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.
Contents
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 or C++ APIs currently. Additional support via the Objective-C API is in progress.
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 may decrease the performance but will provide reference output value without precision loss, which is useful for validation.
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?
Supported ops
Following ops are supported by the CoreML Execution Provider,
| 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:Gemm | Input B should be constant. |
| ai.onnx:GlobalAveragePool | Only 2D Pool is supported. |
| ai.onnx:GlobalMaxPool | Only 2D Pool is supported. |
| ai.onnx:MatMul | Input B should be constant. |
| ai.onnx:MaxPool | Only 2D Pool is supported. |
| ai.onnx:PRelu | Input slope should be constant. Input slope should either have shape [C, 1, 1] or have 1 element. |
| ai.onnx:Relu | |
| ai.onnx:Reshape | |
| ai.onnx:Resize | |
| ai.onnx:Sigmoid | |
| ai.onnx:Squeeze | |
| ai.onnx:Tanh | |
| ai.onnx:Transpose |