プロセッサー・タイマーのアクセス

#include <stdio.h>
#include <sys/time.h>

int main(void) {
   timebasestruct_t start, finish;
   int val = 3;
   int w1, w2;
   double time;

   /* get the time before the operation begins */
   read_real_time(&start, TIMEBASE_SZ);

   /* begin code to be timed */
   printf("This is a sample line %d \n", val);
   /* end code to be timed   */

   /* get the time after the operation is complete
   read_real_time(&finish, TIMEBASE_SZ);

   /* call the conversion routines unconditionally, to ensure    */
   /* that both values are in seconds and nanoseconds regardless */
   /* of the hardware platform.                                  */
   time_base_to_time(&start, TIMEBASE_SZ);
   time_base_to_time(&finish, TIMEBASE_SZ);

   /* subtract the starting time from the ending time */
   w1 = finish.tb_high - start.tb_high; /* probably zero */
   w2 = finish.tb_low - start.tb_low;

   /* if there was a carry from low-order to high-order during  */
   /* the measurement, we may have to undo it.                  */
   if (w2 < 0) {
      w1--;
      w2 += 1000000000;
   }

   /* convert the net elapsed time to floating point microseconds */
   time = ((double) w2)/1000.0;
   if (w1 > 0)
      time += ((double) w1)*1000000.0;

   printf("Time was %9.3f microseconds \n", time);
   exit(0);
}