Libreyolo Export Hailo

Export LibreYOLO models to Hailo (HEF)

There is no format="hef" in LibreYOLO, and there will not be one: the Hailo Dataflow Compiler (DFC) is a proprietary SDK distributed as a private wheel behind Hailo Developer Zone registration. It cannot be a pip dependency or extra. Deployment is a two-stage flow:

1. LibreYOLO exports a plain static ONNX file (format="onnx").
2. The user runs Hailo's DFC to parse, quantize (INT8), and compile to .hef.

Libre<Model>.pt  →  ONNX  →  HAR (parse)  →  HAR (optimize/quantize INT8)  →  HEF
                 [libreyolo]              [Hailo DFC — user-installed]

The DFC cuts the ONNX graph at user-supplied end_node_names (the detection-head convolutions) and discards everything downstream, so LibreYOLO's standard decoded ONNX is acceptable input — the decode tail is simply ignored by the parser.

Will it compile? Decide from the architecture, not a model list

Hailo-8/8L is a fixed-function INT8 CNN accelerator with static shapes. Whether a LibreYOLO model can target it is a property of its architecture, not its name. Apply these rules to any family — including ones added after this skill was written — instead of maintaining a per-model table.

Disqualifiers — if the model contains ANY of these, it will NOT compile

• Attention of any kind. Self-, cross-, deformable, or windowed attention is not supported on Hailo-8/8L. This one rule alone excludes every transformer-based family: all DETR-style detectors (RT-DETR and variants, D-FINE, DEIM, RF-DETR), every open-vocabulary/text-conditioned detector (Grounding DINO, OMDet-Turbo, OWLv2), every ViT backbone (DINOv2, Swin, Depth-Anything, EoMT, and the SAM / MobileSAM encoders), and every language/vision-language tower (BERT, CLIP, VLM). (Hailo's own zoo ships a handful of hand-tuned ViT/DETR HEFs. That is bespoke vendor work and is not evidence that an arbitrary attention graph compiles — treat attention as a hard stop.)
• Dynamic shapes or data-dependent control flow. The DFC compiles one fixed input shape and a static graph. Anything whose graph depends on runtime values — variable query counts, text prompts, dynamic top-k, NonZero, Gather/TopK with dynamic indices, grid_sample — cannot compile. (This is a second, independent reason the open-vocabulary and DETR families are out.)
• LayerNorm-/GELU-dominated designs. BatchNorm folds into convs cleanly; LayerNorm support is poor and GELU is not a native activation. A ConvNeXt-style stack is a bad fit even though it is nominally "convolutional."
• Native-resolution image-to-image with large activations. Restoration/enhancement models (e.g. NAFNet) run at full input resolution and blow past practical Hailo SRAM budgets. Do not attempt.

What DOES compile — pure-CNN, fixed-shape graphs

A family is a candidate when it is convolution-only (conv, pooling, resize, concat, elementwise add/mul), uses BatchNorm + ReLU/SiLU, and has a fixed input size. In the current library that means:

• CNN single-stage detectors with a conv detection head — YOLOX and YOLO9 are the primary targets. These are also the only two that map onto a HailoRT NMS meta-architecture (yolox, and the yolov8-style decoupled head), so Hailo can own NMS in the compiled pipeline.
• Other CNN detectors (PicoDet, YOLO-NAS, RTMDet, and similar conv-headed detectors) compile as graphs, but there is no matching HailoRT NMS meta-arch — the HEF emits raw head tensors and your application must run decode + NMS on the CPU.
• CNN image classifiers (ResNet, MobileNetV4-conv, EfficientNetV2). ResNet is the best-supported classify path because Hailo's Model Zoo ships ResNet recipes.
• Small conv task-heads (FOMO point heads, L2CS gaze on a ResNet backbone, EC pose) are compilable in principle but have no Hailo recipe — application-side postprocess only, and unvalidated.

Rule of thumb for a new family: open the model, look for a transformer block, a LayerNorm, or a dynamic shape. If you find one, stop and recommend YOLOX / YOLO9 (or a different runtime — ONNX Runtime, TensorRT, OpenVINO, all first-class libreyolo export targets). If it is plain CNN, it is a candidate worth trying through the DFC.

Op-level limits behind the rules

If asked why, these are the concrete DFC constraints the rules encode: static shapes only; no attention; BatchNorm folds but LayerNorm support is poor; no dynamic Gather/TopK/NonZero/grid_sample; INT8 only (accuracy loss must be measured); HailoRT NMS exists only for known meta-architectures (yolov8, yolox, nanodet_v8, …), so unknown or NMS-free heads (e.g. yolo9_e2e) get raw tensors and need app-side postprocess.

Status caveat: no LibreYOLO family has been validated end-to-end through the DFC to a running HEF yet. The rules above predict compilability from architecture; parser, quantization, and accuracy remain unproven until a HEF is compiled and measured. Treat every "candidate" as requiring recorded validation evidence.

Step 1 — export static ONNX from LibreYOLO

Hailo needs batch 1, fixed resolution, no dynamic axes. The Python API defaults to dynamic=True, so disable it explicitly:

from libreyolo import LibreYOLO

model = LibreYOLO("LibreYOLO9t.pt")
model.export(format="onnx", imgsz=640, dynamic=False, simplify=True)

CLI equivalent (the CLI already defaults to static shapes, unlike the Python API):

libreyolo export --model LibreYOLO9t.pt --format onnx --imgsz 640

Do not use half=True — the DFC ingests fp32 ONNX and does its own INT8 quantization. Do not use nms=True (embedded ONNX NMS) — Hailo either owns NMS via nms_postprocess or the application does; an NMS subgraph is dead weight past the end nodes. The default opset is fine; if the DFC parser complains, re-export with opset=11. Confirm the input is [1, 3, H, W] with static dims before spending compile time.

