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G4BogackiShampine45.hh
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25 //
26 // G4BogackiShampine45
27 //
28 // Class description:
29 //
30 // An implementation of the embedded RK method from the following paper
31 // by P. Bogacki and L. F. Shampine:
32 // "An efficient Runge-Kutta (4,5) pair"
33 // Comput. Math. with Appl., vol. 32, no. 6, pp. 15-28, Sep. 1996.
34 //
35 // An interpolation method provides the value of an intermediate
36 // point in a step -- if a step was sucessful.
37 //
38 // This version can provide the FSAL property of the method,
39 // which allows the reuse of the last derivative in the next step,
40 // but only by using the additional method GetLastDyDx() (an alternative
41 // interface for simpler use of FSAL is under development).
42 
43 // Created: Somnath Banerjee, Google Summer of Code 2015, 25 May 2015
44 // Supervision: John Apostolakis, CERN
45 // --------------------------------------------------------------------
46 #ifndef BOGACKI_SHAMPINE_45_HH
47 #define BOGACKI_SHAMPINE_45_HH
48 
50 
52 {
53  public:
54 
56  G4int numberOfVariables = 6,
57  G4bool primary = true);
59 
62 
63  void Stepper( const G4double y[],
64  const G4double dydx[],
65  G4double h,
66  G4double yout[],
67  G4double yerr[] ) ;
68 
69  // This Stepper provides 'dense output'. After a successful
70  // step, it is possible to obtain an estimate of the value
71  // of the function at an intermediate point of the interval.
72  // This requires only two additional evaluations of the
73  // derivative (and thus the field).
74 
75  inline void SetupInterpolation()
76  {
77  SetupInterpolationHigh(); // ( yInput, dydx, Step);
78  }
79 
80  // For calculating the output at the tau fraction of Step
81  //
82  inline void Interpolate( G4double tau,
83  G4double yOut[] ) // Output value
84  {
85  InterpolateHigh( tau, yOut);
86  // InterpolateHigh( yInput, dydx, Step, yOut, tau);
87  }
88 
90 
91  // For calculating the output at the tau fraction of Step
92  //
93  void InterpolateHigh( G4double tau,
94  G4double yOut[] ) const;
95 
96  G4double DistChord() const;
97  G4int IntegratorOrder() const { return 4; }
98 
99  void GetLastDydx( G4double dyDxLast[] );
100 
101  void PrepareConstants(); // Initialise the values of the bi[][] array
102 
103  private:
104 
105  G4double *ak2, *ak3, *ak4, *ak5, *ak6, *ak7, *ak8,
106  *ak9, *ak10, *ak11, *yTemp, *yIn;
107 
108  G4double *p[6];
109 
113  // For DistChord calculations
114 
116  // For chord - until interpolation is proven
118 
119  // Class constants
121  static G4double bi[12][7];
122 };
123 
124 #endif