Implementation of BT-trees

Great paper by Lars F. Bonnichsen, Christian W. Probst, Sven Karlsson:

This document presents the full implementation details of BT-trees, a highly efficient ordered map, and an evaluation which compares BT-trees with unordered maps. BT- trees are often much faster than other ordered maps, and have comparable performance to unordered map implementations. However, in benchmarks which favor unordered maps, BT-trees are not faster than the fastest unordered map implementations we know of.