Variance-Reduced Stochastic Learning by Networked Agents under Random Reshuffling

A new amortized variance-reduced gradient (AVRG) algorithm was developed in \cite{ying2017convergence}, which has constant storage requirement in comparison to SAGA and balanced gradient computations in comparison to SVRG. One key advantage of the AVRG strategy is its amenability to decentralized implementations. In this work, we show how AVRG can be extended to the network case where multiple learning agents are assumed to be connected by a graph topology. In this scenario, each agent observes data that is spatially distributed and all agents are only allowed to communicate with direct neighbors. Moreover, the amount of data observed by the individual agents may differ drastically. For such situations, the balanced gradient computation property of AVRG becomes a real advantage in reducing idle time caused by unbalanced local data storage requirements, which is characteristic of other reduced-variance gradient algorithms. The resulting diffusion-AVRG algorithm is shown to have linear convergence to the exact solution, and is much more memory efficient than other alternative algorithms. In addition, we propose a mini-batch strategy to balance the communication and computation efficiency for diffusion-AVRG. When a proper batch size is employed, it is observed in simulations that diffusion-AVRG is more computationally efficient than exact diffusion or EXTRA while maintaining almost the same communication efficiency.Comment: 23 pages, 12 figures, submitted for publicatio

Thirty Years of Machine Learning: The Road to Pareto-Optimal Wireless Networks

Future wireless networks have a substantial potential in terms of supporting a broad range of complex compelling applications both in military and civilian fields, where the users are able to enjoy high-rate, low-latency, low-cost and reliable information services. Achieving this ambitious goal requires new radio techniques for adaptive learning and intelligent decision making because of the complex heterogeneous nature of the network structures and wireless services. Machine learning (ML) algorithms have great success in supporting big data analytics, efficient parameter estimation and interactive decision making. Hence, in this article, we review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning. Furthermore, we investigate their employment in the compelling applications of wireless networks, including heterogeneous networks (HetNets), cognitive radios (CR), Internet of things (IoT), machine to machine networks (M2M), and so on. This article aims for assisting the readers in clarifying the motivation and methodology of the various ML algorithms, so as to invoke them for hitherto unexplored services as well as scenarios of future wireless networks.Comment: 46 pages, 22 fig

Learning and Management for Internet-of-Things: Accounting for Adaptivity and Scalability

Internet-of-Things (IoT) envisions an intelligent infrastructure of networked smart devices offering task-specific monitoring and control services. The unique features of IoT include extreme heterogeneity, massive number of devices, and unpredictable dynamics partially due to human interaction. These call for foundational innovations in network design and management. Ideally, it should allow efficient adaptation to changing environments, and low-cost implementation scalable to massive number of devices, subject to stringent latency constraints. To this end, the overarching goal of this paper is to outline a unified framework for online learning and management policies in IoT through joint advances in communication, networking, learning, and optimization. From the network architecture vantage point, the unified framework leverages a promising fog architecture that enables smart devices to have proximity access to cloud functionalities at the network edge, along the cloud-to-things continuum. From the algorithmic perspective, key innovations target online approaches adaptive to different degrees of nonstationarity in IoT dynamics, and their scalable model-free implementation under limited feedback that motivates blind or bandit approaches. The proposed framework aspires to offer a stepping stone that leads to systematic designs and analysis of task-specific learning and management schemes for IoT, along with a host of new research directions to build on.Comment: Submitted on June 15 to Proceeding of IEEE Special Issue on Adaptive and Scalable Communication Network

A federated learning framework for the next-generation machine learning systems

Dissertação de mestrado em Engenharia Eletrónica Industrial e Computadores (especialização em Sistemas Embebidos e Computadores)The end of Moore's Law aligned with rising concerns about data privacy is forcing machine learning (ML) to shift from the cloud to the deep edge, near to the data source. In the next-generation ML systems, the inference and part of the training process will be performed right on the edge, while the cloud will be responsible for major ML model updates. This new computing paradigm, referred to by academia and industry researchers as federated learning, alleviates the cloud and network infrastructure while increasing data privacy. Recent advances have made it possible to efficiently execute the inference pass of quantized artificial neural networks on Arm Cortex-M and RISC-V (RV32IMCXpulp) microcontroller units (MCUs). Nevertheless, the training is still confined to the cloud, imposing the transaction of high volumes of private data over a network. To tackle this issue, this MSc thesis makes the first attempt to run a decentralized training in Arm Cortex-M MCUs. To port part of the training process to the deep edge is proposed L-SGD, a lightweight version of the stochastic gradient descent optimized for maximum speed and minimal memory footprint on Arm Cortex-M MCUs. The L-SGD is 16.35x faster than the TensorFlow solution while registering a memory footprint reduction of 13.72%. This comes at the cost of a negligible accuracy drop of only 0.12%. To merge local model updates returned by edge devices this MSc thesis proposes R-FedAvg, an implementation of the FedAvg algorithm that reduces the impact of faulty model updates returned by malicious devices.O fim da Lei de Moore aliado às crescentes preocupações sobre a privacidade dos dados gerou a necessidade de migrar as aplicações de Machine Learning (ML) da cloud para o edge, perto da fonte de dados. Na próxima geração de sistemas ML, a inferência e parte do processo de treino será realizada diretamente no edge, enquanto que a cloud será responsável pelas principais atualizações do modelo ML. Este novo paradigma informático, referido pelos investigadores académicos e industriais como treino federativo, diminui a sobrecarga na cloud e na infraestrutura de rede, ao mesmo tempo que aumenta a privacidade dos dados. Avanços recentes tornaram possível a execução eficiente do processo de inferência de redes neurais artificiais quantificadas em microcontroladores Arm Cortex-M e RISC-V (RV32IMCXpulp). No entanto, o processo de treino continua confinado à cloud, impondo a transação de grandes volumes de dados privados sobre uma rede. Para abordar esta questão, esta dissertação faz a primeira tentativa de realizar um treino descentralizado em microcontroladores Arm Cortex-M. Para migrar parte do processo de treino para o edge é proposto o L-SGD, uma versão lightweight do tradicional método stochastic gradient descent (SGD), otimizada para uma redução de latência do processo de treino e uma redução de recursos de memória nos microcontroladores Arm Cortex-M. O L-SGD é 16,35x mais rápido do que a solução disponibilizada pelo TensorFlow, ao mesmo tempo que regista uma redução de utilização de memória de 13,72%. O custo desta abordagem é desprezível, sendo a perda de accuracy do modelo de apenas 0,12%. Para fundir atualizações de modelos locais devolvidas por dispositivos do edge, é proposto o RFedAvg, uma implementação do algoritmo FedAvg que reduz o impacto de atualizações de modelos não contributivos devolvidos por dispositivos maliciosos