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1 //
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25 //
26 // G4ClassicalRK4
27 //
28 // Class description:
29 //
30 // Integrate the equations of the motion of a particle in a magnetic field
31 // using the classical 4th Runge-Kutta method.
32
33 // Created: J.Apostolakis, V.Grichine - 30.01.1997
34 // -------------------------------------------------------------------
35 #ifndef G4CLASSICALRK4_HH
36 #define G4CLASSICALRK4_HH
37
38 #include "G4MagErrorStepper.hh"
39
40 class G4ClassicalRK4 : public G4MagErrorStepper
41 {
42 public:
43
44 G4ClassicalRK4(G4EquationOfMotion* EquationMotion,
45 G4int numberOfVariables = 6) ;
46
47 ~G4ClassicalRK4() override ;
48
49 G4ClassicalRK4(const G4ClassicalRK4&) = delete;
50 G4ClassicalRK4& operator=(const G4ClassicalRK4&) = delete;
51 // Copy constructor and assignment operator not allowed.
52
53 // A stepper that does not know about errors.
54 // It is used by the MagErrorStepper stepper.
55
56 void DumbStepper( const G4double yIn[],
57 const G4double dydx[],
58 G4double h,
59 G4double yOut[] ) override ;
60 // Given values for the variables y[0,..,n-1] and their derivatives
61 // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
62 // method to advance the solution over an interval h and return the
63 // incremented variables as yout[0,...,n-1], which not be a distinct
64 // array from y. The user supplies the routine RightHandSide(x,y,dydx),
65 // which returns derivatives dydx at x. The source is routine rk4 from
66 // NRC p. 712-713 .
67
68 G4int IntegratorOrder() const override { return 4; }
69
70 private:
71
72 void StepWithEst( const G4double yIn[],
73 const G4double dydx[],
74 G4double h,
75 G4double yOut[],
76 G4double& alpha2,
77 G4double& beta2,
78 const G4double B1[],
79 G4double B2[] );
80 // No longer used. Obsolete.
81
82 private:
83
84 G4double *dydxm, *dydxt, *yt; // scratch space - not state
85 };
86
87 #endif
88