I was running some timings in my code to see which of several functions was the best and I've been getting some odd results. Here's the code I'm using:

static double time_loop(int (*foo)(int)) {
	clock_t start, end;
	int n = 0, i = 0;
	start = clock();
	for (; i <= MAXN; i++)
		if ((*foo)(i)) n++;
	end = clock();
	if (n != 50847534)
		return -1;	// Error
	return ((double) (end - start)) / CLOCKS_PER_SEC;
}

static double median3(int (*foo)(int)) {
	double t1 = time_loop(foo);
	double t2 = time_loop(foo);
	double t3 = time_loop(foo);
	printf("  ((%f %f %f))\n", t1, t2, t3);
	int errors = 0;
	if (t1 < 0)
		errors++;
	if (t2 < 0)
		errors++;
	if (t3 < 0)
		errors++;
	if (errors > 0)
		return -errors;
	if (t1 > t2) {
		if (t2 > t3)
			return t2;
		return t3 < t1 ? t3 : t1;
	} else {
		if (t1 > t3)
			return t1;
		return t3 < t2 ? t3 : t2;
	}
}

  ((4.560000 3.750000 6.540000))
Original: 4.560000 s
  ((4.920000 3.760000 6.690000))
Original: 4.920000 s
  ((4.190000 3.750000 6.620000))
Original: 4.190000 s
  ((3.820000 3.130000 5.640000))
New:      3.820000 s
  ((3.580000 3.150000 5.580000))
New:      3.580000 s
	  ((3.670000 3.140000 5.510000))
New:      3.670000 s