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//
//
// Helper class for RNG Engine seeds.
// Used in MT builds to guarantee reproducibility.
// The function of this class is to return a RNG Engine seed
// given its index. It is a simple templated container that
// Allows to add seeds (AddOneSeed) and retrieve a seed (GetSeed)
// by index.
//
// The normal use is with G4RNGHelper where each element of th econtainer
// represents a seed. To enforce strong-reproducibility the variant with
// the RNG Engine status file names is avilable

#ifndef G4RNGHELPER_HH
#define G4RNGHELPER_HH

#include "globals.hh"
#include <queue>
#include <vector>

template <class T>
class G4TemplateRNGHelper
{
 public:
  // The container is modeled as a (shared) singleton
  static G4TemplateRNGHelper<T>* GetInstance();
  static G4TemplateRNGHelper<T>* GetInstanceIfExist();
  typedef std::vector<T> SeedsQueue;
  typedef typename SeedsQueue::size_type SeedsQueueSize_type;

  virtual ~G4TemplateRNGHelper();

  // Returns seed given id
  virtual const T GetSeed(const G4int& sdId)
  {
    G4int seedId = sdId - 2 * offset;
    if(seedId < static_cast<G4int>(seeds.size()))
    {
      T& seed = seeds[seedId];
      return seed;
    }
    G4ExceptionDescription msg;
    msg << "No seed number " << seedId << "(" << seeds.size() << " available)\n"
        << " Original seed number " << sdId << " filled so far " << offset;
    G4Exception("G4RNGHelper::GetSeed", "Run0115", FatalException, msg);
    return T();
  }

  // Adds one seed to the collection
  void AddOneSeed(const T& seed) { seeds.push_back(seed); }

  // Fills N primary seed pairs
  void Fill(G4double* dbl, G4int nev, G4int nev_tot, G4int nrpe)
  {
    seeds.clear();
    for(G4int i = 0; i < nrpe * nev; i++)
    {
      seeds.push_back((G4long)(100000000L * dbl[i]));
    }
    offset        = 0;
    nev_filled    = nev;
    nev_total     = nev_tot;
    nRandParEvent = nrpe;
  }

  void Refill(G4double* dbl, G4int nev)
  {
    if(nev == 0)
      return;
    seeds.clear();
    for(G4int i = 0; i < nRandParEvent * nev; i++)
    {
      seeds.push_back((G4long)(100000000L * dbl[i]));
    }
    offset += nev_filled;
    nev_filled = nev;
  }

  // Number of available seeds
  const SeedsQueueSize_type GetNumberSeeds() const { return seeds.size(); }

  // Empty the seeds container
  virtual void Clear() { seeds.clear(); }

 protected:
  SeedsQueue seeds;
  // Note: following numbers are number of events.
  //       seeds are generated for nRandParEvent times n_event
  G4int offset;
  G4int nev_filled;
  G4int nev_total;
  G4int nRandParEvent;

 private:
  G4TemplateRNGHelper()
  {
    offset        = 0;
    nev_filled    = 0;
    nev_total     = 0;
    nRandParEvent = 0;
  }

 private:
  static G4TemplateRNGHelper<T>* instance;
};

typedef G4TemplateRNGHelper<G4long> G4RNGHelper;
typedef G4TemplateRNGHelper<G4String> G4StringRNGHelper;
typedef std::queue<G4long> G4SeedsQueue;

#endif