2018

Inexact SARAH Algorithm for Stochastic Optimization

Nguyen, Lam M., Scheinberg, Katya, Takáč, Martin

Understand

We develop and analyze a variant of the SARAH algorithm, which does not require computation of the exact gradient.

  • Thus this new method can be applied to general expectation minimization problems rather than only finite sum problems.
  • While the original SARAH algorithm, as well as its predecessor, SVRG, require an exact gradient computation on each outer iteration, the inexact variant of SARAH (iSARAH), which we develop here, requires only stochastic gradient computed on a mini-batch of sufficient size.
  • The proposed method combines variance reduction via sample size selection and iterative stochastic gradient updates.

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