wifi-densepose/crates/ruvector-core/README.md

# Ruvector Core

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**The pure-Rust vector database engine behind RuVector -- HNSW indexing, quantization, and SIMD acceleration in a single crate.**

`ruvector-core` is the foundational library that powers the entire [RuVector](https://github.com/ruvnet/ruvector) ecosystem. It gives you a production-grade vector database you can embed directly into any Rust application: insert vectors, search them in under a millisecond, filter by metadata, and compress storage up to 32x -- all without external services. If you need vector search as a library instead of a server, this is the crate.

| | ruvector-core | Typical Vector Database |
|---|---|---|
| **Deployment** | Embed as a Rust dependency -- no server, no network calls | Run a separate service, manage connections |
| **Query latency** | <0.5 ms p50 at 1M vectors with HNSW | ~1-5 ms depending on network and index |
| **Memory compression** | Scalar (4x), Product (8-32x), Binary (32x) quantization built in | Often requires paid tiers or external tools |
| **SIMD acceleration** | SimSIMD hardware-optimized distance calculations, automatic | Manual tuning or not available |
| **Search modes** | Dense vectors, sparse BM25, hybrid, MMR diversity, filtered -- all in one API | Typically dense-only; hybrid and filtering are add-ons |
| **Storage** | Zero-copy mmap with `redb` -- instant loading, no deserialization | Load time scales with dataset size |
| **Concurrency** | Lock-free indexing with parallel batch processing via Rayon | Varies; many require single-writer locks |
| **Dependencies** | Minimal -- pure Rust, compiles anywhere `rustc` runs | Often depends on C/C++ libraries (BLAS, LAPACK) |
| **Cost** | Free forever -- open source (MIT) | Per-vector or per-query pricing on managed tiers |

## Installation

Add `ruvector-core` to your `Cargo.toml`:

```toml
[dependencies]
ruvector-core = "0.1.0"
```

### Feature Flags

```toml
[dependencies]
ruvector-core = { version = "0.1.0", features = ["simd", "uuid-support"] }
```

Available features:
- `simd` (default): Enable SIMD-optimized distance calculations
- `uuid-support` (default): Enable UUID generation for vector IDs

## Key Features

| Feature | What It Does | Why It Matters |
|---------|-------------|----------------|
| **HNSW Indexing** | Hierarchical Navigable Small World graphs for O(log n) approximate nearest neighbor search | Sub-millisecond queries at million-vector scale |
| **Multiple Distance Metrics** | Euclidean, Cosine, Dot Product, Manhattan | Match the metric to your embedding model without conversion |
| **Scalar Quantization** | Compress vectors to 8-bit integers (4x reduction) | Cut memory by 75% with 98% recall preserved |
| **Product Quantization** | Split vectors into subspaces with codebooks (8-32x reduction) | Store millions of vectors on a single machine |
| **Binary Quantization** | 1-bit representation (32x reduction) | Ultra-fast screening pass for massive datasets |
| **SIMD Distance** | Hardware-accelerated distance via SimSIMD | Up to 80K QPS on 8 cores without code changes |
| **Zero-Copy I/O** | Memory-mapped storage loads instantly | No deserialization step -- open a file and search immediately |
| **Hybrid Search** | Combine dense vector similarity with sparse BM25 text scoring | One query handles both semantic and keyword matching |
| **Metadata Filtering** | Apply key-value filters during search | No post-filtering needed -- results are already filtered |
| **MMR Diversification** | Maximal Marginal Relevance re-ranking | Avoid redundant results when top-K are too similar |
| **Conformal Prediction** | Uncertainty quantification on search results | Know when to trust (or distrust) a match |
| **Lock-Free Indexing** | Concurrent reads and writes without blocking | High-throughput ingestion while serving queries |
| **Batch Processing** | Parallel insert and search via Rayon | Saturate all cores for bulk operations |

## Quick Start

### Basic Usage

```rust
use ruvector_core::{VectorDB, DbOptions, VectorEntry, SearchQuery, DistanceMetric};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a new vector database
    let mut options = DbOptions::default();
    options.dimensions = 384;  // Vector dimensions
    options.storage_path = "./my_vectors.db".to_string();
    options.distance_metric = DistanceMetric::Cosine;

    let db = VectorDB::new(options)?;

    // Insert vectors
    db.insert(VectorEntry {
        id: Some("doc1".to_string()),
        vector: vec![0.1, 0.2, 0.3, /* ... 384 dimensions */],
        metadata: None,
    })?;

    db.insert(VectorEntry {
        id: Some("doc2".to_string()),
        vector: vec![0.4, 0.5, 0.6, /* ... 384 dimensions */],
        metadata: None,
    })?;

    // Search for similar vectors
    let results = db.search(SearchQuery {
        vector: vec![0.1, 0.2, 0.3, /* ... 384 dimensions */],
        k: 10,  // Return top 10 results
        filter: None,
        ef_search: None,
    })?;

    for result in results {
        println!("ID: {}, Score: {}", result.id, result.score);
    }

    Ok(())
}
```

