data.m_segmentDriftCircles[mergeJ].size()
                         << "; difference in the impact par x: " << mergeX0 << " phi: " << mergePhi );
           for (unsigned int i=0; i<event_data.m_segmentDriftCircles[mergeJ].size(); i++) {
              event_data.m_segmentDriftCircles[mergeI].push_back(event_data.m_segmentDriftCircles[mergeJ][i]);
           }
           event_data.m_segmentDriftCircles[mergeJ].clear();
        }
     }
  } // end merge segments
 
 
  if (msgLvl(MSG::DEBUG)) {  // debug: check how many hits per found segments
    msg(MSG::DEBUG) << "find() debug (" << nFoundSegments << ")" ;
    for (unsigned int i=0; i<event_data.m_segmentDriftCircles.size(); i++) {
       msg(MSG::DEBUG) << " " << i << " " << event_data.m_segmentDriftCircles[i].size();
    }
    msg(MSG::DEBUG) << endmsg;
  }
 
  for (unsigned int i=0; i<event_data.m_segmentDriftCircles.size(); i++) { // convert to segments
    if ((int)event_data.m_segmentDriftCircles[i].size()<m_minHitsForSegment) continue;
    double trackpar[] = {x0[i], phi[i]};
    convert(event_data.m_segmentDriftCircles[i], trackpar, event_data);
  }
  ATH_MSG_DEBUG(  "find(), number of converted segments: " << event_data.m_segments.size() );
}

//   the last method inherited from ITRT_TrackSegmentsMaker: next()
//   returns ptr to i-th found TrackSegment, until it returns 0 (no more segments)
//   assumes any provided segments will be deleted by those who request them!!!
 
Trk::TrackSegment *InDet::TRT_TrackSegmentsMaker_BarrelCosmics::next(InDet::ITRT_TrackSegmentsMaker::IEventData &virt_event_data) const
{
  TRT_TrackSegmentsMaker_BarrelCosmics::EventData &
     event_data  = TRT_TrackSegmentsMaker_BarrelCosmics::EventData::getPrivateEventData(virt_event_data);
 
  // next 6 lines: for debugging purposes only
  ATH_MSG_DEBUG( "InDet::TRT_TrackSegmentsMaker_BarrelCosmics::next(): return "
                 << event_data.m_segmentDriftCirclesCount << " out of " << event_data.m_segments.size() );
 
  if (event_data.m_segmentDriftCirclesCount > event_data.m_segments.size())
    msg(MSG::ERROR) << "m_segmentDriftCirclesCount = " << event_data.m_segmentDriftCirclesCount << ", m_segments.size() = "
                      << event_data.m_segments.size() << endmsg;
 
  return (event_data.m_segmentDriftCirclesCount<event_data.m_segments.size())
     ?(event_data.m_segments[event_data.m_segmentDriftCirclesCount++])
     :nullptr;
}
 
 
 
int InDet::TRT_TrackSegmentsMaker_BarrelCosmics::findSeed(double xmin,
                                                          double xmax,
                                                          double phimin,
                                                          double phimax,
                                                          double *bestParameters,
                                                          TRT_TrackSegmentsMaker_BarrelCosmics::EventData &event_data) const
{
  if ((int)event_data.m_listHitCenter.size()<m_minHitsAboveTOT) return 0;
 
  double xbin = (xmax-xmin) / (1.*m_nBinsInX);
  double searchWindow = (xbin>2.) ? xbin : 2.; //searchWindow *= searchWindow;
  double phibin = (phimax-phimin) / (1.*m_nBinsInPhi);
  int maxHits(0), index, indexmin, indexmax;
 
  int binInX[100]; for (int & i : binInX) i = 0;
 
  for (int j=0; j<m_nBinsInPhi; j++) {
 
    double phi = phimin+(0.5+j)*phibin;
    double cosphi( std::cos(phi) ), sinphi( std::sin(phi) );
    for (int i=0; i<m_nBinsInX; i++) binInX[i] = 0;
    double transformXMin(xmin*sinphi); xbin = (xmax-xmin)*sinphi / (1.*m_nBinsInX);
 
