Vision Transformer and MLP-Mixer Architectures

In this repository we release models from the papers

• An Image is Worth 16x16 Words: Transformers for Image Recognition at Scale
• MLP-Mixer: An all-MLP Architecture for Vision
• How to train your ViT? Data, Augmentation, and Regularization in Vision Transformers
• When Vision Transformers Outperform ResNets without Pretraining or Strong Data Augmentations
• LiT: Zero-Shot Transfer with Locked-image text Tuning
• Surrogate Gap Minimization Improves Sharpness-Aware Training

The models were pre-trained on the ImageNet and ImageNet-21k datasets. We provide the code for fine-tuning the released models in JAX/Flax.

The models from this codebase were originally trained in https://github.com/google-research/big_vision/ where you can find more advanced code (e.g. multi-host training), as well as some of the original training scripts (e.g. configs/vit_i21k.py for pre-training a ViT, or configs/transfer.py for transfering a model).

Table of contents:

• Vision Transformer and MLP-Mixer Architectures
  • Colab
  • Installation
  • Fine-tuning a model
  • Vision Transformer
    • Available ViT models
    • Expected ViT results
  • MLP-Mixer
    • Available Mixer models
    • Expected Mixer results
  • LiT models
  • Running on cloud
    • Create a VM
    • Setup VM
  • Bibtex
  • Disclaimers
  • Changelog

Colab

Below Colabs run both with GPUs, and TPUs (8 cores, data parallelism).

The first Colab demonstrates the JAX code of Vision Transformers and MLP Mixers. This Colab allows you to edit the files from the repository directly in the Colab UI and has annotated Colab cells that walk you through the code step by step, and lets you interact with the data.

https://colab.research.google.com/github/google-research/vision_transformer/blob/main/vit_jax.ipynb

The second Colab allows you to explore the >50k Vision Transformer and hybrid checkpoints that were used to generate the data of the third paper "How to train your ViT? ...". The Colab includes code to explore and select checkpoints, and to do inference both using the JAX code from this repo, and also using the popular timm PyTorch library that can directly load these checkpoints as well. Note that a handful of models are also available directly from TF-Hub: sayakpaul/collections/vision_transformer (external contribution by Sayak Paul).

The second Colab also lets you fine-tune the checkpoints on any tfds dataset and your own dataset with examples in individual JPEG files (optionally directly reading from Google Drive).

https://colab.research.google.com/github/google-research/vision_transformer/blob/main/vit_jax_augreg.ipynb

Note: As for now (6/20/21) Google Colab only supports a single GPU (Nvidia Tesla T4), and TPUs (currently TPUv2-8) are attached indirectly to the Colab VM and communicate over slow network, which leads to pretty bad training speed. You would usually want to set up a dedicated machine if you have a non-trivial amount of data to fine-tune on. For details see the Running on cloud section.

Installation

Make sure you have Python>=3.10 installed on your machine.

Install JAX and python dependencies by running:

# If using GPU:
pip install -r vit_jax/requirements.txt

# If using TPU:
pip install -r vit_jax/requirements-tpu.txt

For newer versions of JAX, follow the instructions provided in the corresponding repository linked here. Note that installation instructions for CPU, GPU and TPU differs slightly.

Install Flaxformer, follow the instructions provided in the corresponding repository linked here.

For more details refer to the section Running on cloud below.

Fine-tuning a model

You can run fine-tuning of the downloaded model on your dataset of interest. All models share the same command line interface.

For example for fine-tuning a ViT-B/16 (pre-trained on imagenet21k) on CIFAR10 (note how we specify b16,cifar10 as arguments to the config, and how we instruct the code to access the models directly from a GCS bucket instead of first downloading them into the local directory):

python -m vit_jax.main --workdir=/tmp/vit-$(date +%s) \
    --config=$(pwd)/vit_jax/configs/vit.py:b16,cifar10 \
    --config.pretrained_dir='gs://vit_models/imagenet21k'

In order to fine-tune a Mixer-B/16 (pre-trained on imagenet21k) on CIFAR10:

python -m vit_jax.main --workdir=/tmp/vit-$(date +%s) \
    --config=$(pwd)/vit_jax/configs/mixer_base16_cifar10.py \
    --config.pretrained_dir='gs://mixer_models/imagenet21k'

The "How to train your ViT? ..." paper added >50k checkpoints that you can fine-tune with the [configs/augreg.py] config. When you only specify the model name (the config.name value from [configs/model.py]), then the best i21k checkpoint by upstream validation accuracy ("recommended" checkpoint, see section 4.5 of the paper) is chosen. To make up your mind which model you want to use, have a look at Figure 3 in the paper. It's also possible to choose a different checkpoint (see Colab [vit_jax_augreg.ipynb]) and then specify the value from the filename or adapt_filename column, which correspond to the filenames without .npz from the [gs://vit_models/augreg] directory.

python -m vit_jax.main --workdir=/tmp/vit-$(date +%s) \
    --config=$(pwd)/vit_jax/configs/augreg.py:R_Ti_16 \
    --config.dataset=oxford_iiit_pet \
    --config.base_lr=0.01

Currently, the code will automatically download CIFAR-10 and CIFAR-100 datasets. Other public or custom datasets can be easily integrated, using tensorflow datasets library. Note that you will also need to update vit_jax/input_pipeline.py to specify some parameters about any added dataset.

Note that our code uses all available GPUs/TPUs for fine-tuning.

To see a detailed list of all available flags, run python3 -m vit_jax.train --help.

Notes on memory:

• Different models require different amount of memory. Available memory also depends on the accelerator configuration (both type and count). If you encounter an out-of-memory error you can increase the value of --config.accum_steps=8 -- alternatively, you could also decrease the --config.batch=512 (and decrease --config.base_lr accordingly).
• The host keeps a shuffle buffer in memory. If you encounter a host OOM (as opposed to an accelerator OOM), you can decrease the default --config.shuffle_buffer=50000.

Vision Transformer

by Alexey Dosovitskiy*†, Lucas Beyer*, Alexander Kolesnikov*, Dirk Weissenborn*, Xiaohua Zhai*, Thomas Unterthiner, Mostafa Dehghani, Matthias Minderer, Georg Heigold, Sylvain Gelly, Jakob Uszkoreit and Neil Houlsby*†.

(*) equal technical contribution, (†) equal advising.

Overview of the model: we split an image into fixed-size patches, linearly embed each of them, add position embeddings, and feed the resulting sequence of vectors to a standard Transformer encoder. In order to perform classification, we use the standard approach of adding an extra learnable "classification token" to the sequence.

Available ViT models

We provide a variety of ViT models in different GCS buckets. The models can be downloaded with e.g.:

wget https://storage.googleapis.com/vit_models/imagenet21k/ViT-B_16.npz

The model filenames (without the .npz extension) correspond to the config.model_name in [vit_jax/configs/models.py]

• [gs://vit_models/imagenet21k] - Models pre-trained on ImageNet-21k.
• [gs://vit_models/imagenet21k+imagenet2012] - Models pre-trained on ImageNet-21k and fine-tuned on ImageNet.
• [gs://vit_models/augreg] - Models pre-trained on ImageNet-21k, applying varying amounts of [AugReg]. Improved performance.
• [gs://vit_models/sam] - Models pre-trained on ImageNet with [SAM].
• [gs://vit_models/gsam] - Models pre-trained on ImageNet with [GSAM].

We recommend using the following checkpoints, trained with [AugReg] that have the best pre-training metrics:

The results from the original ViT paper (https://arxiv.org/abs/2010.11929) have been replicated using the models from [gs://vit_models/imagenet21k]: