/* random.c								*/

#undef TRACE
#undef DEBUG

#undef MAIN
#include <grass/gis.h>
#include "ransurf.h"

#define M1 259200
#define IA1 7141
#define IC1 54773
#define RM1 (1.0/M1)
#define M2 134456
#define IA2 8121
#define IC2 28411
#define RM2 (1.0/M2)
#define M3 243000
#define IA3 4561
#define IC3 51349


/* ran1() returns a double with a value between 0.0 and 1.0		*/
double ran1(void)
{
	static long ix1,ix2,ix3;
	static double r[98];
	double temp;
	static int iff=0;
	int j;
	FUNCTION(ran1);

	if (Seed < 0 || iff == 0) {
		iff = 1;
		ix1 = (IC1 - Seed) % M1;
		ix1 = (IA1 * ix1 + IC1) % M1;
		ix2 = ix1 % M2;
		ix1 = (IA1 * ix1 + IC1) % M1;
		ix3 = ix1 % M3;
		for (j=1; j <= 97; j++) {
			ix1 = (IA1 * ix1 + IC1) % M1;
			ix2 = (IA2 * ix2 + IC2) % M2;
			r[j] = (ix1 + ix2 * RM2) * RM1;
		}
		Seed = 1;
	}

	ix1 = (IA1 * ix1 + IC1) % M1;
	ix2 = (IA2 * ix2 + IC2) % M2;
	ix3 = (IA3 * ix3 + IC3) % M3;
	j = 1 + ((97 * ix3) / M3);
	if (j > 97 || j < 1)
		G_fatal_error("RAN1: j==%d shouldn't happen", j);

	temp = r[j];
	r[j] = (ix1 + ix2 * RM2) * RM1;

	return temp;
}

#undef M1
#undef IA1
#undef IC1
#undef RM1
#undef M2
#undef IA2
#undef IC2
#undef RM2
#undef M3
#undef IA3
#undef IC3