PFlow2DClusterizerWithTime.cc

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#include "PFlow2DClusterizerWithTime.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "DataFormats/Math/interface/deltaR.h"
#include "DataFormats/ParticleFlowReco/interface/PFRecHit.h"

#include "Math/GenVector/VectorUtil.h"

#include "vdt/vdtMath.h"

#include "TMath.h"

#include <iterator>

#ifdef PFLOW_DEBUG
#define LOGVERB(x) edm::LogVerbatim(x)
#define LOGWARN(x) edm::LogWarning(x)
#define LOGERR(x) edm::LogError(x)
#define LOGDRESSED(x) edm::LogInfo(x)
#else
#define LOGVERB(x) LogTrace(x)
#define LOGWARN(x) edm::LogWarning(x)
#define LOGERR(x) edm::LogError(x)
#define LOGDRESSED(x) LogDebug(x)
#endif

PFlow2DClusterizerWithTime::
PFlow2DClusterizerWithTime(const edm::ParameterSet& conf) :
    PFClusterBuilderBase(conf),
    _maxIterations(conf.getParameter<unsigned>("maxIterations")),
    _stoppingTolerance(conf.getParameter<double>("stoppingTolerance")),
    _showerSigma2(std::pow(conf.getParameter<double>("showerSigma"),2.0)),
    _timeSigma_eb(std::pow(conf.getParameter<double>("timeSigmaEB"),2.0)),
    _timeSigma_ee(std::pow(conf.getParameter<double>("timeSigmaEE"),2.0)),
    _excludeOtherSeeds(conf.getParameter<bool>("excludeOtherSeeds")),
    _minFracTot(conf.getParameter<double>("minFracTot")),
    _maxNSigmaTime(std::pow(conf.getParameter<double>("maxNSigmaTime"),2.0)),
    _minChi2Prob(conf.getParameter<double>("minChi2Prob")),
    _clusterTimeResFromSeed(conf.getParameter<bool>("clusterTimeResFromSeed")),

    _layerMap({ {"PS2",(int)PFLayer::PS2},
            {"PS1",(int)PFLayer::PS1},
            {"ECAL_ENDCAP",(int)PFLayer::ECAL_ENDCAP},
            {"ECAL_BARREL",(int)PFLayer::ECAL_BARREL},
            {"NONE",(int)PFLayer::NONE},
            {"HCAL_BARREL1",(int)PFLayer::HCAL_BARREL1},
            {"HCAL_BARREL2_RING0",(int)PFLayer::HCAL_BARREL2},
        {"HCAL_BARREL2_RING1",100*(int)PFLayer::HCAL_BARREL2},
            {"HCAL_ENDCAP",(int)PFLayer::HCAL_ENDCAP},
            {"HF_EM",(int)PFLayer::HF_EM},
        {"HF_HAD",(int)PFLayer::HF_HAD} }) { 


  const std::vector<edm::ParameterSet>& thresholds =
    conf.getParameterSetVector("recHitEnergyNorms");
  for( const auto& pset : thresholds ) {
    const std::string& det = pset.getParameter<std::string>("detector");
    const double& rhE_norm = pset.getParameter<double>("recHitEnergyNorm");    
    auto entry = _layerMap.find(det);
    if( entry == _layerMap.end() ) {
      throw cms::Exception("InvalidDetectorLayer")
    << "Detector layer : " << det << " is not in the list of recognized"
    << " detector layers!";
    }
    _recHitEnergyNorms.emplace(_layerMap.find(det)->second,rhE_norm);
  }
  
  if( conf.exists("allCellsPositionCalc") ) {
    const edm::ParameterSet& acConf = 
      conf.getParameterSet("allCellsPositionCalc");
    const std::string& algoac = 
      acConf.getParameter<std::string>("algoName");
    _allCellsPosCalc = std::unique_ptr<PFCPositionCalculatorBase>{PFCPositionCalculatorFactory::get()->create(algoac, acConf)};
  }
  // if necessary a third pos calc for convergence testing
  if( conf.exists("positionCalcForConvergence") ) {
    const edm::ParameterSet& convConf = 
      conf.getParameterSet("positionCalcForConvergence");
    const std::string& algoconv = 
      convConf.getParameter<std::string>("algoName");
    _convergencePosCalc = std::unique_ptr<PFCPositionCalculatorBase>{PFCPositionCalculatorFactory::get()->create(algoconv, convConf)};
  }
  if( conf.exists("timeResolutionCalcBarrel") ) {
    const edm::ParameterSet& timeResConf = 
      conf.getParameterSet("timeResolutionCalcBarrel");
    _timeResolutionCalcBarrel = std::make_unique<CaloRecHitResolutionProvider>(
        timeResConf);
  }
  if( conf.exists("timeResolutionCalcEndcap") ) {
    const edm::ParameterSet& timeResConf = 
      conf.getParameterSet("timeResolutionCalcEndcap");
    _timeResolutionCalcEndcap = std::make_unique<CaloRecHitResolutionProvider>(
        timeResConf);
  }
}

