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Mehrdad Mahdavi

26 accepted papers

2025

Stochastic Compositional Minimax Optimization with Provable Convergence Guarantees

AISTATS 2025poster

Stochastic compositional minimax problems are prevalent in machine learning, yet there exist only limited established findings on the convergence of this class of problems. In this paper, we propose a formal definition of the stochastic compositional minimax problem, which involves optimizing a mini…

Cited by 0SourceScholar
2024

On the Generalization Ability of Unsupervised Pretraining

AISTATS 2024poster

Recent advances in unsupervised learning have shown that unsupervised pre-training, followed by fine-tuning, can improve model generalization. However, a rigorous understanding of how the representation function learned on an unlabeled dataset affects the generalization of the fine-tuned model is la…

Cited by 6SourcePDFScholar
2024

Stochastic Quantum Sampling for Non-Logconcave Distributions and Estimating Partition Functions

ICML 2024poster

We present quantum algorithms for sampling from possibly non-logconcave probability distributions expressed as $\pi(x) \propto \exp(-\beta f(x))$ as well as quantum algorithms for estimating the partition function for such distributions. We also incorporate a stochastic gradient oracle that implemen…

Cited by 4SourcePDFScholar
2023

Distributed Personalized Empirical Risk Minimization

NeurIPS 2023poster

This paper advocates a new paradigm Personalized Empirical Risk Minimization (PERM) to facilitate learning from heterogeneous data sources without imposing stringent constraints on computational resources shared by participating devices. In PERM, we aim at learning a distinct model for each clie…

Cited by 5SourcePDFScholar
2023

Do We Really Need Complicated Model Architectures For Temporal Networks?

ICLR 2023top-5%

Recurrent neural network (RNN) and self-attention mechanism (SAM) are the de facto methods to extract spatial-temporal information for temporal graph learning. Interestingly, we found that although both RNN and SAM could lead to a good performance, in practice neither of them is always necessary. In…

Cited by 156SourcePDFScholar
2023

Efficiently Forgetting What You Have Learned in Graph Representation Learning via Projection

AISTATS 2023poster

As privacy protection receives much attention, unlearning the effect of a specific node from a pre-trained graph learning model has become equally important. However, due to the node dependency in the graph-structured data, representation unlearning in Graph Neural Networks (GNNs) is challenging and…

2023

Mixture Weight Estimation and Model Prediction in Multi-source Multi-target Domain Adaptation

NeurIPS 2023poster

We consider a problem of learning a model from multiple sources with the goal to perform well on a new target distribution. Such problem arises in learning with data collected from multiple sources (e.g. crowdsourcing) or learning in distributed systems, where the data can be highly heterogeneous.…

Cited by 3SourcePDFScholar
2023

Understanding Deep Gradient Leakage via Inversion Influence Functions

NeurIPS 2023poster

Deep Gradient Leakage (DGL) is a highly effective attack that recovers private training images from gradient vectors. This attack casts significant privacy challenges on distributed learning from clients with sensitive data, where clients are required to share gradients. Defending against such att…

2022

Learn Locally, Correct Globally: A Distributed Algorithm for Training Graph Neural Networks

ICLR 2022poster

Despite the recent success of Graph Neural Networks (GNNs), training GNNs on large graphs remains challenging. The limited resource capacities of the existing servers, the dependency between nodes in a graph, and the privacy concern due to the centralized storage and model learning have spurred the…

Cited by 44SourcePDFScholar
2022

Learning Distributionally Robust Models at Scale via Composite Optimization

ICLR 2022poster

To train machine learning models that are robust to distribution shifts in the data, distributionally robust optimization (DRO) has been proven very effective. However, the existing approaches to learning a distributionally robust model either require solving complex optimization problems such as se…

Cited by 6SourcePDFScholar
2022

Local SGD Optimizes Overparameterized Neural Networks in Polynomial Time

AISTATS 2022poster

In this paper we prove that Local (S)GD (or FedAvg) can optimize deep neural networks with Rectified Linear Unit (ReLU) activation function in polynomial time. Despite the established convergence theory of Local SGD on optimizing general smooth functions in communication-efficient distributed optimi…

