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Hongchang Gao

26 accepted papers

2026

Convergence Analysis of Decentralized Hessian-/Jacobian-Free Algorithm for Nonconvex Stochastic Bilevel Optimization

ICML 2026poster

Decentralized stochastic bi-level optimization has been actively studied in recent years. However, existing studies assume that the lower-level loss function is strongly convex, which limits their applicability to many machine learning models. To address this limitation, in this paper, we propose a …

Cited by 0SourceScholar
2026

LS$^{2}$MC-GDA: A Smoothed Algorithm for Federated Stochastic Compositional Minimax Optimization

ICML 2026poster

Federated stochastic multi-level compositional minimax optimization supports a growing number of machine learning applications. However, the interplay of multi-level compositional structure, minimax formulation, and federated setting poses significant optimization challenges, resulting in slow conve…

Cited by 0SourceScholar
2026

On the Convergence of Decentralized Stochastic Minimax Optimization Algorithm with Compressed Communication

ICML 2026poster

The stochastic minimax optimization problem has widespread applications in machine learning. Recently, numerous distributed minimax optimization algorithms have been developed to handle distributed training data. However, most of these algorithms suffer from high communication costs. To address this…

Cited by 0SourceScholar
2025

Federated Stochastic Bilevel Optimization with Fully First-Order Gradients

IJCAI 2025

Federated stochastic bilevel optimization has been actively studied in recent years due to its widespread applications in machine learning. However, most existing federated stochastic bilevel optimization algorithms require the computation of second-order Hessian and Jacobian matrices, which leads t

Cited by 0SourcePDFScholar
2025

On the Convergence of Stochastic Smoothed Multi-Level Compositional Gradient Descent Ascent

NeurIPS 2025poster

Multi-level compositional optimization is a fundamental framework in machine learning with broad applications. While recent advances have addressed compositional minimization problems, the stochastic multi-level compositional minimax problem introduces significant new challenges—most notably, the bi…

Cited by 0SourceScholar
2024

A Doubly Recursive Stochastic Compositional Gradient Descent Method for Federated Multi-Level Compositional Optimization

ICML 2024poster

Federated compositional optimization has been actively studied in the past few years. However, existing methods mainly focus on the two-level compositional optimization problem, which cannot be directly applied to the multi-level counterparts. Moreover, the convergence rate of existing federated two…

Cited by 0SourcePDFScholar
2024

A Federated Stochastic Multi-level Compositional Minimax Algorithm for Deep AUC Maximization

ICML 2024poster

AUC maximization is an effective approach to address the imbalanced data classification problem in federated learning. In the past few years, a couple of federated AUC maximization approaches have been developed based on the minimax optimization. However, directly solving a minimax optimization prob…

Cited by 0SourcePDFScholar
2024

Achieving Fairness through Separability: A Unified Framework for Fair Representation Learning

AISTATS 2024poster

Fairness is a growing concern in machine learning as state-of-the-art models may amplify social prejudice by making biased predictions against specific demographics such as race and gender. Such discrimination raises issues in various fields such as employment, criminal justice, and trust score eval…

2024

Decentralized Multi-Level Compositional Optimization Algorithms with Level-Independent Convergence Rate

AISTATS 2024poster

Stochastic multi-level compositional optimization problems cover many new machine learning paradigms, e.g., multi-step model-agnostic meta-learning, which require efficient optimization algorithms for large-scale data. This paper studies the decentralized stochastic multi-level optimization algorith…

Cited by 4SourcePDFScholar
2024

Discriminative Forests Improve Generative Diversity for Generative Adversarial Networks

AAAI 2024technical

Improving the diversity of Artificial Intelligence Generated Content (AIGC) is one of the fundamental problems in the theory of generative models such as generative adversarial networks (GANs). Previous studies have demonstrated that the discriminator in GANs should have high capacity and robustness…

2023

Communication-Efficient Stochastic Gradient Descent Ascent with Momentum Algorithms

IJCAI 2023poster

Numerous machine learning models can be formulated as a stochastic minimax optimization problem, such as imbalanced data classification with AUC maximization. Developing efficient algorithms to optimize such kinds of problems is of importance and necessity. However, most existing algorithms restri…

