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G4HelixExplicitEuler.cc
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27 // $Id: G4HelixExplicitEuler.cc 97598 2016-06-06 07:19:46Z gcosmo $
28 //
29 //
30 // Helix Explicit Euler: x_1 = x_0 + helix(h)
31 // with helix(h) being a helix piece of length h
32 // most simple approach for solving linear differential equations.
33 // Take the current derivative and add it to the current position.
34 //
35 // W.Wander <wwc@mit.edu> 12/09/97
36 // -------------------------------------------------------------------
37 
38 #include "G4HelixExplicitEuler.hh"
39 #include "G4PhysicalConstants.hh"
40 #include "G4ThreeVector.hh"
41 
42 
44  const G4double*,
45  G4double Step,
46  G4double yOut[7],
47  G4double yErr[])
48 
49 {
50 
51  //Estimation of the Stepping Angle
52 
53  G4ThreeVector Bfld;
54  MagFieldEvaluate(yInput, Bfld);
55 
56  const G4int nvar = 6 ;
57  G4int i;
58  G4double yTemp[8], yIn[8] ;
59  G4ThreeVector Bfld_midpoint;
60  // Saving yInput because yInput and yOut can be aliases for same array
61  for(i=0;i<nvar;i++) yIn[i]=yInput[i];
62 
63  G4double h = Step * 0.5;
64 
65  // Do full step and two half steps
66  G4double yTemp2[7];
67  AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp);
68  MagFieldEvaluate(yTemp2, Bfld_midpoint) ;
69  AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut);
70 
71  // Error estimation
72  for(i=0;i<nvar;i++) {
73  yErr[i] = yOut[i] - yTemp[i] ;
74  }
75 
76 }
77 
79 {
80  // Implementation : must check whether h/R > 2 pi !!
81  // If( h/R < pi) use G4LineSection::DistLine
82  // Else DistChord=R_helix
83  //
84  G4double distChord;
85  G4double Ang_curve=GetAngCurve();
86 
87 
88  if(Ang_curve<=pi){
89  distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
90  }
91  else
92  if(Ang_curve<twopi){
93  distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
94  }
95  else{
96  distChord=2.*GetRadHelix();
97  }
98 
99  return distChord;
100 
101 }
102 void
104  G4ThreeVector Bfld,
105  G4double h,
106  G4double yOut[])
107 {
108 
109  AdvanceHelix(yIn, Bfld, h, yOut);
110 
111 }
void Stepper(const G4double y[], const G4double *, G4double h, G4double yout[], G4double yerr[])
G4double GetAngCurve() const
G4double DistChord() const
void AdvanceHelix(const G4double yIn[], G4ThreeVector Bfld, G4double h, G4double yHelix[], G4double yHelix2[]=0)
double G4double
Definition: G4Types.hh:76
G4double GetRadHelix() const
static constexpr double twopi
Definition: G4SIunits.hh:76
int G4int
Definition: G4Types.hh:78
void DumbStepper(const G4double y[], G4ThreeVector Bfld, G4double h, G4double yout[])
static constexpr double pi
Definition: G4SIunits.hh:75
void MagFieldEvaluate(const G4double y[], G4ThreeVector &Bfield)
Definition: Step.hh:41