G4DormandPrinceRK56.hh

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// G4DormandPrinceRK56
//
// Class description:
//
// Dormand-Prince RK 6(5) non-FSAL method

// Created: Somnath Banerjee, Google Summer of Code 2015, 26 June 2015
// Supervision: John Apostolakis, CERN
// --------------------------------------------------------------------
#ifndef G4DORMAND_PRINCE_RK56_HH
#define G4DORMAND_PRINCE_RK56_HH

#include "G4MagIntegratorStepper.hh"

class G4DormandPrinceRK56 : public G4MagIntegratorStepper
{
  public:

    G4DormandPrinceRK56( G4EquationOfMotion* EqRhs,
                         G4int numberOfVariables = 6,
                         G4bool primary = true ) ;
    
    ~G4DormandPrinceRK56() ;
    
    G4DormandPrinceRK56(const G4DormandPrinceRK56&) = delete;
    G4DormandPrinceRK56& operator=(const G4DormandPrinceRK56&) = delete;
    
    void Stepper( const G4double y[],
                  const G4double dydx[],
                        G4double h,
                        G4double yout[],
                        G4double yerr[] ) ;
    
    G4double  DistChord()   const;
    G4int IntegratorOrder() const { return 5; }
    
    void SetupInterpolate_low( const G4double yInput[],
                               const G4double dydx[],
                               const G4double Step );
      // For preparing the Interpolant and calculating the extra stages
    
    void Interpolate_low( const G4double yInput[],
                          const G4double dydx[],
                          const G4double Step,
                                G4double yOut[],
                                G4double tau );
      // For calculating the output at the tau fraction of Step

    inline void SetupInterpolation()
    {
      SetupInterpolate( fLastInitialVector, fLastDyDx, fLastStepLength);
    }
   
    inline void SetupInterpolate( const G4double yInput[],
                                  const G4double dydx[],
                                  const G4double Step )
    {
      SetupInterpolate_low( yInput, dydx, Step);
    }
    
    inline void Interpolate( const G4double yInput[],
                             const G4double dydx[],
                             const G4double Step,
                                   G4double yOut[],
                                   G4double tau )
    {
      Interpolate_low( yInput, dydx, Step, yOut, tau);
    }
      // For calculating the output at the tau fraction of Step

    inline void Interpolate( G4double tau, G4double yOut[])
    {
      Interpolate( fLastInitialVector, fLastDyDx, fLastStepLength, yOut, tau );
    }

    void SetupInterpolate_high( const G4double yInput[],
                                const G4double dydx[],
                                const G4double Step );
    
    void Interpolate_high( const G4double yInput[],
                           const G4double dydx[],
                           const G4double Step,
                                 G4double yOut[],
                                 G4double tau );
      // For calculating the output at the tau fraction of Step
    
  private:

    G4double *ak2, *ak3, *ak4, *ak5, *ak6, *ak7, *ak8, *ak9;
      // For storing intermediate 'k' values in stepper
    G4double *ak10_low, *ak10, *ak11, * ak12;
      // For the additional stages of Interpolant
    G4double *yTemp, *yIn;
    
    G4double fLastStepLength = -1.0;
    G4double *fLastInitialVector, *fLastFinalVector,
             *fLastDyDx, *fMidVector, *fMidError;
      // For DistChord calculations
    
    G4DormandPrinceRK56* fAuxStepper = nullptr;
};

#endif /* G4DormandPrinceRK56 */