Search Results for author: Giannis Nikolentzos

Found 29 papers, 11 papers with code

Neural Graph Generator: Feature-Conditioned Graph Generation using Latent Diffusion Models

2 code implementations3 Mar 2024 Iakovos Evdaimon, Giannis Nikolentzos, Michail Chatzianastasis, Hadi Abdine, Michalis Vazirgiannis

Graph generation has emerged as a crucial task in machine learning, with significant challenges in generating graphs that accurately reflect specific properties.

Graph Generation

Graph Neural Machine: A New Model for Learning with Tabular Data

1 code implementation5 Feb 2024 Giannis Nikolentzos, Siyun Wang, Johannes Lutzeyer, Michalis Vazirgiannis

We then propose a new machine learning model for tabular data, the so-called Graph Neural Machine (GNM), which replaces the MLP's directed acyclic graph with a nearly complete graph and which employs a synchronous message passing scheme.

Time-Parameterized Convolutional Neural Networks for Irregularly Sampled Time Series

no code implementations6 Aug 2023 Chrysoula Kosma, Giannis Nikolentzos, Michalis Vazirgiannis

We evaluate TPCNN on both interpolation and classification tasks involving real-world irregularly sampled multivariate time series datasets.

Irregular Time Series Time Series

Supervised Attention Using Homophily in Graph Neural Networks

no code implementations11 Jul 2023 Michail Chatzianastasis, Giannis Nikolentzos, Michalis Vazirgiannis

Among the different variants of graph neural networks, graph attention networks (GATs) have been applied with great success to different tasks.

Graph Attention Node Classification

Path Neural Networks: Expressive and Accurate Graph Neural Networks

1 code implementation9 Jun 2023 Gaspard Michel, Giannis Nikolentzos, Johannes Lutzeyer, Michalis Vazirgiannis

We derive three different variants of the PathNN model that aggregate single shortest paths, all shortest paths and all simple paths of length up to K. We prove that two of these variants are strictly more powerful than the 1-WL algorithm, and we experimentally validate our theoretical results.

Graph Classification Graph Regression

What Do GNNs Actually Learn? Towards Understanding their Representations

no code implementations21 Apr 2023 Giannis Nikolentzos, Michail Chatzianastasis, Michalis Vazirgiannis

In recent years, graph neural networks (GNNs) have achieved great success in the field of graph representation learning.

Graph Representation Learning

Weisfeiler and Leman go Hyperbolic: Learning Distance Preserving Node Representations

no code implementations4 Nov 2022 Giannis Nikolentzos, Michail Chatzianastasis, Michalis Vazirgiannis

In recent years, graph neural networks (GNNs) have emerged as a promising tool for solving machine learning problems on graphs.

Graph Classification

Image Keypoint Matching using Graph Neural Networks

no code implementations27 May 2022 Nancy Xu, Giannis Nikolentzos, Michalis Vazirgiannis, Henrik Boström

Image matching is a key component of many tasks in computer vision and its main objective is to find correspondences between features extracted from different natural images.

Graph Matching

NLP Research and Resources at DaSciM, Ecole Polytechnique

no code implementations1 Dec 2021 Hadi Abdine, Yanzhu Guo, Moussa Kamal Eddine, Giannis Nikolentzos, Stamatis Outsios, Guokan Shang, Christos Xypolopoulos, Michalis Vazirgiannis

DaSciM (Data Science and Mining) part of LIX at Ecole Polytechnique, established in 2013 and since then producing research results in the area of large scale data analysis via methods of machine and deep learning.

Permute Me Softly: Learning Soft Permutations for Graph Representations

1 code implementation5 Oct 2021 Giannis Nikolentzos, George Dasoulas, Michalis Vazirgiannis

In this paper, we propose a new graph neural network model, so-called $\pi$-GNN which learns a "soft" permutation (i. e., doubly stochastic) matrix for each graph, and thus projects all graphs into a common vector space.

Graph Classification Graph Regression

Geometric Random Walk Graph Neural Networks via Implicit Layers

no code implementations29 Sep 2021 Giannis Nikolentzos, Michalis Vazirgiannis

The proposed model retains the transparency of Random Walk Graph Neural Networks since its first layer also consists of a number of trainable ``hidden graphs'' which are compared against the input graphs using the geometric random walk kernel.

Graph Classification

Ego-based Entropy Measures for Structural Representations on Graphs

no code implementations17 Feb 2021 George Dasoulas, Giannis Nikolentzos, Kevin Scaman, Aladin Virmaux, Michalis Vazirgiannis

Machine learning on graph-structured data has attracted high research interest due to the emergence of Graph Neural Networks (GNNs).

Graph Classification

An Empirical Study of the Expressiveness of Graph Kernels and Graph Neural Networks

no code implementations1 Jan 2021 Giannis Nikolentzos, George Panagopoulos, Michalis Vazirgiannis

Graph neural networks and graph kernels have achieved great success in solving machine learning problems on graphs.

Graph Similarity

Random Walk Graph Neural Networks

no code implementations NeurIPS 2020 Giannis Nikolentzos, Michalis Vazirgiannis

The first layer of the model consists of a number of trainable ``hidden graphs'' which are compared against the input graphs using a random walk kernel to produce graph representations.

Graph Classification

Transfer Graph Neural Networks for Pandemic Forecasting

5 code implementations10 Sep 2020 George Panagopoulos, Giannis Nikolentzos, Michalis Vazirgiannis

Furthermore, to account for the limited amount of training data, we capitalize on the pandemic's asynchronous outbreaks across countries and use a model-agnostic meta-learning based method to transfer knowledge from one country's model to another's.

Meta-Learning Representation Learning +1

EvoNet: A Neural Network for Predicting the Evolution of Dynamic Graphs

no code implementations2 Mar 2020 Changmin Wu, Giannis Nikolentzos, Michalis Vazirgiannis

Then, we employ a generative model which predicts the topology of the graph at the next time step and constructs a graph instance that corresponds to that topology.

Graph Mining

Ego-based Entropy Measures for Structural Representations

no code implementations1 Mar 2020 George Dasoulas, Giannis Nikolentzos, Kevin Scaman, Aladin Virmaux, Michalis Vazirgiannis

Moreover, on graph classification tasks, we suggest the utilization of the generated structural embeddings for the transformation of an attributed graph structure into a set of augmented node attributes.

General Classification Graph Classification

Message Passing Attention Networks for Document Understanding

2 code implementations17 Aug 2019 Giannis Nikolentzos, Antoine J. -P. Tixier, Michalis Vazirgiannis

In this paper, we represent documents as word co-occurrence networks and propose an application of the message passing framework to NLP, the Message Passing Attention network for Document understanding (MPAD).

document understanding Multi-Modal Document Classification +2

Graph Kernels: A Survey

no code implementations27 Apr 2019 Giannis Nikolentzos, Giannis Siglidis, Michalis Vazirgiannis

Graph kernels have attracted a lot of attention during the last decade, and have evolved into a rapidly developing branch of learning on structured data.

Graph Classification

Message Passing Graph Kernels

1 code implementation7 Aug 2018 Giannis Nikolentzos, Michalis Vazirgiannis

The first component is a kernel between vertices, while the second component is a kernel between graphs.

Graph Similarity

GraKeL: A Graph Kernel Library in Python

1 code implementation6 Jun 2018 Giannis Siglidis, Giannis Nikolentzos, Stratis Limnios, Christos Giatsidis, Konstantinos Skianis, Michalis Vazirgiannis

The problem of accurately measuring the similarity between graphs is at the core of many applications in a variety of disciplines.

Clustering General Classification +1

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