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Disjoint Compatibility via Graph Classes 通过图类实现互不相容
Pub Date : 2024-09-05 DOI: arxiv-2409.03579
Oswin Aichholzer, Julia Obmann, Pavel Paták, Daniel Perz, Josef Tkadlec, Birgit Vogtenhuber
Two plane drawings of graphs on the same set of points are called disjointcompatible if their union is plane and they do not have an edge in common. Let$S$ be a convex point set of $2n geq 10$ points and let $mathcal{H}$ be afamily of plane drawings on $S$. Two plane perfect matchings $M_1$ and $M_2$ on$S$ (which do not need to be disjoint nor compatible) are emph{disjoint$mathcal{H}$-compatible} if there exists a drawing in $mathcal{H}$ which isdisjoint compatible to both $M_1$ and $M_2$ In this work, we consider the graphwhich has all plane perfect matchings as vertices and where two vertices areconnected by an edge if the matchings are disjoint $mathcal{H}$-compatible. Westudy the diameter of this graph when $mathcal{H}$ is the family of all planespanning trees, caterpillars or paths. We show that in the first two cases thegraph is connected with constant and linear diameter, respectively, while inthe third case it is disconnected.
如果在同一个点集合上的两个平面图形的结合是平面的,并且它们没有共同的边,那么这两个平面图形称为不相容的平面图形。设$S$是一个由$2n geq 10$个点组成的凸点集,并设$mathcal{H}$是$S$上的平面图族。如果在 $mathcal{H}$ 中存在一个与 $M_1$ 和 $M_2$ 都不相交的图形,那么 $mathcal{H}$ 上的两个平面完全匹配图形 $M_1$ 和 $M_2$(它们不需要不相交也不兼容)就是 emph{disjoint$mathcal{H}$-compatible} 、在这项工作中,我们考虑这样一个图,它以所有平面完美匹配为顶点,如果匹配是不相交的 $mathcal{H}$ 兼容,则两个顶点由一条边连接。当 $mathcal{H}$ 是所有平面树、毛毛虫或路径的族时,我们研究了这个图的直径。我们证明,在前两种情况下,该图分别以恒定直径和线性直径相连,而在第三种情况下,它是断开的。
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引用次数: 0
Approximation Algorithms for Anchored Multiwatchman Routes 锚定多观察者航线的近似算法
Pub Date : 2024-08-30 DOI: arxiv-2408.17343
Joseph S. B. Mitchell, Linh Nguyen
We study some variants of the $k$-textsc{Watchman Routes} problem, thecooperative version of the classic textsc{Watchman Routes} problem in a simplepolygon. The watchmen may be required to see the whole polygon, or somepre-determined quota of area within the polygon, and we want to minimize themaximum length traveled by any watchman. While the single watchman version ofthe problem has received much attention is rather well understood, it is notthe case for multiple watchmen version. We provide the first tight approximability results for the anchored$k$-textsc{Watchman Routes} problem in a simple polygon, assuming $k$ isfixed, by a fully-polynomial time approximation scheme. The basis for the FPTASis provided by an exact dynamic programming algorithm. If $k$ is a variable, wegive constant-factor approximations.
我们研究了 $k$-textsc{Watchman Routes} 问题的一些变体,它是简单多边形中经典 textsc{Watchman Routes} 问题的合作版本。守望者可能需要看到整个多边形,或者多边形内某个预先确定的区域,我们希望最小化任何一个守望者所走过的最大长度。虽然单个看守人版本的问题已经得到了广泛的关注和深入的理解,但多个看守人版本的问题却并非如此。我们通过全多项式时间近似方案,首次给出了简单多边形中锚定 $k$-textsc{Watchman Routes} 问题(假设 $k$ 是固定的)的严格近似结果。精确动态编程算法为 FPTAS 提供了基础。如果 $k$ 是变量,我们会给出常数因子近似值。
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引用次数: 0
Best of two worlds: Cartesian sampling and volume computation for distance-constrained configuration spaces using Cayley coordinates 两全其美:使用 Cayley 坐标为距离受限的配置空间进行笛卡尔采样和体积计算
Pub Date : 2024-08-29 DOI: arxiv-2408.16946
Yichi Zhang, Meera Sitharam
Volume calculation of configurational spaces acts as a vital part inconfigurational entropy calculation, which contributes towards calculating freeenergy landscape for molecular systems. In this article, we present oursampling-based volume computation method using distance-based Cayleycoordinate, mitigating drawbacks: our method guarantees that the samplingprocedure stays in lower-dimensional coordinate space (instead ofhigher-dimensional Cartesian space) throughout the whole process; and ourmapping function, utilizing Cayley parameterization, can be applied in bothdirections with low computational cost. Our method uniformly samples andcomputes a discrete volume measure of a Cartesian configuration space of pointsets satisfying systems of distance inequality constraints. The systems belongto a large natural class whose feasible configuration spaces are effectivelylower dimensional subsets of high dimensional ambient space. Their topologicalcomplexity makes discrete volume computation challenging, yet necessary inseveral application scenarios including free energy calculation in soft matterassembly modeling. The algorithm runs in linear time and empirically sub-linearspace in the number of grid hypercubes (used to define the discrete volumemeasure) textit{that intersect} the configuration space. In other words, thenumber of wasted grid cube visits is insignificant compared to prevailingmethods typically based on gradient descent. Specifically, the traversal stayswithin the feasible configuration space by viewing it as a branched covering,using a recent theory of Cayley or distance coordinates to convexify the basespace, and by employing a space-efficient, frontier hypercube traversal datastructure. A software implementation and comparison with existing methods isprovided.
