JMH throughput vs average results

Question

Throughput mode gives me 21 ops/ms. So, I'd thought on average one op takes 1/21 ms. Average mode however gives me the score of 0.937 ms/op. How to interpret the results?

Throughput mode:

Result "testMethod":
  21.752 ±(99.9%) 0.081 ops/ms [Average]
  (min, avg, max) = (20.681, 21.752, 22.529), stdev = 0.344
  CI (99.9%): [21.671, 21.834] (assumes normal distribution)


# Run complete. Total time: 00:06:47

Benchmark                Mode  Cnt   Score   Error   Units
MyBenchmark.testMethod  thrpt  200  21.752 ± 0.081  ops/ms

Average mode:

Result "testMethod":
  0.937 ±(99.9%) 0.004 ms/op [Average]
  (min, avg, max) = (0.890, 0.937, 0.979), stdev = 0.019
  CI (99.9%): [0.932, 0.941] (assumes normal distribution)


# Run complete. Total time: 00:06:47

Benchmark               Mode  Cnt  Score   Error  Units
MyBenchmark.testMethod  avgt  200  0.937 ± 0.004  ms/op

Gussy

Ok, that's because I've used -t MAX (20 threads). Removing threading option makes results consistent. Still, multithreaded version is not clear to me – Gussy

I'm not sure why this is surprising. 20 threads working at the same time on an operation that takes 0.937 ms/op on a single thread, or 1.07 ops/ms/thread, makes 20 * 1.07 ops/ms total, which is roughly 21. – Brag

Agree. I was confused that throughput is given for all threads but avg per thread. Would be nice to have more verbose summary – Gussy