Classification with ConvNeXt and OpenVINO¶

The torchvision.models subpackage contains definitions of models for addressing different tasks, including: image classification, pixelwise semantic segmentation, object detection, instance segmentation, person keypoint detection, video classification, and optical flow. Throughout this notebook we will show how to use one of them.

The ConvNeXt model is based on the A ConvNet for the 2020s paper. The outcome of this exploration is a family of pure ConvNet models dubbed ConvNeXt. Constructed entirely from standard ConvNet modules, ConvNeXts compete favorably with Transformers in terms of accuracy and scalability, achieving 87.8% ImageNet top-1 accuracy and outperforming Swin Transformers on COCO detection and ADE20K segmentation, while maintaining the simplicity and efficiency of standard ConvNets. The torchvision.models subpackage contains several pretrained ConvNeXt model. In this tutorial we will use ConvNeXt Tiny model.

Table of contents:¶

Prerequisites
Get a test image
Get a pretrained model
Define a preprocessing and prepare an input data
Use the original model to run an inference
Convert the model to OpenVINO Intermediate representation format
Use the OpenVINO IR model to run an inference

Installation Instructions¶

This is a self-contained example that relies solely on its own code.

We recommend running the notebook in a virtual environment. You only need a Jupyter server to start. For details, please refer to Installation Guide.

Prerequisites¶

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%pip install -q --extra-index-url https://download.pytorch.org/whl/cpu torch torchvision
%pip install -q  "openvino>=2023.1.0"

Get a test image¶

back to top ⬆️ First of all lets get a test image from an open dataset.

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import requests

from torchvision.io import read_image
import torchvision.transforms as transforms


img_path = "cats_image.jpeg"
r = requests.get("https://huggingface.co/datasets/huggingface/cats-image/resolve/main/cats_image.jpeg")

with open(img_path, "wb") as f:
    f.write(r.content)
image = read_image(img_path)
display(transforms.ToPILImage()(image))

Get a pretrained model¶

back to top ⬆️ Torchvision provides a mechanism of listing and retrieving available models.

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import torchvision.models as models

# List available models
all_models = models.list_models()
# List of models by type. Classification models are in the parent module.
classification_models = models.list_models(module=models)

print(classification_models)

We will use convnext_tiny. To get a pretrained model just use models.get_model("convnext_tiny", weights='DEFAULT') or a specific method of torchvision.models for this model using default weights that is equivalent to ConvNeXt_Tiny_Weights.IMAGENET1K_V1. If you don't specify weight or specify weights=None it will be a random initialization. To get all available weights for the model you can call weights_enum = models.get_model_weights("convnext_tiny"), but there is only one for this model. You can find more information how to initialize pre-trained models here.

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model = models.convnext_tiny(weights=models.ConvNeXt_Tiny_Weights.DEFAULT)

Define a preprocessing and prepare an input data¶

back to top ⬆️ You can use torchvision.transforms to make a preprocessing or usepreprocessing transforms from the model wight.

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import torch

preprocess = models.ConvNeXt_Tiny_Weights.DEFAULT.transforms()

input_data = preprocess(image)
input_data = torch.stack([input_data], dim=0)

Use the original model to run an inference¶

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outputs = model(input_data)

And print results

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# download class number to class label mapping
imagenet_classes_file_path = "imagenet_2012.txt"
r = requests.get(
    url="https://storage.openvinotoolkit.org/repositories/openvino_notebooks/data/data/datasets/imagenet/imagenet_2012.txt",
)

with open(imagenet_classes_file_path, "w") as f:
    f.write(r.text)

imagenet_classes = open(imagenet_classes_file_path).read().splitlines()


def print_results(outputs: torch.Tensor):
    _, predicted_class = outputs.max(1)
    predicted_probability = torch.softmax(outputs, dim=1)[0, predicted_class].item()

    print(f"Predicted Class: {predicted_class.item()}")
    print(f"Predicted Label: {imagenet_classes[predicted_class.item()]}")
    print(f"Predicted Probability: {predicted_probability}")

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print_results(outputs)

Convert the model to OpenVINO Intermediate representation format¶

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OpenVINO supports PyTorch through conversion to OpenVINO Intermediate Representation (IR) format. To take the advantage of OpenVINO optimization tools and features, the model should be converted using the OpenVINO Converter tool (OVC). The openvino.convert_model function provides Python API for OVC usage. The function returns the instance of the OpenVINO Model class, which is ready for use in the Python interface. However, it can also be saved on disk using openvino.save_model for future execution.

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from pathlib import Path

import openvino as ov


ov_model_xml_path = Path("models/ov_convnext_model.xml")

if not ov_model_xml_path.exists():
    ov_model_xml_path.parent.mkdir(parents=True, exist_ok=True)
    converted_model = ov.convert_model(model, example_input=torch.randn(1, 3, 224, 224))
    # add transform to OpenVINO preprocessing converting
    ov.save_model(converted_model, ov_model_xml_path)
else:
    print(f"IR model {ov_model_xml_path} already exists.")

When the openvino.save_model function is used, an OpenVINO model is serialized in the file system as two files with .xml and .bin extensions. This pair of files is called OpenVINO Intermediate Representation format (OpenVINO IR, or just IR) and useful for efficient model deployment. OpenVINO IR can be loaded into another application for inference using the openvino.Core.read_model function.

Select device from dropdown list for running inference using OpenVINO

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import requests

r = requests.get(
    url="https://raw.githubusercontent.com/openvinotoolkit/openvino_notebooks/latest/utils/notebook_utils.py",
)
open("notebook_utils.py", "w").write(r.text)

from notebook_utils import device_widget

device = device_widget()

device

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core = ov.Core()

compiled_model = core.compile_model(ov_model_xml_path, device_name=device.value)

Use the OpenVINO IR model to run an inference¶

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outputs = compiled_model(input_data)[0]
print_results(torch.from_numpy(outputs))