Cited by 93SourcePDFScholar
2023

Distributed Stochastic Nested Optimization for Emerging Machine Learning Models: Algorithm and Theory

AAAI 2023technical

Traditional machine learning models can be formulated as the expected risk minimization (ERM) problem: minw∈Rd Eξ [l(w; ξ)], where w ∈ Rd denotes the model parameter, ξ represents training samples, l(·) is the loss function. Numerous optimization algorithms, such as stochastic gradient descent (SGD)…

Cited by 1SourcePDFScholar
2023

Federated Compositional Deep AUC Maximization

NeurIPS 2023poster

Federated learning has attracted increasing attention due to the promise of balancing privacy and large-scale learning; numerous approaches have been proposed. However, most existing approaches focus on problems with balanced data, and prediction performance is far from satisfactory for many real-wo…

Cited by 12SourcePDFScholar
2023

On the Convergence of Distributed Stochastic Bilevel Optimization Algorithms over a Network

AISTATS 2023poster

Bilevel optimization has been applied to a wide variety of machine learning models and numerous stochastic bilevel optimization algorithms have been developed in recent years. However, most existing algorithms restrict their focus on the single-machine setting so that they are incapable of handling…

Cited by 24SourcePDFScholar
2023

Set-level Guidance Attack: Boosting Adversarial Transferability of Vision-Language Pre-training Models

ICCV 2023oral

Vision-language pre-training (VLP) models have shown vulnerability to adversarial examples in multimodal tasks. Furthermore, malicious adversaries can be deliberately transferred to attack other black-box models. However, existing work has mainly focused on investigating white-box attacks. In this p…

Cited by 65PDFcodeScholar
2022

Efficient Decentralized Stochastic Gradient Descent Method for Nonconvex Finite-Sum Optimization Problems

AAAI 2022technical

Decentralized stochastic gradient descent methods have attracted increasing interest in recent years. Numerous methods have been proposed for the nonconvex finite-sum optimization problem. However, existing methods have a large sample complexity, slowing down the empirical convergence speed. To ad…

Cited by 6SourcePDFScholar
2022

On the Convergence of Local Stochastic Compositional Gradient Descent with Momentum

ICML 2022spotlight

Federated Learning has been actively studied due to its efficiency in numerous real-world applications in the past few years. However, the federated stochastic compositional optimization problem is still underexplored, even though it has widespread applications in machine learning. In this paper, we…

Cited by 22SourcePDFScholar
2021

On the Convergence of Communication-Efficient Local SGD for Federated Learning

AAAI 2021technical

Federated Learning (FL) has attracted increasing attention in recent years. A leading training algorithm in FL is local SGD, which updates the model parameter on each worker and averages model parameters across different workers only once in a while. Although it has fewer communication rounds than t…

Cited by 66SourcePDFScholar
2021

On the Convergence of Stochastic Compositional Gradient Descent Ascent Method

IJCAI 2021poster

The compositional minimax problem covers plenty of machine learning models such as the distributionally robust compositional optimization problem. However, it is yet another understudied problem to optimize the compositional minimax problem. In this paper, we develop a novel efficient stochastic co…

Cited by 7SourcePDFScholar
2021

Sample Efficient Decentralized Stochastic Frank-Wolfe Methods for Continuous DR-Submodular Maximization

IJCAI 2021poster

Continuous DR-submodular maximization is an important machine learning problem, which covers numerous popular applications. With the emergence of large-scale distributed data, developing efficient algorithms for the continuous DR-submodular maximization, such as the decentralized Frank-Wolfe method…

Cited by 11SourcePDFScholar
2020

Can Stochastic Zeroth-Order Frank-Wolfe Method Converge Faster for Non-Convex Problems?

ICML 2020poster

Frank-Wolfe algorithm is an efficient method for optimizing non-convex constrained problems. However, most of existing methods focus on the first-order case. In real-world applications, the gradient is not always available. To address the problem of lacking gradient in many applications, we propose…

Cited by 18SourcePDFScholar