Benchmark time units

If we want to get the result in a more readable format, we can specify a time unit. In our case, it would be better to use NANOSECONDS. To do so, we can rewrite our method as follows:

@Benchmark
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public void testMethod() {
    int a = 3;
    int b = 4;
    int c = a + b;
}

The output will now be:

 # Run progress: 0.00% complete, ETA 00:00:10
 # Fork: 1 of 1
 # Warmup Iteration 1: 0.345 ns/op
 # Warmup Iteration 2: 0.342 ns/op
 # Warmup Iteration 3: 0.342 ns/op
 # Warmup Iteration 4: 0.337 ns/op
 # Warmup Iteration 5: 0.342 ns/op
 Iteration 1: 0.336 ns/op
 Iteration 2: 0.333 ns/op
 Iteration 3: 0.342 ns/op
 Iteration 4: 0.340 ns/op
 Iteration 5: 0.340 ns/op
 
 Result "org.sample.MyBenchmark.testMethod":
 0.338 ±(99.9%) 0.015 ns/op [Average]
 (min, avg, max) = (0.333, 0.338, 0.342), stdev = 0.004
 CI (99.9%): [0.323, 0.353] (assumes normal distribution)
 # Run complete. Total time: 00:00:10
 
 Benchmark              Mode Cnt Score Error Units
 MyBenchmark.testMethod avgt 5   0.338 ± 0.015 ns/op

A 0.338 ns/op result is much easier to interpret than 10^-9 s/op. You can specify any TimeUnit:

• NANOSECONDS
• MICROSECONDS
• MILLISECONDS
• SECONDS
• MINUTES
• HOURS
• DAYS

Let's suppose that our variables, a and b, require some time for initialization or are members of some global state. How can we share them between several benchmark methods? How can we initialize them before a scope of a benchmark method? For this, we can use a benchmark state.