#include "genlib.h"
#include <math.h>
#include <time.h>

#define NTAB 32

double gasdev(long* idum, long* idum2, long* iy, long iv[NTAB], int cores) {
    /*returns a normally distributed deviate with 0 mean*/
    /*and unit variance, using ran2(idum) as the source */
    /*of uniform deviates                               */
    double ran2(long* idum, long* idum2, long* iy, long iv[NTAB], int cores);
    static int iset = 0;
    static double gset;
    double fac, rsq, v1, v2;

    if (iset == 0) {
        do {
            v1 = 2.0 * ran2(idum, idum2, iy, iv, cores) - 1.0;
            v2 = 2.0 * ran2(idum, idum2, iy, iv, cores) - 1.0;
            rsq = v1 * v1 + v2 * v2;
        } while (rsq >= 1.0 || rsq == 0.0);

        fac = sqrt(-2.0 * log(rsq) / rsq);
        gset = v1 * fac;
        iset = 1;

        return (v2 * fac);
    } else {
        iset = 0;
        return gset;
    }
}