Why Java (server VM) is faster than D?

[Dmitry Olshansky via Digitalmars-d]

On 03-Aug-2015 19:54, Steven Schveighoffer wrote:
> On 8/3/15 12:50 PM, John Colvin wrote:
>> On Monday, 3 August 2015 at 16:47:14 UTC, Adam D. Ruppe wrote:
>>> You can try a few potential optimizations in the D version yourself
>>> and see if it makes a difference.
>>>
>>> Devirtualization has a very small impact. Test this by making `test`
>>> take `SubFoo` and making `bar` final, or making `bar` a stand-alone
>>> function.
>>>
>>> That's not it.
>>
>> Making SubFoo a final class and test take SubFoo gives a >10x speedup
>> for me.
>
> Let's make sure we're all comparing apples to apples here.
>
> FWIW, I suspect the inlining to be the most significant improvement,
> which is impossible for virtual functions in D.

Should be trivial in this particular case. You just keep the original 
virtual call where it cannot be deduced.

>
> ALSO, make SURE you are compiling in release mode, so you aren't calling
> a virtual invariant function before/after every call.

This one is critical. Actually why do we have an extra call for trivial 
null-check on any object that doesn't even have invariant?


-- 
Dmitry Olshansky