Gergely Ódor
SNSF Postdoc Mobility Fellow
hosted by Mátron Karsai at CEU, Vienna
My research interests are at the interface of probability theory, theoretical computer science and network science.
My PhD advisor was Patrick Thiran, and my thesis was on source identification.
For English speakers, I go by Greg.
For Hungarian speakers, I go by Gergő.
About
I am interested in problems concerning networks that are challenging either from a mathematical modelling or an algorithmic perspective, or both. My thesis is on the source idenitfication problem, which fortunately qualifies as "both": the goal is to design efficient algorithms that find the first infected individual (also called patient zero) during an epidemic, based on sparse measurements about who got infected and when.
On the algorithmic side, I have worked on rigorously quantifying the role of adaptivity in source identification: the difference between the problem settings when the measurements are chosen adaptively vs nonadaptively. If the epidemic spreads very aggressively, the theoretical analysis ([3] and [4]) becomes equivalent to adaptive and nonadaptive versions of the metric dimension from the combinatorics literature. If the epidemic is less aggressive, then there is more stochasticity in the problem, making the analysis more challenging [2]. Interestingly, in some cases adaptivity only plays a small role [3], whereas in others, its role is very substantial [2].
More on the modelling (but still rigorous) side, I have worked on relaxing the assumption in the source identification problem that the underlying contact network is fully known to the algorithm [5]. Also in this direction, we studied the robustness of the metric dimension to single edge changes [6]. Slightly deviating from the algorithmic source identification problem, I have worked on understanding how the location of (multiple) initial seeds affect the outcome of an epidemic [1].
Research
ACCEPTED PAPERS
[1] Gergely Ódor, Domonkos Czifra, Júlia Komjáthy, László Lovász, Márton Karsai
Switchover phenomenon induced by epidemic seeding on geometric networks
Proceedings of the National Academy of Sciences Oct 2021, 118 (41) e2112607118
One sentence abstract: We observe empirically and prove theoretically a new phenomenon related to how the initial seeding affects the outcome of an epidemic.
[2] Victor Lecomte, Gergely Ódor, Patrick Thiran
The power of adaptivity in source identification with time queries on the path
One sentence abstract: We provide the first theoretical results on the query complexity of the source identification problem when queried nodes report their infection time; in the adaptive case we need only Θ(loglog(n)) queries, while in the nonadaptive case Θ(n) queries are needed.
[3] Gergely Ódor, Patrick Thiran
Sequential metric dimension for random graphs
Journal of Applied Probability, Volume 58, Issue 4, December 2021, pp. 909  951
One sentence abstract: We prove that the sequential version of the metric dimension (where the landmarks can be chosen adaptively to distinguish every pair of nodes based on distances) is only a multiplicative constant factor smaller than the (nonadaptive) metric dimension in ErdosRenyi graphs.
[4] Júlia Komjáthy, Gergely Ódor
Metric dimension of critical GaltonWatson trees and linear preferential attachment trees
European Journal of Combinatorics 95 (2021), 103317
One sentence abstract: Building on the literature of fringe trees, we prove law of large numbers type results for the metric dimension of various random trees.
SUBMITTED PAPERS
[5] Gergely Ódor, Jana Vuckovic, MiguelAngel Sanchez Ndoye, Patrick Thiran
Source Detection via Contact Tracing in the Presence of Asymptomatic Patients
One sentence abstract: We define and prove rigorous results about a new source identification framework, where the network is initially not known to the algorithm, but must be explored through queries (similarly to the node infection times), and we evaluate our algorithms on realistic datasets.
[arxiv]
[6] Satvik Mashkaria, Gergely Ódor, Patrick Thiran
On the robustness of the metric dimension of grid graphs to adding a single edge
One sentence abstract: We prove that if we add an extra edge to a (large enough) ddimensional grid graph, then the resulting graph will have metric dimension between d and 2d, and we almost completely settle the case for d=2.
PREPHD PAPERS

Global information loss and criticality in resistance matrices
Gergely Ódor
Master’s Thesis at CEU supervised by Bálint Virág (2017) 
A multicore path to connectomicsondemand
Alexander Matveev, Yaron Meirovitch, Hayk Saribekyan, Wiktor Jakubiuk, Tim Kaler, Gergely Ódor, David Budden, Aleksandar Zlateski, Nir ShavitProceedings of the 22nd ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming (2017)