    for (auto & k : event_data.m_listHitCenter) {
      double transformX = k.x() * sinphi - k.y() * cosphi;
      indexmin = (int) ((transformX-transformXMin-searchWindow)/xbin);
      indexmax = (int) ((transformX-transformXMin+searchWindow)/xbin);
 
      if (indexmin<0) indexmin=0;
      if (indexmax>99) indexmax=99;
      for (index = indexmin; index<=indexmax; index++) binInX[index]++;
    }
    index = -1;
    for (int i=0; i<m_nBinsInX; i++) if (binInX[i]>maxHits) { index = i; maxHits = binInX[i]; }
    if (index>=0) {
      bestParameters[0] = ( xbin * index + transformXMin) / sinphi;
      bestParameters[1] = phi;
    }
  }
 
  return (maxHits>=m_minHitsForSeed) ? 1 : 0;
}
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::findSeedInverseR(double *par,
                                                                   TRT_TrackSegmentsMaker_BarrelCosmics::EventData &event_data) const{
 
  double cosphi = std::cos( par[1] );
  double sinphi = std::sqrt( 1. - cosphi*cosphi );
 
  double parTransformX = par[0] * sinphi;
 
  double meanTransformY(0.);
  int countMeanTransformY(0);
  for (auto & k : event_data.m_listHitCenter) { // first determine the mean
 
    double transformX = k.x() * sinphi - k.y() * cosphi;
    if ( std::abs(transformX-parTransformX) > 2. ) continue;
    meanTransformY += k.x() * cosphi + k.y() * sinphi;
    countMeanTransformY++;
  }
  if (!countMeanTransformY) {
     ATH_MSG_WARNING("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::findSeedInverseR(), no hits in the seed region???" );
    return;
  }
  meanTransformY /= (double) countMeanTransformY;
 
 
// hard-coded parameters in the second part of this function:
// search range: [-0.00202, 0.00202] divided into 101 bins of width 0.00004 (such that range [-0.00002, 0.00002] is bin 50)
// 1/R = 0.002/mm corresponds to R = 0.5 m
// circle search window: 200 mm (for R=1m, circle-to-line distance 0.5 m away from a common point is 130mm)
 
// -> pivot at: x_pivot = meanTransformY * cosphi + parTransformX * sinphi; y_pivot = meanTransformY * sinphi - parTransformX * cosphi;
  double mean[] = { meanTransformY * cosphi + parTransformX * sinphi, meanTransformY * sinphi - parTransformX * cosphi };
  int scanInverseR[101]; for (int & i : scanInverseR)  i = 0;
 
  double window = 10.; // parabola search window BE CAREFULL OF THIS RANGE!
 
  for (auto & it : event_data.m_listHitCenter) {
 
    double transformX = it.x() * sinphi - it.y() * cosphi;
    if ( std::abs(transformX-parTransformX) > 200. ) continue;  // search circles in a broad band
 
    double a = (mean[0]-it.x())*sinphi+(it.y()-mean[1])*cosphi;  // TEST THAT THIS CONDITION ( if ( fabs(a) > 200. ) continue; ) IS THE SAME AS ABOVE!
    double b = 0.5 * (std::pow(it.x()-mean[0], 2.) + std::pow(it.y()-mean[1], 2.) - std::pow(a, 2));
 
