Unbiased least squares regression via averaged stochastic gradient descent
- URL: http://arxiv.org/abs/2406.18623v1
- Date: Wed, 26 Jun 2024 11:39:22 GMT
- Title: Unbiased least squares regression via averaged stochastic gradient descent
- Authors: Nabil Kahalé,
- Abstract summary: We consider an on-line least squares regression problem with optimal solution $theta*$ and Hessian matrix H.
For $kge2$, we provide an unbiased estimator of $theta*$ that is a modification of the time-average estimator.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: We consider an on-line least squares regression problem with optimal solution $\theta^*$ and Hessian matrix H, and study a time-average stochastic gradient descent estimator of $\theta^*$. For $k\ge2$, we provide an unbiased estimator of $\theta^*$ that is a modification of the time-average estimator, runs with an expected number of time-steps of order k, with O(1/k) expected excess risk. The constant behind the O notation depends on parameters of the regression and is a poly-logarithmic function of the smallest eigenvalue of H. We provide both a biased and unbiased estimator of the expected excess risk of the time-average estimator and of its unbiased counterpart, without requiring knowledge of either H or $\theta^*$. We describe an "average-start" version of our estimators with similar properties. Our approach is based on randomized multilevel Monte Carlo. Our numerical experiments confirm our theoretical findings.
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