Search Results for author: Stefan Vlaski

Found 35 papers, 1 papers with code

Attacks on Robust Distributed Learning Schemes via Sensitivity Curve Maximization

no code implementations27 Apr 2023 Christian A. Schroth, Stefan Vlaski, Abdelhak M. Zoubir

Classically, aggregation in distributed learning is based on averaging, which is statistically efficient, but susceptible to attacks by even a small number of malicious agents.

Exact Subspace Diffusion for Decentralized Multitask Learning

no code implementations14 Apr 2023 Shreya Wadehra, Roula Nassif, Stefan Vlaski

Classical paradigms for distributed learning, such as federated or decentralized gradient descent, employ consensus mechanisms to enforce homogeneity among agents.

Decentralized Adversarial Training over Graphs

no code implementations23 Mar 2023 Ying Cao, Elsa Rizk, Stefan Vlaski, Ali H. Sayed

The vulnerability of machine learning models to adversarial attacks has been attracting considerable attention in recent years.

Enforcing Privacy in Distributed Learning with Performance Guarantees

no code implementations16 Jan 2023 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

We study the privatization of distributed learning and optimization strategies.

Distributed Bayesian Learning of Dynamic States

no code implementations5 Dec 2022 Mert Kayaalp, Virginia Bordignon, Stefan Vlaski, Vincenzo Matta, Ali H. Sayed

This work studies networked agents cooperating to track a dynamical state of nature under partial information.

Local Graph-homomorphic Processing for Privatized Distributed Systems

no code implementations26 Oct 2022 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

We study the generation of dependent random numbers in a distributed fashion in order to enable privatized distributed learning by networked agents.

Networked Signal and Information Processing

no code implementations25 Oct 2022 Stefan Vlaski, Soummya Kar, Ali H. Sayed, José M. F. Moura

Moreover, and significantly, theory and applications show that networked agents, through cooperation and sharing, are able to match the performance of cloud or federated solutions, while offering the potential for improved privacy, increasing resilience, and saving resources.

Decision Making Inference Optimization

Quantization for decentralized learning under subspace constraints

no code implementations16 Sep 2022 Roula Nassif, Stefan Vlaski, Marco Carpentiero, Vincenzo Matta, Marc Antonini, Ali H. Sayed

In this paper, we consider decentralized optimization problems where agents have individual cost functions to minimize subject to subspace constraints that require the minimizers across the network to lie in low-dimensional subspaces.

Quantization

Robust and Efficient Aggregation for Distributed Learning

no code implementations1 Apr 2022 Stefan Vlaski, Christian Schroth, Michael Muma, Abdelhak M. Zoubir

This is followed by an aggregation step, which traditionally takes the form of a (weighted) average.

Dencentralized learning in the presence of low-rank noise

no code implementations18 Mar 2022 Roula Nassif, Virginia Bordignon, Stefan Vlaski, Ali H. Sayed

Observations collected by agents in a network may be unreliable due to observation noise or interference.

Explainability and Graph Learning from Social Interactions

no code implementations14 Mar 2022 Valentina Shumovskaia, Konstantinos Ntemos, Stefan Vlaski, Ali H. Sayed

Social learning algorithms provide models for the formation of opinions over social networks resulting from local reasoning and peer-to-peer exchanges.

Graph Learning

Optimal Aggregation Strategies for Social Learning over Graphs

no code implementations14 Mar 2022 Ping Hu, Virginia Bordignon, Stefan Vlaski, Ali H. Sayed

Adaptive social learning is a useful tool for studying distributed decision-making problems over graphs.

Decision Making

Privatized Graph Federated Learning

no code implementations14 Mar 2022 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

Federated learning is a semi-distributed algorithm, where a server communicates with multiple dispersed clients to learn a global model.

Federated Learning

Online Graph Learning from Social Interactions

no code implementations11 Mar 2022 Valentina Shumovskaia, Konstantinos Ntemos, Stefan Vlaski, Ali H. Sayed

For a given graph topology, these algorithms allow for the prediction of formed opinions.

Graph Learning

Learning from Heterogeneous Data Based on Social Interactions over Graphs

1 code implementation17 Dec 2021 Virginia Bordignon, Stefan Vlaski, Vincenzo Matta, Ali H. Sayed

In the proposed social machine learning (SML) strategy, two phases are present: in the training phase, classifiers are independently trained to generate a belief over a set of hypotheses using a finite number of training samples; in the prediction phase, classifiers evaluate streaming unlabeled observations and share their instantaneous beliefs with neighboring classifiers.

Decision Making

Hidden Markov Modeling over Graphs

no code implementations26 Nov 2021 Mert Kayaalp, Virginia Bordignon, Stefan Vlaski, Ali H. Sayed

This work proposes a multi-agent filtering algorithm over graphs for finite-state hidden Markov models (HMMs), which can be used for sequential state estimation or for tracking opinion formation over dynamic social networks.

Competing Adaptive Networks

no code implementations29 Mar 2021 Stefan Vlaski, Ali H. Sayed

Adaptive networks have the capability to pursue solutions of global stochastic optimization problems by relying only on local interactions within neighborhoods.

