N-body bench

[bearophile]

Stanislav Blinov:

> That won't compile with dmd (at least, with 2.064.2): it 
> expects constants as initializers for vectors. :( That's why I 
> rolled up that toDouble2() function.

I see. Then probably I will have to put it back...


>> With N = 5_000_000 my timings on an old CPU are 2.23 seconds 
>> for ldc2 and 1.83 seconds for g++. So there's some performance 
>> difference.
>
> What about 50_000_000?

First let me try to fiddle with the code some more :-)

Once done, this should go somewhere (like the wiki) as a simple 
example of SIMD usage in D.

Bye,
bearophile