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Sivaraman Balakrishnan

22 accepted papers

2023

Complementary Benefits of Contrastive Learning and Self-Training Under Distribution Shift

NeurIPS 2023poster

Self-training and contrastive learning have emerged as leading techniques for incorporating unlabeled data, both under distribution shift (unsupervised domain adaptation) and when it is absent (semi-supervised learning). However, despite the popularity and compatibility of these techniques, their ef…

Cited by 17SourcePDFScholar
2023

Online Label Shift: Optimal Dynamic Regret meets Practical Algorithms

NeurIPS 2023spotlight

This paper focuses on supervised and unsupervised online label shift, where the class marginals $Q(y)$ varies but the class-conditionals $Q(x|y)$ remain invariant. In the unsupervised setting, our goal is to adapt a learner, trained on some offline labeled data, to changing label distributions given…

2023

RLSbench: Domain Adaptation Under Relaxed Label Shift

ICML 2023poster

Despite the emergence of principled methods for domain adaptation under label shift, their sensitivity to shifts in class conditional distributions is precariously under explored. Meanwhile, popular deep domain adaptation heuristics tend to falter when faced with label proportions shifts. While seve…

2022

Domain Adaptation under Open Set Label Shift

NeurIPS 2022accept

We introduce the problem of domain adaptation under Open Set Label Shift (OSLS), where the label distribution can change arbitrarily and a new class may arrive during deployment, but the class-conditional distributions $p(x|y)$ are domain-invariant. OSLS subsumes domain adaptation under label shift…

2022

Heavy-tailed Streaming Statistical Estimation

AISTATS 2022poster

We consider the task of heavy-tailed statistical estimation given streaming $p$-dimensional samples. This could also be viewed as stochastic optimization under heavy-tailed distributions, with an additional $O(p)$ space complexity constraint. We design a clipped stochastic gradient descent algorithm…

Cited by 14SourcePDFScholar
2022

Leveraging unlabeled data to predict out-of-distribution performance

ICLR 2022poster

Real-world machine learning deployments are characterized by mismatches between the source (training) and target (test) distributions that may cause performance drops. In this work, we investigate methods for predicting the target domain accuracy using only labeled source data and unlabeled target d…

2021

Minimax Optimal Regression over Sobolev Spaces via Laplacian Regularization on Neighborhood Graphs

AISTATS 2021poster

In this paper we study the statistical properties of Laplacian smoothing, a graph-based approach to nonparametric regression. Under standard regularity conditions, we establish upper bounds on the error of the Laplacian smoothing estimator \smash{$\widehat{f}$}, and a goodness-of-fit test also based…

Cited by 20SourcePDFScholar
2021

Mixture Proportion Estimation and PU Learning:A Modern Approach

NeurIPS 2021spotlight

Given only positive examples and unlabeled examples (from both positive and negative classes), we might hope nevertheless to estimate an accurate positive-versus-negative classifier. Formally, this task is broken down into two subtasks: (i) Mixture Proportion Estimation (MPE)---determining the fract…

2021

On Proximal Policy Optimization’s Heavy-tailed Gradients

ICML 2021spotlight

Modern policy gradient algorithms such as Proximal Policy Optimization (PPO) rely on an arsenal of heuristics, including loss clipping and gradient clipping, to ensure successful learning. These heuristics are reminiscent of techniques from robust statistics, commonly used for estimation in outlier-…

Cited by 15SourcePDFScholar
2021

RATT: Leveraging Unlabeled Data to Guarantee Generalization

ICML 2021oral

To assess generalization, machine learning scientists typically either (i) bound the generalization gap and then (after training) plug in the empirical risk to obtain a bound on the true risk; or (ii) validate empirically on holdout data. However, (i) typically yields vacuous guarantees for overpara…

2020

A Unified View of Label Shift Estimation

NeurIPS 2020poster

Under label shift, the label distribution $p(y)$ might change but the class-conditional distributions $p(x|y)$ do not. There are two dominant approaches for estimating the label marginal. BBSE, a moment-matching approach based on confusion matrices, is provably consistent and provides interpretable…

2020

On Learning Ising Models under Huber's Contamination Model

NeurIPS 2020poster

We study the problem of learning Ising models in a setting where some of the samples from the underlying distribution can be arbitrarily corrupted. In such a setup, we aim to design statistically optimal estimators in a high-dimensional scaling in which the number of nodes p, the number of edges k…

Cited by 23SourcePDFScholar
2018

How Many Samples are Needed to Estimate a Convolutional Neural Network?

NeurIPS 2018poster

A widespread folklore for explaining the success of Convolutional Neural Networks (CNNs) is that CNNs use a more compact representation than the Fully-connected Neural Network (FNN) and thus require fewer training samples to accurately estimate their parameters. We initiate the study of rigorously c…

Cited by 88SourcePDFScholar
2018

Nonparametric Regression with Comparisons: Escaping the Curse of Dimensionality with Ordinal Information

ICML 2018oral

In supervised learning, we leverage a labeled dataset to design methods for function estimation. In many practical situations, we are able to obtain alternative feedback, possibly at a low cost. A broad goal is to understand the usefulness of, and to design algorithms to exploit, this alternative fe…

Cited by 8SourcePDFScholar
2018

Optimization of Smooth Functions with Noisy Observations: Local Minimax Rates

NeurIPS 2018poster

We consider the problem of global optimization of an unknown non-convex smooth function with noisy zeroth-order feedback. We propose a local minimax framework to study the fundamental difficulty of optimizing smooth functions with adaptive function evaluations. We show that for functions with fast g…

Cited by 21SourcePDFScholar
2018

Stochastic Zeroth-order Optimization in High Dimensions

AISTATS 2018poster

We consider the problem of optimizing a high-dimensional convex function using stochastic zeroth-order queries. Under sparsity assumptions on the gradients or function values, we present two algorithms: a successive component/feature selection algorithm and a noisy mirror descent algorithm using Las…

Cited by 0SourcePDFScholar
2016

Local Maxima in the Likelihood of Gaussian Mixture Models: Structural Results and Algorithmic Consequences

NeurIPS 2016poster

We provide two fundamental results on the population (infinite-sample) likelihood function of Gaussian mixture models with $M \geq 3$ components. Our first main result shows that the population likelihood function has bad local maxima even in the special case of equally-weighted mixtures of well-sep…

Cited by 198SourcePDFScholar
2016

Statistical Inference for Cluster Trees

NeurIPS 2016poster

A cluster tree provides an intuitive summary of a density function that reveals essential structure about the high-density clusters. The true cluster tree is estimated from a finite sample from an unknown true density. This paper addresses the basic question of quantifying our uncertainty by assess…

Cited by 32SourcePDFScholar
2016

Stochastically Transitive Models for Pairwise Comparisons: Statistical and Computational Issues

ICML 2016poster

There are various parametric models for analyzing pairwise comparison data, including the Bradley-Terry-Luce (BTL) and Thurstone models, but their reliance on strong parametric assumptions is limiting. In this work, we study a flexible model for pairwise comparisons, under which the probabilities of…

Cited by 193SourcePDFScholar
2015

Estimation from Pairwise Comparisons: Sharp Minimax Bounds with Topology Dependence

AISTATS 2015poster

Consider the problem of identifying the underlying qualities of a set of items based on measuring noisy comparisons between pairs of items. The Bradley-Terry-Luce (BTL) and Thurstone models are the most widely used parametric models for such pairwise comparison data. Working within a standard minima…

Cited by 211SourcePDFScholar