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25 // 25 //
26 // G4ConstRK4 26 // G4ConstRK4
27 // 27 //
28 // class description: 28 // class description:
29 // 29 //
30 // G4ConstRK4 performs the integration of one 30 // G4ConstRK4 performs the integration of one step with error calculation
31 // in constant magnetic field. The integration 31 // in constant magnetic field. The integration method is the same as in
32 // ClassicalRK4. The field value is assumed co 32 // ClassicalRK4. The field value is assumed constant for the step.
33 // This field evaluation is called only once p 33 // This field evaluation is called only once per step.
34 // G4ConstRK4 can be used only for magnetic fi 34 // G4ConstRK4 can be used only for magnetic fields.
35 35
36 // Created: J.Apostolakis, T.Nikitina - 18.09. 36 // Created: J.Apostolakis, T.Nikitina - 18.09.2008
37 // ------------------------------------------- 37 // -------------------------------------------------------------------
38 #ifndef G4CONSTRK4_HH 38 #ifndef G4CONSTRK4_HH
39 #define G4CONSTRK4_HH 39 #define G4CONSTRK4_HH
40 40
41 #include "G4MagErrorStepper.hh" 41 #include "G4MagErrorStepper.hh"
42 #include "G4EquationOfMotion.hh" 42 #include "G4EquationOfMotion.hh"
43 #include "G4Mag_EqRhs.hh" 43 #include "G4Mag_EqRhs.hh"
44 44
45 class G4ConstRK4 : public G4MagErrorStepper 45 class G4ConstRK4 : public G4MagErrorStepper
46 { 46 {
47 public: << 47 public: // with description
48 48
49 G4ConstRK4(G4Mag_EqRhs* EquationMotion, G << 49 G4ConstRK4(G4Mag_EqRhs* EquationMotion, G4int numberOfStateVariables=8);
50 ~G4ConstRK4() override; << 50 ~G4ConstRK4();
51 51
52 G4ConstRK4(const G4ConstRK4&) = delete; 52 G4ConstRK4(const G4ConstRK4&) = delete;
53 G4ConstRK4& operator=(const G4ConstRK4&) 53 G4ConstRK4& operator=(const G4ConstRK4&) = delete;
54 // Copy constructor and assignment oper 54 // Copy constructor and assignment operator not allowed
55 55
56 void Stepper( const G4double y[], 56 void Stepper( const G4double y[],
57 const G4double dydx[], 57 const G4double dydx[],
58 G4double h, 58 G4double h,
59 G4double yout[], 59 G4double yout[],
60 G4double yerr[] ) ov << 60 G4double yerr[] );
61 void DumbStepper( const G4double yIn[], 61 void DumbStepper( const G4double yIn[],
62 const G4double dydx[], 62 const G4double dydx[],
63 G4double h, 63 G4double h,
64 G4double yOut[] ) << 64 G4double yOut[] ) ;
65 G4double DistChord() const override; << 65 G4double DistChord() const;
66 66
67 inline void RightHandSideConst(const G4d 67 inline void RightHandSideConst(const G4double y[],
68 G4d 68 G4double dydx[] ) const;
69 69
70 inline void GetConstField(const G4double 70 inline void GetConstField(const G4double y[], G4double Field[]);
71 71
72 G4int IntegratorOrder() const override { << 72 public: // without description
>> 73
>> 74 G4int IntegratorOrder() const { return 4; }
73 75
74 private: 76 private:
75 77
76 G4ThreeVector fInitialPoint, fMidPoint, f 78 G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
77 // Data stored in order to find the chord 79 // Data stored in order to find the chord
78 G4double *dydxm, *dydxt, *yt; // scratch 80 G4double *dydxm, *dydxt, *yt; // scratch space - not state
79 G4double *yInitial, *yMiddle, *dydxMid, * 81 G4double *yInitial, *yMiddle, *dydxMid, *yOneStep;
80 G4Mag_EqRhs* fEq = nullptr; 82 G4Mag_EqRhs* fEq = nullptr;
81 G4double Field[3]; 83 G4double Field[3];
82 }; 84 };
83 85
84 // Inline methods 86 // Inline methods
85 87
86 inline void G4ConstRK4::RightHandSideConst(con 88 inline void G4ConstRK4::RightHandSideConst(const G4double y[],
87 89 G4double dydx[] ) const
88 { 90 {
89 91
90 G4double momentum_mag_square = y[3]*y[3] + y 92 G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
91 G4double inv_momentum_magnitude = 1.0 / std: 93 G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
92 94
93 G4double cof = fEq->FCof()*inv_momentum_magn 95 G4double cof = fEq->FCof()*inv_momentum_magnitude;
94 96
95 dydx[0] = y[3]*inv_momentum_magnitude; 97 dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
96 dydx[1] = y[4]*inv_momentum_magnitude; 98 dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
97 dydx[2] = y[5]*inv_momentum_magnitude; 99 dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
98 100
99 dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1] 101 dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1]) ; // Ax = a*(Vy*Bz - Vz*By)
100 dydx[4] = cof*(y[5]*Field[0] - y[3]*Field[2] 102 dydx[4] = cof*(y[5]*Field[0] - y[3]*Field[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
101 dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0] 103 dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0]) ; // Az = a*(Vx*By - Vy*Bx)
102 } 104 }
103 105
104 inline void G4ConstRK4::GetConstField(const G4 106 inline void G4ConstRK4::GetConstField(const G4double y[], G4double B[])
105 { 107 {
106 G4double PositionAndTime[4]; 108 G4double PositionAndTime[4];
107 109
108 PositionAndTime[0] = y[0]; 110 PositionAndTime[0] = y[0];
109 PositionAndTime[1] = y[1]; 111 PositionAndTime[1] = y[1];
110 PositionAndTime[2] = y[2]; 112 PositionAndTime[2] = y[2];
111 // Global Time 113 // Global Time
112 PositionAndTime[3] = y[7]; 114 PositionAndTime[3] = y[7];
113 fEq -> GetFieldValue(PositionAndTime, B); 115 fEq -> GetFieldValue(PositionAndTime, B);
114 } 116 }
115 117
116 #endif 118 #endif
117 119