内置mod('％')与自定义mod功能:提高模数运算的性能 [英] Built-in mod ('%') vs custom mod function: improve the performance of modulus operation

问题描述

最近我知道mod('％')运算符非常慢.所以我做了一个可以像％b一样工作的函数.但是它比mod运算符更快吗?

Recently I came to know that the mod('%') operator is very slow. So I made a function which will work just like a%b. But is it faster than the mod operator?

这是我的职能

int mod(int a, int b)
{
    int tmp = a/b;
    return a - (b*tmp);
}

推荐答案

根据钱德勒·卡鲁斯(Chandler Carruth)在CppCon 2015上的基准测试，最快的模运算符(在x86上，用Clang编译时)是:

According to Chandler Carruth's benchmarks at CppCon 2015, the fastest modulo operator (on x86, when compiled with Clang) is:

int fast_mod(const int input, const int ceil) {
    // apply the modulo operator only when needed
    // (i.e. when the input is greater than the ceiling)
    return input >= ceil ? input % ceil : input;
    // NB: the assumption here is that the numbers are positive
}

我建议您观看整个谈话，他将详细介绍为什么此方法比无条件使用%更快.

I suggest that you watch the whole talk, he goes into more details on why this method is faster than just using % unconditionally.

这篇关于内置mod('％')与自定义mod功能:提高模数运算的性能的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！