libart

This library provides a C99 implementation of the Adaptive Radix Tree or ART. The ART operates similar to a traditional radix tree but avoids the wasted space of internal nodes by changing the node size. It makes use of 4 node sizes (4, 16, 48, 256), and can guarantee that the overhead is no more than 52 bytes per key, though in practice it is much lower.

As a radix tree, it provides the following:

• O(k) operations. In many cases, this can be faster than a hash table since the hash function is an O(k) operation, and hash tables have very poor cache locality.
• Minimum / Maximum value lookups
• Prefix compression
• Ordered iteration
• Prefix based iteration

References

Related works:

• The Adaptive Radix Tree: ARTful Indexing for Main-Memory Databases