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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 #include "G4VIntegrationDriver.hh"
47 #include "G4IntegrationDriver.hh"
48
49 class G4VIntegrationDriver;
50
51 class G4MagIntegratorStepper
52 {
53 public: // with description
54
55 G4MagIntegratorStepper(G4EquationOfMotion* Equation,
56 G4int numIntegrationVariables,
57 G4int numStateVariables = 12,
58 G4bool isFSAL = false );
59
60 virtual ~G4MagIntegratorStepper() = default;
61 // Constructor and destructor. No actions.
62
63 G4MagIntegratorStepper(const G4MagIntegratorStepper&) = delete;
64 G4MagIntegratorStepper& operator=(const G4MagIntegratorStepper&) = delete;
65
66 virtual void Stepper( const G4double y[],
67 const G4double dydx[],
68 G4double h,
69 G4double yout[],
70 G4double yerr[] ) = 0;
71 // The stepper for the Runge Kutta integration.
72 // The stepsize is fixed, with the Step size given by h.
73 // Integrates ODE starting values y[0 to 6].
74 // Outputs yout[] and its estimated error yerr[].
75
76 virtual G4double DistChord() const = 0;
77 // Estimate the maximum distance of a chord from the true path
78 // over the segment last integrated.
79
80 inline void NormaliseTangentVector( G4double vec[6] );
81 // Simple utility function to (re)normalise 'unit velocity' vector.
82
83 inline void NormalisePolarizationVector( G4double vec[12] );
84 // Simple utility function to (re)normalise 'unit spin' vector.
85
86 inline void RightHandSide( const G4double y[], G4double dydx[] ) const;
87 // Utility method to supply the standard Evaluation of the
88 // Right Hand side of the associated equation.
89
90 inline void RightHandSide( const G4double y[],
91 G4double dydx[],
92 G4double field[] ) const;
93 // Calculate dydx and field at point y.
94
95 inline G4int GetNumberOfVariables() const;
96 // Get the number of variables that the stepper will integrate over.
97
98 inline G4int GetNumberOfStateVariables() const;
99 // Get the number of variables of state variables (>= above, integration)
100
101 virtual G4int IntegratorOrder() const = 0;
102 // Returns the order of the integrator
103 // i.e. its error behaviour is of the order O(h^order).
104
105 inline G4int IntegrationOrder();
106 // Replacement method - using new data member
107
108 inline G4EquationOfMotion* GetEquationOfMotion();
109 inline const G4EquationOfMotion* GetEquationOfMotion() const;
110 // As some steppers (eg RKG3) require other methods of Eq_Rhs
111 // this function allows for access to them.
112
113 inline void SetEquationOfMotion(G4EquationOfMotion* newEquation);
114
115 inline unsigned long GetfNoRHSCalls();
116 inline void ResetfNORHSCalls();
117 // Count number of calls to RHS method(s)
118
119 inline G4bool IsFSAL() const;
120
121 // TODO - QSS
122 inline G4bool isQSS() const { return fIsQSS; }
123 void SetIsQSS(G4bool val){ fIsQSS= val;}
124
125 protected:
126
127 inline void SetIntegrationOrder(G4int order);
128 inline void SetFSAL(G4bool flag = true);
129
130 private:
131
132 G4EquationOfMotion* fEquation_Rhs = nullptr;
133 const G4int fNoIntegrationVariables = 0; // Variables in integration
134 const G4int fNoStateVariables = 0; // Number required for FieldTrack
135
136 mutable unsigned long fNoRHSCalls = 0UL;
137 // Counter for calls to RHS method
138
139 // Parameters of a RK method -- must be shared by all steppers of a type
140 // -- Invariants for a class
141
142 G4int fIntegrationOrder = -1; // must be set by stepper !!!
143 // All ClassicalRK4 steppers are 4th order
144 G4bool fIsFSAL = false;
145 // Depends on RK method & implementation
146 G4bool fIsQSS = false;
147
148 };
149
150 #include "G4MagIntegratorStepper.icc"
151
152 #endif /* G4MAGIntegratorSTEPPER */
153