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 // Author: Dmitry Sorokin (CERN), 26.09.2018
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 /**
0046  * @brief G4InterpolationDriver is a templated driver class which uses
0047  * Runge-Kutta stepper with interpolation property to integrate track with
0048  * error control.
0049  */
0050
0051 template <class T, G4bool StepperCachesDchord = true>
0052 class G4InterpolationDriver : public G4RKIntegrationDriver<T>
0053 {
0054   public:
0055
0056     /**
0057      * Constructor for G4IntegrationDriver.
0058      *  @param[in] hminimum Minimum allowed step.
0059      *  @param[in] stepper Pointer to the stepper algorithm.
0060      *  @param[in] numberOfComponents The number of integration variables,
0061      *             if not matching stepper's number of variables, issue exception.
0062      *  @param[in] statisticsVerbosity Verbosity level.
0063      */
0064     G4InterpolationDriver(G4double hminimum,
0065                           T* stepper,
0066                           G4int numberOfComponents = 6,
0067                           G4int statisticsVerbosity = 0);
0068
0069     /**
0070      * Destructor. Provides statistics if verbosity level is greater than zero.
0071      */
0072     ~G4InterpolationDriver() override;
0073
0074     /**
0075      * Copy constructor and assignment operator not allowed.
0076      */
0077     G4InterpolationDriver(const G4InterpolationDriver&) = delete;
0078     const G4InterpolationDriver& operator=(const G4InterpolationDriver&) = delete;
0079
0080     /**
0081      * Computes the step to take, based on chord limits.
0082      *  @param[in,out] track The current track in field.
0083      *  @param[in] hstep Proposed step length.
0084      *  @param[in] eps Requested accuracy, y_err/hstep.
0085      *  @param[in] chordDistance Maximum sagitta distance.
0086      *  @returns The length of step taken.
0087      */
0088     G4double AdvanceChordLimited(G4FieldTrack& track,
0089                                  G4double hstep,
0090                                  G4double eps,
0091                                  G4double chordDistance) override;
0092
0093     /**
0094      * Dispatch interface method for initialisation/reset of driver.
0095      */
0096     void OnStartTracking() override;
0097
0098     /**
0099      * Dispatch interface method for computing step. Does nothing here.
0100      */
0101     void OnComputeStep(const G4FieldTrack* /*track*/ = nullptr) override;
0102
0103     /**
0104      * The driver does not implement re-integration. Returns false.
0105      */
0106     G4bool DoesReIntegrate() const override { return false; }
0107
0108     /**
0109      * Advances integration accurately by relative accuracy better than 'eps'.
0110      * On output the track is replaced by the value at the end of interval.
0111      *  @param[in,out] track The current track in field.
0112      *  @param[in] hstep Proposed step length.
0113      *  @param[in] eps Requested accuracy, y_err/hstep.
0114      *  @param[in] hinitial Initial minimum integration step.
0115      *  @returns true if integration succeeds.
0116      */
0117     G4bool AccurateAdvance(G4FieldTrack& track,
0118                            G4double hstep,
0119                            G4double eps,  // Requested y_err/hstep
0120                            G4double hinitial = 0) override;
0121
0122     /**
0123      * Setter and getter for verbosity.
0124      */
0125     void SetVerboseLevel(G4int level) override;
0126     G4int GetVerboseLevel() const override;
0127
0128     /**
0129      * Writes out to stream the parameters/state of the driver.
0130      */
0131     void StreamInfo(std::ostream& os) const override;
0132
0133   protected:
0134
0135     struct InterpStepper
0136     {
0137       std::unique_ptr<T> stepper;
0138       G4double begin;
0139       G4double end;
0140       G4double inverseLength;
0141     };
0142
0143     using StepperIterator = typename std::vector<InterpStepper>::iterator;
0144     using ConstStepperIterator = typename std::vector<InterpStepper>::const_iterator;
0145
0146     /**
0147      * Takes one Step that is as large as possible while satisfying the
0148      * accuracy criterion.
0149      *  @param[in] it Stepper iterator.
0150      *  @param[in,out] y The current track state, y.
0151      *  @param[in] dydx dydx array.
0152      *  @param[in,out] hstep Step to attempt.
0153      *  @param[in] eps The relative accuracy.
0154      *  @param[in] curveLength Step start, x.
0155      *  @param[in,out] track Pointer to the Field track. Not used.
0156      *  @returns The step achieved.
0157      */
0158     virtual G4double OneGoodStep(StepperIterator it,
0159                                  field_utils::State& y,
0160                                  field_utils::State& dydx,
0161                                  G4double& hstep,
0162                                  G4double eps,
0163                                  G4double curveLength,
0164                                  G4FieldTrack* track = nullptr);
0165
0166     /**
0167      * Track interpolation.
0168      *  @param[in] curveLength Step start, x.
0169      *  @param[in,out] y The current track state, y.
0170      */
0171     void Interpolate(G4double curveLength, field_utils::State& y) const;
0172
0173     /**
0174      * Wrapper method for interpolation.
0175      */
0176     void InterpolateImpl(G4double curveLength,
0177                          ConstStepperIterator it,
0178                          field_utils::State& y) const;
0179
0180     /**
0181      * Methods for calculation of chord step and distance.
0182      */
0183     G4double DistChord(const field_utils::State& yBegin,
0184                              G4double curveLengthBegin,
0185                        const field_utils::State& yEnd,
0186                              G4double curveLengthEnd) const;
0187     G4double FindNextChord(const field_utils::State& yBegin,
0188                                  G4double curveLengthBegin,
0189                                  field_utils::State& yEnd,
0190                                  G4double curveLengthEnd,
0191                                  G4double dChord,
0192                                  G4double maxChordDistance);
0193     G4double CalcChordStep(G4double stepTrialOld,
0194                            G4double dChordStep,
0195                            G4double fDeltaChord);
0196
0197
0198     /**
0199      * Internal methods for printing/checking the state.
0200      */
0201     void PrintState() const;
0202     void CheckState() const;
0203
0204     /**
0205      * Increments number of trials and calls.
0206      */
0207     void AccumulateStatistics(G4int noTrials);
0208
0209   protected:
0210
0211     std::vector<InterpStepper> fSteppers;
0212     StepperIterator fLastStepper;
0213     G4bool fKeepLastStepper = false;
0214
0215     /** Memory of last good step size for integration. */
0216     G4double fhnext = DBL_MAX;
0217
0218     /** Minimum Step allowed (in units of length). */
0219     G4double fMinimumStep;
0220
0221     G4double fChordStepEstimate = DBL_MAX;
0222     const G4double fFractionNextEstimate = 0.98;  // Constant
0223     const G4double fSmallestCurveFraction = 0.01;  // Constant
0224
0225     G4int fVerboseLevel;  // Parameter
0226
0227     field_utils::State fdydx;
0228     G4bool fFirstStep = true;
0229
0230     G4int fMaxTrials = 100;  // Constant
0231     G4int fTotalStepsForTrack = 0;
0232
0233     /** Statistics. */
0234     G4int fTotalNoTrials = 0;
0235     G4int fNoCalls = 0;
0236     G4int fmaxTrials = 0;
0237
0238     using Base = G4RKIntegrationDriver<T>;
0239 };
0240
0241 #include "G4InterpolationDriver.icc"
0242
0243 #endif