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Lisheng Ren

9 accepted papers

2025

Algorithms and SQ Lower Bounds for Robustly Learning Real-valued Multi-Index Models

NeurIPS 2025spotlight

We study the complexity of learning real-valued Multi-Index Models (MIMs) under the Gaussian distribution. A $K$-MIM is a function $f:\mathbb{R}^d\to \mathbb{R}$ that depends only on the projection of its input onto a $K$-dimensional subspace. We give a general algorithm for PAC learning a broad c…

Cited by 0SourceScholar
2025

Statistical Query Hardness of Multiclass Linear Classification with Random Classification Noise

ICML 2025oral

We study the task of Multiclass Linear Classification (MLC) in the distribution-free PAC model with Random Classification Noise (RCN). Specifically, the learner is given a set of labeled examples $(x, y)$, where $x$ is drawn from an unknown distribution on $R^d$ and the labels are generated by…

Cited by 0SourcePDFScholar
2024

Fast Co-Training under Weak Dependence via Stream-Based Active Learning

ICML 2024oral

Co-training is a classical semi-supervised learning method which only requires a small number of labeled examples for learning, under reasonable assumptions. Despite extensive literature on the topic, very few hypothesis classes are known to be provably efficiently learnable via co-training, even un…

Cited by 3SourcePDFScholar
2023

Near-Optimal Cryptographic Hardness of Agnostically Learning Halfspaces and ReLU Regression under Gaussian Marginals

ICML 2023poster

We study the task of agnostically learning halfspaces under the Gaussian distribution. Specifically, given labeled examples $(\\mathbf{x},y)$ from an unknown distribution on $\\mathbb{R}^n \\times \\{\pm 1 \\}$, whose marginal distribution on $\\mathbf{x}$ is the standard Gaussian and the labels $y$…

Cited by 31SourcePDFScholar
2023

SQ Lower Bounds for Non-Gaussian Component Analysis with Weaker Assumptions

NeurIPS 2023poster

We study the complexity of Non-Gaussian Component Analysis (NGCA) in the Statistical Query (SQ) model. Prior work developed a methodology to prove SQ lower bounds for NGCA that have been applicable to a wide range of contexts. In particular, it was known that for any univariate distribution $A$ sati…

Cited by 17SourcePDFScholar
2022

Cryptographic Hardness of Learning Halfspaces with Massart Noise

NeurIPS 2022accept

We study the complexity of PAC learning halfspaces in the presence of Massart noise. In this problem, we are given i.i.d. labeled examples $(\mathbf{x}, y) \in \mathbb{R}^N \times \{ \pm 1\}$, where the distribution of $\mathbf{x}$ is arbitrary and the label $y$ is a Massart corruption of $f(\mathbf…

Cited by 26SourcePDFScholar
2022

Hardness of Learning a Single Neuron with Adversarial Label Noise

AISTATS 2022poster

We study the problem of distribution-free learning of a single neuron under adversarial label noise with respect to the squared loss. For a wide range of activation functions, including ReLUs and sigmoids, we prove hardness of learning results in the Statistical Query model and under a well-studied…

Cited by 14SourcePDFScholar
2022

SQ Lower Bounds for Learning Single Neurons with Massart Noise

NeurIPS 2022accept

We study the problem of PAC learning a single neuron in the presence of Massart noise. Specifically, for a known activation function $f: \mathbb{R}\to \mathbb{R}$, the learner is given access to labeled examples $(\mathbf{x}, y) \in \mathbb{R}^d \times \mathbb{R}$, where the marginal distribution of…

Cited by 5SourcePDFScholar