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G4NystromRK4.hh
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25 //
26 // G4NystromRK4
27 //
28 // Class description:
29 //
30 // Integrates the equations of the motion of a particle in a magnetic field
31 // using 4th Runge-Kutta-Nystrom method with errors estimation
32 // (ATL-SOFT-PUB-2009-01)
33 // Current form can be used only for 'pure' magnetic field.
34 // Notes: 1) field must be time-independent.
35 // 2) time is not integrated
36 
37 // Created: I.Gavrilenko, 15.05.2009 (as G4AtlasRK4)
38 // Adaptations: J.Apostolakis, November 2009
39 // -------------------------------------------------------------------
40 
41 #ifndef G4NYSTROMRK4_HH
42 #define G4NYSTROMRK4_HH
43 
45 #include "G4Mag_EqRhs.hh"
46 #include "G4CachedMagneticField.hh"
47 #include "G4ThreeVector.hh"
48 
49 #include <memory>
50 
52 {
53  public:
54 
55  G4NystromRK4(G4Mag_EqRhs* EquationMotion,
56  G4double distanceConstField = 0.0);
57  // Can be used only for Magnetic Fields - and for 6 variables (x,p)
58 
59  virtual void Stepper(const G4double y[],
60  const G4double dydx[],
61  G4double hstep,
62  G4double yOut[],
63  G4double yError[]) override;
64  // Single call for integration result and error
65  // Provides error via analytical method
66 
69 
70  virtual G4int IntegratorOrder() const override { return 4; }
71  virtual G4double DistChord() const override;
72 
73  private:
74 
75  inline void GetFieldValue(const G4double point[4], G4double field[3]);
76  inline G4double GetFCof();
77 
79  const G4CachedMagneticField* GetField() const;
80 
88 
89  std::unique_ptr<G4CachedMagneticField> fCachedField;
90 };
91 
92 #include "G4NystromRK4.icc"
93 
94 #endif