#include <TrajectorySegmentBuilder.h>

Public Member Functions
TempTrajectoryContainer	segments (const TSOS startingState)
	new segments within layer More...

	TrajectorySegmentBuilder (const LayerMeasurements *theInputLayerMeasurements, const DetLayer &layer, const Propagator &propagator, const TrajectoryStateUpdator &updator, const MeasurementEstimator &estimator, bool lockHits, bool bestHitOnly, int maxCand)
	constructor from layer and helper objects More...

	~TrajectorySegmentBuilder ()
	destructor More...

Private Types
typedef TransientTrackingRecHit::ConstRecHitContainer	ConstRecHitContainer

typedef TransientTrackingRecHit::ConstRecHitPointer	ConstRecHitPointer

typedef FreeTrajectoryState	FTS

typedef std::vector< TempTrajectory >	TempTrajectoryContainer

typedef TrajectoryMeasurement	TM

typedef TrajectoryMeasurementGroup	TMG

typedef std::vector< Trajectory >	TrajectoryContainer

typedef TrajectoryStateOnSurface	TSOS

Private Member Functions
std::vector< TempTrajectory >	addGroup (TempTrajectory const &traj, std::vector< TrajectoryMeasurementGroup >::const_iterator begin, std::vector< TrajectoryMeasurementGroup >::const_iterator end)

void	cleanCandidates (std::vector< TempTrajectory > &candidates) const
	clean a set of candidates More...

void	lockMeasurement (const TM &measurement)
	mark a hit as used More...

std::vector< TrajectoryMeasurement >	redoMeasurements (const TempTrajectory &traj, const DetGroup &detGroup) const
	retrieve compatible hits from a DetGroup More...

std::vector< TrajectoryMeasurement >	unlockedMeasurements (const std::vector< TM > &measurements) const
	get list of unused hits More...

void	updateCandidates (TempTrajectory const &traj, const std::vector< TM > &measurements, TempTrajectoryContainer &candidates)
	creation of new candidates from a segment and a collection of hits More...

void	updateCandidatesWithBestHit (TempTrajectory const &traj, TM measurements, TempTrajectoryContainer &candidates)
	creation of a new candidate from a segment and the best hit out of a collection More...

void	updateTrajectory (TempTrajectory &traj, TM tm) const
	update of a trajectory with a hit More...

void	updateWithInvalidHit (TempTrajectory &traj, const std::vector< TMG > &groups, TempTrajectoryContainer &candidates) const

Private Attributes
bool	theBestHitOnly

bool	theDbgFlg

const MeasurementEstimator &	theEstimator

const Propagator &	theFullPropagator

const Propagator &	theGeomPropagator

const DetLayer &	theLayer

const LayerMeasurements *	theLayerMeasurements

ConstRecHitContainer	theLockedHits

bool	theLockHits

int	theMaxCand

const TrajectoryStateUpdator &	theUpdator

Detailed Description

Definition at line 32 of file TrajectorySegmentBuilder.h.

Member Typedef Documentation

typedef TransientTrackingRecHit::ConstRecHitContainer TrajectorySegmentBuilder::ConstRecHitContainer

private

Definition at line 42 of file TrajectorySegmentBuilder.h.

typedef TransientTrackingRecHit::ConstRecHitPointer TrajectorySegmentBuilder::ConstRecHitPointer

private

Definition at line 43 of file TrajectorySegmentBuilder.h.

typedef FreeTrajectoryState TrajectorySegmentBuilder::FTS

private

Definition at line 36 of file TrajectorySegmentBuilder.h.

typedef std::vector<TempTrajectory> TrajectorySegmentBuilder::TempTrajectoryContainer

private

Definition at line 41 of file TrajectorySegmentBuilder.h.

typedef TrajectoryMeasurement TrajectorySegmentBuilder::TM

private

Definition at line 38 of file TrajectorySegmentBuilder.h.

typedef TrajectoryMeasurementGroup TrajectorySegmentBuilder::TMG

private

Definition at line 39 of file TrajectorySegmentBuilder.h.

typedef std::vector<Trajectory> TrajectorySegmentBuilder::TrajectoryContainer

private

Definition at line 40 of file TrajectorySegmentBuilder.h.

typedef TrajectoryStateOnSurface TrajectorySegmentBuilder::TSOS

private

Definition at line 37 of file TrajectorySegmentBuilder.h.

