Building from source — JAX documentation (original) (raw)

Building from source#

First, obtain the JAX source code:

git clone https://github.com/jax-ml/jax cd jax

Building JAX involves two steps:

  1. Building or installing jaxlib, the C++ support library for jax.
  2. Installing the jax Python package.

Building or installing jaxlib#

Installing jaxlib with pip#

If you’re only modifying Python portions of JAX, we recommend installingjaxlib from a prebuilt wheel using pip:

See the JAX readme for full guidance on pip installation (e.g., for GPU and TPU support).

Building jaxlib from source#

Warning

While it should typically be possible to compile jaxlib from source using most modern compilers, the builds are only tested using clang. Pull requests are welcomed to improve support for different toolchains, but other compilers are not actively supported.

To build jaxlib from source, you must also install some prerequisites:

To build jaxlib for CPU or TPU, you can run:

python build/build.py build --wheels=jaxlib --verbose pip install dist/*.whl # installs jaxlib (includes XLA)

To build a wheel for a version of Python different from your current system installation pass --python_version flag to the build command:

python build/build.py build --wheels=jaxlib --python_version=3.12 --verbose

The rest of this document assumes that you are building for Python version matching your current system installation. If you need to build for a different version, simply append --python_version=<py version> flag every time you callpython build/build.py. Note, the Bazel build will always use a hermetic Python installation regardless of whether the --python_version parameter is passed or not.

If you would like to build jaxlib and the CUDA plugins: Run

python build/build.py build --wheels=jaxlib,jax-cuda-plugin,jax-cuda-pjrt

to generate three wheels (jaxlib without cuda, jax-cuda-plugin, and jax-cuda-pjrt). By default all CUDA compilation steps performed by NVCC and clang, but it can be restricted to clang via the --build_cuda_with_clang flag.

See python build/build.py --help for configuration options. Herepython should be the name of your Python 3 interpreter; on some systems, you may need to use python3 instead. Despite calling the script with python, Bazel will always use its own hermetic Python interpreter and dependencies, only the build/build.py script itself will be processed by your system Python interpreter. By default, the wheel is written to the dist/ subdirectory of the current directory.

Building jaxlib from source with a modified XLA repository.#

JAX depends on XLA, whose source code is in theXLA GitHub repository. By default JAX uses a pinned copy of the XLA repository, but we often want to use a locally-modified copy of XLA when working on JAX. There are two ways to do this:

To contribute changes back to XLA, send PRs to the XLA repository.

The version of XLA pinned by JAX is regularly updated, but is updated in particular before each jaxlib release.

Additional Notes for Building jaxlib from source on Windows#

Note: JAX does not support CUDA on Windows; use WSL2 for CUDA support.

On Windows, follow Install Visual Studioto set up a C++ toolchain. Visual Studio 2019 version 16.5 or newer is required.

JAX builds use symbolic links, which require that you activateDeveloper Mode.

You can either install Python using itsWindows installer, or if you prefer, you can use Anacondaor Minicondato set up a Python environment.

Some targets of Bazel use bash utilities to do scripting, so MSYS2is needed. See Installing Bazel on Windowsfor more details. Install the following packages:

pacman -S patch coreutils

Once coreutils is installed, the realpath command should be present in your shell’s path.

Once everything is installed. Open PowerShell, and make sure MSYS2 is in the path of the current session. Ensure bazel, patch and realpath are accessible. Activate the conda environment.

python .\build\build.py build --wheels=jaxlib

To build with debug information, add the flag --bazel_options='--copt=/Z7'.

Additional notes for building a ROCM jaxlib for AMD GPUs#

For detailed instructions on building jaxlib with ROCm support, refer to the official guide:Build ROCm JAX from Source

Managing hermetic Python#

To make sure that JAX’s build is reproducible, behaves uniformly across supported platforms (Linux, Windows, MacOS) and is properly isolated from specifics of a local system, we rely on hermetic Python (provided byrules_python, seeToolchain Registrationfor details) for all build and test commands executed via Bazel. This means that your system Python installation will be ignored during the build and Python interpreter itself as well as all the Python dependencies will be managed by bazel directly.

