Aharoni et al. [Ron Aharoni et al., 2010] proved the max-flow min-cut theorem for countable networks, namely that in every countable network with finite edge capacities, there exists a flow and a cut such that the flow saturates all outgoing edges of the cut and is zero on all incoming edges. In this paper, we formalize their proof in Isabelle/HOL and thereby identify and fix several problems with their proof. We also provide a simpler proof for networks where the total outgoing capacity of all vertices other than the source is finite. This proof is based on the max-flow min-cut theorem for finite networks.
@InProceedings{lochbihler:LIPIcs.ITP.2021.25, author = {Lochbihler, Andreas}, title = {{A Mechanized Proof of the Max-Flow Min-Cut Theorem for Countable Networks}}, booktitle = {12th International Conference on Interactive Theorem Proving (ITP 2021)}, pages = {25:1--25:18}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-188-7}, ISSN = {1868-8969}, year = {2021}, volume = {193}, editor = {Cohen, Liron and Kaliszyk, Cezary}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2021.25}, URN = {urn:nbn:de:0030-drops-139204}, doi = {10.4230/LIPIcs.ITP.2021.25}, annote = {Keywords: flow network, optimization, infinite graph, Isabelle/HOL} }
Feedback for Dagstuhl Publishing