# BDU Rust Migration - Phase 1 Status

**Date**: 2025-10-17  
**Phase**: 1 - Synaptogenesis Hot Path  
**Status**: 🟡 In Progress - Implementation Complete, Testing Required

---

## What Was Implemented

### 1. Rust Crate Structure
Created new `feagi-bdu` crate with proper hierarchy:

```
feagi-rust/crates/feagi-bdu/
├── Cargo.toml                      # Dependencies and build config
├── src/
│   ├── lib.rs                      # Public API
│   ├── types.rs                    # Core types (Position, Dimensions, etc.)
│   ├── connectivity/
│   │   ├── mod.rs                  # Connectivity module
│   │   ├── synaptogenesis.rs      # Main entry point
│   │   └── rules/
│   │       ├── mod.rs
│   │       └── projector.rs       # ⭐ Critical hot path implementation
│   ├── spatial/
│   │   └── mod.rs                  # Spatial hashing (Phase 2)
│   └── ffi.rs                      # PyO3 Python bindings
```

### 2. Core Implementation

#### `syn_projector` - The Critical Bottleneck
- **Python performance**: 40 seconds for 128×128×3 → 128×128×1
- **Rust target**: <100ms (400x faster)
- **Features**:
  - Vectorized coordinate generation
  - Pre-allocated result vectors
  - Optimized bounds checking
  - Parallel batch processing with rayon

#### Key Functions Implemented:
- ✅ `syn_projector()` - Single neuron projection
- ✅ `syn_projector_batch()` - Parallel batch processing
- ✅ `calculate_axis_projection()` - Per-axis scaling logic
- ✅ `apply_transpose()` - Axis transposition

### 3. Python Integration

#### Bridge Module
`feagi/bdu/connectivity/rust_bridge.py`
- Automatic fallback if Rust not available
- Feature flag for easy enable/disable
- Performance logging
- API compatibility with Python version

#### Usage:
```python
from feagi.bdu.connectivity.rust_bridge import (
    syn_projector_rust, 
    RUST_AVAILABLE,
    enable_rust_synaptogenesis
)

# Check availability
if RUST_AVAILABLE:
    # Use high-performance Rust implementation
    positions = syn_projector_rust(
        src_area, dst_area, neuron_id,
        src_dims, dst_dims, location
    )
```

### 4. Testing
- ✅ Rust unit tests in `projector.rs`
- ✅ Test cases for scale up/down/same size
- ✅ Bounds checking tests
- ✅ FFI compatibility smoke tests
- ⏳ Integration tests with Python (pending build)
- ⏳ Performance benchmarks (pending build)

---

## Build Instructions

### Prerequisites
```bash
# Rust toolchain
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup update stable

# Python development headers
# macOS: included with Xcode
# Linux: apt-get install python3-dev
```

### Build Rust Extension
```bash
cd /Users/nadji/code/FEAGI-2.0/feagi_core/feagi-rust

# Build in release mode (optimized)
cargo build --release --package feagi-bdu

# Build Python bindings
cd crates/feagi-bdu
maturin develop --release
```

### Verify Installation
```python
python3 -c "
from feagi.bdu.connectivity.rust_bridge import RUST_AVAILABLE
print(f'Rust BDU Available: {RUST_AVAILABLE}')
"
```

---

## Integration Steps

### Step 1: Modify Python Synaptogenesis

Update `feagi/bdu/connectivity/rules/functions.py`:

```python
def syn_projector(
    src_area_id, dst_area_id, src_neuron_id,
    src_subregion, connectome_manager,
    transpose=None, project_last_layer_of=None
):
    """Project neurons with optional Rust acceleration."""
    
    # Try Rust implementation first
    try:
        from feagi.bdu.connectivity.rust_bridge import (
            syn_projector_rust, RUST_AVAILABLE
        )
        
        if RUST_AVAILABLE:
            src_dims = src_area.dimensions
            dst_dims = dst_area.dimensions
            neuron_pos = connectome_manager.get_neuron_position(src_neuron_id)
            
            # Convert transpose string to indices if needed
            transpose_indices = _convert_transpose(transpose)
            
            # Call Rust (100-400x faster)
            positions = syn_projector_rust(
                src_area_id, dst_area_id, src_neuron_id,
                src_dims, dst_dims, neuron_pos,
                transpose_indices, project_last_layer_of
            )
            
            logger.info(f"[RUST-BDU] Projected {len(positions)} positions (Rust)")
            return positions
            
    except Exception as e:
        logger.warning(f"[RUST-BDU] Rust projection failed, using Python: {e}")
    
    # Python fallback (existing implementation)
    return _syn_projector_python(...)
```

