dmmlib/examples/lran2.h

/* lran2.h
 * by Wolfram Gloger 1996.
 *
 * A small, portable pseudo-random number generator.
 */

#ifndef _LRAN2_H
#define _LRAN2_H

#define LRAN2_MAX 714025l /* constants for portable */
#define IA	  1366l	  /* random number generator */
#define IC	  150889l /* (see e.g. `Numerical Recipes') */

struct lran2_st {
	long x, y, v[97];
};

	static void
lran2_init(struct lran2_st* d, long seed)
{
	long x;
	int j;

	x = (IC - seed) % LRAN2_MAX;
	if(x < 0) x = -x;
	for(j=0; j<97; j++) {
		x = (IA*x + IC) % LRAN2_MAX;
		d->v[j] = x;
	}
	d->x = (IA*x + IC) % LRAN2_MAX;
	d->y = d->x;
}

	static 
long lran2(struct lran2_st* d)
{
	long j = (d->y % 97);

	d->y = d->v[j];
	d->x = (IA*d->x + IC) % LRAN2_MAX;
	d->v[j] = d->x;
	return d->y;
}

#undef IA
#undef IC

#endif /* _LRAN2_H */