It's all about Gas (Part 1)
(How to play with balloons and validate neural networks in the process.) We have just finished training our model. But the work isn’t over yet. Now we have to figure out whether the training went well. When evaluating both how the training phase unfolded and the final state the model has reached, two fundamental concepts come into play: overfitting and underfitting. In the first case the model has adapted itself excessively to the training data. In the second, on the contrary, it wasn’t able to “learn” enough. In both cases we find ourselves faced with a model incapable of generalizing. ...