ONNXRuntime-Cpp and ONNXRuntime python give different results:

[devendraswamy]

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Question

I am facing the problem with YOLOV5 model. While I am testing my Python ONNX code, all the bounding box (bbox) values are correct. However, when I perform the same process with my C++ code, I am getting incorrect bbox values.

the image processed in ptyhon code: image_data = np.expand_dims(image_data, axis=0) # Add batch dimension

and feed that image to python pyd file (c++ inference file complied to pyd)

auto output_tensors = session.Run(Ort::RunOptions{ nullptr }, input_names, &input_tensor, 1, output_names, 1);

Additional

complied or build C++ code is:

include

include <pybind11/pybind11.h>

include <pybind11/numpy.h>

include

include

include

include

using namespace std; namespace py = pybind11;

class OnnxModel { public: OnnxModel(const std::string& model_path) : env(ORT_LOGGING_LEVEL_WARNING, "OnnxModel"), session(env, std::wstring(model_path.begin(), model_path.end()).c_str(), Ort::SessionOptions()) { Ort::AllocatorWithDefaultOptions allocator;

    // Get input and output names as Ort::AllocatedStringPtr
    Ort::AllocatedStringPtr input_name_alloc = session.GetInputNameAllocated(0, allocator);
    Ort::AllocatedStringPtr output_name_alloc = session.GetOutputNameAllocated(0, allocator);

    // Convert the Ort::AllocatedStringPtr to std::string using the get() method
    input_name = std::string(input_name_alloc.get());
    output_name = std::string(output_name_alloc.get());

    // Optional: Print the input and output names for debugging
    std::cout << "Input name: " << input_name << std::endl;
    std::cout << "Output name: " << output_name << std::endl;
}

// Accept a 4D numpy array: (batch_size, channels, height, width)
py::array_t<float> run(py::array_t<float> input_array) {
    // Request a buffer from the numpy array
    py::buffer_info buf = input_array.request();

    // Check that the input is indeed a 4-dimensional array
    if (buf.ndim != 4) {
        throw std::runtime_error("Input should be a 4-dimensional array (batch_size, channels, height, width)");
    }

    // Convert numpy array data to std::vector<float>
    std::vector<float> input_data(static_cast<float*>(buf.ptr), 
                                  static_cast<float*>(buf.ptr) + buf.size);

    // Run the inference
    return run_inf(input_data, {1, 3, 640, 640});  // Adjust shape based on your model's input
}

py::array_t<float> run_inf(const std::vector<float>& input_data, const std::array<int64_t, 4>& input_shape) {
    // Create input tensor
    Ort::MemoryInfo memory_info = Ort::MemoryInfo::CreateCpu(OrtArenaAllocator, OrtMemTypeDefault);
    Ort::Value input_tensor = Ort::Value::CreateTensor<float>(
        memory_info,
        const_cast<float*>(input_data.data()),
        input_data.size(),
        input_shape.data(),
        input_shape.size()
    );

    // Prepare input and output names
    const char* input_names[] = { input_name.c_str() };
    const char* output_names[] = { output_name.c_str() };

    // Run the model
    auto output_tensors = session.Run(Ort::RunOptions{ nullptr }, input_names, &input_tensor, 1, output_names, 1);

    // Get the output data
    float* output_data = output_tensors[0].GetTensorMutableData<float>();
    size_t output_count = output_tensors[0].GetTensorTypeAndShapeInfo().GetElementCount();

    // Create a numpy array from the output data
    return py::array_t<float>(output_count, output_data);
}

private: Ort::Env env; Ort::Session session; std::string input_name; std::string output_name; };

PYBIND11_MODULE(onnxloader, m) { py::class(m, "OnnxModel") .def(py::init<const std::string&>()) .def("run", &OnnxModel::run); }

Image feeding from python code:

Function to preprocess the image

def preprocess_image(image_path, input_size=(640, 640)):

Load the image using OpenCV

image = cv2.imread(image_path, cv2.IMREAD_COLOR)  # Load image in color mode
if image is None:
    raise ValueError(f"Could not open or find the image: {image_path}")
# Convert from BGR to RGB format
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
# Resize the image to match the input size expected by the model
image = cv2.resize(image, input_size)
# Normalize the image to [0, 1] range
image = image.astype(np.float32) / 255.0  # Convert to float and normalize
# Rearrange the image to CHW format (1, C, H, W)
image_data = np.transpose(image, (2, 0, 1))  # Convert to CHW format
image_data = np.expand_dims(image_data, axis=0)  # Add batch dimension
print(f"Image preprocessed: type = {type(image_data)}, shape = {image_data.shape}")
return image_data, image  # Return the preprocessed image data

[UltralyticsAssistant]

👋 Hello @devendraswamy, thank you for reaching out with your issue regarding YOLOv5 🚀! This is an automated response to guide you further, and an Ultralytics engineer will be with you soon.

Please make sure you are following our Tutorials to ensure your setup is correct. They provide a helpful starting point for concepts including Custom Data Training and Hyperparameter Evolution.

If this is a 🐛 Bug Report, please provide a minimum reproducible example so we can better assist you.

In your case, ensure that both Python and C++ environments use the same preprocessing steps and ONNX model settings. Discrepancies could lead to different outputs.

Requirements

Ensure you have Python>=3.8.0 with all requirements.txt installed and are using PyTorch>=1.8. To set up:

git clone https://github.com/ultralytics/yolov5  # clone
cd yolov5
pip install -r requirements.txt  # install

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