构型空间的体积计算是构型熵计算的重要组成部分,有助于计算分子系统的自由能谱。在本文中,我们介绍了基于采样的体积计算方法,该方法使用基于距离的 Cayley 坐标,可减轻以下缺点:我们的方法可保证采样过程全程停留在低维坐标空间(而不是高维笛卡尔空间);我们的映射函数利用 Cayley 参数化,可同时应用于两个方向,且计算成本较低。我们的方法对满足距离不等式约束系统的点集的笛卡尔配置空间进行均匀采样并计算离散体积度量。这些系统属于一个大的自然类,其可行的配置空间实际上是高维环境空间的低维子集。它们的拓扑复杂性使得离散体积计算具有挑战性,但在软物质组装建模的自由能计算等多个应用场景中又是必要的。该算法的运行时间为线性时间,经验上与配置空间相交的网格超立方体(用于定义离散体积)的数量呈亚线性关系。换句话说,与基于梯度下降的主流方法相比,浪费的网格立方体访问次数微不足道。具体来说,该遍历方法将可行配置空间视为一个分支覆盖,利用最新的 Cayley 或距离坐标理论凸化基底空间,并采用空间效率高的前沿超立方体遍历数据结构,从而保持在可行配置空间内。本文提供了软件实现方法以及与现有方法的比较。
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引用次数: 0
Image Triangulation Using the Sobel Operator for Vertex Selection 使用 Sobel 运算符选择顶点的图像三角剖分法
Pub Date : 2024-08-28 DOI: arxiv-2408.16112
Olivia Laske, Lori Ziegelmeier
Image triangulation, the practice of decomposing images into triangles,deliberately employs simplification to create an abstracted representation.While triangulating an image is a relatively simple process, difficulties arisewhen determining which vertices produce recognizable and visually pleasingoutput images. With the goal of producing art, we discuss an imagetriangulation algorithm in Python that utilizes Sobel edge detection and pointcloud sparsification to determine final vertices for a triangulation, resultingin the creation of artistic triangulated compositions.
图像三角剖分是将图像分解成三角形的一种做法,它有意采用简化的方法来创建抽象的表示形式。虽然图像三角剖分是一个相对简单的过程,但在确定哪些顶点能生成可识别且视觉上悦目的输出图像时却会遇到困难。为了制作艺术作品,我们讨论了 Python 中的一种图像三角剖分算法,该算法利用索贝尔边缘检测和点云稀疏化来确定三角剖分的最终顶点,从而创作出具有艺术性的三角剖分作品。
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引用次数: 0
Approximation Algorithms for Minimum Sum of Moving-Distance and Opening-Costs Target Coverage Problem 最小移动距离和开局成本目标覆盖问题的近似算法
Pub Date : 2024-08-25 DOI: arxiv-2408.13797
Lei Zhao, Zhao Zhang
In this paper, we study the Minimum Sum of Moving-Distance and Opening-CostsTarget Coverage problem (MinMD$+$OCTC). Given a set of targets and a set ofbase stations on the plane, an opening cost function for every base station,the opened base stations can emit mobile sensors with a radius of $r$ from basestation to cover the targets. The goal of MinMD$+$OCTC is to cover all thetargets and minimize the sum of the opening cost and the moving distance ofmobile sensors. We give the optimal solution in polynomial time for theMinMD$+$OCTC problem with targets on a straight line, and present a 8.928approximation algorithm for a special case of the MinMD$+$OCTC problem with thetargets on the plane.
