How to Convert PyTorch Models to ONNX Format?

12 minutes read

To convert PyTorch models to ONNX format, you can follow these steps:

  1. Install the necessary libraries: First, you need to install PyTorch and ONNX. You can use pip to install them using the following commands: pip install torch pip install onnx
  2. Load your PyTorch model: Start by loading your pre-trained PyTorch model using the torch.load function. This function loads the model's state dictionary and model architecture.
  3. Prepare the input data: ONNX models require sample input data to determine the model's structure and shape. Create a sample input tensor that matches the expected input shape of your PyTorch model.
  4. Convert the model to ONNX format: Now, you can convert your PyTorch model to ONNX format using the torch.onnx.export function. This function takes in the loaded PyTorch model, the sample input tensor, and the desired output file name. It generates an ONNX model file containing your model's architecture and weights. import torch import torch.onnx as onnx # Load the PyTorch model model = torch.load('model.pth') # Create a sample input tensor sample_input = torch.randn(1, 3, 224, 224) # Export the model to ONNX onnx.export(model, sample_input, 'model.onnx') This will create a file named 'model.onnx' in the current working directory.
  5. Validate the ONNX model: After conversion, you can validate the ONNX model using the onnx.checker.check_model function. This function ensures that the ONNX model is syntactically valid. import onnx # Load the ONNX model onnx_model = onnx.load('model.onnx') # Check the validity of the ONNX model onnx.checker.check_model(onnx_model) If the model is valid, no error will be raised.


You have now successfully converted your PyTorch model to the ONNX format. This format allows you to deploy your model in frameworks compatible with ONNX, such as TensorFlow, Caffe2, and Microsoft Cognitive Toolkit (CNTK).

Best PyTorch Books to Read in 2024

1
PyTorch 1.x Reinforcement Learning Cookbook: Over 60 recipes to design, develop, and deploy self-learning AI models using Python

Rating is 5 out of 5

PyTorch 1.x Reinforcement Learning Cookbook: Over 60 recipes to design, develop, and deploy self-learning AI models using Python

2
PyTorch Cookbook: 100+ Solutions across RNNs, CNNs, python tools, distributed training and graph networks

Rating is 4.9 out of 5

PyTorch Cookbook: 100+ Solutions across RNNs, CNNs, python tools, distributed training and graph networks

3
Machine Learning with PyTorch and Scikit-Learn: Develop machine learning and deep learning models with Python

Rating is 4.8 out of 5

Machine Learning with PyTorch and Scikit-Learn: Develop machine learning and deep learning models with Python

4
Artificial Intelligence with Python Cookbook: Proven recipes for applying AI algorithms and deep learning techniques using TensorFlow 2.x and PyTorch 1.6

Rating is 4.7 out of 5

Artificial Intelligence with Python Cookbook: Proven recipes for applying AI algorithms and deep learning techniques using TensorFlow 2.x and PyTorch 1.6

5
PyTorch Pocket Reference: Building and Deploying Deep Learning Models

Rating is 4.6 out of 5

PyTorch Pocket Reference: Building and Deploying Deep Learning Models

6
Learning PyTorch 2.0: Experiment deep learning from basics to complex models using every potential capability of Pythonic PyTorch

Rating is 4.5 out of 5

Learning PyTorch 2.0: Experiment deep learning from basics to complex models using every potential capability of Pythonic PyTorch

7
Deep Learning for Coders with Fastai and PyTorch: AI Applications Without a PhD

Rating is 4.4 out of 5

Deep Learning for Coders with Fastai and PyTorch: AI Applications Without a PhD

8
Deep Learning with PyTorch: Build, train, and tune neural networks using Python tools

Rating is 4.3 out of 5

Deep Learning with PyTorch: Build, train, and tune neural networks using Python tools

9
Programming PyTorch for Deep Learning: Creating and Deploying Deep Learning Applications

Rating is 4.2 out of 5

Programming PyTorch for Deep Learning: Creating and Deploying Deep Learning Applications

10
Mastering PyTorch: Build powerful deep learning architectures using advanced PyTorch features, 2nd Edition

Rating is 4.1 out of 5

Mastering PyTorch: Build powerful deep learning architectures using advanced PyTorch features, 2nd Edition


What is the purpose of converting PyTorch models to ONNX format?

The purpose of converting PyTorch models to ONNX (Open Neural Network Exchange) format is to make them compatible with other deep learning frameworks and tools.


ONNX is a cross-platform open standard format that allows models to be interchangeably used in different deep learning frameworks such as TensorFlow, MXNet, and more. This capability enables easier deployment and utilization of the same model across various frameworks without the need for rewriting or retraining models.


