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Nikos Parotsidis

12 accepted papers

2026

Dynamic High-Dimensional Facility Location with Low Recourse

ICML 2026poster

We study the problem of dynamic facility location with non-uniform costs. Facility location is a central problem in unsupervised learning and in recent years the dynamic version of the problem has been extensively studied. In this paper, we study the setting where clients are added and deleted in re…

Cited by 0SourceScholar
2025

Almost Optimal Fully Dynamic $k$-Center Clustering with Recourse

ICML 2025poster

In this paper, we consider the *metric $k$-center* problem in the fully dynamic setting, where we are given a metric space $(V,d)$ evolving via a sequence of point insertions and deletions and our task is to maintain a subset $S \subseteq V$ of at most $k$ points that minimizes the objective $\max_{…

Cited by 0SourcePDFScholar
2024

Dynamic Correlation Clustering in Sublinear Update Time

ICML 2024spotlight

We study the classic problem of correlation clustering in dynamic vertex streams. In this setting, vertices are either added or randomly deleted over time, and each vertex pair is connected by a positive or negative edge. The objective is to continuously find a partition which minimizes the sum of p…

2023

Fully Dynamic $k$-Clustering in $\tilde O(k)$ Update Time

NeurIPS 2023poster

We present a $O(1)$-approximate fully dynamic algorithm for the $k$-median and $k$-means problems on metric spaces with amortized update time $\tilde O(k)$ and worst-case query time $\tilde O(k^2)$. We complement our theoretical analysis with the first in-depth experimental study for the dynamic $k$…

2022

Efficient and Stable Fully Dynamic Facility Location

NeurIPS 2022accept

We consider the classic facility location problem in fully dynamic data streams, where elements can be both inserted and deleted. In this problem, one is interested in maintaining a stable and high quality solution throughout the data stream while using only little time per update (insertion or dele…

2022

Near-Optimal Correlation Clustering with Privacy

NeurIPS 2022accept

Correlation clustering is a central problem in unsupervised learning, with applications spanning community detection, duplicate detection, automated labeling and many more. In the correlation clustering problem one receives as input a set of nodes and for each node a list of co-clustering preference…

Cited by 18SourcePDFScholar
2022

Online and Consistent Correlation Clustering

ICML 2022spotlight

In the correlation clustering problem the input is a signed graph where the sign indicates whether each pair of points should be placed in the same cluster or not. The goal of the problem is to compute a clustering which minimizes the number of disagreements with such recommendation. Thanks to its m…

Cited by 15SourcePDFScholar
2021

Correlation Clustering in Constant Many Parallel Rounds

ICML 2021oral

Correlation clustering is a central topic in unsupervised learning, with many applications in ML and data mining. In correlation clustering, one receives as input a signed graph and the goal is to partition it to minimize the number of disagreements. In this work we propose a massively parallel comp…

Cited by 48SourcePDFScholar
2019

Fully Dynamic Consistent Facility Location

NeurIPS 2019poster

We consider classic clustering problems in fully dynamic data streams, where data elements can be both inserted and deleted. In this context, several parameters are of importance: (1) the quality of the solution after each insertion or deletion, (2) the time it takes to update the solution, and (3)…

2018

Online Reciprocal Recommendation with Theoretical Performance Guarantees

NeurIPS 2018poster

A reciprocal recommendation problem is one where the goal of learning is not just to predict a user's preference towards a passive item (e.g., a book), but to recommend the targeted user on one side another user from the other side such that a mutual interest between the two exists. The problem thus…

Cited by 7SourcePDFScholar
2017

Balancing information exposure in social networks

NeurIPS 2017poster

Social media has brought a revolution on how people are consuming news. Beyond the undoubtedly large number of advantages brought by social-media platforms, a point of criticism has been the creation of echo chambers and filter bubbles, caused by social homophily and algorithmic personalization. In…

Cited by 98SourcePDFScholar