As far as micro-benchmarks go, this one is particularly egregious.  It is likely completely dominated by the array reallocation.  So a runtime that - say - chooses to preallocate an array at size 1000000, or to go to 1000000 at first resize would win at this benchmark.  More realistically, a runtime that conserves memory by reallocating arrays with a 1.5x factor vs a 2x factor will appear slower.<p>It&#x27;s exactly because you don&#x27;t want to rely on the runtime making the right call for your use-case that you preallocate arrays where it makes a difference (i.e. where you&#x27;re appending a million items).<p>And 99% of the time you&#x27;re doing less than 100 items, and so the array reallocation behavior just doesn&#x27;t matter.