    // estimated allowed range in radius: x_1,2 = ( +- window - a ) / b -> get integer as  ((int) (ceil(x/bin-0.5))) + 50
    b *= 0.00004; // multiply by the bin width
 
    int i1(0), i2(0);
    if (std::abs(b)>0.0000001) {
      double i1_tmp = ( window - a ) / b + 0.5;
      double i2_tmp = ( -window - a ) / b + 0.5;
      if (std::abs(i1_tmp)<1000.) { i1 = (int) (std::ceil( i1_tmp )); i1 += 50; }
      if (std::abs(i2_tmp)<1000.) { i2 = (int) (std::ceil( i2_tmp )); i2 += 50; }
    }
    if (i1>100) { i1 = 100; } else { if (i1<0) i1 = 0; }
    if (i2>100) { i2 = 100; } else { if (i2<0) i2 = 0; }
    if (i1+i2==0 || i1+i2==200) continue; // out of search range
    if (i1<=i2) { for (int i=i1; i<=i2; i++) scanInverseR[i]++; }
    else { for (int i=i2; i<=i1; i++) scanInverseR[i]++; }
  }
 
  int iMax(-1), hitsMax(0);
  for (int i=0; i<101; i++) if (scanInverseR[i]>hitsMax) { iMax = i; hitsMax = scanInverseR[i]; } // find max bin
 
  par[2] = 0.00004 * (iMax-50); // save estimated inverse radius
  for (int i=0; i<2; i++) par[3+i] = mean[i]; }

//   convert list of TRT hits to "TrackSegment": convert()
//
//   the only TrackSegment constructor one can use for the purpose:
//
//   TrackSegment( const LocalParameters* locpars,  // LocalParameters(radius, z0, phi0, theta, QoverP) at Surface point "sf"
//                 const ErrorMatrix* locerr,       // error matrix for above params
//                 const Surface* sf,               //
//                 DataVector<const MeasurementBase>* crots, // TRT_DriftCircleOnTrack : RIO_OnTrack : MeasurementBase
//                 FitQuality* fqual,               // FitQuality(float chi2, short ndf)
//                 Segment::Author author = Segment::AuthorUnknown
//               );
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::linearRegressionParabolaFit(double *mean, double *a) { // input: elsewhere calculated mean, output: result a
 
  double A[6], discriminant;
 
  A[0] = mean[8]*mean[8]-mean[4]*mean[9];                    // parabola fit
  A[1] = mean[1]*mean[9]-mean[4]*mean[8];
  A[2] = mean[4]*mean[4]-mean[1]*mean[8];
  A[3] = mean[4]*mean[4]-mean[9];
  A[4] = mean[8]-mean[1]*mean[4];
  A[5] = mean[1]*mean[1]-mean[4];
  discriminant = std::abs( std::pow(mean[4], 3) + mean[8]*mean[8] + mean[1]*mean[1]*mean[9] - mean[4]*(2.*mean[1]*mean[8]+mean[9]) );
 
  a[0] = A[0] * mean[0] + A[1] * mean[2] + A[2] * mean[6];
  a[1] = A[1] * mean[0] + A[3] * mean[2] + A[4] * mean[6];
  a[2] = A[2] * mean[0] + A[4] * mean[2] + A[5] * mean[6];
  discriminant *= -1.;
  for (int i=0; i<3; i++) { a[i] /= discriminant; }
 
  double inverseSin3phi = 1. + a[1]*a[1]; inverseSin3phi *= std::sqrt(inverseSin3phi); // 1/sin^3phi
  a[2] *= 2. / inverseSin3phi; }
 
bool InDet::TRT_TrackSegmentsMaker_BarrelCosmics::sortHits( const InDet::TRT_DriftCircle *dc1, const InDet::TRT_DriftCircle *dc2 ) {
 
  double y1 = (dc1->detectorElement())->surface(dc1->identify()).center().y();
  double y2 = (dc2->detectorElement())->surface(dc2->identify()).center().y();
  return ( y1 > y2 );
}
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::convert(std::vector<const InDet::TRT_DriftCircle *> &hits,
                                                          double *trackpar,
                                                          TRT_TrackSegmentsMaker_BarrelCosmics::EventData &event_data) const {
//Track Segment production - based on TRT_TrackSegmentsMaker_ECcosmics Tool
 
