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//
// G4ChordFinderDelegate
//
// Class description:
//
// Implementation of common algorithm of finding step size 
// with distance to chord less then provided value. 

// Created: D.Sorokin
// --------------------------------------------------------------------
#ifndef G4CHORD_FINDER_DELEGATE_HH
#define G4CHORD_FINDER_DELEGATE_HH

#include "G4VIntegrationDriver.hh"

template <class Driver>
class G4ChordFinderDelegate
{
  public:

    virtual ~G4ChordFinderDelegate();

    G4double AdvanceChordLimitedImpl(G4FieldTrack& track,
                                     G4double hstep,
                                     G4double eps,
                                     G4double chordDistance);
    void ResetStepEstimate();

    void TestChordPrint(G4int noTrials, 
                        G4int lastStepTrial, 
                        G4double dChordStep, 
                        G4double fDeltaChord,
                        G4double nextStepTrial);

    // Get statistics about number of calls & trials in FindNextChord
    G4int GetNoCalls(); 
    G4int GetNoTrials();        // Total number of trials
    G4int GetNoMaxTrials();     // Maximum # of trials for one call

    // Parameters for  performance ... change with great care
    void SetFractions_Last_Next(G4double fractLast = 0.90, 
                                G4double fractNext = 0.95); 
    void SetFirstFraction(G4double fractFirst);

    // Printing for monitoring ...
    G4double GetFirstFraction();         // Originally 0.999
    G4double GetFractionLast();          // Originally 1.000
    G4double GetFractionNextEstimate();  // Originally 0.980

    G4double GetLastStepEstimateUnc(); 
    void SetLastStepEstimateUnc(G4double stepEst);

    void  StreamDelegateInfo( std::ostream& os ) const;
     // Write out the parameters / state of the driver
   
  private:

    Driver& GetDriver();

    G4double FindNextChord(const G4FieldTrack& yStart,
                           G4double stepMax,
                           G4double epsStep,
                           G4double chordDistance,
                           G4FieldTrack& yEnd, // Endpoint
                           G4double& dyErrPos, // Error of endpoint
                           G4double& pStepForAccuracy);

    G4double NewStep(G4double stepTrialOld, 
                     G4double dChordStep, // Curr. dchord achieved
                     G4double fDeltaChord,
                     G4double& stepEstimate_Unconstrained);

    void AccumulateStatistics(G4int noTrials);

    void PrintStatistics();

    G4double fFirstFraction = 0.999;
    G4double fFractionLast = 1.0;
    G4double fFractionNextEstimate = 0.98;
    G4double fLastStepEstimate_Unconstrained = DBL_MAX;

    G4int fTotalNoTrials = 0;
    G4int fNoCalls = 0;
    G4int fmaxTrials = 0;
};

#include "G4ChordFinderDelegate.icc"

#endif