Fig. 3.

Comparison of different number of layers. Shown are learning curves for different number of layers ($L=\mathrm{2,3},\mathrm{4,6}$). As the network goes deeper, the result can be increased. However, deeper structure cannot always lead to better results, sometimes even worse. (Note: for interpretation of the references to color in this figure legend, the reader is referred to the online version of this article.)