Constructor & Destructor Documentation

TrajectorySegmentBuilder::TrajectorySegmentBuilder	(	const LayerMeasurements *	theInputLayerMeasurements,
		const DetLayer &	layer,
		const Propagator &	propagator,
		const TrajectoryStateUpdator &	updator,
		const MeasurementEstimator &	estimator,
		bool	lockHits,
		bool	bestHitOnly,
		int	maxCand
	)

inline

constructor from layer and helper objects

Definition at line 48 of file TrajectorySegmentBuilder.h.

                                                               :
     theLayerMeasurements(theInputLayerMeasurements),
     theLayer(layer),
     theFullPropagator(propagator),
     theUpdator(updator),
     theEstimator(estimator),
     theGeomPropagator(propagator),
 //     theGeomPropagator(propagator.propagationDirection()),
       theLockHits(lockHits),theBestHitOnly(bestHitOnly),theMaxCand(maxCand)
   {}

TrajectorySegmentBuilder::~TrajectorySegmentBuilder ( )

inline

destructor

Definition at line 65 of file TrajectorySegmentBuilder.h.

References begin, objects.IsoTrackAnalyzer::candidates, and end.

65 {}

Member Function Documentation

TrajectorySegmentBuilder::TempTrajectoryContainer TrajectorySegmentBuilder::addGroup	(	TempTrajectory const &	traj,
		std::vector< TrajectoryMeasurementGroup >::const_iterator	begin,
		std::vector< TrajectoryMeasurementGroup >::const_iterator	end
	)

private

Definition at line 228 of file TrajectorySegmentBuilder.cc.

References gather_cfg::cout, cmsutils::bqueue< T >::empty(), TempTrajectory::empty(), TempTrajectory::measurements(), eostools::move(), cmsutils::bqueue< T >::size(), protons_cff::t, and UNLIKELY.

 {
   vector<TempTrajectory> ret;
   if ( begin==end ) {
     //std::cout << "TrajectorySegmentBuilder::addGroup" << " traj.empty()=" << traj.empty() << "EMPTY" << std::endl;
     if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : no groups left" << endl;
     if ( !traj.empty() )
       ret.push_back(traj);
     return ret;
   }
   
   if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : traj.size() = " << traj.measurements().size()
                   << " first group at " << &(*begin)
            //        << " nr. of candidates = " << candidates.size() 
                   << endl;
   
   
   TempTrajectoryContainer updatedTrajectories; updatedTrajectories.reserve(2);
   if ( traj.measurements().empty() ) {
     if ( theMaxCand == 1 ) {
       auto && firstMeasurements = unlockedMeasurements(begin->measurements());
       if (!firstMeasurements.empty()) updateCandidatesWithBestHit(traj,std::move(firstMeasurements.front()),updatedTrajectories);
     } else {
       updateCandidates(traj,begin->measurements(),updatedTrajectories);
     }
     if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : updating with first group - "
                 << updatedTrajectories.size() << " trajectories" << endl;
   }
   else {
     auto && meas = redoMeasurements(traj,begin->detGroup());
     if (!meas.empty()) {
     if ( theBestHitOnly ) {
       updateCandidatesWithBestHit(traj,std::move(meas.front()),
                   updatedTrajectories);
     }else{
       updateCandidates(traj,std::move(meas),
                updatedTrajectories);
     }
     if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : updating"
                 << updatedTrajectories.size() << " trajectories-1" << endl;
     } 
   }
   // keep old trajectory
   //
   updatedTrajectories.push_back(traj);
   
 
   if (begin+1 != end) {
     ret.reserve(4); // a good upper bound
     for (auto const & ut : updatedTrajectories) {
       if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : trying to extend candidate at "
                   << &ut << " size " << ut.measurements().size() << endl;
       vector<TempTrajectory> && finalTrajectories = addGroup(ut,begin+1,end);
       if UNLIKELY(theDbgFlg) cout << "TSB::addGroup : " << finalTrajectories.size()
                   << " finalised candidates before cleaning" << endl;
       //B.M. to be ported later
       // V.I. only mark invalidate
       cleanCandidates(finalTrajectories);
       
       if UNLIKELY(theDbgFlg) {
       int ntf=0; for ( auto const & t : finalTrajectories) if (t.isValid()) ++ntf;
       cout << "TSB::addGroup : got " << ntf
            << " finalised candidates" << endl;
     }
       
       for ( auto & t : finalTrajectories) 
     if (t.isValid()) ret.push_back(std::move(t));
       
