On the performance of multiple choice hash tables with moves on deletes and inserts

In a multiple choice hash table scheme, each item is stored in one of d ges 2 hash table buckets. The ability to choose from multiple locations when storing an item improves space utilization, while the simplicity of such schemes makes them highly amenable to hardware implementation, as in a router. Some variants, such as cuckoo hashing, allow items to be moved among their d choices in order to improve load balance and avoid hash table overflows. We consider schemes that move items on insertion and deletion operations, as arguably one would be willing to incur more time on such operations as opposed to more frequent lookup operations. To keep the schemes as simple as possible for hardware implementation, we focus on schemes that allow a single move on an insertion or deletion. Our results show significant space savings when moving items is allowed, even under the limitation of one move per insertion and deletion operation.