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Delaunay-Like Triangulation of Smooth Orientable Submanifolds by (ell _1)-Norm Minimization 光滑可定向子流形的类delaunay三角剖分(ell _1) -范数最小化

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-03-10 DOI: 10.1007/s00453-025-01367-z

Dominique Attali, André Lieutier

引用次数: 0

The Voronoi Diagram of Rotating Rays with Applications to Floodlight Illumination 旋转光线的Voronoi图及其在泛光灯照明中的应用

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-03-09 DOI: 10.1007/s00453-025-01368-y

Carlos Alegría, Ioannis Mantas, Evanthia Papadopoulou, Marko Savić, Carlos Seara, Martin Suderland

{"title":"The Voronoi Diagram of Rotating Rays with Applications to Floodlight Illumination","authors":"Carlos Alegría, Ioannis Mantas, Evanthia Papadopoulou, Marko Savić, Carlos Seara, Martin Suderland","doi":"10.1007/s00453-025-01368-y","DOIUrl":"10.1007/s00453-025-01368-y","url":null,"abstract":"<div>We study the Voronoi Diagram of Rotating Rays, a Voronoi structure where the input sites are rays and the distance function between a point and a site/ray is their counterclockwise angular distance. This novel Voronoi diagram is motivated by illumination and coverage problems, where a domain must be covered by floodlights, which are wedges of uniform angle, and the goal is to find the minimum angle necessary to cover the domain. This angle is called the Brocard angle and it is encoded in the Voronoi diagram of rotating rays. We study the diagram in the plane and present its structural properties, its combinatorial complexity bounds, and a construction algorithm. If the rays are induced by a convex polygon, we show how to construct the rotating rays Voronoi diagram within the polygon in optimal linear time. We can thus compute the Brocard angle of the polygon in the same time. Floodlights are used to model devices with limited sensing range, like surveillance cameras or directional antennas. In this context, the Brocard angle reveals the minimum range necessary for a set of devices to cover a domain.</div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"88 2","pages":""},"PeriodicalIF":0.7,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147440936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Bipartite Independent Set Reconfiguration: General and RNA-Inspired Parameterized Algorithms 二部独立集重构：一般和rna启发的参数化算法

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-03-05 DOI: 10.1007/s00453-026-01371-x

Théo Boury, Laurent Bulteau, Bertrand Marchand, Yann Ponty

{"title":"Bipartite Independent Set Reconfiguration: General and RNA-Inspired Parameterized Algorithms","authors":"Théo Boury, Laurent Bulteau, Bertrand Marchand, Yann Ponty","doi":"10.1007/s00453-026-01371-x","DOIUrl":"10.1007/s00453-026-01371-x","url":null,"abstract":"<div>Computing the energy barrier between RNA structures is a classic NP-hard problem in bioinformatics, of which the Independent Set (IS) reconfiguration in bipartite graphs represents a natural generalization. Parameterized algorithms, based on parameters taking limited or bounded values on biological instances, are thus crucial towards practical solutions. In this work, we show that bipartite IS reconfiguration is slice-wise Polynomial (XP) solvable for both the range (rho ) of IS sizes allowed along the reconfiguration, and the arboricity (Phi ) when the input is restricted to a circle graph. Such a setting is relevant to Bioinformatics as it provides a solution to the RNA energy barrier problem. We propose algorithms based on a divide-and-conquer approach, yielding a (Oleft( n^{2}right) )-space, (Oleft( n^{2rho +2.5}right) )-time algorithm for the range (rho ), and a (Oleft( n^{Phi + 2}right) )-space, (Oleft( n^{Phi +3}right) )-time algorithm for the arboricity (Phi ). We demonstrate the practicality of our algorithms on benchmarks respectively consisting of random Erdös-Rényi bipartite graphs, random pairs of RNA structures and experimentally-supported instances of RNA kinetics.</div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"88 2","pages":""},"PeriodicalIF":0.7,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Telephone k-Multicast Problem 电话k-多播问题

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-03-02 DOI: 10.1007/s00453-026-01377-5

Daniel Hathcock, Guy Kortsarz, R. Ravi

{"title":"The Telephone k-Multicast Problem","authors":"Daniel Hathcock, Guy Kortsarz, R. Ravi","doi":"10.1007/s00453-026-01377-5","DOIUrl":"10.1007/s00453-026-01377-5","url":null,"abstract":"<div>We consider minimum time multicasting problems in directed and undirected graphs: given a root node and a subset of t terminal nodes, multicasting seeks to find the minimum number of rounds within which all terminals can be informed with a message originating at the root. In each round, the telephone model we study allows the information to move via a matching from the informed nodes to the uninformed nodes. Since minimum time multicasting in digraphs is poorly understood compared to the undirected variant, we study an intermediate problem in undirected graphs that specifies a target (k < t), and requires that only k of the terminals be informed in the minimum number of rounds. For this problem, we improve the implications of the previous results and obtain a multiplicative approximation factor of (tilde{O}(t^{1/3})). For the directed version, we obtain an additive (tilde{O}(k^{1/2})) approximation algorithm (with a polylogarithmic multiplicative factor). Our algorithms are based on reductions to the related problems of finding k-trees of minimum poise (sum of maximum degree and diameter) and applying a combination of greedy network decomposition techniques and set covering under partition matroid constraints. We also study the problem of bounded degree Directed Steiner Tree, for which we obtain improved polylogarithmic approximations for the special case of bounded treewidth graphs. This extends prior work on the Group Steiner Tree problem.</div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"88 2","pages":""},"PeriodicalIF":0.7,"publicationDate":"2026-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-026-01377-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147336138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Graph Exploration: The Impact of a Distance Constraint 图探索：距离约束的影响

