src/external/xgboost/subtree/rabit/README.md
rabit is a light weight library that provides a fault tolerant interface of Allreduce and Broadcast. It is designed to support easy implementations of distributed machine learning programs, many of which fall naturally under the Allreduce abstraction. The goal of rabit is to support portable , scalable and reliable distributed machine learning programs.
All these features comes from the facts about small rabbit:)
Rabit is an open-source library, contributions are welcomed, including: