Exponentially Faster Shortest Paths in the Congested Clique

Michal Dory, Merav Parter

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


We present improved deterministic algorithms for approximating shortest paths in the Congested Cliqe model of distributed computing. We obtain poly(log log n)-round algorithms for the following problems in unweighted undirected n-vertex graphs: • (1 + ∈)-approximation of multi-source shortest paths (MSSP) from [EQUATION] sources. • (2 + ∈)-approximation of all pairs shortest paths (APSP). • (1+∈, β)-approximation of APSP where [EQUATION]. These bounds improve exponentially over the state-of-the-art polylogarithmic bounds due to [Censor-Hillel et al., PODC19]. It also provides the first nearly-additive bounds for the APSP problem in sub-polynomial time. Our approach is based on distinguishing between short and long distances based on some distance threshold [EQUATION] where [EQUATION]. Handling the long distances is done by devising a new algorithm for computing a sparse (1 + ∈, β) emulator with O(n log log n) edges. For the short distances, we provide distance-sensitive variants for the distance tool-kit of [Censor-Hillel et al., PODC19]. By exploiting the fact that this tool-kit should be applied only on local balls of radius t, their round complexities get improved from poly (log n) to poly(log n). Finally, our deterministic solutions for these problems are based on a derandomization scheme of a novel variant of the hitting set problem, which might be of independent interest.

Original languageEnglish
Title of host publicationPODC 2020 - Proceedings of the 39th Symposium on Principles of Distributed Computing
Number of pages10
ISBN (Electronic)9781450375825
StatePublished - 31 Jul 2020
Externally publishedYes
Event39th Symposium on Principles of Distributed Computing, PODC 2020 - Virtual, Online, Italy
Duration: 3 Aug 20207 Aug 2020

Publication series

NameProceedings of the Annual ACM Symposium on Principles of Distributed Computing


Conference39th Symposium on Principles of Distributed Computing, PODC 2020
CityVirtual, Online


  • congested clique
  • near-additive emulator
  • shortest paths

All Science Journal Classification (ASJC) codes

  • Software
  • Hardware and Architecture
  • Computer Networks and Communications


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