Specifying Python version#

When you run build/build.py tool, the version of hermetic Python is set automatically to match the version of the Python you used to run build/build.py script. To choose a specific version explicitly you may pass --python_version argument to the tool:

python build/build.py build --python_version=3.12

Under the hood, the hermetic Python version is controlled by HERMETIC_PYTHON_VERSION environment variable, which is set automatically when you run build/build.py. In case you run bazel directly you may need to set the variable explicitly in one of the following ways:

Either add an entry to your .bazelrc file

build --repo_env=HERMETIC_PYTHON_VERSION=3.12

OR pass it directly to your specific build command

bazel build --repo_env=HERMETIC_PYTHON_VERSION=3.12

OR set the environment variable globally in your shell:

export HERMETIC_PYTHON_VERSION=3.12

You may run builds and tests against different versions of Python sequentially on the same machine by simply switching the value of --python_version between the runs. All the python-agnostic parts of the build cache from the previous build will be preserved and reused for the subsequent builds.

Specifying Python dependencies#

During bazel build all JAX’s Python dependencies are pinned to their specific versions. This is necessary to ensure reproducibility of the build. The pinned versions of the full transitive closure of JAX’s dependencies together with their corresponding hashes are specified inbuild/requirements_lock_<python version>.txt files ( e.g. build/requirements_lock_3_12.txt for Python 3.12).

To update the lock files, make sure build/requirements.in contains the desired direct dependencies list and then execute the following command (which will callpip-compile under the hood):

python build/build.py requirements_update --python_version=3.12

Alternatively, if you need more control, you may run the bazel command directly (the two commands are equivalent):

bazel run //build:requirements.update --repo_env=HERMETIC_PYTHON_VERSION=3.12

where 3.12 is the Python version you wish to update.

Note, since it is still pip and pip-compile tools used under the hood, so most of the command line arguments and features supported by those tools will be acknowledged by the Bazel requirements updater command as well. For example, if you wish the updater to consider pre-release versions simply pass --preargument to the bazel command:

bazel run //build:requirements.update --repo_env=HERMETIC_PYTHON_VERSION=3.12 -- --pre

Specifying dependencies on local wheels#

By default the build scans dist directory in the repository root for any local.whl files to be included in the list of dependencies. If the wheel is Python version specific, only the wheels that match the selected Python version will be included.

The overall local wheel search and selection logic is controlled by the arguments to python_init_repositories() macro (called directly from theWORKSPACE file). You may use local_wheel_dist_folder to change the location of the folder with local wheels. Use local_wheel_inclusion_list andlocal_wheel_exclusion_list arguments to specify which wheels should be included and/or excluded from the search (it supports basic wildcard matching).

If necessary, you can also depend on a local .whl file manually, bypassing the automatic local wheel search mechanism. For example to depend on your newly built jaxlib wheel, you may add a path to the wheel in build/requirements.inand re-run the requirements updater command for a selected version of Python. For example:

echo -e "\n$(realpath jaxlib-0.4.27.dev20240416-cp312-cp312-manylinux2014_x86_64.whl)" >> build/requirements.in python build/build.py requirements_update --python_version=3.12

Specifying dependencies on nightly wheels#

To build and test against the very latest, potentially unstable, set of Python dependencies we provide a special version of the dependency updater command as follows:

python build/build.py requirements_update --python_version=3.12 --nightly_update

Or, if you run bazel directly (the two commands are equivalent):

bazel run //build:requirements_nightly.update --repo_env=HERMETIC_PYTHON_VERSION=3.12

The difference between this and the regular updater is that by default it would accept pre-release, dev and nightly packages, it will also search https://pypi.anaconda.org/scientific-python-nightly-wheels/simple as an extra index url and will not put hashes in the resultant requirements lock file.

Customizing hermetic Python (Advanced Usage)#

We support all of the current versions of Python out of the box, so unless your workflow has very special requirements (such as ability to use your own custom Python interpreter) you may safely skip this section entirely.

In short, if you rely on a non-standard Python workflow you still can achieve the great level of flexibility in hermetic Python setup. Conceptually there will be only one difference compared to non-hermetic case: you will need to think in terms of files, not installations (i.e. think what files your build actually depends on, not what files need to be installed on your system), the rest is pretty much the same.

