Retrieval

Table of Contents Introduction Foundations: Retrieval‑Augmented Generation (RAG) 2.1. Classic RAG Pipeline 2.2. Limitations of Text‑Only RAG Vision‑Language Models (VLMs) – A Quick Primer 3.1. Contrastive vs. Generative VLMs 3.2. Popular Architectures (CLIP, BLIP, Flamingo, LLaVA) Why Multimodal Retrieval Matters Designing a Multimodal RAG System 5.1. Data Indexing: Images, Text, and Beyond 5.2. Cross‑Modal Embedding Spaces 5.3. Retrieval Strategies (Late Fusion, Early Fusion, Hybrid) 5.4. Augmenting the Generator Practical Example: Building an Image‑Grounded Chatbot 6.1. Dataset Preparation 6.2. Index Construction (FAISS + CLIP) 6.3. Retrieval Code Snippet 6.4. Prompt Engineering for the Generator Training Considerations & Fine‑Tuning 7.1. Contrastive Pre‑training vs. Instruction Tuning 7.2. Efficient Hard‑Negative Mining 7.3. Distributed Training Tips Evaluation Metrics for Multimodal Retrieval‑Augmented Systems Challenges and Open Research Questions Future Directions Conclusion Resources Introduction The last few years have witnessed an explosion of retrieval‑augmented generation (RAG) techniques that combine a large language model (LLM) with a knowledge store. By pulling relevant passages from an external corpus, RAG systems can answer questions that lie far outside the model’s pre‑training window, reduce hallucinations, and keep responses up‑to‑date. ...

Introduction The explosion of unstructured data—images, video, audio, text, and sensor streams—has forced modern search engines to move beyond traditional keyword matching. Multimodal search refers to the capability of retrieving relevant items across different media types using a single query that may itself be multimodal (e.g., an image plus a short text caption). At the heart of this capability lies vector similarity search: every item is embedded into a high‑dimensional vector space where semantic similarity translates to geometric proximity. While single‑node approximate nearest neighbor (ANN) libraries such as Faiss, Annoy, or Milvus can handle millions of vectors, real‑world deployments often need to serve billions of vectors, guarantee low latency under heavy load, and support hybrid queries that combine vector similarity with traditional filters (date ranges, categories, user permissions, etc.). ...

Introduction Retrieval‑Augmented Generation (RAG) has become the de‑facto architecture for building knowledge‑intensive language systems. By coupling a retriever—typically a dense vector search over a large corpus—with a generator that conditions on the retrieved passages, RAG can produce answers that are both fluent and grounded in external data. However, two practical bottlenecks often limit the fidelity of such pipelines: Noisy or sub‑optimal retrieval results – the initial retrieval step (e.g., using a bi‑encoder) may return passages that are only loosely related to the query, leading the generator to hallucinate or produce vague answers. Limited context windows in the generator – even when the retrieved set is perfect, many modern LLMs can only ingest a few hundred to a few thousand tokens, forcing developers to truncate or rank‑order passages heuristically. Two complementary techniques have emerged to address these pain points: ...

Table of Contents Introduction Background: Vector Search & Retrieval‑Augmented Generation (RAG) Challenges of Large‑Scale Production Deployments Fundamentals of Quantization 4.1 Scalar vs. Vector Quantization 4.2 Product Quantization (PQ) and Variants Quantization Techniques for Vector Search 5.1 Uniform (Scalar) Quantization 5.2 Product Quantization (PQ) 5.3 Optimized Product Quantization (OPQ) 5.4 Additive Quantization (AQ) 5.5 Binary & Hamming‑Based Quantization Integrating Quantization into RAG Pipelines 6.1 Index Construction 6.2 Query Processing Performance Metrics and Trade‑offs Practical Implementation Walk‑throughs 8.1 FAISS Example: Training & Using PQ 8.2 ScaNN Example: End‑to‑End Pipeline Hyper‑parameter Tuning Strategies Real‑World Case Studies Best Practices & Common Pitfalls 12Future Directions Conclusion Resources Introduction Retrieval‑Augmented Generation (RAG) has become the de‑facto paradigm for building LLM‑powered applications that need up‑to‑date, factual knowledge. At the heart of any RAG system lies a vector search engine that can quickly locate the most relevant passages, documents, or multimodal embeddings from a corpus that can easily stretch into billions of items. ...

Introduction The rapid rise of multi‑modal deep learning—systems that jointly process text, images, video, audio, and even sensor data—has created a new bottleneck: efficient similarity search over massive embedding collections. Modern models such as CLIP, BLIP, or Whisper generate high‑dimensional vectors (often 256–1,024 dimensions) for each modality, and downstream tasks (e.g., cross‑modal retrieval, recommendation, or knowledge‑base augmentation) rely on fast nearest‑neighbor (NN) look‑ups. Traditional single‑node vector stores (FAISS, Annoy, HNSWlib) quickly hit scalability limits when the index grows beyond a few hundred million vectors or when latency requirements dip below 10 ms. The solution is to scale vector databases horizontally, distributing data and query processing across many machines while preserving high recall and low latency. ...