Stochastic Optimization

Deception in Social Learning

no code implementations26 Mar 2021 Konstantinos Ntemos, Virginia Bordignon, Stefan Vlaski, Ali H. Sayed

Then, we will explain that it is possible for such attacks to succeed by showing that strategies exist that can be adopted by the malicious agents for this purpose.

Federated Learning under Importance Sampling

no code implementations14 Dec 2020 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

Federated learning encapsulates distributed learning strategies that are managed by a central unit.

Federated Learning

Second-Order Guarantees in Federated Learning

no code implementations2 Dec 2020 Stefan Vlaski, Elsa Rizk, Ali H. Sayed

Federated learning is a useful framework for centralized learning from distributed data under practical considerations of heterogeneity, asynchrony, and privacy.

Federated Learning

Optimal Importance Sampling for Federated Learning

no code implementations26 Oct 2020 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

Federated learning involves a mixture of centralized and decentralized processing tasks, where a server regularly selects a sample of the agents and these in turn sample their local data to compute stochastic gradients for their learning updates.

Federated Learning regression

Social learning under inferential attacks

no code implementations26 Oct 2020 Konstantinos Ntemos, Virginia Bordignon, Stefan Vlaski, Ali H. Sayed

A common assumption in the social learning literature is that agents exchange information in an unselfish manner.

Graph-Homomorphic Perturbations for Private Decentralized Learning

no code implementations23 Oct 2020 Stefan Vlaski, Ali H. Sayed

Decentralized algorithms for stochastic optimization and learning rely on the diffusion of information as a result of repeated local exchanges of intermediate estimates.

Privacy Preserving Stochastic Optimization

Network Classifiers Based on Social Learning

no code implementations23 Oct 2020 Virginia Bordignon, Stefan Vlaski, Vincenzo Matta, Ali H. Sayed

Combination over time means that the classifiers respond to streaming data during testing and continue to improve their performance even during this phase.

Dif-MAML: Decentralized Multi-Agent Meta-Learning

no code implementations6 Oct 2020 Mert Kayaalp, Stefan Vlaski, Ali H. Sayed

The formalism of meta-learning is actually well-suited to this decentralized setting, where the learner would be able to benefit from information and computational power spread across the agents.

Meta-Learning

Tracking Performance of Online Stochastic Learners

no code implementations4 Apr 2020 Stefan Vlaski, Elsa Rizk, Ali H. Sayed

The utilization of online stochastic algorithms is popular in large-scale learning settings due to their ability to compute updates on the fly, without the need to store and process data in large batches.

Second-Order Guarantees in Centralized, Federated and Decentralized Nonconvex Optimization

no code implementations31 Mar 2020 Stefan Vlaski, Ali H. Sayed

Rapid advances in data collection and processing capabilities have allowed for the use of increasingly complex models that give rise to nonconvex optimization problems.

Dynamic Federated Learning

no code implementations20 Feb 2020 Elsa Rizk, Stefan Vlaski, Ali H. Sayed

Federated learning has emerged as an umbrella term for centralized coordination strategies in multi-agent environments.

Federated Learning

Multitask learning over graphs: An Approach for Distributed, Streaming Machine Learning

no code implementations7 Jan 2020 Roula Nassif, Stefan Vlaski, Cedric Richard, Jie Chen, Ali H. Sayed

Multitask learning is an approach to inductive transfer learning (using what is learned for one problem to assist in another problem) and helps improve generalization performance relative to learning each task separately by using the domain information contained in the training signals of related tasks as an inductive bias.

BIG-bench Machine Learning Inductive Bias +1

Linear Speedup in Saddle-Point Escape for Decentralized Non-Convex Optimization

no code implementations30 Oct 2019 Stefan Vlaski, Ali H. Sayed

Under appropriate cooperation protocols and parameter choices, fully decentralized solutions for stochastic optimization have been shown to match the performance of centralized solutions and result in linear speedup (in the number of agents) relative to non-cooperative approaches in the strongly-convex setting.

Stochastic Optimization

Regularized Diffusion Adaptation via Conjugate Smoothing

no code implementations20 Sep 2019 Stefan Vlaski, Lieven Vandenberghe, Ali H. Sayed

The purpose of this work is to develop and study a distributed strategy for Pareto optimization of an aggregate cost consisting of regularized risks.

Second-Order Guarantees of Stochastic Gradient Descent in Non-Convex Optimization

no code implementations19 Aug 2019 Stefan Vlaski, Ali H. Sayed

Recent years have seen increased interest in performance guarantees of gradient descent algorithms for non-convex optimization.

Distributed Learning in Non-Convex Environments -- Part II: Polynomial Escape from Saddle-Points

no code implementations3 Jul 2019 Stefan Vlaski, Ali H. Sayed

In Part I [2] of this work we established that agents cluster around a network centroid and proceeded to study the dynamics of this point.

Stochastic Learning under Random Reshuffling with Constant Step-sizes

no code implementations21 Mar 2018 Bicheng Ying, Kun Yuan, Stefan Vlaski, Ali H. Sayed

In empirical risk optimization, it has been observed that stochastic gradient implementations that rely on random reshuffling of the data achieve better performance than implementations that rely on sampling the data uniformly.

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