       //        ret.insert(ret.end(),make_move_iterator(finalTrajectories.begin()),
       //       make_move_iterator(finalTrajectories.end()));
     }
   } else {
     ret.reserve(updatedTrajectories.size());
     for (auto & t : updatedTrajectories)
       if (!t.empty()) ret.push_back(std::move(t));
   }
   
   //std::cout << "TrajectorySegmentBuilder::addGroup" << 
   //             " traj.empty()=" << traj.empty() << 
   //             " end-begin=" << (end-begin)  <<
   //             " #updated=" << updatedTrajectories.size() << 
   //             " #result=" << ret.size() << std::endl;
   return ret;
 }

void TrajectorySegmentBuilder::cleanCandidates ( std::vector< TempTrajectory > & candidates ) const

private

clean a set of candidates

Definition at line 495 of file TrajectorySegmentBuilder.cc.

References TrackingRecHit::all, runEdmFileComparison::found, mps_fire::i, lessByFoundHits(), cmsutils::bqueue< T >::rbegin(), cmsutils::bqueue< T >::rend(), and jetUpdater_cfi::sort.

 {
   //
   // remove candidates which are subsets of others
   // assumptions: no invalid hits and no duplicates
   //
   if ( candidates.size()<=1 )  return;
   //RecHitEqualByChannels recHitEqual(false,true);
   //
   const int NC = candidates.size();
   int index[NC]; for (int i=0; i!=NC; ++i) index[i]=i;
   std::sort(index,index+NC,[&candidates](int i, int j) { return lessByFoundHits(candidates[i],candidates[j]);});
 //   cout << "SortedCandidates.foundHits";
 //   for (auto i1 : index) 
 //     cout << " " << candidates[i1].foundHits();
 //   cout << endl;
   //
   for ( auto i1 = index; i1!=index+NC-1; ++i1) {
     // get measurements of candidate to be checked
     const TempTrajectory::DataContainer & measurements1 = candidates[*i1].measurements();
     for ( auto i2=i1+1; i2!=index+NC; ++i2 ) {
       // no duplicates: two candidates of same size are different
       if ( candidates[*i2].foundHits()==candidates[*i1].foundHits() )  continue;
       // get measurements of "reference"
       const TempTrajectory::DataContainer & measurements2 = candidates[*i2].measurements();
       //
       // use the fact that TMs are ordered:
       // start search in trajectory#1 from last hit match found
       //
       bool allFound(true);
       TempTrajectory::DataContainer::const_iterator from2 = measurements2.rbegin(), im2end = measurements2.rend();
       for ( TempTrajectory::DataContainer::const_iterator im1=measurements1.rbegin(),im1end = measurements1.rend();
         im1!=im1end; --im1 ) {
     // redundant protection - segments should not contain invalid RecHits
     // assert( im1->recHit()->isValid());
     bool found(false);
     for ( TempTrajectory::DataContainer::const_iterator im2=from2; im2!=im2end; --im2 ) {
       // redundant protection - segments should not contain invalid RecHits
       // assert (im2->recHit()->isValid());
       if ( im1->recHitR().hit()->sharesInput(im2->recHitR().hit(), TrackingRecHit::all) ) {
         found = true;
         from2 = im2; --from2;
         break;
       }
     }
     if ( !found ) {
       allFound = false;
       break;
     }
       }
       if ( allFound ) { candidates[*i1].invalidate(); statCount.invalid();}
     }
   }
 
 }

void TrajectorySegmentBuilder::lockMeasurement ( const TM & measurement )

private

mark a hit as used

Definition at line 486 of file TrajectorySegmentBuilder.cc.

References TrajectoryMeasurement::recHit().

 {
   theLockedHits.push_back(measurement.recHit());
 }

vector< TrajectoryMeasurement > TrajectorySegmentBuilder::redoMeasurements	(	const TempTrajectory &	traj,
		const DetGroup &	detGroup
	)		const

private

retrieve compatible hits from a DetGroup

Definition at line 347 of file TrajectorySegmentBuilder.cc.

References tracking::TempMeasurements::clear(), gather_cfg::cout, tracking::TempMeasurements::distances, tracking::TempMeasurements::hits, mps_fire::i, GeomDetCompatibilityChecker::isCompatible(), TempTrajectory::lastMeasurement(), MeasurementDetWithData::measurements(), eostools::move(), mps_fire::result, tracking::TempMeasurements::size(), jetUpdater_cfi::sort, UNLIKELY, and TrajectoryMeasurement::updatedState().

