/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/RecoPixelVertexing/PixelTriplets/plugins/ThirdHitPredictionFromInvParabola.cc

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#include "ThirdHitPredictionFromInvParabola.h"

#include <cmath>
#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "DataFormats/GeometryVector/interface/GlobalPoint.h"

#include "RecoTracker/TkHitPairs/interface/OrderedHitPair.h"
#include "RecoTracker/TkTrackingRegions/interface/TrackingRegion.h"
#include "RecoTracker/TkMSParametrization/interface/PixelRecoUtilities.h"

#include "RecoTracker/TkMSParametrization/interface/PixelRecoRange.h"

namespace {
  template <class T> inline T sqr( T t) {return t*t;}
}

using namespace std;

ThirdHitPredictionFromInvParabola::ThirdHitPredictionFromInvParabola( 
    const GlobalPoint& P1, const GlobalPoint& P2,Scalar ip, Scalar curv, Scalar tolerance)
  : theTolerance(tolerance)
{
  init(P1,P2,ip,std::abs(curv));
}


void ThirdHitPredictionFromInvParabola:: init(Scalar x1,Scalar y1, Scalar x2,Scalar y2,  Scalar ip, Scalar curv) {
//  GlobalVector aX = GlobalVector( P2.x()-P1.x(), P2.y()-P1.y(), 0.).unit();
 
  Point2D p1(x1,y1);
  Point2D p2(x2,y2);
  theRotation = Rotation(p1);
  p1 = transform(p1);  // (1./P1.xy().mag(),0); 
  p2 = transform(p2);

 
  u1u2 = p1.x()*p2.x();
  overDu = 1./(p2.x() - p1.x());
  pv = p1.y()*p2.x() - p2.y()*p1.x();
  dv = p2.y() - p1.y();
  su = p2.x() + p1.x();

  RangeD ipRange(-ip, ip); 
  ipRange.sort();
  
  Scalar ipIntyPlus = ipFromCurvature(0.,true);
  Scalar ipCurvPlus = ipFromCurvature(curv, true);
  Scalar ipCurvMinus = ipFromCurvature(curv, false);

  
  RangeD ipRangePlus(ipIntyPlus, ipCurvPlus); ipRangePlus.sort();
  RangeD ipRangeMinus(-ipIntyPlus, ipCurvMinus); ipRangeMinus.sort();

  theIpRangePlus  = ipRangePlus.intersection(ipRange);
  theIpRangeMinus = ipRangeMinus.intersection(ipRange);
}
    


ThirdHitPredictionFromInvParabola::Range 
ThirdHitPredictionFromInvParabola::rangeRPhi(Scalar radius, int icharge) const
{
  bool pos =  icharge>0;

  RangeD ip = (pos) ? theIpRangePlus : theIpRangeMinus;


  //  it will vectorize with gcc 4.7 (with -O3 -fno-math-errno)
  // change sign as intersect assume -ip for negative charge...
  Scalar ipv[2]={(pos)? ip.min() : -ip.min() ,(pos)? ip.max() : -ip.max()};
  Scalar u[2], v[2];
  for (int i=0; i!=2; ++i)
    findPointAtCurve(radius,ipv[i],u[i],v[i]);

  // 
  Scalar phi1 = theRotation.rotateBack(Point2D(u[0],v[0])).barePhi();
  Scalar phi2 = phi1+(v[1]-v[0]); 
  
  if (ip.empty()) {
    Range r1(phi1*radius-theTolerance, phi1*radius+theTolerance); 
    Range r2(phi2*radius-theTolerance, phi2*radius+theTolerance); 
    return r1.intersection(r2);
  }

  if (phi2<phi1) std::swap(phi1, phi2); 
  return Range(radius*phi1-theTolerance, radius*phi2+theTolerance);
  
}

/*
ThirdHitPredictionFromInvParabola::Range ThirdHitPredictionFromInvParabola::rangeRPhiSlow(
    Scalar radius, int charge, int nIter) const
{
  Range predRPhi(1.,-1.);

  Scalar invr2 = 1/(radius*radius);
  Scalar u = sqrt(invr2);
  Scalar v = 0.;

  Range ip = (charge > 0) ? theIpRangePlus : theIpRangeMinus;

  for (int i=0; i < nIter; ++i) {
    v = predV(u, charge*ip.min()); 
    Scalar d2 = invr2-sqr(v);
    u = (d2 > 0) ? sqrt(d2) : 0.;
  }
  Point2D  pred_tmp1(u, v);
  Scalar phi1 = transformBack(pred_tmp1).phi(); 
  while ( phi1 >= M_PI) phi1 -= 2*M_PI;
  while ( phi1 < -M_PI) phi1 += 2*M_PI;


  u = sqrt(invr2); 
  v=0;
  for (int i=0; i < nIter; ++i) {
    v = predV(u, ip.max(), charge); 
    Scalar d2 = invr2-sqr(v);
    u = (d2 > 0) ? sqrt(d2) : 0.;
  }
  Point2D  pred_tmp2(u, v);
  Scalar phi2 = transformBack(pred_tmp2).phi(); 
  while ( phi2-phi1 >= M_PI) phi2 -= 2*M_PI;
  while ( phi2-phi1 < -M_PI) phi2 += 2*M_PI;

// check faster alternative, without while(..) it is enough to:
//  phi2 = phi1+radius*(pred_tmp2.v()-pred_tmp1.v()); 

  if (ip.empty()) {
    Range r1(phi1*radius-theTolerance, phi1*radius+theTolerance); 
    Range r2(phi2*radius-theTolerance, phi2*radius+theTolerance); 
    predRPhi = r1.intersection(r2);
  } else {
    Range r(phi1, phi2); 
    r.sort();
    predRPhi= Range(radius*r.min()-theTolerance, radius*r.max()+theTolerance);
  }
  return predRPhi;

}
*/