  ATH_MSG_DEBUG("InDet::TRT_TrackSegmentsMaker_BarrelCosmics::convert() segment " << event_data.m_segments.size()
                << ", N hits = " << hits.size());
 
  if (hits.size()<5) { msg(MSG::ERROR) << "convert(): empty list of hits! size: " << hits.size() << endmsg; return; }
 
  // sort the vector of hits
  std::sort( hits.begin(), hits.end(), InDet::TRT_TrackSegmentsMaker_BarrelCosmics::sortHits );
 
  // remove hits from the opposite side
  int countOppositeSide(0);
  for (std::vector<const InDet::TRT_DriftCircle *>::iterator it = hits.begin(); it != hits.end(); ) {
    int side = m_trtid->barrel_ec( (*it)->identify() );
    int previous = ( it == hits.begin() ) ? m_trtid->barrel_ec( (*(it+2))->identify() ) : m_trtid->barrel_ec( (*(it-1))->identify() );
    int next = ( it == hits.end()-1 ) ? m_trtid->barrel_ec( (*(it-2))->identify() ) : m_trtid->barrel_ec( (*(it+1))->identify() );
    if ( previous==next && side*next==-1 ) { it = hits.erase( it ); countOppositeSide++; }
    else { ++it; }
  }
  if (countOppositeSide>5) {
     ATH_MSG_DEBUG( "convert(): removed " << countOppositeSide << " hits from the other side, N remaining hits: " << hits.size() );
  }
  if (hits.size()<5) {
     ATH_MSG_WARNING( "convert(): not enough hits after opposite side removal: " << hits.size() << ", removed: "
                      << countOppositeSide );
    return;
  }
 
  // make the linear regression fit
  double mean[10]; for (double & i : mean) i = 0.;
  for (auto & hit : hits) {
 
    mean[0] += (hit->detectorElement())->surface(hit->identify()).center().x();
    mean[1] += (hit->detectorElement())->surface(hit->identify()).center().y();
  }
  for (int i=0; i<2; i++) mean[i] /= (double) hits.size();
  int iPivot(-1); double yPivot(10000000.); // choose pivot closest to the mean
  for (unsigned int i=0; i<hits.size(); i++) {
    double x = (hits[i]->detectorElement())->surface(hits[i]->identify()).center().x() - mean[0];
    double y = (hits[i]->detectorElement())->surface(hits[i]->identify()).center().y() - mean[1];
    double x2 = x * x;
    double y2 = y * y;
    mean[2] += x * y;
    mean[3] += x2;
    mean[4] += y2;
    mean[5] += x2 * y;
    mean[6] += y2 * x;
    mean[7] += x2 * x;
    mean[8] += y2 * y;
    mean[9] += y2 * y2;
    if (x2+y2<yPivot) { yPivot = x2+y2; iPivot = i; }
  }
 
  if (iPivot==-1) {
    msg(MSG::ERROR) << "SF pivot index not found!!! " << yPivot << " " << iPivot << endmsg;
    iPivot = 0;
  }
 
  double cotanPhi = mean[2] / mean[4];
  double phi = std::atan(1./cotanPhi); if (phi<0.) phi += M_PI;
  ATH_MSG_DEBUG("compare parameters X  : " << trackpar[0] << " vs. " << mean[0]-mean[1]*cotanPhi );
  ATH_MSG_DEBUG("compare parameters phi: " << trackpar[1] << " vs. " << phi );
 
  double qOverp = 0.; // units q / MeV, set only if there is magnetic field
 
  if (m_magneticField) { // fit parabola instead of line, add circle if neccessary
 
    double A[6], discriminant, a[3];
 
