G4DormandPrince745.hh

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// G4DormandPrince745
//
// Class desription:
//
//  An implementation of the 5th order embedded RK method from the paper:
//  J. R. Dormand and P. J. Prince, "A family of embedded Runge-Kutta formulae"
//  Journal of computational and applied Math., vol.6, no.1, pp.19-26, 1980.
//
//  DormandPrince7 - 5(4) embedded RK method
//
 
// Created: Somnath Banerjee, Google Summer of Code 2015, 25 May 2015
// Supervision: John Apostolakis, CERN
// --------------------------------------------------------------------
#ifndef G4DORMAND_PRINCE_745_HH
#define G4DORMAND_PRINCE_745_HH
 
#include "G4MagIntegratorStepper.hh"
#include "G4FieldUtils.hh"
 
class G4DormandPrince745 : public G4MagIntegratorStepper
{
  public:
 
    G4DormandPrince745(G4EquationOfMotion* equation,
                       G4int numberOfVariables = 6);
 
    virtual void Stepper(const G4double yInput[],
                         const G4double dydx[],
                         G4double hstep,
                         G4double yOutput[],
                         G4double yError[]) override;
 
    void Stepper(const G4double yInput[],
                 const G4double dydx[],
                 G4double hstep,
                 G4double yOutput[],
                 G4double yError[],
                 G4double dydxOutput[]);
 
    inline void SetupInterpolation() {}
 
    inline void Interpolate(G4double tau, G4double yOut[]) const
    {
        Interpolate4thOrder(yOut, tau);
    }
      // For calculating the output at the tau fraction of Step
 
    virtual G4double DistChord() const override;
 
    virtual G4int IntegratorOrder() const override { return 4; }
 
    const G4String& StepperType() const        { return gStepperType; }
    const G4String& StepperDescription() const { return gStepperDescription; }
   
    const field_utils::State& GetYOut() const { return fyOut; }
 
    void Interpolate4thOrder(G4double yOut[], G4double tau) const;
 
    void SetupInterpolation5thOrder();
    void Interpolate5thOrder(G4double yOut[], G4double tau) const;
 
    G4EquationOfMotion* GetSpecificEquation() { return GetEquationOfMotion(); }
   
  private:
    // Name and description of this steppers - plus details of its implementation
    static const G4String gStepperType;
    static const G4String gStepperDescription;
    // const unsigned int fIntegratorOrder = 4;  // Should it not be 5 ? 
 
    field_utils::State ak2, ak3, ak4, ak5, ak6, ak7, ak8, ak9;
    field_utils::State fyIn, fyOut, fdydxIn;
 
    G4double fLastStepLength = -1.0;
};
#endif