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-02-28 DOI: 10.1007/s00453-026-01378-4

Stéphane Devismes, Yoann Dieudonné, Arnaud Labourel

{"title":"Graph Exploration: The Impact of a Distance Constraint","authors":"Stéphane Devismes, Yoann Dieudonné, Arnaud Labourel","doi":"10.1007/s00453-026-01378-4","DOIUrl":"10.1007/s00453-026-01378-4","url":null,"abstract":"<div>A mobile agent, starting from a node s of a simple undirected graph (G=(V,E)), has to explore all nodes and edges of G. To do so, the agent uses a deterministic algorithm that allows it to gain information on G as it traverses its edges. During its exploration, the agent must always respect the constraint of knowing a path of length at most D to go back to node s. The upper bound D is fixed as being equal to ((1+alpha )r), where r is the eccentricity of node s and (alpha ) is any positive real constant. This task has been introduced by Duncan et al. (ACM Trans Algorithms 2(3):380–402, 2006) and is known as distance-constrained exploration. The penalty of an exploration algorithm running in G is the number of edge traversals made by the agent in excess of |E|. In Panaite and Pelc (J Algorithms 33(2):281–295, 1999), Panaite and Pelc gave an algorithm for solving exploration without any constraint on the moves that is guaranteed to work in every graph G with a (small) penalty in (mathcal {O}(|V|)). Can we obtain a distance-constrained exploration algorithm with the same guarantee? In this paper, we provide a negative answer to this question. We also observe that an algorithm working in every graph G with a linear penalty in |V| cannot be obtained for the task of fuel-constrained exploration, another variant studied in the literature. This solves an open problem posed by Duncan et al. (ACM Trans Algorithms 2(3):380–402, 2006) and shows a fundamental separation with the task of exploration without constraint on the moves.</div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"88 2","pages":""},"PeriodicalIF":0.7,"publicationDate":"2026-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147342689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Towards a Practical, Budget-Oblivious Algorithm for the Adwords Problem Under Small Bids 一种实用的、预算无关的小竞价广告问题算法

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-02-19 DOI: 10.1007/s00453-026-01369-5

Vijay V. Vazirani

引用次数: 0

Convex relaxation for the generalized maximum-entropy sampling problem 广义最大熵抽样问题的凸松弛

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-02-17 DOI: 10.1007/s00453-026-01373-9

Gabriel Ponte, Marcia Fampa, Jon Lee

引用次数: 0

Concentration of Submodular Functions and Read-k Families Under Negative Dependence 负相关下子模函数与Read-k族的集中

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-02-16 DOI: 10.1007/s00453-026-01372-w

Sharmila Duppala, George Z. Li, Juan Luque, Aravind Srinivasan, Renata Valieva

引用次数: 0

Block Crossings in One-Sided Tanglegrams 单侧缠结图中的块交叉

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-02-07 DOI: 10.1007/s00453-025-01363-3

Alexander Dobler, Martin Nöllenburg

引用次数: 0

Rapid Mixing of Global Markov Chains via Spectral Independence: The Unbounded Degree Case 基于谱独立的全局马尔可夫链的快速混合：无界度情况

IF 0.7 4区计算机科学

Algorithmica Pub Date : 2026-01-14 DOI: 10.1007/s00453-025-01353-5

Antonio Blanca, Xusheng Zhang

{"title":"Rapid Mixing of Global Markov Chains via Spectral Independence: The Unbounded Degree Case","authors":"Antonio Blanca, Xusheng Zhang","doi":"10.1007/s00453-025-01353-5","DOIUrl":"10.1007/s00453-025-01353-5","url":null,"abstract":"<div>We consider spin systems on general n-vertex graphs of unbounded degree and explore the effects of spectral independence on the rate of convergence to equilibrium of global Markov chains. Spectral independence is a novel way of quantifying the decay of correlations in spin system models, which has significantly advanced the study of Markov chains for spin systems. We prove that whenever spectral independence holds, the popular Swendsen–Wang dynamics for the q-state ferromagnetic Potts model on graphs of maximum degree (Delta ), where (Delta ) is allowed to grow with n, converges in (O((Delta log n)^c)) steps where (c > 0) is a constant independent of (Delta ) and n. We also show a similar mixing time bound for the block dynamics of general spin systems, again assuming that spectral independence holds. Finally, for monotone spin systems such as the Ising model and the hardcore model on bipartite graphs, we show that spectral independence implies that the mixing time of the systematic scan dynamics is (O(Delta ^c log n)) for a constant (c>0) independent of (Delta ) and n. Systematic scan dynamics are widely popular but are notoriously difficult to analyze. Our result implies optimal (O(log n)) mixing time bounds for any systematic scan dynamics of the ferromagnetic Ising model on general graphs up to the tree uniqueness threshold. Our main technical contribution is an improved factorization of the entropy functional: this is the common starting point for all our proofs. Specifically, we establish the so-called k-partite factorization of entropy with a constant that depends polynomially on the maximum degree of the graph.</div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"88 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-025-01353-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145983138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0