Geant4 Cross Reference

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Geant4/externals/clhep/src/BoostZ.cc

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  1 // -*- C++ -*-
  2 // ---------------------------------------------------------------------------
  3 //
  4 // This file is a part of the CLHEP - a Class Library for High Energy Physics.
  5 //
  6 // This is the implementation of the HepBoostZ class.
  7 //
  8 
  9 #include "CLHEP/Vector/BoostZ.h"
 10 #include "CLHEP/Vector/Boost.h"
 11 #include "CLHEP/Vector/Rotation.h"
 12 #include "CLHEP/Vector/LorentzRotation.h"
 13 
 14 #include <cmath>
 15 #include <iostream>
 16 
 17 namespace CLHEP  {
 18 
 19 // ----------  Constructors and Assignment:
 20 
 21 HepBoostZ & HepBoostZ::set (double bbeta) {
 22   double b2 = bbeta*bbeta;
 23   if (b2 >= 1) {
 24     std::cerr << "HepBoostZ::set() - "
 25       << "Beta supplied to set HepBoostZ represents speed >= c." << std::endl;
 26     beta_  = 1.0 - 1.0E-8;              // NaN-proofing
 27     gamma_ = 1.0 / std::sqrt(1.0 - b2);
 28     return *this;
 29   }    
 30   beta_  = bbeta;
 31   gamma_ = 1.0 / std::sqrt(1.0 - b2);
 32   return *this;
 33 }
 34 
 35 // ----------  Accessors:
 36 
 37 HepRep4x4 HepBoostZ::rep4x4() const {
 38   double bg = beta_*gamma_;
 39   return HepRep4x4(   1,      0,    0,    0,
 40           0,      1,    0,    0,
 41                       0,      0,  gamma_, bg, 
 42           0,      0,   bg,  gamma_ );
 43 }
 44 
 45 HepRep4x4Symmetric HepBoostZ::rep4x4Symmetric() const {
 46   double bg = beta_*gamma_;
 47   return HepRep4x4Symmetric(   1,      0,    0,    0,
 48                      1,    0,    0,
 49                                      gamma_, bg, 
 50                     gamma_ );
 51 }
 52 
 53 // ----------  Decomposition:
 54 
 55 void HepBoostZ::decompose (HepRotation & rotation, HepBoost & boost) const {
 56   HepAxisAngle vdelta = HepAxisAngle();
 57   rotation = HepRotation(vdelta);
 58   Hep3Vector bbeta = boostVector();
 59   boost = HepBoost(bbeta);
 60 }
 61 
 62 void HepBoostZ::decompose (HepAxisAngle & rotation, Hep3Vector & boost) const {
 63   rotation = HepAxisAngle();
 64   boost = boostVector();
 65 }
 66 
 67 void HepBoostZ::decompose (HepBoost & boost, HepRotation & rotation) const {
 68   HepAxisAngle vdelta = HepAxisAngle();
 69   rotation = HepRotation(vdelta);
 70   Hep3Vector bbeta = boostVector();
 71   boost = HepBoost(bbeta);
 72 }
 73 
 74 void HepBoostZ::decompose (Hep3Vector & boost, HepAxisAngle & rotation) const {
 75   rotation = HepAxisAngle();
 76   boost = boostVector();
 77 }
 78 
 79 // ----------  Comparisons:
 80 
 81 double HepBoostZ::distance2( const HepBoost & b ) const {
 82   return b.distance2(*this);
 83 }
 84 
 85 double HepBoostZ::distance2( const HepRotation & r ) const {
 86   double db2 = norm2();
 87   double dr2  = r.norm2();
 88   return (db2 + dr2);
 89 }
 90 
 91 double HepBoostZ::distance2( const HepLorentzRotation & lt ) const {
 92   HepBoost b1;
 93   HepRotation r1;
 94   lt.decompose(b1,r1);
 95   double db2 = distance2(b1);
 96   double dr2  = r1.norm2();
 97   return (db2 + dr2);
 98 }
 99 
100 bool HepBoostZ::isNear (const HepRotation & r, double epsilon) const {
101   double db2 = norm2();
102   if (db2 > epsilon*epsilon) return false;
103   double dr2  = r.norm2();
104   return (db2+dr2 <= epsilon*epsilon);
105 }
106 
107 bool HepBoostZ::isNear ( const HepLorentzRotation & lt, 
108           double epsilon  ) const {
109   HepBoost b1;
110   HepRotation r1;
111   double db2 = distance2(b1);
112   lt.decompose(b1,r1);
113   if (db2 > epsilon*epsilon) return false;
114   double dr2  = r1.norm2();
115   return (db2 + dr2);
116 }
117 
118 // ----------  Properties:
119 
120 void HepBoostZ::rectify() {
121   // Assuming the representation of this is close to a true pure boost,
122   // but may have drifted due to round-off error from many operations,
123   // this forms an "exact" pure BoostZ matrix for again.
124   
125   double b2 = beta_*beta_;
126   if (b2 >= 1) {
127     beta_ = 1.0 - 1.0e-8;     // NaN-proofing
128     b2 = beta_*beta_;
129   } 
130   gamma_ = 1.0 / std::sqrt(1.0 - b2);
131 }
132 
133 // ---------- Application:
134 
135 // ---------- Operations in the group of 4-Rotations
136 
137 HepBoostZ HepBoostZ::operator * (const HepBoostZ & b) const {
138   return HepBoostZ ( (beta()+b.beta()) / (1+beta()*b.beta()) );
139 }
140 HepLorentzRotation HepBoostZ::operator * (const HepBoost & b) const {
141   HepLorentzRotation me (*this);
142   return me*b;
143 }
144 HepLorentzRotation HepBoostZ::operator * (const HepRotation & r) const {
145   HepLorentzRotation me (*this);
146   return me*r;
147 }
148 HepLorentzRotation HepBoostZ::operator * (const HepLorentzRotation & lt) const {
149   HepLorentzRotation me (*this);
150   return me*lt;
151 }
152  
153 // ---------- I/O
154  
155 std::ostream & HepBoostZ::print( std::ostream & os ) const {
156   os << "Boost in Z direction (beta = " << beta_ 
157       << ", gamma = " << gamma_ << ") ";
158   return os;
159 }
160 
161 }  // namespace CLHEP
162