Giannis Nikolentzos

Giannis Nikolentzos

DaSciM
LIX, École Polytechnique
1 rue Honoré d'Estienne d'Orves
91120 Palaiseau, France

e-mail: nikolentzos at lix.polytechnique dot fr

        


Publications - Teaching - Software - Useful Links

I am a Postdoctoral researcher at the Computer Science Laboratory (LIX), École Polytechnique, France.

I received my PhD in Graph Mining from the Athens University of Economics and Business where I was advised by Prof. Michalis Vazirgiannis. Before that, I obtained an MSc in Artificial Intelligence from the University of Southampton and a Diploma in Electrical and Computer Engineering from the University of Patras.

My current research interests are in the fields of learning on graphs and of graph-based information extraction.


Publications


Synthetic electronic health records generated with variational graph autoencoders
G. Nikolentzos, M. Vazirgiannis, C. Xypolopoulos, M. Lingman, and E.G. Brandt.
npj Digital Medicine, Volume 6, No. 1, (2023) [Impact factor: 15.357].

Predicting COVID-19 positivity and hospitalization with multi-scale graph neural networks
K. Skianis, G. Nikolentzos, B. Gallix, R. Thiebaut, and G. Exarchakis.
Scientific Reports, Volume 13, No. 1, (2023) [Impact factor: 4.997].

Geometric Random Walk Graph Neural Networks via Implicit Layers [pdf] [code]
G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 26th International Conference on Artificial Intelligence and Statistics, pp. 2035-2053, 2023.

Weisfeiler and Leman go Hyperbolic: Learning Distance Preserving Node Representations [pdf] [code]
G. Nikolentzos, M. Chatzianastasis and M. Vazirgiannis.
In Proceedings of the 26th International Conference on Artificial Intelligence and Statistics, pp. 1037-1054, 2023.

Graph Alignment Kernels using Weisfeiler and Leman Hierarchies [pdf] [code]
G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 26th International Conference on Artificial Intelligence and Statistics, pp. 2019-2034, 2023.

Permute Me Softly: Learning Soft Permutations for Graph Representations [pdf] [code]
G. Nikolentzos, G. Dasoulas and M. Vazirgiannis.
IEEE Transactions on Pattern Analysis and Machine Intelligence, Volume 45, No. 4, pp. 5087-5098, (2023) [Impact factor: 24.314].

Graph Kernels: A Survey [pdf]
G. Nikolentzos, G. Siglidis and M. Vazirgiannis.
Journal of Artificial Intelligence Research, Volume 72, pp. 943-1027, (2021).

An Empirical Study of the Expressiveness of Graph Kernels and Graph Neural Networks
G. Nikolentzos, G. Panagopoulos and M. Vazirgiannis.
In Proceedings of the 30th International Conference on Artificial Neural Networks, pp. 139-150, 2021.

Ego-Based Entropy Measures for Structural Representations on Graphs
G. Dasoulas, G. Nikolentzos, K. Scaman, A. Virmaux and M. Vazirgiannis.
In Proceedings of the 2021-2021 IEEE International Conference on Acoustics, Speech and Signal Processing, pp. 3210-3214, 2021.

Transfer Graph Neural Networks for Pandemic Forecasting [pdf] [code]
G. Panagopoulos, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 35th AAAI Conference on Artificial Intelligence, pp. 4838-4845, 2021.

Random Walk Graph Neural Networks [pdf] [code]
G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 34th Conference on Neural Information Processing Systems, pp. 16211-16222, 2020.

Image Classification Using Graph-Based Representations and Graph Neural Networks.
G. Nikolentzos, M. Thomas, A.R. Rivera and M. Vazirgiannis.
In Proceedings of the 9th International Conference on Complex Networks and Their Applications, pp. 142-153, 2020.

Graph Auto-Encoders for Learning Edge Representations.
V. Rennard, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 9th International Conference on Complex Networks and Their Applications, pp. 117-129, 2020.

EvoNet: A Neural Network for Predicting the Evolution of Dynamic Graphs.
C. Wu, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 29th International Conference on Artificial Neural Networks, pp. 596-606, 2020.

k-hop Graph Neural Networks [code]
G. Nikolentzos, G. Dasoulas and M. Vazirgiannis.
Neural Networks, Volume 130, pp. 195-205, (2020) [Impact factor: 5.535].

Rep the Set: Neural Networks for Learning Set Representations. [pdf] [code]
K. Skianis, G. Nikolentzos, S. Limnios and M. Vazirgiannis.
In Proceedings of the 23rd International Conference on Artificial Intelligence and Statistics, pp. 1410-1420, 2020.

GraKeL: A Graph Kernel Library in Python. [pdf]
G. Siglidis, G. Nikolentzos, S. Limnios, C. Giatsidis, K. Skianis and M. Vazirgiannis.
Journal of Machine Learning Research 21 (2020) [Impact factor: 4.091].

