Unofficial implementation for MoCo: Momentum Contrast for Unsupervised Visual Representation Learning

Highlight

1. Effective. Carefully implement important details such as ShuffleBN and distributed Queue mentioned in the paper to reproduce the reported results.
2. Efficient. The implementation is based on pytorch DistributedDataParallel and Apex automatic mixed precision. It only takes about 40 hours to train MoCo on imagenet dataset with 8 V100 gpus. The time cost is smaller than 3 days reported in original MoCo paper.

Requirements

The following enverionments is tested:

• Anaconda with python >= 3.6
• pytorch>=1.3, torchvision, cuda=10.1/9.2
• others: pip install termcolor opencv-python tensorboard
• [Optional] apex: automatic mixed precision training.

Train and eval on imagenet

• The pre-training stage:

  data_dir="./data/imagenet100"
  output_dir="./output/imagenet/K65536"
  python -m torch.distributed.launch --master_port 12347 --nproc_per_node=8 \
      train.py \
      --data-dir ${data_dir} \
      --dataset imagenet \
      --nce-k 65536 \
      --output-dir ${output_dir}

  The log, checkpoints and tensorboard events will be saved in ${output_dir}. Set --amp-opt-level to O1, O2, or O3 for mixed precision training. Run python train.py --help for more help.

• The linear evaluation stage:

  python -m torch.distributed.launch --nproc_per_node=4 \
      eval.py \
      --dataset imagenet \
      --data-dir ${data_dir} \
      --pretrained-model ${output_dir}/current.pth \
      --output-dir ${output_dir}/eval

  The checkpoints and tensorboard log will be saved in ${output_dir}/eval. Set --amp-opt-level to O1, O2, or O3 for mixed precision training. Run python eval.py --help for more help.

Pre-trained weights

Pre-trained model checkpoint and tensorboard log for K = 16384 and 65536 on imagenet dataset can be downloaded from OneDrive.

BTW, the hyperparameters is also stored in model checkpoint, you can get full configs in the checkpoints like this:

import torch
ckpt = torch.load('model.pth')
ckpt['opt']

Performance comparison with original paper

K	Acc@1 (ours)	Acc@1 (MoCo paper)
16384	59.89 (model)	60.4
65536	60.79 (model)	60.6

Notes

The MultiStepLR of pytorch1.4 is broken (See pytorch/pytorch#33229 for more details). So if you are using pytorch1.4, you should not set --lr-scheduler to step. You can use cosine instead.

Acknowledgements

A lot of codes is borrowed from CMC and lemniscate.