| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 // G4VFSALIntegrationStepper
27 //
28 // Class description:
29 //
30 // Class similar to G4VMagIntegratorStepper, for steppers which
31 // estimate the value of the derivative at the projected endpoint
32 // of integration - at each successful step.
33 // This ability is known as 'First Same As Last' (FSAL). It
34 // reduces the number of required calls to the equation's
35 // RightHandSide method, and, as such the number of calls to the
36 // (potentially expensive) field evaluation methods.
37 //
38 // Based on G4VMagIntegratorStepper
39
40 // Author: Somnath Banerjee, Google Summer of Code 2015
41 // Supervision: John Apostolakis, CERN
42 // --------------------------------------------------------------------
43 #ifndef G4VFSALINTEGRATOR_STEPPER_HH
44 #define G4VFSALINTEGRATOR_STEPPER_HH
45
46 #include "G4Types.hh"
47 #include "G4EquationOfMotion.hh"
48
49 class G4VFSALIntegrationStepper
50 {
51 public: // with description
52
53 G4VFSALIntegrationStepper (G4EquationOfMotion* Equation,
54 G4int numIntegrationVariables,
55 G4int numStateVariables = 12);
56 virtual ~G4VFSALIntegrationStepper() = default;
57 // Constructor and destructor. No actions.
58
59 G4VFSALIntegrationStepper(const G4VFSALIntegrationStepper&) = delete;
60 G4VFSALIntegrationStepper& operator=(const G4VFSALIntegrationStepper&) = delete;
61
62 virtual void Stepper( const G4double y[],
63 const G4double dydx[],
64 G4double h,
65 G4double yout[],
66 G4double yerr[],
67 G4double lastDydx[]) = 0;
68 // The stepper for the Runge Kutta integration.
69 // The stepsize is fixed, with the Step size given by h.
70 // Integrates ODE starting values y[0 to 6].
71 // Outputs yout[] and its estimated error yerr[].
72
73 virtual G4double DistChord() const = 0;
74 // Estimate the maximum distance of a chord from the true path
75 // over the segment last integrated.
76
77 inline void NormaliseTangentVector( G4double vec[6] );
78 // Simple utility function to (re)normalise 'unit velocity' vector.
79
80 inline void NormalisePolarizationVector( G4double vec[12] );
81 // Simple utility function to (re)normalise 'unit spin' vector.
82
83 void RightHandSide( const double y[], double dydx[] );
84 // Utility method to supply the standard Evaluation of the
85 // Right Hand side of the associated equation.
86
87 inline G4int GetNumberOfVariables() const;
88 // Get the number of variables that the stepper will integrate over.
89
90 inline G4int GetNumberOfStateVariables() const;
91 // Get the number of variables of state variables (>= above, integration)
92
93 virtual G4int IntegratorOrder() const = 0;
94 // Returns the order of the integrator
95 // i.e. its error behaviour is of the order O(h^order).
96
97 inline G4EquationOfMotion* GetEquationOfMotion();
98 // As some steppers (eg RKG3) require other methods of Eq_Rhs
99 // this function allows for access to them.
100 inline void SetEquationOfMotion(G4EquationOfMotion* newEquation);
101
102 public: // without description
103
104 // Debug functions...
105
106 inline G4int GetfNoRHSCalls() { return fNoRHSCalls; }
107 void increasefNORHSCalls();
108 inline void ResetfNORHSCalls() { fNoRHSCalls = 0; }
109
110 private:
111
112 G4EquationOfMotion* fEquation_Rhs = nullptr;
113 const G4int fNoIntegrationVariables = 0; // Variables in integration
114 const G4int fNoStateVariables = 0; // Number required for FieldTrack
115
116 G4int fNoRHSCalls = 0;
117 // Debug...
118 };
119
120 #include "G4VFSALIntegrationStepper.icc"
121
122 #endif
123