    A[0] = mean[8]*mean[8]-mean[4]*mean[9];                    // parabola fit
    A[1] = mean[1]*mean[9]-mean[4]*mean[8];
    A[2] = mean[4]*mean[4]-mean[1]*mean[8];
    A[3] = mean[4]*mean[4]-mean[9];
    A[4] = mean[8]-mean[1]*mean[4];
    A[5] = mean[1]*mean[1]-mean[4];
    discriminant = std::abs( std::pow(mean[4], 3) + mean[8]*mean[8] + mean[1]*mean[1]*mean[9] - mean[4]*(2.*mean[1]*mean[8]+mean[9]) );
 
    a[0] = A[0] * mean[0] + A[1] * mean[2] + A[2] * mean[6];
    a[1] = A[1] * mean[0] + A[3] * mean[2] + A[4] * mean[6];
    a[2] = A[2] * mean[0] + A[4] * mean[2] + A[5] * mean[6];
    discriminant *= -1.;
    for (double & i : a) { i /= discriminant; }
 
    double Xparabola = a[0];
    double cotanParabola = a[1];
    double inverseSin3phi = 1. + a[1]*a[1]; inverseSin3phi *= std::sqrt(inverseSin3phi); // 1/sin^3phi
    double inverseR = 2. * a[2] / inverseSin3phi;
 
    if (msgLvl(MSG::DEBUG)) {
       msg(MSG::DEBUG) << "TRT_TrackSegmentsMaker_BarrelCosmics: parabola fit, X: " << Xparabola << endmsg;
       msg(MSG::DEBUG) << "                                      parabola fit, cotan: " << cotanParabola << " compare to " << cotanPhi << endmsg;
       msg(MSG::DEBUG) << "                                      parabola fit, 1/R: " << inverseR << "/ mm " << endmsg;
    }
 
    qOverp = inverseR / 0.6;  // [1/MeV]; 1 / (eBRC) = 1 / (e 2T 3 100 M m/s mm) / R[mm] = (1/R[mm]) / 0.6
  }
 
// errors from the fit:
// - for d: sigma_r / sqrt(N hits) -> sigma_d^2 =
// - for cotanPhi: sigma_r / (sqrt(N hits * <y^2>) * sinPhi)
// - for phi: 1 / (1 + cotanPhi^2) * DcotanPhi // note that this mthod gives a biased estimate for phi!
 
  Amg::MatrixX cov(5,5);
 
  double f33 = 4. / ( 3. * (1.+cotanPhi*cotanPhi) * mean[4] ); // see above, mean[4] = N hits * <y^2>
  cov<<
    4.  ,    0.,   0.,     0.,  0.,
    0.  ,45633.,   0.,     0.,  0.,
    0.  ,    0.,  f33,     0.,  0.,
    0.  ,    0.,   0.,    0.2,  0.,
    0.  ,    0.,   0.,     0.,   1.;
 
  Amg::Vector3D hepVec( mean[0], mean[1],
             (hits[iPivot]->detectorElement())->surface(hits[iPivot]->identify()).center().z() );
 
 
  Amg::Transform3D htrans = Amg::Transform3D(Amg::Translation3D(hepVec)*Amg::RotationMatrix3D::Identity());
 
 
 
  Trk::StraightLineSurface *sur = new Trk::StraightLineSurface(htrans);
 
  if (phi>0.) phi -= M_PI;
  if (phi<-M_PI || phi>0.) msg(MSG::ERROR) << "phi value problem: " << phi << endmsg;
 
  Trk::LocalParameters par(0., 0., phi, M_PI_2, qOverp);
 
  ATH_MSG_DEBUG("pivot: " << sur->center() << ", cross-check: " << mean[0] << " " << mean[1] );
 
  // calculate TrackParameters so that one can calculate input for TRT_DriftCircleOnTrack
  // Global direction of the track parameters
  Amg::Vector3D dir(std::cos(phi), std::sin(phi), 0.);
 
  auto rio = DataVector<const Trk::MeasurementBase>{};
 
  for (const auto *DC : hits) { // rewrite: InDet::TRT_DriftCircle -> InDet::TRT_DriftCircleOnTrack
  // based on http://atlas-sw.cern.ch/cgi-bin/viewcvs-atlas.cgi/offline/InnerDetector/InDetRecTools/TRT_DriftCircleOnTrackTool/src/TRT_DriftCircleOnTrackNoDriftTimeTool.cxx?revision=1.11&view=markup
 
