An online backpropagation algorithm with validation error-based adaptive learning rate

Abstract

We present a new learning algorithm for feed-forward neural networks based on the standard Backpropagation method using an adaptive global learning rate. The adaption is based on the evolution of the error criteria but in contrast to most other approaches, our method uses the error measured on the validation set instead of the training set to dynamically adjust the global learning rate. At no time the examples of the validation set are directly used for training the network in order to maintain its original purpose of validating the training and to perform "early stopping". The proposed algorithm is a heuristic method consisting of two phases. In the first phase the learning rate is adjusted after each iteration such that a minimum of the error criteria on the validation set is quickly attained. In the second phase, this search is refined by repeatedly reverting to previous weight configurations and decreasing the global learning rate. We experimentally show that the proposed method rapidly converges and that it outperforms standard Backpropagation in terms of generalization when the size of the training set is reduced. © Springer-Verlag Berlin Heidelberg 2007.