&gt;&gt; Edit: This Quora question mentions the performance of Swift before and after unsafe programs were included<p>That Quora answer makes claims which are not true.<p>The Swift benchmarks game programs were always compiled with -Ounchecked (since Dec  7 2015).<p>The <i>before</i> was naive transliterations (from other programming languages) of single-core programs -- just to demonstrate that Swift was installed.<p>The <i>after</i> was someone doing the work and contributing programs written for Swift and written for multi-core.