Incremental Gradient Algorithms with Stepsizes Bounded Away from Zero

  • Authors:
  • M. V. Solodov

  • Affiliations:
  • Instituto de Matemática Pura e Aplicada, Estrada Dona Castorina 110, Jardim Botânico, Rio de Janeiro, RJ 22460-320, Brazil. E-mail: solodov@impa.br

  • Venue:
  • Computational Optimization and Applications
  • Year:
  • 1998

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Abstract

We consider the class of incremental gradient methods for minimizing a sum of continuously differentiable functions. An importantnovel feature of our analysis is that the stepsizes are kept bounded awayfrom zero. We derive the first convergence results of any kind for thiscomputationally important case. In particular, we show that a certainϵ-approximate solution can be obtained and establish the lineardependence of ϵ on the stepsize limit. Incremental gradient methodsare particularly well-suited for large neural network training problemswhere obtaining an approximate solution is typically sufficient and is oftenpreferable to computing an exact solution. Thus, in the context of neuralnetworks, the approach presented here is related to the principle oftolerant training. Our results justify numerous stepsize rules that werederived on the basis of extensive numerical experimentation but for which notheoretical analysis was previously available. In addition, convergence to(exact) stationary points is established when the gradient satisfies acertain growth property.