Geant4  10.01.p02
G4ConstRK4.hh
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27 // $Id: G4ConstRK4.hh 66356 2012-12-18 09:02:32Z gcosmo $
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29 //
30 // Class G4ConstRK4
31 //
32 // class description:
33 //
34 // G4ConstRK4 performs the integration of one step with error calculation
35 // in constant magnetic field. The integration method is the same as in
36 // ClassicalRK4. The field value is assumed constant for the step.
37 // This field evaluation is called only once per step.
38 // G4ConstRK4 can be used only for magnetic fields.
39 
40 // History:
41 // - 18.09.2008 - J.Apostolakis, T.Nikitina - Created
42 // -------------------------------------------------------------------
43 
44 #ifndef G4CONSTRK4_HH
45 #define G4CONSTRK4_HH
46 
47 #include "G4MagErrorStepper.hh"
48 #include "G4EquationOfMotion.hh"
49 #include "G4Mag_EqRhs.hh"
50 
52 {
53  public: // with description
54 
55  G4ConstRK4(G4Mag_EqRhs *EquationMotion, G4int numberOfStateVariables=8);
56  ~G4ConstRK4();
57 
58  void Stepper( const G4double y[],
59  const G4double dydx[],
60  G4double h,
61  G4double yout[],
62  G4double yerr[] );
63  void DumbStepper( const G4double yIn[],
64  const G4double dydx[],
65  G4double h,
66  G4double yOut[] ) ;
67  G4double DistChord() const;
68 
69  inline void RightHandSideConst(const G4double y[],
70  G4double dydx[] ) const;
71 
72  inline void GetConstField(const G4double y[],G4double Field[]);
73 
74  public: // without description
75 
76  G4int IntegratorOrder() const { return 4; }
77 
78  private:
79 
80  G4ConstRK4(const G4ConstRK4&);
82  // Private copy constructor and assignment operator.
83 
84  private:
85 
87  // Data stored in order to find the chord
88  G4double *dydxm, *dydxt, *yt; // scratch space - not state
91  G4double Field[3];
92 };
93 
94 // Inline methods
95 
97  G4double dydx[] ) const
98 {
99 
100  G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
101  G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
102 
103  G4double cof =fEq->FCof()*inv_momentum_magnitude;
104 
105  dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
106  dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
107  dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
108 
109  dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1]) ; // Ax = a*(Vy*Bz - Vz*By)
110  dydx[4] = cof*(y[5]*Field[0] - y[3]*Field[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
111  dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0]) ; // Az = a*(Vx*By - Vy*Bx)
112 }
113 
114 inline void G4ConstRK4::GetConstField(const G4double y[],G4double B[])
115 {
116  G4double PositionAndTime[4];
117 
118  PositionAndTime[0] = y[0];
119  PositionAndTime[1] = y[1];
120  PositionAndTime[2] = y[2];
121  // Global Time
122  PositionAndTime[3] = y[7];
123  fEq -> GetFieldValue(PositionAndTime, B) ;
124 }
125 
126 #endif // G4CONSTRK4_HH
G4ConstRK4(G4Mag_EqRhs *EquationMotion, G4int numberOfStateVariables=8)
Definition: G4ConstRK4.cc:42
CLHEP::Hep3Vector G4ThreeVector
G4double DistChord() const
Definition: G4ConstRK4.cc:213
G4double * yInitial
Definition: G4ConstRK4.hh:89
G4double Field[3]
Definition: G4ConstRK4.hh:91
G4double * dydxm
Definition: G4ConstRK4.hh:88
G4ConstRK4 & operator=(const G4ConstRK4 &)
int G4int
Definition: G4Types.hh:78
G4ThreeVector fFinalPoint
Definition: G4ConstRK4.hh:86
G4double FCof() const
Definition: G4Mag_EqRhs.hh:84
G4ThreeVector fInitialPoint
Definition: G4ConstRK4.hh:86
G4double * dydxMid
Definition: G4ConstRK4.hh:89
void Stepper(const G4double y[], const G4double dydx[], G4double h, G4double yout[], G4double yerr[])
Definition: G4ConstRK4.cc:148
G4double * yMiddle
Definition: G4ConstRK4.hh:89
G4Mag_EqRhs * fEq
Definition: G4ConstRK4.hh:90
G4ThreeVector fMidPoint
Definition: G4ConstRK4.hh:86
G4double * yt
Definition: G4ConstRK4.hh:88
void GetConstField(const G4double y[], G4double Field[])
Definition: G4ConstRK4.hh:114
void RightHandSideConst(const G4double y[], G4double dydx[]) const
Definition: G4ConstRK4.hh:96
G4int IntegratorOrder() const
Definition: G4ConstRK4.hh:76
G4double * yOneStep
Definition: G4ConstRK4.hh:89
G4double * dydxt
Definition: G4ConstRK4.hh:88
double G4double
Definition: G4Types.hh:76
void DumbStepper(const G4double yIn[], const G4double dydx[], G4double h, G4double yOut[])
Definition: G4ConstRK4.cc:92