edgefirst-ara2 0.4.0

Python bindings for the ARA-2 neural accelerator client library

Python Bindings for ARA-2

Python bindings for the ARA-2 neural network accelerator client library, providing efficient NPU inference from Python via a proxy service running on NXP i.MX platforms with Kinara ARA-2 hardware.

Published to PyPI as edgefirst-ara2.

Architecture

Python Application ──(UNIX/TCP socket)──▶ ara2-proxy ──(PCIe)──▶ ARA-2 NPU
       │                                (system service)        (Kinara hardware)
       │
edgefirst-hal ──(DMA-BUF fd)──▶ GPU preprocessing (zero-copy)

Your Python code connects to the ara2-proxy system service (not directly to the hardware). The proxy manages device access and must be running before your application starts.

Installation

From PyPI

pip install edgefirst-ara2

For zero-copy preprocessing with edgefirst-hal:

pip install edgefirst-ara2[hal]

Prerequisites for Development

• Python 3.11 or higher
• Rust stable toolchain (edition 2024)
• maturin (pip install maturin)
• ARA-2 client library (libaraclient.so.1)

Development Install

cd crates/ara2-py
maturin develop --release --features abi3

Quick Start

import edgefirst_ara2

# Connect to ARA-2 proxy
session = edgefirst_ara2.Session.create_via_unix_socket("/var/run/ara2.sock")

# Get version information
versions = session.versions()
print(f"Proxy version: {versions['proxy']}")

# List endpoints
endpoints = session.list_endpoints()
print(f"Found {len(endpoints)} endpoints")

# Check endpoint status
for endpoint in endpoints:
    state = endpoint.check_status()
    stats = endpoint.dram_statistics()
    print(f"State: {state}, Free DRAM: {stats.free_size / stats.dram_size * 100:.1f}%")

Inference with numpy

import numpy as np
import edgefirst_ara2

session = edgefirst_ara2.Session.create_via_unix_socket("/var/run/ara2.sock")
endpoints = session.list_endpoints()
model = endpoints[0].load_model("model.dvm")

# Allocate tensors and run inference
model.allocate_tensors()
input_data = np.zeros(model.input_size(0), dtype=np.uint8)
model.set_input_tensor(0, input_data)
timing = model.run()

print(f"Inference: {timing.run_time_us} us")
output = model.get_output_tensor(0)
dequantized = model.dequantize(0)

Zero-Copy DMA-BUF Pipeline

For maximum throughput, use DMA-BUF tensors with edgefirst-hal for GPU-accelerated preprocessing. This eliminates CPU memory copies between preprocessing and inference:

Path	CPU copies	Flow
Standard (numpy)	2	numpy → shared memory → NPU
DMA-BUF	0	GPU writes directly to NPU input buffer

How it works: allocate_tensors("dma") allocates the model's input tensor in a DMA-BUF — a Linux kernel buffer accessible by multiple hardware devices. input_tensor_fd(0) returns a file descriptor to that buffer. You pass this FD to edgefirst_hal.import_image(), which maps it as a GPU image surface. The GPU writes the preprocessed frame directly into the NPU's input buffer — no CPU copies involved.

import os
import edgefirst_ara2 as ara2
import edgefirst_hal as hal

session = ara2.Session.create_via_unix_socket(ara2.DEFAULT_SOCKET)
endpoint = session.list_endpoints()[0]

with endpoint.load_model("yolov8s.dvm") as model:
    model.allocate_tensors("dma")  # Must use "dma" for tensor FD access

    # Get DMA-BUF FD for the model's input tensor
    input_fd = model.input_tensor_fd(0)
    c, h, w = model.input_shape(0)
    try:
        # Import as PlanarRgb (CHW layout) to match ARA-2 tensor format
        dst = hal.import_image(input_fd, w, h, hal.PixelFormat.PlanarRgb)
    finally:
        os.close(input_fd)  # FD duplicated by import_image; close original

    # GPU-accelerated convert: camera frame -> model input (zero CPU copies)
    processor = hal.ImageProcessor()
    src = hal.load_image("image.jpg", format=hal.PixelFormat.Rgba, mem=hal.TensorMemory.DMA)
    processor.convert(src, dst)

    # Run inference — NPU reads from the same DMA-BUF
    timing = model.run()
    print(f"Inference: {timing.run_time_us} us")

Performance

Benchmarked on NXP FRDM i.MX 95 + ARA-2 with YOLOv8m-seg (640×640). The Python API adds minimal overhead over native Rust thanks to DMA-BUF zero-copy — GPU and NPU operate on the same physical memory buffers.

