A metric space secondary index, based on the M-tree, implemented according to the following paper:

Shichao Jin, Okhee Kim, Wenya Feng: MX-tree: A Double Hierarchical Metric Index with Overlap Reduction. ICCSA (5) 2013: 574-589

• C++ implementation
• object oriented programming
• based on the Gist library (https://gist.cs.berkeley.edu/)

1. deduplicate the building dataset before constructing the index.

2. set the super node's maximum size X10 of a usual node's size.