 {
   vector<TM> result;
   //
   // loop over all dets
   //
   if UNLIKELY(theDbgFlg) cout << "TSB::redoMeasurements : nr. of measurements / group =";
 
   tracking::TempMeasurements tmps;
 
   for (auto const & det : detGroup) {
 
     pair<bool, TrajectoryStateOnSurface> compat = 
       GeomDetCompatibilityChecker().isCompatible(det.det(),
                          traj.lastMeasurement().updatedState(),
                          theGeomPropagator,theEstimator);
     
     if UNLIKELY(theDbgFlg && !compat.first) std::cout << " 0";
 
     if(!compat.first) continue;
 
     MeasurementDetWithData mdet = theLayerMeasurements->idToDet(det.det()->geographicalId());
     // verify also that first (and only!) not be inactive..
     if (mdet.measurements(compat.second, theEstimator,tmps) && tmps.hits[0]->isValid() )
       for (std::size_t i=0; i!=tmps.size(); ++i)
     result.emplace_back(compat.second,std::move(tmps.hits[i]),tmps.distances[i],&theLayer);
 
     if UNLIKELY(theDbgFlg) std::cout << " " << tmps.size();
     tmps.clear();
     
   }
 
   if UNLIKELY(theDbgFlg) cout << endl;  
 
   std::sort( result.begin(), result.end(), TrajMeasLessEstim());
 
   return result;
 }

TrajectorySegmentBuilder::TempTrajectoryContainer TrajectorySegmentBuilder::segments ( const TSOS startingState )

new segments within layer

Definition at line 71 of file TrajectorySegmentBuilder.cc.

References objects.IsoTrackAnalyzer::candidates, constexpr, gather_cfg::cout, LIKELY, TrajectoryStateOnSurface::localError(), funct::m, LocalTrajectoryError::matrix(), dataset::name, and UNLIKELY.

 {
   //
   // create empty trajectory
   //
   theLockedHits.clear();
   TempTrajectory startingTrajectory(theFullPropagator.propagationDirection(),0);
   //
   // get measurement groups
   //
   auto && measGroups = 
     theLayerMeasurements->groupedMeasurements(theLayer,startingState,theFullPropagator,theEstimator);
 
 #ifdef DBG_TSB
   cout << "TSB: number of measurement groups = " << measGroups.size() << endl;
   //  theDbgFlg = measGroups.size()>1;
   theDbgFlg = true;
 #else
   theDbgFlg = false;
 #endif
 
 
 #ifdef TSB_TRUNCATE
   //  V.I. to me makes things slower...
 
   //
   // check number of combinations
   //
   constexpr long long  MAXCOMB = 100000000;
   long long ncomb(1);
   int ngrp(0);
   bool truncate(false);
   for (auto const & gr : measGroups) {
     ++ngrp;
     int nhit(0);
     for ( auto const & m : gr.measurements()) if LIKELY( m.recHitR().isValid() )  nhit++;
     
     if ( nhit>1 )  ncomb *= nhit;
     if UNLIKELY( ncomb>MAXCOMB ) {
     edm::LogInfo("TrajectorySegmentBuilder") << " found " << measGroups.size() 
                          << " groups and more than " << static_cast<unsigned int>(MAXCOMB)
                          << " combinations - limiting to "
                          << (ngrp-1) << " groups";
     truncate = true;
     
     statCount.truncated();
     
     break;
       }
   }  
   //   cout << "Groups / combinations = " << measGroups.size() << " " << ncomb << endl;
   if UNLIKELY( truncate && ngrp>0 )  measGroups.resize(ngrp-1);
 
 #endif
 
 
 #ifdef DBG_TSB
   if ( theDbgFlg ) {
     int ntot(1);
     for (vector<TMG>::const_iterator ig=measGroups.begin();
      ig!=measGroups.end(); ++ig) {
       int ngrp(0);
       const vector<TM>& measurements = ig->measurements();
       for ( vector<TM>::const_iterator im=measurements.begin();
         im!=measurements.end(); ++im ) {
     if ( im->recHit()->isValid() )  ngrp++;
       }
       cout << " " << ngrp;
       if ( ngrp>0 )  ntot *= ngrp;
     }  
     cout << endl;
     cout << "TrajectorySegmentBuilder::partialTrajectories:: det ids & hit types / group" << endl;
     for (vector<TMG>::const_iterator ig=measGroups.begin();
      ig!=measGroups.end(); ++ig) {
       const vector<TM>& measurements = ig->measurements();
       for ( vector<TM>::const_iterator im=measurements.begin();
         im!=measurements.end(); ++im ) {
     if ( im!=measurements.begin() )  cout << " / ";
     if ( im->recHit()->det() )
       cout << im->recHit()->det()->geographicalId().rawId() << " "
            << im->recHit()->getType();
     else
       cout << "no det";
       }
       cout << endl;
     }  
   
