Horovod Horovod fails with 'operation not supported'

What is Horovod Horovod fails with 'operation not supported'

Understanding Horovod: A Distributed Deep Learning Framework

Horovod is an open-source distributed deep learning framework created by Uber. It is designed to make distributed deep learning fast and easy to use. Horovod achieves this by leveraging the MPI (Message Passing Interface) or NCCL (NVIDIA Collective Communications Library) for efficient communication between nodes. This allows data scientists and engineers to scale their training workloads across multiple GPUs and nodes seamlessly.

Identifying the Symptom: 'Operation Not Supported'

When using Horovod, you might encounter an error message stating: operation not supported. This error typically occurs when attempting to execute a function or operation that is not available in the current environment. This can be frustrating, especially when you are in the middle of training a model.

Exploring the Issue: Why Does This Error Occur?

The 'operation not supported' error in Horovod usually arises due to incompatibilities or missing features in the environment where Horovod is running. This could be due to a mismatch in the versions of Horovod, MPI, or NCCL, or because certain operations are not implemented in the version of Horovod you are using. It is crucial to ensure that all components of your distributed training setup are compatible and correctly configured.

Common Causes

Incompatible versions of Horovod and MPI/NCCL. Missing support for specific operations in the installed version of Horovod. Incorrect environment setup or configuration.

Steps to Fix the 'Operation Not Supported' Issue

Resolving this issue involves verifying and updating your environment to ensure compatibility and support for the required operations.

Step 1: Verify Horovod and MPI/NCCL Versions

Ensure that you are using compatible versions of Horovod and MPI/NCCL. You can check the installed versions using the following commands:

horovodrun --versionmpirun --versionnvidia-smi

Refer to the Horovod installation guide for the recommended versions.

Step 2: Update Your Environment

If you find any version mismatches, update your environment. You can reinstall Horovod with the correct dependencies using:

pip uninstall horovodHOROVOD_WITH_MPI=1 pip install --no-cache-dir horovod

Ensure that your MPI or NCCL installations are up-to-date as well.

Step 3: Check for Unsupported Operations

Review your code to identify any operations that might not be supported in your current Horovod setup. Consult the Horovod GitHub repository for a list of supported operations and features.

Conclusion

By ensuring compatibility between Horovod and its dependencies, and verifying that your code only uses supported operations, you can resolve the 'operation not supported' error. For further assistance, consider reaching out to the Horovod community or checking the official documentation.