Transformer Implementation in PyTorch
From Theory to Real-World Application
Master the Transformer architecture from scratch. Learn attention mechanisms, positional encoding, and build a complete German-to-English translation model achieving 30+ BLEU score.
18 chapters— in publication order.
Part I · Chapter 00 · 3 sections · 45 min
Essential knowledge before diving into Transformers
- 0.1Prerequisite Knowledge10m
- 0.2The Core Insight: How Transformers Work15m
- 0.3Softmax and Cross-Entropy Loss20m
Part I · Chapter 01 · 4 sections · 45 min
The evolution of sequence modeling and the Transformer revolution
- 1.1Evolution of Sequence Modeling12m
- 1.2The Transformer Revolution15m
- 1.3Real World Applications and Variants10m
- 1.4Course Roadmap and Project Preview8m
Part I · Chapter 02 · 6 sections · 92 min
Understanding and implementing the core attention mechanism
- 2.1Intuition Behind Attention12m
- 2.2Scaled Dot Product Attention Formula15m
- 2.3Numerical Walkthrough18m
- 2.4Implementing Attention in PyTorch20m
- 2.5Understanding and Implementing Masks15m
- 2.6Attention Visualization and Debugging12m
Part I · Chapter 03 · 5 sections · 69 min
Parallel attention heads for richer representations
- 3.1Why Multiple Heads10m
- 3.2Linear Projections for QKV12m
- 3.3Reshaping for Parallel Heads15m
- 3.4Implementing MultiHeadAttention20m
- 3.5Self vs Cross Attention12m
Part I · Chapter 04 · 6 sections · 87 min
Adding position information to the Transformer
- 4.1The Position Problem10m
- 4.2Sinusoidal Positional Encoding15m
- 4.3Learned Positional Embeddings12m
- 4.4Token Embeddings10m
- 4.5Combined Embedding Layer15m
- 4.6Modern Positional Encodings25m
Part II · Chapter 05 · 5 sections · 70 min
Building vocabulary with subword tokenization
- 5.1Why Subword Tokenization10m
- 5.2Byte Pair Encoding Algorithm15m
- 5.3Implementing BPE from Scratch20m
- 5.4Using SentencePiece for Production15m
- 5.5Special Tokens for Seq2Seq10m
Part III · Chapter 06 · 4 sections · 49 min
The building blocks that complete each layer
- 6.1Position-wise Feed Forward Networks12m
- 6.2Layer Normalization Deep Dive15m
- 6.3Residual Connections10m
- 6.4The Add and Norm Pattern12m
Part III · Chapter 07 · 5 sections · 67 min
Building the complete encoder stack
- 7.1Encoder Layer Architecture12m
- 7.2Implementing TransformerEncoderLayer18m
- 7.3Stacking Encoder Layers12m
- 7.4Complete Encoder Forward Pass15m
- 7.5Source Sentence Encoding10m
Part III · Chapter 08 · 6 sections · 95 min
Building the decoder with masked attention
- 8.1Decoder Architecture Overview12m
- 8.2Causal Masking15m
- 8.3Cross Attention15m
- 8.4Implementing TransformerDecoderLayer18m
- 8.5Complete Transformer Decoder15m
- 8.6Full Encoder-Decoder Transformer20m
Part IV · Chapter 09 · 5 sections · 75 min
Generating sequences token by token
- 9.1Understanding Autoregressive Generation12m
- 9.2Greedy Decoding15m
- 9.3Beam Search18m
- 9.4Sampling Strategies15m
- 9.5KV Caching15m
Part V · Chapter 10 · 5 sections · 74 min
Complete training setup for translation
- 10.1Data Loading and Batching15m
- 10.2Label Smoothing Loss12m
- 10.3Learning Rate Scheduling15m
- 10.4Complete Training Loop20m
- 10.5Checkpointing and Model Selection12m
Part V · Chapter 11 · 4 sections · 52 min
Measuring translation quality
- 11.1Introduction to Translation Metrics10m
- 11.2BLEU Score Implementation15m
- 11.3Other Evaluation Metrics12m
- 11.4Practical Evaluation Pipeline15m
Part VI · Chapter 12 · 4 sections · 55 min
Preparing the translation dataset
- 12.1Multi30k Dataset Overview10m
- 12.2Data Preprocessing15m
- 12.3Vocabulary and Tokenizer Setup15m
- 12.4Data Loading Pipeline15m
Part VI · Chapter 13 · 3 sections · 50 min
Training our Transformer on German-English translation
- 13.1Model Configuration and Setup15m
- 13.2Complete Training Script20m
- 13.3Training Monitoring and Debugging15m
Part VII · Chapter 15 · 3 sections · 45 min
Leveraging pretrained models for translation
- 15.1Introduction to Pretrained Models12m
- 15.2Finetuning mBART18m
- 15.3Advanced Finetuning Techniques15m
Where the book lands in practice.
Training Translation Model
Training our Transformer on German-English translation
Open chapter75 sections. Begin with one.
Chapter 0 — Prerequisites — is where every reader starts.