ARCHIVED: On Libra, how do I time different parts of my program?
Note: UITS will retire Libra in
spring 2009. Accounts are available on Quarry, a general-purpose Unix
computing environment. For more, see ARCHIVED: About the Libra retirement.
If you need a high resolution timer on the Libra Cluster at
Indiana University, use read_real_time(). For more
information, refer to the man page. Following is sample
code adapted from the man page:
#include <stdio.h>
#include <sys/time.h>
int main()
{
int i;
timebasestruct_t start, finish;
int val = 3;
int secs, n_secs;
/* get the time before the operation begins */
read_real_time(&start, TIMEBASE_SZ);
/* begin code to be timed */
for (i=0; i<15; i++)
(void) 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 */
secs = finish.tb_high - start.tb_high;
n_secs = 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 (n_secs < 0) {
secs--;
n_secs += 1000000000;
}
(void) printf("Sample time was %d seconds %d nanoseconds\n",
secs, n_secs);
exit(0);
}
This is document aqpy in domain all.
Last modified on June 30, 2009.
