CODEWITHSUNDEEP
c++timer
GregH
GregH

Reputation: 5461

c++ implementing clock to measure execution time

I have written a program in c++ and am trying to measure the time it takes to execute completely

int main (int argc, char**argv){
    clock_t tStart = clock();
    //doing my program's work here
    printf("Time taken: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
    return 0;
}

My issue is that it will always print out 0.00s for the execution time. Could this be due to using multiple pthreads in my program (my program uses pthread_join to make sure that all threads have completed executing so I don't think this should be an issue)?

edit: //doing program's work =...

for(i = 0;i<4;i++){
    err = pthread_create(&threads[i], NULL, print, NULL); 
    pthread_join(threads[i], NULL);
}

void *print(void *data){
    printf("hello world");
}

Upvotes: 0

Views: 334

Answers (2)

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385405

printf("Time taken: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);

All three of your arithmetic operands are integers, so you perform integer division and get 0.

Cast either the LHS or the RHS of the / symbol to a floating-point type. And run your code more times! Your benchmark is useless if it measures just a single run (which is pretty evident since you got 0, not 1 or like 300 or something).

Upvotes: 1

Peter DeWeese
Peter DeWeese

Reputation: 18343

It really depends on what is in //doing my program's work here. If it is kicking off other threads, then you will definitely need to wait or poll to get a time. Show the code to get more help! In a similar situation I was in recently, however, it turned out that my code was actually running in less than 0.01 seconds.

Upvotes: 0

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