I’m glad to announce the first release of art, an implementation of the Adaptive Radix Tree in OCaml. The goal of this library is to provide a data-structure such as Map.S (and keep the order) with performances of Hashtbl.t.
Performances
art uses Bechamel as a tool for micro-benchmarking and it compares performances about insertion and lookup. As you can see, about insertion, art is definitely faster than Hashtbl.t.
For the lookup operation, we are slightly faster than the Hashtbl.t. The main advantage comparing to Hashtbl.t is the ability to use maximum/minimum or to iter over the whole data-structure with a certain order.
On details, benchmarks use a normal distribution of strings about their lengths. As a practical example where art will be better than Hashtbl.t is when you want to index several words (such as email addresses).
Tests
Of course, the library provide a fuzzer and tests have a coverage of: 91.93 %
Read Optimized Write Exclusion - ROWEX
Even if it’s not a part of the package, the distribution comes with lock-free implementation of art: rowex. This implementation comes from a research paper about data-structure and atomic operations.
ROWEX provides a persistent implementation which manipulates a file to store the whole data-structure. The goal is to provide an indexer free to be manipulated by several processes in parallel.
Currently, the implementation of ROWEX in OCaml is not well-tested and it is no distributed. It does not take the advantage of ocaml-multicore (but it should) but outcomes are good and the development will be more focus on this part.
So feel free to play with it a bit 
.