//timer.h#ifndef W_TIMER_H#define W_TIMER_H #include 
     
      #include 
      
       #include 
       
         class Timer {public:     Timer():_name("Time elapsed:") {        restart();    }     explicit Timer(const std::string &name):_name(name + ":") {        restart();    }     /**    * 启动计时    */    inline void restart() {        _start_time = std::chrono::steady_clock::now();    }     /**    * 结束计时    * @return 返回ms数    */    inline double elapsed(bool restart = false) {        _end_time = std::chrono::steady_clock::now();        std::chrono::duration
        
          diff = _end_time-_start_time;        if(restart)            this->restart();        return diff.count()*1000;    }     /**     * 打印时间并重启计时器     * @param tip 提示     */    void rlog(const std::string &tip){        log(true,tip,true,false);    }     /**    * 打印时间    * @param reset 输出之后是否重启计时器，true重启，false不重启    * @param unit_ms true是ms，false是s    * @param tip 输出提示    * @param kill 输出之后是否退出程序，true退出，false不退出    */    void log(bool reset = false, const std::string &tip = "",             bool unit_ms = true, bool kill = false    ) {        if (unit_ms) {            if (tip.length() > 0)                std::cout << tip+":" << elapsed() << "ms" << std::endl;            else                std::cout << _name << elapsed() << "ms" << std::endl;        } else {            if (tip.length() > 0)                std::cout << tip+":" << elapsed() / 1000.0 << "s" << std::endl;            else                std::cout << _name << elapsed() / 1000.0 << "s" << std::endl;        }         if (reset)            this->restart();         if (kill)            exit(5);    }  private:    std::chrono::steady_clock::time_point _start_time;    std::chrono::steady_clock::time_point _end_time;    std::string _name;}; // timer #endif //W_TIMER_H///chrono::steady_clock::time_point t1 = chrono::steady_clock::now();【某个耗时程序段】chrono::steady_clock::time_point t2 = chrono::steady_clock::now();chrono::duration
         
           time_used = chrono::duration_cast
          
           
            >(t2 - t1);cout << "time_used：" << time_used.count() << " 秒。" << endl;//