Question

我正在使用boost 1.59.0。

我正在尝试使用boost :: chrono :: process_cpu_clock来计算我的代码块。我想以毫秒为单位报告此时间，而不是纳秒。我想使用duration_cast模板函数，虽然我只找到了将一个持续时间值作为参数的示例，而不是process_cpu_clock.now（）返回的三个值的元组。

以下是我写的代码：

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

int main(){
    //Changecase to Uppercase
    string var = "This is a String.";
    for (unsigned int i = 0; i < var.length(); i++){
        if (islower(var[i]))
            var[i] = toupper(var[i]);
    }
    cout << var << endl;
    /*
    Output:
    THIS IS A STRING.
    */
    //Changecase to Lowercase
    var = "This is a String.";
    for (unsigned int i = 0; i < var.length(); i++){
        if (isupper(var[i]))
            var[i] = tolower(var[i]);
    }
    cout << var << endl;
    /*
    Output:
    this is a string.
    */
    //Flip the case
    var = "This is a String.";
    for (unsigned int i = 0; i < var.length(); i++){
        if (isupper(var[i]))
            var[i] = tolower(var[i]);
        else
            var[i] = toupper(var[i]);
    }
    cout << var << endl;
    /*
    Output:
    tHIS IS A sTRING.
    */

    system("pause");
    return 0;
}

chrono::process_cpu_clock mytimer; const auto start = mytimer.now(); // do work const auto duration = mytimer.now() - start; const auto duration_msec = duration_cast<milliseconds>(duration);与duration_msec完全相同;它没有转换为毫秒。

也许duration_cast不打算将process_cpu_clock :: duration类型作为参数;但是，它编译好了。

我做错了什么？

如何将boost :: chrono :: process_cpu_clock :: duration转换为毫秒

0 个答案: