The default value for Keras model.compile metrics parameter is metrics=None. There are a plenty of explanations and information about this parameter different values, and I believe I pretty much understand their meaning and purpose, but what I struggle finding, is what is the behavior of the default value metrics=None.
The official documentation of the model.compile method here doesn't say anything about the default value (which is None), and googling about it for a while hasn't brought any enlightenment for me either so far.
I'd be greatful for any helpful hint on this!
It means it will not calculate any metric, it is not necessary to specifiy a metric. The only parameters that need to be specified are optimizer and loss.
These are the only things necessary to train a model, the metric doesn't go into the calculation for backpropagation.
By not specifing metric, simply no metric will be calculated. A metric is something extra that is calculated for you to simbolize how well a problem is being solved. Usually for classification you would use cross entropy.