Given an undirected graph with integer edge lengths, we study the problem of approximating the distances in the graph by a spanning tree based on the notion of stretch. Our main contribution is a distributed algorithm in the CONGEST model of computation that constructs a random spanning tree with the guarantee that the expected stretch of every edge is O(log^{3} n), where n is the number of nodes in the graph. If the graph is unweighted, then this algorithm can be implemented to run in O(D) rounds, where D is the hop-diameter of the graph, thus being asymptotically optimal. In the weighted case, the run-time of our algorithm matches the currently best known bound for exact distance computations, i.e., O~ (min{sqrt{n D}, sqrt{n} D^{1 / 4} + n^{3 / 5} + D}). We stress that this is the first distributed construction of spanning trees leading to poly-logarithmic expected stretch with non-trivial running time.
@InProceedings{becker_et_al:LIPIcs.DISC.2019.4, author = {Becker, Ruben and Emek, Yuval and Ghaffari, Mohsen and Lenzen, Christoph}, title = {{Distributed Algorithms for Low Stretch Spanning Trees}}, booktitle = {33rd International Symposium on Distributed Computing (DISC 2019)}, pages = {4:1--4:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-126-9}, ISSN = {1868-8969}, year = {2019}, volume = {146}, editor = {Suomela, Jukka}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2019.4}, URN = {urn:nbn:de:0030-drops-113116}, doi = {10.4230/LIPIcs.DISC.2019.4}, annote = {Keywords: distributed graph algorithms, low-stretch spanning trees, CONGEST model, ball decomposition, star decomposition} }
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