Metal backend doesn't support iOS

[nguyenpham]

I can't compile the Metal backend for iOS since some functions are for macOS but not iOS. For example:

'MTLCopyAllDevices' is unavailable: not available on iOS

Please use functions that are also available for iOS.

[borg323]

Is this just an issue of adding an alternative code path that calls MTLCreateSystemDefaultDevice() instead of MTLCopyAllDevices()?

[nguyenpham]

I don't know, just saw the issue when trying to compile and I haven't looked at the code for Metal yet (so hard for me to understand). Just read from the Apple document, MTLCopyAllDevices is for macOS only.

[ChinChangYang]

Your app can use multiple GPUs on an Intel-based Mac, including any built-in and external GPUs.

Mac computers (and iPhone) with Apple silicon have a single, high-performance, and energy-efficient GPU.

Reference

https://developer.apple.com/documentation/metal/gpu_devices_and_work_submission/multi-gpu_systems/finding_multiple_gpus_on_an_intel-based_mac