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

OpenTTD Source 12.0-beta1

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
24 int LeastCommonMultiple(int a, int b)
25 {
26 if (a == 0 || b == 0) return 0; // By definition.
27 if (a == 1 || a == b) return b;
28 if (b == 1) return a;
29
30 return a * b / GreatestCommonDivisor(a, b);
31 }
32
39 int GreatestCommonDivisor(int a, int b)
40 {
41 while (b != 0) {
42 int t = b;
43 b = a % b;
44 a = t;
45 }
46 return a;
47
48 }
49
57 int DivideApprox(int a, int b)
58 {
59 int random_like = ((a + b) * (a - b)) % b;
60
61 int remainder = a % b;
62
63 int ret = a / b;
64 if (abs(random_like) < abs(remainder)) {
65 ret += ((a < 0) ^ (b < 0)) ? -1 : 1;
66 }
67
68 return ret;
69 }
70
77 uint32 IntSqrt(uint32 num)
78 {
79 uint32 res = 0;
80 uint32 bit = 1UL << 30; // Second to top bit number.
81
82 /* 'bit' starts at the highest power of four <= the argument. */
83 while (bit > num) bit >>= 2;
84
85 while (bit != 0) {
86 if (num >= res + bit) {
87 num -= res + bit;
88 res = (res >> 1) + bit;
89 } else {
90 res >>= 1;
91 }
92 bit >>= 2;
93 }
94
95 /* Arithmetic rounding to nearest integer. */
96 if (num > res) res++;
97
98 return res;
99 }
DivideApprox
int DivideApprox(int a, int b)
Deterministic approximate division.
Definition: math_func.cpp:57
math_func.hpp
IntSqrt
uint32 IntSqrt(uint32 num)
Compute the integer square root.
Definition: math_func.cpp:77
GreatestCommonDivisor
int GreatestCommonDivisor(int a, int b)
Compute greatest common divisor (gcd) of a and b.
Definition: math_func.cpp:39
abs
static T abs(const T a)
Returns the absolute value of (scalar) variable.
Definition: math_func.hpp:21
LeastCommonMultiple
int LeastCommonMultiple(int a, int b)
Compute least common multiple (lcm) of arguments a and b, the smallest integer value that is a multip...
Definition: math_func.cpp:24