ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformers (CVPR 2024)

[Project page] [Paper]

"ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformers", by Narges Norouzi, Svetlana Orlova, Daan de Geus, and Gijs Dubbelman, CVPR 2024.

ALGM applied to Segmenter

In this repository, Adaptive Local-then-Global Token Merging (ALGM) is applied to Segmenter: Transformer for Semantic Segmentation by Robin Strudel*, Ricardo Garcia*, Ivan Laptev and Cordelia Schmid, ICCV 2021.

The provided code extends the original code for Segmenter.

Installation

Installation follows the installation of the original Segmenter code. Specifically: define os environment variables pointing to your checkpoint and dataset directory, put in your .bashrc:

export DATASET=/path/to/dataset/dir

1. Clone the repo

git clone https://github.com/tue-mps/algm-segmenter.git
cd algm-segmenter

2. Setting up the virtualenv

Install PyTorch (>= 1.13.1 # For scatter_reduce).

# create environment
conda create -n algm python==3.10
conda activate algm
# install pytorch with cuda
conda install pytorch==1.13.1 torchvision==0.14.1 torchaudio==0.13.1 pytorch-cuda=11.7 -c pytorch -c nvidia
# install required packages
pip install -r requirements.txt

3. Setting up the ALGM package

cd algm
# set up the ALGM package
python setup.py build develop

4. Prepare the datasets To download ADE20K, use the following command:

python -m segm.scripts.prepare_ade20k $DATASET

Similar preparation scripts also exist for Cityscapes and Pascal-Context.

Training

To train Segmenter + ALGM using ViT-S/16 with specific configurations on the ADE20K dataset, use the command provided below. The model is configured to apply ALGM at layers 1 and 5, with a merging window size of 2x2 and a threshold of 0.88.

python -m segm.train  --log-dir runs/vit_small_layers_1_5_T_0.88/ \
                      --dataset ade20k \
                      --backbone vit_small_patch16_384 \
                      --decoder mask_transformer \
                      --patch-type algm \
                      --selected-layers 1 5 \
                      --merging-window-size 2 2 \
                      --threshold 0.88 

For more examples of training commands, see TRAINING.

Inference

To perform an evaluation using Segmenter + ALGM on ADE20K, execute the following command. Ensure you replace path_to_checkpoint.pth with the actual path to your checkpoint file. Additionally, make sure the variant.yaml file is located in the same directory as your checkpoint file. For additional examples covering all available backbones and datasets, refer to the jobs directory.

Note: Please use the specific values for the selected-layers and threshold options for each backbone. You can find these values in the variant.yaml file.

# single-scale baseline evaluation:
python -m segm.eval.miou path_to_checkpoint.pth \
          ade20k \
          --singlescale \
          --patch-type pure 

# Explanation:
# --singlescale: Evaluates the model using a single scale of input images.
# --patch-type pure: Uses the standard patch processing without any modifications.

# single-scale baseline + ALGM evaluation:
python -m segm.eval.miou path_to_checkpoint.pth \
          ade20k \
          --singlescale \
          --patch-type algm \
          --selected-layers 1 5  \
          --merging-window-size 2 2 \
          --threshold 0.88

# Explanation:
# --patch-type algm: Applies the ALGM patch type.
# --selected-layers 1 5: Specifies which layers of the network to apply ALGM. In this case, layers 1 and 5.
# --merging-window-size 2 2: Sets the size of the merging window for the ALGM algorithm, here it is 2x2.
# --threshold 0.90: Sets the confidence threshold for merging patches in ALGM, where 0.90 stands for 90% confidence.

Benchmarking

To calculate the Im/Sec and GFLOPs, execute the following commands. Again, ensure you replace path_to_checkpoint_directory with the actual path to your checkpoint file. Additionally, make sure the variant.yaml file is located in the same directory as your checkpoint file.

Note: Please use the specific values for the selected-layers and threshold options for each backbone. You can find these values in the variant.yaml file.

# Im/sec
python -m segm.speedtest --model-dir path_to_checkpoint_directory \
        --dataset ade20k \
        --batch-size 1 \
        --patch-type algm \
        --selected-layers 1 5 \
        --merging-window-size 2 2 \
        --threshold 0.88

# GFLOPs
python -m segm.flops --model-dir path_to_checkpoint_directory \
          --dataset ade20k \
          --batch-size 1 \
          --patch-type algm \
          --selected-layers 1 5 \
          --merging-window-size 2 2 \
          --threshold 0.88

Results and Models

Below, we provide the results for different network settings and datasets.

ADE20K

Segmenter models with ViT backbone:

Backbone	Crop size	mIoU	Im/sec (BS=32)	GFLOPs	Download
ViT-Ti/16	512x512	38.1	287	12.8	model	config
ViT-Ti/16 + ALGM	512x512	38.9	388	8.4	model	config
ViT-S/16	512x512	45.3	134	38.6	model	config
ViT-S/16 + ALGM	512x512	46.4	192	26.3	model	config
ViT-B/16	512x512	48.5	51	130	model	config
ViT-B/16 + ALGM	512x512	49.4	73	91	model	config
ViT-L/16	640x640	51.8	10	672	model	config
ViT-L/16 + ALGM	640x640	52.7	16	438	model	config

Pascal Context

Backbone	Crop size	mIoU	Im/sec (BS=32)	GFLOPs	Download
ViT-S/16	480x480	53.0	172	32.1	model	config
ViT-S/16 + ALGM	480x480	53.2	217	24.6	model	config

Cityscapes

Backbone	Crop size	mIoU	Im/sec (BS=32)	GFLOPs	Download
ViT-S/16	768x768	76.5	41	116	model	config
ViT-S/16 + ALGM	768x768	76.9	65	76	model	config

Upcoming Features

- [x] Training and Inference code
- [x] Flops and Speedtest code
- [ ] ViT-Large checkpoints for Cityscapes and Pascal-Context datasets
- [ ] COCO-Stuff dataset support
- [ ] Code for merging visulization 

BibTex

@inproceedings{norouzi2024algm,
  title={{ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformers}},
  author={Norouzi, Narges and Sorlova, Svetlana and {de Geus}, Daan and Dubbelman, Gijs},
  booktitle={IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
  year={2024}
}

Acknowledgements

This code uses the ToMe repository for implementing the global merging module and extends the official Segmenter code. The Vision Transformer code in the original repository is based on timm library and the semantic segmentation training and evaluation pipelines are based on mmsegmentation.