G4InterpolationDriver.hh

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// G4InterpolationDriver
//
// Class description:
//
// Driver class which uses Runge-Kutta stepper with interpolation property
// to integrate track with error control
 
// Created: D.Sorokin, 2018
// --------------------------------------------------------------------
#ifndef G4INTERPOLATION_DRIVER_HH
#define G4INTERPOLATION_DRIVER_HH
 
#include "G4FieldUtils.hh"
#include "G4RKIntegrationDriver.hh"
#include "globals.hh"
 
#include <memory>
#include <vector>
 
template <class T, G4bool StepperCachesDchord = true>
class G4InterpolationDriver : public G4RKIntegrationDriver<T>
{
  public:
 
    G4InterpolationDriver(G4double hminimum,
                          T* stepper,
                          G4int numberOfComponents = 6,
                          G4int statisticsVerbosity = 0);
 
   ~G4InterpolationDriver() override;
 
    G4InterpolationDriver(const G4InterpolationDriver&) = delete;
    const G4InterpolationDriver& operator=(const G4InterpolationDriver&) = delete;
 
    G4double AdvanceChordLimited(G4FieldTrack& track,
                                 G4double hstep,
                                 G4double eps,
                                 G4double chordDistance) override;
 
    void OnStartTracking() override;
    void OnComputeStep(const G4FieldTrack* /*track*/ = nullptr) override;
    G4bool DoesReIntegrate() const override { return false; }
      // Interpolation driver does not recalculate when AccurateAdvance
      // is called -- reintegration would require other calls
 
    G4bool AccurateAdvance(G4FieldTrack& track,
                           G4double hstep,
                           G4double eps,  // Requested y_err/hstep
                           G4double hinitial = 0) override;
      // Integrates ODE from current s (s=s0) to s=s0+h with accuracy eps.
      // On output track is replaced by value at end of interval.
      // The concept is similar to the odeint routine from NRC p.721-722.
 
    void SetVerboseLevel(G4int level) override;
    G4int GetVerboseLevel() const override;
 
    void StreamInfo(std::ostream& os) const override;
 
  protected:
 
    struct InterpStepper
    {
      std::unique_ptr<T> stepper;
      G4double begin;
      G4double end;
      G4double inverseLength;
    };
 
    using StepperIterator = typename std::vector<InterpStepper>::iterator;
    using ConstStepperIterator = typename std::vector<InterpStepper>::const_iterator;
 
    virtual G4double OneGoodStep(StepperIterator it,
                                 field_utils::State& y,
                                 field_utils::State& dydx,
                                 G4double& hstep,
                                 G4double eps,
                                 G4double curveLength,
                                 G4FieldTrack* track = nullptr);
      // This takes one Step that is of size htry, or as large
      // as possible while satisfying the accuracy criterion of:
      //     yerr < eps * |y_end-y_start|
      // return hdid
 
    void Interpolate(G4double curveLength, field_utils::State& y) const;
 
    void InterpolateImpl(G4double curveLength,
                         ConstStepperIterator it,
                         field_utils::State& y) const;
 
    G4double DistChord(const field_utils::State& yBegin,
                             G4double curveLengthBegin,
                       const field_utils::State& yEnd,
                             G4double curveLengthEnd) const;
 
    G4double FindNextChord(const field_utils::State& yBegin,
                                 G4double curveLengthBegin,
                                 field_utils::State& yEnd,
                                 G4double curveLengthEnd,
                                 G4double dChord,
                                 G4double maxChordDistance);
 
    G4double CalcChordStep(G4double stepTrialOld,
                           G4double dChordStep,
                           G4double fDeltaChord);
 
    void PrintState() const;
 
    void CheckState() const;
 
    void AccumulateStatistics(G4int noTrials);
 
  protected:
 
    std::vector<InterpStepper> fSteppers;
    StepperIterator fLastStepper;
    G4bool fKeepLastStepper = false;
 
    G4double fhnext = DBL_MAX;
      // Memory of last good step size for integration
 
    G4double fMinimumStep;
      // Minimum Step allowed in a Step (in units of length)   // Parameter
 
    G4double fChordStepEstimate = DBL_MAX;
    const G4double fFractionNextEstimate = 0.98;  // Constant
    const G4double fSmallestCurveFraction = 0.01;  // Constant
 
    G4int fVerboseLevel;  // Parameter
 
    field_utils::State fdydx;
    G4bool fFirstStep = true;
 
    G4int fMaxTrials = 100;  // Constant
    G4int fTotalStepsForTrack = 0;
 
    // statistics
    G4int fTotalNoTrials = 0;
    G4int fNoCalls = 0;
    G4int fmaxTrials = 0;
 
    using Base = G4RKIntegrationDriver<T>;
};
 
#include "G4InterpolationDriver.icc"
 
#endif