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Self-Supervised Learning — Pre-training Revolution

Expert TopicsSelf-Supervised Learning🟢 Free Lesson

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Advanced Topics

Self-Supervised Learning — Learning Without Labels

Master self-supervised learning techniques that leverage unlabeled data to learn powerful representations. The foundation of modern NLP and computer vision.

  • Contrastive Learning — Learning by comparing similar and dissimilar examples
  • Masked Language Modeling — BERT-style pre-training on text
  • SimCLR — Simple framework for contrastive learning of visual representations

"The best way to learn is to teach yourself."

Self-Supervised Learning — Complete Guide

Self-supervised learning creates labels from the data itself, enabling training on massive unlabeled datasets.


Self-Supervised Learning Landscape

Self-Supervised Learning TaxonomySelf-Supervised LearningContrastive MethodsNon-Contrastive MethodsGenerative / PredictiveSimCLRMoCoCLIPBYOLDINOBYOLSimSiamBarlowBERTGPTMAEBARTContrastivePull positive pairs togetherPush negative pairs apartLoss: InfoNCE, NT-XentRequires negative pairsNon-ContrastiveNo negative pairs neededUse stop-gradient, predictionLoss: MSE, cosine similaritySimpler, often betterGenerative / PredictivePredict missing parts of inputMasked tokens, patches, next wordLoss: Cross-entropy, MSEBERT, GPT, MAE

Why Self-Supervised?


Contrastive Learning (SimCLR)

SimCLR: A Simple Framework for Contrastive Learning📷Image xOriginalAugmentx̃ᵢ (view 1)Random crop + colorx̃ⱼ (view 2)Random crop + blurShared f(·)zᵢ = f(x̃ᵢ)zⱼ = f(x̃ⱼ)g(·)hᵢ = g(zᵢ)hⱼ = g(zⱼ)NT-Xent Lossℒᵢⱼ = −log(exp(sim(hᵢ,hⱼ)/τ)Σₖ exp(sim(hᵢ,hₖ)/τ))τ = temperature, k ∈ {1,...,2N}Key Insights1. Data augmentation defines what's "similar" — strong augmentations → better representations2. Projection head g(·) is crucial for training, but z (before g) is better for downstream tasksPositive PairSame image, different viewsNegative PairsDifferent images, pushed apartBatch as negativesFor batch of N pairs:2(N-1) negative pairs per anchorLarger batches → more negatives → better

Masked Language Modeling (BERT/MAE)

Masked Modeling: Predicting Hidden PartsBERT: Masked Token PredictionThecat[MASK]onthe[MASK].Mask 15% of tokens randomlyTransformer Encoder (12-24 layers)Thecatsatontherug.Predict masked tokens: ℒ = −Σ log p(xₘ|x_¬ₘ)MAE: Masked AutoencoderMask 75% of patches (higher ratio than BERT)ViT Encoder (only on visible patches)Lightweight Decoder → Reconstruct masked patchesLoss: MSE between predicted and original patches

BYOL: Bootstrap Your Own Latent


Fine-Tuning Strategies

Pre-train → Fine-tune PipelinePhase 1: Pre-trainingUnlabeled Data (100M-1B samples)Self-Supervised ObjectiveLearned Representations theta-starCost: 1000s of GPU hoursTransferPhase 2: Fine-tuningLabeled Data (100-10K samples per task)Full Fine-tuneLinear Probe OnlyFull fine-tune: Update all layers (better but expensive)Linear probe: Freeze backbone, train classifier (faster)Cost: Minutes to hours per task

Key Takeaways


What to Learn Next

-> BERT and Encoder Models — Complete Guide Learn about bert and encoder models — complete guide.

-> GPT Architecture — Decoder-Only Transformers Complete Guide Learn about gpt architecture — decoder-only transformers complete guide.

-> Transfer Learning — Pre-trained Models Complete Guide Learn about transfer learning — pre-trained models complete guide.

-> Transformers — Attention Is All You Need Complete Guide Learn about transformers — attention is all you need complete guide.

-> Meta-Learning — Learning to Learn Learn about meta-learning — learning to learn.

-> GANs — Generative Adversarial Networks Complete Guide Learn about gans — generative adversarial networks complete guide.

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