Question

How to measure time in milliseconds using C

Answer 1

#include <stdio.h>
#include <time.h>
 
int main() {
    long long startTime = (long long)time(NULL) * 1000;
     
    for (int i = 0; i < 400000000; i++);
     
    long long estimatedTime = ((long long)time(NULL) * 1000) - startTime;
     
    printf("%lld milliseconds\n", estimatedTime);
     
    return 0;
}
 
 
/*
run:
 
1000 milliseconds
 
*/

 

 

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Answer 2

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

int main() {
    clock_t start, stop;
    int i;

    start = clock();
    
    for (int i = 0; i < 400000000; i++);
    
    stop = clock();

    double elapsed_time = (double)(stop - start) / CLOCKS_PER_SEC;
    
    printf("Elapsed time: %.3f milliseconds\n", elapsed_time * 1000);

    return 0;
}


/*
run:

Elapsed time: 835.985 milliseconds

*/

 

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