 
 //   if ( measGroups.size()>4 ) {
     cout << typeid(theLayer).name() << endl;
     cout << startingState.localError().matrix() << endl;
 //     for (vector<TMG>::const_iterator ig=measGroups.begin();
 //   ig!=measGroups.end(); ig++) {
 //       cout << "Nr. of measurements = " << ig->measurements().size() << endl;
 //       const DetGroup& dg = ig->detGroup();
 //       for ( DetGroup::const_iterator id=dg.begin();
 //      id!=dg.end(); id++ ) {
 //  GlobalPoint p(id->det()->position());
 //  GlobalVector v(id->det()->toGlobal(LocalVector(0.,0.,1.)));
 //  cout << p.perp() << " " << p.phi() << " " << p.z() << " ; "
 //       << v.phi() << " " << v.z() << endl;
 //       }
 //     }
 //   }
   }
 #endif
 
   TempTrajectoryContainer candidates = addGroup(startingTrajectory,measGroups.begin(),measGroups.end());
 
   if UNLIKELY(theDbgFlg) cout << "TSB: back with " << candidates.size() << " candidates" << endl;
 
   //
   // add invalid hit - try to get first detector hit by the extrapolation
   //
 
   updateWithInvalidHit(startingTrajectory,measGroups,candidates);
 
   if UNLIKELY(theDbgFlg) cout << "TSB: " << candidates.size() << " candidates after invalid hit" << endl;
 
   statCount.incr(measGroups.size(), candidates.size(), theLockedHits.size());
 
 
   theLockedHits.clear();
 
   return candidates;
 }

vector< TrajectoryMeasurement > TrajectorySegmentBuilder::unlockedMeasurements ( const std::vector< TM > & measurements ) const

private

get list of unused hits

Definition at line 459 of file TrajectorySegmentBuilder.cc.

References TrackingRecHit::all, runEdmFileComparison::found, h, LIKELY, funct::m, mps_fire::result, and UNLIKELY.

 {
 //   if ( !theLockHits )  return measurements;
 
   vector<TM> result;
   result.reserve(measurements.size());
 
   //RecHitEqualByChannels recHitEqual(false,true);
 
   for ( auto const & m : measurements) {
     auto const & testHit = m.recHitR();
     if UNLIKELY( !testHit.isValid() )  continue;
     bool found(false);
     if LIKELY( theLockHits ) {
       for ( auto const & h : theLockedHits) {
     if ( h->hit()->sharesInput(testHit.hit(), TrackingRecHit::all) ) {
       found = true;
       break;
     }
       }
     }
     if LIKELY( !found )  result.push_back(m);
   }
   return result;
 }

void TrajectorySegmentBuilder::updateCandidates	(	TempTrajectory const &	traj,
		const std::vector< TM > &	measurements,
		TempTrajectoryContainer &	candidates
	)

private

creation of new candidates from a segment and a collection of hits

Definition at line 316 of file TrajectorySegmentBuilder.cc.

 {
   //
   // generate updated candidates with all valid hits
   //
   for ( auto im=measurements.begin();
     im!=measurements.end(); ++im ) {
     if ( im->recHit()->isValid() ) {
       candidates.push_back(traj);
       updateTrajectory(candidates.back(),*im);
       if ( theLockHits )  lockMeasurement(*im);
     }
   }
 }

void TrajectorySegmentBuilder::updateCandidatesWithBestHit	(	TempTrajectory const &	traj,
		TM	measurements,
		TempTrajectoryContainer &	candidates
	)

private

creation of a new candidate from a segment and the best hit out of a collection

Definition at line 334 of file TrajectorySegmentBuilder.cc.

References eostools::move().

 {
   // here we arrive with only valid hits and sorted.
   //so the best is the first!
 
   if ( theLockHits )  lockMeasurement(measurement);
   candidates.push_back(traj);
   updateTrajectory(candidates.back(),std::move(measurement));
 }

void TrajectorySegmentBuilder::updateTrajectory	(	TempTrajectory &	traj,
		TM	tm
	)		const

private

update of a trajectory with a hit

Definition at line 198 of file TrajectorySegmentBuilder.cc.

