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Expediting Vision Transformers via Token Reorganizations

This repository contains PyTorch evaluation code, training code and pretrained EViT models for the ICLR 2022 Spotlight paper:

Not All Patches are What You Need: Expediting Vision Transformers via Token Reorganizations

Youwei Liang, Chongjian Ge, Zhan Tong, Yibing Song, Jue Wang, Pengtao Xie

The proposed EViT method reduces computation by progressively discarding or fusing inattentive tokens in Vision Transformers, as illustrated in the following figure.

EViT obtains competitive tradeoffs in terms of speed / precision:

If you use this code for a paper please cite:

@inproceedings{liang2022evit,
title={Not All Patches are What You Need: Expediting Vision Transformers via Token Reorganizations},
author={Youwei Liang and Chongjian Ge and Zhan Tong and Yibing Song and Jue Wang and Pengtao Xie},
booktitle={International Conference on Learning Representations},
year={2022},
url={https://openreview.net/forum?id=BjyvwnXXVn_}
}

Model Zoo

We provide EViT-DeiT-S models pretrained on ImageNet 2012.

Preparation

The reported results in the paper were obtained with models trained using Python3.6 and the following packages

torch==1.9.0
torchvision==0.10.0
timm==0.4.12
tensorboardX==2.4
torchprofile==0.0.4
lmdb==1.2.1
pyarrow==5.0.0
einops==0.4.1

These packages can be installed by running pip install -r requirements.txt.

Data preparation

Download and extract ImageNet train and val images from http://image-net.org/. The directory structure is the standard layout for the torchvision datasets.ImageFolder, and the training and validation data is expected to be in the train/ folder and val folder respectively:

/path/to/imagenet/
  train/
    class1/
      img1.jpeg
    class2/
      img2.jpeg
  val/
    class1/
      img3.jpeg
    class/2
      img4.jpeg

We use the same datasets as in DeiT. You can optionally use an LMDB dataset for ImageNet by building it using folder2lmdb.py and passing --use-lmdb to main.py, which may speed up data loading.

Usage

First, clone the repository locally:

git clone https://github.com/youweiliang/evit.git

Change directory to the cloned repository by running cd evit, install necessary packages, and prepare the datasets.

Training

To train EViT/0.7-DeiT-S on ImageNet, set the datapath (path to dataset) and logdir (logging directory) in run_code.sh properly and run bash ./run_code.sh (--nproc_per_node should be modified if necessary). Note that the batch size in the paper is 16x128=2048.

Set --base_keep_rate in run_code.sh to use a different keep rate, and set --fuse_token to configure whether to use inattentive token fusion.

Training/Finetuning on higher resolution images

To training on images with a (higher) resolution h, set --input-size h in run_code.sh.

Multinode training

Please refer to DeiT for multinode training using Slurm and submitit.

Finetuning

First set the datapath, logdir, and ckpt (the model checkpoint for finetuning) in run_code.sh, and then run bash ./finetune.sh.

Evaluation

To evaluate a pre-trained EViT/0.7-DeiT-S model on ImageNet val with a single GPU run (replacing checkpoint with the actual file):

python3 main.py --model deit_small_patch16_shrink_base --fuse_token --base_keep_rate 0.7 --eval --resume checkpoint --data-path /path/to/imagenet

You can also pass --dist-eval to use multiple GPUs for evaluation.

Throughput

You can measure the throughput of the model by passing --test_speed or --only_test_speed to main.py. We also provide a script speed_test.py for comparing the throughput of many vision backbones (as shown in Figure 4 in the paper).

Visualization

You can visualize the masked image (with image patches dropped/fused) by a command like this:

python3 main.py --model deit_small_patch16_shrink_base --fuse_token --base_keep_rate 0.7 --visualize_mask --n_visualization 64 --resume checkpoint --data-path /path/to/imagenet

License

This repository is released under the Apache 2.0 license as found in the LICENSE file.

Acknowledgement

We would like to think the authors of DeiT and timm, based on which this codebase was built.