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 /**
  * \file CSCSegAlgoShowering.cc
  *
  *  Last update: 17.02.2015
  *
  */
 
 #include "RecoLocalMuon/CSCSegment/src/CSCSegAlgoShowering.h"
 #include "RecoLocalMuon/CSCSegment/src/CSCSegFit.h"
 
 #include "Geometry/CSCGeometry/interface/CSCLayer.h"
 #include <Geometry/CSCGeometry/interface/CSCChamber.h>
 #include "DataFormats/GeometryVector/interface/GlobalPoint.h"
 
 #include "FWCore/ParameterSet/interface/ParameterSet.h"
 #include "FWCore/MessageLogger/interface/MessageLogger.h"
 
 #include <algorithm>
 #include <cmath>
 #include <iostream>
 #include <string>
 
 /* Constructor
  *
  */
 CSCSegAlgoShowering::CSCSegAlgoShowering(const edm::ParameterSet& ps) : sfit_(nullptr) {
   //  debug                  = ps.getUntrackedParameter<bool>("CSCSegmentDebug");
   dRPhiFineMax = ps.getParameter<double>("dRPhiFineMax");
   dPhiFineMax = ps.getParameter<double>("dPhiFineMax");
   tanThetaMax = ps.getParameter<double>("tanThetaMax");
   tanPhiMax = ps.getParameter<double>("tanPhiMax");
   maxRatioResidual = ps.getParameter<double>("maxRatioResidualPrune");
   //  maxDR                  = ps.getParameter<double>("maxDR");
   maxDTheta = ps.getParameter<double>("maxDTheta");
   maxDPhi = ps.getParameter<double>("maxDPhi");
 }
 
 /* Destructor:
  *
  */
 CSCSegAlgoShowering::~CSCSegAlgoShowering() {}
 
 /* showerSeg
  *
  */
 CSCSegment CSCSegAlgoShowering::showerSeg(const CSCChamber* aChamber, const ChamberHitContainer& rechits) {
   theChamber = aChamber;
   // Initialize parameters
   std::vector<float> x, y, gz;
   std::vector<int> n;
 
   for (int i = 0; i < 6; ++i) {
     x.push_back(0.);
     y.push_back(0.);
     gz.push_back(0.);
     n.push_back(0);
   }
 
   // Loop over hits to find center-of-mass position in each layer
   for (ChamberHitContainer::const_iterator it = rechits.begin(); it != rechits.end(); ++it) {
     const CSCRecHit2D& hit = (**it);
     const CSCDetId id = hit.cscDetId();
     int l_id = id.layer();
     const CSCLayer* layer = theChamber->layer(hit.cscDetId().layer());
     GlobalPoint gp = layer->toGlobal(hit.localPosition());
     LocalPoint lp = theChamber->toLocal(gp);
 
     ++n[l_id - 1];
     x[l_id - 1] += lp.x();
     y[l_id - 1] += lp.y();
     gz[l_id - 1] += gp.z();
   }
 
   // Determine center of mass for each layer and average center of mass for chamber
   float avgChamberX = 0.;
   float avgChamberY = 0.;
   int n_lay = 0;
 
   for (unsigned i = 0; i < 6; ++i) {
     if (n[i] < 1)
       continue;
 
     x[i] = x[i] / n[i];
     y[i] = y[i] / n[i];
     avgChamberX += x[i];
     avgChamberY += y[i];
     n_lay++;
   }
 
   if (n_lay > 0) {
     avgChamberX = avgChamberX / n_lay;
     avgChamberY = avgChamberY / n_lay;
   }
 
   // Create a FakeSegment origin that points back to the IP
   // Keep all this in global coordinates until last minute to avoid screwing up +/- signs !
 
   LocalPoint lpCOM(avgChamberX, avgChamberY, 0.);
   GlobalPoint gpCOM = theChamber->toGlobal(lpCOM);
   GlobalVector gvCOM(gpCOM.x(), gpCOM.y(), gpCOM.z());
 
   float Gdxdz = gpCOM.x() / gpCOM.z();
   float Gdydz = gpCOM.y() / gpCOM.z();
 
   // Figure out the intersection of this vector with each layer of the chamber
   // by projecting the vector
   std::vector<LocalPoint> layerPoints;
 
   for (size_t i = 0; i != 6; ++i) {
     // Get the layer z coordinates in global frame
     const CSCLayer* layer = theChamber->layer(i + 1);
     LocalPoint temp(0., 0., 0.);
     GlobalPoint gp = layer->toGlobal(temp);
     float layer_Z = gp.z();
 
     // Then compute interesection of vector with that plane
     float layer_X = Gdxdz * layer_Z;
     float layer_Y = Gdydz * layer_Z;
     GlobalPoint Gintersect(layer_X, layer_Y, layer_Z);
     LocalPoint Lintersect = theChamber->toLocal(Gintersect);
 
     float layerX = Lintersect.x();
     float layerY = Lintersect.y();
     float layerZ = Lintersect.z();
     LocalPoint layerPoint(layerX, layerY, layerZ);
     layerPoints.push_back(layerPoint);
   }
 
   std::vector<float> r_closest;
   std::vector<int> id;
   for (size_t i = 0; i != 6; ++i) {
     id.push_back(-1);
     r_closest.push_back(9999.);
   }
 
   int idx = 0;
 
   // Loop over all hits and find hit closest to com for that layer.
   for (ChamberHitContainer::const_iterator it = rechits.begin(); it != rechits.end(); ++it) {
     const CSCRecHit2D& hit = (**it);
     int layId = hit.cscDetId().layer();
 
     const CSCLayer* layer = theChamber->layer(layId);
     GlobalPoint gp = layer->toGlobal(hit.localPosition());
     LocalPoint lp = theChamber->toLocal(gp);
 
     float d_x = lp.x() - layerPoints[layId - 1].x();
     float d_y = lp.y() - layerPoints[layId - 1].y();
 
     LocalPoint diff(d_x, d_y, 0.);
 
     if (fabs(diff.mag()) < r_closest[layId - 1]) {
       r_closest[layId - 1] = fabs(diff.mag());
       id[layId - 1] = idx;
     }
     ++idx;
   }
 
   // Now fill vector of rechits closest to center of mass:
   protoSegment.clear();
   idx = 0;
 
   // Loop over all hits and find hit closest to com for that layer.
   for (ChamberHitContainer::const_iterator it = rechits.begin(); it != rechits.end(); ++it) {
     const CSCRecHit2D& hit = (**it);
     int layId = hit.cscDetId().layer();
 
     if (idx == id[layId - 1])
       protoSegment.push_back(*it);
 
     ++idx;
   }
 
   // Reorder hits in protosegment
   if (gz[0] > 0.) {
     if (gz[0] > gz[5]) {
       reverse(protoSegment.begin(), protoSegment.end());
     }
   } else if (gz[0] < 0.) {
     if (gz[0] < gz[5]) {
       reverse(protoSegment.begin(), protoSegment.end());
     }
   }
 
   // Fit the protosegment
   updateParameters();
 
   // If there is one very bad hit on segment, remove it and refit
   if (protoSegment.size() > 4)
     pruneFromResidual();
 
   // If any hit on a layer is closer to segment than original, replace it and refit
   for (ChamberHitContainer::const_iterator it = rechits.begin(); it != rechits.end(); it++) {
     const CSCRecHit2D* h = *it;
     int layer = h->cscDetId().layer();
     if (isHitNearSegment(h))
       compareProtoSegment(h, layer);
   }
 
   // Check again for a bad hit, and remove and refit if necessary
   if (sfit_->nhits() > 5)
     pruneFromResidual();
 
   // Does the fitted line point to the IP?
   // If it doesn't, the algorithm has probably failed i.e. that's life!
 
   GlobalVector protoGlobalDir = theChamber->toGlobal(sfit_->localdir());
   double protoTheta = protoGlobalDir.theta();
   double protoPhi = protoGlobalDir.phi();
   double simTheta = gvCOM.theta();
   double simPhi = gvCOM.phi();
 
   float dTheta = fabs(protoTheta - simTheta);
   float dPhi = fabs(protoPhi - simPhi);
   //  float dR = sqrt(dEta*dEta + dPhi*dPhi);
 
   // Flag the segment with chi2=-1 of the segment isn't pointing toward origin
   // i.e. flag that the algorithm has probably just failed (I presume we expect
   // a segment to point to the IP if the algorithm is successful!)
 
   double theFlag = -1.;
   if (dTheta > maxDTheta || dPhi > maxDPhi) {
   } else {
     theFlag = sfit_->chi2();  // If it points to IP, just pass fit chi2 as usual
   }
 
   // Create an actual CSCSegment - retrieve all info from the fit
   CSCSegment temp(sfit_->hits(), sfit_->intercept(), sfit_->localdir(), sfit_->covarianceMatrix(), theFlag);
   delete sfit_;
   sfit_ = nullptr;
 
   return temp;
 }
 
 /* isHitNearSegment
  *
  * Compare rechit with expected position from proto_segment
  */
 bool CSCSegAlgoShowering::isHitNearSegment(const CSCRecHit2D* hit) const {
   const CSCLayer* layer = theChamber->layer(hit->cscDetId().layer());
 
   // hit phi position in global coordinates
   GlobalPoint Hgp = layer->toGlobal(hit->localPosition());
   double Hphi = Hgp.phi();
   if (Hphi < 0.)
     Hphi += 2. * M_PI;
   LocalPoint Hlp = theChamber->toLocal(Hgp);
   double z = Hlp.z();
 
   double LocalX = sfit_->xfit(z);
   double LocalY = sfit_->yfit(z);
   LocalPoint Slp(LocalX, LocalY, z);
   GlobalPoint Sgp = theChamber->toGlobal(Slp);
   double Sphi = Sgp.phi();
   if (Sphi < 0.)
     Sphi += 2. * M_PI;
   double R = sqrt(Sgp.x() * Sgp.x() + Sgp.y() * Sgp.y());
 
   double deltaPhi = Sphi - Hphi;
   if (deltaPhi > 2. * M_PI)
     deltaPhi -= 2. * M_PI;
   if (deltaPhi < -2. * M_PI)
     deltaPhi += 2. * M_PI;
   if (deltaPhi < 0.)
     deltaPhi = -deltaPhi;
 
   double RdeltaPhi = R * deltaPhi;
 
   if (RdeltaPhi < dRPhiFineMax && deltaPhi < dPhiFineMax)
     return true;
 
   return false;
 }
 
 /* Method addHit
  *
  * Test if can add hit to proto segment. If so, try to add it.
  *
  */
 bool CSCSegAlgoShowering::addHit(const CSCRecHit2D* aHit, int layer) {
   // Return true if hit was added successfully
   // Return false if there is already a hit on the same layer
 
   bool ok = true;
 
   // Test that we are not trying to add the same hit again
   for (ChamberHitContainer::const_iterator it = protoSegment.begin(); it != protoSegment.end(); it++)
     if (aHit == (*it))
       return false;
 
   protoSegment.push_back(aHit);
 
   return ok;
 }
 
 /* Method compareProtoSegment
  *      
  * For hit coming from the same layer of an existing hit within the proto segment
  * test if achieve better chi^2 by using this hit than the other
  *
  */
 void CSCSegAlgoShowering::compareProtoSegment(const CSCRecHit2D* h, int layer) {
   // Try adding the hit to existing segment, and removing one from the  same layer
   ChamberHitContainer::iterator it;
   for (it = protoSegment.begin(); it != protoSegment.end();) {
     if ((*it)->cscDetId().layer() == layer) {
       it = protoSegment.erase(it);
     } else {
       ++it;
     }
   }
   bool ok = addHit(h, layer);
   if (ok) {
     CSCSegFit* newfit = new CSCSegFit(theChamber, protoSegment);
     newfit->fit();
     if (newfit->chi2() > sfit_->chi2()) {
       // new fit is worse: revert to old fit
       delete newfit;
     } else {
       // new fit is better
       delete sfit_;
       sfit_ = newfit;
     }
   }
 }
 
 // Look for a hit with a large deviation from fit
 
 void CSCSegAlgoShowering::pruneFromResidual(void) {
   //@@ THIS FUNCTION HAS 3 RETURNS PATHS!
 
   // Only prune if have at least 5 hits
   if (protoSegment.size() < 5)
     return;
 
   // Now Study residuals
 
   float maxResidual = 0.;
   float sumResidual = 0.;
   int nHits = 0;
 
   ChamberHitContainer::iterator ih;
   ChamberHitContainer::iterator ibad = protoSegment.end();
 
   for (ih = protoSegment.begin(); ih != protoSegment.end(); ++ih) {
     const CSCRecHit2D& hit = (**ih);
     const CSCLayer* layer = theChamber->layer(hit.cscDetId().layer());
     GlobalPoint gp = layer->toGlobal(hit.localPosition());
     LocalPoint lp = theChamber->toLocal(gp);
 
     double u = lp.x();
     double v = lp.y();
     double z = lp.z();
 
     //    double du = segfit->xdev( u, z );
     //    double dv = segfit->ydev( v, z );
 
     float residual = sfit_->Rdev(u, v, z);  // == sqrt(du*du + dv*dv)
 
     sumResidual += residual;
     ++nHits;
     if (residual > maxResidual) {
       maxResidual = residual;
       ibad = ih;
     }
   }
 
   float corrAvgResidual = (sumResidual - maxResidual) / (nHits - 1);
 
   // Keep all hits
   if (maxResidual / corrAvgResidual < maxRatioResidual)
     return;
 
   // Drop worst hit
   if (ibad != protoSegment.end())
     protoSegment.erase(ibad);
 
   // Make a new fit
   updateParameters();
 
   return;
 }
 
 void CSCSegAlgoShowering::updateParameters(void) {
   // Create fit for the hits in the protosegment & run it
   delete sfit_;
   sfit_ = new CSCSegFit(theChamber, protoSegment);
   sfit_->fit();
 }

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