WIP [Documentation]: C# Workflow for consuming "Augmented" Onnx model with Custom Operators

3 ways to add a new operator

There is an issue to missing link

Use Case: PyTorch exports a custom_op_test.onnx with TWO custom operators

custom_op_test.onnx

• CustomOpOne
• CustomOpTwo

To consume in CSharp exported PyTorch Onnx with custom operators, it is necessary to register these Custom Operators (written in C++) and provided in a Shared Library

CSharp API for loading Shared Library with Custom Operators

Create Custom_op_library.dll

• Custom_op_library.dll : source files

CSharp api for loading/registrating custom op shared library

RegisterCustomOps

custom_op_library.h

#pragma once
#include "onnxruntime_c_api.h"

#ifdef __cplusplus
extern "C" {
#endif

ORT_EXPORT OrtStatus* ORT_API_CALL RegisterCustomOps(OrtSessionOptions* options, const OrtApiBase* api);

#ifdef __cplusplus
}
#endif

custom_op_library.cc

• With 2 Custom Operators
  • CustomOpOne
  • CustomOpTwo

#include "custom_op_library.h"

#define ORT_API_MANUAL_INIT
#include "onnxruntime_cxx_api.h"
#undef ORT_API_MANUAL_INIT


OrtStatus* ORT_API_CALL RegisterCustomOps(OrtSessionOptions* options, const OrtApiBase* api) {
  OrtCustomOpDomain* domain = nullptr;
  const OrtApi* ortApi = api->GetApi(ORT_API_VERSION);

  if (auto status = ortApi->CreateCustomOpDomain(c_OpDomain, &domain)) {
    return status;
  }

  AddOrtCustomOpDomainToContainer(domain, ortApi);

  if (auto status = ortApi->CustomOpDomain_Add(domain, &c_CustomOpOne)) {
    return status;
  }

  if (auto status = ortApi->CustomOpDomain_Add(domain, &c_CustomOpTwo)) {
    return status;
  }

  return ortApi->AddCustomOpDomain(options, domain);
}

In CSharp Register Custom Operators within the Shared Library: Custom_op_library.dll

CSharp UnitTest: NetCoreApp/InferenceTest.netcore.c

private void TestRegisterCustomOpLibrary()
{
    using (var option = new SessionOptions())
    {
        string libName = "custom_op_library.dll";
        string modelPath = "custom_op_test.onnx";

The c++ unit tests discussion

@natke

WIP for CSharp
[Documentation] How to register custom operator in onnxruntime

Other references:

• NER transformers model packed in one onnx file with Sentencepiece Tokenizer

Start with docs/AddingCustomOp.md, the custom_op_library sources, and csharp/test/Microsoft.ML.OnnxRuntime.Tests.NetCoreApp/InferenceTest.netcore.cs. Trace how custom_op_test.onnx, custom_op_library.dll, and RegisterCustomOps are used in the C# test. Done means the C# workflow for building, loading, and registering the two custom operators is complete and documented.