Project Lambda: Java Language Specification draft

[Zdenek Tronicek]

Hi Remi,

System.nanoTime() is not very suitable for performance tests because
neither Unix nor Windows have resolution of 1ns. The resolution is
typically 100-1000 times lower.
So, I changed System.nanoTime() to System.currentTimeMillis(), increased
the size of the list to 1000000 (million), and looping through get() is
faster than looping through Iterator. Difference is approx. 7%.
(On Windows XP, Intel).

Z.
-- 
Zdenek Tronicek
FIT CTU in Prague


Rémi Forax napsal(a):
> Le 29/01/2010 06:16, Neal Gafter a écrit :
>> On Thu, Jan 28, 2010 at 4:05 PM, Rémi Forax<forax at univ-mlv.fr>  wrote:
>>> Le 28/01/2010 20:11, Neal Gafter a écrit :
>>>> By the way, looping through an ArrayList using indexing happens to be
>>>> faster than looping through using an iterator because the latter
>>>> requires two method calls per element, while the former requires only
>>>> one.  It's not hard to verify this experimentally.
>>> This not true if the code is hot.
>> Have you run experiments to back up that assertion?
>
> Yes,
> I had done a similar experiment one week ago when testing method handles.
> I've updated it this morning to remove method handle things.
> You can find the two codes and the generated assembler codes is here:
> http://cr.openjdk.java.net/~forax/assembly-loop/loop-assembly.zip
>
> Look for a method named __test__  and takes the second one,
> the first one is generated before Hotspot decides to inline iterator's
> methods.
>
> The method increment do parsing/toString to avoid to be inlined,
> __test__ is not inlined too.
> I've also tried to use the Iterator of a LinkedList during the warm-up
> to avoid too easy code for a CHA analysis but it doesn't change the
> generated code.
>
> Rémi
>
>