68c1f26d42
Modify internal structure and functions to support 64-bit values for rates and stats parameters. Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com> Signed-off-by: Lukasz Krakowiak <lukaszx.krakowiak@intel.com> Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
321 lines
8.1 KiB
C
321 lines
8.1 KiB
C
/* SPDX-License-Identifier: BSD-3-Clause
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* Copyright(c) 2010-2014 Intel Corporation
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*/
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#include <stdlib.h>
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#include "rte_approx.h"
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/*
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* Based on paper "Approximating Rational Numbers by Fractions" by Michal
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* Forisek forisek@dcs.fmph.uniba.sk
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*
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* Given a rational number alpha with 0 < alpha < 1 and a precision d, the goal
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* is to find positive integers p, q such that alpha - d < p/q < alpha + d, and
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* q is minimal.
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*
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* http://people.ksp.sk/~misof/publications/2007approx.pdf
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*/
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/* fraction comparison: compare (a/b) and (c/d) */
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static inline uint32_t
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less(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
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{
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return a*d < b*c;
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}
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static inline uint32_t
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less_or_equal(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
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{
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return a*d <= b*c;
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}
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/* check whether a/b is a valid approximation */
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static inline uint32_t
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matches(uint32_t a, uint32_t b,
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uint32_t alpha_num, uint32_t d_num, uint32_t denum)
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{
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if (less_or_equal(a, b, alpha_num - d_num, denum))
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return 0;
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if (less(a ,b, alpha_num + d_num, denum))
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return 1;
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return 0;
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}
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static inline void
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find_exact_solution_left(uint32_t p_a, uint32_t q_a, uint32_t p_b, uint32_t q_b,
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uint32_t alpha_num, uint32_t d_num, uint32_t denum, uint32_t *p, uint32_t *q)
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{
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uint32_t k_num = denum * p_b - (alpha_num + d_num) * q_b;
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uint32_t k_denum = (alpha_num + d_num) * q_a - denum * p_a;
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uint32_t k = (k_num / k_denum) + 1;
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*p = p_b + k * p_a;
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*q = q_b + k * q_a;
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}
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static inline void
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find_exact_solution_right(uint32_t p_a, uint32_t q_a, uint32_t p_b, uint32_t q_b,
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uint32_t alpha_num, uint32_t d_num, uint32_t denum, uint32_t *p, uint32_t *q)
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{
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uint32_t k_num = - denum * p_b + (alpha_num - d_num) * q_b;
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uint32_t k_denum = - (alpha_num - d_num) * q_a + denum * p_a;
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uint32_t k = (k_num / k_denum) + 1;
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*p = p_b + k * p_a;
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*q = q_b + k * q_a;
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}
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static int
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find_best_rational_approximation(uint32_t alpha_num, uint32_t d_num, uint32_t denum, uint32_t *p, uint32_t *q)
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{
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uint32_t p_a, q_a, p_b, q_b;
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/* check assumptions on the inputs */
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if (!((0 < d_num) && (d_num < alpha_num) && (alpha_num < denum) && (d_num + alpha_num < denum))) {
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return -1;
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}
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/* set initial bounds for the search */
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p_a = 0;
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q_a = 1;
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p_b = 1;
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q_b = 1;
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while (1) {
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uint32_t new_p_a, new_q_a, new_p_b, new_q_b;
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uint32_t x_num, x_denum, x;
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int aa, bb;
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/* compute the number of steps to the left */
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x_num = denum * p_b - alpha_num * q_b;
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x_denum = - denum * p_a + alpha_num * q_a;
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x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
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/* check whether we have a valid approximation */
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aa = matches(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
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bb = matches(p_b + (x-1) * p_a, q_b + (x - 1) * q_a, alpha_num, d_num, denum);
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if (aa || bb) {
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find_exact_solution_left(p_a, q_a, p_b, q_b, alpha_num, d_num, denum, p, q);
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return 0;
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}
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/* update the interval */
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new_p_a = p_b + (x - 1) * p_a ;
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new_q_a = q_b + (x - 1) * q_a;
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new_p_b = p_b + x * p_a ;
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new_q_b = q_b + x * q_a;
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p_a = new_p_a ;
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q_a = new_q_a;
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p_b = new_p_b ;
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q_b = new_q_b;
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/* compute the number of steps to the right */
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x_num = alpha_num * q_b - denum * p_b;
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x_denum = - alpha_num * q_a + denum * p_a;
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x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
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/* check whether we have a valid approximation */
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aa = matches(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
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bb = matches(p_b + (x - 1) * p_a, q_b + (x - 1) * q_a, alpha_num, d_num, denum);
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if (aa || bb) {
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find_exact_solution_right(p_a, q_a, p_b, q_b, alpha_num, d_num, denum, p, q);
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return 0;
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}
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/* update the interval */
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new_p_a = p_b + (x - 1) * p_a;
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new_q_a = q_b + (x - 1) * q_a;
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new_p_b = p_b + x * p_a;
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new_q_b = q_b + x * q_a;
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p_a = new_p_a;
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q_a = new_q_a;
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p_b = new_p_b;
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q_b = new_q_b;
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}
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}
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int rte_approx(double alpha, double d, uint32_t *p, uint32_t *q)
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{
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uint32_t alpha_num, d_num, denum;
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/* Check input arguments */
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if (!((0.0 < d) && (d < alpha) && (alpha < 1.0))) {
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return -1;
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}
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if ((p == NULL) || (q == NULL)) {
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return -2;
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}
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/* Compute alpha_num, d_num and denum */
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denum = 1;
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while (d < 1) {
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alpha *= 10;
