Proposal: CI testing for ARM macOS systems, deprecate Intel macOS support

[thewtex]

Proposal

1. Add macOS ARM64 (macos-14) to CI/CD testing matrices.
2. Begin deprecating Intel (x86_64) macOS support in future elastix releases.
3. Align with ITK’s roadmap (Intel deprecation in ITK 6) and Apple’s industry shift.

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Rationale

1. Apple Silicon Dominance

• Apple holds 90% of the ARM-based laptop market¹, with macOS Sonoma (14) and later prioritizing ARM64.
• New GitHub Actions macos-latest runners default to ARM64, and Intel support is emulated (slower, less reliable)².
• macOS 17 (2026) is expected to drop Intel support entirely³⁴.

2. ITK Alignment

• ITK plans to deprecate Intel macOS in ITK 6 (2026), retaining LTS support in ITK 5.
• Continuing Intel support risks compatibility gaps as ITK optimizes for ARM64 (e.g., SIMD, Metal acceleration).

3. Industry Trends

• Developers increasingly exclude Intel from CI/CD pipelines due to performance and maintenance costs².
• Critical tools (Xcode, Homebrew) now prioritize ARM64, limiting Intel debugging/testing capabilities.

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Implementation Steps

1. CI/CD Testing
   • Replace macos-13 (Intel) with explicit macos-14 ARM runners.

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Potential Impact

• Performance: ARM64 builds leverage Apple Silicon optimizations.
• Legacy Users: Researchers with Intel Macs can use Docker/Linux or older elastix versions.

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Supporting Data

Key Point	Source
macOS 14+ runners are ARM64	[GitHub Issue #9741]2
Apple holds 90% ARM laptop market	[Patently Apple]1
macOS Sonoma drops Intel Macs	[9to5Mac]3, [Wikipedia]4

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Request for Feedback

1. Are there critical Intel macOS workflows that require extended support?
2. Should elastix maintain an LTS branch for Intel macOS (aligned with ITK 5) or is this unnecessary?

References inline. Data current as of April 2025.

Footnotes

1. https://www.patentlyapple.com/2023/02/apple-currently-owns-90-of-the-arm-based-laptop-market-and-the-trend-will-continue-to-take-market-share-away-from-intel.html ↩ ↩²

2. https://github.com/actions/runner-images/issues/9741 ↩ ↩² ↩³

3. https://9to5mac.com/2023/06/05/which-macs-support-macos-14/ ↩ ↩²

4. https://en.wikipedia.org/wiki/MacOS_Sonoma ↩ ↩²

[N-Dekker]

Thanks very much for this elaborate proposal, Matt!

We already noticed that https://pytorch.org only offers a macos version of LibTorch/C++ out-of-the-box for arm64 (https://download.pytorch.org/libtorch/cpu/libtorch-macos-arm64-2.7.0.zip) As Valentin Boussot remarked at #1311 (comment) So this proposal would make the CI for the IMPACT metric faster, right, @vboussot?

[vboussot]

Absolutely.
Many projects, like LibTorch, have already moved to macOS ARM64 only, and it makes sense for elastix too.
This would avoid the costly need to compile LibTorch from source on macOS, make the CI for the IMPACT metric faster, and allow us to provide native ARM64 binaries, which is increasingly expected.