PyTorch SimCLR: A Simple Framework for Contrastive Learning of Visual Representations

Blog post with full documentation: Exploring SimCLR: A Simple Framework for Contrastive Learning of Visual Representations

See also PyTorch Implementation for BYOL.

Installation

$ conda env create --name simclr --file env.yml
$ conda activate simclr
$ python run.py

Config file

Before running SimCLR, make sure you choose the correct running configurations on the config.yaml file.

# A batch size of N, produces 2 * (N-1) negative samples. Original implementation uses a batch size of 8192
batch_size: 512 

# Number of epochs to train
epochs: 40

# Frequency to eval the similarity score using the validation set
eval_every_n_epochs: 1

# Specify a folder containing a pre-trained model to fine-tune. If training from scratch, pass None.
fine_tune_from: 'resnet-18_80-epochs'

# Frequency to which tensorboard is updated
log_every_n_steps: 50

# l2 Weight decay magnitude, original implementation uses 10e-6
weight_decay: 10e-6

# if True, training is done using mixed precision. Apex needs to be installed in this case.
fp16_precision: False 

# Model related parameters
model:
  # Output dimensionality of the embedding vector z. Original implementation uses 2048
  out_dim: 256 
  
  # The ConvNet base model. Choose one of: "resnet18" or "resnet50". Original implementation uses resnet50
  base_model: "resnet18"

# Dataset related parameters
dataset:
  s: 1
  
  # dataset input shape. For datasets containing images of different size, this defines the final 
  input_shape: (96,96,3) 
  
  # Number of workers for the data loader
  num_workers: 0
  
  # Size of the validation set in percentage
  valid_size: 0.05

# NTXent loss related parameters
loss:
  # Temperature parameter for the contrastive objective
  temperature: 0.5 
  
  # Distance metric for contrastive loss. If False, uses dot product. Original implementation uses cosine similarity.
  use_cosine_similarity: True

Feature Evaluation

Feature evaluation is done using a linear model protocol.

Features are learned using the STL10 train+unsupervised set and evaluated in the test set;

Check the notebook for reproducibility.

Linear Classifier	Feature Extractor	Architecture	Feature dimensionality	Projection Head dimensionality	Epochs	STL10 Top 1
Logistic Regression	PCA Features	-	256	-		36.0%
KNN	PCA Features	-	256	-		31.8%
Logistic Regression (LBFGS)	SimCLR	ResNet-18	512	256	40	70.3%
KNN	SimCLR	ResNet-18	512	256	40	66.2%
Logistic Regression (LBFGS)	SimCLR	ResNet-18	512	256	80	72.9%
KNN	SimCLR	ResNet-18	512	256	80	69.8%
Logistic Regression (Adam)	SimCLR	ResNet-18	512	256	100	75.4%
Logistic Regression (Adam)	SimCLR	ResNet-50	2048	128	40	74.6%
Logistic Regression (Adam)	SimCLR	ResNet-50	2048	128	80	77.3%