G4ClassicalRK4.hh

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00026 //
00027 // $Id: G4ClassicalRK4.hh 69786 2013-05-15 09:38:51Z gcosmo $
00028 //
00029 //
00030 // class G4ClassicalRK4
00031 //
00032 // Class description:
00033 //
00034 // Integrate the equations of the motion of a particle in a magnetic field
00035 // using the classical 4th Runge-Kutta method.
00036 
00037 // History:
00038 // - Created: J.Apostolakis, V.Grichine - 30.1.97
00039 // - Moved into G4MagErrorStepper: W.Wander <wwc@mit.edu> - 12/09/97
00040 // -------------------------------------------------------------------
00041 
00042 #include "G4MagErrorStepper.hh"
00043 
00044 class G4ClassicalRK4 : public G4MagErrorStepper 
00045 {
00046   public:  // with description
00047 
00048     G4ClassicalRK4(G4EquationOfMotion *EquationMotion, G4int numberOfVariables = 6) ;
00049 
00050     ~G4ClassicalRK4() ;
00051 
00052     // A stepper that does not know about errors.
00053     // It is used by the MagErrorStepper stepper.
00054    
00055     void DumbStepper( const G4double  yIn[],
00056                       const G4double  dydx[],
00057                             G4double  h,
00058                             G4double  yOut[] ) ;
00059       // Given values for the variables y[0,..,n-1] and their derivatives
00060       // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
00061       // method to advance the solution over an interval h and return the
00062       // incremented variables as yout[0,...,n-1], which not be a distinct
00063       // array from y. The user supplies the routine RightHandSide(x,y,dydx),
00064       // which returns derivatives dydx at x. The source is routine rk4 from
00065       // NRC p. 712-713 .
00066 
00067   public:  // without description
00068 
00069     G4int IntegratorOrder() const { return 4; }
00070 
00071   private:
00072 
00073     void StepWithEst( const G4double  yIn[],
00074                       const G4double  dydx[],
00075                             G4double  h,
00076                             G4double  yOut[],
00077                             G4double& alpha2,
00078                             G4double& beta2,
00079                       const G4double B1[],
00080                             G4double B2[] );
00081       // No longer used. Obsolete.
00082 
00083     G4ClassicalRK4(const G4ClassicalRK4&);
00084     G4ClassicalRK4& operator=(const G4ClassicalRK4&);
00085       // Private copy constructor and assignment operator.
00086 
00087   private:
00088 
00089     // G4int fNumberOfVariables ; // is set default to 6 in constructor
00090 
00091     G4double *dydxm, *dydxt, *yt; // scratch space - not state 
00092 };

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