PVFitter.cc

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#include "RecoVertex/BeamSpotProducer/interface/PVFitter.h"

#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "CondCore/DBOutputService/interface/PoolDBOutputService.h"
#include "CondFormats/BeamSpotObjects/interface/BeamSpotObjects.h"
#include "FWCore/Framework/interface/ConsumesCollector.h"

#include "FWCore/Utilities/interface/InputTag.h"
#include "DataFormats/Common/interface/View.h"

#include "DataFormats/TrackCandidate/interface/TrackCandidate.h"
#include "DataFormats/TrackCandidate/interface/TrackCandidateCollection.h"
#include "DataFormats/TrackReco/interface/Track.h"
#include "DataFormats/TrackReco/interface/TrackFwd.h"
#include "DataFormats/TrackReco/interface/HitPattern.h"
#include "DataFormats/VertexReco/interface/Vertex.h"

#include "RecoVertex/BeamSpotProducer/interface/FcnBeamSpotFitPV.h"
#include "FWCore/Utilities/interface/isFinite.h"

#include "Minuit2/FCNBase.h"
#include "Minuit2/FunctionMinimum.h"
#include "Minuit2/MnMigrad.h"
#include "Minuit2/MnPrint.h"
#include "TF1.h"
#include "TDirectory.h"
#include "TMinuitMinimizer.h"

#include <iostream>  
#include <sstream>
using namespace std ;

PVFitter::PVFitter(const edm::ParameterSet& iConfig,
                   edm::ConsumesCollector &&iColl)
  : ftree_(nullptr)
{
  initialize(iConfig, iColl);
}

PVFitter::PVFitter(const edm::ParameterSet& iConfig,
                   edm::ConsumesCollector &iColl)
    :ftree_(nullptr)
{
  initialize(iConfig, iColl);
}

void PVFitter::initialize(const edm::ParameterSet& iConfig,
                          edm::ConsumesCollector &iColl)
{
  //In order to make fitting ROOT histograms thread safe
  // one must call this undocumented function
  TMinuitMinimizer::UseStaticMinuit(false);
  debug_             = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<bool>("Debug");
  vertexToken_       = iColl.consumes<reco::VertexCollection>(
      iConfig.getParameter<edm::ParameterSet>("PVFitter")
      .getUntrackedParameter<edm::InputTag>("VertexCollection", edm::InputTag("offlinePrimaryVertices")));
  do3DFit_           = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<bool>("Apply3DFit");
  //writeTxt_          = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<bool>("WriteAscii");
  //outputTxt_         = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<std::string>("AsciiFileName");
  maxNrVertices_     = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<unsigned int>("maxNrStoredVertices");
  minNrVertices_     = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<unsigned int>("minNrVerticesForFit");
  minVtxNdf_         = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("minVertexNdf");
  maxVtxNormChi2_    = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("maxVertexNormChi2");
  minVtxTracks_      = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<unsigned int>("minVertexNTracks");
  minVtxWgt_         = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("minVertexMeanWeight");
  maxVtxR_           = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("maxVertexR");
  maxVtxZ_           = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("maxVertexZ");
  errorScale_        = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("errorScale");
  sigmaCut_          = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("nSigmaCut");
  fFitPerBunchCrossing=iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<bool>("FitPerBunchCrossing");
  useOnlyFirstPV_    = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<bool>("useOnlyFirstPV");
  minSumPt_          = iConfig.getParameter<edm::ParameterSet>("PVFitter").getUntrackedParameter<double>("minSumPt");
  
  // preset quality cut to "infinite"
  dynamicQualityCut_ = 1.e30;

  hPVx = new TH2F("hPVx","PVx vs PVz distribution",200,-maxVtxR_, maxVtxR_, 200, -maxVtxZ_, maxVtxZ_);
  hPVy = new TH2F("hPVy","PVy vs PVz distribution",200,-maxVtxR_, maxVtxR_, 200, -maxVtxZ_, maxVtxZ_);
}

PVFitter::~PVFitter() {

}


void PVFitter::readEvent(const edm::Event& iEvent)
{

  //------ Primary Vertices
  edm::Handle< reco::VertexCollection > PVCollection;
  bool hasPVs = false;

  if ( iEvent.getByToken(vertexToken_, PVCollection ) ) {
      hasPVs = true;
  }
  //------

  if ( hasPVs ) {

      for (reco::VertexCollection::const_iterator pv = PVCollection->begin(); pv != PVCollection->end(); ++pv ) {
          if (useOnlyFirstPV_){
            if (pv != PVCollection->begin()) break;
          }

          //--- vertex selection
          if ( pv->isFake() || pv->tracksSize()==0 )  continue;
          if ( pv->ndof() < minVtxNdf_ || (pv->ndof()+3.)/pv->tracksSize()<2*minVtxWgt_ )  continue;
          //---

          if (pv->tracksSize() < minVtxTracks_ ) continue;

          const auto& testTrack = pv->trackRefAt(0);
          if(testTrack.isNull() || !testTrack.isAvailable())
          {
              edm::LogInfo("") << "Track collection not found. Skipping cut on sumPt.";
          }
          else
          {
              double sumPt=0;
              for(auto iTrack = pv->tracks_begin(); iTrack != pv->tracks_end(); ++iTrack)
              {
                  const auto pt = (*iTrack)->pt();
                  sumPt += pt;
              }
              if (sumPt < minSumPt_) continue;
          }

          hPVx->Fill( pv->x(), pv->z() );
          hPVy->Fill( pv->y(), pv->z() );

          //
          // 3D fit section
          //
          // apply additional quality cut
          if ( pvQuality(*pv)>dynamicQualityCut_ )  continue;
          // if store exceeds max. size: reduce size and apply new quality cut
          if ( pvStore_.size()>=maxNrVertices_ ) {
             compressStore();
             if ( pvQuality(*pv)>dynamicQualityCut_ )  continue;
          }
          //
          // copy PV to store
          //
          int bx = iEvent.bunchCrossing();
          BeamSpotFitPVData pvData;
          pvData.bunchCrossing = bx;
          pvData.position[0] = pv->x();
          pvData.position[1] = pv->y();
          pvData.position[2] = pv->z();
          pvData.posError[0] = pv->xError();
          pvData.posError[1] = pv->yError();
          pvData.posError[2] = pv->zError();
          pvData.posCorr[0] = pv->covariance(0,1)/pv->xError()/pv->yError();
          pvData.posCorr[1] = pv->covariance(0,2)/pv->xError()/pv->zError();
          pvData.posCorr[2] = pv->covariance(1,2)/pv->yError()/pv->zError();
          pvStore_.push_back(pvData);

      if(ftree_ != nullptr){
        theBeamSpotTreeData_.run(iEvent.id().run());
        theBeamSpotTreeData_.lumi(iEvent.luminosityBlock());
        theBeamSpotTreeData_.bunchCrossing(bx);
        theBeamSpotTreeData_.pvData(pvData);
        ftree_->Fill();
      }

      if (fFitPerBunchCrossing) bxMap_[bx].push_back(pvData);

      }

  }

}

void PVFitter::setTree(TTree* tree){
  ftree_ = tree;
  theBeamSpotTreeData_.branch(ftree_);
}

bool PVFitter::runBXFitter() {

  using namespace ROOT::Minuit2;
  edm::LogInfo("PVFitter") << " Number of bunch crossings: " << bxMap_.size() << std::endl;

  bool fit_ok = true;

  for ( std::map<int,std::vector<BeamSpotFitPVData> >::const_iterator pvStore = bxMap_.begin();
    pvStore!=bxMap_.end(); ++pvStore) {

    // first set null beam spot in case
    // fit fails
    fbspotMap[pvStore->first] = reco::BeamSpot();

    edm::LogInfo("PVFitter") << " Number of PVs collected for PVFitter: " << (pvStore->second).size() << " in bx: " << pvStore->first << std::endl;

    if ( (pvStore->second).size() <= minNrVertices_ ) {
        edm::LogWarning("PVFitter") << " not enough PVs, continue" << std::endl;
    fit_ok = false;
      continue;
    }

    edm::LogInfo("PVFitter") << "Calculating beam spot with PVs ..." << std::endl;