A multipass approach to largescale connectomics
Yaron Meirovitch, Alexander Matveev, Hayk Saribekyan, David Budden, David Rolnick, Gergely Ódor, Seymour KnowlesBarley, Thouis Raymond Jones, Hanspeter Pfister, Jeff William Lichtman, Nir Shavit
arXiv preprint arXiv:1612.02120

FrankWolfe works for nonLipschitz continuous gradient objectives: scalable Poisson phase retrieval
Gergely Ódor, YenHuan Li, Alp Yurtsever, YaPing Hsieh, Quoc TranDinh, Marwa El Halabi, Volkan Cevher
2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Griffiths phases and localization in hierarchical modular networks
Géza Ódor, Ronald Dickman, Gergely Ódor
Scientific reports 5 (1), 115 (2015)

Simulation of 1+ 1 dimensional surface growth and lattices gases using GPUs
Henrik Schulz, Géza Ódor, Gergely Ódor, Máté Ferenc Nagy
Computer Physics Communications 182 (7), 14671476 (2011)
Presentations

2022 July: NetSci 2022 @Shanghai (online)
Title: Switchover phenomenon induced by epidemic seeding on geometric networks (contributed talk) 
2022 July: Epidemology and modelling workshop (Kecskemét)
Title: Identifying patient zero and proximitysensitive awareness (invited speaker) 
2022 May: Erdös Center Workshop: Mathematics of Large Networks (Budapest)
Title: Source Identification via Contact Tracing in the Presence of Asymptomatic Patients (contributed talk) 
2021 November: Budapest Semesters in Mathematics Colloquium (Budapest)
Title: Switchover phenomenon induced by epidemic seeding on geometric networks (invited speaker) 
2021 July: FrancoDutch meeting “BézoutEurandom” (IHP Paris/online)
Title: Switchover phenomenon induced by epidemic seeding on geometric networks 
2021 July: Rátz László Conference of Mathematics Teachers (online)
Title: Random trees and epidemic spreading (invited speaker) 
2020 February: Budapest University of Technology and Economics Stochastic Seminar (TU Budapest)
Title: Sequential metric dimension for random graphs (invited speaker) 
2019 July: 19th International Conference on Random Structures and Algorithms (ETH Zurich)
Title: Sequential metric dimension for random graphs (contributed talk) 
2019 March: YEP XV "Information Diffusion on Random Networks" (TU Eindhoven)
Title: Source localization with adaptive sensor selection in random graphs (contributed talk) 
2018 April: Wiki Workshop at The Web Conference (WWW2018 Lyon)
Title: How did Wikipedia become navigable (poster) 
2014, 2015, 2018 December: Statistical Physics Holiday Seminar, Eotvos Lorand University (ELTE)
Education
2017 – 2022
2016 – 2017
2012 – 2016
PhD student at EPFL
Advisor: Patrick Thiran
Master's student at CEU
Advisor: Bálint Virág
Undergraduate student at MIT
Major: Mathematics with Computer Science (18C)
Teaching

2018 – 2021: Supervised semester projects or internships at EPFL for

Jana Vuckovic

MiguelAngel Sanchez Ndoye

Stanislas Jouven

Victor Lecomte

Satvik Mashkaria

Anastasiia Kucherenko

Nicolas D'Argenlieu

Constantin Isabela

Farzad Pourkamali


2020 – 2021: Volunteer tutor (Maths and English) at the Menetszél association for children with disadvantaged backgrounds

2017 – 2020: TA for various courses at EPFL and CEU

Theory of Computing
 Dynamical Systems Theory

Probability and Statistics

Matrix Computations with Applications


2014 – 2015: Tutor for various undergraduate courses at MIT
Acting and hobbies
I took several theater courses at MIT and at Metro Works, and I performed as an actor in a few plays:

2022 Summer: Played Thomas in "Beszélnünk kell" as part of the Hatásszünet group (created by Szilvia Markos and Heléna Ménesi)

2021  2022: Read various parts in four different short plays while participating in the Okuláré project

2019 Spring: Played Alan in The Time and the Conways by J.B. Priestley (directed by Suzanne Balharry)

2015 Spring: Performed in the Up and Down 24h show (directed by István Cziegler)

2014 Fall: Played Judge John Hathorne in The Curcible by Arthur Miller (directed by Caleb Hammond)

2014 Spring: Played the Intruder in Present Simple by István Cziegler (directed by István Cziegler)
Otherwise, I enjoy hiking, taekwondo and playing ultimate frisbee, among many other things.