MLX Playground

This repository contains machine learning examples implemented using Apple's MLX framework, focusing on efficient implementations for Apple Silicon.

Sparse Auto-Encoder (SAE) [*]

A project exploring sparse auto-encoders and their application to understanding LLM internals. Currently under active development.

Key Features

• Implementation of sparse auto-encoders using MLX
• Tools for analyzing LLM activations
• Focus on understanding feature detection in language models
• Experiments with different sparsity approaches

ChessZero

A chess engine implementation inspired by AlphaZero, using MLX for neural network computations and Monte Carlo Tree Search (MCTS) for move selection.

Key Features

• Neural MCTS implementation with extensive caching
• Highly parallelized self-play and evaluation pipeline
• Process-isolated MCTS for memory safety and parallel execution
• MLX-based neural network with residual blocks
• Automated model selection through competitive self-play evaluation
• Bitboard-based chess engine
• Real-time move evaluation

Architecture

Neural Network

• 19 residual blocks
• 256 filters per layer
• Policy head: 4672 possible moves
• Value head: Position evaluation
• Input: 19-channel board state

Model Configuration:
- Residual Blocks: 19
- Filters: 256
- Policy Output: 4672 moves
- Input Shape: (8, 8, 19)
- Batch Size: 2048

MCTS Implementation

• Process-isolated for memory safety
• Extensive caching system:
  • Position cache
  • Valid moves cache
  • Policy/value cache
  • Transposition table
• Early stopping with clear dominance detection
• Configurable simulation count (default 1000)
• Temperature-based exploration

Training Pipeline

1. Parallel self-play game generation

   • Multiple worker processes generating games simultaneously
   • Configurable number of workers for hardware optimization
   • Process isolation for memory safety and parallel execution

2. Evaluation through self-play

   • Regular evaluation against best model checkpoint
   • Parallel evaluation games for faster assessment
   • Winning evaluation games recycled into training data
   • Automatic model selection based on win rate

3. Training optimization

   • Efficient batch creation from both self-play and evaluation games
   • Regular checkpointing with best model tracking
   • Memory-optimized training process
   • Gradient updates with momentum

Performance Features

• Multi-process game generation for both training and evaluation
• Configurable number of worker processes
• Memory-efficient process isolation
• Progress tracking for individual game workers

Known Limitations

• Memory leaks in core MCTS implementation, fixed through process isolation
• Process isolation adds overhead

Sample Output

  a b c d e f g h
8 · · · · · · · · 8
7 · · · · · ♘ · · 7
6 · · · · · · ♛ · 6
5 · · · ♙ · · · · 5
4 · ♟ · · · · ♝ ♟ 4
3 · · · · ♟ · · · 3
2 · · · ♗ · · ♚ · 2
1 ♔ · · · · · · · 1
  a b c d e f g h

ChessZero Usage

1. Training with parallel processing:

python chesszero/train.py --workers 8  # Adjust worker count based on CPU cores

2. Play against AI:

python chesszero/chess_engine/main.py --mode ai

3. Watch AI self-play:

python chesszero/chess_engine/main.py --mode auto

YOLO Object Detection

A streamlined implementation of YOLOv2 (You Only Look Once v2) object detection using MLX, optimized for Apple Silicon.

Features

• YOLOv2 architecture with anchor boxes
• Training on PASCAL VOC dataset
• Memory-efficient training
• Real-time object detection capabilities
• Optimized for Apple Silicon using MLX

Model Architecture

• Input resolution: 448x448 pixels
• Backbone: darknet-19
• Output: 7x7 grid with 5 anchor boxes per cell
• Anchor box predictions: (x, y, w, h, confidence)
• Classes: 20 PASCAL VOC classes
• Loss: Multi-part loss function (classification, localization, confidence)

Training Modes

1. Development Mode:

python yolo/simple_train.py --mode dev

• Uses small subset of data (10 images)
• Smaller batch size
• Faster iteration for testing changes

2. Full Training:

python yolo/simple_train.py --mode full

• Uses complete dataset
• Larger batch size
• Regular validation and checkpointing

Dataset

The model is trained on PASCAL VOC 2012 with 20 object classes:

• Vehicles: aeroplane, bicycle, boat, bus, car, motorbike, train
• Animals: bird, cat, cow, dog, horse, sheep
• Indoor Objects: bottle, chair, diningtable, pottedplant, sofa, tvmonitor
• People: person

YOLO Usage

1. Setup:

# Clone the repository
git clone https://github.com/yourusername/mlx-playground.git
cd mlx-playground

# Install dependencies
pip install mlx opencv-python pillow numpy

2. Training:

python yolo/train.py \
    --data-dir path/to/VOCdevkit/VOC2012 \
    --save-dir ./checkpoints \
    --batch-size 8 \
    --accumulation-steps 2

Training parameters:

• --batch-size: Number of images per mini-batch
• --accumulation-steps: Number of gradient accumulation steps
• --save-dir: Directory to save model checkpoints
• --data-dir: Path to VOC dataset

3. Detection:

# Image detection
python yolo/detect.py --model path/to/model.npz --image path/to/image.jpg

# Real-time camera detection
python yolo/detect.py --model path/to/model.npz --camera

Implementation Details

• Efficient MLX operations for forward and backward passes
• Gradient accumulation for memory-efficient training
• Non-maximum suppression for post-processing detections
• Configurable confidence thresholds
• Real-time inference optimizations

Project Structure

yolo/
├── model.py      # YOLO model architecture
├── train.py      # Training script
├── loss.py       # Loss function implementation
├── detect.py     # Detection script
└── data/         # Dataset handling
    └── voc.py    # VOC dataset loader

Contributing

Contributions are welcome! Key areas for improvement:

• MCTS memory management
• Evaluation function
• Performance optimizations
• Documentation improvements
• Bug fixes

License

MIT License