    // Straw identification
    const InDetDD::TRT_BaseElement* pE = DC->detectorElement();
    if (!pE) {
      ATH_MSG_ERROR("convert(): no detectorElement info!");
      continue;
    }
    Identifier iD = DC->identify();
    IdentifierHash iH = m_trtid->straw_layer_hash(m_trtid->layer_id(iD));
 
    // TRT_DriftCircleOnTrack production
    Trk::DefinedParameter  radius(0.,Trk::locX);
    Trk::LocalParameters lp(radius);
    Amg::MatrixX cov(1,1); cov<<1.33333;
    const InDet::TRT_DriftCircleOnTrack *element = new InDet::TRT_DriftCircleOnTrack(DC, std::move(lp), std::move(cov),
                                                                                     iH, 1., dir, Trk::NODRIFTTIME);
    rio.push_back( dynamic_cast<const Trk::MeasurementBase *>(element) );
  } // end fill rio
 
  // add pseudo measurement - follow up https://savannah.cern.ch/bugs/?41079
if (1) { // limit the scope of all these variables
 
  Trk::DefinedParameter pseudoz( 0., Trk::locZ);
  Trk::DefinedParameter pseudotheta( M_PI/2., Trk::theta);
  Trk::LocalParameters pseudoPar( pseudoz, pseudotheta );
 
  Amg::MatrixX pseudocov(2,2);
  pseudocov <<
    1.  ,   0.,
    0.  , .001;
 
  const Trk::Surface &surf =  (hits[hits.size()-1]->detectorElement())->surface(hits[hits.size()-1]->identify());
 
  Amg::RotationMatrix3D linerot=surf.transform().rotation();
  Amg::Vector3D         firstcenter=surf.center();
  Amg::Vector3D         faketransl(firstcenter.x(),firstcenter.y()-5.,firstcenter.z());
  Amg::Transform3D     faketransf = Amg::Transform3D(linerot* Amg::Translation3D(faketransl));
  Trk::StraightLineSurface *pseudoSurface = new Trk::StraightLineSurface( faketransf, 99999., 99999. );
 
  Trk::PseudoMeasurementOnTrack *pseudo = new Trk::PseudoMeasurementOnTrack(
    std::move(pseudoPar),
    std::move(pseudocov),
    *pseudoSurface );
  rio.push_back( pseudo );
  delete pseudoSurface;
}
 
  double chi2 = mean[3] - 2.*cotanPhi*mean[2] + mean[4]*cotanPhi*cotanPhi;
  chi2 /= ( 1. + cotanPhi*cotanPhi );
  int ndf = (int) hits.size() - 2;
  ATH_MSG_DEBUG( "Chi2 = " << chi2 << ", ndf = " << ndf << ", chi2/ndf = " << chi2/ndf );
  Trk::FitQuality      * fqu = new Trk::FitQuality(chi2, ndf);
 
  Trk::TrackSegment* segment = new Trk::TrackSegment(
    std::move(par),  std::move(cov), sur, std::move(rio), fqu, Trk::Segment::TRT_SegmentMaker);
 
  //add segment to list of segments
  ATH_MSG_DEBUG( "Add " << event_data.m_segments.size() << "th segment to list" );
  event_data.m_segments.push_back(segment);
}

