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 // Created: J.Apostolakis, V.Grichine - 30.01.1997
0034 // -------------------------------------------------------------------
0035 #ifndef G4CLASSICALRK4_HH
0036 #define G4CLASSICALRK4_HH
0037
0038 #include "G4MagErrorStepper.hh"
0039
0040 class G4ClassicalRK4 : public G4MagErrorStepper
0041 {
0042   public:
0043
0044     G4ClassicalRK4(G4EquationOfMotion* EquationMotion,
0045                    G4int numberOfVariables = 6) ;
0046
0047     ~G4ClassicalRK4() override ;
0048
0049     G4ClassicalRK4(const G4ClassicalRK4&) = delete;
0050     G4ClassicalRK4& operator=(const G4ClassicalRK4&) = delete;
0051       // Copy constructor and assignment operator not allowed.
0052
0053     // A stepper that does not know about errors.
0054     // It is used by the MagErrorStepper stepper.
0055
0056     void DumbStepper( const G4double yIn[],
0057                       const G4double dydx[],
0058                             G4double h,
0059                             G4double yOut[] ) override ;
0060       // Given values for the variables y[0,..,n-1] and their derivatives
0061       // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
0062       // method to advance the solution over an interval h and return the
0063       // incremented variables as yout[0,...,n-1], which not be a distinct
0064       // array from y. The user supplies the routine RightHandSide(x,y,dydx),
0065       // which returns derivatives dydx at x. The source is routine rk4 from
0066       // NRC p. 712-713 .
0067
0068     G4int IntegratorOrder() const override { return 4; }
0069
0070   private:
0071
0072     void StepWithEst( const G4double  yIn[],
0073                       const G4double  dydx[],
0074                             G4double  h,
0075                             G4double  yOut[],
0076                             G4double& alpha2,
0077                             G4double& beta2,
0078                       const G4double B1[],
0079                             G4double B2[] );
0080       // No longer used. Obsolete.
0081
0082   private:
0083
0084     G4double *dydxm, *dydxt, *yt; // scratch space - not state
0085 };
0086
0087 #endif