[M.A.D.M.A.N.]

Генератор случайных чисел по алгоритму Парка-Миллера.
По заверениям дает белый шум.

Код:

#include <stdio.h>

/* Minimal portable random generator by Park and Miller */

/* Lewis-Goodman-Miller constants */
#define IA 16807
#define IM 2147483647
#define AM (1./IM)
/* Scharge constants */
#define IQ 12773
#define IR 2836
#define NTAB 32
#define NWUP 8
#define NDIV (1+(IM-1)/NTAB)
#define EPS 1.2e-7
#define RNMX (1.0-EPS)
/* Special mask to be explained below */
#define MASK 123456789

static long dummy;

/* initial seed, for all the generators here */
void Seed(long dum) {
	dummy = dum;
}

/* returns random uniformly distributed between 0 and 1 */
float unirand0(void) {
	long k;
	float ans;
	
	dummy ^= MASK;	/* avoid dummy==0 */
	k = dummy / IQ;
	
	if ((dummy=IA*(dummy-k*IQ)-IR*k)<0)
		dummy += IM;
		
	ans = AM * dummy;
	
	dummy ^= MASK;	/* restore unmasked dummy */
	
	return(ans);
}

float unirand1(void) {
	int j;
	long k;
	static long iy=0,iv[NTAB];
	float temp;
	
	/* initialize */
	if (dummy <= 0 || !iy) {
		/* avoid negative or zero seed */
		if (dummy < 0) dummy =- dummy; else 
		if (dummy == 0) dummy = 1;
		
		/* after NWUP warmups, initialize shuffle table */
		for(j = NTAB + NWUP - 1; j >= 0; j--) {
			k = dummy / IQ;
			
			if ((dummy = IA * (dummy - k * IQ) - IR * k) < 0)
				dummy += IM;
				
			if (j < NTAB)
				iv[j] = dummy;
		}
		
		/* first specimen from the table */
		iy=iv[0];
	}
	
	/* regular work: generate new number */
	k = dummy / IQ;
	if ((dummy = IA * (dummy - k * IQ) - IR * k) < 0)
		dummy += IM;
		
	/* shuffle output */
	iy = iv[j = iy / NDIV];
	iv[j] = dummy;
	
	/* return */
	if ((temp = AM * iy) > RNMX)
		return(RNMX);
	else
		return(temp);
}

void main(){
	int i;
	Seed(6723);
	for (i = 0; i < 100; i++)
		printf("%f\n", unirand1());
}

>>bcc32 parkmiller.c

З.Ы. Код не совсем нормализован, некоторые места можно сократить.