So, in practice, to gain full control over your Python environment, hermetic or not you need to be able to do the following three things:

  1. Specify which python interpreter to use (i.e. pick actual python orpython3 binary and libs that come with it in the same folder).
  2. Specify a list of Python dependencies (e.g. numpy) and their actual versions.
  3. Be able to add/remove/update dependencies in the list easily. Each dependency itself could be custom too (self-built for example).

You already know how to do all of the steps above in a non-hermetic Python environment, here is how you do the same in the hermetic one (by approaching it in terms of files, not installations):

  1. Instead of installing Python, get Python interpreter in a tar or zipfile. Depending on your case you may simply pull one of many existing ones (such as python-build-standalone), or build your own and pack it in an archive (following officialbuild instructionswill do just fine). E.g. on Linux it will look something like the following:
    ./configure --prefix python
    make -j12
    make altinstall
    tar -czpf my_python.tgz python
    Once you have the tarball ready, plug it in the build by pointingHERMETIC_PYTHON_URL env var to the archive (either local one or from the internet):
    --repo_env=HERMETIC_PYTHON_URL="file:///local/path/to/my_python.tgz"
    --repo_env=HERMETIC_PYTHON_SHA256=<file's_sha256_sum>

OR

--repo_env=HERMETIC_PYTHON_URL="https://remote/url/to/my_python.tgz"
--repo_env=HERMETIC_PYTHON_SHA256=<file's_sha256_sum>

We assume that top-level folder in the tarbal is called "python", if it is

something different just pass additional HERMETIC_PYTHON_PREFIX parameter

--repo_env=HERMETIC_PYTHON_URL="https://remote/url/to/my_python.tgz"
--repo_env=HERMETIC_PYTHON_SHA256=<file's_sha256_sum>
--repo_env=HERMETIC_PYTHON_PREFIX="my_python/install" 2. Instead of doing pip install create requirements_lock.txt file with full transitive closure of your dependencies. You may also depend on the existing ones already checked in this repo (as long as they work with your custom Python version). There are no special instructions on how you do it, you may follow steps recommended in Specifying Python dependenciesfrom this doc, just call pip-compile directly (note, the lock file must be hermetic, but you can always generate it from non-hermetic python if you’d like) or even create it manually (note, hashes are optional in lock files). 3. If you need to update or customize your dependencies list, you may once again follow the Specifying Python dependenciesinstructions to update requirements_lock.txt, call pip-compile directly or modify it manually. If you have a custom package you want to use just point to its .whl file directly (remember, work in terms of files, not installations) from your lock (note, requirements.txt andrequirements_lock.txt files support local wheel references). If yourrequirements_lock.txt is already specified as a dependency topython_init_repositories() in WORKSPACE file you don’t have to do anything else. Otherwise you can point to your custom file as follows:
--repo_env=HERMETIC_REQUIREMENTS_LOCK="/absolute/path/to/custom_requirements_lock.txt"
Also note if you use HERMETIC_REQUIREMENTS_LOCK then it fully controls list of your dependencies and the automatic local wheels resolution logic described in Specifying dependencies on local wheelsgets disabled to not interfere with it.

That is it. To summarize: if you have an archive with Python interpreter in it and a requirements_lock.txt file with full transitive closure of your dependencies then you fully control your Python environment.

Custom hermetic Python examples#

Note, for all of the examples below you may also set the environment variables globally (i.e. export in your shell instead of --repo_env argument to your command) so calling bazel via build/build.py will work just fine.

Build with custom Python 3.13 from the internet, using defaultrequirements_lock_3_13.txt already checked in this repo (i.e. custom interpreter but default dependencies):

bazel build --repo_env=HERMETIC_PYTHON_VERSION=3.13 --repo_env=HERMETIC_PYTHON_URL="https://github.com/indygreg/python-build-standalone/releases/download/20241016/cpython-3.13.0+20241016-x86_64-unknown-linux-gnu-install_only.tar.gz" --repo_env=HERMETIC_PYTHON_SHA256="2c8cb15c6a2caadaa98af51df6fe78a8155b8471cb3dd7b9836038e0d3657fb4"

Build with custom Python 3.13 from local file system and custom lock file (assuming the lock file was put in jax/build folder of this repo before running the command):

