 is that, when using a single thread, only one of the submaps would resize at a time, ensuring that the peak would only be 1/16th of the one for the <em>flat_hash_map</em> (provided of course that the hash function distributes the values somewhat evenly between the submaps).</p>
<p>When running in multi-threaded mode (in this case eight threads), potentially as many as eight submaps can resize simultaneaously, so for a <em>parallel_hash_map</em> with sixteen submaps the memory peak size can be half as large