Pre-trained Axon models for easy inference and boosted training.

Bumblebee provides state-of-the-art, configurable Axon models. On top of that, it streamlines the process of loading pre-trained models by integrating with Hugging Face Hub and 🤗 Transformers.

Usage

You can load one of the supported models by specifying the model repository:

{:ok, model_info} = Bumblebee.load_model({:hf, "bert-base-uncased"})
{:ok, tokenizer} = Bumblebee.load_tokenizer({:hf, "bert-base-uncased"})

Then you are ready to make predictions:

inputs = Bumblebee.apply_tokenizer(tokenizer, "Hello Bumblebee!")
outputs = Axon.predict(model_info.model, model_info.params, inputs)

Tasks

On top of bare models, Bumblebee provides a number of "servings" that act as end-to-end pipelines for specific tasks.

serving = Bumblebee.Text.fill_mask(model_info, tokenizer)
Nx.Serving.run(serving, "The capital of [MASK] is Paris.")
#=> %{
#=>   predictions: [
#=>     %{score: 0.9279842972755432, token: "france"},
#=>     %{score: 0.008412551134824753, token: "brittany"},
#=>     %{score: 0.007433671969920397, token: "algeria"},
#=>     %{score: 0.004957548808306456, token: "department"},
#=>     %{score: 0.004369721747934818, token: "reunion"}
#=>   ]
#=> }

As you can see the serving takes care of pre-processing the text input, runs the model and also post-processes its output into more structured data. In the above example we run serving on the fly, however for production usage you can start serving as a process and it will automatically batch requests from multiple clients. Processing inputs in batches is usually much more efficient, since it can take advantage of parallel capabilities of the target device, which is particularly relevant in case of GPU. For more details read the Nx.Serving docs.

For more examples see the Examples notebook.

Note

The models are generally large, so make sure to configure an efficient Nx backend, such as EXLA or Torchx.

HuggingFace Hub

HuggingFace Hub is a platform hosting models, datasets and demo apps (Spaces), all using Git repositories (with Git LFS for large files). For further information check out the Hub documentation and explore the model repositories.

Models

Model repositories are regular Git repositories, therefore they can store arbitrary files. However, most repositories store models saved using the Python Transformers library. Bumblebee is an Elixir counterpart of Transformers and allows for importing those models, as long as they are implemented in Bumblebee.

A repository in the Transformers format does not store an actual model, only the trained parameters and a configuration file. The configuration file specifies the model type (e.g. BERT) and high-level properties, such as the number layers and their size. The model implementation lives in the library code (both Transformers and Bumblebee). When loading a model, the library fetches the configuration and builds a matching model, then it fetches the trained parameters to pair them with the model. The key takeaway is that in order to use any given model, it needs to have an implementation in Bumblebee.

Model repository

Here is a list of files commonly found in a repository following the Transformers format.

• config.json - model configuration, specifies the model type and model-specific options. You can think of this as a blueprint for how the model should be constructed

• pytorch_model.bin - raw model parameters (tensors) serialized from a PyTorch model using PyTorch format (supported by Bumblebee)

• model.safetensors - raw model parameters (tensors) serialized from a PyTorch model using Safetensors (supported by Bumblebee)

• flax_model.msgpack, tf_model.h5 - raw model parameters (tensors) serialized from Flax and Tensorflow models respectively (not supported by Bumblebee)

• tokenizer.json, tokenizer_config.json - tokenizer configuration, describes how to convert text input to model inputs (tensors). See Tokenizer support

• preprocessor_config.json - featurizer configuration, describes how to convert real-world input (image, audio) to model inputs (tensors)

• generation_config.json - a set of configuration options specific to text generation, such as token sampling strategy and various constraints

Model support

As pointed out above, in order to load a model, the given model type must be implemented in Bumblebee. To find out whether the model is supported you can call Bumblebee.load_model({:hf, "model-repo"}) or use this tool to run a number of checks against the repository.

If you prefer to poke around the code, open the config.json file in the model repository and copy the class name under "architectures". Next, search Bumblebee codebase for that keyword. If you find a match, this indicates the model is supported.

Also note that certain repositories include multiple models in separate repositories, for example stabilityai/stable-diffusion-2. In such case use Bumblebee.load_model({:hf, "model-repo", subdir: "..."}).

Tokenizer support

The Transformers library distinguishes two types of tokenizer implementations:

• "slow tokenizer" - a tokenizer implemented in Python and stored as tokenizer_config.json and a couple extra files

• "fast tokenizer" - a tokenizer implemented in Rust and stored in a single file - tokenizer.json

Bumblebee relies on the Rust implementations (through bindings to Tokenizers) and therefore always requires the tokenizer.json file. Many repositories only include files for a "slow tokenizer". When you stumble upon such repository, there are two options you can try.

First, if the repository is clearly a fine-tuned version of another model, you can look for tokenizer.json in the original model repository. For example, textattack/bert-base-uncased-yelp-polarity only includes tokenizer_config.json, but it is a fine-tuned version of bert-base-uncased, which does include tokenizer.json. Consequently, you can safely load the model from textattack/bert-base-uncased-yelp-polarity and tokenizer from bert-base-uncased.

Otherwise, the Transformers library includes conversion rules to load a "slow tokenizer" and convert it to a corresponding "fast tokenizer", which is possible in most cases. You can generate the tokenizer.json file using this tool. Once successful, you can follow the steps to submit a PR adding tokenizer.json to the model repository. Note that you do not have to wait for the PR to be merged, instead you can copy commit SHA from the PR and load the tokenizer with Bumblebee.load_tokenizer({:hf, "model-repo", revision: "..."}).