//
//   DEBUG FUNCTIONS
//
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::segFit(double *measx, double *measy, int nhits, double *residuals, double *result ) {
 
  if (nhits<10) return;
 
  double shift[] = {0., 0.};                                  // shift the points so that mean x = 0 and mean y = 0
  for (int i=0; i<nhits; i++) { shift[0] += measx[i]; shift[1] += measy[i]; }
  for (double & i : shift) i /= (double) nhits;
  for (int i=0; i<nhits; i++) { measx[i] -= shift[0]; measy[i] -= shift[1]; }
 
  double mean[10]; for (double & i : mean) i = 0.;    // calculate momenta needed for the line, circle and parabola fit
  for (int i=0; i<nhits; i++) {
    double x2 = measx[i]*measx[i];
    double y2 = measy[i]*measy[i];
    mean[0] += measx[i];
    mean[1] += measy[i];
    mean[2] += measx[i]*measy[i];
    mean[3] += x2;
    mean[4] += y2;
    mean[5] += x2 * measy[i];
    mean[6] += y2 * measx[i];
    mean[7] += x2 * measx[i];
    mean[8] += y2 * measy[i];
    mean[9] += y2 * y2;
  }
  for (double & i : mean)  i /= (double) nhits;
 
  double A[6], discriminant, a[3];
 
  A[0] = mean[8]*mean[8]-mean[4]*mean[9];                    // parabola fit, no need for mean[3], [5], [7], se mi zdi
  A[1] = mean[1]*mean[9]-mean[4]*mean[8];
  A[2] = mean[4]*mean[4]-mean[1]*mean[8];
  A[3] = mean[4]*mean[4]-mean[9];
  A[4] = mean[8]-mean[1]*mean[4];
  A[5] = mean[1]*mean[1]-mean[4];
  discriminant = std::abs( std::pow(mean[4], 3) + mean[8]*mean[8] + mean[1]*mean[1]*mean[9] - mean[4]*(2.*mean[1]*mean[8]+mean[9]) );
 
  a[0] = A[0] * mean[0] + A[1] * mean[2] + A[2] * mean[6];
  a[1] = A[1] * mean[0] + A[3] * mean[2] + A[4] * mean[6];
  a[2] = A[2] * mean[0] + A[4] * mean[2] + A[5] * mean[6];
  discriminant *= -1.;
  for (double & i : a) i /= discriminant;
  double Xparabola = a[0];
  double cotanParabola = a[1];
  double inverseSin3phi = 1. + a[1]*a[1]; inverseSin3phi *= std::sqrt(inverseSin3phi); // 1/sin^3phi
  double inverseR = 2. * a[2] / inverseSin3phi;
  double sinphi = std::sqrt(1./(1+a[1]*a[1]));
  double cosphi = std::sqrt(1.-sinphi*sinphi); if (cotanParabola<0.) cosphi *= -1.;
 
  if (result) {
    for (int i=0; i<2; i++) result[i] = shift[i]; // pivot
    result[2] = Xparabola;
    result[3] = cotanParabola;
    result[4] = inverseR;
  }
 
  if (residuals) {
    for (int i=0; i<nhits; i++) {
      double tmp = (Xparabola-measx[i])*sinphi+measy[i]*cosphi;
      double res = (tmp+0.5*inverseR*(std::pow(measx[i]-Xparabola, 2.) + std::pow(measy[i], 2.) - std::pow(tmp, 2)));
      residuals[i] = res;
    }
  }
 
  for (int i=0; i<nhits; i++) { measx[i] += shift[0]; measy[i] += shift[1]; }
 
  }
 

//
//   DEBUG cpu consumption: old find method
//
 
 
void InDet::TRT_TrackSegmentsMaker_BarrelCosmics::findOld(TRT_TrackSegmentsMaker_BarrelCosmics::EventData &event_data) const{
 
   ATH_MSG_DEBUG( "InDet::TRT_TrackSegmentsMaker_BarrelCosmics::find()");
 
  if ((int)event_data.m_listHitCenter.size()<m_minHitsAboveTOT) return;
 
  if (!event_data.m_segmentDriftCircles.empty()) { // debug only
    ATH_MSG_WARNING("find probably called twice per event? or newEvent / newRegion have not been called. check your program" );
    event_data.clear(); return;
  }
 
  std::vector<double> x0, phi;
  std::vector<int> nHitsPosY, nHitsNegY;
 
