PDL Abstract

Practical Batch-Updatable External Hashing with Sorting

Proc. of Meeting on Algorithm Engineering and Experiments (ALENEX), Jan 2013 .

Hyeontaek Lim, David G. Andersen, Michael Kaminsky*

School of Computer Science
Carnegie Mellon University
Pittsburgh, PA 15213

*Intel Labs


This paper presents a practical external hashing scheme that supports fast lookup (7 microseconds) for large datasets (millions to billions of items) with a small memory footprint (2.5 bits/item) and fast index construction (151 K items/s for 1-KiB key-value pairs). Our scheme combines three key techniques: (1) a new index data structure (Entropy-Coded Tries); (2) the use of sorting as the main data manipulation method; and (3) support for incremental index construction for dynamic datasets. We evaluate our scheme by building an external dictionary on flash-based drives and demonstrate our scheme's high performance, compactness, and practicality.