* Use pre-rounding based method to obtain reproducible floating point summation. * GPU Hist for regression and classification are bit-by-bit reproducible. * Add doc. * Switch to thrust reduce for `node_sum_gradient`.
The documentation of xgboost is generated with recommonmark and sphinx. You can build it locally by typing "make html" in this folder. Checkout https://recommonmark.readthedocs.org for guide on how to write markdown with extensions used in this doc, such as math formulas and table of content.