&gt; &quot;But it adds some checks and GC, so Swift also exhibits a serious slowdown, though well within 2x of C++.&quot;<p>Swift does not employ GC, it uses ARC. While that may be a form of GC, it doesn&#x27;t suffer from the same &quot;slowdown&quot; that GC would in this context because ARC is doing exactly what your base case (C++) does at run-time (ARC is a compile-time tool).<p>I think if you&#x27;re going to be doing benchmarks, you should have basic knowledge on how each system works first.