X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;f=lib%2Flibrte_sched%2Frte_approx.c;h=edc8d9113bb319e9a87ce0b329cfac6dab8a62e0;hb=309bf90bf99e1e3b41e2abfdfd0f15f8299034b8;hp=30620b83d0da2eb6e0edb78f0c6f2b49d59eb39a;hpb=369991d997e4abdee355e19ffbb41a4d246cafa2;p=dpdk.git

diff --git a/lib/librte_sched/rte_approx.c b/lib/librte_sched/rte_approx.c
index 30620b83d0..edc8d9113b 100644
--- a/lib/librte_sched/rte_approx.c
+++ b/lib/librte_sched/rte_approx.c
@@ -165,3 +165,156 @@ int rte_approx(double alpha, double d, uint32_t *p, uint32_t *q)
 	/* Perform approximation */
 	return find_best_rational_approximation(alpha_num, d_num, denum, p, q);
 }
+
+/* fraction comparison (64 bit version): compare (a/b) and (c/d) */
+static inline uint64_t
+less_64(uint64_t a, uint64_t b, uint64_t c, uint64_t d)
+{
+	return a*d < b*c;
+}
+
+static inline uint64_t
+less_or_equal_64(uint64_t a, uint64_t b, uint64_t c, uint64_t d)
+{
+	return a*d <= b*c;
+}
+
+/* check whether a/b is a valid approximation (64 bit version) */
+static inline uint64_t
+matches_64(uint64_t a, uint64_t b,
+	uint64_t alpha_num, uint64_t d_num, uint64_t denum)
+{
+	if (less_or_equal_64(a, b, alpha_num - d_num, denum))
+		return 0;
+
+	if (less_64(a, b, alpha_num + d_num, denum))
+		return 1;
+
+	return 0;
+}
+
+static inline void
+find_exact_solution_left_64(uint64_t p_a, uint64_t q_a, uint64_t p_b, uint64_t q_b,
+	uint64_t alpha_num, uint64_t d_num, uint64_t denum, uint64_t *p, uint64_t *q)
+{
+	uint64_t k_num = denum * p_b - (alpha_num + d_num) * q_b;
+	uint64_t k_denum = (alpha_num + d_num) * q_a - denum * p_a;
+	uint64_t k = (k_num / k_denum) + 1;
+
+	*p = p_b + k * p_a;
+	*q = q_b + k * q_a;
+}
+
+static inline void
+find_exact_solution_right_64(uint64_t p_a, uint64_t q_a, uint64_t p_b, uint64_t q_b,
+	uint64_t alpha_num, uint64_t d_num, uint64_t denum, uint64_t *p, uint64_t *q)
+{
+	uint64_t k_num = -denum * p_b + (alpha_num - d_num) * q_b;
+	uint64_t k_denum = -(alpha_num - d_num) * q_a + denum * p_a;
+	uint64_t k = (k_num / k_denum) + 1;
+
+	*p = p_b + k * p_a;
+	*q = q_b + k * q_a;
+}
+
+static int
+find_best_rational_approximation_64(uint64_t alpha_num, uint64_t d_num,
+	uint64_t denum, uint64_t *p, uint64_t *q)
+{
+	uint64_t p_a, q_a, p_b, q_b;
+
+	/* check assumptions on the inputs */
+	if (!((d_num > 0) && (d_num < alpha_num) &&
+		(alpha_num < denum) && (d_num + alpha_num < denum))) {
+		return -1;
+	}
+
+	/* set initial bounds for the search */
+	p_a = 0;
+	q_a = 1;
+	p_b = 1;
+	q_b = 1;
+
+	while (1) {
+		uint64_t new_p_a, new_q_a, new_p_b, new_q_b;
+		uint64_t x_num, x_denum, x;
+		int aa, bb;
+
+		/* compute the number of steps to the left */
+		x_num = denum * p_b - alpha_num * q_b;
+		x_denum = -denum * p_a + alpha_num * q_a;
+		x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
+
+		/* check whether we have a valid approximation */
+		aa = matches_64(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
+		bb = matches_64(p_b + (x-1) * p_a, q_b + (x - 1) * q_a,
+			alpha_num, d_num, denum);
+		if (aa || bb) {
+			find_exact_solution_left_64(p_a, q_a, p_b, q_b,
+				alpha_num, d_num, denum, p, q);
+			return 0;
+		}
+
+		/* update the interval */
+		new_p_a = p_b + (x - 1) * p_a;
+		new_q_a = q_b + (x - 1) * q_a;
+		new_p_b = p_b + x * p_a;
+		new_q_b = q_b + x * q_a;
+
+		p_a = new_p_a;
+		q_a = new_q_a;
+		p_b = new_p_b;
+		q_b = new_q_b;
+
+		/* compute the number of steps to the right */
+		x_num = alpha_num * q_b - denum * p_b;
+		x_denum = -alpha_num * q_a + denum * p_a;
+		x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
+
+		/* check whether we have a valid approximation */
+		aa = matches_64(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
+		bb = matches_64(p_b + (x - 1) * p_a, q_b + (x - 1) * q_a,
+			alpha_num, d_num, denum);
+		if (aa || bb) {
+			find_exact_solution_right_64(p_a, q_a, p_b, q_b,
+				alpha_num, d_num, denum, p, q);
+			return 0;
+		}
+
+		/* update the interval */
+		new_p_a = p_b + (x - 1) * p_a;
+		new_q_a = q_b + (x - 1) * q_a;
+		new_p_b = p_b + x * p_a;
+		new_q_b = q_b + x * q_a;
+
+		p_a = new_p_a;
+		q_a = new_q_a;
+		p_b = new_p_b;
+		q_b = new_q_b;
+	}
+}
+
+int rte_approx_64(double alpha, double d, uint64_t *p, uint64_t *q)
+{
+	uint64_t alpha_num, d_num, denum;
+
+	/* Check input arguments */
+	if (!((0.0 < d) && (d < alpha) && (alpha < 1.0)))
+		return -1;
+
+	if ((p == NULL) || (q == NULL))
+		return -2;
+
+	/* Compute alpha_num, d_num and denum */
+	denum = 1;
+	while (d < 1) {
+		alpha *= 10;
+		d *= 10;
+		denum *= 10;
+	}
+	alpha_num = (uint64_t) alpha;
+	d_num = (uint64_t) d;
+
+	/* Perform approximation */
+	return find_best_rational_approximation_64(alpha_num, d_num, denum, p, q);
+}