CTimeSpan总是为零 [英] CTimeSpan always gets zero

问题描述

我想获得插入排序算法的运行时间。 MSDN说使用CTime可以得到经过时间。但我尝试了很多次，总是为零。我认为运行这个算法的时间是不可能的。必须有一些错误或别的东西。有人帮助我吗？我发布我的代码如下：

I am trying to get the running time of Insertion Sort Algorithm. MSDN said that using CTime could get the Elapsed Time. But I tried many times and always got zero. I thought it is impossible that the time of running this algorithm is zero. There must be some error or something else. Could anybody help me? I posted my code below:

#include <cstdlib>
#include <iostream>
#include <atltime.h> 
using namespace std;
//member function
void insertion_sort(int arr[], int length);
int *create_array(int arrSize);

int main() {
    //Create random array
    int arraySize=100;
    int *randomArray=new int[arraySize];
    int s;
    for (s=0;s<arraySize;s++){
        randomArray[s]=(rand()%99)+1;
    }

    CTime startTime = CTime::GetCurrentTime();

    int iter;
    for (iter=0;iter<1000;iter++){
        insertion_sort(randomArray,arraySize);
    }

    CTime endTime = CTime::GetCurrentTime();
    CTimeSpan elapsedTime = endTime - startTime;
    double nTMSeconds = elapsedTime.GetTotalSeconds()*1000;
    cout<<nTMSeconds;
    return 0;
}//end of main

推荐答案

并不意味着时间的分辨率小于一秒。我想你真正的后是像 GetTickCount 或 GetTickCount64 。请参阅此MSDN 链接 。

CTime isn't meant to time things to a resolution less than one second. I think what you are really after is something like GetTickCount or GetTickCount64 . See this MSDN link .

GetTickCount函数

GetTickCount function

检索自系统以来经过的毫秒数

Retrieves the number of milliseconds that have elapsed since the system was started, up to 49.7 days.

如果使用 GetTickCount64 ，您可以声明 startTime 和 endTime 这样：

If using GetTickCount64 you could declare startTime and endTime this way:

uint64_t endTime, startTime, diffTime;

然后使用 GetTickCount64 毫秒的类似

startTime = GetTickCount64();
... do stuff ...
endTime = GetTickCount64();

diffTime = endTime - startTime;

当然也可以使用diffTime。

And of course diffTime can be used however you want.

如果你不需要时间超过一个月，你可以使用 GetTickCount ，返回的类型将是 uint32_t 而不是 uint64_t

If you don't need to time things for more than a month then you can simply use GetTickCount and the type returned will be a uint32_t instead of uint64_t

如果您需要超过1毫秒的分辨率您的计算机支持高分辨率定时器，则此代码可能工作：

If you need resolution beyond 1 millisecond for timing and your computer supports a high resolution timer then this code may work:

LARGE_INTEGER freq;
double time_sec = 0.0;

if (QueryPerformanceFrequency(&freq))
{
    LARGE_INTEGER start;
    LARGE_INTEGER stop;

    QueryPerformanceCounter(&start);

    // Do Stuff to time Here

    QueryPerformanceCounter(&stop);
    time_sec = (uint64_t)(stop.QuadPart - start.QuadPart) / (double)freq.QuadPart;
}
else {
    cout << "Your computer doesn't have a high resolution timer to use";
} 

有关高性能计时器的信息可以在这个MSDN中找到条目

Information on the high performance timer can be found in this MSDN entry

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