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We propose a $O(\log k \log n)$-competitive randomized algorithm for online node-weighted Steiner forest. This is essentially optimal and significantly improves over the previous bound of $O(\log^2 k \log n)$ by Hajiaghayi et al. [2017]. In…

Data Structures and Algorithms · Computer Science 2024-10-29 Sander Borst , Marek Eliáš , Moritz Venzin

The online bisection problem requires maintaining a dynamic partition of $n$ nodes into two equal-sized clusters. Requests arrive sequentially as node pairs. If the nodes lie in different clusters, the algorithm pays unit cost. After each…

Data Structures and Algorithms · Computer Science 2026-02-12 Mateusz Basiak , Marcin Bienkowski , Guy Even , Agnieszka Tatarczuk

The online (uniform) buy-at-bulk network design problem asks us to design a network, where the edge-costs exhibit economy-of-scale. Previous approaches to this problem used tree- embeddings, giving us randomized algorithms. Moreover, the…

Data Structures and Algorithms · Computer Science 2016-11-02 Anupam Gupta , R. Ravi , Kunal Talwar , Seeun William Umboh

We consider the problem of online Min-cost Perfect Matching with Delays (MPMD) recently introduced by Emek et al, (STOC 2016). This problem is defined on an underlying $n$-point metric space. An adversary presents real-time requests online…

Data Structures and Algorithms · Computer Science 2016-10-18 Yossi Azar , Ashish Chiplunkar , Haim Kaplan

Embeddings of graphs into distributions of trees that preserve distances in expectation are a cornerstone of many optimization algorithms. Unfortunately, online or dynamic algorithms which use these embeddings seem inherently randomized and…

Data Structures and Algorithms · Computer Science 2021-02-11 Bernhard Haeupler , D Ellis Hershkowitz , Goran Zuzic

For the online transportation problem with $m$ server sites, it has long been known that the competitive ratio of any deterministic algorithm is at least $2m-1$. Kalyanasundaram and Pruhs conjectured in 1998 that a deterministic…

Data Structures and Algorithms · Computer Science 2025-04-24 Tsubasa Harada , Toshiya Itoh

In this paper, we investigate the online allocation problem of maximizing the overall revenue subject to both lower and upper bound constraints. Compared to the extensively studied online problems with only resource upper bounds, the…

Machine Learning · Computer Science 2023-01-31 Qixin Zhang , Wenbing Ye , Zaiyi Chen , Haoyuan Hu , Enhong Chen , Yang Yu

We initiate the study of the following general clustering problem. We seek to partition a given set $P$ of data points into $k$ clusters by finding a set $X$ of $k$ centers and assigning each data point to one of the centers. The cost of a…

Data Structures and Algorithms · Computer Science 2024-11-01 Martin G. Herold , Evangelos Kipouridis , Joachim Spoerhase

Random dimensionality reduction is a versatile tool for speeding up algorithms for high-dimensional problems. We study its application to two clustering problems: the facility location problem, and the single-linkage hierarchical clustering…

Data Structures and Algorithms · Computer Science 2021-07-06 Shyam Narayanan , Sandeep Silwal , Piotr Indyk , Or Zamir

In this paper, we study the Min-cost Perfect $k$-way Matching with Delays ($k$-MPMD), recently introduced by Melnyk et al. In the problem, $m$ requests arrive one-by-one over time in a metric space. At any time, we can irrevocably make a…

Data Structures and Algorithms · Computer Science 2023-10-30 Naonori Kakimura , Tomohiro Nakayoshi

Clustering is a fundamental unsupervised learning problem where a dataset is partitioned into clusters that consist of nearby points in a metric space. A recent variant, fair clustering, associates a color with each point representing its…

Machine Learning · Computer Science 2023-01-10 Seyed A. Esmaeili , Brian Brubach , Aravind Srinivasan , John P. Dickerson

We consider metrical task systems on tree metrics, and present an $O(\mathrm{depth} \times \log n)$-competitive randomized algorithm based on the mirror descent framework introduced in our prior work on the $k$-server problem. For the…

Data Structures and Algorithms · Computer Science 2020-11-30 Sébastien Bubeck , Michael B. Cohen , James R. Lee , Yin Tat Lee

Clustering is a fundamental problem in unsupervised machine learning with many applications in data analysis. Popular clustering algorithms such as Lloyd's algorithm and $k$-means++ can take $\Omega(ndk)$ time when clustering $n$ points in…

Machine Learning · Computer Science 2023-10-26 Moses Charikar , Monika Henzinger , Lunjia Hu , Maxmilian Vötsch , Erik Waingarten

Probabilistic metric embedding into trees is a powerful technique for designing online algorithms. The standard approach is to embed the entire underlying metric into a tree metric and then solve the problem on the latter. The overhead in…

Data Structures and Algorithms · Computer Science 2024-09-02 Yair Bartal , Ora N. Fandina , Seeun William Umboh

Online bidding is a classical problem in online decision-making, with applications in resource allocation, hierarchical clustering, and the analysis of approximation algorithms. We study its randomized learning-augmented variant, where an…

Data Structures and Algorithms · Computer Science 2026-05-15 Mathis Degryse , Imrane Saakour , Christoph Dürr , Spyros Angelopoulos

We connect three distinct lines of research that have recently explored extensions of the classical LOCAL model of distributed computing: A. distributed quantum computing and non-signaling distributions [e.g. STOC 2024], B.…

Dasgupta recently introduced a cost function for the hierarchical clustering of a set of points given pairwise similarities between them. He showed that this function is NP-hard to optimize, but a top-down recursive partitioning heuristic…

Data Structures and Algorithms · Computer Science 2016-10-03 Moses Charikar , Vaggos Chatziafratis

Metric embeddings into structured spaces, particularly hierarchically well-separated trees (HSTs), are a fundamental tool in the design of online algorithms. In the classical online embedding setting, points arrive sequentially and must be…

Data Structures and Algorithms · Computer Science 2026-05-13 Christian Coester , Yichen Huang

Clustering is an unsupervised machine learning task that consists of identifying groups of similar objects. It has numerous applications and is increasingly used in fairness-sensitive domains where objects represent individuals, such as…

Machine Learning · Computer Science 2026-05-14 Claudio Mantuano , Manuel Kammermann , Philipp Baumann

We show that on every $n$-point HST metric, there is a randomized online algorithm for metrical task systems (MTS) that is $1$-competitive for service costs and $O(\log n)$-competitive for movement costs. In general, these refined…

Data Structures and Algorithms · Computer Science 2020-09-04 Christian Coester , James R. Lee