A stochastic optimization approach to train non-linear neural networks with regularization of higher-order total variation

While highly expressive parametric models including deep neural networks have an advantage to model complicated concepts, training such highly non-linear models is known to yield a high risk of notorious overfitting. To address this issue, this study considers a $k$th order total variation ($k$-TV) regularization, which is defined as the squared integral of the $k$th order derivative of the parametric models to be trained; penalizing the $k$-TV is expected to yield a smoother function, which is expected to avoid overfitting. While the $k$-TV terms applied to general parametric models are computationally intractable due to the integration, this study provides a stochastic optimization algorithm, that can efficiently train general models with the $k$-TV regularization without conducting explicit numerical integration. The proposed approach can be applied to the training of even deep neural networks whose structure is arbitrary, as it can be implemented by only a simple stochastic gradient descent algorithm and automatic differentiation. Our numerical experiments demonstrate that the neural networks trained with the $K$-TV terms are more ``resilient'' than those with the conventional parameter regularization. The proposed algorithm also can be extended to the physics-informed training of neural networks (PINNs).