// -*- C++ -*-
//
// -----------------------------------------------------------------------
//                             HEP Random
//                         --- RanecuEngine ---
//                          class header file
// -----------------------------------------------------------------------
// This file is part of Geant4 (simulation toolkit for HEP).
//
// RANECU Random Engine - algorithm originally written in FORTRAN77
//                        as part of the MATHLIB HEP library.
// The initialisation is carried out using a Multiplicative Congruential
// generator using formula constants of L'Ecuyer as described in "F.James,
// Comp. Phys. Comm. 60 (1990) 329-344".
// Seeds are taken from a seed table given an index, the getSeed() method
// returns the current index in the seed table, the getSeeds() method
// returns a pointer to the couple of seeds stored in the local table of
// seeds at the current index.

// =======================================================================
// Gabriele Cosmo - Created: 2nd February 1996
//                - Minor corrections: 31st October 1996
//                - Added methods for engine status: 19th November 1996
//                - setSeed() now has default dummy argument
//                  set to zero: 11th July 1997
//                - Added default index to setSeeds(): 16th Oct 1997
// J.Marraffino   - Added stream operators and related constructor.
//                  Added automatic seed selection from seed table and
//                  engine counter: 16th Feb 1998
// Ken Smith      - Added conversion operators:  6th Aug 1998
// Mark Fischler    Methods for distrib. instance save/restore 12/8/04    
// Mark Fischler    methods for anonymous save/restore 12/27/04    
// =======================================================================

#ifndef RanecuEngine_h
#define RanecuEngine_h 1

#include "CLHEP/Random/RandomEngine.h"

namespace CLHEP {

/**
 * @author <Gabriele.Cosmo@cern.ch>
 * @ingroup random
 */
class RanecuEngine : public HepRandomEngine {

public:

  RanecuEngine(std::istream& is);
  RanecuEngine();
  RanecuEngine(int index);
  virtual ~RanecuEngine();
  // Constructors and destructor.

  double flat();
  // Returns a pseudo random number between 0 and 1 
  // (excluding the end points)

  void flatArray (const int size, double* vect);
  // Fills an array "vect" of specified size with flat random values.

  void setIndex (long index);
  // Sets the state of the algorithm according to "index", the position
  // in the local table of seeds.
 
  void setSeed (long index, int dum=0);
  // Resets the state of the algorithm according to "index", the position
  // in the static table of seeds stored in HepRandom.

  void setSeeds (const long* seeds, int index=-1);
  // Sets the state of the algorithm according to the array of seeds
  // "seeds" containing two seed values to be stored in the local table at
  // "index" position.

  void saveStatus( const char filename[] = "Ranecu.conf" ) const;
  // Saves on file Ranecu.conf the current engine status.

  void restoreStatus( const char filename[] = "Ranecu.conf" );
  // Reads from file Ranecu.conf the last saved engine status
  // and restores it.

  void showStatus() const;
  // Dumps the engine status on the screen.

  operator double();
  // Returns same as flat()
  operator float();
  // less precise flat, faster if possible
  operator unsigned int();
  // 32-bit int flat, faster in this case

  virtual std::ostream & put (std::ostream & os) const;
  virtual std::istream & get (std::istream & is);
  static  std::string beginTag ( );
  virtual std::istream & getState ( std::istream & is );

  std::string name() const;
  static std::string engineName() {return "RanecuEngine";}

  std::vector<unsigned long> put () const;
  bool get (const std::vector<unsigned long> & v);
  bool getState (const std::vector<unsigned long> & v);
  
protected:

  // Suggested L'ecuyer coefficients for portable 32 bits generators.
  
  static const int ecuyer_a = 40014;
  static const int ecuyer_b = 53668;
  static const int ecuyer_c = 12211;
  static const int ecuyer_d = 40692;
  static const int ecuyer_e = 52774;
  static const int ecuyer_f = 3791;
  static const int shift1   = 2147483563;
  static const int shift2   = 2147483399;

  static const unsigned int VECTOR_STATE_SIZE = 4;
  
private:

  // private method used to mitigate the effects of using a lookup table
  void further_randomize (int seq, int col, int index, int modulus);

  // Members defining the current state of the generator.

  static const int maxSeq = 215;
  long table[215][2];
  int seq;

};

}  // namespace CLHEP

#endif
