xgboost/doc/gpu/index.rst
Philip Hyunsu Cho cb4de521c1
Document CUDA requirement, lack of external memory on GPU (#3624)
* Document fact that GPU doesn't support external memory

* Document CUDA requirement
2018-08-22 22:47:10 -07:00

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###################
XGBoost GPU Support
###################
This page contains information about GPU algorithms supported in XGBoost.
To install GPU support, checkout the :doc:`/build`.
.. note:: CUDA 8.0, Compute Capability 3.5 required
The GPU algorithms in XGBoost require a graphics card with compute capability 3.5 or higher, with
CUDA toolkits 8.0 or later.
(See `this list <https://en.wikipedia.org/wiki/CUDA#GPUs_supported>`_ to look up compute capability of your GPU card.)
*********************************************
CUDA Accelerated Tree Construction Algorithms
*********************************************
Tree construction (training) and prediction can be accelerated with CUDA-capable GPUs.
Usage
=====
Specify the ``tree_method`` parameter as one of the following algorithms.
Algorithms
----------
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tree_method | Description |
+==============+=======================================================================================================================================================================+
| gpu_exact | The standard XGBoost tree construction algorithm. Performs exact search for splits. Slower and uses considerably more memory than ``gpu_hist``. |
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| gpu_hist | Equivalent to the XGBoost fast histogram algorithm. Much faster and uses considerably less memory. NOTE: Will run very slowly on GPUs older than Pascal architecture. |
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
Supported parameters
--------------------
.. |tick| unicode:: U+2714
.. |cross| unicode:: U+2718
+--------------------------+---------------+--------------+
| parameter | ``gpu_exact`` | ``gpu_hist`` |
+==========================+===============+==============+
| ``subsample`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``colsample_bytree`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``colsample_bylevel`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``max_bin`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``gpu_id`` | |tick| | |tick| |
+--------------------------+---------------+--------------+
| ``n_gpus`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``predictor`` | |tick| | |tick| |
+--------------------------+---------------+--------------+
| ``grow_policy`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
| ``monotone_constraints`` | |cross| | |tick| |
+--------------------------+---------------+--------------+
GPU accelerated prediction is enabled by default for the above mentioned ``tree_method`` parameters but can be switched to CPU prediction by setting ``predictor`` to ``cpu_predictor``. This could be useful if you want to conserve GPU memory. Likewise when using CPU algorithms, GPU accelerated prediction can be enabled by setting ``predictor`` to ``gpu_predictor``.
The device ordinal can be selected using the ``gpu_id`` parameter, which defaults to 0.
Multiple GPUs can be used with the ``gpu_hist`` tree method using the ``n_gpus`` parameter. which defaults to 1. If this is set to -1 all available GPUs will be used. If ``gpu_id`` is specified as non-zero, the gpu device order is ``mod(gpu_id + i) % n_visible_devices`` for ``i=0`` to ``n_gpus-1``. As with GPU vs. CPU, multi-GPU will not always be faster than a single GPU due to PCI bus bandwidth that can limit performance.
.. note:: Enabling multi-GPU training
Default installation may not enable multi-GPU training. To use multiple GPUs, make sure to read :ref:`build_gpu_support`.
The GPU algorithms currently work with CLI, Python and R packages. See :doc:`/build` for details.
.. code-block:: python
:caption: Python example
param['gpu_id'] = 0
param['max_bin'] = 16
param['tree_method'] = 'gpu_hist'
Benchmarks
==========
You can run benchmarks on synthetic data for binary classification:
.. code-block:: bash
python tests/benchmark/benchmark.py
Training time time on 1,000,000 rows x 50 columns with 500 boosting iterations and 0.25/0.75 test/train split on i7-6700K CPU @ 4.00GHz and Pascal Titan X yields the following results:
+--------------+----------+
| tree_method | Time (s) |
+==============+==========+
| gpu_hist | 13.87 |
+--------------+----------+
| hist | 63.55 |
+--------------+----------+
| gpu_exact | 161.08 |
+--------------+----------+
| exact | 1082.20 |
+--------------+----------+
See `GPU Accelerated XGBoost <https://xgboost.ai/2016/12/14/GPU-accelerated-xgboost.html>`_ and `Updates to the XGBoost GPU algorithms <https://xgboost.ai/2018/07/04/gpu-xgboost-update.html>`_ for additional performance benchmarks of the ``gpu_exact`` and ``gpu_hist`` tree methods.
**********
References
**********
`Mitchell R, Frank E. (2017) Accelerating the XGBoost algorithm using GPU computing. PeerJ Computer Science 3:e127 https://doi.org/10.7717/peerj-cs.127 <https://peerj.com/articles/cs-127/>`_
`Nvidia Parallel Forall: Gradient Boosting, Decision Trees and XGBoost with CUDA <https://devblogs.nvidia.com/parallelforall/gradient-boosting-decision-trees-xgboost-cuda/>`_
Authors
=======
* Rory Mitchell
* Jonathan C. McKinney
* Shankara Rao Thejaswi Nanditale
* Vinay Deshpande
* ... and the rest of the H2O.ai and NVIDIA team.
Please report bugs to the user forum https://discuss.xgboost.ai/.