SPEEDING-UP BACKPROPAGATION BY DATA ORTHONORMALIZATION†

In this work we study a network architecture that is able to overcome some of the limitations of conventional second-order acceleration methods of the backpropagation algorithm. This architecture is based on the combination of conventional backpropagation layers with unsupervised layers that perform a simple data orthogonalization. A distributed learning algorithm for these unsupervised layers is briefly reviewed, and a simple learning strategy for the combined architecture is described. The performance of the suggested architecture is evaluated using the well-known “two-spirals” problem, showing speed gains of at least one order of magnitude over conventional acceleration techniques. Moreover, it is shown that rather small feed-forward networks are able to solve this simple classification task within an acceptable learning time.