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data2vec-pytorch

PyTorch implementation of "data2vec: A General Framework for Self-supervised Learning in Speech, Vision and Language" from Meta AI (FAIR)

Disclaimer: This repo's goal is to make data2vec easier to understand hence it's not recommended to use for actual model pretraining but instead you'd better use the official version in fairseq or the ones provided on HuggingFace.

Data2Vec is the first high-performance self-supervised algorithm that learns the same way in multiple modalities, including speech, vision and text. Most machines learn exclusively from labeled data. However, through self-supervised learning, machines are able to learn about the world just by observing it and then figuring out the structure of images, speech or text. This is a more scalable and efficient approach for machines to tackle new complex tasks, such as understanding text for more spoken languages.

In summary, the method is as follows:

  1. The encoder extracts features from the masked inputs. These features are outputs of every transformer/linear layer.
  2. The teacher which is an EMA instance of the encoder (in eval model), extracts features from the unmasked inputs.
  3. Optional normalizations are applied to the layers/outputs of the teacher.
  4. Encoder outputs are regressed by a projection block/layer.
  5. The loss is calculated from encoder outputs and teacher outputs.

You can read the paper for more detail.

Implementation

Data2Vec is already implemented in fairseq in which for all modalities there is a seperate implementation (text, vision, audio). According to the paper:

Our primary is to design a single learning mechanism for different modalities. Despite the unified learning regime, we still use modality-specific features extractors and masking strategies. This makes sense given the vastly different nature of the input data.

This implementation differs in the fact that a single Data2Vec model is provided powered by a custom encoder (implemented using PyTorch + HuggingFace Transformers) and tries to unify the whole concept in a single module. The key concept is that there must be modality-specific feature extractions and masking strategies.

  • Masking: For each modality, the Dataset instance must return the masked source, the target and the mask tensor.

  • Feature Extraction: Features are the outputs from the transformer/attention layers. So the forward method must return outputs from all Encoder blocks of the transformer model. HuggingFace Transformers/Fairseq models return transformer layers outputs separately out of the box.

This implementation uses HuggingFace Transformers models as encoders for Data2Vec which you can inspect in the encoder.py files for each modality. Although, you can provide your own encoder model. Just make sure that your encoder must be Transformer-based according to the paper and outputs from every encoder layer must be provided.

Note: This implementation's goal is to provide the necessary building blocks of Data2Vec so anyone can adapt it to their own use case with ease, so in order to make it easy to get hands on, some functionalities like mixed precision, distributed training, etc are not included to keep it as clean & simple as possible. If you only need to train a standard large scale Data2Vec model use the official repo.

Train

First things first, install the requirements:

pip install -r requirements.txt

NLP

Train a Language Model based on RoBERTa (HuggingFace) on WikiText103

Configure the related properties in text/configs/roberta-pretraining.yaml and run:

python train.py --config text/configs/roberta-pretraining.yaml

Vision

Run a Masked Image modeling training based on BEiT (HuggingFace)

Pass the path to the image dataset in the config file at vision/configs/beit-pretraining.yaml under dataset > path > train/test and modify other properties as you desire and run the following:

python train.py --config vision/configs/beit-pretraining.yaml

Speech

Audio pretraining based on Wav2Vec2 (HuggingFace) on timit dataset. If you want to use other datasets like librispeech provide it in audio/dataset.py (some minor changes to the timit class would do the job because both are loaded from HuggingFace datasets)

Configure other properties as you desire and run the following:

python train.py --config audio/configs/wav2vec2-pretraining.yaml

Pre-trained Weights

Note: The below models' weights were carefully ported from the original checkpoints in the fairseq version.

RoBERTa

Data2Vec model trained with RoBERTa as the encoder (data2vec-roberta-base)

from transformers import AutoModel, AutoConfig
from transformers import RobertaModel

checkpoint = 'arxyzan/data2vec-roberta-base'

# Option 1: load using AutoModel
data2vec_roberta = AutoModel.from_pretrained(checkpoint)

# Option 2: load directly by RobertaModel
data2vec_roberta = RobertaModel.from_pretrained(checkpoint)

BEiT

Data2Vec model trained with BEiT as the encoder (data2vec-beit-base)

from transformers import AutoModel, AutoConfig
from transformers import BeitModel

checkpoint = 'arxyzan/data2vec-beit-base'

# Option 1: load using AutoModel
data2vec_beit = AutoModel.from_pretrained(checkpoint)

# Option 2: load directly by BeitModel
data2vec_beit = BeitModel.from_pretrained(checkpoint)

Wav2Vec2

Data2Vec model trained with Wav2Vec2 as the encoder (data2vec-wav2vec2-base)

from transformers import AutoModel, AutoConfig
from transformers import Wav2Vec2Model

checkpoint = 'arxyzan/data2vec-wav2vec2-base'

# Option 1: load using AutoModel
data2vec_wav2vec2 = AutoModel.from_pretrained(checkpoint)

# Option 2: load directly by Wav2Vec2Model
data2vec_wav2vec2 = Wav2Vec2Model.from_pretrained(checkpoint)

Fine-tuning

  1. Fine-tune using the checkpoints mentioned above:
# Text classification using Roberta model from HuggingFace
from transformers import RobertaModel, RobertaForSequenceClassification

checkpoint = 'arxyzan/data2vec-roberta-base'
# this is exactly a roberta model but trained with data2vec
data2vec_roberta = RobertaModel.from_pretrained(checkpoint)
text_classifier = RobertaForSequenceClassification(data2vec_roberta.config)
# assign `data2vec-roberta` weights to the roberta block of the classifier
text_classifier.roberta = data2vec_roberta
...
  1. In case you trained a model using this codebase, you can fine-tune it by taking out the encoder's state dict from the checkpoint which gives you a HuggingFace model and you can fine-tune it for any downstream task as you'd normally do for HuggingFace models.
# load a checkpoint for finetuning
from transformers import RobertaModel, RobertaConfig
roberta = RobertaModel(RobertaConfig())
checkpoint = torch.load('path/to/data2vec.pt')
roberta_state_dict = checkpoint['encoder']
# load roberta weights from the encoder part of the data2vec model
encoder = roberta.load_state_dict(roberta_state_dict)

# Now fine-tune a regular HuggingFace RoBERTa model
...

Contributions

Any contribution regarding training, development (for Data2Vec2) and issues are welcome!