Figure 2.

For (a) CD-1 and (b) PCD-10, we show the number and relative size of groups emerging from clustering hidden units in the ensemble of RBMs for every position of the secondary structure that we study. In both cases, we conclude the following: for α-helices, N_h = 3 is the optimal number of hidden units, while for β-sheets it is N_h = 2. These are the maximum values where the number of groups matches the number of hidden units and the noise is still tiny, i.e., where each RBM in the ensemble has learned the same set of hidden units.