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Flaxformer: transformer architectures in JAX/Flax

Flaxformer is a transformer library for primarily NLP and multimodal research at Google. It is used for many NLP research use cases, providing both off-the-shelf BERT and T5 models, and several research projects built on shared components.

General library goals

The Flaxformer library aims to provide transformer models that are:

• High performance: Models are annotated for use with the PJIT API, enabling them to be used for training the largest models.
• Reusable: Components have self-contained configuration, and high-level modules like encoders, decoders, etc. don't make too many assumptions about what their sub-modules look like.
• Tested: We aim to employ a reasonable amount of unit testing, and write tests whenever bugs are encountered. However no guarantees are provided.
• Maintainble: We have created a versioning strategy for our modules so code refactors can take place which alter the module structure. This is tricky in Flax, because Flax generates a tree of parameters based on the exact module structure. Our approach lets us maintain compatibility with previously trained model checkpoints.

Code locations

Modeling components such as dense attention, layer norms, and MLP blocks can be found in the components/ directory.

Higher-level classes which combine these components can be found in the architectures/ directory. The current architecture file for the T5 family of models is architectures/t5/t5_architecture.py; this is a mid-level API requiring sub-components to be configured. A high-level starting point, exposing fewer parameters, is architectures/t5/t5_1_1.py.

Relationship to other codebases

Flaxformer is primarily used by other research projects, in particular T5X. We hope to release examples demonstrating the integration of these codebases soon.

If you would like to use Flaxformer independently of T5X, please see the unit tests for examples instantiating the models. In the medium-term future, we hope to provide more stand-alone examples of Flaxformer use.

Contributions

Unfortunately, we cannot accept contributions to the Flaxformer repo at this time, so any pull requests will be automatically closed - but please file issues as needed!

Installing dependencies and running tests

First, we recommend installing a few dependencies manually,

pip3 install numpy sentencepiece tensorflow>=2.14.0

This is a workaround to prevent pip backtracking on package versions; we believe there is either a version conflict in upstream packages, or pip's constraint solving process is imperfect.

Then, check out this repository. In its root directory, you can install it along with test dependencies by running,

pip3 install '.[testing]'

If you like, you can run the tests from pytest with the following invocation,

python3 -m pytest

Uninstalling

If you need to uninstall Flaxformer, please run,

pip3 uninstall flaxformer

Troubleshooting

Flax deps

Flaxformer is developed in close collaboration with the Flax team. There may be bugs if your Flax version is not up to date. To install the latest version from GitHub, please run,

pip3 uninstall flax
pip3 install git+https://github.com/google/flax

Note

Flaxformer is a project maintained by a team in Google Research. It is not an official Google product.