Stage	Rust	Python	Overhead
GPU preprocess (letterbox + RGBA→CHW)	2.85 ms	2.88 ms	+0.03 ms
NPU inference (wall clock)	34.53 ms	34.63 ms	+0.10 ms
NPU execution	26.04 ms	26.04 ms	—
DMA input upload	2.02 ms	2.05 ms	—
DMA output download	3.68 ms	3.68 ms	—
Decode (NMS + dequant)	4.05 ms	4.31 ms	+0.26 ms
Materialize (CPU coeff × proto → bitmaps)	5.67 ms	5.98 ms	+0.31 ms
Draw (GL mask overlay)	5.54 ms	5.71 ms	+0.17 ms
Total pipeline	52.64 ms	53.52 ms	+0.88 ms
Throughput	19.0 FPS	18.7 FPS

Steady-state mean over 30 iterations after warmup. Python overhead is under 1 ms across the entire pipeline.

Run the benchmark yourself. Create a virtual environment on the target and install the packages from PyPI:

python3 -m venv ~/venv
~/venv/bin/pip install edgefirst-ara2 edgefirst-hal
~/venv/bin/python3 yolov8.py model.dvm image.jpg --benchmark 30 --save

DVM Metadata

Read model metadata without loading onto the NPU:

import edgefirst_ara2

metadata = edgefirst_ara2.read_metadata("model.dvm")
if metadata:
    print(f"Task: {metadata.task}")
    print(f"Classes: {metadata.classes}")
    if metadata.compilation and metadata.compilation.ppa:
        print(f"IPS: {metadata.compilation.ppa.ips}")

labels = edgefirst_ara2.read_labels("model.dvm")

API Reference

Session

Connection to the ARA-2 proxy service.

Static Methods:

• create_via_unix_socket(socket_path: str) -> Session
• create_via_tcp_ipv4_socket(ip: str, port: int) -> Session

Methods:

• versions() -> dict[str, str] - Get component versions
• list_endpoints() -> list[Endpoint] - List available endpoints

Properties:

• socket_type: str - "unix" or "tcp"

Endpoint

Represents an ARA-2 accelerator device.

Methods:

• check_status() -> State - Get device state
• dram_statistics() -> DramStatistics - Get memory usage
• load_model(model_path: str) -> Model - Load a .dvm model

Model

Loaded neural network model.

Lifecycle:

• allocate_tensors(memory: str | None = None) - Allocate tensors ("dma", "shm", "mem", or None)
• set_timeout_ms(timeout_ms: int) - Set inference timeout
• run() -> ModelTiming - Execute inference

Tensor I/O (numpy):

• set_input_tensor(index: int, data: np.ndarray) - Copy data into input
• get_output_tensor(index: int) -> np.ndarray - Copy output data out
• dequantize(index: int) -> np.ndarray - Dequantize output to float32

DMA-BUF Zero-Copy:

• input_tensor_fd(index: int) -> int - Get input tensor FD (pass to hal.ImageProcessor.import_image, which dups it — close after)
• output_tensor_fd(index: int) -> int - Get output tensor FD (pass to hal.Tensor.from_fd, which takes ownership — do not close after)
• input_tensor_memory(index: int) -> str - Input memory type
• output_tensor_memory(index: int) -> str - Output memory type

Introspection:

• n_inputs: int, n_outputs: int - Tensor counts
• input_shape(i) -> (C, H, W), output_shape(i) -> (C, H, W)
• input_size(i) -> int, output_size(i) -> int - Size in bytes
• input_bpp(i) -> int, output_bpp(i) -> int - Bytes per element
• input_info(i) -> InputTensorInfo, output_info(i) -> OutputTensorInfo
• input_quants(i) -> InputQuantization, output_quants(i) -> OutputQuantization

Metadata Functions

• read_metadata(path: str) -> DvmMetadata | None
• read_labels(path: str) -> list[str]
• has_metadata(path: str) -> bool

Supporting Types

• State (enum): Init, Idle, Active, ActiveSlow, ActiveBoosted, ThermalInactive, ThermalUnknown, Inactive, Fault
• ModelOutputType (enum): Classification, Detection, SemanticSegmentation, Raw
• DramStatistics: dram_size, free_size, model_occupancy_size, ...
• ModelTiming: run_time_us, input_time_us, output_time_us
• InputQuantization: qn, scale, mean, is_signed
• OutputQuantization: qn, scale, offset, is_signed

Exceptions

Ara2Error (RuntimeError)
 +-- LibraryError       - libaraclient.so loading failures
 +-- HardwareError      - NPU faults, endpoint errors
 +-- ProxyError         - Proxy connection failures
 +-- ModelError         - Model load/inference failures
 +-- TensorError        - Tensor allocation, DMA-BUF errors
 +-- MetadataError      - DVM metadata parsing errors

Building Wheels

cd crates/ara2-py
maturin build --release --features abi3

Wheels are created in target/wheels/.

Stable ABI

The bindings use PyO3's stable ABI (abi3-py311):

• A single wheel works across Python 3.11, 3.12, 3.13, and future versions
• Minimum supported Python version is 3.11

Troubleshooting

"libaraclient.so.1 not found"

export LD_LIBRARY_PATH=/path/to/ara2/lib:$LD_LIBRARY_PATH

Verify Installation

python -c "import edgefirst_ara2; print(edgefirst_ara2.__version__)"

License

Licensed under the Apache License 2.0.

Copyright 2025 Au-Zone Technologies. All Rights Reserved.