Conquering the “"RuntimeError: BlobWriter not loaded" Error: A Step-by-Step Guide to Exporting PyTorch Models to CoreML

Are you tired of encountering the frustrating “"RuntimeError: BlobWriter not loaded"” error when trying to export your PyTorch model to CoreML? You’re not alone! This pesky issue has plagued many a developer, but fear not, dear reader, for we’re about to embark on a journey to vanquish this error once and for all.

What is the “"RuntimeError: BlobWriter not loaded"” Error?

The “"RuntimeError: BlobWriter not loaded"” error typically occurs when trying to export a PyTorch model to CoreML using the torch_mlir package. This error is often accompanied by a cryptic message, leaving you wondering what went wrong. But don’t worry, we’ll get to the bottom of it.

The Root Cause of the Error

The error arises due to a mismatch between the version of torch_mlir and the version of blobconverter, a dependency required for exporting models to CoreML. When these versions are incompatible, the BlobWriter module fails to load, resulting in the dreaded error.

Prerequisites for a Successful Export

Before we dive into the solution, make sure you have the following prerequisites in place:

• PyTorch version 1.9.0 or higher
• torch_mlir version 1.10.0 or higher
• blobconverter version 1.10.0 or higher
• coremltools version 4.1 or higher

Step-by-Step Solution to the “"RuntimeError: BlobWriter not loaded"” Error

Follow these instructions carefully to resolve the error and successfully export your PyTorch model to CoreML:

1. Install Compatible Versions of Required Packages

   Use the following commands to install the compatible versions of torch_mlir, blobconverter, and coremltools:

   pip install torch-mlir==1.10.0
   pip install blobconverter==1.10.0
   pip install coremltools==4.1

2. Verify Package Versions

   Double-check that the installed versions match the required versions:

   pip show torch-mlir
   pip show blobconverter
   pip show coremltools

   Verify that the output shows the correct version numbers.

3. Load the Required Modules

   In your Python script, import the necessary modules:

   import torch
   import torch_mlir
   import coremltools
   import blobconverter

4. Convert Your PyTorch Model to CoreML

   Use the following code to convert your PyTorch model to CoreML:

   # Assume 'model' is your PyTorch model
   mlmodel = torch_mlir.compile(model, input_types=[torch.float32])
   coreml_model = coremltools.convert(mlmodel)

Troubleshooting Tips

If you still encounter issues, try the following troubleshooting steps:

• Check Package Dependencies

  Verify that there are no version conflicts between the installed packages. You can use pipdeptree to visualize the package dependencies:

  pip install pipdeptree
  pipdeptree torch-mlir blobconverter coremltools

• Reinstall Packages

  Uninstall and reinstall the packages to ensure a clean installation:

  pip uninstall torch-mlir blobconverter coremltools
  pip install torch-mlir==1.10.0 blobconverter==1.10.0 coremltools==4.1

• Verify Python Version

  Make sure you’re using a compatible Python version. PyTorch and CoreML support Python 3.7, 3.8, and 3.9.

Conclusion

Congratulations! You’ve successfully conquered the “"RuntimeError: BlobWriter not loaded"” error and exported your PyTorch model to CoreML. Remember to keep your packages up-to-date and ensure version compatibility to avoid similar issues in the future. Happy modeling!

Package	Version
PyTorch	1.9.0 or higher
torch_mlir	1.10.0 or higher
blobconverter	1.10.0 or higher
coremltools	4.1 or higher

Reference the above table to ensure you have the correct package versions. Remember to stay vigilant and update your packages regularly to avoid compatibility issues.

FAQs

Here are some frequently asked questions related to the “"RuntimeError: BlobWriter not loaded"” error:

• What is BlobWriter?

  BlobWriter is a module in the blobconverter package responsible for serializing the model data into a binary format compatible with CoreML.

• Why does the error occur?

  The error occurs due to version mismatches between torch_mlir and blobconverter, causing the BlobWriter module to fail loading.

• Can I use older versions of the packages?

  It’s not recommended to use older versions of the packages, as they may not be compatible with each other and may lead to unexpected errors.

Final Thoughts

In conclusion, the “"RuntimeError: BlobWriter not loaded"” error can be a frustrating obstacle when exporting PyTorch models to CoreML. However, by following the steps outlined in this article, you should be able to resolve the issue and successfully export your model. Remember to stay up-to-date with the latest package versions and troubleshoot any issues that may arise.

Frequently Asked Question

Encountering the pesky “RuntimeError: BlobWriter not loaded” error when exporting a PyTorch model to CoreML? Worry not, friend, for we’ve got the solutions to your problems!