Step 2 — compile with the Hailo DFC (user-side)

Prerequisites, all on the user's side, none installable from PyPI:

• Linux x86_64 machine (WSL2 Ubuntu 22.04 works). Compilation cannot run on ARM — the Raspberry Pi is a runtime target, never the compile host.
• DFC wheel (hailo_sdk_client) from the Hailo Developer Zone (free registration).
• For Hailo-8/8L, pin to the Hailo Model Zoo v2.x line for recipes/NMS configs. Do not use Model Zoo master/v5.x unless targeting Hailo-10/15.
• A GPU is strongly recommended for the quantization step (hours vs minutes without).

Pick hw_arch for the target:

If unsure, run hailortcli fw-control identify on the device.

Compile pipeline (LibreYOLO9 example):

import numpy as np
from hailo_sdk_client import ClientRunner
from PIL import Image
from pathlib import Path

HW_ARCH = "hailo8"          # hailo8 | hailo8l
IMGSZ = 640
NMS_CONFIG = "yolo9_nms_config.json"  # adapt from the Model Zoo config for the closest YOLO
                                      # variant; it is class-count AND imgsz specific — a
                                      # COCO-80 config is wrong for a fine-tuned 3-class model.

# LibreYOLO9 detection-head end nodes (all sizes), verified against the standard
# LibreYOLO ONNX export. NOTE: LibreYOLO graphs use a "/head/..." prefix, not the
# "model.N" prefix seen in other libraries' docs — configs copied from elsewhere will
# not match. If parsing fails, confirm the names in your own export (netron, or grep the
# graph for "cv2.0.2/Conv").
END_NODES = [
    "/head/cv2.0/cv2.0.2/Conv", "/head/cv3.0/cv3.0.2/Conv",
    "/head/cv2.1/cv2.1.2/Conv", "/head/cv3.1/cv3.1.2/Conv",
    "/head/cv2.2/cv2.2.2/Conv", "/head/cv3.2/cv3.2.2/Conv",
]

runner = ClientRunner(hw_arch=HW_ARCH)
runner.translate_onnx_model(ONNX, end_node_names=END_NODES)

# Normalization must match LibreYOLO preprocessing (0-255 → 0-1, no mean/std for YOLO9/YOLOX).
# The convN layer names in change_output_activation are assigned by the DFC at parse
# time and are model-specific — read them from the DFC log, do not copy blindly.
runner.load_model_script(
    "normalization1 = normalization([0.0, 0.0, 0.0], [255.0, 255.0, 255.0])\n"
    f'nms_postprocess("{NMS_CONFIG}", meta_arch=yolov8, engine=cpu)\n'
)

# Calibration: 64-128 images REPRESENTATIVE OF DEPLOYMENT DATA, resized to IMGSZ.
calib_paths = sorted(Path("calib_images").glob("*.jpg"))[:128]
calib = np.stack([
    np.asarray(Image.open(p).convert("RGB").resize((IMGSZ, IMGSZ)), dtype=np.float32)
    for p in calib_paths
])

runner.optimize(calib)
hef = runner.compile()
Path("libreyolo9t.hef").write_bytes(hef)

Path notes by family:

• YOLO9: end nodes above; meta_arch=yolov8 (identical decoupled-head layout).
• YOLOX: run translate_onnx_model(ONNX) without end_node_names first — the DFC log prints suggested end nodes; re-run with those. Use meta_arch=yolox.
• Other conv detectors (PicoDet / YOLO-NAS / RTMDet) and conv task-heads (FOMO / EC / L2CS): compile without nms_postprocess; the HEF outputs raw head tensors and the application owns decode + NMS/argmax.
• Anything the disqualifier rules exclude: stop. Do not try to force a transformer through the DFC.

Random calibration images will compile but silently destroy accuracy. Keep the compile log on failure — fixes always hinge on the exact failing layer/op name.

Step 3 — run on the device

On the target (e.g. Raspberry Pi 5 + AI Kit):

sudo apt install dkms hailo-all      # Raspberry Pi path; other hosts: HailoRT from Developer Zone
hailortcli fw-control identify       # device sanity check
hailortcli run libreyolo9t.hef       # smoke test / FPS

Application inference uses the hailo_platform Python API. With nms_postprocess compiled in, the output is (batch, num_classes, max_dets, 5) with [y1, x1, y2, x2, score] in model coordinates — scale back to the original image size yourself. LibreYOLO's Results pipeline is not involved at runtime; the HEF is a standalone artifact.

Support-claim discipline

Do not tell a user a family "works on Hailo" until all of these exist:

1. A compiled .hef from the exact LibreYOLO checkpoint (with DFC / Model Zoo / HailoRT versions recorded).
2. Representative calibration documented.
3. Accuracy measured on-device against the fp32 baseline (mAP delta, not just FPS).

Until then the honest phrasing is: "pure-CNN detectors like YOLOX/YOLO9 are compile candidates; anything with attention, dynamic shapes, or LayerNorm will not run on Hailo."