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We developed fast direct solver for 3D Helmholtz and Maxwell equations in layered medium. The algorithm is based on the ideas of cyclic reduction for separable matrices. For the grids with major uniform part (within the survey domain in the…

Numerical Analysis · Mathematics 2019-09-04 Vladimir Druskin , Mikhail Zaslavsky

We study the following separation problem: Given a collection of colored objects in the plane, compute a shortest "fence" $F$, i.e., a union of curves of minimum total length, that separates every two objects of different colors. Two…

Computational Geometry · Computer Science 2021-05-11 Mikkel Abrahamsen , Panos Giannopoulos , Maarten Löffler , Günter Rote

We study some variants of the $k$-\textsc{Watchman Routes} problem, the cooperative version of the classic \textsc{Watchman Routes} problem in a simple polygon. The watchmen may be required to see the whole polygon, or some pre-determined…

Computational Geometry · Computer Science 2024-09-02 Joseph S. B. Mitchell , Linh Nguyen

A polygonal curve $P$ with $n$ vertices is $c$-packed, if the sum of the lengths of the parts of the edges of the curve that are inside any disk of radius $r$ is at most $cr$, for any $r>0$. Similarly, the concept of $c$-packedness can be…

Computational Geometry · Computer Science 2022-02-04 Sepideh Aghamolaei , Vahideh Keikha , Mohammad Ghodsi , Ali Mohades

The Fr\'echet distance is a popular measure of dissimilarity for polygonal curves. It is defined as a min-max formulation that considers all direction-preserving continuous bijections of the two curves. Because of its susceptibility to…

Computational Geometry · Computer Science 2022-02-24 Jacobus Conradi , Anne Driemel

In 2015, Driemel, Krivo\v{s}ija and Sohler introduced the $(k,\ell)$-median problem for clustering polygonal curves under the Fr\'echet distance. Given a set of input curves, the problem asks to find $k$ median curves of at most $\ell$…

Computational Geometry · Computer Science 2020-11-04 Maike Buchin , Anne Driemel , Dennis Rohde

We solve two variants of the Reifenberg problem for all coefficient groups. We carry out the direct method of the calculus of variation and search a solution as a weak limit of a minimizing sequence. This strategy has been introduced by De…

Classical Analysis and ODEs · Mathematics 2021-04-27 Camille Labourie

In many combinatorial problems one may need to model the diversity or similarity of assignments in a solution. For example, one may wish to maximise or minimise the number of distinct values in a solution. To formulate problems of this…

Artificial Intelligence · Computer Science 2014-01-17 Emmanuel Hebrard , Dániel Marx , Barry O'Sullivan , Igor Razgon

Computing the Fr\'echet distance between two polygonal curves takes roughly quadratic time. In this paper, we show that for a special class of curves the Fr\'echet distance computations become easier. Let $P$ and $Q$ be two polygonal curves…

Computational Geometry · Computer Science 2019-08-28 Joachim Gudmundsson , Majid Mirzanezhad , Ali Mohades , Carola Wenk

We study the problem of minimizing a nonnegative separable concave function over a compact feasible set. We approximate this problem to within a factor of 1+epsilon by a piecewise-linear minimization problem over the same feasible set. Our…

Optimization and Control · Mathematics 2012-01-17 Thomas L. Magnanti , Dan Stratila

We provide a general framework for getting expected linear time constant factor approximations (and in many cases FPTASs) to several well-known problems in Computational Geometry, such as $k$-center clustering and farthest nearest neighbor.…

Computational Geometry · Computer Science 2026-03-04 Sariel Har-Peled , Banjamin Raichel

We present an algorithm for computing $\epsilon$-coresets for $(k, \ell)$-median clustering of polygonal curves in $\mathbb{R}^d$ under the Fr\'echet distance. This type of clustering is an adaption of Euclidean $k$-median clustering: we…

Computational Geometry · Computer Science 2021-11-22 Maike Buchin , Dennis Rohde

We study the capacitated $k$-facility location problem, in which we are given a set of clients with demands, a set of facilities with capacities and a constant number $k$. It costs $f_i$ to open facility $i$, and $c_{ij}$ for facility $i$…

Data Structures and Algorithms · Computer Science 2014-09-15 Karen Aardal , Pieter van den Berg , Dion Gijswijt , Shanfei Li

The Fr\'{e}chet distance is a well studied and commonly used measure to capture the similarity of polygonal curves. Unfortunately, it exhibits a high sensitivity to the presence of outliers. Since the presence of outliers is a frequently…

Computational Geometry · Computer Science 2013-04-24 Jean-Lou De Carufel , Amin Gheibi , Anil Maheshwari , Jörg-Rüdiger Sack , Christian Scheffer

The contiguous art gallery problem was introduced at SoCG'25 in a merged paper that combined three simultaneous results, each achieving a polynomial-time algorithm for the problem. This problem is a variant of the classical art gallery…

Computational Geometry · Computer Science 2025-08-14 Sarita de Berg , Jacobus Conradi , Ivor van der Hoog , Frank Staals

We consider embedded, smooth curves in the plane which are either closed or asymptotic to two lines. We study their behaviour under curve shortening flow with a global forcing term. Firstly, we prove an analogue to Huisken's distance…

Differential Geometry · Mathematics 2021-05-18 Friederike Dittberner

We consider the problem of computing the Fr\'echet distance between two curves for which the exact locations of the vertices are unknown. Each vertex may be placed in a given uncertainty region for that vertex, and the objective is to place…

Computational Geometry · Computer Science 2023-06-02 Kevin Buchin , Maarten Löffler , Tim Ophelders , Aleksandr Popov , Jérôme Urhausen , Kevin Verbeek

Let P be a polygonal curve in R^d of length n, and S be a point-set of size k. We consider the problem of finding a polygonal curve Q on S such that all points in S are visited and the Fr\'echet distance from $P$ is less than a given…

Computational Geometry · Computer Science 2012-11-12 Paul Accisano , Alper Üngör

We introduce a new technique for designing fixed-parameter algorithms for cut problems, namely randomized contractions. We apply our framework to obtain the first FPT algorithm for the Unique Label Cover problem and new FPT algorithms with…

Data Structures and Algorithms · Computer Science 2016-07-20 Rajesh Chitnis , Marek Cygan , MohammadTaghi Hajiaghayi , Marcin Pilipczuk , Michał Pilipczuk

Suppose that a polygon $P$ is given as an array containing the vertices in counterclockwise order. We analyze how many vertices (including the index of each of these vertices) we need to know before we can bound $P$, i.e., report a bounded…

Computational Geometry · Computer Science 2025-09-05 Mikkel Abrahamsen , Jack Stade , Shuyi Yan , Hanwen Zhang