[英]millisecond-accurate benchmarking in C++?
I do not really wish to profile because I was wanting to do many different small benchmarks on different simple functions. 我真的不想分析,因为我想对不同的简单函数进行许多不同的小型基准测试。 For the life of me I cannot find a way to record the amount of milliseconds in C++, I am using Linux by the way.
在我的一生中,我无法找到一种方法来记录C ++中的毫秒数,因此我正在使用Linux。
Can you suggest the method to get the system clock in milliseconds (I may settle with seconds if I cannot find an easy way..) and what header they are included in? 您能否建议以毫秒为单位获取系统时钟的方法(如果找不到简单的方法,我可能会用几秒钟来解决。)以及它们包含在哪个标头中?
using gettimeofday
function from sys/time.h
header file, i use this class: 使用
sys/time.h
头文件中的gettimeofday
函数,我使用此类:
#include <cstdlib>
#include <sys/time.h>
class Timer
{
timeval timer[2];
public:
timeval start()
{
gettimeofday(&this->timer[0], NULL);
return this->timer[0];
}
timeval stop()
{
gettimeofday(&this->timer[1], NULL);
return this->timer[1];
}
int duration() const
{
int secs(this->timer[1].tv_sec - this->timer[0].tv_sec);
int usecs(this->timer[1].tv_usec - this->timer[0].tv_usec);
if(usecs < 0)
{
--secs;
usecs += 1000000;
}
return static_cast<int>(secs * 1000 + usecs / 1000.0 + 0.5);
}
};
for example: 例如:
#include <iostream>
#include <string>
#include <sstream>
int main()
{
Timer tm;
std::ostringstream ooo;
std::string str;
tm.start();
for(int i = 0; i < 10000000; ++i)
{
ooo << "This is a string. ";
}
tm.stop();
std::cout << "std::ostingstream -> " << tm.duration() << std::endl;
tm.start();
for(int i = 0; i < 10000000; ++i)
{
str += "This is a string. ";
}
tm.stop();
std::cout << "std::string -> " << tm.duration() << std::endl;
}
If you are using x86 CPU, you can use rdtsc assembler instructions http://en.wikipedia.org/wiki/Rdtsc in order to get number of CPU clocks between execution of two (or more) commands. 如果您使用的是x86 CPU,则可以使用rdtsc汇编程序说明http://en.wikipedia.org/wiki/Rdtsc来获取执行两个(或更多)命令之间的CPU时钟数。 But: 1. All rdtsc commands should run on same CPU core (in case if you have multi core CPU).
但是:1.所有rdtsc命令都应在同一CPU内核上运行(如果您有多核CPU)。 2. CPU should run in constant clock frequency (CPU power management should be disabled).
2. CPU应该以恒定的时钟频率运行(应该禁用CPU电源管理)。
Dima 迪玛
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