Some common reasons to convert PyTorch models to ONNX format include:

  1. Interoperability: ONNX allows models to be imported by frameworks other than PyTorch. This is useful for collaborations, team projects, and when different teams or individuals prefer different deep learning frameworks. It eliminates the need for model translation or reimplementation in different frameworks.
  2. Optimization: ONNX models can be further optimized for inference deployment. Framework-specific optimizations can be applied to the converted model to improve runtime performance, memory usage, and reduce resource requirements.
  3. Deployment on edge devices: ONNX models can be deployed on edge devices such as mobile phones, IoT devices, and embedded systems. Many edge devices support ONNX runtimes, making it easier to deploy PyTorch models on devices with limited computational resources.
  4. Access to ecosystem and tools: Converting PyTorch models to ONNX format allows access to a wide range of tools, libraries, and hardware accelerators that support ONNX. This includes inference engines, compilers, and model optimization tools that can significantly improve model performance and accelerate inference time.


Overall, converting PyTorch models to ONNX format enhances model portability, scalability, and compatibility, providing more flexibility in model deployment and utilization.


How to convert a PyTorch model to ONNX and retain custom layers or operations?

To convert a PyTorch model to ONNX and retain custom layers or operations, you can follow these steps:


Step 1: Install the required libraries Install PyTorch and ONNX using pip:

1
2
pip install torch
pip install onnx


Step 2: Define your custom layers or operations If your PyTorch model contains custom layers or operations that are not natively supported by ONNX, you need to define these custom layers in ONNX. This can be done by creating a custom ONNX operator set extension. Refer to the ONNX documentation for more information on creating custom layers or operations.


Step 3: Convert the PyTorch model to ONNX Once your custom layers are defined, you can convert the PyTorch model to ONNX using the torch.onnx.export() function. Set the opset_version parameter according to the version of ONNX you are using, and pass the inputs and output names to the function. For example:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
import torch
import torch.onnx as onnx

# Define your custom layers or operations here

# Load your PyTorch model
model = torchvision.models.resnet18(pretrained=True)

# Export the model to ONNX
input_names = ['input']
output_names = ['output']
onnx_filename = 'model.onnx'
torch.onnx.export(model, torch.randn(1, 3, 224, 224), onnx_filename, input_names=input_names, output_names=output_names, opset_version=11)


Here, you need to replace torchvision.models.resnet18(pretrained=True) with your own PyTorch model.


Step 4: Verify the ONNX model You can verify the converted ONNX model using the ONNX model checker:

1
2
3
4
5
6
7
import onnx

# Load the ONNX model
model = onnx.load(onnx_filename)

# Check the model
onnx.checker.check_model(model)


That's it! Now you have converted your PyTorch model to ONNX while retaining custom layers or operations.


What is the difference between PyTorch and ONNX?

PyTorch and ONNX (Open Neural Network Exchange) are both frameworks primarily used for deep learning, but they serve different purposes:

  1. PyTorch: PyTorch is a popular open-source deep learning framework developed by Facebook's AI Research lab. It provides a flexible and dynamic approach to building neural networks and is widely used for research, prototyping, and developing deep learning models. PyTorch enables dynamic computation graphs, allowing for easier debugging and experimentation. It emphasizes Pythonic coding and provides extensive support for GPU acceleration.
  2. ONNX: ONNX is an open-source framework used for interoperability and exchanging models between different deep learning frameworks. Developed by Microsoft and Facebook, ONNX aims to provide a common format to represent machine learning models, enabling seamless transferability between frameworks such as PyTorch, TensorFlow, and others. ONNX represents deep learning models as a computational graph, allowing models to be trained in one framework and then used in another without the need for conversions.


In summary, PyTorch is a deep learning framework for building models, while ONNX is a format for representing and exchanging deep learning models between different frameworks.

Facebook Twitter LinkedIn Telegram Whatsapp Pocket

Related Posts:

Using pre-trained models in PyTorch allows you to leverage existing powerful models that have been trained on large datasets. These pre-trained models are often state-of-the-art and can be used for a wide range of tasks such as image classification, object det...
To use PyTorch for reinforcement learning, you need to follow specific steps. Here's a brief overview:Install PyTorch: Begin by installing PyTorch on your system. You can visit the official PyTorch website (pytorch.org) to find installation instructions ac...
Transfer learning is a technique commonly used in deep learning to leverage pretrained models for new tasks. It allows the use of knowledge gained from one task to solve a new, related problem. PyTorch, a popular deep learning library, provides a convenient wa...
Contributing to the PyTorch open-source project is a great way to contribute to the machine learning community as well as enhance your own skills. Here is some guidance on how you can get started:Familiarize yourself with PyTorch: Before contributing to the pr...
PyTorch is a popular open-source machine learning library that can be used for various tasks, including computer vision. It provides a wide range of tools and functionalities to build and train deep neural networks efficiently. Here's an overview of how to...
To make a PyTorch distribution on a GPU, you need to follow a few steps. Here is a step-by-step guide:Install the necessary dependencies: Start by installing PyTorch and CUDA on your computer. PyTorch is a popular deep learning library, while CUDA is a paralle...