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//
// $Id$
//
//---------------------------------------------------------------
//
//  G4VelocityTable.hh
//
//  class description:
//    This class keeps a table of velocity as a function of
//    the ratio kinetic erngy and mass
//    This class is used by G4Track::CalculateVelocity
//
//---------------------------------------------------------------
//   created                     17.Aug.  2011 H.Kurashige
//

#ifndef G4VelocityTable_h
#define G4VelocityTable_h 1

#include <vector>
#include <iostream>
#include "globals.hh"
#include "G4ios.hh"

//////////////
class G4VelocityTable
////////////// 
{
  // velocity table for massive particles used in CalculateVelocity 
 private:
  typedef std::vector<G4double> G4VTDataVector;

 public:
  G4VelocityTable();
  ~G4VelocityTable();

  G4double Value(G4double theEnergy);
   // Get the cross-section/energy-loss value corresponding to the
   // given energy. An appropriate interpolation is used to calculate
   // the value. 

  static G4VelocityTable* GetVelocityTable();

  static void SetVelocityTableProperties(G4double t_max, 
					 G4double t_min, 
					 G4int nbin);
  static G4double GetMaxTOfVelocityTable();
  static G4double GetMinTOfVelocityTable();
  static G4int    GetNbinOfVelocityTable();

 private:

  size_t FindBinLocation(G4double theEnergy) const;
   // Find the bin# in which theEnergy belongs - pure virtual function

  G4double Interpolation() const;

  G4double edgeMin;           // Energy of first point
  G4double edgeMax;           // Energy of the last point
  
  size_t numberOfNodes;
  
  G4VTDataVector  dataVector;    // Vector to keep the crossection/energyloss
  G4VTDataVector  binVector;     // Vector to keep energy
  G4VTDataVector  secDerivative; // Vector to keep second derivatives 

  G4double dBin;          // Bin width - useful only for fixed binning
  G4double baseBin;       // Set this in constructor for performance

  G4double lastEnergy;        // Cache the last input value
  G4double lastValue;         // Cache the last output value   
  size_t lastBin;             // Cache the last bin location
  
 private:
  void  PrepareVelocityTable();

  static G4VelocityTable* theInstance;
  G4double             maxT;
  G4double             minT;
  G4int                NbinT;
};

inline
 G4double G4VelocityTable::Interpolation() const
{
  // Linear interpolation is used to get the value. If the give energy
  // is in the highest bin, no interpolation will be Done. Because 
  // there is an extra bin hidden from a user at locBin=numberOfBin, 
  // the following interpolation is valid even the current locBin=
  // numberOfBin-1. 
  
  G4double intplFactor = (lastEnergy-binVector[lastBin]) 
     / (binVector[lastBin + 1]-binVector[lastBin]); // Interpol. factor
  
  return dataVector[lastBin] +
    ( dataVector[lastBin + 1]-dataVector[lastBin] ) * intplFactor;
}

#endif