c – CPP中速度性能的测试功能

我创建了一个简单的函数来将任何小写字母a-z转换为大写,问题可能不是问题,但每个测试都返回0.如果我添加系统(“暂停”),我可以看到一个新值,表示暂停的长度.

有没有更准确的方法来测试速度,或者这实际上是否正确？我想将它与其他函数进行比较,看它是否比标准函数更快地转换.

char* ToUppercase(char* Input)
{
    int Len = Length(Input);
    for (int i = 0; i < Len; i++)
    {
        short keycode = static_cast<short>(Input[i]);
        if (keycode >= 97 && keycode <= 122)
            Input[i] -= 32;
    }
    return Input;
}

我用来测试的当前计时器是(由其他人创建)

template<typename TimeT = std::chrono::milliseconds>
struct measure
{
    template<typename F, typename ...Args>
    static typename TimeT::rep execution(F func, Args&&... args)
    {
        auto start = std::chrono::system_clock::now();
        func(std::forward<Args>(args)...);
        auto duration = std::chrono::duration_cast< TimeT>
            (std::chrono::system_clock::now() - start);
        return duration.count();
    }
};

打电话我用：

void Debug()
{
    char Buffer[10000] = "aaaa /..../ aaaa";
    MyStringControl::ToUppercase(Buffer);
}
int main()
{
    std::cout << measure<std::chrono::nanoseconds>::execution(Debug);
}

解决方法:

你看过std :: chrono :: high_resolution_clock吗？

这是一个例子：

#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>

template<typename TimeT = std::chrono::milliseconds>
struct measure
{
    template<typename F, typename ...Args>
    static typename TimeT::rep execution(F func, Args&&... args)
    {
        auto start = std::chrono::high_resolution_clock::now();
        func(std::forward<Args>(args)...);
        auto duration = std::chrono::duration_cast< TimeT>
                (std::chrono::high_resolution_clock::now() - start);
        return duration.count();
    }
};

int total = 0;

void test()
{
    int foo = 0;
    for (int i=0; i<1000; ++i) ++foo;
    total += foo;
}

int main ()
{
    using namespace std::chrono;

    for (int i = 0; i < 30; ++i)
    {
        total = 0;
        auto t = measure<std::chrono::nanoseconds>::execution(test);
        std::cout << "Calculated total = " << total << " in " << t << " ns." << std::endl;
    }    
    return 0;
}

这使：

Calculated total = 1000 in 64 ns.
Calculated total = 1000 in 21 ns.
Calculated total = 1000 in 22 ns.
Calculated total = 1000 in 21 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 13 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 13 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 13 ns.
Calculated total = 1000 in 21 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 22 ns.
Calculated total = 1000 in 21 ns.
Calculated total = 1000 in 20 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 14 ns.
Calculated total = 1000 in 20 ns.
Calculated total = 1000 in 20 ns.
Calculated total = 1000 in 21 ns.
Calculated total = 1000 in 20 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 15 ns.
Calculated total = 1000 in 14 ns.

标签：c,c11,performance-testing
来源： https://codeday.me/bug/20190824/1710716.html