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25 //
26 // G4RKG3_Stepper
27 //
28 // Class description:
29 //
30 // Runga-Kutta integrator stepper from Geant3.
31
32 // Created: J.Apostolakis, V.Grichine - 30.01.1997
33 // -------------------------------------------------------------------
34 #ifndef G4RKG3_STEPPER_HH
35 #define G4RKG3_STEPPER_HH
36
37 #include "G4Types.hh"
38 #include "G4MagIntegratorStepper.hh"
39 #include "G4ThreeVector.hh"
40
41 class G4Mag_EqRhs;
42
43 class G4RKG3_Stepper : public G4MagIntegratorStepper
44 {
45 public:
46
47 G4RKG3_Stepper(G4Mag_EqRhs* EqRhs);
48 // Integrate over 6 variables only: position & velocity.
49 // Not implemented yet !
50
51 ~G4RKG3_Stepper() override;
52
53 void Stepper( const G4double yIn[],
54 const G4double dydx[],
55 G4double h,
56 G4double yOut[],
57 G4double yErr[] ) override;
58 // The method which must be provided, even if less efficient.
59
60 G4double DistChord() const override ;
61
62 void StepNoErr( const G4double tIn[8],
63 const G4double dydx[6],
64 G4double Step,
65 G4double tOut[8],
66 G4double B[3] );
67 // Integrator RK Stepper from G3 with only two field evaluation per
68 // Step. It is used in propagation initial Step by small substeps
69 // after solution error and delta geometry considerations.
70 // B[3] is magnetic field which is passed from substep to substep.
71
72 void StepWithEst( const G4double tIn[8],
73 const G4double dydx[6],
74 G4double Step,
75 G4double tOut[8],
76 G4double& alpha2,
77 G4double& beta2,
78 const G4double B1[3],
79 G4double B2[3] );
80 // Integrator for RK from G3 with evaluation of error in solution and
81 // delta geometry based on naive similarity with the case of uniform
82 // magnetic field.
83 // B1[3] is input and is the first magnetic field values
84 // B2[3] is output and is the final magnetic field values.
85
86 inline G4int IntegratorOrder() const override { return 4; }
87
88 private:
89
90 G4ThreeVector fyInitial,
91 fyMidPoint,
92 fyFinal;
93 G4ThreeVector fpInitial;
94 G4ThreeVector BfldIn;
95 G4double hStep = 0.0;
96 };
97
98 #endif
99