OpenCL Not Working On MacOS ARM Runners

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OpenCL on macOS ARM Runners: Troubleshooting and Solutions

Introduction: The OpenCL Challenge on macOS ARM Runners

Hey everyone! 👋 We're diving into a tricky issue: OpenCL not working on macOS ARM runners within GitHub Actions. This problem is affecting developers who rely on OpenCL for testing their applications, specifically those built for macOS ARM platforms. Let's break down the problem, explore the steps to reproduce it, and discuss potential solutions. If you're using GitHub Actions and the macos-14, macos-15, or macos-26 runners, this is especially relevant to you.

The Core Problem: Why OpenCL Fails on ARM

The heart of the issue is that the clinfo command, a standard tool for checking OpenCL, fails on these ARM-based macOS runners. When you run clinfo, it throws an error: gatherPlatformInfo:1299: number of devices : error -30. This indicates that the OpenCL implementation isn't correctly detecting or initializing the available compute devices on the ARM architecture. This is a real pain, especially when you need OpenCL for testing purposes.

Impact of the Issue

This malfunction directly impacts the ability to test binaries compiled for macOS ARM platforms within CI (Continuous Integration) pipelines. This means you can't be sure your code is running correctly on these systems before you release it. This can lead to delays in the development process and the potential for bugs in production, which is something we all want to avoid, right?

Reproduction Steps: How to Recreate the OpenCL Issue

Crafting the Test Script: A Simple Workflow

To reproduce this issue, you can use a straightforward GitHub Actions workflow. The steps are pretty simple:

  1. Workflow Trigger: This workflow is triggered manually using workflow_dispatch. This allows for easy testing.
  2. Job Definition: It defines a job called test-opencl to run on different macOS versions to check that everything is working fine. This is the heart of the testing process.
  3. Matrix Strategy: The strategy uses a matrix to run the job on different macOS environments like macos-14, macos-15, and macos-26, as well as a control group macos-15-intel. This allows for a comparison between ARM and x86_64 runners.
  4. Install clinfo: brew install clinfo. This command will install the necessary tool.
  5. Run clinfo: clinfo is executed. This is the command that triggers the error.

Here’s a snippet of how that looks in YAML:

name: Test of OpenCL on MacOS Arm platform

on:
  workflow_dispatch:

jobs:
  test-opencl:
    name: Test OpenCL
    runs-on: ${{ matrix.os }}
    strategy:
      fail-fast: false
      matrix:
        os: [macos-14, macos-15, macos-26, macos-15-intel]
    steps:
      - name: Run clinfo
        shell: bash
        run: |
          brew install clinfo
          clinfo

Observing the Failure: The Error in Action

When this workflow runs on the macos-14, macos-15, and macos-26 runners (which are ARM-based), clinfo will fail. You’ll see the dreaded error -30 message. In contrast, the same workflow will pass on macos-15-intel (an x86_64 runner), showing that OpenCL works correctly on that architecture. It's really frustrating when you have to troubleshoot this type of issue.

Analyzing the Output: What the Logs Tell Us

The output from the failed clinfo command reveals the underlying problem. It shows that the system can detect the OpenCL platform (Apple) but fails to recognize any devices. This means that the OpenCL drivers or the system's ability to access the hardware is somehow limited or blocked on the ARM architecture within the GitHub Actions environment.

Platforms Affected and Runner Images Impacted

Identifying the Problem Areas

As you've probably gathered, this issue primarily affects GitHub Actions users who are using standard runners with the following macOS ARM-based runner images:

  • macos-14-arm64
  • macos-15-arm64
  • macos-26-arm64

The x86_64 runner, macos-15, is unaffected, which makes it easier to pinpoint the problem. These runners are the ones that are not working properly.

Version Specifics: Where the Issue Resides

Here are some of the specific runner images and versions where this problem has been observed:

  • macos-14-arm64: Version 20251020.0056
  • macos-15-arm64: Version 20251021.0066
  • macos-26-arm64: Version 20251022.0070

It’s important to note that this is not a regression. It appears that OpenCL support has never been fully functional on these ARM-based macOS runners in the context of GitHub Actions.

Expected vs. Actual Behavior: The Discrepancy

The Desired Outcome: Successful OpenCL Availability

In an ideal world, when you run clinfo on these runners, it should successfully detect the available OpenCL devices (like the GPU). Subsequent steps in your workflow should then be able to use OpenCL without any issues. This would allow you to fully test your software on the macOS ARM platform.

The Reality: OpenCL's Absence

Unfortunately, the reality is far from ideal. clinfo fails, and OpenCL isn’t available for use. This forces developers to find workarounds or, worse, exclude macOS ARM runners from their CI pipelines, which limits the platform coverage of their software.

Troubleshooting and Potential Solutions

Investigating the Root Cause: What's Going On?

Pinpointing the exact root cause of this failure is tricky. It could be related to:

  • Driver Issues: The OpenCL drivers might not be correctly installed or configured on the ARM-based runners.
  • Environment Variables: There could be environment variables that are set incorrectly, preventing OpenCL from initializing properly.
  • Hardware Access: The GitHub Actions environment might restrict access to the underlying hardware on the ARM runners.
  • Image Configuration: There might be something in the image configuration that prevents OpenCL from working. The clinfo output is a good starting point to analyze the issue.

Possible Workarounds: Bypassing the Problem

Until the root cause is resolved, here are a few workarounds you can explore:

  1. Use x86_64 Runners: If possible, use the macos-15-intel runner for your OpenCL tests. This will allow you to test your software, but it won't give you the exact ARM environment you might need.
  2. Manual Testing: Perform manual testing on an actual macOS ARM device. This can provide more reliable results.
  3. Emulation: Consider using an emulator, like Rosetta 2, to test your code, although this can be slow.
  4. Contact Support: Reach out to GitHub Support. They may have insights or solutions for this issue.

Seeking a Permanent Fix: What Needs to Happen

The best solution would involve fixing the underlying issue within the GitHub Actions runner images. This would likely require updates to the OpenCL drivers or changes to the environment configuration. Keep an eye on the runner image release notes for updates.

Conclusion: Navigating the OpenCL Hurdles

So, guys, we’ve covered the OpenCL issue on macOS ARM runners in GitHub Actions. We've explored the problem, shown you how to reproduce it, and discussed potential workarounds. It's a frustrating situation, but hopefully, this guide helps you to understand the problem and find solutions until the issue is resolved. Stay tuned for updates and fixes! Happy coding! 🚀