Optimal vertex fault-tolerant spanners in polynomial time

G Bodwin, M Dinitz, C Robelle - Proceedings of the 2021 ACM-SIAM …, 2021 - SIAM
Proceedings of the 2021 ACM-SIAM Symposium on Discrete Algorithms (SODA), 2021SIAM
Recent work has pinned down the existentially optimal size bounds for vertex fault-tolerant
spanners: for any positive integer k, every n-node graph has a (2 k–1)-spanner on O (f 1–
1/kn 1+ 1/k) edges resilient to f vertex faults, and there are examples of input graphs on
which this bound cannot be improved. However, these proofs work by analyzing the output
spanner of a certain exponential-time greedy algorithm. In this work, we give the first
algorithm that produces vertex fault tolerant spanners of optimal size and which runs in …
Recent work has pinned down the existentially optimal size bounds for vertex fault-tolerant spanners: for any positive integer k, every n-node graph has a (2k – 1)-spanner on O(f1–1/kn1+1/k) edges resilient to f vertex faults, and there are examples of input graphs on which this bound cannot be improved. However, these proofs work by analyzing the output spanner of a certain exponential-time greedy algorithm. In this work, we give the first algorithm that produces vertex fault tolerant spanners of optimal size and which runs in polynomial time. Specifically, we give a randomized algorithm which takes Õ (f1–1/kn2+1/k + mf2) time. We also derandomize our algorithm to give a deterministic algorithm with similar bounds. This reflects an exponential improvement in runtime over [Bodwin-Patel PODC '19], the only previously known algorithm for constructing optimal vertex fault-tolerant spanners.
Society for Industrial and Applied Mathematics
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