本文研究的是移动距离与开放成本之和最小的目标覆盖问题(MinMD$+$OCTC)。给定平面上的一组目标和一组基站,每个基站有一个开放成本函数,开放的基站可以从基站发射半径为 $r$ 的移动传感器来覆盖目标。MinMD$+$OCTC 的目标是覆盖所有目标,并使开放成本与移动传感器移动距离之和最小。我们在多项式时间内给出了目标在直线上的 MinMD$+$OCTC 问题的最优解,并给出了目标在平面上的 MinMD$+$OCTC 问题特例的 8.928 近似算法。
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引用次数: 0
Critical Point Extraction from Multivariate Functional Approximation 从多元函数近似中提取临界点
Pub Date : 2024-08-23 DOI: arxiv-2408.13193
Guanqun Ma, David Lenz, Tom Peterka, Hanqi Guo, Bei Wang
Advances in high-performance computing require new ways to representlarge-scale scientific data to support data storage, data transfers, and dataanalysis within scientific workflows. Multivariate functional approximation(MFA) has recently emerged as a new continuous meshless representation thatapproximates raw discrete data with a set of piecewise smooth functions. An MFAmodel of data thus offers a compact representation and supports high-orderevaluation of values and derivatives anywhere in the domain. In this paper, wepresent CPE-MFA, the first critical point extraction framework designed for MFAmodels of large-scale, high-dimensional data. CPE-MFA extracts critical pointsdirectly from an MFA model without the need for discretization or resampling.This is the first step toward enabling continuous implicit models such as MFAto support topological data analysis at scale.
高性能计算的发展需要新的方法来表示大规模科学数据,以支持科学工作流中的数据存储、数据传输和数据分析。多变量函数逼近(MFA)是最近出现的一种新的连续无网格表示方法,它可以用一组片断平滑函数逼近原始离散数据。因此,MFA 数据模型提供了一种紧凑的表示方法,并支持对域中任何位置的值和导数进行高估值。在本文中,我们介绍了 CPE-MFA,这是第一个专为大规模、高维数据的 MFA 模型而设计的临界点提取框架。CPE-MFA 可直接从 MFA 模型中提取临界点,而无需离散化或重新采样。这是使 MFA 等连续隐式模型支持大规模拓扑数据分析的第一步。
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引用次数: 0
Targeted Drug Delivery: Algorithmic Methods for Collecting a Swarm of Particles with Uniform External Forces 靶向给药:利用均匀外力收集颗粒群的算法方法
Pub Date : 2024-08-19 DOI: arxiv-2408.09729
Aaron T. Becker, Sándor P. Fekete, Li Huang, Phillip Keldenich, Linda Kleist, Dominik Krupke, Christian Rieck, Arne Schmidt
We investigate algorithmic approaches for targeted drug delivery in acomplex, maze-like environment, such as a vascular system. The basic scenariois given by a large swarm of micro-scale particles (''agents'') and aparticular target region (''tumor'') within a system of passageways. Agents aretoo small to contain on-board power or computation and are instead controlledby a global external force that acts uniformly on all particles, such as anapplied fluidic flow or electromagnetic field. The challenge is to deliver allagents to the target region with a minimum number of actuation steps. We provide a number of results for this challenge. We show that theunderlying problem is NP-complete, which explains why previous work did notprovide provably efficient algorithms. We also develop several algorithmicapproaches that greatly improve the worst-case guarantees for the number ofrequired actuation steps. We evaluate our algorithmic approaches by numeroussimulations, both for deterministic algorithms and searches supported by deeplearning, which show that the performance is practically promising.
我们研究了在复杂的迷宫般环境(如血管系统)中进行靶向给药的算法方法。基本场景是在一个通道系统中,由一大群微尺度粒子("药剂")和特定目标区域("肿瘤")组成。由于微粒太小,无法搭载动力或计算能力,因此需要通过均匀作用于所有微粒的全局外力(如外加流体流或电磁场)进行控制。我们面临的挑战是以最少的驱动步骤将所有试剂输送到目标区域。我们为这一挑战提供了一系列结果。我们证明了基本问题是 NP-完全的,这也解释了为什么以前的工作没有提供可证明的高效算法。我们还开发了几种算法方法,大大提高了对所需执行步骤数的最坏情况保证。我们通过大量的模拟来评估我们的算法方法,包括确定性算法和深度学习支持的搜索,结果表明这些算法的性能是切实可行的。
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引用次数: 0
Polynomial 2D Green Coordinates for High-order Cages 高阶笼的多项式二维绿色坐标
Pub Date : 2024-08-13 DOI: arxiv-2408.06831
Shibo Liu, Ligang Liu, Xiao-Ming Fu
We propose conformal polynomial coordinates for 2D closed high-order cages,which consist of polynomial curves of any order. The coordinates enable thetransformation of the input polynomial curves into polynomial curves of anyorder. We extend the classical 2D Green coordinates to define our coordinates,thereby leading to cage-aware conformal harmonic deformations. We extensivelytest our method on various 2D deformations, allowing users to manipulate theBezier control points to easily generate the desired deformation.