Cited by 16SourcePDFScholar
2022

Tight Analysis of Extra-gradient and Optimistic Gradient Methods For Nonconvex Minimax Problems

NeurIPS 2022accept

Despite the established convergence theory of Optimistic Gradient Descent Ascent (OGDA) and Extragradient (EG) methods for the convex-concave minimax problems, little is known about the theoretical guarantees of these methods in nonconvex settings. To bridge this gap, for the first time, this paper…

Cited by 16SourcePDFScholar
2021

Federated Learning with Compression: Unified Analysis and Sharp Guarantees

AISTATS 2021poster

In federated learning, communication cost is often a critical bottleneck to scale up distributed optimization algorithms to collaboratively learn a model from millions of devices with potentially unreliable or limited communication and heterogeneous data distributions. Two notable trends to deal wit…

2021

Local Stochastic Gradient Descent Ascent: Convergence Analysis and Communication Efficiency

AISTATS 2021poster

Local SGD is a promising approach to overcome the communication overhead in distributed learning by reducing the synchronization frequency among worker nodes. Despite the recent theoretical advances of local SGD in empirical risk minimization, the efficiency of its counterpart in minimax optimizatio…

Cited by 78SourcePDFScholar
2021

Meta-learning with an Adaptive Task Scheduler

NeurIPS 2021poster

To benefit the learning of a new task, meta-learning has been proposed to transfer a well-generalized meta-model learned from various meta-training tasks. Existing meta-learning algorithms randomly sample meta-training tasks with a uniform probability, under the assumption that tasks are of equal im…

2021

On Provable Benefits of Depth in Training Graph Convolutional Networks

NeurIPS 2021poster

Graph Convolutional Networks (GCNs) are known to suffer from performance degradation as the number of layers increases, which is usually attributed to over-smoothing. Despite the apparent consensus, we observe that there exists a discrepancy between the theoretical understanding of over-smoothing an…

2020

GCN meets GPU: Decoupling “When to Sample” from “How to Sample”

NeurIPS 2020poster

Sampling-based methods promise scalability improvements when paired with stochastic gradient descent in training Graph Convolutional Networks (GCNs). While effective in alleviating the neighborhood explosion, due to bandwidth and memory bottlenecks, these methods lead to computational overheads in p…

Cited by 41SourcePDFScholar
2020

Online Structured Meta-learning

NeurIPS 2020poster

Learning quickly is of great importance for machine intelligence deployed in online platforms. With the capability of transferring knowledge from learned tasks, meta-learning has shown its effectiveness in online scenarios by continuously updating the model with the learned prior. However, current o…

Cited by 38SourcePDFScholar
2019

Local SGD with Periodic Averaging: Tighter Analysis and Adaptive Synchronization

NeurIPS 2019poster

Communication overhead is one of the key challenges that hinders the scalability of distributed optimization algorithms. In this paper, we study local distributed SGD, where data is partitioned among computation nodes, and the computation nodes perform local updates with periodically exchanging the…

2019

Trading Redundancy for Communication: Speeding up Distributed SGD for Non-convex Optimization

ICML 2019oral

Communication overhead is one of the key challenges that hinders the scalability of distributed optimization algorithms to train large neural networks. In recent years, there has been a great deal of research to alleviate communication cost by compressing the gradient vector or using local updates a…

Cited by 90SourcePDFScholar
2017

Sketching Meets Random Projection in the Dual: A Provable Recovery Algorithm for Big and High-dimensional Data

AISTATS 2017poster

Sketching techniques scale up machine learning algorithms by reducing the sample size or dimensionality of massive data sets, without sacrificing their statistical properties. In this paper, we study sketching from an optimization point of view. We first show that the iterative Hessian sketch is an…

Cited by 57SourcePDFScholar
2016

Train and Test Tightness of LP Relaxations in Structured Prediction

ICML 2016poster

Structured prediction is used in areas such as computer vision and natural language processing to predict structured outputs such as segmentations or parse trees. In these settings, prediction is performed by MAP inference or, equivalently, by solving an integer linear program. Because of the comple…

Cited by 19SourcePDFScholar