    //
    // LL function and fitter
    //
    FcnBeamSpotFitPV* fcn = new FcnBeamSpotFitPV(pvStore->second);
    //
    // fit parameters: positions, widths, x-y correlations, tilts in xz and yz
    //
    MnUserParameters upar;
    upar.Add("x"     , 0.   , 0.02  , -10., 10.);  // 0
    upar.Add("y"     , 0.   , 0.02  , -10., 10.);  // 1
    upar.Add("z"     , 0.   , 0.20  , -30., 30.);  // 2
    upar.Add("ex"    , 0.015, 0.01  , 0.  , 10.);  // 3
    upar.Add("corrxy", 0.   , 0.02  , -1. , 1. );  // 4
    upar.Add("ey"    , 0.015, 0.01  , 0.  , 10.);  // 5
    upar.Add("dxdz"  , 0.   , 0.0002, -0.1, 0.1);  // 6
    upar.Add("dydz"  , 0.   , 0.0002, -0.1, 0.1);  // 7
    upar.Add("ez"    , 1.   , 0.1   , 0.  , 30.);  // 8
    upar.Add("scale", errorScale_   , errorScale_/10.,
                      errorScale_/2., errorScale_*2.);      // 9
    MnMigrad migrad(*fcn, upar);

    //
    // first iteration without correlations
    //
    upar.Fix(4);
    upar.Fix(6);
    upar.Fix(7);
    upar.Fix(9);
    FunctionMinimum ierr = migrad(0,1.);
    if ( !ierr.IsValid() ) {
        edm::LogInfo("PVFitter") << "3D beam spot fit failed in 1st iteration" << std::endl;
    fit_ok = false;
      continue;
    }
    //
    // refit with harder selection on vertices
    //
    fcn->setLimits(upar.Value(0)-sigmaCut_*upar.Value(3),
           upar.Value(0)+sigmaCut_*upar.Value(3),
           upar.Value(1)-sigmaCut_*upar.Value(5),
           upar.Value(1)+sigmaCut_*upar.Value(5),
           upar.Value(2)-sigmaCut_*upar.Value(8),
           upar.Value(2)+sigmaCut_*upar.Value(8));
    ierr = migrad(0,1.);
    if ( !ierr.IsValid() ) {
      edm::LogInfo("PVFitter") << "3D beam spot fit failed in 2nd iteration" << std::endl;
      fit_ok = false;
      continue;
    }
    //
    // refit with correlations
    //
    upar.Release(4);
    upar.Release(6);
    upar.Release(7);
    ierr = migrad(0,1.);
    if ( !ierr.IsValid() ) {
        edm::LogInfo("PVFitter") << "3D beam spot fit failed in 3rd iteration" << std::endl;
    fit_ok = false;
      continue;
    }

    fwidthX = upar.Value(3);
    fwidthY = upar.Value(5);
    fwidthZ = upar.Value(8);
    fwidthXerr = upar.Error(3);
    fwidthYerr = upar.Error(5);
    fwidthZerr = upar.Error(8);

    reco::BeamSpot::CovarianceMatrix matrix;
    // need to get the full cov matrix
    matrix(0,0) = pow( upar.Error(0), 2);
    matrix(1,1) = pow( upar.Error(1), 2);
    matrix(2,2) = pow( upar.Error(2), 2);
    matrix(3,3) = fwidthZerr * fwidthZerr;
    matrix(4,4) = pow( upar.Error(6), 2);
    matrix(5,5) = pow( upar.Error(7), 2);
    matrix(6,6) = fwidthXerr * fwidthXerr;

    fbeamspot = reco::BeamSpot( reco::BeamSpot::Point(upar.Value(0),
                              upar.Value(1),
                              upar.Value(2) ),
                fwidthZ,
                upar.Value(6), upar.Value(7),
                fwidthX,
                matrix );
    fbeamspot.setBeamWidthX( fwidthX );
    fbeamspot.setBeamWidthY( fwidthY );
    fbeamspot.setType( reco::BeamSpot::Tracker );

    fbspotMap[pvStore->first] = fbeamspot;
    edm::LogInfo("PVFitter") << "3D PV fit done for this bunch crossing."<<std::endl;
    //delete fcn;
    fit_ok = fit_ok & true;
  }

  return fit_ok;
}


bool PVFitter::runFitter() {

    using namespace ROOT::Minuit2;
    edm::LogInfo("PVFitter") << " Number of PVs collected for PVFitter: " << pvStore_.size() << std::endl;

    if ( pvStore_.size() <= minNrVertices_ ) return false;

