Random.cpp

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#include "../Util/Random.h"

// -------------------------------------------------------------------------- ;

// \fdd{This function is an initialization entry point which should
//              be invoked before util\_random() is called although an
//              initializer value (FOR WIN32: derived from time()-function) is
//              supplied automatically.
//              With the same negative seed value a sequence of generated 
//              random values can be reproduced at any time.}

void util_seedRandom(long seedValA)
{
#if defined(_WIN32)
        fut_initRanG = seedValA;
#else
        srand48(seedValA);
#endif
};

// -------------------------------------------------------------------------- ;

// \fdd{This function returns non-negative
//              double-precision floating-point values uniformly distributed
//              over the interval $[0.0, 1.0)$ .}

double util_random()
{
#if defined(_WIN32)

        #define IA 16807
        #define IM 2147483647
        #define AM (1.0/IM)
        #define IQ 127773
        #define IR 2836
        #define NTAB 32
        #define NDIV (1+(IM-1)/NTAB)
        #define EPS 1.2e-7
        #define RNMX (1.0-EPS)

        int j;
        long k;
        static long iy=0;
        static long iv[NTAB];
        double temp;

        if (fut_initRanG <= 0 || !iy) {
                if (-(fut_initRanG) < 1) fut_initRanG=1;
                else fut_initRanG = -(fut_initRanG);
                for (j=NTAB+7;j>=0;j--) {
                        k=(fut_initRanG)/IQ;
                        fut_initRanG=IA*(fut_initRanG-k*IQ)-IR*k;
                        if (fut_initRanG < 0) fut_initRanG += IM;
                        if (j < NTAB) iv[j] = fut_initRanG;
                }
                iy=iv[0];
        }
        k=(fut_initRanG)/IQ;
        fut_initRanG=IA*(fut_initRanG-k*IQ)-IR*k;
        if (fut_initRanG < 0) fut_initRanG += IM;
        j=iy/NDIV;
        iy=iv[j];
        iv[j] = fut_initRanG;
        if ((temp=AM*iy) > RNMX) return RNMX;
        else return temp;
        #undef IA
        #undef IM
        #undef AM
        #undef IQ
        #undef IR
        #undef NTAB
        #undef NDIV
        #undef EPS
        #undef RNMX

#else
        return drand48();
#endif
};

// -------------------------------------------------------------------------- ;

// \fdd{This function returns
//              double-precision floating-point values gaussian distributed
//              with mean $0.0$ and variance $1.0$.  See \emph{Numerical Recipies} , 
//       page 289 for further references. }
double util_gaussRandom()
{
        static int isetL = 0;
        static double gsetL;
        double facL, rsqL, v1L, v2L;

        if( isetL == 0 )
        {
                do
                {
                        v1L = 2.0 * util_random() - 1.0;
                        v2L = 2.0 * util_random() - 1.0;
                        rsqL = v1L * v1L + v2L * v2L;
                }
                while( rsqL >= 1.0 || rsqL == 0.0 );
                facL = sqrt( -2.0 * log( rsqL ) / rsqL );
                gsetL = v1L * facL;
                isetL = 1;
                return v2L * facL;
        }
        else
        {
                isetL = 0;
                return gsetL;
        }
}

// -------------------------------------------------------------------------- ;