Cross-Platform onnxruntime Wrapper for Go

About

This library seeks to provide an interface for loading and executing neural networks from Go(lang) code, while remaining as simple to use as possible.

A few example applications using this library can be found in the onnxruntime_go_examples repository.

The onnxruntime library provides a way to load and execute ONNX-format neural networks, though the library primarily supports C and C++ APIs. Several efforts exist to have written Go(lang) wrappers for the onnxruntime library, but as far as I can tell, none of these existing Go wrappers support Windows. This is due to the fact that Microsoft's onnxruntime library assumes the user will be using the MSVC compiler on Windows systems, while CGo on Windows requires using Mingw.

This wrapper works around the issues by manually loading the onnxruntime shared library, removing any dependency on the onnxruntime source code beyond the header files. Naturally, this approach works equally well on non-Windows systems.

Additionally, this library uses Go's recent addition of generics to support multiple Tensor data types; see the NewTensor or NewEmptyTensor functions.

Note on onnxruntime Library Versions

At the time of writing, this library uses version 1.18.0 of the onnxruntime C API headers. So, it will probably only work with version 1.18.0 of the onnxruntime shared libraries, as well. If you need to use a different version, or if I get behind on updating this repository, updating or changing the onnxruntime version should be fairly easy:

1. Replace the onnxruntime_c_api.h file with the version corresponding to the onnxruntime version you wish to use.

2. Replace the test_data/onnxruntime.dll (or test_data/onnxruntime*.so) file with the version corresponding to the onnxruntime version you wish to use.

3. (If you care about DirectML support) Verify that the entries in the DummyOrtDMLAPI struct in onnxruntime_wrapper.c match the order in which they appear in the OrtDmlApi struct from the dml_provider_factory.h header in the official repo. See the comment on this struct in onnxruntime_wrapper.c for more information.

Note that both the C API header and the shared library files are available to download from the releases page in the official repo. Download the archive for the release you want to use, and extract it. The header file is located in the "include" subdirectory, and the shared library will be located in the "lib" subdirectory. (On Linux systems, you'll need the version of the .so with the appended version numbers, e.g., libonnxruntime.so.1.18.0, and not the libonnxruntime.so, which is just a symbolic link.) The archive will contain several other files containing C++ headers, debug symbols, and so on, but you shouldn't need anything other than the single onnxruntime shared library and onnxruntime_c_api.h. (The exception is if you're wanting to enable GPU support, where you may need other shared-library files, such as execution_providers_cuda.dll and execution_providers_shared.dll on Windows.)

Requirements

To use this library, you'll need a version of Go with cgo support. If you are not using an amd64 version of Windows or Linux (or if you want to provide your own library for some other reason), you simply need to provide the correct path to the shared library when initializing the wrapper. This is seen in the first few lines of the following example.

Note that if you want to use CUDA, you'll need to be using a version of the onnxruntime shared library with CUDA support, as well as be using a CUDA version supported by the underlying version of your onnxruntime library. For example, version 1.18.0 of the onnxruntime library only supports CUDA versions 11.8 or 12.4. See the onnxruntime CUDA support documentation for more specifics.

Example Usage

The full documentation can be found at pkg.go.dev.

Additionally, several example command-line applications complete with necessary networks and data can be found in the onnxruntime_go_examples repository.

The following example illustrates how this library can be used to load and run an ONNX network taking a single input tensor and producing a single output tensor, both of which contain 32-bit floating point values. Note that error handling is omitted; each of the functions returns an err value, which will be non-nil in the case of failure.

import (
    "fmt"
    ort "github.com/yalue/onnxruntime_go"
    "os"
)

func main() {
    // This line _may_ be optional; by default the library will try to load
    // "onnxruntime.dll" on Windows, and "onnxruntime.so" on any other system.
    // For stability, it is probably a good idea to always set this explicitly.
    ort.SetSharedLibraryPath("path/to/onnxruntime.so")

    err := ort.InitializeEnvironment()
    if err != nil {
        panic(err)
    }
    defer ort.DestroyEnvironment()

    // For a slight performance boost and convenience when re-using existing
    // tensors, this library expects the user to create all input and output
    // tensors prior to creating the session. If this isn't ideal for your use
    // case, see the DynamicAdvancedSession type in the documnentation, which
    // allows input and output tensors to be specified when calling Run()
    // rather than when initializing a session.
    inputData := []float32{0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9}
    inputShape := ort.NewShape(2, 5)
    inputTensor, err := ort.NewTensor(inputShape, inputData)
    defer inputTensor.Destroy()
    // This hypothetical network maps a 2x5 input -> 2x3x4 output.
    outputShape := ort.NewShape(2, 3, 4)
    outputTensor, err := ort.NewEmptyTensor[float32](outputShape)
    defer outputTensor.Destroy()

    session, err := ort.NewAdvancedSession("path/to/network.onnx",
        []string{"Input 1 Name"}, []string{"Output 1 Name"},
        []ort.Value{inputTensor}, []ort.Value{outputTensor}, nil)
    defer session.Destroy()

    // Calling Run() will run the network, reading the current contents of the
    // input tensors and modifying the contents of the output tensors.
    err = session.Run()

    // Get a slice view of the output tensor's data.
    outputData := outputTensor.GetData()

    // If you want to run the network on a different input, all you need to do
    // is modify the input tensor data (available via inputTensor.GetData())
    // and call Run() again.

    // ...
}

Deprecated APIs

Older versions of this library used a typed Session[T] struct to keep track of sessions. In retrospect, associating type parameters with Sessions was unnecessary, and the AdvancedSession type, along with its associated APIs, was added to rectify this mistake. For backwards compatibility, the old typed Session[T] and DynamicSession[T] types are still included and unlikely to be removed. However, they now delegate their functionality to AdvancedSession internally. New code should always favor using AdvancedSession directly.

Running Tests and System Compatibility for Testing

Navigate to this directory and run go test -v, or optionally go test -v -bench=.. All tests should pass; tests relating to CUDA or other accelerator support will be skipped on systems or onnxruntime builds that don't support them.

Currently, this repository includes a copy of the onnxruntime shared libraries for a few systems, including AMD64 windows, ARM64 Linux, and ARM64 darwin. These should allow tests to pass on those systems without users needing to copy additional libraries beyond cloning this repository. In the future, however, this may change if support for more systems are added or removed.

You may want to use a different version of the onnxruntime shared library for a couple reasons. In particular:

1. The included shared library copies do not include support for CUDA or other accelerated execution providers, so CUDA-related tests will always be skipped if you use the default libraries in this repo.

2. Many systems, including AMD64 and i386 Linux, and x86 osx, do not currently have shared libraries included in test_data/ in the first place. (I would like to keep this directory, and the overall repo, smaller by keeping the number of shared libraries small.)

If these or other reasons apply to you, the test code will check the ONNXRUNTIME_SHARED_LIBRARY_PATH environment variable before attempting to load a library from test_data/. So, if you are using one of these systems or want accelerator-related tests to run, you should set the environment variable to the path to the onnxruntime shared library. Afterwards, go test -v should run and pass.

Training API Support

This wrapper supports the onnxruntime training API on limited platforms. See the NewTrainingSession and associated data types or functions to use it. So far, the training API has only been tested on Linux, on x86_64 architectures.

If you are not sure whether your platform or build of onnxruntime supports training, you can call onnxruntime_go.IsTrainingSupported(), which will return true if training is supported on your system.

The training API is not currently supported on Windows. While training support has simply not been tested on other Linux and Mac systems, it is currently known to be unsupported on Windows. This is due to NewTrainingSession fundamentally requiring filesystem paths, even within the C API. This is difficult to handle in Windows, since the Windows onnxruntime DLLs require wide-character strings (unlike the Linux and osx shared libraries). This means that calling these functions on Windows would require converting UTF-8 Go strings to compatible strings when invoking the C API on Windows only. This should possible, but it is simply not a development priority at the moment.