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From: gunther@jhunix.HCF.JHU.EDU (Gunther Wil Anderson)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Re: Random Number Generation in Turbo C 2.0
Summary: The Science of Fractal Images
Keywords: Normal/Gaussian Dist.
Message-ID: <4491@jhunix.HCF.JHU.EDU>
Date: 14 Mar 90 19:06:34 GMT
References: <21720@netnews.upenn.edu>
Reply-To: eisen@jhunix.UUCP (Gunther Wil Anderson)
Distribution: usa
Organization: The Johns Hopkins University - HCF
Lines: 40

The code is straightforwardly presented in _The Science of Fractal
Images_ by Heinz-Otto Peitgen and (someone else, I forgot whom).  I
haveincluded it here, but that book is quite worthwhile for not only
fractals of all types in theory and practise, but also general random
number algorithms.

#define MAXLEVEL 200

int 		Arand, Nrand;
double 		GaussAdd, GaussFac;
double		delta[MAXLEVEL];

void InitGauss(seed)
int seed;
{
	Nrand = 4;
	Arand = INT_MAX;
	GaussAdd = sqrt(3.0*(double)Nrand);
	GaussFac = 2*GaussAdd/((double)Nrand*(double)Arand);
	srand((unsigned)seed);
}

double Gauss()
{
	double sum;
	int i;
	
	sum = 0.0;
	for(i = 1; i <= Nrand; i++)
		sum += (double)rand();
	return(GaussFac*sum - GaussAdd);
}

And viola, Gaussian random variables.

Hope this helps,

Gunther Anderson
gunther@jhunix.hcf.jhu.edu
gunther@jhuvms.hcf.jhu.edu
gunther@crabcake.cs.jhu.edu