c++ - 获取 CPU 滴答和测量时间

Question

所以我想测量 C++ 中某些函数的时间，并且我尝试了很多方法。这是我的最终代码:

auto start = chrono::steady_clock::now();
clStart = clock();

for (int o=0; o<100;o++)
{
    sin(o);
   // Sleep(1);
}

auto end = chrono::steady_clock::now();
clEnd = clock();

auto difTime = end-start;
diff = chrono::duration <double,milli> (difTime).count(); //gives me 0
diffTicks = clEnd-clStart; //0 as well

当我在里面插入例如 Sleep() 函数时它工作正常但是当使用 math.h 中的 sin 时我总是得到 0 时间。这是为什么？我知道它可能已优化但 0？我想将它与其他 sin 实现进行比较，但我不确定这里有什么问题。

Answer 1

计算100罪的时间很短，应该用

auto start = chrono::steady_clock::now();
clStart = clock();

for (int o=0; o<100000;o++)
{
    sin(o);
   // Sleep(1);
}

auto end = chrono::steady_clock::now();
clEnd = clock();

auto difTime = end-start;
diff = chrono::duration <double,milli> (difTime).count();
diffTicks = clEnd-clStart;

相反。

此外，您的代码以毫秒为单位。我建议你使用 chrono::duration <double, nano> (diff).count()它使用纳秒来提高精度。

---

来自文档:

The only data stored in a duration is a tick count of type Rep. If Rep is floating point, then the duration can represent fractions of ticks. Period is included as part of the duration's type, and is only used when converting between different durations.

这意味着这不是您正在测量的 CPU 节拍数