CODEWITHSUNDEEP
cperformance
Neri-kun
Neri-kun

Reputation: 193

What is the best/most efficient way to measure time when running a program in C?

How can i record the running time of my program every time I insert an input?I tried this particular method:

clock_t tStart = clock(),tEnd;

And after printing the ouput:

tEnd = clock();
printf("Time taken: %.6fs\n", (double)(tEnd - tStart) / CLOCKS_PER_SEC);

However,I sometimes end up having just a bunch of 0s when calculating the miliseconds.Is there any method to improve this?

Upvotes: 0

Views: 297

Answers (3)

jspcal
jspcal

Reputation: 51934

Perhaps try a higher resolution timer which may be available on your platform:

Linux: clock_gettime(CLOCK_REALTIME, &timeSpec)
Windows: QueryPerformanceCounter(&performanceCount)

Upvotes: 3

wildplasser
wildplasser

Reputation: 44250

In unix,usetime , which forks&execs the program, and does a get_rusage() after the child exited.

So, you don't have to instrument the program itself.

plasser@pisbak:$ time ./a.out omg.dat 

real    0m10.276s
user    0m9.986s
sys 0m0.291s
plasser@pisbak:$

Upvotes: 1

Caleb
Caleb

Reputation: 125037

Is there any method to improve this?

If you don't have a better timer, as suggested in jspcal's answer, then another solution is to repeat the same operation a large number of times and then divide the elapsed time by the number of repetitions:

const int REPS = 10000;
clock_t tStart = clock(),tEnd;
for (int i = 0; i < REPS; i++) {
    // do your work here
}
tEnd = clock();
double time = (double)(tEnd - tStart)/REPS;
printf("Time taken: %.6fs\n", time / CLOCKS_PER_SEC);

Upvotes: 3

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