void PFlow2DClusterizerWithTime::
buildClusters(const reco::PFClusterCollection& input,
          const std::vector<bool>& seedable,
          reco::PFClusterCollection& output) {
  reco::PFClusterCollection clustersInTopo;
  for( const auto& topocluster : input ) {
    clustersInTopo.clear();
    seedPFClustersFromTopo(topocluster,seedable,clustersInTopo);
    const unsigned tolScal = 
      std::pow(std::max(1.0,clustersInTopo.size()-1.0),2.0);
    growPFClusters(topocluster,seedable,tolScal,0,tolScal,clustersInTopo);
    // step added by Josh Bendavid, removes low-fraction clusters
    // did not impact position resolution with fraction cut of 1e-7
    // decreases the size of each pf cluster considerably
    prunePFClusters(clustersInTopo);
    // recalculate the positions of the pruned clusters
    if( _convergencePosCalc ) { 
      // if defined, use the special position calculation for convergence tests
      _convergencePosCalc->calculateAndSetPositions(clustersInTopo);
    } else {
      if( clustersInTopo.size() == 1 && _allCellsPosCalc ) {
    _allCellsPosCalc->calculateAndSetPosition(clustersInTopo.back());
      } else {
    _positionCalc->calculateAndSetPositions(clustersInTopo);
      }   
    }
    for( auto& clusterout : clustersInTopo ) {
      output.insert(output.end(),std::move(clusterout));
    }
  }
}

void PFlow2DClusterizerWithTime::
seedPFClustersFromTopo(const reco::PFCluster& topo,
               const std::vector<bool>& seedable,
               reco::PFClusterCollection& initialPFClusters) const {
  const auto& recHitFractions = topo.recHitFractions();
  for( const auto& rhf : recHitFractions ) {
    if( !seedable[rhf.recHitRef().key()] ) continue;
    initialPFClusters.push_back(reco::PFCluster());
    reco::PFCluster& current = initialPFClusters.back();
    current.addRecHitFraction(rhf);
    current.setSeed(rhf.recHitRef()->detId());   
    if( _convergencePosCalc ) {
      _convergencePosCalc->calculateAndSetPosition(current);
    } else {
      _positionCalc->calculateAndSetPosition(current);
    }
  }
}

void PFlow2DClusterizerWithTime::
growPFClusters(const reco::PFCluster& topo,
           const std::vector<bool>& seedable,
           const unsigned toleranceScaling,
           const unsigned iter,
           double diff,
           reco::PFClusterCollection& clusters) const {
  if( iter >= _maxIterations ) {
    LOGDRESSED("PFlow2DClusterizerWithTime:growAndStabilizePFClusters")
      <<"reached " << _maxIterations << " iterations, terminated position "
      << "fit with diff = " << diff;
  }      
  if( iter >= _maxIterations || 
      diff <= _stoppingTolerance*toleranceScaling) return;
  // reset the rechits in this cluster, keeping the previous position    
  std::vector<reco::PFCluster::REPPoint> clus_prev_pos;  
  // also calculate and keep the previous time resolution
  std::vector<double> clus_prev_timeres2;
  
  for( auto& cluster : clusters) {
    const reco::PFCluster::REPPoint& repp = cluster.positionREP();
    clus_prev_pos.emplace_back(repp.rho(),repp.eta(),repp.phi());
    if( _convergencePosCalc ) {
      if( clusters.size() == 1 && _allCellsPosCalc ) {
    _allCellsPosCalc->calculateAndSetPosition(cluster);
      } else {
    _positionCalc->calculateAndSetPosition(cluster);
      }
    }
    double resCluster2;
    if (_clusterTimeResFromSeed)
      clusterTimeResolutionFromSeed(cluster, resCluster2);
    else
      clusterTimeResolution(cluster, resCluster2);
    clus_prev_timeres2.push_back(resCluster2);
    cluster.resetHitsAndFractions();
  }
  // loop over topo cluster and grow current PFCluster hypothesis 
  std::vector<double> dist2, frac;