References TempTrajectory::emplace(), TrajectoryMeasurement::estimate(), TrajectoryMeasurement::layer(), eostools::move(), TrajectoryMeasurement::predictedState(), and TrajectoryMeasurement::recHit().

 {
   auto &&  predictedState = tm.predictedState();
   auto &&  hit = tm.recHit();
   
   if ( hit->isValid()) {
     auto && upState = theUpdator.update( predictedState, *hit); 
     traj.emplace(std::move(predictedState), std::move(upState),
            std::move(hit), tm.estimate(), tm.layer());
 
 //     TrajectoryMeasurement tm(traj.lastMeasurement());
 //     if ( tm.updatedState().isValid() ) {
 //       if ( !hit.det().surface()->bounds().inside(tm.updatedState().localPosition(),
 //                      tm.updatedState().localError().positionError(),3.f) ) {
 //  cout << "Incompatibility after update for det at " << hit.det().position() << ":" << endl;
 //  cout << tm.predictedState().localPosition() << " " 
 //       << tm.predictedState().localError().positionError() << endl;
 //  cout << hit.localPosition() << " " << hit.localPositionError() << endl;
 //  cout << tm.updatedState().localPosition() << " "
 //       << tm.updatedState().localError().positionError() << endl;
 //       }
 //     }
   }
   else {
     traj.emplace(std::move(predictedState), std::move(hit),0, tm.layer());
   }
 }

void TrajectorySegmentBuilder::updateWithInvalidHit	(	TempTrajectory &	traj,
		const std::vector< TMG > &	groups,
		TempTrajectoryContainer &	candidates
	)		const

private

Definition at line 388 of file TrajectorySegmentBuilder.cc.

References gather_cfg::cout, align_cfg::iteration, LIKELY, TrackingRecHit::missing, UNLIKELY, and TrackingRecHit::valid.

 {
   //
   // first try to find an inactive hit with dets crossed by the prediction,
   //   then take any inactive hit
   //
   // loop over groups
   for ( int iteration=0; iteration<2; iteration++ ) {
       for ( auto const &  gr : groups ) {
       auto const & measurements = gr.measurements();
       for ( auto im=measurements.rbegin(); im!=measurements.rend(); ++im ) {
     auto const & hit = im->recHitR();
     if ( (hit.getType()==TrackingRecHit::valid) |
          (hit.getType()==TrackingRecHit::missing) )  continue;
     //
     // check, if the extrapolation traverses the Det or
     // if 2nd iteration
     //
     if ( hit.det() ) {
       auto const & predState = im->predictedState();
       if ( iteration>0 || 
            (predState.isValid() &&
         hit.det()->surface().bounds().inside(predState.localPosition())) ) {
         // add the hit
             candidates.push_back(traj); 
             updateTrajectory(candidates.back(), *im);
         if UNLIKELY( theDbgFlg ) cout << "TrajectorySegmentBuilder::updateWithInvalidHit "
                   << "added inactive hit" << endl;
         return;
       }
     }
       }
     }
   }
   //
   // No suitable inactive hit: add a missing one
   //
   for ( int iteration=0; iteration<2; iteration++ ) {
     //
     // loop over groups
     //
     for ( auto const &  gr : groups ) {
       auto const & measurements = gr.measurements();
       for ( auto im=measurements.rbegin(); im!=measurements.rend(); ++im ) {
     // only use invalid hits
     auto const & hit = im->recHitR();
     if LIKELY( hit.isValid() )  continue;
 
     // check, if the extrapolation traverses the Det
     auto const & predState = im->predictedState();
     if ( iteration>0 || (predState.isValid() &&
                    hit.surface()->bounds().inside(predState.localPosition())) ) {
         // add invalid hit
             candidates.push_back(traj); 
             updateTrajectory(candidates.back(), *im);
             return;
     }
       }
     }
     if UNLIKELY( theDbgFlg && iteration==0 ) cout << "TrajectorySegmentBuilder::updateWithInvalidHit: "
                     << " did not find invalid hit on 1st iteration" << endl;
   }
 
   if UNLIKELY( theDbgFlg)
            cout << "TrajectorySegmentBuilder::updateWithInvalidHit: "
             << " did not find invalid hit" << endl;
 }