P: Allow users to disable the GPU for AI masking

To show how technically simple it is to control whether AI models execute on the CPU or GPU, I wrote a simple Python script using the same Core ML library used by LR. It loads two instances of the open-source MobileNetV2 image-classification model, with one allowed to use the GPU and the other not. The script then alternates execution of the two models.  The key lines of the script are:

modelGPU = ct.models.MLModel ("MobileNetV2.mlmodel", 
    compute_units = ct.ComputeUnit.ALL)

modelCPU = ct.models.MLModel ("MobileNetV2.mlmodel", 
    compute_units = ct.ComputeUnit.CPU_ONLY)

A prediction using the GPU takes about 9 msecs, while a prediction using the CPU takes 39 msecs. When the GPU model is running, Activity Monitor shows % CPU at about 50% and % GPU at 50%. But when the CPU model is running, % CPU is about 175% and % GPU is 0%.

You can download the entire script and instructions from here:

https://www.dropbox.com/s/0edo6jm2s1sgrc6/coreml-gpu-cpu.2022.11.14.zip?dl=0 

That .zip includes a screen recording of the script in action.

I agree entirely. Lots of people with otherwise perfectly serviceable systems don't have advanced graphics cards (which are more commonly bought for gaming than anything else). We can all appreciate the Lightroom functions which do make use of GPU acceleration but they should still work, even at a slower pace without them.

In another thread, Adobe employee @simonsaith wrote, "To use or not to use the GPU for ML inference for a particular GPU/driver version is not within Lr's control. The platform OS will do the check at runtime."

This is incorrect. LR uses the CoreML library on Mac and the ONNX Runtime on Windows, and both allow the client to control whether the GPU is used to execute a model.

Mac: MLModelConfiguration allows the client to limit execution to the CPU via "computeUnits".  

Win: onnxruntime.InferenceSession() allows the client to specify the "providers" option listing CPUExecutionProvider only.

This would also allow people with older graphics chipsets that lack newer drivers to use Select Sky and Subject.