我们提出了由任意阶多项式曲线组成的二维封闭高阶笼的共形多项式坐标。这些坐标可以将输入的多项式曲线转换成任意阶的多项式曲线。我们扩展了经典的二维格林坐标来定义我们的坐标,从而实现了笼感共形谐波变形。我们在各种二维变形上广泛测试了我们的方法,允许用户操纵贝塞尔控制点,轻松生成所需的变形。
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引用次数: 0
Searching in Euclidean Spaces with Predictions 用预测在欧几里得空间中搜索
Pub Date : 2024-08-09 DOI: arxiv-2408.04964
Sergio Cabello, Panos Giannopoulos
We study the problem of searching for a target at some unknown location in$mathbb{R}^d$ when additional information regarding the position of the targetis available in the form of predictions. In our setting, predictions come asapproximate distances to the target: for each point $pin mathbb{R}^d$ thatthe searcher visits, we obtain a value $lambda(p)$ such that $|pmathbf{t}|lelambda(p) le ccdot |pmathbf{t}|$, where $cge 1$ is a fixed constant,$mathbf{t}$ is the position of the target, and $|pmathbf{t}|$ is theEuclidean distance of $p$ to $mathbf{t}$. The cost of the search is the lengthof the path followed by the searcher. Our main positive result is a strategythat achieves $(12c)^{d+1}$-competitive ratio, even when the constant $c$ isunknown. We also give a lower bound of roughly $(c/16)^{d-1}$ on thecompetitive ratio of any search strategy in $mathbb{R}^d$.
我们研究的问题是,当有关目标位置的额外信息以预测的形式存在时,如何在$mathbb{R}^d$中的某个未知位置搜索目标。在我们的设置中,预测结果是目标的近似距离:对于搜索者访问的 mathbb{R}^d$ 中的每个点 $p,我们都会得到一个值 $/lambda(p)$,使得 $|pmathbf{t}|lelambda(p) le ccdot |pmathbf{t}|$ 、其中 $cge 1$ 是一个固定常数,$mathbf{t}$ 是目标的位置,$|pmathbf{t}|$ 是 $p$ 到 $mathbf{t}$ 的欧几里得距离。搜索成本是搜索者所走路径的长度。我们的主要正面结果是,即使常数 $c$ 未知,也能实现 $(12c)^{d+1}$ 竞争比的策略。我们还给出了$mathbb{R}^d$中任何搜索策略的竞争率的下限,大约为$(c/16)^{d-1}$。
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引用次数: 0
Size Should not Matter: Scale-invariant Stress Metrics 大小无关紧要:规模不变的应力指标
Pub Date : 2024-08-08 DOI: arxiv-2408.04688
Reyan Ahmed, Cesim Erten, Stephen Kobourov, Jonah Lotz, Jacob Miller, Hamlet Taraz
The normalized stress metric measures how closely distances between verticesin a graph drawing match the graph-theoretic distances between those vertices.It is one of the most widely employed quality metrics for graph drawing, and iseven the optimization goal of several popular graph layout algorithms. However,normalized stress can be misleading when used to compare the outputs of two ormore algorithms, as it is sensitive to the size of the drawing compared to thegraph-theoretic distances used. Uniformly scaling a layout will change thevalue of stress despite not meaningfully changing the drawing. In fact, thechange in stress values can be so significant that a clearly better layout canappear to have a worse stress score than a random layout. In this paper, westudy different variants for calculating stress used in the literature (rawstress, normalized stress, etc.) and show that many of them are affected bythis problem, which threatens the validity of experiments that compare thequality of one algorithm to that of another. We then experimentally justify oneof the stress calculation variants, scale-normalized stress, as one that fairlycompares drawing outputs regardless of their size. We also describe anefficient computation for scale-normalized stress and provide an open sourceimplementation.
归一化应力指标衡量的是图形绘制中顶点之间的距离与这些顶点之间的图论距离的匹配程度,它是图形绘制中应用最广泛的质量指标之一,甚至是几种流行图形布局算法的优化目标。然而,在比较两种或更多算法的输出结果时,归一化应力可能会产生误导,因为与所使用的图论距离相比,它对绘图的大小非常敏感。均匀缩放布局会改变应力值,尽管并不会对绘图造成有意义的改变。事实上,应力值的变化可能非常明显,以至于一个明显更好的布局看起来会比随机布局的应力值更差。在本文中,我们研究了文献中使用的计算应力的不同变体(原始应力、归一化应力等),结果表明许多变体都受到这个问题的影响,这威胁到了将一种算法的质量与另一种算法的质量进行比较的实验的有效性。然后,我们通过实验证明了其中一种应力计算变体--标度归一化应力--是一种可以公平比较绘图输出(无论其大小)的算法。我们还描述了规模归一化应力的高效计算方法,并提供了一个开源实现。
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引用次数: 0
期刊
arXiv - CS - Computational Geometry
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