6,311 research outputs found
Flexible Multi-layer Sparse Approximations of Matrices and Applications
The computational cost of many signal processing and machine learning
techniques is often dominated by the cost of applying certain linear operators
to high-dimensional vectors. This paper introduces an algorithm aimed at
reducing the complexity of applying linear operators in high dimension by
approximately factorizing the corresponding matrix into few sparse factors. The
approach relies on recent advances in non-convex optimization. It is first
explained and analyzed in details and then demonstrated experimentally on
various problems including dictionary learning for image denoising, and the
approximation of large matrices arising in inverse problems
On the Optimization of Deep Networks: Implicit Acceleration by Overparameterization
Conventional wisdom in deep learning states that increasing depth improves
expressiveness but complicates optimization. This paper suggests that,
sometimes, increasing depth can speed up optimization. The effect of depth on
optimization is decoupled from expressiveness by focusing on settings where
additional layers amount to overparameterization - linear neural networks, a
well-studied model. Theoretical analysis, as well as experiments, show that
here depth acts as a preconditioner which may accelerate convergence. Even on
simple convex problems such as linear regression with loss, ,
gradient descent can benefit from transitioning to a non-convex
overparameterized objective, more than it would from some common acceleration
schemes. We also prove that it is mathematically impossible to obtain the
acceleration effect of overparametrization via gradients of any regularizer.Comment: Published at the International Conference on Machine Learning (ICML)
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