[FIXED] Tensorflow lite model output always gives same output no matter the input

Issue

My goal is to run a Keras model I have made in my ESP32 microcontroller. I have the libraries all working correctly.

I have created a Keras model using google Collab that looks to be working fine when I give it random test data within google Collab. The model has two input features and 4 different outputs.(a multiple-output regression model)

However, when I export and load the model into my c++ application in the ESP32 it does not matter what the inputs are, it always predicts the same output.

I have based myself in this code in order to load and run the model in c++ : https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/micro/examples/magic_wand/main_functions.cc

And this is my version of the code

namespace {
    tflite::ErrorReporter* error_reporter = nullptr;
    const tflite::Model* model = nullptr;
    tflite::MicroInterpreter* interpreter = nullptr;
    TfLiteTensor* input = nullptr;
    TfLiteTensor* output = nullptr;
    int inference_count = 0;

    // Create an area of memory to use for input, output, and intermediate arrays.
    // Finding the minimum value for your model may require some trial and error.
    constexpr int kTensorArenaSize = 2 * 2048;
    uint8_t tensor_arena[kTensorArenaSize];
}  // namespace 

static void setup(){
    static tflite::MicroErrorReporter micro_error_reporter;
    error_reporter = &micro_error_reporter;

    model = tflite::GetModel(venti_model);
    if (model->version() != TFLITE_SCHEMA_VERSION) {
        error_reporter->Report(
            "Model provided is schema version %d not equal "
            "to supported version %d.",
            model->version(), TFLITE_SCHEMA_VERSION);
        return;
    }

    // This pulls in all the operation implementations we need.
    // NOLINTNEXTLINE(runtime-global-variables)
    static tflite::ops::micro::AllOpsResolver resolver;

    // Build an interpreter to run the model with.
    static tflite::MicroInterpreter static_interpreter(
            model, resolver, tensor_arena, kTensorArenaSize, error_reporter);
    interpreter = &static_interpreter;

    // Allocate memory from the tensor_arena for the model's tensors.
    TfLiteStatus allocate_status = interpreter->AllocateTensors();
    if (allocate_status != kTfLiteOk) {
        error_reporter->Report("AllocateTensors() failed");
        return;
    }

    // Obtain pointers to the model's input and output tensors.
    input = interpreter->input(0);

    ESP_LOGI("TENSOR SETUP", "input size = %d", input->dims->size);
    ESP_LOGI("TENSOR SETUP", "input size in bytes = %d", input->bytes);
    ESP_LOGI("TENSOR SETUP", "Is input float32? = %s", (input->type == kTfLiteFloat32) ? "true" : "false");
    ESP_LOGI("TENSOR SETUP", "Input data dimentions = %d",input->dims->data[1]);

    output = interpreter->output(0);

    ESP_LOGI("TENSOR SETUP", "output size = %d", output->dims->size);
    ESP_LOGI("TENSOR SETUP", "output size in bytes = %d", output->bytes);
    ESP_LOGI("TENSOR SETUP", "Is input float32? = %s", (output->type == kTfLiteFloat32) ? "true" : "false");
    ESP_LOGI("TENSOR SETUP", "Output data dimentions = %d",output->dims->data[1]);

}

static bool setupDone = true;

static void the_ai_algorithm_task(){

    /* First time task is init setup the ai model */
    if(setupDone == false){
        setup();
        setupDone = true;
    }

    /* Load the input data i.e deltaT1 and deltaT2 */
    //int i = 0;
    input->data.f[0] = 2.0;   /* Different values dont change the output */
    input->data.f[1] = 3.2;   


    // Run inference, and report any error
    TfLiteStatus invoke_status = interpreter->Invoke();
    if (invoke_status != kTfLiteOk) {
        error_reporter->Report("Invoke failed");
        // return;
    }

    /* Retrieve outputs Fan , AC , Vent 1 , Vent 2 */
    double fan = output->data.f[0];
    double ac = output->data.f[1];
    double vent1 = output->data.f[2];
    double vent2 = output->data.f[3];


    ESP_LOGI("TENSOR SETUP", "fan = %lf", fan);
    ESP_LOGI("TENSOR SETUP", "ac = %lf", ac);
    ESP_LOGI("TENSOR SETUP", "vent1 = %lf", vent1);
    ESP_LOGI("TENSOR SETUP", "vent2 = %lf", vent2);
    
}

The model seems to load ok as the dimensions and sizes are correct. But the output is always the same 4 values

fan = 0.0087
ac = 0.54
vent1 = 0.73
vent2 = 0.32

Any idea on what can be going wrong? Is it something about my model or am I just not using the model correctly in my c++ application?

Solution

I have found the issue and the answer.

It was not the C++ code, it was the model. Originally, I made my model with 3 hidden layers of 64, 20, and 8 (I am new to ML so I was only playing with random values) and it was giving me the issue.

To solve it I just changed the hidden layers to 32, 16, and 8 and the C++ code was outputting right values.

Answered By - Farynx