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13 --repo_env=HERMETIC_PYTHON_URL="file:///path/to/cpython.tar.gz" --repo_env=HERMETIC_PYTHON_PREFIX="prefix/to/strip/in/cython/tar/gz/archive" --repo_env=HERMETIC_PYTHON_SHA256= --repo_env=HERMETIC_REQUIREMENTS_LOCK="/absolute/path/to/build:custom_requirements_lock.txt"

If default python interpreter is good enough for you and you just need a custom set of dependencies:

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13 --repo_env=HERMETIC_REQUIREMENTS_LOCK="/absolute/path/to/build:custom_requirements_lock.txt"

Note, you can have multiple different requirement_lock.txt files corresponding to the same Python version to support different scenarios. You can control which one is selected by specifying HERMETIC_PYTHON_VERSION. For example inWORKSPACE file:

requirements = { "3.10": "//build:requirements_lock_3_10.txt", "3.11": "//build:requirements_lock_3_11.txt", "3.12": "//build:requirements_lock_3_12.txt", "3.13": "//build:requirements_lock_3_13.txt", "3.13-scenario1": "//build:scenario1_requirements_lock_3_13.txt", "3.13-scenario2": "//build:scenario2_requirements_lock_3_13.txt", },

Then you can build and test different combinations of stuff without changing anything in your environment:

To build with scenario1 dependendencies:

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13-scenario1

To build with scenario2 dependendencies:

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13-scenario2

To build with default dependendencies:

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13

To build with scenario1 dependendencies and custom Python 3.13 interpreter:

bazel test --repo_env=HERMETIC_PYTHON_VERSION=3.13-scenario1 --repo_env=HERMETIC_PYTHON_URL="file:///path/to/cpython.tar.gz" --repo_env=HERMETIC_PYTHON_SHA256=

Installing jax#

Once jaxlib has been installed, you can install jax by running:

pip install -e . # installs jax

To upgrade to the latest version from GitHub, just run git pull from the JAX repository root, and rebuild by running build.py or upgrading jaxlib if necessary. You shouldn’t have to reinstall jax because pip install -esets up symbolic links from site-packages into the repository.

Running the tests#

There are two supported mechanisms for running the JAX tests, either using Bazel or using pytest.

Using Bazel#

First, configure the JAX build by using the --configure_only flag. Pass--wheel_list=jaxlib for CPU tests and CUDA/ROCM for GPU for GPU tests:

python build/build.py build --wheels=jaxlib --configure_only python build/build.py build --wheels=jax-cuda-plugin --configure_only python build/build.py build --wheels=jax-rocm-plugin --configure_only

You may pass additional options to build.py to configure the build; see thejaxlib build documentation for details.

By default the Bazel build runs the JAX tests using jaxlib built from source. To run JAX tests, run:

bazel test //tests:cpu_tests //tests:backend_independent_tests

//tests:gpu_tests and //tests:tpu_tests are also available, if you have the necessary hardware.

To use a preinstalled jaxlib instead of building it you first need to make it available in the hermetic Python. To install a specific version ofjaxlib within hermetic Python run (using jaxlib >= 0.4.26 as an example):

echo -e "\njaxlib >= 0.4.26" >> build/requirements.in python build/build.py requirements_update

Alternatively, to install jaxlib from a local wheel (assuming Python 3.12):

echo -e "\n$(realpath jaxlib-0.4.26-cp312-cp312-manylinux2014_x86_64.whl)" >> build/requirements.in python build/build.py requirements_update --python_version=3.12

Once you have jaxlib installed hermetically, run:

bazel test --//jax:build_jaxlib=false //tests:cpu_tests //tests:backend_independent_tests

A number of test behaviors can be controlled using environment variables (see below). Environment variables may be passed to JAX tests using the--test_env=FLAG=value flag to Bazel.

