CODEWITHSUNDEEP
cmacostimeclock
Crosility
Crosility

Reputation: 111

Bad Results: time(NULL) and clock()

#import <stdio.h>
#import <time.h>

int main (void) {

    printf("Clock ticks per second: %d\n", CLOCKS_PER_SEC);
    double check = clock();
    int timex = time(NULL);

    for (int x = 0; x <= 500000; x++) {

        printf(".");

    }
    puts("\n");

    printf("Total Time by Clock: %7.7f\n", (clock() - check) / CLOCKS_PER_SEC );
    printf("Total Time by Time: %d\n", time(NULL) - timex);

    getchar();
}

When I execute the above code I get results like:

Total Time by Clock: 0.0108240

Total Time by Time: 12

I would like to have clock() represent a number as close to as possible as time.

The total time presented above was done on a macbook, however, the code works excellent on my laptop (windows).

The CLOCKS_PER_SECOND macro returns 1000 on the PC, 1,000,000 on the MAC.

Upvotes: 5

Views: 978

Answers (3)

blaze
blaze

Reputation: 4364

printf() to console makes system call for each functon call, and time spent blocked in console redrawing, etc. do not count for process time.

Make some heavy calculations there.

for (long int x = 0; x <= 5000000000; x++) {
    sqrt(2.9999);
}

Upvotes: 1

pmg
pmg

Reputation: 108986

time() returns a time_t. When you assign that to an int it is possible that you lose information. What happens if you use time_t throughout?

int main(void) {
    time_t timex = time(0);
    /* ... */
    printf("%d", (int)(time(0) - timex));
}

Upvotes: 0

nos
nos

Reputation: 229342

clock() on windows returns the wall clock time. clock() on *nixes return the CPU time your program has spent, which is not going to be a lot, you're likely blocked when doing I/O here.

Upvotes: 8

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