text: Title: Accuracies totally different 
  Body: Hi. I am converting the tree model to C using m2cgen. Although the inference latencies are much lower, the accuracies are way off. Here's how I am converting and reading the .so files
  
  ```
  from xgboost import XGBRFRegressor
  num_est=100
  
  model = XGBRFRegressor(n_estimators=num_est, max_depth=8)
  model.fit(X_train, y_train)
  
  code = m2c.export_to_c(model)
  len(code)
  
  with open('model.c', 'w') as f:
      f.write(code)
  
  !gcc -Ofast -shared -o lgb_score.so -fPIC model.c
  !ls -l lgb_score.so
  
  lib = ctypes.CDLL('./lgb_score.so')
  score = lib.score
  # Define the types of the output and arguments of this function.
  score.restype = ctypes.c_double
  score.argtypes = [ndpointer(ctypes.c_double)]
  ```
  Why is this happening and how can I fix it?