>A quick look at the current state of the art</h3>
<p>If you haven't been living under a rock, you know that Google open sourced late last year their Abseil library, which includes a very efficient flat hash table implementation. The <em>absl::flat_hash_map</em> stores the values directly in a memory array, which avoids memory indirections (this is referred to as closed hashing).</p>
<p><img src="https://github.com/greg7mdp/parallel-hashmap/blob/master/img/closed_hashing.png?raw=true" alt="closed_hashing" /