I actually ran through the intellij version 12 EAP "LEDA" which has Groovy 2 in it for most of the tests.

The @compilestatic stuff should work regardless, but you do need to import the compilestatic transform.

import groovy.transform.CompileStatic

Well I ran it in IntelliJ and saw the same results. Then I found the problem...

I used compile_static3.groovy from your repo for the test which contains the following:

  bench(d, "fib_dynamic", 30, "Full dynamic ")
  bench(d, "fib_integer", 30, "Groovy w/ explicit types")
  bench(d, "fib", 40, "Explicit type w/@CompileStatic")

Notice the '40' on the last line :p

Corrected results:

  Full dynamic  took 305 ms
  Groovy w/ explicit types took 22 ms
  Explicit type w/@CompileStatic took 7 ms

Which is much more like what I expected compared to Ruby at 475ms.

But.... this was in my verbal presentation - move that @compilestatic benchmark to the first test - it'll be different. There's something about running it after the other two which is adding to the benefit - caching maybe? Moving it to the first one gives me 18-20ms generally. Try it :)

Just a guess but the JIT may be detecting the recursion and replacing it with a loop. The recursion signature is the same for each method so the JIT may be able to catch that.

Letting the JIT warm up is enlightening though, I looped the 3 tests 1000 times and also looped my ruby test 1000 times and I get this:

  Explicit type w/@CompileStatic took 5 ms
  Groovy w/ explicit types took 11 ms
  Full dynamic  took 75 ms

  Ruby took 464ms

Very interesting - haven't compared it to Ruby, but the 75ms was interesting on its own. I knew dynamically Groovy would generally be faster than Ruby, but not by that much, given the runtime dynamism.

Thanks! (and thanks for the pull request fix)