Message Passing Attention Networks for Document Understanding. [code]
G. Nikolentzos, A. Tixier and M. Vazirgiannis.
In Proceedings of the 34th AAAI Conference on Artificial Intelligence, pp. 8544-8551, 2020.

Learning Structural Node Representations using Graph Kernels. [pdf] [code]
G. Nikolentzos, M. Vazirgiannis.
IEEE Transactions on Knowledge and Data Engineering, Volume 33, Issue 5, pp. 2045-2056, (2021) [Impact factor: 3.857].

Matching Node Embeddings Using Valid Assignment Kernels.
C. Wu, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 8th International Conference on Complex Networks and Their Applications (Volume 1), pp. 810-821, 2019.

Graph Classification with 2D Convolutional Neural Networks.
A. Tixier, G. Nikolentzos, P. Meladianos and M. Vazirgiannis.
In Proceedings of the 28th International Conference on Artificial Neural Networks: Workshop and Special Sessions, pp. 578-593, 2019.

Rooted Citation Graphs Density Metrics for Research Papers Influence Evaluation.
C. Giatsidis, G. Nikolentzos, C. Zhang, J. Tang and M. Vazirgiannis.
Journal of Informetrics 13 (2019) 757-768 [Impact factor: 3.879].

Learning Structural Node Representations on Directed Graphs.
N. Steenfatt, G. Nikolentzos, M. Vazirgiannis and Q. Zhao.
In Proceedings of the 7th International Conference on Complex Networks and Their Applications, pp. 132-144, 2018.

Enhancing Graph Kernels via Successive Embeddings.
G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 27th International Conference on Information and Knowledge Management, pp. 1583-1586, 2018.

Kernel Graph Convolutional Neural Networks.
G. Nikolentzos, P. Meladianos, A. Tixier, K. Skianis and M. Vazirgiannis.
In Proceedings of the 27th International Conference on Artificial Neural Networks, pp. 22-32, 2018.

A Degeneracy Framework for Graph Similarity. [pdf] [code]
G. Nikolentzos, P. Meladianos, S. Limnios and M. Vazirgiannis.
In Proceeding of the 27th International Joint Conference on Artificial Intelligence, pp. 2595-2601, 2018.

An Optimization Approach for Sub-event Detection and Summarization in Twitter. [pdf]
P. Meladianos, C. Xypolopoulos, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 40th European Conference on Information Retrieval, pp. 481-493, 2018.

Shortest-Path Graph Kernels for Document Similarity. [code]
G. Nikolentzos, P. Meladianos, F. Rousseau, Y. Stavrakas and M. Vazirgiannis.
In Proceedings of the 2017 Conference on Empirical Methods in Natural Language Processing, pp. 1890-1900, 2017.

K-clique-graphs for Dense Subgraph Discovery.
G. Nikolentzos, P. Meladianos, Y. Stavrakas and M. Vazirgiannis.
In Proceedings of the 2017 European Conference on Machine Learning and Principles and Practice of Knowledge Discovery, pp. 617-633, 2017.

Real-Time Keyword Extraction from Conversations.
P. Meladianos, A. Tixier, G. Nikolentzos and M. Vazirgiannis.
In Proceedings of the 15th Conference of the European Chapter of the Association for Computational Linguistics, pp. 462-467, 2017.

Multivariate Gaussian Document Representation from Word Embeddings for Text Categorization. [code]
G. Nikolentzos, P. Meladianos, F. Rousseau, Y. Stavrakas and M. Vazirgiannis.
In Proceedings of the 15th Conference of the European Chapter of the Association for Computational Linguistics, pp. 450-455, 2017.

Matching Node Embeddings for Graph Similarity. [pdf] [code]
G. Nikolentzos, P. Meladianos and M. Vazirgiannis.
In Proceedings of the 31st AAAI Conference on Artificial Intelligence, pp. 2429-2435, 2017.

Degeneracy-based Real-Time Sub-Event Detection in Twitter Stream.
P. Meladianos, G. Nikolentzos, F. Rousseau, Y. Stavrakas and M. Vazirgiannis.
In Proceedings of the 9th AAAI International Conference on Web and Social Media, pp. 248-257, 2015.

AUEB at TREC 2015: Clinical Decision Support Track.
G. Nikolentzos, P. Meladianos, N. Liakis and M. Vazirgiannis.
In Proceedings of TREC 2015.


Preprints

Synthetic electronic health records generated with variational graph autoencoders. [pdf]
G. Nikolentzos, C. Xypolopoulos, M. Vazirgiannis, M. Lingman and E. Brandt.
medRxiv, 2022.


Teaching

I have been a teaching assistant in the following courses at AUEB:


and in the following course at École Polytechnique:


Software

GraKeL: A library for graph kernels



Useful Links


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