XLA

Precompiled Google's XLA binaries for EXLA.

Usage

EXLA already depends on this package, so you generally don't need to install it yourself. There is however a number of environment variables that you may want to use in order to customize the variant of XLA binary.

The binaries are always built/downloaded to match the current configuration, so you should set the environment variables in .bash_profile or a similar configuration file so you don't need to export it in every shell session.

`XLA_TARGET`

The default value is cpu, which implies the final the binary supports targeting only the host CPU.

Value	Target environment
cpu
tpu	libtpu
cuda111	CUDA 11.1+, cuDNN
cuda110	CUDA 11.0, cuDNN
cuda102	CUDA 10.2, cuDNN
cuda	CUDA x.y, cuDNN
rocm	ROCm

To use XLA with NVidia GPU you need CUDA and cuDNN compatible with your GPU drivers. See the installation instructions and the cuDNN support matrix for version compatibility. To use precompiled XLA binaries specify a target matching your CUDA version (like cuda111). When building from source it's enough to specify cuda as the target.

`XLA_BUILD`

Defaults to false. If true the binary is built locally, which may be intended if no precompiled binary is available for your target environment. If using XLA as a dependency, you may need to run mix deps.compile xla explicitly after setting this variable. Building has a number of dependencies, see Building from source below.

`XLA_ARCHIVE_URL`

A URL pointing to a specific build of the .tar.gz archive. When using this option you need to make sure the build matches your OS, CPU architecture and the XLA target.

`XLA_CACHE_DIR`

The directory to store the downloaded and built archives in. Defaults to the standard cache location for the given operating system.

Building from source

To build the XLA binaries locally you need to set XLA_BUILD=true and possibly XLA_TARGET. Keep in mind that the compilation usually takes a very long time.

You will need the following installed in your system for the compilation:

Git for fetching Tensorflow source
Bazel v3.7.2 for compiling Tensorflow
Python3 with NumPy installed for compiling Tensorflow

If running on Windows, you will also need:

Common issues

Bazel version

Use bazel --version to check your Bazel version, make sure you are using v3.7.2. Most binaries are available on Github, but it can also be installed with asdf:

asdf plugin-add bazel
asdf install bazel 3.7.2
asdf global bazel 3.7.2

GCC

You may have issues with newer and older versions of GCC. TensorFlow builds are known to work with GCC versions between 7.5 and 9.3. If your system uses a newer GCC version, you can install an older version and tell Bazel to use it with export CC=/path/to/gcc-{version} where version is the GCC version you installed

Python and asdf

Bazel cannot find python installed via the asdf version manager by default. asdf uses a function to lookup the specified version of a given binary, this approach prevents Bazel from being able to correctly build XLA. The error is unknown command: python. Perhaps you have to reshim?. There are two known workarounds:

Use a separate installer or explicitly change your $PATH to point to a Python installation (note the build process looks for python, not python3). For example, on Homebrew on macOS, you would do:
```
export PATH=/usr/local/opt/python@3.9/libexec/bin:/usr/local/bin:$PATH
```
Use the asdf direnv plugin to install direnv 2.20.0. direnv along with the asdf-direnv plugin will explicitly set the paths for any binary specified in your project's .tool-versions files.

If you still get the error, you can also try setting PYTHON_BIN_PATH, like export PYTHON_BIN_PATH=/usr/bin/python3.9.

After doing any of the steps above, it may be necessary to clear the build cache by removing ~/.cache/xla_extension.

GPU support

To build binaries with GPU support, you need all the GPU-specific dependencies (CUDA, ROCm), then you can build with either XLA_TARGET=cuda or XLA_TARGET=rocm. See the XLA_TARGET for more details.

TPU support

All you need is setting XLA_TARGET=tpu.

Apple Silicon

Building on Apple Silicon requires a newer version of Bazel, it's been verified to work with 4.2.1.

Compilation-specific environment variables

You can use the following env vars to customize your build:

BUILD_CACHE - controls where to store Tensorflow source and builds
BUILD_FLAGS - additional flags passed to Bazel
BUILD_MODE - controls to compile opt (default) artifacts or dbg, example: BUILD_MODE=dbg

Runtime flags

You can further configure XLA runtime options with XLA_FLAGS, see: tensorflow/compiler/xla/debug_options_flags.cc for the list of available flags.

Release process

To publish a new version of this package:

Update version in mix.exs.
Run .github/scripts/publish_release.sh.
Wait for the release workflow to build all the binaries.
Publish the package to Hex.

License

Note that the build artifacts are a result of compiling Google XLA, hence are under their own license. See Tensorflow.

Copyright (c) 2020 Sean Moriarity

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at [http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

fire-archive/xla

XLA