/home/cern/BDSIM_new/include/BDSRK4Stepper.hh

#ifndef BDSRK4Stepper_h
#define BDSRK4Stepper_h 1


#include "globals.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4EquationOfMotion.hh"
#include "G4Mag_EqRhs.hh"
#include "G4ThreeVector.hh"
#include "G4Navigator.hh"

class BDSRK4Stepper : public G4MagIntegratorStepper
{
  
public:  
  
  BDSRK4Stepper(G4EquationOfMotion *EqRhs, int nvar=6);

  
  ~BDSRK4Stepper();
  
  void Stepper( const G4double y[],
                const G4double dydx[],
                const G4double h,
                G4double yout[],
                G4double yerr[]  );
  // The stepper for the Runge Kutta integration.
  // The stepsize is fixed, equal to h.
  // Integrates ODE starting values y[0 to 6]
  // Outputs yout[] and its estimated error yerr[].
  
  G4double DistChord()   const;
  // Estimate maximum distance of curved solution and chord ... 
  
    
  void StepperName();
  
  void SetVolLength(G4double aVolLength);
  
  
  G4int IntegratorOrder()const { return 2; }

  protected:
  //  --- Methods used to implement all the derived classes -----
  
  void AdvanceHelix( const G4double  yIn[],
                     const G4double dydx[],
                     const G4double  h,
                     G4double  yRK[]);    // output 
  // A first order Step along a quad inside the field.
  
private:
  
  G4ThreeVector yInitial, yMidPoint, yFinal;
  // Data stored in order to find the chord.
  
    G4EquationOfMotion* itsEqRhs;
  //    G4ThreeVector itsInitialPoint, itsFinalPoint, itsMidPoint,itsDistVec;
  G4double itsDist;
  
  G4double itsVolLength;
  
  G4double *yt, *dydx, *dydxt, *dydxm, *dydxr, *yTemp, *yIn;

};

inline  void BDSRK4Stepper::SetVolLength(G4double aVolLength)
{itsVolLength=aVolLength;
}
inline void BDSRK4Stepper::StepperName()
{G4cout<<"BDSRK4Stepper"<<G4endl;}

#endif

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