### Batch Operations

```rust
use ruvector_core::{VectorDB, VectorEntry};

// Insert multiple vectors efficiently
let entries = vec![
    VectorEntry {
        id: Some("doc1".to_string()),
        vector: vec![0.1, 0.2, 0.3],
        metadata: None,
    },
    VectorEntry {
        id: Some("doc2".to_string()),
        vector: vec![0.4, 0.5, 0.6],
        metadata: None,
    },
];

let ids = db.insert_batch(entries)?;
println!("Inserted {} vectors", ids.len());
```

### With Metadata Filtering

```rust
use std::collections::HashMap;
use serde_json::json;

// Insert with metadata
db.insert(VectorEntry {
    id: Some("product1".to_string()),
    vector: vec![0.1, 0.2, 0.3],
    metadata: Some(HashMap::from([
        ("category".to_string(), json!("electronics")),
        ("price".to_string(), json!(299.99)),
    ])),
})?;

// Search with metadata filter
let results = db.search(SearchQuery {
    vector: vec![0.1, 0.2, 0.3],
    k: 10,
    filter: Some(HashMap::from([
        ("category".to_string(), json!("electronics")),
    ])),
    ef_search: None,
})?;
```

### HNSW Configuration

```rust
use ruvector_core::{DbOptions, HnswConfig, DistanceMetric};

let mut options = DbOptions::default();
options.dimensions = 384;
options.distance_metric = DistanceMetric::Cosine;

// Configure HNSW index parameters
options.hnsw_config = Some(HnswConfig {
    m: 32,                    // Connections per layer (16-64 typical)
    ef_construction: 200,     // Build-time accuracy (100-500 typical)
    ef_search: 100,          // Search-time accuracy (50-200 typical)
    max_elements: 10_000_000, // Maximum vectors
});

let db = VectorDB::new(options)?;
```

### Quantization

```rust
use ruvector_core::{DbOptions, QuantizationConfig};

let mut options = DbOptions::default();
options.dimensions = 384;

// Enable scalar quantization (4x compression)
options.quantization = Some(QuantizationConfig::Scalar);

// Or product quantization (8-32x compression)
options.quantization = Some(QuantizationConfig::Product {
    subspaces: 8,  // Number of subspaces
    k: 256,        // Codebook size
});

let db = VectorDB::new(options)?;
```

## API Overview

### Core Types

```rust
// Main database interface
pub struct VectorDB { /* ... */ }

// Vector entry with optional ID and metadata
pub struct VectorEntry {
    pub id: Option<VectorId>,
    pub vector: Vec<f32>,
    pub metadata: Option<HashMap<String, serde_json::Value>>,
}

// Search query parameters
pub struct SearchQuery {
    pub vector: Vec<f32>,
    pub k: usize,
    pub filter: Option<HashMap<String, serde_json::Value>>,
    pub ef_search: Option<usize>,
}

// Search result with score
pub struct SearchResult {
    pub id: VectorId,
    pub score: f32,
    pub vector: Option<Vec<f32>>,
    pub metadata: Option<HashMap<String, serde_json::Value>>,
}
```

### Main Operations

```rust
impl VectorDB {
    // Create new database with options
    pub fn new(options: DbOptions) -> Result<Self>;

    // Create with just dimensions (uses defaults)
    pub fn with_dimensions(dimensions: usize) -> Result<Self>;

    // Insert single vector
    pub fn insert(&self, entry: VectorEntry) -> Result<VectorId>;

    // Insert multiple vectors
    pub fn insert_batch(&self, entries: Vec<VectorEntry>) -> Result<Vec<VectorId>>;

    // Search for similar vectors
    pub fn search(&self, query: SearchQuery) -> Result<Vec<SearchResult>>;

    // Delete vector by ID
    pub fn delete(&self, id: &str) -> Result<bool>;

    // Get vector by ID
    pub fn get(&self, id: &str) -> Result<Option<VectorEntry>>;

    // Get total count
    pub fn len(&self) -> Result<usize>;

    // Check if empty
    pub fn is_empty(&self) -> Result<bool>;
}
```

### Distance Metrics

```rust
pub enum DistanceMetric {
    Euclidean,   // L2 distance - default for embeddings
    Cosine,      // Cosine similarity (1 - similarity)
    DotProduct,  // Negative dot product (for maximization)
    Manhattan,   // L1 distance
}
```

### Advanced Features

```rust
// Hybrid search (dense + sparse)
use ruvector_core::{HybridSearch, HybridConfig};

let hybrid = HybridSearch::new(HybridConfig {
    alpha: 0.7,  // Balance between dense (0.7) and sparse (0.3)
    ..Default::default()
});

// Filtered search with expressions
use ruvector_core::{FilteredSearch, FilterExpression};

let filtered = FilteredSearch::new(db);
let expr = FilterExpression::And(vec![
    FilterExpression::Equals("category".to_string(), json!("books")),
    FilterExpression::GreaterThan("price".to_string(), json!(10.0)),
]);

// MMR diversification
use ruvector_core::{MMRSearch, MMRConfig};

let mmr = MMRSearch::new(MMRConfig {
    lambda: 0.5,  // Balance relevance (0.5) and diversity (0.5)
    ..Default::default()
});
```

