Speed of math function atan: comparison D and C++

[Marc]

On Monday, 5 March 2018 at 05:35:28 UTC, J-S Caux wrote:
> I'm considering shifting a large existing C++ codebase into D 
> (it's a scientific code making much use of functions like atan, 
> log etc).
>
> I've compared the raw speed of atan between C++ (Apple LLVM 
> version 7.3.0 (clang-703.0.29)) and D (dmd v2.079.0, also ldc2 
> 1.7.0) by doing long loops of such functions.
>
> I can't get the D to run faster than about half the speed of 
> C++.
>
> Are there benchmarks for such scientific functions published 
> somewhere?

What compiled flags did you used to compile both C++ and D 
versions?