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25 // 25 //
26 // G4ConstRK4 << 26 //
>> 27 // $Id$
>> 28 //
>> 29 //
>> 30 // Class G4ConstRK4
27 // 31 //
28 // class description: 32 // class description:
29 // 33 //
30 // G4ConstRK4 performs the integration of one 34 // G4ConstRK4 performs the integration of one step with error calculation
31 // in constant magnetic field. The integration 35 // in constant magnetic field. The integration method is the same as in
32 // ClassicalRK4. The field value is assumed co 36 // ClassicalRK4. The field value is assumed constant for the step.
33 // This field evaluation is called only once p 37 // This field evaluation is called only once per step.
34 // G4ConstRK4 can be used only for magnetic fi 38 // G4ConstRK4 can be used only for magnetic fields.
35 39
36 // Created: J.Apostolakis, T.Nikitina - 18.09. << 40 // History:
>> 41 // - 18.09.2008 - J.Apostolakis, T.Nikitina - Created
37 // ------------------------------------------- 42 // -------------------------------------------------------------------
>> 43
38 #ifndef G4CONSTRK4_HH 44 #ifndef G4CONSTRK4_HH
39 #define G4CONSTRK4_HH 45 #define G4CONSTRK4_HH
40 46
41 #include "G4MagErrorStepper.hh" 47 #include "G4MagErrorStepper.hh"
42 #include "G4EquationOfMotion.hh" 48 #include "G4EquationOfMotion.hh"
43 #include "G4Mag_EqRhs.hh" 49 #include "G4Mag_EqRhs.hh"
44 50
45 class G4ConstRK4 : public G4MagErrorStepper 51 class G4ConstRK4 : public G4MagErrorStepper
46 { 52 {
47 public: << 53 public: // with description
48 <<
49 G4ConstRK4(G4Mag_EqRhs* EquationMotion, G <<
50 ~G4ConstRK4() override; <<
51 54
52 G4ConstRK4(const G4ConstRK4&) = delete; << 55 G4ConstRK4(G4Mag_EqRhs *EquationMotion, G4int numberOfStateVariables=8);
53 G4ConstRK4& operator=(const G4ConstRK4&) << 56 ~G4ConstRK4();
54 // Copy constructor and assignment oper <<
55 57
56 void Stepper( const G4double y[], 58 void Stepper( const G4double y[],
57 const G4double dydx[], 59 const G4double dydx[],
58 G4double h, 60 G4double h,
59 G4double yout[], 61 G4double yout[],
60 G4double yerr[] ) ov << 62 G4double yerr[] );
61 void DumbStepper( const G4double yIn[], << 63 void DumbStepper( const G4double yIn[],
62 const G4double dydx[], << 64 const G4double dydx[],
63 G4double h, << 65 G4double h,
64 G4double yOut[] ) << 66 G4double yOut[] ) ;
65 G4double DistChord() const override; << 67 G4double DistChord() const;
66 68
67 inline void RightHandSideConst(const G4d << 69 inline void RightHandSideConst(const G4double y[],
68 G4d << 70 G4double dydx[] ) const;
69 71
70 inline void GetConstField(const G4double << 72 inline void GetConstField(const G4double y[],G4double Field[]);
>> 73
>> 74 public: // without description
>> 75
>> 76 G4int IntegratorOrder() const { return 4; }
>> 77
>> 78 private:
71 79
72 G4int IntegratorOrder() const override { << 80 G4ConstRK4(const G4ConstRK4&);
>> 81 G4ConstRK4& operator=(const G4ConstRK4&);
>> 82 // Private copy constructor and assignment operator.
73 83
74 private: 84 private:
75 85
76 G4ThreeVector fInitialPoint, fMidPoint, f 86 G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
77 // Data stored in order to find the chord 87 // Data stored in order to find the chord
78 G4double *dydxm, *dydxt, *yt; // scratch 88 G4double *dydxm, *dydxt, *yt; // scratch space - not state
79 G4double *yInitial, *yMiddle, *dydxMid, * 89 G4double *yInitial, *yMiddle, *dydxMid, *yOneStep;
80 G4Mag_EqRhs* fEq = nullptr; << 90 G4Mag_EqRhs *fEq;
81 G4double Field[3]; 91 G4double Field[3];
82 }; 92 };
83 93
84 // Inline methods 94 // Inline methods
85 95
86 inline void G4ConstRK4::RightHandSideConst(con << 96 inline void G4ConstRK4:: RightHandSideConst(const G4double y[],
87 << 97 G4double dydx[] ) const
88 { 98 {
89 99
90 G4double momentum_mag_square = y[3]*y[3] + y 100 G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
91 G4double inv_momentum_magnitude = 1.0 / std: 101 G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
92 102
93 G4double cof = fEq->FCof()*inv_momentum_magn << 103 G4double cof =fEq->FCof()*inv_momentum_magnitude;
94 104
95 dydx[0] = y[3]*inv_momentum_magnitude; 105 dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
96 dydx[1] = y[4]*inv_momentum_magnitude; 106 dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
97 dydx[2] = y[5]*inv_momentum_magnitude; 107 dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
98 108
99 dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1] 109 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] 110 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] 111 dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0]) ; // Az = a*(Vx*By - Vy*Bx)
102 } 112 }
103 113
104 inline void G4ConstRK4::GetConstField(const G4 << 114 inline void G4ConstRK4::GetConstField(const G4double y[],G4double B[])
105 { 115 {
106 G4double PositionAndTime[4]; << 116 G4double PositionAndTime[4];
107 117
108 PositionAndTime[0] = y[0]; 118 PositionAndTime[0] = y[0];
109 PositionAndTime[1] = y[1]; 119 PositionAndTime[1] = y[1];
110 PositionAndTime[2] = y[2]; 120 PositionAndTime[2] = y[2];
111 // Global Time 121 // Global Time
112 PositionAndTime[3] = y[7]; << 122 PositionAndTime[3] = y[7];
113 fEq -> GetFieldValue(PositionAndTime, B); << 123 fEq -> GetFieldValue(PositionAndTime, B) ;
114 } 124 }
115 125
116 #endif << 126 #endif // G4CONSTRK4_HH
117 127