List of Figures
List of Tables
Author Bios
Foreword
Preface
Contributors

Deep Learning and Transformers: An Introduction
1.1 DEEP LEARNING: A HISTORIC PERSPECTIVE
1.2 TRANSFORMERS AND TAXONOMY
1.2.1 Modified Transformer Architecture
1.2.1.1 Transformer block changes
1.2.1.2 Transformer sublayer changes
1.2.2 Pretraining Methods and Applications
1.3 RESOURCES
1.3.1 Libraries and Implementations
1.3.2 Books
1.3.3 Courses, Tutorials, and Lectures
1.3.4 Case Studies and Details

Transformers: Basics and Introduction
2.1 ENCODER-DECODER ARCHITECTURE
2.2 SEQUENCE TO SEQUENCE
2.2.1 Encoder
2.2.2 Decoder
2.2.3 Training
2.2.4 Issues with RNN-based Encoder Decoder
2.3 ATTENTION MECHANISM
2.3.1 Background
2.3.2 Types of Score-Based Attention
2.3.2.1 Dot Product (multiplicative)
2.3.2.2 Scaled Dot Product or multiplicative
2.3.2.3 Linear, MLP, or additive
2.3.3 Attention-based Sequence to Sequence
2.4 TRANSFORMER
2.4.1 Source and Target Representation
2.4.1.1 Word Embedding
2.4.1.2 Positional Encoding
2.4.2 Attention Layers
2.4.2.1 Self-Attention
2.4.2.2 Multi-Head Attention
2.4.2.3 Masked Multi-Head Attention
2.4.2.4 Encoder-Decoder Multi-Head Attention
2.4.3 Residuals and Layer Normalization
2.4.4 Position-wise Feed-Forward Networks
2.4.5 Encoder
2.4.6 Decoder
2.5 CASE STUDY: MACHINE TRANSLATION
2.5.1 Goal
2.5.2 Data, Tools and Libraries
2.5.3 Experiments, Results and Analysis
2.5.3.1 Exploratory Data Analysis
2.5.3.2 Attention
2.5.3.3 Transformer
2.5.3.4 Results and Analysis
2.5.3.5 Explainability

Bidirectional Encoder Representations from Transformers (BERT)
3.1 BERT
3.1.1 Architecture
3.1.2 Pre-training
3.1.3 Fine-tuning
3.2 BERT VARIANTS
3.2.1 RoBERTa
3.3 APPLICATIONS
3.3.1 TaBERT
3.3.2 BERTopic
3.4 BERT INSIGHTS
3.4.1 BERT Sentence Representation
3.4.2 BERTology
3.5 CASE STUDY: TOPIC MODELING WITH TRANSFORMERS
3.5.1 Goal
3.5.2 Data, Tools, and Libraries
3.5.2.1 Data
3.5.2.2 Compute embeddings
3.5.3 Experiments, Results, and Analysis
3.5.3.1 Building Topics
3.5.3.2 Topic size distribution
3.5.3.3 Visualization of topics
3.5.3.4 Content of topics
3.6 CASE STUDY: FINE-TUNING BERT
3.6.1 Goal
3.6.2 Data, Tools and Libraries
3.6.3 Experiments, Results and Analysis

Multilingual Transformer Architectures
4.1 MULTILINGUAL TRANSFORMER ARCHITECTURES
4.1.1 Basic Multilingual Transformer
4.1.2 Single-Encoder Multilingual NLU
4.1.2.1 mBERT
4.1.2.2 XLM
4.1.2.3 XLM-RoBERTa
4.1.2.4 ALM
4.1.2.5 Unicoder
4.1.2.6 INFOXL
4.1.2.7 AMBER
4.1.2.8 ERNIE-M
4.1.2.9 HITCL
4.1.3 Dual-Encoder Multilingual NLU
4.1.3.1 LaBSE
4.1.3.2 mUSE
4.1.4 Multilingual NLG
4.2 MULTILINGUAL DATA
4.2.1 Pre-training Data
4.2.2 Multilingual Benchmarks
4.2.2.1 Classification
4.2.2.2 Structure Prediction
4.2.2.3 Question Answering
4.2.2.4 Semantic Retrieval
4.3 MULTILINGUAL TRANSFER LEARNING INSIGHTS
4.3.1 Zero-shot Cross-lingual Learning
4.3.1.1 Data Factors
4.3.1.2 Model Architecture Factors
4.3.1.3 Model Tasks Factors
4.3.2 Language-agnostic Cross-lingual Representations
4.4 CASE STUDY
4.4.1 Goal
4.4.2 Data, Tools, and Libraries
4.4.3 Experiments, Results, and Analysis
4.4.3.1 Data Preprocessing
4.4.3.2 Experiments

