OpenTTD Source: src/core/math_func.cpp Source File

OpenTTD Source 14.1

math_func.cpp
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1 /*
2 * This file is part of OpenTTD.
3 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
4 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
5 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
6 */
7
10 #include "../stdafx.h"
11 #include "math_func.hpp"
12
13 #include "../safeguards.h"
14
22 int DivideApprox(int a, int b)
23 {
24 int random_like = ((a + b) * (a - b)) % b;
25
26 int remainder = a % b;
27
28 int ret = a / b;
29 if (abs(random_like) < abs(remainder)) {
30 ret += ((a < 0) ^ (b < 0)) ? -1 : 1;
31 }
32
33 return ret;
34 }
35
42 uint32_t IntSqrt(uint32_t num)
43 {
44 uint32_t res = 0;
45 uint32_t bit = 1UL << 30; // Second to top bit number.
46
47 /* 'bit' starts at the highest power of four <= the argument. */
48 while (bit > num) bit >>= 2;
49
50 while (bit != 0) {
51 if (num >= res + bit) {
52 num -= res + bit;
53 res = (res >> 1) + bit;
54 } else {
55 res >>= 1;
56 }
57 bit >>= 2;
58 }
59
60 /* Arithmetic rounding to nearest integer. */
61 if (num > res) res++;
62
63 return res;
64 }
IntSqrt
uint32_t IntSqrt(uint32_t num)
Compute the integer square root.
Definition: math_func.cpp:42
math_func.hpp
DivideApprox
int DivideApprox(int a, int b)
Deterministic approximate division.
Definition: math_func.cpp:22
abs
constexpr T abs(const T a)
Returns the absolute value of (scalar) variable.
Definition: math_func.hpp:23