    //need to create a unique histogram name to avoid ROOT trying to re-use one
    // also tell ROOT to hide its global state
    TDirectory::TContext guard{nullptr};
    std::ostringstream str;
    str <<this;
    std::unique_ptr<TH1D> h1PVx{ hPVx->ProjectionX( (std::string("h1PVx")+str.str()).c_str(), 0, -1, "e") };
    std::unique_ptr<TH1D> h1PVy{ hPVy->ProjectionX( (std::string("h1PVy")+str.str()).c_str(), 0, -1, "e") };
    std::unique_ptr<TH1D> h1PVz{ hPVx->ProjectionY( (std::string("h1PVz")+str.str()).c_str(), 0, -1, "e") };

    //Use our own copy for thread safety
    // also do not add to global list of functions
    TF1 gausx("localGausX","gaus",0.,1.,TF1::EAddToList::kNo);
    TF1 gausy("localGausY","gaus",0.,1.,TF1::EAddToList::kNo);
    TF1 gausz("localGausZ","gaus",0.,1.,TF1::EAddToList::kNo);

    h1PVx->Fit(&gausx,"QLMN0 SERIAL");
    h1PVy->Fit(&gausy,"QLMN0 SERIAL");
    h1PVz->Fit(&gausz,"QLMN0 SERIAL");


    fwidthX     = gausx.GetParameter(2);
    fwidthY     = gausy.GetParameter(2);
    fwidthZ     = gausz.GetParameter(2);
    fwidthXerr  = gausx.GetParError(2);
    fwidthYerr  = gausy.GetParError(2);
    fwidthZerr  = gausz.GetParError(2);
    
    double estX = gausx.GetParameter(1);
    double estY = gausy.GetParameter(1); 
    double estZ = gausz.GetParameter(1);
    double errX = fwidthX*3.;
    double errY = fwidthY*3.; 
    double errZ = fwidthZ*3.;

    if ( ! do3DFit_ ) {

      reco::BeamSpot::CovarianceMatrix matrix;
      matrix(2,2) = gausz.GetParError(1) * gausz.GetParError(1);
      matrix(3,3) = fwidthZerr * fwidthZerr;
      matrix(6,6) = fwidthXerr * fwidthXerr;

      fbeamspot = reco::BeamSpot( reco::BeamSpot::Point(gausx.GetParameter(1),
                                                        gausy.GetParameter(1),
                                                        gausz.GetParameter(1) ),
                                  fwidthZ,
                                  0., 0.,
                                  fwidthX,
                                  matrix );
      fbeamspot.setBeamWidthX( fwidthX );
      fbeamspot.setBeamWidthY( fwidthY );
      fbeamspot.setType(reco::BeamSpot::Tracker);

    }
    else { // do 3D fit
      //
      // LL function and fitter
      //
      FcnBeamSpotFitPV* fcn = new FcnBeamSpotFitPV(pvStore_);
      //
      // fit parameters: positions, widths, x-y correlations, tilts in xz and yz
      //
      MnUserParameters upar;
      upar.Add("x"     , estX       , errX       , -10.     , 10.       ); // 0
      upar.Add("y"     , estY       , errY       , -10.     , 10.       ); // 1
      upar.Add("z"     , estZ       , errZ       , -30.     , 30.       ); // 2
      upar.Add("ex"    , 0.015      , 0.01       , 0.       , 10.       ); // 3
      upar.Add("corrxy", 0.         , 0.02       , -1.      , 1.        ); // 4
      upar.Add("ey"    , 0.015      , 0.01       , 0.       , 10.       ); // 5
      upar.Add("dxdz"  , 0.         , 0.0002     , -0.1     , 0.1       ); // 6
      upar.Add("dydz"  , 0.         , 0.0002     , -0.1     , 0.1       ); // 7
      upar.Add("ez"    , 1.         , 0.1        , 0.       , 30.       ); // 8
      upar.Add("scale" , errorScale_, errorScale_/10.,errorScale_/2., errorScale_*2.); // 9  
      MnMigrad migrad(*fcn, upar);
      //
      // first iteration without correlations
      //
      migrad.Fix(4);
      migrad.Fix(6);
      migrad.Fix(7);
      migrad.Fix(9);
      FunctionMinimum ierr = migrad(0,1.);
      if ( !ierr.IsValid() ) {
          edm::LogWarning("PVFitter") << "3D beam spot fit failed in 1st iteration" << std::endl;
          return false;
      }
      //
      // refit with harder selection on vertices
      //

      vector<double> results ;
      vector<double> errors  ;
      results = ierr.UserParameters().Params() ;                           \
      errors  = ierr.UserParameters().Errors() ;                           \

