G4ClassicalRK4.hh

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// G4ClassicalRK4
//
// Class description:
//
// Integrate the equations of the motion of a particle in a magnetic field
// using the classical 4th Runge-Kutta method.
 
// Created: J.Apostolakis, V.Grichine - 30.01.1997
// -------------------------------------------------------------------
#ifndef G4CLASSICALRK4_HH
#define G4CLASSICALRK4_HH
 
#include "G4MagErrorStepper.hh"
 
class G4ClassicalRK4 : public G4MagErrorStepper 
{
  public:
 
    G4ClassicalRK4(G4EquationOfMotion* EquationMotion,
                   G4int numberOfVariables = 6) ;
 
    ~G4ClassicalRK4() override ;
 
    G4ClassicalRK4(const G4ClassicalRK4&) = delete;
    G4ClassicalRK4& operator=(const G4ClassicalRK4&) = delete;
      // Copy constructor and assignment operator not allowed.
 
    // A stepper that does not know about errors.
    // It is used by the MagErrorStepper stepper.
   
    void DumbStepper( const G4double yIn[],
                      const G4double dydx[],
                            G4double h,
                            G4double yOut[] ) override ;
      // Given values for the variables y[0,..,n-1] and their derivatives
      // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
      // method to advance the solution over an interval h and return the
      // incremented variables as yout[0,...,n-1], which not be a distinct
      // array from y. The user supplies the routine RightHandSide(x,y,dydx),
      // which returns derivatives dydx at x. The source is routine rk4 from
      // NRC p. 712-713 .
 
    G4int IntegratorOrder() const override { return 4; }
 
  private:
 
    void StepWithEst( const G4double  yIn[],
                      const G4double  dydx[],
                            G4double  h,
                            G4double  yOut[],
                            G4double& alpha2,
                            G4double& beta2,
                      const G4double B1[],
                            G4double B2[] );
      // No longer used. Obsolete.
 
  private:
 
    G4double *dydxm, *dydxt, *yt; // scratch space - not state 
};
 
#endif