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// G4DoLoMcPriRK34
//
// Class description:
//
//  Dormand-Lockyer-McGorrigan-Prince-6-3-4 non-FSAL method
//  ( 6 stage, 3rd & 4th order embedded RK method )

// Created: Somnath Banerjee, Google Summer of Code 2015, 7 July 2015
// Supervision: John Apostolakis, CERN
// --------------------------------------------------------------------
#ifndef DOLO_MCPRI_RK34_HH
#define DOLO_MCPRI_RK34_HH

#include "G4MagIntegratorStepper.hh"

class G4DoLoMcPriRK34 : public G4MagIntegratorStepper
{
  public:

    G4DoLoMcPriRK34( G4EquationOfMotion* EqRhs,
                     G4int numberOfVariables = 6,
                     G4bool primary = true );
      // Constructor using Equation

    ~G4DoLoMcPriRK34();

    G4DoLoMcPriRK34(const G4DoLoMcPriRK34&) = delete;
    G4DoLoMcPriRK34& operator=(const G4DoLoMcPriRK34&) = delete; 
      // Copy constructor and assignment operator not allowed

    void Stepper( const G4double y[],
                  const G4double dydx[],
                        G4double h,
                        G4double yout[],
                        G4double yerr[] ) ;
    
    void SetupInterpolation();
    void SetupInterpolate( const G4double yInput[],
                              const G4double dydx[],
                              const G4double Step );
      // For Preparing the interpolation and calculating the extra stages
    
    void Interpolate( const G4double yInput[],
                      const G4double dydx[],
                      const G4double Step,
                            G4double yOut[],
                            G4double tau );
      // For calculating the output at the tau fraction of Step

    void Interpolate( G4double tau,
                      G4double yOut[]);
    
    void interpolate(const G4double yInput[],
                     const G4double dydx[],
                           G4double yOut[],
                           G4double Step,
                           G4double tau ) ;

    G4double DistChord() const;
    G4int IntegratorOrder() const { return 3; }
    
  private :
    
    G4double *ak2, *ak3, *ak4, *ak5, *ak6, *yTemp, *yIn;
    
    G4double fLastStepLength = -1.0;
    G4double *fLastInitialVector, *fLastFinalVector,
             *fLastDyDx, *fMidVector, *fMidError;
      // for DistChord calculations
    
    G4DoLoMcPriRK34* fAuxStepper = nullptr;
};

#endif