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RAG in Swift with Local LLM Integration

Table of Contents

Introduction

This project implements a Retrieval Augmented Generation (RAG) system in Swift, designed to work with local Large Language Models (LLMs) like Ollama. It enables context-aware AI responses in iOS and macOS applications by combining document retrieval with natural language generation.

Prerequisites

  • Xcode 12.0 or later
  • iOS 14.0+ / macOS 11.0+
  • Ollama installed on your local machine

Setup

  1. Clone this repository
  2. Ensure Ollama is running on your local machine
  3. Add the Swift files to your Xcode project

Code Explanation

Main Components

  1. Document: Represents a single document in the knowledge base
  2. RAGSystem: The core class that handles document storage, retrieval, and response generation

Key Methods

class RAGSystem {
    func addDocument(_ document: Document)
    func searchRelevantDocuments(for query: String, limit: Int = 3) -> [Document]
    func generateResponse(for query: String) -> String
    private func callOllama(with prompt: String) -> String
}

How It Works

  1. Document Embedding: When a document is added, it's converted into a numerical representation (embedding) using Apple's NLP framework.
func addDocument(_ document: Document) {
    let words = document.content.components(separatedBy: .whitespacesAndNewlines)
    let embeddings = words.compactMap { embeddingModel.vector(for: $0) }
    let averageEmbedding = average(embeddings)
    document.embedding = averageEmbedding
    documents.append(document)
}
  1. Relevant Document Retrieval: When a query is received, the system finds the most relevant documents using cosine similarity.
func searchRelevantDocuments(for query: String, limit: Int = 3) -> [Document] {
    let queryEmbedding = getEmbedding(for: query)
    let sortedDocuments = documents.sorted { doc1, doc2 in
        guard let emb1 = doc1.embedding, let emb2 = doc2.embedding else { return false }
        return cosineSimilarity(queryEmbedding, emb1) > cosineSimilarity(queryEmbedding, emb2)
    }
    return Array(sortedDocuments.prefix(limit))
}
  1. Response Generation: The system uses the retrieved documents as context and sends a prompt to Ollama for response generation.
func generateResponse(for query: String) -> String {
    let relevantDocs = searchRelevantDocuments(for: query)
    let context = relevantDocs.map { $0.content }.joined(separator: " ")
    let prompt = """
    Context: \(context)
    Human: \(query)
    Assistant: Based on the given context, I will provide a concise and accurate answer to the question.
    """
    return callOllama(with: prompt)
}
  1. Ollama Integration: The system communicates with the local Ollama instance via HTTP requests.
private func callOllama(with prompt: String) -> String {
    let ollamaURL = URL(string: "http://localhost:11434/api/generate")!
    var request = URLRequest(url: ollamaURL)
    request.httpMethod = "POST"
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    
    let parameters: [String: Any] = [
        "model": "llama3.2:3b",
        "prompt": prompt,
        "stream": false
    ]
    
    // HTTP request and response handling...
}

Usage

Here's a basic example of how to use the RAG system:

let ragSystem = RAGSystem()

// Add documents to the knowledge base
ragSystem.addDocument(Document(id: "1", content: "Swift is a programming language developed by Apple."))
ragSystem.addDocument(Document(id: "2", content: "Swift is designed to be safe, fast, and expressive."))

// Generate a response
let query = "What is Swift and why was it created?"
let response = ragSystem.generateResponse(for: query)
print(response)

Customization

  • Embedding Model: The system uses Apple's NLEmbedding. You can experiment with other embedding techniques for potentially better results.
  • Similarity Metric: Currently using cosine similarity. You might try other metrics like Euclidean distance.
  • Ollama Model: The code uses "llama3.2:3b". You can change this to any other model available in your Ollama installation.

Troubleshooting

  1. Ollama Connection Issues:
    • Ensure Ollama is running (ollama run llama3.2:3b)
    • Check if the URL and port (11434) are correct for your setup
  2. Slow Response Times:
    • Consider reducing the document limit in searchRelevantDocuments
    • Use a smaller Ollama model if available
  3. Out of Memory Errors:
    • Implement pagination or limit the number of documents stored in memory

Remember to handle errors gracefully in a production environment, especially network-related issues when calling Ollama.

This project demonstrates the power of combining Swift's native capabilities with local LLMs. Feel free to contribute, report issues, or suggest improvements!