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Distributed half-integral matching and beyond

Published: 27 February 2024 Publication History

Abstract

By prior work, it is known that any distributed graph algorithm that finds a maximal matching requires Ω ( log ⁎ ⁡ n ) communication rounds, while it is possible to find a maximal fractional matching in O ( 1 ) rounds in bounded-degree graphs. However, all prior O ( 1 )-round algorithms for maximal fractional matching use arbitrarily fine-grained fractional values. In particular, none of them is able to find a half-integral solution, using only values from { 0, 1 2, 1 }. We show that the use of fine-grained fractional values is necessary, and moreover we give a complete characterization on exactly how small values are needed: if we consider maximal fractional matching in graphs of maximum degree Δ = 2 d, and any distributed graph algorithm with round complexity T ( Δ ) that only depends on Δ and is independent of n, we show that the algorithm has to use fractional values with a denominator at least 2 d. We give a new algorithm that shows that this is also sufficient.

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      cover image Theoretical Computer Science
      Theoretical Computer Science  Volume 982, Issue C
      Jan 2024
      363 pages

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      Elsevier Science Publishers Ltd.

      United Kingdom

      Publication History

      Published: 27 February 2024

      Author Tags

      1. Distributed graph algorithms
      2. Computational complexity
      3. Maximal matching
      4. Fractional matching

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