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d *= 10;
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denum *= 10;
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}
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alpha_num = (uint32_t) alpha;
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d_num = (uint32_t) d;
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/* Perform approximation */
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return find_best_rational_approximation(alpha_num, d_num, denum, p, q);
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}
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/* fraction comparison (64 bit version): compare (a/b) and (c/d) */
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static inline uint64_t
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less_64(uint64_t a, uint64_t b, uint64_t c, uint64_t d)
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{
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return a*d < b*c;
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}
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static inline uint64_t
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less_or_equal_64(uint64_t a, uint64_t b, uint64_t c, uint64_t d)
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{
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return a*d <= b*c;
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}
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/* check whether a/b is a valid approximation (64 bit version) */
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static inline uint64_t
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matches_64(uint64_t a, uint64_t b,
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uint64_t alpha_num, uint64_t d_num, uint64_t denum)
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{
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if (less_or_equal_64(a, b, alpha_num - d_num, denum))
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return 0;
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if (less_64(a, b, alpha_num + d_num, denum))
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return 1;
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return 0;
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}
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static inline void
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find_exact_solution_left_64(uint64_t p_a, uint64_t q_a, uint64_t p_b, uint64_t q_b,
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uint64_t alpha_num, uint64_t d_num, uint64_t denum, uint64_t *p, uint64_t *q)
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{
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uint64_t k_num = denum * p_b - (alpha_num + d_num) * q_b;
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uint64_t k_denum = (alpha_num + d_num) * q_a - denum * p_a;
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uint64_t k = (k_num / k_denum) + 1;
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*p = p_b + k * p_a;
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*q = q_b + k * q_a;
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}
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static inline void
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find_exact_solution_right_64(uint64_t p_a, uint64_t q_a, uint64_t p_b, uint64_t q_b,
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uint64_t alpha_num, uint64_t d_num, uint64_t denum, uint64_t *p, uint64_t *q)
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{
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uint64_t k_num = -denum * p_b + (alpha_num - d_num) * q_b;
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uint64_t k_denum = -(alpha_num - d_num) * q_a + denum * p_a;
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uint64_t k = (k_num / k_denum) + 1;
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*p = p_b + k * p_a;
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*q = q_b + k * q_a;
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}
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static int
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find_best_rational_approximation_64(uint64_t alpha_num, uint64_t d_num,
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uint64_t denum, uint64_t *p, uint64_t *q)
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{
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uint64_t p_a, q_a, p_b, q_b;
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/* check assumptions on the inputs */
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if (!((d_num > 0) && (d_num < alpha_num) &&
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(alpha_num < denum) && (d_num + alpha_num < denum))) {
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return -1;
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}
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/* set initial bounds for the search */
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p_a = 0;
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q_a = 1;
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p_b = 1;
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q_b = 1;
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while (1) {
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uint64_t new_p_a, new_q_a, new_p_b, new_q_b;
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uint64_t x_num, x_denum, x;
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int aa, bb;
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/* compute the number of steps to the left */
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x_num = denum * p_b - alpha_num * q_b;
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x_denum = -denum * p_a + alpha_num * q_a;
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x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
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/* check whether we have a valid approximation */
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aa = matches_64(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
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bb = matches_64(p_b + (x-1) * p_a, q_b + (x - 1) * q_a,
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alpha_num, d_num, denum);
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if (aa || bb) {
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find_exact_solution_left_64(p_a, q_a, p_b, q_b,
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alpha_num, d_num, denum, p, q);
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return 0;
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}
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/* update the interval */
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new_p_a = p_b + (x - 1) * p_a;
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new_q_a = q_b + (x - 1) * q_a;
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new_p_b = p_b + x * p_a;
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new_q_b = q_b + x * q_a;
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p_a = new_p_a;
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q_a = new_q_a;
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p_b = new_p_b;
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q_b = new_q_b;
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/* compute the number of steps to the right */
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x_num = alpha_num * q_b - denum * p_b;
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x_denum = -alpha_num * q_a + denum * p_a;
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x = (x_num + x_denum - 1) / x_denum; /* x = ceil(x_num / x_denum) */
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/* check whether we have a valid approximation */
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aa = matches_64(p_b + x * p_a, q_b + x * q_a, alpha_num, d_num, denum);
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bb = matches_64(p_b + (x - 1) * p_a, q_b + (x - 1) * q_a,
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alpha_num, d_num, denum);
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if (aa || bb) {
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find_exact_solution_right_64(p_a, q_a, p_b, q_b,
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alpha_num, d_num, denum, p, q);
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return 0;
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}
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/* update the interval */
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new_p_a = p_b + (x - 1) * p_a;
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new_q_a = q_b + (x - 1) * q_a;
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new_p_b = p_b + x * p_a;
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new_q_b = q_b + x * q_a;
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p_a = new_p_a;
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q_a = new_q_a;
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p_b = new_p_b;
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q_b = new_q_b;
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}
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}
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int rte_approx_64(double alpha, double d, uint64_t *p, uint64_t *q)
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{
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uint64_t alpha_num, d_num, denum;
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/* Check input arguments */
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if (!((0.0 < d) && (d < alpha) && (alpha < 1.0)))
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return -1;
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if ((p == NULL) || (q == NULL))
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return -2;
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/* Compute alpha_num, d_num and denum */
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denum = 1;
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while (d < 1) {
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alpha *= 10;
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d *= 10;
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denum *= 10;
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}
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alpha_num = (uint64_t) alpha;
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d_num = (uint64_t) d;
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/* Perform approximation */
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return find_best_rational_approximation_64(alpha_num, d_num, denum, p, q);
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}
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