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88 lines
2.6 KiB
C
88 lines
2.6 KiB
C
/**
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* @file utils/math.c
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* @author Martin Pulec <martin.pulec@cesnet.cz>
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*/
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/*
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* Copyright (c) 2022-2023 CESNET, z. s. p. o.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, is permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of CESNET nor the names of its contributors may be
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* used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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* EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <limits.h>
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#include "math.h"
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long long gcd(long long a, long long b)
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{
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// Everything divides 0
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if (a == 0) {
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return b;
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}
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if (b == 0) {
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return a;
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}
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// base case
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if (a == b) {
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return a;
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}
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// a is greater
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if (a > b) {
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return gcd(a-b, b);
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}
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return gcd(a, b-a);
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}
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long long lcm(long long a, long long b) {
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return a * b / gcd(a, b);
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}
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bool
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is_power_of_two(unsigned long long x)
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{
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return x != 0 && (x & (x - 1)) == 0;
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}
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/**
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* @returns nearest power of two greater or equal than given number x
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* @retval 0 on overflow (next power of two is ULLONG_MAX + 1)
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*/
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unsigned long long
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next_power_of_two(unsigned long long x)
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{
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if (x <= 1) {
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return 1;
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}
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const int pos = __builtin_clzll(x - 1);
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return pos > 0 ? 1ULL << (sizeof(unsigned long long) * CHAR_BIT - pos)
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: 0;
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}
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