onnxruntime/docs/execution-providers/CoreML-ExecutionProvider.md

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Apple - CoreML	Instructions to execute ONNX Runtime with CoreML	Execution Providers	8	/docs/reference/execution-providers/CoreML-ExecutionProvider

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CoreML Execution Provider

Core ML is a machine learning framework introduced by Apple. It is designed to seamlessly take advantage of powerful hardware technology including CPU, GPU, and Neural Engine, in the most efficient way in order to maximize performance while minimizing memory and power consumption.

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Requirements

The CoreML Execution Provider (EP) requires iOS devices with iOS 13 or higher, or Mac computers with macOS 10.15 or higher.

It is recommended to use Apple devices equipped with Apple Neural Engine to achieve optimal performance.

Install

Pre-built binaries of ONNX Runtime with CoreML EP for iOS are published to CocoaPods.

See here for installation instructions.

Build

For build instructions for iOS devices, please see Build for iOS.

Usage

The ONNX Runtime API details are here.

The CoreML EP can be used via the C, C++, Objective-C, C# and Java APIs.

The CoreML EP must be explicitly registered when creating the inference session. For example:

Ort::Env env = Ort::Env{ORT_LOGGING_LEVEL_ERROR, "Default"};
Ort::SessionOptions so;
uint32_t coreml_flags = 0;
Ort::ThrowOnError(OrtSessionOptionsAppendExecutionProvider_CoreML(so, coreml_flags));
Ort::Session session(env, model_path, so);

Configuration Options

There are several run time options available for the CoreML EP.

To use the CoreML EP run time options, create an unsigned integer representing the options, and set each individual option by using the bitwise OR operator.

uint32_t coreml_flags = 0;
coreml_flags |= COREML_FLAG_ONLY_ENABLE_DEVICE_WITH_ANE;

Available Options

COREML_FLAG_USE_CPU_ONLY

Limit CoreML to running on CPU only.

This decreases performance but provides reference output value without precision loss, which is useful for validation.
Intended for developer usage only.

COREML_FLAG_ENABLE_ON_SUBGRAPH

Enable CoreML EP to run on a subgraph in the body of a control flow operator (i.e. a Loop, Scan or If operator).

COREML_FLAG_ONLY_ENABLE_DEVICE_WITH_ANE

By default the CoreML EP will be enabled for all compatible Apple devices.

Setting this option will only enable CoreML EP for Apple devices with a compatible Apple Neural Engine (ANE). Note, enabling this option does not guarantee the entire model to be executed using ANE only.

For more information, see Which devices have an ANE?

COREML_FLAG_ONLY_ALLOW_STATIC_INPUT_SHAPES

Only allow the CoreML EP to take nodes with inputs that have static shapes. By default the CoreML EP will also allow inputs with dynamic shapes, however performance may be negatively impacted by inputs with dynamic shapes.

COREML_FLAG_CREATE_MLPROGRAM

Create an MLProgram format model. Requires Core ML 5 or later (iOS 15+ or macOS 12+). The default is for a NeuralNetwork model to be created as that requires Core ML 3 or later (iOS 13+ or macOS 10.15+).

Supported operators

NeuralNetwork

Operators that are supported by the CoreML Execution Provider when a NeuralNetwork model (the default) is created:

Operator	Note
ai.onnx:Add
ai.onnx:ArgMax
ai.onnx:AveragePool	Only 2D Pool is supported.
ai.onnx:BatchNormalization
ai.onnx:Cast
ai.onnx:Clip
ai.onnx:Concat
ai.onnx:Conv	Only 1D/2D Conv is supported. Weights and bias should be constant.
ai.onnx:DepthToSpace	Only DCR mode DepthToSpace is supported.
ai.onnx:Div
ai.onnx:Flatten
ai.onnx:Gather	Input indices with scalar value is not supported.
ai.onnx:Gemm	Input B should be constant.
ai.onnx:GlobalAveragePool	Only 2D Pool is supported.
ai.onnx:GlobalMaxPool	Only 2D Pool is supported.
ai.onnx:LeakyRelu
ai.onnx:LRN
ai.onnx:MatMul	Input B should be constant.
ai.onnx:MaxPool	Only 2D Pool is supported.
ai.onnx:Mul
ai.onnx:Pad	Only constant mode and last two dim padding is supported. Input pads and constant_value should be constant. If provided, axes should be constant.
ai.onnx:Pow	Only supports cases when both inputs are fp32.
ai.onnx:PRelu	Input slope should be constant. Input slope should either have shape [C, 1, 1] or have 1 element.
ai.onnx:Reciprocal
ai.onnx.ReduceSum
ai.onnx:Relu
ai.onnx:Reshape
ai.onnx:Resize
ai.onnx:Shape	Attribute start with non-default value is not supported. Attribute end is not supported.
ai.onnx:Sigmoid
ai.onnx:Slice	Inputs starts, ends, axes, and steps should be constant. Empty slice is not supported.
ai.onnx:Squeeze
ai.onnx:Sqrt
ai.onnx:Sub
ai.onnx:Tanh
ai.onnx:Transpose

MLProgram

Operators that are supported by the CoreML Execution Provider when a MLProgram model (COREML_FLAG_CREATE_MLPROGRAM flag is set) is created:

Operator	Note
ai.onnx:Add
ai.onnx:AveragePool	Only 2D Pool is supported currently. 3D and 5D support can be added if needed.
ai.onnx:Clip
ai.onnx:Conv	Only 1D/2D Conv is supported. Bias if provided must be constant.
ai.onnx:Div
ai.onnx:Gemm	Input B must be constant.
ai.onnx:GlobalAveragePool	Only 2D Pool is supported currently. 3D and 5D support can be added if needed.
ai.onnx:GlobalMaxPool	Only 2D Pool is supported currently. 3D and 5D support can be added if needed.
ai.onnx:MatMul	Only support for transA == 0, alpha == 1.0 and beta == 1.0 is currently implemented.
ai.onnx:MaxPool	Only 2D Pool is supported currently. 3D and 5D support can be added if needed.
ai.onnx:Mul
ai.onnx:Pow	Only supports cases when both inputs are fp32.
ai.onnx:Relu
ai.onnx:Reshape
ai.onnx:Sub