### Step 2: Run Performance Test

```bash
cd /Users/nadji/code/FEAGI-2.0/feagi_core

# Test projection mapping (should be <1s instead of 40s)
python3 -c "
from feagi.bdu.connectivity.rules.functions import syn_projector
import time

start = time.time()
# ... run projection test ...
elapsed = time.time() - start
print(f'Projection time: {elapsed:.2f}s')
"
```

---

## Performance Expectations

### Before (Python Only)
- 128×128×3 → 128×128×1: **40 seconds**
- ~49,000 source neurons processed
- Sequential processing
- 3 optimization passes already applied

### After (Rust)
- 128×128×3 → 128×128×1: **<100ms** (target)
- Same workload
- Parallel processing with rayon
- SIMD-optimized operations
- **Expected: 400x faster**

---

## Current Status

### ✅ Complete
- [x] Rust crate structure
- [x] Core `syn_projector` implementation
- [x] FFI bindings via PyO3
- [x] Python bridge module
- [x] Unit tests
- [x] Documentation

### ⏳ In Progress
- [ ] Build and test Rust extension
- [ ] Integrate with Python synaptogenesis
- [ ] Performance benchmarking
- [ ] Integration testing

### 📋 Next Steps (Phase 2)
- [ ] Migrate remaining morphology functions
- [ ] Integrate Morton spatial hash
- [ ] Add remaining connectivity rules
- [ ] Comprehensive benchmarking

---

## Testing Plan

### 1. Unit Tests (Rust)
```bash
cd feagi-rust/crates/feagi-bdu
cargo test
```

### 2. Python Integration Tests
```bash
cd feagi_core
pytest tests/bdu/test_synaptogenesis.py -v -k projector
```

### 3. Performance Benchmark
```bash
python3 tests/performance/bdu/test_synaptogenesis_performance.py
```

### 4. Correctness Validation
- Run same projection in Python and Rust
- Compare results (should be identical)
- Validate all edge cases

---

## Known Limitations (Phase 1)

1. **Only PROJECTOR morphology implemented**
   - Other morphologies (NEIGHBOR, BLOCK, etc.) use Python fallback
   - Phase 2+ will add remaining morphologies

2. **Position→Neuron lookup still in Python**
   - Rust returns positions
   - Python converts positions to neuron IDs
   - Phase 2 will integrate spatial hash for full Rust pipeline

3. **No batch processing optimization yet**
   - Currently processes one neuron at a time
   - Batch API exists but not integrated
   - Phase 2 will optimize for batch operations

---

## Troubleshooting

### Build Failures

**Error: `maturin not found`**
```bash
pip install maturin
```

**Error: `pyo3` version mismatch**
```bash
cargo update
```

**Error: Python headers not found**
```bash
# macOS
xcode-select --install

# Linux
sudo apt-get install python3-dev
```

### Runtime Issues

**ImportError: `feagi_bdu` not found**
- Run `maturin develop --release` in crates/feagi-bdu
- Check Python can import: `python3 -c "import feagi_bdu"`

**Rust slower than expected**
- Ensure release build: `--release` flag
- Check CPU architecture optimization
- Run benchmarks with `cargo bench`

---

## Success Criteria

✅ **Phase 1 Complete When**:
1. Rust extension builds successfully
2. Python can import and use `feagi_bdu`
3. 128×128×3 projection completes in <1 second (down from 40s)
4. All integration tests pass
5. Results match Python implementation exactly

---

## References

- **Assessment**: `BDU_RUST_MIGRATION_ASSESSMENT.md`
- **Python Synaptogenesis**: `feagi/bdu/connectivity/synaptogenesis.py`
- **Python Rules**: `feagi/bdu/connectivity/rules/functions.py`
- **Rust Implementation**: `feagi-rust/crates/feagi-bdu/src/connectivity/rules/projector.rs`

---

**Next Action**: Build and test the Rust extension, then integrate with Python synaptogenesis.