Transformer Modifications
5.1 TRANSFORMER BLOCK MODIFICATIONS
5.1.1 Lightweight Transformers
5.1.1.1 Funnel-Transformer
5.1.1.2 DeLighT
5.1.2 Connections between Transformer Blocks
5.1.2.1 RealFormer
5.1.3 Adaptive Computation Time
5.1.3.1 Universal Transformers (UT)
5.1.4 Recurrence Relations between Transformer Blocks
5.1.4.1 Transformer-XL
5.1.5 Hierarchical Transformers
5.2 TRANSFORMERS WITH MODIFIED MULTI-HEAD SELF-ATTENTION
5.2.1 Structure of Multi-head Self-Attention
5.2.1.1 Multi-head self-attention
5.2.1.2 Space and time complexity
5.2.2 Reducing Complexity of Self-attention
5.2.2.1 Longformer
5.2.2.2 Reformer
5.2.2.3 Performer
5.2.2.4 Big Bird
5.2.3 Improving Multi-head-attention
5.2.3.1 Talking-Heads Attention
5.2.4 Biasing Attention with Priors
5.2.5 Prototype Queries
5.2.5.1 Clustered Attention
5.2.6 Compressed Key-Value Memory
5.2.6.1 Luna: Linear Unified Nested Attention
5.2.7 Low-rank Approximations
5.2.7.1 Linformer
5.3 MODIFICATIONS FOR TRAINING TASK EFFICIENCY
5.3.1 ELECTRA
5.3.1.1 Replaced token detection
5.3.2 T5
5.4 TRANSFORMER SUBMODULE CHANGES
5.4.1 Switch Transformer
5.5 CASE STUDY: SENTIMENT ANALYSIS
5.5.1 Goal
5.5.2 Data, Tools, and Libraries
5.5.3 Experiments, Results, and Analysis
5.5.3.1 Visualizing attention head weights
5.5.3.2 Analysis

Pretrained and Application-Specific Transformers
6.1 TEXT PROCESSING
6.1.1 Domain-Specific Transformers
6.1.1.1 BioBERT
6.1.1.2 SciBERT
6.1.1.3 FinBERT
6.1.2 Text-to-text Transformers
6.1.2.1 ByT5
6.1.3 Text generation
6.1.3.1 GPT: Generative Pre-training
6.1.3.2 GPT-2
6.1.3.3 GPT-3
6.2 COMPUTER VISION
6.2.1 Vision Transformer
6.3 AUTOMATIC SPEECH RECOGNITION
6.3.1 Wav2vec
2.0
6.3.2 Speech2Text2
6.3.3 HuBERT: Hidden Units BERT
6.4 MULTIMODAL AND MULTITASKING TRANSFORMER
6.4.1 Vision-and-Language BERT (VilBERT)
6.4.2 Unified Transformer (UniT)
6.5 VIDEO PROCESSING WITH TIMESFORMER
6.5.1 Patch embeddings
6.5.2 Self-attention
6.5.2.1 Spatiotemporal self-attention
6.5.2.2 Spatiotemporal attention blocks
6.6 GRAPH TRANSFORMERS
6.6.1 Positional encodings in a graph
6.6.1.1 Laplacian positional encodings
6.6.2 Graph transformer input
6.6.2.1 Graphs without edge attributes
6.6.2.2 Graphs with edge attributes
6.7 REINFORCEMENT LEARNING
6.7.1 Decision Transformer
6.8 CASE STUDY: AUTOMATIC SPEECH RECOGNITION
6.8.1 Goal
6.8.2 Data, Tools, and Libraries
6.8.3 Experiments, Results, and Analysis
6.8.3.1 Preprocessing speech data
6.8.3.2 Evaluation

Interpretability and Explainability Techniques for Transformers
7.1 TRAITS OF EXPLAINABLE SYSTEMS
7.2 RELATED AREAS THAT IMPACT EXPLAINABILITY
7.3 EXPLAINABLE METHODS TAXONOMY
7.3.1 Visualization Methods
7.3.1.1 Backpropagation-based
7.3.1.2 Perturbation-based
7.3.2 Model Distillation
7.3.2.1 Local Approximation
7.3.2.2 Model Translation
7.3.3 Intrinsic Methods
7.3.3.1 Probing Mechanism
7.3.3.2 Joint Training
7.4 ATTENTION AND EXPLANATION
7.4.1 Attention is not Explanation
7.4.1.1 Attention Weights and Feature Importance
7.4.1.2 Counterfactual Experiments
7.4.2 Attention is not not Explanation
7.4.2.1 Is attention necessary for all tasks?
7.4.2.2 Searching for Adversarial Models
7.4.2.3 Attention Probing
7.5 QUANTIFYING ATTENTION FLOW
7.5.1 Information flow as DAG
7.5.2 Attention Rollout
7.5.3 Attention Flow
7.6 CASE STUDY: TEXT CLASSIFICATION WITH EXPLAINABILITY
7.6.1 Goal
7.6.2 Data, Tools, and Libraries
7.6.3 Experiments, Results and Analysis
7.6.3.1 Exploratory Data Analysis
7.6.3.2 Experiments
7.6.3.3 Error Analysis and Explainability

Bibliography
Alphabetical Index