include/Geant4/G4DormandPrinceRK56.hh

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0025 //
0026 // G4DormandPrinceRK56
0027 //
0028 // Class description:
0029 //
0030 // Dormand-Prince RK 6(5) non-FSAL method
0031
0032 // Author: Somnath Banerjee (CERN, Google Summer of Code 2015), 26.06.2015
0033 // Supervision: John Apostolakis (CERN)
0034 // --------------------------------------------------------------------
0035 #ifndef G4DORMAND_PRINCE_RK56_HH
0036 #define G4DORMAND_PRINCE_RK56_HH
0037
0038 #include "G4MagIntegratorStepper.hh"
0039
0040 /**
0041  * @brief G4DormandPrinceRK56 implements the 6(5) embedded Runge-Kutta
0042  * non-FSAL method.
0043  */
0044
0045 class G4DormandPrinceRK56 : public G4MagIntegratorStepper
0046 {
0047   public:
0048
0049     /**
0050      * Constructor for G4DormandPrinceRK56.
0051      *  @param[in] EqRhs Pointer to the provided equation of motion.
0052      *  @param[in] numberOfVariables The number of integration variables.
0053      *  @param[in] primary Flag for initialisation of the auxiliary stepper.
0054      */
0055     G4DormandPrinceRK56( G4EquationOfMotion* EqRhs,
0056                          G4int numberOfVariables = 6,
0057                          G4bool primary = true ) ;
0058
0059     /**
0060      * Destructor.
0061      */
0062     ~G4DormandPrinceRK56() override ;
0063
0064     /**
0065      * Copy constructor and assignment operator not allowed.
0066      */
0067     G4DormandPrinceRK56(const G4DormandPrinceRK56&) = delete;
0068     G4DormandPrinceRK56& operator=(const G4DormandPrinceRK56&) = delete;
0069
0070     /**
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      *  @param[in] y Starting values array of integration variables.
0076      *  @param[in] dydx Derivatives array.
0077      *  @param[in] h The given step size.
0078      *  @param[out] yout Integration output.
0079      *  @param[out] yerr The estimated error.
0080      */
0081     void Stepper( const G4double y[],
0082                   const G4double dydx[],
0083                         G4double h,
0084                         G4double yout[],
0085                         G4double yerr[] ) override ;
0086
0087     /**
0088      * Returns the distance from chord line.
0089      */
0090     G4double DistChord() const override;
0091
0092     /**
0093      * Returns the order, 5, of integration.
0094      */
0095     inline G4int IntegratorOrder() const override { return 5; }
0096
0097     /**
0098      * Returns the stepper type-ID, "kDormandPrinceRK56".
0099      */
0100     inline G4StepperType StepperType() const override { return kDormandPrinceRK56; }
0101
0102     /**
0103      * Prepares the interpolant and calculates the extra stages.
0104      * Fifth order interpolant with one extra function evaluation per step.
0105      */
0106     void SetupInterpolate_low( const G4double yInput[],
0107                                const G4double dydx[],
0108                                const G4double Step );
0109
0110     /**
0111      * Wrappers for SetupInterpolate_low() above.
0112      */
0113     inline void SetupInterpolate( const G4double yInput[],
0114                                   const G4double dydx[],
0115                                   const G4double Step )
0116     {
0117       SetupInterpolate_low( yInput, dydx, Step);
0118     }
0119     inline void SetupInterpolation()
0120     {
0121       SetupInterpolate( fLastInitialVector, fLastDyDx, fLastStepLength);
0122     }
0123
0124     /**
0125      * Calculates the output at the tau fraction of Step.
0126      */
0127     void Interpolate_low( const G4double yInput[],
0128                           const G4double dydx[],
0129                           const G4double Step,
0130                                 G4double yOut[],
0131                                 G4double tau );
0132
0133     /**
0134      * Wrappers for Interpolate_low() above.
0135      */
0136     inline void Interpolate( const G4double yInput[],
0137                              const G4double dydx[],
0138                              const G4double Step,
0139                                    G4double yOut[],
0140                                    G4double tau )
0141     {
0142       Interpolate_low( yInput, dydx, Step, yOut, tau);
0143     }
0144     inline void Interpolate( G4double tau, G4double yOut[])
0145     {
0146       Interpolate( fLastInitialVector, fLastDyDx, fLastStepLength, yOut, tau );
0147     }
0148
0149     /**
0150      * Prepares the interpolant and calculates the extra stages.
0151      * Sixth order interpolant with 3 additional stages per step.
0152      */
0153     void SetupInterpolate_high( const G4double yInput[],
0154                                 const G4double dydx[],
0155                                 const G4double Step );
0156
0157     /**
0158      * Calculates the output at the tau fraction of Step, using
0159      * the polynomial coefficients and the respective stages.
0160      */
0161     void Interpolate_high( const G4double yInput[],
0162                            const G4double dydx[],
0163                            const G4double Step,
0164                                  G4double yOut[],
0165                                  G4double tau );
0166
0167   private:
0168
0169     /** For storing intermediate 'k' values in stepper. */
0170     G4double *ak2, *ak3, *ak4, *ak5, *ak6, *ak7, *ak8, *ak9;
0171
0172     /** For the additional stages of Interpolant. */
0173     G4double *ak10_low, *ak10, *ak11, * ak12;
0174
0175     G4double *yTemp, *yIn;
0176
0177     G4double fLastStepLength = -1.0;
0178
0179     /** For DistChord() calculations. */
0180     G4double *fLastInitialVector, *fLastFinalVector,
0181              *fLastDyDx, *fMidVector, *fMidError;
0182
0183     G4DormandPrinceRK56* fAuxStepper = nullptr;
0184 };
0185
0186 #endif