Do everything in Java…

[Rene Zwanenburg via Digitalmars-d]

On Monday, 8 December 2014 at 10:31:46 UTC, John Colvin wrote:
> On Sunday, 7 December 2014 at 22:46:02 UTC, Dmitry Olshansky 
> wrote:
>> 08-Dec-2014 01:38, John Colvin пишет:
>>> On Sunday, 7 December 2014 at 22:13:50 UTC, Dmitry Olshansky 
>>> wrote:
>>>> 08-Dec-2014 00:36, John Colvin пишет:
>>>>> On Sunday, 7 December 2014 at 19:56:49 UTC, Dmitry 
>>>>> Olshansky wrote:
>>>>>> 06-Dec-2014 18:33, H. S. Teoh via Digitalmars-d пишет:
>>>>>>> On Sat, Dec 06, 2014 at 03:26:08PM +0000, Russel Winder 
>>>>>>> via
>>>>>>> Digitalmars-d wrote:
>>>>>>> [...]
>>>>>>>>> primitive are passed by value; arrays and user defined 
>>>>>>>>> types are
>>>>>>>>> passed by reference only (killing memory usage)
>>>>>>>>
>>>>>>>> Primitive types are scheduled for removal, leaving only 
>>>>>>>> reference
>>>>>>>> types.
>>>>>>> [...]
>>>>>>>
>>>>>>> Whoa. So they're basically going to rely on JIT to 
>>>>>>> convert those boxed
>>>>>>> Integers into hardware ints for performance?
>>>>>>
>>>>>> With great success.
>>>>>>
>>>>>>> Sounds like I will never
>>>>>>> consider Java for computation-heavy tasks then...
>>>>>>
>>>>>> Interestingly working with JVM for the last 2 years the 
>>>>>> only problem
>>>>>> I've found is memory usage overhead of collections and 
>>>>>> non-trivial
>>>>>> objects. In my tests performance of simple numeric code 
>>>>>> was actually
>>>>>> better with Scala (not even plain Java) then with D (LDC), 
>>>>>> for
>>>>>> instance.
>>>>>
>>>>> Got an example? I'd be interested to see a numerical-code 
>>>>> example where
>>>>> the JVM can beat the llvm/gcc backends on a real 
>>>>> calculation (even if
>>>>> it's a small one).
>>>>
>>>> It was trivial Gaussian integration.
>>>> http://en.wikipedia.org/wiki/Gaussian_quadrature
>>>>
>>>> I do not claim code is optimal or anything, but it's line 
>>>> for line.
>>>>
>>
>> [snip]
>>
>>> on my machine (Haswell i5) I get scala as taking 1.6x as long 
>>> as the ldc
>>> version.
>>>
>>> I don't know scala though, I compiled using -optimise, are 
>>> there other
>>> arguments I should be using?
>>
>> There is no point in -optimise at least I do not recall using 
>> it.
>> What's your JVM ? It should be Oracle's HotSpot not OpenJDK.
>
> hotspot.
>
> After changing the benchmark to more carefully measure the 
> integration function (ldc was unfairly taking advantage of 
> knowing a and b at compile-time), scala does indeed win by a 
> small margin.
>
> I wonder what it's managing to achieve here? AFAICT there 
> really isn't much scope for optimisation in that while loop 
> without breaking IEEE-754 guarantees.

I don't think 'f' will be inlined in the D version. What happens 
if you make it an alias instead?