A Simple, Fast, and Compact Static Dictionary

We present a new static dictionary that is very fast and compact, while also extremely easy to implement. A combination of properties make this algorithm very attractive for applications requiring large static dictionaries: 1. High performance, with membership queries taking O(1)-time with a near-optimal constant. 2. Continued high performance in external memory, with queries requiring only 1-2 disk seeks. If the dictionary has n items in {0, ..., m−1} and d is the number of bytes retrieved from disk on each read, then the average number of seeks is min ( 1.63, 1 +O (√ n log m d )) . 3. Efficient use of space, storing n items from a universe of size m in n logm− 1 2 n log n+O (n+ log logm) bits. We prove this space bound with a novel application of the Kolmogorov-Smirnov distribution. 4. Simplicity, with a 20-line pseudo-code construction algorithm and 4-line query algorithm.