Syntax
#include <time.h> double difftime(time_t time2, time_t time1);Description
The difftime function returns the elapsed time in seconds from time1 to time2 as a double precision number. Type time_t is defined in <time.h>.
This example shows a timing application using difftime. The example calculates how long, on average, it takes to find the prime numbers from 2 to 10000.
#include <time.h>
#include <stdio.h>
#define RUNS 1000
#define SIZE 10000
int mark[SIZE];
int main(void)
{
time_t start,finish;
int i,loop,n,num;
time(&start);
/* This loop finds the prime numbers between 2 and SIZE */
for (loop = 0; loop < RUNS; ++loop) {
for (n = 0; n < SIZE; ++n)
mark[n] = 0;
/* This loops marks all the composite numbers with -1 */
for (num = 0, n = 2; n < SIZE; ++n)
if (!mark[n]) {
for (i = 2*n; i < SIZE; i += n)
mark[i] = -1;
++num;
}
}
time(&finish);
printf("Program takes an average of %f seconds to find %d primes.\n",
difftime(finish, start)/RUNS, num);
return 0;
/****************************************************************************
The output should be similar to :
Program takes an average of 0.106000 seconds to find 1229 primes.
****************************************************************************/
}
Related Information