include/Geant4/G4ClassicalRK4.hh

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0025 //
0026 // G4ClassicalRK4
0027 //
0028 // Class description:
0029 //
0030 // Integrate the equations of the motion of a particle in a magnetic field
0031 // using the classical 4th Runge-Kutta method.
0032
0033 // Authors: J.Apostolakis, V.Grichine (CERN), 30.01.1997
0034 // -------------------------------------------------------------------
0035 #ifndef G4CLASSICALRK4_HH
0036 #define G4CLASSICALRK4_HH
0037
0038 #include "G4MagErrorStepper.hh"
0039
0040 /**
0041  * @brief G4ClassicalRK4 integrates the equations of the motion of a particle
0042  * in a magnetic field using the classical 4th Runge-Kutta method.
0043  */
0044
0045 class G4ClassicalRK4 : public G4MagErrorStepper
0046 {
0047   public:
0048
0049     /**
0050      * Constructor for G4ClassicalRK4.
0051      *  @param[in] EquationMotion Pointer to the provided equation of motion.
0052      *  @param[in] numberOfVariables The number of integration variables.
0053      */
0054     G4ClassicalRK4(G4EquationOfMotion* EquationMotion,
0055                    G4int numberOfVariables = 6) ;
0056
0057     /**
0058      * Destructor.
0059      */
0060     ~G4ClassicalRK4() override ;
0061
0062     /**
0063      * Copy constructor and assignment operator not allowed.
0064      */
0065     G4ClassicalRK4(const G4ClassicalRK4&) = delete;
0066     G4ClassicalRK4& operator=(const G4ClassicalRK4&) = delete;
0067
0068     // A stepper that does not know about errors.
0069     // It is used by the MagErrorStepper stepper.
0070
0071     /**
0072      * Given values for the variables y[0,..,n-1] and their derivatives
0073      * dydx[0,...,n-1] known at x, uses the classical 4th Runge-Kutta
0074      * method to advance the solution over an interval h and returns the
0075      * incremented variables as yout[0,...,n-1]. The user supplies the
0076      * function RightHandSide(x,y,dydx), which returns derivatives dydx at x.
0077      * The source is routine rk4 from NRC p.712-713.
0078      *  @param[in] yIn Starting values array of integration variables.
0079      *  @param[in] dydx Derivatives array.
0080      *  @param[in] h The given step size.
0081      *  @param[out] yOut Integration output.
0082      */
0083     void DumbStepper( const G4double yIn[],
0084                       const G4double dydx[],
0085                             G4double h,
0086                             G4double yOut[] ) override ;
0087
0088     /**
0089      * Returns the order, 4, of integration.
0090      */
0091     G4int IntegratorOrder() const override { return 4; }
0092
0093     /**
0094      * Returns the stepper type-ID, "kClassicalRK4".
0095      */
0096     G4StepperType StepperType() const override { return kClassicalRK4; }
0097
0098   private:
0099
0100     G4double *dydxm, *dydxt, *yt; // scratch space - not state
0101 };
0102
0103 #endif