Semi-supervised image classification using contrastive pretraining with SimCLR

Description

This is a simple image classification model trained with Semi-supervised image classification using contrastive pretraining with SimCLR The training procedure was done as seen in the example on keras.io by András Béres.

The model was trained on STL-10, which includes ten classes: airplane, bird, car, cat, deer, dog, horse, monkey, ship, truck.

Metrics

There is a public W&B dashboard available here which illustrates the difference in different metrics such as accuracy of a baseline supervised trained model, a purely unsupervised model (pretrain) and the supervised finetuned model based on the unsupervised.

Background

(by András Béres on keras.io ) Semi-supervised learning is a machine learning paradigm that deals with partially labeled datasets. When applying deep learning in the real world, one usually has to gather a large dataset to make it work well. However, while the cost of labeling scales linearly with the dataset size (labeling each example takes a constant time), model performance only scales sublinearly with it. This means that labeling more and more samples becomes less and less cost-efficient, while gathering unlabeled data is generally cheap, as it is usually readily available in large quantities.

Semi-supervised learning offers to solve this problem by only requiring a partially labeled dataset, and by being label-efficient by utilizing the unlabeled examples for learning as well.

In this example, I pretrained an encoder with contrastive learning on the STL-10 semi-supervised dataset using no labels at all, and then fine-tuned it using only its labeled subset.