  // first find seeds
  int nIterations(15), countCalls(0);
  while (countCalls<150) {
 
    double xRange(1000.), phiRange(M_PI_4);
    double par[] = {0., M_PI_2};
    int foundSeed(0);
 
    for (int i=0; i<nIterations; i++) {
 
      countCalls++;
      foundSeed = findSeed( par[0]-xRange, par[0]+xRange, par[1]-phiRange, par[1]+phiRange, par, event_data);
      if ( !foundSeed ) break;
 
      xRange /= 3.;
      phiRange /= 2.;
      if ( xRange < 0.01 || phiRange < 0.00001) break;
 
    }
    if (!foundSeed) break;
 
// remove the hits associated with this region, save this region, search again
    int countAssociatedHits[] = {0, 0};
    double cosphi = std::cos(par[1]);
    double sinphi = std::sqrt(1.-cosphi*cosphi);
 
    for (std::vector< Amg::Vector3D >::iterator it = event_data.m_listHitCenter.begin(); it!=event_data.m_listHitCenter.end(); ) {
 
      if ( std::abs( (par[0]-it->x())*sinphi + it->y()*cosphi ) > 2. ) { ++it; continue; }
      countAssociatedHits[(it->y()>0)?0:1]++;
      it = event_data.m_listHitCenter.erase( it );
    }
 
    if ( countAssociatedHits[0]+countAssociatedHits[1] < m_minHitsAboveTOT ) continue;
 
    x0.push_back( par[0] ); phi.push_back( par[1] ); nHitsPosY.push_back( countAssociatedHits[0] ); nHitsNegY.push_back( countAssociatedHits[1] );
 
  } // end for (int i=0; i<nIterations; i++) loop
// end finding seeds
 
// save all TRT hits for found segments
  int nFoundSegments = x0.size();
  if (nFoundSegments>10) nFoundSegments = 10; // number of found segments
  for (int i=0; i<nFoundSegments; i++) {
     event_data.m_segmentDriftCircles.emplace_back();
  }
 
  for (unsigned int i=0; i<event_data.m_listHits.size(); i++) {
    const Amg::Vector3D &
       center = event_data.m_listHits[i]->detectorElement()->surface(event_data.m_listHits[i]->identify()).center();
 
    for (int j=0; j<nFoundSegments; j++) {
      if (nHitsPosY[j]<5 && center.y()>0.) continue;
      if (nHitsNegY[j]<5 && center.y()<0.) continue;
      double cosphi = std::cos(phi[j]);
      double sinphi = std::sqrt(1.-cosphi*cosphi);
      if ( std::abs((x0[j]-center.x())*sinphi+center.y()*cosphi) < 2.) {
        event_data.m_segmentDriftCircles[j].push_back(event_data.m_listHits[i]);
    break;
      }
    }
  }
  // end saving TRT hits
 
  if (msgLvl(MSG::DEBUG)) {
     // debug: check how many hits per found segments
     msg(MSG::DEBUG) << "find() debug (" << nFoundSegments << ")" ;
     for (unsigned int i=0; i<event_data.m_segmentDriftCircles.size(); i++) {
        msg(MSG::DEBUG) << " " << i << " "                              \
                        << event_data.m_segmentDriftCircles[i].size() ;
     }
     msg(MSG::DEBUG) << endmsg;
  }
 
  for (unsigned int i=0; i<event_data.m_segmentDriftCircles.size(); i++) { // convert to segments
    if ((int)event_data.m_segmentDriftCircles[i].size()<m_minHitsForSegment) continue;
    double trackpar[] = {x0[i], phi[i]};
    convert(event_data.m_segmentDriftCircles[i], trackpar, event_data);
  }
  ATH_MSG_DEBUG( "find(), number of converted segments: " << event_data.m_segments.size() );
}