XGBoost C Package

XGBoost implements a set of C API designed for various bindings, we maintain its stability and the CMake/make build interface. See demo/c-api/README.md for an overview and related examples. Also one can generate doxygen document by providing -DBUILD_C_DOC=ON as parameter to CMake during build, or simply look at function comments in include/xgboost/c_api.h.