A cache-conscious associative array invented at HP Labs. Internally a 256-way digital trie that switches between several node layouts to minimise both cache misses and memory. Very fast — but the implementation is notoriously complex.
Are an associative data structure which tends to have better performance than heaps. It comes with other benefits as well, since it an array, it is more cache friendly.
The performance improvement is not worth the complexity of the implementation
Douglas Baskins named this after his sister, Judy.