2020

Analyzing Finite Neural Networks: Can We Trust Neural Tangent Kernel Theory?

Seleznova, Mariia, Kutyniok, Gitta

Understand

Neural Tangent Kernel (NTK) theory is widely used to study the dynamics of infinitely-wide deep neural networks (DNNs) under gradient descent.

  • But do the results for infinitely-wide networks give us hints about the behavior of real finite-width ones? In this paper, we study empirically when NTK theory is valid in practice for fully-connected ReLU and sigmoid DNNs.
  • We find out that whether a network is in the NTK regime depends on the hyperparameters of random initialization and the network's depth.
  • In particular, NTK theory does not explain the behavior of sufficiently deep networks initialized so that their gradients explode as they propagate through the network's layers: the kernel is random at initialization and changes significantly during training in this case, contrary to NTK theory.

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