On Tuning Neural ODE for Stability, Consistency and Faster Convergence
摘要
Neural-ODE parameterizes a differential equation using continuous depth neural network and solves it using numerical ODE-integrator. This model offer a constant memory cost compared to models with discrete sequence of hidden layers in which memory cost increases linearly with the number of layers. In addition to memory efficiency, other benefits of Neural-ODE include adaptability of evaluation approach to input, and flexibility to choose numerical precision or fast training. However, despite having all these benefits, it still has some limitations. We identify the ODE-integrator (also called ODE-solver) as the weakest link in the chain as it may have consistency, convergence and stability (CCS) issues and may suffer from slower convergence or may not converge at all. We propose a first-order Nesterov’s accelerated gradient descent(NAG) based ODE-solver which is proven to be stable, consistent and convergent. We empirically demonstrate the efficacy of our approach by training faster, while achieving better or comparable performance against Neural-ODE employing other fixed-step explicit ODE-solvers as well as discrete depth models such as ResNet in three different tasks including supervised classification, density estimation, and time-series modelling.