D outperformed by C++, what am I doing wrong?

[Roman Hargrave via Digitalmars-d-learn]

On Sunday, 13 August 2017 at 06:09:39 UTC, amfvcg wrote:
> Hi all,
> I'm solving below task:
>
> given container T and value R return sum of R-ranges over T. An 
> example:
> input : T=[1,1,1] R=2
> output : [2, 1]
>
> input : T=[1,2,3] R=1
> output : [1,2,3]
> (see dlang unittests for more examples)
>
>
> Below c++ code compiled with g++-5.4.0 -O2 -std=c++14 runs on 
> my machine in 656 836 us.
> Below D code compiled with dmd v2.067.1 -O runs on my machine 
> in ~ 14.5 sec.

If I had to guess, this could be due to backend and optimizer.
I don't want to go in to detail on my thoughts because I am not 
an expert
on codegen optimization, but I might suggest running your test 
compiled with
GDC (using identical optimization settings as G++) and ldc2 with 
similar settings.