#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)

float ran1(long *idum)
{
	int j;
	long k;
	static long iy=0;
	static long iv[NTAB];
	float temp;

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

/*****************************************************************************

    Function: rannorm()

    Description: Generates a normal random variate with mean 0 and var 1
    Parameters:  long * idnum (the seed)
    Return:      float

*****************************************************************************/

float rannorm(long * idnum)
{
 int n;
 float value;

 value = -6;
 for (n=0;n<12 ;n++ )
    {
      value += ran1(idnum);
    }

 return value;
}