Grepai Chunking

# GrepAI Chunking Configuration

This skill covers how GrepAI splits code files into chunks for embedding, and how to optimize chunking for your codebase.

## When to Use This Skill

- Optimizing search accuracy
- Adjusting for code style (verbose vs. concise)
- Troubleshooting search results
- Understanding how indexing works

## What is Chunking?

Chunking is the process of splitting source files into smaller segments for embedding:

```
┌─────────────────────────────────────┐
│         Large Source File           │
│         (1000+ tokens)              │
└─────────────────────────────────────┘
                  ↓
┌─────────┐ ┌─────────┐ ┌─────────┐
│ Chunk 1 │ │ Chunk 2 │ │ Chunk 3 │
│ ~512    │ │ ~512    │ │ ~512    │
│ tokens  │ │ tokens  │ │ tokens  │
└─────────┘ └─────────┘ └─────────┘
                  ↓
          Each chunk gets
          its own embedding
```

## Why Chunking Matters

Embedding models have optimal input sizes:
- **Too large chunks:** Less precise search results
- **Too small chunks:** Lost context, fragmented results
- **Just right:** Good balance of precision and context

## Configuration

### Basic Settings

```yaml
# .grepai/config.yaml
chunking:
  size: 512      # Tokens per chunk
  overlap: 50    # Overlap between chunks
```

### Understanding Parameters

#### Chunk Size

The target number of tokens per chunk.

| Size | Effect |
|------|--------|
| 256 | More precise, less context |
| 512 | Balanced (default) |
| 1024 | More context, less precise |

#### Overlap

Tokens shared between adjacent chunks. Preserves context at boundaries.

| Overlap | Effect |
|---------|--------|
| 0 | No overlap, may lose context at boundaries |
| 50 | Standard overlap (default) |
| 100 | More context, larger index |

## Visualization

With size=512 and overlap=50:

```
File: auth.go (1000 tokens)

Chunk 1: tokens 1-512
         ┌────────────────────────────────────┐
         │ func Login(user, pass)...          │
         └────────────────────────────────────┘
                                    ↘
                              50 token overlap
                                    ↙
Chunk 2: tokens 463-974
         ┌────────────────────────────────────┐
         │ ...validate credentials...         │
         └────────────────────────────────────┘
                                    ↘
                              50 token overlap
                                    ↙
Chunk 3: tokens 925-1000
         ┌──────────────┐
         │ ...return    │
         └──────────────┘
```

## Recommended Settings by Language

### Verbose Languages (Java, C#)

```yaml
chunking:
  size: 768    # Larger to capture full methods
  overlap: 75
```

### Concise Languages (Go, Python)

```yaml
chunking:
  size: 512    # Standard size
  overlap: 50
```

### Very Concise (Rust, Zig)

```yaml
chunking:
  size: 384    # Smaller for precise results
  overlap: 40
```

## Recommended Settings by Codebase

### Small Functions (Microservices)

```yaml
chunking:
  size: 384    # Capture individual functions
  overlap: 40
```

### Large Classes (Monolith)

```yaml
chunking:
  size: 768    # Capture more context
  overlap: 100
```

### Mixed Codebase

```yaml
chunking:
  size: 512    # Balanced default
  overlap: 50
```

## How Tokens are Counted

GrepAI uses approximate token counting:
- ~4 characters = 1 token (for English text)
- Code varies based on identifiers and syntax

Example:
```go
func calculateTotal(items []Item) float64 {
    total := 0.0
    for _, item := range items {
        total += item.Price * float64(item.Quantity)
    }
    return total
}
```
≈ 45 tokens

## Impact on Index Size

Larger overlap = more chunks = larger index:

| Size | Overlap | Chunks per 10K tokens | Index Impact |
|------|---------|----------------------|--------------|
| 512 | 0 | ~20 | Smallest |
| 512 | 50 | ~22 | Standard