Francis Bach Blog: Taming Exploding Variance of Exponential Means With Least Squares

BachFrancis · x · 2026-09-25

In a new blog post, machine learning researcher Francis Bach analyzes the exploding variance problem in estimating log-sum-exp functions via sampling: the relative error of estimating E[e^z] grows as (e^σ²-1)/n, exploding exponentially with σ, and taking logarithms doesn't help. He proposes a least-squares-based remedy and, as a bonus, derives a spectral closed-form formula for approximate multinomial logistic regression.

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