CRT random number generator cycle peroid test

cycle-detect.c

#include <stdlib.h>
#include <stdio.h>

/**
 * Return the cycle period
 */
int brent_cycle_detect(int seed) {
	int power = 1;
	int lambda = 1;
	int tortoise = seed;
	int hare;

	srand(seed);
	hare = rand();
	while (hare != tortoise) {
		if (power == lambda) {
			tortoise = hare;
			power *= 2;
			lambda = 0;
		}
		hare = rand();
		lambda++;
	}

	return lambda;
}

void run_test(int repeat) {
	int i;
	int seed;
	int period = 42;

	printf("seed,period\n");
	for (i = 0; i < repeat; i++) {
		srand(period);
		seed = rand();
		period = brent_cycle_detect(seed);
		printf("%d,%d\n", seed, period);
	}
}

int main(int argc, char** argv) {
	if (argc != 2) {
		printf("usage: %s repear-count\n", argv[0]);
		exit(-1);
	} else {
		int repeat = atoi(argv[1]);
		run_test(repeat);
	}

	return 0;

}

cycle-detect_s.c

#define _CRT_RAND_S
#include <stdlib.h>
#include <stdio.h>

/**
 * Return the cycle period
 */
int brent_cycle_detect(unsigned int seed) {
	int power = 1;
	int lambda = 1;
	unsigned int tortoise;
	unsigned int hare;

	rand_s(&tortoise);
	rand_s(&hare);
	while (hare != tortoise) {
		if (power == lambda) {
			tortoise = hare;
			power *= 2;
			lambda = 0;
		}
		rand_s(&hare);
		lambda++;
	}

	return lambda;
}

void run_test(int repeat) {
	int i;
	int seed;
	int period = 42;

	printf("seed,period\n");
	for (i = 0; i < repeat; i++) {
		srand(period);
		seed = rand();
		period = brent_cycle_detect(seed);
		printf("%d,%d\n", seed, period);
	}
}

int main(int argc, char** argv) {
	if (argc != 2) {
		printf("usage: %s repear-count\n", argv[0]);
		exit(-1);
	} else {
		int repeat = atoi(argv[1]);
		run_test(repeat);
	}

	return 0;

}