Some of JAX tests are for multiple accelerators (i.e. GPUs, TPUs). When JAX is already installed, you can run GPUs tests like this:

bazel test //tests:gpu_tests --local_test_jobs=4 --test_tag_filters=multiaccelerator --//jax:build_jaxlib=false --test_env=XLA_PYTHON_CLIENT_ALLOCATOR=platform

You can speed up single accelerator tests by running them in parallel on multiple accelerators. This also triggers multiple concurrent tests per accelerator. For GPUs, you can do it like this:

NB_GPUS=2 JOBS_PER_ACC=4 J=$((NB_GPUS * JOBS_PER_ACC)) MULTI_GPU="--run_under PWD/build/parallelacceleratorexecute.sh−−testenv=JAXACCELERATORCOUNT=PWD/build/parallel_accelerator_execute.sh --test_env=JAX_ACCELERATOR_COUNT=PWD/build/parallelacceleratorexecute.shtestenv=JAXACCELERATORCOUNT={NB_GPUS} --test_env=JAX_TESTS_PER_ACCELERATOR=${JOBS_PER_ACC} --local_test_jobs=$J" bazel test //tests:gpu_tests //tests:backend_independent_tests --test_env=XLA_PYTHON_CLIENT_PREALLOCATE=false --test_tag_filters=-multiaccelerator $MULTI_GPU

Using pytest#

First, install the dependencies by running pip install -r build/test-requirements.txt.

To run all the JAX tests using pytest, we recommend using pytest-xdist, which can run tests in parallel. It is installed as a part ofpip install -r build/test-requirements.txt command.

From the repository root directory run:

Controlling test behavior#

JAX generates test cases combinatorially, and you can control the number of cases that are generated and checked for each test (default is 10) using theJAX_NUM_GENERATED_CASES environment variable. The automated tests currently use 25 by default.

For example, one might write

Bazel

bazel test //tests/... --test_env=JAX_NUM_GENERATED_CASES=25`

or

pytest

JAX_NUM_GENERATED_CASES=25 pytest -n auto tests

The automated tests also run the tests with default 64-bit floats and ints (JAX_ENABLE_X64):

JAX_ENABLE_X64=1 JAX_NUM_GENERATED_CASES=25 pytest -n auto tests

You can run a more specific set of tests usingpytest’s built-in selection mechanisms, or alternatively you can run a specific test file directly to see more detailed information about the cases being run:

JAX_NUM_GENERATED_CASES=5 python tests/lax_numpy_test.py

You can skip a few tests known to be slow, by passing environment variable JAX_SKIP_SLOW_TESTS=1.

To specify a particular set of tests to run from a test file, you can pass a string or regular expression via the --test_targets flag. For example, you can run all the tests of jax.numpy.pad using:

python tests/lax_numpy_test.py --test_targets="testPad"

The Colab notebooks are tested for errors as part of the documentation build.

Hypothesis tests#

Some of the tests use hypothesis. Normally, hypothesis will test using multiple example inputs, and on a test failure it will try to find a smaller example that still results in failure: Look through the test failure for a line like the one below, and add the decorator mentioned in the message:

You can reproduce this example by temporarily adding @reproduce_failure('6.97.4', b'AXicY2DAAAAAEwAB') as a decorator on your test case

For interactive development, you can set the environment variableJAX_HYPOTHESIS_PROFILE=interactive (or the equivalent flag --jax_hypothesis_profile=interactive) in order to set the number of examples to 1, and skip the example minimization phase.

Doctests#

JAX uses pytest in doctest mode to test the code examples within the documentation. You can find the up-to-date command to run doctests inci-build.yaml. E.g., you can run:

JAX_TRACEBACK_FILTERING=off XLA_FLAGS=--xla_force_host_platform_device_count=8 pytest -n auto --tb=short --doctest-glob='.md' --doctest-glob='.rst' docs --doctest-continue-on-failure --ignore=docs/multi_process.md

Additionally, JAX runs pytest in doctest-modules mode to ensure code examples in function docstrings will run correctly. You can run this locally using, for example:

JAX_TRACEBACK_FILTERING=off XLA_FLAGS=--xla_force_host_platform_device_count=8 pytest --doctest-modules jax/_src/numpy/lax_numpy.py

Type checking#

We use mypy to check the type hints. To run mypy with the same configuration as the github CI checks, you can use the pre-commit framework:

pip install pre-commit pre-commit run mypy --all-files

Because mypy can be somewhat slow when checking all files, it may be convenient to only check files you have modified. To do this, first stage the changes (i.e. git addthe changed files) and then run this before committing the changes:

Linting#

JAX uses the ruff linter to ensure code quality. To run ruff with the same configuration as the github CI checks, you can use the pre-commit framework:

pip install pre-commit pre-commit run ruff --all-files

Update documentation#

To rebuild the documentation, install several packages:

pip install -r docs/requirements.txt

And then run:

sphinx-build -b html docs docs/build/html -j auto

This can take a long time because it executes many of the notebooks in the documentation source; if you’d prefer to build the docs without executing the notebooks, you can run:

sphinx-build -b html -D nb_execution_mode=off docs docs/build/html -j auto

You can then see the generated documentation in docs/build/html/index.html.

