Linux下使用clock_gettime给程序计时

   哦，clock_gettime( ) 提供了纳秒的精确度，给程序计时可是不错哦；

 

函数的原型如下：

  
    

   
     int
   
      clock_gettime(clockid_t clk_id, 
   
     struct
   
      timespect 
   
     *
   
     tp);
  
    

clockid_t clk_id用于指定计时时钟的类型，对于我们Programmr以下三种比较常用：

CLOCK_REALTIME, a system-wide realtime clock.

CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.

CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.

CLOCK_REALTIME, a system-wide realtime clock.

CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.

CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.

struct timespect *tp用来存储当前的时间，其结构如下：

     
       

      
        
      
        1 
      
        struct
      
         timespec {

      
        2 
      
         time_t tv_sec; 
      
        /*
      
         seconds 
      
        */
      
        

      
        3 
      
         
      
        long
      
         tv_nsec; 
      
        /*
      
         nanoseconds 
      
        */
      
        

      
        4 
      
        };
     
       

呵呵，好啦！该讲的都刚清楚了，下面我们就上代码把；

代码

      
        

       
         
       
          1 
       
         #include 
       
         <
       
         iostream
       
         >
       
         

       
          2 
       
         #include 
       
         <
       
         time.h
       
         >
       
         

       
          3 
       
          
       
         using
       
          
       
         namespace
       
          std;

       
          4 
       
          

       
          5 
       
         timespec diff(timespec start, timespec end);

       
          6 
       
          

       
          7 
       
          
       
         int
       
          main()

       
          8 
       
         {

       
          9 
       
          timespec time1, time2;

       
         10 
       
          
       
         int
       
          temp;

       
         11 
       
          clock_gettime(CLOCK_PROCESS_CPUTIME_ID, 
       
         &
       
         time1);

       
         12 
       
          
       
         for
       
          (
       
         int
       
          i 
       
         =
       
          
       
         0
       
         ; i
       
         <
       
          
       
         242000000
       
         ; i
       
         ++
       
         )

       
         13 
       
          temp
       
         +=
       
         temp;

       
         14 
       
          clock_gettime(CLOCK_PROCESS_CPUTIME_ID, 
       
         &
       
         time2);

       
         15 
       
          cout
       
         <<
       
         diff(time1,time2).tv_sec
       
         <<
       
         "
       
         :
       
         "
       
         <<
       
         diff(time1,time2).tv_nsec
       
         <<
       
         endl;

       
         16 
       
          
       
         return
       
          
       
         0
       
         ;

       
         17 
       
         }

       
         18 
       
          

       
         19 
       
         timespec diff(timespec start, timespec end)

       
         20 
       
         {

       
         21 
       
          timespec temp;

       
         22 
       
          
       
         if
       
          ((end.tv_nsec
       
         -
       
         start.tv_nsec)
       
         <
       
         0
       
         ) {

       
         23 
       
          temp.tv_sec 
       
         =
       
          end.tv_sec
       
         -
       
         start.tv_sec
       
         -
       
         1
       
         ;

       
         24 
       
          temp.tv_nsec 
       
         =
       
          
       
         1000000000
       
         +
       
         end.tv_nsec
       
         -
       
         start.tv_nsec;

       
         25 
       
          } 
       
         else
       
          {

       
         26 
       
          temp.tv_sec 
       
         =
       
          end.tv_sec
       
         -
       
         start.tv_sec;

       
         27 
       
          temp.tv_nsec 
       
         =
       
          end.tv_nsec
       
         -
       
         start.tv_nsec;

       
         28 
       
          }

       
         29 
       
          
       
         return
       
          temp;

       
         30 
       
         }