include/Geant4/G4FSALDormandPrince745.hh

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0025 //
0026 // G4FSALDormandPrince745
0027 //
0028 // Class description:
0029 //
0030 // DormandPrince7 - 5(4) FSAL stepper
0031
0032 // Author: Somnath Banerjee (CERN, Google Summer of Code 2015), 25.05.2015
0033 // Supervision: John Apostolakis (CERN)
0034 // --------------------------------------------------------------------
0035 #ifndef G4FSALDORMANDPRINCE745_HH
0036 #define G4FSALDORMANDPRINCE745_HH
0037
0038 #include "G4VFSALIntegrationStepper.hh"
0039
0040 /**
0041  * @brief G4FSALDormandPrince745 is an integrator of particle's equation of
0042  * motion based on the DormandPrince7 - 5(4) FSAL implementation.
0043  */
0044
0045 class G4FSALDormandPrince745 : public G4VFSALIntegrationStepper
0046 {
0047   public:
0048
0049     /**
0050      * Constructor for G4FSALDormandPrince745.
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     G4FSALDormandPrince745(G4EquationOfMotion* EqRhs,
0056                            G4int numberOfVariables = 6,
0057                            G4bool primary = true);
0058
0059     /**
0060      * Destructor.
0061      */
0062     ~G4FSALDormandPrince745() override;
0063
0064     /**
0065      * Copy constructor and assignment operator not allowed.
0066      */
0067     G4FSALDormandPrince745(const G4FSALDormandPrince745&) = delete;
0068     G4FSALDormandPrince745& operator=(const G4FSALDormandPrince745&) = 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      *  @param[out] nextDydx Last derivatives array for the next step.
0081      */
0082     void Stepper( const G4double y[],
0083                   const G4double dydx[],
0084                         G4double h,
0085                         G4double yout[],
0086                         G4double yerr[],
0087                         G4double nextDydx[]) override ;
0088
0089     /**
0090      * Calculates the output at the tau fraction of step.
0091      *  @param[in] yInput Starting values array of integration variables.
0092      *  @param[in] dydx Derivatives array.
0093      *  @param[out] yOut Interpolation output.
0094      *  @param[in] Step The given step size.
0095      *  @param[in] tau The tau fraction of the step.
0096      */
0097     void interpolate( const G4double yInput[],
0098                       const G4double dydx[],
0099                             G4double yOut[],
0100                             G4double Step,
0101                             G4double tau ) ;
0102
0103     /**
0104      * Calculates the output at the tau fraction of step. Same as above
0105      * for higher order interpolant.
0106      */
0107     void Interpolate( const G4double yInput[],
0108                       const G4double dydx[],
0109                       const G4double Step,
0110                             G4double yOut[],
0111                             G4double tau );
0112
0113     /**
0114      * Setup method for higher order interpolant.
0115      *  @param[in] yInput Starting values array of integration variables.
0116      *  @param[in] dydx Derivatives array.
0117      *  @param[in] Step The given step size.
0118      */
0119     void SetupInterpolate( const G4double yInput[],
0120                            const G4double dydx[],
0121                            const G4double Step );
0122
0123     /**
0124      * Returns the distance from chord line.
0125      */
0126     G4double DistChord() const override;
0127
0128     /**
0129      * Returns the order, 4, of integration.
0130      */
0131     inline G4int IntegratorOrder() const override { return 4; }
0132
0133     /**
0134      * Returns true as this is a FSAL integrator.
0135      */
0136     inline G4bool isFSAL() const { return true; }
0137
0138   private:
0139
0140     /** Working arrays -- used during stepping. */
0141     G4double *ak2, *ak3, *ak4, *ak5, *ak6, *ak7,
0142              *ak8, *ak9,         // For additional stages in the interpolant
0143              *yTemp, *yIn;
0144
0145     /** Only for use with DistChord(). */
0146     G4double* pseudoDydx_for_DistChord;
0147
0148     G4double fLastStepLength = -1.0;
0149     G4double *fLastInitialVector, *fLastFinalVector,
0150              *fInitialDyDx, *fLastDyDx,
0151              *fMidVector, *fMidError;   // For DistChord() calculations
0152
0153     G4FSALDormandPrince745* fAuxStepper = nullptr;
0154 };
0155
0156 #endif