// $Id: DualRand.h,v 1.12 2002/05/07 16:47:34 mf Exp $
// -*- C++ -*-
//
// -----------------------------------------------------------------------
//                           Hep Random
//                        --- DualRand ---
//                        class header file
// -----------------------------------------------------------------------
//									
//  Canopy random number generator DualRand
//	Re-written as C++ routine for 32-bit ints MF 1/26/98
//
//  Exclusive or of a feedback shift register and integer congruence
//  random number generator.  The feedback shift register uses offsets
//  127 and 97.  The integer congruence generator uses a different
//  multiplier for each stream.  The multipliers are chosen to give
//  full period and maximum "potency" for modulo 2^32.  The period of
//  the combined random number generator is 2^159 - 2^32, and the
//  sequences are different for each stream (not just started in a
//  different place).
//
// =======================================================================
//  Canopy random number generator DualRand.
//      Doug Toussaint   5/25/88
//      Optimized by GMH 7/26/88
//      Optimized by GMH 7/26/88
//      Repaired  by GMH 12/1/88 to update modular congruence state
//      Put into ranlib by GMH 6/23/89
//      Re-written as C++ routine for 32-bit ints MF 1/26/98
//      Re-written for CLHEP package             KLS 6/04/98
//      Removed pow() from flat method for speed KLS 7/21/98
// Ken Smith      - Added conversion operators:  6th Aug 1998
// =======================================================================


#ifndef DualRand_h
#define DualRand_h

#include "CLHEP/Random/RandomEngine.h"

/**
 * @author
 * @ingroup random
 */
class DualRand: public HepRandomEngine {

public:

  DualRand();
  DualRand(long seed);
  DualRand(HepStd::istream & is);
  DualRand(int rowIndex, int colIndex);
  virtual ~DualRand();

  DualRand(const DualRand & p);
  DualRand & operator=(const DualRand & p);

  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 setSeed(long seed, int);
  // Sets the state of the algorithm according to seed.

  void setSeeds(const long * seeds, int);
  // Sets the state of the algorithm according to the zero-terminated 
  // array of seeds.

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

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

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

  operator float();      // flat value, without worrying about filling bits
  operator unsigned int();  // 32-bit flat value, quickest of all

  friend HepStd::ostream & operator<< (HepStd::ostream & os, const DualRand & e);
  friend HepStd::istream & operator>> (HepStd::istream & is,       DualRand & e);

private:

  static int numEngines;

  static double twoToMinus_32;
  static double twoToMinus_53;
  static double nearlyTwoToMinus_54;
  void powersOfTwo();

  // This generator is composed of two others combined:

  class Tausworthe {
  public:
    Tausworthe();
    Tausworthe(unsigned int seed);
    operator unsigned int();
    void put(HepStd::ostream & os) const;
    void get(HepStd::istream & is);
  private:
    int wordIndex;
    unsigned int words[4];
  }; // Tausworthe

  class IntegerCong {
  public:
    IntegerCong();
    IntegerCong(unsigned int seed, int streamNumber);
    operator unsigned int();
    void put(HepStd::ostream & os) const;
    void get(HepStd::istream & is);
  private:
    unsigned int state, multiplier, addend;
  }; // IntegerCong

  Tausworthe  tausworthe;
  IntegerCong integerCong;

}; // DualRand

#endif // DualRand_h