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MILAN: Masked Image Pretraining on Language Assisted Representation

This repository contains the PyTorch implementation of the paper MILAN: Masked Image Pretraining on Language Assisted Representation.

• This repo was built upon the MAE repo. Installation and preparation follow that repo.

Prepare the dataset

• We use ImageNet-1K. Download the images.

• Extract the training data:

mkdir train && mv ILSVRC2012_img_train.tar train/ && cd train
tar -xvf ILSVRC2012_img_train.tar && rm -f ILSVRC2012_img_train.tar
find . -name "*.tar" | while read NAME ; do mkdir -p "${NAME%.tar}"; tar -xvf "${NAME}" -C "${NAME%.tar}"; rm -f "${NAME}"; done
cd ..

• Extract the validation data and move the images to subfolders:

mkdir val && mv ILSVRC2012_img_val.tar val/ && cd val && tar -xvf ILSVRC2012_img_val.tar
wget -qO- https://raw.githubusercontent.com/soumith/imagenetloader.torch/master/valprep.sh | bash

Pretraining

Example of applying MILAN to pretrain ViT-B/16 on ImageNet-1K using 8 GPUs:

python -m torch.distributed.launch --nproc_per_node=8 --use_env main_pretrain.py \
    --model mae_vit_base_patch16 \
    --batch_size 256 \
    --accum_iter 2 \
    --mask_ratio 0.75 \
    --epochs 400 \
    --warmup_epochs 40 \
    --blr 1.5e-4 \
    --weight_decay 0.05 \
    --data_path /dataset/imagenet \
    --output_dir ./milan_vit_base_pretrain_400epoch_useclip_changedecoder_attnmask \ 
    --log_dir ./milan_vit_base_pretrain_400epoch_useclip_changedecoder_attnmask \
    --use_clip \
    --change_decoder \
    --attn_mask

• The available --model choices are listed in models_milan.py.
• Effective batch size is 256 (--batch_size per GPU) * 2 (--accum_iter gradient accumulation) * 8 (GPUs) = 4096.
• Effective learning rate is 1.5e-4 (--blr base learning rate) * 4096 (effective batch size) / 256 = 2.4e-3.
• --mask_ratio: percentage of patches to remove.
• --epochs: total pretraining epochs, --warmup_epochs: learning rate warmup epochs.
• We apply --weight decay of 0.05 during pretraining.
• We use the ViT-B/16 CLIP image encoder obtained from here to produce the reconstruction targets during pretraining.
• --change_decoder: switch to the prompting decoder.
• --attn_mask: switch to the semantic aware masking strategy.
• Training time is ~39h using 8 40GB A100 GPUs for 400 epochs.

Finetuning and linear probing

• Example of finetuning the pretrained ViT-B/16 on ImageNet-1K:

OMP_NUM_THREADS=1 python -m torch.distributed.launch --nproc_per_node=8 main_finetune.py \
    --accum_iter 1 \
    --batch_size 128 \
    --model vit_base_patch16 \
    --finetune ./milan_vit_base_pretrain_400epoch_useclip_changedecoder_attnmask/checkpoint-399.pth \
    --epochs 100 \
    --blr 1e-4 --layer_decay 0.65 \
    --weight_decay 0.05 --drop_path 0.1 --mixup 0.8 --cutmix 1.0 --reprob 0.25 \
    --dist_eval --data_path /data/imagenet \
    --output_dir ./milan_vit_base_finetune_pretrain400epochuseclipchangedecoderattnmask \ 
    --log_dir ./milan_vit_base_finetune_pretrain400epochuseclipchangedecoderattnmask \
    --global_pool

• Example of performing linear probing on the pretrained ViT-B/16:

OMP_NUM_THREADS=1 python -m torch.distributed.launch --nproc_per_node=8 main_linprobe.py \
    --accum_iter 1 \
    --batch_size 2048 \
    --model vit_base_patch16 \
    --cls_token \
    --finetune ./milan_vit_base_pretrain_400epoch_useclip_changedecoder_attnmask/checkpoint-399.pth \
    --epochs 100 \
    --blr 0.05 \
    --weight_decay 0.0 \
    --dist_eval --data_path /data/imagenet \
    --output_dir ./milan_vit_base_linearprobe_pretrain400epochuseclipchangedecoderattnmask \
    --log_dir ./milan_vit_base_linearprobe_pretrain400epochuseclipchangedecoderattnmask

Checkpoints

We provide the pretrained ViT-B/16 and ViT-L/16 checkpoints.

Citation

If you find this repository helpful, please consider citing:

@article{MILAN2022,
  title   = {MILAN: Masked Image Pretraining on Language Assisted Representation},
  author  = {Hou, Zejiang and Sun, Fei and Chen, Yen-Kuang and Xie, Yuan and Kung, Sun-Yuan},
  journal = {arXiv preprint arXiv:2208.06049},
  year    = {2022},
}