  // Store chi2 values and nhits to calculate chi2 prob. inline
  std::vector<double> clus_chi2;
  std::vector<size_t> clus_chi2_nhits;

  double fractot = 0;
  for( const reco::PFRecHitFraction& rhf : topo.recHitFractions() ) {
    const reco::PFRecHitRef& refhit = rhf.recHitRef();
    int cell_layer = (int)refhit->layer();
    if( cell_layer == PFLayer::HCAL_BARREL2 && 
    std::abs(refhit->positionREP().eta()) > 0.34 ) {
      cell_layer *= 100;
    }  
    const double recHitEnergyNorm = 
      _recHitEnergyNorms.find(cell_layer)->second; 
    math::XYZPoint topocellpos_xyz(refhit->position());
    dist2.clear(); frac.clear(); fractot = 0;

    // add rechits to clusters, calculating fraction based on distance
    // need position in vector to get cluster time resolution   
    for (size_t iCluster = 0; iCluster < clusters.size(); ++iCluster) {
      reco::PFCluster& cluster = clusters[iCluster];
      const math::XYZPoint& clusterpos_xyz = cluster.position();
      const math::XYZVector deltav = clusterpos_xyz - topocellpos_xyz;
      double d2 = deltav.Mag2()/_showerSigma2;

      double d2time = dist2Time(cluster, refhit, cell_layer,
        clus_prev_timeres2[iCluster]);
      d2 += d2time;

      if (_minChi2Prob > 0. && !passChi2Prob(iCluster, d2time, clus_chi2, 
        clus_chi2_nhits))
        d2 = 999.;

      dist2.emplace_back( d2);

      if( d2 > 100 ) {
    LOGDRESSED("PFlow2DClusterizerWithTime:growAndStabilizePFClusters")
      << "Warning! :: pfcluster-topocell distance is too large! d= "
      << d2;
      }
      // fraction assignment logic
      double fraction;
      if( refhit->detId() == cluster.seed() && _excludeOtherSeeds ) {
    fraction = 1.0; 
      } else if ( seedable[refhit.key()] && _excludeOtherSeeds ) {
    fraction = 0.0;
      } else {
    fraction = cluster.energy()/recHitEnergyNorm * vdt::fast_expf( -0.5*d2 );
      }      
      fractot += fraction;
      frac.emplace_back(fraction);
    }
    for( unsigned i = 0; i < clusters.size(); ++i ) {      
      if( fractot > _minFracTot || 
      ( refhit->detId() == clusters[i].seed() && fractot > 0.0 ) ) {
    frac[i]/=fractot;
      } else {
    continue;
      }
      // if the fraction has been set to 0, the cell 
      // is now added to the cluster - careful ! (PJ, 19/07/08)
      // BUT KEEP ONLY CLOSE CELLS OTHERWISE MEMORY JUST EXPLOSES
      // (PJ, 15/09/08 <- similar to what existed before the 
      // previous bug fix, but keeps the close seeds inside, 
      // even if their fraction was set to zero.)
      // Also add a protection to keep the seed in the cluster 
      // when the latter gets far from the former. These cases
      // (about 1% of the clusters) need to be studied, as 
      // they create fake photons, in general.
      // (PJ, 16/09/08) 
      if( dist2[i] < 100.0 || frac[i] > 0.9999 ) {  
    clusters[i].addRecHitFraction(reco::PFRecHitFraction(refhit,frac[i]));
      }
    }
  }
  // recalculate positions and calculate convergence parameter
  double diff2 = 0.0;  
  for( unsigned i = 0; i < clusters.size(); ++i ) {
    if( _convergencePosCalc ) {
      _convergencePosCalc->calculateAndSetPosition(clusters[i]);
    } else {
      if( clusters.size() == 1 && _allCellsPosCalc ) {
    _allCellsPosCalc->calculateAndSetPosition(clusters[i]);
      } else {
    _positionCalc->calculateAndSetPosition(clusters[i]);
      }
    }
    const double delta2 = 
      reco::deltaR2(clusters[i].positionREP(),clus_prev_pos[i]);    
    if( delta2 > diff2 ) diff2 = delta2;
  }
  diff = std::sqrt(diff2);
  dist2.clear(); frac.clear(); clus_prev_pos.clear();// avoid badness
  clus_chi2.clear(); clus_chi2_nhits.clear(); clus_prev_timeres2.clear();
  growPFClusters(topo,seedable,toleranceScaling,iter+1,diff,clusters);
}

void PFlow2DClusterizerWithTime::
prunePFClusters(reco::PFClusterCollection& clusters) const {
  for( auto& cluster : clusters ) {
    cluster.pruneUsing( [&](const reco::PFRecHitFraction& rhf)
            {return rhf.fraction() > _minFractionToKeep;} 
            );    
  }
}

void PFlow2DClusterizerWithTime::clusterTimeResolutionFromSeed(reco::PFCluster& 
  cluster, double& clusterRes2) const
{
  clusterRes2 = 10000.;
  for (auto& rhf : cluster.recHitFractions())
  {
    const reco::PFRecHit& rh = *(rhf.recHitRef());
    if (rh.detId() == cluster.seed())
    {
      cluster.setTime(rh.time());
      bool isBarrel = (rh.layer() == PFLayer::HCAL_BARREL1 ||
       rh.layer() == PFLayer::HCAL_BARREL2 ||
       rh.layer() == PFLayer::ECAL_BARREL);
     if (isBarrel)
       clusterRes2 = _timeResolutionCalcBarrel->timeResolution2(rh.energy());
     else
       clusterRes2 = _timeResolutionCalcEndcap->timeResolution2(rh.energy());
     cluster.setTimeError(std::sqrt(float(clusterRes2)));
    }
  }
}

void PFlow2DClusterizerWithTime::clusterTimeResolution(reco::PFCluster& cluster, 
    double& clusterRes2) const
{
  double sumTimeSigma2 = 0.;
  double sumSigma2 = 0.;

  for (auto& rhf : cluster.recHitFractions())
  {
    const reco::PFRecHit& rh = *(rhf.recHitRef());
    const double rhf_f = rhf.fraction();

    if (rhf_f == 0.)
      continue;

    bool isBarrel = (rh.layer() == PFLayer::HCAL_BARREL1 ||
      rh.layer() == PFLayer::HCAL_BARREL2 ||
      rh.layer() == PFLayer::ECAL_BARREL);
    double res2 = 10000.;
    if (isBarrel)
      res2 = _timeResolutionCalcBarrel->timeResolution2(rh.energy());
    else
      res2 = _timeResolutionCalcEndcap->timeResolution2(rh.energy());

    sumTimeSigma2 += rhf_f * rh.time()/res2;
    sumSigma2 += rhf_f/res2;
  }
  if (sumSigma2 > 0.) {
    clusterRes2 = 1./sumSigma2;
    cluster.setTime(sumTimeSigma2/sumSigma2);
    cluster.setTimeError(std::sqrt(float(clusterRes2)));
  } else {
    clusterRes2 = 999999.;
  }
}

double PFlow2DClusterizerWithTime::dist2Time(const reco::PFCluster& cluster, 
  const reco::PFRecHitRef& refhit, int cell_layer, double prev_timeres2) const 
{
  const double deltaT = cluster.time()-refhit->time();
  const double t2 = deltaT*deltaT;
  double res2 = 100.;

  if (cell_layer == PFLayer::HCAL_BARREL1 ||
  cell_layer == PFLayer::HCAL_BARREL2 ||
  cell_layer == PFLayer::ECAL_BARREL) {
    if (_timeResolutionCalcBarrel) {
      const double resCluster2 = prev_timeres2;
      res2 = resCluster2 + _timeResolutionCalcBarrel->timeResolution2(
        refhit->energy());
    }
    else {
      return t2/_timeSigma_eb;
    }
  }
  else if (cell_layer == PFLayer::HCAL_ENDCAP ||
     cell_layer == PFLayer::HF_EM ||
     cell_layer == PFLayer::HF_HAD ||
     cell_layer == PFLayer::ECAL_ENDCAP) {
    if (_timeResolutionCalcEndcap) {
      const double resCluster2 = prev_timeres2;
      res2 = resCluster2 + _timeResolutionCalcEndcap->timeResolution2(
        refhit->energy());
    }
     else {
      return t2/_timeSigma_ee;
    }
  }

  double distTime2 = t2/res2;
  if (distTime2 > _maxNSigmaTime)
    return 999.; // reject hit

  return distTime2;
}

bool PFlow2DClusterizerWithTime::passChi2Prob(size_t iCluster, double dist2, 
  std::vector<double>& clus_chi2, std::vector<size_t>& clus_chi2_nhits) const
{
  if (iCluster >= clus_chi2.size()) { // first hit
    clus_chi2.push_back(dist2);
    clus_chi2_nhits.push_back(1);
    return true;
  }
  else {
    double chi2 = clus_chi2[iCluster];
    size_t nhitsCluster = clus_chi2_nhits[iCluster];
    chi2 += dist2;
    if (TMath::Prob(chi2, nhitsCluster) >= _minChi2Prob) {
      clus_chi2[iCluster] = chi2;
      clus_chi2_nhits[iCluster] = nhitsCluster + 1;
      return true;
    }
  }
  return false;
}