CoreML custom layer implemented by `object-C` doesn't work in `swift` testing project

Question

Created Jan ’22

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I convert a pytorch model to mlmodel with a custom layer, and create a test app in swift to test my model. When i implement the custom layer by swift, it works well. However when i implement the custom layer by object-C, the code return

2022-01-14 17:58:49.964377+0800 CustomLayers[2547:968723] [coreml] Error in adding network -1.
2022-01-14 17:58:49.965023+0800 CustomLayers[2547:968723] [coreml] MLModelAsset: load failed with error Error Domain=com.apple.CoreML Code=0 "Error in declaring network." UserInfo={NSLocalizedDescription=Error in declaring network.}
2022-01-14 17:58:49.965085+0800 CustomLayers[2547:968723] [coreml] MLModelAsset: modelWithError: load failed with error Error Domain=com.apple.CoreML Code=0 "Error in declaring network." UserInfo={NSLocalizedDescription=Error in declaring network.}
Fatal error: 'try!' expression unexpectedly raised an error: Error Domain=com.apple.CoreML Code=0 "Error in declaring network." UserInfo={NSLocalizedDescription=Error in declaring network.}: file CustomLayers/model_2.swift, line 114
2022-01-14 17:58:49.966267+0800 CustomLayers[2547:968723] Fatal error: 'try!' expression unexpectedly raised an error: Error Domain=com.apple.CoreML Code=0 "Error in declaring network." UserInfo={NSLocalizedDescription=Error in declaring network.}: file CustomLayers/model_2.swift, line 114
(lldb)

It seems the model load failed with object-C custom layer. So i wonder does object-C custom layer implementation can't work with swift project? Although i try to set the CustomLayers-Bridging-Header.h. It still doesn't work.

System Information

mac OS: 11.6.1 Big Sur
xcode: 12.5.1
coremltools: 5.1.0
test device: iphone 11

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Answer 1

Engineer OP

Apple

Jan ’22

It may be helpful to double check that the name of your objective-c class conforming to the MLCustomLayer protocol matches the custom layer name described in the model. You can check the name the model expects by looking at the Dependencies tab in Xcodes view of the .mlmodel (or .mlpackage) file.

Note: Another thing to keep in mind is that Swift class names are prefixed with your module/bundle, e.g. YourApp.YourCustomLayerClass. It is best to encode an objective-C compatible class name in your model, e.g. YourCustomLayerClass, if you want the flexibility to implement it in both objective-C and Swift. In Swift, you would use the @objc(YourCustomClass) to expose it to the Core ML runtime without the module prefix.

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Answer 2

stx-000 OP

Jan ’22

This has been solved. I found it's caused by the return value of outputShapesForInputShapes not matching MLCustomLayer protocol. Now i have resolved it. Thanks!

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