X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;ds=sidebyside;f=lib%2Flibrte_sched%2Frte_approx.c;h=edc8d9113bb319e9a87ce0b329cfac6dab8a62e0;hb=22a076367369a04391a7b16d60a2905cf5c1da46;hp=771c9518886e7bbe83986fc83a89a18b19bf8116;hpb=3031749c2df04a63cdcef186dcce3781e61436e8;p=dpdk.git diff --git a/lib/librte_sched/rte_approx.c b/lib/librte_sched/rte_approx.c index 771c951888..edc8d9113b 100644 --- a/lib/librte_sched/rte_approx.c +++ b/lib/librte_sched/rte_approx.c @@ -1,34 +1,5 @@ -/*- - * BSD LICENSE - * - * Copyright(c) 2010-2014 Intel Corporation. All rights reserved. - * All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * - * * Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * * Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in - * the documentation and/or other materials provided with the - * distribution. - * * Neither the name of Intel Corporation nor the names of its - * contributors may be used to endorse or promote products derived - * from this software without specific prior written permission. - * - * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS - * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT - * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR - * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT - * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, - * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT - * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, - * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY - * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT - * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE - * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +/* SPDX-License-Identifier: BSD-3-Clause + * Copyright(c) 2010-2014 Intel Corporation */ #include @@ -50,13 +21,13 @@ static inline uint32_t less(uint32_t a, uint32_t b, uint32_t c, uint32_t d) { - return (a*d < b*c); + return a*d < b*c; } static inline uint32_t less_or_equal(uint32_t a, uint32_t b, uint32_t c, uint32_t d) { - return (a*d <= b*c); + return a*d <= b*c; } /* check whether a/b is a valid approximation */ @@ -194,3 +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); +}