pywebnn 0.5.1

EXPERIMENTAL: Python bindings for W3C WebNN API - Neural network graph validation, ONNX/CoreML conversion, and cross-platform execution with CPU/GPU/NPU support

rustnn / PyWebNN

A Rust implementation of WebNN graph handling with Python bindings that implement the W3C WebNN API specification.

---

[WARNING] EXPERIMENTAL - DO NOT USE IN PRODUCTION

This is an early-stage experimental implementation for research and exploration. Many features are incomplete, untested, or may change significantly.

---

What is rustnn?

rustnn provides:

• Rust Library: Validates WebNN graphs and converts to ONNX/CoreML formats
• Python API: Complete W3C WebNN API implementation via PyO3 bindings
• Runtime Backends: Execute on CPU, GPU, or Neural Engine with backend selection at context creation
• Real Examples: Complete MobileNetV2 (99.60% accuracy) and Transformer text generation

Installation

Python Package (PyWebNN)

PyPI Package (v0.4.0+):

# Install with bundled ONNX Runtime - no additional dependencies needed
pip install pywebnn

# Works immediately with actual execution (no zeros)

Build from Source (For Development):

git clone https://github.com/tarekziade/rustnn.git
cd rustnn
make python-dev  # Sets up venv and builds with ONNX Runtime + CoreML
source .venv-webnn/bin/activate

Requirements: Python 3.11+, NumPy 1.20+

Note: Version 0.4.0+ includes bundled ONNX Runtime. Earlier versions (0.3.0 and below) had no backends and returned zeros.

Rust Library

[dependencies]
rustnn = "0.1"

Quick Start

import webnn
import numpy as np

# Create ML context with device hints
ml = webnn.ML()
context = ml.create_context(accelerated=False)  # CPU execution
builder = context.create_graph_builder()

# Build a simple graph: output = relu(x + y)
x = builder.input("x", [2, 3], "float32")
y = builder.input("y", [2, 3], "float32")
z = builder.add(x, y)
output = builder.relu(z)

# Compile the graph
graph = builder.build({"output": output})

# Execute with real data
x_data = np.array([[1, -2, 3], [4, -5, 6]], dtype=np.float32)
y_data = np.array([[-1, 2, -3], [-4, 5, -6]], dtype=np.float32)
results = context.compute(graph, {"x": x_data, "y": y_data})

print(results["output"])  # [[0. 0. 0.] [0. 0. 0.]]

# Optional: Export to ONNX
context.convert_to_onnx(graph, "model.onnx")

Backend Selection

Following the W3C WebNN Device Selection spec, backends are selected via hints:

# CPU-only execution
context = ml.create_context(accelerated=False)

# Request GPU/NPU (platform selects best available)
context = ml.create_context(accelerated=True)

# Request high-performance (prefers GPU)
context = ml.create_context(accelerated=True, power_preference="high-performance")

# Request low-power (prefers NPU/Neural Engine)
context = ml.create_context(accelerated=True, power_preference="low-power")

Platform-Specific Backends:

• NPU: CoreML Neural Engine (Apple Silicon macOS only)
• GPU: ONNX Runtime GPU (cross-platform) or CoreML GPU (macOS)
• CPU: ONNX Runtime CPU (cross-platform)

Examples

Complete MobileNetV2 Image Classification

# Download pretrained weights (first time only)
bash scripts/download_mobilenet_weights.sh

# Run on different backends
python examples/mobilenetv2_complete.py examples/images/test.jpg --backend cpu
python examples/mobilenetv2_complete.py examples/images/test.jpg --backend gpu
python examples/mobilenetv2_complete.py examples/images/test.jpg --backend coreml

Output:

Top 5 Predictions (Real ImageNet Labels):
  1. lesser panda                                        99.60%
  2. polecat                                              0.20%
  3. weasel                                               0.09%

Performance: 74.41ms (CPU) / 77.14ms (GPU) / 51.93ms (CoreML)

Text Generation with Transformer Attention

# Run generation with attention
make text-gen-demo

# Train on custom text
make text-gen-train

# Generate with trained weights
make text-gen-trained

See examples/ for more samples.

Documentation

• Getting Started - Installation and first steps
• API Reference - Complete Python API documentation
• Examples - Code examples and tutorials
• Architecture - Design principles and structure
• Development Guide - Building and contributing

Implementation Status

• 85 of ~95 WebNN operations (89% spec coverage)
• Shape inference: 85/85 (100%)
• Python API: 85/85 (100%)
• ONNX Backend: 85/85 (100%)
• CoreML MLProgram: 85/85 (100%)
• 1350+ WPT conformance tests passing

See docs/development/implementation-status.md for complete details.

Rust CLI Usage

# Validate a graph
cargo run -- examples/sample_graph.json

# Visualize a graph (requires graphviz)
cargo run -- examples/sample_graph.json --export-dot graph.dot
dot -Tpng graph.dot -o graph.png

# Convert to ONNX
cargo run -- examples/sample_graph.json --convert onnx --convert-output model.onnx

# Execute with ONNX Runtime
cargo run --features onnx-runtime -- examples/sample_graph.json --convert onnx --run-onnx

See make help for all available targets.

Contributing

Contributions welcome! Please see:

• AGENTS.md - Project architecture and conventions
• docs/development/contributing.md - How to add features
• TODO.txt - Feature requests and known issues

Quick Contribution Guide:

1. Fork and create feature branch: git checkout -b feature/my-feature
2. Install hooks (optional): ./scripts/install-git-hooks.sh
3. Make changes and test: make test && make python-test
4. Format code: make fmt
5. Commit and push

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Links

• GitHub: https://github.com/tarekziade/rustnn
• PyPI: https://pypi.org/project/pywebnn/
• Documentation: https://tarekziade.github.io/rustnn/
• W3C WebNN Spec: https://www.w3.org/TR/webnn/

Acknowledgments

• W3C WebNN Community Group for the specification
• Chromium WebNN implementation for reference
• PyO3 and Maturin projects for excellent Python-Rust integration

---

Made with Rust by Tarek Ziade