Kernel and Rich Regimes in Overparametrized Models
Blake E Woodworth, Suriya Gunasekar, Jason Lee, Edward Moroshko, Pedro Henrique Pamplona Savarese, Itay Golan, Daniel Soudry, Nathan Srebro
Subject areas: Neural networks/deep learning,
Presented in: Session 3B, Session 3D
[Zoom link for poster in Session 3B], [Zoom link for poster in Session 3D]
Abstract:
A recent line of work studies overparametrized neural networks in the ``kernel regime,'' i.e.~when during training the network behaves as a kernelized linear predictor, and thus, training with gradient descent has the effect of finding the corresponding minimum RKHS norm solution. This stands in contrast to other studies which demonstrate how gradient descent on overparametrized networks can induce rich implicit biases that are not RKHS norms. Building on an observation by \citet{chizat2018note}, we show how the \textbf{\textit{scale of the initialization}} controls the transition between the ``kernel'' (aka lazy) and ``rich'' (aka active) regimes and affects generalization properties in multilayer homogeneous models. We provide a complete and detailed analysis for a family of simple depth-$D$ linear networks that exhibit an interesting and meaningful transition between the kernel and rich regimes, and highlight an interesting role for the \emph{width} of the models. We further demonstrate this transition empirically for matrix factorization and multilayer non-linear networks.