include/Geant4/G4InterpolationDriver.hh

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0025 //
0026 // G4InterpolationDriver
0027 //
0028 // Class description:
0029 //
0030 // Driver class which uses Runge-Kutta stepper with interpolation property
0031 // to integrate track with error control
0032
0033 // Created: D.Sorokin, 2018
0034 // --------------------------------------------------------------------
0035 #ifndef G4INTERPOLATION_DRIVER_HH
0036 #define G4INTERPOLATION_DRIVER_HH
0037
0038 #include "G4FieldUtils.hh"
0039 #include "G4RKIntegrationDriver.hh"
0040 #include "globals.hh"
0041
0042 #include <memory>
0043 #include <vector>
0044
0045 template <class T, G4bool StepperCachesDchord = true>
0046 class G4InterpolationDriver : public G4RKIntegrationDriver<T>
0047 {
0048   public:
0049
0050     G4InterpolationDriver(G4double hminimum,
0051                           T* stepper,
0052                           G4int numberOfComponents = 6,
0053                           G4int statisticsVerbosity = 0);
0054
0055    ~G4InterpolationDriver() override;
0056
0057     G4InterpolationDriver(const G4InterpolationDriver&) = delete;
0058     const G4InterpolationDriver& operator=(const G4InterpolationDriver&) = delete;
0059
0060     G4double AdvanceChordLimited(G4FieldTrack& track,
0061                                  G4double hstep,
0062                                  G4double eps,
0063                                  G4double chordDistance) override;
0064
0065     void OnStartTracking() override;
0066     void OnComputeStep(const G4FieldTrack* /*track*/ = nullptr) override;
0067     G4bool DoesReIntegrate() const override { return false; }
0068       // Interpolation driver does not recalculate when AccurateAdvance
0069       // is called -- reintegration would require other calls
0070
0071     G4bool AccurateAdvance(G4FieldTrack& track,
0072                            G4double hstep,
0073                            G4double eps,  // Requested y_err/hstep
0074                            G4double hinitial = 0) override;
0075       // Integrates ODE from current s (s=s0) to s=s0+h with accuracy eps.
0076       // On output track is replaced by value at end of interval.
0077       // The concept is similar to the odeint routine from NRC p.721-722.
0078
0079     void SetVerboseLevel(G4int level) override;
0080     G4int GetVerboseLevel() const override;
0081
0082     void StreamInfo(std::ostream& os) const override;
0083
0084   protected:
0085
0086     struct InterpStepper
0087     {
0088       std::unique_ptr<T> stepper;
0089       G4double begin;
0090       G4double end;
0091       G4double inverseLength;
0092     };
0093
0094     using StepperIterator = typename std::vector<InterpStepper>::iterator;
0095     using ConstStepperIterator = typename std::vector<InterpStepper>::const_iterator;
0096
0097     virtual G4double OneGoodStep(StepperIterator it,
0098                                  field_utils::State& y,
0099                                  field_utils::State& dydx,
0100                                  G4double& hstep,
0101                                  G4double eps,
0102                                  G4double curveLength,
0103                                  G4FieldTrack* track = nullptr);
0104       // This takes one Step that is of size htry, or as large
0105       // as possible while satisfying the accuracy criterion of:
0106       //     yerr < eps * |y_end-y_start|
0107       // return hdid
0108
0109     void Interpolate(G4double curveLength, field_utils::State& y) const;
0110
0111     void InterpolateImpl(G4double curveLength,
0112                          ConstStepperIterator it,
0113                          field_utils::State& y) const;
0114
0115     G4double DistChord(const field_utils::State& yBegin,
0116                              G4double curveLengthBegin,
0117                        const field_utils::State& yEnd,
0118                              G4double curveLengthEnd) const;
0119
0120     G4double FindNextChord(const field_utils::State& yBegin,
0121                                  G4double curveLengthBegin,
0122                                  field_utils::State& yEnd,
0123                                  G4double curveLengthEnd,
0124                                  G4double dChord,
0125                                  G4double maxChordDistance);
0126
0127     G4double CalcChordStep(G4double stepTrialOld,
0128                            G4double dChordStep,
0129                            G4double fDeltaChord);
0130
0131     void PrintState() const;
0132
0133     void CheckState() const;
0134
0135     void AccumulateStatistics(G4int noTrials);
0136
0137   protected:
0138
0139     std::vector<InterpStepper> fSteppers;
0140     StepperIterator fLastStepper;
0141     G4bool fKeepLastStepper = false;
0142
0143     G4double fhnext = DBL_MAX;
0144       // Memory of last good step size for integration
0145
0146     G4double fMinimumStep;
0147       // Minimum Step allowed in a Step (in units of length)   // Parameter
0148
0149     G4double fChordStepEstimate = DBL_MAX;
0150     const G4double fFractionNextEstimate = 0.98;  // Constant
0151     const G4double fSmallestCurveFraction = 0.01;  // Constant
0152
0153     G4int fVerboseLevel;  // Parameter
0154
0155     field_utils::State fdydx;
0156     G4bool fFirstStep = true;
0157
0158     G4int fMaxTrials = 100;  // Constant
0159     G4int fTotalStepsForTrack = 0;
0160
0161     // statistics
0162     G4int fTotalNoTrials = 0;
0163     G4int fNoCalls = 0;
0164     G4int fmaxTrials = 0;
0165
0166     using Base = G4RKIntegrationDriver<T>;
0167 };
0168
0169 #include "G4InterpolationDriver.icc"
0170
0171 #endif