Training an artificial neural network involves an optimization process over the landscape defined by the cost (loss) as a function of the network parameters. We explore these landscapes using optimisation tools developed for potential energy landscapes in molecular science. The number of local minima and transition states (saddle points of index one), as well as the ratio of transition states to minima, grow rapidly with the number of nodes in the network. There is also a strong dependence on the regularisation parameter, with the landscape becoming more convex (fewer minima) as the regularisation term increases. We demonstrate that in our formulation, stationary points for networks with $N_h$ hidden nodes, including the minimal network required to fit the XOR data, are also stationary points for networks with $N_{h} +1$ hidden nodes when all the weights involving the additional nodes are zero. Hence, smaller networks optimized to train the XOR data are embedded in the landscapes of larger networks. Our results clarify certain aspects of the classification and sensitivity (to perturbations in the input data) of minima and saddle points for this system, and may provide insight into dropout and network compression.
SGD Provably Prioritizes a Shortcut Spurious Feature in the XOR Model
H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology（霍华德·米尔顿·斯图尔特工业与系统工程学院，佐治亚理工学院）；School of Electrical and Computer Engineering, Georgia Institute of Technology（电气与计算机工程学院，佐治亚理工学院）
On the Theory of Continual Learning with Gradient Descent for Neural Networks
Department of Computer Science and Engineering, University of California, San Diego（加州大学圣地亚哥分校计算机科学与工程系）；Department of Computer Science and Engineering, IIT, Bombay（印度孟买理工学院计算机科学与工程系）；Halicioğlu Data Science Institute, University of California, San Diego（加州大学圣地亚哥分校Halicioğlu数据科学研究所）
