Question

If I measure the running time of a method, shouldn’t it be same if I give the same input data?
I used the Stopwatch:

Stopwatch sw = new Stopwatch();
sw.Start();
//code here
sw.Stop();
label3.Text = "Running Time:"+sw.Elapsed.TotalMilliseconds;

Answer 1

It’s hard to tell without the code.

You could see differences due to several reasons – this is by no means a complete list:

1. Computer is busy – your computer is doing something else which means it gives your code less resources (CPU time).
2. I/O – you do some sort of I/O that can take a little while or a long time.
3. Jitting – the first time you run a method, the JIT compiler compiles it, and it takes time. The second time it takes a lot less.
4. Cache hits and misses – if you measure the same code twice, the second time may be faster because the data used by the code is already in the cache.