include/Geant4/G4MagIntegratorStepper.hh

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0025 //
0026 // G4MagIntegratorStepper
0027 //
0028 // Class description:
0029 //
0030 // Abstract base class for integrator of particle's equation of motion,
0031 // used in tracking in space dependent magnetic field
0032 //
0033 // A Stepper must integrate over NumberOfVariables elements,
0034 // and also copy (from input to output) any of NoStateVariables
0035 // not included in the NumberOfVariables.
0036 //
0037 // So it is expected that NoStateVariables >= NumberOfVariables
0038
0039 // Author: J.Apostolakis, CERN - 15.01.1997
0040 // --------------------------------------------------------------------
0041 #ifndef G4MAGINTEGRATORSTEPPER_HH
0042 #define G4MAGINTEGRATORSTEPPER_HH
0043
0044 #include "G4Types.hh"
0045 #include "G4EquationOfMotion.hh"
0046 #include "G4VIntegrationDriver.hh"
0047 #include "G4IntegrationDriver.hh"
0048
0049 class G4VIntegrationDriver;
0050
0051 class G4MagIntegratorStepper
0052 {
0053   public:  // with description
0054
0055      G4MagIntegratorStepper(G4EquationOfMotion* Equation,
0056                             G4int               numIntegrationVariables,
0057                             G4int               numStateVariables = 12,
0058                             G4bool              isFSAL = false );
0059
0060      virtual ~G4MagIntegratorStepper() = default;
0061        // Constructor and destructor. No actions.
0062
0063      G4MagIntegratorStepper(const G4MagIntegratorStepper&) = delete;
0064      G4MagIntegratorStepper& operator=(const G4MagIntegratorStepper&) = delete;
0065
0066      virtual void Stepper( const G4double y[],
0067                            const G4double dydx[],
0068                                  G4double h,
0069                                  G4double yout[],
0070                                  G4double yerr[] ) = 0;
0071        // The stepper for the Runge Kutta integration.
0072        // The stepsize is fixed, with the Step size given by h.
0073        // Integrates ODE starting values y[0 to 6].
0074        // Outputs yout[] and its estimated error yerr[].
0075
0076      virtual G4double DistChord() const = 0;
0077        // Estimate the maximum distance of a chord from the true path
0078        // over the segment last integrated.
0079
0080      inline void NormaliseTangentVector( G4double vec[6] );
0081        // Simple utility function to (re)normalise 'unit velocity' vector.
0082
0083      inline void NormalisePolarizationVector( G4double vec[12] );
0084        // Simple utility function to (re)normalise 'unit spin' vector.
0085
0086      inline void RightHandSide( const G4double y[], G4double dydx[] ) const;
0087        // Utility method to supply the standard Evaluation of the
0088        // Right Hand side of the associated equation.
0089
0090      inline void RightHandSide( const G4double y[],
0091                                       G4double dydx[],
0092                                       G4double field[] ) const;
0093        // Calculate dydx and field at point y.
0094
0095      inline G4int  GetNumberOfVariables() const;
0096        // Get the number of variables that the stepper will integrate over.
0097
0098      inline G4int  GetNumberOfStateVariables() const;
0099        // Get the number of variables of state variables (>= above, integration)
0100
0101      virtual G4int IntegratorOrder() const = 0;
0102        // Returns the order of the integrator
0103        // i.e. its error behaviour is of the order O(h^order).
0104
0105      inline G4int IntegrationOrder();
0106        // Replacement method - using new data member
0107
0108      inline G4EquationOfMotion* GetEquationOfMotion();
0109      inline const G4EquationOfMotion* GetEquationOfMotion() const;
0110        // As some steppers (eg RKG3) require other methods of Eq_Rhs
0111        // this function allows for access to them.
0112
0113      inline void SetEquationOfMotion(G4EquationOfMotion* newEquation);
0114
0115      inline unsigned long GetfNoRHSCalls();
0116      inline void ResetfNORHSCalls();
0117        // Count number of calls to RHS method(s)
0118
0119      inline G4bool IsFSAL() const;
0120
0121      // TODO - QSS
0122      inline G4bool isQSS() const { return fIsQSS; }
0123      void   SetIsQSS(G4bool val){ fIsQSS= val;}
0124
0125 protected:
0126
0127      inline void SetIntegrationOrder(G4int order);
0128      inline void SetFSAL(G4bool flag = true);
0129
0130   private:
0131
0132      G4EquationOfMotion* fEquation_Rhs = nullptr;
0133      const G4int fNoIntegrationVariables = 0; // Variables in integration
0134      const G4int fNoStateVariables = 0;       // Number required for FieldTrack
0135
0136      mutable unsigned long fNoRHSCalls = 0UL;
0137        // Counter for calls to RHS method
0138
0139      // Parameters of a RK method -- must be shared by all steppers of a type
0140      // -- Invariants for a class
0141
0142      G4int fIntegrationOrder = -1;  // must be set by stepper !!!
0143       // All ClassicalRK4 steppers are 4th order
0144      G4bool fIsFSAL = false;
0145       // Depends on RK method & implementation
0146      G4bool fIsQSS = false;
0147
0148 };
0149
0150 #include  "G4MagIntegratorStepper.icc"
0151
0152 #endif  /* G4MAGIntegratorSTEPPER */