Minimax Efficient Finite-Difference Stochastic Gradient Estimators Using Black-Box Function Evaluations
We consider stochastic gradient estimation using noisy black-box function evaluations. A standard approach is to use the finite-difference method or its variants. While natural, it is open to our knowledge whether its statistical accuracy is the best possible. This paper argues so by showing that central finite-difference is a nearly minimax optimal zeroth-order gradient estimator, among both the class of linear estimators and the much larger class of all (nonlinear) estimators.
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