How accurate is System.Diagnostics.Stopwatch?

Question

How accurate is System.Diagnostics.Stopwatch? I am trying to do some metrics for different code paths and I need it to be exact. Should I be using stopwatc

Answer 1

Why you don't profile your code instead of focusing on micro-benchmarks?

There are some good Open Source profilers like:

• NProf
• Prof-It for C#
• NProfiler
• ProfileSharp

Answer 2

First, exact is of course not a possible or meaningful concept when talking about time or space, since no empyrical measurement of a physical magnitude can ever pretend to be exact.

Second, David Bolton's blog article may be useful. I'm quoting:

If this was timed with the high resolution counter then it will be accurate to microseconds. It is actually accurate to nanoseconds (10-9 seconds, ie a billionth of a second) but there is so much other stuff going on that nanosecond accuracy is really a bit pointless. When doing timing or benchmarking of code, you should do a number of runs and take the average time- because of other processes running under Windows, how much swapping to disk is occurring etc, the values between two runs may vary.