      
      fcn->setLimits(results[0]-sigmaCut_*results[3],
                     results[0]+sigmaCut_*results[3],
                     results[1]-sigmaCut_*results[5],
                     results[1]+sigmaCut_*results[5],
                     results[2]-sigmaCut_*results[8],
                     results[2]+sigmaCut_*results[8]);
      ierr = migrad(0,1.);
      if ( !ierr.IsValid() ) {
          edm::LogWarning("PVFitter") << "3D beam spot fit failed in 2nd iteration" << std::endl;
          return false;
      }
      //
      // refit with correlations
      //
      migrad.Release(4);
      migrad.Release(6);
      migrad.Release(7);
      ierr = migrad(0,1.);
      if ( !ierr.IsValid() ) {
          edm::LogWarning("PVFitter") << "3D beam spot fit failed in 3rd iteration" << std::endl;
          return false;
      }

      results = ierr.UserParameters().Params() ;                           \
      errors  = ierr.UserParameters().Errors() ;                           \

      fwidthX = results[3];
      fwidthY = results[5];
      fwidthZ = results[8];
      fwidthXerr = errors[3];
      fwidthYerr = errors[5];
      fwidthZerr = errors[8];

      // check errors on widths and sigmaZ for nan
      if ( edm::isNotFinite(fwidthXerr) || edm::isNotFinite(fwidthYerr) || edm::isNotFinite(fwidthZerr) ) {
          edm::LogWarning("PVFitter") << "3D beam spot fit returns nan in 3rd iteration" << std::endl;
          return false;
      }

      reco::BeamSpot::CovarianceMatrix matrix;
      // need to get the full cov matrix
      matrix(0,0) = pow( errors[0], 2);
      matrix(1,1) = pow( errors[1], 2);
      matrix(2,2) = pow( errors[2], 2);
      matrix(3,3) = fwidthZerr * fwidthZerr;
      matrix(6,6) = fwidthXerr * fwidthXerr;

      fbeamspot = reco::BeamSpot( reco::BeamSpot::Point(results[0],
                                                        results[1],
                                                        results[2] ),
                                  fwidthZ,
                                  results[6], results[7],
                                  fwidthX,
                                  matrix );
      fbeamspot.setBeamWidthX( fwidthX );
      fbeamspot.setBeamWidthY( fwidthY );
      fbeamspot.setType(reco::BeamSpot::Tracker); 
    }

    return true;
}

void PVFitter::dumpTxtFile(){

}


void
PVFitter::compressStore ()
{
  //
  // fill vertex qualities
  //
  pvQualities_.resize(pvStore_.size());
  for ( unsigned int i=0; i<pvStore_.size(); ++i )  pvQualities_[i] = pvQuality(pvStore_[i]);
  sort(pvQualities_.begin(),pvQualities_.end());
  //
  // Set new quality cut to median. This cut will be used to reduce the
  // number of vertices in the store and also apply to all new vertices
  // until the next reset
  //
  dynamicQualityCut_ = pvQualities_[pvQualities_.size()/2];
  //
  // remove all vertices failing the cut from the store
  //   (to be moved to a more efficient memory management!)
  //
  unsigned int iwrite(0);
  for ( unsigned int i=0; i<pvStore_.size(); ++i ) {
    if ( pvQuality(pvStore_[i])>dynamicQualityCut_ )  continue;
    if ( i!=iwrite )  pvStore_[iwrite] = pvStore_[i];
    ++iwrite;
  }
  pvStore_.resize(iwrite);
  edm::LogInfo("PVFitter") << "Reduced primary vertex store size to "
                           << pvStore_.size() << " ; new dynamic quality cut = "
                           << dynamicQualityCut_ << std::endl;

}

double
PVFitter::pvQuality (const reco::Vertex& pv) const
{
  //
  // determinant of the transverse part of the PV covariance matrix
  //
  return
    pv.covariance(0,0)*pv.covariance(1,1)-
    pv.covariance(0,1)*pv.covariance(0,1);
}

double
PVFitter::pvQuality (const BeamSpotFitPVData& pv) const
{
  //
  // determinant of the transverse part of the PV covariance matrix
  //
  double ex = pv.posError[0];
  double ey = pv.posError[1];
  return ex*ex*ey*ey*(1-pv.posCorr[0]*pv.posCorr[0]);
}