The C `clock()` function just returns a zero

Question

The C clock() function just returns me a zero. I tried using different types, with no improvement... Is this a good way to measure time with good precision?

Answer 1

Calling sleep() isn't going to use up any CPU time. You should see a little difference, though. I corrected your printf type mismatch bug in this line:

printf("start = %.20f\nend   = %.20f\n", start, end);

And it gave reasonable results on my machine:

start = 1419
end   = 1485
delta = 66
cpu_time_used  = 0.000066000000000
CLOCKS_PER_SEC = 1000000

You might try gettimeofday() to get the real time spent running your program.