[FIXED] How to perform operations like transpose or argmax in tensorflow c api

Issue

I have written code base on https://github.com/Neargye/hello_tf_c_api but I have to transpose input tensor and extend its dimensions. On output tensor I have to perform arg_max.

    auto graph = tf_utils::LoadGraph("D:\\projects\\vive\\Vive_Model_4_classes_frozen\\frozen_graph.pb");
    SCOPE_EXIT{ tf_utils::DeleteGraph(graph); }; // Auto-delete on scope exit.
    if (graph == nullptr) {
        std::cout << "Can't load graph" << std::endl;
        return 1;
    }
    
    const std::vector<TF_Output> input_ops = { {TF_GraphOperationByName(graph, "x"), 0} };
    const std::vector<TF_Tensor*> input_tensors = { tf_utils::CreateTensor(TF_FLOAT, shape, floatv) };
    
    SCOPE_EXIT{ tf_utils::DeleteTensors(input_tensors); }; // Auto-delete on scope exit.


    const std::vector<TF_Output> out_ops = { {TF_GraphOperationByName(graph, "Identity"), 0} };
    std::vector<TF_Tensor*> output_tensors = { nullptr };
    SCOPE_EXIT{ tf_utils::DeleteTensors(output_tensors); }; // Auto-delete on scope exit.

    auto session = tf_utils::CreateSession(graph);
    SCOPE_EXIT{ tf_utils::DeleteSession(session); }; // Auto-delete on scope exit.
    if (session == nullptr) {
        std::cout << "Can't create session" << std::endl;
        return 2;
    }

    auto code = tf_utils::RunSession(session, input_ops, input_tensors, out_ops, output_tensors);

    if (code == TF_OK) {
        auto result = tf_utils::GetTensorData<float>(output_tensors[0]);
        outImage = avl::Image(width, height, avl::PlainType::UInt8, 3, atl::NIL);

        //auto values = output.get_data<int64_t>();

        for (int w = 0; w < width; ++w) {
            for (int h = 0; h < height; ++h) {
                //int data = result[width * height *  width * h + w];
                int idx = getMaxIndex(result, 5, width, height, w, h);
                uint8_t* pixel = outImage.Ptr<uint8_t>(w, h);
                *pixel = (uint8_t)inColors[idx].X();
                *(pixel + 1) = (uint8_t)inColors[idx].Y();
                *(pixel + 2) = (uint8_t)inColors[idx].Z();
            }
        }
        //std::cout << "Output vals: " << result[0] << ", " << result[1] << ", " << result[2] << ", " << result[3] << std::endl;
    }
    else {
        std::cout << "Error run session TF_CODE: " << code;
        return code;
    }

But I can not wrap my head around how to perform operations on tensors in C API and documentation is non existing.

Solution

Ok, I managed to found the answer by reading this repo.

First you have to create:

    TF_Tensor* input_tensor = tf_utils::CreateTensor(TF_FLOAT, shape, floatv);
    TF_Status* status = TF_NewStatus();        
    TFE_TensorHandle* input_tensor_tfe_handle = TFE_NewTensorHandle(input_tensor, status);
    TFE_ContextOptions* contx_opts = TFE_NewContextOptions();//, &TFE_DeleteContextOptions);
    TFE_Context* tfe_context = TFE_NewContext(contx_opts, status);

Than you have to pass this variables into something like:

TFE_TensorHandle* TransposeTensor(TF_Status* status, TFE_TensorHandle* tfe_tensor, TFE_Context* context, std::vector<int> perm) {
TFE_Op* op = TFE_NewOp(context, "Transpose", status);

TFE_OpAddInput(op, tfe_tensor, status);


int shape = perm.size();

TF_Tensor* perm_tensor = tf_utils::CreateTensor(TF_INT32, { shape }, perm);
TFE_TensorHandle* perm_tfe = TFE_NewTensorHandle(perm_tensor, status);

TFE_OpAddInput(op, perm_tfe, status);


TF_DataType Tperm = static_cast<TF_DataType>(3);

//// Attributes
TFE_OpSetAttrType(op, "Tperm", Tperm);

SCOPE_EXIT{
        TFE_DeleteTensorHandle(perm_tfe);
TF_DeleteTensor(perm_tensor);
};

//// Execute Op
int num_outputs_op = 1;
TFE_TensorHandle* res[1] = { nullptr };
TFE_Execute(op, res, &num_outputs_op, status);

TF_Code code = TF_GetCode(status);

return res[0];
}

This code basicaly construct egear operation, by first creating op, than adding arguments and arguments type and finally exacuting the operation. To get transformed tensor you have to do:

  TF_Tensor* tensor = TFE_TensorHandleResolve(handle, status);

Answered By - TheDude