使用 boost::timer 计算间隔时间

一般用来统计某操作的耗时。

#include <boost/timer.hpp>

int main() {

    // 初始化 timer
    boost::timer t;

    // 某个耗时的操作
    cost_time_operations();

    // 计算
    double elapsed = t.elapsed();
    std::cout << "cost " << elapsed << " seconds";
}

看了一下 boost.timer 的源码， 挺简单的，就是前后俩时间差。

//  A timer object measures elapsed time.

//  It is recommended that implementations measure wall clock rather than CPU
//  time since the intended use is performance measurement on systems where
//  total elapsed time is more important than just process or CPU time.

//  Warnings: The maximum measurable elapsed time may well be only 596.5+ hours
//  due to implementation limitations.  The accuracy of timings depends on the
//  accuracy of timing information provided by the underlying platform, and
//  this varies a great deal from platform to platform.

class timer
{
 public:
         timer() { _start_time = std::clock(); } // postcondition: elapsed()==0
//         timer( const timer& src );      // post: elapsed()==src.elapsed()
//        ~timer(){}
//  timer& operator=( const timer& src );  // post: elapsed()==src.elapsed()
  void   restart() { _start_time = std::clock(); } // post: elapsed()==0
  double elapsed() const                  // return elapsed time in seconds
    { return  double(std::clock() - _start_time) / CLOCKS_PER_SEC; }

  double elapsed_max() const   // return estimated maximum value for elapsed()
  // Portability warning: elapsed_max() may return too high a value on systems
  // where std::clock_t overflows or resets at surprising values.
  {
    return (double((std::numeric_limits<std::clock_t>::max)())
       - double(_start_time)) / double(CLOCKS_PER_SEC); 
  }

  double elapsed_min() const            // return minimum value for elapsed()
   { return double(1)/double(CLOCKS_PER_SEC); }

 private:
  std::clock_t _start_time;
}; // timer

参考

boost.timer