Even smaller IRIS classification for microcontrollers

smaller_iris_classification.ino

/**
 * Do dot product between vectors
 */
double compute_kernel(double x[3], ...) {
    va_list w;
    double kernel = 0.0;
    va_start(w, 3);
    for (uint16_t i = 0; i < 3; i++)
            kernel += x[i] *  va_arg(w, double) ;
    return kernel;
}

/**
 * Predict class from features
 */
uint8_t predict(double *x) {
  double decision[3] = {0};
  decision[0] = (compute_kernel(x,  7.7, 2.6, 6.9, 2.3) - 81.63139999999996 ) * -0.294744878436046 - 3.616434571769916;
  decision[1] = -0.6931764919596977;
  decision[2] = (compute_kernel(x,  6.3, 3.3, 6.0, 2.5) - 72.44853333333332 ) * 0.2380608846577031 - 2.3493312085177753;
  
  uint8_t idx = 0;
  double val = decision[0];
  for (uint8_t i = 1; i < 3; i++) {
      if (decision[i] > val) {
          idx = i;
          val = decision[i];
      }
  }
  return idx;
}

/**
 * Get accuracy on test set
 */
void self_test() {
    int correct = 0;
    double X[10][4] = {
             {  5.5 , 4.2 , 1.4 , 0.2  }
            , {  5.1 , 3.8 , 1.6 , 0.2  }
            , {  5.5 , 2.6 , 4.4 , 1.2  }
            , {  6.6 , 2.9 , 4.6 , 1.3  }
            , {  6.3 , 2.8 , 5.1 , 1.5  }
            , {  6.1 , 2.6 , 5.6 , 1.4  }
            , {  7.6 , 3 , 6.6 , 2.1  }
            , {  6.3 , 2.7 , 4.9 , 1.8  }
            , {  4.5 , 2.3 , 1.3 , 0.3  }
            , {  6.3 , 2.3 , 4.4 , 1.3  }
    };
    int y[10] = { 0, 0, 1, 1, 2, 2, 2, 2, 0, 1  };
    for (int i = 0; i < 10; i++) {
        int predicted = predict(X[i]);
        Serial.print('#');
        Serial.print(i);
        Serial.print("\t Expected ");
        Serial.print(y[i]);
        Serial.print("\tGot ");
        Serial.print(predicted);
        Serial.print('\t');
        Serial.print(predicted == y[i] ? "OK\n" : "ERR\n");
        correct += (predicted == y[i]) ? 1 : 0;
    }
    Serial.print("Run 10 predictions. ");
    Serial.print(correct);
    Serial.print(" were OK (");
    Serial.print(100 * correct / 10);
    Serial.print("%)");
}


void setup() {
  Serial.begin(115200);
  delay(3000);

  self_test();
  
}

void loop() {}