/* timing.c by R. Teather for COSC 2P91 
 * Simple exmaple of getting timing figure (in milliseconds) using
 * system time library. Note that C's timing features are notoriously
 * unreliable, and timing is not guarunteed. The gettimeofday function
 * provides time (somewhat unreliably) to nanosecond precision, unlike
 * the C standard time functions which are even less reliable.
 */

#include <sys/time.h>	/*need POSIX-compliant time library*/
#include <stdio.h>

int main(void)
{
	int i;
	long usTimeDiff = 0, sTimeDiff = 0;
	double msTimeDiff = 0;
	struct timeval t1, t2;

	gettimeofday(&t1, NULL);

	/* waste some time */

	for(i = 0; i < 1000000000; i ++)
		;

	gettimeofday(&t2, NULL);

	/* gettimeofday provides a structure with a separate
	 * second and usec counter - need to get both
	 * differences, then convert and sum them, and finally
	 * convert the total time diff to ms
	 */
	sTimeDiff = t2.tv_sec - t1.tv_sec;
	usTimeDiff = t2.tv_usec - t1.tv_usec;	

	msTimeDiff = ((sTimeDiff * 1000000) + usTimeDiff)/1000.0f;

	printf("Time diff (ms): %f \n\n", msTimeDiff);

	return 0;
}