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Ankit Pensia

13 accepted papers

2025

Information-Computation Tradeoffs for Noiseless Linear Regression with Oblivious Contamination

NeurIPS 2025poster

We study the task of noiseless linear regression under Gaussian covariates in the presence of additive oblivious contamination. Specifically, we are given i.i.d.\ samples from a distribution $(x, y)$ on $\mathbb R^d \times \mathbb R$ with $x \sim \mathcal N(0,I_d)$ and $y = x^\top \beta + z$, wh…

Cited by 0SourceScholar
2024

Robust Sparse Estimation for Gaussians with Optimal Error under Huber Contamination

ICML 2024poster

We study Gaussian sparse estimation tasks in Huber's contamination model with a focus on mean estimation, PCA, and linear regression. For each of these tasks, we give the first sample and computationally efficient robust estimators with optimal error guarantees, within constant factors. All prior ef…

Cited by 0SourcePDFScholar
2023

A Spectral Algorithm for List-Decodable Covariance Estimation in Relative Frobenius Norm

NeurIPS 2023spotlight

We study the problem of list-decodable Gaussian covariance estimation. Given a multiset $T$ of $n$ points in $\mathbb{R}^d$ such that an unknown $\alpha<1/2$ fraction of points in $T$ are i.i.d. samples from an unknown Gaussian $\mathcal{N}(\mu, \Sigma)$, the goal is to output a list of $O(1/\alpha)…

Cited by 4SourcePDFScholar
2023

Near-Optimal Algorithms for Gaussians with Huber Contamination: Mean Estimation and Linear Regression

NeurIPS 2023poster

We study the fundamental problems of Gaussian mean estimation and linear regression with Gaussian covariates in the presence of Huber contamination. Our main contribution is the design of the first sample near-optimal and almost linear-time algorithms with optimal error guarantees for both thes…

Cited by 4SourcePDFScholar
2023

Nearly-Linear Time and Streaming Algorithms for Outlier-Robust PCA

ICML 2023poster

We study principal component analysis (PCA), where given a dataset in $\mathbb R^d$ from a distribution, the task is to find a unit vector $v$ that approximately maximizes the variance of the distribution after being projected along $v$. Despite being a classical task, standard estimators fail drast…

Cited by 10SourcePDFScholar
2022

List-Decodable Sparse Mean Estimation via Difference-of-Pairs Filtering

NeurIPS 2022accept

We study the problem of list-decodable sparse mean estimation. Specifically, for a parameter $\alpha \in (0, 1/2)$, we are given $m$ points in $\mathbb{R}^n$, $\lfloor \alpha m \rfloor$ of which are i.i.d. samples from a distribution $D$ with unknown $k$-sparse mean $\mu$. No assumptions are made on…

Cited by 15SourcePDFScholar
2022

Outlier-Robust Sparse Mean Estimation for Heavy-Tailed Distributions

NeurIPS 2022accept

We study the fundamental task of outlier-robust mean estimation for heavy-tailed distributions in the presence of sparsity. Specifically, given a small number of corrupted samples from a high-dimensional heavy-tailed distribution whose mean $\mu$ is guaranteed to be sparse, the goal is to efficient…

Cited by 16SourcePDFScholar
2022

Streaming Algorithms for High-Dimensional Robust Statistics

ICML 2022spotlight

We study high-dimensional robust statistics tasks in the streaming model. A recent line of work obtained computationally efficient algorithms for a range of high-dimensional robust statistics tasks. Unfortunately, all previous algorithms require storing the entire dataset, incurring memory at least…

Cited by 29SourcePDFScholar
2021

Statistical Query Lower Bounds for List-Decodable Linear Regression

NeurIPS 2021spotlight

We study the problem of list-decodable linear regression, where an adversary can corrupt a majority of the examples. Specifically, we are given a set $T$ of labeled examples $(x, y) \in \mathbb{R}^d \times \mathbb{R}$ and a parameter $0< \alpha <1/2$ such that an $\alpha$-fraction of the points in $…

Cited by 26SourcePDFScholar
2020

Optimal Lottery Tickets via Subset Sum: Logarithmic Over-Parameterization is Sufficient

NeurIPS 2020spotlight

The strong lottery ticket hypothesis (LTH) postulates that one can approximate any target neural network by only pruning the weights of a sufficiently over-parameterized random network. A recent work by Malach et al. [MYSS20] establishes the first theoretical analysis for the strong LTH: one can pr…

2020

Outlier Robust Mean Estimation with Subgaussian Rates via Stability

NeurIPS 2020poster

We study the problem of outlier robust high-dimensional mean estimation under a bounded covariance assumption, and more broadly under bounded low-degree moment assumptions. We consider a standard stability condition from the recent robust statistics literature and prove that, except with exponential…

Cited by 76SourcePDFScholar