On 29.03.2017 10:19, Paul Moore wrote:
On 28 March 2017 at 22:08, Nelson, Erick <erick.nel...@hdsupply.com> wrote:
Try this...
Thanks for the suggestion - there were some nice improvements in here.
def rng = new MersenneTwister()
def roll = {
rng.nextInt(6) + rng.nextInt(6) + rng.nextInt(6) + 3
}
You changed my definitions to use "def" here. This seems to be the
thing that makes the most difference in performance. I'm really
struggling to find a good explanation as to the effect of using or not
using "def".
basically it depends on if Groovy thinks there has to be a cast here or
not and if the primitive optimizations can kick in.
I had imagined that using "int roll() {..." would be
better, as it explicitly states the types which would help the
compiler avoid the need for generic code. Obviously I was wrong, but
I'm not at all clear why.
yes, it is better, but only if primitive optimizations are working... or
if you compile static. I haven't looked into why, but in
int n = roll()
results[n] = results.containsKey(n) ? results[n] + 1 : 1
result is referenced outside the closure and I think that is already
enough to not have primitive optimizations in use here. Which means you
have to pay the boxing cost from int to Integer and back to int for
every call to roll... and then you have again boxing for
results.containsKey(n) and results[n]= and results[n] + 1. In that case
it looks really much better to just use Integer from the start, thus def
has an advantage here.
Also, if I use "def rng" but keep "int roll()", I get an error "No
such property: rng". I'm not clear why that is.
you wrote a script, not a class, thus
rng = new MersenneTwister()
will set a variable called rng in the binding, and
int roll() {
rng.nextInt(6) + rng.nextInt(6) + rng.nextInt(6) + 3
}
this will use rng from the binding.
def rng = new MersenneTwister()
will make a local variable and leaves the binding rng blank, thus roll
gets into trouble
Do you know of a good resource that explains the difference between
using def and not doing so?
hm... I think the page I wrote back then got lost in the codehaus move :(
bye Jochen
