Search Results for author: Cesare Alippi

Found 46 papers, 22 papers with code

Graph-based Virtual Sensing from Sparse and Partial Multivariate Observations

1 code implementation19 Feb 2024 Giovanni De Felice, Andrea Cini, Daniele Zambon, Vladimir V. Gusev, Cesare Alippi

Virtual sensing techniques allow for inferring signals at new unmonitored locations by exploiting spatio-temporal measurements coming from physical sensors at different locations.

Graph-based Forecasting with Missing Data through Spatiotemporal Downsampling

no code implementations16 Feb 2024 Ivan Marisca, Cesare Alippi, Filippo Maria Bianchi

The input time series are progressively coarsened over time and space, obtaining a pool of representations that capture heterogeneous temporal and spatial dynamics.

Time Series

Graph Deep Learning for Time Series Forecasting

no code implementations24 Oct 2023 Andrea Cini, Ivan Marisca, Daniele Zambon, Cesare Alippi

The conditioning can take the form of an architectural inductive bias on the neural forecasting architecture, resulting in a family of deep learning models called spatiotemporal graph neural networks.

Inductive Bias Time Series +1

A Survey on Graph Neural Networks for Time Series: Forecasting, Classification, Imputation, and Anomaly Detection

1 code implementation7 Jul 2023 Ming Jin, Huan Yee Koh, Qingsong Wen, Daniele Zambon, Cesare Alippi, Geoffrey I. Webb, Irwin King, Shirui Pan

In this survey, we provide a comprehensive review of graph neural networks for time series analysis (GNN4TS), encompassing four fundamental dimensions: forecasting, classification, anomaly detection, and imputation.

Anomaly Detection Imputation +2

Graph-based Time Series Clustering for End-to-End Hierarchical Forecasting

no code implementations30 May 2023 Andrea Cini, Danilo Mandic, Cesare Alippi

Existing relationships among time series can be exploited as inductive biases in learning effective forecasting models.

Clustering Time Series +2

Feudal Graph Reinforcement Learning

no code implementations11 Apr 2023 Tommaso Marzi, Arshjot Khehra, Andrea Cini, Cesare Alippi

In this work, we propose a novel methodology, named Feudal Graph Reinforcement Learning (FGRL), that addresses such challenges by relying on hierarchical RL and a pyramidal message-passing architecture.

Decision Making reinforcement-learning +2

Relational Inductive Biases for Object-Centric Image Generation

no code implementations26 Mar 2023 Luca Butera, Andrea Cini, Alberto Ferrante, Cesare Alippi

Conditioning image generation on specific features of the desired output is a key ingredient of modern generative models.

Image Generation Inductive Bias +1

Graph Kalman Filters

no code implementations21 Mar 2023 Cesare Alippi, Daniele Zambon

The well-known Kalman filters model dynamical systems by relying on state-space representations with the next state updated, and its uncertainty controlled, by fresh information associated with newly observed system outputs.

Taming Local Effects in Graph-based Spatiotemporal Forecasting

1 code implementation NeurIPS 2023 Andrea Cini, Ivan Marisca, Daniele Zambon, Cesare Alippi

Spatiotemporal graph neural networks have shown to be effective in time series forecasting applications, achieving better performance than standard univariate predictors in several settings.

Time Series Time Series Forecasting

Where and How to Improve Graph-based Spatio-temporal Predictors

no code implementations3 Feb 2023 Daniele Zambon, Cesare Alippi

The proposed AZ-analysis constitutes a valuable asset for discovering and highlighting those space-time regions where the model can be improved with respect to performance.

Graph state-space models

no code implementations4 Jan 2023 Daniele Zambon, Andrea Cini, Lorenzo Livi, Cesare Alippi

State-space models constitute an effective modeling tool to describe multivariate time series and operate by maintaining an updated representation of the system state from which predictions are made.

Time Series Time Series Analysis

A Hybrid Active-Passive Approach to Imbalanced Nonstationary Data Stream Classification

no code implementations10 Oct 2022 Kleanthis Malialis, Manuel Roveri, Cesare Alippi, Christos G. Panayiotou, Marios M. Polycarpou

In real-world applications, the process generating the data might suffer from nonstationary effects (e. g., due to seasonality, faults affecting sensors or actuators, and changes in the users' behaviour).

Incremental Learning

Scalable Spatiotemporal Graph Neural Networks

1 code implementation14 Sep 2022 Andrea Cini, Ivan Marisca, Filippo Maria Bianchi, Cesare Alippi

The training procedure can then be parallelized node-wise by sampling the node embeddings without breaking any dependency, thus enabling scalability to large networks.

Temporal Sequences Time Series +1

Learning to Reconstruct Missing Data from Spatiotemporal Graphs with Sparse Observations

2 code implementations26 May 2022 Ivan Marisca, Andrea Cini, Cesare Alippi

In particular, we propose a novel class of attention-based architectures that, given a set of highly sparse discrete observations, learn a representation for points in time and space by exploiting a spatiotemporal propagation architecture aligned with the imputation task.

Multivariate Time Series Imputation Time Series +2

Sparse Graph Learning from Spatiotemporal Time Series

1 code implementation NeurIPS 2023 Andrea Cini, Daniele Zambon, Cesare Alippi

Outstanding achievements of graph neural networks for spatiotemporal time series analysis show that relational constraints introduce an effective inductive bias into neural forecasting architectures.

Graph Learning Inductive Bias +3

AZ-whiteness test: a test for uncorrelated noise on spatio-temporal graphs

1 code implementation23 Apr 2022 Daniele Zambon, Cesare Alippi

We present the first whiteness test for graphs, i. e., a whiteness test for multivariate time series associated with the nodes of a dynamic graph.

Spatio-Temporal Forecasting Time Series +1

A Graph Deep Learning Framework for High-Level Synthesis Design Space Exploration

no code implementations29 Nov 2021 Lorenzo Ferretti, Andrea Cini, Georgios Zacharopoulos, Cesare Alippi, Laura Pozzi

The design of efficient hardware accelerators for high-throughput data-processing applications, e. g., deep neural networks, is a challenging task in computer architecture design.

Graph neural network-based fault diagnosis: a review

no code implementations16 Nov 2021 Zhiwen Chen, Jiamin Xu, Cesare Alippi, Steven X. Ding, Yuri Shardt, Tao Peng, Chunhua Yang

Graph neural network (GNN)-based fault diagnosis (FD) has received increasing attention in recent years, due to the fact that data coming from several application domains can be advantageously represented as graphs.

Graph Attention Time Series +1

Learning Graph Cellular Automata

1 code implementation NeurIPS 2021 Daniele Grattarola, Lorenzo Livi, Cesare Alippi

Cellular automata (CA) are a class of computational models that exhibit rich dynamics emerging from the local interaction of cells arranged in a regular lattice.

Understanding Pooling in Graph Neural Networks

2 code implementations11 Oct 2021 Daniele Grattarola, Daniele Zambon, Filippo Maria Bianchi, Cesare Alippi

Inspired by the conventional pooling layers in convolutional neural networks, many recent works in the field of graph machine learning have introduced pooling operators to reduce the size of graphs.

Filling the G_ap_s: Multivariate Time Series Imputation by Graph Neural Networks

2 code implementations ICLR 2022 Andrea Cini, Ivan Marisca, Cesare Alippi

In particular, we introduce a novel graph neural network architecture, named GRIN, which aims at reconstructing missing data in the different channels of a multivariate time series by learning spatio-temporal representations through message passing.

Multivariate Time Series Imputation Time Series +2

Graph Edit Networks

1 code implementation ICLR 2021 Benjamin Paassen, Daniele Grattarola, Daniele Zambon, Cesare Alippi, Barbara Eva Hammer

With this result, we hope to provide a firm theoretical basis for a next generation of time series prediction models.

Attribute Graph Generation +3

Learn to Synchronize, Synchronize to Learn

no code implementations6 Oct 2020 Pietro Verzelli, Cesare Alippi, Lorenzo Livi

In recent years, the machine learning community has seen a continuous growing interest in research aimed at investigating dynamical aspects of both training procedures and machine learning models.

BIG-bench Machine Learning

Graph Neural Networks in TensorFlow and Keras with Spektral

1 code implementation22 Jun 2020 Daniele Grattarola, Cesare Alippi

In this paper we present Spektral, an open-source Python library for building graph neural networks with TensorFlow and the Keras application programming interface.

General Classification Graph Classification +3

Input-to-State Representation in linear reservoirs dynamics

no code implementations24 Mar 2020 Pietro Verzelli, Cesare Alippi, Lorenzo Livi, Peter Tino

Reservoir computing is a popular approach to design recurrent neural networks, due to its training simplicity and approximation performance.

Deep Reinforcement Learning with Weighted Q-Learning

no code implementations20 Mar 2020 Andrea Cini, Carlo D'Eramo, Jan Peters, Cesare Alippi

In this regard, Weighted Q-Learning (WQL) effectively reduces bias and shows remarkable results in stochastic environments.

Gaussian Processes Q-Learning +3

Hierarchical Representation Learning in Graph Neural Networks with Node Decimation Pooling

1 code implementation24 Oct 2019 Filippo Maria Bianchi, Daniele Grattarola, Lorenzo Livi, Cesare Alippi

In graph neural networks (GNNs), pooling operators compute local summaries of input graphs to capture their global properties, and they are fundamental for building deep GNNs that learn hierarchical representations.

Graph Classification Representation Learning

Mincut Pooling in Graph Neural Networks

no code implementations25 Sep 2019 Filippo Maria Bianchi, Daniele Grattarola, Cesare Alippi

For each node, our method learns a soft cluster assignment vector that depends on the node features, the target inference task (e. g., a graph classification loss), and, thanks to the minCut objective, also on the connectivity structure of the graph.

Graph Classification

Graph Random Neural Features for Distance-Preserving Graph Representations

1 code implementation ICML 2020 Daniele Zambon, Cesare Alippi, Lorenzo Livi

We present Graph Random Neural Features (GRNF), a novel embedding method from graph-structured data to real vectors based on a family of graph neural networks.

Distributed Deep Convolutional Neural Networks for the Internet-of-Things

no code implementations2 Aug 2019 Simone Disabato, Manuel Roveri, Cesare Alippi

Severe constraints on memory and computation characterizing the Internet-of-Things (IoT) units may prevent the execution of Deep Learning (DL)-based solutions, which typically demand large memory and high processing load.

Decision Making Distributed Computing +1

Deep Learning for Time Series Forecasting: The Electric Load Case

2 code implementations22 Jul 2019 Alberto Gasparin, Slobodan Lukovic, Cesare Alippi

Management and efficient operations in critical infrastructure such as Smart Grids take huge advantage of accurate power load forecasting which, due to its nonlinear nature, remains a challenging task.

Load Forecasting Management +3

Echo State Networks with Self-Normalizing Activations on the Hyper-Sphere

1 code implementation27 Mar 2019 Pietro Verzelli, Cesare Alippi, Lorenzo Livi

Finding such a region requires searching in hyper-parameter space in a sensible way: hyper-parameter configurations marginally outside such a region might yield networks exhibiting fully developed chaos, hence producing unreliable computations.

Benchmarking

Autoregressive Models for Sequences of Graphs

2 code implementations18 Mar 2019 Daniele Zambon, Daniele Grattarola, Lorenzo Livi, Cesare Alippi

This paper proposes an autoregressive (AR) model for sequences of graphs, which generalises traditional AR models.

Adversarial Autoencoders with Constant-Curvature Latent Manifolds

1 code implementation11 Dec 2018 Daniele Grattarola, Lorenzo Livi, Cesare Alippi

Constant-curvature Riemannian manifolds (CCMs) have been shown to be ideal embedding spaces in many application domains, as their non-Euclidean geometry can naturally account for some relevant properties of data, like hierarchy and circularity.

Link Prediction

A characterization of the Edge of Criticality in Binary Echo State Networks

no code implementations3 Oct 2018 Pietro Verzelli, Lorenzo Livi, Cesare Alippi

Echo State Networks (ESNs) are simplified recurrent neural network models composed of a reservoir and a linear, trainable readout layer.

Change Point Methods on a Sequence of Graphs

no code implementations18 May 2018 Daniele Zambon, Cesare Alippi, Lorenzo Livi

Given a finite sequence of graphs, e. g., coming from technological, biological, and social networks, the paper proposes a methodology to identify possible changes in stationarity in the stochastic process generating the graphs.

Graph Classification Seizure Detection

Change Detection in Graph Streams by Learning Graph Embeddings on Constant-Curvature Manifolds

1 code implementation16 May 2018 Daniele Grattarola, Daniele Zambon, Cesare Alippi, Lorenzo Livi

A common approach is to use embedding techniques to represent graphs as points in a conventional Euclidean space, but non-Euclidean spaces have often been shown to be better suited for embedding graphs.

Change Detection Seizure Detection

Anomaly and Change Detection in Graph Streams through Constant-Curvature Manifold Embeddings

no code implementations3 May 2018 Daniele Zambon, Lorenzo Livi, Cesare Alippi

The proposed methodology consists in embedding graphs into a geometric space and perform change detection there by means of conventional methods for numerical streams.

Anomaly Detection Change Detection

Concept Drift and Anomaly Detection in Graph Streams

1 code implementation21 Jun 2017 Daniele Zambon, Cesare Alippi, Lorenzo Livi

Graph representations offer powerful and intuitive ways to describe data in a multitude of application domains.

Anomaly Detection Change Detection

Multiplex visibility graphs to investigate recurrent neural networks dynamics

no code implementations10 Sep 2016 Filippo Maria Bianchi, Lorenzo Livi, Cesare Alippi, Robert Jenssen

We show that topological properties of such a multiplex reflect important features of RNN dynamics and are used to guide the tuning procedure.

Time Series Time Series Analysis

One-class classifiers based on entropic spanning graphs

no code implementations8 Apr 2016 Lorenzo Livi, Cesare Alippi

The final partition is derived by exploiting a criterion based on mutual information minimization.

One-class classifier

Determination of the edge of criticality in echo state networks through Fisher information maximization

no code implementations11 Mar 2016 Lorenzo Livi, Filippo Maria Bianchi, Cesare Alippi

In this paper, we aim at addressing this issue by proposing a theoretically motivated, unsupervised method based on Fisher information for determining the edge of criticality in recurrent neural networks.

Investigating echo state networks dynamics by means of recurrence analysis

no code implementations26 Jan 2016 Filippo Maria Bianchi, Lorenzo Livi, Cesare Alippi

We verify that the determination of the edge of stability provided by such RQA measures is more accurate than two well-known criteria based on the Jacobian matrix of the reservoir.

Time Series Time Series Analysis

Change Detection in Multivariate Datastreams: Likelihood and Detectability Loss

no code implementations16 Oct 2015 Cesare Alippi, Giacomo Boracchi, Diego Carrera, Manuel Roveri

We address the problem of detecting changes in multivariate datastreams, and we investigate the intrinsic difficulty that change-detection methods have to face when the data dimension scales.

Change Detection

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