G4FSALBogackiShampine45.hh

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// G4FSALBogackiShampine45
//
// Class description:
//
// Bogacki-Shampine - 8 - 5(4) FSAL stepper

// Created: Somnath Banerjee, Google Summer of Code 2015, 26 May 2015
// Supervision: John Apostolakis, CERN
// --------------------------------------------------------------------
#ifndef G4FSAL_BOGACKI_SHAMPINE_45_HH
#define G4FSAL_BOGACKI_SHAMPINE_45_HH

#include "G4VFSALIntegrationStepper.hh"

class G4FSALBogackiShampine45 : public G4VFSALIntegrationStepper
{
  public:

    G4FSALBogackiShampine45(G4EquationOfMotion* EqRhs,
                            G4int numberOfVariables = 6,
                            G4bool primary = true);
    ~G4FSALBogackiShampine45();
    
    G4FSALBogackiShampine45(const G4FSALBogackiShampine45&) = delete;
    G4FSALBogackiShampine45& operator=(const G4FSALBogackiShampine45&) = delete;

    void Stepper( const G4double y[],
                  const G4double dydx[],
                        G4double h,
                        G4double yout[],
                        G4double yerr[],
                        G4double nextDydx[]) ;
    
    void interpolate( const G4double yInput[],
                      const G4double dydx[],
                            G4double yOut[],
                            G4double Step,
                            G4double tau ) ;

    G4double DistChord() const;
    inline G4int IntegratorOrder() const { return 4; }
    
  private :
    
    void PrepareConstants(); 
   
    // Working arrays -- used during stepping
    //
    G4double *ak2, *ak3, *ak4, *ak5, *ak6, *ak7, *ak8, *ak9, *ak10, *ak11,
             *DyDx, *yTemp, *yIn;
    G4double *pseudoDydx_for_DistChord;

    G4double fLastStepLength = -1.0;
    G4double *fLastInitialVector, *fLastFinalVector,
             *fLastDyDx, *fMidVector, *fMidError;
    // for DistChord calculations

    G4double b[12];     // Working array for interpolation
   
    G4FSALBogackiShampine45* fAuxStepper = nullptr;

    static G4bool fPreparedConstants;
    static G4double bi[12][7];
};

#endif