This is in development and is probably buggy and very unsafe.
This is a work in progress implementation of the Cache-Conscious Hashmap, as described by Askitis and Zobel in Cache-Conscious Collision Resolution in String Hash Tables. This algorithm optimizes for strings by storing the keys and values in a contiguous array. In the best case, the overhead required for pointers is reduced by a factor around 50, to less than two bits per string.