SimCLR-pytorch

An implementation of SimCLR with DistributedDataParallel (1GPU : 1Process) in pytorch.
This allows scalability to batch size of 4096 (suggested by authors) using 64 gpus, each with batch size of 64 at a resolution of 224x224x3 in FP32 (see below for FP16 support).

Usage Single GPU

NOTE0: this will not produce SOTA results, but is good for debugging. The authors use a batch size of 4096+ for SOTA.
NOTE1: Setup your github ssh tokens; if you get an authentication issue from the git clone this is most likely it.

> git clone --recursive git+ssh://git@github.com/jramapuram/SimCLR.git
# DATADIR is the location of imagenet or anything that works with imagefolder.
> ./docker/run.sh "python main.py --data-dir=$DATADIR \  
                                  --batch-size=64 \  
                                  --num-replicas=1 \  
                                  --epochs=100" 0  # add --debug-step to do a single minibatch

The bash script docker/run.sh pulls the appropriate docker container.
If you want to setup your own environment use:

• environment.yml (conda) in addition to
• requirements.txt (pip)

or just take a look at the Dockerfile in docker/Dockerfile.

Usage SLURM

Setup stuff according to the slurm bash script. Then:

> cd slurm && sbatch run.sh

Usage custom cluster / AWS, etc

1. Start each replica worker pointing to the master using --distributed-master=.
2. Set the total number of replicas appropriately using --num-replicas=.
3. Set each node to have a unique --distributed-rank= ranging from [0, num_replicas).
4. Ensure network connectivity between workers. You will get NCCL errors if there are resolution problems here.
5. Profit.

For example, with a 2 node setup run the following on the master node:

python main.py \
     --epochs=100 \
     --data-dir=<YOUR_DATA_DIR> \
     --batch-size=128 \                   # divides into 64 per node
     --convert-to-sync-bn \
     --visdom-url=http://MY_VISDOM_URL \  # optional, not providing uses tensorboard
     --visdom-port=8097 \                 # optional, not providing uses tensorboard
     --num-replicas=2 \                   # specifies total available nodes, 2 in this example     
     --distributed-master=127.0.0.1 \
     --distributed-port=29301 \
     --distributed-rank=0 \               # rank-0 is the master
     --uid=simclrv00_0

and the following on the child node:

export MASTER=<IP_ADDR_OF_MASTER_ABOVE>
python main.py \
     --epochs=100 \
     --data-dir=<YOUR_DATA_DIR> \
     --batch-size=128 \                   # divides into 64 per node
     --convert-to-sync-bn \
     --visdom-url=http://MY_VISDOM_URL \  # optional, not providing uses tensorboard
     --visdom-port=8097 \                 # optional, not providing uses tensorboard
     --num-replicas=2 \                   # specifies total available nodes, 2 in this example
     --distributed-master=$MASTER \
     --distributed-port=29301 \
     --distributed-rank=1 \               # rank-1 is this child, increment for extra nodes
     --uid=simclrv00_0

Setup data

Grab imagenet, do standard pre-processing and use --data-dir=${DATA_DIR}. Note: This SimCLR implementation expects two pytorch imagefolder locations: train and test as opposed to val in the preprocessor above.

FP16 support

If you have GPUs that works well with FP16, you can try the --half flag.
This will allow faster training with larger batch sizes (~95 with a 12Gb GPU memory).
If training doesn't work well try chaning the AMP optimization level here.

IO bound / Slow data processing?

Try increasing --workers-per-replica for dataloading or placing your dataset on a drive with larger IOPS.
Optionally, you can also try to use the Nvidia DALI image loading backend by specifying --task=dali_multi_augment_image_folder. However, the latter is missing the grayscale and gaussian blur augmentations, so model performance might be degraded.

Visualize results

This implementation supports tensorboard and visdom.
Omitting the --visdom-url and --visdom-port args defaults to tensorboard (which stores in ./runs).

Citation

Cite the original authors on doing some great work:

@article{chen2020simple,
  title={A Simple Framework for Contrastive Learning of Visual Representations},
  author={Chen, Ting and Kornblith, Simon and Norouzi, Mohammad and Hinton, Geoffrey},
  journal={arXiv preprint arXiv:2002.05709},
  year={2020}
}

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