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Lichen Zhang

17 accepted papers

2026

Graph-based Nearest Neighbors with Dynamic Updates via Random Walks

ICLR 2026poster

Approximate nearest neighbor search (ANN) is a common way to retrieve relevant search results, especially now in the context of large language models and retrieval augmented generation. One of the most widely used algorithms for ANN is based on constructing a multi-layer graph over the dataset, call…

Cited by 0SourceScholar
2025

Differential Privacy for Euclidean Jordan Algebra with Applications to Private Symmetric Cone Programming

NeurIPS 2025poster

In this paper, we study differentially private mechanisms for functions whose outputs lie in a Euclidean Jordan algebra. Euclidean Jordan algebras capture many important mathematical structures and form the foundation of linear programming, second-order cone programming, and semidefinite programming…

Cited by 0SourceScholar
2025

Efficient Alternating Minimization with Applications to Weighted Low Rank Approximation

ICLR 2025poster

Weighted low rank approximation is a fundamental problem in numerical linear algebra, and it has many applications in machine learning. Given a matrix $M \in \mathbb{R}^{n \times n}$, a non-negative weight matrix $W \in \mathbb{R}_{\geq 0}^{n \times n}$, a parameter $k$, the goal is to output two ma…

Cited by 10SourcePDFScholar
2025

On Differential Privacy for Adaptively Solving Search Problems via Sketching

ICML 2025oral

Recently differential privacy has been used for a number of streaming, data structure, and dynamic graph problems as a means of hiding the internal randomness of the data structure, so that multiple possibly adaptive queries can be made without sacrificing the correctness of the responses. Although…

Cited by 0SourcePDFScholar
2024

Log-concave Sampling from a Convex Body with a Barrier: a Robust and Unified Dikin Walk

NeurIPS 2024poster

We consider the problem of sampling from a $d$-dimensional log-concave distribution $\pi(\theta) \propto \exp(-f(\theta))$ for $L$-Lipschitz $f$, constrained to a convex body (described by $n$ hyperplanes) equipped with a barrier function, contained in a ball of radius $R$ with a $w$-warm start. W…

Cited by 0SourcePDFScholar
2024

Low Rank Matrix Completion via Robust Alternating Minimization in Nearly Linear Time

ICLR 2024poster

Given a matrix $M\in \mathbb{R}^{m\times n}$, the low rank matrix completion problem asks us to find a rank-$k$ approximation of $M$ as $UV^\top$ for $U\in \mathbb{R}^{m\times k}$ and $V\in \mathbb{R}^{n\times k}$ by only observing a few entries specified by a set of entries $\Omega\subseteq [m]\tim…

Cited by 30SourcePDFScholar
2023

A Nearly-Optimal Bound for Fast Regression with $\ell_\infty$ Guarantee

ICML 2023poster

Given a matrix $A\in \mathbb{R}^{n\times d}$ and a vector $b\in \mathbb{R}^n$, we consider the regression problem with $\ell_\infty$ guarantees: finding a vector $x'\in \mathbb{R}^d$ such that $||x'-x^* ||_\infty \leq \frac{\epsilon}{\sqrt{d}}\cdot ||Ax^*-b||_2\cdot ||A^\dagger||$ with $x^*$ being t…

Cited by 0SourcePDFScholar
2023

An Online and Unified Algorithm for Projection Matrix Vector Multiplication with Application to Empirical Risk Minimization

AISTATS 2023poster

Online matrix vector multiplication is a fundamental step and bottleneck in many machine learning algorithms. It is defined as follows: given a matrix at the pre-processing phase, at each iteration one receives a query vector and needs to form the matrix-vector product (approximately) before observi…

Cited by 53SourcePDFScholar
2023

Sketching Meets Differential Privacy: Fast Algorithm for Dynamic Kronecker Projection Maintenance

ICML 2023poster

Projection maintenance is one of the core data structure tasks. Efficient data structures for projection maintenance have led to recent breakthroughs in many convex programming algorithms. In this work, we further extend this framework to the Kronecker product structure. Given a constraint matrix ${…

Cited by 31SourcePDFScholar
2023

Sketching for First Order Method: Efficient Algorithm for Low-Bandwidth Channel and Vulnerability

ICML 2023poster

Sketching is one of the most fundamental tools in large-scale machine learning. It enables runtime and memory saving via randomly compressing the original large problem into lower dimensions. In this paper, we propose a novel sketching scheme for the first order method in large-scale distributed lea…

Cited by 33SourcePDFScholar