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G4RKG3_Stepper.hh
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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"
39 #include "G4ThreeVector.hh"
40 
41 class G4Mag_EqRhs;
42 
44 {
45  public: // with description
46 
48  // Integrate over 6 variables only: position & velocity.
49  // Not implemented yet !
50 
52 
53  void Stepper( const G4double yIn[],
54  const G4double dydx[],
55  G4double h,
56  G4double yOut[],
57  G4double yErr[] );
58  // The method which must be provided, even if less efficient.
59 
60  G4double DistChord() const ;
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  public: // without description
87 
88  inline G4int IntegratorOrder() const { return 4; }
89 
90  private:
91 
93  fyMidPoint,
94  fyFinal;
97  G4double hStep = 0.0;
98 };
99 
100 #endif