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G4MagIntegratorStepper.hh
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25 //
26 // G4MagIntegratorStepper
27 //
28 // Class description:
29 //
30 // Abstract base class for integrator of particle's equation of motion,
31 // used in tracking in space dependent magnetic field
32 //
33 // A Stepper must integrate over NumberOfVariables elements,
34 // and also copy (from input to output) any of NoStateVariables
35 // not included in the NumberOfVariables.
36 //
37 // So it is expected that NoStateVariables >= NumberOfVariables
38 
39 // Author: J.Apostolakis, CERN - 15.01.1997
40 // --------------------------------------------------------------------
41 #ifndef G4MAGINTEGRATORSTEPPER_HH
42 #define G4MAGINTEGRATORSTEPPER_HH
43 
44 #include "G4Types.hh"
45 #include "G4EquationOfMotion.hh"
46 
47 class G4MagIntegratorStepper
48 {
49  public: // with description
50 
51  G4MagIntegratorStepper(G4EquationOfMotion* Equation,
52  G4int numIntegrationVariables,
53  G4int numStateVariables = 12,
54  G4bool isFSAL = false );
55 
56  virtual ~G4MagIntegratorStepper() = default;
57  // Constructor and destructor. No actions.
58 
59  G4MagIntegratorStepper(const G4MagIntegratorStepper&) = delete;
60  G4MagIntegratorStepper& operator=(const G4MagIntegratorStepper&) = delete;
61 
62  virtual void Stepper( const G4double y[],
63  const G4double dydx[],
64  G4double h,
65  G4double yout[],
66  G4double yerr[] ) = 0;
67  // The stepper for the Runge Kutta integration.
68  // The stepsize is fixed, with the Step size given by h.
69  // Integrates ODE starting values y[0 to 6].
70  // Outputs yout[] and its estimated error yerr[].
71 
72  virtual G4double DistChord() const = 0;
73  // Estimate the maximum distance of a chord from the true path
74  // over the segment last integrated.
75 
76  inline void NormaliseTangentVector( G4double vec[6] );
77  // Simple utility function to (re)normalise 'unit velocity' vector.
78 
79  inline void NormalisePolarizationVector( G4double vec[12] );
80  // Simple utility function to (re)normalise 'unit spin' vector.
81 
82  inline void RightHandSide( const G4double y[], G4double dydx[] ) const;
83  // Utility method to supply the standard Evaluation of the
84  // Right Hand side of the associated equation.
85 
86  inline void RightHandSide( const G4double y[],
87  G4double dydx[],
88  G4double field[] ) const;
89  // Calculate dydx and field at point y.
90 
91  inline G4int GetNumberOfVariables() const;
92  // Get the number of variables that the stepper will integrate over.
93 
94  inline G4int GetNumberOfStateVariables() const;
95  // Get the number of variables of state variables (>= above, integration)
96 
97  virtual G4int IntegratorOrder() const = 0;
98  // Returns the order of the integrator
99  // i.e. its error behaviour is of the order O(h^order).
100 
101  inline G4int IntegrationOrder();
102  // Replacement method - using new data member
103 
104  inline G4EquationOfMotion* GetEquationOfMotion();
105  inline const G4EquationOfMotion* GetEquationOfMotion() const;
106  // As some steppers (eg RKG3) require other methods of Eq_Rhs
107  // this function allows for access to them.
108 
109  inline void SetEquationOfMotion(G4EquationOfMotion* newEquation);
110 
111  inline unsigned long GetfNoRHSCalls();
112  inline void ResetfNORHSCalls();
113  // Count number of calls to RHS method(s)
114 
115  inline G4bool IsFSAL() const;
116 
117  protected:
118 
119  inline void SetIntegrationOrder(G4int order);
120  inline void SetFSAL(G4bool flag = true);
121 
122  private:
123 
124  G4EquationOfMotion* fEquation_Rhs = nullptr;
125  const G4int fNoIntegrationVariables = 0; // Variables in integration
126  const G4int fNoStateVariables = 0; // Number required for FieldTrack
127 
128  mutable unsigned long fNoRHSCalls = 0UL;
129  // Counter for calls to RHS method
130 
131  // Parameters of a RK method -- must be shared by all steppers of a type
132  // -- Invariants for a class
133 
134  G4int fIntegrationOrder = -1; // must be set by stepper !!!
135  // All ClassicalRK4 steppers are 4th order
136  G4bool fIsFSAL = false;
137  // Depends on RK method & implementation
138 };
139 
140 #include "G4MagIntegratorStepper.icc"
141 
142 #endif /* G4MAGIntegratorSTEPPER */