skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Towards Scalable and Practical Batch-Dynamic Connectivity
We study the problem of dynamically maintaining the connected components of an undirected graph subject to edge insertions and deletions. We give the first parallel algorithm for the problem that is work-efficient, supports batches of updates, runs in polylogarithmic depth, and uses only linear total space. The existing algorithms for the problem either use super-linear space, do not come with strong theoretical bounds, or are not parallel. On the empirical side, we provide the first implementation of the cluster forest algorithm, the first linear-space and polylogarithmic update time algorithm for dynamic connectivity. Experimentally, we find that our algorithm uses up to 19.7× less space and is up to 6.2× faster than the level-set algorithm of Holm, de Lichten-berg, and Thorup, arguably the most widely-implemented dynamic connectivity algorithm with strong theoretical guarantees.  more » « less
Award ID(s):
2403235
PAR ID:
10636080
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Proceedings of the VLDB Endowment
Date Published:
Journal Name:
Proceedings of the VLDB Endowment
Volume:
18
Issue:
3
ISSN:
2150-8097
Page Range / eLocation ID:
889 to 901
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Bringmann, Karl; Grohe, Martin; Puppis, Gabriele; Svensson, Ola (Ed.)
    We show the first near-linear time randomized algorithms for listing all minimum vertex cuts of polylogarithmic size that separate the graph into at least three connected components (also known as shredders) and for finding the most shattering one, i.e., the one maximizing the number of connected components. Our algorithms break the quadratic time bound by Cheriyan and Thurimella (STOC'96) for both problems that has been unimproved for more than two decades. Our work also removes an important bottleneck to near-linear time algorithms for the vertex connectivity augmentation problem (Jordan '95) and finding an even-length directed cycle in a graph, a problem shown to be equivalent to many other fundamental problems (Vazirani and Yannakakis '90, Robertson et al. '99). Note that it is necessary to list only minimum vertex cuts that separate the graph into at least three components because there can be an exponential number of minimum vertex cuts in general. To obtain a near-linear time algorithm, we have extended techniques in local flow algorithms developed by Forster et al. (SODA'20) to list shredders on a local scale. We also exploit fast queries to a pairwise vertex connectivity oracle subject to vertex failures (Long and Saranurak FOCS'22, Kosinas ESA'23). This is the first application of using connectivity oracles subject to vertex failures to speed up a static graph algorithm. 
    more » « less
  2. null (Ed.)
    Graph compression or sparsification is a basic information-theoretic and computational question. A major open problem in this research area is whether $$(1+\epsilon)$$-approximate cut-preserving vertex sparsifiers with size close to the number of terminals exist. As a step towards this goal, we initiate the study of a thresholded version of the problem: for a given parameter $$c$$, find a smaller graph, which we call \emph{connectivity-$$c$$ mimicking network}, which preserves connectivity among $$k$$ terminals exactly up to the value of $$c$$. We show that connectivity-$$c$$ mimicking networks of size $O(kc^4)$ exist and can be found in time $$m(c\log n)^{O(c)}$$. We also give a separate algorithm that constructs such graphs of size $$k \cdot O(c)^{2c}$$ in time $$mc^{O(c)}\log^{O(1)}n$$. These results lead to the first offline data structures for answering fully dynamic $$c$$-edge-connectivity queries for $$c \ge 4$$ in polylogarithmic time per query as well as more efficient algorithms for survivable network design on bounded treewidth graphs. 
    more » « less
  3. Undergraduate algorithms courses are a natural setting for teaching many of the theoretical ideas of parallel computing. Mergesort is a fundamental sequential divide-and- conquer algorithm often analyzed in such courses. In this work, we present a visualization tool to help demonstrate a novel PRAM algorithm for mergesort that is work efficient and has polylogarithmic span. Our implementation uses the Thread-Safe Graphics Library, which has an existing visualization of parallel mergesort. We demonstrate that our proposed algorithm has better work and span than the one currently visualized. 
    more » « less
  4. null (Ed.)
    We present an algorithm for approximating the diameter of massive weighted undirected graphs on distributed platforms supporting a MapReduce-like abstraction. In order to be efficient in terms of both time and space, our algorithm is based on a decomposition strategy which partitions the graph into disjoint clusters of bounded radius. Theoretically, our algorithm uses linear space and yields a polylogarithmic approximation guarantee; most importantly, for a large family of graphs, it features a round complexity asymptotically smaller than the one exhibited by a natural approximation algorithm based on the state-of-the-art Δ-stepping SSSP algorithm, which is its only practical, linear-space competitor in the distributed setting. We complement our theoretical findings with a proof-of-concept experimental analysis on large benchmark graphs, which suggests that our algorithm may attain substantial improvements in terms of running time compared to the aforementioned competitor, while featuring, in practice, a similar approximation ratio. 
    more » « less
  5. null (Ed.)
    In this article, we show that many sequential randomized incremental algorithms are in fact parallel. We consider algorithms for several problems, including Delaunay triangulation, linear programming, closest pair, smallest enclosing disk, least-element lists, and strongly connected components. We analyze the dependencies between iterations in an algorithm and show that the dependence structure is shallow with high probability or that, by violating some dependencies, the structure is shallow and the work is not increased significantly. We identify three types of algorithms based on their dependencies and present a framework for analyzing each type. Using the framework gives work-efficient polylogarithmic-depth parallel algorithms for most of the problems that we study. This article shows the first incremental Delaunay triangulation algorithm with optimal work and polylogarithmic depth. This result is important, since most implementations of parallel Delaunay triangulation use the incremental approach. Our results also improve bounds on strongly connected components and least-element lists and significantly simplify parallel algorithms for several problems. 
    more » « less