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RNG.h

Go to the documentation of this file.

//===========================================================================
//===========================================================================

#ifndef __RNG_H
#define __RNG_H

#include <cstdlib>
#include <sys/types.h>
#include <ctime>

//===========================================================================
class RNG
{
public:

    virtual ~RNG()
    {};

    //========================================================================
    RNG(long s = 1)
    {
        seed(s);
    }


    //========================================================================
    void       seed(long s = time(NULL))
    {
        //if( s == 0 ) s = time( NULL );
        initialSx = sx = (s         & 0xff) + 1;
        initialSy = sy = ((s >>  8) & 0xff) + 10000;
        initialSz = sz = ((s >> 16) & 0xffff) + 3000;
    }


    //========================================================================
    void       reset()
    {
        sx = initialSx;
        sy = initialSy;
        sz = initialSz;
    }


    //========================================================================
    long       genLong()
    {
        const long MaxRand = 0x7fffffffL;

        return (long)(genDouble() *((double)MaxRand + 1));
    }


    //========================================================================
    double     genDouble()
    {
        double rn;

        // the three congruential generators
        sx = (unsigned)(sx * 171UL % 30269UL);
        sy = (unsigned)(sy * 172UL % 30307UL);
        sz = (unsigned)(sz * 170UL % 30323UL);

        rn = sx / 30269. + sy / 30307. + sz / 30323.;

        return rn - (unsigned)rn;
    }


    //========================================================================
    void       getStatus(unsigned &x, unsigned &y, unsigned &z) const
    {
        x = sx;
        y = sy;
        z = sz;
    }


    //========================================================================
    void       setStatus(const unsigned x, const unsigned y, const unsigned z)
    {
        // initial state is not restored
        sx = x;
        sy = y;
        sz = z;
    }

    //========================================================================
    virtual double operator()()
    {
        return genDouble();
    }


    static RNG globalRng;


private:

    // Seed value for internal generator no. 1.
    unsigned initialSx;

    // Seed value for internal generator no. 2.
    unsigned initialSy;

    // Seed value for internal generator no. 3.
    unsigned initialSz;

    // Current value of ni,1 (see description of class).
    unsigned sx,

    // Current value of ni,2 (see description of class).
    sy,

    // Current value of ni,3 (see description of class).
    sz;
};

#endif  /* !__RNG_H */