include/Geant4/G4RKIntegrationDriver.hh

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0024 // ********************************************************************
0025 //
0026 // G4RKIntegrationDriver
0027 //
0028 // Class description:
0029 //
0030 // Driver class which controls the integration error of a
0031 // Runge-Kutta stepper
0032
0033 // Created: D.Sorokin, 2017
0034 // --------------------------------------------------------------------
0035 #ifndef G4RKINTEGRATIONDRIVER_HH
0036 #define G4RKINTEGRATIONDRIVER_HH
0037
0038 #include "G4VIntegrationDriver.hh"
0039
0040 template <class T>
0041 class G4RKIntegrationDriver : public G4VIntegrationDriver
0042 {
0043   public:
0044
0045     G4RKIntegrationDriver(T* stepper);
0046
0047     G4RKIntegrationDriver(const G4RKIntegrationDriver&) = delete;
0048     G4RKIntegrationDriver& operator=(const G4RKIntegrationDriver&) = delete;
0049
0050     void GetDerivatives(const G4FieldTrack& track,
0051                               G4double dydx[]) const override;
0052
0053     void GetDerivatives(const G4FieldTrack& track,
0054                               G4double dydx[],
0055                               G4double field[]) const override;
0056
0057     G4double ComputeNewStepSize(G4double errMaxNorm, // normalised error
0058                                 G4double hstepCurrent) final;
0059       // Taking the last step's normalised error, calculate
0060       // a step size for the next step.
0061       // - Limits the next step's size within a factor of the current one.
0062
0063     G4EquationOfMotion* GetEquationOfMotion() override;
0064     void SetEquationOfMotion(G4EquationOfMotion* equation) override;
0065
0066     const T* GetStepper() const override;
0067     T* GetStepper() override;
0068
0069     void  StreamInfo( std::ostream& os ) const override;
0070
0071     // Accessors.
0072     G4double GetSafety() const;
0073     G4double GetPshrnk() const;
0074     G4double GetPgrow() const;
0075
0076     void RenewStepperAndAdjust(G4MagIntegratorStepper* stepper) override;
0077
0078     void ReSetParameters(G4double safety = 0.9);
0079     void SetSafety(G4double valS);
0080       //  i) sets the exponents (pgrow & pshrnk),
0081       //     using the current Stepper's order,
0082       // ii) sets the safety
0083
0084      G4int GetMaxNoSteps() const;
0085      void SetMaxNoSteps(G4int val);
0086        // Modify and Get the Maximum number of Steps that can be
0087        // taken for the integration of a single segment -
0088        // (ie a single call to AccurateAdvance).
0089
0090      G4double GetSmallestFraction() const;
0091      void SetSmallestFraction(G4double val);
0092
0093   protected:
0094
0095     G4double ShrinkStepSize(G4double h, G4double error) const;
0096     G4double GrowStepSize(G4double h, G4double error) const;
0097
0098     G4double ShrinkStepSize2(G4double h, G4double error2) const;
0099     G4double GrowStepSize2(G4double h, G4double error2) const;
0100
0101     void UpdateErrorConstraints();
0102
0103   private:
0104
0105     inline void RenewStepperAndAdjustImpl(T* stepper);
0106
0107     G4int fMaxNoSteps;
0108
0109     G4int fMaxStepBase;
0110       // The (default) maximum number of steps is Base
0111       // divided by the order of Stepper
0112
0113     // Parameters used to grow and shrink trial stepsize.
0114     //
0115     G4double safety;
0116     G4double pshrnk;   //  exponent for shrinking
0117     G4double pgrow;    //  exponent for growth
0118
0119     // muximum error values for shrinking / growing (optimisation).
0120     //
0121     G4double errorConstraintShrink;
0122     G4double errorConstraintGrow;
0123
0124     T* pIntStepper = nullptr;
0125 };
0126
0127 #include "G4RKIntegrationDriver.icc"
0128
0129 #endif