The -j auto option controls the parallelism of the build. You can use a number in place of auto to control how many CPU cores to use.

Update notebooks#

We use jupytext to maintain two synced copies of the notebooks in docs/notebooks: one in ipynb format, and one in md format. The advantage of the former is that it can be opened and executed directly in Colab; the advantage of the latter is that it makes it much easier to track diffs within version control.

Editing ipynb#

For making large changes that substantially modify code and outputs, it is easiest to edit the notebooks in Jupyter or in Colab. To edit notebooks in the Colab interface, open http://colab.research.google.com and Upload from your local repo. Update it as needed, Run all cells then Download ipynb. You may want to test that it executes properly, using sphinx-build as explained above.

Editing md#

For making smaller changes to the text content of the notebooks, it is easiest to edit the.md versions using a text editor.

Syncing notebooks#

After editing either the ipynb or md versions of the notebooks, you can sync the two versions using jupytext by running jupytext --sync on the updated notebooks; for example:

pip install jupytext==1.16.4 jupytext --sync docs/notebooks/thinking_in_jax.ipynb

The jupytext version should match that specified in.pre-commit-config.yaml.

To check that the markdown and ipynb files are properly synced, you may use thepre-commit framework to perform the same check used by the github CI:

pip install pre-commit pre-commit run jupytext --all-files

Creating new notebooks#

If you are adding a new notebook to the documentation and would like to use the jupytext --synccommand discussed here, you can set up your notebook for jupytext by using the following command:

jupytext --set-formats ipynb,md:myst path/to/the/notebook.ipynb

This works by adding a "jupytext" metadata field to the notebook file which specifies the desired formats, and which the jupytext --sync command recognizes when invoked.

Notebooks within the Sphinx build#

Some of the notebooks are built automatically as part of the pre-submit checks and as part of the Read the docs build. The build will fail if cells raise errors. If the errors are intentional, you can either catch them, or tag the cell with raises-exceptions metadata (example PR). You have to add this metadata by hand in the .ipynb file. It will be preserved when somebody else re-saves the notebook.

We exclude some notebooks from the build, e.g., because they contain long computations. See exclude_patterns in conf.py.

Documentation building on readthedocs.io#

JAX’s auto-generated documentation is at https://jax.readthedocs.io/.

The documentation building is controlled for the entire project by thereadthedocs JAX settings. The current settings trigger a documentation build as soon as code is pushed to the GitHub main branch. For each code version, the building process is driven by the.readthedocs.yml and the docs/conf.py configuration files.

For each automated documentation build you can see thedocumentation build logs.

If you want to test the documentation generation on Readthedocs, you can push code to the test-docsbranch. That branch is also built automatically, and you can see the generated documentation here. If the documentation build fails you may want to wipe the build environment for test-docs.

For a local test, I was able to do it in a fresh directory by replaying the commands I saw in the Readthedocs logs:

mkvirtualenv jax-docs # A new virtualenv mkdir jax-docs # A new directory cd jax-docs git clone --no-single-branch --depth 50 https://github.com/jax-ml/jax cd jax git checkout --force origin/test-docs git clean -d -f -f workon jax-docs

python -m pip install --upgrade --no-cache-dir pip python -m pip install --upgrade --no-cache-dir -I Pygments==2.3.1 setuptools==41.0.1 docutils==0.14 mock==1.0.1 pillow==5.4.1 alabaster>=0.7,<0.8,!=0.7.5 commonmark==0.8.1 recommonmark==0.5.0 'sphinx<2' 'sphinx-rtd-theme<0.5' 'readthedocs-sphinx-ext<1.1' python -m pip install --exists-action=w --no-cache-dir -r docs/requirements.txt cd docs python which sphinx-build -T -E -b html -d _build/doctrees-readthedocs -D language=en . _build/html