In the k-Edge Connected Spanning Subgraph (k-ECSS) problem we are given a (multi-)graph G = (V,E) with edge costs and an integer k, and seek a min-cost k-edge-connected spanning subgraph of G. The problem admits a 2-approximation algorithm and no better approximation ratio is known. Recently, Hershkowitz, Klein, and Zenklusen [STOC 24] gave a bicriteria (1,k-10)-approximation algorithm that computes a (k-10)-edge-connected spanning subgraph of cost at most the optimal value of a standard Cut-LP for k-ECSS. We improve the bicriteria approximation to (1,k-4) and also give another non-trivial bicriteria approximation (3/2,k-2). The k-Edge-Connected Spanning Multi-subgraph (k-ECSM) problem is almost the same as k-ECSS, except that any edge can be selected multiple times at the same cost. A (1,k-p) bicriteria approximation for k-ECSS w.r.t. Cut-LP implies approximation ratio 1+p/k for k-ECSM, hence our result also improves the approximation ratio for k-ECSM.
@InProceedings{nutov_et_al:LIPIcs.ESA.2025.66, author = {Nutov, Zeev and Cohen, Reut}, title = {{Bicriteria Approximation for k-Edge-Connectivity}}, booktitle = {33rd Annual European Symposium on Algorithms (ESA 2025)}, pages = {66:1--66:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-395-9}, ISSN = {1868-8969}, year = {2025}, volume = {351}, editor = {Benoit, Anne and Kaplan, Haim and Wild, Sebastian and Herman, Grzegorz}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2025.66}, URN = {urn:nbn:de:0030-drops-245343}, doi = {10.4230/LIPIcs.ESA.2025.66}, annote = {Keywords: k-edge-connected subgraph, bicriteria approximation, iterative LP-rounding} }
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