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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 "G4Types.hh"
#include <vector>
#include <queue>
#include "globals.hh"

template <class T>
class G4TemplateRNGHelper {
private:
    static G4TemplateRNGHelper* instance;
public:
    // The container is modeled as a (shared) singleton
    static G4TemplateRNGHelper* GetInstance() {
        if (!instance)
        {
          instance = new G4TemplateRNGHelper();
        }
        return instance;
    }
    typedef std::vector<T> SeedsQueue;
    typedef typename SeedsQueue::size_type SeedsQueueSize_type;
        
private:
    G4TemplateRNGHelper()
    {
          offset=0;
          nev_filled=0;
          nev_total=0;
    }

public:
    virtual ~G4TemplateRNGHelper() {
        Clear();
        instance = 0;
    }
    
    //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","Run0035", 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(double* dbl,int nev,int nev_tot,int nrpe)
    {
      seeds.clear();
      for(int i=0;i<nrpe*nev;i++)
      { seeds.push_back((long)(100000000L*dbl[i])); }
      offset = 0;
      nev_filled = nev;
      nev_total = nev_tot;
      nRandParEvent = nrpe;
    }

    void Refill(double* dbl, int nev)
    {
      if(nev==0) return;
      seeds.clear();
      for(int i=0;i<nRandParEvent*nev;i++)
      { seeds.push_back((long)(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
    int offset;
    int nev_filled;
    int nev_total;
    int nRandParEvent;
};

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

#endif