## Performance

### Latency (Single Query)

```
Operation           Flat Index    HNSW Index
---------------------------------------------
Search (1K vecs)    ~0.1ms       ~0.2ms
Search (100K vecs)  ~10ms        ~0.5ms
Search (1M vecs)    ~100ms       <1ms
Insert              ~0.1ms       ~1ms
Batch (1000)        ~50ms        ~500ms
```

### Memory Usage (1M Vectors, 384 Dimensions)

```
Configuration              Memory      Recall
---------------------------------------------
Full Precision (f32)       ~1.5GB      100%
Scalar Quantization        ~400MB      98%
Product Quantization       ~200MB      95%
Binary Quantization        ~50MB       85%
```

### Throughput (Queries Per Second)

```
Configuration              QPS         Latency (p50)
-----------------------------------------------------
Single Thread             ~2,000      ~0.5ms
Multi-Thread (8 cores)    ~50,000     <0.5ms
With SIMD                 ~80,000     <0.3ms
With Quantization         ~100,000    <0.2ms
```

## Configuration Guide

### For Maximum Accuracy

```rust
let options = DbOptions {
    dimensions: 384,
    distance_metric: DistanceMetric::Cosine,
    hnsw_config: Some(HnswConfig {
        m: 64,
        ef_construction: 500,
        ef_search: 200,
        max_elements: 10_000_000,
    }),
    quantization: None,  // Full precision
    ..Default::default()
};
```

### For Maximum Speed

```rust
let options = DbOptions {
    dimensions: 384,
    distance_metric: DistanceMetric::DotProduct,
    hnsw_config: Some(HnswConfig {
        m: 16,
        ef_construction: 100,
        ef_search: 50,
        max_elements: 10_000_000,
    }),
    quantization: Some(QuantizationConfig::Binary),
    ..Default::default()
};
```

### For Balanced Performance

```rust
let options = DbOptions::default(); // Recommended defaults
```

## Building and Testing

### Build

```bash
# Build with default features
cargo build --release

# Build without SIMD
cargo build --release --no-default-features --features uuid-support

# Build for specific target with optimizations
RUSTFLAGS="-C target-cpu=native" cargo build --release
```

### Testing

```bash
# Run all tests
cargo test

# Run with specific features
cargo test --features simd

# Run with logging
RUST_LOG=debug cargo test
```

### Benchmarks

```bash
# Run all benchmarks
cargo bench

# Run specific benchmark
cargo bench --bench hnsw_search

# Run with features
cargo bench --features simd
```

Available benchmarks:
- `distance_metrics` - SIMD-optimized distance calculations
- `hnsw_search` - HNSW index search performance
- `quantization_bench` - Quantization techniques
- `batch_operations` - Batch insert/search operations
- `comprehensive_bench` - Full system benchmarks

## Related Crates

`ruvector-core` is the foundation for platform-specific bindings:

- **[ruvector-node](../ruvector-node/)** - Node.js bindings via NAPI-RS
- **[ruvector-wasm](../ruvector-wasm/)** - WebAssembly bindings for browsers
- **[ruvector-gnn](../ruvector-gnn/)** - Graph Neural Network layer for learned search
- **[ruvector-cli](../ruvector-cli/)** - Command-line interface
- **[ruvector-bench](../ruvector-bench/)** - Performance benchmarks

## Documentation

- **[Main README](../../README.md)** - Complete project overview
- **[Getting Started Guide](../../docs/guide/GETTING_STARTED.md)** - Quick start tutorial
- **[Rust API Reference](../../docs/api/RUST_API.md)** - Detailed API documentation
- **[Advanced Features Guide](../../docs/guide/ADVANCED_FEATURES.md)** - Quantization, indexing, tuning
- **[Performance Tuning](../../docs/optimization/PERFORMANCE_TUNING_GUIDE.md)** - Optimization strategies
- **[API Documentation](https://docs.rs/ruvector-core)** - Full API reference on docs.rs

## Acknowledgments

Built with state-of-the-art algorithms and libraries:

- **[hnsw_rs](https://crates.io/crates/hnsw_rs)** - HNSW implementation
- **[simsimd](https://crates.io/crates/simsimd)** - SIMD distance calculations
- **[redb](https://crates.io/crates/redb)** - Embedded database
- **[rayon](https://crates.io/crates/rayon)** - Data parallelism
- **[memmap2](https://crates.io/crates/memmap2)** - Memory-mapped files

## License

**MIT License** - see [LICENSE](../../LICENSE) for details.

---

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[Documentation](https://docs.rs/ruvector-core) | [Crates.io](https://crates.io/crates/ruvector-core) | [GitHub](https://github.com/ruvnet/ruvector)

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