RandomGenerator.h

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//
// This file is part of the SHUFFLE program 
// written by Edward H. Trager and
// Copyright (c) 2005 by the
// Regents of the University of Michigan.
// All Rights Reserved.
// 
// The latest version of this program is available from:
// 
//   http://eyegene.ophthy.med.umich.edu/shuffle/
//   
// Released under the GNU General Public License.
// A copy of the GPL is included in the distribution
// package of this software, or see:
// 
//   http://www.gnu.org/copyleft/
//   
// ... for licensing details.
// 

//
// Class RandomGenerator
// 
// The random number generator presented here is based on
// the "ran2" routine presented on page 282 of Press, Flannery, Teukolsky
// and Vetterling's "Numerical Recipes in C" (c) 1992 by Cambridge
// University Press (ISBN 0-521-43108-5).
//
// The routine implements the long-period (>2x10^18) random number generator
// of L'Ecuyer with Bays-Durham shuffle and added safeguards.  Returns a 
// random uniform deviate between 0.0 and 1.0 (exclusive of the endpoint values).
// RNMX should approximate the largest floating value that is less than 1.
//
// I have added the feature of gathering entropy from either
// /dev/random or /dev/urandom in order to get a starting seed.
//
#include <fstream>
#include <iostream>

#define defined_EPS 3.0e-16
#define defined_RNMX (1.0 - defined_EPS )

#ifndef RANDOM_GENERATOR_INCLUDED

class RandomGenerator {
        
public:
        
        //
        // Used for entropy seed: 
        // TRUE_RANDOM grabs from /dev/random
        // PSEUDO_RANDOM grabs from /dev/urandom
        //
        enum ENTROPY_TYPE { TRUE_RANDOM, PSEUDO_RANDOM, UNSPECIFIED_RANDOM };
        
private:
        
        ENTROPY_TYPE _seedSource;
        
        const static int    IM1  = 2147483563;
        const static int    IM2  = 2147483399;
        const static int    IMM1 = IM1-1;
        const static int    IA1  = 40014;
        const static int    IA2  = 40692;
        const static int    IQ1  = 53668;
        const static int    IQ2  = 52774;
        const static int    IR1  = 12211;
        const static int    IR2  = 3791;
        const static int    NTAB = 32;
        const static int    NDIV = 1+IMM1/NTAB;
        
        //const static double EPS = defined_EPS;
        //const static double RNMX = defined_RNMX;
        //const static double AM   = 1.0/IM1;
        const static double EPS;
        const static double RNMX;
        const static double AM;
        
        int _idum;
        int _idum2;
        int iy;
        int iv[NTAB];
        int j;
        int k;
        double temp;
        
        //
        // Private method to gather entropy:
        //
        void _gatherEntropy();
        
        //
        // Private method to initialize the random number generator:
        //
        void _initialize(void);
        
public:
        
        //
        // Constructor:
        //
        // 2006.08.10.ET: Use "PSEUDO_RANDOM" by default:
        //               
        RandomGenerator( ENTROPY_TYPE seedSource = PSEUDO_RANDOM );
        
        //
        // setEntropySource() is used in the case that the constructor
        // for the object had seedSource=UNSPECIFIED_RANDOM:
        //
        void setEntropySource(ENTROPY_TYPE seedSource);
        
        //
        // reset(): Resets the random generator with a new seed 
        //
        void reset( void );
        
        //
        // getDeviate()
        //
        // Returns a number greater than or equal to 0.0
        // and less than 1.0 (*not* less than or equal):
        // 
        double getDeviate( void );
        
        //
        // getIntegerInRange
        //
        // Returns an integer in the range from low *inclusive*
        // to high *inclusive*:
        //
        int getIntegerInRange( int low, int high);
        
};

#define RANDOM_GENERATOR_INCLUDED
#endif

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